A biomechanical comparison of the methods for treating Kienböck's disease

Reduction of lunate compression is thought to promote revascularization of the lunate in patients with Kienböck's disease. The decompressing abilities of ulnar lengthening, radial shortening, capitate-hamate fusion, and scaphoid-trapezium-trapezoid (STT) fusion were examined in axially loaded, whole arm specimens. Lunate strain was monitored by electronic strain gauges and found to be proportional to the axial load borne by the bone. The STT fusions and the procedures to alter relative radial and ulnar length were successful in relieving lunate loading throughout a functional range of wrist motion and forearm rotation, but the capitate-hamate fusion was ineffective. Only the STT fusion resulted in a significant decrease in wrist range of motion. Incremental ulnar lengthening and radial shortening revealed that approximately 2 mm of length change maximizes lunate decompression without greatly increasing the risk of disorders of the distal radioulnar joint and ulnocarpal impingement.