One of the purposes of rehabilitation is patient joint recovery, which consists of providing both pain relief and normal function. A functional evaluation is essential to estimate the clinical results, and this is accomplished by analyzing the joint kinematics. Thousands of cadaveric studies were already reported but these may differ from the in vivo results because they lack ligamentous or muscular effects. Therefore, the development of an in vivo 3D kinematic analysis system was needed for the proper diagnosis of pathological movement and the evaluation of postoperative function. Accordingly, two such systems were developed at our institute. The first system uses 3D CT or MRI and it is suitable for joint movement analysis. The targeted joint is placed in serial positions of the motion plane to evaluate the 3D kinematics of the motion, and images are obtained in each position. The data are saved and transmitted to a computer workstation. Kinematic variables are measured automatically. Animations of the joint movement are then created from the calculated motions. The second system uses a radiographic image intensifier. It can evaluate real-time 3D dynamic motion of metal implants and it is available to evaluate joint kinematics after arthroplasty. The 3D pose-estimation technique is built on a 2D-3D registration algorithm, which determines the spatial pose for each component from the implant contours and computer-assisted design models of the implant. Sequential fluoroscopic images are then taken in the sagittal plane.

BACKGROUND: Nonunion of lateral humeral condyle fracture causes cubitus valgus deformity. Although corrective osteotomy or osteosynthesis can be considered, there are controversies regarding its treatment. To evaluate elbow joint biomechanics in non-united lateral humeral condyle fractures, we analyzed the motion of elbow joint and pseudo-joint via in vivo three-dimensional (3D) kinematics, using 3D images obtained by computed tomography (CT) scan. METHODS: Eight non-united lateral humeral condyle fractures with cubitus valgus and 8 normal elbows were evaluated in this study. CT scan was performed at 3 different elbow positions (full flexion, 90° flexion and full extension). With bone surface model, 3D elbow motion was reconstructed. We calculated the axis of rotation in both the normal and non-united joints, as well as the rotational movement of the ulno-humeral joint and pseudo-joint of non-united lateral condyle in 3D space from full extension to full flexion. RESULTS: Ulno-humeral joint moved to the varus on the coronal plane during flexion, 25.45° in the non-united cubitus valgus group and −2.03° in normal group, with statistically significant difference. Moreover, it moved to rotate externally on the axial plane −26.75° in the non-united cubitus valgus group and −3.09° in the normal group, with statistical significance. Movement of the pseudo-joint of fragment of lateral condyle showed irregular pattern. CONCLUSIONS: The non-united cubitus valgus group moved to the varus with external rotation during elbow flexion. The pseudo-joint showed a diverse and irregular motion. In vivo 3D motion analysis for the non-united cubitus valgus could be helpful to evaluate its kinematics.
Biomechanical Phenomena ; Congenital Abnormalities ; Elbow ; Elbow Joint ; Imaging, Three-Dimensional ; Joints ; Osteotomy ; Tomography, X-Ray Computed