Radiology
Akio Hiwatashi, MD
Ravinder Sidhu, MD
Ryan K. Lee, MD
Ramon R. deGuzman, MD
Diane T. Piekut, PhD
Per-Lennart A. Westesson,
MD, PhD, DDS
Published online
10.1148/radiol.2373041654
Radiology 2005; 237:1115–1119
1
From the Departments of Radiology
(A.H., R.S., R.K.L., R.R.d., P.L.A.W.) and
Neurobiology and Anatomy (D.T.P.),
University of Rochester Medical Center,
601 Elmwood Ave, Box 648, Rochester,
NY 14642-8648. Received September
26, 2004; revision requested December
2; revision received December 21;
accepted January 21, 2005. Address
correspondence to A.H. (e-mail: Akio
[email protected]).
Authors stated no financial relationship
to disclose.
Kyphoplasty versus
Vertebroplasty to Increase
Vertebral Body Height:
A Cadaveric Study1
PURPOSE: To prospectively compare the vertebral height restoration achieved with
kyphoplasty and vertebroplasty in fresh cadavers by using multi– detector row
computed tomography (CT).
MATERIALS AND METHODS: Institutional review board approval was not required because the donors had registered in and consented to an anatomic gift
program prior to their death. Thirty-seven vertebrae were harvested from four
donated cadavers of elderly female individuals (mean age, 82 years; age range at
death, 73– 87 years). The vertebrae were dissected free of the surrounding muscles
and imaged with multi– detector row CT. Compression fractures were induced, and
the vertebrae were again imaged. The vertebrae were randomized to be treated
with kyphoplasty (n ⫽ 19) or vertebroplasty (n ⫽ 18) and were then imaged at
multi– detector row CT. The anterior, central, and posterior vertebral body heights
and wedge angles were measured in the midsagittal plane of the reformatted
images. The amount of cement injected was determined by weighing the vertebrae
before and after treatment. The statistical significance of changes in vertebral body
height, wedge angle, and weight with the two treatment techniques was evaluated
with the independent t test or Mann-Whitney U test.
RESULTS: The increase in vertebral height was greater with kyphoplasty than with
vertebroplasty (5.1 mm vs 2.3 mm, respectively; P ⬍ .05). The original vertebral
height was restored in 93% of vertebrae with kyphoplasty and in 82% with vertebroplasty (P ⬍ .05). There was a greater decrease in wedge angle with kyphoplasty
than with vertebroplasty (3.1° vs 1.6°, respectively); however, this difference was
not significant (P ⬎ .05). There was no significant difference in the amount of
cement injected with kyphoplasty and vertebroplasty (P ⬎ .05).
CONCLUSION: Kyphoplasty increased vertebral body height more than vertebroplasty in this model of acutely created fractures in fresh cadaver specimens.
©
Author contributions:
Guarantors of integrity of entire study,
all authors; study concepts/study design
or data acquisition or data analysis/
interpretation, all authors; manuscript
drafting or manuscript revision for important intellectual content, all authors;
approval of final version of submitted
manuscript, all authors; literature research, A.H., P.L.A.W.; experimental
studies, all authors; statistical analysis,
A.H., P.L.A.W.; and manuscript editing,
A.H., P.L.A.W.
©
RSNA, 2005
RSNA, 2005
Percutaneous vertebroplasty was initially described for the treatment of vertebral hemangiomas (1). It was later applied to multiple myeloma, metastasis, Langerhans cell histiocytosis, and osteoporotic compression fractures (2–16). The main goal of vertebroplasty is
to relieve pain by stabilizing the fracture. Restoration of vertebral body height is a
secondary goal, and recent studies have shown that vertebroplasty can achieve some
height restoration (12–16).
Kyphoplasty is a modification of vertebroplasty in which an expandable balloon is used
to create a space in the central portion of a vertebral body before the injection of cement
(17–29). Like vertebroplasty, the purpose of kyphoplasty is to relieve pain by stabilizing the
vertebrae. Proponents of this technique have stressed the ability of kyphoplasty to restore
vertebral height (18,19). Results of experimental studies (18 –20) have shown better height
restoration with kyphoplasty than with vertebroplasty. These studies, however, were based
on conventional radiograph or magnetic resonance (MR) image findings, and there have
been extensive discussions about which technique should be used clinically. Multi–
detector row computed tomography (CT) with sagittal reformatted images enables the
1115
Radiology
Figure 1. Diagrams illustrate areas used to
measure (a) vertebral body height and
(b) wedge angle in the midsagittal plane on
reformatted CT scans. A ⫽ anterior, C ⫽ central, P ⫽ posterior.
precise measurement of vertebral body
height. Thus, the purpose of our study
was to prospectively compare the height
restoration achieved with kyphoplasty
and vertebroplasty in fresh cadavers by
using multi– detector row CT.
