Pelvic discontinuity is a separation through the acetabulum with the ilium displacing superiorly and the ischium/pubis displacing inferiorly. This is a biomechanically challenging environment with a high rate of failure for standard acetabular components. The cup-cage reconstruction involves the use of a highly porous metal cup to achieve biological bone ingrowth on both sides of the pelvic discontinuity and an ilioischial cage to provide secure fixation across the discontinuity and bring the articulating hip center to the correct level. The purpose of this study was to report long term follow up of the use of the cup-cage to treat pelvic discontinuity. All hip revision procedures between January 2003 and January 2022 where a cup-cage was used for a hip with a pelvic discontinuity were included in this retrospective review. All patients received a Trabecular Metal Revision Shell with either a ZCA cage or TMARS cage (Zimmer-Biomet Inc.). Pelvic discontinuity was diagnosed on pre-operative radiographs and/or intraoperatively. Kaplan-Meier survival analysis was performed with failure defined as revision of the cup-cage reconstruction. Fifty-seven cup-cages in 56 patients were included with an average follow-up of 6.25 years (0.10 to 19.98 years). The average age of patients was 72.09 years (43 to 92 years) and 70.2% of patients were female. The five year Kaplan-Meier survival was 92.0% (95% CI 84.55 to 99.45) and the ten year survival was 80.5% (95% CI 58.35 to 102.65). There were 5 major complications that required revision of the cup-cage reconstruction (3 infections and 2 mechanical failures). There were 9 complications that required re-operation without revision of the cup-cage reconstruction (5 dislocations, 3 washouts for infection and one femoral revision for aseptic loosening). In our hands the cup-cage reconstruction has provided a reliable tool to address pelvic discontinuity with an acceptable complication rate

Cup-cage constructs are one of several methods commonly used to treat severe acetabular bone loss during contemporary revision total hip arthroplasty. The purpose of this study was to provide a long-term results of the technique with emphasis on implant survivorship, radiographic results, and clinical outcomes for both full and half cup-cage reconstructions. We identified 57 patients treated with a cup-cage reconstruction for major acetabular bone loss between 2002–2012. All patients had Paprosky Type 2B through 3B bone loss, with 60% having an associated pelvic discontinuity. Thirty-one patients received a full cup-cage construct, and 26 a half cup-cage. Mean age at reconstruction was 66 years, 75% were female, and the mean BMI was 27 kg/m. 2. Mean follow-up was 10 years. The 10-year cumulative incidences of any revision were 14% and 12% for the full and half cup-cage construct groups, respectively. Of the 9 revisions, 3 were for dislocation, 2 for aseptic loosening and construct failure (both were pelvic discontinuities), 1 for adverse local tissue reaction, and 1 for infection with persistent pelvic discontinuity. The 10-year cumulative incidences of revision for aseptic loosening were 4.5% and 5% for the full and half cup-cage constructs, respectively. Of the unrevised cases, incomplete and non-progressive zone 3 radiolucent lines were observed in 10% of patients in each group. Three patients experienced partial motor and sensory sciatic nerve palsies (2 in the full and 1 in the half cup-cage group). Both the full and half cup-cage cohorts demonstrated significantly improved Harris hip scores. Full and half cup-cage reconstructions for major acetabular defects were successful at 10 years in regards to acetabular fixation without appreciable differences between the two techniques. However, zone 3 radiolucent lines were not uncommon in association with discontinuities, and dislocation continues to be a problem

