Stability and Instrumentation Stresses Among Sacropelvic Fixation Techniques With Novel Porous Fusion/Fixation Implants: A Finite Element Study.

Background: Sacropelvic fixation is frequently combined with thoracolumbar instrumentation for correcting spinal deformities. This study aimed to characterize sacropelvic fixation techniques using novel porous fusion/fixation implants (PFFI).

Methods: Three T10-pelvis finite element models were created: (1) pedicle screws and rods in T10-S1, PFFI bilaterally in S2 alar-iliac (S2AI) trajectory; (2) fixation in T10-S1, PFFI bilaterally in S2AI trajectory, triangular implants bilaterally above the PFFI in a sacro-alar-iliac trajectory (PFFI-IFSAI); and (3) fixation in T10-S1, PFFI bilaterally in S2AI trajectory, PFFI in sacro-alar-iliac trajectory stacked cephalad to those in S2AI position (2-PFFI).

Effect of Sacropelvic Hardware on Axis and Center of Rotation of the Sacroiliac Joint: A Finite Element Study.

Background: The sacroiliac joint (SIJ) transfers the load of the upper body to the lower extremities while allowing a variable physiological movement among individuals. The axis of rotation (AoR) and center of rotation (CoR) of the SIJ can be evaluated to analyze the stability of the SIJ, including when the sacrum is fixed. The purpose of this study was to determine how load intensity affects the SIJ for the intact model and to characterize how sacropelvic fixation performed with different techniques affects this joint.

High-Demand Spinal Deformity With Multi-Rod Constructs and Porous Fusion/Fixation Implants: A Finite Element Study.

Study Design: Basic science (finite element analysis).

Objectives: Pedicle subtraction osteotomy (PSO) at L5 is an effective treatment for sagittal imbalance, especially in select cases of patients showing kyphosis with the apex at L4-L5 but has been scarcely investigated. The aim of this study was to simulate various "high-demand" instrumentation approaches, including varying numbers of rods and sacropelvic implants, for the stabilization of a PSO at L5.

Innovative sacropelvic fixation using iliac screws and triangular titanium implants.

Purpose: Sacropelvic fixation is frequently used in combination with thoracolumbar instrumentation for the correction of severe spinal deformities. The purpose of this study was to explore the effects of the triangular titanium implants on the iliac screw fixation. Our hypothesis was that the use of triangular titanium implants can increase the stability of the iliac screw fixation.

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.

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.

Comparative analysis of the lateral and posterolateral trajectories for fixation of the sacroiliac joint-a cadaveric study.

Background: A number of minimally invasive sacroiliac (SI) joint fusion solutions for placing implants exist, with reduced post-operative pain and improved outcomes compared to open procedures. The objective of this study was to compare two MIS SI joint fusion approaches that place implants directly across the joint by comparing the ilium and sacrum bone characteristics and SI joint separation along the implant trajectories.

Methods: Nine cadaveric specimens (n = 9) were CT scanned and the left and right ilium and sacrum were segmented.

Biomechanical Stability of Primary and Revision Sacroiliac Joint Fusion Devices: A Cadaveric Study.

Study Design: An in vitro biomechanics study.

Objective: To evaluate the efficacy of triangular titanium implants in providing mechanical stabilization to a sacroiliac joint with primary and revision sized implants.

Methods: Ten lumbopelvic cadaveric specimens were tested in 4 stages: intact, pubic symphysis sectioned, primary, and simulated revision.

The use of triangular implants to enhance sacropelvic fixation: a finite element investigation.

Background Context: Long thoracolumbar fixation and fusion have become a consolidated treatment for severe spinal disorders. Concomitant sacropelvic fixation with S2 alar-iliac (S2AI) screws is frequently performed to limit instrumentation failure and pseudarthrosis at the lumbosacral junction.

Purpose: This study explored the use of triangular titanium implants in different configurations in which the implants supplemented standard sacropelvic fixation with S2AI screws in order to further increase the stability of S2AI fixation.

Effects on hip stress following sacroiliac joint fixation: A finite element study.

For those patients who suffer from low back pain generated by the sacroiliac (SI) joint, fusion of the SI joint has proven to be an effective means of stabilizing it and reducing pain. Though it has shown promise, SI joint fusion raises clinical questions regarding its effect on neighboring joints such as the hip. As such, the purpose of this study was to determine the effects of SI joint fixation on the hip.

Sacroiliac joint stability: Finite element analysis of implant number, orientation, and superior implant length.

Aim: To analyze how various implants placement variables affect sacroiliac (SI) joint range of motion.

Methods: An experimentally validated finite element model of the lumbar spine and pelvis was used to simulate a fusion of the SI joint using various placement configurations of triangular implants (iFuse Implant System). Placement configurations were varied by changing implant orientation, superior implant length, and number of implants.

Biomechanics of unilateral and bilateral sacroiliac joint stabilization: laboratory investigation.

OBJECTIVE Bilateral symptoms have been reported in 8%-35% of patients with sacroiliac (SI) joint dysfunction. Stabilization of a single SI joint may significantly alter the stresses on the contralateral SI joint. If the contralateral SI joint stresses are significantly increased, degeneration may occur; alternatively, if the stresses are significantly reduced, bilateral stabilization may be unnecessary for patients with bilateral symptoms.

Fortifying the Bone-Implant Interface Part 2: An In Vivo Evaluation of 3D-Printed and TPS-Coated Triangular Implants.

