Is there any superiority in the clinical outcome of mobile-bearing knee prosthesis designs compared to fixed-bearing total knee prosthesis designs in the treatment of osteoarthritis of the knee joint? A review of the literature

CORIN KneeTec DeepDishTM: Functional outcomes after a follow-up of 12 months and comparison with the STRYKER Triathlon PS

Several competing concepts of anteroposterior stabilization have been developed for total knee arthroplasty (TKA), with an overall great success despite some differences in terms of clinical or radiological outcomes. The CORIN KneeTec DeepDish TM is a novel mobile-bearing implant, stabilized with an ultra-congruent deep-dish poly- ethylene insert. The aim of the present study was to report clinical and radiological outcomes of a series of patients who received the KneeTec DeepDish TM after a follow-up of 12 months, and to compare them to those of a comparable series of patients who received the STRYKER Triathlon ® posterior- stabilized. This was a retrospective comparative cohort study (level of evidence III). Demographic data, radiographic data and range of motion (ROM), as well the International Knee Society score and Oxford Knee Score were collected pre-operatively, and after a follow-up of 12 months. 106 KneeTec DeepDish TM and 80 Triathlon ® PS were evaluated at follow-up. Patients who received the KneeTec DeepDish TM had significant improvement in ROM, radiographic and clinical outcomes. There were no significant differences between the cohorts in terms of ROM, radiographic and clinical outcomes, as well as antero-posterior stability. This study is the first to report the 12-month outcomes of the CORIN KneeTec DeepDish TM. The novel KneeTec DeepDish TM achieved comparable ROM, radiographic and clinical outcomes to the Triathlon ® PS after 12 months. Further studies will be necessary to evaluate the mid- to long-term outcomes of the KneeTec DeepDish TM .

Major Aseptic Revision Following Total Knee Replacement: A Study of 478,081 Total Knee Replacements from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

Major revision is associated with less satisfactory outcomes, substantial complications, and added cost. Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) were analyzed to identify factors associated with major aseptic revision (MAR) of primary total knee replacement (TKR).

METHODS

The cumulative percent major aseptic revision rate following all primary TKRs performed in Australia from September 1, 1999, to December 31, 2015, was assessed. Kaplan-Meier estimates of survivorship were utilized to describe the time to first revision. Hazard ratios (HRs) from Cox proportional hazard models, adjusted for age and sex, were utilized to compare revision rates.

RESULTS

There were 5,973 MARs recorded from the total cohort of 478,081 primary TKRs. The cumulative percent MAR at 15 years was 3.0% (95% confidence interval [CI], 2.8% to 3.2%). Fixed bearings had a significantly lower rate of MAR at 15 years: 2.7% (95% CI, 2.4% to 2.9%) compared with 4.1% (95% CI, 3.8% to 4.5%) for mobile bearings (HR, 1.77 [95% CI, 1.68 to 1.86]; p < 0.001). Age had a significant effect on MAR rates, with a cumulative percent revision at 15 years for patients <55 years old of 7.8% (95% CI, 6.5% to 9.2%) compared with 1.0% for those ≥75 years old (95% CI, 0.8% to 1.1%; p < 0.001). Minimally stabilized TKR had a lower rate of MAR compared with posterior-stabilized TKR after 2 years (HR, 0.83 [95% CI, 0.77 to 0.90]; p < 0.001). Cementless fixation had a higher rate of revision than cemented or hybrid fixation. There was a higher rate of MAR with non-navigated compared with computer navigated TKR (HR, 1.32 [95% CI, 1.21 to 1.44], p < 0.001). The tibial component was revised more commonly than the femoral component.

CONCLUSIONS

Younger age, posterior stabilization, cementless fixation, a mobile bearing, and non-navigation were risk factors for higher rates of MAR following TKR.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

No differences between fixed- and mobile-bearing total knee arthroplasty

PURPOSE

For years, numerous studies have been performed to determine whether mobile-bearing total knee arthroplasty (MB-TKA) or fixed-bearing total knee arthroplasty (FB-TKA) is the preferential design in total knee arthroplasty. Reviews and meta-analyses on this subject have focused on a relatively small number of randomised controlled trials, possibly missing important results of smaller studies. The goal of this review was to provide a comprehensive overview of all literature comparing MB-TKA and FB-TKA in the treatment of osteoarthritis of the knee.

METHODS

An extensive literature search was performed in the PubMed database. All studies that compared MB-TKA with FB-TKA and looked at one of four theorised advantages (insert wear, signs of loosening, survival rate of the prosthesis and clinical outcome) were included.

