Changes in the Centers of Rotation in Different Prosthetic Segments Following Continuous Two-Level Cervical Disc Replacement: A Retrospective Study.

OBJECTIVE: To observe the short to medium-term therapeutic effects and radiological outcomes of adjacent two-level cervical spondylosis treated with artificial cervical disc replacement (ACDR) using Mobi-C and Bryan discs. To observe changes and discrepancies in the flexion-extension centers of rotation (FE-COR) of different ACDR segments. METHODS: Twenty-four patients undergoing 2-level (C4/5 and C5/6) ACDR were analyzed retrospectively (11 patients in the Mobi-C group and 13 patinents in the Bryan group). Clinical outcomes were assessed using modified Japanese Orthopedic Association (mJOA) score, Neck Disability Index (NDI), and visual analog scale (VAS). Preoperative and 2 years' follow-up radiographs were collected to compare total cervical spine curvature (C2-C7) range of motion (ROM), upper and lower ACDR segmental ROM, and the operated adjacent segmental ROM. The FE-COR of the ACDR segment was measured using the mid-plumb line method. The degree of disc degeneration in the adjacent segment were observed. RESULTS: At the 2 years' follow-up, in both group the mJOA score increased significantly, and the NDI, neck and upper extremity VAS scores decreased significantly compared with pre-operative (P<0.05). There were no significant statistical differences in post-operative scores between the two groups (P>0.05). The overall cervical ROM, the upper and lower segmental ROM at the 2 years' follow-up showed no significant statistical differences compared with the pre-operative period (P>0.05). There was no statistically significant difference in the adjacent segmental ROMs compared with the pre-operative period (P>0.05). Furthermore, the statistical analysis revealed no significant differences in the measurements of the ROM at each time points between the Mobi-C Group and the Bryan Group (P>0.05). There was no significant difference in the pre-operative FE-COR-X and FE-COR-Y of upper or lower ACDR segments between the two groups (P>0.05). At the 2 years' follow-up, there were significant differences both in FE-COR-X and FE-COR-Y between the two groups (P<0.05). For the Mobi-C group, in both the upper and lower segment, the FE-COR-X significantly increased compared with pre-operative (P<0.05), while the FE-COR-Y decreased compared with pre-operative (P<0.05). For the Bryan group, no significant changes were observed in the upper or lower segment in both FE-COR-X and FE-COR-Y compared with pre-operative (P>0.05). Fourty-eight adjacent segments (24 superior and 24 inferior segments) were included in the studies of ASD. Four segments showed imaging ASD (4/48, 8.33%) in 4 patients, of which 2 were mild, and 2 were moderate according to the grading criteria. Among them 2 were from the Mobi-C group and 2 were from the Brayn group. No severe imaging degeneration was observed. CONCLUSION: In continuous two-level cervical ACDR surgery, both Mobi-C and Bryan artificial cervical discs achieved satisfactory clinical outcomes in the short to medium term postoperatively. The FE-COR exhibited different trends of change. In the Mobi-C group, the FE-COR for both upper and lower segments shifted anteriorly and inferiorly, whereas in the Bryan group, whether upper or lower, the FE-COR remained closer to the pre-operative state. The changes in FE-COR did not significantly affect the short to medium term clinical outcomes postoperatively.

Analysis of Variation in Sagittal Curvature of the Femoral Condyles.

