Orthopedic testing plays an important role in physical diagnosis
yet little research has been conducted to establish the reliability and validity
of these tests. For the majority of tests we still have no support for their sensitivity
and many are being evaluated for the very first time. When research is conducted, many tests are being shown to be useless or at least not useful unless if used in conjunction with other tests. The following is a brief update of some of the research from the last year related to the diagnosis of sciatica.
Sciatica has been defined in several ways but the most common meaning of the term is “pain in the lower back and hip radiating down the back of the thigh into the leg…”. On the simplest level, it is only a symptom identified from the patient’s history and presenting complaint. The challenge becomes the differential diagnosis of the actual underlying etiology. Understanding the causes of sciatica is important as it is one of the most common conditions seen in chiropractic practices. Based upon epidemiological studies of sciatic patients, we know that nerve root compression is the most common cause.
The physical examination is critical to the differential diagnosis of sciatica. The most commonly used test is the supine SLR (straight leg raise), which is a provocative test designed to tension the sciatic nerve and increase pain. Another common test is the “slump test”. The slump test resembles a seated SLR and involves; slumped sitting with thoracolumbar and cervical flexion along with knee extension and dorsiflexion of the foot (1). Research studies published over the last year have explored the relative value of the SLR and slump tests. One study found substantial agreement between the two tests (kappa = 0.69) (2). In another study the authors compared the two tests for sensitivity and specificity. They concluded “The Slump test was found to be more sensitive (0.84) than the SLR (0.52) in the patients with lumbar disc herniations. However, the SLR was found to be a slightly more specific test (0.89) than the Slump test (0.83) (3).
Figure reprinted with permission from: Walsh J, Flatley, M, Johnson N, Bennett K. Slump Test: Sensory Responses in Asymptomatic Subjects. J Man Manip Ther; 2007; 15(4): 231-238.
As chiropractors it might be easy to fall into the trap and assume that a patient presenting with sciatica is either suffers from nerve root compression or other musculoskeletal causes like piriformis syndrome. Especially in view of the fact that epidemiology studies indicate that nerve root compressions, usually associated with disc pathology is by far the most common cause. In a recent study, 16% of patients with sciatica had no MRI evidence of nerve root compression (4). In this study was much more common for women to have extralumbar sciatica which was usually associated with sacral plexus pathologies related to conditions like ovarian cysts, endometriosis and pregnancy. Piriformis syndrome was a distant third in terms of causes of sciatica. This research concluded that “Female sex, right side involvement, and overlapping sensory disturbance are suggestive of extralumbar spinal sciatica associated with gynecologic conditions.”