Edward M. DelSole

Measuring properties of interfacial and bulk water regions in a reverse micelle with IR spectroscopy: a volumetric analysis of the inhomogeneously broadened OH band.

The water OH stretching band (3000-3600 cm(-1)) was analyzed for absorption contributions from the respective bulk and interfacial water regions of a reverse micelle. This analysis was performed by correlating volume changes of these regions to changes in the OH band absorption as the micelle radius grows. The volumetric analysis is based on the well established expanding core-shell model for AOT reverse micelles and yields the dimensions of the water regions and their individual spectral responses in the OH band. The interfacial shell thickness was determined to be 0.45 nm for AOT reverse micelles in i-octane. It was found that each water region absorbs at most frequencies in the OH band; however, absorption on the red side of the OH band is dominated by bulk water, while absorption on the blue side is dominated by interfacial water. The bulk spectral response was found to be more similar to pure water, while the interfacial spectrum is strongly blue-shifted reflecting the weaker hydrogen bonding in this region. AOT reverse micelles with radii in the range 2-4 nm conformed well to the volumetric model. However, it was found that determination of the bulk water spectral response is particularly sensitive to uncertainty in the micelle radius.

Post-Splinting Radiographs of Minimally Displaced Fractures: Good Medicine or Medicolegal Protection?

BACKGROUND Many institutions perform radiographic documentation following splint application even when no manipulation had been performed. The purpose of this study was to evaluate the utility of post-splinting radiographs of acute non-displaced or minimally displaced fractures that did not undergo manipulation. Our hypothesis was that post-splinting radiographs do not demonstrate changes in fracture alignment or impact the management of the patient. METHODS After institutional review board exemption had been granted, consultations performed by orthopaedic residents at a level-I trauma center from September 2008 to April 2010 were reviewed. Of 2862 consultations, 1321 involved acute fractures that were splinted. Radiographs revealed that 342 (25.9%) of the fractures were non-displaced or minimally displaced and angulated (defined as <5 mm and <10°, respectively) and 204 of them had been assessed with radiographs after splinting. Consults were reviewed to ensure that the patients had not undergone manipulation prior to or during splinting. Consult notes and radiographs obtained in the emergency room (ER), as well as follow-up radiographs, were reviewed to assess ultimate outcome. RESULTS None of the 204 fractures (134 non-displaced and seventy minimally displaced) changed alignment following splinting. Two splints were reapplied, and the fractures sites were reimaged for undocumented reasons. Patients were subjected to an average of ten radiographs (range, four to twenty-five radiographs) of their extremities in the acute setting. On average, three post-splinting radiographs (range, one to ten radiographs) were obtained. The mean time between the initial and post-splinting radiographs was three hours and thirty minutes (range, nine minutes to twenty-four hours). The most common injury was a fracture about the hand or wrist. The 122 patients with that type of injury waited an average of almost three hours for an average of three post-splinting radiographs, contributing to a total of nine radiographs performed acutely. ER visits tended to be longer for patients with post-splinting radiographs compared with those without them (p = 0.06). Follow-up radiographs were available for eighty-two patients. All fractures demonstrated maintained alignment. CONCLUSIONS Post-splinting radiographs of non-displaced and minimally displaced fractures that do not undergo manipulation before or during immobilization are associated with longer ER waits, additional radiation exposure, and increased health-care costs without providing helpful information. While certain circumstances call for additional imaging, routine performance of post-splinting radiography of non-displaced or minimally displaced fractures should be discouraged.

Total Hip Arthroplasty in the Spinal Deformity Population: Does Degree of Sagittal Deformity Affect Rates of Safe Zone Placement, Instability, or Revision?

