A consecutive series of patients with a hydroxyapatite-coated uncemented total knee replacement (TKR) performed by a single surgeon between 1992 and 1995 was analysed. All patients were invited for clinical review and radiological assessment. Revision for aseptic loosening was the primary outcome. Assessment was based on the Knee Society clinical score (KSS) and an independent radiological analysis. Of 471 TKRs performed in 356 patients, 432 TKRs in 325 patients were followed for a mean of 16.4 years (15 to 18). The 39 TKRs in 31 patients lost to follow-up had a mean KSS of 176 (148 to 198) at a mean of ten years. There were revisions in 26 TKRs (5.5%), of which 11 (2.3%) were for aseptic loosening. Other further surgery was carried out on 49 TKRs (10.4%) including patellar resurfacing in 20, arthrolysis in 19, manipulation under anaesthetic in nine and extensor mechanism reconstruction in one.

Survivorship at up to 18 years without aseptic loosening was 96% (95% confidence interval 91.9 to 98.1), at which point the mean KSS was 176 (134 to 200). Of 110 knees that underwent radiological evaluation, osteolysis was observed in five (4.5%), one of which was revised.

These data indicate that uncemented hydroxyapatite-coated TKR can achieve favourable long-term survivorship, at least as good as that of cemented designs.

The optimal management of the tibial slope in achieving a high flexion angle in posterior-stabilised (PS) total knee replacement (TKR) is not well understood, and most studies evaluating the posterior tibial slope have been conducted on cruciate-retaining TKRs. We analysed pre- and post-operative tibial slope differences, pre- and post-operative coronal knee alignment and post-operative maximum flexion angle in 167 patients undergoing 209 TKRs. The mean pre-operative posterior tibial slope was 8.6° (1.3° to 17°) and post-operatively it was 8.0° (0.1° to 16.7°). Multiple linear regression analysis showed that the absolute difference between pre- and post-operative tibial slope (p < 0.001), post-operative coronal alignment (p = 0.02) and pre-operative range of movement (p < 0.001) predicted post-operative flexion. The variance of change in tibial slope became larger as the post-operative maximum flexion angle decreased. The odds ratio of having a post-operative flexion angle < 100° was 17.6 if the slope change was > 2°. Our data suggest that recreation of the anatomical tibial slope appears to improve maximum flexion after posterior-stabilised TKR, provided coronal alignment has been restored.

Cite this article: Bone Joint J 2013;95-B:1354–8.

Aims. The primary objective of this study was to compare migration of the cemented ATTUNE fixed bearing cruciate retaining tibial component with the cemented Press-Fit Condylar (PFC)-sigma fixed bearing cruciate retaining tibial component. The secondary objectives included comparing clinical and radiological outcomes and Patient Reported Outcome Measures (PROMs). Methods. A single blinded randomized, non-inferiority study was conducted including 74 patients. Radiostereometry examinations were made after weight bearing, but before hospital discharge, and at three, six, 12, and 24 months postoperatively. PROMS were collected preoperatively and at three, six, 12, and 24 months postoperatively. Radiographs for measuring radiolucencies were collected at two weeks and two years postoperatively. Results. The overall migration (mean maximum total point motion (MPTM)) at two years was comparable: mean 1.13 mm (95% confidence interval (CI), 0.97 to 1.30) for the ATTUNE and 1.16 mm (95% CI, 0.99 to 1.35) for the PFC-sigma. At two years, the mean backward tilting was -0.43° (95% CI, -0.65 to -0.21) for the ATTUNE and 0.08° (95% CI -0.16 to 0.31), for the PFC-sigma. Overall migration between the first and second postoperative year was negligible for both components. The clinical outcomes and PROMs improved compared with preoperative scores and were not different between groups. Radiolucencies at the implant-cement interface were mainly seen below the medial baseplate: 17% in the ATTUNE and 3% in the PFC-sigma at two weeks, and at two years 42% and 9% respectively (p = 0.001). Conclusion. In the first two postoperative years the initial version of the ATTUNE tibial component was not inferior with respect to overall migration, although it showed relatively more backwards tilting and radiolucent lines at the implant-cement interface than the PFC-sigma. The version of the ATTUNE tibial component examined in this study has subsequently undergone modification by the manufacturer. Level of Evidence: 1 (randomized controlled clinical trial). Cite this article: Bone Joint J 2020;102-B(9):1158–1166

