Total knee arthroplasty with the PFC system. Results at a minimum of ten years and survivorship analysis

Revision Total Knee Arthroplasty with Metaphyseal Sleeves without Stem: Short-Term Results

Purpose  The aim of this study was to evaluate the efficacy of revision total knee arthroplasty (TKA) with cementless metaphyseal sleeves without stems either in the femoral or tibial side or in both.

Methods  In this retrospective study, 51 patients (51 knees) operated in the period 2010 to 2015 met the above-mentioned criteria and were invited to a medical examination including X-rays. Forty-six were available for the study. Mean follow-up was 37 months. Knee Society score (KSS) (objective knee score), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and range of motion (ROM) were used as outcome scores and compared with baseline values. X-rays were also examined and compared with postoperative exams to evaluate the presence of loosening, radiolucent lines, and bone ingrowth. Satisfaction of the patients was also investigated using a linear scale from 1 to 10.

Results  KSS improved from 39 to 77 ( p  < 0.01); WOMAC score improved from 76 to 41 ( p  < 0.01). Twenty-four (52%) patients were satisfied, 15 (32%) were partially satisfied, and 7 (16%) were unsatisfied. ROM improved from 93 to 96 degrees (nonsignificant difference). X-rays showed no loosening of the implants, radiolucent lines in 4 patients (3 of them were asymptomatic) and bone ingrowth in 43 out of 46 patients.

Conclusion  In this short-term retrospective study, the use of sleeves without stem was a safe and effective procedure in revision TKA. We found a significant improvement in clinical results compared with baseline values and no signs of implant loosening.

Level of Evidence  Level IV, therapeutic case series.

Rationale of Cruciate Retaining Design in Rheumatoid Arthritis: A Review of Clinical Analysis and its Role in Rheumatoid Arthritis

Background:

Over the years, proponents of total knee designs (cruciate retaining and posterior stabilised) have conducted several long-term studies to claim the potential of these designs in several subsets of patients. Total knee arthroplasty (TKA) in patients with rheumatoid arthritis has also been one such domain where numerous studies were conducted in the past. A general perception among majority of arthroplasty surgeons is that, posterior stabilised (PS) is the implanted design of choice among patients with Rheumatoid arthritis (RA). However, with the available literature there is a significant disparity related to the selection of implants in patients with rheumatoid RA. In this review of literature, an attempt is made to identify the clinical performance and role of one such implant design, the cruciate retaining (CR) prosthesis in rheumatoid arthritis.

Method:

The review was conducted after a series of advanced search in the following medical databases; Pub med, Biomed central, Cochrane and Google scholar for articles related to long term follow up studies of cruciate retaining total knee arthroplasty in rheumatoid arthritis using the keywords cruciate retaining prosthesis, total knee arthroplasty, rheumatoid arthritis.

Results:

The available data demonstrate that the CR design is attributed with an excellent long term survivorship and functional outcome even in follow up studies up to twenty-five years.

Conclusion:

The advantages of using a CR design are long term survivorship, controlled femoral roll back and preservation of bone stock. Thus, the data gathered in this review lead to a consideration that the CR design is an implant design on par with PS design in patients with RA.

Different patient satisfaction levels between the first and second knee in the early stage after simultaneous bilateral total knee arthroplasty (TKA): a comparison between subjective and objective outcome assessments

Background

Simultaneous bilateral total knee arthroplasty (TKA) is an effective treatment option and safe for properly selected patients. The purpose of this study was to evaluate whether patients have different satisfaction levels between the first and second knee in the early stage after simultaneous bilateral TKA.

Methods

We retrospectively reviewed 46 patients who underwent simultaneous bilateral TKA by a single surgeon in our department between March 2013 and March 2015. The surgeon typically performed first-side TKA (right knee), followed by TKA on the left knee. Tranexamic acid (TXA) (10 mg/kg) was given intravenously, and the tourniquet was released after wound closure. The preoperative KSS, ROM, and pain visual analog scale (VAS); the objective parameters including drainage volume and swelling evaluated by the circumference of the 10 cm above the patella; and the preoperative and postoperative (1st, 3rd, and 7th days) subjective parameters including pain, satisfaction VAS, and patient satisfaction of the first and second surgeries for each knee were analyzed.

