Operative Management of Phalangeal and Sesamoid Fractures: A Comprehensive Surgical Guide

INTRODUCTION TO FOREFOOT FRACTURES

The management of forefoot fractures requires a nuanced understanding of foot biomechanics, particularly regarding the weight-bearing distribution across the first ray. While surgical treatment of phalangeal fractures of the lesser toes is rarely required—given that the vast majority can be treated successfully by conservative measures—injuries to the hallucal sesamoid complex present a distinct and formidable clinical challenge.

The sesamoids of the first metatarsophalangeal (MTP) joint are integral to the function of the flexor hallucis brevis (FHB) musculotendinous unit. Disruption of this complex, whether through acute fracture, stress fracture, or subluxation with spontaneous reduction of the MTP joint, can lead to profound disability. Wide displacement of the sesamoid is poorly tolerated by patients, necessitating a highly specific, evidence-based approach to both conservative and operative management.

SURGICAL ANATOMY AND BIOMECHANICS

To master the operative interventions of the forefoot, the orthopedic surgeon must first appreciate the intricate anatomy of the first MTP joint. The hallucal sesamoids (tibial/medial and fibular/lateral) are embedded within the plantar plate and the two distinct tendons of the FHB.

Biomechanical Function of the Sesamoids

The sesamoids serve three primary biomechanical functions:
1. Lever Arm Augmentation: The tibial sesamoid, in particular, has a significant function in increasing the lever arm and mechanical advantage of the FHB muscle during the push-off phase of the gait cycle.
2. Tendon Protection: They elevate the first metatarsal head, creating a protective groove that shields the flexor hallucis longus (FHL) tendon from direct compressive forces against the ground.
3. Load Distribution: During terminal stance, the sesamoids absorb up to 300% of the body's weight, dispersing the load across the plantar aspect of the first ray.

Clinical Pearl: The tibial (medial) sesamoid is larger, bears more weight, and is consequently fractured much more frequently than the fibular (lateral) sesamoid. Its preservation is paramount whenever clinically feasible.

PHALANGEAL FRACTURES OF THE TOES

Most phalangeal fractures of the lesser toes are minimally displaced and inherently stable due to the surrounding soft tissue envelope. Conservative management, consisting of buddy taping to the adjacent uninjured toe and the use of a rigid-soled post-operative shoe, is almost universally successful.

Indications for Operative Intervention

Surgical fixation of phalangeal fractures is reserved for specific, rare scenarios:
* Open fractures requiring debridement.
* Grossly unstable or irreducible fractures.
* Intra-articular fractures with significant step-off (>2 mm) affecting the MTP or interphalangeal joints.
* Fractures resulting in severe rotational deformity that compromises adjacent toes.

When operative intervention is mandated, closed reduction and percutaneous pinning (CRPP) with a 0.045-inch or 0.062-inch Kirschner wire driven axially through the distal phalanx across the fracture site is the standard of care.

HALLUCAL SESAMOID FRACTURES: PATHOLOGY AND EVALUATION

Sesamoid injuries encompass acute fractures, stress fractures, and symptomatic bipartite sesamoids. Differentiating an acute fracture from a bipartite sesamoid is a classic diagnostic challenge.

Diagnostic Pitfall: Approximately 10% to 30% of the population possesses a bipartite sesamoid, which is bilateral in up to 85% of cases. A bipartite sesamoid typically exhibits smooth, sclerotic, and well-rounded margins, whereas an acute fracture presents with sharp, irregular, and uncorticated edges. Contralateral radiographs are mandatory for comparison.

Mechanism of Injury

Acute sesamoid fractures typically result from a direct axial load or a sudden, forceful hyperextension of the first MTP joint (a "turf toe" variant). This hyperextension can cause disruption of the FHB musculotendinous unit, leading to wide displacement of the sesamoid fragments.

CONSERVATIVE MANAGEMENT PROTOCOLS

Minimally displaced or nondisplaced fractures of the sesamoid, as well as stress fractures, should initially be managed non-operatively. The goal is to offload the sesamoid complex while allowing osteoblastic bridging.

