Risk Of Mechanical Failure Research Articles

Addressing Antibiotic Hip Spacer Instability via Hybrid Screw-cement Fixation of a Constrained Liner and Cement-rebar Interface Techniques: A Technical Narrative.

Prosthetic joint infection is a challenging and devastating complication after total hip arthroplasty. The benchmark for treatment remains two-stage revision arthroplasty, in which an antibiotic-impregnated spacer is used to eradicate the infection. Although several types of spacer constructs have been described, they have historically been associated with high rates of mechanical complications, namely, dislocation, spacer fracture, and periprosthetic femur fracture. Spacer dislocation is the most common, with reported rates as high as 41%. Here, the authors present a surgical technique to improve the mechanical stability of an articulating hip spacer via a hybrid screw-cement fixation technique that allows for joint motion and weight bearing during the treatment period while minimizing the risk of mechanical failure. An additional technique is described to address acetabular bone loss, which has been associated with a higher spacer dislocation rate, through a cement-rebar interface construct.

SOLUTIONS ENSURING SAFETY DURING TRANSPORT OF STATE VIPS BY MILITARY AIRFCRAFT (PART 1)

It should be observed that for the sake of national welfare, while transporting state VIPs by military aircraft, the level of risk that is acceptable is lower than in the case of other passengers. Consequently, normative documentation regarding such transport regulates a range of issues that is considerably wider and more precisely defined than when transporting other passengers, relying on the principle “safety above all.” Regulations contained in normative documents concerning the transport of state VIPs by military aircraft are to protect not only against human mistakes, which might cause an air incident during such flights. Normative documents also regulate additional requirements that concern (1) aviation equipment used during transport of state VIPs by military aircraft (so as to limit the risk of mechanical failure) and (2) in-depth analysis of environmental factors (so as to reduce threat to transport safety as a result of adverse weather conditions).

Study of intertrochenteric fracture treated by bipolar hip replacement

Introduction: Unstable intertrochanteric fractures in osteoporotic bones are difficult to treat. Conservative treatment with traction and prolonged immobilization lands up with many complications and often fatality. Rate of failure in internal fixation, with dynamic hip screws or intramedullary nail has been found high, especially in osteoporotic bones. The weak and porotic bone tolerates screws poorly so cut out is the major problem in internal fixation. The purpose of this study was to determine whether hemiarthroplasty is a reasonable alternative method of treatment for elderly patients in intertrochanteric fracture with osteoporosis to reduce mortality and morbidity in terms of full weight bearing and complications related to prolonged bed rest. Material and methods: 15 patients (6 males and 9 females) above 60 years of age with unstable intertrochanteric fractures who underwent bipolar arthroplasty were prospectively evaluated. Transtrochanteric approach was used in all patients. Greater trochanter tension band wiring was done in some patients. Harris hip score was used for the clinical evaluation. The minimum follow up period was one year. Results: In our study 15 cases were taken, which had a mean age 75years. The mean Harris hip score at one year was 85. Excellent to good results were obtained at one year in 12 cases and fair in 2 cases, poor in 1. Death of two patients occurs due to age related factors. There was one case of superficial infection. Radiological follow-up showed no case with loosening of the prosthesis, break in the cement or sinking of the prosthesis. Conclusion: In conclusion we state that hemireplacement arthroplasty is a valid treatment option for mobile and mentally healthy patients. This procedure offers quick recovery with little risk of mechanical failure, avoids the risks associated with internal fixation and enables the patients to maintain a good level of function beginning in the immediate post-operative period. But the follow up period in our study is not enough to make any clinical recommendations though it can serve as a critical analysis to stimulate future research. Further long-term studies are required.

