Failure of total knee arthroplasty with or without patella resurfacing

The Fate of Unresurfaced Patellae in Contemporary Total Knee Arthroplasty: Early to Midterm Results

BACKGROUND

Leaving the patella unresurfaced in total knee arthroplasty (TKA) has increased significantly over the past decade in the United States, likely due to modern patella-friendly implants, complications with resurfacing, and the knowledge that historical studies were scientifically confounded. This study evaluated revision-free survivorship out to 8.5 years in a cohort of contemporary primary TKAs with patella-friendly femoral components and unresurfaced patellae.

METHODS

A total of 1,053 consecutive primary TKAs with unresurfaced patellae were retrospectively reviewed. A selective patellar nonresurfacing protocol was used for all cases. Kaplan-Meier survivorship estimates were calculated based on patellar revision and the latest follow-up. An aggressive lateral patellar facetectomy was performed in 78% (823 of 1,053) of cases. The cohort was 62% women and 43% American Society of Anesthesiologists physical status classification I or II with a mean age and body mass index of 65 years (range, 35 to 94) and 35 kg/m2 (range, 18 to 65), respectively.

RESULTS

A total of 4 (0.4%, 4 of 1,053) unresurfaced patellae were revised. Three were resurfaced as part of other procedures: 2 for global instability and one for aseptic loosening at a mean of 1.6 years; and one patella was resurfaced by an outside surgeon for unexplained pain. The all-cause revision-free survivorship estimate specifically related to the patella was 98.9% (95% confidence interval, 98 to 100) out to 8.5 years. No significant difference in survivorship was related to patellae with or without a lateral patellar facetectomy (99.5 versus 98.1%, P ≥ .191); however, 3 of 4 patellar revisions occurred in TKAs without a lateral patellar facetectomy (P = .035).

CONCLUSIONS

The results of this study demonstrate excellent revision-free survivorship related to unresurfaced patellae, particularly when a lateral facetectomy was performed. These early to midterm results using modern patella-friendly femoral components are promising and comparable to resurfaced patellae in the literature.

LEVEL OF EVIDENCE

IV.

Patella component diameters of 38 mm and up might be associated with higher revision rates after patella resurfacing

PURPOSE

Patellar resurfacing is considered the standard of care for total knee arthroplasty in the USA. Complications of patella resurfacing include aseptic loosening or patella fractures and can threaten the integrity of the extensor mechanism. The goal of this study was to report on patella button revision rates in posterior stabilized total knee arthroplasty.

MATERIAL AND METHODS

Between 01/2010 and 08/2016 patella buttons were implanted in 1056 patients (267 men and 550 women) as part of a posterior stabilized total knee arthroplasty.

RESULTS

Of 1056 cases, 35 cases (14 women, 15 men, 5 bilateral, 3.3%) showed early loosening at a mean 52.5 months postoperatively. Patella components of 38 mm or larger diameters showed a significantly higher loosening rate than the 29, 32, 35 mm buttons (p < 0.01). Mean BMI of patients identified with aseptic loosening was 31.7 kg/m², mean age at time of revision surgery was 63.3 years. All of the patients with loosening of the patella button required revision surgery; in 33 cases an exchange of the button was performed, in two cases a removal of the button and patellar bone grafting was indicated. No complications occurred after revision surgery.

CONCLUSION

The current study reports a 3.3% patella loosening rate during this mid-term follow-up. Size 38 mm and larger patella components showed a significantly higher revision rate than smaller buttons and the authors advise caution when using large diameter patella components.

Selective Patella Resurfacing in Contemporary Cruciate Retaining and Substituting Total Knee Arthroplasty: A Matched Cohort Analysis

BACKGROUND

Leaving the patella unresurfaced in total knee arthroplasty (TKA) is increasing due to modern patella-friendly implants, awareness that complications are not uncommon with resurfacing, and knowledge that historical studies were scientifically confounded. This study examined the effect of selective patellar resurfacing on patient-reported outcome measures (PROMs) using modern implants and techniques in cohorts rigorously matched for demographics and osteoarthritis severity.

METHODS

A total of 166 TKAs performed without patellar resurfacing were case-control matched to 166 TKAs with patella resurfacing. Case-control matching was based on demographics, American Society of Anesthesiology Physical Status, comorbidities, and osteoarthritis severity. No significant differences were observed between cohorts for demographics (P ≥ .347), comorbidities (P ≥ .443), or radiographic osteoarthritis severity (P ≥ .078). Radiographic alignment and prospectively collected PROMs were evaluated preoperatively and at latest clinical follow-up.

RESULTS

Preoperatively, patellar tilt was less for the unresurfaced patella group (3 versus 4°, P = .003); however, postoperative patellar tilt was not different (3 versus 3°, P = .225). At a mean of 2.1 years follow-up (range, 1 to 7), University of California Los Angeles Activity Level was significantly higher for the unresurfaced patella group (6.3 versus 5.5, P = .002), but the mean group difference did not reach a minimal clinically important difference. There were no other significant differences in PROMs or reoperation rates between cohorts (P ≥ .135).

CONCLUSION

In contemporary cruciate retaining and substituting TKA designs, not resurfacing the patella in select patients may achieve comparable PROMs and re-operation rates; and potentially greater activity level compared to patella resurfacing at early follow-up.

LEVEL OF EVIDENCE

III.

Osteoarthritic Severity in Unresurfaced Patellae Does Not Adversely Affect Patient-reported Outcomes in Contemporary Primary TKA

Introduction:

The degree of osteoarthritis (OA) acceptable to leave in a native patella during unresurfaced total knee arthroplasty (TKA) remains unknown. This study's purpose was to examine the effect of patellofemoral OA severity on patient-reported outcome measures (PROMs) in primary TKAs performed without patellar resurfacing.

Methods:

One hundred ninety-three primary TKAs performed without patellar resurfacing were retrospectively reviewed. Preoperative patellofemoral OA severity was graded on severity, marginal osteophytes, joint space narrowing, and chondral damage using accepted grading systems. Patellar tilt and tibiofemoral alignment were measured radiographically. PROMs were evaluated at a minimum of 1-year follow-up.

Results:

In multivariate regression, preoperative lateral patella Kellgren-Lawrence grade ≥2 was associated with superior change in Knee Society Score pain with level walking, higher absolute change in Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (P ≤ 0.029), and knees ‟always feeling normal” (odds ratio [OR] 3.12; P = 0.005). Osteoarthritis Research Society International atlas grades and Outerbridge classification scores did not significantly influence PROMs.

