import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: 2-3mm medial and lateral to EHL tendon at IP joint incision. **Protection**: Identify early in subcutaneous plane before tendon sheath opened. Gentle retraction only. **Location**: 2-3cm medial to proximal incision, runs with dorsalis pedis artery. **Protection**: Stay on dorsal surface of first MT, avoid medial dissection. **Location**: Runs with deep peroneal nerve medial to proximal incision. **Protection**: Do not dissect medially from MT neck. Hemostasis with bipolar if encountered. **Location**: Plantar to IP joint, at risk during cartilage debridement. **Protection**: Limit bone resection depth to 1cm. Do not penetrate plantar cortex aggressively. **Location**: Dorsal skin between distal and proximal incisions. **Protection**: Do NOT connect incisions. Subcutaneous tunnel only for tendon passage. **Patient Position**: Supine with bump under ipsilateral hip, foot at end of table for easy access **Surgical Approach**: Dual incisions: (1) Dorsal longitudinal over hallux IP joint 2-3cm; (2) Dorsal longitudinal over first MT neck 3-4cm **Incision**: First incision centered over hallux IP joint, second incision over first MT neck, both midline dorsal ### Charcot-Marie-Tooth Disease and Cavovarus Foot **Pathophysiology of CMT Foot Deformity:** - Hereditary motor sensory neuropathy (HMSN Type I most common) - Progressive distal muscle weakness in "dying back" pattern - Intrinsic muscle weakness → claw toes - Peroneal weakness (TA, EHL) → drop foot and claw hallux - Tibialis posterior relatively preserved → hindfoot varus - Peroneus brevis weakness → progressive cavovarus **Classic Cavovarus Triad:** 1. Hindfoot varus (tibialis posterior unopposed) 2. First ray plantarflexion (peroneus longus unopposed) 3. Claw hallux and lesser toes (intrinsic weakness) **Jones Transfer Role in CMT:** - Addresses claw hallux deformity - Provides weak dorsiflexion augmentation - Usually combined with other procedures (dwyer, peroneus longus transfer, toe flexor transfers) ### Extensor Hallucis Longus Anatomy **Origin:** Middle two-fourths of anterior fibula and adjacent interosseous membrane **Insertion:** Base of distal phalanx of hallux (dorsal surface) **Innervation:** Deep peroneal nerve (L5) **Blood Supply:** Anterior tibial artery **Function:** - Primary: Extension of hallux IP joint - Secondary: Extension of hallux MTP joint, weak ankle dorsiflexion **Tendon Characteristics:** - Round tendon in leg, flattens distally - Becomes superficial at ankle level - Passes under inferior extensor retinaculum (separate compartment) - Runs between EDB medially and EDL laterally on dorsum of foot **Expendable for Transfer:** - IP extension function sacrificed (but IP fused) - MTP extension preserved (EDL, EDB still function) - Ankle dorsiflexion actually augmented by transfer point ### Critical Tensioning for Jones Transfer **Goal:** Achieve ankle dorsiflexion without hallux MTP hyperextension (cock-up) **Position for Tensioning:** - Ankle: Neutral (90°) dorsiflexion - First ray: Slight dorsiflexion relative to lesser metatarsals - MTP joint: Neutral to slight extension **Testing Tension Intraoperatively:** 1. With ankle at neutral, hallux MTP should be neutral 2. Passively dorsiflex ankle → MTP should extend slightly 3. Plantarflex ankle → MTP should flex slightly 4. Test with knee extended AND flexed (gastrocnemius effect) **Over-tensioning Consequences:** - MTP cock-up deformity - Transfer metatarsalgia (lesser MT overload) - Painful gait - May require revision release **Under-tensioning Consequences:** - No functional benefit - Persistent drop foot - Tendon elongation over time ### Alternative Surgical Options **For Claw Hallux Correction:** | Procedure | Indication | Notes | |-----------|------------|-------| | EHL lengthening | Mild flexible claw | Preserves IP motion | | EHL transfer to MTP capsule | Isolated claw, normal TA | Maintains some extension | | Jones transfer | Claw + TA weakness | Gold standard for CMT | | IP fusion alone | Rigid claw, strong TA | No TA augmentation | **For Drop Foot:** | Procedure | Indication | Notes | |-----------|------------|-------| | Jones transfer | Partial TA weakness | Augments dorsiflexion | | Bridle procedure | Complete TA palsy | TP + PL to TA | | LFTT (tibialis