Results

In simultaneous bilateral TKA, compared with the second-side TKA (left knee), the first-side TKA (right knee) had a lower mean drainage volume (p < 0.05), but the swelling of the knee was higher on the 1st, 3rd, and 7th postoperative days (p < 0.05). Moreover, the first-side TKA was scored lower in satisfaction VAS but higher in pain VAS at the 1st, 3rd, and 7th postoperative days. The patient satisfaction scores indicated 2 (4.4%) of the 46 patients scored first-side TKA higher than second-side TKA, 34 (73.9%) of the 46 patients scored second-side TKA higher than first-side TKA, and 10 (21.7%) of the 46 patients scored their satisfaction as the same for both knees.

Conclusions

This research study found that there was better patient satisfaction with the second knee in the early stage after simultaneous bilateral TKA, which may provide some considerations for surgeons choosing simultaneous bilateral total knee arthroplasty for patients with osteoarthritis in both knees.

Midterm Clinical and Radiographic Results of Mobile-Bearing Revision Total Knee Arthroplasty

BACKGROUND

Constrained implants are frequently required in revision total knee arthroplasty (TKA) and are associated with an increase in aseptic component loosening and damage or wear to the constraining mechanisms, compared with primary TKA. The purpose of the following study was to evaluate the midterm clinical and radiographic results including the incidence of bearing complications in a group of patients undergoing revision TKA using mobile-bearing revision TKA implants.

METHODS

We retrospectively reviewed 316 consecutive mobile-bearing revision TKAs performed at 2 centers between 2006 and 2010. There were 183 women and 133 men with a mean age of 66 years. The patients were evaluated clinically using the Knee Society scores. A radiographic analysis was performed. Bearing specific complications (ie, instability or dislocation) were recorded.

RESULTS

Patients were followed-up for a minimum of 24 months and a median of 59.88 months (range 24-121.2). The average Knee Society knee score and function scores increased from 40.8 and 47.9 points preoperatively to 80 points and 70.3 points, respectively (P < .01). The average knee flexion improved from 105.6° preoperatively to 117.4° postoperatively (P < .01). Eight patients required subsequent implant revision. No cases of bearing complications were observed.

CONCLUSION

Revision TKA using mobile-bearing revision components demonstrated favorable midterm clinical and radiographic results with no occurrence of bearing instability or dislocation. Longer follow-up is required to evaluate for potential advantages of mobile-bearings over fixed-bearing revision components in terms of polyethylene wear reduction, reduced stress transmission across fixation interfaces, and reduced stress on the polyethylene post.

Correcting Severe Varus Deformity Using Trial Components During Total Knee Arthroplasty

BACKGROUND

Extensive medial soft tissue release may be necessary to correct severe varus deformity during total knee arthroplasty (TKA). However, this procedure may result in instability. Here, we describe a novel soft tissue balancing technique, which can minimize medial release in severe varus deformity during TKA.

METHODS

Fifty knees (40 patients) with hip-knee-ankle angle of more than 20° of varus were corrected using this technique (group 1). After achieving flexion gap balancing by needle puncturing and spreading of the superficial medial collateral ligament, extension gap balancing was obtained by gradual extension with the trial components in place. After group 1 was set, a one-to-one patient-matched control group who had mild varus deformity was selected by propensity score matching (50 knees, 48 patients, group 2). At postoperative 1 year, mediolateral laxity was compared between the 2 groups using the stress radiographs. Clinical outcomes were also compared using the Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index score.

RESULTS

There were no differences in mean medial and lateral laxities between groups 1 and 2 at 1 year after the operation (medial laxity: 2.3° ± 1.4° and 2.7° ± 1.3°, respectively, P = .310) (lateral laxity: 3.6° ± 1.7° and 3.2° ± 2.0°, respectively, P = .459). There were no significant differences in postoperative clinical scores and knee alignment.

CONCLUSION

Our technique of obtaining extension gap balancing using trial components led to safe and effective balancing by avoiding unnecessary extensive release in severe varus deformity during TKA.

