Can real-time tissue elastography be used to assess the healing process of injured superficial digital flexor tendon in horses?

Reasons for performing study:

Real-time tissue elastography (RTE) can provide objective information associated with mechanical properties of tendon tissue and add value to the structural information obtained by greyscale ultrasound. Serial RTE assessment would be useful for monitoring and optimising safe rehabilitation for horses with tendon injury.

Objectives:

To test the hypothesis that RTE could measure change in tissue stiffness in the healing process of injured superficial digital flexor tendon (SDFT) of horses.

Study design:

Prospective field study.

Methods:

Six Thoroughbred horses with SDFT injury and standardised rehabilitation were used. Both greyscale and RTE images were recorded approximately every 4 weeks up to 40 weeks from occurrence. Greyscale ratio (GR: dividing the greyvalue of injured area by it of surrounding noninjured area) and strain ratio (SR: dividing the strain value of stand-off gel pad, which can be a standard, by it of injured area) was calculated at each examination. Tissue strain is displayed by colour which suggests hard (blue), intermediate (yellow), soft (red) on RTE image. Strain of injured area was evaluated by colour-scale grade (CSG) of 1 to 3 (1; blue to green, 2; yellow and 3; red) by 3 veterinarians who didn’t know the case history.

Results:

GR was returned to nearly 1 quickly within 8 weeks and it was unchanged thereafter. This continuous change of GR was best-fitted to logarithmic trendline (r2 = 0.66). SR increased gradually up to the last examination and was best-fitted to linear trendline (r2 = 0.89). CSG was decreased gradually and it was best-fitted to linear trendline (r2 = 0.84). Both change of SR and CSG suggested that an injured tissue would gradually increase in stiffness.

Conclusions:

RTE could provide useful information regarding monitoring and optimising restoration of the tissue stiffness of tendon, even if GR was unchanged by progress of scar formation, for safer and more effective rehabilitation