Although total hip arthroplasty is highly successful for treatment of osteoarthrosis of hip joint, it is skill demanding surgery to perform and even more challenging in case of revision with bone defects. There are many options available for reconstruction of acetabular bony defects. Here, we evaluate the outcome of acetabular bony defect reconstructed with trabecular metal augments in short term. We performed, 22 revision total hip arthroplasties and 6 primary total hip arthroplasties (total 28 in 28 patients) using trabecular metal augments to reconstruct acetabular defect between 2011 to 2015. Out of these 28 patients, 18 were males and 10 were females. Mean age of these patients was 61.2 years (range: 46 years to 79 years). Pre-operative templating was done for all cases and need for trabecular metal augments was anticipated in all cases. All cases were classified according to Paprosky classification for acetabular bone defects. Out of 28 patients, 3 had type 2B, 1 had type 2C, 18 had type 3A and 6 had type 3B acetabular defects. Post operatively, all patients were followed at regular interval for their clinical and radiological outcome. An average follow up was 20.1 months (range: 6 months to 42.5 months). We assessed clinical outcome in the form of Herris hip score (HHS) and radiological outcomes in form of osteolysis in acetabular zones and osseointegration, according to the criteria of Moore. The average Harris hip score (HHS) was improved from 58.0 preoperatively to 87.2 postoperatively. The average degree of cup abduction at the final follow up was 44.29. The centre of rotation of the hip joint was corrected from average 38.90mm (range: 22.15mm to 66.35mm) above the inter-teardrop line preoperatively to average 23.85mm (range: 11.82mm to 37.69mm) above the inter-teardrop line postoperatively. Out of 28 patients, 18 patients had three or more signs of osseointegration, according to the criteria of Moore, at the time of final follow up. Rest of patients, had one or two signs of osseointegration (5 patients had one sign and 5 patients had two signs). We had no patient with migration or loosening of acetabular components. No patient has osteolysis of acetabulum in any zone. Trabecular metal augments provide good initial stability to acetabular cup as well as helpful to bring down the centre of rotation of the hip joint within limit of 35mm above the inter-teardrop line. They also facilitate osseointegration. Our study showed that the results of the trabecular metal augments in reconstruction of acetabular bony defects were successful even in short term. However, long term study is required for better evaluation

Introduction. Primary stability is an important factor for long-term implant survival in total hip arthroplasty. In revision surgery, implant fixation becomes especially challenging due the acetabular bone defects, which are often present. Previous studies on primary stability of revision components often applied simplified geometrical defect shapes in a variety of sizes and locations. The objectives of this study were to (1) develop a realistic defect model in terms of defect volume and shape based on a clinically existing acetabular bone defect, (2) develop a surrogate acetabular test model, and (3) exemplarily apply the developed approach by testing the primary stability of a pressfit-cup with and without bone graft substitute (BGS). Materials & Methods. Based on clinical computed tomography data and a method previously published [1], volume and shape information of a representative defect, chosen in consultation with four senior hip revision surgeons, was derived. Volume and shape of the representative defect was approximated by nine reaming procedures with hemispherical acetabular reamers, resulting in a simplified defect with comparable volume (18.9 ml original vs. 18.8 ml simplified) and shape. From this simplified defect (Defect D), three additional defect models (Defect A, B, C) were derived by excluding certain reaming procedures, resulting in four defect models to step-wise test different acetabular revision components. A surrogate acetabular model made of 20 PCF polyurethane foam with the main support structures was developed [2]. For the exemplary test, three series for Defect A were defined: Native (acetabulum without defect), Empty (defect acetabulum without filling), Filled (defect acetabulum with BGS filling). All series were treated with a pressfit-cup and subjected to dynamic axial load in direction of maximum resultant force during level walking. Minimum load was 300 N and maximum load was increased step-wise from 600 N to 3000 N. Total relative motion between cup and foam, consisting of inducible displacement and migration, was assessed with the optical measurement system gom Aramis (gom GmbH, Braunschweig, DE). Results. Total relative motion increased with increasing load, with a maximum of 0.63 mm for Native, 0.86 mm for Filled, and 1.9 mm for Empty. At load stage 1800 N, total relative motion in Empty was 11.0-fold increased in comparison to Native, but could be reduced to a 3.3-fold increase in Filled. Discussion. The objective of this study was to develop a simplified, yet realistic and modular defect model which could be used to step-wise test different treatment strategies. Applicability of the developed test setup was shown by assessing primary stability of a pressfit-cup in a native, empty, and filled situation. The presented method could potentially be used as a modular test setup to compare different acetabular revision components in a standardized way. For any figures or tables, please contact authors directly

