import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Posterior to short external rotators**. Location: Exits pelvis below piriformis, runs over gemelli and obturator internus, then over quadratus femoris. Protection: KNEE FLEXION relaxes nerve; release rotators at femoral insertion (not proximally); avoid aggressive posterior retraction; maintain awareness during all steps. **Above piriformis**. Location: Exits greater sciatic notch superior to piriformis, courses between gluteus medius and minimus. Protection: Do NOT extend gluteus maximus split more than 5cm above greater trochanter; avoid forceful proximal retraction. **Below piriformis**. Location: Exits below piriformis, supplies gluteus maximus. Protection: Careful dissection near piriformis; avoid blind dissection posterior to rotators; preserve to maintain gluteus maximus function. **Deep to quadratus femoris**. Location: Branch of profunda femoris, passes between quadratus femoris and adductor magnus, supplies femoral head. Protection: Avoid aggressive deep retraction below quadratus femoris; gentle quadratus release if needed. **Anterior to hip capsule**. Location: Femoral nerve, artery, vein in femoral triangle anteriorly. Protection: Avoid overly anterior acetabular retractor placement; check retractor position during cup insertion; protect with anterior labrum. ## Comparison: Minimally Invasive vs Standard Posterior Approach | Feature | MIS Posterior | Standard Posterior | |---------|---------------|-------------------| | Incision length | 6-10cm | 15-20cm | | Muscle approach | Gluteus maximus split | Same | | Rotator management | Tag and repair | Same (essential) | | Visualization | Specialized retractors, lighting | Direct | | Learning curve | Steeper | Established | | Complications | Same when done well | Same | | Recovery | Possibly faster early | Standard | **Key Points:** - Same surgical principles apply to both - Posterior repair ESSENTIAL in both - MIS requires specialized instrumentation - Cosmetic benefit but no proven long-term advantage - Surgeon experience more important than incision length **Evidence:** - No significant difference in long-term outcomes - Early recovery advantages debated - Learning curve associated with higher early complication rates ## Posterior Soft Tissue Repair - The Key to Modern Success **Historical Context:** - Pre-repair era: 4-5% dislocation rate - Modern posterior repair: 1-2% dislocation rate - Comparable or better than DAA rates **Technique:** 1. **Tagging**: Place stay sutures in piriformis and conjoined tendon BEFORE release 2. **Bone tunnels**: Create 2-3 drill holes in posterior facet of greater trochanter 3. **Capsule repair**: First layer - repair posterior capsule with transosseous sutures 4. **Rotator repair**: Second layer - repair external rotators over capsule 5. **Tension**: Aim for snug repair that creates posterior soft tissue tension band **Capsulotomy Options:** - T-shaped: Vertical limb at margin, horizontal at neck - L-shaped: Along acetabular rim and neck - Both allow adequate exposure and repair **Critical Points:** - Both layers (capsule + rotators) should be repaired - Through-bone fixation stronger than soft tissue alone - Test stability BEFORE final closure - Repair should resist posterior translation in at-risk position ## Posterior vs Direct Anterior Approach | Feature | Posterior | DAA | |---------|-----------|-----| | Dislocation rate | 1-2% (with repair) | 0.5-1% | | Muscle cut | Short external rotators | None (internervous) | | Femoral exposure | Excellent | Challenging | | Acetabular exposure | Good | Good | | Learning curve | Established | Significant | | LFCN injury | Rare | 10-15% | | Fluoroscopy | Optional | Commonly used | | Hip precautions | 6-12 weeks | Often none | | Surgeon positioning | Lateral decubitus | Supine | | Obese patients | Feasible | Challenging | **When to Choose Posterior:** - Surgeon familiarity and comfort - Complex anatomy (dysplasia, prior surgery) - Obese patients (better access) - When excellent femoral exposure needed - Revision surgery **Key Message:** - Both approaches have excellent outcomes when done well - Surgeon experience is the most important factor - Posterior with repair has closed the dislocation gap ## Preventing Posterior Dislocation **Risk Factors:** - Failure to repair posterior structures - Malpositioned components (excessive anteversion or inclination) - Inadequate soft tissue tension - Patient non-compliance with precautions - Neuromuscular disease, cognitive impairment **Surgical Prevention:** 1. **Posterior repair** - capsule + rotators (reduces 4-5% to 1-2%) 2. **Component position** - combined anteversion 25-45° 3. **Head size** - larger heads more stable (32mm or 36mm) 4. **Offset restoration** - adequate tension in posterior structures 