Background: A common clinical scenario encountered by an orthopaedic surgeon is a patient with a secure cementless acetabular shell and a failed polyethylene liner. One treatment option is to cement a new liner into the fixed shell. The purpose of this study was to evaluate the radiographic outcome of this technique. Materials and Methods: From November 2001 to April 2006, 11 liner were cemented into well-fixed cementless acetabular shell of 10 patients. There were 6 males and 5 women of average age 54.3 (range 41~73) years at the time of the revision surgery. The indication for the revision procedure were aseptic loosening and wear in 9 cases, and periprosthetic fracture in 2 cases. The pre-existing screws in the shell were removed, and screw holes were filled with allogenic bone graft or cementaion. The patients were evaluated the radiographic evidence of progressive loosening and osteolysis. The average follow up period was 35.2 (range 24~76) months. Results: There were no changes in cup and liner position or progression of osteolytic lesion around the femoral or acetabular components in the last follow-up radiographs. No compications such as a deep or superficial infection or deep vein thrombosis occurred. There were no hip dislocations. Conclusion: A liner cemented into a secure, well-positioned cementless acetabular shell provide stability and durability at short and long term follow up. This technique also has advantages of preventing bone loss associated with removal of a well fixed component, and lower surgical morbidity and more liner options. Careful attention to the preparation of the liner, the sizing of the component, and the cementing technique are likely to reduce the failure of this construct

Introduction: The removal of well-fixed cementless acetabular components can be challenging and may lead to tremendous bone loss. The options for a well-fixed, mal-positioned cup include cup revision, face-changing liners, or eccentrically cementing a liner in a more appropriate position. This study reviews our experience with a technique of eccentrically cemented acetabular liners in wellfixed, malpositioned cementless acetabular components. Methods: From 2002 to 2004, 30 patients underwent acetabular revisions with eccentrically cemented liners into well-fixed, malpositioned acetabular components. The range of malpositioning included excessive abduction, extreme anteversion, retroversion, and neutral cup position. The cemented liners were downsized by 2–4 mm to provide an acceptable cement mantle and were positioned more appropriately in terms of both abduction angle and anteversion. Results: Mean follow-up was 4 years (3–5). Liners were reoriented for the following reasons 7 excessive abduction, 8 extreme anteversion, 10 neutral and retroversion, and 5 combined inappropriate version and abduction. One liner loosened at 18 months and required cup revision. The other 29 functioned well with no dislocations. Radiographic analysis demonstrated no loosening in 29 cups at a mean of 4 years (3–5). Conclusion: Eccentrically cemented liners into well fixed, malpositioned acetabular components in a reasonable option that has promising short-term results

When a constrained liner is used in a non-cemented cup it is advisable to add screw fixation to the cup even if the cup has an excellent press-fit because there is more pull-out pressure on the liner with a constrained cup. It also is necessary for the cup to be in the correct anteversion/inclination. It is not advisable to use a constrained liner to “make up” for poor cup position. The patient can still dislocate and then that will require an open reduction. Our most common use with constrained sockets is to cement a liner into a well fixed cemented cup. We also will cement the liner into two-stage infections to keep it stable between those operations. Failure with the cemented liner into a non-cemented cup only occurs with poor surgical technique. There is only one correct surgical technique and violation of this can cause disassociation of the liner from the cup or dislocation of the head from the liner. The correct technique is: 1.) Preferably there is no hood on the liner because that can increase impingement. 2.) The liner size must have a press-fit of the liner edge to the edge of the metal shell. This is absolutely critical. The liner size cannot sink into the shell or be proud of the shell. 3.) The liner cannot be tilted in the shell to change anteversion or inclination. 4.) The backside of the polyethylene liner must be roughened with a high speed bur preferably in a spider web design. 5.) The inside of the cup should be roughened with a carbide bit of a high speed drill. The screw holes should be cleared of fibrous tissue. 6.) The cement thickness is not a critical factor and 1–2mm is always sufficient. 7.) Maintain pressure on the liner with one size smaller pusher (28mm for 32 inner diameter liner) until the cement is hard