Introduction. Severely comminuted, displaced acetabular fractures with articular impaction in the elderly population present significant treatment challenges. To allow early post-operative rehabilitation and limit the sequelae of immobility, treatment with acute total hip replacement (THA) has been advocated in selected patients. Achieving primary stability of the acetabular cup without early migration is challenging and there is no current consensus on the optimum method of acetabular reconstruction. We present clinical results and radiostereometric analysis of trabecular metal (TM) cup cage construct reconstruction in immediate THA without acetabular fracture fixation. Methods. Between 2011 and 2016, twenty-one acetabular fractures underwent acute THA with a TM cup cage construct. Patient, fracture and surgical demographics were collected. They were followed up for a mean of 24months (range 12–42months). Clinical and patient reported outcome measures were collected at regular post-operative intervals. Radiosterometric analysis (RSA) was used to measure superior migration and sagittal rotation of the acetabular component. Results. Thirteen fractures were classified as anterior column posterior hemi-transverse, two anterior column, two transverse and four associated both column acetabular fractures. There was one case of trochanteric fracture and transient foot drop. Mean Harris Hip Scores at 12months was 79 (range 33–98). The mean proximal migration of the acetabular components at 12months was 0.91mm (range 0.09–5.12 and mean sagittal rotation was 0.52mm (range 0.03–7.35). Conclusion. The TM cup-cage technique requires a single approach and provides immediate cup stability allowing full weight bearing day one post-op. To our knowledge this is the first study to accurately measure cup stability following THA for an acetabular fracture. Our promising early clinical and radiological outcomes suggest this technique may be an alternative to a fix and replace construct for immediate THA for acute acetabular fractures in the elderly

Contemporary acetabular reconstruction in major acetabular bone loss often involves the use of porous metal augments, a cup-cage construct or custom implant. The aims of this study were: To determine the reproducibility of a reconstruction algorithm in major acetabular bone loss. To determine the subsequent success of reconstruction performed in terms of re-operation, all-cause revision and Oxford Hip Score (OHS) and to further define the indications for custom implants in major acetabular bone loss. Consecutive series of Paprosky Type III defects treated according to a reconstruction algorithm. IIIA defects were planned to use a superior augment and hemispherical cup. IIIB defects were planned to receive either augment and cup, cup-cage or custom implant. 105 procedures in cohort 100 patients (5 bilateral) with mean age 73 years (42–94). IIIA defects (50 cases) − 72.0% (95%CI 57.6–82.1) required a porous metal augment the remainder treated with a hemispherical cup alone. IIIB defects (55 cases) 71.7% (95%CI 57.6–82.1) required either augments or cup-cage. 20 patients required a hemispherical cup alone and 6 patients received a custom-made implant. Mean follow up of 7.6 years. 6 re-revisions were required (4 PJI, 2 peri-prosthetic fractures & 1 recurrent instability) with overall survivorship of 94.3% (95% CI 97.4–88.1) for all cause revision. Single event dislocations occurred in 3 other patients so overall dislocation rate 3.8%. Mean pre-op OHS 13.8 and mean follow-up OHS 29.8. Custom implants were used in: Mega-defects where AP diameter >80mm, complex discontinuity and massive bone loss in a small pelvis (i.e., unable to perform cup-cage). A reconstruction algorithm can >70% successfully predict revision construct which thereafter is durable with a low risk of re-operation. Jumbo cup utilized <1/3 of cases when morphology allowed. The use of custom implants has been well defined in this series and accounts for <5% of cases

