The June 2024 Knee Roundup³⁶⁰ looks at: The estimated lifetime risk of revision after primary knee arthroplasty influenced by age, sex, and indication; Should high-risk patients seek out care from high-volume surgeons?; Stability and fracture rates in medial unicondylar knee arthroplasties; Rethinking antibiotic prophylaxis for dental procedures post-arthroplasty; Evaluating DAIR: a viable alternative for acute periprosthetic joint infection; The characteristics and predictors of mortality in periprosthetic fractures around the knee; Patient health-related quality of life deteriorates significantly while waiting six to 12 months for total hip or knee arthroplasty; The importance of looking for diversity in knee implants.

Aims

Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear.

Aims

This study compared patient-reported outcomes of three total knee arthroplasty (TKA) designs from one manufacturer: one cruciate-retaining (CR) design, and two cruciate-sacrificing designs, anterior-stabilized (AS) and posterior-stabilized (PS).

Aims

One of the main causes of tibial revision surgery for total knee arthroplasty is aseptic loosening. Therefore, stable fixation between the tibial component and the cement, and between the tibial component and the bone, is essential. A factor that could influence the implant stability is the implant design, with its different variations. In an existing implant system, the tibial component was modified by adding cement pockets. The aim of this experimental in vitro study was to investigate whether additional cement pockets on the underside of the tibial component could improve implant stability. The relative motion between implant and bone, the maximum pull-out force, the tibial cement mantle, and a possible path from the bone marrow to the metal-cement interface were determined.

Aims

Reverse total shoulder arthroplasty (RTSA) using trabecular metal (TM)-backed glenoid implants has been introduced with the aim to increase implant survival. Only short-term reports on the outcomes of TM-RTSA have been published to date. We aim to present the seven-year survival of TM-backed glenoid implants along with minimum five-year clinical and radiological outcomes.

Aims

Modern total knee arthroplasty (TKA) prostheses are designed to restore near normal kinematics including high flexion. Kneeling is a high flexion, kinematically demanding activity after TKA. The debate about design choice has not yet been informed by six-degrees-of-freedom in vivo kinematics. This prospective randomized clinical trial compared kneeling kinematics in three TKA designs.

Aims

To assess the effect of age on clinical outcome and revision rates in patients who underwent total ankle arthroplasty (TAA) for end-stage ankle osteoarthritis (OA).

Aims

A pragmatic, single-centre, double-blind randomized clinical trial was conducted in a NHS teaching hospital to evaluate whether there is a difference in functional knee scores, quality-of-life outcome assessments, and complications at one-year after intervention between total knee arthroplasty (TKA) and patellofemoral arthroplasty (PFA) in patients with severe isolated patellofemoral arthritis.

Aims

Shoulder arthroplasty using short humeral components is becoming increasingly popular. Some such components have been associated with relatively high rates of adverse radiological findings. The aim of this retrospective review was to evaluate the radiological humeral bone changes and mechanical failure rates with implantation of a short cementless humeral component in anatomical (TSA) and reverse shoulder arthroplasty (RSA).

Objectives

The high revision rates of the DePuy Articular Surface Replacement (ASR) and the DePuy ASR XL (the total hip arthroplasty (THA) version) have led to questions over the viability of metal-on-metal (MoM) hip joints. Some designs of MoM hip joint do, however, have reasonable mid-term performance when implanted in appropriate patients. Investigations into the reasons for implant failure are important to offer help with the choice of implants and direction for future implant designs. One way to assess the performance of explanted hip prostheses is to measure the wear (in terms of material loss) on the joint surfaces.

Total Elbow Arthroplasty (TEA) is a procedure to treat a number of conditions including rheumatoid arthritis (RA), post-traumatic arthritis, and osteoarthritis. To date, there has been minimal literature published on the Latitude since its release in 2001. There is one study reporting outcomes from the Latitude, a German study published in 2010. The purpose of this study was to analyse outcomes from primary Latitude TEAs. We performed a retrospective case series of 23 TEAs performed on 20 patients. 6 patients required revision surgery and were not included in the analysis. One patient was lost to follow up, resulting in 17 patients included for ROM analysis. All patients received Latitude TEA through a posterior approach and underwent a standard rehab protocol. 11 Patients were recalled at least two years post-op and were administered DASH and MAYO questionnaires. Complications such as triceps insufficiency, ulnar nerve dysfunction, infection, and aseptic loosening were recorded. Outcomes were compared using the Wilcoxon Signed-Rank test in STATA. Immediate post-op radiographs and patients most recent radiographs were analysed by a blinded upper-extremity surgeon not involved in the initial operation and analysed for loosening and implant malpostioning. Mean follow up was 4.8 years (range 2.6–7.5 years). Analysis of 17 TEAs in 16 patients revealed no difference in pre-operative ROM and post-operative ROM for flexion (121°±20 vs 129°±16, p=0.13) extension (40°±27 vs 27°±15, p=0.19), pronation (73°±13 vs 75°±24, p=0.55) or supination (64°±22 vs 68°±14, p=0.52). Patients who underwent TEA for RA had a significant improvement in flexion (121°±15 vs 135°±10, p<0.02). There was a statistically significant improvement in flexion-extension arc post-operatively (101°±28) compared to pre-operative scores (83±23 degrees, p<0.02). DASH and MAYO scores were calculated from 11elbows in 11 non-revision patients able to return for examination. The average MAYO score was 87.9 with nine patients in the “excellent” category, two patients in the “good” category, one patient in the “fair” category, and one in the “poor” category. The average DASH score was 32.9. Two patients underwent revision for periprosthetic fractures, two patients underwent revision for infection, one underwent revision for aseptic loosening and two for radial head dissociation (rate of 30%). This is one of the first studies examining the outcomes of the Latitude TEA. This retrospective case series demonstrates that the Latitude TEA has promising outcomes with respect to improving patient pain and functioning as assessed by the MAYO. Treatment using the Latitude TEA results in favorable functional outcomes for a majority of patients and offers an improvement in flexion-extension arc. Furthermore, our results are comparable to the MAYO scores reported by other studies analysing different prosthesis designs. The complication rate in our series was comparable to published rates of 20–40%

