Introduction. Anterior cervical decompression and fusion (ACDF) is considered a standard surgical treatment to degenerative discogenic diseases. Lately, the question arises whether or not ACDF significantly influences the progression of adjacent disc degeneration (ADD). The etiology of ADD is obscure and it has not been fully understood whether ADD is a consequence of fusion or it represents the aging pathway of the degenerative cervical process, thus making it a controversial topic [1-3]. There have been several discussions about the possibility of ACDF altering biomechanical conditions at adjacent segments, therefore resulting in increased load and excessive motion [3,4]. The purpose of this study was to compare the cervical segmental motion pre- and post-ACDF using novel 3D analytical techniques. Methods. Nine patients (2F/7M, mean age: 54.1 years, range 36–76 y.o.) underwent ACDF due to symptomatic cervical degenerative discogenic disease. One-level ACDF was performed in 4 patients, whereas 2-level ACDF was done in five, using cylindrical titanium porous cage implants. Pre- and post (postoperative periods ranged from 11-months, 25 days to 12-months, 22 days, mean postoperative period: 12.09 months) surgery, dynamic-CT examinations were conducted in neutral, flexion and extension positions. Subject-based 3D CT models were created for segmental motion analysis (Fig. 1). Six-degrees-of-freedom 3D segmental movements were analyzed using a validated Volume-Merge methods (accuracy: 0.1 mm in translation, 0.2°in rotation) [5]. The segmental translation was evaluated by the segmental translations of gravity centers of endplates (Fig. 2). Disc-height distribution was measured using a custom-written Visual C++ routine implementing a lease-distance calculation algorithm. The mean translation distance was calculated for the each adjacent level (Fig. 2). Differences of segmental motions and mean disc height between pre- and post-surgery at each level were compared by the Wilcoxon signed rank test. Results were presented mean±SEM. Results. Regarding the fusion level, the data shows decreases in both the flexion/extension (F/E) angular range of motion (ROM) (7.46±1.17°preoperatively vs. 3.14±0.56°post-operatively, p<0.003) and the segmental translation in the anterior/posterior direction (AP translation) after surgery (1.22±0.20 mm pre-operatively and 0.32±0.11 mm post-operatively, p<0.01). For the adjacent levels category (inferior and superior combined), the E/F angular ROM was larger after surgery (6.74±1.22°pre-operatively vs. 8.48±0.56°post-operatively, p<0.03). The lateral and axial rotational angular ranges of motion pre- and post-surgery did not show any statistically differences at the adjacent levels. The AP translation at the adjacent levels did not change after surgery (1.22±0.26 mm pre-operatively and 1.45±0.29 mm post-operatively). Translations in lateral and cranio-caudal directions also did not show change following surgery. The mean disc height in the adjacent level (2.39±0.14 mm) showed no differences with respect to the post-surgical measurements (2.40±0.19 mm). Conclusions. The use of a high-accuracy in vivo 3D kinematic analysis method enabled the detection of subtle changes in segmental movement between pre- and post-ACDF conditions. The result of the current study showed increased segmental movements in F/E angles at the adjacent level. These results are consistent with the some previous studies in the literature [4,6-11]. The magnitude of the increased movement, however, was only 1.74°from full-full-flexion to full-extension and no increase was found in AP translation. No disc height loss associated with disc degeneration was observed during a 1-year period after ACDF. Longer follow-up studies with larger patient cohorts will be required to investigate whether the increased F/E angle at the adjacent level effectively causes symptomatic ADD

Aim: To determine the incidence of adjacent level osteophytes in patients who have had anterior cervical fusion using an anterior cervical plate as compared to those who are fused without an anterior cervical plate. Design: We retrospectively reviewed the lateral radiograms of sixty two patients who have had an anterior cervical fusion with a minimum follow up of twelve months. Materials and methods: We looked for the development of adjacent level osteophytes in these patients at their final follow up, which was generally at the time radiological fusion. There were 27 patients in the first group who had an anterior cervical plate used to fix the vertebrae in addition to the Cervios cage, while the 35 patients in the second group in whom only a Rabea cage was used for the fusion. The mean follow-up was 20.6 months (range 12–48). Results: 64.3% of the patients who had an anterior cervical plate developed adjacent level osteophytes while none of the patients who have had the fusion without the cage developed the osteophytes. Conclusion: We found the patients who had an anterior cervical interbody fusion using a plate had a significant risk of developing adjacent level osteophytes while this is not seen in patients who do not have the plate for the fixation

