The Pfirrman grading system is used to determine the severity of disc degeneration. This is based on magnetic resonance imaging studies and disc height. It was designed to grade the discs of younger persons, with a mean age of 40 years. Grades one through five can be used for each individual disc graded. The authors of this study felt that an expanded grading system would be more appropriate in grading disc degeneration in the elderly population. The authors sought to study the reliability of an expanded grading system, one with eight rather than five grades.
The study involved analyzing 260 lumbar spine discs in 52 subjects, with a mean age of 73 years. Three radiologist were used to read MRI examinations. Interreader, and intrareader reliability was evaluated to assess if the modified Pfirrman grading system could be useful.
Intervertebral discs consist of the inner portion, the nucleus pulposus, the outer annulus fibrosus, and the cartilage endplates. The nucleus pulposus contains a compounds called proteoglycans. These proteoglycans exert a swelling pressure when combined with water. This helps the disc to cushion the spine. This also gives the disc its height, separating one vertebra from the other. When the disc starts to degenerate,proteoglycans are decreased. This causes the disc to contain less water. The disc height will start to decrease and can be evaluated by imaging such as the MRI. The eight grades of the modified Pfirrman system represent a progression from a normal disc, grade one, to severe disc degeneration, grade eight.
The modified Pfirrman grading system for disc degeneration in the elderly was found to have reliability in this study. It was determined to be easy to understand and use.