Objectives

Studies reporting specifically on squeaking in total hip arthroplasty have focused on cementless, and not on hybrid, fixation. We hypothesised that the cement mantle of the femur might have a damping effect on the sound transmitted through the metal stem. The objective of this study was to test the effect of cement on sound propagation along different stem designs and under different fixation conditions.

Objectives

Initial stability of tibial trays is crucial for long-term success of total knee arthroplasty (TKA) in both primary and revision settings. Rotating platform (RP) designs reduce torque transfer at the tibiofemoral interface. We asked if this reduced torque transfer in RP designs resulted in subsequently reduced micromotion at the cemented fixation interface between the prosthesis component and the adjacent bone.

Objective. Tibia vara seen in Japanese patients reportedly influences the tibial component alignment when performing TKA. However, it is unclear whether tibia vara affects the component position and size selection. We therefore determined (1) the amount of medial tibial bow, (2) whether the tibia vara influences the aspect ratio of the tibial resected surface in aligning the tibial component with the tibial shaft axis (TSA), and (3) whether currently available tibial components fit the shapes of resected proximal tibias in terms of aspect ratio. Material and Methods. The study was performed using CT data from 90 lower limbs in 74 Japanese female patients with primary varus knee OA, scheduled for primary TKAs between January 2010 and March 2012. We measured the tibia vara angle (TVA; the angle between the TSA and the tibial mechanical axis), proximal varus angle (PVA; angle between the TSA and the line connecting the center of the tibial eminence and the center of the proximal 1/3 of the tibia) using three-dimensional preoperative planning software [Fig.1]. Then the mediolateral and middle AP dimensions of the resected surface when the tibial component was set so that its center aligned with the TSA was measured. We determined the correlations of the aspect ratio (the ML dimension divided by the AP dimension) of the resected surface with TVA or PVA and compared the aspect ratios to those of five prosthesis designs. Results. The mean TVA and PVA were 0.6° and 2.0°, respectively. The aspect ratio negatively correlated with both TVA and PVA (r = −0.53 and −0.55, respectively) [Fig. 2, 3]. The mean aspect ratio of the resected surface was 1.48 but gradually decreased with increasing AP dimension, whereas four of the five prostheses had a constant aspect ratio. Conclusions. The aspect ratio of resected tibial surface was inversely correlated to the degree of tibia vara, and currently available prosthesis designs do not fit well to the resected surface in terms of aspect ratio

The April 2015 Shoulder & Elbow Roundup³⁶⁰ looks at: Distal clavicular resection not indicated in cuff repair?; Platelet-rich plasma in rotator cuff repair; Radial head geometry: time to change?; Heterotopic ossification in elbow trauma; Another look at heterotopic ossification in the humerus; Triceps on for total elbow arthroplasty?; Predicting outcomes in rotator cuff repair; Deltoid fatty infiltration and reverse shoulder arthroplasty

Introduction

Wear of polyethylene inserts plays an important role in failure of total knee replacement and can be monitored in vivo by measuring the minimum joint space width in anteroposterior radiographs. The objective of this retrospective cross-sectional study was to compare the accuracy and precision of a new model-based method with the conventional method by analysing the difference between the minimum joint space width measurements and the actual thickness of retrieved polyethylene tibial inserts.

