Significance of flexion range of motion as a risk factor for kyphotic change after cervical laminoplasty

Change of cervical flexion range of motion influences postoperative sagittal alignment of the cervical spine after laminoplasty

OBJECTIVE

The relationships between preoperative cervical spine range of motion (ROM) and postoperative cervical sagittal alignment (CSA), and clinical outcomes after laminoplasty (LMP) have been widely studied. However, the impact of ROM changes on postoperative CSA and clinical outcomes after LMP remains unclear. Herein, patients with cervical spondylotic myelopathy (CSM) were retrospectively analyzed to explore the association between postoperative cervical ROM changes and CSA and surgical outcomes.

METHODS

Patients who underwent cervical LMP at our hospital between January 2019 to June 2022 were retrospectively reviewed. CSA parameters were measured before the surgery and at the final follow-up. Loss of cervical lordosis (LCL) was defined as preoperative cervical lordosis (CL) - postoperative CL. An increase in the cervical sagittal vertical axis (I-cSVA) was defined as postoperative cervical sagittal vertical axis (cSVA) - preoperative cSVA. We defined the changes in cervical flexion range of motion (△Flex ROM, preoperative Flex ROM minus postoperative Flex ROM) > 10° as L- Flex ROM group, and △Flex ROM ≤ 10° as S- Flex ROM group. Japanese Orthopedic Association (JOA) score and visual analog score (VAS) were used to assess the surgical outcomes.

RESULTS

The study comprised 74 patients and the average follow-up period was 31.83 months. CL, total ROM, and Flex ROM decreased and cSVA increased after cervical LMP. LCL and I-cSVA were positively correlated with △Flex. Multiple linear regression analysis showed that a decrease in the Flex ROM was a risk factor for LCL and I-cSVA after LMP. LCL and I-cSVA were higher in the L-Flex ROM group than in the S-Flex ROM group. Postoperative JOA and the JOA recovery rate were worse in the L-Flex ROM group than in the S-Flex ROM group.

CONCLUSIONS

Cervical total and Flex ROM decreased after cervical LMP. The reduction of Flex ROM was associated with LCL and I-cSVA after surgery. The preservation of cervical Flex ROM helps maintain CSA after LMP. Therefore, more attention should be paid to maintaining cervical ROM to obtain good CSA and surgical effects after cervical LMP.

Greater cervical kyphosis during flexion increases the risk of kyphotic deformity after laminoplasty in patients with cervical spondylotic myelopathy

Kyphotic deformity following the loss of cervical lordosis can lead to unfavourable neurological recovery after cervical laminoplasty (CLP); therefore, it is essential to identify its risk factors. Recent studies have demonstrated that the dynamic parameters of the cervical spine, based on baseline flexion/extension radiographs, are highly useful to estimate the loss of cervical lordosis after CLP. However, it remains unclear whether such dynamic parameters can predict kyphotic deformity development after CLP. Hence, the present study aimed to investigate whether the dynamic parameters could predict kyphotic deformity in patients with cervical spondylotic myelopathy (CSM) after CLP. This retrospective study included 165 patients, consisting of 10 and 155 patients with and without cervical kyphosis of C2-C7 angle ≤ -10° at the final follow-up period, respectively. Among the static and dynamic parameters of the cervical spine, greater cervical kyphosis during flexion (fC2-C7 angle) demonstrated the best discrimination between these two cohorts, with an optimal cutoff value of -27.5°. Meanwhile, greater gap range of motion (gROM = flexion ROM - extension ROM ) had the highest ability to predict a loss of ≥ 10° in C2-C7 angle after CLP, with an optimal cutoff value of 28.5°. This study suggests that in patients with CSM, fC2-C7 angle ≤ -25° on baseline radiographs is a potential risk for kyphotic deformity after CLP. In clinical practice, the patients with this criterion (fC2-C7 angle ≤ -25°) along with gROM ≥ 30° are at high risk of developing significant kyphotic deformity after CLP.