Introduction Disc replacement surgery is being investigated as an alternative to spinal fusion surgery in the hope that maintaining segment spinal motion will not only relieve pain, but also prevent or reduce the likelihood of symptomatic adjacent segment degeneration that is believed to be a consequence of fusion surgery. The aim of this study was to identify evidence in the medical literature that indicates whether or not spinal fusion surgery increases the likelihood of symptomatic adjacent segment degeneration compared to disc replacement surgery or natural history. Methods A search of the Cochrane Controlled Trials Register, Medline and reference lists of retrieved articles was performed. Search terms included arthroplasty replacement, spinal fusion, prognosis, controlled clinical trials and cohort studies, Studies were included if abstracts were available electronically, were published in the English language before1/3/2005 and involved humans. Levels of evidence were determined using the Oxford Centre for Evidence-Based Medicine criteria (. http://www.cebm.net/levels of evidence.asp. ). Discussion The majority of identified studies were case series of patients presenting with adjacent level disc degeneration following spinal fusion surgery (Level 4) and whilst indicating patients can develop adjacent level disc degeneration following fusion surgery, do not indicate the likelihood of doing so. Uncontrolled prospective cohort studies (Level 4) provide conflicting evidence. One retrospective cohort (Level 2b) studying comparing the incidence of adjacent disc degeneration following spinal fusion and discectomy or decompressive surgery alone found that the incidence of degeneration in the superior adjacent disc was increased in the fusion group, but was not associated with differences in functional outcome. No systematic reviews of inception cohort studies (Level 1) were identified. Conclusions Only poor quality evidence has been published to support the proposition that spinal fusion surgery is associated with an increased likelihood of developing symptomatic adjacent level disc degeneration. Long term follow-up of patients enrolled in prospective randomised controlled trials comparing outcomes of spinal fusion and disc replacement surgery is necessary to determine whether or not disc replacement surgery decreases the likelihood of any symptomatic adjacent level disc degeneration that can be attributed to spinal fusion surgery

Aim. A retrospective review of the management of adjacent level discectomy and fusion using a Zero-P (Synthes) cage and report of ease of technique and outcomes. Method. Surgical approach to adjacent level cervical disc protrusion with previous anterior cervical discectomy and fusion (ACDF) can be difficult. We review 4 patients who had previous ACDF with cage and plate who developed new onset adjacent level cervical disc prolepses causing myelopathy. A retrospective review of demographic data, symptoms, details of surgery, pre and post operative radiology, pre and postoperative ODI and pain score, length of stay, complications and follow-up data were collected in all patients. Results. Previous ACDF with plate was performed in all 4 patients an average of 11.6 years ago. Two patients had bilateral approaches previously and both had previous vascular injuries. The average duration of current symptoms was 9 months with a mean age of 65 years. All patients presented with myelopathy and two also had radiculopathy. Multiple level ACDF were operated in 2 patients previously. Revision surgery and dissection on the disc level was restricted by the previous plate. Screws from the previous plate fusion were removed adjacent to the level of surgery and discectomy was performed using distractor pins through the screw sites. Following discectomy a Zero-P cage was used to fusion with DBX under image intensifier guidance. The advantage was not to remove the previous plate and keep the dissection over the scar tissue to the minimal. All patients improved in their radicular symptoms with improvement of their hand function in the myelopaths. There was no complication and post operative radiographs were satisfactory. Conclusions. Use of the Zero-P cage for adjacent level discectomy and fusion was safe without disturbing the previous cage and plate fusion or stability

Purpose: The objectives of this study were to determine the effect of posterior instrumentation extension and/or cement augmentation on immediate stabilization of the instrumented level and biomechanical changes adjacent to the spinal instrumentation. Methods: This study was designed for repeated measures comparison, using 12 T9-L3 human cadaveric segments, to test the effects of posterior rod extension and cement augmentation following T11 corpectomy. The spine was stabilized with a vertebral body replacement device and with posterior instrumentation from T10 to T12. The T12 pedicle tracts were over-drilled to simulate loosened screws in an osteoporotic spine. The T10 screws were not over-drilled but cemented so as to keep the superior segments constant. Flexibility tests were first carried out on the intact specimen, followed by 3 randomized surgical conditions without cement and lastly the 3 conditions after cement augmentation. The 3 conditions were: 1) no posterior extension rods to L1, 2) flexible extension rods, and 3) rigid extension rods. A combined testing/analysis protocol that used both the traditional flexibility method and a hybrid technique [Panjabi 2005] was adopted. Flexibility tests with +/−5 Nm pure moments in flexion-extension, axial rotation and lateral bending were carried out and vertebral bodies’ motion in 3-D were collected. Two-way repeated measures ANOVA analyses were carried out on ROM between cement augmentation (factor 1) and the posterior rod extension (factor 2) on each flexibility test direction. An alpha of 0.05 was chosen. Newman-Keuls post-hoc analyses were carried out to compare between surgical techniques. Results: Using the flexibility protocol, a reduction in ROMs at the destabilized level was observed with cement augmentation of screws or extension with rigid or flexible posterior rods to adjacent distal level. With the hybrid protocol, ROMs at adjacent level (T12-L1) were reduced with rod extension, but not with cement. Conclusions: The results of this study suggest that cement augmentation would enhance stabilization, but create possible adjacent level effects due to increased motion and strain, while additional flexible extension rods would reduce biomechanical changes at the level of extension. Funding: 2 Funding Parties: CIHR

