Fixed-bearing Research Articles

166 Dual Mobility for Total Hip Arthroplasty Revision Surgery: A Systematic Review and Metanalysis

Abstract Dual Mobility (DM) implants provide greater stability especially in Revision Total Hip Arthroplasty (R-THA) when compared to primary THA. Aim: to identify the current evidence regarding outcomes of DM in R-THA when compared to fixed-bearing (FB) implants. Review in accordance with PRISMA guidelines. Structured electronic searches. Primary outcome measure: dislocation rate following R-THA. Secondary outcome measures: implant survival, aseptic loosening, infection rate. Studies' methodology quality assessed using MINORS criteria. All articles published from 2016 to December 2019 included. 1777 R-THAs were reported (49.9% with DM acetabular component, 50.1% with FB component). Sample size: 67-426 patients. Mean age: 57-73. Mean follow-up period: 12-60 months. Significant risk ratio of 1.08 [1.05, 1.12] (95% CI, I2 = 37%, P < 0.00001) with statistically significant difference between the two groups in favour of DM implant. Statistically significant difference in favour of DM group with respect to dislocation rate (risk ratio 0.22, 95% CI; P < 0.00001) and aseptic loosening (risk ratio 0.51, 95% CI; P < 0.05). No statistical difference between the groups on risk ratio for infection 0.94 (95% CI; P = 0.85). DM implants are beneficial in R-THA when compared to FB implants. However, one needs to balance the benefits of using DM implant considering the patient’s clinical conditions and the costs involved.

589 Early Results of Single Anaesthetic Bilateral Fixed Bearing Cemented Medial Unicompartmental Knee Replacement

Abstract Introduction Unicompartmental knee replacement (UKR) results in less morbidity, early mobilisation, and better PROMs in appropriately selected patients. There has been a steady increase in the number of fixed bearing UKRs in the NJR. We present the early results of single anaesthetic bilateral fixed bearing cemented medial UKR. Method All patients undergoing bilateral UKR using the ZUK prosthesis (LIMA, UK) under a single anaesthetic between March 2013 and March 2019 were included in this study. Demographic data, surgical data, change in haemoglobin after surgery and occurrence of complications were prospectively recorded in the hospital database. Pre-op and follow-up Oxford knee scores were recorded. Statistical analysis was performed using SPSS 25.0 (IBM, USA) and paired t-test was used to analyse improvement in functional score. Results Nine patients were included in this study. The mean age was 53.2years (range 43-71 years). There were 2 females and 7 males. A significant improvement in Oxford knee score from a mean of 37.2 to 53.6(p < 0.01) was seen. The mean drop in Hb was 4.1mg/dl. The mean follow up was 28 months (range 12-76 months). Conclusions There was good improvement in functional scores without any significant drop in Hb. Therefore, it is a safe and beneficial procedure.

In vivo comparison of rotating platform and fixed bearing knee replacements during lunge and pivot activities

BackgroundThe objective of this study was to discover whether notable differences in mobile and fixed-bearing kinematics occur during activity that promotes tibial rotation, and to compare these results with normal healthy kinematics. We hypothesized that rotating-platform knee replacements would exhibit greater rotation of the tibia relative to the fixed-bearing knee replacements. Materials and MethodsThe in vivo motion of the tibia relative to the femur was measured in subjects with posterior stabilized fixed-bearing (FB) and rotating-platform (RP) total knee arthroplasties using a high-speed stereo radiography system during a lunge and gait with a change in direction (pivot). ResultsThe in vivo internal/external (IE) rotation and anterior/posterior translation of the tibia relative to the femur was similar between mobile and fixed-bearing total knee prostheses during two activities of daily living that included an activity that challenged tibial IE rotation. Measurements of IE rotation in participants with RP had higher variability and significantly greater range between maximum internal and external rotation compared with FB participants. The greater amount of variability of RP was not unlike the healthy knee. ConclusionThe pattern of IE rotation and AP translation for both RP and FB designs were similar to healthy kinematics but with less IE rotation. The RP implants more closely replicated the asymmetrical posterior condylar translation and range of IE rotation of the healthy knee during activity that challenged tibial IE rotation.

Total knee replacement wear during simulated gait with mechanical and anatomic alignments.

