THE INFLUENCE OF SHORT ROTATORS ON INTRAARTICULAR PRESSURE IN OSTEOARTHRITIC HIP AND RADIOLOGIC EVALUATION OF DURABILITY OF SHORT ROTATORS RECONSTRUCTION AFTER TOTAL HIP REPLACEMENT

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LITHUANIAN UNIVERSITY OF HEALTH SCIENCES MEDICAL ACADEMY

Valdemar Loiba

THE INFLUENCE OF SHORT ROTATORS

ON INTRAARTICULAR PRESSURE IN

OSTEOARTHRITIC HIP AND RADIOLOGIC

EVALUATION OF DURABILITY OF

SHORT ROTATORS RECONSTRUCTION

AFTER TOTAL HIP REPLACEMENT

Doctoral Dissertation Biomedical Sciences,

Medicine (06B)

Kaunas, 2015

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Dissertation has been prepared at the Department of Orthopedics trauma-tology of Medical Academy of Lithuanian University of Health Sciences during the period of 2010–2015.

Scientific Supervisor:

Prof. Dr. Šarūnas Tarasevičius (Lithuanian University of Health Scien-ces, Medical Academy, Biomedical ScienScien-ces, Medicine – 06B)

Dissertation is defended at the Medical Research Council of the Lithua-nian University of Health Sciences, Medical Academy.

Chairperson:

Prof. Dr. Habil. Virgilijus Ulozas (Lithuanian University of Health Sciences, Medical Academy, Biomedical Sciences, Medicine – 06B)

Members:

Prof. Dr. Alfredas Smailys (Lithuanian University of Health Sciences, Medical Academy, Biomedical Sciences, Medicine – 06B)

Prof. Dr. Saulius Lukoševičius (Lithuanian University of Health Sciences, Medical Academy, Biomedical Sciences, Medicine – 06B) Assoc. Prof. Dr. Annette W-Dahl (Lund University (Sweden), Biome-dical Sciences, Medicine – 06B)

Prof. Dr. Jolanta Dadonienė (Vilnius University, Biomedical Sciences, Medicine – 06B)

Dissertation will be defended at the open session of the Medical Research Council of Lithuanian University of Health Sciences on 3 July, 2015, at 13:00 in the Big (Conference) Hall of the Hospital of Lithuanian University of Health Sciences Kauno Klinikos.

Address: Eivenių 2, LT-50009 Kaunas, Lithuania.

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LIETUVOS SVEIKATOS MOKSLŲ UNIVERSITETAS MEDICINOS AKADEMIJA

Valdemar Loiba

TRUMPUJŲ KLUBO SĄNARIO ROTATORIŲ

ĮTAKA INTRASĄNARINIAM SLĖGIUI

SERGANT OSTEOARTROZE

BEI JŲ

REKONSTRUKCIJOS TVARUMO

RENTGENOLOGINIS ĮVERTINIMAS

PO KLUBO SĄNARIO

ENDOPROTEZAVIMO OPERACIJOS

Daktaro disertacija Biomedicinos mokslai, Medicina (06B) Kaunas, 2015 3

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Disertacija rengta 2010–2015 metais Lietuvos sveikatos mokslų universitete Medicinos akademijos Ortopedijos traumatologijos klinikoje.

Mokslinis vadovas

Prof. dr. Šarūnas Tarasevičius (Lietuvos sveikatos mokslų universitetas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)

Disertacija ginama Lietuvos sveikatos mokslų universiteto Medicinos mokslo krypties taryboje:

Pirmininkas

Prof. habil. dr. Virgilijus Ulozas (Lietuvos sveikatos mokslų universite-tas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)

Nariai:

Prof. dr. Alfredas Smailys (Lietuvos sveikatos mokslų universitetas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)

Prof. dr. Saulius Lukoševičius (Lietuvos sveikatos mokslų universitetas, Medicinos akademija, biomedicinos mokslai, medicina – 06B)

Asoc. Prof. Annette W-Dahl (Lundo universitetas (Švedija), biomedici-nos mokslai, medicina – 06B)

Prof. dr. Jolanta Dadonienė (Vilniaus universitetas, biomedicinos moks-lai, medicina – 06B)

Disertacija bus ginama viešame medicinos mokslo krypties tarybos posėdy-je 2015 m. liepos 3 d. 13 val. Lietuvos sveikatos mokslų universiteto ligoni-nės Kauno klinikų Didžiojoje auditorijoje.

Disertacijos gynimo vietos adresas: Eivenių g. 2, LT-50009 Kaunas, Lietuva.

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ABBREVIATIONS

RR – Relative risk OA – Osteoarthritis

MRI – Magnetic resonance imaging CT – Computed tomography

SPECT – Single photon emission computed tomography PET – Positron emission tomography

IL – Interleukin

TNF – Tumor necrosis factor BMI – Body mass index

ESR – Erythrocyte Sedimentation Rate ACR – American College of Rheumatology NSAID – Nonsteroidal anti-inflammatory drug THA – Total hip replacement

PMMA – Polymethylmethacrylate MIS – Minimally invasive surgery

PROM – Patient-reported outcome measures LUHS – Lithuanian University of Health Sciences SR – Short rotators

SD – Standard deviation

LSMU – Lietuvos sveikatos mokslų universitetas KMI – Kūno masės indeksas

SN – Standartinis nuokrypis

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INTRODUCTION

Sir John Charnley introduced modern total hip replacement (THR) in 1961 [22]. Now it is acknowledged that THR is one of the most successful surgeries [69]. The main reason for THR surgery is osteoarthritis (OA) of the hip that causes pain and stiffness of the affected hip joint. Radiographic signs of hip osteoarthritis can be found from 0.9% to up to 27% in general adult population in different countries [126]. The number of patients in the United States of America affected by OA rose from 21 million in 1995 to 27 million in 2005 [115]. In Lithuania, 3132 primary THR were performed during 2013 and about 6500 patients are waiting for primary THR [103].

The causes of pain in osteoarthritis are still unclear. The role of capsule and short rotators (SR) of the hip is a point of interest. Hypothesis is made that intraarticular effusion with raised intracapsular pressure is a possible mechanism of pain in hip OA [99]. Although it is known that SR do not increase intracapsular pressure, we still lack information on how they influence capsular compliance and pain [118].

With the introduction of new bearing surfaces and improvements in surgery technique dislocation after THR today is one of the leading causes for revision THR surgery [52, 92, 131]. There are different risk factors for revision THR surgery like patients with femoral neck fractures, small head size of femoral implant, posterior surgical approach and others [16]. The first results from the Lithuanian arthroplasty register are in agreement with evidence-based literature, demonstrating that the leading cause for revision THR surgery is instability [121]. Posterior surgical approach is the most common approach used for THR in Lithuania but it is associated with higher risk of dislocation [121]. Detachment of SR and posterior capsule of the hip is probably the main reason for higher rates of dislocation in posterior surgical approach. It has been reported that posterior soft tissue repair significantly decreases dislocation rates after THR [90, 114]. Howe-ver, in Stähelin report it was shown that posterior soft tissue repair is of limited durability with failure rates up to 75% [112, 113]. It is still unknown when exactly in postoperative period posterior soft tissue repair fails. We investigated the effect of SR on capsular compliance and pain and perfor-med radiographic evaluation of repaired SR after THR of the hip to deter-mine the exact time of failure and failure rate.

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Aim of the study

To investigate the role of short rotators in capsular compliance and pain in osteoarthritic hips and their durability after repair in total hip replace-ment.

