Does nanoscale porous titanium coating increase lumbar spinal stiffness of an interbody fusion cage? An in vivo biomechanical analysis in an ovine model.

BACKGROUND: Quantitative objective measures to determine fusion achievement further enable the comparison of new technologies, such as interbody cage surface enhancement. Our aims were to compare in vivo biomechanical responses of ovine L4/5 lumbar motion segments with two cages: 1) Polyetheretherketone or 2) Polyetheretherketone with a nanosurfaced titanium porous scaffold from Nanovis, Inc. METHODS: Fourteen Merino sheep randomly received either 1) standard Polyetheretherketone cage or 2) Nanocoated Polyetheretherketone cage at L4/L5 with autologous bone graft. At baseline and one-year follow-up, dynamic spinal stiffness was quantified in vivo using a validated mechanical assessment at 2 Hz, 6 Hz, and 12 Hz. The dorsoventral secant stiffness (ky = force/displacement, N/mm) and L4-L5 accelerations were determined at each frequency. A repeated measures analysis of variance with Bonferonni correction was used to evaluate within and between group differences among the biomechanical variables. FINDINGS: Both implants increased spinal stiffness at 2 Hz (21 and 39%, respectively, p < .005), and at 6 Hz (12 and 27%, p < .0001). Significantly greater spinal stiffness was observed with Nanocoated Polyetheretherketone at one-year for both frequencies (p < .05). No significant differences were observed at 12 Hz within or between groups. L4-L5 dorsoventral accelerations were significantly decreased one year following cage placement only with Nanocoated Polyetheretherketone (p < .05) and greater reductions in acceleration were observed with Nanocoated Polyetheretherketone compared to standard Polyetheretherketone (p < .05). INTERPRETATION: Both cages increased spinal stiffness, yet, nanosurfaced cages resulted in greater spinal stiffness changes and decreases in L4-L5 accelerations. These findings may assist in clinical decision making and post-operative recovery strategies.

Restoring lumbar spine stiffness using an interspinous implant in an ovine model of instability.

BACKGROUND: The objective of this study was to determine the effect of an interspinous implant on lumbar spine stability and stiffness during dorsoventral loading. METHODS: Twelve Merino lambs were mechanically tested in vivo. Oscillatory (2 Hz) loads were applied to L2 under load control while displacements were monitored. Tri-axial accelerometers further quantified adjacent L3-L4 accelerations. Dorsoventral lumbar spine stiffness and L3 and L4 dorsoventral and axial displacements were determined over six trials of 20 cycles of loading. Four conditions were examined: 1) initial intact, 2) following destabilization at L3-L4, 3) following the insertion of an InSwing(®) interspinous device at L3-L4, and 4) with the implant secured with a tension band. Comparisons were performed using a one-way ANOVA with repeated measures and post-hoc Bonferroni correction. FINDINGS: Compared to the intact condition, destabilization significantly decreased lumbar stiffness by 4.5% (P=.001) which was only recovered by the interspinous device with tension band. The interspinous device caused a significant 9.75% (P=.001) increase in dorsoventral stiffness from destabilization that increased 14% with the tension band added (P=.001). The tension band was responsible for decreased displacements from the intact (P=.038), instability (P=.001), and interspinous device (P=.005) conditions. Dorsoventral L3-L4 motion significantly improved with the interspinous device (P=.01) and the addition of the tension band (P=.001). No significant differences in L3-L4 intersegmental stability were noted for axial motion in the sagittal plane. INTERPRETATION: This ovine model provided objective in vivo biomechanical evidence of lumbar instability and its restoration by means of an interspinous implant during dorsoventral spinal loading.

A new approach to prevent contralateral hip fracture: Evaluation of the effectiveness of a fracture preventing implant.

BACKGROUND: Among the millions of people suffering from a hip fracture each year, 20% may sustain a contralateral hip fracture within 5 years with an associated mortality risk increase reaching 64% in the 5 following years. In this context, we performed a biomechanical study to assess the performance of a hip fracture preventing implant. METHODS: The implant consists of two interlocking peek rods unified with surgical cement. Numerical and biomechanical tests were performed to simulate single stance load or lateral fall. Seven pairs of femurs were selected from elderly subjects suffering from osteoporosis or osteopenia, and tested ex-vivo after implantation of the device on one side. FINDINGS: The best position for the implant was identified by numerical simulations. The loadings until failure showed that the insertion of the implant increased significantly (P<0.05) both fracture load (+18%) and energy to fracture (+32%) of the implanted femurs in comparison with the intraindividual controls. The instrumented femur resisted the implementation of the non-instrumented femur fracture load for 30 cycles and kept its performance at the end of the cyclic loading. INTERPRETATION: Implantation of the fracture preventing device improved both fracture load and energy to fracture when compared with intraindividual controls. This is consistent with previous biomechanical side-impact testing on pairs of femur using the same methodology. Implant insertion seems to be relevant to support multiple falls and thus, to prevent a second hip fracture in elderly patients.

