Clinical outcomes after revision surgery for medial patellofemoral ligament reconstruction

Medial patellofemoral ligament reconstruction (MPFL-R) is the standard surgical intervention for patella instability. However, limited knowledge exists concerning the causes for failure, and outcome after revision MPFL-R. The purpose of this study is to evaluate the causes of primary MPFL-R failure and clinical outcomes after revision MPFL-R.

Twenty-three patients (6 males and 17 females) with failed primary MPFL-R underwent isolated revision MPFL-R or combined revision MPFL-R with tibial tuberosity osteotomy (TTO). The mean age was 23 (SD 8.6). Prior to surgery, dysplasia of the patellofemoral joint, sulcus angle, Insall-Salvati index, cartilage lesions, tibial tuberosity trochlear groove (TTTG) distance, and tunnel placement were evaluated by magnetic resonance imaging (MRI). Their scores on the Kujala Anterior Knee Pain Scale and pain scores were assessed prior to surgery, 1 year post-operatively and at final follow-up. The mean follow-up time was 44 months (median range 39). The radiographic characteristics and clinical outcomes were compared with a 224 primary MPFL-R patient cohort (240 knees).

Non-anatomical fixation of the graft at the medial femoral condyle after primary MPFL-R was seen in 67% of revision patients with anterior/proximal misplacement in most cases. Severe trochlear dysplasia Dejour types C and D were seen in 36% of the patients compared to 30% of primary MPFL-R patients (NS). The mean Kujala Anterior Knee Pain Scale score at final follow-up was 61.7 (SD 18.8) compared to 80.3 (SD 18) in primary MPFL-R patients (P < 0.01). The mean pain score at rest was 2.3 (SD 2.5) for revision MPFL-R patients compared to 1.7 (SD 2.5) in primary MPFL-R patients (NS) and their mean pain score during activity was 5.0 (SD 3.2) compared to 1.3 (SD 2.2) in primary MPFL patients (P < 0.001).

Although revision MPFL-R establishes acceptable patellar stability, the subjective outcomes after revision MPFL-R do not improve significantly, and are poorer than after primary MPFL-R. Non-anatomical graft position can be an important cause of MPFL-R failure. The clinical relevance of this study is that it shows that it may be difficult to improve self-reported outcomes in revision MPFL-R patients.

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