Algorithm

We recommend an algorithmic approach to femoral revision. If the patient is a candidate for a cemented femoral revision, three options may be considered, depending on integrity of the cement mantle and host bone stock. The simplest option is the cement-in-cement technique using a polished, collarless, and tapered cemented stem. Cemented femoral revision is an option only for selected patients. Impaction grafting may be considered using specific allograft techniques and instrumentation.

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Introduction

Cemented femoral revisions have been performed since the first total hip arthroplasty (THA) revision procedures, and they were initially the revision standard for femoral revision surgery. Initial poor results in the 1980s and 1990s prompted an interest in cementless revisions with longer, distal-fixation implants. The long-term data indicate that cemented revisions using modern techniques have excellent long-term survival in selected patients. Cemented revision will continue to play a role in two-stage revision procedures for infected THAs.

As the number of THAs increases, the demand for revision hip surgery will grow. Infection is the third leading cause for revision THA, which typically is a two-stage procedure using antibiotic-loaded cement. Revision surgery presents challenges due to scarring, bone loss, and the difficulty of removing well-fixed implants and cement. Although results of cementless femoral revisions are encouraging, these techniques extend the zone of fixation distally and can cause further proximal bone loss through unloading, distal femur fractures, and thigh pain, making future revision procedures even more difficult. The added risk of intraoperative periprosthetic fracture when impacting cementless stems is reduced with cementing.

Initial stability after surgery is reassuring in a population for whom early ambulation after a two-stage procedure equals lasting clinical results. A cemented revision has the added benefit of local delivery of antibiotics in patients when low-grade infection cannot be ruled out. However, it is not recommended as first-line therapy for an infected THA. Cement creates a seal that prevents the ingress of wear debris or joint fluid under pressure, decreasing the risk of osteolysis in already compromised bone.

Although North American practice has trended toward the use of cementless fixation for primary and revision procedures, cemented THAs remain popular throughout Europe. Several national registry databases have supported the use of cemented femoral implants in primary and revision surgery. Improvements in technique and a focus on proper patient and implant selection have increased the longevity of revisions.

Simpler methods of cemented revision have evolved in response to the challenges of removing a well-fixed cement mantle. The cement-in-cement technique was first described by Eftekhar in 1978, and it has become the most commonly used method in cemented femoral revision. This simple procedure decreases operating times, reduces complications, and does not sacrifice bone. The early results described in the literature led to significantly improved medium- and long-term outcomes as surgeons began selecting appropriate patients with no cement mantle loosening and applying strict surgical technique, including the use of a dual-tapered, collarless, polished stem.

Impaction allografting with a cemented revision stem can restore bone stock, providing initial stability and more options for future revision procedures. With an appropriately selected graft, specialized equipment, and surgical experience, this technique can provide superior long-term results with few complications. In the past, proximal femoral replacement tumor prostheses were used, despite their inherent cost and decreased functionality. Impaction allografting is the only technique that replaces lost bone stock through the creation of a neocortex, particularly in the metaphyseal region. Although allograft struts provide mechanical support, impaction allografting contributes to the existing architecture of the bone. After careful impaction, a femoral implant is cemented into the graft neocortex, achieving good implant stability.

The first cases of allograft impaction were performed in 1987 in Exeter, United Kingdom. This technique is indicated in patients with extensive metaphyseal bone loss (but with an intact femoral canal without cortical defects) after septic causes of failure have been ruled out. Although technically demanding, impaction allografting is the sole option available to restore proximal bone loss in revision surgery. This is beneficial to mechanical stability, allows more options for future revisions, and may decrease periprosthetic fracture risk.

Indications and Contraindications

Cemented femoral revision in THA is classically indicated for elderly, low-demand patients with minimal metaphyseal bone loss and an intact diaphysis. Patients with type C (stove-pipe) femurs and those with osteoporosis are included. Proximal bone stock should be carefully evaluated by preoperative radiographs and at the time of surgery. Radiographs may show significant metaphyseal and diaphyseal bone loss, which is compounded with every subsequent revision. We have found that successful cemented femoral revision relies on intact metaphyseal bone stock and distal bone for bypass fixation.

Indications for using the cement-in-cement technique include aseptic loosening at the cement–implant interface, component malpositioning, recurrent dislocation, leg length discrepancies, conversion from a cemented hemiarthroplasty to a THA, acetabular revision requiring femoral component removal for enhanced exposure, and prosthesis fracture with an intact cement mantle. Occasionally, femoral revision is performed for exposure for acetabular reasons alone, including loosening, malposition, dislocation, liner wear, osteolysis, and fracture. Some surgeons have advocated its use in the treatment of periprosthetic femoral fractures.

Impaction allografting is useful in cases of metaphyseal bone loss. Infection must be meticulously ruled out before implanting massive amounts of allograft. This is accomplished by assessing the patient’s medical history, physical examination findings, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, preoperative hip aspirate results, intraoperative cell count, and intraoperative frozen tissue sections.

Equipment

A large arsenal of equipment is paramount to the success of a cemented femoral revision. Cement removal from the femoral canal during revision surgery is a significant challenge. It is time consuming and can be fraught with complications. Often, bone is removed in conjunction with well-fixed cement. Specialized equipment, including chisels, cement taps, cement drills (e.g., Depuy Moreland cemented revision instruments), long suction tips, mirrors, burs (e.g., Medtronic Midas Rex), fiberoptic lighting or surgeon headlight, and ultrasound devices (e.g., Biomet Ultra-Drive, Ultrasonic Oscar), are frequently necessary. Fluoroscopy can be used intraoperatively to confirm cement removal and rule out intraoperative fractures.

Cement must be prepared and inserted, ideally using third-generation techniques, including canal preparation and drying, cement restrictors (occasionally two), vacuum or centrifuge mixing, antibiotic-loaded cement, and pressurization. Longer stems than those used in the index procedure (extending 2 to 3 diameters distally) may provide improved results. Polished, double-tapered, collarless stem designs may be the ideal implant for cemented femoral revision. The forces through the cement mantle and bone are evenly distributed, making this stem design suited for osteoporotic bone. For moderate metaphyseal bone loss, calcar-replacing cemented components can produce good results. However, calcar-replacing implants are not designed to replace the calcar bone; they intsead allow more distal seating of a collared, cemented implant on compromised distal calcar bone with neck buildup that can reduce the need for a skirted femoral head.

In impaction allografting, the preferred allograft source is fresh-frozen femoral heads, prepared as a corticocancellous graft milled to a length of 2 to 5 mm. All soft tissue and cartilage must be meticulously removed from the allograft. The mechanical and biologic properties of freeze-dried and irradiated bone are questionable for this application, and fresh-frozen graft is preferred. Patients should be warned about the small theoretical risk of viral or bacterial spread through screened tissue donation. There is controversy about washing the graft, because the process removes inhibiting immunogenic factors at the cost of depleting stimulating growth factors. Specialized tamps of graduated sizes are available to impact and appropriately shape the bone aggregate. In cases of massive bone loss, structural mesh cages, cerclage wires, or allograft onlay struts can provide additional support to the femur, and they are often required when using this technique.