Blockchain-Based Dynamic Consent and its Applications for Patient-Centric Research and Health Information Sharing: Protocol for an Integrative Review.

BACKGROUND: Blockchain has been proposed as a critical technology to facilitate more patient-centric research and health information sharing. For instance, it can be applied to coordinate and document dynamic informed consent, a procedure that allows individuals to continuously review and renew their consent to the collection, use, or sharing of their private health information. Such has been suggested to facilitate ethical, compliant longitudinal research, and patient engagement. However, blockchain-based dynamic consent is a relatively new concept, and it is not yet clear how well the suggested implementations will work in practice. Efforts to critically evaluate implementations in health research contexts are limited. OBJECTIVE: The objective of this protocol is to guide the identification and critical appraisal of implementations of blockchain-based dynamic consent in health research contexts, thereby facilitating the development of best practices for future research, innovation, and implementation. METHODS: The protocol describes methods for an integrative review to allow evaluation of a broad range of quantitative and qualitative research designs. The PRISMA-P (Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols) framework guided the review's structure and nature of reporting findings. We developed search strategies and syntax with the help of an academic librarian. Multiple databases were selected to identify pertinent academic literature (CINAHL, Embase, Ovid MEDLINE, PubMed, Scopus, and Web of Science) and gray literature (Electronic Theses Online Service, ProQuest Dissertations and Theses, Open Access Theses and Dissertations, and Google Scholar) for a comprehensive picture of the field's progress. Eligibility criteria were defined based on PROSPERO (International Prospective Register of Systematic Reviews) requirements and a criteria framework for technology readiness. A total of 2 reviewers will independently review and extract data, while a third reviewer will adjudicate discrepancies. Quality appraisal of articles and discussed implementations will proceed based on the validated Mixed Method Appraisal Tool, and themes will be identified through thematic data synthesis. RESULTS: Literature searches were conducted, and after duplicates were removed, 492 articles were eligible for screening. Title and abstract screening allowed the removal of 312 articles, leaving 180 eligible articles for full-text review against inclusion criteria and confirming a sufficient body of literature for project feasibility. Results will synthesize the quality of evidence on blockchain-based dynamic consent for patient-centric research and health information sharing, covering effectiveness, efficiency, satisfaction, regulatory compliance, and methods of managing identity. CONCLUSIONS: The review will provide a comprehensive picture of the progress of emerging blockchain-based dynamic consent technologies and the rigor with which implementations are approached. Resulting insights are expected to inform best practices for future research, innovation, and implementation to benefit patient-centric research and health information sharing. TRIAL REGISTRATION: PROSPERO CRD42023396983; http://tinyurl.com/cn8a5x7t. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/50339.

Biomechanical properties in motion of lumbar spines with degenerative scoliosis.

Degenerative lumbar scoliosis presumably alters spinal biomechanics, but a lack of quantitative reference measurements of these spines exists. We aimed to assess the biomechanical properties of spines with degenerative scoliosis, and to relate these to intervertebral disc degeneration (DD) and Cobb angle. Secondly, we compared these results to previous measurements of non-scoliotic spines. Ten cadaveric spines (Th12-L5, mean age 82 ±â€¯11 years) with Cobb angle ≥10° and apex at L3 were acquired. Three loading cycles (-4 to 4 Nm) were applied in flexion/extension (FE), lateral bending (LB), and axial rotation (AR). The range of motion (ROM), neutral zone (NZ) stiffness, NZ ROM, elastic zone (EZ) stiffness and hysteresis were calculated for each motion segment in the loading direction. ROM was calculated in coupled directions, expressed as a percentage of rotation in the loaded direction. For Th12-L5, there was a ROM (degrees ±â€¯SD) of 14.9 ±â€¯6.5 in FE, 14.9 ±â€¯7.8 in LB, and 10.2 ±â€¯5.5 in AR. The median (Nm/degree (Q1;Q3)) NZs was 0.24 (0.19;0.35) in FE, 0.25 (0.22;0.42) in LB, and 0.49 (0.33;0.99) in AR. Greater coupled motions related to higher Cobb angle, especially during AR on segments around the apex (FE: ρ = 0.539, p = 0.021 and LB: ρ = 0.821, p = 0.000). DD correlated to lower ROM and increased NZs on L2-L3 in FE (ρ = -0.721, p = 0.028 and ρ = 0.694, p = 0.038, respectively). Compared to non-scoliotic spines, smaller ROM in FE (p = 0.030) was found. This study describes the biomechanical properties of lumbar spines with degenerative scoliosis. Compared to non-scoliotic spines, they tended to be stiffer and exhibited smaller ROM in FE. DD only affected the ROM and NZs of the segments around the apex.