A Meta-Analysis Comparing All-Polyethylene Tibial Component to Metal-Backed Tibial Component in Total Knee Arthroplasty: Assessing Survivorship and Functional Outcomes

BACKGROUND

This meta-analysis compares the clinical performance of all-polyethylene tibial (APT) to the metal-backed tibial (MBT) components.

METHODS

We included comparative studies in primary total knee arthroplasty involving APT and MBT implant components. The primary outcomes were function, durability, and reports of adverse events.

RESULTS

Twenty-eight articles with 95 847 knees were available for synthesis. The meta-analysis showed an association of APT with lower revision rates (incidence rate ratio, 0.709; P = .002) and adverse events (incidence rate ratio, 0.785; P = .204). Moderator analyses were performed to determine the effect of posterior cruciate ligament status on outcome, and no statistically significant effect was found for revision risk or adverse events incidence.

CONCLUSION

All-polyethylene tibial components seem to be an equal option, with less financial burden than the MBT.

Prospective comparative clinical study of ceramic and metallic femoral components for total knee arthroplasty over a five-year follow-up period

BACKGROUND

The aim of this prospective comparative study was to evaluate the clinical and radiological outcomes of a TKA system, comparing a ceramic (BIOLOX® delta) and metallic (Co28Cr6Mo) femoral component over a five-year follow-up period.

METHODS

Forty-three TKA patients (17 metallic and 26 ceramic femoral components) were enrolled in the study. Clinical and radiological evaluations were performed preoperatively and at three, 12, 24 and 60months postoperatively, using the HSS-, WOMAC- and SF36-Scores, in addition to standardized X-rays.

RESULTS

The HSS-Score improved significantly from 58.7±12.7 points preoperatively to 88.5±12.3 points at five-years postoperative in the ceramic group, and 60.8±7.7 to 86.2±9.4 points in the metallic group. WOMAC- and SF-36-Scores showed significant improvement over time in both groups. There were no significant differences between groups for HSS-, WOMAC- and SF-36-Scores, nor for range of motion (p≤0.897) at any follow-up evaluation. Furthermore, radiological evaluation showed no implant loosening or migration in either group.

CONCLUSIONS

Mid-term outcomes for the ceramic femoral components demonstrated good clinical and radiological results, as well as comparable survivorship to the metallic femoral component of the same total knee system, and to other commonly used metallic total knee systems. Therefore, ceramic knee implants may be a promising solution for the population of patients with osteoarthritis and metal sensitivity. Long-term studies are required in order to confirm the positive mid-term clinical results, and to follow the implant survival rate in regard to the enhanced wear resistance of ceramic implants.

No Differences Identified in Transverse Plane Biomechanics Between Medial Pivot and Rotating Platform Total Knee Implant Designs

BACKGROUND

Total knee arthroplasties (TKAs) using well-designed, fixed bearing prostheses, such as medial pivot (MP), have produced good long-term results. Rotating-platform, posterior-stabilized (RP-PS) mobile bearing implants were designed to decrease polyethylene wear. Sagittal and coronal plane TKA biomechanics are well examined and correlated to polyethylene wear. However, limited research findings describe this relationship in transverse plane. We assumed that although axial plane biomechanics might not be the most destructive parameters on polyethylene wear, it is important to clarify their role because both joint kinematics and kinetics in all 3 planes are important input parameters for TKA wear testing (International Organization for Standardization 14243-1 and 14343-3). Our hypothesis was that transverse plane overall range of motion (ROM) and/or peak moment show differences that reflect on wear advantages when compared RP-PS implants to MP designs.

METHODS

Two groups (MPs = 24 and RP-PSs = 22 subjects) were examined by using 3D gait analysis. The variables were total internal-external rotation (IER) ROM and peak IER moments.

RESULTS

No statistically significant difference was demonstrated between the 2 groups in kinetics (P = .389) or kinematics (P = .275).

