Dynamic confirmation of fixation techniques of the tibial tubercle osteotomy

The tibial tubercle osteotomy is gaining popularity for revision total knee arthroplasty; however, the potential for tubercle displacement has been a concern. This study compared the mechanical behavior of the tibial tubercle osteotomy after screw and cerclage wire fixation. Tibial tubercle osteotomy was done on 40 tibias from cadavers with equal numbers fixed by either screws or wires. Specimens were loaded cyclically to simulate straight leg raises and then loaded to failure with the patellar tendon oriented 0 degrees or 25 degrees from the tibial axis. Tibial tubercle osteotomy cyclic displacement was greater for wire constructs at 25 degrees than all other constructs. Failure loads were greater for screw constructs at 25 degrees than both wire constructs. Screw constructs failed at 1429 +/- 348 N (0 degrees) and at 1925 +/- 982 N (25 degrees). Wire constructs failed at 1072 +/- 260 N (0 degrees) and at 893 +/- 293 N (25 degrees). Bone mineral density correlated positively with failure loads. Straight leg raise (400 N) and knee extension (250 N) against gravity during rehabilitation should be feasible with either screw or wire fixation after tibial tubercle osteotomy. Special care should be taken for the large patient and patients with decreased bone density.