Introduction. Primary stability is achieved by the press fit technique, where an oversized component is inserted into an undersized reamed cavity. The major geometric design of an acetabular shell is hemispherical type. On the other one, there are the hemielliptical type acetabular shells for enhanced peripheral contact. In the case of developmental dysplasia of the hip (DDH), the aseptic loosening may be induced by instability due to decreased in the contact area between the acetabular shell and host bone. The aim of this study was to assess the effect of reaming size on the primary stability of two different outer geometry shells in DDH models. Materials and methods. The authors evaluated hemispherical (Continuum Acetabular Shell, Zimmer Biomet G.K.) and hemielliptical (Trabecular Metal Modular Acetabular Shell, Zimmer Biomet G.K.) acetabular shells. Both shells had a 50 mm outer diameter and same tantalum 3D highly porous surface. An acetabular bone model was prepared using a solid rigid polyurethane foam block with 20 pcf density (Sawbones, Pacific Research Laboratories Inc.) as a synthetic bone substrate. Press fit conditions were every 1 mm from 4 mm under reaming to 2 mm over reaming. To simulate the acetabular dysplasia the synthetic bone substrate was cut diagonally at 40°. Where, the acetabular inclination and cup-CE angle were assumed to 40° and 10°, respectively. Acetabular components were installed with 5 kN by a uniaxial universal testing machine (Autograph AGS-X, Shimadzu Corporation). Primary stability was evaluated by lever-out test. The lever-out test was performed in 4 mm undersized to 2 mm oversized reaming conditions. Lever out moment was calculated from the multiplication of the maximum load and the moment arm for primary stability of the shell. The sample size was 6 for each shell type. Results. The hemisphererical acetabular shell had the maximum lever out moment in 3 mm under reaming condition (7.4 ± 0.4 N·m). The hemielliptical acetabular shell had the maximum lever out moment in 1 mm under reaming condition (8.7 ± 0.8 N·m). Furthermore, the lever out moment of the hemielliptical acetabular shell was significantly 1.2 times greater by the t-test than the hemispherical acetabular shell under the maximum primary fixation conditions. Discussion. The risk parameter of the acetabular loosening is indicated the lack of lateral bony support. The hemielliptical shell was not adversely effected more than the hemispherical shell. Furthermore, the reaming condition of the most primary fixation on the hemielliptical shell was 1 mm under reaming, and was a more general operating procedure than the hemispherical shell (3 mm under reaming). From this study, it was suggested that the hemielliptical shell might be expected excellent clinical outcomes in severe acetabular dysplasia hips. For any figures or tables, please contact authors directly

A retrospective single-center review has been performed to gather clinical data on the use of polycarbonate-urethane (PCU) as an articulating bearing material inside a cobalt-chrome (Co-Cr) press-fit acetabular shell. As of January 2010, the Co-Cr shell and PCU liner have been implanted into 25 total hip patients which were retrospectively followed. The indications for use were in 24 cases of osteoarthritis, and 1 revision case. No patient was lost to follow-up. The average follow-up time was 17.6 months (range 8-27). The average age of these patients was 67.9 (range 44-84), the sex distribution was 14 female and 11 male patients, of whom 15 were right and 10 left side. 24 patients received a total hip replacement with the metal acetabular system and a cementless femoral stem and 1 patient received the metal acetabular shell coupled to a cemented resurfacing head. None of the cases has had a dislocation, revision, dislodgement, or infection. At follow-up, the mean Harris hip score was 98 points (80-99). X-rays showed good bone-implant contact without any osteolysis or bone rarefaction. A detailed review of the clinical data of these patients shows that a PCU liner inserted into a Co-Cr acetabular shell is as safe and effective as other commonly used acetabular shells in other total hip systems currently available. No new or unintended adverse or device-related events were discovered with the clinical use of PCU in a Co-Cr acetabular shell

