Background. Obesity has been linked with increased rates of knee osteoarthritis. Limited information is available on the survival and functional outcome results of rTKR in the obese patients. This registry-based study aimed to identify whether BMI is an independent risk factor for poorer functional outcomes and /or implant survival in rTKA. Methods. New Zealand Joint Registry (NZJR) data of patients who underwent rTKA from 1st January 2010 to January 2023 was performed. Demographics, American Society of Anesthesiologists (ASA), BMI, Operative time, indications for revision and components revised of the patients undergoing rTKA was collected. Oxford knee score (OKS) at 6 months and rates of second revision (re- revision) were stratified based on standardised BMI categories. Results. Of the 2687 revisions, functional outcome scores were available for 1261 patients. Oxford knee scores following rTKA are significantly inferior in higher BMI patients (36.5 vs 31.5 p<0.001). This held true when adjusted for age (35.7 vs 30.9 p<0.001). Tibial component loosening was a more common indication for revision in patients with BMI >40 (31.1% vs 21% for BMI <25), whereas periprosthetic femoral fracture was significantly more commonly seen in patients with BMI <25. Re-revision rates displayed no significant differences between any pairs of BMI groups (2.18/100 component years) and adjusting for age and sex did not alter this (p= 0.462). Indications for re-revision were also not different between BMI categories. Over 50% of the rTKA patients were obese. Significantly more obese patients were ASA grade 3,4 and more were <75 years. Operative time was longer in the obese patients (p<0.001). Conclusions. Although overall re-revision rates are similar between all BMI categories, the functional outcomes favour those with lower BMI. Patients with higher BMI are younger, more comorbid and carry potentially higher perioperative risks. The registry data provides valuable information when providing counsel to patients undergoing rTKA and lends further support to optimising patients prior to pTKA

Answering the question of what the patient can teach us about the future of joint replacement starts with a look to the past. The modern era of total joint replacement began in the late 1950's with the pioneering work of John Charnley that established the fundamental structure of a total joint replacement with a metal component bearing against polyethylene and provided many disabled patients with a substantial improvement in function. As the application of joint replacement expanded to a broader patient population it became apparent that a better understanding of the mechanics of patient function was needed to provide more rigorous design criteria and objective assessment of design changes. This presentation will examine how improvements in total knee replacement has been aided by objective measures of ambulatory function and the potential for future improvements in joint replacement that can be based on information from testing patients. Specifically, from a historical viewpoint one of the major problems limiting the use of total knee replacement in the 1970's was tibial component loosening. The problem of tibial component loosening could be related to the load imbalance between the medial and lateral surface of the tibia. The load asymmetry at the knee resulting from the adduction moment during gait provided a strong rationale for maintaining proper limb alignment following total knee arthroplasty. The analysis clearly showed that knees with a varus alignment of the mechanical axis were more likely to have a substantial load imbalance creating the type of stresses that would eventually lead to tibial component loosening. When the information from gait studies was combined with both clinical and biomechanical studies, tibial component designs were modified using metal backing of the polyethylene articulating surface and instrumentation was modified to allow for proper alignment of the mechanical axis and avoid residual varus deformity following total knee replacement. Similarly, knee kinematics and moments have been used to differentiate the functional characteristics of different types of designs during stair climbing. Patients with cruciate-sacrificing knee replacements had a tendency to reduce the moment sustained by the quadriceps by leaning forward during the portion of the support phase of ascending stairs when the quadriceps moment would reach a peak value, while patients with a posterior cruciate retaining design were able to sustain normal quadriceps function. The functional differences between the PCL-retaining and sacrificing designs were associated with the normal posterior movement of the femur on the tibia (rollback), with flexion. This finding indicated that TKR design must permit rollback in the early phases of knee flexion to sustain normal stair climbing. This presentation will conclude with a review of the functional performance of patients with an anterior cruciate deficient knee as a basis for addressing the future needs of a knee replacement to permit natural knee movement. Specifically the role of the anterior cruciate ligament will be discussed in the context of the interaction of the curvature of the articulating surfaces in maintaining a functional envelope of movement that is consistent with retaining both cruciate ligaments

