Fixation of revision TKA: a review of the literature

Outcomes of Metaphyseal Cones and Stem Fixation Following Rotating Hinge in Complex Primary and Revision Total Knee Arthroplasty

BACKGROUND

Although hinged prostheses have been used successfully in complex revision total knee arthroplasty (TKA), concerns exist regarding early failure due to aseptic loosening and other mechanical complications. The use of metaphyseal cones and hybrid cement fixation have been studied in unlinked constrained primary or revision TKA, but their impact on the survivorship of hinged prostheses has yet to be investigated.

METHODS

We identified a consecutive series of 164 hinged prostheses and collected data on demographics, indications, complications, and re-revisions in patients who had fully cemented versus hybrid stems, with and without metaphyseal cones. A multivariate analysis was performed to identify independent variables associated with re-revision as the primary end point.

RESULTS

In total, 84 patients (51.2%) had fully cemented stems, and 80 patients (48.8%) had hybrid stems. Cones were used in 73 patients (44.5%). At a mean follow-up of 3.4 ± 2.2 years, 42 patients underwent re-revision (25.8%), most commonly for infection (12.2%), followed by loosening (6.7%) and periprosthetic fracture (3.7%). Patients who had fully cemented stems had lower re-revision rates than hybrid fixation constructs (19 versus 26%, P = .043). Using multivariable regression, a construct with hybrid fixation with cones (odds ratio = 2.39; P = .037) was an independent risk factor for failure. Utilization of cones alone did not have an effect on re-revision rates at 3.4-year follow-up.

CONCLUSIONS

While we found no difference with the use of cones, patients undergoing revision TKA with a hinge prosthesis and fully cemented stems had better overall survivorship than hybrid stems.

Reconstruction of mechanical leg axis using non-modular cemented hinged prosthesis in complex primary total knee arthroplasty

PURPOSE

Modular cementless knee arthroplasty systems are capable of precise reconstruction of the mechanical axis. However, they are considered more susceptible to complications. In contrast, non-modular cemented systems are said to be more forgiving and show good long-term results. The aim of this study was to investigate the resulting leg axis after implantation of a non-modular cemented rotating hinged knee prosthesis. Furthermore, potential risk factors for the occurrence of malalignment and complications should be identified.

METHODS

Between 2005 and 2015, 115 patients could be included in this monocentric retrospective cohort study. All patients underwent primary hinged non-modular cemented total knee arthroplasty. Preoperative and postoperative standardized long radiographs were analysed to determine resulting leg axis. Furthermore, epidemiological and intraoperative data as well as perioperative complications were surveyed.

RESULTS

Average leg axis was 5.8° varus preoperatively and 0.6° valgus postoperatively. Considering an axis deviation of 3° as the target corridor, 27% of all cases examined were outside the desired range. 21% cases showed a femoral deviation from the target corridor and 15% showed a tibial deviation. There was a significant relationship between the preoperative mLDFA and the mechanical alignment of the femoral component (R = 0.396, p < 0.001) as well as between the preoperative mMPTA and the mechanical alignment of the tibial component (R = 0.187, p = 0.045). The mean operative duration was 96 min. No periprosthetic fractures were observed within the study cohort.

CONCLUSION

The main result of the present work is that a non-modular cemented rotating hinged knee arthroplasty system can reconstruct the mechanical leg axis precisely and comparable to modular cementless and unconstrained total knee prostheses. Component malalignment is primarily dependent upon extraarticular deformity preoperatively. Periprosthetic fracture rates and duration of surgery were lower compared with current literature.

LEVEL OF EVIDENCE

Level III: Retrospective cohort study.

A novel quantitative grading system for implant fixation in revision total knee arthroplasty

Aims

Obtaining solid implant fixation is crucial in revision total knee arthroplasty (rTKA) to avoid aseptic loosening, a major reason for re-revision. This study aims to validate a novel grading system that quantifies implant fixation across three anatomical zones (epiphysis, metaphysis, diaphysis).

Methods

Based on pre-, intra-, and postoperative assessments, the novel grading system allocates a quantitative score (0, 0.5, or 1 point) for the quality of fixation achieved in each anatomical zone. The criteria used by the algorithm to assign the score include the bone quality, the size of the bone defect, and the type of fixation used. A consecutive cohort of 245 patients undergoing rTKA from 2012 to 2018 were evaluated using the current novel scoring system and followed prospectively. In addition, 100 first-time revision cases were assessed radiologically from the original cohort and graded by three observers to evaluate the intra- and inter-rater reliability of the novel radiological grading system.

Results

At a mean follow-up of 90 months (64 to 130), only two out of 245 cases failed due to aseptic loosening. Intraoperative grading yielded mean scores of 1.87 (95% confidence interval (CI) 1.82 to 1.92) for the femur and 1.96 (95% CI 1.92 to 2.0) for the tibia. Only 3.7% of femoral and 1.7% of tibial reconstructions fell below the 1.5-point threshold, which included the two cases of aseptic loosening. Interobserver reliability for postoperative radiological grading was 0.97 for the femur and 0.85 for the tibia.

Conclusion

A minimum score of 1.5 points for each skeletal segment appears to be a reasonable cut-off to define sufficient fixation in rTKA. There were no revisions for aseptic loosening at mid-term follow-up when this fixation threshold was achieved or exceeded. When assessing first-time revisions, this novel grading system has shown excellent intra- and interobserver reliability.

A systematic review and meta-analysis of hybrid vs. cemented stems - which method is more optimal for revision total knee arthroplasty?

INTRODUCTION

The number of primary and revision Total Knee Arthroplasty (TKA) cases are expected to increase in future. There are various advantages and disadvantage to employing either of the two main types of stem fixation methods - cemented or hybrid technique. This review aimed to study the most optimal fixation method for revision TKAs by comparing radiological outcomes and re-revision rates.

METHODS

A systematic review and meta-analysis was performed using PubMed and Cochrane Library from 2010 to identify studies explicitly comparing outcomes between cemented against hybrid fixation revision TKA techniques, with a minimum follow up of at least 24 months. A total of 8 studies was included in this review. Egger's test and visual inspection of the funnel plot did not reveal publication bias.

