Healing of Human Achilles Tendon Rupture

Healing of Human Achilles Tendon Rupture: Loading Pattern After Surgical Repair to Achieve Optimal Mechanical Properties and Clinical Outcome

The overall aim of this project is to investigate the healing processes of human tendon after suturing a ruptured Achilles tendon, and more specifically to determine the optimal loading pattern of the tendon during the rehabilitation period to ensure complete and good recovery of tendon structure and function. The investigators hypothesize that restricting early weight bearing and only allowing for passive stretching in the early phase of tendon healing will ensure better tissue regeneration and thereby prevent chronic tendon elongation and improve tendon tissue recovery and the clinical outcome.

Surgical repair of Achilles tendon ruptures is known to significantly reduce the risk of re-rupture and to accelerate the time to return to activity compared with non-surgical treatments (1, 2). Although sutured, Achilles tendon rupture requires an extended rehabilitation period following surgery to function normally again. However, the currently available information on this post-operative treatment suggest that the currently available rehabilitation guidelines, which includes early weight bearing, does not accomplish optimal recovery of muscle-tendon function. It has been demonstrated that reduced capacity to perform heel-rises, diminished range of motion of the ankle joint, and reduced calf muscle mass is correlated with a delay in return to activity, and all of these factors could be related to elongation of the healing tendon (3). Importantly, it appears that preventing tendon elongation during rehabilitation improves the clinical outcome, but the actual mechanism for the elongation and thus how to prevent it remains unknown (4). With newly developed techniques in our laboratory we will determine the mechanical properties of human whole Achilles tendon, in vivo, which makes it possible to explore how tendons respond to the regimes following a suture repair and rehabilitation regime. In contrast to the current rehabilitation regime after tendon surgery, which includes early high loading (weight bearing) already in the first weeks after surgery, we hypothesize that avoiding early weight bearing but allowing for early passive ankle joint range of motion (tissue strain with minimal loading) will prevent chronic tendon elongation, increase tendon stiffness, increase calf strength and muscle volume/thickness, and thus improve the long-term clinical outcome after tendon rupture in humans. Patients with acute Achilles tendon ruptures will undergo a standardized suture repair (a.m. Kessler) using resorbable suture (Vicryl size 1) at Bispebjerg Hospital and be placed in a brace that inhibits ankle joint movement. During surgery, patients will get four tantalum beads with a diameter of 1.0 mm implanted with a venflon needle in the proximal and the distal stub of the tendon. Thereafter they will be randomized to three post-operative treatment regimes: Control, range of motion or immobilized From the currently available data (4, 5, 6) it is suggested that the brace is worn for 6 weeks after surgery in all three groups of the present experiment. The control group will be allowed partial weight-bearing from day 0 and full weight-bearing from week 4, toe rises after 16 weeks, jogging after 24 weeks and return to sports 34 weeks after. The two delayed weight-bearing groups (range motion group and immobilized group) will be restricted completely from weight-bearing initially (6 weeks), allowed partial weight-bearing after 6 weeks and full weight-bearing after 8 weeks.

This constitutes the currently accepted regime and is therefore consider the control group (CTRL) with early range of motion and early weight bearing. The control group was allowed to have partial weight-bearing from day 0 and full weight-bearing from week 4. Furthermore, they were instructed in tendon strain exercise identical with the range of motion group.

Early range of motion and delayed weight bearing (ROM). The range of motion group was restricted completely from weight-bearing until week 6, allowed partial weight-bearing after 6 weeks and full weight-bearing after 8 weeks. In addition to this, the patients were instructed to perform tendon strain exercises, five times a day, from week 2. The exercises were performed by removing the foot from the brace and then perform light dorsal ankle movement, 25 repetitions/time, when sitting on a table.

Delayed weight-bearing or range of motion (IMMOB). The immobilization group was restricted completely from weight-bearing until week 6, allowed partial weight-bearing after 6 weeks and full weight-bearing after 8 weeks.

No weight-bearing during the first six weeks, and partial weight-bearing during the two following weeks

Tendon elongation will be evaluated using x-ray and measurements of the distance between tantalum beads

The number of heel-rises and the heel-rise height will be used for calculation of the heel-rise work.

Tendon stiffness will be evaluated during a voluntary plantar flexion contraction where force and tendon elongation is measured using a force transducer and x-ray, respectively. Tendon size will be evaluated by MRI. Elastic modulus will be calculated based on stiffness and size of the tendon.

Plantar flexion muscle strength will be measured during a maximal voluntary isometric contraction with ankle flexion at -10, 0˚ of dorsiflexion

Inclusion Criteria: Complete Achilles tendon rupture placed in the mid-substance of the Achilles tendon Presented within 14 days from injury Exclusion Criteria: re-rupture other injuries affecting their lower limb functions systemic diseases influencing tendon healing immunosuppressive treatment including systemic corticosteroid treatment inability to follow rehabilitation or follow-ups.

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