Fixed-bearing Research Articles

Will Mobile-Bearing Total Knee Arthroplasty Be Lost to History? A Comparative Study of Long-Term Follow-Up.

Mobile-bearing (MB) total knee arthroplasty (TKA) implants were introduced as an alternative to fixed-bearing (FB) implants because of their theoretical advantages related to femorotibial rotational mismatch. The purpose of this study is to compare the clinical and radiologic outcomes of MB and FB TKA after approximately 13 years of follow-up. We compared the results of 88 patients with a mean age of 66 years who had received a rotating platform MB implant or a FB implant. The mean follow-up was 13.6 years. The patients were assessed clinically (VAS, ROM, KSS, WOMAC scores) and radiographically before and 13 years after operation. There were no statistically significant differences between the FB and MB groups in terms of clinical outcomes and radiological outcomes (p > 0.05 for all). Although the incidence of complications was higher in the MB group, the findings were not statistically significant compared to the FB group (p > 0.05 for all). Although there were no significant differences in the clinical and radiologic outcomes between the FB and MB groups, the possible higher risk of osteolysis or aseptic loosening in the MB group could be an important clinical implication when selecting the TKA implant.

Outcomes of fixed versus mobile-bearing medial unicompartmental knee arthroplasty.

The optimal bearing surface design for medial unicompartmental knee arthroplasty (UKA) remains controversial. The aim of this study was to compare outcomes of fixed-bearing (FB) and mobile-bearing (MB) UKAs from a single high-volume institution. Prospectively collected data were reviewed for all primary cemented medial UKAs performed by seven surgeons from January 2006 to December 2022. A total of 2,999 UKAs were identified, including 2,315 FB and 684 MB cases. The primary outcome measure was implant survival. Secondary outcomes included 90-day and cumulative complications, reoperations, component revisions, conversion arthroplasties, range of motion, and patient-reported outcome measures. Overall mean age at surgery was 65.7 years (32.9 to 94.3), 53.1% (1,593/2,999) of UKAs were implanted in female patients, and demographics between groups were similar (p > 0.05). The mean follow-up for all UKAs was 3.7 years (0.0 to 15.6). Using revision for any reason as an endpoint, five-year survival for FB UKAs was 97.2% (95% CI 96.4 to 98.1) compared to 96.0% for MB (95% CI 94.1 to 97.9; p = 0.008). The FB group experienced fewer component revisions (14/2,315, 0.6% vs 12/684, 1.8%; p < 0.001) and conversion arthroplasties (38/2315, 1.6% vs 24/684, 3.5%; p < 0.001). A greater number of MB UKAs underwent revision due to osteoarthritis progression (FB = 21/2,315, 0.9% vs MB = 16/684, 2.3%; p = 0.003). In the MB group, 12 (1.8%) subjects experienced bearing dislocations which required revision surgery. There were 15 early periprosthetic tibia fractures (0.6%) in the FB group compared to 0 for MB (p = 0.035). In similar patient populations, FB UKAs demonstrated slightly higher survival than a commonly used MB design. Adverse event profiles differed by bearing type, with an increased risk of bearing dislocation and OA progression with MB designs, and early periprosthetic tibia fractures for FB designs.

Outcomes of Dual Mobility Versus Fixed-Bearing Components in Revision Total Hip Arthroplasty: A Systematic Review and Meta-Analysis

BackgroundDual mobility (DM) implants have received increasing interest in revision surgery due to their increased stability. The aim of this systematic review was to compare outcomes of DM versus conventional fixed-bearing (FB) implants in revision total hip arthroplasty (rTHA). MethodsA comprehensive search was performed using the PubMed, Embase, and MEDLINE databases between January 2000 and 2023. Outcome measures included rerevision due to dislocation, rerevision for other causes, all-cause rerevision, total complication rate, and functional outcome measures. The Methodological Index for Nonrandomized Studies assessment tool was used to evaluate methodological quality and the risk of bias. A pooled meta-analysis was conducted, with an assessment of heterogeneity using the Chi-square and Higgins I2 tests. A further subgroup analysis was performed between DM implants and larger femoral head (> 36 mm) FB implants. ResultsA total of 13 studies met the final inclusion criteria, with an overall number of 5,004 rTHA hips included (2,108 DM and 2,896 FB). The DM implants had significantly lower odds of rerevision due to dislocation (odds ratio [OR] 0.38, P < 0.001), aseptic loosening (OR 0.54, P = 0.004), and all-cause rerevision (OR 0.55, P < 0.001) compared to FB implants. No statistically significant difference was seen in the odds of rerevision due to periprosthetic joint infection (OR 0.99, P = 0.94) or periprosthetic fracture (OR 0.59, P = 0.13) between the 2 groups. The total number of complications showed an odds benefit in favor of DM implants (OR 0.43, P < 0.001). In the subgroup analysis, there was no significant difference in the odds of rerevision due to dislocation (OR 0.69, P = 0.11) between DM and larger femoral head FB implants. ConclusionsBased on current literature, it appears DM implants are an effective modality for reducing dislocation following rTHA with lower complication rates compared to FB implants. However, further prospective randomized controlled trials with longer term follow-up are required.