RESULTS

There was no statistically significant difference in radiological failure and loosening (OR 0.79, CI 0.37-1.66, I2 = 29%, p = 0.22), all causes of re-revision (OR 1.03, CI 0.73-1.44, I2 = 0%, p = 0.56) and aseptic revision (OR 0.74, CI 0.27-2.02, I2 = 0%, p = 0.41) between cemented and hybrid techniques. Functional and pain outcomes compared between the two fixation techniques were largely similar across the studies included in this meta-analysis.

CONCLUSION

Despite a trend favouring hybrid stems in revision TKA, current evidence revealed that radiological outcomes and re-revision rates are largely similar between cemented and hybrid fixation techniques.

Is hybrid fixation in revision TKA using LCCK prostheses reliable?

INTRODUCTION

The optimal technique for component fixation in revision total knee arthroplasty (rTKA) remains controversial: full cementation (FC) versus hybrid fixation (HF), which involves press-fit stem with cement fixation in the metaphyseal and epiphyseal zones. Previous series have either demonstrated the superiority of one or the other of these techniques or their equivalence. However, few studies have compared these 2 methods for rTKA using the Legacy® Constrained Condylar Knee (LCCK) prosthesis (Zimmer, Warsaw, Indiana, USA).

HYPOTHESIS

Our hypothesis was that HF of LCCK components is associated with a higher rate of aseptic loosening (AL) than FC.

MATERIALS AND METHODS

This was a single-center, multi-surgeon, retrospective study. Primary revisions between January 2010 and December 2014 were included for all indications. The only exclusion criterion was death without revision before the 5-year follow-up. The primary objective of this study was to compare the survivorship of 2 groups of LCCK components (femoral or tibial), depending on whether their stems had been cemented (HF versus FC), taking AL, revised or not, as the endpoint. The secondary objective was to look for other predictive factors of AL.

RESULTS

A total of 75 rTKAs (150 components) were included. The FC group (51 components) had more Anderson Orthopedic Research Institute (AORI) type 2B and type 3 bone defects (BDs) (p<0.001), more reconstructions using trabecular metal (TM) cones (19 FCs and 5 HFs; p<0.001), and bone allografts (p<0.001). At more than 5 years, none of the FC components were loose compared to 10 HF components (9.4%), with 4 of these stems revised. The only significant difference was survivorship without radiographic AL at 9 years (FC=100%; HF=78.6%; p=0.04). The only predictive factor of AL in the HF group was the filling of the diaphyseal canal (p<0.01). The detrimental effect of BD severity (p=0.78) and the protective effect of TM cones were not demonstrated (p=0.21).

DISCUSSION

Other series studying revisions using the same type of prosthesis also concluded the superiority of FC, not found for other revision prostheses. Despite this study's limitations (retrospective, multi-surgeon, limited sample size, and limited follow-up), all patient outcomes were known, and the difference in survivorship between the groups was very significant.

CONCLUSION

HF has not been proven effective for the LCCK prosthesis. Better diaphyseal filling, wider metaphyseal bone tunnels enabling better cement injections, and stem designs more appropriate for press-fit fixation could improve these results. TM cones are an interesting avenue for further research.

LEVEL OF EVIDENCE

III; retrospective comparative study.

Minimum 5 Year Clinical Outcomes And Survivorship For A Single Revision Total Knee Arthroplasty System Using Hybrid Fixation and Press-Fit Stems

BACKGROUND

Hybrid fixation, utilizing diaphyseal press-fit stems and cement fixation in the tibial and femoral metaphyseal areas, has long been a strategy for revision total knee arthroplasty (rTKA). The purpose of this study was to evaluate the clinical outcomes and survivorships of hybrid fixation using a single rTKA revision system with a minimum of 5 years follow-up.

METHODS

We reviewed our prospectively collected database to identify 281 patients who underwent rTKA using a single revision system with hybrid fixation and press-fit stems between July 2006 and August 2016. We reviewed the clinical outcome scores, including the Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index, and Veterans RAND 12 Item Health Survey (VR-12). We also evaluated the 5- and 10-year survivorships and the indications for re-operations.

RESULTS

The cohort had a mean age of 70 years (range, x to y) and a mean body mass index of 33.4 (range, x to y). The mean time from rTKA surgery was 11.1 years (range, x to y). Above in yellow goes into ethods section Paired t-test analyses showed significant improvements from pre-operative versus post-operative clinical outcome scores (P<0.001) for KSS, WOMAC and VR-12 Physical component. Prosthetic joint infections after index rTKA was the most common failure mode with 29 patients requiring re-operations. Re-revision due to aseptic loosening was uncommon (6 patients) with a cumulative survival rate of 95.2% at 5 years and 94.2% at 10 years.

CONCLUSION

The use of this single rTKA system utilizing press fit stems combined with hybrid fixation provided significant improvements in the clinical outcomes and excellent survivorships at 5 and 10 years.

Similar patient-reported outcomes for hybrid and cemented stem fixation for aseptic tibial revision total knee arthroplasty: a comparison of sequential prospective cohorts

PURPOSE

The tibial stem fixation in an aseptic revision of total knee arthroplasty is poorly studied and controversial. The objective of this study was to prospectively compare clinical outcomes between hybrid and cemented fixation of the stem in aseptic tibial revision after a minimum follow-up of 5 years.

METHODS

Two sequential prospective cohorts of patients who underwent aseptic tibial revision were compared after a minimum follow-up of five years: 31 had both tibial tray and stem cemented (cemented group), and 42 had a hybrid fixation with tibial tray cemented and stem cementless (hybrid group). Clinical assessment was performed by the Knee Society Scores and reduced Western Ontario and McMaster Universities Arthritis Index. Radiological assessment was also performed.

RESULTS

There were no significant differences in preoperative data between groups. Postoperatively, no significant differences between groups in clinical scores or complication rate were found. Survival of the TKA revision at 5-year was 94% (95% CI 89-98%) in the cemented group, and 98% (95% CI 92-100%) in the hybrid group (ns).

CONCLUSION

Clinical outcomes and implant survival were comparable between hybrid and cemented tibial stem fixation.

