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- RA - panarthritis, acetabular protrusio
- OA - mainly at the weight-bearing zone, with osteopenia
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- This is a complex primary.
- Considerations include medications, osteopenia, acetabular protrusio, and a higher risk of dislocation.
- Pre-op
- Anaesthesia review: cervical instability, consider “awake fibreoptic intubation”, consider regional.
- Medication adjustments:
- Methotrexate - continue as it has no impact on wound healing
- Non biological DMARDs e.g. Azathioprine - continue
- Biologics e.g. TNF alpha inhibitor - stop 2–4 weeks before, as they affect wound healing
- Steroids - may need stress dose
- Intra-op (RA): osteopenia (risk of intra-op fractures) → stand by constrained implants/supplemental fixation, cemented implants
- Post-op (RA): wound care is paramount due to higher infection risk
- Stand by implants - cemented hybrid, consider dual mobility if there is also underlying neuromuscular disease
- Templating, LLD correction
- Intra-op
- Exposure - extensile, psoas and glute max release, in situ neck cut
- Address protrusio
- Femur prep - gentle rasping
- Post-op - standard post-op
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- Determine it by drawing Kohler’s line (ilioischial line).
- It is defined by the femoral head crossing or touching the ilioischial line.
- Medial wall > 3 mm medial to the ilioischial line in males, or > 6 mm in females.
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- Coxa profunda is when the floor goes medial to the ilioischial line, but the femoral head does not.
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- Idiopathic (aka Otto pelvis, Arthrokatadysis)
- Secondary -
- Infection - TB
- Inflammatory - RA, AS, Psoriatic Arthropathy
- Metabolic - Paget, OI, Osteomalacia, Renal osteodystrophy
- Connective tissue disorder - Sickle cell, Marfan, Ehler-Danlos
- Tumor
- Trauma - acetabular #
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- Hirst Classifx, JBJS 1987 Wrightington
- Grade 1 5-10mm
- Grade 2 10-15mm
- Grade 3 >15mm
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- Complex primary: consider involving a senior surgeon.
- Goal: restore the hip center (associated with early loosening if not achieved).
- Pre-op
- Templating.
- Stand by equipment:
- antiprotrusio cages [meant to be used without pelvic discontinuity]
- Triflange cages (in the event of pelvic discontinuity).
- Stand by allograft (in case autograft is not enough).
- Intra-op
- Approach: posterior; consider extensile exposure (glute max and psoas release).
- For a standard cup: may require adductor tenotomy, glute max release, and an in situ neck cut.
- For a cage: may require a trans-trochanteric approach to gain exposure to the ilium to insert the iliac flange.
- Address the protrusio defect using one or more of the following:
- Standard hemispherical cup with medial bone grafting.
- Augments.
- Cage.
- Plan for hybrid fixation, based on familiarity and outcomes.
- Post-op
- Consider PWB for a period.
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- It depends on the medial wall bone stock.
- 1. Standard hemispherical cup
- Use a reamer to widen but not deepen the cup
- Insert morsellised graft (can be from the femoral head) into the prepared acetabulum, then impact the graft [impaction bone grafting]
- Insert a cementless cup
- Consider a revision hemispherical cup with multiple holes to allow screw fixation into the ischium, pubis, and ilium
- 2. Antiprotrusio cages
- Apply the plate and fix it with screws
- Cement a liner into the cage
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- Restoration of hip center within 10mm of the anatomical center
- Bayley et al. Journal of Arthroplasty follow up of 93 THR found that
- 50% loosening occurred when the hip center was not within 10mm of the anatomical center.
- 8% loosening occurred when the hip center was restored to within 10mm of the anatomical center
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A soft answer turns away wrath, but a harsh word stirs up anger. Proverbs 15:1