There has been renewed interest in the use of unicompartmental knee arthroplasty (UKA) for patients with limited degenerative disease of the knee due to improved surgical techniques and prosthetic design, and the desire for minimally invasive surgery. However, patient satisfaction following UKA for lateral compartment disease have been suboptimal with increased revision rates. Robotic-assisted UKA has been shown to improve precision and accuracy of component placement, which may improve outcomes of lateral UKA. The purpose of this study was to compare the outcome of robotic-assisted UKA to conventional UKA for degenerative disease of the lateral compartment with the hypothesis that robotic-assisted lateral UKA results in superior outcomes compared to conventional UKA. The institution's joint registry was searched for patients who underwent UKA for limited degenerative disease of the lateral knee compartment between 2004 and 2012 and a total of 125 lateral UKAs were identified. The medical records of all patients were reviewed and assessed for the type of surgical procedure used (robotic-assisted versus conventional), length of hospital stay, Oxford knee score, and occurrence of revision surgery. Preoperative and postoperative radiographs were assessed for tibiofemoral angle, femoral and tibial joint line angle, posterior tibial slope, and orientation of the femoral and tibial components.Introduction
Methods
Bicompartmental knee replacement (BKR) may be an alternative to total knee arthroplasty (TKA) for degenerative disease limited to two knee compartments. Most commonly, BKA is a combination of medial compartment and patellofemoral compartment resurfacing. In contrast to TKA, BKA preserves the uninvolved compartment and cruciate ligaments possibly leading to advanced stability and more physiologic knee kinematics. Robotic-assisted systems for unicompartmental knee arthroplasty have shown to provide improved component positioning with dynamic ligament balancing that may improve outcomes of BKA. The purpose of this study was to evaluate the short-term outcomes of patients undergoing BKA at a single institution by a single surgeon using a robotic-assisted system. A search of the institution's joint registry was conducted to identify patients that underwent robotic-assisted BKA of the patellofemoral compartment and the medial or lateral compartment between December 2009 and April 2012. All medical records were analyzed for patient demographics and comorbidities. The patients were evaluated preoperatively and at 6,12 months and then annually. The patients were contacted by phone when recent follow-up was not available. The radiographic assessment was also undertaken. The orientation of the tibial and femoral implants was assessed radiologically postoperatively. We examined the clinical results with the Oxford Knee Score (OKS)Introduction
Methods
Unicompartmental knee arthroplasty (UKA) has seen renewed interest in recent years and is a viable option for patients with limited degenerative disease of the knee as an alternative to total knee arthroplasty. However, the minimally invasive UKA procedure is challenging, and accurate component alignment is vital to long-term survival. Robotic-assisted UKA allows for greater accuracy of component placement and dynamic intraoperative ligament balancing which may improve clinical patient outcomes. The purpose of this study was to analyse the clinical outcomes in a large, consecutive cohort of patients that underwent robotic-assisted UKA at a single institution with a minimum follow-up of 2 years. The study hypothesis was that robotic-assisted UKA improves patient outcomes by decreasing the rate of revision in comparison to conventional UKA. A search of the institutional joint registry was performed to identify patients that underwent robotic-assisted UKA beginning in August 2008. The patients' electronic medical record was analysed for surgical indication, age at surgery, body mass index (BMI), and American Society of Anesthesiology Physical Status Classification System (ASA). Patient comorbidities were evaluated using the Charlson comorbidity index. Length of surgery and length of hospitalisation were assessed and clinical outcomes were evaluated using the Oxford Knee Score. In addition to postoperative follow-up assessments in clinic, patients without recent follow-up were contacted by telephone to capture the overall revision rate and time to revision.Introduction
Materials and methods
Unicompartmental knee arthroplasty (UKA) has seen renewed interest in recent years due to improved surgical techniques and prosthetic design, and the desire for minimally invasive surgery. For patients with limited degenerative disease, UKA offers a viable alternative to total knee arthroplasty. Historically, the outcomes of lateral compartment UKA have been inferior to medial compartment UKA, with suboptimal patient satisfaction and increased revision rates. Robotic-assisted UKA has been shown to improve precision and accuracy of component placement, which may improve outcomes of lateral UKA. The purpose of this study was to compare the outcome of robotic-assisted UKA to conventional UKA for degenerative disease of the lateral compartment. The hypothesis of the study was that robotic-assisted lateral UKA results in superior outcomes compared to conventional UKA. A search of the institution's joint registry was conducted to identify patients who underwent UKA for limited degenerative disease of the lateral knee compartment. A total of 130 lateral UKAs were identified that were performed between 2004 and 2012. The mean age of the patients was 63.1 years (range, 20 to 88); patients had a mean BMI of 29.9 (range, 18 to 48). The medical records of all patients were reviewed and assessed for the type of surgical procedure used (robotic-assisted versus conventional), length of hospital stay, Oxford knee score, and occurrence of revision surgery.Introduction
Materials and methods