LEVEL OF EVIDENCE

II.

Cemented Versus Hybrid Technique of Fixation of the Stemmed Revision Total Knee Arthroplasty: A Literature Review

Stems are required during revision total knee arthroplasty to bypass damaged periarticular bone and transfer stress to healthier diaphyseal bone. The mode of stem fixation, whether fully cemented or hybrid, remains controversial. Improvements in surgical technique and implant and instrument technology have improved our ability to deal with many of the challenges of revision total knee arthroplasty. Recent publications that reflect contemporary practice has prompted this review of literature covering the past 20 years to determine whether superiority of one fixation mode over the other can be demonstrated. We reviewed single studies of each type of fixation, studies directly comparing both types of fixation, systematic reviews, international registry data, and studies highlighting the pros and cons of each mode of stem fixation. Based on the available literature, we conclude that using both methods of fixation carries comparable outcomes with marginal superiority of the hybrid fixation method, which is of nonstatistical significance, although on an individual case basis, all fixation methods should be kept in mind and the appropriate method implemented when suitable.

Comparing Revision Total Knee Arthroplasty Stems at a High-Volume Revision Center

Introduction

Hybrid fixation and fully cemented fixation are commonly used in revision total knee arthroplasty (rTKA). These two techniques are typically done based on surgeon preference and one has not demonstrated superiority over the other. The purpose of this study was to examine if there was a difference in survivorship between the two different techniques.

Methods

A retrospective cohort study of all consecutive patients undergoing rTKA (CPT 27487) from January 1, 2011 to January 1, 2018 at a single academic center was performed. Patients were divided into cemented and hybrid rTKA groups with comparison of patient demographic, clinical and radiological outcomes, reoperation, change in post-operative hemoglobin (HgB), and length of stay (LOS).

Results

A total of 133 rTKA for 122 patients were identified: 30.1% in the cemented and 69.9% in the hybrid groups. There was no significant difference in age (p = 0.491), sex (p = 0.250), laterality (p = 0.421), or body mass index (BMI) (p = 0.609) between the two groups. Mean LOS (hybrid 4.13 days, cemented 3.65 days; p = 0.356) and change in Hgb (hybrid 2.95 mg/dL, cemented 2.62mg/dL; p = 0.181) were not statistically different between the groups. Mean follow up for the hybrid (25.4 months, range 2–114 months) and cemented (24.6 months, range 3–75.5 months) rTKA was not statistically significant (p = 0.825). Overall survival rates were 80.9% in the hybrid and 84.6% in the cemented groups (p = 0.642).

Conclusions

Hybrid and fully cemented rTKA techniques have similar survival rates at a minimum followup of 2 years. Additionally, in our cohort, age, gender, and BMI were not associated with failure in either group. Furthermore, we did not observe differences in LOS or change in hemoglobin suggesting early postoperative complications may not differ between cemented and hybrid stemmed groups. Continued long-term research is required for defining the best rTKA technique.

Long Term Results of a Rotating Hinge Total Knee Prosthesis With Carbon-Fiber Reinforced Poly-Ether-Ether-Ketone (CFR-PEEK) as Bearing Material

Background: The use of rotating hinge (RH) prostheses for severe primary as well as revision arthroplasty is widely established. Due to the steadily increasing number of RH prostheses, we aimed to assess the complication frequencies, complication types and clinical outcomes of a modern RH hinge prosthesis using a new bearing material with a minimum follow-up of 7 years.

Methods: Fifty-six consecutive patients who received the EnduRo^® RH prosthesis using carbon-fiber reinforced poly-ether-ether-ketone (CFR-PEEK) as bearing material were included in this prospective study: 21 patients (37.5%) received the prosthesis as a primary total knee arthroplasty (TKA) and 35 patients (62.5%) underwent revision total knee arthroplasties (rTKA). Clinical and radiographic examinations were performed preoperatively, postoperatively after three and 12 months and annually thereafter. Clinical scores were documented for each patient. Competing risk analysis was assessed with respect to indication and failure mode.

Results: Knee Society Score (KSS), Western Ontario and McMaster Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS) and range of motion (ROM) improved significantly compared to preoperative values (p < 0.0001). The overall cumulative incidence for revision surgery was 23.6% at 7 years and the cumulative incidence for complications associated with failure of the prothesis was 5.6% at 7 years, respectively. Complications occurred more frequently in the revision group (p = 0.002).

Conclusion: The evaluated RH prosthesis provided reliable and durable results for a minimum follow-up of 7 years. Prosthesis survival was successful considering the complexity of the cases. The use of this RH system in primary patients showed high survival rates and long-term functional outcomes and clinical outcomes proved to be satisfying in both revision and primary cases. No adverse events were associated with the new bearing material CFR-PEEK.

Outcomes in revision total knee arthroplasty (Review)

Revision total knee arthroplasty (TKA) is a challenging surgical procedure. Although good results are presented, the outcomes are worse in comparison with those of primary TKA, with a higher failure rate. The main reasons for the failure of revision TKA include: sepsis, loosening and instability. There are multiple variables linked to these results, and it is difficult to determinate the exact cause as it is often a multifactorial issue. These variables may be related to the quality of the index-procedure (TKA), to the revision procedure or to patient characteristics. The purpose of this review was to highlight the outcomes of revision knee arthroplasty and main factors that may influence the results. Considerable progress has been made during the last 30 years regarding infection treatment and prevention, complex revision prosthetic design and surgical technique development. Although the outcomes have improved over time, patients who undergo revision TKA may need further re-operations in the future.

