Optimization of 3D-printed titanium interbody cage design. Part 1: in vitro biomechanical study of subsidence.

Background Context: Cage subsidence is a complication of interbody fusion associated with poor clinical outcomes. 3D-printed titanium interbody cages allow for the alteration of features such as stiffness and porosity. However, the influence of these features on subsidence and their biological effects on fusion have not been rigorously evaluated.

Preoperative Multifidus and Psoas Major Muscle Quality and Patient-Reported Outcomes After Anterolateral Lumbar Interbody Fusion: Predictors for Preoperative Disability and Back Pain Improvement.

Objective: To investigate associations between preoperative lumbar multifidus muscle (LMM) and psoas major muscle qualities and preoperative and postoperative patient-reported outcomes (PROs) after anterolateral lumbar interbody fusion (A-LLIF).

Methods: A retrospective review was conducted of patients with A-LLIF between L1 and S1 during 2017-2022 at a single institution who had at least approximately 1 year of follow-up and preoperative magnetic resonance imaging available. Preoperative magnetic resonance imaging was analyzed using 2 image analysis platforms (AMBRA and ImageJ).

Biomechanical Effects of a Novel Standalone Posterior Lumbar Facet Joint Stabilization Device: An In Vitro Cadaveric Study.

Objective: Although pedicle screw and rod instrumentation remains the gold standard method of posterior rod fixation, it is associated with complications, including pedicle breach and facet joint violation. There is current interest in facet joint stabilization with the potential to create a less invasive, natural arch of fixation that may avoid the complications associated with pedicle screw and rod instrumentation. This study examined the stabilizing potential of a novel facet joint fixation device for single-level (L4-L5) fixation in a human cadaveric model.

Biomechanical Effects of Facet Joint Violation After Single-Level Lumbar Fusion With Transpedicular Screw and Rod Instrumentation.

Study Design: In vitro biomechanical study.

Objective: This study aimed to investigate the biomechanical effects of facet joint violation (FV) on mobility and optically tracked intervertebral disc (IVD) surface strains at the upper level adjacent to L4-5 pedicle screw-rod fixation.

Summary Of Background Data: FV is a complication that can occur when placing lumbar pedicle screws; the reported incidence is as high as 50%.

Biomechanical Assessment of a Novel Sharp-Tipped Screw for 1-Step Minimally Invasive Pedicle Screw Placement Under Navigation.

Background: The objective of this study was to assess the pullout force of a novel sharp-tipped screw developed for single-step, minimally invasive pedicle screw placement guided by neuronavigation compared with the pullout force for traditional screws.

Methods: A total of 60 human cadaveric lumbar pedicles were studied. Three different screw insertion techniques were compared: (A) Jamshidi needle and Kirschner wire without tapping; (B) Jamshidi needle and Kirschner wire with tapping; and (C) sharp-tipped screw insertion.

Rod Attachment Induces Significant Strain in Lumbosacral Fixation.

Study Design: This was a laboratory investigation.

Objective: Rod attachment can induce significant pedicle screw-and-rod pre- strain that may predispose the instrumentation to failure. This study investigated how in vitro L5-S1 rod strain and S1 screw strain during rod-screw attachment (pre-strain) compared with strains recorded during pure-moment bending ( test- strain).

Biomechanical Effects of Proximal Polyetheretherketone Rod Extension on the Upper Instrumented and Adjacent Levels in a Human Long-Segment Construct: A Cadaveric Model.

Objective: The high mechanical stress zone at the sudden transition from a rigid to flexible region is involved in proximal junctional kyphosis (PJK) physiopathology. We evaluated the biomechanical performance of polyetheretherketone (PEEK) rods used as a nontraditional long semirigid transition phase from a long-segment metallic rod construct to the nonfused thoracic spine.

Methods: Pure moment range of motion (ROM) tests (7.

Influence of Spinal Deformity Construct Design on Adjacent-Segment Biomechanics.

Background: Adjacent level degeneration is a precursor to construct failure in adult spinal deformity surgery, but whether construct design affects adjacent level degeneration risk remains unclear. Here we present a biomechanical profile of common deformity correction constructs and assess adjacent level biomechanics.

Methods: Standard nondestructive flexibility tests (7.

Subtle segmental angle changes of single-level lumbar fusions and adjacent-level biomechanics: cadaveric study of optically measured disc strain.