In designing femoral components, which restore native (i.e., healthy) knee kinematics, the flexion-extension (F-E) axis of the tibiofemoral joint should match that of the native knee. Because the F-E axis is governed by the curvature of the femoral condyles in the sagittal plane, the primary objective was to determine the variation in radii of curvature. Eleven high accuracy three-dimensional (3D) femur models were generated from ultrahigh resolution CT scans. The sagittal profile of each condyle was created. The radii of curvature at 15 deg increments of arc length were determined based on segment circles best-fit to ±15 deg of arc at each increment. Results were standardized to the radius of the best-fit overall circle to 15 deg-105 deg for the femoral condyle having a radius closest to the mean radius. Medial and lateral femoral condyles exhibited multiradius of curvature sagittal profiles where the radius decreased at 30 deg flexion by 10 mm and at 15 deg flexion by 8 mm, respectively. On either side of the decrease, radii of segment circles were relatively constant. Beyond the transition angles where the radii decreased, the anterior-posterior (A-P) positions of the centers of curvature varied 4.8 mm and 2.3 mm for the medial and lateral condyles, respectively. A two-radius of curvature profile approximates the radii of curvature of both native femoral condyles, but the transition angles differ with the transition angle of the medial femoral condyle occurring about 15 deg later in flexion. Owing to variation in A-P positions of centers of curvature, the F-E axis is not strictly fixed in the femur.

Effect of Posterior Cruciate Ligament Resection on Gap Balancing in Robot-assisted Total Knee Arthroplasty.

OBJECTIVE: Retention or sacrifice of the posterior cruciate ligament (PCL) is one of the most controversial issues while performing total knee arthroplasty (TKA). This study aimed to evaluate the impact of PCL resection on flexion-extension gaps, femoral component rotation, and bone resection amounts during robot-assisted TKA. METHODS: This prospective study included 40 patients with knee osteoarthritis who underwent robot-assisted posterior-stabilized (PS) TKA between September 2021 and February 2022. Of the patients, 75% were women (30/40) with a mean age and BMI of 72.6 years and 27.4 kg/m2, respectively. The guidance module and camera stand assembly were used to capture gaps before and after PCL resection. Measurements of femoral component rotation and bone resection amounts were made in cruciate-retaining (CR) TKA mode and PS-TKA mode. RESULTS: After PCL resection, the mean change in the medial and lateral compartments of flexion gaps increased by 2.0 and 0.6 mm, respectively (p < 0.001). Compared with the CR-TKA mode group, the bone resection amounts of the medial posterior condyle and the lateral posterior condyle in the PS-TKA mode group decreased by 2.0 ± 1.1 and 1.1 ± 1.1 mm, respectively, and the external rotation of the femoral prosthesis relative to the posterior condylar axis and trans-epicondylar line was reduced by 1.0° ± 1.3° and 1.2° ± 1.6°, respectively (p < 0.001). CONCLUSION: The release of the PCL did not affect the extension gap, but significantly increased the flexion gap. Moreover, the increases in the medial flexion gap were greater than those of the lateral flexion gap. After PCL resection, less external rotation of the femoral prosthesis and fewer bone cuts of the posterior femur were needed in PS-TKA.

The Association between "Knee Movement" Method and Traditional Radiograph Positioning Procedure with the Incidence of True Lateral Knee Radiograph Achieved.

Introduction: This study aimed to find the association between the Knee Movement or KM method versus the traditional lateral knee radiograph positioning procedure and the incidence of true lateral knee radiographs achieved. Materials and methods: A cross-sectional study of patients with knee problems that underwent lateral knee radiograph using the knee movement method (KM method), starting from March 2022 until August 2022. Fifty knee radiograph results using the KM method (KM group) were compared to retrospective data from fifty knee radiograph from the patients before March 2022 using the traditional method of lateral knee radiograph as the control (TM group). The data were analysed using the Chi-Square test to see if the KM method is associated with more true lateral knee radiograph results achieved compared to the traditional procedure. Results: Fifty patients in the KM method group had 80% (n=40) true lateral knee radiographs and 20% (n=10) untrue lateral knee radiographs, while in the Traditional Procedure group from the retrospective data of 50 patients had 44% (n=22) true lateral knee radiographs and 56% (n=28) untrue lateral knee radiographs (P<0.05). There is no significant association between the type of procedure applied with the types of error (P=0.432). Nevertheless, it helps us as it gives a gross picture that most of the errors are under-rotation of the knee, either from the KM method Group 90% (n=9) or the Traditional procedure Group 79% (n=22). Conclusion: The KM method was associated with achievement of a more true and accurate lateral knee radiograph. Additional studies with a larger sample should be done to evaluate the reliability of this method.