5. **Intraoperative testing** - check stability in at-risk positions **Position of Risk:** - Flexion (more than 90°) - Adduction (crossing midline) - Internal rotation - Combined = maximum posterior stress **Stability Testing:** - Shuck test for component seating - Posterior stress in flexion/adduction/IR - Document stable ROM achieved - If unstable: larger head, constrained liner, revision cup position ## Protecting the Sciatic Nerve **Anatomy:** - Largest nerve in body (L4-S3) - Exits greater sciatic notch BELOW piriformis (90%) - Courses over gemelli, obturator internus, quadratus femoris - Lies 1-2cm posterior to posterior acetabular rim - Divides into tibial and common peroneal at variable level **Risk of Injury:** - Overall: 0.5-1% in primary THA - Higher in revision, dysplasia, lengthening more than 4cm - Peroneal division more susceptible (lateral position) **Protection Strategies:** 1. **Knee flexion** - relaxes nerve, reduces stretch injury 2. **Release rotators at femoral insertion** - away from nerve 3. **Avoid posterior retraction** - nerve is immediately posterior 4. **Limit lengthening** - more than 4cm increases risk significantly 5. **Awareness** - maintain constant attention to posterior structures **If Injury Suspected:** - Check motor function (foot dorsiflexion, plantarflexion) - Document immediately post-operatively - EMG at 3-4 weeks if deficit present - Most stretch injuries recover over months - Surgical exploration only if clear transaction or hematoma **Patient Position**: Lateral decubitus on standard operating table **Setup:** - Bean bag or pelvic posts for stable pelvic positioning - Operative leg freely draped for full mobility - Ensure pelvis is truly vertical - affects cup orientation - Arm support and all pressure points padded **Key Considerations:** - Pelvic tilt DIRECTLY affects cup orientation measurements - Tilted pelvis causes malpositioned cup if not recognized - Mark bony landmarks before draping (ASIS, GT, posterior iliac spine) - Confirm leg length markers before incision ### Step 1: POSITIONING AND LANDMARKS POSITIONING: Lateral decubitus with pelvis stabilized by anterior and posterior posts or bean bag. Confirm pelvis is vertical - any tilt affects cup orientation. Operative leg freely mobile for dislocation and manipulation. Mark greater trochanter and intended incision line. **Technical Tip**: EXAM KEY: LATERAL DECUBITUS is standard for posterior approach. PELVIC TILT directly affects cup position - if tilted anteriorly, measured anteversion will be LESS than actual. Ensure true vertical pelvis positioning. - Pelvic tilt causing cup malposition (unrecognized tilt = maloriented cup) - Inadequate stabilization allowing pelvic movement - Pressure injuries from prolonged positioning ### Step 2: INCISION AND SUPERFICIAL DISSECTION INCISION: MIS posterior = 6-10cm (vs 15-20cm standard). Centered over or slightly posterior to greater trochanter. Oblique direction from posterosuperior to anteroinferior, following gluteus maximus fibers. Incise skin and subcutaneous tissue. Identify fascia lata and gluteus maximus fascia. **Technical Tip**: EXAM KEY: MINI-POSTERIOR = 6-10cm incision. Same surgical principles as standard posterior - just smaller window. Requires specialized retraction and lighting. Do NOT compromise on safety for incision size. - Incision too small limiting visualization and increasing tissue trauma - Excessive skin retraction causing edge necrosis - Wrong incision placement compromising exposure ### Step 3: GLUTEUS MAXIMUS SPLIT GLUTEUS MAXIMUS: Incise gluteus maximus fascia in line with muscle fibers. Split gluteus maximus BLUNTLY between fibers - this is muscle-splitting, NOT detachment. Limit split to 5cm above greater trochanter to protect SUPERIOR GLUTEAL NEUROVASCULAR BUNDLE. Insert self-retaining or specialized MIS retractors. **Technical Tip**: EXAM KEY: GLUTEUS MAXIMUS SPLIT - blunt dissection in line with fibers. Do NOT extend more than 5cm proximal to GT - superior gluteal nerve exits above piriformis and courses between glut med/min. Injury causes Trendelenburg gait. - Superior gluteal nerve injury from excessive proximal split - Excessive muscle damage from forceful retraction - Gluteus maximus denervation from inferior gluteal nerve injury ### Step 4: IDENTIFY SHORT EXTERNAL ROTATORS IDENTIFY SHORT EXTERNAL ROTATORS: Expose posterior hip capsule and overlying short external rotators. From superior to inferior: piriformis (key landmark), gemelli with obturator internus between, quadratus femoris. Sciatic nerve exits BELOW piriformis and runs posterior to these muscles. **Technical Tip**: EXAM KEY: POGO-Q mnemonic for rotators (Piriformis, Obturator internus, Gemelli, Obturator externus, Quadratus). SCIATIC NERVE exits inferior to piriformis in 90% (may