The co-influence of hyaluronic acid and collagen on the development of an engineered annulus tissue model with bone marrow stromal cells.

Inveterbral disc degeneration is a significant musculoskeletal disease that brings huge burden of pain, disability, psychological and social consequences to the affected population worldwide with treatments that only alleviate the pain but does not address the underlying biological problems. For the past decades, tissue engineering of the disc has been investigated with annulus fibrosus (AF) been one of the complicated disc component to be engineered. With the limited source of annulus cells, bone marrow stromal cells (BMSCs) have been frequently investigated as a potental cell candidate to develop an AF-like tissue which often require a multi-disciplinary effort to achieve. The extracellular matrix of AF is largely make up of collagen and proteoglycan which is still unclear how these matrix proteins could influence the BMSCs towards constructing a AF-like tissue. In this study, we adopted a coiled hydrogel microfiber that resembles the micro-architecture of the native AF tissue to encapsulate BMSCs and incorporated collagen type 1 and hyaluronic acid which later demonstrated that the co-presence of hyaluronic acid and collagen could potentially regulated AF-associated biomarkers and protease expression which are critical for later development of an engineered AF tissue construct.

Scaffold-Free tissue engineering with aligned bone marrow stromal cell sheets to recapitulate the microstructural and biochemical composition of annulus fibrosus.

Current tissue engineering strategies through scaffold-based approaches fail to recapitulate the complex three-dimensional microarchitecture and biochemical composition of the native Annulus Fibrosus tissue. Considering limited access to healthy annulus fibrosus cells from patients, this study explored the potential of bone marrow stromal cells (BMSC) to fabricate a scaffold-free multilamellar annulus fibrosus-like tissue by integrating micropatterning technologies into multi-layered BMSC engineering. BMSC sheet with cells and collagen fibres aligned at ~30° with respect to their longitudinal dimension were developed on a microgroove-patterned PDMS substrate. Two sheets were then stacked together in alternating directions to form an angle-ply bilayer tissue, which was rolled up, sliced to form a multi-lamellar angle-ply tissue and cultured in a customized medium. The development of the annulus fibrosus-like tissue was further characterized by histological, gene expression and microscopic and mechanical analysis. We demonstrated that the engineered annulus fibrosus-like tissue with aligned BMSC sheet showed parallel collagen fibrils, biochemical composition and microstructures that resemble the native disk. Furthermore, aligned cell sheet showed enhanced expression of annulus fibrosus associated extracellular matrix markers and higher mechanical strength than that of the non-aligned cell sheet. The present study provides a new strategy in annulus fibrosus tissue engineering methodology to develop a scaffold-free annulus fibrosus-like tissue that resembles the microarchitecture and biochemical attributes of a native tissue. This can potentially lead to a promising avenue for advancing BMSC-mediated annulus fibrosus regeneration towards future clinical applications.

A 10-Year Radiographic Study Comparing Anterior Versus Posterior Instrumented Spinal Fusion in Patients With Lenke Type 5 Adolescent Idiopathic Scoliosis.

