Correlation of wound pain following open heart surgery (median sternotomy) and sternum misalignment assessed using X-ray computed tomography

Abstract

Continuous and uncontrolled wound pain frequently follows open heart surgery (median sternotomy). The authors investigated pain origins with x-ray computed tomography (CT). The assessment included 34 patients (29 males, 5 females, mean age 57 years) who underwent open heart surgery. All received unenhanced CT scans in horizontal 5 mm segments from the upper margin of the aortic arch to the diaphragm. Sternum alignment was measured on the horizontal sections. The maximum slide (mm) and number of slippage sections determined the severity of misalignment. Patients had postoperative wound pain duration (months) measurements and were grouped by an analogic pain scale three months after surgery: group 1, no pain or only slightly painful; group 2, ranging through painful, very painful, and unbearably painful. All received chest x-rays, Holter ECGs, stress ECGs and echocardiograms. Pain originating from angina pectoris, pericardial effusion or pleural effusion was excluded in all patients. Sternums were transfixed by 5 metal wires, and sternum cross-sections were clearly visible on the CT scans. Although no sternum separations existed, 29 of 34 patients had misalignments. The average vertical misalignment measured 5.5±3.6 mm (maximum 11 mm) with the average number of CT sections with misalignments being 21.2±9.5. The duration of post-operative pain was much longer for the 29 patients with misalignments than the 5 without misalignments (17.2±6.2 months and 3.9±2.5 months, respectively, p<0.01). The analogic pain scale included 15 in group 1, and 19 in group 2. The average misalignment was larger in group 2 than in group 1 (6.4±2.1 mm and 3.1±1.8 mm, respectively, p<0.01). CT scans clearly visualize sternum cross-sections. The authors' results suggest that wound pain after open heart surgery (median sternotomy) is directly linked to sternum misalignments.