Three-dimensional in vivo measurement of lumbar spine segmental motion

3.0T magnetic resonance imaging-based hip bone models for femoroacetabular impingement syndrome are equivalent to computed tomography-based models

This study aimed to compare three-dimensional (3D) proximal femoral and acetabular surface models generated from 3.0T magnetic resonance imaging (MRI) to the clinical gold standard of computed tomography (CT). Ten intact fresh-frozen cadaveric hips underwent CT and 3.0T MRI scans. The CT- and MRI-based segmented models were superimposed using a validated 3D-3D registration volume-merge method to compare them. The least surface-to-surface distance between the models was calculated by a point-to-surface calculation algorithm using a custom-written program. The variables of interest were the signed and absolute surface-to-surface distance between the paired bone models. One-sample t-tests were performed using a signed and absolute test value of 0.16 mm and 0.37 mm, respectively, based on a previous study that validated 1.5T MRI bone models by comparison with CT bone models. For the femur, the average signed and absolute surface-to-surface distance was 0.18 ± 0.09 mm and 0.30 ± 0.06 mm, respectively. There was no difference in the signed surface-to-surface distance and the 0.16 mm test value (t = 0.650, p = 0.532). However, the absolute surface-to-surface difference was less than the 0.37 mm test value (t = -4.025, p = 0.003). For the acetabulum, the average signed and absolute surface-to-surface distance was -0.06 ± 0.06 mm and 0.26 ± 0.04 mm, respectively. The signed (t = -12.569, p < 0.001) and absolute (t = -8.688, p < 0.001) surface-to-surface difference were less than the 0.16 mm and 0.37 mm test values, respectively. Our data shows that 3.0T MRI bone models are more similar to CT bone models than previously validated 1.5T MRI bone models. This is likely due to the higher resolution of the 3T data.

Investigating Fryette's mechanics in computed tomography scans: an analysis of vertebrae spinal physiology using open-sourced datasets and three-dimensional vertebral orientation

CONTEXT

Fryette's mechanics is taught as a simplistic model of coupled vertebral movement, fundamental in osteopathic practice. This study seeks to better understand the likelihood of Fryette's model by calculating vertebral orientation in computed tomography (CT) scans. Given previous findings of low angular coupled movements during overall spinal motion, static calculations provide a unique perspective on the likelihood of Fryette's mechanics.

OBJECTIVES

This analysis aims to evaluate the efficacy of Fryette's principles in predicting vertebral positioning in CT scans by comparing their 3-dimensional (3D) orientation to movements described by Fryette.

METHODS

3D models of 953 thoracic and lumbar vertebrae were obtained from 82 CT scans within the VerSe`20 open-source dataset. A stepwise algorithm generated three unique symmetry planes for each vertebra, offering 3D angular orientation with respect to the vertebral level below. A total of 422 vertebrae were omitted from the analysis due to the presence of pathologies significant enough to affect their motion, inaccurate symmetry plane calculations, or absence of vertebral level below. The remaining 531 vertebra were analyzed to compare quantitative coupled positioning against expected coupled spinal movements in line with Fryette's mechanics. One-sample proportional z-scoring was implemented for all vertebral levels with an ∝=0.05 and a null hypothesis of Fryette's primed positioning occurring by chance of 50 %. Further analysis was performed with individual z-scoring for each individual level to see which levels were statistically significant.

RESULTS

Data from the VerSe`20 dataset revealed that 56.9 % of successfully analyzed vertebrae demonstrated positions compatible with Fryette's mechanics (p=0.0014, power=89 %). The 302 vertebral levels that did display coupled positioning consisted of Type I (166 vertebrae) and Type II (136 vertebrae) compatible with Fryette's mechanics. Levels that demonstrated statistical significance consisted of T5 (p=0, power=99 %), T6 (p=0.0023, power=77 %), T7 (p=0.041, power=46 %), and T10 (p=0.017, power=60 %).

CONCLUSIONS

Our analysis suggests that the static positions of vertebrae in CT scans may align with Fryette's descriptions, although not very often. Notably, vertebral levels T5-T7 and T10 exhibit strong evidence of their static positions aligning with expected movements, warranting further investigation into the Fryette phenomenon at these levels. Future studies should explore the dynamic implications of these findings to enhance our understanding of spinal biomechanics.

Reference values of lumbar spine range of motion by sex and age based on the assessment of supine trunk lateral bending-A preliminary study

[Purpose] The purpose of this study was to clarify the preliminary reference values for the lumbar spine range of motion associated with lateral bending exercises by gender and age group. [Methods] Subjects were 82 volunteers without low back pain, including five males and five females in each age group from 16-19 to 80-89 years. All subjects underwent radiographs of the lumbar spine with lateral flexion; the range of lateral flexion of the vertebrae from T12 to the sacrum (ROLB) was measured twice by three observers. [Results] The ROLB of the entire T12-S1 of all subjects showed a significant negative correlation with age in both sexes (p < 0.01). The ROLB of the lumbar spine tended to be greater in females, with a statistically significant difference between those aged 16-19 and 70-79 (p < 0.05). Lateral flexion angles for each intervertebral segment were largest at L3-L4 and smallest at L5-S1 (0.7°). [Conclusion] Lumbar ROLB reference values were examined by gender and age group; ROLB was greatest in L3-L4, and ROLB tended to be lower in older age groups.

Range of rotation of thoracolumbar vertebrae in Japanese macaques

In humans, the range of thoracic vertebral rotation is known to be greater than that of the lumbar vertebrae due to their zygapophyseal orientation and soft tissue structure. However, little is known regarding vertebral movements in non-human primate species, which are primarily quadrupedal walkers. To understand the evolutionary background of human vertebral movements, this study estimated the range of axial rotation of the thoracolumbar spine in macaque monkeys. First, computed tomography (CT) was performed while passively rotating the trunk of whole-body cadavers of Japanese macaques, after which the motion of each thoracolumbar vertebra was estimated. Second, to evaluate the influence of the shoulder girdle and surrounding soft tissues, specimens with only bones and ligaments were prepared, after which the rotation of each vertebra was estimated using an optical motion tracking system. In both conditions, the three-dimensional coordinates of each vertebra were digitized, and the axial rotational angles between adjacent vertebrae were calculated. In the whole-body condition, the lower thoracic vertebrae had a greater range of rotation than did the other regions, similar to that observed in humans. In addition, absolute values for the range of rotation were similar between humans and macaques. However, in the bone-ligament preparation condition, the upper thoracic vertebrae had a range of rotation similar to that of the lower thoracic vertebrae. Contrary to previous speculations, our results showed that the mechanical restrictions by the ribs were not as significant; rather, the shoulder girdle largely restricted the rotation of the upper thoracic vertebrae, at least, in macaques.

Dynamic segmental kinematics of the lumbar spine during diagnostic movements

Background: In vivo measurements of segmental-level kinematics are a promising avenue for better understanding the relationship between pain and its underlying, multi-factorial basis. To date, the bulk of the reported segmental-level motion has been restricted to single plane motions. Methods: The present work implemented a novel marker set used with an optical motion capture system to non-invasively measure dynamic, 3D in vivo segmental kinematics of the lower spine in a laboratory setting. Lumbar spinal kinematics were measured for 28 subjects during 17 diagnostic movements. Results: Overall regional range of motion data and lumbar angular velocity measurement were consistent with previously published studies. Key findings from the work included measurement of differences in ascending versus descending segmental velocities during functional movements and observations of motion coupling paradigms in the lumbar spinal segments. Conclusion: The work contributes to the task of establishing a baseline of segmental lumbar movement patterns in an asymptomatic cohort, which serves as a necessary pre-requisite for identifying pathological and symptomatic deviations from the baseline.

