Sciatica caused by spinal epidural abscess as the initial clinical presentation of colon cancer: a rare case report and review of literature.

BACKGROUND: Colorectal cancer is one of the most frequently diagnosed forms of cancer, and it is associated with several common symptoms and signs such as rectal bleeding, altered bowel habits, abdominal pain, anemia, and unintentional weight loss. Sciatica, a debilitating condition in which the patient experiences paresthesia and pain in the dermatome of associated lumbosacral nerve roots or sciatic nerve distribution, is not considered one of these. Here we present a case of colorectal cancer manifesting symptoms of sciatica alone. CASE PRESENTATION: A 68-year-old male presented with progressive lower back pain radiating to his left thigh and calf over L5/S1 dermatome. Sciatica was suspected and initially underwent conservative treatment with analgesics. However, the symptoms progressed and MRI revealed an epidural abscess surprisingly. Surgical debridement was performed and pus culture isolated Streptococcus gallolyticus. Based on the strong association of S. gallolyticus with colorectal cancer, the presence of this pathogen prompted further tumor evaluation, even in the absence of the typical symptoms and signs. This investigation ultimately leads to the diagnosis of sigmoid adenocarcinoma. CONCLUSIONS: Although rare, sciatica caused by S. gallolyticus infection of the spinal epidural space may serve as the initial presentation of colorectal cancer. Physicians should be aware of the strong association between S. gallolyticus and colorectal cancer. Based on what we currently know about the condition; a thorough systematic assessment of occult neoplasia for patients with S. gallolyticus infection is recommended.

3D-printed porous titanium suture anchor: a rabbit lateral femoral condyle model.

BACKGROUND: The inclusion of a connecting path in a porous implant can promote nutrient diffusion to cells and enhance bone ingrowth. Consequently, this study aimed to evaluate the biomechanical, radiographic, and histopathological performance of a novel 3D-printed porous suture anchor in a rabbit femur model. METHODS: Three test groups were formed based on the type of suture anchor (SA): Commercial SA (CSA, Group A, n = 20), custom solid SA (CSSA, Group B, n = 20), and custom porous SA (CPSA, Group C, n = 20). The SAs were implanted in the lateral femoral condyle of the right leg in each rabbit. The rabbits (New Zealand white rabbits, male, mean body weight of 2.8 ± 0.5 kg, age 8 months) underwent identical treatment and were randomized into experimental and control groups via computer-generated randomization. Five rabbits (10 femoral condyles) were euthanized at 0, 4, 8, and 12 weeks post-implantation for micro-CT, histological analysis, and biomechanical testing. RESULTS: At 12 weeks, the CPSA showed a higher BV/TV (median 0.7301, IQR 0.7276-0.7315) than the CSSA and CSA. The histological analysis showed mineralized osteocytes near the SA. At 4 weeks, new bone was observed around the CPSA and had penetrated its porous structure. By 12 weeks, there was no significant difference in ultimate failure load between the CSA and CPSA. CONCLUSIONS: We demonstrated that the innovative 3D-printed porous suture anchor exhibited comparable pullout strength to conventional threaded suture anchors at the 12-week postoperative time-point period. Furthermore, our porous anchor design enhanced new bone formation and facilitated bone growth into the implant structure, resulting in improved biomechanical stability.

Pullout strength of different pedicle screws after primary and revision insertion: an in vitro study on polyurethane foam.

BACKGROUND: Surgeons are routinely required to remove loose or failed pedicle screws and insert a new screw in their place. However, inserting a new screw into an existing hole may compromise the holding capacity of the pedicle screw. The purpose of this study is to evaluate the pullout strength of pedicle screws with different thread designs after the primary insertion and revision surgery in a synthetic bone model. METHODS: Four pedicle screws with different thread designs (single-lead-thread (SLT) screw, dual-lead-thread (DLT) screw, mixed-single-lead-thread (MSLT) screw, and proximal-unthreaded-dual-thread (PUDL) screw) were inserted into pre-drilled, untapped holes (ø 4.2 mm, length 35 mm) in Sawbone blocks of density 20 pcf. In the first sequence, a 6.0 mm screw was inserted into the predrilled foam block and the primary pullout strength of the screw was measured according to ASTM F543. In the second sequence, a 6.0 mm screw was inserted and removed, and then either a 6.5 mm screw of the same design or a different screw design was inserted into the same hole and the pullout strength recorded. RESULTS: In the first sequence, the mean pullout strength of the MSLT screw was significantly (p < 0.05) greater than all other screw designs. In the second sequence, when the MSLT screw was the primary screw, using a larger MSLT screw (6.5 mm) as the revision screw did not lead to a higher pullout strength than if a 6.0 mm diameter PUDL screw was used for the revision. Using a larger DLT screw (6.5 mm) as the revision screw resulted in a significantly (p < 0.05) greater pullout strength than a 6.0 mm STL, DLT, MSLT, or PUDL screw. CONCLUSIONS: Our results indicate that employing classic oversizing of the same screw design is a safe choice for maintaining screw purchase in the bone after revision. In cases where oversizing with the same screw design is not practical, opting for a PUDL screw with the same original diameter can provide enough purchase in the bone to maintain stability.

