import { OnePagerSummary, ContentSection, ExamWarning, InfoCardGrid, InfoCard, EvidenceCard, ComparisonTable, VivaScenario, MnemonicCard, ExamCheatSheet, Tab, Tabs } from '@/components/mdx' # Tibial Tubercle Osteotomy: Comprehensive Examination Guide ## Introduction and Clinical Context **Tibial tubercle osteotomy (TTO)** is an advanced surgical technique for achieving extensile exposure of the knee joint by creating a **pedicled osteotomy of the anterior tibial cortex** with the attached patellar tendon, allowing the entire extensor mechanism (quadriceps-patella-patellar tendon-tibial tubercle complex) to be reflected proximally while maintaining soft tissue continuity and blood supply. TTO is the PRIMARY technique for managing **difficult knee exposure** in revision TKA (stiff knee with less than 70° flexion, ankylosed knee, severe arthrofibrosis), extensor mechanism reconstruction (patellar tendon avulsion, chronic ruptures), and patellofemoral realignment procedures (severe patellar maltracking with bony deformity requiring tubercle medialization or distalization). ### Historical Development and Surgical Evolution Tibial tubercle osteotomy was first described by **Coonse and Adams (1943)** for patellar fracture exposure and later popularized by **Dolin (1983)** and **Whiteside (1995)** for revision TKA exposure. The technique evolved from **non-pedicled** osteotomies (complete detachment of tubercle with high nonunion rates 20-30%) to **pedicled osteotomies** (medial soft tissue attachment preserved, nonunion rate reduced to 2-5%). Modern TTO techniques emphasize **adequate osteotomy dimensions** (6-8cm length, 1-1.5cm thickness), **preservation of medial soft tissue pedicle** (periosteum and muscle attachments provide blood supply), and **rigid fixation** (2-3 cortical screws or cerclage wires) to maximize union rates and minimize complications. The PRIMARY advantage of TTO over alternative extensor mechanism disruption techniques (**quadriceps snip, V-Y quadricepsplasty, quadriceps turndown**) is PRESERVATION of the extensor mechanism's structural integrity - the patellar tendon remains in continuity with bone throughout the procedure, avoiding tendon-to-bone healing (which has higher failure rates 10-15% vs bone-to-bone healing 2-5%). This makes TTO particularly valuable in **revision TKA** where adequate exposure is critical for component removal, cement extraction, bone preparation, and reimplantation, and where extensor mechanism integrity is already compromised by previous surgery. ## Surgical Anatomy and Key Landmarks ### Surface Anatomy and Planning **Skin incision landmarks:** - **Standard TKA incision**: Midline anterior longitudinal incision from 5cm proximal to patella to 2-3cm distal to tibial tubercle - **TTO modification**: Extend incision distally to 8-10cm below tibial tubercle (allows access to distal extent of osteotomy) **Palpable landmarks:** - **Tibial tubercle**: Prominent anterior bony ridge on proximal tibia, insertion of patellar tendon - **Tibial shaft**: Palpable subcutaneous border (medial surface) - marks medial extent of osteotomy - **Gerdy's tubercle**: Lateral proximal tibia (lateral to tubercle) - marks lateral extent of osteotomy - **Patella**: Inferior pole marks proximal extent of patellar tendon (reference for osteotomy length) **Osteotomy dimensions (CRITICAL):** - **Length**: 6-8cm measured from tibial tubercle distally along anterior tibial cortex - Must extend at least 1-2cm DISTAL to patellar tendon insertion (ensures tendon attachment on bone) - Longer fragment (8-10cm) safer for fixation but requires more dissection - **Thickness**: 1-1.5cm (includes anterior cortex + cancellous bone) - Too thin (less than 1cm) = increased fracture risk (insufficient bone for screw purchase) - Too thick (greater than 2cm) = difficult closure, prominent hardware - **Width**: 2-3cm (medial-to-lateral) - Centered on tibial tubercle (includes patellar tendon insertion site) - Too narrow (less than 2cm) = increased avulsion risk (insufficient bone for tendon forces) ### Layer-by-Layer Anatomic Dissection **Layer 1 - Skin and Subcutaneous Tissue:** - Standard midline anterior knee incision (reopen previous TKA incision if revision) - Extend incision distally to 8-10cm below tibial tubercle - Full-thickness skin flaps