Summary

Trochleaplasty is a safe procedure and has low failure rate – none had significant cartilage lesions such as delamination or avascular necrosis. Trochlea dysplasia can be corrected to normal or nearly normal trochlea by trochleaplasty.

Abstract

Purpose

Patellofemoral instability is a common problem in adolescents and young adults and anatomical patellofemoral abnormalities, especially trochlear dysplasia, increase the risk for recurrent dislocations. To stabilize the dislocating patella, trochleaplasty has become an accepted surgical management strategy. The changes of trochlear morphology and the cartilage viability after trochleaplasty are poorly understood. The purpose of this study was to analyse the changes in cartilaginous shape of the trochlea after trochleaplasty in a consecutive cohort of patients. The secondary purpose of this study was to analyze cartilage viability in MRI after mini-open lateral approach trochleaplasty.

Methods

From January 2009 to December 2015, 68 consecutive patients underwent a mini-open lateral approach trochleaplasty combined with medial patellofemoral ligament (MPFL) reconstruction for the diagnosis of recurrent lateral patellofemoral dislocation. Demographics and presence of risky pathoanatomies were collected prospectively. These included ages at first dislocation, degree of trochlear dysplasia, sulcus depth, sulcus angle, lateral inclination angle, condylar height and patello-trochlear index. Clinical results and subjective outcome were reported at follow-up visits and first 30 patients underwent a control MRI assessment of post-operative trochlear status. Failures of trochleaplasty were defined as recurrent dislocation of the patella or post operative clinical complication warranting revision surgery or other major subjective complaint on clinical examination. For patients with other major anatomical patellofemoral abnormalities than trochlear dysplasia, a surgical algorithm was used to correct patella alta, lateralized tibial tubercle, rotational or axial deformity all at the same surgery, no staged surgery was performed.

Results

Mean age at the time of surgery was 16.9 years (SD 4,63). Majority of the patients were females (53/68, 78%). Patients reported a mean Kujala score 70.6 (SD 17.77 ) preoperatively and postoperatively Kujala score improved to mean 93,5 (SD 4.82) One patient had patellar re-dislocation after surgery. In follow-up MRI’s, no significant cartilage lesions such as delamination or avascular necrosis were seen. The cartilaginous flap at the region where trochleaplasty was performed did not revealed any greater than ICRS grade I cartilage deterioration on control MRI and in majority of the knees no changes were detected. The most common postoperative trochlear shape was somewhat shallow, graded as type A according to Dejour classification - all study patients with type B and D dysplasia with bump deformity were corrected to normal shaped or type A trochlea. All trochleaplasties were combined with MPFL reconstruction and if no overlapping of patellar and trochlear cartilage was present, indicating abnormal patello-trochlear index, tibial tubercle distalization was performed to correct patellar height. MRI analysis of 30 patients showed that the preoperative sulcus depth was mean 1,3mm (SD 0,93) and post-operative mean 3,1mm (SD 1,20) and sulcus angle improved from preoperative mean 162 (SD 9,72) to post-operative mean 149 (SD 5.14), indicating normal or nearly normal features of the patellofemoral joint.

Conclusions

Trochleaplasty is a safe procedure and has low failure rate – none had significant cartilage lesions such as delamination or avascular necrosis. Trochlea dysplasia can be corrected to normal or nearly normal trochlea by trochleaplasty, based on post operative MRI analysis. Satisfying subjective outcome can be expected for trocleaplasty and redislocation rate is low.