Aims. The aim of this study was to determine the influence of developmental spinal stenosis (DSS) on the risk of re-operation at an adjacent level. Patients and Methods. This was a retrospective study of 235 consecutive patients who had undergone decompression-only surgery for lumbar spinal stenosis and had a minimum five-year follow-up. There were 106 female patients (45.1%) and 129 male patients (54.9%), with a mean age at surgery of 66.8 years (. sd. 11.3). We excluded those with adult deformity and spondylolisthesis. Presenting symptoms, levels operated on initially and at re-operation were studied. MRI measurements included the anteroposterior diameter of the bony spinal canal, the degree of disc degeneration, and the thickness of the ligamentum flavum. DSS was defined by comparative measurements of the bony spinal canal. Risk factors for re-operation at the adjacent level were determined and included in a multivariate stepwise logistic regression for prediction modelling. Odds ratios (ORs) with 95% confidence intervals were calculated. Results. Of the 235 patients, 21.7% required re-operation at an adjacent segment. Re-operation at an adjacent segment was associated with DSS (p = 0.026), the number of levels decompressed (p = 0.008), and age at surgery (p = 0.013). Multivariate regression model (p < 0.001) controlled for other confounders showed that DSS was a significant predictor of re-operation at an adjacent segment, with an adjusted OR of 3.93. Conclusion. Patients with DSS who have undergone lumbar spinal decompression are 3.9 times more likely to undergo future surgery at an adjacent level. This is a poor prognostic indicator that can be identified prior to index decompression surgery

Introduction. The influence of lumbar and lumbosacral fusion on adjacent moving segments has been the subject of a number of studies, which have shown the origin and progress of degenerative changes and instability brought about by alterations of kinematics and elasticity of the fused segment. Back pains which emerge later in the postoperative period may be the consequence of degeneration and instability in the adjacent segment to the said fusion. The fusion shifts the centre of rotation to the level adjacent to the fusion, which increases the pressure and pull on both the disk and joints. It can be supposed that the pull and attendant pains are in direct proportion to the rigidity of the spondylodesis that is more pronounced after anterior intersomatic fusion and less so after posterior. The development of hyperlordosis or kyphosis in the lumbar region is also a risk factor for adjacent segment failure. Material and methods. The authors performed a retrospective analysis on a group of 91 patients with spondylolisthesis who had undergone PLIF technique with transpedicular fixation surgery and PLF. A total of 10 (11%) of 91 patients developed symptomatic next segment desease at a previously asymptomatic level. Date were obtained in patients with next – segment failure based on X-rays studies, neurological assessment and sequential follow-up examinations. The aforementioned patients had a mean age of 42.8 years and the mean follow up period was 8.7 years after surgery. 7 cases were isthmic, 2 degenerative and 1 dysplastic spondylolisthesis. Fusion in every case entailed the use of autologinous bone grafts, and with the PLIF technique cages, in 3 cases, dowels, in 6 cases, and autofibula in 1 case were used. The mean follow-up period between original surgery and next-segment failure was 3.8 years. Results. In ten cases from the group there was evidence of instability or degeneration, instability in 3 cases (all above fusion) and degeneration in 7 cases (4 above and 3 below fusion) respectively. All patients with instability in cranial adjacent segment underwent successfully additional surgery by using 360° fusion with instrumentation (ALIF). Discussion. In X-rays conducted prior to surgery, signs of hypermobility were present in the cranial adjacent segment in one case. This hypermobility affected the rigidity of the fusion in the caudal segment, which accelerated the progress of instability and caused further surgery to be necessary. The cause of instability could also be overloading of the spine, damage to the stability of ligament and bone structures sustained during the operation, or a combination of the above