Altered dynamic joint space in the lateral condyle compartment following medial unicompartmental knee arthroplasty

PurposeThe progression of osteoarthritis in lateral compartment has been identified as a primary complication in medial unicompartmental knee arthroplasty (UKA) revisions, irrespective of whether employing fixed bearing (FB) or mobile bearing (MB) designs. Compared to the previous contact point analyses, the tibiofemoral contacts during knee movements are comprehended by a more comprehensive understanding of joint spaces. This study aims to dynamically map the joint spaces in the lateral compartment during the single-leg lunge following FB and MB UKA procedures, and compare them with the respective contralateral native knees. It is hypothesized that the significant change in joint space for post-UKA compared to their native knees. MethodsTwelve patients with unilateral medial FB UKA and eleven patients with unilateral medial MB UKA were included and underwent computed tomography scans. The exclusion criteria included anterior cruciate ligament deficiency, postoperative knee pain, any postoperative complications, and musculoskeletal illnesses. A dual fluoroscopic imaging system was utilized to capture the single-leg lunge, and 2D-to-3D registration facilitated the visualization of knee motion. According to the knee motions, joint spaces on tibial and femoral surfaces in the lateral compartments of native, FB, and MB UKA knees were calculated and mapped. ResultsIn comparison to the native knees, FB UKA knees exhibited significant increases in medial, lateral, central, and posterior joint spaces in the lateral compartment (p < 0.05), while MB UKA knees showed significant increases only in central and posterior joint spaces (p < 0.05). Moreover, FB UKA demonstrated greater increases in medial, central, and posterior joint spaces compared to MB UKA. Tibial varus and valgus during lunges, as well as the Oxford Knee Score (OKS) and Hip-Knee-Ankle angle (HKA), correlated with joint spaces. ConclusionsDynamic joint space analysis provided a more comprehensive insight into contact dynamics. FB UKA led to an enlargement of joint spaces, whereas MB UKA resulted in joint spaces closer to native knees. These findings contribute to understanding potential postoperative complication in UKAs.

Comparison of Outcomes in Dual-Mobility Versus Fixed-Bearing Implants in Primary Total Hip Arthroplasty: A Systematic Review and Meta-Analysis.

Total hip arthroplasty (THA) is often regarded as one of the most successful surgical techniques developed in the twenty-first century. However, it is associated with complications such as prosthetic instability, dislocations, or infections. Dual-mobility (DM) implants have been developed with the goal of reducing the incidence of dislocations by increasing the femoral head-neck ratio, maximising hip stability, and improving the range of motion (ROM) before impingement and dislocation. This systematic review aims to comprehensively compare the safety and efficacy of DM versus fixed-bearing (FB) implants in primary THA patients. A comprehensive search strategy of PubMed, Embase, Scopus, and Web of Science Core Collection databases was executed to identify pertinent literature comparing DM and FB implants in THAs. Eligible studies underwent independent screening, and data were systematically extracted. The analysis employed pooled risk ratios (RR) for dichotomous outcomes and mean differences (MD) for continuous variables, each accompanied by their respective 95% confidence intervals (CI). Our systematic review and meta-analysis included nine studies encompassing 22,277 patients. The DM group had a significantly reduced incidence of dislocations compared to the FB group (RR 0.25, 95%CI [0.13, 0.47]; p-value <0.0001) and a significantly shorter length of stay (MD -9.92, 95%CI [-15.53, -4.32]; p-value = 0.0005). The FB group, however, had a significantly shorter operative time compared to the DM group (MD 10.41, 95%CI [7.64, 13.17]; p-value < 0.00001). We did not identify any significant statistical differences between the DM and FB groups regarding patient-reported outcome measures, the incidence of all-cause readmissions, the incidence of peri-prosthetic fractures, the incidence of infections, or the incidence of groyne pain.

