Comparison of Interface Stresses and Strains for Onlay and Inlay Unicompartmental Tibial Components

Walker, Peter S.; Parakh, Dhiraj S; Chaudhary, Mahesh; Wei, Chih-Shing

doi:10.1055/s-0031-1280873

Cited by 12 publications

(8 citation statements)

References 23 publications

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“…Small et al assessed the maximum shear stress in 12 positions within 3 cm distal to the tibial component and found that the onlay design generates a more favorable strain distribution [ 49 ]. Walker et al also found that inlays generated six times more peak stress than onlay designs, which would increase to 13.5 times when softer bone was present at the tibia [ 61 ]. Scott et al found that inlay implants had a significant increase in damage at the microscopic level compared with onlay implants [ 47 ].…”

Section: Discussionmentioning

confidence: 99%

“…1 b) [ 19 , 43 ]. Studies have shown that inlay components have higher peak stress at the tibial surface compared to onlay components [ 49 , 61 ], which could be explained by the fact that onlay components rest on the cortical bone and that the metal backing distributes forces over the tibia [ 49 , 61 ]. Perhaps, as a result, a higher incidence of tibial subsidence [ 3 , 66 ] and revisions are seen with inlay designs [ 3 , 22 , 66 ].…”

Section: Introductionmentioning

confidence: 99%

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Mid-Term Outcomes of Metal-Backed Unicompartmental Knee Arthroplasty Show Superiority to All-Polyethylene Unicompartmental and Total Knee Arthroplasty

List

Kleeblad

Zuiderbaan

et al. 2017

HSS Journal®: The Musculoskeletal Journal of Hospital for Speci

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BackgroundTwo commonly used tibial designs for unicompartmental knee arthroplasty (UKA) are all-polyethylene “inlay” and metal-backed “onlay” components. Biomechanical studies showed that the metal baseplate in onlay designs better distributes forces over the tibia but studies failed to show differences in functional outcomes between both designs at mid-term follow-up. Furthermore, no studies have compared both designs with total knee arthroplasty (TKA).Questions/PurposesThe goal of this study was to compare outcomes of inlay UKA and onlay UKA at mid-term follow-up and compare these with TKA outcomes.MethodsIn this retrospective study, 52 patients undergoing inlay medial UKA, 59 patients undergoing onlay medial UKA, and 59 patients undergoing TKA were included. Western Ontario and McMaster Universities Arthritis Index scores were collected preoperatively and at mean 5.1-year follow-up (range 4.0–7.0 years).ResultsPreoperatively, no differences were observed in patient characteristics or outcome scores. At mid-term follow-up, patients undergoing onlay medial UKA reported significant better functional outcomes than those of inlay medial UKA (92.0 ± 10.4 vs. 82.4 ± 18.7, p = 0.010) and when compared to TKA (92.0 ± 10.4 vs. 79.6 ± 18.5, p < 0.001) while no significant differences between inlay medial UKA and TKA were noted. No significant differences in revision rates were found.ConclusionFunctional outcomes following onlay metal-backed medial UKA were significantly better compared to inlay all-polyethylene medial UKA and to TKA. Based on the results of this study and on biomechanical and survivorship studies in the literature, we recommended using metal-backed onlay tibial components for unicompartmental knee arthroplasty.Electronic supplementary materialThe online version of this article (doi:10.1007/s11420-017-9557-5) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mid-Term Outcomes of Metal-Backed Unicompartmental Knee Arthroplasty Show Superiority to All-Polyethylene Unicompartmental and Total Knee Arthroplasty

List

Kleeblad

Zuiderbaan

et al. 2017

HSS Journal®: The Musculoskeletal Journal of Hospital for Speci

View full text Add to dashboard Cite

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“…Furthermore, inlays were found to produce strain values which exceeded that of onlays by a factor of 13.5, which was attributed to areas of softer bone at the bone-implant interface. The authors concluded that the metal-backed onlay components were a better option when considering load distribution over the tibial surface [12]. The superior load distribution of the metal-backed onlay design may be a mechanistic explanation for the improved pain relief demonstrated by the onlay components as compared to the inlay devices.…”

