Metal hypersensitivity in hip, knee and spine surgery.

The number of implanted joint prostheses and damaged spinal components is steadily increasing. At the same time, rejection of the implanted material is observed in operated patients, which manifests itself in both skin and general reactions, as well as loosening and earlier wear of implanted prostheses, which was previously referred to as aseptic reactions. However, it has been shown that in a significant proportion of patients, rejection of implanted material may be caused by hypersensitivity to a specific metal. For this reason, patients qualified for implantation of foreign material, mainly nickel, titanium, chromium, molybdenum, and other alloys, should be subjected to allergy tests to detect possible risks in the form of metal sensitivity reactions.

Distal femur reconstruction with modular tumour prostheses: a single Institution analysis of implant survival comparing fixed versus rotating hinge knee prostheses.

PURPOSE: To evaluate the incidence of complications in distal femur reconstructions with modular prostheses, comparing fixed vs rotating hinge knee. METHODS: Retrospective analysis of implant survival, complications, and functional results of the Rizzoli series on distal femur megaprosthesis. Between 1983 and 2010, 687 distal femur tumour modular prostheses were implanted: 491 fixed hinge and 196 rotating hinge knee prostheses. Failures of the prostheses were classified in five types: type 1, soft tissue failure; type 2, aseptic loosening; type 3, structural failure; type 4, infection; type 5, tumour progression. RESULTS: Failure rate was 27 % (185/687). Implant survival to all types of failure was 70 % at ten years and 50 % at 20 years with no significant difference between fixed and rotating hinge knee prostheses (p = 0.0928). When excluding type 5 and type 1 failures, the overall survival was 78 % and 58 % at ten and 20 years. There was not a significant difference in implant survival to aseptic loosening (p = 0.5) and infection (p = 0.2) between fixed and rotating hinge knee prostheses. All cases of breakage of prosthetic components occurred in fixed hinge knee prostheses. Functional results, evaluated in 536 pts, were satisfactory in 91.4 % of cases with a mean score of 23.3 with a significantly better function for rotating hinge knee prostheses (p < 0.001). CONCLUSIONS: The most frequent cause of failure was infection followed by aseptic loosening. Even if better results were expected for rotating hinge knee prostheses, there is no significant difference in overall implant survival. No cases of breakage of prosthetic components occurred in rotating hinge knee prosthesis. Functional results were significantly better for the rotating hinge knee prostheses. LEVEL OF EVIDENCE: Therapeutic study, level IV (case series).

Utilization rates of knee-arthroplasty in OECD countries.

BACKGROUND: The number of knee arthroplasties and the prevalence of obesity are increasing exponentially. To date there have been no published reviews on utilization rates of knee arthroplasty in OECD countries. METHODS: We analysed economic, medical and population data relating to knee arthroplasty surgeries performed in OECD countries. Gross domestic product (GDP), health expenditures, obesity prevalence, knee arthroplasty utilization rates and growth in knee arthroplasty rates per 100,000 population were assessed for total population, for patients aged 65 years and over, and patients aged 64 years and younger. RESULTS: Obesity prevalence and utilization of knee arthroplasty have increased significantly in the past. The mean utilization rate of knee arthroplasty was 150 (22-235) cases per 100,000 total population in 2011. The strongest annual increase (7%) occurred in patients 64 years and under. Differences between individual countries can be explained by economic and medical patterns, with countries with higher medical expenditures and obesity prevalence having significantly higher utilization rates. Countries with lower utilization rates have significantly higher growth in utilization rates. The future demand for knee prostheses will increase x-fold by 2030, with exact rates dependant upon economic, social and medical factors. CONCLUSION: We observed a 10-fold variation in the utilization of knee arthroplasty among OECD countries. A significant and strong correlation of GDP, health expenditures and obesity prevalence with utilization of knee arthroplasty was found. Patients aged 64 years and younger show a two-fold higher growth rate in knee arthroplasty compared to the older population. This trend could result in a four-fold demand for knee arthroplasty in OECD countries by 2030.

Comparing Outcomes of Bicruciate-Stabilized and Cruciate-Retaining Total Knee Arthroplasty.