TOTAL KNEE ARTHROPLASTY REVISION RATES IN MOBILE- VERSUS FIXED-BEARING IMPLANTS: A NEW ZEALAND JOINT REGISTRY STUDY

IntroductionThe mobile-bearing (MB) total knee arthroplasty (TKA) design was introduced with the aim of reducing polyethylene wear and component loosening seen in the fixed-bearing (FB) design. A recent joint registry study has revealed increased risk for all-cause revision, but not revision for infection, in MB-TKA. We used the New Zealand Joint Registry (NZJR) to compare all-cause revision rates, and revision rates for aseptic loosening of MB-TKA compared with fixed bearing (FB) TKA.MethodsAll patients who underwent a primary TKA registered in the NZJR between the 1st January 1999 to 31st December 2021 were identified. Analysis compared MB to FB designs, with sub analysis of implants from a single company. We identified 135,707 primary TKAs, with 104,074 (76.7%) FB-TKAs and 31,633 (23.3%) MB-TKAs recorded. We examined all-cause revision rates, reasons for revision and performed survival analyses.ResultsFor all-comers, MB-TKA had an all-cause revision rate of 0.43/100-component-years (OCY) compared with 0.42/OCY for FB-TKA (p=0.09). The all-cause revision rate was higher for those age &lt; 65 years (MB TKA 0.60/OCY vs. FB-TKA 0.59/OCY) compared to those &gt; 65 years at time of primary TKA (MB-TKA 0.29/OCY vs. FB-TKA 0.32/OCY), however there was no statistically significant difference between implant design in either age group (p=0.16 and p=0.64; respectively). Similarly, there was no difference in revision rates for aseptic loosening between implant designs. Kaplan-Meier survival analysis demonstrates no statistically significant difference in revision-free survival of implants, with both MB-TKA and FB-TKA demonstrating ∼93% revision free survival at 23 years.ConclusionsBoth FB- and MB-TKA demonstrated excellent survivorship, with no significant difference in all-cause revision rates or revision for aseptic loosening between implant designs.

RANDOMIZED PROSPECTIVE TRIAL COMPARING THE SALTO TALARIS FIXED-BEARING AND SALTO MOBILE-BEARING TOTAL ANKLE ARTHROPLASTY

IntroductionComparative studies examining Fixed-Bearing (FB) and Mobile-Bearing (MB) Total Ankle Replacement (TAR) designs have demonstrated similar results and successful long-term outcomes for both. To date there has been no study directly comparing FB and MB designs of the same prosthesis. We present the first prospective randomised trial comparing patient satisfaction, functional outcomes and radiographic results of the Salto Talaris Fixed-Bearing and the Salto Mobile-Bearing Total Ankle Replacement in the treatment of end-stage ankle arthritis.MethodsA total of 108 adult patients with end-stage ankle arthritis were enrolled in the study between November 2014 and October 2021 with similar demographic comparison. Prospective patient-reported outcomes and standardised weightbearing ankle radiographs were performed preoperatively, at 6 weeks, 6 months and 12 months post-operatively, followed by yearly intervals. All surgeries were performed by a single non-design orthopaedic foot and ankle specialist with experience in over 200 Salto and Salto Talaris TAR prior to the study. Radiographs were examined independently by two clinicians. Complete patient data and radiographs were available for 103 patients with an average follow up of 2 years.ResultsBoth groups demonstrated statistically significant improvement from preoperative evaluation to most recent follow up with no statistically significant difference between the two groups in all outcome measures. Radiographic incidence of subchondral cyst formation was 8.9% and 38.2% for FB and MB, respectively. Talar subsidence occurred in 2.2% and 5.5% of FB and MB, respectively.DiscussionOur study demonstrates a higher than previously reported rate of cyst formation in the MB TAR and comparatively higher talar subsidence in the MB TAR vs FB however this did not correlate with clinical outcome measures which were favourable for both groups.ConclusionFixed-Bearing and Mobile-Bearing Total Ankle Replacement demonstrate comparable favourable