Is stemless implant fixation a valid option in total knee revision arthroplasty - Review of in vitro and in vivo studies

Metaphyseal sleeves have shown an improved fixation in Revision Total Knee Arthroplasty (R-TKA) leading to a reduced aspetic loosening rate compared to other stem based fixation options. In the majority of these studies sleeve have been used with stems. Due to that is was not clear how much of this improved fixation could be rated to the sleeve and how much to the additional sleeves. In this review article we analysed the results of sleeve-only obtained in in-vitro or in-vivo studies. In Vitro models showed independent of the set-up a dominant fixation of the sleeve, an additional stem was not adding a lot to the overall fixation. Undersized additional stems showed an increased micromotion and the stem tip, while distal engaging stems showed a proximal stress shielding effect. Very interestingly an increased BMI had not a significant effect on primary fixation of the sleeve. Reduced bone quality on the other hand had and this effect was increased in cases with an increased BMI. In vivo results of sleeve-only patients showed comparable good results to sleeve and stem constructs. In particular on the femoral side the use of an additional stem is required only in a few scenarios. It has to be stated that the numbers of sleeves-only in rotating hinges is too low, to give any recommendation for this high constraint implants. Majority of cases was done with PS and VVC constraint. So far no in vivo data exist on the limitations of sleeve-only in patients with reduced bone quality and increased body weight. In conclusion we can state, that Sleeve-only is an option for R-TKA. In majority of cases the aspetic loosening rate is as low as with additional stems. The borderlines in terms of constraint, bone quality and body weight need to be investigated in future in vivo studies. The in vitro results look so far encouraging.

Comparative Biomechanical In Vitro Study of Different Modular Total Knee Arthroplasty Revision Stems With Bone Defects

BACKGROUND

The aim of this study is to investigate the effects of different stem lengths and types including cones on primary stability in revision total knee arthroplasty with different femoral bone defects and fixation methods in order to maximize bone preservation. It is hypothesized that longer stems provide little additional mechanical stability.

METHODS

Thirty-five human femurs were investigated. A distal bone defect, Anderson Orthopedic Research Institute classification (s. 33) type-F2a, was created in group 1-3 and type-F3 in group 4-6. A cemented, rotating hinge femoral component was combined with different stems (100 and 160 mm total or hybrid cemented cones, or a 100-mm custom-made anatomical cone stem). The femora were loaded according to in vivo loading during gait. Relative movements were measured to investigate primary stability. Pull-out testing was used to obtain a parameter for the primary stability of the construct.

RESULTS

Relative movements were small and similar in all groups (<40 μm). For small defect, the pull-out forces of cemented long (4583 N) and short stems (4650 N) were similar and about twice as high as those of uncemented stems (2221 N). For large defects, short cemented stems with cones showed the highest pull-out forces (5500 N). Long uncemented stems (3324 N) and anatomical cone stems (3990 N) showed similar pull-out forces.

CONCLUSION

All tested stems showed small relative movements. Long cemented stems show no advantages to short cemented stems in small bone defects. The use of cones or an anatomical cone stem with hybrid cementation seems to offer good stability even for larger bone defects. The use of a short cemented stem (with or without cone) may be a suitable choice with a high potential for bone preservation in total knee arthroplasty revision with respective bone defects.

The role of rotating hinge implants in revision total knee arthroplasty

Hinged implants are the most constrained knee replacement prostheses. They are very useful in complex cases of total knee arthroplasty (TKA) revision.

Hinged implants have evolved with rotating bearings and modularity that allows local joint reconstruction or segmental bone replacement.

They are required when significant instability persists in cases with inadequate collateral ligaments and significant flexion laxity.

They are now used when a large bone defect is reconstructed, or when bone fixation of the implant is questionable especially in the metaphyseal zone.

The use of hinged implants in TKA revision is associated with high complication rates. Published outcomes differ based on the patients’ aetiology.

The outcomes of rotating-hinged implants used in septic revisions or salvage situations are poorer than other types of revision and have a higher complication rate.

The poor general health of these patients is often a limitation.

Despite these relatively poor results, hinged implants continue to have a place in revision surgery to solve major instability or to obtain stable bone fixation of an implant when the metaphysis is filled with bone grafts or porous devices.

Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180070

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.

Revision total knee arthroplasty: hybrid vs standard cemented fixation

Introduction

Modular systems with stems are necessary for the stability of revision total knee arthroplasty (rTKA), but controversy remains as to the best fixation method: cemented or hybrid (noncemented stem). The aim of this study was to assess the clinical, X-ray, life-quality and survival results obtained with each fixation method.

Materials and methods

During the period 2000–2013, rTKA was performed on 67 patients (29 cemented arthroplasty and 38 hybrid fixation). The average follow-up was 7 years (range 2–15). All patients were evaluated clinically and radiographically using the American Knee Society Score (AKSS), the Western Ontario and McMaster Universities Arthritis Index (WOMAC), and the Short Form Health Survey (SF-36). A survival study was performed via Kaplan–Meier analysis.

Results

There were no differences between the cemented and hybrid fixation groups in the preoperative and postoperative AKSS clinical evaluation indices and the SF-36 health index. However, the WOMAC assessment scale did reveal statistically significant differences between the groups, with a global classification of 64.9 points weighted at 100 (SD 16.8) for cemented fixation versus 78.9 (SD 9.0) for hybrid fixation (p = 0.001). The corresponding values for stiffness were 61.6 (SD 12.9) and 80.5 (SD 14.7) (p = 0.001), and those for function were 61.3 (SD 19.4) and 78.1 (SD 10.5) (p = 0.001). No significant differences between the groups were recorded with respect to the pain score (p = 0.4) or the results of the Kaplan–Meier survival analysis.

Conclusion

Although the results were similar for the two groups, hybrid fixation tended to produce better results than cemented fixation. In view of the risk of further loosening, we prefer the more conservative approach, i.e. hybrid fixation.

Level evidence

Level III.

Current Epidemiology of Revision Total Knee Arthroplasty in the United States

BACKGROUND

Revision surgery for failed total knee arthroplasty (TKA) continues to pose a substantial burden for the United States healthcare system. The predominant etiology of TKA failure has changed over time and may vary between studies. This report aims to update the current literature on this topic by using a large national database. Specifically, we analyzed: (1) etiologies for revision TKA; (2) frequencies of revision TKA procedures; (3) various demographics including payer type and region; and (4) the length of stay (LOS) and total charges based on type of revision TKA procedure.

METHODS

The Healthcare Cost and Utilization Project (HCUP) National Inpatient Sample (NIS) database was used to identify all revision TKA procedures performed between 2009 and 2013. Clinical, economic, and demographic data were collected and analyzed for 337,597 procedures. Patients were stratified according to etiology of failure, age, sex, race, US census region, and primary payor class. The mean LOS and total charges were also calculated.

