|Year : 2021 | Volume
| Issue : 1 | Page : 29-39
Spondylolysis and pars repair technique: A comprehensive literature review of the current concepts
KS Sri Vijay Anand, Naresh Kumar Eamani, Ajoy Prasad Shetty, S Rajasekaran
Department of Spine Surgery, Ganga Hospital, 313, Mettupalayam Road, Coimbatore, Tamil Nadu, India
|Date of Submission||10-Aug-2020|
|Date of Acceptance||17-Dec-2020|
|Date of Web Publication||28-Jan-2021|
Ajoy Prasad Shetty
Department of Spine Surgery, Ganga Hospital, 313, Mettupalayam Road, Coimbatore, Tamil Nadu.
Source of Support: None, Conflict of Interest: None
Spondylolysis is an important cause of low back pain in children and adolescents, especially in those involved in athletic activities. Spondylolysis is caused either by a fracture or by a defect in the pars inter-articularis and can be unilateral or bilateral. Among the various hypotheses regarding the etiopathogenesis of pars lysis, the occurrence of chronic micro-fractures secondary to repetitive extension and rotational stresses across pars remains the most convincing explanation to date. The majority of these patients remain asymptomatic. Imaging contributes to the staging and prognostication of the lesions, planning the line of management, and monitoring the response to treatment. Nonoperative treatment with activity restriction, braces, graded physiotherapy, and rehabilitation forms the cornerstone of management. Surgery is indicated in a specific cohort of patients whose symptoms persist despite an adequate conservative trial and includes spinal fusion and pars defect repair techniques. Patients who demonstrate good pain relief after diagnostic pars infiltration can be considered for pars repair. Patients aged ≤25 years, those with an athletic background, unilateral pathologies, and those without associated spondylolisthesis, instability, or disc degeneration are ideal candidates for pars repair. The overall outcome in spondylolysis is good, and 85% to 90% of athletes return to sports at 6 months following conservative or surgical line of treatment. In this current narrative review, we comprehensively discuss the etiology, patho-anatomy, natural history, clinical features, diagnostic modalities, and management of spondylolysis with special emphasis on direct repair techniques of pars.
Keywords: Etiopathogenesis, imaging, natural history, pars repair, spondylolysis
|How to cite this article:|
Sri Vijay Anand K S, Eamani NK, Shetty AP, Rajasekaran S. Spondylolysis and pars repair technique: A comprehensive literature review of the current concepts. Indian Spine J 2021;4:29-39
|How to cite this URL:|
Sri Vijay Anand K S, Eamani NK, Shetty AP, Rajasekaran S. Spondylolysis and pars repair technique: A comprehensive literature review of the current concepts. Indian Spine J [serial online] 2021 [cited 2021 May 12];4:29-39. Available from: https://www.isjonline.com/text.asp?2021/4/1/29/308205
| Introduction|| |
Spondylolysis is a developmental or acquired defect of pars inter-articularis resulting from repetitive microtrauma to a healthy or defective neural arch. The population incidence of spondylolysis is reported to be around 6%, with considerable variation across different ethnicities. Spondylolysis commonly occurs at the L5 vertebra (85–95%), followed by the L4 vertebra (5–15%), and can be either unilateral or bilateral., These levels are subjected to the highest degrees of static and dynamic stresses during physiological lumbar motions., Factors including upright posture, bipedal gait, and the presence of lumbar lordosis have been implicated as major reasons underlying the unique occurrence of spondylolysis in hominids. Although most patients remain asymptomatic, it is a well-acknowledged cause for low back pain (LBP) in young athletic individuals. Although various imaging modalities like plain radiograph, magnetic resonance imaging (MRI), computed tomography (CT), and bone scintigraphy have been demonstrated to be useful, there is still considerable ambiguity regarding the relative significance of each modality in the evaluation of spondylolysis. Currently, there is no consensus on the ideal diagnostic and treatment algorithms for patients presenting with pars lysis. Because a significant proportion of patients are young, there has been a considerable emphasis on nonfusion surgeries like direct pars repair in a certain proportion of patients who are eligible for this option. The current narrative review comprehensively discusses etiology, patho-anatomy, natural history, clinical features, diagnostic modalities, and management of spondylolysis, with special emphasis on direct repair techniques of pars.
