Surgical treatment of post-traumatic luxation of rib heads with spinal cord compression in a cat

Background Luxation of the rib head with intrusion into the intervertebral foramen seems to be rare in cats. Only one report has been published describing a cat with non-ambulatory paraparesis, which was managed conservatively. Here we report a case of rib head luxation that was managed surgically. Case presentation A 4-year-old, female domestic shorthair cat with a two-week history of non-ambulatory paraparesis was presented at our clinic. Based on history and neurological examination, a diagnosis of thoracolumbar spinal cord lesion of traumatic origin was made. Computed tomography scanning revealed mild scoliosis, a luxation of the 3rd and 4th right rib heads and penetration into the spinal canal through intervertbral foramina. Surgical management using right dorsal approach to the spine was performed. The spinal cord was decompressed by cutting and removing of proximal ribs’ fragments by rotation and pulling out from the intervertebral foramina. The cat was ambulatory and paraparetic four weeks after surgery. Two years after surgery the cat regained functional gait, but ataxia remained. Conclusions We report the first case of a surgical treatment of rib head luxation and intrusion into the spinal canal in a cat. The applied procedure resulted in an improvement of neurological signs.

Anatomy of the L5 nerve root in the pelvis for safe sacral screw placement: a cadaveric study

OBJECTIVE Previous reports have focused on the complications of L5 nerve root injury caused by anterolateral misplacement of the S1 pedicle screws. Anatomical knowledge of the L5 nerve root in the pelvis is essential for safe and effective placement of the sacral screw. This cadaveric study aimed to investigate the course of the L5 nerve root in the pelvis and to clarify a safe zone for inserting the sacral screw. METHODS Fifty-four L5 nerve roots located bilaterally in 27 formalin-fixed cadavers were studied. The ventral rami of the L5 nerve roots were dissected along their courses from the intervertebral foramina to the lesser pelvis. The running angles of the L5 nerve roots from the centerline were measured in the coronal plane. In addition, the distances from the ala of the sacrum to the L5 nerve roots were measured in the sagittal plane. RESULTS The authors found that the running angles of the L5 nerve roots changed at the most anterior surface of the ala of the sacrum. The angles of the bilateral L5 nerve roots from the right and left L5 intervertebral foramina to their inflection points were 13.77° ± 5.01° and 14.65° ± 4.71°, respectively. The angles of the bilateral L5 nerve roots from the right and left inflection points to the lesser pelvis were 19.66° ± 6.40° and 20.58° ± 5.78°, respectively. There were no significant differences between the angles measured in the right and left nerve roots. The majority of the L5 nerves coursed outward after changing their angles at the inflection point. The distances from the ala of the sacrum to the L5 nerve roots in the sagittal plane were less than 1 mm in all cases, which indicated that the L5 nerve roots were positioned close to the ala of the sacrum and had poor mobility. CONCLUSIONS All of the L5 nerve roots coursed outward after exiting the intervertebral foramina and never inward. To prevent iatrogenic L5 nerve root injury, surgeons should insert the S1 pedicle screw medially with an angle > 0° toward the inside of the S1 anterior foramina and the sacral alar screw laterally with an angle > 30°.

Analysis of risk factors for C5 nerve root paralysis after posterior cervical decompression

Background C5 nerve root paralysis is a nonnegligible complication after posterior cervical spine surgery (PCSS). The cause of its occurrence remains controversial. The purpose of this study was to analyse the incidence of and risk factors for C5 nerve root paralysis after posterior cervical decompression. Methods We retrospectively analysed the clinical data of 640 patients who underwent PCSS in the Department of Orthopaedics, Affiliated Hospital of Qingdao University from September 2013 to September 2019. According to the status of C5 nerve root paralysis after surgery, all patients were divided into paralysis and normal groups. Univariate and multivariate analyses were used to determine the independent risk factors for C5 nerve root paralysis. A receiver operating characteristic (ROC) curve was used to demonstrate the discrimination of all independent risk factors. Results Multivariate logistic regression analysis revealed that male sex, preoperative cervical spine curvature, posterior longitudinal ligament ossification, and preoperative C4/5 spinal cord hyperintensity were independent risk factors for paralysis, whereas the width of the intervertebral foramina was an independent protective factor for paralysis. The area under the curve (AUC) values of the T2 signal change at C4-C5, sex, cervical foramina width, curvature and posterior longitudinal ligament ossification were 0.706, 0.633, 0.617, 0.637, and 0.569, respectively. Conclusions Male patients with C4-C5 intervertebral foramina stenosis, preoperative C4-C5 spinal cord T2 high signal, combined with OPLL, and higher preoperative cervical spine curvature are more likely to develop C5 nerve root paralysis after surgery. Among the above five risk factors, T2 hyperintensity change in C4-C5 exhibits the highest correlation with C5 paralysis and strong diagnostic power. It seems necessary to inform patients who have had cervical spine T2 hyperintensity before surgery of C5 nerve root paralysis after surgery, especially those with altered spinal cord T2 signals in the C4-C5 segment.