Particle Induced X-ray Emission (PIXE) for elemental tissue imaging in hip modular prosthesis fracture case

The increased modularity in the total hip arthroplasty (THA) allows adapting the prosthesis to the specific anatomical characteristics of each patient. However, the advantages of the modular THA are shadowed by the increased number of prosthesis failures observed in patients. The presence of junction in modular THA may increase its risk of mechanical failure. Moreover, the micro movements between neck and stem could lead to the production of metallic debris which may cause tissue inflammation and unsealing of prosthesis due to osseous dissolution. It is necessary to understand the mechanism of dispersion of the metal particles from the prosthesis into the tissue. Techniques currently applied in hospitals, such as X-ray scans or optical tissue microscopies, are able to distinguish metal particles, but unable to identify their specific metallic origin. In this work, within the TissueMaps project, we have proved that Proton Induced X-ray Emission (PIXE) is able to provide the distribution and elemental composition of particles from the prosthesis into the pseudo capsular tissue samples (near the femoral head) and identify the features observed under optical microscopy, in a case of broken neck prosthesis.

Nanohybrid thin-film composite carbon molecular sieve membranes

Industrial separations belong to some of the most energy-intensive technological processes because of the reliance on heat-consuming unit operations involving a phase change, such as distillation. Membrane technology promises large cuts to those energy needs; however, its progression is hindered as currently available membranes lack separation performance as well as chemical and mechanical stability. To address these challenges, carbon molecular sieves (CMSs) have long been suggested as promising candidates providing excellent and robust molecular separation performance. In this work, we introduce nanohybrid CMS membranes fabricated by pyrolyzing a polyimide of intrinsic microporosity (PIM-PI) precursor modified by vapor phase infiltration (VPI). In the VPI process, a metal-organic precursor, trimethylaluminum (TMA), first diffuses into the high free volume matrix of the PIM-PI to form a complex with its functional groups. Afterward, water vapor selectively and locally oxidizes the TMA to form nanodispersed Al2O3 within the PIM-PI matrix. Subsequent inert-atmosphere pyrolysis leads to the formation of Al2O3-doped, high-quality, thin-film composite CMS membranes with excellent molecular separation properties for a number of technologically important gas pairs, e.g. CO2/CH4 > 100, O2/N2 > 9. The introduction of VPI-doped hybrid CMS membranes allows obtaining extraordinary gas separation performance typical to high temperature undoped CMS at much lower pyrolysis temperatures. This presents significant advantages such as reduction of mechanical failure risk, wider spectrum of possible supports, and reduced fabrication complexity.

To study the results of humeral Enders nail in diaphysial fracture of humerus

Introduction: It is generally admitted that most humeral shaft fractures can be managed successfully by non-operative methods. Whenever operative treatment is required, a choice has to be made between plate osteosynthesis and intramedullary nailing. Fixation with plates requires extensive dissection and is complicated by the proximity of the radial nerve and the risk of mechanical failure in osteopenia bones. Biomechanically intramedullary nail is a better implant. They are subjected to smaller bending loads and are less likely to fail by fatigue, they act as load sharing devices, stress shielding with resultant cortical osteopenia is minimum, refracture after implant removal is rare and they do not require extensive exposure Methods: We have done a prospective study of 30 patients with Fracture shaft Humerus stabilized with intramedullary nail of Enders type by antegrade approach. These nails were available in 3 & 3.5 mm diameter and in lengths ranging from 18-28 Cms. The nail by design had proximal band of 6 degrees (apex medial band) to accommodate offset of the infusion portal with the medullary canal. Results: Study shows more incidences of Humerus fractures in young patients as it is active age group in the society, more prone to vehicle accidents and falls. Most of the fracture of shaft humerus unites in 10-14 weeks and in minor cases more than 18 weeks were observed for union. Most common complication associated with operative method of fracture shaft humerus is non union. Joint involvement in form of shoulder or elbow stiffness can occur in small number of cases. There are no cases of infection noted in our study Interpretation and Conclusion: Internal fixation by close intramedullary nail for fractures involving middle two third shaft of humerus is a good technique if facilities are provided for image internsifier machine in operation theater. In comparision to other operative techniques close intramedullary nailing is less invasive with minimal blood loss and hardly any chance of infection. This technique gives rotational as well as torsional stability to fractured bone humerus, allowing faster practice of physiotherapy to achieve full range of motion and power.

