Osteotomies to shorten the ulna have proven to be an effective procedure for ulnar positive wrist syndrome. However, the procedure has been fraught with a number of mechanical problems which have limited its clinical and biological success. This work proposes a solution for some of these mechanical problems and tests this hypothesis in the laboratory and the clinical setting.

Twenty pairs of human ulnas (5 pairs in each group) had shortening osteotomies performed. One side had conventional transverse, “free-hand” cuts, coaptation by hand and compression and neutralization by a standard A0 3.5 mm, 7-hole DCP Plate. The contralateral ulna had a fixture attached to the bone to control the cutting saw and the bone fragments throughout the 45° osteotomy cuts and controlled coaptation and compression with an intrafragmentary lag screw and neutralization with a 2.5 mm, low profile, 7-hole plate. After the co-aptation, compression and neutralization were complete, the fixture was removed, and each ulna was elastically tested for bending (in two planes) and torsion stiffness, and for strength in apex volar bending. Bending stiffness of both plate designs was also measured.

Structural stiffness was clearly greater in torsion testing for the oblique osteotomy at a significance level of P < .04. No biomechanical difference was identified in the AP and lateral bending tests despite the fact that the low profile plate was only half the bending rigidity of the standard plate.

In a clinical trial, twenty-three transverse osteotomies were compared to seventeen oblique osteotomies using the described instruments. The healing rate and consistency was improved for the oblique osteotomy group compared to the transverse osteotomy group by 10.9 versus 20.6 weeks to healing in 100% versus 96% completely healed cases, respectively.

The osteotomy instrumentation system not only provided the surgeon with a means of reducing operative time, post-operative complications, ease of implementation and reduced hardware bulk in the subcutaneous region, but also improved the mechanical and clinical performance for short and long term due to the precision and configuration of the construct, requiring less mechanically demanding hardware.