Dynamic evaluation of the sternoclavicular and acromioclavicular joints using an upright four-dimensional computed tomography

In the analysis of the shoulder complex, the sequential changes occurring in the sternoclavicular and acromioclavicular joints during active shoulder motion are challenging to track. This study aimed to investigate the in vivo sternoclavicular and acromioclavicular joint motions during active elevation, including the sequential changes in these joint spaces using upright four-dimensional computed tomography (4DCT). Bilateral shoulders of 12 healthy volunteers upright 4DCT were obtained during active elevation similar to a "hands up" motion. The sternoclavicular and acromioclavicular rotation angles, joint distances, and closest points on the clavicle relative to the thorax and scapula were evaluated during 10°-140° of humerothoracic elevation. During humerothoracic elevation, the clavicle elevated, retracted, and rotated posteriorly relative to the thorax, whereas the scapula rotated upwardly, internally, and posteriorly relative to the clavicle. All the sternoclavicular and acromioclavicular joint rotation angles were significantly different at ≥ 30°-50° of humerothoracic elevation compared with 10° of humerothoracic elevation. The mean sternoclavicular and acromioclavicular joint distances were 2.2 ± 1.1 mm and 1.6 ± 0.9 mm, respectively. The closest points were located on the anteroinferior part of the medial and lateral clavicle in the sternoclavicular and acromioclavicular joints, respectively. Significant differences were observed in the acromioclavicular joint distance and anterior/posterior movements of the closest points in the sternoclavicular and acromioclavicular joints compared with 10° of humerothoracic elevation. Our sternoclavicular and acromioclavicular closest point results indicate that the impingement tends to occur at the anteroinferior part of the medial and lateral aspects of the clavicle and may be related to osteoarthritis.

Three-dimensional shoulder kinematics: Upright four-dimensional computed tomography in comparison with an optical three-dimensional motion capture system

Although shoulder kinematics have been analyzed by various methods, dynamic shoulder motion is difficult to track. This study aimed to validate the shoulder kinematic analysis using upright four-dimensional computed tomography (4DCT) and to compare the results with optical three-dimensional motion capture. During active elevation, bilateral shoulders of 10 healthy volunteers were tracked using 4DCT and motion capture. The scapulothoracic and glenohumeral rotations and the scapulohumeral rhythm (SHR) at each position were calculated, and the differences between 4DCT and motion capture were compared. During 10-140° of humerothoracic elevation, the scapulothoracic joint showed upward rotation, internal rotation, and posterior tilting, and the glenohumeral joint showed elevation, external rotation, and anterior plane of elevation in both analyses. In scapulothoracic rotations, the mean differences between the two analyses were -2.6° in upward rotation, 13.9° in internal rotation, and 6.4° in posterior tilting, and became significant with humerothoracic elevation ≥110° in upward rotation, ≥50° in internal rotation, and ≥100° in posterior tilting. In glenohumeral rotations, the mean differences were 3.7° in elevation, 9.1° in internal rotation, and -8.8° in anterior plane of elevation, and became significant with humerothoracic elevation ≥110° in elevation, ≥90° in internal rotation, and ≥100° in anterior plane of elevation. The mean overall SHRs were 1.8 in 4DCT and 2.4 in motion capture, and the differences became significant with humerothoracic elevation ≥100°. The 4DCT analysis of in vivo shoulder kinematics using upright computed tomography scanner is feasible, but the values were different from those by skin-based analysis at the elevated arm positions.

Cervical rotational osteotomy for correction of axial deformity in a patient with ankylosing spondylitis

PURPOSE

Severe cervical axial deformity associated with ankylosing spondylitis (AS) is rare in clinic, and there are little concerns about surgical treatment of axial deformity associated with AS. The case study aims to show the surgical technique to perform cervical rotational osteotomy.

METHODS

We present the case of a young AS patient whose neck was fixed in a left-rotational posture at 18°, requiring his trunk to be turned to the right to look forward visually. This made his gait appear to be limping, inconveniencing him with great difficulty. In order to correct this deformity, we performed a novel cervical rotational osteotomy through a one-stage posterior-anterior-posterior approach. Firstly, we performed laminectomies of C7 and T1, followed by a C7/T1 facetectomy with release of the bilateral C8 nerve roots. Next, we performed C7/T1 discectomy, bony resection of the lateral body and uncovertebral joints. The head of the patient was then rotated manually, so that both his face and torso were simultaneously facing frontward. Finally, rods spanning the screws from C6 to T2 were fixed.

RESULTS

Postoperatively, the patient's axial malalignment was significantly improved, and he was able to walk normally. Surgical outcomes were well maintained at a 3-year follow-up.

CONCLUSION

Through this case, we hope to draw the attention to spinal axial deformity and provide a reference point in the surgical treatment of spinal axial deformity.

The 6 degrees-of-freedom range of motion of the L1-S1 vertebrae in young and middle-aged asymptomatic people

STUDY DESIGN

Controlled laboratory study.

OBJECTIVE

To determine the 6 degrees of freedom of lumbar vertebra in vivo during different functional activities in young and middle-aged asymptomatic subjects.

METHODS

A total of 26 asymptomatic subjects (M/F, 15/11; age, 20-55 years) were recruited in this study. They were divided into two groups: young group (number: 14; age: 20-30 years old) and middle-aged group (number: 12; age: 45-55 years old). The lumbar segment of each subject was scanned by computed tomography for the construction of three-dimensional (3D) models of the vertebra from L1 to S1. The lumbar spine was imaged by using a dual fluoroscopic system when the subjects performed different trunk postures. The 3D models of vertebrae were matched to two fluoroscopic images simultaneously in software. The range of motion (ROM) of vertebrae in the young and middle-aged groups was compared by using multiway analysis of variance, respectively.

RESULTS

During the supine to the upright posture, vertebral rotation of the L1-S1 occurred mainly around the mediolateral axis (mean: 3.9 ± 2.9°). Along the mediolateral axis, vertebral translation was significantly lower at L1-2 (7.7 ± 2.4 mm) and L2-3 (8.0 ± 3.5 mm) than at L3-4 (1.6 ± 1.2 mm), L4-5 (3.3 ± 2.6 mm), and L5-S1 (2.6 ± 1.9 mm). At the L4-5 level, the young group had a higher rotational ROM than the middle-aged group around all three axes during left-right bending. Along the anteroposterior axis, the young group had a lower translational ROM at L4-5 than the middle-aged group during left-right bending (4.6 ± 3.3 vs. 7.6 ± 4.8 mm; P < 0.05). At L5-S1, the young group had a lower translational ROM than the middle-aged group during flexion-extension, left-right bending, and left-right torsion.

CONCLUSION

This study explored the lumbar vertebral ROM at L1-S1 during different functional postures in both young and middle-aged volunteers. There were higher coupled translations at L3-4 and L4-5 than at the upper lumbar segments during supine to upright. The vertebral rotation decreased with age. In addition, the older subjects had a higher anteroposterior translation at the L4-5 segment and higher mediolateral translation at the L5-S1 segment than the young group. These data might provide basic data to be compared with spinal pathology.

MRI-- and CT--based metrics for the quantification of arthroscopic bone resections in femoroacetabular impingement syndrome

The purpose of this in vitro study was to quantify the bone resected from the proximal femur during hip arthroscopy using metrics generated from magnetic resonance imaging (MRI) and computed tomography (CT) reconstructed three-dimensional (3D) bone models. Seven cadaveric hemi-pelvises underwent both a 1.5 T MRI and CT scan before and following an arthroscopic proximal femoral osteochondroplasty. The images from MRI and CT were segmented to generate 3D proximal femoral surface models. A validated 3D--3D registration method was used to compare surface--to--surface distances between the 3D models before and following surgery. The new metrics of maximum height, mean height, surface area and volume, were computed to quantify bone resected during osteochondroplasty. Stability of the metrics across imaging modalities was established through paired sample t--tests and bivariate correlation. Bivariate correlation analyses indicated strong correlations between all metrics (r = 0.728--0.878) computed from MRI and CT derived models. There were no differences in the MRI- and CT-based metrics used to quantify bone resected during femoral osteochondroplasty. Preoperative- and postoperative MRI and CT derived 3D bone models can be used to quantify bone resected during femoral osteochondroplasty, without significant differences between the imaging modalities.

