J Am Acad Orthop Sur
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The sacroiliac joint is a source of pain in the lower back and buttocks in approximately 15% of the population. Diagnosing sacroiliac joint-mediated pain is difficult because the presenting complaints are similar to those of other causes of back pain. Patients with sacroiliac joint-mediated pain rarely report pain above L5; most localize their pain to the area around the posterior superior iliac spine. ⋯ Magnetic resonance imaging, computed tomography, and bone scans of the sacroiliac joint cannot reliably determine whether the joint is the source of the pain. Controlled analgesic injections of the sacroiliac joint are the most important tool in the diagnosis. Treatment modalities include medications, physical therapy, bracing, manual therapy, injections, radiofrequency denervation, and arthrodesis; however, no published prospective data compare the efficacy of these modalities.
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Methods of treatment are different for acute and chronic pain. For acute pain, analgesics such as nonsteroidal anti-inflammatory drugs and opiates are commonly used, sometimes combined with regional anesthesia, such as peripheral nerve block or peridural local anesthesia. The mechanism of transition from an acute to a chronic pain state is poorly understood. ⋯ Opiates may be used chronically, but tolerance and lack of efficacy may then develop. In selected patients with refractory chronic pain, centrally administered analgesics may be considered, including opiates, dilute local anesthetic, NMDA receptor antagonists, clonidine, midazolam, baclofen, or calcium channel blockers. For both acute and chronic pain, a single agent may be less effective than combinations of analgesics with different mechanisms of action.
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The transmission of a pain signal from the periphery to the central nervous system is complex and only partially understood. Tissue damage results in peripheral release of endogenous chemicals that can directly activate nociceptive afferent fibers, sensitize nociceptors, or cause increased local extravasation and vasodilatation. These algesiogenic substances may be found in local tissues, plasma, and nerve terminals. ⋯ Modulation of the pain signal in the dorsal horn involves local inhibitory and facilitatory interneurons as well as diverse excitatory and inhibitory neurotransmitters. The neuronal circuitry in the dorsal horn can change and modulate with time so that pain signals sometimes long outlast the original peripheral tissue injury. This central sensitization is thought to be mediated largely through the NMDA receptor complex.