Bone-cement Interface Research Articles

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.

Peri-operative zoledronic acid attenuates peri-prosthetic osteolysis in a rat model of cemented knee replacement.

Progressive osteolysis can occur at the cement-bone interface of joint replacements and the associated loss of fixation can lead to clinical loosening. We previously developed a rat hemiarthroplasty model that exhibited progressive loss of fixation with the development of cement-bone gaps under the tibial tray that mimicked patterns found in human arthroplasty retrievals. Here we explored the ability of a bisphosphonate (zoledronic acid, ZA) to attenuate cement-bone osteolysis and maintain implant stability. Sprague-Dawley rats (n = 59) received a poly(methylmethacrylate) cemented tibial component and were followed for up to 12 weeks. Treatment groups included peri-operative administration of ZA (ZA group), administration of ZA at 6 weeks postop (late ZA group), or vehicle (Veh group). There was a 60% reduction in the rate of cement-bone gap formation for the ZA group (0.15 mm3/week) compared to Veh group (0.38 mm3/week, p = 0.016). Late ZA prevented further progression of gap formation but did not reverse bone loss to the level achieved in the ZA group. Micromotion from five times body weight toggle loading was positively correlated with cement-bone gap volume (p = 0.009) and negatively correlated with the amount of cement in the metaphysis (p = 0.005). Reduced new bone formation and enduring nonviable bone in the epiphysis for the ZA group were found. This suggests that low bone turnover in the epiphysis may suppress the early catabolic response due to implantation, thereby maintaining better fixation in the epiphysis. This preclinical model presents compelling supporting data documenting improved maintenance of the cement-bone fixation with the use of peri-operative bisphosphonates.

Anatomic total shoulder arthroplasty using hybrid glenoid fixation with a porous-coated titanium post. Two- to ten-year follow-up of 256 cases with primary glenohumeral osteoarthritis

BackgroundAnatomic total shoulder arthroplasty is one of the recommended surgical treatments for severe glenohumeral osteoarthritis, providing good pain relief and function. Aseptic loosening of the glenoid component, however, is a major cause for revision. Hybrid components have been introduced, combining traditional cemented fixation with porous titanium bone ingrowth to improve fixation. The purpose of this study was to report our midterm to longterm experience using such a component, including clinical outcomes and implant survival. MethodsWe reviewed all patients who were operated for primary osteoarthritis during the period 2011-19, leaving a minimum of 2-year follow-up. The severity of the osteoarthritis was graded using Samilson-Prieto score, while glenoid morphology was graded using the modified Walch classification. Clinical outcomes included Western Ontario Osteoarthritis of the Shoulder (WOOS) index, EQ-5D-5L, and Constant-Murley score. Postoperative radiographs were analyzed for radiolucent lines. Patient records were studied for complications including revisions. Supplementary data for revision and outcome were obtained from the Danish Shoulder Arthroplasty Registry. Kaplan-Meier estimates for implant survival were calculated. ResultsA total of 256 arthroplasties in 224 patients were included (mean age: 69 years ± 9 years, 149 females). 81% of cases were graded radiographically as severe osteoarthritis, according to Samilson-Prieto. Walch type B1 was most commonly followed by B2 (29% and 28% respectively). The mean follow-up time was 49 months (range 24-127). The response rate for patient reported outcomes was 91%. The median WOOS index was 94% (81%-99%), the median EQ-5D-5L was 0.87 (0.69-0.95), and the mean Constant-Murley score was 75 (SD 17.7). 13 cases (6%) had a WOOS index below 50%. 8.2% had complications related to surgery. A radiolucent line had developed around the central post in six cases and at the bone-cement interface in three cases at follow-up. Six cases had been revised (2.3%); three due to aseptic loosening of the glenoid. The 10-year survival estimate was 95.6 % (95% CI: 87.9%-98.5%). ConclusionAnatomic total shoulder arthroplasty with hybrid glenoid fixation provides excellent clinical outcome with a low complication rate in patients, with primary glenohumeral osteoarthritis. The 10-year survival rate is high and comparable to that reported for the best- performing all-polyethylene components. Longer observation is needed to see if hybrid fixation will outperform standard all-cemented components.

