INTRODUCTION TO FOOT AND ANKLE MALUNIONS
The management of post-traumatic malunions of the foot and ankle presents a formidable challenge to the orthopedic surgeon. Fractures of the metatarsals, tarsals, calcaneus, and talus that heal in non-anatomic positions invariably disrupt the intricate biomechanics of the lower extremity. This disruption leads to altered load distribution, debilitating pain, tendinopathy, and progressive post-traumatic arthrosis.
Surgical intervention demands meticulous preoperative planning, advanced imaging modalities (including weight-bearing computed tomography), and a mastery of osteotomy, arthrodesis, and soft-tissue balancing techniques. The ultimate goal is the restoration of a painless, plantigrade, and biomechanically sound foot.
CORRECTION OF METATARSAL ANGULATION
Metatarsal malunions typically present with sagittal or coronal plane deformities that disrupt the metatarsal parabola. Plantar angulation leads to intractable plantar keratosis and localized metatarsalgia, while dorsal angulation results in transfer metatarsalgia to adjacent rays.
Preoperative Evaluation and Biomechanics
Clinical evaluation must assess the presence of callosities, toe deformities (such as clawing), and the flexibility of the metatarsophalangeal (MTP) joints. Weight-bearing radiographs are essential to evaluate the degree of angulation and the relative lengths of the metatarsals.
🚨 SURGICAL PITFALL: Failure to recognize and correct a shortened metatarsal during angular correction will inevitably lead to transfer metatarsalgia. The metatarsal cascade must be restored.
Surgical Technique: Metatarsal Osteotomy and Realignment
1. Incision and Exposure:
* Make a longitudinal incision on the dorsum of the forefoot, parallel to the shaft of the affected metatarsal.
* Often, a single strategically placed dorsal incision within the intermetatarsal space provides excellent access to two adjacent metatarsals (e.g., between the 2nd and 3rd rays).
* Carefully retract the extensor tendons and protect the dorsal cutaneous nerve branches.
2. Osteotomy and Mobilization:
* Expose the site of the old fracture. Perform a subperiosteal dissection to limit disruption of the osseous blood supply.
* Divide the malunion site using a fine osteotome or an oscillating microsaw.
* In cases of severe angular deformity, a precisely measured dorsal or plantar closing-wedge osteotomy may be required to permit elevation or depression of the distal fragment.
* Crucial Step: Resection must be minimal. Excessive bone resection will result in critical shortening and a high risk of nonunion.
3. Reduction:
* Raise or depress the distal fragment into a slightly overcorrected position. This is achieved by applying manual pressure from the plantar aspect while forcibly flexing the toes to utilize the plantar fascia and intrinsic musculature as a tension band.
4. Fixation:
* Fix the fragments using an intramedullary Kirschner wire (K-wire) or a modern low-profile titanium mini-plate.
* For intramedullary pinning, drive a smooth K-wire retrograde through the metatarsal head, exiting the plantar aspect of the MTP joint, and then advance it antegrade across the osteotomy site into the proximal metatarsal base.
Postoperative Protocol
- 0-3 Weeks: Apply a well-molded short-leg cast from the tibial tuberosity to the toes. The plantar aspect of the cast must be meticulously molded to maintain the overcorrected position and support the transverse arch. Non-weight-bearing is strictly enforced.
- 3 Weeks: Remove the cast and extract the intramedullary pins in the clinic. Transition the patient to a walking boot cast. Insert a custom felt pad beneath the fracture site to hold the toes in slight plantar flexion, neutralizing the pull of the extensor tendons.
- 6 Weeks: Discontinue the walking boot. Transition to a sturdy, stiff-soled shoe fitted with a custom orthotic arch support and a metatarsal pad to offload the surgical site during the final phases of bone remodeling.
CORRECTION OF TARSAL MALUNION
Malunions of the midfoot (navicular, cuboid, and cuneiforms) frequently result in severe midfoot collapse, abduction or adduction deformities, and rigid flatfoot or cavus presentations.
Surgical Technique: Tarsal Osteotomy and Arthrodesis
1. Approach:
* Utilize a dorsal longitudinal incision either lateral to the extensor tendons or middorsally in line with the third metatarsal, depending on the apex of the deformity.
* Reflect the periosteum and expose the old fracture site.
2. Osteotomy (Early vs. Late):
* Early Malunion (Months): If the injury is relatively recent, divide the bones with an osteotome directly through the old fracture line. If the fragments overlap excessively, resect a small section from each to allow anatomic reduction without excessive tension on the soft tissues.
