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

Navigated versus conventional medial unicompartmental knee arthroplasty: Minimum 18 years clinical outcomes and survivorship of the original Cartier design

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is a viable option of treatment in case of osteoarthritis (OA) or avascular osteonecrosis (AVN) isolated to either the medial or the lateral compartment of the knee. The aim of this study was to retrospectively present clinical outcomes and survivorship at minimum 18 years follow up of a fixed bearing (FB) UKA comparing the results of conventional technique and navigation.

METHODS

Patients treated with a medial FB UKA between June 2003 and December 2006 were retrospectively evaluated. From March 2005 all UKAs were performed using a computer navigation system. Patients were divided into two groups: UKAs assisted by navigation (n-UKAs) versus standard UKAs (s-UKAs). For all patients, at final follow up, patient-reported outcome measures (PROMs) were collected: Western Ontario and McMaster Universities (WOMAC) score, Oxford Knee Score (OKS) and Forgotten Joint Score (FJS-12). Survival rate and outcomes were compared between groups.

RESULTS

Fifty-two patients were analyzed in this retrospective evaluation. All UKAs were medial and the tibial component was all polyethylene (AP) in 26 cases and metal backed (MB) in 26. Twenty-six UKAs were implanted with standard technique (AP 10, MB 16) and 26 assisted by a navigation system (AP 16, MB 10). Three patients (5.7%) underwent revision; the average time to revision was 140.7 months (standard deviation 81.2). Average follow up was 216.4 months (standard deviation 10.6). The survivorship of the implant was 94.4% at final follow up. Survivorship and PROMs were not different between groups.

CONCLUSIONS

This study showed excellent survivorship and outcomes at long term follow up of the original fixed bearing Cartier designed implant in both groups with equivalent survivorship and PROMs.

Research Advances in the Application of AI for Preoperative Measurements in Total Knee Arthroplasty

Total knee arthroplasty (TKA) is widely used in clinical practice as an effective treatment for end-stage knee joint lesions. It can effectively correct joint deformities, relieve painful symptoms, and improve joint function. The reconstruction of lower extremity joint lines and soft tissue balance are important factors related to the durability of the implant; therefore, it is especially important to measure the joint lines and associated angles before TKA. In this article, we review the technological progress in the preoperative measurement of TKA.

Referencing the Tibial Plateau With a Probe Improves the Accuracy of the Posterior Slope in Medial Unicompartmental Knee Arthroplasty

Background

There is currently no consensus on intraoperative references for determining the posterior tibial slope (PTS) in medial unicompartmental knee arthroplasty (UKA). The medial tibial plateau could serve as a direct reference for determining the native PTS through the placement of a hook probe in the anteroposterior direction of the medial tibial plateau. This study aimed to examine the accuracy of this new referencing method.

Methods

We consecutively performed 55 medial UKAs using our new method (study group), and the preoperative and postoperative PTS on lateral knee radiographs were examined. These outcomes were then compared with those of consecutive 50 medial UKAs performed using the conventional method (control group), which immediately preceded the start of the use of the new method.

Results

The correlation coefficient between the preoperative and postoperative PTS of the study group was larger than that of the control group (0.887 and 0.482, respectively). The mean implantation error of the PTS in the study group was smaller than that of the control group (-1.1° ± 1.3° and -3.0° ± 3.2°, respectively; P < .0001). The percentages of knees within 2° of implantation error were 73% and 34% in the study and control groups, respectively (P < .0001). The root mean square errors in the study and control groups were 1.7° and 4.3°, respectively.

Conclusions

The direct referencing method with a probe can significantly improve the accuracy of tibial sagittal alignment.

Safety and Efficacy of Unicondylar Knee Prosthesis Treatment for Unicompartmental Osteoarthritis of the Knee Joint

Background

Knee osteoarthritis (KOA) is a chronic disease that seriously endangers the health of the elderly. Choosing appropriate surgery for knee osteoarthritis patients is especially important.

Objective

To investigate the safety and efficacy of unicondylar knee prosthesis treatment for unicompartmental osteoarthritis of the knee.

Materials and Methods

One hundred patients with unicondylar osteoarthritis of the knee treated in our hospital from June 2019 to June 2021 were selected as retrospective study subjects and were divided into 50 cases each in the comparison group and the observation group according to the different surgical methods. Among them, the comparison group was treated with unicondylar knee arthroplasty (UKA), and the observation group was treated with unicondylar knee prosthesis replacement, and the differences in AKS score, knee flexion angle, tibial angle orthosis, joint mobility, and postoperative recovery were compared between the two groups.