Preoperative Cervical Range of Motion in Flexion as a Risk Factor for Postoperative Cervical Sagittal Imbalance After Laminoplasty

STUDY DESIGN

Retrospective study.

OBJECTIVE

To investigate factors associated with cervical sagittal imbalance (CSI) after cervical laminoplasty (LMP).

SUMMARY OF BACKGROUND DATA

Preoperative dynamic cervical sagittal alignment is an important predictor for changes in cervical sagittal alignment and clinical outcomes after LMP. However, the impact of preoperative dynamic cervical sagittal alignment on postoperative changes in the cervical sagittal vertical axis (cSVA) after LMP remains unclear. We hypothesized that preoperative cervical flexion and extension function are associated with the changes in cSVA and clinical outcomes and found potential risk factors for post-LMP CSI.

PATIENTS AND METHODS

Patients undergoing LMP at a single institution between January 2019 and December 2021 were retrospectively reviewed. The average follow-up period was 19 months. The parameters were collected before the surgery and at the final follow-up. We defined the changes in cSVA (△cSVA) ≤ -10 mm as the improvement group, -10 mm < △cSVA ≤ 10 mm as the stable group, and △cSVA > 10 mm as the deterioration group. Multivariate logistic regression was used to evaluate factors associated with postoperative CSI. The χ 2 test was used to compare categorical data between groups. T tests, analysis of variance, Kruskal-Wallis tests, and Mann-Whitney Wilcoxon tests were used to assess the differences between radiographic and clinical parameters among groups. A receiver operating characteristic curve analysis was used to identify optimal cutoff values.

RESULTS

The study comprised 102 patients with cervical spondylotic myelopathy. The Japanese Orthopedic Association recovery rate was better in the improvement group and a significant aggravation in neck pain was observed in the deterioration group after surgery. Cervical Flex range of motion (ROM; spine range of flexion) was significantly higher in the deterioration group. The multivariate logistic regression model suggested that greater Flex ROM and starting LMP at C3 were significant risk factors for postoperative deterioration of cervical sagittal balance. Receiver operating characteristic curves showed that the cutoff value for preoperative Flex ROM was 34.10°.

CONCLUSION

Preoperative dynamic cervical sagittal alignment influences postoperative cervical sagittal balance after LMP. Cervical LMP should be carefully considered for patients with a preoperative high Flex ROM, as CSI is likely to occur after surgery.

LEVEL OF EVIDENCE

Level 3.

Favorable cervical extension capacity preventing loss of cervical lordosis after laminoplasty due to spontaneous restoration of initial lordosis

BACKGROUND CONTEXT

Cervical laminoplasty is a common approach for the treatment of multilevel cervical spondylotic myelopathy (CSM). Postoperative loss of cervical lordosis (LCL) was associated with lower extension motion of the cervical spine before laminoplasty.

PURPOSE

To analyze the possible causes of preoperative cervical extension capacity affecting LCL after laminoplasty by evaluating the changes in cervical lordosis (CL) at different stages.

STUDY DESIGN/SETTING

Retrospective study.

PATIENT SAMPLE

Seventy-two patients undergoing laminoplasty due to multilevel CSM.

OUTCOME MEASURES

Radiographic parameters included CL, extension CL (eCL), flexion CL (fCL), range of motion (ROM), extension ROM (eROM), flexion ROM (fROM) and LCL. Clinical outcomes were assessed using the Japanese Orthopedic Association (JOA) and neck disability index (NDI) score.

METHODS

The data were recorded before surgery and at 3- and 24-month follow-up. All patients completed a cervical extension test preoperatively. A receiver operating characteristic (ROC) curve of eROM was constructed to discriminate the patients with and without postoperative kyphotic deformity.