CONCLUSION

In the present study, no wear advantages were found between 2 TKAs. Both designs showed identical kinetics at the transverse plane in level-ground walking. Kinematic analysis could not illustrate any statistically significant difference in terms of overall IER ROM. Nevertheless, kinematic gait pattern differences observed possibly reflect different patterns of joint surface motion or abnormal gait patterns. Thus, wear testing with various input waveforms combined with functional data analysis will be necessary to identify the actual effects of gait variability on polyethylene wear.

Effect of femoro-tibial component size mismatch on outcome in primary total knee replacement

BACKGROUND

Most total knee arthroplasty systems allow a degree of femoro-tibial component size mismatch. We aim to investigate the influence of size mismatch on outcome after primary total knee arthroplasty.

METHODS

We reviewed 332 patients with cruciate-retaining Genesis II total knee arthroplasty with regard to femoro-tibial component size mismatch and Oxford Knee Score (OKS). We evaluated effects of Body Mass Index, gender and patellar procedure. Minimum follow-up is five years. We divided patients into four groups (tibial component larger than femoral component, no mismatch, femoral component one size larger and femoral component two sizes larger than tibial component).

RESULTS

There was no statistically significant difference in OKS between the four groups. Size mismatch did not have a statistical significant effect on OKS in a multivariate analysis. Women had mismatched components in 66% of all cases and men in 40% of all cases.

CONCLUSIONS

Our study showed no statistically significant effect of femoro-tibial size mismatch on outcome after total knee replacement. Compared to men, women tend to have more component size mismatch.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Are Korean Patients Different from Other Ethnic Groups in Total Knee Arthroplasty?

Most of the implants used for total knee arthroplasty (TKA) in Asian patients have been produced based on anthropometry of Western people. Since anatomic features and life styles are different between Western and Eastern people, there would be ethnic differences in terms of conformity of implants to the patient's anatomy or clinical results after TKA. Therefore, surgeons in Asia are particularly interested in related surgical techniques and implant designs used in TKA for improved clinical results and patient satisfaction. In this review, we investigated the anthropometric differences of Koreans from Westerners. Koreans are of shorter stature, less weight, and smaller skeletal structure and have a higher incidence of constitutional varus alignment of the lower extremity. Moreover, compared to Westerner TKA populations, the proportion of female patients was large and primary osteoarthritis was prevalent in preoperative diagnosis in Korean TKA patients. Culturally, Koreans have life styles that demand high flexion positions of the knee such as squatting, kneeling, and cross-legged sitting. Although there were no notable differences in the complication and revision rates following TKA between Westerners and Koreans, the incidence of postoperative deep vein thrombosis and pulmonary thromboembolism was lower in Koreans than Westerners. We hope that further research on implant designs and more interest in TKA will improve outcomes in Korean patients.

Prospective multi-centre study on a composite ceramic femoral component in total knee arthroplasty: Five-year clinical and radiological outcomes

BACKGROUND

Enhanced wear resistance of ceramics in general and improved mechanical characteristics of composite ceramics in terms of strength and resistance meet the demands for application in TKA. The aim of this prospective international multi-centre study was to evaluate the 5-year clinical and radiological outcomes of an unconstrained TKA with a composite ceramic femoral component.

METHODS

A total of 107 patients (109 knees) underwent TKA with the MULTIGEN-PLUS Ceramic Knee at seven centres in three European countries. Clinical and radiological assessments were performed preoperatively and postoperatively at 3, 12, 24 and 60 months, using HSS, WOMAC, SF-36 and standardised radiographs.

RESULTS

Mean HSS and WOMAC increased significantly from 55.1±11.5 (21-83) and 48.1±16.6 (3-90) preoperatively to 85.6±9.6 (49-98) and 73.3±20.4 (17-100) at 60 months. Mean SF-36 showed significant improvements in patients' quality of life (49.1±17.6 (12-96) preoperatively versus 67.7±23.1 (12-100) at 60 months). Non-progressive radiolucent lines (<1 mm) were observed around the femoral component in four cases. Neither implant migration nor loosening were registered. Kaplan-Meier survivorship was 96.0% at 60 months (92.1-100%, CI 95%).

