From Mechanobiology to Mechanical Repair Strategies: A Bibliometric Analysis of Biomechanical Studies of Intervertebral Discs

Figures & data

Table 1 Search Strategy Used to Identify Original Papers of IVD Biomechanics in the Web of Science Core Collection

Category	Search Field	Search String
Intervertebral discs	TI	((disc OR disk) AND (intervertebral OR lumbar OR cervical OR thoracic OR degenerat* OR herniat*)) OR (“annulus fibrosus” OR “nucleus pulposus” OR endplate)
	OR
	AK	((disc OR disk) AND (intervertebral OR lumbar OR cervical OR thoracic OR degenerat* OR herniat*)) OR (“annulus fibrosus” OR “nucleus pulposus” OR endplate)
	OR
	KP	((disc OR disk) AND (intervertebral OR lumbar OR cervical OR thoracic OR degenerat* OR herniat*)) OR (“annulus fibrosus” OR “nucleus pulposus” OR endplate)
AND
Biomechanics	TI	(biomechanic* or mechanic* or finite element)
	OR
	AK	(biomechanic* or mechanic* or finite element)
	OR
	KP	(biomechanic* or mechanic* or finite element)

Note: Asterisk *is a search wildcard of Web of Science representing any group of characters.

Abbreviations: TI, title; AK, author keyword; KP, keyword plus.

Figure 1 Flowchart of literature selection in this study.

Figure 2 Trends of paper counts of IVD biomechanics. Each blue bar represents how many papers in IVD biomechanics were published each year. The trend of publications is represented by the red line, where the nodes were calculated by average count of two adjacent years.

Table 2 Top 10 Original Papers in IVD Biomechanics with the Highest Annual Average Citation Counts

Papers	Total Citations	Average per Year
Wilke et al. Spine. 1999^Citation9	903	37.63
Vergroesen et al. Osteoarthritis Cartilage. 2015^Citation16	292	36.5
Eck et al. Spine. 2002^Citation57	491	23.38
Adams et al. Spine. 2000^Citation54	451	19.61
Dreischarf et al. J Biomech. 2014^Citation28	176	19.56
Iatridis et al. Spine J. 2013^Citation26	177	17.7
Nerurkar et al. Nat Mater. 2009^Citation44	245	17.5
Adams et al. J Bone Joint Surg Br. 1996^Citation53	469	17.37
Norman et al. Clin Biomech. 1998^Citation67	403	16.12
Sato et al. Spine. 1999^Citation55	373	15.54

Table 3 Largest Clusters in the Co-Citation Network

Cluster ID	Size	Silhouette	Optimal Labels (LLR, P value)	Most Relevant Citer	Average Year
0	148	0.918	Annulus fibrosus tissue engineering (566.81, 0.0001)	Iatridis et al (2013)^Citation26	2007
1	144	0.825	Micromechanical environment (542.97, 0.0001)	Setton et al (2004)^Citation27	2000
2	118	0.828	Ovine lumbar (487.96, 0.0001)	Casaroli et al (2017)^Citation68	2012
3	117	0.905	Mechanical evaluation (227.49, 0.0001)	McNally et al (2002)^Citation69	1999
4	107	0.922	Intervertebral disc (610.11, 0.0001)	Noailly et al (2012)^Citation70	2006
5	99	0.898	Digital volume correlation (492.17, 0.0001)	Tamoud et al (2021)^Citation71	2017
6	97	0.937	Herniation risk (651.98, 0.0001)	Fujii et al (2020)^Citation35	2015
7	62	0.973	Total disc arthroplasties (395.63, 0.0001)	Li et al (2017)^Citation72	2014
8	55	0.963	Induced volume change (66.66, 0.0001)	Pritchard S (2002)^Citation73	1999
9	47	0.952	Human cadaveric spine model (157.73, 0.0001)	Huang RC (2005)^Citation74	2001

Abbreviations: ID, identification; LLR, log-likelihood ratio.