BACKGROUND Changes in spinal alignment and pelvic tilt alter acetabular orientation in predictable ways, which may have implications on stability of total hip arthroplasty (THA). Patients with sagittal spinal deformity represent a subset of patients who may be at particularly high risk of THA instability because of postural compensation for abnormal spinal alignment. METHODS Using standing stereoradiography, we evaluated the spinopelvic parameters, acetabular cup anteversion, and inclination of 139 THAs in 107 patients with sagittal spinal deformity. Standing images were compared with supine pelvic radiographs to evaluate dynamic changes in acetabular cup position. Dislocation and revision rates were procured through retrospective chart review. The spinal parameters and acetabular cup positions among dislocators were compared with those who did not dislocate. RESULTS The rate of THA dislocation in this cohort was 8.0%, with a revision rate of 5.8% for instability. Patients who sustained dislocations had significantly higher spinopelvic tilt, T1-pelvic angle, and mismatch of lumbar lordosis and pelvic incidence. Among all patients, 78% had safe anteversion while supine, which decreased significantly to 58% when standing due to increases in spinopelvic tilt. Among dislocating THA, 80% had safe anteversion, 80% had safe inclination, and 60% had both parameters within the safe zone. CONCLUSION In this cohort, patients with THA and concomitant spinal deformity have a particularly high rate of THA instability despite having an acetabular cup position traditionally thought of as within acceptable alignment. This dislocation risk may be driven by the degree of spinal deformity and by spinopelvic compensation. Surgeons should anticipate potential instability after hip arthroplasty and adjust their surgical plan accordingly.

Subspine impingement: 2 case reports of a previously unreported cause of instability in total hip arthroplasty

Background Instability is a common cause of revision hip arthroplasty and is frequently due to improper component placement and subsequent component impingement. Impingement of the greater trochanter upon the anterior inferior iliac spine (AIIS) has been described as a cause of symptomatic femoroacetabular impingement (FAI), but has never been described as a cause of instability following total hip arthroplasty (THA). Case review We present 2 cases of patients undergoing THA. Each patient was evaluated preoperatively and found to have a prominent AIIS, which was concerning due to it overhanging the anterolateral acetabular lip. Both patients had intraoperative posterior instability of their THA, the cause of which was determined to be impingement of the greater trochanter upon a prominent AIIS. Open resection of the AIIS was performed with subsequent resolution of impingement. Literature review AIIS impingement has been reported as a cause of symptomatic FAI. In these case reports, open or arthroscopic resection of the AIIS resulted in resolution of symptoms. Morphologically distinct subtypes of the AIIS have been previously described based upon computed tomography, and some subtypes are associated with a high risk of impingement in the native hip. No previous studies have described this phenomenon in the setting of THA. Clinical relevance Instability is a common cause of revision THA. Impingement of the greater trochanter upon a prominent AIIS is a previously unreported cause of THA instability which can be addressed with intraoperative resection of the AIIS with good result.

Adverse Outcomes and Prediction of Cardiopulmonary Complications in Elective Spine Surgery

Study Design: Retrospective cohort study. Objectives: The purpose of this study was to report incidence of cardiopulmonary complications in elective spine surgery, demographic and surgical predictors, and outcomes. Understanding the risks and predictors of these sentinel events is important for risk evaluation, allocation of hospital resources, and counseling patients. Methods: A retrospective review of the National Surgical Quality Improvement Program (NSQIP) was performed on 60 964 patients undergoing elective spine surgery (any region; laminectomy, arthrodesis, discectomy, or laminoplasty) between 2011 and 2013. Incidence of myocardial infarction, cardiac arrest, unplanned reintubation, on ventilator >48 hours, perioperative pneumonia, and pulmonary embolism was measured. Demographic and surgical predictors of cardiopulmonary complications and associated outcomes (length of stay, discharge disposition, and mortality) were measured using binary logistic regression controlling for confounders. Results: Incidence rates per 1000 elective spine patients were 2.1 myocardial infarctions, 1.3 cardiac arrests, 4.3 unplanned intubations, 3.5 on ventilator >48 hours, 6.1 perioperative pneumonia, and 3.7 pulmonary embolisms. In analysis of procedure, diagnosis, and approach risk factors, thoracic cavity (odds ratio = 2.47; confidence interval = 1.95-3.12), scoliosis diagnosis, and combined approach (odds ratio = 1.51; confidence interval = 1.15-1.96) independently added the most risk for cardiopulmonary complication. Cardiac arrest had the highest mortality rate (34.57%). Being on ventilator greater than 48 hours resulted in the greatest increase to length of stay (17.58 days). Conclusions: Expected risk factors seen in the Revised Cardiac Risk Index were applicable in the context of spine surgery. Surgical planning should take into account patients who are at higher risk for cardiopulmonary complications and the implications they have on patient outcome.