Jeffrey B. Knox

The Incidence of Low Back Pain in Active Duty United States Military Service Members

Study Design. Epidemiological study. Objective. To investigate the incidence and risk factors for developing low back pain in active duty military population to include age, sex, race, and rank, and military service. Summary of Background Data. Low back pain is among the most common musculoskeletal conditions worldwide and is estimated to affect nearly two-thirds of the US population at some point in their lives. Low back pain is a multifactorial disease and many risk factors have been implicated including age, race, sex, and marital status. Methods. A query was performed using the US Defense Medical Epidemiology Database (DMED) for the International Classification of Diseases, Ninth Revision, Clinical Modification code for low back pain (724.20). 13,754,261 person-years of data were investigated. Multivariate Poisson regression analysis was used to estimate the rate of low back pain per 1000 person-years, whereas controlling for sex, race, rank, service, age, and marital status. Results. The overall unadjusted incidence rate of low back pain was 40.5 per 1000 person-years. Women, compared with men, had a significantly increased incidence rate ratio for low back pain of 1.45. The incidence rate ratio for the 40+ age group compared with the 20 to 29 years of age group was 1.28. With junior officers as the referent category, junior- and senior-enlisted rank groups had increased incidence rate ratio for low back pain, 1.95 and 1.35, respectively. Each service, when compared with the Marines as the referent category, had a significantly increased incidence rate ratio of low back pain: Army: 2.19, Navy: 1.02, and Air Force: 1.54. Compared with single service members, significantly increased incidence rate ratio for low back pain were seen in married service members: 1.21. Conclusion. Female sex, enlisted rank groups, service in the Army, Navy, or Air Force, age greater than 40 years, and a marital status of married were all risk factors for low back pain.

Superior segment facet joint violation and cortical violation after minimally invasive pedicle screw placement

BACKGROUND CONTEXT Minimally invasive approaches to the lumbar spine allow for pedicle screw placement through a muscle-splitting paraspinal approach. These techniques are highly dependent on fluoroscopy and do not allow for direct visualization of anatomic landmarks. The effect of this on the accuracy of pedicle screw placement is not well described. The purpose of this study was to evaluate the rate of violation of the superior segment facet joint and rates of cortical violation after minimally invasive pedicle screw placement. PURPOSE To evaluate the rate of cortical violation and involvement of the superior segment facet after minimally invasive pedicle screw placement. STUDY DESIGN/SETTING Retrospective chart review. PATIENT SAMPLE Patients who underwent minimally invasive pedicle screw placement by a single surgeon between January 2004 and July 2009. OUTCOME MEASURES Violation of the superior segment facet joint or cortical violation identified on computed tomography (CT). METHODS This study consisted of a consecutive series of adult patients undergoing minimally invasive pedicle screw placement by a single surgeon for degenerative lumbar spinal conditions. Routine postoperative CT was obtained and evaluated for involvement of the superior segment facet joint and for cortical violation. RESULTS Sixty-one consecutive patients (282 pedicle screws) met the study criteria and were included in the study, including 42 single-level fusions and 19 two-level fusions. Seven cortical breaches were identified for a rate of 2.48%. Seven patients had involvement of the superior-level facet for an incidence of 11.48%. One patient required revision for a malpositioned pedicle screw. CONCLUSIONS This study revealed a low rate of superior segment facet violation and cortical violation after minimally invasive pedicle screw placement. This rate of superior-level facet involvement is significantly lower than previously reported after open procedures. The rate of cortical violation is similar to previous reports in the literature with a low revision rate.

