Introduction                       

Periprosthetic fractures of the acetabulum are infrequent but complex problems. The fractures may occur during surgery, (primary or revision hip replacement) or in the postoperative period. There is paucity of long-term results in literature describing the results of surgical management. The surgical management is complex and requires training and experience in the techniques of joint replacement surgery and acetabular fracture surgery. We describe our technique and experience in the surgical management of this problem. The fixation techniques described are similar to those used in the management of traumatic acetabular fractures. The technique is combined with the bone grafting and socket implantation techniques used in revision total hip arthroplasty.

 

Management of Periprosthetic Fractures of the Acetabulum

 

Etiological Factors

 

Although periprosthetic acetabular fractures occur infrequently their prevalence seems to be rising. Intraoperative fractures have increased following the increasing utilization of press fit uncemented acetabular components. Under-reaming of the uncemented acetabular component by more than 2 mm appears to increase the risk. Line to line reaming has been recommended in osteoporotic bone.

Intraoperative fractures can also be seen during component removal, particularly if the acetabular component is well fixed or associated with extensive bone loss. Excessive reaming with resultant bone loss also increases the risk of intraoperative or postoperative fractures. Acute pelvic discontinuity has been described in the early postoperative period from unrecognized intraoperative fractures.

Postoperative fractures can occur because of the long-term problems associated with osteolysis during revision hip surgery. Pelvic discontinuity has been described in association with osteolysis. In some cases this may be recognized intraoperatively during revision hip surgery after component removal. In severe osteolysis structural failure of the pelvis occurs from the weakened osteolytic bone. They may not be associated with any significant trauma. When revising the socket with marked pelvic osteolysis, one must be prepared to manage pelvic discontinuity during surgery.

These fractures can also occur after trauma around well fixed and well-functioning prostheses, trivial trauma around loose prostheses with osteolysis or spontaneously after osteolysis around the acetabulum after hip replacements. Insufficiency fractures are occasionally seen. The chronic periprosthetic fractures can be considered pelvic discontinuities, and management principles remain similar (Figs 38.1 to 38.3).

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Figure 38.1: Trivial fall, dislocation, osteolysis, pelvic discontinuity

Figure 38.2: First stage extraction of components, and double plate fixation of the discontinuity via posterior approach with healed discontinuity at roughly 9 months

 

 

 

Figure 38.3: Second stage revision hip replacement

 

The problems seen in association with osteolysis also emphasise the importance of longterm radiological follow up of patients with THA. With progressive osteolysis the patient should be explained the risks and early revision may need to be considered.

 

Anatomy     and     Basic     Considerations             

The acetabulum has been described to have the anterior and posterior columns which are arranged in the shape of an inverted Y. These two columns support the weight bearing dome of the acetabulum. The anterior and posterior walls define the circumferential limit. The

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medial wall or the floor is part of the quadrilateral plate. These anatomical structures can be identified on radiological imaging of the acetabulum and pelvis described in the subsequent section.

Management of Periprosthetic Fractures of the Acetabulum

 

Due consideration has to be given to the soft tissue neurovascular structures and muscu-lature of the hip. Of particular importance are the sciatic nerve, femoral neurovascular bundle, and the abductor muscles of the hip, as well as the superior gluteal neurovascular bundle. The reader is referred to standard textbooks for greater detail. Familiarity of the normal anatomy and surgical pathology is essential for the safe execution of the surgical procedure. A thorough knowledge and familiarity with extensile approaches to the acetabulum, particularly the posterior Kocher Langenbeck approach is important. For those unfamiliar with acetabular trauma fixation techniques, we recommend that the arthroplasty surgeon involves their acetabular trauma surgeon colleague to jointly operate on such patients so as

to optimize outcomes.

 

Natural History and Literature Review

 

As the number of total hip arthroplasties performed each year increases along with the number of patients with severe bone loss who require revision surgery, periprosthetic fractures of the acetabulum are becoming more prevalent. However, there is little information available to guide the orthopedic surgeon in the management of these injuries.

