Is there a time delay to achieve stable compressive osseointegration fixation?

Abstract

Compressive osseointegration fixation using the Compress® is an alternative to traditional intramedullary fixation for endoprosthetic reconstruction. This study aims to evaluate if there is a time delay to achieve stable compressive osseointegration fixation.What is your aim?Current manufacturer recommendations call for 6 weeks of limited weight bearing and limited published research suggests increased early aseptic failure. Between 2006 and 2014, surgeons at one center treated 116 patients with 137 Compress® implants for lower extremity oncologic reconstruction, revision arthroplasty, and fracture nonunion or malunion. Patients were prescribed limited weight bearing for 6 weeks as per manufacturer recommendations and we report on outcome after 116 implants were available for review with a minimum of 2-year follow up (mean 4 years; range 2-9 years). Kaplan-Meier survival plots with 95% Hall-Wellner bands were produced;, survivorship free from overall and aseptic failure at 2 months, 6 months, 1 year and 2 year time points was calculated along with 95% confidence intervals. The relationship with time was further examined via extended Cox pProportion hHazard models. Twenty-seven failures (including 6 aseptic failures) occurred among the 116 implants. Survivorship free from overall failure at 2 months was 92% (95% CI, 84%-100%) for proximal femur reconstructions, 98% (95% CI, 95%-100%) for distal femur reconstructions, and 100% for proximal tibia reconstructions. No aseptic failures were observed prior to 2 months in any group, with the first aseptic failure occurring at 81 days. Extended Cox pProportional hazards modeling demonstrated differences in hazard ratio (HR) by location (p=0.049) with an increased hazard for the proximal tibia group relative to the distal tibia group (HR=4.42, p=0.052) for overall failure but not aseptic mechanical failure. Only the overall failure showed a time dependent interaction (p value=0.008), reflecting that the increased hazard for the proximal tibia group occurred at 4-6 months, with no failures after this point. We were unable to identify a clear temporality for aseptic failure and compressive osseointegration fixation in our patient series and . The 6-week post-operative time point showed no relationship with increased risk of failure. More research is necessary to understand the early biomechanical stability of compressive osseointegration fixation and its ability to withstand physiologic loads, i.e. immediate weight-bearing, prior to biologic osseointegration.