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Cochrane Database of Systematic Reviews Protocol - Intervention

Exercise, orthoses and splinting for treating Achilles tendinopathy

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Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the effects (benefits and harms) of exercise, orthoses and splinting for treating Achilles tendinopathy.

We will compare each of the three intervention categories (exercise, orthoses, splinting) with no intervention, a placebo intervention or advice to rest; and with each other. We will also compare different types, applications and modes of delivery of interventions within the three intervention categories.

Background

The benefits of maintaining an active lifestyle have been well documented and daily exercise can reduce the risk of serious health problems such as obesity and cardiovascular disease (Van Dam 2008). Exercise is, however, associated with a risk of injury, particularly to the musculoskeletal system. Tendons are an integral part of the musculoskeletal system and are subjected to varying forces during movement and exercise. The Achilles tendon is the strongest and thickest tendon in the body and is located at the back of the lower leg where it connects the gastrocnemius and soleus (calf muscles) to the heel bone.

Description of the condition

The Achilles tendon is subjected to large compressive and tensile forces, particularly during running. These forces can approach six to eight times the body weight, with further increases due to abnormal lower limb biomechanics (Pierre‐Jerome 2010). Achilles tendinopathy is typically caused by excessive tendon loading and is classified as an overuse injury. For many years, the pathological process of this condition was described as an inflammatory process, which favoured the term 'tendinitis'. The clinical consensus then progressed to describe the condition as a degenerative pathology that was non‐inflammatory in nature and thus the term 'tendinopathy' became the predominant term. However, contemporary literature now recognises that the degenerative model may be too simplistic and that there may be an inflammatory response associated with chronic tendinopathy (Rees 2013).

Achilles tendinopathy can affect athletes, recreational exercisers and even inactive people (Alfredson 2007). The incidence of Achilles tendinopathy in primary care has been reported as 2.35/1000 adults (aged 21 to 60 years) (De Jonge 2011). There is an increased prevalence in older groups (peaking in incidence in those aged 41 to 60 years) and in females (De Jonge 2011). Recent studies have also identified obesity (Holmes 2006; Gaida 2008), familial hypercholesterolemia (high levels of cholesterol in the blood) (Beeharry 2006) and family history as important risk factors (Kraemer 2012). Other proposed risk factors for the injury include poor vascularity, being female, endocrine and metabolic disorders (Khan 1998). Achilles tendinopathy is also associated with inflammatory and autoimmune diseases (such as rheumatoid arthritis), genetically‐determined collagen abnormalities, infectious diseases, tumours and neurological conditions (Ames 2008).

Achilles tendinopathy is characterised by progressive pain and decreased function. Presentation and prognosis can vary. For instance, De Jonge 2011 found the mean duration of symptoms in the general population to be 11.3 weeks (range 1 to 52 weeks). In the early stages, pain may be limited to the start and end of exercise activity. However, as the disorder progresses, pain becomes persistent and can interfere with everyday activities (Rompe 2008). Tendinopathy is frequently described as 'acute' at the stage of onset of the disorder or 'chronic' when symptoms are established and have been present for some period of time, generally more than four weeks. The underlying cause of pain is not clear; however, neurovascular (nerves and blood vessel) ingrowths into the tendon (neovascularisation) are thought to play a role (Alfredson 2007). Diagnosis is based primarily on clinical history and examination, but is sometimes supplemented with imaging. Ultrasonography may show hypoechoic areas (which appear relatively dark because they are less reflective) and there may be increased signal intensity during magnetic resonance imaging (Alfredson 2007). Nomenclature can vary but the disorder is generally classified as either 'mid‐portion' or 'insertional' tendinopathy. Mid‐portion (or mid‐substance) tendinopathy is characterised by pain typically 2 cm to 7 cm from the tendon's insertion into the heel bone and is accompanied by either diffuse or local swelling. Insertional tendinopathy is defined by pain and localised swelling where the Achilles tendon attaches to the heel bone and is frequently associated with calcification and 'bony spurs', which may be palpable at this site (Van Dijk 2011).

Traditional management of this injury was aimed at reducing inflammation and drug therapy was the treatment of choice. However, better understanding of the condition has influenced treatment approaches with a strong bias towards the use of exercise and alteration of intrinsic risk factors such as abnormal lower limb biomechanics with the use of splinting/orthoses.

