Juan J. Ramı´rez, Erwin Chiquete, Juan J. Ramı´rez, Jr., Ernesto Go´mez-Limo´n, and Juan M. Ramı´rez An expandable vertebral body prosthesis with dual cage-and-plate function in a single device (JR prosthesis) was designed to test the hypothesis that this modular system can provide the biomechanical requirements for immediate and durable spine stabilization after corpectomy. Cadaver assays were performed with a stainless steal device to test fixation and adequacy to the human spine anatomy. Then, 14 patients with vertebral tumors (eight metastatic) underwent corpectomy and vertebral body replacement with a titaniummade JR prosthesis. All patients had neurological deficit, severe pain and spine instability prior to surgery. Mean pain score before surgery on a visual analog scale decreased from 7.6e3.0 points after operation ( p 5 0.002). All patients achieved at least one grade of improvement in the Frankel score ( p 5 0.003), excepting the three patients with Frankel grade A before surgery. Two patients with renal cell carcinoma died during the following 4 days after surgery. The remaining patients attained a painless and stable spine immediately, which was maintained for long periods (mean follow-up: 25.4 months). No significant infections or implant failures were registered. A nonfatal case of inferior vena cava surgical injury was observed (repaired during surgery without further complications). In conclusion, the JR prosthesis stabilizes the spine immediately after surgery and for the rest of the patients’ life. To our knowledge, this is the first report on the clinical experience of any expandable vertebral body prosthesis with dual cage-and-plate function in a single device.

1. Archives of Medical Research 41 (2010) 478e482
BRIEF REPORT
An Expandable Prosthesis with Dual Cage-and-Plate Function
in a Single Device for Vertebral Body Replacement: Clinical
Experience on 14 Cases with Vertebral Tumors
´
´
´
´
´
Juan J. Ramırez,a Erwin Chiquete,b Juan J. Ramırez, Jr.,c Ernesto Gomez-Limon,d and Juan M. Ramırezb
a
Department of Orthopedics, bDepartment of Internal Medicine, dDepartment of Neurology and Neurosurgery, Hospital Civil
´noma de
´xico, cUniversidad Auto
de Guadalajara, Fray Antonio Alcalde, Universidad de Guadalajara, Guadalajara, Me
´xico
Guadalajara, Zapopan, Me
Received for publication April 15, 2010; accepted August 26, 2010 (ARCMED-D-10-00174).
An expandable vertebral body prosthesis with dual cage-and-plate function in a single
device (JR prosthesis) was designed to test the hypothesis that this modular system can
provide the biomechanical requirements for immediate and durable spine stabilization
after corpectomy. Cadaver assays were performed with a stainless steal device to test fixation and adequacy to the human spine anatomy. Then, 14 patients with vertebral tumors
(eight metastatic) underwent corpectomy and vertebral body replacement with a titaniummade JR prosthesis. All patients had neurological deficit, severe pain and spine instability
prior to surgery. Mean pain score before surgery on a visual analog scale decreased from
7.6e3.0 points after operation ( p 5 0.002). All patients achieved at least one grade of
improvement in the Frankel score ( p 5 0.003), excepting the three patients with Frankel
grade A before surgery. Two patients with renal cell carcinoma died during the following
4 days after surgery. The remaining patients attained a painless and stable spine immediately, which was maintained for long periods (mean follow-up: 25.4 months). No significant infections or implant failures were registered. A nonfatal case of inferior vena cava
surgical injury was observed (repaired during surgery without further complications). In
conclusion, the JR prosthesis stabilizes the spine immediately after surgery and for the
rest of the patients’ life. To our knowledge, this is the first report on the clinical experience of any expandable vertebral body prosthesis with dual cage-and-plate function in
a single device. Ó 2010 IMSS. Published by Elsevier Inc.
Key Words: Cage, Corpectomy, Plate, Prosthesis, Spine, Vertebral tumor.
Introduction
Eighty five percent of all cases of spinal metastasis are
located primarily in the vertebral body (1). Spinal cord
lesion in metastatic disease of the spine results from direct
tumor compression, vertebral body collapse and retropulsed
bone fragments (2). As a result, pain, neurological deficit,
spine instability or segmental deformities ensue (1,2). In
order to restore the stability of the spine, it is necessary
´
´
´
Address reprint requests to: Dr. Juan Jose Ramırez Jimenez, Servicio
de Ortopedia, Hospital Civil de Guadalajara Fray Antonio Alcalde,
´
Hospital 278, Col. El Retiro, C.P. 44280 Guadalajara, Jalisco, Mexico;
Phone: (þ52) (33) 3613-3951; FAX: (þ52) (33) 3613-3951; E-mail:
rajj0709@hotmail.com
to recreate the mechanical function by means of a number
of anterior or posterior devices. In our center, until the
1990s, patients with vertebral fractures or tumors were
managed with laminectomy plus Harrington and/or Luque
devices (1,3). Most patients reported that their pain was
not alleviated and the neurological deficit almost always
´
persisted. In 1995, one of the authors (J.J. Ramırez) designed an expandable vertebral body prosthesis (named
the JR prosthesis) to be used for spinal stabilization after
corpectomy. To the best of our knowledge, the JR prosthesis
is the first with dual plate-and-cage function in a single
device (4). Here we describe the characteristics of the JR
prosthesis and the clinical experience with 14 patients with
vertebral tumors who underwent corpectomy and replacement of the vertebral body with this implant.