RESULTS

The initial search yielded 258 articles, of which 127 were included after the first screening. The included studies consisted of 9 meta-analyses, 3 systematic reviews, 48 RCT's, 44 comparative studies, 10 reviews and 13 studies that examined patients who received bilateral TKA (one MB-TKA and one FB-TKA). Combining the results of all studies showed that almost all studies found no difference between MB-TKA and FB-TKA.

CONCLUSIONS

Even when examining all different types of studies on MB-TKA and FB-TKA, the results of this review showed no difference in insert wear, risk of loosening, survivorship or clinical outcome. In daily practice, the choice between MB-TKA and FB-TKA should be based on the experience and judgment of the surgeon, since no clear differences are observed in the scientific literature.

LEVEL OF EVIDENCE

III.

Higher forgotten joint score for fixed-bearing than for mobile-bearing total knee arthroplasty

PURPOSE

To compare the postoperative subjective outcome for fixed- and mobile-bearing total knee arthroplasty (TKA) by using the forgotten joint score (FJS-12), a new patient-reported outcome score of 12 questions evaluating the potential of a patient to forget about his operated joint. The hypothesis of this study was that a mobile-bearing TKA would have a higher level of forgotten joint than a fixed-bearing model of the same design.

METHODS

A retrospective cohort study was conducted in 100 patients who underwent TKA at least 1 year [mean (SD) 18 (5) months] before with either a fixed-bearing (N = 50) or a mobile-bearing (N = 50) TKA from the same implant family. Clinical outcome was evaluated with the knee society score and patient-reported outcome with the forgotten joint score.

RESULTS

No difference was observed for demographics in between both study groups. The mean (SD) postoperative FJS-12 for the fixed-bearing TKA was 71 (28) compared to a mean (SD) of 56.5 (30) for the mobile-bearing TKA.

DISCUSSION

The clinical relevance of the present retrospective study is that it shows for the first time a significant difference between fixed- and mobile-bearing TKA by using a new patient-reported outcome score. The hypothesis that mobile-bearing TKA would have a higher degree of forgotten joint than a fixed-bearing TKA could not be confirmed. A level I prospective study should be set up to objectivise these findings.

LEVEL OF EVIDENCE

IV.

Low-Contact-Stress Knee Arthroplasty: Past History or Ahead of Time?

Low-contact-stress mobile-bearing (MB) total knee arthroplasty (TKA) can rely on a long history. Its concept comprises a combination of high condylar congruency and compensatory bearing rotation to promote load sharing. However, other MB designs have become available, and critical points have been raised about the benefit of MB in general. Although there is kinematic and kinetic support for the low-contact-stress concept, there is no tribologic or clinical proof of its superiority over fixed-bearing concepts. Further study should be controlled for differences in polyethylene quality and need to provide a measure of condylar congruency to differentiate authentic low-contact-stress variants form others. [Orthopedics. 2016; 39(3):e402-e412.].

Cruciate retaining and cruciate substituting ultra-congruent insert

The posterior cruciate ligament (PCL) conservation and the polyethylene insert constraint in total knee arthroplasty (TKA) are still debated. The PCL is one of the primary stabilizers of the joint, but cruciate retaining (CR) implants have the disadvantage of a difficult balancing of the PCL. Postero-stabilized (PS) implants were introduced to reduce this problem. However, also the PS implants have some disadvantages, due to the cam-mechanism, such as high risk of cam-mechanism polyethylene wear. To minimize the polyethylene wear of the cam-mechanism and the bone sacrifice due to the intercondylar box, different types of inserts were developed, trying to increase the implant conformity and to reduce stresses on the bone-implant interface. In this scenario ultra-congruent (UC) inserts were developed. Those inserts are characterized by a high anterior wall and a deep-dished plate. This conformation should guarantee a good stability without the posterior cam. Few studies on both kinematic and clinical outcomes of UC inserts are available. Clinical and radiological outcomes, as well as kinematic data are similar between UC mobile bearing (MB) and standard PS MB inserts at short to mid-term follow-up. In this manuscript biomechanics and clinical outcomes of UC inserts will be described, and they will be compared to standard PS or CR inserts.

Different femorotibial contact points between fixed- and mobile-bearing TKAs do not show clinical impact

PURPOSE

In anteroposterior (AP)-gliding mobile-bearing total knee arthroplasty (TKA), the femoral component can theoretically slide forward resulting in a more anterior contact point, causing pain due to impingement. A lower lever arm of the extensor apparatus can also attribute to higher patella pressures and pain. The goal of this study was to determine the contact point in a cohort of mobile- and fixed-bearing TKAs, to determine whether the contact point lies more anteriorly in mobile-bearing TKA and to confirm whether this results in anterior knee pain.

