Experimental fixation of femoral osteotomies by cerclage with nylon straps.

Following the successful experience of Partridge in the fixation of human femoral fractures by nylon-strap cerclage, this research in 23 mature dogs was performed to compare nylon-strap with wire-loop cerclage for healing periods of up to 12 weeks. Supplemented by intramedullary fixation with Steinmann pins, long oblique femoral osteotomies were fixed in one femur of each dog by nylon straps and in the other femur by wire loops, at separate operations. The nylon straps were all secured at the same tension by a special "gun." The wire loops were all secured at the same tension by the Rhinelander tightener-twister. Half of the nylon straps had "bumps" along the inner surface, which were added by Partridge in an effort to circumvent the microvascular disturbance reported with Parham bands. On examination by microangiography and correlated histology, all of the osteotomies, regardless of the type of fixation, showed good progress toward osseous union. After fixation by wire cerclage no loss of position or disturbance of blood supply was noted. After fixation by nylon straps slight (clinically insignificant) longitudinal displacement, attributed to slight lengthening of the straps, with consequent loosening was noted in all cases. This loosening was considered advantageous because it appeared to be responsible for the unexpected lack of impairment of the vascularization of the underlying cortical bone by any of the straps. The bumps on the undersurface of some of the straps were, thus, of no vascular advantage, and their presence made accurate fixation of the ostectomy fragments more difficult on the small bones. These studies support the value of fixation by plain nylon straps and show their advantage over straps with bumps for fixation of long oblique single osteotomies of bones the size of the canine femur.