Hydrated Nucleus Pulposus Extrusion in Dogs: Thoracolumbar Compared to Cervical Cases

Objective The aim of this study was to review and describe cases of thoracolumbar (TL) hydrated nucleus pulposus extrusion (HNPE) diagnosed with magnetic resonance imaging and surgery, and compare them to cases of cervical (C) HNPE. Study Design Retrospective, single-center study. Results Thirty-six dogs met the inclusion criteria. Fifteen cases were C and 21 TL. Thirteen dogs were chondrodystrophic breeds, mean body weight was 13 kg, median age was 7.5 years, and 30/36 were male. Fewer dogs were chondrodystrophic in the C group compared with the TL group (p = 0.022). More than 90% had an acute onset, and strong activity was more often reported in the TL group. TL HNPE was more often painful, and extruded disc material more often lateralized (p = 0.017). Median Modified Frankel Score at presentation was 3 and 72.2% were non-ambulatory. More TL HNPE (11/21) were treated surgically compared with C HNPE (4/15). Treatment choice was correlated with spinal cord compression (p = 0.0075). Median Modified Frankel Score improved during hospitalization (p = 0.002) and there was no difference in outcome between C and TL HNPE or conservative and surgical treatment. Mean follow-up time was 33 days. All patients were ambulatory at follow-up. Conclusion This study suggests that the HNPE is not limited to the C vertebral column of dogs and can occur in the TL vertebral column as well. Dogs with TL HNPE show spinal hyperesthesia more often and extruded nucleus material is more often lateralized. Outcome is similar to what has previously been described for C HNPE.

Sudden bilateral foot drop due to dorsally unilateral migration of the herniated lumbar disc: A case report

BACKGROUND: Due to the anatomical characteristics of the anterior epidural space, dorsal migration of material from herniated lumbar disc is quite rare. Also, bilateral foot drop due to unilateral dorsal migration of disc herniation is extremely rare. This report presents a case of sudden bilateral foot drop caused by the unilateral dorsal migration of material from a herniated lumbar disc. CASE DESCRIPTION: A 51-year-old male presented with sudden onset severe leg pain with bilateral foot drop. The patient was referred to our emergency department by a local clinic. Neurological examination showed bilateral ankle and big toe dorsiflexion weakness grade 1. There was no perianal anesthesia, anal sphincter weaknesses, or voiding difficulty. Apart from essential hypertension, this patient’s medical history was unremarkable. Magnetic resonance imaging showed that intervertebral disc material in the dorsal extradural space at the L3-4 level had compressed the dural sac from the left side to the center. We performed an emergency operation. The pathologic result revealed fibrous cartilaginous materials. After the operation, the leg pain was markedly resolved. At postoperative three months, the patient showed improvement of foot drop. CONCLUSION: We recommended emergent mass removal, which produced a favorable outcome.

The importance of intervertebral disc material model on the prediction of mechanical function of the cervical spine

Background Linear elastic, hyperelastic, and multiphasic material constitutive models are frequently used for spinal intervertebral disc simulations. While the characteristics of each model are known, their effect on spine mechanical response requires a careful investigation. The use of advanced material models may not be applicable when material constants are not available, model convergence is unlikely, and computational time is a concern. On the other hand, poor estimations of tissue’s mechanical response are likely if the spine model is oversimplified. In this study, discrepancies in load response introduced by material models will be investigated. Methods Three fiber-reinforced C2-C3 disc models were developed with linear elastic, hyperelastic, and biphasic behaviors. Three different loading modes were investigated: compression, flexion and extension in quasi-static and dynamic conditions. The deformed disc height, disc fluid pressure, range of motion, and stresses were compared. Results Results indicated that the intervertebral disc material model has a strong effect on load-sharing and disc height change when compression and flexion were applied. The predicted mechanical response of three models under extension had less discrepancy than its counterparts under flexion and compression. The fluid-solid interaction showed more relevance in dynamic than quasi-static loading conditions. The fiber-reinforced linear elastic and hyperelastic material models underestimated the load-sharing of the intervertebral disc annular collagen fibers. Conclusion This study confirmed the central role of the disc fluid pressure in spinal load-sharing and highlighted loading conditions where linear elastic and hyperelastic models predicted energy distribution different than that of the biphasic model.

