Abstract Title Management of Complex Regional Pain Syndrome Exacerbation After Unilateral Total Knee Arthroplasty: A Case Study Authors: Linares AD, Joohee Y, Qiu C, Ehsan A, Kim K

Background (141) Complex regional pain syndrome (CRPS) is a chronic pain condition characterized by pain most commonly in the distal extremities after surgery or injury like fracture or sprain, where the pain is disproportionately greater than typically experienced after similar tissue trauma. CRPS most commonly affects the arms, hands, legs or feet. Symptoms include severe pain, swelling, restricted range of motion, temperature and skin changes. CRPS is divided into two groups: Type 1, lacking known nerve damage, and Type 2, resulting from specific nerve damage. As in this case, CRPS has been reported as a rare side effect of elective total knee arthroplasty, affecting daily functioning and work, and decreasing quality of life. Treatment is multidisciplinary, including physiotherapy, psychology, and pain management. Pharmacotherapy is aimed at primary mechanisms involved, such as vasomotor disturbances, inflammation, pain or sensory dysfunction, muscular involvement, and psychological factors.

Case Presentation (124) A 53-year-old woman with PMH of chronic pain syndrome, osteoarthritis, and CRPS ten months after left total knee arthroplasty presented to the emergency department with worsening left knee pain radiating to the left hip and limited mobility. Physical examination revealed edema of the left knee without other deformities. Imaging revealed intact hardware with no abnormalities. Lack of fever or leukocytosis effectively ruled out a septic joint. Subsequent pain management included methadone, IV morphine, methocarbamol, acetaminophen, pregabalin, amitriptyline and Lidoderm patch. Her pain remained refractory to the treatment, therefore dexamethasone, capsaicin cream and hydromorphone were added. Even then, continuing pain led to replacing hydromorphone with morphine. Excessive drowsiness complicated treatment, thus adjustments to the pregabalin, methocarbamol and morphine dosages were made.

Discussion (134) Managing CRPS can be extremely complicated due to the varying presentations and responses to treatment for each patient. For each patient that presents with CRPS, a thorough initial evaluation should be done in order to gain a comprehensive understanding of the range of their symptoms. This questioning can often help guide therapy as it may reveal the extent of nerve or muscle involvement in the etiology of pain, as well how much swelling can contribute to their symptoms. With this understanding, a pain control regimen can include muscle relaxants, opioids, and nerve pain medications . As seen with this patient, it is then necessary to closely monitor these patients and adjust the initial regimen in response to any side effects, allowing for effective pain control.