Although there is a general lack of data on the long‐term prognosis of Achilles tendinopathy, a study presenting an eight‐year follow‐up showed that 94% of patients initially reporting with acute or subchronic symptoms were asymptomatic and 84% had returned to full activity (Paavola 2000). Achilles tendon ruptures have been increasingly reported in recent years (Aroen 2004); rupture is frequently preceded by tendinopathy and often necessitates surgery and extensive rehabilitation. Studies have shown that the degenerative process that defines tendinopathy takes place in the tendon as a precursor to rupture and that, while tendinopathy does not always lead to rupture, there is a clear association between tendinopathic and ruptured tendons. It is suggested that the histopathological changes in tendons with tendinopathy are less advanced than those in a ruptured tendon and this would support the emphasis on early conservative intervention in tendinopathy to avoid rupture (Tallon 2001).

Description of the intervention

Exercise therapy, splinting and orthoses are amongst the most commonly used conservative methods for treating Achilles tendinopathy.  

Exercise interventions may be multifactorial and can include: aerobic, strengthening, range of motion (flexibility), co‐ordination and proprioceptive exercises. The primary component of most exercise interventions for Achilles tendinopathy is strengthening exercises: these may involve various forms of concentric, eccentric or isokinetic muscle contractions of the lower leg complex. Concentric contractions are those that cause the muscle tendon unit to shorten as it contracts; an example of this is rising up on toes (heel lift/calf raise exercise). Eccentric contraction occurs when the muscle tendon unit lengthens as it resists force; an example of this is a heel‐drop exercise performed standing on a step or bench. Isokinetic contraction involves a change in muscle length performed at a constant speed.

The volume, speed and technique of strengthening exercises can be altered to target specific muscle groups and different components of fitness. Traditionally, the most popular strengthening protocol employed in the management of Achilles tendinopathy has been progressive heavy‐load eccentric exercises. Much of this is based on Alfredson’s classic heel‐drop exercise programme (Alfredson 1998), in which people undertake 180 repetitions per day over a 12‐week period.

Flexibility is the ability of a joint or series of joints to move through a full range of motion (ROM). Flexibility exercise may comprise static stretches in which positions are held for a specific length of time. Alternatively, stretching exercise may be more dynamic in nature, with joints moved through larger ranges of movement in a steady and rhythmical fashion. Flexibility exercises used as part of a treatment programme for Achilles tendinopathy typically aim to optimise flexibility around the lower leg complex and increase ankle ROM.

Orthoses (also known as 'orthotic devices' or 'foot orthotics') may be used in isolation or in conjunction with an exercise intervention. An orthotic device is a specially fitted insert placed inside a shoe bed. They can be made from a variety of materials such as rigid plastics and carbon fibre as well as more flexible substances. Orthoses may be 'custom made' where they are specifically prescribed based on an individual’s foot shape, size and biomechanical abnormality. Generic or 'off the shelf' orthoses may be used as a cheaper alternative. Orthoses are generally placed within the user's shoe and maybe worn continuously or only during sporting activity.

Splinting is also frequently prescribed for treating Achilles tendinopathy. The primary aim of splinting is to rest the ankle joint (usually overnight) in a neutral or dorsiflexed position. Ankle splints can be made of a variety of materials, usually combining rigid plastics with elasticated strapping. 

How the intervention might work

Although most conservative interventions aim to reduce pain and improve function, the underpinning mechanisms of action are not clear. Exercise may improve strength and endurance in the muscle complex, with subsequent functional improvement. An additional concept is that eccentric training could have a direct mechanical effect on the tendon by stimulating remodelling and tissue repair. The mechanism of exercise in influencing the symptoms of Achilles tendinopathy is unclear but it is thought that eccentric exercise affects type 1 collagen production, thereby increasing tendon volume and tensile strength (Langberg 2007). Eccentric exercise may alter neovascularisation and accompanying nerve ingrowth associated with this condition (Alfredson 2007).

More specific reconditioning strengthening and endurance may be required in addition to eccentric calf drops (Allison 2009). Concentric loading such as a heel raise may be more suitable for developing muscle hypertrophy or contractile strength during rehabilitation. Similarly, stretching exercises may be more appropriate for improving ankle ROM or restoring the mechanical properties of the tendon after injury.

Abnormal lower limb biomechanics may increase the risk of excessive or unaccustomed loading of the Achilles tendon. People with extreme arch heights (high arched cavus foot or low arched planus foot) are often prescribed foot orthoses. A key rationale is that orthoses can correct abnormal foot and lower limb biomechanics. It is also speculated that orthoses can improve neuromuscular adaptations and muscular fatigue (Hirschmuller 2011).