In vivo three-dimensional kinematic comparison of normal knees between flexion and extension activities.

Background/Objective: Normal knee kinematics during flexion and extension activities over the whole range of motion remains unknown. This study aimed to clarify in vivo kinematics during knee flexion and extension activities of normal knees by comparing continuous flexion and extension activities up to a high flexion angle. Methods: Twenty knees of 10 Japanese volunteers were enrolled in this study. Each volunteer performed a continuous squatting motion under fluoroscopy, and a two- or three-dimensional registration technique was used. Rotation and anteroposterior translation of the medial and lateral sides of the femur relative to the tibia at each flexion angle were evaluated. Results: Femoral external rotation was significantly smaller from 10° to 40° flexion during extension activities than during flexion activities. However, the femoral external rotation was larger from 120° to 130° flexion during extension activities than during flexion activities. From 10° to 60° of flexion, the medial side was significantly more posteriorly located during extension activities than during flexion activities. Furthermore, the lateral side was significantly more posteriorly located at 130° of flexion during extension activities than during flexion activities. Conclusion: In vivo kinematics of normal knees during extension activities differ from those during flexion activities in early and high flexion.

Coupled rotation patterns in cervical spine axial rotation can change when the head is kept level.

The biomechanical literature describes axial rotation occurring coupled with lateral bending and flexion in the cervical spine. Since the head is kept level during some activities of daily living, we set out to investigate the changes in total and segmental motion that occur when a level gaze constraint is applied to cadaveric cervical spine specimens during axial rotation. 1.5Nm of left and right axial rotation moment was applied to sixteen C2-T1 cadaveric specimens with C2 unconstrained and C2 constrained to simulate level gaze. Overall and segmental motions were determined using optoelectronic motion measurement and specimen-specific kinematic modeling. Without a kinematic constraint on C2, motions were as described in the literature; namely, flexion and lateral bending to the same side as axial rotation. Keeping C2 level reduced that total axial rotation range of motion of the specimens. Changes were also produced in segmental coupled rotation in all specimens. The observed changes included completely opposite coupled motion than in the uncoupled specimens, and traditional coupled behavior at one load extreme and the opposite at the other extreme. Constraining C2 during axial rotation to simulate level gaze can produce coupled motion that differs from the classically described flexion and lateral bending to the same side as axial rotation. Statement of Clinical Significance: Activities of daily living that require the head to be kept level during axial rotation of the cervical spine may produce segmental motions that are quite different from the classically described motions with implications for biomechanical experiments and implant designers.

Dynamic Flexion-Extension Magnetic Resonance Imaging of the Cervical Spine: An Evolutionary Tool for Diagnosis and Management of Cervical Spondylotic Myelopathy.

Dynamic problems need dynamic solutions. High motility of the cervical spine causes a common age-related degenerative condition called cervical spondylotic myelopathy (CSM), manifested by neurological impairments. An accurate and reliable diagnosis of CSM is crucial for determining appropriate management strategies. Traditional static magnetic resonance imaging (MRI) has been the gold standard for imaging CSM; however, it may not fully capture dynamic changes during neck movement. Dynamic flexion-extension (DFE) MRI is an innovative imaging technique that allows for real-time visualization of cervical spine motion. This review article aims to scrutinize the role of DFE MRI in assessing CSM, its added value to clinical implementations, and its limitations. Finally, by addressing the knowledge gaps, this survey sheds light on the road ahead to incorporate DFE MRI into a standard version of the practice.

Changes in the centre of rotation and the anterior bone loss of the vertebral body in Mobi-C artificial disc replacement segments after cervical hybrid surgery: a retrospective study.