Introduction. Cementation of a new liner into an existing well-fixed acetabular component is common during revision total hip arthroplasties (THAs) for many indications, but most commonly for lack of a modern compatible crosslinked polyethylene liner. However, little is known about the long-term durability of this strategy. The purpose of this study was to evaluate the long-term implant survivorship, risk of complications, clinical outcomes, and radiographic results of cementing a new highly cross-linked polyethylene (HXLPE) liner into a well-fixed acetabular component. Methods. We retrospectively identified 326 revision THAs where a non-constrained HXLPE liner was cemented into a well-fixed acetabular component. Mean age at revision THA was 63 years, with 50% being female. The most common indications for revision THA were wear and osteolysis (49%), aseptic femoral loosening (35%), and instability (8%). Mean follow-up was 10 years. Results. Polyethylene liner failure occurred in 15 cases (5%). In all cases, the cemented liner dissociated from the acetabular component. Survivorships free from any revision and any reoperation were 79% and 77% at 10 years, respectively. The most common reason for re-revision was dislocation (56% of re-revisions). The cumulative incidence of dislocation was 17% at 10 years. Hips revised at the index revision for instability were significantly more likely to have a subsequent dislocation when compared to those revised for polyethylene liner wear (HR 2.5, p<0.01). Harris hip scores significantly improved from a mean of 65 preoperatively to 88 postoperatively (p < 0.01). Conclusions. Cementation of a non-constrained HXLPE liner into a well-fixed acetabular component during revision THA provided durable fixation at 10 years with only a small number of failures at the cement interface (5%). Instability after this procedure remains a concern, but this is likely multi-factorial in nature. These new long-term data support continued use of this technique, when necessary, during revision THAs. For any tables or figures, please contact the authors directly

In primary total hip replacements there are numerous options available for providing hip stability in difficult situations (i.e. Down's syndrome, Parkinson's disease). We have considered constrained liners in some of these cases. However, in the revision situation in general and in revision for recurrent dislocation situation specifically it is important to have all options available including tripolar constrained liners in order to optimise the potential for hip stability as well as function of the arthroplasty. Even with the newer options available dislocation rates of higher than 10–15% have been reported following revision surgery at institutions where high volumes of revision surgery are performed. Because of the deficient abductors, other soft tissue laxity and the requirement for large diameter cups revision cases will always have more potential for dislocation. In these situations in the lower demand patient, constraint has provided excellent success in terms of preventing dislocation and maintaining implant construct fixation to bone at intermediate- term follow-up. Hence in these situations tripolar constrained liners remains the option we utilise. We are also confident in using this device in cases with instability or laxity where there is a secure well- positioned acetabular shell. We cement a dual mobility constrained liner in these situations using the technique described below. Present indication for tripolar constrained liners: low demand patient, large outer diameter cups, instability with well-fixed shells that are adequately positioned, abductor muscle deficiency or soft tissue laxity, multiple operations for instability. Technique of cementing liner into shell: score acetabular shell if no holes, score liner in spider web configuration, all one or two millimeters of cement mantle. Results. Constrained Dual Mobility Liner. For Dislocation: 56 Hips, 10 yr average f/u, 7% failure of device, 5% femoral loosening, 4% acetabular loosening. For Difficult Revisions:101 hips, 10 yr average f/u, 6% failure of device, 4% femoral loosening, 4% acetabular loosening. Cementing Liner into Shell: 31 hips, 3.6 yr average f/u (2–10 years), 2 of 31 failures

In the revision situation in general and for recurrent dislocation specifically, it is important to have all options available including tripolar constrained liners in order to optimise the potential for hip stability as well as function. Even with the newer options available, dislocation rates of higher than 5% have been reported in the first two years following revision surgery at institutions where high volumes of revision surgery are performed (Wera et al). Because of the deficient abductors, other soft tissue laxity and the requirement for large diameter cups, revision cases will always have more potential for dislocation. In these situations, in the lower demand patient, tripolar constrained liners provided excellent success in terms of preventing dislocation and maintaining implant construct fixation to bone at intermediate term follow-up. Hence in these situations, tripolar with constraint remains the option we utilise in many cases. We are also confident in using this device in cases with instability or laxity where there is a secure well positioned acetabular shell. We cement a tripolar constrained liner in these situations using the technique described below. Present indication for tripolar constrained liners: low demand patient, abductor muscle deficiency or soft tissue laxity, large outer diameter cups, multiple operations for instability, instability with well-fixed shells that are adequately positioned. Technique of cementing liner into shell: score acetabular shell if no holes, score liner in spider web configuration, all one or two millimeters of cement mantle. Results: Constrained Tripolar Liner - For Dislocation: 56 Hips; 10 year average f/u; 7% failure of device, 5% femoral loosening, 4% acetabular loosening. Constrained Tripolar Liner - For Difficult Revisions: 101 hips; 10 year average f/u; 6% failure of device, 4% femoral loosening, 4% acetabular loosening. Cementing Liner into Shell: 31 hips; 3.6 year average f/u (2–10 years); 2 of 31 failures. We, like others, are trying to define cases where dual mobility will be as successful or more successful than tripolar constrained liners

