Alan L. Zhang
University of California, San Francisco
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Featured researches published by Alan L. Zhang.
American Journal of Sports Medicine | 2012
Alan L. Zhang; Christopher Kreulen; Stephanie S. Ngo; Sharon L. Hame; Jeffrey C. Wang; Seth C. Gamradt
Background: Treatment of superior labral anterior posterior (SLAP) tears remains controversial, particularly in older age groups. Repair, debridement, biceps tenodesis, tenotomy, and observation have been recommended depending on patient characteristics, but there have not been any large epidemiologic studies investigating treatment trends. Purpose: To investigate current trends in SLAP repair across time, gender, age, and regions in the United States. Study Design: Descriptive epidemiology study. Methods: Patients who underwent arthroscopic SLAP repair (Current Procedural Terminology [CPT] code 29807) were identified using a publicly available national database of insurance records (PearlDiver Patient Records Database) during years 2004 through 2009. Factors identified for each patient included gender, age group, and region in the United States. Logistic regression analysis and the chi-square test were used for statistical measures. Results: From 2004 to 2009 there were 25,574 cases of arthroscopic SLAP repair identified, of which 75% were male patients and 25% were female patients. There was a significant rise in cases of SLAP repair from 2004 to 2009 as the incidence of SLAP repair increased from 17.0 for every 10,000 patients with an orthopaedic International Classification of Diseases, Ninth Revision (ICD-9) or CPT code in 2004 to 28.1 in 2009 (P < .0001). Age analysis revealed the highest incidence in the 20-29–year (29.1 per 10,000) and 40-49–year (27.8 per 10,000) age groups. Men (37.3 per 10,000) had a significantly higher incidence of repairs than did women (10.7 per 10,000). The West (24.6 per 10,000) and South (24.4 per 10,000) regions also demonstrated a higher incidence than the Midwest (20.5 per 10,000) and Northeast (20.1 per 10,000) regions (P < .0001). Conclusion: Our analysis illustrates that surgeons are performing significantly more arthroscopic SLAP repairs each year. The highest incidence of repair is in the 20-29– and 40-49–year age groups, and a significant gender difference exists, with men having a threefold higher incidence of repair.
Arteriosclerosis, Thrombosis, and Vascular Biology | 2006
Paul P. Lau; Lan Li; Aksam J. Merched; Alan L. Zhang; Kerry W.S. Ko; Lawrence Chan
Objective—We investigated the molecular mechanism of nicotine-accelerated atherosclerosis in a hyperlipidemic low-density lipoprotein receptor−/− mouse model. Methods and Results—Low-density lipoprotein receptor−/− mice received time-release nicotine or placebo pellets for 90 days. Aortic lesion size was 2.5 times larger in nicotine-treated than in placebo-treated mice (P<0.001). A mild increase in lipids was seen in treated mice. We quantified 18 different serum cytokines and found a significant increase of tumor necrosis factor &agr;, interleukin 1&bgr;, and keratinocyte-derived chemokine in nicotine-treated mice. Among 107 nuclear factor &kgr;B (NF-&kgr;B) target genes screened from the aorta, we found that nicotine treatment upregulated only 4 atherogenic genes including vascular adhesion molecule 1 and cyclooxygenase 2 on day 60 and platelet-derived growth factor B and platelet 12-lipoxygenase on day 90. At the cellular level, nicotine induced tumor necrosis factor &agr; and inducible nitric oxide synthase expression in RAW264.7 cells via the nicotinic acetylcholine receptors. Induction was confirmed in peritoneal macrophages isolated from nicotine-treated mice. Finally, we showed that preconditioned medium from nicotine-treated RAW264.7 cells activated NF-&kgr;B in human smooth muscle cells and vascular endothelial cells as evidenced by nuclear localization and electromobility shift assay. Conclusions—Chronic nicotine exposure augments atherosclerosis by enhancing the production of proinflammatory cytokines by macrophages, which, in turn, activate atherogenic NF-&kgr;B target genes in the aortic lesions.
