Outcomes of MPFL Reconstruction with Grammont in Pediatric Patients with Patellar Instability and Increased TT-TG Distance: A Comparison Study

Background: Patellar instability in pediatric patients is commonly treated with medial patellofemoral ligament reconstruction (MPFLR). MPFLR alone does not directly address other underlying anatomic risk factors for patellar instability, such as lateralized patella tendon insertion. The Grammont procedure is a technique for medialization of the patella tendon insertion that can correct increased TT-TG distance in skeletally immature patients. This technique has not been studied in acute and recurrent traumatic patellar instability, nor has it been compared as an adjunct procedure to MPFLR. Hypothesis/Purpose: The purpose of this study was to compare medial patellofemoral ligament reconstruction (MPFLR) alone versus MPFLR with a Grammont procedure in pediatric patients. It was hypothesized that combining MPFLR with the Grammont procedure, compared with MPFLR alone, would reduce recurrent patellar instability, achieve greater correction of the tibial tubercle–trochlear groove (TT-TG) (MPFLR alone) or patellar tendon insertion–trochlear groove (PTI-TG) (MPFLR + Grammont) distance, and maintain a comparable complication rate. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective review was performed including all pediatric patients (<19 years) treated surgically for patellar instability at 1 institution between 2010 and 2023. A total of 45 patients underwent MPFLR and 36 patients underwent MPFLR plus Grammont. Rates of recurrent instability and revision surgery were compared. Pre- and postoperative imaging (radiography and magnetic resonance imaging) was used to evaluate changes in Caton-Deschamps ratio and TT-TG (MPFLR alone) or PTI-TG (MPFLR + Grammont). Additionally, the investigators compared the rate of modified Clavien-Dindo grade II and III complications between surgical groups. Results: In the MPFLR + Grammont group vs the MPFLR-only group, patients were younger at the time of surgery (median age 13.4 vs 15.3 years, respectively; P = .013), the percentage of female patients was higher (80.6% vs 55.8%; P = .016), and the mean preoperative TT-TG was larger (18.8 vs 15.7 mm; P = .001). Twenty (25.3%) patients had grade II/III complications, with no significant differences between surgical groups. Twelve patients (14.8%) experienced recurrent instability, with rates of 20.9% in the MPFLR-only group and 8.3% in the MPFLR + Grammont group ( P = .120). Revision surgery for recurrent patellar instability was performed in 4 patients in the MPFLR-only group (9.3%) and 1 patient in the MPFLR + Grammont group (2.8%). In the MPFLR + Grammont group, 1 patient had a growth arrest of the tibial tubercle apophysis resulting in recurvatum deformity. Conclusion: In pediatric patients with patellar instability and increased TT-TG distance, adding a Grammont procedure to MPFLR resulted in similar overall complication rates compared with isolated MPFLR. The MPFLR + Grammont group was younger and had more severe anatomic risk factors; the investigators observed a possibly lower rate of recurrent instability and fewer revision surgeries.