Review Question - QID 218735

Structure A represents the posterior tibialis muscle, the tendon of which can be re-routed to the dorsum of the foot at the level of the lateral cuneiform to overcome a weak tibialis anterior in the setting of a post-compartment syndrome foot drop.

The sequelae of compartment syndrome can be devastating. In children with displaced tibial tubercle fractures, a high suspicion should be held for compartment syndrome when definitive care is delayed and pain requirements are increasing. In this particular setting, when missed, the anterior compartment musculature is most often affected, which can clinically result in a foot drop. In the absence of a functional tibialis anterior, the most suitable tendon transfer to perform involves re-routing the posterior tibialis tendon through the interosseous membrane to the dorsum of the foot. Despite being an out-of-phase muscle (active during terminal stance versus the tibialis anterior, which is active during heel strike and loading), the posterior tibialis is suitable given its location directly behind the tibia and its resting tone capable of providing a stabilizing effect for functional dorsiflexion. It is also a notably stronger muscle and a better donor than the flexor digitorum longus (Structure C). The peroneus longus (Structure D) represents the next best choice, but it is anatomically not as ideal as the posterior tibialis tendon.

Cho et al. reviewed the functional outcomes following anterior transfer of the tibialis posterior tendon for foot drop secondary to peroneal nerve palsy. Seventeen patients were followed for a minimum of 3 years, with the authors finding that restoration of dorsiflexion strength postoperatively was about 33% that of the normal ankle, while function in daily activities and gait ability were satisfactorily improved. They concluded that tibialis posterior tendon transfer demonstrated no definitive radiographic or clinical progression to postoperative flat foot deformity at intermediate-term follow-up, making an anterior transfer of the tibialis posterior tendon an effective surgical option for paralytic foot drop.

Matuszak et al. reviewed the adult paralytic foot. The authors note that the adult paralytic foot is not an uncommonly encountered clinical entity, and it has numerous neurologic, systemic, and traumatic causes that result in muscle imbalance and foot deformity. They conclude that treatment goals should include the establishment of a plantigrade foot, elimination of deforming forces, and, when possible, restoration of active motor control.

Figure A is a lateral radiograph of the knee showing an Ogden type III tibial tubercle fracture. Figure B is an axial cut of a CTA of the lower leg showing the components of the deep posterior, lateral, and anterior compartments: tibialis posterior (Structure A), tibialis anterior (Structure B), Flexor digitorum longus (Structure C), Peroneus longus (Structure D), and extensor digitorum longus (Structure E). Illustration A shows these same muscular compartment structures labeled.

Incorrect Answers:
Answer B: Structure B is the tibialis anterior, which is non-functional in this patient.
Answer C: Structure C is the Flexor digitorum longus (FDL), which is less strong than, and therefore a worse donor than, the posterior tibialis tendon.
Answer D: Structure D is the peroneus longus, which represents a less favorable tendon transfer option given its less ideal anatomic location.
Answer E: Structure E is the extensor digitorum longus (EDL), which is not a described donor for foot drop correction.