Subtrochanteric fractures and other complications related to hardware removal in children with slipped capital femoral epiphysis (SCFE) have been well documented.1-3 Subtrochanteric fractures after cannulated screw fixation of femoral neck fractures in adults have also been well recognized,4 and there are several reports on the topic.4,5 However, there are no reports on subtrochanteric fractures after removal of the screws for femoral neck fractures in children.
In this article, we report the case of a child who sustained a subtrochanteric fracture after the screw removal and healing that followed a femoral neck fracture. The patient’s parent provided written informed consent for print and electronic publication of this case report. In addition, our institutional review board approved this case report.
Case Report
A 10-year-old boy was brought to our emergency department with the chief complaint of left hip pain after a car accident. Anteroposterior and axial lateral radiographs showed a displaced cervicotrochanteric femoral neck fracture (Figures 1A, 1B). The patient was admitted to the hospital and underwent closed reduction and internal fixation with two 3.5-mm cannulated titanium screws within 12 hours of arrival. The screws did not cross the physis to avoid iatrogenic injury of the capital femoral epiphysis (Figures 2A, 2B). The entry point was located at the lower level of the lesser trochanter. The lateral cortex was penetrated only once by the guide wire for the placement of each screw.
The patient was discharged to home care with a crutch and an ischial weight-bearing long leg brace for protection from unexpected external force. Two months after surgery, we allowed the patient to walk with the brace and without the crutch. Full-weight-bearing ambulation was allowed 3 months after surgery.
About 9 months after initial surgery, we removed 2 titanium screws, which were completely covered with growing new bone. The lateral cortex surrounding the screw heads was chiseled from the lower level of the lesser trochanter to remove the completely immersed screw heads (Figures 3A, 3B).
After screw removal, we recommended non-weight-bearing crutch-walking for 2 weeks followed by partial weight-bearing with crutch for another month. However, the patient started full weight-bearing 2 weeks after screw removal. One month after screw removal, he was brought to the emergency department with severe left hip pain after missing a step on a path. Anteroposterior and lateral radiographs showed an oblique subtrochanteric fracture at the empty screw holes (Figures 4A, 4B). A plate and 4 screws were placed to stabilize the subtrochanteric fracture, and a hip spica cast was applied and was to be worn for 3 weeks (Figures 5A, 5B).
At final follow-up, 6 months after the second surgery, the fracture was healed, and there had been no complications, such as avascular necrosis of the femoral head and leg-length discrepancy (Figures 6A, 6B).
Discussion
Although in situ pinning of SCFE is a common procedure with good results, the rate of complications of hardware removal can be as high as 34%; these complications are well documented.5 Subtrochanteric fracture as a complication of proximal femoral neck pinning in adults is also well documented.4,5 However, there are no reports on subtrochanteric fractures after screw removal in the treatment of femoral neck fractures in children.
Brooks and colleagues6 emphasized the point that multiple passes weakened the lateral cortex, decreased the energy-absorbing capacity by 55.2%, and increased local stress. Even if a screw is placed in a relatively safe zone above the lesser trochanter, pie-crusting of the cortex can weaken it enough to predispose it to failure under a relatively normal load.7 We inserted 2 cannulated titanium screws without repositioning or multiple drilling, and the femoral neck fracture was united.
The common denominator for subtrochanteric fractures after screw or pin fixation of femoral neck fractures in adults seemed to be the entry point of the lateral cortex below the level of the most inferior edge of the lesser trochanter.4 The pin should have its entry site proximal to the level of the lesser trochnater. Paloski and colleagues7 and Canale and colleagues8 hypothesized that this screw acted as a stress riser to the normal bone, which underwent abnormal loads caused by the patient’s habitus and later mechanism of injury. In our patient’s case, the appropriate starting point for perpendicular penetration of the femoral neck fracture line was on the lateral femoral cortex at the level of the lesser trochanter. We thought this entry on the lateral cortex might predispose the patient to a subtrochanteric fracture. The starting point of the screw is considered the most important factor in preventing fracture after screw removal.