Study of mechanical effects of lumbar disc arthroplasty on facet joints at the index level/adjacent levels by using a validated finite element analysis.

Introduction: Lumbar disc arthroplasty is a surgical procedure designed to treat degenerative disc disease by replacing the affected disc with a mobile prosthesis. Several types of implants fall under the term total disc replacement, such as ball-and-socket, mobile core or elastic prostheses. Some studies have shown that facet arthritis can develop after arthroplasty, without much precision on the mechanical impact of the different implant technologies on the facet joints. This study aims to create validated patient-specific finite element models of the intact and post-arthroplasty lumbar spine in order to compare the mechanical response of ball-and-socket and elastic prostheses. Methods: Intact models were developed from CT-scans of human lumbar spine specimens (L4-S1), and arthroplasty models were obtained by replacing the L4-L5 disc with total disc replacement implants. Pure moments were applied to reproduce physiological loadings of flexion/extension, lateral bending and axial rotation. Results: Models with ball-and-socket prosthesis showed increased values in both range of motion and pressure at the index level and lower values at the adjacent level. The mechanical behaviour of the elastic prosthesis and intact models were comparable. The dissipated friction energy in the facet joints followed a similar trend. Conclusion: Although both implants responded to the total disc replacement designation, the mechanical effects in terms of range of motion and facet joint loads varied significantly not only between prostheses but also between specimens. This confirms the interest that patient-specific surgical planning using finite element analysis could have in helping surgeons to choose the appropriate implant for each patient.

Stand-alone kyphoplasty in recent thoracolumbar split fractures: A series of 36 patients reviewed at 19months.

INTRODUCTION: Spinal fractures with a split component present specific bone union problems (pseudarthrosis). The purpose of this study was to assess the rate of pseudarthrosis after stand-alone percutaneous kyphoplasties and analyze clinical and radiographic parameters that are predictive of its efficacy in thoracolumbar spine fractures with a split-type of injury. HYPOTHESIS: Stand-alone kyphoplasty results in satisfactory bone union of the treated vertebral body despite the diastasis of fracture fragments. MATERIALS AND METHODS: A retrospective single-center study of 36 patients with posttraumatic monosegmental thoracolumbar vertebral fractures, that were classified as either Magerl A2 or A3.2, without any neurologic deficits. Patients were treated with percutaneous kyphoplasty and PMMA bone cement. The assessment included both clinical (visual analog pain scale [VAS] and Oswestry disability index) and radiographic (pseudarthrosis, fracture gap, disk incarceration, vertebral height and length, and vertebral and regional kyphosis) criteria. RESULTS: A total of 36 patients (mean age 58years) were included, with a mean follow-up of 19.1months. Five of these patients (14%) had a pseudarthrosis. The fracture gap was significantly greater in these patients than in those who had bone union preoperatively (+3.94 mm, p<0.001) and at the last follow-up consultation (+9.3 mm, p<0.001). There was an association between the incarceration of adjacent disks located above (p=0.008) and below (p=0.003) the fracture site and the pseudarthrosis. The mean VAS decreased significantly on the first postoperative day (p<0.001) and remained lower than the initial assessment until the last follow-up (p<0.001). DISCUSSION: Stabilization by stand-alone kyphoplasty produces good clinical and radiographic results for split fractures, provided that the extent of the fragment diastasis has been carefully assessed preoperatively to prevent the risk of pseudarthrosis. LEVEL OF EVIDENCE: IV; retrospective.

Professional Status of Persistent Spinal Pain Syndrome Patients after Spinal Surgery (PSPS-T2): What Really Matters? A Prospective Study Introducing the Concept of "Adapted Professional Activity" Inferred from Clinical, Psychological and Social Influence.

Persistent Spinal Pain Syndrome Type 2 (PSPS-T2) represents a main cause of work disruption. Beyond its societal consequences, occupational inactivity is responsible for a major decrease in physical/mental health in individuals but remains poorly analyzed. We designed a study to prospectively examine Professional Status (PS) evolution and its association with key bio-psychological markers. Data from 151 consecutively included working-age PSPS-T2 patients were analyzed to determine the proportion of professional inactivity and the relationships between PS and Social Gradient of Health (SGH), Numeric Pain Rating Scale (NPRS), EuroQol 5-Dimensional 5-Level (EQ-5D-5L), Oswestry Disability Index (ODI), Hospital Anxiety and Depression Scale (HADS), and Fear-Avoidance Belief Questionnaire work subscale (FABQ-W). Despite optimized medical management, 73.5% of PSPS-T2 patients remained inactive after 1 year of follow-up/p = 0.18. Inactive patients presented a low SGH/p = 0.002, higher NPRS/p = 0.048, lower EQ-5D-5L/p < 0.001, higher ODI/p = 0.018, higher HADS-D/p = 0.019 and higher FABQ-W/p < 0.001. No significant mediation effect of FABQ-W on SGH consequences regarding PS was observed in our structural model/p = 0.057. The link between unemployment and bio-psycho-social pain dimensions appears bidirectional and justifies intense collaboration with social workers. Optimizing therapeutical sequencing towards personalized professional plans implies restoring "Adapted Physical Function" as an initial goal, and tailoring an "Adapted Professional Activity", matching with patient expectations and capabilities, as a final objective.

