Introduction: A prospective study was done to compare the early clinical, radiographic outcomes between the Scorpio CR and Scorpio Flex CR primary total knee replacement. Methods: 130 Scorpio CR and 40 Scorpio Flex CR were implanted. Patients were prospectively evaluated with a mean follow-up of 3,9 years (2–8 years). Knee Society Score, W.O.M.A.C., range of motion and knee pain was compared. Patients age, level of activity, BMI, were criteria selection for implant of Scorpio Flex CR. Results: There was more pain in Scorpio CR group, mean flexion was greater in Scorpio Flex CR (112 vs 108); Knee Society score and WOMAC was better in Scorpio Flex CR group. Conclusion: The Scorpio Flex CR new design may be allow the significant increase in Knee Society score and the better ROM in Scorpio Flex CR group

Background. Soft tissue tension and intra-articular pressure distribution plays a crucial role in postoperative function and survivorship of TKA prosthesis. Although posterior stabilized (PS) and cruciate retaining (CR) knees have both been successful in relieving pain and restore function, it is reported that the joint gaps were significantly distinct between the two designs during flexion. The aim of this study is to find out what is the difference in intra-articular pressure distribution between PS and CR knees. Methods. We prospectively included 45 consecutive patients (50 knees) scheduled for total knee arthroplasty between August, 2013 and April, 2014 in our hospital. 23 patients (25 osteoarthritic knees) received a Genesis II CR TKA (Smith & Nephew, Memphis, USA), and the other 22 patients (25 osteoarthritic knees) received Genesis II PS TKA (Smith & Nephew, Memphis, USA). During operation, after the bone osteotomy and soft tissue balance were completed, we measured and compared the intra-articular pressure distribution at 0°, 30°, 45°, 60°, 90°, and 120° flexion with a previously validated “Wireless Force Measurement System (WFMS)”. Joint gaps were measured at extension and 90° flexion. The soft tissue was not considered balanced until the medial and lateral joint gap difference ≤ 2mm at extension and 90° flexion. There are no significant differences in age, gender, BMI, varus angle and flexion deformity, and preoperative range of motion between the two groups. The medial-lateral pressure distribution and total pressure were compared at different angles between CR and PS knees. Results. During flexion, the total pressure drops sharply at the first 30 degrees, and then goes down slowly for the rest 90 degrees, without significant difference between CR knees and PS knees at any flexion angles [fig.1]. For PS knees, pressure in the medial compartment, accounting for 65.0%∼80.4% of the total pressure, is significantly higher than that in the lateral side at all angles(p<0.05) [fig.2]. For CR knees, pressure in the medial compartment is significantly higher than the lateral side at extension (61.0%, p<0.05), but significantly lower than the lateral side at 45°, 60°, 90°, and 120° flexion (29.2%∼36.3%, p<0.05) [fig.3]. There is no difference between the medial and lateral side in CR knees at 30°[fig.3]. Discussion. Our research demonstrates that the soft tissue tension differs between CR and PS knees. The intra-articular pressure is concentrated in the medial compartment during whole ROM in PS knees. While in CR knees, pressure in the medial compartment is transferred to the lateral side during flexion. The mid flexion stability in the lateral side is significantly better in CR knees than in PS knees, and the soft tissue is better balanced at initial 0°∼30°in CR knees than in PS knees. Our results revealed that the cam-post mechanism cannot replace the PCL's role in modulating pressure distribution and soft tissue tensioning. These findings may guide the future geometrical design and soft tissue balancing techniques of PS and CR knees

