CHAPTER SYNOPSIS

Total hip arthroplasty in the presence of proximal femoral deformity is a technically demanding operation that requires extensive preoperative planning to determine the choice of implants, surgical approach, and the unique surgical techniques that may be required to obtain a well-positioned and stable stem fixation.

IMPORTANT POINTS

• 1
  

  Identify previous implants, surgical approaches, history of infection, and any retained hardware.

  
  
• 2
  

  Distinguish the anatomic site and type of deformity.

  
  
• 3
  

  Consider an osteotomy to the correct deformity.

  
  
• 4
  

  Choose implants that bypass or accommodate the deformity.

  
  
• 5
  

  Discuss the expected outcome and reasonable expectations with the patient preoperatively.

CLINICAL/SURGICAL PEARLS

• 1
  

  Preoperatively template the femur and determine choices of implants with appropriate alternate options.

  
  
• 2
  

  Consider custom implants for hypoplastic femoral canals and diaphyseal stems to bypass metaphyseal deformities.

  
  
• 3
  

  If an osteotomy is performed, use cementless fixation to avoid cement extrusion.

  
  
• 4
  

  If a corrective osteotomy is performed, perform a step cut to enhance contact area for stability and healing.

  
  
• 5
  

  Consider releasing the psoas tendon to decrease deforming forces.

  
  
• 6
  

  Expose the joint and dislocate the hip with retained hardware in situ to avoid creating a stress riser from a screw hole.

CLINICAL/SURGICAL PITFALLS

• 1
  

  Beware of sclerotic, deformed bone causing eccentric broaching and reaming and possible cortical perforation or fracture.

  
  
• 2
  

  Beware of the previously infected hip.

INTRODUCTION

Total hip arthroplasty (THA) in the presence of proximal femoral deformity is a technically demanding operation that requires extensive preoperative planning to determine the choice of implants, surgical approach, and the unique surgical techniques that may be required to obtain a well-positioned and stable stem fixation. This chapter focuses on conversion THA after previous proximal femoral osteotomy. THA after previous hip and acetabular fractures and retained hardware are covered elsewhere in this text.

Regarding THA in the setting of previous femoral osteotomy, this chapter discusses the indications and contraindications for THA, technical suggestions, choice of implants, fixation, clinical and radiographic results, and complications. Conversion THA is defined as THA performed for failure of previous hip surgeries. Many conversion THAs are associated with existing hardware and deformity. A number of variables must be considered: surgical exposure given previous incision(s), femoral canal geometry and preparation, removal of retained hardware, and soft tissue integrity and hip stability.

CLASSIFICATION SYSTEM

Berry reported on the complexity of THA in patients with proximal femoral deformity. He proposed a classification system detailed in Box 17-1 . Deformity was classified by anatomic site and subclassified by geometry and etiology. The deformity may be present in different anatomic sites: greater trochanter, femoral neck, metaphysis, and diaphysis. The geometry of the deformity can be assessed as torsional, angular, or translational and by size. Etiologies of proximal femoral deformities include developmental, metabolic, previous osteotomy, and previous fracture. D’Antonio et al recommended specific steps regarding preoperative planning as described in Box 17-2 . Modifications made to Berry’s classification system for this chapter include (1) anatomic: deformity may include femoral head, femoral neck, deformity at more than one anatomic site, and/or fusion of the femoral head to the acetabulum; (2) geometry: deformity may include segmental or cavitary defects as noted by D’Antonio et al; (3) etiology: deformity may be caused by previous infection; and (4) bone quality and biomechanical significance of the deformity should be considered as noted by D’Antonio et al.

Retained hardware may include screws, plates, pins, nails, bipolar stems, and remnants of vascularized fibular graft. Removing the hardware usually is necessary. Exposing the joint and dislocating the hip with the retained hardware in situ may avoid creating a stress riser from a screw hole. This may require specific extrication instruments, including manufacturer-specific instruments. Obtaining the operative report and determining the make and size of the hardware may be most efficacious.

INDICATIONS AND CONTRAINDICATIONS

Proximal femoral osteotomies are performed for a variety of reasons. Shinar and Harris reported on 11 conversion THAs after previous subtrochanteric osteotomies and nine conversion THAs after previous intertrochanteric osteotomies. The subtrochanteric osteotomy initially was performed for developmental dysplasia in six hips, rheumatoid arthritis in two hips, slipped capital femoral epiphysis in two hips, and polio in one hip. The intertrochanteric osteotomy initially was performed for developmental dysplasia of the hip in three hips, pistol grip deformity in three hips, and one hip each of rheumatoid arthritis, slipped capital femoral epiphysis, and Perthes disease. The osteotomy may be intertrochanteric or subtrochanteric, varus or valgus, rotational or not rotational, minimal or extensive offset. Progression of hip pain and loss of function are the primary indications for conversion to THA and proximal femoral osteotomy. Nonunion of the osteotomy is another possible indication. Contraindications include latent or active infection.

