Free Flaps in Orthopaedics

Definition

• Rockwood & Green's Fractures in Adults, 10th Ed.
• Campbell's Operative Orthopaedics, 15th Ed.

Indications in Orthopaedics

1. Open fractures with bone/soft tissue loss - Gustilo-Anderson type IIIB/IIIC fractures of the tibia, where periosteum is stripped and local coverage is impossible
2. Osteomyelitis - chronic infection with bone loss requiring vascularized tissue to restore vascularity and fill dead space
3. Tumour resection - skeletal and soft tissue reconstruction after sarcoma excision
4. Degloving injuries - circumferential skin loss around limb segments
5. Vascularized bone defects - segmental bone loss where non-vascularized graft would fail (defects > 6 cm)
6. Reconstruction after failed local flap - where the zone of injury has compromised all regional tissue

Classification of Free Flaps Used in Orthopaedics

By tissue composition:

By vascular pedicle (axial pattern):

Common Free Flaps - Specific Details

1. Latissimus Dorsi Free Flap

• Pedicle: Thoracodorsal artery (branch of subscapular artery)
• Size: Up to 35 x 20 cm - largest single muscle flap available
• Uses: Large tibial defects, osteomyelitis, chest wall, scalp
• Advantage: Reliable, large surface area, can include serratus anterior on same pedicle

2. Anterolateral Thigh (ALT) Flap

• Pedicle: Descending branch of lateral circumflex femoral artery (perforators)
• Uses: Medium-to-large limb defects, versatile, can be thinned
• Advantage: Low donor-site morbidity, long pedicle (up to 12-14 cm)

3. Rectus Abdominis Flap

• Pedicle: Deep inferior epigastric artery
• Uses: Tibial coverage, osteomyelitis, perineal/pelvic defects
• Advantage: Large, reliable, can carry skin paddle

4. Radial Forearm Flap

• Pedicle: Radial artery
• Uses: Small-to-medium defects over ankle, hand, face; thin pliable coverage
• Note: Allen's test mandatory preoperatively

5. Free Fibula Flap

• Pedicle: Peroneal artery and comitant veins
• Harvest limits: 2 cm distal to fibula neck (to protect common peroneal nerve) to 6 cm proximal to lateral malleolus (to protect ankle syndesmosis)
• Max bone length: ~25 cm of vascularized cortical bone
• Uses: Segmental tibial defects, pathological fractures through osteomyelitic bone, avascular necrosis of femoral head, mandibular reconstruction
• Advantage: Long bone segment, can include skin paddle up to 5 cm wide, suitable for plating and distraction
• Preoperative requirement: Angiogram of donor limb mandatory (risk of peronea magna variant - 5% incidence)

6. DCIA (Deep Circumflex Iliac Artery) / Iliac Crest Flap

• Pedicle: Deep circumflex iliac artery from femoral vessels just below the inguinal ligament
• Uses: Mandibular reconstruction, calcaneal defects, composite bone + soft tissue loss
• Includes: Cuff of internal oblique muscle to protect terminal arterial branches
• Note: Mesh repair of abdominal wall is almost always required to prevent hernia

7. Free Groin Flap (SCIP Flap)

• Pedicle: Superficial circumflex iliac artery (SCIA) from femoral artery; vessel diameter 1.1-1.4 mm
• Uses: Hand, foot, tibia coverage; ideal for thin patients
• Advantages: Large potential size, sparse hair, minimal donor morbidity, can include iliac crest bone
• Disadvantages: Short and unpredictable pedicle (reduced popularity), excessive bulk in obese patients, colour mismatch, poor innervation
• SCIP evolution: Longer pedicle (up to 5 cm), flaps up to 8 cm wide with direct closure

8. Dorsalis Pedis Flap

• Pedicle: Dorsalis pedis artery + deep peroneal nerve (innervated)
• Uses: Thumb/hand resurfacing, small defects requiring thin sensate coverage
• Advantages: Large-caliber pedicle, long pedicle possible, innervatable, thin
• Disadvantages: Technically demanding, risk of painful donor scar, donor requires skin graft

9. First Web Space (Neurovascular) Free Flap

• Pedicle: First dorsal metatarsal artery or first plantar metatarsal artery
• Uses: Thumb pulp reconstruction - restores protective sensation
• Special point: Three patterns of plantar-dorsal vascular communication - must be assessed by Doppler preoperatively

10. Gracilis Free Flap

• Pedicle: Medial femoral circumflex artery
• Uses: Small-to-medium defects, functional muscle transfer (e.g., facial reanimation, Volkmann's contracture, forearm reconstruction after trauma)

Prerequisites for Safe Free Flap Surgery

1. Well-prepared patient - CT angiography to assess donor and recipient vessel anatomy; identification of variants (e.g., peronea magna); optimization of comorbidities; patient counselled on return-to-theatre risk and flap failure rate (up to 20%)
2. Complete surgical plan - account for the zone of trauma (recipient vessels may be injured subclinically), have backup options ready; inspect recipient vessels before committing
3. Well-equipped operating environment - operating microscope with dual-operator binoculars, microsurgical instruments, adequate space; staff trained to operate the microscope
4. Two-team approach - one team raising the flap, one preparing the recipient site, to reduce total ischaemia time
5. Safe postoperative environment - dedicated nursing staff for flap monitoring

