Biomechanical analysis of flat and oblique tibial tubercle osteotomy for recurrent patellar instability

Both flat (Elmslie-Trillat) and oblique (Fulkerson) osteotomy techniques ar e successful in treating patellar instability episodes by moving the tibial tubercle medially. The oblique osteotomy also results in anterior displace ment that decreases patellofemoral forces. Recent reports have described pr oximal tibial fractures occurring during early weightbearing after oblique osteotomy. We performed oblique and Rat osteotomies on 13 pairs of fresh-fr ozen cadaveric knees. The knees were then tested to failure on a materials testing system by exerting a load through the quadriceps tendon at a rate o f 1000 N/sec to simulate a stumble injury. The failure mechanism for flat o steotomies was more likely to be tubercle "shingle" fracture, while oblique osteotomies more frequently failed through a tibial fracture or fixation f ailure in the posterior tibial cortex. Mean load to failure was significant ly higher in the flat osteotomy specimens (1639 N versus 1166 N), as was to tal energy to failure (224 N.m versus 127 N.m). There was no significant di fference in stiffness (87 N/cm versus 74 N/cm). We recommend the flat osteo tomy for patients with isolated recurrent patellar instability and the obli que osteotomy in patients who have concomitant patellofemoral pain or artic ular degenerative changes. When an oblique osteotomy is used, we recommend postoperative brace protection and restricted weightbearing until the osteo tomy heals.