Both the patient and the surgeon want hip and knee arthroplasties to last a lifetime. As a result, many patients have been told to defer arthroplasty as long as possible. After arthroplasty, many patients have been advised to limit physical activity. Such management strategies prioritise longevity but compromise lifestyle. Given that the technical aspects of the arthroplasty are satisfactory, modern total hip and knee prostheses have demonstrated remarkable durability. Quantitative studies of patient activity have measured up to 48 million cycles in-vivo, with impact, without evidence of loosening, osteolysis, or other impending failure. These data suggest that with current technology, an active lifestyle is compatible with implant longevity

Both the patient and the surgeon want hip and knee arthroplasties to last a lifetime. As a result, many patients have been told to defer arthroplasty as long as possible. After arthroplasty, many patients have been advised to limit physical activity. Such management strategies prioritise longevity but compromise lifestyle. Given that the technical aspects of the arthroplasty are satisfactory, modern total hip and knee prostheses have demonstrated remarkable durability. Quantitative studies of patient activity have measured up to 48 million cycles in vivo, with impact, without evidence of loosening, osteolysis, or other impending failure. These data suggest that with current technology, an active lifestyle is compatible with implant longevity

Increasing pressure to use rapid recovery care pathways when treating patients undergoing total hip arthroplasty (THA) is evident in current health care systems for numerous reasons. Patient autonomy and health care economics has challenged the ability of THA implants to maintain functional integrity before achieving bony union. Although collared stems have been shown to provide improved axial stability, it is unclear if this stability correlates with activity levels or results in improved early function to patients compared to collarless stems. This study aims to examine the role of implant design on patient activity and implant fixation. The early follow-up period was examined as the majority of variation between implants is expected during this time-frame. Patients (n=100) with unilateral hip OA who were undergoing primary THA surgery were recruited pre-operatively to participate in this prospective randomized controlled trial. All patients were randomized to receive either a collared (n=50) or collarless (n=50) cementless femoral stem. Patients will be seen at nine appointments (pre-operative, < 2 4 hours post-operation, two-, four-, six-weeks, three-, six-months, one-, and two-years). Patients completed an instrumented timed up-and-go (TUG) test using wearable sensors at each visit, excluding the day of their surgery. Participants logged their steps using Fitbit activity trackers and a seven-day average prior to each visit was recorded. Patients also underwent supine radiostereometric analysis (RSA) imaging < 2 4 hours post-operation prior to leaving the hospital, and at all follow-up appointments. Nineteen collared stem patients and 20 collarless stem patients have been assessed. There were no demographic differences between groups. From < 2 4 hours to two weeks the collared implant subsided 0.90 ± 1.20 mm and the collarless implant subsided 3.32 ± 3.10 mm (p=0.014). From two weeks to three months the collared implant subsided 0.65 ± 1.54 mm and the collarless implant subsided 0.45 ± 0.52 mm (p=0.673). Subsidence following two weeks was lower than prior to two weeks in the collarless group (p=0.02) but not different in the collared group. Step count was reduced at two weeks compared to pre-operatively by 4078 ± 2959 steps for collared patients and 4282 ± 3187 steps for collarless patients (p=0.872). Step count increased from two weeks to three months by 6652 ± 4822 steps for collared patients and 4557 ± 2636 steps for collarless patients (p=0.289). TUG test time was increased at two weeks compared to pre-operatively by 4.71 ± 5.13 s for collared patients and 6.54 ± 10.18 s for collarless patients (p=0.551). TUG test time decreased from two weeks to three months by 7.21 ± 5.56 s for collared patients and 8.38 ± 7.20 s for collarless patients (p=0.685). There was no correlation between subsidence and step count or TUG test time. Collared implants subsided less in the first two weeks compared to collarless implants but subsequent subsidence after two weeks was not significantly different. The presence of a collar on the stem did not affect patient activity and function and these factors were not correlated to subsidence, suggesting that initial fixation is instead primarily related to implant design

Outcomes in arthroplasty have 3 general sources of variability: the patient, the prosthesis, and the medical-surgical-rehab. services. There are numerous factors that can contribute to earlier-than-usual clinical failure of a TKA (failure = need for revision). There are intense debates regarding design and material factors. There are technical factors such as misalignment, soft tissue imbalance, and inadequate fixation. The greatest source of variability in the outcome equation is, however, the patient. In cohort studies, the amount and type of patient activity influences the longevity of TKA. Quantitative studies have demonstrated >45-fold variation in the number of steps per day. Semi-quantitative data and survey studies show variability in the types of recreational activities and in the intensity. Age is often used as a surrogate, but BMI has a better correlation with activity than age. There is no formula, however, that can predict the longevity of an arthroplasty in a specific patient. For this reason, activity recommendations following arthroplasty continue to be debated. Which do you prioritise; lifestyle or longevity? More importantly, which does the patient prioritise?

There is increased awareness of the health benefits of regular exercise, and quantifying daily activity has become popular. Consequently, there are an increasing number of devices for measuring physical activity. Healthcare professionals and the general public should know the accuracy and limitations of these devices to better determine which ones suit their needs.