Deviating from the Recommended Torque on Set Screws Can Reduce the Stability and Fatigue Life of Pedicle Screw Fixation Devices.

Background and Objectives: Using an appropriate torque to tighten set screws ensures the long-term stability of spinal posterior fixation devices. However, the recommended torque often varies between different devices and some devices do not state a recommended torque level. The purpose of this study is to evaluate the effect of set screw torque on the overall construct stability and fatigue life. Materials and Methods: Two commercial pedicle screw systems with different designs for the contact interface between the set screw and rod (Group A: plane contact, Group B: line contact) were assembled using torque wrenches provided with the devices to insert the set screws and tighten to the device specifications. The axial gipping capacity and dynamic mechanical stability of each bilateral construct were assessed in accordance with ASTM F1798 and ASTM F1717. Results: Increasing or decreasing the torque on the set screw by 1 Nm from the recommended level did not have a significant effect on the axial gripping capacity or fatigue strength of Group A (p > 0.05). For Group B, over-tightening the set screw by 1 Nm did cause a significant reduction in the fatigue strength. Conclusions: Excessive torque can damage the rod surface and cause premature failure. When insertion using a manual driver is preferred, a plane contact interface between the set screw and rod can reduce damage to the rod surface when the set screw is over-torqued.

Optimized decellularization protocol including α-Gal epitope reduction for fabrication of an acellular porcine annulus fibrosus scaffold.

Recent advances in tissue engineering have led to potential new strategies, especially decellularization protocols from natural tissues, for the repair, replacement, and regeneration of intervertebral discs. This study aimed to validate our previously reported method for the decellularization of annulus fibrosus (AF) tissue and to quantify potentially antigenic α-Gal epitopes in the decellularized tissue. Porcine AF tissue was decellularized using different freeze-thaw temperatures, chemical detergents, and incubation times in order to determine the optimal method for cell removal. The integrity of the decellularized material was determined using biochemical and mechanical tests. The α-Gal epitope was quantified before and after decellularization. Decellularization with freeze-thaw in liquid nitrogen, an ionic detergent (0.1% SDS), and a 24 h incubation period yielded the greatest retention of GAG and collagen relative to DNA reduction when tested as single variables. Combined, these optimal decellularization conditions preserved more GAG while removing the same amount of DNA as the conditions used in our previous study. Components and biomechanical properties of the AF matrix were retained. The decellularized AF scaffold exhibited suitable immune-compatibility, as evidenced by successful in vivo remodeling and a decrease in the α-Gal epitope. Our study defined the optimal conditions for decellularization of porcine AF tissues while preserving the biological composition and mechanical properties of the scaffold. Under these conditions, immunocompatibility was evidenced by successful in vivo remodeling and reduction of the α-Gal epitope in the decellularized material. Decellularized AF scaffolds are potential candidates for clinical applications in spinal surgery.

The effect of annular repair on the failure strength of the porcine lumbar disc after needle puncture and punch injury.