Acetabular cages are necessary when an uncemented or cemented cup cannot be stabilised at the correct anatomic level. Impaction grafting with mesh for containment of bone graft is an alternative for some cases in centers that specialise in this technique. At our center we use three types of cage constructs –. (A). Conventional cage ± structural or morselised bone grafting. This construct is used where there is no significant bleeding host bone. This construct is susceptible to cage fatigue and fracture, This reconstruction is used in young patients where restoration of bone stock is important. (B). Conventional cage in combination with a porous augment where contact with bleeding host bone can be with the ilium and then by the use of cement that construct can be unified. The augment provides contact with bleeding host bone and if and when ingrowth occurs, the stress is taken off the cage. (C). Cup-Cage Construct – in this construct there must be enough bleeding host bone to stabilise the ultra-porous cup which functions like a structural allograft supporting and eventually taking the stress off the cage. This construct is ideal for pelvic discontinuity with the ultra-porous cup, i.e., bridging and to some degree distracting the discontinuity. If, however, the ultra-porous cup cannot be stabilised against some bleeding host bone, then a conventional stand-alone cage must be used. In our center the cup-cage reconstruction is our most common technique where a cage is used, especially if there is a pelvic discontinuity. Acetabular bone loss and presence of pelvic discontinuity were assessed according to the Gross classification. Sixty-seven cup-cage procedures with an average follow-up of 74 months (range, 24–135 months; SD, 34.3) months were identified; 26 of 67 (39%) were Gross Type IV and 41 of 67 (61%) were Gross Type V (pelvic discontinuity). Failure was defined as revision surgery for any cause, including infection. The 5-year Kaplan-Meier survival rate with revision for any cause representing failure was 93% (95% confidence interval, 83.1–97.4), and the 10-year survival rate was 85% (95% CI, 67.2–93.8). The Merle d'Aubigné-Postel score improved significantly from a mean of 6 pre-operatively to 13 post-operatively (p < 0.001). Four cup-cage constructs had non-progressive radiological migration of the ischial flange and they remain stable

Pelvic discontinuity is defined as a separation of the ilium superiorly from the ischiopubic segment inferiorly. In 2018, the main management options include the following: 1) hemispheric acetabular component with posterior column plating, 2) cup-cage construct, 3) pelvic distraction, and 4) custom triflange construct. A hemispheric acetabular component with posterior column plating is a good option for acute pelvic discontinuities. However, healing potential is dependent on host's biology and characteristic of the discontinuity. The plate should include 3 screws above and 3 screws below the discontinuity with compression in between. In addition, the hemispherical acetabular component should have at least 50% host bone contact with 3–4 screws superior and 2–3 screws inferior to the discontinuity. On the other hand, a cup-cage construct can be used in any pelvic discontinuity. This includes a highly porous acetabular component placed on remaining host bone. Occasionally, highly porous metal augments are used to fill the remaining bone defects. A supplemental cage is placed over the acetabular component, spanning the discontinuity from the ilium to the ischium. A polyethylene liner is then cemented into place with antibiotic-loaded bone cement. Rarely, pelvic distraction may be needed. With this technique, pelvic stability is obtained via distraction of the discontinuity by elastic recoil of the pelvis and by fixing the superior hemipelvis and inferior hemipelvis to a highly porous metal cup or augment with screws, thereby unitizing the superior and inferior aspects of the pelvis. In essence, the cup acts as a segmental replacement of the acetabulum, with healing occurring to the cup or augment, resulting in a unitised hemipelvis. Frequently, the discontinuity itself does not achieve bony healing. Finally, custom triflange constructs are being utilised with increasing frequency. Triflange cups are custom-designed, porous and/or hydroxyapatite coated, titanium acetabular components with iliac, ischial, and pubic flanges. Rigid fixation promotes healing of the discontinuity and biologic fixation of the implant. It requires a CT scan, dedicated preoperative design, and fabrication costs

Revision surgery for pelvic discontinuity in the presence of bone loss is challenging. The cup-cage reconstruction option has become popular for the management of pelvic discontinuity in the recent years. The aim of this study was to review the clinical, radiological and patient reported outcomes with the use of cup cage construct for pelvic discontinuity at our institution. Twenty-seven patients (27 cup-cage reconstructions) were identified at median 6-year (minimum 2 year, maximum 10 years) follow up. Eight were female patients. The median age was 77 years [mean 72, range 37–90, SD 13.6]. There were 5 deaths and 2 were lost to follow up. Two patients were converted to excision arthroplasty; one for infection and one for failure of the construct. A further 3 patients required revision for instability but the cup cage construct was not revised (2 revisions of cemented cups to a constrained cup and one revision of proximal modular component of the femoral prosthesis). Revision of the cup cage construct was not necessary in any of these cases. We noted excellent pain relief (mean WOMAC pain 85.6) and good functional outcome (mean WOMAC function 78.2, mean UCLA 5, mean OHS 78.6). Patient satisfaction with regards pain relief; function and return to activities were noted to be excellent. Radiological changes were noted in further 4 patients (cup migration in one case; fracture of ischial spike in one case and breakage of the cage screws in 2 patients). No migration of the construct was noted in any of the cases. In conclusion, the cup cage construct is an excellent method of dealing with complex pelvic discontinuity. Our study suggests a low failure rate; high patient satisfaction and pain relief and moderate functional outcome at median 6 year follow up

