title: Fracture of fusion mass after hardware removal in patients with high sagittal imbalance.
abstract: OBJECTIVE
  As spinal fusions become more common and more complex, so do the sequelae of these procedures, some of which remain poorly understood. The authors report on a series of patients who underwent removal of hardware after CT-proven solid fusion, confirmed by intraoperative findings. These patients later developed a spontaneous fracture of the fusion mass that was not associated with trauma. A series of such patients has not previously been described in the literature.
  
  
  METHODS
  An unfunded, retrospective review of the surgical logs of 3 fellowship-trained spine surgeons yielded 7 patients who suffered a fracture of a fusion mass after hardware removal. Adult patients from the West Virginia University Department of Orthopaedics who underwent hardware removal in the setting of adjacent-segment disease (ASD), and subsequently experienced fracture of the fusion mass through the uninstrumented segment, were studied. The medical records and radiological studies of these patients were examined for patient demographics and comorbidities, initial indication for surgery, total number of surgeries, timeline of fracture occurrence, risk factors for fracture, as well as sagittal imbalance.
  
  
  RESULTS
  All 7 patients underwent hardware removal in conjunction with an extension of fusion for ASD. All had CT-proven solid fusion of their previously fused segments, which was confirmed intraoperatively. All patients had previously undergone multiple operations for a variety of indications, 4 patients were smokers, and 3 patients had osteoporosis. Spontaneous fracture of the fusion mass occurred in all patients and was not due to trauma. These fractures occurred 4 months to 4 years after hardware removal. All patients had significant sagittal imbalance of 13-15 cm. The fracture level was L-5 in 6 of the 7 patients, which was the first uninstrumented level caudal to the newly placed hardware in all 6 of these patients. Six patients underwent surgery due to this fracture.
  
  
  CONCLUSIONS
  The authors present a case series of 7 patients who underwent surgery for ASD after a remote fusion. These patients later developed a fracture of the fusion mass after hardware removal from their previously successfully fused segment. All patients had a high sagittal imbalance and had previously undergone multiple spinal operations. The development of a spontaneous fracture of the fusion mass may be related to sagittal imbalance. Consideration should be given to reimplanting hardware for these patients, even across good fusions, to prevent spontaneous fracture of these areas if the sagittal imbalance is not corrected.
authors.affiliation: Departments of 1 Neurosurgery and.
authors.forename: Cara L
authors.initials: CL
authors.lastname: Sedney
authors.affiliation: Orthopaedics, West Virginia University, Morgantown, West Virginia; and.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Daffner
authors.affiliation: Spectrum Orthopaedics, Inc., Canton, Ohio.
authors.forename: Jared J
authors.initials: JJ
authors.lastname: Stefanko
authors.affiliation: Orthopaedics, West Virginia University, Morgantown, West Virginia; and.
authors.forename: Hesham
authors.initials: H
authors.lastname: Abdelfattah
authors.affiliation: Orthopaedics, West Virginia University, Morgantown, West Virginia; and.
authors.forename: Sanford E
authors.initials: SE
authors.lastname: Emery
authors.affiliation: Orthopaedics, West Virginia University, Morgantown, West Virginia; and.
authors.forename: John C
authors.initials: JC
authors.lastname: France
mesh_terms: D000368:Aged; D004185:Disability Evaluation; D005260:Female; D050723:Fractures, Bone / Q000209:etiology / Q000601:surgery*; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013122:Spinal Diseases / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods; D016896:Treatment Outcome
keywords: ASD = adjacent-segment disease; BMP = bone morphogenetic protein; DISH = diffuse idiopathic skeletal hyperostosis; LL = lumbar lordosis; PI = pelvic incidence; SVA = sagittal vertical axis; adjacent-segment disease; back pain; complication; fracture; sagittal balance; spinal fusion; technique