Influence of heterotopic ossification of the hip on bone densitometry: a study in spinal cord injured patients

Abstract

Objective: To evaluate (1) the magnitude of falsely elevated bone density results caused by heterotopic ossi®cation (HO) around the hip and (2) e ect of age of patients when the measurement was taken, age of patients at injury, and age of injury (time since event) to the prevalence of HO. Subjects and methods: We blindly analyzed plain radiographs of the hip [(obtained within 1 month of dual energy X-ray absorptiometry (DEXA)] in 107 spinal cord injured (SCI) patients for HO and matched the result to the three regions of interest (ROI): the femoral neck, Ward's triangle, and the trochanter. The in¯uence of HO on bone densitometric values was determined by the analysis of variance (ANOVA) and post-hoc analysis. Results: Nineteen (18%) patients had HO; overlying the femoral neck (79%), trochanter (74%) and Ward's triangle (37%), respectively. Signi®cant elevation of densitometric values (P50.05 or less) was observed in a various magnitude at each ROI, with the greatest elevation at Ward's triangle. The prevalence of HO was high when the patients were injured at age range of 20 ± 39 years. Conclusions: HO around the hip can cause signi®cantly elevated bone densitometry results at all ROIs, which can obscure underlying osteoporosis, leading to underestimation of fracture risk. Determination of bone density in this region with corresponding plain radiographs would be of help. In SCI patients, prevalence of HO was high when the age of patients at injury was 20 ± 39 years.

Physiological effects of lower extremity functional electrical stimulation in early spinal cord injury: lack of efficacy to prevent bone loss

“…As bone complications, for example, heterotopic ossification, scoliosis, osteomyelitis, arthroses, internal fixation of bone, can influence DEXA precision, 28,29 International Society for Clinical Densitometry (ISCD) scan artefact criteria were applied and scans were extracted accordingly (periarticular hip artefact n ¼ 5, two FES, three CON). Percentage change (%) BMD was derived from baseline BMD (g/cm 2 ) and % fat mass (FM) from total body mass (g).…”

Osteonecrosis after treatment for heterotopic ossification in spinal cord injury with the combination of surgery, irradiation, and an NSAID

“…In spinal cord injured patients, disuse osteoporosis is frequently observed below the level of SCI, and this is more pronounced at the hip. 49 Microfractures of subchondral bone occur in osteoporosis, which is more likely in states of diminished sensibility in particular if there is increased exposure to trauma. 43 Such microfractures could lead to cell death, and the subsequent subarticular collapse of the femoral head.…”

In reply to Dr Papadaki and colleagues

“…That was why we conducted this study using substantial numbers of patients to determine the magnitude of in¯uence of HO on results, and found that HO can cause false elevation ranging from 29 ± 101% for bone mineral content (BMC), 21% for bone mineral density (BMD), and 39 ± 43% for percentage of BMD compared to age-matched controls. 1 The second explanation is criteria of`clinically obvious HO' used in our study. The clinically obvious HO has to do with subjects having fracture before, or they had been noticed due to debridement, or deformities in the hip that indicated HO was present.…”

“…With regards to the letter from Dr Papdaki and colleagues concerning our article, 1 we would like to address certain points.…”