2017 ISAKOS Biennial Congress ePoster #1719

 

Mini-Open Trochleaplasty for Recurrent Patellar Instability – Surgical Technique, Safety Analysis with MRI and Clinical Results

Petri J. Sillanpää, MD, PhD, Tampere FINLAND
Frederick Weitz, MD, Tampere FINLAND

Tampere University Hospital, Tampere, FINLAND

FDA Status Not Applicable

Summary

To stabilize the dislocating patella, trochleaplasty has become an accepted surgical management strategy. Trochleaplasty is a safe procedure and has a low failure rate – none had recurrent patellar dislocation and 2,9% required revision surgery in this consecutive cohort of 68 patients. Trochlear cartilage shape can be corrected safely based on post operative MRI analysis.

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 clinical safety and failure rates for trochleaplasty is unknown. The purpose of this study was to analyse the clinical safety and failure rate of trochleaplasty in a consecutive cohort of patients. The secondary purpose of this study was to describe a new mini-open surgical technique and analyse the algorhitm of combinating patellar stabilizing surgical procedures with trochleaplasty in patients who had more than one pathoanatomical factor.

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 instability. Demographics and presence of risky pathoanatomies were collected prospectively. These included age at first dislocation, degree of trochlear dysplasia, TT-TG, patella alta and rotational abnormalities. Clinical results and subjective outcome were reported at follow-up visits and patients underwent MRI assessment of post-operative trochlear status at mean 12 monts after surgery. 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%). There were no patients with recurrent patellar dislocation after surgery. There were two patients that required revision surgery; one patient due to iatrogenic medial patellar subluxation and one due to painful patellar maltracking, for a failure rate 2,9% (2/68). In follow-up MRI’s, no significant cartilage lesions such as delamination or avascular necrosis were seen. 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. One patient required subsequent tibial tubercle distalization after trochleaplasty due to subjective patellar maltracking symptoms near extension. Another patient required lateralization of the distalized tibial tubercle due to iatrogenic medial subluxation. Three patients with highly increased femoral anteversion (3/68 patients, 4%) underwent additional distal femoral derotational osteotomy. The patients who had one or more additional pathoanatomical factor surgically corrected at the time of trochleaplasty were not at greater risk for postoperative complications if compared to trochleaplasty and MPFL reconstruction alone.

Conclusions

Trochleaplasty is a safe procedure and has a low failure rate – none had recurrent patellar dislocation and 2,9% required revision surgery - in this consecutive series of 68 patients due to intraopearive misinterpretation of patellar height correction. Trochlear cartilage shape can be corrected safely based on post operative MRI analysis. Additional major pathoanatomical factors can be surgically corrected at the time of trochleaplasty with no risk of increased post operative complications.