Abstract
Purpose: In contrast to total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA) is a true resurfacing procedure, as none of the ligaments are replaced or released, and the pre-arthritic leg alignment is the major goal. As such, the alignment of the tibial component plays a crucial role in postoperative knee function and long-term survival. Pinless navigation has shown reliable results in total knee arthroplasty. To the best of our knowledge, the use of pinless navigation has not been investigated for UKA. Therefore, the present study investigated whether implantation of the tibial component in 3° varus, which is closer to the anatomical axis, is feasible with a pinless optical navigation system. Methods: 60 patients with the diagnosis of an unicompartmental arthritis, were eligible for UKA and treated with implantation in 3° varus alignment of the tibial component. Two groups were established. In the treatment group the tibial component was aligned using a pinless navigation technique. In the control group, a conventional extramedullary alignment guide was used. A clinical and radiographic follow up took place within 1 year of operation. Results: 57 Patients were eligible for analysis. No clinical incidents were noted in the follow up period. The desired target value, the position of the tibial component, was accurately achieved with an average of 3° medial inclination using the pinless navigation as well as using the conventional technique. Mean incision to suture time was negligible between the two techniques. The mean suture time was 43.2 min with pinless navigation and 42.7 min with the conventional technique. Conclusions: With pinless navigation in UKA, a method was presented that made it possible to achieve sled prosthesis alignment at the level of a high-volume surgeon. These results were achieved with an irrelevant increase of surgical time and without placement of pins.
Highlights
There is an increasing interest in unicondylar knee arthroplasty (UKA).Compared to total knee arthroplasty (TKA), there are fewer postoperative complications such as wound alterations or periprosthetic infections [1,2]
In UKA, navigation with pins is not appropriate, as the procedure would become unnecessarily invasive due to an extended surgical field. In this prospective, randomized and controlled single-center trial we investigated whether pinless navigation in UKA is suitable and whether implantation accuracy of the tibial implant can be increased by using a pinless navigation system, compared to conventional alignment with an extramedullary alignment rod
Registry data show that experienced surgeons increase the survivorship of unicompartmental knee arthroplasty in contrast to surgeons who present only a low annual volume of UKA [14]
Summary
There is an increasing interest in unicondylar knee arthroplasty (UKA). Compared to total knee arthroplasty (TKA), there are fewer postoperative complications such as wound alterations or periprosthetic infections [1,2]. In some studies it could be shown that the early outcome, especially with regard to function, is better than with TKA [2,3]. UKA seems to have a higher long-term revision rate compared to TKA [1,2]. The reasons for this are quite unclear, as there are almost no studies that investigated to optimal implant position in UKA. While UKA is the only so-called true surface replacement, since both cruciate ligaments are preserved and the aim of the postoperative alignment is the pre-arthritic status, the accuracy of implantation is of high relevance for the long-term success
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