Study design
This study was designed as a single group, interventional feasibility study. The reporting of the study follows the CONSORT 2010 statement, extension to randomised pilot and feasibility trials (20) (Additional file 1). Results will be used in a subsequent randomised controlled trial (RCT), but since the main focus is the patient’s willingness and adherence to the exercise program, there were no comparator used in this feasibility study. The same experienced physiotherapist performed the intervention, monitored the tendon healing process, and collected follow-up data. No blinding was applied for the follow-up.
The study complied with the principles of Helsinki Declaration. It was approved by the Regional Committee on Health Research Ethics in North Denmark Region (N-20180072) and the protocol was prospectively registered in Clinical Trials (NCT04121377).
Participants
Inclusion criteria were patients with acute total Achilles tendon rupture treated non-surgically, with diagnosis established and treatment initiated within 3 days of the injury, aged between 18 and 65 years, able to speak and understand Danish, and able and willing to participate in the intervention. We excluded patients with insertional Achilles tendon rupture on calcaneus, high rupture in the musculo-tendinous junction of the triceps surae, previous Achilles tendon rupture or other conditions in either leg causing lower leg disability (pain, deficits in strength or range of movement), treatment with fluroquinolones or corticosteroids within the last 6 months, diabetes and severe medical illness (American Society of Anesthesiologists (ASA) score higher than or equal to 3) (21).
Participants were recruited from the Orthopaedic Outpatient Clinic at Aalborg University Hospital Denmark from Oct 2019 to January 2020. The primary investigator received referrals from the Emergency Department and contacted potentially eligible participants to schedule an information meeting within a week from the start of treatment. A trial informational document was emailed at least 24 hours before the meeting, where the informed consent was obtained.
Intervention
Patient and clinician involvement
We developed the intervention using the findings from the systematic review, alongside inspiration from informal focus group meetings. To ensure feasibility of the exercise program we invited patients to discuss facilitators and barriers for performing exercises in the early rehabilitation from their own perspective. Physiotherapists, orthopaedic surgeons, and a rheumatologist, all with experience in treating patients with Achilles tendon ruptures, were invited to discuss the literature, clinical relevance, and rationale for an early progressive resistance exercise program.
Development of the intervention
The intervention description followed the Template for Intervention Description and Replication (TIDieR)(22) and The Consensus on Exercise Reporting Template (CERT)(23). The exercises were designed to facilitate muscle activity in the early phase of the immobilisation period and subsequently progress the load to strengthen the muscles within precautions for the healing tendon (Table 1) (Extended version in Additional file 2). The magnitude of this exercise program was designed to leave room for patients with higher physical level or motivation, but the success rate should reflect the reality of compliance for most patients. The strength exercises aimed at loading the Achilles tendon-muscle complex and was supplied as an add-on to the standard program which contained more general exercises with controlled range of motion and exercises for the whole leg.
Table 1
Schedule of exercises and immobilisation
Exercises
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Elastic 2
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Elastic 2
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Elastic 2
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|
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Elastic 1
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Heel-rise
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Heel-rise
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Heel-rise
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Heel-rise
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|
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Heel-rise
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Heel-rise
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Heel-rise
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Iso stand
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Iso stand
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Iso stand
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Iso stand
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|
|
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Iso
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Iso
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Iso
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Elastic 1
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Elastic 1
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Elastic 1
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Elastic 1
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|
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Iso
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ROM
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ROM
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ROM
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ROM
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ROM
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ROM
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ROM
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Weeks
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1
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2
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3
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4
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5
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6
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7
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8
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9
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Immobilising
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Walker, 3 wedges
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Walker, 2 wedges
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Walker, 1 wedge
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Walker, no wedge
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Weightbearing
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Non WB
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P- WB, 2 crutches
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P-WB, 1–2 crutches
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Full WB, crutches for long walk
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Blue: Standard exercise program. Orange: Add-on exercises. Iso: Isometric contractions. ROM: Controlled range of motion. Heel-rise: Seated heel-rise. Elastic 1: Light load(yellow-red). Elastic 2: Progression of load to stronger elastic band (red, blue, green). WB: Weight bearing. P-WB: Partial weight bearing.