RESULTS

According to the optimal cut-off value of eROM, the patients were divided into two groups: extension group (eROM≥9.3°) and control group (eROM<9.3°). The radiographic outcomes demonstrated no significant differences in CL, eCL, fCL and ROM between the two groups. Both eROM and fROM were significantly different in the two groups. There was a significant change in CL in the extension group at 3-month follow-up and in the control group at 24-month follow-up. The extension group exhibited significantly lower LCL compared with the control group at follow-up. No significant difference between the two groups was noted in the JOA recovery rate, while the NDI score was significantly different at 24-month follow-up. The positivity ratio of the extension test was significantly greater in the extension group than that in the control group.

CONCLUSIONS

eROM in patients with favorable preoperative cervical extension capacity (eROM≥9.3°) consisted of the actual extension capacity and compensatory flexion. The cervical alignment would be spontaneously restored to its initial lordosis in the short term after laminoplasty. These patients had no substantial LCL at 24-month follow-up and would be good candidates for laminoplasty.

Assessing Range of Motion Gap in Circumferential Surgery for Cervical Myelopathy due to Ossification of the Posterior Longitudinal Ligament

OBJECTIVE

Only a few studies have investigated the gap range of motion (gROM) in cervical myelopathy or deformity caused by ossification of the posterior longitudinal ligament (OPLL). The aim of this study is to investigate the correlation between the individual gROM and the postoperative clinical outcomes of patients with OPLL.

METHODS

Consecutive patients of cervical myelopathy caused by OPLL were analyzed retrospectively. The clinical outcomes were evaluated using Visual Analogue Scale scores of the neck and arm pain and the Japanese Orthopaedic Association scores. Radiologic measurements included flexion ROM (fROM), which was defined as the difference of cervical lordosis in flexion and neutral positions, extension ROM (eROM), defined as the difference between neutral and extension positions, and gROM, defined as the difference between fROM and eROM. Patients were grouped by the values of gROM, and comparisons of all outcomes were made between the groups.

RESULTS

A total of 42 patients underwent surgery. The patients with greater gROM did not differ from those with smaller gROM by demographic characteristics. During follow-up (mean 45.8 months), both groups had similar improvements, but the C5 palsy rates were higher in the greater gROM group than in the smaller gROM group (71% and 22%, P < 0.05).

CONCLUSIONS

Simultaneous circumferential decompression and fixation is an effective surgical option for patients with cervical myelopathy caused by OPLL. A higher rate of postoperative C5 palsy was observed in the patients with greater gROMs after surgery, although all patients presented with similar clinical improvements.

Preoperative Range of Motion in Extension May Influence Postoperative Cervical Kyphosis After Laminoplasty

STUDY DESIGN

Retrospective observational study.

OBJECTIVE

The objective of this study was to investigate factors associated with cervical kyphosis after laminoplasty.

SUMMARY OF BACKGROUND DATA

Many factors are reportedly associated with the deterioration of cervical curvature after laminoplasty, including cervical lordosis angle, cervical spine range of motion (ROM), T1 slope, and C2-C7 sagittal vertical axis. Postlaminoplasty kyphosis or deterioration of cervical curvature is likely caused by multiple factors. There is currently no consensus on these issues.

MATERIALS AND METHODS

Data of patients treated with laminoplasty for degenerative cervical myelopathy at our institution during 2008-2018 were reviewed. The following variables were collected for each patient: age and sex; follow-up time; surgery involving C3 (yes or no); surgery involving C7 (yes or no); distribution of segments operated on; number of laminae operated on; flexion, extension, and total ROM; cervical lordotic angle; longitudinal distance index; curvature index; C2-C7 sagittal vertical axis; and T1 slope. Logistic regression analysis was used to assess possible risk factors for postoperative kyphosis. Receiver operating characteristic curves were constructed to determine the cutoff values of risk factors.

RESULTS

The study cohort comprised 151 patients. Logistic regression analysis indicated that sex, number of laminae operated on, and preoperative extension ROM were significantly associated with postoperative cervical kyphosis ( P <0.05). There was significantly greater postoperative kyphosis in women than in men; the more segments operated on, the greater the risk of postoperative kyphosis, and the larger the preoperative extension ROM, the lower the risk of postlaminoplasty kyphosis. Receiver operating characteristic curve analysis showed that the cutoff value for preoperative extension ROM is 22.1°.