Abstract. Introduction. Total knee replacement (TKR) in patients with skeletal dysplasia is technically challenging surgery due to deformity, joint contracture, and associated co-morbidities. The aim of this study is to follow up patients with skeletal dysplasia following a TKR. Methodology. We retrospectively reviewed 22 patients with skeletal dysplasia who underwent 31 TKRs at our institution between 2006 and 2022. Clinical notes, operative records and radiographic data were reviewed. Results. Achondroplasia was the most common skeletal dysplasia (8), followed by Chondrodysplasia punctata (7) and Spondyloepiphyseal dysplasia (5). There were fourteen men and eight women with mean age of 51 years (28 to 73). The average height of patients was 1.4 metres (1.16–1.75) and the mean weight was 64.8 Kg (34.3–100). The mean follow up duration was 68.32 months (1–161). Three patients died during follow up. Custom implants were required in twelve patients (38.71%). Custom jigs were utilised in six patients and two patients underwent robotic assisted surgery. Hinged TKR was used in seventeen patients (54.84%), posterior stabilised TKR in nine patients (29.03%), and cruciate retaining TKR in five patients (16.13%). One patient underwent a patella resurfacing for persistent anterior knee pain and another had an intra-operative medial tibial plateau fracture which was managed with fixation. No revisions occurred during the follow up period. Conclusion. Despite the technical challenges and complexity of TKR within this unique patient group, we demonstrate good implant survivorship during the study period. Cross sectional imaging is recommended preoperatively for precise planning and templating

Purpose. The mobile-bearing total knee arthroplasty was designed to increase the contact area with the polyethylene bearing, through the functional range of motion, and subsequently decrease the wear rate previously seen in fixed-bearing implants. In the literature there is no clear clinical advantage between the different designs in the short to mid-term follow-up. The purpose of this study was to compare the results between a cruciate retaining mobile-bearing design (SAL II, Sulzer) and two cruciate retaining fixed-bearing designs (AMK, Depuy, and the Genesis II, Smith and Nephew). Method. Ninety patients were randomised to receive either the mobile-bearing or one of the two fixed-bearing designs between 2000 and 2002. Patients were evaluated preoperatively and postoperatively using the WOMAC and the SF-12, both of which are validated scores. One patient was withdrawn due to dementia before three months and eleven patients died. Two patients were revised due to infection (both had received the SAL II). One patient was revised for aseptic loosening and one patient was revised for pain (both had received the Genesis II). Of the 74 patients (77 knees) that remain, they were last seen on average 6.4 years (2–10) after their surgery. Their average age at the surgery was 69.2 years (52–81). Results. There was no statistically significant difference between the change scores (postoperative score minus preoperative score) for each of the outcome measures between the mobile-bearing and the two fixed-bearing designs. Conclusion. In conclusion, after mid-term follow-up there is no clinical difference between a cruciate retaining mobile-bearing design and two cruciate retaining fixed-bearing designs

Total knee replacement (TKR) design aims to restore normal kinematics with emphasis on flexion range. The survivorship of a TKR is dependent on the kinematics in six-degrees-of-freedom (6-DoF). Stepping up, such as stair ascent is a kinematically demanding activity after TKR. The debate about design choice has not yet been informed by 6-DoF in vivo kinematics. This prospective randomised controlled trial (RCT) compared kneeling kinematics in three TKR designs. 68 participants were randomised to receive either cruciate retaining (CR-FB), rotating platform (CR-RP) or posterior stabilised (PS-FB) prostheses. Image quality was sufficient for 49 of these patients to be included in the final analysis following a minimum 1-year follow-up. Patients completed a step-up task while being imaged using single-plane fluoroscopy. Femoral and tibial computer-aided design (CAD) models for each of the TKR designs were registered to the fluoroscopic images using bespoke software OrthoVis to generate six-degree-of-freedom kinematics. Differences in kinematics between designs were compared as a function of flexion. There were no differences in terminal extension between the groups. The CR-FB was further posterior and the CR-RP was more externally rotated at terminal extension compared to the other designs. Furthermore, the CR-FB designs was more posteriorly positioned at each flexion angle compared to both other designs. Additionally, the CR-RP design had more external femoral rotation throughout flexion when compared with both fixed bearing designs. However, there were no differences in total rotation for either step-up or down. Visually, it appears there was substantial variability between participants in each group, indicating unique patient-specific movement patterns. While use of a specific implant design does influence some kinematic parameters, the overall patterns are similar. Furthermore, there is high variability indicating patient-specific kinematic patterns. At a group level, none of these designs appear to provide markedly different step-up kinematic patterns. This is important for patient expectations following surgery. Future work should aim to better understand the unique patient variability

