Biology subjects

Kumaran, Y.

Publications and source records attributed to Kumaran, Y..

4 recordsLinked to original sources

bioRxiv2024

Pelvic Ring Fractures: Does Spinopelvic Alignment Affect Sacral and Lumbopelvic Fixation Stability?

Background ContextPelvic ring is a complex boney and ligamentous complex and its structural integrity is paramount to be able to withstand the high forces. Pelvic ring fractures, which can result from low-energy impacts or high-velocity injuries and falls from great heights, can severely impair the structural integrity of the pelvic ring. These injuries can be fatal, especially in geriatric patients, with mortality rates ranging between 10% and 16%. Pelvic ring injuries require immediate stabilization, typically performed through internal fixation, to maintain circulatory balance and achieve anatomical restoration of the pelvis. MethodsA previously validated FE model of the spine, pelvis, and femur model was used to evaluate how different fixation techniques for pelvic ring injury affect spinopelvic biomechanics. The SS, PI, PT and LL of the normal, intact model was modified to generate two more SS models for this study. One modified model with an SS of 20{o} was considered the low SS model (SSD), while the second modified model with an SS of 32{o} was termed the high SS model (SSI). A unilateral pelvic ring fracture was simulated by resecting the left side of the sacrum and pelvis. The fractures were stabilized using two different posterior stabilization techniques 1) The fractures were stabilized using two different posterior stabilization techniques, and 2) L5-Ilium posterior screw fixation without cross connector (L5_PF_WO_CC). ResultsSSI demonstrated the higher range of motion, followed by Normal model and least by SSD model at right Sacroiliac Joint. No differences were seen between with and without cross connector model for range of motion at right SIJ. For L5-S1 motion models treated with cross connectors demonstrated the least motion compared to those treated without cross connectors for all configurations and loading conditions. For the sacrum fracture, models with high sacral slopes recorded the least horizontal displacement, followed by decreased sacral slope models for both configurations and loading conditions.

bioengineering↗

bioRxiv2024

Evaluating Paraspinal Muscle Response and Compensation via Musculoskeletal Modeling in Spinal Stenosis Surgeries

IntroductionLumbar spinal stenosis is a common cause of lower back pain and weakness in elderly patients. The gold standard treatment for this is lumbar laminectomy which involves widespread muscle damage to the multifidus, a complete loss of the posterior tension band which contains the supraspinous and interspinous ligaments. However, in recent years minimally invasive techniques such as bilateral and unilateral laminotomy have become more popular and are showing efficacy in the decompression of spinal stenosis. Due to its minimally invasive approach, the muscle retraction required for laminotomy is less intensive than that required for laminectomy. The overall body of literature on the surgical treatment of spinal stenosis is sparse in its interrogation of the biomechanical outcomes of these techniques and to our knowledge, there are no current publications that incorporate muscle forces. MethodsA previously validated thoracolumbar ribcage finite element (FE) model was used for this study. Three different surgeries, traditional laminectomy, unilateral and bilateral midline sparing approaches at L4-L5 segment were simulated by removing the spinous process, supraspinous, and interspinous ligaments. The segmental range of motion (ROM) for all models were acquired and input into a musculoskeletal modelling software to calculate muscle forces. ResultsUnilateral and bilateral laminotomy showed similar muscle forces for every muscle group in both flexion and extension motion. While comparing the muscle forces in laminotomy to the laminectomy in extension motion displayed an increase in Iliocostalis lumborum (IL) by 12 % and multifidus (MF) by 16% and decrease in transverse abdominus (TA) by 138% and erector spine (ES) by 12%. For flexion, there was an increase in IL by 35%, and MF by 12%. ConclusionOur results highlight that laminectomy, which involves the removal of paraspinal muscles and posterior ligamentous structures to relieve stenosis, can lead to increased instability and necessitate muscle compensation, particularly in adjacent and thoracic spine segments. Conversely, midline sparing approaches such as laminotomies, are associated with decreased muscle compensation across spinal segments and enhanced stability.

bioengineering↗

bioRxiv2024

Soft Tissue Mechanics in Hip Distraction after Total Knee Arthroplasty: A Finite Element Analysis