Introduction. Modern acetabular cups require a convenient bone stock for sufficient cup fixation. Thereby, fixation stability is influenced by the chosen interference fit of the acetabular cup, the cup surface structure, circularity of the reamed acetabulum and by the acetabular bone quality. The ideal implantation situation of the cup is commonly compromised by joint dysplasia and acetabular bone defects. The aim of the present experimental study was to characterise implant fixation of primary acetabular cups in case of definite acetabular cavity defects. Materials and Methods. For the experimental determination bone substitute blocks (100 × 100 × 50 mm) made of polymethacrylimide (PMI) foam with a density of 7 pcf were used. The created acetabular defect situations were derived from the defect classification according to Paprosky. The defect geometries in the PMI foam blocks were realised by a CNC drilling machine. Thereby the defects are described in the dorso-ventral direction by the angle α and in medio-lateral direction by the angle β (given as angle combination α/β) related to the centre of rotation of the reamed cavity. For the lever-out tests the defect types IIb and IIIa (each with different α and β angles) were considered and compared to the intact fixation situation. Therefore, a macrostructured titanium cup (Allofit, Zimmer GmbH, Wintherthur, Switzerland) with an outer diameter of 56 mm were displacement-controlled (v = 20 mm/min) pushed into the 2 mm diametric under reamed PMI-foam cavities. Three cups were inserted until the cup overhang pursuant to surgical technique was reached. Subsequently the cups were displacement-controlled (v = 20 mm/min) levered out via a rod which was screwed into the implant pole by perpendicular displacement (U. axial. ) of the rod in direction of the defect aperture. The lever-out moments were calculated by multiplying the first occurring force maximum (F. max. ) with the effective lever arm length (l. lever. ), whereby moments caused by the deadweight of the rod were considered. Primary stability was defined by the first maximum lever-out moment. Results. The calculated lever-out moments were in a range from 15.5 ± 1.4 Nm to 1.4 ± 0.5 Nm. Defects with a 90° dorso-ventral opening angle showed 57 ± 17% lower lever-out moments. Defects with a 120° dorso-ventral opening angle showed 80 ± 6% lower lever-out moments compared to the cup fixation into intact cavities. Moreover, medio-lateral angles greater than 20° reduced the lever-out moment by 79 ± 12% compared to the intact cavities. Conclusion. The determined lever-out moments underline the reduction of fixation stability of acetabular cup by loss of circumferential rim and absent of superior wall support of the acetabular bone. Thereby, the fixation stability is influenced by the degree of dorso-ventral and medio-lateral defect manifestation. Hence, the fixation stability depends on the cavity surface and in particular the surface of the bone-implant interface in the fixation zone of the acetabular cup Thus, dorso-ventral defect sizes with greater opening angle than 60° and medio-lateral defect sizes greater than 20° are critically for sufficient fixation of primary acetabular cup implants

