FRCS: Foot and ankle

None of the above. The talus is made up of a head, neck, body and posterior process. It articulates with the tibia and fibula in the ankle, and the navicular and calcaneum in the foot. It has many ligamentous attachments but no muscle attachments. There is a groove posteriorly in which the flexor hallucis longus tendon runs. It is important to be aware of the blood supply of the talus; the primary source is the artery of the tarsal canal (derived from the posterior tibial artery); additional supply is from the superior neck vessels (derived from the anterior tibial artery) and the artery of the sinus tarsi (derived form the dorsalis pedis).

Cuboid. The calcaneum (anterior), talus and cuboid ossification centres are usually present at birth. The lateral cuneiform appears during the first year, the medial cuneiform appears during the second year, the intermediate cuneiform and navicular appear during the third year and the posterior calcaneal centre appears during the eighth year.

Calcaneum. Each of the tarsal bones has one ossification centre except the calcaneum, which has an anterior and posterior centre.

Closed or open reduction and combined screw and K-wire stabilization. The tarsometatarsal joint is best thought of in three columns: a medial column (first tarsometatarsal joint), a middle column (second and third tarsometatarsal joints) and a lateral column (fourth and fifth tarsometatarsal joints). Any dislocation or subluxation needs reduction. A cast or external fixator does not hold the reduction adequately. Although there are many ways to stabilize the fracture-dislocation after reduction, it is generally accepted that the medial and middle columns should be treated with permanent fixation (for example screws) and the lateral column should have temporary fixation (for example K-wires removed after 6–12 weeks). This is due to the relatively greater mobility of the lateral column.

Medial cuneiform to base of second metatarsal on plantar surface. The Lisfranc ligament is a strong oblique ligament, which arises from the plantar-lateral aspect of the medial cuneiform, passes in front of the intercuneiform ligament, and inserts into the plantar-medial aspect of the second metatarsal. In about 20% of patients, there are two separate bands of the ligament (dorsal and plantar).

Fracture of the lateral process of the talus. This mechanism of injury is typical for a lateral process of the talus fracture. These injuries are common in snowboarders. The mechanism involves dorsiflexion, axial loading, inversion and external rotation. They are often missed and may require MRI, CT or bone scanning 133 to make the diagnosis. Undisplaced fractures can be treated in a cast. Displaced fractures (>2 mm) should be reduced and fixed, or excised if they are too small for fixation.

Synovial cell sarcoma. Although primary cutaneous melanoma is the most common malignant tumour of any type in the foot (acral lentiginous melanoma), the most common primary soft tissue malignant tumour in the foot is synovial sarcoma. They make up approximately 8–10% of all sarcomas and most commonly affect adults in the third to fifth decades of life. They are often seen as soft tissue swelling with calcification on plain radiographs. The characteristic histological feature is a biphasic pattern with an epithelial component and a spindle cell component. Other common tumours or tumour-like conditions in the foot include enchondroma, osteoid osteoma, fibrous dysplasia, adamantinoma, osteochondroma, ganglion, clear cell sarcoma and fibromatosis.

Extensor digitorum brevis. The tibial nerve divides into the medial calcaneal (sensory), medial plantar and lateral plantar nerves after it passes behind the medial malleolus. The medial plantar nerve supplies the flexor digitorum brevis, first lumbrical, flexor hallucis brevis and abductor hallucis. The lateral plantar nerve supplies the abductor digiti minimi, flexor digiti minimi brevis, interossei, second to fourth lumbricals, adductor hallucis and flexor digitorum accessorius. The extensor digitorum brevis is supplied by the deep peroneal nerve.

Intermediate dorsal cutaneous branch of the superficial peroneal nerve. The two most common portals used in ankle arthroscopy are the anterolateral and anteromedial. The anterolateral portal is established medial to the lateral malleolus and lateral to the peroneus tertius, and risks injury to the intermediate dorsal cutaneous branch of the superficial peroneal nerve. The anteromedial portal is made lateral to the medial malleolus and medial to tibialis anterior, and risks injury to the saphenous nerve and vein. The anterocentral portal, medial to extensor digitorum longus and lateral to extensor hallucis longus, risks damaging the deep peroneal nerve and anterior tibial artery.

A post-operative cock-up toe deformity is due to damage to the extensor hallucis longus. A post-operative cock-up toe deformity is as a result of inadvertent damage to flexor hallucis longus. The intermetatarsal angle, between the long axes of the first and second metatarsals, is normally less than 10
, and is increased in hallux valgus and used to determine the severity of the deformity. The distal metatarsal articular angle (DMAA) is between the long axis of the first metatarsal and a line through the base of the distal articular cap. It is usually less than 15
. In a hallux valgus deformity with a normal DMAA, the joint is incongruent, whereas in a deformity with an increase in DMAA, the joint is congruent. The dorsomedial cutaneous branch of the superficial peroneal nerve is at risk during surgery, and damage to it can result in a painful neuroma; it is best to undertake a true medial incision, rather than a dorsomedial incision.