Quantitative MRI in early intervertebral disc degeneration: T1rho correlates better than T2 and ADC with biomechanics, histology and matrix content.

INTRODUCTION: Low-back pain (LBP) has been correlated to the presence of intervertebral disc (IVD) degeneration on T2-weighted (T2w) MRI. It remains challenging, however, to accurately stage degenerative disc disease (DDD) based on T2w MRI and measurements of IVD height, particularly for early DDD. Several quantitative MRI techniques have been introduced to detect changes in matrix composition signifying early DDD. In this study, we correlated quantitative T2, T1rho and Apparent Diffusion Coefficient (ADC) values to disc mechanical behavior and gold standard early DDD markers in a graded degenerated lumbar IVD caprine model, to assess their potential for early DDD detection. METHODS: Lumbar caprine IVDs were injected with either 0.25 U/ml or 0.5 U/ml Chondroïtinase ABC (Cabc) to trigger early DDD-like degeneration. Injection with phosphate-buffered saline (PBS) served as control. IVDs were cultured in a bioreactor for 20 days under axial physiological loading. High-resolution 9.4 T MR images were obtained prior to intervention and after culture. Quantitative MR results were correlated to recovery behavior, histological degeneration grading, and the content of glycosaminoglycans (GAGs) and water. RESULTS: Cabc-injected IVDs showed aberrancies in biomechanics and loss of GAGs without changes in water-content. All MR sequences detected changes in matrix composition, with T1rho showing largest changes pre-to-post in the nucleus, and significantly more than T2 and ADC. Histologically, degeneration due to Cabc injection was mild. T1rho nucleus values correlated strongest with altered biomechanics, histological degeneration score, and loss of GAGs. CONCLUSIONS: T2- and T1rho quantitative MR-mapping detected early DDD changes. T1rho nucleus values correlated better than T2 and ADC with biomechanical, histological, and GAG changes. Clinical implementation of quantitative MRI, T1rho particularly, could aid in distinguishing DDD more reliably at an earlier stage in the degenerative process.

A Novel Spinal Implant for Fusionless Scoliosis Correction: A Biomechanical Analysis of the Motion Preserving Properties of a Posterior Periapical Concave Distraction Device.

STUDY DESIGN: Biomechanical study. OBJECTIVE: Recently, a posterior concave periapical distraction device for fusionless scoliosis correction was introduced. The goal of this study was to quantify the effect of the periapical distraction device on spinal range of motion (ROM) in comparison with traditional rigid pedicle screw-rod instrumentation. METHODS: Using a spinal motion simulator, 6 human spines were loaded with 4 N m and 6 porcine spines with 2 N m to induce flexion-extension (FE), lateral bending (LB), and axial rotation (AR). ROM was measured in 3 conditions: untreated, periapical distraction device, and rigid pedicle screw-rod instrumentation. RESULTS: The periapical distraction device caused a significant (P < .05) decrease in ROM of FE (human, -40.0% and porcine, -55.9%) and LB (human, -18.2% and porcine, -17.9%) as compared to the untreated spine, while ROM of AR remained unaffected. In comparison, rigid instrumentation caused a significantly (P < .05) larger decrease in ROM of FE (human, -80.9% and porcine, -94.0%), LB (human, -75.0% and porcine, -92.2%), and AR (human, -71.3% and porcine, -86.9%). CONCLUSIONS: Although no destructive forces were applied, no device failures were observed. Spinal ROM was significantly less constrained by the periapical distraction device compared to rigid pedicle screw-rod instrumentation. Therefore, provided that scoliosis correction is achieved, a more physiological spinal motion is expected after scoliosis correction with the posterior concave periapical distraction device.

