Excellent clinical and radiological outcomes after both open flake refixation and autologous chondrocyte implantation following acute patella dislocation and concomitant flake fractures

PURPOSE: To investigate clinical and magnetic resonance (MR) imaging results of patients undergoing patella stabilization with either open flake refixation (oFR) or autologous chondrocyte implantation (ACI) and concomitant soft tissue patella stabilization after sustaining primary, acute patella dislocation with confirmed chondral and/or osteochondral flake fractures. It was hypothesized that refixation will lead to better results than ACI at mid-term follow-up. METHODS: A retrospective chart review was conducted to identify all patients undergoing oFR or ACI after sustaining (osteo-)chondral flake fractures and concomitant soft tissue patella stabilization following primary, acute patella dislocation between 01/2012 and 09/2018 at the author’s institution. Patients were excluded if they were aged < 14 years or > 30 and had previous knee surgeries at the index knee. Clinical outcomes were assessed using the Tegner activity score, Kujala score, subjective IKDC score, and the KOOS score at a minimum follow-up of 24 months postoperatively. MR images were assessed using the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) 2.0 knee score. Thirty patients were included in the study, with 16 patients assorted to the oFR group and 14 patients to the ACI group (Follow-up 81%). RESULTS: Demographic data did not show significant group differences (oFR: 6 females, 10 males; age 26.9 ± 5.6 years, FU: 57 months (27–97 months); ACI: 9 females, 5 males; age 25.5 ± 4.9 years, FU: 51 months (29–91 months); n.s.). Defect location was similar in both groups (oFR: 12 × patella/4 × lateral femoral condyle; ACI: 12/2; n.s.). Both groups showed excellent clinical outcomes, with no statistically significant difference between both the groups (oFR group vs. ACI group: Tegner: 5.1 ± 1.8 vs. 5.1 ± 1.4; Kujala: 86.1 ± 12.6 vs. 84.9 ± 9.1; IKDC: 83.8 ± 15.0 vs. 83.6 ± 11.3; KOOS: 83.3 ± 14.0 vs. 83.6 ± 12.0; n.s.). One patient in each group suffered a patella re-dislocation and needed revision surgery. The MOCART 2.0 score showed good results for the oFR group (68.2 ± 11.1) and the ACI group (61.1 ± 16.9) while no significant differences were noted between both the groups. The inter-rater reliability was excellent (0.847). CONCLUSION: Open refixation of (osteo-)chondral fragments in patients after sustaining acute patella dislocation with (osteo)-chondral flake fractures led to good clinical and radiological results at a minimum follow of 24 months, showing that it is a good surgical option in the treatment algorithm. However, if open refixation is not possible, ACI may be an excellent fallback option in these younger patients with equally good clinical and radiological outcomes, but requiring a second minimally invasive surgery. LEVEL OF EVIDENCE: III. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00167-022-06899-3.