EXPERIMENTAL FAILURE OF HIP ARTHROPLASTY UNDER TORSION LOADING

Polymethylmethacrylate (PMMA) bone cement is strong in compression, however it tends to fail under torsion. Sufficient pressurisation and subsequent interdigitation between cement and bone are critical for the mechanical interlock of cemented orthopaedic implants, and an irregular surface on the acetabular cup is necessary for reasonable fixation at the cup-cement interface. There is limited literature investigating discrepancies in the failure mechanisms of cemented all-polyethylene acetabular cups with and without cement spacers, under torsional loading.In vitro experimental comparison of three groups of polyethylene acetabular prosthesis (PAP) cemented into prepared sawbone hemipelvises:* PAP without PMMA spacers maintaining an equal cement mantle circumferentially. (Group 1 n=3)* PAP without PMMA spacers cemented deliberately ‘bottoming-out’ the implant within the acetabulum. (Group 2 n=3)* PAP with PMMA spacers. (Group 3 n=3)The constructs were tested to torstional failure on a custom designed setup, and statistical analysis done by a one-way ANOVA and Tukey-Welsh test.Group 3 demonstrated superior torsional resistance with a statistically significant torque of 145Nm (SD±12Nm) at failure, compared to group 2 (109Nm, SD±7Nm) and group 1 (99Nm, SD±8Nm). Group 3 experienced failure predominantly at the bone-cement interface, in contrast, Groups 1 and 2 exhibited failure predominantly at the cup-cement interface. There was no significant difference between Group 1 and 2. Qualitative analysis of the failure mode indicates the efficient redistribution of stress throughout the cement mantle, consistent with the greater uniformity of cement.PMMA spacers increase the resistance to torsional failure at the implant-cement interface. Acetabular components without spacers (Groups 1 and 2) failed at the implant-cement interface before the cement-bone interface, at a statistically significantly lower level of torque to failure. Although the PMMA spacers may reduce cement interdigitation at the cement-bone interface the torsional forces required to fail are likely supraphysiological.

Do Iliac Screws Placed Close to the Sciatic Notch Have Greater Pullout Strength?

Optimal iliac screw position in relation to the sciatic notch remains unknown. In 12 cadavers undergoing S2 alar-iliac (S2AI) screw placement, we tested the pullout strength of screws placed in proximity to the sciatic notch (≤5 mm) vs farther away from the sciatic notch (>5 mm). A biomechanical, cadaver-based study was performed on 12 cadavers undergoing bilateral S2AI screw insertion. The position of the S2AI screw regarding the sciatic notch was dichotomized as ≤5 mm from the sciatic notch on the right side and >5 mm on the left side, confirmed using c-arm fluoroscopy. The primary outcome was the pullout strength of the screw (N). Secondary outcomes were stiffness (N/mm), yield force (N), and work to failure (N mm). Ischial tuberosity was embedded into polymethyl methacrylate and secured to a custom 3-axis vise grip mounted to a 14.5-kN load cell. Pullout testing was performed at 5 mm/min. Force and displacement data were collected at 100 Hz and evaluated using MATLAB. The Mann-Whitney test was performed. Of 24 S2AI screws, 3 screws could not be tested because of cement-bone interface failure. A positive though nonsignificant trend of screw pullout strength was found for screws close to the notch compared with those farther from the notch (861.8 ± 340.7 vs 778.7 ± 350.8 N, P = .859). Similarly, screws close to the notch demonstrated a higher trend of stiffness (149.4 ± 145.4 vs 111.34 ± 128.2 N/mm, P = .320) and force to yield (806.9 ± 352.0 vs 618.6 ± 342.9 N, P = .455). Conversely, screws farther from the notch had a higher but similarly nonsignificant area under the force-displacement curve (10 867.0 ± 9565.0 vs 14 196.6 ± 9578.3 N mm, P = .455), which might be due to excess sheer/translation force that could not be reliably quantified. Although placing S2AI screws ≤5 mm of the sciatic notch provided stronger fixation in 3 of 4 biomechanical testing categories, these results were not statistically significant. Therefore, placing S2AI screws ≤5 mm of the sciatic notch did not provide stronger fixation.

