Nelson V. Greidanus, Winston Y. Kim, and Bassam A. Masri
DEFINITION
Hip reimplantation refers to the insertion of another prosthesis after removal of the original, infected prosthesis. It may be singleor two-staged, cemented or uncemented.
ANATOMY
The posterolateral approach is the most versatile approach in hip reimplantation surgery. Extended trochanteric osteotomy (ETO) occasionally may be required.
The sciatic nerve is the major nerve most commonly at risk during the posterolateral approach to the hip. In patients with severe scarring, it may be necessary to expose the nerve as it emerges deep and inferior to the piriformis muscle and superficial to the obturator internus muscle.
In a direct lateral (ie, transgluteal) approach, function of the abductors may be compromised if sufficient care is not taken to avoid injury to the superior gluteal nerve, located 5 cm proximal to the greater trochanter.
The selection of prostheses for both femoral and acetabular reconstruction is determined by a number of factors, primarily including femoral and acetabular bone defects, quality and quantity of remaining host bone for osseointegration or cementation, status of the soft tissues and abductors, and surgeon preference.
For acetabular reconstruction, screw fixation often is necessary. The safest zone for insertion of acetabular screws is the posterior superior quadrant.11
PATHOGENESIS
Prosthetic reimplantation usually is performed following resection arthroplasty or first-stage revision arthroplasty for infection. It is essential to ensure a sterile surgical field prior to hip reimplantation surgery, as discussed later in this chapter.
Usually this requires the patient to demonstrate normal values for erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and hip aspiration for culture. Occasionally, test results may be equivocal, in which case nuclear medicine imaging is required to confirm absence of infection.
The organisms most commonly isolated in infected total hip replacements are Staphylococcus aureus, Staphylococcus epidermidis, and gram-negative bacteria, with increasing prevalence of antibiotic-resistant bacteria.
NATURAL HISTORY
Eradication of infection is key to the success of hip reimplantation surgery, regardless of the method of hip reconstruction.
Persistent or recalcitrant infection, suggested by raised CRP and ESR values and confirmed by tissue or fluid culture (aspiration or biopsy), is a contraindication to reimplantation surgery.
The options in such a scenario are to continue with antibiotics, repeat the first-stage procedure, or perform resection arthroplasty.
PATIENT HISTORY AND PHYSICAL FINDINGS
The main presenting symptom of patients with a periprosthetic infection is pain, particularly constant pain while the patient is at rest.
Delayed wound healing, persistent wound drainage, and a history of superficial wound infection after the primary procedure are highly suggestive of infection.
Risk factors for infection include history of diabetes mellitus, chronic skin lesions, the use of corticosteroids, and any type of immunocompromise.
Initial assessment should begin with a general medical examination.
The hip wound is examined for warmth, erythema, fluctuance, discharging sinuses, and the presence of any hematoma.
An erythematous, warm wound with draining sinuses indicates persistent, ongoing infection.
Defects in the underlying fascia often are palpable, and may indicate a higher risk of wound dehiscence postoperatively.
The abductors should be palpated and their function assessed.
Full neurologic examination and palpation of pulses are performed.
Preoperative weakness of leg extensors or a partial foot drop may indicate scarring around the sciatic nerve.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Infection is excluded by serial assessment of the ESR (normal <30 mm/hr) and CRP (normal <10 mg/mL).
ESR and CRP may be elevated if the patient has other inflammatory systemic diseases (eg, rheumatic disease) and therefore may not be completely reliable in such cases.
Preoperative hip aspiration, culture or biopsy, and sensitivity may be necessary if the ESR and CRP remain elevated. Antibiotics should be stopped for a minimum of 2 weeks before aspiration to avoid false-negative results.
Three samples are obtained at the time of hip aspiration, including a tissue sample if feasible. A positive result is considered to be one in which growth is obtained in two separate specimens.
Radiographs are obtained, including an anteroposterior (AP) view of the pelvis, lateral view of the hip, and Judet views, if necessary, to assess integrity of acetabular columns (FIG 1). In some cases, AP and lateral views of the full length of the femur may be necessary. Bone defects should be estimated on plain radiographs and appropriate reconstructive prostheses made available.
CT scans occasionally are helpful to ascertain the magnitude of acetabular bone defects.
Radiographs should be used together with the physical examination to estimate appropriate techniques for leg length restoration or for restoration of hip stability should hip abductors be inadequate, and to minimize risk to neurovascular structures.
FIG 1 • Preoperative radiographs. A. Pelvis. B. AP view of the femur. C. Obturator oblique view. D. Iliac oblique view.
SURGICAL MANAGEMENT
The aims of surgical treatment are to eradicate infection, minimize morbidity, and restore function.
Typically, the hip is flail, but it may contain an antibioticloaded spacer. The goal is to remove any temporary spacer and implant a permanent hip replacement prosthesis.
Preoperative Planning
It is important to anticipate the need for specialized implants and instruments before surgery.
Careful preoperative templating is essential to anticipate implant size, length, and offset (FIG 2).
