Restoring Segmental Spinal Alignment in Mini-Open Lateral Spinal Deformity Surgery—Determiners of Radiographic Outcome

Alexander Spiessberger; Nicholas Dietz; Basil E. Gruter; Justin Virojanapa; Peter Hollis

doi:10.14444/8246

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Figure 1
(A and B) Pre- and postoperative whole spine x-ray images. The correction of coronal deformity can be appreciated. (C and D) Pre- and postoperative whole spine x-ray images in a patient with marked correction of sagittal alignment.
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Figure 2
Restoration of segmental sagittal profile. (A and B) Pre- and postoperative sagittal computed tomography (CT) images of the L3/4 disc space. Preoperatively, there was little loss of disc space height. The perioperative change of segmental sagittal Cobb angle was +3°. (C and D) Pre- and postoperative sagittal CT images of the L3/4 disc space in a patient with marked loss of disc space height. In this case, the perioperative gain in segmental lordosis was 5°.
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Figure 3
Foraminal decompression. (A and B) Pre- and postoperative sagittal views of the L2/3 neuroforamen. The superior articulating process causes significant foraminal stenosis preoperatively. Postoperatively, the SAP is displaced caudally, which leads to foraminal decompression. (C and D) Similarly, Pre- and postoperative views of a left-sided L4/5 foramen. Again, postoperative displacement of the SAP decompresses the neuroforamen. (E and F) Failure of indirect decompression. Even though the craniocaudal dimension of the neuroforamen significantly increases postoperatively, an osteophyte causes persistent nerve root compression.

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Table 1

Patient demographics and overview of surgical details (N = 49).

Demographic	Data
Age, y, mean (SD) (range)	68.7 (8.6) (39.9–84.7)
Sex, female/male	63%/37%
Fusion construct
Distribution of upper instrumented vertebra
T4	2%
T10	6%
T11	2%
T12	2%
L1	17%
L2	60%
L3	10%
Distribution of lower instrumented vertebra
L5^{^a}	60%
S1	35%
Pelvis	15%
No. of levels fused, mean (SD) (range)	4.3 (2.3) (3–15)
Operative complications
Seroma^{^b}	4%
Wound dehiscence	4%
Transient dysesthesia	18%
Transient hip flexor weakness	6%

↵a 4% of L4/5 underwent transforaminal lumbar interbody fusion.
↵b Occurring after open posterior stage of the surgery.

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Table 2

Radiographic measurements on whole spine standing x-rays before and after surgery.

Measurement	Mean (SD) (Range)	P value
C7SVA, mm		0.1
Preoperative	79.6 (63) (−43−254)
Postoperative	60 (51.8) (−26–217)
∆C7SVA	−33.6 (57.9) (−166–60)
TK, °		0.01
Preoperative	36.1 (15.4) (5–77)
Postoperative	43.8 (15) (21−91)
∆	4.2 (15.3) (−35–39)
LL, °		0.003
Preoperative	32.9 (15.9) (−14–78)
Postoperative	41.6 (12.4) (24–84)
∆	9.3 (10.5) (−4–46)
T10-L2 sag Cobb, °		0.8
Preoperative	3 (12.7) (−24–30)
Postoperative	2.3 (11.2) (−30–32)
∆	−1 (9.4) (-21–32)
PI, °	49 (10.7) (21–77)
PT, °		0.7
Preoperative	21.1 (9.6) (−4–54)
Postoperative	21.8 (7.3) (2–34)
∆	0.1 (10) (−28−26)
Degenerative scoliosis	Left convex 63%
Scoliotic apex level
L1	1%
L2	25%
L2/3	4%
L3/4	6%
L4	6%
Coronal Cobb, °		0.02
Preoperative	16.3 (12) (0−48)
Postoperative	10.8 (10.3) (0–45)
∆	−4.8 (8.4) (−24–30)
C7PL, mm		0.6
Preoperative	14.1 (15.1) (0–54)
Postoperative	12.9 (9.1) (0–28)
∆	−3.7 (15.3) (−45–26)

C7PL, C7 plumb line (coronal); C7SVA, C7 sagittal vertical axis; LL, lumbar lordosis; PI, pelvic incidence; PT, pelvic tilt; TK, thoracic kyphosis.

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Table 3

Radiographic measurements before and after surgery for each anatomic level.