Spine Trauma in Very Young Children: A Retrospective Study of 206 Patients Presenting to a Level 1 Pediatric Trauma Center

Background: The immature spine has anatomic and biomechanical properties that differ from the adult spine and result in unique characteristics of pediatric spinal trauma. Although distinct patterns of spinal injury have been identified in children younger than 10 years of age, little research has explored the differing characteristics of spinal trauma within this age group, particularly in the very young. The purpose of this study is to identify differences in the epidemiology and characteristics of spinal trauma between children under the age of 4 years and those between 4 and 9 years of age. Methods: A review of all patients treated for spinal injury at a single large level I pediatric trauma center between 2003 and 2011 was conducted. Demographic data, injury mechanism, neurologic status, and details of any associated injuries were compiled. Radiographic studies were used to determine injury location and fracture classification. The patient population was divided into 2 groups: the infantile/toddler (IT) group (ages 0 to 3 y) and the young (Y) group (ages 4 to 9 y). Data were compared between these groups using the &khgr;2 test and the Student t test to identify differences in injury characteristics. Results: A total of 206 patients were identified. Fifty-seven patients were between 0 and 3 years of age and 149 were between 4 and 9 years old. Although motor vehicle collision was the most common cause of injury in both the groups, nonaccidental trauma was responsible for 19% of spine trauma among patients aged 0 to 3 years. Cervical spine injuries were much more common in the youngest patients (P<0.05) with injuries primarily in the upper cervical spine. Children in the IT group were more likely to sustain ligamentous injuries, whereas Y patients had more compression fractures (P<0.05). Neurologic injury was common in both the groups with IT patients more often presenting with complete loss of function or hemiplegia and Y patients sustaining more spinal cord injuries (P<0.05). IT patients had a 25% mortality rate, which was significantly higher than that of the Y group (P=0.005). Conclusions: This study shows many significant differences in characteristics of spinal injury in infants/toddlers when compared with older children. These differences can help guide diagnostic evaluation and initial management, as well as future prevention efforts. Level of Evidence: Level III.

Characteristics of spinal injuries secondary to nonaccidental trauma

Background: Nonaccidental trauma (NAT) is considered an uncommon cause of spine trauma in the pediatric population. Little has been published on such injuries and no large series is available in the literature. The purpose of this study is to describe the incidence and characteristics of spine trauma secondary to NAT. Methods: An IRB-approved retrospective review of all patients presenting to a single level 1 pediatric trauma center with a spinal injury between 2003 and 2011 was performed. Patients were identified using our institution’s trauma registry. Medical records were reviewed to identify all spine injuries that occurred as a result of NAT. These cases were reviewed for details regarding injury mechanism, type and location of injury, associated injuries, and the treatment. Our institution’s NAT database was also queried to identify the total number of patients formally determined to have sustained any injury as a result of NAT during the same period. Results: NAT was the cause of 11/342 (3.2%) spine injuries diagnosed during the study period. A total of 726 cases of NAT were identified, with spine injury present in 1.5%. All patients with spine trauma secondary to NAT were under the age of 2 years with an average age of 7 months. Among patients below 2 years with spinal trauma, NAT was tied as the most common mechanism, resulting in 38% of injuries. Eight of the 11 patients’ spine injuries were cervical and 7 of these injuries were in the atlanto-occipital and atlantoaxial regions. Multilevel spine trauma was present in 64% of patients. Associated head and thoracic trauma was present in 73% and 36% of patients, respectively. Neurological injury was found in 54% of patients. The majority of injuries were treated nonoperatively and 1 patient required surgical management. Conclusions: NAT represents a very common yet often overlooked cause of spinal trauma in children under the age of 2 years. Because of its frequency in this age group, clinicians should consider including an assessment of the spine in all young NAT patients. Patients with spinal trauma sustained as a result of NAT must undergo a thorough evaluation for associated injuries remote to the spine, neurological deficit, and multilevel spine injury. Summary: NAT is a common mechanism of spinal injury in patients below 2 years of age.

Racial differences in the incidence of acute low back pain in United States military service members.