MINI: This is a long-term prospective cohort study comparing the radiographic outcomes of anterior versus posterior instrumentation for Lenke 5 adolescent idiopathic scoliosis. Both approaches were comparable in terms of radiographic outcomes up to 10 years. The posterior approach is more prone to developing proximal junctional kyphosis. STUDY DESIGN: Prospective cohort study. OBJECTIVE: To compare the long-term, radiographic coronal and sagittal outcomes of these two approaches at 10-year follow-up. SUMMARY OF BACKGROUND DATA: Both anterior and posterior instrumented fusions have been found to be safe and effective treatments for Lenke 5 adolescent idiopathic scoliosis with up to 2 to 5 years of follow-up. Few studies follow patients beyond this duration. METHODS: 36 patients who underwent anterior (n = 25) or posterior instrumented spinal fusion (n = 11) for Lenke 5 adolescent idiopathic scoliosis over a 4-year period were recruited and followed for 10 years. Preoperative clinical data include patient's age and age of menarche. Operative data included instrumented levels, duration of surgery, and surgical blood loss. Postoperative data included duration of hospital stay, duration of intensive care unit stay, and complications. Pre- and postoperative radiographic data collected include coronal Cobb angles for structural thoracolumbar/lumbar curves, and sagittal angles-sagittal vertical axis, thoracic kyphosis, global lumbar angle, pelvic incidence, pelvic tilt, sacral slope, and upper and lower end vertebrae. RESULTS: Posterior surgery had a shorter operative time (P < 0.010) and hospital stay (P < 0.010). Coronal plane deformity improved by a mean of 74% in the anterior group and 71% in the posterior group. There was no significant change at 10 years in both groups (anterior P = 0.455 and posterior P = 0.325). Sagittal parameters remained unchanged. There was a higher incidence of proximal junctional kyphosis in the posterior (45%) compared to the anterior (16%) group (P < 0.010). CONCLUSION: Both anterior and posterior instrumentation and fusion are successful surgeries after 10 years of follow-up. They are comparable with regards to their ability to achieve and maintain good correction of scoliotic deformities and have a low rate of pseudoarthrosis and instrument failure. Ideal sagittal parameters are maintained up to 10 years of follow-up. LEVEL OF EVIDENCE: 3.

Prospective cohort study. To compare the long-term, radiographic coronal and sagittal outcomes of these two approaches at 10-year follow-up. Both anterior and posterior instrumented fusions have been found to be safe and effective treatments for Lenke 5 adolescent idiopathic scoliosis with up to 2 to 5 years of follow-up. Few studies follow patients beyond this duration. 36 patients who underwent anterior (n = 25) or posterior instrumented spinal fusion (n = 11) for Lenke 5 adolescent idiopathic scoliosis over a 4-year period were recruited and followed for 10 years. Preoperative clinical data include patient's age and age of menarche. Operative data included instrumented levels, duration of surgery, and surgical blood loss. Postoperative data included duration of hospital stay, duration of intensive care unit stay, and complications. Pre- and postoperative radiographic data collected include coronal Cobb angles for structural thoracolumbar/lumbar curves, and sagittal angles­sagittal vertical axis, thoracic kyphosis, global lumbar angle, pelvic incidence, pelvic tilt, sacral slope, and upper and lower end vertebrae. Posterior surgery had a shorter operative time (P < 0.010) and hospital stay (P < 0.010). Coronal plane deformity improved by a mean of 74% in the anterior group and 71% in the posterior group. There was no significant change at 10 years in both groups (anterior P = 0.455 and posterior P = 0.325). Sagittal parameters remained unchanged. There was a higher incidence of proximal junctional kyphosis in the posterior (45%) compared to the anterior (16%) group (P < 0.010). Both anterior and posterior instrumentation and fusion are successful surgeries after 10 years of follow-up. They are comparable with regards to their ability to achieve and maintain good correction of scoliotic deformities and have a low rate of pseudoarthrosis and instrument failure. Ideal sagittal parameters are maintained up to 10 years of follow-up. Level of Evidence: 3.

Ossification of the yellow ligament in the cervical spine - an unusual location.

Ossification of the yellow ligament (OYL) or ligamentum flavum, usually occurs in the thoracic spine. Focal OYL occurring in the cervical spine is considered rare and is sparsely reported in the literature. We came across a 30-year-old male patient with progressive left upper limb and bilateral lower limb weakness over a period of 3 months, associated with an unsteady gait. Clinical examination revealed bilateral generalized hyper-reflexia in both upper and lower limbs, inverted supinator jerk, Hoffman's sign and clonus. Myelopathy due to cord compression was suspected and further investigations were done. MRI and CT scans revealed a bony mass in relation to the C6 spinous process projecting anterosuperiorly and narrowing the cervical spinal canal causing cord signal changes from C4 to C6 levels. In view of the deteriorating neurological status, immediate surgery in the form of decompression and posterior stabilization from C4-C6 was performed. Patient gradually recovered after surgery and attained full functional status. We report this case considering the unusual location of OYL and its successful management.

