Reconstruction of the medial patellofemoral ligament (MPFL) is widely acknowledged as an integral part of the available therapeutic armamentarium for recurrent patellar instability. The procedure is often performed with concomitant bony procedures such as distalization of the tibial tuberosity or trochleoplasty in the case of, respectively, high-grade trochlear dysplasia or patella alta. At the present time, there are very few studies that evaluate the clinical effectiveness of MPFL reconstruction as an isolated intervention.
To report the clinical outcomes of isolated MPFL reconstruction in cases of patellar instability and identify predictive factors for failure.
Study design: Case series; Level of evidence 4
A retrospective analysis of prospectively collected data was performed including all patients who had undergone an isolated medial patellofemoral ligament reconstruction between January 2008 and January 2014. Pre and postoperative assessment included the Kujala score, assessment of patella tracking (“J-sign”) and radiographic features including trochlear dysplasia according to Dejour classification and patellar height with the Caton-Deschamps ratio (CDR). The Kujala score was assessed postoperatively. Failure was defined by a postoperative patellar dislocation or a surgical revision for recurrent patellar instability.
A total of 241 MPFL reconstructions were included. 28 cases (11.6%) were uncontactable and were considered lost to follow-up. Thus, 213 reconstructions were analyzed with a mean follow-up of 5.8 years (3-9.3). Mean age at surgery was 20.6 years (11-48); 55% of patients were male. 28% of patients had a preoperative positive J-sign, mean CDR was 1.2 (1.0-1.7, )94% of patients had trochlear dysplasia (A:47%; B:26%; C:15%; D:6%). Mean Kujala score was improved from 56.1 preoperatively to 88.8 (p<0,001). 12 failures were reported requiring a surgical revision for recurrent patellar instability (5.6%). Uni and multi variate analyses highlighted two preoperative failure risk factors: patella alta (CDR >1.3) (OR=4.8; p=0.01) and preoperative positive J-sign (OR=5.2; p=0,01).
In cases of recurrent patellar instability, isolated MPFL reconstruction seems to be a safe and efficient surgical procedure with a low failure rate. In cases of patella alta with a CDR > 1.3 or a preoperative positive J-sign, it is advisable to perform an adjunct procedure such as distalization of the tibial tuberosity or trochleoplasty.