Staged Revision Hip Arthroplasty With Femoral Impaction Bone Grafting for Prosthetic Joint Infections: Radiostereometric Analyses and Clinical Outcomes at Minimum 5-Year Follow-Up.

BACKGROUND: There are ongoing concerns regarding the use of bone graft following prosthetic joint infection and subsequent implant subsidence. The aim of this study was to determine whether the use of a cemented stem combined with femoral impaction bone grafting (FIBG) at second stage revision for infection results in stable femoral stem fixation, determined by accurate methods, and good clinical results. METHODS: A prospective cohort of 29 patients underwent staged revision total hip arthroplasty for infection using an interval prosthesis followed by FIBG at the final reconstruction. The mean follow-up was 89 months (range, 8 to 167 months). Femoral implant subsidence was measured with radiostereometric analysis. Clinical outcomes included the Harris Hip Score, Harris Pain score and Société Internationale de Chirurgie Orthopédique et de Traumatologie activity scores. RESULTS: At 2-years follow-up the median stem subsidence relative to femur was -1.36 mm (range, -0.31 to -4.98), while the cement subsidence relative to femur was -0.05 mm (range, 0.36 to -0.73). At 5-years follow-up, the median stem subsidence relative to femur was -1.89 mm (range, -0.27 to -6.35), while the cement subsidence relative to femur was -0.06 mm (range, 0.44 to -0.55). There were 25 patients who were confirmed infection-free after the second stage revision with FIBG. The median Harris Hip Score improved from 51 pre-operatively to 79 at 5 years (P = .0130), and Harris Pain score from 20 to 40 (P = .0038). CONCLUSIONS: Stable femoral component fixation can be achieved with FIBG when reconstructing the femur after revision for infection without compromising infection cure rates and patient-reported outcomes.

The variation in hip stability measurements between supine and standing radiographs of dysplastic hips.

AIMS: The aims of this study were to compare clinically relevant measurements of hip dysplasia on radiographs taken in the supine and standing position, and to compare Hip2Norm software and Picture Archiving and Communication System (PACS)-derived digital radiological measurements. METHODS: Preoperative supine and standing radiographs of 36 consecutive patients (43 hips) who underwent periacetabular osteotomy surgery were retrospectively analyzed from a single-centre, two-surgeon cohort. Anterior coverage (AC), posterior coverage (PC), lateral centre-edge angle (LCEA), acetabular inclination (AI), sharp angle (SA), pelvic tilt (PT), retroversion index (RI), femoroepiphyseal acetabular roof (FEAR) index, femoroepiphyseal horizontal angle (FEHA), leg length discrepancy (LLD), and pelvic obliquity (PO) were analyzed using both Hip2Norm software and PACS-derived measurements where applicable. RESULTS: Analysis of supine and standing radiographs resulted in significant variation for measurements of PT (p < 0.001) and AC (p = 0.005). The variation in PT correlated with the variation in AC in a limited number of patients (R2 = 0.378; p = 0.012). CONCLUSION: The significant variation in PT and AC between supine and standing radiographs suggests that it may benefit surgeons to have both radiographs when planning surgical correction of hip dysplasia. We also recommend using PACS-derived measurements of AI and SA due to the poor interobserver error on Hip2Norm. Cite this article: Bone Joint J 2021;103-B(11):1662-1668.

Cemented Revision Hip Arthroplasty With Femoral Impaction Bone Grafting.

Long-stemmed uncemented implants are commonly used during revision hip arthroplasty but may be difficult to re-revise. Impaction bone grafting allows for the use of a shorter cemented stem during revision hip arthroplasty and may restore bone stock in patients with substantial femoral defects. Femoral impaction bone grafting is particularly beneficial in younger patients, who are more likely to require additional revision procedures in the future. The surgical technique used at our institution includes improvements to previous methods including the use of modular tamps and nonirradiated, size-profiled bone graft.