Ten devices were tested: one ankle-based device, StepWatch™ Activity Monitor (SAM); two wrist-based devices, FitBit Force™ and Nike+ Fuelband SE; seven waist-based devices, Omron HJ-321 Pedometer, Sportline 340 Strider Pedometer, FitBit One™, Samsung Galaxy S4 utilizing the two most popular applications (Runtastic and Noom Walk), and the iPhone 5 utilizing the two most popular applications (Runtastic and ARGUS). Thirty healthy volunteers, mean age 25.6 years (range 20–30) and mean body mass index 23.5 (range 17.3–29.0), completed the following protocol: (1) walk briskly around a 400-M track simulating community ambulation (2) jog around a 400-M track (3) walk slowly for 10-M, approximating household or workplace pace (4) ascend 10 steps, and (5) descend 10 steps. Each subject completed 3 trials for each task. Manual count was the gold standard (Champion Sports Tally Counter). Accuracy and mean percent error were calculated to demonstrate overall performance and any tendencies for over or undercounting. An Aggregate Accuracy Score was calculated using the mean accuracy of each activity and multiplying by a corresponding weighted value for a prototypical person: 400-M walk represents community ambulation, weighted 40%; 10-M walk represents household and workplace ambulation, weighted 30%; 400-M jog represents jogging or running, weighted 20%; Stair Ascent and Descent represent community and household stair use, weighted 5% each.

Device rank based on the Aggregate Accuracy Score was #1 FitBit One™ (98.0%), #2 Omron HJ-321 (97.0%), #3 StepWatch™ Activity Monitor (93.3%), #4 Runtastic Google App (92.7%), #5 Runtastic iPhone App (89.5%), #6 Fitbit Force™ (88.2%), #7 Argus iPhone App (87.2%), #8 Sportline 340 Strider (85.7%), #9 Nike Fuelband (76.1%), #10 Noom Walk Google App (75.9%). The FitBit One™ was 99.5%, 97.8%, 96.7%, 94.3%, and 96.9% accurate in the 400-M walk, 10-M walk, 400-M jog, 10 stair ascent, and 10 stair descent, respectively. The Omron HJ-321 was 99.3%, 94.9%, 97.9%, 92.2%, and 91.3% accurate, respectively. The SAM performed well (>95% accurate) in all activities except one, consistently undercounting the 400-M jog by about 25% (95% CI: −27.2% – −23.9%). The FitBit ForceTM and Nike+ Fuelband SE wrist devices were ≥90% accurate in the 400-M walk and 400-M jog, but ≤83% accurate for all other activities. Three of the 4 smartphone applications were >97% accurate in the 400-M walk, 1 of 4 was 97.3% accurate in the 400-M jog, but all devices performed poorly (≤90% accurate) for all other activities.

Smartphones are very popular, but current technology is less accurate for measuring overall daily activity. The relatively inexpensive FitBit One™ and Omron HJ-321 pedometer are highly accurate for quantifying a variety of activities, including running. The StepWatch™ Activity Monitor performs well in lower cadence, but consistently undercounted jogging. Wrist-based activity devices are not as accurate as waist-based. Next generation technologies, including smartphones, should undergo accuracy testing before recommending them for daily use.

PROBLEM. Since the COVID-19 pandemic of 2020, there has been a marked rise in the use of telemedicine to evaluate patients following total knee arthroplasty (TKA). Telemedicine is helpful to maintain patient contact, but it cannot provide objective functional TKA data. External monitoring devices can be used, but in the past have had mixed results due to patient compliance and data continuity, particularly for monitoring over numerous years. This novel stem is a translational product with an embedded sensor that can remotely monitor patient activity following TKA. SOLUTION. The Canturio™ TE∗ System (Canary Medical) functions structurally as a tibial extension for the Persona® cemented tibial plate (Zimmer Biomet). The stem is instrumented with internal motion sensors (3-D accelerometer and gyroscope) and telemetry that collects and transmits kinematic data. Raw data is converted by analytics into clinically relevant gait metrics using a proprietary algorithm. The Canturio™ TE∗ will monitor the patient's gait daily for the first year and then with lower frequency thereafter to conserve battery power enabling the potential for 20 years of longitudinal data collection and analysis. A base station in the OR activates the device and links the stem and data to the patient. A base station in the patient's home collects and uploads data to the Cloud Based Canary Data Management Platform (Canary Medical). The Canary Cloud is structured as an FDA regulated and HIPPA-compliant database with cybersecurity protocols integrated into the architecture. A third base station is an accessory used in the health care professional's office to perform an on-demand gait analysis of a patient. A dashboard allows the health care professional and patient to monitor objective data of the patient's activity and progress post treatment. MARKET. The early target market for this device includes total joint surgeons who are early adopters of technology and currently utilize technology in their practice. The kinematic data provided by the Canturio™ TE∗ System will enable clinicians to augment patient care by reviewing their objective gait metrics. In the future, this data has the potential to be integrated with other Zimmer Biomet technologies, such as the Rosa™ Knee robotic platform, mymobility™, and sensored devices like iAssist™, to provide the surgeon with a complete pre-surgical functional assessment, intraoperative data, and post-operative functional data. PRODUCT. Persona IQ will be the combination of the proven Persona personalized total knee system with the Canary Medical Canturio™ TE∗. TIMING AND FUNDING. The Canturio™ TE is currently under De Novo FDA review for market clearance; it is not yet available for commercial distribution. The plan is to launch the product in 2021 pending regulatory De Novo grant. This effort is a partnership between Zimmer Biomet and Canary Medical. ∗ The Canturio™ - TE is currently under De Novo FDA review for market clearance; it is not yet available for commercial distribution

