CUHK Achilles Tendon Disorder Registry
Conditions: Achilles Tendon Injury, Achilles Tendon, Achilles Tendon Pain
Sponsor: Chinese University of Hong Kong

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CUHK Achilles Tendon Disorder Registry
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Research Project Statement
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The Achilles tendon is one of our body’s most important structures, and the' Achilles heel' is
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a real clinical problem. The management of its pathologies—spanning acute ruptures to
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chronic tendinopathies—remains heterogeneous, with a critical absence of high-quality
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longitudinal data to compare treatments and guide personalized rehabilitation strategies. To
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address this evidence gap, we will establish a comprehensive prospective Achilles Tendon
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Disorder Registry.
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The registry will integrate our team's expertise in Achilles tendon research, which
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encompasses standardized assessment tools, biomechanical studies, and treatment evaluation.
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By systematically collecting outcome data, it will enable us to: determine the effectiveness of
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different treatment methods, advance evidence-based knowledge, improve the quality of care,
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enhance patient safety, achieve better patient outcomes, and reduce healthcare costs. This
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longitudinal registry will monitor long term outcome of Achilles tendon problem, and track
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Achilles tendon treatment outcomes, thereby helping to inform precision rehabilitation
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strategies and reduce long-term disability in the future.
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Research Questions
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1. Does the baseline status (e.g., vascularity and elastography metrics) influence the
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prognosis?
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2. Does pre-existing Achilles tendinopathy increase the risk of acute Achilles tendon rupture?
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3. Which group of patients is more responsive to which treatment?
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Hypothesis
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1. Baseline status (e.g., vascularity and elastography metrics) significantly influences
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prognosis.
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2. Pre-existing Achilles tendinopathy significantly increases the risk of acute Achilles tendon
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rupture.
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3. Different patient groups respond differently to various treatment methods.
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Research Methodology
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Study setting
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This prospective cohort study will be conducted at the Prince of Wales Hospital in Hong
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Kong. All self-reported, functional, and ultrasonographic outcomes will be assessed at
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baseline, 6 weeks, 3 months, 6 months, and 1 year. Following the initial 1-year follow-up, all
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self-reported outcomes will be assessed annually through online questionnaires at 2, 3, 4, and
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5 years. All participants must provide written informed consent prior to enrolment. The
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investigator will obtain and document consent before any study procedures are performed.
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All eligible participants will be fully informed about the study and given ample time to
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consider participation; the research team will answer all participant questions. The trial will
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be conducted in accordance with the Declaration of Helsinki.
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Eligibility
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Inclusion:
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
Adults (>18 years of age)
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Exclusion:
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
Any physical or psychological comorbidity that would impair the ability to complete
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study assessments (e.g., significant neurological deficits) or preclude the provision of
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informed consent.
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
Concomitant diseases that severely affect lower limb function or assessment (e.g.,
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severe osteoarthritis of the knee or hip, prior lower limb amputation, peripheral
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vascular disease, active rheumatoid arthritis, lower limb paralysis, etc.)
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Outcome measures
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Baseline demographic data will be collected, including age (date of birth), gender (biological
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sex), occupation, recreational activity (Pre-injury and current activity levels -Tegner score),
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diagnosis (types of Achilles tendon problem) , treatment modalities already tried.
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Time frames for collection include 0 weeks (baseline), 6 weeks, 3 months, 6 months, 1 year.
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Following the initial 1-year follow-up, all self-reported outcomes will be assessed annually
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through online questionnaires at 2, 3, 4, and 5 years.
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Primary Outcome: Victorian Institute of Sports Assessment (VISA-A) Questionnaire
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The primary outcome measure will be the Victorian Institute of Sport Assessment (VISA-A)
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questionnaire, available in either the original English or validated Chinese version, depending
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on the participant's native language. This specific scoring system developed for the Achilles
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tendon is the most widely used score for clinical Achilles research. The VISA-A is scored on
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a scale of 0 to 100; lower scores indicate more severity of symptoms, while a score of 100
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indicates a healthy and pain-free Achilles tendon.
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Secondary Outcomes: Numeric Pain Rating Scale (NPRS); Foot and Ankle Outcome
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Scores (FAOS); Achilles tendon resting angle (ATRA); Royal London hospital test; Calf
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Muscle
Strength;
Heel
raise
test;
Jump
test;
Foot
pressure
distribution;
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Ultrasonographic tendon thickness; Ultrasonographic tendon cross-sectional area;
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Ultrasonographic neovascularity; Ultrasonographic tendon elasticity; Ultrasonographic
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calf muscle quality; Photoacoustic imaging-derived tendon oxygenation and vascularity;
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Thermographic tendon temperature.