Discussion:

Worse preoperative OA severity in the lateral patellar facet, graded with the Kellgren-Lawrence system, predicted superior knee-specific PROMs in patients with unresurfaced patellae after contemporary TKA. This observation supports the clinical finding that patients with more severe OA have optimized patient outcomes and highlights the minimal contribution of patella OA to knee function after primary TKA.

The effect of patient and prosthesis factors on revision rates after total knee replacement using a multi-registry meta-analytic approach

BACKGROUND AND PURPOSE

Characteristics of patients receiving total knee arthroplasty (TKA) and prostheses used vary between regions and change with time. How these practice variations influence revision remains unclear. We combined registry data for better understanding of the impact of variation, which could potentially improve revision rates.

PATIENTS AND METHODS

We used data from 2003 to 2019 for primary TKA from arthroplasty registries of Sweden (SKAR), Australia (AOANJRR), and Kaiser Permanente (KPJRR). We included 1,072,924 TKA procedures for osteoarthritis. Factors studied included age, sex, ASA class, BMI category, prosthesis constraint, fixation, bearing mobility, patellar resurfacing, and polyethylene type. Cumulative percentage revision (CPR) was calculated using Kaplan-Meier estimates, and unadjusted Cox hazard ratios were used for comparisons. Random-effects generic inverse-variance meta-analytic methods were used to determine summary effects.

RESULTS

We found similarities in age and sex, but between-registry differences occurred in the other 7 factors studied. Patients from Sweden had lower BMI and ASA scores compared with other registries. Use of cement fixation was similar in the SKAR and KPJRR, but there were marked differences in patellar resurfacing and posterior stabilized component use. Meta-analysis results regarding survivorship favored patients aged ≥ 65 years and minimally stabilized components. There were inconsistent results with time for sex, fixation, and bearing mobility, and no differences for the patellar resurfacing or polyethylene type comparisons.

INTERPRETATION

Marked practice variation was found. Use of minimally stabilized and possibly also cemented and fixed bearing prostheses is supported.

Patella related problems as common reason for revision of NexGen PS® total knee arthroplasty without patella resurfacing: An analysis of 5911 primary total knee arthroplasties registered in the Dutch Arthroplasty Register

BACKGROUND

Patella resurfacing remains controversial in primary total knee arthroplasty (TKA).The aim of this study was to investigate if there was a difference in revision rate and reason for revision within 8 years after single brand primary cemented TKA with or without patella resurfacing, using data from the Dutch Arthroplasty Register.

METHODS

All primary TKA surgeries with a posterior stabilized cemented primary NexGen®, between 2010 and 2013 with diagnosis osteoarthritis were analyzed (n = 5911). Multivariate cox regression analyses were performed to analyze differences in revision rate between TKA with or without patella component, and was adjusted for age and previous surgery.

RESULTS

Of 5911 TKA surgeries, 4795 were performed without patella resurfacing (81.1%) and 1116 with patella resurfacing (18.9%). There was a significant difference in patellar problems as reason for revision between patients after primary TKA with patella resurfacing (9.3%) and without patella resurfacing (29.9%) (p = 0.01). This was mostly caused by patellar pain (28.0%). There was no significant difference in cumulative revision rate within between TKA with patella resurfacing and without patella resurfacing.

CONCLUSION

In conclusion, 30% of patients who need revision surgery after TKA using NexGen® PS without patella resurfacing the reason for revision is patella related problems, compared to 9% after TKA NexGen® PS with patella resurfacing. There was no difference in cumulative incidence of revision after primary surgery of all TKA's using NexGen® PS with or without patella. To reduce the probability of reoperation for patella related problems, our data suggest the patella should be resurface during primary TKA.

Patellar Resurfacing Does Not Improve Clinical Outcome in Patients with Symptomatic Tricompartmental Knee Osteoarthritis. An RCT Study of 40 Patients Receiving Primary Cruciate Retaining Total Knee Arthroplasty

There is some evidence that patellofemoral (PF) joint osteoarthritis (OA) causes anterior knee pain (AKP) after total knee arthroplasty (TKA). We hypothesized that patellar resurfacing in primary TKA for patients with symptomatic tricompartmental knee OA yields better clinical results after 2 years than non-resurfacing. A single center randomized controlled clinical trial comparing 40 patients receiving 42 cruciate retaining TKAs with (n = 21) or without patellar resurfacing (n = 21) was conducted. Primary outcome was the specific PF joint score HSS Baldini and secondary outcomes were the Knee Society Score (KSS) and the Knee Osteoarthritis Outcome Scale (KOOS). After 2 years no significant differences between both groups and between the groups in time for HSS Baldini, KSS, and KOOS were found. HSS Baldini score improved significantly after 6 weeks in both groups (p < 0.001) and did not improve in time afterward. At final follow-up the HSS Baldini mean score improved from a preoperative mean of 39 to 88 (difference of 49 points; p < 0.001)) for without patellar resurfacing group, and from a preoperative mean of 37 to 81 for patellar resurfacing group (difference of 47 points; p < 0.001). One patient in the patellar resurfacing group underwent a soft tissue re-alignment procedure because of patellar subluxation. Two patients in without patellar resurfacing group received secondary patellar button placement. Patellar resurfacing in primary TKA for patients with symptomatic tricompartmental OA has no beneficial effect over non-resurfacing and seems unnecessary. A special PF joint outcome measurement tool (HSS Baldini) and common knee scores showed no better knee function or AKP outcomes for with patellar resurfacing over without patellar resurfacing group in time and after 2 years of follow-up.

Total knee replacement on more than 20° valgus: A case control study

INTRODUCTION

Lower-limb valgus deformity exceeding 20° is a particular case, with few publications assessing the impact of the severity of the valgus. The present retrospective case control study compared a series of>20° valgus versus a series of 10-20° valgus, assessing (1) operative data [approach, type of total knee replacement (TKR)], (2) complications and implant survival, and (3) clinical and radiological results.

HYPOTHESIS

Severe valgus deformity requires TKR with greater constraint, incurring a higher rate of complications and poorer implant survival.

MATERIAL AND METHOD

A multicenter retrospective study for the period January 2006 to December 2010 included 53 patients, with a mean age of 72±10 years, presenting>20° valgus. The study series was matched for age and gender with a series of 53 cases of 10-20° valgus. Convexity laxity was greater in the>20° group (p=0.004).