Inverse Kinematic Alignment (iKA) and Gap Balancing (GB) aim to achieve a balanced TKA via component alignment. However, iKA aims to recreate the native joint line versus resecting the tibia perpendicular to the mechanical axis. This study aims to compare how two alignment methods impact 1) gap balance and laxity throughout flexion and 2) the coronal plane alignment of the knee (CPAK). Two surgeons performed 75 robotic assisted iKA TKA's using a cruciate retaining implant. An anatomic tibial resection restored the native joint line. A digital joint tensioner measured laxity throughout flexion prior to femoral resection. Femoral component position was adjusted using predictive planning to optimize balance. After femoral resection, final joint laxity was collected. Planned GB (pGB) was simulated for all cases posthoc using a neutral tibial resection and adjusting femoral position to optimize balance. Differences in ML balance, laxity, and CPAK were compared between planned iKA (piKA) and pGB. ML balance and laxity were also compared between piKA and final (fiKA). piKA and pGB had similar ML balance and laxity, with mean differences <0.4mm. piKA more closely replicated native MPTA (Native=86.9±2.8°, piKA=87.8±1.8°, pGB=90±0°) and native LDFA (Native=87.5±2.7°, piKA=88.9±3°, pGB=90.8±3.5°). piKA planned for a more native CPAK distribution, with the most common types being II (22.7%), I (20%), III (18.7%), IV (18.7%) and V (18.7%). Most pGB knees were type V (28.4%), VII (37.8%), and III (16.2). fiKA and piKA had similar ML balance and laxity, however fiKA was more variable in midflexion and flexion (p<0.01). Although ML balance and laxity were similar between piKA and pGB, piKA better restored native joint line and CPAK type. The bulk of pGB knees were moved into types V, VII, and III due to the neutral tibial cut. Surgeons should be cognizant of how these differing alignment strategies affect knee phenotype

Aims. Conflicting clinical results are reported for the ATTUNE Total Knee Arthroplasty (TKA). This randomized controlled trial (RCT) evaluated five-year follow-up results comparing cemented ATTUNE and PFC-Sigma cruciate retaining TKAs, analyzing component migration as measured by radiostereometric analysis (RSA), clinical outcomes, patient-reported outcome measures (PROMs), and radiological outcomes. Methods. A total of 74 primary TKAs were included in this single-blind RCT. RSA examinations were performed, and PROMs and clinical outcomes were collected immediate postoperatively, and at three, six, 12, 24, and 60 months’ follow-up. Radiolucent lines (RLLs) were measured in standard anteroposterior radiographs at six weeks, and 12 and 60 months postoperatively. Results. At five-year follow-up, RSA data from 61 patients were available and the mean maximum total point motion (MTPM) of the femoral components were: ATTUNE: 0.96 mm (95% confidence interval (CI) 0.79 to 1.14) and PFC-Sigma 1.37 mm (95% CI 1.18 to 1.59) (p < 0.001). The PFC-Sigma femoral component migrated more in the first postoperative year, but stabilized thereafter. MPTM of the tibial components were comparable at five-year follow-up: ATTUNE 1.12 mm (95% CI 0.95 to 1.31) and PFC-Sigma 1.25 mm (95% CI 1.07 to 1.44) (p = 0.438). RLL at the medial tibial implant-cement interface remained more prevalent for the ATTUNE at five-year follow-up compared to the PFC-Sigma (20% vs 3%). RLL did not progress over time, and varied between patients at different timepoints for both TKA systems. Clinical outcomes and PROMs improved compared with preoperative scores, and were not different between groups. Conclusion. MTPM migration at five-year follow-up of the femoral and tibial component of the ATTUNE were similar and as low as that of the PFC-Sigma. MTPM migration of both knee implants did not significantly change from one year post-surgery, indicating stable fixation. Long-term ATTUNE performance may be expected to be comparable to the clinically well-performing PFC-Sigma. We have not found evidence of increased tibial component migration as measured by RSA to support concerns about cement debonding and a higher risk of aseptic loosening with the ATTUNE TKA. Cite this article: Bone Joint J 2023;105-B(11):1168–1176

