Extensor function after medial gastrocnemius flap reconstruction of the proximal tibia

BACKGROUND
Reconstruction of the extensor mechanism after resection of the proximal tibia is challenging, and several methods are available. A medial gastrocnemius flap commonly is used, although it may be associated with an extensor lag. This problem also is encountered, although perhaps to a lesser extent, with other techniques for reconstruction of the extensor apparatus. It is not known how such lag develops with time and how it correlates with functional outcome.

QUESTIONS/PURPOSES
We therefore (1) assessed patellar height with time, (2) correlated patellar height with function using the Musculoskeletal Tumor Society (MSTS) score, and (3) correlated patellar height with range of motion (ROM) after medial gastrocnemius flap reconstruction.

METHODS
Sixteen patients underwent tumor endoprosthesis implantation and extensor apparatus reconstruction between 1997 and 2009 using a medial gastrocnemius flap after sarcoma resection of the proximal tibia. These patients represented 100% of the population for whom we performed extensor mechanism reconstructions during that time. The minimum followup was 2 years (mean, 5 years; range, 2-11 years). Fourteen patients were alive at the time of this study. We used the Blackburne-Peel Index to follow patellar height radiographically with time. Functional outcomes were assessed retrospectively using the MSTS, and ROM was evaluated through active extensor lag and flexion.

RESULTS
Eleven patients had patella alta develop, whereby the maximal patellar height was reached after a mean of 2 years and then stabilized. More normal patellar height was associated with better functional scores, a smaller extensor lag, but less flexion; the mean extensor lag (and flexion) of patients with patella alta was 17° (and 94°) compared with only 4° (and 77°) without.

CONCLUSIONS
In our patients patella alta evolved during the first 2 postoperative years. Patella alta is associated with extensor lag, greater flexion, and worse MSTS scores. Surgical fixation of the patellar tendon more distally to its anatomic position or strict postoperative bracing may be advisable.