developed medially and laterally (expose tibial anterior cortex) **Layer 2 - Fascia and Periosteum:** - **Patellar tendon**: Central structure, inserts on tibial tubercle - **Periosteum**: Continuous with patellar tendon distally (forms periosteal sleeve around tubercle) - **Dissection technique**: - Incise periosteum LATERAL to patellar tendon along line of planned osteotomy (lateral border) - Incise periosteum DISTAL to planned osteotomy (distal extent 6-8cm from tubercle) - **DO NOT INCISE medial periosteum** - preserve medial soft tissue attachments (vascular pedicle) - Elevate periosteum laterally (subperiosteal) to expose lateral aspect of anterior tibia **Layer 3 - Osteotomy Creation:** - **Osteotomy plane**: Oblique from anterior cortex (superficial) to deep cortex (deeper distally) - Angle: 30-45° from anterior tibial surface (creates gradually tapered fragment) - Direction: Distal osteotomy cut angles POSTERIORLY (avoids stress riser in anterior cortex distally) - **Osteotomy technique**: - Multiple drill holes along planned osteotomy path (creates perforation line) - Connect holes with thin osteotome (propagates fracture along drill holes) - Gently elevate fragment with wide osteotome from distal to proximal (preserves medial pedicle) **Layer 4 - Medial Soft Tissue Pedicle (PRESERVE):** - **Medial attachments**: Periosteum, pes anserinus tendons (sartorius, gracilis, semitendinosus), MCL superficial fibers - **Vascular supply**: Medial soft tissue pedicle contains periosteal blood vessels (primary blood supply to osteotomy fragment) - **CRITICAL**: Do NOT strip medial soft tissue from fragment (converts to non-vascularized osteotomy with high nonunion risk) ### Neurovascular Anatomy and Relationships **Patellar Tendon Blood Supply:** - **Inferior medial genicular artery** (branch of popliteal artery): Primary blood supply to patellar tendon and tibial tubercle region - **Medial periosteal vessels**: Run along medial periosteum (preserved with medial soft tissue pedicle) - **Infrapatellar fat pad vessels**: Contribute to patellar tendon vascularity proximally **Infrapatellar Branch of Saphenous Nerve:** - **Course**: Runs subcutaneously across anterior knee (medial to lateral) - **Function**: Sensory to anteromedial knee and proximal medial leg - **Risk**: Injured during skin incision or subcutaneous dissection (causes anteromedial knee numbness - NOT functionally limiting but bothersome) - **Protection**: Identify if visible, retract or accept division (numbness unavoidable in many cases) **Popliteal Neurovascular Bundle:** - **Location**: Posterior knee (NOT at risk during TTO if osteotomy stays anterior) - **Risk**: Only at risk if osteotomy extends TOO POSTERIORLY (penetrates posterior cortex) - **Protection**: Ensure osteotomy stays in anterior 50% of tibia (never extends beyond midline of tibia on lateral X-ray) ## Indications and Contraindications ### Primary Indications (Strong Evidence) **ABSOLUTE Indications:** 1. **Revision TKA with stiff knee** (less than 70° flexion) where standard exposure inadequate - Ankylosed knee (0° flexion) - TTO allows atraumatic exposure without extensor mechanism disruption - Severe arthrofibrosis post-TKA (less than 60° flexion despite manipulation) 2. **Revision TKA requiring extensive component removal**: - Well-fixed cemented components requiring power tools for removal (risk of extensor mechanism avulsion with forceful retraction) - Metaphyseal sleeves or cones (require direct access to bone-implant interface) 3. **Patellar tendon avulsion repair** (acute or chronic) - allows anatomic reattachment of tendon to bone 4. **Severe patellofemoral maltracking** requiring tubercle medialization AND distalization: - Combined procedures (anteromedialization or medialization + distalization) with bony correction - Tubercle anteriorization for patellofemoral arthritis (Fulkerson osteotomy) **RELATIVE Indications:** 1. **Primary TKA in very stiff knee** (less than 50° flexion) - consider TTO if quadriceps snip would be needed 2. **Extensor mechanism reconstruction** in chronic patellar tendon ruptures (allows bone-to-bone healing) 3. **Tibial tubercle fracture malunion** with patella baja (allows tubercle distalization and patella height restoration) ### Contraindications **ABSOLUTE Contraindications:** 