Summary

Overlengthening in radial head arthroplasty can reliably be avoided by visualizing the dorsolateral ulnohumeral joint space Intraoperatively

Abstract

Introduction

The correct implantation of radial head arthroplasty to avoid overlengthening is essential for the prognosis of the elbow joint. Frank et al. showed that an overlengthening above 2 mm is visible due to widening of the anterolateral ulnohumeral joint space but intraoperatively, this particular joint space is difficult to visualize. Whereas the commonly used Kocher approach allows visualization of the dorsolateral joint space without additional instruments or further surgical release of the already unstable elbow. Taking this into consideration the aim of our study was to investigate whether the easier visualization of the dorsolateral joint space is also a reliable method to indicate overlengthening in radial head arthroplasty.

Material And Methods

Radial head arthroplasty was performed in 5 human cadaver specimens with the forearm, wrist, and hand intact. The lateral ligament complex was detached and an isometric transosseous refixation was performed. 6 stages of implantation heights were documented for the radial head arthroplasty: native joint with LCL repair (1), perfect height (2), + 2mm (3), + 4mm (4), + 6mm (5) and -2 mm (6). Clinical measurement and image analysis of the dorsolateral and anterolateral ulnohumeral joint space was performed.

Results

The dorsal and anterior lateral ulnohumeral joint space width was negligible in the native joint with LCL repair (1) and the radial head arthroplasty implanted at correct height (2) as well as implantation with -2 mm (6). There was a significant increase in joint space width at all stages of overlengthening (+ 2, + 4 and + 6 mm) compared to stage 1, 2 and 6. Overlengthening of + 2mm showed a mean gap of 1,9 ? 0,97 mm dorsal (p=0,0081) and 1,59 ? 0,61 mm anterior (p.=0,0482). The mean gap size dorsal in + 4 mm was 3,52 ± 1,51 mm and 5,20 ± 1,63 mm at + 6 mm implantation height . Anterior an overlengthening of + 4 mm showed a mean ulnohumeral joint space width of 3,06 ? 0,43 mm and 5,07 ? 0,40 mm at + 6 mm implantation height.
The intraclass correlation coefficient was 0.997 and the 95% confidence interval was 0.9673 to 0.9996 between the dorsal and anterior ulnohumeral joint space.

Conclusion

Visualization of the dorsolateral aspect of the ulnohumeral joint space is a reliable indicator for overlengthening in radial head arthroplasty without further compromising an already unstable elbow. The method from Frank et al. regarding the anterolatral joint space could further be adapted to a alternative radial head arthroplasty system than described in the original paper. Merging the findings of the anterolateral ulnohumeral joint space in different implants leads to the assumption that visualization either of the ulnohumeral joint space dorsally or anteriorly is universally applicable to determine overlengthening in radial head arthroplasty, regardless of the type of the radial head implant.