Acetabular cages are necessary when an uncemented or cemented cup cannot be stabilised at the correct anatomic level. Impaction grafting with mesh for containment of bone graft is an alternative for some cases in centers that specialise in this technique. At our center we use three types of cage constructs –. (A) Conventional cage ± structural or morselised bone grafting. This construct is used where there is no significant bleeding host bone. This construct is susceptible to cage fatigue and fracture. This reconstruction is used in young patients where restoration of bone stock is important. (B) Conventional cage in combination with a porous augment where contact with bleeding host bone can be with the ilium and then by the use of cement that construct can be unified. The augment provides contact with bleeding host bone and if and when ingrowth occurs, the stress is taken off the cage. (C) Cup Cage Construct – in this construct there must be enough bleeding host bone to stabilise the ultra-porous cup which functions like a structural allograft supporting and eventually taking the stress off the cage. This construct is ideal for pelvic discontinuity with the ultra-porous cup, i.e., bridging and to some degree distracting the discontinuity. If, however, the ultra-porous cup cannot be stabilised against some bleeding host bone, then a conventional stand-alone cage must be used. In our center the cup cage reconstruction is our most common technique where a cage is used, especially if there is a pelvic discontinuity. Acetabular bone loss and presence of pelvic discontinuity were assessed according to the Gross classification. Sixty-seven cup-cage procedures with an average follow-up of 74 months (range, 24–135 months; SD, 34.3) months were identified; 26 of 67 (39%) were Gross Type IV and 41 of 67 (61%) were Gross Type V (pelvic discontinuity). Failure was defined as revision surgery for any cause, including infection. The 5-year Kaplan-Meier survival rate with revision for any cause representing failure was 93% (95% confidence interval, 83.1–97.4), and the 10-year survival rate was 85% (95% CI, 67.2–93.8). The Merle d'Aubigné-Postel score improved significantly from a mean of 6 pre-operatively to 13 post-operatively (p < 0.001). Four cup-cage constructs had non-progressive radiological migration of the ischial flange and they remain stable

Aims

Pelvic discontinuity is a rare but increasingly common complication of total hip arthroplasty (THA). This single-centre study evaluated the performance of custom-made triflange acetabular components in acetabular reconstruction with pelvic discontinuity by determining: 1) revision and overall implant survival rates; 2) discontinuity healing rate; and 3) Harris Hip Score (HHS).

Aims

The aim of this study was to assess the clinical and radiological results of patients who were revised using a custom-made triflange acetabular component (CTAC) for component loosening and pelvic discontinuity (PD) after previous total hip arthroplasty (THA).

In our center the cup cage reconstruction is our most common technique where a cage is used, especially if there is a pelvic discontinuity. Cup Cage Construct – in this construct there must be enough bleeding host bone to stabilise the ultraporous cup which functions like a structural allograft supporting and eventually taking the stress off the cage. This construct is ideal for pelvic discontinuity with the ultraporous cup, i.e., bridging and to some degree distracting the discontinuity. If, however, the ultra-porous cup cannot be stabilised against some bleeding host bone, then a conventional stand-alone cage must be used. Acetabular bone loss and presence of pelvic discontinuity were assessed according to the Gross classification. Sixty-seven cup cage procedures with an average follow-up of 74 months (range, 24–135 months; SD, 34.3 months) were identified; 26 of 67 (39%) were Gross Type IV and 41 of 67 (61%) were Gross Type V (pelvic discontinuity). Failure was defined as revision surgery for any cause, including infection. The 5-year Kaplan-Meier survival rate with revision for any cause representing failure was 93% (95% confidence interval, 83.1–97.4), and the 10-year survival rate was 85% (95% CI, 67.2–93.8). The Merle d'Aubigné-Postel score improved significantly from a mean of 6 pre-operatively to 13 post-operatively (p < 0.001). Four cup-cage constructs had non-progressive radiological migration of the ischial flange and they remain stable