Tasks of the study

1. To investigate failure rate after short rotators repair in total hip replacement.

2. To investigate short rotators failure modes in terms of timing after the surgery.

3. To analyze the postoperative changes in leg length and offset with suture durability.

4. To analyze the influence of short rotators pressure on capsule compliance in osteoarthritic hip.

5. To investigate the correlation between capsular compliance and pain in osteoarthritic hip.

Relevance and originality of the study

The exact origin of pain in OA hip is unknown. There are many theories described in the literature which attempt to explain the possible pain etiolo-gies but no one reason is defined and widely accepted. The role of articular capsule as a pain generator in OA hip has recently been investigated. The authors found positive correlation between intracapsular pressure and pain. Also the attempt has been made to correlate pain with the elastic properties of hip joint capsule; however, no pain and capsular compliance correlation was observed. One of the possible explanations of such finding was that the role of short rotators which are lying directly on to the capsule and produ-cing certain mechanical pressure was not investigated as a possible affecting factor. Thus we hypothesized that short rotators in OA hip joint might affect the elastic properties of the capsule and subsequently pain. And we found no reports in the literature describing the role of short rotators in capsular compliance and pain in OA hip.

It has been reported that surgical posterior soft tissue repair signifi-cantly decreases dislocation rates after THR operated through posterior sur-gical approach [90, 114]. However, despite those reports, radiographic evaluations of such repairs show high rates of failure at three months follow-up [112, 113]. We found no reports in the literature investigating the exact time of posterior soft tissue repair failure in a patient group where rehabilitation after THA was conducted without specific limitations. Also

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there is a lack of reports correlating the changes in leg length and offset after THA in relation to the occurrence on short rotators repair failure.

Relevance and practical value of the study

The results of our 1st part of the study will provide more detailed information regarding the posterior soft tissue repair after THA. We will identify the exact time of possible suture failure and provide a description of failure modes.

The results of our 2nd part of the study will provide more information regarding the understanding of pain origin in OA hip. Such knowledge should have a certain influence in development of therapeutical modalities for pain control in OA hip.

Structure and scope of the doctoral dissertation

Doctoral dissertation consists of introduction, literature overview, patients and methods, statistics, results, discusions, conclusions, practical recommendations, references (140 sources), publications, accessories, sum-mary in Lithuanian and curriculum vitae. Doctoral dissertation contains 18 figures, 4 tables and 90 pages.

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1. LITERATURE OVERVIEW

1.1. Osteoarthritis of the hip

Osteoarthritis (OA) is an old disease and is found even in Egyptian mummies [14]. Since then, the understanding of OA has made a long way. Now we understand OA as a degenerative disease characterized by degene-rative changes of affected joints. OA of the hip can be primary or secondary [68]. Risk factors for primary hip OA are older age, higher bone mass and body mass index (BMI), weight-bearing sports at an elite level, genetic factors and occupation associated with heavy manual work or prolonged standing [55, 56, 68, 94]. Secondary hip OA can be divided into systemic or localized. Risk factors for secondary systemic hip OA are hemochromatosis, hyperparathyroidism, hypothyroidism, acromegaly, hyperlaxity syndromes, Paget’s disease, gout, chondrocalcinosis and risk factors for localized OA are joint injury, developmental deformities, Legg-Calvé-Perthes disease, acetabular dysplasia, osteonecrosis of the femoral head and cartilage dama-ging arthritis [94]. There is still a lot of discussion about pathogenesis of OA. Nowadays there is a theory that OA is a result of a complex interplay between mechanical, cellular and biochemical forces [48]. OA involves cartilage, ligaments, tendons, bone and other joint structures [35]. Starting with fibrocartilage degeneration (affecting and meniscus or hip labrum), changing load distribution and damaging hyaline cartilage, later progresses into formation of osteophytes, protrusions, cartilage erosions, synovitis and capsular swelling [35]. Because of synovitis and joint capsular swelling, inhibition of activation of joint surrounding muscles starts, leading to muscles atrophy [35]. The main symptoms of advanced OA is pain and stiffness of affected joints, also reduced movement, crepitus, swelling and others [33, 128]. Radiologic diagnostic criteria of OA are osteophytes, narrowing of the joint space, subchondral sclerosis and bone cysts. Unfortunately all these radiological findings indicate advanced or even severe stages of OA. A wider range of diagnostic tools that can help diagno-se early stages of OA are available nowadays, e.g. magnetic resonance imaging (MRI), computed tomography (CT), single photon emission computed tomography (SPECT)/CT, and positron emission tomography (PET) [64, 108]. Using these novel imaging techniques, cartilage damage could be divided into pre-clinical, pre-radiographic and radiographic dama-ge stadama-ges [82]. Even more – MRI techniques could detect the chandama-ges in the subchondral bone [82]. Biomarkers are another tool to diagnose early OA [75]. Urine, serum, synovial fluid tests can help in diagnosing early OA. In

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2003, the Osteoarthritis Biomarkers Network was established. This organi-zation divides all biomarkers into 5 groups with acronym BIPED: Burden of disease, investigative, prognostic, efficacy of intervention, diagnostic [7]. A lot of biomarkers are under investigation currently and these studies are very promising for diagnosing early OA [102]. American College of Rheumato-logy has described criteria for diagnosis of hip OA [2]. One of them is pain in hip joint during the last month and there must be at least 2 of 3 following features: Femoral and/or acetabular osteophytes on the radiograph; Erythro-cyte sedimentation rate (ESR) < 20 mm/hour; Axial joint space narrowing on radiograph [2].

1.2. Pain in HIP Osteoarthritis

International association for the study of pain describes pain as “An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” [23]. Although mechanisms of OA pain have been studied for a long time, there is still no clear explanation for them. Nowadays we think that OA pain con-sists of interplay between inflammation, local joint tissue damage, periphe-ral and centperiphe-ral nervous systems [101, 111]. The nerve endings in the painful hip can be found almost in all tissues. Haversath et al. studied nociceptive innervation of the painful hips and found free nerve endings in the aceta-bular labrum, capsule and ligamentum teres [42]. Gerhardt with colleagues analyzed neural anatomy of human hip joint and found neural end organs in the capsule, labrum, ligamentum teres and transverse acetabular ligament [37]. Schaible and Grubb explored mechanisms of joint pain and they found different nerve endings in capsule, ligaments, menisci, periosteum and synovial layer [105]. There are nerve endings in subchondral bone, but there are no nerve endings in the cartilage. Articular branches of the obturator, femoral, superior gluteal, and sciatic nerves are responsible for innervation of hip joint [140]. Any disease of mentioned anatomical structures must be treated fast, if not treated it becomes a chronic problem with chronic pain, very difficult to treat. Important role in osteoarthritic pain is set for inflam-mation mediators [9, 73, 105, 111, 133, 137]. The most important inflamma-tion mediators for OA pathogenesis are Interleukin (IL) - 1β, Tumor necro-sis factor (TNF) α, IL-6 and others [137]. They interplay with anti-inflam-matory cytokines (like IL-4, IL-10, IL-14) [137]. Disbalance between inflammatory and anti-inflammatory cytokines results in progress of OA. Salaffi with colleagues made a review of osteoarthritic sources of pain and reported: “The bone-related causes of pain in OA include subchondral

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microfractures, bone stretching with elevation of the periosteum due to osteophyte growth, bone remodeling and repair, bone marrow lesions, and bone angina caused by decreased blood flow and increased intra-osseous pressure.” [101]. However, the exact causes of pain in OA are still poorly understood. Schaible describes secondary synovitis and bone marrow lesions as the main causes for pain in OA [104]. Synovitis (synovium is richly innervated) with joint effusion and bigger capsular tension is one of the causes for OA joint pain [35]. Goddard with Gosling have studied intracapsular pressure in hip OA [38]. They have found that joint effusion and higher intracapsular pressure are associated with more pain [38]. Higher intracapsular pressure affects circulation in periarticular veins and increases intraosal venous pressure [70]. Higher intraosal venous pressure leads to increased joint pain [70].

