Table 1.

Summary of clinical studies on statistic evaluation of the correlation between clinical factors and axial pain after laminoplasty

References	Clinical factors	Correlation description	Statistic analysis
Higashino et al. [6]	JOA recovery rate, C2–7 Cobb angle, ROM	Relationship between the recovery rate of the JOA score; the C2–7 angle, the ROM and AP was NS	NA
Hosono et al. [10]	The facet joint resection ratio	The average resection ratio between the groups with or without AP was NS	NA
Hyun et al. [11]	Postoperative ROM, interval changes in ROM	Relationship between AP NRS scores and ROM or interval changes in ROM was NS	Spearman rank correlation coefficients
Kang et al. [15]	ROM	Relationship between postoperative ROM and postoperative AP was NS	Pearson correlation coefficient test
Kato et al. [16]	Age (>63 years), preservation of muscles attached at C2 or C7, female, types of disease (CSM/OPLL), duration of symptoms, change of alignment, change of ROM, preoperative JOA and recovery rate, operation time and blood loss	Older age and preservation of paraspinal muscles attached at C2 each significantly decreased the risk of postoperative AP. But other factors were each unrelated to AP	Multivariate logistic regression analysis
Kawaguchi et al. [19]	Age, gender, types of disease (CSM/OPLL), pre- or postoperative JOA scores, operation time, and blood loss, number of bone graft, CPK activity, chin–chest distance, rotational neck ROM, number of fused laminae, neck ROM, open-door side or either hinge side	Operation time, chin–chest distance, the number of fused laminae between severe AS group and mild group was significantly different	t test with Welch’s correction
		But other factors were NS between the two groups. The AS area was not related to the open side or either hinge side
Kawakami et al. [20]	Preoperative instability, ROM	The prevalence of AS between patients with and without preoperative instability was NS	χ2 analysis and Student’s t test
		Relationship between postoperative ROM and postoperative AP was NS
Matsumoto et al. [26]	Lamina closure	AP score between the groups with or without lamina closure was NS	Unpaired t test
Nakama et al. [29]	IR in muscle strength, IR = post/pre	In men, the correlation between the IR in muscle strength and alleviation of the AP was strongly negative for extension and flexion. In women, the correlation was significant only for extensor strength	Spearman rank correlation coefficient
Ohnari et al. [30]	Age, sex, surgery time, duration of cervical orthosis, blood loss, reconstructive surgery of SSC muscle, preoperative AP	All the factors between postoperative AP group and no AP group was NS	Fisher exact test and Mann–Whitney U test
Okada et al. [31]	C2–7 Cobb angle	Relationship between positive change of Cobb angle and improvement in AP was minimally significant	Pearson correlation coefficient test
Sasai et al. [37]	The number of EBLP	The postoperative AS score significantly correlated with the numbers of EBLPs	Spearman rank correlation analysis
Yoshida et al. [47]	Age, pre- or postoperative JOA scores, preoperative AP, A–P canal diameter, JOA recovery rate, cervical disease (CSM/CDH/OPLL), cervical alignment	The recovery rate score between the worse than moderate AP and less than mild AP showed significant difference	Student’s t test with Welch’s correction
		But the age, A–P canal diameter, pre- or postoperative JOA scores between the two groups was NS. Relation between AP and cervical disease or cervical alignment was NS. The incidence of postoperative AP was significantly higher in patients beyond 70 years of age and who had preoperative AP

NA not available, AP axial pain, AS axial symptoms, NS not significant, CDH cervical disc herniation, ROM range of motion, IR improvement ratio, EBLP en bloc laminoplasty