Keywords arthroplasty, replacement, hip - surgical planning - 3D printing
Introduction
Revision of total hip arthroplasty (THA) is currently an increasingly-performed procedure.[1 ] The complexity involved in surgeries of this magnitude often requires meticulous
preoperative planning to minimize the risks of possible associated complications.
Although there has been a significant improvement in the materials used during arthroplasty,
after a few years it is inevitable that a considerable part of the patients will progress
to the need to replace the implants, especially due to aseptic loosening, often with
significant acetabular and femoral failure.[2 ]
[3 ]
This increased demand requires the creation and improvement of techniques for THA
reviews. Preoperative imaging has progressed from two to three dimensions and, recently,
to palpable modeling available in real size when using 3D printing.[2 ] This broadens the surgical team's understanding of the pathology in question and,
therefore, expands the understanding of those involved in the procedure to be performed.[3 ] Many orthopedic implants have a standard shape that is not compatible with every
situation, so the preoperative molding of synthesis materials can be more adaptable
according to the need, and it speeds up the surgical procedure, since it avoids this
step during surgery without actually considerably increasing the final costs of the
procedure.
In this sense, the present research presents a comparative study that demonstrates
an unconventional technique in the surgical planning of THA review to evaluate the
practical usefulness of 3D prototyping to abbreviate complex surgeries.
Materials and Methods
The present research was submitted and approved by the Ethics in Research Committee
of our institution. The work consists of a comparison between two situations of an
unconventional surgical technique for the review of THA in which there is a need for
reconstruction of an acetabular failure, with and without the use of 3D printed models.
Two cases (one with and the other without the use of 3D printed models) were selected
in which there were radiological signs of aseptic loosening of the acetabular component
and which fit type 3B in the Paprosky classification.
The cases operated herein reported present a new surgical technique for acetabular
reconstruction. In one of the cases, we used 3D prototyping (PT3D) of the hip that
would be operated on. The technique consists in obtaining the 3D image of the region
that will be reviewed and then processed in the computer-aided design (CAD) environment
and later printed. For this, the patient was initially submitted to a traditional
computed tomography (CT), which provides a computer file in the digital imaging and
communications in medicine (DICOM) format that is then opened and processed in the
InVesalius software (Centro de Tecnologia da Informação Renato Archer, Campinas, SP,,
Brazil) to be converted into the standard triangle language (STL) format. Then, the
file was edited in the MeshMixer software (Autodesk, Inc., San Rafael, CA, US) to
remove the artifacts, the loose implant, and improve the quality of the image to then
print the acetabulum in real size with a Cliever 3D equipment (Cliever Tecnologia,
Belo Horizonte, MG, Brazil), using polylactic acid (PLA) filament. The printing was
performed with a layer thickness of 0.3 mm, filling of 70% and line thickness of 3 mm,
and it took approximately 10 hours. The manufacturing took place in a controlled environment
with a temperature of 25.8°C and air humidity of 47%. After the printing, a post-processing
was performed to remove the excess material used in the part holder. The total cost
of manufacturing the 3D biomodel was U$ 16.00.
We timed the steps of the preoperative and transoperative surgical planning to measure
the comparison of the objective. We estimated the total time to mold the plate, the
study of the acetabular component, the approximate size and direction of the screws,
in addition to the amount of graft required to fill the acetabular failure.
Both revisions were performed in a single surgical time. The access route chosen for
the second procedure was the same incision as that of the primary arthroplasty surgery,
being posterolateral in both cases.
A reconstruction plate (small-fragment box) was molded in both cases, and for one
of them we used as a base the biomodel printed in 3D to make the necessary adjustments
before the procedure, and, for the second case, the modeling occurred during surgery.
The precast plate based on the 3D biomodel was sterilized by the Materials Sector
to be used permanently during surgery. In both acetabular reconstructions, we used
autologous bone grafts of the iliac ipsilaterally to the main procedure. Both arthroplasties
were replaced using a cemented acetabular component (conventional polyethylene) and
a metallic femoral head.
Before the surgery, all patients were previously instructed regarding the technique
to be performed, and they agreed with the process. The patients were operated on by
the authors of the present article.
