Identification of Pedicle Screw Pullout Load Paths for Osteoporotic Vertebrae

Krishnan Venkatesh,Varghese Vicky,Kumar Gurunathan Saravana,Yoganandan Narayan 대한척추외과학회 2020 Asian Spine Journal Vol.14 No.3

Study Design: A biomechanical study.Purpose: To determine the actual load path and compare pullout strengths as a function of screw size used in revision surgeries using postmortem human subject specimens.Overview of Literature: Pedicle screw fixation has become the standard of care in the surgical management of spinal instability. However, pullout failures are widely observed in osteoporotic spines and treated by revision surgeries using a higher diameter screw, performing cement augmentation, or increasing the levels of fixation. While the peak forces to final pullout are reported, the actual load path to achieve the final force level is not available. Methods: Six osteoporotic lumbar spines (L2–L5) were instrumented with 5.5×40 mm polyaxial screws and loaded along the axis of the screw using a material testing machine according to American Society for Testing of Materials 543-07 test protocol. Tests were again conducted by replacing them with 6.5×40 mm (group A) or 7.5×40 mm (group B) screws. Force-displacement data were grouped and load paths (mean±1 standard deviation) were compared.Results: Pullout strength decreased by 36% when the size of the revision screw was increased by 1 mm, while it increased by 35% when the size of the revision screw was increased by 2 mm compared to the index screw value. While the morphologies of the load paths were similar in all cases, they differ between the two groups: the larger screw responded with generally elevated stiffer path than the smaller screw, suggesting that revision surgery using a larger screw has more purchase along the inserted body-pedicle axis.Conclusions: A larger screw enhances strength and increases biomechanical stability in revision surgeries, although the final surgical decision is made by the clinician, which includes the patient’s anatomy and associated characteristics.

Comparative Analysis of Effect of Density, Insertion Angle and Reinsertion on Pull-Out Strength of Single and Two Pedicle Screw Constructs Using Synthetic Bone Model

Venkatesh Krishnan,Vicky Varghese,Gurunathan Saravana Kumar 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.3

Study Design: Biomechanical study. Purpose: To determine the effect of density, insertion angle and reinsertion on pull-out strength of pedicle screw in single and two screw-rod configurations. Overview of Literature: Pedicle screw pull-out studies have involved single screw construct, whereas two screws and rod constructs are always used in spine fusions. Extrapolation of results using the single screw construct may lead to using expensive implants or increasing the fusion levels specifically in osteoporotic bones. Methods: Single screw and two screw pull-out strength tests were carried out according to American Society for Testing and Materials F 543-07 on foam models to test the effect of density, insertion angle and reinsertion using poly axial pedicle screws. Results: Bone density was the most significant factor deciding the pull-out strength in both single and two screw constructs. The difference in pull-out strength between single screw and two screw configurations in extremely osteoporotic bone model (80 kg/m3) was 78%, whereas in the normal bone model it was 48%. Axial pull-out value was highest for the single screw configuration; in the two screw configuration the highest pull-out strength was at 10°–15°. There was an 18% reduction in pull-out strength due to reinsertion in single screw configuration. The reinsertion effect was insignificant in the two screw configuration. Conclusions: A significant difference in response of various factors on holding power of pedicle screw between single and two-screw configurations is evident. The percentage increase in pull-out strength between single and two screw constructs is higher for osteoporotic bone when compared to normal bone. Reinsertion has no significant effect on pull-out strength in the two screw rod configuration.

Spinel CoMn2O4 nano-/micro-spheres embedded RGO nanosheets modified disposable electrode for the highly sensitive electrochemical detection of metol

Krishnan Venkatesh,Balamurugan Muthukutty,Shen-Ming Chen,Periyakaruppan Karuppasamy,Ahmed S. Haidyrah,Chelladurai Karuppiah,Chun-Chen Yang,Sayee Kannan Ramaraj 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.106 No.-