Objective: Changes to segmental lordosis at a single level may affect adjacent-level biomechanics and overall spinal alignment with an iatrogenic domino effect commonly seen in adult spinal deformity. This study investigated the effects of different segmental angles of single-level lumbar fixation on stability and principal strain across the surface of the adjacent-level disc.

Methods: Seven human cadaveric L3-S1 specimens were instrumented at L4-5 and tested in 3 conditions: 1) neutral native angle ("neutral"), 2) increasing angle by 5° of lordosis ("lordosis"), and 3) decreasing angle by 5° of kyphosis ("kyphosis").

Use of digital imaging correlation techniques for full-field strain distribution analysis of implantable devices and tissue in spinal biomechanics research.

Few studies have used optical full-field surface strain mapping to study spinal biomechanics. We used a commercial digital imaging correlation (DIC) system to (1) compare posterior surface strains on spinal rods with those obtained from conventional foil strain gauges, (2) quantify bony vertebral body and intervertebral disc (IVD) surface strains on 3 L3-S cadaveric spines during gold-standard flexibility tests (7.5-Nm flexion-extension and 400-N compression), and (3) report our experience with the application and feasibility of DIC to comprehensively map strain in spinal biomechanics.

Pedicle Subtraction Osteotomy Construct Optimization: A Cadaveric Study of Various Multirod and Interbody Configurations.

Study Design: Fourteen cadaveric specimens were separated into two groups: (1) L3 pedicle subtraction osteotomy (PSO) with transforaminal lumbar interbody fusion (TLIF) or (2) lateral lumbar interbody fusion (LLIF). A 2-rod configuration (2R) was compared with two supplemental rod configurations: 4-rod (4R) with accessory rods (ARs) using connectors or 4R with satellite rods (SRs) without connectors.

Objective: Compare PSO constructs with different rod configurations and adjacent-level interbody support.

Optimizing Cervicothoracic Junction Biomechanics after C7 Pedicle Subtraction Osteotomy: A Cadaveric Study of Stability and Rod Strain.

Objective: To compare biomechanical stability and rod strain among uniform rod (UR), tapered rod (TR), and UR+accessory rod (AR) constructs in a human cadaveric C7 pedicle subtraction osteotomy (PSO) model of cervical deformity correction.

Methods: Fourteen human cadaveric C2-T4 specimens were divided into 2 statistically equivalent groups. Specimens were instrumented from C2 to T3, and a 25° PSO was performed at C7.

Does the Choice of Spinal Interbody Fusion Approach Significantly Affect Adjacent Segment Mobility?

Study Design: Biomechanical study of range of motion (ROM) at the vertebral levels adjacent to the construct of posterior pedicle screw-rod fixation with different types of lumbar interbody fusion techniques (LIF).

Objective: To investigate the differences in adjacent segment mobility among three types of LIF: lateral lumbar interbody fusion (LLIF), transforaminal lumbar interbody fusion (TLIF), and posterior lumbar interbody fusion (PLIF).

Summary Of Background Data: Previous studies have concluded that LLIF, TLIF, and PLIF with posterior pedicle screw-rod fixation (PSR) provide equivalent stability in cadaveric specimens and are comparable in fusion rate and functional outcome.

Influence of Lumbar Lordosis on Posterior Rod Strain in Long-Segment Construct During Biomechanical Loading: A Cadaveric Study.

Objective: The lordotic shape of the lumbar spine differs substantially between individuals. Measuring and recording strain during spinal biomechanical tests is an effective method to infer stresses on spinal implants and predict failure mechanisms. The geometry of the spine may have a significant effect on the resultant force distribution, thereby directly affecting rod strain.

Biomechanics of a laterally placed sacroiliac joint fusion device supplemental to S2 alar-iliac fixation in a long-segment adult spinal deformity construct: a cadaveric study of stability and strain distribution.

Objective: S2 alar-iliac (S2AI) screw fixation effectively enhances stability in long-segment constructs. Although S2AI fixation provides a single transarticular sacroiliac joint fixation (SIJF) point, additional fixation points may provide greater stability and attenuate screw and rod strain. The objectives of this study were to evaluate changes in stability and pedicle screw and rod strain with extended distal S2AI fixation and with supplemental bilateral integration of two sacroiliac joint fusion devices implanted using a traditional minimally invasive surgical approach.

Biomechanics of open versus minimally invasive deformity correction:​ comparison of stability and rod strain between pedicle subtraction osteotomy and anterior column realignment.

