We determined the short-term clinical outcome and migration within the bone of the humeral cementless component of the Instrumented Bone Preserving (IBP) total elbow replacement in a series of 16 patients. There were four men and 12 women with a mean age at operation of 63 years (40 to 81). Migration was calculated using radiostereometric analysis. There were no intra-operative complications and no revisions. At two-year follow-up, all patients showed a significant reduction in pain and functional improvement of the elbow (both p < 0.001). Although ten components (63%) showed movement or micromovement during the first six weeks, 14 (88%) were stable at one year post-operatively. Translation was primarily found in the proximal direction (median 0.3 mm (interquartile range (IQR) -0.09 to 0.8); the major rotational movement was an anterior tilt (median 0.7° (IQR 0.4° to 1.6°)). One malaligned component continued to migrate during the second year, and one component could not be followed beyond three months because migration had caused the markers to break off the prosthesis. This study shows promising early results for the cementless humeral component of the IBP total elbow replacement. All patients had a good clinical outcome, and most components stabilised within six months of the operation. . Cite this article: Bone Joint J 2014;96-B:229–36

1. Distal migration of a femoral intramedullary nail is described in seven patients. Previous reports of proximal and distal migration are reviewed. 2. Factors predisposing to this complication are infection, incorrect nail size, comminution of the fracture and involvement of the medullary isthmus

This was a safety study where the hypothesis was that the newer-design CPCS femoral stem would demonstrate similar early clinical results and micromovement to the well-established Exeter stem. Both are collarless, tapered, polished cemented stems, the only difference being a slight lateral to medial taper with the CPCS stem. A total of 34 patients were enrolled in a single-blinded randomised controlled trial in which 17 patients received a dedicated radiostereometric CPCS stem and 17 a radiostereometric Exeter stem. No difference was found in any of the outcome measures pre-operatively or post-operatively between groups. At two years, the mean subsidence for the CPCS stem was nearly half that seen for the Exeter stem (0.77 mm (−0.943 to 1.77) and 1.25 mm (0.719 to 1.625), respectively; p = 0.032). In contrast, the mean internal rotation of the CPCS stem was approximately twice that of the Exeter (1.61° (−1.07° to 4.33°) and 0.59° (0.97° to 1.64°), respectively; p = 0.048). Other migration patterns were not significantly different between the stems. The subtle differences in designs may explain the different patterns of migration. Comparable migration with the Exeter stem suggests that the CPCS design will perform well in the long term

Migration of 65 Charnley stems implanted with modern cementing techniques was studied by roentgen stereophotogrammetry. There were 25 patients with rheumatoid arthritis (RA) and 40 with osteoarthritis (OA) followed up for two years. In 43 cases a bone sample for histomorphometric analysis was obtained from the femur during the operation. In 22 cases the mean subsidence of the prosthetic head was 0.40 mm and in 20 the mean posterior migration was 1.25 mm. There was no difference in migration between the two diagnostic groups (p = 0.8) after adjusting for variations in gender, age and weight. Male gender was associated with increased subsidence (p = 0.006). Histological examination showed that the RA series had more osteoid surface (p = 0.04), but neither this, nor any of the other histomorphometric variables, influenced migration. These results suggest that, unlike the acetabular socket, the cemented Charnley femoral component is equally secure in osteoarthritis and in rheumatoid arthritis, and that its initial fixation is not influenced by the quality of the local cancellous bone. Our results provide data with which the early performance of new prosthetic designs and fixation methods can be compared

Individual components of a total hip replacement are difficult to evaluate and quantify. We have studied the assessment of the acetabular component, and conclude that the measurement of migration allows the comparison of implants, although there is no established link between migration and significant loosening. A method of measurement based on clinical radiographs has been developed, and its limitations estimated. The accuracy of the technique was calculated to be +/- 3 mm

