A Comparison of the Intramedullary and Extramedullary System for Tibial Component Placement in Total Knee Arthroplasty

• Published in: Japanese Journal of Rheumatism and Joint Surgery Vol. 17; no. 1; pp. 27 - 32
• Main Authors: SAKAI Tsuyoshi, 土井田 稔, 佐浦 隆一, 黒坂 昌弘, 水野 耕作
• Format: Journal Article
• Language: Japanese
• Published: 日本関節病学会 1998; Japanese Society for Joint Diseases
• Subjects: surgical instruments; tibial component; TKA
• ISSN: 0287-3214; 1884-9059
• DOI: 10.11551/jsjd1982.17.27

The accuracy of Intramedullary (IM) versus extramedullary (EM) tibial alignment systems was compared in 71 total knee arthroplasties (TKAs) on postoperative roentgenographs. In 30 knees of patients with osteoarthrosis, and in 11 knees of patients with rheumatoid arthritis, the IM system was used (OA IM group and RA IM group) . In 30 knees of patients with rheuma toid arthritis, the EM system was used (RA EM group) . The AMK total knee system was used in all cases. Roentgenographic measurements were taken of the tibial component in the coronal and sagital plane, named the“medial angle”and“posterior tilting angle.”The average medial angle was 88.9° (standard deviation [SD] ±2.3°) for the OA IM group; 85.8° (SD±2.0°) for the RA EM group; and 88.4° (SD±2.3°) for the RA IM group. These differences were statistically significant between the OA IM group and the RA EM group (p<0.01) and between the RA IM group and the RA EM group (p<0.001) . The average posterior tilting angle was 5.2° (SD±3.4°) for the OA IM group, 3.3° (SD±2.9°) for the RA EM group, and 7.2° (SD±3.0°) for the RA IM group. These differences were statistically significant between the RA EM group and the RA IM group (p<0.01) . The results demonstrated a statistically significant improvement in proximal tibial-bone-resection accuracy when using the IM system. However, the IM rod is not satis factory when the tibia is bowed. If the preoperative planning radiograph suggests it to be nec essary, the entry point should be varied; usually this is in a slight lateral direction.