Pulse lavage in lower limb arthroplasty: awash with carbon saving opportunities

Introduction Pulse lavage is used in cemented orthopaedic procedures to prepare the bone bed, improve fixation strength at the bone-cement interface, and reduce the risk of bone cement implantation syndrome. We sought to calculate the approximate carbon cost of battery-operated pulse lavage in Scotland for the year 2022. Methods We used data from the Scottish Arthroplasty Project and Scottish Hip Fracture Audit to establish the number of primary hip replacements, knee replacements, and hip hemiarthroplasty procedures performed in 2022. We modelled the standard uses of eight AA batteries (at 23g each) per case. To calculate the carbon footprint associated we used the ‘UK Government GHG conversion factors dataset’ to calculate the carbon footprint in material use (materials, manufacture, and transport) and disposal. Results Data from the Scottish Arthroplasty Project and Scottish Hip Fracture Audit established that 11,175 primary hip or knee replacements and 4,036 hip hemiarthroplasty procedures were performed in 2022. Therefore, around 15,000 pulse lavage units were used in primary lower limb arthroplasty. If each case had utilised a system which uses eight AA batteries (at 23g each) then 120,000 batteries equating to 2.76 tonnes, would have been used. The carbon footprint for material use (2.76 x 4633.48 = 12788.40) and for disposal (2.76 x 8.883 = 24.52) demonstrates a total carbon footprint of 12,813KgCO2 associated with the use of disposable batteries in pulse lavage for the year 2022. Conclusions Single-use, disposable battery use in orthopaedic joint surgery creates at a high but preventable carbon burden. Reuseable alternatives which utilise the power tool to drive the motor for pulse lavage may save up to 55% of clinical waste.

Intermittent tourniquet compared to throughout tourniquet use during Total Knee Arthroplasty in patients with Body Mass Index of 30 or more: A retrospective cohort study

BackgroundTourniquet use during total knee arthroplasty (TKA) reduces bleeding which optimises bone-cement interface for prosthesis stability and improves surgical field visualisation. However, prolonged usage can lead to complications and poorer outcomes. Some surgeons advocate for intermittent tourniquet application. Limited literature exists for patients with high body mass index (BMI). This study aims to compare the outcomes of intermittent tourniquet (IT) to throughout tourniquet (TT) use among obese patients undergoing primary TKA for knee osteoarthritis. MethodsThis was a retrospective cohort study. In the TT group, tourniquet was inflated from the beginning and released once the bone cement has hardened. In the IT group, tourniquet was inflated at the beginning, released after initial incision and haemostasis, then inflated again during cementation. Tourniquet was released once the bone cement had set. Categorical outcome measures were analysed using Chi-squared or Fisher's exact test. T-test or Kruskal-Wallis test were used for continuous data. ResultsWhen comparing IT to TT among patients with BMI≥30 (IT n = 48, TT n = 47), the mean duration of surgery was shorter in the TT group (p < 0.05). The difference in haemoglobin drop between the two groups was not statistically significant from post-operative day three onwards. There was no difference in transfusion rate (p > 0.05). ROM was greater in the IT group up to three weeks post-operatively (p < 0.05). When comparing patients with BMI <30 (n = 71) and BMI≥30 (n = 48) with IT use, there was no statistically significant difference in ROM and LOS. ConclusionPatients with BMI≥30 in the IT group had greater ROM in the initial post-operative period. Although operative time and blood loss were greater among the IT group, there was no difference in transfusion rate. Outcomes of TKA performed with IT were similar for patients with BMI≥30 and BMI <30. The authors recommend intermittent tourniquet use during TKA for patients with BMI≥30. Level of evidence3.

Registry-based study of survivorship of cemented femoral components versus collared cementless femoral components in total hip arthroplasty in older patients with osteoarthritis.

