Tibial tubercle fragmentation: a clue to simultaneous patellar ligament avulsion in pediatric tibial tubercle fractures.

Simultaneous avulsions of the tibial tubercle and patellar ligament have been reported, but are rare. We present an 11-year-old boy who was initially diagnosed with a Type IIIA tibial tubercle avulsion fracture after falling off of his bicycle. Intraoperatively, following exposure and fixation of the tibial tubercle fragment, knee range of motion under live fluoroscopy revealed a stationary patella with no tension in the patellar ligament. The incision was extended and a distal avulsion of the patellar ligament from the tibial tubercle was identified, with a small flap of tibial tubercle periosteum remaining attached. Transosseous suture fixation of the avulsed periosteal flap was achieved with 2 No. 5 ethibond sutures placed through connecting drill holes. Postoperatively, the patient was placed in a long leg cast with the knee in extension for 6 weeks. The injury to healed and the patient returned to full activities, although he required 2 courses of physical therapy and 4.5 months to regain full range of motion. Preoperative diagnosis of simultaneous tibial tubercle fracture and patellar ligament avulsion can be difficult. Palpation of the patellar ligament for gaps may not be possible due to a large knee effusion. Most patients do not tolerate quadriceps testing on examination and do not have patella alta on radiographs. In retrospect, a clue to this diagnosis in our patient was the preoperative radiographic finding of multiple calcified fragments below the patella. The calcified fragments likely represent the avulsed tibial tubercle periosteum attached to the distal patellar ligament. In addition, the large tibial tubercle fragment is separated and rotated superiorly, a finding that was also noted in two other similar case reports.