Background: Bicruciate-stabilized (BCS) total knee arthroplasty (TKA) aims to restore normal kinematics by replicating the function of both cruciate ligaments. Conventional cruciate-retaining (CR) design in TKA has shown previous clinical success with lower complication rates. This study compared the patient-reported outcomes between the BCS and CR TKA designs. Methods: This retrospective study examined patients who underwent primary TKA using a CR or a BCS implant. Patient demographics, Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS, JR), and Forgotten Joint Score (FJS) were compared between two cohorts. Patient-reported outcome measures were analyzed using independent samples t-tests. Results: There were no significant preoperative demographic differences between groups. The CR cohort (n = 756) had significantly higher average KOOS, JR Scores compared to the BCS cohort (n = 652) at 3 months (59.7 ± 3.8 vs. 53.0 ± 3.9, p < 0.001) and 2 years (62.6 ± 8.0 vs. 53.8 ± 6.7, p = 0.001) after TKA. Within the cohort, KOOS, JR delta differences were not significant for CR when comparing patient scores 3 months to 1 year after surgery. Meanwhile, the BCS patients did show significant delta improvement (4.1 ± 1.9, p = 0.030) when compared 3 months to 1 year after surgery. One year postoperatively, the BCS cohort (n = 134) showed a significantly higher average FJS score (49.5 ± 31.4, vs. 36.8 ± 28.5, p = 0.028) than the CR cohort (n = 203). Both cohorts displayed a significant difference in delta improvements within their respective cohort when measuring FJS from 3 months to 1 year, 2 years, and 3 years after surgery. Conclusions: The CR cohort performed better on average, compared to the BCS cohort in measures of KOOS, JR scores at the 2-year follow-up. The BCS cohort performed marginally better regarding FJS only at 1-year follow-up.

Comparative efficacy of the different cutting guides in unicompartmental knee arthroplasty: A systematic-review and network meta-analysis.

BACKGROUND: Several cutting guides including conventional, navigation, patient specific instrumentation (PSI) and robotic are currently used in unicompartmental knee arthroplasty (UKA). A network meta-analysis was conducted to compare the most widely used cutting guides regarding the improvement of radiological, functional outcomes and the rate of complications. METHODS: Randomised controlled trials (RCTs) comparing UKA cutting guides were searched in electronic databases, major orthopaedics journals, and oral communications in major orthopaedics meetings, until May 1st, 2022. The primary outcomes were the rate of outliers for the tibial and femoral components in the frontal plane, KSS score and the complication rate. RESULTS: Eighteen RCTs involving 1562 patients with 1564 UKA were included Regarding the prosthetic components' positions, we found a significant increase of the outliers rate using PSI for the femoral component, compared to robotic surgery (risk ratio 0.00 [95% CI 0.00 to 0.55]) and navigated surgery (risk ratio 305.1 [95% CI 1.50 to 1,27e + 07]). We didn't emphasize any difference regarding the tibial component's position, the KSS value at 24 months postoperatively, and the complication rate. Regarding secondary outcomes, robotics provided a better precision in bone cuts in the sagittal plane for the tibial component and the lower limb alignment. No other differences were observed. CONCLUSION: In the light of these results, the robot seems to be the most precise cutting instrument to perform UKA. However, this did not demonstrate any difference in functional or clinical outcome. The cost of this technology can be a major economic brake, especially in surgical centers that do not have an exclusive prosthetic activity. Further outcome and survivorship data is needed to recommend one cutting instrument over the other.

Effectiveness and therapeutic validity of physiotherapeutic exercise starting within one year following total and unicompartmental knee arthroplasty for osteoarthritis: a systematic review.

BACKGROUND: To determine the effectiveness and therapeutic validity of physiotherapeutic exercise after total and unicompartmental knee arthroplasty for osteoarthritis. It was hypothesized that interventions of high therapeutic validity result in superior functional recovery after total and unicompartmental knee arthroplasty versus interventions of low therapeutic validity. METHODS: A systematic review incorporating a comprehensive database search of five major databases relevant to the topic was conducted. Randomized controlled trials were reviewed if they included studies that compared postoperative physiotherapeutic exercise with usual care or compared two types of postoperative physiotherapeutic interventions. All included studies were assessed for risk of bias (using the Cochrane Collaboration's tool) and therapeutic validity (using the Consensus on Therapeutic Exercise Training scale). The characteristics of the included articles and their results on joint and muscle function, functional performance, and participation were extracted. RESULTS: Of the 4343 unique records retrieved, 37 articles were included. Six of them showed good therapeutic validity, suggesting low therapeutic validity in 31 studies. Three articles showed a low risk of bias, 15 studies scored some concerns for risk of bias and 19 studies scored high risk of bias. Only one article scored well on both methodological quality and therapeutic validity. CONCLUSION: Due to heterogeneity of outcome measures and length of follow-up, as well as limited reporting of details of the physiotherapeutic exercises and control interventions, no clear evidence was found on effectiveness of physiotherapeutic exercises after total and unicompartmental knee arthroplasty. Homogeneity in intervention characteristics and outcome measures would enhance comparability of clinical outcomes between trials. Future studies should incorporate similar methodological approaches and outcome measures. Researchers are encouraged to use the Consensus on Therapeutic Exercise Training scale as a template to prevent insufficient reporting.