Introduction. Acetabular bone defects are still challenging to quantify. Numerous classification schemes have been proposed to categorize the diverse kinds of defects. However, these classification schemes are mainly descriptive and hence it remains difficult to apply them in pre-clinical testing, implant development and pre-operative planning. By reconstructing the native situation of a defect pelvis using a Statistical Shape Model (SSM), a more quantitative analysis of the bone defects could be performed. The aim of this study is to develop such a SSM and to validate its accuracy using relevant clinical scenarios and parameters. Methods. An SSM was built on the basis of segmented 66 CT dataset of the pelvis showing no orthopedic pathology. By adjusting the SSM's so called modes of shape variation it is possible to synthetize new 3D pelvis shapes. By fitting the SSM to intact normal parts of an anatomical structure, missing or pathological regions can be extrapolated plausibly. The validity of the SSM was tested by a Leave-one-out study, whereby one pelvis at a time was removed from the 66 pelvises and was reconstructed using a SSM of the remaining 65 pelvises. The reconstruction accuracy was assessed by comparing each original pelvis with its reconstruction based on the root-mean-square (RMS) surface error and five clinical parameters (center of rotation, acetabulum diameter, inclination, anteversion, and volume). The influence of six different numbers of shape variation modes (reflecting the degrees of freedom of the SSM) and four different mask sizes (reflecting different clinical scenarios) was analyzed. Results. The Leave-one-out study showed that the reconstruction errors decreased when the number of shape variation modes included in the SSM increased from 0 to 20, but remained almost constant for higher numbers of shape variation modes. For the SSM with 20 shape variation modes, the RMS of the reconstruction error increased with increasing mask size, whereas the other parameters only increased from Mask_0 to Mask_1, but remained almost constant for Mask_1, Mask_2 and Mask_3. Median reconstruction errors for Mask_1, Mask_2, and Mask_3 were approximately 3 mm in Center of Rotation (CoR) position, 2 mm in Diameter, 3° in inclination and anteversion, as well as 5 ml in volume. Discussion. This is the first study analyzing and showing the feasibility of a quantitative analysis of acetabular bone defects using a SSM-based reconstruction method in the clinical scenario of a defect or implant in both acetabuli and incomplete CT-scans. Validation results showed acceptable reconstruction accuracy, also for clinical scenarios in which less healthy bone remains. Further studies could apply this method on a larger number of defect pelvises to obtain quantitative measures of acetabular bone defects

Introduction. Revision total hip arthroplasty is often associated with acetabular bone defects. In most cases, assessment of such defects is still qualitative and biased by subjective interpretations. Three-dimensional imaging techniques and novel anatomical reconstructions using statistical shape models (SSM) allow a more impartial and quantitative assessment of acetabular bone defects [1]. The objectives of this study are to define five clinically relevant parameters and to assess 50 acetabular bone defects in a quantitative way. Methods. Anonymized CT-data of 50 hemi-pelvises with acetabular bone defects were included in the study. The assessment was based on solid models of the defect pelvis (i.e. pelvis with bone defect) and its anatomical reconstruction (i.e. native pelvis without bone defect) (Fig.1A). Five clinically relevant parameters were defined: (1) Bone loss, defined by subtracting defect pelvis from native pelvis. (2) Bone formation, defined by subtracting native pelvis from defect pelvis. Bone formation represents bone structures, which were not present in the native pelvis (e.g. caused by remodeling processes around a migrated implant). (3) Ovality, defined by the length to width ratio of an ellipse fitted in the defect acetabulum. A ratio of 1.0 would represent a circular acetabulum. (4) Lateral center-edge angle (LCE angle), defined by the angle between the most lateral edge of the cranial roof and the body Z-axis, and (5) implant migration, defined by the distance between center of rotation (CoR) of the existing implant and CoR of native pelvis (Fig. 1B). Results. All data are presented as single values as well as median and [25. th. , 75. th. ]- percentile (Fig.2). Bone loss was 53.6 [41.5, 76.7] ml with a minimum of 19.0 ml and maximum of 103.9 ml. Bone formation was 15.7 [10.5, 21.2] ml with a minimum of 3.5 ml and a maximum of 41.6 ml. Ovality was 1.3 [1.1, 1.4] with a minimum of 1.0 and a maximum of 2.0. LCE angle was 30.4° [21.5°, 40.1°] with a minimum of 11.6° and a maximum of 63.0°. Implant migration was 25.3 [15.1, 32.6] mm with a minimum of 5.4 mm and a maximum of 53.5 mm. Discussion. Within this study, 50 hemi-pelvises with acetabular bone defects were successfully quantified using five clinically relevant parameters. Application of this method provides impartial and quantitative data of acetabular bone defects, which could be beneficial in clinical practice for pre-operative planning or comparison of surgical outcomes. Including a larger number of cases, this method could even serve as a basis for a novel classification system for acetabular bone defects. For any figures or tables, please contact the authors directly

