Journal of Tribology

Wear Performance Study of a Spherical Shaft Designed Rotating Hinge Knee Prosthesis

2026-01-01T00:00:00Z

Wear Performance Study of a Spherical Shaft Designed Rotating Hinge Knee Prosthesis Zhang, Jingyu; Li, Jianpeng; Liu, Jinwei; Wei, Yue; Tian, Dongmu; Hu, Yongcheng; Zhang, Jing Abstract. This study aims to assess the wear performance of the spherical shaft rotating hinge knee (RHK) prosthesis and examine particle release. The wear test was performed for the spherical shaft RHK prosthesis using a knee joint wear simulator for 5 million cycles. The volumetric wear-rate, wear patterns, surface roughness, and wear debris were analyzed. After 5 million cycles of in vitro wear simulation, the volumetric wear-rates were found to be 6.26 ± 0.99, 0.22 ± 0.28, and 0.13 ± 0.13 mm3/million cycles for the tibial insert, rotation bushing, and bushing lock, respectively. Polishing, adhesion, and scratches were observed on the insert's articular and backside surfaces. The wear debris analysis revealed the presence of granular and flaky debris, indicating that the wear mechanisms of the spherical shaft RHK prostheses primarily involved adhesive wear, abrasive wear, and fatigue wear. The knee implant with a spherical shaft rotating hinge exhibited good wear performance, with the tibial insert being identified as the main source of wear debris rather than the bushings.

Optimized Design and Biomechanical Analysis of Novel Hollow-Porous Hip Prosthesis for Enhancing Bone–Implant Interactions

2026-01-01T00:00:00Z

Optimized Design and Biomechanical Analysis of Novel Hollow-Porous Hip Prosthesis for Enhancing Bone–Implant Interactions Le, Nam Bich Thi; Nguyen, Trung Kien; Phung, Lan Xuan; Thanh Le, Dat; Do, Truong Abstract. The increasing demand for total hip arthroplasty, driven by osteoarthritis in the elderly and trauma in younger patients, necessitates implants with high biocompatibility and mechanical longevity. Current metallic implants (titanium, cobalt–chromium) often lead to stress shielding due to their high stiffness compared to human cortical bone, resulting in bone resorption and aseptic loosening. In this study, a porous hip joint structure design is proposed to enhance the load-bearing capacity of the hip joint and mitigate shielding stress after surgery. The hip joint model examined in this article features an improved design, including a hollow head, a porous stem with varying hollow structures and densities, and a stem surrounded by a bone block. The finite element method (based on ansys software) is used to analyze the biomechanical behavior of the artificial hip joint and the interaction between the joint and surrounding bone during the activities of young patients, including daily activities and dynamic movements such as climbing stairs and playing sports. The results presented in this article include stress and deformation distribution on the joint components and the bone. In addition, the sliding distance and contact pressure between the joint components, between the joint and the bone, were also investigated. Wearing mechanics of the liner's surfaces when in contact with the cup and head are also examined. From the results obtained, the study has proposed several hip joint designs that ensure sufficient durability and reduce joint laxity during patient activities.

Failure Analysis of Retrieved Orthopedic Implants: Preliminary Visual Observations

2026-01-01T00:00:00Z

Failure Analysis of Retrieved Orthopedic Implants: Preliminary Visual Observations WaMaina, Mwangi; Rengaraj, Kaajal; Paramasivan, Mareeswari; Perumal, Govindaraj; Choubey, Apurva; Ahmad, Rana; Drake, Brett; Gonzalez, Mark; Mathew, Mathew T. Abstract. It is crucial to further analyze the causes of hip and knee replacement failure to better enhance the success and minimize the shortcomings of joint replacement in patient outcomes. The purpose of this study is to collect samples of failed hip and knee orthopedic implants from surgeons and analyze the features of those implants to find possible reasons for implant failure so that these causes can be successfully prevented and/or mitigated. Twelve implants were collected and cleaned according to a standard protocol. The implants were analyzed using visual observation and an optical microscope, and initial reports are presented in this study. The preliminary findings suggest that a combination of factors, including material, design, patient, and surgical factors, may contribute to the failure of total hip and knee arthroplasties. Mechanical trauma to the implants may be a contributing factor to hip and knee implant failure, as scratch marks and abrasions were common in the implants collected. The study has several limitations, which are clearly stated in the article. Further research is needed to investigate these factors in more detail, using a larger number of implants and a wider population of surgeons, and to develop strategies to improve the success of these procedures.

A Historical Evaluation of Articular Cartilage Lubrication Studies Reveals Distinct Testing Approach Specific Behaviors

2026-01-01T00:00:00Z

A Historical Evaluation of Articular Cartilage Lubrication Studies Reveals Distinct Testing Approach Specific Behaviors Lambeth, Emily P.; Kupratis, Meghan E.; Burris, David L.; Price, Christopher Abstract. Healthy articular cartilage can sustain near-frictionless motion within the joint; in vivo friction coefficients fall well within the superlubricity regime (<0.01). However, despite nearly a century of study, the mechanisms underpinning these behaviors remain unclear. This uncertainty has been compounded by how cartilage's operating conditions have been defined and subsequently extended to explant testing approaches, resulting in drastically varied tribological responses. To address these discrepancies, we compared friction coefficient results from a comprehensive set of historical cartilage explant tribology studies, and from new data evaluating testing configuration (stationary contact area (SCA) versus convergent SCA (cSCA)) and lubricant (phosphate-buffered saline versus synovial fluid (SF)) choice on friction. These data demonstrate that the SCA, the most common testing configuration utilized, consistently reports friction greater than that of the migrating contact area (MCA) and cSCA configurations. Intriguingly, while the SCA and MCA are almost universally slid at sub-physiological speeds (∼1 mm/s), the cSCA has routinely been tested at more physiologically consistent speeds (∼60 mm/s). Nevertheless, SF drives noticeable reductions in friction within both SCA and cSCA studies. Importantly, particularly in vivo, only rapidly slid, SF-lubricated cSCA cartilage explants reliably demonstrate biofidelic friction (<0.005), indicating that hydrodynamic-related phenomena must not be discounted in cartilage lubrication. Collectively, these results underscore the need to further probe mechanisms of sustained cartilage superlubricity, a key finding only recently replicated via the cSCA configuration. Such knowledge will be crucial to understanding the true lubrication capacity of articular cartilage.