Verification of acromion marker cluster and scapula spinal marker cluster methods for tracking shoulder kinematics: a comparative study with upright four-dimensional computed tomography.

BACKGROUND: This study validated the accuracy of the acromion marker cluster (AMC) and scapula spinal marker cluster (SSMC) methods compared with upright four-dimensional computed tomography (4DCT) analysis. METHODS: Sixteen shoulders of eight healthy males underwent AMC and SSMC assessments. Active shoulder elevation was tracked using upright 4DCT and optical motion capture system. The scapulothoracic and glenohumeral rotation angles calculated from AMC and SSMC were compared with 4DCT. Additionally, the motion of these marker clusters on the skin with shoulder elevation was evaluated. RESULTS: The average differences between AMC and 4DCT during 10°-140° of humerothoracic elevation were - 2.2° ± 7.5° in scapulothoracic upward rotation, 14.0° ± 7.4° in internal rotation, 6.5° ± 7.5° in posterior tilting, 3.7° ± 8.1° in glenohumeral elevation, - 8.3° ± 10.7° in external rotation, and - 8.6° ± 8.9° in anterior plane of elevation. The difference between AMC and 4DCT was significant at 120° of humerothoracic elevation in scapulothoracic upward rotation, 50° in internal rotation, 90° in posterior tilting, 120° in glenohumeral elevation, 100° in external rotation, and 100° in anterior plane of elevation. However, the average differences between SSMC and 4DCT were - 7.5 ± 7.7° in scapulothoracic upward rotation, 2.0° ± 7.0° in internal rotation, 2.3° ± 7.2° in posterior tilting, 8.8° ± 7.9° in glenohumeral elevation, 2.0° ± 9.1° in external rotation, and 1.9° ± 10.1° in anterior plane of elevation. The difference between SSMC and 4DCT was significant at 50° of humerothoracic elevation in scapulothoracic upward rotation and 60° in glenohumeral elevation, with no significant differences observed in other rotations. Skin motion was significantly smaller in AMC (28.7 ± 4.0 mm) than SSMC (38.6 ± 5.8 mm). Although there was smaller skin motion in AMC, SSMC exhibited smaller differences in scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation compared to 4DCT. CONCLUSION: This study demonstrates that AMC is more accurate for assessing scapulothoracic upward rotation and glenohumeral elevation, while SSMC is preferable for evaluating scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation, with smaller differences compared to 4DCT.

In Vivo Metacarpophalangeal Joint Kinematics After Silicone Implant Arthroplasty in Patients With Rheumatoid Arthritis.

PURPOSE: The aim of this study was to determine the potential mechanism of implant fracture using 3-dimensional motion analysis of patients with rheumatoid arthritis. METHODS: Active flexion motion in 9 hands (34 fingers) of 6 female patients with rheumatoid arthritis who previously underwent hinged silicone metacarpophalangeal joint arthroplasty was examined using 4-dimensional computed tomography. Positions of the proximal phalanges relative to the metacarpals were quantified using a surface registration method. The deformation of the silicone implant was classified in the sagittal plane in the maximum flexion frame. The longitudinal bone axis of the proximal phalanx and the helical axis of the proximal phalanx were evaluated in 3-dimensional coordinates based on the hinge of the silicone implant. RESULTS: Nineteen fingers were classified into group 1, in which the silicone implant moved volarly during flexion without buckling of the distal stem. Twelve fingers were classified into group 2, in which the distal stem of the silicone implant buckled. Three fingers were classified into group 3, in which the base of the distal stem had already fractured. Quantitatively, the longitudinal bone axes of the proximal phalanges were displaced from dorsal to volar in the middle stage of flexion and migrated in the proximal direction in the late phase of flexion. The helical axes of the proximal phalanges were located on the dorsal and proximal sides of the hinge, and these tended to move in the volar and proximal directions as the metacarpophalangeal joint flexed. CONCLUSIONS: Volar and proximal translation of the proximal phalange was observed on 4-dimensional computed tomography. CLINICAL RELEVANCE: Proximal displacement of the bone axis late in flexion appears to be a contributing factor inducing implant fractures, because the pistoning motion does not allow the implant to move in the proximal direction.

