High Yield Overview

REVISION TOTAL HIP REPLACEMENT FOR ASEPTIC LOOSENING

Utilize previous surgical approach when possible to minimize additional soft tissue trauma and preserve vascularity. Posterior approach most common in Australia (80% of primaries). May require extended exposure compared to primary: proximally for acetabular access, distally for femoral access (especially if well-fixed stem). | advanced

Critical Danger Structures - Specific Locations & Protection

Sciatic Nerve

Location: Exits pelvis through greater sciatic notch inferior to piriformis, courses 2cm posterior to hip capsule at joint level, descends along posterior thigh. Protection: Early identification through scar tissue, vessel loop isolation, protected retractor placement, stay anterior if nerve not found, avoid excessive traction (lengthening >2cm increases palsy risk exponentially)

Superior Gluteal Neurovascular Bundle

Location: Exits pelvis ABOVE piriformis through greater sciatic notch, courses along gluteus medius undersurface, enters muscle belly 3-5cm superior to greater trochanter tip. Protection: Limit proximal dissection to <5cm above GT, stay below medius muscle belly, avoid superior retractor placement beyond safe zone

Femoral Neurovascular Bundle

Location: Femoral triangle 2-3cm anterior to anterior hip capsule. Lateral to medial: Nerve-Artery-Vein (NAV mnemonic). Protection: Anterior approach requires careful identification and retraction, avoid medial cup screws in anteroinferior quadrant (vessels at risk), fluoroscopy for screw depth verification

Iliac Vessels (Intrapelvic)

Location: Iliac vessels lie on inner pelvic wall, vulnerable to medial cup screw penetration. Protection: Anteroinferior quadrant screws AVOIDED (highest vessel risk), medial wall perforation avoided during reaming, fluoroscopy or navigation to verify screw length, posterosuperior quadrant safest for screws

Obturator Nerve and Vessels

Location: Course along obturator foramen inferiorly at level of ischium. Protection: Avoid inferior cup screws directed toward obturator foramen, careful during inferior reaming near teardrop, ischial screws directed posteriorly (not inferiorly through foramen)

Mnemonic

PAPROSKYPAPROSKY - Acetabular Bone Loss Classification

Mnemonic

ETO SAFEETO SAFE - Extended Trochanteric Osteotomy Principles

Comprehensive Assessment

Infection Exclusion (MANDATORY)

Clinical Assessment

Pain pattern: constant pain at rest suggests infection (vs activity-related pain in aseptic loosening)
Constitutional symptoms: fevers, chills, night sweats (infection)
Wound history: prior drainage, dehiscence, delayed healing
Risk factors: diabetes, immunosuppression, prior infection

Laboratory Investigation

ESR: >30mm/hr concerning but nonspecific (also elevated in inflammation, malignancy)
CRP: >10mg/L concerning, more responsive than ESR
CRITICAL: ESR/CRP alone have 30% false negative rate - INADEQUATE for ruling out infection

Joint Aspiration (GOLD STANDARD)

Cell count: >3000 cells/µL highly suggestive of infection (acute), >1100 in chronic
Differential: >80% PMNs highly specific for infection
Culture: MUST hold 14 days for slow-growing organisms (Cutibacterium acnes common in shoulder, can occur in hip)
Alpha-defensin: 97% sensitivity, 96% specificity (rapid point-of-care test)
Synovial fluid CRP: >9.5mg/L or IL-6 >12,000pg/mL suggestive

Advanced Testing if Equivocal

Repeat aspiration if initial non-diagnostic
Nuclear medicine: Indium-111 WBC scan (90% sensitivity), FDG-PET
Tissue cultures at surgery: 5-6 samples from interface, 14-day culture
Sonication of explanted components (increases culture yield)

Radiographic Assessment

Standard X-rays

AP pelvis: assess acetabular bone loss, superior migration, Kohler line
Lateral hip: assess cup version, anterior/posterior column integrity
Full femur if long-standing loosening: assess diaphyseal bone quality

