Accurate Arthroscopic Cam Resection Normalizes Contact Stresses in Patients With Femoroacetabular Impingement

Abstract

Background: 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. FAI 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. Hypothesis: Arthroscopic cam resection can restore the normal mechanical environment of the hip joint in cam-type FAI. Study Design: Descriptive laboratory study. Methods: Patient-specific discrete element models from 10 patients with cam-type FAI (all male; age, 18-40 years) were defined based on preoperative computed tomography scans and postoperative magnetic resonance imaging (MRI) scans. Complete cam resection postoperatively on MRI was confirmed with alpha angles <55°. The preoperative and postoperative peak contact stress findings during impingement testing were compared against a matched control group. Results: 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 was normalized after arthroscopic cam resection and loading patterns matched those of the control group. Conclusion: 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. Clinical Relevance: Treatment of cam-type FAI effectively normalizes hip joint contact mechanics.

Hips 2021

“…The increased rate of reoperation in the control group, detectable as early as 2 years postoperatively, may be interpreted as indirect evidence that the bony abnormalities characteristic of FAI predispose to the painful labral injury and that this labral damage may tend to recur if the underlying bony lesions are not corrected at the time of surgery. 3,21,24,25 A discrete element analysis of hips from 10 patients with cam FAI in this issue of AJSM supports this theory. 24 These authors calculated increased peak joint contact stresses during simulated impingement testing in the hips with cam deformities compared with control hips.…”

“…of hips from 10 patients with cam FAI in this issue of AJSM supports this theory. 24 These authors calculated increased peak joint contact stresses during simulated impingement testing in the hips with cam deformities compared with control hips. After adequate cam resection, the peak contact stresses returned to a normal range.…”

“…3,21,24,25 A discrete element analysisKeywords: hip arthroscopy; femoroacetabular impingement; FAI; cam lesion; acetabuloplastyEditorial…”

Retrospective Analysis of Arthroscopic Cam Decompression. Is Hip Joint Still Preserved Although at Learning Curve?

“…Supporting this, Domb et al (7) also reported that in patients treated with hip arthroscopy and optimal resection, cam deformity (postoperative α angle<55 0 ) had lower incidence of conversion to total hip arthroplasty than incomplete resection (postoperative α>55 0 ). A recent in vitro study also confirmed that accurate cam resection restored normal peak joint contact stresses (8) .…”

Outcomes of Hip Arthroscopy in Patients with Femoroacetabular Impingement and Concomitant Tönnis Grade II Osteoarthritis or Greater: Protocol for a Systematic Review

“…FAI is treated either conservatively with activity-modification and physiotherapy [ 4 ] or with joint-preservation surgery, mainly hip arthroscopy (HA) or in specific cases, periacetabular osteotomies (PAO) or surgical hip dislocations [ 5 ]. The aim of such surgery is to reshape the hip joint to prevent impingement (abnormal mechanical contact) [ 6 ] and normalise stresses in the hip joint [ 7 ] and also address any concomitant extra-articular causes if present [ 8 9 ]. Intra-articular damage is addressed with debridement, repair or reconstruction in cases of labral tears, and a debridement or microfracture with different biological regenerative techniques in cases of articular cartilage damage [ 10 ].…”