RESULTS

Infection was the most common etiology for revision TKA (20.4%), closely followed by mechanical loosening (20.3%). The most common revision TKA procedure performed was all component revision (31.3%). Medicare was the primary payor for the greatest proportion of revisions (57.7%). The South census region performed the most revision TKAs (33.2%). The overall mean LOS was 4.5 days, with arthrotomy for removal of prosthesis without replacement procedures accounting for the longest stays (7.8 days). The mean total charge for revision TKAs was $75,028.07.

CONCLUSION

Without appropriate measures in place, the burden of revision TKAs may become overwhelming and pose a strain on providers and institutions. Continued insight into the etiology and epidemiology of revision TKAs may be the principle step towards improving outcomes and mitigating the need for future revisions.

Comparable Stability of Cemented vs Press-Fit Placed Stems in Revision Total Knee Arthroplasty With Mild to Moderate Bone Loss: 6.5-Year Results From a Randomized Controlled Trial With Radiostereometric Analysis

BACKGROUND

Short-term stability after revision total knee arthroplasty (TKA) with either fully cemented or hybrid-placed implants is comparable. Interestingly, implant micromotion >1 mm/degree occurred with both techniques which might increase the risk of loosening in the midterm or long-term. Therefore, the present study investigated midterm stability and clinical results of fully cemented vs hybrid-placed revision TKA, with mild to moderate bone loss, using radiostereometric analysis (RSA).

METHODS

This study involves the prolonged follow-up of a previous randomized controlled trial. RSA images taken at baseline, 6 weeks, 3 and 6 months, and 1, 2 and 6.5 years of follow-up were analyzed. Stability of the femoral and tibial implants was evaluated using total translation and rotation, based on the micromotion determined with model-based RSA.

RESULTS

Of the 30 patients who completed the 2-year follow-up in the original randomized controlled trial, 23 (12 cement, 11 hybrid) were available for follow-up at 6.5-year (range 5.4-7.3). There were no differences in median total translation and rotation of the femoral and tibial components between the 2 groups, and none of the clinical scores differed between the groups. Interestingly, in the group with cemented stems, 5 tibia implants showed >1 mm/degree micromotion compared to none in the hybrid group.

CONCLUSION

There was no difference in median micromotion and clinical outcome between fully cemented and hybrid-placed revision TKA 6.5 years postoperatively. Two femur components showed progressive migration over time whereas tibia components migrate especially in the first year followed by a stable situation. Whether this will lead to loosening and re-revisions remains to be investigated.

Tibial revision knee arthroplasty: influence of modular stems on implant fixation and bone flexibility in AORI Type T2a defects

BACKGROUND

Due to the varying bone defects presented to surgeons during revision total knee arthroplasty, modular implant systems are preferred over standard implant designs. However, every implant combination (sleeves, stems and augments) can affect the fixation in different ways and thus influence the long-term outcome. We therefore aimed to analyze the effect of large metaphyseal sleeves with and without short modular stems on implant fixation and bone flexibility of a modular tibial revision knee system.

METHODS

A new tibial revision implant (Attune RP Revision; DePuy Synthes) with a sleeve was compared to a sleeve/stem combination implanted in synthetic bones with Anderson Orthopaedic Research Institute (AORI) Type T2a defects and also compared to an intact bone. Implant-bone-interface micromotions and bone deformations during standardized load application were measured using a digital image correlation system.

RESULTS

The lowest relative micromotions were measured more distally for stemmed implants, and more proximally for the stemless group. When compared to an intact bone, there is increased proximal bone deformation in the stemless group.

CONCLUSIONS

Using a short stem in addition to a tibial revision implant with a metaphyseal sleeve in a moderate bone defect provides for more natural bone deformation. Although the main fixation area was shifted distally, relative micromotions were reduced. Based on this biomechanical study, the use of diaphyseal short stems with metaphyseal sleeves seems to be beneficial in terms of the initial implant fixation and for its flexibility, which is similar to that of intact bones in the case of AORI T2a defects.

Fixation of stem in revision of total knee arthroplasty: cemented versus cementless-a meta-analysis

PURPOSE

Revision of total knee arthroplasty (TKA) is growing rapidly all over the world. The introduction of intramedullary stems for additional stability in revision is well accepted by most of the surgeons, while the philosophy of stem fixation is still under controversy. A meta-analysis was performed to compare the survivorship of revised implants with regard to a cemented or cementless stem fixation.

METHODS

Publications with patients who underwent revision TKA with minimum 24-month follow-up were systematically reviewed. Type of intramedullary stem fixation, failure rate for any reason, incidence of aseptic loosening and infection were extracted with follow-up interval specified. Random-effects meta-analysis was used to aggregate incidence data, which was compared between different fixation groups by fitting of logistic regression model.

RESULTS

Seventeen observational studies were included in this meta-analysis. There was a similar likelihood of failure for any reason (risk ratio, RR 0.97), general reoperation (RR 1.02), aseptic loosening (RR 1.0) and infection (RR 1.0) in cemented stem fixation group compared to cementless stem fixation group with follow-up <60 months. When follow-up period extend to more than 60 months, the same likelihood was observed as 0.98, 0.96, 0.97 and 0.98, respectively. There was no significant difference in any of these comparisons of survival-related indices.

CONCLUSION

There was no significant difference in failure for any reason, reoperation, aseptic loosening and infection between revision TKA with cemented or cementless stem fixation. Based on the available literature, no superiority of any type of stem fixation was found. If follow-up period was neglected, aseptic loosening would be the leading reason for pain and dysfunction of patient undertaken revision TKA.

LEVEL OF EVIDENCE

Systematic review of Level IV, Therapeutic studies, Level IV.

