Residency · Residency · Orthopedic Surgery

Femoroacetabular Impingement and Labral Tears

Introduction

Femoroacetabular impingement (FAI) is a motion-related clinical disorder of the hip caused by abnormal morphology of the femoral head-neck junction or the acetabulum, leading to premature contact during hip motion. FAI is increasingly recognized as a significant cause of hip pain in young, active adults and a precursor to early-onset hip osteoarthritis. Labral tears are intimately associated with FAI and contribute to pain, mechanical symptoms, and progressive joint degeneration.

Anatomy of the Labrum

The acetabular labrum is a fibrocartilaginous rim that deepens the acetabular socket by approximately 22%, increasing hip stability. It provides a suction seal effect that maintains negative intra-articular pressure and distributes synovial fluid. The vascular supply comes from the obturator, superior gluteal, and inferior gluteal arteries, with the periphery being vascularized and the free margin avascular. The labrum is thinnest and most frequently torn anterosuperiorly, in the 2 o'clock to 12 o'clock position.

Types of Femoroacetabular Impingement

Cam Impingement

Cam impingement is caused by an aspherical femoral head or decreased head-neck offset that creates a bump (cam lesion) at the anterolateral head-neck junction. During flexion and internal rotation, the cam lesion shears into the acetabulum, causing outside-in labral damage with delamination of articular cartilage from the acetabular rim. It is more common in young males and athletes. An alpha angle greater than 55 degrees on cross-sectional imaging suggests cam morphology.

Pincer Impingement

Pincer impingement results from acetabular overcoverage that crushes the labrum between the acetabular rim and the femoral neck. The overcoverage may be focal (retroversion) or global (coxa profunda, protrusio acetabuli). It leads to labral degeneration and eventual ossification, with contrecoup cartilage damage potentially occurring posteroinferiorly. It is more common in middle-aged females and is assessed with a lateral center-edge angle greater than 40 degrees and the presence of a crossover sign on the AP pelvis.

Mixed Type

Most patients, exceeding 85%, have features of both cam and pincer impingement with combined morphology and overlapping pathomechanics.

Clinical Presentation

Anterior groin pain is the hallmark complaint, exacerbated by prolonged sitting, deep flexion, pivoting, and sport. The pain is typically described as deep and activity-related with an insidious onset. The C-sign, in which the patient cups the hand around the lateral hip and groin to describe the pain location, is characteristic. Clicking, catching, or locking may indicate labral pathology, and loss of internal rotation in flexion is common.

Physical Examination

The FADIR test (flexion, adduction, internal rotation) is the most sensitive provocative test, reproducing anterior impingement pain. The FABER test (flexion, abduction, external rotation) assesses for posterior impingement and SI joint pathology. Internal rotation in 90 degrees of flexion is typically limited to less than 15 degrees. The log roll test assesses for intra-articular pathology, being positive if painful with passive internal or external rotation. Hip flexor tightness (Thomas test) and compensatory lumbar hyperlordosis should also be assessed.

Imaging

An AP pelvis radiograph assesses the lateral center-edge angle, Tonnis angle, crossover sign (retroversion), posterior wall sign, and ischial spine sign. The Dunn lateral view at 45 or 90 degrees provides the best radiographic assessment of the cam lesion and alpha angle. MRI with radial sequences or MR arthrography is the gold standard for labral tears, with sensitivity of 90 to 95%, and also assesses chondral delamination, labral morphology, and paralabral cysts. CT with 3D reconstruction is useful for surgical planning of bony morphology.

Nonoperative Management

Activity modification to avoid provocative positions (deep flexion and internal rotation), physical therapy with core and hip girdle strengthening and correction of muscle imbalances (avoiding aggressive stretching into impingement), NSAIDs for symptom management, and intra-articular injections for both diagnostic and therapeutic purposes constitute the nonoperative approach. Significant pain relief from injection supports intra-articular pathology as the source of symptoms. Nonoperative management is appropriate initial treatment for mild symptoms, though outcomes are variable when structural pathology persists.

Surgical Management

Hip Arthroscopy

Hip arthroscopy is the most common surgical approach for FAI and labral tears. Cam resection (femoroplasty) reshapes the femoral head-neck junction to restore sphericity, with fluoroscopy used to confirm adequate resection and avoid femoral neck fracture. Pincer correction (acetabuloplasty) involves rim trimming to reduce overcoverage. Labral repair using suture anchor fixation to restore the labral seal and function is the standard of care and is superior to debridement. Labral reconstruction is indicated for irreparable labra, using autograft (IT band, ligamentum teres) or allograft. Routine capsular closure is recommended to prevent postoperative instability.