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Numeric Pain Rating Scale (NPRS):The Numeric Pain Rating Scale (NPRS; 0–10, where
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10 represents maximum pain) will be used to assess pain levels, as pain is the primary
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symptom of midportion Achilles tendinopathy. Participants will report their “Worst pain
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during sports in the past two weeks,” “Worst pain during daily activities in the past two
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weeks."
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Foot and Ankle Outcome Scores (FAOS): The FAOS is a validated patient-reported
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scoring system used for general foot and ankle problems. It is split into five categories:
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symptoms, pain, daily activities, sporting function, and quality of life. Scores range from 0
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to 100, with 0 being the lowest and 100 being the highest.
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Achilles tendon resting angle (ATRA): The ATRA will measure participants' tendon
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length/tension. Participants should be positioned in a prone position with the knee flexed to
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90 degrees. The assessor will use a dynamic joint goniometer to measure the angle at which
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the foot passively falls.
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Royal London hospital test: The Royal London Hospital Test is used to help diagnose mid-
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portion Achilles tendinopathy. The patient lies prone with the foot relaxed, and the examiner
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palpates the most tender spot on the Achilles tendon. The patient then moves the ankle
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through dorsiflexion and plantarflexion. A positive test occurs if tenderness decreases during
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dorsiflexion.
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Calf Muscle Strength: The hand-held dynamometer will be used to quantify isometric
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muscle strength during ankle dorsiflexion and plantarflexion. Participants will maintain
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maximal isometric contraction for 3 seconds. Three trials will be recorded for each movement,
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with 30-second rest intervals between trials to prevent fatigue.
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Heel raise test: Participants will be instructed to keep the knee straight and rise as high as
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possible on the toes each time until fatigue. Participants can place two fingertips per hand on
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the wall to maintain balance. The rhythm will be set at a frequency of 30 heel rises per
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minute by following a metronome. Total test duration (in seconds) will be recorded.
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Jump test: Participants will perform three one-legged counter-movement jumps on a
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pressure mat (Tekscan, USA) with jump height (cm) calculated from flight time. After
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demonstration and submaximal practice jumps, the patient executed maximal jumps from a
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standing position by rapidly squatting (flexing knee/hip/ankle) before exploding upward. The
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highest jump was recorded, with NPRS-reported Achilles tendon pain immediately post-test.
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Foot pressure distribution:
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In foot pressure distribution examination, the scan (Tekscan, USA) will be masked and
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divided the foot into eight regions including both forefoot, midfoot and hindfoot: hallux,
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lesser toes, lateral and medial forefoot, lateral and medial midfoot, lateral and medial
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hindfoot. Peak pressure and impulse in each region will be calculated to see the before-and-
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after change. Additionally, the centre of pressure excursion index (CPEI) will also be
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calculated to which reflects the excursion of the centre of pressure. The first and last points of
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a centre of pressure curve will be connected to construct a line measured in the distal tertile
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of the foot and normalized by the foot’s width.
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Zebris Treadmill Gait and Stance Analysis: The Zebris is a treadmill equipped with
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advanced pressure sensors designed to analyze gait and stance. Subjects were instructed to
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walk barefoot on the treadmill at their comfortable pace while maintaining a natural walking
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pattern. During the test, the pressure distribution across the plantar surface of the feet was
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recorded, capturing dynamic data such as force, timing, and spatial parameters of each step,
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which ensures precise measurement of walking and stance characteristics, providing valuable
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insights into balance, weight distribution, and movement symmetry for clinical or research
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purposes.
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Achilles Ultrasonography:
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To ensure reproducibility, a standardised Achilles tendon ultrasound imaging protocol will be
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used to perform the assessment at all time points in the trials. Subjects will lie prone on the
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examination table with knees straight and ankles hanging in a relaxed position. The Achilles
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tendons will be imaged bilaterally using an ultrasound machine equipped with a 12 MHz
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linear transducer (Aixplorer, SuperSonic Imagine, Aix-En-Provence, France). All regions of
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interest (ROIs) will be measured at: (1) the maximum thickness point, and (2) standardized
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locations 2 cm, 4 cm, and 6 cm proximal to the insertion.
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Tendon thickness: Using B-mode ultrasound scanning, the probe is moved from the medial
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to the lateral aspect of the Achilles tendon until a planar image of the Achilles tendon is
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clearly shown. The probe was adjusted straight perpendicular to the tendon fibres. A
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greyscale sonogram is acquired, and the tendon thickness is measured at the maximum
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thickness point and at 2, 4, 6 cm proximal to the insertion. Less than 5.3 mm was considered
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a healthy value for the Achilles tendon.