Most acetabular defects can be treated with a cementless acetabular cup and screw fixation. However, larger defects with segmental bone loss and discontinuity often require reconstruction with augments, a cup-cage, or triflange component – which is a custom-made implant that has iliac, ischial, and pubic flanges to fit the outer table of the pelvis. The iliac flange fits on the ilium extending above the acetabulum. The ischial and pubic flanges are smaller than the iliac flange and usually permit screw fixation into the ischium and pubis. The custom triflange is designed based on a pre-operative CT scan of the pelvis with metal artifact reduction, which is used to generate a three-dimensional image of the pelvis and triflange component. The design of the triflange involves both the manufacturing engineer and surgeon to determine the most appropriate overall implant shape, screw fixation pattern, and cup location and orientation. A plastic model of the pelvis, and triflange implant can be made in addition to the triflange component to be implanted, in order to assist the surgeon during planning and placement of the final implant in the operating room. A wide surgical exposure is needed including identification of the sciatic nerve. Proximal dissection of the abductors above the sciatic notch to position the iliac flange can risk denervation of the abductor mechanism. Blood loss during this procedure can be excessive. Implant survivorship of 88 to 100% at 53-month follow-up has been reported. However, in a series of 19 patients with Paprosky type 3 defects, only 65% were considered successful. The custom triflange also tends to lateralise the hip center which may adversely affect hip mechanics. The use of a triflange component is indicated in cases with massive bone loss or discontinuity in which other reconstructive options are not considered suitable

Using the Mayo Clinic definition (>62mm in women and >66mm in men), the “jumbo acetabular component” is the most successful method for acetabular revisions now, even in hips with severe bone loss. There are numerous advantages: surface contact is maximised; weight-bearing is distributed over a large area of the pelvis; the need for bone grafting is reduced; and usually, hip center of rotation is restored. The possible disadvantages of jumbo cups include: may not restore bone stock; may ream away posterior column or wall; screw fixation required; the possibility of limited bone ingrowth and late failure; and a high rate of dislocation due to acetabular size:femoral head ratio. The techniques for a successful jumbo revision acetabular component involve: sizing-“reaming” of the acetabulum, careful impaction to achieve a “press-fit”, and multiple screw fixation. We recommend placement of an ischial screw in addition to dome and posterior column screw fixation. Cancellous allograft is used for any cavitary defects. The contra-indications for a jumbo acetabular cup are: pelvic dissociation; inability to get a rim fit; and inability to get screw fixation. If stability cannot be achieved with the jumbo cup alone, then use of augment(s), bulk allograft, or cup-cage construct should be considered. Using titanium fiber-metal mesh components, we reported the 15-year survival of 129 revisions. There was 3% revision for deep infection and only 3% revision for aseptic loosening. There were 13 reoperations for other reasons: wear, lysis, dislocation, femoral loosening, and femoral fracture fixation. The survival was 97.3% at 10 years, but it dropped to 82.8% at 15 years. Late loosening of this fiber metal mesh component is likely related to polyethylene wear and loss of fixation. Dislocation is the most common complication of jumbo acetabular revisions, approximately 10%, and these are multifactorial in etiology and often require revision. Based on our experience, we now recommend use of an acetabular component with an enhanced porous coating (tantalum), highly crosslinked polyethylene, and large femoral heads or dual mobility for all jumbo revisions