The purpose of this study was to examine the influence of weight-bearing on the measurement of in vivo wear of total knee replacements using model-based RSA at 1 and 2 years following surgery. Model-based RSA radiographs were collected for 106 patients who underwent primary TKR at a single institution. Supine RSA radiographs were obtained post-operatively and at 6-, 12-, and 24-months. Standing (weight-bearing) RSA radiographs were obtained at 12-months (n=45) and 24-months (n=48). All patients received the same knee design with a fixed, conventional PE insert of either a cruciate retaining or posterior stabilized design. Ethics approval for this study was obtained. In order to assess in vivo wear, a highly accurate 3-dimensional virtual model of each in vivo TKA was developed. Coordinate data from RSA radiographs (mbRSA v3.41, RSACore) were applied to digital implant models to reconstruct each patient's replaced knee joint in a virtual environment (Geomagic Studio, 3D Systems). Wear was assessed volumetrically (digital model overlap) on medial and lateral condyles separately, across each follow-up. Annual rate of wear was calculated for each patient as the slope of the linear best fit between wear and time-point. The influence of weight-bearing was assessed as the difference in annual wear rate between standing and supine exams. Age, BMI, and Oxford-12 knee improvement were measured against wear rates to determine correlations. Weight bearing wear measurement was most consistent and prevalent in the medial condyle with 35% negative wear rates for the lateral condyle. For the medial condyle, standing exams revealed higher mean wear rates at 1 and 2 years, supine, 16.3 mm3/yr (SD: 27.8) and 11.2 mm3/yr (SD: 18.5) versus standing, 51.3 mm3/yr (SD: 55.9) and 32.7 mm3/yr (SD: 31.7). The addition of weight-bearing increased the measured volume of wear for 78% of patients at 1 year (Avg: 32.4 mm3/yr) and 71% of patients at 2 years (Avg: 48.9 mm3/yr). There were no significant (95% CI) correlations between patient demographics and wear rates. Volumetric, weight-bearing wear measurement of TKR using model-based RSA determined an average of 33 mm3/yr at 2 years post-surgery for a modern, non-cross-linked polyethylene bearing. This value is comparable to wear rates obtained from retrieved TKRs. Weight-bearing exams produced better wear data with fewer negative wear rates and reduced variance. Limitations of this study include: supine patient imaging performed at post-op, no knee flexion performed, unknown patient activity level, and inability to distinguish wear from plastic creep or deformation under load. Strengths of this study include: large sample size of a single TKR system, linear regression of wear measurements and no requirement for implanted RSA beads with this method. Based on these results, in vivo volumetric wear of total knee replacement polyethylene can be reliably measured using model-based RSA and weight-bearing examinations in the short- to mid–term. Further work is needed to validate the accuracy of the measurements in vivo

INTRODUCTION. Implant wear testing is traditionally undertaken using standardized inputs set out by ISO or ASTM. These inputs are based on a single individual performing a single activity with a specific implant. Standardization helps ensure that implants are tested to a known set of parameters from which comparisons may be drawn but it has limitations as patients perform varied activities, with different implant sizes and designs that produce different kinematics/kinetics. In this study, wear performance has been evaluated using gait implant specific loading/kinematics and comparing to a combination deep knee bend (DKB), step down (SD) and gait implant specific loading on cruciate retaining (CR) rotating platform (RP) total knee replacements (TKR). This combination activity profile better replicates patient activities of daily living (ADL). METHODS. Two sets of three ATTUNE. ®. size 5 right leg CR RP TKRs (DePuy Synthes, Warsaw, IN) were used in a study to evaluate ADL implant wear. Implant specific loading profiles were produced via a validated finite element lower limb model [1] that uses activity data such as gait (K1L_110108_1_86p), SD (K1L_240309_2_144p), and DKB (K9P_2239_0_9_I1) from the Orthoload database [2] to produce external boundary conditions. Each set of components were tested using a VIVO joint simulator (AMTI, Watertown, MA, Figure 1) for a total of 4.5 million cycles (Mcyc). All cycles were conducted at 0.8Hz in force-control with flexion driven in displacement control. Bovine calf serum lubricant was prepared to a total protein concentration of 18g/L and maintained at 37°±2°C. Wear of the tibial inserts was quantified via gravimetric methods per ISO14243–2:2009(E). Polyethylene tibial insert weights were taken prior to testing and every 0.5Mcyc there after which corresponded to serum exchange intervals. The multi-activity test intervals were split into10 loops of 1,250 DKB, 3,000 SD, and 45,750 gait cycles in series. Based on activity data presented by Wimmer et al. the number of cycles per activity and activities used is sufficient for a person that is considered active [3]. A loaded soak control was used to compensate for fluid absorption in wear rate calculations. Wear rates were calculated using linear regression. RESULTS SECTION. The wear rate for the gait-only activity test was calculated to be 0.20±0.04mg/Mcyc conversely the wear rate for the multi-activity test was 2.65±0.67mg/Mcyc (Figure 2). Wear scars can be found in Figure 3. Using a two-sided t-test of unequal variance, it was found that there was a significant difference between the two wear rates (p=0.004). DISCUSSION. Adding activities to the wear simulation test significantly increased the average wear rate of the test samples, confirming that changes in cross shear from different activities will tend to increase the wear of an implant. The results of this study prove that single activity wear testing may not be the most clinically severe wear testing that can be used for pre-clinical wear assessment. For any figures or tables, please contact the authors directly

