Dorsomedial Approach to the First MTP Joint

The dorsomedial approach to the first MTP joint is the workhorse incision for hallux valgus corrective surgery, cheilectomy for hallux rigidus and first MTPJ arthrodesis. The incision is centered over the first MTPJ on the dorsomedial aspect of the hallux, typically 3 to 5 cm in length, and is kept just dorsal to the abductor hallucis tendon. The single most important structure at risk is the dorsomedial cutaneous nerve to the hallux, a terminal sensory branch that crosses the field and must be identified and protected immediately after skin incision to prevent painful neuroma formation. There is no classical internervous plane because the approach is subcutaneous and extra-compartmental. Deep dissection involves longitudinal or Y-shaped capsulotomy to expose the metatarsal head, proximal phalanx base and sesamoid apparatus. On closure, meticulous capsular plication is performed to restore medial soft-tissue tension. The approach is extensile proximally along the metatarsal shaft and distally along the phalanx, allowing most hallux procedures to be performed through a single incision.

Primary Indications:

• Hallux valgus corrective surgery (chevron osteotomy, scarf osteotomy, proximal metatarsal osteotomy, distal soft tissue procedure)
• First MTPJ cheilectomy for hallux rigidus (dorsal osteophyte resection and joint debridement)
• First MTPJ arthrodesis for severe hallux rigidus, inflammatory arthritis or failed previous surgery
• Synovectomy and debridement in inflammatory arthropathies (rheumatoid, gout)
• Removal of loose bodies, osteochondral lesions or dorsal exostoses
• Biopsy or curettage of benign bone lesions of the metatarsal head

Why This Approach is Chosen:

The dorsomedial approach provides direct, extensile access to the medial eminence, metatarsal head articular surface, proximal phalanx base and sesamoid complex through a single incision that can be extended proximally or distally as needed. It avoids the plantar medial neurovascular bundle while allowing excellent visualization for corrective osteotomies and joint-preserving or fusion procedures. The approach is familiar to all foot and ankle surgeons and has a low complication rate when the dorsomedial cutaneous nerve is protected.

Contraindications:

• Active infection or ulceration over the proposed incision site
• Severe peripheral vascular disease with inadequate skin perfusion
• Previous surgery with extensive scarring that would require a different approach
• Isolated plantar pathology better addressed through a plantar or medial utility incision
• Need for extensive lateral release that may require a separate lateral incision in some techniques

Alternative Approaches:

• Pure medial approach: for isolated medial eminence resection in very mild cases (limited exposure)
• Plantar medial approach: for sesamoid pathology or when extensive plantar release required
• Lateral approach: rarely used alone but can be combined for complete lateral release in severe hallux valgus
• Minimally invasive percutaneous techniques: for chevron or Akin osteotomies in selected patients (different skill set)

Bony Anatomy:

The first metatarsophalangeal joint is formed by the convex metatarsal head and the concave base of the proximal phalanx. The metatarsal head has a sesamoid groove on its plantar surface divided by a crista. The medial eminence is the prominent medial portion of the metatarsal head that becomes enlarged in hallux valgus due to both bony proliferation and capsular thickening. The proximal phalanx base has a medial tubercle for capsular attachment. The joint has approximately 30 to 50 degrees of dorsiflexion and 30 degrees of plantarflexion in normal individuals.

Soft Tissue Layers:

The skin is thin and mobile over the dorsomedial aspect. Immediately deep to skin lies the dorsomedial cutaneous nerve to the hallux, which must be protected. The extensor hallucis longus tendon lies laterally in the field and defines the lateral boundary of safe dissection. The abductor hallucis tendon lies plantar and medial and defines the medial limit of the incision. The joint capsule is relatively thin dorsomedially and thickens medially where it blends with the medial collateral ligament and plantar plate.

Neurovascular Anatomy:

The dorsomedial cutaneous nerve to the hallux is a terminal sensory branch arising from the medial dorsal cutaneous nerve (itself a branch of the superficial peroneal nerve) or occasionally directly from the deep peroneal nerve. It crosses the first MTPJ dorsomedially and supplies sensation to the dorsomedial skin of the hallux. The dorsal metatarsal artery (branch of the dorsalis pedis) and its accompanying veins lie in the subcutaneous plane and may be encountered during flap elevation. The medial plantar nerve and its branches lie plantar to the abductor hallucis and are protected by staying dorsal to this muscle.

