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Tendon injuries are one of the leading causes of retirement in the equine industry. Injuries of the superficial digital flexor tendon account for 75%-93% of soft tissue injury in our equine athletes. The rehabilitation of an SDFT injury is time consuming and can have quite a limited success rate to preinjury level exercise.

Early mobilisation is known to improve the tendon integrity and fiber matrix of a recovering tendon but proves difficult to maintain peak loading. An alternative method is the use of a peak load restriction device

An optimal method of evaluating the peak load of a tendon is Ultrasound Tissue Characterisation (UTC). UTC characterises the tendon by echo-type thus allowing the ability to see the tendon’s functionality throughout recovery. Echo-type I portrays intact fascicles, echo-type II by discontinuous swollen fascicles, echo-type III by fibers in a lesion and echo-type IV by complete lack of fiber structure.

The aim of the study is to monitor the changes of SDFT injuries throughout recovery whilst using a restricted peak loading device. The integrity of the tendon is evaluated by UTC by means of quantifying the tendon matrix.

The population consisted of 32 horses, 19 geldings (59%) and 13 mares (41%) had naturally occurring SDFT injuries entered a standardised rehabilitation schedule with the use of a peak load restriction device.

The results of UTC analysis were used to evaluate the effect of exercise in a predetermined maximum load protocol that was reevaluated every 4 consecutive weeks. Data analysis of the proportions of the 4 echo-types were taken at each timing interval (T1-T6). The peak load restriction device settings were changed at each interval.

Inclusion criteria of the subjects included age, gender, clinical examination, lesion type and discipline of same, pre-injury. Subject mean age of 8.45 years SD± 2.96 (range: 6 - 18 years). The subjects competed in showjumping 10 (32%), eventing 9(28%), or thoroughbred racing 13(40%) before the initial SDFT injury. The interaction for speed-like estimate between clinical group and echo-type I was significant( p-value = <.0001).

A functional tendon should have < 5% of UTC echo-type III and IV combined. In the evaluation of the clinical group echo-types III and IV combined was 27% = T0, 3.66% = T6 compared to the control group 23% and 10.3% respectively. At T3, there was a significant correlation between lameness and echo-type IV in control group (p-value = 0.01). With the use of restricted peak loading, 27 subjects (84%) of the clinical group reached pre-injury level competition or higher after twelve months post-injury compared to 5 (50%) in the control group. (p-value=0.04).

Assessing the effect of loading on a tendon may lead to reducing the injury rate in the equine athletes in the future. UTC has proven to be an accessible and functional aid for the evaluation of tendinopathies.