Results

The AKS score and knee flexion angle score of the observation group were higher than those of the comparison group after surgery. However, the tibial angle orthopedic score of the observation group was significantly lower than that of the comparison group after surgery for comparison, and the VAS score of the observation group was lower than that of the comparison group. However, the Lysholm score of the observation group was higher than that of the control group after surgery (P < 0.05). The complication rate of patients in the observation group was significantly lower than that of the comparison group, and the HSS score, VAS score, and knee mobility (ROM) of the two groups were statistically significant (P < 0.05) when compared at 7 d after surgery and 6 months after surgery.

Conclusion

The clinical efficacy of unicondylar knee prosthesis replacement for osteoarthritis of the knee is better than that of unicondylar knee arthroplasty (UKA) treatment.

Comparison of computer-assisted navigated technology and conventional technology in unicompartmental knee arthroplasty: a meta-analysis

Background

Though unicompartmental knee arthroplasty (UKA) is a useful procedure to treat knee osteoarthritis, it remains a great controversial point as to if navigated systems are able to achieve better accuracy of limb alignment and greater clinic results. Current meta-analysis was conducted to explore if better clinical outcomes and radiographic outcomes could be acquired in the navigated system when compared with conventional procedures.

Methods

We identified studies in the online databases, including Medline, Embase, the Cochrane Library and Web of Science before May 2021. The PRISMA guidelines in this report were strictly followed. Our research was completed via Review Manager 5.4 software.

Results

Fourteen articles were included, involving 852 knees. The present meta-analysis displayed that the navigated system had remarkably improved outcomes in inliers of mechanical axis (MA) (P < 0.01), MA in the Kennedy's central zone (Zone C) (P = 0.04), inliers of the coronal femoral component (P < 0.01), inliers of the coronal tibial component (P = 0.005), inliers of the sagittal femoral component (P = 0.03), inliers of the sagittal tibial component (P = 0.002) and Range Of Motion (ROM) (P = 0.04). No significant differences were observed in Oxford Knee Score (OKS) (P = 0.15), American Knee Society Knee Score (KSS score) (P = 0.61) and postoperative complications (P = 0.73) between these 2 groups. Regarding operating time, the navigated group was 10.63 min longer in contrast to the traditional group.

Conclusion

Based on our research, the navigated system provided better radiographic outcomes and no significant difference in the risk of complications with longer surgical time than the conventional techniques. But no significant differences were found in functional outcomes. Because the included studies were small samples and short-term follow-up, high-quality RCTs with large patients and sufficient follow-up are required to identify the long-term effect of the navigated system.

What is the evidence for clinical use of advanced technology in unicompartmental knee arthroplasty?

BACKGROUND

With an aim of improving prosthesis survivorship of unicompartmental knee arthroplasty (UKA), use of computer-assisted technologies (CATs) such as robotics, has been on the rise to reduce intraoperative errors in surgical technique. In light of recent influx of CATs in the UKA, a review of these innovations will help providers to understand their clinical utility.

METHOD

A systematic literature search was performed following Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines.

RESULTS

Among 19 studies comparing robot-assisted UKA with conventional UKA, only 32% were randomized control trials, 47% reported minimum mean follow-up of 2 years, and 21% evaluated prosthesis survival. Similar results were obtained for navigation-assisted UKA and UKA performed with patient-specific instrumentation.

CONCLUSION

While CATs seem to reduce the surgical errors in UKA, the evidence on the efficacy of any of the studied CATs to improve survivorship remains limited and there are issues related to cost-effectiveness, learning curve, and increase in operating time.

Lateral Unicompartmental Knee Arthroplasty

Lateral unicompartmental knee arthroplasty affords excellent functional results and implant survivorship for properly selected patients. More high-quality studies are necessary to determine whether expanded indications for medial unicompartmental knee arthroplasty also apply to lateral unicompartmental knee arthroplasty. Operative adjuncts such as robotics, custom implants, and navigation technology hold promise in minimizing the technical burden and unfamiliarity of lateral unicompartmental knee arthroplasty. Improvements in lateral-specific implants may translate to operational efficiency and improved outcomes, but few lateral-specific implants currently exist. Mobile-bearing devices have increased rates of failure due to bearing dislocation, and further studies are warranted to evaluate this complication with newer designs. Future registry and cohort studies should show medial unicompartmental knee arthroplasty and lateral unicompartmental knee arthroplasty separately to allow for better understanding of the nuances and technical differences between these uniquely different procedures.