Study Design. An epidemiological study. Objective. To determine the effect of race on the incidence of acute low back pain, resulting in a health care encounter in active duty military service members. Summary of Background Data. Although racial differences in the incidence of low back pain have been documented in previous studies, currently no consensus exists on the relative risk between these groups. Methods. A query was performed using the Armed Forces Health Surveillance Center database for the International Classification of Diseases, Ninth Revision code for low back pain (724.20). A total of 12,399,276 person-years of data were analyzed and stratified by age, race, and sex. Incidence rates were calculated and compared using the multivariate Poisson regression analysis. Results. A total of 467,950 cases of low back pain resulted in a visit to a health care provider in our population, with an overall incidence rate of 37.74 per 1000 person-years. Asians/Pacific Islanders had the lowest incidence rate of 30.7 and blacks had the highest with 43.7. Female sex and older age were also significant risk factors but with significantly different effect sizes between racial groups. Native Americans/Alaskan Natives demonstrated the greatest effect of age on low back pain incidence rates, with a 126% increase between the youngest and oldest age groups compared with a 36% difference in whites. Conclusion. Race, sex, and age were all found to be significant risk factors for acute low back pain. The highest rates were identified in blacks followed by whites, Hispanics, and American Indian/Alaskan Native, and the lowest rates were identified in Asians/Pacific Islanders. Significant differences in the effect of sex and age were identified between the different racial groups.

Occupational driving as a risk factor for low back pain in active-duty military service members

BACKGROUND CONTEXT Although occupational driving has been associated with low back pain, little has been reported on the incidence rates for this disorder. PURPOSE To determine the incidence rate and demographic risk factors of low back pain in an ethnically diverse and physically active population of US military vehicle operators. STUDY DESIGN/SETTING Retrospective database analysis. PATIENT SAMPLE All active-duty military service members between 1998 and 2006. OUTCOME MEASURES Low back pain requiring visit to a health-care provider. METHODS A query was performed using the US Defense Medical Epidemiology Database for the International Classification of Diseases, Ninth Revision, Clinical Modification code for low back pain (724.20). Multivariate Poisson regression analysis was used to estimate the rate of low back pain among military vehicle operators and control subjects per 1,000 person-years, while controlling for sex, race, rank, service, age, and marital status. RESULTS A total of 8,447,167 person-years of data were investigated. The overall unadjusted low back pain incidence rate for military members whose occupation is vehicle operator was 54.2 per 1,000 person-years. Compared with service members with other occupations, motor vehicle operators had a significantly increased adjusted incidence rate ratio (IRR) for low back pain of 1.15 (95% confidence interval [CI] 1.13-1.17). Female motor vehicle operators, compared with males, had a significantly increased adjusted IRR for low back pain of 1.45 (95% CI 1.39-1.52). With senior enlisted as the referent category, the junior enlisted rank group of motor vehicle operators had a significantly increased adjusted IRR for low back pain: 1.60 (95% CI 1.52-1.70). Compared with Marine service members, those motor vehicle operators in both the Army, 2.74 (95% CI 2.60-2.89), and the Air Force, 1.98 (95% CI 1.84-2.14), had a significantly increased adjusted IRR for low back pain. The adjusted IRRs for the less than 20-year and more than 40-year age groups, compared with the 30- to 39-year age group, were 1.24 (1.15-1.36) and 1.23 (1.10-1.38), respectively. CONCLUSIONS Motor vehicle operators have a small but statistically significantly increased rate of low back pain compared with matched control population.