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.

Knee varus alters three-dimensional ankle alignment in standing- a study with upright computed tomography.

BACKGROUND: For knee osteoarthritis (OA) treatment, it is important to correct the lower limb alignment including the foot. However, in the upright position, lower limb alignment is generally assessed from the body surface or radiographs, and it is a challenge to capture the exact characteristics of three-dimensional lower limb alignment. The purpose of the study was to measure lower limb alignment in patients with knee OA using upright computed tomography (CT) and radiography, and to identify features of knee joint deformity. METHODS: A total of 45 limbs in 25 patients with knee OA were enrolled. The subjects underwent both upright CT and radiography for the whole lower limb in the standing position. The joint angles were calculated on both images. The degree of knee OA was classified according to Kellgren-Lawrence (KL) grade by referring to radiography, which is mainly based on the degree of articular cartilage loss and severity of osteophytes, and the characteristics or correlation between knee and ankle joint in each group was investigated. RESULTS: In KL-I, there was an association between varus of the knee joint and internal rotation of the talocrural joint (r = 0.76, P < 0.05). In KL-II, there was an association between varus of the knee joint and eversion of the subtalar joint (r = 0.63, P < 0.05) and talocrural joint (r = - 0.65, P < 0.05). In KL-III, there was an association between varus of the knee joint and internal rotation of the subtalar joint (r = - 0.62, P < 0.05), and in KL-IV, there was an association between varus of the knee joint and internal rotation of the subtalar joint (r = - 0.58, P < 0.05). CONCLUSIONS: The lower limb alignment of patients with knee OA in the standing position was found that as knee OA worsened, it became apparent that compensatory knee joint alignment depended on the ankle joint rather than the subtalar joint. The results may help in the rehabilitation of patients with knee OA, since the ankle joint alignment has a significant impact on the knee joint during coarse movements involving load.

Four-dimensional computed tomographic analysis of screw home movement in patients with anterior cruciate ligament deficient knee - a 3D-3D registration technique.

OBJECTIVE: The tibia externally rotates to the femur during the last 20° of the knee extension motion. This kinematic phenomenon is well known as screw home movement (SHM). The purpose was to clarify the SHM in anterior cruciate ligament deficient (ACLD) knee using four-dimensional computed tomography (4DCT). MATERIALS AND METHODS: Six patients with a unilateral isolated ACLD knee participated. In the static position, CT scan of the both limbs of the femur and tibia were performed. Then, 4DCT was performed around knee. In the CT gantry, subjects were positioned in supine position with 45° of knee flexion on a triangle pillow and were asked to extend the knee to full extension within 10 s on each limb. The CT data were accumulated in digital imaging and communication in medicine (DICOM) data format. From the static CT and 4DCT DICOM data, three-dimensional surfaces of the knee joint were reconstructed. The whole tibia surface was matched into the partial tibia surface of that frame using 3D-3D registration technique. After the assessment of coordination system of the whole leg, knee flexion, abduction, and external rotation angle were calculated. RESULTS: Knee external rotation angle was significantly smaller on the ACLD side than on the contralateral unaffected side in 0-15° of knee flexion (P < 0.05 in 0, 5, 10, and 15 degrees), while the angle was similar during 15-60° of knee flexion. CONCLUSION: The absence of SHM in ACLD knee was detected using 3D-3D registration technique based on 4DCT.

Aggressive and frequent resection of recurrences in retroperitoneal sarcoma contributes to long-term survival.

