Saturday, February 9, 2008

Spring Ligament Tear

The ancient Greek physician Galen is said to have given the first written description of pes planus, or flatfoot. One common cause for flatfoot is tearing and dysfunction of the posterior tibial tendon, which helps maintain the medial longitudinal arch.

Another stabilizer of the medial longitudinal arch is the calcaneonavicular (spring) ligament. The spring ligament is composed of three components: superomedial, medioplantar oblique, and inferoplantar longitudinal. Of these, the superomedial component is the most important component. All three components of the spring ligament can be identified on MRI.

In this case, a 59 year-old woman presents with a flatfoot. (A) There is a complete tear of the superomedial portion of the spring ligament (red arrow). (B) Different patient, with a normal spring ligament (green arrow), for comparison.

Interestingly, this patient's posterior tibial tendon was thickened distally, but remained intact. The medioplantar oblique, and inferoplantar longitudinal ligaments were hypertrophied (not shown). In addition, there was extensive abnormal signal in the sinus tarsi, a common finding in patients with abnormalities of the posterior tibial tendon and spring ligament.

Spring ligament tears can be repaired (typically in conjunction with a repair of the posterior tibial tendon), enhancing the stability of the medial longitudinal arch. It's not enough to look for the integrity of the posterior tibial tendon on MRI- look carefully at the spring ligament as well.

Galen's fame is not restricted to the foot- his work dominated Western medicine for over a millennium. His vivisection experiments included tying off the recurrent laryngeal nerve to show that the brain controls the voice, and tying off the ureters to demonstrate kidney and bladder functions.

Vic David MD

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