Background. To evaluate the causes and modes of complications after unicompartmental knee arthroplasty (UKA), and to identify its prevention and treatment method by analyzing the complications after UKA. Materials and Methods. A total of 1,576 UKAs were performed between January 2002 and December 2014 at a single-institution. Postoperative complications occurred in 89 knees (83 patients, 5.6%), and 86 of them were found in females and 3 in males. Their mean age was 61 years (range, 46 to 81 years) at the time of initial UKA and 66 years (range, 46 to 82 years) at the time of revision surgery. We analyzed the complications after UKA retrospectively andinvestigated the proper methods of treatment (Table 1). Results. A total of 89 complications (5.6%) occurred afterUKA. Regarding the type of complications after UKA, there were bearing dislocation (n=42), component loosening (n=23), 11 cases of femoral component loosening, 8 cases of tibial component loosening, and 4 cases of both femoral and tibial component loosening, periprosthetic fracture (n=6), polyethylene wear/ destruction (n=3), progression of arthritis to the other compartment (n=3), medial collateral ligament (MCL) injury (n=2), impingement (n=2), infection (n=5), ankylosis (n=1), and unexplained pain (n=2) (Table 2). The most common complication after UKA was mobile bearing dislocation in mobile-bearing type and loosening of prosthesis in fixed-bearing type, but polyethylene wear and progression of arthritis were relatively rare. The mean interval from UKA to the occurrence of complications was 4 years and 6 months (range, 0 [during operation] to 12 years). Of those complications following UKA, 58 knees were treated with conversion TKA, 1 with revision UKA, and 21 with simple bearing change. Complications in the remaining knees were treated with arthroscopic management (n=2), open reduction and internal fixation (n=3), closed reduction and internal fixation (n=1), manipulation (n=1), and MCL repair (n=2) (Table 3). Discussion. In this single-center study, we reviewed the causes and types of complications (n=89) that occurred following UKA (n=1,576) and investigated optimal treatment methods. The incidence and type of complications were also compared among patients classified according to gender, medial/lateral UKA, and implant design and type. The strengths of this study include that all the patients were enrolled from the same institution and the sample size (UKA cases and complication cases) was relatively large compared to that in previous publications. The most common complication following UKA was bearing dislocation in the mobile-bearing knees and component loosening in the fixed-bearing knees. The incidence of polyethylene wear and progression of arthritis to the other compartment was relatively low. The results of our study are in some discrepancy with those of studies involving Western patients. This can be attributed to the differences in patient characteristics such as lifestyle and in the type and design of implant used. Conclusion. Thorough understanding of UKA, proper patient selection, appropriate implant choice are essential to reduce complications following UKA and obtain satisfactory outcomes. We suggest that complications following UKA should be treated differently according to the type and cause of complication and conversion TKA can be the most effective treatment when revision operation is determined necessary

Introduction. The precise indications for tibial component metal backing and modularity remain controversial in routine primary total knee arthroplasty. This is particularly true in elderly patients where the perceived benefits of metal backing such as load redistribution and the reduction of polyethylene strain may be clinically less relevant. The cost implications for choosing a metal-backed design over an all-polyethylene design may exceed USD500 per primary knee arthroplasty case. Methods. A prospective randomised clinical trial was carried out at the QEII Health Sciences Centre, Halifax, Nova Scotia, to compare modular metal-backed versus an all-polyethylene tibial component. Outcome measures included clinical range of motion, radiographs, survivorship, Knee Society Clinical Rating System, WOMAC and SF-12. Results. 116 patients requesting primary knee arthroplasty were recruited and randomised between the Smith & Nephew Genesis I non-modular (57) and modular (59) tibial designs between September 1995 and August 1997. At 10 years clinical follow-up, 4 implant revisions or intention-to-revise decisions were recorded in the metal-tray/modular group of which 2 were for aseptic tibial component loosening. 2 implant revisions in the all-polyethylene non-modular group were recorded, neither of which were for tibial component loosening. At 5, 7 and 10 year review; the KSCRS, WOMAC and SF12 scores were similar in both groups. As most patients randomised were over seventy years of age, this impacted significantly on the numbers available for longer term review and data was analysed by comparing pre- and post-operative scores for individual patients. Conclusion. There was no difference in performance between the all-polyethylene tibial component and the metal-backed tibial component. The case for using the all-polyethylene tibia in elderly patients is justified on both clinical efficacy and cost-containment grounds