Section: Discussionmentioning

confidence: 99%

“…1b). Previous research has suggested that metal-backed onlay components exhibit superior biomechanics [12]. However, to our knowledge, there is no published report that compares the clinical outcomes of these two implants.…”

Section: Introductionmentioning

confidence: 99%

Onlay Tibial Implants Appear to Provide Superior Clinical Results in Robotic Unicompartmental Knee Arthroplasty

Gladnick

Nam²,

Khamaisy

et al. 2015

HSS Journal®: The Musculoskeletal Journal of Hospital for Speci

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Background: Unicompartmental knee arthroplasty (UKA) is an increasingly popular option for the treatment of single-compartment knee osteoarthritis (OA) in adults. Two options for tibial resurfacing during UKA are (1) allpolyethylene inlays and (2) metal-backed onlays. Questions/ Purposes: The aim of this study was to determine whether there are any differences in clinical outcomes with inlay versus onlay tibial components. Patients and Methods: We identified 39 inlays and 45 onlays, with average 2.7-and 2.3-year follow-up, respectively, from a prospective robotic-assisted surgery database. The primary outcome was the Western Ontario and McMaster University Arthritis Index (WOMAC), subcategorized by the pain, stiffness, and function subscores, at 2 years postoperatively. The secondary outcome was the need for secondary or revision surgery. Results: Postoperative WOMAC pain score was 3.1 for inlays and 1.6 for onlays (p= 0.03). For 25 inlays and 30 onlays with both preoperative and postoperative WOMAC data, pain score improved from 8.3 to 4.0 for inlays versus from 9.2 to 1.7 for onlays (p=0.01). Function score improved from 27.5 to 12.5 for inlays versus from 32.1 to 7.3 for onlays (p=0.03). Four inlays and one onlay required a secondary or revision procedure (p=0.18). Conclusions:We advise using metal-backed onlays during UKA to improve postoperative clinical outcomes.

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“…However, several studies have shown that allpolyethylene UKA has a higher revision rate than fixed, metalbacked UKA [9,16,18]. This has been attributed to the transmission of higher stresses to the proximal tibia with allpolyethylene tibial components resulting in loosening, subsidence, and tibial fracture [31,33].…”

Section: Introductionmentioning

confidence: 99%

Do Fixed or Mobile Bearing Implants Have Better Survivorship in Medial Unicompartmental Knee Arthroplasty? A Study From the Australian Orthopaedic Association National Joint Replacement Registry

