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1.  Epidemiology and risk factors for perioperative mortality after total hip and knee arthroplasty 
Purpose
The perioperative mortality of total knee and hip arthroplasties (TKA, THA) remains a major concern among health care providers and their patients. The increase in utilization of TKA and THA makes it imperative to be aware of factors that are associated with this unfortunate event.
Methods
Therefore we analyzed the Nationwide Inpatient Sample data from 1998–2008 and compared admissions with perioperative mortality to those that survived their hospitalization.
Results
An estimated total of 4,438,213 TKA and 2,182,121 THA procedures were performed in the United States between 1998 and 2008. The average mortality rate for TKA was 0.13% and 0.18% for THA, or 0.34 and 0.44 events per 1000 inpatient days, respectively. Independent risk factors for in-hospital mortality were advanced age, male gender, ethnic minority background, emergency admission as well as a number of comorbidities and complications. Furthermore, we demonstrated that the timing of death occurred earlier after TKA when compared to THA, with 50% of fatalities occurring by day 4 versus day 6 of the hospitalization, respectively.
Conclusion
This study provides nationally representative information on risk factors for and timing of perioperative mortality after TKA and THA. Our data can be used to assess the risk for perioperative mortality and to develop targeted intervention to decrease such risk.
doi:10.1002/jor.22139
PMCID: PMC3407319  PMID: 22517400
total knee arthroplasty; total hip arthroplasty; joint replacement; complications; mortality
2.  Perioperative mortality after lumbar spinal fusion surgery: an analysis of epidemiology and risk factors 
European Spine Journal  2012;21(8):1633-1639.
Study design
Analysis of the Nationwide Inpatient Sample (NIS) from 1998 to 2008.
Objective
To analyze the most recent available and nationally representative data for risk factors contributing to in-hospital mortality after primary lumbar spine fusion.
Summary of background data
The total number of lumbar spine fusion surgeries has increased dramatically over the past decades. While the field of spine fusion surgery remains highly dynamic with changes in perioperative care constantly affecting patient care, recent data affecting rates and risk for perioperative mortality remain very limited.
Methods
We obtained the NIS from the Hospital cost and utilization project. The impact of patient and health care system related demographics, including various comorbidities as well as postoperative complications on the outcome of in-hospital mortality after spine fusion were studied. Furthermore, we analyzed the timing of in-hospital mortality.
Results
An estimated total of 1,288,496 primary posterior lumbar spine fusion procedures were performed in the US between 1998 and 2008. The average mortality rate for lumbar spine fusion surgery was 0.2 %. Independent risk factors for in-hospital mortality included advanced age, male gender, large hospital size, and emergency admission. Comorbidities associated with the highest in-hospital mortality after lumbar spine fusion surgery were coagulopathy, metastatic cancer, congestive heart failure and renal disease. Most lethal complications were cerebrovascular events, sepsis and pulmonary embolism. Furthermore, we demonstrated that the timing of death occurred relatively early in the in-hospital period with over half of fatalities occurring by postoperative day 9.
Conclusion
This study provides nationally representative information on risk factors for and timing of perioperative mortality after primary lumbar spine fusion surgery. These data can be used to assess risk for this event and to develop targeted intervention to decrease such risk.
doi:10.1007/s00586-012-2298-8
PMCID: PMC3535239  PMID: 22526700
Perioperative mortality; Lumbar spine fusion; Risk factor; Complication; Comorbidity
3.  Neurologic deficit following lateral lumbar interbody fusion 
European Spine Journal  2011;21(6):1192-1199.
Purpose
Lateral lumbar interbody fusion (LLIF) is a minimally invasive technique that has gained growing interest in recent years. We performed a retrospective review of the medical records and operative reports of patients undergoing LLIF between March 2006 and December 2009. We seek to identify the incidence and nature of neurological deficits following LLIF.
Methods
New occurring sensory and motor deficits were recorded at 6 and 12 weeks as well as 6- and 12 months of follow-up. Motor deficits were grouped according to the muscle weakness and severity and sensory deficits to the dermatomal zone. New events were correlated to the patient demographics, pre-operative diagnosis, operative levels, and duration of surgery. At each post-operative time-point patients were queried regarding the presence of leg pain.
Results
A total of 235 patients (139 F; 96 M) with a total of 444 levels fused were included. Average age was 61.5 and mean BMI 28.3. At 12 months’ follow-up, the prevalence of sensory deficits was 1.6%, psoas mechanical deficit was 1.6% and lumbar plexus related deficits 2.9%. Although there was no significant correlation between the surgical level L4–5 and an increased psoas mechanical flexion or lumbar plexus related motor deficit, a trend was observed. Independent risk factors for both psoas mechanical hip flexion deficit and lumbar plexus related motor deficit was duration of surgery.