1. **Active knee infection** (osteotomy will not heal in presence of infection) 2. **Severe osteopenia/osteoporosis** (inadequate bone quality for osteotomy fixation - consider alternative techniques) 3. **Previous failed TTO** with nonunion (repeat osteotomy high failure risk - consider extensor mechanism allograft) **RELATIVE Contraindications:** 1. **Adequate exposure achievable with less invasive techniques** (standard medial parapatellar, subvastus, quadriceps snip) 2. **Poor soft tissue envelope** (previous multiple surgeries, radiation, compromised wound healing) 3. **Patient non-compliance** (cannot follow protected weight-bearing protocol - risk avulsion/nonunion) ## Preoperative Planning and Patient Positioning ### Preoperative Assessment **Clinical Examination:** - **ROM assessment**: Maximum flexion/extension (document limitation - TTO indicated if less than 70° flexion) - **Extensor lag**: Test active straight leg raise (indicates quadriceps function) - **Patellar tracking**: Observe patella tracking during ROM (assess for maltracking requiring correction) - **Soft tissue assessment**: Skin quality, previous incisions, compromised areas (plan incision accordingly) **Radiographic Planning:** - **AP and lateral knee X-rays**: Assess bone quality, existing hardware, component position (if revision TKA) - **Merchant or skyline view**: Patellofemoral alignment, tibial tubercle-trochlear groove (TT-TG) distance - **Measurements**: - **Insall-Salvati ratio** (patellar height): Patellar tendon length / patellar length (normal 0.8-1.2) - Patella baja (less than 0.8): Consider tubercle distalization - **TT-TG distance** (tubercle lateralization): Normal less than 20mm - Greater than 20mm: Consider tubercle medialization - **CT scan** (if revision TKA): Bone stock assessment, cement mantle evaluation, component loosening **Surgical Planning:** - **Osteotomy dimensions**: Template on lateral X-ray (6-8cm length from tubercle) - **Fixation method**: Plan for 2-3 cortical screws (4.0mm or 4.5mm) OR cerclage wires if bone quality poor - **Concomitant procedures**: If tubercle medialization/distalization needed, plan realignment vectors ### Patient Positioning **SUPINE position with leg holder** (STANDARD): - **Position**: Patient supine on operating table - **Leg positioning**: - Leg holder on proximal thigh (allows knee flexion/extension without assistant) - OR foot of bed flexed with bump under thigh (allows gravity-assisted flexion) - Lateral post at thigh (prevents leg from rotating externally) - **Tourniquet**: Proximal thigh (exsanguinate if hemostasis needed, but TTO usually done with tourniquet DOWN for medial pedicle blood flow preservation) - **C-arm access**: Position from contralateral side (for intraoperative fluoroscopy to confirm osteotomy position/fixation) ## Step-by-Step Surgical Technique ### Step 1: Skin Incision and Exposure **Technique:** 1. **Reopen previous TKA incision** (if revision) or make standard midline anterior incision (if primary) - Extend incision distally to 8-10cm below tibial tubercle (allows access to distal osteotomy) 2. **Develop full-thickness skin flaps** medially and laterally - Expose tibial anterior cortex from tubercle to 8-10cm distally - Expose medial and lateral borders of patellar tendon 3. **Identify tibial tubercle** (palpable bony prominence with patellar tendon insertion) ### Step 2: Periosteal Incision and Osteotomy Planning **Technique:** 1. **Mark osteotomy dimensions** on anterior tibia: - **Length**: 6-8cm from tibial tubercle distally (measure with ruler) - **Width**: 2-3cm medial-to-lateral (centered on tubercle) - **Lateral border**: Draw line along lateral edge of planned osteotomy (parallel to patellar tendon) - **Distal border**: Draw transverse line at distal extent (6-8cm from tubercle) 2. **Incise periosteum along LATERAL border**: - Use electrocautery to incise periosteum from tibial tubercle to distal extent - Elevate periosteum laterally (subperiosteal) to expose lateral cortex 3. **Incise periosteum along DISTAL border**: - Transverse incision connecting lateral border to approximate medial border (but DO NOT completely incise medially - preserve medial pedicle) 4. **DO NOT INCISE MEDIAL PERIOSTEUM**: - Leave medial soft tissue attachments intact (periosteum, muscle, MCL fibers) - This