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

We have evaluated the difference in the migration patterns over two years of two cementless stems in a randomised, controlled trial using radiostereophotogrammetric analysis (RSA). The implants studied were the Furlong HAC stem, which has good long-term results and the Furlong Active stem, which is a modified version of the former designed to minimise stress concentrations between the implant and bone, and thus to improve fixation. A total of 23 Furlong HAC and 20 Furlong Active stems were implanted in 43 patients. RSA examinations were carried out immediately post-operatively and at six, 12 and 24 months post-operatively. The subsidence during the first year in the Furlong HAC stem, was approximately one-third that of the Furlong Active stem, the measured mean subsidence of the femoral head at six months being 0.27 mm (95% confidence interval (CI) 0.03 to 0.51) and 0.99 mm (95% CI 0.38 to 1.60), respectively (p = 0.03). One Active stem continued to subside during the second year. All hips, regardless of the type of stem were clinically successful as judged by the Oxford hip score and a derived pain score without any distinction between the two types of stem. The initial stability of the Furlong Active stem was not as good as the established stem which might compromise osseo-integration to the detriment of long-term success. The changes in the geometry of the stem, to minimise stress have affected the attainment of initial stability

Socket migration and rotation in the Charnley total hip replacement were evaluated by roentgen stereophotogrammetric analysis in 23 patients with rheumatoid arthritis and 23 patients with osteoarthritis. The two groups were matched with regard to age and sex. The follow-up time was two years. In the rheumatoid patients socket migration was most prominent in the proximal direction and averaged 0.6 mm at 24 months as compared with 0.1 mm in the osteoarthritic group (p = 0.0003). Within the rheumatoid group a preoperative acetabular protrusion in five patients was associated with increased migration and rotation in all directions. The increased proximal migration in rheumatoid arthritis was consistent (p = 0.0009) even after the exclusion of the five protrusion cases. In the rheumatoid patients there was a correlation between low body-weight and proximal migration, but there was no such correlation in the osteoarthritic group. Our results suggest that socket fixation is less secure in patients with advanced inflammatory arthritis

We investigated the fixation of fully-threaded cementless acetabular prostheses in 20 patients with osteoarthritis, measuring the migration of the cup using roentgen stereophotogrammetric analysis (RSA). All the cups migrated proximally, 13 moved laterally or medially, and nine moved anteriorly or posteriorly in the first two postoperative years, the average migration being 1.1 to 1.4 mm in either direction. Rotatory movements of up to 5.7 degrees were found in nine of the 13 hips where this analysis could be performed. Movements of cobalt-chrome (12) and titanium alloy (8) cups did not differ significantly. Seventeen of the 20 patients had some pain two years after the operation. The migration of the prostheses indicates that 'osseointegration' had not occurred. The combination of this with persistent pain suggests that the long-term results will be unfavourable

We allocated randomly 27 patients undergoing 28 primary uncemented total hip replacements (THR) to receive prosthetic components of similar design with either plasma-sprayed titanium alloy (Ti) coating (n = 13) or hydroxyapatite (HA) coating (n = 15). After some exclusions, 15 of the patients (15 THR; 7 with HA- and 8 with Ti-coating) were followed by roentgen stereophotogrammetric analysis at 3, 6 and 12 months to measure migration of the femoral component. Twenty-six of the patients (26 THR) were followed clinically and by conventional radiography. All the femoral components had migrated at 3 months. From 3 to 12 months, the migration of Ti-coated components continued whereas the HA-coated components had stabilised. At 12 months there was significantly less migration of the HA-coated components (p < 0.05). The maximum subsidence was 0.2 mm in both groups. The Harris hip score was equal in the two groups preoperatively but at follow-up it was better in the HA-coated group (p < 0.05) and visual analogue scale scores showed that they had less pain (p < 0.05)

We analysed in-vivo migration and wear over a long period of all-polyethylene acetabular cups which had not been affected by mechanical loosening. The selection criteria of regular radiological follow-up, good clinical outcome (Charnley score of 5 or 6), continued walking without crutches and no radiological signs of loosening of the acetabular cups were fulfilled by 25 Charnley total hip arthroplasties. Mean migration, measured by the Nunn method, was 0.6 mm in the medial and 0.2 mm in the cranial direction. The mean yearly rate of wear was 0.05 mm and 0.04 mm, with six and two cups having no detectable wear, as measured by the Livermore and Charnley-Cupic methods, respectively. The maximal detected wear was 3.7 mm. There were no changes in the rate of wear with time. Computerised Ein Bild Röntgen Analyse (single-image radiological analysis) measurements of 20 hips indicated plastic deformation of the cups. We conclude that long-term successful cups do not migrate and have a very low rate of wear which was not affected by ageing of the polyethylene. There was no evidence that polyethylene wear alone caused mechanical loosening of the cup but high rates of wear seem to have an adverse prognostic value in terms of the long-term survival of the prosthesis

