In this retrospective study, we retrospectively analyzed 28 pediatric patients at 14 to 17 years of age with Delbet type II to III femoral neck fractures performed internal fixation with cannulated screws. Our results demonstrated that the thread of cannulated screws cross the epiphysis has no adverse influence on the complications and outcomes, especially on femoral head osteonecrosis.
Delbet Type II and type III fractures are the most common types in pediatric patients with hip fractures. Due to the high failure rate of lost reduction of conservative treatment, operative treatment with internal fixation is preferred [4]. Recently, some authors recommendation use cannulated screws for fixation of Type I-III fractures more than ten years old[4,2,10]. However, the treatment of femoral neck fractures in children age between 14 and 17 years with an open physis can be challenging.
Due to lack of biomechanics data to guide the fixation method and specific algorithms or guideline for hardware selection, the means of fixation are primarily dependent on the surgeon’s preferences [10,4]. There is an increasing body of evidence that suggests that stable fixation should be given priority over preservation of the physis [2,10,15,16,1]. On the other hand, the smaller diameter of the pediatric femoral neck carried the risk of injury to the superior and inferior retinacular arteries with additional hardware[4]. Some authors propose that the cannulated screws can achieve firm and compressive fixation of the fragments. The threads can cross the physis from the age above 15 years without the risk of significant limb length discrepancy from premature growth arrest[17]. The use of small diameter smooth pins, in such situations, can lead to inadequate fixation and distraction of fragments[17,15]. However, it is unclear of whether the transphyseal fixation of cancellous screws in femoral neck fractures patients age 14 to 17 years have negative affect on the complications, especially on the incidence of AVN of the femoral head.
The reported incidence of avascular necrosis after femoral neck fractures varies considerably, range from 0 % to 92% in literatures [18,15,5,6,7,8]. The overall rate of osteonecrosis in our study is 10.7%, with type II of 10.5% (2/19 ) and type III 11.1% (1/9), respectively. The rate of AVN was not significantly related to whether the cancellous screws cross the proximal femur epiphysis. We experienced avascular necrosis only in three cases, and our findings are consistent with more earlier literature[18-20]. Flynn et al. reported only a low rate of 6% of AVN in 18 patients[19]. Swiontkowski and Winquist reported an incidence of 10% in children with displaced fractures of the hip, treated by urgent open reduction, internal fixation[21]. Only a prospective multicenter therapeutic study in India reported a low incidence of 14.2% (4/28)[22]. However, these studies failed to evaluate the influence of transphyseal fixation of the cancellous screw on the complications of Delbet type II to III femoral neck fractures patients age from 14 to 17 years.
One possible reason for the low incidence of AVN might be the stable fixation can facilitate earlier rehabilitation after surgery and sequent reduce the occurrence of AVN. Despite the incidence of avascular necrosis in this study was significantly lower than that reported in the most recent series. While we cannot conclude that the transphyseal fixation of screws accounted for the low incidence, rigid internal fixation may have restored the blood supply to the femoral head. The ability to detect a difference was further confounded by the relatively small sample size and retrospective study nature. Further prospective multicenter study deserves to determine whether the screws should be performed transphyseal fixation in this specific age group patients.
Time to diagnosis of osteonecrosis in our study was highly variable. Hence we reported a median time to diagnosis of osteonecrosis of 7.8 months. Many previous reports have suggested that avascular necrosis of the hip after an injury in children usually presents within one year, our minimum follow-up of 22 months should have detected all potential cases. However, more recent studies have suggested that avascular necrosis becomes evident within 12 to 24 months of injury and therefore, patients should be screened up to 2 or 3 years after injury to identify late development of osteonecrosis with repeat clinical examination and MRI as indicated [23,24,2,19,5]. Next, we should extend the follow-up time to determine the mid-term and long-term outcomes of these patients.
Our study encounters a case of late-onset septic arthritis, secondary idiopathic hip subluxation (Figure 2 A-L). This is the first report of an infrequent complication of a pediatric femoral neck fracture. Fortunately, the functional loss of the affected hip in this boy is limited. The incidence of postoperative infection is relatively rare after hip fractures in children and adolescents, generally reported to occur in 1% to 10% of patients and most often after open reductions as well as after closed reduction with percutaneous fixation[2,16,25,26]. Taylor and McHale [27] reported a deep infection after percutaneous pin fixation of a femoral neck fracture in the 12-year patient.
This study has some limitations. First, this retrospective review with small sample size making it difficult to generate guidelines for treating this rare injury. Second, future longitudinal and multi-center studies should deserve to determine whether the screws should be performed transphyseal fixation in this specific age group patients.