222. PI and age-optimal alignment within the fusion in ASD surgery improves outcomes and minimizes mechanical failures?

BACKGROUND CONTEXT Age specific alignment targets have been shown to optimize outcomes and minimizing the risks of mechanical failure like proximal junctional kyphosis (PJK). Recently, PI has been shown to be an important determinant of spinal alignment but the role of PI and age-optimal alignment has not been analyzed simultaneously with respect to PJK and clinical outcomes. Previous PJK studies have used SVA to measure over- or undercorrection, however in patients with PJK, SVA underestimates the overcorrection because of patient compensation and the PJK itself increases the SVA. The T1 Pelvic Angle (TPA) has been proposed as useful perioperative planning parameter; using the component of TPA within the fusion (T10PA) allows for measuring spinopelvic alignment separate from that of the unfused thoracic spine and any PJK that may occur postoperatively. PURPOSE To identify age- and PI-optimal alignment targets using a component angle of TPA within the fusion to define over and under-correction and their relationship to PJK and clinical outcomes. STUDY DESIGN/SETTING Retrospective analysis of a prospective, multicenter database PATIENT SAMPLE Operative ASD patients OUTCOME MEASURES SF36-PCS, PJK METHODS A prospective database of operative ASD patients was analyzed. Patients with fusions to the pelvis and UIV above T11 were included in the PJK analysis. Alignment within the fusion was correlated with clinical outcomes and PI. SF36-PCS normative data were used to compute PI- and age-optimal alignment for each patient. Over-, under- and optimally-corrected groups were determined using intervals from optimal alignment within the fusion to define the group boundaries. The rate of severe PJK (change>20°) was determined for each group. RESULTS A total of 1052 patients met inclusion criteria. Alignment within the fusion correlated with SF36-PCS and PI. At 6 weeks, 40.7% were optimally-corrected vs 39.4% overcorrected vs 20.9% undercorrected. The overall rate of PJK was 13.6%. Overcorrected patients had the highest PJK rate (18.1%) compared with optimally (11.3%) and undercorrected (9.5%), p CONCLUSIONS A component angle of TPA within the fusion, separate from the PJK, was used to determine age and PI-optimal alignment. Correcting ASD patients to optimal alignment within the fusion produced clinical outcome improvements with the lowest rates of PJK. This age and PI-specific approach to spinal alignment within the fusion provides ASD correction targets for surgeons that can be used intraoperatively. Future studies are warranted to verify the reliability of such intraoperative spinopelvic measurements. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Anti-rotation pins for the compress implant do not increase risk of mechanical failure or impair osseointegration

Background: The use of compliant fixation for endoprosthetic implants is gaining popularity. Previous work has shown that anti-rotation pins improve rotational stability at the bone-implant interface, but there is concern that these pins lead to increased risk of mechanical failure. We asked: (I) are anti-rotation pins used with the Compress implant associated with mechanical failure? (II) Are anti-rotation pins associated with less effective osseointegration? Methods: We performed retrospective review of cases using a Compress implant from 2004–2016. Mechanical failure rates and bone growth at the bone-implant interface were compared between pin and no-pin cohorts. Regression models were used to examine patient and surgical factors associated with mechanical failure. Results: Anti-rotation pins were not associated with mechanical failure (P=1.0, odds ratio 1.17, 95% confidence interval: 0.12–15.40). Anti-rotation pins were not associated with impaired osseointegration at any time point (P=1.0 at 3–6 months, P=0.33 at 6-9 months, P=0.34 at 9–12 months, P=0.40 at 12–24 months, P=0.28 at 24–48 months, P=1.0 at >48 months). No patient or surgical variables were predictors of mechanical failure. Conclusions: Anti-rotation pins were not associated with mechanical failure or impaired osseointegration.

Evaluation of iliac screw, S2 alar-iliac screw and laterally placed triangular titanium implants for sacropelvic fixation in combination with posterior lumbar instrumentation: a finite element study

