Mechanoreceptors and length of the patellar ligament after Ho-YAG laser treatment: a long-term follow-up in rabbits.

We studied the shortening and the number of mechanoreceptors in the patellar ligament up to 18 months after Ho-YAG irradiation of the ligament's surface in 35 rabbits. The ligaments shortened an average 13% immediately after irradiation. After treatment, we divided the rabbits into a mobilized or immobilized group. At 2 weeks and 12 months after treatment both groups showed no shortening of the ligament, as compared to the intact ligament while that in the mobilized group had elongated at 12 months. Fewer Pacinian and Ruffini corpuscles were found in the irradiated ligaments than in the intact ones at 2 weeks after treatment, but we found no difference between irradiated and intact ligaments at 18 months after treatment.