Both gap balancing and measured resection for TKA will work and these techniques are often combined in TKA. The only difference is really the workflow. The essential difference in gap balancing is that you determine femoral component rotation by cutting the distal femur and the proximal tibia, and then using a spacer to determine femoral rotation. I prefer measured resection because I am, for most cases, a cruciate retaining surgeon. It is not ideal to determine femoral rotation based upon a gap balancing if you retain the cruciate. It is also important to maintain the joint line, especially in cruciate retention, in order to reproduce more normal kinematics and balance the knee throughout the range of flexion and extension. It is my opinion that the soft tissue balancing is easier to do with measured resection and the workflow is easier. The sequence of cuts and soft tissue balance is different if one is a gap balancing surgeon. This is more conducive for people who are cruciate substituters, but more difficult in a varus cruciate retaining knee. In that situation, if you determine femoral rotation by gap balancing with the tibia before you have cleared the posterior medial osteophytes in the varus knee, and remove the last bit of meniscus, you could artificially over rotate the femoral component causing posteromedial laxity. The major difference is that cutting the posterior cruciate will open the flexion space and allow the surgeon easier access to the posteromedial corner of the knee before the posterior femoral cut is made. It is also important to remember that in most cases cruciate substitution surgeons will make the flexion space 2 mm smaller than the extension space to compensate for the flexion space opening when the posterior cruciate is cut. The extensor mechanism plays an important role in flexion balance and should only be tested once the patella is prepared and the patella is back in the trochlear groove. I prefer gap balancing in most revision knees as I am virtually always substituting for the posterior cruciate in that case. My technique for measured resection is to assess the character of the knee prior to surgery. Is it varus? Is it valgus? Does it hyperextend? Does it have a flexion contracture? Would the knee be considered tight or loose? I cut the distal femur first, based upon measured resection. I use anatomic landmarks to determine femoral rotation. My most consistent landmark is the transtrochlear line, which is not always from the top of the notch to the bottom of the trochlea. I will use the medial epicondyle and the posterior reference in a varus knee, but not in a valgus knee. The tibial cut, also by measured resection, is easier once the femur has been prepared. The patellar cut is also a measured resection. Having done a preliminary soft tissue balance based upon the deformity, I will then use trial components to finish the soft tissue balance. In summary, both techniques can be used successfully in a cruciate substituting knee, but measured resection, in my opinion, is preferable especially in varus arthritis when the posterior cruciate is retained

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL. ®. (mobile bearing) versus the AMK. ®. and Genesis II. ®. (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System). The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL. ®. , Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK. ®. , Depuy and Genesis II. ®. , Smith and Nephew). Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated. No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two year follow up, and one patient was revised for infection at 6 months leaving eighty-seven patients at an average follow-up of 3.37 years (range 2.91 – 4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL - 167, AMK – 158, GenesisII – 166). There were no differences in knee flexion at two years (SAL – 117. °. , AMK – 115. °. , GenesisII – 118. °. ). No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses. In this prospective randomized clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity. Funding: London Health Sciences Centre Internal Research Fund