THA in patients with acetabular bone defects is associated with a high risk of dislocation. Dual mobility (DM) cups are known to prevent and treat chronic instability. The aim of this study was to evaluate the dislocation rate and survival of jumbo DM cups. This was a retrospective, continuous, multicenter study of all the cases of jumbo DM cup implantation between 2010 and 2017 in patients with acetabular bone loss (Paprosky 2A: 46%, 2B: 32%, 2C: 15% and 3A: 6%). The indications for implantation were revisions for aseptic loosening of the cup (n=45), aseptic loosening of the femoral stem (n=3), bipolar loosening (n=11), septic loosening (n=10), periprosthetic fracture (n=5), chronic dislocation (n=4), intraprosthetic dislocation (n=2), cup impingement (n=1), primary posttraumatic arthroplasty (n=8), and acetabular dysplasia (n=4). The jumbo cups used were COPTOS TH (SERF), which combines press-fit fixation with supplemental fixation (acetabular hook, two superior flanges with one to four screws, two acetabular pegs). A bone graft was added in 74 cases (80%). The clinical assessment consisted of the Harris hip score. The primary endpoint was surgical revision for aseptic acetabular loosening or the occurrence of a dislocation episode. In all, 93 patients were reviewed at a mean follow-up of 5.3 ± 2.3 years [0, 10]. As of the last follow-up, the acetabular cup had been changed in five cases: three due to aseptic loosening (3.2%) and two due to infection (2.1%). The survivorship free of aseptic loosening was 96.8%. Three patients (3%) suffered a dislocation. At the last follow-up visit, the mean HSS scores were 72.15, (p < 0.05). Use of a jumbo DM cup in cases of acetabular bone defects leads to satisfactory medium-term results with low dislocation and loosening rates

Aim. Aim of this monocentric, prospective study was to evaluate the safety, efficacy, clinical and radiographical results at 24-month follow-up (N = 6 patients) undergoing hip revision surgery with severe acetabular bone defects (Paprosky 2C-3A-3B) using a combination of a novel phase-pure betatricalciumphosphate - collagen 3D matrix with allograft bone chips. Method. Prospective follow-up of 6 consecutive patients, who underwent revision surgery of the acetabular component in presence of massive bone defects between April 2018 and July 2019. Indications for revision included mechanical loosening in 4 cases and history of hip infection in 2 cases. Acetabular deficiencies were evaluated radiographically and CT and classified according to the Paprosky classification. Initial diagnosis of the patients included osteoarthritis (N = 4), a traumatic fracture and a congenital hip dislocation. 5 patients underwent first revision surgery, 1 patient underwent a second revision surgery. Results. All patients were followed-up radiographically with a mean of 25,8 months. No complications were observed direct postoperatively. HHS improved significantly from 23.9 preoperatively to 81.5 at the last follow-up. 5 patients achieved a defined good result, and one patient achieved a fair result. No periprosthetic joint infection, no dislocations, no deep vein thrombosis, no vessel damage, and no complaint about limbs length discrepancy could be observed. Postoperative dysmetria was found to be + 0.2cm (0cm/+1.0cm) compared to the preoperative dysmetria of − 2.4 cm (+0.3cm/−5.7cm). Conclusions. Although used in severe acetabular bone defects, the novel phase-pure betatricalciumphosphate - collagen 3D matrixshowed complete resorption and replacement by newly formed bone, leading to a full implant integration at 24 months follow-up and thus represents a promising method with excellent bone regeneration capacities for complex cases, where synthetic bone grafting material is used in addition to autografts