The new program consisted of three exercises (Fig. 1) with earlier starting time and gradually more progression to exercises with higher loads than the standard program: a) isometric ankle plantar flexion in a closed walking boot, b) seated heel-rise in open walking boot with wedges according to week number and c) resistance exercises with elastic band. Exercise program and dosage of the exercises are described in additional files (Additional file 3, Additional file 4).
One week after diagnosis, the intervention started with a daily home program and weekly sessions with a physiotherapist to assess the acceptability of the program and to monitor the healing of the Achilles tendon. To protect the tendon while doing range of motion of the foot, dorsiflexion was restricted beyond neutral (0 degrees of dorsiflexion). The load of the strength exercises progressed from isometric contraction without external load to strength resistance exercises with 10–20 RM (repetitive maximum). Each exercise could progress with added weight or stronger elastic band. The Borg CR10 scale was used to guide the participant to progress or regress the load in each exercise (24). The recommended level being “easy” to “hard” (2–5/10). It was emphasized that the exercises should not cause sudden or severe pain in the tendon, but muscle soreness could be expected. To avoid compensatory activity from m. flexor hallucis longus, instructions were to extend the first toe before plantar flexing the ankle. Ultrasound examination of the leg muscle contractions were planned to confirm facilitation of the triceps surae muscles.
Progression was performed individually and with a gradual progression. From 2 to 10% is generally accepted as a reasonable progression in resistance training and for exercise therapy for painful tendinopathy and even though specific research on Achilles tendon rupture is lacking is seems a safe precaution to prescribe in the early rehabilitation of Achilles tendon rupture (25).
The intervention took place at the Physiotherapy and Occupational Therapy Department at Aalborg University Hospital. One experienced physiotherapist supervised in all sessions.
Outcomes
The focus of this study was to test the feasibility of the exercise intervention by setting values for fulfilment of a range of outcomes and process variables deemed of importance to patients and safety. There were two primary outcomes of interest, namely the patient acceptability (willingness) of the intervention and the adherence to the intervention. Follow-up occurred after 9 and 13 weeks.
The exercise program was considered feasible if:
A) The acceptability of the exercise program was 80%. Defined as: ≥13/16 participants rating the acceptability of the intervention as “acceptable” on a 7-point Likert scale (26).
B) The adherence to the exercise program was 50%. Defined as: ≥13/16 participants performing ≥ 50% of the home exercises until the end of week 9.
Patient acceptability was not a measure of whether symptoms had improved to normal physical function or any other satisfactory level at the specific time. Rather, acceptability was defined by how well the intervention matched their expectations of an exercise program in this early phase and how they tolerated performing the exercises. The intervention program was categorised as “Unacceptable” if rated as the three lower scores (very unacceptable, unacceptable, slightly unacceptable) and categorised as “Acceptable” if rated as the four higher scores (“neither acceptable nor unacceptable” to “very acceptable”)
The participants registered the number of training sessions and exercises they performed each day in a training journal. Compliance was measured as the mean number of exercise sessions performed. The timeframe was from the day they started the exercises to the end of week 9.
Clinical relevance: the exercise program was based on home exercises that should be easy to understand and perform without the need for physiotherapist supervision, as this will be both time consuming and incur higher costs. Total (100%) compliance to the exercise program cannot be expected. Prior studies have found exercise compliance to be very poor, with values as low as 45% or less for chronic diseases (27–29). The magnitude of this exercise program leaves room for individuals with higher physical level or motivation, but the success rate reflects the reality of compliance for most individuals.
