Revision Total Hip Arthroplasty - Acetabular Component
advanced Level
180 mins
Primary Indication
Aseptic loosening, instability, wear, osteolysis of acetabular component
Danger Structures
Sciatic nerve - runs 20-30mm posterior to posterior acetabular wall at level of lesser trochanter, at risk during posterior retractor placement and cup extraction, injury causes foot drop (peroneal) and sensory loss (tibial) - EXAM KEY: identify early, gentle retraction, protect during cup manipulation, avoid hip extension with retractors
Superior gluteal neurovascular bundle - exits greater sciatic notch 30-50mm superior to acetabular dome, supplies abductors, injury causes Trendelenburg gait - EXAM KEY: avoid proximal dissection beyond safe zone, do not place screws superior to dome
External iliac vessels - lie 10-20mm medial to inner pelvic wall (quadrilateral plate) at midpoint between ASIS and pubic symphysis, injury catastrophic - EXAM KEY: screws in quadrilateral plate must aim posteriorly not medially, never breach inner wall
Obturator neurovascular bundle - runs along medial acetabular wall 5-15mm from quadrilateral plate inner surface, at risk with quadrilateral plate screws - EXAM KEY: screws should be 20-25mm length maximum in quadrilateral plate, aim posteriorly
Corona mortis - aberrant obturator artery from external iliac (10-30% prevalence), crosses superior pubic ramus 15-25mm from symphysis - EXAM KEY: at risk with anterior column screws, identify if ilioinguinal approach used
Femoral neurovascular bundle - lies 40-60mm anterior and medial to anterior acetabular wall deep to iliopsoas - EXAM KEY: anterior retractors stay on bone (ilium/acetabular rim), never slide medially into soft tissue
Visual Atlas
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Step-by-Step Technique
1
Preoperative Planning & Templating: Review AP pelvis, lateral, Judet views. CT scan mandatory - quantify bone loss, assess columns, detect discontinuity. Apply PAPROSKY CLASSIFICATION. Template cup size, need for augments/cage. Measure leg length discrepancy. Plan screw trajectory (posterior column safest). Stock appropriate implants (jumbo cups, trabecular metal augments, cage if needed). EXAM KEY: 'CT essential for revision - 3D reconstruction shows bone loss not visible on X-ray. Paprosky classification drives entire surgical plan. Type I-IIA = standard revision cup. Type IIB-IIC = jumbo cup or augments. Type IIIA = trabecular metal/cage. Type IIIB = discontinuity needs cup-cage or triflange.'
Surgeon's Tip
Templating determines if anatomic hip center restoration possible or high hip center acceptable
Danger Zone
Inadequate planning leads to intraoperative improvisation and poor outcomes
Positioning & Extended Posterior Approach: LATERAL DECUBITUS with anterior and posterior pelvic supports. Ensure perpendicular pelvis (C-arm check). Extended POSTERIOR APPROACH - may need trochanteric slide/osteotomy for exposure. Split gluteus maximus in line with fibers. Identify SCIATIC NERVE early - may be adherent in scar tissue from previous surgery. Extend as needed for acetabular access. EXAM KEY: 'Stable pelvic positioning critical - rotation causes component malposition. Sciatic nerve at highest risk in revision - identify early, protect throughout. May need trochanteric osteotomy for simultaneous femoral revision or difficult exposure.'
Surgeon's Tip
Wide draping for extensile exposure if needed
Danger Zone
Unstable pelvic positioning leads to malpositioned components
Sciatic nerve injury (2-5% in revision)
3
Exposure & Cup Visualization: Release short external rotators (may be attenuated). Capsulotomy - capsule often thickened/scarred. Dislocate hip (may require femoral neck osteotomy if stable stem). Remove POLYETHYLENE LINER first (easier access). Place HOHMANN RETRACTORS around acetabulum - anterior on ilium, posterior on ischium, superior carefully (avoid superior gluteal neurovascular bundle). Circumferential exposure of cup. EXAM KEY: 'Dislocation more difficult in revision - scarred tissue, stable stem. Liner removal first gives access. Retractor placement: anterior = ilium safe, posterior = ischium safe, superior <5cm from acetabular rim (neurovascular bundle). Never place retractors in soft tissue - stay on bone.'
