Knee injuries concomitant to posterior acetabular fractures: an association to look for

Acetabular fractures are frequently associated with other skeletal injuries, particularly knee injuries. This study aims to evaluate the relationship between posterior acetabular fractures and knee injury, analyzing its patterns and association with other injuries.

This is a retrospective monocentric study in a tertiary referral centre. We reviewed the data (age, sex, type of fracture, and concomitant injury) of patients hospitalized for a posterior acetabular fracture. We recorded concomitant knee injury diagnosed up to one year following acetabular fracture.

Two-hundred-seventeen patients (177 males/40 females) were included. The mean age was 40.5 years. Eighty-five patients (39%) had a concomitant hip dislocation, nine (4.1%) had sciatic nerve palsy, 17 (7.8%) had upper extremity injury, and 18 (8.3%) had lower extremity injury (other than the knee). Eight (3.7%) patients had spine injury, 11 (5.1%) had severe thoracic injury, nine (4.1%) had an abdominal injury, and four (1.8%) had a head injury. There were 33 (15.21%, 95% CI 10.80-20.8%) patients (30 M/3 F) (group 1) with a concomitant knee injury and 184 patients without a concomitant knee injury(group 2). The mean age in group 1 was 34.3 compared to 45.4 in group 2(p = 0.021). The pattern analysis revealed five fractures, 14 ligamentous injuries (PCL injuries = 68%), and 14 soft tissue injuries. Sixteen (48.48%) injuries were identified during hospitalization and 17 (51.51%) during follow-up. There were an association between knee injury and upper extremity injury (OR = 3.49 95% CI 1.12-10.00,p = 0.022) and other lower extremity injury (OR = 3.18 95% CI 1.03-8.95,p = 0.032).

Knee injury is the second most frequent lesion associated with posterior acetabular fractures. Being missed in half of cases, we recommend a systematic examination of ipsilateral knees under general anaesthesia, keeping a high index of suspicion and a low threshold for complementary knee imaging. Knee injury should be mainly looked for in patients younger than 60 years and in those with upper and/or lower extremities injuries.