Arthroscopic management of cam, pincer and mixed FAI with labral preservation | advanced
Surgical Imaging
Location: The lateral femoral cutaneous nerve (LFCN) emerges 2-3 cm medial and inferior to the anterior superior iliac spine and divides into multiple branches that cross the sartorius origin.
Risk: The mid-anterior portal is placed 3-4 cm distal and lateral to the ASIS; a portal placed too medial or too proximal risks direct transection or stretch injury to the LFCN, producing numbness or painful dysaesthesia over the anterolateral thigh.
Protection: Use blunt dissection through subcutaneous tissue, stay lateral to the sartorius, and establish the mid-anterior portal under direct visualisation from the anterolateral portal.
Location: The pudendal nerve exits the pelvis through the greater sciatic notch and re-enters through the lesser sciatic notch, passing medial to the ischial tuberosity and under the sacrospinous ligament.
Risk: Excessive or prolonged traction against a poorly padded perineal post compresses the pudendal nerve against the ischium, producing perineal numbness, erectile dysfunction or urinary retention.
Protection: Position the post laterally against the ischium rather than the midline perineum, use at least 10 cm of padding, limit continuous traction time to less than 90-120 minutes, and release traction during femoral osteochondroplasty.
Location: The lateral retinacular vessels run along the posterolateral femoral neck just distal to the head-neck junction; they are the primary blood supply to the femoral head via the lateral epiphyseal artery.
Risk: Aggressive posterior or lateral cam resection can injure these vessels, resulting in femoral head avascular necrosis (rare but devastating).
Protection: Limit femoral osteochondroplasty to the anterosuperior head-neck junction (12 o'clock to 3 o'clock position); do not extend resection posterior to the 10-11 o'clock position or distal to the retinacular fold.
Location: The acetabular labrum attaches to the acetabular rim via the chondrolabral junction; the free edge of the labrum creates the suction seal with the femoral head.
Risk: Overzealous rim trimming or labral debridement disrupts the seal, leading to persistent pain, microinstability and accelerated chondral wear.
Protection: Preserve at least 3-4 mm of labral width after trimming; use horizontal mattress sutures that evert the labral edge slightly onto the femoral head to restore the seal.
Location: The sciatic nerve lies posterior to the greater trochanter and is at risk with posterior portal placement or excessive hip extension during traction.
Risk: Posterior portal misplacement or prolonged hip extension under traction can stretch the sciatic nerve, producing foot drop or posterior thigh numbness.
Protection: Use only anterolateral and mid-anterior portals for standard FAI surgery; avoid posterior portals unless addressing posterior pathology; keep the hip in slight flexion (10-15 degrees) during traction.
Location: The femoral neck calcar and anterolateral cortex provide structural integrity; excessive cam resection weakens the neck.
Risk: Removing greater than 30 percent of the neck diameter or creating a notch greater than 4-5 mm deep increases fracture risk, particularly in young active patients returning to sport.
Protection: Resect only the cam prominence to restore head-neck offset (alpha angle less than 50 degrees); use intraoperative fluoroscopy in multiple planes to confirm adequate but not excessive resection; avoid creating a cortical notch.
C.A.MCAM — Femoral Morphology Assessment
P.I.N.C.E.RPINCER — Acetabular Morphology Assessment
T.R.A.C.T.I.O.NTRACTION — Safe Hip Distraction Protocol
Surgical Indications
Absolute Indications
- Symptomatic FAI with documented cam or pincer morphology on radiographs and MRI
- Failed non-operative treatment for greater than 3-6 months (activity modification, physiotherapy, intra-articular corticosteroid injection)
- Mechanical symptoms (catching, locking) with labral tear confirmed on MRI arthrogram
- Young active patient (typically less than 40-45 years) with preserved joint space (greater than 2 mm) and no significant osteoarthritis (Tonnis grade 0-1)
Relative Indications
- Mixed cam-pincer morphology with correctable deformity
- Labral pathology amenable to repair rather than debridement
- Athlete with performance-limiting symptoms despite optimised conservative care
- Patient with borderline dysplasia (lateral centre-edge angle 20-25 degrees) where rim trimming is minimal and combined with periacetabular osteotomy consideration
Contraindications
Absolute:
- Advanced osteoarthritis (Tonnis grade 2-3 or joint space less than 2 mm)
- Hip dysplasia with lateral centre-edge angle less than 20 degrees (rim trimming would worsen instability)
- Active infection or inflammatory arthropathy
- Severe femoral retroversion or anteversion requiring corrective osteotomy rather than arthroscopy
Relative:
- Age greater than 50-55 years with early degenerative change
- Body mass index greater than 35-40 (technical difficulty and complication risk)
- Previous open hip surgery with extensive scarring
- Patient expectations inconsistent with realistic outcomes (return to high-impact sport)
Evidence for Non-Operative Treatment
Activity Modification and Physiotherapy
- Core strengthening, hip abductor and external rotator strengthening, and postural correction reduce symptoms in 30-50 percent of mild FAI cases
- A randomised trial (Mansell 2018) found no difference between physiotherapy and hip arthroscopy at 2 years for military patients with FAI; however, 70 percent of the physiotherapy group crossed over to surgery
- Non-operative treatment is first-line for 3-6 months in most patients before considering surgery
Intra-articular Injections
- Corticosteroid injection provides temporary relief (weeks to months) but does not alter morphology
- Hyaluronic acid or platelet-rich plasma injections have limited evidence in FAI; not routinely recommended as disease-modifying therapy
Evidence for Surgery
Hip Arthroscopy Outcomes
- Systematic reviews report 70-90 percent good-to-excellent outcomes at 2-5 years with proper patient selection
- Return to sport rates of 80-90 percent in elite athletes when cam resection and labral repair are performed adequately
- Revision rate 5-15 percent at 5 years; most common reasons are residual cam deformity, incomplete labral repair, and progression of chondral damage
Cam versus Pincer Correction
- Cam resection (femoral osteochondroplasty) improves alpha angle and restores head-neck offset; under-resection is the leading cause of persistent symptoms and revision
- Acetabular rim trimming with labral refixation restores the suction seal and corrects focal overcoverage; excessive rim resection risks iatrogenic dysplasia and instability
Labral Repair versus Debridement
- Labral repair (refixation) demonstrates superior outcomes compared with debridement in multiple cohort studies and meta-analyses
- Repair preserves the labral seal function; debridement is reserved for irreparable labral tissue (ossified, severely damaged)
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 28-year-old professional footballer presents with 8 months of groin pain and mechanical catching in the right hip. AP pelvis and Dunn lateral radiographs demonstrate a cam lesion with alpha angle of 68 degrees and a positive crossover sign. MRI arthrogram shows an anterosuperior labral tear with no significant chondral loss. How do you manage this patient?”
“You are performing hip arthroscopy for cam FAI. After completing the cam resection you notice that the lateral retinacular vessels appear stretched and the femoral head perfusion seems compromised on intraoperative assessment. What do you do?”
“A 35-year-old woman 18 months after hip arthroscopy for mixed FAI presents with recurrent groin pain and a positive impingement test. Postoperative radiographs show an alpha angle of 62 degrees (pre-operative 72 degrees) and a persistent crossover sign. What is your diagnosis and management?”