Advertisement for orthosearch.org.uk
Results 1 - 6 of 6
Results per page:
Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_20 | Pages 12 - 12
12 Dec 2024
Langton D Bhalekar R Wells S Nargol M Natu S Nargol A Waller S Pabbruwe M Sidaginamale R
Full Access

Objectives

Several studies have reported elevated blood cobalt (Co) and chromium (Cr) concentrations in patients with total knee replacements (TKRs). Up to 44% of tissue samples taken from patients with failed TKRs exhibit histological evidence of metal sensitivity/ALVAL. In simulated conditions, metal particles contribute approximately 12% of total wear debris in TKR. We carried out this investigation to determine the source and quantity of metal release in TKRs.

Design and Methods

We analysed 225 explanted fixed-bearing TKRs (Attune, Genesis II, NexGen, PFC, and Vanguard) revised for any indication. These were analysed using peer-reviewed [coordinate measuring machine (CMM)] methodology to measure the volumetric wear of the polyethylene (PE) bearing surfaces and trays. The trays were analysed using 2D profilometry (surface roughness-Ra) and light microscopy. Histological and blood metal ion concentration analyses were performed in a sub-sample of patients.


Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_20 | Pages 13 - 13
12 Dec 2024
Langton D Bhalekar R Wells S Nargol M Natu S Nargol A Waller S Pabbruwe M Sidaginamale R
Full Access

Objectives

We identified an unusual pattern of backside deformation on polyethylene (PE) inserts of contemporary total knee replacements (TKRs). The PE backside's margins were inferiorly deformed in TKRs with NexGen central-locking trays. This backside deformation was significantly associated with tray debonding. Furthermore, recent studies have shown high rate of tray debonding in PS NexGen TKRs. Subsequently, a field safety notice was issued regarding the performance of this particular device combination and the Option tray has been withdrawn from use. Therefore, we hypothesised that the backside deformation of PS inserts may be greater than that of CR inserts.

Design and Methods

At our national implant retrieval centre, we used peer-reviewed techniques to analyse changes in the bearing wear rate and backside surface deformation of NexGen PE inserts using coordinate measuring machines [N=84 (CR-43 and PS-41) TKRs with non-augmented-trays]. Multiple regression was used to determine which variable had the greatest influence on backside deformation. The amount of cement cover on trays was quantified as a %of the total surface using Image-J software.


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_4 | Pages 31 - 31
1 Apr 2022
Langton D Bhalekar R Joyce T Shyam N Nargol M Pabbruwe M Su E Nargol A
Full Access

Cobalt chrome alloy is commonly used in joint replacement surgery. However, it is recognised that some patients develop lymphocyte mediated delayed type hypersensitivity (DTH) responses to this material, which may result in extensive bone and soft tissue destruction.

Phase 1. United Kingdom: From an existing database, we identified extreme phenotype patient groups following metal on metal (MoM) hip resurfacing or THR: ALVAL with low wearing prostheses; ALVAL with high wear; no ALVAL with high wear; and asymptomatic patients with implants in situ for longer than ten years. Class I and II HLA genotype frequency distributions were compared between these patients’ groups, and in silico peptide binding studies were carried out using validated methodology.

Phase 2. United Kingdom: We expanded the study to include more patients, including those with intermediary phenotypes to test whether an algorithm could be developed incorporating “risk genotypes”, patient age, sex and metal exposure. This model was trained in phase 3.

Phase 3. United Kingdom, Australia, United States. Patients from other centres were invited to give DNA samples. The data set was split in two. 70% was used to develop machine learning models to predict failure secondary to DTH. The predictions were tested using the remaining blinded 30% of data, using time-dependent AUROCs, and integrated calibration index performance statistics.

A total of 606 DNA samples, from 397 males and 209 female patients, were typed. This included 176 from patients with failed prostheses, and 430 from asymptomatic patients at a mean of >10 years follow up. C-index and ROC(t) scores suggested a high degree of discrimination, whilst the IBS indicated good calibration and further backed up the indication of high discriminatory ability. At ten years, the weighted mean survival probability error was < 4%.

