ANTERIOR CERVICAL FUSION USING POROUS HYDROXYAPATITE CERAMICS(HAP) FOR CERVICAL MYELOPATHY-RADIOGRAPHIC FINDINGS AND BIOMECHANICAL STUDY

Radiographic findings of bone union and clinical outcome in AF using HAP was evaluated and Biomechanical study was performed to certify that our method is suitable for AF using HAP. Clinically, 33 patients with myelopathy were investigated. The status of bone union was classified into 4 grades. Grade 1 is nonunion. Grade 2 is probable nonunion. Grade 3 is probable union. Grade 4 is bone union. Surgical outcome was evaluated by Japanese Orthopaedic Association(JOA) score. In biomechanical study, two models was examined. One is Robinson method without removal of end plate. The other is our method with exposure of spongy bone. No case showed grade 1 and 2.12% cases showed grade 3 and 88% grade 4. There was 5 cases with cracks. Those showed no instability and no collapse of HAP. The average preoperative and postoperative JOA score was 11.2 and 14.9 points respectively. Recovery rate was 64%. There was breakage of HAP without sinking of HAP in Robinson method. The compressive strength of breakage of HAP in Robinson method were a half to one third of those in our method. Our method gives us satisfactory clinical outcome and radiographic results, and should be used for AF using HAP.