METHODS

We used 38 fixed-bearing TKA and 40 mobile-bearing TKA from a randomized trial with straight lateral knee X-rays and measured the contact point. The functional outcome was measured by Knee Society Score at 12 months postoperatively. Pain scores were analysed using a VAS score (0-100 mm) in all patients at rest and when moving. Difficulty at rising up out of a chair was also assessed using a VAS score.

RESULTS

The contact point in mobile-bearing TKA was situated at 59.5 % of the AP distance of the tibia and in the fixed-bearing TKA group at 66.1 % (P< 0.05). Patients with mobile- and fixed-bearing TKAs had similar knee scores, pain scores and difficulty in chair rise. No significant correlation was found between contact point and knee pain.

CONCLUSION

The hypothesis of a more anterior contact point in the mobile-bearing cohort was confirmed but no correlation with functional and pain scores in this cohort could be found. The tibiofemoral contact point could not be correlated with a different clinical outcome and higher incidence of anterior knee pain. This study further adds to the knowledge on possible differences between mobile- and fixed-bearing prostheses. Next to that, bad outcomes could not be explained by CP.

LEVEL OF EVIDENCE

Case series, Level IV.

Long-term data of gait characteristics and moment-knee angle relations in female total knee arthroplasty patients

BACKGROUND

Despite the clinical success of total knee arthroplasty, impaired gait patterns and quadriceps and hamstring maximal voluntary force production might persist years post-surgery. Long-term data of gait patterns and quadriceps and hamstring maximal force production are rarely published with total knee arthroplasty patients. This work examined gait characteristics and the moment-knee angle relations of the knee extensors and flexors about 10 years post-total knee arthroplasty.

METHODS

About a decade post-surgery, 10 female total knee arthroplasty patients (64 years, mobile-bearing inlay) and 10 age-matched female controls were examined. Sagittal plane kinematics in the hip and knee joint during treadmill walking at 2 kilometres per hour were recorded using motion analysis. Spatiotemporal gait parameters were analyzed at self-selected walking speeds with a pressure-platform. The unilateral isometric moment-knee angle relations of the knee extensors and flexors and the electromyographic knee angle relation of the quadriceps were studied using dynamometry. Due to group differences for body mass index values, univariate analysis of variance (main effect: group, secondary effect: body mass index) was used for statistical analysis.

FINDINGS

Total knee arthroplasty patients demonstrated significant (P<0.05) gait deficits during constant and self-selected walking speeds and lower average absolute values in the moment-knee angle relations of the knee extensors and flexors. Significant (P<0.05) lower body-mass-normalized knee extension moments were detected at all knee joint positions for the patients.

INTERPRETATION

Long-term impairments of gait characteristics and maximal voluntary force production, especially for the knee extensors, might persist after total knee arthroplasty.

Mobile bearing vs fixed bearing prostheses for posterior cruciate retaining total knee arthroplasty for postoperative functional status in patients with osteoarthritis and rheumatoid arthritis

BACKGROUND

It is unclear whether there are differences in benefits and harms between mobile and fixed prostheses for total knee arthroplasty (TKA). The previous Cochrane review published in 2004 included two articles. Many more trials have been performed since then; therefore an update is needed.

OBJECTIVES

To assess the benefits and harms of mobile bearing compared with fixed bearing cruciate retaining total knee arthroplasty for functional and clinical outcomes in patients with osteoarthritis (OA) or rheumatoid arthritis (RA).

SEARCH METHODS

We searched The Cochrane Library, PubMed, EMBASE, CINAHL and Web of Science up to 27 February 2014, and the trial registers ClinicalTrials.gov, Multiregister, Current Controlled Trials and the World Health Organization (WHO) International Clinical Trials Registry Platform for data from unpublished trials, up to 11 February 2014. We also screened the reference lists of selected articles.

SELECTION CRITERIA

We selected randomised controlled trials comparing mobile bearing with fixed bearing prostheses in cruciate retaining TKA among patients with osteoarthritis or rheumatoid arthritis, using functional or clinical outcome measures and follow-up of at least six months.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by The Cochrane Collaboration.

