Background Improvements in metal-on-metal bearings have made hybrid hip surface replacement a potential alternative for the young active patient with end-stage hip disease. Possible advantages ...include greater hip joint stability, bone preservation, and decreased osteolysis. In this study, we compared the clinical and radiographic results of a new resurfacing device with those in a historical group of standard total hip arthroplasties. Methods In 2001, the Cormet 2000 Hip Resurfacing Investigational Device Exemption study was initiated at twelve centers. A total of 337 patients treated with unilateral hip surface replacement with the Cormet device were enrolled in that study. These patients were compared with 266 patients in a previous study who had undergone unilateral total hip arthroplasty with ceramic bearing surfaces. Clinical and radiographic results were compared at similar time intervals. A newly recommended performance standard, the composite clinical success score, was used to assess non-inferiority of the hip resurfacing compared with the total hip arthroplasty used in the historical comparison population. Results At the time of follow-up, at a minimum of two years, the Harris hip scores were comparable between the resurfacing and total hip arthroplasty groups. Statistical evaluation of the composite clinical success scores confirmed the non-inferiority hypothesis. Revision was required in twenty-four patients in the resurfacing group and five patients in the total hip arthroplasty group. The most common cause of revision following resurfacing was failure of the femoral component (fracture of the femoral neck or loosening of the femoral component). Conclusions Careful review of this study population revealed several important criteria for successful introduction of this resurfacing device into the United States. These include careful patient selection based on clinical and radiographic parameters and attention to various surgical details of implantation. These findings can be used to focus the training process for surgeons who wish to add implantation of this device to their surgical armamentarium. Such efforts should help to ensure safe and effective introduction of this new technology. Level of Evidence Therapeutic Level II . See Instructions to Authors for a complete description of levels of evidence.
Periodic breathing with central apneas during sleep is typically triggered by hypocapnia resulting from hyperventilation. We therefore hypothesized that hypocapnia would be an important determinant ...of Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) in patients with congestive heart failure (CHF). To test this hypothesis, 24 male patients with CHF underwent overnight polysomnography during which transcutaneous PCO2 (PtcCO2) was measured. Lung to ear circulation time (LECT), derived from an ear oximeter as an estimate of circulatory delay, and CSR-CSA cycle length were determined. Patients were divided into a CSR-CSA group (n = 12, mean +/- SEM of 49.2 +/- 6.3 central apneas and hypopneas per h sleep) and a control group without CSR-CSA (n = 12, 4.9 +/- 0.8 central apneas and hypopneas per h sleep). There were no significant differences in left ventricular ejection fraction, awake PaO2, mean nocturnal SaO2, or LECT between the two groups. In contrast, the awake PaCO2 and mean sleep PtcCO2 were significantly lower in the CSR-CSA group than in the control group (33.0 +/- 1.2 versus 37.5 +/- 1.0 mm Hg, p < 0.01, and 33.2 +/- 1.2 versus 42.5 +/- 1.2 mm Hg, p < 0.0001, respectively). Neither group had significant awake or sleep-related hypoxemia. In addition, CSR-CSA cycle length correlated with LECT (r = 0.939, p < 0.001). We conclude that (1) hypocapnia is an important determinant of CSR-CSA in CHF and (2) circulatory delay plays an important role in determining CSR-CSA cycle length.
The biomotometer, an electronic device that simultaneously measures activity and provides auditory feedback to the subject, was used in combination with material reinforcers in two experiments ...attempting to modify activity level in children. In the first study the activity level of an 11-year-old highly active boy was decreased below mean baseline during conditioning in a classroom setting. His level of activity returned to baseline when feedback was withdrawn. In the second study, activity level of a 10-year-old hypoactive boy was increased over mean baseline level during conditioning in a free-play setting, and returned to slightly below baseline during five extinction trials. Results of these studies indicate that the biomotometer is a useful instrument for modification of activity level.
The biomotometer, an electronic device that simultaneously measures activity and provides auditory feedback to the subject, was used in combination with material reinforcers in two experiments ...attempting to modify activity level in children. In the first study the activity level of an 11‐year‐old highly active boy was decreased below mean baseline during conditioning in a classroom setting. His level of activity returned to baseline when feedback was withdrawn. In the second study, activity level of a 10‐year‐old hypoactive boy was increased over mean baseline level during conditioning in a free‐play setting, and returned to slightly below baseline during five extinction trials. Results of these studies indicate that the biomotometer is a useful instrument for modification of activity level.
The biomotometer, an electronic device that simultaneously measures activity and provides auditory feedback to the subject, was used in combination with material reinforcers in two experiments ...attempting to modify activity level in children. In the first study the activity level of an 11‐year‐old highly active boy was decreased below mean baseline during conditioning in a classroom setting. His level of activity returned to baseline when feedback was withdrawn. In the second study, activity level of a 10‐year‐old hypoactive boy was increased over mean baseline level during conditioning in a free‐play setting, and returned to slightly below baseline during five extinction trials. Results of these studies indicate that the biomotometer is a useful instrument for modification of activity level.
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