Metal-on-metal hip resurfacing via posterior approach | advanced
Surgical Imaging
The trap: Treating femoral head exposure like a standard THA femoral preparation — aggressive circumferential capsular release or excessive retraction strips the retinacular vessels that supply the femoral head.
The fix: Identify the posterior retinacular vessels under the reflected external rotator tendons before any capsular incision. Keep them continuously moist with saline-soaked swabs. Limit anterior and medial capsular release to what is strictly necessary for acetabular exposure. Never place retractors directly on the posterior neck without protecting the vessels.
Location and mechanism: The femoral neck is at greatest risk during cylindrical reaming if the component is placed in varus (greater than 5 degrees) or if the reamer removes excessive bone laterally, thinning the neck.
Prevention: Use the lateral femoral neck as the reference for component version and inclination. Maintain at least 2 mm of bone circumferentially around the reamed cylinder. Intraoperative check with image intensifier before cementing is mandatory. Varus malposition is the most common technical error leading to fracture.
Pathophysiology: Adverse reaction to metal debris produces a lymphocyte-dominated inflammatory response with tissue necrosis, fluid collections and pseudotumour masses that can compress neurovascular structures or erode bone.
Risk factors: Female sex, small head size (less than 46 mm), malpositioned components (acetabular inclination greater than 55 degrees or anteversion outside 10-25 degrees), and elevated metal ions (cobalt greater than 7 ppb or chromium greater than 7 ppb).
Surveillance: All MoM patients require annual metal ion testing and cross-sectional imaging (MARS MRI preferred) even if asymptomatic. Early detection allows revision before catastrophic soft-tissue destruction.
Safe zone: Acetabular inclination 40-50 degrees, anteversion 15-25 degrees (Lewinnek). Inclination greater than 55 degrees dramatically increases edge loading, wear and ARMD risk.
Technique: Use the transverse acetabular ligament and posterior rim as landmarks. Avoid over-reaming medially which medialises the centre of rotation and increases joint reaction forces. Press-fit with 1-2 mm under-reaming is standard; supplemental screws are rarely required with modern designs.
Contraindications: Known metal allergy (patch testing or lymphocyte transformation test positive), renal impairment (eGFR less than 60 mL/min), and any patient on dialysis. Metal ions are cleared by the kidneys; impaired clearance leads to systemic accumulation.
Pre-operative screening: Document renal function and consider alternative bearing surfaces (ceramic-on-polyethylene or ceramic-on-ceramic) in any patient with borderline renal function or history of metal sensitivity.
Absolute contraindication in most guidelines: Transplacental transfer of cobalt and chromium ions has been documented. Long-term effects on the foetus are unknown. Serum ion levels must be normal before any MoM implant is considered.
Registry and regulatory position: Both MHRA and FDA advise against MoM resurfacing in women. Many centres have abandoned the procedure entirely in females regardless of age.
R.E.S.U.R.F.A.C.E.RESURFACE — Patient Selection and Contraindications
P.O.S.T.E.R.I.O.R.POSTERIOR — Key Technical Principles
Surgical Indications
Ideal Candidate (Strongest Evidence)
- Male, age 40-55 years, high physical demand (manual labour, sport)
- Femoral head diameter greater than 50 mm (measured on AP pelvis radiograph)
- Good femoral neck bone stock (no cysts greater than 1 cm, no osteopenia)
- Primary osteoarthritis or post-traumatic arthritis with preserved femoral head shape
- No metal hypersensitivity on history or testing
- Normal renal function (eGFR greater than 60 mL/min)
Accepted but Higher-Risk Indications
- Male with head size 46-50 mm (registry survivorship acceptable but inferior to larger heads)
- Avascular necrosis Ficat stage II-III with greater than 50 percent head involvement (requires careful femoral head assessment)
- Developmental dysplasia with adequate bone stock after acetabular reaming
Absolute Contraindications (Modern Practice)
- Female sex (most centres)
- Femoral head diameter less than 46 mm
- Known or suspected metal hypersensitivity
- Renal impairment (eGFR less than 60 mL/min) or dialysis
- Active infection or tumour
- Severe femoral head deformity or large cysts compromising component fixation
- Pregnancy or women planning pregnancy
Relative Contraindications
- Acetabular dysplasia requiring structural graft
- Inflammatory arthritis with poor bone quality
- Previous pelvic irradiation
- Morbid obesity (BMI greater than 35) — technical exposure and component positioning difficulties
Evidence Base and Registry Data
Hip resurfacing was introduced in the 1990s with the promise of bone preservation, improved proprioception, and lower dislocation risk. Early enthusiasm was tempered by registry data showing higher revision rates than conventional THA, particularly in women and smaller components. The 2010-2012 regulatory warnings (MHRA, FDA) and subsequent decline in use reflect these findings.
Registry Survivorship — Hip Resurfacing versus Primary THA (10-year data)
Key Evidence
Failure rates of metal-on-metal hip resurfacings: analysis of data from the National Joint Registry for England and Wales
Early failure of metal-on-metal bearings in hip resurfacing and large-diameter total hip replacement: A consequence of excess wear
Results of Birmingham hip resurfacing at 12 to 15 years: a single-surgeon series
Is the Survivorship of Birmingham Hip Resurfacing Better Than Selected Conventional Hip Arthroplasties in Men Younger Than 65 Years of Age? A Study from the Australian Orthopaedic Association National Joint Replacement Registry
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 48-year-old male manual labourer with primary osteoarthritis of the right hip is referred for consideration of hip resurfacing. His femoral head measures 54 mm on the AP pelvis radiograph. He has no medical comorbidities and normal renal function. How do you counsel him and what is your operative plan?”
“You are performing a hip resurfacing via the posterior approach. After cylindrical reaming of the femoral head you notice that the trial component sits in 7 degrees of varus relative to the native neck-shaft angle and the lateral neck cortex has been notched by the reamer. What do you do?”
“A 52-year-old woman who underwent hip resurfacing 7 years ago presents with new-onset groin pain and a limp. Serum cobalt is 12 ppb and chromium is 11 ppb. MARS MRI demonstrates a 4 cm pseudotumour with surrounding muscle oedema and partial abductor detachment. What is your management?”