Paprosky Acetabular Classification

Type I: Intact rim, intact columns, <2mm superior migration → Standard cup
Type IIA: Intact rim, intact columns, 2-3cm superior migration → Jumbo cup
Type IIB: Superior/posterior rim deficiency, >3cm migration → Augments + cup
Type IIC: Medial wall osteolysis, intact rim → Bone graft + cup
Type IIIA: Rim loss but ischium/teardrop intact → Jumbo cup OR cup-cage
Type IIIB: Severe rim loss, ischium/teardrop gone, Kohler line discontinuous → Custom triflange OR complex reconstruction

Paprosky Femoral Classification

Type I: Minimal metaphyseal damage, intact diaphysis → Primary stem
Type II: Damaged metaphysis, intact diaphysis >4cm → Extensively coated stem
Type IIIA: Severe metaphyseal damage, intact diaphysis >4cm, expanded canal → Extensively coated OR modular tapered
Type IIIB: Metaphyseal AND proximal diaphyseal damage, <4cm intact diaphysis → Long extensively coated OR modular tapered
Type IV: Extensive damage, no diaphyseal fixation possible → Megaprosthesis OR allograft-prosthesis composite

Advanced Imaging

CT with 3D reconstruction: Better defines bone defects, aids implant planning (especially Paprosky III defects)
MARS MRI: Soft tissue assessment if metal artifact reduction needed (abductor quality, muscle atrophy)

Implant Planning

Acetabular Options Based on Paprosky

Type I/IIA: Standard uncemented hemispherical cups (multiple sizes), jumbo cups (66-80mm)
Type IIB/IIC: Porous metal augments (trabecular tantalum or titanium), structural allografts
Type IIIA/IIIB: Antiprotrusio cages (Burch-Schneider), custom triflange implants, oblong cups

Femoral Options Based on Paprosky

Type I/II: Standard primary stems, extensively coated stems (6-10 inch coating lengths)
Type IIIA/IIIB: Modular tapered fluted stems (Wagner SL), long extensively coated stems
Type IV: Proximal femoral replacement (megaprosthesis), allograft-prosthesis composite

Adjuncts and Fixation

Morselized allograft for impaction grafting
Cortical strut grafts for defects/perforations
Screws (multiple sizes 3.5-6.5mm, lengths 25-70mm)
Cerclage wires (16-18 gauge) or cables for ETO/fractures

Blood Management

Preoperative Optimization

Hemoglobin optimization: target >120g/L, iron supplementation if anemic (ferritin <30µg/L)
Erythropoietin if severe anemia and time permits (3-4 weeks preop)
Discontinue anticoagulation per protocol (warfarin 5 days, DOACs 2-3 days)

Intraoperative Strategies

Cell saver (can reduce transfusion by 30-50%)
Tranexamic acid: 15-20mg/kg IV at induction, repeat at 3 hours (reduces blood loss 30-50%)
Meticulous hemostasis, hypotensive anesthesia if appropriate

Transfusion Planning

Type and cross 2-4 units (transfusion rate 30-50% in revision)
Restrictive threshold: Hb <70g/L or <80g/L with symptoms

Exam Pearl

EXAM KEY: "Before ANY revision, infection MUST be ruled out - aspiration is GOLD STANDARD: cell count >3000, PMN >80%, 14-day culture. ESR/CRP alone inadequate (30% false negative). Alpha-defensin excellent (97% sensitivity/96% specificity). If infected, management completely different - 2-stage revision mandatory. For aseptic loosening, I classify bone loss using PAPROSKY CLASSIFICATION - guides reconstruction strategy. ACETABULAR: I/IIA = standard/jumbo cup, IIB/IIC = augments + cup, IIIA/IIIB = complex reconstruction (cage, triflange, allograft). FEMORAL: I = primary stem, II/IIIA = extensively coated for diaphyseal fixation (bypass metaphyseal defects), IIIB = long stem, IV = megaprosthesis OR APC. I template extensively, order multiple implant sizes and backup options."

Major Complications: Recognition, Prevention, and Management

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 68-year-old woman presents with progressive groin and thigh pain 12 years after primary total hip replacement. X-rays show acetabular component migration 4mm superiorly with a 3mm radiolucent line at the bone-implant interface, and femoral stem subsidence of 8mm. ESR is 25mm/hr and CRP is 8mg/L. How do you proceed?"

