Robert Pivec

The effects of obesity and morbid obesity on outcomes in TKA.

The negative effects of obesity following total joint arthroplasty, such as increased morbidity and mortality, have been well documented in literature. However, little is known about whether specific body mass indices can be used as cutoffs to determine which patients are most at risk for having a poor postoperative outcome. We evaluated the effects of differing levels of obesity as measured by body mass index (BMI) on implant survivorship, Knee Society scores, complications, and radiographic outcomes. A systematic review of the literature was performed to identify all studies reporting outcomes of total knee arthroplasty in obese (30 ≤ BMI < 40 kg/m2) and morbidly obese patients (40 ≤ BMI < 50 kg/m2). Twenty-four studies were identified in our literature search. At a mean 5-year follow-up, morbidly obese patients (88%) had significantly lower implant survivorship than obese patients (95%) and nonobese patients (97%). Significantly, lower postoperative mean Knee Society objective and function scores (71 and 60 points) were observed for morbidly obese patients than for nonobese patients (75 and 90 points), but obese patients did not have significantly lower Knee Society objective and function scores than nonobese patients (78 and 84 points). Complication rates for nonobese, obese, and morbidly obese patients were 9, 15, and 22%, respectively, all of which were significantly different. However, no significant difference was observed in the incidence of radiolucent lines that were 12, 19, and 14%, respectively. Thus, we conclude that a BMI greater than 40 kg/m2 may be used as a cutoff to help guide patient education and treatment options for primary total knee arthroplasty.

Modular taper junction corrosion and failure: How to approach a recalled total hip arthroplasty implant

Corrosion at the modular neck-stem taper junction has become an increasingly important topic as several reports have identified this couple as a possible source for early failure with findings similar to failed metal-on-metal hip arthroplasties. Recently, two different modular stem systems from a single manufacturer were voluntarily recalled due to concerns of failure of the modular taper junction. We discuss how to approach the diagnosis and management of patients with these particular stem systems. We further reviewed the literature to evaluate whether this is a manufacturer-specific defect or indicative of a broader trend. Recent studies appear to implicate the basic design of the neck-stem taper junction, rather than a single manufacturer, which is at high risk for fretting and corrosion.

Long-Term Implant Survivorship of Cementless Total Knee Arthroplasty: A Systematic Review of the Literature and Meta-Analysis

Cementless total knee arthroplasty (TKA) has had limited use in the United States, however, recent reports have demonstrated promising results, but there has been no meta-analysis to examine these outcomes in the past 5 years. In this review, 37 studies (2,940 patients and 3,568 TKAs) were identified and used, comparing cementless to cemented TKA. Pooled implant survivorship was compared using a fixed-effect meta-analysis between cementless and cemented TKA, and between cementless TKA with and without screw fixation. Cementless TKA had implant survivorship comparable to cemented TKA (odds ratio, 1.1; 95% confidence interval [CI], 0.62-2.00). The mean survivorship at 10 years for cementless TKA was 95.6% compared with 95.3% for cemented TKA. At 20-year follow-up, implant survivorship decreased to 76 and 71%, respectively. No difference was observed between fixation with or without screws (OR, 1.1; 95% CI, 0.16-7.5). Implant survivorship for cementless TKA was comparable to the current gold standard cemented TKAs.

Short bone-conserving stems in cementless hip arthroplasty.

➤ Short bone-conserving femoral stems in total hip arthroplasty were designed to preserve proximal bone stock.➤ Given the distinct fixation principles and location of loading among these bone-conserving stems, a classification system is essential to compare clinical outcomes.➤ Due to the low quality of currently available evidence, only a weak recommendation can be provided for clinical usage of certain stem designs, while some other designs cannot be recommended at this time.➤ A high prevalence of stem malalignment, incorrect sizing, subsidence, and intraoperative fractures has been reported in a subset of these short stem designs.➤ Stronger evidence, including prospective multicenter randomized trials comparing standard stems with these newer designs, is necessary before widespread use can be recommended.

Systematic review comparing static and articulating spacers used for revision of infected total knee arthroplasty.

The purpose of this systematic review was to compare the outcomes of static to articulating antibiotic spacers used in two-stage revision total knee arthroplasty. 48 reports with a total of 962 articulating spacers (949 patients) and 707 static spacers (688 patients) with a mean 4 year follow-up were identified for this review. Data on clinical function scores, range-of-motion, complications, and re-infection rates were collected on static and articulating spacers. Both groups had similar improvement in Knee Society Scores (83 versus 82 points), however, the articulating spacer groups had significantly higher range-of-motion (100° versus 92°). There was no difference in the re-infection rates, complication rates, or re-operation rates between the two groups. Currently no specific recommendation can be made about the superiority of one type of spacer over the other.

