Shoulder & Elbow

Humeral fractures and longevity

X-ref

The proximal humerus is one of the most common sites for fragility fractures, and like the neck of femur fracture, is common amongst the elderly and frail. There is little known about the impact of a proximal humeral fracture on quality and length of life, and our expectations here at 360 were high when we stumbled across this paper from Herley (Denmark) which reports the outcomes of arthroplasty for proximal humeral fractures.⁶ This registry-based study reports mortality as its primary outcome measure and is based on the results of 5853 primary shoulder arthroplasties performed over a six-year period. The authors essentially undertook a rather simple study comparing mortality between groups for diagnoses at the arbitrary end points of 30 days, 90 days and a year. Perhaps unsurprisingly, those patients with a fracture had a six-fold risk of mortality when compared with the general population and those shoulder arthroplasties being performed for arthritis during the first 30 days. While none of the information presented here is new – and we can’t help wondering if more could have been made of a large cohort of patients such as these – it does underline the difficult nature of these injuries, and that it isn’t just hip fractures that carry a significant mortality burden.

The glenosphere and clinical outcomes

Despite the dramatic rise in popularity over the past few years in the use of the reverse shoulder and impressive clinical results seemingly able to salvage a functional shoulder from some of the most bleak of situations, the reverse shoulder suffers from many of the same limitations that the total shoulder does on the glenoid side with regards to bone stock and longevity; however the biomechanics are of course significantly different. It is the impact of these different biomechanics and specifically the glenosphere diameter that is the focus of an important clinical outcomes paper from New York (USA).⁷ The authors report a prospective case-controlled series of 297 primary reverse shoulder arthroplasties. The procedures were undertaken using either a 38 mm or 42 mm glenosphere, and clinical outcomes were measured using the American Shoulder and Elbow Surgeons (ASES) scores and clinical assessment of range of motion. As perhaps could be expected from the small number of preceding biomechnical studies, those patients with the larger 42 mm glenosphere had significantly improved forward elevation and active external rotation. The authors do not however report a clear pattern in clinical outcomes with the male shoulders performing better with the 38 mm glenosphere and the female shoulders performing better with the 42 mm implant. There were no differences in the intra-operative complication rates. It is perhaps not surprising that there is little association between clinical score and implant size; however the clinical improvement in range of motion associated with a larger glenosphere is potentially a very important observation. There are few implant design features in any arthroplasty that have been demonstrated to improve clinical outcomes. We remained potentially slightly concerned about the impact on the biomechanics of the glenoid fixation. A larger glenospehere will result in more torque forces dissipated across the glenoid fixation, and any impact in longevity will of course not be apparent in a two year follow-up series.