EXCEPTIONAL ANSWER

This patient has aseptic loosening of BOTH components (acetabular AND femoral) with migration and radiolucent lines. Despite relatively normal inflammatory markers (ESR 25, CRP 8), I MUST rule out infection before proceeding - this is MANDATORY. Inflammatory markers alone have 30% false negative rate - inadequate. I proceed with: (1) JOINT ASPIRATION (gold standard): cell count (>3000 concerning for infection), differential (>80% PMNs highly specific for infection), 14-day culture (must hold full 14 days for slow-growing organisms like Cutibacterium), alpha-defensin if available (97% sensitivity/96% specificity). (2) If aspiration confirms aseptic (low cell count, negative culture), proceed with revision planning: Comprehensive imaging (AP pelvis, lateral hip, full femur to assess bone loss), Paprosky classification (acetabular: measure superior migration, assess rim/columns - likely Type IIA based on 4mm migration; femoral: assess metaphyseal/diaphyseal bone loss, canal diameter - likely Type II or IIIA based on subsidence), CT with 3D reconstruction to better define defects if extensive bone loss. (3) Implant planning based on classification: Acetabular Type IIA → jumbo cup or elevated hip center, Femoral Type II/IIIA → extensively coated stem for diaphyseal fixation OR modular tapered stem. (4) Medical optimization (cardiac clearance, nutritional status, hemoglobin optimization), blood management (type and cross, cell saver arranged), comprehensive consent (infection 2-5%, dislocation 10-15%, nerve injury 2-5%, transfusion 30-50%, re-revision 10-15% at 10 years). If aspiration shows infection: 2-stage revision protocol (explant, antibiotic spacer, 6 weeks IV antibiotics based on sensitivities, reimplantation after infection eradicated - confirmed by repeat aspiration with normal markers).

VIVA SCENARIOStandard

EXAMINER

"You are performing revision THR for aseptic loosening. After removing the well-fixed cemented femoral stem using high-speed burr and flexible osteotomes, you create a 2cm perforation in the lateral femoral cortex at the mid-diaphyseal level during cement removal. How do you manage this intraoperatively?"

EXCEPTIONAL ANSWER

Femoral perforation is a recognized complication during cement removal (occurs in 1-5% of revision cases). I manage this systematically: (1) IMMEDIATE RECOGNITION: Stop cement removal, assess perforation size (2cm is moderate), location (mid-diaphyseal, good bone proximally and distally for fixation), extent (through cortex into medullary canal). (2) INTRAOPERATIVE MANAGEMENT: Complete cement removal carefully (perforation already created, must remove remaining cement for stem insertion), copious irrigation to remove debris, achieve bleeding bone. (3) RECONSTRUCTION STRATEGY: Mid-diaphyseal 2cm perforation requires: STRUT GRAFT REINFORCEMENT: Cortical allograft strut (or 2 struts) spanning perforation site, extend strut at least 2 cortical diameters (8-12cm) proximal and distal to perforation for adequate stress distribution, CERCLAGE WIRE FIXATION: 3-4 cerclage wires (16 or 18 gauge) or cables to secure strut graft to host bone, position wires proximal to, at, and distal to perforation site, tighten sequentially to compress strut to host bone. (4) STEM SELECTION: May need to REVISE stem choice - if originally planned shorter stem, may need longer extensively coated stem to bypass perforation by 2 cortical diameters distally (achieve fixation in intact bone below perforation), typically need 10-12 inch extensively coated stem OR long modular tapered stem for this level of perforation. (5) FIXATION CONFIRMATION: Stem insertion with gentle impaction (avoid propagating perforation), fluoroscopic confirmation of stem position bypassing perforation adequately, strut graft and wire position verified, assess stability with manual stress (no motion). (6) POST-OPERATIVE MODIFICATION: PROTECTED WEIGHT BEARING: Touch-down or partial weight bearing (20kg) for 6-12 weeks until strut graft incorporation confirmed on X-ray (bridging bone across perforation site), serial X-rays at 6 weeks, 3 months to monitor healing. (7) DOCUMENTATION: Document complication in operative note, explain to patient and family (perforation managed intraoperatively with strut graft reinforcement, expect healing but requires protected weight bearing), modify consent if not already discussed.

