Midtarsal Fracture Dislocation
The Lis Franc’s joint is a combination of joints in the middle of the foot. At the point where the long bones behind the toes, called metatarsals, connect with a grouping of small cube shaped bones, called cuneiform bones, there are several joints the move together in an interlocking fashion. This grouping of interlocking joints is referred to as the Lis Franc’s joint. The Lis Franc’s joint are bound together by a series of transverse ligaments on the top and bottom of the joint, as well as an intermetatarsal ligament. This grouping of joints is clinically called the tarsometatarsal joints. Fracture-dislocations of the tarsometatarsal joint are named for Lis Franc who was a field surgeon in the Napoleonic army. Fracture-dislocations of the tarsometatarsal joint (Lis Franc’s) is extremely significant in that it is a commonly missed diagnoses with a great potential for long term disability.
Lis Franc’s fracture-dislocations can occur in many different ways. It can be caused by both a direct crushing type injury or a force applied to the metatarsal heads (ball of the foot) which both can result in displacement of the Lis Franc’s joint or fractures that in involve the joint. Common causes are motor vehicle accidents, falls from heights, severe foot and ankle sprains, crushing force to the top of the foot. These injuries can occur during strenuous and competitive athletic activities. The athlete who complains of sudden onset of pain, in the middle of the foot during the course of an athletic event should be carefully evaluated for a possible Lis Franc’s injury.
Diagnosis is extremely important following the injury. Early diagnosis and treatment can prevent long-term chronic pain and other sequalae. Diagnosis is made by both clinical and X-ray modalities. On physical examination there is marked tenderness across the tarsometatarsal joint usually with pinpoint tenderness at the articulation of the second metatarsal base and the medial and intermediate cuneiforms. Global forefoot and midfoot swelling is commonly seen from several minutes to several hours following injury. In severe dislocations it is very easy to visualize a change in shape of the foot as compared to the other foot. X-rays may reveal either a partial or total dislocation at the tarsometatarsal joint. The difficult cases to diagnosis are those when the joint dislocates and then relocates on its own. When this occurs there may be little evidence of the injury on an x-ray. If there are no X-ray changes and clinical diagnosis makes the doctor suspicious of injury they may order stress X-ray, bone scan or MRI. In all acute injuries circulation must be monitored to assess the possibility of compartment syndrome (increase in pressures within the foot which can shut off circulation). This could result in loss of oxygen to the tissues, which might result in loss of the foot.
Closed reduction should always be attempted in an acute fracture-dislocation. Treatment involves general anesthesia to relax the patient and an attempted reduction of the second metatarsal base into its anatomic position is attempted. If the second metatarsal can be reduced then metatarsals two through five may reduce without much manipulation. If closed reduction is successful then reduction of the first metatarsal cuneiform joint is performed and pins are inserted to allow for stability during healing. If closed reduction fails it is usually due to one of the foot tendons, which may be caught in the dislocated joint. If closed reduction fails in an acute injury or the injury is old then open reduction must be performed to reduce long-term problems. If vascular compromise is evident this also constitutes a need for immediate surgery. There are usually two to three incisions placed on the top of the foot to allow for adequate visualization and manipulation of the bones. Once the foot has been placed back into anatomic position the tarsometatarsal joint is stabilized with either pins or screws to allow for stability during the healing process. If pins are used they are usually removed in six to eight weeks. Whether pins or screws are used doesn’t really matter as the patient is non-weight bearing for six weeks and is usually casted for at least eight to twelve weeks. Following bony healing and return to ambulation the patient will need a good functional foot orthotic to provide support and relieve stress from the tarsometatarsal joints and assist in pain free ambulation. Long-term prognosis for this injury is guarded. When any injury involves a joint the likelihood of an on-going arthritic process is likely. In sever cases fusion of the joints may be necessary. In the athlete this injury can be devastating. Rehabilitation to return to the same level of performance can takes several months or longer.