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A prospective, randomized, double-blind, placebo-controlled clinical trial was performed to investigate the efficacy of electrical muscle stimulation when combined with a therapist-guided, standardized exercise therapy program in the treatment of nonacute low back pain. Eighty patients with low back pain of at least 6 weeks' duration were randomized into the following 2 groups: standardized exercise therapy with functional electrical muscle stimulation or standardized exercise therapy with placebo electrical stimulation. Subjects were evaluated at baseline, 2 months, and 6 months with a standardized back pain questionnaire and objective measurements of lumbar spine function. Exercise therapy was continued for 6 months, but electrical stimulation was discontinued at the 2-month interval. Of the 80 patients initially enrolled, 42 discontinued or withdrew before completing the entire study protocol. At the 2-month follow-up interval, subjects in the treatment group had statistically significantly improved lumbar spine function compared with the control subjects. This effect continued during the last 4 months of the study after electrical stimulation had been discontinued. This suggests that electrical muscle stimulation can be an effective adjunctive treatment modality for nonacute low back pain. The effects of this combined therapy seem to last beyond the duration of electrical stimulation treatment.

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Revision of well-fixed, metal-backed acetabular components for dislocation or polyethylene failure requires consideration of removing the entire construct or replacing the polyethylene liner only. For non-modular or first-generation modular components with poor locking mechanisms, one option is to cement undersized liners into well-fixed shells. The purpose of this study was to measure the stability of undersized liners cemented into metal acetabular shells and compare the results with those of modular components. Hooded polyethylene liners measuring 28 x 50 mm and 28 x 56 mm were cemented into 66-mm acetabular shells (Smith & Nephew, Inc., Memphis, TN) with Simplex-P polymethylmethacrylate cement (Howmedica, Inc., Rutherford, NJ) giving 4- and 2-mm cement mantles, respectively. The force required to lever-out the liners from the shells was measured using the protocol described by Tradonsky et al. Assemblies with 4-mm mantles dissociated at an average of 322 +/- 47 in-lbf.; however, the assemblies with 2-mm mantles would not dissociate before the polyethylene yielded at torques as high as 600 in-lbf. These results compare favorably with the previously reported range (43 to 684 in-lbf) for modular acetabular components. These results suggest that undersized polyethylene liners can be cemented into well-fixed acetabular shells and expected to be stable.

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Fractures about the shoulder are a frequent occurrence. The clavicle and the proximal humerus are fractured much more often than the scapula. Appropriate diagnosis of these injuries and any associated injuries is essential. The vast majority of these fractures may be treated conservatively with good functional results.

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Biomaterials exposed to blood often fail due to thrombosis. Gas nuclei (air) in the material are thrombogenic and a potential cause of failure. The effects of gas nuclei on patency and blood flow were studied in 4 mm diameter arterial grafts (Gore ePTFE; Johnson and Johnson Vitagraft ePTFE; Bard ACG EXS) in the femoropopliteal position of dogs. Control and denucleated (air-free) grafts were implanted bilaterally. Grafts were denucleated by immersion in degassed saline and exposure to 4 torr vacuum and 3,000-20,000 psig pressure. Graft patency was determined at harvest in 46 dogs. Blood flow was measured with acoustic flow probes in eight dogs. Denucleated graft patency was 60% after 2 days of implant while control patency was 22% (P < .05). Measured blood flow was higher in denucleated grafts than in control grafts (P < .02) in 4 of 5 dogs which had significantly different flows. Patency and flow decreased to zero for both control and denucleated grafts over periods of up to 80 days. Air in the control grafts may have been absorbed within several days, leading to late similarity with the denucleated grafts. Thus, removing the air from 4 mm ePTFE grafts decreased acute thrombosis and increased the patency.

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In vitro methods were developed to measure the air content of vascular graft walls and the thrombogenicity of this air. Gas content (volume %) of expanded polytetrafluoroethylene (ePTFE) grafts from different sources ranged from 75.5 +/- 0.4% to 61.8 +/- 0.3%. Exposure of Vitagraft ePTFE to a vacuum prior to saline immersion replaced 87.5% of the gas nuclei with saline (denucleation). Acetone and ethanol immersion produced 98.9% and 94.3% denucleation, respectively. Denucleation was essentially complete when vacuum exposure was followed by hydrostatic pressure treatment at 500 psig or greater. The influence of gas content on thrombogenicity was determined by immersing graft samples in whole canine blood and weighing the adherent thrombus. Denucleation significantly reduced adherent thrombus weight compared with control grafts (p less than 0.001). Air in Vitagraft walls was responsible for 84% of the adherent thrombus weight at four minutes. The described methods could be employed to assess the hemocompatibility of various biomaterials.

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