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.

Micro-computed tomography analysis of the lumbar pedicle wall.

BACKGROUND: Although the pedicle is routinely used as a surgical fixation site, the pedicle wall bone area fraction (bone area per unit area) and its distribution at the isthmus of the pedicle remain unknown. The bone area fraction at the pedicle isthmus is an important factor contributing to the strength of pedicle screw constructs. This study investigates the lumbar pedicle wall microstructure based on micro-computed tomography. METHODS: Six fresh-frozen cadaveric lumbar spines were analyzed. Left and right pedicles of each vertebra from L1 to L5 were resected for micro-computed tomography scanning. Data was analyzed with custom-written software to determine regional variation in pedicle wall bone area fraction. The pedicular cross-section was divided into four regions: lateral, medial, cranial, and caudal. The mean bone area fraction values for each region were calculated for all lumbar spine levels. RESULTS: The lateral region showed lower bone area fraction than the medial region at all spinal levels. Bone area fraction in the medial region was the highest at all levels except for L4, and the median values were 99.8% (95.9-100%). There were significant differences between the lateral region and the caudal region at L1, L2 and L3, but none at L4 and L5. The bone area fraction in the lateral region was less than 64% at all spinal levels and that in the caudal region was less than 67% at the L4 and L5 levels. CONCLUSIONS: This study provides initial detailed data on the lumbar pedicle wall microstructure based on micro-computed tomography. These findings may explain why there is a higher incidence of pedicle screw breach in the pedicle lateral and caudal walls.

Three-dimensional distribution of CT attenuation in the lumbar spine pedicle wall.

This study investigated in vivo the three-dimensional distribution of CT attenuation in the lumbar spine pedicle wall measured in Hounsfield Unit (HU). Seventy-five volunteers underwent clinical lumbar spine CT scans. Data was analyzed with custom-written software to determine the regional variation in pedicle wall attenuation values. A cylindrical coordinate system oriented along the pedicle's long axis was used to calculate the pedicular wall attenuation distribution three-dimensionally and the highest attenuation value was identified. The pedicular cross-section was divided into four quadrants: lateral, medial, cranial, and caudal. The mean HU value for each quadrant was calculated for all lumbar spine levels (L1-5). The pedicle wall attenuation was analyzed by gender, age, spinal levels and anatomical quadrant. The mean HU values of the pedicle wall at L1 and L5 were significantly lower than the values between L2-4 in both genders and in both age groups. Furthermore, the medial quadrant showed higher HU values than the lateral quadrant at all levels and the caudal quadrant showed higher HU values at L1-3 and lower HU values at L4-5 than the cranial quadrant. These findings may explain why there is a higher incidence of pedicle screw breach in the pedicle lateral wall.

Computed Tomography-Based Three-Dimensional Analyses Show Similarities in Anterosuperior Acetabular Coverage Between Acetabular Dysplasia and Borderline Dysplasia.

PURPOSE: (1) To compare the acetabular coverage between dysplasia, borderline dysplasia, and control acetabulum in a quantitative 3-dimensional manner; and (2) to evaluate correlations between the radiologic parameters and the 3-dimensional zonal-acetabular coverage. METHODS: We reviewed contralateral hip computed tomography images of patients 16 to 60 years of age who underwent 1 of 3 types of surgeries: eccentric rotational acetabular osteotomy, curved intertrochanteric varus osteotomy, and total hip replacement with minimum 1-year follow-up from January 2013 to April 2018. A point-cloud model of the acetabulum created from computed tomography was divided into 6 zones. Three-dimensional acetabular coverage was measured radially at intervals of 1°. Mean radial acetabular coverage for each zone was named ZAC (zonal acetabular coverage) and was compared among the 3 subgroups (control: 25° ≤lateral center-edge angle [LCEA] <40°; borderline: 20° ≤LCEA <25°; and dysplasia: LCEA ≤20°) statistically. Further, the correlations between the ZAC in each zone and the LCEA were analyzed using Pearson's correlation coefficient. RESULTS: One-hundred fifteen hips were categorized as control (36 hips), borderline (32 hips), and dysplasia (47 hips). The mean anterocranial ZAC in the borderline (87.5 ± 5.7°) was smaller than that in the control (92.6 ± 5.9°, P = .005) but did not differ compared with the dysplasia (84.5 ± 7.6°, P = .131). In contrast, the anterocaudal (71.2 ± 5.0°), posterocranial (85.0 ± 6.4°), and posterocaudal (82.4 ± 4.5°) mean ZACs in the borderline were not different from those in the control (anterocaudal, 74.3 ± 4.6°, P = .090; posterocranial, 87.9 ± 4.3°, P = .082; posterocaudal, 85.1 ± 5.0°, P = .069) respectively. Although there was a very strong positive correlation with supra-anterior ZAC and LCEA (r = 0.750, P < .001), the correlation between the anterocranial ZAC and LCEA was relatively weak (r = 0.574, P < .001). CONCLUSIONS: The anterosuperior acetabular coverage in the borderline dysplastic acetabulum is more similar to the dysplastic acetabulum than to the normal acetabulum. CLINICAL RELEVANCE: This study emphasizes the importance of evaluating not only the lateral but also the anterior coverage in borderline dysplasia.

Three-dimensional curvature mismatch of the acetabular radius to the femoral head radius is increased in borderline dysplastic hips.