Study design: Prospective clinical and radiologic study. Objective: The purpose of this study was to investigate the risk factors for adjacent segment degeneration after posterior lumbar interbody fusion (PLIF). Summary of Background data: Although several authors have reported the adjacent segment degeneration after lumbar or lumosacral fusion, there is no consensus regarding the risk factors for adjacent segment degeneration. Methods: Sixty-five patients were studied after PLIF after a minimum follow up time of 6 years. Plain and flexion/ extension radiographs and MRI scans were obtained and compared to preoperative and postoperative. Progression of segment degeneration was defined as a condition in which the distinction between nucleus and annulus is lost, and the disc space is collapsed according to the grading system (Grade 1–5) described by Pfirrmann et al evaluated with T2 weighted MRI scans. Patients were divided into three groups: Group 1 with no radiological progression of disc degeneration, Group 2 with radiological progression of disc degeneration, and Group 3 with radiological progression of disc degeneration and clinical deterioration. Risk factors for progression of adjacent disc degeneration as lumbar lordosis, lordosis at the fused segment, facet sagittalization, and pre-existing disc degeneration were evaluated. The images were evaluated by two independent radiologists. Results: Fifteen patients (23%) showed no radiological progression of disc degeneration on MRI scans and were classified into Group 1. Forty patients (62%) developed some cranial or caudal deterioration of the adjacent segment without clinical deterioration and were classified into Group 2. Ten patients (15%) required reoperation for neurological and clinical deterioration caused by cranial or caudal degeneration of the adjacent disc (Group 3). No statistically significant differences were found in lumbar lordosis, lordosis at the fused segment, facet sagittalization between each group. Patients in Group 3 showed on preoperative MRI already moderate to severe alteration of the adjacent disc (mean Grade 4) compared to Group 1 (mean Grade 2) and 2 (mean Grade 2,5) (p< 0.01). Conclusion: After PLIF disc degeneration appear homogeneously at several levels cranial and caudal to fusion over the years in most of the patients (79%). Only pre-existing degeneration of the adjacent cranial and caudal segment is a potential risk factor for clinical deterioration caused by disc collapse

Introduction Adjacent segment disease with radiculopathy and neurologic deficit adjacent to a non-mobile spinal segment is the ideal application for cervical arthroplasty. Not only are the stresses and loads increased but unfortunately the previously fused segment is further compromised by being fixed in a kyphotic position. Methods This is a prospective study of 40 PCM prostheses inserted in thirty patients with 50 adjacent segments previously fused or rendered immobile—ten cases were performed as bi-level implantations. The inclusion and exclusion criteria were otherwise identical to the normal FDA prospective IDE criteria with all patients presenting with radiculopathy and a corresponding neurologic deficit confirmed by an MRI compressive lesion. Results The mean preoperative cervical lordosis was 2.65 degrees (−32 to 25), mean postoperative lordosis 12.3 degrees (−17 to 30), and the mean improvement was 9.4 degrees of cervical lordosis (range (−15 to 23). EBL = 0 to 100 cc with no patients requiring blood transfusions, Length of surgery = mean 104 minutes (60 to 150) and the length of hospital stay = mean 1.17 days (0 to 3 days). The clinical follow-up was greater than 2 years. All patients were neurologically intact at follow up with a mean improvement of NDI = 50 % and mean improvement in VAS = 58.3 %.The range of flexion and extension motion at the level of the prosthesis was a mean of 8.9 degrees (range 4 to 20 degrees). Discussion Naturally, the adjacent segment application of a cervical disc replacement is a challenging clinical environment for cervical arthroplasty – by definition every case had prior surgery. Not only is the cervical spine position often compromised by being in excessive kyphosis, but seventeen of the 50 previously fused levels had prior cervical instrumentation. 5 patients had previous cervical cages, 2 had cage-plates, 5 patients had previous anterior cervical plates, one had a prior arthroplasty device with HO, and 4 patients had PMMA which required revision. Despite the complicated nature of the presenting pathology, the Porous Coated Motion Cervical prosthesis successfully restored some element of cervical lordosis, and restored stability to the cervical segments. An added potential bonus is the preserved 9.4 degrees of flexion – extension mobility. The PCM appeared to work well in these revision cases. This is the world’s largest study to date investigating prospectively the value of cervical arthroplasty in adjacent segment disease

