Load Sharing Dynamic Anterior Cervical Plate چاپ
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جمعه, 27 مهر 1386 ساعت 10:05
Clinical Experience with a New Load Sharing Dynamic Anterior Cervical Plate
Ronald I. Apjlbaum, MD
Andrew T. Dailey, MD (Salt Lake City, UT)
Jose Barbera, MD (Valencia, Spain)
A new dynamic plating system (ABC plate) has been developed to avoid stress shielding of the graft by allowing vertical migration of the fixation screws within the plate while preventing screw back-out and still effectively stabilizing the spine to restore or preserve lordosis.
149 patients were implanted at two different centers. Indications were herniated disks in 43%, degenerative disease in 38%, trauma in 13%, deformity and failed fusion in 2% each, and tumors and OPLL in 1% each. Patients ranged in age from 18 to 76 years (average 46 yrs.). Screw placement was unicortical in 55%, bicortical in 45%. Single level plates were used in 43%, two level plates in 44%, and three or more levels were plated in 1 3%. Corpectomies were used in 24% with the remainder being interbody fusions. Allograft was used in 56%, autograph in 44%. Patients are seen and follow-up radiographs, including lateral flexion/extension views, are taken at the 1, 3, 6 and 12 month intervals after surgery. Settling was measured and corrected for magnification. Cobb angles were measured to determine changes in angulation from immediately preoperatively to subsequent interval films. Fusion was determined by bridging trabecular bone and the absence of motion at the tips of the spinous processes on flexion and extension films.
Minimum follow-up of 3 months was available on 93 patients, involving 174 instrumented levels.
Settling occurred in most patients. It was more pronounced with the use of allograft, but averaged 1 to 2 mm/level overall with a maximum of 6 mm in one patient with a three level fusion. Ninety-five percent of the settling occurred in the first month, at which time the grafts often were indistinguishable from the three month grafts in rigidly plated patients. No settling occurred after 3 months.
Virtually all levels showed impressive early graft incorporation. Using the strict criteria defined above, 122 of 174 levels (70%) were fused at 3 months and 103 of 120 levels (86%) at 6 months. No translational instability was observed.
Kyphotic Angulation:
Lordosis was preserved unchanged in 141 patients, while there was a 5º loss of lordosis in 2 patients. Kyphosis in 6 patients was maintained within 5º of the postoperative correction. There were no hardware-related complications and no patients had a
painful nonunion.
This constrained true load sharing system appears to attain the goals of stabilizing the spine after surgery or trauma while promoting earlier and more substantial graft incorporation. Since no negative downside has been identified, the use of this type of anterior cervical plating system would seem to confer a significant benefit to the patient.

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