split piriformis in 10%). Always know its location. - Sciatic nerve injury from blind dissection - Failure to identify correct anatomy - Damage to inferior gluteal nerve and vessels ### Step 5: TAG AND RELEASE SHORT EXTERNAL ROTATORS TAG AND RELEASE ROTATORS: Place tagging sutures in piriformis and conjoined tendon (superior gemellus, obturator internus, inferior gemellus) BEFORE release. Incise rotators close to their femoral insertion (away from sciatic nerve). Protect quadratus femoris if possible (MCFA runs deep to it). Maintain knee flexed to relax sciatic nerve. **Technical Tip**: EXAM KEY: TAG rotators with sutures BEFORE cutting - this is CRITICAL for repair. Release at femoral insertion, NOT proximally near nerve. Piriformis + conjoined tendon most important for repair. Knee flexion protects sciatic nerve. - Inadequate tagging preventing later repair (increases dislocation) - Sciatic nerve injury during rotator release (release close to femur) - MCFA injury with aggressive quadratus release ### Step 6: CAPSULOTOMY CAPSULOTOMY: Expose posterior capsule. Perform T-shaped or L-shaped capsulotomy. TAG capsule edges for repair. Clear capsule from acetabular rim as needed for exposure. The capsule is an important stabilizer - preserve for repair. **Technical Tip**: EXAM KEY: TAG CAPSULE for repair - capsular repair + rotator repair together reduce dislocation to less than 1-2%. T-capsulotomy: vertical along margin, horizontal at neck. Both capsule AND rotators must be repaired. - Failure to tag capsule preventing repair - Excessive capsule excision compromising repair - Injury to labrum affecting press-fit stability ### Step 7: HIP DISLOCATION HIP DISLOCATION: Dislocate hip posteriorly with flexion, adduction, internal rotation. May use corkscrew device in femoral head to control dislocation. Controlled dislocation prevents fracture. Remove femoral head after neck osteotomy if preferred. **Technical Tip**: EXAM KEY: POSTERIOR DISLOCATION = FLEXION, ADDUCTION, INTERNAL ROTATION. Controlled technique prevents fracture. Some surgeons prefer neck cut in situ then extraction. Corkscrew provides control during dislocation. - Uncontrolled dislocation causing soft tissue damage - Femoral neck fracture with forceful dislocation - Acetabular rim fracture with leveraging ### Step 8: FEMORAL NECK OSTEOTOMY AND HEAD REMOVAL FEMORAL NECK OSTEOTOMY: Neck cut with oscillating saw per template. Standard 45° angle from lesser trochanter. Remove femoral head. Excellent visualization of femoral canal is a KEY ADVANTAGE of posterior approach. **Technical Tip**: EXAM KEY: FEMORAL EXPOSURE is EXCELLENT in posterior approach - major advantage over anterior approaches. Direct visualization of canal for accurate broaching and stem placement. Version typically 10-15° anteversion. - Incorrect neck cut level affecting leg length/offset - Femoral calcar fracture during head removal - Inadequate bone removal causing femoral fracture during broaching ### Step 9: FEMORAL PREPARATION FEMORAL PREPARATION: Box osteotome to open canal. Sequential broaching with trial stems. Ensure appropriate version (10-15° anteversion typically). Posterior approach allows direct visualization of canal and version. Confirm stable broach seating before final implant. **Technical Tip**: EXAM KEY: Femoral version is DIRECTLY visualized in posterior approach - align with posterior femoral condyles as reference. Canal preparation straightforward with direct visualization. Avoid varus or retroversion. - Incorrect version (excessive anteversion increases anterior dislocation risk) - Femoral fracture from aggressive broaching - Varus stem positioning from inadequate lateralization ### Step 10: ACETABULAR EXPOSURE AND PREPARATION ACETABULAR EXPOSURE: Retractors around acetabulum - anterior (inferior to ASIS), inferior (in obturator foramen), posterior as needed. Retract femur anteriorly with bone hook or dedicated retractor. Sequential reaming to bleeding subchondral bone. Maintain peripheral rim for press-fit. **Technical Tip**: EXAM KEY: Femur must be retracted ANTERIORLY for acetabular visualization. Target cup position: 40° ± 10° inclination, 15° ± 10° anteversion (Lewinnek). Combined anteversion (cup + stem) = 25-45° for stability. - Cup malposition (most common technical error in THA) - Anterior wall perforation with over-medialization - Femoral nerve injury from aggressive anterior retraction ### Step 11: ACETABULAR COMPONENT IMPLANTATION ACETABULAR IMPLANTATION: Press-fit cup with 1-2mm under-ream. Confirm position before final impaction. Supplemental screws if questionable fixation. Insert liner (polyethylene, ceramic, or dual mobility per plan). **Technical Tip**: EXAM KEY: Cup orientation by direct visualization or with guides. In lateral decubitus, account for pelvic