Increase in tibial internal rotation due to weight-bearing is a key feature to diagnose early-stage knee osteoarthritis: a study with upright computed tomography

Background

The classification of knee osteoarthritis is an essential clinical issue, particularly in terms of diagnosing early knee osteoarthritis. However, the evaluation of three-dimensional limb alignment on two-dimensional radiographs is limited. This study evaluated the three-dimensional changes induced by weight-bearing in the alignments of lower limbs at various stages of knee osteoarthritis.

Methods

Forty five knees of 25 patients (69.9 ± 8.9 years) with knee OA were examined in the study. CT images of the entire leg were obtained in the supine and standing positions using conventional CT and 320-row detector upright CT, respectively. Next, the differences in the three-dimensional alignment of the entire leg in the supine and standing positions were obtained using 3D-3D surface registration technique, and those were compared for each Kellgren–Lawrence grade.

Results

Greater flexion, adduction, and tibial internal rotation were observed in the standing position, as opposed to the supine position. Kellgren–Lawrence grades 1 and 4 showed significant differences in flexion, adduction, and tibial internal rotation between two postures. Grades 2 and 4 showed significant differences in adduction, while grades 1 and 2, and 1 and 3 showed significant differences in tibial internal rotation between standing and supine positions.

Conclusions

Weight-bearing makes greater the three-dimensional deformities in knees with osteoarthritis. Particularly, greater tibial internal rotation was observed in patients with grades 2 and 3 compared to those with grade 1. The greater tibial internal rotation due to weight-bearing is a key pathologic feature to detect early osteoarthritic change in knees undergoing osteoarthritis.

Four-dimensional computed tomography evaluation of shoulder joint motion in collegiate baseball pitchers

The purpose of this study is to evaluate the glenohumeral contact area, center of glenohumeral contact area, and center of humeral head during simulated pitching motion in collegiate baseball pitchers using four-dimensional computed tomography (4D CT). We obtained 4D CT data from the dominant and non-dominant shoulders of eight collegiate baseball pitchers during the cocking motion. CT image data of each joint were reconstructed using a 3D reconstruction software package. The glenohumeral contact area, center of glenohumeral contact area, center of humeral head, and oblateness of humeral head were calculated from 3D bone models using customized software. The center of glenohumeral contact area translated from anterior to posterior during maximum external rotation to maximum internal rotation (0.58 ± 0.63 mm on the dominant side and 0.99 ± 0.82 mm on the non-dominant side). The center of humeral head translated from posterior to anterior during maximum external rotation to maximum internal rotation (0.76 ± 0.75 mm on the dominant side and 1.21 ± 0.78 mm on the non-dominant side). The increase in anterior translation of the center of glenohumeral contact area was associated with the increase in posterior translation of the center of humeral head. Also, the increase in translation of the center of humeral head and glenohumeral contact area were associated with the increase in oblateness of the humeral head. 4D CT analyses demonstrated that the center of humeral head translated in the opposite direction to that of the center of glenohumeral contact area during external rotation to internal rotation in abduction in the dominant and non-dominant shoulders. The oblateness of the humeral head may cause this diametric translation. 4D CT scanning and the software for bone surface modeling of the glenohumeral joint enabled quantitative assessment of glenohumeral micromotion and be used for kinematic evaluation of throwing athletes.

Kinematics of the Cervical Spine Under Healthy and Degenerative Conditions: A Systematic Review

Knowledge of spinal kinematics is essential for the diagnosis and management of spinal diseases. Distinguishing between physiological and pathological motion patterns can help diagnose these diseases, plan surgical interventions and improve relevant tools and software. During the last decades, numerous studies based on diverse methodologies attempted to elucidate spinal mobility in different planes of motion. The authors aimed to summarize and compare the evidence about cervical spine kinematics under healthy and degenerative conditions. This includes an illustrated description of the spectrum of physiological cervical spine kinematics, followed by a comparable presentation of kinematics of the degenerative cervical spine. Data was obtained through a systematic MEDLINE search including studies on angular/translational segmental motion contribution, range of motion, coupling and center of rotation. As far as the degenerative conditions are concerned, kinematic data regarding disc degeneration and spondylolisthesis were available. Although the majority of the studies identified repeating motion patterns for most motion planes, discrepancies associated with limited sample sizes and different imaging techniques and/or spine configurations, were noted. Among healthy/asymptomatic individuals, flexion extension (FE) and lateral bending (LB) are mainly facilitated by the subaxial cervical spine. C4-C5 and C5-C6 were the major FE contributors in the reported studies, exceeding the motion contribution of sub-adjacent segments. Axial rotation (AR) greatly depends on C1-C2. FE range of motion (ROM) is distributed between the atlantoaxial and subaxial segments, while AR ROM stems mainly from the former and LB ROM from the latter. In coupled motion rotation is quantitatively predominant over translation. Motion migrates caudally from C1-C2 and the center of rotation (COR) translocates anteriorly and superiorly for each successive subaxial segment. In degenerative settings, concurrent or subsequent lesions render the association between diseases and mobility alterations challenging. The affected segments seem to maintain translational and angular motion in early and moderate degeneration. However, the progression of degeneration restrains mobility, which seems to be maintained or compensated by adjacent non-affected segments. While the kinematics of the healthy cervical spine have been addressed by multiple studies, the entire nosological and kinematic spectrum of cervical spine degeneration is partially addressed. Large-scale in vivo studies can complement the existing evidence, cover the gaps and pave the way to technological and clinical breakthroughs.

Reaction Forces and Flexion-Extension Moments Imposed On Functional Spinal Units with Constrained and Unconstrained in Vitro Testing Systems

A mechanical goal of in vitro testing systems is to minimize differences between applied and actual forces and moments experienced by spinal units. This study quantified the joint reaction forces and reaction flexion-extension moments during dynamic compression loading imposed throughout the physiological flexion-extension range-of-motion. Constrained (fixed base) and unconstrained (floating base) testing systems were compared. Sixteen porcine spinal units were assigned to both testing groups. Following conditioning tests, specimens were dynamically loaded for 1 cycle with a 1 Hz compression waveform to a peak load of 1 kN and 2 kN while positioned in five different postures (neutral, 100% and 300% of the flexion and extension neutral zone), totalling ten trials per FSU. A six degree-of-freedom force and torque sensor was used to measure peak reaction forces and moments for each trial. Shear reaction forces were significantly greater (25.5 N - 85.7 N) when the testing system was constrained compared to unconstrained (p < 0.029). The reaction moment was influenced by posture (p = 0.037), particularly in C5C6 spinal units. In 300% extension (C5C6), the reaction moment was, on average, 9.9 Nm greater than the applied moment in both testing systems and differed from all other postures (p < 0.001). The reaction moment error was, on average, 0.45 Nm at all other postures. In conclusion, these findings demonstrate that comparable reaction moments can be achieved with unconstrained systems, but without inducing appreciable shear reaction forces.

Three-Dimensional Measures of Bony Resection During Femoral Osteochondroplasty Are Related to Alpha Angle Measures: A Cadaveric Study

Purpose

Methods

Results

Conclusions

Clinical Relevance

Lumbar Bone Mineral Adaptation: The Effect of Fast Bowling Technique in Adolescent Cricketers

INTRODUCTION

Localised bone mineral density (BMD) adaptation of the lumbar spine, particularly on the contralateral side to the bowling arm, has been observed in elite male cricket fast bowlers. No study has investigated this in adolescents, or the role of fast bowling technique on lumbar BMD adaptation. This study aims to investigate lumbar BMD adaptation in adolescent cricket fast bowlers, and its relationship with fast bowling technique.

