Introduction & aims. The magnitude and pattern of acceptable migration in clinically successful cementless stems is not well understood. Radiostereometric analysis (RSA) is a well-recognised method of assessing implant migration. Previous studies have reported long term RSA results for cemented stems. The aim of this study was to assess the long-term migration characteristics of the Corail hydroxyapatite-coated cementless stem at 10 years using RSA. Method. A prospective cohort of 30 patients undergoing primary total hip arthroplasty for primary hip osteoarthritis were enrolled into a study to characterise the migration behaviour of a cementless stem. Tantalum markers were attached to the stem and placed in the bone intraoperatively, allowing for RSA measurements to be taken in vivo. Previous 5-year results have been presented. A total of 14 patients (total 15 hips, one bilateral) with mean age 82 years (range, 69–92 years) underwent repeat long-term RSA radiographs at minimum 10 years post op. The mean time to follow up was 13.9 years (range, 13.3–14.4 years). The RSA radiographs were analysed to assess for implant rotation and translation. Results. None of the 14 patients (15 hips) followed up have been revised. The migration (rotation and translation) at 6 months, 1 year, 2 years, and 6 years has been described previously. No stems had additional subsidence of more than 0.25 mm between 6 months and 6 years. The resultant mean subsidence between 2 years and 6 years was 0.03 mm, which is below the limit measurable by RSA. The long-term, 10-year results, on implant rotation and translation will be presented. Conclusions. The Corail stem exhibited variable subsidence within the first 6 months after which there is persistent stabilisation through to 6 years. 10-year results on long-term migration show no further migration. These results can be used as a gold standard for other uncemented stems

Introduction: The aim of this study was to evaluate the in vivo migration patterns using EBRA-FCA of a consecutive series of polished femoral components cemented line-toline.

Materials and Methods: Between January 1988 and December 1989, 164 primary total hip arthroplasties were performed in 155 patients. The mean age at the time of the index arthroplasty was 63.8 ± 11.6 years. A single design prosthesis was used combining an all-polyethylene socket and a 22.2 mm femoral head. The mono-block double tapered (5.2°) femoral component made of 316-L stainless steel had a highly polished surface (Ra = 0.04 μm) and a quadrangular section(Kerboull^® MKIII, Stryker). The femoral preparation included removal of diaphyseal cancellous bone to obtain primary rotational stability of the stem prior to the line-to-line cementation. For each patients, all available AP radiographs of the pelvis were digitized (Vidar Sierra Plus, Vidar System Corporation, Herdon, Virginia) and linked to an IMB-compatible computer. The EBRAFCA software is a validated method designed to assess migration of a femoral component through comparable pairs of radiographs.

Results: At the minimum 15-year follow-up, 73 patients (77 hips) were still alive and had not been revised at a mean of 17.3 ± 0.8 years (15–18 years), 8 patients (8 hips) had been revised for high polyethylene wear associated with periacetabular osteolysis, 66 patients (69 hips) were deceased, and 8 patients (10 hips) were lost to follow-up. Among the 8 revision procedures, the femoral component was loose in 3 hips. A total of 1689 radiographs (mean 10.3 per hip) were digitized. At the last follow-up, the mean subsidence of the entire series was 0.63 ± 0.49 mm (median of 0.61 mm; range 0 to 1.94 mm). When using a 1.5 mm threshold (accuracy of the EBRAFCA method) for subsidence, 4 of the 142 stems with adequate EBRA-FCA data were considered to have migrated. Using a threshold of 2 mm for subsidence, none of the 142 stems were considered to have migrated. The patterns of migration were calculated every 2 years giving 9 intervals. The evolution of mean subsidence during the whole follow-up period remained below 1.5 mm.

