Physical Parameters Beyond BMI Affect TKA Outcomes
It is well established that obese patients who undergo total joint arthroplasty have increased risks of complications and infections. But what about folks who are not obese, but are just generally large? Do they also have increased post-arthroplasty complications, compared to their smaller counterparts? That is the question Christensen et al. explored in a registry-based study in the November 7, 2018 edition of JBJS.
In addition to BMI, the authors examined 3 other physical parameters—body surface area, body mass, and height—to determine whether these less-studied characteristics (all contributing to “bigness”) were associated with an increased rate of various adverse outcomes, including mechanical failure and infection, after primary total knee arthroplasty (TKA). They evaluated data from more than 22,000 TKAs performed at a single institution and found that the risk of any revision procedure or revision for a mechanical failure was directly associated with every 1 standard deviation increase in BMI (Hazard Ratio [HR], 1.19 and 1.15, respectively), body surface area (HR, 1.37 and 1.35, respectively), body mass (HR, 1.30 and 1.27, respectively), and height (HR, 1.22 and 1.23, respectively). In this study, 1 standard deviation was equivalent to 6.3 kg/m2 for BMI, 0.3 m2 for body surface area, 20 kg for body mass, and 10.5 cm for height.
These findings, while not all that surprising, are enlightening nonetheless. The study shows that increasing height has a greater negative impact on TKA outcomes than previously thought. While I spend a lot of time counseling patients with high BMIs about the increased risks of undergoing a TKA (and while such patients can take certain actions to lower their BMI prior to surgery), I do not spend nearly as much time counseling patients who are much taller than normal about their increased risks (and height is not a modifiable risk factor). Nor do I spend much time thinking about a patient’s overall body mass or body surface area in addition to their BMI. This study will remind me not to overlook these less commonly examined physical parameters when discussing TKA with patients in the future.
Chad A. Krueger, MD
JBJS Deputy Editor for Social Media
Fluctuating Glucose Levels Linked to Post-TJA Problems
At any given time, a patient’s blood-glucose level is easy to measure. Beyond the standard pre/postoperative lab values, there are finger sticks, transdermal meters, and other modalities that make taking a patient’s glucose “snapshot” pretty straightforward. So why don’t we surgeons keep track of it more frequently before and after joint replacement, when, according to the prognostic study by Shohat et al. in the July 5, 2018 issue of JBJS, fluctuating glucose levels can have a critical impact on outcomes?
By retrospectively studying more than 5,000 patients who had undergone either total hip or total knee arthroplasty, the authors found that increased variability of glucose levels (measured by a coefficient of variation) was associated with increased risks of 90-day mortality, surgical-site infection, and periprosthetic joint infection. Specifically, the authors demonstrated that for every 10-percentage-point increase in the glycemic coefficient of variation, the risk of 90-day mortality increased by 26%, and the risk of periprosthetic or surgical-site infection increased by 20%. These are remarkable increases in extremely important outcome measures, and the associations held regardless of the patient’s mean glucose values prior to or after the surgery. In fact, some of the highest levels of glucose variability were found in patients who had well-controlled glucose levels preoperatively. Furthermore, as Charles Cornell, MD points out in a commentary on this study, “Glucose variability appears to affect surgical prognosis more than chronic hyperglycemia.”
These findings were surprising and a bit concerning. I don’t tend to order routine blood-glucose measurements postoperatively on patients who appear to be euglycemic based on preoperative testing. Yet, according to these data, maybe I should. Findings of high glucose variability postoperatively might now prompt me to consult with endocrine or perioperative medicine specialists or at least consider informing patients with fluctuating glucose levels that they may be at increased risk of serious postoperative complications.
Measuring a patient’s blood sugar is neither challenging nor prohibitively expensive. So why don’t we monitor it more closely? Probably because, until now, we have not had a compelling reason to do so with “low-risk” patients. What this study suggests is that our definition of a “low-risk” patient from a glycemic-control standpoint may be misinformed. And while further research needs to be performed to corroborate these findings, that is a pretty scary thought to digest.
Chad A. Krueger, MD
JBJS Deputy Editor for Social Media
Updated Knee Content from JBJS
The recently launched JBJS Knee Spotlight offers highly relevant and potentially practice-changing knee content from the most trusted source of orthopaedic information.
