Migration measurement of the cemented Lubinus SP II hip stem - a 10-year follow-up using radiostereometric analysis

Mid-Term Migration Pattern of a Cemented Collared Anatomical Stem-A Retrospective Study Using EBRA-FCA

Background: Aseptic loosening is one of the leading causes of stem revision. Einzel Bild Röntgen Analyse-Femoral Component Analysis allows for the detection of distal stem migration, which is used as a predictive factor for implant longevity. This study aims to demonstrate the migration behavior of a cemented collared anatomical stem. Methods: This study retrospectively examined all patients who received a cemented Lubinus SP II stem (Waldemar Link, Hamburg, Germany) between 2003 and 2019. We used the EBRA-FCA software (University of Innsbruck, Austria) to determine the migration patterns and thoroughly examined the patients' medical histories. In addition, the potential influence of femoral configuration and BMI on the migration behavior was assessed. Results: This study included 61 patients (48 females and 13 males) with a total of 61 stems that met our inclusion criteria. The mean age at surgery was 76 years (ranging from 30 to 93 years). According to EBRA-FCA migration analysis, a median subsidence of 0.7 mm was observed at 24 months and at the final follow-up (median 78 months). Distal stem migration was significantly higher at the 6-month time point in patients with Dorr type A femurs compared to Dorr type B femurs (p = 0.016). Body mass index (BMI) had no significant effect on stem migration. Conclusions: The measured subsidence of the Lubinus SP 2 stem using EBRA-FCA was below established thresholds, indicating excellent long-term outcomes. Although there was significantly increased subsidence in Dorr type A femurs during the initial 6 months, thereafter, no statistically significant difference was observed compared to Dorr type B femurs.

Experience of an anatomic femoral stem in a UK orthopaedic centre beyond 20 years of follow-up

INTRODUCTION

Increasing interest in the use of anatomical stems has developed as the prevalence of periprosthetic fractures (PPFs) continues to increase. The primary aim of this study was to determine the long-term survivorship and PPF rate of an anatomical femoral stem in a single UK centre.

PATIENTS AND METHODS

Between 2000 and 2002, 94 consecutive THAs were performed using the 170 mm Lubinus SP II anatomical femoral stem in our institution. Patient demographics, operative details and clinical outcomes were collected prospectively in an arthroplasty database. Patient records and national radiographic archives were reviewed finally at a mean of 21.5 years (SD 0.7) following surgery to identify occurrence of subsequent revision surgery, dislocation or periprosthetic fracture.

RESULTS

Mean patient age at surgery was 65.8 years (SD 12.5, 34-88 years). There were 48 women (51%). Osteoarthritis was the operative indication in 88 patients (94%). Analysis of all-cause THA failure demonstrated a survivorship of 98.5% (95% confidence interval [CI], 98.0-99.3%) at 10 years and 96.7% (94.5-98.9%) at 21 years. The 20-year stem survival for aseptic loosening was 100% with no cases of significant lysis found (lucent line > 2 mm) and no stems required revision. Patient demographics did not appear to influence risk of revision (p > 0.05). There were 2 revisions in total (2 for acetabular loosening with original stems retained). There were no PPFs identified at mean 21.5 year follow-up and 5 dislocations (5%).

CONCLUSIONS

The Lubinus SP II 170 mm stem demonstrated excellent survivorship and negligible PPF rates over 20 years following primary THA.

Experience of an Anatomic Femoral Stem in a United Kingdom Center - Excellent Survivorship and Negligible Periprosthetic Fracture Rates at Mean 12 Years Following Primary Total Hip Arthroplasty

BACKGROUND

As the clinical burden of periprosthetic fractures (PPFs) continues to increase, it has been suggested that the use of anatomical femoral stems may help reduce PPF risk. The primary aim of this study was to determine the survivorship and PPF rate of an anatomical femoral stem in a single center at minimum 10-year follow-up.

METHODS

A total of 1,000 consecutive total hip arthroplasties (THAs) performed using an anatomical femoral stem were identified from a prospectively collected arthroplasty database. Patient radiographs were reviewed finally at a mean of 12 years (range, 10 to 16 years) following surgery to identify any revision surgery, dislocations or PPFs. Mean patient age at surgery was 69 years (range, 24 to 93). There were 634 women (63%). Osteoarthritis was the operative indication in 946 patients (95%).

RESULTS

All-cause THA survivorship was 99.1% (95% confidence interval (CI), 99.0-99.3%) at 10 years and 97.9% (CI, 97.8 - 98.0%) at 15 years. Stem survivorship at 10 years was 99.6% (CI, 99.5-99.7%) and at 15 years was 98.2% (CI, 98.1-98.3%). The 15-year stem survival for aseptic loosening was 100% with no cases of significant lysis found (lucent line >2mm). Implant survivorship was not significantly impacted by patient sex (P = .65), body mass index (P = .49), deprivation level (P = .284), operative indication (P = .33), or American Society of Anesthesiologists class (P = .374). There were 3 PPFs identified (0.3%) at mean 12-year follow-up and 15 dislocations (1.5%).