PURPOSE: Retroperitoneal sarcoma (RPS) is a rare tumor with a poor prognosis and is often undetected until it is significantly enlarged. While surgical resection remains the primary treatment, there is little research on its benefits, especially that concerning the reoperation of recurrent disease. This study investigated the impact of surgical procedures, especially reoperation of recurrent RPS, on prognosis. METHODS: This retrospective study included 51 patients who underwent radical resection surgery (R0 status) for primary or recurrent RPS without distant metastasis. Patient outcomes and prognosis were defined in terms of the clinicopathologic factors and surgical techniques performed. RESULTS: In all cases, the 5-year disease-free survival (DFS) rate was 28.2%, 5-year overall survival rate was 89.9%, and 5-year no residual liposarcoma rate was 54.3% after operation and re-reoperation. There was a statistically significant difference between the 5-year DFS rate and 5-year no residual liposarcoma rate due to frequent re-reoperation (p = 0.011). On univariate analysis of primary and recurrent lesions, the histological type and the number of organs involved were identified as statistically significant prognostic factors. Patients with well-differentiated liposarcomas had a statistically better prognosis than those with other cancer types (primary RPS, p = 0.028; recurrence, p = 0.024). CONCLUSIONS: Aggressive and frequent resection of recurrent RPS with combined resection of adjacent organs contributes to long-term survival. The establishment of a surgical strategy for RPS will require a prospective study.

A Pilon Fracture With Fibular Head Dislocation Treated With the Use of 3D Preoperative Planning: A Case Report and Literature Review.

Pilon fractures with intact fibula have been associated with low-energy trauma. However, the compression force onto the ankle joint can damage the tibiofibular linkage as in a Maisonneuve fracture. Herein, we describe a case of a patient who had a pilon fracture (AO type 43 C3.2) without a fibular fracture. Three-dimensional preoperative simulation by reduction with the surface registration technique was performed as the fibular length was intact and there was no reference for the tibial length. The preoperative simulation revealed superior fibular head dislocation and shortening of the distal tibia. After emergency external fixation on the day of arrival, a 2-staged surgery was performed. During the first operation, the fibular head was reduced and the tibial posterolateral fragment was fixed to restore the tibia length. During the second operation, medial and anterolateral fragments were fixed in order to reduce joint surface of the distal tibia. In general, proximal fibular head fractures are easily overlooked. In the case of pilon fractures with severe length shortening of the tibia without a fibular fracture, a proximal tibiofibular injury should be suspected.

Clinical Implications of Pretreatment: Lymphocyte-to-Monocyte Ratio in Patients With Rectal Cancer Receiving Preoperative Chemoradiotherapy.

BACKGROUND: Despite advances in local control of rectal cancer, recurrence in distant organs is still one of the main causes of mortality. Prognostic biomarkers would be valuable for the treatment of patients who have rectal cancer. OBJECTIVE: The aim of our study was to investigate the prognostic impact of lymphocyte-to-monocyte ratio in patients with rectal cancer receiving preoperative chemoradiotherapy, and to clarify the clinical significance of lymphocyte-to-monocyte ratio. DESIGN: Prospectively maintained data of patients with rectal cancer were retrospectively evaluated to clarify the clinical relevance of the lymphocyte-to-monocyte ratio. SETTING: This study was conducted at a single expert center. PATIENTS: A total of 119 consecutive patients with rectal cancer through chemoradiotherapy followed by total mesorectal excision at our institute were enrolled in this study. Eight patients were excluded because of a lack of laboratory data, and finally 111 patients were assessed in this study. MAIN OUTCOME MEASURES: The primary outcome measured was the clinical relevance of the lymphocyte-to-monocyte ratio in patients with rectal cancer receiving chemoradiotherapy. RESULTS: Patients with a low pretreatment lymphocyte-to-monocyte ratio showed poor prognosis significantly both in overall survival and disease-free survival of those with rectal cancer receiving chemoradiotherapy. Multivariate analyses showed that low pretreatment lymphocyte-to-monocyte ratio level, presence of pathological lymph node metastasis (ypN(+)), and high pretreatment serum C-reactive protein level were independent prognostic factors of overall survival and disease-free survival. In addition, time-to-event analysis divided into 2 groups by ypN status showed that low pretreatment lymphocyte-to-monocyte ratio was correlated with poor overall survival and disease-free survival not only in group ypN(-) but also in group ypN(+). LIMITATIONS: The present study had several limitations, including that it was a retrospective observational and single institutional study with Japanese patients. CONCLUSIONS: The combination of lymphocyte-to-monocyte ratio and ypN status can be a predictive marker of poor prognosis and recurrence among patients with rectal cancer undergoing preoperative chemoradiotherapy. See Video Abstract at http://links.lww.com/DCR/A780.