Discussion: Mean subsidence of this quadrangular highly polished femoral component remained below the accuracy of the method (± 1.5 mm) throughout the entire follow-up period. Of the 142 hips analyzed, only four (2.8%) had subsided of more than 1.5 mm and none more than 2 mm. This study demonstrates that contrary to other cemented femoral components that have provided excellent survival in the long term frequently associated with stem subsidence, a highly polished cemented double tapered femoral component with a quadrangular cross-section cemented line to line does not subside up to 18-year follow-up.

This single-blinded randomised controlled trial investigated whether one design of mobile-bearing (MB) total knee replacement (TKR) has any advantage over a fixed-bearing (FB) design on long-term fixation as measured by radiostereometry. The amount of wear underneath the mobile bearing was also evaluated. A series of 42 knees was randomised to MB or FB tibial components with appropriate polyethylene inserts and followed for between ten and 12 years, or until the death of the patient. The polyethylene in the MB group was superior in that it was gamma-irradiated in inert gas and was calcium-stearate free; the polyethylene in the FB group was gamma-irradiated in air and contained calcium stearate. In theory this should be advantageous to the wear rate of the MB group. At final follow-up the overall mean migration was 0.75 mm (sd 0.76) in the MB group and 0.66 mm (sd 0.4) in the FB group, with the FB group demonstrating more posterior tilt and the MB group more internal rotation. In the FB group there was one revision for aseptic loosening, but none in the MB group. There were no significant differences in clinical or radiological scores.

For the MB group, the mean linear wear rate on the under-surface was 0.026 mm/year (sd 0.014). This was significantly smaller than the wear rate of 0.11 mm/year (sd 0.06) in the MB between femur and polyethylene (p < 0.001). Nevertheless, even in a best-case setting the mobile bearings of this TKR design had no apparent advantage in terms of fixation over the FB knee prosthesis at ten to 12 years. The wear underneath the mobile bearing was small and is unlikely to be clinically relevant.

Aims. Early implant migration measured with radiostereometric analysis (RSA) has been proposed as a useful predictor of long-term fixation of tibial components in total knee arthroplasty. Evaluation of actual long-term fixation is of interest for cemented components, as well as for cementless fixation, which may offer long-term advantages once osseointegration has occurred. The objective of this study was to compare the long-term migration with one- and two-year migration to evaluate the predictive ability of short-term migration data and to compare migration and inducible displacement between cemented and cementless (porous metal monoblock) components at least ten years postoperatively. Patients and Methods. Patients who had participated in RSA migration studies with two-year follow-up were recruited to return for a long-term follow-up, at least ten years from surgery. Two cemented tibial designs from two manufacturers and one porous metal monoblock cementless tibial design were studied. At the long-term follow-up, patients had supine RSA examinations to determine migration and loaded examinations (single leg stance) to determine inducible displacement. In total, 79 patients (54 female) returned, with mean time since surgery of 12 years (10 to 14). There were 58 cemented and 21 cementless tibial components. Results. Migration at one year and two years was significantly correlated with long-term migration (p < 0.001). Median migration at the long-term follow-up was 0.6 mm (maximum total point motion; interquartile range (IQR) 0.4 to 0.9) for the cemented group and 0.6 mm. (IQR 0.3 to 1.1) for the cementless group with no difference between groups (p = 0.99). Inducible displacement was significantly lower for the cementless components (p < 0.001). Conclusion. Long-term migration was strongly correlated with two-year migration. Although long-term migration was not different for cemented or cementless tibial components, inducible displacement at the long-term visit was significantly lower for these cementless components, suggesting superior fixation. These findings support the predictive value of short-term migration in determining long-term fixation. Cite this article: Bone Joint J 2019;101-B(7 Supple C):55–60