PURPOSE: The purpose was to quantify the structural integrity of annulus fibrosis (AF) after injuries with repair. METHODS: Punctures in the AF of 6-month-old porcine spine specimens were made with 18-, 20-, 22-, 24-, and 26-gauge needles. Leakage testing was performed immediately after needle puncture (Group 1), after the puncture was repaired with a modified purse-string suture (MPSS) (Group 2), and after needle puncture with immediate repair (Group 3). Punch injuries repaired with the MPSS alone, or with an AF graft and MPSS were also examined. RESULTS: There was no leakage from 26-gauge needle punctures. Pressures at which the nucleus pulposus leaked from the 24-, 22-, 20- and 18-gauge needle punctures (Group 1) were 4.28, 2.03, 1.27, and 1.06 MPa, respectively. Failure pressure after repair (Group 2, 3) was significantly greater than without (Group 1). Failure pressure in Group 3 was much greater than in Group 2 with 18- and 20-gauge punctures. Punch injury repaired with a graft and MPSS had significantly greater failure pressure than repair with MPSS alone (1.88 vs. 1.02 MPa, p = 0.0001). CONCLUSIONS: The MPSS can restore the mechanical integrity of the AF after needle puncture. An annular graft along with a MPSS may increase the structural integrity of the AF after a punch injury. As this was an acute animal study, the measurements and results may not directly translate to the human intervertebral disc.

Mechanical stress-induced apoptosis of nucleus pulposus cells: an in vitro and in vivo rat model.

BACKGROUND: Un-physiological loads play an important role in the degenerative process of inter-vertebral discs (IVD). In this study, we used an in vitro and in vivo rat model to investigate the mechanism of nucleus pulposus (NP) cells apoptosis induced by mechanical stress. METHODS: Static compressive load to IVDs of rat tails was used as the in vivo model. For the in vitro model, NP cells were tested under the physiological and un-physiological loading. For histological examination, apoptotic index study, and apoptotic gene expression, we also selected cytokines [bone morphogenetic protein (BMP)-2/7, insulin-like growth factor (IGF)-1, platelet-derived growth factor (PDGF)] to be analyzed. RESULTS: Under mechanical loading, cellular density was significantly decreased, but there was an increase of TUNEL positive cells and apoptosis index. In a dose-dependent manner; the necrosis became apparent in the un-physiologic strain. The selected cytokines (BMP-2/7, IGF-1, PDGF) can significantly reduce the percentage of apoptotic and necrotic cells. CONCLUSIONS: We conclude that the intrinsic (mitochondrial) apoptotic pathway plays an important role in the compressive load-induced apoptosis of NP cells. Combination therapy reducing the mechanical load and selected cytokines (BMP-2/7, IGF-1 and PDGF) may have considerable promise in the treatment of spine disc degeneration.

Incidence and predictors of acute kidney injury after elective surgery for lumbar degenerative disease: A 13-year analysis of the US Nationwide Inpatient Sample.

BACKGROUND: Acute kidney injury (AKI) is a severe postoperative complication associated with poor clinical outcomes, including the development of chronic kidney disease (CKD) and death. This study aimed to investigate the incidence and determinants of AKI following elective surgeries for degenerative lumbar spine disease. METHODS: All patient data were extracted from the US Nationwide Inpatient Sample database. After surgery, AKI's incidence and risk factors were identified for lumbar degenerative disease. ICD-9 and ICD-10 codes defined lumbar spine degenerative disease, fusion, decompression, and AKI. The study cohort was categorized by type of surgery, that is, decompression alone or spinal fusion. Regression analysis was used to identify associations between AKI and risk factors organized by surgery type. RESULTS: The incidence of AKI after decompression or fusion was 1.1% and 1.8%, respectively. However, the incidence of AKI in the United States is rising. The strongest predictor of AKI was underlying CKD, which was associated with an 9.0- to 12.9-fold more significant risk of AKI than in subjects without comorbid CKD. In this setting, older age, congestive heart failure, anemia, obesity, coagulopathy and hospital-acquired infections were also strong predictors of AKI. In contrast, long-term aspirin/anticoagulant usage was associated with lowered AKI risk. CONCLUSION: Findings of this study inform risk stratification for AKI and may help to optimize treatment decisions and care planning after elective surgery for lumbar degenerative disease.

Life-threatening perioperative complications among older adults with spinal metastases: An analysis based on a nationwide inpatient sample of the US.