METHODS

39 adolescent fast bowlers underwent antero-posterior DXA scan of their lumbar spine. Hip, lumbopelvic and thoracolumbar joint kinematics, and vertical ground reaction kinetics were determined using 3D motion capture and force plates. Significant partial (covariate: fat free mass) and bivariate correlations of the technique parameters with whole lumbar (L1-L4) BMD and BMD asymmetry (L3 and L4) were advanced as candidate variables for multiple stepwise linear regression.

RESULTS

Adolescent fast bowlers demonstrated high lumbar Z-Scores (+1.0; 95%CI: 0.7 - 1.4) and significantly greater BMD on the contralateral side of L3 (9.0%; 95%CI: 5.8 - 12.1%) and L4 (8.2%; 95%CI: 4.9 - 11.5%). Maximum contralateral thoracolumbar rotation and maximum ipsilateral lumbopelvic rotation in the period between back foot contact (BFC) and ball release (BR), as well as contralateral pelvic drop at front foot contact (FFC), were identified as predictors of L1-L4 BMD, explaining 65% of the variation. Maximum ipsilateral lumbopelvic rotation between BFC and BR, as well as ipsilateral lumbopelvic rotation and contralateral thoracolumbar side flexion at BR, were predictors of lumbar asymmetry within L3 and L4.

CONCLUSION

Thoracolumbar and lumbopelvic motion are implicated in the aetiology of the unique lumbar bone adaptation observed in fast bowlers whereas vertical ground reaction force, independent of body mass, was not. This may further implicate the osteogenic potential of torsional rather than impact loading in exercise-induced adaptation.

Effect of soft inflatable orthosis on the medial longitudinal arch in patients with flexible flatfoot deformity

BACKGROUND

Orthoses can stabilize the foot and restore the medial longitudinal arch for symptomatic flexible flatfoot. However, the effectiveness of orthoses remains controversial. The purpose of this study was to evaluate effectiveness of a customized soft inflatable orthosis on the medial longitudinal arch of flexible flatfoot patients under load.

METHODS

We obtained CT scans of the feet of 14 healthy volunteers and 14 patients with flexible flatfoot under non- and simulated weight-bearing conditions. Then CT scans under the same conditions were taken for patients with flexible flatfoot equipped with soft inflatable orthosis. Three-dimensional models of the medial longitudinal arch and hindfoot were constructed from CT images. The three-dimensional mobility of the medial longitudinal arch joints under load was compared between patients with flexible flatfoot equipped with soft inflatable orthosis or not.

FINDINGS

From non- to simulated weight-bearing condition, the eversion and dorsiflexion of the talocalcaneal joint, the eversion of the talonavicular joint, the abduction and dorsiflexion of the cuneonavicular joint, and the dorsiflexion of the first tarsometatarsal joint were significantly larger in patients with flexible flatfoot than healthy volunteers. The customized soft inflatable orthosis could reduce the eversion of the talonavicular joint and the eversion and dorsiflexion of the talocalcaneal joint.

INTERPRETATION

The soft inflatable orthosis is effective to improve medial longitudinal arch height and reduce excessive mobility of joints for flexible flatfoot deformity. The results of this study could provide evidence for the optimal orthosis design to treat flexible flatfoot in the future.

The relationship between external thoracopelvic angle and lumbar segmental axial twist angle using an ultrasound imaging technique

The relationship between externally measured and internal spine axial twist motion (rotation about a vertical axis) is not well understood. Ultrasound is a validated technique for measurement of vertebral axial twist motion and has the potential for measuring segmental vertebral axial twist in vivo. The objective of this study was to evaluate lumbar segmental axial twist in relation to external thoracopelvic twist from optical motion capture using an ultrasound imaging technique. Sixteen participants were tested in a custom-built axial twist jig, which isolated motion to the lumbar spine. Participants were moved from neutral to 75% of maximum axial twist range of motion in an upright kneeling posture. Thoracopelvic motion was recorded with a motion capture system and L1 to S1 vertebral axial twist was recorded using ultrasound. From motion capture, maximum thoracopelvic axial twist motion was 41.1 degrees. From ultrasound, the majority of axial twist motion occurred at the L2-L3 (46.8% of lumbar axial twist motion) and L5-S1 (33.5%) intervertebral joints. Linear regression linking axial twist at each vertebral level to thoracopelvic axial twist ranged from 0.43 to 0.79. These findings demonstrate a mathematical relationship between internal and external axial twist motion and the distribution of motion across the lumbar spine suggests that classic use of L4-L5 to represent lumbar spine motion may not be appropriate for axial twist modelling approaches.

How to Select the Lower Instrumented Vertebra in Traditional Growing Rods Index Surgery

BACKGROUND

There are still no consensus criteria on how to select the lower instrumented vertebra (LIV) for traditional growing rods (TGRs) at index surgery. The aim was to evaluate whether the criteria used for adolescent idiopathic scoliosis fusion adapts to early onset scoliosis (EOS).

METHODS

Retrospective analysis of prospectively longitudinal collected data in a consecutive cohort of patients with EOS treated with TGR, expanding from index surgery to 2 years after graduation. The LIV was analyzed regarding its relation to the stable vertebra (SV), substantially touched vertebra (STV), and not STV (NSTV). Failure of LIV selection was considered when revision surgery with distal extension was needed during follow up, due to adding on (ΔLIV tilt > 10°).

RESULTS

A total of 25 patients met inclusion criteria. Mean age was 8.6 ± 3 (at index surgery), 15.1 ± 1.8 (at graduation), and 17.8 ± 1.6 (at final follow up). The most frequent LIV at index surgery was L3 (13/25); in 13 cases, STV was selected as LIV; in 7, it was NSTV; and in 5, SV on the standard postero-anterior radiographs. During follow up, a significant increase in the mean LIV tilt (P = .049) and distal junctional angle (P = .017) was found. Nine of the 25 patients (36%) developed adding on: 20% (1/5) of those with LIV at SV, 38.5% (5/13) at STV, and 42.8% (3/7) at NSTV. Of those 9 cases of adding on, only four needed distal extension (mean LIV tilt = 17.6°): 2 STV patients (15.4%), and 2 NSTV patients (28.6%). None of the patients with the LIV chosen at SV needed distal extension due to adding on.

CONCLUSIONS

The more cranial the selection of the LIV above the SV, the higher the risk of adding on and of revision surgery with distal extension during follow up. Saving motion segments could be justified by choosing STV as LIV because the need for distal extension is not high, and it can be scheduled during lengthening procedures or at graduation surgery.

LEVEL OF EVIDENCE

4.

CLINICAL RELEVANCE

Choosing the correct LIV in TGR index surgery is crucial to have a secure distal foundation, control and correct the deformity during growth, and save distal segments to allow growth and mobility.

Assignment of local coordinate systems and methods to calculate tibiotalar and subtalar kinematics: A systematic review

The introduction of biplane fluoroscopy has created the ability to evaluate in vivo motion, enabling six degree-of-freedom measurement of the tibiotalar and subtalar joints. Although the International Society of Biomechanics defines a standard method of assigning local coordinate systems for the ankle joint complex, standards for the tibiotalar and subtalar joints are lacking. The objective of this systematic review was to summarize and appraise the existing literature that (1) defined coordinate systems for the tibia, talus, and/or calcaneus or (2) assigned kinematic definitions for the tibiotalar and/or subtalar joints. A systematic literature search was developed with search results limited to English Language from 2006 through 2020. Articles were screened by two independent reviewers based on title and abstract. Methodological quality was evaluated using a modified assessment tool. Following screening, 52 articles were identified as having met inclusion criteria. Methodological assessment of these articles varied in quality from 61 to 97. Included articles adopted primary methods for defining coordinate systems that included: (1) anatomical coordinate system (ACS) based on individual bone landmarks and/or geometric shapes, (2) orthogonal principal axes, and (3) interactive closest point (ICP) registration. Common methods for calculating kinematics included: (1) joint coordinate system (JCS) to calculate rotation and translation, (2) Cardan/Euler sequences, and (3) inclination and deviation angles for helical angles. The methods each have strengths and weaknesses. This summarized knowledge should provide the basis for the foot and ankle biomechanics community to create an accepted standard for calculating and reporting tibiotalar and subtalar kinematics.