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Tendon vascularity: Vascularity will be documented using the Ohberg score. Using the
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Doppler mode on the ultrasound machine, the transducer is placed vertically to obtain a
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sagittal view of the softest area of the Achilles tendon. Pressure on the skin from the
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transducer should be kept to a minimum to prevent occlusion of blood vessels. The colour
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box is focused on the dorsal aspect of the tendon. The assessor will spend one minute
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exploring the blood flow over the tendon to find the area of maximum Doppler flow. After
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locating the area, sonograms are taken to determine the
Öhberg score. The Öhberg score
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ranges from 0 to 3 points. In this scoring system, the score is defined as 0 (no
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neovascularisation, healthy), 1 (mild neovascularisation with a few single vessels), 2
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(moderate neovascularisation with a moderate number of mostly transverse vessels), and 3
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(multiple, mostly transverse vessels distributed throughout the depth of the tendon). Higher
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scores indicate more Doppler blood flow in the peritendinous and intratendinous tissues.
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Healthy tendons (Ohberg score of 0) have no blood vessels in the Achilles tendon.
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Tendon elasticity :
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Shear wave elastography (SWE) can be used to quantify soft tissue stiffness. Once the
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optimal scan plane of the tendon is determined, the SWE function is activated. It enters
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penetration mode and the measured stiffness range is normalized to 0-600 kPa. The SWE
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color card (H × W: 1.4 cm × 1.3 cm) is placed immediately above the upper edge of the
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calcaneus. After the color signal stabilized for five seconds, the elastogram was recorded and
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stored. Tendon stiffness was measured using a Q-box stiffness meter. Depending on the size
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of the tendon, the diameter of the circular measuring area (Q-box) is set to 2 mm, which
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covers the Achilles tendon and excludes other adjacent soft tissues. The Q-box is located in
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the center of the maximum thickness point and 2, 4, 6 cm proximal to the calcaneal insertion
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site. For each Q-box, the average tendon stiffness (in kPa) is measured.
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Tendon oxygenation and vascularity: The pathological tendon's oxygenation and
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vascularity were quantified using a multiwavelength photoacoustic ultrasound (PAUS)
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system equipped with a 7Hz probe and dual-wavelength LED sources (850nm/750nm). The
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participant assumes a prone position with heels extended beyond the examination table. The
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probe is positioned on the target tendon, with mode-specific presets selected ("Deep PA" for
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vascularity at 850nm; "Deep Oxy" for oxygenation at 750nm). Each 20-second acquisition
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captures 200 frames, with two repeated scans per mode to ensure data reliability.
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Thermographic tendon temperature: Participants will be advised to avoid physical
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exercise and hot baths before the procedure to ensure data reliability. Each participant will
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rest in a seated position for 10 minutes followed by 2 minutes without socks. The room will
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be maintained at 20-24°C. The infrared camera will be positioned one meter from the
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participant, using a ThermaCam FLIR-T8210. Images will be analyzed with ThermaCAM
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Researcher Pro 2.8 SR-1 software, and a rectangular area covering the Achilles tendon will
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be used for temperature assessment.
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Sample size
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As a prospective registry study, this study plans to consecutively enroll all eligible patients
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presenting to the Prince of Wales Hospital between 2025 and 2028. Based on the annual
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patient volume, a minimum of 500 participants is expected to be recruited, which is
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anticipated to provide sufficient statistical power for the planned multivariable analyses.
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Recruitment
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Participants will be recruited through multiple concurrent strategies. Our primary recruitment
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site is the Prince of Wales Hospital. We will also utilize our sports medicine network, which
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includes school sports teams, professional organizations (e.g., Kitchee Football Club), and an
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extensive alumni network of doctors and sports medicine professionals from our MSc
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program. Simultaneously, study advertisements will be distributed to all staff and students of
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The Chinese University of Hong Kong through the CUHK Mass Mail System to ensure
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comprehensive outreach.
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Data collection and management
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Plans to promote participant retention and complete follow-up: The schedule for all the
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outcome measure appointments will be provided from the beginning. For patients who have
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missed their scheduled appointments for follow-up assessments, additional hours will be
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extended to the evenings at the Sports Performance and Biomechanics laboratory at CUHK
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so that participants may come for assessment (e.g., after work, rescheduled due to illness,
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etc.).