This work focussed on the fabrication of synergetic spinel CoMn2O4 embedded reduced graphene oxide(CoMn2O4@RGO) nanocomposite over the surface of modified screen-printed carbon electrode (SPCE) forhighly sensitive and enhanced electrochemical detection of metol (MTL) in 0.05 M phosphate buffer electrolyte. The CoMn2O4@RGO nanocomposite material was synthesized by sonochemical method and wellcharacterizedusing various spectral and analytical (XRD, TGA, Raman spectroscopic, FE-SEM, HR-TEM &EA) techniques. Cyclic and differential pulse voltammetry techniques were used for the detection of MTLat CoMn2O4@RGO modified SPCE. The present electrochemical sensor shows a dynamic linear responserange from 0.01 to 137.65 mM and the detection limit, quantification, sensitivity were estimated to be0.050 mM, 1.64 mM, and 3.77 mA mM1 cm2. Furthermore, the proposed MTL sensor was exhibited numerousadvantages including very ease fabrication, high selectivity, stability, and reproducibility for thedetection of MTL. Based on the obtained experimental data a plausible MTL redox mechanism was proposed. In addition, the present electrochemical sensor was applied in real sample analysis at the spikedsamples (lake water samples + MTL) observed with good recovery results.

Assessment of Genotoxic potential of Annonacin and Annona muricata L. extracts on human breast cancer (MCF-7) cells

Naik Aditi Venkatesh,Sellappan Krishnan 경희대학교 융합한의과학연구소 2021 Oriental Pharmacy and Experimental Medicine Vol.21 No.4

The use of plants as a source of palliative or treatment for cancer is quite widespread worldwide. Annona muricata L. (Graviola) exhibits a wide array of ethno-medicinal and curative properties, accredited to different plant organs. The bio-activity of this plant is characterized by the production of secondary metabolites like alkaloids, phenols and most importantly annonaceous acetogenins found uniquely in this plant group. While A. muricata is gaining recognition as anti-cancer treating plant, the present study was undertaken to affirm probable genotoxic effect of pulp and leaf hydro-methanolic extracts in comparison with potent acetogenin, Annonacin on DNA of breast cancer (MCF-7) cells using alkaline comet assay. Genotoxic effects were evaluated using single cell gel electrophoresis (SCGE) method and the tail parameters from pooled comets were scored using TriTek CometScore Pro ver. 1.01.44 software. The average tail length (TL), percentage of tail DNA (TD), tail moment (TM) and Olive tail moment (OTM) were calculated which indicates the extent of DNA damage in cells followed by Statistical analysis. Study revealed the highest DNA damage toward MCF-7 cells in the form of comet streak or tails in 0.01 mg/mL Annonacin treatment. While the leaf extracts of A. muricata showed significantly higher tail parameters than the pulp extract in relation to untreated control. Our findings indicated that among the two extracts from A. muricata tested, the leaf exhibited better genotoxic potential compared to pulp extract, however, the plant extracts showed lesser efficacy in comparison with standard annonacin compound. Thus, this study further calls for more methodical safety evaluation and other end-points of genotoxicity apart from DNA damage.

Evaluating Pedicle-Screw Instrumentation Using Decision-Tree Analysis Based on Pullout Strength

Vicky Varghese,Venkatesh Krishnan,Gurunathan Saravana Kumar 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.4

Study Design: A biomechanical study of pedicle-screw pullout strength. Purpose: To develop a decision tree based on pullout strength for evaluating pedicle-screw instrumentation. Overview of Literature: Clinically, a surgeon’s understanding of the holding power of a pedicle screw is based on perioperative intuition (which is like insertion torque) while inserting the screw. This is a subjective feeling that depends on the skill and experience of the surgeon. With the advent of robotic surgery, there is an urgent need for the creation of a patient-specific surgical planning system. A learning-based predictive model is needed to understand the sensitivity of pedicle-screw holding power to various factors. Methods: Pullout studies were carried out on rigid polyurethane foam, representing extremely osteoporotic to normal bone for different insertion depths and angles of a pedicle screw. The results of these experimental studies were used to build a pullout-strength predictor and a decision tree using a machine-learning approach. Results: Based on analysis of variance, it was found that all the factors under study had a significant effect (p <0.05) on the holding power of a pedicle screw. Of the various machine-learning techniques, the random forest regression model performed well in predicting the pullout strength and in creating a decision tree. Performance was evaluated, and a correlation coefficient of 0.99 was obtained between the observed and predicted values. The mean and standard deviation of the normalized predicted pullout strength for the confirmation experiment using the current model was 1.01±0.04. Conclusions: The random forest regression model was used to build a pullout-strength predictor and decision tree. The model was able to predict the holding power of a pedicle screw for any combination of density, insertion depth, and insertion angle for the chosen range. The decision-tree model can be applied in patient-specific surgical planning and a decision-support system for spine-fusion surgery.