Aims. Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes. Methods. A total of 28 patients received one-stage bilateral primary THA with cementless femoral stems (56 hips). They were randomized to compaction on one femur and broaching on the contralateral femur. Overall, 13 patients were lost to the ten-year follow-up leaving 30 hips to be evaluated in terms of stem migration (using radiostereometry), radiological changes, Harris Hip Score, Oxford Hip Score, and complications. Results. Over a mean follow-up period of 10.6 years, the mean stem subsidence was similar between groups, with a mean of -1.20 mm (95% confidence interval (CI) -2.28 to -0.12) in the broaching group and a mean of -0.73 mm (95% CI -1.65 to 0.20) in the compaction group (p = 0.07). The long-term migration patterns of all stems were similar. The clinical and radiological outcomes were similar between groups. There were two intraoperative fractures in the compaction group that were fixed with cable wire and healed without complications. No stems were revised. Conclusion. Similar stem subsidence and radiological and clinical outcomes were identified after the use of compaction and broaching techniques of the femur at long-term follow-up. Only the compaction group had intraoperative periprosthetic femur fractures, but there were no long-term consequences of these. Cite this article: Bone Jt Open 2021;2(12):1035–1042

Introduction. Cementless fixation in total knee arthroplasty has been proposed to offer advantages long-term once osteointegration has occurred as there is no substrate between the implant and the bone to fail. Radiostereometric analysis (RSA) is a useful tool to study fixation, but typically focused on early migration in the first two post-operative years. Few studies have looked at 10-year RSA migration in cementless fixation and those that have contain small numbers of subjects. The objective of this study was to compare implant migration and inducible displacement between cemented and cementless TKA at 10 years and to compare the 10-year migration to the 2-year data in an effort to validate the predictive modelling of RSA. Methods. Subjects who had previously participated in RSA migration studies with 2-year follow-up were recruited to return for a long-term follow-up exam, at least 10 years from their surgery. The implants under study included two cemented designs from two manufacturers and one porous metal monoblock cementless design. At the 10-year visit, subjects had supine RSA exams to determine long-term migration as well as a loaded exam (single leg stance) to determine inducible displacement. Differences between cemented and cementless groups were evaluated with the Mann Whitney U test and Spearman's rank correlation coefficients were calculated for early and late migrations. Significance was set at p < 0.05. Results. Seventy-five subjects were available for long-term follow-up, with average time since surgery of 12 years. This cohort contained 51 women and 24 men with cemented tibial components in 53 cases (37 female) and cementless tibial components in 22 cases (14 female). At the time of surgery, the subjects were 62±7 years old with BMIs of 33±6 m/kg2 (mean±standard deviation). Median migration at the long-term follow-up was 0.6 mm (MTPM; range 0.2–2.8 mm) and was not different between the cemented and cementless groups (p = 0.9, Mann Whitney U Test). Inducible displacement at 10 years was significantly lower for the cementless implants (p<0.001, Figure 1). Migration at one, two, and 10 years did not correlate with inducible displacement at 10 years. However, migration at one year and two years did correlate with long-term migration, with the strongest correlation at two years (Spearman's rank correlation coefficient for all components = 0.74, p < 0.001, Figure 2). Conclusion. Although long-term migration was not different for cemented or cementless (porous metal monoblock) tibial components, inducible displacement at the 10-year visit was significantly lower for these cementless components, suggesting superior fixation. Additionally, long-term migration was strongly correlated to two-year migration, regardless of fixation. These findings support the predictive value of short-term migration in determining long-term fixation. For any figures or tables, please contact authors directly

