Functional outcomes of paediatric medial patellofemoral ligament (MPFL) reconstruction surgery with or without patella distalisation and medialisation for recurrent patella instability

Background

No studies to date have compared the outcome of isolated medial patellofemoral ligament reconstruction (MPFLR) surgery with MPFLR plus re-alignment procedures (MPFLR+) in the paediatric population, making it unclear when additional re-alignment procedures are required.

By retrospectively reviewing and comparing our MPFLR patient cohorts’ we aim to generate guidance to aid surgical planning.

Methods

University of Salford ethical approval was secured and theatre records were retrospectively reviewed, identifying all patients less than 18 years-of-age who received MPFLR surgery between October 01, 2015 and October 01, 2019.

All patients were contacted for documented consent. Pre-operative and post-operative outcome questionnaires were reviewed in conjunction with patient’s medical records and radiological imaging.

Results

A total of 75 MPFLR surgeries were identified and 33 patients (40 knees) consented for inclusion in the study; 23 MPFLR and 17 MPFLR+. Mean improvement in outcome scores achieved statistical significance (P < 0.05) in almost all questionnaire subtypes for both groups. A greater improvement in Quality of life (QoL) correlated with an increased tibial tuberosity–trochlear groove distance (TT-TG) in the MPFLR group 0.557 (P = 0.025) and a lower Patellotrochlear index (PTI) - 0.549 (P = 0.034) in the MPFLR + group.

Increased Body Mass Index (BMI) correlated with worse outcomes in numerous questionnaire subtypes (P = 0.05 and P = 0.01) for the MPFLR + group.

Increased Trochlear dysplasia correlated – 0.541 (P = 0.03) with less improvement in symptoms following MPFLR + surgery and an increased need for revision surgery 0.312 (P = 0.053) in both groups.

Conclusions

Both groups achieved good outcomes and statistically significant improvements in almost all mean outcome scores following MPFLR surgery, suggesting that our current described selection criteria are appropriate. While we were unable to identify any absolute radiological cut off figures in this diverse population with changing anatomy, we recommend additional procedures be considered for high TT-TG distances and or significant patella alta.

Patients with a high BMI should be supported in losing weight prior to surgery and patients with trochlear dysplasia need counselling with regard to potential lesser improvements in symptoms, a higher risk of failure and need for revision surgery. Additional realignment procedures did not appear to offer any improved outcome in the presence of trochlear dysplasia.

Level of Evidence IV: Case series.