Hip Arthroscopy

Hip arthroscopy is a minimally invasive surgical technique for diagnosing and treating intra-articular and periarticular hip pathology. The primary indication is femoroacetabular impingement (FAI) with associated labral tears, though indications continue to expand.

Epidemiology of FAI:

• Imaging morphology is common and often asymptomatic: a systematic review of 2114 asymptomatic hips found cam morphology in 37% overall - 54.8% in athletes versus 23.1% in the general population (Frank 2015)
• Symptomatic FAI (FAI syndrome): Presents in athletes and active individuals, typically 20-45 years; diagnosis requires symptoms plus signs plus imaging (Warwick Agreement 2016)
• Sex distribution: Cam more common in males; Pincer more common in females; Mixed most common overall
• Athletic association: High-risk flexion-loading sports include ice hockey, football/soccer, martial arts, ballet and Australian Rules football

Pathophysiology:

• Cam mechanism: Aspherical femoral head-neck junction causes outside-in abrasion of acetabular cartilage during flexion and internal rotation. The abnormal convexity shears against the labrum and cartilage.
• Pincer mechanism: Acetabular overcoverage causes labral crush injury and countrecoup lesions on posterior acetabulum. Overcoverage may be global (coxa profunda) or focal (acetabular retroversion).
• Natural history: Untreated FAI leads to progressive cartilage damage and eventual osteoarthritis

Indications for Hip Arthroscopy:

• Femoroacetabular impingement (cam, pincer, or mixed)
• Labral tears
• Chondral lesions (debridement, microfracture)
• Ligamentum teres tears
• Loose bodies
• Synovial disorders (PVNS, synovial chondromatosis)
• Hip instability (capsular plication)
• Iliopsoas tendon release

Hip Joint Anatomy: The hip is a ball-and-socket joint with inherent bony stability enhanced by the acetabular labrum, capsule, and ligaments. The femoral head is covered by hyaline cartilage except at the fovea (ligamentum teres attachment).

Labrum:

• Fibrocartilaginous ring attached to the acetabular rim
• Deepens the acetabulum by 21% and increases surface area by 28%
• Creates a suction seal that provides joint stability
• Blood supply from superior gluteal, inferior gluteal, and obturator vessels
• Vascularity is better peripherally than centrally (important for repair)

Capsule and Ligaments:

• Iliofemoral ligament (Y-ligament of Bigelow): strongest ligament, anterior
• Pubofemoral ligament: inferior, limits abduction
• Ischiofemoral ligament: posterior, limits internal rotation
• Zona orbicularis: circular fibers around femoral neck

Neurovascular Structures:

• Femoral neurovascular bundle: anterior, protected by iliopsoas
• Lateral femoral cutaneous nerve: crosses 1-2cm distal and medial to ASIS
• Superior gluteal nerve: exits above piriformis, at risk with proximal portals
• Sciatic nerve: posterior, at risk with traction and posterior portals

FAI Pathoanatomy:

Cam Morphology:

• Abnormal bump at femoral head-neck junction (anterosuperior most common)
• Results from developmental abnormality during skeletal maturation
• Alpha angle greater than 55° is diagnostic
• Causes outside-in cartilage abrasion during flexion/internal rotation

Pincer Morphology:

• Acetabular overcoverage (global or focal)
• Center-edge angle greater than 40° suggests overcoverage
• Crossover sign on AP pelvis indicates focal retroversion
• Causes labral crush injury and countrecoup posterior cartilage damage

Femoroacetabular Impingement Classification:

Labral Tear Classification (Seldes):

• Type 1: Detachment of labrum from acetabular cartilage (most common)
• Type 2: Cleavage plane within labral substance

Beck Cartilage Damage Classification:

• Grade 0: Normal cartilage
• Grade 1: Softening (malacia)
• Grade 2: Partial thickness defect
• Grade 3: Full thickness defect
• Grade 4: Exposed subchondral bone

Acetabular Rim Classification:

• Focal pincer: Retroversion of superior acetabulum
• Global pincer: Coxa profunda/protrusio acetabuli

History:

Physical Examination:

Differential Diagnosis of Young-Adult Groin / Hip Pain:

Because cam and pincer morphology is common in asymptomatic people (37% asymptomatic cam in athletes/general population; Frank 2015), FAI syndrome is a clinical diagnosis of exclusion as much as inclusion. Actively exclude these mimics before attributing pain to impingement.

