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.
LEVEL OF EVIDENCE
Level IV, clinical cohort study. See the Guidelines for Authors for
a complete description of levels of evidence.
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