Tibial tray debonding from the cement mantle is associated with deformation of the backside of polyethylene tibial inserts

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. Results A total of 114 explanted fixed-bearing TKAs were examined. This included 76 used with contemporary PE inserts which were compared with 15 used with older generation PEs. The Attune and NexGen (central locking) trays were found to have significantly less cement cover than Triathlon and PFC trays (peripheral locking group) (p = 0.001). The median planicity values of the PE inserts used with central locking trays were significantly greater than of those with peripheral locking inserts (205 vs 85 microns; p < 0.001). Attune and NexGen inserts had a characteristic pattern of backside deformation, with the outer edges of the PE deviating inferiorly, leaving the PE margins as the primary areas of articulation. Conclusion Explanted TKAs with central locking mechanisms were significantly more likely to debond from the cement mantle. The PE inserts of these designs showed characteristic patterns of deformation, which appeared to relate to the manufacturing process and may be exacerbated in vivo. This pattern of deformation was associated with PE wear occurring at the outer edges of the articulation, potentially increasing the frictional torque generated at this interface.

352 Did the Discontinuation of Pulse-Lavage Have A Detrimental Effect on The Quality of Hip Hemiarthroplasties Performed During the First COVID-19 Wave?

Introduction The standard of practice for performing hip hemiarthroplasty is to thoroughly wash and dry the femur with pulse-lavage. With the COVID-19 pandemic we were issued with guidance to minimise Aerosol Generating Procedures (AGPs) and discontinued the use of pulse lavage. Instead, we used a bladder syringe to wash the femoral canal. Method We retrospectively assessed 100 post-operative radiographs following hemiarthroplasties for neck of femur fractures. We used the Barrack classification to assess the bone cement mantle which is an indicator of aseptic loosening. We assessed 50 radiographs pre-covid (using pulse lavage) and 50 radiographs during covid (without pulse lavage). Results Pre-COVID-19, 30% of hemiarthroplasties were deemed as being ‘at risk’. During COVID-19, 64% of hips were deemed as being ‘at risk’. This represents an absolute increase of 34%. Conclusions This forced service change had a detrimental effect on the quality of the bone cement mantle following hip hemiarthroplasty. We recommend following these patients up at 2 years to assess for signs of aseptic loosening. In future pandemics, we recommend carefully weighing up the dangers of using AGPs against the detriment in patient outcomes likely to be experienced.

Significant differences in rates of aseptic loosening between two variations of a popular total knee arthroplasty design

Purpose The NexGen Legacy Posterior Stabilised (LPS) prosthesis (Zimmer Biomet, Warsaw, IN, USA) has augmentable and non-augmentable tibial baseplate options. We have noted an anecdotal increase in the number of cases requiring early revision for aseptic loosening since adopting the non-augmentable option. The purpose of this study was to ascertain our rates of aseptic tibial loosening for the two implant types within five years of implantation and to investigate the causes for any difference observed. Methods A database search was performed for all patients who underwent primary total knee arthroplasty (TKA) using the NexGen LPS between 2009 and 2015. Kaplan–Meier curves were plotted to assess for differences in revision rates between cohorts. We collected and compared data on gender, age, body mass index, component alignment and cement mantle quality as these were factors thought to affect the likelihood of aseptic loosening. Results Two thousand one hundred seventy-two TKAs were included with five year follow-up. There were 759 augmentable knees of which 14 were revised and 1413 non-augmentable knees of which 48 were revised. The overall revision rate at five years was 1.84% in the augmentable cohort and 3.4% in the non-augmentable cohort. The revision rate for aseptic loosening was 0.26% in the augmentable group and 1.42% in the non-augmentable group (p = 0.0241). Conclusions We have identified increased rates of aseptic loosening in non-augmentable components. This highlights the effect that minor implant changes can have on outcomes. We recommend that clinicians remain alert to implant changes and publish their own results when important trends are observed.

Vancouver B and C periprosthetic fractures around the cemented Exeter Stem: sex is associate with fracture pattern

Introduction The aim of this study was to identify factors associated with the level of periprosthetic fracture involving a cemented polished tapered stem: Vancouver B or Vancouver C. Methods A retrospective cohort study of 181 unilateral periprosthetic fractures involving Exeter stems was assessed by three observers (mean age 78.5, range 39–103; mean BMI 27.1, 17–39; 97 (54%) male). Patient demographics, deprivation scores, BMI and time since primary prosthesis were recorded. Femoral diameter, femoral cortical thickness, Dorr classification and distal cement mantle length were measured from calibrated radiographs. Interobserver reliability was calculated using intraclass correlation coefficients (ICCs). Univariate and multivariate analysis was performed to identify associations with Vancouver B or C fractures. Results 160/181 (88%) Vancouver B and 21/181 (12%) Vancouver C-level fractures occurred at a mean of 5.9 ± 5.4 years (0.2–26.5) following primary surgery. Radiographic measurements demonstrated excellent agreement (ICC > 0.8, p < 0.001). Mortality was significantly higher following Vancouver C compared to B fractures: 90 day 14/160 Vs 5/21 (p = 0.05); 1 year 29/160 Vs 8/21 (p = 0.03). Univariate analysis demonstrated that Vancouver C fractures were associated with female sex, bisphosphonate use, cortical bone thickness, and distal cement mantle length (p < 0.05). On multivariate analysis, only female sex was an independent predictor of Vancouver C-level fractures (R2 =0.354, p = 0.005). Conclusion Most PFFs involving the Exeter stem design are Vancouver B-type fractures and appear to be independent of osteoporosis. In contrast, Vancouver C periprosthetic fractures display typical fragility fracture characteristics and are associated with female sex, thinner femoral cortices, longer distal cement mantles and high mortality.

