Pincer-Type Femoroacetabular Impingement

This patient has developed **iatrogenic hip dysplasia** from **over-aggressive acetabular rim trimming** during pincer FAI surgery - a **catastrophic technical complication** that has converted a stable hip with overcoverage (LCE 42°) into an **unstable dysplastic hip (LCE 18°)** with symptoms of instability and subluxation. This is one of the **worst complications of FAI surgery** and is **more disabling than the original pathology**. The complete labral debridement (rather than repair) further compounds the instability by removing the hip's suction seal. This case requires **urgent specialist assessment** and likely **major reconstructive surgery** to restore stability. I would assess and manage as follows: **Assessment - Iatrogenic Dysplasia with Instability:** **Understanding the Complication:** **Normal LCE angle**: 25-40° (adequate femoral head coverage). **Dysplasia threshold**: less than 25° (borderline), less than 20° (definite dysplasia). **This patient**: Pre-op LCE 42° (mild overcoverage/pincer) → Post-op LCE 18° (iatrogenic dysplasia). **Result of over-resection**: Approximately **24° of acetabular rim removed** - massively excessive (safe rim trimming typically **5-8mm or 5-10° maximum**). The surgeon has **removed critical structural bone** creating undercoverage and instability. **Mechanisms of Instability:** **(1) Insufficient bony coverage** (LCE 18°): Femoral head not adequately contained by acetabulum, allows lateral subluxation. **(2) Absent labrum** (debrided not repaired): Loss of suction seal that normally stabilizes hip, loss of proprioceptive feedback, no structure to deepen socket. **(3) Anterior rim deficiency** (visible on MRI): Creates anterior instability with apprehension during extension-ER (hip wants to dislocate posteriorly as head escapes anteriorly). **Clinical Assessment:** **History**: Instability symptoms (clicking, feeling of 'coming out', apprehension), worse with pivoting/dynamic activities, progressive over 6 months (suggests worsening subluxation), now requires stick for stability. **Examination**: Apprehension sign with extension-ER (pathognomonic for instability), hip feels subluxable on dynamic testing, likely positive Trendelenburg (abductor insufficiency from lateral subluxation), assess ROM (may have compensatory limitations). **Radiographic assessment**: LCE 18° confirms dysplasia, femoral head lateralization (subluxation) on standing AP pelvis, assess for acetabular retroversion (cross-over sign), measure Tonnis angle (likely increased greater than 10° indicating steepness), assess joint space preservation (3mm - favorable for reconstruction). **Differential Diagnosis (Causes of Post-Operative Instability):** **(1) Over-aggressive rim trimming** (this case - most likely): LCE reduced from 42° to 18°, 24° of rim removed. **(2) Unrecognized pre-existing dysplasia**: Unlikely given pre-op LCE 42° (overcoverage not dysplasia). **(3) Labral deficiency**: Complete debridement removed labral seal (compounds instability). **(4) Capsular laxity**: Possible contribution but not primary cause. **(5) Abductor weakness**: May result from instability (secondary) rather than cause. **Investigations:** **Plain radiographs**: Already obtained - confirm LCE 18°, femoral subluxation, assess Tonnis angle, joint space preserved. **CT scan**: Assess **3D acetabular morphology**, quantify anterior/posterior/superior rim deficiency, measure acetabular version (likely retroverted given cross-over sign pre-op), evaluate for rim fracture. **MRI**: Already obtained - absent labrum, anterior rim thinning, assess cartilage status (Outerbridge grading - critical for prognosis), check for labral remnant that could be reconstructed. **Management Options:** **Option 1: Non-Operative Management** (Trial Initially): **Rationale**: Major revision surgery has risks, some patients may compensate. **Protocol**: (1) **Activity modification** - avoid pivoting sports, running, dynamic activities that provoke instability, (2) **Physiotherapy** - hip stabilization exercises (strengthen gluteus medius/minimus, deep hip rotators), core strengthening, proprioception training, (3) **Bracing** - hip brace may provide external stability (limited evidence), (4) **Walking aids** - continue stick to reduce load and improve stability, (5) **Pain management** - NSAIDs, paracetamol for discomfort. **Trial period**: 3-6 months to assess if patient can compensate and symptoms stabilize. **Limitations**: Does not address structural deficiency, symptoms likely to persist given LCE 18° (significant undercoverage), progressive cartilage damage expected from edge loading and instability. **Option 2: Periacetabular Osteotomy (PAO) with Structural Bone Graft** (Likely Required): **Rationale**: Addresses **structural deficiency** by reorienting acetabulum to improve coverage and adding bone graft to restore rim. **Bernese PAO technique**: (1) Multiple osteotomies around acetabulum (iliac, ischial, pubic), (2) Rotate acetabular fragment to improve coverage (increase LCE to 30-35°, correct version if retroverted), (3) **Structural bone graft** to anterior rim (autograft from iliac crest) to restore rim deficiency, (4) Fix with screws. **Advantages**: Corrects underlying bony deficiency, restores normal acetabular coverage and version, avoids arthroplasty in 35-year-old. **Disadvantages**: Major surgery (Smith-Petersen or ilioinguinal approach), prolonged recovery (6-9 months), TTWB 6-8 weeks, risks (nerve injury, non-union, over-correction, heterotopic ossification). **Outcomes**: Good results if performed before advanced cartilage damage, 70-80% avoid THA at 10 years if joint space preserved. **Combined with labral reconstruction**: May perform concurrent hip arthroscopy to reconstruct labrum using allograft (ITB or gracilis) - restores seal function and depth. **Option 3: Shelf Acetabuloplasty:** **Alternative to PAO**: Extra-articular bone graft placed over anterolateral femoral head to improve coverage. **Advantages**: Less invasive than PAO, provides lateral coverage. **Disadvantages**: Does not correct version, does not restore intra-articular anatomy, inferior outcomes compared to PAO. **Consider if**: Patient not candidate for PAO (older, lower demand), isolated lateral deficiency. **Option 4: Total Hip Arthroplasty:** **Last resort in 35-year-old**: Only if advanced cartilage damage (Outerbridge IV, severe OA) or failed PAO. **This patient** has preserved joint space (3mm) - **THA not indicated**, joint preservation with PAO preferred. **THA in young patient**: High revision burden (15-20% revision rate at 15 years in patients less than 55), delay as long as possible. **Recommended Management:** Given age 35, preserved joint space, iatrogenic dysplasia LCE 18°, and disabling instability, I would: (1) **Refer to specialist hip preservation surgeon** for PAO assessment (this requires expertise in complex osteotomies), (2) **Trial conservative management** 3 months while organizing tertiary referral (physiotherapy, activity modification, stick), (3) **Likely proceed with PAO + structural bone graft** to correct dysplasia and restore rim, consider concurrent labral reconstruction if remnant tissue present, (4) **Counsel** about major surgery required to correct iatrogenic problem, prolonged recovery, good outcomes possible if joint space preserved. **Patient Communication and Consent Discussion:** **Acknowledge complication**: Explain previous surgery resulted in over-resection of bone creating instability (iatrogenic dysplasia). **Not patient's fault**: This is surgical complication from excessive rim trimming. **Severity**: More disabling than original pincer FAI, requires major reconstructive surgery to correct. **Options**: Conservative management unlikely to succeed given LCE 18°, PAO can restore stability but major operation. **Prognosis**: If joint space preserved and early intervention, good chance of successful reconstruction; delay risks progressive cartilage damage. **Support**: Offer to liaise with original surgeon for records, support through revision process.