With the increase in the elderly population, there is a dramatic increase in the number of spinal fusions. Spinal fusion is usually performed in cases of primary instability. However it is also performed to prevent iatrogenic instability created during surgical treatment of spinal stenosis in most cases. In literature, up to 75% of adjacent segment disease (ASD) can be seen according to the follow-up time. 1. Although ASD manifests itself with pathologies such as instability, foraminal stenosis, disc herniation or central stenosis. 1,2. There are several reports in the literature regarding lumbar percutaneous transforaminal endoscopic interventions for lumbar foraminal stenosis or disc herniations. However, to the best our knowledge, there is no report about the treatment of central stenosis in ASD. In this study, we aimed to investigate the short-term results of unilateral biportal endoscopic decompressive laminotomy (UBEDL) technique in ASD cases with symptomatic central or lateral recess stenosis. The number of patients participating in the prospective study was 8. The mean follow-up was 6.9 (ranged 6 to 11) months. The mean age of the patients was 68 (5m, 3F). The development of ASD time after fusion was 30.6 months(ranged 19 to 42). Mean fused segments were 3 (ranged 2 to 8). Preoperative instability was present in 2 of the patients which was proven by dynamic lumbar x-rays. Preoperative mean VAS-back score was 7.8, VAS Leg score was 5.6. The preoperative mean JOA (Japanese Orthopaedic Association) score was 11.25. At 6th month follow-up, the mean VAS back score of the patients was 1, and the VAS leg score was 0.5. This improvement was statistically significant (p = 0.11 and 0.016, respectively). The mean JOA score at the 6th month was 22.6 and it was also statistically significant comparing preoperative JOA score(p = 0.011). The preoperative mean dural sac area measured in MR was 0.50 cm2, and it was measured as 2.1 cm. 2. at po 6 months.(p = 0.012). There was no progress in any patient's instability during follow-up. In orthopedic surgery, when implant related problems develop in any region of body (pseudoarthrosis, infection, adjacent fracture, etc.), it is generally treated by using more implants in its final operation. This approach is also widely used in spinal surgery. 3. However, it carries more risk in terms of devoloping ASD, infection or another complications. In the literature, endoscopic procedures have almost always been used in the treatment of ventral pathologies which constitute only 10%. In ASD, disease devolops as characterized by wide facet joint arthrosis and hypertrophied ligamentum flavum in the cranial segment and it is mostly presented both lateral recess and santal stenosis symptoms (39%). In this study, we found that UBEDL provides successful results in the treatment of patients without no more muscle and ligament damage in ASD cases with spinal stenosis. One of the most important advantages of UBE is its ability to access both ventral and dorsal pathologies by minimally invasive endoscopic aproach. I think endoscopic decompression also plays an important role in the absence of additional instability at postoperatively in patients. UBE which has already been described in the literature given successful results in most of the spinal degenerative diseases besides it can also be used in the treatment of ASD. Studies with longer follow-up and higher patient numbers will provide more accurate results

INTRODUCTION. The elimination of motion and disc stress produced by spinal fusion may have potential consequences beyond the index level overloading the spinal motion segments and leading to the appearance of degenerative changes. So the “topping-off” technique is a new concept instructing dynamic fixation such as interspinous process device (IPD) for the purpose of avoiding adjacent segment disease (ASD) proximal to the fusion construct. MATERIALS AND METHODS. The study simulated spinal fusion in L4-L5, fusion combined DIAM in L3-L4. The ROM and maximum von Miss stresses were analyzed in flexion, extension, lateral bending, and torsion in response to hybrid method, compared to intact modeland fusion model. RESULTS. The investigation revealed that decreased ROM, intradiscal stress in implanted level but a considerable increase in stresses at more upper level (L2-L3) during flexion and extension in hybrid model, comparing with the fusion model. CONCLUSIONS. The raise of intradiscal pressure at the adjacent segment to a rigid fusion segment can be reduced when the rigid construct is augmented with an interspinous process device. However, the burden of stress over total spinal segments was still the same, the stress and ROM were just shift to supraadjacent levels

