Introduction. Early complication post total knee replacement reported to be higher in obese patient in general. Also the outcome of cruciate retaining and PS knee has been fully discussed before and there was no major difference in the outcome. However, the purpose of this paper is to find out if early complication postTKR such as fracture and instability is more common in PS implant than in CR knee. This is a retrospective study comparing two groups of obese patients. The first using PS implant and the other using CR implant. These two groups were matched for age, body mass and severity of deformity. We clearly showed that there is significant increase in peri-prosthetic fracture and instability in the group that use PS implant. Materials & Methods. At our institution we have been using Persona implant which has the option of using PS insert or a CR. The decision to proceed with CR or PS mainly depends on the availability of the implant and also the ability to well balance the knee in patients. In most patients we try to proceed with CR implant. However, the flow of implant sometime sometimes limit us from using CR or the imbalance in the ligament force us to process with PS implant. We have reviewed a chart of over 200 patients in each group of obese patient they were done within the last three years. All cases had a minimum follow up of 6 months. Those groups were matched for body mass, age and severity of deformity. After matching the groups we documented knee score, blood loss, post – operative pain and complications. All surgeries were performed by the same surgeon. Results. We had 7 cases of per-prosthetic fracture in the PS group and non in the CR implant. We had 3 revisions in the PS group for instability and MCL insufficiency. We had non in the CR implant. Infection, wound complication, blood loss, knee score and patient satisfaction were same in both groups. Discussion. Our study clearly show that the decrease incidence of peri-prosthetic fracture in the CR implant which could be easily explained by the fact that a good cortical bone is resected in order to make room for the PS spine. Also, the fact that resecting the posterior cruciate ligament might cause more stress on the implant versus the CR. Instability also were more common in the PS group. We believe this has to do with the fact that the PCL serve as a secondary constraint to the MCL. The presence of the PCL help maintain the stability in case of incidental injury to the MCL during surgery which was reported to be higher in obese patients. Practically the same in both group shows there is no apparent advantage of either implant. Conclusion. There is clear advantage of decreasing the early postoperative complications in obese patient using CR knee and we strongly recommend using CR implant in obese patients in order to reduce the incidence of peri-prosthetic fracture and the revision for instability

Introduction. Early complication post total knee replacement reported to be higher in obese patient in general. Also the outcome of cruciate retaining and PS knee has been fully discussed before and there was no major difference in the outcomes for all the patients overall regardless of their weight. However, the purpose of this paper is to find out if the CR knee has superiority over PS knee in terms of clinical and functional outcomes and if early complication postTKR such as fracture and instability is more common in PS implant than in CR knee. This is a retrospective study comparing two groups of obese patients. The first using PS implant and the other using CR implant. These two groups were matched for age, body mass and severity of deformity. Materials & Methods. At our institution we have been using Persona implant which has the option of using PS insert or a CR. The decision to proceed with CR or PS mainly depends on the availability of the implant and also the ability to well balance the knee in patients. In most patients we try to proceed with CR implant. However, the flow of implant sometime sometimes limit us from using CR or the imbalance in the ligament force us to process with PS implant. We have reviewed a chart of over 200 patients in each group of obese patient they were done within the last three years. All cases had a minimum follow up of 6 months. Those groups were matched for body mass, age and severity of deformity. After matching the groups we documented Knee Society Score (KSS), Knee Society Function Score (KSFS), blood loss, post – operative pain and complications. All surgeries were performed by the same surgeon. Results. Our study showed that the clinical scores (KSS) in both groups were very close while significant differences were observed in functional scores (KSFS) for the CR knee. We had 8 cases of per-prosthetic fracture in the PS group and one in the CR implant. We had 4 revisions in the PS group for instability and MCL insufficiency and non in the CR implant. Infection, wound complication, blood loss, and patient satisfaction were same in both groups. Discussion. This study suggests a significant difference in functional outcomes, especially walking, stair climbing and the use of walking aids, between CR and PS that favors CR implant which may be related to the CR knee retaining proprioception and ligaments tension with balance. In addition, PS knee have more varus-valgus and mid-flexion laxity than CR knee throughout the range of motion which appear clearly in obese patient. On the other hand, the study clearly shows that the decrease incidence of peri-prosthetic fracture in the CR implant which could be easily explained by the fact that a good cortical bone is resected in order to make room for the PS spine. Also, the fact that resecting the posterior cruciate ligament might cause more stress on the implant versus the CR. Instability also were more common in the PS group. We believe this has to do with the fact that the PCL serve as a secondary constraint to the MCL. The presence of the PCL help maintain the stability in case of incidental injury to the MCL during surgery which was reported to be higher in obese patients. Conclusion. There is clear advantage of improving the outcomes or knee scores and decreasing the early postoperative complications in obese patient using CR knee and we strongly recommend using CR implant in obese patients in order to restore functionality faster and reduce the incidence of peri-prosthetic fracture and the revision for instability