Total knee replacements (TKR) have historically been implanted perpendicular to the mechanical axis of the knee joint, with a commensurate external rotation of the femur in flexion relative to the posterior condylar axis (PCA). Although this mechanical alignment (MA) method has typically offered good long-term survivorship of implants, it may result in alignment of the implant that departs significantly from the native Joint Line (JL) in extension and flexion for a considerable portion of the patient population. There is a growing interest with surgeons to implant TKR components more closely aligned to the natural JL (Anatomic Alignment-AA) of the patient's knee joint to reduce the need for soft tissue releases during surgery, potentially improving knee function and patient satisfaction. Using a previously-validated finite element model of the lower extremity, implant- and alignment-specific loading conditions were developed and applied in a wear experiment via a six-degree-of-freedom joint simulator. MA was defined as 0° Joint Line (JL), 0° varus hip-knee-ankle (HKA) angle, and 3° external femoral rotation. AA was defined as 5° varus JL, 3° varus HKA, and 0° femoral rotation. The experiment returned wear rates of 3.76 ± 0.51 mg/million cycles (Mcyc) and 2.59 ± 2.11 mg/Mcyc for ATTUNE® cruciate-retaining (CR) fixed bearing (FB) in MA and AA, respectively. For ATTUNE posterior-stabilized (PS) FB in AA, the wear rate was 0.97 ± 1.11 mg/Mcyc. For ATTUNE CR rotating platform (RP), the wear rates were 0.23 ± 0.19 mg/Mcyc, 0.48 ± 1.02 mg/Mcyc in MA and AA respectively. Using a two-way ANOVA, it was determined that there was no significantly difference in the wear rates between AA and MA (p = 0.144) nor the wear rate of ATTUNE PS FB in AA significantly different from either ATTUNE CR FB or ATTUNE CR RP.

Effects of contact stress on patellarfemoral joint and quadriceps force in fixed and mobile-bearing medial unicompartmental knee arthroplasty

BackgroundUnicompartmental knee arthroplasty (UKA) is an effective treatment for end-stage, symptomatic unicompartmental osteoarthritis of the knee joint. However, patellofemoral joint degeneration is a contraindication to medial UKA. Therefore, the objective of this study was to evaluate the biomechanical effect of medial UKA using fixed-bearing (FB) and mobile-bearing (MB) design prostheses on the patellofemoral joint.MethodsA three-dimensional finite-element model of a normal knee joint was developed using medical image data. We performed statistical analysis for each model. The differences in contact stress on the patellofemoral joint and the quadriceps force between the FB and MB designs were evaluated under a deep-knee-bend condition.ResultsAt an early flexion angle, the results of contact stress showed no significant difference between the FB and MB medial UKA models compared with the intact model. However, at high flexion angles, we observed a significant increase in contact stress with the FB models compared with the intact model. On the contrary, in the case of the MB models, we found no statistically significant increment compared with the intact model. A larger quadriceps force was needed to produce an identical flexion angle for both the FB and MB UKA designs than for the intact model. At high flexion angles, a significant increase quadriceps force whit the FB model compared with the intact model.ConclusionsOur results indicate that with medial UKA, the contact stress increased and greater quadriceps force was applied to the patellofemoral joint. However, performing UKA on a patellofemoral joint with osteoarthritis should not be difficult, unless anterior knee pain is present, because the increase in contact stress is negligible.

Fixed- versus mobile-bearing unicompartmental knee arthroplasty: a meta-analysis

Unicompartmental knee arthroplasty (UKA) can be either a fixed bearing (FB) or a mobile bearing (MB) construct with controversy as to which design is superior. This question is addressed with a systematic review and meta-analysis. A literature search was performed using PubMed, Embase and the Cochrane Library. Studies were reviewed according to the inclusion and exclusion criteria developed in advance. We compared the differences in clinical and radiological outcomes between the FB and MB UKAs. Analyses were performed with the Review Manager and STATA software. A total of 17 studies involving 2612 knees were included. No significant differences were presented between the FB and MB prostheses in clinical and radiological outcomes. However, it was evident that there were differences in the modes and timing of the failures, bearing dislocation led to earlier failures in the MB prosthesis, while the FB prosthesis failed later due to polyethylene wear. There was no evidence of publication bias using the incidence of revisions. There is no significant difference between the FB and MB UKAs; however, there are differences in the modes and timing of failures.