In recent years, the use of a collared cementless femoral prosthesis has risen in popularity. The design intention of collared components is to transfer some load to the resected femoral calcar and prevent implant subsidence within the cancellous bone of the metaphysis. Conversely, the load transfer for a cemented femoral prosthesis depends on the cement-component and cement-bone interface interaction. The aim of our study was to compare the three most commonly used collared cementless components and the three most commonly used tapered polished cemented components in patients aged ≥ 75 years who have undergone a primary total hip arthroplasty (THA) for osteoarthritis (OA). Data from the Australian Orthopaedic Association National Joint Replacement Registry from 1 September 1999 to 31 December 2022 were analyzed. Collared cementless femoral components and cemented components were identified, and the three most commonly used components in each group were analyzed. We identified a total of 11,278 collared cementless components and 47,835 cemented components. Hazard ratios (HRs) from Cox proportional hazards models, adjusting for age and sex, were obtained to compare the revision rates between the groups. From six months postoperatively onwards, patients aged ≥ 75 years undergoing primary THA with primary diagnosis of OA have a lower risk of all-cause revision with collared cementless components than with a polished tapered cemented component (HR 0.78 (95% confidence interval 0.64 to 0.96); p = 0.018). There is no difference in revision rate prior to six months. Patients aged ≥ 75 years with a primary diagnosis of OA have a significantly lower rate of revision with the most common collared cementless femoral component, compared with the most common polished tapered cemented components from six months postoperatively onwards. The lower revision rate is largely due to a reduction in revisions for fracture and infection.

The Effect of Tranexamic Acid With or Without Tourniquet on Blood Loss in Total Knee Arthroplasty at a Community Hospital.

Tourniquets have long been used in total knee arthroplastydue to the theoretical improvement of bleeding control, integration of cement-bone interface, visibility, and efficiency of the overall surgery. However, this has become increasingly disputed. Comparative studies in total knee arthroplasty employing chemical prophylaxis, i.e., tranexamic acid, have been conducted. This retrospective cohort study evaluated the effect of tranexamic with or without a tourniquet on mean blood loss, hemoglobin, and length of stayin total knee arthroplasty patients. A total of 153 patients' records met the inclusion criteria, 95 patients (62%) were in the tranexamic acid-only group while 58 patients (38%) were in the tranexamic acid plus tourniquet group. Based on mean blood loss in mL (827.5 without vs. 810.1 with the tourniquet, p=0.805), hemoglobin counts in g/dL (12.6 without vs. 12.5 with the tourniquet, p=0.598), and length of stay in days (1.0 days without vs. 1.1 with the tourniquet, p=0.204), there was no statistical difference between the tranexamic alone vs. tranexamic plus tourniquet groups. There were no statistical differences in the mean BMI between groups (32.3 without vs. 32.4 with tourniquets, p=0.901). The patient population had more women (64.1%) than men (35.9%) (p=0.001), but no significant difference in gender based on tourniquet use (p=0.521). The tourniquet group averaged three years younger than the tranexamic alone group (age mean 68.2 without vs 65.3 with tranexamic, p=0.029). This study found no identifiable difference in the three observed variables, indicating that tourniquet provides limited to no additional benefit in reducing blood loss over tranexamic alone in total knee arthroplasty, while tranexamic alone has no deleterious decrease in mean hemoglobin or increase in length of stay.

[Artículo traducido] Aparición temprana de líneas radiolúcidas alrededor de la artroplastia total de rodilla en pacientes con artritis reumatoide. ¿Cuál es su impacto en la tasa de fracaso aséptico y los resultados funcionales a los 13 años de seguimiento?

IntroductionAseptic total knee arthroplasty (TKA) failure has been associated with radiolucent lines. This study aimed to determine the impact of the early appearance of radiolucent lines (linear images of 1, 2, or > 2mm at the cement–bone interface) around the TKA on prosthetic survival and functional outcomes in rheumatoid arthritis (RA) patients during a 2–20 years follow-up. MethodsWe retrospectively analyzed a consecutive series of RA patients treated with TKA between 2000 and 2011. We comparatively analyzed patients with and without radiolucent lines around implants. Clinical outcomes were assessed with the knee society score (KSS) collected before surgery, at years 2, 5, and 10, and at the last postoperative follow-up. The knee society roentgenographic evaluation system was used to analyze the impact of radiolucent lines around the implants at 1, 2, 5, and more than ten years of follow-up. The reoperation and prosthetic survival rates were calculated at the end of the follow-up. ResultsThe study series included 72 TKAs with a median follow-up of 13.2 years (range: 4.0–21.0), of which 16 (22.2%) had radiolucent lines. We did not observe aseptic failure, and prosthetic survival at the end of the study was 94.4% (n=68). The KSS improved significantly (p<0.001) between preoperative values at 2, 5, and 10 years and the end of follow-up, with no differences between patients with and without radiolucent lines. ConclusionsOur study demonstrates that the early appearance of radiolucent lines around a TKA in RA patients does not significantly impact prosthetic survival or long-term functional outcomes at 13 years of follow-up.

