Physeal Closure and Fracture Pattern in Adolescent Transitional Distal Radius Fractures.

PURPOSE: To show a correlation between grade of physeal closure and fracture pattern in adolescent transitional distal radius fractures. METHODS: A retrospective chart review was performed of 490 distal radius fractures, ages 14 to 18, at a single institution between 2007 and 2020. A board-certified orthopaedic hand surgeon reviewed all images. Thirty-six distal-radius fractures were considered adolescent transitional fractures. The review included Salter-Harris classification, fracture fragments, and grade of physeal closure. RESULTS: Distal radial physeal closure is 50 times more likely to be of a higher grade in the presence of Salter-Harris type IV fractures ( P <0.001). Closure of the physis is also 7.37 and 13.08 times more likely to be of higher grade in the absence of a dorsal metaphyseal fracture and in the presence of an ulnar corner fracture, respectively ( P =0.011 and 0.021). CONCLUSION: Adolescent transitional fractures of the distal radius occur when the growth plate has a partial closure. The closure pattern of the distal radial physis begins centrally, with subsequent ulnar and then radial closure. In this cohort, there is a correlation between grade of physeal closure and fracture pattern in adolescent transitional distal radius fractures. LEVEL OF EVIDENCE: Level IV-diagnostic.

The internal joint stabilizer for chronic elbow dislocation: a surgical technique.

The main goal of treatment for chronically unreduced elbow dislocations is to restore a stable, concentric joint and regain a satisfactory arc of motion. Due to the conflicting goals of restoring elbow stability and regaining a good arc of motion, the treatment of chronic elbow dislocation remains a challenge for even the experienced orthopedic surgeon. The standard treatment of these dislocations consists of open reduction, V-Y muscleplasty of the triceps, and temporary arthrodesis or cast immobilization. However, prolonged postoperative immobilization may result in elbow stiffness, which significantly limits the functional outcome. We present our surgical technique with a focus on restoring stable reduction such that early motion can be instituted and complications of prolonged immobilization can be avoided. From position to wound closure, surgical steps are presented in detail, with pearls for practice and a discussion on chronic elbow dislocation. The internal joint stabilizer is a safe and effective implant that complements the management of chronic elbow dislocations. This reproducible surgical technique allows for stability and early mobility while having the added benefit of circumventing complications associated with prolonged immobilization and hinged external fixation. Understanding the surgical indications, as well as the nuances of the surgical technique utilizing the internal joint stabilizer, is critical in order to improve patient outcomes and avoid complications.

Biosynthesis and transport of the lantibiotic mutacin 1140 produced by Streptococcus mutans.

UNLABELLED: Lantibiotics are ribosomally synthesized peptide antibiotics composed of an N-terminal leader peptide that is cleaved to yield the active antibacterial peptide. Significant advancements in molecular tools that promote the study of lantibiotic biosynthesis can be used in Streptococcus mutans. Herein, we further our understanding of leader peptide sequence and core peptide structural requirements for the biosynthesis and transport of the lantibiotic mutacin 1140. Our study on mutacin 1140 biosynthesis shows a dedicated secondary cleavage site within the leader peptide and the dependency of transport on core peptide posttranslational modifications (PTMs). The secondary cleavage site on the leader peptide is found at the -9 position, and secondary cleavage occurs before the core peptide is transported out of the cell. The coordinated cleavage at the -9 position was absent in a lanT deletion strain, suggesting that the core peptide interaction with the LanT transporter enables uniform cleavage at the -9 position. Following transport, the LanP protease was found to be tolerant to a wide variety of amino acid substitutions at the primary leader peptide cleavage site, with the exception of arginine at the -1 position. Several leader and core peptide mutations produced core peptide variants that had intermediate stages of PTM enzyme modifications, supporting the concept that PTM enzyme modifications, secondary cleavage, and transport are occurring in a highly coordinated fashion. IMPORTANCE: Mutacin 1140 belongs to the class I lantibiotic family of ribosomally synthesized and posttranslationally modified peptides (RiPPs). The biosynthesis of mutacin 1140 is a highly efficient process which does not lead to a discernible level of production of partially modified core peptide variants. The products isolated from an extensive mutagenesis study on the leader and core peptides of mutacin 1140 show that the posttranslational modifications (PTMs) on the core peptide occur under a highly coordinated dynamic process. PTMs are dictated by the distance of the core peptide modifiable residues from PTM enzyme active sites. The formation of lanthionine rings aids in the formation of successive PTMs, as was observed in a peptide variant lacking a C-terminal decarboxylation.

The leader peptide of mutacin 1140 has distinct structural components compared to related class I lantibiotics.

Lantibiotics are ribosomally synthesized peptide antibiotics composed of an N-terminal leader peptide that promotes the core peptide's interaction with the post translational modification (PTM) enzymes. Following PTMs, mutacin 1140 is transported out of the cell and the leader peptide is cleaved to yield the antibacterial peptide. Mutacin 1140 leader peptide is structurally unique compared to other class I lantibiotic leader peptides. Herein, we further our understanding of the structural differences of mutacin 1140 leader peptide with regard to other class I leader peptides. We have determined that the length of the leader peptide is important for the biosynthesis of mutacin 1140. We have also determined that mutacin 1140 leader peptide contains a novel four amino acid motif compared to related lantibiotics. PTM enzyme recognition of the leader peptide appears to be evolutionarily distinct from related class I lantibiotics. Our study on mutacin 1140 leader peptide provides a basis for future studies aimed at understanding its interaction with the PTM enzymes.