Robotic arm-assisted versus conventional unicompartmental knee arthroplasty: Exploratory secondary analysis of a randomised controlled trial

Robotic-assisted vs conventional surgery in medial unicompartmental knee arthroplasty: a clinical and radiological study

BACKGROUND

The use of unicompartmental knee arthroplasty (UKA) has increased and new technologies have been developed to improve patient survival and satisfaction, soft tissue balance, alignment, and component size. Robot-assisted systems offer an increase in surgical precision and accuracy. The purpose of this study is to evaluate the precision of component position using five radiological parameters in conventional and robotic-assisted medial UKA using the NAVIO system.

METHODS

A cohort study was designed for patients who underwent medial UKA between April 2017 and March 2019 in a single center. Patients were allocated in the conventional (UKA-C) or robotic-assisted (UKA-R) group. The variables analyzed were age, gender, affected knee side, length of hospital stay, surgical time, and radiological measurements such as anatomical medial distal femoral angle (aMDFA), anatomical medial proximal tibial angle (aMPTA), tibial slope, the sagittal femoral angle, and the component size. A target was defined for each measurement, and a successful UKA was defined if at least four radiological measures were on target after surgery. Also, patients' reported outcomes were evaluated using the Oxford Knee Score (OKS) and a numeric rating scale (NRS) for pain.

RESULTS

Thirty-four patients were included, 18 of them underwent UKA-R. The success rate for UKA in the UKA-R group was 87%; meanwhile, in the UKA-C group this was 28%, this difference was significant and powered (Fisher's exact test, p = 0.001; 1 - β = 0.95). Also, a 5-point difference in favor of the UKA-R group in the median OKS (p = 0.01), and a significantly lower median NRS for pain (p < 0.000) were found after surgery.

CONCLUSIONS

UKA-R achieved more precision in the radiological parameters' measure in this study. Also, UKA-R has a trend towards a better OKS and a lower NRS for pain at short-term follow-up.

Not All Robotic-assisted Total Knee Arthroplasty Are the Same

Because value in healthcare has shifted to a measurement of quality relative to the cost, a greater emphasis exists on improving clinical and functional outcomes and patient satisfaction. Despite advances in implant design, surgical technique, and postoperative rehabilitation, multiple studies demonstrate that nearly 20% of patients remain dissatisfied with their overall outcomes after primary total knee arthroplasty (TKA). Because implant positioning, alignment, and equal soft-tissue balance are critical for a successful TKA, malalignment in the coronal, sagittal, and rotational planes continue to increase failure rates and cause poor clinical outcomes. Robotic-assisted TKA has gained momentum within the past 10 years to better control surgical variables by mitigating technical errors caused by insecure cutting guides and imprecise bone cuts. Contemporary robotic platforms have evolved along with our ability to collect high-quality patient-reported outcome measures data, and this combination is proving the clinical effectiveness. This comprehensive review investigates the advent of robotic-assisted TKA including advantages, disadvantages, historical, and commercially available newer generation systems, clinical outcomes, and cost analysis to better understand the potential added value of this technology.

A progressive scholarly acceptance analysis of robot-assisted arthroplasty: a review of the literature and prediction of future research trends

Robot-assisted arthroplasty (RAA) is increasingly practised in orthopaedic surgery. The aim of this study was to perform a bibliometric analysis of all published primary research into RAA and to apply the Progressive Scholarly Acceptance (PSA) model to evaluate its acceptance as an orthopaedic surgical technique. A literature search was performed that included all peer-reviewed, primary, English language publications on RAA from its introduction in 1992 up to 2019. RAA was defined as robot-assisted hip or knee arthroplasty. A bibliometric analysis was performed to categorise articles by type of study and level of evidence. Studies were also categorised as initial investigations (II) or refining studies (RS). A PSA analysis was performed, with the end-point being defined as the point in time when the number of RS exceeded the number of II. Of the 199 studies originating from 19 countries and 101 institutions, only 16 (8.04%) were randomised-controlled trials. Fifty-one percent of studies had been published since 2015. Using PSA analysis, 161 (80.9%) studies were categorised as II and 38 (19.1%) were categorised as RS. This demonstrates that RAA has not yet reached the point of scholarly acceptance. Scholarly acceptance of RAA as an orthopaedic surgical technique has yet to be reached. However, there has been an exponential increase in the number of publications on RAA in the last 5 years, reflecting renewed interest this technique. We predict that, for the next 5 years, RAA will remain in the experimental phase due to the rapid development of new technology in this field.

Research quality and transparency, outcome measurement and evidence for safety and effectiveness in robot-assisted surgery: systematic review

BACKGROUND

Robot-assisted surgery (RAS) has potential panspecialty surgical benefits. High-quality evidence for widespread implementation is lacking. This systematic review aimed to assess the RAS evidence base for the quality of randomized evidence on safety and effectiveness, specialty 'clustering', and outcomes for RAS research.

METHODS

A systematic review was undertaken according to PRISMA guidelines. All pathologies and procedures utilizing RAS were included. Studies were limited to RCTs, the English language and publication within the last decade. The main outcomes selected for the review design were safety and efficacy, and study purpose. Secondary outcomes were study characteristics, funding and governance.

RESULTS

Searches identified 7142 titles, from which 183 RCTs were identified for data extraction. The commonest specialty was urology (35·0 per cent). There were just 76 unique study populations, indicating significant overlap of publications; 103 principal studies were assessed further. Only 64·1 per cent of studies reported a primary outcome measure, with 29·1 per cent matching their registration/protocol. Safety was assessed in 68·9 per cent of trials; operative complications were the commonest measure. Forty-eight per cent of trials reported no significant difference in safety between RAS and comparator, and 11 per cent reported RAS to be superior. Efficacy or effectiveness was assessed in 80·6 per cent of trials; 43 per cent of trials showed no difference between RAS and comparator, and 24 per cent reported that RAS was superior. Funding was declared in 47·6 per cent of trials.

CONCLUSION

The evidence base for RAS is of limited quality and variable transparency in reporting. No patterns of harm to patients were identified. RAS has potential to be beneficial, but requires continued high-quality evaluation.

Robotic arm-assisted bi-unicompartmental knee arthroplasty maintains natural knee joint anatomy compared with total knee arthroplasty: a prospective randomized controlled trial

AIMS

The aim of this study was to compare robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) in order to determine the changes in the anatomy of the knee and alignment of the lower limb following surgery.

METHODS

An analysis of 38 patients who underwent TKA and 32 who underwent bi-UKA was performed as a secondary study from a prospective, single-centre, randomized controlled trial. CT imaging was used to measure coronal, sagittal, and axial alignment of the knee preoperatively and at three months postoperatively to determine changes in anatomy that had occurred as a result of the surgery. The hip-knee-ankle angle (HKAA) was also measured to identify any differences between the two groups.

RESULTS

The pre- to postoperative changes in joint anatomy were significantly less in patients undergoing bi-UKA in all three planes in both the femur and tibia, except for femoral sagittal component orientation in which there was no difference. Overall, for the six parameters of alignment (three femoral and three tibial), 47% of bi-UKAs and 24% TKAs had a change of < 2° (p = 0.045). The change in HKAA towards neutral in varus and valgus knees was significantly less in patients undergoing bi-UKA compared with those undergoing TKA (p < 0.001). Alignment was neutral in those undergoing TKA (mean 179.5° (SD 3.2°)) while those undergoing bi-UKA had mild residual varus or valgus alignment (mean 177.8° (SD 3.4°)) (p < 0.001).

CONCLUSION

Robotic-assisted, cruciate-sparing bi-UKA maintains the natural anatomy of the knee in the coronal, sagittal, and axial planes better, and may therefore preserve normal joint kinematics, compared with a mechanically aligned TKA. This includes preservation of coronal joint line obliquity. HKAA alignment was corrected towards neutral significantly less in patients undergoing bi-UKA, which may represent restoration of the pre-disease constitutional alignment (p < 0.001). Cite this article: Bone Joint J 2020;102-B(11):1511-1518.

