OLIVER M. CROWE, BVSc Cert ES (Orth) 1,2 , RICHARD J. HEPBURN, BVSc Cert EM Diplomate ACVIM 1,2 , SVEND E. KOLD, DVM PhD 1,2 , and ROGER K. SMITH, MA Vet MB PhD DEO Diplomate ECVS 1,2 1 Willesley Equine Clinic, Willesley, Gloucestershire, UK ; and 2 Department of Veterinary Clinical Sciences, The Royal Veterinary College, North Mymms, UK Veterinary Surgery January 2010 39 1 107 - 114 Objective—To report long-term outcome after arthroscopic removal of fragmentation of the extensor process of the distal phalanx in horses. Study Design—Case series. Animals—Adult horses (n=13). Methods—Medical records (2003–2004) of horses that had arthroscopic debridement of fragmentation of the extensor process of the distal phalanx were reviewed. Inclusion criteria included: lameness localized to the foot, fragmentation of the extensor process of the distal phalanx debrided arthroscopically, and a follow-up period of ≥4 years. Results—Of the 13 horses, lameness was resolved in 11 (85%) initially but distal interphalangeal joint pain recurred in 2 (15%) within 1 year of surgery. Three (23%) other horses were retired because of lameness at other sites during the follow-up period resulting in 46% (6/13) being not lame and in full work after 4 years. Substantial changes were identified at surgery in the contralateral joint of 7 horses, even when fragments were only present unilaterally. Conclusions—Arthroscopic debridement of fragmentation of the extensor process of the forelimb distal phalanx has a good short-term prognosis for resolution of lameness and return to work but a more guarded prognosis for long-term soundness. Clinical Relevance—These results allow for more accurate prognostication preoperatively and may support early debridement of fragmentation of the extensor process of the distal phalanx.