Aims. The treatment of patients with allergies to metal in total joint arthroplasty is an ongoing debate. Possibilities include the use of hypoallergenic prostheses, as well as the use of standard cobalt-chromium (CoCr) alloy. This non-designer study was performed to evaluate the clinical outcome and survival rates of unicondylar knee arthroplasty (UKA) using a standard CoCr alloy in patients reporting signs of a hypersensitivity to metal. Patients and Methods. A consecutive series of patients suitable for UKA were screened for symptoms of metal hypersensitivity by use of a questionnaire. A total of 82 patients out of 1737 patients suitable for medial UKA reporting cutaneous metal hypersensitivity to cobalt, chromium, or nickel were included into this study and prospectively evaluated to determine the functional outcome, possible signs of hypersensitivity, and short-term survivorship at a minimum follow-up of 1.5 years. Results. At a mean follow-up of three years (1.5 to 5.7), no local or systemic symptoms of hypersensitivity to metal were observed. One patient underwent revision surgery to a bicondylar prosthesis due to a tibial periprosthetic fracture resulting in a survival rate of 98.8% (95% confidence interval (CI) 91.7 to 99.8; number at risk, 28) at three years with the endpoint of revision for any reason and a survival rate of 97.6% (95% CI 90.6 to 99.3; number at risk, 29) for the endpoint of all reoperations. Clinical outcome was good to excellent with a mean Oxford Knee Score of 42.5 (. sd. 2.5; 37 to 48). Conclusion. This study is the first demonstrating clinical results and survival analysis of UKA using a CoCr alloy in patients with a history of metal hypersensitivity. Functional outcome and survivorship are on a high-level equivalent to those reported for UKA in patients without a history of metal hypersensitivity. No serious local or systemic symptoms of metal hypersensitivity could be detected, and no revision surgery was performed due to an adverse reaction to metal ions

We have performed a prospective double-blind, randomised controlled trial over two years to evaluate the efficacy and safety of an intra-operative peri-articular injection of triamcinolone acetonide in patients undergoing medial unicondylar knee replacement. We randomised 90 patients into two equal groups. The study group received an injection of triamcinolone acetonide, bupivacaine, and epinephrine into the peri-articular tissues at the end of the operation. The control group received the same injection mixture but without the addition of triamcinolone. The peri-operative analgesic regimen was standardised. The study group reported a significant reduction in pain (p = 0.014 at 12 hours, p = 0.031 at 18 hours and p = 0.031 at 24 hours) and had a better range of movement (p = 0.023 at three months). There was no significant difference in the rate of infection and no incidence of tendon rupture in either group. The addition of corticosteroid to the peri-articular injection after unicondylar knee replacement had both immediate and short-term benefits in terms of relief from pain, and rehabilitation with no increased risk of infection

Introduction. Unicondylar knee replacement (UKR) surgery is proven long term results in its benefit in medial compartment OA. However, its results are sensitive to component alignment with poor alignment leading to early failure. The advent of computer navigation has resulted in improved mechanical alignment, but little has been published on the outcomes of navigated UKR surgery. We present the results of 253 consecutive Computer Assisted UKR's performed by a single surgeon. Objective. Assess clinical and radiological outcomes of Computer Assisted Unicondylar Knee Replacement at 5 years follow-up. Methods. Between August 2003 and June 2007, 253 UKR's were performed by a single surgeon using the Stryker Knee navigation system. Pre-operative Knee Society Scores (KSS) were recorded. The UKR's consisted of 98 oxford UKR's and 155 MG UKR's. Tourniquet time, time to straight leg raise and time to discharge was also recorded. All patients had post op KSS scores and long leg standing radiographs. Data regarding revision surgery was also collected. Results. Pre-op mean KSS scores was 54 (24–62) and post-op scores were a mean of 89 (75–100). 92% percent of femoral components were aligned at 90+/− 4 degrees from neutral in the coronal plane whilst eighty nine percent of tibial components were aligned at 90+/− 4 degrees from neutral in the coronal plane. Mean tourniquet time was 53 minutes whilst 98% of patients had SLR at 24hours. Only two percent of patients had an overall valgus alignment of their limb at the end of the procedure on long leg radiographs. 1% of the UKRs underwent revision for loosening of the femoral component. 1 oxford UKR was revised for progression of patello-femoral disease. One MG UKR was revised for unexplained pain. Conclusion. Our single surgeon series of Computer Assisted UKR demonstrates favourable outcomes in the medium term with 98% survival at 5 years. Computer Assisted UKR allows accurate and reproducible alignment of the tibial and femoral component. We recommend the use of Computer Navigation in performing Unicondylar Knee Replacements

Utilisation of unicondylar knee arthroplasty (UKA) has been limited due in part to high revision rates. Only 8% of knee arthroplasty surgeries completed in England and Wales are UKAs. It is reported that the revision rate at 9 years for Total Knee Arthroplasty (TKA) was 3% compared to 12% for UKAs. In the last decade semi active robots have been developed to be used for UKA procedures. These systems allow the surgeon to plan the size and orientation of the tibial and femoral component to match the patient's specific anatomy and to optimise the balancing the soft tissue of the joint. The robotic assistive devices allow the surgeon to execute their plan accurately removing only ‘planned’ bone from the predefined area. This study investigates the accuracy of an imageless navigation system with robotic control for UKA, reporting the errors between the ‘planned’ limb and component alignment with the post-operative limb and component alignment using weight bearing long leg radiographs. We prospectively collected radiographic data on 92 patients who received medial UKA using an imageless robotic assisted device across 4 centres (4 surgeons). This system is CT free, so relies on accurate registration of intra-operative knee kinematic and anatomic landmarks to determine the mechanical and rotational axis systems of the lower limb. The surface of the condylar is based on a virtual model of the knee created intra-operatively by ‘painting’ the surface with the tip of a tracked, calibrated probe. The burring mechanism is robotically controlled to prepare the bone surface and remove the predefined volume of bone. The study shows the 89% of the patients' post-operative alignment recorded by the system was within 30 of the planned coronal mechanical axis alignment. The RMS error was 1.980. The RMS errors between the robotic system's implant plan and the post-operative radiographic implant position was; femoral coronal alignment (FCA) 2.6o, tibial coronal alignment (TCA) 2.9o and tibial slope (TS) 2.9o. In conclusion, the imageless robotic surgical system for UKA accurately prepared the bone surface of the tibia and femur which resulted in low errors when comparing planned and achieved component placement. This resulted in a high level of accuracy in the planned coronal mechanical axis alignment compared to that measured on post-operative radiographs

Summary Statement. Uptake of robotically-assisted orthopaedic surgery may be limited by a perceived steep learning curve. We quantified the technological learning curve and 5 surgeries were found to bring operating times to appropriate levels. Implant positioning was as planned from the outset. Introduction. Compared to total knee replacement, unicondylar knee replacement (UKR) has been found to reduce recovery time as well as increase patient satisfaction and improve range of motion. However, contradictory evidence together with revision rates concern may have limited the adoption of UKR surgery. Semi-active robotically-assisted orthopaedic tools have been developed to increase the accuracy of implant position and subsequent mechanical femorotibial angle to reduce revision rates. However, the perceived learning curve associated with such systems may cause apprehension among orthopaedic surgeons and reduce the uptake of such technology. To inform this debate, we aimed to quantify the learning curve associated with the technological aspects of the NavioPFS™ (Blue Belt Technologies Inc., Pittsburgh, USA) with regards to both operation time and implant accuracy. Methods. Five junior orthopaedic trainees volunteered for the study following ethical permission. All trainees attended the same initial training session and subsequently each trainee performed 5 UKR surgeries on left-sided synthetic femurs and tibiae (model 1146–2, Sawbones-Pacific Research Laboratories Inc, Vashon, WA, USA). A few days lapsed between surgeries, which were all completed in a two week window. Replica Tornier HLS Uni Evolution femoral and tibial implants (Tornier, France) were implanted without cementation. Each surgery was videoed and timings taken for key operation phases, as well as the overall operative time. A ball point probe with four reflective spherical markers attached was used to record the position of manufactured divots on the implant, which allowed the 3D position of the implant to be compared to the planned position. Absolute translational and rotational deviations from the planned position were analysed. Results. Total surgical time decreased significantly with surgery number (p < 0.001) from an initial average of 85 minutes to 48 minutes after 5 surgeries. All stages, except the cutting tool set up, demonstrated a significant difference in operative time with increasing number of surgeries performed (all p < 0.05) with the cutting phase decreasing from 41 to 23 minutes (p < 0.001). The translational and rotational accuracy of the implants did not significantly vary with surgery number. Discussion and Conclusion. The accuracy in implant position obtained by trainee surgeons on synthetic bones were similar to published data for experienced orthopaedic surgeons on other systems on cadavers. Whilst cadaver operations increase the complexity of operation, this should not theoretically affect the robotic system in preventing innaccurate implantation. Moreover, the fact that this accuracy was obtainable on the first surgery clearly demonstrates the system's ability in ensuring accurate implantation. Five surgeries dramatically reduced the total operative time, and moreover, the trend suggests that more surgeries would further decrease the total operation time. It was not the intention of the study to compare absolute trainee times on synthetic bones to surgeons with cadavers, but the learning curve of the protocol and technology suggests a halving of the operation time after 5 sessions would not be unrealistic

