Migration Of Femoral Component Research Articles

A PROSPECTIVE RANDOMIZED CONTROLLED TRIAL COMPARING THE DIRECT SUPERIOR APPROACH WITH THE POSTERIOR APPROACH FOR TOTAL HIP ARTHROPLASTY

The direct superior approach (DSA) is a modification of the posterior approach (PA) that preserves the iliotibial band and short external rotators except for the piriformis or conjoined tendon during total hip arthroplasty (THA). The objective of this study was to compare postoperative pain, early functional rehabilitation, functional outcomes, implant positioning, implant migration, and complications in patients undergoing the DSA versus PA for THA.This study included 80 patients with symptomatic hip arthritis undergoing primary THA. Patients were prospectively randomised to receive either the DSA or PA for THA, surgery was undertaken using identical implant designs in both groups, and all patients received a standardized postoperative rehabilitation programme. Predefined study outcomes were recorded by blinded observers at regular intervals for two-years after THA. Radiosteriometric analysis (RSA) was used to assess implant migration.There were no statistical differences between the DSA and PA in postoperative pain scores (p=0.312), opiate analgesia consumption (p=0.067), and time to hospital discharge (p=0.416). At two years follow-up, both groups had comparable Oxford hip scores (p=0.476); Harris hip scores (p=0.293); Hip disability and osteoarthritis outcome scores (p=0.543); University of California at Los Angeles scores (p=0.609); Western Ontario and McMaster Universities Arthritis Index (p=0.833); and European Quality of Life questionnaire with 5 dimensions scores (p=0.418). Radiographic analysis revealed no difference between the two treatment groups for overall accuracy of acetabular cup positioning (p=0.687) and femoral stem alignment (p=0.564). RSA revealed no difference in femoral component migration (p=0.145) between the groups at two years follow-up.There were no differences between patients undergoing the DSA versus PA for THA with respect to postoperative pain scores, functional rehabilitation, patient-reported outcome measurements, accuracy of implant positioning, and implant migration at two years follow-up. Both treatment groups had excellent outcomes that remained comparable at all follow-up intervals.

Five-year migration of uncemented femoral components in total knee arthroplasty with either highly cross-linked or conventional polyethylene inserts: a blinded randomized controlled trial using radiostereometric analysis.

The aim of this study was to compare the migration of the femoral component, five years postoperatively, between patients with a highly cross-linked polyethylene (HXLPE) insert and those with a conventional polyethylene (PE) insert in an uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary aims included clinical outcomes and patient-reported outcome measures (PROMs). We have previously reported the migration and outcome of the tibial components in these patients. A double-blinded randomized controlled trial was conducted including 96 TKAs. The migration of the femoral component was measured with radiostereometry (RSA) at three and six months and one, two, and five years postoperatively. PROMs were collected preoperatively and at all periods of follow-up. There was no clinically relevant difference in terms of migration of the femoral component or PROMs between the HXLPE and PE groups. The mean difference in migration (maximum total point motion), five years postopeatively, was 0.04 mm (95% CI -0.06 to 0.16) in favour of the PE group. There was no clinically relevant difference in migration of the femoral component, for up to five years between the two groups. These findings will help to establish a benchmark for future studies on migration of femoral components in TKA.

Multidisciplinary approach to the treatment of patients with periprosthetic joint infection of the hip complicated by injury to the great vessels

Introduction Total counts of total hip arthroplasty (THA) have been increasing for several decades, and the procedures are associated with considerable risk of intra- and postoperative complications. Vascular complications are defined as multiple pathological conditions. They are subdivided into acute adverse events such as intraoperative bleeding, acute ischemia and hematoma and chronic complications such as pseudoaneurysms and arteriovenous fistulas which can cause late ischemic events. A specialized and well-trained multidisciplinary team is required to perform surgical interventions due to the small number of intravascular lesions. The objective was to demonstrate findings of clinical, instrumentation methods and staged treatment of patients with periprosthetic joint infection (PJI) of the hip and complications associated with injury to the great vessels.Material and methods We report two cases of vascular complications in patients with PJI and migration of femoral components into the lesser pelvis.Results An integrated approach to the diagnosis and treatment of patients with PJI and complications associated with injury to the great vessels helped to avoid lethal outcomes of the Girdlestone operation.Discussion Revision THA requires careful planning and an interdisciplinary approach with the help of a clinical pharmacologist, microbiologist, plastic or angiosurgeon. PJI is associated with a high risk of recurrence that would require two-stage, three-stage surgical interventions. With the bone deficiency of the acetabulum and the proximal femur the Girdlestone operation is performed as the final procedure with resultant significant decrease in the functional adaptation of patients.Conclusion Careful preoperative preparation of patients with unstable hip replacement components including migration of the acetabular component into the pelvic cavity and associated PJI would help to avoid such a devastating complication as great vessel injury.