High tensile stress has been considered as a contributing factor to the rim fracture of polyethylene acetabular cup liner. We performed the 3 D Finite Element Analysis (FEA) to compare the stress patterns at the polyethylene liner rim as a function of polyethylene thicknesses and whether or not rim was supported by the titanium acetabular shell extension. Two 3.1 mm thick generic 52 mm titanium alloy acetabular shells with and without 2 mm high rim support extension were modelled. Six corresponding Ultra High Molecular Weight Polyethylene (UHMWPE) liners with inner bearing diameters ranging from 22 mm to 44 mm and same outer diameters, were fixed in the shells. A 2 450 N load was applied through the corresponding CoCr femoral heads to the rims of liners while the acetabular shells were fixed on the outer spherical surface. The FEA was performed in half body of the assembly. The maximum principal stresses at the rim regions of UHMWPE liners were recorded. The results showed that in all rim supported conditions, the maximum principal stress were in compressive patterns, a preferred pattern to reduce the potential polyethylene liner fracture. In rim unsupported conditions, the stresses was in tensile on the internal bearing surface when polyethylene liner thickness was bellow 5 mm, or was bellow 9 mm if the average maximum principal stress cross the rim was considered. We conclude that the metal rim support changes the stress pattern in the rim region of UHMWPE liner to compressive for all liner thicknesses. The stress pattern turns to tensile, or there will be a higher potential for rim fracture, if UHMWPE liner is unsupported and the polyethylene rim thickness is less than 9 mm. Although components used this study did not include the locking details which add higher stress concentrations, the trend of stress patterns should follow the results found in this study

INTRODUCTION. Deformation of modular acetabular press-fit shells is a topic of much interest for surgeons and manufacturer. Such modular components utilise a titanium shell with a liner manufactured from metal, polyethylene or ceramic. Initial fixation is achieved through a press-fit between shell and acetabulum with the shell mechanically deforming upon insertion. Shell deformation may disrupt the assembly process of inserting the bearing liner into the acetabular shell for modular systems. This may adversely affect the integrity and durability of the components and the tribology of the bearing. OBJECTIVE. Most clinically relevant data to quantify and understand such shell deformation can be achieved by cadaver measurements. ATOS Triple Scan III was identified as a measurement system with the potential to perform those measurements. The study aim was to validate an ATOS Triple Scan III optical measurement system against a co-ordinate measuring machine (CMM) using in-vitro testing and to check capability/ repeatability under cadaver lab conditions. METHODS. Two sizes of custom-made acetabular shells were deformed using a uniaxial/ two-point loading frame and measured repeatedly at different loads. Roundness measurements were performed using both the ATOS Triple Scan III optical system and a co-ordinate measuring machine and then compared. The repeatability was also tested by measuring shells pre and post insertion in a cadaver lab multiple times. RESULTS. The in-vitro comparison with CMM demonstrated a maximum difference of 5 µm at the rim and 9 µm at the measurement point closest to the pole of the shell. Deviation between the two systems increased towards the pole for the in-vitro measurements. However as press fit shells are designed to be loaded at the rim, this is likely where the maximum deflection will occur as a result of the highest force. Therefore, the increased difference between the systems towards the pole is of less importance compared with accuracy at the rim. Maximum repeatability was below 1 µm for the CMM and 3 µm for the ATOS Triple Scan III optical system. Repeatability of the ATOS Triple Scan III optical system was comparable between pre insertion (below 2 µm) and post insertion (below 3 µm) measurements in the cadaver lab. In addition these values were comparable to the repeatability measured during the in-vitro validation study (below 3 µm). This proves high repeatability not only for in-vitro conditions, but also for the cadaver lab as well. CONCLUSIONS. This study supports the view that the ATOS Triple Scan III optical system fulfils the necessary requirements to accurately measure shell deformation in cadavers. As a result, the authors propose further studies using cadavers to identify the impact of other factors upon shell deformation. Other factors to be measured include bone strength, shell diameter, under reaming and wall thickness