Background. In this study, we assessed implant survivorship, patient satisfaction, and patient-reported functional outcomes at two years for patients implanted with a customized, posterior stabilized knee replacement system. Methods. Ninety-three patients (100 knees) with the customized PS TKR were enrolled at two centers. Patients’ length of hospitalization and preoperative pain intensity were assessed. At a single time point follow-up, we assessed patient reported outcomes utilizing the KOOS Jr., satisfaction rates, implant survivorship, patients’ perception of their knee and their overall preference between the two knees, if they had their contralateral knee replaced with an off-the-shelf (OTS) implant. Results. At an average of 1.9-years implant survivorship was found to be 100%. From pre-op until time of follow-up, we observed an average decrease of 5.4 on the numeric pain rating scale. Satisfaction rate was found to be high with 90% of patients being satisfied or very satisfied and 88% of patients reporting a “natural” perception of their knee some or all the time. Patients with bilateral implants mostly (12/15) stated that they preferred their customized implant over the standard TKR. The evaluation of KOOS Jr. showed an average score of 90 at the time of the follow up. Conclusion. Based on our results, we believe that the customized PS implant provides patients with excellent outcomes post-surgery. Moreover, a subset of patients with an OTS implant in one knee and a customized PS implant in the other, we observed a trend in patients preferring the customized PS device over their OTS counterparts

Introduction. Large variations in knee kinematics existed after conventional TKA. Different design of TKA showed different intra-operative kinematics with navigation system. Purpose. The purpose of this study was to compare the kinematics of the three different types of prosthesis in navigation-based in vivo simulation. (Material and Method) Studies were carried out on 15 osteoarthritis Knees using the CT-free navigation system (Kolibri Knee, Brain LAB). Fourteen patients were female and one patient was male with mean age of 72 years. Five knees were implanted with the CR knee, 5 knees were implanted with the PS knee and 5 knees were implanted with PS mobile knee by navigated measured resection technique (PFC-sigma knee system, DePuy, Warsaw, IN). Intra-operative knee kinematics during passive range of motion from full extension to 130 degrees of knee flexion was measured after implantation while patella reduced and tourniquet released. While supporting the foot with one hand, the surgeon used his opposite hand to gently lift the thigh, flexing the hip and knee. Three types of prosthesis were compared for following factors: Presence of condylar lift-off (the gap difference greater than 1mm between medial gap and lateral gap) and anterior-posterior (AP) displacement of the center of femur relative to the tibia. Results. Lateral condylar lift-off was found in patients with the PS implant between 120° and 130° of flexion. Remaining two types of implant did not show the condyar lift-off (Fig. 1). The pattern of AP displacement showed the same manner in three implants. Femur moved anterior side form extension to 50∼55° of flexion, after that, femur moved posterior side to full flexion. The mean maximum anterior movement and angle in CR implant was 14mm @ 55°, PS implant was 17mm ï¼ 50° and PS-mobile implant was 17mm @ 55°. The mean maximum posterior movement @ 130°, CR implant was −10.5mm, PS implant was −8.3mm and PS-mobile implant was −6.9mm. There was no significant difference among three groups. Discussion. In CR implant, the function of PCL could influence to prevent the condyar lift-off. In PS-mobile implant, the mechanism of rotation platform might have contributed to prevent the condylar lift-off. The paradoxical anterior slide of the femoral condyles during mid flexion was observed in all types of implant. We could not find any difference in AP displacement of these 3 types of prosthesis

INTRODUCTION. Applying the proper amount of tension to knees collateral ligaments during surgery is a prerequisite to achieve optimal performance after TKA. It must be taken into account that lower values of ligament tension could lead to an instable joint while higher values could induce over-tensioning thus leading to problems at later follow-up: a “functional stability” must then be defined and achieved to guarantee the best results. In this study, an experimental cadaveric activity was performed to measure the minimum tension required to achieve functional stability in the knee joint. METHODS. Ten cadaveric knee specimens were investigated; each femur and tibia was fixed with polyurethane foam in specific designed 3D-printed fixtures and clamped to a loading frame. A constant displacement rate of 0.05 mm/s was applied to the femoral clamp in order to achieve joint stability and the relative force was measured by the machine: the lowest force guaranteeing joint stability was then determined to be the one corresponding to the slope change in the force/displacement curve, representing the activation of the elastic region of both collateral ligaments. The force span between the slack region and the found point was considered to be the tension required to reach the functional stability of the joint. This methodology was applied on intact knee, after ACL-resection and after further PCL-resection in order to simulate the knee behavior in CR and PS implants. The test was performed at 0, 30, 60 and 90° of flexion using a specifically designed device. Each configuration was analyzed three times for the sake of repeatability. RESULTS. Results demonstrated that an overall tension of 40–50N is sufficient to reach stability in native knee with intact cruciate ligaments. Similar values appear to be sufficient in an ACL-resected knee, while higher tension is required (up to 60N) for stability after ACL and PCL resection. Moreover, the tension required for stabilization was slightly higher at 60° of flexion compared to the one required at the other angles, reflecting thus the mid-flection instability behavior. DISCUSSION AND CONCLUSIONS. The results are in agreement to other experimental studies. 1,2. and show that the tensions necessary to stabilize a knee joint in different ligament conditions are way lower than the ones usually applied via tensioners nowadays. To reach functional stability, surgeons should consider such results intraoperatively to avoid laxity, mid-flexion instability or ligament over-tension