Whether borderline hip dysplasia is pathologic remains unclear. In order to evaluate the three-dimensional joint congruity, this study sought to answer the question: are borderline dysplastic hip curvature mismatch and eccentricity between the acetabulum and the femoral head different from dysplastic or control hips three-dimensionally? The 113 hips, categorized as: dysplastic (LCEA ≤ 20°), 47 hips; borderline (20° ≤ LCEA < 25°), 32 hips; and control (25° ≤ LCEA < 35°), 34 hips; were evaluated. Three-dimensional (3D) femoral and coxal bone models were reconstructed from CT images. Using a custom-written Visual C++ routine, the femoral head and acetabular radii of curvature, and the femoral head and the acetabular curvature center were calculated. Then the ratio of the acetabular radius to the femoral head radius (3D curvature mismatch ratio), and the distance between the acetabular curvature center and the femoral head center (3D center discrepancy distance) were calculated. These indices were compared statistically among the three groups using Tukey's post hoc test. The mean 3D curvature mismatch ratio in the borderline (1.13 ± 0.05) was smaller than in the dysplasia (1.23 ± 0.08, p < 0.001), and larger than in the control (1.07 ± 0.02, p < 0.001). The mean 3D center discrepancy distance in the borderline (3.2 ± 1.4 mm) was smaller than in the dysplasia (4.8 ± 2.3, p < 0.001) and larger than in the control (1.6 ± 0.7, p < 0.001). These results demonstrated that three-dimensional congruity of the borderline dysplastic hip is impaired, but its incongruity is not as severe as in dysplastic hips. The 3D curvature mismatch ratio and the 3D center discrepancy distance can be valuable signs of joint congruity in patients with borderline dysplasia. However, future studies are necessary to clarify any associations between curvature mismatch and pathogenesis of osteoarthritis in borderline dysplasia.

Three-dimensional hip joint congruity evaluation of the borderline dysplasia: Zonal-acetabular radius of curvature.

In theory, a hemispherical acetabulum provides the ideal hip congruity in any hip position. However, it remains unknown how the three-dimensional acetabular morphology of borderline dysplastic and frank dysplastic hips compare to normal hips. This study inquires if borderline dysplastic zonal-acetabular curvatures in the anterior, superior, and posterior zones are different from normal or dysplastic hips three-dimensionally. One-hundred and fifteen hips, grouped as control (25°≤ LCEA <40°), 36 hips; borderline (20°≤ LCEA <25°), 32 hips; dysplasia (LCEA ≤20°), 47 hips were analyzed. The radii of acetabular curvature for the anterior, superior, and posterior zones were calculated as the zonal-acetabular radius of curvature (ZARC). The mean acetabular roof obliquity of the borderline (10.6 ± 4.3 [SD]°) was significantly larger than the control (3.0° ± 5.4°; P < .001) and smaller than the dysplasia (19.3° ± 5.7°; P < .001). Although the mean acetabular anteversion angle of the borderline (21.3° ± 3.7°) was significantly larger than control (17.9 ± 3.5°; P = .001), that of the borderline was not different from the dysplasia (23.3° ± 4.0°; P = .053). The mean anterior ZARC in the borderline (29.8 ± 2.6 mm) was significantly larger than the control (28.0 ± 2.2 mm; P = .011) and smaller than the dysplasia (31.5 ± 2.7 mm; P = .009). The mean superior ZARC in the borderline (25.7 ± 3.0 mm) was not different from the control (25.9 ± 2.2 mm; P = .934) or the dysplasia (25.8 ± 2.5 mm; P = .991). Although the mean posterior ZARC in the borderline (27.2 ± 2.5 mm) was not different from the control (26.4 ± 1.9 mm; P = .455), that of the borderline group was significantly smaller than the dysplasia (30.4 ± 3.3 mm; P < .001); that is, the severity of lateral under-coverage affects the anterior and/or posterior zonal-acetabular curvature.

Absence of flexor carpi radialis identified during volar approach for fixation of distal radius fracture: a case report.

BACKGROUND: Volar locking plate fixation of distal radius fractures is commonly performed because of its good clinical outcomes. The flexor carpi radialis (FCR) approach is one of the most popular approaches to dissecting the volar side of the distal radius because of its simplicity and safety. We describe an extremely rare case of an absent FCR identified during a volar approach for fixation of a distal radius fracture. CASE PRESENTATION: A 59-year-old woman with distal radius fracture underwent surgery using the usual FCR approach and volar locking plate. We could not identify the absence of the FCR tendon preoperatively because of severe swelling of the distal forearm. At first, we wrongly identified the palmaris longus tendon as the FCR because it was the tendinous structure at the most radial location of the volar distal forearm. When we found the median nerve just radial to the palmaris longus tendon, we were then able to identify the anatomical abnormality in this case. To avoid iatrogenic neurovascular injuries, we changed the approach to the classic Henry's approach. CONCLUSIONS: Although the FCR approach is commonly used for fixation of distal radius fractures because of its simplicity and safety, this is the first report of complete absence of the FCR during the commonly performed volar approach for fixation of a distal radius fracture, to our knowledge. Because the FCR is designated as a favorable landmark because of its superficially palpable location, strong and thick structure, and rare anatomical variations, there is the possibility of iatrogenic complications in cases of the absence of the FCR. We suggest that surgeons should have a detailed knowledge of the range of possible anomalies to complete the fixation of a distal radius fracture safely.