INTRODUCTION: We aimed to investigate the prognostic determinants of life-threatening and fatal complications in patients <80 and ≥ 20 years of age and those ≥80 years who were undergoing surgery for spinal metastases. MATERIALS AND METHODS: Based on data between 2005 and 2018 extracted from National Inpatient Sample as the largest longitudinal hospital inpatient databases in the United States, statistical analyses were performed to identify prognostic factors (age, sex, household income, insurance status, major comorbidities, primary site of malignancy, types of surgery, surgical approaches, types of hospital admission, and hospital-related characteristics) for major and fatal perioperative complications among older adult patients. RESULTS: A total of 31,925 patients aged ≥ 20y who were undergoing surgery for spinal metastasis were identified (< 80 y: n = 28,448; ≥ 80 y: n = 35,37). After adjustment, age ≥80 y was significantly associated with greater risk of perioperative cardiac arrest (adjusted odds ratio [aOR]: 1.34, 95% confidence interval [CI]: 1.03-1.73) and acute kidney injury (AKI) (aOR: 1.23, 95% CI: 1.07-1.41) but lower risk of venous thromboembolic event (VTE) (aOR: 0.80, 95% CI: 0.66-0.96) than <80y. Factors predicting life-threatening complications among patients ≥ 80y were: male sex (<80 y: aOR = 1.14; ≥ 80 y: aOR = 1.35), higher score on Charlson Comorbidity Index (CCI) (80 y, aOR = 1.21-2.67; ≥ 80 y: aOR = 1.25-2.55), open surgery (<80 y: aOR = 1.24; ≥ 80 y: aOR = 1.35), and greater Metastatic Spinal Tumor Frailty Index (MSTFI) (<80 y: aOR = 2.48-10.03; ≥ 80 y: aOR = 2.69-11.21). Among patients <80y, factors predicting life-threatening complications were: male sex, Black race, greater CCI score, primary tumor at kidney, hematologic cancer, other/unspecified primary site, certain surgical procedures, open surgery, greater MSTFI, emergent admission, and low hospital volume. DISCUSSION: This study identifies a list of independent risk factors for the presence of life-threatening complications among patients <80 and ≥ 80y who were undergoing surgery for spinal metastasis. The findings contribute to the development of clinical strategies for the surgical management of spinal metastasis, especially for octogenarians, and lower the risk of unfavorable inpatient outcomes.

Pullout Strength of Pedicle Screws Inserted Using Three Different Techniques: A Biomechanical Study on Polyurethane Foam Block.

Pullout strength is an important indicator of the performance and longevity of pedicle screws and can be heavily influenced by the screw design, the insertion technique and the quality of surrounding bone. The purpose of this study was to investigate the pullout strength of three different pedicle screws inserted using three different strategies and with two different loading conditions. Three pedicle screws with different thread designs (single-lead-thread (SLT) screw, dual-lead-thread (DLT) screw and mixed-single-lead-thread (MSLT) screw) were inserted into a pre-drilled rigid polyurethane foam block using three strategies: (A) screw inserted to a depth of 33.5 mm; (B) screw inserted to a depth of 33.5 mm and then reversed by 3.5 mm to simulate an adjustment of the tulip height of the pedicle screw and (C) screw inserted to a depth of 30 mm. After insertion, each screw type was set up with and without a cyclic load being applied to the screw head prior to the pullout test. To ensure that the normality assumption is met, we applied the Shapiro-Wilk test to all datasets before conducting the non-parametric statistical test (Kruskal-Wallis test combined with pairwise Mann-Whitney-U tests). All screw types inserted using strategy A had a significantly greater pullout strength than those inserted using strategies B and C, regardless of if the screw was pre-loaded with a cyclic load prior to testing. Without the use of the cyclic pre-load, the MSLT screw had a greater pullout strength than the SLT and DLT screws for all three insertion strategies. However, the fixation strength of all screws was reduced when pre-loaded before testing, with the MSLT screw inserted using strategy B producing a significantly lower pullout strength than all other groups (p < 0.05). In contrast, the MSLT screw using insertion strategies A and C had a greater pullout strength than the SLT and DLT screws both with and without pre-loading. In conclusion, the MSLT pedicle screw exhibited the greatest pullout strength of the screws tested under all insertion strategies and loading conditions, except for insertion strategy B with a cyclic pre-load. While all screw types showed a reduced pullout strength when using insertion strategy B (screw-out depth adjustment), the MSLT screw had the largest reduction in pullout strength when using a pre-load before testing. Based on these findings, during the initial screw insertion, it is recommended to not fully insert the screw thread into the bone and to leave a retention length for depth adjustment to avoid the need for screw-out adjustment, as with insertion strategy B.

Nanoparticle-Hydrogel Composite Drug Delivery System for Potential Ocular Applications.