Surgeon's Tip
Consider leaving well-positioned, well-fixed cup if only liner issue
Danger Zone
Sciatic nerve injury with posterior retractor
Superior gluteal neurovascular injury if retractors too superior
Femoral shaft fracture during dislocation
4
Cup Removal: Remove screws first (may need to drill out if broken). Use CURVED OSTEOTOMES around cup-bone interface starting posteriorly. Work circumferentially with gentle malleting - avoid levering. For well-fixed cups: EXPLANT DEVICES (threaded extractors screwed into screw holes). Avoid aggressive levering (fracture risk). Protect medial wall - catastrophic if breached (iliac vessels 10-20mm medial). EXAM KEY: 'Cup extraction is highest risk step. Osteotomes break osseointegration - work around entire circumference before levering. Explant devices use cup screw holes for threaded extraction. NEVER lever against medial wall - iliac vessels 10-20mm deep, breach = life-threatening hemorrhage. If stuck: multiple small osteotomies better than forceful extraction.'
Surgeon's Tip
Fluoroscopy helpful to confirm complete cement/cup removal
Defect Assessment - Paprosky Classification: With cup removed, assess bone loss. Identify TRUE ACETABULUM - may be superior/medial to defect. Palpate columns - intact vs. deficient. Test for PELVIC DISCONTINUITY (manual stress - column separation). Classify: TYPE I = intact bone, minor cavitary. TYPE IIA = superomedial cavitary, rim intact. TYPE IIB = superolateral, superior migration <3cm. TYPE IIC = medial wall defect. TYPE IIIA = severe segmental loss, superior migration >3cm, rim present. TYPE IIIB = discontinuity or massive ischial lysis. EXAM KEY: 'Intraop assessment confirms preop CT classification. Discontinuity test: manual stress with finger on inner/outer wall - palpable motion = separation. Type determines reconstruction: I/IIA = standard cup, IIB/IIC = jumbo/augments, IIIA = trabecular metal/cage, IIIB = cup-cage or triflange. Identify quadrilateral plate integrity - determines medial support.'
Surgeon's Tip
Take photos for documentation and future reference
Danger Zone
Misclassification leads to inadequate reconstruction
Unrecognized discontinuity = failure
6
Bone Preparation & Defect Management: Ream to BLEEDING BONE - removes fibrous tissue, creates prepared surface. Start with small reamer, increase 2mm increments. Ream concentrically if possible (restore center). CAVITARY DEFECTS (Type I-IIC): morselized allograft (impaction grafting). SEGMENTAL DEFECTS (Type IIB-IIIA): options = (1) TRABECULAR METAL AUGMENTS (highly porous tantalum), (2) STRUCTURAL ALLOGRAFT (distal femur, femoral head), (3) JUMBO CUP (>62mm diameter), (4) HIGH HIP CENTER (acceptable if <35mm superior migration). EXAM KEY: 'Bleeding bone essential for ingrowth. Contained cavitary defects: morselized graft works well. Uncontained segmental defects need structural support - augments most common (trabecular metal 90-95% survival), allograft alternative (70-80% survival), jumbo cup if enough rim. High hip center biomechanically inferior but acceptable if restore offset.'
Surgeon's Tip
Preserve as much host bone as possible - avoid over-reaming
Implant Selection & Trial: TYPE I/IIA: Uncemented porous revision cup, supplemental screws. TYPE IIB/IIC: Jumbo cup (>62mm) to span defect + screws, OR standard cup + augments. TYPE IIIA: Trabecular metal augments (screw to pelvis) + cup, OR cup-cage construct. TYPE IIIB: CUP-CAGE (cage fixed to ilium + ischium, cup inside cage) OR custom TRIFLANGE. Trial component: assess POSITION (40-45° inclination, 15-25° anteversion), STABILITY, COVERAGE (maximize bone contact). EXAM KEY: 'Match implant to defect type. Jumbo cups span defects but require adequate rim. Augments fill segmental gaps - trabecular metal preferred (high porosity, friction). Cup-cage for severe loss - cage protects cup, fixed to intact bone. Trial confirms: adequate coverage, no impingement, leg length, offset. Screws in posterior column (safest) and dome.'
Surgeon's Tip
Augments should contact bleeding host bone for ingrowth
Danger Zone
Undersized cup = poor stability
Oversized = fracture risk
Malposition = dislocation/impingement
8
Cup Fixation: PRESS-FIT technique: impact cup to stable seating (machined underreamed 1-2mm). Ensure adequate bone contact (minimum 50% host bone, 70% ideal). Supplemental SCREWS: posterior column best (up to 70mm safe), dome acceptable (25-30mm), AVOID anterior-inferior (vessels). If using AUGMENTS: screw to pelvis first, then cup. If CAGE: fix cage to ilium (superiorly) and ischium (inferiorly) with multiple screws, then insert cup inside cage. Confirm stability - no gross motion. EXAM KEY: 'Press-fit primary stability essential. Screws supplement but don't replace press-fit. Posterior column = thickest bone, safest for screws. Cage provides structural support when bone inadequate - must achieve stable fixation to ilium and ischium. Multiple screws needed (typically 4-6). Cup inside cage protected from load. Confirm no impingement with trial reduction.'