Introduction. The Flexible Nichidai Knee (FNK) System (Nakashima Medical, Japan) was designed to fit Asian knees. Especially, the posterior stabilized(PS) prosthesis was designed as semi-constrained posterior stabilized system that had a large tibial post and femoral articulation. We hypothesized that the semi-constrained PS implant design would have a positive influence on vivo kinematics after total knee arthroplasty (TKA). Materials and Methods. A total of 16 patients (21 knees) who had undergone TKA using PS implant were randomly recruited from our database. Of the 16 patients, all patients were women. Fourteen patients had osteoarthritis and 2 patients had rheumatoid arthritis. The average age was 72.3± 9.5 years, and the average postoperative duration was 23.4 ± 19.3 months. The subject performed sequential deep knee bends under WB from 0° to maximum flexion under fluoroscopic monitoring in the sagittal plane. Conversely, under NWB, the patient sat on a chair and was asked to perform active assisted knee flexion. To estimate spatial position and orientation of the artificial knee prosthesis, a 2D to 3D registration technique was used. We evaluated knee range of motion, femoral axial rotation relative to the tibial component, and anteroposterior translation of the femorotibial contact point for both medial and lateral sides. Closest distances between femoral cam and tibial post engagement were measured,. Results. Range of Motion. The mean full extension angle between femoral and tibial components, was −8.1±8.8°and −7.5±5.5°in WB and NWB, respectively. The mean maximum-flexion angle was 110.0±18.1°and 119.3±8.9°in WB and NWB, respectively. Femoral Axial Rotation. Fig.1 shows the mean degree of femoral axial rotation relative to the tibial components in WB and NWB. The femur was externally rotated 0.7±3.9°and 0.3±4.7°at 0° degree in WB and NWB, respectively. The external rotation increased to 4.8±5.2°and 6.2±5.9°at 120°flexion in WB and NWB, respectively. Anteroposterior Translation. The mean femorotibial contact point under WB and NWB was shown in Fig.2 for medial contact and Fig. 3 for lateral contact. Under WB, the mean medial contact point moved posteriorly from −1.6±2.0mm at 0° flexion. The point then moved gradually anteriorly with flexion to −9.3±1.5mm at 120°flexion. The mean lateral contact point moved posteriorly from −1.9±1.7mm at 0° flexion, and then moved anteriorly to at −8.9±2.7mm 120° flexion. Under NWB conditions, the mean medial contact point moved posteriorly from −1.1±1.8mm at 0° flexion. The point then moved gradually posteriorly with flexion to −6.6±2.8mm at 120° flexion. The mean lateral contact point in PS TKA moved posteriorly from −4.4±3.3mm at 0° flexion, and then moved posteriorly to −12.3±3.6mm at 120°flexion. Post-Cam Engagement. The mean knee flexion angle at initial post-cam engagement was 61.9 ± 15.9° under WB and 57.5 ± 16.0° under NWB. Discussion. Our study showed external rotation and bycondylar posterior rollback pattern in the entire range of knee flexion. The reason for this might be that the post cam design was high(20mm), which does not allow for high external rotation. The in vivo kinematics of the semi-constrained PS FNK prosthesis showed similar kinematic patterns due to the development concept of the implant design

Patellofemoral complaints are the common and nagging problem after total knee arthroplasty. Crepitus occurs in 5% to over 20% of knee arthroplasty procedures depending on the type of implant chosen. It is caused by periarticular scar formation with microscopic and gross findings indicating inflammatory fibrous hyperplasia. Crepitus if often asymptomatic and not painful, but in some cases can cause pain. Patella “Clunk Syndrome” is less common and represents when the peripatella scarring is abundant and forms a nodule which impinges and “catches” on the implant's intercondylar notch. Patella Clunk was more common with early PS designs due to short trochlear grooves with sharp transition into the intercondylar notch. Clunks are very infrequent with modern PS implants. This syndrome has been reported in CR implants as well. Thorough debridement of the synovium and scarring at the time of arthroplasty is thought to reduce the occurrence of crepitus and clunks. Larger patella with better coverage of the cut bone may also be helpful. The diagnosis can be made on history and physical exam. X-rays are also helpful to assess patella tracking. MRI or ultrasound can be used to identify and confirm the diagnosis, but this is not mandatory. Painful crepitus and clunk syndrome that fail conservative management of NSAIDS and physical therapy may require surgery. Both crepitus and clunk can be treated with arthroscopic removal of the peripatella scar. Patella maltracking should also be assessed and treated. While recurrence may occur, it is uncommon

Introduction & aims. Patient specific instrumentation (PSI) is a useful tool to execute pre-operatively planned surgical cuts and reduce the number of trays in surgery. Debate currently exists around improved accuracy, efficacy and patient outcomes when using PSI cutting guides compared to conventional instruments. Unicompartmental Knee Arthroplasty (UKA) revision to Total Knee Arthroplasty (TKA) represents a complex scenario in which traditional bone landmarks, and patient specific axes that are routinely utilised for component placement may no longer be easily identifiable with either conventional instruments or navigation. PSI guides are uniquely placed to solve this issue by allowing detailed analysis of the patient morphology outside the operating theatre. Here we present a tibia and femur PSI guide for TKA on patients with UKA. Method. Patients undergoing pre-operative planning received a full leg pass CT scan. Images are then segmented and landmarked to generate a patient specific model of the knee. The surgical cuts are planned according to surgeon preference. PSI guide models are planned to give the desired cut, then 3D printed and provided along with a bone model in surgery. PSI-bone and PSI-UKA contact areas are modified to fit the patient anatomy and allow safe placement and removal. The PSI-UKA contact area on the tibia is defined across the UKA tibial tray after the insert has been removed. Further contact is planned on the tibial eminence if it can be accurately segmented in the CT and the anterior superior tibia on the contralateral compartment, see example guide in Figure 1. Contact area on the femur is defined on the superior trochlear groove, native condyle, femur centre and femoral UKA component if it can be accurately segmented in the CT. Surgery was performed with a target of mechanical alignment using OMNI APEX PS implants (Raynham, MA). The guide was planned such that the OMNI cut block could be placed on the securing pins to translate the cut. Component alignment and resections values were calculated by registering the pre-operative bones and component geometries to post-operative CT images. Results. Four UKA to TKA surgeries have been performed using revision PSI guides. The maximum difference from planned to achieved component alignments are: Femoral valgus = 2.4â□°, Tibial varus = 2.5â□°, Femoral internal rotation = 3.6â□°, Femoral flexion = 5.1â□° and tibial slope = 2.9â□°, see boxplot of results in Figure 2. All median values are within 2.5â□° of the planned alignment. A further five cases are to be analysed. Conclusions. A PSI guide designed for UKR to TKR revision surgery has been successfully used in surgery with acceptable errors. A larger study must be performed to determine the reliability and reproducibility of the design and method over a wide range of patient anatomy and UKA imaging flare

