Surface finish of the Exeter Trauma Stem

Periprosthetic Femoral Fractures-Beyond B2

The proliferation of hip arthroplasty has seen concomitant increases in periprosthetic femoral fractures (PFFs). The most common pattern involves fracture at the level of a loose prosthesis (B2). B2 PFFs have a unique mechanopathogenesis linked to the tendency of polished taper-slip cemented stems to subside in the cement. Such stems carry a much higher PFF risk than other cemented designs. Mega-data, consistent across national registries, suggest that increasing application of the taper-slip principle has resulted in the emergence of highly polished, very low friction cemented prostheses. These have the propensity to migrate within the cement, increasing B2 PFF risk. This would explain the strong association between cobalt-chromium stems and PFF. Is PFF the mode of failure of polished taper-slip stems rather than aseptic loosening? Established wisdom teaches that B2 PFFs should be managed with revision surgery. There is a large body of new evidence that, in certain instances, fixation results in outcomes at least equivalent to revision arthroplasty, with shorter surgical time, decreased transfusion requirements, and lower dislocation risk. This is so in B2 PFFs around cemented polished taper-slip stems with an intact bone-cement interface. We outline advances in understanding of B2 PFF with special reference to mechanopathogenesis and indications for fixation.

Migration and clinical outcomes of a novel cementless hydroxyapatite-coated titanium acetabular shell: two-year follow-up of a randomized controlled trial using radiostereometric analysis

Aims

The objective of this study was to compare the two-year migration and clinical outcomes of a new cementless hydroxyapatite (HA)-coated titanium acetabular shell with its previous version, which shared the same geometrical design but a different manufacturing process for applying the titanium surface.

Methods

Overall, 87 patients undergoing total hip arthroplasty (THA) were randomized to either a Trident II HA or Trident HA shell, each cementless with clusterholes and HA-coating. All components were used in combination with a cemented Exeter V40 femoral stem. Implant migration was measured using radiostereometric analysis (RSA), with radiographs taken within two days of surgery (baseline), and at three, 12, and 24 months postoperatively. Proximal acetabular component migration was the primary outcome measure. Clinical scores and patient-reported outcome measures (PROMs) were collected at each follow-up.

Results

Mean proximal migrations at three, 12, and 24 months were 0.08 mm (95% confidence interval (CI) 0.03 to 0.14), 0.11 mm (95% CI 0.06 to 0.16), and 0.14 mm (95% CI 0.09 to 0.20), respectively, in the Trident II HA group, versus 0.11 mm (95% CI 0.06 to 0.16), 0.12 mm (95% CI 0.07 to 0.17), and 0.14 mm (95% CI 0.09 to 0.19) in the Trident HA group (p = 0.875). No significant differences in translations or rotations between the two designs were found in any other direction. Clinical scores and PROMs were comparable between groups, except for an initially greater postoperative improvement in Hip disability and Osteoarthritis Outcome Symptoms score in the Trident HA group (p = 0.033).

Conclusion

The Trident II clusterhole HA shell has comparable migration with its predecessor, the Trident hemispherical HA cluster shell, suggesting a similar risk of long-term aseptic loosening.

Implant and patient survival rates using Exeter Trauma Stem hemiarthroplasty in fracture neck of femur patients: The largest study to date

INTRODUCTION

Exeter Trauma Stems (ETS) femoral hemiarthroplasties are based on Exeter THR stems with a few design changes. Little has been published on ETS survival rates to justify their high cost compared to other cheaper implants. This is the largest prospective study to assess ETS implant failure-free survival rates in fracture neck of femur patients (NOF). This non-developing-centre study examined whether these design differences have altered implant survival (compared with Exeter THR's published survival data).

METHODS

Data were prospectively collected by independent audit officers. Dislocation, periprosthetic fracture, re-admission with severe hip pain, deep infection and revision surgery were considered events of interest in implant failure-free survival.

RESULTS

This study assessed 1,123 ETS stems (36 patients received bilateral ETS) in NOF patients. The mean patient age at the time of operation was 83 years (range; 49 - 102 years). The mean observation period was 2.5 years (range; 0 days - 8 years). Only 29 implants failed. All failure events were reported within the first year. Stem failure-free survival was 97.2% at eight years (CI 95.9% - 98%). Dislocation occurred in 10 patients (1%), periprosthetic femoral fracture in 4 (0.4%), and deep infection in 11 patients (1.2%). Patient survival rates were 75% and 48% at one and five years respectively.

CONCLUSION

ETS has high implant failure-free survival rates when used in hip fractures. ETS design changes have not altered ETS survival when used in hip fractures compared with the published literature of Exeter THR stem when used as a treatment for OA. Exeter Trauma Stems in NOF patients might last these elderly patients their entire short lifetime.