This study aimed to implement laterally placed triangular titanium implants as a technique of sacropelvic fixation in long posterior lumbar instrumentation and to characterize the effects of iliac screws, S2 alar-iliac screws and of triangular implants on rod and S1 pedicle screw stresses. Four female models of the lumbopelvic spine were created. For each of them, five finite element models replicating the following configurations were generated: intact, posterior fixation with pedicle screws to S1 (PED), with PED and iliac screws (IL), with PED and S2 alar-iliac (S2AI) screws, and with PED and bilateral triangular titanium implants (SI). Simulations were conducted in compression, flexion-extension, lateral bending and axial rotation. Rod stresses in the L5-S1 segment as well as in the S1 pedicle screws were compared. One anatomical model was not simulated due to dysmorphia of the sacroiliac joints. PED resulted in the highest implant stresses. Values up to 337MPa in lateral bending were noted, which were more than double than the other configurations. When compared with IL, S2AI and SI resulted in lower stresses in both screws and rods (on average 33% and 41% for S2AI and 17% and 50% for SI). Implant stresses after S2AI and SI fixations were lower than those attributable to IL. Therefore, pedicle screws and rods may have a lower risk of mechanical failure when coupled with sacropelvic fixation via S2AI or triangular titanium implants, although the risk of clinical loosening remains an area of further investigation. These slides can be retrieved under Electronic Supplementary Material.

Cement augmentation of the proximal humerus internal locking system in elderly patients: a multicenter randomized controlled trial

IntroductionCement augmentation of the proximal humerus internal locking system (PHILOS) screws might reduce complication rates in osteoporotic bones. This study compared the risk of mechanical failure during the first year after PHILOS™ treatment of proximal humerus fractures (PHF) without (control group) and with (augmented group) screw augmentation. Secondary objectives were to report shoulder functions, quality of life (QoL), adverse events (AEs), and reoperation rates.Materials and methodsThis multicenter randomized trial enrolled patients aged ≥ 65 years with displaced/unstable PHF from eight European centers. Randomization was performed during surgery through sealed opaque envelopes. Mechanical failures were assessed by two independent reviewers via radiographs, shoulder function by Quick DASH, SPADI, and Constant Murley scores, and QoL by EQ-5D. Follow-ups were planned at postoperative 6 weeks, 3, 6, and 12 months.ResultsThe preliminary analysis of 6-week radiographs of the first 59 enrolled patients suggested a mechanical failure rate lower than expected and the difference between groups was too small to be detected by the planned sample size of 144. The trial was prematurely terminated after 67 patients had been enrolled: 34 (27 eligible) in the control group and 33 (29 eligible) in the augmented group. Follow-ups were performed as planned. Nine patients had mechanical failures and the failure rates (95% CI) were: augmented group, 16.1% (5.5; 33.7); control group, 14.8% (4.2; 33.7); the relative risk (95% CI) for the augmented group was 1.09 (0.32; 3.65) compared to the control group (p = 1.000). No statistically significant differences in shoulder function, QoL, and AEs were observed between study groups at 1 year. Nine patients (15.8%) underwent a revision.ConclusionsDue to premature termination, the study was underpowered. A larger study will be necessary to determine if cement augmentation lowers the risk of mechanical failure rate.

Ability of the Global Alignment and Proportion Score to Predict Mechanical Failure Following Adult Spinal Deformity Surgery—Validation in 149 Patients With Two-Year Follow-up

Study DesignRetrospective analysis of prospectively collected data. ObjectivesTo validate the Global Alignment and Proportion (GAP) score in a single-center cohort of adult spinal deformity (ASD) patients. Summary of Background DataSurgical treatment for ASD is associated with a high risk of mechanical failure and consequent revision surgery. To improve prediction of mechanical complications, the GAP score was developed with promising results. Development was based on the assumption that not all patients would benefit from the same fixed radiographic targets as pelvic incidence is an individual, morphological parameter that greatly influences the sagittal curves of the spine. MethodsIn a validation study of the GAP score, patients undergoing ASD surgery with four or more levels of instrumentation were consecutively included at a tertiary spine unit. Patients were followed for a minimum of two years. Pre- and postoperative GAP score and categories were calculated for all patients, and the association with mechanical failure and revision surgery was analyzed. ResultsA total of 149 patients with a mean age of 57.4 years were included. Overall, the rates of mechanical failure and revision surgery were 51% and 35% respectively. The area under the curve (AUC) using receiver operating characteristic was classified as “no or low discriminatory power” for the GAP score in predicting either outcome (AUC = 0.50 and 0.49, respectively). Similarly, there were no significant associations between GAP categories and the occurrence of mechanical failure or revision surgery when using Cochran-Armitage test of trend (p = .28 for mechanical failure and p = .58 for revision surgery). ConclusionsIn a consecutive series of surgically treated ASD patients, we found no significant association between postoperative GAP score and mechanical failure or revision surgery. Despite minor limitations in similarities to the original study cohort, further validation studies or adjustments to the original scoring system are proposed. Level of EvidenceLevel II.

