The Birmingham hip resurfacing (BHR) arthroplasty is a metal-on-metal prosthesis for which no medium- or long-term results have been published. Despite this, it is increasing in popularity as an alternative to stemmed prostheses for younger patients. Since the fixation of the socket is conventional, the major concern is long-term failure of the femoral component. This can be predicted by the use of roentgen stereophotogrammetric analysis (RSA). We have therefore undertaken such a study of the BHR femoral component over a period of two years. Twenty patients (22 hips) underwent a standard BHR procedure. Migration of the femoral component was measured by RSA at intervals of three, six, 12 and 24 months. At 24 months the total three-dimensional migration of the head was 0.2 mm. This was not statistically significant. Previous studies have shown that implants which loosen quickly have rapid early migration. Our results therefore suggest that the BHR femoral component is an inherently stable device which is likely to perform well in the long term

Early micromotion of joint prostheses with respect to the bone can be assessed very accurately by a method called Roentgen Stereophotogrammetric Analysis (RSA); a method that uses two simultaneous X-ray exposures of the joint and has an accuracy of 0.1 mm for translations and 0.3 degree for rotations [. 1. ]. In order to reach this accuracy, metallic markers are inserted into the bone and attached to the surface of the prosthesis. These markers can then be identified automatically in the two radiographs [. 2. ]. Since the adjustments to the prosthesis are difficult, time-consuming and expensive, RSA has only been applied in a limited number of clinical trials. In a previous study we have developed a Model-based RSA algorithm, which does not require the attachment of markers to the prosthesis [. 3. ]. This algorithm is based on minimisation of the non-overlapping area (NOA) between the automatically detected contour of the prosthesis from the roentgen image, with the virtually projected contour of a three-dimensional model of the prosthesis. Because the accuracy of this NOA algorithm was not as high as the accuracy of the currently used Marker-based RSA, we have studied alternative algorithms for Model-based RSA. From a simulation study in which we used models of the Interax Total Knee Prosthesis (Stryker-Howmedica) and the G2 Hip Prosthesis (Johnson & John-son), we found that the results of the NOA algorithm can be improved substantially. The newly developed Model-based RSA algorithm is based on minimisation of the mean distance between the points of the actual contour and the virtually projected contour. The simulation study shows that the new algorithm is superior to the NOA-algorithm in situations where part of the contour is occluded, as well as in situations where the contour is distorted by noise. With the new algorithm, the residual position error can be reduced to 0.1 mm. and also the residual orientation error can be reduced to 0.3 degree, making Model-based RSA a future alternative to Marker-based RSA

Roentgen stereophotogrammetric analysis (RSA) is the most accurate radiographic technique for the assessment of three-dimensional micromotion in joints. RSA has been used previously to study the kinematics of the anterior cruciate ligament (ACL)-deficient knee and to measure knee laxity after bone-tendon-bone (BTB) reconstructions. There is no published evidence on its use in assessing hamstring grafts in vivo, in comparing hamstring versus BTB reconstruction, or in-depth analyses of graft performance. The aim of this project was to use RSA to measure laxity in both BTB and hamstring reconstructions, and to attempt a detailed analysis of graft behaviour in both reconstructions, with particular attention to graft stretching and slippage of the bony attachments. A prospective study was undertaken on 14 patients who underwent ACL reconstruction. Seven had BTB reconstruction, and seven had four-stranded semitendinosus/gracilis (STG). Tantalum markers were inserted at the time of surgery, into distal femur and proximal tibia, and also directly into the graft itself. Stress radiographs (90N anterior and 90N posterior force) were taken early post-operatively, and then at 6 weeks, and 3, 6 and 12 months. In addition to measuring total anteroposterior knee laxity, a detailed analysis of the graft itself was possible. The BTB grafts had stretched by an average of 1.54%, and the bone plugs had migrated by 0.50 mm at the femoral end and by 0.61mm at the tibial end. The hamstring grafts had stretched on average 3.94%, and the intraosseous ends had migrated by 3.96mm at the femoral end and by 7.10mm at the tibial end. This is believed to be the most detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction. Details such as graft stretching and fixation slippage have not been available previously; the data obtained in this study may have implications for clinical practice

