The friction of explanted hip prostheses

Charnley prostheses, retrieved at revision surgery, were studied to assess the effects of friction on the total hip replacement procedure. Frictional resistance was measured using the Durham hip function simulator under both dry and lubricated conditions. The friction factor values (f) for the explanted prostheses were found to have a non- Gaussian distribution with medians of 0.13 [inter-quartile range (IQR) 0.10-0.16] and 0.06 (IQR 0.005-0.08) for dry and lubricated (n = 0.01 Pa s) regimes, respectively. New Charnley prostheses had values of f equal to 0.11 +/- 0.025 and 0.04 +/- 0.01 under the same conditions, and showed no large deviation from a Gaussian distribution. There was found to be a statistically significant difference in the medians of the friction factors for new and retrieved prostheses in the lubricated regime. Ingression of cement into the worn region of the cup was found to increase the friction factor significantly under dry conditions. There was no evidence of an increase in the friction factor or torque for those joints that had a loose socket with respect to those that were fixed at revision. A decrease in the frictional torque against number of cycles undergone by the joint in vivo may indicate that a fatigue-type process may have a role in the loosening of the socket. However, this relationship was found not to be significant for friction measured under lubricated conditions and it seems unlikely that the frictional torque generated in this type of prosthesis will contribute significantly to the long-term loosening of the socket.      

A standard definition of major hepatectomy: resection of four or more liver segments

BackgroundWhile commonly used to describe liver resections at risk for post-operative complications, no standard definition of ‘major hepatectomy’ exists. The objective of the present retrospective study is to specify the extent of hepatic resection that should describe a major hepatectomy.MethodsDemographics, diagnoses, surgical treatments and outcomes from patients who underwent a liver resection at two high-volume centres were reviewed.ResultsFrom 2002 to 2009, 1670 patients underwent a hepatic resection. Post-operative mortality and severe, overall and hepatic-related morbidity occurred in 4.4%, 29.7%, 41.6% and 19.3% of all patients. Mortality (7.4% vs. 2.7% vs. 2.6%) and severe (36.7% vs. 24.7% vs. 24.1%), overall (49.3% vs. 40.6% vs. 35.9%) and hepatic-related (25.6% vs. 16.4% vs. 15.2%) morbidity were more common after resection of four or more liver segments compared with after three or after two or fewer segments (all P < 0.001). There were no significant differences in any post-operative outcome after resection of three and two or fewer segments (all P > 0.05). On multivariable analysis, resection of four or more liver segments was independently associated with post-operative mortality and severe, overall, and hepatic-related morbidity (all P < 0.01).ConclusionsA major hepatectomy should be defined as resection of four or more liver segments.     

Sports participation, perceived neighborhood safety, and individual cognitions: how do they interact?

After publication of this work [Beenackers et al: Int J Behav Nutr Phys Act 2011, 8:76] it was realized that formula 3 and formula 4 in the Statistical Analysis section of the Methods were incorrectly listed. Since the formulas were correctly used in the analysis, this correction does not affect the results or conclusions of the paper.     

The Relationship Between Nocturnal Blood Pressure and Hemorrhagic Stroke in Chinese Hypertensive Patients

To study the relationship between nocturnal blood pressure (BP) variation and spontaneous intracerebral hemorrhage (ICH) among Chinese hypertensive patients and its clinical significance, the authors retrospectively screened 371 patients with primary hypertension (189 patients with ICH, 182 patients without ICH) in Shanghai and analyzed their demographics, clinical information, nocturnal blood pressure variability and medication. Compared with the control group, the levels of blood glucose, triglycerides, and creatinine were significantly increased in the ICH group, along with a marked reduction in nocturnal BP drop (P<.05). Multivariate logistic regression indicated that blood glucose, creatinine, and nocturnal mean arterial pressure were risk factors for ICH, and the magnitude of nocturnal BP drop was negatively related to the risk for ICH. There was no significant difference in the prevalence of reverse dippers between the large hematoma volume group and the small hematoma volume group (χ²=2.529, P=.112), nor among the patients taking angiotensin‐converting enzyme inhibitors, angiotensin receptor blockers, or calcium channel blockers (χ²=1.981, P=.371). Reverse dipping is associated with the risk for ICH, suggesting that appropriate antihypertensive drug and chronotherapy might be effective to normalize the rhythm of abnormal circadian variation in hypertensive patients.