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. A majority of the acetabular shells used today are designed to be press-fit into the acetabulum. Adequate initial stability of the press-fit implant is required to achieve biologic fixation, which provides long-term stability for the implant. Amongst other clinical factors, shell seating and initial stability are driven by the interaction between the implant's outer geometry and the prepared bone cavity. The goal of this study was to compare the seating and initial stability of commercially available hemispherical and rim-loading designs. Materials and Methods. The hemispherical test group (n=6) consisted of 66mm Trident Hemispherical shells (Stryker, Mahwah NJ) and the rim-loading test group (n=6) consisted of 66mm Trident PSL shells (Stryker, Mahwah NJ). The Trident PSL shell outer geometry is hemispherical at the dome and has a series of normalizations near the rim. The Trident Hemispherical shell outer geometry is completely hemispherical. Both shells are clinically successful and feature identical arc-deposited roughened CpTi with HA coatings on their outer geometry. Hemispherical cavities were machined in 20pcf polyurethane foam blocks (Pacific Research Laboratories, WA) to replicate the press-fit prescribed in each shell's surgical protocol. The cavity for the hemispherical design was machined to 65mm (1mm-under ream) and the cavity for the rim-loading design was machined to 67mm (1mm- over ream). Note that the rim-loading design features ∼2mm build-up of material at the rim when compared to the hemispherical design. The shells were seated into the foam blocks using a drop tower (Instron Dynatup 9250G, Instron Corporation, Norwood, MA) by applying 7 impacts of 6.58J/ea,. The number and energy of impacts are clinically relevant value obtained from surgeon data collection through a validated measurement technique. Seating height was measured from the shell rim to the cavity hemispherical equator (top surface foam block) using a height gage, thus, a low value indicates a deeply seated shell. A straight torque out bar was assembled to the threads at the shell dome hole and a linear load was applied with a MTS Mechanical Test Frame (MTS Corporation, Eden Prairie, MN) to create an angular displacement rate of 0.1 degrees/second about the shell center. Yield moment of the shell-cavity interface, representing failure of fixation, was calculated from the output of force, linear, displacement, and time. Two sample T-tests were conducted to determine statistical significance. Results. Seating height for the rim-loading design was 0.041 ± 0.005in (1.0 ± 0.1mm) compared to 0.049 ± 0.008in (1.2 ± 0.2mm) for the hemispherical design. Initial stability for the rim-loading design was 33.5 ± 2.9Nm compared to 29.9 ± 4.1Nm for the hemispherical design. Discussion. This study evaluated the seating height and initial stability of two different acetabular shell designs. Results indicate that there is no evidence for a difference in seating height (p > 0.05) and initial stability (p > 0.05) between rim-loading and hemispherical designs

1) INTRODUCTION. Acetabular fixation in cementless total hip arthroplasty (THA) relies on new technology for stability and survivorship of the implant. A highly porous 3D titanium coating was developed with a biologically inspired pore structure to improve initial friction fixation with mechanical stability and long term biological fixation. Ongoing research is investigating potential radiographic phenomenons these coatings produce, resulting in the presence of lucent lines. The purpose of this study was to evaluate clinical and radiographic outcomes of a 3D highly porous-coated titanium acetabular shell. 2) METHODS. One hundred and sixty-two cases as part of a non-randomized, post-market, multicenter study received a primary cementless THA. Clinical outcomes including the Harris Hip Score (HHS), Lower Extremity Activity Scale (LEAS), Short Form 12 (SF12), and EuroQol 5D Score (EQ-5D) were collected preoperatively and at six weeks, one year postoperative. Additionally, radiographs, radiographic parameters and techniques were analyzed for institutional differences. 3) RESULTS. Significant postoperative improvements were seen in pain, function and quality of life outcomes through one year. The HHS improved significantly (p< 0.0001) by 28.9 points at six weeks and 41.7 points at one year postoperative (Figure 1), with 53.4% of patients scoring Excellent or Good at six weeks and 87.5% at one year (Figure 2). Pain and physical functioning reported by the SF-12, EQ-5D and LEAS showed further clinical improvements at one year (Figure 1). Radiographically, 9.5% of cases reviewed displayed ‘radiolucent lines’ of less than 2mm in all three acetabular zones at six weeks. These cases only displayed radiolucent lines in one zone at the one year timepoint (Figure 3). Patients with radiolucent lines reported an average HHS score of 77 and 96 at six weeks and one year, respectively, with no radiographic failures or any revisions to date. The radiographic parameters and techniques were collected to analyze differences between the imaging techniques between institutions. Institutions utilizing digital radiography with an automatic exposure control technique, had cases where ‘radiolucent lines’ were present. One institution utilizing computed radiography with a manual technique did not have any cases display ‘radiolucent lines’. 4) DISCUSSION and CONCLUSION. Despite the appearance of transient radiographic lucent lines, patients in this study have shown positive clinical outcomes and initial stability through one year postoperative. These results do not correlate with the presence of radiolucent lines. Additionally, there may be a correlation between the imaging techniques and the presence of ‘radiolucent lines.’ As this device is still widely implanted using the same surgical technique, longer follow-up is needed to confirm a true biologic fixation and survivorship of the shell