* Late Malunion (Years): If the malunion is chronic, the tarsus may be completely autofused, rendering the original fracture line indistinguishable. In these instances, perform a corrective osteotomy (e.g., a dorsal closing wedge or biplanar osteotomy) through the apex of the deformity, without regard to the obliterated joints or the original fracture site. Severe deformities may require wide resection of bone to achieve a plantigrade foot.
3. Reduction and Fixation:
* Using a bone skid or a Cobb periosteal elevator, forcefully lever the fragments into anatomic alignment.
* While reduction in the rigid midfoot is often inherently stable, rigid internal fixation is mandatory. Utilize bone staples, crossed K-wires, or modern locking compression plates to maintain apposition and compression.
CLINICAL PEARL: Tarsal malunions frequently cause secondary tenosynovitis of the extensor tendons and dorsal contracture of the toes. Do not attempt to correct severe claw toes during the index midfoot reconstruction. These deformities should be addressed sequentially via a separate claw toe correction operation once the midfoot architecture is stabilized.
Postoperative Protocol
- 0-1 Week: Apply a non-weight-bearing plaster cast from the toes to just below the knee, holding the foot at a strict 90-degree angle to the leg.
- 1 Week: Obtain radiographs through the cast to confirm maintenance of reduction.
- 2 Weeks: Remove the cast and sutures. Inspect the foot. If any residual deformity is noted, perform a manipulation under general anesthesia (MUA) to optimize alignment. Apply a new short-leg cast for 1 month.
- 6 Weeks: Take impressions for custom arch supports. Apply a walking boot cast, well-molded beneath the metatarsal necks and longitudinal arch, for an additional 4 weeks.
- 10+ Weeks: Remove the cast. Initiate aggressive physical therapy focusing on foot and toe exercises. The patient must wear custom arch supports for 4 to 6 months to protect the reconstruction.
MANAGEMENT OF CALCANEAL MALUNION
Calcaneal fractures are notorious for healing with complex, multiplanar deformities. The classic pathoanatomy of a calcaneal malunion includes heel widening, subtalar incongruity, loss of calcaneal height (decreased Böhler angle), and varus alignment.
Biomechanical Consequences
- Heel Widening: Leads to lateral wall blowout, causing subfibular impingement and mechanical dysfunction or tearing of the peroneal tendons.
- Decreased Calcaneal Height: Results in a horizontally oriented talus. This causes anterior tibiotalar impingement, severely restricted ankle dorsiflexion, and a profound decrease in push-off strength during the gait cycle.
- Anterolateral Overhang: Impairs calcaneocuboid joint motion.
- Varus Deformity: Shifts the mechanical axis laterally, leading to excessive stress on the lateral column of the foot and chronic lateral ankle instability.
- Subtalar Incongruity: Inevitably progresses to painful post-traumatic subtalar arthrosis.
Preoperative Evaluation
Because pain and functional deficits may spontaneously improve for 1 to 2 years post-injury as the foot adapts, surgical treatment is generally deferred as long as the patient demonstrates progress in rehabilitation.
When function plateaus, meticulous clinical evaluation is required to pinpoint the pain generator:
* Lateral Pain: Suggests lateral wall impingement or peroneal tendinitis.
* Circumferential Pain: Suggests global subtalar arthrosis.
* Anterior Ankle Pain: Suggests anterior tibiotalar impingement due to talar dorsiflexion.
* Posterior Ankle Pain: Suggests impingement from a posterior calcaneal bone spike behind the posterior facet.
CLINICAL PEARL: A diagnostic injection of 1% lidocaine into the subtalar joint under fluoroscopic guidance is invaluable. Complete relief of pain confirms the subtalar joint as the primary pain generator, indicating the need for arthrodesis.
Imaging and Classification:
Standard lateral, axial, and weight-bearing radiographs are mandatory. A Broden view assesses the posterior facet. However, a Computed Tomography (CT) scan (transverse and coronal planes) is the gold standard.
Stephens and Sanders utilized CT to classify calcaneal malunions and guide treatment:
* Type I: Lateral wall exostosis with an intact, congruent subtalar joint. Treatment: Lateral wall exostectomy and peroneal tenolysis.
* Type II: Lateral wall exostosis with subtalar arthrosis, but normal calcaneal alignment. Treatment: Lateral wall exostectomy and in situ subtalar arthrodesis.
* Type III: Lateral wall exostosis, subtalar arthrosis, and severe varus malalignment with loss of height. Treatment: Lateral wall exostectomy and subtalar bone-block distraction arthrodesis.
🚨 SURGICAL PITFALL: Smoking is a profound risk factor. It exponentially increases the incidence of nonunion after subtalar arthrodesis and the likelihood of catastrophic wound complications. Smokers must be aggressively counseled to cease smoking preoperatively.