The patient data were kept confidential, serving only for the recording or illustration
of the technique presented.
Description of Case 1
A 64-year-old female patient sought care for progressive chronic pain in the right
hip. Ten years before, she had undergone a cemented THA on the right side due to fractured
femoral neck. In the first care, anteroposterior (AP) radiographs of the hip and AP
and profile (P) radiographs of the coxofemoral joint were performed ([Figure 1A, 1B, 1C ]). In addition, laboratory tests (blood count, c-reative protein [C-RP] and erythrocyte
sedimentation rate [ESR]) were requested, and they did not show abnormalities. We
indicated revision of the arthroplasty due to aseptic loosening in a single stage
surgery (type 3B acetabular failure in the Paprosky classification). The femoral stem
did not present radiographic signs of loosening. The 3D prototype (3DPT) was printed
for the preoperative planning ([Figure 2 ]) based on a computed tomography of the coxofemoral joint. Using the 3D biomodel
of the pelvis, we molded the reconstruction plate before the procedure, and then sent
it to the Sterilization Sector so that it was ready to be used at the time of the
review ([Figure 3G ]). The access route chosen for the right hip was posterolateral, and another incision
was performed for the removal of a homolateral iliac graft ([Figure 3A ]). During surgery, stability tests confirmed that the stem remained fixed, only the
femoral metal head was replaced. The acetabular component was extracted, and a large
local debridement was performed ([Figure 3B,C, D, E ]) and the molded plate was introduced ([Fig. 3F ]), observing the same cavity that was previously viewed when molding the plate with
the aid of a 3D printed model ([Fig. 3G ]). The size of the acetabular prosthesis was also estimated during planning using
cutters of varying sizes ([Figure 4A ]). We used a structured autologous graft of the ipsilateral iliac to prevent cement
extravasation into the pelvis, as well as impacted spongy graft ([Figure 4B,C ]). The acetabular component was cemented on the reconstruction plate, and to the
new bone layer the stability tests performed were adequate ([Figure 4D ]). The immediate postoperative outcome is shown in [Figure 1B ]. Currently, the patient has been under follow-up for two years and three months.
Fig. 1 (A ) Preoperative radiographs (case 1). (B ) Postoperative radiographs.
Fig. 2 3D prototype (case 1) printed after being processed based on a computed tomography
scan.
Fig. 3 (A ) Ipsilateral iliac and posterolateral incisions (case 1). (B ) Transoperative image of cemented acetabular component to be revised. (C-D ) Acetabular component removed. (E ) Acetabular failure after removal of the acetabular component. (F ) Molded reconstruction plate embedded in the acetabulum. (G ) Planning using the 3D biomodel with the precast plate.
Fig. 4 (A ) Reconstruction plate and acetabular cutter for preoperative planning. (B ) Autologous bone graft of the iliac structured as a lid. (C ) Graft cover used in the acetabular fundus to avoid cement extravasation into the
pelvis. (D ) Final result of the cemented acetabular component reviewed.
Description of Case 2
A 58-year-old male patient sought care for chronic pain and functional limitation
in the right hip. In the first care, AP radiographs of the pelvis and AP and P radiographs
of the coxofemoral joint were performed ([Figure 5A ]). Total hip arthroplasty was indicated for osteoarthrosis in the right hip ([Figure 5B ]). After 15 years, the patient returned for a consultation with significant failure
of the acetabulum classified as Paprosky type 3B ([Figure 5C ]) and signs of osteolysis in the femoral stem in Gruen zones 1, 2, 6, and 7, Laboratory
tests (blood count, C-RP and ESR) were requested, but they did not show abnormalities.
We decided to perform a review of the THA in a single surgical time ([Figure 5D ]). The stem was stable during the transoperative tests, and we chose to maintain
it. Currently, the patient has been under follow-up for two years ([Figure 5E ]).
Fig. 5 (A ) Preoperative radiograph evidencing important osteoarthrosis in the right hip (case
2). (B ) Immediate postoperative radiograph. (C ) Postoperative radiograph 15 years later, with Paprosky type-3B failure. (D ) Immediate postoperative radiograph of the revision sugery. (E ) Postoperative radiograph with two years of evolution, evidencing osteointegration
of the graft in the acetabular fundus.