Objective: Anterior column realignment (ACR) is a new minimally invasive approach for deformity correction that achieves a degree of lordosis similar to that obtained with pedicle subtraction osteotomy (PSO). This study compared the biomechanical profiles of ACR with PSO using range of motion (ROM) and posterior rod strain (RS) to gain insight into the ACR technique and the necessary surgical strategies to optimize longevity and stability.

Methods: An in vitro biomechanical study using standard flexibility testing (7.

Prediction of cow's fertility based on data recorded by automatic milking system during the periparturient period.

The results of most studies show the beneficial effect of milking automation on production parameters of dairy cows, but its effect on fertility traits is debatable. Therefore, a study was undertaken to predict cow fertility - services per conception (SC) and calving interval (CI) - based on automatic milking system (AMS) data collected in the periparturient period subdivided into the second and first week before calving, 1-4, 5-7, 8-14, 15-21 and 22-28 days of lactation. SC and CI were predicted using daily indicators such as concentrate intake, number of milkings, cow box time, milking time, milking speed, colostrum and milk yield, composition, temperature and electrical conductivity.

Adjacent-segment effects of lumbar cortical screw-rod fixation versus pedicle screw-rod fixation with and without interbody support.

Objective: Cortical screw-rod (CSR) fixation has emerged as an alternative to the traditional pedicle screw-rod (PSR) fixation for posterior lumbar fixation. Previous studies have concluded that CSR provides the same stability in cadaveric specimens as PSR and is comparable in clinical outcomes. However, recent clinical studies reported a lower incidence of radiographic and symptomatic adjacent-segment degeneration with CSR.

Biomechanical effects of a novel posteriorly placed sacroiliac joint fusion device integrated with traditional lumbopelvic long-construct instrumentation.

Objective: S2-alar-iliac (S2AI) screw fixation effectively ensures stability and enhances fusion in long-segment constructs. Nevertheless, pelvic fixation is associated with a high rate of mechanical failure. Because of the transarticular nature of the S2AI screw, adding a second point of fixation may provide additional stability and attenuate strains.

Biomechanics of Circumferential Cervical Fixation Using Posterior Facet Cages: A Cadaveric Study.

Objective: Anterior cervical discectomy and fusion (ACDF) is a common procedure for the treatment of cervical disease. Circumferential procedures are options for multilevel pathology. Potential complications of multilevel anterior procedures are dysphagia and pseudarthrosis, whereas potential complications of posterior surgery include development of cervical kyphosis and postoperative chronic neck pain.

Dimensional Characterization of the Human Lumbar Interlaminar Space as a Guide for Safe Application of Minimally Invasive Dilators.

Background: The risk of interlaminar passage of a dilator into the lumbar spinal canal in minimally invasive approaches is currently unknown. Among anthropometric data reported in the medical literature, there is no cadaveric report of the interlaminar dimensions of the lumbar spine.

Objective: To report the lumbar interlaminar dimensions in neutral, flexion, and extension postures.

Prediction of Lactational Milk Yield of Cows Based on Data Recorded by AMS during the Periparturient Period.

Early prediction of lactation milk yield enables more efficient herd management. Therefore, this study attempted to predict lactation milk yield (LMY) in 524 Polish Holstein-Friesian cows, based on information recorded by the automatic milking system (AMS) in the periparturient period. The cows calved in 2016 and/or 2017 and were used in 3 herds equipped with milking robots.

Impact of dual-headed pedicle screws on the biomechanics of lumbosacral junction multirod constructs.

Objective: The objective of this study was to evaluate a novel connector design and compare it with traditional side connectors, such as a fixed-angle connector (FAC) and a variable-angle connector (VAC), with respect to lumbosacral stability and instrumentation strain.

Methods: Standard nondestructive flexibility tests (7.5 Nm) and compression tests (400 N) were performed using 7 human cadaveric specimens (L1-ilium) to compare range of motion (ROM) stability, posterior rod strain (RS), and sacral screw bending moment (SM).

Variations Among Human Lumbar Spine Segments and Their Relationships to In Vitro Biomechanics: A Retrospective Analysis of 281 Motion Segments From 85 Cadaveric Spines.

Background: Biomechanical properties of intact spinal motion segments are used to establish baseline values during in vitro studies evaluating spinal surgical techniques and implants. These properties are also used to validate computational models (ie, patient-specific finite element models) of human lumbar spine segments. Our laboratory has performed a large number of in vitro mechanical studies of lumbar spinal segments, using a consistent methodology.