Avulsion fracture of the medial head of the gastrocnemius muscle is a very rare phenomenon; to the best of our knowledge, only three cases have been reported to date. Maehara and Sakaguchi [
1] reported a case of isolated avulsion fracture without ligament injury. The patient sustained an avulsion fracture in a skiing accident and underwent surgery to repair the bone fragment using a cancellous screw. Patterson
et al. [
2] reported satisfactory results using conservative treatment for an isolated avulsion fracture in a 14-year-old man, who was a wrestler and returned to competition. Mio
et al. [
3] reported a case involving a 51-year-old man with an avulsion fracture associated with multiple ligament injuries and posterior dislocation of the knee in a high-energy traffic accident. The avulsion fracture of the medial head of the gastrocnemius muscle was combined with ACL, PCL, and MCL injuries. The MCL was avulsed from the tibial attachment and reattached to its tibial insertion using suture anchors. The avulsion fracture of the medial head of the gastrocnemius muscle was reduced and fixed using a screw.
Our case involved a sports injury and an avulsion fracture combined with multiple ligament injuries before closure of the growth plate. We suspected that the knee had severe valgus stress, same as in the case described by Mio
et al., [
3] and the avulsion fracture occurred at the femoral attachment of the MCL, which is a weak part in mechanical strength. Regarding whether to repair an avulsed fragment, Maehara and Sakaguchi [
1] reported that the case was an isolated fracture; however, the authors chose surgery to address the large displaced bone fragment. In a case reported by Patterson
et al. [
2], a fracture was found 4 weeks after injury, and there was no instability of the knee and only limited range of motion. As such, they did not perform surgery, and the patient returned to competition 8 weeks after injury. On the other hand, Mio
et al. [
3] reported that they initially repaired the avulsed bone fragment of the gastrocnemius muscle and repaired the MCL and planned to reconstruct the ACL and PCL. They also reported that, although the posterior dislocation of the knee was easily reduced manually, the knee easily dislocated again because of gross instability; however, the reduced position could be maintained by repairing the MCL and gastrocnemius muscles. Inoue
et al. [
4] performed electromyographic analyses in 12 patients with PCL-deficient knees to compare electrical activity in the quadriceps, hamstring, and gastrocnemius muscles between the uninjured and involved knees. The authors reported that before generation of flexion torque, the gastrocnemius muscle was significantly electrically activated earlier in the PCL-deficient knees than in uninjured knees. They suggested that early contraction of the gastrocnemius muscle may be part of a compensatory mechanism in PCL-deficient knees. Mio
et al. [
3] also reported that reduction of the bone fragment attached to the medial head of the gastrocnemius muscle was crucially important to regain stability of the knee. Similarly, although slight posterior instability after surgery remained in our case, we speculate that fixation of the avulsion fracture of the MCL and gastrocnemius muscle may have contributed to posterior stability. Therefore, we believe that the avulsion fracture of the medial head of the gastrocnemius muscle associated with PCL injury should be repaired. Regarding the mechanism of injury, Arner and Lindholm [
5] reported that rupture of the gastrocnemius muscle probably occurs with sudden dorsiflexion of the foot with the knee joint in extension. Maehara and Sakaguchi [
1] suggested that the mechanism of avulsion fracture of the gastrocnemius muscle may be sudden dorsiflexion of the foot with full extension of the knee. Mio
et al. [
3] suspected that the mechanism of injury may be hyperextension and severe valgus stress on the knee and increased mechanical torsion to the medial head of the gastrocnemius muscle by knee hyperextension, and that contraction of the gastrocnemius muscle likely produced the avulsion fracture. Considering these reports, we believe that the mechanism of injury in our case involved hyperextension and valgus stress on the knee and sudden dorsiflexion of the foot. As a result, we considered that the avulsion fracture occurred at the femoral attachment of the MCL, which is a weak part in mechanical strength and at the insertion of the medial head of the gastrocnemius muscle. Regarding the material used for fixation, we used an absorbable screw so that it did not have to be removed. Because bone union was achieved 1 year after surgery, there was no problem in terms of strength, and we considered the absorbable screw as a suitable option for fixation.
We described a rare case of avulsion fracture of the gastrocnemius muscle combined with multiple ligament injuries before closure of the growth plate. A satisfactory result was obtained by fixation of the avulsed bone fragments of the gastrocnemius muscle and MCL. We believe that the avulsion fracture of the medial head of the gastrocnemius muscle associated with PCL injury should be repaired.