0188-4409/$ - see front matter. Copyright Ó 2010 IMSS. Published by Elsevier Inc.
doi: 10.1016/j.arcmed.2010.08.013

2. Expandable Plate-and-Cage Prosthesis for Spine Stabilization after Corpectomy
479
Materials and Methods
Prosthesis Design
The vertebral bodies excepting C1 and C2 were measured
in appropriate adult cadaver preparations of the Department
of Anatomy of the Universidad de Guadalajara, Mexico.
After anatomic studies and measurements of the lumbar
and thoracic vertebrae, drafts were performed and waxand-plaster prosthesis models were created accordingly.
Using the lost-wax casting method, a chromium-cobalt
prototype was created and later was modified to an expandable stainless steel model, which finally resulted in a titanium device. The JR prosthesis (U.S. Pat. No. 5,458,641)
has five components: a) cephalad, b) caudad, c) central
cylinder, d) anti-rotational guide bolt, and e) fixation screw
(Figure 1A, left). Its components, once assembled, work
well together to create a modular and expandable cageand-plate device. The cephalad and caudad components
have three elements: 1) horizontal; 2) vertical; and 3)
central (Figure 1A, left). The horizontal elements of both
the caudad and cephalad components have conical projections in their sustentation surface in order to enhance
fixation and to avoid shearing between the implant and
the vertebral body. These horizontal elements also have
a centered hole, which continues distally in the cephalad
component and proximately in the caudad component to
create a cylindrical cage that can support bone grafts inside.
The central elements of both the cephalad and caudad
components have an external thread in such a way that by
rotating the central cylinder (component C) in a clockwise
direction the components move away from each other. To
avoid great vessel injury, the vertical element is located at
the patient’s right side for the upper and mid-thoracic
regions and at the left side for the lower thoracic and
lumbar spine. The vertical element of the cephalad component has a hole in the lower aspect and in the caudad
component on the higher part in order to lodge an antirotational guide bolt (Figure 1A, right). This modular,
anatomic and expandable design allows that, with little
changes, the cage-and-plate prosthesis can be used for all
vertebral bodies with exception of C1 and C2 (Figures 1B
and 1C). Due to its characteristic design, its anterior location to the instantaneous axis of rotation and its cage-andplate function, the prosthesis offers crossed and opposed
vectors to the flexion, extension and rotation moments of
the spine. The cross-sectional area of both the cephalad
and caudad components are approximately equal to that
of the vertebral end plates.
Cadaver Assays
The prosthesis was implanted into a cadaver donated by the
Department of Anatomy of our University. This cadaver
had the L1 and L2 vertebral bodies removed, which were
replaced with a prototypic implant. The spine was exposed
Figure 1. (A) Components: a) cephalad, b) caudad, c) central cylinder, d)
anti-rotational guide bolt, and e) fixation screw and elements: 1) horizontal, 2) central, and 3) vertical of the JR prosthesis. On the right side
of panel (A) a thoracolumbar JR device diagram is shown. (B) Cervical
JR device. (C) L5 JR device. (D) The case of a 46-year-old female with
plasmacytoma affecting T12 (left). Postoperative radiograph showing the
application of the JR prosthesis (right). (A color figure can be found in
the online version of this article.)
by an antero-lateral and retroperitoneal left approach. The
T12-L1 and L2eL3 discs and the L1 and L2 vertebral
bodies were removed by using osteotomes and rongeur.
