VOL. 94-B, No. 5, MAY 2012 663  LOWER LIMB: RESEARCH Biomechanical comparison of four methods of repair of the Achilles tendon A LABORATORY STUDY WITH BOVINE TENDONS C. Ortiz, E. Wagner, P. Mocoçain, G. Labarca, A. Keller, A. Del Buono, N. Maffulli From Clinica Alemana de Santiago, Santiago, Chile and Centre for Sport and Exercise Medicine, London, United Kingdom  C. Ortiz, MD, Foot and Ankle Surgeon, Chief of Foot and Ankle Surgery  E. Wagner, MD, Foot and Ankle Surgeon  P. Mocoçain, MD, Resident in Orthopedic Surgery  G. Labarca, Medical Student  A. Keller, MD, Foot and Ankle Surgeon Clinica Alemana de Santiago, Orthopedics and Traumatology Department, 6th floor, Vitacura 5951, Santiago, Chile.  A. Del Buono, MD, Orthopaedic Surgeon Campus Biomedico, University of Rome, Department of Orthopaedic and Trauma Surgery, Via Álvaro del Portillo 21, 00128 Rome, Italy.  N. Maffulli, MD, MS, PhD, FRCS(Orth), Professor of Sports and Exercise Medicine, Consultant Trauma and Orthopaedic Surgeon Centre for Sports and Exercise Medicine, Barts and The London School of Medicine and Dentistry, Mile End Hospital, 275 Bancroft Road, London E1 4DG, UK. Correspondence should be sent to Professor N. Maffulli; e-mail: n.maffulli@qmul.ac.uk ©2012 British Editorial Society of Bone and Joint Surgery doi:10.1302/0301-620X.94B5. 27642 $2.00 J Bone Joint Surg Br 2012;94-B:663–7. Received 25 May 2011; Accepted after revision 31 January 2012 We tested four types of surgical repair for load to failure and distraction in a bovine model of Achilles tendon repair. A total of 20 fresh bovine Achilles tendons were divided transversely 4 cm proximal to the calcaneal insertion and randomly repaired using the Dresden technique, a Krackow suture, a triple-strand Dresden technique or a modified oblique Dresden technique, all using a Fiberwire suture. Each tendon was loaded to failure. The force applied when a 5 mm gap was formed, peak load to failure, and mechanism of failure were recorded. The resistance to distraction was significantly greater for the triple technique (mean 246.1 N (205 to 309) to initial gapping) than for the Dresden (mean 180 N (152 to 208); p = 0.012) and the Krackow repairs (mean 101 N (78 to 112; p < 0.001). Peak load to failure was significantly greater for the triple-strand repair (mean 675 N (453 to 749)) than for the Dresden (mean 327.8 N (238 to 406); p < 0.001), Krackow (mean 223.6 N (210 to 252); p < 0.001) and oblique repairs (mean 437.2 N (372 to 526); p < 0.001). Failure of the tendon was the mechanism of failure for all specimens except for the tendons sutured using the Krackow technique, where the failure occurred at the knot. The triple-strand technique significantly increased the tensile strength (p = 0.0001) and gap resistance (p = 0.01) of bovine tendon repairs, and might have advantages in human application for accelerated post-operative rehabilitation. The ideal form of treatment of a rupture of the Achilles tendon remains controversial. 1-5 Some authors recommend surgery for young and physically active patients, 6,7 but although open and minimally invasive techniques have been used, few studies have examined the biome- chanical characteristics of different configura- tions of sutures and the quality of repair using these techniques. 8-12 Early weight-bearing mobilisation and strengthening exercises are increasingly being used to accelerate recovery and time of return to sport. 13-17 Therefore, strong repairs should resist distraction, allowing early rehabilitation and promoting tendon healing. 18 We assessed load to failure and gapping of different suture configurations in order to test the null hypothesis that the modified percuta- neous technique of Amlang et al 19 does not provide greater tensile strength. Materials and Methods The Achilles tendons were obtained from 20 cows aged two years old, < 24 hours after slaughter, and immediately frozen at -20°C. The tendons, which had been harvested up to the myotendinous junction, were defrosted and maintained in normal saline solution for ten minutes. We measured the width and thick- ness of all specimens at the narrowest portion using a vernier caliper. 20 All the tendons were transected cleanly using a knife at 4 cm proxi- mal to the calcaneal insertion and all were repaired using a number 2 Fiberwire suture (Arthrex, Naples, Florida). Five tendons were repaired using the Dresden technique described previously by Amlang et al 19 (group 1), five using the Krackow repair 21 (group 2), five using the modified triple-strand Dresden technique (triple technique, group 3), and five with the modified oblique Dresden technique (oblique technique, group 4) (Fig. 1). Briefly, the Amlang technique uses a 2 cm long incision, 2 cm proximal to the rupture. The interval between the paratenon and the superficial fascia is identified, and through this interval two Dresdner instruments are intro- duced from proximal to distal, until the most distal aspect of the tendon is reached. Two sutures are passed through the distal end of the tendon, 1 cm apart, piercing the skin and pass- ing through the Dresdner instrument on one side and on the opposite side of the tendon. Retrieving the instrument from the incision will bring the sutures through the interval described above, between the paratenon and