Revision of total hip arthroplasty (THA) is being performed with increasing frequency. However, outcomes of repeated revisions have been rarely reported in the literature, especially for severe defects. Cup revision can be a highly complex operation depending on the bone defect. In acetabular defects like Paprosky types 1 and 2 porous cementless cups fixed with screws give good results. Modern trabecular metal designs improve these good results. Allografts are useful for filling cavitary defects. In acetabular defects Paprosky types 3A and 3B, especially the use of trabecular metal cups, wedges, buttresses and cup-cage systems can produce good results. Difficult cases in combination with pelvic discontinuity require reconstruction of the acetabulum with acetabular plates or large cup-cages to solve these difficult problems. However, there is still no consensus regarding the best option for reconstructing hips with bone loss. Although the introduction of ultraporous metals has significantly increased the surgeon's ability to reconstruct severely compromised hips, there remain some that cannot be managed readily using cups, augments, or cages. In such situations custom acetabular components may be required. Individual implants represent yet another tool for the reconstructive surgeon. These devices can be helpful in situations of catastrophic bone loss. Ensuring long-term outcome, mechanical stability has a greater impact than restoring an ideal center of rotation. However, despite our consecutive case series there are no mid- to long-term results available so far. Re-revision for failed revision THA acetabular components is a technically very challenging condition

The Vancouver classification separates periprosthetic femur fractures after THA into three regions (A - trochanteric, B - around or just below the stem, and C - well below the stem), with fractures around or just below the stem further separated into those with a well-fixed (B1) or loose stem and good (B2) or poor (B3) bone stock. Trochanteric fractures may be associated with osteolysis and require treatment that addresses osteolysis as well as ORIF of displaced fractures. Fractures around a well-fixed stem can be treated with ORIF using cerclage or cable plating, while those around a loose stem require implant revision usually to a longer cementless tapered or distally porous coated cementless stem. Fractures around a loose stem with poor bone stock in which salvage of the proximal femur is not possible require replacement of the proximal femur with an allograft prosthetic composite or proximal femoral replacement. Fractures well below the stem can be treated with conventional plating methods. Periprosthetic acetabular fractures are rare and usually occur in the early post-operative period or late as a result of osteolysis or trauma. These can generally be separated into those with a stable acetabular component which can be treated non-operatively, and those with an unstable component often with discontinuity or posterior column instability which require complex acetabular reconstruction utilizing plating or revision to a cup-cage

Introduction. The mid- or long-term results of acetabular revision total hip arthroplasty (THA) in Korea are rare. The purpose of this study is to report the mid-term radiographic results (> 5 years) of acetabular revision THA with porous-coated cementless Trilogy. ®. cup (Zimmer, Warsaw, IN, USA). Materials and Methods. Between 1999 and 2010, 77 patients (79 hips) had underwent acetabular revision THA with Trilogy. ®. cup. Eight patients (8 hips) were excluded due to death before 5-year follow-up, and 22 patients (23 hips) were excluded due to less than 5-year follow-up or follow-up loss. Forty-seven patients (48 hips) were included in our study. The mean age was 57.9 years (range, 36 to 76 years) and the mean follow-up was 9.8 years (range 5.0 to 16.2 years). The causes of revision were aseptic loosening in 40 hips, and septic loosening in 8 hips, respectively. Both acetabular and femoral revisions were performed in 14 hips and isolated acetabular revision was done in 34 hips. Preoperetive acetabular bone defect according to Paprosky classification was; 1 in type I, 6 in IIA, 11 in IIB, 9 in IIC, 15 in IIIA, and 6 in IIIB. Results. Radiolucent lines less than 2mm were found in 2 hips; one in zone I, another in zone I, II, III. Four hips (1 in type IIC, 1 in IIIA and 2 in IIIB) showed cup migration greater than 5 mm accompanying change of position greater than 5 degrees. However, these patients did not complain pain and showed fixation by secondary stabilization. The Kaplan-Meier survivorship with aseptic loosening as the end point at 10 years was 92.6% (95% confidence interval [CI], 82.6 – 100) and at 15 years was 83.8 % (95% CI, 69.1 – 98.6), respectively. Non-recurrent dislocations occurred in 4 hips. There were no other complication such as sciatic nerve palsy, infection and deep vein thrombosis. Conclusion. Mid-term radiographic results (>5 years) of acetabular revision THA with porous-coated cementless Trilogy. ®. cup showed durable longevity. However, other options such as anti-protrusio cage or cup-cage construct should be considered in severe acetabular bone defect