Here are the five JBJS articles to which you will have full-text access through the Knee Spotlight during the month of December 2016:
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Adult Human Mesenchymal Stem Cells Delivered via Intra-Articular Injection to the Knee Following Partial Medial Meniscectomy
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Computer Navigation for Total Knee Arthroplasty Reduces Revision Rate for Patients Less Than Sixty-five Years of Age
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Comparison of Closing-Wedge and Opening-Wedge High Tibial Osteotomy for Medial Compartment Osteoarthritis of the Knee
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Weight-Bearing Compared with Non-Weight-Bearing Following Osteochondral Autograft Transfer for Small Defects in Weight-Bearing Areas in the Femoral Articular Cartilage of the Knee
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Early Patient Outcomes After Primary Total Knee Arthroplasty with Quadriceps-Sparing Subvastus and Medial Parapatellar Techniques
Knee studies offered on the JBJS Knee Spotlight will be updated monthly, so check the site often.
JBJS Supplement Cites New Findings from International Device Registries
Surgeons performed more than 1.1 million joint replacements in the US in 2011. That same year, the International Consortium of Orthopaedic Registries (ICOR) was launched to help close gaps in evidence and data collection related to orthopaedic implants. The ICOR network now consists of more than 70 stakeholders and more than 30 orthopaedic registries representing 14 nations.
The December 17, 2014 edition of The Journal contains an online supplement with 14 articles highlighting the achievements of international registries and the findings from 12 ICOR-initiated registry studies. The first article in the supplement (National and International Postmarket Research and Surveillance Implementation) summarizes the findings from the 12 registry studies. The second article (A Distributed Health Data Network Analysis of Survival Outcomes) provides an overview of the data extraction processes and analytic strategies used in the studies.
Key findings from the 12 studies contained in the supplement:
There were no differences in revision risk when metal-on-HXLPE (highly cross-linked polyethylene) implants with larger and smaller femoral head sizes were compared.
Non-cross-linked polyethylene was not associated with significantly worse revision outcomes when compared with metal-on-HXLPE.
Large-head-size metal-on-metal implants were associated with increased risk of revision after two years, compared with metal-on-HXLPE implants.
Use of ceramic-on-ceramic implants with a smaller head size was associated with a higher revision risk compared with metal-on-HXLPE implants and ceramic-on-ceramic implants with head sizes >28 mm.
When compared with hybrid fixation, cementless fixation was associated with an approximately 58% higher risk of revision surgery in patients aged 75 years or older.
Mobile-bearing, non-posterior-stabilized knee designs presented a 40% higher risk of failure than that found with fixed-bearing, non-posterior-stabilized designs.
Compared with fixed-bearing posterior-stabilized knee prostheses, patients who received mobile bearings had an 85% higher chance of revision within the first postoperative year.
Fixed non-posterior-stabilized (cruciate-retainin0 TKA performed better (with or without patellar resurfacing) than did fixed posterior-stabilized (cruciate-substituting) TKA.
Reported revision rates of TKA and THA among pediatric and young-adult patients is currently similar to that for older patients, but the dearth of data makes it incumbent on registries to continue collecting and analyzing data relevant to younger populations.
This systematic review and meta-analysis concluded that surgeons performing a primary THA should use an implant that outperforms benchmarks established by the UK’s National Institute for Health and Care Excellence (NICE).
Among 19 registry reports and 1052 articles examined, only one report and two studies mentioned patient-reported outcome measures (PROMs) and minimum clinically important differences in connection with revision rates after TKA or THA.
Successful collection of PROM data is possible with careful attention to selection of outcome measure(s) and minimizing the data-collection burden on physicians and patients.
Patient Personality Affects TKA Outcomes
A 2007 JBJS study suggested that patients who are psychologically distressed have slightly greater levels of postoperative pain following total knee arthroplasty than non-distressed patients. Now, a study in the Journal of Orthopaedic Science finds that a patient’s overall personality can also influence outcomes after TKA. Using the Eysenck Personality Questionnaire, Chinese researchers divided 387 TKA patients into one of four personality types: choleric, sanguine, melancholic, and phlegmatic. They then measured clinical TKA outcomes and satisfaction using the SF-36 and WOMAC instruments. Melancholic patients had the worst outcome scores, with sanguine patients (who are typically sociable, cooperative, and easygoing) scoring highest. The authors say clinicians could use these findings to identify people at risk of poor postoperative outcomes, and that such people might benefit from “better communication and individual treatment strategies during perioperative periods.”
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