Comparison of cementless twin-peg, cemented twin-peg and cemented single-peg femoral component migration after medial unicompartmental knee replacement: a 5-year randomized RSA study

BackgroundThe component design and fixation method of joint arthroplasty may affect component migration and survival. The aim of this study was to compare fixation of cementless twin-peg (CLTP), cemented twin-peg (CTP) and cemented single-peg (CSP) femoral components of medial unicompartmental knee replacement (UKR).MethodsEighty patients (mean age = 63 years, 48 males) with medial knee osteoarthritis were randomized in three ways to CLTP (n = 25), CTP (n = 26) or CSP (n = 29) femoral UKR components. The patients were followed 5 years postoperatively with RSA, bone mineral density (BMD), PROMs and radiological evaluation of radiolucent lines (RLL), femoral component flexion angle and complications.ResultsAt the 5-year follow-up, femoral component total translation was comparable between the three groups (p = 0.60). Femoral component internal rotation was 0.50° (95% CI 0.3; 0.69) for the CLTP group, 0.58° (95% CI 0.38; 0.77) for the CTP group and 0.25° (95% CI 0.07; 0.43) for the CSP group (p = 0.01). BMD decreased peri-prosthetically (range − 11.5%; − 14.0%) until 6-month follow-up and increased toward the 5-year follow-up (range − 3.6%; − 5.8%). BMD change did not correlate with component migration. Lower flexion angle was correlated with higher 5-year subsidence, total translation, varus rotation and maximum total point motion (p = 0.01). Two patients (1 CLTP, 1 CTP) had RLL in the posterior zone. There were two revisions.ConclusionAt 5-year follow-up, fixation of UKA femoral components with twin-peg was not superior to the single-peg design. Cementless and cemented twin-peg femoral components had similar fixation. A lower flexion angle was correlated with higher component migration.

Similar results after five years with the use of the Fitmore or the CLS femoral components.

Although the Fitmore Hip Stem has been on the market for almost 15 years, it is still not well documented in randomized controlled trials. This study compares the Fitmore stem with the CementLeSs (CLS) in several different clinical and radiological aspects. The hypothesis is that there will be no difference in outcome between stems. In total, 44 patients with bilateral hip osteoarthritis were recruited from the outpatient clinic at a single tertiary orthopaedic centre. The patients were operated with bilateral one-stage total hip arthroplasty. The most painful hip was randomized to either Fitmore or CLS femoral component; the second hip was operated with the femoral component not used on the first side. Patients were evaluated at three and six months and at one, two, and five years postoperatively with patient-reported outcome measures, radiostereometric analysis, dual-energy X-ray absorptiometry, and conventional radiography. A total of 39 patients attended the follow-up visit at two years (primary outcome) and 35 patients at five years. The primary outcome was which hip the patient considered to have the best function at two years. At two and five years, more patients considered the hip with the CLS femoral component as superior but without a statistically significant difference. There were no differences in clinical outcome, magnitude of femoral component migration, or change of bone mineral density at five years. At three months, the Fitmore femoral component had subsided a median -0.71 mm (interquartile range (IQR) -1.67 to -0.20) and the CLS femoral component -0.70 mm (IQR -1.53 to -0.17; p = 0.742). In both groups the femoral head centre had migrated posteriorly (Fitmore -0.17 mm (IQR -0.98 to -0.04) and CLS -0.23 mm (IQR -0.87 to 0.07; p = 0.936)). After three months neither of the femoral components showed much further migration. During the first postoperative year, one Fitmore femoral component was revised due to aseptic loosening. Up to five years, we found no statistically significant difference in outcomes between the Fitmore and the CLS femoral components. The slightly worse outcomes, including one revised hip because of loosening, speaks against the hypothesis that the Fitmore femoral component should be advantageous compared to the CLS if more patients had been recruited to this study.