Shift to low-impact sports and recreational activities following total knee replacement.

BACKGROUND: A growing number of physically active patients undergoing total knee replacement (TKR) desires to resume their preoperative activity levels and to be able to engage in sports after surgery. The purpose of this study was to assess the sporting and physical activities of patients who had undergone TKR. It was hypothesized that the majority of patients treated by TKR would have been able to return to amateur sports and recreational activity . METHODS: Ninety-seven patients who underwent TKR between 2014 and 2016, were retrospectively reviewed. Mean age was 70.1 years (range 64-83). Average follow-up time was 4.2 years (SD: 1.7). Assessment included Knee Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC), and Tegner activity level. Sporting and physical activities of all patients were reported. Wilcoxon's signed ranks test was used for comparison between pre-operative and follow-up data. Significance was set at p < 0.05. RESULTS: Both KOOS score and IKDC significantly improved after surgery (p < 0.001). No statistically significant differences were reported concerning Tegner activity level before and after surgery (p = n.s.). After surgery, a total number of 52 patients (53.6%) successfully returned to sporting and recreational activities, such as cycling, hiking, dancing and swimming. A return to activity rate of 81% of patients practicing sport before surgery was reported. CONCLUSIONS: TKR provides a high rate of return to sport postoperatively and confirms improved subjective results and reduced pain compared to preoperative status. However, most patients returned to low-impact activities, while a significant decrease was reported for mid- and high-impact sports.

Finite element evaluation of the newest ISO testing standard for polyethylene total knee replacement liners.

Current treatment for end-stage osteoarthritis is total knee replacement. Given that the number of total knee replacement surgeries is expected to approach 3.48 million by 2030, understanding long-term failure is important. One of the preclinical tests for total knee replacements is carried out using mechanical wear testing under generic walking conditions. Used for this purpose is the International Standards Organization's generic walking profile. Recently this standard was updated by reversing the direction of anterior/posterior translation and internal/external rotation. The effects of this change have not been investigated, and therefore, it is unknown if comparisons between wear tests utilizing the old and new version of the standard are valid. In this study, we used a finite element model along with a frictional energy-based wear model to compare the kinematic inputs, contact conditions, and wear from the older and newer versions of the ISO standard. Simulator-tested components were used to validate the computational model. We found that there were no visible similarities in the contact conditions between the old and new versions of the standard. The new version of the standard had a lower wear rate but covered a larger portion of the articular surface. Locations of wear also varied considerably. The results of the study suggest that major differences between the old and new standard exist, and therefore, historical wear results should be compared with caution to newly obtained results.

The influence of malalignment and ageing following sterilisation by gamma irradiation in an inert atmosphere on the wear of ultra-high-molecular-weight polyethylene in patellofemoral replacements.

Complications of patellofemoral arthroplasty often occur soon after implantation and, as well as other factors, can be due to the design of the implant or its surgical positioning. A number of studies have previously considered the wear of ultra-high-molecular-weight polyethylene patellae following suboptimal implantation; however, studies have primarily been carried out under a limited number of degrees of freedom. The aim of this study was to develop a protocol to assess the wear of patellae under a malaligned condition in a six-axis patellofemoral joint simulator. The malalignment protocol hindered the tracking of the patella centrally in the trochlear groove and imparted a constant 5° external rotation (tilt) on the patella button. Following 3 million cycles of wear simulation, this condition had no influence on the wear of ultra-high-molecular-weight polyethylene patellae aged for 4 years compared to well-positioned non-aged implants (p > 0.05). However, under the malaligned condition, ultra-high-molecular-weight polyethylene patellae aged 8-10 years after unpacking (following sterilisation by gamma irradiation in an inert atmosphere) and worn ultra-high-molecular-weight polyethylene components also aged 4 years after unpacking (following the same sterilisation process) exhibited a high rate of wear. Fatigue failure due to elevated contact stress led to delamination of the ultra-high-molecular-weight polyethylene and in some cases complete failure of the patellae. The results suggest that suboptimal tracking of the patella in the trochlear groove and tilt of the patella button could have a significant effect on the wear of ultra-high-molecular-weight polyethylene and could lead to implant failure.