Background. Instability and dislocation are some of the most important postoperative complications and potential causes of failure that dual mobility total hip arthroplasty (THA) systems continue to address. Studies have shown that increasing the relative head size provides patients implanted with smaller and larger cups increased stability, greater ROM and a lesser incidence of impingement, without compromising clinical results. The purpose of the current study was to review clinical outcomes in three groups of primary THA patients receiving a dual mobility acetabular shell. Methods. In two US based, post-market, multicenter studies, 450 patients received a primary cementless dual mobility THA. Patients were split into three groups based on cup size: ≤ 50mm, 52mm–56mm, and ≥ 58mm. Harris Hip Scores (HHS), Short Form 12 Physical Components (SF12 PCS), Lower Extremity Activity Scores (LEAS), and Euroqol 5D Score (EQ-5Ds) were collected preoperatively and through 2 years postoperative. Results. The current study displays gender differences among the three groups, with 90% female patients in the ≤ 50mm group, 66% male patients in the 52mm–56mm group and 100% males in the largest cup size group. A posterior/posterolateral approach was used in 94% of cases. The mean age range among the 3 groups was 60.5–61.7 and the two most common concurrent medical conditions were cardiovascular and musculoskeletal. There were no differences observed in clinical outcomes among any of the groups, all of which displayed significant increasing trends through 2 years postoperative (Figure 1). The HHS increased significantly from an average preoperative score of 54.5 to 92.9 and 93.7 at 1 and 2 years. Clinically significant improvements were seen at 2 years in SF12 PCS (+16.5) and the LEAS (+2.4) (Figures 1 and 3). The EQ-5D TTO increased from 0.62 preoperative to 0.91 at 2 years postoperative (Figure 2). There have been no failures due to dislocation reported in the current study population. Conclusion. Positive clinical outcomes for primary THA patients receiving a dual mobility system were seen in the current study, supporting their effectiveness. Regardless of the relative head size, all patients showed significant improvements postoperative with continued stability. As the primary risk factors for instability can include gender, age and increased comorbidities, the contemporary dual mobility system used in this study can address each patient's anatomic differences, improving quality of life and reducing the risk for dislocation, as well as the significant cost implications

Introduction:. The management strategy regarding optimally addressing polyethylene wear with a well-fixed acetabular shell remains controversial. The purpose of the present study was to document outcomes of cementation of a highly cross-linked polyethylene (PE) liner into a well-fixed acetabular metal shell in 36 hips. Materials & Methods:. We identified 37 patients (39 hips) who had undergone revision THA by cementation of a highly cross-linked PE liner into a well-fixed metal shell between June 2004 and April 2009. Of these patients, one (1 hip) died before the end of the 3-year evaluation and another was lost to follow-up. Thus, the study cohort consisted of 35 patients (36 hips). There were 23 males (24 hips) and 12 female (12 hips) patients with a mean age at time of revision surgery of 57.6 years (range, 38–79 years). All operations were performed by a single surgeon using only one type of liner. Clinical and radiographic evaluation was performed at a mean of 6.1 years (range, 3–8 years) postoperatively. Results:. Mean Harris hip score improved from 58.1 (range, 39–81 points) preoperatively to 91.3 (range, 45–100 points) postoperatively (p < 0.001). Of the 36 hips, 29 (80.1%) had an excellent result, 6 (16.7%) a good result, and 1 (2.8%) a poor result. The patient with a poor clinical result had aseptic cup loosening with a greater trochanteric fracture at 2 years postoperatively and was treated by acetabular cup revision and internal fixation of the fracture. However, no case of PE liner dislodgement from the cement or of dissociation of the PE-cement construct from the metal shell was encountered. At last follow-up, no new osteolytic lesion was identified and previous osteolytic lesions filled with bone graft were completely or partially incorporated. Other complications included 1 incomplete peroneal nerve palsy and 1 dislocation. Conclusions:. The results of this study and previous reports demonstrated that cementation of highly cross-linked PE liner into well-fixed metal shell could provide good midterm durability

