Two-year radiologic assessment of the Trident Peripheral Self-Locking cup using EBRA

[Implant anchorage: In vivo and in vitro analyses : Clusters for implant anchorage and safety]

Aseptic implant loosening is the primary cause of revisions in arthroplasty. Various in vitro and in vivo methods are available for assessing implant fixation and stability. The aim of the Musculoskeletal Biomechanics Research Network (MSB-NET) is to continuously improve or develop these methods. In vitro analyses are often conducted using static and dynamic ISO and ASTM standards, while RSA, DXA, and EBRA analyses are established in vivo methods for evaluating implant fixation. Primary stability analyses, as well as acoustical methods, provide additional opportunities to detect loosening early and precisely evaluate implant stability. The cluster serves as a link between basic research, clinical practice, and end users to promote in vitro and in vivo methods to improve implant safety.

Accuracy of digital templating of uncemented total hip arthroplasty at a certified arthroplasty center: a retrospective comparative study

INTRODUCTION

To investigate the accuracy of preoperative digital templating for total hip arthroplasty (THA) at a certified arthroplasty center (EndoCert EPZmax).

MATERIALS AND METHODS

In a retrospective study design, we analysed 620 uncemented primary THAs for templating accuracy by comparing the preoperatively planned THA component size and the implanted size as documented by the surgeon. Templating was determined to be a) exact if the planned and the implanted component were the same size and b) accurate if they were exact ± one size. Moreover, we investigated factors that potentially influence templating accuracy: overweight and obesity (WHO criteria), sex, implant design, surgeon experience, preoperative diagnosis. Digital templating was done with MediCAD software. The Mann-Whitney U test and the Kruskal-Wallis test were used for statistical analysis.

RESULTS

Templating was exact in 52% of stems and 51% of cups and was accurate in 90% of the stems and 85% of the cups. Regarding the factors potentially influencing templating accuracy, the type of cup implant had a significant influence (p = 0.016). Moreover, greater accuracy of stem templating was achieved in female patients (p = 0.004). No such effect was determined for the other factors investigated.

CONCLUSIONS

We conclude that preoperative 2D templating is accurate in 90% of the stems and 85% of the cups. Greater accuracy may be achieved in female patients. In addition to gender, the type of implant used may influence planning accuracy as well. Surgeon experience, BMI and preoperative diagnosis did not influence templating accuracy.

LEVEL OF EVIDENCE

Level III (retrospective comparative study with prospective cohort).

Good mid-term results with the trident peripheral self-locking cup: a clinical evaluation and migration measurement with EBRA

INTRODUCTION

The most common cause of failure in total hip arthroplasty (THA) is aseptic loosening. Uncemented cup migration analysis by means of Einzel-Bild-Roentgen-Analyse (EBRA) has shown to be a good predictive indicator for early implant failure if the cup migrates more than 2 mm within 4 years after surgery. In this study, we performed a migration analysis of an uncemented peripheral self-locking (PSL) press-fit cup after 4 years follow-up.

MATERIALS AND METHODS

We retrospectively reviewed all patients who received a trident PSL press-fit cup at our department between 2004 and 2017. A total of 636 patients were identified. As inclusion criteria for radiological analysis, a minimum follow-up of 2 years was defined. We reviewed medical histories and performed radiological analysis using EBRA software. EBRA measurements and statistical investigations were performed by two independent investigators.

RESULTS

A total of 149 cups in 146 patients (female 82; male 64) met our inclusion criteria. Mean age at surgery was 65 years (33-89). We found a significant improvement in the WOMAC score pre- to postoperative (p < 0.0001). EBRA migration analysis showed a mean total migration of 0.6 mm (0.0-8.2) over our follow-up period of 4 years. Of the investigated cups, 69.8% showed a migration rate smaller than 2 mm in the investigated follow-up.

CONCLUSION

The acetabular cup used in our study provides low migration at final follow-up. Therefore, a good long-term outcome can be expected for the PSL cup.

TRIAL REGISTRATION

Trial registration number is 20181024-1875 and date of registration is 2018-10-24.

Outcome and EBRA migration analysis of a reconstruction cage in acetabular revision arthroplasty: a clinical and radiological study

PURPOSE

Restoration cages and bone allografts have been proposed to manage severe acetabular bone defects. We aimed to investigate the migration behaviour of a restoration cup and impacted allograft bone in severe acetabular defects with Einzel-Bild-Röntgen-Analyse (EBRA).

METHODS

Applying a retrospective study design, 64 cases treated between 2009 and 2016 were reviewed. We determined the preoperative Charlson Comorbidity Index (CCI), pre- to postoperative WOMAC score, blood loss and functional outcome. From preoperative x rays, the acetabular deficiencies were classified according to Paprosky. Cup migration analyses were performed with EBRA.

RESULTS

Mean age at surgery was 73 (range: 38-93) years. According to the classification by Paprosky et al., 50% (n = 32) of our patients showed a type III B and 28.1% (n = 18) a type III A defect. Radiological follow-up for migration analysis was 35 (range: 4-95) months. Migration analysis showed a mean cup migration of 0.7 mm (range: 5.7-9.6) medial and 1.8 mm (range: 1.7-12.6) cranial.