We investigated the stability of seven Schatzker type II fractures of the lateral tibial plateau treated by subchondral screws and a buttress plate followed by immediate partial weight-bearing. In order to assess the stability of the fracture, weight-bearing inducible displacements of the fracture fragments and their migration over a one-year period were measured by differentially loaded radiostereometric analysis and standard radiostereometric analysis, respectively. The mean inducible craniocaudal fracture fragment displacements measured −0.30 mm (−0.73 to 0.02) at two weeks and 0.00 mm (−0.12 to 0.15) at 52 weeks. All inducible displacements were elastic in nature under all loads at each examination during follow-up. At one year, the mean craniocaudal migration of the fracture fragments was −0.34 mm (−1.64 to 1.51). Using radiostereometric methods, this case series has shown that in the Schatzker type II fractures investigated, internal fixation with subchondral screws and a buttress plate provided adequate stability to allow immediate post-operative partial weight-bearing, without harmful consequences

We report the ten-year results for three designs of stem in 240 total hip replacements, for which subsidence had been measured on plain radiographs at regular intervals. Accurate migration patterns could be determined by the method of Einzel-Bild-Roentgen-Analyse-femoral component analysis (EBRA-FCA) for 158 hips (66%). Of these, 108 stems (68%) remained stable throughout, and five (3%) started to migrate after a median of 54 months. Initial migration of at least 1 mm was seen in 45 stems (29%) during the first two years, but these then became stable. We revised 17 stems for aseptic loosening, and 12 for other reasons. Revision for aseptic loosening could be predicted by EBRA-FCA with a sensitivity of 69%, a specificity of 80%, and an accuracy of 79% by the use of a threshold of subsidence of 1.5 mm during the first two years. Similar observations over a five-year period allowed the long-term outcome to be predicted with an accuracy of 91%. We discuss the importance of four different patterns of subsidence and confirm that the early measurement of migration by a reasonably accurate method can help to predict long-term outcome. Such methods should be used to evaluate new and modified designs of prosthesis

We determined the cumulative survival rates, in arthroplasty of the knee, of three designs of tibial component, using a change of position on standard radiographs or revision for aseptic loosening as criteria of failure. The average migration of each of the three designs in the first postoperative year is known from roentgen stereophotogrammetric analysis reported by other authors. The ranking order of the components as judged by cumulative survival is the same as that determined by early migration. This finding supports the view that the measurement of early migration can predict late aseptic loosening and therefore that such measurements are clinically of value

We have studied the beneficial effects of a hydroxyapatite (HA) coating on the prevention of the migration of wear debris along the implant-bone interface. We implanted a loaded HA-coated implant and a non-coated grit-blasted titanium alloy (Ti) implant in each distal femoral condyle of eight Labrador dogs. The test implant was surrounded by a gap communicating with the joint space and allowing access of joint fluid to the implant-bone interface. We injected polyethylene (PE) particles into the right knee three weeks after surgery and repeated this weekly for the following five weeks. The left knee received sham injections. The animals were killed eight weeks after surgery. Specimens from the implant-bone interface were examined under plain and polarised light. Only a few particles were found around HA-coated implants, but around Ti implants there was a large amount of particles. HA-coated implants had approximately 35% bone ingrowth, whereas Ti implants had virtually no bone ingrowth and were surrounded by a fibrous membrane. Our findings suggest that HA coating of implants is able to inhibit peri-implant migration of PE particles by creating a seal of tightly-bonded bone on the surface of the implant

