The posterior tibial tendon is a frequently injured tendon in the foot and the rupture of this tendon has received increased attention in the literature since Key first described it in 1953.1 Failure of the posterior tibial tendon results in adult-acquired flatfoot deformity. The medial longitudinal arch’s mechanical integrity relies on the dynamic support of muscles, the static support of ligaments and joint capsules, and the behavior in which the tarsal bones interlock.2
The chief dynamic stabilizer of the hindfoot is the posterior tibial muscle-tendon unit. After rupture of the posterior tibial tendon, the ligaments and joint capsules appear to tear, stretch or rupture under amplified stress.2 With ensuing adult-acquired flatfoot deformity, one will note valgus alignment of the calcaneus, plantarflexion of the talus, abduction of the forefoot and pronation of the foot.2 The static structures of the arch of the foot may offer the most support, especially during stance, regardless of the posterior tibial tendon’s vital role.
The spring ligament, which physicians also refer to as the calcaneonavicular ligament, extends from the sustentaculum talus to the navicular tuberosity and supports the plantar medial aspect of the talar head. The spring ligament is made up of the superomedial and inferior calcaneonavicular ligaments. The superomedial component lies medial to the talar head and blends with the deltoid ligament, which frequently has attenuation or gross tears in patients with adult-acquired flatfoot.2,3
Authors have reported the connection between tear of the posterior tibial tendon and injury to the spring ligament. Patients with more severe abnormalities of the hindfoot may have injuries to both the tibial tendon and the spring ligament. Gazdag and Cracchiolo have promoted the idea that one should also inspect the spring ligament in patients with posterior tibial tendon pathology.2 Gazdag and Cracchiolo note if surgeons find a damaged spring ligament, they must repair it during surgery for the posterior tibial tendon insufficiency.
Yao and colleagues depicted the appearance of spring ligament insufficiency on magnetic resonance imaging (MRI) and also noted its association with posterior tibial tendon tears.4 When examining patients with a surgically verified spring ligament tear, Yao and co-workers found the superomedial portion of the spring ligament to be thickened with a heterogenous signal as it coursed along the medial aspect of the talar head.
Balen and Helms found abnormality of the spring ligament to have a high association with advanced posterior tibial tendon injury.5 On MRI, they found the spring ligament to be abnormal in 23 of 25 patients with a posterior tibial tendon injury.
A Look At The Classification System Based On Surgical Intervention
At the University Foot and Ankle Institute, we categorize spring ligament injuries into three classes and determine an appropriate treatment course accordingly.
The first category consists of a spring ligament that may have mild fraying or weakening without a gross tear and no talar head protrusion. In such cases, a surgical repair is not usually necessary and the main treatment is arch support through bracing or orthotics. At our institute, we have also used platelet rich plasma injections to augment the healing process in chronic cases of stage one spring ligament disorder.
Category two refers to cases of partial to compete tear of the spring ligament. In such cases, the tear is most often of the navicular tuberosity and there is an associated talar “unroofing” with medial protrusion. In category two cases, there is a substantial increase in the medial arch collapse. When the spring ligament is partially to completely torn, as in our second category, we have found that a direct repair is best with placement of one or two suture anchors into the navicular and imbrication of the spring ligament back into the navicular tuberosity under the proper tension. In cases that demonstrate a severe tear with shredding of the spring ligament with no primary repair possible, one should perform biotenodesis of the spring ligament with an allograft for greater strength and tension. One would anchor an allograft tendon strip with a biotenodesis screw into the talus and navicular.
In our last category, category three, we have found that there is significant unroofing of the talus associated with arthritic changes. A talonavicular arthrodesis is the final resort in cases in which one finds the integrity spring ligament to be very poor and arthritic changes are present.
In Conclusion
More recently, we are regarding the function of the spring ligament complex as more essential than in the past and placing a significant amount of emphasis on its repair when it is ruptured. Traditionally, there had been a great deal of focus on rupture of the posterior tibial tendon because of its enhanced frequency. However, we have discovered that the pathology of the static stabilizers such as the spring ligament can play just as much a role as the posterior tibial tendon rupture on the adult-acquired flatfoot.
Magnetic resonance imaging is a valuable modality for the diagnosis of injury to the posterior tibial tendon. With insufficiency and flatfoot deformity, a tear of either the posterior tibial tendon, spring ligament or both may cause collapse and pain. Researchers have acknowledged an increased incidence of abnormality of the spring ligament on MRI in patients with advanced posterior tibial tendon injury.5
It is imperative to inspect and repair the spring ligament in conjunction with flatfoot reconstruction procedures. In following a classification system to aid in determining the surgical intervention warranted, our practice has had relatively great results and patient satisfaction. We have outlined that systematic approach above and hope it helps others with diagnosis and repair of the spring ligament complex.
Dr. Baravarian is an Assistant Clinical Professor at the UCLA School of Medicine. He is the Chief of Podiatric Foot and Ankle Surgery at the Santa Monica UCLA Medical Center and Orthopedic Hospital, and is the Director of the University Foot and Ankle Institute in Los Angeles.
Dr. Chandler is a fellow at the University Foot and Ankle Institute in Los Angeles.
References:
- Key J. Partial rupture of the tendon of the posterior tibial muscle. J Bone and Joint Surg. 1935;35-A(4):1006-1008.
- Gazdag AR, Cracchiolo A. Rupture of the posterior tibial tendon. J Bone Joint Surg Am. 1997;79(5):675-681.
- Davis WH, Sobel M, DiCarlo EF, et al. Gross histological, and microvascular anatomy, and biomechanical testing of the spring ligament complex. Foot Ankle Int. 1996;17(2):95-102.
- Yao L, Gentilli A, Cracchiolo A. MR imaging findings in spring ligament insufficiency. Skeletal Radiol. 1999;28(5):245-250.
- Balen P, Helms C. Association of posterior tibial tendon injury with spring ligament injury, sinus tarsi abnormality, and plantar fasciitis on MR imaging. AJR Am J Roentgenol. 2001;176(5):1137-1143.