Background. Total knee arthroplasty (TKA) is the highly developed procedure for sever osteoarthritic knee, in which there are two major concepts; Cruciate Retaining design (CR) and Posterior Stabilized design (PS). The femoral roll back movement is enforced with the post-cam mechanism in the PS, however, this structure associates with the complications, i.e. wear and dislocation. The CR has been developed to obtain the knee stability with native posterior cruciate ligament (PCL) in TKA. However, the preservation of the PCL can limit knee exposure and increase the technical challenge of surgery. We hypothesized that the knee exposure was easily achieved after the PCL was released, however, the PCL was repaired and the posterior stability was re-established after the TKA with time if it was released subperiostealy. Objective. The objective of this study was to evaluate the varying of the posterior stability after the PCL-released CR TKA. Methods. Patients were performed the CR TKA with 3DKnee (DJO Global, Vista, CA), in which the entire PCL was subperiostealy released at its femoral insertion (Fig. 1). Following that, the patients were examined with the Knee Society Score and the KT-2000 knee ligament arthrometer (MedMetric Corp., San Diego, CA) firstly between 3 weeks and 7 weeks and secondly between 12 weeks and 20 weeks postoperatively. Results. There were 8 cases in 2 female and 6 male knees, and the age was 63.3 ± 11.1 (ranging from 51 to 79). Once the PCL was released, the tibia was easy to subluxate, and the knee was clearly exposed intraoperatively. The Knee Society knee score at the first evaluation was 74.4 ± 10.7 (59 to 90), which was significantly improved compared to the preoperative score of 37.0 ± 9.4 (25 to 50) (p<0.001). Then, the score increased up to 89.4 ± 11.6 (70 to 100) at the second evaluation. The function score was 35.6 ± 19.9 (5 to 55) preoperatively and decreased to 24.4 ± 12.2 (20 to 55) at the first evaluation. After that, it increased to 82.5 ± 14.1 (65 to 100) (p<0.001) at the second evaluation. The anteroposterior laxity was 5.2 ± 1.9 (3 to 7.5) mm at the first evaluation, and was improved to 3.6 ± 1.2 (2 to 5) mm (p<0.046). Therefore, the posterior stability was confirmed to be re-established. We also confirmed the re-establishment of the PCL integrity at a revision TKA, in which the original procedure had been performed 7 years ago (Fig. 2). Conclusion. The re-establishment of the posterior stability after the PCL-released CR TKA was demonstrated. This procedure to release the entire PCL subperiostealy is recommended as a means of facilitating CR TKA

Observations of knee arthroplasty kinematics generally show differences in anteroposterior translation when comparing posterior cruciate retaining (CR) and posterior stabilised (PS) designs. However, the PS cam/post mechanism is not engaged in extension. We hypothe-sised that there would be little difference between CR and PS knee kinematics during stance in gait. Videofluoroscopy and shape matching techniques were used to quantify motions of 47 fixed-bearing knee arthroplasties (24 CR, 23 PS) during gait and stair-climbing in consenting patients with excellent clinical/ functional performance at least one year post-surgery. The average centre of rotation (COR) was computed for each knee during the two activities; a lateral COR (−50% to 0%) indicates anterior femoral translation with flexion, a medial COR (0% to +50%) indicates posterior femoral translation with flexion. There was a significant difference between the average COR in the PS (+9%) and CR (−15%) knees for the stair climbing activity (p< 0.001), but not the stance phase of gait (−5% vs. −14%, respectively, p=0.664). The COR was more lateral for the stance phase of gait than for stair climbing in the PS knees (p=0.008), but not the CR knees (p=0.948). All knees showed more axial rotation during the stair activity (8°) than the stance phase of gait (5°, p< 0.001). During stance in gait, there were small but not significant differences in the centre of rotation between the CR and PS knees. For stair climbing, there were significant differences between CR and PS knee kinematics. These observations are consistent with the hypothesis that CR and PS kinematics ought to be similar near extension, where the articular constraints are similar, but might differ in deeper flexion activities where the intrinsic constraints of the arthroplasty are different. An improved understanding of arthroplasty function should facilitate further evolution of design, surgical techniques, and numerical analyses to optimise patient performance

