Posterior tibialis tendon transfer via the circumtibial route: a cadaveric limb analysis

Abstract

Background: Studies have yet to determine the optimal height at which the posterior tibial tendon (PTT) can be re-routed and the tendon length discrepancy at different height levels in terms of PTT transfer via the circumtibial route. This cadaveric study was conducted to determine the optimal height of PTT subcutaneous transfer and to compare tendon length discrepancies at different heights.

Materials and methods: Twenty-five fresh normal cadaveric lower legs were used for measurements. PTT was exposed and then isolated. An incision along the calf was made to re-route PTT outside the fascia. The upper edge of the incision was classified as point "a." The distal tip of the tendon was classified as point "b." The midpoints of the intermediate cuneiform, the lateral cuneiform, and the cuboid were defined as points "c," "d," and "e," respectively. The lengths of "ab," "ac," "ad," and "ae" were measured and compared at different height levels above the distal tip of the medial malleolus. Angles α, β, and γ between the tendon outside the fascia connecting to different bones and the tendon inside the fascia were also measured as tendons were transferred at different bones and different height levels. Experimental data were collected and analyzed.

Results: At a height of ≥5 cm, all of the PTTs could reach the midpoints of the three bones. The lengths of ac, ad, and ae were significantly less than the length of ab (p < 0.05). At a height of 10 cm, angles α, β, and γ were 177° ± 2.1°, 170° ± 3.1°, and 164° ± 3.7°, respectively. These angles were not significantly different from those at a height of 11 cm (p >0.05).

Conclusions: PTT transfer via the subcutaneous route could achieve an adequate length to be transferred to the intermediate cuneiform, the lateral cuneiform, and the cuboid from a height of 5 cm above the distal tip of the medial malleolus. A height of 10 cm could be optimal for PTT transfer in the three bones via the subcutaneous route.

Figure 1

Procedures used to expose and isolate the PTT. (A) With a 2-cm medial incision, the tendon was divided at its insertion to the navicular region, preserving as much length as possible. (B) The distal tip of the medial malleolus was confirmed with a small screw as a marker. (C) A second 2-cm long incision posterior to the medial region of the tibial crest was made along the fascia of the calf, where the upper edge was 3 cm proximal to the distal tip of the medial malleolus. (D) PTT was isolated and then re-routed.

Figure 2

An X-ray machine was used to determine the midpoints of the (A) intermediate cuneiform, (B) lateral cuneiform, and (C) cuboid.

Figure 3

Procedures used for measurement. (A) We classified the point of the upper edge of the second incision as point “a,” which can be changed according to different height levels for transfer. The distal tip of the tendon was classified as point “b.” The midpoints of the intermediate cuneiform, the lateral cuneiform, and the cuboid were defined as points “c,” “d,” and “e,” respectively. PTT was re-routed to reach the midpoints of the (A) intermediate cuneiform, (B) the lateral cuneiform, and (C) the cuboid by applying tension to some extent. During this procedure, the limb was kept in a neutral position.