Acetabular defects reconstruction with tantalum constructions.

Background Total hip replacement (THR) is a common procedure that is performed increasingly often. Al though most patients have satisfactory long-term stability, approximately 17% of prosthetic hips fail, thus requiring revision. Frequently, when hip prosthesis revision is undertaken, there is significant ace tabular bone deficiency present; this clinical setting presents one of the most challenging circu m ‐ stances in hip surgery. There is a variety of surgical hardware and strategies available to address this problem. Preoperative planning is a critical aspect of any reconstructive hip surgery but is particularly im por tant in revision surgery. The surgeon must anticipate instrument, bone graft, and implant requi ‐ re ments for the surgery, as well as which reconstructive options may be needed, based on what may be found intraoperatively. The purpose of this study was to evaluate early functional results of hip arthroplasty with acetabular defects, pelvic bone loss revised with porous tantalum acetabular components. Methods 56 patients were operated during research period with different kind of acetabular defects. W.G. Paprosky classification was used to classify existing acetabular defect. From 56 patients 26 was primary hip replacement and 30 – revision. Results Different kind of tantalum constructions were used to reconstruct acetabular defects during replacement surgery. During research period three patient had complications: two cases of dislocation after revision replacement (3,6%) and one – after primary replacement (1,8%), one suppuration case (1,8%). Conclusions According research results possible to make conclusion: using tantalum augments during acetabular region reconstruction allow to avoid non-biological fixators – support rings and structural grafts; tantalum augments are successfully applicable during all kinds of acetabular defects reconstruction, in primary and revision replacement; using tantalum augments during acetabular region reconstruction allow to achieve components stable primary fixation.


Introduction
Total hip replacement (THR) is a common procedure that is performed increasingly often. Although most patients have satisfactory long-term stability, approximately 17% of prosthetic hips fail, thus requiring revision. Frequently, when hip prosthesis revision is undertaken, there is significant acetabular bone deficiency present; this clinical setting presents one of the most challenging circumstances in hip surgery. There is a variety of surgical hardware and strategies available to address this problem.
Indications for acetabular revision include symptomatic aseptic loosening, failure of fixation, infection, wear, osteolysis, and instability. Bozic and associates, using the Healthcare Cost and Utilization Project Nationwide Inpatient Sample database, recently found that the most common cause of revision hip surgery was instability or dislocation (22.5%). 1

AAOS Classification
The American Academy of Orthopaedic Surgeons (AAOS) classification of bone defects, as described by D'Antonio and associates, identifies the pattern and location of bone loss but does not quantify the defect. 2,3 This system, which was developed by evaluating AP and lateral hip radiographs and comparing results intraoperatively, is probably the most commonly used classification in the literature.

Paprosky Classification
The Paprosky classification system is based on the severity of bone loss and on the ability to obtain cementless fixation for a given bone loss pattern. [4][5][6] It was initially developed by evaluating the AP pelvis radiograph and comparing this information with intraoperative findings.
Careful interpretation of the AP radiograph can predict the type of defect and can allow the surgeon to plan for the acetabular reconstruction. Four criteria are used to assess the preoperative radiograph: (1) superior migration of the hip center, (2) ischial osteolysis, (3) teardrop osteolysis, and (4) position of the implant relative to Kohler's line.

Preoperative Planning
Preoperative planning is a critical aspect of any reconstructive hip surgery but is particularly important in revision surgery. The surgeon must anticipate instrument, bone graft, and implant requirements for the surgery, as well as which reconstructive options may be needed, based on what 4 may be found intraoperatively.
Every patient undergoing revision surgery should be screened for infection with at least an erythrocyte sedimentation rate and C-reactive protein. The erythrocyte sedimentation rate should be less than 30 mm/hr and the C-reactive protein less than 10 mg/L.

Treatment Options For Acetabular Defects
Several options are available for acetabular revision. These options are divided into two major categories based on the type of fixation. Biological fixation refers to any surgical option that requires direct contact with host bone and osteointegration into the acetabular shell to provide long-term

Own Experience For Acetabular Defects Reconstruction
This chapter presented our own experience for acetabular defects reconstruction. 56 patients were operated during the research period: 26 -primary hip replacement and 30 patients with revision hip (Fig 3.1).
Only W.G. Paprosky classification was used to classify acetabular defects during our investigation ( Fig.   3.