Nonsteroidal anti-inflammatory drugs in chronic pain: implications of new data for clinical practice.

COX2-selective and nonselective (ns) nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for chronic pain management. There are marked differences in the risk of adverse gastrointestinal (GI) and cardiovascular (CV) events among different NSAIDs. In 2017, publication of two randomized controlled trials and an individual patient-data meta-analysis provided robust data on the relative GI and CV tolerability profiles of currently available NSAIDs. The PRECISION study showed similar CV-event rates with celecoxib vs naproxen and ibuprofen, but GI tolerability was better for celecoxib. In the CONCERN study of high-GI-risk patients, celecoxib was associated with fewer adverse GI-tract events than naproxen. The meta-analysis showed no significant difference between celecoxib and ns-NSAIDs in the rate of acute myocardial infarction, and celecoxib was the only COX2-selective NSAID with a lower risk of adverse CV and GI events vs ns-NSAIDs. These data add to the body of knowledge about the relative tolerability of different NSAIDs and were used to propose an updated treatment algorithm. The decision about whether to use an NSAID and which one should be based on a patient's risk of developing adverse GI and CV events. Lower- and upper-GI-tract events need to be considered. Celecoxib has a better lower-GI-tract tolerability profile than ns-NSAIDs plus a proton-pump inhibitor. In addition, the latest data suggest that long-term use of celecoxib 200 mg/day may be appropriate for patients at increased CV risk.

Hydrogel based cartilaginous tissue regeneration: recent insights and technologies.

Hydrogels have been extensively employed as an attractive biomaterial to address numerous existing challenges in the fields of regenerative medicine and research because of their unique properties such as the capability to encapsulate cells, high water content, ease of modification, low toxicity, injectability, in situ spatial fit and biocompatibility. These inherent properties have created many opportunities for hydrogels as a scaffold or a cell/drug carrier in tissue regeneration, especially in the field of cartilaginous tissue such as articular cartilage and intervertebral discs. A concise overview of the anatomy/physiology of these cartilaginous tissues and their pathophysiology, epidemiology and existing clinical treatments will be briefly described. This review article will discuss the current state-of-the-art of various polymers and developing strategies that are explored in establishing different technologies for cartilaginous tissue regeneration. In particular, an innovative approach to generate scaffold-free cartilaginous tissue via a transient hydrogel scaffolding system for disease modeling to pre-clinical trials will be examined. Following that, the article reviews numerous hydrogel-based medical implants used in clinical treatment of osteoarthritis and degenerated discs. Last but not least, the challenges and future directions of hydrogel based medical implants in the regeneration of cartilaginous tissue are also discussed.

Subsequent Vertebral Fractures Post Cement Augmentation of the Thoracolumbar Spine: Does it Correlate With Level-specific Bone Mineral Density Scores?

STUDY DESIGN: A case-control study. OBJECTIVE: In this study, we investigated the correlation between level-specific preoperative bone mineral density and subsequent vertebral fractures. We also identified factors associated with subsequent vertebral fractures. SUMMARY OF BACKGROUND DATA: Complications of cement augmentation of the spine include subsequent vertebral fractures, leading to unnecessary morbidity and more treatment. Ability to predict at-risk vertebra will help guide management. METHODS: We studied all patients with osteoporotic compression fractures who underwent cement augmentation in a single institution from November 2001 to December 2010 by a single surgeon. Association between level-specific bone mineral density T-scores and subsequent fractures was assessed. Multivariable analysis was performed to identify significant factors associated with subsequent vertebral fractures. RESULTS: 93 patients followed up for a mean duration of 25.1 months (12-96) had a mean age of 76.8 years (47-99). Vertebroplasty was performed in 58 patients (62.4%) on 68 levels and kyphoplasty in 35 patients (37.6%) on 44 levels. Refracture was seen in 16 patients (17.2%). The time to subsequent fracture post cement augmentation was 20.5 months (2-90). For refracture cases, 43.8% (7/16) fractured in the adjacent vertebrae. Subsequently fractured vertebra had a mean T-score of -2.860 (95% confidence interval -3.268 to -2.452) and nonfractured vertebra had a mean T-score of -2.180 (95% confidence interval -2.373 to -1.986). A T-score of -2.2 or lower is predictive of refracture at that vertebra (P = 0.047). Odds ratio increases with decreasing T-scores from -2.2 or lower to -2.6 or lower. A T-score of -2.6 or lower gives no additional predictive advantage. After multivariable analysis, age (P = 0.049) and loss of preoperative anterior vertebral height (P = 0.017) are associated with refracture. CONCLUSION: Level-specific T-scores are predictive of subsequent fractures and the odds ratio increases with lower T-scores from -2.2 or less to -2.6 or less. They have a low positive predictive value, but a high negative predictive value for subsequent fractures. Other significant associations with subsequent refractures include age and anterior vertebral height. LEVEL OF EVIDENCE: 4.

