LITHUANIAN UNIVERSITY OF HEALTH SCIENCES
VETERINARY ACADEMY
Faculty of Veterinary Medicine
Sarah Sörensson
Evaluation of tibial plateau angle and other factors in cases of
canines stifle joint diseases
Blauzdikaulio plokštumos kampo ir kitų veiksnių įtaką šunų
kelio sąnario ligoms
MASTER THESIS
of Integrated Studies of Veterinary Medicine
Supervisor: DVM, assist. Kristina Ramanauskaite
THE WORK WAS DONE IN THE DEPARTMENT OF DR. L. KRIAUČELIŪNAS SMALL ANIMAL CLINIC
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TABLE OF CONTENTS
SUMMARY ... 4
SANTRAUKA ... 5
ABBREVIATIONS ... 6
INTRODUCTION ... 7
1. LITERATURE REVIEW ... 8
1.1 Anatomy of the stifle joint ... 8
1.2 Diseases of the stifle joint ... 9
1.2.1. Cranial cruciate ligament ... 9
1.2.2. Patella luxation ... 11
1.2.3. Osteoarthritis ... 11
1.3 Kinematics of the stifle joint and orthopedic examination ... 12
1.4 Radiography – an important diagnostic tool ... 14
1.5 The Tibial plateau angle ... 15
2. METHODS AND MATERIALS ... 17
2.1 General examination, orthopedic examination and gait evaluation ... 17
2.2 Imaging and TPA measurements ... 19
2.3 Statistical analysis ... 20
3. RESULTS ... 21
3.1 Descriptive statistics ... 21
3.2 Breed and gender representation of stifle joint disease ... 24
4. DISCUSSION OF RESULTS ... 28
CONCLUSIONS ... 30
RECOMMENDATIONS ... 31
ACKNOWLEDGEMENT ... 32
REFERENCES ... 33
1 ANNEX ... 36
EVALUATION OF TIBIAL PLATEAU ANGLE AND OTHER FACTORS IN
CASES OF CANINES STIFLE JOINT DISEASES
Sarah Sörensson
Master Thesis
SUMMARY
Canine stifle joint problems are amongst the most common within veterinary orthopedics. There are several different reasons a dog may need veterinary care because of hindlimb lameness. These reasons include: cranial cruciate ligament rupture, patella luxation or osteoarthritis and other conditions.
The objective of this work was to discover if there was any correlation between physiological factors and tibial plateau angle in canine stifle joint disease.
The degree of the tibial plateau angle can be an indicator of how different components of the stifle joint will act during movement and if there is a bigger risk of being exposed to disease or injury.
A study of 13 dogs was conducted where they were seeking veterinary care for hind limb lameness and diagnosed with a stifle joint disease. Physiological factors such as age, breed, weight, body condition score, which leg was affected and if the dog was castrated or not castrated was collected. In all of these dogs a mediolateral radiograph was taken, and both the stifle joint and the tarsal joint was included positioned in 90-degree angles. From these radiographs the tibial plateau angle was measured (TPA).
The results were statistical statistically insignificant between the different physiological factors and the tibial plateau angle (p>0,05). The mean age in the group of dogs was 7,46 years old and the relationship of age and TPA showed no statistical significance (p>0,05). The relationship of weight and TPA was not statistically significant (p>0,05). The breeds of dogs that had the highest frequency were the Bernese Mountain Dog and mixed breed dogs. Male dogs were most commonly represented in this group, 69 % and 31 % were females.
From these results, it was concluded that a similar study is suggested to be completed where more patients and factors are included to determine if TPA has a depending factor in stifle joint disease.
BLAUZDIKAULIO PLOKŠTUMOS KAMPO IR KITŲ VEIKSNIŲ ĮTAKĄ ŠUNŲ
KELIO SĄNARIO LIGOMS
Sarah Sörensson
Magistro baigiamasis darbas
SANTRAUKA
Kelio sąnarių ligos yra vienas dažniausiai sutinkamų susirgimų veterinarinėje ortopedijoje. Priežastys kodėl gyvūnai šlubuoja, o jų savininkai kreipiasi i veterinarijos gydytojus yra skirtingos. Tai gali būti kelio sąnario priekinio kryžminio raiščio plyšimas, kelio girneles išnirimas,
osteoartritas ir kt.
Šio darbo tikslas buvo ištirti ar skirtingi fiziologiniai veiksniai ir blauzdikaulio sąnarinio paviršiaus kampas turi įtakos kelio sąnario patologijų pasireiškimui. Blauzdikaulio sąnarinio paviršiaus kampas gali būti indikatorius parodantis kaip skirtingi kelio sąnario komponentai reaguoja judesio metu ir ar turi poveiki ligų ar traumų pasireiškimui.
Tyrimo metu buvo tiriama 13 šunų, kurių savininkai kreipėsi i veterinarijos gydytojus dėl šlubavimo galine koja ir jiems buvo diagnozuotos įvairios kelio sąnario ligos. Buvo surinkta ir susisteminta informacija apie tokius fiziologinius faktorius kaip amžius, veislė, svoris, kūno masės indeksas, kuria koja gyvūnas šlubuoja, gyvūnas kastruotas ar ne. Taip pat visiems gyvūnams buvo atliktas rentgenins mediolateralinės projekcijos kelio sąnario tyrimas, o rentgenogramose buvo išmatuotas blauzdikaulio sąnarinio paviršiaus kampas (TPA).
