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.

Biomechanical analysis of single-level interbody fusion with different internal fixation rod materials: a finite element analysis.

BACKGROUND: Lumbar spinal fusion with rigid spinal fixators as one of the high risk factors related to adjacent-segment failure. The purpose of this study is to investigate how the material properties of spinal fixation rods influence the biomechanical behavior at the instrumented and adjacent levels through the use of the finite element method. METHODS: Five finite element models were constructed in our study to simulate the human spine pre- and post-surgery. For the four post-surgical models, the spines were implanted with rods made of three different materials: (i) titanium rod, (ii) PEEK rod with interbody PEEK cage, (iii) Biodegradable rod with interbody PEEK cage, and (iv) PEEK cage without pedicle screw fixation (no rods). RESULTS: Fusion of the lumbar spine using PEEK or biodegradable rods allowed a similar ROM at both the fusion and adjacent levels under all conditions. The models with PEEK and biodegradable rods also showed a similar increase in contact forces at adjacent facet joints, but both were less than the model with a titanium rod. CONCLUSIONS: Flexible rods or cages with non-instrumented fusion can mitigate the increased contact forces on adjacent facet joints typically found following spinal fixation, and could also reduce the level of stress shielding at the bone graft.

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.

Thermosensitive Chitosan-Gelatin-Glycerol Phosphate Hydrogels as Collagenase Carrier for Tendon-Bone Healing in a Rabbit Model.

Healing of an anterior cruciate ligament graft in bone tunnel yields weaker fibrous scar tissue, which may prolong an already prolonged healing process within the tendon-bone interface. In this study, gelatin molecules were added to thermosensitive chitosan/ß-glycerol phosphate disodium salt hydrogels to form chitosan/gelatin/ß-glycerol phosphate (C/G/GP) hydrogels, which were applied to 0.1 mg/mL collagenase carrier in the tendon-bone junction. New Zealand white rabbit's long digital extensor tendon was detached and translated into a 2.5-mm diameter tibial plateau tunnel. Thirty-six rabbits underwent bilateral surgery and hydrogel injection treatment with and without collagenase. Histological analyses revealed early healing and more bone formation at the tendon-bone interface after collagenase partial digestion. The area of metachromasia significantly increased in both 4-week and 8-week groups after collagenase treatment (p < 0.01). Micro computed tomography showed a significant increase in total bone volume and bone volume/tissue volume in the 8 weeks after collagenase treatment, compared with the control group. Load-to-failure was significantly higher in the treated group at 8 weeks (23.8 ± 8.13 N vs 14.3 ± 3.9 N; p = 0.008). Treatment with collagenase digestion resulted in a 66% increase in pull-out strength. In conclusion, injection of C/G/GP hydrogel with collagenase improves tendon-to-bone healing in a rabbit model.

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.

Assessment of the suitability of biodegradable rods for use in posterior lumbar fusion: An in-vitro biomechanical evaluation and finite element analysis.

Interbody fusion with posterior instrumentation is a common method for treating lumbar degenerative disc diseases. However, the high rigidity of the fusion construct may produce abnormal stresses at the adjacent segment and lead to adjacent segment degeneration (ASD). As such, biodegradable implants are becoming more popular for use in orthopaedic surgery. These implants offer sufficient stability for fusion but at a reduced stiffness. Tailored to degrade over a specific timeframe, biodegradable implants could potentially mitigate the drawbacks of conventional stiff constructs and reduce the loading on adjacent segments. Six finite element models were developed in this study to simulate a spine with and without fixators. The spinal fixators used both titanium rods and biodegradable rods. The models were subjected to axial loading and pure moments. The range of motion (ROM), disc stresses, and contact forces of facet joints at adjacent segments were recorded. A 3-point bending test was performed on the biodegradable rods and a dynamic bending test was performed on the spinal fixators according to ASTM F1717-11a. The finite element simulation showed that lumbar spinal fusion using biodegradable implants had a similar ROM at the fusion level as at adjacent levels. As the rods degraded over time, this produced a decrease in the contact force at adjacent facet joints, less stress in the adjacent disc and greater loading on the anterior bone graft region. The mechanical tests showed the initial average fatigue strength of the biodegradable rods was 145 N, but this decreased to 115N and 55N after 6 months and 12 months of soaking in solution. Also, both the spinal fixator with biodegradable rods and with titanium rods was strong enough to withstand 5,000,000 dynamic compression cycles under a 145 N axial load. The results of this study demonstrated that biodegradable rods may present more favourable clinical outcomes for lumbar fusion. These polymer rods could not only provide sufficient initial stability, but the loss in rigidity of the fixation construct over time gradually transfers loading to adjacent segments.