Image Quiz

A High-Energy Ski Injury1 (continued)

Answer: Avulsion fracture of the medial head of the gastrocnemius muscle

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Fig. 1
Fig. 2
Fig. 3
Fig. 1 Plain radiograph showing a bone fragment in the popliteal space (arrow).
Fig. 2 Computed tomography scan showing a fracture in the posterior part of the medial condyle of the femur (arrowhead) and a bone fragment in the popliteal space (arrow).
Fig. 3 A STIR (short-T1-inversion-recovery) magnetic resonance imaging scan showing a bone fragment connected to the medial head of the gastrocnemius muscle (arrow).

Open reduction and internal fixation with a cancellous screw was performed sixteen days after the injury (Fig. 4).


Fig. 4		 Fig. 4 Postoperative lateral radiograph showing internal fixation with a cancellous screw.

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Discussion

The gastrocnemius muscle is commonly injured at the musculotendinous junction. Avulsion fracture of the medial head of the gastrocnemius appears to be a rare injury that has not been well documented. Rupture of the medial head of the gastrocnemius muscle at its origin has been reported only once, to our knowledge. Arner and Lindholm reported that rupture of the gastrocnemius muscle probably occurs with sudden dorsiflexion of the foot with the knee joint in extension. This combination of movements produces maximal contraction of the medial head of the gastrocnemius muscle. Our patient's booted left foot was fixed to his ski. Thus, the mechanism of the avulsion fracture may have been sudden dorsiflexion of the foot with full extension of the knee.

Magnetic resonance imaging can demonstrate disruption of the muscles or tendons surrounded by tissue of increased signal intensity, corresponding to hemorrhage. The plain radiographs of our patient revealed a bone fragment. Magnetic resonance imaging revealed no abnormalities of the gastrocnemius muscle belly and showed that the fragment of the medial condyle of the femur was linked with the medial head of the gastrocnemius muscle.

Gilcreest reported a case of rupture of the gastrocnemius muscle at its origin. The patient was initially treated conservatively but, thirteen months after the injury, surgical treatment was needed because of persistent knee pain. In our patient, the fragment was detached from the medial condyle of the femur and a good clinical result was achieved with surgical treatment.

Reference

1. Maehara H, Sakaguchi Y. Avulsion fracture of the medial head of the gastrocnemius muscle: a case report. J Bone Joint Surg Am. 2004;86:373-5.