Aims. To compare the in vivo long-term fixation achieved by two acetabular components with different porous ingrowth surfaces using radiostereometric analysis (RSA). Methods. This was a minimum ten-year follow-up of a prospective randomized trial of 62 hips with two different porous ingrowth acetabular components. RSA exams had previously been acquired through two years of follow-up. Patients returned for RSA examination at a minimum of ten years. In addition, radiological appearance of these acetabular components was analyzed, and patient-reported outcome measures (PROMs) obtained. Results. In all, 15 hips were available at ten years. There was no statistically significant difference in PROMS between the two groups; PROMs were improved at ten years compared to preoperative scores. Conventional radiological assessment revealed well-fixed components. There was minimal movement for both porous surfaces in translation (X, Y, Z, 3D translation in mm (median and interquartile range (IQR)), StikTite (Smith and Nephew, Memphis, Tennessee, USA): 0.03 (1.08), 0.12 (0.7), 0.003 (2.3), 0.37 (0.30), and Roughcoat (Smith and Nephew): -0.6 (0.59),–0.1 (0.49), 0.1 (1.12), 0.48 (0.38)), and rotation (X, Y, Z rotation in degrees (median and IQR), (Stiktite: -0.4 (3), 0.28 (2), -0.2 (1), and Roughcoat: - 0.4 (1),–0.1 (1), 0.2 (2)). There was no statistically significant difference between the two cohorts (p-value for X, Y, Z, 3D translation - 0.54, 0.46, 0.87, 0.55 and for X, Y, Z rotation - 0.41, 0.23, 0.23 respectively) at ten years. There was significant correlation between two years and ten years 3D translation for all components (r = 0.81(p =< 0.001)). Conclusion. Both porous ingrowth surfaces demonstrated excellent fixation on plain radiographs and with RSA at ten years. Short-term RSA data are good predictors for long-term migration data

Aims

Limited implant survival due to aseptic cup loosening is most commonly responsible for revision total hip arthroplasty (THA). Advances in implant designs and materials have been crucial in addressing those challenges. Vitamin E-infused highly cross-linked polyethylene (VEPE) promises strong wear resistance, high oxidative stability, and superior mechanical strength. Although VEPE monoblock cups have shown good mid-term performance and excellent wear patterns, long-term results remain unclear. This study evaluated migration and wear patterns and clinical and radiological outcomes at a minimum of ten years’ follow-up.

Aims

Both the femoral and tibial component are usually cemented at revision total knee arthroplasty (rTKA), while stems can be added with either cemented or press-fit (hybrid) fixation. The aim of this study was to compare the long-term stability of rTKA with cemented and press-fitted stems, using radiostereometric analysis (RSA).

The design philosophy of polished tapered total hip replacements (THR), such as the Exeter, intends for them to migrate distally within the cement mantle. As well as migration, dynamically induced micromotion (DIMM) occurs as a result of functional activity between the implant and the cement. The aim of the current study was to develop and validate a finite element (FE) model of the Exeter/cement/bone system which can be used to predict DIMM and investigate the stresses induced in the cement mantle during functional activity. In the context of the current study, DIMM is defined as the displacement of the implant component relative to the bone when moving from double leg stance to single leg stance on the operated limb. Using Roentgen Stereo-photogrammetric Analysis (RSA), DIMM was measured in 21 patients implanted with Exeter stems 3 months post-operatively. A previous study, using a reduced FE model of the Exeter stem and the surrounding cement mantle focused on the solution of the contact problem at the stem-cement interface. It was demonstrated that sliding contact combined with Coulomb friction and an appropriate parameter setting could be used to predict DIMM of a polished tapered stem. For the purposes of the current study, the previous simple model was incorporated into the FE model of the Muscle Standardised Femur and validated against the RSA measurements for DIMM. For the current extended model, loading included muscle forces representing all active muscles acting on the femur. The effect of initial cement stresses and interdigitation was also considered. The Exeter stem demonstrated significant DIMM (p< 0.017). The FE model, accounting for sliding contact at the cement–implant interface was able to predict similar distal migration of the head and the tip. The results of both the calculations and the measurements showed that the femoral head moves medially, distally and posteriorly relative to the bone. In the cement mantle, maximum principal stresses were oriented circumferentially, minimum principal stresses were oriented radially. When the taper got engaged, submicroscopic movements which did not recover following unloading still took place and accumulated. The results of the present study showed that it is possible to measure DIMM in the Exeter stem and combine this with FE modelling of the contact mechanism. Future studies will include various activities, such as walking or stair climbing. Based on accumulated submicroscopic movements, short-, mid- or long-term migration patterns will be predicted

Cementless knee arthroplasty has seen a recent resurgence in popularity due to conceptual advantages, including improved osseointegration providing biological fixation, increased surgical efficiency, and reduced systemic complications associated with cement impaction and wear from cement debris. Increasingly younger and higher demand patients are requiring knee arthroplasty, and as such, there is optimism cementless fixation may improve implant survivorship and functional outcomes.

