Addressing Stretch Myelopathy in Multilevel Cervical Kyphosis with Posterior Surgery Using Cervical Pedicle Screws

Influence of clinical and radiological parameters on the likelihood of neurological improvement after surgery for degenerative cervical myelopathy

OBJECTIVE

Degenerative cervical myelopathy (DCM) is routinely treated with surgical decompression, but disparate postoperative outcomes are frequently observed, ranging from complete neurological recovery to persistent decline. Although numerous clinical and radiological factors have been independently associated with failure to improve, the relative impact of these proposed risk factors remains obscure. In this study, the authors assess the combined role of clinical and radiographic parameters in contributing to failure to attain neurological improvement after surgery.

METHODS

A consecutive series of patients who underwent surgery for DCM between July 2013 and August 2018 at a single institution was identified from a prospectively maintained database. Retrospective chart review was undertaken to record perioperative clinical and radiographic parameters. Failure to improve on the last follow-up evaluation after surgery, defined as a change in modified Japanese Orthopaedic Association (mJOA) score less than 2, was the primary outcome in univariate and multivariate analyses.

RESULTS

The authors included 183 patients in the final cohort. In total, 109 (59.6%) patients improved (i.e., responders with ΔmJOA score ≥ 2) after surgery and 74 (40.4%) were nonresponders with ΔmJOA score < 2. Baseline demographic variables and comorbidity rates were similar, whereas baseline Nurick score was the only clinical variable that differed between responders and nonresponders (2.7 vs 3.0, p = 0.02). In contrast, several preoperative radiographic variables differed between the groups, including presence and degree of cervical kyphosis, number of levels with bidirectional cord compression, presence and number of levels with T2-weighted signal change, intramedullary lesion (IML) length, Torg ratio, and both narrowest spinal canal and cord diameter. On multivariate analysis, preoperative degree of kyphosis at C2-7 (OR 1.19, p = 0.004), number of levels with bidirectional compression (OR 1.83, p = 0.003), and IML length (OR 1.14, p < 0.001) demonstrated the highest predictive power for nonresponse (area under the receiver operating characteristic curve 0.818). A risk factor point system that predicted failure of improvement was derived by incorporating these 3 variables.

CONCLUSIONS

When a large spectrum of both clinical and radiographic variables is considered, the degree of cervical kyphosis, number of levels with bidirectional compression, and IML length are the most predictive of nonresponse after surgery for DCM. Assessment of these radiographic factors can help guide surgical decision-making and more appropriately stratify patients in clinical trials.

Techniques of cervical pedicle screw insertion in lower cervical spine - A review

Cervical pedicle screws (CPS) have been used for stabilization of lower cervical spine since its first description by Abumi et al., in 1994^, but the usage has been limited due to the feared complications. Cadaveric studies have discouraged use of CPS in lower cervical spine due to high misplacement rates. On the contrary, clinical studies have shown limited complications due to screw misplacements and have highlighted the benefits of CPS with its superior biomechanical strength. Therefore surgeons have always tried to find a reliable, reproducible and safe CPS insertion technique to expand the usage of CPS with minimal complications. As of today Abumi et al. technique is the most popular free-hand technique used by surgeons, though many modifications have evolved to make the CPS insertions more safe and reproducible. The free hand technique should be considered as the cornerstone technique for CPS insertion and the navigation tools are essential to improve the safety of CPS in complex surgeries with altered cervical anatomy. The present review brings together the literature on the various aspects of cervical pedicle anatomy, the free-hand screw insertion techniques with their modifications, the screw misplacement rates and complications.

Cervical Spine Deformity: Indications, Considerations, and Surgical Outcomes

Cervical spinal deformity (CSD) in adult patients is a relatively uncommon yet debilitating condition with diverse etiologies and clinical manifestations. Similar to thoracolumbar deformity, CSD can be broadly divided into scoliosis and kyphosis. Severe forms of CSD can lead to pain; neurologic deterioration, including myelopathy; and cervical spine-specific symptoms such as difficulty with horizontal gaze, dysphagia, and dyspnea. Recently, an increased interest is shown in systematically studying CSD with introduction of classification schemes and treatment algorithms. Both major and minor complications after surgical intervention have been analyzed and juxtaposed to patient-reported outcomes. An ongoing effort exists to better understand the relationship between cervical and thoracolumbar spinal alignment, most importantly in the sagittal plane.

Clinical outcomes of anterior correction and reconstruction for neurofibromatosis-associated severe cervical kyphotic deformity

PURPOSE

To assess the clinical outcome of anterior correction and reconstruction for severe cervical kyphotic deformity due to neurofibromatosis type 1 (NF-1).

METHODS

In this study, we reviewed a series of seven patients who underwent anterior procedures for correction of NF-1-associated cervical kyphotic deformity. After continuous preoperative skull traction, all patients received anterior corpectomy and fusion (ACCF), anterior discectomy and fusion (ACDF), or combined ACCF and ACDF for surgical correction and reconstruction. Pre- and postoperative local and global Cobb angles, correction rate, sagittal vertical axis (SVA), and T1-slope were assessed by X-ray. Japanese Orthopaedic Association (JOA) score, JOA recovery rate, visual analog scale (VAS), and Neck Disability Index (NDI) scores were recorded to assess the outcome.

RESULTS

Kyphosis was corrected successfully in all patients in terms of local and global Cobb angles (P < 0.05), with a correction rates of 83.1% (range, 66.0 to 115.5%) and 88.6% (range, 61.1 to 125.0%), respectively. JOA scores of patients were improved from preoperative 10.4 (range, 6 to 14) to postoperative 15.4 (range, 14 to 17), with a recovery rate as 77.6% (range, 66.7 to 100%). NDI scores were reduced from preoperative 25.1 (range, 13 to 35) to postoperative 8.7 (range, 5 to 12). VAS scores were reduced from preoperative 7.0 (range, 4 to 9) to postoperative 2.3 (range, 1 to 3).

CONCLUSION

This study has demonstrated that anterior correction and reconstruction is an alternative option for the treatment of NF-1-associated severe cervical kyphosis when deformity is localized, flexible, or fixed.