Lumbar Stabilization with DSS-HPS® System: Radiological Outcomes and Correlation with Adjacent Segment Degeneration

Arthrodesis has always been considered the main treatment of degenerative lumbar disease. Adjacent segment degeneration is one of the major topics related to fusion surgery. Non-fusion surgery may prevent this because of the protective effect of persisting segmental motion. The aims of the study were (1) to describe the radiological outcomes in the adjacent vertebral segment after lumbar stabilization with DSS-HPS® system and (2) to verify the hypothesis that this system prevents the degeneration of the adjacent segment. This is a retrospective monocentric analysis of twenty-seven patients affected by degenerative lumbar disease underwent spinal hybrid stabilization with the DSS-HPS® system between January 2016 and January 2019. All patients completed 1-year radiological follow-up. Preoperative X-rays and magnetic resonance images, as well as postoperative radiographs at 1, 6 and 12 months, were evaluated by one single observer. Pre- and post-operative anterior and posterior disc height at the dynamic (DL) and adjacent level (AL) were measured; segmental angle (SA) of the dynamized level were measured. There was a statistically significant decrease of both anterior (p = 0.0003 for the DL, p = 0.036 for the AL) and posterior disc height (p = 0.00000 for the DL, p = 0.00032 for the AL); there were a statistically significant variations of the segmental angle (p = 0.00000). Eleven cases (40.7%) of radiological progression of disc degeneration were found. The DSS-HPS® system does not seem to reduce progression of lumbar disc degeneration in a radiologic evaluation, both in the dynamized and adjacent level.

Influence of posterior pedicle screw fixation at L4–L5 level on biomechanics of the lumbar spine with and without fusion: a finite element method

Background Posterior pedicle screw (PS) fixation, a common treatment method for widespread low-back pain problems, has many uncertain aspects including stress concentration levels, effects on adjacent segments, and relationships with physiological motions. A better understanding of how posterior PS fixation affects the biomechanics of the lumbar spine is needed. For this purpose, a finite element (FE) model of a lumbar spine with posterior PS fixation at the L4–L5 segment level was developed by partially removing facet joints (FJs) to imitate an actual surgical procedure. This FE study aimed to investigate the influence of the posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion by determining which physiological motions have the most increase in posterior instrumentation (PI) stresses and FJ loading. Results It was determined that posterior PS fixation increased FJ loading by approximately 35% and 23% at the L3–L4 adjacent level with extension and lateral bending motion, respectively. This increase in FJ loading at the adjacent level could point to the possibility that adjacent segment disease has developed or progressed after posterior lumbar interbody fusion. Furthermore, analyses of peak von Mises stresses on PI showed that the maximum PI stresses of 272.1 MPa and 263.7 MPa occurred in lateral bending and flexion motion before fusion, respectively. Conclusions The effects of a posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion were investigated for all physiological motions. This model could be used as a fundamental tool for further studies, providing a better understanding of the effects of posterior PS fixation by clearing up uncertain aspects.

Analysis of the structure of revision interventions in elderly and senile patients with degenerative pathology of the lumbar spine

The study objective is to study the causes of repeated surgical treatment in patients of an older age group with degenerative pathology of the lumbar spine.Materials and methods. A retrospective analysis of the treatment of 962 patients who underwent surgical treatment of degenerative pathology on the basis of the FCN of Novosibirsk from 2013 to 2017. A total of 360 men, 602 women; average age 66 years. 624 (64.9 %) patients underwent decompression, 338 patients (35.1 %) underwent stabilizing intervention in combination with decompression. The study group consisted of 98 (10.2 %) patients who underwent repeated operations taking into account the inclusion and exclusion criteria. On average, the period after the previous intervention is 17 months (from 1 day to 6 year). 68 patients (69.4 %) previously underwent decompression interventions, 30 (30.6 %) rigid stabilization. The indication for revision treatment was the presence of pain and (or) neurological deficiency, resistant to treatment for at least 6 weeks. Evaluation criteria are described, and the structure of complications is analyzed. The minimum follow-up period after repeated surgery was 1 year, the maximum 6 years.Results. Iatrogenic factors were detected in 39 patients (39.8 %). Progression of degenerative pathology in 59 (60.2 %) patients. More often, repeated intervention was performed at the level of L4–L5 (36.1 %), the cranial adjacent segment was 76.5 %, and the caudal segment was 23.5 %. The minimum period of manifestation of continued degeneration is 3 months. The development of the disease of the adjacent segment after fixation is higher in the period of 3–4 years (p = 0.015). Patients with repeated surgical treatment after decompression for continued degeneration had a higher BMI of 32.3 (p = 0.12), as well as patients with damage to the adjacent segment 32.5 (p = 0.10), compared with the group of primary patients (BMI 30.6 on average). The similar dependance is registered for patients after stabilization: BMI of patients with repeated interventions is 34.5 that is higher than BMI of primary interventions group (on average 33.2, р = 0.13).Conclusions. The main reason for repeated interventions in patients of an older age group is the progression of degenerative pathology on the segments on the segment operated as as well as the adjacent segments (60.2 % repeated interventions, 46.9 % at the adjacent level including).Repeated surgical treatment of patients of an older age group in the early period (for up to 1 year) is most often due to insufficiently effective primary surgical intervention with prevailing early recurrence of disk herniation (1.6 % patients of total number of primarily operated). In the long term (more than 3 years), the reason for repeated surgical treatment is due to the development of an adjacent segment disease where the number of operations of patients with primarily made rigid fixation is increasing progressively in the course of time.High BMI is a predictor of the development of instability of the vertebral motor segment and continued degeneration of the operated one as well as the adjacent level in the long follow-up time.

