Abstract
IntroductionConventionally, posterior C1-C2 fusion has been performed using a sublaminar wiring technique with a structural bone graft. Subsequent advent of newer fixation devices, such as the C1 lateral mass screw and C1 hook, has achieved more solid fixation with improved surgical outcome; however, in these fixation systems, the protruding end of the metal implant above the level of the atlas may result in a complication due to contact with the surrounding structures.Case descriptionTwo men and two women whose ages at the time of surgery ranged from 14 to 72 years. A supralaminar hook was used as a fixation device for C1 in two cases, whereas a lateral mass screw (Tan’s method) and an atlas claw hook were employed for one each of the remaining 2 cases. We retrospectively reviewed the clinical features and postoperative course of these patients using the clinical records. Moreover, we measured the protruding height of the instrument above the atlas as well as the Redlund-Johnell (R-J) value on postoperative radiographs. All patients complained of crepitus and/or pain on neck extension. Erosion in the occipital bone was detected on multiplanar reconstruction computed tomography (MPR-CT), whereas plain radiographs failed to reveal the bony change. In those cases, protruding instruments used for C1 fixation contacted the occipital bone resulting in an erosive change at the impingement point. We removed the implant in all four cases after confirmation of solid bony union.Discussion and evaluationTwo of the four patients complained of occipital crepitus alone without pain. The management options for this condition may be controversial; however, progression of bony erosion may result in perforation of the occipital bone. This may possibly be associated with the serious complication of cerebrospinal fluid leakage. Considering this potential sequela, we removed the implants from all our reported cases after confirmation of solid bony union.ConclusionsWe treated four cases that developed erosion in the occipital bone after posterior spinal instrumentation was performed for upper cervical lesions including C1. MPR-CT was useful in detecting the erosive changes in the occipital bone.
Highlights
Posterior C1-C2 fusion has been performed using a sublaminar wiring technique with a structural bone graft
We treated four cases that developed erosion in the occipital bone after posterior spinal instrumentation was performed for upper cervical lesions including C1
multiplanar reconstruction computed tomography (MPR-CT) was useful in detecting the erosive changes in the occipital bone
Summary
We detected erosion in the occipital bone of three recent cases on MPR-CT an average of 7 months postoperatively (range: 6–8 months). We detected erosion in the occipital bone of one previous case using an atlas claw on MPR-CT 8 years postoperatively. Radiological and CT examinations showed non-union of an odontoid fracture (Anderson type II) that was sustained 4 months before his visit to our institute. He underwent C1-C2 fusion using supra- and infralaminar hooks for C1 and a laminar screw for C2. The postoperative MPR-CT at 8 months showed bony union, whereas erosive changes were identified in the occipital bone corresponding to the location of the tip of the rod of the C1 supralaminar hook (Figure 1). C1: lateral mass screw (Tan technique), infra-laminar hook C2: laminar screw C3,4: LMS
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