For practical reasons, splints are usually provided for use at night as walking is often not possible while they are being worn. Night splints may reduce swelling and discomfort (Knobloch 2008), and may allow lengthening of the muscle and tendon, thus reducing strain on the tendon (Roos 2004).

Why it is important to do this review

Achilles tendinopathy is a common disorder, which is associated with protracted periods of morbidity, increased risk of tendon rupture and a reduction in physical activity and exercise. Currently there are no clear guidelines for clinicians and patients regarding appropriate interventions for effective management. Exercises, orthoses and splinting are all commonly prescribed interventions, but their effectiveness has not been established. All three interventions come in various forms and can be applied in a variety of ways. It is not clear what is the optimal frequency, intensity, time and specific type of exercise prescription, nor what is the most effective method and mode of delivery of exercise (e.g. exercise classes versus home‐based programmes). Similar uncertainty applies to the use and type of orthoses and splints. Therefore, there is a need for a review of the existing evidence from randomised trials testing these interventions to help inform their use and application in the management of Achilles tendinopathy.

Objectives

To assess the effects (benefits and harms) of exercise, orthoses and splinting for treating Achilles tendinopathy.

We will compare each of the three intervention categories (exercise, orthoses, splinting) with no intervention, a placebo intervention or advice to rest; and with each other. We will also compare different types, applications and modes of delivery of interventions within the three intervention categories.

Methods

Criteria for considering studies for this review

Types of studies

We will include randomised controlled trials and quasi‐randomised controlled clinical trials (which use a method of allocating participants to a treatment that is not strictly random, e.g. by date of birth, record number) evaluating either exercise, orthoses or splinting for treating Achilles tendinopathy. Cross‐over trials will be included. Studies that evaluate a combination of the interventions will also be included. Studies using within‐participant designs where contralateral limbs act as controls will be excluded.

Types of participants

We will include people with an investigator‐reported diagnosis of Achilles tendinopathy (also described as 'tendinitis' or 'tendinosis'). There will be no restrictions placed on recruitment setting, gender, age or activity levels of participants or duration of symptoms.

Types of interventions

We will include trials comparing any of the three categories of interventions (exercise, orthoses or splinting) with no intervention or placebo intervention or advice to rest; and trials comparing different types, applications and modes of delivery of interventions within the three intervention categories. Studies that include co‐interventions (such as drug therapies) will be allowed provided these are applied to all participants. These interventions can be applied in any setting and may be home‐based (unsupervised) or clinic‐based (supervised).

We propose to make the following comparisons.

  • Intervention versus control

    • Exercise therapy versus no exercise therapy, placebo therapy or advice to rest

    • Orthoses versus no orthoses, placebo therapy or advice to rest

    • Splints versus no splints, placebo therapy or advice to rest

  • Any one of the three intervention categories versus any one of the other two intervention categories.

    • Exercise versus orthoses

    • Exercise versus splinting

    • Orthoses versus splinting

  • Different types, applications and modes of delivery of exercise therapy.

    • Specific examples are:

      • Strengthening versus proprioceptive exercises

      • Strengthening versus ROM (stretching) exercise

      • Eccentric strengthening versus concentric strengthening

      • More intensive or longer duration exercise versus less intensive or shorter duration exercise

      • Clinic‐based (supervised) versus home‐based (unsupervised) exercise programme

  • Different types, applications and modes of delivery of orthoses

    • Specific examples of comparisons are:

      • Rigid orthoses versus semi‐rigid orthoses

      • Orthoses prescribed for all day use versus those prescribed for exercise only

      • Custom‐made versus generic orthoses

  • Different types, applications and modes of delivery of splinting

    • Specific examples of comparisons are:

      • Rigid splints versus semi‐rigid splints

      • Night splints versus day splints

      • Custom made versus generic splints

In general, when deciding on which is the experimental and which the control intervention in a comparison, we will make the control intervention the least active, intensive, innovative or sophisticated intervention of the two interventions. All types of exercise (aerobic, strengthening, ROM and proprioceptive) will be included and examined individually and in combination with each other. No restrictions will be placed on the type or material of orthoses or splinting devices. Duration and frequency of usage will be examined in orthotic and splint prescription.