Sesamoid Complex:

The two sesamoid bones (medial/tibial and lateral/fibular) lie within the flexor hallucis brevis tendons and articulate with the plantar grooves of the metatarsal head. The sesamoid complex is critical for hallux function and must be preserved or realigned during hallux valgus surgery. The dorsomedial approach allows inspection of the sesamoid-metatarsal articulation by plantarflexing the hallux and retracting the complex.

Deep Internervous Plane:

There is no true internervous plane in the classical sense. The dorsomedial approach to the first MTP joint is a subcutaneous, extra-compartmental exposure. The dissection passes between the extensor hallucis longus tendon (innervated by the deep peroneal nerve) laterally and the abductor hallucis muscle (innervated by the medial plantar nerve) medially, but these structures are simply retracted rather than divided. The key to safety is identification and protection of the dorsomedial cutaneous nerve rather than reliance on an internervous interval.

Superficial Dissection:

The skin and subcutaneous tissue are incised in a single layer. The dorsomedial cutaneous nerve is identified immediately beneath the skin or within the subcutaneous fat and is protected throughout the procedure. No muscle is divided. The approach relies on careful retraction of the extensor hallucis longus tendon laterally and the abductor hallucis medially to expose the joint capsule.

Structures at Risk in Each Layer:

Position: Supine with Sandbag under Ipsilateral Hip

Pre-positioning Checklist:

• Confirm tourniquet available and tested (thigh or ankle tourniquet)
• Radiolucent table or foot extension for fluoroscopy if needed (rarely required for soft tissue procedures)
• Foot positioned at end of table for easy access
• Padding for contralateral leg and pressure points
• Head ring and arm positioning for patient comfort
• Local anaesthetic block (ankle or forefoot) considered for postoperative analgesia

Positioning Details:

• Patient supine with sandbag or bump under ipsilateral hip to internally rotate the leg and bring the medial forefoot into view
• Knee slightly flexed over a bolster if needed for relaxation
• Ankle in neutral or slight plantarflexion
• Tourniquet applied high on thigh or at ankle level depending on surgeon preference and case duration
• Foot prepped and draped free or with a window for easy manipulation

Alternative Positioning:

• Lateral decubitus rarely needed but can be used if combined procedures on lateral foot required
• Prone position not applicable for this approach
• Some surgeons prefer the patient positioned with the foot at the side of the table for ergonomic access

Key Bony Landmarks:

• First metatarsal head - palpable prominence on medial forefoot, enlarged in hallux valgus
• First MTP joint line - palpated by moving the hallux through range of motion
• Medial eminence - prominent medial bony and soft tissue mass in hallux valgus
• Proximal phalanx base - palpable just distal to joint line
• First metatarsal shaft - palpable dorsomedially for proximal extension planning

Key Soft Tissue Landmarks:

• Dorsomedial cutaneous nerve to the hallux - often visible or palpable as a thin cord crossing dorsomedially over the joint (may be rolled under the skin with gentle pressure)
• Extensor hallucis longus tendon - visible and palpable laterally, defines lateral boundary
• Abductor hallucis tendon - palpable on the plantar medial aspect, defines medial limit of incision
• Dorsal veins - superficial veins crossing the field that can be preserved or cauterized

Incision Planning:

• Longitudinal or gently curved incision centered over the first MTP joint
• Length typically 3 to 5 cm, extendable proximally along the metatarsal shaft or distally along the phalanx
• Placed just dorsal to the abductor hallucis tendon (approximately 5 to 10 mm dorsal to the most medial prominence)
• Avoids the weight-bearing plantar skin and the plantar medial neurovascular bundle
• For cheilectomy, the incision may be placed more dorsally to optimize dorsal osteophyte access
• For arthrodesis, the incision is centered to allow preparation of both joint surfaces

Nerve Injury Management:

• If nerve identified as damaged intra-operatively: primary repair if clean transection or bury ends in muscle/bone to minimize neuroma formation
• If neurapraxia suspected postoperatively: observe, document, follow up closely
• Painful neuroma: desensitization therapy, local anaesthetic injections, surgical exploration and burial if refractory