CONCLUSIONS

Preoperative extension ROM may be associated with the development of postoperative kyphosis. The cutoff value of preoperative extension ROM that suggested the prospect of postoperative kyphosis in our sample was 22.1°.

Effect of preoperative dynamic cervical sagittal alignment on the loss of cervical lordosis after laminoplasty

PURPOSE

Cervical laminoplasty (CLP) is a developed surgical procedure for the treatment of cervical spondylotic myelopathy (CSM), but only a few of those studies focus on preoperative dynamic cervical sagittal alignment and the study of different degrees of loss of cervical lordosis (LCL) is lacking. This study aimed to analyze patients who underwent CLP to investigate the effect of cervical extension and flexion function on different degrees of LCL.

METHODS

In this retrospective case-control study, we analyzed 79 patients who underwent CLP for CSM between January 2019 and December 2020. We measured the cervical sagittal alignment parameters on lateral radiographs (neutral, flexion, and extension positions) and used Japanese Orthopedic Association (JOA) score to assess clinical outcomes. We defined the extension ratio (EXR) as 100 × Ext ROM (cervical range of extension)/ROM (cervical range of motion). We observed the relationships between collected variables (demographic and radiological variables) and LCL. Patients were classified into the following three groups according to the LCL: stability group: (LCL ≤ 5°); mild loss group (5° < LCL ≤ 10°); and severe loss group (LCL > 10°). We compared the differences of collected variables (demographic, surgical and radiological variables) among the three groups.

RESULTS

Seventy-nine patients were enrolled (mean age 62.92 years; 51 men, 28 women) in the study. Among the three groups, cervical Ext ROM was the best in the stability group (p < 0.01). Compared with the stability group, range of flexion (Flex ROM) was significantly higher (p < 0.05) and EXR was significantly lower (p < 0.01) in the severe loss group. Compared with the severe loss group, JOA recovery rates were better (p < 0.01) in the stability group. Receiver-operating characteristic curve (ROC) analysis to predict LCL > 10° (area under the curve = 0.808, p < 0.001). The cutoff value for EXR was 16.80%, with sensitivity and specificity of 72.5% and 82.4%, respectively.

CONCLUSION

CLP should be carefully considered for patients with a preoperative low Ext ROM and high Flex ROM, as a significant kyphotic change is likely to develop after surgery. EXR is a useful and simple index to predict significant kyphotic changes.

Predictors for cervical kyphotic deformity following laminoplasty: a systematic review and meta-analysis

OBJECTIVE

Laminoplasty is a common treatment for cervical spondylotic myelopathy (CSM) and for ossification of the posterior longitudinal ligament (OPLL). However, approximately 21% of patients undergoing laminoplasty develop cervical kyphotic deformity (KD). Because of the high prevalence rate of KD, several studies have sought to identify predictors for this complication, but the findings remain highly inconsistent. Therefore, the authors performed a systematic review and meta-analysis to establish reliable preoperative predictors of KD.

METHODS

PubMed, Scopus, and Web of Science databases were used to systematically extract potential references. The first phase of screening required the studies to be written in the English language, involve patients treated for CSM and/or OPLL via laminoplasty, and report postoperative cervical KD. The second phase required the studies to provide more than 10 patients and include a control group. The mean difference (MD) and odds ratio (OR) were calculated for continuous and dichotomous parameters. Study quality was evaluated using the Newcastle-Ottawa Scale. CSM and OPLL patients were further assessed by performing subgroup analyses.