The Exeter Trauma Stem: A radiographic follow-up at minimum of five years post implantation

INTRODUCTION

The Exeter Trauma Stem (ETS) has been recommended by National Institute of Clinical Excellence (NICE) guidelines in the United Kingdom as a proven, cemented stem. A single laboratory study in the literature has raised possible concerns about the polished finish of the ETS and subsequent potential for accelerated loosening although there is little clinical evidence to support or refute this.

METHODS

The aim of this study was to assess clinical outcomes of the ETS at a minimum of five years post implantation. Primary outcomes were radiological loosening at a minimum of five years along with survivorship of the implant. Patient demographics were prospectively collected and followed up.

RESULTS

218 ETS's (in 214 patients) were implanted from June 2002 until August 2008 in a single centre by a wide variety of surgeons of differing grades. Of these, 16 underwent revision surgery for fracture (2), dislocation (3), infection (1) and acetabular erosion (10) but there were no revisions for aseptic loosening of the implant. There were 64.0% (137/214) patients that had died by the time of this study. Of the remaining patients, 90 had radiographs of their hips at a minimum of 5 years with 36 of these at a minimum of 7 years post implantation. None of these had evidence of loosening.

CONCLUSION

The ETS is a robust and suitable stem for implantation in patients with hip fractures. There are no clinical suspicions or increased rates of loosening with the ETS in our study. The concerns about surface finish are not borne out in our clinical study which shows no evidence of loosening at a minimum of five years post operation. It confers many advantages including ease of revision and it should continue to be used as per NICE guidelines.

Medium to long term follow up of a consecutive series of 604 Exeter Trauma Stem Hemiarthroplasties (ETS) for the treatment of displaced intracapsular femoral neck fractures

The aim of this study was to evaluate the medium to long term follow up results for the Exeter Trauma Stem (ETS) in the treatment of displaced femoral neck fractures. We retrospectively evaluated 604 consecutive cemented ETS hemiarthroplasties performed at our institution between 2007 and 2012. The range of follow up was 2-7 years with a mean follow-up of 4.1 years for the surviving patients. The mean age of the patient population was 84 years (range 46-106) with 81.3% female patients. 382 patients (63.2%) died within the follow up period. Postoperative superficial soft tissue infection occurred in 11 patients and deep prosthetic infection in 5 patients. Dislocation occurred in 11 patients and periprosthetic fracture occurred in 7 patients. 11 patients underwent Girdlestone excision arthroplasty and 6 patients were revised to total hip replacement. This paper represents the largest consecutive series for this implant, with the longest follow up currently available. The results confirm that the prosthesis is an excellent implant for these patients with a low risk of needing revision surgery.

Changes in surface topography at the TKA backside articulation following in vivo service: a retrieval analysis

PURPOSE

With the advent of modular total knee arthroplasty (TKA) systems, backside wear at the articulation between the ultra-high-molecular-weight-polyethylene (UHMWPE) component undersurface and the tibial baseplate has received increasing attention as a source of clinically significant polyethylene wear debris. The aim of this study was to investigate the reciprocating interface at the TKA undersurface articulation using profilometry after in vivo service. Our null hypothesis was that there would be no discernible pattern or relationship between the metal tibial baseplate and UHMWPE surface profile.

METHODS

A nanoscale analysis of thirty retrieved fixed-bearing TKA explants was performed. Surface roughness (Sa) and skewness (Ssk) were measured on both the UHMWPE component undersurface and the tibial baseplate of explants using a non-contacting profilometer (1 nm resolution). Four pristine unimplanted components of two different designs (Stryker Kinemax and DePuy PFC) were examined for control purposes.

RESULTS

Mean explant baseplate surface roughness was 1.24 μm (0.04-3.01 μm). Mean explant UHMWPE undersurface roughness was 1.16 μm (0.23-2.44 μm). Each explant had an individual roughness pattern with unique baseplate and undersurface UHMWPE surface roughness that was different from, but closely related to, surface topography observed in control implants of the same manufacturer and design. Following in vivo service, UHMWPE undersurface showed changes towards a negative skewness, demonstrating that wear is occurring at the backside interface.

CONCLUSION

In vivo loading of the TKA prosthesis leads to measurable changes in surface profile at the backside articulation, which appear to be dependent on several factors including implant design and in vivo duration. These findings are consistent with wear occurring at this surface. Findings of this study would support the use of a polished tibial tray over an unpolished design in total knee arthroplasty with the goal of reducing PE wear by means of providing a smoother backside countersurface for the UHMWPE component.

Pre-operative templating for trauma hemiarthroplasty (Thompson's)

INTRODUCTION

Surgical complications may be avoided by preoperative templating in trauma hemiarthroplasty.