No Difference in Implant Micromotion Between Hybrid Fixation and Fully Cemented Revision Total Knee Arthroplasty: A Randomized Controlled Trial with Radiostereometric Analysis of Patients with Mild-to-Moderate Bone Loss

BACKGROUND

In revision total knee arthroplasty (TKA), the femoral component and tibial baseplate are usually cemented. However, stems can be fixed either with cement or with a press-fit technique, with the latter resulting in hybrid fixation. There is no consensus on the preferred stem fixation technique. Therefore, we compared the stability of cemented TKA implants with the stability of TKA implants fixed with the hybrid technique in a prospective randomized trial using radiostereometric analysis (RSA).

METHODS

Thirty-two patients with a Type-I or II bone defect who needed revision TKA and were randomly allocated at the time of surgery into either the cemented or hybrid-fixation group were included in the study. The radiographs for the RSA were obtained during hospitalization (baseline); at 6 weeks; and at 3, 6, 12, and 24 months. Migration of the femoral and tibial implants was measured using model-based RSA and expressed along or around the 3 orthogonal axes and as total translation (TT) and total rotation (TR). Clinical results were evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), active flexion, and visual analog scale (VAS) scores for pain and satisfaction. Mann-Whitney and chi-square tests were used to compare migration and clinical outcomes between the cement and hybrid techniques.

RESULTS

At 24 months, no difference in median migration or the number of migrating components was found between the cemented and hybrid-fixation groups. In each group, approximately one-third of the tibial components had total rotation of >1°. The clinical scores did not differ between the techniques.

CONCLUSIONS

At 24 months after revision TKAs, cemented and hybrid-fixation replacements were equally stable. Unexpectedly, both groups had implants with >1 mm or >1° of micromotion although there were no clinical or radiographic signs of loosening. Whether these findings indicate the possibility of loosening with longer follow-up remains to be investigated.

LEVEL OF EVIDENCE

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

Extent of vertical cementing as a predictive factor for radiolucency in revision total knee arthroplasty

PURPOSE

Limited information is available regarding the effects of cementing extent on implant stability in patients who have undergone revision total knee arthroplasty (TKA). As such, the goals of this study were: (1) to determine the correlation between the extent of vertical cementing and implant loosening; (2) to determine whether the extent of cementing is a potential predictive factor for radiolucency; and (3) to evaluate the minimal amount of cement needed for a stable implant during revision TKA using a hybrid technique.

METHODS

One hundred nine stemmed/revision TKAs with a mean follow-up period of 5 years were retrospectively analysed. In each case, a single varus-valgus constrained implant was used and fixed with a hybrid technique. Implant stability was evaluated according to the modified Knee Society radiographic scoring system. The extent of vertical cementing was defined as the longitudinal length from the implant base to the end of the radiopaque line around the stem on radiograph. Its correlation with implant stability was analysed, and the minimal value for a stable implant was evaluated with a receiver operating characteristic (ROC) analysis.

RESULTS

The mean extent of vertical cementing was longer in stable implants (femur: p = 0.001, tibia: p = 0.004) and significantly correlated with implant stability (femur: p < 0.001, tibia: p = 0.001). A logistic regression analysis revealed that the risk of loosening was 8.7-16.1 times higher when the extent of cementing was <40 mm, which was located at the stem-implant junction of the modular implant. The minimal extent of vertical cementing was estimated to be 60 mm for a stable femoral implant and 50 mm for a tibial implant.

CONCLUSIONS

The hybrid fixation technique with a cementing extent >60 mm for the femur and 50 mm for the tibia was durable at a mean follow-up period of 5 years. Vertical cementing 10-20 mm above the stem-implant junction is recommended when performing revision TKA using this technique.

LEVEL OF EVIDENCE

IV.

Radiological Stability after Revision of Infected Total Knee Arthroplasty Using Modular Metal Augments

PURPOSE

To evaluate the radiological stability according to the number of modular augments after revision of infected total knee arthroplasty (TKA).

MATERIALS AND METHODS

Between February 2006 and September 2013, 37 patients (39 knees) followed ≥2 years after revision of infected TKA using modular metal augments for bone defects were reviewed retrospectively. We divided the patients into 3 groups according to the number of augments into group A (≤2 augments, 14 knees), group B (3-4 augments, 18 knees), and group C (5≥ augments, 7 knees) and evaluated the width of radiolucent zones around the implant at the last follow-up.

RESULTS

There were 3 Anderson Orthopedic Research Institute type I, 33 type II, and 3 type III bone defects. The mean number of radiolucent zones of group A was 3 and the sum of width averaged 4.4 mm. In group B, the values were 4.8 and 6.2 mm, respectively. In group C, the values were 8.1 and 12.9 mm, respectively. The differences between the three groups were statistically significant.

CONCLUSIONS

In revision TKA with modular metal augmentation caused by infected TKA, increased modularity can result in radiological instability.

Computer-assisted navigation is beneficial both in primary and revision surgery with modular rotating-hinge knee arthroplasty

PURPOSE

The objective of the present study was to explore the effect of navigation on the reconstruction of the mechanical leg axis, implant positioning and the restoration of the joint line in hinged knee arthroplasty in vivo. We present the first 1- to 3-year clinical and radiological results following computer-navigated implantation of the EnduRo modular rotating-hinge knee arthroplasty system (Aesculap AG, Tuttlingen, Germany) as a primary or revision implant.

METHODS

Thirty-one patients were analysed retrospectively. Indication was revision surgery in 18 patients and complex primary surgery in 13. The clinical and radiological results of 31 patients with a minimum follow-up of 12 months (mean 22.2 ± 6.2 months) were recorded. Age at follow-up was 55.2 ± 9.9 years.

RESULTS

The absolute varus-valgus deviation from the neutral mechanical leg axis was determined at 5.1° ± 5.1° preoperatively and 2.1° ± 1.4° postoperatively. No intraoperative complications or problems with the navigation system were observed. At latest follow-up, no component loosening was detected. Based on the Knee Society Score, a knee score of 64.9 ± 17.7 points and a function score of 67.2 ± 27.3 points were achieved.

CONCLUSIONS

Encouraging short-term clinical and radiological results with the computer-navigated implantation of the modular rotating-hinge EnduRo knee arthroplasty system were found in both primary and revision surgery. The navigation facilitated the reconstruction of the leg axis, implant positioning and the restoration of the joint line.

LEVEL OF EVIDENCE

IV.