RESULTS

There was no significant inter-group difference in approach (p=0.13). Greater constraint was more frequent in the>20° group (7/53 versus 1/53; p=0.03), independently of convexity laxity or Krackow grade (p=0.14). There were 7 complications (13.2%) in the>20° group and 7 in the 10-20° group (NS). Eight-year survivorship was 95.12% in the>20° group and 94.9% in the 10-20° group (p=0.63). There were no significant differences in Oxford score (p=0.30) or HKA angle (p=0.78) at last follow-up.

CONCLUSION

The study hypothesis was partially confirmed: greater constraint was more frequent in>20° valgus. The number of complications was low, and survival was identical to that of a control group with less severe deformity.

LEVEL OF EVIDENCE

III, retrospectivecase controlstudy.

Patellofemoral design enhancements reduce long-term complications of postero-stabilized total knee arthroplasty

PURPOSE

Few studies investigated whether trochlear and patellar design enhancements improve long-term outcomes of total knee arthroplasty (TKA). This study aimed to compare the long-term survival and complication rates of two consecutive generations of the same TKA system with identical tibiofemoral geometry, but different patellofemoral designs.

METHODS

The authors retrieved the records of 93 patients (104 knees) operated with the HLS II system and 116 patients (122 knees) operated with HLS Evolution system. Patients were evaluated preoperatively and at a minimum of 10 years noting all complications. Kaplan-Meier (KM) survival was compared for two endpoints: (1) revision of all components and (2) revision of any component.

RESULTS

From the HLS II series, the incidence of revision of all components was 6.4%, and of any component was 9.8%. From the HLS Evolution series, the incidence of revision of all components was 4.1%, and of any component was 5.1%. Comparing the survival at equivalent follow-up of 14 years, considering revision of all components, the HLS II had higher survival than the HLS Evolution (98.9% vs 95.9%), while considering revision of any component, the HLS II had lower survival than the HLS Evolution (93.0% vs 94.9%). The differences in survival of the two implants were not significant, neither at equivalent follow-up of 14 years (n.s.), nor at maximum follow-up of each cohort (n.s.). The complication rate was higher for the HLS II series compared to the HLS Evolution (28% vs 12%, p = 0.009), but patellofemoral complications were not more frequent (8% vs 6%, n.s.).

CONCLUSIONS

Though the differences in survival of the two implants were not significant, conflicting findings are observed due to partial revisions for patellar fractures (5 in the HLS II series and 1 in the HLS Evolution series) which could be related to patellofemoral design enhancements. This study highlights the importance of patello-femoral geometry, which is often overlooked in TKA.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Total knee arthroplasty in patients with varus deformities greater than ten degrees: survival analysis at a mean ten year follow-up

INTRODUCTION

Total knee arthoplasty (TKA) is a secure procedure with more than 90% survival at ten years. The purpose of this study was to report both clinical and radiological outcomes of TKA with a varus > 10°. The second objective was to identify risk factors for failure or bad clinical results. Our hypothesis was that results and survey are comparable to TKA with lesser deformities.

METHODS

Eighty-two TKA (69 patients) between January 2004 and December 2008 with a varus > 10° were reviewed retrospectively. The endpoints were clinical (range of motion, IKS knee score, Oxford, and SF-12) and radiological (HKA post-operative and the existence of radiolucent lines or loosening at last follow-up).

RESULTS

Sixty-three TKA (55 patients) were assessed with a mean follow-up of 10.9 years. The global IKS score significantly increased (p = 0.04). Seven TKA needed a revision: two for sepsis, four for aseptic loosening, and one for polyethylene wear, with an overall survival of 91.6% at ten years. For aseptic loosening, the survival rate was 94.7% at ten years. Risk factors for failure were age (p = 0.001), weight (p = 0.04), and a post-operative HKA lesser than 175° (p = 0.05) for aseptic loosening.

DISCUSSION

The hypothesis was confirmed: the results showed a significant improvement of function and quality of life with a survival rate comparable to those found in the literature for greater varus but also inferior to 10°. Three risk factors have been identified suggesting increased surveillance in these cases.

CONCLUSION

The results of this survey confirm the work hypothesis. Total knee arthroplasty in patients with important axial deformities is a confirmed, reliable, patient-friendly and predictable good outcome procedure.

Computer-aided planning with exact implementation into surgical technique in TKA is as accurate as intraoperative navigation

BACKGROUND

Exact positioning of implants and accuracy of alignment are important parameters to provide an long survivorship of endoprostheses after total knee arthroplasty. It was suggested that an alignment within 3∘ from centerline provides the best long-term survivorship of TKA. Therefore, computer-assisted navigation became more important in TKAs. Another tool to improve the accuracy in TKA is the preoperative planning software.

OBJECTIVE

Main goal was to determine if advantages of an intraoperative navigation system during TKA can be reached by an exact implementation of a preoperative computer-aided planning.

METHODS

Based on all patients (n= 100) underwent primarily TKA in 2015 and 2016 two groups were declared: (1) conventionally operated TKA without navigation system and (2) operation with an optical navigation system. Data on age, sex, date, operative time, severe complications and preoperative vs. postoperative alignment were collected retrospectively.

RESULTS

The two groups do not differ in postoperative alignment and frequency of outliers. Furthermore, there was no difference referring to complications and the length of stay in hospital, but operative time was prolonged in the navigation-assisted group.

CONCLUSIONS

It can be stated that conventional surgical techniques in TKA are as accurate as navigated ones if an exact preoperative computer aided planning is implemented during surgery.

Early aseptic loosening of a mobile-bearing total knee replacement

Background and purpose - Registry-based studies have reported an increased risk of aseptic tibial loosening for the cemented Low Contact Stress (LCS) total knee replacement compared with other cemented designs; however, the reasons for this have not been established. We made a retrieval analysis with the aim of identifying the failure mechanism. Patients and methods - We collected implants, cement, tissue, blood, and radiographs from 32 failed LCS Complete cases. Damage to the tibial baseplate and insert was assessed. Exposure to wear products was quantified in 11 cases through analysis of periprosthetic tissue and blood. Implant alignment and bone cement thickness was compared with a control group of 43 non-revised cases. Results - Loosening of the tibial baseplate was the reason for revision in 25 retrievals, occurring at the implant-cement interface in 16 cases. Polishing was observed on the lower surface of the baseplate and correlated to the level of cobalt, chromium, and zirconium in the blood. No evidence of abnormally high polyethylene wear was present. For each 1 mm increase in cement thickness the odds of failure due to aseptic loosening decreased by 61%. Greater varus alignment was associated with a shorter time to failure. The roughness, Ra, of a new LCS baseplate's lower surface was 3.7 (SD 0.7) µm. Interpretation - Debonding of the tibial component at the implant-cement interface was the predominant cause of tibial aseptic loosening. A thin cement layer may partly explain the poor performance. Furthermore, the comparatively low tibial surface roughness and the lack of a keeled stem may have played a role in the failures observed.