MATERIALS AND METHODS

Digital templates for the Stryker™ range of Thompson's prostheses were created and fifty trauma patients that had undergone cemented hemiarthroplasty were retrospectively templated by 2 blinded surgeons.

RESULTS

Templating for prosthesis size was highly accurate with excellent Inter and intra-observer reproducibility. Sensitivity for identifying femoral canals too narrow for a Thompsons was 100%.

CONCLUSIONS

Templating is a valuable tool and should be standard practice in trauma. We have demonstrated that it is possible to generate custom templates to allow accurate templating.

Hemiarthroplasty versus internal fixation for displaced intracapsular fractures of the hip in elderly men: a pilot randomised trial

A total of 56 male patients with a displaced intracapsular fracture of the hip and a mean age of 81 years (62 to 94), were randomised to be treated with either a cemented hemiarthroplasty (the Exeter Trauma Stem) or reduction and internal fixation using the Targon Femoral Plate. All surviving patients were reviewed one year after the injury, at which time restoration of function and pain in the hip was assessed. There was no statistically significant difference in mortality between the two groups (7/26; 26.9% for hemiarthroplasty vs 10/30; 33.3% for internal fixation). No patient treated with a hemiarthroplasty required further surgery, but eight patients treated by internal fixation did (p = 0.005), five requiring hemiarthroplasty and three requiring total hip arthroplasty. Those treated by internal fixation had significantly more pain (p = 0.02). The restoration of mobility and independence were similar in the two groups. These results indicate that cemented hemiarthroplasty gives better results than internal fixation in elderly men with a displaced intracapsular fracture of the hip.

Total wrist arthroplasty: a systematic review of the evidence from the last 5 years

We reviewed evidence on total wrist replacement from the last 5 years. Eight articles met a minimum set standard. The results of 405 prostheses were available, including seven different manufacturers. The mean follow up was 2.3-7.3 years with an average age of 52-63. Rheumatoid arthritis was the indication in 42% of patients. Motec demonstrated the best post-operative DASH scores. Only Maestro achieved a defined functional range of motion post-operatively. Universal 2 displayed the highest survival rates (100% at 3-5 years), while Elos had the lowest (57% at 5 years). Biaxial had the highest complication rates (68.7%), while Remotion had the lowest (11%). Wrist arthroplasty preserves some range of motion. Functional scores improved and were maintained over the mid- to long-term. Complication rates were higher than wrist fusion, with reports of radiological loosening and osteolysis. The evidence does not support the widespread use of arthroplasty over arthrodesis, and careful patient selection is essential.

Variations in the trunnion surface topography between different commercially available hip replacement stems

Modular hip implants allows for the adjustment of leg length, offset, and the ability to remove the head for acetabular exposure during primary and revision surgery. The design of the Morse taper facilitates the intimate contact of the conical trunnion of the femoral stem (male component), with the conical bore of the femoral head (female component). Orthopaedic trunnion tapers are not standardized and vary in length, taper angle, and base dimension. Variations in the design and surface characteristics of the trunnion, will directly reflect on the interface at the taper junction and can influence the likelihood of subsequent wear, corrosion and longevity of the implant. The effect of surface topography of trunnions on commercially available hip stems has not yet been considered as a possible contributing factor in the corrosion observed at taper junctions. In this study we analyzed the surface topography and surface roughness of randomly selected commercially available femoral hip stem trunnions to obtain a greater insight into their surface characteristics.

Cemented Thompson's hemiarthroplasty in patients with intracapsular neck of femur fractures: survival analysis of 1,670 procedures

Cemented Thompson's prostheses have been used to treat elderly patients with displaced intracapsular hip fractures at our two units for the last 15 years, amid growing support for the use of newer implant designs for hip hemiarthroplasty. This provided us with an opportunity to investigate survival of the Thompson's stem in our patients. A retrospective cohort study was set up to review previously collected data on patients who underwent Thompson's hemiarthroplasty over a 7-year period. These were linked to surgical notes, clinical letters and radiographs to record post-operative course and subsequent admissions and procedures. The identifiers were then linked to mortality data from the Office of 'National Statistics. Kaplan-Meier survival analyses were done for implants and patients. A total of 1,632 patients (mean age 82.7 years) underwent 1,670 procedures. Five-year implant survival was 95.4 %. A total of 36 stems were revised, including 14 revisions to total hip arthroplasty and 22 excision arthroplasties. Reasons for revision included infection (2.1 %), dislocation (1.1 %) and aseptic loosening (0.5 %). Symptomatic aseptic loosening and acetabular erosion occurred late (mean time 3.2 and 5.7 years, respectively following surgery). Aseptic loosening and erosion following hemiarthroplasty are relatively late complications.