RESULTS

Thirteen studies comprising patients who developed cervical KD (n = 296) and no KD (n = 1254) after receiving cervical laminoplasty for CSM or OPLL were included in the meta-analysis. All studies were retrospective cohorts and were rated as high quality. In the combined univariate analysis of CSM and OPLL patients undergoing laminoplasty, statistically significant predictors for postoperative KD included age (MD 2.22, 95% CI 0.16-4.27, p = 0.03), preoperative BMI (MD 0.85, 95% CI 0.06-1.63, p = 0.04), preoperative C2-7 range of flexion (MD 10.42, 95% Cl 4.24-16.59, p = 0.0009), preoperative C2-7 range of extension (MD -4.59, 95% CI -6.34 to -2.83, p < 0.00001), and preoperative center of gravity of the head to the C7 sagittal vertical axis (MD 26.83, 95% CI 9.13-44.52, p = 0.003). Additionally, among CSM patients, males were identified as having a greater risk for postoperative KD (OR 1.73, 95% CI 1.02-2.93, p = 0.04).

CONCLUSIONS

The findings from this study currently provide the largest and most reliable review on preoperative predictors for cervical KD after laminoplasty. Given that several of the included studies identified optimal cutoff points for the variables that are significantly associated with KD, further investigation into the development of a preoperative risk scoring system that can accurately predict KD in the clinical setting is encouraged. PROSPERO registration no.: CRD42022299795 (https://www.crd.york.ac.uk/PROSPERO/).

Does the asymmetry and extension function of the preoperative cervical paraspinal extensor predict postoperative cervical sagittal deformity in patients who undergo modified laminoplasty?

BACKGROUND CONTEXT

A previous study found that the cross-sectional area (CSA) of the preoperative cervical paraspinal extensors (CPEs) was associated with loss of cervical lordosis after laminoplasty, while a recent study found that CPE asymmetry was associated with symptoms of degenerative cervical myelopathy. Whether preoperative CPE asymmetry can predict cervical sagittal deformity (CSD) after laminoplasty is unknown.

PURPOSE

To assess whether asymmetry, degree of degeneration, and extension function of the CPE can be used as predictors of postoperative CSD in patients who undergo laminoplasty.

STUDY DESIGN

A retrospective study.

PATIENT SAMPLE

From January 2017 to December 2019, 55 patients with multilevel cord compression and myelopathic symptoms were enrolled.

OUTCOME MEASURES

The visual analog scale (VAS), neck disability index (NDI), and modified Japanese Orthopedic Association (mJOA) were used to assess cervical spinal function and quality of life.

METHODS

From January 2017 to December 2019, 55 patients undergoing modified laminoplasty were included. The following parameters were measured preoperatively and 24 months postoperatively on X-ray: (1) C0-C2 Cobb angle; (2) C2-C7 Cobb angle (CL); (3) T1 slope (T1S); (5) C2-C7 sagittal vertical axis (SVA); (6) T1S minus CL; (7) Preoperative extension function: Extension CL minus Neutral CL (EF). Preoperative global alignment parameters: (8) spino cranial angle, (9) C7-S1 sagittal vertical axis (C7 SVA), (10) pelvic incidence, (11) lumbar lordosis, (12) thoracic kyphosis. (13) Preoperative CPE parameters: Summation of bilateral total cross-sectional area (STCSA), summation of bilateral total cross-sectional area ratio (STCSAR), total cross-sectional area asymmetry, summation of bilateral functional cross-sectional area of muscle (SFCSA), summation of bilateral functional cross-sectional area of muscle ratio (FCSAR), and functional cross-sectional area of muscle asymmetry (FCSAA). The VAS, mJOA, and NDI were used to evaluate cervical spine function and quality of life. Patients were divided into the CSD group and the non-deformed group (N-CSD) group postoperatively, and the parameters between the two groups were compared. The Pearson correlation coefficient was used to evaluate the relationship between the parameters, and multiple regression analysis and ROC curve analysis were used to determine the predictors and key values.