Atlikus statistinę analize nustatyta, kad gauti rezultatai buvo statistiškai nereikšmingi ir neįrodė ryšio tarp fiziologinių faktorių ir blauzdikaulio sąnarinio paviršiaus kampo poveikio šunų kelio sąnarių ligų. Vidutinis šunų amžius grupėje buvo 7,46 m. ir ryšys tarp amžiaus ir TPA buvo statistiškai nereikšmingas (p>0,05). Ryšys tarp svorio ir TPA buvo statistiškai nereikšmingas (p>0,05). Veislės, kurioms dažniausiai pasireiškė kelio sąnario patologijos, buvo Berno zenenhundai ir mišrūnai. Tirtoje grupėje buvo daugiau patelių (69%) nei patinų.
Šis tyrimas įrodo, kad reikia įvertinti daugiau pacientų ir daugiau fiziologiniu faktorių, taip pat reikėtų sudaryti kontrolinę grupę, norint ištirti ar TPA yra svarbus faktorius šunų kelio sąnarių ligų pasireiškime.
Raktažodžiai: Šuo, kelio sąnarys, blauzdikaulio sąnarinio paviršiaus kampas, priekinis kryžminis raištis
ABBREVIATIONS
TPA = Tibial Plateau AngleCCL = Cranial Cruciate ligament
CCLR = Cranial cruciate ligament rupture DJD = Degenerative joint disease
OA = Osteoarthritis
INTRODUCTION
There are many knee and stifle joint disorders which may arise in dogs, all of which have the ability to affect various structures of the surrounding joint. These arthropathies are divided into different categories. The main categories being inflammatory and noninflammatory which can further be divided into subcategories. Noninflammatory arthropathies include degenerative joint diseases such as osteoarthritis and traumas such as cranial cruciate ligament rupture, meniscal injury and patella luxation in the stifle joint (1).
When a stifle joint disease is first expressed, the patient tends to present acute lameness or stiff movement of the affected hind limb (2). Radiographs of the joints and other structures of the hindlimbs can aid in many ways in order to come to a clear diagnosis (3).
The biomechanics of the hindlimbs during weightbearing provides a clear indication of the direction of forces, how the bones are compressed against one another, and how the full thrust is reduced by muscles, tendons and ligaments. If a pathology test is present it will also reveal how the forces will be directed, how they will affect the joint´s movement and predict further damages that may occur. There are several factors that could influence how the femur is compressed against the caudal- and distal-sloped proximal tibial plateau. Normally, a healthy cranial cruciate ligament prohibits abnormal stifle extension and internal rotation. However, when those movements exceed norms and/or a pathological process is taking place, it will then lead to a traumatic rupture of the cranial cruciate ligament (4). Sometimes, if the tibial plateau angle (TPA) is greater than normal, it could be associated with a deformity of the caudal proximal tibia which can lead to excessive stress on the cranial cruciate ligament. If a rupture has occurred the TPA will help in planning the surgery which will stabilize the joint (5).
The objective of this work was to discover if there is any correlation between physiological factors and tibial plateau angle in cases of canine stifle joint diseases.
Tasks of the work:
1. Evaluate age influence on tibial plateau angle (TPA).
2. Evaluate if weight and body condition score have an influence on the tibial plateau angle (TPA).
3. Investigate if breed and gender (neutered or not) is more represented to have stifle joint disease.
1. LITERATURE REVIEW
1.1 Anatomy of the stifle joint
The canine stifle joint is a complex joint with several different components. It is a composite joint, which signifies that it is made up of more than two bones. It consists of the femur, tibia and patella. Also, it compromises of two different joints, between the condyles of the femur and the proximal end of the tibia which make the femorotibial joint and the femoropatellar joint between the femur and the patella. The stifle joint is a hinge joint which can be described as a cylindrical part which fits into a corresponding socket. This type of joint structure can only move in one singular plane. Between the femur and tibia there is a meniscus which permits better surface alignment, allowing for smooth movements to be possible during both flexion and extension. The meniscus is made out of fibrocartilage and is attached inside the joint by ligaments (6).
Fig. 1. The canine stifle joint (From: Anatomy of the Dog: With Aaron Horowitz and Rolf Berg,
2010)
The ligaments keep the two major long-bones together and the smaller components of the joint like the meniscus and the patella in their designated locations. The ligaments of the femorotibial joint are the medial and lateral collateral ligaments, cranial and caudal cruciate ligaments and the cranial and caudal tibial ligaments of the menisci. Attachments of the femoropatellar joint are the patellar retinacula, medial and lateral femoropatellar ligaments and the patellar ligament (7).
The patellar ligament supports the stifle joint and it is a part of the patellar tendon and connects the patella and the tibial tuberosity (8).