VIVA SCENARIOStandard

EXAMINER

"Describe your systematic approach to acetabular reconstruction in a patient with Paprosky Type IIIB acetabular bone loss (severe rim loss, ischium and teardrop gone, 6cm superior migration, Kohler line discontinuous). What are your reconstruction options and how do you choose between them?"

EXCEPTIONAL ANSWER

Paprosky Type IIIB represents SEVERE acetabular bone loss - the most challenging scenario in revision hip surgery. This requires complex reconstruction with structural support. My systematic approach: (1) CONFIRM CLASSIFICATION: Intraoperatively assess: rim completely deficient (no superior or posterior rim to support cup), ischium eroded (no posteroinferior reference), teardrop obliterated (no medial reference), Kohler line discontinuous (massive medial bone loss), 6cm superior migration (massive defect to span). (2) ASSESS FOR PELVIC DISCONTINUITY: Feel for motion between superior and inferior hemipelvis (fracture), if discontinuity present, MUST be addressed (plate fixation across discontinuity OR cage spanning discontinuity). (3) RECONSTRUCTION OPTIONS for IIIB: OPTION 1: CUSTOM TRIFLANGE IMPLANT - ADVANTAGES: Patient-specific implant based on CT, three flanges for ilium, ischium, and pubis fixation (maximum stability), biological fixation potential (porous coating), best long-term outcomes, restores hip center. DISADVANTAGES: 3-6 month lead time for manufacture (requires preoperative planning), expensive (30-40k), requires precise intraoperative positioning, learning curve. TECHNIQUE: CT-based design preoperatively, intraoperative positioning using guides, screw fixation to all three columns (ilium 4-6 screws, ischium 2-3 screws, pubis 2-3 screws), trabecular metal or titanium for ingrowth. OPTION 2: CUP-CAGE CONSTRUCT + AUGMENTS + ALLOGRAFT - ADVANTAGES: Can be done acutely (no lead time), allows bone restoration with allograft, trabecular metal augments for segmental defects. DISADVANTAGES: Complex construct with multiple components, cage has no biological fixation (relies entirely on screws, can fail), technically demanding. TECHNIQUE: Fill segmental defects with trabecular metal augments (screw to pelvis), pack structural or morselized allograft into remaining defects, place antiprotrusio cage (Burch-Schneider or equivalent) spanning from ilium to ischium (screws into remaining bone), insert cup within cage for articulation, cup cemented into cage. OPTION 3: OBLONG/ELLIPTICAL TRABECULAR METAL CUP - ADVANTAGES: Conforms to defect shape, trabecular metal for ingrowth, can restore hip center. DISADVANTAGES: Requires adequate remaining bone for fixation, less structural support than cage, expensive. TECHNIQUE: Ream defect to elliptical shape matching oblong cup, multiple screws (8-12) for fixation, must achieve 40-50% host bone contact. (4) MY APPROACH TO CHOOSING: If time permits (elective revision, able to plan ahead): CUSTOM TRIFLANGE is best option - superior outcomes, biological fixation. If acute/urgent (cannot wait 3-6 months): CUP-CAGE + AUGMENTS + ALLOGRAFT is most reliable. OBLONG CUP: Consider if remaining bone adequate but defect is elliptical rather than circular. (5) GOALS FOR RECONSTRUCTION: Achieve stable fixation (cage or triflange screwed to remaining bone), restore hip center of rotation to anatomic position when possible (better biomechanics, less dislocation), 40-50% host bone contact if using trabecular metal cup (biological fixation), fill defects with bone graft (restore bone stock for potential future revision). (6) POST-OPERATIVE: Protected weight bearing if questionable fixation, surveillance X-rays for migration/loosening, counsel realistic expectations (IIIB has lower survival than I/II, but significant improvement expected from pre-revision state).