| Materials and Methods|| |
A comprehensive search was done in PubMed database and Google Scholar using the following terms as MeSH headings and keywords: “spondylolysis,” “pars defect,” “pars repair,” “spondylolysis nonoperative treatment” on 24 May 2020. Only full-text articles with no restriction of language were included. The search resulted in a total of 5761 articles initially. Articles not pertaining to spondylolysis, articles with details not related to the current topic of interest, and duplicates were excluded. All original articles pertaining to the subject of interest were included. Furthermore, additional articles from recent reviews were handpicked and included in this review, resulting in a total of 232 studies.
Ever since the initial description by Sir Robert of Coblenz in 1855, the etiopathogenesis of spondylolysis has been extensively debated in the literature.,, It is now well established that spondylolysis is a developmental anomaly and is absent at birth. This has been confirmed by cadaveric and radiographic studies on stillborn/newborn babies, which showed no evidence of pars lysis at this age.,,, In a prospective study, Fredrickson noted that the first-degree relatives of patients with spondylolysis had a higher incidence (23%) than the general population. The contribution of the genetic component in the etiology has also been reported by Wiltse,, Wynne-Davies, and Albanese.
It is now well accepted that spondylolysis occurs due to repetitive stress to the pars inter-articularis primarily due to hyperextension. Wiltse et al. were the first to propose that spondylolysis results from fatigue fracture of the pars inter-articularis. This hypothesis was supported by a 47% incidence of lysis in young athletes, who presented with LBP. Particularly sports like gymnastics, diving, weight lifting, swimming, rowing, football, and volleyball that involve repetitive lumbar extension activities have a higher reported incidence of pars lysis., The effect of mechanical factors on lysis development is also supported by the 0% incidence in a group of 143 patients who never walked. Using a 3-D finite element model (FEM), Sairyo et al. analyzed stress lines at pars inter-articularis of a lumbar motion segment (L3-S1) in various modes. They found that stresses were high during extension and rotational movements and were the highest when the lumbar spine was subjected to combined extension and rotational forces. These stresses result in microcellular injury to the bone, and when the rate of injury far exceeds the rate of repair, fracture ensues.
There is a progressive increase in the strength of the neural arch from childhood to 50 years of age, following which it decreases. The elastic intervertebral discs and weaker pars in children cause increased stress to be placed on the pars inter-articularis on repeated extension during sporting events. The increased incidence of spondylolysis has been reported in athletes,, osteopetrosis,, athetoid cerebral palsy,, Scheuermann kyphosis.,
Anatomical factors pertaining to pars inter-articularis
The “lateral buttress,” which is the bony bridge across the superolateral edge of the inferior facet to pedicle/transverse process (TP) junction, grows progressively thinner, smaller, and structurally weaker as we caudally move from L1 to L5. The medial angulation of the isthmus is also significantly greater at L5 than proximal levels, which makes the L5 pars most vulnerable for failure under stresses.
Peleg et al. postulated that a horizontal sacral orientation puts L5 pars under significant stress due to the “pincer effect” exerted between the L4 inferior articular process and the S1 superior articular process during repetitive activities. It has also been shown that the pincer effect is significantly enhanced in increased lordosis between lower lumbar levels (L4-S1 levels). The fractures typically originate from the infero-medial margin and propagate in a superolateral direction.,
Natural history of spondylolysis
Fredrickson, in his landmark prospective study, reported that the prevalence of spondylolysis at birth was zero and increased progressively to 4.4%, 5.2%, and 6% by the ages 6 years, 12 years, and adulthood, respectively. Sairyo et al. reported that a majority of acute pars fractures have excellent healing potential in the early stages and heal with early immobilization and activity restriction. Nevertheless, if abnormal stresses persist, the fracture can progress to chronic pseudoarthrosis. The development of spondylolisthesis and slip progression has always remained major topics for debate in spondylolysis.,
The slippage in spondylolysis has been reported to be most prevalent during growth, particularly around growth spurt, and rarely progresses during adulthood., In a longitudinal study with a mean follow-up of 6 years, Sairyo et al. classified the children into three categories based on skeletal age: (a) cartilaginous (absent secondary ossification center), apophyseal (the apophyseal ring is present but not fused), and epiphyseal stages (fused apophysis). Overall, the majority of slippage (80%) occurred between the cartilaginous and apophyseal stages. Slip progression in spondylolysis is relatively uncommon and is extremely rare beyond the age of 16. Based on a 20-year follow-up study, Saraste reported a mean slip progression of 4 mm in spondylolysis, with only 11% and 5% of adolescents and adults progressing to greater than 10 mm, respectively. Beutler et al. performed a 45-year follow-up of the patients from the Fredrickson et al. study and noted spondylolysis in 6% of the patients. He also observed that unilateral spondylolysis did not show any slip progression, and only 22 patients with bilateral lysis had developed spondylolisthesis.
