A comprehensive analysis with minimum 1-year follow-up of vertically unstable transforaminal sacral fractures treated with triangular osteosynthesis.

PURPOSE
To analyze the radiographic, clinical, and functional results of triangular osteosynthesis constructs for the treatment of vertically unstable comminuted transforaminal sacral fractures.


SETTING
Level I trauma center.


METHODS
During a 3-year period (July 1, 2003 to June 30, 2006), 58 patients with vertically unstable pelvic injuries were treated with triangular osteosynthesis fixation by a single surgeon at a single institution. Patients were followed-up prospectively as a single cohort, with institutional review board approval. Inclusion criteria for this study were skeletally mature patients with a vertically unstable pelvic ring injury associated with a comminuted transforaminal sacral fracture. Minimum follow-up, both clinically and radiographically, was 1 year. Computed tomography scan was performed on all patients at 6 months to assess healing of the fracture. If the fracture healed, the fixation was removed. Functional outcome was assessed using the Short Form 36, version 2, and short version of Musculoskeletal Functional Assessment questionnaires at 6 months (before fixation removal) and 12 months.


RESULTS
Forty of 58 patients with an average age of 39 years were available for a minimum of 1-year follow-up. Wound complications requiring surgical debridement occurred in 5 patients (13%), all of whom had severe soft tissue wounds with internal degloving. Two patients required removal of infected fixation. Iatrogenic L5 nerve injury occurred in 5 patients (13%). Ten patients (25%) had a delayed union on computed tomography scans, and 3 patients had a nonunion as a result of residual fracture gap and incomplete reduction. Six patients (15%) were found to have pronounced tilting of the L5 vertebral body (scoliosis) and distraction of the L5/S1 facet joint ipsilateral to the fixation. This did not correct with removal of the fixation. Failure of the triangular osteosynthesis construct resulting in malunion occurred in 2 patients (5%). All but 2 patients (95%) complained of painful and prominent implants. Functional outcome scoring showed that patients continued to function below the population mean at 1 year but continued to improve, particularly with function and daily activity. Ninety-seven percent of patients returned to some form of work or schooling.


CONCLUSIONS
Triangular osteosynthesis fixation is a reliable form of fixation that allows early full weight-bearing at 6 weeks while preventing loss of reduction in comminuted vertical shear transforaminal sacral fractures. For this study group, operative reduction was maintained until healing in 95% of patients. However, the 1-year follow-up shows a substantial rate of potential technical problems and complications. Of primary concern were the asymmetric L5 tilting with L5-S1 facet joint distraction and the need for a second surgery in all patients to remove painful fixation. Iatrogenic nerve injury occurred in 5 patients (13%) and is thought to arise secondary to fracture manipulation and reduction. We recommend selective use of this technique for comminuted transforaminal sacral fractures in situations only where reliable iliosacral or trans-sacral screw fixation is not obtainable.