Biomechanical Study of Patellar Component Fixation with Varying Degrees of Bone Loss.

BACKGROUND: The decision as to whether or not to resurface the patella in revision total knee arthroplasty (TKA) is affected by the amount of patellar bone stock remaining; however, the impact of the cancellous bone status on patellar component fixation has not been studied. Therefore, we conducted a biomechanical study of patellar component fixation with varying degrees of cancellous bone loss. METHODS: Sixty pairs of cadaveric patellae were randomly assigned between 3 groups and prepared in similar manner to a TKA with the standard 3-hole configuration. A control patella and an experimental patella were designated in each pair. To simulate bone loss in the experimental patellae, 1, 2, and 3 of the standard drill holes were uniformly enlarged to 12 mm in group 1, group 2, and group 3, respectively. Afterward, an all-polyethylene patellar component was cemented to each patella, as done intraoperatively. Patellar components were then sheared off using a materials testing system. The resulting mean offset yield force was analyzed within each group using paired t-tests. RESULTS: The mean offset yield force for the control patellae was greater than the experimental patellae in group 1. In groups 2 and 3, the experimental patellae produced a greater mean offset yield force than the control patellae. Comparison within each group did not demonstrate a statistically significant difference. CONCLUSION: Bone loss with enlargement of the patellar fixation holes, as is frequently seen in revision TKA, with holes up to 12 mm, does not significantly decrease patellar component fixation shear strength in this biomechanical cadaveric study.

Association between depression and hypertension using classic and revised blood pressure thresholds.

BACKGROUND: In a primary care population, the relationship between treatment of depression and hypertension (HTN) under the recently revised American College of Cardiology and American Heart Association HTN thresholds for diagnosing HTN is unknown. OBJECTIVE: To compare the association between changes in severity of co-occurring depression and HTN over time using the newly revised versus previous HTN guidelines. METHODS: In this retrospective cohort study, outpatients ≥18 years (n = 3018) with clinically significant depressive symptoms and elevated blood pressure at baseline were divided into a 'revised' guideline group (baseline blood pressure ≥130/80 mmHg), a 'classic' guideline group (≥140/90 mmHg) and a 'revised-minus-classic' group (≥130/80 and <140/90 mmHg). Depressive symptom change was assessed using the Patient Health Questionnaire-9 (PHQ-9). Correlations between changes in PHQ-9 scores and HTN levels by group over a 6- to 18-month observation period were assessed using robust regression analysis. RESULTS: There were demographic and clinical differences between groups. A total of 41% of study subjects (1252/3018) had a visit during the follow-up period where additional PHQ-9 and HTN results were available. Depressive symptom change was unrelated to change in blood pressure in the revised and revised-minus-classic groups. The classic HTN group demonstrated a clinically insignificant change in systolic blood pressure for each unit change in PHQ-9 score (ß = 0.23, P-value =0.02). CONCLUSIONS: Although a statistically significant association between reduced HTN levels and improvement in depressive symptoms was demonstrated under classic HTN guidelines, there was no clinically meaningful association between treatment of depression and improved HTN levels under either guideline.