OBJECTIVE: To examine the short-term efficacy and imaging results of using the Mobi-C in cervical hybrid surgery on 2-level cervical spondylolisthesis. To observe post-operative changes in the flexion-extension centre of rotation (FE-COR) and anterior bone loss (ABL) of the anterior cervical disc replacement (ACDR) segment. METHODS: Forty-two patients (20 males and 22 females, aged 42‒67 years) who underwent cervical hybrid surgery were retrospectively analysed. Their ACDR segment used Mobi-C, and the fusion segment used ROI-C, with a follow-up of 25‒42 months (31.1 ± 4.8 months). The modified Japanese Orthopaedic Association (mJOA) score, Neck Disability Index (NDI), and visual analogue scale (VAS) were used to assess clinical outcomes. Pre-operative, 6-month post-operative, and final follow-up radiographs were collected to compare total cervical spine curvature (C2-C7), curvature of the operated segments, range of motion (ROM) in the total cervical spine, operated segmental ROM, ACDR segmental ROM, and operated adjacent segmental ROM. The height of the superior articular process (HSAP), the orientation of zygapophyseal joint spaces (OZJS), and the length of the superior articular surface (LSAS) were measured. The FE-COR of the ACDR segment was measured using the mid-plumb line method. The translation distance of the Mobi-C was measured. The degree of disc degeneration in the adjacent segment, bony fusion of the ACDF segment, and ABL of the upper and lower vertebra of the ACDR segment were observed. RESULTS: In our group, all patients have shown improvements in their postoperative mJOA, NDI, and VAS scores. Overall cervical ROM and surgical segmental ROM decreased (P < 0.05). However, there was no significant decrease in ACDR segmental ROM and upper or lower adjacent segmental ROM compared with pre-operatively (P > 0.05). For FE-COR-X, only the last follow-up compared with pre-surgery showed statistical significance (46.74 ± 7.71% vs. 50.74 ± 6.92%, P < 0.05). For FE-COR-Y, the change was statistically significant at both 6 months post-operation and the final follow-up compared to pre-operation (45.37% ± 21.11% vs. 33.82% ± 10.87%, 45. 37% ± 21.11% vs. 27.48% ± 13.58%, P < 0.05). No significant difference in the Mobi-C translation distance was observed (P > 0.05). Moreover, the difference in HSAP was not statistically significant at each node (P > 0.05). The OZJS and LSAS were significantly different at the final follow-up compared to the pre-operative period (P < 0.05). All the ACDF segments were observed in a stable condition at the final follow-up. Furthermore, 9 of the adjacent segments showed imaging ASD (9/82, 10.98%), and all were present at the last follow-up, of which 6 were mild, and 3 were moderate. Twenty of the 42 Mobi-C segments had no significant ABL (grade 0) 6 months post-operatively (47.62%). Sixteen cases (38.10%) showed mild ABL (grade 1), and 6 cases (14.28%) showed moderate ABL (grade 2). No severe ABL occurred. CONCLUSION: The cervical hybrid surgery using Mobi-C artificial cervical discs can achieve satisfactory results. The Mobi-C segmental FE-COR-X shows a slow forward shift trend, and FE-COR-Y drops noticeably within 6 months post-surgery before stabilizing. It's common to see mild to moderate ABL after cervical hybrid surgery using Mobi-C, and significant progression is unlikely in the short term. Furthermore, changes in the FE-COR after hybrid surgery in the Mobi-C segment might not affect clinical outcomes.

Pelvic flexion/extension and its impact on functional acetabular alignment and stability following total hip replacement.

PURPOSE: Dislocation following total hip arthroplasty (THA) remains a significant clinical problem and can occur even with optimal implant alignment. We hypothesized that different patterns of pelvic flexion/extension (PFE) during daily activities may influence acetabular alignment and contribute to impingement and instability following THA. Recently, there has been an increased interest in spinopelvic alignment and its impact on THA. Therefore, this study aimed to identify different patterns of PFE that could be predictive of instability following THA. METHODS: A range of motion (ROM) simulator was used to demonstrate the effects of different patterns of PFE on ROM and impingement. The findings were applied to PFE measurements obtained from 84 patients in standing and sitting positions. RESULTS: Three different categories of PFE were identified: normal, hypermobile, and stiff. ROM simulator revealed that changes in PFE had affected ROM and impingement significantly. Patients in the stiff pelvis category, even with "optimal" implant alignment, were more susceptible to implant impingement. CONCLUSIONS: The different patterns of PFE during daily activities could affect acetabular alignment and stability following THA. We propose a classification system that can identify different types of PFE and predict their effects on the stability of prostheses following THA. Hence, we believe that patients with unfavorable PFE may require modified cup alignment.