Another important point of discussion in spondylolysis is its role in contributing to degeneration at the involved and adjacent levels. While it is well acknowledged that degeneration is accelerated at the disc level just caudal to the level of lysis, studies have also demonstrated enhanced degenerative changes at the segment cranial to bilateral pars lysis.
A majority of patients with spondylolysis are asymptomatic. The most common complaint in symptomatic patients is focal, predominantly axial LBP. Spondylolysis must always be one of the differential diagnoses to be considered in a highly athletic adolescent patient who presents with exertional LBP. Some common physical findings include antalgic gait, exaggerated lumbar lordosis, paraspinal spasm, and hamstring tightness. The only reported pathognomonic finding is the reproduction of pain with a single-leg hyperextension test (patient stands on ipsilateral leg and hyperextends his lumbar spine; sensitivity 81%, specificity 39.7%).,,
Imaging modalities are of immense benefit not only in diagnosing but also in staging, prognosticating, treatment planning, and monitoring treatment response.
The current recommendation is to use anteroposterior (AP) and lateral views as the initial investigation. Dynamic X-rays (flexion and extension) may help to assess instability., In comparison with CT and bone scan, plain radiograph only has a sensitivity of 74% in detecting spondylolysis and therefore has a limited role in confirming the diagnosis and treatment planning. Indirect signs of spondylolysis on AP radiographs include spinous process deviation and “pedicle anisocory” (pedicle asymmetry)., On lateral radiographs, spondylolysis appears as pars lucency. While acute injuries have narrow and irregular edges, chronic lesions have smooth and rounded edges. Oblique views are useful in suspected cases and the typical description for pars defect is a “collared Scottie dog,” where collar denotes the defect.,
The presence of a discontinuity in the neural arch (incomplete ring sign) at the level of pedicle on axial CT is pathognomonic.,, It is extremely valuable in differentiating incomplete fractures from complete ones, as well as in identifying contralateral pedicle sclerosis in unilateral spondylolysis. The overall sensitivity of CT is around 85% (as compared with SPECT).
Morita et al. classified spondylolysis based on CT into three stages, namely early, progressive, and terminal stages [Table 1]. Defects with narrow, noncorticated margins have a good potential for healing with conservative management. On the other hand, lesions with a wide defect and sclerotic margins have low healing potential., CT is also the most sensitive investigation to confirm bony union, and typically the healing proceeds from the superior to the inferior cortex.
|Table 1: Morita classification of lytic lesions of pars inter-articularis|
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CT’s major limitations include relatively high radiation exposure, inability to diagnose early stress reactions, and difficulty in reliably distinguishing fresh fractures from nonunion.
Magnetic resonance imaging
MRI is the most useful investigation during the early stages of spondylolysis. Hyperintense signal changes on T2WI and short tau inversion and recovery sequences, at the level of pars, are indicative of edema secondary to active inflammation due to stress reaction or acute fracture. More chronic defects are characterized by focal hypo-intense regions on T1- and T2WI sagittal sequences [Figure 1]. Similarly, MRI also clearly depicts the tissue contained within the defect. While fibro-cartilaginous tissues appear hypointense on T1- and hypo- to isointense on T2WI, osseo-fibrous tissues appear as hypointense signals on both T1- and T2WI. High-intensity signals on T2WI represent inflammatory tissues or fluid. MRI is also useful in assessing Pfirrmann’s grading of degeneration of the disc, evaluating neural compression, and ruling out other pathologies.