Surgeon's Tip
Fluoroscopy to confirm screw trajectory and cup position
Danger Zone
Screws into quadrilateral plate medially = vessel injury
Inadequate press-fit = early loosening
Malpositioned cup = dislocation
9
Liner Selection & Insertion: HIGHLY CROSS-LINKED POLYETHYLENE standard (reduces wear). DUAL MOBILITY if instability risk: (1) Abductor deficiency, (2) Recurrent dislocation, (3) Neuromuscular disease, (4) Poor soft tissue, (5) Cannot correct malposition. Dual mobility = inner head (22-28mm) snaps in poly liner, liner articulates with metal shell - effectively large head (jumbo diameter). CONSTRAINED liner alternative (locking mechanism, 10-15° arc) but higher failure rate than dual mobility. Impact liner firmly, confirm seating. EXAM KEY: 'HXLPE reduces wear vs conventional poly. Dual mobility dramatically reduces dislocation in revision (15% → <2%). Preferred over constrained liner (lower failure rate). Mechanism: small head-liner articulation normally, liner-shell at extremes of motion. Dislocation requires extreme ROM. Use liberally in revision - abductor deficiency common, soft tissue quality poor.'
Surgeon's Tip
Elevated rim liner (posterior lip) alternative if dual mobility not available
Danger Zone
Standard liner in high-risk patient = recurrent dislocation
Constrained liner may fail at locking mechanism
10
Restore Offset & Leg Length: Assess OFFSET: palpate greater trochanter relative to pelvis. Inadequate offset = abductor weakness, instability, impingement. Restore with: (1) Cup lateralization (improves offset but may compromise coverage), (2) Femoral head size/offset, (3) Femoral stem with increased offset. Assess LEG LENGTH: compare to opposite side, measure from ASIS to medial malleolus. Target ±5mm of opposite side. Adjust with head size, neck length (modular), stem depth. EXAM KEY: 'Offset restoration critical for abductor function and stability. Under-offset = impingement, instability, abductor insufficiency. Over-offset = joint reaction force increases, loosening risk. Leg length discrepancy >10mm clinically significant - gait abnormality, back pain. Most common medicolegal claim in arthroplasty. Optimize via combination: cup position, head size, neck length, stem depth.'
Surgeon's Tip
Intraoperative measurement: mark pre-incision from ASIS to GT and medial malleolus
Danger Zone
Under-offset = instability, dislocation
Leg length discrepancy >10mm = patient dissatisfaction, litigation
11
Trial Reduction & Stability Assessment: Insert femoral head (appropriate size for offset/length). Reduce hip. Assess: (1) STABILITY: posterior dislocation test (flexion 90° + adduction + internal rotation - should resist). Anterior test (extension + external rotation). (2) RANGE OF MOTION: flexion to 110°, extension, abduction without impingement. (3) SOFT TISSUE TENSION: not floppy (dislocates easily) or excessively tight (difficult reduction). If UNSTABLE: assess cause (malposition, inadequate offset, soft tissue loss) and correct. EXAM KEY: 'Stability testing before final implants. Combined flexion + adduction + internal rotation = posterior dislocation position - should resist. If unstable: check position (Lewinnek safe zone 40° inclination, 15-20° anteversion), offset (restore), soft tissue tension. Instability = needs dual mobility, constrained liner, or component repositioning. ROM assessment: impingement causes dislocation - identify contact points.'
Surgeon's Tip
Fluoroscopy confirms component position before final implants
Danger Zone
Proceeding with unstable hip = early dislocation
Impingement = late dislocation, component wear
12
Soft Tissue Repair & Closure: Repair POSTERIOR STRUCTURES: capsule (if adequate tissue), short external rotators (piriformis, gemelli, obturators) to greater trochanter via bone tunnels or suture anchors. Reattach gluteus maximus to fascia lata. ENHANCED POSTERIOR REPAIR reduces dislocation (5-10% → 1-2%). If abductor deficiency: consider advancement, augmentation, or accept dual mobility. Drain placement optional (many use in revision). Close fascia lata, subcutaneous tissue, skin. EXAM KEY: 'Posterior repair essential for stability. Short external rotators primary posterior stabilizers - reattach to GT. Capsule repair if tissue adequate. Enhanced repair (SER + capsule) reduces dislocation by 50%. Abductor deficiency common in revision - assess integrity, repair if possible, dual mobility if insufficient. Drains controversial - many avoid in revision (hematoma = infection risk).'