BIOMECHANICAL COMPARISON OF FIXATION METHODS IN TRANSVERSE PATELLA FRACTURES

Objective: To compare monofilament wire versus braided cable for stabi lizing transverse patella fractures using the modified AO tension band technique. Design: A randomized blocked (paired) study comparing two fixation methods. Statistical analysis was performed using a nested re peated measures analysis, followed by Bonferroni post hoc testing. Met hods: Seven paired embalmed knees (mean age 71.8 years, SD 14.6 years) were dissected, and transverse fractures were simulated. The knees we re reduced and randomly fixed by either two parallel 0.062-inch Kirsch ner wires with a 1.0-millimeter-diameter 316L stainless steel monofila ment wire tension loop or two Kirschner wires with a 1.0-millimeter-di ameter 316L stainless steel braided cable tension loop. Knees were tes ted by applying a cyclic load through the suprapatellar tendon between twenty and 300 newtons for thirty cycles. Results: The maximum fractu re displacement increased with each cycle of lending for both the brai ded cable and monofilament wire tension loop configurations (p = 0.000 1). The average peak displacement at the thirtieth cycle was 2.25 mill imeters for monofilament wire and 0.73 millimeters for the cable. When comparing both methods for all cycles, the braided cable allowed less fracture displacement than did the monofilament wire (p = 0.002), and the rate of increase per cycle of maximum fracture displacement was l ess for the cable than for the wire (p = 0.0001). Conclusions: In tran sverse, noncomminuted patella fractures, fixation with two Kirschner w ires and a 1.0-millimeter braided cable tension loop was superior to t he monofilament wire tension loop. Most importantly, the braided cable afforded more predictable results during cyclic loading.