TENDON-LENGTHENING IN CONTINUITY: DESCRIPTION OF A NEW METHOD OF HELICAL CUTTING

Abstract

Introduction: Additional tendon length is occasionally needed for the surgical reattachment of retracted tendons and for lengthening of intact but contracted tendons. To achieve additional length with the known techniques such as the z-plasty, the tendon needs to be cut through entirely and loses its continuity. The purpose of this study was to develop a new method for tendon lengthening, where continuity is preserved and a high amount of additional length is achievable.

Methods: Calf Achilles tendons (n=35) were harvested immediately after slaughter and 5 tendons were assigned to groups I to VII. Angles of 60° (group I and IV), 45° (group II and V) and 30° (group III and VI) were cut. In group IV to VI mattress suture stitches were made along the cutting lines. The mean length increase of the helical cuts was used to define the intended length of group VII, where a z-plasty was performed. Maximal tensile force (Fmax) and additional achieved lengthening at Fmax (LFmax) were determined for each tendon using a materials testing machine. Data were statistically analyzed using ANOVA for inter-group differences and Spearman-correlation for cut angle to additional length relations at a significance level of p< 0.05.

Results: Tendons which were cut helically and sutured (group IV to VI) could achieve higher Fmax than the helically cut tendons without suturing (group I to III). The length and tensile force could be partially controlled by choice of the angle of the helical cut; In the groups for which the cut tendons were not sutured, LFmax was negatively correlated to the cut angle (r=−0.66, p=0.010) and positively correlated to the Fmax (r=0.72, p=0.003). If the helical cut tendons were sutured, there was no correlation of LFmax and cut angle (r=−0.01, p=0.96), but strong positive correlation of Fmax and cut angle (r=0.89, p< 0.0001). Helical cut tendon could achieve higher amount of additional length and tensile strength than tendons lengthened using z-plasty; in group VII, a LFmax of 72%±10% was achieved by a Fmax of 70N±15N. Other than in groups III and IV, where the cut angle was 30°, resulting in 179%±80% and 113%±10%, respectively, significant higher tensile force capacities (from a minimum of 80N±54N in group II to maximally 222N±62N in group IV) was achieved.

Discussion: Helical cutting of tendons allows lengthening tendons to an amount not possible with conventional methods. The lengthened coil-shaped tendon remains in continuity and has the potential to withstand considerable loads also without additional suture reinforcement. The behavior of the helical cut tendon in vivo is not known. However, the preservation of continuity might be favorable not only in regard to high tensile forces but also to healing.