Open and minimally invasive transforaminal lumbar interbody fusion: comparison of intermediate results and complications.

STUDY DESIGN: Prospective study. PURPOSE: To compare clinical and radiological outcomes of open vs. minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). OVERVIEW OF LITERATURE: MI-TLIF promises smaller incisions and less soft tissue dissection resulting in lower morbidity and faster recovery; however, it is technically challenging. METHODS: Twenty-five patients with MI-TLIF were compared with 25 matched open TLIF controls. A minimum 2 year follow-up and a statistical analysis of perioperative and long-term outcomes were performed. Potential complications were recorded. RESULTS: The mean ages for the open and MI-TLIF cases were 44.4 years (range, 19-69 years) and 43.6 years (range, 20-69 years), respectively. The male:female ratio was 13:12 for both groups. Average follow-up was 26.9 months for the MI-TLIF group and 29.3 months for the open group. Operative duration was significantly longer in the MI-TLIF group than that in the open group (p<0.05). No differences in estimated blood loss, duration to ambulation, or length of stay were found. Significant improvements in the Oswestry disability index and EQ-5D functional scores were observed at 6-, 12-, and 24-months in both groups, but no significant difference was detected between the groups. Fusion rates were comparable. Cage sizes were significantly smaller in the MI-TLIF group at the L5/S1 level (p<0.05). One patient had residual spinal stenosis at the MI-TLIF level, and one patient who underwent two-level MI-TLIF developed a deep vein thrombosis resulting in a pulmonary embolism. CONCLUSIONS: MI-TLIF and open TLIF had comparable long-term benefits. Due to technical constraints, patients should be advised on the longer operative time and potential undersizing of cages at the L5S1 level.

Spinal stenosis presenting with scrotal and perianal claudication.

A 63-year-old gentleman presented with a one-year duration of progressive neurogenic claudication. However, unlike most patients who presents with leg symptoms, his pain was felt in his scrotal and perianal region. This was exacerbated with walking and standing, but he had immediate relief with sitting. An magnetic resonance imaging (MRI) was performed which showed severe central canal stenosis. An L3/4 and L4/5 surgical decompression and a transforaminal lumbar interbody fusion was performed, and the patient made good recovery with immediate resolution of symptoms. Although rare, spinal stenosis should be considered a differential when approaching a patient with perianal and scrotal claudication, even in the absence of leg claudication. An MRI is useful to confirm the diagnosis. This rare symptom may be a sign of severe cauda equina compression and we recommend decompression with predictable good results.

Three-dimensional development of tensile pre-strained annulus fibrosus cells for tissue regeneration: an in-vitro study.

Prior research has investigated the immediate response after application of tensile strain on annulus fibrosus (AF) cells for the past decade. Although mechanical strain can produce either catabolic or anabolic consequences to the cell monolayer, little is known on how to translate these findings into further tissue engineering applications. Till to date, the application and effect of tensile pre-strained cells to construct a three-dimensional (3D) AF tissue remains unknown. This study aims to investigate the effect of tensile pre-strained exposure of 1 to 24h on the development of AF pellet culture for 3 weeks. Equibiaxial cyclic tensile strain was applied on AF monolayer cells over a period of 24h, which was subsequently developed into a cell pellet. Investigation on cellular proliferation, phenotypic gene expression, and histological changes revealed that tensile pre-strain for 24h had significant and lasting effect on the AF tissue development, with enhanced cell proliferation, and up-regulation of collagen type I, II, and aggrecan expression. Our results demonstrated the regenerative ability of AF cell pellets subjected to 24h tensile pre-straining. Knowledge on the effects of tensile pre-strain exposure is necessary to optimize AF development for tissue reconstruction. Moreover, the tensile pre-strained cells may further be utilized in either cell therapy to treat mild disc degeneration disease, or the development of a disc construct for total disc replacement.