The stifle joint is a synovial joint which permits a lot of movement. This type of joint will consist of a joint capsule, synovial fluid and articular cartilage. The joint capsule is the largest in the body and is divided into separate layers. These layers include: the outer fibrous layer and the inner
synovial membrane. At the inner synovial membrane, the synovial fluid is produced which is a vascular connective tissue. It can form sleeves that have the ability to wrap around any structure nearby such as ligaments, muscles, tendons, nerves and/or vessels. The synovial fluid is responsible for ensuring that the joint surfaces are moist and movements operate smoothly without any
interference of rough surfaces. The capsule of the stifle joint consists of three sacs where two are located between the femoral and tibial condyles and the last positioned underneath the patella. The capsule that extends distally to the patella is a fibrous layer which consists of a large quantity of fat and makes up the infrapatellar fat body. The stifle joint also consists of three sesamoid bones which include the patella and two located caudodistal on the medial and lateral condyles of the femur. The last two vary in size as the medial one is smaller when compared to the lateral (9). The sesamoid bones are embedded in muscles or tendons. The patella is located in the quadriceps femoris muscle and is the largest of the sesamoid bones in the stifle joint. The two located in the caudal stifle joint are embedded in the heads of the gastrocnemius muscle and together they are referred to as
fabellae. The gastrocnemius muscle´s distal attachment is in the common calcaneal tendon. It is a
talocrural extensor which the superficial digital flexor is as well. The cranial tibial muscle makes the talocrural flexors. The quadriceps femoris muscle is divided into four extensor muscles and they are the rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. The stifle joint flexor muscles are the biceps femoris, semitendinosus and semimembranosus which makes up both the cranial and caudal groups of the hamstring muscles. The hamstring muscles has its origin on the ischial tuberosity, and they are large, meaning they have large force capacity (10).
1.2 Diseases of the stifle joint
1.2.1. Cranial cruciate ligamentA disease or damage of the cranial cruciate ligament is one of the most common causes of hindlimb lameness in dogs (11). The CCL can be affected by a degenerative disease or it can tear either partially or completely. This is most common in large breed dogs and in one study the median age was 5,5 years old (12). Damage to this ligament will in return cause the stifle joint to become unstable and unable to function healthily. The entire joint is considered an organ where all tissues have the responsibility of functioning in unison. If one part is abnormal, the entire joint will be negatively affected. If the cranial cruciate disease is not discovered early on, it will continue to progress which can lead to the development of osteoarthritis (13). If a dog is obese, the heavier total mass on the joint which will put more pressure on the articular cartilage which will eventually cause it to begin to wear down. It is also possible that the adipose tissue stored in the body will be
From within the intercondyloid fossa the CCL arises. It can be found on the caudomedial part of the lateral condyle of the femur. Diagonally, it extends to the cranial intercondyloid area of the tibia. The CCL is divided into a craniomedial band and a caudolateral portion and they serve different functions. The craniomedial band is stretched during proper range of motion and the caudolateral portion is stretched in extension but not tensed during flexion. The CCL is composed of bundles of collagen fibers which are grouped into fascicles. Within the interfascicular
membranes, nerves and blood vessels can be found. These fascicles provide protection from stresses and maintain joint stability during joint range of motion. The CCL prevents the cranial drawer motion and hyperextension. The etiology of cranial cruciate rupture is not entirely known but it is thought that the strength of the CCL declines with age because there is a loss of fiber bundle organisation in addition to the metaplastic changes of cellular elements. The deterioration of the ligament is occurring more often in the central core which could be related to the smaller number of vessels supplying this region. Physical properties of the ligament could be different between
varying breeds so that one breed requires less stress on the CCL to cause a rupture. Abnormal confirmation of the limb could be a cause for degenerative joint disease which over time, with excessive stressors, could cause chronic deterioration and rupture of the ligament (15).
One study investigated if a dogs signalment including breed, age, gender, weight and reproductive status had any significance in a cranial cruciate rupture. The results proved that some purebred dogs were more likely to suffer a CCLR. These breeds included: Rottweilers, Labradors, Golden Retrievers, West Highland Terriers and Yorkshire Terriers. This study also determined that females were more likely to have a cranial cruciate ligament rupture than males and also
spayed/neutered animals (16).
In an alternate study the objective was to discover if morphometric characteristics of the hind limb in Labrador Retrievers were associated with CCL deficiency. The pelvic limbs of the dogs in the study were classified as normal, cranial cruciate ligament deficient or sound
contralateral limbs. Physical examinations were performed, goniometric angle measurements for the range of motion of the joints and radiographs were taken to measure bone length and muscle width. It was concluded that in all diseased stifles joints effusion and laxity was present. Another conclusion stated that 10° of extension was lost when cranial cruciate ligament deficiency was present. On lateral radiographs the measurements depicted that the quadriceps muscle width, ratio of quadriceps muscle to tibial length and hamstring width were decreased when the stifle joint had a CCL deficiency. In turn, this concludes that there is an atrophy of this muscle in the affected leg. On the contrary, when the ratio between the gastrocnemius and quadriceps muscles were
1.2.2. Patella luxation
One of the most commonly occurring orthopedic conditions in small animal practice - medial patella luxation being the one to occur most often which can also occur as a lateral luxation. Small dog breeds are most susceptible, and it is occurring more frequently in some larger breeds such as Labrador Retrievers and Akitas. In a large amount of cases, patella luxation is congenital but
certainly does occur from trauma as well. During physical examination the patella is manipulated to see how much it will luxate and a grading system has been developed in order to describe the variation of luxation (18).
When examining the stifle joint and assessing the mobility of the patella, the patella is pushed with the examiner’s fingers medially and laterally. It is performed in different degrees of flexion. During the examination it will be assessed if the patella will luxate, in which direction and in what position the stifle joint is in when the patella luxate (19).
