Chondrogenesis is accompanied by not only cellular renovation, but also metabolic stress. Therefore, macroautophagy/autophagy is postulated to be involved in this process. Previous reports have shown that suppression of autophagy during chondrogenesis causes mild growth retardation. However, the role of autophagy in chondrocyte differentiation still largely remains unclear. Here, we show the important role of autophagy on chondrogenesis. The transition of mesenchymal cells to chondrocytes was severely impaired by ablation of Atg7, a gene essential for autophagy. Mice lacking Atg7 after the transition exhibited phenotypes severer than mutant mice in which Atg7 was removed before the transition. Atg7-deficient chondrocytes accumulated large numbers of glycogen granules, hardly proliferate and died specifically in the proliferative zone without any ER-stress signal. Our results suggest that the suppression of autophagy in prechondrogenic cells drives compensatory mechanism(s) that mitigate defective chondrogenesis, and that autophagy participates in glycogenolysis to supply glucose in avascular growth plates.

Background: Several researchers consider the clinical epicondylar axis (CEA) as the functional flexion-extension axis of the knee. The anterior pelvic plane (APP) is commonly used as an anatomical reference plane of the pelvis. However, no study has investigated the relationship of the APP with the CEA and PCA. In this study, we aimed to investigate the relationship of the APP with the CEA and posterior condylar axis (PCA) in the standing and supine positions. Methods: We recruited 77 healthy Japanese subjects for this study, and carried out measurements using the Hip CAS ® system, a 3D system used for the assessment of lower extremity alignment. Results: The mean femoral neck anteversion was 16.33˚. There was an approximate discrepancy of 6˚ between the male and the female in anatomy (15.73˚ and 21.15˚ in the male and female subjects, respectively). The mean condylar twist angle (CTA) was 6.86˚ and the mean APP-PCA value in the standing position was −6.88˚. The mean APP-CEA value in the standing position was 0.02˚, and the discrepancy between males and females was only 0.21˚ (0.09˚ and −0.13˚ for the male and female subjects, respectively). This meant that Xp axis of APP and CEA were almost parallel. On the other hand, the mean APP-CEA value in the supine position was 7.07˚ (male subjects = 9.48˚; female subjects = 5.62˚). Here, the CEA was approximately parallel to the horizontal axis of the APP, which was compatible with the neutral position of the knee and hip joint, and anatomically and kinesiologically justified in normal subjects. Conclusion: CEA was approximately parallel to the horizontal axis of the APP. These results are compatible with regard to the neutral position of the knee and hip joints, and anatomically and kinesiologically justified in normal subjects. Moreover, CEA is a potential reference axis for the insertion of the femoral component in THA.

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The maximum CSA of the gluteus maximus was found just above the femoral head and that of the gluteus medius was near the lowest end of the sacroiliac joint; hence, CSAs should be calculated at these sites. The CSA reflected muscle volume and strength.

Background: Malpositioning during total hip arthroplasty may cause dislocation, pain, and other complications. To evaluate the potential of sacral slope (SS) as a reliable parameter of pelvic flexion. Methods: We developed a model of pelvic flexion to determine the intraobserver and interobserver variability and reliability of SS measurements by lateral radiography by three independent observers. Results: Measurement error was 1.2° and the intraobserver reliability was moderate to substantial (Interclass correlation coefficient: 0.31 to 0.66). Based on the Spearman-Brown formula, the measurement is reliable if it is done at least seven times by two observers, and four times by three observers. Conclusions: The data suggest that measurement of SS of pelvic flexion is a clinically useful parameter for the optimization of THA conditions.