The Tiny Problem of Obese Patients | Orthopedics This Week

The Tiny Problem of Obese Patients


If Centers for Disease Control data is to be believed, roughly one in four patients crossing the clinic threshold in Oklahoma, Mississippi, Tennessee, South Carolina—indeed 32 states, is technically obese. For reasons every physician understands, the obese patient presents a series of unique challenges and risks. But, the “problem” of the obese patient is both less than expected and, based on a review of the literature, not nearly as critical to clinical outcomes as aging or, interestingly, malnutrition. 

Before Your Very Eyes, Obesity Transforms

One complication that does NOT appear to be associated with the obese orthopedic patient is cardiovascular disease. In a Mayo clinic study titled “Body Mass Index and Risk of Adverse Cardiac Events in Elderly Patients with Hip Fracture: A Population-Based Studywhich was conducted by Batsis, Huddleston, et al., (Dartmouth-Hitchcock Medical Center, Orthopedic Surgery, College of Medicine, Mayo Clinic) between 1988 and 2002 the conclusion was that overweight and obese patients had NO excess risk of ANY cardiac complications. (We added the emphasis).

The Mayo study was designed to discover the relationship between patient obesity and the incidence of cardiac complications after hip fracture repair. Patient body size in the study was measured using the standard body mass index (BMI) and was categorized as:

  • underweight (<18.5 kg/m2)—184 repaired hip fractures
  • normal-weight (18.5–24.9 kg/m2)—640 repaired hip fractures
  • overweight (25.0–29.9 kg/m2)—251 repaired hip fractures
  • obese (≥30 kg/m2)—105 repaired hip fractures

Postoperative complications for the purposes of the study were defined as:

  • myocardial infarction
  • angina pectoris
  • congestive heart failure
  • new-onset arrhythmias 

All within one year of surgery.

Finally, overall cardiac complications were assessed using Cox proportional hazards models adjusted for age, sex, year of surgery, use of beta-blockers, and the Revised Cardiac Risk Index.

Here is what the Mayo/Dartmouth researchers found:

  1. Underweight patients had a significantly higher risk of developing myocardial infarction (odds ratio (OR) 1.44, 95% confidence interval (CI)=1.0–2.1; P=.05) and arrhythmias (OR=1.59, 95% CI=1.0–2.4; P=.04) than normal-weight patients. Multivariate analysis demonstrated that underweight patients had a higher risk of developing an adverse cardiac event of any type (OR=1.56, 95% CI=1.22–1.98; P<.001).

  2. Overweight and obese patients with hip fracture had NO excess risk of any cardiac complication.

Then we happened upon this interesting and supporting paper titled Comparison of Tools for Nutrition Assessment and Screening for Predicting the Development of Complications in Orthopedic Surgery” from Ozkalkanli, Ozkalkanli and Katircioglu, et al., (Izmir Ataturk Training and Research Hospital, Imir, Turkey).

In Imir, Turkey, the issue is patient malnutrition—which doesn’t mean lack of nutrition. Malnutrition refers to poor nutrition—a condition that may be an independent variable to obesity. In other words, a patient may be obese AND malnourished or obese and NOT malnourished. The researchers used two assessment tools—the Nutritional Risk Screening 2002 (NRS 2002) and subjective global assessment (SGA)—to try to predict the incidence rate of complications in orthopedic surgery patients.

The researchers performed a nutrition screening on 256 consecutively admitted patients scheduled for orthopedic surgery as well as recording each patient’s age, gender, body mass index, and American Society of Anesthesiologists (ASA) physical status.

And here is what the researchers found:

  1. Malnourished patients stayed in the hospital longer and had higher morbidity and mortality rates. Sensitivity was 50% with the SGA and 69% with the NRS 2002; specificity was 77% with the SGA and 80% with the NRS 2002. Agreement between two methods was 0.672. The odds ratio for the association between malnutrition or risk of malnutrition and the occurrence of complications was 3.5 (1.7-7.1) for the SGA and 4.1 (2.0-8.5) for NRS 2002.

  2. Malnourished or nutritionally at-risk patients were significantly older than non-malnourished or not-at-risk patients according to the SGA and NRS 2002

Knee Replacement/Wikimedia Commons
For the elderly, both of these studies seem to be saying, malnourishment is a more worrisome co-morbidity than obesity.

Then there is this study by Naal, Neuerburg, et al., (Schulthess Clinic, Zurich, Switzerland and Technical University of Munich, Munich, Germany) which was published online April 15, 2008, and which tackled the issue of unicompartmental knee arthroplasty (UKA) surgery and the obese patient. 