Radiological evaluation of cemented acetabular component in primary total hip arthroplasty with or without interface bioactive bone cement technique

PurposeWe evaluated the medium-term radiological outcomes of the interface bioactive bone cement (IBBC) technique used in the acetabular component in primary cemented total hip arthroplasty (THA). MethodsIn total, 79 patients (88 hips) who underwent primary THA at our hospital between January 2004 and April 2009 were divided into the non-IBBC (NIBBC; n ​= ​39 patients, 44 hips) and IBBC (n ​= ​40 patients, 44 hips) groups. A clear zone (CZ) at the cement-bone interface around the cup was evaluated 5 and 10 years postoperatively. The CZ score, which indicates the spread of the CZ, and loosening of the cup (CZ ​> ​2 ​mm on all sides or movement of the cup >4°) were also evaluated. ResultsNo patient had loosening of the cup. The mean patient age at surgery was 66.5 ​± ​9.2 years in the NIBBC group and 61.9 ​± ​7.7 years in the IBBC group (p ​= ​0.012). At 5 years postoperatively, the incidence of CZ was 36.4 ​% in the NIBBC group and 18.2 ​% in the IBBC group (p ​= ​0.056). At 10 years postoperatively, the incidence of CZ was 36.4 ​% in the NIBBC group and 20.1 ​% in the IBBC group (p ​= ​0.098). Age at surgery (p ​= ​0.045) significantly affected the incidence of CZ at 5 years but not at 10 years. The IBBC technique (p ​= ​0.042) and age at surgery (p ​= ​0.028) significantly affected the CZ score at 5 years. The IBBC technique (p ​= ​0.036) significantly affected the CZ score at 10 years. ConclusionsThe IBBC technique resulted in a significantly lower CZ score than the NIBBC technique in patients undergoing THA.

Using novel porous metal pillars for tibial bone defects in primary total knee arthroplasty

BackgroundThe optimal method to treat tibial bone defects during primary total knee arthroplasty (TKA) is still unclear. A novel technique of porous metal pillar augmentation has been applied recently. This study aimed to assess the short-term outcomes of primary TKA with the use of novel porous metal pillars for tibial bone defects.MethodsA total of 24 cases (22 patients) of primary TKA between January 2019 and December 2020 using porous metal pillars for tibial bone defects were reviewed. Clinical results were evaluated using the Knee Society knee score (KSKS) and function score (KSFS), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and range of motion (ROM). Hip-knee-ankle angle (HKAA), femorotibial angle (FTA), and radiolucent lines were assessed radiologically.ResultsThe median follow-up period was 36.0 months (interquartile range: 31–37 months). The KSKS, KSFS, WOMAC score, and ROM improved significantly at the final follow-up assessment compared with the preoperative evaluation. Both of the HKAA and FTA were corrected after surgery. Only one knee had a nonprogressive radiolucent line at the bone-cement interface. No radiolucent lines were detected around the pillar in any of the cases. There were no cases of prosthesis loosening and revision.ConclusionsThe use of novel porous metal pillars yielded satisfactory clinical outcomes and reliable radiological evidence of fixation in this study with a minimum 2-year follow-up. Porous metal pillar augmentation can be considered as a valuable and easy-to-use method for the management of tibial bone defects in primary TKA.