|Figure 1: T1-weighted (A) and T2-weighted (B) sagittal MRI images of pars lysis|
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When compared with CT, MRI has 80% sensitivity in diagnosing spondylolysis, and is now recommended as the preferred investigation over CT and SPECT in the evaluation of spondylolysis. CT and MRI scans are corroborative and guide the management of lysis.,, Single photon emission tomography (SPECT) and hybrid SPECT-CT are preferred over the Tc99m bone scan but should be interpreted cautiously. SPECT is not recommended as an initial investigation in pars lysis. The current indications only include (a) detecting early stress reaction in patients with high suspicion when MRI is negative, (b) to differentiate acute lesions from pseudoarthrosis, (c) in determining the stage of healing and monitoring the response to conservative management.,
Tofte et al. have recommended an imaging approach for patients with suspected spondylolysis [Figure 2]. Similarly, Cheung et al. has recommended an approach for imaging in athletic patients with suspected spondylolysis. The classification put forth by Tatsamura et al., which uses both CT and MRI scans, guides the treatment and also predicts healing. The classification has two components, namely axial slice and sagittal slice classifications [Table 2]. On the basis of the imaging features, patients are divided into (a) curable stage—pre-lysis, early, and progressive—axial and sagittal stages of 0 to 2. (b) Pseudoarthrosis stage—terminal axial and sagittal stage 3.
|Figure 2: Diagnostic algorithm in a young patient suspected with spondylolysis [Tofte et al.]|
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Fluoroscopy-guided pars injection is an invasive procedure described as a therapeutic and diagnostic tool in symptomatic spondylolysis. Patients with ≥80% symptomatic pain relief for at least 60min after diagnostic pars block are reported to have a good prognostic outcome following pars repair., Pars injection has also been used therapeutically, using a combination of steroid and local anesthetic.,
The overall aim of treatment in active children with spondylolysis is to enable a return to regular activity or competitive sports without LBP. The goal of treating curable lesions with bone marrow edema is to achieve fusion through conservative measures. In patients with pseudo-arthritic lesions, aggressive physical rehabilitation should be performed to have relief from pain. Pars repair may be indicated in a small group of patients who have persistent pain despite conservative treatment.
Activity restriction, including timely cessation of sports in young athletes, is often the first step in the management of patients with symptomatic spondylolysis; this should be supplemented with a semi-hard lumbosacral brace to prevent lumbar extension and rotation. A full-time (≥20h/day) brace wear for at least 3 months has been demonstrated to result in complete osseous healing in ≥90% of patients. Physiotherapy protocol involving core strengthening and hamstring stretching exercises can be helpful after the completion of brace treatment., Sakai et al., based on their study involving 60 patients, reported 100% healing in the very early stage, 93.8% healing in the early stage, and 80% healing in the progressive stage. They did not try conservative treatment in the terminal group.
Low-intensity pulsed ultrasound therapy (LIPUS therapy)
The rationale underlying LIPUS is the stimulation of cellular production of cyclo-oxygenase 2 and consequent mineralization., LIPUS therapy, involving the use of ultrasound carriers at a frequency of 1.5 MHz, output intensity of 60 mW/cm2, and exposure time of 20min/day, has been demonstrated to significantly enhance healing rates. Busse et al. performed a meta-analysis and reported an average decrease in the healing time of 64 days in the LIPUS group when compared with the control. Though the initial results are promising, larger studies are necessary to assess the effectiveness.
Predictors of union
Overall, 87.5% of athletes returned to sports at a mean of 5.4 months following conservative treatment. Patients with a stress reaction on MRI and absent fracture line on CT show the best healing rates (almost 100%). Although unilateral spondylolysis has traditionally been considered to have high healing rates (around 70%), recent studies have also revealed that such lesions are not entirely benign and can potentially exert enormous amounts of stresses across the contralateral neural arches resulting in lysis of contralateral pars, pedicle, or lamina.,, The various predictive factors for a good outcome after conservative treatment of spondylolysis have been enumerated in [Table 3].