In primary total hip replacements there are numerous options available for providing hip stability in difficult situations (i.e. Down's syndrome, Parkinson's disease). However, in the revision situation in general and in revision for recurrent dislocation specifically, it is important to have all options available including dual mobility constrained liners in order to optimise the potential for hip stability as well as function of the arthroplasty. Even with the newer options, available dislocation rates of higher than 5% have been reported in the first two years following revision surgery at institutions where high volumes of revision surgery are performed. Because of the deficient abductors, other soft tissue laxity and the requirement for large diameter cups, revision cases will always have more potential for dislocation. In these situations in the lower demand patient and where, a complex acetabular reconstruction that requires time for ingrowth before optimal implant bone stability to occur isn't present, dual mobility with constraint has provided excellent success in terms of preventing dislocation and maintaining implant construct fixation to bone at intermediate term follow-up. Hence in these situations dual mobility with constraint remains the option we utilise. We are also confident in using this device in cases with instability or laxity where there is a secure well-positioned acetabular shell. We cement a dual mobility constrained liner in these situations using the technique described below. Present indication for dual mobility constrained liners: low demand patient, large outer diameter cups, instability with well-fixed shells that are adequately positioned, abductor muscle deficiency or soft tissue laxity, multiple operations for instability. Technique of cementing liner into shell: score acetabular shell if no holes, score liner in spider web configuration, all one or two millimeters of cement mantle. Results: Constrained Dual Mobility Liner – For Dislocation: 56 Hips, 10 year average follow-up, 7% failure of device, 5% femoral loosening, 4% acetabular loosening. For Difficult Revisions: 101 hips, 10 year average follow-up, 6% failure of device, 4% femoral loosening, 4% acetabular loosening. Cementing Liner into Shell: 31 hips, 3.6 year average follow-up (2–10 years), 2 of 31 failures

In primary total hip replacements there are numerous options available for providing hip stability in difficult situations i.e. Down's syndrome, Parkinson's disease. However, in the revision situation, in general, and in revision for recurrent dislocation situations specifically, it is important to have all options available including dual mobility constrained liners in order to optimise the potential for hip stability as well as function of the arthroplasty. Even with the newer options available dislocation rates of higher than 5% have been reported in the first two years following revision surgery at institutions where high volumes of revision surgery are performed [Della Valle, Sporer, Paprosky unpublished data]. Because of the deficient abductors, other soft tissue laxity and the requirement for large diameter cups, revision cases will always have more potential for dislocation. In these situations in the lower demand patient and where, a complex acetabular reconstruction that requires time for ingrowth before optimal implant bone stability to occur isn't present, dual mobility with constraint has provided excellent success in terms of preventing dislocation and maintaining implant construct fixation to bone at intermediate term follow-up. Hence in these situations dual mobility with constraint remains the option we utilise. We are also confident in using this device in cases with instability or laxity where there is a secure well-positioned acetabular shell. We cement a dual mobility constrained liner in these situations using the technique described below. Present indication for dual mobility constrained liners: low demand patient, abductor muscle deficiency or soft tissue laxity, large outer diameter cups, multiple operations for instability, and instability with well-fixed shells that are adequately positioned. Technique of cementing liner into shell: score acetabular shell if no holes; score liner in spider web configuration; all one or two millimeters of cement mantle. Results. Constrained Dual Mobility Liner. For Dislocation: 56 Hips 10 yr average f/u, 7% failure of device, 5% femoral loosening, 4% acetabular loosening. For Difficult Revisions: 101 hips 10 yr average f/u, 6% failure of device, 4% femoral loosening, 4% acetabular loosening. Cementing Liner into Shell: 31 hips 3.6 yr average f/u (2–10 years), 2 of 31 failures

