One of the problems with fractures of the talus is that the blood supply to the bone is vulnerable to damage. The main blood supply to the bone enters the talus through the tarsal sinus from a branch of the posterior tibial artery. This vessel supplies most of the neck and the body of the talus. Branches of the dorsalis pedis artery enter the superior aspect of the talar neck and supply the dorsal portion of the head and neck, and branches from the fibular artery supply a small portion of the lateral talus.
Fractures of the neck of the talus often interrupt the blood supply to the talus, so making the body and posterior aspect of the talus susceptible to osteonecrosis, which may in turn lead to premature osteoarthritis and require extensive surgery.
In the clinic
An appreciation of ankle anatomy is essential to understand the wide variety of fractures that may occur at and around the ankle joint.
The ankle joint and related structures can be regarded as a fibro-osseous ring oriented in the coronal plane.
The upper part of the ring is formed by the joint between the distal ends of the fibula and tibia and by the ankle joint itself.
The sides of the ring are formed by the ligaments that connect the medial malleolus and lateral malleolus to the adjacent tarsal bones.
The bottom of the ring is not part of the ankle joint, but consists of the subtalar joint and the associated ligaments.
Visualizing the ankle joint and surrounding structures as a fibro-osseous ring allows the physician to predict the type of damage likely to result from a particular type of injury. For example, an inversion injury may fracture the medial malleolus and tear ligaments anchoring the lateral malleolus to the tarsal bones.
The ring may be disrupted not only by damage to the bones (which produces fractures), but also by damage to the ligaments. Unlike bone fractures, damage to ligaments is unlikely to be appreciated on plain radiographs. When a fracture is noted on a plain radiograph, the physician must always be aware that there may also be appreciable ligamentous disruption.
The Ottawa ankle rules were developed to assist clinicians in deciding whether patients with acute ankle injuries require investigation with radiographs in order to avoid unnecessary studies. Named after the hospital where they were developed, the rules are highly sensitive and have reduced the utilization of unwarranted ankle radiographs since their implementation.
An ankle x-ray series is required if there is ankle pain and any of the following:
Bone tenderness along the distal 6 cm of the posterior tibia or tip of the medial malleolus
Bone tenderness along the distal 6 cm of the posterior fibula or tip of the lateral malleolus
Inability to bear weight for four steps both immediately after the injury and in the emergency department
A foot x-ray series is required if there is midfoot pain and any of the following:
Bone tenderness at the base of the fifth metatarsal
Bone tenderness at the navicular bone
Inability to bear weight for four steps both immediately after the injury and in the emergency department
In the clinic
A bunion occurs on the medial aspect of the first metatarsophalangeal joint. This is an extremely important area of the foot because it is crossed by tendons and ligaments, which transmit and distribute the body’s weight during movement. It is postulated that abnormal stresses in this region of the joint may produce the bunion deformity.
Clinically, a bunion is a significant protuberance of bone that may include soft tissue around the medial aspect of the first metatarsophalangeal joint. As it progresses, the toe appears to move toward the smaller toes, producing crowding of the digits.
This deformity tends to occur among people who wear high-heeled or pointed shoes, but osteoporosis and a hereditary predisposition are also risk factors.
Typically the patient’s symptoms are pain, swelling, and inflammation. The bunion tends to enlarge and may cause problems in obtaining appropriate footwear.