Hip Arthroscopy: Beyond the "Clean Out"

Hip arthroscopy has evolved from a diagnostic curiosity and "clean out" procedure to a powerhouse of modern orthopaedics. Over the last two decades, it has become the gold standard for treating Femoroacetabular Impingement (FAI) syndrome and associated labral pathology. However, with great power comes great responsibility. The rapid expansion and popularization of hip arthroscopy have led to a new and challenging problem for revision arthroplasty and preservation surgeons alike: the "failed hip scope."

Success in hip preservation surgery is not primarily about technical wizardry or mastering complex portal placements; it is fundamentally about rigorous patient selection and recognizing the limits of the procedure. Operating on the wrong patient—specifically those with unrecognized dysplasia or established osteoarthritis—will reliably lead to early failure and conversion to a Total Hip Arthroplasty (THA).

This comprehensive guide covers the pathophysiology, diagnostic workup, decision-making algorithms, and surgical principles required for both safe clinical practice and success in your orthopaedic surgery fellowship exams.

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

Pathophysiology: The FAI Concept

Pioneered by Reinhold Ganz and colleagues in the early 2000s, Femoroacetabular Impingement (FAI) is a dynamic, mechanical condition where abnormal bony morphology leads to pathological contact forces during terminal hip motion. This repetitive microtrauma progressively destroys the acetabular labrum and, crucially, the adjacent articular cartilage. FAI is now recognized as a leading cause of early-onset osteoarthritis in the non-dysplastic hip.

1. Cam Impingement (The Femoral Side)

• Mechanism: Characterized by an aspherical femoral head-neck junction, representing a loss of the normal femoral offset. As the hip is brought into flexion and internal rotation, this prominent "Cam" bump acts like a cam-shaft, forcefully entering the joint and grinding into the acetabulum.
• The Damage: This creates an outside-in shear force that causes delamination of the acetabular cartilage from the subchondral bone, typically at the anterosuperior chondrolabral junction. The labrum is often detached from the cartilage (the "car-bumper" effect) but may remain macroscopically intact initially.
• Patient Profile: Typically young, active males, often involved in sports requiring deep flexion and rotation (ice hockey, soccer, martial arts). Often associated with silent or subclinical Slipped Capital Femoral Epiphysis (SCFE) during adolescence.

2. Pincer Impingement (The Acetabular Side)

• Mechanism: Characterized by over-coverage of the femoral head by the acetabulum. This can be focal (e.g., cranial retroversion) or global (e.g., coxa profunda or protrusio acetabuli).
• The Damage: During motion, the normal femoral neck strikes the overhanging acetabular rim. This creates a crush injury directly to the labrum. The forces are linear, often causing intra-substance labral tearing or ossification of the labrum. A "contre-coup" cartilage lesion may also develop in the posteroinferior acetabulum due to the femoral head being levered posteriorly during anterior impingement.
• Patient Profile: Typically middle-aged females, though cranial retroversion is seen across all demographics.

3. Mixed Impingement

• The most common presentation by far. Approximately 80% of patients with symptomatic FAI possess elements of both Cam and Pincer morphology. Treating only one component during surgery is a common cause of persistent postoperative pain.

Clinical Assessment: The Foundation of Patient Selection

A meticulous history and physical examination are your first defenses against the "failed hip scope." You must differentiate intra-articular hip pathology from extra-articular sources (lumbar spine, SI joint, core muscle injuries/athletic pubalgia, and extra-articular snapping hips).

History

• Pain Characteristics: The classic presentation is insidious onset, activity-related anterior groin pain. Patients frequently demonstrate the C-sign, cupping their hand over the greater trochanter with the thumb posterior and fingers deep in the anterior groin.
• Exacerbating Factors: Pain is characteristically worse with prolonged sitting, driving, or putting on socks and shoes (activities requiring deep hip flexion).
• Mechanical Symptoms: Patients often report clicking, catching, locking, or a feeling of giving way, which heavily suggests a labral tear or loose body.