Revision total hip replacements are likely to have higher complication rates than primary procedures due to the poor quality of the original bone. This may be constrained to achieve adequate fixation strength to prevent future “aseptic loosening” [1]. A thin, slightly flexible, acetabular component with a three dimensional, titanium foam in-growth surface has been developed to compensate for inferior bone quality and decreased contact area between the host bone and implant by better distributing loads across the remaining acetabulum in a revision situation. This is assumed to result in more uniform bone apposition to the implant by minimizing stress concentrations at the implant/bone contact points that may be associated with a thicker, stiffer acetabular component, resulting in improved implant performance.[2] To assemble the liner to the shell, the use of PMMA bone cement is recommended at the interface between the polyethylene insert and the acetabular shell as a locking mechanism configuration may not be ideal due to the flexibility in the shell [3]. The purpose of this study was to quantify the mechanical integrity of a thin acetabular shell with a cemented liner in a laboratory bench-top total hip revision condition. Two-point loading in an unsupported cavity was created in a polyurethane foam block to mimic the contact of the anterior and posterior columns in an acetabulum with superior and inferior defects. This simulates the deformation in an acetabular shell when loaded anatomically [4]. The application has been extended to evaluate the fatigue performance of the Titanium metal foam Revision Non-Modular Shell Sequentially Cross Linked PE All-Poly Inserts and its influence on liner fixation

Introduction. This study was performed to evaluate the minimum 5-year clinical and radiological results of liner cementation into a stable acetabular shell using a metal-inlay, polyethylene liner during revision total hip arthroplasty (THA). Methods. Sixty-six hips (63 patients) that underwent revision THA using a metal-inlay polyethylene liner cementation were included. The causes of revision were; polyethylene wear in 37 cases, femoral stem loosening in 20 cases, ceramic head fracture in 4 cases, and recurrent dislocation in 5 cases. Clinical results were graded at final follow-up using Harris hip scores, and radiographs were evaluated to determine acetabular component inclination, the stabilities of acetabular and femoral components, correction of hip centers, and the progression of osteolysis. Results. The average follow-up was 87.3 months (range 60.1∼134.3). Mean Harris hip scores improved from 64 preoperatively to 87.6 at final follow-up. Seven cases (10.6%) of dislocations occurred after revision surgery and 2 cases (3.0%) underwent acetabular revision or soft tissue augmentation. One cemented liner (1.5%) was dislodged and acetabular revision was performed using an acetabular reinforcement ring and a morselized bone graft. Two cases (3.0%) developed an infection and both underwent debridement and prosthesis with antibiotic-loaded acrylic cement (PROSTALAC) and intravenous antibiotics. Radiographic evaluations revealed osteolytic progression in the acetabular cup in 3 cases and osteolytic progression at the femoral stem in 7 cases, but none of these 10 cases underwent revision of the acetabular or femoral component. No cases of metallosis, metallic hypersensitivity, or cancer were encountered. Conclusion. This study shows that liner cementation into a stable metal shell provides relatively good clinical results. This technique offers lower surgical morbidity, a short operation time, and rapid patient recovery. Summary. Good clinical and radiologic outcomes were obtained at more than 5-years after liner cementation into a stable acetabular shell using a metal-inlay polyethylene liner during revision THA

Introduction: Recurrent dislocation can be a significant problem after total hip replacement. The use of a constrained tripolar liner is an option in the surgical treatment of dislocation or instability. Methods: A retrospective review was carried out of patients identified from a prospective database. All patients had a constrained liner cemented onto a satisfactory pre-existing cement mantle, cemented into a reconstruction ring, or cemented into a well fixed cementless shell. The Osteonics Tripolar Liner was used in all cases; the outer aspect of the liner was prepared with a burr to create grooves and thus improve cement interlock. Data collected included demographics, reason for revision, re-revision rate, outcome and survival. Results: There were 58 cases identified where a cemented constrained liner was inserted at revision hip surgery. Average age at time of surgery was 77years (range 40–94). There were 9 patients who died with less than 2 years follow-up; they were excluded, leaving a study group of 49 cases. No cases were lost to follow-up. Average duration of follow-up was 46months (range 24–76). There have been 4 infections, one of which required removal of prostheses and a 2-stage revision. There was one case of fall post-operatively and fracture of the contra-lateral femoral neck. There have been 4 implant failures requiring re-revision. All failures were due to disarticulation of the liner, 2 of which occurred in the same patient on separate occasions. There have been no revisions for loosening, and there have been no cases of failure at the bone-cement interface or at the cement-cement interface with the cement-in-cement technique. Overall survival of the cemented constrained liner was 90% at average 3.8years. Conclusion: This study demonstrates that cementing a constrained liner into the acetabulum is a viable option in revision hip surgery, particularly in the management of instability