Introduction: ACDF involves cancellation of the diseased spinal motion segment, the neighboring spinal segments take the burden of excessive compensatory spinal movements and strain resulting in early degeneration. Adjacent segment degeneration with new, symptomatic radiculopathy occurs after ACDF in 2–3% of patients per year on cumulative basis. An estimated 15% of patients ultimately require a secondary procedure at an adjacent level. An alternative to fusion is total disc arthroplasty (TDA). The key advantage of this promising technology is restoration and maintenance of normal physiological motion rather than elimination of motion. We describe 4 patients with a serious complication observed following implantation of the Bryan disc prosthesis in our cohort of 48 patients. Material and Results:. Patient #1: 43 M, with neck pain & left brachalgia, with left C6 dermatome signs, with MRI findings of C5/6 disc prolapse with left C6 root impingement, undergoing C5/6 Bryan TDA in April 2004, with treatment recommendation of C3/4 and C6/7 Bryan TDA in January 2006. Patient #2: 47 M, with worsening gait over 2 years with right brachalgia, with findings of progressive cervical myelopathy with right C5 radiculopathy, with MRI findings of severe C5/6 disc degeneration with spinal cord compression, undergoing C5/6 Bryan TDA in January 2003, with MRI FU findings after 16/12 with new left C6/7 disc prolapse and left C6 radiculopathy, with treatment recommendation of C6/7 Bryan TDA, on waiting list. Patient #3: 45 F, 6 years of neck pain with right brachialgia, with right C5 dermatome signs, with MRI findings of C5/6 central disc herniation with cord compression, undergoing C5/6 Bryan TDA in December 2000, with FU MRI showing after 5 years and 7/12 (67/12) new C6/7 canal narrowing with right C6 radiculopathy, and treatment recommendation of C6/7 Bryan TDA. Patient #4: 38 M, worsening gait over 5 years and exam findings of progressive cervical myelopathy, with MRI findings of severe C5/6 disc degeneration with spinal cord compression, undergoing C5/6 Bryan TDA in August 2003, with FU MRI showing after 3 years new C4/5 disc prolapse with C5 radiculopathy, followed by treatment recommendation of C4/5 Bryan TDA. Discussion & Conclusions: Bryan TDR did not prevent the development of accelerated ASD. Evidence from in vivo X ray studies suggested that the range of motion across the operated levels did not match the physiological ROM. Despite the MRI images preoperatively, it is difficult to exclude the natural progression of degeneration as a reason for ASD

Introduction: We report a series of 10 cases from a cohort of 421 Dynesys procedures in which evidence of Accelerated Adjacent Disc Disease (AASDD). Spinal fusion for degenerative disc disease is known to have inconsistent outcomes. One concern is the possibility of AASDD as a result of the altered kinematics. The Dynamic Neutralisation System (Dynesys) appears to offer an advantage in that it restricts, rather than abolishes movement at the treated segment, and should thereby reduce the problem of AASDD, In the event of failure, it can in addition be removed, returning the spine to the former status quo. Various biomechanical studies confirmed flexibility of Dynesys. Method: Ten patients developed new and symptomatic disc disease within segments adjacent to Dynesys. The average age of patients was 49 year with range between 36–70 years. Average post Dynesys to secondary surgery for ASD was 24.7 months. Previous discography and MRI in all cases had shown no evidence of disc disease within these adjacent segements prior to Dynesys. All patients were evaluated preoperatively using Oswestry Disability Index, SF 36 and Visual Analogue Scores together with plain x ray imaging, MRI scanning and discography. Of this cohort Dynesys was indicated to treat single disc level in 7 and two levels in 3. Results: Incidence of AASDD associated with Dynesys was 2.1%. Further surgical intervention included:. Extension of Dynesys10. Dynesys combined with MIF2. Dynesys combined with PLIF2. There was no caudal ASD in our cohort. Discussion & Conclusions: Dyensys did not prevent the development of accelerated ASD. Evidence from Aylott cadaver studies suggests that Dynesys instrumentation alters the Kinematics of the adjacent segment and increases the excursion. It is unclear whether the small number of AASDD reported here is other than the natural progression of degenerative change. 95.7 cases did not progress