Periprosthetic fractures of the acetabulum vary in severity and may involve stress fractures of the pubis or medial wall. They may be associated with significant bone loss secondary to osteolysis and subsequent loss of column integrity, or complete pelvic discontinuity. Treatment techniques may differ depending on the complexity of the fracture and the stability of the acetabular component. The goals of surgical treatment include stabilization of the fracture (including bony columns of the acetabulum), bone grafting of defects, and revision to a stable acetabular implant. Strict adherence to the principles of fracture surgery is required to achieve reliable bony union of the acetabular columns and provide a stable environment for re-implantation of the socket. Conservative treatment has been described in literature in some cases but may be associated with delayed loosening of the socket even if the fracture heals. The literature consists of few published articles with small number of cases. The overall evidence suggests that undisplaced periprosthetic acetabulum fractures may heal with conservative management but there is a described and high incidence of loosening of the socket. This may then need later revision surgery after the fracture has healed. Surgical management is generally recommended for displaced fractures. Column fixation for displaced fractures is emphasized in reviews but long-term results after surgical management are lacking. Acetabular reinforcement rings or cages have been used in chronic pelvic discontinuities with bone grafting but the problems associated with such devices are well

described in literature such as breakage of the cage, loosening, and dislocation.

Many authors have highlighted the importance of preventing the occurrence of intraoperative acetabular fractures, particularly with uncemented components, and also stress the importance of intraoperative recognition of the fracture to guide appropriate management.

 

Classification                   Systems                   

Various factors can be considered when describing these fractures. Earlier systems focus on:

• Timing of occurrence of fractures (intraoperative or postoperative)

• Etiological influences (traumatic or iatrogenic)

• Fracture displacement (undisplaced or displaced)

• Stability of the socket (loose or well-fixed)

• Anatomical areas involved (anterior wall, posterior wall, medial floor, columns, etc)

• Associated bone loss (less than or greater than 50%).

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  The classification system given by Paprosky is comprehensive and gives some useful guidance in their management. It also emphasizes the need for thorough preoperative assessment of fracture anatomy, displacement, and bone loss and thus may help the surgeon plan the reconstruction. However, there is not enough data to link the subtypes with outcomes. Based on our experience in managing acetabular fractures after trauma, we prefer to use and adapt the Letournel classification system that describes fractures in terms of the columns or wall involved. The details of this classification system can be found in several excellent trauma textbooks or Letournel’s original publications. We are familiar with this system in trauma and it helps us assess the fracture configuration and plan surgical management. Use of a systematic approach can help determine if the columns have been involved, whether the wall has been fractured, the degree of displacement, the type of acetabular component used,

  whether the socket is stable or loose and the surgical tactic needed.

  We also study the degree of bone loss to anticipate any intraoperative difficulties and plan the reconstructive technique. One must pay special attention to the specific areas and extent of bone loss particularly in the posterior wall and column of the acetabulum, in addition to the ischium, medial wall and superior dome. The system provided by Paprosky to methodically assess bone loss is quite useful, although it must be appreciated that quite often the bone loss is more extensive than anticipated.

   

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  Radiological                  Assessment                  

  The fracture and the prosthetic components of the failed arthroplasty must be studied in detail by various imaging techniques including plain radiographs and computerized tomography.

  A well centred good quality anteroposterior view of the pelvis helps in assessing the anterior and posterior columns of the acetabulum using the iliopectineal and ilioischial lines. The anterior and posterior walls of the acetabulum may be obscured by the acetabular component. Judet views (external or iliac oblique) and (internal or obturator oblique) well known in acetabular trauma surgery help in further assessment of the columns involved and plan the internal fixation as described below.

  In addition the radiographic principles and landmarks described by Paprosky in revision hip surgery such as the Kohler line tear drop, ischial osteolysis, and superior migration helps the surgeon to assess the bone loss.

   

   

  We find CT scans and three-dimensional reconstructions using specialized software performed by experienced musculoskeletal radiologists useful in differentiating between the metal from the previous arthroplasty and the bony structure of the column and wall (Fig. 38.4).

   

  Figure 38.4: Three-dimensional reconstruction showing different colors which allows differentiation of prosthesis from posterior column

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  Management of Periprosthetic Fractures of the Acetabulum

   

  Figure 38.5: Chronic pelvic discontinuity/periprosthetic fracture, loose C stem, 52 years female

  Figure 38.6: Single stage reconstruction

   

  Treatment                    Principles                   

  Periprosthetic acetabular fractures can be compared to acetabular fractures seen after trauma, but with the additional complicating factors such as loosening of a prosthetic component and bone loss. Similarly pelvic discontinuity can be considered to be an ununited fracture of the acetabulum combined with a loose socket and bone loss. In such cases the fracture continuity between the superior and inferior portions of the acetabulum can be achieved using column plating techniques via a variety of surgical approaches (Figs 38.5 and 38.6).