Figure 3 Co-citation network of the references and its clustering. Nodes in the network represent references, and their size indicates citation counts contributed by IVD biomechanical studies. A node may have a number of rings with different colors, which means that they were cited in different time slices.²³ Connections represent co-citation relationships.

Table 4 References Most Highly Cited by Papers of IVD Biomechanics

References	Citation Counts	Cluster ID
Newell et al. J Mech Behav Biomed. 2017^Citation5	50	5
Dreischarf et al. J Biomech. 2014^Citation28	44	2
Rohlmann et al. J Biomech. 2006^Citation29	43	0
Schmidt et al. Clin Biomech. 2006^Citation64	40	0
Vergroesen et al. Osteoarthr Cartilage. 2015^Citation16	40	6
Goel et al. Spine. 2005^Citation59	35	4
Nerurkar et al. J Biomech. 2010^Citation39	32	0
Iatridis et al. Spine J. 2013^Citation26	32	6
Schmidt et al. J Biomech. 2010^Citation75	31	0
Guerin et al. J Biomech. 2006^Citation76	29	0

Table 5 Top 10 References with the Strongest Citation Bursts

References	Cluster ID	Strength	Start	End	2000–2022
Newell et al. J Mech Behav Biomed. 2017^Citation5	5	23.75	2018	2022
Dreischarf et al. J Biomech. 2014^Citation28	2	19.74	2015	2019
Rohlmann et al. J Biomech. 2006^Citation29	0	19.67	2007	2011
Vergroesen et al. Osteoarthr Cartilage. 2015^Citation16	6	18.81	2017	2020
Schmidt et al. Clin Biomech. 2006^Citation64	0	18.29	2007	2011
Goel et al. Spine. 2005^Citation59	4	16.88	2006	2010
Iatridis et al. Spine J. 2013^Citation26	6	14.81	2014	2018
Nerurkar et al. J Biomech. 2010^Citation39	0	14.42	2011	2015
Galbusera et al. J Mech Behav Biomed. 2011^Citation30	2	14.09	2013	2016
OConnell et al. J Mech Behav Biomed. 2011^Citation31	2	14.09	2013	2016

Note: In the right-most column, the color represents the strength of the citation burst (red, strong burst; green, weak burst).

Figure 4 Citation bursts in the co-citation network. Red rings around the nodes represent the years when citation bursts can be found.

Table 6 References with the Highest Betweenness Centrality in the Co-Citation Network

References	Cluster ID	Centrality
MacLean et al. J Orthop Res. 2005^Citation32	1	0.22
Hsieh et al. Spine. 2009^Citation77	0	0.13
Iatridis et al. Spine J. 2013^Citation26	6	0.12
Elliott et al. J Biomech Eng-T ASME. 2001^Citation14	1	0.12
Mcnally et al. Spine. 1996^Citation78	3	0.12
Adams et al. Spine. 2000^Citation54	3	0.10
Nerurkar et al. Nat Mater. 2009^Citation44	0	0.10
Guilak et al. Spine. 1999^Citation52	1	0.10
Holzapfel et al. Biomech Model Mechan. 2005^Citation33	0	0.10
Olmarker et al. Spine. 1995^Citation79	3	0.10

Figure 5 Nodes positioned between clusters #0 and #1. There were five nodes with highest betweenness centrality highlighted by purple rings, where the thickness indicated the strength of betweenness centrality. Specifically, MacLean et al (2005)³² and Holzapfel et al (2005)³³ were positioned between clusters #1 and 0, which are more likely to provide insights into topics evolution or emerging trends, while the other highlighted nodes were highly connected to other nodes within the same cluster, which may make them less important than the former. (A) Spotlight model of the co-citation network, which highlights nodes with high betweenness centrality. Close-ups of MacLean et al (2005)³² (B) and Holzapfel et al (2005)³³ (C), which are positioned between clusters #0 and #1.