Background. There is increasing impetus to use rapid recovery care pathways when treating patients undergoing total hip arthroplasty (THA). The direct anterior (DA) approach is a muscle sparing technique that is believed to support these new pathways. Implants designed for these approaches are available in both collared and collarless variations and understanding the impact each has is important for providing the best treatment to patients. Purpose/Aim of Study. This study aims to examine the role of implant design on implant fixation and patient recovery. Materials and Methods. Patients (n=50) with unilateral hip OA who were undergoing primary DA THA surgery were recruited pre-operatively to participate in this prospective randomized controlled trial. All patients were randomized to receive either a collared (n=25) or collarless (n=25) cementless, fully hydroxyapatite coated femoral stem. Patients were seen at nine appointments (pre-operative, <24 hours post-operation, two-, four-, six-weeks, three-, six-months, one-, and two-years). Patients underwent supine radiostereometric analysis (RSA) imaging <24 hours post-operation prior to leaving the hospital, and at all follow-up appointments. Patients also completed an instrumented timed up-and-go (TUG) test using wearable sensors at each visit, excluding the day of their surgery. Participants logged their steps using Fitbit activity trackers and a seven-day average prior to each visit was recorded. Findings/Results. Twenty-two patients that received a collared stem and 27 patients that received a collarless stem have been assessed. There were no demographic differences between groups. From <24 hours to two weeks the collared implants subsided 0.90 ± 1.20 mm and the collarless implants subsided 3.80 ± 3.37 mm (p=0.001). From two weeks to three months the collared implants subsided 0.67 ± 1.61 mm and the collarless implants subsided 0.45 ± 0.46 mm (p=0.377). Step count was reduced at two weeks to 3108 ± 1388 steps for collared patients and 2340 ± 1685 steps for collarless patients (p=0.072). Step count was increased at three months to 8939 ± 3494 steps for collared patients and 6114 ± 2529 steps for collarless patients (p=0.034). TUG test time was increased at two weeks compared to pre-operatively by 3.45 ± 6.01 s for collared patients and 2.29 ± 4.92 s for collarless patients (p=0.754). TUG test time decreased from two weeks to three months by 6.30 ± 6.05 s for collared patients and 5.68 ± 4.68 s for collarless patients (p=0.922). Conclusions. Collared implants subsided less in the first two weeks compared to collarless implants but subsequent subsidence after two weeks was not significantly different. Presence of a collar on the stem impacted patient activity but not function. This suggests that both the implant design as well as the surgical technique may play a role in the patient's early post-operative experience

Introduction. Retrieval investigations have shown that cracking or rim failure of polyethylene hip liners may occur at the superior aspect of the liner, in the area that engages the locking ring of the shell. 1. Failure could occur due to acetabular liner/stem impingement and/or improper cup position. Other contributing factors may include high body mass index, patient activity and design characteristics such as polyethylene material properties, thin liner rim geometry and cup rim design. Currently no standard multi-axis simulator methodology exists for high angle rim fatigue testing, although tests have been developed using static uniaxial load frames. 2. The purpose of this study was to develop a technique to create a clinically relevant rim crack/fracture event on a 4-axis hip simulator, and to understand the contribution of component design and loading and motion parameters. Method. A method for creating rim fracture in vitro was developed to evaluate implant design features and polyethylene liner materials. Liners were secured into acetabular shells, fixtured in resin mounted at a 55° (in vitro; 65° in vivo) inclination to ensure high load/stress was at the area of interest. Ranges of kinematic and maximum applied load profiles were investigated (parameters summarized in Table 1). Testing was conducted on an AMTI 12-station hip simulator for 0.25–1.0 million cycles or until fracture (lubrication maintained with lithium grease). At completion, liners were cleaned and examined for crack propagation/fracture. Inspection of the impingement site on the opposite rim was also analyzed. Additional assessments included liner disassociation/rock out, deformation of characteristics such as anti-rotation devices and microscopic inspection of high-stress regions. Results/Discussion. This study summarizes testing on hip wear simulators to create rim cracking/fracture in vitro. Results indicate that cup/stem angles must be controlled to ensure contact areas are reproducible, and therefore on a multi-station machine (i.e. AMTI), only one test station can/should be run at a time to ensure repeatability. Component design characteristics, such as head size and liner material had a marked effect on the results. It is noted that the kinematics, load and cycle count must be adjusted per the component design to create rim fracture in the high-risk region. Finite element analysis modeling may help identify the high-stress region(s) prior to simulator testing. Deformation of the rim opposite the fracture region (rim/taper impingement) was observed due to the high angle of inclination combined with the abduction/adduction angles. Conclusion. Rim fractures similar in location and morphology to those seen in retrieval studies can be created using a multi-axis hip simulator in vitro. It is noted, however, that the factors presented in this study must be considered and controlled to assure a repeatable method, as the differences in component design investigated and simulator inputs were seen significantly affect the outcome. This study was limited and did not attempt to reproduce rim damage seen in all implant retrievals (e.g. lateralized liners, high offset implants, etc.). These design inputs are being investigated and will be reported upon in the future. For any figures or tables, please contact the authors directly

