Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
Introduction
The acetabular fractures are the result of significant trauma. The anatomic location as well as the complexity of the three-dimensional structure make the treatment of these fractures extremely challenging. Overall, fractures of the pelvis make upto 0.3 to 6% of all fractures, with 44% of these occurring as either isolated fractures of the acetabulum or as combined acetabulum and pelvic ring injuries.1
The management of acetabular fractures depends upon the age of the patient, fracture anatomy and stability, bone quality, presence of comorbidities and any associated injuries. So, the spectrum of the treatment includes conservative methods, percutaneous fixation, open reduction for acetabular fixation and acute total hip arthroplasty. Although most of the displaced acetabular fractures are treated with open reduction and fixation, the total hip arthroplasty in acute acetabular fracture has a definite role to play in selected situations.
The total hip arthroplasty is generally reserved for the late sequelae of acetabular fractures, mainly secondary arthritis and avascular necrosis of femoral head. However, acute total hip replacement, either alone or combined with fixation is indicated in selected cases. This is generally accomplished either with the cementless multihole acetabular shells or with use of acetabular cages and rings, which help to support and stabilize the acetabular fracture.
Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
Timing for a Total Hip Arthroplasty
There are three time periods in which total hip arthroplasty may be considered after an acetabular fracture.2
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Early acute period: from the day of the injury to 3 weeks.
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Delayed reconstruction: from 3 weeks to 3 months.
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Late reconstruction: more than 3 months of fracture.
Indications and Contraindications for Acute Total Hip Arthroplasty
The main indications for the total hip arthroplasty include significant destruction of the articular surface (full thickness articular cartilage) of the acetabulum and/or femoral head, impaction of the femoral head or acetabulum, pre-existing arthritis of the hip, associated femoral head splitting and femoral neck fractures, and, pathologic fractures.3,4
In elderly patients, the posterior wall fracture with impaction is considered as an indication of acute total hip arthroplasty. Also, in these age groups, there is frequent association of the osteoporosis and the various co-morbidities. These elderly patients are vulnerable to fixation
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failures and wound complications after the extensile approaches, which have a negative outcome for the subsequent total hip arthroplasty. Doing second surgery in these patients further poses a high-risk. There are reports with poor results and high failure rates in elderly population who were managed conservatively or with open reduction and fixation even in simple fracture patterns.5 So, the decision between fixation and arthroplasty should be carefully taken in elderly population.
A transverse or T- type fracture has a very bad prognosis after open reduction and fixation, and these are usually associated with femoral head impaction. Similarly, posterior wall fracture with severely comminuted posterior column often gives poorer results with fixation. The total hip arthroplasty should be considered in these situations as an option even in relatively young patients.
The contraindication to performing acute total hip arthroplasty is simple fracture pattern which is easily fixable. Some of the others are poor medical fitness, open fractures and prior irradiation therapy to the hemipelvis.6
Total Hip Arthroplasty
Acute Total Hip Arthroplasty Using Acetabular Rings/Cages
It is relatively easier to perform acute total hip arthroplasty in isolated posterior wall/column fractures with an intact anterior column, because this column can be utilized for screw fixation through cages/rings.
There are many different types of reconstruction cages and rings which can be used to stabilize the acetabulum and hence insert the acetabular component. The authors prefer to use the Octopus® system (DePuy, Johnson and Johnson, USA). This is the only available cage which provides biological fixation as its hydroxyapatite outer coating helps integration in the host bone and thus provide stability. All other cages are purely mechanical devices and prone to structural failure over time. Besides this, the octopus cage acts as a hemispherical plate with a multiple screw options, so as to stabilize the acetabulum.
Octopus System (Fig. 32.1)
The octopus acetabular system offers an effective strategy for dealing with acute acetabular fracture. Its titanium structure can be manipulated to reconstruct the patient’s normal anatomy, to achieve accurate positioning and alignment of the cup. The three support legs or wings are strategically located to gain secure peripheral fixation in healthy bone.
Figure 32.1: Octopus system
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Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
Figure 32.2: Octopus acetabular ring with three supports
COMPONENTS OF THE OCTOPUS SYSTEM
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Outer acetabular ring with three legs/supports
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Hemispherical acetabular shell
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Inner polyethylene liner
The Acetabular Ring (Fig. 32.2)
Precise acetabular reconstruction and alignment: Ring is manufactured from pure titanium. Its malleability and mechanical integrity allow the ring to be easily and safely contoured to achieve an accurate reconstruction of the acetabular ring.