Conclusion
LLIF is a valuable tool for achieving fusion through a minimally invasive approach with little risk to neurovascular structures.
doi:10.1007/s00586-011-2087-9
PMCID: PMC3366130  PMID: 22130617
Lateral transpsoatic interbody fusion; Lateral lumbar interbody fusion; Lumbar plexus injury; Anterior thigh pain; Neurologic deficit; Motor deficit
4.  Metabolic syndrome and lumbar spine fusion surgery: epidemiology and perioperative outcomes 
Spine  2012;37(11):989-995.
Study Design
Analysis of the National Inpatient Sample database from 2000 to 2008.
Objective
To identify if metabolic syndrome is an independent risk factor for increased major perioperative complications, cost, length of stay and non-routine discharge.
Summary of Background Data
Metabolic syndrome is a combination of medical disorders that has been shown to increase the health risk of the general population. No study has analyzed its impact in the perioperative spine surgery setting.
Methods
We obtained the National Inpatient Sample from the Hospital Cost and Utilization Project for each year between 2000 and 2008. All patients undergoing primary posterior lumbar spine fusion were identified and separated into groups with and without metabolic syndrome. Patient demographics and health care system related parameters were compared. The outcomes of major complications, non-routine discharge, length of hospital stay and hospitalization charges were assessed for both groups. Regression analysis was performed to identify if the presence of metabolic syndrome was an independent risk factor for each outcome.
Results
An estimated 1,152,747 primary posterior lumbar spine fusion were performed between 2000 and 2008 in the US. The prevalence of metabolic syndrome as well as the comorbidities of the patients increased significantly over time. Patients with metabolic syndrome had significantly longer length of stay, higher hospital charges, higher rates of non-routine discharges and increased rates of major life-threatening complications compared to patients without metabolic syndrome.
Conclusion
Patients with metabolic syndrome undergoing primary posterior lumbar spinal fusion represent an increasing financial burden on the health care system. Clinicians should recognize that metabolic syndrome represents a risk factor for increased perioperative morbidity.
doi:10.1097/BRS.0b013e31823a3a13
PMCID: PMC3288758  PMID: 22024892
metabolic syndrome; spinal fusion; lumbar spine; complications; risk factors; perioperative
5.  Degenerative Scoliosis: A Review 
HSS Journal  2011;7(3):257-264.
Degenerative lumbar scoliosis is a coronal deviation of the spine that is prevalent in the elderly population. Although the etiology is unclear, it is associated with progressive and asymmetric degeneration of the disc, facet joints, and other structural spinal elements typically leading to neural element compression. Clinical presentation varies and is frequently associated with axial back pain and neurogenic claudication. Indications for treatment include pain, neurogenic symptoms, and progressive cosmetic deformity. Non-operative treatment includes physical conditioning and exercise, pharmacological agents for pain control, and use of orthotics and invasive modalities like epidural and facet injections. Operative treatment should be contemplated after multi-factorial and multidisciplinary evaluation of the risks and the benefits. Options include decompression, instrumented stabilization with posterior or anterior fusion, correction of deformity, or a combination of these that are tailored to each patient. Incidence of perioperative complications is substantial and must be considered when deciding appropriate operative treatment. The primary goal of surgical treatment is to provide pain relief and to improve the quality of life with minimum risk of complications.
doi:10.1007/s11420-011-9204-5
PMCID: PMC3192887  PMID: 23024623
degenerative scoliosis; adult scoliosis; adult deformity; spinal stenosis; secondary scoliosis
6.  Cervical Radiculopathy: A Review 
HSS Journal  2011;7(3):265-272.
Background
Cervical radiculopathy is defined as a syndrome of pain and/or sensorimotor deficits due to compression of a cervical nerve root. Understanding of this disease is vital for rapid diagnosis and treatment of patients with this condition, facilitating their recovery and return to regular activity.
Purpose
This review is designed to clarify (1) the pathophysiology that leads to nerve root compression; (2) the diagnosis of the disease guided by history, physical exam, imaging, and electrophysiology; and (3) operative and non-operative options for treatment and how these should be applied.
Methods
The PubMed database was searched for relevant articles and these articles were reviewed by independent authors. The conclusions are presented in this manuscript.