CONCLUSION

This anatomical femoral stem demonstrated excellent survivorship and negligible PPF rates at mean 12-year follow-up following primary THA.

[Early assessment of the risk of later implantloosening using Roentgen Sterophotogrammetric Analysis (RSA)]

BACKGROUND

Aseptic implant loosening is the most common cause of implant revisions in total hip and total knee arthroplasty. Roentgen Stereophotogrammetric Analysis (RSA) represents the current gold standard for the in-vivo assessment of implant fixation.

PRESENT SITUATION

Long-term clinical trials have shown that continuous implant migration within the first two postoperative years correlates strongly with a later aseptic loosening. Thus, the implant migration measured with RSA can be regarded as a reliable surrogate marker for later implant loosening. Over the past 40 years, RSA has been continuously further developed, and the model-based RSA approach has reduced the effort involved since markers attached to implant are no longer needed.

PERSPECTIVES

The RSA method is gaining importance in the certification process of new orthopaedic implants-for example, the Dutch Orthopedic Society has recommended phased-introduction and RSA studies for new hip implants. Furthermore, in the context of the new EU Medical Device Regulation (MDR), which took effect in May 2017, RSA gained relevance for investigating clinically unproven implants. Critics who associate MDR with hindering innovation can be countered in that the RSA method provides a predictive assessment of implant fixation after only two years of follow-up, which is significantly shorter than standard long-term clinical trials.

A phantom and cadaveric study of radiostereometric analysis in posterior cervical and lumbar spinal fusion

BACKGROUND CONTEXT

Detecting pseudarthrosis following spinal fusion is important for accurate diagnosis and treatment. Current diagnostic measures hold certain drawbacks. Radiostereometric analysis (RSA) is a radiographic technique with the capability to measure intervertebral segment changes and may be a novel way of assessing fusion.

PURPOSE

The purpose of this work was to measure the accuracy and precision of RSA in instrumented posterior cervical and lumbar spinal fusion for measuring intervertebral movement. Further, to gain surgical practice with RSA in spine and determine optimal bead placements.

STUDY DESIGN

Artificial bone and cadaveric spine models were used to simulate a 3-level cervical (C3-C6) and a 2-level (L4-S1) lumbosacral posterior spinal fusion to analyze bead placements and to measure RSA accuracy and precision.

METHODS

Preliminary RSA bead placements were planned and measured in the artificial model. Secondary bead placements were adjusted slightly in the cadaveric model to consider additional fusion scenarios. Bead spread, detectability, and stability were measured to determine optimal placements. Translational and rotational precision of both models were measured. Accuracy was measured in the artificial spine model. Model-based RSA software was used for analysis.

RESULTS

Optimal bead placements were found to be throughout the lateral mass of C3-C6 and in the spinous process, transverse process, and within the screw canal of L4-S1. Detectability was high among all segments. Spread was greater in L4-S1 than C3-C6 due to bead collinearity along the transverse axis of the cervical vertebrae. Translational and rotational RSA accuracy in cervical and lumbosacral regions ranged between 0.005 to 0.014 mm and 0.058 to 0.208°. Translational and rotational precision measured in the phantom models ranged 0.017 to 0.131 mm and 0.058 to 0.394° in C3-C6, and 0.086 to 0.191 mm and 0.200 to 0.369° in L4-S1. Translational and rotational precision measured in the cadaveric models ranged 0.054 to 0.548 mm and 0.148 to 1.386° in C3-C6, and 0.068 to 0.164 mm and 0.100 to 0.270° in L4-S1.

CONCLUSIONS

RSA was found to be a feasible radiographic technique in C3-C6 and L4-S1 spinal fusion when measured in artificial and cadaveric models. Optimal bead placements were determined. Bead spread was shown to be better throughout the lumbar region than the cervical region due to anatomical size variations. RSA accuracy and precision were within acceptable RSA criteria.

CLINICAL SIGNIFICANCE

The results from this work contribute to the accuracy, precision, and bead placements for studying RSA in cervical and lumbar spinal fusions. This work may further support the development of clinical studies to assess spinal fusion by evaluating postoperative intervertebral movement using RSA.

Current concepts and outcomes in cemented femoral stem design and cementation techniques: the argument for a new classification system

Cemented implant fixation design principles have evolved since the 1950s, and various femoral stem designs are currently in use to provide a stable construct between the implant-cement and cement-bone interfaces.Cemented stems have classically been classified into two broad categories: taper slip or force closed, and composite beams or shaped closed designs. While these simplifications are acceptable general categories, there are other important surgical details that need to be taken into consideration such as different broaching techniques, cementing techniques and mantle thickness.With the evolution of cemented implants, the introduction of newer implants which have hybrid properties, and the use of different broaching techniques, the classification of a very heterogenous group of implants into simple binary categories becomes increasingly difficult. A more comprehensive classification system would aid in comparison of results and better understanding of the implants' biomechanics.We review these differing stem designs, their respective cementing techniques and geometries. We then propose a simple four-part classification system and summarize the long-term outcomes and international registry data for each respective type of cemented prosthesis. Cite this article: EFORT Open Rev 2020;5:241-252. DOI: 10.1302/2058-5241.5.190034.