The preoperative Oxford Knee Score is an independent predictor of achieving a postoperative ceiling score after total knee arthroplasty

Aims

The primary aim of this study was to assess whether the postoperative Oxford Knee Score (OKS) demonstrated a ceiling effect at one and/or two years after total knee arthroplasty (TKA). The secondary aim was to identify preoperative independent predictors for patients that achieved a ceiling score after TKA.

Methods

A retrospective cohort of 5,857 patients undergoing a primary TKA were identified from an established arthroplasty database. Patient demographics, body mass index (BMI), OKS, and EuroQoL five-dimension (EQ-5D) general health scores were collected preoperatively and at one and two years postoperatively. Logistic regression analysis was used to identify independent preoperative predictors of patients achieving postoperative ceiling scores. Receiver operating characteristic curve was used to identify a preoperative OKS that predicted a postoperative ceiling score.

Results

The ceiling effect was 4.6% (n = 272) at one year which increased significantly (odds ratio (OR) 40.3, 95% confidence interval (CI) 30.4 to 53.3; p < 0.001) to 6.2% (n = 363) at two years, when defined as those with a maximal score of 48 points. However, when the ceiling effect was defined as an OKS of 44 points or more, this increased to 26.3% (n = 1,540) at one year and further to 29.8% (n = 1,748) at two years (OR 21.6, 95% CI 18.7 to 25.1; p < 0.001). A preoperative OKS of 23 or more and 22 or more were predictive of achieving a postoperative ceiling OKS at one and two years when defined as a maximal score or a score of 44 or more, respectively.

Conclusion

The postoperative OKS demonstrated a small ceiling effect when defined by a maximal score, but when defined by a postoperative OKS of 44 or more the ceiling effect was moderate and failed to meet standards. The preoperative OKS was an independent predictor of achieving a ceiling score. Cite this article: Bone Joint J 2020;102-B(11):1519–1526.

Robotic-assisted surgery in medial unicompartmental knee arthroplasty: does it improve the precision of the surgery and its clinical outcomes? Systematic review

There is a high prevalence of knee osteoarthritis that affects only the medial tibiofemoral compartment. In this group of patients with severe disease, the medial unicompartmental knee arthroplasty (UKA) is an excellent choice. However, this technique has a great learning curve due to the lower tolerance of improper positioning and alignment. In this context, the robotic-assisted surgery (RAS) arises as an option to improve the accuracy and secondarily enhance the clinical outcomes related to the UKA. The objective in this study is to determine if there are significant advantages with the use of RAS over conventional surgery (CS). In the systematic review of the literature, classification of the results in three main subjects: (A) precision and alignment; (B) functional results and clinical parameters; (C) survivorship. We found 272 studies, of which 15 meet the inclusion and exclusion criteria. There is mostly described that RAS significantly improves the accuracy in position (80-100% of planned versus performed P < 0.05), alignment (2-3 times less error variance P < 0.05) and selection of the proper size of the implants (69.23% of correct size femoral implants versus 16.67% using CS P < 0.0154). Recently, there is mild evidence about benefits in the early rehabilitation and post-operative pain, but in all studies reviewed, there is no advantages of RAS in the long-term functional evaluation. There is no strong literature that supports a longer survival of the prothesis with RAS, being the longest mean follow-up reported of 29.6 months. RAS is a useful tool in increasing the precision of the medial UKA implant placement. However, there is still a lack of evidence that properly correlates this improvement in accuracy with better clinical, functional and survival results.

Robotic-assisted total knee arthroplasty is comparable to conventional total knee arthroplasty: a meta-analysis and systematic review

BACKGROUND

Total knee arthroplasty (TKA) is a successful procedure in managing end-stage arthritis when non-operative treatments fail. New technologies such as robotic TKA (rTKA) have been developed to improve the accuracy of prosthesis implantation. While short-term cohort studies on rTKA have shown excellent results, the evidence comparing between rTKA and conventional TKA (cTKA) is not yet well established. This meta-analysis aims to compare the efficacy and safety of rTKA versus cTKA in terms of clinical outcomes, radiographic results, complications, peri-operative parameters and costs.

METHODS

A multi-database search was performed according to PRISMA guidelines. Data from studies comparing between rTKA and cTKA were extracted and analyzed.

RESULTS

Eighteen studies were included in this review, consisting of 2234 rTKA and 4300 cTKA. Robotic TKA led to a more precise prosthesis implantation with significantly fewer outliers in the mechanical axis (p < 0.001), femoral coronal (p = 0.002) and tibial sagittal (p = 0.01) alignments. Only the Hospital for Special Surgery (HSS) (p < 0.001) score at final follow-up was significantly better in rTKA than cTKA. rTKA also had a lower mean blood loss (p < 0.001) despite a longer mean operation time (p = 0.006). There were no statistically significant difference in terms of other clinical outcome measures, range of motion and complications.

CONCLUSION

Both rTKA and cTKA are reliable and safe to perform. However, rTKA is capable of achieving superior alignment in several axes, lower mean blood loss and this may lead to marginally better clinical outcomes than cTKA.

EVIDENCE LEVEL

Level II, Meta-analysis of non-homogeneous studies.

Comparison of robotic-assisted versus conventional unicompartmental knee arthroplasty for the treatment of single compartment knee osteoarthritis: A meta-analysis

BACKGROUND

The robotic-assisted unicompartmental knee arthroplasty (UKA) is proposed to improve the accuracy of component positioning.

METHODS

We conducted a literature search in Medline, Embase, Web of Science and the Cochrane Library until April 2020.

RESULTS

Our meta-analysis included 10 articles, involving 1231 knees. Our meta-analysis demonstrated that the robotic group had significantly better results in outliers of limb alignment (p < 0.001) and outliers of tibial alignment (p < 0.001). No statistical differences were found in the American Knee Society Score (p = 0.63), range of motion (p = 0.93), pain (p = 0.27), rate of revisions (p = 0.73) and rate of complications (p = 0.67).

CONCLUSIONS

Robotic-assisted UKA has better component position accuracy compared with conventional UKA. But there was no significant difference in clinical results. In order to further evaluate the utility of robotic-assisted UKA, long-term follow-up randomized controlled trials (RCTs) are needed, as well as studies to evaluate the correlation between postoperative alignment and long-term clinical results.

Unicondylar knee arthroplasty versus total knee arthroplasty in adults with isolated medial osteoarthritis: A matched study protocol

BACKGROUND

The choice between unicondylar knee arthroplasty (UKA) and total knee arthroplasty (TKA) is likely to have long-term implications for patient-reported health outcomes. However, high-quality studies that compare the outcomes of TKA and UKA and their effects are still lacking in the literature. Thus, the aim of the present study was to compare the UKA and TKA techniques with regard to functional outcomes and perioperative complications in patients who had isolated medial osteoarthritis.

METHODS

This was a retrospective, single-center, matched-controlled study performed with approval of our hospital (Kunshan hospital of Traditional Chinese Medicine affiliated to Nanjing University of Traditional Chinese Medicine), with the ethics number KZY2020-37. To reduce the effect of selection bias and potential confounding in this observational study, a 1:1 matching algorithm was applied. The groups were split by sex, age to within 6 years, and body mass index within 5 kg/m. Thus, we retrospectively reviewed the records of 240 consecutively enrolled patients who underwent UKA and 240 patients who underwent TKA from January 2013 to June 2015 from the database of our institution. Written informed consent was obtained from all subjects participating in the trial. Clinical outcomes included range of motion, Short Form 12 score, new Knee Society Score, Western Ontario and McMaster Universities Arthritis Index, and the complications. The outcome measures were evaluated by a physiotherapist and were assessed preoperatively and postoperatively at 6 months and 2 years. The mean follow-up time was 3 years.