To evaluate the short-term clinical outcomes of patients treated arthroscopically with chitin-based scaffolding for acetabular chondral defects in conjunction with microfracture compared to microfracture alone. This study is a retrospective analysis of prospectively collected data. A review of charts was performed (2014–2016) on all patients who underwent hip arthroscopy and had microfracture +/− scaffolding for acetabular chondral defects, intraoperative details (lesion size, grade, labral repair/reconstruction) and postoperative complications were recorded with a minimum follow-up of 2 years. Clinical outcomes were assessed by analysing iHOT and HOS scores which were obtained pre-operatively, at six months, one year and two years post-surgery. Plain radiographs were assessed for hip osteoarthritis by Kellgren & Lawrence grading. A total of 60 patients (microfracture=25, scaffolding=35) were included. Patients had a mean age of 36.2 years at the time of the index operation. There were no major adverse events of deep vein 36.2 years at the time of the index operation. There were no major adverse events of deep vein thrombosis, blood vessel or nerve damage, hemarthrosis or device related adverse events in both groups. Two patients were readmitted due to pain as a result of an inflammatory reaction in the scaffolding group. Both treatments of microfracture and scaffolding showed significant improvement in outcome score (iHOT) (p < 0 .001) when compared postoperative to preoperative. Both the arthroscopic treatment of chondral acetabular defects with chitin based scaffolding and microfracture demonstrated significant improvement from their pre-operative outcomes

Introduction. The number of complex revision total hip arthroplasties (THA) is predicted to rise. The identification of acetabular bone defects prior to revision THA has important implications on technique and complexity of acetabular reconstruction. Paprosky et al. proposed a classification system including 3 main types with up to 3 subtypes focused on the integrity of the superior rim of the acetabulum and medial wall. However, the classification system is complex and its reliability has been questioned. The purpose of this study was to evaluate the effectiveness of different radiologic imaging modalities (plain radiographs, 2-D CT, 3-D CT reconstructions) in classifying acetabular defects in revision hip arthroplasty cases and their value of at different levels of orthopaedic training. Methods. Patients treated with revision total hip arthroplasty for acetabular bone defects between 2002–2012 were identified and 22 cases selected that had plain radiographs, 2-D CT and 3-D reconstructions available. Bone defects were classified independently by two fellowship-trained adult reconstruction surgeons. Representative sections were chosen and compiled into a timed presentation. Thirty-five residents from PGY-1 to PGY-5 and 4 attending orthopaedic surgeons were recruited for this study and received a 15-minute introduction to the classification system. Chi square analysis was utilized to examine the influence of image modality and level of training on the correct classification of acetabular bone loss using the Paprosky classification system with alpha=0.05. Results. The correct classification regardless of imaging of PGY levels was 30%. The level of training did not influence the ability to classify an acetabular defect (p=0.918). Correct classification was significantly influenced by the imaging used. Using x-ray led to 37% correctly identified defects, CT scans to 33% and 3D modeling to 30% of correct answers (p<0.001). For Class 1 defects, x-ray imaging had significantly higher number of correct classification (93%) compared to CT scans (67%) and 3D modeling (31%, p<0.001). Similarly, 2A defects were classified correctly with higher frequency on x-ray (49%) compared to CT scans (36%) or 3D modeling (15%, p=0.007). For type 2B, 2C, 3A and 3B defects, the type of imaging did not influence the frequency of correct answer. The level of training did not influence the frequency of correct classification regardless of the type of defect (p<0.05). However, there was a significant difference based on the defect type (p<0.001). Regardless of level of training or imaging, 64% of observers recognized type 1 defects, compared to only 16% correct recognition of 3B defects. Discussion. In the current study using different image modalities, residents regardless of the level of training were only able to classify 30% of defects correctly using the Paprosky classification system of acetabular defects. Using plain x-rays led to an increased number of correct classification, while regular CT scan and 3D CT reconstructions did not improve accuracy. The cost for advanced imaging when using this classification may not be justified. The Paprosky classification system of acetabular defects can be used for treatment decisions; however, it is complex and residents may require increased education in its use and identification of defects