Static axial overloading primes lumbar caprine intervertebral discs for posterior herniation.

INTRODUCTION: Lumbar hernias occur mostly in the posterolateral region of IVDs and mechanical loading is an important risk factor. Studies show that dynamic and static overloading affect the nucleus and annulus of the IVD differently. We hypothesize there is also variance in the effect of overloading on the IVD's anterior, lateral and posterior annulus, which could explain the predilection of herniations in the posterolateral region. We assessed the regional mechanical and cellular responses of lumbar caprine discs to dynamic and static overloading. MATERIAL AND METHODS: IVDs (n = 125) were cultured in a bioreactor and subjected to simulated-physiological loading (SPL), high dynamic (HD), or high static (HS) overloading. The effect of loading was determined in five disc regions: nucleus, inner-annulus and anterior, lateral and posterior outer-annulus. IVD height loss and external pressure transfer during loading were measured, cell viability was mapped and quantified, and matrix integrity was assessed. RESULTS: During culture, overloaded IVDs lost a significant amount of height, yet the distribution of axial pressure remained unchanged. HD loading caused cell death and disruption of matrix in all IVD regions, whereas HS loading particularly affected cell viability and matrix integrity in the posterior region of the outer annulus. CONCLUSION: Axial overloading is detrimental to the lumbar IVD. Static overloading affects the posterior annulus more strongly, while the nucleus is relatively spared. Hence, static overloading predisposes the disc for posterior herniation. These findings could have implications for working conditions, in particular of sedentary occupations, and the design of interventions aimed at prevention and treatment of early intervertebral disc degeneration.

Market approval processes for new types of spinal devices: challenges and recommendations for improvement.

BACKGROUND: Spinal pathology and related symptoms are among the most common health problems and are associated with high health care costs and productivity losses. Due to the aging population, these costs are further increasing every year. Another important reason for the increasing costs is the market approval of new technologies, such as spinal devices that are usually more expensive than the existing technologies. Previous cases of medical device failure led to concern about possible deficiencies in the market approval process. OBJECTIVE: The objective is to provide an overview of U.S. Food and Drug Administration (FDA) regulation regarding spinal implants to delineate the challenges and opportunities that spine surgery currently faces. METHODS: In this paper, two cases of market entries of spinal devices are presented and evaluated to illustrate these deficiencies. RESULTS: Spinal implant regulation is facing several challenges. New spinal devices should increase patient outcomes and safety at reasonable societal costs. The main challenge is to have a rigorous evaluation before dissemination, while still leaving room for innovative behavior that thrusts the healthcare practice forward. CONCLUSION: We have provided recommendations to enhance spinal implant regulation and improve and ensure the patient's safety and the future of spine surgery.

The effects of single-level instrumented lumbar laminectomy on adjacent spinal biomechanics.