MATERIALS AND METHODS
Cadavers
We harvested 37 fresh vertebral bodies
from donated cadavers of four women
(mean age, 82 years; age range at death,
73– 87 years). Institutional review board
approval was not required because these
donors had registered in and consented
to our anatomic gift program prior to
their death. Vertebrae with severe compression fracture (more than 50% height
loss) and those that were damaged during dissection were excluded. There were
16 lumbar (three L1, four L2, three L3,
three L4, three L5) and 21 thoracic (one
T2, one T3, one T4, one T5, two T6, three
T7, two T8, two T9, two T10, three T11,
three T12) vertebrae. The vertebrae were
dissected free of surrounding paraspinal
muscles and separated from each other.
CT Image Acquisition and
Interpretation
CT scans were obtained by using a four–
detector row CT scanner (GE LightSpeed
QX/i; GE Medical Systems, Milwaukee,
Wis) and the following parameters:
1.25-mm collimation, 7.5 mm/sec table
1116
䡠
Radiology
䡠
December 2005
Figure 2. Images of the L3 vertebral body from an 87-year-old woman. The vertebra was treated
with kyphoplasty. The posterior elements of the vertebral body have been resected. A ⫽ anterior,
C ⫽ central, P ⫽ posterior. (a– c) Sagittal reconstructed CT scans obtained in the middle portion
of the vertebral body. (a) CT scan obtained before fracture. (b) CT scan obtained after fracture
shows a decrease in vertebral body height. (c) CT scan obtained after kyphoplasty shows a 4-mm
increase in vertebral height in the anterior and central portions. The height increase was less than
1 mm in the posterior portion of the vertebral body. The wedge angle decreased from 8° to 2°.
(d–f) Schematics used to measure vertebral body height overlaid over the sagittal CT scans in a–c.
(d) Before fracture, the vertebral body was 26 mm in anterior, 23 mm in central, and 28 mm in
posterior portions. The wedge angle was 5°. (e) After fracture, the vertebral body was 18 mm in
anterior, 13 mm in central, and 23 mm in posterior portions. The wedge angle was 8°. (f) After
kyphoplasty, the vertebral body was 22 mm in anterior, 17 mm in central, and 24 mm in
posterior portions. The wedge angle was 2°.
speed, 16-cm field of view, 150 mAs, and
120 kVp. Reconstructions were performed
by using 1.25-mm-thick sections with a
0.625-mm overlap. CT was performed after
excision, after the creation of compression
fractures, and after treatment.
The raw CT data were transferred to a
workstation (Advantage Windows 4.0; GE
Medical Systems). Sagittal reformatted images were created, and one author (A.H.,
with 7 years experience in spinal CT) measured vertebral height in the anterior, cen-
tral, and posterior portions of the vertebra
and wedge angle in the midsagittal plane
(Figs 1–3). The measurements were performed twice at the workstation, and the
mean was recorded.
All specimens were stored in a refrigerator after harvesting and moved to room
temperature 8 hours before compression
fractures were induced. Compression
fractures were created with a compression device consisting of two pieces of
oak wood connected with a hinge. The
Hiwatashi et al
Radiology
Figure 3. Sagittal reconstructed CT images of
the L4 vertebral body from an 87-year-old
woman. The vertebra was treated with vertebroplasty. The posterior elements of the vertebral body have been resected. A ⫽ anterior, P ⫽
posterior. (a) Scan obtained in the middle portion of the vertebral body before fracture.
(b) Scan obtained in the middle portion of the
vertebral body after fracture shows a decrease
in the vertebral body height. (c) Scan obtained
in the middle portion of the vertebral body
after vertebroplasty shows a 1-mm increase in
the vertebral body height in anterior and central portions. No significant height increase is
noted in the posterior portion. The change in
wedge angle was less than 1°. There is leakage
of the cement superiorly (arrow).
or kyphoplasty. Nineteen vertebral bodies were treated with kyphoplasty, and 18
were treated with vertebroplasty. These
procedures were performed by one author (P.L.A.W.), who had 5 years experience in vertebroplasty. Two other authors (A.H. and R.S.) assisted with the
procedure.