Model-Based Roentgen Stereophotogrammetric Analysis to Monitor the Head-Taper Junction in Total Hip Arthroplasty in Vivo-And They Do Move

Model-based Roentgen stereophotogrammetric analysis (RSA) using elementary geometrical shape (EGS) models allows migration measurement of implants without the necessity of additional attached implant markers. The aims of this study were: (i) to assess the possibility of measuring potential head–taper movement in THA in vivo using model-based RSA and (ii) to prove the validity of measured head–taper migration data in vitro and in vivo. From a previous RSA study with a 10 years follow-up, retrospectively for n = 45 patients head–taper migration was calculated as the relative migration between femoral ball head and taper of the femoral stem using model-based RSA. A head–taper migration of 0.026 mm/year can be detected with available RSA technology. In vitro validation showed a total migration of 268 ± 11 µm along the taper axis in a similar range to what has been reported using the RSA method. In vivo, a proof for interchangeable applicability of model-based RSA (EGS) and standard marker-based RSA methods was indicated by a significant deviation within the migration result after 12-month follow-up for all translation measurements, which was significantly correlated to the measured head–taper migration (r from 0.40 to 0.67; p < 0.05). The results identified that model-based RSA (EGS) could be used to detect head–taper migration in vivo and the measured movement could be validated in vitro and in vivo as well. Those findings supported the possibility of applying RSA for helping evaluate the head–taper corrosion related failure (trunnionosis).

The design of the cemented stem influences the risk of Vancouver type B fractures, but not of type C: an analysis of 82,837 Lubinus SPII and Exeter Polished stems

Background and purpose - In total hip replacements, stem design may affect the occurrence of periprosthetic femoral fracture. We studied risk factors for fractures around and distal to the 2 most used cemented femoral stems in Sweden. Patients and methods - This is a register study including all standard primary Lubinus SPII and Exeter Polished stems operated in Sweden between 2001 and 2009. The outcome was any kind of reoperation due to fracture around (Vancouver type B) or distal to the stem (Vancouver type C), with use of age, sex, diagnosis at primary THR, and year of index operation as covariates in a Cox regression analysis. A separate analysis of the primary osteoarthritis patient group was done in order to evaluate eventual influence of the surgical approach (lateral versus posterior) on the risk for Vancouver type B fractures. Results - The Exeter stem had a 10-times (95% CI 7-13) higher risk for type B fractures, compared with the Lubinus, while no statistically significant difference was noticed for type C fractures. The elderly, and patients with hip fracture or idiopathic femoral head necrosis, had a higher risk for both fracture types. Inflammatory arthritis was a risk factor only for type C fractures. Type B fractures were more common in men, and type C in women. A lateral approach was associated with decreased risk for Type B fracture. Interpretation - Stem design influenced the risk for type B, but not for type C fracture. The influence of surgical approach on the risk for periprosthetic femoral fracture should be studied further.

CD3+ lymphocytosis in the peri-implant membrane of 222 loosened joint endoprostheses depends on the tribological pairing

Background and purpose - The most frequent cause of arthroplasty failure is aseptic loosening-often induced by particles. Abrasion material triggers inflammatory reactions with lymphocytic infiltration and the formation of synovial-like interface membranes (SLIM) in the bone-implant interface. We analyzed CD3 quantities in SLIM depending on articulating materials and possible influences of proven material allergies on CD3 quantities. Patients and methods - 222 SLIM probes were obtained from revision surgeries of loosened hip and knee arthroplasties. SLIM cases were categorized according to the SLIM-consensus classification and to the particle algorithm. The CD3 quantities were analyzed immunohistochemically, quantified, and correlated to the particle types. Results - Metal-metal pairings showed the highest CD3 quantities (mean 1,367 counted cells). CD3 quantities of metal-polyethylene (mean 243), ceramic-polyethylene (mean 182), and ceramic-ceramic pairings (mean 124) were significantly smaller. Patients with contact allergy to implant materials had high but not statistically significantly higher CD3 quantities than patients without allergies. For objective assessment of the CD3 response as result of a pronounced inflammatory reaction with high lymphocytosis (adverse reaction), a defined CD3 quantity per high power field was established, the "CD3 focus score" (447 cells/0.3 mm², sensitivity 0.92; specificity 0.90; positive predictive value 0.71; negative predictive value 0.98). Interpretation - The high CD3 quantities for metal-metal pairings may be interpreted as substrate for previously described adverse reactions that cause severe peri-implant tissue destruction and SLIM formation. It remains unclear whether the low CD3 quantities with only slight differences in the various non-metal-metal pairings and documented contact allergies to implant materials have a direct pathogenetic relevance.