Results of all-polyethylene tibial components as a cost-saving technique.

Since 1992, the authors have used an all polyethylene tibial component in relatively less active patients older than 70 years of age who present for primary total knee replacement. Results of 312 knee replacements performed between March 1992 and March 1998 are presented in the hopes of showing this technique as a viable cost saving measure. Three hundred twelve primary total knee replacements were performed by the same group of surgeons. Fourteen patients died before the first year postoperative evaluation, leaving an index group of 298 knees in 231 patients. All components were evaluated using the radiographic and clinical parameters of the Knee Society. Hospital for Special Surgery scores also were calculated. All patients were given the Short Form-36 Quality of Life Assessment preoperatively and annually postoperatively. Clinical scores showed dramatic improvement. There have been three revisions (0.7%) but none were for aseptic loosening. Radiographic review revealed 295 replacements with optimum fixation. To date, no patient has osteolysis. The cost differential was significant. The use of this type of tibial component has, to date, afforded excellent clinical and radiographic results. Additional followup is needed to show the longevity of these results and to monitor wear or subsidence of these prostheses. Should these results continue to prove satisfactory in this particular group of patients with relatively low physical demands, significant cost savings may be realized.

Effects of sex steroids on sleep.

Sex steroid secretions are generally synchronous with the circadian rhythm and sleep, and there is evidence that prolactin secretion is sleep-dependent. Polysomnographically assessed changes in sleep during the menstrual cycle are characterized by increased EEG activity in the 14-15-Hz (sleep spindle) range in the luteal phase accompanying an increase in core temperature. There are no other consistent changes in sleep architecture associated with the menstrual cycle. The hot sweats which disturb sleep in menopausal women are attributable to oestrogen deficiency and are reduced by oestrogen replacement therapy. Although it is often assumed that the psychological changes during the menopause are attributable to chronic sleep disturbance caused by hot sweats, the evidence for this is uncertain. Sex steroids have also been shown to have a role in the aetiology of obstructive sleep apnoea and its treatment. It is clear that the sex steroids are all implicated in sleep and thermoregulatory processes, although we cannot as yet define their precise roles.

Hormone replacement therapy, sleep quality and psychological wellbeing.

OBJECTIVE: To examine the effect of hormone replacement therapy upon sleep quality and duration in postmenopausal women. DESIGN: Randomised, single-blind, placebo-controlled trial. SETTING: Sleep research laboratory. SUBJECTS: Thirty-three healthy postmenopausal women. INTERVENTIONS: Continuous 0.625 mg conjugated equine oestrogens with 0.15 mg cyclic norgestrel taken for 12 days per 28 day cycle. MAIN OUTCOME MEASURES: Occurrence of vasomotor symptoms, polysomnographic sleep stage measures, Stanford sleepiness questionnaire, Crown-Crisp experiential index and the cognitive failures questionnaire. RESULTS: Hormone replacement therapy results in an improvement in menopausal symptoms but not in parameters of sleep quality. Despite this, certain measures of psychological wellbeing showed significant improvement in the hormone replacement therapy group. CONCLUSION: Hormone replacement therapy results in a measurable improvement in physical and psychological welfare, the latter being independent of improvement in sleep quality.

Slow potentials preceding vocalisation.

Twenty-four subjects equally represented by males and females, and left- and right-handers, had slow potentials recorded prior to vocalisation of the same word 25 times ('Yes'), or a different word every sweep, chosen by the subject 5. Negativity on the scalp preceding generated words came earlier than preceding repetitions. Asymmetry in EEG was dependent on handedness, and occurred frontally in females, centrally in males. It is suggested that task-related differences in slow potentials preceding speech, and asymmetries associated with handedness, provide evidence that these potentials are not irretrievably contaminated by movement and respiratory artefacts.

Auditory evoked potentials and transcendental meditation.

Auditory evoked potentials to tone stimuli were recorded from 8 practised meditators before, during, and after meditation, and also during light sleep. No consistent changes were noted between baseline and meditating AEPs, or between meditating and sleep AEPs.

REM sleep and memory consolidation.

One proposal referring to a specific function of REM sleep has been that it is necessary for, or at least conductive to, the progress of memory consolidation. This hypothesis was tested by comparing the effects on story retention of REM deprivation against an S4 deprived control. It was found that recall accuracy following REM deprivation was significantly poorer than following S4 deprivation. Furthermore, the degree of deterioration in recall accuracy during REM recovery sleep was less than during S4 recovery sleep. These findings were interpreted as evidence for active REM facilitation of memory consolidation. However, alternative explanations based upon proactive influences need to be investigated.