Study Design Biomechanical study. Objective Posterior instrumentation is used to stabilize the spine after a lumbar laminectomy. However, the effects on the adjacent segmental stability are unknown. Therefore, we studied the range of motion (ROM) and stiffness of treated lumbar spinal segments and cranial segments after a laminectomy and after posterior instrumentation in flexion and extension (FE), lateral bending (LB), and axial rotation (AR). These outcomes might help to better understand adjacent segment disease (ASD), which is reported cranial to the level on which posterior instrumentation is applied. Methods We obtained 12 cadaveric human lumbar spines. Spines were axially loaded with 250 N for 1 hour. Thereafter, 10 consecutive load cycles (4 Nm) were applied in FE, LB, and AR. Subsequently, a laminectomy was performed either at L2 or at L4. Thereafter, load-deformation tests were repeated, after similar preloading. Finally, posterior instrumentation was added to the level treated with a laminectomy before testing was repeated. The ROM and stiffness of the treated, the cranial adjacent, and the control segments were calculated from the load-displacement data. Repeated-measures analyses of variance used the spinal level as the between-subject factor and a laminectomy or instrumentation as the within-subject factors. Results After the laminectomy, the ROM increased (+19.4%) and the stiffness decreased (-18.0%) in AR. The ROM in AR of the adjacent segments also increased (+11.0%). The ROM of treated segments after instrumentation decreased in FE (-74.3%), LB (-71.6%), and AR (-59.8%). In the adjacent segments after instrumentation, only the ROM in LB was changed (-12.9%). Conclusions The present findings do not substantiate a biomechanical pathway toward or explanation for ASD.

The effect of neighboring segments on the measurement of segmental stiffness in the intact lumbar spine.

BACKGROUND CONTEXT: Degeneration, injury, and surgical interventions may alter the mechanical properties of spinal motion segments, but the quantification of these alterations in vivo is problematic. Manual or instrumented loading of single segments in the intact spine as applied intraoperatively may overestimate the mechanical properties of this segment, because the applied load is partly sustained by the adjacent segments. PURPOSE: The distribution of stiffness values of individual spinal segments within and across spines was determined so as to use these data as input to a model simulation of segment stiffness tests in intact spines, to assess measurement errors. STUDY DESIGN: Biomechanical stiffness measurements on human cadaveric spines and model simulation to assess measurement errors. METHODS: Seventeen human cadaveric lumbar spines were loaded with pure moments in flexion/extension, lateral bending, and torsion. An optical system was used to measure the angular rotations of each motion segment and load-displacement curves were used to determine stiffness. With the distribution of measured stiffness data as input, a stochastic mechanical model was constructed to investigate how the stiffness of adjacent segments influences stiffness estimates obtained by loading a single segment in the intact spine. RESULTS: The variance in stiffness values was high for all directions, but covaried between segments within a spine. Model simulations indicated that stiffness estimates obtained by loading a single segment in an intact spine are highly correlated with actual stiffness, but overestimate stiffness by a median of 18% with peak errors of close to 400%. CONCLUSION: Current measurement devices and manual assessment substantially overestimate segmental stiffness due to the effect of adjacent spinal levels. In addition, the variance in stiffness within spines can occasionally cause large errors, which might lead to erroneous surgical decisions.

How Does Spinal Release and Ponte Osteotomy Improve Spinal Flexibility? The Law of Diminishing Returns.

STUDY DESIGN: Experimental study. OBJECTIVES: To evaluate the effect of stepwise resection of posterior spinal ligaments, facet joints, and ribs on thoracic spinal flexibility. SUMMARY OF BACKGROUND DATA: Posterior spinal ligaments, facet joints and ribs are removed to increase spinal flexibility in corrective spinal surgery for deformities such as adolescent idiopathic scoliosis (AIS). Reported clinical results vary and biomechanical substantiation is lacking. METHODS: Ten fresh-frozen human cadaveric thoracic spinal specimens (T6-T11) were studied. A spinal motion simulator applied a pure moment of ±2.5 Nm in flexion, extension, lateral bending (LB) and axial rotation (AR). Range of motion (ROM) was measured for the intact spine and measured again after stepwise resection of the supra/interspinous ligament (SIL), inferior facet, flaval ligament, superior facet, and rib heads. RESULTS: SIL resection increased ROM in flexion (10.2%) and AR (3.1%). Successive inferior facetectomy increased ROM in flexion (4.1%), LB (3.8%) and AR (7.7%), and flavectomy in flexion (9.1%) and AR (2.5%). Sequential superior facetectomy only increased ROM in flexion (6.3%). Rib removal provided an additional increase in flexion (6.3%), LB (4.5%) and AR (13.0%). Extension ROM increased by 10.5% after the combined removal of the SIL, inferior facet and flaval ligament. CONCLUSIONS: Posterior spinal releases in these non-scoliotic spines led to an incremental increase in spinal flexibility, but each sequential step had less effect. As compared to SIL resection with inferior facetectomy, additional superior facetectomy did not improve flexibility in AR and LB and only 6.3% in flexion. The data presented from this in vitro study should be interpreted with care, as no representative cadaveric spine model for AIS was available, However, the results presented here at least question the benefits of performing routine complete facetectomies (i.e. Ponte osteotomies) to increase spinal flexibility in scoliosis surgery.