2).
Different kind of tantalum constructions were used to reconstruct existing acetabular defects during replacement surgery.
Porous tantalum is an alternative metal for total joint arthroplasty components that offers several unique properties. Its high volumetric porosity (70% to 80%), low modulus of elasticity (3 MPa), and 5 high frictional characteristics make it conducive to biologic fixation. Tantalum has excellent biocompatibility and is safe to use in vivo. The low modulus of elasticity allows for more physiologic load transfer and relative preservation of bone stock. Because of its bioactive nature and ingrowth properties, tantalum is used in primary as well as revision total hip arthroplasty components, with good to excellent early clinical results. In revision arthroplasty, standard and custom augments may serve as a structural bone graft substitute.
Now some patients' X-rays will be presented before and after operation and we will try to make a conclusion according to this experience.
In the Fig. 3 In next case also possible to see III A acetabular defect (Fig. 3.9). Patient had bone deficiency in the central part of acetabulum.
During next three cases we want to present patients with III A and B acetabular defects with severe bone loosening.
The first patient had dislocation after replacement surgery and instability for all component of endoprosthesis. In Fig. 3.10 we can see X-Ry before operation and after the first operation. Aim of the first operation was removing previous prosthesis and putting spacer. There was huge bone defect in acetabular region, III B (Fig. 3.10 B, Fig. 3.11). In Fig. 3.12 possible to see acetabular defect 6 reconstruction with tantalum augment, during the surgery A (intraoperative pictures) and after surgery B (postoperative X-Ry).
The second case -32 years old patient, Y.W.Z., after acetabular region plating operation. Patient had deformity in the hip joint and severe pain. In Fig. 3.13 possible to see preoperative X-Rys, III A defect according to W.G. Paprosky classification and in Fig. 3.14 -postoperative X-Rys, after the reconstraction surgery with tantalum construction.
The third patient -73 years old female, H.Y.Z., after bilateral hip replacement (Fig. 3.15). In the right side possible to see huge bone defect (III B) in the acetaular region, cup loosening and fracture, in the left side also bone defect and cup loosening. Fig. 3.16 presented tantalum augments preparation with using bone cement. In the Fig. 3.17 we can see postoperative X-Rys, after the right acetabulum reconstruction with augments and in the Fig. 3.18 possible to compare difference between using cup cage technic and tantalum augment.

1.
Using tantalum augments during acetabular region reconstruction allow to avoid non-biological fixators -support rings and structural grafts.

2.
Augments selection is conducted according to preoperative planning, in which is necessary performing CT with 3D reconstruction.

3.
Tantalum augments are successfully applicable during all kinds of acetabular defects reconstruction, in primary and revision replacement.

4.
For augments successful osseointegration is necessary close contact between tantalum and bone.

5.
Using tantalum augments during acetabular region reconstruction allow to achieve components stable primary fixation.      15 Figure 11 3.10. A Preoperative X-ry with dislocation and instability. B X-Ry after the first operation. Figure 12 3.11. In CT possible to see huge bone defect in acetabular region, III B defect according to W.G. Paprosky. Figure 13 3.12. Acetabular defect reconstruction with tantalum augment during the surgery A (intraoperative pictures) and after surgery B (postoperative X-Ry). Figure 14 3.13. In preoperative X-Rys possible to see deformity in the hip joint and bone loosening, acetabular region III A defect according to W.G. Paprosky. Figure 15 3.14. Postoperative X-Rys, after the reconstruction surgery with tantalum augment. 18 Figure 17 3.16. Tantalum augments preparation with using bone cement. Figure 18 3.17. Postoperative X-Rys, after the right acetabulum reconstruction with augments.
19 Figure 19 3.18. In these X-Rys possible to compare deferens between augment reconstruction (right side) and cup cage technic (left side). 3.20. Dislocation case after reconstruction surgery. A Before dislocation, B after dislocation. Figure 22 3.21. Suppuration case after reconstruction surgery.