Use of the Straight-Leg Test for Upper Extremity Involvement

The nervous system has to adapt mechanically during movement. For example, the spinal canal is 5cm-9cm longer in flexion than extension.¹ And because the nervous system is a continuous tract, any limb movement must have mechanical consequences for nerve trunks and the neuraxis (the term used when the CNS is considered along its length irrespective of its bends and folds).²

According to Breig,¹ a straight-leg raise test (SLR) moves and tensions the nervous system from the foot and along the neuraxis to the brain. Cyriax³ mentioned that referred pain does not follow a dermatomal pathway and may originate with the dura. Lew and Puentedura⁴ found that it was not the length of the hamstrings but the neural tissue that limited the SLR, and Hall⁵ found patients with the same SLR had different hamstring lengths.

Gaynor Jarvis⁶ recently wrote a most interesting paper which found that patients with upper limb pain expressed a limited SLR which reproduced the upper limb symptoms in 60% of the subjects studied. The upper limb disorder patients complained of diffuse pain which was burning, stabbing or cramping; muscle tenderness with possible paraesthesia extending from the wrist, hand and forearm, proximally to the upper arm, shoulder, scapula and neck. There were no objective signs of any particular tissue disease. We often see these patients diagnosed as cervicobrachial disorder, overuse syndrome, cumulative trauma disorder, fibromyalgia, etc. The patients studied did not have any connective tissue, neurological or psychiatric disease, nor did they have any lower extremity or back problems.

In a normal person, the SLR pulls the neuraxis caudally, stretching the lumbar intervertebral roots in the lumbosacral foramen all the way to the cervical nerve roots.⁷ It is proposed that in these types of upper extremity cases that if there are adhesions in the cervical area, the movement or extensibility of the neuraxis would be limited during either cephalad or caudal traction. "The widespread symptoms of the patient group could be produced by the mechanical effects of neural fibrosis causing unequal tensioning and 'double' or 'multiple crush' of the nerve. This will in turn impede microcirculation of blood, nerve growth factor and axoplasm and could evoke ectopic impulse generation from excitable pacemaker sites and alteration in function of the dorsal root ganglion."¹

The lack of local pathology to tendons or joints (in these types of upper extremity problems) and the widespread symptoms points to a "central sensory processing abnormality maintained by abnormal neural pathophysiology."¹ The controls (no upper body symptoms) in this study during the SLR test tended to show either an increase or maintained the same range of SLR after repeated testing. The patients tended toward a decrease of SLR during repeated testing. In this study, the patients without paraesthesia had a significantly higher mean SLR when compared to the mean of the entire patient group. The production of upper limb symptoms by movement of the lower extremity on SLR testing was most probably due to altered neurodynamics of the neuraxis. The authors mentioned that 32 volunteers were used, 16 controls and 16 who met the criteria for the upper limb symptoms mentioned above. They recommended further study with larger groups of chronic diffuse upper extremity patients.

References

1. Brieg A. Adverse Mechanical Tension in the Central Nervous System. Stockholm, Amqvist & Wiskell, 1978.
2. Butler DS. Mobilisation of the Nervous System. New York, Churchill Livingstone, 1991.
3. Cyriax J. Textbook of Orthopaedic Medicine, Vol 1. London, Balliere Tindall, 1982.
4. Lew PC, Puentedura EJ. The straight leg raise test and spinal posture. (Is the straight leg raise a tension test or a hamstring length measure in normals?) Proceedings of the 4th Biennial Conference of the MTAA, Brisbane, 1989. In: Jarvis G. The relationship between upper limb disorder and lower limb neurodynamics. Journal of Orthopaedic Medicine 1997;19(2):35-42.
5. Hall T, et al. The effect of the lumbosacral posture on a modification of a straight leg raise test. Physiotherapy 1993;79(8):566-570. In: Jarvis G. The relationship between upper limb disorder and lower limb neurodynamics. Journal of Orthopaedic Medicine 1997;19(2):35-42.
6. Jarvis G. The relationship between upper limb disorder and lower limb neurodynamics. Journal of Orthopaedic Medicine 1997;19(2):35-42.
7. Breig A, Udg T. Biomechanical considerations of the straight leg raising test. Spine 1979;4(3):242-250. In: Jarvis G. The relationship between upper limb disorder and lower limb neurodynamics. Journal of Orthopaedic Medicine 1997;19(2):35-42.