A Cadaveric Biomechanical Comparison of a Triple vs Quintuple Hemi-Section Achilles Tendon Lengthening

Abstract

Category: Ankle; Hindfoot Introduction/Purpose: Achilles tendon lengthening is commonly performed percutaneously, and the triple hemi-section step cut technique proposed by Hoke (1) is the method most commonly used. Despite its popularity, Hoke’s technique has been found to have limited lengthening capacity compared to the traditionally used open lengthening technique and therefore is only used in treating mild Achilles contracture. The senior author (MSM) developed a 5-step (quintuple) percutaneous hemi-section technique for lengthening, demonstrated to be a reliable procedure. The purpose of this cadaveric study was to evaluate the efficacy and safety of the quintuple compared to the triple cut technique. Methods: Four matched pairs of above-knee specimens were randomly assigned to the triple and the other to the quintuple hemi-section group. The Achilles insertion and musculotendinous junction were fully exposed to ensure that tenotomies were performed in a standardized manner. Lengthening was measured with optical markers at the most distal cut and 15 cm proximally. Measurements were performed on a universal testing machine (Instron) with the forefoot and femur fixed, and the knee in extension (Figure 1). The ankle was dorsiflexed under a constant load to 45N. Lengthening was performed 1 cm above the Achilles insertion following a medial-lateral-medial order at 3 cm intervals. The load was gradually increased until maximum dorsiflexion. The dorsiflexion angle, the tendon lengthening, the load needed to achieve the maximum ankle dorsiflexion and any rupture of the Achilles was recorded. Two-sample t-test was used for comparing continuous variables. Statistical analysis was performed with SAS 9.4. Results: There was no statistical difference between the dorsiflexion angle of the two groups under 45N load with an intact Achilles. The quintuple procedure achieved more lengthening than the triple group, reflected in both the maximum dorsiflexion angle under 45N and the lengthening of the tendon between the optical markers. The quintuple technique produced an average of 34.41mm of lengthening, and the triple cut 11.36mm under 45N force. The quintuple technique produced an average of 16.58 degrees of dorsiflexion compared with the triple cut of 10.53 degrees under 45N force. The load required to reach the maximum ankle dorsiflexion in the quintuple group was less (222.9N) than that in the triple group (334.6N). There were no ruptures of the Achilles in the quintuple group and 2 tendon ruptures in the triple technique. Conclusion: The quintuple lengthening is safe and has an increased capacity for tendon lengthening, an advantage over the triple hemi-section technique. Excessive force on the foot attempting to gain more dorsiflexion using the triple cut technique can be avoided with the quintuple procedure in all cases, particularly when adequate dorsiflexion cannot be obtained. References Hoke M. An operation for the correction of extremely relaxed flat feet. J Bone Joint Surg Am. 1931;13:773-783. Hoefnagels EM, Waites MD, Belkoff SM, Swierstra BA. Percutaneous Achilles tendon lengthening: a cadaver-based study of failure of the triple hemisection technique. Acta Orthop. 2007 Dec;(6):808-12