After vertebral body removal, the implant was placed in
the corpectomy site and the prosthesis was expanded by
rotating the central cylinder with a lever bar until compression was applied to the end plates of T12 and L3 vertebral

3. 480
Ramı´rez et al./ Archives of Medical Research 41 (2010) 478e482
Table 1. General characteristics of the patients who received vertebral body replacement with the JR prosthesis
Case
Age/sex
Diagnosis
Spine level
1
2
3
24/M
61/M
72/M
Plasmacytoma
Adenocarcinoma
Renal carcinoma
T11
T11
L3
4
5
6
7
8
9
10
11
12
35/F
28/M
50/F
46/F
11/M
10/M
44/M
42/F
62/M
Cervical cancer
Plasmacytoma
Thyroid cancer
Cervical cancer
Osteosarcoma
Osteosarcoma
Renal carcinoma
Plasmacytoma
Renal carcinoma
L2
T8
L3
L1e2
T8
T8e9
L3
T12
L3
13
14
56/M
52/F
Hemangioma
Breast cancer
T11
T11
Follow-up
(months)
Frankel grade
Pre/postoperatively
VAS pain grade
Pre/postoperatively
AL/Left
AL/Left
AL/Left
84
6
0
A/A
A/A
A/NA
8/3
9/3
8/NA
AL/Left
AL/Left
AL/Left
AL/Left
AL/Right
AL/Left and P
AL/Left
AL/Left
AL/Left
6
60
96
9
11
48
7
16
0
C/D
C/E
D/E
C/E
C/D
C/E
C/D
C/D
C/NA
8/3
5/2
8/3
7/4
8/5
7/4
9/4
8/3
8/NA
9
4
C/E
C/E
Approach
AL/Left
AL/Left
6/1
8/2
Complications
None
None
Massive bleeding during
surgery causing death
None
Atelectasis
Vena cava lesion
None
None
None
None
None
Renal failure 4 days after
surgery causing death
None
None
AL, antero-lateral; F, female; L, left; M, male; NA, not applicable; P, posterior; R, right; VAS, visual analog scale.
bodies. The prosthesis was fixated to T12 and L3 with two
screws (length: 6.5 mm). With a hook attached directly to
the prosthesis, the cadaver was raised until completely
hanged. While suspended, radiographs were taken at the
site of the corpectomy. Later, the body was taken down
and subjected to flexion, rotation and extension forces by
six research collaborators while observing the implant’s
behavior in situ.
Statistical Analysis
Descriptive statistics were analyzed as simple frequencies
for nominal variables and as means for continuous variables. Wilcoxon’s signed rank test for paired related
samples was used to compare scores of visual analog scale
(VAS) and Frankel scale before and after surgery. All
p values !0.05 were considered significant. SPSS v.17.0
statistical package was used for all calculations.
Trial on Patients
From March 1995eDecember 2007, 14 patients with vertebral tumors underwent corpectomy and vertebral body
replacement with the JR prosthesis in our center: at one
level for 12 patients and at two different spine levels in
the other two patients. The ethics committee of our hospital
approved this study. The main inclusion criteria for corpectomy and vertebral body replacement were severe pain,
neurological deficit, spinal instability and having a medical
status suitable for surgery. The patient was placed in the
lateral decubitus position. The spine was exposed one
segment above and one segment below the injured vertebra.
The adjacent discs were removed and then the tumorous
vertebra was initially excised using osteotomes and rongeur. All retropulsed tumor fragments were excised with
a curette. The implant was placed and the central sleeve
was rotated counterclockwise to expand the prosthesis.
By this manner, kyphosis was corrected and soft tissue
tension was achieved. A fluoroscopic view was performed
at this time to evaluate device orientation. Once the expansion was completed and the orientation of the device satisfactory, it was fixated laterally with two screws above and
two screws below located in the vertical device’s elements,
forming the expandable lateral plate.
Results
We studied 14 patients (nine males, mean age: 42.4 years,
range: 10e72 years) with vertebral tumors. Of the 14
tumors, three were plasmacytomas, two osteosarcomas,
one hemangioma and eight metastatic tumors: three renal
carcinomas, one thyroid carcinoma, two cervical cancers,
one breast cancer and one adenocarcinoma of primary
unknown (Table 1). Mean surgical time was 242 min
(range: 210e360 min). Pain improved from a mean VAS
of 7.6 preoperatively to 3.0 after surgery in the 12 patients
who were alive within 2 weeks postoperatively ( p 5
0.002). This improvement in VAS was maintained to the
last follow-up evaluation, excepting in two patients with
tumor relapse. Indeed, neurological deficit did not improve
in patients with Frankel A score but did change satisfactorily by one or two grades in patients with Frankel C or D
presurgery (no cases with Frankel B were observed) ( p 5
0.003). Spine stability was immediately reached in all
cases. All patients achieved mobility or could be moved
48e72 h postoperatively, which facilitated nursing care.
The need for analgesics for postoperative pain management
was minimal. Complications related to the surgical event
included mild inferior vena cava lesion in one case

4. Expandable Plate-and-Cage Prosthesis for Spine Stabilization after Corpectomy
(repaired without further complications) and pulmonary
atelectasis in two patients who underwent thoracotomy,
necessitating a chest tube for lung re-expansion. Excluding
two patients who died perioperatively, minimal survival
length was 6 months with a maximum of 8 years (mean
follow-up period: 25.4 months). Three out of 14 patients
are currently alive: one with plasmacytoma, one with osteosarcoma and one with a spinal hemangioma. The patient with
osteosarcoma (Frankel grade C preoperatively) who is still
alive 5 years after corpectomy of two levels also received
a posterior instrumentation with Luque rod because the
posterior spinal elements were also removed. This patient
walked without pain (Frankel grade E postoperatively).
