Combined Tibial Tubercle Avulsion Fracture and Patellar Avulsion Fracture: An Unusual Variant in an Adolescent Patient
Traumatic extensor dysfunction of the knee in children is a rare injury, with the majority resulting from tibial tubercle avulsion fracture or patellar sleeve fracture. We report a rare case of combined patellar avulsion fracture and tibial tubercle fracture. With open anatomic reduction, both injuries were successfully treated. While many variations of tibial tubercle fracture have been reported, the authors believe this to be the first report in the English-language literature of this particular combined injury to the knee extensor mechanism in an adolescent. Advanced imaging with computed tomography provided vital information to aid with operative planning, especially since the majority of the unossified tubercle was not seen on plain radiographs, and all fracture fragments were originally believed to be from the tibial tubercle. Computed tomography distinguished the patellar fracture from the tibial tubercle fragments, verifying preoperatively the complexity of the injury.
Discussion
Tibial tubercle fractures typically result from quadriceps contraction during sporting activities, predominantly in adolescent boys with open physes. Numerous modifications and additions have been made to the original classification of such fractures by Watson-Jones,2 most notably by Ogden and colleagues3 in 1980. These additions have included combined tendon avulsions and tubercle fractures as described by Frankl and coauthors,4 complete proximal tibial physeal separation now classified as type 4 by Ryu and Debenham,5 and a “Y” fracture configuration now termed type 5 by McKoy and Stanitski.6 Pandya and colleagues8 reported on 41 tibial tubercle fractures and described a new classification scheme based on the known anatomical closure pattern of the proximal tibial physis and tibial tubercle apophysis. The authors stressed the role of advanced imaging, such as CT or magnetic resonance imaging, in preoperative management of these complex high-energy fractures in adolescents, and the need for intraoperative arthroscopy or arthrotomy to ensure anatomical reduction of the articular involvement.
Tibial tubercle fractures and extensor mechanism injuries that do not fit these classification patterns have also been described. In 1979, Houghton and Ackroyd9 reported 3 cases of acute loss of extensor mechanism secondary to a traumatic patellar sleeve avulsion. In 1995, Berg10 described an ipsilateral inferior pole osteochondral patellar avulsion fracture with patellar tendon avulsion without fracture at the tubercle in a 12-year-old boy. Another variant was described in a 2002 case series of 3 adolescent boys who underwent operative fixation for tibial metaphyseal partial-sleeve avulsion injuries.11
Conclusion
We report a case of combined ipsilateral inferior lateral patellar avulsion fracture and an intra-articular tibial tubercle avulsion fracture with intervening longitudinal patellar tendon split. Preoperative standard radiographs were confusing, given the bony fragment high up by the patella, but use of advanced imaging, in this case CT, allowed us to fully characterize the origin of fracture fragments and realize we were dealing with a unique fracture pattern previously unreported in a pediatric patient. The CT findings allowed us to be better prepared preoperatively by having options for fixation of the patellar fracture, and the extent of articular involvement led us to decide that intra-articular evaluation would be required. Through the use of an open arthrotomy, anatomical articular reduction could be visualized and stabilized with screw fixation of the large, mostly cartilaginous tubercle fracture. Following the principles described by Pandya and colleagues,8 anatomical reduction was achieved, and, 6 months after the original surgery, the patient had return of full motion, clinical and radiographic union, and no clinical pain or limp, with no retained metallic implants across the tibial apophysis. Longer-term follow-up as planned will demonstrate any growth abnormality that would require further surgical intervention.