MAIN RESULTS

We found 19 studies with 1641 participants (1616 with OA (98.5%) and 25 with RA (1.5%)) and 2247 knees. Seventeen new studies were included in this update.Quality of the evidence ranged from moderate (knee pain) to low (other outcomes). Most studies had unclear risk of bias for allocation concealment, blinding of participants and personnel, blinding of outcome assessment and selective reporting, and high risk of bias for incomplete outcome data and other bias. Knee painWe calculated the standardised mean difference (SMD) for pain, using the Knee Society Score (KSS) and visual analogue scale (VAS) in 11 studies (58%) and 1531 knees (68%). No statistically significant differences between groups were reported (SMD 0.09, 95% confidence interval (CI) -0.03 to 0.22, P value 0.15). This represents an absolute risk difference of 2.4% points higher (95% CI 0.8% lower to 5.9% higher) on the KSS pain scale and a relative percent change of 0.22% (95% CI 0.07% lower to 0.53% higher). The results were homogeneous. Clinical and functional scores The KSS clinical score did not differ statistically significantly between groups (14 studies (74%) and 1845 knees (82%)) with a mean difference (MD) of -1.06 points (95% CI -2.87 to 0.74, P value 0.25) and heterogeneous results. KSS function was reported in 14 studies (74%) with 1845 knees (82%) as an MD of -0.10 point (95% CI -1.93 to 1.73, P value 0.91) and homogeneous results. In two studies (11%), the KSS total score was favourable for mobile bearing (159 vs 132 for fixed bearing), with MD of -26.52 points (95% CI -45.03 to -8.01, P value 0.005), but with a wide 95% confidence interval indicating uncertainty about the estimate.Other reported scoring systems did not show statistically significant differences: Hospital for Special Surgery (HSS) score (seven studies (37%) in 1021 knees (45%)) with an MD of -1.36 (95% CI -4.18 to 1.46, P value 0.35); Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score (two studies (11%), 167 knees (7%)) with an MD of -4.46 (95% CI -16.26 to 7.34, P value 0.46); and Oxford total (five studies (26%), 647 knees (29%) with an MD of -0.25 (95% CI -1.41 to 0.91, P value 0.67). Health-related quality of lifeThree studies (16%) with 498 knees (22%) reported on health-related quality of life, and no statistically significant differences were noted between the mobile bearing and fixed bearing groups. The Short Form (SF)-12 Physical Component Summary had an MD of -1.96 (95% CI -4.55 to 0.63, P value 0.14) and heterogeneous results. Revision surgeryTwenty seven revisions (1.3%) were performed in 17 studies (89%) with 2065 knees (92%). In all, 13 knees were revised in the fixed bearing group and 14 knees in the mobile bearing group. No statistically significant differences were found (risk difference 0.00, 95% CI -0.01 to 0.01, P value 0.58), and homogeneous results were reported. MortalityIn seven out of 19 studies, 13 participants (37%) died. Two of these participants had undergone bilateral surgery, and for seven participants, it was unclear which prosthesis they had received; therefore they were excluded from the analyses. Thus our analysis included four out of 191 participants (2.1%) who had died: one in the fixed bearing group and three in the mobile bearing group. No statistically significant differences were found. The risk difference was -0.02 (95% CI -0.06 to 0.03, P value 0.49) and results were homogeneous. Reoperation ratesThirty reoperations were performed in 17 studies (89%) with 2065 knees (92%): 18 knees in the fixed bearing group (of the 1031 knees) and 12 knees in the mobile group (of the 1034 knees). No statistically significant differences were found. The risk difference was -0.01 (95% CI -0.01 to 0.01, P value 0.99) with homogeneous results. Other serious adverse eventsSixteen studies (84%) reported nine other serious adverse events in 1735 knees (77%): four in the fixed bearing group (of the 862 knees) and five in the mobile bearing group (of the 873 knees). No statistically significant differences were found (risk difference 0.00, 95% CI -0.01 to 0.01, P value 0.88), and results were homogeneous.

AUTHORS' CONCLUSIONS

Moderate- to low-quality evidence suggests that mobile bearing prostheses may have similar effects on knee pain, clinical and functional scores, health-related quality of life, revision surgery, mortality, reoperation rate and other serious adverse events compared with fixed bearing prostheses in posterior cruciate retaining TKA. Therefore we cannot draw firm conclusions. Most (98.5%) participants had OA, so the findings primarily reflect results reported in participants with OA. Future studies should report in greater detail outcomes such as those presented in this systematic review, with sufficient follow-up time to allow gathering of high-quality evidence and to inform clinical practice. Large registry-based studies may have added value, but they are subject to treatment-by-indication bias. Therefore, this systematic review of RCTs can be viewed as the best available evidence.

The self-aligning knee prosthesis: clinical and radiological outcome and survival analysis of a cruciate retaining meniscal bearing knee at 10-year follow-up

PURPOSE

Previously, the clinical and radiological results of the self-aligning cruciate retaining total knee prosthesis at 5-years follow-up were described. The 10-year follow-up is now reported to determine the clinical and radiological results and the survival of the prosthesis.

METHODS

A 10-year follow-up was performed in this prospectively followed cohort of 246 (232 patients) self-aligning, cruciate retaining total knee arthroplasties performed between 1995 and 1998. Because patients had died and others suffered from comorbidities making them unable to attend a follow-up consultation, data could be obtained for 105 prostheses. Clinical results were evaluated by the Knee Society Score, and radiological follow-up was performed on standard AP and lateral X-rays. All radiographs were evaluated for the presence of radiolucencies, osteolysis and wear.

