By: Robert H. Sheinberg, D.P.M., D.A.B.P.S., F.A.C.F.A.S.
The sesamoids can be normally in two or more pieces. These pieces are connected by cartilage. This is referred to as a synchondrosis. Cartilage has a very poor blood supply to the area. When an injury occurs to the synchondrosis it may appear as a fracture on an x-ray but it is not a fracture of the bone but a fracture of the cartilage connecting the bones. Injuries to the synchondrosis can be very difficult to treat. X-rays may be taken on the unaffected side to compare. However, both sides may have what appears to be sesamoids in multiple pieces. When pain persists, then an MRI may be necessary to fully evaluate the injury. We often see bone marrow swelling on two or more bone segments, which indicates the injury to that area. Clinically, there is pinpoint tenderness to the bone on the ball of the foot. Swelling may or may not be present. There will be difficulty walking in long strides or running on the ball of the foot. Dancing can become near impossible because of the pain that patients may experience. Treatment includes immobilization in a boot and often nonweightbearing to allow the area to heal.
These injuries will most often heal with conservative care but it may take many months before it goes on to complete healing. During the healing process, x-rays will not change, as the bones will not grow back together because of the cartilage that is between them. We can evaluate the healing based on the patient’s pain that they are experiencing while walking and examining them to check for tenderness. Once tenderness and pain are diminished, then an orthotic is made to go in the patient’s shoes or sneakers to unload the metatarsal further and allow the patient to return to sports and activities as desired. In some cases, these injuries do not heal and one or more of the pieces of bone on the ball of the foot needs to be removed. A small incision is placed on the inside of the first metatarsal joint and a piece of the bone is removed. The soft tissue is repaired and immobilization for 3-6 weeks is necessary to allow the area to heal completely. The long-term prognosis is usually excellent.
Intraop Pics of Synchondrosis sesamoid fracture
The fracture can be seen. Due to continued pain, a sesamoidectomy was performed. The bone is unhealthy and was removed.
Xray and MRI of Synchondrosis Fracture to Sesamoid. On the MRI (right), the bone is supposed to be black and the white is inflammation in the bone.