Multi-Segment Foot and Ankle Gait Kinematics Following Total Ankle Arthroplasty

Category:Ankle Arthritis; Ankle.Introduction/Purpose:Ankle arthritis is a painful disease resulting in limited function, mobility, and quality of life.1 Total ankle arthroplasty (TAA) a widely accepted treatment to reduce pain while maintaining joint motion.2,3 There are two common types of implants: fixed bearing (FB) and mobile bearing (MB). Comparisons of these implants have shown similar patient and clinical outcomes;4 however, post-operative gait kinematics from a multi-segment foot and ankle model have not been compared. This study assessed multi-segmental foot and ankle gait kinematics between persons following TAA with MB and FB implants and compared them to control data of adult ambulators without lower extremity pathology.Methods:This was a prospective analysis of persons who had previously underwent TAA with a MB (n=6; average follow-up period of 2.5 years) implant. After consenting to the IRB-approved study, participants were fitted with reflective markers for the Milwaukee Foot Model (MFM).5 Participants walked barefoot along a 30-foot walkway at a comfortable, self-selected pace for a minimum of ten trials while twelve infrared motion capture cameras recorded data. Kinematic data from the MB group and historical data from a FB population who underwent the same protocol with the MFM (n=7; average follow-up period of 2 years) were compared to control data (n=37). Welch’s two-tailed t-tests were used to calculate statistical significance at an alpha level of 0.05. Deviation from control data was compared between both implant groups.Results:In the MB group, sagittal motion of the hindfoot, forefoot, and hallux were significantly different from control for the majority of stance. The only significant MB group swing phase differences were early swing sagittal kinematics in the tibia, forefoot, and hallux segments. The FB data differed significantly for the majority of stance phase for sagittal tibia motion, all hindfoot planes, sagittal and coronal forefoot motion, and all hallux planes. The FB group kinematics also significantly differed throughout most of swing phase across all planes and segments, except coronal hindfoot motion. All FB kinematic data deviated further from control than the MB data except stance phase coronal tibia and transverse forefoot motion, where the data overlapped (Figure 1).Conclusion:Multi-segment foot and ankle gait kinematics following TAA showed the MB implant better restores healthy ambulatory motion than the FB implant. Abnormal stance phase kinematics lead to altered joint loading. This can accelerate adjacent joint arthritis, which has been seen following ankle arthrodesis.6 Both populations showed diminished forefoot plantarflexion throughout gait, compensating for decreased hindfoot dorsiflexion. Because the joints are not heavily loaded during swing phase, the primary concerns of alterations are regarding ground clearance and foot position prior to the next step. The MB implant better restores normal gait, minimizing compensations and likely decreasing arthritis-inducing stress on adjacent joints.

Mobile Bearing versus Fixed Bearing for Total Knee Arthroplasty: Meta-analysis of Randomized Controlled Trials at Minimum 10-Year Follow-up.

This meta-analysis aimed to compare the clinical and radiographic outcomes between mobile-bearing total knee arthroplasty (MB-TKA) and fixed-bearing total knee arthroplasty (FB-TKA) at a minimum 10-year follow-up. PubMed, EMBASE, and Cochrane databases were searched. All included articles were evaluated by two trained reviewers according to the guidelines of the Cochrane Collaboration Handbook for potential risk, and the Consolidated Standards on Reporting Trials (CONSORT) checklist and scoring system was also used to assess the methodological quality of each study. The extracted data included function scores, range of motion (ROM) of the knee, incidence of adverse events or revision, survivorship analysis, and radiographic outcomes. Seven randomized controlled trials (RCTs) were included in this meta-analysis, and all RCTs had a follow-up period longer than 10 years. This meta-analysis shows no significant difference between the two groups with respect to the Keen Society Score (KSS; p = 0.38), KSS function score (p = 0.30), the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC; p = 0.59), ROM (p = 0.71), radiolucent line (p = 0.45), femoral and tibial component positions in the coronal plane (p = 0.55 and 0.35, respectively), revision incidence (p = 0.77), and survivorship rates (p = 0.39). Meanwhile, it showed a slight difference between the two groups in the tibial component position in the sagittal plane (p = 0.003). According to this meta-analysis, the current best available evidence suggests no significant difference between the MB-TKA and FB-TKA groups with respect to the clinical outcomes, radiographic outcomes, revision, and survivorship at a minimum 10-year follow-up. This is a Level II, meta-analysis study.

Comparison of implant position and joint awareness between fixed- and mobile-bearing unicompartmental knee arthroplasty: a minimum of fiveyear follow-up study.

To compare the implant position and patient-reported outcomes (PROs) regarding joint awareness using the Forgotten Joint Score (FJS) following between fixed-bearing (FB) and mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) with a minimum of fiveyears' follow-up. One hundred fifteen consecutive UKAs (58 FB UKAs and 57 MB UKAs) performed were retrospectively evaluated. We compared the radiographic parameters including component positions and relationships as well as lower extremity alignment. Post-operative clinical outcomes were assessed using Knee Society Score (KSS), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, Tegner activity score, and FJS. The MB UKA group showed more convergent componentry relationship between femoral and tibial components (p < 0.001). The joint line of the MB UKA group was restored significantly better (p < 0.05). In addition, the positioning of femoral and tibial components of the MB UKA group showed less deviation from the weight-bearing line (WBL) (p < 0.05). Although there were no differences in KSS, WOMAC, and Tegner activity scores between the groups, the MB UKA group showed significantly better FJS than did the FB UKA group atfive years post-operatively (p < 0.05). The MB UKA group had a more convergent componentry relationship, less deviation from WBL, better joint-line restoration, and reduced joint awareness than did the FB UKA group at fiveyears follow-up.