The effect of defect size and location on the fracture risk of proximal tibia, following tumor curettage and cementation: An in-silico investigation

Even though, proximal tibia is a common site of giant cell tumor and bone fractures, following tumor removal, nonetheless very little attention has been paid to affecting factors on the fracture risk. Here, nonlinear voxel-based finite element models based on computed tomography images were developed to predict bone fracture load with defects with different sizes, which were located in the medial, lateral, anterior, and posterior region of the proximal tibia. Critical defect size was identified using One-sample t-test to assess if the mean difference between the bone strength for a defect size was significantly different from the intact bone strength. Then, the defects larger than critical size were reconstructed with cement and the mechanics of the bone-cement interface (BCI) was investigated to find the regions prone to separation at BCI. A significant increase in fracture risk was observed for the defects larger than 20 mm, which were located in the medial, lateral and anterior regions, and defects larger than 25 mm for those located in the posterior region of the proximal tibia. Furthermore, it was found that the highest and lowest fracture risks were associated with defects located in the medial and posterior regions, respectively, highlighting the importance of selecting the initial location of a cortical window for tumor removal by the surgeon. The results of the BCI analysis showed that the location and size of the cement had a direct impact on the extent of damage and its distribution. Identification of critical regions susceptible to separation at BCI, can provide critical comments to surgeons in selecting the optimal cement augmentation technique, which may ultimately prevent unnecessary surgical intervention, such as using screws and pins.

Knee

The August 2023 Knee Roundup360 looks at: Curettage and cementation of giant cell tumour of bone: is arthritis a given?; Anterior knee pain following total knee arthroplasty: does the patellar cement-bone interface affect postoperative anterior knee pain?; Nickel allergy and total knee arthroplasty; The use of artificial intelligence for the prediction of periprosthetic joint infection following aseptic revision total knee arthroplasty; Ambulatory unicompartmental knee arthroplasty: development of a patient selection tool using machine learning; Femoral asymmetry: a missing piece in knee alignment; Needle arthroscopy – a benefit to patients in the outpatient setting; Can lateral unicompartmental knees be done in a day-case setting?

Does lucency equate to revision? A five-year retrospective review of Attune and Triathlon total knee arthroplasty.

The Attune® total knee arthroplasty system was introduced in 2013 to address lingering issues of patient dissatisfaction. However, recent literaturereportsconcerns ofearly tibial tray debonding. The aim of this study was to compare the incidence of radiolucent lines, survivorship and patient reported outcome-measuresbetween the Attune® system and the well-established Triathlon® system. This retrospective database review was conducted at a single institution in Cork, Ireland. All primary Attune® (N = 445) and Triathlon® (N = 285) systems implanted between 2015 and 2016 were reviewed. Radiolucent lines were assessed for those with a minimum two-year radiological follow-up (Attune® = 338; Triathlon® = 231). X-rays were taken post op, at 6months, 2years and 5years. Radiolucent lines were documented using the Modern Knee Society Radiographic System. Five-year survival was assessed using Kaplan-Meier analysis with theLog Rank method to determine statisticalsignificance. The Oxford Knee Score and EQ-5D-5L, were collected pre-op, at 6months, 2years and 5years post-operatively and compared using the Kruskal-Wallis Test. The Attune® had a higher proportion of radiolucent lines at the tibial tray [87.1% (54/62) vs 61.4% (27/44); p = 0.001] and at the implant-cement interface [62.9% (39/62) vs 43.2% (19/44); p = 0.02]. Conversely, the Triathlon® had a higher proportion AT the femur [38.6% (17/44) vs 12.9% (8/62); p = 0.001] and at the cement-bone interface [56.8% (25/44) vs 37.1% (23/62); p = 0.02]. The overall frequency of radiolucent lines was similar in both the Attune® and Triathlon® groups [17.8%, (60/338) vs 17.7%, (41/231); p = 0.49]. There was no difference in revision-free survival analysis at 5 years(Attune® 97.8% vs Triathlon® 95.8%; p = 0.129). The Attune® performed better at 5years in the Oxford Knee Score [Attune® = 42.6 (SD 5.2) vs Triathlon® = 41 (SD 6.4); p = 0.001] and in the EQ-5D [Attune® = 0.773 (SD 0.187) vs Triathlon® = 0.729 (SD 0.218); p = 0.013]. There was no difference at 5years in the EQ-VAS [Attune® = 80.4 (SD 13.7) vs Triathlon® = 78.5 (SD 15.3); p = 0.25]. The Attune® system exhibited a higher incidence of radiolucent lines at the tibial tray. However, this did not lead to decreased survivorship at medium term follow-up compared to the Triathlon®. Furthermore, improvements in patient reported outcomes modestly favoured the Attune® system. III.