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Data management: Data collected will be securely stored in password-protected computers
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and archived for five years after publication. The Principal Investigator (PI) and research
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assistants will oversee data collection, entry, and analysis. To ensure accuracy, a double data
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entry method and range checks will be implemented. Data will be restored into an Excel files
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and then transferred to SPSS software for analysis.
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Confidentiality: To ensure the highest level of privacy and security, the Sports Performance
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and Biomechanics Laboratory stores all personal information and consent forms in securely
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locked cabinets. Our online electronic database is protected by password-protected computers,
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ensuring the utmost confidentiality. Access to the collected data is strictly limited to trusted
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trial team members, with no access granted to participants. De-identified participant data may
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be shared with other researchers upon reasonable request and after execution of appropriate
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data sharing agreements, subject to approval by the ethics committee.
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There is no plan for using biological specimens outside of this study plan.
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Statistical methods for primary and secondary outcomes: Statistical analyses will be
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performed using SPSS (version 28.0), with a two-sided significance level of α = 0.05.
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Continuous outcomes (e.g., VISA-A, NPRS, tendon thickness, dynamometry) will be
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summarized as mean ± standard deviation, assessed by Shapiro–Wilk test. Categorical
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variables will be presented as frequencies and percentages.
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To address Q1 (prognostic influence of baseline status), multivariable linear or logistic
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regression models will be constructed to evaluate the association between baseline metrics
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(e.g., vascularity, elastography) and functional outcomes (e.g., VISA-A, heel raise capacity),
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adjusting for covariates such as age, sex, and symptom duration.
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For Q2 (risk assessment), a Cox proportional hazards model or logistic regression will be
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used to examine whether pre-existing tendinopathy (dichotomized: yes/no) predicts
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subsequent acute rupture, with results reported as hazard ratios or odds ratios and 95%
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confidence intervals.
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For Q3 (treatment responsiveness), interaction terms between patient subgroups (e.g., defined
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by baseline severity, structural metrics) and treatment types will be incorporated into
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regression models to identify effect modifiers. Should significant interactions be detected,
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stratified analyses will be performed.
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Interim analyses: An interim analysis will be performed on the primary endpoint when 20%
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of participants completed the 1-year follow-up. The interim analysis ensures that no serious
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adverse event happened during the study period.
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Methods in analysis to handle protocol non-adherence and any statistical methods to
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handle missing data: Missing data will be handled using multiple imputation under the
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missing-at-random assumption. Sensitivity analyses will include complete-case assessments.
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Model assumptions (e.g., linearity, proportionality) will be verified graphically and
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analytically.
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Plans to give access to the full protocol, participant-level data, and statistical code: The
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protocol will be registered on clinicaltrials.gov. The participant-level data and statistical code
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can be provided upon request.
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Oversight and monitoring: The principal investigator will monitor the progress of the study.
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The trial steering committee consists of research team members who will participate in
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participant recruitment, data collection, and management. The trial steering committee
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consists of orthopaedic surgeons and researchers (research assistants and biostatisticians).
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The orthopaedic surgeons and research assistants will participate in data collection and
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analysis. The biostatistician will monitor data collection and perform interim analysis. There
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is no independent data monitoring committee, as the ethics committee does not require this.
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Adverse events reporting and harms: The procedure will be supervised by orthopaedic
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surgeons licensed under the Medical Council of Hong Kong. If a participant experiences a
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severe adverse reaction to the intervention, it will be reported to the trial steering committee
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immediately, and the participant will be removed from the trial.
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Frequency and plans for auditing trial conduct: An independent auditor from the ethics
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committee will conduct the trial conduct annually. The principal investigator will complete a
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progress report form for the ethics committee to review conduct annually during the trial
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period.
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Plans for communicating necessary protocol amendments to relevant parties: The
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investigators will seek protocol amendments from the ethics committee, which must approve
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them before implementation. Trial participants will be notified of any changes to the protocol.
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Furthermore, the protocol modifications will be publicly available in the Trial Register.
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Funding and Sponsors:
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There are no declared funding sources or sponsors at this stage.
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Institutional Affiliations:
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The study is conducted by the Department of Orthopaedics and Traumatology, Faculty of
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Medicine, The Chinese University of Hong Kong (CUHK).
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Potential Conflicts of Interest:
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All investigators involved in this study have declared no competing interests.
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Incentives for Subjects:
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No financial or material incentives are provided for participation.
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Provisions for Harm:
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Participants who experience adverse effects directly attributable to the study will receive
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appropriate medical care at the Prince of Wales Hospital, CUHK, at no additional cost.
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Compensation for research-related harm will follow institutional and ethical guidelines.
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