Background. Use of a robotic tool to perform surgery introduces a risk of unexpected soft tissue damage due to the uncommon tactile feedback for the surgeon. Early experience with robotics in total hip and knee replacement surgery reported having to abort the procedure in 18–34 percent of cases due to inability to complete preoperative planning, hardware and soft tissue issues, registration issues, as well as concerns over actual and potential soft tissue damage. These can result in significant morbidity to the patient, negating all the desired advantages of precision and reproducibility with robotic assisted surgery. The risk of soft tissue damage can be mitigated by haptic software prohibiting the cutting tip from striking vital soft tissues and by the surgeon making sure there is a clear workspace path for the cutting tool. This robotic total knee system with a semi-active haptic guided technique was approved by the FDA on 8/5/2015 and commercialized in August of 2016. Two year clinical results have not been reported to date. Objective. To review an initial and consecutive series of robotic total knee arthroplasties for safety in regard to avoidance of known or delayed soft tissue injuries and the necessity to abort the using the robot to complete the procedure. Report the clinical outcomes with robotic total knee replacement at or beyond two years to demonstrate no delayed effect on expected outcome. Methods. The initial consecutive series of 65 Triathlon. TM. total knee replacements using a semi-active haptic guided system that were performed after commercialization that would be eligible for two year follow-up were reviewed. Pre-operative planning utilizing CT determined the implant placement and boundaries and thus the limit of excursion from any part of the end effector saw tip. Self-retaining retractors were also utilized. Operative reports, 2, 6, and 12 week, and yearly follow-up visit reports were reviewed for any evidence of inadvertent injury to the medial collateral ligament, patellar tendon, or a neurovascular structure from the cutting tool. Operative notes were also reviewed to determine if the robotic procedure was partially or completely aborted due to any issue. Knee Society Knee Scores (KS-KS) and Functional Scores (KS-FS) were recorded from pre-operative and yearly. Any complications were recorded. Results. 40 cases had two year follow-up. The average follow-up for this series was 1.51 years. No cases were unable to be completed robotically. No case had evidence for acute or delayed injury to the medial collateral ligament, patellar tendon, or neurovascular structure. The only complication was a revision total knee for tibial component loosening after a fall induced periprosthetic tibial fracture. Average pre-operative KS-KS and KS-FS improved from 46.9 and 52.1 to 99.2 and 88.6 at one year follow-up, 100.5 and 86.9 at two year follow-up. Conclusions. A semi-active haptic guided robotic system is a safe and reliable method to perform total knee replacement surgery. This series of initial robotic arm assisted surgery had no intraoperative or delayed soft tissue injuries. Preliminary short-term outcomes at up to two years show excellent outcomes

Loosening is generally the most common reason for revision TKA. In the AOA NJR, the rate of revision varies depending on fixation. Cemented fixation has a lower rate of revision than cementless fixation; 6.7% vs. 8.2% at 14 years. Loosening does occur more frequently in younger patients and in males. Tibial component loosening is the most common. There is an opportunity for improvement. More durable fixation can be achieved through improved cement technique, rather than going cementless. De-bonding of the tibial baseplate from the cement is the mechanism of failure in up to 2.9% of total knee arthroplasties. Among seven surgeons at one center, there was a 6.4 fold range (0.7%-4.5%) in the occurrence of such loosening with the same prosthesis. This surgeon-related variability in tibial component de-bonding indicates that surgical technique influences loosening. In a laboratory study, earlier application of cement to metal increases bond strength (p<0.01) while later application reduces bond strength (p<0.05). Fat contamination of the tibial tray-cement interface reduces bond strength, but application of cement to the underside of the tibial tray prior to insertion substantially mitigates this (p<0.05)

