Patellar stress fracture after transosseous extensor mechanism repair: report of 3 cases.

Extensor mechanism injuries are unusual and require early operative intervention to optimally restore extensor mechanism continuity, strength, and function. Quadriceps tendon ruptures typically occur in patients older than 40 years and can be associated with degenerative tendon changes, obesity, systemic illnesses, and trauma. Patellar tendon ruptures are usually seen in younger patients as a result of eccentric trauma. In the acute setting, primary repair is usually undertaken. For tears within the quadriceps or patellar tendon substance, direct repair can be performed, with or without augmentation. When the rupture occurs at the junction of the tendon and the patella, transosseous sutures or suture anchors can be used to reapproximate the tendon-bone interface. Stress fractures of the patella are reportedly rare. They can be seen in association with knee arthroplasty, anterior cruciate ligament (ACL) surgery, and rarely after impact sports. The fracture pattern is usually transverse. Longitudinal stress fractures do not typically disrupt the extensor mechanism and have not, to our knowledge, ever been identified as a postoperative complication of extensor mechanism repair. One instance of a traumatic transverse patellar fracture and extensor mechanism disruption after patellar tendon repair has been described, and a transosseous suture technique was used in that case. No instances of patellar fracture after quadriceps tendon repair have been reported. We report 3 cases of longitudinal patellar stress fractures after extensor mechanism repair using a transosseous suture technique, 2 of which occurred after quadriceps tendon repair and 1 of which occurred after patellar tendon repair.