CONCLUSION

We hypothesized that there was no significant difference between the 2 groups in terms of postoperative outcomes.

TRIAL REGISTRATION

Our study was registered in Research Registry (researchregistry5828).

Robotic-arm assisted medial unicondylar knee arthroplasty versus jig-based unicompartmental knee arthroplasty with navigation control: study protocol for a prospective randomised controlled trial

Background

There remains a paucity of clinical studies assessing how any differences in accuracy of implant positioning between robotic-arm assisted unicompartmental knee arthroplasty (RO UKA) and conventional jig-based unicompartmental knee arthroplasty (CO UKA) translate to patient satisfaction, functional outcomes, and implant survivorship. The objectives of this study are to compare accuracy of implant positioning, limb alignment, patient satisfaction, functional outcomes, implant survivorship, cost-effectiveness, and complications in CO UKA versus RO UKA. Computer navigation will be used to assess intraoperative knee kinematics in all patients undergoing CO UKA.

Methods and analysis

This prospective randomised controlled trial will include 140 patients with symptomatic medial compartment knee arthritis undergoing primary UKA. Following informed consent, patients will be randomised to CO UKA (control group) or RO UKA (investigation group) at a ratio of 1:1 using an online random number generator. The primary objective of this study is to compare accuracy of implant positioning in CO UKA versus RO UKA. The secondary objectives are to compare the following outcomes between the two treatment groups: limb alignment, surgical efficiency, postoperative functional rehabilitation, functional outcomes, quality of life, range of motion, resource use, cost effectivness, and complications. Observers will review patients at regular intervals for 2 years after surgery to record predefined study outcomes pertaining to these objectives. Ethical approval was obtained from the London-Bloomsbury Research Ethics Committee, UK. The study is sponsored by University College London, UK.

Discussion

This study compares a comprehensive and robust range of clinical, functional, and radiological outcomes in CO UKA versus RO UKA. The findings of this study will provide an improved understanding of the differences in CO UKA versus RO UKA with respect to accuracy of implant positioning, patient satisfaction, functional outcomes, implant survivorship, cost-effectiveness, and complications.

Trial registration

ClinicalTrials.gov NCT04095637. Registered on 19 September 2019.

A systematic review of MAKO-assisted unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty (UKA), which has many potential advantages compared with total knee arthroplasty, was widely used across the world in recent years. The introduction of the robot systems greatly makes up for the defects of the conventional UKA surgery such as higher complication rates and revision rates. MAKO system, a new image-guided robot system relies on a preoperative computed tomography scan to assist in preoperative mapping and planning, offers an opportunity to improve the outcome of UKA surgeries. In order to have a more comprehensive and in-depth understanding of MAKO-assisted UKA, the studies on MAKO-assisted UKA were summarized. MAKO-assisted UKA is better than conventional UKA surgery on implant accuracy, soft tissue balance, patient function scores and satisfaction, complications rates, and learning curve in short-term outcome; however, the mid-term and long-term outcomes of MAKO-assisted UKA need to be further studied.

A systematic review of imageless hand-held robotic-assisted knee arthroplasty: learning curve, accuracy, functional outcome and survivorship

The aim of this systematic review was to present and assess the quality of evidence for learning curve, component positioning, functional outcomes and implant survivorship for image-free hand-held robotic-assisted knee arthroplasty.Searches of PubMed and Google Scholar were performed in line with the Preferred Reporting Items for Systematic Review and Meta-Analysis statement. The criteria for inclusion was any published full-text article or abstract assessing image-free hand-held robotic knee arthroplasty and reporting learning curve, implant positioning, functional outcome or implant survival for clinical or non-clinical studies.There were 22 studies included. Five studies reported the learning curve: all were for unicompartmental knee arthroplasty (UKA) - no learning curve for accuracy, operative time was reduced after five to 10 cases and a steady surgical time was achieved after eight cases.There were 16 studies reporting accuracy: rate of outliers was halved, higher rate of joint line and mechanical axis restoration, supported by low root mean square error values.Six studies reported functional outcome: all for UKA, improvement at six to 52 weeks, no difference from manual UKA except when assessed for lateral UKA which showed improved clinical outcomes.Two studies reported survivorship: one reported an unadjusted revision rate of 7% at 20 months for medial UKA and the other found a 99% two-year survival rate for UKA.There was evidence to support more accurate implant positioning for UKA, but whether this is related to superior functional outcomes or improved implant survivorship was not clear and further studies are required. Cite this article: EFORT Open Rev 2020;5:319-326. DOI: 10.1302/2058-5241.5.190065.

Robotic-assisted unicompartmental knee arthroplasty has a greater early functional outcome when compared to manual total knee arthroplasty for isolated medial compartment arthritis

Aims

The primary aim of the study was to compare the knee-specific functional outcome of robotic unicompartmental knee arthroplasty (rUKA) with manual total knee arthroplasty (mTKA) for the management of isolated medial compartment osteoarthritis. Secondary aims were to compare length of hospital stay, general health improvement, and satisfaction between rUKA and mTKA.

Methods

A powered (1:3 ratio) cohort study was performed. A total of 30 patients undergoing rUKA were propensity score matched to 90 patients undergoing mTKA for isolated medial compartment arthritis. Patients were matched for age, sex, body mass index (BMI), and preoperative function. The Oxford Knee Score (OKS) and EuroQol five-dimension questionnaire (EQ-5D) were collected preoperatively and six months postoperatively. The Forgotten Joint Score (FJS) and patient satisfaction were collected six months postoperatively. Length of hospital stay was also recorded.

Results

There were no significant differences in the preoperative demographics (p ⩾ 0.150) or function (p ⩾ 0.230) between the groups. The six-month OKS was significantly greater in the rUKA group when compared with the mTKA group (difference 7.7, p < 0.001). There was also a greater six-month postoperative EQ-5D (difference 0.148, p = 0.002) and FJS (difference 24.2, p < 0.001) for the rUKA when compared to the mTKA. No patient was dissatisfied in the rUKA group and five (6%) were dissatisfied in the mTKA, but this was not significant (p = 0.210). Length of stay was significantly (p < 0.001) shorter in the rUKA group (median two days, interquartile range (IQR) 1 to 3) compared to the mTKA (median four days, IQR 3 to 5).

Conclusion

Patients with isolated medial compartment arthritis had a greater knee-specific functional outcome and generic health with a shorter length of hospital stay after rUKA when compared to mTKA.

Cite this article: Bone Joint Res 2019;9(1):15–22.

Robotic technology: current concepts, operative techniques and emerging uses in unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty (UKA) is associated with improved functional outcomes but reduced implant survivorship compared to total knee arthroplasty (TKA).

Surgeon-controlled errors in component positioning are the most common reason for implant failure in UKA, and low UKA case-volume is associated with poor implant survivorship and earlier time to revision surgery.

Robotic UKA is associated with improved accuracy of achieving the planned femoral and tibial component positioning compared to conventional manual UKA.

Robotic UKA has a learning curve of six operative cases for achieving operative times and surgical team comfort levels comparable to conventional manual UKA, but there is no learning curve effect for accuracy of implant positioning or limb alignment.

Robotic UKA is associated with reduced postoperative pain, decreased opiate analgesia requirements, faster inpatient rehabilitation, and earlier time to hospital discharge compared to conventional manual UKA.

Limitations of robotic UKA include high installation costs, additional radiation exposure with image-based systems, and paucity of studies showing any long-term differences in functional outcomes or implant survivorship compared to conventional manual UKA.

Further clinical studies are required to establish how statistical differences in accuracy of implant positioning between conventional manual UKA and robotic UKA translate to long-term differences in functional outcomes, implant survivorship, complications, and cost-effectiveness.