Arthroscopy | 2013
Alan L. Zhang; Scott R. Montgomery; Stephanie S. Ngo; Sharon L. Hame; Jeffrey C. Wang; Seth C. Gamradt
PURPOSE The purpose of this study was to identify current trends in open and arthroscopic surgical treatment of rotator cuff tears across sex, age, and region in the United States. METHODS Using the PearlDiver Patient Record Database (PearlDiver, Fort Wayne, IN), a publicly available national database of insurance records, patients who underwent rotator cuff repair from 2004 through 2009 were identified. The number of open (CPT codes 23410, 23412, 23420) and arthroscopic (CPT code 29827) rotator cuff repairs were quantified in isolation and in combination with acromioplasty (CPT codes 23415, 29826). The type of procedure, date, sex, and region of the country was identified for each patient. Trend tests (χ(2) and Cochran-Armitage) were used to determine statistical significance. RESULTS There were 151,866 rotator cuff repair procedures identified in the database from 2004 through 2009, which represented an incidence of 13.6 for every 1,000 patients assigned an orthopaedic International Classification of Diseases, Ninth Revision (ICD-9) or Current Procedural Terminology (CPT) code. Male patients accounted for 60% of the repairs and female patients for 40%. There were 98,174 arthroscopic cuff repairs (65%) and 53,692 open repairs (35%). The annual percentage of arthroscopic cases increased from 48.8% in 2004 to 74.3% in 2009, whereas the percentage of open cases decreased from 51.2% in 2004 to 25.7% in 2009 (P < .0001). Acromioplasty was also performed in 47.3% of cases, and the rate showed only a slight increase (from 46.6% to 47.8%) between 2004 and 2009 (P < .01). All regions of the United States showed similar surgical trends and trends for sex and age distributions. CONCLUSIONS Our analysis shows that the majority of rotator cuff repairs in the United States are now performed arthroscopically (>74%) and there has been a recent steady decline in performance of open rotator cuff repair. Concomitant acromioplasty is performed approximately half the time, and this trend is increasing slightly. These findings were consistent across age, sex, and region in the United States. LEVEL OF EVIDENCE IV, cross-sectional study.
Journal of Shoulder and Elbow Surgery | 2014
William W. Schairer; Alan L. Zhang; Brian T. Feeley
BACKGROUND Although shoulder arthroplasty procedures are more frequently performed in the United States, there is insufficient information on outcome measures such as hospital readmission rates or factors for readmission after surgery. METHODS The State Inpatient Database from 7 different states was used to identify patients who underwent hemiarthroplasty, total shoulder arthroplasty (TSA), or reverse total shoulder arthroplasty (RTSA) from 2005 through 2010. The database was used to determine the 90-day readmission rate, causes of readmission, and risk factors for readmission. Multivariate modeling and a Cox proportional hazards model were used to measure factors and risk for readmission. RESULTS Included were 26,218 patients receiving shoulder arthroplasty, with an overall 90-day readmission rate of 7.3%. RTSA had the highest rate (11.2%), followed by hemiarthroplasty (8.2%) and TSA (6.0%; P < .001). Medical complications contributed to 82% of readmissions, and surgical complications contributed to 18%. Osteoarthritis was the most common medical diagnosis (11%), followed by deep venous thrombosis or pulmonary embolism (4.4%) and pneumonia (3.9%). Infection was the most common surgical cause of readmission (4.8%), followed by dislocation (4.6%). There was a stepwise increase in risk of readmission with increasing age. Patients with Medicaid insurance had more than a 50% greater risk of readmission than patients with Medicare. Procedures performed at medium-volume and high-volume hospitals showed lower risk of readmission than low-volume centers. CONCLUSIONS Patients undergoing RTSA had higher hospital readmission rates than those undergoing hemiarthroplasty or TSA, but most readmissions after shoulder arthroplasty were due to medical causes.