Purpose. The purpose of this study was to examine the influence of weight-bearing on the measurement of in vivo wear of total knee replacements using model-based RSA at 1 and 2 years following surgery. Methods. Model-based RSA radiographs were collected for 106 patients who underwent primary TKR at a single institution. Supine RSA radiographs were obtained post-operatively and at 6-, 12-, and 24-months. Standing (weight-bearing) RSA radiographs were obtained at 12-months (n=45) and 24-months (n=48). All patients received the same knee design with a fixed, conventional PE insert of either a cruciate retaining or posterior stabilized design. Ethics approval for this study was obtained. In order to assess in vivo wear, a highly accurate 3-dimensional virtual model of each in vivoTKA was developed. Coordinate data from RSA radiographs (mbRSA v3.41, RSACore) were applied to digital implant models to reconstruct each patient's replaced knee joint in a virtual environment (Geomagic Studio, 3D Systems). Wear was assessed volumetrically (digital model overlap) on medial and lateral condyles separately, across each follow-up. Annual rate of wear was calculated for each patient as the slope of the linear best fit between wear and time-point. The influence of weight-bearing was assessed as the difference in annual wear rate between standing and supine exams. Age, BMI, and Oxford-12 knee improvement were measured against wear rates to determine correlations. Results. Weight bearing wear measurement was most consistent and prevalent in the medial condyle with 0–4% of calculated wear rates being negative compared to 29–39% negative wear rates for the lateral condyle. For the medial condyle, standing exams revealed higher mean wear rates at 1 and 2 years; supine, 16.3 mm. 3. /yr (SD: 27.8) and 11.2 mm. 3. /yr (SD: 18.5) versus standing, 51.3 mm. 3. /yr (SD: 55.9) and 32.7 mm. 3. /yr (SD: 31.7). The addition of weight-bearing increased the measured volume of wear for 78% of patients at 1 year (Avg: 32.4 mm. 3. /yr) and 71% of patients at 2 years (Avg: 48.9 mm. 3. /yr). There were no significant (95% CI) correlations between patient demographics and wear rates. Discussion and Conclusion. This study demonstrated TKA wear to occur at a rate of approximately 10 mm. 3. /year and 39 mm. 3. /year in patients imaged supine versus standing, respectively, averaged over 2 years of clinical follow-up. In an effort to eliminate the effect of PE creep and deformation, wear was also calculated between 12 and 24 months as 9.3 mm. 3. (standing examinations), This value is comparable to wear rates obtained from retrieved TKRs. Weight-bearing exams produced better wear data with fewer negative wear rates and reduced variance. Limitations of this study include: supine patient imaging performed at post-op, no knee flexion performed, and unknown patient activity level. Strengths of this study include: large sample size of a single TKR system, linear regression of wear measurements and no requirement for implanted RSA beads with this method. Based on these results, in vivo volumetric wear of total knee replacement polyethylene can be reliably measured using model-based RSA and weight-bearing examinations in the short- to mid–term. For any figures or tables, please contact authors directly

Durable humeral component fixation in shoulder arthroplasty is necessary to prevent painful aseptic loosening and resultant humeral bone loss. Causes of humeral component loosening include stem design and material, stem length and geometry, ingrowth vs. ongrowth surfaces, quality of bone available for fixation, glenoid polyethylene debris osteolysis, exclusion of articular particulate debris, joint stability, rotator cuff function, and patient activity levels. Fixation of the humeral component may be achieved by cement fixation either partial or complete and press-fit fixation. During the past two decades, uncemented humeral fixation has become more popular, especially with short stems and stemless press fit designs. Cemented humeral component fixation risks difficult and complicated revision surgery, stress shielding of the tuberosities and humeral shaft periprosthetic fractures at the junction of the stiff cemented stem and the remaining humeral shaft. Press fit fixation may minimise these cemented risks but has potential for stem loosening. A randomised clinical trial of 161 patients with cemented vs. press fit anatomic total shoulder replacements found that cemented fixation of the humeral component provided better quality of life, strength, and range of motion than uncemented fixation but longer operative times. Another study found increased humeral osteolysis (43%) associated with glenoid component loosening and polyethylene wear, while stress shielding was seen with well-fixed press fit humeral components. During reverse replacement the biomechanical forces are different on the humeral stem. Stem loosening during reverse replacement may have different factors than anatomic replacement. A systemic review of 41 reverse arthroplasty clinical studies compared the functional outcomes and complications of cemented and uncemented stems in approximately 1800 patients. There was no difference in the risk of stem loosening or revision between cemented and uncemented stems. Uncemented stems have at least equivalent clinical and radiographic outcomes compared with cemented stems during reverse shoulder arthroplasty. Durable humeral component fixation in shoulder arthroplasty is associated with fully cemented stems or well ingrown components that exclude potential synovial debris that may cause osteolysis

BACKGROUND. Telerehabilitation has been shown to both promote effective recovery after shoulder arthroplasty and may improve adherence to treatment. Such systems require demonstration of feasibility, ease of use, efficacy, patient and clinician satisfaction, and overall cost of care, and much of this data has yet to be provided. Few augmented reality rehabilitation approaches have been developed to date. Evidence suggests augmented reality rehabilitation may be equivalent to conventional methods for adherence, improvement of function, and relief of pain seen in these musculoskeletal conditions. We proposed that the development of an augmented reality rehabilitation platform during the pre and postoperative period (including post-shoulder arthroplasty) could be used to track patient activity and range of motion as well as promote recovery. METHODS. A prototype augmented reality platform equipped with a motion sensor system optimised for the upper arm was developed to be used to validate 4 arcs of shoulder motion and complete directed upper arm exercises designed for post-shoulder arthroplasty rehabilitation was built and tested. This system combined augmented reality instructions and motion tracking to follow patients over the course of their therapy, along with a telehealth patient-clinician interface. FINDINGS. The augmented reality platform was tested to validate shoulder range of motion examination similar to that of standard goniometer measurements. Healthy test subjects without shoulder pain or prior shoulder surgery performed the arcs of motion for 5 repetitions as part of a home therapy program. Each motion was measured with angular measurements as a proof of concept with high degree precision (less than 5 degrees). Remote patient-clinician interface testing was also conducted along with a clinician established therapy plan. DISCUSSION. Augmented reality systems that track patients' complex movements, including clinical shoulder range of motion, suggest the promising future of telerehabilitation in arthroplasty, particularly in telemonitoring before and after surgery. As this technology continues to gain acceptance, further studies that evaluate the outcomes of augmented reality rehabilitation for long-term follow-up are needed

