[Importance of computer-assisted navigation in total knee arthroplasty - results of a nationwide survey in Germany]

The Impact of Pinless Navigation in Conventionally Aligned Total Knee Arthroplasty

Background

Restoration of the mechanical axis is a main objective in total knee replacement (TKR). Aim of this study was to analyse the verification tool of a pinless navigation system in conventional TKR (cTKR).

Methods

In a prospective study, 147 TKR were performed by conventional technique. Using the “pinless verification” mode of a smartphone based navigation system, the cutting block position and final resection plane for distal femur and proximal tibial resection were measured. If necessary, the block position or resection level were optimized, corrections were protocolled. Postoperatively, standardized radiographs were performed.

Results

In 65.3%, intraoperative measurements changed the surgical procedure (corrections: 20.4% femoral, 25.9% tibial, 19% both). The additional time for surgery compared to cTKR averaged 6 minutes (79 ± 15 versus 73 ± 17 minutes). Using navigation data, the final femoral and tibial axes were in 93% within a range of ±2°. A mean difference of 1.4° and 1.6° could be shown between the final measurement of the navigation system and the postoperative mLDFA and mMPTA.

Conclusion

Intraoperative pinless navigation has impact on the surgical procedure in the majority of cTKR. It represents a less time-consuming tool to improve implant position while maintaining the routine of conventional technique.

[Anterior knee pain after total knee arthroplasty : Causes, diagnosis and treatment]

BACKGROUND

Anterior knee pain is one of the most common complications after total knee arthroplasty. An incidence of up to 30 % has been reported in peer-reviewed studies.

TARGET

The purpose of this study was to systematically review the literature and to identify determinants that have been analyzed with regard to anterior knee pain.

CAUSES

Patient- and knee-specific characteristics, prosthetic designs and operative techniques are addressed as well as functional and neurologic determinants. Instability, increased contact pressure in the patellofemoral joint and patella maltracking due to malrotation of components, offset errors, ligament insufficiencies or patella baja are mechanical reasons for anterior knee pain. Functional causes include pathologic gait patterns, quadriceps imbalance and dynamic valgus. They have to be differentiated from infectious and inflammatory causes as well as soft tissue impingement, arthrofibrosis and neurologic diseases.

TREATMENT

A differentiated treatment algorithm is recommended. Often conservative treatment options exist, however, particularly with most mechanical causes revision surgery is necessary.

Computer-assisted navigation is beneficial both in primary and revision surgery with modular rotating-hinge knee arthroplasty

PURPOSE

The objective of the present study was to explore the effect of navigation on the reconstruction of the mechanical leg axis, implant positioning and the restoration of the joint line in hinged knee arthroplasty in vivo. We present the first 1- to 3-year clinical and radiological results following computer-navigated implantation of the EnduRo modular rotating-hinge knee arthroplasty system (Aesculap AG, Tuttlingen, Germany) as a primary or revision implant.

METHODS

Thirty-one patients were analysed retrospectively. Indication was revision surgery in 18 patients and complex primary surgery in 13. The clinical and radiological results of 31 patients with a minimum follow-up of 12 months (mean 22.2 ± 6.2 months) were recorded. Age at follow-up was 55.2 ± 9.9 years.

RESULTS

The absolute varus-valgus deviation from the neutral mechanical leg axis was determined at 5.1° ± 5.1° preoperatively and 2.1° ± 1.4° postoperatively. No intraoperative complications or problems with the navigation system were observed. At latest follow-up, no component loosening was detected. Based on the Knee Society Score, a knee score of 64.9 ± 17.7 points and a function score of 67.2 ± 27.3 points were achieved.

CONCLUSIONS

Encouraging short-term clinical and radiological results with the computer-navigated implantation of the modular rotating-hinge EnduRo knee arthroplasty system were found in both primary and revision surgery. The navigation facilitated the reconstruction of the leg axis, implant positioning and the restoration of the joint line.

LEVEL OF EVIDENCE

IV.

[Computer-assisted systems in total knee arthroplasty. Useful aid or only additional costs]

BACKGROUND

The primary goal of computer-assisted surgery (CAS) in total knee arthroplasty is to increase the accuracy in terms of prosthesis positioning. In theory, this would lead to longer implant survival and a reduction of malpositioning. Thus, a better clinical outcome and lower revision rates would be expected. However, the necessary technical equipment represents significant additional effort and cost factors which are not included in the current diagnosis-related groups (DRG) system.

OBJECTIVE

The objective of this article is a critical review of the current literature to examine whether these costs are reasonable by taking the additional benefits of the technology into account.

METHODS

This review is based on a selective PubMed search on CAS and navigation in primary total knee arthroplasty.

RESULTS

The current evidence base on CAS suggests that at least the primary outcome parameter, the improvement of the radiological alignment, is achieved by the technique. However, the claimed secondary effects are not yet proven. In particular, an improvement of clinical outcome and patient satisfaction has not been demonstrated so far. Furthermore, there is some evidence of increased complication rates by the use of CAS.

CONCLUSION

Against this background and with respect to further cost-benefit analyses, the technology has to be reviewed critically. In particular, low-volume units do not seem to benefit from the use of CAS. However, the assessment of long-term effects is still pending.