Orthopedics | 2013
Scott R. Montgomery; Alan L. Zhang; Stephanie S. Ngo; Jeffrey C. Wang; Sharon L. Hame
Knee arthroscopy to address meniscus tears is among the most common orthopedic procedures performed, and technical advances in the treatment of meniscus tears have affected the treatment options available to orthopedic surgeons. The purpose of this study was to perform a large cross-sectional analysis of orthopedic patients to investigate trends in arthroscopic meniscectomy and meniscus repair in the United States. Patients who underwent arthroscopic meniscectomy (Current Procedural Terminology codes 29881 and 29880) and arthroscopic meniscus repair (Current Procedural Terminology codes 29882 and 29883) were identified using the PearlDiver Patient Record Database, which is a national database of insurance records. The authors identified 187,607 arthroscopic medial or lateral meniscectomies and repairs performed between 2004 and 2009. Ninety-six percent of patients underwent meniscectomy and 4% underwent repair. No change occurred in the incidence of medial or lateral meniscectomy. The incidence of medial meniscus repair decreased from 5.3 cases per 10,000 patients in 2004 to 3.8 in 2009 (P<.001), although no significant change occurred in the incidence of lateral meniscus repair. Medial meniscectomy was most commonly performed in patients aged 50 to 59 years, whereas lateral meniscectomy demonstrated a bimodal age distribution. Conversely, meniscus repairs were most frequently performed in patients aged 10 to 19 years. Sex differences were more pronounced with meniscus repair (63% male vs 37% female) compared with meniscectomy (53% male vs 47% female). A high frequency of meniscus debridement can be expected in arthroscopic knee surgery. Despite advances in meniscus repair techniques and devices, no increase occurred in the performance of meniscus repair compared with meniscectomy.
Journal of Bone and Joint Surgery, American Volume | 2016
Alan L. Zhang; David C. Sing; Debbie Y. Dang; C. Benjamin Ma; Dennis M. Black; Thomas P. Vail; Brian T. Feeley
BACKGROUND The practice of a surgeon performing procedures in two operating rooms during overlapping time frames has been described as concurrent surgery if critical portions occur simultaneously, or overlapping surgery if they do not. Although recent media reports have focused on the potential adverse effects of these practices, to our knowledge, there has been no previous research investigating outcomes of overlapping procedures in orthopaedic surgery. METHODS A retrospective review of an institutional clinical database from 2012 to 2015 was utilized to collect data from all surgical cases (including sports medicine, hand, and foot and ankle) performed at an ambulatory orthopaedic surgery center. Patient demographic characteristics, types of procedures, operating room time, procedure time, and 30-day outcomes including complications, unplanned hospital readmissions, unplanned reoperations, and emergency department visits were collected. The amount of overlap time between cases was also analyzed. Pearson chi-square tests, Student t tests, and logistic regression were used for statistical analysis. RESULTS Of 3,640 cases performed, 68% were overlapping procedures and 32% were non-overlapping. There was no difference in the mean age, sex, body mass index, American Society of Anesthesiologists rating, or Charlson Comorbidity Index between patients who had overlapping procedures and those who did not. Comparison of overlapping surgery cases and non-overlapping surgery cases revealed no difference in the mean procedure time (70.7 minutes compared with 72.8 minutes; p = 0.116) or total operating room time (105.4 minutes compared with 105.5 minutes; p = 0.949). Complications were tracked for 30 days after procedures and yielded a rate of 1.1% for overlapping surgeries and 1.3% for non-overlapping surgeries (p = 0.811). Stratification based on subspecialty surgery also demonstrated no difference in complications between the cohorts. Fifty percent of overlapping cases overlapped by <1 hour of operating room time, but 7% overlapped by >2 hours. The rate of complications was found to have no association with the amount of overlap between cases (p = 0.151). CONCLUSIONS Overlapping surgery yields equivalent patient operating room time, procedure time, and 30-day complication rates as non-overlapping surgery in the ambulatory orthopaedic setting. Further investigation is warranted for inpatient orthopaedic procedures and across all orthopaedic subspecialties. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