CONCLUSIONS

Five-year implant survival rate of the ceramic knee is comparable to other metallic and ceramic unconstrained TKA systems. Although the assessment of long-term implant survivorship is still pending, the ceramic implants represent a promising solution for patients with allergies against metallic components and furthermore for the general osteoarthritis population due to enhanced wear resistance.

Higher Rate of Revision in PFC Sigma Primary Total Knee Arthroplasty With Mismatch of Femoro-Tibial Component Sizes

Total knee arthroplasty (TKA) systems permit a degree of femoro-tibial component size mismatch. The effect of mismatched components on revision rates has not been evaluated in a large study. We reviewed 21,906 fixed-bearing PFC Sigma primary TKAs using the Australian Orthopaedic Association National Joint Replacement Registry, dividing patients into three groups: no femoro-tibial size mismatch, tibial component size > femoral component size, and femoral component > tibial component. Revision rates were higher when the femoral size was greater than the tibia, compared to both equal size (HR = 1.20 (1.00, 1.45), P = 0.047) and to tibial size greater than femoral (HR = 1.60 (1.08, 2.37), P = 0.019). Potential mechanisms to explain these findings include edge loading of polyethylene and increased tibial component stresses.

Trends in total knee arthroplasty implant utilization

The incidence of total knee arthroplasty (TKA) has increased alongside our knowledge of knee physiology, kinematics, and technology resulting in an evolution of TKA implants. This study examines the trends in TKA implant utilization. Data was extracted from The Orthopedic Research Network to evaluate trends in level of constraint, fixed vs. mobile bearing, fixation, and type of polyethylene in primary TKAs. In 2012, 88% used cemented femoral and tibial implants, and 96% involved patellar resurfacing. 38% of implants were cruciate retaining, 53% posterior stabilized or condylar stabilized, 3% constrained. 91% were fixed-bearing, 7% mobile-bearing. 52% of tibial inserts were HXLPE. TKA implant trends demonstrate a preference for cemented femoral and tibial components, patellar resurfacing, fixed-bearing constructs, metal-backed tibial components, patellar resurfacing, and increased usage of HXLPE liners.

Femoral condylar contact points start and remain posterior in high flexing patients

This study compares kinematic patterns of 136 patients following total knee arthroplasty with high post-operative knee flexion (HighFlex) versus kinematics of 114 patients with limited knee flexion (LowFlex) using a blocked stratified random sampling study design to reduce confounding and bias. The kinematics was collected using fluoroscopy and 2D to 3D registration for a weight-bearing deep knee bend activity. Both the lateral and the medial condylar contact positions for the HighFlex subjects were significantly more posterior than the LowFlex subjects at full extension and remained that way at all flexion angles. The amount translation of the contact points, axial orientation angle and axial rotation were found to be similar for the two groups. Lift-off was significantly higher in the LowFlex indicating mid-flexion instability.

Mobile bearing or fixed bearing? A meta-analysis of outcomes comparing mobile bearing and fixed bearing bilateral total knee replacements

BACKGROUND

To compare outcomes between mobile-bearing (MB) and fixed-bearing (FB) in bilateral total knee replacements.

METHODS

The MEDLINE, EMBASE and Cochrane Library databases were searched. Randomized controlled trials of bilateral total knee arthroplasty with one of each design implanted were identified. Weighted mean differences (WMDs) and pooled risk ratios (RRs) were calculated using fixed- or random-effects models.

RESULTS

Twelve studies were identified with a total of 807 patients and 1614 knees. All RCTs were of high quality with a low risk of bias. No statistical difference was found between MB and FB at 2- to 5-year follow-up in terms of America Knee Society score (WMD: -1.29, 95% CI: -5.65 to 3.06), pain score (WMD: -3.26, 95% CI: -10.45 to 3.93), range of motion (WMD: -4.16, 95% CI: -9.97 to 1.66), reoperation (RR: 1.00, 95% CI: 0.28 to 3.60), and radiolucent lines (RR: 1.51, 95% CI: 0.70 to 3.24). The results were similar at 1-, 5- to 8-, or >8-year follow-up. Patient's satisfaction (RR: 0.85, 95% CI: 0.54 to 1.34), and complication (≤2-year, RR: 0.55, 95% CI: 0.29 to 1.04; >2-year, RR: 1.0, 95% CI=0.73 to 1.38) also showed no difference between two groups.