Intravitreal injections are clinically established procedures in the treatment of posterior eye diseases, such as wet age-related macular degeneration (wet AMD) which requires monthly intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) protein drugs that can lead to complications due to frequent dosing. In this study, we designed a composite drug delivery system (DDS) consisting of drug-loaded poly (lactide-co-glycolide) (PLGA) nanoparticles and a chemically crosslinked hyaluronan hydrogel to reduce the dosing frequency. The morphology, size, composition, and drug loading efficiency of the prepared nanoparticles were characterized. The properties of the modified hyaluronan polymers used were also examined. The degree of swelling/degradation and controlled release ability of the hyaluronan hydrogel and the composite DDS were identified using bovine serum albumin (BSA) as a model drug. The results show that this system can retain 75% of its wet weight without losing its integrity and release the model drug at the rate of 0.4 µg/day for more than two months under physiological conditions. In addition, the nanoparticulate formulation of the system can further improve bioavailability of the drugs by penetrating deep into the retinal layers. In conclusion, the proposed composite DDS is easily prepared with biocompatible materials and is promising for providing the sustained release of the protein drugs as a better treatment for ocular neovascular diseases like wet AMD.

Effects of applying platelet-rich plasma during arthroscopic rotator cuff repair: a systematic review and meta-analysis of randomised controlled trials.

Because of its healing properties, platelet-rich plasma (PRP) has been applied to the bone-tendon interface during arthroscopic rotator cuff repair to improve surgical outcomes. However, its effects remain ambiguous. Therefore, we conducted this systematic review and meta-analysis to assess the effects of PRP on retear rate and functional outcomes. Randomised control trials were identified and extracted. Data collection was completed on 15 February 2020. The results are expressed as the risk ratio (RR) for the categorical variables and weighted mean difference for the continuous variables, with 95% confidence intervals (CIs). Analyses were performed using RevMan 5.3 software. Seven randomised controlled trials published from 2013 to 2018, with 541 patients in total, were included. The results revealed a significant decrease in retear rate [RR 0.38, 95% CI (0.22, 0.68), P = 0.0009). Furthermore, a significant improvement was observed regarding short-term Constant score [mean difference = 3.28, 95% CI (1.46, 5.11), P = 0.0004), short-term University of California at Los Angeles activity score [mean difference = 1.60, 95% CI (0.79, 2.42), P = 0.0001], and short-term visual analogue scale score [mean difference = - 0.14, 95% CI (- 0.23, - 0.05), P = 0.002]. This systematic review indicates the efficacy of PRP when applied to the bone-tendon interface during arthroscopic rotator cuff repair.

Monostotic Vertebral Paget's Disease of the Lumbar Spine.

Paget's disease in the Far East is quite rare. Age at diagnosis is usually greater than 50 years, and the disease typically affects the spine. Most patients are usually diagnosed with Paget's disease following radiographic examination for other purposes. It usually occurs at multiple vertebral levels, with only 10-25% of vertebral Paget's disease being monostotic. The disease rarely causes neurologic complications resulting from compression of intraspinal nerve tissue. Here, we present 2 cases of monostotic vertebral Paget's disease of the third lumbar vertebra. The first patient, who may be the first documented case of Paget's disease in the lumbar spine with progressive neurologic deficiency in an Asian population, received decompressive laminectomy due to marked spinal stenosis with neurologic deficits. The symptoms were greatly relieved following surgery, and ambulatory ability was restored. The second patient was diagnosed with Paget's disease following surgical biopsy. He remained asymptomatic at the most recent follow-up.

Radiofrequency neurotomy in chronic lumbar and sacroiliac joint pain: A meta-analysis.

BACKGROUND: Effective treatment of low back pain (LBP) originating in the lumbar and sacroiliac joints is difficult to achieve. The objective of the current study was to compare the clinical effectiveness of radiofrequency (RF) neurotomy versus conservative nonsurgical approaches for the management of chronic lumbar and sacroiliac joint pain. METHODS: The PICOS framework was adhered to (P [population]: patients with a history of chronic function-limiting lumbar and sacroiliac joint pain lasting at least 6 months; I [intervention]: RF neurotomy; C [comparator]: other nonsurgical treatments; O [outcomes]: the Oswestry Disability Index (ODI), measurement for pain, and a quality of life (QoL) questionnaire; S [study design]: meta-analysis). Two trained investigators systematically searched Medline, Cochrane, EMBASE, and ISI Web of Knowledge databases for relevant studies published in English through March 2019. RESULTS: Patients treated with RF neurotomy (n = 528) had significantly greater improvement in ODI scores, pain scores and QoL measured by EQ-5D compared with controls (n = 457); however, significant heterogeneity was observed when data were pooled from eligible studies. In subgroup analyses, patients who received RF neurotomy had a significantly greater improvement in ODI scores compared with those with sham treatment. Patients treated with RF achieved significantly greater improvement in pain scores compared with controls who received sham treatment or medical treatment. In a subgroup analysis of pain in the sacroiliac joint and in lumbar facet joints, the RF neurotomy group achieved a significantly greater improvement in ODI score and pain scores compared with the control group. The ODI score and pain score were improved after 2 months of follow up in the analyses stratified by follow-up duration. CONCLUSIONS: Use of RF neurotomy as an intervention for chronic lumbar and sacroiliac joint pain led to improved function; however, larger, more directly comparable studies are needed to confirm this study's findings.

