Introduction

Several hexapod external fixator devices are used in the treatment of bone fracture and deformity corrections. One characteristic of all of them is the requirement for manual adjustment of the fixator struts. The purpose of this study was to introduce a novel robotic system that executes automatic adjustment of the struts.

Introduction: School screening for scoliosis aims to reduce the need for surgery by detecting curve changes in children at an early stage when bracing may be effective in halting the progression of the deformity. Although the effectiveness of the current screening techniques has not been established yet, AAOS and SRS continue to support school screening.. The major criticism focuses on the cost-ineffectiveness of the process, as too many students are unjustifiably referred to specialists. Moreover, examiner’s skills and experience are important factors in screening outcome. An ongoing, large-scale study of school screening is conducted in public schools at the northern part of Israel comparing the screening performance of a Scoliometer and a new, hand-held computerized device (SpineScan). SpineScan was designed to automatically measure the “angle of trunk inclination” (ATI), and is less dependent on examiner’s level of medical training. Furthermore, this tool enables also fast assessment of the kyphosis angle.

Methods: In a first phase of the study, 1000 children aged 10 to 14 years were screened. Each child underwent “blinded” examinations by two examiners with different skills (a pediatric orthopaedic surgeon and a physiotherapist), each of whom using a different tool (a Scoliometer and SpineScan, respectively). Screening was performed in examination positions specific for true scoliosis (standing and sitting forward bending) and ATI measurements were compared. Children with an ATI =or > 7º measured with either tool at both positions were referred to undergo a standard full spine X-ray in standing position, on which an experienced pediatric orthopaedic surgeon measured the Cobb angles. Curves = or > 10º were considered true positive findings for scoliosis. Statistical analysis included specificity, sensitivity and predictive value estimates of both methods.

Results: Referral rate for Scoliometer was 2.5% and for SpineScan 1.9%. SpineScan reached 80% sensitivity vs. 70% of the Scoliometer. Moreover, SpineScan achieved higher PPV values than the Scoliometer (80% vs. 54% respectively).

Discussion: These results imply that efficient and cost effective screening can be performed by minimally skilled examiner using SpineScan.

Introduction: Accurate and quantitative measurements of the spine are essential for deformity diagnosis and assessment of curve progression. There is much concern related to the multiple exposures to ionizing radiation associated with the Cobb method of radiographic measurement, currently the standard procedure for diagnosis and follow-up of the progression of scoliosis. In addition, the Cobb method relies on two-dimensional analysis of a three-dimensional deformity. The Ortelius800TM aims to provide a radiation-free method for scoliosis assessment in three planes (coronal, sagittal, apical) with simultaneous automatic calculation of the Cobb angle in both coronal and sagittal views. This new device is based on direct measurement of the position of the tips of the spinous processes in space. A low intensity electromagnetic field records the spatial position of a sensor attached to the examiner’s finger while palpating the patient’s spinous processes. This study investigates the correlation of spinal deformity measurements with Ortelius800TM radiation-free system as compared to standard radiographic measured Cobb angles in order to assess Ortelius800TM clinical value while enabling a significant reduction of x-ray exposure.

Methods: 124 patients diagnosed with Adolescent Idiopathic Scoliosis (AIS) from four different medical centers were measured with the Ortelius800TM system using the same standard protocol. The entire process required an average of 2 minutes. The Ortelius800TM measurements were correlated with the standard Cobb angle as measured on routine standing coronal and sagittal radiographs. The Pearson correlation coefficient was calculated for matched pair measurements. The mean difference and the absolute mean difference between measurements with the two methods was estimated.

Results: Standing full-spine coronal radiographs were obtained for each patient. Radiograph analysis for these 124 patients revealed 249 deformity measurements. The deformity measurements were comprised of 142 thoracic curves with a mean of 18.3° and 107 lumbar curves with a mean of 17.4°. Lateral radiographs were obtained from 38 patients with a mean of 36.1°. Correlation between Cobb angles measured manually on standard erect posteroanterior radiographs and those calculated by this new technique showed an absolute difference between the measurements to be significantly less than +\−5° for coronal measurements and significantly less than +\−6° for sagittal measurements indicating good correlation between the two methods.

Pearson’s correlation coefficient between deformity angles obtained by the two methods was highly significant (0.86) with a P value < 0.0001. The measurements from four independent sites were not significantly different.

Discussion: The results reveal good correlation between the two measuring methods in both coronal and sagittal views. We propose the Ortelius800TM as a clinical tool for the routine follow-up measurements of AIS patients, thus enabling a significant reduction of radiation exposure.

Introduction: Hook displacement or pullout is a common complication compromising the stability of spinal instrumentation. The two most common causes are the loss of the optimal adjustment between hook and lamina during the connection of the implant to the rod and the displacement of the hook during correction maneuvers.

Therefore, a partially constrained rod-implant link was conceived allowing for free rotation in the sagittal plane while maintaining the possibility for transverse loading during correction maneuvers. One of the possible benefits of this system is the preservation of the adjustment between hook and lamina.

Purpose of Study: To compare the adjustment obtained between hook and lamina by using a partially constrained pivot link (PL), connecting the hook to the rod while allowing for rotation in the sagittal plane, versus the common fully constrained link (FCL) connecting the hook rigidly to the rod.

Methods: A plastic model of the lumbar spine was instrumented on one side with a L1 supralaminar hook and a L3 infralaminar hook. Seven lordotic configurations (range: −45° to −30°) were randomly assigned to the model. A prebent rod with a −41° lordosis between the fixation points was used for all tests. Compression was applied to the claw construct until the best fit between hooks and laminae was achieved. The PL hooks were secured to the rod by a top-loading clip system allowing for rotation in the sagittal plane until final fixation with an incorporated setscrew. The FCL hooks were secured to the rod with a top-loading plug screw. The length of the hook blade in contact with the lamina, the initial and final lordosis of the construct were measured.

Results: The mean length of the hook blade in contact with the lamina was 6.9 mm for the PL infralaminar hooks versus 4.2 mm for the FCL infralaminar hooks (p< 0.0005). There was no statistically significant correlation between the degree of initial lordosis and the amountof contact achieved by both the FCL and PL infralaminar hooks (FCL: r = −0.052; PL: r = −0.585).

Discussion: Using a partially constrained pivot link achieves a larger contact between hook and lamina than the common fully constrained link. This was statistically highly significant at the level of the strategically most important infralaminar hooks in a lordotic construct. Early clinical experience using a spinal instrumentation based on the pivot link principle in seventy patients seems to confirm the enhanced strength of fixation. Especially, the management of spinal deformities in patients with severe osteoporosis or dystrophic lesions of the spine is significantly improved. Significant implant volume reduction allows for the use of this system even in young children.