Cite this article: EFORT Open Rev 2020;5:312-318. DOI: 10.1302/2058-5241.5.190089

Robots in the Operating Room During Hip and Knee Arthroplasty

PURPOSE OF THE REVIEW

The utilization of technology has increased over the last decade across all surgical specialties. Robotic-assisted surgery, among the most advanced surgical technology, applied to hip and knee arthroplasty has experienced rapid growth in utilization, surgical applications, and robotic platforms. The goal of this study is to provide a comprehensive review of the most commonly utilized robotic platforms for hip and knee arthroplasty and the most up to date literature on the benefits and limitations of robotic arthroplasty.

RECENT FINDINGS

Studies consistently demonstrate that that robotic-assisted surgery during total hip arthroplasty (THA), total knee arthroplasty (TKA), and unicompartmental knee arthroplasty (UKA) improves component position and alignment. There is also growing evidence that robotic-assisted UKA improves clinical outcomes and implant survivorship and, therefore, may be cost-effective. However, there remains to be convincing evidence that robotic-assisted arthroplasty improves clinical outcome measures or reduces revision rates for THA and TKA. Potential disadvantages of robotic arthroplasty remain, including a learning curve, potential for additional radiation exposure preoperatively, and the financial costs. Robotic hip and knee arthroplasty remains attactive as studies show that it consistently improves implant position and alignment over conventional techniques. There is growing evidence that robotic UKA may improve patient outcomes and reduce revision rates, but further study is needed. In addition, further and longer-term studies are needed to determine if improved component position and alignment in TKA and THA leads to improved clinical outcomes and reduced revision rates.

Robotic-Assisted Knee Arthroplasty (RAKA): The Technique, the Technology and the Transition

BACKGROUND

There has been an exponential increase in knee arthroplasty over the past 20 years. This has led to a quest for improvement in outcomes and patient satisfaction. While the last decade of last century proved to be the decade for Computer-Assisted Surgery (CAS) or Computer Navigation wherein the technology demonstrated a clear benefit in terms of improving mechanical axis alignment and component positioning, this decade is likely to belong to Robotics. Robotics adds an independent dimension to the benefits that CAS offers. The article deals with the generation of robots, technical steps in robotics, advantages and downsides of robotics and way forward in the field of knee arthroplasty.

MATERIALS AND METHODS

The review article was designed and edited by six different authors reviewing 32 relevant pubmed-based articles related to robotics in arthroplasty and orthopaedics. The concept, design and the definition of the intellectual content were based on the internationally published literature and insightful articles. The review is also based on the clinical experimental studies published in the literature.

DISCUSSION

The robotic arm is actively involved with surgeon to achieve the precision and outcomes that the surgeon aims for. With the concept of haptic boundaries and augmented reality being incorporated in most systems, Robotic Assisted Arthroplasty (RAA) is likely to offer several advantages. The potential advantages of these systems may include accuracy in gap balancing, component positioning, minimal bone resection, reduced soft tissue handling and trauma, patient anatomy specific resection, and real time feedback. They, however, come with their own downsides in terms of capital cost, learning curve, time consumption and unclear advantages in term of long-term clinical outcomes.

CONCLUSION

To conclude, this review article offers a balanced view on how the technology is impacting current arthroplasty practice and what can be expected in coming years. The commitment of almost all major implant manufacturers in investing in robotics likely means that the evolution of Robotic technology and this decade will be exciting with rapid strides revealing paradigm shift and evolution of technology with significant reductions of cost enabling it to be available universally. For technology to populate in operating room, I think it will be result of exposure of young surgeons to these computers and robotics, as they grow in with confidence with technology from residency days to offer better precision in future.

Surgeon-robot interface development framework

The progress of robotic medicine leads to the emergence of an increasing number of highly specialized automated systems based on specialized software. In any such system, there is the task of translating the surgeon's requests into the process of automated procedure execution. The hardware and software system that provides the translation is the interface between the surgeon and the robot. This paper proposes a generalized framework architecture for the development of such software - the surgeon-robot interface. Existing implementations of such an interface are considered, solutions for the internal structure design of the framework are proposed. Experiments were performed using a prototype of the proposed framework. Such a development framework will allow one to effectively implement the surgeon-robot interfaces at all stages of the robotization of medical procedures, from prototype to final use in the operating room.

Comparison of 1-year outcomes between MAKO versus NAVIO robot-assisted medial UKA: nonrandomized, prospective, comparative study

Background

We have conducted a prospective cohort study with the aim of comparing operative time, intraoperative blood loss, and radiologic and clinical outcomes between imageless (NAVIO) and image-based (MAKO) robot-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis (OA) of the knee.

Methods

A total of 33 patients with medial compartment OA of the knee were prospectively allocated on alternate operative days of their surgery to MAKO (16 patients) or NAVIO (17 patients) robot-assisted UKA. The primary outcome (Knee Society Score [KSS] and Knee Functional Score [KFS]) and the secondary outcomes (intraoperative time of seven steps [registration of hip and ankle, femur and tibia, ligament tension, implant planning, preparation femur, tibia and trial implant], component alignment [coronal and sagittal of femur, tibia implant], blood loss, complications, and revision at 1 year after surgery) were compared between two groups. Statistical significance was set at P < 0.05.

Results

Mean KSS measured at baseline and 1 year were, respectively, 70.3 (5.6) and 96.9 (5.7) in the NAVIO group and 72.3 (4.5) and 94.7 (10.01) in the MAKO group. Mean KFS measured at baseline and 1 year were, respectively, 95.5 (7.9) and 99.9 (0.25) in the NAVIO group and 67.3 (7.8) and 99.5 (1.2) in the MAKO group. There were no significant differences for KFS and KSS outcomes (P = 0.203 and P = 0.457, respectively) between the NAVIO and MAKO groups. Mean operative time and blood loss in the NAVIO versus MAKO robot-assisted UKA groups were 98 min versus 82.5 min and 136.3 ml versus 80 ml, respectively, and these differences were statistically significant. In the MAKO group, the intraoperative time was statistically significantly shorter in registration of hip and ankle center, femur and tibia, femur preparation, and trial implantation compared with the NAVIO group. There were no significant differences of component alignment and radiologic alignment at 1 year between the two groups. No perioperative or delayed complications (infection, periprosthetic fracture, thromboembolism, and compromised wound healing) and revisions were reported in either group.

Conclusions

This study demonstrated that two robotic systems showed no difference in clinical outcomes at 1 year and radiologic alignment of implants, whereas operative time and intraoperative blood loss were found to be less in MAKO robot-assisted UKA.

Trial registration

ClinicalTrials.gov, NCT03954912. Registered on 17 May 2019.

Level of evidence

II

Postoperative outcomes of total knee arthroplasty compared to unicompartmental knee arthroplasty: A matched comparison

BACKGROUND

The purpose of this study was to evaluate early postoperative outcomes in patients following UKA (unicompartmental knee arthroplasty) compared to a matched cohort of TKA (total knee arthroplasty) patients.

METHODS

Patients who met radiographic criteria for a medial UKA who underwent either a TKA or UKA at a single institution were matched based on age, gender, and BMI.

RESULTS

One hundredy and fifty UKA in 138 patients and 150 TKA in 148 patients were included in this retrospective analysis. Mean age was 62.6 ± 9 years and 65.2 ± 9 years in the UKA and TKA groups respectively (p = .01). Patients who underwent UKA had significantly less pain at two and six weeks postoperatively compared to TKA patients with mean Numeric Pain Rating Scale (NPRS) scores of 3.7 ± 1.1 vs. 7.8 ± 1.2, p < .001 and 2.6 ± 1.3 vs. 4.6 ± 1.6, p < .001 respectively. Knee Society Scores (KSS) were higher in the UKA group at six weeks and two years postoperative (86.5 ± 2.8 vs. 81.4 ± 3.6, p < .001 and 89.5 ± 2.4 vs. 84.5 ± 3.3, p < .001 respectively). Return to work was faster in the UKA group (mean 20.6 ± 7.89 vs. 38.6 ± 6.23 days, p < .001). The UKA group also had higher mean Forgotten Joint Scores of 90.5 ± 3.6 vs. 79.5 ± 9.5 (p < .001).

