Abstract
Biomechanical properties of the femoral heads of six cases with osteoporosis who underwent hip surgery were investigated by ultrasonic methods. Ultrasonic velocities and moduli of elasticity in the tangential, radial and axial directions were determined experimentally. Ultrasonic attenuation in terms of Broad-band ultrasonic attenuation Index (BUA) in osteoporosis was attempted to be determined in three directions using three different frequencies. The results were compared to the Singh indices of the same specimens and the efficiency of the methods was discussed. Seven specimens were prepared in nearly 2x1x1 cm dimension. The direction of the primary compressive trabeculae was mainly chosen to be one of the primary direction and the Iong axis of the femoral head was inscribed as the tangential direction. The time of the ultrasonic waves was measured at the three different frequencies (54 kHz, 200 kHz and 1 MHz) using the pulse transmission technique. Specimens were connected to the PUNOIT device (CNS Electronics). Pulse repetition frequency was 50 pps. The amplitudes of the transmitted and received signals were measured. Grease-oil was used as coupling medium. Following the first set of experiments the specimens were cut into smaller sizes, nearly 10x5x5 mm. Ultrasonic velocity measurements were repeated on these specimens. For each specimen, attenuation (dB) versus frequency data were plotted on a graph. Best Iines fitted to these data and attenuation in all directions were presented. Results of this study indicate that ultrasonic velocity and modulus of elastioity increase with increasing frequency. Velocities and moduli of elasticy show no significant difference between the tangenital and radial directions but both are slightly higher in the axial direction particularly at higher frequencies. This finding may be related to the transverse isotropy of the cancellous bone. Moduli of elasticity appear to be smaller in case of small specimens. Structural moduli in this case are in accordance with the evidence. Clinically, the highest velocity ahd the highest modulus of elasticity at Iow ultrasonic frequency correspound to the Iowest osteoporotic case. No relationship between the ultrasonic velocity and the Singh index was found at higher frequencies. Ultrasonic velocity decreases with age, particularly after menopause.
Özet
Ses dalgaları günümüzde değişik yapıların mekanik özelliklerini incelemek amacıyla yaygın olarak kullanılmaktadır. Çalışmada klinik olarak osteoporoz saptanmış altı hastanın femur başları artroplasti sırasında alınarak ultrasonik yöntemlerle incelenmiştir. Femur başlarından kesitler alınarak çevresel radyal ve eksternal yönlerdeki ultrasonik hızlar ölçülmüş ve elastik modüller deneysel olarak saptanmıştır. Üç farklı frekansla yapılan incelemelerde ultrasonik sönümlenme geniş bantlı ultrasonik sönümlenme indeksi cinsinden araştırılmıştır. Elde edilen sonuçlar klinikte yaygın kullanılan Singh indeksi ile karşılaştırılmıstır. Ultrasonik ölçümlerle elde edilen sonuçlar radyolojik yönteme oranla daha hassastır. Kemiğin yapısal özelliğinin dışında yoğunluk ve biyomekanik özellikleri hakkında ayırıntılı bilgi vermektedir. Ultrasonik yöntemlerden klinikte etkin yararlanabilmek için hastamn yaşı, cinsi ve osteoporozun derecesi bilinmeli ve ölçüm yapılacak preparat standart yöntemlerle hazırlanmalıdır. Ayrıca trabeküllerin spesman içindeki yönü ve spesmanın konumu gözönünde bulundurularak düzenli örnekleme gereklidir.