Direct, Cementless, Metaphyseal Fixation in Knee Revision Arthroplasty With Sleeves-Short-Term Results

Different options for implant fixation in revision TKA exist. Small series have been published on direct cementless fixation with sleeves. The objective of this study was to analyze the short- and mid-term results of sleeve-fixation in a large revision TKA series. In this prospective study 121 patients with 193 sleeves (119 tibial and 74 femoral) were included. Mean follow-up was 3.6 years (2-6.1 years). Analysis included clinical and radiographic assessment. ROM, KSS and Functional Score improved significantly. Fourteen patients (11.4%) underwent operative re-revision during the follow-up period. Direct cementless fixation in the metaphysis by sleeves is a promising option for implant fixation in revision TKA, both on the tibial and femoral side.

Stemmed femoral implants show lower failure rates in revision total knee arthroplasty

BACKGROUND

Stemmed femoral implants are not universally used in revision total knee arthroplasty. The aim of this study was to evaluate whether the re-revision rate would be greater for revision total knees performed without stemmed femoral implants compared with revision total knees performed with stemmed femoral implants.

METHODS

All revision cases performed at a single institution between 2004 and 2011 were retrospectively reviewed. A total of 130 revision total knee arthroplasty procedures (63 Group 1; 67 Group 2) met the inclusion criteria.

RESULTS

Revisions performed without femoral stems failed more often than revisions with femoral stems (44% vs 9%, p<0.001) despite more severe pre-operative bone loss in groups that were revised with stems (p<0.05).

CONCLUSIONS

We recommend that femoral stems be used routinely in procedures where a femoral implant is revised following a prior total knee arthroplasty.

Zonal fixation in revision total knee arthroplasty

Revision knee arthroplasty presents a number of challenges, not least of which is obtaining solid primary fixation of implants into host bone. Three anatomical zones exist within both femur and tibia which can be used to support revision implants. These consist of the joint surface or epiphysis, the metaphysis and the diaphysis. The methods by which fixation in each zone can be obtained are discussed. The authors suggest that solid fixation should be obtained in at least two of the three zones and emphasise the importance of pre-operative planning and implant selection.

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.

[Knee revision arthroplasty : cementless, metaphyseal fixation with sleeves]

OBJECTIVE

Primary and long-term fixation of cementless metaphyseal implants in knee revision arthroplasty cases with large bone defects.

INDICATIONS

All tibial and femoral bone defects AORI grade 2 and 3.

CONTRAINDICATIONS

Cases where stable uncemented fixation of the metaphyseal implant is not possible.

SURGICAL TECHNIQUE

Pre-operative evaluation of the failure mode and implant fixation planning. After opening the joint, a synovectomy and mobilisation of medial and lateral recesses routinely performed. Testing of ligamentous stability and implant fixation undertaken before explantation. Removal of the bearing, femoral and tibial components with osteotomes or oscillating saw. Tibial diaphysis prepared with reamers, and metaphyseal preparation with broaches and stem extension. Placement of the metaphyseal broach for height with respect to the tibial joint line and rotational stability assessed. Tibial tray size and position determined before implanting the sleeve, stem and tray trial. The tibial trial provides a stable platform for analysis of the extension and flexion gaps with spacer blocks. Diaphyseal reamers used to identify the anterior femoral bow. Metaphyseal broaches used to achieve stable fixation up to the resection line marked on the handle. Distal femoral freshening cut in 5° or 7° of valgus made to accommodate distal augments as needed. Positioning of the 4-in-1 block with reconstruction of the posterior off-set and cutting for posterior augmentation. Selection of a box cut corresponding to the amount of constraint needed. Trial insert with appropriate, stem, sleeve, condylar femur and augments introduced. Bearing size, joint stability and ROM assessed. Patella alignment and the need for patella replacement or revision determined. The definitive implants are cemented at the joint surface, with metaphyseal sleeves and diaphyseal stems are uncemented.

POSTOPERATIVE MANAGEMENT

Full weight bearing as tolerated, physiotherapy, lymph drainage and pain therapy are routine with no specific post-operative management required.

RESULTS

Between 2007 and 2011, 193 sleeves (119 tibial/74 femoral) were implanted in 121 aspetic knee revision arthroplasties. After average of 3.6 years they were analysed clinically and radiographically. The AKSS (American Knee Society Score) increased from 88 ± 18 to 147 ± 23 points (p < 0.01). ROM (range of motion) increased from 89 ± 6° to 114 ± 4°. Overall revision rate was 11.6 %. Only 4 sleeves revised for aseptic loosening (2 % of total sleeves). An additional 10 revisions performed mainly for infection (3.3 %) or ligament instability (3.3 %).

A 30-mm cemented stem extension provides adequate fixation of the tibial component in revision knee arthroplasty

BACKGROUND

The optimal stem length and method of fixation for the tibial component in revision knee arthroplasty remains controversial. The use of a cemented 30-mm stem extension provides certain advantages compared with other methods of fixation, but there are few published results.

QUESTIONS/PURPOSES

We therefore asked (1) what is the survivorship (with respect to loosening and repeat revision) of tibial component revisions when a 30-mm stem extension is used; and (2) what factors are associated with the appearance tibial radiolucent lines?

METHODS

We retrospectively reviewed 54 patients (58 knees) with fixation of the revision tibial component with a 30-mm cemented stem extension; another seven patients died and 11 patients had these components but were lost to followup. These implants represented 74% of our tibial revisions during the period in question (76 of 103); general indications for using them were need for a varus-valgus constrained liner or proximal bone loss requiring a metaphyseal cone or metal augment with an intact diaphysis. The Anderson Orthopaedic Research Institute tibial defect was Grade 1 in 37, 2A in 10, 2B in four, and Grade 3 in seven knees; constrained liners were used in 34% (20 of 58 knees). Patients were evaluated and followed for a mean of 5 years (range, 2-12 years).

RESULTS

There were no revisions for tibial component loosening. One patient had débridement and liner exchange for late infection. Radiolucent lines were seen in 25 tibial components but only eight knees had radiolucencies in four or more zones. There were significantly fewer radiolucencies in revisions that used metaphyseal cones (20 in eight knees with cones compared with 53 in 17 without, p=0.013).