Laminectomy; Laminoplasty; Finite element analyses

Vicky Varghese,Venkatesh Krishnan,Gurunathan Saravana Kumar 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.3

Study Design: A biomechanical study. Purpose: A new biomechanical model of the vertebra has been developed that accounts for the inhomogeneity of bone and the contribution of the pedicle toward the holding strength of a pedicle screw. Overview of Literature: Pullout strength studies are typically carried out on rigid polyurethane foams that represent the homogeneous vertebral framework of the spine. However, the contribution of the pedicle region, which contributes to the inhomogeneity in this framework, has not been considered in previous investigations. Therefore, we propose a new biomechanical model that can account for the vertebral inhomogeneity, especially the contribution of the pedicles toward the pullout strength of the pedicle screw. Methods: A bilayer foam model was developed by joining two foams representing the pedicle and the vertebra. The results of the pullout strength tests performed on the foam models were compared with those from the tests performed on the cadaver lumbar vertebra. Results: Significant differences (p <0.05) were observed between the pullout strength of the pedicle screw in extremely osteoporotic (0.18±0.11 kN), osteoporotic (0.37±0.14 kN), and normal (0.97±0.4 kN) cadaver vertebra. In the monolayer model, significant differences (p <0.05) were observed in pullout strength between extremely osteoporotic (0.3±0.02 kN), osteoporotic (0.65±0.12 kN), and normal (0.99±0.04 kN) bone model. However, the bilayer foam model exhibited no significant differences (p >0.05) in the pullout strength of pedicle screws between osteoporotic (0.85±0.08 kN) and extremely osteoporotic bone models (0.94±0.08 kN), but there was a significant difference (p <0.05) between osteoporotic (0.94±0.08 kN) and normal bone models (1.19±0.05 kN). There were no significant differences (p >0.05) in pullout strength between cadaver and bilayer foam model in normal bones. Conclusions: The new synthetic bone model that reflects the contribution of the pedicles to the pullout strength of the pedicle screws could provide a more efficacious means of testing pedicle-screw pullout strength. The bilayer model can match the pullout strength value of normal lumbar vertebra bone whereas the monolayer foam model was able to match that of the extremely osteoporotic lumbar vertebra.

Symptomatic Solitary Osteochondroma of the Subaxial Cervical Spine in a 52-Year-Old Patient

Vijay Sekharappa,Rohit Amritanand,Venkatesh Krishnan,Kenny Samuel David 대한척추외과학회 2014 Asian Spine Journal Vol.8 No.1

Osteochondromas are the most common benign tumors of the bone. They mostly arise from the appendicular skeleton and present clinically in the second or third decade of life. Ostechondromas arising from the subaxial cervical spine and presenting after the 5th decade of life are extremely rare. We report a 52-year-old male patient who presented with numbness and subjective weakness of left upper and lower limbs and neck pain, and had lobulated bony hard fixed swelling in the right lower cervical paraspinal region. Radiological images revealed a bony swelling arising from C4 and C5 lamina with a cartilaginous cap and intraspinal extension. Excision biopsy with stabilisation of the spine was performed. Histopathalogical examination of the specimen confirmed the diagnosis of osteochondroma. We conclude surgical excision of such rare tumors, including the cartilaginous cap as well as the intraspinal component can reliably produce a good clinical outcome.

The Extended Posterior Circumferential Decompression Technique in the Management of Tubercular Spondylitis with and without Paraplegia

Barani Rathinavelu,Justin Arockiaraj,Venkatesh Krishnan,Rohit Amritanand,Gabriel David Sundararaj 대한척추외과학회 2014 Asian Spine Journal Vol.8 No.6