position. Navigation can improve accuracy if available. Confirm rigid fixation before liner insertion. - Cup malposition causing impingement or dislocation - Inadequate press-fit (consider screws if any movement) - Liner malseating ### Step 12: FEMORAL COMPONENT IMPLANTATION FEMORAL IMPLANTATION: Insert final femoral stem (cemented or press-fit per plan). Confirm version and stable seating. Trial head for stability and leg length assessment. **Technical Tip**: EXAM KEY: Posterior approach allows excellent femoral component insertion. Confirm appropriate version by aligning with posterior condyles. Trial extensively before final head placement. - Incorrect version (critical for stability) - Periprosthetic fracture during insertion - Cement extravasation (if cemented technique) ### Step 13: TRIAL REDUCTION AND STABILITY TESTING TRIAL REDUCTION: Reduce hip with trial head. Test stability in ALL positions, especially the POSTERIOR DISLOCATION POSITION - flexion, adduction, internal rotation. This is the position of risk with posterior approach. Assess leg length with contralateral comparison. Confirm adequate soft tissue tension. **Technical Tip**: EXAM KEY: CRITICAL to test stability in POSTERIOR DISLOCATION POSITION - flexion past 90°, adduction, internal rotation. If unstable: larger head, higher offset, constrained liner, or adjust components. Document stable ROM achieved. - Unrecognized instability (will dislocate postoperatively) - Leg length discrepancy (measure carefully) - Over-lengthening (sciatic nerve risk if more than 4cm) ### Step 14: FINAL COMPONENTS AND REDUCTION FINAL COMPONENTS: Insert definitive head. Reduce hip. Final stability check. Confirm leg length and offset acceptable. Irrigate joint thoroughly. **Technical Tip**: EXAM KEY: Final components should replicate trial findings. Head size affects stability - larger heads (32mm, 36mm) more stable. Adequate offset restores abductor tension and posterior soft tissue tension. - Component mismatch from trial - Inadequate irrigation leaving debris - Failure to confirm final stability ### Step 15: POSTERIOR REPAIR - CRITICAL STEP POSTERIOR REPAIR: THE KEY TO MODERN POSTERIOR APPROACH SUCCESS. Create 2-3 drill holes in posterior facet of greater trochanter. Pass transosseous sutures. First repair posterior capsule to bone. Then repair short external rotators (piriformis + conjoined tendon) over capsule as second layer. Creates posterior soft tissue tension band preventing posterior dislocation. **Technical Tip**: EXAM KEY: POSTERIOR REPAIR = CAPSULE + ROTATORS through bone tunnels. Reduces dislocation from 4-5% to 1-2%. This is THE difference in modern posterior approach. Both layers important - capsule first, then rotators over top. - Inadequate repair strength (use transosseous, not soft tissue only) - Failure to repair one or both layers - Trochanter fracture from aggressive drilling **Closure:** - Irrigate wound thoroughly (minimum 3L) - Gluteus maximus fascia reapproximated - Subcutaneous closure with absorbable sutures - Skin closure (staples or subcuticular) - Sterile dressing **Post-operative Care:** - Weight bearing as tolerated immediately - Hip precautions 6-12 weeks: - Avoid flexion more than 90° - Avoid adduction past midline - Avoid internal rotation - VTE prophylaxis per institutional protocol - Standard THA rehabilitation pathway **References:** 1. Pellicci PM, et al. Posterior approach to total hip replacement: results of 526 consecutive cases. J Bone Joint Surg Am. 1998;80(4):519-525. 2. Kwon MS, et al. Does surgical approach affect total hip arthroplasty dislocation rates? Clin Orthop Relat Res. 2006;447:34-38. 3. Goldstein WM, et al. Posterior soft-tissue repair in primary total hip replacement. J Bone Joint Surg Am. 2001;83(10):1496-1500. 4. Berry DJ, et al. Posterior approach THA: comparison with and without soft tissue repair. J Arthroplasty. 2011;26(6 Suppl):132-137. 5. Chechik O, et al. Surgical approach and prosthesis fixation in hip arthroplasty: a meta-analysis. Hip Int. 2009;19(1):44-48. 6. Weeden SH, Paprosky WG. Minimal incision total hip arthroplasty: posterior approach. Clin Orthop Relat Res. 2004;429:227-234. 7. Ogonda L, et al. A minimal-incision technique in total hip arthroplasty does not improve early postoperative outcomes. J Bone Joint Surg Am. 2005;87(4):701-710. 8. Demos HA, et al. Surgical approach and dislocation rate in primary total hip replacement. J Arthroplasty. 2001;16(2):139-146. 9. Masonis JL, Bourne RB. Surgical approach, abductor function, and total hip arthroplasty dislocation. Clin Orthop Relat Res. 2002;405:46-53. 10. Sibia US, et al. Incidence and risk factors for sciatic nerve injury in primary total hip arthroplasty. J Arthroplasty. 2017;32(8):2431-2434.

Minimally Invasive Posterior THA

Minimally Invasive Posterior THA