Aims

This systematic review aims to identify 3D predictors derived from biplanar reconstruction, and to describe current methods for improving curve prediction in patients with mild adolescent idiopathic scoliosis.

Aims. The aim of this study is to test the hypothesis that three grades of sagittal compensation for standing posture (normal, compensated, and decompensated) correlate with health-related quality of life measurements (HRQOL). Methods. A total of 50 healthy volunteers (normal), 100 patients with single-level lumbar degenerative spondylolisthesis (LDS), and 70 patients with adult to elderly spinal deformity (deformity) were enrolled. Following collection of demographic data and HRQOL measured by the Scoliosis Research Society-22r (SRS-22r), radiological measurement by the biplanar slot-scanning full body stereoradiography (EOS) system was performed simultaneously with force-plate measurements to obtain whole body sagittal alignment parameters. These parameters included the offset between the centre of the acoustic meatus and the gravity line (CAM-GL), saggital vertical axis (SVA), T1 pelvic angle (TPA), McGregor slope, C2-7 lordosis, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), PI-LL, sacral slope (SS), pelvic tilt (PT), and knee flexion. Whole spine MRI examination was also performed. Cluster analysis of the SRS-22r scores in the pooled data was performed to classify the subjects into three groups according to the HRQOL, and alignment parameters were then compared among the three cluster groups. Results. On the basis of cluster analysis of the SRS-22r subscores, the pooled subjects were divided into three HRQOL groups as follows: almost normal (mean 4.24 (SD 0.32)), mildly disabled (mean 3.32 (SD 0.24)), and severely disabled (mean 2.31 (SD 0.35)). Except for CAM-GL, all the alignment parameters differed significantly among the cluster groups. The threshold values of key alignment parameters for severe disability were TPA > 30°, C2-7 lordosis > 13°, PI-LL > 30°, PT > 28°, and knee flexion > 8°. Lumbar spinal stenosis was found to be associated with the symptom severity. Conclusion. This study provides evidence that the three grades of sagittal compensation in whole body alignment correlate with HRQOL scores. The compensation grades depend on the clinical diagnosis, whole body sagittal alignment, and lumbar spinal stenosis. The threshold values of key alignment parameters may be an indication for treatment. Cite this article: Bone Joint J 2020;102-B(10):1359–1367

Aims

The aim of this study was to assess whether supine flexibility predicts the likelihood of curve progression in patients with adolescent idiopathic scoliosis (AIS) undergoing brace treatment.

Background. Achieving optimal prosthesis alignment during total knee arthroplasty (TKA) is essential. Imageless computer-assisted surgery (CAS) is developed to improve knee prosthesis alignment and with CAS it is possible to perform intraoperative alignment measurements. Lower limb alignment measurements are also performed for preoperative planning and postoperative evaluation. A new stereoradiography system, called EOS, can be used to perform these measurements in 3D and thus measurement errors due to malpositioning can be eliminated. Since both CAS and EOS are based on 3D modeling, measurements should theoretically correlate well. Therefore, objective was to compare intraoperative CAS-TKA measurements with pre- and postoperative EOS 3D measurements. Methods. In a prospective study 56 CAS-TKAs were performed and alignment measurements were recorded two times: before bone cuts were made and after implantation of the prosthesis. Pre- and postoperative coronal alignment measurements were performed using EOS 3D. CAS measurements were compared with EOS 3D reconstructions. Measured angles were: varus/valgus (VV), mechanical lateral distal-femoral (mLDFA) and medial proximal tibial angle (mMPTA). Results. Significantly different VV angles were measured pre- and postoperatively with CAS compared to EOS. For preoperative measurements, mLDFA did not differ significantly, but a significantly larger mMPTA in valgus was measured with CAS. Conclusions. EOS 3D measurements overestimate VV angle in lower limbs with substantial mechanical axis deviation. For lower limbs with minor mechanical axis deviation as well as for mMPTA measurements, CAS measures more valgus compared to EOS. Results of this study indicate that differences in alignment measurements between CAS measurements and pre- and postoperative EOS 3D are mainly due to the difference between weight bearing and non-weight bearing position and potential errors in validity and reliability of the CAS system. Surgeons should be aware of these measurement differences and the pitfalls of both measurement techniques. Level of evidence. IIb. Disclosures. The department of Orthopaedics, University of Groningen, University Medical Center Groningen receives research institutional support from InSpine (Schiedam, NL) and Stryker (Kalamazoo, Mich. USA). One of the authors (ALB) will be and has been paid as a consultant by Zimmer (Warsaw, IN, USA) for purposes of education and training in knee arthroplasty

