**8. Peri-operative considerations in rheumatoid patients undergoing arthrodesis**

A complete assessment of the patient by an internal medicine physician and an anaesthetist is vital prior to the patient undergoing general anaesthesia. Cardiological manifestations such as pericarditis, arrhymthmias, and valvular incompetence occur at much greater incidence in this cohort when compared with their peers (Conlon et al 1966, Del Rincón. et al 2001). Similarly rheumatoid patients have twice the mortality rate from pulmonary disease (Gonzolez–Juanatey et al 2003). We do routinely monitor these patients in a high dependency setting postoperatively, until they are stable enough to be transferred to a low dependency and rehabilitation setting. Anaemia is a common finding in patients with well established rheumatoid arthritis (Doyle et al 2000), though in our experience pre-operative transfusion is the exception as opposed to the rule. It is our practice to continue intravenous antibiotics for a period of 3 days post-operatively, with the initial dose being administered at time of induction, due these patients tendency to develop both early and late infections (Maury et al 1988, Wimmer et al 1998, Carpenter et al 1996).

A particularly difficult issue for surgeons to grapple with is the question of when to discontinue disease modifying drugs. Though a recent trial failed to show any significant difference (Grennan et al 2001),these medications had previously been shown to delay wound healing, a most undesirable complication in an already vulnerable group of patients (Abhilash et al 2002, Hamalainen et al 1984). Our practice is to discontinue such medications four weeks prior to surgery, having discussed the case with the patient's rheumatologist.

Surgical Considerations of Rheumatoid Disease

(Ebraheim et al 2000).

Involving the Craniocervical Junction and Atlantoaxial Vertebrae 287

foraminae or aberrant vertebral artery (Ebraheim et al 1998, Golanki & Crockard 1999, Nagaria et al 2009). We routinely use stealth neuronavigation when planning screw trajectories to minimise the risk to both vertebral arteries and neural structures. In our experience myelopathic patients who have successful reduction and immobilisation of the C1C2 segment will not require laminar decompression. In cases of aberrant vertebral arteries we place a unilateral transarticular screw, with a lateral mass screw in C1 and a pars screw in C2 being placed on the "aberrant" side, if safe to do so, however, an aberrant vertebral artery can also preclude safe C2 pars screw insertion and we have not experienced any failures over a 15 year period with unilateral screw placement. Though some authors routinely reinforce their constructs with a Gallie or Brooks fusion, this has not been our practice. Successful placement of bilateral transarticular screws provides 38mm of fixation which more than adequately stabilises the segment (Yoshida et al 2006), without the added 5 - 7% risk of neurologic injury associated with wire constructs

Having applied the Mayfield skull clamp either to the skull or to the halo ring itself if previously applied, an image intensifier is used to confirm correct alignment of the atlantoaxial joint and the subaxial cervical spine. A midline posterior incision from C1 arch to C2/C3 spinous interspace level is followed by a subperiosteal exposure of both atlas and axis, and of the occiput itself in cases of occipitocervical fusion. The posterior arches of C1 and C2 are exposed at C1 as far laterally as the medial border of the lateral mass and inferiorly as far as the C2/3 joint avoiding disruption of the joint itself. The destruction wrought by the rheumatoid inflammatory process on the normal anatomical landmarks of the atlas and axis makes placing C1-C2 screws without the use of neuronavigation hazardous at best, and foolhardy in some cases. The pars of C2 is exposed subperiostially as far as the C1/C2 joint remaining anterior to the traversing C2 root. Blunt dissection along the superior aspect of the C2 lamina allows the operator to appreciate the medial aspect of the C2 pedicle. Successful identification of the C2 pedicle and the pars as it extends superiorly toward the C1-C2 articulation, allows a safe entry into the C1-C2 joint. It is important in this area to maintain a subperiosteal approach with a sharp dissector to avoid venous haemorrhage. The joint may be entered, curetted and graft inserted directly. This step may be facilitated with the use of an operating microscope. It has been our practice to perform this additional step where the space between the articular surfaces of C1 and C2 allow it, particularly in those cases with incomplete reduction of C1 on C2. The approximate entry point for transarticular screw placement is 2mm lateral to the medial border of the C2-C3 facet joint. Stab incisions as per image guidance bilaterally allow the desired screw trajectory aiming toward the upper half of the C1 anterior tubercle. Use of neuronavigation to confirm screw trajectory minimises the danger of encountering either the vertebral artery (which may easily be damaged with a lateral or inferior trajectory (Geremia et al 1985) or the spinal cord. The vertebral artery is most at risk from a trajectory that is too low rather than one that is too lateral. This is especially important in cases when incomplete reduction of C1 and C2 has been achieved where an anterior target above the tubercle of C1 should be chosen. In these cases the choice of the anterior tubercle of C1 as a target causes a low trajectory through C2 with the risk of cortical perforation inferiorly. If this is kept in mind, incomplete reduction of C1 on C2 does not preclude C1/C2 transarticular screw fixation. An image-guided drill-guide is passed percutaneously to the posterior arch of C2, and aligned with the planned entry point on the neuronavigation. A guide K-wire is drilled

Such disease-modifying agents are recommenced after a period of 12 weeks to allow the maximum bony fusion to occur around the arthrodesis. The one exception in the disease modifying drug group is glucocorticoids. Rheumatoid patients have commonly been receiving oral glucocorticoids as a adjunct to other agents for a few decades by the time surgical intervention is recommended. By such a stage the hypothalamic-pituitary-adrenal has been completely suppressed, placing them at risk of an Addisonnian crisis if such medications are not administered. A large bolus of steroids is usually administered at the same time as that of antibiotics, with "stress-doses" continued for 3 days post-operatively. Due to the severity of the subluxation and deformity seen in the spines of these patients, along with accompanying cricoarytenoid and temporomandibular arthritis (Chen et al 2005, Paulsen 2000), the anaesthetists fibreoptically place the endotracheal tube whilst the patient remains awake.