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL. ®. (mobile bearing) versus the AMK. ®. and Genesis II. ®. (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System). The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL. ®. , Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK. ®. , Depuy and Genesis II. ®. , Smith and Nephew). Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated. No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two year follow up, and one patient was revised for infection at 6 months leaving eighty-seven patients at an average follow-up of 3.37 years (range 2.91 – 4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL - 167, AMK – 158, GenesisII – 166). There were no differences in knee flexion at two years (SAL – 117. °. , AMK – 115. °. , GenesisII – 118. °. ). No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses. In this prospective randomized clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity. Funding: London Health Sciences Centre Internal Research Fund

Introduction and Aims: Fixed bearing and mobile bearing knee designs are currently used in clinical practice with little evidence based research available to determine superiority of one system. The purpose of this study was to compare the results between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses. Method: We performed a prospective, randomised, blinded clinical trial to compare a mobile bearing to two standard fixed-bearing implants. We evaluated the short- and long-term outcomes of the SAL. ®. (Sulzer) mobile bearing versus the AMK. ®. (Depuy) and Genesis II. ®. (Smith & Nephew) fixed bearing, total knee joint replacements. Ninety patients were randomised to receive one of the three prostheses. Patients were evaluated pre-operatively, at three, 12 months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated. A single observer was used to measure range of motion scores. Results and Discussion: No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two-year follow-up, and one patient was revised for infection at six months, leaving 87 patients at an average follow-up of 3.37 years (range 2.91–4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL – 167, AMK – 158, GenesisII – 166 ). There were no differences in WOMAC scores or SF-12 survey scores. There were no differences in knee flexion at two years (SAL – 117. °. , AMK – 115. °. , GenesisII – 118. °. ). Therefore, no differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses. Conclusion: In this prospective randomised clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity

Range of motion after total knee replacement is an important outcome variable. Motion impacts the patient’s ability to perform a variety of activities of daily living. In addition, a stiff knee is also a painful knee secondary to continuous soft tissue irritation. Appropriate knowledge in terms of variables that effect range of motion as well as evaluation of the stiff knee are therefore important in the practice of total knee arthroplasty. The most important and consistent factor in determining postoperative flexion is preoperative flexion. Other factors that have been invariably associated with flexion after knee replacement include weight of the patient, age, preoperative diagnosis, and implant design. In terms of implant design, cruciate substituting designs have been reported in several studies to have better motion than cruciate retaining designs. Recent data also suggests that patients with a high visual analogue scale for pain also had poor range of motion following total knee replacement. In analysing a patient with a stiff knee it is thus first important to try and determine what the patients preoperative range of motion was. This helps in determining what the biologic capacity for range of motion after knee replacement. Evaluation of the preoperative x-ray is important in determining factors such as elevation of the joint line and matching the tibial slope especially in cruciate retaining implants. Failure to appropriately match the patient’s tibial slope leads to a tight flexion gap and a decrease in flexion. Malrotation of the components and stuffing the patello-femoral compartment with a thick patellar reconstruction can also decrease postoperative flexion. Balancing of the posterior cruciate ligament in cruciate retaining designs is obviously critical. It is difficult to tell based on physical examination whether the cruciate ligament is in fact tight as secondary contractures develop. If preoperative evaluation determines that the implants are well-positioned manipulation under anaesthesia is a viable option. In both cruciate retaining and posterior cruciate substituting designs this can be safely done up to three months after surgery. For patients who present late after total knee replacement with significant complaints of stiffness, an arthrotomy with debridement of the of the suprapatellar pouch, recreation of the medial and lateral gutters and resection of the posterior cruciate ligament can be successful. Finally implant revision is sometimes required

Bicruciate ligament retaining total knee arthroplasty preserves all of the ligaments of the knee while still addressing the ligament balance and the flexion-extension gaps. The concept of cruciate ligament preservation is not new and both Townley and Cartier designed prostheses in the late 1980s that did preserve all of the ligaments. Their results were quite acceptable for that time in knee replacement surgery but the posterior stabilised and cruciate retaining designs controlled most of the market. The surgical technique for cruciate ligament preservation was more difficult, and without clear clinical benefit, most surgeons gravitated towards the cruciate retaining and posterior stabilised designs. In the late 1990s, evaluation of the total knee arthroplasty began to assess knee kinematics in addition to pain and functional outcomes. At the same time, studies on the unicondylar knee arthroplasty demonstrated impressive scores in motion and patient satisfaction with preservation of all of the ligamentous structures of the knee. Over the past two years, new designs that preserve all of the ligaments of the knee have returned to the market. The instruments have been improved and the prostheses have been changed to respect the kinematics of the knee. Fifteen to twenty percent of all total knee replacement patients are not completely satisfied with the surgery and the authors believe that complete ligament preservation may address this complaint

