1 Introduction

Many articles have reported that subcutaneous edema on a patient's back is caused by obesity, but senile hospitalized patients are usually not obese. Almost all hospitalized patients after vertebral compression fractures are checked for vertebral compression fractures by MRI and could conveniently be assessed for subcutaneous edema. It is empirically known that patients with subcutaneous edema on their back have vertebral kyphotic deformity and have low activity in daily life. It is felt that the senile hospitalized patients with subcutaneous edema on their back seem likely to have another vertebral compression fracture in the future.

In this article subcutaneous edema on the back detected by MRI in hospitalized vertebral osteoporotic compression fracture patients was studied to determine whether there were any differences between patients who had subcutaneous edema on their back and those who did not. Especially, a history of compression fractures and the occurrence of another vertebral compression fracture during the observation period would be reported.

2 Materials and methods

Lumbar osteoporotic compression fractures were assessed by MRI (Siemens Healthineers, Japan) conducted at 1.5 T and evaluated by STIR (short T1 inversion recovery) sagittal images. Delicate care was needed to find subcutaneous edema, so it was graded as follows: Grade 0, subcutaneous edema was not found; Grade 1, faint subcutaneous edema was found; Grade 2, subcutaneous edema score between 1 and 3; and Grade 3, obvious subcutaneous edema was found. Grade 0 was assigned if there were no subcutaneous edemas on back, and grades 1 to 3 were assigned for those with subcutaneous edema (Fig. 1). If a patient was checked many times, the highest grade was used for the evaluation.

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Fig. 1 Grading of the MRI-detected subcutaneous edema on the back detected in Sagittal STIR (short T1 inversion recovery) images. Arrows indicate subcutaneous edema. Grade 0: A subcutaneous edema on the back was not found. Grade 1: A slight subcutaneous edema on the back was found. Grade 2: Between Grades 1 and 3. Grade 3: An obvious subcutaneous edema on the back was found.

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The observation period was between January 1, 2009, and December 31, 2020. All patients were on the ward, with a total of 375 patients (male: 114; female: 261) whose ages ranged from 66 to 98 years old (mean: 81.1 years). The patients underwent MRI within 10 days after their injuries.

The patients were separated into two groups: those who had subcutaneous edema on their back and those who did not (Grade 0 and Grades 1–3). Sex, age, BMI (body mass index), serum total protein and albumin, osteoporosis diagnosis by BMD (bone mineral density) and X-ray images, Japanese senile independence score, presence of decubitus, history of vertebral compression fracture and incidents of vertebral compression fracture during the observation period were assessed.

Osteoporosis was evaluated by BMD and X-ray imaging. By BMD the patients with less than −1.0 SD (standard deviation) T-score were diagnosed osteoporosis. And by X-ray imaging the patients were checked using Saville grading, Grade 0 was considered to indicate no osteoporosis, and Grades 1 to 3 were considered to indicate osteoporosis.¹

The Japanese senile independence score is described in the Long-Term Care Insurance Act in Japan 2007, Articles 27–39. The grading evaluated people as J1, J2, A1, A2, B1, B2, C1 and C2, with the J grades considered independent and grades A to C dependent (Table 1).

Skin decubitus was assessed on the posterior head, scapula, spina process, iliac bone, sacrum, ischium, fibula head and heel.

History of lumbar compression fracture was diagnosed by X-ray imaging or MRI. Incident of compression fracture was checked from January 1, 2009 to December 31, 2020. The patient who was suffered another lumbar compression fracture during the period would be counted both history of compression fracture and incident of compression fracture.

A Mann-Whitney U test was applied to assess the independence of the two groups, and a chi-square test was applied to assess the differences between the two groups. P values below 0.05 were considered statistically significant.

3 Results

Subcutaneous edema on the back was detected by MRI in 261 of 375 hospitalized patients (69.6%). Some patients had been checked by MRI a couple of times, and the most frequently checked patient was examined 6 times during the observation period. He had subcutaneous edema twice detected and it was not detected four times.

