AN INVASION OF THE ATLAS

Analysis of a radiographic parameter K-line tilt following adjacent two-level anterior cervical discectomy and fusion: a retrospective study

BACKGROUND

T1s, C2-7 lordosis, and C2-7 sagittal vertical axis (SVA) are the three most important sagittal parameters in the cervical spine. This study was conducted to investigate the relationships between classical sagittal alignment parameters and a new parameter, K-line tilt, and to study the impact of K-line tilt.

MATERIAL AND METHODS

A total of 72 patients who underwent adjacent two-level anterior cervical discectomy and fusion (ACDF) were retrospectively analyzed. Radiographic measurements included T1 slope (T1s), C2-7 lordosis, segment angle (SA), C2-7 SVA, and K-line tilt. The Neck Disability Index (NDI) scores were used to evaluate the clinical prognosis. Pearson correlation coefficients were calculated between radiographic measures. Linear regression analysis was used to analyze the relationship between follow-up K-line tilt and NDI.

RESULTS

ΔNDI was positively correlated with ΔT1s (r = 0.620, p < 0.05), ΔC2-7 SVA (r = 0.645, p < 0.05), and ΔK-line tilt (r = 0.702, p < 0.01); ΔK-line tilt was positively correlated with ΔT1s (r = 0.650, p < 0.05), ΔSA (r = 0.269, p < 0.05), and ΔC2-7 SVA (r = 0.293, p < 0.05); ΔT1s was positively correlated with ΔC2-7 lordosis (r = 0.428, p < 0.05), ΔSA (r = 0.631, p < 0.01), and ΔC2-7 SVA (r = 0.235, p < 0.05); ΔC2-7 lordosis was positively correlated with ΔSA (r = 0.666, p < 0.05) and negatively correlated with ΔC2-7 SVA (r = - 0.467, p < 0.01). The preoperative and postoperative K-line tilt values were statistically significant (p < 0.01), increasing from (7.50 ± 6.48)° to (9.95 ± 5.09)°. Preoperative NDI was positively correlated with preoperative C2-7 SVA (r = 0.639, p = 0.011) and K-line tilt (r = 0.516, p = 0.026); follow-up NDI was positively correlated with follow-up T1s (r = 0.664, p = 0.038), C2-7 SVA (r = 0.756, p = 0.004), and K-line tilt (r = 0.832, p = 0.006). The linear regression model showed that when the follow-up K-lint tilt was > 23.75°, NDI scores were > 25 (R² = 0.737, p = 0.000).

CONCLUSION

This study showed that the K-line tilt was strongly correlated with the C2-C7 SVA, indicating that the K-line tilt can be used as another cervical parameter to evaluate cervical alignment in adjacent two-level ACDF. K-line tilt is an important parameter similar to the classical parameter C2-C7 SVA. In particular, a K-line tilt greater than 23.75 corresponded to a worse clinical prognosis, which was defined as an NDI score greater than 25.

Adult cervical deformity: radiographic and osteotomy classifications

Cervical spine deformity represents a broad spectrum of pathologies that are both complex in etiology and debilitating towards quality of life for patients. Despite advances in the understanding of drivers and outcomes of cervical spine deformity, only one classification system and one system of nomenclature for osteotomy techniques currently exist. Moreover, there is a lack of standardization regarding the indications for each technique. This article reviews the adult cervical deformity (ACD) and current classification and nomenclature for osteotomy techniques, highlighting the need for further work to develop a unified approach for each case and improve communication amongst the spine community with respect to ACD.

[Normal sagittal profile of the cervical spine - must the cervical spine always be lordotic?]

BACKGROUND

The cervical spine is very complex, and it allows the largest range of motion relative to the rest of the spine. The fundamental function of the cervical spine is to maintain the head balanced over the trunk and to maintain horizontal gaze. The cervical spine must be both stable and flexible to guarantee function. Changes of the sagittal profile of the cervical spine may affect function and quality of life. The relationship between full body alignment and maintaining gaze necessitates a thorough understanding of the cranio-spino-pelvic alignment as a component of balance.

QUESTION

Now the question is, what kind of sagittal profile does the cervical spine need for proper function? In the literature, normal sagittal alignment of the cervical spine is controversial. In general, there is the assumption that the alignment is lordotic. Does the data in the literature support this?

RESULTS

The present literature review supports the following facts: Ideal cervical spine alignment is mostly lordotic, but not always; ideal cervical spine alignment can be lordotic, neutral or kyphotic; ideal cervical spine alignment is driven by the necessity of supporting the head and maintaining horizontal gaze; the cervical spine is in harmony with regional alignment (thoracic kyphosis) and sagittal global alignment (SVA): TK (↑) → T1 Slope (↑) → CL (↑), TK (↓) → T1 Slope (↓) → CL (↓), SVA >50 mm: the cervical curve should be lordotic to maintain horizontal gaze, SVA <0 mm: the cervical curve should be kyphotic to maintain horizontal gaze.