Pelvic discontinuity with associated bone loss is a complex challenge acetabular revision surgery. Reconstruction by the use of ilio-ischial cages combined with trabecular metal acetabular components and morsellised bone (the component-cage technique) is a relatively new method of treatment. The trabecular cup provides a good environment for bone graft remodeling and eventual bone or fibrous ingrowth. The cage protects the trabecular metal cup until stabilisation occurs. The cage not only protects the cup but places the articulating center at the correct level. We reviewed a consecutive series of 32 cases of acetabular revision reconstructions with pelvic discontinuity who had been treated by the cup-cage technique. The mean follow-up was 38 months (24.0 to 68.0). Failure was defined as a migration of a component of >5mm. In 29 hips there was no clinical or radiological evidence of loosening at the last follow-up. The Harris hip scores improved significantly from 44.6 (sd 10.4) to 78.7 (sd 10.4) points (p<0.001). In three hips (11.5%) the construct migrated at one year after surgery. The complications included two cases of dislocations, one of infection and one of partial palsy of the peroneal nerve. Our findings indicated that the treatment of pelvic discontinuity by the component-cage construct is a reliable option

The custom triflange acetabular component has been advocated for severe acetabular defects and pelvic discontinuity, cases in which a porous-coated hemisphere will not work. These are AAOS type III or IV defects, or alternatively classified as Paprosky 3B. Many have a pelvic discontinuity. A pre-operative CT of the pelvis is sent to the manufacturer who generates a one-to-one scale 3D model of the hemipelvis. The surgeon can review either a pdf file or an actual model. If the visualised defect cannot be treated with traditional methods then a triflanged component is created. The components have backside porous and hydroxyapatite coating. Initial rigid fixation is obtained with screw fixation to the ilium and ischium. Subsequent bone ingrowth can provide long term fixation. The goal is to span the acetabular defect and obtain fixation to the ilium and ischium with a third arm which rests on the pubis. Christie first reported on 67 hips (half with a discontinuity) with a mean follow-up of 53 months. No components were removed. There was an 8% reoperation for dislocation, 6% partial sciatic nerve palsy. 46% walked without support. Dennis reported 26 hips with a mean 54 month follow-up. Eighty-eight percent were considered successful. One implant was removed and left with a resection arthroplasty and 2 others had loose components but refused reoperation. Loosening of the ischial screws was a sign of failure in the three cases. Taunton reported 57 cases with a pelvic discontinuity treated with a triflange at mean follow-up of 65 months. Eighty-one percent had a stable component and a healed pelvic discontinuity. These authors also compared a custom triflange to a trabecular metal cup-cage construct finding similar implant costs of $12,500 and $11,250, respectively. All advocates of custom triflange acetabular components believe the results are similar or superior to other options in these very challenging cases at early follow-up. The primary disadvantage of the technique is the pre-operative time required to manufacture the device – typically 4–8 weeks