  The goals of treatment are:

• Achieving stable fixation of the fracture

• Restoration of the bone stock loss and preserving biology by bone grafting

• Achieving a stable arthroplasty after socket implantation

• Functional rehabilitation of the patient

• Avoidance of complications.

We believe that column fixation by posterior column plating of the displaced fractured acetabulum or pelvic discontinuity (similar to tension band plating of the convex surface of a long bone) gives a better fixation of the fracture or discontinuity compared to cages or isolated fixation of acetabular uncemented cups with screws (akin to an internal plate). Stable fixation is essential to promote bony union of the superior and inferior portions of the acetabulum which in turn provides long-term stability to the arthroplasty.

Our earlier experience during the evolution of this technique consisted of a two stage reconstruction. We continue to use a two stage approach if there are concerns about bone or soft tissue quality, deep infection, healing potential, or when there is extensive bone loss such as after a previously failed cage for pelvic discontinuity. The first stage consists of removal of the loose arthroplasty followed by reduction and fixation of the periprosthetic fracture or pelvic discontinuity. The second stage consists of bone grafting and socket implantation during revision total hip replacement (Figs 38.7 to 38.13).

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Figure 38.7: 72-year-old female, ununited insufficiency fracture anterior column, uncemented stem and dysplasia cup with large head MOM THA. Loose and migrated at 3 weeks. See surgical Figures 38.8 to 38.13

 

 

 

Figure 38.8: Stage I: Posterior K-L approach, short ETO, removal of components

 

Figure 38.9: Stage I: Fixation of ununited insufficiency fracture, no superior and posterior wall of acetabulum left

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Management of Periprosthetic Fractures of the Acetabulum

 

Figure 38.10: Stage II: Six months later after healing of fracture, reconstruction with femoral head allograft fixed with plate and screws to reconstruct posterior and superior large segmental defect

 

Figure 38.11: Reaming into the graft, floor impaction grafted

 

 

Figure 38.12: Implantation of cemented socket

 

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Figure 38.13: 30 months postoperative follow-up

 

Fracture Description and Strategies for Management

 

Intraoperative fractures may involve the anterior wall or posterior wall of the acetabulum. These in turn may be minor undisplaced cracks or displaced unstable fractures. The fracture may also involve the medial floor (or quadrilateral plate) with or without involvement of the posterior column (Figs 38.14 and 38.15).

Minor undisplaced anterior wall cracks may heal without the need for additional fixation using standard arthroplasty techniques and protected weight bearing. Previous publications recommend the use of cementless sockets with additional screws and protected weight-

 

 

 

 

Figure 38.14: Intraoperative acetabulum fracture, unstable despite larger cup with mesh and screws, early cup migration at 2 weeks

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Management of Periprosthetic Fractures of the Acetabulum

 

Figure 38.15: Early revision at 3 weeks, bone grafting with femoral allograft slices, impaction grating, revision TM shell, satisfactory at 20 months

 

bearing. We have not encountered these fracture types frequently because our arthroplasty practice being predominantly cemented at Wrightington hospital. Also such fractures when they do occur tend to be successfully managed by the primary arthroplasty surgeon without the need for a tertiary referral. However based on our experience if the posterior wall or the column fracture is detected during surgery, we would prefer to fix it using posterior plating, bone grafting and then proceed with the arthroplasty.

Displaced medial wall or floor fractures are usually encountered during surgery. Bone grafting of the central defect is necessary before acetabular reconstruction. Various options include cementless rim fit sockets on morsellized bone grafts, or wire mesh with impaction grafting. We prefer to deal with these using slices of bone graft from a femoral head allograft, as previously described in the management of protrusio at Wrightington. This can also be treated using the impaction grafting technique described by the Nijmegen group (Figs 38.14 and 38.15).

If the posterior wall is fractured and contributes to the overall containment of the socket, we prefer stable fixation using posterior plating combined with bone grafting if necessary. We have used a femoral head allograft to reconstruct a deficient segment of the superior or posterior wall in chronic cases stabilized with screws and posterior plates as shown later in the surgical technique. This can then be combined with standard socket reconstruction techniques. We prefer cemented socket reconstruction with impaction bone grafting.