Patella luxation is graded from one to four depending on the degree of luxation. The clinical signs will vary depending on which degree the luxation has. A grade 1 is given when the patella is manually luxated and the stifle joint is held in full extension. When the manual pressure of the patella is released it will immediately return to its normal location in the trochlear groove. There are usually no clinical signs present. A grade 2 patella luxation usually cause some degree of lameness but it resolves with spontaneous reduction. This grade of luxation can be demonstrated during physical examination when there is internal tibial rotation combined with stifle joint flexion and it will result in a medial patellar luxation. The patellar luxation is a grade 3 when the patella is luxated continuously during movement. In these cases, severe skeletal deformities can be present which can be related with some degree of cartilage erosion. A grade 4 is the most severe form of patellar luxation. The patella is permanently luxated and manual reduction cannot put it back into its normal location. If there would be acute lameness or acute worsening of a chronic lameness then it is many times associated with concurrent cruciate ligament disease (20).
The results of an epidemiological study of patellar luxation in dogs in England depicted that genetic factors play a big role in the predisposition of patella luxation. It also proved that some small breeds had increased risk of having patellar luxation such as the Pomeranian, Chihuahua, Yorkshire Terrier and French Bulldog. 40 % of the dogs in this study with patella luxation had treated the condition medically and 13 % surgically (21).
1.2.3. Osteoarthritis
Osteoarthritis (OA) is a common cause of hindlimb lameness in dogs and is also referred to as a degenerative joint disease (DJD). It can be both primary or secondary and the latter is most
trauma could be when the cranial cruciate ligament ruptures which initiates an inflammatory cascade in the stifle joint. There are several different signs that can be associated with OA which can be both clinical and physical. Signs other than lameness include unwillingness to exercise, appearing stiff after rest, showing signs of pain, joint effusion, atrophy of adjacent muscles and altered motion (22).
In a study performed to evaluate if there was any correlation between osteoarthritis and different diagnostic methods, it was discovered that there was a correlation between joint effusion and osteophytosis in a stifle joint with osteoarthritis. The diagnostic methods used were orthopedic examination, radiology, ultrasonography and arthroscopic examination. Ultrasonography is only recommended as a complement to radiography which is the primary choice when diagnosing stifle joint disease. They also found that there were risk factors which led to OA. These included cranial cruciate ligament rupture or patella luxation. It was also most commonly occurring in female dogs who weighed over ten kilograms (23).
Osteoarthritis is a very common joint disease in small animals, and it has some specific features in a radiological image. Early on in the development of the disease it is possible to see joint effusion following by periarticular soft tissue swelling. During the progression of the disease
osteophytes will form in a predilection site of the joint. Osteophytosis occur in different rates depending on the injury or pathology. After some time sclerosis and irregularities of subchondral bone will be observed (24).
In a systemic review created to determine what management methods are used to treat canine osteoarthritis, it was found that there are six core methods. The most prominent and effective method was by pharmacological treatment with different analgesics and anti-inflammatories. The others included specially composed diet, nutraceuticals, physical therapies, surgery and weight control. These management methods will not cure the disease, but instead will help to slow down the progression and relieve some pain (25).
1.3 Kinematics of the stifle joint and orthopedic examination
Every orthopedic examination should begin with a general examination and collection of an adequate history. If a systemic approach is applied then nothing will be missed and variousproblems can be discovered. The history should include the dogs breed, age, gender, weight, if there was a trauma, what leg the owner thinks was involved, description of the lameness or gait
abnormality, how the abnormality has evolved, if there have been any previous treatments and how it varies between resting and being active. It is also important to note if there have been any other general abnormalities like fever, inappetence, lethargy or weight loss. General questions give the veterinarian clues and the ability to formulate more detailed questions as the interview with the
owner continues. Before performing a physical examination of the dog, a distant observation and gait evaluation should be performed. Distant observation includes looking at the animal’s posture, willingness to move around and weight bearing of the limbs. Gait evaluation is helpful for the physical examination because it can determine which leg is affected. It is performed in a walk and a trot. On occasion a lameness grading system is used and the most common one is numbered
between one and five where one denotes no lameness and five - a non-weight bearing lameness is present (26).
The orthopedic examination of the rear limb should begin in the standing animal with the examiner standing behind it. Firstly, the paw of the unaffected leg is examined by palpating each digit individually and all nails and nail beds to see if any swelling can be observed. Each joint is flexed and extended carefully, looking for any signs of pain. Moving up the metatarsals, palpating them to see if there is any heat or irregularities. The next joint is the crurotarsal joint, it should also be palpated and should be stressed in medial and lateral directions and also in the flexed and extended positions. Then, the examiners fingers should run along the tibia, reaching the stifle joint. Both stifles should be palpated simultaneously to see if the problem is only unilateral. The patellar tendon should be palpated, if no edges can be felt in this structure it is a sign of joint effusion. Both tibias are palpated at the proximal medial aspect, if a hard and round swelling is felt it is called a fibrous “buttress” and it occurs together with the CCL disease. The patella is palpated to determine if there is a luxation and if there is, in what direction. Palpation is performed over femur and then the hip and pelvis. Both sides are compared to determine if asymmetry is present. The next step in the orthopedic examination is performing it in a lateral recumbency. The examination will be more effective if the dog is lightly sedated. The joints of the tarsus should be stressed in the same way as before to assess if there is any excessive laxity. The stifle joint is palpated while it is put in full range of motion to see if there are any signs of pain or crepitus. If clicking or popping sounds can be heard, it could indicate a meniscal tear. Deep palpation is performed along the femur and the hip joint is examined in both flexion and extension (27).
