JR prosthesis for vertebral body

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
de Guadalajara, Fray Antonio Alcalde, Universidad de Guadalajara, Guadalajara, Me ´xico, cUniversidad Auto
´noma de
Guadalajara, Zapopan, Me ´xico
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 fixa-
tion and adequacy to the human spine anatomy. Then, 14 patients with vertebral tumors
(eight metastatic) underwent corpectomy and vertebral body replacement with a titanium-
made 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 immedi-
ately, which was maintained for long periods (mean follow-up: 25.4 months). No signif-
icant 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 experi-
ence 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 to recreate the mechanical function by means of a number
of anterior or posterior devices. In our center, until the
Eighty five percent of all cases of spinal metastasis are
1990s, patients with vertebral fractures or tumors were
located primarily in the vertebral body (1). Spinal cord
managed with laminectomy plus Harrington and/or Luque
lesion in metastatic disease of the spine results from direct
devices (1,3). Most patients reported that their pain was
tumor compression, vertebral body collapse and retropulsed
not alleviated and the neurological deficit almost always
bone fragments (2). As a result, pain, neurological deficit,
´
persisted. In 1995, one of the authors (J.J. Ramırez) de-
spine instability or segmental deformities ensue (1,2). In
signed an expandable vertebral body prosthesis (named
order to restore the stability of the spine, it is necessary
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
´ ´ ´
Address reprint requests to: Dr. Juan Jose Ramırez Jimenez, Servicio device (4). Here we describe the characteristics of the JR
de Ortopedia, Hospital Civil de Guadalajara Fray Antonio Alcalde,
´
Hospital 278, Col. El Retiro, C.P. 44280 Guadalajara, Jalisco, Mexico;
prosthesis and the clinical experience with 14 patients with
Phone: (þ52) (33) 3613-3951; FAX: (þ52) (33) 3613-3951; E-mail: vertebral tumors who underwent corpectomy and replace-
rajj0709@hotmail.com ment 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 wax-
and-plaster prosthesis models were created accordingly.
Using the lost-wax casting method, a chromium-cobalt
prototype was created and later was modified to an expand-
able stainless steel model, which finally resulted in a tita-
nium 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 cage-
and-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 projec-
tions 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 compo-
nent has a hole in the lower aspect and in the caudad
component on the higher part in order to lodge an anti-
rotational 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 Figure 1. (A) Components: a) cephalad, b) caudad, c) central cylinder, d)
and 1C). Due to its characteristic design, its anterior loca- anti-rotational guide bolt, and e) fixation screw and elements: 1) hori-
tion to the instantaneous axis of rotation and its cage-and- zontal, 2) central, and 3) vertical of the JR prosthesis. On the right side
plate function, the prosthesis offers crossed and opposed 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
vectors to the flexion, extension and rotation moments of
plasmacytoma affecting T12 (left). Postoperative radiograph showing the
the spine. The cross-sectional area of both the cephalad application of the JR prosthesis (right). (A color figure can be found in
and caudad components are approximately equal to that the online version of this article.)
of the vertebral end plates.
by an antero-lateral and retroperitoneal left approach. The
T12-L1 and L2eL3 discs and the L1 and L2 vertebral
Cadaver Assays
bodies were removed by using osteotomes and rongeur.
