What Is the Latest Update on Hip Impingement

1. High-Yield Summary

• Definition: Femoroacetabular impingement (FAI) syndrome is a motion-related clinical triad of abnormal osseous morphology (cam, pincer, or mixed), mechanical abutment between the proximal femur and acetabular rim, and reproducible motion-dependent hip pain.
• Clinical Hallmark: Deep anterior groin pain aggravated by prolonged sitting, deep flexion, and internal rotation, with a positive flexion-adduction-internal rotation (FADIR) provocative maneuver.
• Diagnostic Benchmarks: Alpha angle > 55° on 45° Dunn lateral radiographs indicates cam morphology; lateral center-edge angle (LCEA) > 40° or positive crossover sign indicates pincer retroversion/overcoverage.
• Management Standard: First-line personalized physiotherapy targeting hip abductor and core stabilization; failure of conservative care (> 3–6 months) warrants hip arthroscopic labral preservation/refixation and femoral osteochondroplasty.
• Critical Safety Principle: Femoral cam osteochondroplasty must preserve the lateral synovial retinaculum carrying the deep branch of the medial femoral circumflex artery (MFCA) to prevent avascular necrosis (AVN) of the femoral head.

2. Anatomy

The hip is a highly constrained ball-and-socket joint stabilized by the fibrocartilaginous acetabular labrum and the capsuloligamentous complex (iliofemoral, pubofemoral, and ischiofemoral ligaments). The acetabular labrum seals the joint fluid, increases effective acetabular depth by 20% to 30%, and dissipates cartilage contact stresses.

Internervous Planes & Danger Zones

Hip arthroscopic instrumentation utilizes standard anterolateral (AL), modified anterior (MAP), and mid-anterior portals placed through the internervous interval between the tensor fasciae latae (superior gluteal nerve) and the rectus femoris (femoral nerve):

• Lateral Femoral Cutaneous Nerve (LFCN): Traverses within 2 to 4 mm of the anterior portal; injury causes dysesthesia over the anterolateral thigh (meralgia paresthetica). Establishing the AL portal first under fluoroscopy and establishing the MAP under direct intra-articular visual guidance minimizes LFCN traction.
• Femoral Neurovascular Bundle: Lies approximately 3.5 to 4.0 cm medial to the modified anterior portal. Instrument trajectory must never deviate medial to the sagittal line through the anterior superior iliac spine (ASIS).
• Medial Femoral Circumflex Artery (MFCA): The deep branch courses posterosuperiorly along the femoral neck beneath the obturator externus tendon before penetrating the capsule at the posterolateral head-neck junction. Cam resection must be restricted to the anterior and anterosuperior quadrants (between 12 o’clock and 6 o’clock), strictly avoiding the posterior superior retinacular vessels.

3. Pathogenesis

FAI syndrome involves dynamic abutment between pathological osseous contours during terminal ranges of physiological motion:

• Cam Impingement: An aspherical prominence at the anterosuperior femoral head-neck junction (pistol-grip deformity) is driven into the acetabulum during flexion and internal rotation. This creates high shear stresses that peel the articular cartilage off the subchondral bone from the outside-in (chondrolabral delamination) before secondary labral detachment occurs.
• Pincer Impingement: General overcoverage (coxa profunda, acetabular protrusio) or focal cranial overcoverage (acetabular retroversion) causes the prominent acetabular rim to impact the normal femoral neck. This creates primary labral crushing, intrasubstance ossification, and secondary posteroinferior “contrecoup” chondral wear.
• Mixed Impingement: Coexistence of both cam asphericity and pincer overcoverage occurs in > 75% of clinical presentations.

4. Natural History

Asymptomatic cam and pincer morphologies are highly prevalent in active cohorts (present on plain radiographs in 20% to 35% of male athletes). However, in individuals with symptomatic FAI syndrome, repetitive mechanical abutment produces progressive chondral flap tears, subchondral cyst formation, and accelerated joint space narrowing. Longitudinal cohort studies demonstrate that an alpha angle > 65° confers an independent relative risk of 2.8 for developing moderate-to-severe hip osteoarthritis (Tönnis Grade ≥ 2) within 10 to 19 years.

5. Clinical Presentation

History

Patients are typically active adolescents or young adults (18–45 years old) presenting with insidious-onset anterior groin pain exacerbated by athletic pivots, deep squats, cutting maneuvers, or prolonged sitting (the “automobile sign”). Patients characteristically cup their hand over the anterolateral hip between the thumb and forefinger (the pathognomonic C-sign).

