Analyzing on the location of the bicipital groove for alignment in shoulder arthroplasty of Chinese.

BACKGROUND: Many anthropometric studies of the normal glenohumeral relationship have been performed for the implant design and to identify reference points for the correct placement of the prosthesis in glenohumeral joint replacement. However, whether those implantation marks, which adopted from European or American, can achieve the same precision to Eastern Asian, specifically Chinese is still unknown.

MATERIALS AND METHODS: One hundred eighty healthy were scanned using CT. Their humeri were measured to determine humeral head retroversion and its relation to the location of the bicipital groove. The angle between the transepicondylar axis and the line connected the centre of the head sphere and the lateral lip point of the bicipital groove, and the plane through the humerus shaft axis and the lateral lip of the bicipital groove in the horizontal plane were measured and denoted by angle-α and angle-β, respectively. The biceps distance (BD) from the lateral lip of the bicipital groove proximally to the axis of humeral head in the horizontal plane was also measured.

RESULTS: The average angle α and β was 40.08° (±11.15°) and 42.19° (±12.64°). The average BD was 7.15 mm (range 0.87-13.94 mm; SD 2.55 mm). The linear relationship between humeral head retroversion and the bicipital groove angle α can expressed as α = 0.7125 × retroversion+24.8128 (R2  = 0.5956). If the centre of the lateral aspect of the stem has a posteriorly offset of 20° from the lateral lip of the bicipital groove, the component would have a proximal 20° of retroversion.

CONCLUSION: The results indicate that the bicipital groove can be used as a landmark for prosthetic stem positioning in shoulder arthroplasty. Moreover, it is different from the current standard technique of cutting the proximal humerus at 30° of retroversion with the epicondyles or forearm used as a guide.