Literature Review and Meta-Analysis of Transcutaneous Electrical Nerve Stimulation in Treating Chronic Back Pain.

BACKGROUND AND OBJECTIVES: This study is a meta-analysis of randomized controlled trials comparing the efficacy of transcutaneous electrical nerve stimulation (TENS) to a control and to other nerve stimulation therapies (NSTs) for the treatment of chronic back pain. METHODS: Citations were identified in MEDLINE, the Cochrane Library, Google Scholar, and ClinicalTrials.gov through June 2014 using the following keywords: nerve stimulation therapy, transcutaneous electrical nerve stimulation, back pain, chronic pain. Control treatments included sham, placebo, or medication only. Other NSTs included electroacupuncture, percutaneous electrical nerve stimulation, and percutaneous neuromodulation therapy. RESULTS: Twelve randomized controlled trials including 700 patients were included in the analysis. The efficacy of TENS was similar to that of control treatment for providing pain relief (standardized difference in means [SDM] = -0.20; 95% confidence interval [CI], -0.58 to 0.18; P = 0.293). Other types of NSTs were more effective than TENS in providing pain relief (SDM = 0.86; 95% CI, 0.15-1.57; P = 0.017). Transcutaneous electrical nerve stimulation was more effective than control treatment in improving functional disability only in patients with follow-up of less than 6 weeks (SDM = -1.24; 95% CI, -1.83 to -0.65; P < 0.001). There was no difference in functional disability outcomes between TENS and other NSTs. CONCLUSIONS: These results suggest that TENS does not improve symptoms of lower back pain, but may offer short-term improvement of functional disability.

Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis.

BACKGROUND DATA: Combined usage of posterior lumbar interbody fusion and transpedicular fixation has been extensively used to treat the various lumbar degenerative disc diseases. The transpedicular fixator aims to increase stability and enhance the fusion rate. However, how the fused disc and bridged vertebrae respectively affect adjacent-segment diseases progression is not yet clear. METHODS: Using a validated lumbosacral finite-element model, three variations at the L4-L5 segment were analyzed: 1) moderate disc degeneration, 2) instrumented with a stand-alone cage and pedicle screw fixators, and 3) with the cage only after fusion. The intersegmental angles, disc stresses, and facet loads were examined. Four motion tests, flexion, extension, bending, and twisting, were also simulated. FINDINGS: The adjacent-segment disease was more severe at the cephalic segment than the caudal segment. After solid fusion and fixation, the increase in intersegmental angles, disc stresses and facet loads of the adjacent segments were about 57.6%, 47.3%, and 59.6%, respectively. However, these changes were reduced to 30.1%, 22.7%, and 27.0% after removal of the fixators. This was attributed to the differences between the biomechanical characteristics of the fusion and fixation mechanisms. INTERPRETATION: Fixation superimposes a stiffer constraint on the mobility of the bridged segment than fusion. The current study suggested that the removal of spinal fixators after complete fusion could decrease the stress at adjacent segments. Through a minimally invasive procedure, we could reduce secondary damage to the paraspinal structures while removing the fixators, which is of utmost concern to surgeons.

Biomechanical arrangement of threaded and unthreaded portions providing holding power of transpedicular screw fixation.