Pseudomonas aeruginosa. Although the most common organisms responsible for infections after penetrating wounds are Staphylococcus aureus, beta-haemolytic streptococci and various anaerobic bacteria, 134 Pseudomonas aeruginosa is usually responsible for infection when the injury is the result of object penetration through shoes and socks. Such infection may present a few days or weeks after the injury, with pain and swelling. It requires surgical debridement and intravenous antibiotics. Pasteurella multocida is seen after dog or cat bites, and puncture wounds from claws.

A varus malunion causes decreased eversion. Talar neck fractures are the commonest fracture of the talus, and follow forced dorsiflexion with axial load. They present a difficult problem, mainly due to the high complication rate, particularly osteonecrosis and post-traumatic osteoarthritis. The Hawkins classification is used for these fractures: I – undisplaced II – associated subtalar dislocation III – associated subtalar and tibiotalar dislocation IV(added by Canale) – associated subtalar, tibiotalar and talonavicular dislocation Type I injuries can be treated non-operatively, but the others need reduction and fixation. Hawkins sign refers to a subchondral lucency see on an anteroposterior radiograph at 6 to 8 weeks, and represents resorption, implying good vascularity, and hence is a good prognostic sign. A varus malunion occurs in one-third of cases and results in decreased eversion.

Spring. The intertarsal ligaments in the foot are important for stability. The cervical is also termed the interosseous talocalcaneal. The bifurcate is composed of two ligaments, which are also termed calcaneocuboid and calcaneonavicular. The long plantar is also termed calcaneocuboid-metatarsal: it arises from the calcaneum and inserts into the cuboid and all five metatarsals. The short plantar is the plantar calcaneocuboid. The spring ligament is the plantar calcaneonavicular and arises from the sustentaculum tali.

Decreased risk of re-injury. This patient has an Achilles tendon rupture. Operative and non-operative management are both acceptable options, but the principal advantage of the former is a decreased risk of re-rupture. This benefit has to be balanced against the complications of surgery, which include wound breakdown, infection and nerve injury. Some of these risks may be reduced by performing surgery percutaneously. Pain and speed of recovery are not necessarily improved by surgery. Surgery may allow a shorter immobilization time, but this is not the principal benefit.

Supination-adduction. An understanding of the Lauge-Hansen classification of ankle fractures is needed to answer this question. The first word in each type refers to the foot’s position at the time of injury and the second word refers to the direction of the deforming force. A supination-adduction gives rise to the injury described.

Forefoot pronation. Congenital talipes equinovarus (clubfoot) is a deformity of the foot with an incidence of 1 in 250–1000. It is more common in males and is often bilateral. There may be associated 135 musculoskeletal anomalies. A number of deformities are seen: forefoot adduction (tibialis posterior), forefoot supination (tibialis anterior), midfoot cavus (intrinsics, flexor hallucis longus, flexor digitorum longus), hindfoot varus (Achilles tendon, tibialis posterior) and hindfoot equinus (Achilles tendon). Dr Ponseti has revolutionized the treatment of clubfoot from a surgical (posteromedial release) to a non-surgical one (serial casting).

Arthroscopy, excision and microfracture. The Berndt and Harty classification refers to osteochondral lesions of the talus. It is a radiographic classification: I – compression of the subchondral bone II – a partially detached osteochondral fracture III – completely detached, non-displaced fragment IV – a detached and displaced osteochondral fragment Osteochondral lesions of the talar dome are commonly anterolateral or posteromedial; they are often traumatic in origin, particularly the anterolateral lesions, but may also have an osteonecrosis/atraumatic aetiology. Type IV lesions are best treated by excision and microfracture, with good results in up to 86% of patients. Microfracture is usually undertaken arthroscopically. If simple debridement and microfracture is ineffective in reducing symptoms, chondral or osteochondral grafting is considered. Ankle arthrodesis or arthroplasty is the definitive treatment.

A University of Colarado Biomechanics Laboratory orthosis is often effective treatment. Tibialis posterior tendon dysfunction is very common and often misdiagnosed as a ‘sprain’ or ‘arthritis’. Johnson and Strom described three stages and Myerson added a fourth: I – tenosynovitis, normal tendon length, no deformity II – tendon lengthening, flexible planovalgus deformity III – rigid planovalgus deformity IV – valgus ankle tilt The ‘too many toes’ sign refers to the number of toes seen from behind; normally up to three, but with a planovalgus deformity, more may be seen. Treatment is always non- operative in the first instance, and can include a University of California (not Colorado) Biomechanics Laboratory heel cup orthosis. Surgery may include tendon debridement, tendon reconstruction, medial displacement calcaneal osteotomy, lateral column lengthening and triple or pantalar arthrodesis. If the tendon is acutely ruptured, which is rare, the flatfoot develops over time as the static stabilizers fail. Normally the tibialis posterior stabilizes the midtarsal joint, if it is absent or defunctioned the midtarsal joint is overloaded and the static supporters (spring ligament, talonavicular capsule, plantar fascia) fail. The arch eventually collapses and a flatfoot ensues.