Superior Mid- to Long-Term Clinical Outcomes of Mobile-Bearing Total Knee Arthroplasty Compared to Fixed-Bearing: A Meta-Analysis Based on a Minimum of 5 Years of Study.

As more patients undergo total knee arthroplasty (TKA) each year, and the average age of patients gets younger, the patients are generally more active requiring a greater physiological demand and increasing range of motion on the prosthesis than the previous patients. However, there is no consensus on the optimal TKA tibial bearing design. We performed this systematic review to compare the clinical differences between mobile and fixed bearing constructs used in contemporary TKA. We searched PubMed, EMBASE, and Cochrane Library databases, identifying 515 total publications, including 17 randomized controlled trials (RCTs). A meta-analysis was performed, while the quality and bias of the evidence were rated according to the Grading of Recommendations Assessment Development and Evaluation (GRADE) guidelines and the Cochrane Database questionnaire. The meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Seventeen studies were included, with a total of 1505 knees receiving a mobile bearing TKA and 1550 knees receiving a fixed bearing TKA. The meta-analysis compared clinical outcomes between mobile bearing (MB)-TKA and fixed bearing (FB)-TKA using postoperative Knee Society Score, postoperative ROM, and survivorship and showed that there was a distinct difference in Knee Society Score between the mobile-bearing and fixed-bearing groups (overall standardized mean difference = 1.38; 95% confidence interval (CI): 0.50-2.25; p = 0.002; I2 = 60%). Patients treated with mobile-bearing prostheses were more likely to report good or excellent range of motion results (overall standardized mean difference = 2.06; 95% CI: 0.65-3.47; p = 0.004). No difference in implant survivorship or reoperation rate were identified. The fixed-bearing and mobile-bearing TKA designs are both capable of producing excellent long-term results with excellent clinical outcomes if properly implanted; however, the mobile-bearing TKA have superiority in mid- to long-term clinical results. Trial registration number for PROSPERO was CRD42019126402.

No difference in patient satisfaction after mobile bearing or fixed bearing medial unicompartmental knee arthroplasty.

Medial unicompartmental knee arthroplasty (UKA) has excellent survival rates using one of the two implant designs: mobile bearing (MB) or fixed bearing (FB). There is a lack of studies comparing patient-reported outcomes (PROs) of both implants. This study aimed to document and compare PROs of MB UKA to FB UKA at 6, 12 and 24months after surgery. A single high-volume surgeon, retrospective cohort study with prospectively collected data of two groups of UKA patients, with a MB (n = 66) or FB (n = 97) implant. Primary outcome was patient satisfaction (0-10; NRS). Secondary outcomes were pain at rest (NRS), pain during activity (NRS), function (OKS, KOOS-PS), quality of life (EQ-5D-3L), anchor pain, anchor function and anchor recovery. PROs were collected 6, 12 and 24months postoperatively. The complication rate and revision rate within one year after surgery were recorded. For the MB group, the median NRS satisfaction score was 9.0 (8.0-10.0) compared to 9.0 (8.0-9.5) for the FB group at 6months (p = 0.620). Similar scores were found at 12 and 24months; both MB 9.0 (8.0-10.0) and FB 9.0 (8.0-10.0) (p = 0.556 and p = 0.522, respectively). There were no statistically significant differences between MB and FB groups in all secondary outcomes postoperatively. Medial UKA performed by a high-volume surgeon, using a MB or a FB implant, results in excellent patient satisfaction, pain relief, functional improvement and quality of life improvement at 6, 12 and 24months after surgery. The recommendation and use of one over the other is not justified based on the outcomes in the current study. III.

Mobile bearing leads to less proximal medial tibial strain following UKA in comparison with fixed bearing in a cadaver setup

Aims and Objectives:Inexplicable pain to the medial proximal tibia is a frequent finding leading to revision after unicondylar knee arthroplasty (UKA). This study is an effort to find out, if there are any differences between mobile (MB) and fixed bearing (FB) UKA designs in terms of resulting strain in the medial proximal tibia as measured in an in vitro cadaver setup. It was hypothesized that MB UKA would result in lower bone strain.Materials and Methods:Five pairs of fresh-frozen full leg cadaver specimens were mounted in a kinematic rig that applied a dynamic squatting motion knee flexion after prior 3D CT. The rig allowed for 6 degrees-of-freedom at the knee while forces were applied to the quadriceps and hamstrings. During testing, an infrared camera system tracked the location of reflective markers attached to the tibia and femur with bicortical bone pins. Tibial cortical bone strain was measured with stacked strain gauge rosettes attached at predefined anterior and posterior positions on the medial cortex. Sensor outputs were recorded at 2000 Hz and synchronized with kinematic data prior and after pairwise implantation of MB and FB UKA directly comparing those between left and right knees from the same donor.Results:Bone strain values consistently increased with increasing flexion angle. FB UKA significantly increased strain in the anterior region of the medial tibial bone, while MB closely replicated strain values of the native knee.Conclusion:Proximal tibial bone strain seems to be lesser following MB UKA in comparison with FB UKA. Clinical studies will have to show, if this translates into a higher rate of pain problems with FB UKA.