In lateral recumbency the cranial drawer test is performed in the stifle joint with the affected leg above the other. The examiner should stand behind the tail and hind legs and with the right hand place the thumb on the lateral fabella and the index finger on the patella. The left hand is placed below the joint and the thumb and index finger is placed in an equal manner but on the caudal tibial plateau, on the tibial tuberosity. An attempt should be made to move the tibia cranially from the femur. If there is just the slightest movement and not a clear end point the test will be positive. In some cases of chronic cranial cruciate ligament disease or if a partial rupture, the test could show a false negative result. If the dog is in much pain it will usually be sedated, ensuring more accuracy of the test result (28).
The tibial compression test can also be performed to investigate the stifle joint´s instability and evaluate the cranial tibial thrust. This will mimic the position and movements when the leg is weightbearing and force the gastrocnemius muscle to tense and make a cranial tibial thrust force. When performing the tibial compression test on the left knee the examiner places the right index finger on the tibial tuberosity and pushes toward the right thumb which is located behind the lateral fabella. The tibia will move caudally under the femur which is the normal anatomic position. Still with the right hand the knee should be held in a standing position while the left hand will flex the hock. If the stifle joint has a deficient cranial cruciate ligament the force which is directed cranially will move the tibia in that direction relative to the femur. (4)
In one study the femorotibial kinematics in dogs with a natural insufficiency in the cranial cruciate ligament was investigated because of the lack of knowledge about how the stifle
kinematics changes in vivo. The investigation was carried out with three-dimensional models of the femur and tibia from computed tomography scans. Fluoroscopic images were collected from dogs walking on a treadmill. Angles were measured from the flexion and extension of the stifle,
craniocaudal translation and internal and external rotation. These were measured through several gait cycles. The result they obtained from this study was that when the CrCL is deficient the stifle will be maintained in a greater flexion through the whole gait cycle. A cranial tibial subluxation will also be present during the whole gait cycle. There will also be a greater internal tibial rotation during the stance phase (29).
1.4 Radiography – an important diagnostic tool
After some of the physical tests are completed, it is very valuable to obtain a radiographic evaluation of the stifle joint to confirm the diagnosis. The projections made are mediolateral and craniocaudal. Both limbs should be evaluated in order to compare the healthy stifle joint versus the diseased one. In a radiographic image structures will be seen in different colours of white, black and shades of grey. The bones are the most radiopaque and will be white. Soft tissues will appear in different shades of grey. Findings in the radiographic images which show sign of disease could be a compressed infrapatellar fat pad, an abnormal joint space, increased synovial fluid, mineralization of soft tissues or other structures, joint malformation, and increased or decreased subchondral bone opacity. Based on the assessment of the radiographs taken the veterinarian will decide if any further diagnostic tests are necessary (30).
The signs mentioned earlier could vary throughout the course of the disease. If a cranial
cruciate ligament rupture is present, there will be some displacement of the joint, but it can be quite minor. If the ligament has been torn for a longer period of time and there is abnormal loading on the joint cartilage it could eventually lead to the formation of osteophytes. These are formed three days
after the rupture and can be seen from two weeks’ time once they become ossified. They are usually located at the margins of the femoral trochlea. Enthesophytes will also form at the ligaments point of origin and insertion. When there is progression of osteoarthritis in dogs the stifle joint is often used as an example. The first stages of OA will be asymptomatic, and radiographs will be normal but later nonsuppurative synovitis will appear together with synovial mass. This will alter the shape of the infrapatellar fat pad and followed by focal articular cartilage degeneration. Osteophytosis is progressive in degenerative joint disease. A patellar luxation is best evaluated by taking
craniocaudal projections of the stifle joint. When the patella is luxated it is displaced from the trochlear groove, either medially or laterally (31).
Another method of diagnosing ligament and meniscal injury in the stifle joint is by computed tomographic arthrography. In one study where they examined twenty-five stifles, they saw that the CT arthrography is a useful tool to identify canine cruciate ligament pathology but was limited when assessing the menisci (32).
1.5 The Tibial plateau angle
When a dog is in motion there are forces projected in different directions on the hindlimbs. If there is a CCL deficiency, the stifle joint flexor muscles are weak. Subsequently, if there are any degenerative changes in the joint it will wear down the cranial cruciate ligament and eventually lead to a rupture. When the hindlimb is in the stance gait there is a ground force which is transmitted along the tibial axis and simultaneously there is a compression of the femur against the tibial plateau slope. The magnitude of the slope decides the movement of the femur and how much force is put on the cranial cruciate ligament. In a normal stifle joint, the cranial cruciate ligament prevents a cranial tibial translation with other elements of the joint. These proposed elements are the stifle joint flexor muscles and the medial meniscus. When cranial tibial translation occurs the flexor muscles are not able to neutralize the forces which take place during stifle joint compression. If the tibial plateau angle is reduced it will then eliminate the cranial tibial translation (33).
In a subsequent study where hindlimbs were collected from euthanised middle sized dogs and investigated if the pre-activation of the quadriceps muscle would prevent the cranial tibial
translation. The legs were adjusted and placed in a mechanical device in a natural leg position which allows the correct percentage of body weight to be distributed on the leg while obtaining measurements. Joint angles, TPA, radiograph measurements and biomechanical testing were
performed. During these experiments a conclusion was reached that stated: if the quadriceps muscle were preactivated, cranial tibial translation was prevented in the hindlimbs of dogs. From these results, the muscle was observed to have had an effect when the dog had a lower TPA. The mean tibial plateau angle in this research was ~ 23° which was measured before the biomechanical testing
in standard radiographs. The results depicted this when the TPA was > 23° during quadriceps preactivation the cranial tibial translation was higher (34).