Three-dimensional computed tomographic evaluation of lateral lumbar interbody fusion: morphometric change of intervertebral structure

PURPOSE

Two-dimensional (2D) analyses of intervertebral disc (IVD) height and foramen measurements following lateral lumbar interbody fusion (LLIF) have been reported. However, three-dimensional (3D) morphometric analysis of intervertebral structure using 3D computed tomography (3D CT) provides increased precision for measuring morphological changes. The purpose of this study was to evaluate 3D changes of lumbar IVD height and foramen diameter in degenerative lumbar disease patients following LLIF.

METHODS

Subject-based 3D CT lumbar models were created for 26 patients before and following LLIF. IVD height (whole and five anatomical zones) and foramen diameter (minimum and maximum) were measured based on the model using custom software. The sagittal placement of cages (SPC) and cross-sectional area of the thecal sac (CSA) were measured. Changes in these parameters by LLIF were quantified and statistically analysed.

RESULTS

Following LLIF, disc height increased by an average of 2.9 mm (P < 0.01). Post-operative measurements of both minimum and maximum diameters of the foramen were significantly increased by 1.0 mm and 1.9 mm, respectively (P < 0.01). Change in maximum foramen diameter was significantly correlated with change in disc height (P < 0.05). The SPC was significantly correlated with the changes in disc height and foraminal diameters (P < 0.05, respectively). No significant change between the change in disc height and CSA was found.

CONCLUSION

This preliminary study quantifies disc height and foramen diameter changes in 3D following LLIF. The presented data provide baseline intervertebral changes for future comparisons with follow-up studies and clinical outcomes.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Quantitative analysis of metacarpophalangeal joints during active flexion using four-dimensional computed tomography

BACKGROUND

The metacarpophalangeal joint has a unique morphology with a high degree of freedom. However, few studies have analyzed the kinematics of fingers owing to the rapid movement of the small bones involved. The in-vivo kinematics of metacarpophalangeal joints were analyzed by four-dimensional computed tomography (4DCT) and associated with its morphology.

METHODS

The flexion motion of the fingers of bilateral hands in 10 volunteers were examined using 4DCT. Iterative surfaces were registered to trace the surface of the proximal phalanges with respect to metacarpals. Rotation angles were calculated using Euler/Cardan angles.

FINDINGS

In the index finger, the proximal phalange supinated to a maximum flexion of 40° and then pronated, and its range of rotation was larger than the previous reports. In the other fingers, the proximal phalanges continued to supinate during flexion. The helical axis of the proximal phalange passed a point extremely close to the center point of bilateral condyles, and it moved toward the proximal and palmar directions until the middle stage of flexion and toward the proximal and dorsal directions during the late stage of flexion. The translation of the rotation axis was larger in the ring and little fingers.

INTERPRETATION

The rotation in the index finger was larger than previously reported. The helical axes moved in the dorsal direction and proximally during the latter phase of the flexion. These results can be employed to better understand the causes of implant failure of the metacarpophalangeal joints.

1.5 T magnetic resonance imaging generates accurate 3D proximal femoral models: Surgical planning implications for femoroacetabular impingement

The objective of this study was to validate three-dimensional (3D) proximal femoral surface models generated from a 1.5 T magnetic resonance imaging (MRI) by comparing these 3D models to those derived from the clinical "gold standard" of computed tomography (CT) scan and to ground-truth surface models obtained by laser scans (LSs) of the excised femurs. Four intact bilateral cadaveric pelvis specimens underwent CT and MRI scans and 3D surface models were generated. Six femurs were extracted from these specimens, and the overlying soft tissues were removed. The extracted femurs were then laser scanned to produce a ground-truth surface model. A 3D-3D registration method was used to compare the signed and absolute surface-to-surface distances between the 3D models. Absolute agreement was evaluated using a 95% confidence interval (CI) derived from the precision of the LS ground-truth. Paired samples t tests and Kolmogrov-Smirnov tests were performed to compare the differences between the signed and absolute surface-to-surface distances between the models. The average signed surface-to-surface distances for the MRI vs LS and MRI vs CT models were 0.07 and 0.16 mm, respectively. These differences fell within the 95% CI of ±0.20 mm indicating absolute agreement between the surface models generated from these modalities. The signed surface-to-surface distance was significantly smaller for MRI vs LS ground truth model as compared with the CT vs LS model. Femoral models derived from a 1.5 T MRI scan demonstrated absolute agreement with the clinical gold standard of CT-derived models and were most like LS ground truth models of the excised femurs.

Effect of facet-joint degeneration on the in vivo motion of the lower lumbar spine

Objective

This research studied the in vivo motion characteristics of the L3–S1 lumbar spine with facet-joint degeneration during functional activities.

Methods

Thirteen male and 21 female patients with facet-joint degeneration at the L3–S1 spinal region were included in the study. The L3–S1 lumbar segments of all the patients were divided into 3 groups according to the degree of facet-joints degeneration (mild, moderate, or severe). The ranges of motion (ROM) of the vertebrae were analyzed using a combination of computed tomography and dual fluoroscopic imaging techniques. During functional postures, the ROMs were compared between the 3 groups at each spinal level (L3–L4, L4–L5, and L5–S1).

Results

At L3–L4 level, the primary rotations between the mild and moderate groups during left-right twisting activity were significantly different. At L4–L5 level, the primary rotation of the moderate group was significantly higher than the other groups during flexion-extension. During left-right bending activities, a significant difference was observed only between the moderate and severe groups. At L5–S1 level, the rotation of the moderate group was significantly higher than the mild group during left-right bending activity.

Conclusions

Degeneration of the facet joint alters the ROMs of the lumbar spine. As the degree of facet-joint degeneration increased, the ROMs of the lumbar vertebra that had initially increased declined. However, when there was severe facet-joint degeneration, the ROMs of the lumbar spine declined to levels comparative to the moderate group. The relationship between the stability of the lumbar vertebra and the degree of facet-joint degeneration requires further study.

A new approach to the treatment of spinal instability: Fusion or structural reinforcement without surgery?

Spinal instability related low back pain is a common condition resulting from degeneration and loss of stiffness of the intervertebral joint. In order to restore stability, highly invasive surgical fusion is needed for patients who are not responding to conservative treatment. Given the risk and complications of surgery, there has been the urge for improvement with a less invasive solution. Formation of vertebral body osteophytes is a common observation that has been treated as a degenerative condition. However, recent studies have associated it with reduced motion of spinal segments. Unlike the traditional view, we regard it as adaptive reactions aiming to repair and hypothesize that the spinal segments could be stabilized or fused by intentionally induced osteophytes growth at the mobile parts of the intervertebral joint. This could be achieved by injecting Bone Morphogenetic Proteins to the anterior ends of the vertebral bodies and/or the facet joints on both sides of two consecutive vertebrae percutaneously. If verified, it would be the first time that fusion could be achieved without surgery. Hence it would provide a valuable alternative to current treatments of spinal instability. Preliminary test in favor of this hypothesis is presented and we recommend that a formal study with sufficient number of samples is needed for verification.

New classification of facet joint synovial cysts

PURPOSE

Facet cysts develop due to degeneration of the zygapophyseal joints and can lead to radiculopathy and neurogenic claudication. Various surgical options are available for facet cyst excision. The aim was to facilitate surgical treatment of lumbar facet cysts based on a new classification.

METHODS

We retrospectively analyzed all patients of the last 10 years in whom a facet cyst was surgically removed (ipsilateral laminotomy, contralateral laminotomy, and segmental fusion). Several radiological parameters were analyzed and correlated with the patients' outcome (residual symptoms, perioperative complications, need for re-operation, need for secondary fusion, facet cyst recurrence).

