An article in Bioelectromagnetics (“Electromagnetic Effects on Forearm Disuse Osteopenia: A Randomized, Double-Blind, Sham-Controlled Study,” Vol. 32, 2011, pp. 273–282) described a randomized, double-blind, sham-controlled, feasibility and dosing study to determine if a common pulsing electromagnetic field (PEMF) treatment could moderate the substantial osteopenia that occurs after forearm disuse. Subjects were randomized into four groups after a distal radius fracture, or carpal surgery requiring immobilization in a cast. Active or identical sham PEMF transducers were worn on the distal forearm for 1, 2, or 4 h/day for 8 weeks starting after cast removal (“baseline”) when bone density continues to decline. Bone mineral density (BMD) and bone geometry were measured in the distal forearm by dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). The data below are the percent losses in BMD measurements on the radius after 16 weeks for patients wearing the active or sham PEMF transducers for 1, 2, or 4 h/day (data were constructed to match the means and standard deviations read from a graph in the paper).

(a) Is there evidence to support a claim that PEMF usage affects BMD loss? If so, analyze the data to determine which specific treatments produce the differences.

(b) Analyze the residuals from this experiment and comment on the underlying assumptions and model adequacy.

Sham PEMF 1 h/day PEMF 2 h/day PEMF 4 h/day 4.51 5.32 4.73 7.03 7.95 6.00 5.81 4.65 4.97 5.12 5.69 6.65 3.00 7.08 3.86 5.49 7.97 5.48 4.06 6.98 2.23 6.52 6.56 4.85 3.95 4.09 8.34 7.26 5.64 6.28 3.01 5.92 9.35 7.77 6.71 5.58 6.52 5.68 6.51 7.91 4.96 8.47 1.70 4.90 6.10 4.58 5.89 4.54 7.19 4.11 6.55 8.18 4.03 5.72 5.34 5.42 2.72 5.91 5.88 6.03 9.19 6.89 7.50 7.04 5.17 6.99 3.28 5.17 5.70 4.98 5.38 7.60 5.85 9.94 7.30 7.90 6.45 6.38 5.46 7.91