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study in Standardbred racehorses do not concur with this information. A poorer prognosis has been suggested for SDFT branch injuries in a post mortem study (Webbon 1977) and in eventers and steeplechasers as a clinical impression (Dyson and Denoix 1995). However, it was not clear from these data whether the authors considered SDFT branch lesions in isolation or lesions as an extension of a more proximal tendon injury. If the branch injury is an extension of a metacarpal injury, we can undeniably expect a worse prognosis based on the amount of damaged tissue as larger tendon lesions seem to have a poorer prognosis for functional repair than smaller lesions (Genovese et al. 1990; Marr et al. 1993). For SDFT pastern lesions in isolation, the type of sport activity and breed could be responsible for the difference in prognosis. Our rehabilitation programme was mainly composed of
paddock resting, as was the case in the Thoroughbred racehorses study (Gibson et al. 1997). This relatively ‘uncontrolled’ rehabilitation programme contrasts with what has been previously described (Reef and Genovese 2011), which corresponds to what is used for metacarpal SDFT lesions. Our rehabilitation programme seemed cost effective for our Standardbred racehorse population but we can question if a more controlled exercise programme would not have led to better results. For SDFT lesions proximal to the fetlock, a more controlled rehabilitation programme is recommended to improve the prognosis and decreases the recurrence rate (Dyson 2004; Godwin et al. 2012). It is important to recognise that there is some evidence to support a controlled exercise programme over a totally unrestricted/free field exercise programme (Dyson 2004; David et al. 2012; Godwin et al. 2012). However, various types of rehabilitation programmes have not yet been compared and recommendations remain largely empirical. Ultrasonographic monitoring of tendon healing is an
important aid at the start of the rehabilitation programme. Unfortunately, after 6 months, very little change is noted during the remodelling phase of tendon healing on traditional 2D ultrasonography. The changes are mainly subtle modifications in fibre pattern alignment. The subjectivity of this type of assessment is our main threat. A central echogenic scar surrounded byahypoechoic halomaybedetected in the SDFT branch with healed core lesions (Reef and Genovese 2011). Peritendinous echogenic tissue representing immature and maturing fibrous tissue is often imaged adjacent to the injured SDFT branch and can be the result of adhesions between the branch and surrounding structures (Reef and Genovese 2011). Towards the end of the rehabilitation programme, once speed work is reintroduced, clinicians can only perceive undesired signs of tendon injury relapse (hypoechogenic zones, peritendinous fluid, enlargement of the structure) with traditional 2D ultrasonography. More sophisticated and accurate pieces of equipment measuring tendon microarchitecture or function such as ultrasonographic tissue characterisation or ultrasonoelastography, respectively would be useful to prevent early reinjuries during the second part of the rehabilitationphase(Docking et al. 2012;Cadbyet al. 2013; Reyes et al. 2014). Finally, the limitation of the study resides in the small
caseload. However, this injury is not common and the study on Thoroughbred racehorses also recorded only 14 cases (Gibson et al. 1997). This consequently decreased the statistical power of performance analysis.
Conclusion
Superficial digital flexor tendon branch injuries diagnosed in isolation and treated conservatively carry a good prognosis for a sustained return to athletic function in Standardbred racehorses. All performance parameters were not significantly different before and after injury, regardless of medial or lateral SDFT branch lesions. A higher return to racing and a lower reinjury rate compared with SDFT tendonitis in the metacarpal region treated conservatively can be expected but more comparative studies are needed to support this statement.
Authors’ declaration of interests No conflicts of interest have been declared.
Acknowledgement
The authors thank Delphine Le Chevallier for the review of the manuscript.
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