PREFERRED TREATMENT

Appropriate preoperative evaluation is conducted, including complete history and physical examination of patient (e.g., location of incision, leg lengths, range of motion), copy of prior operative report(s), identification of retained hardware and instruments needed to remove this hardware, infectious workup (complete blood count, erythrocyte sedimentation rate, C-reactive protein, positive or negative bone scan if concern for prior infection), radiographic workup (anteroposterior pelvis, anteroposterior hip, frog-lateral of hip, Judet views, computed tomography of pelvis), and templating to determine need for osteotomy for deformity or access and implant selection (e.g., custom miniature, modular, metaphyseal, or diaphyseal).

Intraoperatively, if the patient has had a prior operation, specimens of the capsule should be sent to check for signs of inflammation, including number of polymorphonuclear cells per high-powered field. Specimens of the capsule and joint fluid also should be sent for aerobic, anaerobic, and fungal cultures. Any record of previous infection with the prior surgeries should be noted. White blood cell count, erythrocyte sedimentation rate, and C-reactive protein may be helpful to identify latent infection (although normal values do not rule out an infection and intraoperative cultures should still be obtained).

A modified Hardinge approach typically is used and an extended trochanteric osteotomy performed only in exceptional cases. Cementless fixation is used for both the cup and the stem. Trabecular metal cups are preferred. Depending on the location of the deformity, either a metaphyseal M-L taper stem is chosen, or a long, modular diaphyseal fitting stem is used. Reaming and broaching are undertaken with caution with the use of high-speed burrs and sequentially larger drills to identify the intramedullary canal. Intraoperative radiographs are obtained to check final cup and stem position and the integrity of the femoral cortex.

Appropriate thromboembolic prophylaxis and perioperative antibiotics are administered. Patients are not routinely given heterotopic ossification prophylaxis. Postoperative restrictions include no active abduction and partial weight bearing for 6 weeks.

SURGICAL TECHNIQUE

Iwase et al reviewed 30 conversion THAs after failed intertrochanteric valgus osteotomy. They reported the 10- and 15-year failure rates of proximal femoral valgus osteotomy to be 38% and 66%, respectively. The mean age of the patient at the time of valgus osteotomy was 42 years (range, 30 to 63 years). The mean age of the patients at the time of conversion THA was 57 years (range, 43 to 76 years), with the mean interval between osteotomy and THA being 14 years (3 to 24 years).

Boos et al reported that the mean interval between osteotomy and THA was 10 years (range, 1 to 20 years) in 74 hips. There were 39 men and 35 women, with a mean age of 57.4 years (range, 34 to 79 years). The primary diagnoses were osteoarthritis in 39 hips, developmental dysplasia in 25 hips, and osteonecrosis in four hips. There were 71 intertrochanteric osteotomies: 33 varus (range, 5 to 30 degrees) and 12 valgus (range, 20 to 40 degrees). There were three subtrochanteric osteotomies. In 55 patients, the internal fixation hardware had been removed at a separate operation preceding the THA.

Shinar and Harris did not find any infections in their 19-patient series. Therefore they did not recommend the routine removal of osteotomy hardware before THA. They also concluded that the removal of osteotomy hardware at the time of the THA did not affect the cement mantle, but it did cause endosteal reaction that required extensive reaming to convert the canal to a larger diameter. Although Boos et al noted that pressurizing the cement may be difficult because of extravasation of cement from empty screw holes, they found no compelling evidence that early removal of the hardware changes the outcome of subsequent THA.