Physical Exam

• Gait: Observe for an antalgic gait or an abductor lurch (Trendelenburg gait), which might suggest gluteus medius/minimus pathology rather than intra-articular disease.
• Range of Motion: Typically, FAI patients have restricted Internal Rotation (IR) in 90 degrees of flexion (often < 10 degrees).
• FADIR Test (Flexion, Adduction, Internal Rotation): The most sensitive screening test for anterosuperior intra-articular pathology. The examiner passively moves the hip into this position to recreate the mechanical impingement. Reproduction of the patient's specific groin pain constitutes a positive test. (Highly sensitive, poorly specific).
• FABER Test (Flexion, Abduction, External Rotation): Also known as Patrick's test. Assess the distance of the lateral knee to the exam table compared to the contralateral side.
  • Interpretation: Anterior groin pain suggests hip capsule/iliopsoas pathology. Posterior pain points toward the Sacroiliac (SI) joint.
• Stinchfield Test (Resisted Straight Leg Raise): With the patient supine, they actively elevate the leg to 30 degrees against resistance. Anterior groin pain strongly implicates the hip joint or iliopsoas.
• Dial Test & Log Roll: Assess for capsular laxity and generalized hypermobility (always calculate a Beighton score).

Imaging Workup: Precision is Mandatory

The radiographic assessment of the young adult hip requires perfectly positioned, standardized views. You cannot safely scope a hip without high-quality plain films.

Plain Radiographs (The Foundation)

1. AP Pelvis: Must be strictly standardized (tip of coccyx pointing to symphysis pubis, 1-2 cm distance between them).
   • Assess: Joint space (must be > 2mm throughout).
   • Dysplasia: Measure the Lateral Center Edge Angle (LCEA - Normal is 25-40°). Calculate the Tönnis angle (Normal 0-10°).
   • Version: Look for the "Cross-over sign," "Ischial spine sign," and "Posterior wall sign" to diagnose focal acetabular retroversion.
2. Dunn View (45° or 90°) or Modified Cross-Table Lateral: These are the "money views" for evaluating the anterolateral femoral head-neck junction, where Cam lesions predominantly reside.
   • Measure: The Alpha angle (Normal is generally considered < 50-55°). An increased alpha angle indicates loss of concavity and presence of a Cam bump.
3. False Profile View (Lequesne): Essential for evaluating anterior acetabular coverage (Anterior Center Edge Angle) and detecting early joint space narrowing in the anterosuperior quadrant, which is often missed on an AP pelvis.

Advanced Imaging: MRI / MRA and CT

• MRI / MR Arthrogram (MRA): MRA is traditionally the gold standard for detecting labral tears and evaluating the articular cartilage. Look for labral detachment, intra-substance tearing, or paralabral cysts. Crucially, scrutinize the anterosuperior acetabular cartilage for signs of delamination or thinning. 3T non-contrast MRI with radial sequences is increasingly replacing MRA in specialized centers.
• 3D CT Scan: Many hip preservation surgeons now consider a low-dose 3D CT scan essential for preoperative planning. It provides a comprehensive 360-degree map of the Cam deformity and accurately measures femoral version and acetabular version, which cannot be fully appreciated on plain films.

The "Grey Zone": Borderline Dysplasia and Early OA

The absolute most common cause of failed hip arthroscopy is violating the indications regarding arthritis or dysplasia. Surgical decision-making in the "grey zone" separates the master surgeon from the novice.

The Osteoarthritis Cut-off

Hip arthroscopy is a preservation operation, not a salvage operation. Operating on a hip with established osteoarthritis will accelerate the disease process.

Tönnis Classification of OA:

• Grade 0: Normal joint space, no signs of OA. (Ideal candidate).
• Grade 1: Sclerosis of head or acetabulum, minor osteophytes, slight joint space narrowing. (Proceed with caution; counsel patient heavily on guarded prognosis).
• Grade 2: Small cysts, moderate joint space narrowing, moderate loss of sphericity. (Contraindication for isolated arthroscopy).
• Grade 3: Large cysts, severe narrowing or obliteration of joint space (bone-on-bone), severe deformity. (Absolute Contraindication).

