The influence of total disc arthroplasty with Mobidisc prosthesis on lumbar spine and pelvic parameters: a prospective in vivo biomechanical study with a minimum 3 year of follow-up.

BACKGROUND: This study examined the impact of Mobidisc implant on spinopelvic parameters, with particular focus on the preservation of the lumbar lordosis (LL) and on the segmental lordosis (SL) of the treated and adjacent segments. METHODS: A prospective study was conducted on 63 consecutive patients with symptomatic degenerative disc disease who underwent Mobidisc implantation at the Clinic for Spinal Diseases in Strasbourg, France. Based on the profile images of the whole, the following static spinopelvic parameters were measured and analysed: lumbar lordosis L1-S1 (LL), SL for L3-L4, L4-L5 and L5-S1, sacral slope (SS), pelvic tilt (PT) and pelvic incidence. In the lumbar spine images, the anterior (ADH) and posterior disc height (PDH) were measured prior to surgery and at the different follow-up appointments. The preoperative and postoperative values were compared and statistically analysed at different time intervals. RESULTS: Sixty-three patients were included in the study. The average age of the patients was 41.4 years (range 27-59 years). The mean follow-up was 44 months (range 36-71 months). Overall, total disc replacement (TDR) led to an increase in LL which increased TED over time. The preoperative LL measured 48.9° ± 10.1° and 53.4° ± 9.9° at 3 years follow-up (p < 0.0001). In the cohort of patients who underwent TDR at L4-5, the LL increased from 51.6° ± 10° to 56.2° ± 9.2° at the last FU (p = 0.006). All other spinopelvic parameters remained stable between the preoperative values and the last follow-up. In the patients who underwent L5-S1 TDR, a significant increase in LL was also observed between preoperative data and at the last FU (from 47.8° ± 10.1° to 53.3° ± 10.1°, p < 0.0001). Following L5-S1 TDR, the SS increased from 32.9° ± 8.3° to 35.6° ± 7.4° (p = 0.05) and the PT decreased from 15.4° ± 6.2° to 11.6° ± 5.7° between preoperative values and the last follow-up. Considering the entire cohort, the SL L5-S1 increased significantly from 5.9° ± 4.2° preoperatively to 8.1° ± 4.4° (p < 0.01) at the last FU, while at the L4-L5 level, the SL remained stable from 9.9 ± 4.5° to 10.7° ± 3.8° (p = 0.3). After L4-5 TDR, an increase in ADH and PDH at the treated level was observed, while these parameters progressively decreased in the adjacent segment. In patients who underwent L5-S1 TDR, a significant increase in L5-S1 ADH and PDH was observed from 18.8 ± 9.1 to 28.4 ± 11.1 and from 9.5 ± 3.8 to 17.6 ± 9.5 pixels, respectively. ADH and PDH at the proximal adjacent levels L3-4 and L4-5 were reduced. We did not observe any case of implant failure or damage to the bone/implant interface. CONCLUSION: TDR with Mobidisc allows for an improvement of LL and SL at the treated level. An increase in both anterior and posterior disc height was observed at the treated level. While disc height decreased at the adjacent level, further studies are required to investigate whether these changes are clinically relevant.

Open versus percutaneous instrumentation in thoracolumbar fractures: magnetic resonance imaging comparison of paravertebral muscles after implant removal.