Introduction: Porous Tantalum has been used in a variety of clinical settings since 1997. The use of trabecular metal backed prostheses and augments in the revision hip scenario is attractive due to the higher propensity of bony ingrowth than traditional porous coatings, and also the high coefficient of friction with bone leads to excellent press fit. We describe the early results of twenty trabecular metal backed acetabular components in the revision setting. Methods: From 2004, 20 patients received trabecular metal backed acetabular components as a revision hip procedure. The average age of the patients was 69 (42–84) yrs at the time of surgery. 4 patients had trabecular metal shells with cemented liners, 16 patients had modular trabecular metal implants. Structural allograft was used in 2 cases, trabcular metal augment in 1. Revision was for aseptic loosening in 17 cases, infection in 3. Acetabular defects were graded according to Paprosky as 2A(10), 2B(1), 2C(1), 3A(6) and 3B(2). Fixation was augmented in all cups with at least one screw. Patients were evaluated with standard x-rays for osteolysis and migration, Harris hip score, SF 36 and Oxford hip score. Results: Average follow up was 12 months (24–5). 100% follow up was achieved. There were no complications directly related to the acetabular surgery. There were no revisions. There are no progressive radiolucencies or detectable migration in any of the cups. There were no dislocations. Conclusion: These early results suggest that trabecular metal backed acetabular components may be confidently used in the setting of hip revision surgery and show promise for the more severe defects for which a reliably reproducible solution has yet to be proven

Introduction: Recurrent dislocation is a significant problem after total hip replacement. Aetiology is multifactorial and treatment should address the reason for dislocation. The use of a constrained tripolar liner is an option in the surgical treatment of dislocation. Methods: A retrospective review was carried out of patients who have undergone revision hip surgery and had a constrained liner cemented into the acetabulum. Patients were identified from a computer database. All patients had a constrained liner cemented onto a satisfactory pre-existing cement mantle, cemented into a reconstruction ring, or cemented into a well fixed cementless shell. The Osteonics Tripolar Liner was used in all cases and the outer aspect of the tripolar liner was prepared with a burr to create grooves and thus improve cement interlock. Data collected included demographics, reason for revision, components used, re-revision rate, outcome and survival. Results: There were 58 cases identified where a cemented constrained liner was inserted at revision hip surgery. Average age at time of surgery was 77years (range 40–94). Reason for use of a constrained liner was recurrent dislocation in over 95% of cases. There were 9 patients who died with less than 2 years follow-up; they were excluded, leaving a study group of 49 cases. Average duration of follow-up was 46months (range 24–76). There have been 4 infections, one of which required removal of prostheses and 2 stage revision. There was one case of fall post-operatively and fracture of the contra-lateral femoral neck. There have been 3 implant failures requiring re-revision. All failures were due to disarticulation of the liner, 2 of which occurred in the same patient on separate occasions. There have been no revisions for loosening, and there have been no cases of failure at the bone-cement interface or at the cement-cement interface with the cement-in-cement technique. Overall survival of the cemented constrained liner was 91.8% at average 3.8years. Conclusion: This study demonstrates that a cemented constrained tripolar liner is a viable option in revision hip surgery, particularly in the treatment of recurrent dislocation

The number of joint revision surgeries is rising, and the complexity of the cases is increasing. In 58% of the revision cases, the acetabular component has to be revised. For these indications, literature decision schemes [Paprosky 2005] point at custom pre-shaped implants. Any standard device would prove either unfeasible during surgery or inadequate in the short term. Studies show that custom-made triflanged implants can be a durable solution with good clinical results. However, the number of cases reported is few confirming that the device is not in widespread use. Case Report. A patient, female 50 yrs old, diagnosed having a pseudotumor after Resurfacing Arthroplasty for osteo-arthritis of the left hip joint. The revision also failed after 1 y and she developed a pelvic discontinuity. X-ray and Ct scans were taken and sent to a specialized implant manufacturer [Mobelife, Leuven, Belgium]. The novel process of patient-specific implant design comprises three highly automated steps. In the first step, advanced 3D image processing presented the bony structures and implant components. Analysis showed that anterior column was missing, while the posterior column was degraded and fractured. The acetabular defect was diagnosed being Paprosky 3B. The former acetabular component migrated in posterolateral direction resulting in luxation of the joint. The reconstruction proposal showed the missing bone stock and anatomical joint location. In the second step, a triflanged custom acetabular metal backing implant was proposed. The bone defect (35ml) is filled with a patient-specific porous structure which is rigidly connected to a solid patient-specific plate. The proposed implant shape is determined taking into account surgical window and surrounding soft tissues. Cup orientation is anatomically analyzed for inclination and anteversion. A cemented liner fixation was preferred (Biomet Advantage 48mm). Screw positions and lengths are pre-operatively planned depending on bone quality, and transferred into surgery using jig guiding technology (Materialise NV, Leuven, Belgium). In the third step, the implant design was evaluated in a fully patient-specific manner in dedicated engineering (FEA) software. Using the novel automated CT-based methodology, patient-specific bone quality and thickness, as well as individualised muscle attachments and muscle and joint forces were included in the evaluation. Implants and jig were produced with Additive Manufacturing techniques under ISO 13485 certification, using respectively Selective Laser Melting (SLM) techniques [Kruth 2005] in medical grade Ti6Al4V material, and the Selective Laser Sintering technique using medical grade epoxy monomer. The parts were cleaned ultrasonically, and quality control was performed by optical scanning [Atos2 scanning device, GOM Intl. AG, Wilden, Switzerland]. Sterilization is performed in the hospital. CONCLUSION. A unique combination of advanced 3D planning, patient-specific designed and evaluated implants and drill guides is presented. This paper illustrates, by means of a clinical case, the novel tools and devices that are able to turn reconstruction of complex acetabular deficiencies into a reliable procedure