1.3. Treatment methods 1.3.1. Conservative treatment of hip OA

Conservative treatment of hip OA consists of pharmacological and non-pharmacological treatment [33, 68]. Conservative treatment is started first and only after failure of conservative treatment there is an option for surgi-cal treatment. Non-pharmacologisurgi-cal treatment consists of patient education and lifestyle change, physical therapy, exercise, weight loss, use of joint unloading devices (canes, insoles, orthosis), acupuncture [29, 33, 36, 45, 68, 93]. Scientists from American College of Rheumatology (ACR) have revie-wed evidence-based literature and divided all recommendations for non-pharmacological treatment of hip OA into 3 groups [45]: 1. ACR strongly recommends for patients with hip OA to participate in cardiovascular and/or land based exercises, aquatic exercises ant for overweight patients to lose weight. 2.ACR conditionally recommends to participate in self-management programs, receive manual therapy in combination with supervised exercises, receive psychosocial interventions, be instructed in the use of thermal agents and receive walking aids.3.Participation in balance exercises(with or without strengthening exercises), participation in tai chi, and receiving manual therapy alone are not recommended. Although non-pharmacological treatment seems to be the best option to treat hip OA; however, pain in the affected hip limits patients in exercise performance and makes weight loss more complicated. Next step in conservative treatment of hip OA is pharma-cological treatment. The first choice of medicament is acetaminophen [45, 84]. If acetaminophen is not effective, the use of oral nonsteroidal anti-inflammatory drugs (NSAID’s) is recommended then and if it is not

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effective, Tramadol is recommended. Intraarticular injections of corticoste-roids are also recommended for hip OA treatment [45, 65]. ACR conditio-nally recommends use of acetaminophen, oral NSAID’s, Tramadol and intraarticular injections of corticosteroids. ACR conditionally recommends for patients with hip OA not to use glucosamine and chondroitin sulfate and has no recommendations for use of topical NSAID’s, intraarticular hyalu-ronate injections, duloxetine and opioid analgesics [45, 72]. Very similar recommendations for conservative treatment of hip OA have been proposed by scientists from National Institute for Health and Care Excellence [36]. The graphical representation of their recommendations is presented in Figure 1.3.1.1.

Figure 1.3.1.1. Pain management in hip OA [36]

1.3.2. Surgical treatment of hip OA

There are a variety of surgical methods recommended to treat hip OA: arthroscopy, periacetabular or femur osteotomies, arthrodesis and the most popular and effective of which is hip joint arthroplasty [34, 46, 95, 109]. Although hip arthroscopy is a very effective treatment method for acetabular labrum tears, removing free bodies from hip joint, Pinzer and Cam type impingement, synovitis or synovial chondromatosis of hip joint, there is still a discussion about the effectiveness of arthroscopic treatment for hip joint OA [34, 40]. Domb with other authors have investigated the indications of hip arthroscopy for treatment of OA [34]. They recommend arthroscopic treatment for hip OA only for patients with grade 1 of Tönnis classification

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of OA (Radiographic changes like increased sclerosis, slight narrowing of the joint space, no or slight loss of head sphericity) and joint space with ≥2 mm [34]. If hip OA is ≥2 grade of Tönnis classification or joint space is ≤ 2 mm, the authors recommend hip arthrolasty [34].

Osteotomies of acetabulum or proximal femur are another tool for surgical treatment of hip OA [4, 24, 41]. Osteotomies mostly are used for prevention of secondary localized hip OA for very young patients and they still have their role in treatment of early but not advanced hip OA [4, 24, 41]. A lot of different types of osteotomies for different deformities are available: varus or valgus trochanteric, femoral neck, greater trochanter distalization with relative neck lengthening, lesser trochanter excision or distalization with relative neck lengthening, femoral head reduction osteotomy and different types of periacetabular osteotomies [4, 24, 41]. The advantages of osteotomies are good clinical results, possible subsequent other types of surgery after not successful primary procedure while the main disadvantage is that osteotomy is technically very difficult type of surgery.

Arthrodesis of hip joint also is still an option in surgical treatment of hip OA [8, 46, 109]. If osteotomies are mostly recommended for young patients with not advanced hip OA, arthrodesis of hip joint is recommended for young patients with advanced or severe hip OA [8]. Arthrodesis also is a highly demanding procedure that needs a proper position of femur and functional results are not as good as total hip replacement (THR), but results are good for pain management [8]. If hip fusion fails, there is possibility of conversion to THR [8, 53, 98, 109]. Sirikonda with colleagues shows excellent results of THA after hip arthrodesis [109]. But other authors show that results of conversion of hip joint fusion to THA are not so optimistic [53, 98]. Other indication for this type of surgery is economic. In the count-ries where THA is still very expensive and not easily accessible surgery, hip joint fusion is a method of choice for treatment of advanced or severe hip OA.

Currently, THR is the most popular type of surgical hip OA treatment. The first attempts to treat hip arthritis surgically were made more than 100 years ago, but it was sir John Charnley who made a revolution introducing his model of total hip arthroplasty [53, 81]. Sir John Charnley introduced 3 new ideas: principle of low friction torque arthroplasty, he used acrylic cement for fixing components to bone and he introduced high-density polyethylene [69, 81, 139]. Twenty five years after THR with Chanley type implant clinical results were very good, with 77% of patients still alive retaining original prosthesis [20]. During THR surgery, natural hip joint is replaced with artificial implants. Nowadays a lot of different types of hip prosthetic implants are available, e.g. total hip prosthesis, hemi prosthesis,

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bipolar prosthesis and different resurfacing systems. For treatment of hip OA surgeons mainly use total hip replacement, when hemiarthroplasty is used mostly for old patients with displaced femoral neck fractures with absence of hip OA symptoms [21]. There area number of prosthesis representing different philosophies available on the market. Components could be fixed using cement (so called cemented THR) or other implants are designed for initial press-fit fixation (uncemented systems) [1]. Artificial joint bearing surfaces are made from different materials, such as Ceramic on Ceramic (CoC), Ceramic on Polyethylene (CoP); Metal on Polyethylene (MoP); Metal on Metal (MoM) and Ceramicised metal on Polyethylene [32, 122]. According to fixation method, THR are divided into cemented, uncemented and hybrid fixation types [89]. Hybrid fixation is defined as cemented stem and uncemented acetabular cup (Figure 1.3.2.1). Reverse hybrid is defined as cemented acetabular cup and uncemented femoral stem (Figure 1.3.2.1). Cementless implants vary by surface coating and structure [39, 60, 95]. Surface of implant could be with grit-blasting scratches or porous coated (with or without hydroxyapatit) [39, 60, 95]. When bone grows inside a porous surface of implant it is called bone ingrowth and when bone grows on a roughened surface it is called ongrowth [39, 60]. There are different surgical approaches used for implantation of hip joint prosthesis such as anterior, anterolateral, lateral and posterior [86]. With a general tendency for a minimal invasive surgery (MIS) in medicine the same tendency is clearly seen in THR [110, 117, 136]. With evolution of instrumentation many different MIS surgical approaches have been implemented in THR [110, 117, 136]. Nowadays computer-assisted naviga-tion systems are used in THR surgery with the purpose of ensuring more accurate positioning of components [110].

Figure 1.3.2.1. Different types of fixation in THR

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1.4. Data analysis after THR

Because of the huge amount of different THR implants, surgical approaches, diagnoses and other factors affecting THR surgery there was a need for the national arthroplasty registry [30, 66]. Regional or National registry collects all information about THR surgery, its outcomes and provi-des evidence-based results and recommendations [30, 66, 121]. The first nationwide knee replacement surgery registry was established in Sweden in 1975 [30]. Patient survival, implant survival, other adverse events and patient-reported outcome measures (PROM) are the most valuable results to evaluate outcomes after THR. Patient survival rate is recognized in the literature as the most important outcome measure for any type of surgery. Most often a 90-day mortality rate is estimated. A 1% 90-day mortality rate after THR is reported, which is similar to general population mortality rate at that age [49].