The tibial plateau angle is measured to determine how much it deviates from the normal physiological angle where the joint is stable. The TPA is mostly used to plan the tibial plateau levelling osteotomy surgery. The surgeon uses the TPA to plan how many degrees the tibial plateau should be levelled to, so that the forces created from moving the stifle will act as in a healthy stable joint. The measurements are made from mediolateral radiographs where the leg is placed so that both the stifle and the hock joint are positioned at 90 degrees. The medial and lateral femoral condyles should be superimposed, and the medial tibial plateau should be fully visible. When the radiograph is obtained lines are drawn from different points to receive the TPA. The first line is the tibial functional axis which is drawn between the midpoint of the talocrural joint and the
intercondylar tibial tubercles. A line is drawn over the tibial plateau slope from the cranial point to the caudal point of the medial tibial condyle. The last line is placed perpendicular to the tibial functional axis. Between the perpendicular line and the tibial plateau slope the tibial plateau angle can be measured (35).
A study was performed to compare the TPA angles in small and large breed dogs and the results showed that small dogs had higher mean TPA than large breed dogs. Small breed dogs in this study had a mean TPA of 29.2° while large breed dogs - TPA of 26.1°. Their measurements also displayed that the mean TPA of male castrated dogs was higher than when the male dog was uncastrated. In small breed dogs with medial patella luxation had a lower TPA than those that had a normal patella. They also show that there are some breed variations of the TPA but that it can also vary within the breed itself (36).
2. METHODS AND MATERIALS
This research work was carried out in an animal hospital in Southern Sweden. The sampling procedure was performed from November 2019 until June 2020.
For this study the patients were selected based on the reason of various criteria. The first criteria were that the species of animal had to be dogs with apparent hindlimb lameness. Depending on the course of examination and localisation of hind limb disease it was decided if the patient could be included in the study.
When the patient filled all the criteria to be included in this work all animals’ information were collected by filling questionnaire. (1 annex). The information collected of the dog were the age, breed, weight, body condition score, gait assessment result (graded from 1-5) and which leg was affected. The sample consist of 13 dogs where all dogs had a type of disorder of the stifle joint.
2.1 General examination, orthopedic examination and gait evaluation
When first meeting the patient, a history was collected and in the meantime, I was observing the general behaviour and posture of the dog. Observations such as if the dog wanted to sit or lie down were taken into consideration. When all information was collected I performed a gaitobservation in an indoor corridor. The owner was asked to walk the dog down the corridor and then come back. Then they ran down the corridor and the dog were trotting and the same on the way back. This was performed until the affected leg had been determined.
The general examination I performed on an examination table where I started from the head and evaluated the symmetry of the head, the eyes, teeth and gingiva and the ears. I continued systematically from the head to palpate the submandibular lymph nodes and ran my hands on each side of the chest and down along each limb. I auscultated the heart and lungs, and the result was determining the suitability for sedation and anaesthesia.
The next step was the orthopedic examination where the unaffected limbs was examined first. The dogs were placed on the floor, standing and facing away from me and I assessed how the dogs weightbearing was. The whole spine was deeply palpated to check for pain. The thoracic limbs were firstly examined by checking for asymmetry by comparing the musculature on both sides. Each front limb was examined by starting distally and continued proximally, from the paw up to the scapula. Each joint and bone was palpated and evaluated for its range of motion by flexing and extending the joints (37). Both hind limbs were examined in a similar manner from the paw, tarsal bones, tarsocrural joint, the tibia, the stifle joint including the patella, the femur, the hip joint and the pelvis. The lame leg was examined last. In a lateral recumbency I performed the “Cranial drawer”-test and the cranial tibial thrust (28).
Canine hindlimb lameness Collecting signalment and History Clinical examination Orthopedic examination Gait assessment X-ray
Tibial plateau angle (TPA) measurements
• Species
• Date of birth (Age) • Breed
• Sex (Male/female, Castrated/ Uncastrated)
• Weight
• Previous medical history or joint disease
Determination of affected leg and stifle joint
Mediolateral projection à focus on the stifle joint but including the tarsal joint as well
Both joints placed in a 90-degree angle
Lines drawn to receive TPA: • Tibial functional axis
• Line over the tibial plateau slope • Perpendicular line
2.2 Imaging and TPA measurements
Mediolateral projections of both stifle joints were performed to be able to compare their radiological structure. The dogs were placed in lateral recumbency with the leg to be x-rayed down towards the table. To be able to measure the tibial plateau angle the leg had to be positioned in a certain way. Both the stifle joint and the tarsus joint had to be included in the image and both joints were placed in a 90° angle (3).
When measuring tibial plateau angle from the mediolateral radiograph, lines were drawn. Firstly, the centre of the trochlea of the talus was marked and also the centre of the intercondylar eminence of the tibial plateau. Between these two marked points a line was drawn. A second line was drawn over the tibial plateau and the third line was drawn perpendicular to the first line. On the caudal side of the stifle joint an angle was created between the tibial plateau line and the
perpendicular line. The angle is the tibial plateau angle.
The radiology software used at this small animal hospital is from Sectra which provide all different kinds of digital imaging tools.