Model-based Roentgen Stereophotogrammetric Analysis (RSA) measures micromotion of an orthopaedic implant with respect to its surrounding bone, without the use of markers on the implant. In previous studies with a total knee prosthesis, Model-based RSA showed to be very accurate. In this study, Model-based RSA is validated in a phantom experiment of a total hip prosthesis. A metal backed, elliptical shaped EP-FIT PLUS ®cup was used in combination with a SL-PLUS ® hip-stem from PLUS Endoprothetik AG. In vivo conditions were simulated by using sawbones and perspex plates to mimic the bones and soft tissue. Virtual projections of the CAD models of the implant were fitted on the automatically detected contours in nine RSA radiographs and the error inmigration calculation was determined. The standard deviations of the error in translation for the cup were: 0.03, 0.05, and 0.21 mm. (x, y, z-direction) The standard deviations of the error in orientation were respectively 0.56, 0.48, and 0.18 degrees (n = 10). For the stem, the standard deviations of the error in translation are: 0.09, 0.11, and 0.29 mm and for the orientation: 0.63, 2.03, and 0.24 degrees (n = 0). The results for the cup are satisfactory, and make Model-based RSA a good alternative for conventional RSA. Especially for this type of metal backed, non hemispherical cup for which no markerless alternative is available. The error in orientation around the y-axis of the stem is of concern. Experiments with models from Reversed Engineering had similar low accuracy. We expect that the cause of these inaccuracies is the rectangular cross sectional shape of this specific hip stem, and we expect better results from experiments with differently shaped stems. The results of this study make very clear that Model-based RSA is avaluable and accurate technique, but phantom studies are always necessary to validate the accuracy for a specific implant shape

Introduction Roentgen stereophotogrammetric analysis (RSA) is the most accurate radiographic technique for measuring three-dimensional micromotion in joints, and is now being developed for the study of anterior cruciate ligament (ACL) injury and outcome after surgical reconstruction. Using RSA a prospective study of ACL reconstruction is being undertaken. The aim is to obtain accurate information on the performance of both bone-patellar tendon-bone (BPTB) and hamstring grafts post-operatively. Materials and methods 14 patients with a unilateral ACL tear who underwent ACL reconstruction have been studied prospectively. Seven had BPTB grafts, and seven had four-stranded semitendinosus/gracilis. Tantalum markers were inserted at the time of surgery, 4 each into the femur and tibia, and 8 into the graft, at regular intervals along the length. Stress stereo radiographs (90N anterior and posterior draw forces) were taken at 1, 6, 12 and 24 weeks post-operatively. They were analysed using Medis RSA software. Results Initial results suggest that in addition to measuring total anteroposterior knee laxity, detailed analysis of the graft itself is possible. Beads placed in the bone blocks of the BPTB grafts, and in the intraosseous ends of the hamstrings, enable calculation of slippage of the fixation. The BPTB bone plugs moved 0.6 to 1.2mm by 12 weeks, the Hamstrings fixation was more variable. Beads placed in the intraarticular graft may enable measurement of any post-operative stretching, but are also somewhat erratic. Identification of the site of stretching – around the tunnel entrances, or intraarticularly, should be possible. Conclusions We believe that this detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction has not been previously described. We hope to gain valuable insight into the behaviour of both graft types and reasons for graft failure. This presentation will demonstrate the methods developed and include the technical difficulties encountered in this on-going study