Surgical Technique: The Extensile Lateral Approach
The extensile lateral approach allows comprehensive access for peroneal decompression, lateral wall exostectomy, and bone-block arthrodesis through a single incision.
1. Exposure:
* Create an L-shaped extensile lateral incision. Develop a full-thickness subperiosteal flap, meticulously protecting the sural nerve and the peroneal tendons.
* Retract the flap using "no-touch" techniques with K-wires driven into the talus and cuboid to minimize skin edge necrosis.
2. Lateral Wall Decompression:
* Identify the bulging lateral wall of the calcaneus. Perform a generous exostectomy using an osteotome or oscillating saw.
* Decompress the subfibular space completely. Perform a thorough tenolysis of the peroneus longus and brevis tendons, repairing any longitudinal split tears.
3. Subtalar Distraction Arthrodesis (For Type III Deformities):
* Denude the remaining cartilage from the posterior facet of the subtalar joint down to bleeding subchondral bone.
* Insert a laminar spreader into the subtalar joint to distract the calcaneus, restoring calcaneal height and correcting the varus deformity. This maneuver simultaneously plantarflexes the talus, resolving anterior tibiotalar impingement.
* Harvest a tricortical structural autograft from the iliac crest (or utilize a structural allograft). Shape the graft to fit the distracted defect.
* Impact the bone block into the subtalar joint.
* Secure the arthrodesis with two large-fragment (6.5 mm or 7.3 mm) cannulated screws placed from the posterior calcaneal tuberosity, across the graft, and into the body and neck of the talus.
MANAGEMENT OF TALAR MALUNION
Malunions of the talus are rare but carry a devastating prognosis due to the bone's precarious extraosseous blood supply and its central role in both the ankle and subtalar joints.
Malunion of the Talar Neck
Talar neck fractures frequently malunite in varus and dorsal extension. A varus malunion locks the transverse tarsal joint, severely restricting midfoot flexibility and causing the patient to walk on the lateral border of the foot. Dorsal displacement of the distal fragment painfully blocks the ankle joint anteriorly.
Surgical Correction:
* Osteotomy: A corrective opening-wedge osteotomy at the apex of the deformity is indicated for symptomatic varus malunions without severe adjacent joint arthritis.
* Grafting: A rhomboid-shaped autogenous tricortical iliac crest bone graft is impacted into the osteotomy site to restore the medial column length and correct forefoot rotation.
* Vascular Preservation: Extreme care must be taken to preserve the remaining extraosseous blood supply (specifically the artery of the tarsal canal and deltoid branches) to prevent iatrogenic osteonecrosis.
* Salvage: If the deformity is rigid or accompanied by severe subtalar arthrosis, a triple arthrodesis with resection of suitable bone wedges is required to correct heel inversion and forefoot varus. If the anterior impingement is isolated to a dorsal bony prominence, a simple exostectomy may restore motion, though traumatic arthritis often eventually necessitates ankle arthrodesis.
Malunion of the Talar Body
Fractures of the talar body that unite in malposition cause extreme disability, as they directly involve the tibiotalar and subtalar articular surfaces.
Surgical Management:
* Isolated Joint Arthrosis: If traumatic arthritis is limited to either the ankle or the subtalar joint, an isolated ankle arthrodesis or subtalar fusion is indicated.
* Global Arthrosis (Viable Talus): When both superior and inferior articular surfaces are destroyed, but the talar body remains viable and uninfected, a tibiotalocalcaneal (TTC) arthrodesis using a retrograde intramedullary nail or rigid plating is the procedure of choice.
* Avascular Necrosis (AVN) / Nonviable Talus: When the talar body is avascular or collapsed, a Blair tibiotalar fusion or a calcaneotibial arthrodesis is indicated. This involves excision of the necrotic talar body and fusion of the tibia directly to the calcaneus, preserving some motion in the midtarsal joints.
* Infection and Bone Loss: For open fractures complicated by deep sepsis, draining sinuses, and sequestration of the talus, radical debridement and talectomy are mandatory.
ADVANCED SALVAGE TECHNIQUE: To preserve limb length following a talectomy for infection, modern limb salvage employs Ilizarov circular fixation techniques. Following radical debridement and appropriate culture-directed antibiotic therapy, a proximal tibial corticotomy is performed. Bone segment transport is utilized to gradually lengthen the tibia, facilitating a delayed calcaneotibial arthrodesis without sacrificing leg length. This highly complex technique requires a compliant patient and meticulous pin-site care.