|Table 3: Positive predictors for pars defect union with conservative management|
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Surgery in spondylolysis has been recommended in symptomatic patients with pseudoarthrosis (terminal stage) following failed conservative management (≥6 months). The surgical options for these patients are either direct pars repair or lumbar fusion. Direct pars repair is preferred, as spinal fusion causes a decreased range of motion and may result in adjacent segment degeneration.,,
Candidates likely to have good outcomes after Pars repair
Patients ≤25 years of age, those with an athletic background, unilateral pathologies, and those without associated spondylolisthesis or instability or disc degeneration (Pfirmann grade 1–3) are ideal candidates for pars repair [Table 4].,, Suh et al. advocated that good pain relief after pars infiltration is also a good predictor for a successful outcome following pars repair. Patients with spina bifida occulta with hypoplastic posterior elements are poor candidates for pars repair.
Surgical techniques of pars repair
The surgical techniques can be classified as open and minimally invasive approaches. The basic principles underlying pars repair include debridement of pseudoarthrosis, placement of the bone graft, and achieving compression across the defect. Kimura was the first to perform a direct, noninstrumented pars repair. The various surgical techniques of pars repair have been discussed below.
Buck’s single lag screw fixation—
This technique involves direct internal fixation of pars defect with a lag screw (4.0 mm or 4.5 mm cortical screw) and autologous cancellous bone graft. The entry point is prepared by creating a notch in the inferior margin of the lamina, 10 mm lateral to the base of the spinous process. The screw trajectory is made across the defect with a 3.2 drill bit, in an upward, forward, and lateral direction (towards ipsilateral pedicle) [Figure 3]. Multiple studies have reported good results following Buck’s repair in 82%–100% of patients.,,,, It offers stable low-profile fixation, making it an excellent option in minimally invasive repairs. Disadvantages include difficult screw placement in the presence of narrow lamina and decreased amount of bone graft due to the screw.,,,
|Figure 3: Buck’s repair. A preoperative lateral radiograph (A), CT scan (B), and postoperative radiographs of a patient who underwent Buck’s repair|
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In 1986, Nicol and Scott described this technique of pars repair using stainless steel (SS) cerclage wire and bone grafting. In this technique, a 20-gauge SS wire is looped around the TPs bilaterally, and the four-wire ends are passed caudally to the spinous process of the affected segment. After bone grafting, the wires are tightened to achieve compression. Satisfactory results varying between 80% and 100% have been reported.,, Although technically more straightforward, this technique has many disadvantages, including significant muscle stripping, nerve root injury around TP, weak anchor points, implant failure, fatigue fracture of the spinous process, and need for postoperative bracing., A modification of the Scott technique is popular, and it involves the passage of wire around the pedicle screws passed into the pedicle of the affected vertebrae.
Cable-pedicle screw construct—
This technique described by Songer and Rovin involved the use of a special cable-screw construct. A double cable is passed under the lamina and threaded through a hole in the pedicle screw. It is then wrapped around the superior border of the spinous process before passing through a loop on the opposite end of the cable. Both cables are then tensioned simultaneously to achieve compression.
Morscher’s hook-screw technique—
Morscher designed a special hook-screw in which a spring-loaded screw holds the lamina snuggly and provides compression across the defect. Overall, studies have reported satisfactory results in 56%–83% of patients.,,, The major criticism against this technique is the high possibility of inaccurate screw placement, potentially leading to implant failure.
Pedicle screw hook fixation—
Tokuhashi and Matsuzaki described this modification of Morscher’s screw hook technique, wherein compression across the defect is achieved with the help of a proximal pedicle screw and a distal, infra-laminar hook connected by a 3/16 inch rod [Figure 4]. The implant failure rates are significantly less with this technique, and the overall good outcome has been reported in 79%–100% of patients.,,, The main advantages are the availability of a large area for bone grafting and the absence of a need for postoperative bracing.
|Figure 4: Pedicle screw-hook fixation. A preoperative lateral radiograph (A), CT scan (B), and postoperative radiographs of a patient who underwent Buck’s repair on the right side and pedicle screw-hook construct on the left side|
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Butterfly plate fixation technique—
Louis, in 1988, reported a 93.5% success rate using his construct of a specially designed butterfly plate and screws.