A Method for Quantifying Back Flexion/Extension from Three Inertial Measurement Units Mounted on a Horse's Withers, Thoracolumbar Region, and Pelvis.

Back mobility is a criterion of well-being in a horse. Veterinarians visually assess the mobility of a horse's back during a locomotor examination. Quantifying it with on-board technology could be a major breakthrough to help them. The aim of this study was to evaluate the accuracy of a method of quantifying the back mobility of horses from inertial measurement units (IMUs) compared to motion capture (MOCAP) as a gold standard. Reflective markers and IMUs were positioned on the withers, eighteenth thoracic vertebra, and pelvis of four sound horses. The horses performed a walk and trot in straight lines and performed a gallop in circles on a soft surface. The developed method, based on the three IMUs, consists of calculating the flexion/extension angle of the thoracolumbar region. The IMU method showed a mean bias of 0.8° (±1.5°) (mean (±SD)) and 0.8° (±1.4°), respectively, for the flexion and extension movements, all gaits combined, compared to the MOCAP method. The results of this study suggest that the developed method has a similar accuracy to that of MOCAP, opening up possibilities for easy measurements under field conditions. Future studies will need to examine the correlations between these biomechanical measures and clinicians' visual assessment of back mobility defects.

Machine learning for lumbar and pelvis kinematics clustering.

Clustering algorithms such as k-means and agglomerative hierarchical clustering (HCA) may provide a unique opportunity to analyze time-series kinematic data. Here we present an approach for determining number of clusters and which clustering algorithm to use on time-series lumbar and pelvis kinematic data. Cluster evaluation measures such as silhouette coefficient, elbow method, Dunn Index, and gap statistic were used to evaluate the quality of decision making. The result show that multiple clustering evaluation methods should be used to determine the ideal number of clusters and algorithm suitable for clustering time-series data for each dataset being analyzed.

Cervical Disc Arthroplasties Fail to Maintain Physiological Kinematics Under Lateral Eccentric Loads.

STUDY DESIGN: In vitro human cadaveric biomechanical analysis. OBJECTIVES: Optimization of prostheses for cervical disc arthroplasties (CDA) reduces the risk of complications. The instantaneous helical axis (IHA) is a superior parameter for examining the kinematics of functional spinal units. There is no comprehensive study about the IHA after CDA considering all 3 motion dimensions. METHODS: Ten human functional spinal units C4-5 (83.2 ± 7.9 yrs.) were examined with an established measuring apparatus in intact conditions (IC), and after CDA, with 2 different types of prostheses during axial rotation, lateral bending, and flexion/extension. Eccentric preloads simulated strains. The IHA orientation and its position at the point of rest (IHA0-position) were analyzed. RESULTS: The results confirmed the existing data for IHA in IC. Lateral preloads showed structural alterations of kinematics after CDA: During axial rotation and lateral bending, the shift of the IHA0-position was corresponding with the lateral preloads' applied site in IC, while after CDAs, it was vice versa. During lateral bending, the lateral IHA orientation was inclined, corresponding with the lateral preloads' applied site in the IC and oppositely after the CDAs. During flexion/extension, the lateral IHA orientation was nearly vertical in the IC, while after CDA, it inclined, corresponding with the lateral preloads' applied site. The axial IHA orientation rotated to the lateral preloads' corresponding site in the IC; after CDA, it was vice versa. CONCLUSION: Both CDAs failed to maintain physiological IHA characteristics under lateral preloads, revealing a new aspect for improving prostheses' design and optimizing their kinematics.

A Soft-Tissue Landmark to Assess Humeral Component Rotation in Total Elbow Arthroplasty.

HYPOTHESIS: Assessing the rotational alignment of the humeral component during total elbow arthroplasty is dependent upon bony landmarks that can be absent or altered in cases of distal humerus fractures, revision arthroplasty, severe bone loss, or deformity. We hypothesize that the intermuscular septum can be used as a reliable soft-tissue landmark to set the rotation of the humeral component intra-operatively when previously described bony landmarks are not reliable or present. MATERIALS AND METHODS: Forty-eight unpaired cadaveric human subjects (mean age and standard deviation 63 ± 12 years; 24 males, 24 females) underwent computed tomography (CT) scans. The geometric centers of the trochlea and capitellum were assessed, and the line through these two points was set as the flexion-extension axis (FEA) of the elbow. The intermuscular septum axis (IMSA) was drawn proximal to the olecranon fossa and at least 4 cm proximal to the most distal point of the articular surface, where the posterior humeral cortex was flat. The angles between the FEA and IMSA were calculated and compared using a two-tailed t-test. Regression analysis was used to assess the inter- and intra-observer reliability of the IMSA. RESULTS: The IMSA was externally rotated 10.3° ± 2.8 compared to the FEA (p < 0.001 and confidence interval (CI) of 2.8 with α set to 0.01). The inter- and intra-observer reliability of the IMSA was high, with an R-value of 0.91 and 0.97, respectively. CONCLUSIONS: The intermuscular septum can be used as a soft-tissue landmark to set humeral component rotation and is 10.3° externally rotated with respect to the FEA of the ulnohumeral joint.

Utility of Seated Lateral Radiographs in the Diagnosis and Classification of Lumbar Degenerative Spondylolisthesis.

STUDY DESIGN: Retrospective cohort study. PURPOSE: Our goal was to determine which radiographic images are most essential for degenerative spondylolisthesis (DS) classification and instability detection. OVERVIEW OF LITERATURE: The heterogeneity in DS requires multiple imaging views to evaluate vertebral translation, disc space, slip angle, and instability. However, there are several restrictions on frequently used imaging perspectives such as flexion-extension and upright radiography. METHODS: We assessed baseline neutral upright, standing flexion, seated lateral radiographs, and magnetic resonance imaging (MRI) for patients identified with spondylolisthesis from January 2021 to May 2022 by a single spine surgeon. DS was classified by Meyerding and Clinical and Radiographic Degenerative Spondylolisthesis classifications. A difference of >10° or >8% between views, respectively, was used to characterize angular and translational instability. Analysis of variance and paired chi-square tests were utilized to compare modalities. RESULTS: A total of 136 patients were included. Seated lateral and standing flexion radiographs showed the greatest slip percentage (16.0% and 16.7%), while MRI revealed the lowest (12.2%, p <0.001). Standing flexion and lateral radiographs when seated produced more kyphosis (4.66° and 4.97°, respectively) than neutral upright and MRI (7.19° and 7.20°, p <0.001). Seated lateral performed similarly to standing flexion in detecting all measurement parameters and categorizing DS (all p >0.05). Translational instability was shown to be more prevalent when associated with seated lateral or standing flexion than when combined with neutral upright (31.5% vs. 20.2%, p =0.041; and 28.1% vs. 14.6%, p =0.014, respectively). There were no differences between seated lateral or standing flexion in the detection of instability (all p >0.20). CONCLUSIONS: Seated lateral radiographs are appropriate alternatives for standing flexion radiographs. Films taken when standing up straight do not offer any more information for DS detection. Rather than standing flexion-extension radiographs, instability can be detected using an MRI, which is often performed preoperatively, paired with a single seated lateral radiograph.

Measurement of interspinous motion in dynamic cervical radiographs using a deep learning-based segmentation model.

