OBJECTIVE SOUND WAVE AMPLITUDE MEASUREMENT GENERATED BY A TUNING FORK – AN ANALYSIS OF ITS USE AS A DIAGNOSTIC TOOL IN SUSPECTED FEMORAL NECK FRACTURES

Abstract

Objectives: The objective of this study was to assess the reliability of measured sound waves amplitude using the 3M Littmann Sound Analysis Software as a diagnostic tool in suspected femoral neck fractures.

Methodology: Sound waves generated by 125 Hz tuning fork was placed on both patella and then stored on the 3M Electronic Stethoscope Model 4000 placed at both anterior superior iliac spines. Data was then transferred by an infrared transmitter to a computer with the 3M Littmann sound analysis software to convert the sound to a universally recognised format * (wav) for audio feedback and visual display (phonocardiogram) as amplitude height. The amplitude ratio was defined as the proportion of the amplitude height between the fracture side and the normal side for femoral neck fractures, between the right and left side for controls, and between the painful hip and normal side for suspected hip fractures. MRI and clinical progression were used as gold standard test to confirm diagnosis.

Results: A total of 65 patients were studied which consisted of 25 patients with femoral neck fractures, 20 patients with suspected femoral neck fractures, and 20 patients served as controls without hip pathology. There were 48 females and 17 male patients and the mean age of the study population was 82 years (s.d:8.2 yrs) which was similar in all groups. The mean amplitude ratio of sound waves in the control group was 0.91(s.d:0.1), and in patients with femoral neck fractures 0.21(s.d:0.12), this differences were statistically significant (p< 0.001). In patients with extracapsular femoral neck fractures, the mean amplitude ratio of 0.16 (s.d:0.1) was significantly lower when compared with intracapsular fractures (0.26 s.d:0.13, p=0.03). Using an amplitude ratio of less than 0.45 as indication of fracture, tuning fork test had a sensitivity of 85.7% and specificity of 87.5% in diagnosis of suspected femoral neck fractures when compared with MRI and clinical monitoring. The Positive Predictive Value (PPV) was 85.7% and the Negative Predictive Value (NPV) was 87.5& .

Conclusions: We conclude that sound wave amplitude measured objectively by a 125Hz tuning fork is a reliable and cost-effective tool as an initial screening test for patient with suspected hip fractures