Title: Superficial Versus Deep Transfer of the Posterior Tibialis Tendon
Authors: D’Astous JL, MacWilliams BA, Kim SJ, Bachus KN
Source: Journal of Pediatric Orthopedics 2005; 25(2): 245-247
PODIATRIC RELEVANCE:
Patients that suffer from a foot drop commonly have a posterior tibialis tendon transfer to the dorsum of the foot in order to augment weakened ankle dorsiflexors. The tendon can be passed both superficial and deep to the extensor retinaculum. This study compares the biomechanics of the two procedures.
METHODS:
Seven fresh-frozen cadaveric specimens were utilized in this study with a mean age of 48 years (range 41-56). Prior to testing, the specimens were thawed to room temperature (20 degrees) and the surgical procedures performed. The tendon was passed through the interosseous membrane, over or under the extensor retinaculum and attached by tying the suture to the head of a 3.5mm cortical screw that was inserted into the second cuneiform. To measure the rotation of the foot relative to the tibia, an optoelectronic motion measurement system (OptoTrak Model 3020, Northern Digital, Waterloo, Ontario, Canada) was used.
For each specimen, the two methods of routing the posterior tibialis tendon were tested utilizing a randomized order. After testing one condition, the anchoring suture was freed from the screw and the tendon was rerouted according to the remaining condition, and then reattached to the screw. All tendon forces were normalized to the foot weight. To compare the normalized force values, data were interpolated at each 0.5 foot weight from 0 to 3.5 times foot weight.
RESULTS:
The two transfer procedures were compared and the posterior tibialis tendon transfer superficial to the extensor retinaculum was found to be more biomechanically efficient. A two-tailed paired t test was used to compare the procedures and P<0.05 was considered significant. The motion pattern of the foot dorsiflexion was found to be similar with each method when compared. With this similarity in the two procedures, significantly greater dorsiflexion power (P<0.05) was achieved at load levels higher than 0.5 foot weight.
COMMENTS:
The results of this study should allow us to make more informed decisions when rerouting the posterior tibialis tendon. There often is the thought that by routing the tendon superficial to the extensor retinaculum there will be bowing of the tendon at the ankle level. This is a possibility with spasticity or a strong tendon, but often this will not be a problem as the tendon will lose one grade in muscle strength with a transfer. As a result of this decrease in strength, this article points out the benefits of transferring the posterior tibialis tendon so as to allow a more biomechanically efficient transfer in the surgical treatment of a drop foot.
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Disclaimer:
Scientific Abstract Monthly postings are submitted by podiatric surgical residents. The ideas presented are not the opinions of the American College of Foot and Ankle Surgeons (ACFAS), nor are they presented as facts. ACFAS presents this information without any warranty of any kind, expressed or implied, and is not liable for its accuracy nor for any loss or damage caused by the user's reliance on information obtained in these areas.