Revision is Not Difficult!
Thorsten Gehrke
Summary
Aseptic and septic prosthesis exchange is a challenge for every surgeon. Intra- and postoperative complications are frequent and may have serious negative effects on the outcome of the operation. Suitable instruments and surgi- cal techniques can, however, considerably lower the risk of complication. With the techniques described in this chapter and personal experience, readers will find that prosthesis exchange need not necessarily be a difficult procedure. Special emphasis is given to revisional surgery of cemented implants.
Preparation
During preparation for prosthesis exchange the possibility of septic loosening or periprosthetic infection must first of all be excluded as the cause of the patient’s problem.
Diagnostics
Laboratory: CRP!, ESR, (leukocyte count).
> Note: CRP and ESR always rise postoperatively. CRP should return to normal after 2 to 3 weeks, while ESR may remain elevated for up to one year. Therefore, CRP monitoring is of decisive importance. The leukocyte count is of no or only small importance as this usually remains within the normal range.
Radiology: Plain X-rays in standardised planes, to scale if necessary.
Scintigraphy: Expensive, but does not yield very much useful information.
CT: Artifacts, used only for design of custom-made im- plants for large bone defects.
MRI: Artifacts, expensive, does not yield very much useful information. More suitable for assessment of soft tissues.
Arthrocentesis (Joint Aspiration)
Pathogen identification: Arthrocentesis or aspiration of joint fluid is the method of choice for obtaining a rep- resentative sample of fluid for successful detection and identification of pathogens.
The most suitable transport medium is the aspirated fluid itself. Swabs should not be used at all, culture tubes only in emergencies
> Note:
▬ Systemic antibiotic therapy must be discontinued 10–14 days prior to arthrocentesis.
▬ No local anaesthesia during arthrocentesis (antimi- crobial effect).
▬ No irrigation or contrast media (diluting effect).
▬ Fluid samples must be cultured in the laboratory for at least 14 days.
General Preoperative Planning Anaesthesia
▬ Clinical and anaesthesiologic assessment of operation risk,
▬ preoperative autologous blood or perioperative recov- ery and retransfusion,
▬ adequate quantity of additional donor blood,
▬ in case of long exchange operations preoperative administration of fibrinolysis inhibitors (e.g. Trasilol) is recommended. Cave: risk of anaphylactic shock!
Radiological Preparation
▬ Conventional X-rays in two or three planes in a stan- dardised position are usually adequate.
▬ In some cases, X-rays may have to be taken with a radiopaque scale which allows exact definition of the film-focus distance, especially when special implants or megaprostheses (e.g. total femur replacement) are required.
Patient Information
▬ Risk of infection – about 5–8% during exchange oper- ations,
▬ impaired wound healing requiring reoperation,
▬ damage to the sciatic and femoral nerves,
▬ severe haemorrhaging, especially in cases with acetab- ular implant protrusion into the pelvis,
▬ loss of function and stability in the muscles encom- passing the hip,
▬ leg-length discrepancy,
▬ risk of fracture, intra- and postoperatively,
▬ rate of dislocation after aseptic and septic prosthesis exchange is markedly higher and is quoted in litera- ture between 5 and 30%,
▬ increased risk of new aseptic loosening and also early loosening,
▬ range of movement may be restricted,
▬ partial weight-bearing is often necessary for up to 12 weeks.
Surgeon’s Preparation Choice of Implant
▬ Implants of different lengths and stem thicknesses must be at hand.
▬ Loss of bone substance, the possibility of intraoperative complications such as shaft fractures, perforations of the cortex, windows and destroyed pelvic bone must be taken into consideration when choosing the implant.
▬ Large defects in the pelvis can cause difficulties as here special acetabular components or rings and in some cases partial pelvis replacements may have to be implanted.
▬ If the pelvis is involved and there is a risk of injury to the iliac vessels or bladder, a vascular or abdominal surgeon or urologist should be present during surgery.
