The results of patellar stainless steel wire extensor mechanism reconstruction in proximal tibial tumour excision mega-prosthesis surgeries for proximal tibial sarcomas

Background Extensor mechanism function after a proximal tibial tumour excision is the major determining factor for the limb function. However, problems of extensor lag, delayed healing and poor functional outcomes exist with the previous methods of its reconstruction. We describe a novel technique of using a patellar stainless steel (SS) wire to reconstruct the extensor apparatus of the knee in non-porous coated implants and examine the functional outcome and associated complications. Methods This was a retrospective analytical interventional study. Twenty-six patients operated between 2011 and 2019 were included. Extensor lag measured at 6 months and 12 months postoperative, total range of motion at 12 months and Musculoskeletal Tumor Society (MSTS) score at the final visit were retrieved. Complications that occurred during the follow up period were noted. Patellar position was measured using comparative patellar-position-ratio. Results Mean extensor lag at 6 months was 18.5° which improved to 8.7° at 12 months. Patellar malposition and deep infection were found to be the causes of poor functional outcome. A patellar-position-ratio between 0.9 and 1.1 led to a well-functioning extensor apparatus. Four patients underwent above-knee amputations. Deep infection and amputations reduced the MSTS score. An SS wire give way after 6 months did not affect the extensor power. A medial gastrocnemius flap reduced the infection rates. Conclusion Patellar SS wiring is an effective technique for reconstructing the knee extensor apparatus following a proximal tibial tumour excision mega-prosthesis. Proper position of the SS wire prevents wire-related complications. For a well-functioning extensor apparatus, use of a gastrocnemius flap cover intra-operatively is pertinent along with lack of infection for a pain-free, stable and mobile limb.