CORR Insights^®: How Often Does Spindle Failure Occur in Compressive Osseointegration Endoprostheses for Oncologic Reconstruction?

Where Are We Now?

For patients with a primary bone tumor of the lower extremity, limb-salvage surgery is the preferred approach when it is feasible to perform [4]. For patients undergoing distal-femur resections, endoprosthetic reconstructions allow immediate partial weight bearing and generally restore an acceptable level of limb function [9]. Traditional fixation approaches, including cement or press-fit intramedullary stems, depend in large measure on the amount of remaining bone into which the surgeon can anchor the device; the longer-term survivorship of these implants becomes critically dependent upon that sometimes-scarce resource. Among patients who survive for longer periods of time, aseptic loosening can result in additional disability and major surgery [6, 10].

Some patients simply do not have enough remaining host bone to allow secure fixation of the endoprosthesis. The Compress® Compliant Pre-stress implant (Biomet Inc, Warsaw, IN USA) was designed to promote osseointegration at the bone-prosthesis interface [2, 3, 8], particularly in patients with severe bone loss. In that setting, traditional cemented or cementless devices would have a high risk of failure. Compress^® secures a titanium porous-coated spindle to the bone through a spring-loaded device anchored to a short-traction bar. A recent long-term outcome study demonstrated a survivorship of 80% using this fixation technique for distal femur implants [6]. However, little information has been reported analyzing the frequency of compressive osseointegration spindle failure in distal femoral reconstructions, nor have studies focused on the characteristics of rotational failure and the risk factors for this mechanical complication.

While we have some insight into this important complication—patients with less remaining host bone seem to be at risk for it [5, 7]—a recent study that sought to attribute these failures to rotational stresses was unable to prove this contention, perhaps because of insufficient sample size [6].

Where Do We Need To Go?

The present study showed that, while failures of compressive osseointegration implant do occur, and that spindle revision is sometimes called for, these events are uncommon and the overall survival rate from spindle failure is relatively high even at long-term followup. Injuries with a twisting mechanism produce the most rotational failures. It is recommended that we include antirotation pins at the fixation during the surgical procedure in order to prevent these failures. However, results from the current study showed that when omitting antirotational pins from surgery, the rate of rotational failures did not increase. More information is needed before we can properly determine whether to use antirotation pins.

How Do We Get There?

A future controlled study to determine the effect of these antirotation pins on the frequency of rotational failure is necessary in order to speak more definitively to this important unanswered question. Biomechanical studies should evaluate different stresses in heavy loading between stemmed implants (cemented and uncemented) and osseointegration implants. Results of such studies might also be applicable to the care of patients undergoing nononcological reconstructions, including revisions of traditional total hip, knee, or upper-extremity joint replacements.