The number of patients with subcutaneous edema Grades 0, 1, 2 and 3 was 114, 122, 70 and 69, respectively. The number of patients with Japanese senile independence score grades J, A, B and C was 82, 160, 87 and 46, respectively. In the Grade J patients the details of subcutaneous edema in Grades 0, 1, 2 and 3 were 37, 25, 12 and 8. And in the Grades A to C patients, the details of subcutaneous edema Grades 0, 1, 2 and 3 were 77, 105, 62 and 49.

Significant differences were not observed for sex, BMI, blood serum total protein and albumin, osteoporosis diagnosed by BMD or the presence of skin decubitus. However, significant differences were found for age, osteoporosis diagnosed by X-ray imaging, Japanese senile independence score, history of vertebral compression fracture, and incident of another vertebral compression fracture during the observation period. In particular, incident of vertebral compression fractures were observed in only 5 of 114 edema (−) patients, but they were observed in 60 of 261 edema (+) patients (Table 2).

In subcutaneous edema Grade-C patients, incidents of vertebral compression fractures were observed in 15 of 69.

4 Discussion

In this study, if the patient was checked by MRI many times, the highest grade had been used for evaluation, and a subtle edema was picked up, so 69.6% patients had subcutaneous edema detected on their back. In the daily clinic it was thought that subcutaneous edemas would be noticed less frequently, and conceivably only subcutaneous edema Grade-C (69/375: 18.4%) patients might be noticed. The Grade-C patients were fewer and statistically significant differences were hard to obtain in some items (data was not shown). There were hospitalized patients who had been checked a couple of times during the observation period and it would also be one of the reasons why so many patients were positive for subcutaneous edemas.

Lakadamyali reported that the STIR (short T1 inversion recovery) sequence was useful to depict lumbar degenerative changes, and subcutaneous edema and muscle edema were found to increase with age.² There are two main factors causing skin edema: bodily condition and mechanical stress. Several articles have pointed out that lumbar subcutaneous edema was observed in patients who were overweight^3–5; however, in this study, there was no significant difference in edema (+) and edema (−) patients according to BMI. This finding might be seen because most patients were emaciated and needed to be treated in hospital with osteoporotic vertebral compression fracture. There were no significant differences in serum total protein and albumin, possibly for the same reason.

Significant differences were not observed for osteoporosis diagnosed by BMD, but by X-ray imaging osteoporosis was found. There were too few to see the statistical difference and the deformed spine with compression fracture might be difficult to estimate osteoporosis by BMD. The relationship between severity of osteoporosis and frequency of subcutaneous edemas were not demonstrated either (data was not shown).

There was a significant difference in the independence score because immobility would promote subcutaneous edema. But there was no significant difference in the presence of decubitus. In this study, patients were periodically rolled over even if the patients were totally dependent, and skin decubitus was rarely observed during hospitalization.

Another vertebral compression fracture during the observation period was found in only 4.4% (5/114) of edema (−) patients; on the other hand, it was found in 23.0% (60/261) of edema (+) patients. All patients were hospitalized, so outpatients were not included, and it was likely that there would be many outpatients who had not experienced another vertebral compression fracture with skin edema. The hospitalized patients would be less active than outpatients and might be more risky for falling down, and low activity would be also the reason for subcutaneous edema on their back.

The risk of future vertebral compression fracture might be associate the subcutaneous edema, but the severity of edema would not be related (data was not shown). The back edemas could be disappeared or aggravated, and it would be more important whether skin edema had existed or not than the severity of edema for the risk of future vertebral compression fracture.

A history of vertebral compression fracture increased the risk of another osteoporotic fracture threefold.⁶ It might be common for patients with subcutaneous edema on their back to have a history of vertebral compression fracture and they would likely suffer another vertebral compression fracture.

5 Conclusion

It was suggested that the hospitalized patients who had MRI-detected subcutaneous edema on their back had often had a history of vertebral compression fracture and would tend to suffer another vertebral osteoporotic compression fracture when compared to those who did not.

All procedures performed in studies involving human patients were conducted in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.

Informed consent was obtained from all individual participants included in the study.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.