Anatomic Radial Head Arthroplasty: The Importance of Implant Angle

Multifragmentary radial head and neck fractures not amenable to open reduction and internal fixation are usually treated with radial head arthroplasty (RHA). Although the optimal implant design is still subject to debate, anatomic designs are common. We hypothesized that positioning of the implant leading to increased radial stem angle (RSA) (angle of the RHA stem with respect to the proximal radius shaft, RSA) in anatomic RHA designs will contribute to failures. The aim of this study was to characterize the risk of RHA failure with respect to the stem angle in anatomic RHA design. A retrospective review of patients who underwent anatomic RHA for acute fractures between 2006 and 2019 at 2 academic centers was conducted. Initial postoperative elbow radiographs were reviewed to measure RSA on the anterior-posterior and lateral views. Radiolucency, stress shielding, and radiocapitellar arthritis were also evaluated. Implant failure was defined as prosthesis removal or revision. Implant failure was associated with significantly larger lateral RSA than that in intact implants. Increasing stem shaft angle on a lateral radiograph was associated with decreased implant survival. Radiolucency, stress shielding, and radiocapitellar arthritis were similar between the 2 groups. Anatomic radial head implants are commonly used; however, the importance of prosthesis positioning, specifically that of the stem within the proximal radius, remains understudied. Higher RSA is associated with the risk of implant failure and need for revision. Prognostic IV.