Asymptomatic cement embolism in the right atrium after vertebroplasty using high-viscosity cement: a case report.

A 52-year-old woman underwent vertebroplasty for fractures of the T10, T11, and L2 vertebrae secondary to multiple myeloma. She was discharged uneventfully within a week. Nine months later, she was readmitted for syncope. Echocardiography revealed a mass in the right atrium. Magnetic resonance imaging (MRI) revealed a low signal intensity irregular mass (8x7 mm) and a comma-shaped mass (12 mm) in the right atrium. She was prophylactically anticoagulated for the probable emboli. Repeat cardiac MRI performed 2 weeks later showed that the size of the masses remained unchanged. Surgical intervention was not suggested by the cardiothoracic surgeons. Three months later, the patient remained uneventful.

Spinal cord ischemia secondary to hypovolemic shock.

A 44-year-old male presented with symptoms of spinal cord compression secondary to metastatic prostate cancer. An urgent decompression at the cervical-thoracic region was performed, and there were no complications intraoperatively. Three hours postoperatively, the patient developed acute bilateral lower-limb paralysis (motor grade 0). Clinically, he was in class 3 hypovolemic shock. An urgent magnetic resonance imaging (MRI) was performed, showing no epidural hematoma. He was managed aggressively with medical therapy to improve his spinal cord perfusion. The patient improved significantly, and after one week, he was able to regain most of his motor functions. Although not commonly reported, spinal cord ischemia post-surgery should be recognized early, especially in the presence of hypovolemic shock. MRI should be performed to exclude other potential causes of compression. Spinal cord ischemia needs to be managed aggressively with medical treatment to improve spinal cord perfusion. The prognosis depends on the severity of deficits, and is usually favorable.

Is hybrid surgery of the cervical spine a good balance between fusion and arthroplasty? Pilot results from a single surgeon series.

PURPOSE: Few studies have investigated the role of hybrid surgery (HS) that incorporates anterior cervical discectomy and fusion (ACDF) and artificial disc replacement (ADR) techniques. To our knowledge, this is the first study that provides a direct comparison of all three groups in terms of intra-operative parameters and outcomes with a minimum follow-up of 2 years. METHODS: Seven consecutive patients who underwent HS were matched with another seven patients who underwent ACDF and ADR based on levels of surgery. Prospective data on demographics, pre-operative and post-operative assessments, complications and functional scores (VAS, NDI, EQ-5D health score and index) were analysed using Mann-Whitney U test. Type I error was set at 5 %. RESULTS: Duration of surgery was significantly shorter for ACDF at 135 min (p = 0.025) compared with HS and ADR. ACDF also had greater blood loss when compared with ADR (p < 0.036). ADR has the shortest duration of hospitalization followed by HS and ACDF (p < 0.031). The HS group returned to work fastest (54 days) when compared with both ACDF (107 days) and ADR (73 days) with statistical significance seen between HS and ACDF (p = 0.035). Cervical range of motion (ROM) and functional scores did not show any significant differences. CONCLUSION: HS is comparable to ACDF and ADR in terms of safety and feasibility. Findings of shorter in-hospital stay and earlier return to work in HS group may be further explored in large, randomised controlled trials.

Paradoxical motion in L5-S1 adult spondylolytic spondylolisthesis.

