8. Foot and Ankle MCQs

The most common tarsal fracture associated with lateral dislocations is the cuboid, although the anterior process of the calcaneus and the lateral process of the talus can also be affected. In medial dislocations, the dorsomedial talar head, the posterior tubercles of the talus, and the lateral navicular are most often fractured. Post-reduction x-rays need to be scrutinized carefully for fractures of the tarsal bones as this is the most common injury associated with subtalar dislocations.

The patient has myasthenia gravis, which has its onset in middle age and causes progressive weakness because of the loss of acetylcholine receptors secondary to autoimmune antibodies at the NM junction. Rest periods allow uptake of acetylcholine and initial strength, but easy fatigability. Treatment is aimed at immunomodulation; acetyl cholinesterase inhibitors often coupled with thymectomy can control symptoms. Decreased release of acetylcholine at the NM junction is the effect of a nondepolarizing drug or toxin botulinum. Patients with muscular dystrophy lack dystrophin that acts at the sarcolemma to regulate calcium channels, and onset of this condition occurs at a younger age. The decrease in myelin indicates Charcot-Marie-Tooth disease and is often seen with long axon degeneration, such as in the feet and lower legs.

Discussion: The clinical photograph shows a hallux valgus and a crossover toe deformity. The plantar plate must be damaged for a crossover toe deformity to develop. The surgeon must assume that the open joint is at least colonized and at significant risk for postsurgical infection; consequently, it is best to cancel elective surgery, and surgical debridement of soft tissue and bone with deep cultures is recommended.

Discussion: In the Lauge-Hansen classification, the characteristic fibular fracture pattern in a pronation-abduction injury is a comminuted fibular fracture above the level of the syndesmosis. In the first stage of this injury pattern, the deltoid fails in tension, or an avulsion fracture of the medial malleolus occurs. In the second stage, the anterior inferior tibiofibular ligament ruptures, or a small bony avulsion of this ligament's insertion/origin occurs. The final stage includes the creation of a comminuted fibular fracture above the level of the syndesmosis.

Ankle arthrodesis for posttraumatic ankle arthrosis provides reliable pain relief. However, the long-term sequela of joint arthrodesis is the development of arthrosis in the surrounding joints. Over time, following ankle arthrodesis, the ipsilateral hindfoot and midfoot joints show signs of joint space wear, and this may be symptomatic.

The radiographs show a comminuted talar body fracture. The goal of treatment is to minimize the risks of posttraumatic arthrosis of the ankle and subtalar joint and to maintain vascularity. Open reduction and internal fixation with an attempt at anatomic reduction will lead to improved outcomes. Attempting to repair this fracture via an arthrotomy only is extremely difficult, and the addition of a medial malleolar osteotomy is warranted.

Calcaneal apophysitis (Sever disease) is a common cause of heel pain in adolescent athletes who participate in running or jumping sports. The condition occurs primarily before or during peak growth and is characterized by a tight Achilles tendon, a positive squeeze test, and tenderness over the calcaneal apophysis. Pain is localized to the heel and exacerbated by running.

DISCUSSION: The ankle equinus allows the patient to keep his weight-bearing line anterior to the axis of the hyperextended knee joint. With time, pain has developed because of continued stretching and now incompetence of the posterior capsule of the knee joint. Several soft-tissue and bony procedures have been designed to provide knee stability in this situation; however, the results have been either short-lived or inconsistent. Tenodeses, capsular plications, and bony blocks have had limited success and generally fail over time. Current orthotic technology makes soft-tissue release and orthotic control the most predictable option. To decrease the hyperextension moment on the knee joint, the ankle deformity also must be corrected. The most predictable method of achieving stability and diminished pain during walking is with soft-tissue release of the ankle and a knee-ankle-foot orthosis with a locked ankle and drop-lock knee joint. REFERENCE: Michael JW: Lower limb orthoses, in Goldberg B, Hsu JD (eds): Atlas of Orthoses and Assistive Devices. St Louis, MO, Mosby, 1997, pp 209-224.

DISCUSSION: Plantar fasciitis is inflammation of the plantar fascia at its insertion onto the medial calcaneus. The T2-weighted sagittal MR image reveals thickening of the plantar fascia with no evidence of a calcaneal stress fracture, coalition, or inflammation of the insertion of the Achilles tendon. RECOMMENDED READINGS: Lareau CR, Sawyer GA, Wang JH, DiGiovanni CW. Plantar and medial heel pain: diagnosis and management. J Am Acad Orthop Surg. 2014 Jun;22(6):372-80.