The advent of modern anatomic shoulder arthroplasty occurred in the 1990's with the revelation that the humeral head dimensions had a fixed ratio between the head diameter and height. As surgeons moved from the concept of balancing soft tissue tension by using variable neck lengths for a given humeral head diameter, a flawed concept based on lower extremity reconstruction, improvements in range of motion and function were immediately observed. Long term outcome has validated this guiding principle for anatomic shoulder replacement with improved longevity of implants, improved patient and surgeon expectations and satisfaction with results. Once the ideal humeral head prosthesis is identified, and its position prepared, the surgeon must use a method to fix the position of the head that is correct in three dimensions and has the security to withstand patient activities and provide maximal longevity. Based again on lower extremity concepts, long stems were the standard of care, initially with cement, and now, almost universally without cement for a primary shoulder replacement. The incredibly low revision rates for humeral stem aseptic loosening shifted much of the attempted innovation to the challenges on the glenoid side of the reconstruction. However, glenoid problems including revision surgery, infections, periprosthetic fractures, and other complications often required the removal of the humeral stem. And, in many cases, the overall results of the procedure and the patient's long-term outcome was affected by the difficulty in removing the stem, leading surgeons to compromise the revision procedure, avoid revision surgery, or add to the overall morbidity with humeral fractures and substantial bone loss. With improved technology, including bone ingrowth methods, better matching of the proximal stem geometry to the humerus, and an understanding that the center of rotation (torque) on the humeral component is at the level of the humeral osteotomy, shorter stems and stemless humeral components were developed, now more than 10 years ago, primarily in Europe. With more than a decade of experience, our European colleagues have shown us that stemless humeral component replacement with a device that has both cortical and cancellous fixation is as effective as a stemmed device, easier to implant as well as revise when needed. The short-term results of the cancellous fixation stemless devices are acceptable, but longer follow-up is needed. Currently, the most widely used humeral components in the USA are short stem components, although the recent FDA approval of numerous stemless devices has initiated a shift from short stems to stemless devices. The truth is, short stem devices have a firm position in the USA surgeons' armamentarium today due to regulatory restrictions. A decade ago, without a predicate on the market, it was not conceivable that a stemless device that was already gaining popularity in Europe would be able to get 510K approval, and therefore would require a lengthy and expensive FDA IDE process. However, shorter stems had already been approved in the USA, as long as the stem length was 7 centimeters, matching the market predicate. Now, in 2018, based on evidence and outcomes, stemless humeral components should be the first choice when treating primary osteoarthritis of the glenohumeral joint. Short stem or longer stem devices should be reserved for those cases where stemless fixation is not possible, which is less than 10% of patients with primary OA of the shoulder

INTRODUCTION. Porous metal bone fillers are frequently used to manage bony defects encountered in revision total knee arthroplasty (rTKA). Compared to structural graft, porous metal bone fillers have shown significantly lower loosening and failure rates potentially due to osseointegration and increased material strength [1]. The strength of porous metal bone fillers used in lower extremities is frequently assessed using compression/shear/torsion test methods, adapted from spine standards. However, these basic methods may lack clinical relevance, and do not provide any insight on the relationship between patient activity and anticipated prosthesis performance. The goal of this study was to evaluate the response of bone fillers under different activities of daily living, in order to define physiologically relevant worst case biomechanics for component evaluation. METHODS. A bone filler tibial augment is shown in Figure 1. A test construct for tibial augments (half-block each for medial and lateral sides) is shown in Figure 2, along with compatible rTKA components. An additional void in the bone was filled using bone cement. Loading was applied through the tibiofemoral contact patches created on polyethylene tibial insert. Loading was used for two activities of daily living; walking and deep knee bend [2–3]. During walking, the tibiofemoral contact patch on the anterior tibial post gets loaded due to femoral hyperextension with 1.2xbody weight (BW), whereas the medial and lateral condyles get loaded with 3xBW compressive load. For deep knee bend, only the condyles get loaded with 4.34xBW. Compared to walking, 45% higher compressive load magnitude in deep knee bend located further posterior was anticipated to create a larger bending moment and induce higher stress on the half augments. A finite element analysis (FEA) was performed by modeling this test construct with a medium size tibial augment. All components were modeled using linear elastic material properties. All interfaces, including the augment-bone interface (representing full bony ingrowth construct) were modeled using bonded contact. The inferior surface of the bone analogue was constrained. Linear static analyses were performed and peak von mises stress predicted in the tibial augments was compared between activities. RESULTS. Deep knee bend resulted in 31% higher stresses in the tibial augments than for walking. High von mises stresses were mostly predicted at the superior/posterior aspect of the internal side of the augment and in the corners of the cutouts. Figure 3 presents the von mises stresses in the tibial augments for both loading scenarios. DISCUSSION. This study revealed that the 45% increased posterior compressive load associated with deep knee bend is a more significant factor than the moment applied to the post during walking gait for a hyperextended knee, when considering the stress in bone filler augments in revision TKA. The stress in the augments can depend on multiple factors and the proposed FEA method can be used to compare stresses in different porous material bone fillers to determine worst case for assessing its strength

The treatment of medial knee osteoarthritis (OA) in conjunction with anterior knee laxity is an issue of debate. Current treatment options include knee joint distraction, unicompartmental knee replacement (UKR) or high tibial osteotomy with anterior cruciate ligament (ACL) reconstruction or total knee replacement. Bone-conserving options are preferred for younger and active patients with intact lateral and patello-femoral compartment. However, still limited experience exists in the field of combining medial UKR and ACL reconstruction. The aim of this study is to retrospectively evaluate the results of combined fixed-bearing UKR and ACL reconstruction, specifically with regard to patient satisfaction, activity level, and postoperative functional outcomes. The hypothesis was that this represents a safe and viable procedure leading to improved stability and functional outcome in patients affected by isolated unicompartmental OA and concomitant ACL deficiency. Fourteen patients with ACL deficiency and concomitant medial compartment symptomatic osteoarthritis were treated from 2006 to 2010. Twelve of them were followed up for an average time of 7.8 year (range 6–10 years). Assessment included Knee Osteoarthritis Outcome Score (KOOS), Oxford Knee score (OKS), American Knee Society scores (AKSS), WOMAC index of osteoarthritis, Tegner activity level, objective examination including instrumented laxity test with KT-1000 arthrometer and standard X-rays. Wilcoxon test was utilized to compare the pre-operative and follow-up status. Differences with a p value <0.05 were considered statistically significant. KOOS score, OKS, WOMAC index and the AKSS improved significantly at follow-up (p < 0.05). There was no clinical evidence of instability in any of the knees as evaluated with clinical an instrumented laxity testing (p < 0.05). No pathologic radiolucent lines were observed around the components. In one patient a total knee prosthesis was implanted due to the progression of signs of osteoarthritis in the lateral compartment 3 years after primary surgery. UKR combined with ACL reconstruction is a valid therapeutic option for young and active patients with a primary ACL injury who develop secondary OA and confirms subjective and objective clinical improvement up to 8 years after surgery