Implant survival rate shows survival of the implanted prosthesis and is characterized by two values: re-operation (any surgery affecting operated hip) and revision (surgery when the implant is removed, exchanged or added) [30]. Infection, periprostethic fracture, loosening, instability, implant fracture are the most common reasons of repeated surgeries after THR.

PROM is becoming increasingly important because of very similar implant survival and revision rates when different type of implants is used. The most often used PROMs are: Harris Hip score, short form 36 (SF-36), Euroqol 5 dimensions, Western Ontario and McMaster Universities Osteo-arthritis Index (WOMAC), Hip disability and osteoOsteo-arthritis outcomescore (HOOS) and other [6, 10, 15, 85, 106, 116]. Another very important part of the registry is a fast ability to discover implant design errors [25] which are reflected in lower than average implant survival rates.

1.5. Hip joint capsule compliance in OA hip

Consensus has still not been reached in the literature regarding the etiology and pathogenesis of pain in OA hip. Some authors suggest that pain in OA hip could be of capsular origin because of a great number of free nerve endings observed in the capsule [42]. In 1953, Lloyd-Roberts investi-gated capsular changes in hip OA [74]. His main conclusion was that hip joint capsule is particularly sensitive to traction, tight in extension(weight bearing position) and hypothesis was that during stretching of shortened capsule(extension of the hip) pain occurs [74]. Myers and Palmer analyzed capsular compliance and pressure-volume relationship in arthritic and normal knee joints [83]. They investigated those parameters in 3 young

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healthy volunteers, 14 patients with rheumatoid arthritis and 3 OA knees. They found greater capsular compliance and higher intra-articular pressures in younger and healthy persons, while older and disease-affected persons had lower intra-articular pressure and capsular compliance. Goddard and Gosling found significant linear correlation between intra-articular pressure of the synovial fluid and pain – patients with higher intraarticular pressure had more painful hip [38]. Authors also reported that younger patients with mobile and more painful hips had higher intracapsular pressures if compared to older patients with stiffer and not so painful joints [38]. Wingstrand and Wingstrand in a cadaver study explored biomechanical aspects of hip joint capsule and developed a mathematical model [134]. The main conclusions of his study were that in healthy hips there is very small amount of fluid, no intracapsular pressure and tension in the capsule, and no change in intracap-sular volume or pressure within the normal range of hip joint motion. In another study Wingstrand et al. investigated intracapsular pressure changes in the hip joint [135]. In a cadaveric study the authors discovered that in normal hip there was no increase in intracapsular in normal range of rota-tion. After injection of saline into the joint, pressureless range of motion decreased until finally ceased. Therefore the authors suggest that increase of tension in a capsule can be a cause of pain especially in movement of the hip joint. Bierma-Zeinstra with other authors investigated the correlation between sonographicaly diagnosed effusion of hip joint capsule and pain in adults [11]. High prevalence of ultrasonic joint effusion was found in adults with hip pain. This finding also supports the hypothesis that presence of joint effusion or greater intracapsular pressure can be considered as one of the causes of hip joint pain. Similarly, Robertsson et al. investigated the correlation between intracapsular pressure and pain in hip OA. He reported a strong correlation between intracapsular pressure and pain at night, when starting to walk and when walking [99]. In another study Tarasevicius et al. investigated intracapsular pressure and capsular compliance in hip OA [119]. The authors found correlation between severity of hip OA and intra-capsular pressure/capsule compliance. Patients with less severe hip OA had higher intracapsular pressures and higher capsular compliance. The authors did not find any correlation between sonographicaly measured capsular dis-tension and pain. They did not find any correlation between higher intra-capsular pressure and pain and it was a different result from that of Robert-sson et al. and Goddard and Gosling. A possible explanation for that finding was a high prevalence of severe OA patients included in this study. Another important issue which could explain absence of correlation between hip joint pain and intracapsular pressure is the difference in pressure measuring technique. Robertsson et al. measured intracapsular pressure before surgery

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after the spinal anesthesia, while Tarasevicius et al. measured pressure intra-operatively after the short rotator tendons had been released and hip joint capsule was visualized. Thus subsequently the hypothesis has been raised that intraarticular pressure might be affected by short rotators, lying directly on the posterior capsule, which might produce some mechanical pressure. However, other study performed by Tarasevicius et al. has rejected this hypothesis reporting no changes in intracapsular pressure were observed after the release of short rotators [118]. The drawback of Tarasevicius et al. study is that the compliance of the capsule which might affect pain in OA hip has not been investigated. Thus hypothetically the mechanical pressure of short rotators could have some influence on capsular compliance. The short external rotators of the hip include 5 muscles: piriformis, superior and inferior gemellus, obturator internus, quadratus femoris [51]. Gemellus superior, Gemellus inferior and obturator internus formed a so-called conjoi-ned tendon [51]. Walters et al. studied anatomy of hip capsule and pericap-sular structures and discovered that obturator internus and conjoined tendon lie on the posterior aspect of the hip capsule and have small adhesions on posterior capsule near acetabular rim [129].

So it is possible that short external rotators of the hip can have influence on capsule compliance and pain. After all these studies we know that short rotators of the hip do not increase intracapsular pressure, but we still lack information on how they affect capsular compliance and pain.

1.6. Dislocations after THA

Dislocation after THA is one of the most common complications and one of the main reasons for reoperation [131]. There is a great variety in dislocation rates after primary THA reported in a number of studies [28, 57, 87, 92, 120, 124, 130, 132, 138]. Dislocation rates after primary THR vary from 0.3% to 10% [92]. Such differences can be explained as the authors investigate different patient groups operated on for different reasons with a number of approaches and implants, which have a direct correlation with dislocation rates. Most often dislocation occurs early after THA [79, 80, 138]. Meek et al. investigated the time of dislocation after surgery and discovered that 23% of dislocations occur within the first 3 months and 43% between 3–12 months [80]. In total 66% of dislocations occur during the first year after surgery [80]. Woo and Morrey found that 59% of disloca-tions occur within the first 3 months and 77% during the first year after THR [138]. The first dislocations after THA are usually treated conserva-tively by closed reduction. Recurrent dislocations or instability are a major

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problem leading to revision hip surgeries [52, 92, 131]. Brooks et al. over-viewed the most common causes for dislocation after THR [16]. He divided the most common causes into 3 groups: patient, implant and surgeon related risk factors. Patient related risk factors are age above 70, medical comorbi-dities, cognitive impairment, female gender, laxity of ligaments and musc-les, abductors weakness, trochanteric problems. Implant related factors: head size of femoral implant, head-neck junction design, offset, proper position of polyethylene liners with elevated rims. Surgeon related factors like experience, quantity of THR performed per year, proper patient positio-ning on operating table, surgical approach and proper implant positiopositio-ning. Proper acetabular component position is essential to reduce dislocation risk. In 1978 Lewinnek et al. investigated dislocations after THR in 300 THR group and they found correlation between anterior dislocation rate and increased acetabular component anteversion [71]. The authors recommen-ded that acetabular component position should be with anteversion of 15±10 degrees and lateral opening of 40±10 degrees. When components were placed within this range dislocation rate was 1.5%, and when position of acetabular components was outside this recommended range dislocation rate was 6.1%. The same recommendations about degree of inclination for safe placement of acetabular component were made by McCollum and Grey [78]. Kluess et al. investigated the range of motion of hip prosthesis until dislocation occurs [63]. For posterior and anterior dislocation acetabular cup position of 45° of inclination and 15–30° of anteversion was associated with appropriate range of motion and dislocation stability [63].

