Limited Durability of Extensor Mechanism Reconstruction Following Total Knee Arthroplasty: Mesh and Allograft Show Equivalent Outcomes at Five-Year Follow-Up.

BACKGROUND: Extensor mechanism disruption is a challenging complication following total knee arthroplasty. The purpose of this study was to compare outcomes between patients who received mesh versus allograft extensor mechanism reconstruction. METHODS: All patients who underwent extensor mechanism reconstruction at a single institution were screened. Demographic and surgical variables were recorded, including technique (ie, synthetic mesh versus allograft reconstruction). Patients were assessed for preoperative and postoperative extensor lag, revision, and duration of follow-up. Analyses, including Kaplan-Meier survivorships, were performed to compare mesh to allograft reconstruction. In total, 50 extensor mechanism reconstructions (30 mesh and 20 allograft) were conducted between January 1st, 2001, and December 31st, 2022. RESULTS: There were no differences between the cohorts with respect to revision (26.7 [8 of 30] versus 35.0% [7 of 20], P = .680) or failure defined as above knee amputation or fusion (6.7 [2 of 30] versus 5.0% [1 of 20], P = .808). There were also no differences in time to reoperation (average 27 months [range, 6.7 to 58.8] versus 29 months [range, 1.2 to 84.9], P = .910) or in postoperative extensor lag among patients who did not undergo a reoperation (13 [0 to 50] versus 11° [0 to 30], P = .921). The estimated 5-year Kaplan-Meier survival with extensor mechanism revision as the endpoint was similar between the 2 groups (52.1, 95% confidence interval [CI] = 25.4 to 73.3 versus 55.0%, 95% CI = 23.0 to 78.4%, P = .990). CONCLUSIONS: The purpose of this study was to present the findings of a large cohort of patients who required extensor mechanism reconstruction. Regardless of the reconstruction type, the 5-year outcomes of patients requiring extensor mechanism reconstruction are suboptimal.

The role of the AT4 and cholinergic systems in the Nucleus Basalis Magnocellularis (NBM): effects on spatial memory.

The brain AT(4) and cholinergic systems play a pivotal role in learning and memory. Studies have investigated the nootropic and amnesic properties of both systems. The cholinergic system has received the most attention for its contribution to cognitive functioning. For example, one of the best known cognitive disorders, Alzheimer's disease (AD), is treated with cholinergic-directed drugs, and post-mortem studies of AD patient brains show neurodegenerative devastation in cholinergic areas of the brain. Studies suggest that potentiation of cholinergic transmission may be a mechanism by which the AngIV/AT(4) receptor system enhances cognition. Since the Nucleus Basalis Magnocellularis (Meynert in humans and primates) (NBM) is a main source of cholinergic innervation to cognitive areas of the brain, this site was chosen to investigate the role and interaction of the two systems. Rats were fitted with permanent bilateral cannulas targeting the NBM for drug administration. Divalinal-AngIV, an AT(4) receptor antagonist produced profound deficits in performance in the Circular water maze. Nicotine treatment reversed these impairments whereas carbachol did not. Similar to the AT(4) antagonist, scopolamine and mecamylamine prevented acquisition of the water maze. Based on these results, it appears that blocking any one of these systems results in impaired spatial learning, while activating the nicotinic receptor system counteracts the effects of AT(4) receptor blockade. These findings suggest a functional role for both the cholinergic and AT(4) receptor systems in spatial learning, and indicate for the first time a functional role for the AngIV/AT(4) receptor system in the NBM.