Unicompartmental knee arthroplasty (UKA) has seen renewed interest in recent years and is a viable option for patients with limited degenerative disease of the knee as an alternative to total knee arthroplasty. However, the minimally invasive UKA procedure is challenging and accurate component alignment is vital to long-term survival. Robotic-assisted UKA allows for greater accuracy of component placement and dynamic intraoperative ligament balancing which may improve clinical patient outcomes. The purpose of this study was to examine the clinical outcomes in a large, consecutive cohort of patients that underwent robotic-assisted UKA. A search of the institutional joint arthroplasty registry identified 507 patients with a mean age of 63 years (range, 28 to 88 years) who underwent robotic-assisted UKA between July 2008 and June 2010. 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.Introduction
Materials and Methods
The knee is one of the most commonly affected joints in osteoarthritis. Unicompartmental knee replacement (UKA) was developed to address patients with this disease in only one compartment. The conventional knee arthroplasty jigs, while usually being accurate, may result in the prosthesis being inserted in an undesired alignment which may lead to poor post-operative outcomes. Common modes of failure in UKA include edge loading due to incorrect sizing or positioning, development of disease in the other compartment due to over-stuffing or over-correction and early loosening or stress fractures due to inaccurate bone cuts. Computer navigation and robotically assisted unicompartmental knee replacement were introduced in order to improve the surgical accuracy of both the femoral and tibial bone cuts. The aim of this study was to assess accuracy and reliability of robotic assisted, unicondylar knee surgery in producing reported bony alignment. Two hundred and twenty consecutive patients with a mean age of 64 + 11 years who underwent successful medial robotic assisted unicondylar knee surgery performed by two senior total joint arthroplasty surgeons were identified retrospectively. The mean body mass index of the cohort was 33.5 + 8 kg/m2 with a minimum follow-up of 6 months (range: 6–18 months). Femoral and tibial sagittal and coronal alignments as well as the posterior slope of the tibial component were measured in the post-operative radiographs. These measurements were compared with the equivalent measurements collected during intra-operative period by the navigation to study the reliability and accuracy of femoral and tibial cuts. Radiographic evaluation was independently conducted by two observers. There was an average difference of 2.2 to 3.6 degrees between the intra-operatively planned and post-operative radiological equivalent measurements. For the femur, mean varus/valgus angulation was 2.8 + 2.5 degrees with 83% of those measured within 5% of planned. For the tibia mean varus/valgus angulation was 2.4 + 1.9 degrees with 93% within 5% of planned resection. There was minimal inter-observer variability between radiographic measurements. There were no infections in the evaluated group at the time of radiographic examination. Alignment for unicondylar knee arthroplasty is important for implant survival and is a more difficult procedure to instrument as it is a minimally invasive surgery. Assuming appropriate planning, robotically assisted surgery in unicondylar knee replacement will result in reliably accurate positioning of component and reduce early component failures caused by malpositioning. A mismatch between pre-planning and post-operative radiography is often caused by poor cementing technique of the prosthesis rather than incorrect bony cuts. Addressing these factors can lead to greater success and improved outcomes for patients.
Unicompartmental knee arthroplasty (UKA) was first described over 30 years ago and allows replacement of a single compartment in patients who have isolated osteoarthritis. However, UKA is more technically challenging than total knee arthroplasty due to limited exposure as a minimally invasive procedure. In addition to component alignment and fixation, ligament balancing plays an important role in implant survival. Some failures of early UKA systems were attributed to a failure to adequately balance the knee. The development of robots to aid in performing the procedure has lead to renewed interest in this surgical technique. The use of a robot-assisted system allows the orthopaedic surgeon to verify that balancing sought pre-operatively correlates with that obtained at surgery. Some studies have shown good post-operative mechanical alignment utilizing this method. The aim of this study was to examine the variation in pre-operative templated ligament balance and that obtained during the operation. Data were prospectively collected on 51 patients (52 knees) undergoing robot-assisted unicompartmental knee arthroplasty by a single surgeon. For pre-operative planning, dynamic ligament balancing was obtained of the operative knee under valgus stress, prior to any bony cuts. Final intra-operative images with the prosthesis in place were taken without valgus stress. Positive values denoted loose ligamentous balancing while negative values indicated ligament tightness. A small variation of less than 1 mm was measured between the pre-operative plan and the final image with the implant in place. At 0 degrees the mean change was −0.26 mm (range, −4.40 to 2.20 mm), at 30 degrees −0.53 mm (range, −5.30 to 1.80 mm), at 60 degrees −0.04 mm (range, −3.10 to 2.30 mm) and at 90 degrees 0.16 mm (range, −2.70 to 2.00 mm). These results show that planned dynamic ligament balancing is accurate to within 0.52 mm. The technological advancements with robotic feedback in orthopaedic surgery can aid in the success of unicompartmental knee replacement surgery. Ensuring that pre-operative templated changes match those performed during surgery is an important predictor of outcome. With proper planning prior to surgery, the use of a robot in UKA can improve ligament balancing. This can be done at various angles, ensuring excellent ligament balancing throughout the entire range of motion. Correct component alignment reduces the risk of prosthetic failure and may increase the length of implant survival. Further fine-tuning of the accuracy of feedback between the robot and the anatomical points will improve the accuracy of UKA.