CONCLUSIONS

Based on this meta-analysis we are unable to detect the superiority of MB as compared to FB. More randomized trials with a larger sample size and longer follow-up are needed to evaluate these two kinds of prosthesis.

LEVEL OF EVIDENCE

Therapeutic Level II.

Hybrid total knee arthroplasty revisited: midterm followup of hybrid versus cemented fixation in total knee arthroplasty

The optimal method of fixation in total knee arthroplasty is still debated. Hybrid total knee arthroplasty (TKA), with cemented tibial and cementless femoral components, is a proposed method of fixation to improve outcomes. Although several studies have shown favorable outcomes, there is still lack of consensus in the literature. We hypothesized that hybrid TKA yields similar clinical, radiographic, and survivorship results compared to fully cemented TKA. The clinical and radiographic outcomes of 304 cruciate retaining TKAs with minimum two-year followup, including 193 hybrid (mean followup of 4.1 years) and fully cemented TKAs (mean followup of 3.2 years) were evaluated. Knee society scores were similar between the two groups. The total number of femoral radiolucencies was also similar between the two groups, while a greater number of femoral Zone 4 radiolucencies were seen in the cemented group (9% versus 1.6%, P = 0.005). The hybrid group demonstrated a 99.2% survival rate of the femoral component out to seven years for aseptic loosening. No significant difference in survivorship was seen between the groups for all cause or aseptic failure at seven years. We conclude that hybrid fixation leads to similar intermediate-term outcomes as fully cemented components and remains a viable option in total knee arthroplasty.

Modular versus all-polyethylene tibial components: comparison of pre- and early post-operative patient scores in total knee replacement

INTRODUCTION

All-polyethylene (AP) tibial components of total knee replacement (TKR) are substantially cheaper than their modular counterparts. It is well established that their survivorship and radiographic outcomes are comparable. In this study, patient-derived outcome measures were used to compare these two implant types.

METHODS

A cohort of 456 primary TKRs (142 AP, 314 modular) were assessed with preoperative and 1-year post-operative Oxford Knee Score, Western Ontario and McMaster Universities Arthritis Index and Short Form - 12 scores.

RESULTS

Both groups performed well with no significant difference in improvement and final scores at 1 year. Although there was a significant difference in mean age among the groups (P < 0.001) age-adjusted scores continued to show no significant difference between the two groups.

DISCUSSION

Our results support the more frequent use of AP tibial components for uncomplicated TKR.

Intraoperative joint gaps affect postoperative range of motion in TKAs with posterior-stabilized prostheses

BACKGROUND

Joint gaps and mediolateral (ML) soft tissue balance have long been known to affect clinical scores and patient function after TKA, but the relationship between gaps and soft tissue balance remain poorly defined. If specific relationships exist between soft tissue tension and patient function, then objective targets could be established to assist surgeons in achieving more consistent postoperative knee function.

QUESTIONS/PURPOSES

By performing instrumented gap measurements during TKA, we sought to quantify the relationships between intraoperative soft tissue tension and clinical scores and patient function.

METHODS

We prospectively followed 57 patients with 63 primary TKAs with posterior-stabilized prostheses. Joint gaps and ML soft tissue balance were measured intraoperatively from 0° to 135° with the patella reduced after independent bone cuts and soft tissue releases. We determined the relationships between these intraoperative measurements and postoperative ROM and Knee Society scores at minimum 2-year followup.

RESULTS

Larger joint gaps at 120° and 135° flexion predicted larger postoperative knee flexion (r=0.296 and r=0.393, respectively), whereas larger gaps at 10° flexion predicted greater postoperative knee extension (r=0.285). Knees with rectangular joint gaps did not show better ROM or Knee Society scores compared with knees with trapezoidal joint gaps. In the range of normal surgical variation, neither joint gaps nor gap asymmetry affected the incidence of postoperative instability.