Prognostic predictions based on pathological findings of peritoneal dissemination in patients with stage IV colorectal cancer without residual disease (R0 status).

PURPOSE: This study aimed to clarify the prognosis of patients after resection of stage IV colorectal cancer and synchronous peritoneal metastasis (no residual disease: R0 status) based on histopathologic findings. METHODS: The subjects of this study were 26 patients who underwent radical resection of synchronous peritoneal metastases of stage IV colorectal cancer. Only patients with one synchronous peritoneal metastasis were included in this study. The peritoneal lesions were initially classified into two categories based on the presence or absence of adenocarcinoma on their surface: RM-negative or RM-positive. The lesions were subsequently classified as being of massive or diffuse type and of small (< 6 mm) or large (≥ 6 mm) type according to the maximum metastatic tumor dimension. RESULTS: Multivariate analysis revealed that massive type metastatic tumors were associated with a better disease-free survival (DFS; p = 0.047) and overall survival (OS; p = 0.033), than diffuse type tumors. CONCLUSION: A detailed stratification of pathological findings could contribute remarkably to prognostic predictions for patients with synchronous peritoneal metastases.

Glenohumeral translation during active external rotation with the shoulder abducted in cases with glenohumeral instability: a 4-dimensional computed tomography analysis.

BACKGROUND: Although glenohumeral instability is common, the mechanism of instability remains unclear. The purpose of this study was to quantitatively evaluate humeral head translation during active external rotation with abduction in patients with glenohumeral instability by use of 4-dimensional computed tomography scans. METHODS: Ten patients with unilateral glenohumeral instability with a positive fulcrum test were prospectively included in this study. Sequential computed tomography of bilateral shoulders during active external rotation at 90° of shoulder abduction was performed for 6 seconds at 5 frames per second. The 3-dimensional positions of the humeral head center in the anteroposterior, superoinferior, and mediolateral directions were calculated at 0°, 20°, 40°, 60°, and maximum shoulder abduction-external rotation from the starting position. Translation of the humeral head center from the starting position was evaluated using Dunnett multiple-comparison tests, and the differences between the affected and intact shoulders were assessed using Wilcoxon signed rank tests. RESULTS: The humeral head center translated posteriorly, inferiorly, and medially during glenohumeral external rotation with the shoulder in the abducted position on the intact side. However, the affected humeral head showed significantly less posterior translation (P = .028), greater inferior translation (P = .047), and less medial translation (P = .037) than the contralateral side. CONCLUSIONS: This study indicated that dysfunction of the anterior band of the inferior glenohumeral ligament causes decreased posterior, increased inferior, and decreased medial translation of the humeral head during active shoulder abduction-external rotation.

The relationship between the morphological axis and the kinematic axis of the proximal radius.

PURPOSE: Surgical procedures for impaired forearm rotation such as for chronic radial head dislocation remain controversial. We hypothesized that the morphological axis of the proximal radius is important for stable forearm rotation, and we aimed to clarify the relationship between the morphological axis and the kinematic axis of the proximal radius using four-dimensional computed tomography (4DCT). METHODS: Ten healthy volunteers were enrolled. Four-dimensional CT of the dominant forearm during supination and pronation was obtained. The rotation axis of forearm rotation was calculated from all frames during supination and pronation. The principle axis of inertia, which represents the most stable rotation axis of a rigid body, was calculated for the proximal radius by extending its surface data incrementally by 1% from the proximal end. The angle between the kinematic rotation axis and the morphological rotation axis of each length was calculated. RESULTS: The rotation axis of the forearm was positioned on the radial head 0.0 mm radial and 0.4 mm posterior to the center of the radial head proximally and 2.0 mm radial and 1.2 mm volar to the fovea of the ulnar head distally. The principle axis at 15.9% of the length of the proximal radius coincided with the forearm rotation axis (kinematic axis). Individual differences were very small (SD 1.4%). CONCLUSION: Forearm rotation was based on the axis at 16% of the length of the proximal radius. This portion should be aligned in cases of severe morphological deformity of the radial head that cause "rattling motion" of the radial head after reduction procedures.