CONCLUSIONS

Patients with primarily medial compartment OA who underwent UKA had less postoperative pain, earlier return to work, and higher KSS compared to a matched group who underwent TKA.

Mid-term survivorship and patient-reported outcomes of robotic-arm assisted partial knee arthroplasty

Aims

Limited evidence is available on mid-term outcomes of robotic-arm assisted (RA) partial knee arthroplasty (PKA). Therefore, the purpose of this study was to evaluate mid-term survivorship, modes of failure, and patient-reported outcomes of RA PKA.

Methods

A retrospective review of patients who underwent RA PKA between June 2007 and August 2016 was performed. Patients received a fixed-bearing medial or lateral unicompartmental knee arthroplasty (UKA), patellofemoral arthroplasty (PFA), or bicompartmental knee arthroplasty (BiKA; PFA plus medial UKA). All patients completed a questionnaire regarding revision surgery, reoperations, and level of satisfaction. Knee Injury and Osteoarthritis Outcome Scores (KOOS) were assessed using the KOOS for Joint Replacement Junior survey.

Results

Mean follow-up was 4.7 years (2.0 to 10.8). Five-year survivorship of medial UKA (n = 802), lateral UKA (n = 171), and PFA/BiKA (n = 35/10) was 97.8%, 97.7%, and 93.3%, respectively. Component loosening and progression of osteoarthritis (OA) were the most common reasons for revision. Mean KOOS scores after medial UKA, lateral UKA, and PFA/BiKA were 84.3 (SD 15.9), 85.6 (SD 14.3), and 78.2 (SD 14.2), respectively. The vast majority of the patients reported high satisfaction levels after RA PKA. Subgroup analyses suggested tibial component design, body mass index (BMI), and age affects RA PKA outcomes. Five-year survivorship was 98.4% (95% confidence interval (CI) 97.2 to 99.5) for onlay medial UKA (n = 742) and 99.1% (95% CI 97.9 to 100) for onlay medial UKA in patients with a BMI < 30 kg/m2 (n = 479).

Conclusion

This large single-surgeon study showed high mid-term survivorship, satisfaction levels, and functional outcomes in RA UKA using metal-backed tibial onlay components. In addition, favourable results were reported in RA PFA and BiKA. Cite this article: Bone Joint J 2020;102-B(1):108–116

Robot-assisted unicompartmental knee arthroplasty can reduce radiologic outliers compared to conventional techniques

Background

The aim of this study was to compare the clinical and radiologic outcomes of robot-assisted unicompartmental knee arthroplasty (UKA) to those of conventional UKA in Asian patients.

Methods

Fifty-five patients underwent robot-assisted UKA and 57 patients underwent conventional UKA were assessed in this study. Preoperative and postoperative range of motion (ROM), American Knee Society (AKS) score, Western Ontario McMaster University Osteoarthritis Index scale score (WOMAC), and patellofemoral (PF) score values were compared between the two groups. The mechanical femorotibial angle (mFTA) and Kennedy zone were also measured. Coronal alignments of the femoral and tibial components and posterior slopes of the tibial component were compared. Additionally, polyethylene (PE) liner thicknesses were compared.

Results

There was no significant difference between the two groups regarding postoperative ROM, AKS, WOMAC and PF score. Robot group showed fewer radiologic outliers in terms of mFTA and coronal alignment of tibial and femoral components (p = 0.022, 0.037, 0.003). The two groups showed significantly different PE liner thicknesses (8.4 ± 0.8 versus 8.8 ± 0.9, p = 0.035). Robot group was the only influencing factor for reducing radiologic outlier (postoperative mFTA) in multivariate model (odds ratio: 2.833, p = 0.037).

Conclusion

In this study, robot-assisted UKA had many advantages over conventional UKA, such as its ability to achieve precise implant insertion and reduce radiologic outliers. Although the clinical outcomes of robot-assisted UKA over a short-term follow-up period were not significantly different compared to those of conventional UKA, longer follow-up period is needed to determine whether the improved radiologic accuracy of the components in robotic-assisted UKA will lead to better clinical outcomes and improved long-term survival.

Reduction in tibiofemoral conformity in lateral unicompartmental knee arthroplasty is more representative of normal knee kinematics

AIMS

Commonly performed unicompartmental knee arthroplasty (UKA) is not designed for the lateral compartment. Additionally, the anatomical medial and lateral tibial plateaus have asymmetrical geometries, with a slightly dished medial plateau and a convex lateral plateau. Therefore, this study aims to investigate the native knee kinematics with respect to the tibial insert design corresponding to the lateral femoral component.

METHODS

Subject-specific finite element models were developed with tibiofemoral (TF) and patellofemoral joints for one female and four male subjects. Three different TF conformity designs were applied. Flat, convex, and conforming tibial insert designs were applied to the identical femoral component. A deep knee bend was considered as the loading condition, and the kinematic preservation in the native knee was investigated.

RESULTS

The convex design, the femoral rollback, and internal rotation were similar to those of the native knee. However, the conforming design showed a significantly decreased femoral rollback and internal rotation compared with that of the native knee (p < 0.05). The flat design showed a significant difference in the femoral rollback; however, there was no difference in the tibial internal rotation compared with that of the native knee.

CONCLUSION

The geometry of the surface of the lateral tibial plateau determined the ability to restore the rotational kinematics of the native knee. Surgeons and implant designers should consider the geometry of the anatomical lateral tibial plateau as an important factor in the restoration of native knee kinematics after lateral UKA.Cite this article: Bone Joint Res 2019;8:593-600.

Less iatrogenic soft-tissue damage utilizing robotic-assisted total knee arthroplasty when compared with a manual approach: A blinded assessment

Objectives

The use of the haptically bounded saw blades in robotic-assisted total knee arthroplasty (RTKA) can potentially help to limit surrounding soft-tissue injuries. However, there are limited data characterizing these injuries for cruciate-retaining (CR) TKA with the use of this technique. The objective of this cadaver study was to compare the extent of soft-tissue damage sustained through a robotic-assisted, haptically guided TKA (RATKA) versus a manual TKA (MTKA) approach.

Methods

A total of 12 fresh-frozen pelvis-to-toe cadaver specimens were included. Four surgeons each prepared three RATKA and three MTKA specimens for cruciate-retaining TKAs. A RATKA was performed on one knee and a MTKA on the other. Postoperatively, two additional surgeons assessed and graded damage to 14 key anatomical structures in a blinded manner. Kruskal–Wallis hypothesis tests were performed to assess statistical differences in soft-tissue damage between RATKA and MTKA cases.

Results

Significantly less damage occurred to the PCLs in the RATKA versus the MTKA specimens (p < 0.001). RATKA specimens had non-significantly less damage to the deep medial collateral ligaments (p = 0.149), iliotibial bands (p = 0.580), poplitei (p = 0.248), and patellar ligaments (p = 0.317). The remaining anatomical structures had minimal soft-tissue damage in all MTKA and RATKA specimens.

Conclusion

The results of this study indicate that less soft-tissue damage may occur when utilizing RATKA compared with MTKA. These findings are likely due to the enhanced preoperative planning with the robotic software, the real-time intraoperative feedback, and the haptically bounded saw blade, all of which may help protect the surrounding soft tissues and ligaments.

Cite this article: Bone Joint Res 2019;8:495–501.

Robot-assisted unicompartmental knee arthroplasty for patients with isolated medial compartment osteoarthritis is cost-effective

Aims

The primary aim of the study was to perform an analysis to identify the cost per quality-adjusted life-year (QALY) of robot-assisted unicompartmental knee arthroplasty (rUKA) relative to manual total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) for patients with isolated medial compartment osteoarthritis (OA) of the knee. Secondary aims were to assess how case volume and length of hospital stay influenced the relative cost per QALY.