Orthopaedic Journal of Sports Medicine | 2016
Alan L. Zhang; David C. Sing; Caitlin M. Rugg; Brian T. Feeley; Carlin Senter
Background: Concussion injuries have been highlighted to the American public through media and research. While recent studies have shown increased traumatic brain injuries (TBIs) diagnosed in emergency departments across the United States, no studies have evaluated trends in concussion diagnoses across the general US population in various age groups. Purpose: To evaluate the current incidence and trends in concussions diagnosed across varying age groups and health care settings in a large cross-sectional population. Study Design: Descriptive epidemiological study. Methods: Administrative health records of 8,828,248 members of a large private-payer insurance group in the United States were queried. Patients diagnosed with concussion from years 2007 through 2014 were stratified by year of diagnosis, age group, sex, classification of concussion, and health care setting of diagnosis (eg, emergency department vs physician’s office). Chi-square testing was used for statistical analysis. Results: From a cohort of 8,828,248 patients, 43,884 patients were diagnosed with a concussion. Of these patients, 55% were male and over 32% were in the adolescent age group (10-19 years old). The highest incidence of concussion was seen in patients aged 15 to 19 years (16.5/1000 patients), followed by those aged 10 to 14 years (10.5/1000 patients), 20 to 24 years (5.2/1000 patients), and 5 to 9 years (3.5/1000 patients). Overall, there was a 60% increase in concussion incidence from 2007 to 2014. The largest increases were in the 10- to 14-year (143%) and 15- to 19-year (87%) age groups. Based on International Classification of Disease–9th Revision classification, 29% of concussions were associated with some form of loss of consciousness. Finally, 56% of concussions were diagnosed in the emergency department and 29% in a physician’s office, with the remainder in urgent care clinics or inpatient settings. Conclusion: The incidence of concussion diagnosed in the general US population is increasing, driven largely by a substantial rise in the adolescent age group. The youth population should be prioritized for ongoing work in concussion education, diagnosis, treatment, and prevention. Clinical Relevance: The rise of concussions in the adolescent age group across the general population is concerning, and clinical efforts to prevent these injuries are needed.
Journal of Shoulder and Elbow Surgery | 2016
Richard J. Han; David C. Sing; Brian T. Feeley; C. Benjamin Ma; Alan L. Zhang
BACKGROUND With an aging population, fragility fractures including injuries to the proximal humerus continue to rise in the United States. The purpose of this study was to investigate recent trends in the incidence and treatment of proximal humerus fractures (PHFs) in a cross-sectional elderly population. METHODS Medicare data from 2005 to 2012 were queried to identify patients treated for PHF. Associated patient demographics, hospitalization data, treatment, and revision status were obtained. Statistical analyses were performed to identify significant trends in treatment. RESULTS There were 259,506 PHFs recorded, with 79% occurring in female patients. In all age groups, nonoperative treatment of PHF was the most common method (67%). Within the surgical group, open reduction with internal fixation was most frequently used, and total shoulder arthroplasty (TSA) or reverse total shoulder arthroplasty (RTSA) was the least common (11%). However, although the overall rate of surgical intervention remained constant, there was a significant increase in treatment with TSA from 3% in 2005 to 17% in 2012. In particular, RTSA represented 89% of all TSAs for PHF in 2011. All surgical treatment options demonstrated high 2-year survival rates without revision surgery (97%). CONCLUSION Recent trends show that in the elderly population, nonoperative management remains the most common treatment for PHFs. Within the surgically treated cohort, there has been an increase in treatment with arthroplasty including RTSA, with a low rate of early revisions. There are excellent survival rates in all surgically treated PHFs, but long-term data will be required to fully evaluate the viability of these surgical options.