Study Design: Retrospective clinical series. Purpose: To study the clinical, functional and radiological results of patients with tuberculous spondylitis with and without paraplegia, treated surgically using the “Extended Posterior Circumferential Decompression (EPCD)” technique. Overview of Literature: With the increasing possibility of addressing all three columns by a single approach, posterior and posterolateral approaches are gaining acceptance. A single exposure for cases with neurological deficit and kyphotic deformity requiring circumferential decompression, anterior column reconstruction and posterior instrumentation is helpful. Methods: Forty-one patients with dorsal/dorsolumbar/lumbar tubercular spondylitis who were operated using the EPCD approach between 2006 to 2009 were included. Postoperatively, patients were started on nine-month anti-tuberculous treatment. They were serially followed up to thirty-six months and both clinical measures (including pain, neurological status and ambulatory status) and radiological measures (including kyphotic angle correction, loss of correction and healing status) were used for assessment. Results: Disease-healing with bony fusion (interbody fusion) was seen in 97.5% of cases. Average deformity (kyphosis) correction was 54.6% in dorsal spine and 207.3% in lumbar spine. Corresponding loss of correction was 3.6 degrees in dorsal spine and 1.9 degrees in the lumbar spine. Neurological recovery in Frankel B and C paraplegia was 85.7% and 62.5%, respectively. Conclusions: The EPCD approach permits all the advantages of a single or dual session anterior and posterior surgery, with significant benefits in terms of decreased operative time, reduced hospital stay and better kyphotic angle correction.

Orthopaedics, PostGraduate Institute of Medical Education and Research, Chandigarh, India

Vijay Sekharappa,Rohit Amritanand,Venkatesh Krishnan,Kenny Samuel David 대한척추외과학회 2014 Asian Spine Journal Vol.8 No.1

Study Design: Retrospective analysis of radiological images. Purpose: To determine the prevalence of lumbosacral transition vertebra (LSTV) and to study its significance with respect to clinically significant spinal symptoms, disc degeneration and herniation. Overview of Literature: LSTV is the most common congenital anomaly of the lumbosacral spine. The prevalence has been debated to vary between 7% and 30%, and its relationship to back pain, disc degeneration and herniation has also not been established. Methods: The study involved examining the radiological images of 3 groups of patients. Group A consisted of kidney urinary bladder (KUB) X-rays of patients attending urology outpatient clinic. Group B consisted of X-rays with or without magnetic resonance images (MRIs) of patients at-tending a spine outpatient clinic, and group C consisted of X-rays and MRI of patients who had undergone surgery for lumbar disc herniation. One thousand patients meeting the inclusion criteria were selected to be in each group. LSTV was classified by Castellvi’s classification and disc degeneration was assessed by Pfirrmann’s grading on MRI scans. Results: The prevalence of LSTV among urology outpatients, spine outpatients and discectomy patients was 8.1%, 14%, and 16.9% respectively. LSTV patients showed a higher Pfirrmann’s grade of degeneration of the last mobile disc. Results were found to be significant statistically. Conclusions: The prevalence of LSTV in spinal outpatients and discectomy patients was significantly higher as compared to those attending the urology outpatient clinic. There was a definite causal relationship between the transitional vertebra and the degeneration of the disc immediately cephalad to it.

Recurrent Lumbar Disc Herniation: Results of Revision Surgery and Assessment of Factors that May Affect the Outcome. A Non-Concurrent Prospective Study

Mohammed Ibrahim,Justin Arockiaraj,Rohit Amritanand,Krishnan Venkatesh,Kenny Samuel David 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.5

Study Design: Non-concurrent prospective study. Purpose: To determine the functional outcome after open ‘fragment’ discectomy for recurrent lumbar disc herniation, and to analyze the factors that may affect the outcome. Overview of Literature: Literature search revealed only four studies where the factors affecting the outcome of a revision surgery for recurrent disc herniation have been evaluated. None of these studies analyzed for diabetes, disc degeneration and facet arthropathy. We have analyzed these features, in addition to the demographic and clinical factors. Methods: Thirty-four patients who underwent the procedure were followed up for an average period of 27.1 months. The Japanese Orthopaedic Association (JOA) score and Oswestry disability index (ODI) were used to assess the functional outcome. Age, gender, smoking, diabetic status, duration of recurrent symptoms, the side of leg pain, level and type of disc herniation, degree of disc degeneration on magnetic resonance imaging, and facet joint arthritis before first and second surgeries, were analyzed as factors affecting the outcome. Results: The average Hirabayashi improvement in JOA was 56.4%. The mean preoperative ODI was 74.5% and the mean ODI at final follow-up was 32.2%, the difference being statistically significant (p <0.01). Patients with diabetes, all of whom had poor long term glycemic control, were found to have a poor outcome in terms of ODI improvement (p =0.03). Conclusions: Open fragment discectomy is a safe and effective surgical technique for the treatment of recurrent disc herniation. However, patients with uncontrolled diabetes may have a less favorable outcome.