Immobilization Phase

Initial treatment consists of strict cast immobilization. A short-leg walking cast or a rigid fracture boot incorporating a toe plate is utilized for 3 to 4 weeks. The toe plate prevents dorsiflexion of the hallux, thereby neutralizing the pull of the FHB. If symptoms have not resolved after the initial period, repeat casting for another 3 to 4 weeks may be necessary.

Transition and Orthotic Phase

Following successful clinical union or resolution of acute pain, the toe is protected by placing a full-length rigid carbon plate and a custom orthotic with a dancer’s pad in an athletic shoe. The dancer's pad (a U-shaped felt or foam pad) is strategically placed proximal to the first metatarsal head to offload the sesamoids directly.

INDICATIONS FOR OPERATIVE TREATMENT OF THE SESAMOID

Patients who do not respond to an exhaustive trial of conservative treatment (typically 3 to 6 months) are candidates for operative intervention. Furthermore, acute injuries with specific morphological characteristics warrant early surgical consideration.

Absolute and Relative Indications:
* Disruption of the FHB musculotendinous unit with wide displacement of the sesamoid.
* Significant fragment displacement (> 5 mm).
* Symptomatic nonunion of a sesamoid fracture.
* Painful bipartite sesamoid refractory to orthotic management.

The following options are available for surgical treatment:
1. Open reduction and internal fixation (ORIF) with or without cancellous bone grafting.
2. Partial excision of a painful bipartite sesamoid or nonunion.
3. Complete excision of the sesamoid.

SURGICAL TECHNIQUES

1. Open Reduction and Internal Fixation (ORIF)

If the sesamoid fragments are of roughly equal size, and the displacement is significant (> 5 mm), ORIF is the procedure of choice to restore the functional integrity of the FHB.

Patient Positioning and Preparation:
The patient is placed supine on the operating table with a bump under the ipsilateral hip to internally rotate the leg to a neutral position. A thigh or calf tourniquet is applied.

Surgical Approach:
A medial longitudinal incision is made along the first MTP joint, centered over the tibial sesamoid. The incision is carried through the skin and subcutaneous tissue.

Surgical Warning: Meticulous dissection is required to identify and protect the plantar medial cutaneous nerve of the hallux, which courses directly over or immediately adjacent to the medial sesamoid.

Preparation of the Fracture Site:
The capsule is incised longitudinally. The fracture site or nonunion is identified. Fibrous tissue interposed between the fragments is meticulously debrided using a curette or a fine rongeur until bleeding, healthy cancellous bone is exposed.

Bone Grafting:
To achieve union, especially in cases of delayed presentation or nonunion, autologous bone grafting is highly recommended. Cancellous bone graft can be harvested from the ipsilateral calcaneus or the supramalleolar area of the distal tibia. The graft is packed tightly into the prepared defect.

Fixation Techniques:
* Mini-Fragment Screws: For fragments of sufficient size, one or two 1.5-mm or 2.0-mm headless compression screws or cortical mini-fragment screws (Fig. 88-80) are placed from proximal to distal.
* Figure-of-Eight Wiring: Alternatively, an 18-gauge wire or heavy non-absorbable suture (e.g., FiberWire) can be looped around the proximal and distal poles. The wire is placed in a figure-of-eight configuration over the plantar aspect of the sesamoid to provide dynamic compression during FHB contraction.

2. Partial Sesamoid Excision

Historically, complete excision was the standard for failed conservative treatment. However, modern orthopedic practice favors excising the smaller fragment of a painful bipartite sesamoid or trying to preserve most of the sesamoid in the setting of a nonunion.

Technique:
Through the medial approach, the capsule is opened. The smaller, typically distal, fragment is carefully shelled out of the plantar plate and FHB tendon using a #15 blade. It is critical to stay strictly subperiosteal to avoid damaging the FHL tendon or the intersesamoidal ligament.