For patients suffering from osteoarthritis confined to one compartment of the knee joint, a successful unicondylar knee arthroplasty (UKA) has demonstrated an ability to provide pain relief and restore function while preserving bone and cruciate ligaments that a total knee arthroplasty (TKA) would sacrifice. Long-term survival of UKA has traditionally been inconsistent, leading to decreased utilisation in favour of alternative surgical treatment. Robot-assisted UKA has demonstrated an ability to provide more consistent implantation of UKA prosthesis, with the potential to increase long-term survivorship. This study reports on 65 patients undergoing UKA using an image-free, handheld robotic assistive navigation system. The condylar surface was mapped by the surgeon intra-operatively using a probe to capture a 3-dimensional representation of the area of the knee joint to be replaced. The intra operative planning phase allows the surgeon to determine the size and orientation of the femoral and tibial implant to suit the patients’ anatomy. The plan sets the boundaries of the bone to be removed by the robotic hand piece. The system dynamically adjusts the depth of bone being cut by the bur to achieve the desired result. The planned mechanical axis alignment was compared with the system's post-surgical alignment and to post-operative mechanical axis alignment using long leg, double stance, weight bearing radiographs. All 65 knees had knee osteoarthritis confined to the medial compartment and UKA procedures were completed using the handheld robotic assistive navigation system. The average age and BMI of the patient group was 63 years (range 45–82 years) and 29 kg/m. 2. (range 21–37 kg/m. 2. ) respectively. The average pre-operative deformity was 4.5° (SD 2.9°, Range 0–12° varus). The average post-operative mechanical axis deformity was corrected to 2.1° (range 0–7° varus). The post-operative mechanical axis alignment in the coronal plane measured by the system was within 1° of intra-operative plan in 91% of the cases. 3 out of 6 of the cases where the post-operative alignment was greater than 1° resulted due to an increase in the thickness of the tibia prosthesis implanted. The average difference between the ‘planned’ mechanical axis alignment and the post-operative long leg, weight bearing mechanical axis alignment was 1.8°. The average Oxford Knee Score (old version) pre and post operation was 38 and 24 respectively, showing a clinical and functional improvement in the patient group at 6 weeks post-surgery. The surgical system allowed the surgeons to precisely plan a UKA and then accurately execute their intra operative plan using a hand held robotically assisted tool. It is accepted that navigation and robotic systems have a system error of about 1° and 1mm. Therefore, this novel device recorded accurate post-operative alignment compared to the ‘planned’ post-operative alignment. The patients in this group have shown clinical and functional improvement in the short term follow up. The importance of precision of component alignments while balancing existing soft-tissue structures in UKA has been documented. Utilisation of robotic-assisted devices may improve the accuracy and long-term survivorship UKA procedure

Unicondylar knee arthroplasty (UKA) is a treatment for osteoarthritis when the disease only affects one compartment of the knee joint. The popularity in UKA grew in the 1980s but due to high revision rates the usage decreased. A high incidence of implant malalignment has been reported when using manual instrumentation. Recent developments include surgical robotics systems with navigation which have the potential to improve the accuracy and precision of UKA. UKA was carried out using an imageless navigation system – the Navio Precision Freehand Sculpting system (Blue Belt Technologies, Pittsburgh, USA) with a medical Uni Knee Tornier implant (Tornier, Montbonnot Saint Martin, France) on nine fresh frozen cadaveric lower limbs (8 males, 1 females, mean age 71.7 (SD 13.3)). Two users (consultant orthopaedic surgeon and post doctoral research associate) who had been trained on the system prior to the cadaveric study carried out 4 and 5 implants respectively. The aim of this study was to quantify the differences between the planned and achieved cuts. A 3D image of the ‘actual’ implant position was overlaid on the planned implant image. The errors between the ‘actual’ and the planned implant placement were calculated in three planes and the three rotations. The maximum femoral implant rotational error was 3.7° with a maximum RMS angular error of 2°. The maximum femoral implant translational error was 2.6mm and the RMS translational error across all directions was up to 1.1mm. The maximum tibial implant rotational error was 4.1° with a maximum RMS angular error was 2.6°. The maximum translational error was 2.7mm and the RMS translational error across all directions was up to 2.0mm. The results were comparable to those reported by other robotic assistive devices on the market for UKA. This technology still needs clinical assessment to confirm these promising results

NavioPFS™ is a hand-held robotic technology for bone shaping that employs computer control of a high-speed bone drill. There are two control modes – one based on control of exposure of the cutting bur and another based on the control of the speed of the cutting bur. The unicondylar knee replacement (UKR) application uses the image-free approach in which a mix of direct and kinematic referencing is used to define all parameters relevant for planning. After the bone cutting plan is generated, the user freely moves the NavioPFS handpiece over the bone surface, and carves out the parts of the bone targeted for removal. The real-time control loop controls the depth or speed of cut, thus resulting in the planned bone preparation. This experiment evaluates the accuracy of bone preparation and implant placement on cadaveric knees in a simulated clinical setting. Three operators performed medial UKR on two cadaver specimens (4 knees) using a proprietary implant design that takes advantage of the NavioPFS approach. In order to measure the placement of components, each component included a set of 8 conical divots in predetermined locations. To establish a shared reference frame, a set of four fiducial screws is inserted in each bone. All bones were cut using a 5 mm spherical bur. Exposure Control was the primary mode of operation for both condylar cuts – although the users utilised Speed Control to perform some of the more posterior burring activities and to prepare the peg holes. Postoperatively, positions of conical divots on the femoral and tibial implants and on the respective four fiducial screws were measured using a Microscribe digitising arm in order to compare the final and the planned implant position. All implants were placed within 1.5 mm of target position in any particular direction. Maximum translation error was 1.31 mm. Maximum rotational error was 1.90 degrees on a femoral and 3.26 degrees on a tibial component. RMS error over all components was 0.69mm/1.23 degrees. This is the first report of the performance of the NavioPFS system under clinical conditions. Although preliminary, the results are overall in accordance with previous sawbones studies and with the reports from comparable semi-active robotic systems that use real time control loop to control the cutting performance. The use of NavioPFS in UKR eliminates the need for conventional instrumentation and allows access to the bone through a reduced incision. By leveraging the surgeon's skill in manipulating soft tissues and actively optimising the tool's access to the bone, combined with the precision and reproducibility of the robotic control of bone cutting, we expect to make UKR surgery available to a wider patient population with isolated medial osteoarthritis that might otherwise receive a total knee replacement. In addition to accurate bone shaping with a handheld robotically controlled tool, NavioPFS system for UKR incorporates a CT-free planning system. This approach combines the practical advantages of not requiring pre-operative medical images, while still accurately gathering all key information, both geometric and kinematic, necessary for UKR planning

Knee osteoarthritis results in pain and functional limitations. In cases where the arthritis is limited to one compartment of the knee joint then a unicondylar knee arthroplasty (UKA) is successful, bone preserving option. UKA have been shown to result in superior clinical and functional outcomes compared to TKA patients. However, utilisation of this procedure has been limited due primarily to the high revision rates reported in joint registers. Robotic assisted devices have recently been introduced to the market for use in UKA. They have limited follow up periods but have reported good implant accuracy when compared to the pre-operative planned implant placement. UKA was completed on 25 cadaver specimens (hip to toe) using an image-free approach with infrared optical navigation system with a hand held robotically assisted cutting tool. Therefore, no CT scan or MRI was required. The surface of the condylar was mapped intra operatively using a probe to record the 3 dimensional surface of the area of the knee joint to be resurfaced. Based on this data the size and orientation of the implant was planned. The user was able to rotate and translate the implant in all three planes. The system also displays the predicted gap balance graph through flexion as well as the predicted contact points on the femoral and tibial component through flexion. The required bone was removed using a bur. The depth of the cut was controlled by the robotically controlled freehand sculpting tool. Four users (3 consultant orthopaedic surgeon and a post-doctoral research associate) who had been trained on the system prior to the cadaveric study carried out the procedures. The aim of this study was to quantify the differences between the ‘planned’ and ‘achieved’ cuts. A 3D image of the ‘actual’ implant position was overlaid on the ‘planned’ implant image. The errors between the ‘actual’ and the ‘planned’ implant placement were calculated in three planes and the three rotations. The maximum femoral RMS angular error was 2.34°. The maximum femoral RMS translational error across all directions was up to 1.61mm. The maximum tibial RMS angular error was 2.60°. The maximum tibial RMS translational error across all directions was up to 1.67mm. In conclusion, the results of this cadaver study reported low RMS errors in implant position placement compared to the plan. The results were comparable with those published from clinical studies investigating other robotic orthopaedic devices. Therefore, the freehand sculpting tool was shown to be a reliable tool for cutting bone in UKA and the system allows the surgeon to plan the placement of the implant intra operatively and then execute the plan successfully

Aims: Prospectivemulti-centre study evaluating minimally invasive unicondylar knee arthroplasty (UKA). Methods: Between 1997 and 2001 435 UKA were performed using the minimally invasive technique according to Repicci. 420 patients with an average age of 66 years were evaluated after a follow up of 32 weeks. In 96,8% the medial and in 3,2% the lateral compartement were involved. The clinical results were evaluated with the Knee Society Clinical Rating System (KSS) and correlated with Body-Mass-Index (BMI) and pain, rated on a Visual Analogue Scale (VAS). Radiographical scoring were evaluated according to Ahlback. Results: The results of the KSS show a signiþcant postoperative increase of average 73 points. 86,8% patients were conþdent with the treatment. The statistical analysis revealed correlation between pain and patients age. BMI shows signiþcant correlation with all other parameters. Conclusion: Minimally invasive unicondylar knee arthroplasty shows very good results, espeically for pain and patientsñ conþdence. BMI and arthrosis of the patella might have the gratest inßuence for the outcome. Deþcient pre- and postoperative extension might be an unsolved problem