Secure three-point peripheral fixation: Three support legs enable cup alignment in addition to providing reliable initial mechanical stability, an essential factor in long-term biological fixation. Hooked inferior leg aligned from the obturator foramen prevents superior or lateral malpositioning of the cup. Superior iliac wing has three fixation holes and the posterior iliac T-leg has two fixation holes. These two iliac wings are used to adjust anteversion and abduction. The 6.5 mm screws are used for fixation of this ring.
The Shell
Mechanical stability: Shell is mounted on acetabular ring by four connecting screws through multiple holes in its outer flange. In addition, there is also choice of four cancellous screws, which are used to secure bone graft to underlying healthy bone, ensuring integrity. Five screw holes in the periphery of the hemisphere allow the surgeon to compress the bone graft.
Long-term biological fixation: Outer shell is spray coated with hydroxyapatite (Figs 32.3A and B) and its highly osteoconductive nature helps in incorporation of the surrounding graft, leading to long-term biological fixation.
Liner
Liner is available in two choices:
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Standard hooded liner
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Figures 32.3A and B: Hydroxyapatite coated shell
Total Hip Arthroplasty
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15° reorientation liner—this lateralizes the center of rotation of head by 2.8 mm and increases head coverage posteriorly when pelvic geometry dictates a more medial placement of the cup.
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ADVANTAGES OF OCTOPUS SYSTEM
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It provides a large contact area between the implant and host bone without intervening cement thereby decreasing the chances of implant migration.
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It acts as a hemispherical plate to hold the acetabular fracture in place and thus helps in initial stability.
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The holes in the ring provide multiple options for screw fixation and filling the defects with the morselized graft through holes.
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The hydroxyapatite spray coating outside the shell helps in integration with the host bone or bone graft.
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It provides a method of successful bone augmentation by protecting the bone grafts during revascularization, incorporation, and remodelling.
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Center of rotation can be correctly positioned and aligned relative to Shenton’s line.
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Octopus system has the advantage of choosing from two liners types – standard and lateral offset liner which allow appropriate balancing and tensioning of the soft tissues to assure joint stability through a full range of movement.
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SURGICAL TECHNIQUE
Surgical technique for the total hip arthroplasty in acute acetabular fracture using the Octopus® cage is discussed below in reference to an unpublished series including the senior author.
Preoperative Planning
Clinically, the skin status of the planned incision site is assessed to look for and rule out any signs of closed degloving injury, e.g. Morel-Lavallee lesion, which dictates the need to delay the surgery. The radiographic assessment of the acetabulum includes the pelvis anterior-posterior (AP), Iliac and Obturator views. These are done to assess the fracture type and extent. Computed tomographic (CT) scans are done along with 3D reconstruction (Figs 32.4A and B). The acetabular fracture is classified according to the Letournel and Judet’s classification.7 The CT images are carefully evaluated for the extent of comminution and the marginal impaction, if any. The surgical approach for the total hip arthroplasty depends partly on the fracture location and classification and partly on the surgeon’s preference. Templating is done for accurate preoperative assessment of appropriate size, position and alignment for acetabular ring relative to the obturator foramen, to obtain a smooth Shenton’s line and restore equal leg length. Templates should also be used to assess the length of the superior iliac leg and number of holes
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Figures 32.4A and B: X-rays and 3D reconstruction CT showing comminuted posterior wall fracture in a 65-year-old patient
Figure 32.5: Showing exposed posterior wall fracture through posterolateral approach
Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
needed to assure fixation in healthy bone stock. Obvious defect or areas with severe comminution that will require grafting should also be identified.
Exposure
Any of the standard surgical approaches may be used. However the wound should be enlarged to expose the anterior inferior iliac spine and allow the anterior and posterior rim of the acetabulum to be fully visualized (Fig. 32.5). Retraction to extend exposure superiorly should be carried out with care to preserve the gluteal muscles.
Acetabular Reconstruction and Preparation
The wall and roof of the acetabulum are repaired using K-wires, screws and/or plates (Figs 32.6 and 32.7). Solid corticocancellous allografts or autografts can be used if necessary. After that the trial ring is overlaid above the acetabulum. The inferior leg is engaged in the obturator foramen using the hook positioner. Using the ring positioner, the ring is oriented in 45° of abduction and 15° of anteversion. This instrument has a dual function; it is used to orientate the ring and also serves as a cup sizer. Once in position, this will provide an indication of the bone defect to be filled, if it remains after reconstruction.