medial pedicle provides blood supply for osteotomy healing ### Step 3: Osteotomy Creation **Technique:** 1. **Drill multiple holes along osteotomy path**: - Use 3.2mm drill bit (for 4.0mm or 4.5mm screws) - **Lateral border**: Drill holes every 5-10mm along lateral line (from tubercle to distal extent) - **Distal border**: Drill holes every 5-10mm along distal transverse line - **Angle drill 30-45° posteriorly** (osteotomy angles deep from anterior to posterior) - Drill to depth of 1-1.5cm (includes anterior cortex + cancellous bone, does NOT penetrate posterior cortex) 2. **Connect drill holes with thin osteotome**: - Insert 10-15mm wide osteotome into drill holes - Gently tap to propagate fracture along perforation line (connects holes) - Work from DISTAL to PROXIMAL (easier to control fragment elevation) - Work from LATERAL to MEDIAL (preserves medial pedicle until last) 3. **Complete osteotomy medially**: - With lateral and distal cuts complete, insert wide (20-25mm) osteotome at distal-medial corner - Gently lever osteotomy fragment ANTERIORLY (propagates fracture through medial cancellous bone) - **PRESERVE medial periosteum** - fracture should propagate THROUGH bone, not along periosteum - Fragment remains attached to medial soft tissue pedicle (pedicled osteotomy) 4. **Elevate osteotomy fragment**: - Insert wide osteotomes under fragment from distal to proximal - Gently elevate fragment WITH attached patellar tendon proximally - Fragment hinges on medial soft tissue pedicle (like opening a book) - Protect fragment during knee flexion/manipulation (pad with moist sponge, avoid excessive traction) ### Step 4: Knee Exposure and Procedure **After TTO complete:** 1. **Reflect extensor mechanism proximally**: - With tubercle osteotomy hinged medially, entire extensor mechanism (quadriceps-patella-patellar tendon-tubercle) can be reflected proximally - Provides EXTENSILE exposure of knee joint (full visualization of femur, tibia, patella) 2. **Perform intended procedure**: - **Revision TKA**: Remove components, extract cement, prepare bone, insert new components - **Extensor mechanism repair**: Anatomic reattachment of patellar tendon to bone - **Tubercle realignment**: Medialization, distalization, or anteriorization as needed 3. **Minimize manipulation trauma**: - Handle tubercle fragment gently (avoid excessive traction or rotation) - Keep medial pedicle moist (prevents desiccation of vascular supply) - Irrigate frequently (prevents heat necrosis from power tools) ### Step 5: Osteotomy Fixation **Technique:** 1. **Position tubercle fragment anatomically**: - Return fragment to EXACT original position (no medialization/lateralization unless planned) - Ensure congruent bone contact (no gaps - may need to debride fracture surfaces if comminuted) - Temporary fixation with pointed reduction clamps OR K-wires (holds position during screw insertion) 2. **Drill for screw fixation**: - **Number of screws**: 2-3 cortical screws (4.0mm or 4.5mm diameter) - **Screw position**: Perpendicular to osteotomy plane (achieves compression when tightened) - Proximal screw: Through proximal fragment (at level of tibial tubercle) - Middle screw: Through mid-fragment (3-4cm distal to tubercle) - Distal screw (optional): Through distal fragment (5-6cm distal to tubercle) - **Drilling technique**: Drill through NEAR cortex only (fragment), engage FAR cortex (proximal tibia) - Use drill guide to control angle (perpendicular to osteotomy) - Measure screw length (ensure bicortical purchase - engages both cortices of proximal tibia) 3. **Insert screws**: - Place 4.0mm or 4.5mm cortical screws (fully threaded) - Tighten screws to COMPRESSION (pulls fragment against tibia - no gap at osteotomy) - Use washers if bone quality poor (distributes load, prevents screw pull-through) 4. **Alternative: Cerclage wire fixation** (if poor bone quality): - Pass 18-gauge or 16-gauge cerclage wire around tibia (circumferential) - Position wire proximal and distal to osteotomy (2 wires minimum) - Use washers under wire (prevents wire cutting through bone) - Tighten wires to compression (wire tensioner) - Less rigid than screws but safer in osteoporotic bone 5. **Confirm fixation**: - Palpate fragment (should be immobile - no toggle with stress) - Fluoroscopy: AP and lateral views confirm