import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Primary Indications for Conversion** | Indication | Presentation | Urgency | |------------|--------------|---------| | Acetabular erosion | Groin pain, medial migration on XR | Semi-elective | | Recurrent dislocation | Multiple dislocations, instability | Semi-elective | | Stem loosening | Thigh pain, stem subsidence | Elective | | Periprosthetic fracture | Acute pain, unable to weight-bear | Urgent | | Infection | Pain, systemic symptoms, elevated CRP | Staged/urgent | **Timing of Conversion** - Average time to conversion: 6-8 years (AOANJRR) - 50% of conversions occur within 5 years - Late presentation may have severe erosion/protrusio **Patient Factors Favouring Primary THA** - Age less than 70 years (cognitive function) - High functional demand - Pre-existing hip arthritis - Long life expectancy **Clinical Assessment** - Groin pain: Suggests acetabular erosion - Thigh pain: Suggests stem loosening - Buttock pain: May be referred from spine - Dislocation history: Number, direction, mechanism - Functional status: Walking distance, aids, ADLs **Imaging Protocol** | Modality | Purpose | Key Findings | |----------|---------|--------------| | AP pelvis | Both hips comparison, erosion | Medial migration, Shenton's line break | | Lateral hip | Stem version, head position | Anterior/posterior migration | | Judet views | Acetabular columns | Defect location and extent | | CT scan | Bone stock, stem loosening | Paprosky classification, bone loss | **Laboratory Workup** - FBC, ESR, CRP: Exclude infection - Aspiration if any concern (hold antibiotics 2 weeks) - Nutritional markers if concern (albumin, lymphocyte count) **Implant Identification** - Manufacturer and model of existing stem - Modular vs monoblock head - Taper dimensions (12/14, V40, Type 1, etc.) - Head offset options available **Stem Retention Criteria (ALL must be met)** | Criterion | Assessment Method | Threshold | |-----------|-------------------|-----------| | Fixation | Radiographs, intraop testing | No subsidence, no toggle | | Modular design | Implant records | Head must be removable | | Taper compatibility | Manufacturer cross-reference | Matching head available | | Taper condition | Intraoperative inspection | No corrosion, no damage | | Position | Radiographs | Acceptable version and offset | **Indications for Stem Revision** - Stem loosening (subsidence, radiolucency) - Monoblock design (non-modular) - No compatible THA head available - Taper corrosion or damage - Malposition affecting stability or leg length - Varus subsidence with poor bone stock **Taper Compatibility** - MUST have manufacturer-matched head - Cross-manufacturer heads increase corrosion risk - Common tapers: 12/14, V40, Type 1 - If uncertain, default to stem revision **Essential Equipment** - Standard THA instrument set - Full revision instrument set available - Compatible modular heads (if retaining stem) - Acetabular reamers (line-to-line and under-ream options) - Various cup sizes including jumbo options - Augments and trabecular metal options - Dual mobility cup system **Femoral Revision (if needed)** - Cement removal tools (if cemented) - Extended trochanteric osteotomy set - Revision stems (modular, fully porous) - High-speed burr, osteotomes **Specific Needs** - Fluoroscopy (recommended) - Intraoperative templating - Cell saver (higher blood loss) - Nerve monitoring (optional for revision) **Lies 2-3cm posterior to hip capsule, at increased risk in revision surgery due to scarring** - May be adherent to capsule/scar tissue. Traction injury during leg lengthening (greater than 4cm). EXAM KEY: Identify nerve early if posterior approach, limit lengthening to 4cm, flex knee during retraction, consider nerve monitoring. **Lies anterior to hip capsule, 4-5cm from acetabulum** - At risk with aggressive anterior retraction, especially if medialized acetabulum with erosion. EXAM KEY: Anterior retractors on bone only (not soft tissue), be aware of protrusio bringing medial wall closer to vessels. **Exits greater sciatic notch and runs with superior gluteal vessels 3-5cm above acetabular rim** - Injury causes abductor weakness and Trendelenburg gait. EXAM KEY: Do not extend split in gluteus medius more than 5cm from tip of greater trochanter. **Often eroded/paper-thin in conversion cases, may have protrusio** - Aggressive reaming risks medial wall perforation and injury to intrapelvic vessels (obturator, iliac). EXAM KEY: Assess medial wall on CT preoperatively, ream carefully, consider medialised cup design. **Cement mantle and osteoporotic bone increase fracture risk