Peroneus brevis tendon. This is an uncommon scenario, but is most likely to be caused by interposition of the peroneus brevis tendon. The ankle ligaments do not usually prevent reduction. The tibialis posterior tendon is unlikely to be the cause, although it has been reported as a cause of an irreducible ankle dislocation. 136

A V-Y advancement of the gastrocnemius would be required if the gap is 6 cm. Repair of an Achilles tendon is usually undertaken with the patient prone, and an incision just medial to midline to avoid sural nerve injury. Immobilizing the foot in 20
plantarflexion allows maximum skin perfusion over the tendon, by decreasing skin tension, and protects the tendon repair. A direct repair is usually possible if the gap is less than 3 cm. A V-Y advancement of the gastrocnemius can be considered if the gap is between 3 and 5 cm, and if greater than 5 cm, a flexor hallucis longus transfer must be considered.

5º valgus, 10º external rotation, 0º flexion, 5 mm posterior talar translation. It is extremely important to fuse the ankle in the correct position. The position affects knee function and the ability to walk on uneven ground. The ideal position of arthrodesis is neutral flexion, 0–5
valgus of hindfoot valgus, 5–10
of external rotation, and slight posterior displacement of the talus under the tibia (5 mm). Posterior displacement normalizes the gait pattern and decreases the stress on the knee.

Abductor. There is no abductor compartment in the foot. Traditionally, nine compartments are described. The names and muscular contents are: Calcaneal – quadratus plantae Interosseus (4) – interossei Adductor – adductor hallucis Medial – flexor hallucis brevis, abductor hallucis Lateral – abductor digiti minimi, flexor digiti minimi Superficial – flexor digitorum brevis, lumbricals, flexor digitorum longus

Bilateral fractures occur in 5–10% of cases. Calcaneal fractures occur after an axial load and are bilateral in 5–10% of cases. They are associated with a spinal injury in about 10%. The majority (75%) are intra-articular, and result in a decreased Bohler’s angle (line drawn by connecting the anterior process, highest point on posterior articular surface and superior tuberosity on the lateral radiograph). The Sanders classification is based upon the number and location of articular fragments on the coronal CT scan, with four types, based on the number of fragments of the posterior facet, with displacement of 2 mm considered significant. The wound complication rate is reported to be up to 30%.

Calcaneonavicular coalition. A painful flatfoot in a child is likely to be secondary to a tarsal coalition. The two commonest tarsal coalitions are talocalcaneal and calcaneonavicular. The anteater sign is visualized on a lateral radiograph of the foot, and is caused by the elongated anterior process of the calcaneum. It is associated with a calcaneonavicular coalition. The coalition may be fibrous, cartilaginous or osseous. Observation, orthoses or plaster immobilization are the initial management modalities. If non-operative treatment fails, surgical excision and soft tissue interposition is an option, although arthrodesis may be required if degenerative changes are present.

Claw toe. These features describe a claw toe deformity. A hammer toe is only flexed at the proximal interphalangeal joint and a mallet toe is only flexed at the distal interphalangeal joint. A bunionette is characterized by a prominence of the fifth metatarsal head. 137 1. A 12-year-old boy presents with a 2 month history of right knee pain after a fall. He has lost 3 kg in weight but is otherwise well. He is pale, apyrexial and his right knee is slightly swollen and warm on examination. Plain radiographs reveal areas of dense sclerosis admixed with areas of radiolucency in the distal femoral metaphysis. Aggressive periosteal new bone formation is also noted. Which of the following is the most likely diagnosis? a. Parosteal osteosarcoma. b. Periosteal osteosarcoma. c. High-grade intramedullary osteosarcoma. d. Telangiectatic osteosarcoma. e. Osteomyelitis. 2. Prognostic factors that adversely affect survival in osteosarcoma include expression of all of the following except? a. Anti-shock protein 90 antibodies. b. Chemokine receptor type 4(CXCR-4). c. Alkaline phosphatase (ALP). d. Vascular endothelial growth factor (VEGF). e. P-glycoprotein. 3. A 28-year-old female presents to your clinic with progressively increasing pain in her left wrist. She has also recently been having repeated episodes of abdominal discomfort, nausea and vomiting. A plain radiograph of the wrist reveals an eccentrically placed lytic lesion in the metaphysis and epiphysis with thinning of the cortex. You suspect a giant cell tumour of bone. What is the most appropriate next step in the management of this patient? a. Perform a bone biopsy. b. Curettage alone. c. Curettage and phenolization. d. Curettage, high-speed burr, cement and bone graft. e. Check serum parathyroid hormone (PTH) and calcium. # Cambridge University Press 2012. 144