AB - Background: Patients with failed distal femoral megaprostheses often have bone loss that limits reconstructive options and contributes to the high failure rate of revision surgery. The Compress® Compliant Pre-stress (CPS) implant can reconstruct the femur even when there is little remaining bone. It differs from traditional stemmed prostheses because it requires only 4 to 8 cm of residual bone for fixation. Given the poor long-term results of stemmed revision constructs, we sought to determine the failure rate and functional outcomes of the CPS implant in revision surgery. Questions/purposes: (1) What is the cumulative incidence of mechanical and other types of implant failure when used to revise failed distal femoral arthroplasties placed after oncologic resection? (2) What complications are characteristic of this prosthesis? (3) What function do patients achieve after receiving this prosthesis? Methods: We retrospectively reviewed 27 patients who experienced failure of a distal femoral prosthesis and were revised to a CPS implant from April 2000 to February 2013. Indications for use included a minimum 2.5 mm cortical thickness of the remaining proximal femur, no prior radiation, life expectancy > 10 years, and compliance with protected weightbearing for 3 months. The cumulative incidence of failure was calculated for both mechanical (loss of compression between the implant anchor plug and spindle) and other failure modes using a competing risk analysis. Failure was defined as removal of the CPS implant. Followup was a minimum of 2 years or until implant removal. Median followup for patients with successful revision arthroplasty was 90 months (range, 24–181 months). Functional outcomes were measured with the Musculoskeletal Tumor Society (MSTS) functional assessment score. Results: The cumulative incidence of mechanical failure was 11% (95% confidence interval [CI], 4%–33%) at both 5 and 10 years. These failures occurred early at a median of 5 months. The cumulative incidence of other failures was 18% (95% CI, 7%–45%) at 5 and 10 years, all of which were deep infection. Three patients required secondary operations for cortical insufficiency proximal to the anchor plug in bone not spanned by the CPS implant and unrelated to the prosthesis. Median MSTS score was 27 (range, 24–30). Conclusions: Revision distal femoral replacement arthroplasty after a failed megaprosthesis is often difficult as a result of a lack of adequate bone. Reconstruction with the CPS implant has an 11% failure rate at 10 years. Our results are promising and demonstrate the durable fixation provided by the CPS implant. Further studies to compare the CPS prosthesis and other reconstruction options with respect to survival and functional outcomes are warranted. Level of Evidence: Level IV, therapeutic study.
Aseptic loosening is well known following endoprosthetic replacement (EPR) using cemented intramedullary stems (CISs). The Compress® (CPS) implant uses a novel spring system, achieving immediate, high compression fixation that induces bone hypertrophy and avoids stress shielding. We compared 26 oncologic distal femoral CPS patients treated at the University of California, San Francisco (UCSF, USA) with 26 matched CIS patients from the Royal Orthopaedic Hospital, Birmingham (ROH, UK). The predominant diagnosis was osteosarcoma. Each centre had only one device-related prosthetic failure. In the short term these results show CPS to be safe and effective. We await longer follow-up to assess the ongoing potential for prosthetic failure.
COMPRESS SEGMENTAL FEMORAL REPLACEMENT …
Summary of Technologies: The Compress® Segmental Femoral Replacement System (Short Spindle andAnchor Plug) utilizes the same spring-enhanced, stress-sharing design as the predicate Compress® device togenerate stress on the host bone which helps prevent bone atrophy and promotes bone growth.