RESULTS

At the 10-year follow-up, there were no new cases of revision so that the cumulative survival rate at 10 years remains 95%. The 10-year follow-up shows good clinical results with an average Knee Society Score of 154 (SD 35.7) and an average range of motion of 109° (SD 13.7). After excluding 25 prostheses for comorbidities, the mean 10-year KSS score increased from 154 to 163 (SD 26.2). On the other hand, for the ROM, the exclusion of the 25 prostheses had no influence on the mean ROM value of 109°. At the 10-year follow-up, none of the 100 available radiographs showed any radiolucencies >2 mm on any component.

CONCLUSIONS

Long-term follow-up of the mobile bearing, cruciate retaining, SAL-II total knee arthroplasty shows excellent clinical and radiological results without bearing dislocation.

LEVEL OF EVIDENCE

Prospective cohort, Level IV.

The Rotaglide mobile-bearing total knee arthroplasty: no difference between cemented and hybrid implantation

PURPOSE

The optimal fixation of the Rotaglide total knee arthroplasty's (TKA) components is controversial. It is hypothesized that the hybrid fixation (cementless femoral component) in a mobile-bearing TKA system might cause increased rate of loosening--especially in the femoral part--and finally failure of the arthroplasty. Consequently, the aim of this study was to compare the survival and revision rates and also the clinical and radiological outcomes of the cemented and hybrid fixation of the Rotaglide TKA.

METHODS

One hundred patients, who underwent TKA with the Rotaglide prosthesis, were randomly placed in two groups. In the first group, the prosthesis was cemented, and in the second group, the hybrid technique was used. Revision and mortality rates were compared after 8-12 years of follow-up. Knee and Osteoarthritis Outcome Score (KOOS) questionnaire and the Knee Society Roentgenographic Evaluation and Scoring System were used to demonstrate clinical and radiographic differences.

RESULTS

There were no statistically significant differences in revision (n.s.) or mortality (n.s.) rates between the two treatment arms. The clinical outcome at the time of last follow-up (mean 9.5 years, SD ± 1.4) ranged from very good to excellent (77.8 ± 17.5 for the cemented group and 77.2 ± 20.4 for the hybrid group). No statistically significant differences in all KOOS subscales. Radiographs showed no significant difference in prosthesis alignment and no evidence of loosening between groups.

CONCLUSION

The hypothesis that the hybrid fixation in a mobile-bearing TKA system might cause increased rate of loosening and finally failure of the arthroplasty was not confirmed. The fixation technique (cemented or hybrid) had no influence on the prosthesis's survivorship, and also on mortality rates, clinical and radiographic outcomes in a mean follow-up time of 9.5 ± 1.4 years. The Rotaglide TKA is a safe and reliable prosthesis regardless the fixation technique.

Anterior knee pain after a total knee arthroplasty: What can cause this pain?

Total Knee Arthroplasty has been shown to be a successful procedure for treating patients with osteoarthritis, and yet approximately 5%-10% of patients experience residual pain, especially in the anterior part of the knee. Many theories have been proposed to explain the etiology of this anterior knee pain (AKP) but, despite improvements having been made, AKP remains a problem. AKP can be described as retropatellar or peripatellar pain, which limits patients in their everyday lives. Patients suffering from AKP experience difficulty in standing up from a chair, walking up and down stairs and riding a bicycle. The question asked was: “How can a ‘perfectly’ placed total knee arthroplasty (TKA) still be painful: what can cause this pain?”. To prevent AKP after TKA it is important to first identify the different anatomical structures that can cause this pain. Greater attention to and understanding of AKP should lead to significant pain relief and greater overall patient satisfaction after TKA. This article is a review of what pain is, how nerve signalling works and what is thought to cause Anterior Knee Pain after a Total Knee Arthroplasty.

Rotating-platform TKA no different from fixed-bearing TKA regarding survivorship or performance: a meta-analysis

BACKGROUND

Mobile bearings have been compared with fixed bearings used in TKA. However, rotating platforms, a specific type of mobile bearing, have not been compared with fixed-bearings using meta-analysis.

QUESTIONS/PURPOSES

We asked whether the performance of a rotating-platform bearing is superior to, comparable to, or worse than a fixed bearing. Four areas were investigated: clinical performance, component alignment, adverse event rates, and revision rates.

METHODS

Searches of Medline, EMBASE, Google Scholar, and the Cochrane databases, combined with reference lists from published meta-analyses and systematic reviews of mobile-bearing versus fixed-bearing prostheses used in TKAs, provided 17 nonlanguage-restricted studies consisting of 1910 TKAs (966 rotating platform versus 944 fixed bearing). Random-effect modeling was used for all meta-analyses, thereby mitigating possible effects of heterogeneity among studies. All meta-analyses were examined for publication bias using funnel plots; publication bias was not detected for any meta-analysis.

