Introduction Sacroiliac joint pain is resistant to diagnosis by clinical methods. CT guided diagnostic blocks are the gold standard in diagnosing SI joint pathology (Maigne J.Y. et al, Spine 1996). The current blocks have various pit falls. We have devised a new functional diagnostic block which is a modification of the currently available blocks for diagnosing sacroiliac joint pain.

Methods The patient suspected of having sacroiliac joint pain undergoes a CT-guided sacroiliac joint catheterisation. The patient is subsequently admitted to the hospital for two full days. On admission patient is charted for an injection of either a local anaesthetic or normal saline (placebo) through the catheter into the joint 2–3mls every 3–4 hourly. Only one drug is administered on any given day. On day one, the nurse in charge of the patient by the flip of a coin will decide to give one of the drugs for the day, the patient or the treating doctor not aware of the drug injected. The first injection starts at 0600hrs and the last injection at 2200 hrs. The injection details and pain score are documented on a standardised form. The patient is then taken through a range of physical activity which usually provokes the sacroiliac joint pain. The next day, the patient receives the alternate drug and undergoes the same protocol. On the third morning the patient is discharged with an appropriate follow-up. The injection given, average pain score and the level of comfort with physical activity are summarised into a form.

Discussion Our modified block has the following advantages, it is a double blinded assessment, the effect of a placebo can be tested, and it is also a functional assessment which is recorded over two days and not just a one-off response. The conclusion of the block is determined by the patient’s response and not examiner depended.