Dependence of knee range of motion on the alignment of femoral and tibial components after medial unicompartmental knee arthroplasty

INTRODUCTION

This study evaluated the relationship between postoperative knee flexion angles and the position of femoral and tibial components in unicompartmental knee arthroplasty (UKA).

MATERIALS AND METHODS

Eighteen patients (a total of 22 knees: three men, four knees; 15 females, 18 knees) who underwent navigation-assisted UKA were included. Pre- and postoperative computed tomography images were applied on 3D software, which were matched and used to calculate the position of femoral and tibial components. Correspondingly, we investigated the relationship between the knee range of motion (ROM) at 1-year postoperative follow-up and the position of femoral and tibial components.

RESULTS

At 1-year post-UKA, the knee flexion angle was associated with the posterior flexion angle of tibial components. This particular angle was significantly greater in the group with equal or greater postoperative knee ROM compared to preoperative ROM (5.2 ± 2.1°) than in the group with less postoperative knee ROM compared to preoperative ROM (2.6 ± 1.6°, p < 0.01). There was no significant difference between both groups in the femoral component position, preoperative posterior slope of the medial tibial plateau, change in the pre- to postoperative posterior tibial slope, and postoperative knee society score.

CONCLUSION

The posterior flexion angle of the tibial component affected the improvement/deterioration of the postsurgery knee flexion angle in navigation-assisted UKA. For improved outcomes after UKA using navigation systems, surgeons should aim to achieve a 5° to 8° posterior flexion angle of the tibial component.

Robotic-assisted unicompartmental knee replacement offers no early advantage over conventional unicompartmental knee replacement

PURPOSE

Unicompartmental knee arthroplasty (UKA) is effective for treating degenerative joint disease in a single compartment. Robotic-arm-assisted arthroplasty (RAA) has gained popularity and has theoretical benefits of improved outcomes over conventional (CONV) UKA due to the technical precision of bone preparation. This study compares the short-term clinical outcomes, including survivorship and patient-reported functional outcomes, for a series of medial UKAs performed with RAA and CONV.

METHODS

One hundred seventy-six consecutive fixed-bearing medial UKAs were retrospectively identified with a minimum follow-up of 2 years. One hundred and eighteen CONV and 58 RAA were performed. Pre- and post-operative SF12, WOMAC, and KSS Functional Questionnaires were available for all patients.

RESULTS

At 2 years, both groups improved in all functional outcomes, with no significant difference between the RAA and CONV cohorts. However, the RAA cohort had a significantly longer operative time (p < 0.001) and a higher early revision rate than the CONV group (7 [12.0%] vs. 7 [6.8%]; p < 0.05).

CONCLUSIONS

These results demonstrate that at short-term follow-up of 2 years, RAA was not superior to CONV in terms of functional scores and instead was associated with greater operative time and cost and lower survivorship. Therefore, at this time usage of RAA in UKA is not recommended compared to conventional UKA. Longer term studies are necessary to draw conclusions about the overall outcomes of RAA compared to CONV.

LEVEL OF EVIDENCE

III.

The effect of C-arm fluoroscope on unicompartmental knee replacement arthroplasty

Purpose

The aim of this study was to identify the effectiveness of C-arm fluoroscope in unicompartmental knee replacement arthroplasty through the clinical and radiologic results.

Materials and methods

We investigated the 33 cases of unicompartmental knee replacement arthroplasty in 31 patients who diagnosed degenerative arthritis of knee between February 2011 and March 2014. We divided 2 groups, one is 15 cases using C-arm fluoroscope during operation (group A), the other is 18 cases not using that (group B). We measured femoro-tibial angle (FTA), medial proximal tibial angle (MPTA), posterior tibial slope angle (PTSA), femoral component coronal rotation angle (FCRA) by simple X-ray. We evaluated femur and tibia varus/valgus mismatch and posterior slope mismatch by above parameters after operation. And also we evaluated clinically by knee and functional score.

Results

In group A, FTA average changes from -0.6° to 6.1°, MPTA changes from 84.5° to 87.6°, PTSA changes from 6.2° to 5.2° through operation. In group B, FTA changes from -0.4° to 5.8°, MPTA changes from 84.7° to 87.1°, PTSA changes from 6.3° to 5.5°, and FCRA is 0.6° in A group, 0.4° in B group after operation. The tibial varus/valgus mismatch cases after operation (nl.:87 ± 3°) was 1 in group A, 5 in group B. Post. slope mismatch cases after operation (nl.:7 ± 3°) was 1 in group A, 1 in group 31 B. All cases in both A and B group were not included in femoral varus/valgus mismatch (nl.:0 ± 3°) after operation. In group A, Knee score improved from 56.3 to 90.7, Functional score from 54.3 to 86.9 through operation. In group B, Knee score improved from 54.9 to 89.8, Functional score from 52.8 to 84.6.