Introduction. Gait laboratory measurement of whole-body kinematics and ground reaction forces during a wide range of activities is frequently performed in joint replacement patient diagnosis, monitoring, and rehabilitation programs. These data are commonly processed in musculoskeletal modeling platforms such as OpenSim and Anybody to estimate muscle and joint reaction forces during activity. However, the processing required to obtain musculoskeletal estimates can be time consuming, requires significant expertise, and thus seriously limits the patient populations studied. Accordingly, the purpose of this study was to evaluate the potential of deep learning methods for estimating muscle and joint reaction forces over time given kinematic data, height, weight, and ground reaction forces for total knee replacement (TKR) patients performing activities of daily living (ADLs). Methods. 70 TKR patients were fitted with 32 reflective markers used to define anatomical landmarks for 3D motion capture. Patients were instructed to perform a range of tasks including gait, step-down and sit-to-stand. Gait was performed at a self-selected pace, step down from an 8” step height, and sit-to-stand using a chair height of 17”. Tasks were performed over a force platform while force data was collected at 2000 Hz and a 14 camera motion capture system collected at 100 Hz. The resulting data was processed in OpenSim to estimate joint reaction and muscle forces in the hip and knee using static optimization. The full set of data consisted of 135 instances from 70 patients with 63 sit-to-stands, 15 right-sided step downs, 14 left-sided step downs, and 43 gait sequences. Two classes of neural networks (NNs), a recurrent neural network (RNN) and temporal convolutional neural network (TCN), were trained to predict activity classification from joint angle, ground reaction force, and anthropometrics. The NNs were trained to predict muscle and joint reaction forces over time from the same input metrics. The 135 instances were split into 100 instances for training, 15 for validation, and 20 for testing. Results. The RNN and TCN yielded classification accuracies of 90% and 100% on the test set. Correlation coefficients between ground truth and predictions from the test set ranged from 0.81–0.95 for the RNN, depending on the activity. Predictions from both NNs were qualitatively assessed. Both NNs were able to effectively learn relationships between the input and output variables. Discussion. The objective of the study was to develop and evaluate deep learning methods for predicting patient mechanics from standard gait lab data. The resulting models classified activities with excellent performance, and showed promise for predicting exact values for loading metrics for a range of different activities. These results indicate potential for real-time prediction of musculoskeletal metrics with application in patient diagnostics and rehabilitation. For any figures or tables, please contact authors directly

Introduction. First-generation annealed HXLPE has been clinically successful at reducing both clinical wear rates and the incidence of osteolysis in total hip arthroplasty. However, studies have observed oxidative and mechanical degradation occurring in annealed HXLPE. Thus, it is unclear whether the favorable clinical performance of 1st generation HXLPE is due to the preservation of bearing surface tribological properties or, at least partially, to the reduction in patient activity. The purpose of this study was to evaluate the in vitro wear performance (assessed using multidirectional pin-on-disk (POD) testing) of 1. st. -generation annealed HXLPE with respect to in vivo duration, clinical wear rates, oxidation, and mechanical properties. Materials and Methods. 103 1. st. -generation annealed HXLPE liners were collected at revision surgery. 39 annealed HXLPE liners were selected based on their implantation time and assigned to three equally sized cohorts (n=13 per group); short-term (1.4–2.7y), intermediate term (5.2–8.0y) and long-term (8.3–12.5y). From each retrieved liner, two 9-mm cores were obtained (one from the superior region and one from the inferior region). Sixteen cores were fabricated from unimplanted HXLPE liners that were removed from their packaging and six pins from unirradiated GUR 1050 resin served as positive controls. Multidirectional POD wear testing was conducted against wrought CoCr disks in a physiologically relevant lubricant (20 g/L protein concentration) using a 100-station SuperPOD (Phoenix Tribology, UK). Each pin had its own chamber with 15mL lubricant maintained at 37±1°C. An elliptical wear pattern with a static contact stress of 2.0 MPa was employed. Testing was carried out to 1.75 million cycles at 1.0 Hz and wear was assessed gravimetrically. POD wear rates were calculated using a linear regression of volumetric losses. In vivo penetration was measured directly using a calibrated micrometer. Oxidation was assessed on thin films obtained from superior and inferior regions of the liners (ASTM 2102). Mechanical properties were assessed using the small punch test (ASTM 2183). Results. In vitro wear rates from the SuperPOD were positively correlated with implantation time (Rho=0.27; p=0.015) and average oxidation (Rho=0.36; p=0.004) at the bearing surface of the retrieved HXLPE liners. All retrieved HXLPE cohorts had lower in vitro wear rates than uncrosslinked positive control (p≤0.03) and higher wear rates than the never-implanted HXLPE cohort (p <0.001). POD wear rates were negatively correlated with small punch ultimate load (p<0.01). However, the in vitro wear rates were not correlated with clinical penetration rates (p=0.71). Discussion. This study investigated the effects of in vivo degradation on 1. st. -generation annealed HXLPE liners. The data in this study suggest that the tribological properties degrade due to in vivo oxidation as the liner is exposed to the in vivo environment. The clinical implications of these findings, however, are not clear as the clinical penetration rates were not correlated with the in vitro POD wear rates. This may be partially due, to decreasing patient activity as they age. These findings will be useful for comparison for evaluating the in vitro wear properties of other HXLPEs, including 2nd generation HXLPE. Acknowledgements. This study was supported by the NIH(NIAMS) R01AR47904