Comparison of the histopathological differences between the spinal material and posterior longitudinal ligament in patients with lumbar disc herniation: A focus on the etiopathogenesis

BACKGROUND: Lumbar disc herniation (LDH) occurs owing to the inability of the posterior longitudinal ligament (PLL) to preserve the disc material within the intervertebral space. There is apparently no study that has investigated the histopathological changes occurring in both PLL and disc material in patients with LDH. OBJECTIVE: Investigate and compare the histopathological changes occurring in PLL and disc material of the patients who underwent a surgical operation for LDH. DESIGN: Descriptive, cross-sectional. SETTING: Pathology and neurosurgery departments of a tertiary health care institution PATIENTS AND METHODS: The study included patients who underwent surgical operation for LDH from January 2018 to May 2019 and whose PLL and disc material were removed together, and had disc degeneration findings that were radiologically and histologically concordant. MAIN OUTCOME MEASURES: PLL degeneration scores according to the histopathological findings, changes in disc materials according to the MRI findings, disc degeneration scores according to the histo-pathological findings. SAMPLE SIZE: 50. RESULTS: MRI and histological examinations showed fully degenerated black discs (Grade 2) in 12 patients, partially degenerated discs (Grade 1) in 29 patients and fresh/acute discs (Grade 0) in 9 patients. The PLL showed grade 0 degeneration in 2 patients, grade 1 degeneration in 23 patients, and grade 2 degeneration in 25 patients. PLL degeneration grades were higher than the disc degeneration grades ( P =.002). CONCLUSION: Longitudinal ligament degeneration can play a significant role in the pathogenesis of LDH. To the best of our knowledge, this study represents the first to focus on the histopathological changes occurring in both the PLL and disc material in patients with LDH. LIMITATIONS: Small sample, retrospective CONFLICT OF INTEREST: None.

Influence of anisotropy on creep in functionally graded variable thickness rotating disc

The study is carried out to develop a mathematical model to analyze creep response of a varying thickness rotating disc made of anisotropic functionally graded 6061Al-SiCw.composite. The thickness and content of reinforcement (SiCw) in the disc are assumed to decrease radially according to power law. The yielding of disc material is according to Hill’s criterion and creeping as per threshold stress based law. The developed model is used to obtain the creep stresses and strain rates in the disc for various types of materials’ anisotropy. The stresses and strain rates are noticed to depend on the materials’ anisotropy. The study reveals that the presence of kind of anisotropy wherein the disc material exhibits lower yield strength toward the radial and tangential directions than the axial direction is beneficial in reducing the creep stresses and creep rates in the disc, in comparison to isotropic FGM disc. An anisotropic FG disc, which has highest and the lowest yield strengths, respectively, along the axial and radial directions shows superior creep response.

How to Confirm and Document Adequate Lumbar Spine Discectomy Intraoperatively?

Lumbar discectomy is a common procedure for acute disc prolapse, especially in patients with neurological deficit [1]. The literature describes using fluoroscopy intraoperatively to avoid wrong level and side [2]. However, there is no method to confirm/document adequate discectomy apart from a postoperative MRI. The authors' technique involves taking clinical photos of the removed disc material. This technique provides accurate, low-cost documentation, and the patient can review it post-operatively. This could be of significant value in large disc prolapse and cauda equina syndrome surgery.

Clinical outcome of biportal endoscopic revisional lumbar discectomy for recurrent lumbar disc herniation