during stem removal** - Cemented stems require careful extraction. EXAM KEY: If stem revision needed for cemented stem, consider extended trochanteric osteotomy. Have plating and cerclage available. **Acetabular Assessment** 1. **Centre of Rotation (CoR)** - Compare to contralateral normal hip - Erosion causes medial and superior migration - Plan to restore anatomic CoR if possible 2. **Bone Stock Assessment (Paprosky)** | Type | Description | Treatment | |------|-------------|-----------| | I | Supportive rim, minimal bone loss | Standard cementless cup | | IIA | Superior dome loss, less than 30% | Cementless cup, screws | | IIB | Less than 50% superolateral loss | Cementless cup, possible augment | | IIC | Medial wall deficient | Medial augment or protrusio cup | | IIIA | Greater than 40% host bone contact | Jumbo cup, augments | | IIIB | Less than 40% host bone contact | Cage, cup-cage, custom triflange | 3. **Templating** - Template cup size and position - Assess head size needed for stability - Plan offset and leg length restoration **Femoral Assessment** 1. **Stem Fixation** - Subsidence on serial radiographs - Radiolucent lines (complete vs partial) - Endosteal sclerosis (stable fibrous fixation) 2. **Stem Type Identification** - Manufacturer and model - Cemented vs cementless - Modular vs monoblock - Collar presence 3. **Taper Compatibility** - Confirm manufacturer has THA head for this stem - Document taper dimensions (12/14, V40, etc.) - If uncertain, plan for stem revision ### Step 1: Positioning and Approach Patient lateral decubitus. Use previous incision - typically posterior approach for hemiarthroplasty. May need to extend proximally or distally for exposure. Prepare for extensile approach if needed. **Approach Selection**: Use the previous approach. If lateral approach used for original hemiarthroplasty, can still use posterior for conversion if preferred - just be aware of previous scar and gluteal insertion. ### Step 2: Exposure and Dislocation Identify and protect sciatic nerve (if posterior approach). May be embedded in scar tissue - careful blunt dissection. Release short external rotators (tag for repair if posterior approach). Capsulectomy around femoral neck and acetabulum. Dislocate hip with internal rotation and flexion. Nerve may be adherent to scar tissue. Palpate nerve before any sharp dissection posterior to hip. Keep knee flexed during retraction to reduce tension. ### Step 3: Femoral Component Assessment With hip dislocated: 1. Remove hemiarthroplasty head (modular) - note taper condition 2. Test stem stability: rotational torque, axial stress 3. If ANY toggle or rotation, stem requires revision 4. Inspect taper for corrosion, fretting, or damage 5. If taper damaged, stem requires revision **Taper Inspection**: Clean taper with saline, dry thoroughly, use magnification or loupe. Any visible corrosion or pitting = revise stem. Corrosion products cause ALTR (adverse local tissue reaction). ### Step 4: Acetabular Exposure Elevate labrum and capsular remnants. Identify transverse acetabular ligament. Place retractors on anterior wall (protected) and posterior wall. Assess acetabular cartilage wear and bone stock. ### Step 5: Acetabular Preparation Remove remaining articular cartilage with curettes. Ream from peripheral rim - do NOT follow eroded medialized centre of rotation. Sequential reaming to healthy bleeding bone. Assess rim for defects. Medial wall may be paper-thin from erosion. Do NOT breach medial wall. If protrusio present, may need bone graft or medialised cup design rather than aggressive reaming. ### Step 6: Acetabular Component Insertion **Standard Bone Stock (Paprosky I-IIA)** - Cementless press-fit cup - Line-to-line or 1-2mm under-ream - Screws for supplemental fixation - Target: 40-45° inclination, 15-20° anteversion **Medial Wall Deficiency (Paprosky IIC)** - Consider protrusio ring or medialised cup design - Bone graft medial defect if large - May need larger cup to span defect **Significant Bone Loss (Paprosky III)** - Trabecular metal augments - Jumbo cups - Cup-cage constructs - Consider reconstruction cage ### Step 7: Head Selection and Trialling Select THA head compatible with retained stem taper. Trial different neck lengths for: - Stability (no impingement, adequate tension) - Leg length (equal to contralateral) - Offset (adequate abductor tension) Consider larger head (36mm) and/or dual mobility for instability risk. ### Step 8: Final Reduction and Closure Place final head with single firm impaction. Reduce hip. Test stability in flexion/IR (posterior) and extension/ER (anterior). Document ROM