Uncontained acetabular defects with loss of superior iliac and posterior column support (Paprosky 3) represent a reconstructive challenge as the deficient bone will preclude the use of a conventional hemispherical cup. Such defects can be addressed with large metallic constructs like cages with and without allograft, custom tri-flange cups, and more recently with trabecular metal augments. An underutilised alternative is impaction bone grafting, after creating a contained cavitary defect with a reinforcement mesh. This reconstructive option delivers a large volume of bone while using a small-size socket fixed with acrylic cement. Between 2005 and 2014, 21 patients with a Paprosky 3B acetabular defect were treated with cancellous, fresh frozen impaction grafting supported by a peripheral reinforcement mesh secured to the pelvis with screws. A cemented all-polyethylene cup was used. Pre-operative diagnosis was aseptic loosening (15 cemented and 6 uncemented). The femoral component was revised in 10 patients. Post-operative course consisted of 3 months of protected weight bearing. Patients were followed clinically and radiographically. One patient had an incomplete post-operative sciatic palsy. After a mean follow up of 47 months (13 to 128) none of the patients required re-revision of the acetabular component. One asymptomatic patient presented with aseptic loosening 9 years post-operatively. Hardware failure was not observed. All patients had radiographic signs of graft incorporation and bone remodeling. There were no dislocations. The early and mid-term results of revisions of large acetabular defects with this technique are encouraging. Reconstitution of hip center of rotation and bone stock with the use of a small-size implant makes this technique an attractive option for large defects. Longer follow-up is needed to assess survivability

Introduction. The goal of revision total hip arthroplasty (THA) for acetabular defects is to achieve the best stability and fixation with available host bone. Tritanium is a highly porous metal construct with a titanium matrix coating. We are reporting our experience of utilizing this material in patients with major acetabular defects. Methods. Between February 2007 and August 2010, 24 consecutive hips (23 patients) underwent acetabular reconstruction using the Tritanium cups. The acetabular defects were assessed using the Paprosky classification. Anteroposterior and lateral radiographs were analyzed at follow-up based for the presence of radiolucent lines more than 2 mm in any of the 3 zones. Results. Mean follow-up was 3.6 ± 1.1 years (range 1.5–5 years). There were 12 males and 11 females. The acetabular defects were type 2a (2 hips), 2b (3 hips), 2c (5 hips), 3a (8 hips), and 3b (6 hips). Two patients had pelvic dissociation. Mean anteversion and abduction angles were 43 ± 4.6 and 19.5 ± 4.4 degrees respectively. All hips had radiographic evidence of osteointegration. Four hips had small demarcation at zones 1 and 3 (<1 mm), however, there were no hips with circumferential or more than 2 mm demarcation. There was no intra-operative fracture or post-operative dislocation, instability, or infection. Discussion and Conclusion. The short-term results of titanium cups in major acetabular defects are encouraging. Our results demonstrate excellent safety and efficacy of this material in revision THA

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 maybe 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, impacted morselised allografts with a cemented cup technique produce good results. Difficult cases 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. We have done so far 15 3D Printed Individual Implants. All of them where Paprosky Type 3B defects, 10 with a additional pelvis discontinuity. The mean follow-up is 18 months. All implanted devices are still in place, no infection, no loosening. 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 3D Printed Individual Implants have a lot of advantages, like excellent surgical planning and a very simple technique (operative time, blood loss, instruments). They are a very stable construct for extensive acetabular defects and pelvic discontinuity

Uncontained acetabular defects with loss of superior iliac and posterior column support (Paprosky 3B) represent a reconstructive challenge as the deficient bone will preclude the use of a conventional hemispherical cup. Such defects can be addressed with large metallic constructs like cages with and without allograft, custom tri-flange cups, and more recently with trabecular metal augments. An underutilised alternative is impaction bone grafting, after creating a contained cavitary defect with a reinforcement mesh. This reconstructive option delivers a large volume of bone while using a small-size socket fixed with acrylic cement. Between 2006 and 2014, sixteen patients with a Paprosky 3B acetabular defect were treated with cancellous, fresh frozen impaction grafting supported by a peripheral reinforcement mesh secured to the pelvis with screws. A cemented all polyethylene cup was used. Preoperative diagnosis was aseptic loosening (10 cemented and 6 non-cemented). The femoral component was revised in 9 patients. Postoperative course consisted of 3 months of protected weight bearing. Patients were followed clinically and radiographically. One patient had an incomplete postoperative sciatic palsy. After a mean follow up of 40 months (24 to 104) none of the patients required re-revision. One asymptomatic patient presented with aseptic loosening 9 years postoperatively. Hardware failure was not observed. All patients had radiographic signs of graft incorporation and bone remodeling. There were no dislocations. The early and mid-term results of revisions for large acetabular defects with this technique are encouraging. Reconstitution of hip center of rotation and bone stock with the use of a small-size implant make this technique an attractive option for these large defects. Longer follow-up is needed to assess survivability