OBJECTIVE Percutaneous instrumentation in thoracolumbar fractures is intended to decrease paravertebral muscle damage by avoiding dissection. The aim of this study was to compare muscles at instrumented levels in patients who were treated by open or percutaneous surgery. METHODS Twenty-seven patients underwent open instrumentation, and 65 were treated percutaneously. A standardized MRI protocol using axial T1-weighted sequences was performed at a minimum 1-year follow-up after implant removal. Two independent observers measured cross-sectional areas (CSAs, in cm2) and region of interest (ROI) signal intensity (in pixels) of paravertebral muscles by using OsiriX at the fracture level, and at cranial and caudal instrumented pedicle levels. An interobserver comparison was made using the Bland-Altman method. Reference ROI muscle was assessed in the psoas and ROI fat subcutaneously. The ratio ROI-CSA/ROI-fat was compared for patients treated with open versus percutaneous procedures by using a linear mixed model. A linear regression analyzed additional factors: age, sex, body mass index (BMI), Pfirrmann grade of adjacent discs, and duration of instrumentation in situ. RESULTS The interobserver agreement was good for all CSAs. The average CSA for the entire spine was 15.7 cm2 in the open surgery group and 18.5 cm2 in the percutaneous group (p = 0.0234). The average ROI-fat and ROI-muscle signal intensities were comparable: 497.1 versus 483.9 pixels for ROI-fat and 120.4 versus 111.7 pixels for ROI-muscle in open versus percutaneous groups. The ROI-CSA varied between 154 and 226 for open, and between 154 and 195 for percutaneous procedures, depending on instrumented levels. A significant difference of the ROI-CSA/ROI-fat ratio (0.4 vs 0.3) was present at fracture levels T12-L1 (p = 0.0329) and at adjacent cranial (p = 0.0139) and caudal (p = 0.0100) instrumented levels. Differences were not significant at thoracic levels. When adjusting based on age, BMI, and Pfirrmann grade, a significant difference between open and percutaneous procedures regarding the ROI-CSA/ROI-fat ratio was present in the lumbar spine (p < 0.01). Sex and duration of instrumentation had no significant influence. CONCLUSIONS Percutaneous instrumentation decreased muscle atrophy compared with open surgery. The MRI signal differences for T-12 and L-1 fractures indicated less fat infiltration within CSAs in patients who received percutaneous treatment. Differences were not evidenced at thoracic levels, where CSAs were smaller. Fat infiltration was not significantly different at lumbar levels with either procedure in elderly patients with associated discopathy and higher BMI. In younger patients, there was less fat infiltration of lumbar paravertebral muscles with percutaneous procedures.

Temporary Percutaneous Instrumentation and Selective Anterior Fusion for Thoracolumbar Fractures.

STUDY DESIGN: Prospective clinical trial in thoracolumbar trauma with 5-year follow-up. OBJECTIVE: To analyze clinical and radiographic outcomes of minimal invasive surgery, and the rational of circumferential fracture treatment with regard to age, degenerative changes, bone mineral density, and global sagittal balance. SUMMARY OF BACKGROUND DATA: Non-neurologic fractures with anterior column defect can be treated by posterior percutaneous instrumentation and selective anterior fusion. After consolidation, instrumentation can be removed at 1 year to provide mobility in non-fused segments. METHODS: Fifty-one patients, 47 (18-75) years, were operated for A2, A3, or B-type fractures. Visual analog scale (VAS) for back pain and Oswestry Disability Index (ODI) were assessed. Radiographic measurements were: sagittal index, regional kyphosis, T4-T12 kyphosis, L1-S1 lordosis, pelvic incidence, pelvic tilt, sacral slope, and T9 tilt. Anterior fusion and facet joints were analyzed on computed tomography (CT) at 1 year. RESULTS: The ODI was 8.8 before accident, 35.4 at 3 months, 17.8 at 2 years, 14.4 at 5 years. The VAS was 2.0 at 3 months and 1.0 at 5 years. The sagittal index was 18.0° preoperatively and 1.0° at 3 months (P < 0.0001). A loss of reduction of 1.1° occurred after implant removal (P = 0.009). Global sagittal balance remained unchanged. Ten patients with osteopenia or osteoporosis had a worse ODI: 24.7 versus 11.9 (P = 0.016), and a greater loss of correction: 4.9° versus 1.3° (P = 0.007). Cages filled with cancellous bone from the fractured vertebra fused regularly. Spontaneous facet joint fusions were observed in two patients at the fracture level in B-type injuries. CONCLUSION: Percutaneous instrumentation and selective anterior fusion using autologous bone and mesh cages lead to high fusion rates, which provided good long-term clinical results in younger patients with thoracolumbar fractures. Sagittal alignment was maintained after instrumentation removal without damaging paravertebral muscles. Outcomes were worse in elderly patients presenting osteopenia or osteoporosis. LEVEL OF EVIDENCE: 3.

Fusion Rates of Different Anterior Grafts in Thoracolumbar Fractures.

