Mariner 9 celestial mechanics experiment: gravity field and pole direction of Mars.

Analysis of the Mariner 9 radio-tracking data shows that the Martian gravity field is rougher than that of Earth or the moon, and that the accepted direction of Mars's rotation axis is in error by about 0.5 degrees . The new value for the pole direction for the epoch 1971.9, referred to the mean equatorial system of 1950.0, is right ascension alpha= 317.3 degrees +/- 0.3 degrees , declination delta = 52.6 degrees +/- 0.2 degrees . The values found for the coefficients of the low-order harmonics of Mars's gravity field are as follows: J(2)=(1.96+/-0.01)x10(-3), referred to an equatorial radius of 3394 kilometers; C(22) = -(5 +/- 1) x 10(-5); and S(22) = (3 +/- 1) x 10(-5). The value for J(2) is in excellent agreement with the result from, Wilkins' analysis of the observations of Phobos. The other two coefficients imply a value of (2.5 +/- 0.5) x 10(-4) for the fractional difference in the principal equatorial moments of inertia; the axis of the minimum moment passes near 105 degrees W.

Endoscopic plantar fascia release: a case series.

Plantar fasciitis is a common disabling condition that can be recalcitrant to treatment. Endoscopic Plantar Fascia Release (EPFR) has received greater attention in recent years as a viable, and possibly superior, alternative to established open procedures for the treatment of plantar fasciitis. In a series of 17 patients (17 feet) with follow-up over an average of 16 months, we report a two portal endoscopic technique of partial release of the plantar fascia, as a successful, safe and reliable procedure for the treatment of plantar fasciitis in the patient group selected. The surgical results of 17 EPFR's performed by the same surgeon were reviewed. All patients had preoperative symptoms of subcalcaneal heel pain for greater than 12 months, all having undergone nonsurgical measures for at least 12 months. Of 17 feet, all reported marked improvement of preoperative symptoms within two months. Patients' subjective assessment of the procedure was strongly supportive, 100% totally satisfied or satisfied with only minor restrictions. Postoperatively, 82.4% reported mild or no pain, and 100% had improvement in walking distance. Complications all resolved within two to six months; there were no re-operations and no infections.

Treatment of septic arthritis of the hip by arthroscopic lavage.

Since 1987, nine cases of septic arthritis of the hip joint in children were treated by arthroscopic lavage. The technique of arthroscopic hip examination is described. This treatment, when combined with standard medical therapy, was effective in ablating septic disease in all patients. No complications were attributable to the surgical procedure. We emphasize the value of large-bore, large-volume lavage, direct suction to remove joint debris, and postoperative suction drainage. The technique is an attractive alternative to arthrotomy and offers low surgical morbidity, effective joint cleansing, and early return of joint mobility.

Measurement of periprosthetic bone density in hip arthroplasty using dual-energy x-ray absorptiometry. Reproducibility of measurements.

To define the precision (reproducibility) of measurement of periprosthetic bone mineral density and bone mineral content, dual-energy x-ray absorptiometry scans were obtained on 45 randomly selected patients who had had a unilateral total hip arthroplasty within the previous 3 years. The coefficients of variation of the bone mineral density in the proximal Gruen zones were 5.0 and 5.3%, corresponding to errors of 0.07 and 0.11 g/cm2. The coefficients of variation of the bone mineral density for the distal zones averaged 2.8%, with an error of 0.08 g/cm2. The coefficients of variation of the bone mineral content were 4.8 and 2.9% for the proximal and distal zones. The contralateral femur was also scanned in 32 of the patients. For the contralateral femur bone mineral density, the coefficients of variation were 5.0% for the proximal zones and 4.8% for the distal zones. The bone mineral content was 6.0% for the contralateral regions. These results imply that differences in bone mineral density greater than 0.16 g/cm2 (2 standard errors) can be reliably measured. Dual-energy x-ray absorptiometry therefore provides a highly reproducible technique for quantitatively monitoring the changes in bone density that occur after total hip arthroplasty.