Types of outcome measures

Primary outcomes

  • Functional assessment measures, preferably patient‐reported measures; e.g. the VISA‐A (Victoria Institute of Sport Assessment‐Achilles Questionnaire); a reliable and valid measure of severity and functional limitations associated with Achilles tendinopathy (Robinson 2001)

  • Assessment of pain; e.g. the visual analogue scale

  • Quality of life measure; e.g. the SF36, a valid and reliable battery of health status questions (Garratt 1993)

Secondary outcomes

  • Return to previous level of activity

  • Adverse effects (any increase in pain, specific decrease in function or tendon rupture)

  • Patient satisfaction

  • Recurrence of symptoms

  • Radiographic findings (ultrasound and magnetic resonance imaging (MRI))

Timing of outcome measurement

Where possible, we will present results for the following time periods: short term (0 to 12 weeks), intermediate term (3 to 12 months) and long term (longer than 12 months).

Search methods for identification of studies

Electronic searches

We will search the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to present), the Cochrane Central Register of Controlled Trials (current issue), MEDLINE (1946 to present), EMBASE (1980 to present), the Cumulative Index to Nursing and Allied Health Literature (CINAHL, 1937 to present), Allied and Complementary Medicine (AMED, 1985 to present), PEDro and the Science Citation Index (1945 to present). We will also search the WHO International Clinical Trials Registry Platform, Current Controlled Trials and ClinicalTrials.gov for ongoing or recently published trials. There will be no restrictions based on language or publication status.

In MEDLINE (PubMed), we will combine subject‐specific terms with the sensitivity‐maximising version of the Cochrane Highly Sensitive Search Strategy for identifying randomised trials (Lefebvre 2011). Search strategies for the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL and AMED are shown in Appendix 1.

Searching other resources

We will search grey literature, which will include reference lists of published studies and conference proceedings of the following organisations:

We will contact experts in the field to access published or unpublished ongoing trials.

Data collection and analysis

Selection of studies

Two review authors (FW and CB) will select trials for inclusion independently based on the titles, keywords and abstracts (generated from the search strategy) to determine whether they meet the inclusion criteria in terms of intervention, participants and design. All relevant trials will be retrieved and the full version of each study will be accessed. Independently, the review authors will select trials eligible for inclusion using a customised assessment form. We will resolve disagreement by consensus and referral to a third author (DM) if required. There will be no blinding to study author, institution or journal throughout.

Data extraction and management

Two review authors (FW and CB) will extract data independently using a customised data extraction form. Extracted data will include details of methods, eligibility criteria, interventions (including detailed characteristics of the exercise protocols employed and details of orthotic and splint prescriptions), comparisons, co‐interventions and outcome measures. We will resolve any disagreement by consensus or third party adjudication. We will contact trial authors to clarify any omitted data or study characteristics. To perform intention‐to‐treat analysis, we will extract data according to the original allocation groups and note losses to follow‐up where possible.

Assessment of risk of bias in included studies

Two review authors (FW and CB) will assess the risk of bias in included studies independently using the The Cochrane Collaboration's 'Risk of bias' tool (Higgins 2011). To minimise bias in the interpretation of this tool, review authors (FW and CB) will initially assess a small sample of unrelated studies (not included in the current review); disparities in risk of bias judgements will be discussed prior to evaluating any of the included studies.

Each study will be graded for risk of bias in each of the following domains: sequence generation; allocation concealment; blinding (participants and personnel) and blinding (outcome assessment); incomplete outcome data; selective outcome reporting, and other sources of bias. We will perform separate risk of bias assessments for subjective and objective outcomes for each of the blinding and incomplete outcome data domains.

For each study, the domains will be described as reported in the published study report (or, if appropriate, based on information from related protocols, published comments, or after discussion with the relevant authors) and their risks of bias judged by the review authors. We will resolve disagreements between authors concerning the risk of bias assessments by consensus.

Measures of treatment effect

We will report dichotomous data as risk ratios with 95% confidence intervals. The mean difference with 95% confidence intervals will be calculated for continuous data. For continuous data reported on different scales, we will use standardised mean difference. Preferentially, we will extract continuous data based on follow‐up scores; change from baseline (mean change scores) will be used when these are not available. To avoid applying parametric tests to non‐parametric data, included studies must include standard deviations (or these must be obtained from trial authors) and the standard deviation must be less than the mean when multiplied by two.