Long-Term Outcomes of Staged Revision Surgery for Chronic Periprosthetic Joint Infection of Total Hip Arthroplasty.

Periprosthetic joint infection (PJI) is a serious complication of total hip arthroplasty. Staged revision surgery is considered effective in eradicating PJI. We aimed to determine the rate of infection resolution after each stage of staged revision surgery (first stage, repeat first stage, second stage, excision arthroplasty, and reimplantation) and to assess functional outcomes and the mortality rate at ten years in a consecutive series of 30 chronic PJI of total hip arthroplasties. Infection resolution was defined as no clinical nor laboratory evidence of infection at 24 months after the last surgery and after a minimum of 12 months following cessation of antimicrobial treatment. Four patients died within 24 months of their final surgery. Nineteen patients, 73% (worst-case analysis (wca) 63%), were infection free after 1 surgery; 22 patients, 85% (wca 73%), were infection free after 2 surgeries; and 26 patients, 100% (wca 87%), were infection free after three and four surgeries. The median Harris Hip Score was 41 prior to first revision surgery and improved to 74 at twelve months and 76 at ten years after the final surgery. Thirteen patients died at a mean of 64 months from first revision, giving a mortality rate of 43% at ten years, which is approximately 25% higher than that of an age-matched general population. The results show that with repeated aggressive surgical treatment, most PJIs of the hip are curable. Ten years after successful treatment of PJI, functional outcomes and pain are improved and maintained compared to before initial surgery, but this must be balanced against the high 10-year mortality. Level of evidence: cohort studies.

Highly Porous Tantalum Acetabular Components Without Ancillary Screws Have Similar Migration to Porous Titanium Acetabular Components With Screws at 2 Years: A Randomized Controlled Trial.

BACKGROUND: It is proposed that highly porous coatings on acetabular components, such as a porous tantalum coating, provide adequate fixation without ancillary screw fixation in primary total hip arthroplasty (THA). However, tantalum acetabular components have been associated with higher rates of revision than other uncemented components in national registries. The aim of this randomized controlled trial is to determine whether the early migration of a solid-backed tantalum acetabular component was no greater than that of a titanium acetabular component with ancillary screw fixation that has proven good clinical results. METHODS: Sixty-six patients aged 40 to 64 years, with osteoarthritis and Charnley grade A or B activity grade and who underwent primary THA, were recruited into the trial. Patients were randomized intraoperatively to receive either the tantalum or titanium acetabular component. All patients received the same cemented polished tapered femoral stem, 28-mm cobalt-chromium femoral head, and highly cross-linked polyethylene liner. Acetabular component migration was measured using radiostereometric analysis at 4-6 days postoperatively and at 6 weeks, 3 months, 1 and 2 years following THA. RESULTS: The mean proximal migration at 2 years for the tantalum cohort was 0.17 mm (95% confidence interval, 0.09-0.24) which was no greater than that of the titanium cohort which was 0.19 mm (0.07-0.32). Harris hip scores and functional activity scores were similar between groups. CONCLUSION: These results demonstrate that early stability can be achieved without ancillary screw fixation through the use of a highly porous high friction coating on a solid-backed modular acetabular component. LEVEL OF EVIDENCE: Level I.

Acetabular Component Migration Measured Using Radiostereometric Analysis Following Revision Total Hip Arthroplasty: A Scoping Review.

* Radiostereometric analysis (RSA) studies of acetabular component migration following revision total hip arthroplasty (THA) have a large variation in their methodology and reporting of results, and, therefore, they may not be directly comparable. Standardization of RSA reporting is recommended. * In our review of RSA studies, there was a trend for cemented acetabular components to have larger amounts of early proximal migration than uncemented acetabular components. Results regarding cemented and uncemented components should be reported separately. * Cohorts that addressed larger acetabular defects were associated with a larger amount of early migration. * Reporting the migration result at 1 and 2 years postoperatively may enable earlier identification of poorly performing implants.