Table 7 Top 10 Authors with the Highest Citation Counts Contributed by Papers of IVD Biomechanics

Rank	Up to Jan 2022	Jan 2002–Dec 2006	Jan 2007–Dec 2011	Jan 2012–Dec 2016	Jan 2017–Dec 2021
1	Adams MA (917)	Adams MA (91)	Adams MA (196)	Adams MA (258)	Adams MA (267)
2	Panjabi MM (747)	Panjabi MM (84)	Panjabi MM (165)	Wilke HJ (229)	Wilke HJ (238)
3	Wilke HJ (692)	Iatridis JC (71)	Goel VK (149)	Panjabi MM (217)	Schmidt H (234)
4	Iatridis JC (611)	Goel VK (65)	Iatridis JC (147)	Iatridis JC (181)	Panjabi MM (201)
5	Goel VK (562)	Shiraziadl A (63)	Wilke HJ (146)	Schmidt H (153)	Iatridis JC (187)
6	Urban JPG (500)	Nachemson A (60)	Urban JPG (102)	Rohlmann A (150)	Urban JPG (149)
7	Schmidt H (473)	Urban JPG (58)	Nachemson A (100)	Urban JPG (146)	Oconnell GD (147)
8	Nachemson A (430)	Wilke HJ (57)	Rohlmann A (98)	Goel VK (142)	Goel VK (140)
9	Shiraziadl A (416)	White AA (46)	Natarajan RN (89)	Oconnell GD (100)	Rohlmann A (137)
10	Rohlmann A (406)	Lotz JC (44)	Schmidt H (84)	Nachemson A (99)	Shiraziadl A (117)

Note: Data are presented as “first or corresponding author (citation count in corresponding time slice)”.

Table 8 Top 10 Most Productive Journals in IVD Biomechanics

Journal	Count (%)	IF (2020)	JCR (Rank/Category)
Spine	414 (12.98%)	3.468	Q1/Orthopedics Q2/Clinical Neurology
J Biomech	208 (6.52%)	2.712	Q3/Biophysics Q3/Engineering, Biomedical
Eur Spine J	158 (4.96%)	3.134	Q2/Orthopedics Q3/Clinical Neurology
J Biomech Eng-T ASME	103 (3.23%)	2.097	Q3/Engineering, Biomedical Q4/Biophysics
Clin Biomech	97 (3.04%)	2.063	Q3/Engineering, Biomedical Q3/Orthopedics
Spine J	86 (2.70%)	4.166	Q1/Orthopedics Q2/Clinical Neurology
J Orthop Res	84 (2.63%)	3.494	Q1/Orthopedics
J Mech Behav Biomed Mater	79 (2.48%)	3.902	Q2/Engineering, Biomedical Q2/Materials Science, Biomaterials
Comput Methods Biomech Biomed Engin	52 (1.63%)	1.763	Q4/Computer Science, Interdisciplinary Applications Q4/Engineering, Biomedical
J Neurosurg Spine	46 (1.44%)	3.602	Q1/Surgery Q2/Clinical Neurology

Abbreviations: IF, impact factor; JCR, journal citation report.

Figure 6 Top 20 journals with the most citations contributed by papers of IVD biomechanics in each 5-year slice. The fluctuation of top 10 journals with the most citations were presented. The gray straight line showed the ranking change of a certain journal in each 5-year slice. Spine, Eur Spine J, and J Biomech were the journals cited most by papers in IVD biomechanics in each time slice.

Table 9 Most Productive Countries/Regions in Two Recent 5-Year Time Slices

2012–2016		2017–2021
Countries/Regions	Paper Counts	Countries/Regions	Paper Counts
United States	336	United States	293
China	118	China	275
Canada	85	Germany	81
Germany	74	Canada	60
England	56	England	58
Netherlands	47	Australia	47
Switzerland	45	Switzerland	43
South Korea	43	France	34
Taiwan	35	Netherlands	33
Italy	33	India	32

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