Tendon transfer to unossified bone in a porcine model: Potential implications for early tibialis anterior tendon transfers in children with clubfeet

Abstract

PurposeTibialis anterior tendon transfers (TATT) are commonly performed in young children following Ponseti casting for clubfeet. The classic TATT involves advancing the tendon through a hole drilled in the ossified cuneiform. The aim of this study was to determine if tendons transferred through unossified bones have untoward effects on subsequent bone development.MethodTwenty-five piglets underwent one of five surgical procedures. An 18-gauge needle was then used to place a tunnel through the bony or cartilaginous portion of the calcaneus (through direct visualization) and isolated slips of the flexor digitorum superficialis (FDS) were placed through the tunnels, as determined by surgical procedure. Radiographic and/or histologic evaluations of the calcaneal apophyses were then performed. A discrete (1–4) and dichotomous “Normal” or “Abnormal” scoring system was developed and its reliability assessed to grade the appearance of the calcanei. Calcaneal appearances following the surgical procedures were then compared with controls. The average load to failure of a subset of transferred tendons was then compared using an MTS machine.ResultsThe proposed apophyseal grading system (1–4) demonstrated an intraclass correlational coefficient (ICC) for consistency of 0.92 [95% confidence interval (CI) 0.88 < ICC < 0.95] and ICC for agreement of 0.91 (95% CI 0.86 < ICC < 0.95), indicating strong agreement and consistency. Similarly, Fleiss’ kappa for the 1–4 scoring system was found to be 0.67, indicating substantial agreement between reviewers. When the 1–4 system was translated into the dichotomous scheme “Normal” and “Abnormal”, the kappa value increased to 0.94, indicating strong agreement. Forty-six apophyses (13 control and 33 operative) were assessed using this scoring scheme. Apophyseal transfers were significantly more abnormal than controls (p < 0.0001), while no difference in abnormalities was found following tunnel placement alone (p = 1). Mechanical testing of the tendons transferred to bone or through the cartilaginous apophysis demonstrated no significant differences (p = 0.2).ConclusionTendon transfers through unossified bones altered subsequent bone development.SignificanceWhile the long-term consequence of these structural changes is unknown, these findings suggest that tendon transfers through unossified bones should be avoided and alternative methods of tendon fixation explored.Electronic supplementary materialThe online version of this article (doi:10.1007/s11832-016-0799-4) contains supplementary material, which is available to authorized users.

Histological and radiographic evaluation of three common tendon transfer techniques in an un-ossified bone porcine model: Implications for early anterior tibialis tendon transfers in children with clubfeet

“…Apophyseal tunnel and suture techniques were found to alter subsequent apophyseal ossification to varying degress, with less disruption of ossification in the tunnel cohort than would have been expected from our previous report. 12 This could be the result of examining the bisected calcaneii (including both histological and radiographic imaging of the samples) in the previous study and imaging of intact calcaneii in the current study. Despite assessing histological healing in the current study, we did not assess the mechanical properties of the transfers which will be important clinically.…”

“…Nine newborn (< 48 hours of age) mixed breed piglets 12 were anesthetized, placed in a prone position and the lower extremities prepped and draped for surgery. A midline posterior incision was performed extending proximal to the os calcis distal towards the midfoot.…”

“…A semi-quantitative grading system, 12 was used to grade healing at the enthesis. This is an aggregated scoring system with values ranging from 0 (poor) to 15 (excellent) enthesis healing ( Table 1 ).…”

“…The radiographic images were deidentified and provided to five independent readers who graded the apophyseal appearance using a modified one to four grading system previously described 12 ( Fig. 2 ; supplementary material ).…”

“…To answer these questions, we utilized a previously described porcine model 12 to compare the histological and radiographic effects of tendons transferred using metallic suture anchors (new technique), suture fixation (similar to that described for vertical talus) and the classic bone tunnel (as described for clubfoot) to both ossified and unossified bone. Our null hypotheses was that no differences in histological healing or radiographic appearances will be found between fixation techniques.…”