RESULTS

One hundred eleven patients (55 women; median age 64 years) could be identified. Thirty-three (48%) of 69 cases, for which MRI data were available, were classified as medial facet cyst (compressing the spinal canal), 6 facet cysts were localized intraforaminal (9%) and 30 cases (43%) mediolateral (combination of both). The contralateral approach had the lowest rate for revision surgery (7.5%, p = .038) and the lowest prevalence of residual complaints (7.5%, p = .109). A spondylolisthesis and a higher/steeper angle of the facet joints were associated with poorer patient outcome.

CONCLUSIONS

Lateral facet joint cysts are best resected by a contralateral approach offering the best outcome while medial cysts are suitable for removal by an ipsilateral laminotomy. The approach of mediolateral cysts can be determined by the width of the lamina and the angle of the joint. Segmental fusion should be considered in cases with detected spondylolisthesis and/or steep facet joints.

Assessment of Hip Translation In Vivo in Patients With Femoracetabular Impingement Syndrome Using 3-Dimensional Computed Tomography

Purpose

To determine the 3-dimensional (3D) in vivo hip translation in patients with symptomatic femoroacetabular impingement syndrome (FAIS) using 3D computed tomography (CT) models with the hip in neutral and FABER (flexion, abduction, and the external rotation) positions and to identify patient predictors associated with the degree of hip translation.

Methods

Seventy-eight patients with FAIS and cam lesions underwent CT scans in neutral and FABER positions. Demographics including age, sex, and body mass index (BMI) were recorded for each patient. The cam deformity was characterized both in plain x-ray film and 3D. Translation between both positions was calculated using a validated high-precision 3D-3D registration technique. Univariate and multivariate regression analyses sought factors correlated with translation.

Results

The mean age of the patients included in the analysis was 36.3 ± 9.2 years, with 51% of the study group being female. The mean 3D femoral head center translation was 0.84 ± 0.37 mm, decomposed into vectors on standard anatomical directions as 0.13 ± 0.58 mm medial, 0.10 ± 0.54 mm posterior, and 0.08 ± 0.46 mm inferior. Multivariate analysis demonstrated that total translation was associated with larger alpha angles (β = 0.014; 95% confidence interval [CI] 0.003-0.024; P = .013), and greater BMI (β = 0.033; 95% CI 0.001-0.065; P = .042). Furthermore, posterior–inferior translation was associated with BMI (β = 0.032; 95% CI 0.003-0.061; P = .031), whereas medial–lateral translation is associated with the female sex (β = 0.388; 95% CI 0.124-0.634; P = .002), and smaller head radius (β = –0.068; 95% CI –0.128 to –0.007; P = .029).

Conclusions

As a provocative maneuver, FABER positioning in patients with FAIS resulted in an average measurable translation of the femoral head center in the posterior, medial, and inferior direction. Factors including sex, BMI, and alpha angle predicted the degree of translation.

Clinical Relevance

The current study demonstrates that there is measurable hip translation between the neutral and FABER positions in patients with symptomatic FAIS, which may cause hip microinstability. Furthermore, the study found an association between hip translation and both modifiable and nonmodifiable factors. This may indicate the need for more comprehensive preoperative surgical planning, intraoperative dynamic examination of the hip, and consideration of capsular plication in certain patients.

Correlation between three-dimensional medial longitudinal arch joint complex mobility and medial arch angle in stage II posterior tibial tendon dysfunction

BACKGROUND

The purpose of this study was to evaluate correlation between three-dimensional medial longitudinal arch joint complex mobility and medial arch angle in stage II posterior tibial tendon dysfunction flatfoot under loading.

METHODS

CT scans of 15 healthy feet and 15 feet with stage II posterior tibial tendon dysfunction flatfoot were taken both in non- and simulated weight-bearing condition. The CT images of the hindfoot and medial longitudinal arch bones were reconstructed into three-dimensional models with Mimics and Geomagic reverse engineering software. The three-dimensional complex mobility of each joint in the medial longitudinal arch and their correlation with the medial arch angle change were calculated.

RESULTS

From non- to simulated weight-bearing condition, the medial arch angle change and the medial longitudinal arch joints mobility were significant larger in stage II posterior tibial tendon dysfunction flatfoot (p<0.05). The eversion of the talocalcaneal joint, the proximal translation of the calcaneus relative to the talus, the dorsiflexion of the talonavicular joint, the dorsiflexion and abduction of the medial cuneonavicular joint, and the lateral translation of the medial cuneiform relative to the navicular, and the dorsiflexion of the first tarsometatarsal joint were all significantly correlated to the medial arch angle change in stage II posterior tibial tendon dysfunction flatfoot (all r>0.5, p<0.05).

CONCLUSIONS

There is increased mobility in the medial longitudinal arch joints in stage II posterior tibial tendon dysfunction flatfoot and the medial arch angle change under loading causes displacement not only at hindfoot joints but also involve midfoot and forefoot joint.

Three-dimensional kinematic change of hindfoot during full weightbearing in standing: an analysis using upright computed tomography and 3D-3D surface registration

Background

Weightbearing of the hindfoot affects positional changes of the ankle joint and subtalar joint (ankle-joint complex [AJC]). However, it is difficult to assess the kinematic changes in the hindfoot in a natural full weightbearing condition using conventional CT or cone beam computed tomography (CT) due to limitations of acquiring foot images under a physiological weightbearing condition using those imaging modalities. Analysis of AJC kinematics using fluoroscopy and 2D-3D registration technique requires data on the number of steps and amount of time to build and match the bones. This study aimed to analyze the effect of full weightbearing on hindfoot motion when standing using upright CT and 3D-3D surface registration.

Methods

Forty-eight AJCs of 24 asymptomatic volunteers (13 women, 11 men) were examined under no weightbearing, 50% weightbearing, and single leg full weightbearing conditions while standing. The CT images were acquired from the distal femur to the whole foot using a 320-row upright CT scanner. The condition of each weightbearing stance was measured using a pressure mat. Bone-to-bone rotations of the talus relative to the tibia and calcaneus relative to the talus were evaluated using the surface registration technique. Image quality of the CT and intra- and interobserver reliabilities of the rotation angle were also evaluated.

Results

All CT images were excellent or good quality and the intra- and interobserver correlation coefficients for the angle were 0.996 and 0.995, respectively. The motion of the ankle joint and subtalar joint under 50% and 100% weightbearing were as follows (in degrees); the talus plantarflexed (5.1 ± 4.5 and 6.8 ± 4.8), inverted (1.3 ± 1.4 and 2.0 ± 1.6), and internally rotated (2.4 ± 4.2 and 4.3 ± 4.6) relative to the tibia, and the calcaneus dorsiflexed (2.8 ± 1.4 and 3.8 ± 1.7), everted (5.3 ± 2.6 and 8.0 ± 3.6), and externally rotated (3.0 ± 2.0 and 4.1 ± 2.4) relative to the talus, respectively.

Conclusions

The effect of weightbearing was clearly identified using an upright CT and the 3D-3D registration technique. Three-dimensional kinematics under static full weightbearing were opposite between the ankle and subtalar joints on their respective axes.

The geometrical axis of the talocrural joint-Suggestions for a new measurement of the talocrural joint axis

BACKGROUND

Despite intensive research there is no consensus about the talocrural joint axis. The aim of the present study is a new method to determinate the geometric rotational axis of the talocrural joint.

METHODS

We analyzed 98 CT-scans of full cadaver Caucasian legs. We generated three-dimensional reconstruction models of the talus. A best fitting cone was orientated to the talar articular surface. The geometric rotational axis was defined to be the axis of this cone.

RESULTS

The geometric rotational axis of the talocrural joint is orientated from lateral-distal to medial-proximal (85.6°±10 compared to anatomical tibial axis in torsional plane), from posterior-distal to anterior-proximal (81.43°±44.35 compared to anatomical tibial axis in sagittal plane) and from posterior-medial to anterior-lateral (169.2°±5.91 compared to intermalleolar axis in axial plane).