The tibial components in 143 patients with total knee replacements performed before 1988 were assessed for micromotion using roentgen stereophotogrammetric analysis (RSA) over a period of 13 years. The fixation of the prostheses remained clinically sound in all cases, although revision had been required for other reasons in seven. In a second group taken from all cases with RSA available on our full database to 1990, 15 tibial components had been followed by RSA from the insertion until, 1 to 11 years after the initial arthroplasty, they were revised for mechanical loosening of the tibial component; 12 of these comprised all the loosenings in the base group, thus making a total of 155 consecutive cases, while an additional three were inserted after the base material had been compiled. The mean migration in the first group was about 1 mm at one year, but subsequent migration was slower, reaching a mean of about 1.5 mm after ten years. About one-third migrated continuously throughout follow-up, while two-thirds ceased to migrate after one to two years. In the revision group, 14 components had migrated continuously and at one year significantly more than those in the first group. One revision case lacked the crucial one-year follow-up and could not be classified. These findings suggest that mechanical loosening begins early in the postoperative period. Clinical symptoms which necessitate revision, seen at this stage in 20% of abnormally migrating tibial components, may not appear until up to ten years after the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

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

There is no non-invasive gold standard for measuring gap formation following rotator cuff repair; re-tears are reported both on MRI and Ultrasound. Roentgen Stereophotogrammetric Analysis (RSA) has previously been used to monitor microscopic migration of markers in rigid bodies. We present a novel RSA technique using a combination of 1mm tantalum beads and metal sutures to allow accurate monitoring of gap formation following rotator cuff repair. The RSA system combines a commercially made calibration cage with software developed at Imperial College. We verified the RSA system by analysing a movable glass phantom and comparing the data with precise physical measurements of the same object: it identified a 2mm distraction of the phantom to within 0.05mm. In vitro work involved cadaveric human shoulders. We placed three 1mm RSA tantalum beads in the greater tuberosity and three metal sutures in supraspinatus tendon. We then created a tear in supraspinatus at its insertion into the greater tuberosity. We were able to show that RSA images taken before and after the tear correlated closely with direct measurements. The processed data demonstrated movement associated with gap formation. We have performed two open rotator cuff repairs using trans-osseous sutures. During surgery RSA markers were inserted into the shoulder to allow post-operative monitoring of the repair (guided by the in vitro work). Direct measurements of the distance between markers each side of the repair were taken intra-operatively (T=O). RSA images were taken immediately post-operatively (T=1 hours), day 3, day 14, and day 84. The RSA data suggests gapping of typically 3mm may have occurred at the repair sites in both patients. Ultrasound imaging was performed at the same intervals by consultant musculoskeletal radiologists blinded to the RSA data. Preliminary results correlating the two modalities suggest that ultrasound can visualise gap formation accurately even immediately post-operatively

Aim of many surgical operations on the spine is very often to achieve a solid fusion between two or more vertebrae (arthrodesis). Describing lumbar spine mobility radiographically has been determined to be very imprecise with measurement errors of three to six mm in the sagittal plane. Using roentgen stereophotogrammetric analysis (RSA) it is possible to perform clinical kinematic lumbar studies with high accuracy. Many experimental studies have presented basic data on the stabilising implant effect in human cadaver lumbar spines, but no study compared the in vivo stabilising effect in different types of implant. The RSA was performed in a radiographic set-up with two 40° angulated roentgen tubes with simultaneous exposures. A combined reference plate and calibration device with 0.8 mm tantalum balls at known positions was situated between the patient and the uniplanar film cassette, enabling simultaneous calibration and patient examination. At each RSA the patients were examined in supine and erect positions without corset. The translatory movements, induced by the change in position, of the 0.8 mm tantalum balls implanted into the fused vertebrae were calculated by computed data processing. These translations visualised the movements of the most proximal vertebra of the fusion in relation to the most distal. The present study has demonstrated the in vivo stability of lumbar fusion augmented with transpedicular screws to be adequate. Sagittal translation seems to be easier to elicit than movements along the other three-dimensional axes. A widely decompressed and destabilised vertebra without screw fixation increases the risk for persisting intervertebral translations. The RSA technique described seems to be a good way for comparing the in vivo behaviour of different implant systems

