Does reverse total shoulder arthroplasty for proximal humeral fracture portend poorer outcomes than for elective indications?

BACKGROUND: The number of reverse total shoulder arthroplasties (RTSAs) performed annually has increased, and the indications for RTSA have expanded beyond rotator cuff arthropathy to include treatment of complex proximal humeral fractures. No studies exist comparing clinical, functional, and radiographic outcomes in patients receiving RTSA for the treatment of acute fracture vs. those undergoing the procedure for degenerative conditions. This study was designed to fill the void in this knowledge gap. We hypothesized that patients undergoing RTSA for fracture treatment would experience worse clinical outcomes than those undergoing elective RTSA. METHODS: A prospectively collected database was queried for patients undergoing RTSA between 2007 and 2016. Patients were sorted based on the indication for RTSA: treatment of acute proximal humeral fracture vs. "elective" treatment of degenerative conditions of the shoulder. Baseline demographic characteristics, intraoperative and perioperative complications, and clinical, functional, and radiographic outcomes were collected. Only patients with ≥2 years' follow-up were included. Final outcomes were compared between the fracture and elective groups. RESULTS: In total, 1984 patients met the inclusion criteria, with 1876 in the elective group and 108 in the fracture group. Compared with the elective RTSA group, the group undergoing RTSA for fracture treatment was older, was female dominant, and was less likely to have undergone a previous operation on the ipsilateral shoulder. RTSA for fracture was associated with a longer hospital length of stay and greater intraoperative blood loss. The incidence of postoperative adverse events was 7.1% in the elective group vs. 4.6% in the fracture group. Functional outcomes did not differ beyond 1 year or at mean final follow-up > 40 months. CONCLUSION: Despite differences in patient demographic characteristics, the outcome and complication profiles are similar between patients undergoing RTSA for acute fracture and those indicated for the treatment of degenerative conditions of the shoulder.

The Effect of Divalent Cations on the Thermostability of Type II Polyketide Synthase Acyl Carrier Proteins.

The successful engineering of biosynthetic pathways hinges on understanding the factors that influence acyl carrier protein (ACP) stability and function. The stability and structure of ACPs can be influenced by the presence of divalent cations, but how this relates to primary sequence remains poorly understood. As part of a course-based undergraduate research experience, we investigated the thermostability of type II polyketide synthase (PKS) ACPs. We observed an approximate 40 °C range in the thermostability amongst the 14 ACPs studied, as well as an increase in stability (5 - 26 °C) of the ACPs in the presence of divalent cations. Distribution of charges in the helix II-loop-helix III region was found to impact the enthalpy of denaturation. Taken together, our results reveal clues as to how the sequence of type II PKS ACPs relates to their structural stability, information that can be used to study how ACP sequence relates to function.