CONCLUSIONS

The consideration of our results might be helpful for better understanding of ankle biomechanics.

Validation of an Ultrasound Protocol to Measure Intervertebral Axial Twist during Functional Twisting Movements in Isolated Functional Spinal Units

Ultrasound has potential for use in evaluation of bone and joint movement during axial twist of the lumbar spine both in vivo and in vitro. Such segmental rotations could then be measured under controlled external thoracic axial twist conditions and in response to mechanical loading. The purpose of this study was to measure vertebral segmental rotations in a porcine model of the human lumbar spine using an ultrasound imaging protocol and to validate use of this imaging technique with an optical motion capture system. In part 1, ultrasound transducer angle was confirmed to have no effect on sonogram point digitization. In part 2, 12 porcine functional spinal units were fixed to a mechanical testing system, and compression (15% of compressive tolerance), flexion-extension and axial twist (0°, 2°, 4° or 6°) were applied. Axial twist motion was tracked using an optical motion capture system and posterior surface ultrasound. Correlation between the two measurement systems was >0.903, and absolute system error was 0.01° across all flexion-extension postures. These findings indicate that ultrasound can be used to track axial twist motion in an in vitro spine motion segment and has the potential for use in vivo to evaluate absolute intervertebral axial twist motion.

Facet Joint Osteoarthritis Affects Spinal Segmental Motion in Degenerative Spondylolisthesis

STUDY DESIGN

This is a retrospective clinical case series (case-control study).

OBJECTIVE

To clarify the influence of facet joint osteoarthritis (FJOA) on the pathology of degenerative spondylolisthesis (DS) using in vivo 3-dimensional image analysis.

SUMMARY OF BACKGROUND DATA

There are no radical treatments to prevent progression of DS in patients with lumbar spinal canal stenosis associated with DS. Therefore, an effective treatment method based on the pathology of DS should be developed.

PATIENTS AND METHODS

In total, 50 patients with lumbar spinal canal stenosis involving L4/5 who underwent dynamic computed tomography were divided into 2 groups: with DS [spondylolisthesis (Sp) group; 12 male, 14 female; mean age, 74 y]; and without DS (non-Sp group; 15 male, 9 female; mean age, 70 y). Degeneration of the intervertebral disk and FJOA at L4/5 were evaluated using magnetic resonance imaging. Disk and intervertebral foramen heights, the distance between the craniocaudal edges of the facet joint, and the interspinous distance were measured on dynamic computed tomographic images. Also, in vivo 3-dimensional segmental motion was evaluated using the volume merge method.

RESULTS

There were no significant differences in degenerative findings for the intervertebral disk; however, progressive FJOA was detected in the Sp group. Dynamic changes in the distance between the craniocaudal edges of the facet joints were significantly larger in the Sp group.

CONCLUSIONS

In this study, progressive FJOA and larger segmental motion in the distance between the craniocaudal edges of the facet joints were found in the Sp group. We clarified for the first time that DS involves ligament laxity due to FJOA that affects spinal segmental motion in vivo. We consider that a treatment method based on FJOA would be useful for treating patients with DS.

LEVEL OF EVIDENCE

Level IV.

A model-based approach for estimation of changes in lumbar segmental kinematics associated with alterations in trunk muscle forces

The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental kinematics of lumbar spine was estimated for a single static trunk flexed posture involving, respectively, 40° and 10° of thoracic and pelvic rotations. Minimum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 0° to 0.7° and 0 mm to 0.04 mm, respectively. Maximum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 2.4° to 7.6° and 0.11 mm to 0.39 mm, respectively. The differences in kinematics of lumbar segments between each combination of two sets of TMFs in 97% of cases for angular deformation and 55% of cases for translational deformation were within the reported accuracy of current imaging techniques. Therefore, it might be possible to use image-based kinematics of lumbar segments along with computational modeling for personalized assessment of TMFs.

The Kinematics and Spondylosis of the Lumbar Spine Vary Depending on the Levels of Motion Segments in Individuals With Low Back Pain

STUDY DESIGN

A prospective cohort study.

OBJECTIVE

The aim of this study was to identify associations of spondylotic and kinematic changes with low back pain (LBP).

SUMMARY OF BACKGROUND DATA

The ability to characterize and differentiate the biomechanics of both the symptomatic and asymptomatic lumbar spine is crucial to alleviate the sparse literature on the association of lumbar spine biomechanics and LBP.

METHODS

Lumbar dynamic plain radiographs (flexion-extension), dynamic computed tomography (CT) scanning (axial rotation, disc height), and magnetic resonance imaging (MRI, disc and facet degeneration grades) were obtained for each subject. These parameters were compared between symptomatic and control groups using Student t test and multivariate logistic regression, which controlled for patient age and sex and identified spinal parameters that were independently associated with symptomatic LBP. Disc grade and mean segmental motion by level were tested by one-way analysis of variance (ANOVA).

RESULTS

Ninety-nine volunteers (64 asymptomatic/35 LBP) were prospectively recruited. Mean age was 37.3 ± 10.1 years and 55% were male. LBP showed association with increased L5/S1 translation [odds ratio (OR) 1.63 per mm, P = 0.005], decreased flexion-extension motion at L1/L2 (OR 0.87 per degree, P = 0.036), L2/L3 (OR 0.88 per degree, P = 0.036), and L4/L5 (OR 0.87 per degree, P = 0.020), increased axial rotation at L4/L5 (OR 2.11 per degree, P = 0.032), decreased disc height at L3/L4 (OR 0.52 per mm, P = 0.008) and L4/L5 (OR 0.37 per mm, p < 0.001), increased disc grade at all levels (ORs 2.01-12.33 per grade, P = 0.001-0.026), and increased facet grade at L4/L5 (OR 4.99 per grade, P = 0.001) and L5/S1 (OR 3.52 per grade, P = 0.004). Significant associations were found between disc grade and kinematic parameters (flexion-extension motion, axial rotation, and translation) at L4/L5 (P = 0.001) and L5/S1 (P < 0.001), but not at other levels (P > 0.05).

CONCLUSION

In symptomatic individuals, L4/L5 and L5/S1 levels were affected by spondylosis and kinematic changes. This study clarifies the relationships between kinematic alterations and LBP, mostly observed at the above-mentioned segments.

LEVEL OF EVIDENCE

N/A.

Adjacent Segment Disease in the Cervical and Lumbar Spine

Adjacent segment disease (ASD) is disappointing long-term outcome for both the patient and clinician. In contrast to adjacent segment degeneration, which is a common radiographic finding, ASD is less common. The incidence of ASD in both the cervical and lumbar spine is between 2% and 4% per year, and ASD is a significant contributor to reoperation rates after spinal arthrodesis. The etiology of ASD is multifactorial, stemming from existing spondylosis at adjacent levels, predisposed risk to degenerative changes, and altered biomechanical forces near a previous fusion site. Numerous studies have sought to identify both patient and surgical risk factors for ASD, but a consistent, sole predictor has yet to be found. Spinal arthroplasty techniques seek to preserve physiological biomechanics, thereby minimizing the risk of ASD, and long-term clinical outcome studies will help quantify its efficacy. Treatment strategies for ASD are initially nonoperative, provided a progressive neurological deficit is not present. The spine surgeon is afforded many surgical strategies once operative treatment is elected. The goal of this manuscript is to consider the etiologies of ASD, review its manifestations, and offer an approach to treatment.

Facet Effusion without Radiographic Instability Has No Effect on the Outcome of Minimally Invasive Decompression Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Lumbar segmental instability is a key factor determining whether decompression alone or decompression and fusion surgery is required to treat lumbar spinal stenosis (LSS). Some recent reports have suggested that facet joint effusion is correlated with spinal segmental instability. The aim of this study is to report the effect of facet effusion without radiographic segmental instability on the outcome of less-invasive decompression surgery for LSS.

