Rethinking Femoroacetabular Impingement: Evidence, Indications, and Surgical Timing

The Clinical Dilemma

Few conditions in contemporary sports medicine and joint preservation generate as much debate as femoroacetabular impingement (FAI). Every orthopaedic surgeon recognizes the classic presentation: an active young adult presenting with insidious groin pain, positive FADIR testing, and an anterolateral cam deformity on Dunn lateral radiography. The diagnostic dilemma lies not in identifying the bony morphology, but in determining which hips warrant surgical correction versus nonoperative preservation.

As advanced imaging modalities became widespread over the past two decades, our understanding of hip biomechanics shifted rapidly. Asymptomatic individuals frequently demonstrate elevated alpha angles and acetabular overcoverage. Operating strictly on imaging findings is an error: radiographic impingement morphology without mechanical symptoms does not justify surgical intervention. Conversely, delaying intervention in symptomatic patients with recurrent mechanical catching and progressive chondral delamination risks accelerating irreversible joint degeneration.

The Landmark Evidence: What the Data Shows

For years, proponents of hip arthroscopy relied on retrospective case series and single-surgeon cohorts. That paradigm changed with the publication of multi-center randomized controlled trials evaluating arthroscopic osteochondroplasty against structured conservative rehabilitation. The landmark investigation is the UK FASHIoN trial (Full Assessment of the Short-term effectiveness of arthroscopic Hip surgery compared with personalised Hip therapy), published by Griffin and colleagues in The Lancet.

The trial randomized 348 patients across 23 hospitals in the United Kingdom to either hip arthroscopy (labral repair and osteochondroplasty) or personalized hip therapy (a structured physiotherapist-led program). At 12 months of follow-up, both cohorts demonstrated clinically meaningful improvements. However, the surgical group achieved a statistically significant and clinically superior improvement in the primary endpoint, the International Hip Outcome Tool (iHOT-33), with an adjusted mean difference of 6.8 points favoring arthroscopy. Similar multi-center trials, including the Australian FAIT trial, corroborated that mechanical decompression yields superior functional relief in properly selected candidates.

Connecting the Data to Practice: The OrthopaedicsOne Synthesis

While randomized trials prove the efficacy of surgical intervention, successful clinical outcomes depend entirely on surgical execution, anatomical precision, and avoiding common pitfalls. This is where our foundational knowledge base bridges trial data with daily operating room practice.

On OrthopaedicsOne, our fully modernized clinical guide, What Is the Latest Update on Hip Impingement, synthesizes the complete diagnostic and operative algorithm. The guide integrates Dr. Trousdale’s faculty lecture directly alongside detailed measurements: calculating the alpha angle on Dunn 45-degree lateral projections, identifying retroversion through the crossover sign and ischial spine sign, and evaluating chondral delamination staging.

Crucially, our article details the hard exclusion criteria that prevent surgical failure: hips presenting with advanced Tonnis osteoarthritis (Grade 2 or 3) or joint space narrowing below 2 mm fail rapidly after arthroscopic debridement. For those patients, arthroplasty provides reliable pain relief, whereas arthroscopy merely delays definitive reconstruction.

Surgical Decision-Making Pearls

From an academic reconstructive perspective, three fundamental rules govern the management of femoroacetabular impingement:

• Define the Target Morphology with Exact Radiographs: Standard anteroposterior pelvis views are inadequate in isolation. Always obtain a Dunn 45-degree or Dunn 90-degree lateral view to evaluate the anterior femoral head-neck junction where cam deformities predominate. An alpha angle exceeding 55 degrees confirms pathologic asphericity in a symptomatic joint.
• Respect the Femoral Neck Resection Margin: Over-resection of the femoral neck is a catastrophic error that predisposes the patient to post-arthroscopy femoral neck fracture. The osteochondroplasty resection must never exceed 30 percent of the femoral neck diameter. Intraoperative dynamic fluoroscopy or optical navigation confirms complete clearance without compromising cortical hoop strength.
• Prioritize Labral Refixation Over Debridement: The acetabular labrum provides a crucial fluid suction seal that distributes hydrostatic pressure across articular cartilage. Selective debridement should be restricted to degenerative, non-viable fraying. Whenever viable tissue exists, anatomically repair the labrum back to the acetabular rim using knotless or low-profile suture anchors.

The Bottom Line

The management of FAI has matured from speculative intervention into an evidence-based discipline. Level I randomized trials support arthroscopic osteochondroplasty for young patients with mechanical symptoms, defined cam or pincer deformities, and preserved joint space. Precision in patient selection remains the single most important variable: identify the deformity accurately, preserve the labral suction seal, and avoid operating on joints that have already progressed to advanced chondrosis.

How is your practice approaching borderline dysplasia with concomitant cam lesions? Review our complete clinical monograph and share your perspective: