In vivo measurement of distance between scapular neck and polyethylene insert during active external rotation in shoulders with Grammont type reverse prosthesis.

BACKGROUND: Scapular notching is a frequently observed complication after reverse shoulder arthroplasty. Impingement of the humeral plastic insert against the scapular neck is believed to be the cause of notching. There have been no in vivo studies that analyzed the positional relationship between the scapular neck and humeral insert. The purpose of this study was to measure the distance between the scapular neck and insert in shoulders with Grammont-type prostheses during active external rotation at the side. METHODS: Eighteen shoulders with Grammont-type prostheses were enrolled in this study. There were 13 males and 5 females, and the mean age at surgery was 74 years (range, 63-91). Fluoroscopic images were recorded during active external rotation at the side from maximum internal to external rotation at an average of 14 months (range, 7-24) after surgery. Implant kinematics were determined with three-dimensional models of the implants and fluoroscopic images using model-image registration techniques. Based on the implant kinematics, the closest distance between the scapular neck and insert was computed at each 5° increment of glenohumeral internal/external rotation. RESULTS: Mean glenohumeral abduction during rotation was 17°-22°. The mean distance between the neck and insert was approximately 1 mm throughout the activity. The separation distance tended to narrow with arm external rotation, but the change was not significant. INTERPRETATION: The small distance between the scapular neck and insert in early post-operative reverse shoulder arthroplasty patients may be associated with the high incidence of scapular notching in Grammont-type prostheses.

In vivo kinematics of early-stage osteoarthritic knees during pivot and squat activities.

Kinematic changes have been shown to accompany severe knee osteoarthritis, but no studies have analyzed early-stage osteoarthritic knee kinematics in the transverse plane during functional activities. The purpose of this study was to analyze kinematics of early-stage osteoarthritic knees using model registration techniques. Fifteen early-stage osteoarthritic knees from eight females with a mean age of 52 years old (range, 43-57years old) were involved in this study. A radiologist confirmed with plain radiographs that knees had Kellgren-Lawrence grade-1 or -2 arthritic changes. Fluoroscopic images of squat and pivot activities were recorded for each subject. Three-dimensional surface models of the distal femur and proximal tibia were created from CT images, and anatomic coordinate systems were embedded in each model. The three-dimensional position and orientation of the femur and the tibia were determined using model-image registration techniques, and tibial anteroposterior translation and internal/external rotation relative to the femur were calculated. The contact points of the medial and lateral femoral condyle were also computed. Compared to healthy knees, osteoarthritic knees showed lateral contact points that were significantly shifted anteriorly in both pivot (P<0.001) and squat (P=0.001) activities and greater tibial external rotation in pivot activity (P=0.007). The medial contact point location was similar to healthy knees, but the amount of anteroposterior translation was smaller (P<0.001). These kinematic changes might change stress distributions in the medial compartment during weight-bearing activities. The changes in kinematics possibly have some influence on initiation or progression of knee osteoarthritis.

In vivo 3D analysis of clavicular kinematics during scapular plane abduction: comparison of dominant and non-dominant shoulders.

The purpose of this study was to evaluate side-to-side differences in three-dimensional clavicle kinematics in normal shoulders during dynamic scapular plane elevation using model-image registration techniques. Twelve healthy males with a mean age of 32 years (range, 27-36 years old) were enrolled in this study. Clavicle rotations were computed with bilateral fluoroscopic images and CT-derived bone models using model-image registration techniques and compared between dominant and nondominant shoulders. There was no difference in retraction between both shoulders. The clavicle in dominant shoulders was less elevated during abduction than in nondominant shoulders (P=0.03). Backward rotation angles of dominant shoulders were significantly smaller than those of nondominant shoulders throughout the activity (P=0.03). Clavicular kinematics during scapular plane abduction were different according to hand-dominance.

Dynamic in vivo glenohumeral kinematics during scapular plane abduction in healthy shoulders.

STUDY DESIGN: Controlled laboratory study. OBJECTIVES: To measure superior/inferior translation and external rotation of the humerus relative to the scapula during scapular plane abduction using 3-D/2-D model image registration techniques. BACKGROUND: Kinematic changes in the glenohumeral joint, including excessive superior translation of the humeral head and inadequate external rotation of the humerus, are believed to be a possible cause of shoulder impingement. Although many researchers have analyzed glenohumeral kinematics with various methods, few articles have assessed dynamic in vivo glenohumeral motion. METHODS: Twelve healthy males with a mean age of 32 years (range, 27-36 years) were enrolled in this study. Fluoroscopic images of the dominant shoulder during scapular plane elevation were taken, and computed tomography-derived 3-D bone models were matched with the silhouette of the bones in the fluoroscopic images using 3-D/2-D model image registration techniques. The kinematics of the humerus relative to the scapula were determined using Euler angles. RESULTS: On average, there was 2.1 mm of initial humeral translation in the superior direction from the starting position to 105° of humeral elevation. Subsequently, an average of 0.9 mm of translation in the inferior direction occurred between 105° and maximum arm elevation. The average amount of external rotation of the humerus was 14° from the starting position to 60° of humeral elevation. The humerus then rotated internally an average 9° by the time the shoulder reached maximum elevation. These changes in superior/inferior translation and external/internal rotation were statistically significant (P<.001 and P = .001, respectively), based on 1-way repeated-measures analysis of variance. CONCLUSION: The observed glenohumeral translations and rotations characterize healthy shoulder function and serve as a preliminary foundation for quantifying pathomechanics in the presence of glenohumeral joint disorders.