The prosthesis was implanted into a cadaver donated by the After vertebral body removal, the implant was placed in
Department of Anatomy of our University. This cadaver the corpectomy site and the prosthesis was expanded by
had the L1 and L2 vertebral bodies removed, which were rotating the central cylinder with a lever bar until compres-
replaced with a prototypic implant. The spine was exposed sion 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
Follow-up Frankel grade VAS pain grade
Case Age/sex Diagnosis Spine level Approach (months) Pre/postoperatively Pre/postoperatively Complications
1 24/M Plasmacytoma T11 AL/Left 84 A/A 8/3 None
2 61/M Adenocarcinoma T11 AL/Left 6 A/A 9/3 None
3 72/M Renal carcinoma L3 AL/Left 0 A/NA 8/NA Massive bleeding during
surgery causing death
4 35/F Cervical cancer L2 AL/Left 6 C/D 8/3 None
5 28/M Plasmacytoma T8 AL/Left 60 C/E 5/2 Atelectasis
6 50/F Thyroid cancer L3 AL/Left 96 D/E 8/3 Vena cava lesion
7 46/F Cervical cancer L1e2 AL/Left 9 C/E 7/4 None
8 11/M Osteosarcoma T8 AL/Right 11 C/D 8/5 None
9 10/M Osteosarcoma T8e9 AL/Left and P 48 C/E 7/4 None
10 44/M Renal carcinoma L3 AL/Left 7 C/D 9/4 None
11 42/F Plasmacytoma T12 AL/Left 16 C/D 8/3 None
12 62/M Renal carcinoma L3 AL/Left 0 C/NA 8/NA Renal failure 4 days after
surgery causing death
13 56/M Hemangioma T11 AL/Left 9 C/E 6/1 None
14 52/F Breast cancer T11 AL/Left 4 C/E 8/2 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 Statistical Analysis
screws (length: 6.5 mm). With a hook attached directly to
Descriptive statistics were analyzed as simple frequencies
the prosthesis, the cadaver was raised until completely
for nominal variables and as means for continuous vari-
hanged. While suspended, radiographs were taken at the
ables. Wilcoxon’s signed rank test for paired related
site of the corpectomy. Later, the body was taken down
samples was used to compare scores of visual analog scale
and subjected to flexion, rotation and extension forces by
(VAS) and Frankel scale before and after surgery. All
six research collaborators while observing the implant’s
p values !0.05 were considered significant. SPSS v.17.0
behavior in situ.
statistical package was used for all calculations.
Trial on Patients
Results
From March 1995eDecember 2007, 14 patients with verte-
bral tumors underwent corpectomy and vertebral body We studied 14 patients (nine males, mean age: 42.4 years,
replacement with the JR prosthesis in our center: at one range: 10e72 years) with vertebral tumors. Of the 14
level for 12 patients and at two different spine levels in tumors, three were plasmacytomas, two osteosarcomas,
the other two patients. The ethics committee of our hospital one hemangioma and eight metastatic tumors: three renal
approved this study. The main inclusion criteria for corpec- carcinomas, one thyroid carcinoma, two cervical cancers,
tomy and vertebral body replacement were severe pain, one breast cancer and one adenocarcinoma of primary
neurological deficit, spinal instability and having a medical unknown (Table 1). Mean surgical time was 242 min
status suitable for surgery. The patient was placed in the (range: 210e360 min). Pain improved from a mean VAS
lateral decubitus position. The spine was exposed one of 7.6 preoperatively to 3.0 after surgery in the 12 patients
segment above and one segment below the injured vertebra. who were alive within 2 weeks postoperatively ( p 5
The adjacent discs were removed and then the tumorous 0.002). This improvement in VAS was maintained to the
vertebra was initially excised using osteotomes and ron- last follow-up evaluation, excepting in two patients with
geur. All retropulsed tumor fragments were excised with tumor relapse. Indeed, neurological deficit did not improve
a curette. The implant was placed and the central sleeve in patients with Frankel A score but did change satisfacto-
was rotated counterclockwise to expand the prosthesis. rily by one or two grades in patients with Frankel C or D
By this manner, kyphosis was corrected and soft tissue presurgery (no cases with Frankel B were observed) ( p 5
tension was achieved. A fluoroscopic view was performed 0.003). Spine stability was immediately reached in all
at this time to evaluate device orientation. Once the expan- cases. All patients achieved mobility or could be moved
sion was completed and the orientation of the device satis- 48e72 h postoperatively, which facilitated nursing care.
factory, it was fixated laterally with two screws above and The need for analgesics for postoperative pain management
two screws below located in the vertical device’s elements, was minimal. Complications related to the surgical event
forming the expandable lateral plate. included mild inferior vena cava lesion in one case

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