Strategies to Minimize Invasiveness and Optimize Success: OC Fusion

47 Strategies to Minimize Invasiveness and Optimize Success: OC Fusion

Bernhard Meyer and Sandro M. Krieg

Summary

OC fusion could be one of the most complex and incapacitating procedures in spine surgery. However, true indications for OC fusion are almost unavoidable. Due to this, it is relevant to study, understand and improve our strategies to minimize invasiveness and improve outcomes. In this chapter, the authors share their experience after several publications and a thorough literature analysis about how to achieve this. In this chapter, the reader will find more information on how to avoid occipital inclusion, how to spare subaxial levels, how to avoid anterior surgery or when a transnasal approach could be better than a transoral approach all of these through a couple of case examples.

Keywords: spine occipitocervical fusion

47.1 Introduction

47.1.1 General Considerations

The craniocervical junction (CCJ) is defined as occiput, C1 plus C2. It is a complex anatomical area, which can be affected by a range of different pathologies causing pain, myelopathy, and instability. Basis each pathology need to be taken into consideration when planning surgical treatment. Occipitocervical (OC) fusion is the treatment of choice for craniocervical instability. Most of the rotation of the spine, its flexion, and extension occur at the CCJ.1 It is thus a procedure with considerable impact on the patients’ quality of life (QOL).

In the past, several techniques were used for OC fusion, such as noninstrumented onlay graft or an onlay graft plus wire fusion and halo placement, semirigid and sublaminar–occipital wire fixation, and rigid rods with occipital plating combined with lateral mass or pedicle screws.²^,³^,⁴^,⁵The latter should be regarded as today’s standard of care,⁶ making short constructs from C0 to C2 or C3 possible. Sparing segments is the most efficient way to reduce invasiveness of OC fusion, especially sparing the C0/C1 segment whenever possible, despite the fact that most of the cervical range of motion (ROM) happens in the atlantoaxial complex. Having the head additionally fixed in a given position has a clear negative impact on the patient’s life. Because we still observe a rather liberal inclusion of the occiput into pure C1/C2 instabilities, we would primarily like to advocate a prudent use of OC fusion.

47.2 Indications for OC Fusion

As mentioned above, indications for OC fusion can be instability due to neoplastic, infectious, degenerative, inflammatory, congenital, or traumatic pathologies. Neural decompression can also require OC fusion because it may cause instability in a prior stable situation.⁷

The most common indication is still rheumatoid arthritis (RA) of the CCJ, which causes instability plus myelopathy and pain in most cases.⁴^,⁶ Especially in RA, most cases can be handled by atlantoaxial fixation alone. Moreover, the anterior decompression, formerly considered a standard, is unnecessary in almost every case, because the retrodental mass disappears usually after stabilization.⁸ The strict indication for respective avoidance of anterior decompression in these procedures reduces the invasiveness of surgery even more.

Cranial settling is also not in all cases an indication for OC fusion followed by anterior decompression. One option is to distract the atlantoaxial joint with cages and fuse C1/C2 alone as popularized by Goel. If not feasible, distraction and OC fusion without anterior decompression would be second best option.

In trauma, only atlanto-occipital dislocation indicates OC fusion, a condition which is however rarely treated, because it is associated with a high rate of immediate on-site death. Any form of atlantoaxial instability even when combined (C1 ring plus C2 fracture) is nowadays not necessarily an indication to fuse the occiput. Modern screw-rod techniques make this unnecessary.

The above concepts should also be applied for tumorous, infectious, or any other indications.

