Background/Purpose: Sacral insufficiency fracture (SIF) is a poorly recognised cause of lower back pain in the elderly with significant potential morbidity. Diagnosis is often slow as the typical clinical picture is poorly recognised. SIFs are seldom seen on plain radiographs, and routine lumbar MRI rarely includes the sacrum. However they can be reliably identified on isotope bone scan.

Existing studies are small (cohorts up to 25 patients) and primarily highlight radiological findings rather than clinical outcomes. We report a cohort of 124 patients with SIF, describing patient outcomes and associated health care costs.

Objectives:1 To describe patient outcomes following SIF.

2 To determine delays in diagnosis and length of hospital stay.

3 To estimate the financial healthcare costs of SIF.

Methods: Patients were identified retrospectively from isotope bone scans performed at Southend hospital from 2000-2012. Case notes were reviewed for clinical features, time to diagnosis, length of hospital stay, IV bisphosphonate use and mobility and functional status pre- and post-fracture. Mortality was calculated using Kaplan Meier analysis.

Results: 135 patients were identified, of which case notes for 124 patients were reviewed.

Clinical: 83.9% were female. The mean age was 79 years (range 44-96). 51.6% were inpatients at the time of diagnosis. 54.8% presented with back pain, 17.7% groin pain, 17.7% thigh pain and 20.7% buttock pain. 39.2% had preceding minor trauma. 58.9% had a previous fracture, most commonly vertebral and pubic ramus. 23/34 (67.6%) had known osteoporosis. Median time to diagnosis was 13 days (longest 345 days). The median inpatient stay was 22 days (longest 76 days).

Radiology: In 58.1%, bilateral SIF were seen on bone scan. SIF was suspected in only 37.9% of patients prior to scan. 30.6% of bone scans showed co-existing pubic rami fractures. Of 110 patients with pelvic radiographs, only 2 had sacral fractures visible on plain films.

Outcomes: Although 62.1% were fully independent and 30.6% at home with care prior to fracture, functional status fell in 32.5% and 15.8% of these patients respectively following fracture. Prior to fracture 45.3% were independently mobile and 33.3% used a stick.  Similarly mobility fell in 32.1% and 41% respectively. The mean survival was 76.2 months, compared to a UK life expectancy of 118 months at 80 years of age.

Based on UK national average figures, the estimated cost per stay for inpatient bed alone is £8159 (US$12587), and the average increase in weekly cost of long-term care post SIF is £115 ($177). A single dose of intravenous bisphosphonate post-fracture was associated with a better outcome, with functional status preserved in 45/49 (91.8%) treated patients, compared to 39/65 (60%) of those untreated. The cost of a single 60mg dose of pamidronate is £55 ($84.9).

Conclusion: Our data suggest that SIF is associated with delayed diagnosis, long hospital stays, poor functional outcomes and decreased life expectancy, with large financial costs per patient. The morbidity, mortality and economic burden may be comparable to hip fracture. Intravenous bisphosphonate use post-fracture may help preserve function.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/outcomes-and-costs-of-sacral-insufficiency-fractures/