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 who fail nonoperative treatment Epidemiology Incidence 1% of women >55 y/o increases with age estimated to increase by 23% each year Demographics 2:1 female:male ratio average age 69 y/o 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, or hip fractures) Anatomy Osteology formed by fusion of 5 sacral vertebrae articulates with 5th lumbar vertebra proximally coccyx distally ilium laterally at the sacroiliac joints contains 4 foramina that transmit sacral nerves Nerves L5 nerve root runs on top of the sacral ala S1-4 nerve roots pass through the sacral foramina S1 and S2 nerve roots have a higher rate of injury lower sacral nerve roots (S2-5) function anal sphincter tone / voluntary contraction bulbocavernosus reflex perianal sensation unilateral preservation of nerves is adequate for bowel and bladder control Biomechanics transmission of load from the first sacral segment through the iliac wings to the acetabulum Classification Denis Classification Zone 1 Fracture lateral to the foramina Zone 2 Fracture through the foramina Zone 3 Fracture medial to the foramina extending into the spinal canal Presentation History low-energy trauma (i.e. ground level fall) Symptoms pain groin, low-back, or buttock pain worse with weight bearing Physical exam limited hip motion neurologic deficits are rare Imaging Radiographs recommended views AP lateral inlet view best assessment of the sacral spinal canal and superior view of S1 outlet view provides a true AP view of the 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, and treatment indications first-line 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 extrusion avoid sacroplasty in displaced fractures because of the risk of symptomatic cement extrusion ORIF technique unilateral iliosacral screws place two parallel 7-8 mm cannulated screws perpendicular to the fracture plane two screws provide greater stability than one screw screws should cross midline stability depends 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 a 6 mm screw through the sacral corridor of S1 posterior bridging plate place the plate against the sacrum and posterior part of the ilium acts as a tension band complications specific to this treatment implant loosening hardware failure Complications Nonunion Persistent pain