Conclusion

There was no statistically significant difference in radiologic and clinical results between group A and B, but the number of tibial varus/valgus mismatch case were fewer in fluoroscope guided group. Sowe consider that thefluoroscope is helpful for tibial cuttingin unicompartmental knee replacement arthroplasty.

Improved Survival of Computer-Assisted Unicompartmental Knee Arthroplasty: 252 Cases With a Minimum Follow-Up of 5 Years

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is an underutilized implant for medial tibiofemoral arthritis despite proven benefits in performance and reduced complications. This is likely related to registry recorded higher revision rates compared with total knee arthroplasty. It is our feeling that better component alignment resulting from the usage of computer-assisted surgery should improve longer-term functional results and survival of UKAs.

METHODS

Between August 2003 and June 2007, 265 medial UKAs were performed in 264 consecutive patients using navigation.

RESULTS

Eighty-eight women and 176 men with an average age of 51.7 (±4.63) years were assessed for function and survival over a follow-up period of 92.6 (63-120) months (7.7 years). The final survival rate over 5 years for this cohort was 97.6% at 5 years.

CONCLUSION

We conclude that computer-assisted UKA, to treat medial tibiofemoral joint arthritis, produces 5-year survival rates that are comparable with total knee arthroplasty.

Current state of computer navigation and robotics in unicompartmental and total knee arthroplasty: a systematic review with meta-analysis

Recently, there is a growing interest in surgical variables that are intraoperatively controlled by orthopaedic surgeons, including lower leg alignment, component positioning and soft tissues balancing. Since more tight control over these factors is associated with improved outcomes of unicompartmental knee arthroplasty and total knee arthroplasty (TKA), several computer navigation and robotic-assisted systems have been developed. Although mechanical axis accuracy and component positioning have been shown to improve with computer navigation, no superiority in functional outcomes has yet been shown. This could be explained by the fact that many differences exist between the number and type of surgical variables these systems control. Most systems control lower leg alignment and component positioning, while some in addition control soft tissue balancing. Finally, robotic-assisted systems have the additional advantage of improving surgical precision. A systematic search in PubMed, Embase and Cochrane Library resulted in 40 comparative studies and three registries on computer navigation reporting outcomes of 474,197 patients, and 21 basic science and clinical studies on robotic-assisted knee arthroplasty. Twenty-eight of these comparative computer navigation studies reported Knee Society Total scores in 3504 patients. Stratifying by type of surgical variables, no significant differences were noted in outcomes between surgery with computer-navigated TKA controlling for alignment and component positioning versus conventional TKA (p = 0.63). However, significantly better outcomes were noted following computer-navigated TKA that also controlled for soft tissue balancing versus conventional TKA (mean difference 4.84, 95 % Confidence Interval 1.61, 8.07, p = 0.003). A literature review of robotic systems showed that these systems can, similarly to computer navigation, reliably improve lower leg alignment, component positioning and soft tissues balancing. Furthermore, two studies comparing robotic-assisted with computer-navigated surgery reported superiority of robotic-assisted surgery in controlling these factors. Manually controlling all these surgical variables can be difficult for the orthopaedic surgeon. Findings in this study suggest that computer navigation or robotic assistance may help managing these multiple variables and could improve outcomes. Future studies assessing the role of soft tissue balancing in knee arthroplasty and long-term follow-up studies assessing the role of computer-navigated and robotic-assisted knee arthroplasty are needed.

Superior alignment but no difference in clinical outcome after minimally invasive computer-assisted unicompartmental knee arthroplasty (MICA-UKA)

PURPOSE

Variety of clinical trials have been published comparing the alignment of MICA-UKA with MI-UKA. However, to the best of our knowledge, no published study has showed whether radiological alignment by MICA-UKA has influence on the clinical results. The present study was conducted to compare the short-term results of MICA-UKA with MI-UKA. It was hypothesized that better alignment as well as clinical results was achieved by MICA-UKA as compared to MI-UKA.

METHODS

The clinical and radiological results of 87 subjects who underwent primary UKA using either minimally invasive and computer-assisted technique (45 patients Group A) or minimally invasive technique (42 patients, Group B) were reported. Knee Society scores (KSSs), Knee Society functional scores (KSFSs), range of motion (ROM), and radiographic results were assessed and reported preoperatively and at 24-month follow-up. Total blood loss, operative time, and length of skin incision were compared.

