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. The aims of this retrospective review are to evaluate if there is a time delay to achieve stable compressive osseointegration fixation using the Compress device, and to determine if anatomic location affected any time delay. 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 and we report on 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. Cox and extended cox models were used to examine the relationship between location and time with hazard of failure. Twenty-seven failures (including 6 aseptic failures) occurred among the 116 implants. No aseptic failures were observed prior to 2 months in any group, with the first aseptic failure occurring at 81 days. Cox proportional hazards modeling demonstrated differences in hazard ratio (HR) by location (p=0.049). The extended cox model demonstrated an increased hazard for the proximal tibia group relative to the proximal femur group (HR=4.42, p=0.052) for overall failure, along with a time dependent interaction (p =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 stability of compressive osseointegration fixation and its ability to withstand physiologic loads, i.e. immediate weight-bearing, prior to biologic osseointegration.