RESULTS

There were no statistically or clinically significant differences in clinical performance (clinical scores, ROM, and radiographic evaluation), component alignment, revision rates, or adverse event rates except for tibial component alignment in the AP plane, which favored TKA with fixed-bearings (p = 0.020; standardized mean difference, 0.229; 95% CI, 0.035-0.422), but the effect size was small enough that it was not considered clinically important.

CONCLUSIONS

Based on our findings, which agree substantially with those of prior systematic reviews of TKAs with mobile-bearing versus fixed-bearing prostheses, there is no compelling case for either rotating-platform or fixed-bearing implant design in terms of clinical performance, component alignment, adverse event frequencies, or survivorship. This dataset, which was limited to a maximum 6 years followup, is insufficient to address questions related to wear or late revisions. We therefore suggest that implant choice should be made on the basis of other factors, perhaps including cost or surgeon experience.

The Advantage of a Total Knee Arthroplasty with Rotating Platform is Only Theoretical: Prospective Analysis of 1,152 Arthroplasties

Background:

The aim of total knee surgery is to provide patients with end-stage osteoarthritis of the knee with both pain relief and a functional range of motion with a securely fixed prosthesis for the long term. Many types of implants are designed to achieve these goals. Only clinical outcome studies are able to substantiate the superiority of one design over another. Our primary research question was to determine whether patients receiving a rotating platform implant had a better functional outcome.

Methods:

A total of 1,152 Performance Total Knee Arthroplastiesin 943 patients were studied prospectively. In 561 cases, the cruciate retaining model (CR) was used. In 591 cases the cruciate substituting with posterior-stabilized model (PS) was implanted (324 cases with a fixed bearing (PSFB) and 267 cases with a rotating platform (PSRP)).

Results:

The Clinical KSS score was similar for the three types at 1, 5, 10 and 15 years post-operatively. The Functional score also remained similar for all types until 10 years; at 15 years functional results of the CR group decreased.

Conclusions:

Neither clinically nor radiographically did the use of a rotating platform prove to be more advantageous than fixed bearing tibial components. Thus, the advantage of a Total Knee Arthroplasty with Rotating Platform remains theoretical.

Single-radius, multidirectional total knee replacement

PURPOSE

The present study was designed to evaluate the mid-term (5- to 8-year) survival rate of a new total knee replacement (TKR) with a single-radius femoral component and a multidirectional, highly congruent tibial component, in comparison with an historical group (TKR with multi-radius design and fixed bearing).

METHODS

Four hundred and thirty patients were included, of which 369 patients (86 %) completed the 5-year follow-up with Knee Society Score evaluation and radiograph examination (study group = 387, control group = 83).

RESULTS

There was a significant improvement for all analysed items between pre-operative status and late follow-up. Mean knee score was 93 ± 9 points in the study group and 88 ± 16 points in the control group (p < 0.001). Mean flexion angle was not different (118 ± 11 vs. 114 ± 13 degrees). Mean functional score was 87 ± 16 points in the study group and 71 ± 24 points in the control group (p < 0.001). Survival rate at 5-year follow-up was 98.8 % (vs. 98.0 %) for mechanical revisions only, and 96.4 % (vs. 98.1 %) for all revisions.

CONCLUSIONS

The new TKR allowed obtaining significantly better results than the fixed-bearing TKR. These results are in line with the best series published in the current literature, but there was no evidence of any superiority of this TKR against already published standards.

Evidence-based review for patients undergoing elective hip and knee replacement

BACKGROUND

The objective of this study was to evaluate the evidence for different interventions in the preoperative, perioperative and post-operative care for people undergoing elective total hip (THR) and knee (TKR) replacement surgery.

METHOD

A multidisciplinary working group comprising consumers, managers and clinicians from the areas of orthopaedics, rheumatology, aged care and rehabilitation evaluated randomized controlled trials (RCTs) and systematic reviews/meta-analyses concerning aspects of preoperative, perioperative and post-operative clinical care periods for THR/TKR through systematic searching of Medline, Embase, CENTRAL and the Cochrane Database of Systematic Reviews from May 2007 to April 2011. Multiple reviewers determined study eligibility and one or more members extracted primary study findings. The body of evidence were assessed and specific recommendations made according to NHMRC guidelines.