RESULTS

The accuracy of the implantations in relation to the coronal mechanical axis in Group A was significantly superior to that of Group B (P = 0.033). The femoral rotational profile revealed the prosthesis in Group A that was implanted with significantly less internal rotation than Group B (P = 0.025). Clinical results, with regard to ROMs and KSSs, as well as KSFSs were equally good in both the groups. The average blood loss in patients of Group A was significantly reduced as compared to patients of Group B. No significant difference was detected in terms of operative time or length of skin incision.

CONCLUSIONS

It is suggested that MICA-UKA improves the implant alignment without increasing clinical results versus MI-UKA. We advocate that computer navigation should be considered when minimally invasive unicompartmental knee arthroplasty is performed.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

Computerised navigation of unicondylar knee prostheses: from primary implantation to revision to total knee arthroplasty

AIM

Computerized navigation of unicondylar knee arthroplasties (UKA) is not a widespread technique. The lifespan of a UKA depends on the quality of its implantation. We know that overcorrection leads to a rapid extension of the osteoarthritis to the opposite side of the knee and undercorrection to a rapid loosening or wear of the prosthesis. Because of these difficulties and following a long experience with navigation of total knee arthroplasties (TKA) and osteotomies around the knee, we began using navigation for revisions to TKA in 2003 and for UKAs in 2008. The aim of this work is to present, firstly, the axial alignment of 79 medial and 19 lateral computer-assisted UKAs and, secondly, the axial alignment of 23 computer-assisted UKA revisions to TKA.

METHODS

In all the cases we used the Orthopilot^® device (BBraun-Aesculap, Tuttlingen, Germany), which is a non image-based navigation system.

RESULTS

For medial prostheses, the main objective was to obtain a post-operative HKA angle of 177° ± 2°, i.e. an under correction of 1-5°. This objective was met in 88.5 % of the cases. For lateral prostheses, the main objective was to achieve a post-operative HKA angle of 183° ± 2°, i.e. also an under correction of 1-5°. This objective was met in 84 % of the cases (3 cases at 186° and no cases of over correction). Regarding UKA revisions, the main objective was to ensure an HKA angle of 180° ± 3°. This was met in 92.4 % of the cases.

CONCLUSION

As for TKA and osteotomies, computerized navigation of UKAs and UKA revisions allows the pre-operative goal to be met easily.

Is tibial cut navigation alone sufficient in medial unicompartmental knee arthroplasty? Continuous series of fifty nine procedures

PURPOSE

Our purpose was to assess medial unicompartmental knee arthroplasty with navigation alone for the tibial cut and limb alignment. We hypothesised that this technique could be used routinely in practice.

METHODS

Outcome measures were tibial cut orientation and residual varus. Six-month post-operative radiographs of 59 knees were assessed.

RESULTS

Tibial cut orientation was within 2° of planned in 70.2 and 76.3 % of knees in the coronal and sagittal planes, respectively (49.1 % in both), within 4° in 91.2 and 91.5 %, respectively (82.5 % in both). All coronal-plane errors were in varus. Excessive planed tibial slope was at risk of excessive varus of the tibial cut. The hip-knee-ankle angle was ≤179° in 81.4 % and the mechanical axis through Kennedy Zone 2 in 59.3 % of knees. Risk factors for inadequate varus were pre-operative hip-knee-ankle angle >176° and strictly articular varus.

CONCLUSIONS

Our results are not as good as previously reported with this technique, but taking into account the factors of failure identified, we could enhance the results.

Comparison of Outcome and Survival After Unicompartmental Knee Arthroplasty Between Navigation and Conventional Techniques With an Average 9-Year Follow-Up

BACKGROUND

Unicompartmental knee arthroplasty(UKA) has become a treatment of choice for many patients with isolated unicomparmental arthritis due to its specific advantages over total knee arthroplasty, but few studies have compared conventional and navigational UKA with similar instrumentation on mid- to long-term results. We investigated whether the use of imageless navigation can improve implant positioning and clinical outcomes of UKA at a long-term follow-up compared to the conventional technique.

METHODS

We prospectively studied clinical and radiological results in 68 patients with an average age of 64.0 years (range, 50 to 81 years) who received UKA between January 2003 and December 2005 using the conventional or navigational technique. Clinical evaluations were performed preoperatively and the last follow-up included knee range of motion, Hospital for Special Surgery (HSS) scores, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores and Visual Analogue Scale (VAS) pain score. For radiologic evaluation, the mechanical alignment of the lower limb was measured using mechanical femoro-tibial angle (mFTA) and Kennedy protocol.