1.6.1. Underlying diagnosis

Preoperative diagnoses have been recognized as one of the factors affecting dislocation rates after THA. Conroy et al. investigated diagnoses for THR that have significantly increased relative risk (RR) of revision for dislocation if compared to OA [26]. The authors investigated data of 65,992 primary THR provided by the Australian Orthopaedic Association National Joint Replacement Registry and reported that patients with femoral neck fractures (RR 2.03, p<0.001), rheumatoid arthritis (RR 2.01, p<0.01) or avascular necrosis of the femoral head (RR 1.57, p<0.05) had greater relative risk of revision for dislocation [26]. Meek et al. analyzed data of 62 175 patients from the Scottish National arthroplasty non-voluntary registry and confirmed higher risk of dislocation for patients with fractures of femoral neck and rheumatoid arthritis [80]. Patients with fractures of the femoral neck had more than 50% higher dislocation risk [80]. Khatod with colleagues found higher risk of dislocation in rheumatoid arthritis patients

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[61]. Byström et al. investigated 42,987 primary THR patients from Norwe-gian Arthroplasty Register and found that patients with sequel of femoral neck fractures had higher risk for dislocation and there were no higher risks for dislocation in rheumatoid arthritis and other patients [12]. Why are fractures of the femoral neck associated with greater risk of dislocation of THR? This is probably because of older age, comorbidities and weakness of muscles, tendons and ligaments.

1.6.2. Head size of implant

A lot of evidence shows that small size of head of the femoral implant is associated with higher risk of dislocations after THR [16, 27, 61, 76, 96, 131]. Randomized controlled trial performed by Howie et al. clearly shows how dislocation rates after THR are affected by size of femoral head [47]. A total of 644 patients undergoing primary or revision THR were randomized for this study and received 36 or 28 mm metal femoral head on highly cross-linked polyethylene [47]. Patients with higher risk of dislocations and revision THR patients because of recurrent hip dislocation or infection were excluded [47]. Dislocation rates following primary arthroplasty were significantly lower for hips with a 36 mm femoral head articulation (0.8% or 2 of 258) than for patients with a 28 mm articulation (4.4% or 12 of 275). Byström et al. in the already mentioned study from Norwegian Arthroplasty Register investigated the effect of head size for dislocations after THR [12]. Results also clearly showed that THR with 32 mm femoral head size had lower risk for dislocation than 28mm [12]. Adjusted failure rate ratio for 28 mm femoral head was 4.0 if compared to 1.0 in 32 mm femoral head [12]. In the already mentioned study performed by Conroy et al. it was confirmed that a 28 mm diameter head has minor risk of dislocation after THR as compared with head of 22 mm or 26 mm and if femoral head size is more than 30 mm, relative risk for dislocation is even lower [26]. Relative risk for dislocation is 1.0 for femoral head ≥ 30 mm, 1.76 for 28 mm head, 3.02 for 26 mm head and 3.11 for 22 mm femoral head [26]. Why are smaller diameters of head associated with higher risk of dislocations? Amstutz with colleagues explained that this is because of the impingement between neck of implanted femoral component and acetabular rim [3]. Bigger femoral head of implant prevents that type of impingement [17].

1.6.3. Surgical approach

The influence of surgical approach for dislocations after THR has also been widely studied. Masonis and Bourne investigated all information about the influence of surgical approach on dislocation rate reviewing scientific

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papers between 1970 and 2001 [77]. They reported that dislocation rates were for transtrochanteric approach – 1.27%, for posterior approach – 3.23% (3.95% without posterior repair and 2.03% with posterior repair), for anterolateral approach – 2.18% and 0.55% for the direct lateral approach [77]. Other authors also showed greater risk of dislocation in posterior surgical approach [44, 100]. Higgins et al. performed a systematic review and meta-analysis of papers comparing anterior and posterior approach in THR and found significant differences in dislocation rates in favour of anterior approach [44]. Rogmark et al. analyzed data of patients after hemiarthroplasty of the hip in Norwegian and Swedish national registries [100]. From 33,205 patients for whom hemiarthroplasty was performed 1,164 patients were reoperated and the main reason for reoperation was dislocation [100]. Hazard ratio for dislocation after hemiarthroplasty was 2.2 for posterior approach and 1 for direct lateral approach (p<0.001) for patients of all ages [100]. Why do surgeons use posterior surgical approach? Mainly because of the good visibility of anatomic structures, if needed revision surgery is easier to perform, less assistant needed for surgery, lower risk of heterotopic ossification and preservation of abductor mechanism [125]. Also authors show a difference for dislocations rates in THR perfor-med through posterior surgical approach when posterior soft tissue repair was performed [90, 114]. Pellicci, Bostrom and Poss reported 4% in 395 THR patients dislocation rate with only short rotators repair, and 0% in 395 patients dislocation rate after enhanced posterior soft tissue repair in Pellicci experience [90]. In Poss experience, dislocation rate without repair was 6.2% in 160 THR patients and 0.8% in 124 patients after enhanced repair [90]. Suh et al. demonstrate decrease in dislocation rates from 6.4% in 250 THR patients without posterior soft tissue repair to 1% in 96 patients after repair of posterior soft tissues [114]. Iorio et al. evaluated three different posterior approaches and posterior soft tissue repair methods in 390 consecutive primary THR patients with overall dislocation rate of 2.3% (9 of 390 patients) [50]. For the first group of 90 patients with a simple posterior repair of the external rotators (repair performed through three drill holes) dislocation rate was 5.5% [50]. In the second group of 180 patients for whom enhanced posterior soft tissue repair (repair of short rotators and posterior capsule in one continuous sleeve) was performed dislocation rate was 1.3% [50]. In the third group of 120 patients for whom 10cm mini incision with the same type of enhanced soft tissue repair was performed dislocation rate was 1.7% [50]. Kwon et al. made a systematic literature overview and meta-analysis comparing dislocation rates after THR through posterior approach with or without soft tissue repair [67]. Analysis shows that posterior approach in THR without soft tissue repair had 8.21 times

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higher relative risk of dislocation than posterior approach with performed soft tissue repair [67]. Brown et al. investigated the mechanisms of disloca-tions after THR [39]. They concluded that posterior or postero-lateral capsu-le detachments are a major factor in risk of dislocation and posterior soft tissue repair is a dislocation preventing factor [39]. Mahoney and Pellicci also overviewed the main causes of dislocations after THR and recommen-ded using enhanced posterior soft tissue repair during posterior surgical approach for prevention of dislocations [76]. Zhang et al. performed meta-analysis on effectiveness and safety of posterior approach with soft tissue repair after THR [125]. Results of this meta-analysis clearly demonstrated lower dislocation rates when posterior soft tissue repair had been performed [125]. Also posterior approach with soft tissue repair was associated with higher Harris hip score results and had no statistically significant difference in sciatic nerve palsy if compared to posterior approach without soft tissue repair [125].