Postoperative traumatic fractures and pelvic discontinuity are complex problems. There is usually more significant bone loss and the acetabular component is usually loose. There is commonly significant column displacement. This can be reconstructed using column reduction and fixation, structural femoral head and impaction bone grafting and socket reconstruction in one or two stages (Figs 38.1, 38.5, 38.16 and 38.17).

The stem may need to be revised if loose, malaligned, or if there are issues surrounding trunnion damage or compatibility. A single stage can be implemented if the soft tissue and bony status and quality allow simultaneous fixation, grafting and revision of the prosthesis, particularly if the rim is intact in an acute fracture situation.

Our initial experience with these problems was associated with higher than expected rate of dislocations when we routinely retained the original stem if well fixed. After our

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Figure 38.16: 58-year-old female, acute periprosthetic fracture after uncemented MoM THA trivial fall

 

 

 

Figure 38.17: Postoperative X-ray 2 years follow-up

 

initial experience with this technique, we now have a low threshold to revise the stem to prevent postoperative dislocation.

 

Preoperative Assessment and Planning

 

Experience in acetabular fracture surgery and arthroplasty is necessary in the usage of the described techniques. A multidisciplinary approach with input from anesthetists, physicians, and radiologists is essentially. Aggressive medical work up is often needed. We routinely use cell salvage techniques during surgery. Tranexamic acid is used where no contra-indication exists. Antibiotic prophylaxis and prophylaxis against venous thromboembolism is routinely used. Our policy is to use a low molecular weight heparin preparation in the early postoperative period, mechanical prophylaxis intraoperatively, and Warfarin for 3 months post-operatively. Consideration is given to using an inferior vena cava filter after discussion with the interventional radiologist or vascular surgeon in difficult situations such as recent or concurrent thromboembolic events. All necessary equipment including that needed for

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Management of Periprosthetic Fractures of the Acetabulum

 

fracture fixation and for revision arthroplasty should be available. The entire team should be familiar with the surgical tactic. Intraoperative imaging may occasionally be needed. The available imaging should be thoroughly studied to plan the reconstructive technique and bone grafting.

 

Choice          of          Prostheses                   

 

 

Pelvic and acetabular fracture surgery instrumentation is required to fix the fracture. Similarly appropriate instrumentation is needed for component extraction. We prefer cemented reconstructions, particularly where femoral head allografting is used for segmental defect, and with impaction grafting. In acute periprosthetic fractures occurring after trauma, we have successfully used trabecular metal revision components (Figs 38.18 and 38.19) where stable primary press fit on the acetabular rim can be achieved after column plating. We have noted good ability to achieve primary press fit fixation of the uncemented components even after a fractured acetabulum after posterior column plating. Additional screws are usually recommended to ensure reliable biological osseo-integration of the acetabular component.

 

 

 

Figure 38.18: 52-year-old female, RTA traumatic displaced periprosthetic fracture around uncemented MoM (right hip)

 

Figure 38.19: Single stage THA, impaction grafting, revision trabecular meta socket, cemented stem, 2 years follow-up

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Trabecular metal augments are an option in elderly patients. Various stem options need to be available.

 

Surgical                    Technique                    

POSITION AND APPROACH

The patient is positioned in the lateral decubitus position with adequate padding of pressure areas. Routine double prepping of the surgical field is done. The affected leg is draped free to allow intraoperative manipulation. Trained assistants are invaluable. Mechanical prophylaxis is used on the opposite leg.

The hip is kept extended and the knee flexed with the foot resting on a padded Mayo trolley to relax the sciatic nerve. We routinely use this technique to minimize the possibility of injuring the sciatic nerve.

The posterior Kocher Langenbeck approach is used to expose the acetabulum. This is our main approach where the reconstruction is done in a single stage or for the first stage of a two stage strategy. In a single stage reconstruction, the bone grafting and socket revision is performed through the same approach. In two stage reconstructions, we have used both the posterior and in some cases the trans-trochanteric approaches for second stage implantation with success. We describe the posterior approach in this section.

After dividing the fascia lata, the gluteus maximus tendon is identified and divided. The sciatic nerve is identified and protected. Tissue planes are developed with care. A useful technique is to follow normal anatomy into the scarred area. Culture swabs and specimens of tissue for microbiology are routinely sent. If the short external rotators and capsule can be identified, these are divided after placing stay sutures. When separate layers are not available, the layer can be divided en masse to enter the hip joint. Joint fluid is sent for microbiology.