Clinical Impact of Preoperative Albumin-Globulin Ratio in Patients with Rectal Cancer Treated with Preoperative Chemoradiotherapy.

OBJECTIVE: The serum albumin-globulin ratio (AGR) is associated with malignancy outcomes. However, among patients with rectal cancer (RC) who undergo neoadjuvant chemoradiotherapy (nCRT), the clinical and prognostic significance of the pretreatment AGR is unclear. METHODS: We investigated whether the pre-nCRT AGR can help predict oncological outcomes in patients with RC receiving nCRT. We analyzed 114 patients with RC who received nCRT followed by total mesorectal excision at our institution. RESULTS: A lower AGR in pre-nCRT serum was significantly correlated with shorter overall survival and disease-free survival in patients with nCRT-treated RC. In multivariate analysis, a high carcinoembryonic antigen (CEA) level and a low AGR in pre-nCRT serum were independent predictors of a poor prognosis in these patients. Furthermore, combining the AGR with CEA provided a more accurate indicator of poor prognosis and early recurrence in these patients. In particular, a low pre-nCRT AGR was a stronger indicator of a poor prognosis and early recurrence in patients without than with pathological lymph node metastasis. Combining the pre-nCRT AGR with CEA could more precisely stratify patients' oncological outcome risks. CONCLUSION: Assessment of the pretreatment AGR with or without CEA can guide postoperative treatment in patients with RC who undergo nCRT.

Computed tomography-based 3-dimensional preoperative planning for unlinked total elbow arthroplasty.

HYPOTHESIS: Three-dimensional (3D) surgical planning for unlinked total elbow arthroplasty (TEA) would be helpful for estimation of the implant size and accurate placement of implants. METHODS: We included 28 patients who underwent TEA with an unlinked total elbow implant in this study. All patients underwent computed tomography scans of the elbow before surgery, and a 3D digital model of the elbow was reconstructed. After the appropriate size and position of the prosthesis were determined, 10 points around the bone tunnel (4 on the humerus and 6 on the ulna) were measured to plan the insertion of the humeral and ulnar stems. Two-dimensional planning was also performed using anteroposterior and lateral radiographs. Intraoperatively, the surgeon measured the planned parameters using a slide gauge to reproduce the 3D planned position of the stem insertion. RESULTS: The stem sizes were accurately estimated in 57% of patients for the humerus and 68% for the ulna with 2-dimensional planning and in 86% for the humerus and 96% for the ulna with 3D planning. The mean differences between the positions of the prostheses after surgery with reference to the planned positions were 0.8° of varus and 1.5° of flexion for the humeral component and 0.7° of varus and 2.9° of flexion for the ulnar component. We did not evaluate rotational positioning in this study. CONCLUSIONS: The 3D surgical planning allowed accurate estimation of the implant size and appropriate placement of implants. This method may contribute to a reduced incidence of complications and improved long-term outcomes from TEA.

Three-dimensional quantitative analysis of humeral head and glenoid bone defects with recurrent glenohumeral instability.