RESULTS

Twenty-five aspects were identified for review. Recommendations for 16 of 25 areas of care were made: impact of waiting, multidisciplinary preparation, preoperative exercise, smoking cessation, interventions for comorbid conditions, predictors of outcome, clinical pathways, implementation of a blood management programme, antibiotic prophylaxis, regional anaesthesia and analgesia, use of a tourniquet in knee replacement, venous thromboembolism prophylaxis, early post-operative cryotherapy, early mobilization and continuous passive motion. In the post-operative period, study heterogeneity across all aspects of care precluded specific recommendations.

CONCLUSIONS

There was a deficiency in the quality of the evidence supporting key aspects of the continuum of care for primary THR/TKR surgery. Consequently, recommendations were limited. Prioritization and funding for research into areas likely to impact clinical practice and patient outcomes after elective joint replacement surgery are the next important steps.

Differences in long-term fixation between mobile-bearing and fixed-bearing knee prostheses at ten to 12 years’ follow-up

This single-blinded randomised controlled trial investigated whether one design of mobile-bearing (MB) total knee replacement (TKR) has any advantage over a fixed-bearing (FB) design on long-term fixation as measured by radiostereometry. The amount of wear underneath the mobile bearing was also evaluated. A series of 42 knees was randomised to MB or FB tibial components with appropriate polyethylene inserts and followed for between ten and 12 years, or until the death of the patient. The polyethylene in the MB group was superior in that it was gamma-irradiated in inert gas and was calcium-stearate free; the polyethylene in the FB group was gamma-irradiated in air and contained calcium stearate. In theory this should be advantageous to the wear rate of the MB group. At final follow-up the overall mean migration was 0.75 mm (sd 0.76) in the MB group and 0.66 mm (sd 0.4) in the FB group, with the FB group demonstrating more posterior tilt and the MB group more internal rotation. In the FB group there was one revision for aseptic loosening, but none in the MB group. There were no significant differences in clinical or radiological scores.

For the MB group, the mean linear wear rate on the under-surface was 0.026 mm/year (sd 0.014). This was significantly smaller than the wear rate of 0.11 mm/year (sd 0.06) in the MB between femur and polyethylene (p < 0.001). Nevertheless, even in a best-case setting the mobile bearings of this TKR design had no apparent advantage in terms of fixation over the FB knee prosthesis at ten to 12 years. The wear underneath the mobile bearing was small and is unlikely to be clinically relevant.

Predisposing factors which are relevant for the clinical outcome after revision total knee arthroplasty

PURPOSE

The objective of this study was to investigate the outcome of revision total knee arthroplasty (TKA) in relation to the cause of index failure, the characteristics of the index procedure, and the elapsed time between index TKA and revision.

METHODS

A retrospective review based on a prospective database was performed on 146 consecutive revision TKA's. Variables tested were the cause of index failure; the elapsed time between the index and revision procedure; patient age at time of revision; partial or total revision of the implants; the performance of a tibial tubercle osteotomy; the presence of radiolucent lines; postoperative patellar tracking; and coronal plane alignment. Outcomes were measured with the Knee Society Knee Score (KS), Function Score (FS), and X-ray evaluation.

RESULTS

Mean KS improved from 27.6 (SD 21.6) to 71.5 (SD 24.2) after revision (P < 0.0001), mean FS from 27.5 (SD 22.7) to 53.3 (SD27.7), P < 0.0001. Overall survival rate was 90% at 5 years and 85% at 10 and 14 years. The cause of index failure had no significant influence on any of the outcome parameters. Significantly, better outcomes were noted for partial revisions and for revisions in older patients. Early revisions (<2 years) were mostly performed for infection and instability, whereas late revisions (>2 years) were mostly performed for polyethylene wear and loosening. The survival rate for late revisions was significantly better than for early revisions (P = 0.002).

CONCLUSION

Revision TKA leads to a significant reduction in symptoms and improvement in function. The worst results can be expected for early revisions in young patients. Revision TKA is a demanding procedure with variable results and should therefore be performed by experienced surgeons.

LEVEL OF EVIDENCE

Therapeutic study-Level IV.

Kinematics and early migration in single-radius mobile- and fixed-bearing total knee prostheses

BACKGROUND

The mobile-bearing variant of a single-radius design is assumed to provide more freedom of motion compared to the fixed-bearing variant because the insert does not restrict the natural movements of the femoral component. This would reduce the contact stresses and wear which in turn may have a positive effect on the fixation of the prosthesis to the bone and thereby decreases the risk for loosening. The aim of this study was to evaluate early migration of the tibial component and kinematics of a mobile-bearing and fixed-bearing total knee prosthesis of the same single-radius design.

METHODS

Twenty Triathlon single-radius posterior-stabilized knee prostheses were implanted (9 mobile-bearing and 11 fixed-bearing). Fluoroscopy and roentgen stereophotogrammetric analysis (RSA) were performed 6 and 12 months post-operatively.