Physical Exam

A standardized bedside physical exam battery must be systematically performed:

• FADIR Test (Flexion, Adduction, Internal Rotation): Passive hip flexion to 90°, maximal adduction, and internal rotation -> Sharp anterior groin pain reproducing primary symptoms [Sensitivity 94%–99%, Specificity 10%–25%] (excellent screening test).
• FABER Test (Flexion, Abduction, External Rotation): Figure-four posture -> Pain located deep in the anterior groin confirms intra-articular pathology; posterior buttock pain suggests sacroiliac joint etiology [Sensitivity 82%, Specificity 58%].
• Log-Roll Test: Passive internal and external rotation of the supine extended leg -> True groin discomfort indicates active synovitis or joint irritability [Sensitivity 60%, Specificity 75%].
• Abductor Strength & Core Control: Assessment of Trendelenburg sign and single-leg squat dynamics, identifying abductor insufficiency and pelvic tilt dyskinesia.

6. Imaging and Diagnostic Studies

The diagnostic workup requires a precise radiographic and advanced imaging sequence:

• AP Pelvis Radiograph (Neutral Rotation & Tilt): Must demonstrate a 1.0 to 3.0 cm distance between the coccyx tip and the superior pubic symphysis to avoid false-positive retroversion. Evaluates lateral center-edge angle (LCEA; normal 25°–39°; pincer > 40°; dysplasia < 20°), Tönnis angle (< 0° = overcoverage), and the crossover sign (anterior wall crossing lateral to posterior wall).
• 45° and 90° Dunn Lateral Views: Essential for quantifying anterosuperior cam morphology. The alpha angle is calculated at the point where the femoral head contour departs from sphericity (normal ≤ 55°; borderline 56°–60°; pathological cam > 60°).
• Magnetic Resonance Arthrography (MRA) or High-Resolution 3.0T MRI: Evaluates labral tearing (chondrolabral junction separation), articular delamination, and subchondral edema. Radial sequence reconstructions perpendicular to the femoral head-neck axis provide 3D spatial mapping of the cam lesion.
• Diagnostic Intra-Articular Fluoroscopic Injection: Local anesthetic injection (> 80% immediate pain relief during provocative maneuvers) confirms that symptoms originate from intra-articular hip pathology rather than lumbar spine or sports hernia etiologies.

7. Classification

8. Treatment

Medical / Nonoperative

Initial therapy consists of a structured 12-week rehabilitation protocol focusing on pelvic stabilization, core neuromuscular retraining, strengthening of deep hip external rotators, and avoidance of deep provocative flexion/internal rotation. Activity modification and NSAIDs are employed adjunctively. If structured conservative therapy fails to achieve the minimum clinically important difference (MCID) on validated patient-reported outcomes after 3 to 6 months, surgical intervention is indicated.

Operative

Surgical management aims to eliminate mechanical impingement, restore physiological carpal/femoral kinematics, and preserve the acetabular labrum:

• Hip Arthroscopy (Standard of Care):
  • Labral Management: Anatomic labral refixation using knotless or knotted suture anchors (1.3 mm to 1.8 mm) placed on the acetabular rim. Primary labral repair demonstrates statistically superior survivorship and patient-reported outcomes compared to labral debridement.
  • Acetabular Rim Trimming: Conservative resection of the overcovering pincer rim using a motorized burr while preserving the native chondral-bone junction.
  • Femoral Cam Osteochondroplasty: Systematic reshaping of the anterosuperior femoral neck using a 4.0 mm or 5.5 mm motorized burr under dynamic fluoroscopy to restore normal offset and reduce the alpha angle to < 50°.
  • Capsular Closure: Complete repair of the interportal capsulotomy using braided sutures to preserve hip micro-stability and prevent iatrogenic anterior subluxation.
• Surgical Hip Dislocation (Ganz Approach): Indicated for complex multi-planar deformities, severe retroversion, or global pincer overcoverage with femoral head deformity where full 360° direct visualization is required.

Indications & Contraindications

Primary Indications: Persistent hip pain matching FAI clinical criteria, verified cam/pincer morphology on radiographs, failure of ≥ 3 months of conservative therapy, and preserved articular cartilage (joint space ≥ 2 mm, Tönnis Grade 0 or 1).
Contraindications: Advanced joint degeneration (Tönnis Grade ≥ 2, joint space < 2 mm); severe dysplasia (LCEA < 20° without concurrent periacetabular osteotomy); active infection; uncorrected skeletal immaturity.