Aims. The aims of this study were first, to determine if adding fusion to a decompression of the lumbar spine for spinal stenosis decreases the rate of radiological restenosis and/or proximal adjacent level stenosis two years after surgery, and second, to evaluate the change in vertebral slip two years after surgery with and without fusion. Methods. The Swedish Spinal Stenosis Study (SSSS) was conducted between 2006 and 2012 at five public and two private hospitals. Six centres participated in this two-year MRI follow-up. We randomized 222 patients with central lumbar spinal stenosis at one or two adjacent levels into two groups, decompression alone and decompression with fusion. The presence or absence of a preoperative spondylolisthesis was noted. A new stenosis on two-year MRI was used as the primary outcome, defined as a dural sac cross-sectional area ≤ 75 mm. 2. at the operated level (restenosis) and/or at the level above (proximal adjacent level stenosis). Results. A total of 211 patients underwent surgery at a mean age of 66 years (69% female): 103 were treated by decompression with fusion and 108 by decompression alone. A two-year MRI was available for 176 (90%) of the eligible patients. A new stenosis at the operated and/or adjacent level occurred more frequently after decompression and fusion than after decompression alone (47% vs 29%; p = 0.020). The difference remained in the subgroup with a preoperative spondylolisthesis, (48% vs 24%; p = 0.020), but did not reach significance for those without (45% vs 35%; p = 0.488). Proximal adjacent level stenosis was more common after fusion than after decompression alone (44% vs 17%; p < 0.001). Restenosis at the operated level was less frequent after fusion than decompression alone (4% vs 14%; p = 0.036). Vertebral slip increased by 1.1 mm after decompression alone, regardless of whether a preoperative spondylolisthesis was present or not. Conclusion. Adding fusion to a decompression increased the rate of new stenosis on two-year MRI, even when a spondylolisthesis was present preoperatively. This supports decompression alone as the preferred method of surgery for spinal stenosis, whether or not a degenerative spondylolisthesis is present preoperatively. Cite this article: Bone Joint J 2022;104-B(12):1343–1351

The primary objective is to compare revision rates for lumbar disc replacement (LDR) and fusion at the same or adjacent levels in Ontario, Canada. The secondary objectives include acute complications during hospitalization and in 30 days, and length of hospital stay. A population-based cohort study was conducted using health administrative databases including patients undergoing LDR or single level fusion between October 2005 to March 2018. Patients receiving LDR or fusion were identified using physician claims recorded in the Ontario Health Insurance Program database. Additional details of surgical procedure were obtained from the Canadian Institute for Health Information hospital discharge abstract. Primary outcome measured was presence of revision surgery in the lumbar spine defined as operation greater than 30 days from index procedure. Secondary outcomes were immediate/ acute complications within the first 30 days of index operation. A total of 42,024 patients were included. Mean follow up in the LDR and fusion groups were 2943 and 2301 days, respectively. The rates of revision surgery at the same or adjacent levels were 4.7% in the LDR group and 11.1% in the fusion group (P=.003). Multivariate analysis identified risk factors for revision surgery as being female, hypertension, and lower surgeon volume. More patients in the fusion group had dural tears (p<.001), while the LDR group had more “other” complications (p=.037). The LDR group had a longer mean hospital stay (p=.018). In this study population, the LDR group had lower rates of revision compared to the fusion group. Caution is needed in concluding its significance due to lack of clinical variables and possible differences in indications between LDR and posterior decompression and fusion

Cervical spinal arthrodesis is the standard of care for the treatment of spinal diseases induced neck pain. However, adjacent segment disease (ASD) is the primary postoperative complication, which draws great concerns. At present, controversy still exists for the etiology of ASD. Knowledge of cervical spinal loading pattern after cervical spinal arthrodesis is proposed to be the key to answer these questions. Musculoskeletal (MSK) multi-body dynamics (MBD) models have an opportunity to obtain spinal loading that is very difficult to directly measure in vivo. In present study, a previously validated cervical spine MSK MBD model was developed for simulating cervical spine after single-level anterior arthrodesis at C5-C6 disc level. In this cervical spine model, postoperative sagittal alignment and spine rhythms of each disc level, different from normal healthy subject, were both taken into account. Moreover, the biomechanical properties of facet joints of adjacent levels after anterior arthrodesis were modified according to the experimental results. Dynamic full range of motion (ROM) flexion/extension simulation was performed, where the motion data after arthrodesis was derived from published in-vivo kinematic observations. Meanwhile, the full ROM flexion/extension of normal subject was also simulated by the generic cervical spine model for comparative purpose. The intervertebral compressive and shear forces and loading-sharing distribution (the proportions of intervertebral compressive and shear force and facet joint force) at adjacent levels (C3-C4, C4-C5 and C6-C7 disc levels) were then predicted. By comparison, arthrodesis led to a significant increase of adjacent intervertebral compressive force during the head extension movement. Postoperative intervertebral compressive forces at adjacent levels increased by approximate 20% at the later stage of the head extension movement. However, there was no obvious alteration in adjacent intervertebral compressive force, during the head flexion movement. For the intervertebral shear forces in the anterior-posterior direction, no significant differences were found between the arthrodesis subject and normal subject, during the head flexion/extension movement. Meanwhile, cervical spinal loading-sharing distribution after anterior arthrodesis was altered compared with the normal subject's distribution, during the head extension movement. In the postoperative loading-sharing distribution, the percentage of intervertebral disc forces was further increased as the motion angle increased, compared with normal subject. In conclusion, cervical spinal loading after anterior arthrodesis was significantly increased at adjacent levels, during the head extension movement. Cervical spine musculoskeletal MBD model provides an attempt to comprehend postoperative ASD after anterior arthrodesis from a biomechanical perspective