	Mean (SD) (Range)
Measurement	L1/2	L2/3	L3/4	L4/5
Sagittal Cobb, °
Preoperative	−1.8 (5.6) (−11–13)	2.5 (4) (−6-16)	5.6 (4.9) (−5–21)	9.5 (5.7) (1–21)
Postoperative	2.2 (4.9) (−5–17)	5.2 (3.8) (0–18)	7.3 (4.4) (0–14)	11 (4.8) (3–24)
∆	4 (3.2) (0–11)	2.7 (3.4) (−5–10)	1.8 (4.2) (−10–14)	1.6 (4.6) (−7–17)
Coronal Cobb, °
Preoperative	5.5 (5.1) (0–16)	7.4 (5.8) (0–26)	5.8 (5.6) (0–23)	4.2 (3.8) (0–15)
Postoperative	4.2 (3.5) (0–11)	3.4 (3.8) (0–17)	3.3 (4) (0−20)	2.7 (2.2) (0–9)
∆	−1.3 (6) (−14−11)	−4 (4.6) (−14–6)	−2.4 (5.5) (−22–18)	4.4 (2.5) (−1–11)
Foraminal height, mm
Preoperative	15.2 (3.8) (11–23)	16.5 (4) (8−26)	15.7 (3.8) (8–24)	15.5 (3.6) (6–24)
Postoperative	18 (5.1) (11–30)	19.6 (4.4) (9–37)	19.3 (4) (8-32)	18.6 (3.5) (9–25)
∆	2.8 (2.6) (−1–7)	3.1 (3.2) (−2–16)	3.6 (3.5) (−3–14)	2.7 (4.7) (−16–13)
Foraminal width, mm
Preoperative	7.1 (2) (3-10)	8 (2) (5−13)	8.3 (1.6) (5–12)	8.5 (1.9) (5–14)
Postoperative	9.5 (3) (6−15)	9.4 (2.1) (5–14)	9.8 (1.9) (7–14)	9.8 (1.9) (6–13)
∆	2.4 (2.7) (−1–7)	1.4 (2.2) (−2–8)	1.4 (2.4) (−5–7)	1 (2.5) (−6–7)
Disc space height, mm
Preoperative	4 (3) (1−11)	5 (2.6) (1–11)	5.8 (2.9) (1–12)	6.5 (3) (2−13)
Postoperative	9.2 (2.2) (7–16)	9.8 (2) (7−15)	10.6 (1.5) (8–14)	10.9 (1.7) (8–16)
∆	5.2 (2.3) (−1–9)	4.8 (2.5) (−1–10)	4.7 (2.9) (0–11)	4.4 (2.5) (−1–11)

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Table 4

Correlation between baseline radiographic measurements and perioperative change in segmental sagittal Cobb angle.

Measurement	Unstandardized Coefficients		Standardized Coefficient		P Value
Measurement	B	Standard Error	Beta	t	P Value
Preoperative segmental sagittal Cobb angle, °	−0.4	0.1	−0.5	−5.7	0.01
Preoperative disc space height, mm	−0.2	0.1	−0.2	−1.7	0.09
Preoperative osteophytes grade^{^a}	−0.3	0.6	−0.05	−0.5	0.59
Preoperative facet joint degeneration grade^{^b}	−0.1	0.3	−0.02	−0.2	0.81
Anatomic level	0.8	0.4	0.2	1.9	0.06
Preoperative coronal Cobb angle, °	0.1	0.1	0.2	2.3	0.02

↵a Three grades: I, nonbridging disc space osteophytes; II, small bridging disc space osteophytes; III, ankylosed disc space.
↵b Three grades: I, nonbridging osteophytes of the facet joint; II, small bridging osteophytes of the facet joint; III, ankylosed facet joint.

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Table 5

Correlation between baseline radiographic measurements and perioperative change in neuroforaminal height.

	Unstandardized Coefficients		Standardized Coefficient		Significance
	B	Standard Error	Beta	t	Significance
Preoperative disc space height, mm	−0.1	.01	−0.04	−0.4	0.71
Preoperative osteophytes grade^{^a}	0.7	0.6	0.1	1.3	0.18
Preoperative foraminal height, mm	−0.3	0.1	−0.3	−2.7	0.01
Preoperative foraminal width, mm	0.2	0.2	0.1	0.9	0.36
Preoperative facet joint degeneration grade^{^b}	−0.1	0.3	−0.02	−0.2	0.81
Preoperative coronal Cobb angle, °	0.02	0.1	0.03	0.3	0.74
Implant position^{^c}	−0.3	0.6	-0.04	−0.5	0.65
Anatomic level	0.2	0.4	0.04	0.4	0.68

↵a Three grades: I, nonbridging disc space osteophytes; II, small bridging disc space osteophytes; III, ankylosed disc space.
↵b Three grades: I, nonbridging osteophytes of the facet joint; II, small bridging osteophytes of the facet joint; III, ankylosed facet joint.
↵c Location of the center of the interbody device in relation to 4 quadrants, which the disc space has been divided into on sagittal imaging (I anterior to IV posterior).

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Table 6

Correlation between baseline radiographic measurements and perioperative change in neuroforaminal width.

	Unstandardized Coefficients		Standardized Coefficient		Significance
	B	Standard Error	Beta	t	Significance
Preoperative disc space height, mm	−0.02	0.1	−0.02	−0.2	0.82
Preoperative osteophytes grade^{^a}	−0.6	0.3	−0.2	−1.8	0.08
Preoperative foraminal width, mm	−0.7	0.1	−0.5	−6.8	0.01
Preoperative facet joint degeneration^{^b}	0.4	0.2	0.2	1.8	0.08
Preoperative coronal Cobb angle, °	−0.01	0.03	−0.03	−0.4	0.73
Implant position^{^c}	−0.3	0.4	−0.1	−0.9	0.37
Anatomic level	−0.3	0.2	−0.1	−1.1	0.26

a Three grades: I, nonbridging disc space osteophytes; II, small bridging disc space osteophytes; III, ankylosed disc space.
↵b Three grades: I, nonbridging osteophytes of the facet joint; II, small bridging osteophytes of the facet joint; III, ankylosed facet joint.
↵c Location of the center of the interbody device in relation to 4 quadrants, which the disc space has been divided into on sagittal imaging (I anterior to IV posterior).