The First Algorithm Calculating Cement Injection Volumes in Patients with Spine Metastases Treated with Percutaneous Vertebroplasty

Figures & data

Figure 1 53-year-old male with esophageal cancer. (A and B) Preoperative X-ray showed bone destruction at L1~L4; (C and D) Preoperative MRI showed multiple spine metastases (L1~L4); (E) MRI showed transversal spine metastases at L1, and it had deformation of the dural sac, but without spinal cord or nerve root compression; (F) MRI showed transversal spine metastases at L2, and it had epidural impingement, but without deformation of the dural sac; (G) MRI showed transversal spine metastases at L3, and it had complete posterior wall; (H) MRI showed transversal spine metastases at L4, and it had complete posterior wall. The pattern diagrams were shown just below the transversal MRI image of L1 to L4. It indicated that L1 was classified into group C, L2 was classified into group B, and L3 and L4 were classified into group A. And the patient was classified into group C.

Table 1 Preoperative Clinical Characteristics of Patients

Characteristics	Groups			P
	A (n=145)	B (n=83)	C (n=23)
Age (years)	64.9 ± 1.0	64.1 ± 1.5	62.4 ± 3.0	0.488
Gender
Male	87	45	12	0.606
Female	58	38	11
Type of Primary Cancer
Slow	38	26	5	0.774
Middle	19	13	3
Fast	88	44	15
The Number of Vertebrae
Single	64	30	10	0.503
Multiple	81	53	13
Injected bone cement volume (mL)	2.8 ± 0.1	3.2 ± 0.1	2.6 ± 0.3	0.080
Treated Vertebrae Level*
Cervical	11 (2.6%)	2 (1.5%)	0 (0.0%)	0.006
Upper thoracic	49 (11.5%)	27 (20.5%)	6 (21.4%)
Lower thoracic	131 (30.9%)	44 (33.3%)	11 (39.3%)
Lumbar	195 (46.0%)	58 (43.9%)	9 (32.1%)
Sacrum	38 (9.0%)	1 (0.8%)	2 (7.2%)

Note: *Indicating 584 treated vertebrae.

Table 2 Postoperative Pain and Function Improvements

Outcomes	Groups			P
	A (n=145)	B (n=83)	C (n=23)
Pre-OP VAS score	7.24 ± 1.37	7.44 ± 1.53	7.35 ± 1.24	0.575
Post-OP VAS at the time of discharge	4.32 ± 0.92 ^a	4.37 ± 1.01 ^a	4.53 ± 0.98 ^a	0.104
Post-OP VAS at 3 months	3.96 ± 1.15 ^a	4.13 ± 1.05 ^a	3.94 ± 0.64 ^a	0.246
Post-OP VAS at 6 months	4.38 ± 0.96 ^a	4.23 ± 0.83 ^a	4.15 ± 1.06 ^a	0.327
Pre-OP ADL Grading
Normal (n, %)	38 (26.2%)	29 (34.9%)	6 (26.1%)	0.230
Mild (n, %)	54 (37.2%)	37 (44.6%)	9 (39.1%)
Moderate (n, %)	39 (26.9%)	12 (14.5%)	7 (30.4%)
Severe (n, %)	14 (9.7%)	5 (6.0%)	1 (4.4%)
Post-OP ADL Grading at the Time of Discharge
Improve (n, %)	32 (22.1%)	15 (18.1%)	5 (21.7%)	0.676
Not change (n, %)	84 (57.9%)	52 (62.6%)	16 (69.6%)
Aggravate (n, %)	29 (20.0%)	16 (19.3%)	2 (8.7%)
Post-OP ADL Grading at 3 Months ^b
Improve (n, %)	30 (24.8%)	18 (25.4%)	7 (35.0%)	0.687
Not change (n, %)	72 (59.5%)	41 (57.7%)	12 (60.0%)
Aggravate (n, %)	19 (15.7%)	12 (16.9%)	1 (5.0%)
Post-OP ADL Grading at 6 Months ^c
Improve (n, %)	24 (22.2%)	13 (20.6%)	4 (25.0%)	0.759
Not change (n, %)	64 (59.3%)	36 (57.2%)	7 (43.8%)
Aggravate (n, %)	20 (18.5%)	14 (22.2%)	5 (31.2%)

Notes: ^aAs compared with pre-operative VAS, all P˂0.01. Pre-OP, indicating pre-operative; Post-OP, indicating post-operative; VAS, indicating visual analogy score; ADL, indicating activity of daily living. ^b24 patients died in group A, 12 patients died in group B, and 3 patients died in group C; ^c37 patients died in group A, 20 patients died in group B, and 9 patients died in group C.

