Artificial radial head replacement for Mason type III comminuted fracture

Radial head fractures are relatively common. The radial head is a pivotal point for stability in relation to elbow valgus. Furthermore, maintenance of radial length and preservation of the radial head are important for preventing proximal movement of the radius. We present the case of a woman in her 50s who fell while riding her bicycle and injured her left radial head fracture. Although osteosynthesis was attempted, intraoperative findings indicated severe comminution, resulting in poor plate fixation. Therefore, artificial radial head replacement was performed. The utility of an artificial radial head replacement for severe radial head fractures has been reported. We also achieved a good functional outcome at a 6-month follow-up.


Background
Radial head fractures are relatively common, accounting for approximately 18% of elbow trauma [1,2]. The radial head is a pivotal point for stability in relation to elbow valgus and is also responsible for load transmission dispersal. Furthermore, maintenance of radial length and preservation of the radial head are important for preventing proximal movement of the radius [3]. We will report on how we achieved a good outcome by performing radial head replacement in a case of radial head comminuted fracture for which plate fixation was impossible.

Case presentation
A previously healthy woman in her 50s fell while riding her bicycle and injured her left radial head fracture (AO21-B2.3, Mason Type 3; Figures 1A and 1B). Although osteosynthesis was attempted with an LCP Radial Head Rim Plate, intraoperative findings indicated severe radial head comminution, resulting in poor plate fixation ( Figure 1C). Therefore, the radial head was removed, a radial head made with bone cement was used to fix the diaphysis with the plate, and surgery was concluded. Postoperatively, left elbow range of motion (ROM) was -30/110° and external/internal rotation (ER/IR) was 25/60°. Two months after initial surgery, radial head replacement was performed using an EVOLVE implant (Figures 2A and 2B). At 6 months postoperatively, the left elbow improved to ROM -20/130°, with ER/IR 90/90°. Motion was smooth and daily lifestyle was not impaired, although the patient experienced pain in her elbow when lifting heavy objects.

Discussion
As in our patient, internal fixation is difficult in radial head comminuted fractures, which are classified as Mason Type 3 injuries. Cases such as this have used to undergo radial head resection because the long postoperative casting period makes elbow contracture a concern [4]. However, the radial head is associated with valgus instability and joint pain due to distal radioulnar joint impingement caused by proximal movement of the radius. The utility of an artificial radial head replacement for cases such as this has been reported [5,6].
Ruan et al. [7] performed artificial radial head replacement in 14 Mason type 3 cases and achieved satisfactory outcomes in 13 (92.9%); in contrast, a satisfactory outcome was only achieved in 1 of 8 cases (12.5%) that underwent open reduction and internal fixation. Judet et al. [8] performed artificial radial head replacement in 12 Morrey Type  3 cases and reported favorable outcomes for in of the 12 after 2 or more years of follow-up. We also achieved a clinically favorable outcome for our patient with artificial radial head replacement.
Bipolar and loose-fitting implants are currently available [9]. With a bipolar artificial radial head prosthesis, the stem is fixed with cement and a movable part is created between the head and stem to respond to individual differences in radial head shape [10]. With loose-fitting artificial radial head prostheses, however, the fixation between the stem and radial diaphysis is actually loosened to respond to individual differences in radial shape [11].
We used a loose-fitting artificial implant in our patient. Harrington et al. reported on outcomes over a mean period of 12 years (6-29 years) for loose-fitting radial head prostheses in 20 cases, indicating that a gap of 1 -2 mm was noted around the stem in all cases at final evaluation [12]. Shore et al. reported on outcomes over a mean period of 8 years for two-stage surgery using loose-fitting radial head prostheses in 31 cases for which osteosynthesis failed and indicated that looseness was seen in 16 cases at final evaluation [13]. Based on the implant concept itself, it is conceivable that loosening will develop between the stem and radial head diaphysis, but there is no consensus regarding adverse events associated with progression of loosening.