Single level lumbar laminectomy alters segmental biomechanical behavior without affecting adjacent segments.

BACKGROUND: Degenerative lumbar spinal stenosis causes neurological symptoms due to neural compression. Lumbar laminectomy is a commonly used treatment for symptomatic degenerative spinal stenosis. However, it is unknown if and to what extent single level laminectomy affects the range of motion and stiffness of treated and adjacent segments. An increase in range of motion and a decrease in stiffness are possible predictors of post-operative spondylolisthesis or spinal failure. METHODS: Twelve cadaveric human lumbar spines were obtained. After preloading, spines were tested in flexion-extension, lateral bending, and axial rotation. Subsequently, single level lumbar laminectomy analogous to clinical practice was performed at level lumbar 2 or 4. Thereafter, load-deformation tests were repeated. The range of motion and stiffness of treated and adjacent segments were calculated before and after laminectomy. Untreated segments were used as control group. Effects of laminectomy on stiffness and range of motion were tested, separately for treated, adjacent and control segments, using repeated measures analysis of variance. FINDINGS: Range of motion at the level of laminectomy increased significantly for flexion and extension (7.3%), lateral bending (7.5%), and axial rotation (12.2%). Range of motion of adjacent segments was only significantly affected in lateral bending (-7.7%). Stiffness was not affected by laminectomy. INTERPRETATION: The increase in range of motion of 7-12% does not seem to indicate the use of additional instrumentation to stabilize the lumbar spine. If instrumentation is still considered in a patient, its primary focus should be on re-stabilizing only the treated segment level.

Which factors prognosticate rotational instability following lumbar laminectomy?

PURPOSE: Reduced strength and stiffness of lumbar spinal motion segments following laminectomy may lead to instability. Factors that predict shear biomechanical properties of the lumbar spine were previously published. The purpose of the present study was to predict spinal torsion biomechanical properties with and without laminectomy from a total of 21 imaging parameters. METHOD: Radiographs and MRI of ten human cadaveric lumbar spines (mean age 75.5, range 59-88 years) were obtained to quantify geometry and degeneration of the motion segments. Additionally, dual X-ray absorptiometry (DXA) scans were performed to measure bone mineral content and density. Facet-sparing lumbar laminectomy was performed either on L2 or L4. Spinal motion segments were dissected (L2-L3 and L4-L5) and tested in torsion, under 1,600 N axial compression. Torsion moment to failure (TMF), early torsion stiffness (ETS, at 20-40 % TMF) and late torsion stiffness (LTS, at 60-80 % TMF) were determined and bivariate correlations with all parameters were established. For dichotomized parameters, independent-sample t tests were used. RESULTS: Univariate analyses showed that a range of geometric characteristics and disc and bone quality parameters were associated with torsion biomechanical properties of lumbar segments. Multivariate models showed that ETS, LTS and TMF could be predicted for segments without laminectomy (r (2) values 0.693, 0.610 and 0.452, respectively) and with laminectomy (r (2) values 0.952, 0.871 and 0.932, respectively), with DXA-derived measures of bone quality and quantity as the main predictors. CONCLUSIONS: Vertebral bone content and geometry, i.e. intervertebral disc width, frontal area and facet joint tropism, were found to be strong predictors of ETS, LTS and TMF following laminectomy, suggesting that these variables could predict the possible development of post-operative rotational instability following lumbar laminectomy. Proposed diagnostic parameters might aid surgical decision-making when deciding upon the use of instrumentation techniques.

