Decreased medial patellar width associated with lateral patellar dislocation

ByMax R. Wursta

Fact checked byKristen Dowd

Key takeaways:

Decreased medial patellar width may be a more accurate risk factor for lateral patellar dislocation vs. traditional femoral and tibial measurements.
Patellar shape should be considered during decision-making.

Perspective from John P. Fulkerson, MD

According to published results, decreased medial patellar width may be a more accurate indicator for recurrent lateral patellar dislocation compared with traditional measures such as trochlear dysplasia and patella alta.

Frances T. Sheehan, PhD, and colleagues at the rehabilitation medicine department of the NIH performed a cohort study of 21 patients with lateral patellar dislocation (mean age, 29.7 years) vs. a height- and sex-matched cohort of 21 healthy control patients (mean age, 27.2 years).

Knee MRI — Decreased medial patellar width may be a more accurate risk factor for lateral patellar dislocation vs. traditional measurements. *Image: Adobe Stock*

According to the study, researchers used 3D axial fat-saturated MRI to assess several patellar morphological parameters including patellar width, patellar volume, patellar facet length, Wiberg index and traditional measurements such as tibial tuberosity to trochlear groove distance and trochlear dysplasia.

Compared with the control group, patients with lateral patellar dislocation had decreased medial patellar width (change, –3.6 mm), decreased medial facet length (change, –3.7 mm), decreased total patellar width (change, –3.2 mm), decreased patellar volume (change, –0.3 cm³) and an increased Wiberg index (change, 0.05). Researchers found no other differences in patellar measurements between the cohorts.

Researchers noted medial patellar width was the strongest single indicator for recurrent lateral patellar dislocation with 83.3% accuracy. They noted a combination of

medial patellar width, patellofemoral tilt and trochlear groove length increased indication accuracy to 92.9%.

“Although current interventional decision-making tools post-lateral patellar dislocation focus primarily on femoral and tibial measures, the study results suggest that information regarding patellar shape should be added to this decision process, as it has stronger discriminatory ability than traditional trochlear shape and tibiofemoral alignment measures have,” the researchers wrote.

Perspective

John P. Fulkerson, MD

This is a good article that raises a good point when treating patellofemoral patients. It harkens back to the Wiberg classification of patella shape that was more popular 3 to 4 decades ago. Perhaps the most important aspect of the MRI findings is how it might relate to the complex geometry of the opposing dysplastic trochlea. How do the 3D replications relate to treatment? We should increasingly look at both the trochlea and patella with 3D imaging to better understand and treat patients with patella instability.

John P. Fulkerson, MD

Professor of orthopedic surgery

Yale University

Department of orthopedic surgery

President, Patellofemoral Foundation

New Haven, Connecticut

Disclosures: Fulkerson reports no relevant financial disclosures.

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Sources/Disclosures

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Source:

Sheehan FT, et al. Am J Sports Med. 2024;doi:10.1177/03635465241233732.

Disclosures: The authors report receiving funding from the Intramural Research Program of the NIH Clinical Center and the Medical Research Scholars Program for the conduct of the study.

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Decreased medial patellar width associated with lateral patellar dislocation

Key takeaways:

Perspective

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