Relationship between the tilt angle of bipolar radial head prostheses and radiological radiocapitellar instability.

OBJECTIVE: This study aimed to radiologically assess the relationship between the tilt angle of the bipolar radial head prostheses and radiocapitellar instability. METHODS: In this radiological study, 28 consecutive patients (13 females and 15 males: mean age=47 years and age range=23-77 years) who underwent cemented bipolar radial head arthroplasty (Judet CRF II) because of comminuted radial head fracture with elbow instability were retrospectively reviewed. RESULTS: There was excellent intra- and interobserver reliability for the measurements of the tilt angle and the radiocapitellar distance. ICC for interobserver reliability of the tilt angle was 0.93, and ICC for intraobserver reliability for the 2 observers was 0.96 and 0.97, respectively. ICC for interobserver reliability of the radiocapitellar distance was 0.87, and ICC for intraobserver reliability for the 2 observers was 0.91 and 0.93, respectively. The mean tilt angle was 17.6° (range=1°-35°), and the mean radiocapitellar distance was 8 mm (range=1-17 mm). Pearson's correlation revealed a strong significant positive correlation between the tilt angle and the radiocapitellar distance (r=0.77 and p<0.001). CONCLUSION: Evidence from this study has demonstrated a strong positive correlation between the tilt angle of bipolar radial head prostheses and radiocapitellar instability. The tilt angle can be used as an indicator of radiocapitellar joint instability following bipolar radial head prostheses. LEVEL OF EVIDENCE: Level IV, Diagnostic study.