BackgroundNo clear trend has emerged from the literature regarding three-dimensional (3D) translations of the humerus relative to the scapula in shoulders with rotator cuff tears (RCTs). The purpose of this study was to evaluate the kinematics of RCT shoulders using 3D-to-two-dimensional (2D) model-to-image registration techniques.MethodsDynamic glenohumeral kinematics during scapular plane abduction and axial rotation were analyzed in 11 RCT patients and 10 healthy control subjects. We measured the 3D kinematic parameters of glenohumeral joints using X-ray images and CT-derived digitally reconstructed radiographs.ResultsFor scapular plane abduction, the humeral head center was positioned significantly more medially in shoulders with RCTs than in controls at 135° of humeral abduction (p = 0.02; RCTs versus controls: − 0.9 ± 1.6 versus 0.3 ± 1.3 mm). There was no significant difference in the superior/inferior translation of the humeral head center (p = 0.99). For axial rotation in adducted position, the humeral head center was positioned significantly more anteriorly in shoulders with RCTs than in controls at − 30° of glenohumeral external rotation (p < 0.0001; RCTs versus controls: 3.0 ± 1.7 versus 0.3 ± 1.5 mm).ConclusionsThis study revealed the kinematics of shoulders with large to massive full-thickness RCTs: the humeral head center showed a medial shift at the late phase of scapular plane full abduction, and an anterior shift at the internal rotation position during full axial rotation. The kinematic data in this study, which describe the patterns of movement of shoulders with large to massive full-thickness RCTs, provide valuable information for future studies investigating glenohumeral translations in other pathological conditions of the shoulder. For clinical relevance, quantitative assessment of the dynamic kinematics of shoulders with RCTs might be a therapeutic indicator for achieving functional restoration.

Introduction Tendon tissue engineering requires scaffold-free techniques for safe and long-term clinical applications and to explore alternative cell sources to tenocytes. Therefore, we histologically assessed tendon formation in a scaffold-free Bio-three-dimensional (3D) construct developed from normal human dermal fibroblasts (NHDFs) using our Bio-3D printer system under tensile culture in vitro . Methods Scaffold-free ring-like tissues were constructed from 120 multicellular spheroids comprising NHDFs using a bio-3D printer. Ring-like tissues were cultured in vitro under static tensile-loading with or without in-house tensile devices (tension-loaded and tension-free groups), with increases in tensile strength applied weekly to the tensile-loaded group. After a 4 or 8-week culture on the device, we evaluated histological findings according to tendon-maturing score and immunohistological findings of the middle portion of the tissues for both groups ( n = 4, respectively). Results Histology of the tension-loaded group revealed longitudinally aligned collagen fibers with increased collagen deposition and spindle-shaped cells with prolonged culture. By contrast, the tension-free group showed no organized cell arrangement or collagen fiber structure. Additionally, the tension-loaded group showed a significantly improved tendon-maturing score as compared with that for the tension-free group at week 8. Moreover, immunohistochemistry revealed tenascin C distribution with a parallel arrangement in the tensile-loading direction at week 8 in the tension-loaded group, which exhibited stronger scleraxis-staining intensity than that observed in the tension-free group at weeks 4 and 8. Conclusions The NHDF-generated scaffold-free Bio-3D construct underwent remodeling and formed tendon-like structures under tensile culture in vitro .

BackgroundDespite recent advancements in rheumatoid arthritis (RA) pharmacotherapy, surgeons still encounter severely damaged knees. The purpose of the present study was to analyze the mid-term clinical results of total knee arthroplasty (TKA) with metal block augmentation and stem extension.MethodsA total of 26 knees in 21 patients who underwent primary TKA with metal block augmentation and stem extension were retrospectively reviewed. All patients with a mean age of 63 years had RA for a mean duration of 15 years. Functional and radiographic results as well as complications were evaluated at the mean follow-up period of 6 years after TKA. Eight knees were lost follow-up after the two-year evaluation.ResultsTibial bone defects with average depth of 19 mm were preoperatively recognized in all 26 knees. The postoperative joint line was reconstructed on average 11 mm above the fibular head using average thickness of 11 mm tibial inserts and 9 mm metal blocks with stem extension. Significant improvements (p < 0.05 for all comparisons) were observed postoperatively in maximum extension angle from −10° to −1°, range of motion from 101 ° to 115 °, and Knee Society Score (knee score/function score) from 35/18 to 90/64. Non-progressive radiolucent lines beneath the metal block and osteosclerotic changes around the medullary stem were found in 16 knees (62 %) and 14 knees (54 %), respectively. There was two failures (8 %): fragile supracondylar femur fractures and knee instability. No knees showed any radiographic implant loosening, dislocation, polyethylene insert breakage, peroneal palsy, or infection.ConclusionsPrimary TKA with metal block augmentation and stem extension could effectively restore function in RA patients with advanced forms of knee joint destruction, and be reliable and durable for a mean postoperative period of 6 years. Further study is needed to determine the long-term results of TKA using metal block augmentation and stem extension.

Introduction: Assessment of scapular kinematics and the dynamics of the scapulohumeral rhythm (SHR) would be important for understanding pathologies of the shoulder and to inform treatment. Our aim in this study was to evaluate the SHR and scapular kinematics in patients with a rotator cuff tear (RCT), compared to a control group with healthy shoulders using image-matching techniques. Materials and Methods: The shoulder kinematics of large or massive RCT patients were evaluated and compared to a control group with healthy shoulders. Radiographic surveillance was performed throughout the full range of external rotation and scapular plane abduction. Computed tomography imaging of the shoulder complex was performed, with three-dimensional image reconstruction and matching to the radiographs to measure three-dimensional positions and orientations. SHR and angular values of the scapula were measured. Results: Scapular external rotation in the late phase of external rotation movement was greater in the RCT group than in the control group ( p < 0.05), but with no difference in the SHR. During scapular plane abduction, there were significant differences in SHR, scapular posterior tilt and scapular upward rotation between the RCT and control group ( p < 0.05). Conclusions: Regarding clinical relevance, this study clarified the differences of SHR and angular values of the scapula between the RCT and control group. These results underline the importance of assessment the SHR and scapular kinematics in individuals with a RCT. RCT is associated with specific compensation in the kinematics of the scapula and SHR during external rotation and scapular plane abduction, which could inform treatment.

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