Two-year fixation and ten-year clinical outcomes of total knee arthroplasty inserted with normal-curing bone cement and slow-curing bone cement: A randomized controlled trial in 54 patients

BackgroundThe normal-curing Refobacin® Bone Cement R (RR) and slow-curing Refobacin® Plus Bone Cement (RP) were introduced after discontinuation of the historically most used bone cement, Refobacin®-Palacos® R, in 2005. The aim of this study was to compare total knee arthroplasty component fixation with the two bone cements. Methods54 patients with primary knee osteoarthritis were randomized to either RR (N = 27) or RP (N = 27) bone cement and followed for two years with radiostereometric analysis of tibial and femoral component migration and dual-energy x-ray absorptiometry measured periprosthetic bone mineral density (BMD). Further, patients were followed up at ten years with clinical outcome scores (OKS and KOOS). ResultsAt two-years follow-up, tibial total translation was 0.31 mm (95% CI: 0.19 – 0.42) for the RP group and 0.56 mm (95% CI: 0.45 – 0.67) (p < 0.01) for the RR group. There was continuous tibial component migration from one to two years follow-up (MTPM > 0.2 mm) in 13/27 patients from the RR and in 12/26 patients from the RP group. There was no difference between groups in BMD baseline values or changes during follow-up, as well as no correlation between change in BMD and tibial component migration. At ten-years follow-up, the improvement in the clinical outcome scores was similar between groups. There were no prosthesis related complications during the 10-year follow-up. ConclusionAt two years, tibial total translation was lower in the RP compared with the RR cement group, but BMD changes were similar. At ten years, no components were revised and clinical outcome scores were similar between groups.

Biomechanical Evaluation of the Accuracy in Radiographic Assessment of Femoral Component Migration Measurement after Total Hip Arthroplasty

Implant subsidence is one criteria utilized to monitor for prosthesis loosening after total hip arthroplasty (THA) with initial implant subsidence assessment often done utilizing plain radiographs. The specific aim of this study was to identify the most reliable references when using plain radiographs to establish an image magnification with the goals being easy to use, inexpensive, reliable, and accurate. Two femoral stem implants (stem lengths: 127 mm, 207 mm) were utilized to simulate hemiarthroplasty of the hip with composite femurs. Different combinations of femoral stem distances from the radiographic film (ODD), source-detector differences (SDD), hip rotation, and hip flexion were elected. Standardized anterior-posterior pelvis for each parameter combination setup were taken. Radiographic measurements (head diameter, stem length, stem seating length) were undertaken five times by three examiners. Radiographic image magnification factors were generated from two references (head diameter and stem length). Radiograph measurement reproducibility and stem seating length errors using these magnification factors were evaluated. High level of repeated measurements reliability was found for head diameter (99 ± 0%) and stem length (90 ± 7%) measurements, whereas seating length measurements were less reliable (76 ± 6%). Stem length error using the femoral head magnification factor yielded 11% accuracy. Stem seating length error using both magnification factors were not reliable (< 7% accuracy). All parameters, except SDD, showed significant effect on calibrated measurement error. Current methods of assessing the implant subsidence after THA are inaccurate and unreliable. Clinicians should recognize these limitations and be cautious when diagnosing implant stability using plain radiographs alone.

A randomized controlled trial investigating the value of patient-specific instrumentation for total knee arthroplasty in the Canadian healthcare system.

