Background and Rationale Achilles tendon rupture (ATR) is a common injury in active adults and is increasingly managed non-surgically using structured, functional rehabilitation pathways. The Swansea Morriston Achilles Rupture Treatment (SMART) protocol is a widely implemented conservative pathway emphasising protected weight-bearing, staged mobilisation, and progressive strengthening. Although early functional outcomes with non-surgical care are encouraging, there remains limited single-time-point data at \~12 months post-injury combining objective plantarflexor strength with patient-reported function in routine NHS practice. This cross-sectional observational study addresses that gap by quantifying isokinetic strength and self-reported outcomes at 12-15 months after ATR managed non-operatively.
Objectives Primary objectives are to (1) quantify plantarflexor strength of the injured limb (peak torque and peak torque normalised to bodyweight) and (2) estimate recovery using Limb Symmetry Index (LSI) relative to the contralateral limb; and (3) describe patient-reported function using the Achilles Tendon Total Rupture Score (ATRS). A secondary objective is to examine the association between objective strength metrics and ATRS.
Design and Setting This is a single-organisation, cross-sectional cohort study conducted within Liverpool University Hospitals NHS Foundation Trust (LUHFT), with testing delivered at Aintree University Hospital or Broadgreen Hospital physiotherapy departments. Each participant attends one study visit (approximately 60-90 minutes). No randomisation, blinding, investigational product, or longitudinal follow-up is involved.
Study Population and Identification Adults (≥18 years) with a confirmed ATR treated non-surgically using the SMART protocol and now 12-15 months post-injury are identified by authorised clinicians from an existing LUHFT clinical database. Potential participants are approached by their direct care team or via text and provided with a Letter of Invitation and Participant Information Leaflet. Written informed consent is obtained prior to any study procedures.
Study Procedures Pre-test instructions: Participants are asked to avoid vigorous lower-limb activity for 24 hours pre-visit.
Warm-up: \~5 minutes of gentle cycling at a self-selected pace to elevate heart and breathing rate while maintaining conversational effort.
Isokinetic Strength Testing: Conducted with a clinic isokinetic dynamometer in a semi-reclined position with knee flexed to \~90°. The ankle joint is aligned with the dynamometer axis; the foot is strapped to the footplate; trunk/pelvis/thigh stabilised with padded straps. Testing range spans approximately 15° dorsiflexion to 40° plantarflexion. After sub-maximal familiarisation repetitions, participants perform maximal-effort concentric plantarflexion contractions at 90°/s and 30°/s on the uninjured limb first, then the injured limb.
Patient-Reported Outcome: Participants complete the ATRS (0-100; higher scores indicate better function).
Risk Management and Safety Monitoring The procedures are low-risk and part of routine rehabilitation assessment. Minor, transient muscle soreness (DOMS) or fatigue may occur. Testing is supervised by trained physiotherapists and is stopped immediately if pain or undue discomfort is reported. Any adverse events during the visit are documented and handled per local clinical governance; related and unexpected serious events would be reported to the sponsor and REC in line with policy.
Data Elements and Outcomes:
Objective outcomes include peak plantarflexion torque (Nm), peak torque normalised to bodyweight (Nm/kg), and LSI (%) calculated as (injured/uninjured) × 100. Subjective outcome is ATRS (0-100). Data are collected at a single time point only (12-15 months post-injury).
Sample Size and Feasibility A paired comparison of injured vs. uninjured limbs informed the sample size. Assuming 80% power (α=0.05), 92 participants were required to detect a clinically meaningful difference in peak torque; to allow for unusable data or non-completion, the target enrolment is 115.
Sampling Method Convenience sampling from the pre-existing clinical database of eligible ATR patients managed non-surgically with SMART in LUHFT. This approach reflects real-world NHS practice and facilitates operational feasibility for a single-visit assessment.
Statistical Analysis Plan Descriptive statistics will summarise all outcomes. Normality will be assessed. Between-limb comparisons for peak torque may be summarised descriptively; LSI will be presented as percentage. Association between strength metrics (peak torque, Nm/kg, and LSI) and ATRS will be assessed with Pearson's correlation when assumptions are met; otherwise, Spearman's rank correlation will be used. No imputation is planned; missing data will be described and analyses conducted on available data. All analyses are exploratory and hypothesis-generating within a cross-sectional framework.
Data Quality and Management Data are recorded on standardised case report forms and transferred to a secure, password-protected NHS server. Identifiable information is stored separately from research data; a study ID links records. Data entry checks and plausibility rules (e.g., range checks for torque values, internal consistency across speeds and limbs) are applied. Source documentation (e.g., printouts from the isokinetic system) is retained in site files. Only authorised staff have access to identifiable data. Pseudonymised datasets are used for analysis. No data are transferred outside approved secure environments.
Confidentiality and Governance The study complies with UK GDPR and the Data Protection Act 2018. Participation is voluntary and withdrawal can occur at any time without impact on care. Publications and presentations will report only aggregated, anonymised results; no individual-level data will be publicly shared.
Dissemination:
Findings will be submitted to peer-reviewed journals and presented at relevant conferences. Participants may opt to receive a lay summary of study results after analysis is complete.
Current Status:
Single-visit assessments will commence after all approvals and registrations are in place. Recruitment will continue until the planned sample size is achieved.
