Wind waves and the reaeration coefficient in open channel flow: technical report

CER69-70AFE2.August 1969.Includes bibliographical references (pages 114-118).Prepared under National Science Foundation Grant No. GK 2142.The reaeration rates with and without wind blowing along the water surface have been studied in the laboratory. The reaeration results, without wind, have been compared with those obtained by previous investigators. Based on the concept that the reaeration rate is controlled by an effective turbulent diffusion coefficient at the surface and by rate of surface renewal, an equation was developed to predict reaeration rates in natural streams and rivers with wind blowing over the water surface. The state of turbulence, beneath the water surface, was considered as a good measure of the rate of surface renewal. The experimental results gave support to the theoretically developed equation. The properties of water surface give good agreement with the results reported by previous investigators. Experimental results indicate that reaeration rates are significantly increased when waves appear on the surface. The increase is very much more than can be accounted for by the increase in surface area. The increase was attributed to the dynamic effect of separation, occurring at the lee side of the waves.Under grant no. GK 2142

Dynamic Measurement of Patellofemoral Compression Forces: A Novel Method for Patient-Specific Patella Resurfacing in Total Knee Replacement

Functional dissatisfaction following total knee replacement (TKR) is recorded as high as 20%. The majority of these patients report anterior knee pain (AKP) as the main source of dissatisfaction. Elevated patellofemoral compression forces and soft tissue extensor hood strain have been implicated in the generation of significant AKP. A novel method of assessing and measuring patellofemoral compression forces dynamically in the native and resurfaced patella for TKR in four different quadrants of the patella is described. Results are reported from an in vitro model and cadaveric studies in the native and resurfaced knee. Patellofemoral compression forces are shown to be characteristic and consistent over repeated assessments in the native knee. Placement of a TKR significantly alters this pattern. Furthermore, over-stuffing or under-stuffing the resurfaced patella also significantly alters the nature and magnitude of patellofemoral compression forces. These studies may lead to an improved understanding of the nature of AKP following TKR, and using this assessment tool presents an opportunity to more effectively balance the third space, reproduce the native patellofemoral forces, and subsequently reduce AKP following TKR

Basic Shoulder Arthroscopy: Lateral Decubitus Patient Positioning

Shoulder arthroscopy offers a minimally invasive surgical approach to treat a variety of shoulder pathologies. The patient can be positioned in either the lateral decubitus or the beach chair position. This note and accompanying video describe the operating room setup for shoulder arthroscopy in the lateral decubitus position, including positioning of the arms, head, and sterile preparation and draping. Appropriate lateral decubitus positioning for shoulder arthroscopy with careful attention to detail will promote ease of surgical intervention and minimize complications

Basic Shoulder Arthroscopy: Beach Chair Patient Positioning

Abstract: Shoulder arthroscopy is an orthopaedic procedure that has grown significantly in popularity over the last 40 years. The 2 principle patient positions during shoulder arthroscopy include the beach chair position and lateral decubitus position. This Technical Note details the operating room setup for shoulder arthroscopy in the beach chair position. Proper positioning for this procedure will minimize potential complications and facilitate ease of surgical intervention

<em>Botulinum Neurotoxin</em> A Injections Influence Stretching of the Gastrocnemius Muscle-Tendon Unit in an Animal Model

<em>Botulinum Neurotoxin</em> A (BoNT-A) injections have been used for the treatment of muscle contractures and spasticity. This study assessed the influence of (BoNT-A) injections on passive biomechanical properties of the muscle-tendon unit. Mouse<strong> </strong>gastrocnemius muscle (GC) was injected with BoNT-A (<em>n</em> = 18) or normal saline (<em>n</em> = 18) and passive, non-destructive, <em>in vivo</em> load relaxation experimentation was performed to examine how the muscle-tendon unit behaves after chemical denervation with BoNT-A. Injection of BoNT-A impaired passive muscle recovery (15% <em>vs.</em> 35% recovery to pre-stretching baseline, <em>p</em> < 0.05) and decreased GC stiffness (0.531 ± 0.061 N/mm <em>vs.</em> 0.780 ± 0.037 N/mm, <em>p</em> < 0.05) compared to saline controls. The successful use of BoNT-A injections as an adjunct to physical therapy may be in part attributed to the disruption of the stretch reflex; thereby modulating <em>in vivo</em> passive muscle properties. However, it is also possible that BoNT-A injection may alter the structure of skeletal muscle; thus modulating the <em>in vivo</em> passive biomechanical properties of the muscle-tendon unit

An Orthopedic-Hospitalist Comanaged Hip Fracture Service Reduces Inpatient Length of Stay

Introduction: Hip fractures are common in the elderly patients with an incidence of 320 000 fractures/year in the United States, representing a health-care cost of US$9 to 20 billion. Hip fracture incidence is projected to increase dramatically. Hospitals must modify clinical models to accommodate this growing burden. Comanagement strategies are reported in the literature, but few have addressed orthopedic-hospitalist models. An orthopedic-hospitalist comanagement (OHC) service was established at our hospital to manage hip fracture patients. We sought to determine whether the OHC (1) improves the efficiency of hip fracture management as measured by inpatient length of stay (LOS) and time to surgery (TTS) and (2) whether our results are comparable to those reported in hip fracture comanagement literature. Methods: A comparative retrospective–prospective cohort study of patients older than 60 years with an admitting diagnosis of hip fracture was conducted to compare inpatient LOS and TTS for hip fracture patients admitted 10 months before (n = 45) and 10 months after implementation (n = 54) of the OHC at a single academic hospital. Secondary outcome measures included percentage of patients taken to surgery within 24 or 48 hours, 30-day readmission rates, and mortality. Outcomes were compared to comanagement study results published in MEDLINE-indexed journals. Results: Patient cohort demographics and comorbidities were similar. Inpatient LOS was reduced by 1.6 days after implementation of the OHC ( P = .01) without an increase in 30-day readmission rates or mortality. Time to surgery was insignificantly reduced from 27.4 to 21.9 hours ( P = .27) and surgery within 48 hours increased from 86% to 96% ( P = .15). Discussion: The OHC has improved efficiency of hip fracture management as judged by significant reductions in LOS with a trend toward reduced TTS at our institution. Conclusion: Orthopedic-hospitalist comanagement may represent an effective strategy to improve hip fracture management in the setting of a rapidly expanding patient population