DUAL-MOBILITY IMPLANTS IN PRIMARY AND REVISION TOTAL HIP ARTHROPLASTY: A SYSTEMATIC REVIEW AND META-ANALYSIS

In this study, we examined the impact of dual-mobility (DM) versus fixed-bearing (FB) implants on outcomes following total hip arthroplasty (THA), a common and successful operation. We examined all-cause revision, revision due to dislocation, postoperative complications and functional scores in patients undergoing primary and revision THA.A systematic review was performed according to PRISMA guidelines, and was registered in PROSPERO (ID CRD42023403736). The Cochrane Library, Embase, MEDLINE, Web of Science, and Scopus were searched from inception to 12th March 2023. Eligible studies underwent meta-analysis and methodological assessment using the ROBINS-I tool. Data were pooled using a random-effects maximum-likelihood model.Eight comparative, non-randomised studies involving 2,810 DM implants and 3,188 FB implants were included. In primary THA, the difference in all-cause revision was imprecise (OR 0.82, 95% CI 0.25–2.72), whilst the DM cohort had a statistically significant benefit in revision due to dislocation (OR 0.08, 95% CI 0.02–0.28). In revision THA, the DM cohort showed significant benefit in all-cause revision (OR 0.57, 95% CI 0.31–1.05) and revision due to dislocation (OR 0.14, 95% CI 0.04–0.53). DM implants were associated with a lower incidence of implant dislocation and infection. Functional outcome analysis was limited due to underreporting. No intraprosthetic dislocations were observed.The results suggest that contemporary DM designs may be advantageous in reducing the risk of all-cause revision, revision due to dislocation, and postoperative complication incidence at mid-term follow-up. Further high-quality prospective studies are needed to evaluate the long-term performance of this design, especially in revision cases.

3D kinematics of tibiotalar motion in patients with mobile bearing and fixed bearing total ankle arthroplasty: In vivo videofluoroscopic feasibility study

BackgroundAs total ankle arthroplasty (TAA) is an increasingly common surgical intervention for patients with end-stage ankle arthritis, there is a need to better understand the dynamic performance of prosthetic implants during activities of daily living. Our purpose was to quantify and compare relative tibiotalar motion during gait in persons with a fixed-bearing (FB) and mobile-bearing (MB) total ankle arthroplasty. We hypothesized a FB prosthesis would have lower tibiotalar range of motion (ROM). MethodsPatients at least 12 months postoperative with either a FB (n=5) or MB (n=3) total ankle arthroplasty were tested. We used high-speed biplanar videoradiography to quantify tibiotalar kinematics during self-selected gait. Angular and linear ROM in three axes were compared between the groups. ResultsROM for dorsiflexion-plantarflexion, internal-external rotation, and inversion-eversion angles in FB subjects averaged 7.47±4.05°, 7.39±3.63°, and 4.51±2.13°, respectively. ROM in MB subjects averaged 6.74±2.04°, 6.28±4.51°, and 5.68±2.81°, respectively. Linear ROM along anteroposterior, mediolateral, and superior-inferior axes in FB subjects averaged 1.47±2.07 mm, 1.13±1.49 mm, and 0.28±0.30 mm, respectively. Linear ROM in MB subjects averaged 0.68±1.44 mm, 0.60±1.41 mm, and 0.20±0.13 mm, respectively. We found no significant difference between the two groups for any of these ROM parameters (p>0.05). ConclusionTotal ankle arthroplasty using either FB or MB design appears to confer similar ankle motion during the gait cycle in this biplanar fluoroscopic model. Level of evidenceLevel IV, case series.

The use of dual mobility acetabular cups in total hip replacement reduces dislocation rates in hip dysplasia patients

Total hip replacement arthroplasty (THA) in hip dysplasia patients has a higher dislocation rate than in patients with simple hip osteoarthritis due to anatomical deformation. Therefore, to reduce postoperative THA dislocation is the challenge for arthroplasty surgeons. From 2015 to 2020, 1525 patients underwent THA performed by two surgeons at a single institution. A total of 152 patients involving 172 THAs were included. The patients were classified into dual-mobility (DM) and fixed-bearing (FB) acetabular cup groups. The occurrence of postoperative dislocation and functional evaluation of the hip joint, was analyzed before and after surgery using the modified Harris hip score(mHHS). There was no difference in the preoperative demographics and radiographic parameters between the groups. The incidence of postoperative hip dislocation was significantly lower in the DM group (DM 0% vs. FB 9.0%) (P value = 0.003). The mHHS showed no difference before surgery and after surgery (DM 91.80 vs FB 92.03). Treating hip dysplasia patients with THA using a dual-mobility acetabular cup can reduce postoperative dislocations, and could be used for the better management of these patients.

