Dorsal Approach to the Metacarpals and Phalanges

The dorsal approach to the metacarpals and phalanges is the workhorse exposure for the majority of metacarpal and proximal/middle phalanx fractures requiring open reduction and internal fixation. A straight or gently curved longitudinal incision is made directly over the metacarpal or between metacarpal heads for multiple rays. The dorsal veins and sensory branches of the radial and ulnar nerves are identified and protected in the subcutaneous plane. The extensor tendon is mobilized by splitting or retracting the sagittal band at the MCP level or by developing the interval between the extensor tendon and the dorsal cortex more distally. Juncturae tendinum are divided only when necessary for exposure. Subperiosteal dissection exposes the dorsal cortex for plate application. The approach is extensile proximally to the wrist and distally to the DIP joint. Closure emphasizes repair of any divided sagittal bands to maintain extensor tendon centralization.

Primary Indications:

• Displaced metacarpal shaft, neck, or base fractures requiring ORIF
• Displaced proximal or middle phalanx fractures
• Intra-articular fractures of the MCP, PIP, or DIP joints with greater than 2 mm step-off
• Metacarpal or phalangeal malunion requiring corrective osteotomy
• MCP joint arthroplasty or synovectomy
• Extensor tendon repair or reconstruction requiring dorsal exposure
• Metacarpal or phalangeal nonunion

Why This Approach is Chosen:

The dorsal surface provides direct access to the metacarpal and phalangeal shafts and the dorsal half of the articular surfaces. Plates applied dorsally are biomechanically favorable for resisting bending forces in the hand. The approach avoids the critical neurovascular structures on the volar side (common digital arteries and nerves).

Contraindications:

• Active infection over the planned incision
• Severe dorsal soft-tissue loss or burn requiring alternative coverage
• When volar pathology (flexor tendon, digital nerve) is the primary target - use volar or Bruner approach
• Isolated volar plate avulsion injuries better accessed volarly

Alternative Approaches:

• Volar approach (Bruner or midlateral): For flexor tendon or digital neurovascular pathology
• Lateral approach: For collateral ligament or condylar fractures
• Combined dorsal-volar: For complex intra-articular fractures with both dorsal and volar fragments

Bony Anatomy:

The metacarpals form the skeletal framework of the hand. Each metacarpal has a base, shaft, neck, and head. The phalanges (proximal, middle, distal) follow a similar pattern. The dorsal cortex is relatively flat and subcutaneous, making it ideal for plate application. The metacarpal heads articulate with the proximal phalanges at the MCP joints; the proximal phalanx head articulates with the middle phalanx at the PIP joint.

Soft Tissue Layers - Dorsal Hand:

From superficial to deep:

1. Skin and subcutaneous fat
2. Dorsal venous network and sensory nerve branches (SRN and SUN)
3. Extensor tendons enveloped by loose areolar tissue
4. Sagittal bands at MCP level (stabilize extensor tendon centrally)
5. Juncturae tendinum (interconnect extensor tendons)
6. Periosteum and dorsal cortex of metacarpal/phalangeal bone
7. Joint capsule (MCP, PIP, DIP)

Extensor Mechanism Details:

• Extensor digitorum communis (EDC): central tendon to each finger
• Extensor indicis proprius (EIP) and extensor digiti minimi (EDM): independent extensors to index and little finger
• Sagittal bands: transverse fibers at MCP joint that centralize the extensor tendon over the metacarpal head
• Juncturae tendinum: oblique interconnecting bands between EDC tendons proximal to the MCP joints
• Lateral bands: formed by contributions from interossei and lumbricals, converge to form terminal extensor tendon at DIP

Neurovascular Anatomy:

• Superficial radial nerve (SRN): supplies dorsal thumb, index, middle, and radial ring finger skin
• Dorsal cutaneous branch of ulnar nerve (SUN): supplies dorsal ulnar ring and little finger skin
• These nerves lie in the subcutaneous plane and cross the operative field

Deep Internervous Plane:

There is no true classical internervous plane in the dorsal approach to the metacarpals and phalanges. The extensor tendons are all supplied by the radial nerve (posterior interosseous nerve for finger extensors). The approach is therefore an intertendinous or sub-tendinous interval rather than an internervous one.

• At the metacarpal level the interval is developed between the extensor tendon and the dorsal periosteum after the tendon is mobilized.
• At the MCP joint the sagittal band may be split longitudinally or the tendon retracted after partial release.
• Distally on the phalanx the extensor tendon is mobilized or the interval between the central slip and lateral band is used.