CONCLUSIONS

The cemented 30-mm tibial stem extension provided excellent fixation in knee revision arthroplasty, even with metaphyseal defects and constrained polyethylene liners, although this series included relatively few patients with severe tibial defects. Longer followup is required for patients with radiolucent lines to confirm that the fixation will remain durable.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Bone loss following knee arthroplasty: potential treatment options

INTRODUCTION

The management of bone loss is a crucial aspect of the revision knee arthroplasty. Bone loss can hinder the correct positioning and alignment of the prosthetic components, and can prevent the achievement of a stable bone-implant interface. There is still controversy regarding the optimal management of knee periprosthetic bone loss, especially in large defects for which structural grafts, metal or tantalum augments, tantalum cones, porous metaphyseal sleeves, and special prostheses have been advocated. The aim of this review was to analyze all possible causes of bone loss and the most advanced strategies for managing bony deficiency within the knee joint reconstruction.

MATERIALS AND METHODS

Most significant and recent papers about the management of bone defects during revision knee arthroplasty were carefully analyzed and reviewed to report the most common causes of bone loss and the most effective strategies to manage them.

RESULTS

Modular metal and tantalum augmentation showed to provide more stable and durable knee revisions compared to allografts, limited by complications such as graft failure, fracture and resorption. Moreover, modular augmentation may considerably shorten operative times with a potential decrease of complications, above all infection which has been frequently associated to the use of allografts.

CONCLUSIONS

Modular augmentation may significantly reduce the need for allografting, whose complications appear to limit the long-term success of knee revisions.

Modular augmentation in revision total knee arthroplasty

PURPOSE

Controversy exists about the real effectiveness of modular augmentation to manage bone defects in revision total knee arthroplasty. The purpose of this study was to determine whether use of modular augmentation to reconstruct severe defects (1) significantly increased overall outcomes, (2) caused radiolucency or osteolysis and (3) affected mid-term survivorship of knee revisions. The hypothesis was that modular augmentation provides a good survivorship of knee revisions.

METHODS

Thirty-eight consecutive revision knee arthroplasties were followed for a median follow-up period of 7 (4.5-9) years. Type 2 and 3 defects were treated with metal augments, tantalum cones and modular cementless stems. Patients were assessed using the IKS knee and function scores and the HSS score.

RESULTS

The median IKS knee and function scores and HSS score were 34 (15-58), 19.5 (13-39) and 30 (24-60) points before the operation, respectively, and 78 (49-97), 76 (58-90) and 80.5 (64-98) points (p < 0.001) at the latest follow-up. The median knee flexion increased from 82° (31°-110°) to 116° (100°-129°) (p < 0.01). Tibial radiolucencies were observed in 2 (5.2 %) cases. Re-revision was necessary in three (7.9 %) patients.

CONCLUSIONS

Modular augmentation may reduce the need for allografting to treat severe bone defects, providing a well-functioning and durable knee joint reconstruction.

The influence of stem length and fixation on initial femoral component stability in revision total knee replacement

Objectives

Orthopaedic surgeons use stems in revision knee surgery to obtain stability when metaphyseal bone is missing. No consensus exists regarding stem size or method of fixation. This in vitro study investigated the influence of stem length and method of fixation on the pattern and level of relative motion at the bone–implant interface at a range of functional flexion angles.

Methods

A custom test rig using differential variable reluctance transducers (DVRTs) was developed to record all translational and rotational motions at the bone–implant interface. Composite femurs were used. These were secured to permit variation in flexion angle from 0° to 90°. Cyclic loads were applied through a tibial component based on three peaks corresponding to 0°, 10° and 20° flexion from a normal walking cycle. Three different femoral components were investigated in this study for cementless and cemented interface conditions.

Results

Relative motions were found to increase with flexion angle. Stemmed implants reduced relative motions in comparison to stemless implants for uncemented constructs. Relative motions for cemented implants were reduced to one-third of their equivalent uncemented constructs.

Conclusions

Stems are not necessary for cemented implants when the metaphyseal bone is intact. Short cemented femoral stems confer as much stability as long uncemented stems.

Functional outcome following aseptic single-stage revision knee arthroplasty

PURPOSE

This study attempts to quantify the influence of constraint and various indications upon functional outcome following aseptic first-time revision knee arthroplasty.

METHODS

A single-centre prospective study was performed to examine the outcome for 175 consecutive total revision knee replacements performed between 2003 and 2008 with a minimum follow-up of 2 years. Patient-reported outcome data were used to determine the influence of final level of component constraint, its relationship with primary indication for surgery and the predictor variable for functional outcome at 1 year.

RESULTS

All patients were found to have a significant improvement for WOMAC pain, function and stiffness score and physical functioning, role physical, bodily pain and social functioning components of SF-36 score. About 69% were satisfied with the overall procedure. WOMAC function, pain and stiffness score was significantly worse for patients revised for instability (27%) compared to that for aseptic loosening (46%). A significantly higher proportion of patients were satisfied with the procedure, had a better quality of life and would have the surgery again in the aseptic loosening group as compared to the instability group. Revision to a higher level of constraint did not improve knee function irrespective of the primary indication for surgery.

CONCLUSION

This study has found that revision for instability, irrespective of choice of new device, was met with significantly poorer functional outcome. The level of constraint did not influence functional outcome.

LEVEL OF EVIDENCE

II.

[Revision implants of the future: trends and new developments]

According to current prognostic studies the numbers of revision operations of hip and knee arthroplasty will increase worldwide. As many patients undergo several revisions and become older at the same time, orthopedic surgeons will have to cope with vast bony defects during operations. The introduction of highly porous metals as surface layer or metal augments has facilitated primary stabilization of prostheses. Short and mid-term results of these new products are promising. New developments in coatings, such as cationic antimicrobial peptides represent new alternatives for antibacterial therapy of periprosthetic infections and increase osteointegration of prosthesis components. Furthermore, the new revision systems have a modular design and can be individually adapted to the patient's bony conditions during operations. In most cases this can be done without cement or in a hybrid technique.