BACKGROUND: Although bone defects of the humeral head and glenoid could affect glenohumeral instability, bone loss has not been sufficiently evaluated. The purpose of this study was to quantify bone defects 3-dimensionally in cases with glenohumeral instability. METHODS: Three-dimensional surface models of bilateral proximal humeri and glenoids were reconstructed from computed tomography scans of 90 patients with symptomatic, unilateral, recurrent glenohumeral instability. The left-side models were mirrored, and intact bone areas were matched to those of the right-side models. The volume, length, width, and depth of identified bone defects were assessed. After the values were corrected by patient height, the characteristics of the bone defects were evaluated. RESULTS: Bone defects were present in 97.8% of the humeral heads and 96.7% of the glenoids, and women had significantly smaller bone defects than men did. The volume of humeral head defects had a mild correlation with that of glenoid defects. The number of traumatic episodes was not correlated with humeral head bone defects, but it was positively correlated with glenoid bone defects. Patients with recurrent dislocations had significantly deeper and larger Hill-Sachs lesions than the other cases. CONCLUSION: Bone defects of the humeral head and the glenoid in cases with symptomatic traumatic glenohumeral instability were quantified 3-dimensionally using a computed tomography surface-matching technique. Almost all cases showed bone defects in the humeral head and glenoid compared with the intact shoulder, and such bone defects may be more common than previously reported. This study suggested that bipolar bone lesions are not always created by the same mechanism.

Laparoscopic repair of bladder rupture in a neonate.

Bladder rupture in a fetus is a rare occurrence. We report the first neonatal case of laparoscopic repair for prenatally diagnosed bladder rupture. A male neonate, who had presented with megacystis, bilateral hydronephrosis and hydroureters since 27 weeks-of-gestation, was delivered by emergency cesarean section because of sudden collapse of the bladder with massive ascites at 37 weeks-of-gestation. The diagnosis of bladder rupture was made by retrograde urethrocystography. Laparoscopic repair was carried out subsequent to urethral catheterization. Intraoperatively, laceration from the left side of the bladder dome to the posterior wall was observed. This tear was successfully repaired using a two-layer interrupted suture without any postoperative complications. Laparoscopic repair could be the treatment of choice for bladder rupture, because it has the advantage of closure of the perforated site more certainly than bladder decompression alone, and with better cosmesis than open repair.

Three-dimensional anthropometric analysis of the glenohumeral joint in a normal Japanese population.

BACKGROUND: An understanding of normal glenohumeral geometry is important for anatomical reconstruction in shoulder arthroplasty. Unfortunately, the details of the glenohumeral joint in Asian populations have not been sufficiently evaluated. The purpose of this study was to evaluate the 3-dimensional geometry of the glenohumeral joint in the normal Japanese population and to clarify its morphologic features. METHODS: Anthropometric analysis of the glenohumeral joint was performed using computed tomography scans of 160 normal shoulders from healthy Japanese volunteers. The glenohumeral dimensions and orientation were analyzed 3-dimensionally. Sex differences and correlations between sides and among the respective parameters in the glenohumeral dimensions were evaluated. RESULTS: The normal Japanese humeral head has an average width of 41.4 mm, thickness of 13.2 mm, diameter of 42.9 mm, retroversion of 32°, and inclination of 135°. The glenoid has an average height of 31.5 mm, width of 23.1 mm, diameter of 62.0 mm, retroversion of 0°, and inferior inclination of 2°. The values of the glenohumeral dimensions were uniform in men and women, and the humeral head and glenoid were larger in men than in women. The glenohumeral size was well correlated between the 2 sides, and there were direct correlations among the heights, humeral length, humeral head size, and glenoid size. CONCLUSIONS: The present study revealed the glenohumeral geometry in the normal Japanese population. The present results would be useful to determine the size of implants and to improve the design of shoulder prostheses that reflect the normal anatomy of the Asian glenohumeral joint.

Morphologic features of humeral head and glenoid version in the normal glenohumeral joint.

BACKGROUND: The morphologic features and clinical significance of version of the humeral head and glenoid remain unclear. The purpose of this study was to evaluate the normal values of humeral head version and glenoid version on computed tomography scans and to clarify their features in the normal glenohumeral joint. METHODS: Images for analysis were computed tomography scans of 410 normal shoulders from healthy volunteers. Values of humeral head and glenoid version were measured. In glenoid version measurement, 3-dimensionally corrected slices were reconstructed to eliminate scapular inclination. Differences in humeral head version and glenoid version were assessed between dominant and nondominant shoulders and between men and women. Correlation analyses were also performed in the values of version between dominant and nondominant shoulders and between humeral head version and glenoid version. RESULTS: The values of humeral head retroversion were widely distributed from -2° to 60°, with an average of 26° ± 11°. Average glenoid retroversion was 1° ± 3°, ranging from -9° to 13°. Both humeral head retroversion and glenoid retroversion were significantly higher on the dominant side than on the nondominant side and significantly higher in men than in women. Humeral head version and glenoid version values were well correlated with those of the contralateral shoulder. No correlation was found between humeral head version and glenoid version. CONCLUSIONS: This study found differences in humeral head version and glenoid version by sex and shoulder dominance in a large sample. Both the humeral head and glenoid are thought to be more retroverted in high-demand shoulders.