1.7. Posterior soft tissue repair in posterior surgical approach (THR)

Nowadays surgeons use many different posterior soft tissue repair techniques to prevent dislocations after THR performed through posterior approach [18, 43, 54, 59, 62, 90, 91, 107, 112–114, 120, 124, 127, 130]. One technique consists of osteotomy of greater trochanter in one flap together with SR, posterior capsule and posterior part of gluteus medius [107]. After implantation of prosthesis, osteotomized part of greater trochanter together with posterior soft tissues is fixed with 2 cancellous screws. Posterior soft tissue repair can consist of repair of capsule, short external rotators or both of them. Repair of posterior capsule, tendinous external short rotators, quadratus femoris and tendinous insertion of gluteus maximus with a suture passing through drill holes in the greater trochanter was introduced by Pellicci et al. in 1998 [90]. The authors called that type of repair enhanced posterior soft tissue repair [90]. In their study, the authors showed significant decrease in dislocation rates after enhanced posterior soft tissue repair had been performed (Table 1.7.1) [90]. Although posterior soft tissue repairs showed great results in reducing dislocation rates after THR, the investigations performed by Kao and Woolson, also by Stähelin et al. demonstrated high failure rates of repairs [58, 112, 113]. Kao and Woolson in 1992 performed a study of 10 THR patients [58]. The authors excised posterior and anterior capsule and repaired only piriformis tendon. For radiologic evaluation the authors used metallic radiomarkers in piriformis tendon and greater trochanter. Anteroposterior and axial radiographs of the

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operated hip joints were performed and distance between radiomarkers was measured. Distance more than 25 mm was considered as piriformis tendon repair failure. In 8 out of 10 patients repair failure occurred. Repair was intact in two cases, although one dislocation occurred in intact repair patient [58]. In 2002, Stähelin et al. investigated 27 THR in 26 patients with 50 short external rotators repaired with posterior capsule excised [113]. Repair was performed on piriformis, triceps coxae or obturator externus muscles only if tension of tendons was low enough for reinsertion. A total of 50 tendons were reinserted with modified Mason-Allen stitch applied to tendon and 2 mm holes drilled in the posterior aspect of the greater trochanter for transosseous suture fixation. Radiological markers like 2-0 USP Ethicon stainless steel wire were appliedto the tendon, and tantalum ball was applied at the tendon insertion point to the surface of greater trochanter. Distance between radiological markers measured intraoperatively was not more 1cm. Postoperative regimen included non full weight bearing and limitations in flexion and internal rotation of the hip. On 1st postoperative day and 3 months after surgery axial and anteroposterior radiographs of the hip were performed. If measured distance between wire knot and tantalum ball at any radiograph was ≥ 2.5 cm, repair was considered as failure. Of the 50 repai-red tendons 35 (70%) failed within 3 months. In 26 cases failure occurrepai-red on 1st day after surgery and in 9 cases failure occurred at 3 months follows up. In 2004, Stähelin et al. conducted another study with 20 THR patients [112]. This time capsular enhanced posterior soft tissue repair was per-formed [112]. During surgery piriformis, conjoined tendons and capsule were released from greater trochanter in single tendon-capsule flap. After components had been implanted, this flap was reattached with 3 grasping stitches: first stitch applied to piriformis tendon-capsule junction and second–third stitches were applied to conjoined tendons tendon-capsule junction. The 2 mm drill holes were drilled in the greater trochanter for transosseous fixation. One radiopaque wire was stitched to the piriformis tendon and second to the conjoined tendon. Tantalum ball was applied at the tendon insertion point to the greater trochanter. Knotting of sutures was performed in 10° of internal rotation and 45° of flexion. The same post-operative regimen was applied and radiologic evaluation of repair was performed as described before [113]. Repair failed in 15 of 20 (75%) patients within 3 months after surgery: 3 repairs failed on 1st day after surgery and 12 repairs failed 3 months after surgery. From 15 failed repairs in 5 cases only capsular enhanced piriformis tendon repair failed and in 10 cases piriformis and conjoined tendons repairs failed. Pellicci et al. in 2009 carried out a study to evaluate durability of enhanced posterior soft tissue repair with the use of MRI [91]. A total of 36 patients participated in this

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study. During surgery the authors released piriformis and conjoined tendons from greater trochanter as close as possible to get single wide tendon belly and after release tendons were looped with two No. 2 Ethibond sutures [13]. Capsule incision starts from 1 o’clock descending anteriorly to greater trochanter. The authors recommend continuing of capsule release in line with femoral neck to preserve more capsule. After implantation of prosthesis, two 2.3 mm drill holes are made in the posterolateral edge of greater trochanter and only then tagging of posterior capsule with two No. 2 ethibond sutures is done. Knots for capsule and short external rotators must be tightened separately. After repair, internal rotation up to 30° must be possible without tension. Patients were mobilized on 1st day after surgery with weightbearing as tolerated. It was recommended for patients to avoid flexion more 90° and any internal rotation. MRI with 1.5-Tesla unit was performed for all 36 patients at average 3.6 days after surgery and for 30 patients at average of 107 days after surgery. Repair of capsule was considered as intact if there was contact between capsule and greater trochanter in proximal and distal parts. If contact was only in distal or proximal part, repair of capsule was considered as partially intact. If there was no contact between capsule and greater trochanter, repair was considered as failed. For assessment of short external repair integrity distance between tendon and greater trochanter was calculated. If distance was ≥25 mm, repair was considered as failure. Piriformis and quadratus internus muscles were also evaluated on MRI. Their changes were rated as no atrophy, mild, moderate and severe atrophy. Three months after surgery MRI showed that in 90% (27 of 30) cases there was at least partial contact between greater trochanter and capsule. In 43% (13 of 30) cases piriformis repair failure occurred and in 53% cases conjoined tendon repair failed. The authors also found a correlation between gap (distance between tendons and greater trochanter) and increased range of postoperative motion (internal rotation and flexion) at 6 weeks after surgery. Ranawat et al. also used MRI investigating posterior soft tissue repair through posterior approach in THR [97]. During THR surgery through posterior approach short external rotators and posterior capsule were detached in one layer and repaired through trochanteric drill holes with two stitches. Six weeks after surgery limitations in hip movement were applied. MRI was performed for 23 patients at a mean 1.8 years (range 1–3 years) after surgery. Posterior capsule was intact in 19 of 23 (82.6%) cases. Not as good results were found in tendon repair with 19 of 23 (82.6%) cases where tendon-to-bone distance was more than 25 mm.

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Table 1.7.1. Overview of posterior soft tissue repair after primary THR. Simple capsuloraphy and revision surgeries

excluded

Author Year Study

type

Innovative repair group (A)

Control group (B)

Layers Suture type Dislocation rate Radiologic

evaluation of repair Repair of short rotators (SR) Capsule repair (A) (B) 1 2 3 4 5 6 7 8 9 10 11 Hedley et al. [43] 1990 Prospec-tive

Yes Yes NA one 1-Vicryl 6-8

secure sutures to greater trochanter 2 from 259 0.77% NA Not done Khan et al. [59]

2007 Trial Yes. Piri-formis was left intact during surgery.

Yes NA one 2-Vicryl

2 transosseous sutures 0% 0 of 10 NA Radiostereometri c. In 8 of 10 cases reconstruction was intact 3 months after surgery (marker was in capsule and greater trochanter) Stähelin et al. [112] 2004 Prospec-tive

Yes Yes NA one TICRON USP

No. 5 and Vicryl USP No. 2 Transosseous sutures and tendon grasping stitch Unknown NA X.Ray. In 15 of 20 patients recon-struction failed 3 months after surgery 26

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Table 1.7.1. Continued 1 2 3 4 5 6 7 8 9 10 11 Suh et al. [114] 2004 Retro-spective

Yes Yes Posterior

capsulecto my. No repair Two Unknown non-absorbable Transosseous tendon Mattress sutures 1% 1 in 96 hips 6.4% 16 in 250 hips Not done. Weeden et al. [130] 2003 Retro-spective

Yes Yes NA one Unknown

non-absorbable Soft tissue/ bone suture 0.85% 8 from 945 patients NA Not done Stähelin et al. [113] 2002 Prospec-tive Yes (piri-formis, conjoined tendon and obturator externus – all 3 or 1 or 2 of them)

No NA one Ethibond Excel

No. 2 A modified Mason-Allen tendon suture. Transosseus fixation. Unknown. NA X-Ray. 35 of 50 (70%) repairs failed 3 months after surgery. 26 of 50 repairs failed 1st day after surgery Browne and Pagnano [18] 2012 Retro-spective