The effects of restraint type on pattern of spine injury in children

Introduction: While the use of vehicular restraints has reduced the morbidity and mortality of children involved in motor vehicle collisions (MVC), to our knowledge, no study has examined the relationship between restraint type and patterns of pediatric spinal injuries. The purpose of this study is to evaluate this association and review the spinal injuries sustained in children involved in MVC. Methods: We completed an IRB-approved, retrospective chart review of all patients below 10 years of age presenting to a level 1 pediatric trauma hospital with spine injuries sustained in MVC from 2003 to 2011. We reviewed prehospital data, medical records, and radiographs to establish the restraint type and characterize the spinal injuries sustained. Results: A total of 97 patients were identified with spinal trauma secondary to MVC with appropriate and documentation of restraint type. Results are reported regardless of whether the restraint employed was properly used per established guidelines. Car seat/booster seat (C/B) patients sustained significantly higher rates of cervical spine (62%) and ligamentous (62%) injuries than the 2-point (2P) (10%) and 3-point (3P) restraint (24%) groups (P<0.001). Two-point and 3P restraint use was associated with significantly higher rates of thoracolumbar injuries (67% and 62%, respectively) than the C/B (14%) and unrestrained (0%) groups (P<0.001). Two-point and 3P passengers also had a higher rate of flexion-distraction injuries (P<0.001). Patients in the unrestrained group sustained a significantly higher rate of cervical spine (80%) and ligamentous (40%) injuries than the 2P and 3P groups (P<0.001). No differences were found in the type or location of injury between the 2P and 3P groups. Significant differences in proper restraint use were identified between age groups with younger children demonstrating higher rates of proper restraint use (P<0.01). Conclusions: Two-point or 3P seatbelt use is associated with lower rates of cervical spine trauma but higher rates of thoracic and lumbar trauma, particularly flexion-distraction injuries, when compared with car or booster seats. Children in C/B and those who are unrestrained sustain high rates of cervical spine injury. Level of Evidence: Level III—prognostic study.

Pediatric lateral distraction injury of the lumbar spine: a case report

BACKGROUND CONTEXT Lateral distraction injuries represent a very rare pattern of injury with only five cases reported in the literature. Such injuries are a result of high-energy trauma and have a high association with severe concomitant injuries. All previous reports of this injury are in skeletally mature individuals, and this has not been previously described in young children. PURPOSE To report a case of a lateral distraction injury in a young child secondary to improper seat belt use. STUDY DESIGN Case report and review of the literature. PATIENT SAMPLE Case report of an 8-year-old girl involved in a highway speed head-on collision. METHODS We report here on an 8-year-old girl who was lying supine in the backseat of a motor vehicle while wearing a lap belt when the vehicle was involved in a high-speed motor vehicle crash. She presented with focal back pain, abdominal pain, and a seat belt sign. Imaging demonstrated focal coronal plane deformity with unilateral ligamentous disruption. The patient was diagnosed with a ligamentous lateral distraction injury of the lumbar spine. This injury was treated with open reduction and posterior spinal fusion with pedicle screw fixation. RESULTS The patient tolerated the procedure well and had an uneventful postoperative course. CONCLUSIONS In this case, we describe a lateral distraction injury in a young child secondary to improper seat belt use. This represents the first description of such an injury in this age group, and this case highlights the spectrum of injury caused by improper seat belt use in the pediatric population.

Flexion-distraction injuries in children and adolescents

Flexion-distraction injuries represent an uncommon pattern of injury in the pediatric population. Although this is a well-studied topic in adults, the literature on such injuries in children and adolescents is relatively sparse, with only low levels of evidence available to guide treatment. These injuries carry a high rate of concomitant injuries and a high morbidity and mortality in this population. Proper understanding of these complex injuries is important to ensure proper management and avoid complications.

Thoracic and Lumbar Spine Injuries

The thoracic and lumbar spine is among the most common sites of injury in the military population. These injuries result in a significant burden to the military healthcare system and carry significant implications for military readiness. The causes of these injuries are numerous with complex interactions between external and intrinsic factors. Military-specific activities and training are commonly implicated in the development of back pain including fitness training, marching, and combat training. Within the military, specific occupations have also been shown to be associated with higher rates of injury and back pain. Such occupations include aviators, drivers, and those involved in military parachuting. Military deployments also represent high-risk periods for development of back pain, which results in a significant amount of lost duty days and evacuations from theater. Such injuries range from minor back injuries to serious combat-related spine trauma. Combat-related spine trauma is an increasingly common injury in modern combat environments due to an increase in survival from other injuries as well as a shift in tactics from previous combat engagements. These injuries carry some important differences from civilian spine trauma with important implications in evaluation and management.