Creatinine and nonprotein nitrogen plasma levels: possible etiopathogenetic factors in rotator cuff tears

To determine the plasma levels of nonprotein nitrogen (NPN) and creatinine in healthy patients with rotator cuff tears. The study included 400 subjects. The study group included 200 patients (93 men and 107 women; mean age, 56.8 years; range, 23-81 years) who underwent arthroscopic repair of a rotator cuff tear from 2004 to 2007. The control group included 200 patients (93 men and 107 women; mean age, 53.9 years; range, 20-81 years) who underwent arthroscopy for management of a meniscal tear, with or without articular cartilage damage, in the same period. The 2 groups were frequency-matched by age and sex. Measurement of plasma levels of NPN and creatinine were performed in all patients. Patients with rotator cuff tears showed higher plasma NPN levels within the normal range (P = 0.035) than patients with knee disorders (control group). Creatinine levels were comparable (P = 0.66) in both groups. There appears to be an association between plasma NPN levels and rotator cuff tears. On the basis of our findings, plasma NPN could be involved in the pathogenesis of rotator cuff tears, although we advocate further research to draw more definitive conclusions.