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CT scans predict humeral stability in total shoulder arthroplasty patients
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Shoulder CT scans may be used to predict implant size and fixation method for patients with osteoarthritis who undergo total shoulder arthroplasty, according to this study.
“In addition to preoperative planning, study results indicate that shoulder CTs may be of diagnostic value because they can be used to screen patients for metabolic bone diseases, such as osteoporosis, at no additional cost to the patient,” the researchers stated. “These data, as well as the risk factors we have identified, will assist the physician in surgical decision making and may leverage the need for secondary workup in patients with undiagnosed poor bone quality.”
Researchers collected data on preoperative dual energy X-ray absorptiometry (DEXA) and shoulder computed tomography (CT) scans from 2004 to 2010 for 230 patients undergoing total shoulder arthroplasty (TSA).
Patients were analyzed for osteoporosis risk factors and univariate analysis determined the correlation between individual risk factors and BMD. Researchers also analyzed the total number of risk factors on BMD, correlated hip bone mineral density (BMD) and T scores and Hounsfield units (HU) attenuation in the humerus.
Researchers identified significant correlations between HU and hip BMD and T score, as well as HU value ranges that may alert the surgeon of metabolic bone disease. Low BMD and certain osteoporosis risk factors had a significant correlation. Age at surgery was a predictor of cemented stem fixation. Patients with lower BMDs were more likely to receive a larger diameter humeral stem.
Perspective
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Anthony A. Romeo, MD
Pervaiz and colleagues evaluated the ability to detect osteoporosis in a group of patients who presented with glenohumeral arthritis and were subsequently treated with a shoulder replacement. They hypothesized that 1) preoperative CT scans of the proximal humerus, obtained during the normal course of preoperative planning, can provide accurate information regarding the diagnosis of osteoporosis; 2) risk factors for osteoporosis can be correlated to the CT-based diagnosis; and 3) patients with decreased bone density in their humerus will require larger humeral stem sizes to achieve press fit fixation.
The results of their analysis confirm that CT scans are a reliable method to evaluate bone density and can provide evidence of osteoporosis or osteopenia. Risk factor analysis was limited by a homogenous group of patients, but confirmed previous studies which have demonstrated a variety of positive risk factors for osteoporosis including age older than 65 years, female gender, sedentary lifestyle and family history of fragility fractures. Since this study was performed by one surgeon, using only one implant design, the conclusions regarding the method of fixation of the humeral stem may be biased, but clearly the osteoporotic bone leads to greater humeral canal diameter and therefore the surgeon should have those options available.
The take-home messages of this well-written publication include the fact that osteoporosis and glenohumeral arthritis coexist in a patient population older than 65 years old. Preoperative CT scan for assessment of the glenoid morphology can have increased value to the overall care of the patient when also used as a screening tool for osteoporosis. For many patients, the orthopedic surgeon may be the “primary care” physician for bone-related disorders. We have the ability to screen for this important health risk factor using readily available data acquired with subjective questionnaires and preoperative CT scans. Identifying patients with clinically relevant osteoporosis and then referring them for appropriate multidisciplinary care may help to reduce the impact of fragility fractures, which is the most common orthopedic condition in our aging population responsible for consuming substantial health care resources.
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