Journal of Shoulder and Elbow Surgery | 2016
Stephanie E. Wong; Alan L. Zhang; Jonathan L. Berliner; C. Benjamin Ma; Brian T. Feeley
BACKGROUND Total shoulder arthroplasty and reverse total shoulder arthroplasty are increasingly used to improve pain and function in patients with glenohumeral arthritis or cuff tear arthropathy. Our objective was to determine if preoperative patient-reported outcome measures predict which patients will achieve clinically meaningful improvements after shoulder arthroplasty. METHODS Preoperative and 1-year postoperative 12-Item Short Form Health Survey (SF-12) Physical Component Summary (PCS) and Mental Component Summary (MCS) scores and American Shoulder and Elbow Surgeons (ASES) pain and function scores were prospectively collected from 107 patients who underwent total or reverse shoulder arthroplasty. The minimum clinically important difference (MCID) defined meaningful clinical improvement. Receiver operating characteristic analysis was used to calculate threshold values and C statistic. Multivariate logistic regression analysis was performed to determine preoperative measures that were indicative of achieving the MCID postoperatively. RESULTS Threshold values below which patients were more likely to achieve MCID were 12 for ASES function, 25 for ASES pain, 46 for SF-12 PCS, and 42 for SF-12 MCS. Multivariate analysis revealed that preoperative ASES function (area under the curve, 0.79; P = .006) and ASES pain (area under the curve, 0.90; P < .001) measures were predictive of achieving the MCID postoperatively. Patients with higher preoperative SF-12 MCS scores had a higher likelihood of achieving MCID for each measure. CONCLUSION We determined threshold values that predict clinically meaningful improvement after shoulder arthroplasty. Patients with higher preoperative mental health scores and lower physical function and pain scores were more likely to gain significant benefits from surgery. These results can be used to facilitate shared decision-making and to forecast expected benefits after shoulder arthroplasty.
Journal of Shoulder and Elbow Surgery | 2015
Mia Smucny; Mariano E. Menendez; David Ring; Brian T. Feeley; Alan L. Zhang
BACKGROUND Surgical site infection (SSI) after joint arthroplasty is associated with prolonged hospitalization, reoperation, inferior outcomes, and substantial resource utilization. As the number of shoulder replacements performed in the United States continues to rise, measuring the incidence of inpatient SSI after hemiarthroplasty (HSA) and total shoulder arthroplasty (TSA), and associated risk factors for infection is worthwhile. METHODS Using the Nationwide Inpatient Sample (NIS), we reviewed 241,193 patients undergoing TSA or reverse TSA and 159,795 undergoing HSA between 2002 and 2011 and identified patients with an associated diagnosis of SSI during the admission. Demographic characteristics, preoperative diagnoses, further surgical procedures, associated comorbidities, and in-hospital events associated with SSI were sought in multivariable logistic regression analysis. RESULTS An in-hospital SSI developed in 0.08% of patients undergoing TSA or reverse TSA and in 0.11% of patients undergoing HSA. Independent risk factors for inpatient SSI included TSA vs HSA (odds ratio [OR], 1.83), Medicaid insurance vs private insurance (OR, 3.93), diagnosis of fracture nonunion (OR, 5.76), avascular necrosis (OR 2.71), or proximal humeral fracture (OR, 2.62) vs primary osteoarthritis, comorbidities, in-hospital events (blood transfusion, pneumonia, and acute renal failure), and increased duration of hospital stay. CONCLUSIONS The small percentage of SSI that occurs during the initial inpatient stay after shoulder arthroplasty is related to diagnoses other than primary osteoarthritis in more infirm patients with low-income government insurance (Medicaid). Patients considering shoulder arthroplasty can use this information to help decide between the potential improvement in comfort and function of the shoulder and the potential for major adverse events such as infection.