The following approaches are recommended for revision and exchange operations:
> Note:
Recommended approaches to the hip for prosthesis exchange:
▬ Posterior approach
▬ Transtrochanteric approach
▬ Anterolateral, transgluteal approach (Hardinge, Bauer)
▬ Transfemoral approach
Less suitable approaches to the hip for prosthesis ex- change:
▬ Anterolateral approach (Watson-Jones)
▬ Anterior approach
The posterior approach offers a number of important advantages, also for revision surgery. Firstly, it avoids damage to the abductors which are the most important stabilising muscles for the pelvis in the frontal plane. An- terior neurovascular structures are rarely damaged and the sciatic nerve, which may lie very close to the site, can be easily palpated and monitored. This approach provides good exposure of the superior and postero-superior ac- etabular region which is the most frequent site of deficient bone stock and allows extensive reconstructive proce- dures. The surgeon can obtain almost complete exposure of the ilium by extending the incision proximally. The particular advantage is that, even if an extended trochan- teric osteotomy is required or if an osteolytic proximal femur disintegrates, the vasto-gluteal sling remains intact, thus minimising the risk of proximal trochanter migra- tion and gluteal weakness.
A clear disadvantage is the higher risk of disloca- tion, which can be reduced by careful orientation of the acetabular cup and reconstruction of the posterior soft tissues during wound closure.
Skin and Fascial Incision
▬ Old scars in the line of the skin incision should be excised. If a prior incision does not lie in this line, the surgeon should maintain sufficient distance between it and the new incision (
⊡Fig. 18.1).
▬ Crossing the old scar at an acute angle or deviating from it should be avoided.
▬ Fistulae should be integrated into the skin incision if possible and radically excised all the way to the joint.
If fistulae lie too far anteriorly or posteriorly, they are
handled by means of a separate incision.
of all accessible lateral cement around the shoulder of the stem prior (see below).
Instruments for Removing Cemented Stems
▬ Extraction instruments (
⊡Fig. 18.2):
– system-specific extraction instruments, – punches,
– taper extraction instrument (Nieder, from Walde- mar Link,
⊡Fig. 18.2, top),
– box-type stem extractor for firmly fixed or non- modular heads (
⊡Fig. 18.2, bottom).
▬ Chisels (osteotomes) and graspers in different lengths and widths (
⊡Figs. 18.3 and 18.4):
18
⊡ Fig. 18.2. Selection of instruments for stem extraction
Biopsy
Biopsy material, preferably 5–6 samples, should be taken as a routine measure from all relevant areas of the opera- tion site for microbiological evaluation.
> Note:
Biopsy (routine):
▬ Joint capsule
▬ Entrance to femoral shaft
▬ Interior of femoral shaft
▬ Acetabular floor Biopsy (if necessary):
▬ Fistulae
▬ Abscesses
Removing Hip Implants (Cemented Stems) Removing cemented stems is generally much easier and less invasive than removing cementless stems. Polished cemented stems are considered revision friendly, but tex- tured stems, particularly those with a collar, can be dif- ficult to remove.
The key to remove any cemented stem without risking fracture or avulsion of the greater trochanter is removal
⊡ Fig. 18.1a,b. Previous incision scars must be excised. In infection (b) all sinus formations must also be included and excised
a
b
⊡ Fig. 18.3a,b. Osteotomes and chisels for cement removal in various sizes and thickness
a
b
> Note: All instruments must be long enough (up to 30 cm).
– osteotomes/cement chisels (long, flat),
– gouges (sharpened on the inside or outer edges), – Lambotte chisels,
– angled (lug) chisel, – hook-shaped chisel.
▬ Grasping instruments for cement fragment removal.
▬ Curetting instruments and taps with different diam- eters (
⊡Figs. 18.5 and 18.6):
– long curettes and sharp spoons (different lengths and sizes),
– ball headed reamers ( ∅ 8–16 mm) – reduced risk of canal perforation,
– cement taps for cement removal (technique see operative steps),
– pulsatile jet lavage.
Operative Steps Implant Removal
▬ Remove all accessible bone cement between greater trochanter and implant shoulder to allow stem extrac- tion and minimise the risk of trochanter fracture and avulsion (
⊡Fig. 18.7).
▬ Remove cement between implant collar and femoral cortex.