Plain Radiographs:

MRI and MR Arthrogram:

Standard MRI: Evaluates labrum, cartilage, and periarticular soft tissues. Axial oblique views best for alpha angle measurement.

MR Arthrogram: Gold standard for labral pathology. Intra-articular gadolinium improves labral tear detection. Sensitivity greater than 90% for labral tears.

Radial MRI: Series of views radiating from femoral neck axis. Best for comprehensive assessment of cam lesion location.

CT Scan:

3D CT: Provides excellent bony detail of cam and pincer morphology. Useful for surgical planning. Less radiation with low-dose protocols.

Diagnostic Injection:

Intra-articular injection of local anesthetic under fluoroscopic guidance can confirm intra-articular source of pain. Greater than 50% pain relief suggests intra-articular pathology.

Indications for Non-Operative Treatment:

• Mild symptoms with minimal functional limitation
• Patient preference
• Significant osteoarthritis (relative contraindication to arthroscopy)
• Medical contraindications to surgery
• Initial management while diagnosis is being confirmed

Non-Operative Protocol:

Algorithm

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Decision-Making Framework for Hip Arthroscopy:

Key Decision Points:

1. Joint space greater than 2mm → Good candidate for arthroscopy
2. Joint space less than 2mm with arthritis → Consider arthroplasty
3. Positive impingement test + positive injection → Best outcomes
4. Mixed FAI → Must address both components

Patient Positioning:

Traction and Joint Access:

Traction Requirements:

• Force: 25-50 pounds typically needed
• Technique: Apply longitudinal traction, then internal rotation to break vacuum seal
• Confirmation: Fluoroscopic confirmation of 6mm distraction minimum
• Time limit: Maximum 2 hours - release if prolonged case

Portal Establishment:

Standard Portals:

• Anterolateral (AL): Primary viewing portal, 1cm anterior and superior to greater trochanter tip
• Anterior: Primary working portal, intersection of ASIS horizontal line and GT vertical line
• Posterolateral (PL): 1cm posterior and superior to GT, supplementary viewing/working

Technique: Establish portals under fluoroscopic guidance with air arthrogram. Use spinal needle to confirm trajectory. Make skin incision, then blunt trocar insertion to avoid nerve injury.

Central Compartment Procedures:

• Labral repair: Suture anchors for peripheral labral tears
• Labral debridement: For non-repairable tears
• Acetabular rim trimming: For pincer lesions
• Microfracture: For focal cartilage defects
• Ligamentum teres debridement: For symptomatic tears
• Loose body removal

Peripheral Compartment Procedures:

• Osteochondroplasty: Cam lesion resection to restore head-neck offset
• Capsulotomy management: Repair or plication as needed
• Iliopsoas release: If symptomatic internal snapping hip

Nerve Injuries:

Other Complications:

In the largest prospective multicentre series (1615 hips), the overall complication rate was 8.3% with mostly low-grade events; rates below are from that series unless stated otherwise (Larson 2016).

• Fluid extravasation: Risk of abdominal compartment syndrome with prolonged cases (no extra-abdominal extravasation observed in the 1615-hip series)
• Femoral neck fracture / stress fracture: 0.1%; risk from excessive osteochondroplasty (avoid resecting more than ~30% of neck circumference)
• Instability: From excessive rim trimming or unrepaired capsulotomy (no iatrogenic instability in the 1615-hip series)
• Iatrogenic chondral injury: 1.2%; iatrogenic labral puncture: 0.9%
• Heterotopic ossification: 0.8%; NSAID prophylaxis reduces incidence
• Avascular necrosis: Rare (none in the 1615-hip series), associated with lateral epiphyseal vessel damage
• Superficial portal infection: 1.1%
• DVT 0.1% / PE 0.1%: Standard VTE risk-stratified prophylaxis

Post-Operative Protocol:

Procedure-Specific Considerations:

Labral repair:

