Transverse stress fracture of the proximal patella
A 10-year-old boy presented to a clinic complaining of moderate-to-severe knee pain while playing football. He was a sports person and was an active participant of multiple games including basketball, running events, javelin throw, and so on. He was experiencing moderate knee pain since past one and half months. However, since the pain was gradually worsening, he rushed to the clinic. Upon presentation, there were no signs of external injury or hemorrhage.
The most likely diagnosis of this presentation is
- Transverse stress fracture
- Knee dislocation
- Ligament/tendon tear
Stress fractures are one of the most common sports injuries and often characterized by localized bone or periosteal pain, especially during the physical activity or playing. Stress fractures can result from participation in multiple activities and sports, especially those involving running, jumping and repetitive motions causing stress. However, sports including hockey, golf, swimming, fencing, and softball are rarely associated with stress fractures. Athletics, or track and field sports, account for 50% of stress fractures in men and 64% in women.1 Fractures of the patella account for around 1% of all fractures, indicating the rare prevalence of patellar stress fractures. The recommended treatment approach for these fractures include surgical or conservative approach. 2
There were no signs of ligamentous laxity and effusion. The range of motion was normal. However, there was a mild stiffness at the left proximal patella. The x-ray showed a transverse fracture of the left proximal patella suggesting a diagnosis of transverse stress fracture of the left proximal patella. The femorotibial angle of the left knee was 174° and that of the right knee was 176°. The roentgenographic patellofemoral congruence was almost normal.
Initially, the patient was treated conservatively for almost months and he was asked not to play any kind of sports during the treatment. However, conservative treatment failed to relieve the pain completely and the patient presented to the orthopedic department of the hospital. Since the diagnosis of nonunion of a proximal transverse patella stress fracture was confirmed through the radiograph, the surgical approach was undertaken. Surgery involved a 2-cm anterior longitudinal incision over the superior portion of the patella and the fracture was drilled and internally fixed using Acutrak mini screws. Upon follow up after three months of surgery, the knee pain was completely resolved and he returned to his previous sports activities and daily routine.
The most common sites of stress fractures in adult athletes include tibia, tarsal bones, metatarsal bones, femur, fibula, pelvis, sesamoids, the spine. While in children, the common sites included tibia, fibula, femur, radius, metatarsals, and the humerus. Risk factors for stress factors are listed in Table 1. Stress fractures of the patella are comparatively rare. In this case, the patient had fracture at the proximal 1/3.
Previous papers have reported patellar stress fractures in soccer players, basketball players, and runners.In this case, the repetitive increase in the patellofemoral joint reaction force due to the Kendo, in addition to the sprints could be an important aspect in the development of the transverse stress fracture.
A surgical approach involving internal fixation with the tension band technique,the cannulated screw technique,curettage, bone grafting, or drilling have all been reported to be effective.
In this case, the repetitive movement with 90° left knee flexion induced by running sprints might have led to the transverse stress fracture of the proximal patella. The nonunion of the transverse stress fracture can be successfully treated with internal fixation using Acutrak screws.
- Sanderlin BW, Raspa RF, et al. Common Stress Fractures. Am Fam Physician. 2003 Oct 15;68 (8): 1527-1532.
- Sayum Filho J, Lenza M, Teixeira de Carvalho R, et al. Interventions for treating fractures of the patella in adults. Cochrane Database Syst Rev. 2015 Feb 27;2:CD009651.
- Atsumi S, Arai Y, Kato K, Nishimura A, et al. Transverse Stress Fracture of the Proximal Patella: A Case Report. Medicine (Baltimore). 2016 Feb; 95 (6): e2649.