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Purpose Clinical and radiographic findings are of little value in the diagnosis of hip endoprothesis loosening. Refined contrast and radionuclide arthrographic techniques are more precise in predicting endoprothesis loosening. Here we compare both techniques with respect to the surgical result. Material and methods 68 patients with hip pain after various arthroplasty procedure were investigated by clinical examination, X-ray, DSAr and AS. Surgical proof was obtained in 73.5%. Results An acetabular component loosening was detected in 89% by DSAr and in 86% by AS with a specificity for both methods of 93%. The femoral component loosening was seen with a sensitivity of 89% by DSAr and 100% by AS, respectively. Specificity of DSAr in the femoral compartment was 94%, of AS 88%. Conclusions DSAr and AS are useful tools in the diagnosis of hip endoprothesis loosening and in planning surgical treatment. Both methods are comparable concerning the acetabular component, whereas AS is more sensitive in detecting femoral stem loosening. Combination of both methods is not recommended for routine diagnosis.

Combined contrast and radionuclide arthrography was performed in 71 cemented, non-cemented and hybrid hip arthroplasties for diagnosis of component loosening. In 31 cases, either one or two prosthesis components were clearly loose upon clinical and radiological diagnosis, with subsequent intraoperative confirmation. The other 40 cases had doubtful component loosening, with discrepancy between clinical and radiological findings, and were investigated for clarification. Contrast and radionuclide arthrograms were compared with sequential plain radiographs and their ability to indicate component loosening was evaluated. The combined contrast and radionuclide arthrograms proved in 90.9% of the cases whether a loose component existed as confirmed by intraoperative findings. They had a high sensitivity, specificity and predictive accuracy for both the acetabular and the femoral component. Sensitivity and predictive accuracy were remarkably precise in comparison to those of plain radiographs on the acetabular side. In nearly all patients with contradictory clinical and radiological findings, conclusive diagnosis was possible on the basis of the contrast and radionuclide arthrograms. Coinciding positive results in both contrast and radionuclide arthrograms were verified in each operated case. The combination of contrast and radionuclide arthrography is an useful method to diagnose doubtful loosening of hip arthroplasty components, especially in addition to routine sequential plain radiographs.

An analysis of sequential plain radiographs (XR), radionuclide arthrography, (RNA), and radiographic arthrography (RGA) was performed to determine the efficacy and usefulness of each study in the diagnosis of loosening of prosthetic hip components. Over a 2-year period, 65 hip prostheses were assessed before operation using each type of study; these results were compared to the intraoperative assessment of the status of the components. Of the three studies, sequential plain radiographs were overall the most accurate, sensitive, and specific. Radionuclide arthrography was of no use on the acetabular side but quite useful on the femoral side, especially in cases with only minimal femoral component loosening. Radiographic arthrography was overall the least accurate or sensitive of the three studies performed.

Background Radionuclide arthrography (RNA) is an established technique in the evaluation of hip prostheses but there is scant literature on its role in knee prostheses and no data specifically related to unicompartmental knee prostheses. We reviewed our experience with radionuclide arthrography in total (TKRs) and unicompartmental (UKRs) knee arthroplasties. Methods A retrospective review of 66 consecutive RNA studies that either had direct surgical correlation or arthroscopic assessment in conjunction with at least 12 months of clinical and radiological follow-up. These formed the basis of our case note review. 26 studies had a confirmed diagnosis of prosthetic loosening. Results By using standardised criteria for diagnosis and an early and late imaging protocol at 30 min and 4 h, RNA had an overall sensitivity of 88% and a specificity of 88% for the diagnosis of prosthetic loosening. The individual sensitivities and specificities were 93% and 86% for TKRs and 82% and 92% for UKRs. The technique was unable to detect femoral component loosening unless a long femoral stem was present, although only 8% of episodes of prosthetic loosening did not involve the tibial component. Conclusion Radionuclide arthrography should be considered as a useful diagnostic test for the evaluation of loosening of the tibial component of knee prostheses but requires early and late imaging and close attention to detail to achieve optimal results.