The short external rotators are then followed to the posterior edge of the posterior column and the ischial spine is identified. The posterior border of the column is followed inside the pelvic inlet to facilitate derotation of a malrotated column fragment. Ischial spine osteotomy is occasionally helpful to derotate a malaligned posterior column. These techniques and steps are used as standard steps in acetabular fixation surgery. The capsule is released and circumferential exposure of the acetabulum is obtained. The hip is dislocated gently to avoid further fracturing or bone damage. Retractors are positioned anteriorly and inferiorly with care to demarcate the anterior wall and transverse ligament and help identify some standard anatomic landmarks. The posterior column and the fracture is exposed as is the acetabular component.

 

COMPONENT REMOVAL

Scar tissue is excised around the acetabulum. Usually the component is loose in displaced fractures and also in most undisplaced fractures. The loose acetabular component is extracted with care. Care is taken to minimize bone loss.

 

FIXATION OF THE FRACTURE AND RECONSTRUCTION

Once the acetabulum is exposed, debridement of the membrane and fibrous tissue is performed to obtain fresh bleeding cancellous bone surfaces. Reaming is restricted to a minimum only to scratch and to freshen the surface to avoid further bone loss.

The bone loss is then assessed. Fixation and grafting is planned. The pelvic fracture instrumentation set and the surgeons preferred arthroplasty components should be available. It is good to have a back up strategy or “plan B”, and keep the necessary equipment available. The fracture surfaces are freshened using curettes, and chisels to bleeding bone. Fibrous tissue is excised from the facture surface in the floor of the acetabulum. Impaction grafting

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Management of Periprosthetic Fractures of the Acetabulum

 

Figure 38.20: Single stage component extraction, column fixation, and THA

 

Figure 38.21: Second plate for bone graft fixation, reaming into the graft

 

is performed after column stabilization to avoid propagating or displacing the fracture and to achieve a stable bed.

The posterior column is reduced. A Schantz screw inserted into the ischial tuberosity and used as a joy-stick serves as a good technique to derotate and manipulate the inferior segment of the fractured acetabulum and reduce it to the superior segment. Additional pelvic reduction clamps can be used as required. Provisional reduction can be achieved using screws positioned on either side of the column fracture and pelvic reduction clamps which are designed to grasp screws, in order to approximate and compress the fracture. A posterior column pelvic reconstruction contoured plate is prepared and can be fixed along the posterior edge of the column to achieve stable fixation. Two plates may occasionally be needed to achieve good rotational stability (Figs 38.2, 38.9, 38.20 and 38.21).

 

IMPACTION BONE GRAFTING

Where there is no additional segmental bone loss, final acetabular preparation and grafting can commence. A fresh frozen femoral head is broken down into bone chips as described by

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the Nijmegen group. We prefer to prepare the bone chips manually rather than a bone mill. The bone chips are then packed into the floor of the acetabulum and impacted with serial impaction instruments to achieve the desired bed of bone graft against bleeding host bone. Caution is required during impaction to avoid further fragmentation. Trial components are used frequently at this stage to ensure the impacted bone graft bed is prepared to an appropriate but not excess thickness, and to ensure an appropriate socket size with good cement mantle and adequate thickness of polyethylene (Figs 38.10 to 38.12).

Where there is a central defect, the femoral head is used to fashion wafers or slices of bone about 2-3 mm thick. These can be used to plug a hole and impaction usually allows the bone to conform to the defect. After a few slices have been impacted quite a stable base can be obtained. We have used slices of bone graft to plug central defects and prefer that to a wire mesh (Figs 38.14 and 38.15—three femoral heads were used to bone graft this fracture).

 

SEGMENTAL BONE GRAFT

If there is additional posterior and superior bone loss of the segment of the acetabular wall, then a fresh frozen femoral head allograft is fashioned to fit the defect. This bone is then held with Kirschner wires. Fixation is achieved with partially threaded cancellous screws. An accurately matched convex surface of the bone graft against a matching concave surface of the host bone helps stable fixation (Figs 38.10 to 38.12, 38.20 and 38.21). The head can be debulked to avoid prominence. Then the fixed head can be reamed to achieve the desired size and shape of the newly reconstructed socket with its missing segment restored (Figs 38.10, 38.11, 38.20 and 38.21).

