John P. Fulkerson, MD

The following are important points to consider regarding Diduch’s presentation regarding their trochleoplasty results at the 2019 American Orthopedic Society of Sports Medicine Annual Meeting:

1. Half of their trochleoplasty patients were revisions of unsuccessful earlier surgeries;

2. Twenty percent of their trochleoplasty patients developed arthrofibrosis and required manipulation. Eight of 64 needed an arthroscopic lysis of adhesions. Trochleoplasty undoubtedly adds risks beyond doing MPFL surgery alone;

3. Their trochleoplasty patients all had MPFL reconstruction also, so we cannot assume, based on their findings, that trochleoplasty alone confers stability. With added MPFL reconstruction, trochleoplasty confers stable 1-year follow-up results; and

4. We do not yet know the long-term consequences of trochlea articular alteration.

At the same session in which Diduch presented his study, Beth Shubin Stein, MD, reiterated her earlier findings that isolated MPFL reconstruction works well despite trochlea dysplasia at the 2019 American Orthopedic Society of Sports Medicine Annual Meeting in Boston. In this study of 121 patients, isolated MPFL reconstructions were done for patella instability patients, 92% of whom had Dejour B, C or D trochlea dysplasia. Only three patients had postoperative instability and 94.5% of the patients returned to sports at 1 year.

Diduch presented his successful 1-year results using trochleoplasty combined with MPFL reconstruction for treatment of recurrent patella dislocations in patients with Dejour B and D dysplasia. Additionally, Seth Sherman, MD, presented another study at this meeting showing that tibial tubercle transfer, when needed in the treatment of recurrent patella instability, adds no significant morbidity.

Those treated in the Erickson and Shubin Stein study using MPFL reconstruction alone to treat recurrent patella instability had very low morbidity and no redislocation at 2 years.

The patients treated in Diduch’s study presumably had more serious structural dysplasia and Diduch illustrated in his presentation the need for trochleoplasty in patients with a prominent jumping J sign — in other words, a patella that is visually and structurally impaired by a very prominent supratrochlear spur causing the patella to jump laterally in extension. Such patients likely comprise less than 5% of patella instability patients seen in an average sports medicine practice.

Some take-home messages are:

1. Despite trochlea dysplasia, which is often present in patella instability patients, MPFL reconstruction works well for treatment of recurrent patella instability, so one must have a very good reason to add anything more;

2. Tibial tubercle transfer, when needed, adds little risk and is important to unload lateral articular lesions or establish balanced tracking and minimize risk of future arthritis; and

3. Trochleoplasty, when accompanied by MPFL reconstruction, is effective treatment for recurrent patella instability but has a 20% risk of arthrofibrosis and should be reserved for revision surgery and patients with a prominent J sign. Patella alta lowers the threshold for a trochleoplasty. Also, it is a difficult surgery to do well that alters articular cartilage as well as subchondral bone with unknown long-term consequences. Trochleoplasty candidates should perhaps be referred to an expert skilled in this procedure. 

A key point of Diduch’s study is that, properly done, by a highly trained and skilled trochleoplasty surgeon, trochleoplasty when combined with MPFL reconstruction, works well for patella stabilization for those relatively few patients with a prominent J sign and severe trochlea dysplasia. One might choose to add trochleoplasty when MPFL reconstruction alone, with or without tibial tubercle transfer surgery is insufficient, by objective criteria, and in selected revision surgeries of failed previous patella instability surgery in the presence of severe trochlea dysplasia. This is likely less than 5% of patella instability patients in a standard sports medicine practice

My own experience of more than 40 years in a patellofemoral surgery practice, is that very few patients need a trochleoplasty (less than 5% of my instability patients) including patients with a flat, Dejour B proximal trochlea when patella malalignment and articular damage are corrected by tibial tubercle transfer, medially, distally and/or anteromedially, and then stabilized anatomically by MPFL or MQTFL reconstruction.

Medial patellofemoral complex (as described by Tanaka) reconstruction (MPFL or MQTFL) alone, with tibial tubercle transfer to correct alignment and/or unload patella articular lesions, remains the mainstay of patella stabilization surgery, with minimal risk of complication. Diduch’s study gives us further insight into the short-term benefit of well-done trochleoplasty when needed for severe trochlea dysplasia and combined with MPFL reconstruction, despite a 20% risk of arthrofibrosis.

Reference:

Erickson BJ, et al. Am J Sports Med. 2019;doi:10.1177/0363546519835800.