Accuracy of EBRA-cup measurements after reconstruction of severe acetabular defects at revision THR.

Radiostereometric analysis (RSA) is the most accurate method of measuring component migration using radiographs but is restricted to use in prospective studies. Ein-Bild-Roentgen-analyze (EBRA)-Cup can be used retrospectively, but its accuracy to measure component migration following revision is unknown. This study aimed to determine the accuracy of EBRA-Cup measurements of uncemented acetabular component migration after revision total hip replacement (THR). The secondary aim was to compare the number of cases identified using EBRA-Cup and RSA as having proximally migrated above and below 1 mm at 2 years postoperatively. EBRA-Cup measurements were performed on plain antero-posterior pelvic radiographs taken at the same time as RSA radiographs in a prospective cohort of 53 hips undergoing acetabular revision. At 2 years, the mean difference between the RSA and EBRA-Cup measurements for 17 components used to treat pelvic discontinuity was 0.90 mm, significantly greater than the mean difference of 0.28 mm for 36 components without discontinuity (P = .0001). The mean difference between the RSA and EBRA-Cup measurements at 2 years for hips that were reconstructed with an acetabular component alone, 0.28 mm, was significantly lower than hips that were reconstructed with an acetabular component in combination with an augment and/or cage, 0.74 mm (P = .0005). In conclusion, EBRA-Cup can accurately measure migration of uncemented acetabular components used at revision THR. The presence of pelvic discontinuity, and addition of augments and cages, significantly influenced the accuracy of EBRA-Cup measurements. EBRA-Cup and RSA had good agreement on classification of components that migrated proximally above or below 1 mm at 2 years, with 100% sensitivity, and 87% specificity.

Surgical Technique to Manage Periprosthetic Fractures of the Knee in Patients with Infected Leg Ulcers: A Report of Two Cases.

CASES: We describe 2 cases of nonagenarians with periprosthetic knee fractures that were not amenable to either standard internal fixation nor prosthesis revision because of infected leg ulcers in the same limb. The fractures were internally fixed by percutaneous insertion of medial and lateral plates that spanned the knee. Both patients returned to their baseline level of activity without developing surgical site infections. CONCLUSIONS: Percutaneous bridging plates that span the knee are a useful option for treating these difficult cases.

Vancouver B2 Peri-Prosthetic Fractures in Cemented Femoral Implants can be Treated With Open Reduction and Internal Fixation Alone Without Revision.

BACKGROUND: The aim of this study is to assess the outcomes of 52 consecutive Vancouver B2 peri-prosthetic fractures around cemented polished double-tapered stems treated by open reduction and internal fixation in 2 trauma centers in 2 countries. METHODS: Outcomes included modified Harris Hip Score (mHHS), Harris Pain Score, and return to pre-injury mobility. Fracture healing was assessed; implant subsidence measured and complications including re-operations reported. RESULTS: No patient was lost to follow-up. Median patient age at operation was 82 years (range 43-98); Harris pain scores showed minimal pain (median 42, range 10-44) at latest follow-up. Median total subsidence at 1 year was 1.1 mm (range 0-5.4), the majority of which occurred within the cement mantle. No subsequent femoral stem revision was required (median 2.9 years, 0-10); however, there were 3 re-operations: 1 re-operation for pre-existing recurrent dislocation involving head liner exchange and 2 for repeat fixation due to metal fatigue. Two additional fractures occurred below the new plating, requiring further plating whilst still retaining the original stems. CONCLUSION: Anatomical reduction and open reduction and internal fixation of Vancouver B2 peri-prosthetic fractures should be considered as an appropriate treatment solution for frail elderly patients with a peri-prosthetic fracture around cemented polished double-tapered stems.

The Stability of the Porous Tantalum Components Used in Revision THA to Treat Severe Acetabular Defects: A Radiostereometric Analysis Study.