Have the Causes of Revision for Total and Unicompartmental Knee Arthroplasties Changed During the Past Two Decades?

BACKGROUND

Revisions after knee arthroplasty are expected to increase, and the epidemiology of failure mechanisms is changing as new implants, technology, and surgical techniques evolve.

QUESTIONS/PURPOSES

(1) Was there improvement in survival for TKA and unicompartmental knee arthroplasty (UKA) when comparing two consecutive 11-year periods with similar followups in a national registry? (2) Were there changes in the causes of revision during the two times? (3) Could the changes in revision causes be attributed to patient or implant characteristics?

METHODS

A total of 60,623 TKAs (2426 revisions) and 7648 UKAs (725 revisions) were selected from the Norwegian Arthroplasty Register and analyzed based on year of primary surgery: 1994 to 2004 (Period 1) and 2005 to 2015 (Period 2). TKAs had median followup of 3.5 years in Period 1 and 4.2 years in Period 2. Median followup for UKAs was 2.7 years in Period 1 and 4.6 years in Period 2. Of the patients included in the registry, 99.6% were accounted for at the time of analysis, whereas 0.4% had moved abroad. We used Kaplan-Meier analyses and log-rank test to investigate changes in survival. Relative risk of revision in Period 2 relative to Period 1 was calculated for each registered revision cause in a Cox regression model adjusted for age, sex, diagnosis, fixation, and patella resurfacing.

RESULTS

For TKAs, the 10-year Kaplan-Meier survival free from revision improved from Period 1 to Period 2 from 91% (95% CI, 90%-92%) to 94% (95% CI, 94%-95%; p < 0.001). Revisions resulting from aseptic loosening of the femoral component, polyethylene wear/breakage, patellar dislocation, and unexplained pain decreased, whereas revisions resulting from early infection increased. Patients in Period 2 were younger and more often men compared with patients in Period 1. A higher risk of revision was found for male sex (relative risk [RR], 1.1; 95% CI, 1.0-1.2; p = 0.048) and age younger than 65 years (RR, 1.7; 95% CI, 1.6-1.9; p < 0.001). With UKAs, the 10-year survival free from revision was 80% (95% CI, 76%-84%) in Period 1 and 81% (95% CI, 79%-83%; p = 0.261) in Period 2. Revisions resulting from tibial aseptic loosening, polyethylene wear/breakage, and periprosthetic fractures decreased, but there were more revisions resulting from progression of osteoarthritis. In Period 2, there were more men and the average age was younger than for patients in Period 1. For UKAs, age younger than 65 years had a higher risk of revision (RR, 1.7; 95% CI, 1.5-2.0; p < 0.001), whereas sex did not affect the risk of revision.

CONCLUSIONS

We found an improvement in survival free from revision for TKA in the last period, but no similar improvement for UKA, and the survivorship for UKAs remains rather dramatically lower than that observed for TKAs. The decision to perform a UKA should be made with the explicit awareness that its survivorship is substantially inferior to that of TKA; any perceived advantages of UKA should be balanced against this issue of its decreased durability.

LEVEL OF EVIDENCE

Level III, therapeutic study.

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.

Does patellofemoral congruence following total knee arthroplasty correlate with pain or function? Intraoperative arthroscopic assessment of 30 cases

BACKGROUND

Anterior knee pain (AKP) is observed in total knee arthroplasty (TKA) both with and without patellar resurfacing, and neither patellar denervation nor secondary resurfacing are effective for treating the symptoms. The exact causes for pain remain unclear, though abnormal patellofemoral forces due to patellar malalignment or inadequate implant design can play an important role. The purpose of this study was to arthroscopically evaluate patellofemoral congruence after wound closure following TKA without patellar resurfacing and correlate it to patellar morphology and postoperative pain and function.

METHODS

The authors prospectively studied 30 patients that received uncemented mobile-bearing TKA. Patellofemoral congruence was assessed arthroscopically after wound closure by estimating the contact area between the native patella and the prosthetic trochlea (> two-thirds, > one-third, < one-third). The findings were correlated to preoperative assessments of patellar geometry (Wiberg classification using X-rays) and clinical outcomes [Knee Society Score (KSS), AKP on Visual Analogic Scale (VAS), and patient satisfaction].

RESULTS

Knees of 22 women and 8 men aged 69.8 years (range, 61-84 years) were analyzed at 16 months (range, 12-23 months). Preoperative patellar geometry was Wiberg type A in 11, type B in 12 and type C in 7 knees. Postoperative KSS was 79.1 (range, 50.0-94) and the VAS for AKP was 1.6±1.3 (median, 1; range, 0-5). Patellar congruence was correlated with patellar morphology (P<0.001) but not correlated with any clinical outcomes (KSS, VAS or satisfaction). There were also no statistical correlations between patellar morphology or patellofemoral congruence and patient characteristics.

CONCLUSIONS

While patellar morphology and patellofemoral congruence are strongly related, they are not associated with clinical outcomes or patient demographics. Considering that numerous incongruent patellofemoral joints were pain-free, and conversely, many perfectly congruent patellofemoral joints had anterior pain, the authors suppose that pain is probably caused by mechanisms other than patellofemoral pressures.

Improving patient reported outcome measures (PROMs) in total knee replacement by changing implant and preserving the infrapatella fatpad: a quality improvement project

Patient reported outcome measures (PROMs) were introduced in 2009 to allow patient perspectives to potentially influence change and improvement. In collaboration with the national joint registry (NJR), PROMs data has been examined on a national basis to compare surgical factors in total knee replacement (TKR). Initial results demonstrated there were statistically significant differences in Oxford Knee Score (OKS) when using different brands of implant. Preservation of the infrapatella fatpad (IFP) has also been shown improve outcomes. This led Northumbria Healthcare NHS Foundation Trust to make a mass move to the Zimmer Nexgen TKR and later change surgeons' routine practice to preserving the IFP. The PROMs were recorded pre and six months post operation to obtain improvement scores. The baseline improvement in OKS was 14.0. After changing implant to the Zimmer Nexgen in Plan-Do-Study-Act (PDSA) cycle 1 the average improvement score was 16.7. After implementing default preservation of the IFP in PDSA cycle 2 the average OKS improvement score was 17.3. The results from this project demonstrate a significant improvement in local services after implementing changes based on national and local evaluations. This initiative is an excellent example of improvement by evidence based practice and success of the English National Health Service PROMs scheme.