Figure 2 VAS in the three groups before and after surgery (* indicates P ˂0.01, as compared with pre-operative VAS.

Abbreviation: Pre-OP, pre-operation; Post-OP, post-operation.

Table 3 Cement Leakage Distribution in Different Groups of Vertebrae

Cement Leakage and Position		Groups			P
		A (n=424)	B (n=132)	C (n=28)
Leakages	No	363 (85.6%)	101 (76.5%)	20 (71.4%)	0.014
	Yes	61 (14.4%)	31 (23.5%)	8 (28.6%)
Positions	Extra-spinal canal	56 (91.8%)	28 (90.3%)	4 (50.0%)	0.003
	Intra-spinal canal	5 (8.2%)	3 (9.7%)	4 (50.0%)

Figure 3 A 59-year-old male with lung cancer who treated with PVP suffered from intra-spinal canal cement leakage. (A) CT sagittal plane showed T8 and T10 destructions; (B) CT horizontal plane of T8; (C) CT horizontal plane of T10; (D) MRI sagittal plane showed T8 metastatic lesion and T10 metastatic spinal cord compression; (E) MRI horizontal plane of T8; (F) MRI horizontal plane of T10; (G and H) postoperative X-ray; (I) CT horizontal plane of T8 showed intra-spinal canal cement leakage; (J) CT horizontal plane of T10 showed intra-spinal canal cement leakage.

Table 4 Risk Factors for Intra-Spinal Canal Cement Leakage

Characteristics	Leakages (n=12/584)	The Simple Logistic Regression		The Multiple Logistic Regression
		OR (95% CI)	P	OR (95% CI)	P
Treated Vertebrae Level
Thoracic	2.61% (7/268)	1.67 (0.52–5.32)	0.39	Not included
Non-thoracic	1.58% (5/316)
Vertebrae Collapse
No collapse	1.65% (8/486)	2.28 (1.10–4.72)	0.03	Not included
Less than 50%	1.52% (1/66)
More than 50%	9.38% (3/32)
Cortical Osteolytic Destruction in Posterior Wall
No	1.41% (6/425)	2.74 (0.87–8.62)	0.09	Not included
Yes	3.77% (6/159)
Groups*
A	1.18% (5/424)	3.59 (1.70–7.60)	<0.001	Not included
B	2.27% (3/132)
C	14.29% (4/28)
Bilsky Scale
0	1.14% (6/525)	3.34 (1.90–5.87)	<0.001	3.34 (1.90–5.87)	<0.001
1	6.45% (2/31)
2	12.50% (3/24)
3	25.00% (1/4)

Notes: *Indicates vertebrae with complete posterior wall of vertebrae were classified into group A, vertebrae without complete posterior wall of vertebrae but with normal Dural sac were classified into group B, and vertebrae with deformation of the Dural sac but without neurological symptom.

Abbreviations: OR, odds ratio; CI, confident interval.

Figure 4 ROC curves for variables of vertebrae collapse (ROC=0.60), groups (ROC=0.69), Bilsky scale (ROC=0.71), and model including all the three significant factors (ROC=0.73).

Table 5 An Algorithm to Calculate Injected Bone Cement Volumes

Characteristics	Cement (mL)	Scores	The Multiple Linear Regression
			OR (95% CI)	P
Intercept			3.1627	<0.001
Treated Vertebrae Level
Thoracic	2.44	1	–0.8677	<0.001
Non-thoracic	3.27	0
Vertebrae collapse
No collapse	2.87	1	Not included
Less than 50%	3.20	2
More than 50%	2.59	3
Cortical Osteolytic Destruction in Posterior Wall
No	3.15	0	–0.6182	<0.001
Yes	2.79	1
Groups*
A	2.80	1	Not included
B	3.23	2
C	2.64	3
Bilsky Scale
0	2.89	0	–0.2819	0.014
1	3.11	1
2	2.79	2
3	1.75	3

Notes: Model: Y=3.1627–0.8677×treated vertebrae level–0.6182×cortical osteolytic destruction in posterior wall–0.2819×Bilsky scale. *Indicates vertebrae with complete posterior wall of vertebrae were classified into group A, vertebrae without complete posterior wall of vertebrae but with normal Dural sac were classified into group B, and vertebrae with deformation of the Dural sac but without neurological symptom.

Abbreviations: OR, odds ratio; CI, confident interval.

Figure 5 Residual plot for fitting effectiveness of multiple linear regression: The formula was Y=3.1627–0.8677×treated vertebrae level (x1)–0.6182×cortical osteolytic destruction in posterior wall (x3)–0.2819×Bilsky scale (x5).