Purpose: Adjacent Segment Degeneration (ASD) can occur after spinal fusion. Disc degeneration, spinal stenosis, deformity, spondylolisthesis and fracture are observed. The incidence is unknown and its occurrance difficult to predict. Further major surgery is required to correct the clinical problem that exists although not all cases of ASD are symptomatic. The primary purpose of this study was to identify the incidence of ASD after multilevel(> /=3) thoracolumbar fusions for degenerative disorders. Risk factors for ASD were to be determined. Methods: Over 400 spinal fusions of 3 levels or greater, minimum 5 year follow-up were assessed for ASD. Radiographic data were available from a prospective data bank. The radiological incidence of ASD was distinguished from those that were clinically significant as determined by Oswestry, back and leg pain scores. |Personal and telephone interviews were conducted along with most recent plain xrays. Data was analyzed (ANOVA) from a single surgeon’s practice. Radiographic assessment was performed by the author with radiologist’s opinions available. Results: The incidence of ASD after extended spinal fusions overall was 20%. Clinically significant ASD requiring further surgery was 12%. The incidence varied according to location of the fusion, number of levels, age and preexisting disc degeneration and or deformity at the end vertebrae. Overall it was difficult to predict risk factors but trends were noted. Long fusions(greater than or equal to 3 levels) has a significantly high risk of ASD by 5 yrs after the index operation. Conclusions: The incidence of ASD by 5 years post spine fusion of 3 or more levels is 20% in over 400 cases.12% of these index cases needed further surgery. ASD is a clinically significant entity that deserves study to aid in its prevention

Purpose: Adjacent Segment Degeneration (ASD) can occur after spinal fusion, disc degeneration, spinal stenosis, deformity, spondylolisthesis and fracture. The incidence is unknown and its occurence difficult to predict. Further major surgery is required to correct the clinical problem that exists although not all cases of ASD are symptomatic. The primary purpose of this study was to identify the incidence of ASD after multilevel (> /= 3 level) thoracolumbar fusions for degenerative disorders at a minimum 5 year followup. Risk factors for ASD were to be determined. Method: 405 spinal fusions of three levels or greater, performed between 1988 and 2001, minimum five year followup were assessed for ASD. Radiographic data was available from a prospective data bank. The radiological incidence of ASD was distinguished from those that were clinically significant as determined by Oswestry Disability Index, back and leg pain visual analog scales. Results: The incidence of ASD after extended spinal fusions overall was 28%, based on radiological evaluation. There was an 18% incidence of clinically significant ASD. 10% of the entire group required surgery to address ASD. The incidence varied according to the location of the fusion, number of levels, age and pre-existing disc degeneration and/or deformity at the end vertebrae. Overall it was difficult to predict risk factors but trends were noted. Long fusion (> /= 3 levels) have a significantly high risk of ASD by five years after the index operation. Adjacent level degenerative disc disease and spinal stenosis were the most common type of ASD. Conclusion: The incidence of ASD by five years post spine fusion of three or more levels is 28% in over 405 cases. 10% of these cases needed further surgery. ASD is a clinically significant entity that deserves further study to aid in its prevention

Spondylolysis can be associated with severe back or leg pain requiring surgical management.

Fusion is the most often performed procedure since disk degeneration is frequently present. In a limited number of cases, when there is no disk disease or only limited dehydration, isthmic reconstruction may be considered, saving mobility and avoiding adjacent level stress.

We review 30 patients submitted to L4 or L5 posterior arch reconstruction and 60 patients submitted to a one level (L4L5 or L5S1) posterior or interbody fusion.

Through Prolo scores, SF36 and Oswestry questionnaires, the every day, professional and sports functional and satisfaction rates are evaluated.

Present data fail to show better functional results in the isthmic reconstruction group. However, even longer follow up will be necessary in these groups of young adults with a great life expectancy to show potentially less degenerative deterioration in adjacent levels. Meanwhile, isthmic reconstruction proved to be an effective technique, comparable to fusion in patients with no associated disk disease, with no need for further surgery and minimal complications.

Objective: To document the incidence of adjacent superior segment facet joint violation following transpedicular instrumentation in the lumbar spine as it has been postulated that this can lead to long term deterioration There has been no study so far determining this incidence. Design: Patients undergoing lumbar fusion were prospectively evaluated with a CT scan and plain radiographs six months following surgery. These were blindly and independantly evaluated by a consultant radiologist and a research fellow. Subjects: 106 patients (212 top level facet screws) between 1996 and 1999 were evaluated. All patients had their screws and instrumentation inserted through a Wiltse muscle splitting approach and a lateral entry point in the pedicle so as to reduce the risk of facetal impingement. . 1. Outcome Measures: Kappa co-efficient and chi-squared analysis. Results: The Kappa co-efficient for the CT scan and plain radiographs were 0.88 and 0.39 respectively. On the CT scan both observers noted facet joint impingement in just over 20% of the screws and just over 30% of the patients. The impingement was independent of the level and diagnosis (p> 0.05) and it occurred with uniform incidence in each of the year. Conclusion: This study raises the theoretical possibility of long term deterioration in the clinical results following the use of transpedicular instrumentaion

