[Minimally invasive medial unicompartmental knee replacement]

Proprioception and Knee Arthroplasty: A Literature Review

Proprioceptive mechanoreceptors provide neural feedback for position in space and are critical for three-dimensional interaction. Proprioception is decreased with osteoarthritis of the knees, which leads to increased risk of falling. As the prevalence of osteoarthritis increases so does the need for total knee arthroplasty (TKA), and knowing the effect of TKA on proprioception is essential. This article reviews the literature regarding proprioception and its relationship to balance, aging, osteoarthritis, and the effect of TKA on proprioception. Knee arthroplasty involving retention of the cruciate ligaments is also reviewed, as well the evidence of proprioception in the posterior cruciate ligament after TKA.

Minimally invasive versus conventional unicompartmental knee arthroplasty

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) has been proven to be a viable procedure in case of medial osteoarthritis of the knee joint. Minimally invasive surgery (MIS) techniques have been described to facilitate recovery after surgery. The aim of this study was to rule out major failure mechanisms and to obtain clinical data for comparison between a conventional and the MIS approach.

MATERIALS AND METHODS

A consecutive series of 163 UKA (160 patients) were retrospectively included (83 conventional and 80 MIS interventions). Patients were invited for a clinical examination including clinical scores (KSS, Lequesne, UCLA, VAS, Feller- and Turba Patella Scores). Seven patients (4.3%) were lost to follow-up.

RESULTS

Average follow-up was 4.6 ± 1.3 (1.5-6.8) years. Average age at operation was 67.5 ± 7.9 (45-81) years. Fifteen implants had been converted to TKA (9.2%). There were seven conversions to TKA in the MIS and 8 in the conventional group. Of the applied clinical scores there were better values for the Turba patella score in the MIS group. Differences of the other scores were not statistically significant.

CONCLUSION

Comparable functional results for both UKA procedures could be shown. There were no significant differences in terms of clinical scores or revision rates. The MIS approach in medial UKA did not show any major complications. Its use seems to be safe.

Comparison of minimally invasive unicompartmental knee arthroplasty with or without a navigation system

The authors investigated the hypothesis that navigation system-assisted minimally invasive unicompartmental knee arthroplasty (NA-MIS UKA) produces better short-term clinical results than MIS UKA without a navigation system. After a minimum 2-year follow-up, short-term functional results and component alignment accuracies of 31 knees that underwent NA-MIS UKA (the NA-MIS group) were compared with those of 33 knees that underwent MIS UKAs without a navigation system (the MIS group). The Hospital for Special Surgery and Western Ontario and McMaster Universities Osteoarthritis Index scores of 2 groups showed significant improvement at final follow-ups, but no significant intergroup differences were observed (P = .071 and P = .096, respectively). However, NA-MIS UKA produced more improvement in the desired mechanical axis and a lower percentage of prosthetic alignment outliers than MIS UKA.

[Minimally invasive implantation in unicondylar arthroplasty]

Knee arthroplasty has become one of the most successful standard procedures in orthopaedic surgery. With a more frequent use in young and active patients bone-saving procedures have become more important. The goal is to save good bone stock for the revision procedure. Therefore, unicompartmental knee arthroplasty is a good example. Instrumentation and minimally invasive surgical techniques have been improved so very good long-term results and early functional results are achieved. The paper describes the surgical technique with true capsule incision and extramedullary alignment technique. In a prospective study, the early functional results with the ZUK implant were excellent. The implant may not be indicated for every knee situation and an exact differential indication and sound surgical technique are necessary. Its use, however, in cases with unicompartmental knee arthritis, contributes to excellent early rehabilitation and to maintaining autologous bone. Therefore, the minimally invasive unicompartmental knee arthroplasty is a sensible alternative to other options.

Minimal-invasive navigiert implantierte unikondyläre Knieendoprothese

METHODS

From January 2003 to July 2005 a total of 50 St Georg medial knee monosleds with metal-backed tibial components in stably seated form and Uniglide prostheses (Alphanorm/Corin) with mobile bearing onlays were implanted in minimally invasive operations. Postoperatively the alignment-especially of the tibial components-was investigated, to check whether we had achieved the dorsal slope we had been aiming at, i.e. 5-7 degrees , in the region of these knee replacements.

RESULTS

Before surgery there were initial malalignments of up to 10 degrees varus and 3 degrees valgus. All leg axes were restored to between -3 degrees and +3 degrees . The desired dorsal slope of 5-7 degrees for the knee monosleds relative to the tibial component was realized, the average slope being 5.3 degrees . The a-p alignment of the tibial component and of the femoral component was correct.

CONCLUSIONS

Use of the navigation system leads to more accurate and reproducible results in terms of tibial dorsal slope, which is extremely important when these monosleds are used. Overcorrection of the leg axis is generally avoided. The use of too-high medial onlays is also reliably avoided by the navigation system's monitoring of the level of the cut.

[The minimally invasive unicompartmental knee system "Preservation"First clinical results and analysis of complications]

The Preservation uni knee system is a minimally invasive procedure for implantation of a unicompartmental knee prosthesis. The early results show that the rehabilitation process is quick; the postoperative pain and blood loss is less than after conventional knee arthroplasty. Still there are some pitfalls. The implantation of the tibial mobile-bearing component requires a sound operative technique; otherwise complications will occur. The combination of the available navigation system with the Preservation uni will improve operative accuracy.