How do different anterior tibial tendon transfer techniques influence forefoot and hindfoot motion?

Abstract

Background: Idiopathic clubfoot correction is commonly performed using the Ponseti method and is widely reported to provide reliable results. However, a relapsed deformity may occur and often is treated in children older than 2.5 years with repeat casting, followed by an anterior tibial tendon transfer. Several techniques have been described, including a whole tendon transfer using a two-incision technique or a three-incision technique, and a split transfer, but little is known regarding the biomechanical effects of these transfers on forefoot and hindfoot motion.

Questions/purpose: We used a cadaveric foot model to test the effects of three tibialis anterior tendon transfer techniques on forefoot positioning and production of hindfoot valgus.

Methods: Ten fresh-frozen cadaveric lower legs were used. We applied 150 N tension to the anterior tibial tendon, causing the ankle to dorsiflex. Three-dimensional motions of the first metatarsal, calcaneus, and talus relative to the tibia were measured in intact specimens, and then repeated after each of the three surgical techniques.

Results: Under maximum dorsiflexion, the intact specimens showed 6° (95% CI, 2.2°-9.4°) forefoot supination and less than 3° (95% CI, 0.4°-5.3°) hindfoot valgus motion. All three transfers provided increased forefoot pronation and hindfoot valgus motion compared with intact specimens: the three-incision whole transfer provided 38° (95% CI, 33°-43°; p < 0.01) forefoot pronation and 10° (95% CI, 8.5°-12°; p < 0.01) hindfoot valgus; the split transfer, 28° (95% CI, 24°-32°; p < 0.01) pronation, 9° (95% CI, 7.5°-11°; p < 0.01) valgus; and the two-incision transfer, 25° (95% CI, 20°-31°; p < 0.01) pronation, 6° (95% CI, 4.2°-7.8°; p < 0.01) valgus.

Conclusion: All three techniques may be useful and deliver varying degrees of increased forefoot pronation, with the three-incision whole transfer providing the most forefoot pronation. Changes in hindfoot motion were small.

Clinical relevance: Our study results show that the amount of forefoot pronation varied for different transfer methods. Supple dynamic forefoot supination may be treated with a whole transfer using a two-incision technique to avoid overcorrection, while a three-incision technique or a split transfer may be useful for more resistant feet. Confirmation of these findings awaits further clinical trials.

Fig. 1

A–D Orientation of the anterior tibialis tendon is shown for (A) an intact tendon; (B) with the two-incision anterior tibial tendon transfer, routed distally; (C) with the three-incision anterior tibial tendon transfer, routed proximally; and (D) with a split anterior tibial tendon transfer.

Fig. 2

The loading configuration shows the tibia secured to aluminum ring and attached to the load actuator (A); the pulley system attached to aluminum ring and stationary load frame (B; rope secured to the load cell (C); and motion tracker flags rigidly attached to the tibia, first metatarsal, calcaneus, and talus (D).

Fig. 3

For each of the three procedures, increase in pronation of the forefoot compared with pronation of the corresponding forefoot when measured intact is shown. The increases are shown for neutral dorsiflexion and maximum dorsiflexion. The bars represent the means, with error bars representing SD.

Fig. 4

For each of the three procedures, increase in valgus motion of the hindfoot compared with valgus motion of the corresponding hindfoot when measured intact is shown. The increases are shown for neutral dorsiflexion and maximum dorsiflexion. The bars represent the means, with error bars representing SD.