Reimers’ hip migration percentage is commonly used to document the extent of subluxation of the hip in children with spasticity. In this study, two measurers, with six months paediatric orthopaedic experience, measured the migration percentage on 44 pelvic radiographs of children with cerebral palsy, aged between two and eight years. Unknown to the measurers, each radiograph was duplicated, giving 22 non-identical radiographs (44 hips) which were measured twice at time 0 and twice six weeks later. The intra-measurer, intra-sessional absolute differences between the first and second measurements ranged from 0% to 23%, with median values of 2.5% to 3.6%. The intra-sessional median absolute differences were not statistically different between the two measurers and measuring sessions (p = 0.42, Kruskal-Wallis test). The inter-sessional absolute differences for measurements made by the same measurers ranged from 0% to 18% with a median absolute difference of 1.7% to 3.2%. Overall, only 5% of the intra-measurer measurement differences, within and between sessions, were above 13%. Repeated measurements by one measurer over time must, therefore, vary by more than 13% in order to be 95% confident of a true change. The inter-measurer error was higher with median absolute differences between the two measurers’ measurements of the same hip of 3.25% to 5% (0% to 26%) and a 95. th. upper confidence interval of 21% to 23%. Averaging the four separate measurements over the two sessions reduced the inter-measurer error to a median absolute difference of 2.8%, but did not improve the 95. th. upper confidence interval, which measured 22.4%. Such inter-measurer errors may be clinically unacceptable

We report the theoretical basis of a method to measure axial migration of femoral components of total hip replacements (THR). The use of the top of the greater trochanter and a lateral point on the collar of the stem, allowing for variations of up to 10 degrees rotation of the femur in any direction between successive radiographs, gave a maximum error of 0.37 mm. At a more realistic 5 degrees rotational variation, the error was only 0.13 mm. These data were confirmed in an experimental study using digitisation of points and special software. We also showed that the centre of the femoral head, the stem tip, and the lesser trochanter provided less accurate landmarks. In a second study we digitised a series of radiographs of 51 Charnley and 57 Stanmore THRs; the mean migration rates were found to be identical. We then studied 46 successful stems with a minimum follow-up of eight years and 46 stems which had failed by aseptic loosening at different times. At two years, the successful stems had migrated by a mean of 1.45 +/- 0.68 mm, but the failed cases had a mean migration of 4.32 +/- 2.58 mm (p < 0.0001). Of the successful cases 76% had migrated less than 2 mm, while in the failed group 84% had migrated more than 2 mm. For any particular case migration of more than 2.6 mm at two years had only a 5% chance of continuing success and would therefore merit special follow-up. Only 24% of the eventually successful stems showed migration at the stem-cement interface, but this had happened in every failed stem. We conclude that it would be possible to evaluate a new cemented design of femoral stem over a two-year period by the use of our method and to compare its performance against the reported known standard of the Charnley and Stanmore designs

We studied two groups of femoral hip prostheses: 43 TiAlV ridged press-fit stems, and 26 with similar stems coated with hydroxyapatite on the proximal half. At one year, radiological measurement showed a mean downward migration of 0.99 mm for the TialV prostheses and 0.12 mm for the HA-coated prostheses (p = 0.0002). Hydroxyapatite coating appeared to provide effective bio-active supplementary fixation

We report the initial results of an ongoing randomised, prospective study on migration of the Exeter and Elite Plus femoral stems after impaction allografting, as measured by radiostereometry. Clinically, the impaction technique gave good results for both stems. The mean subsidence in the first year was 1.30 mm and 0.20 mm for the Exeter and the Elite Plus stems, respectively. In the second year, the Exeter stem continued to subside further by a mean of 0.42 mm, while the Elite Plus stem did not do so. Subsidence of the Exeter stem correlated with deficiency of bone stock as graded on the Gustilo and Pasternak scale. This correlation was not found for the Elite Plus stem. None of the other parameters which were studied predisposed to subsidence. There was no significant association between the amount of subsidence and the radiological appearance of the graft for either stem. Our findings do not support the theory that radial compression, due to subsidence of the Exeter stem, is the essential stimulus for remodelling in impaction allografting

Our aim was to determine whether tantalum markers improved the accuracy and/or precision of methods for the measurement of migration in total hip replacement based on conventional measurements without mathematical correction of the data, and with Ein Bild Roentgen Analyse – Femoral Component Analysis (EBRA-FCA) which allows a computerised correction. Three observers independently analysed 13 series of roentgen-stereophotogrammetric-analysis (RSA)-compatible radiographs (88). Data were obtained from conventional measurements, EBRA-FCA and the RSA method and all the results were compared with the RSA data. Radiological evaluation was also used to quantify in how many radiographs the intraosseous position of the bone markers had been simulated. The results showed that tantalum markers improve reliability whereas they do not affect accuracy for conventional measurements and for EBRA-FCA. Because of the danger of third-body wear their implantation should be avoided unless they are an integral part of the method