Lack of early dislocation for dual mobility vs. fixed bearing total hip arthroplasty: A multi-center analysis of comparable cohorts

BackgroundDislocation is a major cause of morbidity and revision surgery following total hip arthroplasty (THA). To address such issues, dual mobility (DM) bearings were introduced as a more stable alternative to fixed-bearing (FB) prostheses. As such, we compared DM and FB systems in a cohort study in terms of dislocations, readmissions, and revisions. MethodsA 27 multi-center retrospective review was performed of 664 DM and 218 FB cases from the same manufacturer with mean follow-up of 2.09 years and 1.83 years, respectively. Patient reported outcome measures (PROMs) including Harris Hip Score (HHS), SF12, EQ5D, and Lower Extremity Activity Score (LEAS) were evaluated as well as dislocation rates, readmissions, and revisions rates. We also performed a survivorship analysis through Kaplan-Meier estimator. Students t-test was used for normally distributed continuous data and Fisher exact test (P < 0.05) was used for discrete data. ResultsThere were 0 dislocations in the DM (0%) group and 2 dislocations in the FB (0.92%) group (p = 0.06). Latest follow up HHS revealed a significant difference between groups (91.44 DM and 87.81 FB; p = 0.006). In addition, there was significant difference between DM and FB on SF12 Physical Component Score (PCS) (46.83 and 44.55, respectively, p = 0.015). Also, readmission rates at 30, 60 and 90 days remained lower for DM than for FB at each time point (1.05% vs. 2.75%, 1.81% vs. 2.75%, and 1.81% vs. 2.75, respectively). Overall, DM had a lower revision rate at 1.51% compared to 2.29% for FB (p = 0.24). The revision breakdown for DM revealed 0 (0%) for both Anatomic Dual Mobility (ADM) and Modular Dual Mobility (MDM) due to the acetabular component.) There was a difference, 14 (87.5%) for ADM and 2 (12.5%) due to the femoral component. The survivorship analysis revealed no significance difference between DM and FB at 4 years (97.90% and 97.26%, respectively). ConclusionIn comparison to patients who undergo FB THA, DM bearings have improved PROMs and a lower rate of dislocation, readmission, and revision.

Does mobile-bearing have better flexion and axial rotation than fixed-bearing in total knee arthroplasty? A randomised controlled study based on gait

ObjectiveTo analyse the 6 degrees of freedom of the knee and gait data of patients with medial knee osteoarthritis before and after fixed-bearing (FB) and mobile-bearing (MB) total knee arthroplasty (TKA) ​and examine the influence of TKA on gait characteristics and the difference between FB and MB prosthesis. We also sought to explore the prosthesis options available for TKA in these patients. MethodsThirty patients who underwent TKA at the Department of Orthopedics at our hospital from June to October 2017 were included. All patients had a lower limb mechanical axis (hip-knee-ankle angle) of less than 180° which were regarded as genu varum knees and had medial knee osteoarthritis. Patients were randomised divided into the FB group ​and the MB group according to the knee prosthesis implanted. An infrared navigation three-dimensional portable knee motion analysis system (Opti-Knee®, Shanghai Innomotion, Inc.) was used to acquire data on the 6 degrees of freedom of both knees when walking on flat ground before and after surgery (angle of tibia relative to femur parameters: flexion-extension, internal rotation–external rotation, abduction–adduction; displacement parameters: anterior–posterior, proximal–distal, medial–lateral). Postoperative follow-up efficacy was assessed using the Oxford Knee Score system. ResultsThere were significant differences in the maximum values of the internal/external rotation and flexion/extension angle between patients post-TKA and the healthy population, p values were 0.007 and <0.001,respectively. The postoperative maximum values of genu varum and internal rotation in both FB [(−9.49 ​± ​5.99°), (−5.77 ​± ​3.42°), respectively] and MB [(−9.64 ​± ​4.83°), (−7.54 ​± ​4.51°), respectively] groups were lower than the preoperative ones [FB (−15.13 ​± ​6.78°), (−8.28 ​± ​4.83°); MB (−13.28 ​± ​3.98°), (−9.46 ​± ​4.99°), respectively] (p ​≤ ​0.001), while the postoperative maximum values of flexion angle and anterior displacement in both FB [(46.11 ​± ​4.14°), (0.71 ​± ​0.35 ​cm), respectively] and MB [(49.33 ​± ​3.98°), (0.75 ​± ​0.89 ​cm), respectively] groups were larger than the preoperative ones [FB (43.15 ​± ​3.77°), (0.26 ​± ​0.74 ​cm); MB (44.62 ​± ​5.92°), (0.33 ​± ​0.79°), respectively] (p ​≤ ​0.001). The postoperative range of flexion/extension angle in both FB (40.13 ​± ​4.14°) and MB (45.82 ​± ​3.76°) groups was significantly larger than the preoperative one [FB (36.17 ​± ​6.07°), MB (37.09 ​± ​3.93°), respectively] (p ​≤ ​0.001). There were also significant increases in range of anterior–posterior displacement in the FB group (0.85 ​± ​0.32 ​cm) postoperatively compared with the preoperative one (0.71 ​± ​0.92 ​cm) (p ​= ​0.016) ​and significant increases in range of medial-lateral displacement (0.64 ​± ​0.73 ​cm) in the MB group postoperatively compared with the preoperative one (0.52 ​± ​0.91 ​cm) (p ​= ​0.025). The mean flexion/extension angle of the MB group was significantly greater than the FB group after surgery in both the stance phase and the swing phase (p ​< ​0.001). There were significant differences in postoperative knee axial rotation during the gait cycle between the MB and FB groups (p ​= ​0.028) ​and that postoperative internal rotation of the tibia relative to the femur increased in the MB group. The Oxford Knee Score at the last follow-up visit about 7.5 months after surgery was 15.6 ​± ​1.3 and 15.1 ​± ​1.1 points for FB and MB groups, respectively. This difference was not significant (p ​= ​0.428). ConclusionsTKA can make the parameters of knee gait characteristics closer to the normal population. Medial knee osteoarthritis patients who received a MB prosthesis in TKA had better joint flexion function and axial rotation than the FB one. However, there is insufficient evidence to suggest that the MB prosthesis is a better option for patients with medial knee osteoarthritis. The translational potential of this articleTo date, no consensus for prosthesis selection in TKA has been established. This study found significant differences in joint flexion/extension angle and internal/external rotation during gait post-TKA surgery in medial knee osteoarthritis patients who received different prostheses. This will provide some references for prosthesis selection for a large number of genu varum patients in clinical practice.