Unit of analysis issues

If studies include multiple observations over time of the same outcome, we will extract data at clinically relevant time points: i.e. short term (0 to 12 weeks), intermediate term (3 to 12 months) and long term (longer than 12 months). In studies that use a randomised cross‐over design, we will aim to undertake paired analysis when sufficient data are available and the design is appropriate; otherwise, data will be analysed as if these studies used a parallel group design using the first stage only (Deeks 2011). In the event that studies have two or more intervention groups, we will include each pair‐wise comparison separately with shared intervention groups divided out approximately equally among the comparisons.

Although most studies are likely to target treatment to individuals, treatment allocation in some trials may be randomised by clusters. If this is the case, these trials will have their sample size adjusted using an estimate of the intra‐cluster correlation coefficient taken from the trial, or related trials. We will perform a sensitivity analysis to assess the effect of the inclusion of these data.

Dealing with missing data

In cases in which there are missing data, we will consider why the data are missing. Whenever possible, we will contact the original study authors to request missing data. If standard deviations are missing from continuous data, we will scan studies for any other statistics (confidence intervals, standard errors, T values, P values and F values) that allow for their calculation. We will ignore data that are missing at random and we will focus on the available data only. If data are deemed to be missing non‐randomly, we will not impute replacement values. We will undertake sensitivity analyses to assess the effect of missing data on final results. 

Assessment of heterogeneity

We will assess clinical heterogeneity based on information from the participants of each study, interventions and outcome measurements. We will assess statistically heterogeneity by visual inspection of the overlap of the confidence intervals on the forest plots, and consideration of the Chi² test (P value < 0.1 will be interpreted as significant heterogeneity) and the I² statistic. We will base our interpretation of the I² results in as suggested in Higgins 2011: 0% to 40% might not be important; 30% to 60% may represent moderate heterogeneity; 50% to 90% may represent substantial heterogeneity; and 75% to 100% may represent considerable (very substantial) heterogeneity.

Assessment of reporting biases

Where at least 10 studies contribute data to a meta‐analysis, we will generate a funnel plot to assess for publication bias based on the effect estimates (horizontal scale) against standard error (on a reversed scale, vertical) using Review Manager software (RevMan 2011); with continuous data represented as standardised mean differences and dichotomous data represented as risk ratios on a logarithmic scale.

Data synthesis

When considered appropriate, we will pool results of comparable groups of trials using both fixed‐effect and random‐effects models. The choice of the model to report will be guided by careful consideration of the extent of heterogeneity and whether it can be explained, in addition to other factors, such as the number and size of included studies. Ninety‐five per cent confidence intervals will be used throughout. We will consider not pooling data where there is considerable heterogeneity (I² > 75%) that cannot be explained by the diversity of methodological or clinical features among trials. Where it is inappropriate to pool data, we will still present trial data in the analyses or tables for illustrative purposes and will report these in the text.

Subgroup analysis and investigation of heterogeneity

We will perform subgroup analysis based on age of participants (under 35 years versus over 35 years), gender (male versus female) and activity status (athletic versus non‐athletic). We will investigate whether the results of subgroups are significantly different by inspecting the overlap of confidence intervals and performing the test for subgroup differences available in RevMan.

Sensitivity analysis

We will perform sensitivity analysis based on individual risk of bias domains including randomisation (the inclusion of quasi‐randomised trials), unit of analysis (the inclusion of cluster‐randomised controlled trials) and the effect of missing data. We will also carry out sensitivity analysis to explore the impact of using fixed‐effect or random‐effects analyses for outcomes with statistical heterogeneity. We will also undertake sensitivity analysis to explore the effects of including trials that do not describe the exclusion of conditions that strongly mimic Achilles tendinopathy; in particular Sever's disease (inflammation of the heel's growth plates) in skeletally‐ immature children.

Assessing the quality of the evidence

We will use the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of the body of evidence (Schünemann 2011) for each of the primary outcomes and the first four secondary outcomes listed in Types of outcome measures. The quality rating 'high' is reserved for a body of evidence based on randomised controlled trials. We may ‘downgrade’ the quality rating to 'moderate', 'low' or 'very low' depending on the presence and extent of five factors: study limitations, inconsistency of effect, imprecision, indirectness or publication bias.

'Summary of findings' tables

Where data are sufficient, we will present the results and the quality assessments for the main comparisons described in Types of interventions in 'Summary of findings' tables (Schünemann 2011).