Assessment of wear and periacetabular osteolysis using dual energy computed tomography on a pig cadaver to identify the lowest acceptable radiation dose.

OBJECTIVES: Computed tomography (CT) plays an important role in evaluating wear and periacetabular osteolysis (PAO) in total hip replacements. One concern with CT is the high radiation exposure since standard pelvic CT provides approximately 3.5 millisieverts (mSv) of radiation exposure, whereas a planar radiographic examination with three projections totals approximately 0.5 mSv. The objective of this study was to evaluate the lowest acceptable radiation dose for dual-energy CT (DECT) images when measuring wear and periacetabular osteolysis in uncemented metal components. MATERIALS AND METHODS: A porcine pelvis with bilateral uncemented hip prostheses and with known linear wear and acetabular bone defects was examined in a third-generation multidetector DECT scanner. The examinations were performed with four different radiation levels both with and without iterative reconstruction techniques. From the high and low peak kilo voltage acquisitions, polychrmoatic images were created together with virtual monochromatic images of energies 100 kiloelectron volts (keV) and 150 keV. RESULTS: We could assess wear and PAO while substantially lowering the effective radiation dose to 0.7 mSv for a total pelvic view with an accuracy of around 0.5 mm for linear wear and 2 mm to 3 mm for PAO. CONCLUSION: CT for detection of prosthetic wear and PAO could be used with clinically acceptable accuracy at a radiation exposure level equal to plain radiographic exposures.Cite this article: B. Sandgren, M. Skorpil, P. Nowik, H. Olivecrona, J. Crafoord, L. Weidenhielm, A. Persson. Assessment of wear and periacetabular osteolysis using dual energy computed tomography on a pig cadaver to identify the lowest acceptable radiation dose. Bone Joint Res 2016;5:307-313. DOI: 10.1302/2046-3758.57.2000566.

Three-dimensional movements of the lumbar spine facet joints and segmental movements: in vivo examinations of normal subjects with a new non-invasive method.

INTRODUCTION: Examination with CT and image registration is a new technique that we have previously used to assess 3D segmental motions in the lumbar spine in a phantom. Current multi-slice computed tomography (CT) offers highly accurate spatial volume resolution without significant distortion and modern CT scanners makes it possible to reduce the radiation dose to the patients. Our aim was to assess segmental movement in the lumbar spine with the aforementioned method in healthy subjects and also to determine rotation accuracy on phantom vertebrae. MATERIAL AND METHOD: The subjects were examined in flexion-extension using low dose CT. Eleven healthy, asymptomatic subjects participated in the current study. The subjects were placed on a custom made jig which could provoke the lumbar spine into flexion or extension. CT examination in flexion and extension was performed. The image analysis was performed using a 3D volume fusion tool, registering one of the vertebrae, and then measuring Euler angles and distances in the registered volumes. RESULTS: The mean 3D facet joint translation at L4-L5 was in the right facet joint 6.1 mm (3.1-8.3), left facet joint 6.9 mm (4.9-9.9), at L5-S1: right facet joint 4.5 mm (1.4-6.9), and for the left facet joint 4.8 mm (2.0-7.7). In subjects the mean angles at the L4-L5 level were: in the sagittal plane 14.3°, coronal plane 0.9° (-0.6 to 2.8), and in the transverse plane 0.6° (-0.4 to 1.5), in the L5-S1 level the rotation was in sagittal plane 10.2° (2.4-16.1), coronal plane 0° (-1.2 to 1.2), and in the transverse plane 0.2° (-0.7 to 0.3). Repeated analysis for 3D facet joint movement was on average 5 mm with a standard error of mean of 0.6 mm and repeatability of 1.8 mm (CI 95%). For segmental rotation in the sagittal plane the mean rotation was 11.5° and standard error of mean 1°. The repeatability for rotation was 2.8° (CI 95%). The accuracy for rotation in the phantom was in the sagittal plane 0.7°, coronal plane 1°, and 0.7 in the transverse plane. CONCLUSION: This method to assess movement in the lumbar spine is a truly 3D method with a high precision giving both visual and numerical output. We believe that this method for measuring spine movement is useful both in research and in clinical settings.

Model studies on segmental movement in lumbar spine using a semi-automated program for volume fusion.