Cervical radiographical alignment: comprehensive assessment techniques and potential importance in cervical myelopathy

STUDY DESIGN

Narrative review.

OBJECTIVE

To provide a comprehensive narrative review of cervical alignment parameters, the methods for quantifying cervical alignment, normal cervical alignment values, and how alignment is associated with cervical deformity and myelopathy with discussions of health-related quality of life.

SUMMARY OF BACKGROUND DATA

Indications for surgery to correct cervical alignment are not well-defined and there is no set standard to address the amount of correction to be achieved. In addition, classifications of cervical deformity have yet to be fully established and treatment options defined and clarified.

METHODS

A survey of the cervical spine literature was conducted.

RESULTS

New normative cervical alignment values from an asymptomatic volunteer population are introduced, updated methods for quantifying cervical alignment are discussed, and describing the relationship between cervical alignment, disability, and myelopathy are outlined. Specifically, methods used to quantify cervical alignment include cervical lordosis, cervical sagittal vertical axis, and horizontal gaze with the chin-brow vertical angle. Updated methods include T1 slope. Evidence from a few recent studies suggests correlations between radiographical parameters in the cervical spine and health-related quality of life. Analysis of the cervical regional alignment with respect to overall spinal pelvic alignment is emerging and critical. Cervical myelopathy and sagittal alignment of the cervical spine are closely related as cervical deformity can lead to spinal cord compression and tension.

CONCLUSION

Cervical deformity correction should take on a comprehensive approach in assessing global cervical-pelvic relationships and the radiographical parameters that effect health-related quality of life scores are not well-defined. Cervical alignment may be important in assessment and treatment of cervical myelopathy. Future work should concentrate on correlation of cervical alignment parameters to disability scores and myelopathy outcomes. SUMMARY STATEMENTS: STATEMENT 1: Cervical sagittal alignment (cervical SVA and kyphosis) is related to thoracolumbar spinal pelvic alignment and to T1 slope. STATEMENT 2: When significant deformity is clinically or radiographically suspected, regional cervical and relative global spinal alignment should be evaluated preoperatively via standing 3-foot scoliosis X-rays for appropriate operative planning. STATEMENT 3: Cervical sagittal alignment (C2-C7 SVA) is correlated to regional disability, general health scores and to myelopathy severity. STATEMENT 4: When performing decompressive surgery for CSM, consideration should be given to correction of cervical kyphosis and cervical sagittal imbalance (C2-C7 SVA) when present.

Spinal intraosseous schwannoma : a case report and review

A case of spinal intraosseous schwannoma (SIS) in the lumbar vertebra is reported. Clinical and radiologic characteristics of 16 reported cases of SIS were reviewed. SIS can be a rare differential diagnosis for intraosseous tumors.

Circumferential fusion for cervical kyphotic deformity

Object

The treatment of cervical kyphotic deformity is challenging. Few prior reports have examined combined anterior/posterior correction methods, and fusion rates and standardized outcomes are rarely cited in literature examining these techniques. The authors present their midterm results with cervical kyphosis correction.

Methods

The authors retrospectively reviewed the charts of 30 patients with cervical kyphotic deformity who underwent circumferential spine surgery between 2001 and 2007. The causes of the deformity included chronic fracture in 17 patients, degenerative disease in 10, and tumor in 3. Anterior procedures included discectomies and corpectomies/osteotomies at 1 or more levels with fusion. Posterior operations included decompression and/or osteotomies with lateral mass or pedicle fixation. Preoperative and postoperative Ishihara kyphosis indices, modified Japanese Orthopaedic Association (mJOA) scores, and Nurick grades were analyzed. Arthrodesis was assessed via dynamic radiographs, and CT scans were used to assess fusion in questionable cases.

Results

One patient was lost to follow-up. Two patients died within 1 month of surgery. The follow-up period in the remaining 27 patients ranged from 1 to 6.4 years (mean 2.6 years). Ishihara indices improved from a preoperative mean of −17.7 to a postoperative mean of +11.4. The mean Nurick grades improved from 3.2 preoperatively to 1.3 postoperatively. The mJOA scores improved from a preoperative mean of 10 to 15 postoperatively. All surviving patients who underwent follow-up showed postoperative fusion except 1 patient with renal failure and osteoporosis (95% fusion rate). The overall rate of complications (major and minor) was 33.3%.

Conclusions

In cases of cervical kyphosis, management with decompression, osteotomy, and stabilization from both anterior and posterior approaches can restore cervical lordosis. Furthermore, such surgical techniques can produce measurable improvements in neurological function (as measured with Nurick grades and mJOA scores) and achieve high fusion rates. However, there is a significant rate of complications.