McCartney WT. Marie Louise Veterinary Hospital, 38 Warrenhouse Road, Baldoyle, Dublin 13, Republic of Ireland. E-mail: billymccartney@gmail.com. VCOT 2008 21 5 446-50 OBJECTIVE: To report three clinical cases suffering from limb shortening secondary to monostotic physeal closure, in which distraction osteogenesis had been performed without a latency period and with high distraction rates. METHODS: Three dogs had limb lengthening performed, using an Ilizarov ring fixator in two dogs and a linear dynamic fixator in the other dog. Bone lengthening achieved for a radius/ulna was 27 mm at 2 mm per day , a tibia was 78 mm at 3 mm per day, and a femur of 45 mm was 3 mm per day . RESULTS: Complications related to pin loosening occurred in each case, thus requiring surgical corrective procedures, but these did not affect the final outcome. Lateral bowing of the bar and bone and some musculo-cutendinous contracture occurred in the femur. Fixation frames were on for 12 weeks in Case 1, eight weeks in Case 2 and nine weeks in Case 3. All three of the cases had a good functional outcome. DISCUSSION: The faster rates of lengthening were not associated with any long-term deleterious soft tissue complications, but they were associated with pin loosening and bending of the bar. In each case there was excellent osteogenesis. CONCLUSIONS: From the results achieved in these three cases it can be concluded that a latency period prior to distraction osteogenesis may not be necessary. Also, distraction rates up to 3 mm per day can be used to shorten the time needed to achieve lengthening; however further studies are needed to investigate the high level of complications.