The 2mm Rule: If the joint space on the AP Pelvis or False Profile view is < 2mm at any point, hip arthroscopy outcomes are demonstrably poor. Studies show these patients fare no better than a placebo at 2 years, and up to 80% will convert to a Total Hip Arthroplasty within 3 to 5 years. Do not offer a scope; offer a THA.

Patient Age

Chronological age is less important than physiological age and cartilage status, but outcomes generally begin to decline in patients over 40, and drop precipitously in those over 50, primarily due to unrecognized chondral wear.

Surgical Techniques: Principles of the Procedure

Hip arthroscopy is technically demanding. It involves working in a tight, deep joint enveloped by a thick, robust capsule.

Setup and Access

• Positioning: Supine or lateral decubitus, depending on surgeon preference.
• Traction: Essential to distract the joint enough to safely introduce instruments (typically 10-12mm of distraction is required).
  • The Perineal Post: Historically used to provide counter-traction, but carries a high risk of pudendal neuropraxia. The modern trend is moving toward "post-less" traction systems utilizing a friction pad, dramatically reducing groin soft-tissue complications.
  • Time Limit: Traction time should be strictly limited to under 2 hours (ideally < 90 minutes) to prevent nerve injury.
• Portals: The Anterolateral (AL) and Mid-anterior (MA) portals are the workhorses. The Modified Anterolateral Portal (MAP) or Distal Anterolateral Accessory (DASA) are frequently added to optimize the angle for suture anchor placement along the acetabular rim.
• Capsulotomy: An interportal capsulotomy (connecting the AL and MA portals) is standard to open the joint and access the central compartment. A T-capsulotomy extending distally down the femoral neck may be required for large Cam lesions, but necessitates rigorous closure later.

1. The Central Compartment (Labrum and Cartilage)

Once in the joint, the labrum, cartilage, and ligamentum teres are systematically inspected.

• Debridement: Simply cutting away the torn labrum is largely historical and reserved only for severely macerated, completely irreparable tissue in older patients. Excision removes the critical "suction seal" of the hip, leading to altered biomechanics.
• Labral Repair: The modern gold standard. Using specialized arthroscopic suture anchors placed carefully on the acetabular rim (avoiding joint penetration), the labrum is re-approximated and fixed. The goal is to restore the native anatomy and the fluid seal. Techniques include simple, mattress, and looped stitch configurations.
• Labral Reconstruction: If the labrum is completely ossified, hypoplastic, or absent from previous surgery, reconstruction using an autograft (e.g., Iliotibial band, semitendinosus) or allograft is indicated to recreate the seal.
• Chondral Lesions: Small, full-thickness cartilage flaps are debrided to stable borders. Microfracture can be utilized for contained, focal grade IV defects, though its long-term durability in the hip remains a subject of intense debate.

2. The Peripheral Compartment (Bone Resection)

After addressing the central pathology, traction is released, and the arthroscope is moved to the peripheral compartment to address the bony morphology.

• Acetabuloplasty (Rim Trimming): Using a high-speed burr, the overhanging Pincer lesion is resected.
  • Crucial Trap: Do not over-resect. Removing too much rim induces iatrogenic dysplasia and devastating micro-instability.
• Femoro-osteochondroplasty (Cam Resection): The Cam bump is burred away to restore a normal, spherical femoral head-neck offset.
  • Dynamic Testing: The resection must be verified intraoperatively by taking the hip through its full range of motion (flexion and internal rotation) on the table, visualizing directly that the impingement has been eliminated.

3. Capsular Management: The Modern Mandate

The hip capsule, particularly the robust iliofemoral ligament, is a massive static stabilizer of the hip.

• Capsular Closure: In the early days of hip arthroscopy, capsulotomies were left open. We now know this leads to micro-instability, delayed recovery, and chronic pain, especially in young females, athletes, and patients with borderline dysplasia or hyperlaxity.
• The Rule: Complete closure of the capsulotomy using heavy, non-absorbable or long-lasting absorbable sutures is now the standard of care.