Yes Yes NA one Ethibond No. 5

Figue-of-eight suture only soft tissues 0.56% 1 patient of 178 NA Not done Tarasevicius et al. [120] 2010 Rando-mized cotrolled trial

Yes Yes No

resec-tion and no repair

one Vicryl 1 sutures 2 Grasping stitches transosseus 2% 3 of 134 in repaired group. 5% 7 of 141 in unre-paired group Not done 27

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Table 1.7.1. Continued 1 2 3 4 5 6 7 8 9 10 11 Kim et al. [62] 2008 Retro-spective Yes No Capsule excised

one No. 2 Ethibond 3.9% 11 of 282 hips in repair group 5.3% 9 of 168 hips in non-re-paired group Not done Zhang et al. [127] 2013 Retro-spective

Yes Yes NA one Twinfix Ti 5.0

suture anchor in greater trochanter with 2 transos-seus fiberwire sutures 0% 0 of 220 hips. NA Not done Pellicci et al. [91] 2009 Prospec-tive

Yes Yes NA two Number 2

Ethibond Transosseus sutures

Unknown NA MRI. 30 patients at 3 months. 90% capsule, 97% quadratus femoris, 57% piriformis and 43% conjoined tendon repairs were intact Pellicci et al. [90]. 1. Pellicci repair 1998 Control-led clini-cal trial

Yes Yes Conjoined

tendon repair two Ethibond Transosseus sutures 0% 0 in 395 patients 4% 16 in 395 pa-tients Not done 28

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Table 1.7.1. Continued 1 2 3 4 5 6 7 8 9 10 11 Pellicci et al. [90]. 2. Poss repair 1998 Control-led clini-cal trial

Yes Yes No repair two Ethibond

Transosseus sutures 0.8% 1 in 124 hips 6.2% 10 in 160 hips Not done Tsai et al. [124] 2008 Retro-spective

Yes Yes Only SR

repaired

Two Capsule repaired with 1-0 Dexon 5 stitches. SR repair unknown 0% 0 from 62 7.04% 10 from 142 Not done Ji et al. [54] 2012 Rando-mized cotrolled trial

Yes Yes Lateral

approach

Two Unknown non-absorbable Transosseous Mattress sutures 0% 0 from 99 3.1% 3 from 97 Not done Ranawat et al. [97] 2011 Prospec-tive

Yes Yes NA One Unknown 2

transosseus sutures 0% 0 from 23 patients with MRI performed NA MRI after ~1.8 years. 82.6% capsule was intact, 17.4% SR were intact. Archbold et al. [5] 2006 Prospec-tive

Yes Yes NA two 5 Ethibond

transosseous sutures 0.6% 6 from 1000 THR NA Not done 29

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2. PATIENTS AND METHODS

In the first part of our study, 37 consecutive OA patients for whom posterior soft tissue repair had been performed during THR were included into the study. Surgeries were performed in 2011–2012 at the Department of Orthopedics traumatology of the Lithuanian University of Health Sciences Kauno klinikos hospital. The study was approved by the Ethical Committee of the institution (BE-2-19). We investigated the durability of the posterior soft tissue repair, exact time of repair failure and correlation between changes in leg length and offset postoperatively with suture durability.

In the second part of our study, 68 OA patients undergoing THR were included in the study. Patients were randomized in order to investigate the effect of short rotators pressure on the elastic properties of hip joint capsule and pain. All procedures were performed at the same institution. The study was approved by the Ethical Committee of the institution.

2.1. Evaluation of posterior soft tissue repair after THR 2.1.1. Inclusion criteria

1. Adult patients (at least 18 year old).

2. Patients diagnosed with hip OA and admitted for elective THR. 3. Patients with signed informed consent.

4. Patients operated with one type of implant.

2.1.2. Exclusion criteria

1. Pregnancy.

2. Patients did not agree to participate in the study.

3. Patients for whom THR was performed because of other diagnosis than hip OA.

4. Patients with oncologic disease.

2.1.3. Data registration and surgical technique

All data were registered prospectively. Every patient got his/her own number and no personal patient data were used. All the data were saved and used in computerized form.

Before surgery, radiographic severity of OA for all included patients was evaluated according to Burnett et al. [19]. Osteophytes, narrowing of the joint space, sclerosis and bone cysts were evaluated on anteroposterior radiographs and overall OA severity score was calculated. Osteophytes on

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lateral edge of acetabulum 0–3 points, osteophytes on femoral head 0– 3 points, narrowing of the joint space 0–3 points, acetabular or femoral head cysts 0–1 point (Yes – 1 point; No – 0 points), sclerosis 0–1 point (Yes – 1 point; No – 0 points). Maximum score which means most severe hip OA is 11.

During the surgery (THR), a patient was positioned in lateral decubitus position. Surgery was performed through posterior approach. Curved 10-12cm incision was performed, fascia lata was incised with scalpel, gluteus medius fibers were divided with scissors. After that a retractor was inserted for a good visualization of short rotators (Figure 2.1.3.1).

Figure 2.1.3.1. Posterior approach with short rotators exposed

Fat tissue from short rotators was removed. Then short rotators (m. piri-formis, m. gemellus superior et m. gemellus inferior, m. obturator internus et m. obturator externus) tendons were released with a scalpel from greater trochanter just at insertion point. Insertion point of released tendons is marked with electrocautery on greater trochanter. Modified Mason-Allen sutures with two non-absorbable 1-0 TI-CRON (Syneture, Tyco Healthcare, US Surgical, Mansfield, MA) sutures were applied to piriformis and conjoi-ned tendons (Figure 2.1.3.2).

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Figure 2.1.3.2. Short rotators released with 2 sutures applied to tendons

M. quadratus femoris muscle was partially released if necessary. The capsule was incised, but not excised. After that standard THR was perfor-med. All patients received the same type of implant, the same cementing technique and all surgeries were performed by one surgeon. After prosthesis had been implanted and joint reduced, the repair of short rotators was performed. Two 2 mm drill holes were made in the greater trochanter with exit point at marked place (Figure 2.1.3.3).

Figure 2.1.3.3. Performing of 2 mm drill holes in greater trochanter

Sutures applied to the short rotators were passed through drill holes, tightened and fixed with two stitches on lateral part of greater trochanter. Separate reconstruction of the capsule was not performed and short rotators were reattached exactly at the insertion point (Figure 2.1.3.4).

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Figure 2.1.3.4. Applying stitches and final view after repair

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Metal indicator wire 2–0 FSL Ethicon (Johnson and Johnson Intl.) was stitched into the short external rotators at 1 cm distance from greater trochanter which was measured with a caliper. After this procedure the surgery was completed in a standard manner.

Immediately after a patient had been returned from operating theatre to intensive care unit postoperative anteroposterior radiographs were taken and radiologic evaluation was performed. All radiographs were taken in the same standardized supine position to obtain the same position of femoral rotation. Feet were fixed in 90° of flexion and film focus at a distance of 115 cm.

The next day after surgery, mobilization of patient was started. A patient started walking with full weight bearing using a walking frame. There was no limitation in internal rotation and flexion. After the first mobilization for those patients having non-migrated metal wire indicator on first postoperative radiographs additional anteroposterior radiographs were taken to evaluate the location of metal wire indicator after walking. Using the same methodology patients were evaluated on 5th postoperative day and finally at three months follow-up.

2.1.4. Radiologic evaluation of radiographs

Postoperatively acetabular component inclination, changes in limb length and lateral offset after THR and position of metal wire indicator in respect to greater trochanter were calculated.

The measurements were calibrated by using the periosteal diameter of the femur just below the minor trochanter which had been defined using a true 28 mm femoral head diameter as a reference on the postoperative radiographs.