INTRODUCTION. Patellofemoral compilcations are among the most frequently observed adverse events after total knee arthroplasty. The posterior location with Femoral component of conventional TKA in AP alignment cause paradoxical movement, but, guide motion TKA (Journey.2.BCS) with anterior post-cam remain a correct AP alignment. The purpose of this study was to investigate patellofemoral (PF) contact stress between Bi-Cruciate Substituting TKA (Journey.2.BCS) and CR TKA (Journey.CR). METHODS. We evaluated 22 knees with medial compartment osteoarthritis who underwent. Simultaneous bilateral TKA. The prospective randomized study was to measure intraoperative PF contact stress by a patellofemoral sensor (Kyowa Co., Ltd., Tokyo, Japan) comparing the identical Bi-Cruciate Substituting or CR Journey.2 total knee prostheses implanted bilaterally in the same patient. RESULTS. The PF contact stress showed significantly greater at CR TKA than at BCS TKA in 120 and 140 degrees of flextion (p=0.04, p=0.018). and showed no significant correlations with postoperative flextion angles. DISCUSSION AND CONCLUSION. In guide motion TKA, CR prosthesis increases PF contact stress than Bi-Cruciate Substituting prosthesis. The femoral rollback with medial pivot motion at CR TKA decreases more as the BCS TKA. Increased PF contact stress in guided motion TKA is not necessarily decrease postoperative flextion angle

This research is to relate functional outcomes to kinematics in high flexion CR and PS total knees by using the Total Knee Function Questionnaire in patients who had previously undergone kinematic analyses. Patients were identified who had primary total knee arthroplasty and had undergone kinematic analyses using fluoroscopy. The Total Knee Function Questionnaire was sent to these patients, and data was obtained for 14 CR knees (NexGen CR-Flex, Zimmer) and for 13 PS knees (Legacy LPS-Flex, Zimmer). The questionnaire evaluates baseline activities of daily living, advanced activities, and recreational activities and exercises. CR patients reported higher satisfaction and that their knees felt more “normal” than PS patients. Some baseline activity scores were significantly higher for CR than for PS knees. Limitations in baseline activities were related to kinematic constraints, including flexion, lateral and medial anterior-posterior (A-P) translations, and tibiofemoral axial rotation. Kinematic data were related to difficulty data for advanced and recreational activities of kneeling, squatting, gardening, and stretching. Comparisons between kinematic data and patient feedback on knee function provided unique information about differences between CR and PS high flexion implants. CR patients had better function than PS patients in walking on even ground or uphill or sitting. CR patients had higher activity scores for recreational than for advanced activities, while activity scores for the PS patients were similar between these activities. Kinematic variables that affected function for some activities included extremes of flexion, A-P translations of lateral and medial condyles, and axial rotation intervals

Summary Statement. Femorotibial constraint is a key property of a total knee arthroplasty (TKA) prosthesis and should reflect the intended function of the device. With a validated simulation methodology, this study evaluated the constraint of two TKA prostheses designed for different intentions. Introduction. TKA prostheses are semi-constrained artificial joints. Femorotibial constraint level is a major property of a prosthesis and should be designed to match the device's intended function. Cruciate Retaining (CR) prostheses are usually indicated for patients with a functioning posterior cruciate ligament (PCL). For patients without a fully functioning PCL, CR-Constrained (CRC) prostheses with additional built-in constraint may be indicated. A CRC prosthesis usually consists of a CR femoral component and a tibial insert which has a more conforming sagittal profile to offer an increased femorotibial constraint. This study evaluated the anterior-posterior (AP) constraint behavior of two lines of prostheses (CR and CRC) from a same TKA product family. Using a validated computer simulation approach, multiple sizes of each product line were evaluated. Methods. Both the CR and CRC prostheses are from the same TKA product family (Optetrak Logic, Exactech, FL, USA) and share identical femoral components and tibial baseplates. The CRC tibial inserts have a more conforming sagittal profile than the CR tibial inserts, especially in the anterior aspect. Three sizes (sizes 1, 3, and 5) from each product line were included in this study. Computer simulations using finite element analysis (FEA) were performed to evaluate the femorotibial constraint of each prosthesis per ASTM F1223 standard [1]. The simulation has been validated by comparison with physical testing (more details submitted in a separate paper to CORS 2013). Briefly, FEA models were created using 10-node tetrahedral elements with all materials considered linear elastic. The tibial baseplate was distally fixed and a constant compressive force (710 N) was applied to the femoral component. Nonlinear Surface-Surface-Contact was established at the articulating surfaces, as well as between the tibial insert and the tibial baseplate. A coefficient of friction of 0.1 was assumed for all articulations [2]. The femoral component was driven under a displacement-controlled scheme to slide along AP direction on the tibial insert. Constraint force occurring at the articulation was derived from the reaction force at the distal fixation; thus, the force-displacement curve can be plotted to characterise the constraint behavior of the prosthesis. A nonlinear FEA solver (NX Nastran SOL601, Siemens, TX, USA) was used to solve the simulations. Results. The force-displacement curves predicted by the simulation exhibited the hysteresis loop appearance for both CR and CRC prostheses. The profile of the curves was generally consistent across different sizes for both product lines. The anterior constraint of the CRC prosthesis was significantly greater than the CR prosthesis. The posterior constraint of the CRC prosthesis was also slightly greater. Larger sizes exhibited reduced constraint compared to smaller sizes. Discussion/Conclusion. The increased constraint of the CRC prosthesis revealed in the study is consistent with the geometrical characteristics and the functional intent of the device. The CRC tibial insert is expected to provide significantly greater anterior constraint than the CR prosthesis to prevent paradoxical femoral translation when the patient's PCL is not fully functioning. The CRC tibial insert is also expected to provide slightly increased posterior constraint due to its elevated posterior lip. The observed hysteresis loop appearance is consistent with physical testing and the existence of friction. The reduced constraint on larger sizes is functionally desirable to offer proportional translation freedom. This study demonstrated the effectiveness of the simulation approach in quantifying the constraint behavior of different TKA prosthesis designs