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Total Hip Arthroplasty
Figure 32.6: Posterior wall fragments being fixed with screws after provisionally fixing with K-wires
Figure 32.7: Final fixation with two screws
Once complete, the reconstructed or grafted acetabulum should be reamed to produce a consistent hemispherical dome. Utmost care should be taken to avoid disturbing the graft or displacing the fragments.
Contouring the Trial Acetabular Ring
The final reamer size corresponds to the outer diameter of the definitive cup: either 50 mm or 55 mm. The trial ring is reintroduced. The inferior leg is engaged in the obturator foramen using the hook positioner, and the superior leg placed on the ilium and by using the ring positioner the trial ring is oriented in 45° abduction and 15° anteversion (Fig. 32.8). The superior legs are contoured to match the patient’s anatomy and to fit any reconstructed acetabular anatomy. After that the trial ring is carefully removed.
Contouring and Placement of Definitive Acetabular Ring
The acetabular trial ring should be used as a template to assess the ideal position of three legs. It is essential to secure the definitive acetabular ring on the contouring block
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Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
Figure 32.8: After reaming, the trial ring has been inserted and held in place with the ring positioner. The legs are contoured to sit over the host bone
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Figure 32.9: Contoured trial ring placed in the block Figure 32.10: Final contoured definitive ring should match with
the trial ring
(Fig. 32.9), in order to preserve the perfect circular space; the shaping device is used to contour each leg in turn. The definitive acetabular ring should match exactly with the trial ring (Fig. 32.10). Repeated flexing should be avoided as this may weaken the legs.
The acetabular ring is positioned over the grafted acetabulam (Fig. 32.11). The hook positioner is used to ensure that the inferior leg is fully inserted into the obturator foramen for initial stability. The acetabular ring positioner is used to locate the acetabular ring in its correct position (15° anteversion and 45° abduction), and the cancellous screws inserted through the fixation holes in the legs (Fig. 32.12). Extreme care should be taken to avoid misalignment. It is recommended to use as many screws as necessary to achieve secure anchoring of the legs in healthy bone stock.
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Total Hip Arthroplasty
Figure 32.11: Showing the definitive acetabular ring with its contoured legs over the bone
Figure 32.12: Rechecking the sphericity of acetabulum after screw placement
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Figures 32.13A and B: Morselized acetabular graft impaction for acetabular defect
Bone Graft Impaction
Any remaining defects are repaired using cancellous bone grafts, by using acetabular graft impactor (Figs 32.13A and B). It is important at this stage to check, using the ring positioner, that the hemispherical dome shape of the acetabulum has been preserved.
Acetabular Shell Insertion
The acetabular shell is introduced so that its flange rests on the acetabular ring, taking care to avoid trapping soft tissues. The shell is fixed to the ring using the four connecting screws (Fig. 32.14) and for enhancing mechanical stability, the ring is fixed to the underlying bone by placing four cancellous screws through the graft into the underlying healthy bone stock.
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Figure 32.14: Shell fixed on the definitive ring with 4 screws
Figure 32.15: Standard hooded liner inserted. Note: The extended posterior wall is positioned towards the posterosuperior sector of the acetabulum
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Figure 32.16: Shows final reconstructed hip joint
Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
Liner Insertion
Once the definitive femoral head diameter has been determined, the trial liner is used to select the appropriate liner option. If the shell is accurately oriented, a standard hooded liner may be selected (Fig. 32.15). It is inserted using the appropriate impactor, so that its extended posterior wall is positioned towards the posterosuperior sector of the acetabulum. If additional head coverage is required, a 15° reorientation liner may be selected. This not only lateralizes the center of rotation of the femoral head by 2.8 mm but also provides even greater superior coverage. The appropriate head, put over the femoral stem is then reduced into the reconstructed acetabulum and its stability rechecked (Fig. 32.16).
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Tips and Pearls
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While contouring, it is essential to secure the definitive acetabular ring on the contouring block, in order to preserve the perfect circular space
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Recheck acetabular inclination and anteversion before fixing the ring because once it is fixed with screws, these parameters cannot be changed.
Total Hip Arthroplasty
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If additional head coverage is requires after trial, use of 15° reorientation liner is recommended.