Introduction. Cementless Total Knee Replacement (TKR) was introduced to improve the longevity of implant; but has yet to be widely adopted because of reports of higher earlier failures in some series. The cementless TKR design has evolved recently and we have been using cementless component – both femoral and tibial on our patients. The long follow-up for fully TKR has been scarce in the literature. The purpose of this study isto investigate the minimum of ten years clinical and radiographic result of cementless titanium component and cementless tantalum component in primary TKR. Material & method. From 2008 to 2010 317 TKR underwent primary total knee with cementless femoral component titanium based (Zimmer Nexgen) and cementless tantalum component monoblock tibial component, The surgery was performed mainly on younger patients - average age was 48 yrs old ranging from 26 yrs old to 62 yrs old. All surgeries were performed by single surgeon. All patients were followed clinically and radiographically for a minimum of 8 yrs. Mean 7.8 years and range from 7 to 9 years. The underlying diagnosis for majority of the cases were degenerative arthritis in 97 of the cases and rheumatoid arthritis on the 3%. Result. We have revised 6 cases − 3 cases were for sepsis. They were revised in 2 stages. And we also revised 5 cases for loosening of femoral component. The tibial component revision for aseptic loosening or osteolysis for an end point for survivorship was a 100% for the tibia monoblock design. There was no radiographic evidence of tibial component loosening or subsidence, or migration at the time of the latest follow-up for tibia monoblock. On the femoral part we documented 16 cases other than those 4 revision for osteolysis, where limited osteolysis happened in some area of the tibial component but it did not affect stability and those has been followed up for a longer term. There was interesting phenomena in some of those cases where bone growth happened around the anterior cortex where it sealed the component entirely. Knee society scores improved from 51 pre-operatively to 94 pre-operatively on the last clinical visit. We had 32 cases where the patientswere able to regain their full mobility flexion of over 150 degrees. Conclusion. Our data clearly shows that the cementless TKR has excellent result as compared to the cemented with a good survival ship at 10 years. The tantalum tibial component shows an excellent survivorship. The femoral component also present reasonably good result but we still faced a few cases of loosening. The functional outcome for the implant with the surgery was satisfactory. With this result we strongly recommend using the cementless implant in young patients. We believe that cementless tibial is totally safe at this point as well as the femoral cementless prosthesis. However, we expect some improvement with the outcome with the femoral component when using the tantalum

Loosening is generally the most common reason for revision TKA. In the AOA NJR, the rate of revision varies depending on fixation. Cemented fixation has a lower rate of revision than cementless fixation; 6.7% vs. 8.2% at 14 years. Loosening does occur more frequently in younger patients and in males. Tibial component loosening is the most common. There is an opportunity for improvement. More durable fixation can be achieved through improved cement technique. De-bonding of the tibial baseplate from the cement is the mechanism of failure in up to 2.9% of total knee prostheses. Among seven surgeons at one center, there was a 6.4-fold range (0.7%-4.5%) in the occurrence of such loosening with the same prosthesis. This surgeon-related variability in tibial component de-bonding suggests that surgical technique influences loosening rates. In a laboratory study, earlier application of cement to metal increases bond strength (p<0.01) while later application reduces bond strength (p<0.05). Fat contamination of the tibial tray-cement interface reduces bond strength, but application of cement to the underside of the tibial tray prior to insertion substantially mitigates this (p<0.05)

Tibial component loosening is an important failure mode in unicompartmental knee arthroplasty (UKA) which may be due to the 6–8 mm of bone resection required or the limited surface area. To address component loosening and fixation, a new Early Intervention (EI) design is proposed which reverses the traditional material scheme between femoral and tibial components. That is, the EI design consists of a plastic inlay component for the distal femur and a thin metal plate for the proximal tibia. With this reversed materials scheme, the EI design requires minimal tibial bone resection compared to traditional UKA to preserve the dense and stiff bone in the proximal tibia. This study investigated, by means of finite element (FE) simulations, the potential advantages of a thin metal tibial component compared with traditional UKA tibial components, such as an all-plastic inlay or a metal-backed onlay. We hypothesized that an EI component would produce comparable stress, strain, and strain energy density characteristics to an intact knee and more favorable values than UKA components. Indeed, the finite element results showed that an EI design reduced stresses, strains and strain energy density in the underlying support bone compared to an all-plastic UKA component. Analyzed parameters were similar for an EI and a metal-backed onlay, but the EI component had the advantage of minimal resection of the stiffest bone

There is a report that higher failure rate in uncemented total knee replacement components due to loosening. However, uncemented fixation has been an attractive concept because of bone preservation and revision surgery, potential improved load transfer, and decreased surgical time. “Regenerex” is a porous titanium layer with excellent initial fixation, and the promise of providing favourable biological fixation. This is used with the Biomet Vanguard total knee replacement. 14 patients had undergone total knee replacement surgery comprising 11 men and three women with an average age of 63.07 years, and a body mass index of 30.33. Three of these patients required revision, because of tibial component loosening within 12 months of surgery. There were two men and one woman with an average age of 63.33 and BMI of 34.55. Clinically, patients developed pain and a gradual deformity as a result of a symmetrical collapse of the proximal tibial bony support surface. Histopathology on the removed specimens shows the development of fibre cartilaginous metaplasia with evidence of necrotic bone. This was similar in all patients. There was no foreign body giant cell reaction, and no evidence of infection. The appearance was suggested of osteonecrosis, occurring gradually. The incidence of frequency of this complication with this component in our experience is of concern, and the aim of this presentation is to determine whether this is a more widespread phenomenon