Vertebroplasty was performed with a
bipedicular approach by using 13-gauge
bone biopsy needles (Osteo-site; Cook,
Bloomington, Ind) placed in the anterior
third of the vertebral body. The procedure
was performed under fluoroscopic control,
and once the needles were in place, polymethylmethacrylate (Cranioplastic; Codman, Raynham, Mass) was mixed with barium sulfate (Bryan, Woburn, Mass) until a
doughlike consistency was achieved. The
cement was injected via the 13-gauge bone
biopsy needles by using 1-mL syringes alternatively from the left and right. The injection continued until the vertebrae were
filled toward the posterior quarter of the
vertebrae or substantial leakage was observed. We simulated the technique used
clinically with respect to needle placement, cement injection, and end point.
Kyphoplasty was also performed with a
bipedicular approach by using bone biopsy needles (KyphX; Kyphon, Sunnyvale, Calif). The introducers were removed, and exchange wires and working
cannulas were applied. Via the working
cannula, a drill was used to create an
entrance point for the balloon. Fifteenmillimeter balloons were placed in the
anterior vertebrae under fluoroscopic
guidance and inflated to their maximum
size. The balloons were removed, and cement was injected by using the kyphoplasty cement delivery system.
The vertebrae were weighed with a
scale (Pennsylvania Scale, Leona, Pa) before and after treatment to determine
how much cement was injected. One author (R.S.) weighed the vertebrae without
knowledge about which treatment had
been performed in the specific vertebral
body.
Statistical Analyses
vertebral bodies were placed near the
hinge, and a compression was performed
by manually pushing the two wooden
arms together until approximately 30%–
50% loss of anterior vertebral body
height had been achieved.
Treatment
The 37 vertebral bodies were randomly
assigned to be treated with vertebroplasty
Volume 237
䡠
Number 3
Statistical analyses were performed with
commercially available software (SPSS for
Windows, version 11; SPSS, Chicago, Ill).
The statistical significance of changes in
vertebral body height, wedge angle, and
weight with the two treatment techniques was evaluated with the independent t test or Mann-Whitney U test according to the results of an F test. If the P
value with the F test was less than .05,
the Mann-Whitney U test was used for
analysis. If the P value with the F test was
more than .05, the independent t test was
used. A P value of less than .05 was considered to indicate a statistically significant difference.
RESULTS
On average, kyphoplasty increased vertebral height by 5.1 mm, which was significantly more than the 2.3-mm increase
achieved with vertebroplasty (P ⬍ .05)
(Table 1). Vertebral height was restored
in 93% of vertebrae with kyphoplasty
and in 82% of vertebrae with vertebroplasty (P ⬍ .05). These differences were
seen in the anterior, central, and posterior portions.
There was no statistically significant
difference in the decrease in wedge angle.
On average, wedge angle was decreased
by 3.1° with kyphoplasty and by 1.6°
with vertebroplasty (P ⫽ .15) (Table 2).
An average of 7.5 g of cement was injected with kyphoplasty compared with
an average of 10.3 g injected with vertebroplasty. This difference was not statistically significant (P ⫽ .98).
DISCUSSION
The results of our study of fresh cadaver
vertebrae have shown that both kyphoplasty and vertebroplasty can restore vertebral height and wedge angle. This is in
accordance with clinical studies that have
shown increased height after treatment
with both vertebroplasty (13–16) and kyphoplasty (21–26). These findings are also
consistent with those from previous reports of correction of the wedge angle after
vertebroplasty (15). In our study, kyphoplasty restored initial vertebral height
more often than vertebroplasty (93% vs
82%). This confirms the results of earlier
experimental studies, which showed kyphoplasty to have superior capability in
restoring the vertebral body height (18 –
20). Belkoff et al (18) used dual-energy xray absorptiometry and showed that kyphoplasty restored vertebral body height
more often than vertebroplasty (97% vs
30%, respectively). It is likely that the use
of a balloon to expand the center of the
vertebral body and create a void before the
injection of cement helps restore vertebral
body height.
To the best of our knowledge, no cadaveric comparison study regarding a
change in kyphotic angles after vertebroplasty and kyphoplasty has been published. In a clinical setting, Teng et al (15)
reported that vertebroplasty reduced the
Kyphoplasty versus Vertebroplasty
䡠
1117
TABLE 1
Mean Vertebral Heights with Kyphoplasty and Vertebroplasty
Radiology
Anterior Portion
Central Portion
Posterior Portion
Parameter
Kyphoplasty
Vertebroplasty
Kyphoplasty
Vertebroplasty
Kyphoplasty
Vertebroplasty
Initial height (mm)
Height after compression fracture (mm)
Height after treatment (mm)
Restoration of initial height (%)
21.9
15.1
20.7
95
20.9
15.2
17.6
85
20.1
12.2
18.3
92
19.9
12.7
15.3
77
24.6
18.7
22.4
91
24.5
18.2
20.0
82
Note.—Nineteen vertebral bodies were treated with kyphoplasty, and 18 were treated with vertebroplasty. Restoration of initial height was determined
by dividing the vertebral height after treatment by the initial vertebral height.
wedge angle by 7.4°. Some authors reported a 4°–10° reduction in wedge angle
after kyphoplasty (23,25). Our results
showed a 3.1° reduction in wedge angle
after kyphoplasty and a 1.6° reduction
after vertebroplasty. This difference was
not statistically significant.