METHODS

Seventy-nine patients with LSS (32 women, mean age: 69.1 ± 9.1 years) who had no segmental instability on dynamic radiographs before undergoing L4-L5 microsurgical decompression and who were followed for at least 2 years postoperatively were analyzed. They were divided into three groups on the basis of the existence and size of L4-L5 facet effusion using preoperative magnetic resonance imaging: grade 0 had no effusion (n = 31), grade 1 had measurable effusion (n = 35), and grade 2 had large effusion (n = 13). Japanese Orthopedics Association (JOA) score, visual analog scale (VAS), and the Short-Form (SF)-36 scores were recorded preoperatively and 12 and 24 months postoperatively.

RESULTS

JOA score; VAS of low back pain, leg pain, and numbness; and SF-36 (physical component summary and mental component summary) scores did not differ significantly between the three groups in every terms (p = 0.921, 0.996, 0.950, 0.693, 0.374, 0.304, and 0.624, respectively, at final follow-up).

CONCLUSION

In the absence of radiographic instability, facet joint effusion has no effect on the outcome of less-invasive decompression surgery.

Utilizing the "Stable-to-be Vertebra" Saves Motion Segments in Growing Rods Treatment for Early-Onset Scoliosis

BACKGROUND

There is no consensus on the selection of distal instrumentation levels in growing rod surgery. Many surgeons utilize the stable zone of Harrington, but there is not overwhelming evidence to support this preference. The aim of this study was to determine the value of bending/traction radiographs in selection of distal instrumentation levels of a growing rod construct in children with idiopathic or idiopathic-like early-onset scoliosis (EOS).

METHODS

Twenty-three consecutive patients with idiopathic or idiopathic-like EOS who underwent growing rod surgery at 2 separate institutions between 2006 and 2011 were included. Lengthening procedures were performed periodically at 6-month intervals. Analyses were performed retrospectively for age at index surgery, follow-up period, and radiographic measurements. Lower instrumented levels, neutral vertebra, stable vertebrae (SV), and stable-to-be vertebrae (StbV) were identified on the preoperative radiographs. Coronal Cobb angles, tilt of lower instrumented vertebra (LIV) and LIV+1, and disk wedging under the LIV and LIV+1 were measured on the early postoperative and latest follow-up radiographs.

RESULTS

Average age at index surgery was 83.6 months. Mean follow-up period was 68.1 months. Initial analysis showed that the relationship of LIV to the StbV was a better predictive of LIV+1 tilt than the SV at the final follow-up. Therefore, the patients were grouped according to the relationship of the LIV to the StbV. LIV was the StbV in 9 patients, proximal to the StbV in 8 patients, and distal to the StbV in 6 patients. At the latest follow-up, tilt of LIV+1 exceeded 10 degrees in 7 of the 8 patients where LIV was proximal to the StbV, whereas only in 1 of 9 patients where LIV was StbV, and in none of the 6 patients where LIV was distal to the StbV. The data indicate that selection of the StbV as the LIV could spare an average of 1.8 vertebral segments when compared with the SV, as StbV is never distal but almost always proximal to the SV.

CONCLUSIONS

Choosing the StbV as the LIV saves motion segments and prevents distal adding on, while providing satisfactory deformity correction in idiopathic and idiopathic-like EOS.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Effects of Axial Torsion on Disc Height Distribution: An In Vivo Study

OBJECTIVES

Axial rotation of the torso is commonly used during manipulation treatment of low back pain. Little is known about the effect of these positions on disc morphology. Rotation is a three-dimensional event that is inadequately represented with planar images in the clinic. True quantification of the intervertebral gap can be achieved with a disc height distribution. The objective of this study was to analyze disc height distribution patterns during torsion relevant to manipulation in vivo.

METHODS

Eighty-one volunteers were computed tomography-scanned both in supine and in right 50° rotation positions. Virtual models of each intervertebral gap representing the disc were created with the inferior endplate of each "disc" set as the reference surface and separated into 5 anatomical zones: 4 peripheral and 1 central, corresponding to the footprint of the annulus fibrosus and nucleus pulposus, respectively. Whole-disc and individual anatomical zone disc height distributions were calculated in both positions and were compared against each other with analysis of variance, with significance set at P < .05.

RESULTS

Mean neutral disc height was 7.32 mm (1.59 mm). With 50° rotation, a small but significant increase to 7.44 mm (1.52 mm) (P < .0002) was observed. The right side showed larger separation in most levels, except at L5/S1. The posterior and right zones increased in height upon axial rotation of the spine (P < .0001), whereas the left, anterior, and central decreased.

CONCLUSIONS

This study quantified important tensile/compressive changes disc height during torsion. The implications of these mutually opposing changes on spinal manipulation are still unknown.

Weight-bearing three-dimensional computed tomography analysis of the forefoot in patients with flatfoot deformity

BACKGROUND

The recent classifications for posterior tibial tendon dysfunction (PTTD) stage II are based on forefoot deformity, but there is still no consensus regarding a detailed explanation of the clinical condition. The purposes of this study were to clarify the clinical condition of flatfoot deformity using three-dimensional (3D) computed tomography (CT) imaging under loading on both healthy and flat feet and to compare 3D movement of the forefoot in response to load.

METHODS

Ten volunteers and 10 PTTD stage II patients with symptomatic flatfoot deformity were examined. CT scans of 20 healthy and 20 flat feet were performed under non-loading and full weight-bearing conditions. Images of the tibia and foot arch bones (talus, calcaneus, navicular, and first and fifth metatarsal bones) were reconstructed into 3D models. Rotations of individual tarsal bone or metatarsal bone were described by the Eulerian angles.

RESULTS

Compared with healthy feet, flat feet experienced plantarflexion of the fifth metatarsal bone relative to the first metatarsal bone under loading conditions. We defined this phenomenon as synonymous with forefoot varus on the coronal plane.

CONCLUSIONS

The results of this study have clarified part of the clinical condition of the forefoot in flatfoot deformity and may have applications in basic research of the staging advancement and substage classification of PTTD.

Biomechanical Evaluation of Capsulotomy, Capsulectomy, and Capsular Repair on Hip Rotation

PURPOSE

To determine the effect of different types of capsulotomies on hip rotational biomechanical characteristics.

METHODS

Seven fresh-frozen cadaveric hip specimens were thawed and dissected, leaving the hip capsule and labrum intact. The femur was transected and potted, and each specimen was placed in a custom loading apparatus that allowed for adjustment of flexion, extension, and axial rotation of the femur. Six reflective infrared markers were attached to the specimens to track the motion of the femoral head with respect to the acetabulum in real time, and external rotation was produced by applying a torque of 10 Nm to the hip specimens. Data analysis was performed using the 3-dimensional position of the markers in space. The specimens were tested in neutral flexion and 40° of flexion in the following capsular states: intact, interportal capsulotomy, T-capsulotomy, repaired capsulotomy, and capsulectomy. Paired t tests and analysis of variance were used with an α value of .05 set as significant.

RESULTS

With the hip in neutral flexion, there was increased external rotation with a T-capsulotomy (91.1° ± 20.3°, P = .029) and capsulectomy (91.9° ± 19.6°, P = .015) compared with the intact hip (83.2° ± 20.5°). After complete repair of the T-capsulotomy (87.4° ± 20.6°), there was no significant difference in external rotation compared with the intact hip. No significant differences were seen between groups at 40° of hip flexion.

CONCLUSIONS

A T-capsulotomy showed significantly increased external rotation versus the intact and interportal capsulotomy states. The repaired T-capsulotomy restored the rotational profile back to the native state.

CLINICAL RELEVANCE

Many methods of capsular treatment during hip arthroscopy exist. Capsulotomy and capsulectomy do not restore the external rotation restraint of the hip back to its native state.