Objective. To investigate the reasons for revision of Oxford Unicondylar Knee Replacement (UKR). Does insert size used relate to requirement for revision?. Methods. We retrospectively reviewed the cases needing revision from a single surgeon consecutive series of 209 ‘Oxford’ UKRs. 10 cases required early (within 2 years) revision. The reasons for revision were investigated. A comparison of cases requiring revision by insert size implanted was made. Results. 10 cases required revision. 2 patients suffered from Sjorgens Syndrome which was undiagnosed at the time of primary surgery and underwent revision for ongoing pain, 2 cases fractured the tibia beneath the implant, 2 were revised for sepsis, and 3 cases were revised for ongoing pain without obvious cause. 1 case was revised for tibial component loosening. A significantly greater proportion of cases in which a size 6 insert was used required revision (4 of 11), compared with size 4 (1 of 44)(p=0.001) or size 5 (0 of 28)(p=0.002), and also compared with size 3 (3 of 31)(p=0.005). In cases where a size 3 insert is measured with this prosthesis, one option is to take a further tibial cut to rather use a size 6 insert. Given the five-fold increase in likelihood for requiring revision found in our series, we would recommend against this step. Conclusion. In conclusion we report a successful series of Oxford unicondylar knees taking early revision surgery as the endpoint. We recommend caution when considering a further cut when initial measurement suggests a size 3 insert, as in our series size 6 inserts showed a 5 fold increase in revision rate when compared to size 3

In total knee arthroplasty, navigation systems that help achieve accurate alignment of the lower limbs have been applied widely, and these techniques are currently being used in minimally invasive unicondylar knee arthroplasty (MIS UKA) with good alignment results. To the best of our knowledge, there are no studies showing whether or not MIS UKA using a navigation system has a significant influence on the clinical results. This prospective study investigated the hypothesis that minimally invasive uni-compartmental knee arthroplasty using navigation system (NA-MIS UKA) will produce better short-term clinical results than MIS UKA without navigation system. After a minimum two-year follow-up, the short-term functional results included the ranges of motion, Hospital for Special Surgery (HSS) scores, and WOMAC scores and the alignment accuracy of the components of 31 NA-MIS UKAs (NA-MIS group) compared with those of 33 MIS UKAs without a navigation system (MIS group). The surgery time was also recorded and compared. The HSS and WOMAC scores showed significant improvement at the final follow-up in both groups, showing no significant inter-group difference (p=0.071, p=0.096, respectively). The ranges of motion also showed significant improvements in both groups, but there was no significant difference between two groups (p=.687). However, the surgery time was longer in MIS group than in NA-MIS group. NA-MIS UKA produces significant improvement in the desired mechanical axis with prosthetic alignment outliers compared with that without the navigation system. However, at the final follow-up, there were no significant differences in any of the functional parameters between the two groups

Unicondylar knee arthroplasty (UKA) is growing in popularity with an increase in utilisation. As a less invasive, bone preserving procedure suitable for knee osteoarthritic patients with intact cruciate ligaments and disease confined to one compartment of the knee joint. The long term survival of a UKA is dependent on many factors, including the accuracy of prosthesis implantation and soft tissue balance. Robotic assisted procedures are generally technically demanding, can increase the operation time and are associated with a learning curve. The learning curve for new technology is likely to be influenced by previous experience with similar technologies, the frequency of use and general experience performing the particular procedure. The purpose of this study was to determine the time to achievement of a steady state with regards to surgical time amongst surgeons using a novel hand held robotic device. This study examined consecutive UKA cases which used a robotic assistive device from five surgeons. The surgeons had each performed at least 15 surgeries each. Two of the surgeons had previous experience with another robotic assistive device for UKA. All of the surgeons had experience with conventional UKA. All of the surgeons have used navigation for other knee procedures within their hospital. The system uses image free navigation with infrared optical tracking with real time feedback. The handheld robotic assistive system for UKA is designed to enable precision of robotics in the hands of the surgeon. The number of surgeries required to reach ‘steady state’ surgical time was calculated as the point in which two consecutive cases were completed within the 95% confidence interval of the surgeon's ‘steady state’ time. The average surgical time (tracker placement to implant trial acceptance phase) from all surgeons across their first 15 cases was 56.8 minutes (surgical time range: 27–102 minutes). The average improvement was 46 minutes from slowest to quickest surgical times. The ‘cutting’ phase was reported as decreasing on average by 31 minutes. This clearly indicates the presence of a learning curve. The surgeons recorded a significant decrease in their surgical time where the most improvement was in the process of bone cutting (as opposed to landmark registration, condyle mapping and other preliminary or planning steps). There was a trend towards decreasing surgical time as case numbers increase for the group of five surgeons. On average it took 8 procedures (range 5–11) to reach a steady state surgical time. The average steady state surgical time was 50 minutes (range 37–55 minutes). In conclusion, the average operative time was comparable with clinical cases reported using other robotic assistive devices for UKA. All five surgeons using the novel handheld robotic-assisted orthopaedic system for UKA reported significant improvement in bone preparation and overall operative times within the first 15 cases performed, reaching a steady state in surgical times after a mean of 8 cases. Therefore, this novel handheld device has a similar learning curve to other devices on the market

We reviewed 35 patients who underwent a medial unicondylar knee replacement, with an average follow up of 4 years (for functional assessment). All patents had a weight bearing AP and lateral X rays and were clinically assessed using Hospital for Special surgery score, Bristol Knee Score and SF 36 health assessment form. Five angles were measured on the x-rays to assess the alignment of the tibial and femoral alignment. There was a significant relation between the femoral component varus/valgus angle and three sub scores (fixed flexion contracture, maximum valgus/varus and range of movement) in Bristol Knee scores. The best functional out come correlated with femoral components of 4–8 degrees of valgus

Lower limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare it to alignment outcomes after medial UKA, making our understanding of this issue based on medial UKA studies. Unfortunately, since the geometry, mechanics, and ligamentous physiology are different between these two compartments, drawing conclusions for lateral UKAs based on medial UKA results may be imprecise and misleading. The purpose of this study was to compare the risk for limb alignment overcorrection and the ability to predict postoperative limb alignment between medial and lateral UKA. We evaluated the results of mechanical limb alignment in 241 patients with unicompartmental knee osteoarthritis who underwent medial or lateral UKA; there were 229 medial UKAs and 37 lateral UKAs. Mechanical limb alignment was measured in standing long limb radiographs pre and post-operatively, intra-operatively it was measured using a computer assisted navigation system. Between the two cohorts, we compared the percentage of overcorrection and the difference between post-operative alignment and alignment measured by the navigation system. The percentage of overcorrection was significantly higher in the lateral UKA group (11%), when compared to the medial UKA group (4%), (p= 0.0001). In the medial UKA group, the mean difference between the intraoperative “virtual” alignment provided by the navigation system, and the post-operative, radiographically measured mechanical axis, was 1.33°(±1.2°). This was significantly lower than the mean 1.86° (±1.33°) difference in the lateral UKA group (p=0.019). Our data demonstrated an increased risk of mechanical limb alignment overcorrection and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs

Lower limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare it to alignment outcomes after medial UKA, making our understanding of this issue based on medial UKA studies. Unfortunately, since the geometry, mechanics, and ligamentous physiology are different between these two compartments, drawing conclusions for lateral UKAs based on medial UKA results may be imprecise and misleading. The purpose of this study was to compare the risk for limb alignment overcorrection and the ability to predict postoperative limb alignment between medial and lateral UKA. We evaluated the results of mechanical limb alignment in 241 patients with unicompartmental knee osteoarthritis who underwent medial or lateral UKA; there were 229 medial UKAs and 37 lateral UKAs. Mechanical limb alignment was measured in standing long limb radiographs pre and post-operatively, intra-operatively it was measured using a computer assisted navigation system. Between the two cohorts, we compared the percentage of overcorrection and the difference between post-operative alignment and alignment measured by the navigation system. The percentage of overcorrection was significantly higher in the lateral UKA group (11%), when compared to the medial UKA group (4%), (p= 0.0001). In the medial UKA group, the mean difference between the intraoperative “virtual” alignment provided by the navigation system, and the post-operative, radiographically measured mechanical axis, was 1.33°(±1.2°). This was significantly lower than the mean 1.86° (±1.33°) difference in the lateral UKA group (p=0.019). Our data demonstrated an increased risk of mechanical limb alignment overcorrection and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs

Introduction. Limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare alignment outcomes between medial and lateral UKA. In this study, we retrospectively compare a single surgeon's alignment outcomes between medial and lateral UKA using a robotic-guided protocol. Methods. All surgeries were performed by a single surgeon using the same planning software and robotic guidance for execution of the surgical plan. The senior surgeon's prospective database was reviewed to identify patients who had 1) undergone medial or lateral UKA for unicompartmental osteoarthritis; and 2) had adequate pre- and post-operative full-length standing radiographs. There were 229 medial UKAs and 37 lateral UKAs in this study. Mechanical limb alignment was measured in standing long limb radiographs both pre- and post-operatively. Intra-operatively, limb alignment was measured using the computer assisted navigation system. The primary outcome was over-correction of the mechanical alignment (i.e, past neutral). Our secondary outcome was the difference between the radiographic post-operative alignment and the intra-operative “virtual” alignment as measured by the computer navigation system. This allowed an assessment of the accuracy of our navigation system for predicting post-operative limb alignment after UKA. Results. The percentage of overcorrection was significantly higher in the lateral UKA group (11%), when compared to the medial UKA group (4%), (p = 0.0001). In the medial UKA group, the mean difference between the intraoperative “virtual” alignment provided by the navigation system, and the post-operative, radiographically measured mechanical axis, was 1.33° (± 1.2°). This was significantly lower than the mean difference between these two parameters in the lateral UKA group, 1.86° (± 1.33°) (p = 0.019). Conclusions. Our data demonstrated an increased risk of “overcorrection,” and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs

Introduction An approximation of normal knee kinematics after knee replacement may improve knee function and implant fixation and reduce wear of the prosthesis. This study describes the knee joint kinematics after unicondylar knee arthroplasty (UKA) in general, and compares the Miller-Glante (MG, fixed bearing) and Oxford (mobile bearing) implants in particular. Methods Twenty-two knees in 17 patients (11 males, six females, mean age of 69.7 yrars) were randomized into MG (11 knees) or Oxford (11 knees). No clinical complications or signs of loosening were observed. At the one year follow-up, RSA (Radiosterometry) x-rays were taken by using two x-ray tubes positioned at knee level and exposing the knee simultaneously from the side. Four pairs of weight bearing x-ray were obtained at zero degrees, 30°, 60°, 90° of knee flexion, with zero as reference position. Tibial rotation, rollback, translation of tibia-femur contact point, and the bearing movement were analyzed using UmRSA software. Results With the MG implant, the tibia internally rotated 3.0°, 3.0°, and 4.2° respectively at 30°, 60°, and 90° of flexion, while with the Oxford implant, the tibia internally rotated 4.3°, 7.6°, and 9.5° respectively at 30°, 60°, and 90°. No significant difference was found between the two groups (P> 0.05, Repeated-measures ANOVA). The medial femoral condyle moved backward (1.8 and 1.5 mm respectively in MG and Oxford) from zero degrees to 30° of flexion. At 60°, it moved anteriorly in both knees, in MG to 0.9 mm anteriorly and in Oxford to 0.6 mm posteriorly to the reference position. At 90° the condyle moved 4.2 mm (MG) and 0.7 mm (Oxford) anteriorly to the reference position. No significant difference between the groups (P> 0.05). The femur-tibia contact point in MG moved anteriorly 2.8, 5.1, and 3.9 mm, respectively at 30°, 60°, and 90° of flexion, whereas the contact point in Oxford moved posteriorly 2.6, 1.8, 2.4 mm respectively at 30°, 60°, and 90°. A significant difference was found between the groups (P=0.003). The bearing in the Oxford implant moved backward of 2.2, 2.0, and 0.9 mm respectively at 30°, 60°, and 90° of knee flexion. Conclusions The in-vivo weight bearing 3D knee kinematics after UKA with fixed or mobile bearing was described. In MG the medial femoral condyle moved forward with knee flexion, whereas in Oxford it moved backward together with the bearing, which is closer to normal knee kinematics

Background. Current analysis of unicondylar knee replacements (UKR) by national registries is based on the pooled results of medial and lateral implants. Using data from the National Joint Registry for England and Wales (NJR) we aimed to determine the proportion of lateral UKR implanted, their survival and reason for failure in comparison to medial UKR. Methods. By combining information on the side of operation with component details held on the NJR we were able to determine implant laterality (medial vs. lateral) for 32,847 of the 35,624 (92%) UKR registered before December 2010. Kaplan Meier plots, Life tables and Cox' proportion hazards were used to compare the risk of failure for lateral and medial UKRs after adjustment for patient and implant covariates. Results. 2,052 (6%) UKR were inserted on the lateral side of the knee. The rates of survival at 5 years were 93.1% (95%CI 92.7 to 93.5) for medial and 93.0% (95%CI 91.1% to 94.9%) for lateral replacements (p=0.49). The rates of failure remained equivalent after adjustment for patient age, gender, ASA grade, indication for surgery and implant type using Cox's proportional hazards (HR=0.87, 95%CI 0.68 to 1.10, p=0.24). For medial implants covariates found to influence the risk of failure were patient age (p< 0.001) and ASA grade (p=0.04). Age similarly influenced the risk of failure for lateral UKRs. Implant design (Mobile versus Fixed bearing) did not influence the risk of failure in either the medial or lateral compartment. Aseptic loosening/lysis and unexplained pain were the main reasons for revision in both groups. Conclusion. The mid-term survival of medial and lateral UKRs are equivalent. This supports the on-going use of pooled data by registries for the reporting on unicondylar outcomes in the future

Background. In a mobile-bearing unicondylar knee arthroplasty (UKA) stability is very important for the knee function and to prevent dislocation of the insert. A tension-guided technique to determine the position of the optimal posterior bone cut should theoretically lead to a better varus-valgus stability. The goal of this study was to measure the difference in valgus laxity in flexion and extension between a tension-guided and spacer-guided system for mobile-bearing UKA. Also clinical function was evaluated between the groups. Patients and Methods. A tension-guided UKA system (BalanSys. TM. , Mathys, Bettlach, Switzerland) was compared with a retrospective group of a spacer-guided system (Oxford, Biomet Ltd, Bridgend, UK). A total of 30 tension-guided UKAs were placed and compared to 35 spacer-guided prostheses. Valgus laxity was measured at least 6 months postoperatively in both groups using stress radiographs. The flexion stress radiographs were made fluoroscopically aided in 70 degrees of knee flexion. Laxity measurements in extension were performed on stress radiographs obtained with the Telos device. Knee Society Scores (KSS) were obtained at follow-up. Results. Valgus laxity in flexion was significantly higher in the tension-guided group compared to the spacer-guided group: 3.9° and 2.4°, respectively, p<0.001) In extension, valgus laxity was 1.8° in the tension-guided group compared to 2.7° in the spacer-guided group, which was significantly different (p<0.001). There was no significant difference between the two groups in the KSS at 6 months follow-up. (p=0.31). Discussion and conclusion. The tensor-guided system resulted in significantly more valgus laxity in flexion compared to the spacer-guided system. However, in extension the situation was reversed: the tension-guided system resulted in less valgus laxity than the spacer-guided system. Clinically, there were no differences between the groups. The valgus laxity found with the spacer-guided system better approximates the valgus laxity values of healthy elderly

The objective of this study was to determine if pre-operative gait patterns could predict which patients selected for unicondylar knee replacement (UKR) actually received a UKR or a total knee replacement (TKR). At the time of surgery, ten of the twenty-two UKR candidates presented with extensive degenerative changes and received total knee replacements. We analyzed gait, radiographic, and anthropometric data with a pattern recognition technique designed to detect biomechanical differences between the two groups. The groups were indistinguishable clinically, and radiographically, yet the pattern recognition technique identified features that completely separated the two groups based on the biomechanical differences. The objective of this study was to determine if pre-operative gait patterns could predict which patients selected for UKR actually received a UKR or a TKR. The UKR and TKR groups were indistinguishable visibly, clinically, and radiographically, yet the pattern recognition technique employed in this analysis identified features that completely separated the two groups. Biomechanical differences between the pre-operative groups could lead to more accurate diagnosis of unicompartmental knee OA as well as further understanding of the pathomechanics of knee OA. Twenty-two patients were initially diagnosed with unicompartmental knee OA of the medial side, and prescribed to receive unicompartmental knee replacements (UKR). At the time of surgery, ten of the twenty-two UKR candidates presented with more extensive degenerative changes and received total knee replacements (TKR). We measured gait data including knee joint angles forces and moments, velocity, stride length, stance percentage, and stance time as well as body mass index. Furthermore radiographic measures were taken including the Hip Knee Ankle (HKA) angle, the standing knee flexion angle, and the medial and lateral condyle joint spaces. The data were analysed using a pattern recognition technique that used principal component analysis to extract features from the data and discriminant analysis to separate the two groups. The discriminant function completely separated the UKR and TKR patients based on their pre-operative data. The most discriminatory feature represented a difference in early swing phase in the knee internal rotation moments

