Location-dependent depth and undermining formation of pressure ulcers.

AIM OF THE STUDY: We examined the location-specific properties of pressure ulcers, focusing on depth and undermining formation, which are often unfavorable factors for ulcer healing. METHODS: We conducted a retrospective observational study of 2 independent databases on pressure ulcers. Databases from a 200-bed hospital (database A) and a 300-bed hospital (database B) were collected during different time periods. Relationships between ulcer location, ulcer depth, and undermining formation were analyzed. All pressure ulcers were accurately diagnosed and classified according to their locations. RESULTS: A total of 282 pressure ulcers in 189 patients from database A and 232 pressure ulcers in 154 patients from database B were analyzed. It was found that pressure ulcers primarily developed over the sacrum. Ratio of stages III and IV pressure ulcers was high in pressure ulcers of the foot, ankle, and crus on the lower leg. Among the deep pressure ulcers, undermining formation was frequently observed on the greater trochanter, ilium, and sacrum. In contrast, pressure ulcers of the foot, ankle, and crus did not exhibit undermining formation. CONCLUSION: Our results revealed marked differences in pressure ulcer properties depending on their location. Factors affecting depth and undermining of pressure ulcers appear to be related to anatomical and physical properties of the bone and subcutaneous tissue.