INTRODUCTION. Deformation of modular acetabular press-fit shells is of much interest for surgeons and manufacturers. Initial fixation is achieved through press-fit between shell and acetabulum with the shell mechanically deforming upon insertion. Shell deformation may disrupt the assembly process of modular systems and may adversely affect integrity and durability of the components and tribology of the bearing. The aim of the study was to show shell deformation as a function of bone and shell stiffness. METHODS. The stiffness of the generic shells was determined using a uniaxial/ two point loading frame by applying different loads, and the change in dimension was measured by a coordinate measurement machine (CMM). Cadaver lab deformation measurements were done before and after insertion for 32 shells with 2 wall thicknesses and 11 shell sizes using the ATOS Triple Scan III (ATOS) optical system previously validated as a suitable measurement system to perform those measurements. Multiple deformation measurements per cadaver were performed by using both hip sides and stepwise increasing the reamed acetabulum by at least 1 mm, depending on sufficient residual bone stock. The under-reaming was varied between 0mm and 1mm, respectively. From the deformations, the resulting forces on the shells and bone stiffness were calculated assuming force equilibrium as well as linear-elastic material behaviour in each point at the rim of the shell. RESULTS. Radial stiffness for shells with 3 mm wall thickness ranged between 6257 N/mm and 2920 N/mm, with 4 mm wall thickness it ranged between 14341 N/mm and 6875 N/mm. The radial shell deformation ranged between 3 µm and 187 µm. The resulting maximum radial forces acting on the shells ranged between 26 N and 916 N. From these values, bone stiffness [N/mm] at the point of the maximum deformation has been calculated. Adding the bone stiffness and the shell stiffness using the equation for serial springs, one obtains a positive correlation between total stiffness and maximum deformation. DISCUSSION. The measured deformation values are within the same order of magnitude previously published [Lin 2006, Squire 2006]. The large variations of resulting maximum forces exhibit the need to further investigate shell deformation using commercial shell systems. The calculated bone stiffness at the point of the maximum deformation seems to be a valid predictor for expected shell deformation, but this also needs more data. A future goal is to determine expected shell deformation from bone data as a design rational

Introduction: From June 1991 to June 1995, 256 consecutive total hip arthroplasties using the Duraloc 100 TM acetabular shell, manufactured by Depuy, were performed by two surgeons. The acetabular component featured a non-locking apex hole eliminator. In January 1995 the first patient with extrusion of the apex hole eliminator was seen. Since that time 21 patients, or 8% (21/256) have been seen with partial or complete extrusion. This study reports the outcomes and discusses a possible rationale for this finding. Methods: The study group comprises 12 men, nine women, mean age was 59 years (32-86), mean weight 180 lbs. 18 (86%) femurs were cementless, three (14%) were cemented. Mean acetabular component size was 58 mm (52-64), with 18 acetabular liners manufactured with HylamerTM, and three liners EnduronTM. Sixteen (76%) liners were 10 degree hooded, and five (24%) were non-hooded. Eighteen (86%) femoral heads were ceramic, and three (14%) were chrome-cobalt. 15 (71%) femoral heads were 28 mm diameter, and six (29%) were 32 mm. Results: Radiographs were obtained at routine follow-up in 20 (95%) patients. One (5%) patient had groin pain as the indication for radiographs. Four (19%) patients had complete extrusion in to the pelvis of the apex hole eliminator, and 17 (81%) had partial backout with the apex hole eliminator still within the confines of the acetabular component. On the antero-posterior radiograph visible pelvic osteolysis was seen in the four patients with complete extrusion of the apex hole eliminator, all in zone B. Zone one femoral osteolysis was seen in one patient with incomplete extrusion of the apex hole eliminator. Sixteen patients had incomplete extrusion of the apex hole eliminator associated with no visible radiographic pelvic or femoral osteolyisis. Two (10%) patients have undergone revision with curettage and allografting of the pelvic lesion and head and liner exchange. At the time of revision surgery liner motion was grossly obvious. Discussion: The apex hole eliminator is neither watertight nor locking. Our hypothesis is that activity-related hydraulic pressure generated from excessive liner motion causes a high-pressure fluid leak into the pelvis. This fluid contains sub-micron particles generated by backside wear. The combination of particulates and fluid under pressure produces retro-acetabular osteolysis. The cyclic pressure then allows the non-locking plug to advance into the osteolytic pelvic defect

Acoustic emission is an uncommon but well-recognised phenomenon following total-hip arthroplasty using hard-on-hard bearing surfaces. The incidence of squeak has been reported between 1% – 10%. The squeak can be problematic enough to warrant revision surgery. Several theories have been proposed, but the cause of squeak remains unknown. Acoustic analysis shows squeak results from forced vibrations that may come from movement between the liner and shell. A potential cause for this movement is deformation of the shell during insertion.

6 cadaver hemipelvises were prepared to accept ace-tabular components. A shell was selected and pre-insertion the inner shape was measured using a profilometer. The shell was implanted and re-measured. 2x screws were then placed and the shells re-measured. The results were assessed for deformation.