Fig. 3. The mediolateral x-ray of the stifle joint and tarsal joint and the lines placement to measure
2.3 Statistical analysis
The statistical analysis was carried out by using IBM SPSS Statistics Base 22.0 for Windows and Microsoft Excel for Mac. The data was analysed using descriptive statistics (mean ± SD and standard error of mean), regression analysis which calculate a coefficient for each factor and significance (p-value), those values describe what influence age, weight and body condition score has on tibial plateau angle. Pearson correlation was calculated to see if there was correlation between age, weight and body condition score. The values range from -1 to 1, the closer the values are to those values, it is considered a strong, negative or positive relationship. If the value is close to or is 0, it is a very weak or no relationship. Independent Sample T-test compared TPA between gender groups (females and males) and castrated and uncastrated groups.
3. RESULTS
3.1 Descriptive statistics
Results of the physiological data about the patients are presented in Table 1. The mean age of the dogs when they presented with stifle joint disease were 7.46 ± 2.33 years old. The result shows a middle age occurrence. The weight of dogs was taken before the consultation and the mean value were 32.97 ± 16.70 kilograms. The body condition score which is graded on a scale of one to nine describes each individual and if the dogs are underweight, normal weight or overweight. The mean BCS in this group of dogs were 5.23 ± 0.725. The tibial plateau angle ranged from 24 degrees to 34 degrees and the mean values was 28.00 ± 3.06.
Table 1. Mean values of age, weight, BCS and tibial plateau angle (TPA) of the dogs in the
investigated group.
N Minimum Maximum Mean Std. Error of
Mean Std. Deviation Age of the patients 13 3 10 7.46 0.65 2.33 Weight of the Patients 13 6.00 63.00 32.97 4.63 16.70 Body Condition Score of the patients 13 4 7 5.23 0.20 0.725 Tibial Plateau angle° (TPA) 13 24 34 28.00 0.85 3.06
Presented in Table 2 is the relationship between age and tibial plateau angle. The coefficient -0.124 has a negative value which means that the tibial plateau angle would decrease when age increased. The influence of age on tibial plateau angle is not statistically significant (p>0,05). (Table 2)
The weight coefficient, -0.054, of patients describe that TPA would have a slight decrease when weight increase by one unit but since the p-value is 0.395 it shows that the influence of weight on TPA is not statistically significant either at 5 % or 10 % (p>0.05).
The body condition score coefficient from this analysis is -1.407 is also negative and will decrease when the BCS increases by one unit. The p-value is 0.308, which means that the body condition score has no influence on tibial plateau angle and is not statistically significant.
Table 2. TPA influence on age, weight and body condition score
Model Unstandardized Coefficients t Sig. (p-value) 95.0% Confidence Interval for B B Std. Error Lower Bound Upper Bound (Constant) 38.064 7.085 5.373 0.000 22.037 54.091
Age of the Patients -0.124 0.445 -0.278 0.787 -1.130 0.883 Weight of the Patients -0.054 0.061 -0.892 0.395 -0.191 0.083 Body Condition Score of
the Patients
-1.407 1.303 -1.080 0.308 -4.354 1.541
Goodness of fit of the Model, R2: 0.213
The total variation, which was 21.3 % of the tibial plateau angle (the dependent variable) is explained by the independent variables. The explained variation is relatively poor in this case. It was measured to find out if there were any statistical association between the physiological parameters and the tibial plateau angle. The Pearson correlation for the age of dogs and the tibial plateau angle variable is -0.047 which is very close to 0. This means that there is no correlation. It provides no positive or negative relationships. The statistical analysis also indicates no correlation and is not statistically significant (p>0.05).
The Pearson correlation of -0.280 describe that there is no relationship between the two variables (weight and TPA). The correlation is not statistically significant (p>0.05). (Fig.5)
Fig. 4. The correlation between age (years) and TPA
Fig. 5. The correlation between weight (kilograms) and TPA
0 5 10 15 20 25 30 35 40 0 1 2 3 4 5 6 7 8 9 10 11 T ibi al P la te au a ngl e, de gr ee s Age, years 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70 T ibi al pl at ea u a ngl e, de gr ee s Weight, kilograms
Figure 6 shows the relationship between the body condition score and the tibial plateau angle. The Pearson correlation, -0.376, of the body condition score and tibial plateau angle variables shows a weak correlation and no straight-line relationship (p>0,05).
Fig. 6. The correlation between body condition score (scale 1-9) and TPA
3.2 Breed and gender representation of stifle joint disease
In the evaluated patients with stifle joint disease, sixty nine percent of the dogs were male and thirty one percent were females. Males were more represented in this group.
An Independent Sample T-test was performed comparing females and males TPAs. There was no significant difference between the means of the female group and the male group (p>0,05).
0 5 10 15 20 25 30 35 40 0 1 2 3 4 5 6 7 8 T ibi al pl at ea u a ngl e, de gr ee s
Fig. 7. The representation of gender having stifle joint disease
The Independent Sample t-test was performed comparing if there were any difference of the tibial plateau angle between the dogs that were castrated and the dogs that were not. There were no differences in variation between the two groups and the result was non-significant (p>0,05).
Fig. 8. Representation of dogs being castrated and not castrated when diagnosed with stifle joint
disease. 31% 69%
Gender
Female Male 61% 39%Castration status
Uncastrated CastratedThe breeds represented in this group are almost all middle sized to large dogs except for two that was a Bichon Havanais and mixed breed. Those breeds with the highest frequency were Berner Sennenhund and mixed breed dogs. They both represented 15.4 % of the breeds in the group.