Compared to cemented implants, the National Joint Registry (NJR) currently reports higher revision rates in cementless total knee arthroplasty (TKA), but lower in unicompartmental knee arthroplasty (UKA). However, recent studies are beginning to show excellent outcomes with cementless implants, particularly with UKA which has shown superior performance to cemented varieties. Cementless TKA has yet to show long-term benefit, and currently performs equivalently to cemented in short- to medium-term cohort studies. However, with novel concepts including 3D-printed coatings, robotic-assisted surgery, radiostereometric analysis, and kinematic or functional knee alignment principles, it is hoped they may help improve the outcomes of cementless TKA in the long-term. In addition, though cementless implant costs remain higher due to novel implant coatings, it is speculated cost-effectiveness can be achieved through greater surgical efficiency and potential reduction in revision costs. There is paucity of level one data on long-term outcomes between fixation methods and the cost-effectiveness of modern cementless knee arthroplasty.

This review explores recent literature on cementless knee arthroplasty, with regards to clinical outcomes, implant survivorship, complications, and cost-effectiveness; providing a concise update to assist clinicians on implant choice.

Cite this article: Bone Jt Open 2021;2(1):48–57.

Aims

The aim of this study was to evaluate the long-term inducible displacement of cemented tibial components ten years after total knee arthroplasty (TKA).

The Exeter femoral stem is a double-tapered highly polished collarless cemented implant with good long-term clinical results. In order to determine why the stem functions well we have undertaken a long-term radiostereometric analysis (RSA) study.

A total of 20 patients undergoing primary Exeter total hip replacement for osteoarthritis using the Hardinge approach were recruited and followed with RSA for ten years. The stems progressively subsided and internally rotated with posterior head migration. The mean subsidence was 0.7 mm (95% confidence interval (CI) 0.5 to 0.9) at two years and 1.3 mm (95% CI 1.0 to 1.6) at ten years. The mean posterior migration of the head was 0.7 mm (95% CI 0.5 to 0.9) at two years and 1.2 mm (95% CI 1.0 to 1.4) at ten years. There was no significant cement restrictor migration.

The Exeter stem continues to subside slowly into the cement mantle in the long term. This appears to compress the cement and the cement bone interface, contributing to secure fixation in the long term.

Cite this article: Bone Joint J 2013;95-B:605–8.

This study explored the relationship between the initial stability of the femoral component and penetration of cement into the graft bed following impaction allografting.

Impaction allografting was carried out in human cadaveric femurs. In one group the cement was pressurised conventionally but in the other it was not pressurised. Migration and micromotion of the implant were measured under simulated walking loads. The specimens were then cross-sectioned and penetration of the cement measured.

Around the distal half of the implant we found approximately 70% and 40% of contact of the cement with the endosteum in the pressure and no-pressure groups, respectively. The distal migration/micromotion, and valgus/varus migration were significantly higher in the no-pressure group than in that subjected to pressure. These motion components correlated negatively with the mean area of cement and its contact with the endosteum.

The presence of cement at the endosteum appears to play an important role in the initial stability of the implant following impaction allografting.

We undertook a review of the literature relating to the two basic stem designs in use in cemented hip replacement, namely loaded tapers or force-closed femoral stems, and the composite beam or shape-closed designs. The associated stem fixation theory as understood from in vitro studies and finite element modelling were examined with reference to the survivorship results for each of the concepts of fixation.

It is clear that both design principles are capable of producing successful long-term results, providing that their specific requirements of stem metallurgy, shape and surface finish, preparation of the bone and handling of the cement are observed.