FINDINGS

The 1 year post-operative RSA results showed considerable early migrations in 3 out of 9 mobile-bearing patients and 1 out of 11 fixed-bearing patients. The range of knee flexion was the same for the mobile-bearing and fixed-bearing group. The mobile insert was following the femoral component during motion.

INTERPRETATION

Despite the mobile insert following the femoral component during motion, and therefore performing as intended, no kinematic advantages of the mobile-bearing total knee prosthesis were seen. The fixed-bearing knee performed as good as the mobile-bearing knee and maybe even slightly better based on less irregular kinematics and less early migrations.

Functional performance of mobile versus fixed bearing total knee prostheses: a randomised controlled trial

PURPOSE

The primary goal of this study was to assess the difference in active flexion between patients with a mobile versus a fixed bearing, cruciate retaining, and total knee arthroplasty. The study was designed as a randomised controlled multi-centre trial.

METHODS

Participants were assigned to interventions by using block-stratified, random allocation. Outcome parameters were active flexion, passive flexion, and Knee Society Score (KSS). Outcome parameters were assessed preoperatively and at 3, 6, and 12 months postoperatively by an independent nurse.

RESULTS

Ninety-two patients from one centre were included, 46 in each group. Active flexion was comparable for the two groups, 99.9° for the mobile bearing group and 101° for the fixed bearing group with a baseline controlled difference of 1.0 (95% CI -3.9 to 5.8, n.s.). The Clinical KSS was comparable between the two bearing groups (Mobile 90.0 vs. fixed 92.4, n.s.). The functional KSS showed a difference that was attributable to the stair climbing subscore, which showed a difference in favour of the fixed bearing design between preoperative and 3 months (7.3 point difference; 95% CI 2.3-12.5; P = 0.005) as well as 12 months (4.8 point difference; 95% CI 0.1-9.6; P = 0.045).

CONCLUSIONS

There were no short-term differences in active flexion between fixed bearing and mobile bearing total knee arthroplasty.

LEVEL OF EVIDENCE

I.

Angiographic findings in patients with postoperative soft tissue defects following total knee arthroplasty

PURPOSE

A postoperative defect of the surrounding soft tissue is one main risk factor for implant exposure and infection following total knee arthroplasty (TKR). The main factors that promote infection, tissue ischemia, and hypoxia are strongly associated with arterial insufficiency and the prevalence of impaired peripheral perfusion. We hypothesized that vascular malperfusion is the predisposing reason for soft tissue complications following TKR necessitating plastic reconstructive surgery.

METHODS

A retrospective chart review was made among patients (n = 12) with soft tissue defects due to wound infection following a total knee arthroplasty referred to plastic reconstructive surgery. All patients presented with an exposed implant, and angiographic imaging was performed prior to reconstructive procedures.

RESULTS

Eight out of twelve patients (67%) had a pathological vascular status. In three of these patients, interventional procedures were performed to ameliorate perfusion. In ten patients (83%), the defect was covered with a plastic reconstructive regional or free tissue transfer. Four patients received a free latissimus dorsi flap and six patients a pedicled a gastrocnemius muscle flap. In one patient, a secondary wound closure was needed after knee arthrodesis and an amputation was performed in another patient due to a multiresistant staphylococcus aureus infection and massive tissue destruction at the time of admission.

CONCLUSIONS

We suggest to rule out peripheral occlusive disease among patients undergoing TKR at best prior to orthopedic surgery using pulses and, if in doubt ankle-brachial index and doppler sonography Consequently, if vascular occlusions are then confirmed by angiography, dilatation and stenting or revascularization should be performed, to ameliorate perfusion.

One year after navigated total knee replacement, no clinically relevant difference found between fixed bearing and mobile bearing knee replacement in a double-blind randomized controlled trial

Background:

The mobile bearing designs have not yet been shown to improve clinical outcome of total knee arthroplasty (TKA). In this prospective randomized study, we compared the short-term clinical results of a mobile bearing implant with those of the fixed bearing version of the same implant.

Methods:

We randomized 100 knees into two double-blind groups who received either the fixed (FB, 52 knees) or the mobile bearing (MB, 48 knees) version of the same implant. We used navigation to standardize the surgical technique. For up to one year, we recorded the Knee Society (KSS) and Oxford (OXF) scores. We performed an exploratory analysis of variance (ANOVA) to determine the influence of baseline scores as covariate and the extent of improvement in clinical outcome over time.

Results:

After one year, we did not detect any statistically significant difference between the two groups. The KSS scores differed by 2 points, the OXF scores by 1.1 points.

Conclusion:

Even with identical geometry of implant surfaces and a navigated surgical technique, first-year results do not support a preference for either a fixed or a mobile design.