▬ Extract implant stem using stem-extraction instru- ments. If no collar is present, the Nieder extrac- tion device (
⊡Fig. 18.8) can be used, which is firmly screwed onto the stem neck taper with sharp pointed screws denting into the metal taper.
⊡ Fig. 18.4. A variety of special grasping instruments are required including bone nibblers, needle holder, long forceps and rongeurs
⊡ Fig. 18.5. A selection of instruments for curettage is necessary inclu- ding curettes and ball headed reamers
⊡ Fig. 18.6. Self-cutting cement extractors (taps) and long drills (not shown) for cutting a thread in the cement mantle and distal cement plug
⊡ Fig. 18.7a,b. Removal of the cement between trochanter and shoul- der of the prosthesis
a
b
Cement Removal
> Note: In aseptic revisions, there is often no need to removal all cement. Only the loose cement should be removed and often the distal cement plug can be kept and used as distal cement restrictor if a cemented revi- sion is performed. More importantly, if both clinically and radiographically the cement-bone interface is still intact, a simple re-cementation into the old cement mantle can be performed by down-sizing the new im- plant. If revising to an uncemented implant all cement must be removed!
1. Remove all accessible proximal cement using narrow straight osteotomes with symmetrically honed blade.
> Note: To remove cement from the femoral medul- lary canal, the cement must always be split and chiselled away in a radial and longitudinal fashion (
⊡Fig. 18.9) to avoid perforating or damaging the cortex (
⊡Fig. 18.10).
2. Taps are used to remove a closed cement mantle from the distal cortical bone (
⊡Fig. 18.10). In the ideal case the cement mantle fractures on-bloc below the tap tip. In this fashion, the entire cement can be removed down to the distal cement plug.
18
⊡ Fig. 18.8a,b. Stem removal of a collared stem with punch (a). Remo- val of collarless stem using the Nieder extraction device (b), where the neck taper is drilled and the device is firmly attached using pointed screws
a
b
⊡ Fig. 18.9a,b. Cement must always be split in radial and longitudinal fashion (a) to avoid damage to the cortex. In b the incorrect method
of using the osteotome between bone and cement is shown, which commonly results in a fracture of the surrounding cortex!
a b
> Note: Always use the largest tap that the cement man- tle will accommodate. The tap is »screwed« into the ce- ment mantle cavity with a few turns until the surgeon feels resistance and hears an audible grinding sound.
Taps are only practical when the cement mantle is circular and closed. If the mantle is open on one side, the tap can penetrate (via falsa) and may fracture the cancellous or cortical bone.
3. In between the stepwise cement mantle removal, it may be necessary to clean the endosteal canal surface and trim the cement edges to a similar level using ball headed reamers (
⊡Figs. 18.5 and 18.11) to facili- tate the next step of cement extraction with the taps (
⊡Fig. 18.10).
4. The distal plug, if not removed with the last tap extraction, needs to be drilled using intramedullary drill guides to ensure a central canal for the taps (
⊡Fig. 18.12). In some situations, usage of the ultra- sound cement melting device (Ultradrive, Biomet) can be helpful. However, the usage of ultrasound seems less favourable in infection due to the resulting cement smear and the risk of remnant cement smear within the endosteum.
5. After the cement has been completely removed, the wear membrane membrane lining the medullary canal is meticulously curetted.
6. During and after removal of cement, the femur must be inspected for possible perforation or fracture using a flexible probe (
⊡Fig. 18.13).
⊡ Fig. 18.11. Curettage of the medullary canal with a ball reamer to clean endosteal surface and to trim cement edges to same level before next step of cement mantle removal (see ⊡ Fig. 18.10)
⊡ Fig. 18.13. Inspection of the femur using a flexible probe for pos- sible damage
⊡ Fig. 18.10a,b. Method or removing an intact cement mantle using taps. In the ideal case the cement mantle fractures on-bloc below the tip of the extractor tap
a
b
⊡ Fig. 18.12a,b. The distal cement plug can be drilled centrally and then removed by a tap (extractor)
a
b
> Note: If there is a high risk that the cortical bone might be perforated due to extreme antecurvation of the femur or loose slivers of cement, the cement mantle should be removed through a cortical window (
⊡Fig. 18.14).