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The inferior hook should be properly inserted in the obturator foramen.
POSTOPERATIVE MANAGEMENT
Thromboprophylaxis is started on the night of surgery and is continued till full mobilization is achieved, usually after 7-8 days. The postoperative dressing is changed on the second day of the surgery. Early weightbearing is normally permitted using crutches or two sticks. Full weightbearing is not resumed until 6 weeks after the operation, depending on the stability of reconstruction.
OTHER OPTIONS FOR RECONSTRUCTION (FIGS 32.17A TO D)
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Figures 32.17A to D: Different designs of the cages by various manufacturers. (A) Burch-Schneider Cage (B) Contour reconstruction ring-Smith and Nephew (C) Recovery Protrusio cage-Biomet (D) Ganz Ring
BURCH-SCHNEIDER CAGE® (ZIMMER)
The implant is characterized by a hemispherical shell that holds a polyethylene inlay, which in turn has a proximal flange and a distal nose (Figs 32.17A to D). The implant bridges an acetabular bone defect of 5 to 7 cm by means of a proximal flange to the ilium and a distal nose to the ischium. The cage must be adapted to the bone, and the bone must be adapted to the implant (smoothing the irregularities, removal of osteophytes), independently of the definitive angle and antetorsion of the polyethylene inlay.
The cage allows the relatively simple and stable repair of bony defects in the acetabulum using bone grafts, if required. The Burch-Schneider cage allows weight bearing on the affected joint soon after the operation. In many cases, this implant offers the last chance for endoprosthetic acetabular repair if other acetabular implants cannot be securely attached to the acetabulum.
PROTRUSIO® CAGE (DePuy, JOHNSON AND JOHNSON, USA)
The Protrusio Cage is intended to be used to reinforce a deficient or weakened medial acetabular wall to prevent the protrusion of acetabular cup prosthesis into the abdominal
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Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
Figure 32.18: Trabecular metal shell
cavity. It may be indicated for use in cases involving acetabular revision procedures, severe osteoporosis, protrusio acetabuli, and/or a shallow acetabular roof. The Protrusio Cage may be considered as a method of enhancing cemented acetabular reconstruction when traditional biologic fixation with a hemispherical porous-coated acetabular component is not indicated. The Protrusio Cage aids the surgeon in restoring the hip’s center of rotation while gaining secure fixation to host or allograft bone through iliac and ischial fixation. By addressing medial wall deficiencies, Protrusio Cages have proven to work well in the revision setting.
TRABECULAR METAL® SHELL (ZIMMER)
The shell is designed for use in primary and revision cases. Trabecular Metal® material has physical and mechanical properties similar to cancellous bone due to its high compressive strength, low modulus of elasticity and high coefficient of friction against bone with up to 80% porosity to enable ingrowths (Fig. 32.18). So, it is to be placed in best position for maximum host bone contact. One-piece construct, created by cementing the liner, eliminates concerns about backside wear and dome screw holes allow for additional fixation into structural bone. Highly cross linked polyethylene liners (0 degree neutral and 10 degree oblique) allow for preferred version.
Complications
The hemorrhage may be a concern in immediate postoperative period. This can be partly due to bleeding of cancellous surface especially if done in first 48 hours. Therefore, the blood products should be arranged adequately prior to the surgery. Sciatic nerve is at higher risk than the usual total hip procedure due to extensive dissection required for the fracture component. Thus, the nerve should be identified and dissected free. It should be minimally retracted.
The Octopus system allows us to mobilize the patient very early, so the thromboembolic phenomenon is minimal. Still, the normal anticoagulant prophylaxis is started till the patient is fully mobilized. Other complications can be arthroplasty related like dislocation, loosening or premature fixation loss. Therefore, the acetabular ring should be fixed with extreme caution taking into consideration the required anteversion and abduction, because once it is fixed, we cannot change these parameters.
Discussion and Results
During the preoperative evaluation, it is very difficult to determine precisely the extent of the damage to the cartilage of femoral head or acetabulum. So, in elderly patients, where the risk of the second surgery or an extensile primary surgery to fix the fracture is high, acute
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Total Hip Arthroplasty
total hip arthroplasty appears to hold great promise. In selected patients with a displaced acetabular fracture, we believe that an acute THA may provide several advantages including only one procedure and quick weight bearing with a lower rate of decubitus complications. The difficulty of holding the acetabular component in an acute fracture has been addressed by the availability of the cages and rings. The earlier metallic designs were fitted over the acetabular defects over which cemented polyethylene cups were mounted. This made them vulnerable to loosening. These have been replaced by the cementless designs of acetabular cups with good results in various studies. The morselized autografts/allografts are placed through the holes provided in the rings/cages. Huo et al8 reported only one case of acetabular component loosening in 21 patients.