Purpose: The purpose of this study was to compare the outcomes of cruciate retaining (CR) and cruciate sacrificing (CS) total knee arthroplasty (TKA) in a multi-center randomized clinical trial with greater than 5 year follow-up. Methods: One hundred and eighty five patients (189 knees) participated in a double-blinded randomized clinical trial. 96 cruciate retaining and 93 cruciate sacrificing total knee arthroplasties (Genesis II, Smith & Nephew, Memphis, TN) were performed between 1997 and 2000. All surgical procedures were performed by twelve surgeons at twelve medical centers. The average follow-up was 5.8 (5.0–7.3) years. Clinical outcomes (Knee Society Clinical Rating, WOMAC, SF-12, Radiographic Findings) were evaluated preoperatively and at the latest follow-up. Postoperative complications were also examined. Results: There were no significant differences when comparing cruciate retaining knees to cruciate sacrificing knees in patient demographics and preoperative clinical evaluation. At the latest follow-up, clinical outcomes (CR versus CS) were as follows: Knee Society Clinical Rating (163±26 versus 165±29), knee flexion (114±11& #12539;versus 118±10& #12539; p< 0.05), WOMAC (12±7 versus 8±6, p< 0.05), and SF-12 (mental: 52±9 versus 58±4, physical: 41±11 versus 42±10). Radiographic outcomes showed there were no differences in radiolucent lines or loosening, and postoperative complication rate was also not significantly different. Conclusions: In this randomized clinical trial, both posterior cruciate preserving (CR) and sacrificing (CS) total knee replacements offer excellent clinical outcomes at five or more years follow-up, with the cruciate sacrificing implant studied demonstrating small, but significant improvements in both range of motion, WOMAC, and disease specific outcomes

Aims. Total knee arthroplasty is an established treatment for knee osteoarthritis with excellent long-term results, but there remains controversy about the role of uncemented prostheses. We present the long-term results of a randomized trial comparing an uncemented tantalum metal tibial component with a conventional cemented component of the same implant design. Methods. Patients under the age of 70 years with symptomatic osteoarthritis of the knee were randomized to receive either an uncemented tantalum metal tibial monoblock component or a standard cemented modular component. The mean age at time of recruitment to the study was 63 years (50 to 70), 46 (51.1%) knees were in male patients, and the mean body mass index was 30.4 kg/m. 2. (21 to 36). The same cruciate retaining total knee system was used in both groups. All patients received an uncemented femoral component and no patients had their patella resurfaced. Patient outcomes were assessed preoperatively and postoperatively using the modified Oxford Knee Score, Knee Society Score, and 12-Item Short-Form Health Survey questionnaire (SF-12) score. Radiographs were analyzed using the American Knee Society Radiograph Evaluation score. Operative complications, reoperations, or revision surgery were recorded. A total of 90 knees were randomized and at last review 77 knees were assessed. In all, 11 patients had died and two were lost to follow-up. Results. At final review all patients were between 11 and 15 years following surgery. In total, 41 of the knees were cemented and 36 uncemented. There were no revisions in the cemented group and one revision in the uncemented group for fracture. The uncemented group reported better outcomes with both statistically and clinically significant (p = 0.001) improvements in knee-specific Oxford and Knee Society scores compared with the cemented group. The global SF-12 scores demonstrated no statistical difference (p = 0.812). Uncemented knees had better radiological analysis compared with the cemented group (p < 0.001). Conclusion. Use of an uncemented trabecular metal tibial implant can afford better long-term clinical outcomes when compared to cemented tibial components of a matched design. However, both have excellent survivorship up to 15 years after implantation. Cite this article: Bone Joint J 2020;102-B(8):1025–1032

