Arthroscopic cam resection can restore the normal mechanical environment of the hip joint in cam-type femoroacetabular impingement, a new study finds.
Cam Resection’s Effect on Hip Joint Mechanics Data
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The researchers wrote, “Femoroacetabular impingement (FAI) is increasingly recognized as a cause of hip pain in young adults. The condition leads to chondrolabral separation and chondral delamination and eventually predisposes to osteoarthritis of the hip.”
“Femoroacetabular impingement that inflicts cartilage damage has been observed in hips with abnormal morphological characteristics and is related to a long-term evolution toward osteoarthritis. Arthroscopic surgery, which allows for correction of morphological characteristics and restores impingement-free motions, is the current standard of treatment.”
For the study, “Accurate Arthroscopic Cam Resection Normalizes Contact Stresses in Patients With Femoroacetabular Impingement,” published online on November 25, 2020 in The American Journal of Sports Medicine, the research team analyzed patient-specific discrete element models from 10 patients with cam-type femoroacetabular impingement (FAI). All of the patients were male and between the ages of 18 and 40 years.
The team confirmed cam resection postoperatively using MRI with alpha angles less than 55˚. The researchers also compared the patients’ preoperative and postoperative peak contact stress findings to those of a matched control group.
Overall, peak contact stress was significantly elevated in patients with cam-type FAI during impingement testing, with increasing amounts of internal hip rotation (26.6 ±11.64 MPa in cam patients preoperatively, 12.1 ±4.62 MPa in those same patients postoperatively, and 11.4 ±1.72 MPa in the virtual control group during impingement testing at 20˚of internal hip rotation, p < .01).
This effect, however, was normalized after arthroscopic cam resection and loading patterns matched those of the control group.
The study authors wrote, “Accurate arthroscopic cam resection restored the normal peak joint contact stresses in the hip joint. This highlights the importance of early and complete cam resections in the face of a positive diagnosis of cam-type FAI. Treatment of cam-type FAI effectively normalizes hip joint contact mechanics.”
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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