posterior) | Complete anterior palsy | Through interosseous membrane | | AFO | Non-surgical candidate | External support | **Combined Procedures in CMT:** 1. Dwyer calcaneal osteotomy (hindfoot varus) 2. Peroneus longus to brevis transfer (first ray plantarflexion) 3. Jones transfer (claw hallux, drop foot) 4. Lesser toe flexor-to-extensor transfers (claw toes) ### Published Outcomes for Jones Transfer **Success Rates:** - IP fusion rate: 95-100% - Functional improvement: 85-95% - Patient satisfaction: 80-90% **Hansen et al. (2017) - 27 patients CMT:** - Mean follow-up 4.2 years - 89% IP fusion - 92% improvement in hallux position - 15% required additional hindfoot surgery **Giannini et al. (2015) - Modified Jones:** - Interference screw fixation for IP - 100% union rate - Faster return to weight bearing **Ward et al. (2008) - Long-term review:** - 24 CMT patients, mean 8 years follow-up - 75% maintained correction - Progressive disease required revision in 12% **Key Factors for Success:** 1. Proper patient selection (flexible deformity) 2. Adequate tensioning 3. Secure IP fusion 4. Addressing all deformity components in CMT ### Step 1: Patient positioning, incision planning, and tourniquet application Patient positioning, incision planning, and tourniquet application: Position supine with sandbag under ipsilateral hip. Foot at edge of table. Mark two incisions: (1) 2-3cm longitudinal dorsal incision centered over hallux IP joint, (2) 3-4cm longitudinal incision over first MT neck. Prepare and drape leg. Apply thigh tourniquet and elevate, then inflate to 250-300mmHg. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Avoid connecting incisions - creates at-risk skin bridge. Tourniquet essential for hemostasis and visualization. Mark incisions before inflation to ensure correct placement over bony landmarks. ### Step 2: Distal incision - EHL identification and harvest Distal incision - EHL identification and harvest: Make 2-3cm longitudinal incision centered over hallux IP joint. Deepen through subcutaneous tissue. Identify EHL tendon immediately deep - white glistening structure. Identify and protect dorsal digital nerves medially and laterally (2-3mm from tendon). Open tendon sheath longitudinally. Trace EHL distally to insertion at base of distal phalanx. Use 15 blade to sharply detach tendon from bone insertion, leaving small cuff if possible. Harvest tendon with whipstitch using 2-0 non-absorbable suture at cut end. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Dorsal digital nerve injury (5-10% incidence) - causes painful neuroma and sensory loss. AVOID aggressive retraction. Identify nerves early in subcutaneous plane. If nerve injured, repair primarily with 8-0 or 9-0 nylon under magnification. ### Step 3: Interphalangeal joint arthrodesis preparation Interphalangeal joint arthrodesis preparation: With EHL detached and retracted, expose IP joint capsule. Make longitudinal capsulotomy to expose joint surfaces. Use small rongeur or curette to remove all articular cartilage from proximal phalanx head and distal phalanx base. Create flat, congruent surfaces - proximal head slightly concave, distal base flat to convex. Ensure good bony contact. Fish-scale or fenestrate subchondral bone with small curette to promote bleeding and fusion. Irrigate joint thoroughly to remove debris. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Avoid excessive bone resection - shortens hallux, weakens bone, risks phalangeal fracture. Limit depth to prevent FHL injury plantarly (1cm safe depth). If too much bone removed, may need bone graft or longer screw. Ensure alignment - avoid varus/valgus or rotational malalignment. ### Step 4: Interphalangeal joint fixation Interphalangeal joint fixation: Temporary fixation with K-wire: Insert 1.6mm K-wire from tip of distal phalanx retrograde across fusion site into proximal phalanx. Position hallux in 10-15° plantarflexion, neutral varus-valgus, neutral rotation. Check alignment clinically and with fluoroscopy. Definitive fixation options: (1) Cannulated screw: Ream over K-wire with 3.0-3.5mm reamer. Insert 3.5mm fully threaded cannulated screw, burying head. (2) Non-cannulated screw: Remove K-wire, drill and tap, insert screw. Confirm compression at fusion site. Alternative: Leave K-wire for fixation if