The effects of cages implantation on surgical and adjacent segmental intervertebral foramina

Objection The overarching goal of our research was to compare the clinical and radiological outcomes with different sizes of cages implantation in anterior cervical discectomy and fusion (ACDF), and to evaluate the effects on surgical and adjacent segmental intervertebral foramina. Methods The clinical data of 61 patients were analyzed retrospectively. The radiological data included the surgical intervertebral disk space height before (H0) and after surgery (H), the preoperative mean height of adjacent segments (Hm), the area and height of the surgical and adjacent segment foramen, the surgical segmental Cobb angle (α1), and C2-7Cobb angle (α2). The calculation of clinical data was conducted by Japanese Orthopaedic Association Scores (JOA), the recovery rate of JOA scores and visual analog scales (VAS). In accordance with the different ranges of distraction (H/Hm), patients were classified into three groups: group A (H/Hm<1.20, n=13), group B (1.20≤H/Hm≤1.80, n=37), and group C (H/Hm>1.80, n=11). Results After the operation and at the final follow-up, our data has demonstrated that the area and height of surgical segmental foramen all increased by comparing those of preoperation in three groups (all P<0.05). However, except for a decrease in group C (all P<0.05), the adjacent segmental foramina showed no significant changes (all P>0.05). The area and height of the surgical segment foramen and the distraction degree were positively correlated (0<R<1, all P<0.05), while the adjacent segments were negatively correlated with it (0<R<1, P=0.002~0.067). JOA scores improved markedly in all groups with similar recovery rates. However, during the final follow-up (P=0.034), it was observed that there were significant differences in visual simulation scores among the three groups. Conclusion The oversize cage might give a rise to a negative impact on the adjacent intervertebral foramen in ACDF. The mean value of the adjacent intervertebral disk space height (Hm) could be used as a reference standard. Moreover, the 1.20~1.80 fold of distraction (H/Hm) with optimal cages would achieve a better long-term prognosis.

The Biomechanical Effect on the Adjacent L4/L5 Segment Under S1 Superior Facet Arthroplasty: A Finite Element Analysis

Background. The superior facet arthroplasty is important for intervertebral foramen microscopy. To our knowledge, no study about the postoperative biomechanics of adjacent L4/L5 segments after different methods of S1 superior facet arthroplasty. To evaluate the effect of S1 superior facet arthroplasty on lumbar range of motion and disc stress of adjacent segment (L4/L5) under the intervertebral foramina plasty.Methods. Eight finite element models (FEMs) of lumbosacral vertebrae (L4/S) had been established and validated. The S1 superior facet arthroplasty was simulated with different methods. Then, the models were imported into Nastran software after optimization. 500N preload was imposed on the L4 superior endplate and 10 Nm was given to simulate flexion, extension, lateral flexion and rotation. The range of motion (ROM) and intervertebral disc stress of L4-L5 spine were recorded.Results. The ROM and disc stress of L4/L5 increased with the increasing of the proportions of S1 superior facet arthroplasty. Compared with the normal model, the ROM of L4/L5 significantly increase in most directions of motion when S1 superior facet formed greater than 3/5 from ventral to dorsal or 2/5 from apex to base. The disc stress of L4/L5 significantly increase in most directions of motion when S1 superior facet formed greater than 3/5 from ventral to dorsal or 1/5 from apex to base.Conclusion. In this study, the ROM and disc stress of L4/L5 were effected by the unilateral S1 superior facet arthroplasty. It is suggested that the forming range from ventral to dorsal should be less than 3/5 of S1 upper facet joint. It is not recommended to form from apex to base.

Extradural Peripheral Nerve Sheath Tumour at T7 Level in a 2-Year-Old Dog

The aim of this report is to describe an unusual localization of nerve sheath tumour (NST), clinical presentation, imaging, surgical management, and outcome in a 2-year-old dog. A 2-year-old female American Staffordshire Terrier presented with nonambulatory paraparesis, thoracolumbar hyperaesthesia, hindlimb hyperreflexia, and mild muscle atrophy. Computed tomography and magnetic resonance imaging revealed an extradural mass at T7-T8, without vertebral lesions. Surgical treatment consisted in resection of the soft tissue mass through dorsal laminectomy. The dog was ambulatory within 24 hours and free of recurrence at 18 months postoperatively. Histopathologic and features of immunohistochemistry were consistent with NST. The NST of this report was similar to those described before, but exhibited unusual characteristics, such as being extradural, without extension into intervertebral foramina, and being located in an atypical region (T7-T8). Moreover, survival time and relapse-free interval are greater than previously reported for similar cases.

Biomechanical study of the C5–C8 cervical extraforaminal ligaments

Background The anatomical distribution of the extraforaminal ligaments in the cervical intervertebral foramina has been well studied. However, detailed descriptions of the biomechanical characteristics of these ligaments are lacking. Methods The paravertebral muscles were dissected, and the extraforaminal ligaments and nerve roots were identified. The C5 and C7 or C6 and C8 cervical nerve roots on both sides were randomly selected, and a window was opened on the vertebral lamina to expose the posterior spinal nerve root segments. Five needles were placed on the nerve root and the bone structure around the intervertebral foramen; the distal end of the nerve root was then tied with silk thread, and the weights were connected across the pulley. A weight load was gradually applied to the nerve root (50 g/time, 60 times in total). At the end of the experiment, segments of the extraforaminal ligaments were selectively cut off to compare the changes in nerve root displacement. Results The displacement of the C5, C6, C7, and C8 nerve roots increases with an increasing traction load, and the rate of change of nerve root displacement in the intervertebral foramen is smaller than that in the nerve root on the outside area (p < 0.05). Extraforaminal ligaments can absorb part of the pulling load of the nerve root; the C5 nerve root has the largest load range. Conclusions Cervical extraforaminal ligaments can disperse the tension load on the nerve root and play a role in protecting the nerve root. The protective effect of the C5 nerve root was the strongest, and this may anatomically explain why the C5 nerve roots are less prone to simple avulsion.