Introduction. High BMI has been classically regarded as a contraindication for unicompartmental knee arthroplasty (UKA) as it can potentially lead to poor clinical outcomes and a higher risk of failure. In recent years, UKA has increased in popularity and, as a result, patient selection criteria are beginning to broaden. However, UKA performed manually continues to be technically challenging and surgical technique errors may result in suboptimal implant positioning. UKA performed with robotic assistance has been shown to improve component positioning, overall limb alignment, and ligament balancing, resulting in overall improved clinical outcomes. The purpose of this study is to examine the effect of high BMI in patients receiving UKA with robotic assistance. Methods. 1007 patients (1135 knees) were identified in an initial and consecutive multi-surgeon multi-center series receiving robotically assisted medial UKA, with a fixed bearing metal backed onlay tibial component. As part of an IRB approved study, every patient in the series was contacted at a minimum two year (±2 months) follow up and asked a series of questions to determine implant survivorship and satisfaction. 160 patients were lost to follow up, 35 patients declined to participate, and 15 patients were deceased. 797 patients (909 knees) at a minimum two year follow up enrolled in the study for an enrollment rate of 80%. 45% of the patients were female. The average age at time of surgery was 69.0 ± 9.5 (range: 39–93). BMI data was available for 887 knees; the average BMI at time of surgery was 29.4 ± 4.9. Patients were stratified in to five categories based on their BMI: normal (< 25; 16%), overweight (25–30; 46%), obese class I (30–35; 25%), obese class II (35–40; 11%) and obese class III (>40; 2%). Results. Across all BMI groups, nine knees were reported as revised at two years post-operative yielding a two year revision rate of 0.99%, 4 in the overweight group, 2 in the obese class I group and 3 in the obese class II group. There was no significant difference in the rate of revision between the BMI groups (c. 2. (4, N = 887) = 6.04, p = 0.20). Of the 3 revisions for tibial component loosening, one occurred in the overweight group, one in the obese group and one in the morbidly obese group. The overall patient satisfaction rate for the entire population was 92% with the following distribution: normal: 92%, overweight: 93%, obese class I: 92%, obese class II: 87% and obese class III: 83%. While the most severely obese patients tended to be less satisfied, this was not statistically significant between the groups (c. 2. (4, N = 887) = 5.12, p = 0.27). Conclusion. These results suggest that BMI does not effect the survivorship or the satisfaction of patients undergoing robotically assisted UKA. Advancement in UKA implant designs and improvements in surgical technique may help to broaden indications and patient selection for UKA. This study will continue to track patients mid to long term to determine the longer term effect of robotically assisted UKA on high BMI patients

Background. Navigation systems that increase alignment accuracies of the lower limbs have been applied widely in total knee arthroplasty and are currently being adopted for minimally invasive UKA (MIS UKA) with good alignment results. There is little debate that when compared with total knee arthroplasty (TKA), UKA is less invasive, causes less morbidity, better reproduces kinematics, and therefore offers quicker recovery, better range of movement and more physiologic function. However, despite improved alignment accuracies, advantages of use of navigation system in UKA in clinical outcomes and survivals are still debatable. To the best of our knowledge, no reports are available on the long-term results after UKA performing using a navigation system. The purpose of this prospective study was to compare the radiological, clinical, and survival outcomes of UKA that performed using the navigation system and using the conventional technique at average 8 years follows up. Methods. Between January 2003 and December 2005, Total of 98 UKAs were enrolled for this study, 56 UKAs in the navigation group and 42 UKAs in conventional group were included in this study after a average 8 years follow-up. At the final follow up, the radiological measurements with regard to the mechanical axis, the inclination of the femoral and tibial components, and radiolucent line or loosening were evaluated and compared between two groups. The clinical evaluations were performed using range of motion, Western Ontario and McMaster Arthritis index (WOMAC) scores and Knee Society (KS) score. Results. Of the 98 patients (98 UNI knees), 2 (2.0%) had died at a mean 5.8years after surgery because of cardiovascular disease, 3 (3.1%) underwent revision surgery that 1 cases of periprosthetic stress fractures in medial tibial plateaus in the navigation group and a case of tibial component loosening and polyethylene wear in conventional groups were observed. At a final follow up, the mean of mechanical axis was statistically different between two groups (2.7 vs. 3.9 of varus). And there were significant difference between 2 groups in terms of the mean values (p=0.042) for the tibial component coronal alignment, mean coronal alignments of tibial components were 89.1 ± 2.4° in the NA-MIS and 87.6 ± 1.8° in the MIS group, however outlier result were similar in the 2 group (5 and 5 knees, respectively, p=0.673). Sagittal alignments of femoral and tibial component were similar in the two groups (p>0.05) Significant differences were found in WOMAC or HSS knee scores, in which, stiffness did not show any difference between two groups, but pain and function showed difference at the last follow-up. The mean knee flexion has improved from 135.0 ± 14.8° and 135.0 ± 14.1° preoperatively to 137.1 ± 6.5° and 136.5 ± 7.2° in the NA-MIS and MIS groups on the latest follow-up, which was not significants different (p =0.883). Conclusion. The navigation system in UKA can provide improved alignment accuracy. And better clinical outcomes in pain and HSS score compared with conventional technique after a average of 8 year follow-up