STUDY DESIGN: Retrospective CT analysis of anterior fusion in thoracolumbar trauma. OBJECTIVE: The aim of this study was to compare fusion rates of different bone grafts and to analyze risk factors for pseudarthrosis. SUMMARY OF BACKGROUND DATA: Interbody fusion is indicated in anterior column defects. Different grafts are used: autologous iliac crest, titanium mesh cages filled with cancellous bone, and autologous ribs. It is not clear which graft offers the most reliable fusion. MATERIAL AND METHODS: Radiologic data of 116 patients (71 men, 45 women) operated for type A2, A3, B, or C fractures were analyzed. The average age was 44.6 years (range, 16-75 y) and follow-up was 2.7 years (range, 1-9 y). All patients were treated by posterior instrumentation followed by an anterior graft: 53 cases with iliac crest, 43 cases with mesh cages, and 20 with rib grafts. Fusion was evaluated on CT and classified into complete fusion, partial fusion, unipolar pseudarthrosis, and bipolar pseudarthrosis. RESULTS: Iliac crest fused in 66%, cages in 98%, and rib grafts in 90%. The fusion rate of cages filled with bone was significantly higher as the iliac graft fusion rate (P=0.002). The same was applied to rib grafts compared with iliac crest (P=0.041). Additional bone formation around the main graft, bridging both vertebral bodies, was observed in 31 of the 53 iliac crests grafts. Pseudarthrosis occurred more often in smokers (P=0.042). A relationship between fracture or instrumentation types, sex, age, BMI, and fusion could not be determined. CONCLUSIONS: Tricortical iliac crest grafts showed an unexpected high pseudarthrosis rate in thoracolumbar injuries. Their cortical bone is dense and their fusion surface is small. Rib grafts led to a better fusion when used in combination with the cancellous bone from the fractured vertebral body. Titanium mesh cages filled with cancellous bone led to the highest fusion rate and built a complete bony bridge between vertebral bodies. Smoking seemed to influence fusion. LEVEL OF EVIDENCE: Case control study, Level III.

Surgical-site infection in spinal injury: incidence and risk factors in a prospective cohort of 518 patients.

PURPOSE: To investigate the incidence of surgical-site infection (SSI) and determinate the risk factors of SSI in the context of spinal injury. METHODS: From February 1, 2011 to July 31, 2011, for a multicentre cohort of patients with acute spinal injury, we prospectively censored those with SSI for at least 12 months. We recorded epidemiologic characteristics and details of surgical procedure and postoperative care for each patient. We calculated the incidence of SSI at 1, 3 and 12 months after surgery. Univariate and multivariate analysis were used to establish the association of risk factors and SSI. We studied clinical outcomes by a visual analog scale for pain and physical and mental component summaries (PCS and MCS) of the Medical Outcomes Survey 36-Item Short Form (SF-36). RESULTS: At 1 year, among 518 patients, we recorded 25 SSI events, with median occurrence at 16 days (25-75 % quartile: 13-44 days). Incidence of SSI was 3.2 % (95 % confidence interval [1.9-5.3 %]) at 1 month, 3.7 % (95 % [2.2-5.8 %]) at 3 months and 4.6 % (95 % CI [3-6.9 %]) at 12 months. On multivariate analysis, age, presence of diabetes and surgical duration were predictors of SSI (p = 0.009, p = 0.047, and p = 0.015 respectively). At 12 months, infected and non-infected patients did not differ in pain (p = 0.58) or SF-36 PCS (p = 0.8) or MCS (p = 0.68). CONCLUSIONS: In this large prospective multicentre study in the context of spinal injury, we obtained an equivalent incidence rate and risk factors of SSI as found in the literature for elective spinal surgery.

Sagittal balance correction of idiopathic scoliosis using the in situ contouring technique.