INTRODUCTION: In patients with spondylolisthesis, it is assumed that flexion accentuates anterior displacement, whereas extension causes some reduction. Paradoxical movement-where flexion causes reduction of spondylolisthesis and extension increases the anterior translation, is rarely described. In this study, we investigate the prevalence of paradoxical motion in patients with L5-S1 spondylolytic spondylolisthesis and why this abnormal motion occurs. MATERIALS AND METHODS: Flexion and extension radiographs of 41 patients with grade I and II spondylolytic spondylolisthesis of the L5-S1 segment were analysed. Patients who had previous lumbar spine surgery, recent lumbar spine trauma, those more than 50 years of age and those with poor quality radiographs were excluded. RESULTS: There were 24 male and 17 female patients. The average age was 32.7 years. Of the 41 patients, 29 (70.7%) showed no significant instability. Six (15%) patients showed anterolisthesis, where flexion accentuated the forward displacement, while further six (15%) patients showed paradoxical motion. Statistical analyses found that patients with paradoxical motion had a significantly higher slip angle. CONCLUSION: In this study, we have demonstrated that: (1) paradoxical motion in spondylolytic spondylolisthesis is more common than previously thought. (2) Patients without anterolisthesis during flexion in dynamic radiographs may still have (paradoxical) instability. (3) Paradoxical motion may be more common in patients with a low sacral slope and increased lumbosacral lordosis.

Vascularization and morphological changes of the endplate after axial compression and distraction of the intervertebral disc.

STUDY DESIGN: An in vivo study of the rabbit's endplate and intervertebral disc (IVD). OBJECTIVE: To assess the histologic features and vascularization of the endplate after axial compression and distraction, along with the degeneration and regeneration status of IVD. SUMMARY OF BACKGROUND DATA: Current studies mainly focus on the changes in the IVD in response to degeneration and regeneration. However, the basic science regarding degenerative changes of the vertebral endplate and its actions on the IVD is lacking. The endplate is responsible for nutrient flow to the IVD through diffusion. It has been postulated that changes in the endplate may be responsible for the degeneration of the IVD. METHODS: Twenty New Zealand white rabbits were equally divided into 4 groups as follows; group A, 28 days of compression only; group B, 28 days of disc compression followed by 28 days of unloading; group C, 28 days of disc compression followed by 28 days of distraction; and group D, sham operated animals with apparatus placement only. At the end of the study, all the animals in the 4 groups were killed and the lumbar segments harvested for analysis of their disc height, vascularity, and histologic examination. RESULTS: Compression decreased the disc height and the rabbits showed signs of disc degeneration. Ossified endplates with decreased cells and extracellular matrix, and decreased vascular channel volume were observed. Cellular and morphologic regeneration were observed on unloading and distraction of the compressed discs, although the cartilaginous endplates were partially ossified. The volume of vascular channels increased significantly after distraction. Fluorescent vascular tracer showed the presence of active blood flow in the vascular channels near the cartilaginous endplates. CONCLUSION: Compression resulted in degeneration of the cartilaginous endplate and decrease in the osseous endplate vascular channel volume, both of which led to the degeneration of the IVD. Unloading and distraction allowed the regeneration of the extracellular matrix in both the endplate and the recovery of vascular channels.

An in vitro study of dynamic cyclic compressive stress on human inner annulus fibrosus and nucleus pulposus cells.