Secondary outcomes
Self-reported outcomes. The Achilles Tendon total Rupture Score (ATRS) is the most common used self-reported outcome measure and it contains 10 questions about physical performance in a scale from zero to ten with a maximum total score of 100 (30). International Physical Activity Questionnaire (IPAQ) short form Danish version which consists of 7 items concerning physical activity during the past week estimating the total weekly physical activity measured in MET-minutes per week (metabolic equivalent of task) (31).
The Tampa scale of Kinesiophobia (TSK) 17-item version is used as a measure for fear of movement. As it was developed for chronic pain, we subsequently asked the participants to rate the appropriateness of the score on a Likert scale (32).
Objective outcomes. The Achilles tendon resting angle (ATRA) was measured with a standard goniometer (33). Ultrasound imaging was used to measure Achilles tendon length following the Copenhagen Achilles Length Measurement (CALM) (34) and Achilles tendon cross-sectional area measured at the midpoint of the rupture site (35). Muscle endurance was measured in the seated position with the MuscleLab measurement system (Ergotest Technology, Oslo, Norway) with an external weight equal to 50% of bodyweight (36). Ability to perform a single standing heel-rise on the injured leg with a minimum height of 2 cm (32).
Follow-up visits
Follow-up visits were scheduled at 9- and 13 weeks. At the 9-week visit in the outpatient clinic treatment recommendations for walking changed, and the participants transitioned from wearing a walking boot to protective weightbearing in shoes with 1 cm heel inserts for 3 months. In the first two weeks it was advised to use crutches. ATRS and IPAQ were not measured at the 9-week follow-up due to the physical activity restrictions. Muscle endurance was not measured at the 9-week follow-up for safety reasons to protect the tendon from overuse at the time of transition.
Adverse events
At the scheduled two weeks visit to the outpatient clinic all participants were clinically assessed. The decision for progression of the treatment in both treatment groups followed the common patient pathway for Achilles tendon rupture based on a combination of clinical assessments of the tendon structure and risk assessment (no palpable gap at the rupture site, the foot positioned in equinus, some tenderness at the tendon allowed but no pain, some swelling of the surrounding tissue allowed but no large edema)
Serious and minor adverse events were registered in a pre-defined list based on Common Terminology Criteria for Adverse Events(37) and the participants were asked open questions at each session. Each exercise session began with assessing symptoms, adverse events, and the progression of the tendon healing. Serious adverse events were re-rupture, non-union of the tendon or deep vein thrombosis (DVT). Muscle soreness or mild pain was considered inevitable and normal when initiating exercises after a period of immobilisation.
A safety committee assessed and graded symptoms that were not within normal injury- or exercise reactions. Adverse events was graded 1 to 5 according to the Common Terminology Criteria for Adverse Events v4.03 (37). In case of serious adverse events, it would be decided whether to delay the proceeding of the intervention or withdraw the participant from the study.
Sample size considerations and Statistical methods
Since this was a feasibility study and we primarily were interested in estimates of feasibility and acceptability, no formal sample size calculation was performed. Estimated number of participants were 16, which seemed appropriate to evaluate the feasibility outcomes(38). The overall incidence of Achilles tendon ruptures presenting at our hospital are approximately 80 per year.
Acceptability are presented as median and quartiles with criteria for fulfilment defined as 80% of participants scoring “acceptable”. Adherence to the intervention was defined by number of fulfilled sessions and percentage with criteria for fulfilment of 50% of participants performing ≥ 50% of the exercises. Descriptive information was registered at baseline: Age, sex, height, weight, IPAQ, ATRS. Baseline and follow-up data is presented as means with standard deviations. Reasons for exclusion or withdrawal are summarised. Safety is presented as number and percentage of participants reporting adverse events divided in major and minor events. Time from treatment start to beginning exercises is reported as mean days and range. The intention-to-treat principle was used for analyses and all participants were included in the analyses regardless of the acceptability or compliance to the intervention. Data were entered in REDCap hosted at Aalborg University Hospital (39). If the feasibility definition for acceptability and adherence are not met, we will not pursue a definitive randomised trial.