A second column plate can then be used particularly if the segmental bone loss is quite posterior where greater shear force is likely against the grafted femoral head. A pelvic reconstruction plate is contoured and fixed to the ischial tuberosity inferiorly. At its superior extent, it is used to buttress the femoral head graft, and then fixed to the ilium. This double plating technique in our experience provides very stable fixation, and avoids the problems of plate breakage.

Thus the preparation for socket implantation can be completed after column fixation is achieved and bone grafting has been done. Trial components are used to decide on the size of the final component. A cemented socket can be implanted (Figs 38.12).

 

 

In acute periprosthetic fractures where the rim of the acetabulum is intact or can be reconstructed to be intact after reduction of the column, or where the segmental defect is quite small and a press-fit fixation can be obtained, we have use a trabecular metal revision socket with predictable osseointegration. This socket allows the liner to be implanted with cement (Figs 38.16 to 38.23).

 

Figure 38.22: Revision trabecular metal shell fixed with screws. After column fixation, primary pressfit stability can often be obtained

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Management of Periprosthetic Fractures of the Acetabulum

 

Figure 38.23: Cemented polyethylene liner in revision TM shell

 

The stem can then be checked for alignment, and trial reduction is performed to ensure appropriate restoration of leg lengths, offset, movement and stability. If the original stem is mal-aligned or there is damage to the trunnion, or if the hip remains unstable, we have a low threshold for revising the stems. Standard component extraction and revision techniques are used and further details of femoral reconstruction are outside the scope of this chapter.

The short external rotators and capsule are repaired back to the bone of the tip of the greater trochanter using trans-osseous sutures and the wound is closed in usual fashion over a deep drain.

 

POSTOPERATIVE PROTOCOL

The salvaged blood is usually transfused back during surgery and occasionally during postoperative period in recovery. The requirement for allogenic blood is reduced after using cell savage (internal unpublished data from the authors’ institute). Antibiotic prophylaxis is given as per our protocol. Our protocol for these cases consists of 5 days of intravenous Teicoplanin and oral Ciprofloxacin, or as guided by our microbiologist. Thromboembolic prophylaxis consists of Dalteparin after surgery followed by Warfarin for 3 months (target INR between 2 and 3). Mechanical thromboprophylaxis is used. The patients are kept non-weightbearing for up to 12 weeks. They are mobilized after the first 2-3 days.

 

Summary                        

Our technique has evolved over the years. The surgery is extremely challenging and adequate counseling of the patient and informed consent is necessary. Majority of these patients referred into our institution have had multiple previous operations. The early short to medium term results of this technique up to 3 years continue to show promise. Excellent pain relief and significant functional improvement is seen. This approach requires the experience of pelvi-acetabular fixation and revision arthroplasty. We continue to monitor and report our long-term results of this surgical philosophy.

 

Bibliography                       

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2. Sánchez-Sotelo J, McGrory BJ, Berry DJ. Acute periprosthetic fracture of the acetabulum associated with osteolytic pelvic lesions: a report of 3 cases. J Arthroplasty 2000;15(1):126-30.

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5. Helfet DL, Ali A. Periprosthetic fractures of the acetabulum. Instr Course Lect 2004;53:93-8.

6. Dean DB, Moed BR. Late salvage of failed open reduction and internal fixation of posterior wall fractures of the acetabulum. J Orthop Trauma 2009;23(3):180-5.

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8. Gras F, Marintschev I, Klos K, Fujak A, Mückley T, Hofmann GO. Navigated percutaneous screw fixation of a periprosthetic acetabular fracture. Arthroplasty 2010;25(7):1169.e1-4. Epub 2009 Oct 17.

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10. Sharkey PF, Hozack WJ, Callaghan JJ, Kim YS, Berry DJ, Hanssen AD, LeWallen DG. Acetabular fracture associated with cementless acetabular component insertion: a report of 13 cases. J Arthroplasty 1999;14(4):426-31.

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13. Arihiko Kanaji, Kenichi Ando, Masato Nakagawa, Eiichi Fukaya, Hideki Date, Harumoto Yamada. Insufficiency fracture in the medial wall of the acetabulum after total hip arthroplasty. The Journal of Arthroplasty 2007;22(Issue 5):763-7.

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18. van Egmond N, De Kam DC, Gardeniers JW, Schreurs BW. Revisions of extensive acetabular defects with impaction grafting and a cement cup. Clin Orthop Relat Res 2011;469(2):562-73. Epub 2010 Oct