Introduction. The biomechanical behavior of lumbar spine instrumentation is critical in understanding its efficacy and durability in clinical practice. In this study, we aim to compare the biomechanics of the lumbar spine instrumented with single-level posterior rod and screw systems employing two distinct screw designs: paddle screw versus conventional screw system. Method. A fully cadaveric-validated 3D ligamentous model of the lumbopelvic spine served as the foundation for our comparative biomechanical analysis. 1. To simulate instrumentation, the intact spine was modified at the L4L5 level, employing either paddle screws or standard pedicle screws (SPS). The implants were composed of Ti-6AL-4V. Fixation at the S1 ensured consistency across loading scenarios. Loading conditions included a 400-N compressive load combined with a 10 N.m pure bending moment at the level of L1, replicating physiological motions of flexion-extension, lateral bending and axial rotation. We extracted data across various scenarios, focusing on the segmental range of motion at both implanted and adjacent levels. Result. In the flexion of L4L5, the applied force ranged from -29.2 to 29.3 N in the paddle screw, while it ranged from -25 to 25 N in the PS system. Similarly, the extension of L4L5 ranged from -3.1 to 2.6 N in the paddle and ranged from -4.5 to 3.9 N in the SPS system. In terms of stress distributions on the screw, stress concentrations decreased in several cases in the paddle design compared to the SPS systems. Top of Form. Conclusion. The paddle screw enhanced the range of motion overall in both the upper adjacent segment (L3L4) and the lower adjacent segment (L5S1) compared to the conventional SPS system. The stability of the aimed segment was increased by 33% on average with the paddle screw compared to conventional PS. Increasing the stability of the host segment decreases the possibility of non-union and the rate of fusion failure . 2.

Low back pain is the single most common cause for disability in individuals aged 45 years or younger, it carries tremendous weight in socioeconomic considerations. Degenerative aging of the structural components of the spine can be associated with genetic aspects, lifetime of tissue exposure to mechanical stress & loads and environmental factors. Mechanical consequences of the disc degenerative include loss of disc height, segment instability and increase the load on facets joints. All these can lead to degenerative changes and osteophytes that can narrow the spinal canal. Surgery is indicated in patients with spinal stenosis who have intractable pain, altered quality of life, substantially diminished functional capacity, failed non-surgical treatment and are not candidates for non-surgical treatment. The aim was to determine the reasons for refusal of surgery in patients with established degenerative lumber spine pathology eligible for surgery. All patients meeting the study criteria, patients older than 18 years, patients with both clinical and radiological established symptomatic degenerative lumbar spine pathology and patients eligible for surgery but refusing it were recruited. Questionnaire used to investigate reasons why they are refusing surgery. Results 59 were recruited, fifty-one (86.4 %) females and eight (13.6 %) males. Twenty (33.8 %) were between the age of 51 and 60 years, followed by nineteen (32.2 %) between 61 and 70 years, and fourteen (23.7 %) between 71 and 80 years. 43 (72 %) patients had lumber spondylosis complicated by lumber spine stenosis, followed by nine (15.2 %) with lumbar spine spondylolisthesis and four (6.7 %) had adjacent level disease. 28 (47.4 %) were scared of surgery, fifteen (25.4 %) claimed that they are too old for surgery and nine (15.2 %) were not ready. Findings from this study outlined that patients lack information about the spinal surgery. Patients education about spine surgery is needed

INTRODUCTION. Several clinical studies demonstrated long-term adjacent-level effects after implantation of spinal fusion devices[1]. These effects have been reported as adjacent joint degeneration and the development of new symptoms correlating with adjacent segment degeneration[2] and the trend has therefore gone to motion preservation devices; however, these effects have not been understood very well and have not been investigated thoroughly[3]. The aim of this study is to investigate the effect of varying the stiffness of spinal fusion devices on the adjacent vertebral levels. Disc forces, moments and facet joint forces were analyzed. METHODS. The AnyBody Modeling System was used to compute the in-vivo muscle and joint reaction forces of a musculoskeletal model. The full body model used in this study consists of 188 muscle fascicles in the lumbar spine and more than 1000 individual muscle branches in total. The model has been proposed by de Zee et al.[3], validated by Rasmussen et al.[4] and by Galibarov et al.[5]. The new model[5] determines the individual motions between vertebrae based on the equilibrium between forces acting on the vertebrae from muscles and joints and the passive stiffness in disks and ligaments, figure 1a. An adult of 1.75 m and 75 kg with a spinal implant in L4L5 was modeled. This model was subjected to a flexion-extension motion using different elastic moduli to analyze and compare to a non-implanted scenario. The analyzed variables were vertebral motion, the disc reaction forces and moments, as well as facet joint forces in the treated and the adjacent levels: L2L3, L3L4, L4L5 and L5-Sacrum. RESULTS. When introducing a spinal fusion device in the L4L5 joint the reaction forces and moments decreased in this joint with stiffer devices leading to lower joint loads. However, in the adjacent joints, L3L4 and L5Sacrum, an increase was observed when implanting stiffer devices. Similar trends could be found for the L2L3 joint. The loads in the facet joints showed the same trends. While introducing a spinal fusion device reduced the facet joint forces in the treated joint, the loads in the adjacent facet joints were increased according to the stiffness of the implanted device, figure 1b. DISCUSSION. While the treated disc joint showed reduced motion and loads, the adjacent levels demonstrated a significant increase. In particular, the increased facet joint forces in the adjacent levels can lead to adjacent level facet pain or accelerated facet joint degeneration. Introducing a device resulted in preventing facet contact and therefore facet joint loads, even using the device with the lowest stiffness. CONCLUSION. The presented model shows that clinical complications such as facet joint degeneration in adjacent levels after implantation of spinal fusion device are consistent with the change in the mechanical-stimulus distribution in the system

