Biomechanical effects of the transcondylar approach on the craniovertebral junction.

The transcondylar variation of the far-lateral, retrosigmoid approach is intended for pathologies in the anterolateral portion of the foramen magnum. That area is more clearly visualized when a fraction of the ipsilateral occipital condyle is removed. In this study, the biomechanical effect of this approach on occiput-C2 rotation was investigated. Our hypothesis was that the biomechanical characteristics are significantly altered following the transcondylar approach. Five human cadaveric upper cervical spine specimens (occiput-C7) were used in the study. Torsional moments were applied from zero to a maximum of 1.5 N m to the left and to the right using a mechanical testing machine. The resulting rotational motions of the O-C1, C1-2, and O-C2 segments were measured in the intact specimen and after a simulated right-sided transcondylar approach with resection of 2/3 of the condyle, confirmed by CT scanning and visual inspection. After the posterior two-thirds of the occipital condyle were removed, the neutral zone (NZ) increased 1.3° to the left and 2° to the right at C0-C1, and 7.4° to the left and 6.2° to the right at C1-2. The cumulative increase in NZ between O and C2 was 8.7° to the left and 8.2° to the right. The transcondylar approach also resulted in significant increases in range of motion (ROM) in axial rotation to both sides in all segments. ROM increased 2.8° to the left and 2.4° to the right between C0 and C1, 7.3° to the left and 5.4° to the right between C1 and C2, and 10.1° to the left and 7.8° to the right between CO and C2. Upon inspection, the area of the occipital condyle where the alar ligament attaches had been completely removed in three of the five specimens. Removing the posteromedial two-thirds of one occipital condyle alters the normal axial rotational movements of the craniovertebral junction on both sides. The insertion of the alar ligament can be inadvertently removed during condylar resection, and this could contribute to atlanto-axial instability. There is a biomechanical substrate to cranio-cervical instability following a transcondylar approach; these patients may need to be followed over several years to ensure it does not progress and necessitate occipito-cervical fusion.

Long-term outcomes of 2 cervical laminoplasty methods: midline splitting versus unilateral single door.

BACKGROUND: Two major current methods are midline splitting laminoplasty (MSL) and unilateral single-door laminoplasty (USDL). Few studies have compared the 2 techniques. METHODS: We retrospectively analyzed the outcomes of 100 consecutive myelopathy patients who underwent decompressive laminoplasty between January 2004 and June 2008. The mean follow-up duration was 48.2 months. RESULTS: The mean Japanese Orthopedic Association scores changed from 6.9 to 11.9 in the MSL group and from 6.2 to 12.4 in the USDL group, resulting in mean calculated recovery rates of 55.5% and 63.0%, respectively (P = 0.14). Mean cervical lordosis declined from 12.0 to 10.2 degrees in the MSL group and from 10.3 to 8.5 degrees in the USDL group (P = 0.24). Mean cervical range of motion declined from 27.8 to 25.6 degrees in the MSL group, and from 23.4 to 16.0 degrees in the USDL group (P = 0.38). Bony spinal canal dimension increased from 201.2 to 280.8 mm in the MSL group and from 204.3 to 331.7 mm in the USDL group (P < 0.001). In the USDL group, 6 patients experienced postoperative neck pain, 7 experienced C5 palsy, and 2 experienced cerebrospinal fluid leakage. No such complications occurred in the MSL group (P ≥ 0.05 for both complications). CONCLUSIONS: MSL and USDL patients had similar long-term clinical and radiologic outcomes, except that bony canal expansion was greater in the latter. We believe that removal of the ligamentum flavum and drilling of the internal bony edge were factors in the favorable clinical outcomes and low rate of complications in the MSL group.

Airway Management Protocol After Anterior Cervical Spine Surgery: Analysis of the Results of Risk Factors Associated With Airway Complication.

STUDY DESIGN: Retrospective comparative cohort analysis. OBJECTIVE: To evaluate the effect of postoperative airway management protocol (ASAN Extubation Protocol, AEP) on incidence of airway complications for patients undergoing anterior cervical spine surgery (ACSS). BACKGROUND: Postoperative airway compromise remains crucial for patients undergoing ACSS. Despite the potential severity of these complications, the data in the published literature addressing this issue is sparse. METHODS: A retrospective cohort study was performed regarding airway complications (postoperative airway edema requiring unplanned reintubation or tracheostomy) between groups of patients undergoing ACSS before and after applying our standardized protocol (AEP) for postoperative extubation. The AEP was developed based on 5 clinical risk factors reported having relation to airway complication. Postoperative patients with any oneor more risk factors were kept intubated for at least overnight and extubation was conducted according to the amount of prevertebral soft tissue swelling. RESULTS: A total of 538 ACSS patients were identified from 2008 to 2016. The nonprotocol group (before protocol application, 275 patients) and the Protocol group (after protocol, 263 patients) were compared; airway complication rates were significantly different between two groups (nonprotocol: 3.64% (10/275) vs. PROTOCOL: 0.76% (2/263), P = 0.024). The possible factors that may increase airway complication include operative indications (P = 0.002), trauma (P = 0.000), medical comorbidity risk (P = 0.011), combined anterior and posterior surgery (P = 0.002), and operation time longer than 5 hours (P = 0.045). In multivariate analysis, medical comorbidity risk, trauma, and airway protocol adoption were significant factors. AEP reduced the airway complication rate by odds ratio 0.125 (P = 0.013). CONCLUSION: Postoperative airway complication is not very common after ACSS. AEP contributed to reduce the incidence of airway complications. The potentially life-threatening event of loss of airway patency, even though it is a rare complication, should be cautiously analyzed with identification of risk factors before the surgery. LEVEL OF EVIDENCE: 2.