Fig. 9. The representation of breeds having stifle joint disease
In this group of dogs 54 % had stifle joint disease in the right leg and 46 % had it in the left leg. The independent sample t-test was performed to see if there was any variance of tibial plateau angle between the two groups of having stifle joint disease in left or right leg. It was found to be non-significant (p>0,05). 1 2 1 1 1 1 1 2 1 1 1 0 1 2 Ameri can S taffor dshir e Terr ier Berne r Senne nhund Bichon Hava nais Cane Cor so Kees hond Labr ador Retr ieve r Lands eer Mixe d Bree d Perro De A gua E spanol Pyrené erhund Sibe rian H usky N um be r of dogs
Breed
Fig. 10. The most common leg being affected by stifle joint disease in this group of dogs (n=13) 46% 54%
The hindlimb most commonly affected
Left Leg Right Leg4. DISCUSSION OF RESULTS
During this research the dogs came to the veterinarian initially because of hindlimb lameness. After examinations of the dogs and it was determined that they had a stifle joint condition, the joint was radiographed. Later the tibial plateau angle was measured from the radiographs.
In a study conducted by Reif et al. where the TPA was compared between normal and cranial cruciate deficient stifles in Labrador Retrievers the first group with CCLR had a mean age of 5.4 years whereas in this study the mean age was 7.26 years of having stifle joint disease. The Labrador Retrievers had a mean TPA of 23.5 ± 3.1 degrees and in this study the mean TPA was 28.0 ± 3.0 degrees. The mean age of the normal group was 10 years and mean TPA was 23.6 ± 3.5 degrees. They found no significant difference when comparing the TPA of the two groups (38). The same occurred in this work but here there was no comparison between a normal group and group with cranial cruciate stifles.
The relationship between age and TPA was investigated in a study by Zeltzman P. A. DVM et al. where the dogs had a ruptured cranial cruciate ligament. The relationship between the two
variables could not explain the frequency in young large breed dogs because it was not strong enough (39).
In another study by Fujita et al. they predicted correlations between osteoarthritic score from radiographs and TPA and the osteoarthritic score and body weight (40).
A study of Griffon D. J. concluded that one of the most common stifle joint diseases, CCL deficiency in dogs was multifactorial. Factors including genetics, conformation and inflammation which create an imbalance of the forces placed on the ligaments of the joint and being able to endure those loads. The imbalances will eventually lead to instability of the joint (41).
In a study by Morris E. et al. two groups of dogs were compared, one group had no cranial cruciate injuries and one had it. In the first group the mean age was 5.7 years and mean weight was 37.91 kg. The second group without any CCL injuries had a mean age of 4.83 years and weight was 35.85 kg (42). The mean weight in this current study was 32,97 kg which is close to previous performed studies. It could indicate that stifle joint disease is more common when a dog is in that weight-class.
In a study by Seo B. S. et al. they found that all studied male small breed dogs had a higher TPA than the females. Even when they were compared within specific weight classes and within specific breeds the males had a higher TPA (43). This study could not display that there was any difference in TPA between male and female dogs, it could be because of too small groups of animals.
A study by Su L. et al described in their results that the TPA in castrated males and spayed females was higher for all dogs included, than in intact males. They were 3.6° ± 1.0° and 2.7° ± 1.0°, respectively higher (36). This study could not show any difference of TPA between castrated males, spayed females and dogs that were intact.
CONCLUSIONS
1. The age did not have an influence on TPA. There was no statistically significant correlation between age and the tibial plateau angle (TPA) (p>0.05).
2. Weight had no effect on TPA. There was no correlation between the weight of the dogs and the TPA (p>0.05). Body condition score did not have any influence on the tibial plateau angle either (p>0.05).
3. Gender had no influence on the TPA. There was no statistically significant correlation between gender and TPA (p>0.05).
4. Both right (46.2%) and left (53.8%) leg was almost equally represented of having stifle joint disease. There was no significant difference of TPA between the left and the right leg (p>0.05).
RECOMMENDATIONS
In this research a larger group of patients should have been included for the results to be more significant. Two groups should have been studied, one control group with dogs with healthy stifle joints and one group with stifle joint problems. More related factors should have been measured, for example measuring the length of long bones.
ACKNOWLEDGEMENT
Firstly, I would like to express my deepest gratitude towards the animal hospital in Lund, Sweden who allowed me to see patients, collect data and make measurements from radiographs for my final thesis.
I would like to give my sincere thanks to my supervisor DVM assist. Kristina Ramanauskaite who has guided and pushed me through this tough and challenging work.
To the Veterinary academy of Lithuanian University of Health Sciences, I would like to give my thanks for giving me the knowledge and tools to carry out this work.
Finally, I would like to thank my family and friends which has given me tremendous support and encouragement during this challenging task. I am very grateful for them.
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1 ANNEX
Questionnaire of animal informationAnimal number: Age: ________________________________________________________________ Breed: _______________________________________________________________ Gender: _____________________________________________________________ Neutered or intact: ____________________________________________________ Weight: ______________________________________________________________ Body condition score: __________________________________________________ Gait analysis walk/trot (category/score 1-5): _______________________________
1 No lameness noted at a walk or trot
2 No lameness at a walk, mild lameness at a trot
3 Mild lameness at a walk, significant lameness at a trot 4 Significant lameness at a walk, non-weight bearing at a trot 5 Non-weight-bearing lameness at a walk and a trot
Limb of lameness: ______________________________________________________ Diagnosis of the stifle joint:_______________________________________________ _______________________________________________________________________