BACKGROUND: Failure of pedicle screw is a major concern in spinal surgery. The threaded and unthreaded portions of the pedicle screw provide the ability to anchor and squeeze the surrounding bone, respectively. This study aimed to investigate the anchoring and squeezing effects of different design of the threaded/unthreaded portions of a pedicle screw to vertebrae. METHODS: Four variations (one fully and three partially threaded, with a 1/3, 1/2, and 2/3 unthreaded designs at the proximal portion) of screws were used to measure pullout strength and withdrawn energy using synthetic and porcine specimens. The tests were conducted in static and dynamic fashions, in that the screws were axially extracted directly and after 150,000cycles of lateral bending. The load-displacement curves were recorded to gain insight into the peak load (pullout strength) and cumulative work (withdrawn energy). FINDINGS: The two testing results of the synthetic and porcine specimens consistently showed that the 1/3 unthreaded screw provides significantly higher pullout strength and withdrawn energy than the fully threaded screw. The withdrawn energy of the three unthreaded screws was significantly higher than that of the threaded counterpart. INTERPRETATION: The holding power of a pedicle screw was the integration of the anchoring (cancellous core) and squeezing (compact pedicle) effects within the threaded and unthreaded portions. The current study recommends the 1/3 unthreaded screw as an optimal alternative for use as a shank-sliding mechanism to preserve the holding power within the pedicle isthmus.

Time course investigation of intervertebral disc degeneration in a rat-tail puncture model.

AIMS: Intervertebral disc (IVD) degeneration was believed to contribute to lower back pain. The aim of the study was to investigate the pathogenesis and regulatory mechanism of puncture-induced IVD degeneration. MAIN METHODS: We established a rat-tail puncture model using Kirschner wire and a homemade stopper. The progress of disc degeneration was evaluated by histological examination and the quantitative measurement of type I, type II collagen and other factors expression at 0.5, 1, 2, 6, and 12weeks after puncture and was compared with control rats of the same age. KEY FINDINGS: Histological examination and Safranin-O staining revealed progressive degeneration of the punctured disc. Matrix metalloproteinase 13 (MMP13) was increased at 1week after puncture but did not change in the control group. The interleukin-1 beta (IL-1ß) mRNA expression level was elevated at the acute stage after puncture compared with the control group. The hypoxia inducible factor 2 (HIF-2) increased expression in punctured groups. Additionally, compare to adjacent non-punctured segments, HIF-2α expression level transiently increased and then decreased in the nucleus pulposus immediately following puncture, and it then increased 12weeks after puncture. SIGNIFICANCE: The degenerative changes observed in this rat-tail puncture model are similar to human disc degeneration and that this model may be valuable for elucidating the molecular mechanisms and pathways underlying disc degeneration.

In vitro Penetration and in vivo Distribution of Honokiol into the Intervertebral Disc in Rat.

Honokiol is a potential candidate for the treatment of intervertebral disc (IVD) degeneration. In this study, we develop in vitro and in vivo methods to detect the distribution of honokiol in intervertebral discs using high-performance liquid chromatography. A rat tail disc was used for both experimental models. For the in vivo animal experiment, blood samples and tail discs were collected at 15, 30, 60, 120 and 240 min after honokiol administration (30 mg/kg, i.v.). The analyte was separated by a mobile phase of methanol and 10 mM NaH2PO4 buffer at pH 2.8 (78:22, v/v) and pumped through a reversed-phase analytical column (250 × 4.6 mm, particle size 5 µm) at room temperature. The in vitro experimental results demonstrated that honokiol diffused into the intervertebral disc and was concentration-dependent. The active concentration is obtained for the therapeutic level at 15 and 30 min after honokiol administration in the in vivo model.

Neglected ruptured flexor carpi ulnaris tendon mimics a soft tissue tumor in the wrist.

A wrist mass is rarely caused by a ruptured tendon in the forearm. The common pathologies are ganglia, tendon tenosynovitis, and giant cell tumors of tendon sheaths. Less common causes are nerve sheath tumors, vascular lesions, or an accessory muscle belly. The authors investigated a case of neglected ruptured flexor carpi ulnaris tendon that mimics a mass in the wrist. To the authors' knowledge, this is the first case report in relevant literature. During investigation, the high-resolution musculoskeletal ultrasound suggested a soft tissue tumor or a ruptured flexor carpi ulnaris tendon. The magnetic resonance imaging scan indicated an accessory flexor carpi ulnaris muscle belly. The diagnosis of ruptured flexor carpi ulnaris tendon was confirmed by surgical exploration. This case indicates that ultrasound may be better suited than magnetic resonance imaging in evaluating a wrist mass for its accuracy, availability, and portability.