Special Situations and Tricks
Scenario 1: Cup Loosening With Well-Fixed Cemented Stem
In case of a socket revision with well-preserved femo- ral bone stock and well-fixed and intact cement–bone interface, it is sometimes useful to remove the stem to get better exposure of the acetabulum. In this situation, a polished tapered stem has the significant advantage of easy removal without destroying the cement mantle (
⊡Fig. 18.15). In this case, a simple re-cementation (ce- ment-in-cement revision) is best. In those cases after exchanging the cup, the stem can be reinserted into the old cement mantle. The Exeter group reported five years’
results of 189 patients with 100% survival by performing this method (
chapter 8.3).
Scenario 2: Removing Well-Integrated Cement or Cementless Stems
Removing well-integrated cement or cementless stems in infection can be difficult. The reason in many cases is that the infection affects only part of the bone–implant interface, while the rest of the implant is still well inte- grated into the bone. Cementless implants with coarsely structured surfaces are especially likely to cause large bone defects during removal.
Very fine flexible osteotomes are useful in this sce- nario to loosen the bone–implant interface (
⊡Fig. 18.16).
Via a cortical window the interface can be loosened using curved sawblades to cut around the implant circumfer- ence (
⊡Fig. 18.17).
18
⊡ Fig. 18.15a–c. Cup loosening with a well fixed stem after 16 years (a). Radiographically the femoral cement-bone interface is intact and apart from two minor cement cracks the cement mantle is intact (b),
allowing for simple stem cement-in-cement revision. Postoperative radiograph (c) show revised acetabulum with impaction grafting and preserved femoral cement which was not removed
a b c
⊡ Fig. 18.14a,b. If necessary, the window should be located in the anterior femur. Drill holes will prevent extension of the fenestration. The saw cuts should be directed obliquely in a converging manner to create a cortical fragment, which can later be replaced with intrinsic stability
a
b
> Note: When removing cementless stems the deci- sion to open a window should be taken at a very early stage. In many cases, a window is the most time-saving and least invasive method. Windows should be located in the anterior femur (see
⊡Fig. 18.14
).
After drilling a hole in the stem with a carbide-tipped drill bit, in most cases the stem can then be quite easily extracted using a pointed punch and a mallet.
Scenario 3: Removing Well-Cemented Cups
Removing cemented acetabular cups does not usually pres- ent any significant problems. Cups which are very loose are removed by drilling a hole in the centre of the cup with a
4.5 mm drill and extracted by retrograde application of a tap (
⊡Fig. 18.18) or using a Moreland extractor (DePuy).
A crescent-shaped osteotome with a curved shaft is used to disrupt the polyethylene-cement interface of firm- ly fixed cups. If the cup cannot be removed with chisels, it must be cut into segments using a fine, sharp chisel/osteo- tomes (e.g. Lambotte chisel) using the central drill hole as the centre for the »cake segments«. The residual cement in the acetabular floor is divided into radial segments with an osteotome or scraped out with a sharp gouge.
Errors and Risks
When loosening the cup with a chisel, great care must be taken not to damage the bone especially near the roof of the acetabulum. No levering against acetabular bone!
⊡ Fig. 18.16a,b. Using fine, flexible osteotomes the interface of well ingrown implants can be loosened
a b
⊡ Fig. 18.17a,b. The interface of well integrated implants can be loosened with curved saw blades via a cortical fenestration a b
Removing Cementless Acetabular Cups
After exposure of the cup rim, the polyethylene inlay is first levered out using a straight osteotome. Threaded or press-fit cups are loosened by circular chiselling around the using curved cup chisels while taking great care to damage the bone as little as possible. The cup can then be pulled out with a bone hook or by applying a few blows with a mallet (
⊡Fig. 18.19a) if the design has a central hole. A new and elegant method uses a cup ex- traction device (Zimmer), which utilised curved blades of varying sizes, which can be hammered around the acetabular component with the device centred within the PE inlay (
⊡Fig. 18.19b). This allows fairly atrau- matic removal of ingrown sockets with preservation of bone stock.