An analysis of plain radiographs, digital subtraction arthrography, and radionuclide arthrography was performed in 25 revision hip arthroplasties to evaluate the efficacy and usefulness of these methods in the diagnosis of loosening. The findings by each method were compared with intraoperative assessment of the status of components and expressed in terms of sensitivity, specificity, and predictive accuracy. Overall accuracy for the acetabular component by plain radiographs was 80%; by digital subtraction arthrography, 88%; by radionuclide arthrography, 68%. Overall accuracy for the femoral component by plain radiographs was 92%; by digital subtraction arthrography, 84%; radionuclide arthrography, 76%. We consider subtraction arthrography and radionuclide arthrography to be adjuvant diagnostic tools which may be indicated in individual cases of suspected implant loosening of total hip arthroplasty. The routine use of these two methods is not warranted when compared to plain radiographs. In 25 Fällen von Revisionsoperationen von Hüftgelenksersatz wurden Röntgenbilder, digitale Subtraktionsarthrographien und Radionuklidarthrographien analysiert, um die Effizienz dieser Methoden hinsichtlich der Diagnose von Implantatlockerungen festzustellen. Die Ergebnisse der drei genannten radiologischen Untersuchungsmethoden wurden mit der intraoperativ festgestellten Implantatstabilität verglichen. Es wurde die Sensitivität, Spezifität und die Vorhersagegenauigkeit für alle drei Methoden bestimmt. Die Vorhersagegenauigkeit für die acetabulären Komponenten betrug 80% für Röntgenbilder, 88% für digitale Subtraktionsarthrographien und 68% für Radionuklidarthrographien. Die Vorhersagegenauigkeit für die femoralen Komponenten betrug 92% für Röntgenbilder, 84% für digitale Subtraktionsarthrographien und 76% für Radionuklidarthrographien.Wir sehen in der Subtraktionsarthrographie und der Radionuklidarthrographie adjuvante diagnostische Mittel, welche im Einzelfall bei fraglich gelockerten Implantaten indiziert sind. Als Routinemassnahme scheinen diese beiden Methoden im Vergleich zu einfachen Röntgenbildern aber nicht indiziert zu sein.