BACKGROUND: The acetabular components used in revision total hip arthroplasty (THA) to treat severe acetabular bone defects have high rates of re-revision at mid to long-term follow-up. Early translation of acetabular components used in revision THA is a good predictor of later loosening, and radiostereometric analysis (RSA) is the most sensitive method to measure migration. The objectives of the present study were to use RSA to compare the migration of the porous tantalum acetabular components used to treat severe bone defects with the previously established acceptable proximal translation threshold of ≤1 mm within 2 years, and to determine the effect on migration of the addition of inferior screws through the component into the ischium or pubis. METHODS: RSA was utilized to measure the migration of 55 porous tantalum components used to treat severe acetabular defects (28 Paprosky IIIA, 27 Paprosky IIIB; 21 hips with pelvic discontinuity) at a mean follow-up of 4 years (range, 2 to 12 years). RESULTS: Forty-eight of the 55 components migrated less than the threshold that predicts later loosening (>1 mm) and 50 had not been re-revised at the time of the latest follow-up. Seven components, none of which had inferior screw fixation, exceeded the translation threshold. Of these, 6 were implanted to treat pelvic discontinuity. Of those 6 components, 5 were re-revised for loosening related to patient symptoms. At 2 years, the absolute median proximal translation of components with inferior screw fixation was |0.3| mm (range, |0.1| to |0.9| mm), compared with |0.4| mm (range, |0.03| to |16.4| mm) for those without inferior screws (p = 0.04). CONCLUSIONS: As measured with use of RSA, the majority of porous tantalum acetabular components used in a revision THA to treat severe acetabular defects had acceptable early migration. This predicts good long-term survivorship of these components. The use of inferior screws further improved acetabular component fixation. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Advantages in Using Cemented Polished Tapered Stems When Performing Total Hip Arthroplasty in Very Young Patients.

BACKGROUND: The risk of revision following primary total hip arthroplasty (THA) is increased in young patients who undergo THA for pathologies other than primary osteoarthritis. We report the results of primary THA performed with cemented polished stems in patients aged 40 years and younger for pathologies other than primary osteoarthritis. METHODS: We investigated 52 patients (65 hips) who underwent primary THA for secondary osteoarthritis with a cemented tapered polished stem between 1990 and 2007. Clinical and radiographic outcomes, available in 46 patients (57 hips), included the Harris Hip Scores, Societe Internationale de Chirurgie Orthopedique et de Traumatologie activity, patient satisfaction, stem survival and reoperations, and assessment of prosthesis-cement-bone radiolucencies, osteolysis, and femoral bone deficiencies. RESULTS: Median patient age was 34 years (16-40) and follow-up was 14 years (mean 13, range 5-22). Stem survival to the endpoint revision for loosening was 100% and to the endpoint revision for any reason, excluding infection was 88% (95% confidence interval 78-98) at 16 years. No stem was revised for aseptic loosening. Nine stems were revised for other reasons. Radiographically, one stem was definitely loose at 16 years. The median patient Harris pain score improved from marked pain to no pain at latest follow-up. Patient activity level improved, albeit minimally, for 8 years after surgery. At latest follow-up, 98% of the patients remained satisfied with their surgery. CONCLUSION: Primary THA with a cemented polished stem shows excellent results in young patients with pathology other than primary osteoarthritis. In addition, the stem design facilitates cement within cement exchange and therefore preservation of proximal femoral bone stock at revision surgery.

Accuracy of methods to measure femoral head penetration within metal-backed acetabular components.