Cementing a collarless polished tapered femoral stem through the anterior approach

Aims The aim of this study was to radiologically evaluate the quality of cement mantle and alignment achieved with a polished tapered cemented femoral stem inserted through the anterior approach and compared with the posterior approach. Methods A comparative retrospective study of 115 consecutive hybrid total hip arthroplasties or cemented hemiarthroplasties in 110 patients, performed through anterior (n = 58) or posterior approach (n = 57) using a collarless polished taper-slip femoral stem, was conducted. Cement mantle quality and thickness were assessed in both planes. Radiological outcomes were compared between groups. Results No significant differences were identified between groups in Barrack grade on the anteroposterior (AP) (p = 0.640) or lateral views (p = 0.306), or for alignment on the AP (p = 0.603) or lateral views (p = 0.254). An adequate cement mantle (Barrack A or B) was achieved in 77.6% (anterior group, n = 45) and in 86% (posterior group, n = 49), respectively. Multivariate analysis revealed factors associated with unsatisfactory cement mantle (Barrack C or D) included higher BMI, left side, and Dorr Type C morphology. A mean cement mantle thickness of ≥ 2 mm was achieved in all Gruen zones for both approaches. The mean cement mantle was thicker in zone 7 (p < 0.001) and thinner in zone 9 for the anterior approach (p = 0.032). Incidence of cement mantle defects between groups was similar (6.9% (n = 4) vs 8.8% (n = 5), respectively; p = 0.489). Conclusion An adequate cement mantle and good alignment can be achieved using a collarless polished tapered femoral component inserted through the anterior approach. Cite this article: Bone Joint J 2021;103-B(7 Supple B):46–52.

Mind the gap! The Lucent Line Sign: A Pathognomonic Radiographic Finding in Periprosthetic Hip Fractures Around Cemented Polished Tapered Femoral Stems

Introduction: Diagnosing minimally displaced femoral PPFs using plain-film radiographs can be challenging. As a result, fractures can be missed. Case Report: We present four cases of minimally displaced PPFs around cemented polished tapered stems. In each case, radiographs demonstrate no clear cortical breach, but the presence of a fracture is highlighted by a pathognomic lucent line between the cement mantle and the prosthesis: The Lucent Line Sign. Conclusion: Paying attention to the Lucent Line Sign can be pivotal in the diagnosis of minimally displaced PPFs around cemented polished tapered stems. Keywords: Periprosthetic fracture, hip fracture, femoral fracture, taper-slip stem, polished-tapered stem, radiographs.

The Effect of Cement Aging on the Stability of a Cement-in-Cement Revision Construct

A revision surgery can be a complicated procedure. The prevention of the removal of a well-integrated cement mantle can minimize intraoperative complications. With the cement-in-cement technique, the implant will be fixated with a layer of bone cement onto the remaining cement mantle. In our experimental in vitro study, we investigated the effect of cement aging of a cement-in-cement revision construct and regular cement mantle on the bending strength. Two different types of bone cement were tested at four different stages of aging. The Palacos cement showed no significant difference in bending strength at any aging point, regardless of whether it was used primarily or as a cement-in-cement revision. In contrast, the SmartSet MV cement showed a significant difference between the primary and cement-in-cement applications depending on cement aging time. The comparison of the two cement-in-cement structures investigated showed significant differences between the manufacturers depending on the cement aging.

The impact of tourniquet on tibial bone cement penetration in different zones in primary total knee arthroplasty: a meta-analysis

Background Cement mantle penetration and the cement–bone interface strength were critical to a successful primary total knee arthroplasty (TKA). It remained unclear whether decreased blood and fat in the cancellous bone achieved with the use of a tourniquet increases tibial cement mantle penetration in different zones on AP and lateral view in TKA according to criteria defined by the Knee Society Scoring System (KSS). The purpose of this study was to determine whether tourniquet use influences tibial cement mantle penetration in different zones on AP and lateral view in TKA according to KSS. Methods We conducted a meta-analysis to identify studies involving the impact of tourniquet use and no tourniquet use on tibial bone cement penetration in primary TKA in electronic databases, including Web of Science, Embase, PubMed, Cochrane Controlled Trials Register, Cochrane Library, Highwire, CBM, VIP, Wanfang database, up to January 2021. Finally, we identified 1231 patients (1231 knees) assessed in twelve studies. Results Tourniquet use increases the cumulative cement mantle penetration (P < 0.00001), mean cement mantle penetration (P = 0.004), and cement mantle in zone 3(P < 0.0001) on AP view. However, there were no significant differences in cement mantle in zone 1(P = 0.5), zone 2(P =0 .54), zone 4(P = 0.07) on AP view, and zone 1(P = 0.32), zone 2(P = 0.38) on lateral view between two groups. There were also no significant differences in length of surgery(P = 0.7), change in hemoglobin(P = 0.4), transfusion rates(P = 0.47), and complications such as muscular calf vein thrombosis(P = 0.21), superficial infection (P = 0.72), and deep vein thrombosis (P = 0.66) between two groups. Conclusion The application of a tourniquet increases the thickness of the tibial bone cement penetration—the increase in the thickness of bone cement penetration mainly located in zone 3 on the anteroposterior (AP) view.