Osteoporosis, hypothyroidism linked with increased scapular fracture risk after RSA
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SAN DIEGO — A study that identified the incidence and predictors of scapular fractures in patients after primary reverse shoulder arthroplasty showed an estimated incidence of 6.9% and that hypothyroidism was among the fracture predictors.
Vahid Entezari, MD, of the Cleveland Clinic Foundation, presented the findings of the study at the American Academy of Orthopaedic Surgeons Annual Meeting, which included 930 consecutive patients treated with RSA from 2006 to 2019. Researchers reviewed patients’ preoperative and postoperative radiographs and advanced imaging to determine the presence of preoperative scapular fractures, os acromiale or postoperative scapular fractures. Entezari and colleagues classified scapular fractures found with the Levy system and excluded patients with preoperative fractures from their analysis. They reviewed the patient demographics, Charlson comorbidity index and management of any fractures.
Among the 51 postoperative scapular fractures identified, for which the estimated incidence was 6.9%, the fracture rate was 3.5% in men and was 9% in women, which was statistically significantly different.
Compared with patients without a fracture, patients with fractures had significantly lower BMI and a significantly higher prevalence of osteoporosis and hypothyroidism, according to the abstract. Patients with fractures were also followed up longer than the non-fracture group.
“These fractures kind of happen in certain groups of patients – more female patients, more patients that are smaller stature and have lower BMI – and also, when you look at their comorbidities, that’s one of things in the study that cued us, their hypothyroidism,” Entezari told Healio Orthopedics.
Independent predictors of scapular fracture identified through the multivariate analysis were BMI, osteoporosis diagnosis history and hypothyroidism.
“Because it’s 15-year (data) and the surgeons are constant, then you can look at what other factors changed over time. The major factor is you had two different implants that, over time, evolved ... from more of a Grammont-style reverse shoulder replacement done initially and then a newer design of reverse shoulder replacement, which is more of a DJO and lateralized center of rotation,” Entezari told Healio Orthopedics.
“I know there are some data out there that say there are certain design factors that lead to more acromial stress fractures or, if you do more Grammont-style, you tension the deltoid more and potentially you can have [more fractures]. But, in our study, we have 7% and 6.8% – no statistical difference if you use this implant vs. that implant,” he said.
“When you put these numbers together, 9% of women get acromial stress fractures. When you add to that osteoporosis, if you are a female with a history of osteoporosis, that number jumps to 13%. Now you’re talking about more than one in 10 patients having the complication,” Entezari said.
Researchers found one-third of fractures were initially missed on imaging. This resulted in a 9-month average delay in treatment, according to the abstract.
Entezari said what is important is “having a high index of suspicion for patients who are having pain or their rehab is taking longer or had an injury, because sometimes it’s not obvious on the X-ray and you need to get advanced imaging to pick this up early on. You don’t want a fracture that is nondisplaced displace and have patients develop further dysfunction by not recognizing the fracture at a right time and kind of slowing down the patient’s rehab or telling them they need to stay in the sling for some time.”
The abstract showed there were nine type 1; 26 type 2; and 16 type 3 fractures based on the Levy classification and fractures occurred postoperatively at a median of 6.1 months.
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Entezari V, et al. Paper 26. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; Aug. 31-Sept. 3, 2021; San Diego.
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