Midfoot Fractures and Dislocations

Introduction

Injuries to the foot are common in the athletic population, accounting for approximately 16% of all sports injuries. Trauma to the tarsometatarsal (TMT) joints is the second most common injury pattern, second only to metatarsophalangeal (MTP) joint injuries. The Lisfranc joint complex is the most commonly involved in injuries to the midfoot due to the limited static and dynamic stability of this region. Stress fractures, especially of the fifth metatarsal, continue to be a common reason for loss of time in athletes.

Misdiagnosis or maltreatment of these potentially career-ending injuries may not only prolong return to competitive play but can also lead to post-traumatic degenerative changes and pain that limit activity and quality of life in the future.

Clinical Diagnosis

In evaluating patients with trauma to the foot, it is essential to obtain a thorough, detailed history to direct the examiner in physical and radiographic examination. In addition, it will provide a clue to the associated degree of soft tissue injury.

Physical examination should be meticulous and systematic ( Video 7.1 ). It is recognized that although most forefoot injuries are easily diagnosed, midfoot injuries often go undetected. Because of the high incidence of multiple fractures or fracture/dislocations in the injured foot, careful examination and palpation of points of tenderness should be performed to detect evidence of occult injury. Evaluation of range of motion of the ankle, subtalar midtarsal, and MTP joints is incorporated into every routine examination. A careful motor examination, both intrinsic and extrinsic, as well as a sensory examination are performed. Vascular examination, including Doppler studies, is essential. Radiographs are guided by the examiner’s history and physical examinations. Because of the complexity of the anatomy and lack of uniform appreciation or interpretation of the foot radiographs, adjunctive studies, such as computed tomography (CT), especially weight bearing CT, bone scan, and magnetic resonance imaging (MRI), can be of tremendous value. These also are particularly useful because of the subtle nature of many foot and ankle injuries.

Weight-bearing anteroposterior (AP), 30-degree oblique, and lateral radiographs are the first and typically most valuable imaging studies obtained for a patient with a foot injury. If the patient is too painful for a standing radiograph, an ankle block, or intra-articular local anesthetic, could be performed to obtain adequate weight-bearing radiographs. It will also allow stress x-rays to be performed ( Video 7.2 ). A comparison weight-bearing AP radiograph of the contralateral foot should be obtained to identify subtle subluxation or translation at the Lisfranc joint complex, which appears asymmetric in the injured foot. This is particularly useful for cases with less than 2 mm of instability, as this amount of displacement is often difficult to assess on a plain radiograph.

The oblique view, for example, is particularly useful for evaluating joints, such as the calcaneal cuboid joint and the 4-5 TMT joints, that typically are hidden or poorly examined in AP view. Specialty views, such as axial views of the heel, Broden’s view of the subtalar joint, and stress views of the foot, also are helpful in certain circumstances.

Advanced imaging studies are utilized to identify or confirm a subtle injury, especially as up to 20% of Lisfranc complex injuries are missed on initial radiographs. Thin-cut CT imaging with reconstruction views will identify small fractures or possibly subluxation at the TMT joints, and may be particularly helpful if the foot can be loaded with a simulated weight-bearing study. MRI is both sensitive and specific in identifying partial and complete ligamentous injuries at the Lisfranc joint complex, but it is unnecessary for evaluation of injuries with obvious subluxation or dislocation. A normal appearance of the plantar Lisfranc ligament on MRI is highly suggestive of a stable midfoot whereas the best predictor for instability is a rupture or a grade-2 sprain of this ligament. MRI has demonstrated a sensitivity, specificity, and positive predictive value for detecting injury to the plantar Lisfranc ligament of 95%, 75%, and 94%, respectively.