The template is used to restore leg lengths, medial hip offset, and hip center of rotation.
Insufficiency of hip abductors may require constrained acetabular implants or large-diameter femoral head components.
The microbiology laboratory should be informed of the possibility that intraoperative frozen section analysis may be required in equivocal cases of persistent infection.
Alternative surgical plans are useful to have at hand in case of unexpected intraoperative findings or complications.
FIG 2 • Preoperative templating is essential to determine the diameter and length of the implant that may be needed.
Positioning
The patient is positioned in the lateral decubitus position with anterior and posterior supports (FIG 3).
The pelvis must be vertical, and it must be confirmed that the supports are stable.
Patient positioning must be performed under surgeon supervision, because errors in positioning may result in acetabular component malalignment.
Approach
The surgical approach is chosen after careful preoperative consideration of important factors, including:
Previous approach
Anatomic location and extent of bone loss
Anticipated instability
Function of the abductors
Surgeon preference and training
The main options are:
Direct lateral (transgluteal) approach
Posterolateral approach
Trochanteric osteotomy
Trochanteric slide osteotomy
ETO
FIG 3 • Patient positioned in the lateral decubitus position.
TECHNIQUES
HIP EXPOSURE AND REMOVAL OF ANTIBIOTIC SPACERS
The posterior approach can be used for surgical exposure.
The sciatic nerve is identified and is protected throughout the procedure. This is facilitated by placement of the foot on a padded stand with the hip in internal rotation during exposure.
The short external rotators and posterior capsule are identified and incised as a composite flap. These are tagged with sutures for later repair. The gluteus maximus tendon must be released in most cases due to severe scarring and the need to mobilize the femur.
Samples are obtained from within the hip joint, for bacteriology.
Intraoperative frozen sections are obtained if persistent infection is suspected.
The hip is dislocated, with internal rotation of the femur.
The femur is further mobilized by incising the anterior scar tissue that tethers it onto the acetabular bone. It may be necessary to release the anterior femoral capsule with cautery, with a femoral retractor placed anteriorly to expose the femoral canal (TECH FIG 1A).
Removal of cement, soft tissue, and bone from the shoulder of the prosthesis and greater trochanter facilitates removal of the preexisting antibiotic implant spacer, and reduces the risk of greater trochanter fracture (TECH FIG 1B).
A femoral extractor should be used to remove the femoral antibiotic spacer (TECH FIG 1C), ensuring complete removal of the antibiotic-loaded cement and implant (TECH FIG 1D).
The acetabular antibiotic spacer is removed with a Cobb elevator, ensuring no further bone loss (TECH FIG 1E).
Acetabular débridement is performed using a combination of curettes, rongeurs, and Cobb elevators to remove any residual necrotic tissue, ensuring complete exposure of the acetabulum (TECH FIG 1F).
TECH FIG 1 • A. Incising the anterior femoral capsule with electrocautery to allow exposure of the proximal femur. B. Removal of bone and soft tissue from the collar of the femoral prosthesis. C. Femoral extractor facilitates safe removal of the femoral component. D. Complete removal of the antibiotic cement–coated femoral prosthesis is confirmed. E. Safe removal of the acetabular antiobiotic spacer with a Cobb elevator. F. The acetabulum is fully exposed after complete débridement.
ACETABULAR REIMPLANTATION
The acetabulum is reamed sequentially in 2-mm increments to obtain a concentric, hemispheric surface, taking care to preserve the rim of the acetabulum (TECH FIG 2A).
Press-fit of an implant 1 to 2 mm larger than the last reamer is used.
The implant is inserted in 40 degrees of lateral opening and 15 to 20 degrees of anteversion (TECH FIG 2B).
It is ascertained that the component is uniformly in contact with the underlying host bone.
Supplementary screw fixation is required in most cases.
The appropriate trial liner is placed into the acetabulum, for later trial reduction after femoral canal preparation.
TECH FIG 2 • A. The acetabulum is reamed sequentially. B. Alignment of the acetabular component is confirmed with use of an external alignment jig.
TWO-STAGE REIMPLANTATION WITH UNCEMENTED EXTENSIVELY POROUS-COATED FEMORAL STEM
Femoral preparation may begin after a thorough débridement and after acetabular reconstruction. The length and diameter of the femoral canal are anticipated by careful preoperative templating.
Femoral débridement is performed with reverse hooks, curettes and brushes, and pulsed lavage.
The femoral canal is sequentially reamed, guided by preoperative templating, until cortical resistance is encountered over a length of at least 5 to 6 cm (TECH FIG 3A).
Trial reduction is performed, ensuring satisfactory leg lengths, soft tissue tension, range of motion, and a stable hip (TECH FIG 3B).
Under-reaming the femoral canal by 0.5 mm compared with the diameter of the actual femoral implant is confirmed by checking with a “hole gauge.”
In an extensively porous-coated femoral component, 5 to 6 cm of diaphyseal fit (so-called “scratch fit”) is required to provide axial and rotational stability.