Results
Facet joint spondylosis and herniation of the intervertebral disc are the most common causes of nerve root compression. The clinical consequence of radiculopathy is arm pain or paresthesias in the dermatomal distribution of the affected nerve and may or may not be associated with neck pain and motor weakness. Patient history and clinical examination are important for diagnosis. Further imaging modalities, such as x-ray, computed tomography, magnetic resonance imaging, and electrophysiologic testing, are of importance. Most patients will significantly improve from non-surgical active and passive therapies. Indicated for surgery are patients with clinically significant motor deficits, debilitating pain that is resistant to conservative modalities and/or time, or instability in the setting of disabling radiculopathy. Surgical treatment options include anterior cervical decompression with fusion and posterior cervical laminoforaminotomy.
Conclusion
Understanding the pathophysiology, diagnosis, treatment indications, and treatment techniques is essential for rapid diagnosis and care of patients with cervical radiculopathy.
doi:10.1007/s11420-011-9218-z
PMCID: PMC3192889  PMID: 23024624
cervical radiculopathy; disc herniation; ACDF; ADF; posterior cervical laminoforaminotomy; posterior cervical foraminotomy
7.  The effects of fixed electrical charge on chondrocyte behavior 
Acta biomaterialia  2011;7(5):2080-2090.
In this study, we have compared the effects of negative and positive fixed charge on chondrocyte behavior in vitro. Electrical charges have been incorporated into oligo(poly(ethylene glycol) fumarate) (OPF) using small charged monomers such as sodium methacrylate (SMA) and (2-(methacryloyloxy) ethyl)-trimethyl ammonium chloride (MAETAC) to produce negatively and positively charged hydrogels, respectively. The hydrogel physical and electrical properties were characterized through measuring and calculating the swelling ratio and zeta potential, respectively. Our results revealed that the properties of these OPF modified hydrogels varied according to the concentration of charged monomers. Zeta potential measurements demonstrated that the electrical property of the OPF hydrogel surfaces changed due to incorporation of SMA and MAETAC and that this change in electrical property was dose-dependent. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy was used to determine the hydrogel surface composition. To assess the effects of surface properties on chondrocyte behavior, primary chondrocytes isolated from rabbit ears were seeded as a monolayer on top of the hydrogels. We demonstrated that the cells remained viable over 7 days and began to proliferate while seeded on top of the hydrogels. Collagen type II staining was positive in all samples; however, the intensity of the stain was higher on negatively charged hydrogels. Similarly, GAG production was significantly higher on negatively charged hydrogels compared to neutral hydrogel. Reverse transcription polymerase chain reaction showed up-regulation of collagen type II and down-regulation of collagen type I on the negatively charged hydrogels. These findings indicate that charge plays an important role in establishing an appropriate environment for chondrocytes and hence in the engineering of cartilage. Thus, further investigation into charged hydrogels for cartilage tissue engineering is merited.
doi:10.1016/j.actbio.2011.01.012
PMCID: PMC3103083  PMID: 21262395
hydrogel; cartilage tissue engineering; OPF; scaffold
8.  A Stimuli-Responsive Hydrogel for Doxorubicin Delivery 
Biomaterials  2010;31(31):8051-8062.
The goal of this study was to develop a polymeric carrier for delivery of anti-tumor drugs and sustained release of these agents in order to optimize anti-tumor activity while minimizing systemic effects. We used oligo(poly(ethylene glycol) fumarate) (OPF) hydrogels modified with small negatively charged molecules, sodium methacrylate (SMA), for delivery of doxorubicin (DOX). SMA at different concentrations was incorporated into the OPF hydrogel with a photo-crosslinking method. The resulting hydrogels exhibited sensitivity to the pH and ionic strength of the surrounding environment. Our results revealed that DOX was bound to the negatively charged hydrogel through electrostatic interaction and was released in a timely fashion with an ion exchange mechanism. Release kinetics of DOX was directly correlated to the concentration of SMA in the hydrogel formulations. Anti-tumor activity of the released DOX was assessed using a human osteosarcoma cell line. Our data revealed that DOX released from the modified, charged hydrogels remained biologically active and had the capability to kill cancer cells. In contrast, control groups of unmodified OPF hydrogels with or without DOX did not exhibit any cytotoxicity. This study demonstrates the feasibility of using SMA-modified OPF hydrogels as a potential carrier for chemotherapeutic drugs for cancer treatments.
doi:10.1016/j.biomaterials.2010.06.054
PMCID: PMC2936247  PMID: 20696470

Results 1-8 (8)