OBJECTIVE: Interspinous motion (ISM) is a representative method for evaluating the functional fusion status following anterior cervical discectomy and fusion (ACDF) surgery, but the associated measuring difficulty and potential errors in the clinical setting remain concerns. The aim of this study was to investigate the feasibility of a deep learning-based segmentation model for measuring ISM in patients who underwent ACDF surgery. METHODS: This study is a retrospective analysis of flexion-extension dynamic cervical radiographs from a single institution and a validation of a convolutional neural network (CNN)-based artificial intelligence (AI) algorithm for measuring ISM. Data from 150 lateral cervical radiographs from the normal adult population were used to train the AI algorithm. A total of 106 pairs of dynamic flexion-extension radiographs from patients who underwent ACDF at a single institution were analyzed and validated for measuring ISM. To evaluate the agreement power between human experts and the AI algorithm, the authors assessed the interrater reliability using the intraclass correlation coefficient and root mean square error (RMSE) and performed a Bland-Altman plot analysis. They processed 106 pairs of radiographs from ACDF patients into the AI algorithm for autosegmenting the spinous process created using 150 normal population radiographs. The algorithm automatically segmented the spinous process and converted it to a binary large object (BLOB) image. The rightmost coordinate value of each spinous process from the BLOB image was extracted, and the pixel distance between the upper and lower spinous process coordinate value was calculated. The AI-measured ISM was calculated by multiplying the pixel distance by the pixel spacing value included in the DICOM tag of each radiograph. RESULTS: The AI algorithm showed a favorable prediction power for detecting spinous processes with an accuracy of 99.2% in the test set radiographs. The interrater reliability between the human and AI algorithm of ISM was 0.88 (95% CI 0.83-0.91), and its RMSE was 0.68. In the Bland-Altman plot analysis, the 95% limit of interrater differences ranged from 0.11 to 1.36 mm, and a few observations were outside the 95% limit. The mean difference between observers was 0.02 ± 0.68 mm. CONCLUSIONS: This novel CNN-based autosegmentation algorithm for measuring ISM in dynamic cervical radiographs showed strong agreement power to expert human raters and could help clinicians to evaluate segmental motion following ACDF surgery in clinical settings.

Evaluation of segmental mobility in patients with lumbar spondylolisthesis : A comparison of images from standing flexion-extension and standing/supine slippage.

PURPOSE: To evaluate segmental mobility with degenerative lumbar spondylolisthesis (DLS), upright lateral flexion-extension radiographs (FE) are widely used. However, some authors have described that a combination of lateral radiographs in the standing position and supine sagittal image (SS) reveal more segmental mobility than FE. The purpose of this study was to investigate the optimal method for evaluating segmental mobility with DLS. METHODS: We included 92 consecutive Japanese patients diagnosed with DLS. Sagittal translation (ST) determined by FE and SS were compared. Pathological instability was defined as ST more than 8% of the upper vertebra. Patients were divided into those diagnosed with pathological instability in FE (PI-FE) and those diagnosed with SS (PI-SS), and lumbar lordosis (LL) in the standing position in each group were compared. RESULTS: ST in FE was significantly greater than in SS. Of 92 patients, 31 had pathological instability in FE or SS ; 17 patients had PI-FE, and 10 patients had PI-SS. LL in the standing position in PI-FE was significantly smaller than in PI-SS. CONCLUSIONS: ST in FE was greater than that in SS, contrary to previous studies' reports on Caucasians. Since Japanese individuals have smaller LL than Caucasians, FE tends to reveal more segmental mobility than SS. J. Med. Invest. 70 : 135-139, February, 2023.

Novel Grading Scales for Static and Flexion-Extension Magnetic Resonance Imaging in Patients with Cervical Spondylotic Myelopathy.

