Removal of a well-fixed stem in revision THA requires substantial resources
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Although modern femoral components have generally exhibited excellent survivorship regardless of cementless or cemented fixation, indications remain for removal of a well-fixed femoral hip stem.
The primary indications for total hip arthroplasty stem removal are infection and malposition. Stem removal for infection as part of a single-stage or two-stage revision remains the dominant indication and continues to prove challenging as the surrounding soft tissue envelope is usually greatly affected with edema and obscured soft tissue planes. In terms of malposition, abnormality of stem version and length comprise the main indications for well-fixed stem removal. Versional problems are seen in female patients with underlying hip dysplasia. Length issues occur in cases of proximal stem placement resulting in limb discrepancy and in stem subsidence associated with subsequent bone ingrowth. Regardless of the indication, removal of a well-fixed femoral stem requires a methodical approach, substantial tools and resources, and a patient surgical team.
Proximal femoral exposure
Principles of stem removal include adequate surgical exposure, efficient use of surgical tools for stem removal and bone preservation. Whether an anterior-based or posterior approach is used, proximal femoral exposure is acheived by aggressive tissue removal so the bone-implant interface is well visualized. Often, femoral neck bone removal above the lesser trochanter with a saw or osteotome expedites visualization of this interface. Clearing bone and soft tissue from the lateral greater trochanter helps prevent isolated trochanter fracture during stem extraction. In terms of instrumentation, the mainstay is high-speed pencil-tip burrs used 360° around the implant. Additionally, stacked K-wires, flexible osteotomes and Steinmann pins can be helpful.
A key need is for a universal stem extraction system with screw-in adapters and trunion adapters, such as provided the Xtract-All Universal Hip Stem Extraction System (Shukla). Cement removal hand tools and, occasionally, more specialized systems that use ultrasonic technology can expedite cement removal.
Extended trochanteric osteotomy
The extended trochanteric osteotomy (ETO), first developed and described by Wayne G. Paprosky, MD, FACS, and colleagues has become a powerful technique to expedite stem removal and preserve proximal femoral bone. ETO can be accomplished with either a posterior approach or an anterior-based approach. Perhaps most commonly performed with a posterior approach, the goal of the ETO is to osteotomize the greater trochanter and lateral femoral cortex as one unit to gain direct access to the femoral stem- endosteal bone interface. Disruption of this interface is then accomplished under direct vision with hand tools or high-speed pencil-tipped burrs.
A key concept is to vary the length of the ETO fragment to balance the dual goals of stem-bone interface disruption and femoral isthmus or bone preservation for subsequent revision stem fixation. Preoperative templating can facilitate determination of appropriate ETO length; the typically optimal distal extent of the osteotomy is about 2 cm proximal to the existing stem. The posterolateral osteotomy can be accomplished with an oscillating saw or pencil-tip burr followed by osteotome (Figure 1). The transverse distal osteotomy is best performed with a pencil-tipped burr and is ideally curvilinear to avoid stress risers. The anterior cortex is typically perforated with small holes such that a controlled fracture occurs as the lateral fragment is sequentially mobilized. The use of stacked or sequentially placed broad osteotomes to slowly and methodically mobilize the ETO fragment is a key concept (Figure 2). Fracture of the fragment can occur at the trochanteric ridge where the bone junction between the greater trochanter and the lateral cortex is thin. This complication can make subsequent ETO fragment removal more difficult. Preservation of the vastus lateralis muscle attachments to the ETO is important and this likely facilitates osteotomy union. The osteotomy can be closed with a number of different techniques, such as Luque wires, cables or via direct fixation to the implant (Figure 3).
Source: Christopher L. Peters, MD, FAAOS
Stage-one spacers
The success and utility of the ETO has recently been documented by Michael-Alexander Malahias, MD, and colleagues in a systematic review of 19 studies that comprised nearly 1,500 ETOs. Researchers demonstrated a 93% union rate, revision stem subsidence greater than 5 mm in 7.1% and the highest complication rate among patients undergoing revision for periprosthetic fracture that required ETO. Our experience matches these results. We continue to liberally use the ETO technique in our revision THA population.
One caveat to the use of ETO associated with stage-one antibiotic spacers that have inferior mechanical properties is that spacer fracture or failure can be an issue. Currently, our preferred technique for use of stage-one spacers associated with use of an ETO is to bypass the ETO with an actual long femoral stem that is designed for cement fixation rather than use a prefabricated or intraoperatively manufactured Prostalac component (DePuy Synthes).
- References:
- Malahias MA, et al. J Arthroplasty. 2020;doi:10.1016/j.arth.2020.07.034.
- Miner TM, et al. J Arthroplasty. 2001;doi:10.1054/arth.2001.29385.PMID: 11742474.
- Pelt CE, et al. Arthroplasty Today. 2018;doi:10.1016/j.artd.2018.10.004.
- Pelt CE, et al. J Arthroplasty. 2014;doi:10.1016/j.arth.2014.04.042.
- For more information:
- Christopher L. Peters, MD, FAAOS, can be reached at department of orthopedic surgery, University of Utah, 590 Wakara Way, Salt Lake City, Utah 84108; email: chris.peters@hsc.utah.edu.
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