Introduction The NexGen-CR-Knee System ( Zimmer, Inc.) was developed for cruciate ligament retaining TKA, preserving as much of the function of the normal knee as possible. It was cleared by the FDA in 1995. Prerequisites are good bone quality and intact ligaments. It is part of a modular system for primary and some revision cases with a large selection of sizes, augmentation blocks and stem extensions. Material In the Orthopedic Center in Kassel about 1500 NexGen Cr devices were implanted and documented since October 1998. The 5-in-1 milling system was used and all components were cemented. Prospective evaluation pre-, intra- and postoperatively, at 1, 2 and 5 years was performed with a low drop out rate. 232 consecutive cases will have the 5 year data. The outcome will be presented, among others the Knee Society Score (function & knee), range of motion, complications and reasons for revisions. Comparison with the worldwide register of this implant is made. Conclusion The NexGen CR Knee Solution implants and the technique of implantation appear to be very successful in mid term results. It is a good basis for further developments such as highly crosslinked Polyethylene and the new CR Flex design

Introduction. Radiostereometric Analysis (RSA) is an imaging method that is increasingly being utilized for monitoring fixation of orthopaedic implants in randomized clinical trials. Extensive RSA research has been conducted over the last 35+ years using standard clinical x-ray acquisition modalities that irradiate screen/film media or Computed Radiography (CR) plates. The precision of RSA can depend on a number of factors including modality image quality. Objective. This study assesses the precision of RSA with a novel Digital Radiography (DR) system compared to a CR imaging system using different imaging techniques. Additionally, the study assesses the precision of locating beads embedded in a modified spine pedicle screw. Methods. A modified titanium spinal pedicle screw 4.5 mm diameter, 35 mm length, marked with two 1.0 mm tantalum beads, one inside the head and one near the screw tip was inserted into a bovine tibia segment. Six additional 1.0 mm tantalum beads were inserted into the bone segment superiorly, distally and adjacent to the pedicle screw. The phantom was placed on a standard clinical diagnostic imaging bed above a custom RSA carbon fiber calibration cage (Halifax Biomedical Inc.). A pair of DR or CR imaging plates were placed below the calibration cage and irradiated 8 times at 100, 125 kV at 2.5 mAs. For DR additional test were performed at 150 kV, and again at 100 kV at 0.5 mAs. At the time of abstract submission CR results at these settings were not available. To determine precision, the standard deviation of 3D vector distances between beads was determined using RSA for each of the different imaging parameters. Results. Standard deviations of the inter-bead distances measured in the pedicle screw were 44.4 and 32.1 μm (N=8) respectively for the 100 and 125 kV settings at 2.5 mAs using the DR system, compared to 109.0, 55.8 μm for CR [Fig. 1]. The distances between the bone implanted beads provided standard deviations of 24.4 and 22.7 μm respectively for the 100 and 125 kV settings at 2.5 mAs using the DR system, compared to 33.1 and 33.0 μm with the CR system. Further increasing the photon energy to 150 kV with the DR system reduces the precision error to 22.4 μm in the pedicle screw and remains approximately the same at 21.0 μm in bone. Lowering the mAs while maintaining 100 kV increases the precision error in the pedicle screw (64 μm) and showed no significant difference in bone (24.4 μm). Conclusion. The current phantom design is basic in nature and does not account for any soft tissue scatter. However, initial results indicate a considerable reduction in precision error when using DR compared to CR imaging equipment for RSA analysis. Increasing the kV did not significantly influence the precision in measuring bead locations in bone. For embedded tantalum beads within a titanium pedicle screw, imaging at higher kV values with the described DR imaging system did allow more precise localization. This approach may be useful in assessing the in vivo position of spine or other titanium implants

