Hip Arthroscopy: Beyond the "Clean Out"

Hip arthroscopy has evolved from a diagnostic curiosity to a powerhouse of modern orthopaedics. It is the gold standard for treating Femoroacetabular Impingement (FAI) and labral pathology. However, with great power comes great responsibility. The rapid expansion of hip arthroscopy has led to a new problem: the "failed hip scope."

Success in hip preservation is not about technical wizardry; it is about rigorous patient selection. This comprehensive guide covers the pathophysiology, diagnostic workup, and surgical principles required for the Fellowship exam.

Visual Element: A high-resolution 3D anatomical render of the hip joint, highlighting the labrum, the femoral neck junction (Cam zone), and the acetabular rim (Pincer zone).

Pathophysiology: The FAI Concept

Femoroacetabular Impingement (FAI) is a dynamic condition where bony morphology leads to abnormal contact forces, destroying the labrum and eventually the cartilage.

1. Cam Impingement (The Femoral Side)

• Mechanism: An aspherical femoral head-neck junction (loss of femoral offset). The "Cam" acts like a cam-shaft, grinding into the acetabulum during flexion and internal rotation.
• The Damage: Delamination of the acetabular cartilage (chondrolabral junction). This is a "shear" injury.
• Patient: Typically young, active males.

2. Pincer Impingement (The Acetabular Side)

• Mechanism: Over-coverage of the femoral head. Can be focal (retroversion) or global (coxa profunda/protrusio).
• The Damage: The femoral neck hits the labrum, crushing it against the rim. "Linear" damage.
• Patient: Typically middle-aged females.

3. Mixed Impingement

• The most common presentation (approx. 80% of cases).

Visual Element: Side-by-side diagrams comparing the mechanics of Cam (Shear force) vs Pincer (Crush force) damage on the labrum.

Clinical Assessment

History

• Pain: Groin pain (C-sign). Worse with sitting, putting on socks/shoes (flexion).
• Mechanical Symptoms: Clicking, catching, locking.

Physical Exam

• FADIR Test (Flexion, Adduction, Internal Rotation): The sensitive screening test. Recreates the impingement. Pain = Positive.
• FABER Test (Flexion, Abduction, External Rotation): Assess the distance of knee to table. Pain posterior = SI joint; Pain anterior = Hip capsule/Iliposoas.
• Gait: Look for Trendelenburg or antalgic gait.

Imaging Workup

X-Ray Series (The Foundation)

You cannot scope a hip without plain films.

1. AP Pelvis: Assess joint space (must be >2mm), LCEA (Lateral Center Edge Angle - Normal 25-40°), Cross-over sign (Retroversion).
2. Dunn View (45° or 90°): The money view for the Cam lesion (Alpha angle > 55°).

MRI / MRA

• Labrum: Look for detachment or intrasubstance tear.
• Cartilage: This is the prognostic factor. Look for delamination.
• Measurement: Alpha angle can be measured on oblique axial cuts.

The "Grey Zone": Borderline Dysplasia and Early OA

The most common cause of failed hip arthroscopy is operating on arthritis or dysplasia.

Tönnis Classification of OA:

• Grade 0: Normal.
• Grade 1: Sclerosis, minor cystic changes. (Caution).
• Grade 2: Joint space narrowing. (Contraindication).
• Grade 3: Bone on bone. (Absolute Contraindication).

Clinical Pearl: If the joint space is < 2mm, hip arthroscopy outcomes are no better than placebo at 2 years, and 80% convert to THA within 3 years.

Surgical Techniques

Setup and Access

• Traction: Essential to distract the joint (10-12mm). Risk of pudendal neurapraxia (limit time < 2 hours).
• Portals: Anterolateral (AL) and Mid-anterior (MA) are standard. Modified Anterolateral (MAP) used for anchor placement.
• Capsulotomy: Interportal capsulotomy to access the central compartment.

1. The Central Compartment (Labrum)

• Debridement: Only for frayed, irreparable tissue (rarely done now).
• Repair: The gold standard. Using suture anchors to re-fix the labrum to the rim. Restores the "suction seal."
• Reconstruction: Using allograft or autograft (ITB) if the labrum is calcified or nonexistent.

2. The Peripheral Compartment (Bone)

• Acetabuloplasty: Trimming the Pincer (rim trimming). Caution: Do not take too much (instability).
• Femoro-plasty: Resecting the Cam bump. The goal is to restore the head-neck offset. Verified with dynamic exam on table.

3. Capsular Management

• Closure: The capsule MUST be closed in most cases, especially in borderline dysplasia or hyperlaxity. Failure to close leads to micro-instability.

Visual Element: Intraoperative photos showing: 1. Labral tear, 2. Anchor placement, 3. Completed repair with restored suction seal.

Rehabilitation: The Long Road

Patient expectations must be managed. This is not a "quick scope."

• Phase 1 (0-4 weeks): Protection. Crutches (20kg weight bearing). Limit flexion > 90°. Anti-rotation boots.
• Phase 2 (4-12 weeks): Activation. Gluteal strengthening. Core stability. Normalizing gait.
• Phase 3 (3-6 months): Sport specific. Running program.
• Return to Sport: Average 6-9 months for elite athletes.

Complications

• Neuropraxia: Pudendal (traction) or Lateral Femoral Cutaneous Nerve (portal placement). Most resolve.
• Heterotopic Ossification: Prophylaxis with NSAIDs (Indomethacin/Naproxen) for 3 weeks is standard.
• Instability: Iatrogenic due to excessive rim trimming or failure to close capsule.
• Femoral Neck Fracture: Rare (<1%) but disastrous. Avoid excessive resection of the Cam (keep depth < 30% of neck diameter).

Evidence Corner

• FASHIoN Trial (UK, 2018): RCT Hip Arthroscopy vs Personalised Hip Therapy. Surgery showed superior improvement in iHOT-33 scores at 12 months.
• FAIT Trial (2019): Surgery vs Physio. Surgery significantly better for pain and function.

Summary

Hip arthroscopy is a precise procedure for a specific mechanical problem (FAI). It is NOT a treatment for hip pain "NOS" (Not Otherwise Specified).

• Good Candidate: Young, Cam lesion, good cartilage, mechanical symptoms.
• Bad Candidate: >45 years, joint space narrowing, dysplasia, chronic pain > 2 years.

Related Topics:

• Periacetabular Osteotomy (PAO)
• Total Hip Arthroplasty in the Young Patient
• Hip Anatomy & Biomechanics
• Extra-articular Hip Endoscopy (Gluteus Medius Repair)