Background. It has become increasingly important to conduct studies assessing clinical outcomes, reoperation rates, and revision rates to better define the indications and efficacy of lumbar spinal procedures and its association with symptomatic adjacent segment degeneration (sASD). Adjacent segment degeneration (ASD) is defined as the radiographic change in the intervertebral discs adjacent to the surgically treated spinal level. SASD represents adjacent segment degeneration which causes pain or numbness due to post-operative spinal instability or nerve compression at the same level. The most common reason for early reoperation and late operation is sASD, therefore is in our best interest to understand the causes of ASD and make steps to limit the occurrence. Method. A comprehensive literature search was performed selecting Randomized controlled trials (RCTs) and retrospective or prospective studies published up to December 2023. Meta-analysis was performed on 38 studies that met the inclusion criteria and included data of clinical outcomes of patients who had degenerative disc disease, disc herniation, radiculopathy, and spondylolisthesis and underwent lumbar fusion or motion-preservation device surgery; and reported on the prevalence of ASD, sASD, reoperation rate, visual analogue score (VAS), and Oswestry disability index (ODI) improvement. Results. When compared to fusion surgery, a significant reduction of ASD, sASD and reoperation was observed in the cohort of patients that underwent motion-preserving surgery. Conclusion. Dynamic fusion constructs are treatment options that may help to prevent sASD. Conflicts of interest. This research was funded by Paradigm Spine. Sources of funding. Paradigm Spine

The August 2024 Spine Roundup. 360. looks at: Laminectomy adjacent to instrumented fusion increases adjacent segment disease; Influence of the timing of surgery for cervical spinal cord injury without bone injury in the elderly: a retrospective multicentre study; Lumbar vertebral body tethering: single-centre outcomes and reoperations in a consecutive series of 106 patients; Machine-learning algorithms for predicting Cobb angle beyond 25° in female adolescent idiopathic scoliosis patients; Pain in adolescent idiopathic scoliosis; Teriparatide prevents surgery for osteoporotic vertebral compression fracture

The April 2023 Spine Roundup. 360. looks at: Percutaneous transforaminal endoscopic discectomy versus microendoscopic discectomy; Spine surgical site infections: a single debridement is not enough; Lenke type 5, anterior, or posterior: systematic review and meta-analysis; Epidural steroid injections and postoperative infection in lumbar decompression or fusion; Noninferiority of posterior cervical foraminotomy versus anterior cervical discectomy; Identifying delays to surgical treatment for metastatic disease; Cervical disc replacement and adjacent segment disease: the NECK trial; Predicting complication in adult spine deformity surgery

Aims. The aim of this study was to determine how the short- and medium- to long-term outcome measures after total disc replacement (TDR) compare with those of anterior cervical discectomy and fusion (ACDF), using a systematic review and meta-analysis. Patients and Methods. Databases including Medline, Embase, and Scopus were searched. Inclusion criteria involved prospective randomized control trials (RCTs) reporting the surgical treatment of patients with symptomatic degenerative cervical disc disease. Two independent investigators extracted the data. The strength of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. The primary outcome measures were overall and neurological success, and these were included in the meta-analysis. Standardized patient-reported outcomes, including the incidence of further surgery and adjacent segment disease, were summarized and discussed. Results. A total of 22 papers published from 14 RCTs were included, representing 3160 patients with follow-up of up to ten years. Meta-analysis indicated that TDR is superior to ACDF at two years and between four and seven years. In the short-term, patients who underwent TDR had better patient-reported outcomes than those who underwent ACDF, but at two years this was typically not significant. Results between four and seven years showed significant differences in Neck Disability Index (NDI), 36-Item Short-Form Health Survey (SF-36) physical component scores, dysphagia, and satisfaction, all favouring TDR. Most trials found significantly less adjacent segment disease after TDR at both two years (short-term) and between four and seven years (medium- to long-term). Conclusion. TDR is as effective as ACDF and superior for some outcomes. Disc replacement reduces the risk of adjacent segment disease. Continued uncertainty remains about degeneration of the prosthesis. Long-term surveillance of patients who undergo TDR may allow its routine use. Cite this article: Bone Joint J 2018;100-B:991–1001

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.