The influence of implant design and limb alignment on in vivo wear rates of fixed-bearing and rotating-platform knee implant retrievals.

Analysis of polyethylene (PE) wear in knee implants is crucial for understanding the factors leading to revision in total knee arthroplasty. Importantly, current experimental and computational methods for predicting insert wear can only be validated against true in vivo measurements from retrievals. This study quantitatively investigated in vivo PE wear rates in fixed-bearing (FB) (n = 21) and rotating-platform (n = 53) implant retrievals. 3D surface geometry of the retrievals was measured using a structured light scanner. Then, a reference surface that included the deformation, but not the wear that the retrievals had experienced in vivo, was constructed using a fully automatic surface reconstruction algorithm. Finally, wear volume was calculated from the deviation between the worn and reconstructed surfaces. The measurement and analysis techniques were validated and the algorithm was found to produce errors of only 0.2% relative to the component volumes. In addition to quantifying cohort-level wear rates, the effect of mechanical axis limb alignment on mediolateral wear distribution was examined for a subset of the retrievals (n = 14 + 26). Our results show that FB implants produce significantly (p = 0.04) higher topside wear rates (24.6 ± 10.1 mm3/year) than rotating-platform implants (15.3 ± 8.0 mm3/year). This effect was larger than that of limb alignment, which had a smaller and nonsignificant influence on overall wear rates (+4.5 ± 11.6 mm3/year, p = 0.43). However, increased varus alignment was associated significantly with greater medial compartment wear in both the FB and rotating-platform designs (+1.7 ± 1.3%/° and +1.8 ± 1.6%/°). Our findings emphasize the importance of implant design and limb alignment on wear outcomes, providing reference data for improving implant performance and longevity.

Less wear in deep-dished mobile compared to fixed bearing total knee arthroplasty of the same design at 5-year follow-up: a randomised controlled model-based Roentgen stereophotogrammetric analysis trial.

The aim of this prospective randomised controlled study was to compare wear characteristics and functional outcome between deep-dished mobile bearing (MB) and fixed bearing (FB) cemented total knee arthroplasty (TKA). We hypothesised that deep-dished MB reduces polyethylene wear and improves patient-reported outcome measures. A total of 50 patients were randomised to receive a MB or FB tibia component of the same cemented TKA design. Patients were evaluated over a 5-year follow-up period. Medial and lateral wear were assessed using model-based Roentgen Stereophotogrammetric Analysis (RSA) and compared with the direct postoperative minimal joint space measurement. Functional outcome was assessed by the clinician-derived KSS and OKS, WOMAC, LEAS, and FJS-12. All data were derived using a general linear mixed model. At 5-year follow-up, decreased wear in the MB compared to the FB group was observed on the lateral side (0.07 ± 0.17mm, p = 0.026), but not on the medial side (0.31 ± 0.055mm, p = 0.665). Functional outcomes improved with a statistical significant effect over time, with no significant differences between groups (all p > 0.17). This model-based RSA study with 5-year follow-up showed that cemented deep-dished MB reduced lateral polyethylene wear as compared to FB in a single TKA system, whilst clinical outcomes were comparable. Longer follow-up is needed to establish clinical implications of these altered wear patterns and determine type of wear. Level 1 randomised controlled trial.

Wider translations and rotations in posterior-stabilised mobile-bearing total knee arthroplasty compared to fixed-bearing both implanted with mechanical alignment: a dynamic RSA study

