Extensor Mechanism Injuries of the Knee: Demographic Characteristics and Comorbidities from a Review of 726 Patient Records

Abstract

Background: The purpose of our study was to describe and compare extensor mechanism injuries with regard to age, sex, body mass index (BMI), and comorbidities.

Methods: We identified patients who had undergone surgical management of an extensor mechanism injury at two institutions between 1986 and 2012. Data analyzed included age at the time of surgery, sex, height, weight, and the presence of medical comorbidities. Patients with chronic disruption of the quadriceps or patellar tendon, those undergoing revision surgery, or those with injuries in the setting of total knee arthroplasty were excluded.

Results: Seven hundred and twenty-six patients were included. There were 427 (58.8%) patellar fractures, 210 (28.9%) quadriceps tendon ruptures, and eighty-nine (12.3%) patellar tendon ruptures. Sixty-seven percent of the patellar fractures occurred in females, while 91% of the quadriceps and 95.5% of the patellar tendon ruptures occurred in males (p < 0.001). Age distribution was significantly different among the groups: the mean patient age (and standard deviation) was 61.0 ± 13.1 years (range, twenty to ninety-two years) for quadriceps tendon rupture, 56.3 ± 17.4 years (range, sixteen to ninety-one years) for patellar fracture, and 39.5 ± 12.2 years (range, eighteen to seventy-two years) for patellar tendon rupture. Patellar fractures showed a bimodal distribution with regard to both age and sex: the median age of females was sixty-two years (range, sixteen to ninety-one years), and the median age of males was forty-seven years (range, sixteen to ninety-one years) (p < 0.001). BMI varied significantly among the cohorts: a mean of 25.0 ± 5.2 kg/m2 for patellar fracture, 28.7 ± 4.97 kg/m2 for patellar tendon rupture, and 30.0 ± 6.05 kg/m2 for quadriceps tendon rupture (p < 0.001). Ninety-six percent of the females with a quadriceps or patellar tendon injury had an underlying medical comorbidity compared with 68% of the males (p = 0.008). Of the patients with underlying comorbidities, 61% of the females had comorbidities that were considered to be risk factors for tendinopathy compared with 34% of the males (p = 0.008).

Conclusions: Females with an extensor mechanism injury are more likely to sustain a patellar fracture compared with males. Younger males are more likely to sustain a patellar fracture or patellar tendon rupture; however, we found that 43% of the patellar tendon ruptures were in patients over the age of forty. Medical comorbidities were common with tendon ruptures, and we found that they were significantly more common in females than in males.

Clinical relevance: Surgeons treating female patients with a tendinous extensor mechanism disruption should have a low threshold to initiate a medical work-up in search of a possible undiagnosed medical comorbidity.