The final implant is inserted into the femoral canal. It should be inserted to within 5 cm of its final position by hand, otherwise it should be reamed line to line to avoid inadvertent femoral fracture (TECH FIG 3C).
TECH FIG 3 • A. Femoral canal preparation with reamers. B. Trial components inserted. C. Insertion of the definitive, extensively coated femoral implant.
TWO-STAGE REIMPLANTATION WITH UNCEMENTED TAPERED FLUTED FEMORAL STEM
Femoral preparation may begin after a thorough débridement and after acetabular reconstruction.
Femoral débridement is performed with reverse hooks, curettes and brushes, and pulsatile lavage (TECH FIG 4A).
Femoral canal reaming is performed with tapered reamers, with the depth and diameter guided by preoperative templating until endosteal contact is made (TECH FIG 4B).
The aim of diaphyseal reaming is to ensure implant stability, which will resist stem subsidence.
The length of the stem, as determined by preoperative templating, should be at least 2 cortical diameters distal to any potential stress risers, eg, the tip of an ETO.
Unlike fully porous-coated cylindrical stems, underreaming the femoral canal by 0.5 mm compared with the diameter of the actual femoral implant is not recommended. Line-to-line reaming is preferred.
Proximal femoral preparation is then performed using conical reamers.
Trial reduction is performed for assessment of correct femoral stem anteversion, limb length, soft tissue tension, range of motion, and hip stability (TECH FIG 4C).
The modularity of the uncemented tapered fluted femoral stem allows adjustment of femoral anteversion (TECH FIG 4D).
Torsional and axial stability of the implanted prosthesis may be ensured by test torquing the femoral component.
TECH FIG 4 • A. Femoral canal débridement. B. Femoral canal preparation with reamers. C. Trial components inserted. D. The modular uncemented tapered fluted stem.
POSTOPERATIVE CARE
Postoperative care is individualized, depending on the complexity of the reimplantation procedure.
The quality of implant fixation, severity of preoperative bone loss, hip stability, technical factors encountered during the operation, and patient compliance influence the amount of weight bearing permitted and restrictions on hip range of movement.
If a transgluteal (direct lateral) approach was used, restriction of active abduction may be necessary.
Clear postoperative instructions and frequent communication with the multidisciplinary team are essential. Instructions include postoperative blood work, deep venous thrombosis prophylaxis, and perioperative antibiotic requirements.
OUTCOMES
An uncemented two-stage procedure may successfully eradicate infection in 92% to 93% of cases.4,5,7
Single-staged reimplantation with the use of antibioticloaded cement has a success rate of 77% to 86%.1,10
A two-reimplantation procedure with the use of antibioticcontaining bone cement in the reimplantation procedure attains a success rate of 90% to 95%.6,8
A two-staged hip reimplantation is the procedure of choice in most cases.
COMPLICATIONS
Recurrent infection after reimplantation is a devastating complication, and is associated with a poor outcome.9
Recurrent infection may be either recurrence of the initial infection, which typically is due to failure of the reimplantation procedure, or a new infection by a different organism, which often is due to multiple patient risk factors and indicates host failure.7
Hip dislocation, leg-length discrepancy, venous thromboembolism, nerve and vessel injury, fracture, and a small mortality risk are potential complications, as they are for any revision arthroplasty.
REFERENCES
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2. Callaghan JJ, Katz PR, Johnston RC. One-stage revision surgery of the infected hip: A minimum 10-year follow-up study. Clin Orthop 1999;369:139–143.
3. Elson RA. One-stage exchange in the treatment of the infected total hip arthroplasty. Semin Arthroplasty 1994;5:137–141.
4. Faddad FS, Muirhead-Allwood SK, et al. Two-stage uncemented revision hip arthroplasty for infection. J Bone Joint Surg Br 2000;82B:689–694.
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6. Garvin KL, Evans BG, Salvati EA, et al. Palacos gentamicin for the treatment of deep periprosthetic hip infections. Clin Orthop 1994;298:97–105.
7. Kraay MJ, Goldberg V, Fitzgerald SJ, et al. Cementless two-staged total hip replacement for deep periprosthetic infection. Clin Orthop Relat Res 2005;441;243–249.
8. Lieberman JR, Callaway GH, Salvati EA, et al. Treatment of the infected total hip arthroplasty with a two staged reimplantation protocol. Clin Orthop Relat Res 1994;301:205–212.
9. Pagnano MW, Trousdale RT, Hanssen AD. Outcome after reinfection following reimplantation hip arthroplasty. Clin Orthop Relat Res 1997;338:192–204.
10. Raut VV, Siney PD, Wroblewski BM. One-stage revision of total hip arthroplasty for deep infection: long term follow-up. Clin Orthop Relat Res 1995;321:202–207.
11. Wasielewski RC, Cooperstien LA, Kruger MP, et al. Acetabular anatomy and the transacetabular fixation of screws in total hip arthroplasty. J Bone Joint Surg Am 1990;72A:501–508.