Acetabular inclination angle on postoperative X-rays was measured between two lines. One line was drawn between the inferior aspects of medial acetabular teardrops while second line between superolateral and inferomedial corners of acetabular implant (Figure 2.1.4.1).

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Figure 2.1.4.1. Measurement of acetabular inclination

The changes in limb length before and after THR were measured as a difference between two vertical lines. One line was drawn between the bottoms of acetabular teardrops. A second line was alower parallel line passing through the distal end of the trochanter minor on the operated side [88]. Difference in preoperative and postoperative measurement was acknowledged as a change in limb length (Figure 2.1.4.2).

Figure 2.1.4.2. Measurement of vertical distance

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The change in lateral offset was measured as distance between two vertical lines, one going through the middle of the intramedullary femoral canal and the other parallel through the bottom of the teardrop. The difference between pre and postoperative measurements was acknowledged as change in lateral offset (Figure 2.1.4.3).

Figure 2.1.4.3. Measurement of lateral offset

A metal wire indicator was inserted at the distance of 10 mm from greater trochanter perioperatively. The distance of metal wire indicator was measured intraoperatively using a caliper. For postoperative evaluation the closest distance between metal wire indicator and greater trochanter was measured and calculated on postoperative radiographs. If this distance exceeded 25 mm, repair was considered as a failure (Figure 2.1.4.4).

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Figure 2.1.4.4. On the left – metal wire indicator in place.

On the right – metal wire indicator-greater trochanter distance >25 mm The distance between the wire knot and the greater trochanter was measured on the radiographs. On the immediate postoperative radiograph (left) the metal indicator is in place, while on the first postoperative day radiograph (right) it is just behind the femoral head >2.5 cm from the reference point.

2.2. Influence of short rotators on capsular compliance and pain 2.2.1. Inclusion criteria

1. Adult patients (≥18 years).

2. Patients scheduled for THR because of hip joint OA. 3. Patients with signed informed consent.

2.2.2. Exclusion criteria

1. Pregnancy

2. Patients did not agree to participate in the study. 3. Patients with oncologic disease.

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2.2.3. Data registration

All data were registered prospectively. Every patient received a unique registration number, no personal patient data were used. All the data were saved and used in computerized form.

Severity of hip OA was assessed using Burnett et al. radiographic atlas [19] as described in Chapter 2.1.

Before surgery, all included patients were evaluated for their hip disability and osteoarthritis outcome score (HOOS) [85]. HOOS consists of 5 different patient-relevant dimensions, which include 40 items: 1) Pain (10 items); 2) Symptoms (5 items); 3) Activity limitations-daily living (17 items); 4) Sport and Recreation Function (4 items); 5) Hip Related Quality of Life (4 items). We evaluated 3 dimensions: pain, symptoms and activity limitations-daily living. There are 5 standard answer options in HOOS questionnaire. Score from 0 to 4 is available for each question. Each subsca-le has normalized score from 0 to 100, where 0 indicates the most severe possible symptoms and 100 shows no symptoms. We asked patients to consider the previous week when answering the questions.

Before surgery, the data about range of motion were collected. Flexion, extension, internal and external rotation of the affected hips were assessed.

All patients meeting inclusion criteria were randomized in two groups, depending on the method of capsular compliance measurements, using envelope method.

Surgery was performed under spinal anesthesia. Spinal anesthesia was done using a 9 cm long (3.5 inches) 27-gauge spinal needle, injecting 3–4 millilitres of 0.5% Levobupivacaine into the subarachnoid space.

Total hip replacement surgery was performed as described in Chapter 2.1.3. After incision and subcutaneous dissection, SR were visualized. Tendons of m. piriformis, m. gemellus superior, m. gemellus inferior, m. obturatos externus et m. obturator internus were dissected or left intact depending on results of randomization. Capsular compliance (elasticity) was measured for all patients using a closed non-volume consuming, sterile, monitoring set (Braun, Combidyn Monitoring Set, Sensonor 840) connected to a pressure transducer. The capsule was penetrated with a 0.8 mm needle and the needle was advanced to the middle part of the femoral neck (Figure 2.2.3.1).

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Figure 2.2.3.1. On the left – capsule compliance measurement performed

with short rotators intact. On the right – short rotators are released. After that,the needle was twisted and retracted about 1mm. This was done to secure free intra-articular position of the tip of the needle. After that, injection of saline to the joint was started. 1ml of saline was injected at a time with 3-second intervals until intracapsular pressure reached 300 mm Hg (upper limit set on the pressure transducer). The volume of injected sa-line was recorded and then capsular compliance was calculated (ml/mm Hg) (Figure 2.2.3.2).

Figure 2.2.3.2. A syringe with saline and monitor showing

pressure measurements

The study was approved by the ethical committee of our institution.

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3. STATISTICS

3.1. Evaluation of posterior soft tissue repair after THR

The measurements were compared using nonparametric Mann-Whitney U for the comparison of two numerical variables or Kruskal-Wallis test to compare multiple numerical variables for independent samples. χ² test was used to compare the proportions of tendon ruptures with respect to gender and the use of high offset stems or high profile cups. A p-value of < 0.05 was considered significant. SPSS 20.0 software (SPSS, Chicago, Ili) was used for the calculations.

3.2. The influence of short rotators on capsule compliance and pain

The primary effect variable, used for power calculation analysis, was capsular elasticity, i.e. the number of ml injected until intracapsular pressure reached 300 mmHg. With an assumption of a difference in means of 2 ml, and SD of 1.5 ml for both groups, aiming at a power of 0.90 and a risk of 0.05 for type-1 error, 24 patients were required in each group. Due to possible dropouts, we randomized 68 OA patients. The data were presented as mean and standard deviation (SD).The measurements between the groups were compared using nonparametric (Mann-Whitney U) tests. Spearman correlation was performed to assess the correlation between the elastic properties of the hip joint capsule and the HOOS pain subscale in both groups. A p value of < 0.05 was considered significant. SPSS 20.0 software was used for the calculations.

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4. RESULTS

4.1. Evaluation of posterior soft tissue repair after THR

A total of 37 patients with posterior soft tissue repair of whom 23 (62%) were females, were included into the study. The mean age was 69.73 SD 10.7, BMI 28.76 SD 4.15 and hip OA radiographic grade according to Burnett et al. was 8.46 SD 1.48. Patients age (p=0.913), BMI (p=0.643) and hip OA radiographic grade according to Burnett et al. (p=0.541) had no correlation with repair durability.

Components to be used were selected according to preoperative templating. This resulted in the use of 7 high offset Exeter stems (44 mm), 30 standard offset stems (37.5 mm), 19 high profile all polyethylene cups and 18 low profile cups. The patients with high offset stems or high profile cups had no higher rupture rate (21 hips) as compared to the patients with standard offset stems or low profile cups (13 hips) (p = 1). In males, all the posterior soft tissue repairs failed as compared to 3 durable sutures in females at 3 months follow up (p = 0.3).

The mean inclination angle of implanted acetabular cup was 47.22 degrees (SD 6.85).

Out of 37 posterior soft tissue repairs, 6 (16%) had failed when the patient arrived at the intensive care unit immediately after surgery. Additional 25 (68%) had failed on the 1st postoperative day after having been mobilized, 2 (5%) had failed on the 5th postoperative day, and 1 (3%) 3 months after the surgery. No failure of repair was observed in the remaining 3 (8%) hips (Figure 4.1.1).

Figure 4.1.1. Time and quantity of repair failures

THE INFLUENCE OF SHORT ROTATORS ON INTRAARTICULAR PRESSURE IN OSTEOARTHRITIC HIP AND RADIOLOGIC EVALUATION OF DURABILITY OF SHORT ROTATORS RECONSTRUCTION AFTER TOTAL HIP REPLACEMENT

Valdemar Loiba