Patients and Methods

A Markov decision analysis was performed, using known parameters for costs, outcomes, implant survival, and mortality, to assess the cost-effectiveness of rUKA relative to manual TKA and UKA for patients with isolated medial compartment OA of the knee with a mean age of 65 years. The influence of case volume and shorter hospital stay were assessed.

Results

Using a model with an annual case volume of 100 patients, the cost per QALY of rUKA was £1395 and £1170 relative to TKA and UKA, respectively. The cost per QALY was influenced by case volume: a low-volume centre performing ten cases per year would achieve a cost per QALY of £7170 and £8604 relative to TKA and UKA. For a high-volume centre performing 200 rUKAs per year with a mean two-day length of stay, the cost per QALY would be £648; if performed as day-cases, the cost would be reduced to £364 relative to TKA. For a high-volume centre performing 200 rUKAs per year with a shorter length of stay of one day relative to manual UKA, the cost per QALY would be £574.

Conclusion

rUKA is a cost-effective alternative to manual TKA and UKA for patients with isolated medial compartment OA of the knee. The cost per QALY of rUKA decreased with reducing length of hospital stay and with increasing case volume, compared with TKA and UKA. Cite this article: Bone Joint J 2019;101-B:1063–1070.

The evolution of patellofemoral prosthetic design in total knee arthroplasty: how far have we come?

Total knee arthroplasty (TKA) has evolved into a successful, cost-effective treatment for end-stage knee arthrosis.The patellofemoral articulation in TKA has largely been ignored during its development despite being an important determinant of outcome.New technologies still need further development to incorporate the patella in TKA surgical planning and operative technique.Alternative approaches to alignment in TKA will have a secondary impact on patellofemoral mechanics and possibly future implant designs.Technologies that assist with precise implant positioning may alter our understanding and overall practice of TKA. Cite this article: EFORT Open Rev 2019;4:503-512. DOI: 10.1302/2058-5241.4.180094.

Robotic arm-assisted vs conventional unicompartmental knee arthroplasty: A meta-analysis of the effects on clinical outcomes

BACKGROUND

Robotic arm-assisted unicompartmental knee arthroplasty (UKA) has been recommended for treatment of unicompartmental knee osteoarthritis. However, its effectiveness and safeness remain controversial compared with conventional UKA. Therefore, the goal of this study was to perform a meta-analysis to re-evaluate the effects of robotic arm-assisted UKA on clinical functional outcomes.

METHODS

PubMed, Embase, and Cochrane Library databases were searched to screen the relevant studies. Continuous data (surgical time, knee excursion during weight acceptance, American knee society score [AKSS], Oxford knee score [OKS], forgotten joint score [FJS], visual analog scale [VAS], and range of motion [ROM]) were pooled using a standardized mean difference (SMD) with their corresponding 95% confidence intervals (CIs) to estimate the effect size, while dichotomous data (complication rate, revision rate) were pooled to obtain the relative risk (RR) with a 95% CI by STATA 13.0 software.

RESULTS

Eleven studies involving 498 patients undergoing robotic-assisted UKA and 589 patients receiving conventional UKA were included. Our pooled results demonstrated that robotic-assisted could significantly reduce the complication rate (RR: 0.62, 95% CI: 0.45-0.85; P = .0041) and improve the knee excursion during weight acceptance (SMD: 0.62, 95% CI: 0.25-1.00; P = .001), but prolonged the surgical time (SMD: 0.74, 95% CI: 0.40-1.08; P < .001). No significant difference in the revision rate, AKSS, OKS, FJS, VAS, and ROM between robotic-assisted and conventional UKA groups.

CONCLUSION

This meta-analysis demonstrates robotic-assisted UKA may be an effective and safe surgical procedure for treatment of unicompartmental knee osteoarthritis.

A systematic review of robotic-assisted unicompartmental knee arthroplasty: prosthesis design and type should be reported

AIMS

Robotic-assisted unicompartmental knee arthroplasty (UKA) promises accurate implant placement with the potential of improved survival and functional outcomes. The aim of this study was to present the current evidence for robotic-assisted UKA and describe the outcome in terms of implant positioning, range of movement (ROM), function and survival, and the types of robot and implants that are currently used.

MATERIALS AND METHODS

A search of PubMed and Medline was performed in October 2018 in line with the Preferred Reporting Items for Systematic Review and Meta-Analysis statement. Search terms included "robotic", "knee", and "surgery". The criteria for inclusion was any study describing the use of robotic UKA and reporting implant positioning, ROM, function, and survival for clinical, cadaveric, or dry bone studies.

RESULTS

A total of 528 articles were initially identified from the databases and reference lists. Following full text screening, 38 studies that satisfied the inclusion criteria were included. In all, 20 studies reported on implant positioning, 18 on functional outcomes, 16 on survivorship, and six on ROM. The Mako (Stryker, Mahwah, New Jersey) robot was used in 32 studies (84%), the BlueBelt Navio (Blue Belt Technologies, Plymouth, Minnesota) in three (8%), the Sculptor RGA (Stanmore Implants, Borehamwood United Kingdom) in two (5%), and the Acrobot (The Acrobot Co. Ltd., London, United Kingdom) in one study (3%). The most commonly used implant was the Restoris MCK (Stryker). Nine studies (24%) did not report the implant that was used. The pooled survivorship at six years follow-up was 96%. However, when assessing survival according to implant design, survivorship of an inlay (all-polyethylene) tibial implant was 89%, whereas that of an onlay (metal-backed) implant was 97% at six years (odds ratio 3.66, 95% confidence interval 20.7 to 6.46, p < 0.001).

CONCLUSION

There is little description of the choice of implant when reporting robotic-assisted UKA, which is essential when assessing survivorship, in the literature. Implant positioning with robotic-assisted UKA is more accurate and more reproducible than that performed manually and may offer better functional outcomes, but whether this translates into improved implant survival in the mid- to longer-term remains to be seen. Cite this article: Bone Joint J 2019;101-B:838-847.

Revision Analysis of Robotic Arm-Assisted and Manual Unicompartmental Knee Arthroplasty

BACKGROUND

The purpose of this study was to evaluate hospital admissions for revision surgeries associated with robotic arm-assisted unicompartmental knee arthroplasty (rUKA) vs manually instrumented UKA (mUKA) procedures.

METHODS

Patients ≥18 years of age who received either a mUKA or a rUKA procedure were candidates for inclusion and were identified by the presence of appropriate billing codes. Procedures performed between March 1, 2013 and July 31, 2015 were used to calculate the rate of surgical revisions occurring within 24-months of the index procedure. Following propensity matching, 246 rUKA and 492 mUKA patients were included. Revision rates and the associated costs were compared between the two cohorts. The Mann-Whitney U test was used to compare continuous variables, and Fisher's exact tests was used to analyze discrete categorical variables.

RESULTS

At 24 months after the primary UKA procedure, patients who underwent rUKA had fewer revision procedures (0.81% [2/246] vs 5.28% [26/492]; P = .002), shorter mean length of stay (2.00 vs 2.33 days; P > .05), and incurred lower mean costs for the index stay plus revisions ($26,001 vs $27,915; P > .05) than mUKA patients. Length of stay at index and index costs were also lower for rUKA patients (1.77 vs 2.02 days; P = .0047) and ($25,786 vs $26,307; P > .05).

CONCLUSIONS

The study results demonstrate that patients who underwent rUKA had fewer revision procedures, shorter length of stay, and incurred lower mean costs (although not statistically different) during the index admission and at 24 months postoperatively. These results could be important for payers as the prevalence of end-stage knee osteoarthritis increases alongside the demand for cost-efficient treatments.

Does component placement affect short-term clinical outcome in robotic-arm assisted unicompartmental knee arthroplasty?