Investigation of Complications Following Port Insertion in a Cancer Patient Population: A Retrospective Analysis.

Central venous access devices, specifically implantable ports, play an essential role in the care of oncology patients; however, complications are prevalent. This retrospective single-institutional review was performed to identify rates of complications from port placement and potential factors associated with these events. A retrospective analysis of 539 cancer patients who underwent port insertion between March 2016 and March 2017 at our institution was conducted. Data examining 18 potentially predictive factors were collected, and multivariate analysis was conducted using logistic regression and odds ratios (ORs) with standard errors to determine predictive factors. Out of 539 patients, 100 patients (19%) experienced 1 complication, and 12 patients (2%) experienced 2 or more complications. An overall lower rate of complications was seen in patients on therapeutic anticoagulation (OR: 0.17, P < .001) or on antiplatelet agents (OR: 0.47, P = .02). No patients on therapeutic anticoagulation developed venous thromboembolism (VTE; 0%). Right-sided port insertion was associated with decreased rates of infection (OR: 0.44, P = .04). Insertion as inpatient was associated with an increased risk for mechanical failure (OR: 4.60, P < .01). This analysis identified multiple predictive factors that can potentially put patients at a higher risk of experiencing complications following port insertion. Our data show lower rates of VTE for patients on anticoagulation or antiplatelet therapy. Further analysis is also necessary to determine why port insertion as an inpatient places patients at a higher risk of complications. This study highlights the risks associated with port placement and prompts the clinician to have an informed discussion with the patient weighing the risks and benefits.

Cyclic loading impact on screw loosening of internally connected implants: an experimental study

Objective The aim of this study was to assess impact of cyclic loading on screws attached to four different abutments to internally connected implants. Materials and methods Four groups (seven implants each) of dissimilar abutments were included in this study. Abutments were connected to Straumann tissue-level implants. Each implant was rigidly secured in a stainless steel cylindrical jig. A torque controller was used to tighten the abutments at 35 N cm. A 150 N cyclic load for 1 million cycles was applied to the implant at a 30° angle to the long axis to the implants. Periotest values (PTVs) were measured before and after cyclic loading and a digital torque gauge used to detect the removal torque values (RTVs) of abutments. The data were analyzed statistically using SPSS and Kruskal–Wallis tests and one-way analysis of variance were used to compare RTVs and PTVs after application of equal loads for each group. The Spearman correlation coefficient was applied to compare RTVs and PTVs after loading. Results The Straumann solid abutment and the Southern solid abutment showed no mechanical failures. Screws fracture was noted in nearly 85% of Implant Direct abutment, and 55% of the Blue Sky Bio abutments. The final mean PTV of the Blue Sky Bio abutments, the Southern Implants, and Implant Direct straight abutment was considerably higher than the final mean PTVs of Straumann solid abutment. Conclusion Abutments from the different manufacturers have different physical and chemical characteristics. So there was a potential risk of mechanical failure when the interchangeable abutments are used. Thus, the use of an abutment manufactured by the same implant company is highly recommended for the avoidance of loosening of the abutment screws.

Central venous access in oncology patients: A pragmatic approach to minimizing complications following port insertion.