BACKGROUND CONTEXT: Intervertebral disc (IVD) cells exhibit diverse biologic responses to compressive stress depending on the compressive stress type, magnitude, duration, and anatomic zone of IVD cell origin. The previous studies mainly focused on the effects of compressive stress on animal IVD tissue. Few studies have investigated the response of human IVD tissue to compressive stress. PURPOSE: To assess the effect of dynamic cyclic compressive stress on biosynthesis of collagen and glycosaminoglycan of human inner annulus fibrosus (AF) and nucleus pulposus (NP) cells. STUDY DESIGN/SETTING: Observation of moderate and high magnitudes of compressive stress on human IVD cell biosynthesis. PATIENT SAMPLE: Human IVD of adolescent idiopathic scoliosis case undergoing thoracoscopic discectomy and fusion was collected. OUTCOME MEASURES: Cell morphology, cell proliferation assay, as well as collagen and glycosaminoglycan content were examined in vitro. METHODS: Intervertebral discs were cultured under 0.2 or 0.4 MPa of compressive stress at 1 Hz for 2 hours twice a day up to 7 days. These were compared with samples unloaded. The analysis was done via electron microscopy examination, cell proliferation assay, as well as collagen and glycosaminoglycan content analysis. RESULTS: Collagen and glycosaminoglycan content in the inner AF and NP cells cultured under 0.2 MPa of compressive stress was significantly higher than that in the control cells but was significantly lower than that in the control cells under 0.4 MPa of compressive stress. The number of endoplasmic reticulum in the inner AF and NP cells cultured under 0.2 MPa of compressive stress was significantly higher than that in the control cells but was significantly lower than that in the control cells under 0.4 MPa of compressive stress. CONCLUSION: These findings imply that biosynthetic characteristics of human inner AF and NP cells may vary under varying degrees of compressive stresses, which may result in varying amounts of extracellular matrix being secreted.

Lumbar degenerative spinal deformity: Surgical options of PLIF, TLIF and MI-TLIF.

Degenerative disease of the lumbar spine is common in ageing populations. It causes disturbing back pain, radicular symptoms and lowers the quality of life. We will focus our discussion on the surgical options of posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) and minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) for lumbar degenerative spinal deformities, which include symptomatic spondylolisthesis and degenerative scoliosis. Through a description of each procedure, we hope to illustrate the potential benefits of TLIF over PLIF. In a retrospective study of 53 ALIF/PLIF patients and 111 TLIF patients we found reduced risk of vessel and nerve injury in TLIF patients due to less exposure of these structures, shortened operative time and reduced intra-operative bleeding. These advantages could be translated to shortened hospital stay, faster recovery period and earlier return to work. The disadvantages of TLIF such as incomplete intervertebral disc and vertebral end-plate removal and potential occult injury to exiting nerve root when under experienced hands are rare. Hence TLIF remains the mainstay of treatment in degenerative deformities of the lumbar spine. However, TLIF being a unilateral transforaminal approach, is unable to decompress the opposite nerve root. This may require contralateral laminotomy, which is a fairly simple procedure. The use of minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) to treat degenerative lumbar spinal deformity is still in its early stages. Although the initial results appear promising, it remains a difficult operative procedure to master with a steep learning curve. In a recent study comparing 29 MI-TLIF patients and 29 open TLIF, MI-TLIF was associated with longer operative time, less blood loss, shorter hospital stay, with no difference in SF-36 scores at six months and two years. Whether it can replace traditional TLIF as the surgery of choice for degenerative lumbar deformity remains unknown and more studies are required to validate the safety and efficiency.

Effects of cyclic dynamic tensile strain on previously compressed inner annulus fibrosus and nucleus pulposus cells of human intervertebral disc-an in vitro study.

Our objective was to investigate whether dynamic tensile strain on previously compressed human intervertebral disc (IVD) cells can restore the biosynthetic effects of collagen and glycosaminoglycan. Inner annulus fibrosus (AF) and nucleus pulposus (NP) tissues of adolescent idiopathic scoliosis cases undergoing thoracoscopic discectomy and fusion were cultured on compressive plates. Compressive stress was applied using 0.4 MPa at 1 Hz, for 2 h twice a day for 7 days, to the inner AF and NP tissues, followed by equibiaxial cyclic tensile strain to deform the released cells onto the plate's flexible bottom. With 10% elongation at a rate of 1 Hz, for 2 h twice a day for 7 days, a significant increase in the level of collagen and glycosaminoglycan of the previously compressed inner AF, as well as the level of glycosaminoglycan of the previously compressed NP cells were found. The DNA content and number of endoplasmic reticulum under transmission electron micrograph of the previously compressed inner AF and NP cell were also significantly increased. The results suggested that equibiaxial cyclic tensile strain at a rate of 1 Hz with 10% tensile strain was capable of increasing collagen and glycosaminoglycan synthesis of previously compressed inner AF cells, and glycosaminoglycan synthesis of previously compressed NP cells.