summary Sacral Insufficiency Fractures are fragility fractures of the sacral spine that occur more commonly in elderly women with osteoporosis. Diagnosis can be made with inlet and outlet radiographs of the pelvis. CT or MRI may be helpful for fracture characterization and operative planning. Treatment is usually observation and pain control. Surgical management is indicated for patients with progressive pain and/or difficulty ambulating that fail nonoperative treatment. Epidemiology Incidence 1% of women > 55 years old increases with age estimated to increase by 23% each year Demographics females more commonly affected 2:1 average age is 69 years old Risk factors osteoporosis vitamin D deficiency rheumatoid arthritis prolonged immobilization long-term steroid use pelvic radiation Etiology Pathophysiology mechanism of injury low energy trauma (i.e. ground level fall) Associated conditions other fragility fractures (i.e. distal radius, vertebral, hip) Anatomy Osteology formed by fusion of 5 sacral vertebrae articulates with 5th lumbar vertebra proximally coccyx distally ilium laterally at sacroiliac joints contains 4 foramina which transmit sacral nerves Nerves L5 nerve root runs on top of sacral ala S1-S4 nerve roots are transmitted through the sacral foramina S1 and S2 nerve roots carry higher rate of injury lower sacral nerve roots (S2-S5) function anal sphincter tone / voluntary contracture bulbocavernosus reflex perianal sensation unilateral preservation of nerves is adequate for bowel and bladder control Biomechanics transmission of load distributed by first sacral segment through iliac wings to the acetabulum Classification Denis Classification Zone 1 Fracture lateral to foramina Zone 2 Fracture through foramina Zone 3 Fracture medial to foramina into the spinal canal Presentation History low-energy trauma (i.e. ground level fall) Symptoms pain groin, low back, buttock worse with weightbearing Physical exam limited hip motion neurologic deficits are rare Imaging Radiographs recommended views AP lateral inlet view best assessment of sacral spinal canal and superior view of S1 outlet view provides true AP of sacrum CT indications negative radiographs but high suspicion for fracture confirmed fracture on radiographs MRI indications negative radiographs and CT but high suspicion for occult fracture Bone scan indications no longer used findings Honda or H sign seen with H-type fractures Studies Serum labs evaluate for causes of osteoporosis Treatment Nonoperative observation, mobilization, analgesia, osteoporosis screening & treatment indications first line of treatment Operative sacroplasty indications minimally displaced zone 1 injuries after failed nonoperative treatment ORIF indications displaced zone 1 injuries after failed nonoperative treatment zone 2 or 3 injuries after failed nonoperative treatment Techniques Sacroplasty technique injection of polymethylmethacrylate cement complications specific to this treatment cement leakage avoid sacroplasty in displaced fractures due to risk of symptomatic cement leakage ORIF technique unilateral iliosacral screws place 2 parallel 7-8mm cannulated screws perpendicular to the fracture plane 2 screws have more stability than 1 screw screws should cross midline stability is dependent on the strength of the sacral cancellous bone use washers to prevent penetration of the screw head through the lateral cortex of the posterior part of the ilium trans-sacral screw place 6mm screw through the sacral corridor of S1 posterior bridging plate place plate against sacrum and posterior part of ilium acts as tension band complications specific to this treatment implant loosening hardware failure Complications Non-union Persistent pain