Lumbar disc height and vertebral Hounsfield units: association with interbody cage subsidence.

OBJECTIVE: Postoperative subsidence of transforaminal lumbar interbody fusion (TLIF) cages can result in loss of lordosis and foraminal height, and potential recurrence of nerve root impingement. The objectives of this study were to determine factors associated with TLIF cage subsidence. Specifically, the authors sought to determine if preoperative disc height compared to cage height could be used to predict TLIF interbody cage subsidence, and if decreased postoperative vertebral Hounsfield units (HUs) predisposed to cage subsidence. METHODS: The authors retrospectively reviewed all patients undergoing instrumented TLIF from two institutions between July 2004 and June 2014. The preoperative disc height was measured for the operative and adjacent-level disc on MRI. The difference between cage and disc heights was measured and compared between the subsidence and nonsubsidence groups. The average HUs of the L1 vertebral body were measured on CT scans. RESULTS: Eighty-nine patients were identified with complete imaging and follow-up information. Forty-five patients (50.6%) had evidence of interbody cage subsidence on follow-up CT. The average cage subsidence was 5.5 mm (range 2.2-10.8 mm). The average implant height was significantly higher in the subsidence group compared to the nonsubsidence group (12.6 vs 11.2 mm). Additionally, the difference between cage height and preoperative adjacent-level disc height was also significantly larger in the subsidence group (3.8 vs 1.2 mm). First lumbar vertebral body (L1) HUs were significantly higher in the nonsubsidence versus the subsidence group (167.8 vs 137.71 HUs, p = 0.002). Multivariate logistic regression analysis identified suprajacent disc height and L1 HUs to be independent predictors of interbody cage subsidence. Receiver operating characteristic curves identified a suprajacent to cage height difference > 1.3 mm to have a 93.3% sensitivity for cage subsidence. CONCLUSIONS: This study is the first of its kind to demonstrate the association between vertebral body HUs and suprajacent disc height with the development of interbody cage subsidence after TLIF. The authors found that patients with lower HUs in the L1 vertebral body were more likely to experience subsidence, regardless of surgical level. Additionally, the study demonstrated that interbody cage height > 1.3 mm above the height of the suprajacent level is an independent risk factor for cage subsidence, with 93.3% sensitivity. These findings suggest that these factors may be utilized to create a template preoperatively for intraoperative cage selection.

Fascia Iliaca Blockade With the Addition of Liposomal Bupivacaine Versus Plain Bupivacaine for Perioperative Pain Management During Hip Arthroscopy: A Double-Blinded Prospective Randomized Control Trial.

PURPOSE: To determine in a prospective, randomized fashion whether liposomal bupivacaine extends the effectiveness of decreased pain scores and reduces narcotic requirements following hip arthroscopy when used in addition to a fascia iliaca blockade with plain bupivacaine alone. METHODS: Double-blinded prospective randomized controlled trial of participants undergoing hip arthroscopy. Randomized to receive a fascia iliaca blockade with 40 mL 0.25% plain bupivacaine (100 mg; control group) or 20 mL 0.5% plain bupivacaine (100 mg) plus 20 mL liposomal bupivacaine (266 mg; study group). The primary outcome was Defense and Veterans Pain Rating Scale (DVPRS) scores in the postanesthesia care unit and on postoperative days (POD) 1, 2, 3, and 14. Secondary outcomes included postoperative opioid consumption and subjective loss of anterior thigh sensation. RESULTS: Seventy-four patients were enrolled, and 70 completed the study; 37 were randomized to the control group and 33 to the study group. There was no significant difference in postoperative DVPRS scores at any time point. There was no significant difference in total postoperative opioid use during any postoperative time points. While most patients reported anterior thigh numbness at discharge, significantly more patients in the study group reported anterior thigh numbness at POD2 (control, 19/37 numb vs study, 32/33 numb; P < .0001) and at POD3 (control, 8/37 numb vs study, 26/33 numb; P < .0001). CONCLUSIONS: In this prospective evaluation comparing plain bupivacaine versus the liposomal formulation administered via a fascia iliaca blockade there were no significant differences in postoperative pain scores and narcotic pill usage. Given the highly significant findings of prolonged anterior thigh numbness out to POD3 in patients who received liposomal bupivacaine, this formulation did exhibit prolonged effects; however, it did not provide improved pain control when used in this surgical population, likely due to the innervation of the hip capsule from differential nerve plexi. Given the 6-fold increased cost of using the liposomal formulation, we are unable to recommend its use via a fascia iliaca blockade for hip arthroscopy. LEVEL OF EVIDENCE: Level I, therapeutic study.

Incidence and Risk Factors of Acute Patellar Tendon Rupture, Repair Failure, and Return to Activity in the Active-Duty Military Population.