Deformation of the shells occurred in 5 of the 6 hemi-pelvises following insertion. The hemipelvis of the non-deformed shell fractured during insertion. Following screw insertion no further shell deformation occurred.

The deformation was beyond the acceptable standards of a morse taper which may allow movement between components, and this may produce an acoustic emission. Further in-vitro testing is being conducted to see whether shell deformation allows movement producing an acoustic emission.

Introduction: Trabecular Metal (Tantalum) has been successfully used in Neurosurgery for many years. Acetabular components have only been available in the UK since 2004. The metal’s properties of porosity and a high friction coefficient are attractive, particularly in complex primary and revision hip arthroplasty when surgical challenges include abnormal, deficient or limited bone.

Methods: Two year results of 110 consecutive acetabular reconstructions are presented. The age range was between 27 and 95 years with a predominance of females. The indication in 75 primary hip replacements included, Destructive Osteoarthritis, Dysplasia, Rheumatoid Arthritis, Paget’s and AVN. 35 revisions were performed either two-component or single acetabular exchanges.

Clinical results have been obtained using the Merle d’Aubigne score and bone deficiencies were classified according to the AAOS system.

Results: There have been no failures and radiologically, serial X-rays demonstrate osseo-integration at an early stage.

We have had no cases of deep infection but there have been 3 femoral peri-prosthetic fractures, (1 late) and 2 dislocations.

All patients have been allowed early weight bearing and those patients with over 12 months follow up have an improved Merle d’Aubigne score.

Discussion: The biomechanical properties of Trabecular metal and a modular design permit a press fit technique supplemented by dome screws combined with the possibility of using varying sizes of liner to minimise dislocation or to retain well fixed femoral stems in revision surgery.

The ease of use of the implant has now led to us largely abandoning other reconstructive techniques such as impaction allo-grafting or cages in revision or complex primary hip surgery.

We consider Trabecular metal to be a major advance in acetabular reconstruction on the basis of our initial experience

Introduction

Many surgeons are reluctant to use a constrained liner at the time of acetabular component revision given concerns this might result in early acetabular component loosening. We hypothesized that with appropriate initial implant stabilization of highly porous acetabular components with supplemental screw fixation, constrained liners could be safely used at the time of acetabular revision.

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

BACKGROUND. During revision hip arthroplasty, removal of a well-fixed, ingrown metal acetabular component may not be possible. Therefore, a new polyethylene liner can be cemented into the existing shell via the cement locking mechanism. We report the indications, technique, and results of cementing an acetabular liner into a well-fixed cementless acetabular shell. PATIENTS AND METHODS. All patients were given informed consent to participate in this study, and the study was approved by our hospital institutional review board. Of 95 revision total hip arthroplasty (THA) between 2005 and 2014, five hips in 5 patients (4 female and a male) were operated by the cemented socket into metal shell technique. The mean age was 70.6 years (range, 59–84 years) (Table 1). Operative Technique. All operations were performed with the patient in the lateral decubitus position and using a posterolateral approach without osteotomy of the greater trochanter. After removal of broken polyethylene liner, an all-polyethylene socket (manufactured by Kyocera Corporation, Osaka, Japan) was cemented in the metal shell. In case of small metal shell, bone bed around the shell were augmented by the use of an impaction morselized allogeneic bone grafting, and the socket was cemented both in the metal shell and in the bone bed (Fig. 1). Postoperative Regimen. On the third postoperative day, the patients began a rehabilitation programmed by clinical path under the supervision of a physiotherapist. The use of crutches for ambulation was begun on the 10th to 14th postoperative day, with progressive weight-bearing as tolerated. Time to full weight-bearing was 3 to 4 weeks postoperatively. RESULTS. All of the cemented sockets functioned well and there were no failure cases during average follow-up period of 5 years (range, 0.7–9.5 years). DISCUSSION. Cementation of polyethylene liners into well-fixed metal shells has become a popular option during revision total hip arthroplasty (THA). Failure was always observed at the metal shell/cement interface whenever it did occur. The cement locking mechanism can be strengthened by roughening the backside of a smooth polyethylene liner to improve the cement-polyethylene interface, or by using an all-polyethylene acetabular component that is designed to be used with cement. Saw roughening of the polyethylene liner strengthens the poly-cement interface. We have used the all-polyethylene acetabular component with macrotexture anchoring form to cement fixation. To perform this procedure, an adequate shell diameter is necessary to accept an acetabular liner that will enable 2 mm of cement mantle around it. If an oversized polyethylene liner is cemented into a small acetabular metal shell, then there is the theoretical risk that the increased shear force will damage the cement locking mechanism, thus leading to failure of the construct. The case 1 in the current series, the hips had this situation, but no loosening occurred at final follow-up of 9.5 years postoperatively (Fig. 1). CONCLUSIONS. We reported good results with the use of a “cemented cup in cementless cup” technique in revision THAs, although follow-up periods were short-term to midterm. To view tables/figures, please contact authors directly