screw position (bicortical, no intra-articular penetration) - Flex knee to 90° (ensure fragment stable during ROM) ### Step 6: Closure and Postoperative Care **Technique:** 1. **Repair periosteum** (if possible): - Reapproximate lateral periosteum to medial periosteum with absorbable sutures (0-Vicryl) - Creates periosteal sleeve around osteotomy (improves healing) 2. **Deep fascia closure**: - Close in layers with absorbable sutures 3. **Subcutaneous and skin closure**: - 2-0 or 3-0 Vicryl for subcutaneous - Staples or subcuticular closure for skin 4. **Dressing**: Sterile gauze, compressive wrap (minimize swelling) 5. **Immobilizer or brace**: Knee immobilizer in extension (optional first 2-4 weeks for comfort and protection) **Postoperative Protocol:** - **Immediate**: Check extensor mechanism function (active straight leg raise - should be intact if TTO healed primarily) - **Weeks 0-6**: TOUCH weight-bearing only (with crutches/walker), knee immobilizer for ambulation (remove for exercises) - ROM: Passive and active-assisted ROM 0-90° (prevents stiffness but limits stress on osteotomy) - Quadriceps sets, straight leg raises (maintain extensor strength) - **Weeks 6-12**: Radiographic assessment (expect early callus by 6-8 weeks) - Advance to PARTIAL weight-bearing (25-50%) if callus visible - Progress ROM to full (0-120° goal) - **Week 12+**: Radiographic union confirmed (bridging callus 3-4 cortices) - Advance to FULL weight-bearing - Progress strengthening (resistance exercises) - **Follow-up**: Weeks 2, 6, 12, 24 with X-rays (assess union, hardware position) ## Complications and Management ### Intraoperative Complications **1. Osteotomy Fragment Fracture (3-5% incidence)** **Recognition:** - Fracture during osteotomy creation (fragment cracks/shatters during elevation) - Fragments too small for screw fixation **Management:** - **Small crack** (non-displaced): Proceed with fixation as planned (screw compression closes crack) - **Large fracture** (displaced, comminuted): - Option 1: Abort TTO, use alternative exposure technique (quadriceps snip or turndown) - Option 2: Fix fracture with screws/wires, proceed with TTO (higher nonunion risk 15-20%) - Option 3: Convert to extensor mechanism allograft reconstruction (complex, reserved for salvage) **Prevention:** - Adequate dimensions (6-8cm long, 1-1.5cm thick, 2-3cm wide) - Gentle handling (wide osteotomes, slow elevation, avoid torsion/bending forces on fragment) - Multiple drill holes (perforates bone, reduces force needed to propagate osteotomy) **2. Inadvertent Complete Detachment of Medial Pedicle** **Recognition:** - Fragment completely free (no soft tissue attachment) - converted to non-pedicled osteotomy **Management:** - **IMMEDIATE**: - Preserve ALL soft tissue on fragment (do not strip further) - Return fragment to anatomic position, rigid fixation with 3 screws - Bone graft around osteotomy (autograft or allograft) to enhance healing - **Post-operative**: Extended protected weight-bearing (8-10 weeks), bone stimulator (consider) - **Expected outcome**: Higher nonunion risk (15-20% vs 2-5% with pedicle preserved) **Prevention:** - **Plan medial pedicle preservation** - do NOT incise medial periosteum during dissection - Propagate osteotomy medially last (lateral and distal cuts first, then medial cancellous bone) - If inadvertently stripping medial soft tissue - STOP immediately, preserve remaining attachments **3. Posterior Cortex Penetration** **Recognition:** - Drill/osteotome penetrates posterior tibia (risks popliteal neurovascular injury) - Blood welling up from deep in wound (arterial injury) **Management:** - **IMMEDIATE**: Extend wound posteriorly, expose popliteal vessels - Vascular surgery consultation if arterial injury (primary repair or graft) - Neural injury: Document, observe (most recover if incomplete) **Prevention:** - Control osteotomy depth (1-1.5cm - anterior 30-40% of tibia only, never beyond midline on lateral X-ray) - Use fluoroscopy intraoperatively (lateral view confirms osteotomy depth) - Angle osteotomy anteriorly (parallel to anterior cortex, away from posterior structures) ### Early Postoperative Complications (0-12 weeks) **1. Wound Complications (5-8% incidence)** **Recognition:** - Wound dehiscence, drainage, erythema - Exposed hardware (osteotomy