COMPARING TRANSVERSE PLANE BIOMECHANICS BETWEEN FIXED- AND MOBILE-BEARING TOTAL KNEE ARTHROPLASTY DURING LEVEL WALKING, STAIR NEGOTIATION AND PIVOTING

Compared with fixed-bearing (FB) total knee arthroplasty (TKA), mobile-bearing (MB) TKA may promote knee rotation and reduce rotational load at bone–implant interface. Unfortunately, this hypothesis has not been examined with neither knee rotation during stance of pivoting nor knee rotational moment during activities other than level walking. This study used 3D motion analysis to obtain the rotation of tibia relative to the femur and knee rotation moment during stance phase of level walking, stair ascent/descent, step and spin turn for 17 FB, 20[Formula: see text]MB and 28 healthy knees. Statistical comparisons revealed that transverse plane biomechanics was similar between MB and FB knees. Compared with healthy knees ([Formula: see text]), both FB ([Formula: see text]) and MB knees ([Formula: see text]) reduced internal rotation during step turn at early stance. During spin turn, FB knees ([Formula: see text] vs. [Formula: see text]) reduced internal rotation at late stance, whereas MB knees ([Formula: see text] versus [Formula: see text]) reduced external rotation at early stance. MB knees (0.064% and 0.126% body weight [Formula: see text] height) had lower peak external rotation moments during early stance phase of both level walking and spin turn than healthy knees (0.108% and 0.238% body weight [Formula: see text] height). Using FB for TKA surgery without bias and step-turn strategy for pivoting were recommended.

Equal tibial component fixation of a mobile-bearing and fixed-bearing medial unicompartmental knee arthroplasty: a randomized controlled RSA study with 2-year follow-up

Background and purpose — Differences in stress distribution in a mobile-bearing and fixed-bearing unicompartmental knee arthroplasty (UKA) design might lead to a difference in fixation of the tibial component. We compared tibial component migration of a mobile-bearing (MB) UKA and a fixed-bearing (FB) UKA using radiostereometric analysis.Patients and methods — In a randomized, patient-blinded clinical trial 62 patients received either the MB Oxford UKA or the FB Sigma UKA. The patients were followed for 24 months with radiostereometric analysis. Clinical outcome was assessed with Oxford Knee Score (OKS), RAND-36 and leg extension power.Results — Migration of the tibial components was similar between groups throughout follow-up. At 12 months, MTPM of the tibial component was 0.44 mm (95% CI 0.34–0.55) for the MB group and 0.40 mm (CI 0.31–0.50) for the FB group. Between 12 and 24 months, the tibial components migrated with a median MTPM increase of 0.03 mm (CI –0.02 to 0.08) in the MB group and 0.03 mm (CI –0.02 to 0.07) in the FB group. Continuous migration of the tibial component was found for 1 MB UKA and 2 FB UKAs. Both groups showed similar and clinically relevant improvement in clinical outcome.Interpretation — MB and FB tibial components had similar good fixation and clinical improvement until 2 years. Based on this study, a low 5- to 10-year revision rate can be expected for both implants.Trial registration: ClinicalTrials.gov identifier: NCT03434600.