RESULTS

After an average 9-year follow-up (range, 7.4 to 10.8 years), the navigation group showed better coronal alignments of the components, fewer radiological outliers and better clinical scores, but similar estimated 10-year prosthesis survival rates.

CONCLUSION

This study indicates that the use of navigation significantly contributes to the desired mechanical axis and improved component placement as compared to the conventional technique.

LEVEL OF EVIDENCE

Prospective comparative study, Level III.

Twice cutting method reduces tibial cutting error in unicompartmental knee arthroplasty

BACKGROUND

Bone cutting error can be one of the causes of malalignment in unicompartmental knee arthroplasty (UKA). The amount of cutting error in total knee arthroplasty has been reported. However, none have investigated cutting error in UKA. The purpose of this study was to reveal the amount of cutting error in UKA when open cutting guide was used and clarify whether cutting the tibia horizontally twice using the same cutting guide reduced the cutting errors in UKA.

METHODS

We measured the alignment of the tibial cutting guides, the first-cut cutting surfaces and the second cut cutting surfaces using the navigation system in 50 UKAs. Cutting error was defined as the angular difference between the cutting guide and cutting surface.

RESULTS

The mean absolute first-cut cutting error was 1.9° (1.1° varus) in the coronal plane and 1.1° (0.6° anterior slope) in the sagittal plane, whereas the mean absolute second-cut cutting error was 1.1° (0.6° varus) in the coronal plane and 1.1° (0.4° anterior slope) in the sagittal plane. Cutting the tibia horizontally twice reduced the cutting errors in the coronal plane significantly (P<0.05).

CONCLUSION

Our study demonstrated that in UKA, cutting the tibia horizontally twice using the same cutting guide reduced cutting error in the coronal plane.

Accuracy of Individualized Custom Tibial Cutting Guides in UKA

BACKGROUND

Component malposition is one of the major reasons for early failure of unicompartmental knee arthroplasty (UKA).

QUESTIONS/PURPOSES

It was investigated how reproducibly patient-specific instrumentation (PSI) achieved preoperatively planned placement of the tibial component in UKA specifically assessing coronal alignment, slope and flexion of the components and axial rotation.

PATIENTS AND METHODS

Based on computer tomography models of ten cadaver legs, PSI jigs were generated to guide cuts perpendicular to the tibial axis in the coronal and sagittal planes and in neutral axial rotation. Deviation ≥3° from the designed orientation in a postoperative CT was defined as outside the range of acceptable alignment.

RESULTS

Mean coronal alignment was 0.4 ± 3.2° varus with two outliers. Mean slope was 2.8 ± 3.9° with six components in excessive flexion. It was noted that the implants were put in a mean of 1.7 ± 8.0° of external rotation with seven outliers.

CONCLUSIONS

PSI helped achieve the planned coronal orientation of the component. The guides were less accurate in setting optimal tray rotation and slope.

Robotic guidance does not improve component position or short-term outcome in medial unicompartmental knee arthroplasty

We performed a retrospective review in a matched group of patients on the use of robotic-assisted UKA implantation versus UKA performed using standard operative techniques to assess differences between procedures. While both techniques resulted in reproducible and excellent outcomes with low complication rates, the results demonstrate little to no clinical or radiographic difference in outcomes between cohorts. Average operative time differed significantly with, and average of 20 minutes greater in, the robotic-assisted UKA group (P=0.010). Our minimal clinical and radiographic differences lend to the argument that it is difficult to justify the routine use of expensive robotic techniques for standard medial UKA surgery, especially in a well-trained, high-volume surgeon. Further surgical, clinical and economical study of this technology is necessary.

Improved accuracy in computer-assisted unicondylar knee arthroplasty: a meta-analysis

PURPOSE

Inaccurate implantation rates of up to 30 % have been reported in cases using the conventional technique for implantation of a unicompartmental knee arthroplasty. Navigation should permit a more precise implantation, and several studies have investigated its role, albeit with a limited number of patients and inconsistent results. The aim of this meta-analysis was to compare risks of unsatisfactory outcomes in patients with navigated and conventional technique.

METHODS

An electronic search was performed, and ten studies were eligible and included in the meta-analysis, with a total of 258 prostheses implanted with the navigated technique and 295 with the conventional one. The following items were analysed: radiological positioning of the femoral and the tibial component in the AP and lateral view, radiological analysis of the tibiofemoral mechanical axis and the difference in operating time between the two groups. Relative risks (RR) were calculated from the reported percentages of implants outside the optimal ranges defined by the manufacturers or the study groups. Natural logarithms of the relative risks were pooled by means of random effects models.