Clinical Relevance:

Because there is no internervous plane, muscle denervation is not a concern. The critical structures to protect are the sensory nerve branches (subcutaneous) and the extensor mechanism itself (to preserve gliding and prevent subluxation).

Structures at Risk in Each Layer:

Position: Supine with Hand on Hand Table

Pre-positioning Checklist:

• Arm board attached to operating table
• Radiolucent hand table confirmed
• Tourniquet applied to upper arm (250 mmHg)
• Fingers prepared for possible Chinese finger trap suspension
• C-arm positioned for AP, lateral, and oblique views of hand
• Headlight or loupes available for fine dissection

Positioning Details:

• Patient supine, arm abducted on hand table
• Shoulder slightly externally rotated, elbow flexed 90 degrees
• Hand and forearm prepped to above elbow
• Tourniquet inflated after exsanguination with Esmarch bandage
• Fingers can be suspended with Chinese finger traps and weights (2-3 kg) for traction if fracture reduction requires it
• Surgeon sits at the end of the hand table

Alternative Positioning:

• For combined dorsal and volar work, the hand can be pronated or supinated as needed during the case
• For thumb metacarpal or trapezium access, the thumb is abducted and the incision placed more radially

Key Bony Landmarks:

• Metacarpal heads: palpable knuckles when fist made
• Metacarpal bases: palpable at carpometacarpal junction, especially 2nd and 5th
• MCP joint line: 1 cm proximal to metacarpal head prominence
• PIP joint: middle knuckle, easily palpable
• DIP joint: distal knuckle

Key Soft Tissue Landmarks:

• Extensor tendons: visible and palpable on dorsum when fingers extended against resistance
• Dorsal veins: visible blue network under thin dorsal skin
• Skin creases: MCP and PIP flexion creases (volar) correspond to joint levels

Incision Planning:

• Single metacarpal: straight longitudinal incision centered over the metacarpal shaft, from 1 cm proximal to MCP joint to 1 cm distal to fracture or as needed
• Multiple metacarpals: longitudinal incision in the intermetacarpal valley (between extensor tendons) or two separate incisions
• MCP joint access: gently curved incision centered over the MCP joint, convex ulnar or radial depending on which side needs exposure
• Length typically 4-8 cm for metacarpal shaft, shorter or longer as required for phalangeal exposure

Nerve Injury Management:

• If nerve transected intra-operatively: primary microsurgical repair with 9-0 nylon under microscope
• If neurapraxia suspected: observe, document, follow up at 3 months with EMG if no recovery
• Painful neuroma: desensitization, steroid injection, or surgical excision with burial into muscle

Proximal Extension:

The incision can be extended proximally along the radial or ulnar border of the hand to access the carpometacarpal joints or the distal radius. The same subcutaneous nerve protection principles apply. For thumb metacarpal base fractures the incision is placed more radially and can be extended into the anatomic snuffbox if needed for scaphoid or trapezium access.

Distal Extension:

For middle and distal phalanx exposure the incision is carried distally. At the PIP joint the central slip insertion on the middle phalanx base must be protected. If the central slip is divided it must be repaired. For DIP joint exposure the terminal extensor tendon is protected and repaired if divided.

Combined Approaches:

For complex intra-articular fractures with volar and dorsal fragments a combined dorsal and volar (Bruner) approach may be required. Staged or simultaneous depending on soft tissue condition.

Limited Open Techniques:

For selected fractures percutaneous or limited-open techniques with mini-incisions can be used, but the principles of nerve and extensor protection remain identical.

Intra-operative Complications:

Post-operative Complications:

Immediate Post-operative:

• Document neurovascular status (especially SRN/SUN sensation and extensor tendon function)
• Light compressive dressing with plaster slab in intrinsic plus position
• Elevate hand above heart level for 48-72 hours
• Tourniquet time documented

Mobilization Protocol:

• Days 0-3: Elevation, finger pumps, active ROM of uninvolved joints
• Days 3-14: Early active and passive ROM of MCP, PIP, DIP as fixation stability allows
• Weeks 2-6: Progressive strengthening, tendon gliding exercises
• Weeks 6-12: Full active use, return to light work
• 3 months: Full unrestricted activity

Follow-up Schedule:

• 2 weeks: wound check, suture removal, radiographs
• 6 weeks: radiographs, assess healing, progress activity
• 3 months: functional assessment, return to full duties
• 6-12 months: final review for malunion or stiffness

DVT Prophylaxis:

Not routinely required for isolated hand surgery unless patient has additional risk factors.