achieved. Repair posterior structures if posterior approach. Layered closure over drain. ### When Stem Revision Required - Stem loosening (subsidence, toggle) - Monoblock head (non-modular) - No compatible THA head available - Taper corrosion or damage - Malposition (version, offset, leg length) ### Step 1: Head Removal For monoblock stems, apply axial traction and rotation to remove entire stem with head. For modular stems with incompatible/corroded taper: - Remove modular head using head extractor - Inspect taper - if corroded, must revise stem ### Step 2: Cemented Stem Removal If cemented hemiarthroplasty: 1. Extended Trochanteric Osteotomy (ETO) - Mark 10-12cm from tip of trochanter distally - Oscillating saw for longitudinal cuts - Thin osteotome to complete - Protects from perforation, allows cement removal 2. Cement Removal - Remove bulk cement with osteotomes - Ultrasonic cement removal device - High-speed burr for residual cement - Remove all cement to distal extent 3. Canal Preparation - Sequential broaching - Revision stem (modular, fully porous) ### Step 3: Cementless Stem Removal 1. Interface disruption - Flexible osteotomes around stem - ETO if extensively ingrown 2. Extraction - Stem extractor with axial pull - May need trephine for bony ingrowth ### Step 4: Revision Stem Insertion Select stem based on remaining bone: - Metaphyseal fixation if diaphysis intact - Diaphyseal fixation (fully porous) if metaphysis deficient - Modular stems allow independent offset/length adjustment Secure ETO with cerclage wires if used. **Risk Factors for Dislocation** | Factor | Risk Level | Management | |--------|------------|------------| | Previous dislocation | High | Dual mobility or constrained | | Abductor deficiency | High | Dual mobility | | Cognitive impairment | Moderate | Consider constrained | | Posterior approach | Moderate | Repair posterior structures | | Revision surgery | Moderate | Consider dual mobility | | Neuromuscular disease | High | Constrained liner | **Dual Mobility Cup** - Inner head articulates with mobile polyethylene liner - Outer liner articulates with metal shell - Increases effective head size and jump distance - Reduces dislocation to less than 1% in revision - AOANJRR shows excellent results **Constrained Liner** - Capture mechanism locks head into liner - Reserved for highest risk cases - Higher stress on fixation interface - Requires excellent cup fixation **Dual Mobility Indication**: Consider for ALL conversion THA cases given inherently higher dislocation risk. Especially indicated if: previous dislocation, abductor weakness, cognitive impairment, or cannot comply with precautions. 1. Australian Orthopaedic Association National Joint Replacement Registry. Annual Report 2023. Adelaide: AOA; 2023. 2. Bhandari M, Devereaux PJ, Tornetta P 3rd, et al. Operative management of displaced femoral neck fractures in elderly patients. An international survey. J Bone Joint Surg Am. 2005;87(9):2122-2130. 3. Archibeck MJ, Carothers JT, Tripuraneni KR, White RE Jr. Total hip arthroplasty after failed hemiarthroplasty or internal fixation. J Arthroplasty. 2013;28(1):168-171. 4. Tidermark J, Ponzer S, Svensson O, et al. Internal fixation compared with total hip replacement for displaced femoral neck fractures in the elderly. A randomised, controlled trial. J Bone Joint Surg Br. 2003;85(3):380-388. 5. Diwanji SR, Kim SK, Seon JK, et al. Clinical results of conversion total hip arthroplasty after failed bipolar hemiarthroplasty. J Arthroplasty. 2008;23(7):1009-1015. 6. Parvizi J, Picinic E, Sharkey PF. Revision total hip arthroplasty for instability: surgical techniques and principles. J Bone Joint Surg Am. 2008;90(5):1134-1142. 7. Hailer NP, Weiss RJ, Stark A, Kärrholm J. The risk of revision due to dislocation after total hip arthroplasty depends on surgical approach, femoral head size, sex, and primary diagnosis. An analysis of 78,098 operations in the Swedish Hip Arthroplasty Register. Acta Orthop. 2012;83(5):442-448. 8. Civinini R, Carulli C, Matassi F, et al. A dual-mobility cup reduces risk of dislocation in isolated acetabular revisions. Clin Orthop Relat Res. 2012;470(12):3542-3548. 9. Laffosse JM, Tricoire JL, Chiron P, Puget J. Acetabular reconstruction using a cementless cup and structural allograft for severe acetabular bone loss. J Arthroplasty. 2007;22(7):993-1001. 10. Younger TI, Bradford MS, Magnus RE, Paprosky WG. Extended proximal femoral osteotomy. A new technique for femoral revision arthroplasty. J Arthroplasty. 1995;10(3):329-338.

Conversion THA after Failed Hemiarthroplasty

Conversion THA after Failed Hemiarthroplasty