gms | German Medical Science

Questionnaire: It is widely acknowledged that computer aided instrumentation in total knee arthroplasty contributes to increased alignment accuracy. With respect to the postop. mechanical axis (0±3°) the frequency of outliers is reduced approximately from 1/4 using manual implantation technique to 1/10 with the use of a navigation system (Joskowicz et al, 2006, Bäthis et al, 2006, Mason et al, 2007). The aim of the study presented here was to evaluate whether a well trained knee surgeon would benefit from years of clinical experience with a navigation system in terms of improving alignment accuracy with conventional instrumentation technique.

Methods: Three consecutive series of seventyfive TKA's per group of one single surgeon were compared with respect to alignment of prosthetic components. One historical group (A) was recruited from a period of time, immediately before computer assisted instrumentation was introduced. At that time the surgeon had more than twenty years of surgical experience with artificial knee replacement. The two other groups ended eight years later. Group B included manually implanted total knees, using intramedullary femoral and extramedullary tibial alignment, whereas group C included the navigated cases. In group C the OrthoPilot Navigation System by BBraun AESCULAP was used. Alignment accuracy was evaluated by means of standardized one leg stance and lateral radiographs at first clinical review.

Results and Conclusions: Groups A, B and C were comparable with reference to sex, weight, hight, BMI and stage of the underlying disease. The complication rate was significantly higher in the historical group, however, on a low level. Radiographical alignment of the mechanical leg axis was significantly better in group B compared with group A (p<0.01) and significantly superior in group C with respect to group B (p<0.01). When the rates of very good cases of each group [mech. axis (0±3°), single femoral and tibial axes (90±2°)] were compared the differences were significant as well between the three groups (p<0.05). Group B was significantly superior over group A (p<0.05).

1.

The results of axis alignment are superior when computer aided instrumentation was used. The data of this study favourably compare with current literature data.

2.

The results of the historical series (group A) are comparable with those of the literature at that time.

3.

The significant difference between groups A and B indicates that even an experienced knee surgeon may derive considerable benefit from the use of a navigation system with respect to his manual skills in total knee arthroplasty. The intraop. data made available by a navigation system are doubtlessly more exact in comparison to conventional instrumentation sets and, therefore, contribute to a learning effect.