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:. Due to improvement in overall prosthesis designs and surgical methods, there have been increasing numbers of total ankle arthroplasty performed with encouraging intermediate results. While European registries have been able to perform long term follow-ups and analysis on total ankle arthroplasty patients, majority of the US studies have been based on experiences at a single institution. There is currently limited data on the recent trends of total ankle arthroplasty. The purpose of our study is to evaluate the in-patient demographics, complications and readmission rate in patients after total ankle arthroplasty at academic medical centers in United States. Patients & Methods:. We queried the University Healthsystems Consortium (UHC) administrative database from 2007 to 2011 for patients who underwent total ankle arthrolasty by ICD-9 procedure code 81.56. A descriptive analysis of demographics was performed, followed by a similar analysis of patient clinical benchmarks, including hospital length of stay, hospital direct cost, in-hospital mortality, and 30-day readmission rates. Results:. Our cohort consisted of 2,361 adult patients who underwent a total ankle arthroplasty at 95 different academic medical centers across the country during the specified time period. The annual surgical volume for individual surgeons who performed this procedure was 5 cases +/− 3. The cohort was comprised of 47% male and 53% female patients. The majority of the cohort 2,091 (88.5%) was white, 85 (3.6%) were black, 23 (1%) were Hispanic, and 162 (6.8%) other. The mean age of the cohort was 62 years old +/− 11. At least 70% of the cohort had one or more chronic medical conditions. The mean LOS for the cohort was 2.2 days +/− 1.26. The mean total direct cost for the hospital was $16,000 +/− 7,000 per case. 83% of the cohort had private insurance, 15% had Medicare, and 2% had Medicaid. In hospital mortality was less than 1% for the cohort during their index hospitalization. Inpatient complication rate include: DVT 2.3%, re-operation 0.7%, and infection 3.2%. There was a readmission rate of 2.6% within the first 30 days from the time of discharge. Discussion/Conclusion:. Total ankle arthroplasty in the United States is a relatively safe procedure with low overall complication rates including infection (3.2%), DVT (2.3%), and re-operation (0.7%). Length of stay after the procedure is around 2 days with a total direct hospital cost of $16,000 +/− $7,000 and 2.6% readmission rate (30 days). Majority of the patients were Caucasian and had private insurance

Representative pre-clinical analysis is essential to ensure that novel prosthesis concepts offer an improvement over the state-of-the-art. Proposed designs must, fundamentally, be assessed against cyclic loads representing common daily activities [Bergmann 2001] to ensure that they will withstand conceivable in-vivo loading conditions. Fatigue assessment involves:. –. cyclic mechanical testing, representing worst-case peak loads encountered in-vivo, typically for 10 million cycles, or. –. prediction of peak fatigue stresses using Finite Element (FE) methods, and comparison with the material's endurance limit. Cyclic stresses from gait loading are super-imposed upon residual assembly stresses. In thick walled devices, the residual component is small in comparison to the cyclic component, but in thin section, bone preserving devices, residual assembly stresses may be a multiple of the cyclic stresses, so a different approach to fatigue assessment is required. Modular devices provide intraoperative flexibility with minimal inventories. Components are assembled in surgery with taper interfaces, but resulting residual stresses are variable due to differing assembly forces and potential misalignment or interface contamination. Incorrect assembly can lead to incomplete seating and dissociation [Langdown 2007], or fracture due to excessive press-fit stress or point loading [Hamilton 2010]. Pre-assembly in clean conditions, with reproducible force and alignment, gives close control of assembly stresses. Clinical results indicate that this is only a concern with thick sectioned devices in a small percentage of cases [Hamilton 2010], but it may be critical for thin walled devices. A pre-clinical analysis method is proposed for this new scenario, with a case study example: a thin modular cup featuring a ceramic bearing insert and a Ti-6Al-4V shell (Fig. 1). The design was assessed using FE predictions, and manufacturing variability from tolerances, surface finish effects and residual stresses was assessed, in addition to loading variability, to ensure physical testing is performed at worst case:. –. assembly loads were applied, predicting assembly residual stress, verified by strain gauging, and a range of service loads were superimposed. The predicted worst-case stress conditions were analysed against three ‘constant life’ limits [Gerber, 1874, Goodman 1899, Soderberg 1930], a common aerospace approach, giving predicted safety factors. Finally, equivalent fatigue tests were conducted on ten prototype implants. Taking a worst-case size (thinnest-walled 48 mm inner/58 mm outer), under assembly loading the peak tensile stress in the titanium shell was 274 MPa (Fig. 2). With 5kN superimposed jogging loading, at an extreme 75° inclination, 29 MPa additional tensile stress was predicted. This gave mean fatigue stress of 288.5 MPa and stress amplitude of 14.5 MPa (R=0.9). Against the most conservative infinite life limit (Soderberg), the predicted safety factor was 2.40 for machined material, and 2.03 for forged material, or if a stress-concentrating surface scratch occurs during manufacturing or implantation (Fig. 3). All cups survived 10,000,000 fatigue cycles. This study employed computational modelling and physical testing to verify the strength of a joint prosthesis concept, under worst case static and fatigue loading conditions. The analysis technique represents an improvement in the state of the art where testing standards refer to conventional prostheses; similar methods could be applied to a wide range of novel prosthesis designs