Increased Femoral Anteversion Influence Over Surgically Treated Recurrent Patellar Instability Patients

Abstract

To verify the influence that increased femoral anteversion (FA) has on patients with recurrent patellar instability (RPI) treated by anteromedialization tibial tubercle osteotomy (TTO) combined with medial patellofemoral ligament reconstruction (MPFLR) and to present the midterm outcomes of these patients. From January 2008 to August 2013, skeletally mature patients with RPI and tibial tubercle (TT)-trochlear groove (TG) ≥ 17mm who underwent anteromedialization TTO combined with MPFLR were evaluated for J sign, patellar glide, apprehension test, increased FA, Caton index, trochlea dysplasia, TT-TG, Kujala, International Knee Documentation Committee subjective knee evaluation form, and Tegner. Increased FA was determined clinically by a difference of more than 30° between hip internal and external rotation, 70° or more of hip internal rotation, and 30° or more of femoral neck anteversion. A subgroup analysis involving increased FA was made. Forty-eight patients composed the study group. Mean follow-up was 41.5 ± 11.05months. The J-sign was present in 86% before surgery and none postoperatively (P < .001). All patients had a positive apprehension test or a patellar luxation at the patellar glide test rated as grade 4 before surgery. After surgery, the mean glide was 1.29 ± 0.45 with no apprehension (P < .001). Increased FA was present in 18.7%. Caton index before surgery was 1.11 ± 0.21 and 0.99 ± 0.11 postoperatively (P= .004). Trochlea dysplasia was present in all patients. TT-TG preoperatively was 20.77 ± 2.12mm and 11.33 ± 1.24mm postoperatively (P < .001). Functional scores improved preoperatively to postoperatively (P < .001) with Kujala and International Knee Documentation Committee means: 59.08 to 84.37; 52.6 to 85.5, respectively. Tegner preinjury score was 5.4 and postoperatively was 5.2 (P= .01). Increased FA group had worse Kujala compared with the normal FA group and worse Kujala improvement: 77.7 and 85.89 (P= .012), and 21.7 and 26.1, respectively (P < .001). Increased FA in patients with RPI had a negative effect on the outcome of anteromedialization TTO combined with MPFLR. Combined anteromedialization TTO and MPFLR had good functional midterm outcomes in treating patients with RPI and TT-TG ≥ 17 mm. Level III, comparative study.