Results
The cases herein reported demonstrate a new option of surgical technique to solve
complex problems involving the review of THA in cases of Paprosky type-3B failures.
The patients were successfully operated on using a reconstruction plate on the acetabular
fundus as support for the structural graft associated with impaction grafting for
reconstruction of the acetabulum for further cementation of the acetabular component
of the prosthesis.
The total time spent in the pre- and transoperative (with and without the use of a
3D printed mold, respectively) moldings of the reconstruction plate was 8 minutes
and 27 minutes, until they were adequately adjusted.
The total time it took to choose the size of the cemented acetabular component pre-
and transoperative (with and without the use of a 3D printed mold, respectively) was
2 and 6 minutes. The size and direction of the screws until the fixation of the reconstruction
plate in the acetabulum were of 7 and 25 minutes respectively.
In order to obtain the necessary amount of graft, without counting the extraction
time, it took 3 and 6 minutes respectively. The total time of the procedure in case
1 was of 123 minutes, and in case 2, 179 minutes, a difference of 56 minutes.
During the transoperative period, we did not need to perform additional moldings on
the reconstruction plate, previously made using the 3D printed model. The cemented
acetabular component coincided exactly with what had been planned according to the
tests during the prototyping, and the size of the screws was within a variation of ± 2 mm.
Discussion
The use of 3DPTs is a reality that has become familiar to orthopedic surgeons.[3 ] Although not yet widely available, full-size printing facilitates the understanding
and planning of the proposed procedure. The costs regarding the production of the
part are easily supplanted by the shorter surgical time, not to mention all the known
benefits that involve a faster procedure.[3 ]
[4 ]
[5 ]
Another important point to be emphasized is that, during a THA review, we often find
a difficult surgical exposure due to the non-anatomical presence of periprosthetic
fibrotic tissues.[5 ]
[6 ] With prototyping, there is the possibility of using anatomical landmarks previously
defined in the biomodel as an intraoperative reference. We know that not all acetabular
failures are the same; therefore, when we mold the material we can make the necessary
adjustments.[7 ] The individualization of the treatment to the demands of the patient is a medical
trend, reinforcing the importance of a detailed preoperative planning, which provides
more consistent results.[2 ]
[3 ]
[4 ]
[5 ]
The understanding of the patient is fundamental, especially regarding a complex THA
review and the challenges faced by the surgeon, in order to demystify the concept
that the exchange of components is often simple. In this sense, 3D printing can be
a tactile tool that helps explain the procedure to be performed. While there are other
positive points to note, we must recognize that the cost of 3D printers is still high.
We present here not only a description of two cases, but also an innovative technique
that has been used in our service, given the limitation of materials we face in the
Brazilian Unified Health System (Sistema Único de Saúde, SUS, in Portuguese) and the
higher demand for revision surgeries due to the greater longevity of the population.
Through the cases herein reported, we demonstrated a new option of surgical technique
to solve complex problems involving the THA review in type-3B Paprosky failures. In
these cases, we used a reconstruction plate on the acetabular fundus as a support
for the structural graft associated with impaction grafting for acetabular reconstruction.
This technique has shown excellent results to date. Furthermore, the procedure can
be optimized with the use of 3D printing for a better understanding of the pathology
by the surgical team, for the training of residents, the reduction of the surgical
time, and, consequently, of the risks to the patients. We understand that the number
of cases is still small, and that we cannot make generalizations regarding the two
cases herein reported. However, the technique effectively solved the problems presented
and undeniably led to a shorter surgical time. A greater follow-up and a greater number
of cases treated with the proposed technique are still needed, and the use of 3D prototyping
can offer a cost-effective alternative to solve specific cases.
Final Comments
The technique herein presented for the reconstruction of Paprosky type-3B defects
demonstrated excellent results, especially when associated with some of the various
benefits of using a 3DPT for the planning of surgical procedures. Preoperative molding
of the synthesis material to be used may decrease the surgical time.