Posterior stabilized (PS) total knee arthroplasty (TKA), wherein mechanical engagement of the femoral cam and tibial post prevents abnormal anterior sliding of the knee, is a proven surgical technique. However, many patients complain about abnormal clicking sensation, and several reports of severe wear and catastrophic failure of the tibial post have been published. In addition to posterior cam-post engagement during flexion, anterior engagement with femoral intercondylar notch can also occur during extension. The goal of this study was to use dynamic simulations to explore sensitivity of tibial post loading to implant design and alignment, across different activities. LifeModeler KneeSIM software was used to calculate tibial post contact forces for four contemporary PS implants (Triathlon PS, Stryker; Journey BCS and Legion PS, Smith & Nephew; LPS Flex, Zimmer Biomet). An average model of the knee, including cartilage and soft tissue insertion locations, created from MRI data of 40 knees was used to mount and align the component. The Triathlon femoral component was mounted with posterior and distal condylar tangency at: a) both medial and lateral condylar cartilage (anatomic alignment), b) at the medial condylar cartilage and perpendicular to mechanical axis (mechanical alignment with medial tangency), and c) at lateral condylar cartilage and perpendicular to mechanical axis (mechanical alignment with lateral tangency). The influence of implant design was assessed via simulations for the other implant systems with the femoral components aligned perpendicular to mechanical axis with lateral tangency. Five different activities were simulated. The anterior contact force was significantly smaller than the posterior contact force, but it varied noticeably with tibial insert slope and implant design. For Triathlon PS, during most activities anatomic alignment of the femoral component resulted in greater anterior contact force compared to mechanical alignment, but absolute magnitude of forces remained small (<100N). Mechanical alignment with medial tangency resulted in greater posterior contact force for deep knee bend and greater anterior force for chair sit activity. For all implants, peak posterior contact forces were greater for activities with greater peak knee flexion. The magnitude of posterior contact forces for the various implants was comparable to other reports in literature. Overall activity type, implant design and slope had greater impact on post loading than alignment method. Tibial insert slope was shown to be important for anterior post loading, but not for posterior post loading. Anatomic alignment could increase post loading with contemporary TKA systems. In the case of the specific design for which effect of alignment was evaluated, the changes in force magnitude with alignment were modest (<200N). Nonetheless, results of this study highlight the importance of evaluating the effect of different alignment approaches on tibial post loading

Many patients who undergo a total knee arthroplasty (TKA) wish to return to a more active lifestyle. The implant must be able to restore adequate muscle strength and function. However, this may not be a reality for some patients as quadriceps and hamstrings muscle activity may remain impaired following surgery. The purpose of this study was to compare muscle activity between patients implanted with a medial pivot (MP) or posterior stabilized (PS) implant and controls (CTRL) during ramp walking tasks. Fifteen patients were assigned to either a MP (n=9) or PS (n=6) TKA operated by the same surgeon. Nine months following surgery, the 15 patients along with nine CTRL patients completed motion and EMG analysis during level, ramp ascent & descent walking tasks. Wireless EMG electrodes were placed on six muscles: vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), semimembranosus (SM) muscles, gastrocnemius medial head (GM), and gastrocnemius lateral head (GL). Participants completed three trials of each condition. EMG data were processed for an entire gait cycle of the operated limb in the TKA groups, and for the dominant limb in the CTRL group. The maximum muscle activity achieved with each muscle during the level trial was used to normalize the ramp trials. The onset and offset of each muscle was determined using the approximated generalized likelihood ratio. Peak muscle activity (PeakLE), total muscle activity (iEMG), and muscle onsets/offsets were determined for each muscle for the ramp ascent and descent trials. Non-parametric Kruskal Wallace tests were used to test for statistical significance between groups with α=0.05. During the ramp up task, both MP and PS groups had significantly greater PeakLE and iEMG for the hamstring muscles compared to the CTRL, whereas the PS group had significantly greater PeakLE compared with the MP group for the SM muscle. During the ramp down task, both MP and PS groups had significantly greater PeakLE and iEMG for the SM and GL muscles compared to the CTRL. The PS group also had significantly greater iEMG for the BF and VM muscles compared to the CTRL. The MP group had a significantly earlier offset for the SM muscle compared to the CTRL. Stability in a cruciate removing TKA is partially controlled by the prosthetic design. During the ramp up task, the TKA groups compensated the tibial anterior translation by activating their hamstrings more and for a longer duration. The MP group required less hamstrings activation than the PS group. During the ramp down task, TKA patients stiffened their knee in order to stabilize the joint. The quadriceps, hamstrings and GL muscle were activated more and for a longer duration than the CTRL group to protect the tibial posterior translation. The PS group required greater BF and VM iEMG than the MP group. Even if surgery reduced pain, differences in muscle activity exist between TKA patients and healthy controls. The prosthetic design provides some stability to the knee, and the MP implant required less muscle activation than the PS implant to stabilize the knee joint

