CALCIUM PYROPHOSPHATE DIHYDRATE CRYSTAL DEPOSITION DISEASE AS A CAUSEOF LUMBAR CANAL STENOSIS

Study Design. This study measured the incidence of calcium pyrophospha te dihydrate crystal deposition in specimens of ligamenta flava in con secutive patients undergoing decompressive laminectomy between 1984 an d 1991. The results were compared to determine the difference between calcium pyrophosphate dihydrate-positive and calcium pyrophosphate dih ydrate-negative patients with lumbar canal spinal stenosis. Objectives . The results were compared with cadaver specimens and literature valu es to determine if calcium pyrophosphate dihydrate crystal deposition disease contributes to the thickening of the ligamentum flavum and the reby contributes to spinal stenosis. Summary of Background Data. Calci um pyrophosphate dihydrate crystal deposition disease has been describ ed in the axial skeleton. Hypertrophy of the ligamentum flavum has bee n suggested to contribute to stenosis. The association of calcium pyro phosphate dihydrate disease and hypertrophied ligamenta flava has not been fully defined nor linked to neurologic symptoms and signs. Method s. The incidence of calcium pyrophosphate dihydrate crystal deposition in specimens of ligamenta flava obtained from four groups was measure d: specimens obtained during surgery from 102 consecutive patients und ergoing decompression laminectomy between 1984 and 1991, 47 additional pathologic specimens of ligamentum flavum tested between 1984 and 199 1, 222 calcium pyrophosphate dihydrate-positive Pathology Department s pecimens collected between 1980 and 1991, and, as control specimens, s pecimens from 20 cadavers. The associated patient histories were revie wed for the first two groups; no histories were available for the cada ver group. Results. The incidence of calcium pyrophosphate dihydrate c rystal deposition was 24.5% in the ligamentum flavum among the surgica l patients, 31% among the Pathology Department specimens, 33.8% among the calcium pyrophosphate dihydrate-positive Pathology Department spec imens, and 5% among the cadavers. No associated medical conditions wit h calcium pyrophosphate dihydrate crystal deposition were found among the medical histories. Patients with the symptoms of spinal stenosis w ho were also calcium pyrophosphate dihydrate-positive presented with m ore acute symptoms than calcium pyrophosphate dihydrate-negative patie nts with symptoms of less than 6 months' and less than 24 months' dura tion (P < 0.001). Except for time to presentation, calcium pyrophospha te dihydrate-positive and calcium pyrophosphate dihydrate-negative pat ients had similar signs and symptoms of lumbar canal spinal stenosis. Having previous spine surgery did not produce a statistically signific ant risk of having calcium pyrophosphate dihydrate crystal deposition. No specific laboratory tests were found to be of predictive value. Co nclusions. These findings suggest that calcium pyrophosphate dihydrate crystal deposition may indeed be associated with the thickening of th e ligamentum flavum. If so, patients may benefit from medical treatmen t before undergoing surgical treatment of lumbar canal spinal stenosis .