Chronic Nerve Root Injury in Pediatric Patients With Chronic Lumbar Stress Fractures: A Retrospective Review.

INTRODUCTION: Many orthopedic providers currently treat chronic spondylolysis as self-limited fractures. While the condition has previously been associated with back pain in pediatrics, there has been little attention on the risk of neurologic harm. Electromyography (EMG) is a common study used to evaluate nerve injury, but it has not been previously reported for testing pediatric patients with stress fractures. In this study, pediatric patients with chronic pars fractures and muscle extremity weakness who underwent EMG testing were reviewed to analyze their risk of chronic nerve injury. METHODS: 120 pediatric patients who underwent EMG testing between 2015 and 2021 were analyzed, and 41(21F,20M) patients with a mean age of 16(13-20) met criteria of chronic lumbar pediatric spondylolysis with weakness on ankle dorsiflexion or plantarflexion. No exclusions were made. Initial EMG testing was indicated for the extremity weakness; pain was not the major concern. All exams were completed by JWM. Thin-cut lumbar CT studies were done at the same institution, and EMGs were completed by one of three physiatrists. EMGs were determined as normal, abnormal but not meeting chronic nerve injury threshold, or abnormal and meeting threshold for chronic nerve injury. RESULTS: Of the 41 patients, 33 had bilateral and 8 had unilateral fractures with 95% (39/41) of them located at L4 or L5. 55% (18/33) of the bilateral fractures had abnormal EMGs and demonstrated chronic nerve injury; 1 had an abnormal EMG but did meet chronic injury threshold. 75% (6/8) of the unilateral fractures had abnormal EMGs and demonstrated chronic nerve injury; 1 had an abnormal EMG but did meet chronic injury threshold. Overall, 36% (15/41) had normal EMGs, 5% (2/41) had abnormal results but did not reach chronic injury threshold, and 59% (24/41) met threshold for chronic nerve injury. CONCLUSION: Chronic pars fractures have historically been treated as a benign and self-limited sports injury. However, our analysis showed that 59% of adolescent patients presenting with chronic pars fractures and dorsiflexion or plantarflexion weakness have developed a chronic nerve injury. This study is the first to demonstrate the risk of neurologic harm in unhealed pediatric lumbar stress fractures, and it indicates the importance of EMG testing in young patients presenting with chronic spondylolysis and extremity weakness.

Should 25-hydroxyvitamin D and bone density using DXA be tested in adolescents with lumbar stress fractures of the pars interarticularis?

STUDY DESIGN: Retrospective study. OBJECTIVE: To determine if 25-hydroxyvitamin D (25[OH]D) level measurement and bone mineral density (BMD) using dual-energy x-ray absorptiometry (DXA) are indicated in children with a history of stress fracture of the pars interarticularis. SUMMARY OF BACKGROUND DATA: Healing rates of 4%-25% for bilateral and unilateral pars fractures, respectively, have previously been reported. Factors that may contribute to osteomalacia, rickets, and poor bone healing include low (25[OH]D) and low BMD. METHODS: Patients were seen at the Nebraska Spine Center between 2008 and 2010. Selection criteria included a diagnosis of pars fracture with DXA Z-score values (lumbar and hip) and pretreatment serum (25[OH]D) level measurement. Twenty-four patients were included. Vitamin D was defined as sufficient when ≥ 32 ng/mL, insufficient when 20 to < 32 ng/mL, and deficient when < 20 ng/mL. BMD was interpreted from DXA Z-scores using reference intervals defined in the literature. A Z-score <-2.0 was considered low for chronological age. RESULTS: The mean (± SD) vitamin D level was 29.9 ng/mL ± 10.8 (range, 9-56 ng/mL). Values were ≤ 10 ng/mL in 1 patient (4%), 11-20 ng/mL in 4 patients (17%), 21-30 ng/mL in 8 patients (33%), 31-50 ng/mL in 10 patients (42%), and > 50 ng/mL in 1 patient (4%). This correlated to 3 (13%) patients with deficient vitamin D (≤ 15 ng/mL), 12 (50%) patients with insufficient levels, and 9 (38%) with sufficient levels of vitamin D. The mean Z-scores were 0.43 ± 0.93 (lumbar, range, -1.3 to 2.8) and 1.0 ± 1.11 (hip, range, -0.5 to 3.0). All scores were consistent with normal bony mineralization for age. CONCLUSIONS: On the basis of these data, we recommend routine vitamin D testing and do not recommend routine DXA in adolescents with lumbar stress fractures of the pars interarticularis.

Vertebral bone resorption after transforaminal lumbar interbody fusion with bone morphogenetic protein (rhBMP-2).

OBJECTIVE: Bone morphogenetic protein (rhBMP-2) has demonstrated an increased rate of interbody fusion when placed in the intervertebral space. Owing to this advantage, rhBMP-2 is being implanted with increasing frequency in the lumbar spine. The purpose was to quantify and describe the presence of bone resorption within the vertebral body after transforaminal lumbar interbody fusion with placement of rhBMP-2 within the disc space. METHODS: Twenty-six patients were selected from a clinical database. Patients included in the study had undergone a transforaminal lumbar interbody fusion with BMP. Interbody implants included allograft dowels or interbody cages augmented with autograft or allograft bone. A computed tomography study of the lumbar spine a minimum of 3-month postoperatively was another inclusion criterion. Osteolytic defects were grouped into 3 categories on the basis of the size and extent of involvement in the vertebral body. RESULTS: A total of 32 lumbar levels were reviewed. Fourteen males and 12 females with an average age of 46.0 years were included in the study. Bone resorption defects were noted in 22 of the 32 levels reviewed (69%). The defects were characterized as mild in 50% (11 of 22), moderate in 18% (4 of 22), and severe in 31% (7 of 22). CONCLUSIONS: The benefit of rhBMP-2 to promote interbody fusion in the lumbar spine has been well documented. BMP has demonstrated an increased fusion rate and the ability to produce a robust fusion mass. rh-BMP-2's osseous remodeling potential may lead to bone resorption within the vertebral body.