Acromioclavicular joint ligamentous system contributing to clavicular strut function: a cadaveric study.

HYPOTHESIS: We hypothesized that the clavicle overrides the acromion during certain shoulder motions for individuals with acromioclavicular (AC) joint separation producing clinical symptoms. We measured 3-dimensional clavicular and scapular motions in AC joint separation models during humerothoracic motions, which should be impacted by the loss of AC joint continuity. MATERIALS AND METHODS: Ten shoulders from 6 whole cadavers were used. The scapular and clavicular motions were measured in intact and AC joint separation models using an electromagnetic tracking device. The measurement was performed during shoulder abduction with humerothoracic neutral rotation. It was also measured during shoulder abduction with humerothoracic internal rotation, which could cause clavicular overriding. The kinematic changes caused by ligament sectioning were evaluated in these 2 arm motions. RESULTS: The clavicle completely overrode the acromion in all AC separation models during abduction with internal rotation, but not in any shoulders during abduction with neutral rotation. Upward clavicular rotation increased, posterior clavicular rotation decreased, and external scapular rotation decreased with ligament sectioning. These kinematic changes were common for both of the measured arm motions. Scapular upward rotation and posterior tilt did not change because of ligament sectioning during abduction with neutral rotation. However, these scapular rotations significantly decreased with ligament sectioning during shoulder abduction with internal rotation. CONCLUSION: Scapular and clavicular kinematics were affected in AC separation models. Abduction with humeral internal rotation resulted in a decrease in scapular posterior tilt and upward rotation in AC separation models, and thereby could lead to AC joint articulation dysfunction.

Influence of Proximal Humeral Cortical Bone Thickness on the Radiographic Outcome After Osteosynthesis of Proximal Humeral Fractures: Propensity Matching Score Analysis.

Introduction: Osteoporosis can affect the surgical outcomes of proximal humeral fractures in older people. Recently, the cortical bone thickness of the proximal humerus on plain radiograph has been proposed to reflect local osteoporosis of the proximal humerus; however, its effect on the surgical outcome of proximal humeral fractures remains unclear. The purpose of this study is to investigate the influence of cortical bone thickness on postoperative radiographic outcomes after osteosynthesis for proximal humeral fractures. Materials and Methods: We retrospectively identified 190 patients (≥50 years) who underwent osteosynthesis with an intramedullary nail or plate for proximal humeral fractures. The patients were categorized into 2 groups according to the cut-off value of an average proximal humerus cortical bone thickness of 6 mm on plain radiographs: patients with and without local osteoporosis. After propensity score matching, we compared the incidence of postoperative radiographic complications between the 2 groups. We also performed subgroup analyses of outcomes in a subgroup of patients who underwent intramedullary nailing and those who underwent plate fixation. Results: Propensity score matching yielded 60 patients in each group. No significant difference in complication rates was observed between the 2 groups. However, in the intramedullary nailing subgroup, the incidence of reduction loss was significantly higher in patients with local osteoporosis than in those without local osteoporosis (51.7% vs 14.3%, P = .002). Discussion: The proximal humeral cortical bone thickness had no significant effect on the overall radiographic outcome; however, reduction loss after intramedullary nailing was susceptible to local osteoporosis of the proximal humerus. Conclusion: Our study suggests that plate fixation is advantageous in preventing postoperative reduction loss in patients with lower cortical bone thickness.

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.