Soft Tissue Reconstruction:
Once the fragment is excised, repairing the flexor hallucis brevis is the most critical step of the procedure. The remaining tendon must be securely sutured to the preserved sesamoid fragment or the plantar plate using non-absorbable sutures. Failure to repair this defect will lead to weakness in hallux plantarflexion and potential deformity.

Patient Communication: If a partial sesamoid excision is performed, the patient must be informed preoperatively that the remaining sesamoid fragment may continue to be symptomatic and may need to be excised in a subsequent procedure.

3. Complete Sesamoid Excision (Sesamoidectomy)

Complete excision is reserved for severely comminuted fractures, avascular necrosis, or failed partial excisions.

Technique and Pitfalls:
The entire sesamoid is enucleated from its tendinous envelope.
* Tibial Sesamoid Excision: Excision of the medial sesamoid weakens the medial head of the FHB. If the defect is not tightly imbricated, the unopposed pull of the adductor hallucis (attaching to the fibular sesamoid) can lead to an iatrogenic hallux valgus deformity.
* Fibular Sesamoid Excision: Conversely, excision of the lateral sesamoid can lead to an iatrogenic hallux varus deformity due to the unopposed pull of the abductor hallucis.
* Bilateral Excision: Excision of both sesamoids is strongly discouraged as it destroys the intrinsic plantarflexion power of the MTP joint, inevitably resulting in a severe "cock-up" deformity (hyperextension of the MTP and flexion of the IP joint).

POSTOPERATIVE REHABILITATION PROTOCOL

The postoperative protocol is dictated by the specific procedure performed, but generally follows a strict timeline to protect the soft tissue repair and bony fixation.

Phase 1: Maximum Protection (Weeks 0-2)
* The patient is placed in a bulky compressive dressing and a posterior splint.
* Strict non-weight-bearing status is maintained.
* Elevation and cryotherapy are utilized to minimize edema.

Phase 2: Controlled Mobilization (Weeks 2-6)
* Sutures are removed at 14 days.
* The patient is transitioned to a rigid fracture boot with a toe-spica extension to prevent MTP dorsiflexion.
* For ORIF and bone grafting, non-weight-bearing is continued until week 4, followed by progressive heel-touch weight-bearing.
* For partial/complete excisions, protected weight-bearing in the boot is permitted as tolerated.
* Gentle, passive plantarflexion exercises are initiated, but active dorsiflexion is strictly prohibited to protect the FHB repair.

Phase 3: Strengthening and Return to Function (Weeks 6-12)
* Radiographs are obtained to confirm union (in ORIF) or maintenance of joint alignment (in excisions).
* The patient transitions to a stiff-soled shoe with a custom orthotic and dancer's pad.
* Active range of motion exercises for the MTP joint are initiated.
* Progressive resistance exercises for the intrinsic foot musculature begin.
* Return to high-impact sports or running is typically delayed until 3 to 4 months postoperatively, contingent upon complete radiographic healing and symmetric strength.

COMPLICATIONS

Orthopedic surgeons must be vigilant regarding the complications associated with sesamoid surgery:
1. Iatrogenic Deformity: Hallux valgus (after tibial sesamoidectomy) or hallux varus (after fibular sesamoidectomy) due to failure to adequately repair the FHB and plantar plate.
2. Nerve Injury: Neuroma formation or numbness secondary to injury of the plantar medial cutaneous nerve.
3. Nonunion/Delayed Union: Particularly common in ORIF due to the tenuous blood supply of the sesamoids, which enters predominantly from the proximal and plantar aspects.
4. Stiffness: Arthrofibrosis of the first MTP joint is common; aggressive postoperative physical therapy is required once the repair is deemed stable.

By adhering to strict indications, respecting the biomechanical importance of the sesamoid complex, and executing meticulous surgical technique, the orthopedic surgeon can successfully navigate the complexities of phalangeal and sesamoid fractures, restoring optimal function to the forefoot.