At present, there are no tests in widespread clinical use which use a patient's genetic profile to guide implant selection or inform post-operative management. The algorithm described herein may address this issue and we suggest that the application may not be restricted to the field of MoM hip arthroplasty.


The Bone & Joint Journal
Vol. 103-B, Issue 12 | Pages 1791 - 1801
1 Dec 2021
Bhalekar RM Nargol ME Shyam N Nargol AVF Wells SR Collier R Pabbruwe M Joyce TJ Langton DJ

Aims

The aim of this study was to investigate whether wear and backside deformation of polyethylene (PE) tibial inserts may influence the cement cover of tibial trays of explanted total knee arthroplasties (TKAs).

Methods

At our retrieval centre, we measured changes in the wear and deformation of PE inserts using coordinate measuring machines and light microscopy. The amount of cement cover on the backside of tibial trays was quantified as a percentage of the total surface. The study involved data from the explanted fixed-bearing components of four widely used contemporary designs of TKA (Attune, NexGen, Press Fit Condylar (PFC), and Triathlon), revised for any indication, and we compared them with components that used previous generations of PE. Regression modelling was used to identify variables related to the amount of cement cover on the retrieved trays.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_I | Pages 2 - 2
1 Jan 2011
Baker RP Kilshaw M Pabbruwe M Blom A Bannister GC
Full Access

Resurfacing hip arthroplasty is a successful option for the treatment of the young and active patient with hip arthritis. However, it is complicated by femoral neck fracture and avascular necrosis, which result from devascularisation during surgery. Devascularisation maybe caused by thermal necrosis. Thermal necrosis of bone has been shown to occur in temperatures of 47°C and above. We investigated the temperatures generated during femoral head preparation to see if the temperatures reached were great enough to induce osteonecrosis.

Method: Eight patients with osteoarthritis underwent standard resurfacing hip arthroplasty through the posterior approach. From the first over-drilling of the femoral heads until the prosthesis was cemented in place the temperatures generated at the bone surface were recorded using an infra-red thermal imaging camera. Images were captured every 4 seconds as the operation was performed with no interference to the surgeon

Results: The maximum temperatures generated occurred during sleeve reaming at 88.4°C. Seven patients had a temperature recorded greater than 47°C. Removing the femoral caput with an oscillating saw had the highest mean temperature 62.2°C, followed by sleeve reaming (mean 48.7°C). Female patients had the lowest temperature rises and patients receiving the larger femoral prosthesis the greatest temperatures at the bone surface.

Conclusions: Heat generated during femoral head preparation exceeded 47°C in all but one case. Osteonecrosis secondary to thermal insult is likely to occur during femoral head preparation. Strategies need to be devised to decrease the temperatures generated during femoral head preparation.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_III | Pages 407 - 407
1 Sep 2009
Baker RP Kilshaw M Pabbruwe M Blom A Bannister GC
Full Access

Introduction: Resurfacing hip arthroplasty is a successful option for the treatment of the young and active patient with hip arthritis. However, it is complicated by femoral neck fracture and avascular necrosis, which may result from devascularisation during surgery. Devascularisation maybe caused by thermal necrosis. Thermal necrosis of bone has been shown to occur in temperatures of 47°C and above. We investigated the temperatures generated during femoral head preparation to see if the temperatures reached were great enough to induce osteonecrosis.

Method: Eight patients with osteoarthritis underwent standard resurfacing hip arthroplasty through the posterior approach. From the first over-drilling of the femoral heads until the prosthesis was cemented in place the temperatures generated at the bone surface were recorded using an infra-red thermal imaging camera. Images were captured every 4 seconds as the operation was performed with no interference to the surgeon

Results: The maximum temperatures generated occurred during sleeve reaming at 88.4°C. Seven patients had a temperature recorded greater than 47°C. Removing the femoral caput with an oscillating saw had the highest mean temperature 62.2°C, followed by sleeve reaming (mean 48.7°C). Female patients had the lowest temperature rises and patients receiving the larger femoral prosthesis the greatest temperatures at the bone surface.

Conclusions: Heat generated during femoral head preparation exceeded 47°C in all but one case. Osteonecrosis secondary to thermal insult is likely to occur during femoral head preparation. Strategies need to be devised to decrease the temperatures generated during femoral head preparation.