Highly porous tantalum cups have been used in complex acetabular revisions for nearly 20 years but reports of long term results are limited. This study was designed to report ten year results of revision using a single porous tantalum cup design with special attention to re-operation for any reason, all-cause revision, and revision for aseptic loosening. Retrospective review of all revision THA cases performed from 1999–2006 using a highly porous tantalum acetabular component design with multiple screw holes and a cemented polyethylene liner (Zimmer Biomet, Warsaw, IN). Our institutional medical record and total joint registry were used to assess follow-up and xrays were reviewed. The Paprosky classification system was used to rate acetabular bone loss. Radiographic loosening was defined as new/progressive radiolucencies in all 3 acetabular zones, or cup migration (>2mm). Kaplan-Meier survivorship was used to assess survivorship free of cup revision/removal for any reason, and free of revision for aseptic loosening. Between 1999 and 2006 this tantalum cup was used in 916 revisions. Mean age: 66 (±6), BMI: 29 (±6), and male: 42%. Indications for revision: aseptic loosening 346 (38%), osteolysis 240 (26%), and infected arthroplasty 168 (18%). Large (3A or 3B) bone defects were present in 260, and pelvic discontinuity in 61. Reoperation for any reason: 133 (15%), but 84 of 133 cases did not require cup revision for instability (38) or femoral failure (24). Tantalum cup removal/revision was required in 49 (5.3%) for deep infection (39) and recurrent dislocation (6), and aseptic loosening (4). 10 year survivorship free of cup revision for any reason: 95% and for aseptic loosening: 99%. Radiographic review (mean 10 years): suspicious for aseptic loosening in another 4 cups. A highly porous tantalum acetabular component with multiple screws and a cemented polyethylene insert provided durable long term fixation for an array of acetabular revision problems. Long term aseptic loosening was very rare (<1%) and cup removal was mainly related to deep infection, and rarely dislocation