Introduction. John Insall described medial release to balance the varus knee; the release he described included releasing the superficial MCL in severe varus cases. However, this release can create instability in the knee. Furthermore, this conventional wisdom does not correct the actual pathology which normally exists at the joint line, and instead it focuses on the distal end of the ligament where there is no pathology. We have established a new protocol consisting of 5 steps to balance the varus knee without releasing the superficial MCL and we tried this algorithm on a series of 115 patients with varus deformity and compared it to the outcome with a similar group that we have performed earlier using the traditional Insall technique. Material and method. 115 TKR were performed by the same surgeon using Zimmer Persona implant in varus arthritic knees. The deformities ranged from 15 to 35 degrees. First, the bony resection was made using Persona instrumentation as recommended by the manufacturer. The sequential balancing was divided into 5 steps (we will show a short video demonstrating the surgical techniques for each step) as follows:. Step 1: Releasing of deep MCL Step 2: Excising of osteophyte. Step 3: Excising of scarred tissue in the posteromedial corner soft phytes Step 4: Excision of the posteromedial capsule in case of flexion contracture Step 5: Releasing the semi-membranous (in gross deformity). We used soft tissue tensioner to balance the medial and lateral gaps. When the gaps are balanced at early step, there was no need to carry on the other steps. We used only primary implant and we did not have to use any constrained implant. We have compared this group with a similar group matched for deformity from previous 2 years where the conventional medial release as described by Insall. Results. We could balance all knees without releasing the superficial MCL ligament as follows:. -In[H1] 31 cases, we were able to balance the knees performing step 1 and step 2 only. -In 35 cases, we had to do step three in addition to 1 and 2 to achieve balance of cases. -In 25 cases, we performed step 4- those cases had pre-operative flexion contracture. -We had to proceed to step 5 only in 14 cases. These patients had the worst deformity in the group. We have used primary TKR in all cases; in 83 cases, we used a CR implant and in the rest, we used PS implant. Comparing this to the earlier conventional release we had to use 11 CCK implant on severe cases. Patient satisfaction was better with the new algorithm group when compared with the traditional release. Preserving the superficial MCL allowed us to maintain stability post-operatively and allowed us to use minimum constraint such as CR in severe deformity. Discussion. Many literatures have confirmed that cutting superficial MCL causes major medial instability after TKA. Releasing or pie crusting the superficial MCL can cause MCL insufficiency. Our protocol enable the surgeon to tackle the pathology rather than take a short-cut and releasing the superficial MCL. Reserving the superficial MCL allowed us to use minimal constraint even in severe deformity of 40 degrees of varus deformity. The conventional release has resulted in some cases instability, forcing us to use higher constraint such as CCK. Conclusion. Although releasing the superficial MCL has been described in different ways in multiple literature, little attention has been paid to the pathology of the posteromedial corner. This paper clearly shows that the complex anatomy of the posteromedial corner require us to pay better attention and this paper present better algorithm reserving the superficial MCL and enabling us to correct the deformity and balancing the soft tissue without instability. We strongly recommend surgeons not to release the superficial MCL because this will create instability in some cases

The most recent Australian registry has a database of 547,407 knee arthroplasties, having added over 52,000 in 2016. Total knee arthroplasties (TKA) comprise 83.8%, revisions (RevTKA) 8.1% and “partials of all types” 8.1%. Since 2003, the percent of TKA has increased from 76.7%, RevTKA has stayed stable and partial replacements have declined from 14.5%. In the last year, however, TKA declined slightly. There is a slightly higher percentage of women (56.1%) undergoing TKA and this has remained very stable since 2003. Revision rates are slightly higher for men. Percentages of the youngest (<55) and oldest (>85) are small and stable. The 75–84 year olds have declined as 55–74 year olds have increased. This represents a gradual shift to earlier TKA surgery. More patella are resurfaced and this is a gradual trend with a cross over in 2010 when half were resurfaced. Computer navigation is progressively more popular and now accounts for almost 30% of cases. Cement fixation is also increasing and accounts for about 65% of cases. Crosslinked polyethylene is gradually replacing non crosslinked and in 2014 was used in 50% of cases. Revisions are performed most commonly for loosening and infection. Revision rates correlate directly with age. Loosening is the most common indication for revision in both genders, but males have a distinctly higher revision rate due to infection. Revision rates are slightly higher in all forms of mobile bearing than fixed bearing. Minimally constrained (cruciate retaining) devices are used in the majority of TKAs. Posterior stabilised implants are in slight decline, having peaked in about 2008–2010. Minimally constrained implants are in slight decline as medial pivot/medial congruent devices have been used more frequently. Revision rates are similar amongst all three implant types: PS implants are revised at a slightly higher rate. When an early Medial Pivot (MP) implant is excluded the newer version has better results. The reasons for revision are similar amongst all 3 groups with slightly higher loosening rates for PS designs. (Could this represent backside wear with older locking mechanisms, surface finish and non crosslinked poly?) The MP designs had slightly higher revision rates for “pain”, which is not recognised as a reasonable indication for revision. Revision rates are steadily higher for TKAs without patella resurfacing over 16 years, but the questions as to whether: i. the surgeries were secondary resurfacings or full revisions or ii. if secondary resurfacings eliminated pain are unknown. The combinations at greatest risk of revision were a posterior stabilised or medial pivot arthroplasty without patellar resurfacing. Cementless fixation leads to a higher revision rate. If age and computer navigation are evaluated in terms of revision rates, young patients with and without computer navigated arthroplasties failed at the highest rates, distinct from patients >65. However, if failure rates due only to loosening are evaluated, then computer navigation leads to a lower revision rate in the <65 group. This has been interpreted as the protective effect of better component position that only shows up in patients who use the arthroplasty more aggressively. Patient specific instrumentation (PSI) or Individual Designed Instrumentation (IDI) were revised at marginally higher rates than conventional instrumentation. Crosslinked polyethylene appears to be superior at 12 years (CRR= 4%) versus non crosslinked polyethylene (CRR>7%). This is the result of fewer failures due to loosening with crosslinked poly. The superiority of crosslinked poly was greater in the younger, more active patient