There were several limitations to our
study. The experimental situation in this
cadaveric study with freshly created compression fractures and no opposing vertebrae above or below is different from
clinical situations. It is probably easier to
restore vertebral body height in this situation, in which the fractures are fresh
and there is no resistance to expansion.
In this experimental study, we did not
manually manipulate the vertebrae before injecting the cement as we would in
the clinical setting with hyperextension.
Thus, the height gain achieved was the
result of the procedure itself rather than
the result of manipulation. We do not
know if our findings would translate to
the clinical situation with different biomechanics. Moreover, there are no clinical data about the value of height restoration. We are currently comparing height
restoration in patients treated with kyphoplasty and vertebroplasty.
Compared with vertebroplasty, kyphoplasty seems to provide better height
gain and correction of kyphosis. The clinical importance of these postural changes,
however, is unknown. A randomized
study comparing the results of kyphoplasty and vertebroplasty seems justified.
In conclusion, kyphoplasty increased
vertebral body height more than vertebroplasty in our experimental model of
fresh cadavers with created compression
fractures. The differences in height restoration between the two techniques were
small, and the clinical importance of the
restoration of vertebral body height and
wedge angle remains to be documented.
Acknowledgment: We thank Xiang Liu,
MD, PhD, for statistical analysis.
1118
䡠
Radiology
䡠
December 2005
TABLE 2
Mean Wedge Angles with Kyphoplasty and Vertebroplasty
Parameter
Kyphoplasty
Vertebroplasty
Initial angle
Angle after compression fracture
Angle after treatment
Reduction of wedge angle
4.0°
5.6°
2.5°
3.1°
4.1°
4.4°
2.8°
1.6°
Note.—Nineteen vertebral bodies were treated with kyphoplasty, and 18 were treated with
vertebroplasty. Reduction of wedge angle was determined by subtracting the wedge angle after
treatment from that after compression fracture.
References
1. Galibert P, Deramond H, Rosat P, Le Gars
D. Preliminary note on the treatment of
vertebral angioma by percutaneous acrylic
vertebroplasty [in French]. Neurochirurgie
1987;33:166 –168.
2. Kaemmerlen P, Thiesse P, Bouvard H, Biron P, Mornex F, Jonas P. Percutaneous
vertebroplasty in the treatment of metastases: technic and results [in French]. J Radiol 1989;70:557–562.
3. Gangi A, Kastler BA, Dietemann JL. Percutaneous vertebroplasty guided by a combination of CT and fluoroscopy. AJNR Am J
Neuroradiol 1994;15:83– 86.
4. Cardon T, Hachulla E, Flipo RM, et al. Percutaneous vertebroplasty with acrylic cement in the treatment of a Langerhans cell
vertebral histiocytosis. Clin Rheumatol
1994;13:518 –521.
5. Weill A, Chiras J, Simon JM, Rose M, SolaMartinez T, Enkaoua E. Spinal metastases:
indications for and results of percutaneous
injection of acrylic surgical cement. Radiology 1996;199:241–247.
6. Cotten A, Dewatre F, Cortet B, et al. Percutaneous vertebroplasty for osteolytic metastases and myeloma: effects of the percentage of lesion filling and the leakage of
methyl methacrylate at clinical follow-up.
Radiology 1996;200:525–530.
7. Jensen ME, Evans AJ, Mathis JM, Kallmes DF,
Cloft HJ, Dion JE. Percutaneous polymethylmethacrylate vertebroplasty in the treatment of osteoporotic vertebral body compression fractures: technical aspects. AJNR
Am J Neuroradiol 1997;18:1897–1904.
8. Cotten A, Boutry N, Cortet B, et al. Percutaneous vertebroplasty: state of the art. RadioGraphics 1998;18:311–320.
9. Mathis JM, Barr JD, Belkoff SM, Barr MS,
Jensen ME, Deramond H. Percutaneous
vertebroplasty: a developing standard of
10.
11.
12.
13.
14.
15.
16.
17.