CONCLUSIONS

Avoiding small joint gaps in extension and in deep flexion should allow patients who undergo TKAs to obtain maximum ROM.

LEVEL OF EVIDENCE

Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Comparison of cementless and hybrid cemented total knee arthroplasty

Cementless total knee arthroplasty (TKA) implants were designed to provide long-term fixation without the risk of cement-associated complications. The purpose of this study was to evaluate the outcome of titanium-coated cementless implants compared with hybrid TKA implants with a cemented tibial and a cementless femoral component. The authors performed a case-control, single-center study of 120 TKAs performed between 2003 and 2007, including 60 cementless and 60 hybrid cemented TKAs. The authors prospectively analyzed the radiographic and clinical data and the survivorship of the implants at a minimum follow-up of 5 years. Ninety patients who underwent TKA completed the 5-year assessment. Knee Society Scores increased significantly in both groups (P<.001). In both groups, 2 patients underwent revision due to aseptic tibial component loosening, resulting in a 96% implant survival rate. Radiographs showed significantly less radiolucent lines around the tibial baseplate in the cementless group (n=12) than in the hybrid cemented group (n=26) (P=.009).At 6-year mean follow-up, no significant difference existed between the cementless and hybrid cemented tibial components in TKA in terms of clinical and functional results and postoperative complications. The significantly smaller number of radiolucent lines in the cementless group is an indicator of primary stability with the benefit of long-term fixation durability of TKA.

Tibial component designs in primary total knee arthroplasty: should we reconsider all-polyethylene component?

PURPOSE

Despite the frequency with which total knee arthroplasties (TKAs) are performed, whether they are best performed using all-polyethylene or metal-backed tibial components remains a controversy. The aim of the present study was to determine the advantages and disadvantages of metal-backed compared with all-polyethylene tibial components during TKAs through an evaluation of current literature.

METHODS

A meta-analysis and systematic review of randomized and non-randomized comparative studies comparing metal-backed with all-polyethylene tibial components during TKAs were performed. The focus of the analysis was on the outcomes of knee score, range of motion (ROM), quality of life, implant alignment, tibial migration, radiolucent line, complication, reoperation, and implant survivorship.

RESULTS

A total of 10 randomized/quasi-randomized controlled trials and 13 non-randomized comparative studies assessing 19,767 TKAs were eligible. On the basis of these studies, no significant differences were found between the 2 groups with regard to knee score, ROM, quality of life, complication, and reoperation. The findings indicated that using all-polyethylene tibial components is associated with lower continuous migration rate compared with metal-backed tibial components. Only 13 studies provided adequate data on implant survivorship during intermediate or long-term follow-up. Of these, 9 found that no statistical significance existed between the 2 groups. The other 3 studies found that using all-polyethylene components yielded a higher survival rate than using metal-backed components.

CONCLUSIONS

Metal-backed tibial components had no obvious advantages over all-polyethylene tibial components in TKAs. However, this finding should be interpreted with caution due to publication bias, low methodological quality of the included studies, and different surgical interventions.

LEVEL OF EVIDENCE

Therapeutic study (systematic review and meta-analysis), Level III.

Full and surface tibial cementation in total knee arthroplasty: a biomechanical investigation of stress distribution and remodeling in the tibia

BACKGROUND

Aseptic tibial component loosening remains a major cause of total knee arthroplasty failure. The cementation technique used to achieve fixation may play a major role in loosening. Despite this, the optimum technique remains unanswered. This study aims to investigate stress and strain distributions in the proximal tibia for full cementation and surface cementation of the Genesis II tibial component.

METHODS

Principal cortical bone strains were measured experimentally in intact, surface cemented and fully cemented synthetic tibiae using strain gauges. Both axial and 15° flexion loading were considered. Finite element models were used to assess both cortical and cancellous bone stresses and strains. Using a bone remodeling algorithm potential sites of bone formation and resorption were identified post-implantation.