BACKGROUND: Patellar tendon ruptures have a reported incidence of 0.68 per 100,000 person-years in the general population. The epidemiology of surgically treated patellar tendon ruptures in the US military has yet to be reported, which would provide opportunity for identification of risk factors for these otherwise healthy and active patients. PURPOSE: To determine the incidence of patellar tendon rupture in the Military Health System (MHS) population and to analyze demographic patterns, surgical fixation methods, and rerupture rates. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: We utilized the MHS Data Repository (MDR) to identity active-duty military servicemembers surgically treated for patellar tendon rupture between 2010 and 2015. Records were reviewed for demographic information, injury characteristics, fixation technique, and occurrence of rerupture. Risk factors for rupture were calculated using Poisson regression based on population counts and demographic data obtained in the MDR. Risk factors for rerupture and return to duty were analyzed via univariate analysis and multivariate regression. RESULTS: A total of 504 operatively treated primary patellar tendon repairs in 483 patients were identified, with an overall incidence of 6 per 100,000 person-years. Mean age was 33.6 years (range, 17-54 years) and 98% of patients were male. Fixation method was 81% bone tunnels and 7% suture anchors, and 12% were unknown. Black race had a higher relative rate ratio for rupture compared with the race categories White (9.21; P < .0001) and Other (3.27; P < .0001). The rupture rate was higher in 35- to 44-year-old patients compared with those aged 18 to 24 years (P < .0001), 25 to 34 years (P < .0001), and 45 to 64 years (P = .004). Return to full previous level of activity occurred in 75.8% of patients, 14.6% returned to activity with limitations, and 9.5% were medically separated. The rerupture rate was 3%. Fixation method, tobacco usage, body mass index, and race were not significant risk factors for rerupture. CONCLUSION: The incidence of patellar tendon rupture in the US military population is substantially higher than has been reported in the civilian population. Among military personnel, men, Black servicemembers, and those aged 35 to 44 years were at highest risk for patellar tendon rupture. Three-quarters of patients were able to return to full activity without limitations. The rerupture rate was low and unaffected by fixation method.

The effect of lumbar corticosteroid injections on postoperative infection in lumbar arthrodesis surgery.

We sought to characterize the association between lumbar corticosteroid injections and postoperative infection rate for patients in the Military Health System undergoing lumbar arthrodesis. The Military Health System Data Repository was searched for all patients undergoing lumbar arthrodesis from 2009 to 2014. Current Procedural Terminology (CPT) codes were used to identify the subset of patients who also received preoperative lumbar corticosteroid injections. These patients were stratified by timing, type, and number of injections. Infection rates were compared to the control group of patients who did not receive preoperative lumbar corticosteroid injections. The search identified 3403 patients who had undergone lumbar arthrodesis from 2009 to 2014 within the Military Health System. 612 patients had received lumbar corticosteroid injections prior to surgery (348 epidural, 264 facet). The control group consisted of the remaining 2791 patients. Overall post-operative infection rate was 1.47% with an infection rate in the injection group of 1.14% versus 1.54% in the control group. When stratified by time, infection rates ranged from 0% to 1.85% in the injection groups. No differences between injection and control groups reached statistical significance in any subgroup analysis. Post-operative infection rate is not significantly increased in patients receiving lumbar corticosteroid injections (LCSIs) prior to lumbar arthrodesis. No differences were observed in infection rates based on timing, type, or number of injections prior to surgery.

Population-based Risk Factors for the Development of Degenerative Disk Disease.

STUDY DESIGN: This is a retrospective case control study. OBJECTIVE: Identify risk factors and assess their relative impact on the development of degenerative disk disease (DDD). SUMMARY OF BACKGROUND DATA: DDD is responsible for widespread disability in the civilian and military population. Despite the impact of low back pain and DDD, its multifactorial etiology is not entirely understood. MATERIALS AND METHODS: The Defense Medical Surveillance System was searched for military members with the diagnosis of DDD as identified with the use of International Classification of Disease, 9th Revision (ICD-9) codes. These patients were compared with an age-matched and sex-matched control of military members without DDD from the Defense Medical Surveillance System. The prevalence of risk factors (obesity, hip, and knee osteoarthritis, tobacco dependence, diabetes, and type of employment) was then determined for both groups. In total, 160,911 patients with DDD were identified compared with 315,225 controls. Multivariate conditional logistical regression analysis was utilized to determine odds ratio (OR) for these groups based on data matched by age and sex and were adjusted for military rank and race/ethnicity. RESULTS: Diabetes showed an OR of 1.469 [confidence interval (CI), 1.350-1.598]. Hip and knee arthritis produced an OR of 2.925 (CI, 2.685-3.187) and tobacco dependency showed an OR of 1.799 (CI, 1.762-1.836). The comparison of overweight to normal body mass index produced an OR of 1.334 (CI, 1.307-1.361) and the analysis of obese to normal body mass index had an OR of 1.556 (CI, 1.497-1.618). There failed to be a clinically significant association between military duty assignments and the presence of DDD. CONCLUSIONS: Our research failed to show a clinical significance association between military duty assignment and DDD. However, we were able to identify a significant association between concomitant hip and knee osteoarthritis, obesity, diabetes, and tobacco dependency with the development of DDD. LEVEL OF EVIDENCE: Level IV.