PurposeThe purpose of this study was to investigate the in vivo kinematics of the same femoral design mechanically aligned posterior-stabilised (PS) total knee arthroplasty (TKA) with either fixed-bearing (FB) or mobile-bearing (MB) inlay, implanted by the same surgeon, using model-based dynamic radiostereometric analysis (RSA). The hypothesis of the present study was that the MB design would show wider axial rotation than the FB design, without affecting the clinical outcomes.Materials and methodsA cohort of 21 non-randomised patients (21 DePuy Attune PS-FB) was evaluated by dynamic RSA analysis at a minimum 9-month follow-up, while performing differently demanding daily living activities such as sit to stand (STS) and deep knee lunge (DKL). Kinematic data were compared with those of a cohort of 22 patients implanted with the same prosthetic design but with MB inlay. Anterior–posterior (AP) translations, varus–valgus (VV) and internal–external (IE) rotations of the femoral component with respect to the tibial baseplate were investigated. Translation of medial and lateral compartment was analysed using the low point method according to Freeman et al. Questionnaires to calculate objective and subjective clinical scores were administered preoperatively and during follow-up visit by the same investigator.ResultsThe FB TKA design showed lower AP translation during STS (6.8 ± 3.3 mm in FB vs 9.9 ± 3.7 mm in MB, p = 0.006*), lower VV rotation (1.9 ± 0.8° in FB vs 5.3 ± 3.3° in MB, p = 0.005) and lower IE rotation (2.8 ± 1.1° in FB vs 9.5 ± 4.3° in MB, p = 0.001) during DKL than the mobile-bearing TKA design. Posterior-stabilised FB group showed significant lower translation of the low point of the medial compartment than the MB group (p = 0.008). The percentage of patients performing medial pivot in the FB group was higher compared to MB group in the examined motor tasks. No significant differences in post-operative range of motion (117° ± 16° for FB group and 124° ± 13° for MB group) and in clinical outcomes emerged between the two cohort.ConclusionsThe FB and MB designs differed in AP translations, VV rotations and IE rotations of the femoral component with respect to the tibial component in STS and DKL. Furthermore, FB cohort reported a significant higher percentage of medial pivot with respect to MB cohort. Despite this, no differences in clinical outcomes were detected between groups. Both designs showed stable kinematics and represent a viable option in primary TKA.Level of evidenceProspective cohort study, II.

Do Articular Surfaces of Dual Mobility Hips Have More Wear and Friction? An In Vitro Investigation

BackgroundLarger head-to-neck ratio of dual mobility (DM) hip arthroplasties provide greater range of motion/less risk of dislocation, but raise concerns for high wear and friction. We measured in vitro, the wear rates of contemporary DM hips with highly cross-linked ultra high molecular weight polyethylene (UHWMPE), where it came from, and their frictional torques. MethodsHip simulators were used to compare the wear of DM to fixed-bearing (FB) designs of 2 different implants. Each of 8 different configurations underwent millions of simulated walking cycle tests, some as full DM, some as FB controls, some DM with the outer-articulation deliberately immobilized, and some the inner. Wear and 3-dimensional-frictional torques were measured and friction independent of size was deduced. ResultsThe DM hips produced lower wear and friction-torque than the FB hips. The DM wear during walking gait comes mostly from the smaller inner articular surface. If the outer surface was immobilized, the wear and torque of the inner alone would be small, but the full DM (inner and outer free-to-move) wear and torque were smallest of all. Friction measurements expectedly showed larger hips having higher frictional torques, but the DM showed the lowest, again because its motion was mostly the smaller inner articulation; smaller than even a modern fixed-bearing hip. ConclusionThe DM hips appear to combine the benefits of greater range of motion and less impingement of larger hips, with the lower wear and friction of smaller FB hips, with some benefits compromised if the outer or inner articulations are immobilized.

Fixed-bearing is superior to mobile-bearing in lateral unicompartmental knee replacement: a retrospective matched-pairs analysis

PurposeDue to low incidence of isolated lateral osteoarthritis (OA), there are limited data on whether a fixed-bearing (FB) or a mobile-bearing (MB) design is superior for lateral unicompartmental knee replacement (UKR). The aim of this matched-pairs analysis was to compare both designs in terms of implant survival and clinical outcome.MethodsPatients who received MB-UKR (Group A) and FB-UKR (Group B) at a single centre were matched according to gender, age at time of surgery and body mass index (BMI). Survivorship analysis was performed with the endpoint set as “revision for any reason”. Clinical outcome was assessed using the Oxford knee score (OKS), visual analogue scale for pain (VAS), patients’ satisfaction, University of California Los Angeles activity scale (UCLA) and the Tegner activity score (TAS).ResultsA total of 60 matched pairs were included with a mean follow-up (FU) of 3.4 ± 1.3 (range 1.2–5.0) years in Group A and 2.7 ± 1.2 (range 1.0–5.0) years in Group B. Survivorship between both groups differed significantly (Group A: 78.7%; Group B: 98.3%, p = 0.003) with bearing dislocation being the most common reason for revision in Group A (46.2%). The relative and absolute risk reduction were 92.2% and 20%, respectively, with 5 being the number needed to treat. There were no differences in OKS (Group A: 41.6 ± 6.5; Group B: 40.4 ± 7.7), VAS (Group A: 2.9 ± 3.2; Group B: 1.6 ± 2.2), UCLA (Group A: 5.7 ± 1.3; Group B: 5.9 ± 1.8) and TAS (Group A: 3.0 ± 1.0; Group B: 3.1 ± 1.2) between both groups on follow-up.ConclusionDespite modern prosthesis design and surgical technique, implant survival of lateral MB-UKR is lower than that of FB-UKR on the short- to mid-term due to bearing dislocation as the most common cause of failure. Since clinical results are equivalent in both groups, FB-UKR should be preferred in treatment of isolated lateral OA.Level of evidenceRetrospective case–control study, Level III.

