Beth E. Shubin Stein, MD

I commend the authors on a well-done study. The survey responses indicate an overall lack of consensus on the treatment of complex patella instability. The survey questions they used are based off a study Joe N. Liu, MD, and our group performed in 2017. We created several case scenarios to include simple patellar instability, as well as more complex instability, and we surveyed the International Patellofemoral Study Group. The goal of that study, which used the Delphi technique, was to create consensus statements on the treatment of patellofemoral instability in the absence of literature-based treatment guidelines.

This study used the same questions, modified slightly, to find areas of agreement within a primarily German-speaking surgeon population.

Alexander Geierlehner, MD, MSc, and colleagues demonstrated similar results to our study, with most surgeons 1) getting an MRI in patients with a first-time dislocation, 2) opting for nonoperative treatment in a first-time dislocator without a loose body or osteochondral fracture regardless of age and growth plate status, 3) fixing or removing the osteochondral fracture, if it is present in a first-time dislocator, but also concomitantly addressing the patellofemoral instability, 4) favoring medial patellofemoral ligament reconstruction as the primary surgical intervention in patients with recurrent instability and 5) agreement that isolated lateral release was not a treatment for instability.

This study highlights several areas of agreement, mainly which patients to treat nonoperatively and which require surgery. It also details the lack of agreement as to what surgery should be done when operative intervention is indicated.

This study shines a light on the big question in recurrent patellar instability: ‘When is a medial patellofemoral ligament reconstruction enough and when do we need to add bony procedures?’

The paper highlights the need to obtain outcome-based guidelines and algorithms for treatment in these complex patients.

This question is not unique to patella instability. It has been asked in many other fields including shoulder and hip. If we look to the shoulder literature to help guide us, we find the instability severity index score which was created by Pascal Boileau, MD, to help determine which patients had a high risk of failure and recurrent instability with an isolated soft tissue or Bankart repair. This score helps determine which patients would likely do better with a bony procedure such as a Latarjet.

The field of patellar instability needs a similar index, the patella instability severity index score, to help us identify patients with a high risk of failure of an isolated medial patellofemoral ligament reconstruction and who would benefit from an added bony surgery (tibial tubercle transfer, distal femoral osteotomy, trochleoplasty, guided growth or de-rotational osteotomy).

Our group has identified this need and we currently have a prospective study underway. We published our early results in the American Journal of Sports Medicine in 2019. The goal of this prospective study is to perform isolated medial patellofemoral ligament reconstructions on all patients with recurrent instability regardless of bony measurements, to follow them and to perform a logistic regression analysis on the failures/patients with recurrent instability to identify risk factors for failure of an isolated medial patellofemoral ligament. We look forward to being able to identify a scoring algorithm that will help all of us treat these patients in a more standardized fashion and hopefully see fewer recurrences and complications as a result.

References:

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

Liu JN, et al. Am J Sports Med. 2018;doi:10.1177/0363546517732045.