Dislocation after total hip replacement (THR) is a devastating complication. Risk factors include patient and surgical factors. Mitigation of this complication has proven partially effective. This study investigated a new innovating technique to decrease this problem using rare earth magnets. Computer simulations with design and magnetic finite element analysis software were used to analyze and quantitate the forces around hip implants with embedded magnets into the components during hip range of motion. N52 Neodymium-Iron-Boron rare earth magnets were sized to fit within the existing acetabular shells and the taper of a hip system. Additionally, magnets placed within the existing screw holes were studied. A 50mm titanium acetabular shell and a 36mm ceramic liner utilizing a taper sleeve adapter were modeled which allowed for the use of a 12mm × 5mm magnet placed in the center hole, an 18mm × 15mm magnet within the femoral head, and 10mm × 5mm magnets in the screw holes. Biomechanical testing was also performed using in-vitro bone and implant models to determine retention forces through a range of hip motion. The novel system incorporating magnets generated retentive forces between the acetabular cup and femoral head of between 10 to 20 N through a range of hip motion. Retentive forces were stronger at the extreme position hip range of motion when additional magnets were placed in the acetabular screw holes. Greater retentive forces can be obtained with specially designed femoral head bores and acetabular shells specifically designed to incorporate larger magnets. Mechanical testing validated the loads obtained and demonstrated the feasibility of the magnet system to provide joint stability and prevent dislocations. Rare earth magnets provide exceptional attractive strength and can be used to impart stability and prevent dislocation in THR without the complications and limitations of conventional methods

Total hip arthroplasty (THA) is an effective treatment for symptomatic hip osteoarthritis (OA). Computer-navigation technologies in total knee arthroplasty show evidence-supported survivorship advantages and are used widely. The aim of this study was to determine the revision outcome of hip commercially available navigation technologies. Data from the Australian Orthopaedic Association National Joint Replacement Registry from January 2016 to December 2020 included all primary THA procedures performed for osteoarthritis (OA). Procedures using the Intellijoint HIP® navigation were identified and compared to procedures inserted using ‘other’ computer navigation systems and to all non-navigated procedures. The cumulative percent revision (CPR) was compared between the three groups using Kaplan-Meier estimates of survivorship and hazard ratios (HR) from Cox proportional hazards models, adjusted for age and gender. A prosthesis specific analysis was also performed. There were 1911 procedures that used the Intellijoint® system, 4081 used ‘other’ computer navigation, and 160,661 were non-navigated. The all-cause 2-year CPR rate for the Intellijoint HIP® system was 1.8% (95% CI 1.2, 2.6), compared to 2.2% (95% CI 1.8, 2.8) for other navigated and 2.2% (95% CI 2.1, 2.3) for non-navigated cases. A prosthesis specific analysis identified the Paragon/Acetabular Shell THAs combined with the Intellijoint HIP® system as having a higher (3.4%) rate of revision than non-navigated THAs (HR = 2.00 (1.01, 4.00), p=0.048). When this outlier combination was excluded, the Intellijoint® system group demonstrated a two-year CPR of 1.3%. There was no statistical difference in the CPR between the three groups before or after excluding Paragon/Acetabular Shell system. The preliminary data presented demonstrate no statistical difference in all cause revision rates when comparing the Intellijoint HIP® THA navigation system with ‘other’ navigation systems and ‘non-navigated’ approaches for primary THAs performed for OA. The current sample size remains too small to permit meaningful subgroup statistical comparisons