Kannan

Lewis

Dyer

et al. 2021

Clin Orthop Relat Res

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Background During the last 5 years, there has been an increase in the use of unicompartmental knee arthroplasty (UKA) to treat knee osteoarthritis in Australia, and these account for almost 6% of annual knee replacement procedures. However, there is debate as to whether a fixed bearing or a mobile bearing design is best for decreasing revision for loosening and disease progression as well as improving survivorship. Small sample sizes and possible confounding in the studies on the topic may have masked differences between fixed and mobile bearing designs. Questions/purposes Using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), we selected the four contemporary designs of medial compartment UKA: mobile bearing, fixed modular, all-polyethylene, and fixed molded metal-backed used for the treatment of osteoarthritis to ask: (1) How do the different designs of unicompartmental knees compare with survivorship as measured by cumulative percentage revision (CPR)? (2) Is there a difference in the revision rate between designs as a function of patient sex or age? (3) Do the reasons for revision differ, and what types of revision procedures are performed when these UKA are revised? Methods The AOANJRR longitudinally maintains data on all primary and revision joint arthroplasties, with nearly 100% capture. The study population included all UKA procedures undertaken for osteoarthritis between September 1999 and December 2018. Of 56,628 unicompartmental knees recorded during the study period, 50,380 medial UKA procedures undertaken for osteoarthritis were included in the analysis after exclusion of procedures with unknown bearing types (31 of 56,628), lateral or patellofemoral compartment UKA procedures (5657 of 56,628), and those performed for a primary diagnosis other than osteoarthritis (560 of 56,628). There were 50,380 UKA procedures available for analysis. The study group consisted of 40% (20,208 of 50,380) mobile bearing UKA, 35% (17,822 of 50,380) fixed modular UKA, 23% (11,461 of 50,380) all-polyethylene UKA, and 2% (889 of 50,380) fixed molded metal-backed UKA. There were similar sex proportions and age distributions for each bearing group. The overall mean age of patients was 65 ± 9.4 years, and 55% (27,496 of 50,380) of patients were males. The outcome measure was the CPR, which was defined using Kaplan-Meier estimates of survivorship to describe the time to the first revision. Hazard ratios from Cox proportional hazards models, adjusted for sex and age, were performed to compare the revision rates among groups. The cohort was stratified into age groups of younger than 65 years and 65 years and older to compare revision rates as a function of age. Differences among bearing groups for the major causes and modes of revision were assessed using hazard ratios. Results At 15 years, fixed modular UKA had a CPR of 16% (95% CI 15% to 17%). In comparison, the CPR was 23% (95% CI 22% to 24%) for mobile bearing UKA, 26% (95% CI 24% to 27%) for all-polyethylene UKA, and 20% (95% CI 16% to 24%) for fixed molded metal-backed UKA. The lower revision rate for fixed modular UKA was seen through the entire period compared with mobile bearing UKA (hazard ratio 1.5 [95% CI 1.4 to 1.6]; p < 0.001) and fixed molded metal-backed UKA (HR 1.3 [95% CI 1.1 to 1.6]; p = 0.003), but it varied with time compared with all-polyethylene UKA. The findings were consistent when stratified by sex or age. Although all-polyethylene UKA had the highest revision rate overall and for patients younger than 65 years, for patients aged 65 years and older, there was no difference between all-polyethylene and mobile bearing UKA. When compared with fixed modular UKA, a higher revision risk for loosening was shown in both mobile bearing UKA (HR 1.7 [95% CI 1.5 to 1.9]; p < 0.001) and all-polyethylene UKA (HR 2.4 [95% CI 2.1 to 2.7]; p < 0.001). The revision risk for disease progression was higher for all-polyethylene UKA at all time points (HR 1.4 [95% CI 1.3 to 1.6]; p < 0.001) and for mobile bearing UKA after 8 years when each were compared with fixed modular UKA (8 to 12 years: HR 1.4 [95% CI 1.2 to 1.7]; p < 0.001; 12 or more years: HR 1.9 [95% CI 1.5 to 2.3]; p < 0.001). The risk of revision to TKA was higher for mobile bearing UKA compared with fixed modular UKA (HR 1.4 [95% CI 1.3 to 1.5]; p < 0.001). Conclusion If UKA is to be considered for the treatment of isolated medial compartment osteoarthritis, the fixed modular UKA bearing has the best survivorship of the current UKA designs. Level of Evidence Level III, therapeutic study.

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Comparison of Interface Stresses and Strains for Onlay and Inlay Unicompartmental Tibial Components

Cited by 12 publications

References 23 publications

Mid-Term Outcomes of Metal-Backed Unicompartmental Knee Arthroplasty Show Superiority to All-Polyethylene Unicompartmental and Total Knee Arthroplasty

Mid-Term Outcomes of Metal-Backed Unicompartmental Knee Arthroplasty Show Superiority to All-Polyethylene Unicompartmental and Total Knee Arthroplasty

Onlay Tibial Implants Appear to Provide Superior Clinical Results in Robotic Unicompartmental Knee Arthroplasty

Do Fixed or Mobile Bearing Implants Have Better Survivorship in Medial Unicompartmental Knee Arthroplasty? A Study From the Australian Orthopaedic Association National Joint Replacement Registry

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