The interest in osteolysis has waned largely due to the impact of crosslinked polyethylene and the “rarity” of this phenomenon. However, the basic process still remains: particles, motion observed with unstable implants and host specific factors all play a role in bone loss around implants. There are 2 predominant patterns of lysis: Linear versus Expansile. Linear Lysis: is focal bone loss at the interface as seen in the bone cement interface in when using acrylic or at the implant-host interface with porous ingrowth/ongrowth implants. Expansile Lysis: is observed in less contained regions such as the retro- and supra-acetabular regions around the socket. These lesions can also be quite extensive yet may be subtle in appearance. Imaging is essential in identifying the extent and magnitude of osteolysis. Available modalities include plain radiographs although they can be of limited value in that even with oblique views, they often underestimate the degree of bone loss. CT scans are useful but can be limited by artifact. Several centers have explored the role of MRI in assessing lysis. It can be useful for bone loss and provides excellent assessment for soft tissue: abductors, neurovascular structures. Metal artifact reduction sequencing is required to maximise information obtainable. Management of osteolysis: Identification and monitoring periprosthetic osteolysis is a crucial element of patient care. Progressive bone loss leading to loss of fixation and the potential risk for periprosthetic fracture is a real possibility and early recognition and intervention is a priority. The basic Guiding Principles of management are centered around several key elements including the source of osteolysis and degree, the fixation of implant, the location of lysis, the track record of implant system, the presence of patient symptoms (if any), and finally the patient age, activity level, and general health. Specifics of treatment of osteolysis around the acetabulum: With cemented sockets, lysis is typically seen late and frequently at the bone-cement interface. It is often associated with a loose implant and the prime indication for surgery may be pain. Treatment involves implant removal and revision with an uncemented cup and bone grafting or augmentation as needed. With uncemented sockets in the setting of osteolysis, there are several factors to consider. These have been stratified by Rubash, Maloney, and Paprosky. The treatment of these sockets has been summarised as follows: for Type I and Type II with limited lysis, lesional treatment such as debridement and bone grafting with head and polyethylene exchange has been suggested. WATCH for impingement!!!! Graft defects via trap-doors can be performed but make the door big enough to graft. Small doors and grafting through screw holes is at best marginal. In instances of compromised locking mechanisms, consider cementing the liner into the shell. For Type II and Type III implants, revision of the component is recommended. With the currently available cementless cup extraction tools, I rarely hesitate to remove a cup with moderate lysis and a broken locking mechanism: better access to lytic areas, better grafting achieved. CAVEAT #1: the disadvantage of implant removal is that it is clearly a bigger procedure and fixation of the new implant may be more difficult. Risks vs. rewards. CAVEAT #2: Socket revision in the setting of failed MOM implants has some unique “issues”. In the Vancouver series, almost 25% of the revision cups failed to achieve biologic fixation. As such, recommendation for using “enhanced” porous implants during revision seems prudent. Additionally, despite the use of larger diameter heads, instability rates remain high

Wear and osteolysis are the major problems limiting the longevity of total hip arthroplasty. There is general agreement that if left untreated osteolysis will eventually lead to loosening of the acetabular component. In many cases polyethylene liner exchange may be preferable to revision of a well-fixed acetabular component. If there is osteolysis present the question is when should the polyethylene liner exchange be performed? The answer to that question has not been definitively defined at the present time. There are few studies available that evaluate the timing of surgical intervention when acetabular osteolysis is present. Indications for surgical intervention include prevention of complete wear of the head through the polyethylene liner (liner thickness < 1.5 mm) and when the osteolysis involves 50% or more of the shell circumference on AP or lateral x-rays. Of course persistent pain with wear or osteolysis is another indication for surgery. Contraindications to cup retention and liner exchange include: 1) Malpositioned component; 2) Non-modular component; 3) Unable to obtain hip stability; 4) Thin polyethylene liner (relative); 5) Severe damage to acetabular shell; and 6) Poor track record of the acetabular component. If one decides to retain the component the following steps are generally involved in operative management. Remove the liner and assess component stability. Assess the locking mechanism for the polyethylene. If the locking mechanism is not intact one can consider cementing the liner in place. In general, it is recommended to debride and bone graft the osteolytic lesion. The author prefers to use an access hole at the periphery of the component or at times a trapdoor can be made in the ilium. It is essential not to de-stabilise the acetabular component. At the present time there is no optimal graft material to use. Potential graft options include demineralised bone matrix or cancellous bone chips. Since dislocation is the number one complication after polyethylene liner exchange, it is a good idea to use a larger femoral head whenever possible. In some cases it is also worthwhile to consider bracing the patient after the surgery. It is essential to be ready to perform a complete revision. Therefore, when planning to perform a polyethylene liner exchange one needs to have the appropriate components available to completely revise the acetabular component