Open/Mini-Open Surgical Hip Dislocation

Open approaches are indicated for extensive cam lesions, combined procedures, or revision cases. The Ganz surgical hip dislocation uses a trochanteric flip osteotomy with Z-shaped capsulotomy, providing full circumferential access. It carries higher morbidity but allows treatment of posterior and global pathology.

Outcomes and Prognosis

Hip arthroscopy for FAI demonstrates 85 to 90% good-to-excellent outcomes at 5 years in appropriately selected patients. Predictors of poor outcomes include Tonnis grade greater than 1, joint space less than 2 mm, age over 40, elevated BMI, and prolonged symptom duration. Incomplete cam resection is the most common cause of revision arthroscopy. Whether successful FAI treatment delays or prevents progression to osteoarthritis remains an area of ongoing study.

Clinical Pearls

FAI is a motion-related clinical disorder requiring both abnormal morphology and symptoms; morphology alone is not an indication for surgery. The FADIR test is the most sensitive provocative maneuver for anterior impingement. Cam lesions cause outside-in chondral damage, while pincer lesions crush the labrum with contrecoup posterior cartilage injury. Labral repair is preferred over debridement to restore the suction seal and improve outcomes. Joint space narrowing (Tonnis grade 2 or greater) is a relative contraindication to arthroscopic treatment.

References

1. Griffin DR, Dickenson EJ, O'Donnell J, et al. "The Warwick Agreement on Femoroacetabular Impingement Syndrome (FAI Syndrome): An International Consensus Statement." British Journal of Sports Medicine. 2016;50(19):1169-1176.
2. Domb BG, Stake CE, Botser IB, Harris TJ. "Surgical Dislocation of the Hip Versus Arthroscopic Treatment of Femoroacetabular Impingement: A Prospective Matched-Pair Study." Arthroscopy. 2013;29(12):1506-1513.
3. Minkara AA, Westermann RW, Rosneck J, Lynch TS. "Systematic Review and Meta-Analysis of Outcomes After Hip Arthroscopy in Femoroacetabular Impingement." American Journal of Sports Medicine. 2019;47(2):488-500.
4. Nepple JJ, Prather H, Trousdale RT, et al. "Clinical Diagnosis of Femoroacetabular Impingement." Journal of the American Academy of Orthopaedic Surgeons. 2013;21(Suppl 1):S16-S19.

For the intern

At 3am, Femoroacetabular Impingement (FAI) and labral tears are rarely emergencies. If you're called about anterior hip pain in a young patient post-operatively, assess for compartment syndrome (unlikely but catastrophic), neurovascular compromise, or infection signs. Otherwise, manage pain with NSAIDs and let it wait for morning rounds. New presentations of chronic groin pain can be scheduled outpatient—these patients have had symptoms for months to years. Your main role overnight is ruling out acute hip pathology like septic arthritis (fever, inability to bear weight, elevated inflammatory markers) or fracture, which present differently than FAI.

Common pitfalls

• Treating imaging findings instead of clinical syndrome: Many asymptomatic athletes have cam or pincer morphology on imaging. Surgery is indicated only when abnormal morphology causes symptoms—don't recommend arthroscopy based on an incidental finding from a CT done for another reason.

• Missing advanced arthritis as a contraindication: Check the joint space width carefully. Tönnis grade 2 or higher (joint space <2mm) predicts poor arthroscopic outcomes. These patients need hip preservation counseling or arthroplasty discussion, not FAI correction.

• Forgetting the contrecoup injury pattern: In pincer impingement, the labrum gets crushed anteriorly, but cartilage damage occurs posteroinferiorly from the femoral head levering backward. Always assess the entire joint.

• Inadequate cam resection: This is the most common reason for revision surgery. Fluoroscopy confirms adequate sphericity restoration intraoperatively.

<image>Simple decision algorithm with three panels: Panel 1 shows "Young adult with anterior groin pain" branching based on physical exam (positive FADIR test vs negative). Panel 2 shows the positive FADIR pathway leading to AP pelvis and MR arthrography, identifying cam lesion, pincer morphology, or labral tear. Panel 3 shows treatment decision tree: if Tönnis grade 0-1 and joint space >2mm, proceed to arthroscopy (cam resection, acetabuloplasty, labral repair); if Tönnis grade ≥2 or joint space <2mm, consider hip preservation alternatives or arthroplasty discussion. Include arrow showing nonoperative management (PT, activity modification, NSAIDs) as initial treatment before surgery.</image>

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