RESULTS

For all the analysed radiological parameters, the RR of measurements outside the optimal ranges were less than 1 in the navigation group suggesting a reduction in the risk of outliers with navigation. The average operating time in the navigated group was 15.4 min (95 % CI: 10.2-20.6) longer than in the conventional group.

CONCLUSION

The meta-analysis shows that the use of navigation systems in UKA leads to a more precise component position. Whether the more accurate position in UKA results in a better clinical outcome or long-term survival is yet unknown. Nevertheless, as a precise implant position appears to be beneficial, the use of navigation should be recommended for UKA. The limits defined by the manufacturers for an optimal positioning are not consistent.

Navigation of the tibial plateau alone appears to be sufficient in computer-assisted unicompartmental knee arthroplasty

PURPOSE

The aim of this study was to present our technique to implant unicompartmental knee arthroplasty (UKA) using navigation and to give our first results regarding the accuracy of the device.

METHODS

A total of 33 patients with medial femorotibial osteoarthritis (31) or avascular necrosis (2) were included in this study. The mean preoperative hip-knee-ankle (HKA) angle was 172.7 ± 2.2° (range 167-177°) and the preoperative planning aimed to reach an HKA angle between 175 and 179° (177 ± 2°), a tibial varus at 3 ± 1°, which means a tibial mechanical angle (TMA) close to 87 ± 1°, and posterior tibial slope at 3 ± 2°. In all cases, we used the OrthoPilot® device with dedicated software allowing us to navigate only the tibial plateau.

RESULTS

The preoperative plan was reached in 93.9 % of cases for HKA angle, 84.8 % for TMA and 100 % for the posterior slope.

CONCLUSIONS

Unicompartmental knee navigation is reliable. The navigation of only the tibial bone cut is a reasonable option as has been shown in this study. Its role is invaluable in the positioning of mobile-bearing UKA, where the risk of overcorrection should not be underestimated.

Accuracy of dynamic tactile-guided unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty (UKA) can achieve excellent clinical and functional results for patients having single-compartment osteoarthritis. However, UKA is considered to be technically challenging to perform, and malalignment of implant components significantly contributes to UKA failures. It has been shown that surgical navigation and tactile robotics could be used to provide very accurate component placement when the bones were rigidly fixed in a stereotactic frame during preparation. The purpose of this investigation was to determine the clinically realized accuracy of UKA component placement using surgical navigation and tactile robotics when the bones are free to move. A group of 20 knees receiving medial UKA with dynamically referenced tactile-robotic assistance was studied. Implant placement errors were comparable with those achieved using tactile robotics with rigid stereotactic fixation.

Navigation in minimally invasive unicompartmental knee arthroplasty has no advantage in comparison to a conventional minimally invasive implantation

INTRODUCTION

Minimally invasive implantation of unicompartmental knee prostheses can shorten rehabilitation time and lead to better functional results than conventional implantation. Exact positioning of the implant should be achieved, as this is a factor for the long-term survival of the prosthesis, although malpositioning can result due to the poor intraoperative view when using the minimally invasive approach. Navigation of the unicompartmental prosthesis could lead to a better implant positioning without losing the advantages of a minimally invasive approach.

MATERIALS AND METHODS

The same unicondylar knee prosthesis was implanted in a total of 40 patients, of whom 20 were implanted using navigation (kinematic navigation) and 20 using a conventional technique. The operating time was assessed in both groups. The orientation of the tibial and femoral implants was assessed radiologically postoperatively. We analysed these results according to the optimal positioning range proposed by the manufacturer. Furthermore, we examined the clinical results with the knee society score (KSS).

RESULTS

A good positioning of the prosthesis was observed in both techniques with only 11% of the radiologic measurements out of the proposed optimal range in each group. The operating time was significantly longer in the navigation group (17 min). The KSS did not differ between both groups at a follow-up of 16 resp. 18 months (navigated group: 184 points, conventional group: 178 points).

CONCLUSIONS

Navigation did not lead to a better positioning of the prosthesis than the conventional method and the operating time was longer. The clinical results were similar in both groups. The navigation may be a useful help for surgeons performing less unicompartmental knee arthroplasty using a minimally invasive approach.

