TRANSFORMING GROWTH-FACTOR-BETA-1 ENHANCES BONE HEALING TO UNLOADED TRICALCIUM PHOSPHATE COATED IMPLANTS - AN EXPERIMENTAL-STUDY IN DOGS

Growth of bone into cementless prosthetic components is compromised af ter revision of failed joint prostheses and by osteoporosis, gaps, and micromotion. We studied the effects of recombinant human transforming growth factor-beta 1 adsorbed on ceramic coated implants on the impro vement of mechanical fixation and bone growth on the implant. Unloaded cylindrical grit-blasted titanium alloy implants were inserted bilate rally into both the medial and lateral femoral condyles of 10 skeletal ly mature mongrel dogs. The implants measured 10 mm in length and 6 mm in diameter and were initially surrounded by a 2 mm gap. One implant had an uncoated titanium surface and three implants were coated with t ricalcium phosphate and 0, 0.3, or 3.0 mu g of recombinant human trans forming growth factor-beta 1. The dogs were killed at 6 weeks. Mechani cal testing showed a 3-fold increase in fixation for the 0.3 mu g dose of recombinant human transforming growth factor-beta 1 and a 2-fold i ncrease for the 3.0 mu g dose. Histological analysis of bone growth on the implant demonstrated that maximal stimulation occurred with the 0 .3 mu g dose, but bone volume in the gap was maximally stimulated by t he 3.0 mu g dose and increased 2-fold over control values. The majorit y of tricalcium phosphate was resorbed after the 6-week observation pe riod. This study suggests that recombinant human transforming growth f actor-beta 1 adsorbed onto implants coated with tricalcium phosphate c eramic can enhance mechanical fixation and bone growth on the implant. The use of transforming growth factor-beta 1 on ceramic coated prosth etic components may help to improve the functional outcome of cementle ss total joint replacements.