The custom triflange acetabular component has been advocated for severe acetabular defects and pelvic discontinuity, cases in which a porous-coated hemisphere will not work. These are AAOS type III or IV defects, or alternatively classified as Paprosky 3B. Many have a pelvic discontinuity. A preoperative CT of the pelvis is sent to the manufacturer who generates a one-to-one scale 3D model of the hemipelvis. The surgeon can review either a pdf file or an actual model. If the visualised defect cannot be treated with traditional methods then a triflanged component is created. The components have backside porous and hydroxyapatite coating. Initial rigid fixation is obtained with screw fixation to the ilium and ischium. Subsequent bone ingrowth can provide long term fixation. The goal is to span the acetabular defect and obtain fixation to ilium and ischium with a third arm which rests on the pubis. Christie first reported on 67 hips (half with a discontinuity) with a mean follow-up of 53 months. No components were removed. There was an 8% reoperation for dislocation, 6% partial sciatic nerve palsy. 46% walked without support. Dennis reported 26 hips with a mean 54 month follow-up. 88% were considered successful. One implant was removed and left with a resection arthroplasty and 2 others had loose components but refused reoperation. Loosening of the ischial screws was a sign of failure in the three cases. Taunton reported 57 cases with a pelvic discontinuity treated with a triflange at mean follow-up of 65 months. 81% has a stable component and a healed pelvic discontinuity. These authors also compared a custom triflange to a trabecular metal cup-cage construct finding similar implant costs of $12,500 and $11,250, respectively. All advocates of custom triflange acetabular components believe the results are similar or superior to other options in these very challenging cases at early follow-up. The primary disadvantage of the technique is the preoperative time required to manufacture the device – typically 4–8 weeks

Major bone loss involving the acetabulum can be seen during revision THA due to component loosening, migration or osteolysis and can also occur as a sequela of infected THA. Uncemented highly porous ingrowth acetabular components can be used for the reconstruction of the vast majority of revision cases, especially where small to mid-sized segmental or cavitary defects are present which do not compromise stable mechanical support by the host bone for the cup after bone preparation is complete. A mechanically stable and near motionless interface between the host bone and the implant is required over the initial weeks post-surgery for bone ingrowth to occur, regardless of the type of porous surface employed. As bone deficiency increases, the challenge of achieving rigid cup fixation also increases, especially if the quality of the remaining host bone is compromised. A stepwise approach to enhanced fixation of the highly porous revision acetabular component is possible as follows:. Maximise Screw Fixation. Use of a limited number of screws in the dome only (as routinely occurs with a cluster hole design) is inadequate, except for primary arthroplasty cases or very routine revision cases with little or no bone loss and good bone quality. Otherwise an array of screws across the acetabular dome and continuing around the posterior column to base of the ischium is strongly recommended. This can help prevent early rocking of the cup into a more vertical position due to pivoting on dome screws used alone, via cup separation inferiorly in zone 3. A minimum of 3 or 4 screws in a wide array are suggested and use of 6 or more screws is not uncommon if bone quality is poor or defects are large. Cement the Acetabular Liner into the Shell. This creates a locking screw effect, which fixes the screw heads in position and prevents any screws from pivoting or backing out. Acetabular Augments (vs Structural Allograft). When critical segmental defects are present which by their location or size preclude stable support of the cup used alone, either a structural allograft or highly porous metal augment can provide critical focal support and enhance fixation. Highly porous metal augments were initially developed as a prosthetic allograft substitute in order to avoid the occasional graft resorption and loss of fixation sometimes seen with acetabular allograft use. Cup-Cage Construct. If one or more of the above strategies are used and fixation is deemed inadequate, it is possible to add a ½ or full acetabular cage “over the top” of the acetabular component before cementing a polyethylene liner in place. The full cup cage construct can be used for maximal fixation in cases of pelvic dissociation, alone or in combination with the distraction method as described by Paprosky. Use of a ½ cage is technically simpler and requires less exposure than a full cage, but still greatly enhances rigidity of fixation when transverse screws into the ilium are combined with standard screws in the cup including vertically into the dome. These techniques used in combination with highly porous tantalum implants have allowed durable fixation for the full range of reconstructive challenges and bone defects encountered. Newer 3-D printed titanium highly porous materials have recently been introduced by multiple manufacturers as a potential alternative that may be more cost effective, but these implants and materials will require clinical validation over the years ahead