The treatment of extensive bone loss and massive acetabular defects is a challenging procedure, especially in cases with concomitant pelvic discontinuity (PD). Pelvic discontinuity describes the separation of the ilium proximally from the ischio-pubic region distally. The appropriate treatment strategy is to restore a stable continuity between the ischium and the ilium to reconstruct the anatomical hip center. Several treatment options such as antiprotrusio cages, metal augments, reconstruction cages with screw fixation, structural allograft with plating, jumbo cups, oblong cups and custom-made triflange acetabular components have been described as possible treatment options. Cage and/or ring constructs or acetabular allograft are commonly used techniques with unsatisfactory results and high failure rates. More favorable results have been presented with custom triflange acetabular components (CTAC), although the results are still unsatisfactory. Three-dimensional printing technology (3DP) has already become part of the surgical practice. In this context, preliminary clinical and radiological results using a 3D-printed custom acetabular component in the management of extensive acetabular defects are presented. The overall complication rate was 33.3 %. In one out of 15 patients (6.6 %), implant-associated complication occurred revealing an overall implant-associated survival rate of 93.3%. The 3D-printed custom acetabular component suggests a promising future, although the manufacturing process has high costs and the complication rate is still high

Introduction. Acetabular osteotomy is considered to be an alternative treatment for acetabular dysplasia, particularly in adolescents and young adults because the long-term results of total hip arthroplasty (THA) in such patients remain controversial. To our knowledge, few reports have described the relationship between the types of osteotomies and surgical difficulty. We compared the operative and clinical results of THA following the 3 main types of acetabular osteotomies, including Chiari osteotomy, rotational periacetabular osteotomy (RAO), and shelf acetabuloplasty. Methods. Operative records of 13 hips following Chiari osteotomy (Chiari group), 22 hips following RAO (RAO group), and 16 hips following shelf acetabuloplasty (Shelf group) were retrospectively reviewed. Operative records of 2475 primary THAs without previous osteotomies during the same period were reviewed as a control. The direct anterior approach was used for all hips. Results. The mean operative time was 57.7 ± 11.7 min in the Chiari group, 68.7 ± 25.7 min in the RAO group, 57.4 ± 20.5 min in the shelf group, and 50.6 ± 18.5 min in the Control group. The operative time was significantly longer in the RAO group than in the Control group (p < 0.05). The mean operative blood loss was 406 ± 277 g in the Chiari group, 439 ± 400 g in the RAO group, 377 ± 163 g in the Shelf group, and 379 ± 270 g in the Control group. Allogeneic blood transfusion was performed in 1 patient (4%) in the RAO group and in 26 patients (1%) in the Control group. Bulk bone augmentation to the acetabular defect was performed in 2 hips (15%) in the Chiari group, 7 hips (32%) in the RAO group, and 87 hips (3.5%) in the Control group. The requirement for bulk bone augmentation to the acetabular defect was significantly higher in the Chiari and RAO groups than in the Control group (p < 0.05). Aseptic loosening occurred in 2 cups in the RAO group and postoperative dislocation occurred in 1 hip in the Chiari group. Conclusion. RAO made the conversion to THA complicated because of acetabular defects. Chiari osteotomy was less effective and shelf acetabuloplasty had no effect on surgical results of conversion THA

The treatment of extensive bone loss and massive acetabular defects is a challenging procedure, especially the concomitant pelvic discontinuity (PD) can be compounded by several challenges and pitfalls. The appropriate treatment strategy is to restore a stable continuity between the ischium and the ilium and to reconstruct the anatomical hip center. Antiprotrusio cages, metal augments, reconstruction cages with screw fixation, structural allograft with plating, jumbo cups, oblong cups and custom-made triflange acetabular components have been reported as possible treatment options. Nevertheless, the survivorship following acetabular revision with extensive bone loss is still unsatisfactory. The innovation of three-dimensional printing (3DP) has become already revolutionary in engineering and product design. Nowadays, the technology is becoming part of surgical practice and suitable for the production of precise and bespoke implants. The technique of a 3D-printed custom acetabular component in the management of extensive acetabular defect is presented