A decade's experience in lumbar spine surgery in Belgium: sickness fund beneficiaries, 2000-2009.

PURPOSE: The purpose is to study rates, trends, geographic variations and outcome of lumbar spine surgery in the Belgian population during the last decade. METHODS: This is a retrospective cohort study using administrative data of the largest Belgian sickness fund from January 1, 2000 through December 31, 2009. Cases included lumbar laminectomy, combined discectomy and fusion, posterior interarticular fusion, anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF) and standard discectomy. The main outcome measures were age- and sex-adjusted rates of lumbar spine surgery, 1-year mortality, 1-year iterative surgery, no return to work (RTW) rate 1 year after surgery and length of hospital stay. Multivariate logistic regression analysis was used to determine the association between age, sex, geographic region, type of surgery, year of intervention and duration of pre-operative sick leave on outcome. RESULTS: Spine surgery rates rose 44 % from 2001 through 2009 and data for 2009 showed twofold variations in spine surgery rates among 10 Belgian provinces. Reported 1-year mortality varied from 0.6 to 2.5 % among surgical procedures performed in 2008. The overall 5-year reoperation rate was 12 %. RTW rates 1 year after standard discectomy, ALIF, PLIF and combined discectomy and fusion for the follow-up sample of 2008 were 14.4, 22.7, 26.1 and 30.6 %, respectively. The median length of hospital stay significantly decreased throughout the decade. Type of surgery and geographic region were significantly related to patient outcomes. CONCLUSIONS: Regional variations highlight professional uncertainty and controversy. The study results point to the need for peer comparisons and surgeon feedback.

Biomechancial quantification of pathologic manipulable spinal lesions: an in vivo ovine model of spondylolysis and intervertebral disc degeneration.

OBJECTIVE: The purposes of this study were to quantify the biomechanical and pathologic consequences of surgically induced spinal lesions and to determine their response to spinal manipulation (SMT) in an in vivo ovine model. METHODS: Of 24 Merino sheep, 6 received L5 spondylolytic defects, 6 received L1 annular lesions, and 12 served as respective controls. Dorsoventral (DV) stiffness was assessed using oscillatory loads (2-12 Hz). Two SMT force-time profiles were administered in each of the groups using a randomized and repeated-measures design. Stiffness and the effect of SMT on the DV motions and multifidus needle electromyographic responses were assessed using a repeated-measures analysis of variance (α = .05). Postmortem histologic analysis and computed tomography validated the presence of lesions. RESULTS: L5 DV stiffness was significantly increased (40.2%) in the spondylolysis (6.28 N/mm) compared with the L5 control group (4.48 N/mm) (P < 03). Spinal manipulations delivered to the spondylolysis group resulted in less DV vertebral displacement (P < .01) compared with controls. Dorsoventral stiffness of the disc degeneration group was 5.66 N/mm, 94.5% greater than in the L1 control group (2.91 N/mm) (P < .01). One hundred-millisecond SMTs resulted in significantly reduced DV displacements in the disc degeneration group compared with the L1 control group (P < .01). Animals in the disc degeneration group showed a consistent 25% to 30% reduction in needle electromyographic responses to all SMTs. CONCLUSIONS: Quantifiable objective evidence of spinal lesions and their response to SMT were confirmed in this study. Neuromechanical alterations provide novel insights into quantifying manipulable spinal lesions and a means to biomechanically assess SMT outcomes.

The association between isoinertial trunk muscle performance and low back pain in male adolescents.

The literature reports inconsistent findings regarding the association between low back pain (LBP) and trunk muscle function, in both adults and children. The strength of the relationship appears to be influenced by how LBP is qualified and the means by which muscle function is measured. The aim of this study was to examine the association between isoinertial trunk muscle performance and consequential (non-trivial) low back pain (LBP) in male adolescents. Healthy male adolescents underwent anthropometric measurements, clinical evaluation, and tests of trunk range of motion (ROM), maximum isometric strength (STRENGTH) and peak movement velocity (VEL), using an isoinertial device. They provided information about their regular sporting activities, history and family history of LBP. Predictors of "relevant/consequential LBP" were examined using multivariable logistic regression. LBP status was reassessed after 2 years and the change from baseline was categorised. At baseline, 33/95 (35%) subjects reported having experienced consequential LBP. BMI, a family history of LBP, and regularly playing sport were each significantly associated with a history of consequential LBP (p < 0.05). 85/95 (89%) boys participated in the follow-up: 51 (60%) reported no LBP at either baseline or follow-up (never LBP); 5 (6%) no LBP at baseline, but LBP at follow-up (new LBP); 19 (22%) LBP at baseline, but none at follow-up; and 10 (12%) LBP at both time-points (recurrent/persistent LBP). The only distinguishing features of group membership in these small groups were: fewer sport-active in the "never LBP" group); worse trunk mobility, in the "persistent LBP" group, lower baseline sagittal ROM in the "never LBP" and "new LBP" (p < 0.05). Regular involvement in sport was a consistent predictor of LBP. Isoinertial trunk performance was not associated with LBP in adolescents.