Survivorship of unicondylar knee replacement (UKR) exceeds 85% at 10 years. During long term follow-up, progressive osteoarthritis (OA) and loosening are typical of UKR failure. The decision to revise UKR is complex as radiographic findings are not always consistent with clinical symptoms. This study of revised UKR compares intraoperative assessment of component fixation and progressive OA with prerevision radiographic evaluations. Twenty-seven UKR were retrieved from 22 female and 5 male patients. Patient age and time in situ averaged 76 (68–87) years and 79 (25–156) months, respectively. At index arthroplasty, all knees received a fixed-bearing medial UKR with cement fixation. Prior to revision, radiolucent lines and component alignment were assessed on radiographs according to Knee Society guidelines. Suspected revision reasons based on clinical and radiographic evaluation included aseptic loosening (63%), progressive OA (22%), and wear (15%). During revision surgery, component fixation was manually assessed and graded as well-fixed or loose, and progressive OA was graded using Outerbridge classification. Intraoperative and radiographic assessments were completed independently. Average Knee Society Scores declined > 30 points to 53+18 (pain) and 43+11 (function) before revision. During revision surgery, femoral and tibial component fixation were graded as loose in 19 (70%) and 9 (33%) knees, respectively. There was Grade III or IV progressive OA in the lateral or patellofemoral compartment of 15 (56%) and 16 (59%) knees, respectively. Radiolucent lines were evident in 8 of 19 loose femoral components and 5 of 9 loose tibial components. In contrast, 3 of 8 well-fixed femoral components and 6 of 18 well-fixed tibial components had radiolucent lines. There were 11 loose femoral components and 4 loose tibial components without radiolucent lines. Radiographic limb alignment averaged 3°+3° valgus immediately after index UKR. Change in limb alignment ranged from 0° to 17° at revision. Tibial or femoral component alignment changed 5° to 9° in 12 (44%) knees and > 10° in 5 (19%) knees. Eight of these 17 knees (47%) had malaligned components graded as loose. The prevalence of progressive OA at revision UKR was more than double occurrence suspected from radiographs. Interpreting radiographic indications for loosening was difficult. Radiolucent lines predicted loosening in 46% (13/28) of the components graded as loose and falsely predicted loosening in 35% (9/26) of the components graded as well-fixed. Radiolucent lines were absent in 15/28 (54%) of the loose components and changes in component alignment > 5° were associated with component loosening in < 50% of the knees. Rigorous attention to clinical symptoms and careful interpretation of radiographic phenomena are needed to determine indications for revision in UKR patients

Purpose. The purpose of this study was to examine the progression of osteoarthritis (OA) on patella-femoral joint (PFJ) after open wedge high tibial osteotomy (OWHTO) and unicondylar knee arthroplasty (UKA) in correlation with pain and functional outcomes. Methods. We conducted a retrospective analysis of 101 knees (89 patients), which received an OWHTO in 42 knees and UKA in 59 knees between 2003 and 2008 with minimum 5-years follow-up. Preoperative and the last follow-up radiologic evaluations were performed on the specific radiographic parameters that reflect the patella and knee alignment. Progressions of OA on PFJ at pre-operation and the last follow up were assessed and compared with modified OA grading system. The patella-femoral (PF) pain and function score were recorded using modified PF scoring system at the last follow up. Results. Among the radiologic parameters, mechanical axis (MA) and lateral patella tilt (LPT) showed statistically significant differences between OWHTO and UKA. Most of cases showed no progression or just only 1 grade step-up progression on PFJ in both groups and the amount of progression showed no statistical significant between OWHTO and UKA. In comparison of the preoperative and the final follow-up OA grades, medial PFJ in UKA group showed statistically significant differences. The PF pain and function score were comparable in both groups at the final follow up which showed no statistical differences regardless of OA progression. Conclusions. Overall, 40 ∼ 70% of cases did not occurred the progression of OA in PFJ after OWHTO and UKA. Additionally, at last follow up, the most cases showed the grade 0 or 1 OA in PFJ of both groups. Compared with HTO group, in UKA group, there were tendency of more progression of PFJ compared with preoperative OA status. Finally the degree of OA progressions did not affect the PF pain and functional outcomes

Intramedullary (IM) femoral alignment guide for unicondylar knee arthroplasty (UKA) is a classic and generally accepted technique to treat unicompartmental knee osteoarthritis. However, IM system has a risk of excessive blood loss, fat embolism and activation of coagulation.Moreover, the implant placement and limb alignment may be less accurate in IM for UKA than total knee arthroplasty. So we try to use extramedullary (EM) femoral alignment for UKA to avoid above disadvantages. To our knowledge, few current studies have been reported by now. We reported a series of cases treated through a newly developed EM technique and evaluated the accuracy of femoral component alignment and preliminary clinical results. Between January 2009 and January 2010, 11 consecutive patients(15 knees)consisting of 8 males and 3 females were enrolled. There were 7 cases in unilateral knee and 4 cases in bilateral knees. The mean age was 65.2 years (range 60∼72 years). Incision, surgical time, blood loss and complications were measured. The pre- and post operative function of the knees were evaluated by HSS score system. The pre- and postoperative femoral component alignment was measured and compared. All cases were followed up for average 15 months (10-22 months). The mean length of incision was 7.2cm (range 6 to 8cm), the mean surgical time was 115.0min(range 90 to 125min),the mean blood loss was 50.8ml (range 50 to 80ml). The mean preoperative HSS score increased from 75 (range 63 to 83) to 95 (range 88 to 97) postoperatively (p<0.05). All femoral components were within the recommended range for varus/valgus (±10 degree) and lexion/extension (±5 degree) angle. None had complications associated with reamed canal injury. By using our EM technique, we could achieve an accurate femoral component alignment and satisfactory clinical effect. However, strict comparison between EM and cconventional IM technique and large amount of cases are essential. Further mid- and long-term studies are required

Current analysis of unicondylar knee replacements (UKRs) by national registries is based on the pooled results of medial and lateral implants. Consequently, little is known about the differential performance of medial and lateral replacements and the influence of each implant type within these pooled analyses. Using data from the National Joint Registry for England and Wales (NJR) we aimed to determine the proportion of UKRs implanted on the lateral side of the knee, and their survival and reason for failure compared with medial UKRs. By combining information on the side of operation with component details held on the NJR, we were able to determine implant laterality (medial versus lateral) for 32 847 of the 35 624 unicondylar replacements (92%) registered before December 2010. Of these, 2052 (6%) were inserted on the lateral side of the knee. The rates of survival at five years were 93.1% (95% confidence interval (CI) 92.7 to 93.5) for medial and 93.0% (95% CI 91.1 to 94.9) for lateral UKRs (p = 0.49). The rates of failure remained equivalent after adjusting for patient age, gender, American Society of Anesthesiologists (ASA) grade, indication for surgery and implant design using Cox’s proportional hazards method (hazard ratio for lateral relative to medial replacement = 0.88 (95% CI 0.69 to 1.13); p = 0.32). Aseptic loosening/lysis and unexplained pain were the main reasons for revision in both groups, although the reasons did vary depending on whether a mobile- or a fixed-bearing design was used. At a maximum of eight years the mid-term survival rates of medial and lateral UKRs are similar.

Introduction: Unicondylar knee arthroplasty (UKA) has seen a resurgence in the past decade. Perpetuation of this trend can only be supported through prospective demonstration of efficacy with validated outcomes measures. Materials & Methods: Thirty-three consecutive cemented medial Miller-Galante UKA’s (Zimmer, Warsaw, IN) were performed in 32 patients (7 males/25 females; mean age of 67 ± 9 years). Average weight, height, and body mass index (BMI) of the patient population was 189 ± 31 lbs (Range, 145–293), 65 ± 4 in (range, 60–75), and 33 ± 5 BMI (range, 25–43), respectively. Average polyethylene thickness (as labelled) for this cohort was 8.3mm (range, 8–12mm). Outcomes were prospectively assessed via the SF-12, WOMAC, and Knee Society Score (KSS). No patients were lost to follow-up. Kaplan-Meier survivorship and Student’s t-test were performed using GraphPad Prism 4 software (GraphPad Software Inc., San Diego, CA). Results: Minimum follow-up was 39 months with a mean follow up period of 49 (range, 39–59) months. One knee was converted at 6 months at another institution to a TKA. Kaplan-Meier survivorship analysis reported 97% survivorship at 59 months (95% CI). Of the 32 knees remaining, mean preoperative KSS and WOMAC pain scores improved significantly from 52 ± 7 (range, 37–67) to 89 ± 9 (range, 67–100) (p< 0.0001) and from 40 ± 22 (range, 0–80) to 93 ± 14 (range, 35–100) (p< 0.0001), respectively. Additionally, average SF-12 Physical Component scores significantly increased from 30 ± 7 (range, 18–51) at baseline to 49 ± 10 (range, 28–59) at time of follow-up (p< 0.0001). Overall stiffness and physical function assessed via the WOMAC index also exhibited statistically significant improvement, bettering from mean baseline scores of 54 ± 24 (range, 0–100) and 52 ± 19 (range, 25–87) to 84 ± 19 (range, 50–100, p< 0.0001) and 88 ± 15 (range, 44–100, p< 0.0001), respectively. No significant cement/bone interface radiolucencies were found upon thorough radiographic review at 3 years post UKA. Discussion & Conclusion: The significant improvements observed in knee function & stiffness, and decreases in pain at a mean of 4 years after medial UKA are encouraging. Coinciding results from the physical component of the SF-12 assessment indicate reassurance of physical improvements regarding patient lifestyle. 97% survivorship in the short term would be discouraging if not for the specific circumstances of the sole conversion to TKA. This specific patient went against the advice of the operative surgeon and solicited services at an outside institution in conversion to a TKA despite markedly improved function (Pre-op/3 month post-op WOMAC and KSS of 30/75 and 60/91). Clinical and radiographic follow-up will continue in order to assess the long-term efficacy of medial UKA with the Miller-Galante prosthesis using strict patient selection criteria

Introduction

Both mobile bearing and fixed bearing unicompartmental knee arthroplasty (UKA) have demonstrated clinical success. However, much debate persists about the superiority of a single design. Currently most clinical data is based on high volume centers data, however to reduce bias, we undertook a through review of retrospective national joint registries. In this study, we aim to investigate UKA implant utilization and survivorship between 2000 and 2018.

