Ossification of the posterior longitudinal ligament (OPLL) is a multi-factorial disease involving an ectopic bone formation of spinal ligaments. It affects 0.8-3.0% aging Asian and 0.1-1.7% aging European Caucasian. The ossified ligament compresses nerve roots in the spinal cord and causes serious neurological problems such as myelopathy and radiculopathy. Research in understanding pathogenesis of OPLL over the past several decades have revealed many genetic and non-genetic factors contributing to the development and progress of OPLL. The characterizations of aberrant signaling of bone morphogenetic protein (BMP) and mitogen-activated protein kinases (MAPK), and the pathological phenotypes of OPLL-derived mesenchymal stem cells (MSCs) have provided new insights on the molecular mechanisms underlying OPLL. This paper reviews the recent progress in understanding the pathophysiology of OPLL and proposes future research directions on OPLL.

UV-irradiation induces the formation of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts in DNA. These two types of lesions can be directly photorepaired by CPD photolyases and 6-4 photolyases, respectively. Recently, a new class of 6-4 photolyases named iron-Sulphur Bacterial Cryptochromes and Photolyases (FeS-BCPs) were found, which were considered as the ancestors of all photolyases and their homologs — cryptochromes. However, a controversy exists regarding 6-4 photoproducts only constituting ∼10-30% of the total UV-induced lesions that primordial organisms would hardly survive without a CPD repair enzyme. By extensive phylogenetic analyses, we identified a novel class of proteins, all from eubacteria. They have relatively high similarity to class I/III CPD photolyases, especially in the putative substrate-binding and FAD-binding regions. However, these proteins are shorter, and they lack the "N-terminal α/β domain" of normal photolyases. Therefore, we named them Short Photolyase-Like (SPL). Nevertheless, similar to FeS-BCPs, some of SPLs also contain four conserved cysteines, which may also coordinate an iron-sulphur cluster as FeS-BCPs. A member from Rhodococcus fascians was cloned and expressed. It was demonstrated that the protein contains a FAD cofactor and an iron-sulphur cluster, and has CPD repair activity. It was speculated that this novel class of photolyases may be the real ancestors of the cryptochrome/photolyase family.

Background: It is di cult to locate the real acetabulum in the total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH), The goal of this study was to explore the application of 3D printing navigation template used in total hip arthroplasty (THA) for developmental dysplasia of the hip. Methods: Between February 2017 and May 2018, THAs were performed in 25 patients with DDH, all patients (12 cases undergoing THA with 3D printing navigation template, 13 cases undergoing traditional THA) were followed-up for an average of 14.6 months. Surgical information and outcomes treated with different approaches were compared.Results: The 3D printing group provided shorter operation time, lower intra-and post-operative hemorrhage and higher post-operative Harris scores. postoperative infection and prosthetic loosening were 0 in two groups. There were no signi cant differences in anteversion angle, abduction angle and the distance from rotation center to the ischial tuberosity connection between ipsilateral and contralateral sides in 3D printing group. The abduction angle and the distance from rotation center to the ischial tuberosity connection were signi cantly different between the two sides in the traditional group. Conclusion:The nding suggests that 3D printing navigation template used in total hip arthroplasty is an individualized, accurate technology.