Rare case of posterior hip dislocation caused by low-energy trauma in a boy in early adolescence: acute and long-term management–review of the literature

Background

Traumatic posterior hip dislocation is an uncommon injury in children, constituting less than 5% of paediatric dislocations. In a young child (less than 5 years), minor trauma such as a slip or fall from a low height may result in hip dislocation; whereas in an adolescent, a hip dislocation is usually caused by major trauma (eg, motor vehicle accident).1 In children less than 5 years of age, the dislocation can occur due to the soft pliable acetabulum and ligamentous laxity. As the skeleton progressively matures with age, and the surrounding ligaments thicken, a greater force is required to dislocate the hip joint. In this report, we present a case of hip dislocation from a low-velocity fall on grass in a healthy, young adolescent boy. Early diagnosis with urgent closed reduction ensured good outcome in our case. A high index of suspicion is necessary to achieve satisfactory reduction within 6 hours of dislocation since reduction after this period will greatly increase the risk of complications (eg, avascular necrosis (AVN) of the hip, skeletal deformities).

Case presentation

A boy in early adolescence was brought to the emergency department with severe pain in the right hip following a fall while running on grass. He was noted to be in a fetal position with restricted movement on examination. There was severe tenderness in the right groin area with noted internal rotation and adduction of the right lower extremity. The range of motion in the right hip was difficult to assess due to the patient’s discomfort and distress, but no neurovascular impairment was determined. The patient was guarding the testicular area making it difficult to examine and raise concerns for testicular torsion by Accident and Emergency staff.

The medical history of the patient revealed a healthy, well-developing child with occasional asthma episodes controlled by inhalers. There was no history of trauma, developemental dysplasia of the hip (DDH) or joint laxity.

Investigation

An X-ray of the pelvis was performed (figure 1) and showed a posterior dislocation of the right hip joint. The patient was brought to the operating room and closed reduction of the hip was performed under general anaesthesia (GA) within 4 hours of the dislocation using the Allis method very gently (figure 2). The fluoroscopic examination following the reduction confirmed a stable reduction of the right hip joint. Post-reduction stability of the right hip joint was also assessed and showed a stable hip at 100° of flexion and 20° of adduction. A detailed testicular examination after the reduction was additionally performed while under GA and excluded any testicular pathology. An above the knee skin traction was applied following the procedure and the patient was scheduled for an MRI of the right hip.

Figure 1

X-ray of the hips and pelvis performed on admission.

Figure 2

X-ray of the right hip performed immediately after the hip reduction in operating theatre under general anaesthesia.

The MRI report (figure 3) revealed concentric reduction of the right hip with normal anatomical positioning of the femoral head and a small separate bony fragment found posteriorly of the femoral head, which is consistent with a posterior acetabular wall fracture, and a diagnosis of a type 1 acetabular fracture was made according to the Thompson-Epstein classification. The MRI also accentuated the extensive soft-tissue oedema and a horizontally oriented partial tear of the proximal right piriformis muscle. The scan failed to display any evidence of underlying developmental abnormalities of the hip joint itself. The skin traction was removed following completion and reading of the MRI scan.

Figure 3

Post-reduction MRI of the right hip.

Outcome and follow-up

The patient was immobilised for 6 weeks following the reduction of the right hip. A repeat MRI was performed after this period of immobilisation and showed a properly healed fracture in the posterior acetabular wall. He was then allowed to partially weight-bear for 2 weeks before transitioning to full weight-bear. He safely returned to sports at 12 weeks postoperatively and denied any pain or complications. He was last seen in the office for his 1-year follow-up, and clinical examination at that time showed a stable and non-painful hip with full range of motion. The patient moved with his family to another town and was lost to follow-up. He was contacted to sign the consent form for publication and denied any problems with the hip joint.