Factors associated with adjacent-level tumor progression in patients receiving surgery followed by radiosurgery for metastatic epidural spinal cord compression

OBJECTIVE Separation surgery followed by spine stereotactic radiosurgery (SSRS) has been shown to achieve favorable rates of local tumor control and patient-reported outcomes in patients with metastatic epidural spinal cord compression (MESCC). However, rates and factors associated with adjacent-level tumor progression (ALTP) in this population have not yet been characterized. The present study aimed to identify factors associated with ALTP and examine its association with overall survival (OS) in patients receiving surgery followed by radiosurgery for MESCC. METHODS Thirty-nine patients who underwent separation surgery followed by SSRS for MESCC were identified using a prospectively collected database and were retrospectively reviewed. Radiological measurements were collected from preoperative, postoperative, and post-SSRS MRI. Statistical analysis was conducted using the Kaplan-Meier product-limit method and Cox proportional hazards test. Subgroup analysis was conducted for patients who experienced ALTP into the epidural space (ALTP-E). RESULTS The authors’ cohort included 39 patients with a median OS of 14.7 months (range 2.07–96.3 months). ALTP was observed in 16 patients (41.0%) at a mean of 6.1 ± 5.4 months postradiosurgery, of whom 4 patients (10.3%) experienced ALTP-E. Patients with ALTP had shorter OS (13.0 vs 17.1 months, p = 0.047) compared with those without ALTP. Factors associated with an increased likelihood of ALTP included the amount of bone marrow infiltrated by tumor at the index level, amount of residual epidural disease following separation surgery, and prior receipt of radiotherapy at the index level (p < 0.05). Subgroup analysis revealed that primary tumor type, amount of preoperative epidural disease, time elapsed between surgery and radiosurgery, and prior receipt of radiotherapy at the index level were significantly associated with ALTP-E (p < 0.05). CONCLUSIONS To the authors’ knowledge, this study is the first to identify possible risk factors for ALTP, and they suggest that it may be associated with shorter OS in patients receiving surgery followed by radiosurgery for MESCC. Future studies with higher power should be conducted to further characterize factors associated with ALTP in this population.

Kinematics of a Novel Canine Cervical Fusion System

Objective The aim of this study was to determine the biomechanical behaviour of a novel distraction–fusion system, consisting of an intervertebral distraction screw, pedicle locking screws and connecting rods, in the canine caudal cervical spine. Study Design Biomechanical study in cadaveric canine cervicothoracic (C3–T3) spines (n = 6). Cadaveric spines were harvested, stripped of musculature, mounted on a four-point bending jig, and tested using non-destructive four-point bending loads in extension (0–100 N), flexion (0–60 N) and lateral bending (0–40 N). Angular displacement was recorded from reflective optical trackers rigidly secured to C5, C6 and C7. Data for primary and coupled motions were collected from intact spines and following surgical stabilization (after ventral annulotomy and nucleotomy) with the new implant system. Results As compared with the intact spine, instrumentation significantly reduced motion at the operated level (C5-C6) with a concomitant non-significant increase at the adjacent level (C6-C7). Conclusion The combination of a locking pedicle screw-rod system and intervertebral spacer provides an alternative solution for surgical distraction–stabilization in the canine caudal cervical spine and supports the feasibility of using this new implant system in the management of disc-associated cervical spondylomyelopathy in dogs. The increase in motion at C6-C7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this.

Reasons for revision following stand-alone anterior lumbar interbody fusion and lateral lumbar interbody fusion

OBJECTIVE Anterior lumbar interbody fusion (ALIF) and lateral lumbar interbody fusion (LLIF) are alternative and less invasive techniques to stabilize the spine and indirectly decompress the neural elements compared with open posterior approaches. While reoperation rates have been described for open posterior lumbar surgery, there are sparse data on reoperation rates following these less invasive procedures without direct posterior decompression. This study aimed to evaluate the overall rate, cause, and timing of reoperation procedures following anterior or lateral lumbar interbody fusions without direct posterior decompression. METHODS This was a retrospective cohort study of all consecutive patients indicated for an ALIF or LLIF for lumbar spine at a single academic institution. Patients who underwent concomitant posterior fusion or direct decompression surgeries were excluded. Rates, causes, and timing of reoperations were analyzed. Patients who underwent a revision decompression were matched with patients who did not require a reoperation, and preoperative imaging characteristics were analyzed to assess for risk factors for the reoperation. RESULTS The study cohort consisted of 529 patients with an average follow-up of 2.37 years; 40.3% (213/529) and 67.3% (356/529) of patients had a minimum of 2 years and 1 year of follow-up, respectively. The total revision rate was 5.7% (30/529), with same-level revision in 3.8% (20/529) and adjacent-level revision in 1.9% (10/529) of patients. Same-level revision patients had significantly shorter time to revision (7.14 months) than adjacent-level revision patients (31.91 months) (p < 0.0001). Fifty percent of same-level revisions were for a posterior decompression. After further analysis of decompression revisions, an increased preoperative canal area was significantly associated with a lower risk of further decompression revision compared to the control group (p = 0.015; OR 0.977, 95% CI 0.959–0.995). CONCLUSIONS There was a low reoperation rate after anterior or lateral lumbar interbody fusions without direct posterior decompression. The majority of same-level reoperations were due to a need for further decompression. Smaller preoperative canal diameters were associated with the need for revision decompression.