267 Background: Subcutaneous venous access devices, specifically implantable ports, are vital in the care of oncology patients. Despite routine use, complications remain prevalent. This retrospective single-institutional review was performed to identify rates of complications following port placement and target areas to improve patient outcomes. Methods: Retrospective analysis of 539 cancer patients who underwent port insertion in a one-year span at University of Florida was conducted. Data examining 18 potentially predictive factors was collected, and multivariate analysis was conducted using logistic regression and odds ratios with standard errors to determine predictive factors. Results: Of 539 patients, 100 (19%) experienced a complication, and 12 (2%) experienced 2 or more complications. An overall lower rate of complications was seen in patients on therapeutic anticoagulation (OR 0.17, p &lt; 0.001) or on antiplatelet agents (OR 0.47, p = 0.02). No patients on therapeutic anticoagulation developed VTE (0%). Right-sided port insertion was associated with decreased rates of infection (OR 0.44, p = 0.04). Insertion as inpatient was associated with increased risk for mechanical failure (OR 4.60, p &lt; 0.01) and catheter migration (OR 4.33, p &lt; 0.01). Conclusions: This analysis identified multiple predictive factors that can potentially put patients at higher risk of complication following port insertion. A thorough risk assessment for VTE should be done prior to port insertion, and high-risk patients (i.e. prior VTE, Khorana score &gt; 3) should be considered for prophylactic anticoagulation. Further analysis on optimal port insertion site (right/left) and location (inpatient/outpatient) are also targets that can potentially decrease complication rates. As ports inserted while inpatient had increased risk of both mechanical failure and catheter migration, and as ports inserted on the left side had increased risk of infectious complications, a prospective quality improvement initiative coordinated between Oncology and Interventional Radiology departments as to whether insertion of right-sided ports on an outpatient basis may improve outcomes is the next step in our investigation.

Stress-limited fast charging methods with time-varying current in lithium-ion batteries

This article sheds light on advantages of fast charging methods with time-varying current. Analytical solutions of concentration and stress for charging processes with general time-varying currents are derived. A fast charging protocol for a multistage constant current of gradually decreasing value is first evaluated. A properly designed multistage constant-current method is able to simultaneously suppress stress overflow and accelerate charging, but stress undulation induced by sharp switching between stages is inevitable. A charging scheme with a nonlinear exponential current is then investigated. The applied current varies continuously and smoothly with time so stress undulation is avoided. Suggestions for the design of an exponential current method are proposed to achieve the best charging acceleration without sacrificing charging capacity or increasing risk of mechanical failures. A well-designed exponential-current method is superior to a multistage constant-current method in accelerating charging speed.

Polytrauma from Unintentional Pressure Cooker Explosion: A Case Report

BackgroundPressure cookers are common kitchen appliances with a good safety record and only rare associated explosions. Case ReportHere we present a case of unintentional pressure cooker explosion leading to polytrauma with injuries including pneumothorax, intracranial hemorrhage, open skull fracture, and multiple facial fractures. Why Should an Emergency Physician Be Aware of This?Extreme forces and temperatures are involved in pressure cooking. Given the infrequent but real risk of mechanical failure and the increasing use of such devices to create intentional explosions, emergency physicians should be aware of the potentially significant blast injuries that can be associated with them.

Bone combined cement grafting in giant cell tumor around the knee reduces mechanical failure

ObjectivesThe aims of our study are (1) to explore the risk factors of mechanical failure (MF), (2) to figure out an index to evaluate this risk, and (3) to select an optimal reconstruction strategy to reduce this risk.MethodsWe retrospectively reviewed 104 patients from Dec. 2008 to Mar. 2016, undergone extensive knee curettages in our institution. Radiographs and post-operative interviews were used to classified cases of MF. Relative factors (age, tumor location, the invaded area, etc.) were also collected and analyzed by SPSS software.ResultsThick subchondral bony layer (p = 0.006) and combined grafting of the cement and bone (p = 0.006) had lower risk of mechanical failure. Mechanical failure appeared to happen in the femur (p = 0.012) more easily. The ROC curve (AUC = 0.722) reveals that less post-operative bony layer (≤ 3.3 mm) is more likely to cause mechanical failure. The Kaplan-Meier survival curve showing increased survival in those patients after a combination grafting surgery (HR, 3.799; p = 0.006).ConclusionBased on our study results, combined grafting of the cement and bone reduced the risk of mechanical failure in the knee due to the thin subchondral bone layer (SCB), especially in the femur.