A Comparison of Cyst Formation and Management in Mobile-Bearing and Fixed-Bearing Total Ankle Arthroplasty

Category:Ankle ArthritisIntroduction/Purpose:The Scandinavian Total Ankle Replacement(STAR) system and Salto Talaris(ST) total ankle system are two of the more commonly studied total ankle implants. As the STAR is one of the oldest total ankle arthroplasty (TAA) implants still in use today, most studies focus on longevity and survivorship. Reported rates of cyst formation for these two prosthesis in most series vary from 11-22% but no large study has focused on surgical management of these cysts or included patient reported outcomes after surgery. In this series, we aimed to investigate rates of cyst formation between mobile(MB) and fixed-bearing(FB) TAA and examine clinical and patient reported outcomes of bone grafting or cementing of large cysts surrounding the STAR and ST implants.Methods:A prospectively collected database at a high volume total ankle replacement center was retrospectively reviewed to identify patients who underwent TAA with either the STAR or the ST total ankle system between 2007 and 2015. Cysts were identified and measured on standard weight bearing radiographs and confirmed on computed tomography(CT) when available. Visual analog scale (VAS) score, Short Form-36 (SF-36) physical and mental component scores, Short Musculoskeletal Function Assessment(SMFA), and AOFAS hindfoot scores were collected from all patients preoperatively and then at 6 months, 1 year and annually postoperatively. Patients with a minimum 2 years follow-up who underwent revision TAA secondary to catastrophic bone cysts or who were managed with either curettage and bone grafting or curettage and cementing of bone cysts surrounding the TAA prosthesis were included in the patient reported outcomes (PRO) analysisResults:Excluding 53 patients for inadequate follow-up, 232 patients (29% female, 71% male; follow-up 6.7 years) who underwent STAR-TAA and 147 patients (26.6% female, 73.5% male; follow-up 7 years) who underwent ST-TAA were identified. Cysts <20 mm diameter occurred more often in the MB TAAs, and more often in the tibia than talus (table). Cysts >10 mm were identified in 95/232 (41%) STAR and 24/147 (16%) ST ankles. In the STAR group, 24 patients underwent cyst bone grafting (13), cementing (6) or both (8) at a mean 4.8 years. In the ST group, 14 patients underwent cyst bone grafting (6), cementing (4), or both (4) at a mean of 2.7 years. PRO data improved significantly for both the STAR and ST group in all questionnaires (p<0.05 for all).Conclusion:Mobile-bearing total ankle arthroplasty in this cohort had a higher rate of cyst formation greater than 10 mm (95/232 patients, 41%) when compared to a fixed-bearing TAA (24/147, 16.3%). Only 24/95 (25%) of STAR patients and 14/24 (58%) of ST patients required surgical intervention for cyst management. Patient reported outcomes after cyst surgery improved significantly when compared to pre-cyst management surgery and did not differ between MB and FB cohorts (p=0.424). Successful surgical management of large cyst surrounding either mobile-bearing or fixed-bearing total ankle systems can be expected based on the results of this study.Mobile-Bearing TAAFixed-Bearing TAA Total patients (n) 232147 Total Patients with Cysts >10mm95(41%)24 (16%) Patients Requiring Cyst Surgery24/95 (25%)14/24 (58%) Age (years) 61.863.3 Sex Male165(71%)107(73%) Female67(29%)40(27%) Time Until Cysts Visible (years) 1.821.63 Cysts <20mm Diameter Tibia89 patients10 patients Talus51 patients4 patients Both Tibia and Talus29 patients1 patients Cysts >20mm Diameter Tibia28 patients4 patients Talus4 patients2 patients Both0 Patients2 patients Reoperation for Cyst n=24n=14 Management mean 4.8 years post-opmean 2.7 years post-op Bone Grafting136 Cementing64 Both84 SF-36 Before Cyst Surgery Physical Function23.819.9 Mental Health75.177.9 SF-36 After Cyst Surgery Physical Function68.367.6 Mental Health89.488.8 VAS Before Cyst Surgery 62.759.4 VAS After Cyst Surgery 4.13.7

Minimum twelve-year follow-up of fixed- vs mobile-bearing total knee arthroplasty: Double blinded randomized trial