Modelling creep behaviour of the human intervertebral disc.

The mechanical behaviour of an intervertebral disc is time dependent. In literature different constitutive equations have been used to describe creep. It is unsure whether these different approaches yield valid predictions. In this study, we compared the validity of different equations for the prediction of creep behaviour. To this end, human thoracic discs were preloaded at 0.1 MPa for 12h, compressed (0.8 MPa) for 24h and finally unloaded (0.1 MPa) for 24h. A Kohlrausch-Williams-Watts (KWW) model and a Double-Voight (DV) model were fitted to the creep data. Model parameters were calculated for test durations of 4, 8, 12, 16, 20 and 24h. Both models described the measured data well, but parameters were highly sensitive to test duration. The estimated time constant varied with test duration from 3.6 to 17h. When extrapolating beyond test duration, the DV model under-estimated and the KWW model over-estimated creep. The 24h experiment was still too short for an accurate determination of the parameters. Therefore, parameters obtained in this paper can be used to describe normal behaviour, but are not suitable for extrapolation beyond the test duration.

Torsion biomechanics of the spine following lumbar laminectomy: a human cadaver study.

PURPOSE: Lumbar laminectomy affects spinal stability in shear loading. However, the effects of laminectomy on torsion biomechanics are unknown. The purpose of this study was to investigate the effect of laminectomy on torsion stiffness and torsion strength of lumbar spinal segments following laminectomy and whether these biomechanical parameters are affected by disc degeneration and bone mineral density (BMD). METHODS: Ten human cadaveric lumbar spines were obtained (age 75.5, range 59-88). Disc degeneration (MRI) and BMD (DXA) were assessed. Disc degeneration was classified according to Pfirrmann and dichotomized in mild or severe. BMD was defined as high BMD (≥median BMD) or low BMD (

Effects of repetitive movement on range of motion and stiffness around the neutral orientation of the human lumbar spine.

In loading experiments on the lumbar spine, typically three consecutive loading cycles are applied of which the third cycle is used for analysis. The aim of this study was to investigate whether the use of ten instead of three loading cycles reduces effects of viscoelastic behavior in the assessment of range of motion (ROM) and stiffness around the neutral orientation of the human lumbar spine. To this end, twelve cadaveric human lumbar spines (L1-L5) were obtained (mean age: 76.9 years). Before testing, the spines were subjected to a compressive load of 250 N for 1 h. To each spine, ten consecutive loading cycles were applied (-4 Nm to+4 Nm) in flexion and extension (FE), lateral bending (LB) and axial rotation (AR). The ROM and stiffness within the neutral zone were calculated per motion segment (L2-L3, L3-L4 or L4-L5) from load-displacement data. It was found that the ROM increased significantly (all p<0.001) in all directions after three (FE: 0.07 degree/1.0%, LB: 0.08 degree/1.5%, and AR: 0.04 degree/1.5%) and after ten loading cycles (FE: 0.20 degree/2.9%, LB: 0.16 degree/3.3%, and AR: 0.09 degree/3.3%). Stiffness was not significantly affected, but varied considerably over cycles. Although effects were small, assessment of the tenth cycle instead of the third cycle reduces viscoelastic effects in repeated measurements of ROM, because the spine is closer to a steady state condition, while averaging over loading cycles would improve the assessment of stiffness estimates.

Which factors prognosticate spinal instability following lumbar laminectomy?

