Table 7.

Cluster summary of co-citation network

Cluster ID	Size	Silhouette	Mean (Year)	Label (LLR)
0	69	0.925	2006	Spinal stenosis, sciatica
1	63	0.982	2009	Anterior cervical discectomy and fusion, clinical outcome
3	57	0.952	2002	Chronic low back pain, degenerative disc disease
5	22	0.968	2003	Cloward, nerve injury
6	21	0.991	2011	Spine Patient Outcomes Research Trial (SPORT), National Surgical Quality Improvement Project (NSQIP)
9	13	0.963	2010	Minimally invasive decompression, multicenter study
11	11	1	2005	Discogenic, Prospective randomized multicenter clinical study
14	6	0.995	2008	Biologics, extreme lateral interbody fusion

Silhouette is a parameter in CiteSpace software to analyze the clustering effect in terms of homogeneity of the network. A value closer to 1 means higher homogeneity and results more than 0.7 has high reliability.