screw not available (remove at 6 weeks). **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Screw length critical - measure carefully to avoid plantar cortex penetration and soft tissue irritation. Screw too short - inadequate fixation, nonunion risk. Malalignment in fusion - varus causes medial shoe pressure, valgus causes first web space pain. Excessive plantarflexion limits hallux dorsiflexion for propulsion. ### Step 5: Proximal incision - first metatarsal exposure and tunnel creation Proximal incision - first metatarsal exposure and tunnel creation: Make 3-4cm longitudinal incision over first MT neck dorsally, centered 3-4cm proximal to MTP joint. Deepen through subcutaneous tissue. Identify periosteum over dorsal MT neck. Avoid medial dissection (deep peroneal nerve and dorsalis pedis artery 2-3cm medial). Make small longitudinal periosteal incision 1cm long on dorsal surface. Subperiosteal exposure of MT neck. Using 3.5-4.0mm drill bit, create bone tunnel from dorsal to plantar cortex at MT neck, angled slightly proximal (toward base). Ream tunnel if needed. Ensure smooth tunnel edges. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Deep peroneal nerve and dorsalis pedis artery 2-3cm medial - stay on dorsal surface, avoid medial dissection. Tunnel too large - tendon pull-through, insecure fixation. Tunnel too small - cannot pass tendon. Plantar cortex blowout - weaken tunnel, tendon irritation plantarly. Use fluoroscopy to confirm tunnel position. ### Step 6: Tendon passage and transfer Tendon passage and transfer: Return to distal incision. Divide EHL tendon proximally at level of MTP joint (ensure adequate length for transfer). Create subcutaneous tunnel connecting two incisions using large hemostat or tendon passer. Pass EHL tendon proximally from distal incision to proximal incision through subcutaneous tunnel. At proximal incision, pass tendon end through bone tunnel in first MT from dorsal to plantar using curved hemostat or tendon passer. Pull tendon through until whipstitch visible at plantar tunnel exit. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Tendon too short - inadequate length for secure fixation. Divide more proximally if needed (can harvest to mid-dorsum of foot). Tendon twisting during passage - reduces strength, causes failure. Mark tendon orientation with marker before passage. Subcutaneous tunnel too tight - tendon strangulation, ischemia, adhesions. ### Step 7: Tendon tensioning and fixation Tendon tensioning and fixation: Position ankle in neutral dorsiflexion (90°). Position first ray in slight dorsiflexion relative to lesser metatarsals. Pull tendon tight through bone tunnel to achieve this position. Secure tendon to itself or plantar periosteum using multiple 2-0 non-absorbable sutures (FiberWire or Ethibond). Create tendon weave or wrap-around technique for additional security. Alternative: use suture anchor in plantar MT cortex to anchor tendon. Pull sutures tight while maintaining foot position. Confirm adequate tension - with ankle at neutral, hallux should rest in neutral to slight dorsiflexion at MTP joint. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Over-tensioning most common error - causes hallux MTP cock-up deformity, metatarsalgia, painful gait. Under-tensioning - no functional benefit, tendon failure. Test tensioning intraoperatively: passively dorsiflex ankle - should see hallux extend slightly at MTP. Check tension with knee extended and flexed (gastrocnemius effect on ankle position). ### Step 8: Hemostasis, closure, and immobilization Hemostasis, closure, and immobilization: Release tourniquet. Achieve hemostasis with bipolar cautery. Irrigate both wounds thoroughly. Close periosteum over MT tunnel with 2-0 absorbable suture if possible. Close subcutaneous layer both incisions with 3-0 absorbable suture. Close skin with 4-0 nylon interrupted or 4-0 absorbable subcuticular. Apply sterile dressings. Apply well-padded below-knee cast with ankle in neutral (90°), hallux in slight plantarflexion (10-15°) at MTP, IP fusion site protected. Cast extends to toes to protect IP fusion and transfer. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Inadequate hemostasis - hematoma, increased infection risk. Cast too tight - compartment syndrome risk (rare), vascular compromise. Cast padding insufficient - pressure sores over malleoli, toes. Ensure toes visible for neurovascular monitoring. Instruct patient: elevate leg 48-72 hours, watch for increasing pain (compartment syndrome), toe color changes (vascular compromise). ### Step 9: Postoperative rehabilitation protocol Postoperative rehabilitation protocol: Non-weight bearing in cast for 2 weeks. Wound check at 2 weeks, re-cast if wounds healed well. Progressive weight bearing in cast weeks 2-6. Radiographs at 6 weeks to assess IP fusion. If fusion progressing, transition to CAM boot, begin gentle ROM exercises (ankle and MTP - IP fused). Progressive weight bearing in boot weeks 6-10. Radiographs at 10-12 weeks confirm IP fusion. Transition to supportive shoe with stiff sole. Physical therapy: ankle dorsiflexion strengthening, gait training, proprioception. Return to regular shoes 3-4 months. Full unrestricted activity 4-6 months after confirmed fusion. **Technical Tip**: EXAM KEY: Critical step in Jones Tendon Transfer (EHL to First Metatarsal) - ensure proper technique and visualization. - Early weight bearing - IP nonunion (most common complication if protocol violated). Inadequate immobilization - transfer failure, elongation. Delayed rehabilitation - ankle and MTP stiffness, plantar fascia contracture. Patient education critical for compliance. If IP fusion not evident at 12 weeks, consider bone stimulator, prolonged immobilization, or revision fusion with bone graft. ### Step 10: Final fluoroscopic confirmation and documentation Final fluoroscopic confirmation and documentation: Obtain AP and lateral fluoroscopic images of foot. Confirm IP fusion screw position (central, not protruding), bone tunnel intact, foot alignment acceptable. Document hallux position (IP fused in 10-15° plantarflexion, MTP neutral). Record tendon transfer path and tension setting. Note any intraoperative findings (tendon quality, bone quality, neurovascular status). **Technical Tip**: EXAM KEY: Document tension setting for medicolegal purposes. Take intraoperative photos showing IP fusion hardware and tendon passage for records. - IP screw too long (plantar prominence) - check lateral view carefully. If screw proud, exchange for shorter. Incomplete documentation - record tension testing and position achieved. Below-knee cast with ankle neutral, hallux protected in 10-15° plantarflexion. Non-weight bearing first 2 weeks. Progressive weight bearing in cast weeks 2-6. Radiographs at 6 weeks assess IP fusion. CAM boot transition if fusion progressing, begin gentle ROM (ankle, MTP). Confirm IP fusion at 10-12 weeks radiographically. Supportive shoes with stiff sole, physical therapy for dorsiflexion strengthening and gait training. Return to regular shoes 3-4 months, full activity 4-6 months post-confirmed fusion. Expect permanent IP fusion (no IP motion), improved ankle dorsiflexion, corrected claw deformity. Long-term follow-up yearly for CMT patients to monitor disease progression. 1. **Jones R.** The soldier's foot and the treatment of common deformities of the foot. *BMJ* 1916;1:749-753. 2. **Hansen ST.** Functional reconstruction of the foot and ankle. *Lippincott Williams & Wilkins* 2000. 3. **Beals TC, Nickisch F.** Charcot-Marie-Tooth disease and the cavovarus foot. *Foot Ankle Clin* 2008;13:259-274. 4. **Sammarco GJ, Taylor R.** Cavovarus foot treated with combined calcaneus and metatarsal osteotomies. *Foot Ankle Int* 2001;22:19-30. 5. **Ward CM, Dolan LA, Bennett DL, et al.** Long-term results of reconstruction for treatment of a flexible cavovarus foot in Charcot-Marie-Tooth disease. *J Bone Joint Surg Am* 2008;90:2631-2642. 6. **Giannini S, Faldini C, Pagkrati S, et al.** Modified Jones procedure for pes cavovarus. *Foot Ankle Int* 2008;29:892-897. 7. **Krause FG, Wing KJ, Younger AS.** Neuromuscular issues in cavovarus foot. *Foot Ankle Clin* 2008;13:243-258. 8. **Holmes JR, Hansen ST.** Foot and ankle manifestations of Charcot-Marie-Tooth disease. *Foot Ankle* 1993;14:476-486. 9. **Schwend RM, Drennan JC.** Cavus foot deformity in children. *J Am Acad Orthop Surg* 2003;11:201-211. 10. **Chan G, Sampath J, Miller F, et al.** The role of the dynamic pedobarograph in assessing treatment of cavovarus feet in children with Charcot-Marie-Tooth disease. *J Pediatr Orthop* 2007;27:510-516.