Introduction. Robotics have been applied to total knee arthroplasty (TKA) to improve surgical precision in component placement and joint function restoration. The purpose of this study was to evaluate prosthetic component alignment in robotic arm-assisted (RA)-TKA performed with functional alignment and intraoperative fine-tuning, aiming for symmetric medial and lateral gaps in flexion/extension. It was hypothesized that functionally aligned RA-TKA the femoral and tibial cuts would be performed in line with the preoperative joint line orientation. Methods. Between September 2018 and January 2020, 81 RA cruciate retaining (CR) and posterior stabilized (PS) TKAs were performed at a single center. Preoperative radiographs were obtained, and measures were performed according to Paley's. Preoperatively, cuts were planned based on radiographic epiphyseal anatomies and respecting ±3° boundaries from neutral coronal alignment. Intraoperatively, the tibial and femoral cuts were modified based on the individual soft tissue-guided fine-tuning, aiming for symmetric medial and lateral gaps in flexion/extension. Robotic data were recorded. Results. A total of 56 RA-TKAs performed on varus knees were taken into account. On average, the tibial component was placed at 1.9° varus (SD 0.7) and 3.3° (SD 1.0) in the coronal and sagittal planes, respectively. The average femoral component alignment, based on the soft tissue tensioning with spoons, resulted as follows: 0.7° varus (SD 1.7) in the coronal plane and 1.8° (SD 2.1) of external rotation relative to surgical transepicondylar axis in the transverse plane. A statistically significant linear direct relationship was demonstrated between radiographic epiphyseal femoral and tibial coronal alignment and femoral (r=0.3, p<0.05) and tibial (r=0.3, p<0.01) coronal cuts, resepctively. Conclusion. Functionally aligned RA-TKA performed in varus knees, aiming for ligaments’ preservation and balanced flexion/extension gaps, provided joint line respecting femoral and tibial cuts on the coronal plane

Introduction. Revision for instability has supplanted revision for aseptic loosening and revision for osteolysis since the advent of improved polyethylene inserts with changes in both sterilization techniques and cross-linking. Having the ability to judiciously choose a higher level of constraint may be beneficial in complex primary total knee arthroplasty (TKA) scenarios which can not be balanced through traditional surgical methods. The purpose of this work was to investigate short term outcomes and survivorship in cases where a greater stabilizing insert was used with a posterior stabalizing (PS) femur to address instability in flexion or extension. Methods. Two high volume TKA centers retrospectively reviewed cases in which a greater stabilizer insert was used with a primary PS knee system. The studied insert had +/− 2 degrees of varus-valgus coronal restraint as opposed the standard with no coronal constraint. The study inserts had 7 degrees of transverse plane rotational freedom. The inserts were used when extension balance was not achieved despite the usual soft tissue releases and a thicker insert resulted in a flexion contracture statically during the procedure. This situation typically occurred in the following patient groups: valgus knees with medial collateral (MCL) stretching, iatrogenic MCL injury, varus knees with lateral ligament complex stretching, the “double-varus” knee, and patients with a previous high tibial osteotomy. Intra-operatively patients were taken through a range of motion and trial implants were then placed. A cruciate retaining trial insert was then used to assess stability so that a true assessment could be made of ligament balance. Bone cuts were checked before ligament release. The usual releases were then performed to achieve balance including subperiosteal releases medially and laterally and pie-crusting when indicated. Repeat trial reductions were then performed once the final implants were cemented in place again using the cruciate retaining insert. If the soft tissue releases did not achieve balance and a thicker insert resulted in a flexion contracture then the greater stabilizer insert was selected over the PS insert. Knee Society Score and plain radiographs were collected at pre-op, 2 year and 5 year follow-up. Results. One hundred seventy two cases with 2 year minimum follow-up and 41 cases with 5 year minimum follow up were assessed. All patients had good to excellent Knee Society Scores with good range of motion and pain relief. There were no aseptic revisions of the TKA's over this period. Specifically, there were no revisions for loosening, osteolysis, instability, or post breakage. Conclusions. A more stabilized tibial post insert which provides valgus-varus constraint but permits rotational freedom may provide needed stability in select primary situations without predisposing to early post failure or implant loosening or lysis

