Lumbar safety triangle: comparative study of coronal and coronal oblique planes in 3.0-T magnetic resonance imaging

Dannebrock, Fernando Augusto; Zardo, Erasmo de Abreu; Ziegler, Marcus Sofia; Vialle, Emiliano; Soder, Ricardo Bernardi; Schwanke, Carla Helena Augustin

doi:10.1590/0100-3984.2023.0022

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Original Article • Radiol Bras 56 (6) • Nov-Dec 2023 • https://doi.org/10.1590/0100-3984.2023.0022 copy

Lumbar safety triangle: comparative study of coronal and coronal oblique planes in 3.0-T magnetic resonance imaging

Triângulo de segurança lombar: estudo comparativo dos planos coronal e coronal oblíquo em ressonância magnética 3.0-T

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objective:

To compare the measurements of the lumbar safety triangle (Kambin’s triangle) and the invasion of the dorsal root ganglion in the triangle in coronal and coronal oblique planes.

Materials and Methods:

A cross-sectional study, in which 210 3.0-T magnetic resonance images of L2-L5 were analyzed in coronal and coronal oblique planes. Exams with lumbar spine anomalies were excluded. Demographic (sex and age) and radiological variables were recorded by a single evaluator.

Results:

Most sample was female (57.1%), mean age 45.5 ± 13.3 (18–98 years). The measurements average, as well as the areas, gradually increased from L2 to L5. The dorsal root ganglion invaded the triangle in all images. The safety triangle average area was smaller in the coronal oblique plane than in the coronal plane. Of the seven dimensions of safety triangle obtained for each level of the lumbar spine, six were significantly smaller in the coronal oblique plane than in the coronal plane. The only dimension that showed no difference was the smallest ganglion dimension.

Conclusion:

The dimensions and areas investigated were smaller in coronal oblique plane, especially the area (difference > 1 mm). The analysis of the triangular zone in this plane becomes important in the preoperative assessment of minimally invasive procedures.

Keywords:
Spine; Spinal ganglia; Magnetic resonance imaging; Minimally invasive surgical procedures; Spinal nerve roots

