THE EVALUATION OF GEOMETRIC PARAMETERS OF LUMBOSACRAL VERTEBRAE (A RADIOGRAPHIC STUDY)
1.1 BACKGROUND OF THE STUDY
Wilhelm Conrad Roentgen accidentally discovered x-rays in 1895 while conducting some experiments in his laboratory (Yochum and Rowe 2005). The “X” in x-rays represented the unknown ray as Roentgen did not know what to name the invisible rays. One of the significant aspects of this discovery was the development of the clinical radiography which allows us to “see” the internal structures of the body especially bony tissue. Although the x-ray was considered an excellent diagnostic imaging tool, the harmful aspect of radiation could not be ignored (Yochum and Rowe 2005). Since its discovery, it has been of immense value in the evaluation of skeletal disorders (Yochum and Rowe 2005; Kendrik et al., 2001). Most patients requiring medical attention for low back pain have routine x-rays taken of the lumbosacral spine as part of the initial evaluation. The radiographs may be evaluated utilizing the ABCS approach (A = Alignment; B = Bone; C = Cartilage; S = Soft tissue). Routinely two views are taken anteroposterior (AP) and lateral (L) views. Igbinedion and Akhigbe (2011) recorded that transition vertebrae cause low back pain. Transition vertebrae involved the downward migration of L5 (sacralisation) or upward migration of S1 (lumbarisation) (Igbinedion and Akhigbe, 2011).Igbinedion and Akhigbe (2011); Osunwoke et al., (2009), however, recorded that 32.3% of their patients had transitional vertebrae, of which 5.9% had lumbarisation and 26.4% sacralisation. In that same study, 2.4% males and 3.6% females had lumbarisation and 15.7% males and 10.7% females had sacralisation. In the study recorded by Uduma et al., (2013), lumbarisation was seen in four cases (7.02%) with equal male to female ratio. The earliest age of discovery was 4th decade. This late presentation of an anatomical variant is probably due to its asymptomatic nature. Symptomatology, therefore, arose on receipt of secondary spondylosis. However, Igbinedion and Akhigbe (2011), did not observed any statistical correlation between transitional vertebrae with sex, age group, body mass index, osteophyte formation, vacuum phenomenon, disk degeneration, and spondylolisthesis. Measurement of the lumbar spine radiographic parameters may be useful in the investigation of low back pain (Amonoo-Kuofi 1992) and in the design and development of spinal implants and instrumentation (Zhou et al., 2000).
The radiographic parameters evaluated during an assessment of the lumbosacral vertebrae are:
- Lumbosacral angle (LSA)
- Lumbar lordosis angle (LLA)
- Sacral Inclination angle (SIA)
- Lumbosacral disc angle (LDA)
Lumbosacral Angle (LSA): Lumbosacral angle is also known as sacral base angle (SBA) or Ferguson’s angle (Yochum and Rowe 2005). There is very little research available on the precise causes of LSA alterations and the effects on spinal biomechanics. The available data often differ in opinion. Chung et al., (1981) in a study on 132 symptomatic Korean males and females reported that males have a slightly greater LSA than females. On the contrary, Fernand and Fox (1985) reported a significantly higher mean LSA in females; the males had a mean LSA of 43.3° while the females had a mean of 47.2°. However, Rosok and Peterson (1993) noted no difference in the mean LSA between males and females. LSA was noted to be greater in females who had a history of previous pregnancy than females who had no offspring (Bryner and Moussali 1992). Middleditch and Oliver (2005) reported that the LSA is greater in females during child-bearing years than in post-menopausal females and the difference was presumed to be due to hormones. Few studies have examined the effects of body type and size on LSA (Andrews et al., 2001; Brunaugh et al.,2002). There is paucity of data on the effects if obesity and excess body fat distribution on LSA. Andrews et al., (2001) reported no correlation between BMI and LSA. This study was however said to be unreliable due to its inability to differentiate between abnormal BMI and WHR. Ridola et al.,(1994) noted that in the obese individual, the weight of the trunk at the base of the sacrum is displaced anteriorly. This displacement will cause the pubis to rotate posteroinferiorly, while the sacrum tends to rise superiorly and assume a more horizontal orientation thus increasing the LSA. Brunaugh et al., (2002) noted a significant correlation between BMI and WHR, and LSA. A wide range of variation in this measurement has been noted. Yochum and Rowe (2005) reported a range of 26 – 57º with a mean of 41º ± 7º. They also noted that the value increases from the recumbent to upright position by 7 – 12º. Kim et al., (2006) noted a normal value of 39.8º ± 8º with a range of 11 – 58º. These findings show that the LSA varies widely among individuals. There is no consensus of opinion on the significance of either a decreased or an increased LSA. An increased angle has been implicated as a mechanical factor in low back pain by increasing shearing and compressive forces on the lumbosacral posterior joints (Bogduk 2005; Yochum and Rowe 2005).