Aim. The purpose of this study is to compare the pre and post-operative magnetic resonance image clarity of titanium and PEEK based cervical arthroplasty devices at the level of implantation and adjacent level discs. Methodology and Results. This is a prospective, blinded, randomised study on imaging of cervical arthroplasty devices. The pre and postoperative MRI images of 16 patients who underwent cervical arthroplasty using Prestige LP(r) (Medtronic Sofamor Danek) and NuNec(tm) Cervical Arthroplasty System (Pioneer Surgical Technology, Marquette, Mich., USA) were assessed. Two independent radiologists who were blinded and provided with a sets of random images to score using a four point Jarvick grading system. Statistical analysis was completed using SPSS 16.0 statistical package (SPSS Inc, Chicago, IL) and analysis included comparing MR image quality before and after cervical arthroplasty at the operated and adjacent levels, and in between two types of implant. The pre-operative MR image quality at operated and adjacent levels was excellent in both groups. In the post-operative images, the adjacent level visualisation was adequate in both groups without much difference in average scores. However, at operated level, the quality of MR images in the NuNec group (PEEK on PEEK articulating disc) was excellent and clear visualisation of the cord, central canal, foramen and disc. Conclusion. Previous studies have shown that titanium devices allow satisfactory monitoring of adjacent and operated levels by providing good quality MRI images. Our studies confirm that using titanium based cervical arthroplasty implants provide clear visualisation of the adjacent level, however, provide less than satisfactory images at operated level. But the PEEK devices provide excellent quality images even at the operated level, with clear visualisation of neural structures and are valuable, if one wishes to assess the adequacy of neural decompression at operated level

Background: Cervical myelopathy and radiculopathy has been treated commonly with anterior cervical decompression and fusion with autologous bone graft and anterior cervical plating. Long term results have shown excellent pain relief and 73%–90% fusion rates. However, the development of late adjacent-level disease has been reported following anterior cervical arthrodesis which recently have been correlated to clinical findings. The Bryan disc arthroplasty device was developed to preserve the kinematics of the functional spine unit thus preventing adjacent level disease. There have been few studies comparing the incidence of adjacent level changes in patients undergoing ACDF compared to implantation of a Bryan disc arthroplasty device. Objectives: The object of this study is to compare the clinical results and radiographic outcomes of anterior cervical decompression and fusion versus cervical disc replacement using the Bryan Cervical Disc Prosthesis (Medtronic Sofamor Danek, Memphis, TN) in terms of overall range of motion (ROM) of the cervical spine; ROM, anterior intervertebral height (AIH), posterior intervertebral height (PIH) and radiographic changes at the implanted and adjacent levels. Methods: The study consisted of 105 patients with symptomatic single or two-level cervical disc disease. Fifty-one received the Bryan Cervical Artificial Disc Prosthesis (Medtronic Sofamor Danek, Memphis, TN). A total of 63 Bryan disc were placed in these 51 patients. A single-level procedure was performed in 39 patients and a two-level procedure in the other twelve. The patient group who underwent ACDF totaled 54 patients which consisted of 26 single level cases and 28 double level cases. The Bryan group had a mean follow-up 19 months (12–38). The mean follow-up for the ACDF group was 20 months (12–40 months). All patients were evaluated using static and dynamic cervical spine radiographs as well as MR imaging. All patients underwent anterior cervical discectomy followed by anterior cervical plating or implantation of the Bryan artificial disc prosthesis, done by one surgeon. Clinical evaluation included the visual analogue scale (VAS), and neck disability index (NDI). Radiographic evaluation included static and dynamic flexion-extension radiographs in an upright position using the computer software (Infinitt PiviewSTAR 5051) program. Range of motion/disc space angle and inter vertebral height were measured at the operative site and adjacent levels. Functional spinal unit (FSU) and overall sagittal alignment (C2–C7) were also measured pre-operatively, postoperatively and at final follow-up. ROM was calculated for all 3 areas and data collected were compared from pre operative to last follow-up as well as between the two groups. Radiographic assessment for adjacent level changes was also done. Radiologic change was analyzed using chi square test (95% confidence interval). Other data were analyzed using the mixed model. (SAS enterprise guide 4.1 version). Results: There was clinical improvement within each group in terms of VAS and NDI scores from pre-op to final follow-up for both single (VAS: p=0.8371, NDI: p=0.2872) and double (VAS: p=0.2938, NDI: p=0.6753) level surgeries but not significantly between the two groups. Overall, ROM and intervertebral height was relatively well maintained during the follow-up in the Bryan group compared to ACDF. Comparing the pattern of ROM measurements from pre-op to final follow-up between the two arms regardless of the number of levels operated on; significant differences were noted for overall ROM of the cervical spine (p< .0001) and all other levels except at the upper level for single level surgeries (p=0.2872). In terms of inter vertebral height measurements from pre-op to final follow-up, statistically significant (p< 0.0001 and p=0.0172) differences in the pattern between the two groups were noted at all levels except for the AIH of single level surgeries at the upper (p=0.1264) and lower (p=0.7598) levels as well as PIH for double level surgeries at the upper (p=0.8363) level. Radiologic change was 3.5 times more observed for the ACDF group compared to the Bryan group. Conclusion: Clinical status of both groups, regardless of the number of levels, showed improvement. Although clinical outcomes between the two groups were not significantly different at final follow-up, radiographic parameters, namely ROM and intervertebral heights at the operated site, some adjacent levels as well as FSU and overall sagittal alignment of the cervical spine were relatively well maintained in our Bryan group compared to our ACDF group. We surmise that to a certain degree, the maintenance of these parameters could contribute to reduce development of adjacent level change. Noteworthy is that radiographic change was 3.5 times more observed for ACDF surgeries. A longer period of evaluation is needed, to see if all these radiographic changes will translate to symptomatic adjacent level disease