Following arthroplasty of the knee, the patient’s perception of improvement in symptoms is fundamental to the assessment of outcome. Better clinical outcome may offset the inferior survival observed for some types of implant. By examining linked National Joint Registry (NJR) and patient-reported outcome measures (PROMs) data, we aimed to compare PROMs collected at a minimum of six months post-operatively for total (TKR: n = 23 393) and unicondylar knee replacements (UKR: n = 505). Improvements in knee-specific (Oxford knee score, OKS) and generic (EuroQol, EQ-5D) scores were compared and adjusted for case-mix differences using multiple regression. Whereas the improvements in the OKS and EQ-5D were significantly greater for TKR than for UKR, once adjustments were made for case-mix differences and pre-operative score, the improvements in the two scores were not significantly different. The adjusted mean differences in the improvement of OKS and EQ-5D were 0.0 (95% confidence interval (CI) -0.9 to 0.9; p = 0.96) and 0.009 (95% CI -0.034 to 0.015; p = 0.37), respectively.

We found no difference in the improvement of either knee-specific or general health outcomes between TKR and UKR in a large cohort of registry patients. With concerns about significantly higher revision rates for UKR observed in worldwide registries, we question the widespread use of an arthroplasty that does not confer a significant benefit in clinical outcome.

Introduction

With the introduction of minimally invasive surgery techniques and improved polyethylene wear properties, there has been a renewed interest in Unicondylar Knee Replacements (UKR). Customized, Individually Made (CIM) UKR have been in the market for some time, and have shown to provide improved coverage and fit. The purpose of this study was to assess clinical and patient-reported outcomes utilizing CIM-UKR prostheses.

Introduction:

Two fixed bearing options exist for tibial resurfacing when performing unicompartmental knee arthroplasty (UKA). Inlay components are polyethylene-only implants inserted into a carved pocket on the tibial surface, relying upon the subchondral bone to support the implant. Onlay components have a metal base plate and are placed on top of a flat tibial cut, supported by a rim of cortical bone. To our knowledge, there is no published report that compares the clinical outcomes of these two implants using a robotically controlled surgical technique. We performed a retrospective review of a single surgeon's experience with Inlay versus Onlay components, using a robotic-guided protocol.

Introduction

Historically, the outcomes of knee replacement were evaluated based on implant longevity, major complications and range of motion. Over the last recent years however, there has been an intensively growth of interest in the patient's perception of functional outcome. However, the currently used patient related outcome (PRO) scores are limited by ceiling effects which limit the possibility to distinguish between good and excellent results post knee arthroplasty. The Forgotten Joint Score (FJS) is a new PRO score which is not influenced by ceiling effects, therefore making it the ideal instrument to compare functional outcome between various types of implants. It is based on the thought that the ultimate goal in joint arthroplasty is the ability of a patient to forget their artificial joint in everyday life.

The aim of this study is to compare the FJS between patients who undergo TKA and patients who undergo medial UKA at least 12 months post-operatively. We hypothesized that the UKA which is less extensive surgical procedure will present better FJS than TKA, even 12 month postoperative.

Background: In a recent publication from the National Joint Registry it was suggested that prosthesis type influenced patient satisfaction at one year following knee arthroplasty. In this report Unicondylar Replacement (UKR) was associated with lower levels of patient satisfaction when compared to cemented TKR. The unicondylar group did however have a significantly lower Oxford Knee Score (OKS) than the TKR group and this occurred irrespective of patient age.

A common perception is that UKR is only offered to patients with lesser disease, with a decreased clinical profile. This may explain their higher levels of dissatisfaction as the overall change in their OKS from pre to post operation would be relatively smaller than for TKR.

Aim: We hypothesised that patients listed for UKR have less severe disease and therefore a lower preoperative OKS when compared to TKR.

Methods: After sample size calculation we retrospectively analysed 76 patients who underwent either UKR or TKR under the care of a single surgeon. OKS was recorded at a dedicated pre-assessment clinic. The decision to offer UKR was based on clinical and radiological criteria as outlined by the Oxford group.

Results: There were 38 patients in either group. The mean pre-operative OKS was 39.5 (26–56, SD 7.6) in the UKR group and 41.6 (31–51, SD 5.7) in the TKR group. There was no statistical difference between these two groups (p=0.18).

Discussion: Patients listed for knee replacement have significant pain and functional impairment. In our population those suitable for UKR have similarly severe symptoms to those who do not meet the criteria for UKR and are only eligible for TKR. It remains unclear why patients undergoing UKR should be less satisfied when they have better post operative patient reported outcome scores. It emphasizes the need for careful patient selection and counselling in patient undergoing UKR.

Introduction

Kneeling ability is better in unicompartmental than total knee arthroplasty. There is also an impression that mobile bearing knees achieve better functional outcome than their fixed bearing cousins in unicompartmental and to a lesser extent total joint arthroplasty. In the UK, the market leading unicompartmental replacement is mobile bearing.

Aims

The aim of this independent multicentre study was to assess the mid-term results of mobile bearing unicondylar knee arthroplasty (UKA) for isolated lateral osteoarthritis of the knee joint.

We present detailed information about early morbidity after aseptic revision knee replacement from a nationwide study. All aseptic revision knee replacements undertaken between 1st October 2009 and 30th September 2011 were analysed using the Danish National Patient Registry with additional information from the Danish Knee Arthroplasty Registry. The 1218 revisions involving 1165 patients were subdivided into total revisions, large partial revisions, partial revisions and revisions of unicondylar replacements (UKR revisions). The mean age was 65.0 years (27 to 94) and the median length of hospital stay was four days (interquartile range: 3 to 5), with a 90 days re-admission rate of 9.9%, re-operation rate of 3.5% and mortality rate of 0.2%. The age ranges of 51 to 55 years (p = 0.018), 76 to 80 years (p < 0.001) and ≥ 81 years (p < 0.001) were related to an increased risk of re-admission. The age ranges of 76 to 80 years (p = 0.018) and the large partial revision subgroup (p = 0.073) were related to an increased risk of re-operation. The ages from 76 to 80 years (p < 0.001), age ≥ 81 years (p < 0.001) and surgical time > 120 min (p <  0.001) were related to increased length of hospital stay, whereas the use of a tourniquet (p = 0.008) and surgery in a low volume centre (p = 0.013) were related to shorter length of stay.

In conclusion, we found a similar incidence of early post-operative morbidity after aseptic knee revisions as has been reported after primary procedures. This suggests that a length of hospital stay ≤ four days and discharge home at that time is safe following aseptic knee revision surgery in Denmark.

Cite this article: Bone Joint J 2014;96-B:1649–56.

Aims. The aim of this study was to determine the risk of tibial eminence avulsion intraoperatively for bi-unicondylar knee arthroplasty (Bi-UKA), with consideration of the effect of implant positioning, overstuffing, and sex, compared to the risk for isolated medial unicondylar knee arthroplasty (UKA-M) and bicruciate-retaining total knee arthroplasty (BCR-TKA). Methods. Two experimentally validated finite element models of tibia were implanted with UKA-M, Bi-UKA, and BCR-TKA. Intraoperative loads were applied through the condyles, anterior cruciate ligament (ACL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), and the risk of fracture (ROF) was evaluated in the spine as the ratio of the 95. th. percentile maximum principal elastic strains over the tensile yield strain of proximal tibial bone. Results. Peak tensile strains occurred on the anterior portion of the medial sagittal cut in all simulations. Lateral translation of the medial implant in Bi-UKA had the largest increase in ROF of any of the implant positions (43%). Overstuffing the joint by 2 mm had a much larger effect, resulting in a six-fold increase in ROF. Bi-UKA had ~10% increased ROF compared to UKA-M for both the male and female models, although the smaller, less dense female model had a 1.4 times greater ROF compared to the male model. Removal of anterior bone akin to BCR-TKA doubled ROF compared to Bi-UKA. Conclusion. Tibial eminence avulsion fracture has a similar risk associated with Bi-UKA to UKA-M. The risk is higher for smaller and less dense tibiae. To minimize risk, it is most important to avoid overstuffing the joint, followed by correctly positioning the medial implant, taking care not to narrow the bone island anteriorly. Cite this article: Bone Joint Res 2022;11(8):575–584

The December 2023 Knee Roundup. 360. looks at: Obesity is associated with greater improvement in patient-reported outcomes following primary total knee arthroplasty; Does mild flexion of the femoral prosthesis in total knee arthroplasty result in better early postoperative outcomes?; Robotic or manual total knee arthroplasty: a randomized controlled trial; Patient-relevant outcomes following first revision total knee arthroplasty, by diagnosis: an analysis of implant survivorship, mortality, serious medical complications, and patient-reported outcome measures using the National Joint Registry data set; Sagittal alignment in total knee arthroplasty: are there any discrepancies between robotic-assisted and manual axis orientation?; Tourniquet use does not impact recovery trajectory in total knee arthroplasty; Impact of proximal tibial varus anatomy on survivorship after medial unicondylar knee arthroplasty; Bone cement directly to the implant in primary total knee arthroplasty?; Maintaining joint line obliquity optimizes outcomes in patients with constitutionally varus knees

The June 2024 Knee Roundup. 360. looks at: The estimated lifetime risk of revision after primary knee arthroplasty influenced by age, sex, and indication; Should high-risk patients seek out care from high-volume surgeons?; Stability and fracture rates in medial unicondylar knee arthroplasties; Rethinking antibiotic prophylaxis for dental procedures post-arthroplasty; Evaluating DAIR: a viable alternative for acute periprosthetic joint infection; The characteristics and predictors of mortality in periprosthetic fractures around the knee; Patient health-related quality of life deteriorates significantly while waiting six to 12 months for total hip or knee arthroplasty; The importance of looking for diversity in knee implants