Practical Tip
Retrograde extraction using a retrograde chisel hooked into the central drill-hole in the acetabular floor has proved to be a very efficient procedure for preserving as much bone as possible.
Re-Implantation of the Acetabular Cup
The principles of operative technique as used in primary THA (
chapter 2.1) also apply to the cemented cup re- implantation.
A No significant loss of bone stock in the acetabulum (
⊡Fig. 18.20a):
1. ream to diameter of anterior and posterior wall with acetabular reamers,
2. for severe sclerosis use a high speed burr to expose bleeding cancellous bone,
3. drill anchoring holes with a 4.5 to 6 mm drill, 4. generous irrigation with the jet lavage,
5. implantation of a cemented socket using modern cementing techniques.
B Cavernous defect with closed protrusion or minor floor defects (
⊡Fig. 18.20b,c)
1. as A),
2. impaction grafting of washed morcelised bone graft mixed with croutons,
3. if minor floor defects are present, these are first closed with structural bone graft (
⊡Fig. 18.20c).
18
⊡ Fig. 18.18a,b. A drill hole is made (a) and a corresponding self-cut- ting tap is placed (b) in the dome of the cup, which allows removal of a loose cemented component
a
b
⊡ Fig. 18.19a,b. A hook can be useful to extract uncemented cups with a central hole (a). The new Zimmer cup explantation device utili- zes centred curved blades to loosen the interface
a
b
The choice of stem and stem length depends on preopera- tive planning, the bone defects found intraoperatively and the extent of remaining bone stock. As it is not always possible to assess the situation definitely in advance, the surgeon should ensure that a sufficient number of alter- native implants will be at hand during the operation (see above). As a general rule, a simple re-cementation should only be carried out in an intact femoral tube if residual cancellous bone is present or if marked cortical thinning and osteoporosis make successful fixation of a press-fit uncemented stem unlikely. The distal cement plug should end immediately distal to the implant tip so that it does not impede reconstruction of the femur later.
The procedure for re-cementation is according to the rules of modern cementing techniques (
chapter 2.2), but often 120 g of cement are necessary.
Principles for Stem Re-Implantation in Infection
▬ Cemented stems should be used (antibiotic loaded cement!).
▬ The stem must be anchored at least 10 cm deep in healthy bone which is able to provide support for the implant.
▬ If the femur has been resected, the implant stem should be at least as long as the section of resected bone to achieve stable anchorage.
▬ If stable anchorage of the implant is not possible, a temporary long-stem prosthesis must first be implant- ed to act as a spacer. After infection has been elimi- nated this temporary implant can be exchanged for a total femur replacement.
> Note: The aim is to achieve adequate anchorage in healthy bone which is able to provide support for the implant. The stem should extend about 10 cm beyond the femoral defect. If the femur has been resected the implant stem should be at least as long as the section of resected bone.
Take Home Messages
I I
▬
Appropriate planning is mandatory for all revi- sional hip surgery (approach, op-tactics, implant selection, expected complications).▬
Always exclude infection with CRP and (!) joint aspiration.▬
Excise previous scars (and in infection include sinus tracts in incision).▬
The posterior approach is the most suitable approach for revision.After this impaction grafting with bone chips is carried out;
4. the acetabular cup is then cemented in place, 5. all larger defects with loss of roof or floor will
require mesh or mostly acetabular cages.
⊡ Fig. 18.20a–c. In »near primary« situation with well preserved bone a simple re-cementation can be carried out using modern cementing techniques is present stock. In cavitary defects and with marked socket sclerosis impaction grafting is required (b). In cases with a central floor defect a structural graft is necessary to contain the defect prior to impaction grafting (c)
a
b
c
▼
▬
An extensive selection of specialised instruments for stem extraction and cement removal must be available (appropriate length!).▬
Polished and smooth cemented stems are more revision friendly.▬
Uncemented stems are often »unfriendly«.▬
Always remove all accessible lateral cement from the stem shoulder to prevent trochanter fracture/avulsion.
