Hidetomo Saito

Heart rate variability under acute simulated microgravity during daytime waking state and nocturnal sleep: Comparison of horizontal and 6° head-down bed rest

This study examined the acute effect of cephalad fluid shift under simulated microgravity on heart rate variability (HRV) during both daytime waking state and nocturnal sleep. Seven healthy male volunteers (21-31 years) underwent a series of experiments involving 6 degrees head-down bed rest (HD) for 3 days. A control experiment on the same subjects was conducted under horizontal bed rest (HZ) in the same series. HRV from electrocardiogram signals was periodically calculated by the MemCalc method during daytime on the first and second days of both conditions. Nocturnal sleep on the first night of bed rest was monitored by polysomnography. HRV during stage 2 sleep and REM sleep were assessed in the former and latter halves of the sleep period time. Nocturnal sleep architecture under both conditions was normal, but a slight decrease in stage 4 sleep and an increase in the number of arousals occurred under HD. On both the first and second days, HRV during the daytime did not differ between HZ and HD. In contrast, high frequency components in HRV during sleep stage 2 were significantly higher in the latter half of sleep under HD than under HZ, although there were no differences in the ratio of low frequency to high frequency components during both stage 2 and the REM stage between the conditions. These results suggest that the acute effect of the cephalad fluid shift on cardiac autonomic nervous activity might be affected by the sleep/wake state modulating the dominance between sympathetic and parasympathetic nervous activity.

Arthroscopic Quadriceps Tendon Repair: Two Case Reports

Recently, although some studies of open repair of the tendon of the quadriceps femoris have been published, there have been no reports in the literature on primary arthroscopic repair. In our present study, we present two cases of quadriceps tendon injury arthroscopically repaired with excellent results. Case 1 involved a 68-year-old man who was injured while shifting his weight to prevent a fall. MRI showed complete rupture at the insertion of the patella of the quadriceps tendon. The rupture was arthroscopically repaired using both suture anchor and pull-out suture fixation methods via bone tunnels (hereafter, pull-out fixation). Two years after surgery, retearing was not observed on MRI and both Japan Orthopedic Association (JOA) Knee and Lysholm scores had recovered to 100. Case 2 involved a 50-year-old man who was also injured when shifting his weight to prevent a fall. MRI showed incomplete superficial rupture at the insertion of the patella of the quadriceps tendon. The rupture was arthroscopically repaired using pull-out fixation of six strand sutures. One year after surgery, MRI revealed a healed tendon and his JOA and Lysholm scores were 95 and 100, respectively. Thus, arthroscopic repair may be a useful surgical method for repairing quadriceps tendon injury.

Relationship between Pain and Medial Meniscal Extrusion in Knee Osteoarthritis

Purpose. In knee osteoarthritis, the degree of pain varies despite similar imaging findings. If there were quantitative findings related to the pain of knee osteoarthritis, it could be used for diagnosis or screening. The medial meniscal extrusion was investigated as a candidate quantitative finding related to the pain of knee osteoarthritis. Methods. Seventy-six knees of 38 patients (mean age, 73 years) who received intra-articular injections of hyaluronic acid into unilateral knees at the time of diagnosis of knee arthritis were investigated. Cartilage thickness of the femoral medial condyle and medial meniscal extrusion of bilateral knees were measured by ultrasonography. Thirty-eight knees that had hyaluronic acid injections were compared with 38 other side knees from the same patients as the control group. Results. The average cartilage thicknesses of the knees with pain that received intra-articular injections and the knees without pain that received no injections were 1.02 and 1.05 mm, respectively (P = 0.6394). On the other hand, the average medial meniscal extrusions of the knees with and without pain were 7.58 and 5.88 mm, respectively (P = 0.0005); pain was associated with greater medial meniscal extrusions. Conclusion. Medial meniscal extrusion is a quantitative finding related to the pain of knee osteoarthritis.

Gait Analysis of Conventional Total Knee Arthroplasty and Bicruciate Stabilized Total Knee Arthroplasty Using a Triaxial Accelerometer

One component of conventional total knee arthroplasty is removal of the anterior cruciate ligament, and the knee after total knee arthroplasty has been said to be a knee with anterior cruciate ligament dysfunction. Bicruciate stabilized total knee arthroplasty is believed to reproduce anterior cruciate ligament function in the implant and provide anterior stability. Conventional total knee arthroplasty was performed on the right knee and bicruciate stabilized total knee arthroplasty was performed on the left knee in the same patient, and a triaxial accelerometer was fitted to both knees after surgery. Gait analysis was then performed and is reported here. The subject was a 78-year-old woman who underwent conventional total knee arthroplasty on her right knee and bicruciate stabilized total knee arthroplasty on her left knee. On the femoral side with bicruciate stabilized total knee arthroplasty, compared to conventional total knee arthroplasty, there was little acceleration in the x-axis direction (anteroposterior direction) in the early swing phase. Bicruciate stabilized total knee arthroplasty may be able to replace anterior cruciate ligament function due to the structure of the implant and proper anteroposterior positioning.

Non-traumatic femoral head fracture forming bone fragments

Femoral head fracture generally occurs due to high-energy injury such as dislocation of the hip joint. However, femoral head fracture forming bone fragments without apparent trauma has not previously been reported. We describe herein a unique case of non-traumatic femoral head fracture leading to rapid destruction of the femoral head and osteoarthritic changes in the hip joint, along with a review of the literature. The patients and their families were informed that data from the case would be submitted for publication, and gave their consent.

Massive Deposition and Accumulation of Hydroxyapatite Crystal after Total Hip Arthroplasty: A Case Report

We presented a case in which massive hydroxyapatite accumulation was observed around the artificial hip joint. A 66-year-old female showed a massive accumulation of fluid in and around the hip joint, and milk-like aspirate was obtained. Her aspirate culture was negative, and sediment analysis by X-ray diffraction showed that its component was hydroxyapatite. Since pain was mild, the patient was treated conservatively. To our knowledge, this is the first case in which liquid hydroxyapatite (milk of calcium) was accumulated around the artificial hip joint.