Aims

The purpose of this multicentre observational study was to investigate the association between intraoperative component positioning and soft-tissue balancing on short-term clinical outcomes in patients undergoing robotic-arm assisted unicompartmental knee arthroplasty (UKA).

Patients and Methods

Between 2013 and 2016, 363 patients (395 knees) underwent robotic-arm assisted UKAs at two centres. Pre- and postoperatively, patients were administered Knee Injury and Osteoarthritis Score (KOOS) and Forgotten Joint Score-12 (FJS-12). Results were stratified as “good” and “bad” if KOOS/FJS-12 were more than or equal to 80. Intraoperative, post-implantation robotic data relative to CT-based components placement were collected and classified. Postoperative complications were recorded.

Results

Following exclusions and losses to follow-up, 334 medial robotic-arm assisted UKAs were assessed at a mean follow-up of 30.0 months (8.0 to 54.9). None of the measured parameters were associated with overall KOOS outcome. Correlations were described between specific KOOS subscales and intraoperative, post-implantation robotic data, and between FJS-12 and femoral component sagittal alignment. Three UKAs were revised, resulting in 99.0% survival at two years (95% confidence interval (CI) 97.9 to 100.0).

Conclusion

Although little correlation was found between intraoperative robotic data and overall clinical outcome, surgeons should consider information regarding 3D component placement and soft-tissue balancing to improve patient satisfaction. Reproducible and precise placement of components has been confirmed as essential for satisfactory clinical outcome. Cite this article: Bone Joint J 2019;101-B:435–442.

Improved implant position and lower revision rate with robotic-assisted unicompartmental knee arthroplasty

PURPOSE

The aim of this case-control study was to compare implant position and revision rate for UKA, performed with either a robotic-assisted system or with conventional technique.

METHODS

Eighty UKA (57 medial, 23 lateral) were performed with robotic assistance (BlueBelt Navio system) between 2013 and 2017. These patients were matched with 80 patients undergoing UKA using the same prosthesis, implanted using conventional technique. The sagittal and coronal component position was assessed on postoperative radiographs. The revision rate was reported at last follow-up.

RESULTS

The mean follow-up was 19.7 months ± 9 for the robotic-assisted group, and 24.2 months ± 16 for the control group. The rate of postoperative limb alignment outliers (± 2°) was significantly higher in the control group than in the robotic-assisted group for both lateral UKA (26% in robotic group versus 61% in control group; p = 0.018) and medial UKA (16% versus 32%, resp.; p = 0.038). The coronal and sagittal tibial baseplate position had significantly less outliers (± 3°) in the robotic-assisted group, than in the control group. Revision rates were: 5% (n = 4/80) for robotic assisted UKA and 9% (n = 7/80) for conventional UKA (n.s.). The reasons for revision were different between groups, with 86% of revisions in the control group occurring in association with component malposition or limb malalignment, compared with none in the robotic-assisted group.

CONCLUSION

Robotic-assisted UKA has a lower rate of postoperative limb alignment outliers, as well as a lower revision rate, compared to conventional technique. The accuracy of implant positioning is improved by this robotic-assisted system.

LEVEL OF EVIDENCE

Level of evidence III. Retrospective case-control study CLINICAL RELEVANCE: This is the first paper comparing implant position, clinical outcome, and revision rate for UKA performed using the Navio robotic system with a control group.

The effect of malalignment on proximal tibial strain in fixed-bearing unicompartmental knee arthroplasty: A comparison between metal-backed and all-polyethylene components using a validated finite element model

Objectives

Elevated proximal tibial bone strain may cause unexplained pain, an important cause of unicompartmental knee arthroplasty (UKA) revision. This study investigates the effect of tibial component alignment in metal-backed (MB) and all-polyethylene (AP) fixed-bearing medial UKAs on bone strain, using an experimentally validated finite element model (FEM).

Methods

A previously experimentally validated FEM of a composite tibia implanted with a cemented fixed-bearing UKA (MB and AP) was used. Standard alignment (medial proximal tibial angle 90°, 6° posterior slope), coronal malalignment (3°, 5°, 10° varus; 3°, 5° valgus), and sagittal malalignment (0°, 3°, 6°, 9°, 12°) were analyzed. The primary outcome measure was the volume of compressively overstrained cancellous bone (VOCB) < -3000 µε. The secondary outcome measure was maximum von Mises stress in cortical bone (MSCB) over a medial region of interest.

Results

Varus malalignment decreased VOCB but increased MSCB in both implants, more so in the AP implant. Varus malalignment of 10° reduced the VOCB by 10% and 3% in AP and MB implants but increased the MSCB by 14% and 13%, respectively. Valgus malalignment of 5° increased the VOCB by 8% and 4% in AP and MB implants, with reductions in MSCB of 7% and 10%, respectively. Sagittal malalignment displayed negligible effects. Well-aligned AP implants displayed greater VOCB than malaligned MB implants.

Conclusion

All-polyethylene implants are more sensitive to coronal plane malalignments than MB implants are; varus malalignment reduced cancellous bone strain but increased anteromedial cortical bone stress. Sagittal plane malalignment has a negligible effect on bone strain.

Cite this article: I. Danese, P. Pankaj, C. E. H. Scott. The effect of malalignment on proximal tibial strain in fixed-bearing unicompartmental knee arthroplasty: A comparison between metal-backed and all-polyethylene components using a validated finite element model. Bone Joint Res 2019;8:55–64. DOI: 10.1302/2046-3758.82.BJR-2018-0186.R2.

Robotic-assisted Medial Unicompartmental Knee Arthroplasty: Options and Outcomes

Medial unicompartmental knee arthroplasty (UKA) has several benefits over total knee arthroplasty for the surgical treatment of isolated medial compartmental arthritis in the knee, including reduced surgical risk and postoperative morbidity, rapid recovery, more normal kinematics, greater patient satisfaction, and shorter hospitalization. Nonetheless, there is substantial concern about the higher revision rates and lower survivorship in UKA compared to those in total knee arthroplasty. Robotic assistance has been advanced to improve the precision of bone preparation, component alignment, and quantified ligament balance in UKA, with the ultimate goal of improving kinematics and implant survivorship. Two currently available semiautonomous robotic platforms have demonstrated improved accuracy, and emerging short-term follow-up has demonstrated satisfactory functional outcomes. Further studies will be needed to determine if these technologies indeed have a meaningful impact on patient outcomes and survivorship in the mid- to long term.

An assessment of early functional rehabilitation and hospital discharge in conventional versus robotic-arm assisted unicompartmental knee arthroplasty: a prospective cohort study

AIMS

The objectives of this study were to compare postoperative pain, analgesia requirements, inpatient functional rehabilitation, time to hospital discharge, and complications in patients undergoing conventional jig-based unicompartmental knee arthroplasty (UKA) versus robotic-arm assisted UKA.

PATIENTS AND METHODS

This prospective cohort study included 146 patients with symptomatic medial compartment knee osteoarthritis undergoing primary UKA performed by a single surgeon. This included 73 consecutive patients undergoing conventional jig-based mobile bearing UKA, followed by 73 consecutive patients receiving robotic-arm assisted fixed bearing UKA. All surgical procedures were performed using the standard medial parapatellar approach for UKA, and all patients underwent the same postoperative rehabilitation programme. Postoperative pain scores on the numerical rating scale and opiate analgesia consumption were recorded until discharge. Time to attainment of predefined functional rehabilitation outcomes, hospital discharge, and postoperative complications were recorded by independent observers.

RESULTS

Robotic-arm assisted UKA was associated with reduced postoperative pain (p < 0.001), decreased opiate analgesia requirements (p < 0.001), shorter time to straight leg raise (p < 0.001), decreased number of physiotherapy sessions (p < 0.001), and increased maximum knee flexion at discharge (p < 0.001) compared with conventional jig-based UKA. Mean time to hospital discharge was reduced in robotic UKA compared with conventional UKA (42.5 hours (sd 5.9) vs 71.1 hours (sd 14.6), respectively; p < 0.001). There was no difference in postoperative complications between the two groups within 90 days' follow-up.