BACKGROUND: Flexion-extension magnetic resonance imaging (MRI) has potential to identify cervical pathology not detectable on conventional static MRI. Our study evaluated standard quantitative and novel subjective grading scales for assessing the severity of cervical spondylotic myelopathy in dynamic sagittal MRI as well as in static axial and sagittal images. METHODS: Forty-five patients underwent both conventional and flexion-extension MRI prior to anterior cervical discectomy and fusion from C4 through C7. In addition to measuring Cobb angles and cervical canal diameter, grading scales were developed for assessment of vertebral body translation, loss of disc height, change in disc contour, deformation of cord contour, and cord edema. Data were collected at all levels from C2-C3 through C7-T1. Variations in measurements between cervical levels and from flexion through neutral to extension were assessed using Mann-Whitney, Kruskal-Wallis, and two-way ANOVA tests. RESULTS: Cervical canal diameter, vertebral translation, and posterior disc opening changed significantly from flexion to neutral to extension positions (P < 0.01). When comparing operative versus nonoperative cervical levels, significant differences were found when measuring sagittal cervical canal dimensions, vertebral translation, and posterior disc opening (P < 0.01). Degenerative loss of disc height, disc dehydration, deformation of ventral cord contour, and cord edema were all significantly increased at operative levels versus nonoperative levels (P < 0.01). CONCLUSIONS: Flexion-extension MRI demonstrated significant changes not available from conventional MRI. Subjective scales for assessing degenerative changes were significantly more severe at levels with operative cervical spondylotic myelopathy. The utility of these scales for planning surgical intervention at specific and adjacent levels is currently under investigation.

The flexion-extension gap is predictive of patient-reported outcome measures after cruciate-retaining total knee arthroplasty.

BACKGROUND: We aimed to evaluate the association between the flexion-extension gap difference and patient-reported outcome measures after total knee arthroplasty (TKA). METHODS: This was a retrospective case-control study of 60 cruciate-retaining single-radius TKAs. Soft tissue balancing was measured using an offset seesaw tensioner and centre-type digital knee balancer under joint distraction forces of 20-50 lbf and 1.5 times body mass index (1.5 BMI). At the last follow up of 2.0-6.5 (mean, 4.5) years postoperatively, patients were asked if they perceived their knee joint as 'natural' (26 knees) or 'artificial' (34 knees). Age, sex, and the flexion-extension gap were compared between the two groups. A receiver operating characteristic curve was used to determine cut-off values of variables predictive of a natural joint perception. RESULTS: Natural joint perception was associated with a greater flexion-extension gap difference under a distraction force of 1.5 BMI (P = 0.016), higher knee function (Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, P = 0.019), and quality of life (EuroQol 5-Dimension, P = 0.029). A gap difference of 0.95 mm under 1.5 BMI distraction predicted a natural joint perception post-TKA (sensitivity, 97.1%; specificity, 88.5%). Using a gap threshold of 1.0 mm under a 1.5 BMI distraction force yielded significant between-group differences in postoperative flexion (P = 0.040), satisfaction (P = 0.043), knee joint function (P < 0.001), quality of life (P = 0.032), and posterior femoral condylar offset (P = 0.037) CONCLUSION: A flexion-extension gap difference ≥1.0 mm under a distraction force of 1.5 BMI predicted superior outcomes, including patient satisfaction, after cruciate-retaining TKA. It was suggested that posterior femoral condylar offset could influence this finding.

Construct validity of gymnastics-specific assessment on the neuromuscular function of shoulder flexor and extensor muscles.

The present study examined the construct validity of gymnastics-specific measurements of the shoulder flexor and extensor neuromuscular function. Fifteen male gymnasts and 18 male physical education (PE) students participated voluntarily. The electromyogram (EMG) of 3 flexor and 3 extensor shoulder muscles was assessed during isometric (45, 90, and 135º) and isokinetic (concentric and eccentric 60, 180, and 300º/s) shoulder flexion/extension. Peak torque (PT) and neuromuscular function in terms of neuromuscular efficiency (NME, i.e. torque to EMG ratio) and antagonist/agonist coactivation index were evaluated. The construct validity of the measurements was supported by the ability to discriminate between gymnasts and physical education (PE) students, taking into consideration the shoulders' neuromuscular function parameters (37%-57% of the variability explained). After accounting for the limitations of the study, these findings may assist gymnastics coaches and researchers to develop and evaluate more effective training methods for athletes related to shoulder joint physiological characteristics and level of expertise.