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Can ulnar variance be used to detect overstuffing after radial head arthroplasty?
Jun-Gyu Moon1, Jin-Ho Hong, Nitin Bither
1Department of Orthopedic Surgery, Korea University Guro Hospital, 97 Gurodong-gil, Guro-gu, Seoul, 152-703, Korea, moon@korea.ac.kr.
Background:
Overstuffing of the radiocapitellar joint during metallic radial head arthroplasty has been reported to cause loss of elbow flexion, capitellar erosion, and early-onset osteoarthritis. Although this is known, there is no agreed-on measurement approach to determine whether overstuffing has occurred.
Questions/Purposes:
We therefore hypothesized that overlengthening the radial head during radial head arthroplasty changes the ulnar variance in the wrist.
Methods:
Seven cadaveric radii were implanted with radial head prostheses of increasing thickness. Each specimen was implanted successively with increasingly thick radial head prostheses measuring 2, 4, and 6 mm thicker than the native radial head, and radiographs were taken after implantation of each prosthesis. The ulnar variance with each prosthesis was measured using the method of perpendiculars.
Results:
The ulnar variance of the native and 2-mm (p = 0.04), 4-mm (p = 0.008), and 6-mm (p = 0.008) overly thick radial head prosthesis-implanted states decreased significantly with each incremental increase in prosthetic head thickness.
Conclusions:
Implantation of thicker radial head prostheses decreased the ulnar variance. Our results indicate ulnar variance could be used to detect overstuffing of radial head prostheses.
Clinical Relevance:
The simplicity and reliability of ulnar variance make it a potentially useful indicator of overlengthening after radial head arthroplasty.
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