The purpose of the present study was to compare patient-specific instrumentation (PSI) and conventional surgical instrumentation (CSI) for total knee arthroplasty (TKA) in terms of early implant migration, alignment, surgical resources, patient outcomes, and costs. The study was a prospective, randomized controlled trial of 50 patients undergoing TKA. There were 25 patients in each of the PSI and CSI groups. There were 12 male patients in the PSI group and seven male patients in the CSI group. The patients had a mean age of 69.0 years (sd 8.4) in the PSI group and 69.4 years (sd 8.4) in the CSI group. All patients received the same TKA implant. Intraoperative surgical resources and any surgical waste generated were recorded. Patients underwent radiostereometric analysis (RSA) studies to measure femoral and tibial component migration over two years. Outcome measures were recorded pre- and postoperatively. Overall costs were calculated for each group. There were no differences (p > 0.05) in any measurement of migration at two years for either the tibial or femoral components. Movement between one and two years was < 0.2 mm, indicating stable fixation. There were no differences in coronal or sagittal alignment between the two groups. The PSI group took a mean 6.1 minutes longer (p = 0.04) and used a mean 3.4 less trays (p < 0.0001). Total waste generated was similar (10 kg) between the two groups. The PSI group cost a mean CAD$1787 more per case (p < 0.01). RSA criteria suggest that both groups will have revision rates of approximately 3% at five years. The advantages of PSI were minimal or absent for surgical resources used and waste eliminated, and for meeting target alignment, yet had significantly greater costs. Therefore, we conclude that PSI may not offer any advantage over CSI for routine primary TKA cases. Cite this article: Bone Joint J 2019;101-B:565-572.

Randomised clinical trial assessing migration of uncemented primary total hip replacement stems, with and without autologous impaction bone grafting.

Uncemented stems in primary total hip replacement (THR) are concerning in the elderly due to ectatic femoral canals and cortical thinning resulting in higher incidence of fracture and subsidence in this population. To obviate this concern, the authors developed a technique using autologous impaction bone grafting to achieve a better fitting femoral stem. The aim of this randomised clinical trial was to assess the efficacy of the technique. From 2013 to 2015, a total of 98 consecutive participants (100 primary THR procedures) were inducted into a single-institution, single-blinded, randomised clinical trial assessing, with radiostereometric analysis (RSA), the efficacy of autologous impaction bone grafting in uncemented primary THR compared with traditional uncemented primary THR technique. The primary outcome measure was femoral component migration using RSA. Secondary outcomes were post-operative proximal femoral bone density (using DEXA), hip function and quality of life using Oxford Hip Score (OHS) and Short Form-12 Health Survey (SF-12), hip pain and patient satisfaction. There was no difference in femoral component stability (p > 0.5) or calcar resorption between the Graft and No Graft Groups at two years. There was also no difference in OHS, SF-12, pain or satisfaction between the Graft and No Graft Groups at two years (p > 0.39). Autologous impaction bone grafting in uncemented primary THR has shown its short-term post-operative outcomes to be equivalent to standard uncemented technique, whilst offering a better fit in patients who are between femoral stem sizes. ACTRN12618000652279.

The Effects of Resection Technique on Implant Migration in Single Radius Posterior-Stabilized Total Knee Replacement.

The purpose of the present study was to measure the effects of gap balancing and resection techniques on migration of a single total knee replacement implant design. A total of 23 patients (24 knees) were recruited on referral to either a surgeon performing gap balancing or a surgeon performing measured resection and followed prospectively. All patients received a fixed bearing, posterior stabilized total knee replacement implant of a single radius femoral component design with cement fixation, and all aspects of care outside of resection technique were identical. Patients underwent radiostereometric analysis (RSA) at 2 weeks (baseline), 6 weeks, 3 months, 6 months, 1 year, and 2 years. Migration of the tibial and femoral components was compared between groups. Tibial component migration was greater at 2 years in the gap balancing group (mean difference = 0.336 mm, p = 0.036), but there was no difference at 1 year. One measured resection and three gap balancing tibial components demonstrated continuous migration > 0.2 mm between years 1 and 2. There was no difference in femoral component migration. Small differences in tibial component migration were found between the gap balancing and measured resection techniques. However, comparing the migration to established predictive thresholds for long-term loosening risk, implants performed with both techniques were found to have equally low revision risk.