Introduction. While clinically successful for decades, CR TKA is persistently compromised by inconsistent PCL function. Problems of mid-flexion instability, incomplete knee flexion, erratic kinematic behavior and posterior instability, not seen with PS devices, raise concerns about the consistency of the technique, and the devices used. Most TKA systems offer at least 2 different geometries of tibial inserts to address this clinical problem. We hypothesize these problems are a result of compromise of PCL anatomy. To avoid compromise to the PCL 3 steps are required: 1) The slope of tibial resection must be less than 5°; 2) the depth of tibial resection must be based off the insertion footprint of the PCL, not the deficiencies of the tibial articular surface; and 3) the tibial insert must be modified to allow intraoperative balancing of the PCL. Results. The CR Slope ™ implants and technique (Exactech) (“Posterior Cruciate Referencing Technique (PCRT)”) reflect this philosophy and have allowed consistent surgical intervention without PCL release and without multiple inserts. We present data identifying, the footprint, and the instrument and technique modifications that allow for predictable identification of the depth and angle of resection. At 2 years post implantation in the first 100 patients implanted, the study group has demonstrated similar operative time, LOS and Oxford knee scores (OKS), while ROM averaged 5° greater, and time to achieved flexion was decreased. Conclusion. The PCRT offers a new conceptual and clinical approach to predictable CR TKA

Introduction: Highly crosslinked UHMWPEs have been widely used in total hip replacements but have seen limited use at the knee due to concerns over strength characteristics. A new process, sequential irradiation and annealing, overcomes these limitations. Materials and Methods: GUR 1020 polyethylene was sequentially crosslinked using three separate gamma radiation doses of 3 Mrad with an annealing step at 130 degrees C after each irradiation (SXL). Wear was determined by weight loss under normal walking and stair climbing conditions (MTS knee simulator, 5 to 10 million cycles, 1 Hz, maximum load of 2600 N to 3800 N, alpha fraction bovine calf serum). Scorpio CR and PS knees were evaluated using SXL and UHMWPE gamma sterilized to 3 Mrad in nitrogen (gamma-N2). Oxidative challenge was in 5 atmospheres of oxygen at 70 degrees C for 14 days. Results: Scorpio gamma-N2 CR knees under normal walking conditions had a weight loss of 32.6 +/− 1.9 mg/million cycles compared to 6.5 +/− 1.6 mg/million cycles for SXL (p of 0.024). With Scorpio PS knees, the wear was 33.5 +/− 1.6 for gamma-N2 versus 7.7 +/− 0.7 mg/million cycles for SXL (p of 0.000009) subject to stair climbing simulation. Wear particle size was similar for SXL and gamma-N2. SXL knees showed no effect of oxidative challenge in a 10 million-cycle knee study. Discussion and Conclusions: Wear is reduced by 80 percent and 77 percent respectively for CR and PS knees with SXL compared to gamma-N2. SXL has high resistance to oxidative challenge as shown by the lack of effect on knee wear results