INTRODUCTIONImprovement in diagnostic and surgical techniques in hip arthroscopy have led to a surge in hip distraction procedures over the recent years with the predicted annual frequency being four out of every 10,000 orthopedic procedures in 2017. Due to the large traction force required to achieve the appropriate joint spacing intra-operatively, an emergence of traction-related neurological and soft tissue injuries have surfaced. Pre-existing hip joint pathologies and surgical procedures disrupt the biomechanical stability of the joint and significantly increase the risk of iatrogenic damage. Furthermore, patients with total knee arthroplasties are often subject to intra-articular ligament releases, leading to reduced stability; however, it is not well understood how this may impact their outcomes of hip arthroscopic procedures. The current study aims to investigate the biomechanical behavior of various instrumented knee joints subjected to traction forces to aid clinical understanding and advancements of hip arthroscopy techniques. METHODSA validated finite element (FE) model of the pelvis and lower extremity was developed from computed tomography (CT) scans of a healthy 45-year-old female. Three different models were assembled according to different TKA techniques performed: Bi-Cruciate Retaining (BCR) model, Posterior-Cruciate Retaining (PCR) model, and Posterior Stabilized (PS) model. The BCR model is noted by retaining all native ligaments of the knee joint (ACL, PCL, MCL, and LCL), whereas the PCR model was subject to ACL removal and the PS model required ACL and PCL removal (Figure 1). The pelvis was encastered to prevent translation under the traction forces as motion of the patients trunk is restrained, intraoperatively. To simulate the loading condition of hip distraction, an axial force was coupled to the distal fibula and tibia and incrementally increased from 100N to 500N. Joint spacing and ligament strain in the hip and knee joint were analyzed to assess the effects of traction forces. O_FIG O_LINKSMALLFIG WIDTH=174 HEIGHT=200 SRC="FIGDIR/small/580129v2_fig1.gif" ALT="Figure 1"> View larger version (70K): org.highwire.dtl.DTLVardef@1494014org.highwire.dtl.DTLVardef@e0fdeorg.highwire.dtl.DTLVardef@133cb56org.highwire.dtl.DTLVardef@16aaf02_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Meshed parts of the A.) Posterior Cruciate retaining total knee replacement system and the B.) Bi-cruciate retaining total knee replacement system. C_FIG RESULTSThe medial and lateral compartment stiffness of the knee joint was analyzed under hip distraction for the three different TKA scenarios. The BCR model displayed the greatest average knee complex stiffness. Release of the ACL resulted in a larger decrease of stiffness compared to release of the PCL. There was no change in forces required for hip distraction as result of changes in the knee joint stiffness (Figure 3). The PCR and PS models were subject to excess knee joint distraction that exceeded 12 mm and ligament strain greater than 20% before adequate hip joint distraction of 10 mm was achieved. The BCR model remained below 10 mm of knee distraction and 15% ligament strain at 10 mm of hip joint distraction. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/580129v2_fig3.gif" ALT="Figure 3"> View larger version (90K): org.highwire.dtl.DTLVardef@107c292org.highwire.dtl.DTLVardef@77351corg.highwire.dtl.DTLVardef@40011aorg.highwire.dtl.DTLVardef@88e9c_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 3.C_FLOATNO FE models of instrumented TKA. A) PCR TKA with simulated ACL release. B) PS TKA with simulated ACL and PCL releases. C) BCR TKA with intact ligaments. C_FIG DISCUSSIONOur study reveals patients undergoing hip distraction with a prior TKA may experience increased soft tissue damage or iatrogenic dislocation due to reduced knee joint stability. The PCR and PS models outline a trend suggesting patients who have undergone ligament sacrificing TKAs experience large reductions in knee joint stability, causing strain levels that are indicative of soft tissue injury. The BCR TKA was indicated to be the safest under the distraction conditions as joint spacing and strain levels were largely reduced comparatively; however, when surpassing 10 mm of knee joint distraction at forces greater than 350 N, the strain levels in the ACL suggest minor injury may occur.

bioengineering↗

bioRxiv2024

Biomechanical Implications of Spinopelvic Alignment on Femoral Head Cartilage and the Proximal Femoral Physis in Slipped Capital Femoral Epiphysis: A Theoretical Finite Element Analysis

BackgroundSlipped capital femoral epiphysis (SCFE) is a prevalent pediatric hip disorder. Recent studies suggest the spines sagittal profile may influence the proximal femoral growth plates slippage, an aspect not extensively explored. This study utilizes finite element analysis to investigate how different spinopelvic alignments affect shear stress and potential slippage at the growth plate. MethodsA finite element model was developed from CT scans of a healthy adult male lumbar spine, pelvis, and femurs. The model was subjected to various sagittal alignments through rotational boundary conditions. Simulations of two-leg stance, one-leg stance, walking heel strike, ascending stairs heel strike, and descending stairs heel strike were conducted. Parameters measured included hip joint contact area, stress, and maximum Tresca (shear) stress on the growth plate. FindingsPosterior pelvic tilt cases indicated larger shear stresses compared to the anterior pelvic tilt variants except in two leg stance. Two leg stance resulted in decreases in the posterior tilted pelvi variants compared to anterior tilted pelvi, however a combination of posterior pelvic tilt and high pelvic incidence indicated larger shear stresses on the growth plate. One leg stance and heal strike resulted in higher shear stress on the growth plate in posterior pelvic tilt variants compared to anterior pelvic tilt, with a combination of posterior pelvic tilt and high pelvic incidence resulting in the largest shear stress. InterpretationOur findings suggest that posterior pelvic tilt and high pelvic incidence can lead to increased shear stress at the growth plate. Activities performed in patients with these alignments may predispose to biomechanical loading that shears the growth plate, potentially causing slippage.

bioengineering↗