Visual Element: A series of intraoperative arthroscopic photos demonstrating: 1. A detached labrum with underlying cartilage delamination. 2. Suture anchor placement on the acetabular rim. 3. The completed labral repair demonstrating a restored, watertight suction seal against the femoral head.

Rehabilitation: Managing the Long Road

Patient expectations must be aggressively managed preoperatively. Hip arthroscopy is a major biomechanical reset, not a "quick scope" like a simple knee meniscectomy. Full recovery frequently takes 6 to 9 months, and sometimes up to a year.

• Phase 1 (0-4 weeks - Protection): Strict protection of the repair and bone resections. Patients use crutches with partial weight-bearing (typically 20kg). Deep flexion (> 90°) and active straight leg raises are prohibited to protect the labrum and the iliopsoas. Anti-rotation boots may be used at night.
• Phase 2 (4-12 weeks - Activation & Control): Weaning off crutches. Focus shifts to normalizing gait mechanics, restoring core stability, and isolated gluteal strengthening. The hip rotators and abductors are targeted to re-establish dynamic pelvic control.
• Phase 3 (3-6 months - Strength & Power): Progression to closed-chain exercises, plyometrics, and the initiation of a progressive running program.
• Phase 4 (6+ months - Return to Sport): Sport-specific drills, cutting, and pivoting. Clearance for elite athletic competition averages 6-9 months but requires passing stringent functional testing criteria.

Complications: What You Must Know for the Boards

You must be able to rattle these off confidently in a viva scenario.

• Neuropraxia: The most common complication.
  • Pudendal Nerve: Due to prolonged perineal post pressure (numbness in perineum/genitalia). Usually transient, resolving in days to weeks. Avoided by strict time limits and post-less traction.
  • Lateral Femoral Cutaneous Nerve (LFCN): Injured during anterior portal placement (causing meralgia paresthetica—numbness on anterolateral thigh).
• Heterotopic Ossification (HO): The hip capsule is prone to forming bone after surgical trauma.
  • Prophylaxis: Routine administration of NSAIDs (e.g., Indomethacin 75mg SR daily or Naproxen 500mg BD) for 2 to 3 weeks postoperatively is standard practice to prevent HO formation.
• Iatrogenic Instability: Caused by excessive acetabular rim trimming (creating dysplasia) or failure to close the capsule in a hyperlax patient. Presents with profound, intractable mechanical groin pain and feelings of subluxation. Difficult to salvage.
• Femoral Neck Fracture: Rare (< 1%) but completely disastrous. Typically occurs in the first 6 weeks post-op if the patient violates weight-bearing restrictions.
  • Prevention: Avoid excessive resection of the Cam lesion. The resection depth must strictly remain less than 30% of the total femoral neck diameter to preserve structural integrity.

Evidence Corner: Landmark Literature

For fellowship exams, citing key papers elevates your answer from good to consultant-level.

• The FASHIoN Trial (Griffin et al., UK, 2018): A landmark multicenter Randomized Controlled Trial (RCT) comparing hip arthroscopy to Personalized Hip Therapy (physiotherapy) for FAI. Surgery showed statistically superior, clinically meaningful improvements in iHOT-33 scores at 12 months.
• The FAIT Trial (Palmer et al., 2019): Another high-quality RCT comparing surgery to non-operative management. Again, surgery was significantly better for pain reduction and functional improvement.
• Byrd & Jones (10-Year Follow-up): Established that isolated labral debridement has deteriorating results over time compared to modern labral repair, cementing repair as the procedure of choice.

Summary: The Fellowship Exam Checklist

Hip arthroscopy is an incredibly effective, precision procedure for a highly specific mechanical problem (FAI). It is absolutely NOT a treatment for non-specific hip pain ("Hip Pain NOS").

Mastering the indications and having the discipline to say "no" to the wrong patient is the ultimate hallmark of a safe, effective hip preservation surgeon.

Related Topics for Study:

• Periacetabular Osteotomy (PAO): Indications and Execution
• Total Hip Arthroplasty in the Young, Active Patient
• Surgical Anatomy of the Hip Joint and Retinacular Vessels
• Extra-articular Endoscopy: Gluteus Medius Repair and Ischiofemoral Impingement