Osteoporosis is a systemic musculoskeletal disease that gradually reduces bone mineral density (BMD) and changes bone microarchitectures (1). Vertebral compression fractures are one of the most common osteoporotic fractures with an incidence of 700,000 cases per year in the United States (2), and in South Korea the incidence of osteoporotic fractures is on the rise (3).

Regarding the treatment of an osteoporotic vertebral compression fracture (OVCF), conservative treatments like bed rest, medication, and braces used to be the norm. However, for persistent-painful OVCF resistant to conservative treatments, percutaneous vertebroplasty and kyphoplasty are now considered the treatments of choice, because both have been demonstrated to achieve satisfactory pain relief in the majority of OVCF patients (4). However, a significant proportion of OVCF patients complain of consistent chest or flank pain (5), and experience no meaningful pain relief even after percutaneous vertebroplasty or kyphoplasty, whereas others experience some relief of back pain, but still suffer from continuous chest or flank pain.

In a previous study, the authors found that rib fractures are one of main causes of persistent chest or flank pain (6). In fact, rib fractures are one of the most common osteoporotic non-vertebral fractures in the elderly (7). And it has been reported that the presence of a rib fracture is associated with an elevated risk of new osteoporotic fractures (8). Therefore, the authors sought to document the frequency of rib fractures in OVCF patients and to identify factors that affect their occurrence by conducting bone scans. In addition, the authors tried to confirm the efficacy of bone scan as a screening tool for OVCF. Therefore, we analyzed cases of non-adjacent multiple fractures unconfirmed by single-site MRI scans due to the co-occurrence of OVCF in the thoracic and lumbar spines. In addition, the authors investigated cases of fractures that might have been overlooked due to the indication of minute reductions in anterior height at initial plain radiography, noting the report that fracture diagnosis is delayed or neglected in about 25 to 50% of OVCF patients (9).

In general, the most common sites of osteoporotic fractures are vertebrae, proximal femur, and distal radius. Sontag et al. (11) reported that vertebral fractures and distal radius fractures accounted for 66% of initial osteoporotic fractures in their study on post-menopausal women. Also, proximal femur fractures accounted for a mere 2.2% of initial osteoporotic fractures, and the frequency of rib fracture was higher than that of proximal femur fracture. Barret-Connor et al. (8) in a prospective cohort study found that the rib is the most common site for osteoporotic non-vertebral fractures, and that rib fractures account for around 24% of total fractures. They also reported that a history of rib fracture increased the risks of an additional rib fracture, a hip fracture, or a distal radius fracture by more than two-fold, and thus, highlighted the significance of rib fracture. In a previous study conducted at our center, the frequency of rib fracture in OVCF patients was 57.7% and in the present study the frequency was 43%, which is reaffirming that the rib is a common site for osteoporotic fractures (6). The authors consider that the present study was conducted on patients who had undergone vertebroplasty or kyphoplasty, which is why the frequency rate of rib fracture at our center is high, compared to other studies. Regarding to factors that affect the occurrence of rib fractures, Siris et al. (12) in a cohort study of 170,083 women found that a low BMD increases the risks of all types of osteoporotic fractures, and reported that the risk of OVCF increases with age. Barrett-Connor et al. (8) proposed that an age over 80, a low BMD, a history of fracture before age 50, and injuries from falls are risk factors of rib fracture, but in the present study, no apparent correlation was found between age and rib fracture and no statistical relation was found between BMD and rib fracture. In addition, factors presumed to be correlated with the occurrence of rib fracture, that is, sex, number and locations of fractured vertebrae, and initial amount of anterior height loss, were not found to be statistically significant, but they were associated with rib fracture frequency. Accordingly, further studies are needed on larger number of patients.

To diagnose rib fractures, conventional methods, such as, history-taking, chest PA and rib series are employed, but these methods are considered nonspecific and comparatively inaccurate (13, 14). Diagnostic ultrasonography was introduced to increase the accuracy of recognizing rib fractures, but the technique remains controversial (15). On the other hand, a bone scan has high sensitivity for the diagnosis of occult fractures (16), and for detecting systemic skeletal diseases or metastatic bone tumors (17). Therefore, bone scan is useful for confirming the occurrence of associated diseases in older patients with OVCF. Manyard et al. (10) stressed the usefulness of bone scan as a means for predicting favorable clinical outcomes, based on the rationale that strong hot uptake by bone scan is highly predictive sign of clinical response to vertebroplasty.

MRI is highly sensitive at detecting bone edema induced by micro fracture, which difficult to be recognized on plain radiographs or CT scans (18), and MRI is indispensable for confirming degrees of soft tissue injury like injuries to the posterior ligament complex or an intervertebral disc. However, MRI is usually performed at a single-site due to its cost, which causes to be unable to detect unexpected additional lesions that were no adjacent to OVCF recognized by initial plain radiography. In this regard, bone scan is more useful for the detection of unexpected additional OVCF because it provides whole body images.

In most OVCF cases, fractures are triggered by minor trauma and degrees of vertebrae compression are slight, which makes fractures indistinct on plain radiographs. Delmas et al. (19) in a multi-center study reported that fractures were not diagnosed by initial plain radiography in 29.5-46.5% of patients with a vertebral fracture, and urged surgeons to be cautious when diagnosing OVCF. This is why most surgeons are now conducting imaging studies in addition to plain radiography when diagnosing OVCF. Accordingly, bone scans provide a powerful means of screening for OVCF, considering the shortcomings of MRI mentioned above.

In the present study, the authors were able to confirm the frequency rate of rib fractures radiologically, but clinical assessments based on treatment results and outcomes were not conducted, and thus, additional studies are considered necessary. Regarding problems associated with bone scan, there is a possibility that hot uptakes may be observed for 2 yr after fracture (10), which increases the risk of false positive findings. For this reason, patients with less than a 2-yr history of osteoporotic fractures were excluded from the present study. On the other hand, during the early stage, false negative results can be obtained (20).

Rib fractures do not infrequently accompany OVCF, and when accompanied, chest or flank pain can remain after vertebroplasty or kyphoplasty. Furthermore because rib fracture per se increases the risk of additional osteoporotic fracture, confirmation of its existence is necessary. The authors recommend that bone scans should be performed for the diagnosis of rib fracture accompanying OVCF. And bone scans have outstanding screening ability for patients with concurrent non-adjacent multiple fractures of the thoracic and lumbar spines or fractures not definitively detected by plain radiography.