Parameter	Total sample (N = 210) Mean ± SD (range)	Sex			Age group
Parameter	Total sample (N = 210) Mean ± SD (range)	Female (n = 120) Mean ± SD	Male (n = 90) Mean ± SD	p*	18–39 years (n = 75) Mean ± SD	40–65 years (n = 116) Mean ± SD	66–98 years (n = 19) Mean ± SD	p†
At L2–L3
Lumbar safety triangle
Height, mm	14.9 ± 2.7 (8.6–22.6)	14.5 ± 2.7	15.4 ± 2.7	0.017	14.5 ± 2.8	15.2 ± 2.7	14.7 ± 2.1	0.254
Base, mm	11.8 ± 2.6 (6.8–19.3)	11.5 ± 2.4	12.2 ± 2.8	0.069	11.1 ± 2.5^a	12.2 ± 2.6^b	12.0 ± 2.3^a, ^b	0.016
Hypotenuse, mm	15.5 ± 3.3 (7.3–23.7)	15.0 ± 3.2	16.2 ± 3.3	0.009	15.0 ± 3.2	15.8 ± 3.4	15.7 ± 2.5	0.233
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	90.0 ± 32.7 (37.8–191.0)	85.3 ± 29.3	96.4 ± 35.9	0.018	82.7 ± 31.5^a	95.0 ± 33.9^b	89.1 ± 25.0^a, ^b	0.038
Dorsal root ganglion
Largest dimension, mm	6.1 ± 1.0 (3.3–9.2)	5.9 ± 0.9	6.4 ± 1.1	0.002	6.1 ± 1.0	6.1 ± 1.0	6.2 ± 1.0	0.888
Smallest dimension, mm	5.0 ± 0.8 (3.1–7.0)	4.8 ± 0.7	5.3 ± 0.9	< 0.001	5.1 ± 0.8	5.0 ± 0.8	4.9 ± 0.6	0.600
Invasion into the triangle, mm	1.1 ± 0.2 (0.6–1.5)	1.0 ± 0.2	1.1 ± 0.2	0.190	1.1 ± 0.2	1.1 ± 0.2	1.1 ± 0.2	0.886
At L3–L4
Lumbar safety triangle
Height, mm	15.7 ± 2.6 (9.9–25.2)	15.3 ± 2.6	16.2 ± 2.5	0.015	15.3 ± 2.8	15.9 ± 2.5	15.4 ± 1.8	0.286
Base, mm	12.2 ± 2.5 (6.9–19.5)	11.8 ± 2.3	12.6 ± 2.7	0.028	11.6 ± 2.5	12.5 ± 2.6	12.1 ± 1.9	0.069
Hypotenuse, mm	16.2 ± 3.1 (8.6–23.8)	15.7 ± 2.9	16.9 ± 3.2	0.007	15.5 ± 3.1	16.6 ± 3.2	16.5 ± 2.3	0.060
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	97.4 ± 32.8 (34.1–204.7)	92.3 ± 30.0	104.2 ± 35.7	0.009	91.4 ± 33.4	101.8 ± 33.6	94.2 ± 21.2	0.093
Dorsal root ganglion
Largest dimension, mm	6.4 ± 0.9 (4.2–9.6)	6.2 ± 0.8	6.7 ± 1.0	< 0.001	6.4 ± 0.9	6.5 ± 0.9	6.4 ± 1.0	0.983
Smallest dimension, mm	5.2 ± 0.8 (3.2–7.3)	5.1 ± 0.7	5.4 ± 0.9	0.001	5.3 ± 0.8	5.2 ± 0.8	5.1 ± 0.7	0.714
Invasion into the triangle, mm	1.1 ± 0.2 (0.7–1.6)	1.1 ± 0.2	1.2 ± 0.2	0.040	1.1 ± 0.2	1.1 ± 0.2	1.2 ± 0.1	0.736
At L4–L5
Lumbar safety triangle
Height, mm	16.4 ± 2.6 (9.4–28.4)	15.7 ± 2.3	17.3 ± 2.7	< 0.001	16.3 ± 3.0	15.5 ± 2.5	16.1 ± 1.7	0.670
Base, mm	12.9 ± 2.3 (6.9–19.7)	12.4 ± 2.1	13.5 ± 2.4	0.001	12.5 ± 2.3	13.2 ± 2.3	12.6 ± 2.0	0.155
Hypotenuse, mm	17.3 ± 3.0 (10.5–26.4)	16.5 ± 2.8	18.3 ± 3.0	< 0.001	17.0 ± 3.2	17.4 ± 2.9	17.2 ± 2.3	0.638
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	107.5 ± 32.8 (45.5–242.8)	99.1 ± 27.8	118.6 ± 35.7	< 0.001	104.1 ± 35.6	110.5 ± 32.2	102.1 ± 22.7	0.318
Dorsal root ganglion
Largest dimension, mm	6.7 ± 1.0 (4.2–10.4)	6.4 ± 0.8	7.0 ± 1.0	< 0.001	6.7 ± 0.9	6.7 ± 1.0	6.6 ± 1.2	0.952
Smallest dimension, mm	5.3 ± 0.8 (2.9–8.4)	5.2 ± 0.7	5.5 ± 0.9	0.003	5.4 ± 0.8	5.3 ± 0.8	5.2 ± 0.2	0.414
Invasion into the triangle, mm	1.2 ± 0.2 (0.6–1.8)	1.2 ± 0.2	1.3 ± 0.2	0.010	1.2 ± 0.2	1.2 ± 0.2	1.2 ± 0.2	0.844