A number of different software programs are used to investigate the in vivo wear of polyethylene bearings in total hip arthroplasty. With wear rates below 0.1 mm/year now commonly being reported for highly cross-linked polyethylene (XLPE) components, it is important to identify the accuracy of the methods used to measure such small movements. The aims of this study were to compare the accuracy of current software programs used to measure two-dimensional (2D) femoral head penetration (FHP) and to determine whether the accuracy is influenced by larger femoral heads or by different methods of representing the acetabular component within radiostereometric analysis (RSA). A hip phantom was used to compare known movements of the femoral head within a metal-backed acetabular component to FHP measured radiographically using RSA, Hip Analysis Suite (HAS), PolyWare, Ein Bild Roentgen Analyse (EBRA), and Roentgen Monographic Analysis Tool (ROMAN). RSA was significantly more accurate than the HAS, PolyWare, and ROMAN methods when measuring 2D FHP with a 28 mm femoral head. Femoral head size influenced the accuracy of HAS and ROMAN 2D FHP measurements, EBRA proximal measurements, and RSA measurements in the proximal and anterior direction. The use of different acetabular reference segments did not influence accuracy of RSA measurements. The superior accuracy and reduced variability of RSA wear measurements allow much smaller cohorts to be used in RSA clinical wear studies than those utilizing other software programs. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:988-996, 2017.

The Wear Rate of Highly Cross-Linked Polyethylene in Total Hip Replacement Is Not Increased by Large Articulations: A Randomized Controlled Trial.

BACKGROUND: Larger articulations reduce the risk of dislocation following primary total hip arthroplasty, leading to increased use of these articulations. The wear rate of highly cross-linked polyethylene (XLPE) is low in standard-diameter articulations but remains unclear in larger articulations. The aim of this randomized controlled trial was to compare the mean wear rates of 36-mm and 28-mm metal-on-XLPE articulations between 1 and 3 years postoperatively. METHODS: Fifty-six elderly patients undergoing primary total hip arthroplasty were randomized intraoperatively to receive either a 36-mm or 28-mm metal-on-XLPE articulation. Factors that may affect wear were controlled by study design. Wear was measured using radiostereometric analysis. RESULTS: Mean annual proximal wear rates between 1 and 3 years were 0.00 and 0.01 mm/yr for the 36 and 28-mm articulation cohorts, respectively. No patient had a proximal wear rate of >0.1 mm/yr. Mean wear was very low in all directions, and the wear rate of 36-mm articulations was not significantly greater than that of 28-mm articulations on the basis of proximal, medial 2-dimensional, and 3-dimensional wear. CONCLUSIONS: The wear rate of a larger 36-mm metal-on-XLPE articulation between 1 and 3 years following primary total hip arthroplasty was low and no greater than that of a 28-mm articulation. However, before a 36-mm metal-on-XLPE articulation is widely recommended, particularly in young active patients, long-term wear rates and association between wear and periprosthetic osteolysis should be determined. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Exposure of the superior gluteal neurovascular bundle for the safe application of acetabular reinforcement cages in complex revisions.

The posterior approach to the hip is the most common extensile approach used, however exposure is limited superiorly by the superior gluteal neurovascular bundle (SGNB). The extra-pelvic course of the SGNB demonstrates variability between individuals, occasionally located only 1 cm from the acetabular rim. In complex acetabular reconstructions where the application of a reinforcement cage maybe required protecting the SGNB is challenging. The flanges of these cages are designed to sit on the ilium superior to the acetabular rim and to receive screws for fixation. The application of such cages may result in iatrogenic injury to the SGNB by way of forceful retraction or entrapment. We describe a technique that involves exposure and release of the SGNB such that the flanges of cage constructs may be safely applied.

Early acetabular cartilage wear following hemiarthroplasty: An ovine model.