Patellofemoral complaints are the common and nagging problem after Total Knee Arthroplasty. Crepitus occurs in 5% to over 20% of knee arthroplasty procedure depending on the type of implant chosen. It is caused by periarticular scar formation with microscopic and gross findings indicating inflammatory fibrous hyperplasia. Crepitus if often asymptomatic and not painful, but in some cases can cause pain. Patella “Clunk Syndrome” is less common and represents a when the peripatella scarring is abundant and forms a nodule which impinges and “catches” on the implants intercondylar notch. Patella Clunk was more common with early PS designs due to short trochlear grooves with sharp transition into the intercondylar notch. Clunks are very infrequent with modern PS implants. This Syndrome has been reported in CR implants as well. Thorough debridement of the synovium and scarring at the time of Arthroplasty is thought to reduce the occurrence of crepitus and clunks. Larger patella with better coverage of the cut bone may also be helpful. The diagnosis can be made on history and physical exam. X-rays are also helpful to assess patella tracking. MRI or ultrasound can be used to identify and confirm the diagnosis but this is not mandatory. Painful crepitus and clunk syndrome that fail conservative management of NSAIDS and physical therapy may require surgery. Both crepitus and clunk can be treated with arthroscopic removal of the peripatella scar. Patella maltracking should also be assessed and treated. While recurrence may occur it is uncommon

Aim. Computer-navigated total knee arthroplasty has been shown to improve the outcome in outliers with consistent results. The aim of this study is to evaluate the clinical and radiographic outcomes of computer-navigated knee arthroplasty with respect to deformity and body mass index (BMI). Materials and Methods. Data was prospectively collected for 117 consecutive patients undergoing primary computer-navigated total knee arthroplasty using Ci Brainlab system with J&J PFC PS implants by a single surgeon utilising a tibia cut first, gap-balancing technique. Pre-operative and post-operative long-leg films, weight-bearing, films were taken and the long-axis was measured by a single observer. Intra-operative computer navigation long-axis values were stored as screenshots intra-operatively after registration and after implant was cemented. BMI, range of motion (ROM), SF 36 and Oxford knee scores were recorded both before surgery and on follow-up. Minimum 2-year follow-up. Eight patients were lost to follow-up and 8 had incomplete 2 year data. Data was analysed using the Chi-squared test for categorical variables and the t-test for continuous variables. Results. Eighty-four (83.2%) female, 17 (16.8%) male patients age 65.3±6.9 years with a pre-operative BMI of 27.2±4.1 (18.6 to 40.0). Eighty-eight (87.1%) met the Singapore definition of overweight with BMI>23 kg/m2. Forty-two (41.6%) had a BMI>27.5 kg/m2 indicative of obesity in Singapore. Pre-operative radiographic axis was 9.3±10.6° varus. Thirty (29.7%) patients had a pre-operative coronal plane deformity of more than 15°. Meanoperative duration 96.0±10.7 mins. Post-operative radiographic axis was 0.05±3.0° valgus. Significant improvement was seen in knee extension, knee flexion, SF 36 and Oxford knee scores at 2 years. No significant improvement in extensor lag and straight leg-raising at 2 years. Pre-operative axis >15° was not significantly related to operative duration. BMI>23 kg/m2 was significantly related to longer operative time (88.8±10.8 vs. 97.1±10.3 min, p<0.021). BMI >27.5 kg/m2 not significantly related to operative duration, pre-operative SF36 or Oxford knee scores. Post-operative axis deviation of more than 3° not significantly related to BMI > 23 or 27.5 kg/m2, similar to post-implant navigation axis. BMI >23 kg/m2 not significantly related to 2 year SF36, Oxford knee score and range of motion at 2 years. BMI >27.5 kg/m2 not significantly related to 2 year SF36 or Oxford knee scores. Conclusion. Although restoration of coronal alignment even in deformity >15° is possible with computer navigation, post-operative extensor lag and weakness is still a problem determined by pre-operative extensor lag and weakness in straight leg raising. Computer navigation is useful when exposure and landmarks to assess alignment are difficult such as in obesity where the standard external tibia jig doesn't sit well with the thick subcutaneous layer and for determining the epicondylar axis of the femur in a deep wound. Despite the technical challenges of performing a total knee arthroplasty with obesity, BMI is not a determinant of functional scores when computer navigation is used

