Radial head arthroplasty (RHA) mal-alignment can occur when there is excessive tilt of the radial head stem relative to the radial canal. The clinical significance, cause and management for increased RHA tilt is poorly understood. Our primary objective was to compare clinical outcomes in patients with excessive radiographic RHA tilt to controls. A secondary objective was to determine whether radiographic stem alignment measurements can predict clinical outcomes. We performed a retrospective chart review of patients who underwent isolated RHA between 1999–2021 for acute radial head fractures using a smooth-stemmed modular metallic radial head implant. Excessive RHA tilt was defined as patients with a high-neck shaft angle in AP view (greater than 1SD above the mean). Patient demographics, clinical outcomes (PREE, QuickDASH, MEPI, ROM, complications, reoperations), and radiographic measurements were compared between patients with excessive RHA tilt and controls (Figure 1). Radial head alignment was assessed using several parameters including radial neck-shaft angle, lateral overhang distance RHA implant, PRUJ angle, radial neck length, radial neck width, radial neck cut angle, and radial tuberosity width (Figure 2). Regression modelling was used to determine whether the radiographic alignment parameters were predictive of outcomes (PREE, QuickDASH, MEPI), complications and reoperations. Sixty-one patients were included in the study, 10 patients with mal-alignment of the RHA and 51 patients in the control group. There was no significant difference in patient characteristics between groups (age, gender, handedness, smoking, time to surgery, follow-up time) (p>0.01). Mean follow-up time was 6.9±2.7 years for RHA tilt and 8.0±7.7 years for controls. In the tilt group, there were significantly higher neck-shaft angles, lateral overhang of RHA implant, PRUJ angles, and lucency grading around the implant (p 0.01). There were no differences in RHA stem alignment between groups at 6 weeks postoperatively. Excessive RHA tilt was observed as a late finding, at least 1 year after surgery. The excessive RHA tilt cohort had higher reported pain and disability; however they did not demonstrate higher rates of complications or revision surgery compared to the control group. RHA overhang distance relative to the capitellum was the only other radiographic parameter that significantly predicted clinical outcomes. Excessive RHA tilt appeared to develop over time as it was not typically seen in the early postoperative period. We speculate that preserving more radial neck length where possible and performing a radial neck cut that is perpendicular to the radial neck may help to reduce the risk of developing excessive implant tilt when using a smooth stem RHA. For any figures or tables, please contact the authors directly.
Tat et al. (Wed,) studied this question.