Abstract
Background
Navigation in total knee replacement is controversially discussed in the literature. In our previous study, femoral component positioning was more accurate with computed navigation than with conventional implantation techniques, however tibial positioning showed similar results. Moreover there were no differences between image-free and image-based navigation techniques. To what extent more accurate femoral positioning has an impact on the clinical mid-term follow up is not known.
Methods
At a mean follow-up interval of 5.3 years, seventy-one patients (84.5%) returned for a review and were examined clinically and radiographically, with use of a methodology identical to that used preop and at 2 years, using the subjective value, the Knee Society Score (KSS), and a.p. and true lateral standard radiographs respectively. Complications, re-operations, persisting pain and resulting range of motion were registered.
Results
Four patients in the image-based (2x late-onset infection, 1x femoral impingement, 1x component malalignment), 2 in the conventional group (2x component malalignment) and 1 patient in the image-free navigated group (arthoscopic debridement for arthrofibrosis) needed reoperation in the mean time. 59 of the 71 patients were very satisfied and satisfied at 5.3 years folllow up: (conventional: 19 of 25 (77±8 years); image-based navigation: 18 of 22 (77±10 years); image-free navigation: 22 of 24 (78±7 years)). The mean average of the Knee Society Score was 92.3(range 47 to 98). Compared to the conventional (KSS: 93.9±8,0) and image-free (KSS: 94.0±6,43) group, the KSS in the image-based group was insignificantly lower (KSS: 90±13,6) (p< 0,05). Radiographically, two patients in the conventional group showed a lysis on the lateral and medial tibia plateau of <1 mm without any clinical significance. There was no need for reintervention. There were no significant differences concerning remainig pain (conventional: 24%; image-based 18%; image-free: 8,5%), ROM and ligamental stability.
Conclusion
Radiographical and clinical mid-term results after TKA yielded good and excellent results independent of the computed navigation and its type. Even a more accurate femoral component positioning in the patients cohort has been shown, we couldn't find a significant difference concerning the clinical outcome 5.3 years after conventional, image-based and image-free total knee arthroplasty. Despite of increased costs and time for navigated techniques we cannot show a mid-term benefit in functional and subjectiv outcome compared to conventional techniques.