CONCLUSION

In conclusion, acetabular restoration cages in combination with bone impaction grafting showed a low revision rate at a mean follow-up of 35 months. Mean cup migration revealed low rates after 2 years and suggested a stable postoperative implant position.

Different wear in two highly cross-linked polyethylene liners in THA: wear analysis with EBRA

INTRODUCTION

The purpose of this study was (1) to compare early wear rates in bedding-in periods of two highly cross-linked polyethylene liners frequently used in THA and (2) to evaluate risk factors indicating a possible higher wear rate.

MATERIALS AND METHODS

1120 patients who received a Crossfire or a Marathon highly cross-linked (HXLPE) ultra-high-molecular-weight polyethylene liner in primary THA at our Department between 2004 and 2018 were retrospectively reviewed. Patients with (1) only alumina heads on HXLPE acetabular bearings, (2) a minimum of four radiographs per patient for EBRA analysis, (3) no osteolysis around the acetabular cup and (4) no dislocations that occurred during the study period were included.

RESULTS

A total of 328 patients (female: 183; male: 145; Marathon: 179; Crossfire: 149) fulfilled the inclusion criteria. Mean follow-up was 24 (range 7-51) months. With 0.22 (SD 0.27) mm mean total wear for the Marathon was three times greater than for the Crossfire, namely 0.07 (SD 0.14) mm. Mean cup migration during the investigated follow-up period was 0.7 (SD 0.8) mm for the Pinnacle and 0.5 mm (SD 0.7) for the Trident PSL cups.

CONCLUSION

Initial early wear of highly cross-linked polyethylene in combination with alumina heads differs strongly between products. Long-term survivorship of these liners should be observed to determine whether early wear has an impact on aseptic loosening.

LEVEL OF EVIDENCE

Level III (retrospective comparative study with prospective cohort).

Clinical evaluation of a novel press-fit acetabular cup using "Ein-Bild-Roentgen-Analysis" (EBRA): A positive short-term prognosis

Introduction

Demographic change and demand for high quality of life lead to increasing implantation numbers. Aim of this study was to compare the Plasmafit® cup to Allofit® and Plasmacup®.

Methods

The study included 174 patients who had received 33 Plasmacup®, 68 Allofit® and 73 Plasmafit® cup implants. These were reviewed postoperatively, after 6 months control and after 12 months.

Results

No significant progressive migration could be discovered in any of the cup systems. At each follow-up the cups showed nearly constant values.

Conclusions

All examined acetabular cups showed excellent migration behavior within the first 12 postoperative months.

Shell design and reaming technique affect deformation in mobile-bearing total hip arthroplasty acetabular components

Press-fit acetabular components are susceptible to rim deformation. The inherent variability within acetabular reaming techniques may generate increased press-fit and, subsequently, additional component deformation. The purpose of this study was to analyze the insertion and deformation characteristics of acetabular components designed for dual-mobility systems based on component design, size, and reaming technique. Shell deformation was quantified in a validated worst-case scenario foam pinch model. Thin-walled, one-piece, and modular dual-mobility shells of varying size were implanted in under- and over-reamed cavities with insertion force measured and shell deformation assessed using digital image correlation. Increased shell size resulted in larger rim deformation in one-piece components, with a reduction in press-fit by 1 mm resulting in up to 48% reduction in insertion forces and between 23% and 51% reduction in shell deformation. Lower insertion forces and deformations were observed in modular components. Variability in acetabular reaming plays a significant role in the ease of implantation and component deformation in total hip arthroplasty. Modular components are less susceptible to deformation than thin-walled monoblock shells. Care should be taken to avoid excessive under-reaming, particularly in the scenario of large shell size and high-density patient bone stock.

Primary stability of two uncementedacetabular components of different geometry: hemispherical or peripherallyenhanced?

Objective

This study compared the primary stability of two commercially available acetabular components from the same manufacturer, which differ only in geometry; a hemispherical and a peripherally enhanced design (peripheral self-locking (PSL)). The objective was to determine whether altered geometry resulted in better primary stability.

Methods

Acetabular components were seated with 0.8 mm to 2 mm interference fits in reamed polyethylene bone substrate of two different densities (0.22 g/cm³ and 0.45 g/cm³). The primary stability of each component design was investigated by measuring the peak failure load during uniaxial pull-out and tangential lever-out tests.

Results

There was no statistically significant difference in seating force (p = 0.104) or primary stability (pull-out p = 0.171, lever-out p = 0.087) of the two components in the low-density substrate. Similarly, in the high-density substrate, there was no statistically significant difference in the peak pull-out force (p = 0.154) or lever-out moment (p = 0.574) between the designs. However, the PSL component required a significantly higher seating force than the hemispherical cup in the high-density bone analogue (p = 0.006).

Conclusions

Higher seating forces associated with the PSL design may result in inadequate seating and increased risk of component malpositioning or acetabular fracture in the intra-operative setting in high-density bone stock. Our results, if translated clinically, suggest that a purely hemispherical geometry may have an advantage over a peripherally enhanced geometry in high density bone stock.

Cite this article: Bone Joint Res 2013;2:264–9.