Neutral mechanical alignment: Stickin’ with the one that brung ya- Affirms

Restoring the overall mechanical alignment to neutral has been the gold standard in total knee arthroplasty since the 1970s. Recently, there has been renewed interest in alternative alignment goals that place implants in a more “physiologic” position with the hope of improving clinical outcomes. However, placing components outside of the classic “safe zone” of ± 3° is controversial, as studies have shown increased risk of mechanical failure, especially in obese patient populations. This paper will outline mechanical and kinematic alignment and present the evidence for why mechanical alignment is still the gold standard in total knee arthroplasty.

Femoral Bone Restoration Patterns in Revision Total Hip Arthroplasty Using Distally Fixed Modular Tapered Titanium Stems and an Extended Trochanteric Osteotomy Approach

BackgroundMechanical failure of modular revision stems is a serious complication in revision total hip arthroplasty. The lack of adequate osseous support to the proximal component, especially in cases of an extended trochanteric osteotomy approach, is considered a risk factor for stem failure. In this study, we analyze proximal bone regeneration patterns in patients undergoing revision total hip arthroplasty for aseptic stem loosening through an extended trochanteric osteotomy approach using an uncemented dual modular stem. MethodsFifty-four patients treated for aseptic stem loosening were radiologically reviewed. The femur was divided according to the Gruen zones. Preoperative bone loss, formation of new cancellous bone, and presence of direct osseous contact to the stem were noted right away for each Gruen zone. The presence of osseous support at the modular junction and the proximal component were examined. ResultsAll patients showed restoration of proximal bone mass at final follow up. New bone formation was first seen in more distally located Gruen zones. Cases with longer proximal components had a trend toward earlier osseous support at the modular junction. Overall, 75% of patients showed osseous support at the modular junction 2 years after surgery. ConclusionRestoration of proximal bone occurs in a distal to proximal direction. Shorter proximal components require more time until osseous support to the modular junction is achieved, which may result in a higher risk of mechanical failure. Based on this study, bony support at the modular junction should not be expected in 25% of cases 2 years after surgery.

Tantalum Components in Difficult Acetabular Revisions Have Good Survival at 5 to 10 Years: Longer Term Followup of a Previous Report.

The best method for acetabular revisions in patients with severe bone loss remains controversial; typical approaches include jumbo cups, cages, cup-cages, and custom components. Tantalum (TM) components have good results at midterm followup, but the longer term survival and complications are not available. We previously reported on a series of such reconstructions; here we provide additional followup on that group along with a larger study cohort. (1) What is the survival at a minimum followup of 5 years of these components implanted in difficult revisions and what is the mechanism of failure? (2) What is the most common complication of these reconstructions, and what hip scores did these patients achieve? Between 2001 and 2010, one surgeon performed 150 acetabular revisions, of which 74 (49%) were done using TM components. The general indication for use of these devices was the surgeon's perception that there was sufficient bone loss to place the reconstruction at a high risk of mechanical failure (generally Paprosky Type 3 or 4 or lower Paprosky type with < 50% host bone coverage or morbid obesity). No cages were used during this time. Fifteen patients died and 11 were lost or did not return, leaving 48 hips (46 patients) with a mean followup of 8 years (range, 5-14 years). Of these, 39 were reported on in our previous series, and nine are new in the present series; the overall group here has an additional median of 5 years followup (range, 3-7 years). Five hips had six augments placed to obtain stability. Patients were evaluated by the Harris hip score and standard radiographs; survivorship was estimated using the cumulative incidence competing risks survival analysis. The primary outcome was fixation and survival of the TM component and the secondary outcome was complications. Cumulative incidence competing risks estimate survival free from aseptic loosening was 92% at 10 years (95% confidence interval [CI], 0.81-0.98). Dislocation, the most common complication, occurred in seven of 48 (15%) patients, and five of 48 (10%) had a reoperation for it. Survival free from any reoperation was 84% at 10 years (95% CI, 0.72-0.92). The Harris hip score improved from a mean of 50 points (SD 17) before surgery to 85 points (SD 10; p < 0.001) at latest followup. Given the findings of this study, TM components appear to provide durable fixation at midterm followup in complex acetabular revisions. Steps to minimize dislocation, the most frequent complication of these revisions, may include the routine use of larger femoral heads. Future studies likely will need to be multisurgeon or multicenter and should evaluate different techniques and components for long-term fixation and the prevention of dislocation. Level IV, therapeutic study.