The researchers in this study reviewed the clinical data for 83 consecutive UKAs, two years post- surgery and looked for any statistically significant connection between the patient’s BMI and outcomes from a UKA. Naal, Neuerburg, et. al., measured the Knee Society Score (KSS), the University of California at Los Angeles (UCLA) activity level index, the anterior knee pain score (AKP), range of motion and, finally implant failure. 

Here is what they found:

  1. All of the changes in patient outcome measures occurred independently of the BMI index. So, for example, the fact that the KSS and UCLA indexes increased significantly (from 132 and 4.7 preoperatively to 187.5 and 7.1, respectively, postoperatively) or that knee flexion improved significantly (from 123.7 to 128.4o) or that knee extension deficiencies fell (from 28.9 to 15.7%)—there was no measurable connection to BMI. Three knees (3.6%) failed and were converted to total knee arthroplasty. But, again, none of these changes were associated with BMI.

  2. Patient BMI had no significant association with KSS values, UCLA levels or implant failure. Indeed, there was a weak negative correlation between BMI and postoperative knee flexion (r= -0.285, P=0.0009) and a moderate positive correlation between BMI and the intensity of anterior pain score (r=0.525, P<0.001).

  3. The BMI of patients undergoing UKA had no major impact on the clinical outcomes during the first two years post-surgery. There was, however, a definite correlation between BMI and AKP.

One element that may help the obese patient undergoing orthopedic surgery is a comparatively stronger bone stock and, indeed, several researchers noticed the association of obesity and a reduced risk of osteoporosis.

What about the obese spine patient? In a study titled “Lumbar Spine Fusion in Obese and Morbidly Obese Patients” by Vaidya, Carp, Bartol, et al., researchers found that obese patients:

  • Had lower American Association of Anesthesiologists scores
  • Had the same surgical time as non-obese patients
  • Lost marginally more blood during surgery
  • All surgical outcome measures (Oswestry score, Visual Analog Scale) were independent of the BMI of the patient
  • The incidence of postoperative complications was significant in 45% of morbidly obese and 44% of obese patients

How About the Formerly Obese?

In a study titled; “The effects of obesity surgery on bone metabolism: what orthopedic surgeons need to know” written by Wang A, Powell A. (Department of Orthopaedic Surgery, University of Utah) researchers took a look at the effects of the bariatric surgery on the bone stock of patients.

Bariatric surgery (for example, the Roux-en-Y procedure) reduces the size of the stomach or intestines in order to help obese patients (BMI 35+) lose weight. One of the effects of the surgery is that the primary sites for calcium absorption are bypassed. Bariatric surgery patients may become thinner, but they also become calcium and Vitamin D deficient. 

The body’s natural response to bariatric surgery is to up-regulate parathyroid hormones which, in turn, trigger production of Vitamin D—which also creates higher rates of calcium resorption from the patient’s bone.

Bottom line say Wang and Powell, surgeons treating gastric by-passed patients should be alert to bone density problems, fracture risk, and slow fracture healing.

Keys to a Successful Surgery in the Obese Patient

Generally, obese patients can successfully undergo virtually all orthopedic procedures. But the key to a successful surgery in the obese patient is about reducing risk. So, based on such studies as Drs. Daniel Guss and Timothy Bhattacharyya’s (Harvard Combined Orthopedic Residency Program, Massachusetts General Hospital and Brigham and Women’s Hospital) study and Winiarsky, Barth and Lotke’s study “Total Knee Arthroplasty in Morbidly Obese Patients (The Journal of Bone and Joint Surgery 80:1770-4 (1998) here are the keys to successful surgery in the obese patient:

Knee surgery/Wikimedia Commons

Prepare for increased risks of:

a.  Post-op deep vein thrombosis

b.  Avulsion of the medial collateral ligament (TKA patients)

c.  Post-op wound sepsis

d.  Higher rates of hardware failure long term

e.  Fracture mal-union

Make use of:

a.  Adaptive OR equipment

b.  Proper patient positioning and alignment

c.  New tools which improve component alignments

d.  Aggressive post-op infection control

e.  Careful and proper intravenous line placement

f.  Central monitoring lines

g.  Anesthesia specific to the physiologic changes in obese patients

Finally, pay attention to the nutritional health of the patient. Patients who live at or below the poverty level or are elderly and do not live in areas where they have easy access to healthy foods and dietary supplements or have, for whatever reason, begun consuming foods that are high in fats, sugars, and calories are, in effect, starving themselves. These patients may be obese, but they are also starving—nutritionally. 

Studies clearly say that malnutrition may be more important than obesity in determining the likelihood of successful orthopedic surgery. For the wellbeing of patients, the final key is address deficiencies of vitamins and minerals and put steps in place to improve the nutritional content of patient’s diet with fish, meat, fresh fruits and vegetables, and whole grains.


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