Morton neuroma is a compressive neuropathy of the interdigital nerves of the forefoot that most commonly is noted in the third web space. Perineural fibrosis is commonly noted on microscopic examination of resected tissue. This accounts for the relatively higher failure rate of neuroma decompression by transection of the intermetatarsal ligament as opposed to resection. Wallerian degeneration is seen following axonal transection in the distal part of the nerve. Distal axonopathy is degeneration of the axon and myelin and is associated with "stocking-glove" distribution neuropathy. Segmental demyelination is characterized by breakdown of myelin with an intact axon and is associated with lead poisoning and hereditary sensory motor neuropathy.

The images demonstrate a L5 selective root block as it exits the L5-S1 foramen. This root block best helps relieve pain or paresthesias in the L5 distribution, which is the dorsal first web space and the great toe. The lateral foot is an S1 distribution and would need to be blocked through the posterior first sacral foramen. The anterior shin and thigh represent the L4 root which exits a level above this at the L4-5 foramen. A stocking distribution is nonanatomic and not indicative of a specific root.

Because the patient has a hallux valgus with increased intermetatarsal and hallux valgus angles and advanced degenerative arthritis of the joint, arthrodesis of the first metatarsophalangeal joint will provide the most predictable pain-free result. An attempt to correct the bunion with a bunionectomy or osteotomy would most likely fail. The hallux valgus and advanced degenerative changes put the foot beyond the indications for a cheilectomy. Long-term results with silicone arthroplasty have been disappointing.

The preferred approach is posterolateral, placing the sural nerve most at risk. The dorsal intermediate cutaneous nerve is anterolateral to the ankle, and the medial and lateral plantar branches are medial and inferior to the surgical site. The saphenous nerve is anteromedial and away from the surgical approach.

The current extensile lateral approach was described by Zwipp and associates. The surgical exposure uses an L-shaped incision, with the vertical component positioned one half a finger’s breadth anterior to the Achilles tendon and extending distally to the junction of the lateral skin and the plantar skin. Borrelli and Lashgari mapped the angiosome of the lateral calcaneal flap and found that the major arterial blood supply to this flap consisted of three arteries: the lateral calcaneal artery, the lateral malleolar artery, and the lateral tarsal artery. The lateral calcaneal artery appeared to be responsible for most of the blood supply to the corner of the flap. This was found 1.5 cm anterior to the Achilles tendon. Division of this artery with inaccurate placement of the vertical limb of the incision can cause ischemia of the lateral skin flap.

Normal rotation in the hips should total approximately 100 degrees. Hip internal rotation is usually greater than external rotation, especially in girls. The thigh-foot angle is measured in a prone position and measures the angle the midaxis of the foot subtends with the midline of the thigh. The thigh-foot angle quantifies tibial rotation. Normal adult thigh-foot angle is approximately 10 to 15 degrees. This patient has increased internal rotation of the right tibia compared with the left; this is the likely cause of her gait problem.

The central one third has been established as the watershed zone by angiographic studies, and has been borne out in clinical conditions involving the navicular, such as stress fractures and osteonecrosis.

The examination and radiographs reveal a closed fracture-dislocation of the ankle with tibiofibular diastasis. Immediate fixation of the medial malleolus and plating of the fibula are indicated. If residual tibiofibular diastasis occurs with lateral translation of the fibula after plating, a syndesmotic screw is placed to stabilize the syndesmosis. Ankle fracture-dislocations associated with a proximal fibular fracture (Maisonneuve fracture) require syndesmotic fixation, but the fibula is not plated. Unstable ankle fractures require surgical treatment. If swelling is severe (fracture blisters, loss of skin wrinkling), a compressive splint is applied and surgery is delayed for 5 to 7 days.

The patient has a pronounced deformity with pain and degenerative arthritis; therefore, triple arthrodesis is the treatment of choice. Gastrocnemius or Achilles tendon lengthening may be a necessary adjunct to the triple arthrodesis, but alone is inadequate to allow for correction.

Ecchymosis on the medial side of the ankle is distributed in the posterior tibialis tendon sheath location, posterior to the medial malleolus, and extending inferiorly to the tendon’s attachment on the navicular. MRI is the imaging study of choice to determine the extent of tendon damage.

DISCUSSION: The MRI scans show a complete disruption of the sesamoid complex with proximal retraction of the medial sesamoid and high signal originating from the site normally occupied by the plantar plate (metatarsophalangeal ligament). This injury is the result of a hyperextension injury and is a severe variant of a turf toe.