BackgroundTotal knee arthroplasty (TKA) with fixed-bearing (FB) implants have demonstrated impressive functional results and survival rates. Meanwhile, rotating-platform (RP) constructs have biomechanically shown to reduce polyethylene wear, lower the risk of component loosening, and better replicate anatomic knee motion. There is growing question of the clinical impact these design changes have long-term.Questions/purposes: The aim of this double-blinded prospective randomized trial was to compare function and implant survival in patients who received either FB or RP press-fit condylar Sigma (PFC Sigma, DePuy, Warsaw, IN) total knee replacements at a minimum follow-up of twelve years. Patients and methodsPatient reported outcome measures used included the functional Knee Society Score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) scores, Medical Outcomes Short Form-36 (SF-36) score, and satisfaction assessment on a four-point Likert scale. The data was collected from times preoperative, two-years, and final encounter (mean 13.95 years). A total of 28 RP and 19 FB knees (58.8%) were analyzed at the final follow-up. ResultsAmong all patients, KSS and WOMAC scores statistically improved from pre-op to 2-year, while KSS statistically worsened from 2-year to final follow-up. The RP group averaged better follow-up scores in all assessments at the final follow-up with exception of overall satisfaction. There was no statistically significant difference in the functional Knee Society Score, Short Form-36, WOMAC scores, patient satisfaction or implant survival between the two groups at any measured period. ConclusionsThe use of a fixed-bearing or rotating-platform design does not convey significant superiority in terms of function or implant longevity at a minimum twelve years after total knee arthroplasty. Level of evidenceLevel I, Experimental study, randomized controlled trial (RCT).

Temporal patterns of commonly used clinical outcome scales during a 5-year period after total knee arthroplasty

BackgroundIt is not established beyond doubt whether improvements in functional outcome after total knee arthroplasty (TKA) are maintained in the long term. We therefore investigated the temporal patterns of functional outcome [using range of motion (ROM), American Knee Society (AKS) score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and 36-Item Short Form Health Survey (SF-36) score] over a 5-year period after uncomplicated TKA, and whether these patterns differed by implant type and patient age.Materials and methodsThis prospective study evaluated 138 patients who underwent unilateral TKA with either a mobile-bearing (MB) or fixed-bearing (FB) posterior-stabilized prosthesis. An independent investigator evaluated the functional outcome at five time points: preoperatively and at 6-month, 1-year, 2-year, and 5-year follow-up. Differences in functional outcomes between adjacent time points were evaluated by mixed-effect model repeat measurement (MMRM).ResultsThe different functional outcome scores showed improvement till 6 months–2 years, followed by a variable decline. In patients aged ≥ 68 years with an MB implant, most of the functional outcome scores declined between 2 and 5 years after variable initial improvement till 6 months–2 years, whereas the parameters plateaued after 2 years in those aged < 68 years and in older patients with an FB implant.ConclusionsA decline in function and pain relief occurs 2 years after TKA. This decline is more evident in older patients with an MB prosthesis. Based on these findings, we believe that use of MB implants in older patients (≥ 68 years) requires further investigation.Level of evidenceLevel 3.

New design total knee arthroplasty shows medial pivoting movement under weight-bearing conditions.

To assess, using model-based dynamic radiostereometric analysis (RSA), the biomechanical behaviour of a new design posterior-stabilized (PS) fixed-bearing (FB) total knee arthroplasty (TKA) in vivo while patients performing two common motor tasks. The hypothesis was that model-based dynamic RSA is able to detect different behaviour of the implant under weight-bearing and non-weight-bearing conditions. A cohort of 15 non-consecutive patients was evaluated by dynamic RSA 9months after TKA implantation. The mean age of patients was 73.4 (65-72) years. The kinematic evaluations were performed using an RSA device (BI-STAND DRX 2) developed in our Institute. The patients were asked to perform two active motor tasks: sit-to-stand in weight-bearing condition; range of motion (ROM) while sitting on the chair. The motion parameters were evaluated using the Grood and Suntay decomposition and the low-point kinematics methods. The dynamic RSA evaluation showed a significant difference (p < 0.05) between the biomechanical behaviour of the prosthesis during the two motor tasks. When subjected to the patient weight (in the sit-to-stand) the low point of the medial compartment had a shorter motion (5.7 ± 0.2mm) than the lateral (11.0 ± 0.2mm). This realizes a medial pivot motion as in the normal knee. In the ROM task, where the patient had no weight on the prosthesis, this difference was not present: the medial compartment had a displacement of 12.7 ± 0.2mm, while the lateral had 17.3 ± 0.2mm. Model-based RSA proved to be an effective tool for the evaluation of TKA biomechanics. In particular, it was able to determine that the fixed-bearing posterior-stabilized TKA design evaluated in this study showed a medial pivoting movement under weight-bearing conditions that was not present when load was not applied. Under loading conditions what drives the pattern of movement is the prosthetic design itself. By the systematic use of this study protocol future comparisons among different implants could be performed, thus contributing significantly to the improvement of TKA design. IV.