Does obesity affect the outcomes of primary total knee arthroplasty

The purpose of this study was to compare the clinical and radiographic outcomes of primary total knee arthroplasty (TKA) in obese and nonobese patients. A total of 210 knees in 174 obese patients who had a mean body mass index (BMI) of 34 kg/m2 (range, 30 to 39.9 kg/m2) and who had undergone a primary TKA between 2006 and 2010 were reviewed. There were 115 women and 59 men who had a mean age of 62 years (range, 36 to 84 years) and a mean follow-up of 57 months (range, 24 to 82 months). These patients were compared with a group of nonobese patients who had a BMI of less than 30 kg/m2 (range, 19 to 29.9 kg/m2). The evaluated outcomes included implant survivorship, Knee Society objective and functional scores, complication rates, radiographic outcomes, University of California Los Angeles (UCLA) activity score, and the length of hospital stay between obese and nonobese patients. There were no significant differences in the overall septic and aseptic implant survivorship (98.8 vs. 98.6%) and mean postoperative Knee Society objective and function scores (90 and 87 points vs. 91 and 89 points), respectively. Obese patients had significantly higher complication rates (10.5 vs. 3.8%) and had achieved a significantly lower mean postoperative UCLA activity score (5 vs. 6 points). However, there were no differences in the length of hospital stay for the two cohorts. Although the authors encourage all patients to lose weight as much as possible prior to their TKA, it is encouraging that obese patients had achieved excellent clinical outcomes at early to mid-term follow-up.

Tobacco Use May Be Associated With Increased Revision and Complication Rates Following Total Hip Arthroplasty

The purpose of this study was to compare the clinical outcomes of total hip arthroplasty in patients who were smokers to patients who were non-smokers. All total hip arthroplasties performed between 2007 and 2009 were reviewed to identify patients who indicated tobacco use. There were 110 smokers who were matched in a 1:2 ratio to 220 non-smoking patients. At a mean follow-up of 51 months (range, 24 to 72 months), smokers had an overall significantly lower survivorship of 92% (n = 9 revisions), compared to 99% (n = 2 revisions) in non-smokers. In addition, there were five complications in smokers (one pneumonia, three superficial infections, and one deep peroneal nerve palsy) compared to none in non-smokers. These results indicate that patients who smoke had higher overall revisions and postoperative complications.

Outcomes of short stems in total hip arthroplasty

Short-stem total hip arthroplasty has been proposed as a bone-conserving procedure for the younger and more active population undergoing total hip arthroplasty. Although various short stems are currently available, no studies compare the outcomes between these stems. The aim of the current study was to conduct a systematic review of the clinical and radiographic outcomes of the various short stems that have been approved for use in the United States by the Food and Drug Administration. Outcomes that were assessed included implant survivorship, Harris Hip scores, thigh pain, periprosthetic fracture, subsidence, proximal stress shielding, and the prevalence of stem malalignment and inappropriate implant sizing.

Long-term outcomes of MUA for stiffness in primary TKA.

Knee stiffness following primary total knee arthroplasty (TKA) is a well-recognized problem which leads to poor patient outcomes and may limit patient activities of daily living. Manipulation under anesthesia (MUA) is one option for the treatment of knee stiffness. However, there has been controversy regarding the safety and long-term efficacy of this procedure. A systematic review of the literature was performed to identify studies that reported the clinical outcomes and measured range of motion for patients undergoing MUA. Fourteen studies (913 patients) reported range of motion results following MUA at up to 10-year follow-up. The mean premanipulation and final range of motion were 66 and 99 degrees, respectively. Compared with preoperative range of motion, the gain in the range-of-motion arc at 1-, 5-, and 10-year follow-up was 30, 33, and 33 degrees, respectively. Complications were rare with only two reported periprosthetic fractures, resulting in an incidence of 0.2%. MUA for a stiff primary TKA is an efficacious procedure to restore range of motion. Early gains in motion appear to be maintained at long term, and in some cases patients may gradually improve further at mid-term follow-up. The risk of periprosthetic fracture is low, making MUA a safe option for improving knee range of motion.

Excellent results of primary THA using a highly porous titanium cup.

Cementless acetabular cups for primary total hip arthroplasty have had excellent results, with failure rates typically less than 5% at up to 10-year follow-up. Tritanium is a 3-dimensional metal interface that has been used for porous biological fixation. The purpose of this study was to review the clinical and radiographic results of the use of Tritanium cups (Stryker Orthopaedics, Mahwah, New Jersey) for primary total hip arthroplasty. Two hundred eighty-eight total hip arthroplasties performed using a porous titanium acetabular cup in 252 patients between 2008 and 2010 were reviewed. One hundred thirty-three men and 119 women with a mean age of 58 years (range, 18-88 years) were included. Mean follow-up was 36 months (range, 24-56 months). Outcomes evaluated were implant survivorship, Harris Hip Score, complications, and radiographic outcomes. At final follow-up, no cup failures had occurred. Mean Harris Hip Score improved from 53 points (range, 33-82 points) preoperatively to 91 points (range, 64-100 points) postoperatively. One complication occurred; a 64-year-old woman with recurrent postoperative effusions underwent hip exploration and required abductor mechanism repair. On radiologic evaluation, no signs existed of progressive radiolucencies or changes in cup position. The survivorship of the Tritanium cup and the low complication rate is comparable with previous studies using other porous-metal prostheses. Longer follow-up study is needed and assessment of the results of using this implant in the revision setting is important.