Two out of three patients with metastases from renal cancer
died perioperatively: one during surgery due to massive
bleeding, and the other patient 4 days after surgery due to
renal failure. The third patient with renal cell carcinoma died
7 months after surgery due to cancer complications. The
patient with metastasis from thyroid cancer (a 50-year-old
female) has the longest survival (8 years) of our cohort.
She finally presented lumbar pain and lower limb weakness
due to local relapse and died in a second surgery (posterior
instrumentation and laminectomy) due to pulmonary embolism. Of the immediate survivors, the patient with the shortest survival (6 months) had an adenocarcinoma from an
unknown primary. Regarding the patients with plasmacytoma, one out of three is currently alive. The other two patients
died after 6 and 7 years postsurgery, respectively. There have
been no implant failures, screw fractures or the need for prosthesis removal in any case. Spinal stability was maintained
for the rest of the patients’ life (Figure 1D).
Discussion
With modern devices, few complications associated with
anterior implants are reported (5e7); however, these
include screw and bolt fractures as well as loss of reduction
and progressive kyphosis. Kaneda (8) reported that the most
common complications with anterior instrumentations are
accidental sympathectomy (10%), subclinical pseudoarthrosis (7%) and implant failure (7%). Here we confirmed
the hypothesis that the biomechanical features of the JR
prosthesis provide spinal stability for the patient’s lifespan,
and no implant failures or fractures were observed.
However, it is necessary to note that the concept of spinal
stability is rather subjective, except in cases of overt
kyphosis or translation. According to Holdsworth (9),
spinal stability depends on the integrity of the posterior osteoligamentary complex. Denis (10) further divided the
Holdsworth’s anterior column in anterior and middle and
suggested that spinal stability depends on the integrity of
two columns. Kostuik et al. (11) based their model of
stability on Denis’ concept by dividing the spinal columns
in two further halves (obtaining six columns: three lefts and
three rights). According to this model, the spine will be
481
mechanically stable if only one or two columns are
destroyed but instable if there are three or more. The JR
prosthesis provides mechanical stability because it restores
the Holdsworth’s anterior column, the Denis’ anterior and
middle columns and the four Kostuik’s anterior columns.
Based on White and Panjabi’s concept (12), the JR prosthesis also provides clinical stability because it avoids
displacement by offering opposed and crossed vectors to
the main deforming forces of the spine so as not to damage
or irritate the spinal cord or nerve roots.
A number of expandable devices exist (13,14), and their
utility has been proven in vertebral tumors (15), demonstrating that spinal stability can be attained immediately
and that it represents a sufficient procedure in spinal tumor
surgery (15). Expandable implants are preferred over traditional devices, and it is possible that variations in cage
design are of little importance in terms of effectiveness
(16). Cages were created to provide mechanical support
after corpectomy (5,6,8,17,18). However, cages were not
designed as stand-alone devices because the construction
is instable in rotation. Therefore, a lateral plate is needed
to control rotational moment (11e19).
This is a rather small cohort on the experience with this
implant in patients with vertebral tumors, which represents
only a subset of all cases in whom the JR prosthesis has
been used in our hospital. The experience according to
other indications for vertebral body replacement (e.g.,
trauma, posttraumatic kyphosis, Pott’s disease) with the
implant will be reported shortly. The design of the JR
prosthesis makes its placement easy and with remarkable
duration. This first communication should be considered
hypothesis-generating work waiting for systematic confirmation or for the test of time.
Acknowledgments
´
´
Dr. Juan Jose Ramırez is the inventor of the JR Prosthesis (US Pat.
No. 5,458,641) without any commercial relationship with external
parts. The authors are indebted to Dr. Fernando Hiramuro-Hirotani
´
(Chief, Orthopedics Department), Dr. Luis Navarro-Rodrıguez
´
(Former Chief, Orthopedics Department), Dr. Jaime Agustın
´
´
Gonzalez-Alvarez (General Director, OPD Hospital Civil de
´
´
Guadalajara), Dr. Antonio Luevanos-Velazquez (Education and
Research Director, OPD Hospital Civil de Guadalajara), Dr.
´
´
´
Martın Gomez and Dr. Sergio Sanchez (Department of Thoracic
Surgery), as well as the Department of Anatomy of the Universidad de Guadalajara for the support provided for this work. The
authors would like to thank the patients and their families for their
trust and endurance in this endeavor.
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