Uncemented Total Knee Arthroplasty (TKA) is an alternative to cemented TKA and hybrid fixation. We present incidence of loosening of uncemented porus coated tibial trays (two to five years with a mean of 3.8 years) in our retrospective clinical and radiological follow up of 53 uncemented TKA in 40 patients. Between 2001 and 2007, 53 uncemented primary TKA were performed by two senior surgeons in 53 knees for 40 patients. This was for diagnosis of Osteoarthritis. Five patients underwent patellar resurfacing. Patients were evaluated at the six week mark, three months, one year and then yearly using Knee Society knee score. In addition, radiograph analysis was done to all patients during each visit and evaluated using Knee Society roentgenographic evaluation and scoring system. The follow-ups have been done by independent surgeons. End point of failure is defined as revision. There were 14 revisions (12 for aseptic loosening, none for infection and one for component malposition, one for instability) among 53 knees. We found that there is significant increase in rate of tibial component loosening (26%), which is very high compared to rate of loosening with other series. There is radiographic evidence of loosening in four femoral prosthesis but one required revision. Intraoperatively we noticed that there is very poor osseointegration into tibial components. All of them have been revised with cemented tibial component. With our experience we conclude that uncemented porus coated Tibial trays have higher rates of failures because of poor osseointegration. And we recommend that all tibial trays need to be cemented

Osteoarthritis of the knee is a debilitating condition affecting millions of persons, often requiring arthroplasty to relieve pain and improve mobility. For those patients with disease in only one compartment of the knee, unicompartmental knee arthroplasty (UKA) can be a viable surgical alternative. To date, there has not been a large series reported in the literature of UKAs performed with robotic assistance. The aim of this study was to examine the clinical outcomes of patients who underwent this procedure. Five hundred and ten procedures in patients with a mean age of 63.7 years (range, 28 to 88 years) who underwent unicompartmental knee arthroplasty using a robotic-assisted system between July, 2008 and June, 2010 were identified. Clinical outcomes were evaluated using the Oxford Knee Score and patients without recent follow-up were contacted by telephone. The revision rate and time to revision were also examined. The average length of stay for patients who underwent robot-assisted UKA was 1.4 days (range, 1 to 7 days). There was minimal blood loss with most procedures. At latest clinical follow-up, most patients were doing well after UKA with a mean Oxford Knee Score of 36.1 + 9.92. The revision rate was 2.5% with 13 patients being either converted from an inlay to onlay prosthesis or conversion to total knee arthroplasty. The most common indication for revision was tibial component loosening, followed by progression of arthritis. Mean time to revision was 9.55 + 5.48 months (range, 1 to 19 months). Unicompartmental arthroplasty with a robotic system provides good pain relief and functional outcome at short-term follow-up. Ensuring correct component alignment and ligament balancing increases the probability of a favorable outcome following surgery. Proper patient selection for appropriate UKA candidates remains an important factor for successful outcomes