Purpose. Radiostereometric Analysis (RSA) is a well developed imaging technique used to estimate implant fixation of orthopaedic implants in randomized clinical trials. The precision of RSA depends on a number of factors including image quality related to the individual modality properties. This study assesses the precision of RSA with a novel Digital Radiography (DR) system compared to a CR imaging system using different imaging techniques. Additionally, the study assesses the precision of locating beads embedded in a modified spine pedicle screw. Method. A modified titanium spinal pedicle screw 4.5 mm diameter, 35 mm length, marked with two 1.0 mm tantalum beads, one inside the head and one near the screw tip was inserted into a bovine tibia segment. Six additional 1.0 mm tantalum beads were inserted into the bone segment – superiorly, distally and adjacent to the pedicle screw. The phantom was placed on a standard clinical diagnostic imaging bed above a custom RSA carbon fiber calibration cage (Halifax Biomedical Inc.). A pair of DR or CR imaging plates were placed below the calibration cage and irradiated 15 times at 100, 125 kV at 2.5 mAs. To determine precision, the standard deviation of 3D vector distances between beads was determined using RSA for each of the different imaging parameters. Results. The precision error (PE), defined as the standard deviation of the 3D Bone Marker marker locations for CR is 35.5 m for 100kV at 0.5 mAs setting and 42.2, 39.4, and 26.7 m for the 2.5 mAs at 100, 125, and 150 kV settings respectively. However, for DR, the PE is 27.5 m for 100kV at 0.5 mAs setting and 25.7, 25.1, and 20.1 m for the 2.5 mAs at 100, 125, and 150 kV settings. The PE for Screw Marker 3D locations, for CR is 38.2 m for the 100kV at 0.5 mAs setting and 55.2, 47.3, and 37.1 m for the 2.5 mAs at 100, 125, and 150 kV settings respectively. However for DR, the PE is 40.3 m for 100kV at 0.5 mAs setting and 33.2, 24.9, and 17.0 m for the 2.5 mAs at 100, 125, and 150 kV settings respectively. The PE for all Bone Marker and Screw Marker 3D locations were significantly lower (P<0.05) for the DR technology than the CR technology except at the 100kV at 0.5 mAs exposure of the Screw Marker, P = 0.589. Conclusion. The PE decreases for increasing kV, especially in the case of screw markers where the error goes from 33 micron (100kV) to 17 micron (150 kV). Increasing the mAs reduces the error for the DR, but increases the error for CR. Increasing the kV did not significantly influence the precision in measuring bead locations in bone. For embedded tantalum beads within a titanium pedicle screw, imaging at higher kV values with the described DR imaging system did allow more precise localization. The current phantom design is basic in nature and does not account for any soft tissue scatter. However, initial results indicate a gain in precision when using DR compared to CR imaging equipment for RSA analysis

Tibial component loosening continues to be the most common mode of TKA failure. A debate persists on the dependence of mobilisation of this component on the equilibrium between mechanical load transfer and counterbalancing bone resistance. The aim of the present work is to study the in-vivo kinematics of TKA and to relate it with the degree of posterior slope with which the tibial component was implanted for two prosthesis designs with congruent polyethylene insert. Twenty-three patients with osteoarthritis of the knee had TKA using a cemented prosthesis (OPTETRAK, Exactech). A cruciate retaining (CR, 10 knees) or a posterior stabilized (PS, 13 knees) implant was randomly assigned at operation. Standard pre- and post-operative antero-posterior and lateral roentgenograms of the knee were taken. Fluoroscopic analysis was performed after at least 18 and 7 months after surgery for the CR and the PS group, respectively. Patients performed stair ascending, chair rising-sitting and step up-down motor tasks. Articular contacts were assumed as the two points on the medial and lateral femoral prosthetic condyles closest to the tibial component base-plate. The spine-cam distance was calculated as the minimum distance between corresponding surfaces. Only small differences in the position of the contacts over knee flexion angles were found among the motor tasks and between the two TKA designs. An overall posterior location of the tibio-femoral contact points was found at the medial and lateral compartments over all motor tasks, a little more pronounced for the PS patients. Statistically significant correlation over the three motor tasks analysed was found between posterior position of the tibio-femoral medial contact in maximum knee flexion and the post-operative tibial posterior slope. This is true for the PS and for the aggregated groups. Although no statistically significant, a general trend is observed of higher degree of flexion at which the cam contacts the spine as the post-operative posterior slopes increases: a 35 higher knee flexion angle for a tibial component implanted with a 5 of posterior slope. Generally, even when the correlations were statistically significant the correlation coefficients were always lower than 0.4. The present work reports combined measurements of post-operative posterior slope and full in-vivo relative motion of the components in both CR and PS TKAs. General trends were found between posterior slope of the tibial component and positions of the tibio-femoral contacts, but a statistically significant correlation was found only for the tibio-femoral medial contact in maximum knee flexion in the PS and in the aggregated. General trends were found between posterior slope of the tibial component and degree of flexion at which the cam starts to be in contact with the spine. The nearly standard antero-posterior translation of the tibio-femoral contacts can be bigger in flatter polyethylene inserts