Surgical approach is important in the presence of previous incision(s) and deformities. The deformity may be angular, translational, or rotational. Canal narrowing may be present from endosteal new bone formation. The transtrochanteric approach is the most extensile. A trochanteric osteotomy provides the best access to the femur for reaming and broaching. Finally, torsional deformities may result in prosthetic impingement from excessive stem anteversion, resulting in instability. Boos et al reported using a transtrochanteric approach in 88% of their THAs. The advantages include eliminating the trochanter overhang at the entry point of the femoral canal and improving abductor tension. Haverkamp et al used a trochanteric osteotomy in only 30% of their cases. Reaming and broaching are complicated by the deformity and the sclerotic bone in patients with previous osteotomies. A high-speed burr occasionally is helpful. Deformity and altered bone quality may compromise stem fixation with or without cement. Stem-bone contact often is suboptimal compared with primary THAs. Shinar and Harris reported that six of 19 stems were inserted with only diaphyseal contact and without calcar contact. They also reported that eight stems were inserted in valgus and four in varus. In addition, seven patients required custom miniature stems. Custom miniature stems were necessary only in patients with previous subtrochanteric osteotomies, but were not necessary in those who had undergone an intertrochanteric osteotomy. An option to custom stems is to use modular designs that allow more versatility to optimize contact with both the metaphysis and the diaphysis.

Implant selection and surgical technique must be based on the anatomic restraints in each patient. Berry provided an excellent outline regarding deformities around the femoral neck. Varus deformities typically result in a shortened limb. Care should be taken to avoid excess lengthening leading to nerve palsy. In addition to lengthening, extended offset stems should be considered to restore femoral offset and abductor tension. Valgus deformities are problematic and may require implant designs with reduced medial metaphyseal flare to allow neutral stem alignment. Finally, torsional deformities require attention to avoid impingement from excessive stem anteversion, resulting in instability. Marega noted that a varus deformation of the femur may be accommodated by undersizing the implant or performing an osteotomy. If an undersized implant is chosen, it should have fluted stems to obtain rotational stability with three-point fixation in the diaphysis. Marega also recommended modular stems for retroversion of the femur.

Cameron recommended the use of a reduction osteotomy when the proximal femur is patulous. This involves a series of vertical cuts and cerclage wires or cables to sequentially reduce the proximal femoral diameter. If a corrective osteotomy is necessary to best place the femoral stem into the canal, several techniques have been described. The goals of any corrective osteotomy are (1) to correct all components (angular and rotational) of the malalignment at the level of most severe deformity, (2) to remove as little bone as possible, (3) to fix the osteotomy securely, and (4) to choose a long-stem implant that bypasses the osteotomy. Cabanela reported the use of a V-osteotomy in an anteroposterior direction to reduce an expansile proximal femur to optimize fit and bone contact with the stem. He noted that, especially in patients with a previous subtrochanteric osteotomy, performing a corrective osteotomy may be necessary, and consideration should be given to performing a two-stage procedure.

Papagelopoulos et al reviewed their experience with 31 THAs in 28 patients (20 primary and 11 revisions) combined with femoral osteotomy. Of the 20 primary THAs (17 patients), the most common reason was previous failed proximal femoral osteotomy in 10 cases (eight for developmental dysplasia of the hip, one for femoral fibrous dysplasia, and one for slipped capital femoral epiphysis). Other indications for corrective osteotomy included six hips with developmental dysplasia, one bilateral congenital bowing of the femur, one case of Paget disease, and one malunited subtrochanteric fracture. The authors noted that careful preoperative templating to determine the level, angle of correction, and type of osteotomy was critical. The level of the osteotomy was placed such that the femoral component could fit in both the metaphysis and the diaphysis. They recommended achieving distal fixation by selecting the femoral component that extended at least twice the diameter of the femoral shaft beyond the site of the osteotomy. The mean operative time was 5.45 hours (range, 3.5 to 8.3 hours). The most commonly used surgical approach was anterolateral (20 hips). A uniplanar wedge osteotomy was performed in 19 hips, a biplanar osteotomy in four hips, and a step-cut procedure in eight hips. In 14 hips a derotational osteotomy was necessary. In four cases of high developmental hip dislocation, a shortening osteotomy was performed. Twenty-two cementless and nine cemented stems were used. Bone grafting at the osteotomy site was performed in 29 hips (93%), of which 22 were cancellous autograft.

Papagelopoulos et al made several recommendations: (1) preservation of soft tissue attachments, (2) an extended trochanteric osteotomy to avoid devitalizing a small trochanteric fragment, (3) cementless fixation to avoid cement extrusion at the osteotomy site that may contribute to delayed union or nonunion, (4) a step cut to enhance contact area for stability and healing, (5) consideration of psoas tendon release to decrease deforming forces, (6) strut graft to minimize risk of fractures, and (7) bone clamps and/or a plate to keep the bone fragments securely reduced while reaming and broaching to avoid eccentric bone preparation. Marega recommended preparing the diaphysis with reaming before corrective osteotomy. This was believed to reduce the risk of inadvertent fracture of the fragments during reaming.