Periacetabular osteolysis is seen in response to particles (polyethylene, ceramic, metal or cement), at times in the presence of an unstable implant, and perhaps made worse by the unique host response to the particle burden. The impact of wear modes: due to either the primary bearing surface (MOP, MOM, COC) or unintended surfaces as seen in impingement, as well as the quality of the bearing counterface all influence the extent of the osteolytic response. The final common pathway appears to be via macrophage stimulation, an upregulation of cytokines leading to a resorption of bone. The patterns of lysis range from linear resorption at the implant interface to more expansile patterns which can be more dramatic in size and may place the implant at jeopardy for loosening. Assessment of implant fixation as well as extent of the lytic process employs the use of plain radiographs (including oblique views), computerised tomography and magnetic resonance imaging. The utility of MRI for the quantification of bone loss as well as the newer phenomena of associated soft tissue lesions (pseudotumors, adverse tissue reactions) has turned out to be a valuable tool in helping determine timing and need for revision. The basic principles in determining need for revision surgery revolve around: degree of lysis, integrity of the soft tissues, fixation of the implant, track record of the implant, as well as patient factors including symptoms, age and activity. In cemented sockets, progressive bone loss, pain with or without overt loosening is indication for revision which is generally accomplished using an uncemented hemispherical acetabular component with bone graft and screw augmentation. In the uncemented socket, the decision to revise is based upon a) implant stability, 2) the integrity of the locking mechanism, 3) degree of bone loss. With stable implants, polyethylene exchange and “lesional” treatment is appropriate. Well fixed implants with extensive lysis can be successfully managed with liner exchange and bone grafting as necessary. If the liner locking mechanism is compromised, cementing a liner into place is an excellent strategy. Removing a well fixed cup with extensive lysis runs the risk of encountering a large acetabular defect which may be difficult to reconstruct. Loose implants clearly require revision. In the era of “hard bearings”, progressive soft tissue expansion leading to damage of the abductor and other soft tissue constraints about the hip is an indication for revision. Revision of MOM THR's may be performed by maintaining the femoral component and performing an isolated acetabular revision or in some instances of modular acetabular components, maintaining the shell and inserting a new liner. In all instances of implant retention, it is critical to confirm that the components are in optimised position: implants retained in suboptimal position are at risk for early failure

Reoperation on the acetabular side of the total hip arthroplasty construct because of acetabular liner wear with or without extensive osteolysis is the most common reoperation performed in revision hip surgery today. The options of revision of the component or component retention, liner exchange (cemented or direct reinsertion) and bone grafting represent a classic surgeon dilemma of choices and compromises. CT scanning is helpful in determining the size and location of osteolytic lesions. My preference is to retain the existing shell when possible especially when there are large osteolytic lesions but where structural support is maintained. The advantages of complete revision are easy access to lytic lesions, ability to change component position and the ability to use contemporary designs with optimal bearing surfaces (for wear and dislocation prevention). The disadvantage is bone disruption including pelvic discontinuity with component removal (less so with Explant Systems) and difficult reconstructions due to excessive bone loss from the osteolytic defects (sometimes requiring cup cages). The advantage of component retention is that structural integrity of the pelvis is maintained and in general, a higher quality polyethylene is utilised. For large lesions I use windows to debride and bone graft the lesions. If the locking mechanism is inadequate, cementing a liner, including a constrained liner in some cases, that has been scored in a spider web configuration provides durable results at 5-year follow-up. The downside to liner exchange is potential instability. We immobilise all liner exchange patients postoperatively

In the revision situation, there are times where larger heads are just not enough to obtain and maintain stability. The two most relevant times that this is the case is in patients with very lax tissues, or in patients with insufficient or absent soft tissues, especially abductor mechanisms. In addition, in cases where a revision is being performed for dislocation and components looked well-positioned, constrained liners have been extremely beneficial in our hands. Constrained acetabular liners have been available for close to two decades. Two basic types of liners are available. The type first developed by Joint Medical Products was the SROM constrained liner which captured the femoral head with a locking ring in the polyethylene. These liners may have better results with larger head sizes because the hip can be taken through a larger range of motion (with larger head sizes) before the locking ring is stressed. The second type of constraining liner was developed by Osteonics (Stryker). It consisted of a tripolar replacement which is constrained by a locking ring in the outer polyethylene of the device. Indications for constrained liners include patients undergoing primary arthroplasty who are low demand and have dementia or hip muscle weakness or spasticity. Indications for constrained liners in the revision situation include cases with previously failed operations for instability, elderly low demand patients with instability, cases with poor or absent hip musculature, and cases with well positioned acetabular and femoral components and with hip instability. In this last scenario we cement the liners into fixed shells. Our results at average 10-year follow-up in 101 hips, demonstrate a 6% failure of the device. Four hips were revised for acetabular loosening and four hips for femoral loosening. One additional hip was revised for acetabular osteolysis. Considering the difficulty of the cases we consider these results to be quite encouraging. At average 3.9 year follow-up of 31 cases where the liner was cemented into the secure shell only one case failed by dislodgement of the liner and one case by fracture of the locking mechanism. Our experience has led to the following technical recommendation: (1) if cementing the component score the liner and make sure it is contained within the shell (2) avoid inserting the liner into a grossly malpositioned shell (3) avoid positioning the elevated rim of the liner into a position where impingement might occur and (4) avoid placing the shell and constrained liner in cases with massive acetabular allografts unless additional fixation, i.e. cages, are utilized. Especially in the elderly, these liners are our components of choice for many pre-operative and intra-operative cases of instability