Introduction. The purpose of this study was to characterize the recovery of physical activity following knee arthroplasty by means of step counts and flight counts (flights of stairs) measured using a smartphone-based care platform. Methods. This is a secondary data analysis on the treatment cohort of a multicenter prospective trial evaluating the use of a smartphone-based care platform for primary total and unicondylar joint arthroplasty. Participants in the treatment arm that underwent primary total or unicondylar knee arthroplasty and had at least 3 months of follow-up were included (n=367). Participants were provided the app with an associated smart watch for measuring several different health measures including daily step and flight counts. These measures were monitored preoperatively, and the following postoperative intervals were selected for review: 2–4 days, 1 month, 1.5 month, 3 months and 6 months. The data are presented as mean, standard deviation, median, and interquartile range (IQR). Signed rank tests were used to assess the difference in average of daily step counts over time. As not all patients reported having multiple stairs at home, a separate analysis was also performed on average flights of stairs (n=214). A sub-study was performed to evaluate patients who returned to preoperative levels at 1.5 months (step count) and 3 months (flight count) using an independent samples T test or Fisher's Exact test was to compare demographics between patients that returned to preoperative levels and those that did not. Results. The mean age of the step count population was 63.1 ± 8.3 years and 64.31% were female, 35.69% were male. The mean body mass index was 31.1 ± 5.9 kg/m. 2. For those who reported multiple stairs at home, the mean age was 62.6 ± 8.3 years and 62.3% were female. The mean body mass index was 30.7 ± 5.4 kg/m. 2. . As expected, the immediate post-op (2–4 days) step count (median 1257.5 steps, IQR 523 – 2267) was significantly lower than preop (median 4160 steps, IQR 2669 – 6034, p < 0.001). Approximately 50% of patients returned to preoperative step counts by 1.5 months postoperatively with a median 4,504 steps (IQR, 2711, 6121, p=0.8230, Figure 1). Improvements in step count continued throughout the remainder of follow-up with the 6-month follow-up visit (median 5517 steps, IQR 3888 – 7279) showing the greatest magnitude (p<0.001). In patients who reported stairs in their homes, approximately 64% of subjects returned to pre-op flight counts by 3 months (p=0.085), followed similar trends with significant improvements at 6 months (p=0.003). Finally, there was no difference in age, sex, BMI, or operative knee between those that returned to mean preoperative step or flight counts by 1.5 months and 3 months, respectively. Discussion and Conclusion. These data demonstrated a recovery curve similar to previously reported curves for patient reported outcome measures in the arthroplasty arena. Patients and surgeons may use this information to help set goals for recovery following total and unicondylar knee arthroplasty using objective activity measures. For any figures or tables, please contact the authors directly

Abstract. Introduction. Patient selection is key to the success of medial unicondylar knee arthroplasty (UKA). Progression of arthritis is the most common indication for revision. Various methods of assessing the lateral compartment have been used including stress radiography, radioisotope bone scanning, MRI, and visualisation at the time of surgery. Arthroscopy is another means of assessing the integrity of the lateral compartment. Methods. We used per-operative arthroscopy as a means to confirm suitability for UKA in a consecutive series of 279 Oxford medial UKA. This study reports the long-term results of a previously published cohort of knees. Our series of UKA with per-operative arthroscopy (Group 1) was compared to all Oxford UKA (Group 2) and all UKA in the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) (Group 3). Results. The 14-year cumulative percentage revision (CPR) was 18.5% (95% CI 12.7, 26.4) for group 1, 19.7% (95% CI 18.8, 20.6) for group 2, and 19.2% (95% CI 18.5, 19.8) for group 3. There was no statistically significant difference in the (CPR) for the entire period when group 1 was compared to groups 2 or 3. Progression of arthritis was the indication for revision in similar proportions for the three groups (Group 1: 32.3%, Group 2: 35.7% and Group 3: 33.5%). Following per-operative arthroscopy 21.6% (77/356) of knees underwent a change of surgical plan from UKA to TKA. Conclusion. Per-operative arthroscopy may improve medium-term medial unicompartmental knee survivorship but does not improve long-term survivorship nor reduce revision due to progression of arthritis

Abstract. Background. The use of tourniquet in knee arthroplasty is common but in recent times, it has initiated a debate on its use. Complications from use of tourniquet are well documented in literature but there is less evidence on thigh pain, blood loss and length of stay post arthroplasty. Methods. We included 62 patients undergoing knee arthroplasty either Unicondylar knee arthroplasty or total knee arthroplasty. Patients were allocated randomly in tourniquet and without tourniquet groups. Half of the patients had UKA and other half TKA. Thigh pain was recorded using Visual analogue scale on day 1, 2 and on discharge. A drop in pre-operative and post operative haemoglobin level was recorded too. Independent sample t-test was done to compare the difference between the 2 groups mainly, drop in haemoglobin, thigh pain, knee pain and length of stay. Results. The mean drop in haemoglobin was comparable and was not statistically significant. Thigh pain on day 1 in no tourniquet group had a mean value of 0 and statistically significant difference in thigh pain at day 1,2 and discharge. In subgroup analysis between TKA and UKA the latter had improved results. Conclusions. Knee arthroplasty surgery without the use of tourniquet provides less thigh pain in the post-operative period and there isn't any significant difference in post op haemoglobin drop. None of the patient required any blood transfusion. A trend of early discharge was noted too but probably due to sample size, it wasn't statistically significant

Background: Unicondylar knee arthroplasty (UKA) are being expanded to include younger patients with more active lifestyles because of its minimally invasive nature. Prior to expanding this role, it is important to examine mode of failure and implication of conversion to TKA in the low demand elderly patients. Aim: To ascertain the modes of early failure of unicondylar knee Arthroplasty and assess whether the conversion to TKA improved the functional scores, range of motion, pain, and patient satisfaction. Method: A retrospective study to evaluate the results of 14 revision procedures after failed unicompartmental knee arthroplasty (UKA). Patients’ operative charts were reviewed. Details of modes of failure, technical difficulty of revision including exposure, component removal, and management of bone loss were noted. Post operative functional outcome was assessed using WOMAC osteoarthritis index and SF-36. Result: Total of 106 primary unicondylar knee arthroplasty procedures was performed between 2003 and 2007 in our institution. Oxford unicondylar implant was used in all patients. 13.21% of these were revised to total knee replacement. Revisions were performed 4 months to 36 months after the primary procedure; 86% of these were required within the first 12 months. The average time to failure was 15.6 months. The modes of failure were aseptic loosening (4), progression of osteoarthritis (2), instability (3), infection (2), dislocated insert (1) and persistent pain after UKA (2). Tibia insert exchange was done in one patient and the rest were converted to primary Scorpio and PFC components. Three of the patients had significant defect in femoral condyle. Fourteen percent of cases required femoral stem extension or metal wedge augmentation. Nine of the 14 knees (64%) were followed up for an average of 15 months. The mean WOMAC and SF-36 scores at latest follow up were 33.33 and 63.79 respectively. Conclusion: Despite the advantage of minimally invasive UKA, early failure can occur in the face of good surgical technique. The higher long-term success rate claimed by implant manufacturer is challengeable and patient should be informed during consent

Introduction. Recent advances in algorithms developed with passively collected sensor data from smart phones and watches demonstrate new, objective, metrics with the capacity to show qualitative gait characteristics. The purpose of this feasibility study was to assess the recovery of gait quality following primary total hip and knee arthroplasty collected using a smartphone-based care platform. Methods. A secondary data analysis of an IRB approved multicenter prospective trial evaluating the use of a smartphone-based care platform for primary total knee arthroplasty (TKA, n=88), unicondylar knee arthroplasty (UKA, n=28), and total hip arthroplasty (THA, n=82). Subjects were followed from 6 weeks preoperative to 24 weeks postoperative. The group was comprised of 117 females and 81 males with a mean age of 61.4 and BMI of 30.7. Signals were collected from the participants' smartphones. These signals were used to estimate gait quality according to walking speed, step length, and timing asymmetry. Post-operative measures were compared to preoperative baseline levels using a Signed-Rank test (p<0.05). Results. Mean walking speeds were lowest at postoperative week 2 for all three procedures (p<.001). The TKA population stabilized to preoperative speeds by week 17. For UKA cases, mean walking speeds rebounded to preoperative speed consistently by week 9 (p>.05). THA cases returned to preoperative walking speeds with a stable rebound starting at week 6 (p>.05), and improvement was seen at week 14 (p=.025). The average weekly step length was lowest in postoperative week 2 for both TKA and UKA (p<.001), and at week 3 for THA (p<.001). The TKA population rebounded to preoperative step lengths at week 9 (p=0.109), UKA cases at week 7 (p=.123), and THA cases by week 6 (p=.946). For TKA subjects, the change in average weekly gait asymmetry peaked at week 2 postoperatively (p <0.001), returning to baseline symmetry by week 13 (p=.161). For UKA cases, mean gait asymmetry also reached its maximum at week 2 (p =.006), returning to baseline beginning at week 7 (p=0.057). For THA cases mean asymmetry reached its maximum in week 2 (p <0.001) and was returned to baseline values at week 6 (p=.150). Discussion and Conclusion. Monitoring gait quality in real-world patient care following hip and knee arthroplasty using smart phone technology demonstrated recovery curves similar to previously reported curves captured by traditional gait analysis methods and patient reported outcome scores. Capturing such real-world gait quality metrics passively through the phone may also provide the advantage of removing the Hawthorne effect related to typical gait assessments and in-clinic observations, leading to a more accurate picture of patient function