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.
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. 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.INTRODUCTION
METHODS
Unicompartmental knee arthroplasty (UKA) was first described over 30 years ago and allows replacement of a single compartment in patients who have isolated osteoarthritis.1 However, UKA is more technically challenging than total knee arthroplasty due to limited exposure as a minimally invasive procedure. In addition to component alignment and fixation, ligament balancing plays an important role in implant survival.2 Some failures of early UKA systems were attributed to a failure to adequately balance the knee. The development of robots to aid in performing the procedure has lead to renewed interest in this surgical technique. The use of a robot-assisted system allows the orthopaedic surgeon to verify that balancing sought pre-operatively correlates with that obtained at surgery. Some studies have shown good post-operative mechanical alignment utilizing this method.3 The aim of this study was to examine the variation in pre-operative templated ligament balance and that obtained during the operation. Data were prospectively collected on 52 patients (51 knees) undergoing robot-assisted unicompartmental knee arthroplasty by a single surgeon. For pre-operative planning, dynamic ligament balancing was obtained of the operative knee under valgus stress, prior to any bony cuts. Final intra-operative images with the prosthesis in place were taken without valgus stress. Positive values denoted loose ligamentous balancing while negative values indicated ligament tightness.Introduction
Methods
The conventional Knee arthroplasty jigs, while being usually accurate, often result in prostheses being inserted in an undesired alignment resulting in poor postoperative outcome. This is especially true about unicompartmental knee replacement. Computer navigation and roboticaly assisted unicompartmental knee replacement were introduced in order to improve surgical accuracy of the femoral and tibial bone cuts. The aim of this study was to assess accuracy and reliability of robotic assisted, unicondylar knee surgery (Makoplasty) in producing reported bony alignment. Two hundred and twenty consecutive patients who underwent medial robotic assisted unicondylar knee surgery (Makoplasty) performed by two surgeons (RJ & GP) were retrospectively identified and included in the study. Femoral and tibial sagittal and coronal alignments and posterior slope of the tibial component were measured in the post-operative radiographs. These measurements were compared with the equivalent measurements collected during intra-operative period by the navigation to study the reliability and accuracy of femoral and tibial cuts. We found an average difference of 2.2 to 3.6 degrees between the intra-operatively planned and post-operative radiological equivalent measurements. In conclusion: assuming appropriate planning, robotically assisted surgery in unicondylar knee replacement will result in reliably accurate positioning of component and reduce early component failures caused by malpositioning. Mismatch between preplanning and post-op radiography is caused by poor cementing technique of the prosthesis rather than wrong bony cuts.Results
Recently in the literature the indications of unicompartmental knee arthroplasty have been extended by the inclusion of patients with arthritis which is predominantly but not exclusively effecting the medial compartment. The aim of this study is to evaluate the outcome of MAKO unicondylar replacement in the treatment of knee osteoarthritis after the initial surgical insult is worn off to evaluate the impact of residual patellofemoral and lateral osteoarthritis on the outcome of medial unicompartmental knee replacement. 135 patients who underwent uncomplicated 144 MAKO medial unicondylar replacements for knee arthritis were identified and studied. Original radiographs were used to classify severity of patellofemoral and lateral compartmental osteoarthritis in these patients. Severity of patellofemoral and lateral compartmental osteoarthritis was analyzed against Oxford and Knee Society (AKSS) scores and amount of ipsilateral residual knee symptoms at 6 months post-operative period. Pre-operative Oxford and Knee Society scores, and other comorbidities and long term disability were studied as confounding variables. We found significant improvement in symptoms and scores in spite of other compartment disease. Poorer outcome was seen in association with comorbidities and long term disability but not when radiographic signs of arthritis in the other compartments were present. Six patients required revision of which three had (lateral facet) patellofemoral disease in the original x-rays. In conclusion there is no direct relationship between postoperative symptoms and poor outcome and radiographic disease in the other compartments. However when symptoms are severe enough to necessitate revision this is due to patellofemoral and not lateral compartment disease.
