Working Diagnosis:
Fracture of pedunculated osteochondroma.

Treatment:
Surgical excision of fragment and stalk Case Photo #4

Outcome:
Patient returned to full activity 2 weeks post-operatively

Author's Comments:
An osteochondroma is a cartilage-capped bony spur arising on the external surface of a bone. Osteochondromas usually occur around the knee or the proximal humerus. The distal femur is the most common location. Osteochondromas can cause pain, functional problems, deformity, pathologic fracture and there is a small lifetime risk of malignant transformation to chondrosarcoma.

The differential diagnosis of osteochondroma includes periosteal osteosarcoma and this needs to be excluded as part of the management. Osteochondromas grow throughout childhood; they generally stop growing when the physes (growth plates) close and remain static throughout adulthood.

Editor's Comments:
An osteochondroma is the most common benign bone tumor and is typically noted incidentally or if there is an associated complication, as in this case. More than one within the same patient should prompt investigation into hereditary multiple exostoses which is a disorder inherited in an autosomal dominant pattern. When managing osteochondromas, they can be observed without the need for resection as long as they are asymptomatic and there are no concerning features on imaging. The risk of malignant transformation is 1% overall and rises with increasing thickness of the cartilage cap. Approximately half of all osteochondromas are located around the knee at the distal femur or proximal tibia, 10-20% are located in the humerus, followed by smaller contributions from the feet and hands, and flat bones which account for only 5% of cases. They are most often found at the metaphysis and grow in the opposite direction from the joint, as in this case.

This case additionally highlights an important point in this patient population. While we, as clinicians, often attempt to avoid imaging in the pediatric population when possible, we also need to have a low threshold to pursue imaging when a patient’s symptoms dont explain the clinical scenario as was done in this case. In this patient there was a clear trauma, although not ordinarily one that would provoke us to consider a fracture as it appears to be relatively low velocity. Despite the fact that all of the typical musculoskeletal exam maneuvers did not yield any clues to the diagnosis, imaging was ordered for this patient. In this case the imaging was the key component in making the diagnosis and arranging appropriate referral for this patient to have an optimal outcome.

References:
1. Kose O1, A. Ertas, M. Celiktas, B. Kisin. Fracture of an osteochondroma treated successfully with total excision: two case reports. Cases J, 2 (2009), p. 8062.
2. Davids JR1, G.L. Glancy, R.E. Eilert. Fracture through the stalk of pedunculated osteochondromas. A report of three cases. Clin Orthop Relat Res, 271 (1991), pp. 258-26
3. Mishra PK, Gupta A, Gaur SC, Dwivedi R. Non-Traumatic Fracture Of Pedunculated Osteochondroma - A case report and brief review of literature. J Orthop Case Rep. 2013;3(4):46-48.
4. Tepelenis K, Papathanakos G, Kitsouli A, et al. Osteochondromas: An Updated Review of Epidemiology, Pathogenesis, Clinical Presentation, Radiological Features and Treatment Options. In Vivo. 2021;35(2):681-691.
5. Kai Tong, Hongzhe Liu, Xiang Wang, Ziyi Zhong, Shenglu Cao, Chengjie Zhong, YunPing Yang, Gang Wang, Osteochondroma: Review of 431 patients from one medical institution in South China, Journal of Bone Oncology, Volume 8, 2017,Pages 23-29.

Acknowledgments:
NA

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