Total Knee Replacement (TKR) has been proven to be an effective procedure not only to eliminate pain but also to achieve better knee function. Recent rehabilitation is basically focused on achieving better ROM and muscle strength. However, improvements of balancing or walking ability in detail have not been sufficiently elucidated yet. Methods. 91 consecutive knees of 70 patients, with medial osteoarthritis undergone TKR have been nominated in this study. All were done by a single surgeon, via mid vastus approach, using cemented PS implant with patellar resurfacing. Patients were arrowed to start full weight bearing from the next day. Assessing walking ability, gait speed and width of a step were measured. As for balancing, “Functional Reach (FR)” which was the difference between arm's length and maximal forward reach (Duncan PW et al), “Timed Up and Go Test (TUG)” which was time while a patient rose from an arm chair, walked 3 meters, turned, walked back, and sat down again (Podsiadlo D et al), and possible period standing on one leg (one leg standing) were used. Every measurement was performed prior to the operation, 1,2,3,4 weeks, 2 months and 6 months after operation. Data of prior to the operation, 2, and 6 monts after the operation were analyzed by one-way repeated ANOVA, and then differences among means were analyzed using Bonferroni procedures. P-value lower than 5% is regarded as significant. Result. Every result except for one-leg standing time on contralateral leg (non-operative side) showed the worst during the first week, followed by better results over time (Fig. 1,2,3). One leg standing time of operative leg reached maximum at 2 months of time, while the others revealed improvement even at 6 months of time. Interestingly, postoperative one leg standing period of contra-lateral leg showed improvement with similar tendency until 4 weeks, followed by reaching plateau over time. Discussion. In 6 months after operation, every result showed better function than that of prior to operation. Generally, the factors other than ROM and muscle strength are hard to be measured for both clinician and patients. However, this study showed total function including dynamic and static balancing ability certainly improved correlatively after TKR until at least 6 months

Total Knee Replacement (TKR) has been proven to be an effective procedure not only to eliminate pain but also to achieve better knee function. However, details improvements of balancing or walking ability have not been sufficiently elucidated yet. Methods. 25 consecutive knees of 21 patients, with medial osteoarthritis undergone TKR have been nominated in this study. All were done by a single surgeon, via mid vastus approach, using cemented PS implant with patellar resurfacing. Patients were arrowed to start full weight bearing from the next day. Assessing walking ability, gait speed and width of a step were measured. As for balancing, “Functional Reach (FR)” which was the difference between arm's length and maximal forward reach (Duncan PW et al), “Timed Up and Go Test (TUG)” which was time while a patient rose from an arm chair, walked 3 meters, turned, walked back (Podsiadlo D et al), and sat down again, and possible period standing on one leg (one leg standing) were used. Every measurement was performed prior to the operation, and every 1-week after operation until 4-weeks postoperatively. Data were analyzed by one-way ANOVA, and then differences among means were analyzed using Bonferroni procedures. Also, the relation of improvements between ROM and each data were investigated by Pearson's correlation coefficient test. Result. Every result showed the worst during the first week, followed by better results over time (p<0.05) (Fig. 1–3). The time point when better result than that of pre-operation could be achieved was 2 weeks in FR and one leg standing, 3 weeks in gait speed and width of a step, and 4 weeks in TUG, though statistically not significant. Each of the result was not correlated with its recovery rate of the ROM when compared at 4 weeks of time (r = 0.2–0.3). Interestingly, postoperative one leg standing period of contra-lateral leg showed improvement with similar tendency. Discussion. In 4 weeks after operation, every result showed better function than that of prior to operation. In general, improvement in knee function after TKR is associated with muscle recovery, better ROM, and other undetectable factors. This study showed balancing ability is also assisting the knee function correlatively after TKR. Further, as far as knee function is concerned, recovery time from TKR can be regarded as about 3–4 weeks, which could be one of the predictable factors for reasonable rehabilitation and hospitalization period

Introduction. There is no criteria to select cruciate retaining (CR) or posterior substitute (PS) component in total knee arthroplasty (TKA). In this study, extension and flexion gaps were measured intra-operatively with posterior cruciate ligament (PCL) remained to reveal characteristics of the gaps. Component type selection, CR or PS, was decided intra-operatively according to the gaps in each knee. Materials and methods. One hundred and sixty knees with osteoarthritis were investigated. Extension gap (EG) was made by resection of 8 mm distal femur and 10 mm proximal tibia. After measurement of femoral AP size, about 4 mm bigger 4-in-1 femoral cutting guide than measured size was used for pre-cut of femoral posterior condyle[Figure 1]. With this technique, flexion gap (FG) was made 4 mm smaller than usual measured resection. The gaps were measured by a tension device with 30 pounds tension and FG was corrected by the amount of pre-cut. According to the EG and corrected FG, component type was decided. Too small FG usually needed PCL resection or (and) smaller size of femoral component to make enough final FG. On the other hand, large FG needed careful consideration to sacrifice PCL for adequate final FG. In these cases, CR component was selected usually. If necessary, soft tissue was released for good ligament balance. As the final step of the surgical procedure, the size of femoral component was decided for adequate final FG. It was changeable up to 4 mm larger than measured size[Figure 2]. Results. After pre-cut of femoral posterior condyle and correction of FG by the amount of pre-cut, the range of the gaps were 10∼31 mm (average 20.6±3.7) in flexion and 8∼29 mm (average 17.5±3.4) in extension. There were wide variations in both gaps. The range of the difference between corrected FG and EG was –4∼12 mm (average 3.1±3.3) and corrected FG was significantly larger than EG (P<0.001). Since PCL resection makes FG wider than EG, selection of PS implant would result in much larger final FG in many cases. Of course, larger size of femoral component was available to make FG smaller, but there was limitation. These cases were not suitable for PS component. On the other hand, there were some cases with smaller FG than EG. To select CR component in these cases, it was necessary to use smaller size of femoral component for enough final FG. It led to smaller posterior condylar offset and posterior flexion space. These cases were not suitable for CR component. Considering adequate size of femoral component, CR was used in 122 knees and PS in only 38 knees from the gaps. Conclusion. Because of wide variations in EG and FG, it is difficult to use only one component, CR or PS, in every cases. Larger femoral component with PS or smaller component with CR than measured size is possible to use, but there is limitation. Considering adequate size of femoral component and the final gaps, selection of component type should be decided by intra-operative gap measurement in each knee