Background: The X stop interspinous process decompression device has been used effectively in symptomatic lumbar spinal stenosis. It holds the spinal segment in a flexed position maintaining increase in dural sac and foraminal areas. Aim: To study the effect of X-stop on the lumbar spine kinematics at 24 months post operatively at the instrumented and adjacent levels. Design: Prospective Observational Study of 48 patients. Methods: Patients had a positional MRI scan preoperatively, 6 and 24 months post operatively in erect, flexion, extension and neutral positions. Disc heights, endplate angles, segmental and lumbar spine motion were measured at stenosed instrumented and adjacent levels. Osiris 4.17 software program was used for measurements. The data was analysed using paired t test on SPSS ver.15.01. Results: 48 patients underwent scans preoperatively. At 2 years 40 patients were scanned (3 patients had removal of X stop and 5 were not scanned). Of these, 38 scans were complete. Mean anterior disc height reduced from 7.2 mm to 5.9 mm (p< 0.001) at 24 months at the instrumented level. There were no significant changes in posterior disc height at instrumented or adjacent levels. The mean lumbar spine motion was 22o and 20o (p=0.366) in single level cases and 24.5o and 22.8o (p=0.547) in double level cases preoperatively and at 24 months. There was no significant change in the segmental range of motion at instrumented or adjacent levels. Conclusion: X-stop device does not significantly alter the kinematics of lumbar spine at instrumented or adjacent levels at 24 months postoperatively

Aim: To study the effect of X-stop interspinous decompression device on the lumbar spine kinematics at 6 and 24 months post operatively at the instrumented and adjacent levels in patients with symptomatic lumbar canal stenosis. Design: Prospective Observational Study of 48 patients. Methods: Patients due to have an X stop procedure were included and had a positional MRI scan preoperatively, 6 and 24 months post operatively in erect, flexion, extension and neutral position. Disc heights, endplate angles, segmental and lumbar spine motion was measured at stenosed instrumented and adjacent levels. Osiris 4.17 software program was used to measure the canal and foraminal dimensions. The data was analysed using paired t test on SPSS ver.15.01. Results: Forty-eight patients (25 Male and 23 Female) underwent scans preoperatively and at 6 months. Twenty-nine patients had single level and 19 had double level procedures. Three patients had removal of X stop and 5 did not have scan at 24 months, leaving 40 patients scanned at 24 months. Of these, 38 scans were complete and were included. Mean anterior disc height reduced from 7.1 mm to 6.3 mm (p=0.004) from 48 scans at 6 months and from 7.2 mm (pre-operative) to 5.9 mm (at 24 months) – (p=0.000) from 38 scans at 24 months at the instrumented level. We hypothesise that the reduction in anterior disc heights could be a result of the interspinous distraction plus the natural progression of spinal stenosis and ageing. There was no significant change in posterior disc heights at instrumented level or adjacent levels. The mean lumbar spine motion was 22.89o, 21.3 o and 21o (p=0.183) preoperatively, 6 and 24 months respectively. The total range of movements of lumbar spine and individual segments were measured. There was no significant change in the segmental range of motion at instrumented and adjacent levels. Conclusion: X-stop interspinous device does not significantly alter the kinematics of lumbar spine at instrumented and adjacent levels at 6 and 24 months postoperatively

