Fibular hemimelia and risk of patellar dislocations: A case series

Abstract

The likelihood of patellar instability and consequently, risk of patellar dislocations is higher in those with anatomical abnormalities. Fibular hemimelia is a congenital disorder resulting in partial or full absence of the fibula, often with absence of the lateral and cruciate ligaments, although this patient group rarely undergoes ligament reconstruction. There is potential for adverse outcomes, in the longer term, including, possible increased risk of patellar dislocation and pain in the knee and hip. We aim to investigate the potential risk of spontaneous, unprovoked patellar dislocation among patients with fibular hemimelia, through a review of medical records and radiological investigations. All patients with a diagnosis of fibular hemimelia were included (n = 25), regardless of ultimate approach to management. Tibiofemoral angle measurement and Caton-Deschamps indices were calculated where suitable radiology was available, to better establish extent of potential patellar instability. All the patients with normal Caton-Deschamps indices had only partial fibular absence, although this does not detract from absence or hypoplasia of the anterior cruciate ligament, as a risk factor for patellar dislocation by predisposing to anterior tibial translation. Notably, of the three patients with increased Caton-Deschamps indices, two had complete fibular absence and underwent definitive amputation surgery at age 18 months and 3 years, respectively. Ultimately, this was a young patient group and on-going follow-up might yield better understanding of knee stability. Maintaining a well-aligned lower limb throughout growth might be protective even in the presence of anatomical abnormalities. This article mainly aims to raise awareness among prosthetic and orthotic professionals regarding the increased risk of patella dislocations.