Historical studies in TKA suggest that 82–89% of patients are satisfied with TKA. Bourne et al. reviewed 1703 patients and reported that in newer designs that things have not improved much. Approximately one in five (19%) primary TKA patients were not satisfied with the outcome. Satisfaction with pain relief varied from 72–86% and with function from 70–84% for specific activities of daily living. The burden of OA is increasing in society and younger patients are undergoing TKA. A customised, individually made (CIM) knee arthroplasty (iTotal, ConforMIS Inc., Bedford, MA USA) has been introduced by individualising component geometry; exact sizing- medial – lateral and anterior–posterior, restoring medial and lateral joint lines, and restoring individual “J Curves” of the patients’ native femur as it was prior to the arthritic condition. This is done by preoperative CT scanning to include hip-knee-ankle and software to CAD-CAM manufacture of the individualised implants, with accompanying individualised cutting jigs. The hypothesis is to restore form and ultimately function. Will this lead to improved patient satisfaction?. Cadaveric comparison on an “Off The Shelf ” (OTS) implant to CIM implant in 9 matched pair analyses before and after TKA demonstrated that the CIM implant motion was not different than their preoperative kinematics of the knee but the OTS implant was. In vivo comparisons performed fluoroscopically of CIM implants versus OTS implants further demonstrated a more normal knee in terms of kinematics and stability in the CIM knee. Follow up of 110 consecutive patients undergoing a CIM CR TKA revealed patient satisfaction of 98%. Patient average age was 56.1 years old, average follow up 20 months. Two patients required revision- (both dissatisfied)- one for tibial subsidence 18 months after TKA (osteoporosis and obesity) the other developed global laxity at 9 months postoperatively. Both revised with stabilised PS OTS implants. At this early average follow up of <2 years it appears that patient satisfaction improves over prior OTS implant satisfaction with a CIM TKA that restores native size and geometry

Achieving a primary outcome with revision UKR is possible but it depends on an understanding of the main failure modes and avoiding the obvious pitfalls. The most common failure mode in the long term is lateral compartment progression at 2.5% at 28 years. The most common failure overall is misdiagnosis of a painful radiolucency leading to unnecessary revision. There are a number of potential pitfalls:. Do not revise for unexplained pain. 75% of patients will go on to fail because of continuing pain. A distinction must be made to differentiate between a physiological radiolucency (with a narrow lucency accompanied by a sclerotic margin which is normal) and a pathological radiolucency (with a poorly defined lucency without surrounding sclerotic margin which is indicative of loosening and/or infection). Femoral loosening can present with subtle findings. Flexion/extension views are helpful to diagnose this problem. Wear can be a problem with fixed bearing in the second decade and can present with subtle findings. Infection can present with contralateral compartment joint space narrowing. The approach and exposure is usually straightforward and component removal is generally easy. Tibial resection is undertaken referenced from the normal lateral condyle removing 10mm of bone. Femoral preparation is generally straightforward but care must be taken to dial in correct rotation in the absence of the posterior medial condyle which was resected in the first operation. Generally a CR or PS primary implant is used with 2–4mm extra polyethylene thickness than is used in primary case. Revision for infection and stress fracture led to difficult revisions where revision components are usually required. The results for Revision UKR approach those of a primary procedure in all cases except revision for unexplained pain, infection and a stress fracture

Purpose. Many TKA instruments were developed in these days. Distal femoral cutting guide using intra-medullary system were divided into two methods, from anterior or medial. Many companies employed anterior cutting guide, however these guides have a disadvantage of wide skin and quadriceps incision. Only Zimmer provided medial cut guide which performed short skin and quadriceps incision. However, reference point (medial femoral condyle) will be a risk of imprecise cutting for a medial condyle defect cases. We tried L-shaped new distal femoral cutting guide, reference point will be both femoral condyle and cutting from antero-medial side. The purpose of this study was to prove usefulness of the new guide. Materials and Methods. Twenty-nine knees were employed in this study. All knees were treated with Optetrak knee system (Exactec). Surgical methods were as follows, mid line skin incision, short para-patellar deep incision, no patellar resurfacing, PS type implant and cement fixation were employed. 13 knees were used original anterior cutting guide (O group) and 16 knees were used new antero-medial cut guide (N group). Study items were length of skin incision, length of Quadriceps incision, surgical time, JOA score, and component tilting angles (implant position were compared to femoral axis with AP and lateral view of roentgenograms). Results. Average skin incision was 11.7cm in O group and 10.6cm in N group. Average Quadriceps incision was 4.1cm in O group and 2.9cm in N group. There were significant difference in length of skin incision and length of Quadriceps incision. Average surgical time was 155min in O group and 147min in N group. Average component angles of AP view were 84 deg. in O group and 83 deg. in N group. Average component angles of lateral view were 99 deg. in O group and 99 deg. in N group. There were no significant differences between O group and N group in surgical time, component angles, amount of bleeding, and post surgical JOA scores. Conclusions. New distal femoral cutting guide demonstrated same precise cutting compared to original guide. New distal femoral cutting guide achieved small skin incision and small quadriceps incision which is useful for MIS-TKA