Introduction. The ESP prosthesis is a one-piece deformable but cohesive interbody spacer. it provides 6 full degrees of freedom about the 3 axes including shock absorption (fig1). The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion in this “silentblock” implant. It thus differs substantially from current prostheses. Material and methods. Surgeries were performed by 2 senior surgeons in 54 women and 34 men (1level in 72 cases, 2 levels in 3 cases, hybrid construct in 13 cases). Average age was 42 (SD: 7). Average BMI was 24.2kg/m2 (SD: 3,4). Clinical data and X-rays were collected at the preoperative time and at 3, 6, 12, 24, and 60 months post-op. The analysis was performed by a single observer independent from the selection of patients and from the surgical procedure. The radiological analysis at 60 months follow-up could be realized in only 76 cases because the quality of the dynamic Xrays was not sufficient in 12 patients. We measured the ROM and the location of mean center of rotation (MCR) of the implanted and adjacent levels using the Spineview® software. The MCR is considered to reflect the quality of movement of a segment; it is localized thanks its co-ordinates. X is expressed as a percentage of the length of the vertebral end plate, and Y as a percentage of the height of the posterior wall. The usual location of the MCR is in a circle, whose center is placed between 30 and 50% of the superior vertebral endplate of the vertebra below, and whose diameter is 70% of the vertebral endplate size. Results. We did not observe device-related complications. All clinical outcomes significantly improved when compared to the pre-operative status (table 1, table 2). Mean ROM was 6,3° (SD 3,2) at the implanted level, 6,7°(5,2) at the above level, 7°(4,9) at the below level. Mean x-MCR value at the implanted level was 33.1% ± 20.8 % and mean y-MCR value −12,41% ± 30.1%. Mean x- MCR value at the above adjacent level was 25,7% ± 30.1% and mean y-MCR value 16%± 39.4%. Mean x- MCR value at the below adjacent level were 31.1% ± 29.8 % and mean y-MCR value − 0,61% ± 46.8. Conclusion. The concept of the viscoelastic ESP prosthesis is different from that of the “first generation” disc implants. This study reports encouraging clinical results about pain, function, and radiological kinematic behavior especially because the MCR appears similar to those of the natural disc described in the literature. The adaptation ability is one of the main feature of this concept as we need to consider the long term evolution of the global posture and mobility after disc replacement. For figures/tables, please contact authors directly.

Following studies in 2007-08 comparing cervical discs devices, satisfaction and accuracy of operated and adjacent levels was observed with titanium devices. Patients were followed up and surgical assessments recorded. MRI with 12 patients were first assessed for imaging quality. Two independent radiologists scored twice sagittal and axial T2 – weighted images using the Jarvik four point scale. Statistical analysis was performed on operated and adjacent levels and between devices. Length of surgery, blood loss, approach and time of exposure to radiation were recorded. Patients were followed up at two years. BAGUERA C containing titanium metal allowed satisfactory visualization of the canal, exit foramina, cord and adjacent levels. PCM and PRODISC C visualization was significantly impaired at operated level and in both spinal cord and neural foramina. At adjacent levels, image quality was statistically poorer for those two devices. 6 patients were operated at C5-C6 and 6 at C6-C7. Mean age was 49. Approach was from the right, length of surgery and blood loss were: mean 46 min and 16.25 cc for BAGUERA C; mean 70 min and 27.5 cc for PCM and mean 63 min with 26.25 cc for PRODISC C. Exposure to radiation presented also significant difference between devices. Clinical outcomes reveal similar VAS and patient's satisfaction scores. Titanium device with polyethylene allow for satisfactory monitoring with adequacy in the assessment of neural decompression. BAGUERA C surgical outcomes indicate potential benefits that may be related to technique and simplicity of implantation

INTRODUCTION. Lumbar total disc replacement (TDR) is an alternative treatment to avoid fusion related adverse events, specifically adjacent segment disease. New generation of elastomeric non-articulating devices have been developed to more effectively replicate the shock absorption and flexural stiffness of native disc. This study reports 5 years clinical and radiographic outcomes, range of motion and position of the center of rotation after a viscoelastic TDR. Material and methods. This prospective observational cohort study included 61 consecutive patients with monosegmental TDR. We selected patients with intermediate functional activity according to Baecke score. Hybrid constructs had been excluded. Only cases with complete clinical and radiological follow-up at 3, 6, 12, 24 and 60 months were included. Mean age at the time of surgery was 42.8 +7.7 years-old (27–60) and mean BMI was 24.2 kg/m² +3.4 (18–33). TDR level was L5-S1 in 39 cases and L4-L5 in 22 cases. The clinical evaluation was based on Visual Analog Scale (VAS) for pain, Oswestry Disability Index (ODI) score, Short Form-36 (SF36) including physical component summary (PCS) and mental component summary (MCS) and General Health Questionnaire GHQ28. The radiological outcomes were range of motion and position of the center of rotation at the index and the adjacent levels and the adjacent disc height changes. Results. There was a significant improvement in VAS (3.3±2.5 versus 6.6±1.7, p<0.001), in ODI (20±17.9 versus 51.2±14.6, p<0.001), GHQ28 (52.6±15.5 versus 64.2±15.6, p<0.001), SF 36 PCS (58.8±4.8 versus 32.4±3.4, p<0.001) and SF 36 MCS(60.7±6 versus 42.3±3.4, p<0.001). Additional surgeries were performed in 5 cases. 3 additional procedures were initially planified in the surgical program: one adjacent L3-L5 ligamentoplasty above a L5S1 TDR and two L5S1 TDR cases had additional laminectomies. Fusion at the index level was secondary performed in 2 L4L5 TDR cases but the secondary posterior fusion did not bring improvement. In the 56 remaining patients none experienced facet joint pain. One patient with sacroiliac pain needed local injections. Radiological outcomes were studied on 56 cases (exclusion of 5 cases with additional surgeries). The mean location centers of the index level and adjacent discs were comparable to those previously published in asymptomatic patients. According to the definition of Ziegler, all of our cases remained grade 0 for disc height (within 25% of normal). Discussion. The silent block design of LP-ESP provides an interesting specificity. It could be the key factor that makes the difference regarding facets problems and instability reported with other implants experimentally or clinically. Unfortunately no other comparative TDR series are available yet in the literature. Conclusion. This series reports significant improvement in mid-term follow up after TDR which is consistent with previously published studies but with a lower rate of revision surgery and no adjacent level disease pathologies. The radiographic assessment of the patients demonstrated the quality of functional reconstruction of the lumbar spine after LP ESP viscoelastic disc replacement