Background: Minimally invasive surgical fusion of the sacroiliac (SI) joint using machined solid triangular titanium plasma spray (TPS) coated implants has demonstrated positive clinical outcomes in SI joint pain patients. Additive manufactured (AM), 3D-printed, fenestrated triangular titanium implants with porous surfaces and bioactive agents, such as nanocrystalline hydroxyapatite (HA) or autograft, may further optimize bony fixation and subsequent biomechanical stability.

Methods: A bilateral ovine distal femoral defect model was used to evaluate the cancellous bone-implant interfaces of TPS-coated and AM implants.

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces.

Background: An aging society and concomitant rise in the incidence of impaired bone health have led to the need for advanced osteoconductive spinal implant surfaces that promote greater biological fixation ( for interbody fusion cages, sacroiliac joint fusion implants, and artificial disc replacements). Additive manufacturing, 3D-printing, may improve bone integration by generating biomimetic spinal implant surfaces that mimic bone morphology. Such surfaces may foster an enhanced cellular response compared to traditional implant surfacing processes.

Sacroiliac Joint Fusion Minimally Affects Adjacent Lumbar Segment Motion: A Finite Element Study.

Background: Adjacent segment disease is a recognized consequence of fusion in the spinal column. Fusion of the sacroiliac joint is an effective method of pain reduction. Although effective, the consequences of sacroiliac joint fusion and the potential for adjacent segment disease for the adjacent lumbar spinal levels is unknown.

Biomechanical Determination of Distal Level for Fusions across the Cervicothoracic Junction.

Study Design In vitro testing. Objective To determine whether long cervical and cervicothoracic fusions increase the intradiscal pressure at the adjacent caudal disk and to determine which thoracic end vertebra causes the least increase in the adjacent-level intradiscal pressure. Methods A bending moment was applied to six cadaveric cervicothoracic spine specimens with intact rib cages.

The effect of implant placement on sacroiliac joint range of motion: posterior versus transarticular.

Study Design: A human cadaveric biomechanical study of 2 sacroiliac (SI) joint fusion implant placement techniques.

Objective: To evaluate and compare the biomechanical properties of 2 implant placement techniques for SI joint fusion.

Summary Of Background Data: Minimally invasive placement of SI joint fusion implants is a potential treatment of SI joint disruptions and degenerative sacroiliitis.

Evaluation of a minimally invasive procedure for sacroiliac joint fusion - an in vitro biomechanical analysis of initial and cycled properties.

Introduction: Sacroiliac (SI) joint pain has become a recognized factor in low back pain. The purpose of this study was to investigate the effect of a minimally invasive surgical SI joint fusion procedure on the in vitro biomechanics of the SI joint before and after cyclic loading.

Methods: SEVEN CADAVERIC SPECIMENS WERE TESTED UNDER THE FOLLOWING CONDITIONS: intact, posterior ligaments (PL) and pubic symphysis (PS) cut, treated (three implants placed), and after 5,000 cycles of flexion-extension.

Decellularized tendon-bone composite grafts for extremity reconstruction: an experimental study.

Background: Restoration of biomechanical strength following surgical reconstruction of tendon or ligament insertion tears is challenging because these injuries typically heal as fibrous scars. The authors hypothesize that injuries at the tendon-bone interface would benefit from reconstruction with decellularized composite tendon-bone grafts.

Methods: Tendon-bone grafts were harvested from Sprague-Dawley rats.

A quantitative assessment of the insertional footprints of the hip joint capsular ligaments and their spanning fibers for reconstruction.

Quantitative descriptions of the hip joint capsular ligament insertional footprints have been reported. Using a three-dimensional digitizing system, and computer modeling, the area, and dimensions of the three main hip capsular ligaments and their insertional footprints were quantified in eight cadaveric hips. The iliofemoral ligament (ILFL) attaches proximally to the anterolateral supra-acetabular region (mean area = 4.

Trapezium trabecular morphology in carpometacarpal arthritis.

Purpose: In thumb carpometacarpal osteoarthritis, current evidence suggests that degenerative, bony remodeling primarily occurs within the trapezium. Nevertheless, the pathomechanics involved and the most common sites of wear remain controversial. Quantifying structural bone morphology characteristics with high-resolution computed tomography CT (micro-CT) infer regions of load transmission.

Locked versus nonlocked plate fixation for first metatarsophalangeal arthrodesis: a biomechanical investigation.

Background: First metatarsophalangeal (MTP) arthrodesis using dorsal plate fixation is a common procedure for painful conditions of the great toe. Locked plates have become increasingly common for arthrodesis procedures in the foot, including the hallux MTP joint. The biomechanical advantages and disadvantages of these plates are currently unknown.

A viscoelastic constitutive model can accurately represent entire creep indentation tests of human patella cartilage.

Cartilage material properties provide important insights into joint health, and cartilage material models are used in whole-joint finite element models. Although the biphasic model representing experimental creep indentation tests is commonly used to characterize cartilage, cartilage short-term response to loading is generally not characterized using the biphasic model. The purpose of this study was to determine the short-term and equilibrium material properties of human patella cartilage using a viscoelastic model representation of creep indentation tests.

In vitro analysis of peri-articular soft tissues passive constraining effect on hip kinematics and joint stability.

Purpose: Aim of the study is to assess the contribution of peri-articular soft tissues to hip joint kinematics and their influence on hip stability.

Methods: Four hemi-corpse specimens (3 males, average age 72 years) were studied using a custom navigation system. Hip kinematics (femoral head motion relative to the acetabulum and joint range of motion) were evaluated with the hip manually positioned in 36 different positions with (I) soft tissues intact, (II) after removal of the skin and muscles and (III) after partial capsulectomy.