Background. Recent clinical studies have suggested that systemic metal ion levels are significantly elevated at midterm follow-up after ceramic-on-metal (COM) bearing. However, it is not clear whether there is a correlation between patient- and surgical-related factors including the lifestyle and elevated levels of serum metal ions following COM total hip arthroplsty (THA). Material and Methods. Two hundred and one patients (234 hips) including 121 COM patients (140 hips) and 80 non-COM patients (94 hips) were enrolled in accordance with the inclusion criteria. The patients were divided into three groups based on the type of surgical bearings used. The Harris Hip Score (HHS), University of California, Los Angeles (UCLA) activity scale score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were measured, and radiographs were obtained for the analysis. Serum metal ion levels of cobalt and chromium were measured using a high-resolution inductively coupled plasma mass spectrometry. Patient- and surgical-related factors were analyzed to determine which group of patients is at a high risk of metal ion-related problems. Results. Significantly higher serum levels of Co and Cr were detected in the serum of the COM THA group (Co: 1.86±4.0 µg/L, range: 0.30 to 34.20 µg/L; Cr: 1.81±2.87 µg/L, range: 0.10 to 27.80 µg/L) than in the serum of the non-COM THA group (Co: 0.27±0.14 µg/L, range: 0.15 to 0.90 µg/L; Cr: 0.19±0.25 µg/L, range; 0.10 to 2.30 µg/L) (p<0.001). The HHS in the COM group was significantly better than that in the non-COM group (p=0.013). The total ROM of the THAs was significantly greater in the 36-mm COM THA group (272.7°, range: 200°–345°) than in the non-COM group (248.5°, range: 135°–300°) (p<0.001). No radiolucency, osteolysis, or loosening was found during the follow-up radiographic examination. The serum Co levels of patients who achieved the squatting position were significantly higher than those of patients who could not squat (Co: p=0.033; Cr: p=0.074). The serum Co and Cr levels of patients who achieved the kneeling position were significantly higher than those of patients who could not kneel (Co: p=0.049; Cr: p=0.031). There was no significant difference between the two groups in the cross-legged sitting position. The metal ion levels of the COM THA group correlated with the total ROM (Co: p=0.0293; Cr: p=0.0399), and those of the patients who were capable of squatting and kneeling were significantly higher than those of the patients who were unable (p<0.05). However, age, BMI, acetabular cup position and patient activity did not show significant correlations with the serum metal ion levels. Conclusions. Patients who underwent a 36-mm COM THA had good clinical outcomes with an excellent hip function at the short and midterm follow-up intervals. However, high levels of metal ions were detected in the serum of COM THA patients. We found that COM THA patients who were capable of greater ROMs, squatting, and kneeling are at risk of metal ion-related problems

Introduction. Measured outcomes from knee joint arthroplasty (TKA) have primarily focused on surgeon-directed criteria, such as alignment, range of motion measured in the clinic, and implant durability, rather than on functional outcomes. There is strong evidence that subjective reporting by patients fails to capture objective real-life function. 1,2. We believe that the recent emphasis on clinical outcomes desired by the patient, as well as the need to demonstrate value, requires a new approach to patient outcomes that directly monitors ambulatory activity after surgery. We have developed and tested a system that: 1) autonomously identifies patients who are not progressing well in their recovery from TKA surgery; 2) characterizes patient activity profiles; 3) automatically alerts health care providers of patients who should be seen for additional follow-up. We anticipate that such a system could decrease secondary procedures such as manipulation under anesthesia (MUA) and reduce hospital re-admission rates thereby resulting in significant cost savings to the patient, the care providers, and insurers. Methods. The components of the system include: 1) A sensor package that is mounted correctly in relation to the knee joint (Figure 1a) and is suitable for long term use; 2) An application that runs under the Android operating system to communicate with the sensor and to gather subjective information (pain, satisfaction, perceived stability etc. together with a photograph of the surgical site (Figure 1b); 3) Software to upload the data from the phone to a remote server; 4) An analysis and reporting package that generates, among other metrics, a profile describing the patient's activity throughout the day, trends in the recovery process, and alerts for abnormal findings (Figure 1c). The system was pilot tested on 12 patients (7 females) who underwent TKA. Complete days of data collection were scheduled for each patient every two weeks until 12 weeks, starting during the second week after surgery. Results. Patients tolerated the system well and datasets of up to 13 hours long were recorded. There was a considerable variation between patients in the use of the prosthetic knee joint at a given time point after surgery. At 6 weeks post-surgery, for example, some relatively inactive subjects had less than 50 excursions per hour while active subjects exhibited more than 750 excursions per hour. It was notable that, in activities of daily living, subjects rarely used the extremes of the flexion range that had been measured during post-operative clinic visits. Examples of activity recognition during free-living will be presented. Discussion. A remote knee monitoring system has been designed and successfully tested in an outpatient setting. The system has revealed discrepancies between knee function measured during clinic visits and that measured remotely during free living. Remote monitoring after orthopaedic procedures adds an important new dimension to the assessment of patient outcome. Acknowledgments. This work was supported by grants from the Washington Research Foundation and The Wallace H. Coulter Translational Partnership at the University of Washington