There have been very few studies for the octopus system. The studies favour the use of this system in managing acetabular defects along with the use of bone grafts.9,10 There are various studies in the literature to prove the role of cages and rings in both primary and revision total hip arthroplasties for acetabular defects. Tidermark et al11 in 2003 reported excellent results in their study of 10 patients (mean age 73 years) who underwent acute total hip arthroplasty following displaced acetabular fractures. They used Burch-Schneider antiprotrusion cage (BS-APC) and autologous bone grafts in all the patients. At an average of 38 months follow up, there were no signs of loosening. In a long follow-up of 5-21 years, BS-APC has been proved to be a durable option in managing acetabular defects.12
Octopus cage system has all the advantages of the conventional cages along with the additional benefits due to its design features preventing superior and lateral migration as well as hydroxyapatite coating of the shell promoting the osseointegration with the host bone.
Illustrative Case
A 65-year-old male patient was admitted with a 3-week-old fracture acetabulum. He was a known diabetic patient. Keeping in view of his age and comorbidities, total hip arthroplasty was performed using Octopus system (Fig. 32.19A). Posterolateral approach was done. The morcellized autograft from the femoral head was used to fill the defects. He was mobilized with toe touch weight bearing on 2nd day of the surgery. Weightbearing was allowed after 6 weeks. His postoperative X-rays are shown as well as the X-ray at the latest follow-up after 10 years (Fig. 32.19B). He is doing his normal activities and has no complaints.
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Figure 32.19A: Preoperative and postoperative X-rays
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Total Hip Arthroplasty in Acute Acetabular Fractures Using Octopus System
Figure 32.19B: Showing 10 year follow-up X-rays. Both the acetabular and femoral components are well aligned. The Octopus system is fully integrated with the host bone
References
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Melton LJ, Sampson JM, Morrey BF, Ilstrup DM. Epidemiologic features of pelvic fractures. Clin Orthop 1981;155:43-7.
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Mears DC, Velyvis JH. Primary total hip arthroplasty after acetabular fracture. J Bone Joint Surg Am 2000;82:1328-53.
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Jimenez ML, Tile M, Schenk RS. Total hip replacement after acetabular fracture. Orthop Clin North Am 1997;28:435-46.
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Mears DC, Velyvis JH. Acute total hip arthroplasty for selected displaced acetabular fractures: 2-12-year results. J Bone Joint Surg 2002;84(A):1-9.
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Moed BR, Willson Carr SE, Watson JT. Results of operative treatment of fractures of the posterior wall of the acetabulum. J Bone Joint Surg Am 2002;84:752-8.
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Tai P, Hammond A, Van Dyk J, et al. Pelvic fractures following irradiation of endometrial and vaginal cancers: A case series and review of the literature. Radiother Oncol 2000;56:23-8.
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Letournel E, (Ed). Fractures of the Acetabulum, 2nd ed. New York: Springer-Verlag, 1993.
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Huo MH, Solberg BD, Zatorski LE, Keggi KJ. Total hip replacements done without cement after acetabular fractures in 4-to 8-year follow-up study. J Arthroplasty 1999;14:827-31.
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Marinoni EC, Fontana A, Castellano S, Denti M. The Octopus System for acetabular reconstruction, Chir Org Mov 1994;79(4):357-60.
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Vojtassák J, Jány R. Incorporation of bone allografts with use of Octopus revision system in total hip arthroplasty [article in Slovak]. Acta Chir Orthop Traumatol Cech 2004;71(4):210-3.
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Tidermark J, Blomfeldt R, Ponzer S, et al. Primary total hip arthroplasty with a Burch-Schneider antiprotrusion cage and autologous bone grafting for acetabular fractures in elderly patients. J Orthop Trauma 2003;17:193-7.
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Symeonides PP, Petsatodes GE, et al. The Effectiveness of the Burch-Schneider Antiprotrusio Cage for Acetabular Bone Deficiency: Five to Twenty-one Years’ Follow-up. The Journal of Arthroplasty 2009;24:168-74.