fragment prominent anteriorly) **Management:** - **Superficial dehiscence**: Local wound care, delayed closure or healing by secondary intention - **Deep infection**: Return to OR for irrigation/debridement, IV antibiotics, may require hardware removal (if infection not controlled - risk nonunion but preferable to chronic infection) - **Exposed hardware**: Soft tissue coverage (local flaps, gastrocnemius flap if large defect) **Prevention:** - Meticulous wound closure (layered, tension-free) - Avoid excessive fragment prominence (ensure anatomic position, not anterior to native tibia) - Prophylactic antibiotics (cefazolin 2g pre-op) **2. Early Osteotomy Avulsion (1-3% incidence)** **Recognition:** - Acute pain, inability to perform straight leg raise - Radiographs: Fragment displacement (pulled proximally by patellar tendon) - Usually occurs weeks 2-6 (before solid union) **Mechanism:** - Premature weight-bearing (patient non-compliance) - Fall or traumatic event (axial load on flexed knee) - Inadequate fixation (insufficient screws, poor bone quality) **Management:** - **URGENT return to OR**: - Re-reduce fragment to anatomic position - Revision fixation (add screws, augment with cerclage wires, bone graft if bone quality poor) - Extended protected weight-bearing (8-10 weeks) - Expected outcome: 80-90% healing with revision fixation (Whiteside 1990) **Prevention:** - Rigid initial fixation (minimum 2-3 screws, compression at osteotomy) - Patient education (strict touch weight-bearing 6 weeks) - Immobilizer for ambulation (prevents eccentric quadriceps contraction) ### Late Postoperative Complications (12+ weeks) **1. Nonunion (2-5% with pedicle preserved, 15-20% without pedicle)** **Recognition:** - Persistent pain at osteotomy site beyond 4-6 months - Radiographs: No bridging callus, persistent lucency at osteotomy, hardware loosening/migration - CT scan confirms if X-rays equivocal (no bony bridging) **Risk factors:** - Loss of medial soft tissue pedicle (converts to non-vascularized osteotomy) - Inadequate fixation (fragment mobile - no compression) - Infection - Smoking (impairs bone healing) - Early weight-bearing (disrupts healing) **Management:** - **Revision fixation with bone grafting**: - Expose osteotomy site, remove loose hardware - Debride fibrous tissue (restore bleeding bone surfaces) - Bone graft (autograft from iliac crest or allograft cancellous chips) to fill gap - Rigid re-fixation (longer screws, cerclage wires, plate if bone allows) - BMP-2 augmentation (consider if high-risk patient - smoker, osteoporotic) - Extended protected weight-bearing (10-12 weeks) - Bone stimulator (adjunct, limited evidence) - Expected healing: 85-90% with revision + bone graft **2. Tubercle Malposition (if realignment performed)** **Recognition:** - Patellar maltracking persists (if medialization inadequate) - Patella baja (if distalization excessive or proximal migration during healing) - Radiographs: Tubercle position not as planned (measure TT-TG distance, Insall-Salvati ratio) **Management:** - If symptomatic: Revision osteotomy (complex, high failure risk 20-30%) - If asymptomatic: Observe **Prevention:** - Careful pre-operative planning (template realignment on imaging) - Intraoperative measurement (confirm tubercle position before fixation) - Temporary K-wire fixation (check position with fluoroscopy before screw insertion) **3. Prominent Hardware (10-15% incidence)** **Recognition:** - Palpable screw heads anteriorly (painful with kneeling, direct pressure) - Skin irritation over hardware **Management:** - Observation if asymptomatic and osteotomy healed - **Hardware removal** after union (12-18 months post-surgery) - Remove screws, preserve osteotomy fragment - Protect from re-fracture (avoid excessive loading 4-6 weeks post-removal) **Prevention:** - Low-profile screws (countersink screw heads into bone) - Ensure adequate soft tissue coverage - Warn patient (kneeling difficulty common even with hardware removed due to tubercle prominence) ## Comparison with Alternative Exposure Techniques ## Pearls, Pitfalls, and Expert Tips ### Surgical Pearls (What Separates Good from Great) **Pearl 1: Adequate dimensions are NON-NEGOTIABLE** - **Length**: Minimum 6-8cm (longer better for fixation - more screw purchase) - **Thickness**: 1-1.5cm (enough