Early appearance of radiolucent lines around total knee arthroplasty in rheumatoid arthritis patients. How does it impact the aseptic failure rate and functional outcomes at 13 years of follow-up?

IntroductionAseptic total knee arthroplasty (TKA) failure has been associated with radiolucent lines. This study aimed to determine the impact of the early appearance of radiolucent lines (linear images of 1, 2, or >2mm at the cement–bone interface) around the TKA on prosthetic survival and functional outcomes in rheumatoid arthritis (RA) patients during a 2–20 years follow-up. MethodsWe retrospectively analyzed a consecutive series of RA patients treated with TKA between 2000 and 2011. We comparatively analyzed patients with and without radiolucent lines around implants. Clinical outcomes were assessed with the knee society score (KSS) collected before surgery, at years 2, 5, and 10, and at the last postoperative follow-up. The knee society roentgenographic evaluation system was used to analyze the impact of radiolucent lines around the implants at 1, 2, 5, and more than ten years of follow-up. The reoperation and prosthetic survival rates were calculated at the end of the follow-up. ResultsThe study series included 72 TKAs with a median follow-up of 13.2 years (range: 4.0–21.0), of which 16 (22.2%) had radiolucent lines. We did not observe aseptic failure, and prosthetic survival at the end of the study was 94.4% (n=68). The KSS improved significantly (p<0.001) between preoperative values at 2, 5, and 10 years and the end of follow-up, with no differences between patients with and without radiolucent lines. ConclusionsOur study demonstrates that the early appearance of radiolucent lines around a TKA in RA patients does not significantly impact prosthetic survival or long-term functional outcomes at 13 years of follow-up.

Second-generation bone cement-injectable cannulated pedicle screws for osteoporosis: biomechanical and finite element analyses

BackgroundBiomechanical and finite element analyses were performed to investigate the efficacy of second-generation bone cement-injectable cannulated pedicle screws (CICPS) in osteoporosis.MethodsThis study used the biomechanical test module of polyurethane to simulate osteoporotic cancellous bone. Polymethylmethacrylate (PMMA) bone cement was used to anchor the pedicle screws in the module. The specimens were divided into two groups for the mechanical tests: the experimental group (second-generation CICPS) and control group (first-generation CICPS). Safety was evaluated using maximum shear force, static bending, and dynamic bending tests. Biomechanical stability evaluations included the maximum axial pullout force and rotary torque tests. X-ray imaging and computed tomography were used to evaluate the distribution of bone cement 24 h after PMMA injection, and stress distribution at the screw fracture and screw–cement–bone interface was assessed using finite element analysis.ResultsMechanical testing revealed that the experimental group (349.8 ± 28.6 N) had a higher maximum axial pullout force than the control group (277.3 ± 8.6 N; P < 0.05). The bending moments of the experimental group (128.5 ± 9.08 N) were comparable to those of the control group (113.4 ± 20.9 N; P > 0.05). The screw-in and spin-out torques of the experimental group were higher than those of the control group (spin-in, 0.793 ± 0.015 vs. 0.577 ± 0.062 N, P < 0.01; spin-out, 0.764 ± 0.027 vs. 0.612 ± 0.049 N, P < 0.01). Bone cement was mainly distributed at the front three-fifths of the screw in both groups, but the distribution was more uniform in the experimental group than in the control group. After pullout, the bone cement was closely connected to the screw, without loosening or fragmentation. In the finite element analysis, stress on the second-generation CICPS was concentrated at the proximal screw outlet, whereas stress on the first-generation CICPS was concentrated at the screw neck, and the screw–bone cement–bone interface stress of the experimental group was smaller than that of the control group.ConclusionThese findings suggest that second-generation CICPS have higher safety and stability than first-generation CICPS and may be a superior choice for the treatment of osteoporosis.