OBJECTIVES: Hemiarthroplasty induces degenerative changes in the hip joint, which are difficult to evaluate in vivo. Radiostereometric analysis (RSA) is a radiographic measurement technique that has recently been used to measure acetabular cartilage wear in vivo. The aim of the study was to measure acetabular cartilage wear, using this technique, in an ovine model during the first 14 weeks post-implantation. METHODS: Measurements of three-dimensional femoral head migration, combined with visual assessments at necropsy and safranin O staining for cartilage integrity, were undertaken. RESULTS: Mean femoral head migration during the first six weeks was 0.525 mm in the medial, 0.144 mm in the cranial, and 0.517 mm in the dorsal direction. The majority of this migration was confirmed to be cartilage wear in the medial and dorsal aspects of the acetabulum at necropsy and with subsequent histological evaluation depicting significant cartilage degeneration. CLINICAL SIGNIFICANCE: Radiostereometric analysis is the current gold standard technique for in vivo assessment of implant migration following total hip replacement. This study has utilized RSA to quantify the amount of early cartilage wear in vivo, which was supported by ex vivo evaluations. Accurately measuring the amount of cartilage wear will allow future studies to compare component material and design characteristics prior to clinical use.

Does cup-cage reconstruction with oversized cups provide initial stability in THA for osteoporotic acetabular fractures?

BACKGROUND: The incidence of acetabular fractures in osteoporotic patients is increasing. Immediate total hip arthroplasty (THA) has potential advantages, but achieving acetabular component stability is challenging and, at early followup, reported revision rates for loosening are high. QUESTIONS/PURPOSES: This study measured acetabular component stability and the initial surface contact achieved between the acetabular component and unfractured region of the pelvis after THA using an oversized acetabular component and cup-cage reconstruction. METHODS: Between November 2011 and November 2013, we treated 40 acute acetabular fractures in patients older than 70 years of age. Of these, 12 (30%) underwent immediate THA using an oversized acetabular component with screws inserted only into the ilium and a cup-cage construct. Postoperatively all patients were mobilized without weightbearing restrictions. Indications for immediate THA after acetabular fractures were displaced articular comminution deemed unreducible. Eleven of the 12 were prospectively studied to evaluate the initial stability of the reconstructions using radiostereometric analysis. One of the patients died of a pulmonary embolism after surgery, and the remaining 10 (median age, 81 years; range, 72-86 years) were studied. Of these, five were analyzed at 1 year and five were analyzed at 2 years. Acetabular component migration was defined as acceptable if less than the limits for primary THA that predict later loosening (1.76 mm of proximal migration and 2.53° of sagittal rotation). The contact surface between the acetabular component and ilium in direct continuity with the sacroiliac joint, and the ischium and pubis in direct continuity with the symphysis pubis, was measured on postoperative CT scans. RESULTS: At 1 year the median proximal migration was 0.83 mm (range, 0.09-5.13 mm) and sagittal rotation was 1.3° (range, 0.1°-7.4°). Three of the 10 components had migration above the suggested limits for primary THA at 1 year postoperatively. The contact surface achieved at surgery between the acetabular component and pelvis ranged from 11 to 17 cm(2) (15%-27% of each component). CONCLUSIONS: The majority of acetabular components in this cohort were stable despite the small contact surface achieved between the component and pelvic bone. Three of 10 migrated in excess of the limits that predict later loosening in primary THA but it remains to be seen whether these limits apply to this selected group of frail osteoporotic patients. We continue to use this technique routinely to treat patients with the same indications, but since the analysis of these data we have added screw fixation of the acetabular component to the ischial tuberosity and the superior pubic ramus. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Wear of highly crosslinked polyethylene acetabular components.