18.
care for vertebral compression fractures.
AJNR Am J Neuroradiol 2001;22:373–381.
Uppin AA, Hirsch JA, Centenera LV, Pfiefer
BA, Pazianos AG, Choi IS. Occurrence of
new vertebral body fracture after percutaneous vertebroplasty in patients with osteoporosis. Radiology 2003;226:119 –124.
Lin EP, Ekholm S, Hiwatashi A, Westesson
PL. Vertebroplasty: cement leakage into
the disc increases the risk of new fracture
of adjacent vertebral body. AJNR Am J
Neuroradiol 2004;25:175–180.
Belkoff SM, Mathis JM, Jasper LE, Deramond H. An ex vivo biomechanical evaluation of a hydroxyapatite cement for use
with vertebroplasty. Spine 2001;26:1542–
1546.
McKiernan F, Jensen R, Faciszewski T,
McKiernan F, Jensen R, Faciszewski T. The
dynamic mobility of vertebral compression fractures. J Bone Miner Res 2003;18:
24 –29.
Hiwatashi A, Moritani T, Numaguchi Y,
Westesson PL. Increase in vertebral body
height after vertebroplasty. AJNR Am J
Neuroradiol 2003;24:185–189.
Teng MM, Wei CJ, Wei LC, et al. Kyphosis
correction and height restoration effects of
percutaneous vertebroplasty. AJNR Am J
Neuroradiol 2003;24:1893–1900.
McKiernan F, Faciszewski T, Jensen R. Reporting height restoration in vertebral compression fractures. Spine 2003;28:2517–2521.
Wilson DR, Myers ER, Mathis JM, et al.
Effect of augmentation on the mechanics
of vertebral wedge fractures. Spine 2000;
25:158 –165.
Belkoff SM, Mathis JM, Fenton DC, Scribner
RM, Reiley ME, Talmadge K. An ex vivo biomechanical evaluation of an inflatable bone
tamp used in the treatment of compression
fracture. Spine 2001;26:151–156.
Hiwatashi et al
Radiology
19. Belkoff SM, Mathis JM, Deramond H, Jasper LE. An ex vivo biomechanical evaluation of a hydroxyapatite cement for use
with kyphoplasty. AJNR Am J Neuroradiol
2001;22:1212–1216.
20. Verlaan JJ, van Helden WH, Oner FC, Verbout AJ, Dhert WJ. Balloon vertebroplasty
with calcium phosphate cement augmentation for direct restoration of traumatic
thoracolumbar vertebral fractures. Spine
2002;27:543–548.
21. Garfin SR, Yuan HA, Reiley MA. New technologies in spine: kyphoplasty and vertebroplasty for the treatment of painful osteoporotic compression fractures. Spine
2001;26:1511–1515.
22. Lieberman IH, Dudeney S, Reinhardt MK,
Bell G. Initial outcome and efficacy of “kyphoplasty” in the treatment of painful
Volume 237
䡠
Number 3
osteoporotic vertebral compression fractures. Spine 2001;26:1631–1638.
23. Theodorou DJ, Theodorou SJ, Duncan TD,
Garfin SR, Wong WH. Percutaneous balloon kyphoplasty for the correction of spinal deformity in painful vertebral body
compression fractures. Clin Imaging 2002;
26:1–5.
24. Dudeney S, Lieberman IH, Reinhardt MK,
Hussein M. Kyphoplasty in the treatment
of osteolytic vertebral compression fractures as a result of multiple myeloma.
J Clin Oncol 2002;20:2382–2387.
25. Fourney DR, Schomer DF, Nader R, et al.
Percutaneous vertebroplasty and kyphoplasty for painful vertebral body fractures
in cancer patients. J Neurosurg 2003;98:
21–30.
26. Ledlie JT, Renfro M. Balloon kyphoplasty:
1-year outcomes in vertebral body height
restoration, chronic pain, and activity levels. J Neurosurg 2003;98:36 – 42.
27. Phillips FM. Minimally invasive treatments of osteoporotic vertebral compression fractures. Spine 2003;28(15 suppl):
S45–S53.
28. Lieberman I, Reinhardt MK. Vertebroplasty and kyphoplasty for osteolytic vertebral collapse. Clin Orthop Relat Res
2003;415(suppl):S176 –S186.
29. Rao RD, Singrakhia MD. Painful osteoporotic vertebral fracture: pathogenesis, evaluation, and roles of vertebroplasty and kyphoplasty in its management. J Bone Joint
Surg Am 2003;85:2010 –2022.
Kyphoplasty versus Vertebroplasty
䡠
1119