Collarless Polished Tapered Stems of Identical Shape Provide Differing Outcomes for Stainless Steel and Cobalt Chrome: A Biomechanical Study

Cemented polished tapered femoral stems (PTS) made of cobalt-chrome alloy (CoCr) are a known risk factor for periprosthetic fracture (PPF). The mechanical differences between CoCr-PTS and stainless-steel (SUS) PTS were investigated. CoCr stems having the same shape and surface roughness as the SUS Exeter® stem were manufactured and dynamic loading tests were performed on three each. Stem subsidence and the compressive force at the bone-cement interface were recorded. Tantalum balls were injected into the cement, and their movement was tracked to indicate cement movement. Stem motions in the cement were greater for the CoCr stems than for the SUS stems. In addition, although we found a significant positive correlation between stem subsidence and compressive force in all stems, CoCr stems generated a compressive force over three times higher than SUS stems at the bone-cement interface with the same stem subsidence (p < 0.01). The final stem subsidence amount and final force were greater in the CoCr group (p < 0.01), and the ratio of tantalum ball vertical distance to stem subsidence was significantly smaller for CoCr than for SUS (p < 0.01). CoCr stems appear to move more easily in cement than SUS stems, which might contribute to the increased occurrence of PPF with the use of CoCr-PTS.

Which Unified Classification System type B periprosthetic fractures around cemented polished tapered stems should not be fixed?

The Unified Classification System (UCS), or Vancouver system, is a validated and widely used classification system to guide the management of periprosthetic femoral fractures. It suggests that well-fixed stems (type B1) can be treated with fixation but that loose stems (types B2 and B3) should be revised. Determining whether a stem is loose can be difficult and some authors have questioned how to apply this classification system to polished taper slip stems which are, by definition, loose within their cement mantle. Recent evidence has challenged the common perception that revision surgery is preferable to fixation surgery for UCS-B periprosthetic fractures around cemented polished taper slip stems. Indications for fixation include an anatomically reducible fracture and cement mantle, a well-fixed femoral bone-cement interface, and a well-functioning acetabular component. However, not all type B fractures can or should be managed with fixation due to the risk of early failure. This annotation details specific fracture patterns that should not be managed with fixation alone.

Study of a constrained finite element elbow prosthesis: the influence of the implant placement

BackgroundThe functional results of total elbow arthroplasty (TEA) are controversial and the medium- to long-term revision rates are relatively high. The aim of the present study was to analyze the stresses of TEA in its classic configuration, identify the areas of greatest stress in the prosthesis–bone–cement interface, and evaluate the most wearing working conditions.Materials and methodsBy means of a reverse engineering process and using a 3D laser scanner, CAD (computer-aided drafting) models of a constrained elbow prosthesis were acquired. These CAD models were developed and their elastic properties, resistance, and stresses were studied through finite element analysis (finite element method—FEM). The obtained 3D elbow-prosthesis model was then evaluated in cyclic flexion–extension movements (> 10 million cycles). We highlighted the configuration of the angle at which the highest stresses and the areas most at risk of implant mobilization develop. Finally, we performed a quantitative study of the stress state after varying the positioning of the stem of the ulnar component in the sagittal plane by ± 3°.ResultsThe greatest von Mises stress state in the bone component for the 90° working configuration was 3.1635 MPa, which occurred in the most proximal portion of the humeral blade and in the proximal middle third of the shaft. At the ulnar level, peaks of 4.1763 MPa were recorded at the proximal coronoid/metaepiphysis level. The minimum elastic resistance and therefore the greatest stress states were recorded in the bone region at the apex of the ulnar stem (0.001967 MPa). The results of the analysis for the working configurations at 0° and 145° showed significant reductions in the stress states for both prosthetic components; similarly, varying the positioning of the ulnar component at 90° (− 3° in the sagittal plane, 0° in the frontal plane) resulted in better working conditions with a greater resulting developed force and a lower stress peak in the ulnar cement.ConclusionThe areas of greatest stress occur in specific regions of the ulnar and humeral components at the bone–cement–prosthesis interface. The heaviest configuration in terms of stresses was when the elbow was flexed at 90°. Variations in the positioning in the sagittal plane can mechanically affect the movement, possibly resulting in longer survival of the implant.Level of evidence: 5