Aims. Severe, superior acetabular bone defects are one of the most challenging aspects to revision total hip arthroplasty (THA). We propose a new concept of “superior extended fixation” as fixation extending superiorly 2 cm beyond the original acetabulum rim with porous metal augments, which is further classified into intracavitary and extracavitary fixation. We hypothesized that this new concept would improve the radiographic and clinical outcomes in patients with massive superior acetabular bone defects. Patients and Methods. Twenty eight revision THA patients were retrospectively reviewed who underwent reconstruction with the concept of superior extended fixation from 2014 to 2016 in our hospital. Patients were assessed using the Harris Hip Score (HHS) and the Western Ontario and McMaster Universities Osteoarthritis Index score (WOMAC). In addition, radiographs were assessed and patient reported satisfaction was collected. Results. At an average follow-up of 28 months (range 18 – 52 months), the postoperative HHS and WOMAC scores were significantly improved at the last follow-up (p < 0.001). The postoperative horizontal and vertical locations of the COR from the interteardrop line were significantly improved from the preoperative measurements (p < 0.001). One (3.6 %) patient was dissatisfied due to periprosthetic joint infection. Conclusion. Extracavitray and intracavitary superior extended fixation with porous metal augments and cementless cups are effective in reconstructing severe superior acetabular bone defects, with promising short-term clinical and radiographic outcome

Introduction. Reinforcement ring with allograft bone is commonly used for acetabular reconstruction of bone defects because it can achieve stable initial fixation of the prosthesis. It is not clear whether the allograft bone can function as a viable host bone and provide long-standing structural support. The purpose of this study was to assess to long-term survival of the reinforcement rings and allograft bone incorporation after acetabular revisions. Methods. We retrospectively reviewed 39 hips (37 patients) who underwent reconstruction of the acetabulum with a Ganz reinforcement ring and allograft bone in revision total hip arthroplasty. There were 18 females and 19 males with a mean age of 55.9 years (35–74 years). The minimum postoperative follow-up period was 10 years (10∼17 years). We assessed the acetabular bone defect using the Paprosky's classification. We determined the rates of loosening of the acetabular reconstructions, time to aseptic loosening, integration of the allograft bone, resorption of the allograft bone, and survival rate. Aseptic loosening of the acetabular component was defined as a change in the cup migration of more than 5 mm or a change in the inclination angle of more than 5° or breakage of the acetabular component at the time of the follow-up. Graft integration was defined as trabecular remodelling crossing the graft-host interface. Resorption of the allograft bone was classified as minor (<1/3), moderate (1/3–1/2) or severe (>1/2). Kaplan-Meier survivorship analysis was performed for aseptic loosening of the acetabular component. The results. The acetabular bone defects were classified as follows: 8 type II hips (4 type IIB, 4 type IIC), and 31 type III hips (17 type IIIA, 14 type IIIB). Fourteen (35.9%) of 39 hips was defined as aseptic loosening of an acetabular component. Loosening was more frequent in type IIIB (57.1%) than in type IIIA hips (29.4%). Mean time to aseptic loosening of the acetabular reconstructions was 6.3 years in type IIIA and from 5 years in type IIIB defects, respectively. Allograft bone incorporation was satisfactory in 66.7% of hips. There was minor bone resorption in 14.3% and moderate bone resorption in 10.2%. In 9 hips (23.1%), severe resorption of the allograft bone was observed and early component loosening was observed in these cases. The survival rate of acetabular component at 10 years of follow-up was 63.6% (95% confidence interval, 49–77%) with aseptic loosening as endpoints. Conclusions. The long-term survival rate of acetabular revision using the reinforcement ring and allograft bone in the reconstruction of severe acetabular bone defects was unsatisfactorily low due to loosening of acetabular components. Because of unfavorable graft incorporation into a host bone, an alternative component and structural support may be employed in the reconstruction of severe acetabular bone defects

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. If the visualised defect cannot be treated with traditional methods then a triflanged component is created. 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 flange 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. Dennis reported 26 hips with a mean 54 month follow-up. Eighty-eight percent were considered successful. 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. The primary disadvantage of the technique is the preoperative time required to manufacture the device – typically 4–8 weeks

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