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1.  Clinically important body weight gain following total hip arthroplasty: A cohort study with five-year follow-up 
Literature examining the effects of total hip arthroplasty (THA) on subsequent body weight gain is inconclusive. Determining the extent to which clinically relevant weight gain occurs following THA has important public health implications.
We used multivariable logistic regression to compare data from one of the largest US-based THA registries to a population-based control sample from the same geographic region. We also identified factors that increased risk of clinically important weight gain specifically among persons undergoing THA. The outcome measure of interest was weight gain of ≥ 5% of body weight up to 5 years following surgery.
The multivariable adjusted (age, sex, BMI, education, comorbidity and pre-surgical weight change) odds ratio for important weight gain was 1.7 (95% CI, 1.06, 2.6) for a person with THA as compared the control sample. Additional arthroplasty procedures during the 5-year follow-up further increased odds for important weight gain (OR=2.0, 95% CI, 1.4, 2.7) relative to the control sample. A patient with THA had increased risk of important post-surgical weight gain of 12% (OR=1.12; 95%CI,1.08, 1.16) for every kilogram of pre-operative weight loss.
While findings should be interpreted with caution because of missing follow-up weight data, patients with THA appear to be at increased risk of clinically important weight gain following surgery as compared to peers. Patients less than 60 years and who have lost a substantial amount of weight prior to surgery appear to be at particularly high risk of important postsurgical weight gain.
PMCID: PMC4169300  PMID: 23047011
knee; hip; arthroplasty; obesity
2.  Aseptic Tibial Debonding as a Cause of Early Failure in a Modern Total Knee Arthroplasty Design 
We observed isolated tibial component debonding from the cement in one modern primary TKA design (NexGen LPS 3° tibial tray; Zimmer, Warsaw, IN, USA). This failure mechanism is sparsely reported in the literature.
We (1) assessed survivorship of this tibial tray with special emphasis on debonding; (2) described clinical and radiographic features associated with tibial failure; and (3) compared patient and radiographic features of the failures with a matched cohort.
A total of 1337 primary TKAs were performed with a cemented NexGen LPS 3° tibial tray over an 11-year period. Twenty-five knees (1.9%) were revised for tibial debonding. BMI and radiographic alignment in the tibial debonding group were compared with a matched control group. Implant survivorship was assessed using tibial debonding as the end point.
Survival free of revision from tibial debonding was 100% at 1 year and 97.8% at 5 years. The tibial failures shared a typical radiographic pattern with debonding at the cement-implant interface and subsidence into varus and flexion. We found no link between limb alignment or individual component alignment and failure because 22 of the 25 failures occurred in well-aligned knees.
Our standardized followup of patients undergoing TKA at routine intervals allowed us to discover a higher rate of revision resulting from tibial debonding. We have discontinued the use of this particular tibial tray for primary TKA and surveillance for patients undergoing TKA continues to be warranted.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC3528903  PMID: 22790529
3.  Determinants of Direct Medical Costs in Primary and Revision Total Knee Arthroplasty 
TKA procedures are increasing rapidly, with substantial cost implications. Determining cost drivers in TKA is essential for care improvement and informing future payment models.
We determined the components of hospitalization and 90-day costs in primary and revision TKA and the role of demographics, operative indications, comorbidities, and complications as potential determinants of costs.
We studied 6475 primary and 1654 revision TKA procedures performed between January 1, 2000, and September 31, 2008, at a single center. Direct medical costs were measured by using standardized, inflation-adjusted costs for services and procedures billed during the 90-day period. We used linear regression models to determine the cost impact associated with individual patient characteristics.
The largest proportion of costs in both primary and revision TKA, respectively, were for room and board (28% and 23%), operating room (22% and 17%), and prostheses (13% and 24%). Prosthesis costs were almost threefold higher in revision TKA than in primary TKA. Revision TKA procedures for infections and bone and/or prosthesis fractures were approximately 25% more costly than revisions for instability and loosening. Several common comorbidities were associated with higher costs. Patients with vascular and infectious complications had longer hospital stays and at least 80% higher 90-day costs as compared to patients without complications.