Introduction. Femoral periprosthetic fractures above TKA are commonly treated with retrograde intramedullary nailing (IMN). This study determined if TKA design and liner type affect the minimum knee flexion required for retrograde nailing through a TKA. Methods. Twelve cadaveric specimens were prepared for six single radius (SR) TKAs and six asymmetric medial pivot (MP) TKAs. Trials with 9mm polyethylene liners were tested with cruciate retaining (CR), cruciate substituting (CS) and posterior stabilizing (PS) types. The knee was extended to identify the minimum knee flexion required to allow safe passage of the opening reamer while maintaining an optimal fluoroscopic starting point for retrograde nailing. Furthermore, the angle of axis deviation between the reamer and the femoral shaft was calculated from fluoroscopic images. Results. In all specimens, the reamer entry point was posterior to Blumensaat's line. In the SR TKA, the average flexion required was 70, 71 and 82 degrees for CR, CS and PS respectively. The required flexion in PS was significantly greater than the other designs (p=0.03). In the MP TKA, the average flexion required was 74, 84 and 123 degrees for CR, CS and PS respectively. The required flexion was significantly greater in CS and PS designs (p<0.0001). Femoral component size did not affect the minimum flexion required. Furthermore, the entry reamer required 9.2 (SR) and 12.5 (MP) degrees of posterior axis deviation from the femur. Conclusions. Our study illustrates four novel factors to consider when performing retrograde nailing through TKA. First, significant knee flexion is required to obtain an ideal radiographic starting point when retaining the liner. Second, PS implants require more flexion with both TKA designs. Third, femoral component size does not affect the flexion required. Fourth, there is a consistent posterior axis deviation of the entry reamer from the femoral shaft, explaining the commonly created extension deformity

Background. While posterior cruciate retaining (PCR) implants are a more common total knee arthroplasty (TKA) design, newer bi-cruciate retaining (BCR) TKAs are now being considered as an option for many patients, especially those that are younger. While PCR TKAs remove the ACL, the BCR TKA designs keep both cruciate ligaments intact, as it is believed that the resection of the ACL greatly affects the overall kinematic patterns of TKA designs. Various fluoroscopic studies have focused on determination of kinematics but haven't defined differentiators that affect motion patterns. This research study assesses the importance of the cruciate ligaments and femoral geometry for Bi-Cruciate Retaining (BCR) and Posterior Cruciate Retaining (PCR) TKAs having the same femoral component, compared to the normal knee. Methods. The in vivo 3D kinematics were determined for 40 subjects having a PCR TKA, 10 having a BCR TKA, and 10 having a normal knee, in a retrospective study. All TKA subjects had the same femoral component. All subjects performed a deep knee bend under fluoroscopic surveillance. The kinematics were determined during early flexion (ACL dominant), mid flexion (ACL/PCL transition) and deep flexion (PCL dominant). Results. During the first 30 degrees of flexion, the ACL played an important role, as subjects having a BCR TKA experienced kinematic patterns more similar to the normal knee. During mid flexion, both TKAs experienced random kinematic patterns, which could be due to the ACL and PCL being less active or resected in PCR TKA. In deeper flexion, both TKAs experienced kinematic patterns similar to the normal knee, thus supporting the assumption that the PCL played a dominant role [Fig. 1, Fig. 2]. All three groups generally experienced progressive axial rotation throughout flexion [Fig. 3]. On average, subjects having a PCR TKA experienced 112.3° of flexion, which was greater than the BCR subjects. Conclusions. Both the BCR TKA and normal groups experienced similar kinematic patterns, but the femoral geometrical differences from the anatomical condition may have influenced decreased motion compared to the normal knee. Both TKAs experienced similar kinematic patterns in deeper flexion, with the PCR TKA experiencing excellent weight-bearing flexion. Results from this study suggest that the cruciate ligaments can play a role in kinematics, but femoral geometry working with the ligaments may be an option to consider