The metal on metal implants was introduced without the proper stepwise introduction. The ASR resurfacing hip arthroplasty (RHA) withdrawn due to high clinical failure rates and the large diameter head THA (LDH-THA) are also widely abandoned. Early (2 year) radiostereometry studies does not support early instability as cause of failure but more likely metal wear products. A possible advantage may be maintenance of bone mineral density (BMD). We present 5 year prospective follow up from a randomized series, aiming to report changes from baseline and to investigate links between implant micromotion, Cr & Co ions and BMD. Patients eligible for an artificial hip were randomized to RHA, Biomet LDH-THA or standard Biometric THA. 19, 17 and 15 patients completed 5 year follow-up. All followed with BMD of the femur, acetabulum and for RHA the collum. RHA and THA with whole blood Co and Co. LDH-THA only at 5 year. RHA had marker based RSA of both components, cup only for LDH-THA. Translations were compiled to total translation (TT= √(x. 2. +y. 2. +z. 2. )). Data were collected at baseline, 8 weeks, 6 months, 1, 2 and 5 years. Statistical tests: ANCOVA for TT movement, Spearman's correlation for BMD, Cr, Co and BMI to TT at 5 years. RSA: The 5 year median (25%to75%) RHA cup translations were X=-0.00(−0.49 to 0.19) Y=0.15(−0.03 to 0.20), z=0.24(−0.42 to 0.37) and TT 0.58 (0.16 to 1.82) mm. For the LDH-THA X=−0.33(−0.90 to 0.20) Y=0.28(0.02 to 0.54), z=0.43(−1.12 to −0.19) and TT 1.06 (0.97 to 1.72) mm. The TT was statistically different (p<0.05) for the two cups. The RHA femoral component moved X=0.37(0.21 to 0.56) Y=0.02(−0.07 to 0.11), z=-0.01(−0.07 to 0.26) and TT 0.48 (0.29 to 0.60) mm at 5 years. There was no TT movement from year 2. The mean (SD) acetabular BMD was diminished to 93(90–97)% for RHA and 97(93–99.9)% for THA, but LDH-THA maintained 99(95–103)%. Overall femoral BMD was unchanged at 5 years for all interventions, but both stemmed implants lost 17% at the calcar. Median (25%to75%) whole-blood Cr peaked in the LDH-THA group with 1.7 (0.9 to 3.1) followed by RHA 1.2 (0.8 to 5.0) and THA with 0.5 (0.4 to 0.7)ppb. For Co the highest levels were found in RHA with 1.6(0.8 to 4.7) followed by LDH-THA 1.2 (0.7–1.7) and THA 0.2 (0.2 to 0.6) ppb. The only correlations above +/−0.3 for TT were the RHA femoral component with a correlation of 0.47 to BMI, 0.30 to Co and Cr. The ASR cup conversely had a negative correlation of −0.60 to BMI and again, the LDH-THA cup had a negative correlation of −0.37 to Cr. In contrast to registered revision rates, we found significantly larger movement for the Biomet cup than the ASR cup. The metal ion levels were similar. The LDH-THA cup maintained the acetabular BMD best at 5 years, but the difference was small, we are limited by small numbers and the correlations between TT and the covariates showed no clear pattern

Aims

The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA).

