The diagnosis and treatment of sacroiliac joint pain is fraught with difficulties. Consequently, when a new paper is published advocating a sophisticated method of fusing the sacroiliac joint for pain, a degree of critical interest might be anticipated. In this study, Khurana and his coworkers evaluate the clinical and radiological outcomes of fusing the sacroiliac joint percutaneously with hollow screws filled with demineralised bone matrix. They made the diagnosis of sacroiliac joint pain on the basis of clinical presentation, radiological investigations including plain radiographs, CT and MRI, and sacroiliac joint injections.
But just how common is sacroiliac joint pain and how did they get to the point where they were sufficiently sure of their diagnosis to offer their patients this procedure? On the basis of two papers they claim that the sacroiliac joint is the source of pain in between 10% and 32% of patients presenting with low back pain.1,2 The first paper, by Hansen and his coworkers mildly misinterprets a paper by Manchikanti et al.3 The original paper reports only a 2% prevalence of confirmed sacroiliac joint pain from a population of 120 with low back pain of more than six months duration. The figure of 10% applies to "patients who were suspected to have sacroiliac joint pain”. The second paper refers to low back pain after spinal fusion when sacroiliac joint pain might be expected to be more prevalent. The real prevalence is likely to be between 2%3 and 27%1 but how does one know?
Historically, the diagnosis of sacroiliac joint pain has been based on clinical examination and a variety of pain provocation tests. These include Patrick’s test, Gaenslen’s test, and the sacral sulcus test (tenderness over the posterior SI joint) which were used in this study and confirmed by sacroiliac joint injection. However, numerous papers attest to the fact that individual tests for sacroiliac pain are unreliable.1,4,5 There is also a disturbing 20% false positive rate in asymptomatic adults.6 Laslett et al have claimed that greater sensitivity and specificity can be obtained by adding a McKenzie assessment (to exclude discogenic pain) to three positive provocation tests for sacroiliac joint pain but their numbers were small and their confidence intervals wide.7
The situation becomes even more confused when sacroiliac joint injections are introduced. These would seem to be a simple method by which to confirm that the sacroiliac joint is the source of pain. A review of the literature suggests that nothing could be further from the truth. In an elegant analysis of the problem, Cohen4 reviews the factors that can affect the sensitivity and specificity of these diagnostic blocks. He comments "these include the placebo effect, convergence and referred pain, neuroplasticity and central sensitization, expectation bias, unintentional sympathetic blockade, systemic absorption of LA, and psychosocial issues". Extravasation of local anaesthetic can give false positive results and failure to anaesthetise the whole joint false-negative results. Moreover, a single injection is insufficient to make a firm diagnosis of sacroiliac pain. The current "gold standard" is to carry out two separate injections under image intensification (with contrast if necessary) at an interval of three weeks to a month using a different anaesthetic agent on each occasion. Even this is not infallible. Without wishing to complicate the matter further, what percentage relief of pain should be regarded as being indicative of sacroiliac joint pain? In the studies cited so far, this ranges from 70% to 90%, thereby introducing another variable.
Nonetheless, Khurana and his colleagues achieved a good or excellent result in 13 of their 15 (87%) patients using the technique they describe. For this, they should be congratulated. However, in their conclusion they quite correctly state that their technique is a "satisfactory way to achieve sacroiliac stabilisation once an accurate diagnosis has been made". The devil is in the diagnosis.
1. Hansen HC, McKenzie-Brown AM, Cohen SP, et al. Sacroiliac joint interventions: a systematic review. Pain Physician 2007;10:165-84.
2. Katz V, Schofferman J and Reynolds J. The sacroiliac joint: a potential cause of pain after lumbar fusion to the sacrum. J Spinal Disord Tech 2003;16:96–99.
3. Manchikanti L, Singh V, Pampati V, Damron KS, Barnhill RC, Beyer C, Cash KA. Evaluation of the relative contributions of various structures in chronic low back pain. Pain Physician 2001;4:308-316.
4. Cohen SP. Sacroiliac joint pain: a comprehensive review of anatomy, diagnosis, and treatment. Anesth Analg 2005;101:1440–53.
5. Dreyfuss P , Michaelsen M, Pauza K, McLarty J, Bogduk N. The value of medical history and physical examination in diagnosing sacroiliac joint pain. Spine 1996;21:2594-2602.
6. Dreyfuss P, Dreyer S, Griffin J, et al. Positive sacroiliac screening tests in asymptomatic adults. Spine 1994;19:1138–43.
7. Laslett M, Young SB, Aprill CN, McDonald B. Diagnosing painful sacroiliac joints: A validity study of a McKenzie evaluation and sacroiliac provocation tests. Austr J Physio 2003;49:89-97.
Ross A, FRCS, Consultant Orthopaedic Surgeon
Bath, United Kingdom