Introduction and Aims: A significant proportion of patients currently undergoing total knee arthroplasty have uni-compartmental disease. Unicondylar knee replacement (UKA) offers the benefits of less bone resection and better soft tissue retention. However, knee kinematic changes after UKA have not been established. Method: A significant proportion of patients currently undergoing total knee arthroplasty have uni-compartmental disease. Unicondylar knee replacement (UKA) offers the benefits of less bone resection and better soft tissue retention. However, knee kinematic changes after UKA have not been established. Results: In the normal knee, knee flexion was accompanied by femoral rollback and tibial internal rotation. Similar patterns of rollback and rotation were seen after UKA. Surprisingly, resecting the ACL did not affect rollback or tibial rotation. However, tibial rotation was significantly different and was more variable after TKA. This suggests that loss of the ACL may not be the major cause of abnormal kinematics after TKA. Conclusion: Abnormal kinematics have been previously reported after TKA. However, UKA appeared to maintain normal kinematics. This study reported kinematic advantages to UKA, in addition to less bone resection and better recovery

Background. The purpose of this study is to evaluate the early perioperative outcomes after primary knee arthroplasty with the use of a smartphone-based exercise and educational platform compared to a standard of care control group. Methods. A multicenter prospective randomized control trial was conducted evaluating the use of the mymobility smartphone-based care platform for primary total knee arthroplasty (TKA) and unicondylar knee arthroplasty (UKA). Patients in the control group (224 patients) received the respective institution's standard of care typically with formal physical therapy. Those randomized to mymobility treatment group (192 patients) were provided an Apple Watch and mymobility smartphone application. The treatment group was not initially prescribed physical therapy, but could if their surgeon determined it necessary. Early outcomes assessed included 90-day knee range of motion, KOOS Jr scores, 30-day single leg stance (SLS) time, Time up and Go (TUG) time and need for manipulation under anesthesia (MUA). There was no significant difference in age, BMI or gender between groups. Results. The 90-day knee flexion was not significantly different between controls (118.3±11.8) and mymobility (118.8 ±12) (p=0.7), nor was knee extension (1.6 ±3.5 vs. 1 ±3.1, p=0.16). KOOS Jr scores were not significantly different between control group (74 ±13.1) and mymobility group (71 ±13.3) (p=0.06). 30-day SLS was 22.3 ± 19.5 sec in controls and 24 ± 20.8 sec in mymobility (p=0.2). 30-day TUG times were 16 ± 44.3 sec in control and 15 ± 40.6 sec in mymobility (p=0.84). MUAs were performed in 4.02% of patients in the control group and 2.8% in the mymobility group (p=0.4%). Conclusion. The use of the mymobility care platform demonstrated similar early outcomes to traditional care models, while providing communication and insights into patient engagement with the care plan. There was no significant difference in 90-day range of motion or need for MUA

Aim of the Study: Evaluation of differences in pro-prioception, gait analysis, electromyography in consideration of clinical results in patients with unicondylar and bicondylar knee arthroplasty. Material and Methods: 17 patients with mean age of 62.5 years were examined after a mean time of 21.5 months after unicondylar knee arthroplasty and compared with 15 patients with a mean age of 67 years and a mean time of 31.9 months after bicondylar knee arthroplasty. For clinical examination the Knee Society, Hospital for Special Surgery and Patella Score were used. Proprioception was examined using the Balance test. In addition each patient was examined by gait analysis with three-dimensional-kinematics and force plate. M. rectus femoris, M. vastus medialis/lateralis, M. semiten-dinosus, M. biceps femoris, M. tibialis anterior and M. gastrocnemius were examined by electromyography. Results: There were neither significant deviations in demographic data, clinical scores, electromyography results (except M. vastus lateralis), gait analysis nor in proprioception. Conclusion: There were no deviations in any clinical or functional results in patients with unicondylar and bicon-dylar knee arthroplasty. Because of the uncertain long term results of unicondylar knee arthroplasty in respect of loosening and development of contralateral osteoarthritis, bicondylar knee arthroplasty can be approved

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/m. 2. 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

Introduction. Precision Freehand Sculpting(PFS), is a hand-held semi-active robotic technology for bone shaping that works within the surgical navigation framework. PFS can alternate between two control modes – one based on control of exposure of the cutting bur (“Exposure Control”) and another based on the control of the speed of the cutting bur (“Speed Control”). In this study we evaluate the performance of PFS in preparing the femoral bone surface for unicondylar knee replacement (UKR). Methods. The experiment is designed to prepare a synthetic bone for unicondylar knee replacement (UKR). The implant plan is mapped to individual specimen using a jig that fit in a unique and repeatable way to all specimens. During bone preparation, the PFS handpiece and the specimen are both tracked with the Polaris Spectra (Northern Digital Inc.) using passive reflective markers. The cutting plan is specified so that the specimens can receive a specially designed implant after the cut is finished. The implant is a modified commercial design with three planar back faces and two pegs. In addition there are 10 conical divots on the implant surface that can be used to register the implant after it is placed on the prepared bone surface. The distal and distal-anterior facets were cut with a 5 mm cylindrical bur using Extension Control. The posterior facet and the post holes were cut using 6 mm spherical bur using Speed Control. Three subjects cut 5 specimens each. One subject was an experienced PFS user. The second user was somewhat less experienced, and the third user was completely inexperienced with the use of PFS. The performance was evaluated in terms of the implant fit and the performance time. The final implant fit was characterized using a MicroScribe MX desktop coordinate measuring arm. Results. The average cut times for the first two cuts combined were 4:45 min, and for the posterior cut 3:26 min. The average distances/st.dev. from the planned implant position were 0.54 /0.23 mm and the angular differences were average/st.dev. of 1.08/ 0.53 degrees. Conclusions. All specimens were cut accurately, and with clinically acceptable surface finish. No implants were significantly malpositioned, nor were any unable to be positioned due to poor fit or planar malalignment. For both experienced users, the procedure times were short, averaging below 8 min, whereas the inexperienced user demonstrated rapid improvement in performance time

We identified 148 patients who had undergone a revision total knee replacement using a single implant system between 1990 and 2000. Of these 18 patients had died, six had developed a peri-prosthetic fracture and ten had incomplete records or radiographs. This left 114 with prospectively-collected radiographs and Bristol knee scores available for study. The height of the joint line before and after revision total knee replacement was measured and classified as either restored to within 5 mm of the pre-operative height or elevated if it was positioned more than 5 mm above the pre-operative height. The joint line was elevated in 41 knees (36%) and restored in 73 (64%). Revision surgery significantly improved the mean Bristol knee score from 41.1 (. sd. 15.9) pre-operatively to 80.5 (. sd. 15) post-operatively (p < 0.001). At one year post-operatively both the total Bristol knee score and its functional component were significantly better in the restored group than in the elevated group (p < 0.01). Overall, revision from a unicondylar knee replacement required less use of bone graft, fewer component augments, restored the joint line more often and gave a significantly better total Bristol knee score (p < 0.02) and functional score (p < 0.01) than revision from total knee replacement. Our findings show that restoration of the joint line at revision total knee replacement gives a significantly better result than leaving it unrestored by more than 5 mm. We recommend the greater use of distal femoral augments to help to achieve this goal

Introduction: The optimal treatment of osteoarthritis of the medial compartment of the knee joint is still controversial. Optional procedures include arthroscopic knee debriedement, high tibial osteotomy, and total knee arthroplasty. In the last decade the use of unicompart-mental knee arthroplasty (UKA) for localized knee arthritis has become more and more common. This study reviews our experience with unicondylar meniscal bearing knee arthroplasty in patients with localized osteoarthritis of the medial compartment of the knee joint. Material & Methods: Between 2001–2004, 26 Pts. (17F, 9M; 52–74 year old, mean 63Y) underwent surgery using the Medial Oxford Unicompartmental Knee. Four of them had since been operated on their other knee, usually 1–2 years after the first UKA. The mean age at surgery was 63 years (52–74). There were 17 women and 9 males. All patients had a stable knee and their preoperative ROM was between −10 degrees to full extension and between 100 to 120 degrees of flexion. Patients were followed for 1.5 – 4 years (mean 2.5Y), and evaluated by the Knee Society Score and radiographs. Results: 24/26 (92%) patients, including the four patients who had staged bilateral procedures of both knees, had satisfactory results, of them 16/26 (61%) had excellent results and 8/26 (31%) had good results. They were almost free of pain, and most of them had marked improvement in knee function. Similar results were observed in each of both knees of the patients who had staged bilateral unicondylar knee arthroplasty. The remaining 2 patients (8%) had fair results. A second look arthroscopy of these patients revealed a progressive development of degenerative changes of the lateral compartment in one patient, and development of degenerative changes of the patella and patellar groove in the second patient. Conclusions: Based on this study it seems that unicondylar knee arthroplasty is a favourable procedure in patients with localised arthritis of the medial compartment. This procedure allows replacement of only the affected joint compartment with less bone loss, and therefore enables preservation of healthy tissue and bone. Recovery following surgery is fast, rehabilitation is quick and ambulation is early. The ideal patient for UKA is a relatively young patient with localized degenerative changes, who has a stable knee, a flexion contracture less than 15 degrees and a mechanical axis of less than 10 degrees from neutral for a varus knee, or less than 5 degrees for a valgus knee