Selective Use of Dual-Mobility Did Not Significantly Reduce 90-Day Readmissions or Reoperations After Total Hip Arthroplasty

BackgroundSelective use of dual mobility (DM) implants in total hip arthroplasty (THA) patients at high dislocation risk has been proposed. However, evidence-based utilization thresholds have not been defined. We explored whether surgeon-specific rates of DM utilization correlate with rates of readmission and reoperation for dislocation. MethodsWe retrospectively reviewed 14,818 primary THA procedures performed at a single institution between 2011 and 2021, including 14,310 fixed-bearing (FB) and 508 DM implant constructs. Outcomes including 90-day readmissions and reoperations were compared between patients who had FB and DM implants. Cases were then stratified into 3 groups based on the attending surgeon’s rate of DM utilization (≤ 1, 1 to 10, or > 10%) and outcomes were compared. ResultsThere were no differences in 90-day outcomes between FB and DM implant groups. Surgeon frequency of DM utilization ranged from 0% to 43%. There were 48 surgeons (73%) who used DM in ≤ 1% of cases, 11 (17%) in 1% to 10% of cases, and 7 (10%) in > 10% of cases. The 90-day rates of readmission (7.3% versus 7.6% versus 7.2%, P = .7) and reoperation (3.4% versus 3.9% versus 3.8%, P = .3), as well as readmission for instability (0.5% versus 0.6% versus 0.8%, P = .2) and reoperation for instability (0.5% versus 0.5% versus 0.8%, P = .6), did not statistically differ between cohorts. ConclusionSelective DM utilization did not reduce 90-day readmissions or reoperations following primary THA. Other dislocation-mitigation strategies (ie, surgical approach, computer navigation, robotic assistance, and large diameter FBs) may have masked any benefits of selective DM use.

No difference in mobile and fixed bearing partial knee arthroplasty in octogenarians: a clinical trial

BackgroundA clinical trial comparing MB (mobile-bearing) versus FB (fixed-bearing) in medial partial knee arthroplasty (PKA) in octagenarians has been conducted. The focus of the present study was on PROMs, range of motion (ROM), implant positioning and implants survivorship. The hypothesis of the present study was that MB implants performed better than FB in PKA in octogenarians.MethodsThe first group received FB PKA-PPK®; the second received MB PKA-Oxford. Patients were not randomly allocated. The following PROMs were administered at T0 (pre-operatively), T1 (1 year after surgery), and T2 (3 years after surgery): visual analogue scale (VAS), Knee Society Score (KSS) and Oxford Knee Score (OKS). Data regarding the implant survivorship and ROM were also collected. Furthermore, the following radiographic parameters were measured: Femoral component varus/valgus; Tibial component varus/valgus; Anteroposterior slope.ResultsAt T0, 28 patients were included in the FB and 33 in the MB group. The surgical time was shorter in the FB group (p < 0.001). No difference between FB and MB in ROM, VAS, KSS, and OKS at each follow-up (p > 0.05). No difference was found in implant positioning (p > 0.05). At last follow-up, FB group reported three failures caused by aseptic loosening. Four failures were observed in the MB cohort: two for bearing dislocation and two for aseptic loosening. The Kaplan–Meier Curve found no differences in implant survivorship.ConclusionsAccording to the main findings of the present clinical trial, MB implants performed similar to FB in PKA in octogenarians. The FB group demonstrated shorted surgical time. No difference was found in patient reported outcome measures, ROM, implant positioning, and survivorship.Level of evidenceLevel II, prospective study.

