COMPUTER-ASSISTED IMPLANTATION OF A SINGLE-COMPARTEMENT KNEE PROSTHESIS: COMPARISON WITH TRADITIONAL INSTRUMENTATION

Abstract

Purpose: The quality of implantation of single-compartment knee prostheses is a recognised prognostic factor. Acceptable reproducibility can be achieved with traditional instrumentations, although the rate of error can be significant. Computer-assisted implantation might improve results. Most of the currently proposed techniques require supplementary preoperative imaging or implantation of metallic material for guidance. The Orthopilot® system is a purely peroperative system and could thus provide better cost-effectiveness.

Material and methods: We implanted 30 single-compartment knee prostheses using the Orthopilot® computerised system (Aesculap, Chaumont, Group A) and compared the radiographic quality of the implant on telemetric AP and lateral views with those from a control group of 30 single-compartment prostheses implanted with a traditional instrumentation with a femoral centromedullary aiming device (group B). All patients underwent surgery for primary degeneration and were operated on by the same surgeon using the same implant (Search®, Aesculap, Chaumont). The control group was selected among a consecutive series of 250 implants to match the study group for age, gender, importance of the degeneration and frontal femorotibial mechanical angle.

Results: The mechanical femorotibial angle was within desired limits (177±3°) in 26 patients in group A and in 20 patients in group B. Frontal orientation of the femoral component was within desired limits (90±2°) in 27 patients in group A and in 19 in group B (p< 0.05). Frontal orientation of the tibial piece was within desired limits (90±2°) in 27 patients in group A and in 19 patients in group B (p < 0.02). The original level of the joint line was reconstructed with a 2 mm margin in 30 patients in group A and in 24 patients in group B (p < 0.05). Eighteen patients in group A and four patients in group B had optimal implantation for all criteria studied (p < 0.001). There were no system-related complications.

Discussion, conclusion: Computer-assisted implantation is more reliable and more reproducible than traditional instrumentation for the implantation of a single-compartment knee prosthesis. Follow-up results with these prostheses may be better. Systematic preoperative imaging, or preoperative implantation of metallic guide pins is not necessary with this system. The system appears to offer a better cost-effectiveness.