Introduction. A variety of porous coatings and substrates have been used to obtain fixation at the bone-implant interface. Clinical studies of porous tantalum, have shown radiographically well-fixed implants with limited cases of loosening. However, there has been limited retrieval analysis of porous tantalum hip implants. The purpose of this study was to investigate factors affecting bone ingrowth into porous tantalum hip implants. Methods. 126 porous tantalum acetabular shells and 7 femoral stems, were collected under an IRB-approved multicenter retrieval program. Acetabular shells that were grossly loose, cemented or complex revisions were excluded. Shells with visible bone on the surface were chosen. 20 acetabular shells (10 primary) and all femoral stems were dehydrated, embedded, sectioned, polished and bSEM imaged (Figure-1). Main shell revision reasons were infection (n=10,50%), femoral loosening (n=3,15%) and instability (n=3,15%). Analyzed implants were implanted for 2.3±1.7 years (shells) and 0.3±0.3 years (stems). Eight slices per shell and 5–7 slices per stem were analyzed. The analysis included bone area/pore area (BA/PA), BA/PA zonal depth analysis, extent of ingrowth and maximum depth of bone ingrowth. BA/PA zone depths were: Zone-1 (0–500um), Zone-2 (500–1000um) and Zone-3 (1000um-full depth). Nonparametric statistical tests investigated differences in bone measurements by location within an implant and implant type (Friedman's Variance and Kruskal-Wallis). Post-hoc Dunn tests were completed for subsequent pairwise comparisons. Spearman's rank correlation identified correlations between bone measurements and patient related variables (implantation time, age, height, weight, UCLA Activity Score). Statistical analyses were performed using PASW Statistics package. Results. BA/PA was not significantly different between acetabular shells (3.6±3.3%) and femoral stems (5.8% ± 3.9%, p=0.068). Extent of ingrowth was similar between shells (42 ± 28%) and stems (47±26%, p=0.825). Acetabular shells (76±23%) and stems (82±23%, p=0.707) had a similar maximum ingrowth depth. There were 9 shells and 2 stems (Figure-2) with full bone ingrowth into the porous tantalum substrate. When bone did not bridge the entire depth, a superficial layer of dense trabecular bone integrated with the porous layer was often observed. Localized regions of increased ingrowth were observed around screw holes. BA/PA in the superior region (4.1±2.4%) of the acetabular shells was significantly higher than in the inferior region (2.0±2.1%, p=0.047, Figure-3). Acetabular shells BA/PA in Zone-1(10.8%) was significantly higher than Zone-2 (4.9%, p=0.013) and Zone-3 (1.6%, p<0.001). BA/PA was significantly higher in Zone-1 (10.8%) than Zone-3 (2.3%, p=0.043) for femoral stems. There were no correlations between patient variables and bone measurements. Discussion. Our results demonstrate that bone ingrowth in porous tantalum hip components is concentrated in the superficial 500 um (Zone-1). This may provide the opportunity to reduce the thickness of the porous layer thus conserving more bone in future designs. Bone ingrowth in the acetabular shells was preferentially located around screw holes and superior region, similar to previous studies of other cementless designs. Only 40% of analyzed acetabular shells had implantation times greater than 2 years. Further work focused on longer term retrievals will increase understanding of the bone-implant interface. This study was supported by Zimmer and NIH (NIAMS) R01 AR47904

In revision total hip arthroplasty (THA), acetabular reconstruction while dealing with severe bone loss is a challenge. The porous tantalum revision acetabular shells have been in use for the past decade. Several reports have documented successful use at early to mid-term follow up. There is, however, very little literature around the long-term survival and quality of life outcome with the use of these shells. We reviewed the results of 46 acetabular revisions with Paprosky 2 and 3 acetabular bone defects reconstructed with a hemispheric, tantalum acetabular shell and multiple supplementary screws. There were 31 females. Average age at revision was 64 years (range 23–85 years). The mean and median follow up was 11 years (range 10–12 years, SD 1). Morselised femoral allograft was used in 34 hips to fill contained cavitary defectes. Bulk femoral allografting was performed in 2 hips. At a minimum follow-up of 10 (range 10–12) years, the survivorship of the porous tantalum acetabular shell, with revision of the shell as end point was 96%. The minimum 10-year survivorship with hip revision for any reason as end point was 92%. We noted excellent pain relief (mean WOMAC pain 92.6) and good functional outcome (mean WOMAC function 90.3, mean UCLA 5); and generic quality of life measures (mean SF-12 physical component 48.3; mean SF-12 mental component 56.7). Patient satisfaction with pain relief, function and return to recreational activities were noted to be excellent. Cementless acetabular revision with the tantalum acetabular shell demonstrated excellent clinical and quality of life outcomes at minimum 10-year follow-up. As far as we are aware this is the first report of minimum 10-year follow up of use of this technique for revision hip arthroplasty