Persistent Spinal Pain Syndrome Type 2 (PSPS-T2), a Social Pain? Advocacy for a Social Gradient of Health Approach to Chronic Pain.

The Social Gradient of Health (SGH), or position in the social hierarchy, is one of the major determinants of health. It influences the development and evolution of many chronic diseases. Chronic pain dramatically affects individual and social condition. Its medico-economic impact is significant and worldwide. Failed Back Surgery Syndrome or Persistent Spinal Pain Syndrome type 2 (PSPS-T2) represents one of its most fascinating and disabling conditions. However, the influence of SGH on PSPS-T2 has been poorly explored. We designed a prospective multicentric study (PREDIBACK study) to assess the SGH prevalence, and to examine its association with medical and psychological variables, in PSPS-T2 patients. This study included 200 patients to determine the SGH association with pain (NPRS), Quality of life (EQ-5D-5L), kinesiophobia (FABQ-Work), catastrophism (CSQ), and functional capacity (ODI). Around 85.3% of PSPS-T2 patients in our study had low SGH. Low SGH patients had a higher FABQ-Work and CSQ-Catastrophizing score than high SGH patients (p < 0.05). High SGH patients have a higher ODI score than low SGH patients (p < 0.10). Our results suggest that SGH is a relevant factor to guide prevention, research, and ultimately intervention in PSPS-T2 patients and could be more widely transposed to chronic pain.

Vertebral balloon kyphoplasty versus vertebral body stenting in non-osteoporotic vertebral compression fractures at the thoracolumbar junction: a comparative radiological study and finite element analysis (BONEXP study).

OBJECTIVE: To compare radiologically balloon kyphoplasty (BKP) and vertebral compression fracture (VCF) expansion and corroborate with a finite element (FE) analysis. The principle of BKP is to stabilize VCF by restoring vertebral body anatomy using bone expansion and cement filling. More recently, vertebral body stenting (VBS) has been developed to reduce the loss of vertebral height observed after balloon deflation. METHODS: A retrospective, monocentric and continuous study of 60 non-osteoporotic fractures of the thoracolumbar junction treated by vertebral bone expansion was carried out over three years. The main endpoint was radiological correction of vertebral kyphosis (VK) at 3 months. The other studied parameters were vertebral height, index of Farcy, index of Beck, cement leakages and their location. A FE model was developed to analyze effects linked to the stent during cement injection, specifically throughout the risk of cement leakage evaluation. RESULTS: After three months, average reduction of VK was 4.73° ± 4.8° after BKP, and 4.63° ± 2.7° after VBS. There was no difference between the two techniques, but cement leakage was significantly greater with BKP (41.7%) than with VBS (4.2%). FE analysis showed substantial changes of the cement flow orientation in the presence of a stent. CONCLUSION: BKP and VBS offer comparable expansion with no added value of VBS in non-osteoporotic VCF reduction. VBS technique appears to prevent cement leakage due to its mesh architecture hindering the leaking process. In counterpart, such balloon expansion is likely to require higher pressure to deploy the stent. This could be an important parameter to take into account in young patients with high bone density.

Acrylic kyphoplasty in recent nonosteoporotic fractures of the thoracolumbar junction: a prospective clinical and 3D radiologic study of 54 patients.

STUDY DESIGN: Prospective clinical and radiological study. OBJECTIVES: To evaluate the impact of stand-alone acrylic kyphoplasty in the treatment of recent traumatic fractures of the thoracolumbar spine in young patients. SUMMARY OF BACKGROUND DATA: The management of fractures of the thoracolumbar spine without neurological deficit remains controversial. For a long time clinicians could only chose between functional treatment, orthopedic treatment, and traditional surgery. The recent advent of minimally invasive surgical techniques is an interesting alternative. MATERIALS AND METHODS: Fifty-four patients with a mean age of 45.8±18.2 years and who had recently sustained a fracture of the thoracolumbar junction were enrolled into the study. Balloon kyphoplasty was performed using acrylic cement. Radiologic assessments (computed tomography scans) and clinical assessments (including Visual Analog Scale and Oswestry Disability Index scores) were used to determine kyphoplasty success and measure patient recovery over 2 years. RESULTS: Kyphoplasty reduced mean vertebral kyphosis from 12.8±5.0 degrees at trauma to 8.2±5.1 degrees at 2-year follow-up. Mean vertebral kyphosis was corrected by -5.7±4.7 degrees (P=0.0001) at the point of first verticalization, with no significant change at the 2-year follow-up visit (+1.1±4.3 degrees, P=0.1058). Kyphoplasty significantly augmented the height of the 6 anterior and intermediate segments. Maximum mean augmentation of intermediate vertebral height after 6 months was (11.6%±15.5%, P<0.0001). Patients tolerated the procedure well and 56% of them returned to work 3 months after kyphoplasty. CONCLUSION: Kyphoplasty is safe and effective in the correction of nonosteoporotic fractures of the thoracolumbar junction in young patients, and remains stable for at least 2 years postsurgery.