Introduction. The degeneration of the adjacent segment in lumbar spine with spondylodesis is well known, though the exact incidence and the mechanism is not clear. Several implants with semi rigid or dynamic behavior are available to reduce the biomechanical loads and to prevent an adjacent segment disease (ASD). Randomized controlled trials are not published. We investigated the biomechanical influence of dynamic and semi rigid implants on the adjacent segment in cadaver lumbar spine with monosegmental fusion (MF). Materials and Methods. 14 fresh cadaver lumbar spines were prepared; capsules and ligaments were kept intact. Pure rotanional moments of ±7.5 Nm were applied with a Zwick 1456 universal testing machine without preload in lateral bending and flexion/extension. The intradiscal pressure (IDP) and the range of motion (ROM) were measured in the segments L2/3 and L3/4 in following situations: in the native spine, monosegmental fusion L4/5 (MF), MF with dynamic rod to L3/4 (Dynabolt), MF with interspinous implant L3/4 (Coflex), and semi rigid fusion with PEEK rod (CD Horizon Legacy) L3-L5. Results. Under flexion load all implants reduced the IDP of segment L2/L3, whereas the IDP in the segment L3/4 was increased using interspinous implants in comparison to the other groups. The IDP was reduced in extension in both segments for all semi rigid or dynamic implants. Compared under extension to the native spine the MF had no influence on the IDP of the adjacent disc. The rod instrumentation (Dynabolt, PEEK rod) lead to a decreased IDP in lateral bending tests. The ROM in L3 was reduced in all groups compared to the native spine. The dynamic and semi rigid stabilization in the segment L3/4 limited the ROM more than the MF. Discussion. The MF reduced the ROM in all directions, whereas the IDP of the adjacent segment remained unaffected. The support of the adjacent segment by semi rigid and dynamic implants decreased the IDP of both segments in extension mainly. This fact is an agreement with other studies. Compared to our data, no significant effect on the adjacent levels was observed. Interestingly, in our study, the IDP of the adjacent segment is unaffected by MF. The biomechanical influence in the view of an ASD could be comprehended, but is not completely clear. The fact of persistent IDP in the adjacent segment suggests that MF has a lower effect on the adjacent segment degeneration as presumed. Biomechanical studies with human cadaver lumbar spines are limited and depend on age and degenerative situation. The effect on supporting implants on adjacent segment disease in lumbar spine surgery has to be investigated in clinical long term studies

Aims. Whether to perform hybrid surgery (HS) in contrast to anterior cervical discectomy and fusion (ACDF) when treating patients with multilevel cervical disc degeneration remains a controversial subject. To resolve this we have undertaken a meta-analysis comparing the outcomes from HS with ACDF in this condition. Methods. Seven databases were searched for studies of HS and ACDF from inception of the study to 1 September 2019. Both random-effects and fixed-effects models were used to evaluate the overall effect of the C2-C7 range of motion (ROM), ROM of superior/inferior adjacent levels, adjacent segment degeneration (ASD), heterotopic ossification (HO), complications, neck disability index (NDI) score, visual analogue scale (VAS) score, Japanese Orthopaedic Association (JOA) score, Odom’s criteria, blood loss, and operating and hospitalization time. To obtain more credible results contour-enhanced funnel plots, Egger’s and Begg’s tests, meta-regression, and sensitivity analyses were performed. Results. In total, 17 studies involving 861 patients were included in the analysis. HS was found to be superior to ACDF in maintaining C2-C7 ROM and ROM of superior/inferior adjacent levels, but HS did not reduce the incidence of associated level ASD. Also, HS did not cause a higher rate of HO than ACDF. The frequency of complications was similar between the two techniques. HS failed to achieve more favourable outcomes than ACDF using the NDI, VAS, JOA, and Odom’s scores. HS did not show any more advantages in operating or hospitalization time but did show reduction in blood loss. Conclusion. Although HS maintained cervical kinetics, it failed to reduce the incidence of ASD. This finding differs from previous reports. Moreover, patients did not show more benefits from HS with respect to symptom improvement, prevention of complications, and clinical outcomes. Cite this article: Bone Joint J 2020;102-B(8):981–996