Effect of correction of the contractured flexed osteoarthritic knee on the sagittal alignment by total replacement.

STUDY DESIGN: A prospective analysis of an adaptive change of the spinopelvic alignment after total knee arthroplasty. PURPOSE: To evaluate the effect of correction of the contractured knee in flexion on the spinopelvic alignment by total knee arthroplasty. OVERVIEW OF LITERATURE: Flexion contracture of the knee joint may affect the body posture and precipitate the symptoms in the lumbar spine, which is known as the 'knee-spine syndrome'. METHODS: Fifteen patients who could be followed at least over 12 months were used in this study. Neutral whole spine lateral standing radiograms taken at certain intervals were analyzed. The subjects were divided into two groups (group A, the patients who obtained over 10° correction; group B, the others). The sacral slope, the pelvic tilt and the pelvic incidence were measured preoperatively and at 12 months and thereafter postoperatively in all the patients. Also, the thoracic kyphosis, lumbar lordosis, and lumbosacral angle were measured, including the spinal sagittal balance, S1 overhang and spino-sacral angle. RESULTS: The average correction of the contractured knee in flexion were 13.8° in group A and 2.7° in group B. The median of changes of the sacral slope were 4.2° in group A and -0.4° in group B. These results revealed that there was a significant increase of the sacral slope for group A (p=0.001). However, there were no significant differences between the other parameters. CONCLUSIONS: The sacral slope appears to be affected by the change of the flexion contracture after total knee arthroplasty.