Parameter	Total sample (N = 210) Mean ± SD (range)	Sex			Age group
Parameter	Total sample (N = 210) Mean ± SD (range)	Female (n = 120) Mean ± SD	Male (n = 90) Mean ± SD	p*	18–39 years (n = 75) Mean ± SD	40–65 years (n = 116) Mean ± SD	66–98 years (n = 19) Mean ± SD	p†
At L2–L3
Lumbar safety triangle
Height, mm	14.7 ± 2.7 (8.7–22.2)	14.4 ± 2.7	15.2 ± 2.8	0.030	14.3 ± 2.8	15.0 ± 2.8	14.6 ± 2.1	0.188
Base, mm	11.7 ± 2.5 (6.8–19.1)	11.4 ± 2.4	12.1 ± 2.7	0.063	11.4 ± 2.4^a	12.1 ± 2.6^b	11.8 ± 2.3^a, ^b	0.014
Hypotenuse, mm	15.3 ± 3.3 (7.6–23.4)	14.8 ± 3.2	15.9 ± 3.5	0.022	14.7 ± 3.3	15.6 ± 3.4	15.5 ± 2.6	0.181
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	88.5 ± 32.2 (36.9–187.1)	84.1 ± 29.0	94.5 ± 35.3	0.024	81.1 ± 31.0^a	93.6 ± 33.3^b	86.9 ± 24.4^a, ^b	0.029
Dorsal root ganglion
Largest dimension, mm	6.0 ± 1.0 (3.3–9.1)	5.8 ± 0.9	6.3 ± 1.1	0.001	6.0 ± 1.1	6.0 ± 1.0	6.0 ± 1.0	0.978
Smallest dimension, mm	5.0 ± 0.7 (3.0–6.80	4.8 ± 06	5.2 ± 0.8	< 0.001	5.0 ± 0.8	5.0 ± 0.7	4.9 ± 0.6	0.632
Invasion into the triangle, mm	1.0 ± 0.2 (0.5–1.5)	1.0 ± 0.2	1.0 ± 0.2	0.245	1.0 ± 0.2	1.0 ± 0.2	1.0 ± 0.2	0.931
At L3–L4
Lumbar safety triangle
Height, mm	15.4 ± 2.6 (10.0–25.2)	15.1 ± 2.6	15.9 ± 2.6	0.025	15.1 ± 2.8	15.7 ± 2.5	15.1 ± 1.9	0.238
Base, mm	12.1 ± 2.4 (7.5–19.2)	11.7 ± 2.2	12.6 ± 2.6	0.011	11.6 ± 2.4	12.4 ± 2.5	12.0 ± 1.8	0.086
Hypotenuse, mm	16.0 ± 3.1 (8.1–23.7)	15.5 ± 3.0	16.6 ± 3.2	0.010	15.2 ± 3.1^a	16.4 ± 2.4^b	16.2 ± 2.4^a, ^b	0.045
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	95.5 ± 32.1 (38.5–198.7)	90.3 ± 29.0	102.4 ± 34.8	0.007	89.8 ± 32.7	99.7 ± 32.8	91.8 ± 21.1	0.101
Dorsal root ganglion
Largest dimension, mm	6.3 ± 0.9 (4.0–9.2)	6.1 ± 0.8	6.6 ± 1.0	0.001	6.3 ± 0.9	6.3 ± 0.9	6.3 ± 1.0	0.956
Smallest dimension, mm	5.2 ± 0.7 (3.1–7.2)	5.0 ± 0.6	5.5 ± 0.8	< 0.001	5.3 ± 0.7	5.2 ± 0.7	5.0 ± 0.7	0.195
Invasion into the triangle, mm	1.1 ± 0.2 (06–1.5)	1.1 ± 0.1	1.1 ± 0.2	0.100	1.1 ± 0.2	1.1 ± 0.2	1.1 ± 0.1	0.942
At L4–L5
Lumbar safety triangle
Height, mm	16.1 ± 2.6 (9.2–26.9)	15.5 ± 2.3	17.0 ± 2.8	< 0.001	16.0 ± 2.9	16.3 ± 2.5	15.8 ± 1.7	0.531
Base, mm	12.8 ± 2.3 (7.0–19.5)	12.3 ± 2.0	13.4 ± 2.4	0.001	12.5 ± 2.3	13.0 ± 2.3	12.5 ± 1.9	0.311
Hypotenuse, mm	16.9 ± 3.0 (10.1–25.5)	16.2 ± 2.7	17.8 ± 3.2	< 0.001	16.5 ± 3.2	17.1 ± 3.0	16.8 ± 2.4	0.409
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	105.0 ± 32.8 (41.8–242.1)	97.0 ± 27.1	115.6 ± 36.6	< 0.001	102.2 ± 36.1	107.7 ± 31.9	99.1 ± 22.2	0.377
Dorsal root ganglion
Largest dimension, mm	6.5 ± 0.9 (4.0–9.8)	6.3 ± 0.8	6.9 ± 1.0	< 0.001	6.5 ± 0.9	6.5 ± 0.9	6.5 ± 1.1	0.976
Smallest dimension, mm	5.4 ± 0.8 (3.3–8.1)	5.2 ± 0.7	5.6 ± 0.9	< 0.001	5.5 ± 0.7	5.3 ± 0.8	5.1 ± 0.7	0.082
Invasion into the triangle, mm	1.1 ± 0.2 (0.7–1.6)	1.1 ± 0.1	1.2 ± 0.2	0.155	1.1 ± 0.2	1.1 ± 0.2	1.1 ± 0.2	0.998

