- Department of Neurosurgery, Desert Regional Medical Center, Palm Springs, California, United States.
- College of Arts and Sciences, University of Michigan Flint, Flint, United States.
- College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan, United States.
- School of Medicine, Georgetown University, Washington, District of Columbia, United States.
- College of Osteopathic Medicine, William Carey University, Hattiesburg, Mississippi, United States.
Brian Fiani, D.O. Department of Neurosurgery, Desert Regional Medical Center, Palm Springs, California, United States.
DOI:10.25259/SNI_456_2021Copyright: © 2021 Surgical Neurology International This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
How to cite this article: Brian Fiani1, Ryan Jarrah2, Erika Sarno3, Athanasios Kondilis3, Kory Pasko4, Brian Musch5. An investigation of craniocervical stability post-condylectomy. 27-Jul-2021;12:380
How to cite this URL: Brian Fiani1, Ryan Jarrah2, Erika Sarno3, Athanasios Kondilis3, Kory Pasko4, Brian Musch5. An investigation of craniocervical stability post-condylectomy. 27-Jul-2021;12:380. Available from: https://surgicalneurologyint.com/surgicalint-articles/10989/
Background: Occipital condylectomy is often necessary to gain surgical access to various neurological pathologies. As the lateral limit of the craniovertebral junction (CVJ), partial condylectomy can lead to iatrogenic craniocervical instability. What was once considered an inoperable location is now the target of various complex neurosurgical procedures such as tumor resection and aneurysm clipping.
Methods: In this study, we will review the anatomical structure of the CVJ and provide the first comprehensive assessment of studies investigating craniovertebral stability following condylectomy with the transcondylar surgical approaches. Furthermore, we discuss future considerations that must be evaluated to optimize the chances of preserving craniocervical stability postcondylectomy.
Results: The current findings postulate upward of 75% of the occipital condyle can be resected without significantly affecting mobility of the CVJ. The current findings have only examined overall dimensions and have not established a significant correlation into how the shape of the occipital condyles can affect mobility. Occipitocervical fusion should only be considered after 50% condyle resection. In terms of indicators of anatomical stability, components of range of motion (ROM) such as the neutral zone (NZ) and the elastic zone (EZ) have been discussed as potential measures of craniocervical mobility. These components differ by the sense that the NZ has little ligament tension, whereas the EZ does represent ROM where ligaments experience tension. NZ is a more sensitive indicator of instability when measuring for instability postcondylectomy.
Conclusion: Various transcondylar approaches have been developed to access this region including extreme-lateral and far-lateral condylectomy, with hopes of preserving as much of the condyle as possible and maintaining postoperative craniocervical stability.
Keywords: Biomechanics, Condylectomy, Craniocervical stability, Craniovertebral junction
The craniovertebral junction (CVJ), separating the base of the skull from the subaxial cervical spine, has unique and complex bone structure and neurovascular architecture.[
Despite the potential risk of iatrogenic CVJ instability, partial occipital condylectomy, or resection of a portion of the occipital condyle, is used in surgical procedures for the treatment of spasmodic torticollis,[
Occipital condylectomy involves resection of the occipital condyle. The occipital condyles are two masses comprising the lateral limit of either side of the CVJ and the foramen magnum, while the medial tubercles of the condyles serve as an attachment point for the alar ligament.[
Partial condylectomy is performed to access either intra- or extra-dural pathology positioned anterior or anterolateral to the cervicomedullary region or to treat cranial nerve compression.[
Several studies have assessed the stability of the craniocervical region through various condylectomy approaches. While there has yet to be a predisposed algorithm for determining craniocervical stability following a condylectomy, several trials involving cadaveric specimens have found indications of CVJ stability based on kinematic and biomechanical analysis. In a study by Vishteh et al., the authors sought to determine the biomechanical stability of the occipitoatlantal occiput (Oc-C1) and atlantoaxial (C1-2) motion segments following a unilateral gradient condylectomy.[
The aftermath of the study from Vishteh et al. found that performing a fusion postcondylectomy of the occipitoatlantal motion segments should be considered only if half or more of the occipital condyle is resected.[
As previously mentioned, many of these studies are limited by having to mimic spinal loading and cardinal motions on cadavers, having small sample sizes, and comparing different approaches to one another. This makes the assessment of CVJ instability challenging for spine and skull base surgeons alike. In addition, there has yet to be a consensus on the ideal treatment of craniocervical stability [
In light of advances in approach to condylectomy, it is imperative future research continues to establish the extent of resection in condylectomy on craniovertebral hypermobility. The current findings postulate upward of 75% of the occipital condyle can be resected without significantly affecting mobility of the CVJ. However, there is still a lack of research exploring how the shape of the resected condyle may affect stability, as the current findings have only examined overall dimensions and not established a significant correlation into how the shape of the occipital condyles can affect mobility.
Further, it will be helpful to examine long-term changes in craniovertebral stability following condylectomy as the majority of tests examining ROM utilized cadaveric samples in the acute setting to establish a relative ROM, however, this may not be the most accurate representation of a patient population that is capable of recovery and physical therapy following a condylectomy procedure.
Condylectomy will continue to be performed to expose the surgical window necessary for various neurosurgical procedures. When condylectomy is performed, surgical approach must be considered as similar magnitude of condylar resection may lead to varying degrees of craniocervical stability depending on the approach used. Furthermore, each individual patient’s pre- and post-operative soft-tissue stability must be taken into consideration when estimating the degree of condylar resection that will allow for preserved postoperative stability. When CVJ stability is iatrogenically compromised, occipitocervical fusion may be a useful means of restoring stability. Future studies comparing the various condylectomy approaches and the degree to which condylar resection may be performed while simultaneously maintain postoperative craniocervical stability are necessary to establish more definitive surgical recommendations.
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