OBJECTIVE: To validate a new non-invasive CT method for measuring segmental translations in lumbar spine in a phantom using plastic vertebrae with tantalum markers and human vertebrae. MATERIAL AND METHODS: One hundred and four CT volumes were acquired of a phantom incorporating three lumbar vertebrae. Lumbar segmental translation was simulated by altering the position of one vertebra in all three cardinal axes between acquisitions. The CT volumes were combined into 64 case pairs, simulating lumbar segmental movement of up to 3 mm between acquisitions. The relative movement between the vertebrae was evaluated visually and numerically using a volume fusion image post-processing tool. Results were correlated to direct measurements of the phantom. RESULTS: On visual inspection, translation of at least 1 mm or more could be safely detected and correlated with separation between the vertebrae in three dimensions. There were no significant differences between plastic and human vertebrae. Numerically, the accuracy limit for all the CT measurements of the 3D segmental translations was 0.56 mm (median: 0.12; range: -0.76 to +0.49 mm). The accuracy for the sagittal axis was 0.45 mm (median: 0.10; range: -0.46 to +0.62 mm); the accuracy for the coronal axis was 0.46 mm (median: 0.09; range: -0.66 to +0.69 mm); and the accuracy for the axial axis was 0.45 mm (median: 0.05; range: -0.72 to + 0.62 mm). The repeatability, calculated over 10 cases, was 0.35 mm (median: 0.16; range: -0.26 to +0.30 mm). CONCLUSION: The accuracy of this non-invasive method is better than that of current routine methods for detecting segmental movements. The method allows both visual and numerical evaluation of such movements. Further studies are needed to validate this method in patients.

The addition of tramadol to morphine via patient-controlled analgesia does not lead to better post-operative pain relief after total knee arthroplasty.

BACKGROUND: Tramadol is used as an analgesic in post-operative pain treatment. Intravenous tramadol is often combined with morphine to achieve better pain relief and less side-effects after orthopaedic surgery. However, the available evidence is insufficient to support this combination. For this reason, we conducted the present non-commercial, randomized, double-blind clinical trial. METHOD: Sixty-three patients with osteoarthritis of the knee, selected for primary total knee arthroplasty (TKA), were randomized to receive saline or tramadol 100 mg/ml intravenously every 6 h during the first post-operative day (total, 400 mg/24 h). All patients had access to morphine via a patient-controlled analgesia (PCA) pump. RESULTS: Neither during the 6 h after the first dose nor during the first post-operative day could we detect any statistically significant difference with regard to pain intensity, sedation and nausea between patients treated with tramadol and the placebo group. However, the withdrawal rate caused by insufficient pain relief was greater in the tramadol group (7/31) than in the saline group (2/32). This difference did not reach statistical significance. In the group of patients who remained in the study for 24 h ('per protocol'), those randomized to receive tramadol had a significantly (P < 0.05) lower morphine consumption (20 mg or 31%) than the placebo group. CONCLUSION: Our study does not support the combination of tramadol and morphine via PCA for post-operative pain relief after primary TKA. In addition, our study indicates that morphine via PCA as the sole means of post-operative analgesia does not provide sufficient pain relief after TKA. Thus, other means of post-operative analgesia should be used following TKA.

Osteoblast dysfunction in male idiopathic osteoporosis.

The etiology of primary osteoporosis in young and middle-aged men is unknown. We have studied osteoblast function in cells derived from men with idiopathic osteoporosis and in control cells from age-matched men with osteoarthrosis. Osteoblasts were isolated from transiliac bone biopsies. Osteoblast function was measured as vitamin D-stimulated osteocalcin production and production of cytokines and factors involved in osteoclast activation and bone formation. Cell proliferation was measured as (3)H-thymidine incorporation. Parathyroid hormone-related peptide (PTHrP) mRNA was measured using reverse-transcriptase polymerase chain reaction. In osteoporotic men, bone mineral density at the femoral neck was correlated to in vitro production of osteocalcin. Osteoblasts from osteoporotic men produced significantly less osteocalcin after vitamin D stimulation but had increased production of macrophage colony-stimulating factor (M-CSF) compared to controls. The osteocalcin response was negatively correlated to production of M-CSF, interleukin-6, and C-terminal propeptide of type I collagen. Basal (3)H-thymidine incorporation was similar in cells from osteoporotic patients and controls. PTHrP (10(-9 )M) significantly increased cell proliferation in control cells but not in osteoporotic cells. Basal PTHrP mRNA levels were significantly higher in osteoporotic cells than in cells from controls. The results are in agreement with previous histomorphologic studies indicating that men with idiopathic osteoporosis have an osteoblast dysfunction with decreased osteocalcin production and increased production of factors stimulating osteoclast activation. This indicates a catabolic cellular metabolic balance leading to negative bone turnover, resulting in osteoporosis. The cause of such cellular dysfunction needs further evaluation.

