Novel custom made composite spacer for first-stage revision total hip replacement in the presence of extensive acetabular/femoral bone loss with abductor deficiency

Abstract

A two-stage revision total hip replacement (THR) remains the gold standard for treating chronic periprosthetic joint infection. The goals for the first stage are twofold: (1) remove infected tissue/implants, obtaining tissue samples for culture; (2) deliver local antibiotics and maintain hip function with a prosthesis with antibiotic-loaded acrylic cement. With extensive bone loss prefabricated spacers are not sufficient, therefore customised spacers are required. The current technique, coating cephalomedually femoral nail in cement, is complex, time consuming, functions poorly and causes wear debris from excessive friction at the femoral/acetabular articulation. We report a technique to create a custom made composite spacer using a short femoral nail, standard Exeter femoral stem (Stryker), Trident acetabular cup (Stryker) and polymethyl methacrylate (PMMA) bone cement with antibiotics. This technique restores hip biomechanics and gives a stable articulation, even in the presence of abductor deficiency, due to dual mobility bearings.

Background

In the UK, the rate of prosthetic joint infection (PJI) after revision total hip replacement (THR) can be up to 17%,¹ depending on indication for revision. A two-stage revision THR remains the gold standard for treating chronic PJI. Eradication rates range between 83%–98%.² The goals for the first stage are twofold: (1) remove infected tissue/implants, obtaining tissue samples for culture; (2) deliver local antibiotics and maintain hip function with a prosthesis with antibiotic-loaded acrylic cement.³ With extensive bone loss, prefabricated spacers are not sufficient; therefore, customised spacers are required. A technique for doing this is to coat a cephalomedullary nail in cement and shape a femoral head with cement around the lag screw, then to shape an acetabular cup to match the head, again with cement. This technique is complex, time consuming and does not achieve the goal of maintaining hip function as hip biomechanics are not restored correctly. The two cement surfaces are not designed to be bearing surfaces and therefore do not articulate smoothly, causing friction with movement, increasing the risk of spacer displacement and generation of third body wear particles.

We therefore report a novel custom made composite spacer that can be used in the presence of extensive femoral and acetabular bone loss, but that maintains hip function by providing two primary bearing surfaces for articulation. This technique can also be used in the presence of abductor deficiency as the articulation is stable due to the use of dual mobility bearings.

Case presentation

This case is of a 71-year-old woman with type 2 diabetes who underwent bilateral THR in the 1990s. The right hip was revised due to infection 12 years ago. The patient presented to our unit with a 14-month history of right thigh swelling, 4 months of surgical site erythema, 4 weeks of abscess formation and C reactive protein of 40. The preoperative X-rays can be seen in figures 1 and 2. Staphylococcus epidermidis was grown in multiple preoperative extended MC+S joint aspiration samples.

Figure 1.

Preoperative anteroposterior (AP) X-ray.

Figure 2.

Preoperative LAT (lateral) X-ray.

A two-stage revision procedure was planned. The first stage intraoperative findings included: two sinuses over the greater trochanter, osteomyelitis and osteolysis of the proximal of femur, the abductor complex was deficient but otherwise soft-tissue infection was minimal. A full debridement was performed including excision of 230 mm of the proximal femur. The acetabular component was loose and following removal, a Paprosky IIa defect was noted with loss of posterior and anterior wall also.

A custom acetabular spacer was created by using a Stryker Trident cluster hole acetabular shell with an MDM liner. The construct was cemented in place with a double mix of Refobacin R bone cement (Biomet) plus gentamicin with 2 g vancomycin added.

A custom femoral composite spacer was created using a standard Exeter femoral stem (Stryker) impacted into a 260 mm short Gamma 3 femoral nail (Stryker). Three double mixes of Refobacin R bone cement (Biomet) plus gentamicin with 6 g vancomycin added was packed around the construct to reconstitute the proximal femur and increase construct strength. A dual mobility femoral head was used (28 mm V40 inner head with MDM X3 outer head that corresponds with the acetabular liner). See figures 3–5 for postoperative X-rays.