High prosthesis costs in revision TKA represent a factor potentially amenable to cost containment efforts. Increased costs associated with demographic factors and comorbidities may put providers at financial risk and may jeopardize healthcare access for those patients in greatest need.
Level of Evidence
Level IV, economic and decision analyses. See Instructions for Authors for a complete description of levels of evidence
PMCID: PMC3528929  PMID: 22864619
4.  Tantalum Acetabular Cups Provide Secure Fixation in THA after Pelvic Irradiation at Minimum 5-year Followup 
Pelvic radiation has been commonly used to treat gastrointestinal, genitourinary, or hematopoietic malignancies. Conventional THA in these patients reportedly have high rates of fixation failure. Although secure short-term fixation reportedly occurs with trabecular metal implants following pelvic radiation, it is unclear whether the fixation is durable.
We determined the survival of trabecular metal acetabular components in patients having THA following pelvic radiation and assessed function and radiographic loosening.
We retrospectively reviewed 29 patients with prior pelvic radiation who had 34 arthroplasties using trabecular metal acetabular components from 1998 and 2005. The mean pelvic radiation dose was 6300 cGy. We collected the following data: patient demographics, surgery and implant information, clinical and radiographic followup, and tumor and radiotherapy related details. We obtained Harris hip scores (HHS) on all patients. Ten patients died of disease prior to 5 years and two patients were excluded, leaving 17 patients (22 hips) with a minimum of 5 years of clinical (mean, 78 months; median, 71; range, 57–116) and radiographic (mean, 73; median, 65; range, 51–116) followup.
All implants were in place in the surviving patients. The mean HHS improved from 36 preoperatively to 80 at latest followup. There were no reoperations for any reason, and we observed no implant loosening or migration at final followup in surviving or deceased patients.
Tantalum trabecular metal acetabular components restored function and provided durable reconstruction in patients undergoing THA following prior pelvic radiation. We observed no clinical or radiographic failures at a minimum 5-year followup.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC3462848  PMID: 22576931
5.  Total Knee Arthroplasty in Morbidly Obese Patients Treated with Bariatric Surgery: A Comparative Study 
The Journal of arthroplasty  2012;27(9):1696-1700.
Our objective was to compare outcomes (anesthesia time, total operative time, tourniquet time, duration of hospital stay, 90-day complication rate and transfusion rates) of patients with total knee arthroplasty (TKA) who underwent bariatric surgery before or after TKA. One-hundred-twenty-five patients were included: TKA before bariatric surgery (group 1; n=39); TKA within two years of bariatric surgery (group 2; n=25); and TKA more than 2 years after bariatric surgery (group 3; n=61). Patients with TKA more than 2 years after bariatric surgery had shorter anesthesia, total operative and tourniquet times than other groups; differences were significant between groups. Ninety-day complication and transfusion rates approached but did not meet statistical significance. Ninety-day complication rates and duration of hospital stay did not differ significantly between the three groups.
PMCID: PMC3413743  PMID: 22554730
Total knee arthroplasty; morbidly obese; bariatric surgery; outcomes
6.  Ninety-day Mortality in Patients Undergoing Elective Total Hip or Total Knee Arthroplasty 
The Journal of arthroplasty  2012;27(8):1417-1422.e1.
Using an institutional Joint Registry, we studied frequency, trends and predictors of mortality following elective total hip or knee arthroplasty (THA/TKA). Of the 12,727 and 12,484 patients who underwent THA and TKA respectively, all-cause mortality rates at 7-, 30- and 90-days were as follows: THA, 0.1%, 0.2% and 0.5%; TKA 0.1%. 0.2% and 0.4%, respectively. Statistically significant downward time-trend in 90-day mortality was noted after TKA (p=0.02), but not after THA (p=0.41). In multivariable-adjusted analyses of THA patients, older age, higher comorbidity index, and prior cardiac disease were significantly associated with higher 90-day mortality. In TKA patients, older age, male gender, ASA class of 3-4, and higher comorbidity index were associated with higher 90-day all-cause mortality. Optimization of disease management may reduce postoperative mortality after THA/TKA.