BACKGROUND AND PURPOSE: Wear rates of highly crosslinked polyethylene (XLPE) acetabular components have varied considerably between different published studies. This variation is in part due to the different techniques used to measure wear and to the errors inherent in measuring the relatively low amounts of wear in XLPE bearings. We undertook a scoping review of studies that have examined the in vivo wear of XLPE acetabular components using the most sensitive method available, radiostereometric analysis (RSA). METHODS: A systematic search of the PubMed, Scopus, and Cochrane databases was performed to identify published studies in which RSA was used to measure wear of XLPE components in primary total hip arthroplasty (THA). RESULTS: 18 publications examined 12 primary THA cohorts, comprising only 260 THAs at 2-10 years of follow-up. The mean or median proximal wear rate reported ranged from 0.00 to 0.06 mm/year. However, differences in the manner in which wear was determined made it difficult to compare some studies. Furthermore, differences in RSA methodology between studies, such as the use of supine or standing radiographs and the use of beaded or unbeaded reference segments, may limit future meta-analyses examining the effect of patient and implant variables on wear rates. INTERPRETATION: This scoping review confirmed the low wear rates of XLPE in THA, as measured by RSA. We make recommendations to enhance the standardization of reporting of RSA wear results, which will facilitate early identification of poorly performing implants and enable a better understanding of the effects of surgical and patient factors on wear.

Is internal fixation alone advantageous in selected B2 periprosthetic fractures?

BACKGROUND: Revision surgery is currently the recommended treatment for Vancouver B2 femoral periprosthetic fractures, but isolated open reduction and internal fixation (ORIF) might be an effective treatment for these fractures around cemented collarless polished tapered (CCPT) stems, as these stems can re-engage in the cement mantle, regaining stability following internal fixation. The aim of this study was to determine the operative risks, post-operative complications, and radiographic and functional outcomes in two cohorts of Vancouver B2 femoral fractures around CCPT stems treated either by ORIF alone or revision surgery. METHODS: The results of 12 patients with B2 periprosthetic fractures around a CCPT stems treated by ORIF alone (median follow-up 67 months) were compared with those of nine patients with a similar fracture treated by revision surgery (median follow-up 59 months). RESULTS: All fractures treated by ORIF alone healed and all stems restabilized and remained stable within their original cement mantle. These patients had significantly shorter overall operating room times (P = 0.002), surgical times (P = 0.002) and required fewer units of blood transfusion (P = 0.008) than patients in the revision cohort. In the ORIF cohort, one patient had two dislocations. In the revision cohort, one patient had delayed wound healing, a second patient had delayed wound healing and two dislocations, and a third patient had two dislocations. CONCLUSION: Although further studies with larger numbers are required, treatment of these fractures with ORIF alone may be a viable alternative to revision surgery as it reduces the operative risks involved.

Altered load transfer in the pelvis in the presence of periprosthetic osteolysis.

Periprosthetic osteolysis in the retroacetabular region with cancellous bone loss is a recognized phenomenon in the long-term follow-up of total hip replacement. The effects on load transfer in the presence of defects are less well known. A validated, patient-specific, 3D finite element (FE) model of the pelvis was used to assess changes in load transfer associated with periprosthetic osteolysis adjacent to a cementless total hip arthroplasty (THA) component. The presence of a cancellous defect significantly increased (p < 0.05) von Mises stress in the cortical bone of the pelvis during walking and a fall onto the side. At loads consistent with single leg stance, this was still less than the predicted yield stress for cortical bone. During higher loads associated with a fall onto the side, highest stress concentrations occurred in the superior and inferior pubic rami and in the anterior column of the acetabulum with larger cancellous defects.

The variability of the volume of os coxae and linear pelvic morphometry. Considerations for total hip arthroplasty.

This study investigated the variability of os coxae's volume and linear morphometry in 50 dry adult bones. There was a wide variability, with coefficients of variation exceeding 30%, of the bones' volumes (mean 142 ml, range 80 to 300 ml) and distances between the acetabular rim and the horizontal plane through the sciatic notch (mean 10.6 mm, range -7 to 19 mm). The smallest width of the ilium ranged between 3 and 9 mm at a level between 1.5 and 4 cm above the acetabulum. The volume of os coxae correlated with the acetabular diameter (r = 0.79), the height of os coxae (r = 0.88) and antero-posterior length of the ilium at mid-acetabular level (r = 0.70). Knowledge of the variability of os coxae may be useful during preoperative planning in primary and revision hip arthroplasty.