gms | German Medical Science

Objective: In instrumented fusion of C1 and C2, transarticular screw fixation is seen as the gold standard. However, drawbacks of the technique are the necessity for a preliminary reduction before instrumentation and a significant risk of vertebral artery injury especially in patients with a high riding transverse foramen. Therefore, the Harms technique – C1 lateral mass screws and C2 pedicle or isthmic screws – is a reasonable alternative to the Magerl technique. This study describes our experience in a prospective design.

Methods: All data of patients treated at our institution since May 2006 were collected in a database. All patients underwent C1 lateral mass and C2 isthmic instrumentation. Screw position and reduction/alignment was assessed by postoperative thin-cut CT scans. Surgical parameters, outcome parameters related to QoL (VAS, SF-36, EQ5D) and radiographic data were collected.

Results: Between May 2006 and June 2007, 13 patients requiring atlantoaxial fusion for instabilities were treated. Six patients were operated for traumatic, 3 for neoplastic, 2 for infectious and 1 each for degenerative and congenital instabilities. Of 26 implanted C1 lateral mass screws, 23 had an ideal position while in 3 the placement was suboptimai. However, there was sufficient bone contact for stability without harming neuronal structures. Of 26 C2 isthmic screws, 4 were not ideal but acceptable in position while 22 were placed in an optimal position. There was one case of neurological deterioration after instrumented fusion from C1 to C7 in a multimorbid patient but this was not related to surgery. Furthermore, no neurological or vascular injuries occurred. Realignment was correct in all patients. After a mean follow-up of 9 months,the patients were found to have a reduction on the VAS pain score, decreased disability as assessed by the Oswestry score and improvements in all items of EQ5D. SF36 was not acquired prior to surgery, therefore data are only comparable to normative population data. Thereby, C1-2 fused pts showed a lower level of function in certain aspects of the test.

Conclusions: C1-C2 instrumented fusion with lateral mass and isthmic screws is a safe procedure without a need for navigated surgery. Adequate screw position without harming the vertebral artery was possible in all cases. Therefore, at our institution transarticular screws were abandoned in favor of C1 lateral mass and C2 isthmic screws.