Albumin Protein Cleavage Affects the Wear and Friction of Ultra-High Molecular Weight Polyethylene.

It is well established that the total protein concentration and albumin-to-globulin ratio influence the wear of ultra-high molecular polyethylene (UHMWPE, "polyethylene") in joint prostheses. A factor on wear not yet studied, but of possible clinical relevance, is protein cleavage. Such cleavage is expected in the presence of an inflammatory response and as a result of wear processes at the articular interface. The aim of this study was to compare the tribological behavior of polyethylene articulated against an orthopedic wrought CoCrMo alloy for three lubricants: cleaved albumin, uncleaved albumin, and newborn calf serum (control). We hypothesized that the cleavage of albumin will increase the friction and wear rate of polyethylene, with a concomitant roughening of the polymer surface and the generation of larger wear debris particles. Cleavage of the bovine albumin into five fragments was performed by digestion with cyanogen bromide. In pin-on-flat (POF) wear tests of polyethylene pins made of Ticona GUR® 1020/1050 against CoCrMo alloy discs, the cleaved albumin led to the lowest polyethylene wear and highest friction coefficients, whereas albumin led to the highest wear rates. In knee simulator tests, the albumin lubricant also led to a 2.7-fold increase in the tibial insert wear rate compared to the regular bovine serum lubricant (a wear rate for the cleaved albumin could not be obtained). The generated polyethylene wear particles were of increasing size and fibrillar shape in going from serum to albumin to cleaved albumin, although only the shape achieved statistical significance. Unlike bovine serum, cleaved albumin led to wear scars for both the POF and simulator wear tests that closely emulated the morphological features observed on explanted polyethylene tibial inserts from total knee replacements. We posit that the smaller protein fragments can more efficiently adsorb on the surfaces of both the polyethylene and the metal, thus offering protection against wear, while at the same time leading to an increase in friction, particle size, and particle elongation, as the protein fragment films interact adhesively during sliding. The results of this study have implications for pre-clinical wear testing methodology as they suggest that albumin concentration may be more pertinent than total protein concentration for wear testing polyethylene.

The mechanical response of a polyetheretherketone femoral knee implant under a deep squatting loading condition.

The current study was designed to investigate the mechanical response of a polyetheretherketone-on-polyethylene total knee replacement device during a deep squat. Application of this high-demand loading condition can identify weaknesses of the polyetheretherketone relative to cobalt-chromium. This study investigated whether the implant is strong enough for this type of loading, whether cement stresses are considerably changed and whether a polyetheretherketone femoral component is likely to lead to reduced periprosthetic bone loss as compared to a cobalt-chromium component. A finite element model of a total knee arthroplasty subjected to a deep squat loading condition, which was previously published, was adapted with an alternative total knee arthroplasty design made of either polyetheretherketone or cobalt-chromium. The maximum tensile and compressive stresses within the implant and cement mantle were analysed against their yield and fatigue stress levels. The amount of stress shielding within the bone was compared between the polyetheretherketone and cobalt-chromium cases. Relative to its material strength, tensile peak stresses were higher in the cobalt-chromium implant; compressive peak stresses were higher in the polyetheretherketone implant. The stress patterns differed substantially between polyetheretherketone and cobalt-chromium. The tensile stresses in the cement mantle supporting the polyetheretherketone implant were up to 33% lower than with the cobalt-chromium component, but twice as high for compression. Stress shielding was reduced to a median of 1% for the polyetheretherketone implant versus 56% for the cobalt-chromium implant. Both the polyetheretherketone implant and the underlying cement mantle should be able to cope with the stress levels present during a deep squat. Relative to the cobalt-chromium component, stress shielding of the periprosthetic femur was substantially less with a polyetheretherketone femoral component.

The influence of simulator input conditions on the wear of total knee replacements: An experimental and computational study.

