To preserve the occipitocervical tension band, decreasing morbidity of traditional procedures, and less postoperative pain, we performed a prospective nonrandomized study starting in May 2007 [2] using a minimally invasive trans-muscular approach through a 2.5 cm bilateral paramedian skin incision (Fig. 3a), using the access MIS platform MaXcess® (NuVasive Inc., San Diego, CA, USA) (Fig. 3b), and subsequently placing screws according to the modified Harms technique (Fig. 3c).

This approach uses a progressive tubular dilator system through the superficial nuchal musculature (trapezius and semispinalis capitis) and then through the anatomical corridor previously described between the posterior major rectus capitis and the inferior obliquus capitis. A three-valve spreader MaXcess® with optical fiber light is then placed, allowing good exposure and illumination of the working area (Fig. 3b). Under fluoroscopic guidance, the system is anchored on the access point of the C2 pedicle, trying to avoid obstaculization of the posterior arch of C1 during opening of the retractor. With monopolar cautery the bony surface of C2 is exposed, following it until the lateral border C1–C2 articulation is also visualized. At this point an epidural venous plexus usually bleeds, but it is effectively controlled with a combination of bipolar cautery and Gelfoam®. The C1–C2 bone joint surface is exposed and the C2 root identified and then coagulated and sacrificed to allow adequate insertion of the screw. At this point 3.5 mm diameter polyaxial screws are inserted using Harms technique (Fig. 3c, d). The articular surfaces of C1 and C2 are decorticated using micro-curettes and demineralized bone matrix (Grafton® DBM-Putty, Osteotech®, Inc. New Jersey, USA) mixed with bone marrow aspirates (BMA) is placed inside the joint to obtain second fusion (Fig. 3d, e). The same procedure is made in the contralateral side in the same way.

Until December 2011 a total of 16 patients were treated using this technique; mean age was 57.5 years old. Eight patients presented unstable C2 fracture and 8 patients atlantoaxial instability secondary to RA. Mean surgical time and blood loss was 193. 7 min and 403. 5 cc, respectively. Patients experienced minimal postoperative pain and were discharged before 46.8 h mean time; also there was no hardware failure.