IntroductionThe treatment of most spinal diseases is a difficult task because of the rate of immediate, mid-and long-term complications and failures [16]. Surgical planning and clinical follow up often rely on postural and/or dynamic X-ray exams, among other imaging options.Many authors investigated the radiological parameters liable to rule patient's evolution, such as postural and balance parameters [2,4,8,9,11,12,26]. These parameters might be classified in pelvic parameters, either morphologic (incidence) or positional (sacral slope [4,11,12], pelvic angle [8,9]), and spinal parameters (such as lordosis, kyphosis [4,11,12] or plumblines [8,9]). Their measurement is tedious and time consuming while the accuracy of the results may be highly variable depending on the method employed. Furthermore, when trying to compare the results between studies, a major difficulty comes from the differences in the definition, identification and measurement of parameters.Recent computer-based tools allowed for a rapid progress in quantitative measurements of a large range of parameters [9,17,19,20,23,26]. Moreover, these tools allow easy standardisation of X-ray films measurements, which is of paramount importance when comparing studies in multicentric analysis. However, validation of these tools is essential [3,17,18].In 1999, the team of LBM and LIO developed an Xray films analysis software (SpineView 1.0) allowing for the measurement of the main lumbar dynamic and sagittal postural parameters of the spine. The evaluation of this first software was achieved by comparison with direct measurements on plain X-ray films [17,18], and showed good reliability of the measurements. Abstract The objective of this study was to evaluate an X-ray films analysis software, i.e. to estimate the reliability and validity of clinical measurements by means of this software. The authors first performed tests of precision and reproducibility of measures. The precision for dynamic modules was estimated at ±2°for the lumbar analysis and ±3°for the cervical one. Mean reproducibility coefficients calculated for postural modules are about 4°for the angular parameters and 3 mm for the linear ones. We also evaluated clinical applicability of the software through its validity. Reference values calculated on a population of healthy subjects showed agreement with the literature. Then, when analysing postural X-ray films of severe scoliotic patients, we found that inter-observer reproducibility coefficients show a lower reliability of measurements; the main cause seems to be the low visibility of anatomic landmarks due to the quality of X-ray films and to the degree of deformity. This study allowed to better estimate the reliability and the usefulness of this tool, allowing for multicentric studies and exchanges.Keywords Spine AE X-ray AE Quantitative analysis AE Software AE Motion AE Balance Eur Spine J (2006) 15: 982-991

Dynamic systems in the lumbar spine are believed to reduce main fusion drawbacks such as pseudarthrosis, bone rarefaction, and mechanical failure. Compared to fusion achieved with rigid constructs, biomechanical studies underlined some advantages of dynamic instrumentation including increased load sharing between the instrumentation and interbody bone graft and stresses reduction at bone-to-screw interface. These advantages may result in increased fusion rates, limitation of bone rarefaction, and reduction of mechanical complications with the ultimate objective to reduce reoperations rates. However published clinical evidence for dynamic systems remains limited. In addition to providing biomechanical evaluation of a pedicle-screw-based dynamic system, the present study offers a long-term (average 10.2 years) insight view of the clinical outcomes of 18 patients treated by fusion with dynamic systems for degenerative lumbar spine diseases. The findings outline significant and stable symptoms relief, absence of implant-related complications, no revision surgery, and few adjacent segment degenerative changes. In spite of sample limitations, this is the first long-term report of outcomes of dynamic fusion that opens an interesting perspective for clinical outcomes of dynamic systems that need to be explored at larger scale.

Background The purpose of the study was to report radiological outcomes after total disc replacement (TDR) in the cervical spine through a 24 months follow-up (FU) prospective study with a special focus on sagittal alignment and kinematics at instrumented and adjacent levels. Materials and methods Thirty-two patients, who sustained one-level TDR with a ball-and-socket arthroplasty (Discocerv TM implant, Scient'x/Alphatec Spine, USA) were consecutively included in the study. Clinical (visual analogical scale and neck disability index) and radiological parameters were measured preoperatively and postoperatively at 3/6 months, 1-year and 2-year FU. Sagittal alignment, ranges of motion (ROM) and center of rotations (CORs) were analyzed using specific motion analysis software (Spineview TM , Paris, France). Patients CORs were compared with those of a control group of 39 normal and asymptomatic subjects.Results Both local and C3-C7 lordosis significantly increased postoperatively (?8°and ?13°at 2 years, respectively). At instrumented level ROM in flexionextension (FE) was measured to 10.2°preoperatively versus 7.5°at 1 year and 6.1°at 2 years. There were no differences in ROM at adjacent levels between pre and postoperative assessments. When compared with control group and preoperative measurements, we noted postoperative cranial shift of the COR at instrumented level for patients group. In contrast, there was no difference in CORs location at adjacent levels. Conclusion Through this prospective study, we observed that cervical lordosis consistently increased after TDR. In addition, although ball-and-socket arthroplasty did not fully restore native segmental kinematics with significant reduction of motion in FE and consistent cranial shift of the COR, no significant changes in terms of ROM and CORs were observed at adjacent levels.

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