Cost-Effectiveness of Five Commonly Used Prosthesis Brands for Total Knee Replacement in the UK: A Study Using the NJR Dataset

BACKGROUND

There is a lack of evidence on the effectiveness or cost-effectiveness of alternative brands of prosthesis for total knee replacement (TKR). We compared patient-reported outcomes, revision rates, and costs, and estimated the relative cost-effectiveness of five frequently used cemented brands of unconstrained prostheses with fixed bearings (PFC Sigma, AGC Biomet, Nexgen, Genesis 2, and Triathlon).

METHODS

We used data from three national databases for patients who had a TKR between 2003 and 2012, to estimate the effect of prosthesis brand on post-operative quality of life (QOL) (EQ-5D-3L) in 53 126 patients at six months. We compared TKR revision rates by brand over 10 years for 239 945 patients. We used a fully probabilistic Markov model to estimate lifetime costs and quality-adjusted life years (QALYs), incremental cost effectiveness ratios (ICERs), and the probability that each prosthesis brand is the most cost effective at alternative thresholds of willingness-to-pay for a QALY gain.

FINDINGS

Revision rates were lowest with the Nexgen and PFC Sigma (2.5% after 10 years in 70-year-old women). Average lifetime costs were lowest with the AGC Biomet (£9 538); mean post-operative QOL was highest with the Nexgen, which was the most cost-effective brand across all patient subgroups. For example, for 70-year-old men and women, the ICERs for the Nexgen compared to the AGC Biomet were £2 300 per QALY. At realistic cost per QALY thresholds (£10 000 to £30 000), the probabilities that the Nexgen is the most cost-effective brand are about 98%. These results were robust to alternative modelling assumptions.

CONCLUSIONS

AGC Biomet prostheses are the least costly cemented unconstrained fixed brand for TKR but Nexgen prostheses lead to improved patient outcomes, at low additional cost. These results suggest that Nexgen should be considered as a first choice prosthesis for patients with osteoarthritis who require a TKR.

No difference in clinical and radiologic outcomes after total knee arthroplasty with a new ultra-congruent mobile bearing system and rotating platform mobile bearing systems after minimum 5-year follow-up

We retrospectively compared the clinical and radiographic results between 76 primary total knee arthroplasties (TKAs) using the e.motion Ultra-Congruent prosthesis and 155 primary TKAs using the Low Contact Stress rotating platform. All patients had a minimum 5-year follow-up. Range of motion, Hospital for Special Surgery score, Knee Society Knee Score and Knee Society Functional Score significantly increased in both groups postoperatively, but there was no significant difference between the two groups. The mechanical femorotibial angle improved in both groups postoperatively. Coronal and sagittal component angles were well maintained at the final follow-up. This study demonstrates that a new mobile-bearing prosthesis, designed to be highly congruent with a rotating bearing, could be considered with theoretical advantages and comparable outcomes of established mobile-bearing prostheses.

Selective patellar resurfacing in total knee arthroplasty: a prospective, randomized, double-blind study

350 knees were evaluated in a prospective, randomized, double-blinded study of selective patellar resurfacing in primary total knee arthroplasty. Knees with exposed bone on the patellar articular surface were excluded. 327 knees were evaluated at a mean follow-up of 7.8years. 114 knees followed for greater than 10 years were analyzed separately. Satisfaction was higher in patients with a resurfaced patella. In patients followed for at least 10 years, no significant difference was found. No difference was found in KSS scores or survivorship. No complications of patellar resurfacing were identified. The vast majority of patients with remaining patellar articular cartilage do very well with total knee arthroplasty regardless of patellar resurfacing. Patient satisfaction may be slightly higher with patellar resurfacing.

Failure of aseptic revision total knee arthroplasties

BACKGROUND AND PURPOSE

In Norway, the proportion of revision knee arthroplasties increased from 6.9% in 1994 to 8.5% in 2011. However, there is limited information on the epidemiology and causes of subsequent failure of revision knee arthroplasty. We therefore studied survival rate and determined the modes of failure of aseptic revision total knee arthroplasties.

METHOD

This study was based on 1,016 aseptic revision total knee arthroplasties reported to the Norwegian Arthroplasty Register between 1994 and 2011. Revisions done for infections were not included. Kaplan-Meier and Cox regression analyses were used to assess the survival rate and the relative risk of re-revision with all causes of re-revision as endpoint.

RESULTS

145 knees failed after revision total knee arthroplasty. Deep infection was the most frequent cause of re-revision (28%), followed by instability (26%), loose tibial component (17%), and pain (10%). The cumulative survival rate for revision total knee arthroplasties was 85% at 5 years, 78% at 10 years, and 71% at 15 years. Revision total knee arthroplasties with exchange of the femoral or tibial component exclusively had a higher risk of re-revision (RR = 1.7) than those with exchange of the whole prosthesis. The risk of re-revision was higher for men (RR = 2.0) and for patients aged less than 60 years (RR = 1.6).

INTERPRETATION

In terms of implant survival, revision of the whole implant was better than revision of 1 component only. Young age and male sex were risk factors for re-revision. Deep infection was the most frequent cause of failure of revision of aseptic total knee arthroplasties.

International comparative evaluation of fixed-bearing non-posterior-stabilized and posterior-stabilized total knee replacements

BACKGROUND

Differences in survivorship of non-posterior-stabilized compared with posterior-stabilized knee designs carry substantial economic consequences, especially with limited health-care resources. However, these comparisons have often been made between relatively small groups of patients, often with short-term follow-up, with only small differences demonstrated between the groups. The goal of this study is to compare the outcomes of non-posterior-stabilized and posterior-stabilized total knee arthroplasties with use of a unique collaboration of multiple established knee arthroplasty registries.

METHODS

A distributed health data network was developed by the International Consortium of Orthopaedic Registries and was used in this study to reduce barriers to participation (such as security, propriety, legal, and privacy issues) compared with a centralized data warehouse approach. The study included only replacements in osteoarthritis patients who underwent total knee procedures involving fixed-bearing devices from 2001 to 2010. The outcome of interest was time to first revision.