The Oxford unicompartmental knee replacement (UKR) was designed to minimise wear utilising a fully-congruent, mobile, polyethylene bearing. Wear of polyethylene is a significant cause of revision surgery in UKR in the first decade, and the incidence increases in the second decade. Our study used model-based radiostereometric analysis to measure the combined wear of the upper and lower bearing surfaces in 13 medial-compartment Oxford UKRs at a mean of 20.9 years (17.2 to 25.9) post-operatively.

The mean linear penetration of the polyethylene bearing was 1.04 mm (0.307 to 2.15), with a mean annual wear rate of 0.045 mm/year (0.016 to 0.099). The annual wear rate of the phase-2 bearings (mean 0.022 mm/year) was significantly less (p = 0.01) than that of phase-1 bearings (mean 0.07 mm/year).

The linear wear rate of the Oxford UKR remains very low into the third decade. We believe that phase-2 bearings had lower wear rates than phase-1 implants because of the improved bearing design and surgical technique which decreased the incidence of impingement. We conclude that the design of the Oxford UKR gives low rates of wear in the long term.

Purpose: Scoliosis is a three-dimensional deformation of the spinal column. Modern surgical techniques have attempted to address this 3D component of the problem but pre- and postoperative measurements lack precision. A solution is stereoradiographic 3D reconstruction providing 1.1 mm precision for vertebral shape and 1.4° precision for axial rotation. Material and methods: Ten patients (seven adolescents and three adults) with idiopathic scoliosis (mean 56°, range 36°–78°) were treated with an in situ arching method. A calibrated teleradiogram (AP and lateral view) was obtained before and after surgery. The spinal columns were reconstructed by stereoradiography. Six rotation angles were measured in the three planes for each vertebra and each intervertebral space, taking into account the curvatures and their apical and junctional zones. Results: Preoperatively, for thoracic scoliosis, measurements were: mean vertebral axial rotation (VAR) measured at the apex = 20°; mean lateral axial rotation (LAR) of the junctional zones = 30°; mean intervertebral rotation (IVR) = 10°. Depending on the curvatures, in situ arching yielded a 52–60% correction of the VAR at the apex, and 78–79% correction of the junctional zones. VLR of the junctional zoenes was improved 58–74%. Intervertebral sagittal rotation (ISR) at the summit (kyphosis) was improved 5.5° on the average. Discussion: Unlike computed tomoraphy where scans are obtained in the supine position, three-dimensional reconstruction of the spinal column enables a precise analysis of the loaded spine. Improvement was significant in the frontal plane with 18.3° and 21.4° improvement of the VLR for the thoracic and thoracolumbar junctional zones respectively, compared with the rod rotation where the peroperative stereophotogram showed a 9.6° and 8.6° gain respectively. There was a real improvement in VAR, differing from the literature where the rotation of the rod appears to be less pronounced. Conclusion: Three-dimensional reconstruction of the spinal column enables a segmentary analysis of scoliosis deformations. In addition, by enabling a view of the spinal column in all directions, angle measurements can be made with precision allowing repeated measurements and comparisons. This technique demonstrated the efficacy of in situ arching in improving vertebral rotation

Stereoradiography with a base shift of the source of illumination was used to produce pairs of radiographs to be measured by stereophotogrammetric techniques. The direction of shift was parallel with the longitudinal axis of the body, so that each radiograph in the stereopair could be used for other clinical purposes. A base shift of 10 centimetres with a distance of 100 centimetres between the focus and the film gave acceptable value of stereoscopic parallax. The radiographs were measured using a Hilger and Watts medical stereometer. This method was checked with test specimens, namely an osteotomised pelvis in which one acetabulum could be rotated and an osteotomised femur in which the whole upper portion could be rotated against the shaft. Measurements made on the acetabulum and its radiographs showed a correlation coefficient of 0.9838 over the range 0 to 30 degrees of anteversion, with a mean error +2.54 degrees and a standard deviation of +/- 1.52 degrees (n = 21). For the femoral neck, over the range from 10 degrees of retroversion to 80 degrees of anteversion, the correlation coefficient was 0.9979, the mean error +2.46 and the standard deviation +/- 1.48 degrees (n = 30)