Burden of blood transfusion in knee and hip surgery in the US and Belgium.

OBJECTIVE: Transfusion services in orthopaedic surgery can lead to unnecessary complications and increased healthcare costs. The objective of this study was to assess treatments and costs associated with blood and blood product transfusions in a historical cohort of 189,457 inpatients in the US and 34,987 inpatients in Belgium undergoing knee or hip surgery. METHODS: Descriptive analysis, logistic regression and ordinary least squares regression were used to describe the factors associated with the use and cost of allogeneic blood transfusion. RESULTS: Hospitalisation costs for joint replacement surgery totalled $12,718 (SD=6,356) and averaged 4.33 days in the US, while costs in Belgium were $6,526 (SD=3,192) and averaged 17.1 days. The use of low molecular weight heparin and tranexamic acid was much higher in Belgium than the US (36% and 99% compared to 0% and 40%, respectively). Patients in the US spent 12.7 (p<0.0001) fewer days in the hospital, 0.3 (p<0.0001) fewer days in the intensive care unit and were 88% less likely to have allogeneic blood transfusions (OR=0.22, 95% CI 0.22-0.23), but incurred $6,483 (p<0.0001) more costs per hospitalisation than patients in Belgium. CONCLUSIONS: While hospital costs for patients were greater in the US, length of stay was shorter and patients were less likely to have transfusion services than those patients in Belgium. While this study is limited by factors inherent to observational studies, such as omitted variable bias, misclassification, and disease comorbidity, there are substantial differences in the use of blood products between Belgium and the US.

Effect of a novel interspinous implant on lumbar spinal range of motion.

Interspinous devices have been introduced to provide a minimally invasive surgical alternative for patients with lumbar spinal stenosis or foraminal stenosis. Little is known however, of the effect of interspinous devices on intersegmental range of motion (ROM). The aim of this in vivo study was to investigate the effect of a novel minimally invasive interspinous implant, InSwing, on sagittal plane ROM of the lumbar spine using an ovine model. Ten adolescent Merino lambs underwent a destabilization procedure at the L1-L2 level simulating a stenotic degenerative spondylolisthesis (as described in our earlier work; Spine 15:571-576, 1990). All animals were placed in a side-lying posture and lateral radiographs were taken in full flexion and extension of the trunk in a standardized manner. Radiographs were repeated following the insertion of an 8-mm InSwing interspinous device at L1-L2, and again with the implant secured by means of a tension band tightened to 1 N/m around the L1 and L2 spinous processes. ROM was assessed in each of the three conditions and compared using Cobb's method. A paired t-test compared ROM for each of the experimental conditions (P < 0.05). After instrumentation with the InSwing interspinous implant, the mean total sagittal ROM (from full extension to full flexion) was reduced by 16% from 6.3 degrees to 5.3 +/- 2.7 degrees. The addition of the tension band resulted in a 43% reduction in total sagittal ROM to 3.6 +/- 1.9 degrees which approached significance. When looking at flexion only, the addition of the interspinous implant without the tension band did not significantly reduce lumbar flexion, however, a statistically significant 15% reduction in lumbar flexion was observed with the addition of the tension band (P = 0.01). To our knowledge, this is the first in vivo study radiographically showing the advantage of using an interspinous device to stabilize the spine in flexion. These results are important findings particularly for patients with clinical symptoms related to instable degenerative spondylolisthesis.

Comparison between spinal surgery blood transfusion services costs and associated treatment practices in the United States and Belgium.

OBJECTIVE: This study assessed utilization and cost of allogeneic blood transfusion (ABT) associated with spinal surgery in the United States (US) and Belgium. METHODS: A retrospective cohort of 292,864 spinal surgery inpatients in US hospitals was pooled with a cohort of 27,952 inpatients who had similar procedures in Belgian hospitals. Utilization and cost data were derived from hospital accounting systems. Costs were converted to US dollars. Descriptive and multivariate statistics were used to describe the factors associated with the use and cost of ABT. Missing data, confounding, and variable measurement error were addressed using standard approaches for observational studies. RESULTS: US hospitalizations cost $12,044 (SD = 15,920) over 3.6 days compared to $4010 (SD = 3586) over 10.3 days in Belgium. Low molecular weight heparin was used by 78% of Belgian patients and 4% of US patients. Red blood cell utilization occurred in approximately 7% of patients from both countries; however US patients received 6 units compared to 3 units by Belgian patients. US patients spent 3.5 (p < 0.0001) less days in hospital, 1.0 (p < 0.0001) more days in an intensive care unit, used 64% more allogeneic blood (OR = 1.64, 95% CI 1.53-1.75), and incurred $13,647 (p < 0.0001) more per hospitalization than Belgian patients. CONCLUSIONS: US patients used more blood products, had shorter hospital stays, and incurred greater costs than Belgian patients. Specialists as attending physicians were associated with lower utilization of ABT; this may be an administrative change that hospitals can implement to reduce utilization and costs.