PURPOSE: Idiopathic scoliosis can lead to sagittal imbalance. The relationship between thoracic hyper- and hypo-kyphotic segments, vertebral rotation and coronal curve was determined. The effect of segmental sagittal correction by in situ contouring was analyzed. METHODS: Pre- and post-operative radiographs of 54 scoliosis patients (Lenke 1 and 3) were analyzed at 8 years follow-up. Cobb angles and vertebral rotation were determined. Sagittal measurements were: kyphosis T4-T12, T4-T8 and T9-T12, lordosis L1-S1, T12-L2 and L3-S1, pelvic incidence, pelvic tilt, sacral slope, T1 and T9 tilt. RESULTS: Thoracic and lumbar curves were significantly reduced (p = 0.0001). Spino-pelvic parameters, T1 and T9 tilt were not modified. The global T4-T12 kyphosis decreased by 2.1° on average (p = 0.066). Segmental analysis evidenced a significant decrease of T4-T8 hyperkyphosis by 6.6° (p = 0.0001) and an increase of segmental hypokyphosis T9-T12 by 5.0° (p = 0.0001). Maximal vertebral rotation was located at T7, T8 or T9 and correlated (r = 0.422) with the cranial level of the hypokyphotic zone (p = 0.003). This vertebra or its adjacent levels corresponded to the coronal apex in 79.6 % of thoracic curves. CONCLUSIONS: Lenke 1 and 3 curves can show normal global kyphosis, divided in cranial hyperkyphosis and caudal hypokyphosis. The cranial end of hypokyphosis corresponds to maximal rotation. These vertebrae have most migrated anteriorly and laterally. The sagittal apex between segmental hypo- and hyper-kyphosis corresponds to the coronal thoracic apex. A segmental sagittal imbalance correction is achieved by in situ contouring. The concept of segmental imbalance is useful when determining the levels on which surgical detorsion may be focused.

Thoracolumbar fracture reduction by percutaneous in situ contouring.

PURPOSE: Percutaneous in situ contouring is based on bilateral bending of rods on the spine, thus increasing lordosis at the fracture. It was analyzed if this technique would provide a better reduction than prone positioning and how sagittal alignment would behave. METHODS: Twenty-nine patients were operated using in situ contouring and selective anterior fusion for non-neurologic A2, A3 or B2 fractures. Clinical results were assessed prospectively using visual analog scale (VAS) and Oswestry Disability Index (ODI). The radiographic deformity correction was measured by sagittal index and regional kyphosis. Sagittal balance was assessed using kyphosis, lordosis, T9 tilt, pelvic incidence, pelvic tilt and sacral slope. Posterior wall fragment reduction was evaluated by computed tomography. RESULTS: After 2 years, VAS and ODI were comparable to the status prior to the accident. The sagittal index was 19.7° preoperatively, 5.3° after prone positioning and -1.1° after in situ contouring (p < 0.001). The loss of correction was 2.4°, mainly during the first 3 months. Similar observations were made for regional kyphosis. The sagittal spino-pelvic alignment was stable postoperatively. A preoperative canal obstruction ≥50 % was observed in 16 patients, and the fragments migrated anteriorly in all patients. CONCLUSIONS: Percutaneous instrumentation and anterior fusion provides good clinical results. In situ contouring increases lordosis obtained by prone positioning. Anterior column lengthening and ligamentotaxis reduce posterior wall fragments, which decompress the canal without laminectomy. The fusion of anterior defects prevents the loss of correction and provides a stable sagittal profile. The instrumentation may be removed without damaging the paravertebral muscles and loss of correction.

Could an osteoinductor result in degeneration of a neurofibroma in NF1?

We report a case of fatal evolution of neurofibromatosis in a young boy. A laminectomy was performed when he was 9 years old. A secondary hyperkyphosis led to many surgeries resulting in recurrent malunions. When he was 23 years old, a breakage of his rods was treated by a new instrumentation and a T12-L1 interbody cage fitted with rh-BMP. Five months later, he developed a huge posterior tumour on his back. The biopsy diagnosed a neurofibrosarcoma. The growth of the tumour was extremely rapid. He died after several months from a septic shock. NF1 is characterised by neurofibromas that have a possibility of malign degeneration and conversion to a sarcoma. However, the chronology, rapidity of evolution and the exceptional volume of the tumour made us wonder whether the BMP had a part of responsibility as osteoinductor in the malignant degeneration, in this particular case, of neurofibromatosis. It seemed important to point out this case to the medical community.