RESULTS

Compared with functional scores, mJOA in the CSD group was significantly lower than that in the N-CSD group, while NDI and VAS were significantly higher. Postoperative CL was significantly correlated with EF, SFCSA/STCSA (C3-C6), SFCSAR (C4 and C6), STCSAR (C6), and FSCAA (C6). T1S minus CL was significantly correlated with EF, SFCSA/STCSA (C3-4 and C6), SFCSAR (C4 and C6), STCSAR (C6) and FSCAA (C6). C2-7 SVA was significantly correlated with EF, SFCSAR (C4 and C6), STCSAR (C6), and FSCAA (C6). Multiple regression analysis showed that FCSAA (C6), SFCSAR (C6), SFCSAR (C4), and EF were significant predictors of postoperative CSD. ROC curve analysis showed that the optimal cutoff points were 18.405, 2.95, 4.47, and 11.96.

CONCLUSIONS

The present study found that preoperative extension dysfunction of CPEs, asymmetry at the C6 level cervical extensors, and cervical extensor CSAs without fatty infiltration at the C4 and C6 levels were associated with cervical sagittal imbalance after modified laminoplasty. These factors can be considered when future spine surgeons formulate surgical plans.

Segmental cervical instability does not drive the loss of cervical lordosis after laminoplasty in patients with cervical spondylotic myelopathy

BACKGROUND/CONTEXT

Kyphotic deformity after cervical laminoplasty (CLP) often leads to unfavorable neurological recovery due to insufficient indirect decompression of the spinal cord. Existing literature has described that segmental cervical instability is a contraindication for CLP because it is a potential risk factor for kyphotic changes after surgery; however, this has never been confirmed in any clinical studies.

PURPOSE

To confirm whether segmental cervical instability was an independent risk factor for postoperative kyphotic change and to examine whether segmental cervical instability led to poor neurological outcomes after CLP for cervical spondylotic myelopathy (CSM).

STUDY DESIGN/SETTING

A retrospective study PATIENT SAMPLE: Patients who underwent CLP for CSM between January 2013 and January 2021 with a follow-up period of ≥1 year were enrolled.

OUTCOME MEASURES

Cervical radiographic measurements including C2-C7 lordosis (C2-7 angle), cervical sagittal vertical axis, C7 slope, flexion range of motion (fROM) and extension ROM (eROM) were assessed using neutral and flexion-extension views. Segmental cervical instability was classified into anterolisthesis (AL) of ≥2 mm displacement, retrolisthesis (RL) of ≥2 mm displacement, and translational instability (TI) of ≥3 mm translational motion. The amount of C2-7 angle loss at the follow-up period compared to the preoperative measurements was defined as cervical lordosis loss (CLL). Neurological outcomes were assessed using the recovery rate of the Japanese Orthopedic Association score (JOA-RR).

METHODS

CLL was compared among patients with and without segmental cervical instability. Further, multiple linear regression model for CLL was built for the evaluation with adjustment of the reported risks, including cervical sagittal vertical axis, C7 slope, fROM, eROM, and patient age together with AL, RL, and TI, as independent variables. The JOA-RR was also compared between patients with and without segmental cervical instability.

RESULTS

A total of 138 patients (mean age, 68.7 years; 65.9% male) were included in the analysis. AL, RL, and TI were found in 12 (8.7%), 33 (23.9%), and 16 (11.6%) patients, respectively. Comparisons among the groups showed that AL led to greater CLL; however, RL and TI did not. Multiple linear regression analysis revealed that greater CLL is significantly associated with greater fROM and smaller eROM (regression coefficient [β]=0.328, 95% confidence interval: 0.178 to 0.478, p<.001; β=-0.372, 95% confidence interval: -0.591 to -0.153, p=.001, respectively). However, there were no significant statistical associations in the AL, RL, and TI. Whereas, patients with AL tended to exhibit lower JOA-RR than those without AL (37.8% vs. 52.0%, p=.108).

CONCLUSIONS

Segmental cervical instability is not the definitive driver for loss of cervical lordosis after CLP in patients with CSM; thus, is not a contraindication in and of itself. However, it is necessary to consider the indications for CLP, according to individual cases of patients with AL on baseline radiograph, which is a sign of poor neurological recovery.

