Computational analysis of tibial slope adjustment with fixed-bearing medial unicompartmental knee arthroplasty in ACL- and PCL-deficient models.

AIMS: A functional anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) has been assumed to be required for patients undergoing unicompartmental knee arthroplasty (UKA). However, this assumption has not been thoroughly tested. Therefore, this study aimed to assess the biomechanical effects exerted by cruciate ligament-deficient knees with medial UKAs regarding different posterior tibial slopes. METHODS: ACL- or PCL-deficient models with posterior tibial slopes of 1°, 3°, 5°, 7°, and 9° were developed and compared to intact models. The kinematics and contact stresses on the tibiofemoral joint were evaluated under gait cycle loading conditions. RESULTS: Anterior translation increased in ACL-deficient UKA cases compared with intact models. In contrast, posterior translation increased in PCL-deficient UKA cases compared with intact models. As the posterior tibial slope increased, anterior translation of ACL-deficient UKA increased significantly in the stance phase, and posterior translation of PCL-deficient UKA increased significantly in the swing phase. Furthermore, as the posterior tibial slope increased, contact stress on the other compartment increased in cruciate ligament-deficient UKAs compared with intact UKAs. CONCLUSION: Fixed-bearing medial UKA is a viable treatment option for patients with cruciate ligament deficiency, providing a less invasive procedure and allowing patient-specific kinematics to adjust posterior tibial slope. Patient selection is important, and while AP kinematics can be compensated for by posterior tibial slope adjustment, rotational stability is a prerequisite for this approach. ACL- or PCL-deficient UKA that adjusts the posterior tibial slope might be an alternative treatment option for a skilled surgeon. Cite this article: Bone Joint Res 2022;11(7):494-502.

Biomechanical effect of anatomical tibial component design on load distribution of medial proximal tibial bone in total knee arthroplasty : finite element analysis indicating anatomical design prevents stress-shielding.

AIMS: This study aimed to identify the effect of anatomical tibial component (ATC) design on load distribution in the periprosthetic tibial bone of Koreans using finite element analysis (FEA). METHODS: 3D finite element models of 30 tibiae in Korean women were created. A symmetric tibial component (STC, NexGen LPS-Flex) and an ATC (Persona) were used in surgical simulation. We compared the FEA measurements (von Mises stress and principal strains) around the stem tip and in the medial half of the proximal tibial bone, as well as the distance from the distal stem tip to the shortest anteromedial cortical bone. Correlations between this distance and FEA measurements were then analyzed. RESULTS: The distance from the distal stem tip to the shortest cortical bone showed no statistically significant difference between implants. However, the peak von Mises stress around the distal stem tip was higher with STC than with ATC. In the medial half of the proximal tibial bone: 1) the mean von Mises stress, maximum principal strain, and minimum principal strain were higher with ATC; 2) ATC showed a positive correlation between the distance and mean von Mises stress; 3) ATC showed a negative correlation between the distance and mean minimum principal strain; and 4) STC showed no correlation between the distance and mean measurements. CONCLUSION: Implant design affects the load distribution on the periprosthetic tibial bone, and ATC can be more advantageous in preventing stress-shielding than STC. However, under certain circumstances with short distances, the advantage of ATC may be offset. Cite this article: Bone Joint Res 2022;11(5):252-259.

New steroidal anti-inflammatory antedrugs: 21-thioalkylether derivatives of methyl 16-prednisolone carboxylates.

Antedrug approach of the corticosteroids has been described as a fundamentally sound approach for the development of safer anti-inflammatory steroids devoid of systemic side effects. In our continued efforts under the antedrug paradigm, we have recently extended this effort to synthesize the 21-thioalkylether derivatives of methyl 16-prednisolonecarboxylates. The 21-mesylate of the methyl-16-perdnisolonecarboxylates and 9-fluoro-17-dehydro methyl 16-prednisolonecarboxylate were reacted with Na-thioalkoxides to furnish the desired thioalkylethers in 60-75% yields. These newly synthesized thioalkylether steroid series were tested for their in vitro metabolism and corticosteroid receptor binding affinity. They were metabolized in predictable manner to inactive 16-carboxylic acids. All the newly synthesized antedrugs showed lowered glucocorticoid receptor binding affinity than prednisolone indicating that the replacement of the 21-OH function with thioalkylether of the 16-prednisolone carboxylate esters decreases their receptor binding affinity.

In vitro anti-inflammatory activities of new steroidal antedrugs: [16alpha,17alpha-d] Isoxazoline and [16alpha,17alpha-d]-3'-hydroxy-iminoformyl isoxazoline derivatives of prednisolone and 9alpha-fluoroprednisolone.

A series of new anti-inflammatory steroidal antedrugs with C-16,17-isoxazoline ring system were synthesized and their pharmacological activities were evaluated. We reported earlier that these compounds are promising antedrugs based on the results of 5-day rat croton oil ear edema assay. In the present study, most of these compounds showed high binding affinities to the glucocorticoid receptor of liver cytosol. 21-acetyloxy-9alpha-fluoro-11beta-hydroxy-3,20-dioxo-1,4-pregnadieno [16alpha,17alpha-d] isoxazoline (FP-ISO-21AC) and 11beta,21-dihydroxy-9alpha-fluoro-3,20-dioxo-1,4-pregnadieno [16alpha,17alpha-d] isoxazoline (FP-ISO-21OH) were found 5.0-, 5.3-fold more potent than prednisolone, respectively. Inhibitory effects of the antedrugs on the nitric oxide (NO) production were assessed using LPS-stimulated RAW 264.7 murine macrophage cells. All these steroidal antedrugs exhibited concentration-dependent inhibition of NO production, but their relative potencies were lower than prednisolone. In vitro metabolism study in rat plasma showed that FP-ISO-21AC and 21-acetyloxy-9alpha-fluoro-11beta-hydroxy-3,20-dioxo-1,4-pregnadieno [16alpha,17alpha-d]-3'-hydroxyiminoformyl isoxazoline (FP-OXIM-21AC) were hydrolyzed rapidly, with the half-lives of 2.1 and 4.2 min, respectively. The half-lives of FP-ISO-21OH and 11beta,21-dihydroxy-9alpha-fluoro-3,20-dioxo-1,4-pregnadieno [16alpha,17alpha-d]-3'-hydroxyiminoformyl isoxazoline (FP-OXIM-21OH) were 92.2 and 110.2 min, respectively.

Antedrugs: an approach to safer drugs.

The antedrug concept was introduced by Lee and Soliman in 1982 in designing potent, yet safer locally active anti-inflammatory steroids. Antedrug is defined as an active synthetic derivative that is designed to undergo biotransformation to the readily excretable inactive form upon entry in the systemic circulation. Thus, are minimizing systemic side effects and are increasing the therapeutic indices. Steroid-21-oate esters have been developed as the first of this kind, which quickly hydrolyzed to the corresponding inactive steroid acids thereby exerting minimal systemic side effects. Later, other steroidal and nonsteroidal antedrugs have also been developed. The cost, complexity and length in development of a new therapeutic drug, in addition to the adverse drug reactions, the potential risk factors causing the withdrawal of the drugs from the market, have made the approach of antedrug design unique and attractive to the scientists involved in drug design. Considering these factors, the concept which strictly designed to eliminate the deleterious adverse systemic effects, is becoming an affordable approach in drug development arena. This review is not intended to be comprehensive; instead the focus will be on the recent advances in steroidal as well as nonsteroidal antedrugs, which appear to offer new leverage to the development of safer and more efficacious therapeutic agents.