Timing

• Godina's landmark (1986): flap within 72 hours = lowest failure rate
• Delays beyond 7 days significantly increase failure due to inflammatory changes and vessel fragility in wound bed
• The orthoplastic model (simultaneous orthopaedic fixation + plastic soft tissue coverage) achieves best results
• For open Gustilo IIIB tibial fractures: infection rates remain >20% without timely orthoplastic intervention

Postoperative Monitoring and Flap Salvage

• Clinical monitoring: colour, capillary refill, temperature, tissue turgor every hour for 48-72 hours
• Handheld Doppler to assess pedicle signal
• Implantable Doppler probes used in buried flaps
• Most vascular complications present within 48-72 hours of surgery
• Arterial insufficiency: pale, cool, non-bleeding flap - requires urgent return to theatre
• Venous congestion (more common): purple/congested, brisk dark bleeding - urgent re-exploration; medicinal leeches may be used as temporizing measure
• Timing of salvage intervention is critical: the earlier the first signs are detected and acted upon, the higher the salvage rate

Complications

Key Points for Exam

• Free flap = tissue transferred with its vascular pedicle divided and reanastomosed (distinguishes from pedicled flap)
• Requires microsurgical anastomosis of vessels typically 1-3 mm in diameter
• Godina's rule: within 72 hours gives best results
• Orthoplastic approach: simultaneous orthopaedic + plastic input is current standard of care
• Gustilo IIIB open tibial fractures are the commonest indication
• Latissimus dorsi = largest, most versatile muscle flap; free fibula = gold standard for vascularized bone
• Preoperative CT angiography/Doppler essential for both donor and recipient vessels
• Venous thrombosis > arterial thrombosis as cause of flap compromise
• Free flap surgery is contraindicated in patients on inotropic support (vasospasm risk)

Pedicled Flap vs Perforator Flap - Key Differences

1. Fundamental Distinction: What Supplies the Blood?

2. Pedicled Flap - Detailed

"In contrast to a graft which has no intrinsic blood supply, a flap is a block of tissue that is moved with an inherent blood supply. For both local and regional flaps, the vessels that constitute this blood supply are left in continuity."

• Rockwood & Green's Fractures in Adults, 10th Ed.

"Flaps are divided into two main categories, based on whether the pedicle remains attached to the donor site or not; pedicled and free flaps."

• Scott-Brown's Otorhinolaryngology Head & Neck Surgery

Sub-types of pedicled flaps:

• Random pattern pedicled flap - no named vessel; relies on the subdermal microcirculation (e.g., rotation flaps, advancement flaps). Limited length-to-width ratio (1:1 max).
• Axial pattern pedicled flap - based on a single named arteriovenous pedicle (e.g., gastrocnemius rotated to cover proximal tibia, pectoralis major for chest/neck defects). More reliable, larger arc of rotation.
• Regional pedicled flap - pedicle long enough to swing tissue from a nearby but non-adjacent region (e.g., latissimus dorsi as a pedicled flap for shoulder/chest wall).

• Medial gastrocnemius - proximal third tibial fractures
• Soleus - middle third tibial fractures
• Abductor digiti minimi - heel/plantar
• Cross-finger flap - finger tip reconstruction

3. Perforator Flap - Detailed

"As microsurgery field research advanced, it became evident that any clinically relevant perforator has the potential to be harvested as either a pedicle perforator flap or a free flap, depending on the diameter and length of the source artery and vein."

• Scott-Brown's Otorhinolaryngology

How it works:

• A longer, more mobile pedicle
• A skin island that can be islanded (completely free of surrounding tissue attachment)
• The muscle is left intact and functional

Types by perforator course:

• Musculocutaneous perforator (MC perforator) - vessel travels through the muscle belly (e.g., TRAM → DIEP: same skin territory, vessel goes through rectus muscle)
• Septocutaneous perforator - vessel travels in the intermuscular septum, not through muscle (e.g., ALT sometimes, radial forearm flap)

The "Perforasome" concept:

4. The Propeller Flap - a Pedicled Perforator Flap

"A propeller flap is a fasciocutaneous flap based on a perforator that can be rotated up to 180 degrees. Microsurgical techniques are employed to circumferentially dissect the vascular pedicle proximally enough to allow rotation of the flap without twisting or kinking the blood vessels."

• Fischer's Mastery of Surgery, 8th Ed.

5. Side-by-Side Comparison Summary

6. Practical Hierarchy of Reconstruction (Reconstructive Ladder)

Direct closure
    ↓
Skin graft
    ↓
Local random flap
    ↓
Local/regional pedicled axial flap
    ↓
Pedicled perforator flap (propeller)
    ↓
Free flap (fasciocutaneous / muscle / perforator free flap)