CONCLUSION

Robotic-arm assisted UKA was associated with decreased postoperative pain, reduced opiate analgesia requirements, improved early functional rehabilitation, and shorter time to hospital discharge compared with conventional jig-based UKA.

The learning curve associated with robotic-arm assisted unicompartmental knee arthroplasty

Aims

The primary aim of this study was to determine the surgical team’s learning curve for introducing robotic-arm assisted unicompartmental knee arthroplasty (UKA) into routine surgical practice. The secondary objective was to compare accuracy of implant positioning in conventional jig-based UKA versus robotic-arm assisted UKA.

Patients and Methods

This prospective single-surgeon cohort study included 60 consecutive conventional jig-based UKAs compared with 60 consecutive robotic-arm assisted UKAs for medial compartment knee osteoarthritis. Patients undergoing conventional UKA and robotic-arm assisted UKA were well-matched for baseline characteristics including a mean age of 65.5 years (sd 6.8) vs 64.1 years (sd 8.7), (p = 0.31); a mean body mass index of 27.2 kg.m2 (sd 2.7) vs 28.1 kg.m2 (sd 4.5), (p = 0.25); and gender (27 males: 33 females vs 26 males: 34 females, p = 0.85). Surrogate measures of the learning curve were prospectively collected. These included operative times, the Spielberger State-Trait Anxiety Inventory (STAI) questionnaire to assess preoperative stress levels amongst the surgical team, accuracy of implant positioning, limb alignment, and postoperative complications.

Results

Robotic-arm assisted UKA was associated with a learning curve of six cases for operating time (p < 0.001) and surgical team confidence levels (p < 0.001). Cumulative robotic experience did not affect accuracy of implant positioning (p = 0.52), posterior condylar offset ratio (p = 0.71), posterior tibial slope (p = 0.68), native joint line preservation (p = 0.55), and postoperative limb alignment (p = 0.65). Robotic-arm assisted UKA improved accuracy of femoral (p < 0.001) and tibial (p < 0.001) implant positioning with no additional risk of postoperative complications compared to conventional jig-based UKA.

Conclusion

Robotic-arm assisted UKA was associated with a learning curve of six cases for operating time and surgical team confidence levels but no learning curve for accuracy of implant positioning. Cite this article: Bone Joint J 2018;100-B:1033–42.

Robotic-Assisted Unicompartmental Knee Arthroplasty: State-of-the Art and Review of the Literature

BACKGROUND

Unicompartmental knee arthroplasty is a successful treatment for unicompartmental knee osteoarthritis that has lower complication rates, faster recovery, and a more natural feeling knee compared to total knee arthroplasty. However, long-term survival has been a persistent concern. As more surgeon-controlled variables have been linked to survival, interest in robotic-assisted surgery has continued to grow.

METHODS

A review and synthesis of the literature on the subject of robotic-assisted unicompartmental knee arthroplasty was performed.

RESULTS

We present the driving factors behind the development of robotic-assisted techniques in unicompartmental knee arthroplasty and the current state-of-the art. The ability of surgeons to achieve intraoperative targets with robotic assistance and the outcomes of robotic-assisted surgery are also described.

CONCLUSION

Robotic-assisted surgery has become increasingly popular in unicompartmental knee arthroplasty, as it allows surgeons to more accurately and reproducibly plan and achieve operative targets during surgery. Cost remains a concern, and it remains to be seen whether robotic-assisted surgery will improve long-term survivorship after unicompartmental knee arthroplasty.

Robotic-Arm-Assisted vs Conventional Unicompartmental Knee Arthroplasty. The 2-Year Clinical Outcomes of a Randomized Controlled Trial

BACKGROUND

Unicompartmental knee arthroplasty (UKA) for treatment of medial compartment osteoarthritis has potential benefits over total knee arthroplasty but UKA has a higher revision rate. Robotic-assisted UKA is increasingly common and offers more accurate implant positioning and limb alignment, lower early postoperative pain but evidence of functional outcome is lacking. The aim was to assess the clinical outcomes of a single-centre, prospective, randomised controlled trial, comparing robotic-arm-assisted UKA with conventional surgery.

METHODS

A total of 139 participants were recruited and underwent robotic-arm-assisted (fixed bearing) or conventional (mobile bearing) UKA. Fifty-eight patients in the robotic-arm-assisted group and 54 in the manual group at 2 years. The main outcome measures were the Oxford Knee Score, American Knee Society Score and revision rate.

RESULTS

At 2 years, there were no significant differences for any of the outcome measures. Sub-group analysis (n = 35) of participants with a preoperative University of California Los Angeles Activity Scale >5 (more active) was performed. In this sub-group, the median Oxford Knee Score at 2 years was 46 (IQR 42.0-48.0) for robotic-arm-assisted and 41 (IQR 38.5-44.0) for the manual group (P = .036). The median American Knee Society Score was 193.5 (IQR 184.0-198.0) for the robotic-arm-assisted group and 174.0 (IQR 166.0-188.5) for the manual group (P = .017). Survivorship was 100% in robotic-arm-assisted group and 96.3% in the manual group.

CONCLUSION

Overall, participants achieved an outcome equivalent to the most widely implanted UKA in the United Kingdom. Sub-group analysis suggests that more active patients may benefit from robotic-arm- assisted surgery. Long term follow-up is required to evaluate differences in survivorship.

Pros and Cons: A Balanced View of Robotics in Knee Arthroplasty

In both unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA), compared with conventional techniques robotic technology has been shown to optimize the precision of bone preparation and component alignment, reducing outliers and increasing the percentage of components aligned within 2° or 3° of the target goal. In addition, soft tissue balance can be quantified through a range of motion in UKA and TKA using the various robotic technologies available. Although the presumption has been that the improved alignment associated with robotics will improve function and implant durability, there are limited data to support that notion. Based on recent and emerging data, it may be unreasonable to presume that robotics is necessary for both UKA and TKA. In fact, despite improvements in various proxy measures, the precision of robotics may be more important for UKA than TKA, although if system costs and surgical efficiencies continue to improve, streamlining perioperative processes, reducing instrument inventory, and achieving comparable outcomes in TKA may be a reasonable goal of robotic surgery.

What Percentage of Patients is a Candidate for Unicompartmental Knee Replacement at a Chinese Arthroplasty Center?

Background:

Data on indication of Unicompartmental Knee Arthroplasty (UKA) in the Asian population are currently not available. The current paper evaluates patients undergoing knee replacement at a Chinese Orthopaedic Specialty Hospital to report the percentage of patients who meet radiographic and clinical indication criteria for UKA.

Methods:

Over a one-year period 463 consecutive patients (515 knees) underwent primary knee replacement surgery. Clinical data were recorded and preoperative radiographs were assessed. Patients were classified as suitable candidates for UKA based on the degree of deformity, preoperative ROM and radiographic appearance of osteoarthritis. The different indication criteria for body weight and extend of patellofemoral osteoarthritis as reported by Kozinn and Scott as well as the Oxford Group were applied.

Results:

160 knees (31%) were excluded because of inflammatory and posttraumatic arthritis. 55 knees had to be excluded because of incomplete radiographs. Of the remaining 300 knees with osteoarthritis, 241 knees were excluded because of extend of deformity (n=156), decreased range of motion (n=119), advanced patellofemoral arthritis with bone loss (n=11) and AP instability (n=1). Of the remaining 63 knees, 54 knees (18%) met the modified Oxford criteria for mobile UKA and only 25 knees (8%) met the Scott and Kozinn criteria for fixed UKA.

Conclusion:

The current paper suggests that in comparison to Caucasian population, only a smaller percentage of patients at a Chinese Orthopaedic Specialty Hospital meet the indication criteria for UKA. Therefore, it might make sense to concentrate UKA surgeries in high volume centers.