RESULTS

On average, not resurfacing showed a more harmful effect than resurfacing did when posterior-stabilized and non-posterior-stabilized knee replacements were compared, while the risk of revision for posterior-stabilized compared with non-posterior-stabilized knees was highest in year zero to one, followed by year one to two, years eight through ten, and years two through eight. Posterior-stabilized knees did significantly worse than non-posterior-stabilized knees did when the patella was not resurfaced. This difference was most pronounced in the first two years (year zero to one: hazard ratio [HR] = 2.15, 95% confidence interval [CI] = 1.56 to 2.95, p < 0.001; year one to two: HR = 1.61, 95% CI = 1.48 to 1.75, p < 0.001). When the patella was resurfaced, posterior-stabilized knees did significantly worse than non-posterior-stabilized knees did. This was again most pronounced in the first two years (year zero to one: HR = 1.75, 95% CI = 1.27 to 2.42, p = 0.001; year one to two: HR = 1.31, 95% CI = 1.19 to 1.45, p < 0.001). There was a reduced risk of revision with a patient age of more than sixty-five years (HR = 0.57, 95% CI = 0.55 to 0.60, p < 0.001).

CONCLUSIONS

We found that fixed non-posterior-stabilized total knee arthroplasty performed better with or without patellar resurfacing than did fixed posterior-stabilized total knee arthroplasty. This effect was most pronounced in the first two years. The risk of revision for posterior-stabilized total knee arthroplasties was reduced with patellar resurfacing. Also, a patient age of more than sixty-five years and female gender reduced the risk of revision.

All-Polyethylene Versus Metal-Backed Tibial Components-An Analysis of 27,733 Cruciate-Retaining Total Knee Replacements from the Swedish Knee Arthroplasty Register

BACKGROUND

Currently, the use of metal-backed tibial components is more common than the use of all-polyethylene components in total knee arthroplasty. However, the available literature indicates that all-polyethylene tibial components are not inferior to the metal-backed design. We hypothesized that there would be no difference in the ten-year survival rate between all-polyethylene and metal-backed tibial components of a specific design in a large nationwide cohort.

METHODS

In the Swedish Knee Arthroplasty Register, we identified 27,733 cruciate-retaining total knee replacements using the press-fit condylar prosthesis with either metal-backed or all-polyethylene tibial components inserted from 1999 to 2011. Unadjusted survival functions were calculated with the end points of revision for any reason, revision due to infection, and revision due to reasons other than infection, and the differences between the groups were investigated with the log-rank test. Cox proportional hazard models were fitted to analyze the influence of various covariates on the adjusted relative risk of revision.

RESULTS

The median duration of follow-up was 4.5 years (range, zero to 12.9 years). Of all total knee replacements, 16,896 (60.9%) were in women and 10,837 (39.1%) were in men. Metal-backed components were used in 16,011 total knee arthroplasties (57.7%) and all-polyethylene in 11,722 total knee arthroplasties (42.3%). With revision for any reason as the end point, the all-polyethylene tibial component had slightly superior, unadjusted ten-year survival compared with the metal-backed component: 97.2% (95% confidence interval [CI], 96.7% to 97.7%) compared with 96.6% (95% CI, 96.2% to 96.9%; p = 0.002). Cox multiple regression analysis adjusting for age group, sex, and patellar resurfacing showed that all-polyethylene components had a reduced risk of revision for any reason (relative risk = 0.75; 95% CI, 0.64 to 0.89) and a reduced risk of revision due to infection (relative risk = 0.63; 95% CI, 0.46 to 0.86). Patellar resurfacing and male sex increased the risk of revision due to infection (relative risk = 2.22 [95% CI, 1.37 to 3.62] and 2.21 [95% CI, 1.66 to 2.94], respectively).

CONCLUSIONS

These all-polyethylene tibial components were at least as good as or superior to metal-backed tibial components with respect to implant survivorship at ten years in cruciate-retaining total knee replacements. We concluded that these less expensive all-polyethylene tibial components can be safely and effectively used in total knee arthroplasty.

LEVEL OF EVIDENCE

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

Joint registries as continuous surveillance systems: the experience of the Catalan Arthroplasty Register (RACat)

The aim was to present results on prosthesis performance in Catalonia for the period 2005-2010. All publicly funded hospitals submit in an electronic format data on hip and knee arthroplasties: patients' insurance identification number, hospital, joint (hip/knee), type of arthroplasty (primary/revision), side (right/left), date of surgery and prosthesis (manufacturer name and catalogue number). A standard survival analysis based on Kaplan-Meier estimation was carried out. Fifty-two hospitals have sent information to the RACat which has data on 36,951 knee and 26,477 hip arthroplasties. Cumulative prostheses revision risks at 3 years were 3.3% (95% CI: 3.1-3.6) for knee, 2.9% (95% CI: 2.5-3.3) for total hip and 2.5% (95% CI: 2.0-3.1) for partial hip. When compared to other registries a higher risk of revision was observed.

Haemophilic arthropathy: long-term outcomes in 107 primary total knee arthroplasties

BACKGROUND

Arthropathy of the knee is a frequent complication in patients with severe bleeding disorders leading to considerable pain and disability. Total knee arthroplasty (TKA) provides marked pain relief. However, a modest functional outcome and a high number of complications due to prosthetic infection and loosening are reported. Data on long-term outcomes are scarce, and most case series include few patients. We have studied clinical outcomes and complications of TKAs with special emphasis on prosthetic survival and periprosthetic infection.

METHODS

A consecutive series of 107 TKAs in 74 patients with haemophilic arthropathy were retrospectively reviewed. Follow-up was mean 11.2 years (range 0.8-33.1 years).

RESULTS

Five- and 10-year survival rates, with component removal for any reason as the end point, were 92% and 88%, respectively. Twenty-eight TKAs were removed after median 10 years (range 0.8-28 years). The most common cause of failure was aseptic loosening (14 knees) and periprosthetic infection (seven knees). The overall infection rate was 6.5%. The mean postoperative drop in haemoglobin levels was 4.3 g/dL (range 0.5-9.4) with a significant difference between haemophilia A patients with and without inhibitor (6.3 g/dL (range 3.6-9.4) versus 3.7 g/dL (range 0.5-8.1) (p<0.001). A painless knee was reported in 93% of the TKAs at the latest follow-up.

CONCLUSIONS

The medium and long-term results of primary TKA in a large haemophilic population show good prosthetic survival at five and 10 years with an excellent relief of pain. Periprosthetic infection is still a major concern compared to the non-haemophilic population.

LEVEL OF EVIDENCE

Level IV.