Proximal Extension along Metatarsal Shaft:

• Indication: scarf osteotomy, proximal metatarsal osteotomy, shaft pathology
• Technique: extend incision proximally along dorsomedial border of first metatarsal
• Key protection: identify and retract extensor hallucis longus tendon, protect proximal nerve branches
• Fixation: standard osteotomy fixation techniques apply

Distal Extension along Proximal Phalanx:

• Indication: first MTPJ arthrodesis, Akin osteotomy, Keller-Brandes procedure
• Technique: extend incision distally along dorsomedial border of proximal phalanx
• Key protection: continue nerve protection, identify EHL insertion
• Fusion preparation: flat cuts or reamers through the same exposure

Combined Lateral Release:

• Can often be performed through the same incision by retracting the metatarsal head laterally
• Alternatively, a small separate incision in the first web space for complete lateral release in severe deformities
• Decision based on deformity severity and surgeon preference

Revision Surgery Considerations:

• Previous incisions may require modification of the approach
• Scarring increases nerve identification difficulty
• Consider more extensile exposure or alternative approach in heavily scarred fields

Intra-operative Complications:

Post-operative Complications:

Hallux Valgus Corrective Surgery:

• Distal soft tissue procedure (modified McBride)
• Chevron (Austin) osteotomy
• Scarf osteotomy
• Proximal metatarsal osteotomy
• Akin phalangeal osteotomy
• Medial eminence resection and capsular plication

Hallux Rigidus Surgery:

• Cheilectomy (dorsal osteophyte resection and joint debridement)
• Dorsal exostectomy
• Joint debridement and loose body removal

First MTPJ Arthrodesis:

• Joint preparation (flat cuts or reaming)
• Fusion with screws, plates or other constructs
• Bone graft insertion if required

Other Procedures:

• Synovectomy for inflammatory arthropathy
• Removal of osteochondral lesions or loose bodies
• Biopsy or curettage of benign bone lesions (e.g., intraosseous ganglion, enchondroma)
• Keller-Brandes resection arthroplasty (historical, rarely performed)

Combined Procedures:

Most hallux valgus operations combine soft tissue balancing, osteotomy and Akin procedure through this single extensile approach. Lateral release can be added through the same incision or via a separate web space incision.

Layered Closure:

• Capsule: absorbable suture (Vicryl or equivalent), pants-over-vest or imbrication technique for plication
• Subcutaneous tissue: absorbable suture if required
• Skin: non-absorbable interrupted or running subcuticular suture
• Dressing: sterile non-adherent dressing, light compression, postoperative shoe or splint

Post-operative Protocol:

• Weight bearing as tolerated in postoperative shoe for most procedures
• Elevation for 48 to 72 hours to reduce swelling
• Early active and passive range of motion exercises begin at 7 to 14 days
• Sutures removed at 10 to 14 days
• Transition to normal footwear at 6 to 12 weeks depending on procedure and healing
• Full return to sport or heavy activity at 3 to 6 months

Rehabilitation Principles:

• Protect the capsular repair in the early phase
• Gradual increase in weight bearing and range of motion
• Monitor for recurrence of deformity or hallux varus
• Address any neuroma symptoms early with desensitization

Global Epidemiology:

Hallux valgus affects approximately 20 to 30 percent of adults worldwide, with higher prevalence in females and in populations that wear constrictive footwear. First MTPJ arthrodesis and cheilectomy are among the most common forefoot procedures performed by orthopaedic foot and ankle surgeons globally.

Guidelines and Evidence:

• AAOS and AOFAS clinical practice guidelines emphasize the importance of nerve protection and proper capsular management in hallux valgus surgery
• NICE and BOA guidance highlight the need for patient counseling regarding nerve injury risk
• EFORT and national foot and ankle societies recommend the dorsomedial approach as the standard for most first MTPJ procedures
• Registry data from NJR, AJRR and national foot and ankle registries show low revision rates for properly performed chevron osteotomy and arthrodesis when nerve complications are avoided

Key Technical Principles Accepted Worldwide:

• Early identification and protection of the dorsomedial cutaneous nerve
• Capsular plication to maintain correction
• Avoidance of excessive medial release to prevent hallux varus
• Appropriate patient selection and deformity-matched procedure choice