Extra-Articular Retained Missiles; Is Surveillance of Lead Levels Needed?

Background: Although gunshot wounds are relatively common, lead toxicity associated with extra-articular retained missiles (EARMs) is an uncommon, yet potentially devastating, complication. Although the risk of lead toxicity with intra-articular retained missiles is well known, EARMs are routinely left in situ or only removed in selected circumstances secondary to the relatively rare occurrence of complications. Methods: We first describe a patient with systemic lead poisoning associated with retained lead fragments after a gunshot-induced left femoral shaft fracture. We then performed a systematic review of the literature to answer the following questions: (1) In the setting of retained extra-articular bullets and/or bullet fragments, is regular monitoring and/or surveillance of lead levels in the blood routinely indicated? and, if so, (2) what are the selected factors that portend an increased risk for elevations in blood lead levels in the setting of retained extra-articular bullets and/or bullet fragments? The systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines, of the English language literature utilizing Medline (PubMed), EMBASE, Cochrane, and CINAHL on the topic of lead poisoning, retained bullet, and gunshot wound, and then searched for additional references by manually searching of bibliographies of the included references. Studies were included if they provided clinical data on one or both of our study questions; included studies were evaluated using the accepted levels of evidence. Findings: Routine monitoring or surveillance of lead levels in blood is recommended in all cases of EARM at the time of hospital admission and again at discharge, followed by monthly intervals until 3 mo post-injury and then again at 1 yr post-injury. The studies identified demonstrated significant risk factors for elevated blood lead levels in the setting of EARM, which included the number of retained missiles and concomitant fracture. Discussion: Recommendations for routine monitoring and surveillance of blood lead levels in all cases of EARM are conflicting, but such monitoring appears to be warranted given that the potential risks and morbidity associated with systemic lead poisoning are outweighed by any potential harm of short-term, blood lead level monitoring. Outside of concomitant fracture, the evidence for making further clinical recommendations regarding selected risk factors that portend an increased risk for elevated blood lead levels after gunshot injury is weak. Larger level II and III studies are needed to determine the indications for and frequency of lead toxicity screening after retained EARM.

The effect of preoperative lumbar epidural corticosteroid injection on postoperative infection rate in patients undergoing single-level lumbar decompression.

BACKGROUND CONTEXT: Lumbar epidural corticosteroid injections (LECIs) are frequently used in the treatment of lumbar intervertebral disc herniation with radiculopathy and lumbar spinal stenosis. Although widely used, their effect on the outcomes and complications of subsequent surgery is unclear. Postoperative infection can be a morbid complication following spine surgery, and recent literature has suggested that the risk may be increased in patients undergoing lumbar spinal surgery who had previously received LECIs. PURPOSE: The purpose of this study is to define the overall postoperative infection rate in patients undergoing lumbar spine decompression surgery in the Military Health System (MHS) patient population and examine the effects of LECIs on postoperative infection rates. STUDY DESIGN/SETTING: This is a retrospective case control database study (Level III study). PATIENT SAMPLE: The sample comprised all patients in the MHS who had a LECI before single-level lumbar decompression surgery from 2009 to 2014. OUTCOME MEASURES: Postoperative infection within 90 days of surgery was used as the primary outcome measure for this study. Postoperative infection was identified using the International Classification of Diseases, 9th revision (ICD-9) diagnosis codes for postoperative infection. METHODS: The Military Health System Data Repository (MDR) database was searched for all patients who underwent single-level lumbar spine decompression surgery from 2009 to 2014 using Current Procedural Terminology (CPT) codes. Current Procedural Terminology codes were used to identify the subset of patients who received preoperative LECIs. For patients receiving an injection, cohorts were established based on the timing of the preoperative injection: <30 days, 30-90 days, 91-180 days, 181-365 days, and >365 days. An age-based cohort, composed of patients 65 years of age and older, was also analyzed. A subgroup analysis of patients receiving more than one preoperative injection was performed. Postoperative infection within 90 days of surgery was identified using ICD-9 codes, and infection rates for all groups were calculated and compared with the control group who did not receive preoperative LECIs. No external funding was received for this study. RESULTS: We identified 6,535 patients (847 preoperative LECI and 5,688 control) for analysis. The overall infection rate for patients undergoing single-level lumbar decompression surgery in the MHS was 0.81%. The rate ranged from 0% to 1.57% in the injection groups, with an overall infection rate in the injection group of 1.18% versus 0.76% in the control group. Despite an increased odds ratio of 1.57 following injection, no statistically significant differences were found between the control group and any injection group based on timing of injection, patient age, or number of preoperative injections. CONCLUSIONS: The results of this study suggest that within the MHS, preoperative LECIs do not significantly increase the risk of postoperative infection after single-level lumbar decompression. If a difference does exist, it is likely small.