Ex vivo pilot study evaluating needle tenoscopy of the digital flexor tendon sheath and its suitability to assist palmar annular ligament transection

Background: The digital flexor tendon sheath (DFTS) is a common site of pathology in the UK equine population, often necessitating tenoscopic exploration. Common intrathecal pathologies may lead to fetlock canal constriction. The palmar/plantar annular ligament (PAL) is often surgically transected to relieve constriction or to facilitate surgical access and instrumentation.Objectives: The objectives of this study were (1) to establish whether diagnostic quality needle tenoscopy can be achieved in the proximal DFTS in cadaver limbs; (2) to determine if needle tenoscopy can be used to safely guide PAL transection; and (3) to evaluate iatrogenic damage when undertaking needle tenoscopy and PAL transection.Study design: Ex vivo experimental.Methods: Six cadaveric limbs were used and needle tenoscopy of the DFTS was performed via biaxial approach at the base of the sesamoids. Access to and diagnostic assessment of the proximal DFTS, as well as the completeness of needle tenoscopically guided transection of the PAL was recorded. Limbs were dissected and examined for iatrogenic damage and completion of PAL transection.Results: Positioning of the cannula/obturator unit was achieved on the first attempt 11/12 times. Laterally 16/24 and medially 18/24 proximal DFTS channels were accessed. Images were of diagnostic quality in 12/24 and 11/24 channels following lateral and medial approach, respectively. The PAL was completely transected in 4/6 limbs with partial transection in 1/6 limbs. The superficial digital flexor tendon (SDFT) was longitudinally lacerated instead of the PAL in one limb, with other iatrogenic damage limited to mild fibrillation to the intersesamoidean ligament.Main limitations: Ex vivo and sample size.Conclusions: The findings in this pilot study suggest that needle tenoscopically guided PAL transection in the live horse is not recommended currently. While diagnostic needle tenoscopy offered partial assessment of most of the proximal DFTS, further refinement is necessary before needle tenoscopy could be considered a viable alternative to traditional tenoscopy.