Effects on inadvertent endplate fracture following lateral cage placement on range of motion and indirect spine decompression in lumbar spine fusion constructs: A cadaveric study

Brandon G. Santoni; Gerald E. Alexander; Aniruddh Nayak; Andres Cabezas; German A. Marulanda; Ryan Murtagh; Antonio E. Castellvi

doi:10.1016/j.ijsp.2013.09.001

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Fig. 1
Radiographic representative images of 2 endplate fractures sustained during lateral interbody cage implantation.
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Fig. 2
Test setup for pure moment (A) and cyclic (B) loading of the instrumented lumbar spine fusion constructs.
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Fig. 3
Sagittal CT images illustrating posterior disc height (DH), foraminal area (FA), and canal area (CA) measurements. Disc height measurements were made in the sagittal plane. Canal area was measured at the level of the disc for all instrumented levels.

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Table 1

Bone quality, measured cage subsidence, and cage dimensions in levels with endplate fracture

	L1-L4 BMD (g/cm²)	T-Score and WHO classification	Interbody cage subsidence (mm)			Cage height (mm)	Cage dimensions (w × l) (mm)

			Anterior	Posterior	Average
Pedicle screw/rod
Inferior endplate at L4-L5	0.901	−2.7 Osteoporotic	5.7	7.2	6.5	10	18 × 55
Lateral plate/screw
^AInferior endplate at L3-L4	1.008	−1.5 Osteopenic	2.7	3.3	3.0	10	18 × 55
Inertior endplate at L3-L4	0.807	−3.5 Osteoporotic	5.7	10.9	8.3	12	18 × 55
Superior endplate at L4-L5	1.494	2.4 Normal	2.4	2.0	2.2	12	18 × 55
^BInferior endplate at L3-L4	0.939	−2.1 Osteopenic	3.4	4.0	3.7	10	18 × 55

Abbreviations: BMD, bone mineral density; WHO, World Health Organization.

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Table 2

ROM results for specimens with endplate fracture subsequent to interbody cage implantation

Endplate fracture location and level	Range of motion (degree)

	F/E			LB			AR

	Intact XLIF Percentage reduction (%)			Intact XLIF Percentage reduction (%)			Intact XLIF Percentage reduction (%)
Pedicle screw/rod Inferior endplate at L4-L5	8.3	5.7	32.3	12.8	5.0	61.1	7.8	6.3	19.5
	^*PSR groupavg.			^*PSR groupavg.			^*PSR groupavg.

	n = 17 levels		85.4	n = 17 levels		91.3	n = 17 levels		64.0
Lateral plate/screw
^AInferior endplate at L3-L4	7.6	11.1	−45.7	7.5	13.4	−77.8	1.7	3.6	−111.6
Inertior endplate at L3-L4	11.1	9.1	17.5	11.4	12.9	−12.9	3.3	2.7	20.2
Superior endplate at L4-L5	16.5	15.6	5.8	19.5	8.8	54.7	5.1	7.2	−42.4
^BInferior endplate at L3-L4	9.8	5.5	44.5	15.5	7.1	54.1	8.6	3.6	58.0
Average	11.3	10.3	5.5	13.5	10.6	4.5	4.7	4.3	−19.0
	^*ALP group avg.			^*ALP group avg.			^*ALP group avg.

	n = 14 levels		49.5	n = 14 levels		67.3	n = 14 levels		48.2

Abbreviations:avg., average; XLIF, extreme lateral interbody fusion.
↵* Average ROM for the respective treatments (PSR and ALP) in specimens with intact endplates.

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Table 3

Cage motion results for pedicle/screw rod and anterior-lateral plate specimens with endplate fracture during interbody cage placement

Endplate fracture location and level	Lateral cage translation (mm)

	F/E			LB			AR

	A-P	M-L	I-S	A-P	M-L	I-S	A-P	M-L	I-S
Pedicle screw/rod Inferior endplate at L4-L5	0.5	0.1	0.3	0.4	0.1	0.5	3.3	1.2	1.0
	^*PSR groupavg.(StDev)

	n = 17 levels
	0.4	0.1	0.2	0.2	0.1	0.2	0.8	0.3	0.2
	(0.1)	(0.1)	(0.1)	(0.1)	(0.1)	(0.2)	(0.4)	(0.3)	(0.1)
Lateral plate/screw
^AInferior endplate at L3-L4	0.1	0.1	0.1	3.2	0.5	1.8	0.5	0.2	0.2
Inferior endplate at L4-L5	0.1	0.0	0.1	0.2	0.0	0.2	0.4	0.1	0.3
Superior endplate at L4-L5	0.3	0.1	0.7	0.4	0.8	2.1	2.1	1.5	0.5
^BInferior endplate at L3-L4	0.5	0.1	0.0	0.2	0.1	0.0	0.7	0.2	0.2
	^*ALP groupavg.(StDev)

	n = 14 levels
	0.3	0.1	0.2	0.2	0.2	0.2	0.8	0.2	0.4
	(0.2)	(0.1)	(0.4)	(0.1)	(0.4)	(0.2)	(1.0)	(0.3)	(0.4)

Abbreviations: avg., average; StDev, standard deviation. Lateral cage translations were measured during cyclic loading along theanterior-posterior (A-P), medial-lateral (M-L), and inferior-superior (I-S) axes for each loading mode.
↵* Average cage translations for the respective treatments (PSR and ALP) inspecimens with intact endplates.

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Table 4

Radiographic indirect decompression results for pedicle screw/rod and anterior-lateral plate specimens with endplate fracture subsequent to lateral cage implantation

Endplate fracture location and level	Radiographic metric

	Posterior disc height (DH, mm)			Foraminal area (FA, mm²)			Canal area (CA, mm²)

	Intact XLIF Percentage increase (%)			Intact XLIF Percentage increase (%)			Intact XLIF Percentage increase (%)
Pedicle screw/rod Inferior endplate at L4-L5	7.0	9.7	38.1	112.0	154.0	37.5	108.0	161.0	49.1
	^*PSR group avg.			^*PSR group avg.			^*PSR group avg.

	n = 17 levels		61.8	n = 17 levels		62.0	n = 17 levels		34.5
Lateral plate/screw
^AInferior endplate at L3-L4	6.0	4.0	−33.3	100.5	92.0	−8.5	177.0	183.0	3.4
Inertior endplate at L4-L5	5.0	7.0	40.0	117.5	170.0	44.7	162.5	205.5	26.5
Superior endplate at L4-L5	5.0	7.7	53.4	152.3	226.0	48.4	131.0	189.0	44.3
^BInferior endplate at L3-L4	8.0	13.0	62.5	119.5	193.0	61.5	128.0	173.5	35.5
	^*ALP group avg.			^*ALP group avg.			^*ALP group avg.

	n = 14 levels		37.6	n = 14 levels		43.4	n = 14 levels		38.1

Abbreviations: avg., average; XLIF, extreme lateral interbody fusion.
↵* Average radiographic measures for the respective treatments (PSR and ALP) in specimen swith intact endplates.