Background. Roentgen Stereophotogrammetric Analysis (RSA) represents nowadays an excellent solution for high-accuracy fixation measurement of UKAs. To date, to the best of our knowledge, no previous study has investigated long-term micromotions of a UKA using RSA. For this reason, the main purpose of the present study is to determine long-term implant fixation of 15 UKAs with all-poly tibial component using RSA at a mean 10-years follow-up. The secondary purpose was to investigate whether the progressive loss of implant's fixation correlates with a reduction of KSS scores. Methods. Fifteen non-consecutive patients with primary knee osteoarthritis received a UKA with an all-poly tibial component between January 1995 and April 2003 in the Authors' institution. Pre and post-operative KSS scores were recorded. RSA evaluation was performed on day 2 after surgery, than at 3, 6, and 12 months and yearly thereafter. The patients were evaluated with a mean follow-up of 10 years. Results. An increase of MTPM (Maximum Total Point Motion) values from 6 months to 1 year post-operatively was found respect to post-operative reference. Implants' displacement values were always less than 2 mm during the first 6 months, than two different trends were noticed in revised and non-revised implants. A linear and inverse correlation with statistical significance was found between MTPM and both clinical and functional KSS scores. Conclusion. Also in a long term follow up evaluation, RSA is an effective tool to predict functional results after an all-poly UKA

Objective: There is no non-invasive gold standard for measuring gap formation following rotator cuff repair; re-tears are reported both on MRI and Ultrasound. We present a novel RSA technique using a combination of 1mm tantalum beads and metal sutures to allow monitoring of gap formation following rotator cuff repair.

Methodology: We carried out ten open rotator cuff repairs with using trans-osseous sutures on patients with moderate to massive tears. During surgery RSA markers were inserted into the shoulder to allow postoperative monitoring of the repair. These markers took the form of 1mm RSA tantalum beads in the greater tuberosity, distal to the repair site, and three metal sutures in tendon, proximal to the repair site. Direct measurements of the distance between the markers each side of the repair were taken intra-operatively (T=O). RSA images were taken of the repair immediately postoperatively (T=1–2 hours), day 3, 2 weeks, 3 months and 1 year post-operatively. Ultrasound imaging was performed at the same intervals by consultant musculo-skeletal radiologists blinded to the RSA data.

Results: At the 3 month stage post-operatively RSA data shows an increase in the average gap between the 2 sets of markers, with considerable variation between patients (5mm to 19mm).

Conclusion: The results are highly suggestive of gap formation in the repair. The greatest increase in gap formation has been seen between 2 weeks and 3 months. During this time patients come out of their abduction arm sling and commence physiotherapy. It may be that due to excessive loading on the repair before it has fully healed has causes failure in some cases.

Introdution:

Over the last years research has focused on attempts to achieve better fixation in knee prosthesis by improving cementing techniques and prosthetic designs; thus prosthetic fixation is critical while loosening at the bone-cement interface is still an important matter for the orthopaedic surgeon.

Aims: To study prospectively the characteristic migration of four different cemented femoral stems using Radiostereometry. Methods: 96 patients undergoing cemented femoral hip replacement for osteoarthritis were randomised to receive an Exeter (Howmedica Stryker), Ultima Tapered Polished Stem [TPS], Ultima straight stem [USS] (Johnson and Johnson) or Charnley Elite (Depuy/Johnson and Johnson) stem. RSA migration measurements were performed postoperatively and at 6,12,18 and 24 months post surgery using the UMRSA system. Results: Two signiþcantly distinct patterns of distal migration in the y direction (subsidence) were seen, compatible with previous studies. Tapered stems subsided rapidly by six months, Exeter 0.85mm (±0.15) UTPS 0.85mm (±0.15), stabilising by 2 years, Exeter 1.3mm (±0.35), UTPS 1.2mm (±0.25). The USS and Elite designs showed lower migrations of 0.1mm (±0.1) and 0.15 (±0.15) mm at six and 0.25mm (±0.15) and 0.35mm (±0.15) at 24 months. For migrations and rotations in other directions, differences were seen between prostheses with the same design concept. Whilst both the UTPS and Exeter exhibited posterior migration of the head, by 24 months this was expressed as a rotation about the transverse axis for the TPS and the axial axis for the Exeter. The Elite and USS differed in rates of posterior migration and varus tilt. Conclusions: Patterns of migration for stems with the same design concept may vary due to subtle differences in prosthesis shape. These variations produce a distinct migration Ç signature È for each stem.