Rod-screw construct/V-rod technique—
Gillet and Petit in 1999 described a technique of repairing pars defect with a V-shaped rod and pedicle screw construct. In a patient with L5 spondylolysis, pedicle screws are inserted into the L5 vertebra bilaterally, and a V-shaped 6 mm rod is passed through the L5-S1 interspinous ligament. Both limbs of the rods are fixed to the pedicle screws with compression across the defect. A similar technique was described by Noordeen, where the V-shaped rod is replaced by a U shaped modular link, popularly described as the “Smiley face technique” [Figure 5]. The overall success rates with this technique have been reported to be around 80%.
|Figure 5: Smiley face technique. A preoperative lateral radiograph (A), postoperative radiographs (B), and clinical photos (C) of a patient who underwent pars repair by smiley face technique (screw-rod technique). Image courtesy: Dr. Subbaiah M, Madurai|
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Temporary short segment fixation—
Huang et al. described a “temporary short segment fixation” technique using pedicle screws and transverse connecting rod, wherein the implant removal is performed after the complete bony union. He reported 100% success rates with this technique. Although it is a safe and stable construct, it is more invasive and necessitates a second surgery for implant removal.
Fan et al. studied the biomechanical effects of various surgical techniques on calf cadaveric spines. They found no significant difference between Modified Scott, screw-rod-hook, screw-rod, and Buck’s techniques with regard to rotational and lateral flexion stresses. The screw-rod-hook and Buck’s techniques demonstrated more excellent stability in flexion and extension. In a prospective study, Lee et al. compared 87 conservatively treated patients to another group of 62 patients treated by Buck’s repair. The surgically treated group had significant pain relief at a 1-month follow-up. However, there was no statistically significant difference in the functional and radiological outcome between the two groups at 1-year follow-up.
Based on a systematic review, Drazin et al. reported that 84% of patients were able to return to sports after pars repair, and no significant difference was observed between the outcomes following different pars repair procedures.
Recent advances in pars repair
Minimally invasive surgery
With the significant advancements in present-day technology, it is possible to perform pars repair by minimally invasive techniques using fluoroscopic, microscopic (with tubular retractors), endoscopic, robotic, or navigation-assisted approaches.,, The techniques utilize tubular retractors or endoscopy to access the pseudoarthrosis and perform debridement and add bone graft, while the screws, as in Buck’s repair, are placed accurately by image or navigation guidance.
Studies have shown that microscopy/endoscopy-assisted pseudoarthrosis debridement and navigation-assisted lag screw placement can significantly enhance the accuracy and outcome following pars repair by Buck’s technique. Recent literature suggests that the healing rates are significantly enhanced by using such advanced modalities, with reported success rates ranging between 81.3% and 91.7%.,,
In a recent systematic review, Kolcun et al. concluded that minimally invasive approaches were associated with significantly higher pain resolution, shorter recovery, and better clinical outcomes. Nevertheless, MIS techniques are still evolving, and large-scale prospective studies in the future are necessary to throw more light on their benefits over conventional techniques.
Postoperative rehabilitation and follow-up
There is no standard recommendation for the postoperative rehabilitative protocol following pars repair. The protocol must be tailor-made based on the patient profile, surgeon’s preference, and technique employed. [Figure 6] describes a postoperative rehabilitative protocol (based on the suggestions by Radcliff) for patients undergoing pars repair.
|Figure 6: Flowchart showing postoperative rehabilitative protocol after pars repair (Radcliff)|
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| Conclusion|| |
Spondylolysis is an important differential diagnosis to be considered in all children, adolescents, and young sportspersons presenting with LBP. Treatment decisions and prognosis depend on staging and, therefore, an early diagnosis is crucial for better outcomes. Imaging modalities must be used with discretion to aid in diagnosis and treatment planning. Most symptomatic patients respond well to conservative treatment, and high success has been reported in early and progressive lesions. In a specific subset of patients with persistent symptoms, pars repair provides good relief of symptoms. Recently, technological advancements have paved the way for minimally invasive approaches to repair the pars defects. Such approaches can potentially enhance the healing rates and ameliorate the clinical outcome in these children.
The authors thank Dr. Vibhukrishnan Vishwanathan for his valuable help in editing the manuscript.
Financial support and sponsorship
Conflict of interest
None of the authors has any conflict of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4]