Transthecal Arthroscopy of the Palmar Distal Interphalangeal Joint in the Horse: A Cadaver Study

Objective: To describe a transthecal approach to the palmar pouch of the distal interphalangeal joint (DIPJ) in horses and compare it with the conventional blind arthroscopic technique. Study Design: Ex vivo study. Sample Population: Cadaver forelimbs (n=26 pairs) from mature horses. Methods: One limb from each pair was randomly assigned to each arthroscopic approach (conventional or transthecal). The conventional arthroscopic approach was performed as previously described and the transthecal approach was performed through sharp dissection of the distal reflection of the digital flexor tendon sheath (DFTS). The proportion (0-100%) of the navicular bone, palmar aspect of the condyles of the 2nd phalanx, collateral sesamoidean ligaments, and palmar synovial pouches of the DIPJ visualized by each approach was estimated. Limbs were dissected and iatrogenic damage of relevant structures was assessed. Nondirectional Mann-Whitney U-test was used to compare groups. Significance was set at P<.05. Results: The transthecal approach provided greater visualization of the navicular bone (P<.001), palmar aspect of the 2nd phalanx (P<.001), and palmar synovial pouches of the DIPJ (P<.001) than the conventional approach. There were no significant differences in iatrogenic damage between approaches. Conclusion: The transthecal approach provides improved visualization of the palmar aspect of the DIPJ compared to the conventional blind approach and may be useful in nonseptic conditions of the DIPJ. However, because of the creation of communication with the DFTS, use of the transthecal approach for suspected synovial sepsis of the DIPJ may be contraindicated.