Introduction: In total knee arthroplasty (TKA) it remains a topic if cementless designs offer long-term stability equivalent to cemented procedures and if the components should be coated with calciumphosphate to enhance fixation. This study compares the three-dimensional migration patters of cemented and uncoated and periapatite (PA) coated tibial trays during a 2-year clinical follow-up study using roentgen stereophotogram-metric analysis (RSA) measurements as a predictor of long-term implant loosening (Ryds definition).

Methods: A double blind randomized prospective study was performed on 101 osteoarhtritic patients receiving 115 Duracon TKA. The tibial tray was either cemented (25), uncoated and uncemented (46) or PA-coated and uncemented (44). The groups were matched for sex, age, BMI and pre-op Insall score. Patients were evaluated at 1 week, 3, 6, 12 and 24 months post-operatively using standard radiographs and Insall scores. At each evaluation RSA measurements determined the translational (medial-lateral (ML), caudal-cranial (CC), anterior-posterior(AP)) and rotational (anterior tilt, external and valgus rotation) displacements of the tibial tray.

Results: Insall scores were not statistically different between the groups. Average component displacement was low for the cemented components in all directions. For the uncemented trays migration was highest in the CC direction (subsidence) and steep during the first 6 weeks. At two years the uncoated trays showed significantly more subsidence (−0.5 0.63 mm, range: −2.1 to 0.5 mm) than the cemented components (0.1 0.17 m, range: −0.2 to 0.4 mm, p< 0.05) and the PA-coated group (−0.1 0.60 mm, range: −2.8 to 0.3 mm, p< 0.05). Average subsidence of the cemented and PA-coated implants was nearly the same but variability was higher for the coated trays (p=0.01). Displacements in all other directions were not significantly different between the groups. Using Ryds definition, a total of 10 tibial trays from the cemented group (40%), 29 trays from the uncoated group (63%) and 11 trays from the PA-coated group (26%) were identified to be at risk for long-term loosening. In seven cases (all cemented) component tilt was critical.

Conclusion: At 2 years no clinical differences were found between cemented, uncoated and PA-coated tibial trays. However, RSA measurements showed significantly different migration patterns and predictions for long-term implant stability. Steep initial subsidence before stabilisation seems an inherent characteristics of uncemented fixation. In contrast, the cement layer below cemented trays can lead to AP tilt. Uncoated uncemented components migrate significantly indicating a high risk of late loosening. PA-coating reduces tray migration and the risk of long-term failure to levels equivalent to cemented fixation.

Introduction

The Accolade II taper stem incorporates design features which maximize proximal stem fit and bone contact and avoids more distal taper engagement which has been shown to be problematic. RSA was used in this study to analyze stem micromotion to 2 years post-surgery, providing an indication of long-term fixation. Pain, function and health-related quality of life were also compared before and after total hip arthroplasty (THA.)

We treated 34 patients with recurrent dislocation of the hip with a constrained acetabular component. Roentgen stereophotogrammetric analysis was performed to assess migration of the prosthesis. The mean clinical follow-up was 3.0 years (2.2 to 4.8) and the radiological follow-up was 2.7 years (2.0 to 4.8). At the latest review six patients had died and none was lost to follow-up. There were four acetabular revisions, three for aseptic loosening and one for deep infection. Another acetabular component was radiologically loose with progressive radiolucent lines in all Gruen zones and was awaiting revision. The overall rate of aseptic loosening was 11.8% (4 of 34). Roentgen stereophotogrammetric analysis in the non-revised components confirmed migration of up to 1.06 mm of translation and 2.32° of rotation at 24 months. There was one case of dislocation and dissociation of the component in the same patient. Of the 34 patients, 33 (97.1%) had no further episodes of dislocation. The constrained acetabular component reported in our study was effective in all but one patient with instability of the hip, but the rate of aseptic loosening was higher than has been reported previously and requires further investigation