Aims. The aims of this study were to determine if an increasing serum cobalt (Co) and/or chromium (Cr) concentration is correlated with a decreasing Harris Hip Score (HHS) and Hip disability and Osteoarthritis Outcome Score (HOOS) in patients who received the Articular Surface Replacement (ASR) hip resurfacing arthroplasty (HRA), and to evaluate the ten-year revision rate and show if sex, inclination angle, and Co level influenced the revision rate. Methods. A total of 62 patients with an ASR-HRA were included and monitored yearly postoperatively. At follow-up, serum Co and Cr levels were measured and the HHS and the HOOS were scored. In addition, preoperative patient and implant variables and the need for revision surgery were recorded. We used a linear mixed model to relate the serum Co and Cr levels to different patient-reported outcome measures (PROMs). For the survival analyses we used the Kaplan-Meier and Cox regression model. Results. We found that an increase of one part per billion (ppb) in serum Co and Cr levels correlated significantly with worsening of the HHS in the following year. This significant correlation was also true for the HOOS-Pain and HOOS-quality of life sub scores. The overall ten-year survival rate in our cohort was 65% (95% confidence interval (CI) 52.5 to 77.6). Cox regression analysis showed a significant hazard ratio (HR) of 1.08 (95% CI 1.01 to 1.15; p = 0.028) for serum Co level. No significance was found with sex or inclination angle. Conclusion. This study shows that increasing serum Co and Cr levels measured in patients with an ASR-HRA are predictive for deterioration in HHS and HOOS subscales in the following year. Increasing serum Co and Cr should forewarn both surgeon and patient that there is a heightened risk of failure. Continued and regular review of patients with an ASR-HRA implant by measurement of serum Co/Cr levels and PROMs remains essential. Cite this article: Bone Joint J 2023;105-B(7):775–782

Aims. The first aim of this study was to evaluate whether preoperative renal function is associated with postoperative changes in whole blood levels of metal ions in patients who have undergone a Birmingham Hip Resurfacing (BHR) arthroplasty with a metal-on-metal bearing. The second aim was to evaluate whether exposure to increased cobalt (Co) and chromium (Cr) levels for ten years adversely affected renal function. Methods. As part of a multicentre, prospective post-approval study, whole blood samples were sent to a single specialized laboratory to determine Co and Cr levels, and the estimated glomerular filtration rate (eGFR). The study included patients with 117 unrevised unilateral BHRs. There were 36 females (31%). The mean age of the patients at the time of surgery of 51.3 years (SD 6.5), and they all had preoperative one-, four-, five-, and ten-year laboratory data. The mean follow-up was 10.1 years (SD 0.2). Results. Median Co levels at one year postoperatively increased significantly compared with the preoperative values, by a factor of 9.7, from 0.13 to 1.26 ppb (p < 0.001), and the median Cr levels increased significantly by a factor of 2.5, from 0.60 to 1.50 ppb (p < 0.001). Lower preoperative eGFRs were associated with significantly larger increases in Co at one year compared with the preoperative levels (ρ = -0.26; p = 0.005), but there was no relationship between preoperative eGFRs and changes in Cr at one year (ρ = -0.13; p = 0.153). Metal levels remained relatively constant with the passage of time, with a median ten-year value of 1.12 ppb for Co and 1.29 ppb for Cr. There was no significant relationship between the Co and Cr levels at ten-year follow-up and the change in eGFR from the preoperative level to that at ten years (ρ = -0.02; p = 0.827 for Co; ρ = -0.008; p = 0.933 for Cr). Conclusion. Although patients with lower preoperative eGFRs tended to have larger increases in Co levels at one year, increased metal levels for patients who underwent unilateral BHR did not adversely affect renal function during the first ten postoperative years. Cite this article: Bone Joint J 2024;106-B(3 Supple A):44–50