Accurate Leg Length Measurement in Total Hip Arthroplasty: A Comparison of Computer Navigation and a Simple Manual Measurement Device

BACKGROUND: Several studies have shown that better placement of the acetabular cup and femoral stem can be achieved in total hip arthroplasty (THA) by using the computer navigation system rather than the free-hand alignment methods. However, there have been no comparisons of the relevant clinical advantages in using the computer navigation as opposed to the manual intraoperative measurement devices. The purpose of this study is to determine whether the use of computer navigation can improve postoperative leg length discrepancy (LLD) compared to the use of the measurement device. METHODS: We performed a retrospective study comparing 30 computer-assisted THAs with 40 THAs performed using a simple manual measurement device. RESULTS: The postoperative LLD was 3.0 mm (range, 0 to 8 mm) in the computer-assisted group and 2.9 mm (range, 0 to 10 mm) in the device group. Statistically significant difference was not seen between the two groups. CONCLUSIONS: The results showed good equalization of the leg lengths using both computed tomography-based navigation and the simple manual measurement device.

The effect of bench-stepping exercise training on BMD, BMC and bone metabolism in menopausal women / 体力科学

Since the effect of the submaximal aerobic exercise on bone had been controversial, the aim of this study was to elucidate the effect of the bench step (BS), that seemed to deliver higher mechanical load on bone than any other aerobic exercises, on the total bone mineral content (BMC) and the bone metabolism of menopausal women. Sixteen menopausal women (65 ± 9 years old) as the exercise group (ExG) and 28 pre-menopausal women (43 ± 3 years old) as the control group (CG) were studied. ExG carried out BS training with the exercise intensity at lactate threshold (LT) for 21 weeks. In ExG, BMC was measured by dual energy X-ray absorptiometry (DXA) at one year before the intervention (A year before), pre-intervention (Pre) and post-intervention (Post). Serum osteocalcin (OC) as the marker of bone formation and serum type I collagen cross-linked N-telopeptide (NTx) as the marker of bone absorption at Pre, 11th week of the intervention and Post. In CG, BMC was measured annually without the intervention. In ExG, OC was not changed, but NTx was significantly decreased by intervention (<i>p</i><0.05). The decreased amount of annual change in BMC between a year before and Pre (T1) was significantly higher compared to that between Pre and Post (T2) (<i>p</i><0.01) and CG (<i>p</i><0.001). There was no significant difference between T2 and CG. In conclusion, BS with LT could prevent decreasing BMC in menopausal women, and maintain the same level of BMC in pre-menopausal women by suppressing the bone absorption.

Change in heart rate at double product break point and validity of utilizing age-predicted heart rate at 50%VO₂max due to improvement of cardiovascular fitness / 体力科学

Previously, we have reported that age-predicted heart rate at 50%VO₂max (HR@50%VO₂max) is an effective index of adjusting appropriate exercise intensity for health promotion exercise. Thus, the aim of this study is to elucidate the change in HR at double product break point (HR@DPBP) and the validity of HR@50%VO₂max due to improvement of cardiovascular fitness. Ninety two healthy adults (57 +/- 9 years old), who participated in the health exercise training course, were studied. Participants were instructed how to control the intensity of physical activity for DPBP during their daily life. DPBP was determined with the use of incremental exercise test, and METs at DPBP (METs@DPBP), HR@DPBP, ratings of perceived exertion at DPBP (RPE@DPBP) were measured before and after the course. HR@50%VO₂max was calculated with the following formula; 138 - age/2 (bpm). METs@DPBP significantly increased (p<0.001) after 10 weeks of the course, whereas HR@DPBP did not change. Interestingly, however, there was a significantly positive correlation (p<0.001) between amount of change in METs@DPBP and that in HR@DPBP (ΔHR@DPBP). Multiple linear regression analysis indicated this correlation was independent from sex, age and amount of change in HR at rest (p<0.001). Before and after the course, proportion of study subjects’ %ΔHRs ((HR@50%VO₂max - HR@DPBP) / HR@DPBP x 100) within -10% ~ +10% were both 48.9%, and proportion of study subjects’ RPEs@DPBP within 11~13 were 92% and 85%, respectively. In this study, it was identified that significantly positive relation between amount of change in cardiovascular fitness and that of ΔHR@DPBP. This finding was independent from potentially affecting factors. In conclusion, this longitudinal study could suggest that HR@50%VO₂max and RPE were valuable indexes of determining exercise intensity for health promotion exercise.