Figure 3.

Postoperative AP pelvis X-ray (first-stage revision).

Figure 4.

Postoperative AP femur X-ray (first-stage revision).

Figure 5.

Postoperative LAT femur X-ray (first-stage revision).

The patients intraoperative tissue samples grew Staphlococcus epidermis and she was treated with 6 weeks of oral ciprofloxacin and rifampicin therapy, as per sensitivities. There was good hip function postoperatively with minimal pain or swelling. The patient was allowed to mobilise weight bearing as pain allows with walking aids.

The patient returned to theatre 10 weeks later for the second-stage procedure. No further debridement was required during the second stage as all tissue appeared healthy. The acetabular and femoral spacers were removed easily. As expected, no macroscopic third-body wear particles were present due to the use of dual mobility bearing surfaces rather than a cement-on-cement bearing. Definitive acetabular components were trabecular metal acetabular revision shell (Zimmer Biomet) inserted with screws covered in bone wax and an Advantage (Zimmer Biomet) cemented dual mobility cup. Definitive femoral components were: the Stanmore METS system proximal femoral replacement with Agluna silver coating (Stryker). The acetabular and femoral implants were cemented using Heraeus Copal Revision cement (gentamicin, clindamycin and vancomycin added). Stimulan beads, containing vancomycin and gentamicin, were inserted to increase local antibiotic delivery. See figures 6–9 for postoperative X-rays.

Figure 6.

Postoperative AP pelvis X-ray (second-stage revision).

Figure 7.

Postoperative AP femur X-ray (second-stage revision).

Figure 8.

Postoperative LAT hip X-ray (second-stage revision).

Figure 9.

Postoperative LAT femur X-ray (second-stage revision).

Intraoperative tissue samples, from the second-stage revision, grew Staphlococcus capitis from one sample thought to be a contaminant. Antibiotic therapy was stopped after definitive culture results following discussion with a microbiologist.

Outcome and follow-up

The patient has been followed up to 18 months postoperatively with good hip function, pain free and normal infection markers.

Discussion

Five-year mortality of PJI, following a two-stage revision, is estimated 21%,⁴ highlighting the importance of getting it right first time. We have reported on a novel custom made composite femoral spacer which can be used with significant femoral and acetabular bone loss. Our technique of cementing an uncemented acetabular component into the acetabular defect allows for stable fixation of an acetabular spacer even in the presence of significant bone loss. However, if additional fixation is required, screws through the acetabular component could also be used (not done in this case). Our technique of impacting an Exeter Femoral Stem (Stryker) into a short Gamma Nail (Stryker) supplemented with bone cement creates a composite construct that is strong, allows accurate restoration of hip biomechanics and provides stable fixation that again can be supplemented with screws through the nail distally if additional stability is required (not done in this case). The use of bone cement also allows customised local antibiotics as per preoperative plan. This technique can be used with complete abductor complex loss as the articulation is stable due to the use of dual mobility bearings. If however additional stability is required, this technique can also be used with constrained bearings. Due to the satisfactory restoration of hip biomechanics, and the strength of the construct, the patient was able to mobilise well with good hip function prior to second stage.

Patient’s perspective.

Very pleased with the first operation as I was almost pain free while waiting for the second procedure. I could use my hip without too much problem and was walking.

Learning points.

• We describe a novel composite cement spacer technique to use in first-stage revision total hip replacements.

• This technique is useful when there is extensive acetabular/femoral bone loss and abductor deficiency.

• The custom-made cement spacer is made from a short femoral nail, standard Exeter femoral stem, Trident acetabular cup and polymethyl methacrylate (PMMA) cement with antibiotics.

• The advantage is restoration of hip biomechanics with stable articulation and reduced friction/wear debris.