Journal of Spinal Surgery

EDITORIAL
Year
: 2022  |  Volume : 9  |  Issue : 2  |  Page : 70--72

Does cervical laminoplasty cause postoperative kyphosis?


Sachin Anil Borkar 
 Additional Professor, Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India

Correspondence Address:
Sachin Anil Borkar
AIIMS, New Delhi
India




How to cite this article:
Borkar SA. Does cervical laminoplasty cause postoperative kyphosis?.J Spinal Surg 2022;9:70-72


How to cite this URL:
Borkar SA. Does cervical laminoplasty cause postoperative kyphosis?. J Spinal Surg [serial online] 2022 [cited 2022 Aug 20 ];9:70-72
Available from: http://www.jossworld.org/text.asp?2022/9/2/70/346355


Full Text

[AUTHOR:1]

Cervical lordosis is essential for maintaining the line of sight with minimal stress on extensor muscles of the neck. Many pathologies of the cervical spine warrant posterior decompression at multiple levels, a few prominent examples being ossified posterior longitudinal ligament (OPLL) and degenerative cervical spondylotic myelopathy (CSM). It is generally believed that long-segment laminectomy may lead to postoperative kyphosis. Laminoplasty while providing adequate although slightly inferior decompression compared to laminectomy and instrumentation is believed to lower the chances of postoperative kyphotic deformity.[1] In recent years, there is a lot of literature on cervical spine alignment following cervical laminoplasty.[1],[2],[3],[4] Laminoplasty also causes disruption of the posterior musculoligamentous complex (PMLC). Hence, theoretically, it can also cause postoperative changes in spinal alignment, although not frank kyphosis; but some loss of cervical lordosis (LOCL) may be seen after cervical laminoplasty.

Although LOCL is not entirely preventable, radiologic factors have been described which can predict LOCL and clinical outcomes following laminoplasty.[5] C2-C7 sagittal vertical axis (C2-7 SVA), preoperative cervical lordosis in the form of C2-C7 Cobb's angle (CA), C2-C3 disc angle, T1 slope (T1S), delta angle (DA), and dynamic extension reserve (DER) are some of the parameters which have been studied.[1] Some of these parameters are described in [Table 1] and are illustrated in [Figure 1]. C2-C7 SVA, CA, and T1S are well-established parameters for objectively depicting the degree of lordosis and anatomic demand of lordosis. It could be postulated that a high preoperative T1S places a high demand for cervical lordosis in the form of propensity of C2-C7 SVA to increase which in turn is met by increased CA and preoperative lordosis. A higher incidence and degree of postoperative LOCL are observed in such patients as the role of PMLC becomes crucial in maintaining lordosis.[6]{Table 1}{Figure 1}

A study including 50 patients with either OPLL or CSM who underwent 2–4 level hinge laminoplasty evaluated the role of T1S as a predictor of LOCL and functional outcomes postoperatively and at 1-year follow-up.[6] It revealed findings supporting the aforementioned postulate. Patients with higher T1S (>26°) had higher preoperative CA and C2-C7 SVA, greater incidence and degree of postoperative LOCL, and reduced improvement in Oswestry Disability Index (ODI) score while having similar improvement in modified Japanese Orthopedic Association score. A T1S cutoff of 29.5° could significantly predict increased LOCL and worse ODI scores [Figure 2] and [Figure 3].{Figure 2}{Figure 3}

Thus, T1S has emerged as a robust preoperative predictor of LOCL following laminoplasty. However, differences in outcomes seen in patients with similar preoperative T1S could not be adequately explained with the established parameters, with higher C2-C7 SVA nonuniformly predicting LOCL in patients with lower preoperative T1S.[7] Hence, other objective parameters need to be investigated in this subset of patients.

DER is a relatively newer radiologic parameter that could predict postoperative LOCL and functional outcomes.[3] DER is the difference between neutral CA and extension CA. It is thus a marker of the functional reserve of the PMLC to produce extension. It has been postulated to dynamically interact with preoperative T1S and CA – a higher preoperative T1S produces higher anatomic demands for extension and patients with higher T1S but normal CA or C2-C7 SVA thus are using more of their functional reserve in normal conditions to maintain lordosis. Conceivably, the patient most vulnerable to developing postoperative LOCL would be ones with a higher preoperative T1S and low DER.

A study investigating DER in this context included 121 patients undergoing laminoplasty for OPLL or CSM.[3] Preoperative CA, T1S, and DER could predict LOCL. Preoperative T1S and C2-C7 SVA could predict worse ODI scores. Based on ROC curve analysis, a classification system was developed for predicting the preoperative risk of LOCL based on T1S, CA, and DER. Patients with high T1S and low DER were most vulnerable to developing LOCL and vice versa.[3] DER thus predicted LOCL in patients with similar T1S.

Delta angle (DA) is a parameter which objectively depicts the compensation in C2-C7 SVA in patients with high T1S in resting state.[8] It is thus an indicator of the effectiveness of DER in maintaining lordosis at rest. It was originally described in the context of cervical spine deformity correction. Its role in predicting LOCL is yet to be majorly investigated.

In summary, although cervical laminoplasty is an effective and physiologically sound method of dealing with CSM/OPLL, it can also cause LOCL. It is thought to happen due to disruption of PMLC generated compensatory mechanisms for maintaining cervical lordosis; thus, predictably arising in patients with preexisting high anatomic demand represented as high preoperative T1S. Patients with similar anatomic demand, i.e., similar T1S can have different degrees of LOCL based upon their functional reserve to combat the resultant kyphotic deformity as signified by DER. Newer parameters such as DA could provide interesting insights and have not been extensively investigated. It is imperative for spine surgeons to preoperative look for all these sagittal balance parameters before subjecting the patient for cervical laminoplasty. A simple X-ray of cervical spine can provide valuable information which can help in predicting postoperative outcomes.

Acknowledgments

The author wishes to thank Dr. Ravi Sharma and Dr. Akshay Ganeshkumar of the Department of Neurosurgery, AIIMS, New Delhi, for the data collection and literature review for writing this editorial.

References

1Sharma R, Borkar SA, Goda R, Kale SS. Which factors predict the loss of cervical lordosis following cervical laminoplasty? A review of various indices and their clinical implications. Surg Neurol Int 2019;10:147.
2Borkar SA, Sreenivasan R, Sharma R, Sinha S, Joseph SL, Garg A, et al. Cervical rotation before and after hinge-door cervical laminoplasty for cervical spondylotic myelopathy. J Craniovertebr Junction Spine 2019;10:114-8.
3Sharma R, Borkar S, Katiyar V, Goda R, Phalak M, Joseph L, et al. Interplay of dynamic extension reserve and T1 slope in determining the loss of cervical lordosis following laminoplasty: A novel classification system. World Neurosurg 2020;136:e33-40.
4Wang Z, Xu JX, Liu Z, Li RY, Wang ZW, Chang HR, et al. Spino cranial angle as a predictor of loss of cervical lordosis after laminoplasty in patients with cervical myelopathy. BMC Surg 2021;21:291.
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8Goldschmidt E, Angriman F, Agarwal N, Trevisan M, Zhou J, Chen K, et al. A new piece of the puzzle to understand cervical sagittal alignment: Utilizing a novel angle δ to describe the relationship among T1 vertebral body slope, cervical lordosis, and cervical sagittal alignment. Neurosurgery 2020;86:446-51.