Comparison of MRI-based assessment systems for osteoarthritic knees: the irregularity index system and WORMS.

PURPOSE: Several MRI-based evaluation systems for osteoarthritis (OA) of the knee have been developed. Among them the whole-organ magnetic resonance imaging score (WORMS), which evaluates the status of the entire knee joint, appears to be representative. We developed an irregularity index system to measure irregularities of the contours of the femoral condyle on MRI. Only the contour of the condyle was assessed by the irregularity index, whereas several items comprising the knee joint were taken into account by WORMS. This study compared the irregularity index and WORMS in terms of their correlations with clinical scores. METHODS: Thirty-one medial-type OA knees were studied. Kellgren-Lawrence grading was used for X-ray grading: 8 were grade II, 11 were grade III, and 12 were grade IV. Japanese Orthopaedic Association scores and Japanese knee osteoarthritis measure scores were used for clinical assessments. We determined the correlations between MRI-based assessment scores and clinical scores. RESULTS: Both the irregularity index and WORMS exhibited positive correlations with these clinical scores. The irregularity index was associated with bone cysts of the medial compartment and menisci in the articular features of WORMS. CONCLUSIONS: These MRI-based methods are useful for evaluating OA severity. However, the irregularity index may have advantages over WORMS because of its semi-automatic features.

In vivo 3-dimensional analysis of scapular kinematics: comparison of dominant and nondominant shoulders.

BACKGROUND: Alterations in scapular motion frequently are seen in association with various shoulder disorders. It is common clinically to compare the pathological shoulder with the contralateral shoulder, in spite of arm dominance, to characterize the disorder. However, there have been few articles that test the underlying assumption that dominant and nondominant shoulders exhibit comparable dynamic kinematics. The purpose of this study was to compare the 3-dimensional (3-D) scapular kinematics of dominant and nondominant shoulders during dynamic scapular plane elevation using 3-D-2-D (2-dimensional) registration techniques. MATERIALS AND METHODS: Twelve healthy males with a mean age of 32 years (range, 27-36) were enrolled in this study. Bilateral fluoroscopic images during scapular plane elevation and lowering were taken, and CT-derived 3-D bone models were matched with the silhouette of the bones in the fluoroscopic images using 3-D-2-D registration techniques. Angular values of the scapula and scapulohumeral rhythm were compared between dominant and nondominant shoulders with statistical analysis. RESULTS: There was a significant difference in upward rotation angles between paired shoulders (P < .001), while significant differences were not found in the other angular values and scapulohumeral rhythm. The dominant scapulae were 10° more downwardly rotated at rest and 4° more upwardly rotated during elevation compared to the nondominant scapulae. DISCUSSION/CONCLUSION: Scapular motion was not the same between dominant and nondominant arms in healthy subjects. The dominant scapula was rotated further downward at rest and reached greater upward rotation with abduction. These differences should be considered in clinical assessment of shoulder pathology.

In vivo 3D kinematics of normal forearms: analysis of dynamic forearm rotation.

BACKGROUND: Forearm rotation is an indispensable activity of daily living and comprises complex motions with rotational and translational components. It is thought that changes in these motions with injury or disease may affect diagnostic indices. Several studies have assessed in vivo forearm kinematics with static conditions, but dynamic forearm kinematics have not yet been reported. The purpose of this study was to analyze forearm kinematics during dynamic rotation using radiographic 3D-2D registration methods. METHODS: Ten forearms of five healthy males with the mean age of 37 years old were enrolled. Lateral fluoroscopic images were taken during forearm rotation from maximum supination to maximum pronation with their elbows flexed to approximately 45°. Geometric bone models were created from CT scans of the humerus, the radius and the ulna. Three-dimensional kinematics were determined using 3D-2D model registration techniques with the images and models, and the arc of axial rotation of the radius, volar/dorsal translation of the ulna at the distal radioulnar joint and rotation axis of forearm were computed. FINDINGS: The radial rotation arc was 157°. The ulna translated 3.9 mm (SD 1.5mm) dorsally during activity. The rotation axis of the forearm passed through the center of the radial head and the ulnar head at the 1.9 mm (SD 0.7 mm) posterior from its geometric centroid. INTERPRETATION: The posteriorly deviated rotation axis at the ulnar head may result in the ulnar head translating dorsally during pronation. These data provide a basis for objective assessment of pathological forearm function.