Non-surgical treatment for acute patellar dislocation with special emphasis on the MPFL injury patterns.

PURPOSE: The objective of present study was to propose a new classification for acute MPFL injury, which can help choose optimal treatment method for certain injury type. METHODS: Eighty-five patients with acute patellar dislocation treated non-surgically were retrospectively reviewed. They were assigned into two groups according to the newly introduced classification scheme, which classified MPFL injury into three types: injury in overlap region, injury in non-overlap region and combined injury of both regions. For study purpose, patients with combined injury were not included. Of 85 patients, 33 were in the overlap-region group (Group 1) and 52 in the non-overlap-region group (Group 2). Clinical patellar instability rate and patellofemoral score were measured and recorded at 2-year follow-up. RESULTS: The patellar instability rate was 15.2 % in Group 1 and 38.5 % in Group 2, with statistically significant difference between the two groups (P = 0.022). The mean visual analogue scale for Group 1 and Group 2 was 15.6 points and 28.3 points, respectively (P = 0.026). The mean Kujala score was 91.1 points and 82.6 points (P = 0.009), with a good or excellent subjective result recorded for 27 of 33 patients (81.8 %) in Group 1 compared with 30 of 52 patients (57.7 %) in Group 2 (P = 0.021). CONCLUSIONS: Non-surgical treatment achieves better clinical outcomes with respect to a lower patellar instability rate and better subjective function for the overlap-region injury of MPFL than for the non-overlap-region injury, and can be considered as treatment of choice for overlap-region injury of MPFL. The optimal choice for the non-overlap-region injury still requires further researches. LEVEL OF EVIDENCE: Therapeutic, Level IV.