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Radiostereometric Analysis of Stability and Inducible Micromotion After Locked Lateral Plating of Distal Femur
Vincent P Galea1, Mina A Botros1, Michael F McTague2,3
1Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, MA.
Objectives:
To evaluate interfragmentary motion over 1 year after distal femoral fracture fixation using radiostereometric analysis (RSA). The secondary aim was to assess whether RSA data are consistent with diagnoses of nonunion.
Design:
Prospective cohort study.
Setting:
Level I urban trauma center.
Patients:
Sixteen patients between 22 and 89 years of age with distal femoral fracture (OTA/AO type 33).
Intervention:
All fractures were treated with a lateral locking plate, and tantalum markers were inserted into the main proximal and distal fracture fragments. RSA was performed at 2, 6, 12, 18, and 52 weeks postoperatively. Both unloaded and loaded RSA measurements were performed.
Main Outcome Measurements:
Unloaded fracture migration over time and inducible micromotion at the fracture site in the coronal plane were determined at each follow-up interval.
Results:
RSA precision in the coronal plane of interfragmentary motion over time and inducible micromotion were 1.2 and 0.9 mm in the coronal plane, respectively. Two cases required revision surgery for nonunion 1 year postoperatively. For cases of union, unloaded fracture migration stopped being detectable between 12 and 18 weeks, and inducible micromotion was no longer detectable by the 12-week visit. For cases of nonunion, both unloaded migration and inducible micromotion were detected throughout the study period.
Conclusions:
RSA may be used to reliably assess distal femoral fracture healing. RSA revealed differences in cases of union and nonunion by 3 months and more consistently than traditional x-rays.
Level Of Evidence:
Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.
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