Background Although literature provides evidence regarding the superiority of surgery over conservative treatment in patients with lumbar disc herniation, recurrent lumbar disc herniation (RLDH) was the indication for reoperation in 62% of the cases. The major problem with revisional lumbar discectomy (RLD) is that the epidural scar tissue is not clearly isolated from the boundaries of the dura matter and nerve roots; therefore, unintended durotomy and nerve root injury may occur. The biportal endoscopic (BE) technique is a newly emerging minimally invasive spine surgical modality. However, clinical evidence regarding BE-RLD remains limited. We aimed to compare the clinical outcomes after performing open microscopic (OM)-RLD and BE-RLD to evaluate the feasibility of BE-RLD. Methods This retrospective study included 36 patients who were diagnosed with RLDH and underwent OM-RLD and BE-RLD. RLDH is defined as the presence of herniated disc material at the level previously operated upon in patients who have experienced a pain-free phase for more than 6 months. BE-RLD was performed as follows: two independent surgical ports were made inside the medial pedicular line of the target segment and on the intact upper and lower laminas. Peeling off the soft tissue from the vertebral lamina helps to easily identify the traversing nerve root and the recurrent disc material without dealing with the fibrotic scar tissue. Clinical outcomes were obtained using a visual analog scale (VAS) and the modified Macnab criteria before and at 2 days, 2 and 6 weeks, and 3, 6, and 12 months after surgery. Results The data of 20 and 16 patients who underwent OM-RLD and BE-RLD, respectively, were evaluated. The demographic and perioperative data were comparable between the groups. During the year following the surgery, in the BE-RLD group, the VAS scores at each point were significantly improved over the baseline and remained improved up to 2 weeks after surgery (p < 0.05); however, no statistical difference between the two groups was observed after 6 weeks of surgery (p > 0.05). According to the modified Macnab criteria on the follow-up, the excellent or good satisfaction rates reported at 2 weeks, 6 weeks, 6 months, and 12 months after surgery were 81.25%, 81.25%, 75%, and 81.25%, respectively, in the BE-RLD group, and 50%, 75%, 75%, and 80%, respectively, in the OM-RLD group. Conclusion BE-RLD yielded similar outcomes to OM-RLD, including pain improvement, functional improvement, and patient satisfaction, at 1 year after surgery. However, faster pain relief, earlier functional recovery, and better patient satisfaction were observed when applying BE-LRD. Trial registration Retrospectively registered

STUDI EKSPERIMENTAL KEAUSAN KUNINGAN MENGGUNAKAN PIN-ON-DISC TIPE POINT CONTACT

Keausan adalah hilangnya materi yang timbul sebagai akibat interaksi mekanik dua permukaan yang saling bergesekan dan dibebani, maka akan terjadi keausan, atau perpindahan materi. Kontak yang terjadi antara dua benda dapat berupa titik (point), garis (line), ataupun elips. Analisis keausan dapat dicari menggunakan beberapa metode diantaranya dengan hasil perhitungan secara analitik dan hasil penelitian secara eksperimental. Tribometer pin-on-disc adalah alat uji untuk mengetahui kedalaman dan volume keausan. Penelitian ini bertujuan untuk mengetahui keausan bola kuningan yang digesekkan dengan disc. Material untuk pin terbuat dari kuningan dan disc terbuat dari baja. Pembebanan yang digunakan adalah 6, 8, dan 10 N. Variasi waktu yang digunakan adalah 2,4,8, dan 16 menit. Hasil dari penelitian ini pada pembebanan 10 N pada jarak sliding 180,48 m hasil keausannya adalah 3,047E-05 m. Volume keausan pada jarak 180,48 m dengan pembebanan 10 N hasil volume keausannya adalah 2,165E-11 m3. Semakin bertambah pembebanan dan jarak sliding maka nilai keausan semakin bertambah. Kata kunci: Keausan, pin-on-disc, point contact

Mutual inclinations between giant planets and their debris discs in HD 113337 and HD 38529

ABSTRACT HD 113337 and HD 38529 host pairs of giant planets, a debris disc, and wide M-type stellar companions. We measure the disc orientation with resolved images from Herschel and constrain the three-dimensional orbits of the outer planets with Gaia DR2 and Hipparcos astrometry. Resolved disc modelling leaves degeneracy in the disc orientation, so we derive four separate planet–disc mutual inclination (ΔI) solutions. The most aligned solutions give ΔI = 17°–32° for HD 113337 and ΔI = 21°–45○ for HD 38529 (both 1σ). In both systems, there is a small probability (&lt;0.3 per cent) that the planet and disc are nearly aligned (ΔI &lt; 3○). The stellar and planetary companions cause the orbits of disc material to precess about a plane defined by the forced inclination. We determine this as well as the precession time-scale to interpret the mutual inclination results. We find that the debris discs in both systems could be warped via joint influences of the outer planet and stellar companion, potentially explaining the observed misalignments. However, this requires HD 113337 to be old (0.8–1.7 Gyr), whereas if young (14–21 Myr), the observed misalignment in HD 113337 could be inherited from the protoplanetary disc phase. For both systems, the inclination of the stellar spin axis is consistent with the disc and outer planet inclinations, which instead supports system-wide alignment or near alignment. High-resolution observations of the discs and improved constraints on the planetary orbits would provide firmer conclusions about the (mis)alignment status.