TT-TG vs. modified lateral patellar edge for determination of tibial tubercle transfer distance in Fulkerson osteotomy procedures.

Background: Tibial tubercle-trochlear groove (TT-TG) distance is currently used at our institution to determine tibial tubercle medialization required in Fulkerson osteotomies. If the correlation between a modified lateral patellar edge (LPE) and the transfer distance was found to be stronger than its correlation with TT-TG, it would suggest that the best measurement to use is actually modified LPE.

Methods: The electronic medical records of 32 patients who underwent Fulkerson osteotomy procedures with femoral nerve stimulation were reviewed and measured. For each patient, modified LPE was measured on quadriceps active hyperextension MRI, and TT-TG was measured on passive extension MRI. Correlation between both TT-TG and LPE and tibial tubercle transfer distance was then determined and analysed.

Results: The correlation between TT-TG and actual intra-operative tibial tubercle transfer distance in Fulkerson osteotomy procedures with intra-operative femoral nerve stimulation was found to be weak at 0.436 (p<0.05). The correlation between modified LPE and actual intra-operative tibial tubercle transfer distance was found to be strong at 0.697 (p<0.001).

Conclusions: The correlation between modified LPE and actual intra-operative tibial tubercle transfer distance was stronger than the correlation between TT-TG and tibial tubercle transfer distance. This suggests that the modified LPE may actually be a better preoperative determinant than the currently-utilized TT-TG of the transfer distance required during Fulkerson osteotomy procedures.

Level Of Evidence: Level II, diagnostic study.