Standard orientation of the pelvis: validation on a model and ten patients.

PURPOSE: To validate an image post-processing method for re-orienting the pelvis in CT volumes to a standardized orientation in a model and in 10 patients. MATERIAL AND METHODS: Twenty-four CT volumes of a pelvic model and 10 pairs of postoperative total hip arthroplasty (THA) patient CT scans were rotated to a defined pelvic standard orientation and the rotation was recorded. For precision, a test-retest procedure was used. For accuracy, three exactly represented coordinate points were used. For clinical application, the standard orientation was used for calculating the direction of acetabular cup migration from a previous model study. RESULTS: Precision of pelvic standard orientation, calculated as maximal directional error, was better than 1 degrees in the model study and better than 1.5 degrees in the patient study. Accuracy, expressed as angle between ideal and measured coordinate axes, was 0.1 degrees for x, y, z axes. No measurable systematic errors were found. When applied to acetabular cup migration in the model, standardization of pelvic orientation had no significant effect on the measurements. CONCLUSION: Reorienting the pelvis during image post-processing was shown to be accurate. It enables measurements relative to the pelvis and minimizes the dependency of patient positioning.

Gait and clinical measurements in patients with knee osteoarthritis after surgery: a prospective 5-year follow-up study.

The aim of this prospective follow-up study was to determine if gait measurements and/or clinical measurements could detect differences in treatment outcome between two surgical interventions in patients with knee osteoarthritis (OA). The patients were followed for 5 years after surgery. Forty patients, 55-70 years of age, with unilateral knee OA were included. The patients were treated either with a high tibial osteotomy (HTO) (n=18) or a unicompartmental knee arthroplasty (UKA) (n=22). Clinical outcome measures were the British Orthopaedic Association (BOA) score, pain during walking, passive range of knee motion (PROM) and patients' subjective opinion. The gait variables were free walking speed, step frequency, step length and single and double-stance phase for each leg. The patients were examined before surgery and 3 months, 1 year and 5 years after surgery. The time-distance variables of gait could detect differences in treatment outcome, 3 months after surgery, while the clinical outcome measures, as given here, could not detect any differences between the two groups of patients. Measurements of free walking speed could be recommended for clinical evaluation, after surgical interventions, in patients with knee OA.

Assessing wear of the acetabular cup using computed tomography: an ex vivo study.

PURPOSE: To validate a clinically useful method for measuring acetabular cup wear using computed tomography (CT). MATERIAL AND METHODS: Eight uncemented acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral component head into the cup and the thickness of the remaining polyethylene liner were measured in the CT volumes using dedicated software. Two independent examiners twice assessed each volume. The CT measurements were compared to direct measurements using a coordinate measuring device and micrometer measurements. RESULTS: Accuracy of wear measurements expressed as penetration depth was +/-0.6 and +/- 1.0 mm for the two examiners, respectively, with no significant differences between examiners, trials, and CT scans. Accuracy of measurements of remaining polyethylene was +/- 1.3 and +/- 1.0 mm, respectively, for the two examiners. Systematic differences between examiners were found, but no significant differences between trials and CT scans. These differences were due to different interpretations of metal artifacts in the volumes. CONCLUSION: The proposed CT method for evaluating wear as head penetration depth allows for reliable wear detection at a clinically relevant level. Measurements of remaining polyethylene on CT volumes are not as reliable as wear measurements owing to metal artifacts.

Stability of acetabular axis after total hip arthroplasty, repeatability using CT and a semiautomated program for volume fusion.