Advancements in knee replacement design, material and sterilisation processes have provided improved clinical results. However, surface wear of the polyethylene leading to osteolysis is still considered the longer-term risk factor. Experimental wear simulation is an established method for evaluating the wear performance of total joint replacements. The aim of this study was to investigate the influence of simulation input conditions, specifically input kinematic magnitudes, waveforms and directions of motion and position of the femoral centre of rotation, on the wear performance of a fixed-bearing total knee replacement through a combined experimental and computational approach. Studies were completed using conventional and moderately cross-linked polyethylene to determine whether the influence of these simulation input conditions varied with material. The position of the femoral centre of rotation and the input kinematics were shown to have a significant influence on the wear rates. Similar trends were shown for both the conventional and moderately cross-linked polyethylene materials, although lower wear rates were found for the moderately cross-linked polyethylene due to the higher level of cross-linking. The most important factor influencing the wear was the position of the relative contact point at the femoral component and tibial insert interface. This was dependent on the combination of input displacement magnitudes, waveforms, direction of motion and femoral centre of rotation. This study provides further evidence that in order to study variables such as design and material in total knee replacement, it is important to carefully control knee simulation conditions. This can be more effectively achieved through the use of displacement control simulation.

PEEK-OPTIMA™ as an alternative to cobalt chrome in the femoral component of total knee replacement: A preliminary study.

PEEK-OPTIMA™ (Invibio Ltd, UK) has been considered as an alternative joint arthroplasty bearing material due to its favourable mechanical properties and the biocompatibility of its wear debris. In this study, the potential to use injection moulded PEEK-OPTIMA™ as an alternative to cobalt chrome in the femoral component of a total knee replacement was investigated in terms of its wear performance. Experimental wear simulation of three cobalt chrome and three PEEK-OPTIMA™ femoral components articulating against all-polyethylene tibial components was carried out under two kinematic conditions: 3 million cycles under intermediate kinematics (maximum anterior-posterior displacement of 5 mm) followed by 3 million cycles under high kinematic conditions (anterior-posterior displacement 10 mm). The wear of the GUR1020 ultra-high-molecular-weight polyethylene tibial components was assessed by gravimetric analysis; for both material combinations under each kinematic condition, the mean wear rates were low, that is, below 5 mm3/million cycles. Specifically, under intermediate kinematic conditions, the wear rate of the ultra-high-molecular-weight polyethylene tibial components was 0.96 ± 2.26 mm3/million cycles and 2.44 ± 0.78 mm3/million cycle against cobalt chrome and PEEK-OPTIMA™ implants, respectively (p = 0.06); under high kinematic conditions, the wear rates were 2.23 ± 1.85 mm3/million cycles and 4.44 ± 2.35 mm3/million cycles, respectively (p = 0.03). Following wear simulation, scratches were apparent on the surface of the PEEK-OPTIMA™ femoral components. The surface topography of the femoral components was assessed using contacting profilometry and showed a statistically significant increase in measured surface roughness of the PEEK-OPTIMA™ femoral components compared to the cobalt chrome implants. However, this did not appear to influence the wear rate, which remained linear over the duration of the study. These preliminary findings showed that PEEK-OPTIMA™ gives promise as an alternative bearing material to cobalt chrome alloy in the femoral component of a total knee replacement with respect to wear performance.

Wear simulation of total knee prostheses using load and kinematics waveforms from stair climbing.

Knee wear simulators are meant to perform load cycles on knee implants under physiological conditions, matching exactly, if possible, those experienced at the replaced joint during daily living activities. Unfortunately, only conditions of low demanding level walking, specified in ISO-14243, are used conventionally during such tests. A recent study has provided a consistent knee kinematic and load data-set measured during stair climbing in patients implanted with a specific modern total knee prosthesis design. In the present study, wear simulation tests were performed for the first time using this data-set on the same prosthesis design. It was hypothesised that more demanding tasks would result in wear rates that differ from those observed in retrievals. Four prostheses for total knee arthroplasty were tested using a displacement-controlled knee wear simulator for two million cycles at 1.1 Hz, under kinematics and load conditions typical of stair climbing. After simulation, the corresponding damage scars on the bearings were qualified and compared with equivalent explanted prostheses. An average mass loss of 20.2±1.5 mg was found. Scanning digital microscopy revealed similar features, though the explant had a greater variety of damage modes, including a high prevalence of adhesive wear damage and burnishing in the overall articulating surface. This study confirmed that the results from wear simulation machines are strongly affected by kinematics and loads applied during simulations. Based on the present results for the full understanding of the current clinical failure of knee implants, a more comprehensive series of conditions are necessary for equivalent simulations in vitro.