- General
- 3 types of cervical deformity (Kim 2019) found via Cluster analysis
- Assessed in dynamic imaging: esp extension lateral c spine xray
- No statistically significant differences in patient-reported outcomes (NDI, mJOA, NRS neck, or NRS back scores) between the groups.
- Group 1 (cervical flat-neck group)
- Patients had a large cervical mismatch (TS-CL) despite having some ability to compensate for their deformity.
- 46.2% of patients
- Characterised by a
- Large thoracic slope minus cervical lordosis (TS-CL) mismatch
- Had the largest TS-CL (57.2° ± 19.2°) and largest cSVA (58.6 mm ± 11.7 mm) among the groups.
- despite flexibility in cervical lordosis.
- Not compensate
- The driver for deformity
- 80% driven by the cervicothoracic region.
- These patients might benefit from longer cervicothoracic constructs that extend into the upper thoracic spine.
- Extreme flat neck can also be categorized as having a “chin-on-chest” deformity or those patients with poor muscle health who are unable to maintain horizontal gaze.
- Given that the deformity is more likely passively correctable, the use of preoperative traction might be avoided for these patients.
- Flat-neck patients might also benefit from longer-length cervicothoracic constructs that extend into the cervical spine and distally past the cervicothoracic junction, given their flexible CD
- Surgical plan
- Patients without prior spine surgery:
- CD operation that extends distally from the cervical spine to the upper thoracic spine.
- Patients with prior fusions or thoracolumbar reconstructions, revision surgery:
- would likely need to extend proximally past the cervicothoracic junction into the upper cervical spine.
- Approaches for correction of a patient’s deformity remain controversial
- Group 2 (focal cervical deformity)
- Large focal kyphosis between 2 adjacent vertebrae without a necessarily large regional cervical kyphosis.
- 30.8% of patients
- Characterised by
- focal kyphosis between 2 adjacent levels but no large regional cervical kyphosis, under the setting of a low T1 slope (< 22°).
- The driver for deformity
- 99.3% driven by the cervical region.
- Surgical plan
- might require focal correction.
- These patients likely do not have a large global CD, and addressing the specific levels with malalignment may provide significant correction.
- This might allow for constructs that stay within the cervical spine.
- Had the smallest T1S (21.5° ± 12.3°) and smallest cSVA (30.3 mm ± 15.9 mm).
- Group 3 (CT deformity)
- Cervicothoracic deformity causing compensatory cervical deformity
- 23.1% of patients
- Characterised by
- a very large T1 slope (> 50°) with a compensatory hyperlordosis of the cervical spine.
- Had the largest T1S (54.0° ± 13.2°) and largest cervical lordosis (13.0° ± 23.3°).
- These patients had hyperlordosis of the cervical spine as a compensatory mechanism that was not able to compensate enough to meet the T1S and resulted in CD.
- The driver of deformity
- 55% Thoracic
- 45% Thoracolumbar.
- There is a longer, more sweeping deformity with the individual having minimal ability to fully compensate alignment with extension, largely due to the high T1S.
- This cohort of patients would likely require further study to answer:
- Which level should be used as the upper instrumented vertebra or the lower instrumented vertebra in the setting of a thoracolumbar fusion
- Whether this cohort of patients is more at risk of proximal junctional kyphosis, in addition to adequately characterizing the location of the deformity driver that is resulting in the high T1S.
- For example, if the high T1S is driven by a large proximal junctional kyphosis in the lower thoracic spine, adequate correction of the lower thoracic kyphosis may, in some cases, result in a normalization of the T1S without necessitating a fusion that extends into the cervical spine.
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