Worldwide, millions of total hip and knee replacements are inserted every year and new designs are introduced continuously, sometimes with catastrophic results. In 1995, Henrik Malchau (Malchau 1995) presented an algorithm for optimal introduction of new implants. The algorithm was based on 15 years of clinical research including the Swedish Hip Arthroplasty project and the development of radiostereometric analysis (RSA) to evaluate implant fixation. Bengt Mjoberg, one of the pioneers of RSA, used implant migration as detected by RSA to define loosening (Mjoberg 1986, 1991). He compared contrast and radionuclide arthrography, bone scintimetry, and RSA and concluded that RSA was the most sensitive method for detection of loosening. He also noted that implant migration over time was more sensitive for detection of loosening than prevocational investigations with RSA. He suggested that mechanical loosening should be defined as early migration after the operation. 10 years later, sufficiently large patient materials were available to study the clinical relevance of early implant migration measured with RSA (Karrholm et al. 1994, Ryd et al. 1995). These 2 studies evaluated the predictive value of early migration for the risk of subsequent revision of a cemented matte stem and different designs of tibial components. The hypothesis that early migration could be used as a surrogate variable for clinically relevant loosening was confirmed. These findings were supported by observations of a high degree of early migration for certain implant designs, which after longer follow-up showed high clinical failure rates (Mogensen et al. 1982, Snorrason and Karrholm 1990, Thanner et al. 1995). Further development of the RSA technique enabled measurement of stem/cement interface motion, which was necessary to understand the behavior of polished stems and the failure patterns of stems with a rough surface. Polished stems showed continuous subsidence inside the cement mantle and, early after implantation, a magnitude of migration well above what was acceptable for a cemented stem with matte or rough surface. Even though polished stems may subside substantially more than matte or rough ones, there is also an upper limit for polished stems being well above the average value for the specific stem studied (Nieuwenhuijse et al. 2012). Pioneer studies of early designs of uncemented prostheses with smooth surfaces that were not designed for biological fixation showed high degrees of early migration, but at that time the clinical implications of this finding were not always understood (Wykman et al. 1988). Uncemented implants should preferably not migrate at all, but many designs still do. Wolf et al. (2010) reported a mean subsidence of 1.7 mm after 5 years for the clinically well-documented CLS stem. Most of this subsidence probably occurred within 1 year, which appears to be the maximum time limit for migration of cementless stems to not result in fibrous fixation or loosening. Thus, the upper limit and time frame for acceptable early migration vary depending on several factors such as type of implant and type of fixation, and also other circumstances such as whether bone graft has been used. For some types of implant with several interfaces such as cemented stems and modular implant designs, motion may occur at different interfaces, which makes interpretation of migration data complicated. With these concerns in mind, it is gratifying that the 2 papers by Piljs et al. (2012a,b) in this issue of Acta Orthopaedica show that acceptable migration during the first postoperative year of the tibial component in total knee replacement and during the first 2 postoperative years of acetabular cups stays within 0.2–0.5 mm depending on the implant type studied and the migration parameter used (MTPM, proximal migration). These studies also established an unacceptable upper limit of 1.6 mm migration at 1 year for tibial components and 1 mm at 2 years for cups. This magnitude of unacceptable cup migration confirms earlier observations of the Lubinus SP1 stem, where the upper limit of acceptable subsidence was 1 mm (Karrholm et al. 1994). It should be emphasized that these limits are based on revision rates within 5 or 10 years. With longer follow-up and inclusion of younger and more active patients, these limits should probably be adjusted downwards. Some implants such as cemented polished stems and many designs of uncemented stems might tolerate subsidence of about 1 mm, and occasionally more during the first year. In these cases, migration between 1 and 2 years and even up to 3 years might have a predictive value. Some cemented stems with a comparatively rough surface such as the Spectron EF Primary stem may occasionally destabilize in the cement mantle after the first 2 years, and there may be also other designs that require longer follow-up before a reliable prediction of long-term performance can be made. Better knowledge is needed for interpretation of the clinical significance of early migration of different implant designs. According to our current understanding, there is no doubt that migration below or just above the detection level of RSA is a good prognostic sign concerning risk for clinical loosening, even if many types of implant can tolerate higher levels of early migration. Loosening and wear are 2 important reasons for failure, which can be predicted with RSA, but failure of total joint replacements may have many other causes. Modern surface replacements may fail because of fracture, synovitis, pseudotumors, and high metal ion levels. The ASR design, now withdrawn from the market because of a high frequency of fractures and build-up of wear debris, showed good early fixation—illustrating that methods other than RSA are necessary to detect failure mechanisms (Penny et al. 2012). Some patients are dissatisfied for unknown reasons. However, the absence of implant-related complications is a prerequisite for good long-term outcome. Despite the fact that the algorithm for introduction of new implant designs was established more than 15 years ago, new and unproven prostheses still find their way onto the market too quickly. Some of them have been used extensively without having passed all the steps in the stair of optimal introduction, and have resulted in large-scale failures. Today, most of the commonly used implants, which are suitable for most of our patients, have an outstanding track record that new implants must compete with. These new designs often have inferior—or at best equal—performance to contemporary standards. The growing evidence that measurement of early implant migration is one of the ways of avoiding large-scale failures reminds us that all new implants should be studied in this way, as part of a stepwise introduction. Fast spread of undocumented new implants should be part of orthopedic history.

UNLABELLED Interpretation of radionuclide arthrograms (RNA) of the knee after total knee joint replacement (TKR) may be difficult because of the lack of sufficient anatomic reference information. Additional transmission images may provide the necessary reference information required for correct interpretation of RNA of the knee. METHODS Tc-99m tin colloid (20 MBq) RNA was combined with cobalt-57 transmission imaging in six patients with painful TKRs in whom loosening of the TKR was suspected. Knee surgery was then performed on these six cases. RESULTS RNA correctly detected loosening of the tibial component in five of six cases, but did not detect loosening of the femoral component in any of three cases. CONCLUSION RNA combined with transmission imaging is recommended for detection of loosening of the tibial component of a TKR. RNA may not be of value for detecting loosening of the femoral component.

A 64-year-old woman had an acutely painful, swollen right calf. A Tc-99m labeled RBC venogram performed to rule out deep vein thrombosis in the right lower leg showed an area devoid of radioactivity in the medial posterior aspect of the right calf. Rupture of a popliteal cyst was suspected. A radionuclide arthrogram and subsequent surgery confirmed the diagnosis.

Radionuclide arthrography has been found to be valuable in the diagnosis of a loose hip prosthesis. The appearance of one normal case with no loosening and two abnormal cases with loosening of femoral and acetabular components are described. To diagnose this difficult problem, radionuclide arthrography should be used more frequently.