Variables (mm)	Plane		p*
Variables (mm)	Coronal Mean ± SD	Coronal oblique Mean ± SD	p*
At L2–L3
Lumbar safety triangle
Height, mm	14.9 ± 2.7	14.7 ± 2.7	< 0.001
Base, mm	11.8 ± 2.6	11.7 ± 2.5	0.003
Hypotenuse, mm	15.5 ± 3.3	15.3 ± 3.3	< 0.001
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	90.0 ± 32.7	88.5 ± 32.2	< 0.001
Dorsal root ganglion
Largest dimension, mm	6.1 ± 1.0	6.0 ± 1.0	< 0.001
Smallest dimension, mm	5.0 ± 0.8	5.0 ± 0.7	0.461
Invasion into the triangle, mm	1.1 ± 0.2	1.0 ± 0.2	< 0.001
At L3–L4
Lumbar safety triangle
Height, mm	15.7 ± 2.6	15.4 ± 2.6	< 0.001
Base, mm	12.2 ± 2.5	12.1 ± 2.4	0.050
Hypotenuse, mm	16.2 ± 3.1	16.0 ± 3.1	< 0.001
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	97.4 ± 32.8	95.5 ± 32.1	< 0.001
Dorsal root ganglion
Largest dimension, mm	6.4 ± 0.9	6.3 ± 0.9	< 0.001
Smallest dimension, mm	5.2 ± 0.8	5.2 ± 0.7	0.751
Invasion into the triangle, mm	1.14 ± 0.17	1.10 ± 0.16	< 0.001
At L4–L5
Lumbar safety triangle
Height, mm	16.4 ± 2.6	16.1 ± 2.6	< 0.001
Base, mm	12.9 ± 2.3	12.8 ± 2.3	< 0.001
Hypotenuse, mm	17.3 ± 3.0	16.9 ± 3.0	< 0.001
Area, mm³3 Kim DY, Lee SH, Chung SK, et al. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30:123–9.	107.5 ± 32.8	105.0 ± 32.8	< 0.001
Dorsal root ganglion
Largest dimension, mm	6.7 ± 1.0	6.5 ± 0.9	< 0.001
Smallest dimension, mm	5.3 ± 0.8	5.4 ± 0.8	0.343
Invasion into the triangle, mm	1.2 ± 0.2	1.1 ± 0.2	< 0.001

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[1] Correspondence: Dr. Fernando Augusto Dannebrock. Avenida Ipiranga, 6690, cj. 310, Jardim Botânico. Porto Alegre, RS, Brazil, 90610-000. Email: fdannebrock@gmail.com.