Working Diagnosis:
Patellar dislocation with loose bodies

Treatment:
Right knee arthroscopy was performed and multiple non-viable chondral loose bodies were found and removed. Medial patellofemoral ligament reconstruction with semitendinosus autograft was performed for the treatment of patellar instability.

Outcome:
The patient was discharged after surgery with brace locked in full extension and physical therapy. After physical therapy, icing, and anti-inflammatory medications, her range of motion and tenderness improved. She had consistent brace progression. At week 6, the patient continued to do well and was coached to wean off crutches during weeks 6-7 and to discontinue her brace on weeks 8-10.

Author's Comments:
The patient's history of a noncontact instability episode with early effusion was concerning for ACL tear or patellar dislocation. By the time of presentation, physical exam was limited due to pain tolerance. Initial Xrays revealed a cortical avulsion fracture (Segond fracture) which is commonly thought pathognomonic for ACL tear. There are reports of a 75-100 percent correlation between a Segond fracture and ACL injury (1). However there were also findings suggesting possible patellar dislocation (trochlear dysplasia, open growth plates). Recurrence rates for patellar dislocation are high depending on the number of risk factors a patient has (3). Children have up to a 71 percent recurrence risk(2). Non-operative treatment is reasonable for a primary dislocation provided there are no osteochondral fragments or loose bodies(3).

Editor's Comments:
A Segond fracture is considered pathognomonic for ACL tear; however, other pathology like patellar dislocation should not be ruled out if the exam is not consistent with an ACL tear.

There is a high risk of recurrence of patellar dislocation. Identification of this pathology, especially if recurrent, will direct treatment options.

References:
1.Goldman, AB, et al. The Segond Fracture of the Proximal Tibia A Small Avulsion That Reflects Major Ligamentous Damage. American Journal of Roentgenology, vol. 151, no. 6, 1988, pp. 1163 to 1167.

2.Poeze, M. Acute Patellar Dislocation in Children and Adolescents A Randomized Clinical Trial. Nederlands Tijdschrift Voor Traumatologie, vol. 16, no. 5, 2008, pp. 158 to 159.

3.Cash, James D., and Jack C. Hughston. Treatment of Acute Patellar Dislocation. The American Journal of Sports Medicine, vol. 16, no. 3, 1988, pp. 244 to 249.

4. Runow, Anders. The Dislocating Patella. Acta Orthopaedica Scandinavica, vol. 54, no. sup201, 1983, pp. 1 to 53.

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