[Management Strategy and Evaluation of Surgical Outcomes in Patients with Recurrent Patellar Instability between 2010-2020]

Abstract

PURPOSE OF THE STUDY The study retrospectively reviews the outcomes of patella stabilisation surgeries performed at our department in the period 2010-2020. It aimed to provide a more thorough evaluation, to compare the respective types of MPFL reconstruction and to confirm the beneficial effect of tibial tubercle ventromedialization on patella height. MATERIAL AND METHODS In the period 2010-2020, a total of 72 stabilisation surgeries of patellofemoral joint in 60 patients with objective patellar instability (OPI) were performed at our department. The surgical treatment outcomes were evaluated retrospectively using a questionnaire, including the postoperative Kujala score. A comprehensive examination was carried out in 42 patients (70%) who had completed the questionnaire. In case of distal realignment, the TT-TG distance and a change in the InsallSalvati index which serve as an indication for surgery, were assessed. RESULTS Altogether 42 patients (70%) and 46 surgical interventions (64%) were evaluated. The follow-up period was 1-11 years, with the mean follow-up of 6.9 years. In the studied group of patients, only 1 case (2%) of new dislocation was seen, in 2 cases (4%) the patients reported a subluxation episode. The mean score using the school grades was 1.76. Thirty-eight patients (90%) were satisfied with the surgical outcome, 39 patients would undergo a surgery in case of identical problems with the other limb. The mean postoperative Kujala score was 76.8 points, range 28-100 points. The mean TT-TG distance in the studied group with the preoperative CT scan (33x) was 15.4 mm (12-30 mm). The mean TT-TG distance in the cases indicated for tibial tubercle transposition was 22.2 mm (15-30 mm). The mean Insall-Salvati index prior to the performance of tibial tubercle ventromedialization was 1.33 (1-1.74). Postoperatively, the index decreased by 0.11 on average (-0.00 to -0.26) to 1.22 (0.92-1.63). No infectious complications were presented in the studied group. DISCUSSION In patients with recurrent patellar dislocation, the instability is often times caused by pathomorphologic anomalies of the patellofemoral joint. In patients with clinically expressed patellar instability and physiological values of the TT-TG distance, an isolated proximal realignment is performed by medial patellofemoral ligament (MPFL) reconstruction. In the case of pathological values of the TT-TG distance, distal realignment is performed by tibial tubercle ventromedialization to achieve physiological values of the TT-TG distance. In the studied group, tibial tubercle ventromedialization helped decrease the Insall-Salvati index by 0.11 points on average. This has a positive side effect on the patella height, thus on increasing its stability in the femoral groove. In patients with both proximal and distal malalignment, a two-stage surgery is performed. In the isolated cases of severe instability or if symptoms of lateral patellar hyperpressure are present, musculus vastus medialis transfer or arthroscopic lateral release are performed as well. CONCLUSIONS When correctly indicated, proximal, distal realignment or their combination can bring very good functional outcomes with a low risk of recurrent dislocation and postoperative complications. The importance of MPFL reconstruction is confirmed by low incidence of recurrent dislocation in the group investigated in this study, namely when compared with studies referred to in this paper, in which the patients underwent patellar stabilisation using the Elmslie-Trillat procedure. Conversely, leaving the bone malalignment untreated during the isolated MPFL reconstruction increases the risk of its failure. Judging from the obtained results, tibial tubercle ventromedialization also has a positive effect on the patella height through its distalization. Provided the stabilisation procedure is correctly indicated and performed, the patients can get back to their normal activities, often even sports activities. Key words: objective patellar instability, patellar stabilisation, MPFL, tibial tubercle transposition.