Chronic postoperative pain after total knee arthroplasty: The potential contributions of synovitis, pain sensitization and pain catastrophizing-An explorative study.

BACKGROUND: A subset of osteoarthritis patients will experience chronic postoperative pain after total knee arthroplasty (TKA), but the source of pain is unclear. The aim of this exploratory study was to assess patients with and without postoperative pain after TKA using magnetic resonance imaging (MRI), quantitative sensory testing (QST), clinical assessment of pain and assessments of catastrophizing thoughts. METHODS: Forty-six patients completed the 6-month postoperative assessment. MRI findings were scored according to the MRI Osteoarthritis Knee Score recommendation for Hoffa synovitis, effusion size and bone marrow lesions. QST included assessment of pressure pain thresholds (PPTs), temporal summation of pain (TSP) and conditioned pain modulation (CPM). Pain catastrophizing was assessed using the Pain Catastrophizing Scale (PCS). Clinical pain assessment was conducted using a visual analogue scale (VAS, 0-10 cm), and groups of moderate-to-severe (VAS > 3) and none-to-mild postoperative pain (VAS ≤ 3) were identified. RESULTS: Patients with moderate-to-severe postoperative pain (N = 15) demonstrated higher grades of Hoffa synovitis (p < 0.001) and effusion size (p < 0.001), lower PPTs (p = 0.039), higher TSP (p = 0.001) and lower CPM (p = 0.014) when compared with patients with none-to-mild postoperative pain (N = 31). No significant difference was found in PCS scores between the two groups. Multiple linear regression models found synovitis (p = 0.036), effusion size (p = 0.003), TSP (p = 0.013) and PCS (p < 0.001) as independent parameters contributing to the postoperative pain intensity. CONCLUSION: These exploratory findings could indicate that chronic postoperative pain after TKA is a combination of joint-related synovitis and effusion, sensitization of central pain mechanisms and potentially pain catastrophizing thoughts, but larger studies are needed to confirm this. SIGNIFICANCE: The end-stage treatment of knee osteoarthritis is total knee arthroplasty. Some patients experience chronic postoperative pain after total knee arthroplasty, but the mechanism for chronic postoperative pain is widely unknown. The current study indicates that higher levels postoperative of synovitis and effusion, higher temporal summation of pain and higher pain catastrophizing scores could be associated with higher chronic postoperative pain.

Single photon emission computerized tomography and reverse gantry computerized tomography findings in patients with back pain investigated for spondylolysis.

BACKGROUND: Athletes with low back pain may have sustained a bone stress injury in the lumbar neural arch, including spondylolysis. Single photon emission computerized tomography (SPECT) and reverse gantry computerized tomography (rg-CT) help localize bone stress response and spondylolyses. OBJECTIVES: To describe the SPECT and rg-CT findings in those patients suspected of suffering from a spondylolysis. STUDY DESIGN: Large retrospective case series. SETTING: Secondary and tertiary care center in England. PATIENTS: A total of 213 patients presenting to the Spinal Unit and Sports Medicine Clinics between 1995 and 2000 with low back pain and subsequently investigated for spondylolysis by SPECT and rg-CT. METHODS: An experienced consultant musculoskeletal radiologist reported the SPECT and rg-CT, and these results along with data from the patient's medical records were analyzed. MAIN OUTCOME MEASURES: Sites and sides of increased scintigraphic activity in the lumbar neural arch seen on SPECT and complete and incomplete spondylolyses were recorded. RESULTS: Single photon emission computerized tomography scan showed increased scintigraphic uptake in 145 patients, mostly (42.3%) at L5. Marked increase in scintigraphic uptake was noted on the left side of the neural arch in 31 patients and on the right in 17 (chi; P < 0.05). Spondylolysis was identified on rg-CT in 81 patients. Spondylolyses were bilateral on 44 occasions, but unilateral lesions occurred in the left pars 36 times and on the right 16 times (chi; P < 0.01) CONCLUSIONS: Spondylolyses were a frequent finding on rg-CT in young athletes with low back pain. The sports most commonly associated with this stress response in the pars interarticularis were cricket and soccer. The lower lumbar levels are more likely to show abnormalities on SPECT and computerized tomography. Among those investigated for spondylolysis, left-sided lower lumbar pain was more common than right, and a marked increase in scintigraphic uptake was noted on the left more often than the right. Although bilateral spondylolyses were common, left-sided spondylolyses were more common than right. The asymmetric repetitive movements of certain sports may be responsible. In particular, fast bowlers developed spondylolysis on the opposite side of the body to their bowling arm.