Measuring the migration of the components and polyethylene wear after total hip arthroplasty

This paper describes the methodology, validation and reliability of a new computer-assisted method which uses models of the patient's bones and the components to measure their migration and polyethylene wear from radiographs after total hip arthroplasty (THA). Models of the patient's acetabular and femoral component obtained from the manufacturer and models of the patient's pelvis and femur built from a single computed tomography (CT) scan, are used by a computer program to measure the migration of the components and the penetration of the femoral head from anteroposterior and lateral radiographs taken at follow-up visits. The program simulates the radiographic setup and matches the position and orientation of the models to outlines of the pelvis, the acetabular and femoral component, and femur on radiographs. Changes in position and orientation reflect the migration of the components and the penetration of the femoral head. Validation was performed using radiographs of phantoms simulating known migration and penetration, and the clinical feasibility of measuring migration was assessed in two patients. Migration of the acetabular and femoral components can be measured with limits of agreement (LOA) of 0.37 mm and 0.33 mm, respectively. Penetration of the femoral head can be measured with LOA of 0.161 mm. The migration of components and polyethylene wear can be measured without needing specialised radiographs. Accurate measurement may allow earlier prediction of failure after THA. Cite this article: Bone Joint J 2017;99-B:1290-7.

Primary stability of unicompartmental knee arthroplasty under dynamic flexion movement in human femora

BackgroundThe objective of our study was to evaluate the impact of a trabecular stem fixation versus a cortical teeth fixation technique on the primary stability of cemented unicompartmental femoral components under dynamic flexion movement loading conditions in human femora. MethodsTen fresh-frozen human knees of a mean donor age of 73.9years were used to perform medial unicompartmental knee arthroplasty under a less invasive parapatellar surgical approach. The femora were divided into two groups of matched pairs based on comparable trabecular bone mineral density. To assess the primary stability, a new method based on a combination of dynamic flexion movement, double-peak loading simulating stair climbing, kinematic analysis of the femoral component migration relative to the bone and an evaluation of the cement layer by fragments cut through the implant-cement-bone interface in the sagittal plane of the medial condyle was introduced. FindingsFor the “trabecular stem fixation” technique the mean load to failure was 2340 (SD 650) N and for “cortical teeth fixation” it was 1080 (SD 455) N, with a substantially enhanced dynamic fixation strength for the “trabecular stem fixation” (p=0.008). In the distal area the cement layer of the “trabecular stem fixation” showed a significant decreased thickness compared to the “cortical teeth fixation” (p=0.029), while a substantially deeper cement penetration (p=0.044) has been achieved for the “trabecular stem fixation”. InterpretationFrom our observations, we conclude that there is a significantly enhanced primary stability with a “trabecular stem fixation” compared to a “cortical teeth fixation” technique of cemented unicompartmental femoral components, in terms of dynamic failure load and migration characteristics.

Comparison of femoral component migration between Refobacin bone cement R and Palacos R + G in cemented total hip arthroplasty: A randomised controlled roentgen stereophotogrammetric analysis and clinical study.

The widely used and well-proven Palacos R (a.k.a. Refobacin Palacos R) bone cement is no longer commercially available and was superseded by Refobacin bone cement R and Palacos R + G in 2005. However, the performance of these newly introduced bone cements have not been tested in a phased evidence-based manner, including roentgen stereophotogrammetric analysis (RSA). In this blinded, randomised, clinical RSA study, the migration of the Stanmore femoral component was compared between Refobacin bone cement R and Palacos R + G in 62 consecutive total hip arthroplasties. The primary outcome measure was femoral component migration measured using RSA and secondary outcomes were Harris hip score (HHS), Hip disability and Osteoarthritis Outcome Score (HOOS), EuroQol 5D (EQ-5D) and Short Form 36 (SF-36). Femoral component migration was comparable between Refobacin bone cement R and Palacos R + G during the two-year follow-up period with an estimated mean difference of 0.06 mm of subsidence (p = 0.56) and 0.08° of retroversion (p = 0.82). Five hips (three Refobacin bone cement R and two Palacos R + G) showed non-stabilising, continuous migration; the femoral cement mantle in these hips, was mean 0.7 mm thicker (p = 0.02) and there were more radiolucencies at the bone-cement interface (p = 0.004) in comparison to hips showing stabilising migration. Post-operative HHS was comparable throughout the follow-up period (p = 0.62). HOOS, EQ5D, and SF-36 scores were also comparable (p-values >0.05) at the two-year follow-up point. Refobacin bone cement R and Palacos R + G show comparable component migration and clinical outcome during the first two post-operative years. Hips showing continuous migration are at risk for early failure. However, this seems to be unrelated to cement type, but rather to cementing technique. Cite this article: Bone Joint J 2016;98-B:1333-41.