• Protect repair for 4-6 weeks with ROM restrictions
• Avoid FADIR position during healing
• Full return to sport: 4-6 months

Microfracture:

• Protected weight-bearing 6-8 weeks
• CPM encouraged for cartilage healing
• Return to sport: 6-12 months

Osteochondroplasty alone:

• Earlier weight-bearing (2 weeks)
• Less ROM restriction needed
• Return to sport: 3-4 months

Short-Term Outcomes:

• Patient satisfaction: 85-90% satisfaction at 2 years
• Return to sport: 80-90% return to sport, 70-80% at same level
• Pain improvement: Significant improvement in pain scores (70-80% reduction)
• Functional improvement: Improved modified Harris Hip Score in 85%+

Long-Term Outcomes:

Prognostic Factors:

Favorable:

• Young age (less than 40 years)
• Minimal osteoarthritis (Tonnis 0-1)
• Preserved joint space (greater than 2mm)
• Labral repair (vs debridement)
• Positive injection response pre-operatively

Unfavorable:

• Advanced osteoarthritis
• Joint space less than 2mm
• Full-thickness cartilage loss
• Age greater than 50 years
• Significant acetabular dysplasia

Borderline Dysplasia:

• Center-edge angle 20-25° is borderline
• May benefit from arthroscopy if FAI component present
• Higher failure rate than non-dysplastic hips
• Consider periacetabular osteotomy (PAO) if significant dysplasia

Revision Hip Arthroscopy:

• Success rates lower than primary (60-70%)
• Most common reasons for failure: inadequate cam resection, missed pincer, untreated labral tear
• Better outcomes if clear identifiable pathology for revision

Hip Arthroscopy in Adolescents:

• FAI morphology develops during skeletal maturation
• Arthroscopy may be considered in skeletally mature adolescents
• Must ensure physes are closed before aggressive osteochondroplasty

Labral Reconstruction:

• Indicated when labrum is deficient and cannot be repaired
• Options: iliotibial band autograft, tensor fascia lata, allograft
• Emerging technique with promising early results

Associated Hip Instability:

• Can result from excessive capsulotomy or rim trimming
• Capsular plication may be needed
• Important to balance impingement correction with stability preservation

Global epidemiology. FAI morphology is common and frequently asymptomatic, so imaging must always be correlated with symptoms and signs. A PRISMA systematic review of 2114 asymptomatic hips (mean age 25 years) found asymptomatic cam morphology in 37% overall - 54.8% in athletes versus 23.1% in the general population - and the mean alpha angle in asymptomatic hips was 54° (Frank 2015). This is the single most important framing fact: morphology alone is not disease.

The diagnosis is a triad, not a radiograph. The 2016 Warwick Agreement (international consensus, 25 endorsing societies) introduced the term FAI syndrome, requiring symptoms + clinical signs + imaging findings together. Imaging morphology without symptoms is not FAI syndrome and should not be treated (Warwick 2016).

Guidance side by side

Patient selection drives outcome (global, evidence-led). Across health systems the same predictors apply: preserved joint space (2mm or more) and labral repair predict better results, while advanced arthritis (Tönnis 2 or more) and joint space less than 2mm predict failure and conversion to total hip replacement (Philippon 2009). The decisive modifiable intra-operative safety factor is traction - time greater than 60 minutes raises the complication rate (Larson 2016).

Registries and practice variation. Hip arthroscopy is a hip-preservation rather than an arthroplasty procedure, so it is not captured by the major joint replacement registries (NJR England & Wales, AOANJRR Australia, AJRR USA, SHAR Sweden). These registries are nonetheless relevant downstream: a meaningful minority of arthroscopy patients with pre-existing chondral wear later convert to total hip arthroplasty, and registry analyses are used to compare outcomes of THA after prior hip arthroscopy. Volume and access vary widely - arthroscopy is concentrated in high-resource centres with fluoroscopy and traction tables and a learning curve effect on complications, whereas in many regions open surgical hip dislocation or non-operative care predominate. FAI syndrome is recognised worldwide in flexion-loading sports (football/soccer, ice hockey, Australian Rules football, dance, martial arts), reflecting the higher cam prevalence seen in athletes.