PMCID: PMC3413788  PMID: 22554727
7.  Predictors of use of pain medications for persistent knee pain after primary Total Knee Arthroplasty: a cohort study using an institutional joint registry 
Arthritis Research & Therapy  2012;14(6):R248.
To study the use of pain medications for persistent index knee pain and their predictors after primary Total Knee Arthroplasty (TKA).
The Mayo Total Joint Registry collects patient-reported data including pain medication use on all patients who undergo TKA. We used data from patients who underwent primary TKA from 1993-2005. We examined whether gender, age (reference, ≤60 yrs), body mass index (BMI; reference, <25 kg/m2), comorbidities measured by Deyo-Charlson index (5-point increase), anxiety and depression predicted use of pain medications (non-steroidal anti-inflammatory drugs (NSAIDs) and opioids) 2- and 5-years after primary TKA. Multivariable logistic regression additionally adjusted for operative diagnosis, American Society of Anesthesiologists (ASA) score, implant fixation and distance from the medical center.
7,139 of the 10,957 eligible (65%) at 2-years and 4,234 of 7,404 eligible (57%) completed questionnaires. Significant predictors of NSAIDs use were (Odds ratio (95% confidence interval)): male gender at 2- and 5-years, 0.5 (0.4, 0.6) and 0.6 (0.5, 0.8); age >70-80 years, 0.7 (0.5, 0.9), 0.6 (0.4, 0.8); and depression, 1.4 (1.0, 1.8) and 1.7 (1.1, 2.5). BMI ≥40 was associated with NSAIDs use only at 2-years, 1.6 (1.1, 2.5). Significant predictors of opioid pain medication use at 2- and 5-years were: male gender, 0.5 (0.3, 0.9) and 0.4 (0.2, 0.8); age >70-80 years, 0.3 (0.1, 0.6), 0.3 (0.1, 0.8); and anxiety, 3.0 (1.6, 5.7) and 4.0 (1.7, 9.4).
Female gender and younger age were associated with higher risk of use of NSAIDs and opioids after primary TKA. Depression was associated with higher NSAID use and anxiety with higher opioid pain medication use after primary TKA.
PMCID: PMC3674590  PMID: 23157942
8.  Peptic ulcer disease and heart disease are associated with periprosthetic fractures after total hip replacement 
Acta Orthopaedica  2012;83(4):353-359.
Background and purpose
There have been no published studies assessing the possible association of medical comorbidities with periprosthetic fracture risk. We therefore assessed whether medical comorbidity is associated with risk of periprosthetic fractures after total hip replacement (THR).
Material and methods
We used prospectively collected data from 1989–2008 in the Mayo Clinic Total Joint Registry for 2 cohorts: primary THR and revision THR. The main variables of interest were Deyo-Charlson comorbidities at the time of surgery. Outcome of interest was p ostoperative periprosthetic fracture at postoperative day 1 onwards. Multivariable
Cox regression models were additionally adjusted for age, sex, body mass index, American Society of Anesthesiology (ASA) class, and operative diagnosis.
We identified 14,065 primary THRs and 6,281 revision THRs with mean follow-up times of 6.3 and 5.6 years, respectively. There were 305 postoperative periprosthetic fractures in the primary THR cohort and 330 in the revision THR cohort. In patients who underwent primary THR, 2 comorbidities were associated with higher risk of periprosthetic fracture: peptic ulcer disease with adjusted hazard ratio of 1.5 (95% CI: 1.1–2.2) and heart disease with adjusted hazard ratio of 1.7 (CI: 1.2–2.4). In patients with revision THR, peptic ulcer disease was associated with a higher adjusted risk of periprosthetic fracture, 1.6 (CI: 1.1–2.3).
Peptic ulcer disease and heart disease in primary THR patients and peptic ulcer disease in revision THR patients were associated with higher postoperative periprosthetic fracture risk. Further studies are needed to understand whether disease severity or specific medications used for treatment, or both, are responsible for this association. This may allow identification of modifiable factors.
PMCID: PMC3427625  PMID: 22900908

Results 1-8 (8)