PURPOSE: To validate a CT method for detecting changes in acetabular cup orientation after THA. MATERIAL AND METHODS: 26 CT examinations were obtained from a pelvic model with an uncemented acetabular cup. The model position was altered between acquisitions, but the cup axis angle vis-à-vis the pelvis was maintained. Data sets were combined into 37 pairs, each containing a unique positioning error. The pelvi in different examinations were fused, creating transformed volumes. Landmarks corresponding to the cup before and after fusion were placed interactively by two independent examiners. The orientation of the acetabular axis was calculated for each volume and compared across volumes. RESULTS: Before fusion the mean angle error between the acetabular axes was 4.17 degrees (SD +/- 1.95 degrees ). After fusion the mean angle error was 0.36 degrees (SD +/- 0.17). The 95% repeatability limits were below 0.7 degrees. There was no significant interobserver difference. Analysis of the cup landmarking pattern by condition numbers and individual landmark errors showed stability. CONCLUSION: Non-invasive fusion of CT volumes and a stable landmarking pattern for the acetabular cup outperforms routine plain radiography in detecting changes in the orientation of the acetabular axis over time. The method delivers both visual and numerical output and could be used in clinical practice.

Model studies on acetabular component migration in total hip arthroplasty using CT and a semiautomated program for volume merging.

PURPOSE: Validation of a non-invasive CT method for detection of acetabular cup migration after total hip arthroplasty in a phantom study. MATERIAL AND METHODS: 26 CT examinations were obtained of a pelvic model while altering the position of the acetabular cup. Using a previously described program for volume merging, the pelvi in different examinations were fused and the 3D alterations of the position of the acetabular cup were evaluated visually and numerically and correlated to direct measurements on the model. RESULTS: Visually, two independent examiners differentiated between 0, 1 and 2 to 3 mm migration with 100% specificity and sensitivity. Numerically, the mean error over all cases between model and CT measurements was 0.04 mm (SD +/- 0.33). The mean absolute error between model and CT data was 0.26 mm (SD +/- 0.19). Intra- and interobserver 95% accuracy and repeatability limits were below 0.5/0.7 mm, respectively. No significant interobserver difference occurred. The data were normally distributed and not dependent on observer. CONCLUSION: The accuracy of this non-invasive method out-performs routine plain radiography. The method gives both visual and numerical correlates to migration and can be used in clinical practice.

Spatial component position in total hip arthroplasty. Accuracy and repeatability with a new CT method.

PURPOSE: 3D detection of centerpoints of prosthetic cup and head after total hip arthroplasty (THA) using CT. MATERIAL AND METHODS: Two CT examinations, 10 min apart, were obtained from each of 10 patients after THA. Two independent examiners placed landmarks in images of the prosthetic cup and head. All landmarking was repeated after 1 week. Centerpoints were calculated and compared. RESULTS: Within volumes, all measurements of centerpoints of cup and head fell, with a 95% confidence, within one CT-voxel of any other measurement of the same object. Across two volumes, the mean error of distance between center of cup and prosthetic head was 1.4 mm (SD 0.73). Intra- and interobserver 95% accuracy limit was below 2 mm within and below 3 mm across volumes. No difference between intra- and interobserver measurements occurred. A formula for converting finite sets of point landmarks in the radiolucent tread of the cup to a centerpoint was stable. The percent difference of the landmark distances from a calculated spherical surface was within one CT-voxel. This data was normally distributed and not dependent on observer or trial. CONCLUSION: The true 3D position of the centers of cup and prosthetic head can be detected using CT. Spatial relationship between the components can be analyzed visually and numerically.

Acetabular component migration in total hip arthroplasty using CT and a semiautomated program for volume merging.

PURPOSE: To develop a non-invasive method for detection of acetabular cup migration after total hip arthroplasty (THA) with a higher degree of accuracy than routine plain radiography. MATERIAL AND METHODS: Two CT examinations, 10 min apart, were obtained from each of 10 patients that had undergone THA. Using an in-house developed semiautomated program for volume merging, the pelves in the two examinations were fused and the acetabular cup was visually and numerically evaluated to test the method's accuracy in detecting migration. RESULTS: In the visual evaluation of the best match a 1-mm translation of the cup was detectable. The numerical evaluation, comparing landmarks placed in the images of the acetabular cup and the head of the femur component in the two examinations, showed the mean difference in orientation of acetabular axes to be 2.5 degrees, the mean distance between centre of cup face to be 2.5 mm and the mean distance between centre of the head of the prosthetic femoral component to be 1 mm. CONCLUSION: This method has a significantly higher accuracy than routine plain radiography in detecting acetabular cup migration and could be used in clinical practice. It gives both a visual and a numerical correlate to migration.