Outcomes of 447 SCORE® highly congruent mobile-bearing total knee arthroplasties after 5-10 years follow-up

INTRODUCTION

The goal of mobile-bearing total knee arthroplasties (TKA) with an anatomical trochlea is to reduce polyethylene wear, the risk of loosening, and patellofemoral complications. Rotating mobile-bearing SCORE(®) TKA was designed according to these principles with standard instrumentation for component placement and a specific computer navigation system, Amplivision(®).

HYPOTHESIS

We hypothesized that the results of SCORE(®) TKA would be satisfactory and better using computer navigation with or without patellar resurfacing and that there would be no specific patellofemoral complications associated with this trochlear design.

MATERIALS AND METHODS

Four hundred and forty-seven SCORE(®) TKA were performed. Outcome assessment was based on the IKS score, and component survival calculated by Kaplan-Meier analysis.

RESULTS

Mean follow-up was 6.6 years (maximum 10.6 years). Six percent of patients were lost to follow-up. Ninety-eight percent of the patients were satisfied or very satisfied. The IKS knee score was 89 points and the function score was 86. The mechanical axis was 180° (174-186), and it was significantly improved if the initial deformity was severe and TKA was computer navigated. There were nine revisions (one for fracture, two for pain, two for stiffness, four for infection).

DISCUSSION

This study confirmed our hypothesis: the results of SCORE(®) TKA were very satisfying after at least 5 years of follow-up because there was no mechanical loosening, no bearing dislocation and no patellofemoral complications with or without patellar resurfacing. Results were identical whether patellar resurfacing was performed or not. Although clinical results were not better for computer- navigated TKA, radiological results were. At 98 months of follow-up, component survival in relation to the risk of aseptic loosening or patellofemoral complications was 100%.

LEVEL OF EVIDENCE

Level IV continuous retrospective study.

Influence of hospital volume on revision rate after total knee arthroplasty with cement

BACKGROUND

The number of total knee replacements has substantially increased worldwide over the past ten years. Several studies have indicated a correlation between high hospital procedure volume and decreased morbidity and mortality following total knee arthroplasty. The purpose of the present study was to evaluate whether there is a correlation between procedure volume and the risk of revision following total knee arthroplasty with use of hospital volume data from the Norwegian Arthroplasty Register.

METHODS

Thirty-seven thousand, three hundred and eighty-one total knee arthroplasties that were reported to the Norwegian Arthroplasty Register from 1994 to 2010 were used to examine the annual procedure volume per hospital. Hospital volume was divided into five categories according to the number of procedures performed annually: one to twenty-four (low volume), twenty-five to forty-nine (medium volume), fifty to ninety-nine (medium volume), 100 to 149 (high volume), and ≥150 (high volume). Cox regression (adjusted for age, sex, and diagnosis) was used to estimate the proportion of procedures without revision and the risk ratio (RR) of revision. Analyses were also performed for two commonly used prosthesis brands combined.

RESULTS

The rate of prosthetic survival at ten years was 92.5% (95% confidence interval, 91.5 to 93.4) for hospitals with an annual volume of one to twenty-four procedures and 95.5% (95% confidence interval, 94.1 to 97.0) for hospitals with an annual volume of ≥150 procedures. We found a significantly lower risk of revision for hospitals with an annual volume of 100 to 149 procedures (relative risk = 0.73 [95% confidence interval, 0.56 to 0.96], p = 0.03) and ≥150 procedures (relative risk = 0.73 [95% confidence interval, 0.54 to 1.00], p = 0.05) compared with hospitals with an annual volume of one to twenty-four procedures. Similar results were found when we analyzed two commonly used prosthesis brands.

CONCLUSIONS

In the present study, there was a significantly higher rate of revision knee arthroplasties at low-volume hospitals as compared with high-volume hospitals.

Mobile- versus fixed-bearing modern total knee replacements- which is the more patella-friendly design?: The 11-year New Zealand Joint Registry study

OBJECTIVES

Our study aimed to examine if a mobile-bearing total knee replacement (TKR) offered an advantage over fixed-bearing designs with respect to rates of secondary resurfacing of the patella in knees in which it was initially left unresurfaced.

METHODS

We examined the 11-year report of the New Zealand Joint Registry and identified all primary TKR designs that had been implanted in > 500 knees without primary resurfacing of the patella. We examined how many of these were mobile-bearing, fixed-bearing cruciate-retaining and fixed-bearing posterior-stabilised designs. We assessed the rates of secondary resurfacing of the patella for each group and constructed Kaplan-Meier survival curves.

RESULTS

Our study showed a significantly higher rate of revision for secondary resurfacing of the patella in the fixed-bearing posterior-stabilised TKR designs compared with either fixed-bearing cruciate-retaining or mobile-bearing designs (p = 0.001 and p = 0.036, respectively).

CONCLUSIONS

This New Zealand Registry study shows that during the last 11 years, revision procedures to resurface an unresurfaced patella in primary TKR occurred at a higher rate in fixed-bearing posterior-stabilised designs.

Survival rates and causes of revision in cemented primary total knee replacement: a report from the Norwegian Arthroplasty Register 1994-2009

We evaluated the rates of survival and cause of revision of seven different brands of cemented primary total knee replacement (TKR) in the Norwegian Arthroplasty Register during the years 1994 to 2009. Revision for any cause, including resurfacing of the patella, was the primary endpoint. Specific causes of revision were secondary outcomes. Three posterior cruciate-retaining (PCR) fixed modular-bearing TKRs, two fixed non-modular bearing PCR TKRs and two mobile-bearing posterior cruciate-sacrificing TKRs were investigated in a total of 17 782 primary TKRs. The median follow-up for the implants ranged from 1.8 to 6.9 years. Kaplan-Meier 10-year survival ranged from 89.5% to 95.3%. Cox's relative risk (RR) was calculated relative to the fixed modular-bearing Profix knee (the most frequently used TKR in Norway), and ranged from 1.1 to 2.6. The risk of revision for aseptic tibial loosening was higher in the mobile-bearing LCS Classic (RR 6.8 (95% confidence interval (CI) 3.8 to 12.1)), the LCS Complete (RR 7.7 (95% CI 4.1 to 14.4)), the fixed modular-bearing Duracon (RR 4.5 (95% CI 1.8 to 11.1)) and the fixed non-modular bearing AGC Universal TKR (RR 2.5 (95% CI 1.3 to 5.1)), compared with the Profix. These implants (except AGC Universal) also had an increased risk of revision for femoral loosening (RR 2.3 (95% CI 1.1 to 4.8), RR 3.7 (95% CI 1.6 to 8.9), and RR 3.4 (95% CI 1.1 to 11.0), respectively). These results suggest that aseptic loosening is related to design in TKR.