INTRODUCTION. Unicompartmental knee arthroplasty (UKA) allows replacement of a single compartment in patients who have isolated osteoarthritis as a minimally invasive procedure. However, limited visualization of the surgical site provides challenges in ensuring accurate alignment and placement of the prosthesis. With robot-assisted surgery, correct implant positioning and ligament balancing are obtainable with increased accuracy. To date, there has not been a large series reported in the literature of UKAs performed with robotic assistance. The aim of this study was to examine the clinical outcomes of robot-assisted UKA patients. METHODS. 510 patients who underwent robotic-assisted UKA between July 2008 and June 2010 were identified (average age 63.7 years, range: 22 to 28 years). Clinical outcomes were evaluated using the Oxford Knee Score (OKS) and patients without recent follow-up were phoned. Revision rate and time to revision were also examined. RESULTS. Average length of stay was 1.4 days (range: 1 to 7 days). There was minimal blood loss with most procedures. There were two intra-operative complications, both in early patients in the series. The first intra-operative complication was broken alignment pins in both the femur and tibia. In the second complication, preparation was finished manually with a burr due to registration problems with the software. Both patients were doing well at most recent follow up and neither experienced further complications. At latest clinical follow-up, patients reported a mean OKS of 36.1 + 9.92. The revision rate was 2.5% with 13 patients either converted from an inlay to onlay prosthesis or conversion to TKA. The most common indication for revision was tibial component loosening, followed by progression of arthritis. One patient was revised due to infection. Mean time to revision was 9.55 + 5.48 months (range: 1 to 19 months). CONCLUSION. UKA with a robotic system provides good pain relief and functional outcomes at short-term follow-up. Ensuring correct component alignment and ligament balancing increases the probability of a favorable outcome. Proper patient selection for appropriate UKA candidates remains an important factor for successful outcomes. In combination with robotic assistance there can be a reduction in many of the failures seen with early systems

Navigation systems that increase alignment accuracies of the lower limbs have been applied widely in total knee arthroplasty and are currently being adopted for minimally invasive UKA (MIS UKA) with good alignment results. There is little debate that when compared with total knee arthroplasty (TKA), UKA is less invasive, causes less morbidity, better reproduces kinematics, and therefore offers quicker recovery, better range of movement and more physiologic function. However, despite improved alignment accuracies, advantages of use of navigation system in UKA in clinical outcomes and survivals are still debatable. To the best of our knowledge, no reports are available on the long-term results after UKA performing using a navigation system. The purpose of this prospective study was to compare the radiological, clinical, and survival outcomes of UKA that performed using the navigation system and using the conventional technique at average 8 years follows up. Between January 2003 and December 2005, Total of 98 UKAs were enrolled for this study, 56 UKAs in the navigation group and 42 UKAs in conventional group were included in this study after a average 8 years follow-up. At the final follow up, the radiological measurements with regard to the mechanical axis, the inclination of the femoral and tibial components, and radiolucent line or loosening were evaluated and compared between two groups. The clinical evaluations were performed using range of motion, Western Ontario and McMaster Arthritis index (WOMAC) scores and Knee Society (KS) score. Of the 98 patients (98 UNI knees), 2 (2.0%) had died at a mean 5.8years after surgery because of cardiovascular disease, 3 (3.1%) underwent revision surgery that 1 cases of periprosthetic stress fractures in medial tibial plateaus in the navigation group and a case of tibial component loosening and polyethylene wear in conventional groups were observed. At a final follow up, the mean of mechanical axis was statistically different between two groups (2.7 vs. 3.9 of varus). And there were significant difference between 2 groups in terms of the mean values (p=0.042) for the tibial component coronal alignment, mean coronal alignments of tibial components were 89.1 ± 2.4° in the NA-MIS and 87.6 ± 1.8° in the MIS group, however outlier result were similar in the 2 group (5 and 5 knees, respectively, p=0.673). Sagittal alignments of femoral and tibial component were similar in the two groups (p>0.05) Significant differences were found in WOMAC or HSS knee scores, in which, stiffness did not show any difference between two groups, but pain and function showed difference at the last follow-up. The mean knee flexion has improved from 135.0 ± 14.8° and 135.0 ± 14.1° preoperatively to 137.1 ± 6.5° and 136.5 ± 7.2° in the NA-MIS and MIS groups on the latest follow-up, which was not significant different (p=0.883). The navigation system in UKA can provide improved alignment accuracy. And better clinical outcomes in pain and HSS score compared with conventional technique after a average of 8 year follow-up