Yet, revision of failed C1–C2 fixation may be an infrequent indication requiring OC fusion as presented in case 1.⁴

47.3 Risks

Bhatia and colleagues not only analyzed their own series of 100 patients who underwent OC fusion, they also performed a literature review providing comprehensive data on the largest eight series of OC fusion.⁶ Follow-up of these series was between 8 and 50 months. Instrumentation failure, such as screw-rod breakage or screw loosening, averaged 4% but some series even reported up to 25%.⁵^,⁶ Yet, such high rates were only reported in older series. With the currently used technique of occipital plating and lateral mass/pedicle screws, implant failures were considerably lower. Besides this major risk, other complications, such as wound infection (4–15%), vertebral artery injury (1–4%), cerebrospinal fluid (CSF) leak (1%), and misplaced screws (4%), were reported. Due to the general state of health of most patients necessitating OC fusion, mortality rates of 1 to 8% were reported.⁶

47.4 Outcomes

Winegar et al analyzed 34 articles reporting 799 patients who underwent OC fusion due to various indications and via several techniques (graft plus wire, wire plus rod, screws, and rod).⁹ In general, outcomes for OC fusion are reasonably good. Although surgical and medical adverse events sum up to around 33%, long-term outcome is usually good. Around 93% of patients show bony fusion, 82% improvement in neurology, and up to 100% improvement in pain scores.⁹ On a larger scale, modern constructs using occipital plating and lateral mass screws show superior results compared to wiring plus bone graft or wiring plus rods. Moreover, patients undergoing OC fusion due to inflammatory disease, such as RA, show better results than tumor patients.⁹ Yet, it needs to be taken into account that no published series provides a level of evidence better than IV.⁹

47.5 Options for Reducing Invasiveness

In the last years, several articles were published on different decompression and fusion techniques.10^,¹¹ In all series and analyses, constructs using plates, screws, and rods showed the best results. Not only in our opinion but also after performing an extensive literature search, there are only few published minimally invasive surgery (MIS) techniques for OC instrumentation per se using transarticular screws.¹²^,¹³

Instead of this, as already alluded to above, the only option to reduce invasiveness, complications, recovery rates, and impact on QOL is to think “laterally,” which implies (1) avoiding inclusion of the occiput whenever possible; (2) sparing subaxial segments by the use of modern constructs; (3) avoiding anterior decompression; and, if unavoidable, (4) using the endoscopic transnasal or transcervical route instead of the transoral.

As outlined above, for example, in many RA cases, fusion of the C0–C1 joint is not required pathophysiologically, which allows treating many patients by pure C1–C2 fixation. Although there are some transarticular techniques published in which C1–C2 instrumentation is done percutaneously, this technique does not allow proper preparation for bony fusion and also no distraction of the C1–C2 joint. Its indication is thus somewhat unclear to us. We advocate Harms-Goel technique for C1–C2 fusion as the default procedure. By distracting and by opening the joints on each side plus insertion of bone or cage into the joint, this technique helps to avoid anterior decompression in most cases. Moreover, in many RA cases, posterior fusion leads to shrinking of the anterior pannus within the first weeks after surgery.⁸^,¹⁴

If anterior decompression is still required, the option to do it via MIS is the transnasal endoscopic route, which shows proven and distinct reduction of invasiveness, complication, and recovery rate over the traditional transoral route.

Although for many years anterior decompression of the CCJ via odontoid resection was performed transorally, peaking in the 1980s and 1990s, the considerably high morbidity of this approach led to a much stricter indication in recent years.¹⁴^,¹⁵

According to us, it should be avoided if possible. Especially infection, dysphagia, and wound healing problems are clear arguments against the transoral route increasing the complication rates by up to 19% and above. The time for recovery is significantly longer due to the necessity of N/G tubes and/or even tracheotomies.

Thus, endoscopic transnasal odontoid resections are increasingly performed. No necessity for splitting of the soft palate, a less aggressive nasal flora, and immediate postoperative oral intake are only some of the advantages.¹⁵ The only limitation of this approach is the rhinopalatine line, which limits the extent of resection caudally as we present in case 2 (Fig. 47.1).¹⁶^,¹⁷ However, the second MIS option for anterior decompression is also presented in case 2, that is, an anterior transcervical submandibular approach for decompressions caudal to the rhinopalatine line (Fig. 47.2).

Fig. 47.1 Postoperative computed tomography (CT) and magnetic resonance imaging (MRI) scan after second surgery. This CT (a) and MRI (b) scans show the decompression of the medulla oblongata after the transnasal resection. As the white rhinopalatine line shows, the inferior extent of the endonasal odontoidectomy is limited by the nasal bone and hard palate.

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