Bracing versus nonbracing in rehabilitation after anterior cruciate ligament reconstruction: a randomized prospective study with 2-year follow-up.

This study prospectively randomized 62 patients to rehabilitation programs either with or without postoperative brace for 6 weeks following bone-tendon-bone anterior cruciate ligament reconstruction. The nonbraced group had a smaller knee circumference 2 weeks after surgery. At 6-month follow-up the nonbraced group had a better Tegner score. At 2 years there was no difference between the groups. There was one partial rupture of the graft in the nonbraced group after a new trauma 1 year after surgery. There were no differences between the groups in either subjective or objective knee stability at 2 or 6 weeks or at follow-up 3, 6, and 24 months after surgery. This study found no benefit of using a postoperative knee brace on patients' knee function at any stage up to 24 months after surgery. Furthermore, the braced group was not more stable than the nonbraced group, indicating that the brace does not contribute to a more stable knee during rehabilitation or 2-year follow-up.

Does metal backing improve fixation of tibial component in unicondylar knee arthroplasty? A randomized radiostereometric analysis.

In a prospective, randomized study, patients with medial gonarthrosis stage I to III according to Ahlbäck were allocated to a unicondylar knee arthroplasty (Miller-Galante, Zimmer, Inc., Warsaw, IN) with an all-polyethylene tibial component or metal-backed tibial component of the same design. The purpose of the study was to evaluate if metal backing enhanced tibial component fixation. A total of 45 knees (42 patients; 23 metal-backed components and 22 all-polyethylene components) were examined. We used radiostereometric analysis to measure micromotion of the tibial component over a period of 2 years after surgery. Hospital for Special Surgery score was used for clinical evaluation. We found no statistically significant differences in clinical results or migration of the tibial component over a 2-year follow-up period. These findings do not support better fixation of metal-backed tibial components. Because of these findings, we advocate all-polyethylene tibial components in unicondylar knee arthroplasties because of optimal biomechanical strength at a given height of tibial component, avoiding potential problems of modularity and minimizing the amount of interfaces, at a lower cost.

Can local anesthesia be recommended for routine use in elective knee arthroscopy? A comparison between local, spinal, and general anesthesia.

Local anesthesia (LA) for outpatient knee arthroscopy is not a standard procedure at most hospitals. To evaluate the LA technique for knee arthroscopy on medically healthy patients, this study compared 3 anesthesia techniques. Four hundred patients were randomized to either local (n = 200), general (n = 100), or spinal (n = 100) anesthesia. Evaluated outcomes included the patient's subjective view of the procedure, and nausea and pain at rest and during active movement. All variables were recorded perioperatively and postoperatively. In addition, the performing surgeon's opinion of the degree of patient pain and the technical difficulty of the procedure were noted. Three hundred forty-two patients completed the study. In the group receiving local anesthesia (n = 180) the median visual analog scale pain score during surgery was 6 mm (mean, 17.5; SD, 23.2; range, 0 to 100 mm). Twenty-one LA patients would have preferred another form of anesthesia. In 29 patients, LA was not considered as the optimal anesthesia by the performing surgeon. Eight LA patients agreed with the surgeon that the anesthesia method used was not optimal, of these patients, 5 had synovitis (3%). In 5% of the LA patients there were technical problems. Thus, this study shows that elective knee arthroscopy can be performed under local anesthesia in 92% of the patients from a technical point of view. Excluding patients who do not choose local anesthesia and those who have hypertrophic synovitis preoperatively, knee arthroscopies can be performed as safely and effectively under local anesthesia as under any other form of anesthesia. For most patients, local anesthesia can be recommended as the standard procedure for outpatient knee arthroscopy.

Knee arthroscopy in local versus general anaesthesia. The incidence of rearthroscopy.

