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An ash study was performed to analyze the accuracy of forearm measurements at the one-third site of three dual x-ray absorptiometry (DXA) systems using 20 cadavers. A Hologic QDR-2000, a Hologic QDR-1000/W, and a Lunar DPX-L system were used. The correlations between ash weight and DXA BMC were excellent for the three instruments (r0.97, p0.001), with accuracy errors5.2%. To perform a forearm cross-calibration of bone mineral content (BMC) and density (BMD) between the scanners, 10 healthy volunteers were additionally scanned at the distal one-third radius. The correlations among the DXA machines were excellent (r0.95); the absolute BMC and BMD values were significantly different between the two Hologics and the Lunar machine. The slope and intercept of both the BMC and BMD between the two Hologic systems were close to unity. In conclusion, the DXA forearm software packages provide accurate methods for assessing bone mineral content and density. The conversion of data among different manufacturers should be performed by careful cross-calibration measurements.

Ulnar nerve-innervated intrinsic muscle weakness, in the absence of sensory complaints or deficits, usually is the result of compression at the ulnar nerve in zone II of Guyon's canal. In rare instances the problem is not caused by a compressive neuropathy but by a demyelinating focal motor neuropathy. Demyelinating neuropathies have been well documented in the neurologic literature but they have received little attention in the hand surgery literature. We report on one such case and the importance of differentiating the 2 neuropathies. Although surgery often is necessary for a compressive neuropathy it is contraindicated for a demyelinating neuropathy.

The accuracy of a radiographic absorptiometry (RA) technique called digital image processing (DIP), discriminative ability of RA for osteoporotic fracture, and the relationship between RA and dual X-ray absorptiometry (DXA) of the spine and forearm were evaluated. We measured 16 cadaver hands, 32 healthy non-black premenopausal women, 39 healthy non-black postmenopausal women, and 35 non-black osteoporotic postmenopausal females. The overall correlation between the ash weights of the entire metacarpal and the DIP values was excellent (r = 0.954, P < 0.001, SEE = 0.14, CV = 6.4%). Short-term precision error of DIP was 3.5%. Age-related bone loss determined by DIP is comparable to that of spinal and forearm DXA: annual BMD decreases were 0.46% for DIP, 0.45% for forearm, and 0.32% for the spine. DIP of the 2nd metacarpal shows a gradient of risk for spinal fracture only slightly below that of forearm DXA, but substantially below that of spinal DXA. Age-adjusted odds ratios were 1.81 for RA, 2.45 for spinal DXA, and 1.94 for forearm DXA.