[Arthroplasty registers as post-marketing surveillance systems: the Catalan Arthroplasty Register]

OBJECTIVE

The aim is to present the functioning and results of the Catalan Arthroplasty Registry (RACat).

MATERIAL AND METHOD

The RACat arose by the initiative of the Catalan Society of Orthopaedic Surgery and Traumatology, the Catalan Health Service (CHS) and the Catalan Agency for Health Information Assessment and Quality. Publicly funded hospitals sent information through the Internet (CHS Applications website) on knee and hip arthroplasties: patient identification, hospital, joint (hip/knee), type (primary/revision), side of operation, date of surgery and prosthesis (manufacturer's name and reference number). The quality of the data is analysed regularly. We estimate the risk of replacement by the Kaplan-Meier method.

RESULTS

A total of 52 hospitals out of 62 send data to RACat, and information on 36,951 knee and 26,477 hip arthroplasties is available. Data quality improved between 2005 and 2010. In 2010 coverage exceeded 70%, with side of operation 97%, and prostheses identification of 80%. The risk of replacement at three years was 3.3% (95% CI:3.1-3.6) for knee, 2.9% (95% CI:2.5-3.3) for total hip, and 2.5% (95% CI:2.0-3.1) for partial hip.

DISCUSSION

Risk of replacement is higher than that observed in other registers, although data quality and its improvement over time should be taken into account.

CONCLUSIONS

The information available in the RACat will help to establish a standard that will enable hospitals to compare results.

Little clinical advantage of computer-assisted navigation over conventional instrumentation in primary total knee arthroplasty at early follow-up

PURPOSE

Even though computer-assisted navigation systems have been shown to improve the accuracy of implantation of components into the femur and tibia, long-term results are lacking and there is little evidence yet that navigation techniques also improve functional outcomes and implant longevity following total knee arthroplasty (TKA). The aim of this study was to summarize and compare the clinical outcomes of total knee arthroplasties (TKAs) performed using navigation-assisted and conventional techniques.

METHODS

The study was conducted according to the guidelines described in the Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statements. Methodological features were rated independently by two reviewers. A meta-analysis of randomized controlled trials (RCTs) or quasi- randomized controlled trials (qRCTs) was carried out to evaluate the efficacy of CAS versus conventional TKA. Data were pooled in fixed and random effects models and the weighted mean difference (WMD) and odds ratio (OR) were calculated. Heterogeneity across studies was determined, and subgroup analyses by the type of navigation system (image-based or image-free navigation system) were conducted.

RESULTS

Twenty-one studies that included 2333 knees were collected from different countries. The surgical time was longer for CN TKA than for the conventional procedure. There was no significant difference in the Knee Society Score between the two groups at the 3-month and 6-month follow-up. The rates of postoperative complications in patients who had CN TKA were similar to those in the patients who had conventional TKA.

CONCLUSION

No significant differences in short-term clinical outcomes were found following TKAs performed with and without computer navigation system. However, there is clearly a need for additional high-quality clinical trials with long-term follow-up to confirm the clinical benefits of computer-assisted surgery.

Biological activity of polyethylene wear debris produced in the patellofemoral joint

Polyethylene wear is considered a threat to the long-term survival of total knee replacements. The aim of this study was to investigate the contribution that resurfacing the patella makes to wear debris-induced osteolysis following total knee replacement. Ultra-high molecular-weight polyethylene wear particles were isolated from simulator lubricant. Particle shape, size, and volume distributions were recorded allowing the osteolytic potential of the wear debris produced in the patellofemoral joint to be estimated using the concept of specific biological activity and functional biological activity. Values were compared with those reported for the tibiofemoral joint. Specific biological activity for the patellofemoral joint was not significantly different from the values for the tibiofemoral joint of total knee replacement devices, and therefore, has a similar potential to stimulate osteolytic cytokine release from macrophages. Functional biological activity was significantly lower for the patellofemoral joint compared with the tibiofemoral joint. Functional biological activity was significantly lower for the patellofemoral joint compared with the fixed bearing and rotating platform total knee replacement devices. However, as patellar resurfacing is commonly fitted as part of a total knee replacement system, this results in a 20% increase in overall functional biological activity for the system. Therefore, implanting a patellar resurfacing will increase the potential for osteolysis in the knee.

MODERN TRENDS IN ORTHOPEDICS: THE KNEE ARTHROPLASTY

Using PubMed the authors analyzed publications dedicated to knee arthroplasty that were published in 2011. The modern trends of knee joint replacement include improvement of implants and instruments; partial knee replacement as alternative to TKA; reducing of surgical trauma due to less-invasive approaches; achieving of deep flexion after TKA; using of computer navigation and individual cutting blocks to make surgery more precise; optimization of rehabilitation process in pre-, intra-and postoperative period; including multimodal pain control; development of complex strategies for prevention of intra- and postoperative complications. In this review the attention was attracted to the most discussed in 2011 subjects: development of new designs and materials of knee implants; navigation, robotics and individualized resection blocks; partial knee replacement; infection, blood loss and venous thromboembolism after TKA; influence of different factors on arthroplasty outcomes, especially components and leg alignment, patella resurfacing, PCL retention or substitution, uncemented fixation, mobility of PE insert, severe pre-op deformities or stiffness, previous intra-articular fractures and tibia or femur osteotomies, soft tissue deficit etc.

Comparison of the Norwegian knee arthroplasty register and a United States arthroplasty registry

Several national total joint arthroplasty registries exist outside of the United States (U.S.) and have been used to compare rates and outcomes of total knee arthroplasty. Within the U.S., regional arthroplasty registries provide an opportunity to compare U.S. practices and outcomes with those of other countries. The purpose of this study was to compare the demographics, choice of implants, techniques, and outcomes of total knee arthroplasties in Norway to those from a large, U.S. integrated health-care system and to determine the feasibility of using aggregate-level data for international registry comparisons. The study sample consisted of 25,004 primary total knee arthroplasties performed in Norway and 56,208 from the Kaiser Permanente health-care system. Summary-level data were used to compare the two cohorts. At the time of the seven-year follow-up, the cumulative survival of the total knee prosthesis was 94.8% for the arthroplasties performed in Norway and 96.3% for those performed at Kaiser Permanente. The primary reasons for revision arthroplasty included infection, instability, pain, and aseptic loosening. Patient characteristics, selection of implants, surgical techniques, and outcomes differed between the cohorts. Harmonization of data elements and definitions is necessary for future international research.