UNICOMPARTMENTAL KNEE ARTHROPLASTY: CURRENT PERSPECTIVES AND TRENDS IN BRAZIL

Objective: The aim of this study was to evaluate the approaches and procedures used by Brazilian orthopedic surgeons for treating osteoarthrosis by means of unicompartmental knee arthroplasty and high tibial osteotomy of the knee. Methods: A questionnaire with 14 closed questions was developed and applied to Brazilian knee surgeons during the three days of the 43^rd Brazilian Congress of Orthopedics and Traumatology. Results: A total of 113 surgeons filled out the questionnaire completely and became part of the sample analyzed. In this study, the majority of the surgeons performed fewer than five unicompartmental knee arthroplasty procedures/year (61.1%) and between 5 and 15 high tibial osteotomy procedures/year (37.2%). Use of computerized navigation systems during surgery remains uncommon in our environment, since only 0.9% of the specialists were using it. 65.5% of the surgeons reported that they had chosen to use total knee arthroplasty rather than partial arthroplasty due to lack of familiarity with the surgical technique. When asked about the possibility that the number of unicompartmental prostheses used in Brazil would grow as surgeons in this country become increasingly familiar with the technique, 80.5% of the respondents believed in this hypothesis. In this sample, we found that the greater the surgeon's experience was, the greater the numbers of unicompartmental prostheses and tibial osteotomies performed annually were (r = 0.550 and r = 0.465, respectively; p < 0.05). Conclusions: There is a clear evolutional trend towards treatment of unicompartmental osteoarthritis using partial knee arthroplasty in Brazil. However, further prospective controlled studies are needed in order to evaluate the clinical and scientific benefits of these trends.

Quantification of the difference between 3D CT and plain radiograph for measurement of the position of medial unicompartmental knee replacements

The aim of this study was to quantify the differences in measurements obtained from 3D Computed Tomography and plain radiograph, for the positioning of the tibial component of the Oxford unicompartmental knee replacement. Post-operative 3D Computed Tomography data and plain radiographs (long antero-posterior (AP) and short lateral) were obtained for 28 knees of patients who had undergone medial unicompartmental knee replacement. Parameters of the orientation/positioning of the tibial component: Varus/valgus, posterior tibial slope and rotation were measured with both modalities. Bland-Altman plots were used to calculate the 1.96 standard deviation limits of agreement (LOA) between imaging modalities. Intra class correlation was used to assess inter-method and inter-rater reliability (>0.81 = very good reliability). Radiographs were less reliable in all parameters, when compared with 3D CT (intra class correlation coefficients: tibial rotation 0.94 vs 0.96, varus/valgus 0.76 vs 0.94, and posterior tibial slope 0.82 vs 0.92). The LOA were -4.9° to 3.4° for varus/valgus (bias -0.7°, one third >3° different); -4.9° to 0.1° for posterior tibial slope (bias -2.4°, one third >3° different); and -20.6° to 16.1° for rotation (bias -2.2°, one third >10° different). There was some disagreement between measurement by 3D Computed Tomography and plain radiograph for all three parameters of tibial component orientation, especially tibial rotation. This will be particularly relevant to research into the relationship between the accuracy of implant positioning/orientation and patient satisfaction/implant survival rates. This method offers a more reliable standard for the reporting of knee arthroplasty.

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.

The long-term benefit of computer-assisted surgical navigation in unicompartmental knee arthroplasty

We reviewed the outcomes of 30 consecutive primary unicompartmental knee arthroplasties (UKA) performed by a single surgeon for medial compartmental osteoarthritis. Fifteen Allegretto knees were implanted without computer navigation and 15 EIUS knees were implanted with navigation. We compared the survivorship, radiological and clinical outcomes of the two groups at an average of 8.9 years and 6.9 years respectively. The patients were assessed clinically using the Oxford Knee Score (OKS) and radiologically using long-leg weightbearing films and non-weightbearing computed tomography alignment measurements. The overall survivorship was 86.7% at 9 years. A higher proportion of navigated knees were well aligned with a more reproducible position and malaligned knees tended to have a less favourable OKS. However, we found no statistically significant difference in survivorship, clinical outcome and radiological alignment between the two groups.

Scientific evidence for the use of modern unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty as a surgical treatment for monocompartmental knee arthritis remains a controversial procedure with questions surrounding the benefits and survivorship of the procedure versus osteotomies or total knee arthroplasties. The authors, by examining the complete body of literature for scientific evidence concerning the procedure, will describe the history of usage of these prostheses, their rationale for usage, modern devices and their results, and why they may have advantages as a treatment modality for monocompartmental knee arthritis. Outcomes of current unicompartmental designs will be presented and evaluated to determine which aspects of the design and patient selection technique are associated with success or failure. Commonly asked questions regarding the use of these devices will be addressed. The authors will also describe some potential modifications that might affect the use of these components in the future, including minimally invasive procedures and robotics, and how these devices may change over the next 5 years.