The cementless fibre mesh coated anatomic femoral stem: 12 to 23 years clinical and radiological outcome study.

The aim of this study was to assess the long-term clinical and radiographic results, and possible reasons for failure of two versions of the cementless fibre-metal coated anatomical femoral component. 99 patients (119 hips) were evaluated at an average of 16.7 years (range, 12 to 23 years) following primary THA. Developmental dysplasia of the hip (DDH) was the most common pathology (n = 37 hips). Structural femoral head autografts were used to increase cup coverage in 23 hips. Vertical and horizontal migration of acetabular and femoral components and osteolysis around the components were assessed using conventional radiolography. For clinical evaluation, the Harris Hip Score and Merle D'Aubigne scale were used preoperatively and at final follow up. Implant survival was calculated according to the Kaplan-Meier survivorship analysis and failure was defined as component's revision for any reason. The cumulative survival rate of the anatomical femoral stem was 64.2% at 19.8 years, with a worst-case scenario of 41%. The cumulative survival rate of the total hip arthroplasty was 51% at 19.8 years, with a worse case scenario of 38%. The mean preoperative Harris Hip Score of 42 points improved to 88 postoperatively. The mean preoperative Merle D'Aubigne functional score of 3.5 improved to 5.2 points at the time of final follow-up. In 36 hips (41.6%) osteolysis was found in Gruen zone 1, proximal to the ingrowth surface. The cementless fibre-metal coated anatomical femoral component showed favourable long-term clinical and radiological results. Proximal coating seems to protect bone implant interface from wear debris induced osteolysis during the second decade.

A novel method to measure femoral component migration by computed tomography: a cadaver study.

Radiostereometric analysis (RSA) is the most accurate technique to measure implant migration. However, it requires special equipment, technical expertise and analysis software and has not gained wide acceptance. The current paper analyzes a novel method to measure implant migration utilizing widely available computer tomography (CT). Three uncemented total hip replacements were performed in three human cadavers and six tantalum beads were inserted into the femoral bone similar to RSA. Six different 28mm heads (-3, 0, 2.5, 5.0, 7.5 and 10mm) were added to simulate five reproducible translations (maximum total point migration) of the center of the head. Implant migration was measured in a 3-D analysis software (Geomagic Studio 7). Repeat manual reconstructions of the center of the head were performed by two investigators to determine repeatability and accuracy. The accuracy of measurements between the centers of two head sizes was 0.11mm with a CI 95% of 0.22mm. The intra-observer repeatability was 0.13mm (CI 95% 0.25mm). The interrater-reliability was 0.943. CT based measurement of head displacement in a cadaver model were highly accurate and reproducible.

Results of Monolithic and Modular Femoral Components Use at Total Hip Revision Arthroplasty

Results of 28 total hip revision arthroplasties using distal fixation stems were analyzed. In 18 operations revision stems Wagner SL (1 st group) and in 10 interventions modular revision stems Cerafit revision (2 nd group) were used. Mean follow up period made up 3 years. Course of operation and peculiarities of bone canal treatment prior to stem implantation were described in detail. In 1 st group excellent results were achieved in 2 (11.11%), good in 8 (44.44%) satisfactory in 4 (22.22%) and poor in 4 (22.22%) of patients. In 2 nd group in 2 (20%), 4 (40%), 3 (30%) and 1 (10%) patient, respectively. Poor treatment outcomes resulted from suppuration and distal migration offemoral component. Rate of intraoperative femur cracks and fractures for two study groups was not higher than at revision arthroplasty using other implants. Taking into account intraoperative advantages the use of modular femoral components in complicated cases is a good alternative to monolithic stems.