bone for screws - too thin fractures, too thick difficult closure) - **Width**: 2-3cm centered on tubercle (distributes patellar tendon forces) **Pearl 2: Medial soft tissue pedicle is the KEY to healing** - Preserve ALL medial attachments (periosteum, muscle, MCL fibers) - This pedicle provides blood supply (osteotomy heals as vascularized bone graft) - Loss of pedicle increases nonunion risk from 2-5% to 15-20% **Pearl 3: Multiple drill holes reduce fracture risk** - Perforate entire osteotomy path with drill holes (5-10mm spacing) - Reduces force needed to propagate osteotomy (less stress on fragment) - Connect holes with osteotome (controlled fracture propagation) **Pearl 4: Compression is critical for healing** - Screws must achieve COMPRESSION at osteotomy (no gap) - Insert screws perpendicular to osteotomy plane (achieves compression when tightened) - Test fragment stability after fixation (should be rock-solid, no toggle) **Pearl 5: Protected weight-bearing until union confirmed** - Touch weight-bearing 6 weeks (allows initial healing without stress) - Advance to partial weight-bearing ONLY after radiographic callus visible - Full weight-bearing at 12 weeks (union confirmed - bridging callus 3-4 cortices) ### Common Pitfalls (and How to Avoid Them) **Pitfall 1: Fragment too small (inadequate dimensions)** - **Problem**: Short (less than 6cm) or thin (less than 1cm) fragment fractures during creation or avulses post-op - **Solution**: Plan 6-8cm length, 1-1.5cm thickness BEFORE starting osteotomy (measure and mark on bone) - **Recovery**: If fragment fractures - abort TTO, use alternative exposure (quadriceps snip/turndown) **Pitfall 2: Stripping medial soft tissue pedicle** - **Problem**: Inadvertent detachment of medial periosteum converts to non-vascularized osteotomy (nonunion risk 15-20%) - **Solution**: DO NOT incise medial periosteum during dissection, propagate osteotomy medially LAST (lateral and distal first) - **Recovery**: If pedicle lost - bone graft around osteotomy, extended protected weight-bearing, accept higher nonunion risk **Pitfall 3: Inadequate fixation (too few screws)** - **Problem**: Single screw or insufficient compression allows fragment motion (nonunion risk) - **Solution**: Minimum 2-3 screws for standard osteotomy, perpendicular to osteotomy plane for compression - **Recovery**: If nonunion develops - revision fixation with additional screws, bone graft **Pitfall 4: Posterior cortex penetration** - **Problem**: Drill or osteotome too deep (greater than 1.5cm), penetrates posterior tibia (popliteal vessel injury risk) - **Solution**: Control osteotomy depth (anterior 30-40% of tibia only), use fluoroscopy (lateral view confirms depth), angle osteotomy anteriorly - **Recovery**: If posterior penetration - extend wound posteriorly, vascular surgery consultation if bleeding **Pitfall 5: Early weight-bearing** - **Problem**: Patient bears weight before healing (weeks 0-6) - avulsion risk - **Solution**: Patient education (strict touch weight-bearing 6 weeks), immobilizer for ambulation (prevents eccentric quadriceps contraction) - **Recovery**: If avulsion - urgent return to OR for re-reduction and revision fixation (80-90% healing with revision) ### Expert Tips (From High-Volume Surgeons) **Tip 1: Use tourniquet DOWN for TTO** - Allows medial pedicle blood flow during procedure (prevents ischemia) - Tourniquet up for intra-articular work (after TTO complete), then down for closure **Tip 2: Pad fragment during knee manipulation** - After TTO complete, place moist sponge over fragment (protects from direct trauma) - Avoid excessive traction on extensor mechanism (risks fragment fracture/avulsion) **Tip 3: Check fixation with knee flexion before closure** - Flex knee to 90° after screw fixation (tests fragment stability under load) - Fragment should be IMMOBILE - any motion indicates inadequate fixation (add screws or wires) **Tip 4: Template osteotomy on pre-op lateral X-ray** - Measure 6-8cm from tibial tubercle distally (mark distal extent) - Ensures adequate length before starting osteotomy **Tip 5: Consider bone graft if non-congruent reduction** - If fracture surfaces irregular/comminuted (gap at osteotomy after reduction), add cancellous bone graft to fill gaps - Improves healing biology, reduces nonunion risk