9. Outcome

Level I randomized clinical trials (UK FASHIoN, Australian FAIT, and US trials) demonstrate that hip arthroscopy yields clinically and statistically significant improvements over non-operative physical therapy:

• Patient-Reported Outcomes: Mean International Hip Outcome Tool (iHOT-33) scores improve by an average of 25 to 30 points at 12 to 24 months, with > 75% of patients achieving the MCID threshold (6.1 points).
• Return to Athletic Competition: 82% to 88% of competitive athletes return to sport, with 75% returning to their pre-injury level of performance within 7 to 9 months postoperatively.
• Survivorship & Conversion: 10-year survivorship free from conversion to total hip arthroplasty (THA) exceeds 85% in patients with preserved baseline cartilage (Tönnis Grade 0), but plummets to < 50% in patients with pre-existing joint space narrowing < 2 mm.

10. Complications

11. Pearls and Pitfalls

• Dynamic Fluoroscopic Tracking: Do not rely solely on static views to gauge cam resection. Rotate the hip continuously under live fluoroscopy from 0° to 90° flexion with varying internal/external rotation to confirm a smooth, concave head-neck junction without residual shelf.
• Preserve the Chondrolabral Junction: When trimming acetabular rim overcoverage, use a fine motorized burr or osteotome from the capsular side to preserve the healthy chondrolabral transition rather than detaching pristine labrum.
• Avoid the Under-Resection Trap: The most common cause for revision hip arthroscopy (accounting for > 70% of revision cases) is persistent residual cam morphology, particularly at the 1 o’clock to 2 o’clock anterosuperior position.
• Respect Capsular Biology: Leaving a T-capsulotomy open causes persistent anterior translation, micro-instability, and accelerated capsular scarring. Routine interportal and T-capsulotomy suture repair restores normal joint biomechanics.

12. Controversy

Significant debate centers on the management of borderline hip dysplasia (LCEA 20°–25°) with concurrent cam morphology. Performing isolated arthroscopic cam resection and rim trimming in an under-covered hip destabilizes the joint and accelerates chondral failure. Multicenter cohorts currently debate whether borderline dysplasia warrants arthroscopic labral repair with aggressive capsular plication vs. simultaneous periacetabular osteotomy (PAO). Furthermore, while labral reconstruction using iliotibial band or semitendinosus autograft is increasingly favored for hypotrophic, ossified, or irreparable labra, long-term randomized comparisons against primary refixation remain under active investigation.

13. Evidence-Based Synthesis

Modern clinical decision-making for femoroacetabular impingement syndrome is grounded in high-quality multicenter randomized controlled trials comparing arthroscopic surgical preservation against structured physical therapy, supported by seminal morphological and biomechanical investigations.

14. References

• Griffin DR, Dickenson EJ, Wall PDH, et al. Hip arthroscopy versus best conservative care for the treatment of femoroacetabular impingement syndrome (UK FASHIoN): a multicentre randomised controlled trial. Lancet. 2018;391(10136):2225-2235. doi:10.1016/S0140-6736(18)31202-9 [Level I: Therapeutic Randomized Controlled Trial]
• Palmer AJR, Aiekens V, Allardice G, et al. Arthroscopic hip surgery compared with physiotherapy and activity modification for the treatment of femoroacetabular impingement: multicentre randomised controlled trial (FAIT). BMJ. 2019;364:l186. doi:10.1136/bmj.l185 [Level I: Therapeutic Randomized Controlled Trial]
• Beck M, Kalhor M, Leunig M, Ganz R. Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br. 2005;87(7):1012-1018. doi:10.1302/0301-620X.87B7.15203 [Level IV: Prognostic Case Series]
• Ganz R, Parvizi J, Beck M, Leunig M, Nötzli H, Siebenrock KA. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003;(417):112-120. doi:10.1097/01.blo.0000096804.78689.c2 [Level V: Expert Conceptual Review]

15. Master Class Pro-Tip

“When performing cam decompression at the anterosuperior head-neck junction, the greatest mistake is extending resection too far posteriorly into the lateral retinacular vascular corridor. Always locate the lateral synovial fold before powering the burr. Stop your osteochondroplasty 2 mm anterior to this fold. Furthermore, never gauge the depth of resection in a single plane; rotate the leg under direct visualization and dynamic fluoroscopy. If the hip does not glide effortlessly past 95° of flexion with 25° of internal rotation without labral impingement, your cam resection is incomplete.”

Master Class Surgical Pearl: Hip Preservation & Arthroscopy