The aim of the study was to assess the results of treating knee osteoarthrosis with total knee arthroplasty (TKA) after previous tibia and/or femur fractures resulting in axial limb deformities. Thirty-six knees (34 patients) were operated on. At the most recent follow-up, 4.8 years after surgery, all but one patient demonstrated an improvement in both clinical and functional KSS. This male patient required revision after 2 years due to tibial component aseptic loosening. Improved range of motion was generally noted, especially extension, however, two patients with both tibia and femur fractures had worse results. TKA is an effective method of treatment for patients with arthrosis after a previous femur or tibia fractures. When deformity is severe semi-constrained or constrained, implants with extensions may be necessary

Total knee arthroplasty is a reliable and durable solution to knee arthritis that fails conservative management. However, there are clinical pitfalls awaiting the surgeon, which can be avoided with forethought and analysis. The majority of early TKR failures are related to technical error on the part of the surgeon! The top 10 errors are: . 10. The knee attached to secondary gain: worker's comp, depression, etc. will make a successful outcome less likely. 9. Wound complications: raising large subcutaneous flaps, failure to respect pre-existing incisions about the knee, and delay in obtaining closure with flaps, etc. will almost guarantee infection!. 8. Prolonged observation of the draining wound: another invitation to infection!. 7. Internal rotation of the femoral component: patellar maltracking, and flexion instability await!. 6. Infection: discipline for the OR staff and surgeon alike are necessary to minimise this complication. 5. Varus position of the tibial component: early loosening and accelerated polyethylene wear are assured. 4. Failure to restore a neutral mechanical axis of the limb: early wear and loosening are the outcome of failure to pay attention to this very important basic principle of TKR. 3. Patellar tilt or dislocation: lateral retinacular release is less common with current designs, but is still required for proper patellar tracking. 2. Failure to balance soft tissue: collateral ligament, and the posterior cruciate ligament must be balanced throughout the range of motion for a successful result. And the #1 way to ruin a good result is…. Operating too early! Don't operate on the x-ray, and exhaust all reasonable conservative therapy and non-arthroplasty alternatives before resorting to prosthetic arthroplasty. The patient needs to understand the limitations of technology, and have reasonable expectations. Make sure the pre-op symptoms justify the procedure!

Critics of Unicompartmental knee replacement (UKR) highlight poor survivorship in national joint registries and argue that revision to Total Knee Replacement (TKR) is technically difficult with inferior function and survivorship compared to primary TKR. We prospectively reviewed outcomes of UKRs in our institution undergoing early revision to a TKR, comparing conventional revisions to those performed using computer navigation. 20 cases were identified, 7 conventional and 13 navigated. 13 were male and 7 female, mean age at primary UKR was 63.6 years (range: 47–81). Mean follow up time after revision was 5.2 years (2–9.5). Mean surgical time was 152 mins in conventional revisions and 163 mins for navigated. 43% of conventional cases required revision stems or augments, compared to 15% of conventional cases. Mean Oxford Knee Scores for revised knees were 32.8 in the conventional group and 34.64 in the navigated group, compared to 30.02 in the national joint registry. This compares to a mean Oxford score of 37.16 for primary TKRs in the registry. One of the conventional revisions required a further revision of the tibial component for loosening. This equates to a 95% suvivorship at mean 5 year follow up, or 1.10 revisions per 100 component years. Joint registry data had 1.97 revisions per 100 component years for UKR to TKR revisions, and 0.48 for primary TKRs. Our results are significantly improved compared to other published series of UKR revisions to TKRs. Only one other series has reported outcomes of these revisions using navigation. Despite small numbers, our results suggest that navigation makes revisions of UKRs more straightforward with similar surgical times. Fewer revision components were required with navigation and functional scores were marginally improved

The use of robots in orthopaedic surgery is an emerging field that is gaining momentum. It has the potential for significant improvements in surgical planning, accuracy of component implantation and patient safety. Advocates of robot-assisted systems describe better patient outcomes through improved pre-operative planning and enhanced execution of surgery. However, costs, limited availability, a lack of evidence regarding the efficiency and safety of such systems and an absence of long-term high-impact studies have restricted the widespread implementation of these systems. We have reviewed the literature on the efficacy, safety and current understanding of the use of robotics in orthopaedics.

Cite this article: Bone Joint J 2015; 97-B:292–9.