Result of PCL Substitution Type Total Knee Arthroplasty with Scorpio® System (minimum 3-year follow up)

Purpose: To evaluate the clinical and radiologic result of total knee arthroplasty using Scorpio total knee system retrospectively. Materials and Methods: Between January 1999 and December 2001, 71 knees in 51 patients who had been followed up mean 3.6 years (minimum 3.0 years) after total knee arthroplasty with Scorpiosystem (posterior substitution type) were evaluated retrospectively for clinical result, active range of motion, flexion contracture and radiologic result. Results: The average active range of motion increased from (75-) preoperatively to (90-) at last follow up. The average flexion contracture improved from (0-) preoperatively to (0-) at last follow up. The average HSS knee score was measured 54 preoperatively and was measured 88 postoperatively. There was no difference in clinical result, active range of motion and flexion contracture between resurfaced patella group and nonresurfaced patella group. Radiologic evaluation revealed radiolucency rate of 11% in Tibia anteroposterior view and 10% in femur. Complications were periprostheitc fracture in one case, deep infection in one case and peroneal nerve palsy in one case. In one case, femoral and tibial component migration due to aseptic loosening was noted. Revision of tibial and femoral component was done. Conclusion: The 3.6 years follow up results of Scorpio system (posterior substitution type) were excellent in range of motion and function. There was no difference between resurfaced patella group and nonresurfaced patella group in clinical result.

Mechanical simulation of muscle loading on the proximal femur: analysis of cemented femoral component migration with and without muscle loading

Objective. This study examines the effect of including muscle forces in fatigue tests of cemented total hip arthroplasty reconstructions. Design. An experimental device capable of applying the joint reaction force, the abductor force, the vastus lateralis force, and the tensor fasciae latae force to the implanted femur is described. Background. Current in vitro fatigue tests of cemented total hip arthroplasty reconstructions do not apply physiological muscle loads. Experimental and numerical studies report significant differences in stresses obtained in the cement mantle depending on the loads applied. The differing stresses may alter the outcome of an in vitro test. Methods. Ten femoral components were reproducibly implanted into proximal composite femurs. Five of these femoral components were tested using a loadprofile which included muscle loading, five were tested without muscle loading. The migration of each femoral component was monitored continuously during dynamic fatigue tests. Results. Clinically comparable migration amounts were found for both sets of femoral components, with the femoral components tested with muscle loading experiencing lower mean migration, lower mean inducible displacement, and less experimental scatter. Conclusions. The inclusion of muscle forces seems to stabilise the femoral component during the test. In vitro fatigue tests of cemented total hip arthroplasty reconstructions should include muscle loading to provide increased confidence in the results obtained. Relevance This study examines how the migration of cemented femoral hip prostheses is influenced by muscle forces. Hip prostheses are one of the few medical devices for which pre-clinical testing protocols have emerged, and this study ascertains whether or not the inclusion of muscle forces is necessary for pre-clinical tests. The conclusion that muscle loading should be included, and that it is important for the development of a new generation of standardised tests to provide enhanced patient protection against functionally poor prostheses.

Accuracy of EBRA-FCA in the measurement of migration of femoral components of total hip replacement

Several methods of measuring the migration of the femoral component after total hip replacement have been described, but they use different reference lines, and have differing accuracies, some unproven. Statistical comparison of different studies is rarely possible. We report a study of the EBRA-FCA method (femoral component analysis using Einzel-Bild-Röntgen-Analyse) to determine its accuracy using three independent assessments, including a direct comparison with the results of roentgen stereophotogrammetric analysis (RSA). The accuracy of EBRA-FCA was better than ±1.5 mm (95% percentile) with a Cronbach’s coefficient alpha for interobserver reliability of 0.84; a very good result. The method had a specificity of 100% and a sensitivity of 78% compared with RSA for the detection of migration of over 1 mm. This is accurate enough to assess the stability of a prosthesis within a relatively limited period. The best reference line for downward migration is between the greater trochanter and the shoulder of the stem, as confirmed by two experimental analyses and a computer-assisted design.

Migration of the uncemented CLS femoral component.

The migration of uncemented CLS (Cementless Total Hip Replacement System) femoral stems was measured retrospectively from standard anteroposterior pelvic radiographs using a digitizer and software specifically designed for this study. The study population was comprised of 117 patients with 126 uncemented CLS femoral stems. All radiographs were reviewed and the incidence of thigh pain obtained by means of a questionnaire. The mean clinical follow-up was 3 years and the mean follow-up for radiographic review was 2.77 years. The mean femoral stem migration was 2 mm at 2 years and 3.66 mm at 7 years. Radiographic features varied little with no specific predictive features in patients with excessive early migration or those who complained of thigh pain. There was no statistical relationship between the presence of thigh pain and femoral stem migration.