PURPOSE: Reduced strength and shear stiffness (SS) of lumbar motion segments following laminectomy may lead to instability. The purpose of the present study was to assess a broad range of parameters as potential predictors of shear biomechanical properties of the lumbar spine. METHODS: Radiographs and MRI of all lumbar spines were obtained to classify geometry and degeneration of the motion segments. Additionally, dual X-ray absorptiometry (DXA) scans were performed to measure bone mineral content and density (BMC and BMD). Facet sparing lumbar laminectomy was performed either on L2 or L4, in 10 human cadaveric lumbar spines (mean age 72.1 years, range 53-89 years). Spinal motion segments were dissected (L2-L3 and L4-L5) and tested in shear, under simultaneously loading with 1600 N axial compression. Shear stiffness, shear yield force (SYF) and shear force to failure (SFF) were determined and statistical correlations with all parameters were established. RESULTS: Following laminectomy, SS, SYF, and SFF declined (by respectively 24, 41, and 44%). For segments with laminectomy, SS was significantly correlated with intervertebral disc degeneration and facet joint degeneration (Pfirrmann: r = 0.64; Griffith: r = 0.70; Lane: r = 0.73 and Pathria: r = 0.64), SYF was correlated with intervertebral disc geometry (r = 0.66 for length; r = 0.66 for surface and r = 0.68 for volume), BMC (r = 0.65) and frontal area (r = 0.75), and SFF was correlated with disc length (r = 0.73) and BMC (r = 0.81). For untreated segments, SS was significantly correlated with facet joint tropism (r = 0.71), SYF was correlated with pedicle geometry (r = 0.83), and SFF was correlated with BMC (r = 0.85), BMD (r = 0.75) and frontal area (r = 0.75). SS, SYF and SFF could be predicted for segments with laminectomy (r (2) values respectively: 0.53, 0.81 and 0.77) and without laminectomy (r (2) value respectively: 0.50, 0.83 and 0.83). CONCLUSIONS: Significant loss of strength and SS are predicted by BMC, BMD, intervertebral disc geometry and degenerative parameters, suggesting that low BMC or BMD, small intervertebral discs and absence of osteophytes could predict the possible development of post-operative instability following lumbar laminectomy.

The impact of bone mineral density and disc degeneration on shear strength and stiffness of the lumbar spine following laminectomy.

PURPOSE: Laminectomy is a standard surgical procedure for elderly patients with symptomatic degenerative lumbar stenosis. The procedure aims at decompression of the affected nerves, but it also causes a reduction of spinal shear strength and shear stiffness. The magnitude of this reduction and the influence of bone mineral density (BMD) and disc degeneration are unknown. We studied the influence of laminectomy, BMD, and disc degeneration on shear force to failure (SFF) and shear stiffness (SS). METHODS: Ten human cadaveric lumbar spines were obtained (mean age 72.1 years, range 53-89 years). Laminectomy was performed either on L2 or L4, equally divided within the group of ten spines. BMD was assessed by dual X-ray absorptiometry (DXA). Low BMD was defined as a BMD value below the median. Intervertebral discs were assessed for degeneration by MRI (Pfirrmann) and scaled in mild and severe degeneration groups. Motion segments L2-L3 and L4-L5 were isolated from each spine. SFF and SS were measured, while loading simultaneously with 1,600 N axial compression. RESULTS: Low BMD had a significant negative effect on SFF. In addition, a significant interaction between low BMD and laminectomy was found. In the high BMD group, SFF was 2,482 N (range 1,678-3,284) and decreased to 1,371 N (range 940-1,886) after laminectomy. In the low BMD group, SFF was 1,339 N (range 909-1,628) and decreased to 761 N (range 561-1,221). Disc degeneration did not affect SFF, nor did it interact with laminectomy. Neither low BMD nor the interaction of low BMD and laminectomy did affect SS. Degeneration and its interaction with laminectomy did not significantly affect SS. CONCLUSIONS: In conclusion, low BMD significantly decreased SFF before and after lumbar laminectomy. Therefore, DXA assessment may be an important asset to preoperative screening. Lumbar disc degeneration did not affect shear properties of lumbar segments before or after laminectomy.