The choice of anaesthesia in routine knee arthroscopy varies considerably. Concerns about local anaesthesia include the fear that it will take longer to perform surgery and that the anaesthesia will be inadequate, leading to patient discomfort. In this study, data from all patients (n = 6519) who had undergone a knee arthroscopy at St Göran Hospital Artro Clinic, in Stockholm, Sweden, during a 3.5 year period, between January 1993 and July 1996, were reviewed. Of these 6519 primary arthroscopies, 4101 were performed under local anaesthesia and 2418 under general anaesthesia. The purpose of the study was first to identify those arthroscopies that could not be successfully performed because the local anaesthesia was inadequate, and second, to investigate if arthroscopy under local anesthesia was associated with an increased number of rearthroscopies compared to general anaesthesia. The total number of rearthroscopies, performed within 180 days from the primary arthroscopy, was 214. Of these 214 rearthroscopies, 146 were due to a new indication for surgery and 30 were due to persisting clinical symptoms (true rearthroscopies). The remaining 38 rearthroscopies were due to an incomplete examination (because of patient discomfort) in a primary procedure where local anaesthesia was used. Of the 30 true rearthroscopies, 19 originated from the 4101 primary arthroscopies performed under local anaesthesia (0.46%) and 11 originated from the 2418 primary arthroscopies performed under general anaesthesia (0.45%). It is concluded that 0.9% of the primary arthroscopies performed under local anaesthesia could not be performed safely due to patient discomfort. There was no difference in the frequency of rearthroscopy between the arthroscopies performed under local anaesthesia compared to those performed under general anaesthesia.

Femoral bone regeneration subsequent to impaction grafting during hip revision: histologic analysis of a human biopsy specimen.

Cemented revision with impaction grafting shows encouraging early clinical results; postoperative biopsy specimens taken from the proximal femur in humans have demonstrated viable trabecular and cortical bone. Human radiographic studies also illustrate density changes within the proximal femur, consistent with remodeling of bone-graft. In an animal experiment, bone incorporation was shown in the proximal femur, but graft lysis was reported around the distal portion of the implant. We report on a patient who sustained a traumatic femoral fracture at the level of the tip of the femoral component 27 months after revision with impaction grafting and a collarless polished taper stem. At the time of open reduction and internal fixation of the fracture, we obtained circumferential biopsy specimens from the fracture site. Three distinct zones could be identified histologically: i) an inner zone consisting of bone-cement, fibrous tissue, and partially necrotic trabeculae with evidence of bone remodeling; ii) a middle zone consisting of viable trabecular bone and probable neocortex formation with fewer particles of bone-cement; and iii) an outer zone with viable cortex. Fibrous tissue was present around some of the incorporating bone-graft fragments, but no continuous fibrous membrane was present. Cement particles were identified, but no polyethylene debris was found by light microscopy. Biopsy specimens from the distal aspect of the prosthesis may not reflect changes seen proximally, but based on the available tissue, this case illustrated histological evidence of bone-graft remodeling after impaction grafting. These results are consistent with our expectations based on radiographic findings and clinical results.

Complex cemented revision using polished stem and morselized allograft. Minimum 5-years' follow-up.

The aim of this study was to evaluate the results of complex hip revision using a cemented, collarless and polished femoral stem design (CPT, Zimmer, Warsaw, In.) within a tightly impacted morselized allograft. We have now been using the impaction grafting technique in combination with the CPT stem (Zimmer) for 10 years in complex cases of severe bone loss. In this study we have elected to report only those patients who have been revised at least once before revision using the impaction grafting technique. All the patients in the study group have a minimum follow-up of 5 years after the impaction grafting revision. In total, 43 consecutive hips in 40 patients, 22 men and 18 women, with a follow-up time of between 5 and 7 years are included in the study. The complications related to the revised hip consist of three early dislocations managed by closed reduction. Two patients suffered from periprosthetic fracture, both managed with plate osteosynthesis. Two cementless sockets were revised due to aseptic socket loosening. The Endoklinik rating of preoperative bone loss for the revised hips was 2 in 13 hips, 3 in 23 hips, and 4 in 7 hips. During the first year 29 stems subsided 2-4 mm within the cement mantle. In 8 cases, a subsidence of 5-9 mm was measured. The subsidence was nonprogressive, and no subsidence occurred after the 1st year. The Charnley, D'Aubigne, Postel scoring (maximum 6 points) for pain improved from 2.2 points preoperatively to 4.4 postoperatively, function from 2.3 to 4.3, and movement from 2.3 to 4.1. In conclusion, the concept of impaction grafting in THR revision in our study has so far proven to be successful with good clinical results at 5 years despite the relatively high early subsidence of the femoral component.