Objectives

An important measure for the diagnosis and monitoring of knee osteoarthritis is the minimum joint space width (mJSW). This requires accurate alignment of the x-ray beam with the tibial plateau, which may not be accomplished in practice. We investigate the feasibility of a new mJSW measurement method from stereo radiographs using 3D statistical shape models (SSM) and evaluate its sensitivity to changes in the mJSW and its robustness to variations in patient positioning and bone geometry.

Aims. Short, bone-conserving femoral components are increasingly used in total hip arthroplasty (THA). They are expected to allow tissue-conserving implantation and to render future revision surgery more straightforward but the long-term data on such components is limited. One such component is the global tissue-sparing (GTS) stem. Following the model for stepwise introduction of new orthopaedic implants, we evaluated early implant fixation and clinical outcome of this novel short-stem THA and compared it to that of a component with established good long-term clinical outcome. Methods. In total, 50 consecutive patients ≤ 70 years old with end-stage symptomatic osteo-arthritis were randomized to receive THA with the GTS stem or the conventional Taperloc stem using the anterior supine intermuscular approach by two experienced hip surgeons in two hospitals in the Netherlands. Primary outcome was implant migration. Patients were followed using routine clinical examination, patient reported outcome using Harris Hip Score (HHS), Hip Disability And Osteoarthritis Outcome Score (HOOS), EuroQol five-dimension questionnaire (EQ5D), and Roentgen Stereophotogrammetric Analysis (RSA) at three, six, 12, and 24 months. This study evaluated the two-year follow-up results. Results. In addition to the initial migration pattern of distal migration (subsidence, Y-translation) and retroversion (Y-rotation) also exhibited by the Taperloc stem, the GTS stem showed an initial migration pattern of varization (X-translation combined with Z-rotation) and posterior translation (Z-translation). However, all components stabilized aside from one Taperloc stem which became loose secondary to malposition and was later revised. Clinical outcomes and complications were not statistically significantly different with the numbers available. Conclusion. A substantially different and more extensive initial migration pattern was seen for the GTS stem compared to the Taperloc stem. Although implant stabilization was achieved, excellent long-term survival similar to that of the Taperloc stem should not be inferred. Especially in the absence of clinically proven relevant improvement, widespread usage should be postponed until long-term safety has been established. Cite this article: Bone Joint J 2020;102-B(6):699–708

We performed a clinical and radiological study to determine the rate of failure of the Charnley Elite-Plus femoral component. Our aim was to confirm or refute the predictions of a previous roentgen stereophotogrammetric analysis study in which 20% of the Charnley Elite-Plus stems had shown rapid posterior head migration. It was predicted that this device would have a high early rate of failure. We examined 118 patients at a mean of nine years after hip replacement, including the 19 patients from the original roentgen stereophotogrammetric study. The number of revision procedures was recorded and clinical and radiological examinations were performed. The rate of survival of the femoral stems at ten years was 83% when revision alone was considered to be a failure. It decreased to 59% when a radiologically loose stem was also considered to be a failure. All the patients previously shown in the roentgen stereophotogrammetric study to have high posterior head migration went on to failure. There was a highly significant difference (p = 0.002) in posterior head migration measured at two years after operation between failed and non-failed femoral stems, but there was no significant difference in subsidence between these two groups. Our study has shown that the Charnley Elite-Plus femoral component has an unacceptably high rate of failure. It confirms that early evaluation of new components is important and that roentgen stereophotogrammetric is a good tool for this. Our findings have also shown that rapid posterior head migration is predictive of premature loosening and a better predictor than subsidence