Introduction This in-vitro biomechanical study was undertaken to compare the multi-directional flexibility kinematics of single versus multi-level lumbar Charité reconstructions and determine the optimal biomechanical method for surgical revision – posterior instrumentation alone or circumferential spinal arthrodesis. Methods A total of seven human cadaveric lumbosacral spines (L1 to Sacrum) were utilized in this investigation and biomechanically evaluated under the following L4-L5 reconstruction conditions: 1) Intact Spine; 2) Diskectomy Alone, 3) Charité, 4) Charité + Pedicle Screws, 5) Two Level Charité (L4-S1), 6) Two Level Charité + Pedicle Screws (L4-S1), 7) Charité L4-L5 with Pedicle Screws and Femoral Ring Allograft (L5-S1) and 8) Pedicle Screws and Femoral Ring Allograft (L4-S1). Multi-directional flexibility testing utilized the Panjabi Hybrid Testing protocol, which includes pure moments for the intact condition with the overall spinal motion replicated under displacement control for subsequent reconstructions. Hence, changes in adjacent level kinematics can be obtained compared to pure moment testing strategies. Unconstrained intact moments of ±7Nm were used for axial rotation, flexion-extension and lateral bending testing, with quantification of the operative and adjacent level range of motion (ROM) and neutral zone (NZ). All data was normalized to the intact spine condition. Results In axial rotation, single and two level Charité reconstructions produced significantly more motion than pedicle screw constructs combined with the Charité or femoral ring allograft (p< 0.05). There were no differences between the Charité augmented with pedicle screws or pedicle screws with femoral ring allograft (p> 0.05). Similar trends were observed under flexion-extension and lateral bending conditions with the Charité reconstructions demonstrating no significant differences compared to the intact spine (p> 0.05). However, the Charité combined with pedicle screws or pedicle screws with femoral ring allograft significantly reduced motion at the operative level compared to the Charité reconstruction (p< 0.05). The most pronounced changes in adjacent level kinematics were observed at the inferior level. The addition of pedicle screw fixation, in all cases, increased segmental motion at the inferior adjacent level (L5-S1) compared to the intact and Charité reconstruction groups (p< 0.05). Discussion Single and two level total disc arthroplasty using the Charité device preserved segmental motion at the operative and adjacent levels compared to pedicle screw stabilization constructs. In terms of revision strategies, posterior pedicle screw reconstruction combined with an existing Charité is not statistically different from pedicle screws combined with femoral ring allograft. As we enter an era of total disc replacement and the impending necessity for surgical revision, the current study provides a biomechanical basis for posterior re-stabilization alone in lieu of combined anteroposterior revision

Purpose: Perispinal core muscle strength has been theorized to be an important component in the pathogenesis of back pain. Recent research has demonstrated a strong association between preoperative perispinal musculature, adjusted for fatty infiltration and prospective outcomes and improvements in back pain in patients undergoing lumbar laminectomy without fusion. The purpose of this study is to determine if a similar relationship exists in patients undergoing elective posterior lumbar fusion and decompression (PLFD) surgery. Method: A retrospective observational study of prospectively collected outcomes data was conducted in which pre-operative function and patient variables of those undergoing PLFD were derived from a functional status questionnaire and medical records. ImageJ Digital Imaging Software was utilized to measure the total (CSA) and percentage of fatty infiltration of the psoas, multifidus, and erector spinae muscles in pre-operative L4 axial CT images. Pre-operative and post-operative lateral images were evaluated for degree of post-operative adjacent level degeneration. Follow-up consisted of a functional status questionnaire. Outcomes measured were improvements in back pain, leg pain, and Oswestry disability scores. Results: Twenty-three patients were analyzed with a mean follow-up of 2 years (range 1 – 5 years). Outcomes improved following surgery. There were strong to moderate correlations between percentage of fat in the pre-operative posterior spinal muscles and improvements in leg pain (r = 0.63, p = < 0.001) and improvements in back pain (r = 0.41, p = 0.05). There was a moderate trend towards greater adjacent level degeneration (r = 0.37, p = 0.1) in patients with higher percentage of fat in the pre-operative posterior spinal muscles. There was a strong relationship between greater adjacent level degeneration and pre-operative disability as measured by the Oswestry (r = 0.62, p = 0.03). Conclusion: The results demonstrate that a potential relationship exists between pre-operative fatty infiltration of posterior perispinal muscles and post-operative outcomes, and adjacent level degeneration following lumbar fusion surgery. This suggests that perispinal muscle atrophy and conditioning may play a role in these outcomes. Results may be used for prognostication, surgical candidate selection, and interventional strategies