Joint awareness after fixed and mobile-bearing total knee arthroplasty with minimum 12 years of follow-up: A propensity matched-pair analysis

BackgroundMany comparative articles studied mobile-bearing (MB) and fixed-bearing (FB) total knee arthroplasties (TKAs). Meta-analyses found no difference in survival or biomechanical outcome. This study aimed to compare long-term clinical results between fixed-bearing (FB) and mobile-bearing (MB) total knee arthroplasty (TKA) as well as patients’ adaptation to their artificial joints. MethodTKAs performed with the same surgical protocol divided into categories according to the insert design preferred. 70 MB design TKAs were compared with 70 FB design TKAs utilizing propensity matching for parameters; gender, age, body mass index, coronal plane deformity, range of motion (ROM) and appropriateness criteria. Forgotten Joint Score-12 (FJS-12) was used to assess patients’ ability to forget their artificial joints in daily life. ResultsPatients had a mean follow-up of 15.6 (±2.2) years. No difference was observed between groups for post-operative ROM, WOMAC, Knee Society Knee and Function Scores. The FJS-12 in the MB and FB groups were 66.1 and 72.8, respectively (P = 0.026). There was no significant difference in survival between both designs. ConclusionThis study suggests that in TKA, joint awareness is higher in MB compared to FB design. FJS-12 appears to be a sensitive measuring tool when comparing two designs and should be implemented in long-term follow-up.

Short- to mid-term results of minimally invasive lateral unicompartmental knee replacement: 133 cases in a non-designer series

IntroductionThe aim of the current study was to demonstrate short- to mid-term survivorship as well as clinical outcome of lateral unicompartmental knee replacement (UKR) with a fixed-bearing (FB) design from a non-designer center using the Oxford Fixed Lateral prosthesis.Materials and methodsThis single-center retrospective cohort study reports the results of 133 consecutive lateral FB-UKR. Survivorship analysis was performed with different endpoints and clinical outcome was measured using the Oxford-Knee-Score (OKS), American-Knee-Society-Score (AKSS-O), range-of-motion (ROM) and visual-analog-scale for pain (VAS).ResultsThere were two revision surgeries with conversion to total knee replacements (TKR) due to persistent pain resulting in a survival rate of 98.5% (95% CI 93.5–99.6) with a mean follow-up (FU) of 3.3 ± 1.8 years (range 1–8.5). All outcome scores, VAS and ROM showed a significant improvement at final FU (p < 0.001). The OKS improved from 26 ± 7.8 (range 11–45) preoperatively to 39 ± 8.3 (range 13–48), the AKSS-O from 49.2 ± 14.6 (range 18–90) to 81.8 ± 15.1 (range 40–100), the AKSS-F from 53 ± 23.7 (range 0–100) to 80.4 ± 21.4 (range 5–100) and the ROM from 118 ± 17 (range 90–160) to 134 ± 9.5 (range 100–155).ConclusionsThe short- to mid-term results following lateral FB-UKR demonstrate a high survivorship and good clinical outcome from an independent series. We, therefore, suggest that FB-UKR is a safe treatment option for isolated lateral OA if sufficient surgical experience is provided.Level of evidenceRetrospective cohort study, level IV.

Less groin pain with dual-mobility bearings versus fixed bearings in total hip arthroplasty.

The relationship between implant type, dual mobility (DM) or fixed bearing (FB), and postoperative groin pain remains unexplored. We examined the incidence of groin pain in DM implants and compare this to a cohort of FB THA patients. From 2006 to 2018, a single surgeon performed 875 DM THA and 856 FB THA procedures with 2.8-year and 3.1-year follow-up, respectively. Each patient received a questionnaire postoperatively and was asked if they had any groin pain (yes/no). Secondary measurements were implant characteristics such as head size, head offset, cup size, and cup-to-head ratio. Additional PROMs that were collected included: Veterans RAND 12 (VR-12), University of California Los Angeles (UCLA) activity score, Pain visual analogue scale (Pain VAS), and range of motion (ROM). The incidence of groin pain was 2.3% in the DM THA cohort and 6.3% in the FB THA group (p < 0.001). Also, low head offset (⩽0 mm) had a significant odds ratio (1.61) for groin pain in both cohorts. There was no significant difference in terms of revision rate between the cohorts (2.5% vs. 3.3%, p = 0.39) at the latest follow up. This study demonstrated a lower incidence of groin pain (2.3%) in patients with a DM bearing compared to a FB (6.3%) and a greater risk of groin pain with low head offset (<0 mm). As such, surgeons should try to recreate offset of the hip compared to the contralateral side to avoid groin pain.