Gap between flexion and extension ranges of motion: a novel indicator to predict the loss of cervical lordosis after laminoplasty in patients with cervical spondylotic myelopathy

OBJECTIVE

Kyphotic deformity resulting from the loss of cervical lordosis (CL) is a rare but serious complication after cervical laminoplasty (CLP), and it is essential to recognize the risk factors. Previous studies have demonstrated that a greater flexion range of motion (fROM) and smaller extension ROM (eROM) in the cervical spine are associated with the loss of CL after CLP. Considering these facts together, one can hypothesize that an indicator representing the gap between fROM and eROM (gROM) is highly useful in predicting postoperative CL loss. In the present study, the authors aimed to investigate the risk factors of marked CL loss after CLP for cervical spondylotic myelopathy (CSM), including the gROM as a potential predictor.

METHODS

Patients who had undergone CLP for CSM were divided into those with and those without a loss of more than 10° in the sagittal Cobb angle between C2 and C7 at the final follow-up period compared to preoperative measurements (CL loss [CLL] group and no CLL [NCLL] group, respectively). Demographic characteristics, surgical information, preoperative radiographic measurements, and posterior paraspinal muscle morphology evaluated with MRI were compared between the two groups. fROM and eROM were examined on neutral and flexion-extension views of lateral radiography, and gROM was calculated using the following formula: gROM (°) = fROM - eROM. The performance of variables in discriminating between the CLL and NCLL groups was assessed using the receiver operating characteristic (ROC) curve.

RESULTS

This study included 111 patients (mean age at surgery 68.3 years, 61.3% male), with 10 and 101 patients in the CLL and NCLL groups, respectively. Univariate analyses showed that fROM and gROM were significantly greater in the CLL group than in the NCLL group (40.2° vs 26.6°, p < 0.001; 31.6° vs 14.3°, p < 0.001, respectively). ROC curve analyses revealed that both fROM and gROM had excellent discriminating capacities; gROM was likely to have a higher area under the ROC curve than fROM (0.906 vs 0.860, p = 0.094), with an optimal cutoff value of 27°.

CONCLUSIONS

The gROM is a highly useful indicator for predicting a marked loss of CL after CLP. For CSM patients with a preoperative gROM exceeding 30°, CLP should be carefully considered, since kyphotic changes can develop postoperatively.

Nomogram for predicting kyphotic deformity after laminoplasty in cervical spondylotic myelopathy patients without preoperative kyphotic alignment

BACKGROUND

Kyphotic deformity occurrence after cervical laminoplasty is not rare. Several studies have emphasized the development of postoperative kyphotic deformity (PKD) will impair the functional outcome of cervical laminoplasty. We established and validated a nomogram prediction model for kyphotic deformity after laminoplasty in cervical spondylotic myelopathy patients (CSM) without preoperative kyphotic alignment.

METHODS

Preoperative and 1-year postoperative data of 369 patients who underwent single-door cervical laminoplasty (SDCL) at the author's hospital between July 2010 and February 2018 were collected. Using the least absolute shrinkage and selection operator (LASSO) method, significant parameters were selected to develop a nomogram prediction model. The prognostic performance of the model was evaluated using concordance index (C-index) and calibration curve. The discriminatory ability of the prediction model was evaluated by the area under (receiver operating characteristic) curve (AUC).

RESULTS

Of the 369 patients, 31 developed PKD in 1 year after the surgery. Using the LASSO regression, six significant variables composed the final model: age, C2-7 sagittal vertical axis, C7 slope, C2-7 angle, flexion range of motion and operation level were selected. The AUC of the nomogram was 0.771. The C-index for the prediction nomogram was 0.771 (95 % CI: 0.672-0.870). The calibration curve also indicated good consistency.

CONCLUSION

A nomogram for predicting PKD after SDCL was established and validated. For patients evaluated by this model with predictive high risk of developing postoperative kyphosis, an alternative approach to the subaxial cervical spine such as anterior surgery should be considered.