FINDINGS

Principal cortical bone strain results demonstrate strong correlations between the experimental and finite element analyses (R(2)≥0.81, RMSE(%)≤17.5%). Higher cortical strains are measured for surface cementation, as full cementation creates a stiffer proximal tibial structure. Simulations reveal that both cementation techniques result in lower cancellous stresses under the baseplate compared to the intact tibia, with greater reductions being computed for full cementation. The surface cementation model displays the closest cancellous stress distribution to the intact model. In addition, bone remodeling simulations predict more extensive bone resorption under the baseplate for full cementation (43%) than for surface cementation (29%).

INTERPRETATION

Full cementation results in greater stress reduction under the tibial baseplate than surface cementation, suggesting that surface cementation will result in less proximal bone resorption, thus reducing the possibility of aseptic loosening.

A new high-flexion knee scoring system to eliminate the ceiling effect

BACKGROUND

Various scoring systems document improvement after TKA, but most are associated with a ceiling effect that may fail to distinguish between patients having different levels of knee function after TKA. We therefore developed a new scoring system for patients with higher levels of flexion to eliminate ceiling effects observed with current systems.

QUESTIONS/PURPOSES

The purposes of this study were (1) to determine whether the high-flexion knee score eliminates the ceiling effect, (2) to assess the validity and responsiveness of the high-flexion knee score, and (3) to determine whether the high-flexion knee score can aid in differentiation of the knee status of patients at the ceiling level.

METHODS

We prospectively studied 165 patients with 201 well-functioning knees who had undergone primary TKA. We obtained Knee Society scores, WOMAC scores, Feller scores, SF-36 scores, and high-flexion knee scores for all patients. The high-flexion knee score includes items that reflect knee function in the high functional range, such as sitting on or rising from the floor, squatting, or kneeling. We determined the ceiling effects and score distributions of various scoring systems. We performed a convergent validity test of the high-flexion knee score by correlation analysis with these various scoring systems. Responsiveness of the high-flexion knee score was assessed by correlation analysis of changes in various scoring systems. To determine whether the high-flexion knee score can aid in differentiation of knee status of patients at the ceiling level, relative responsiveness of the various scores in the ceiling versus below the ceiling range was determined.

RESULTS

The high-flexion knee score showed no ceiling effect, whereas the other systems did. Addition of the high-flexion knee score to the other scoring systems eliminated these ceiling effects and resulted in more normalized score distributions. The high-flexion knee score correlated (r = -0.77) with WOMAC in postoperative scores, and it also correlated with the changes in WOMAC (r = -0.69) and SF-36 physical functioning (r = 0.62). The correlation of WOMAC score with SF-36 physical function score was lower in patients at the ceiling level of the Knee Society knee score and Knee Society function score, compared with the correlation at below-ceiling range, whereas the high-flexion knee score maintained a correlation with the SF-36 physical function score, even at the ceiling level of the Knee Society knee score and Knee Society function score.

CONCLUSIONS

Compared with other systems, the high-function knee score appears valid for evaluating the knee status in the high-flexion range. Our data suggest the high-flexion knee score differentiates among the knee status in the high-function range. Furthermore, the high-function knee score eliminates the ceiling effect of the currently used scoring tools, and thus may be useful when combined with other scoring systems.

LEVEL OF EVIDENCE

Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

All-polyethylene and metal-backed tibial components are equivalent with BMI of less than 37.5

BACKGROUND

Modular, metal-backed tibial (MBT) components are associated with locking mechanism dysfunction, breakage, backside wear, and osteolysis, which compromise survivorship. All-polyethylene tibial (APT) components eliminate problems associated with MBTs, but, historically, APT utilization has generally been limited to older, less active patients. However, it is unclear whether APT utilization can be expanded to a nonselected patient population.

QUESTIONS/PURPOSES

We therefore determined the survivorship of APT components compared with MBT components in a non-age- or activity-selected population who underwent TKA.

METHODS

Using a longitudinal database, we identified 775 patients with primary TKAs utilizing a single implant design between 1999 and 2007. Of these, 558 (72%) patients had APT components (APT2), while 217 (28%) patients with tibial bone loss or defects, contralateral MBT components, or a BMI of greater than 37.5 received MBT components. We determined the survivorship in the two groups. The minimum followup was 2 years for both groups (mean ± SD: MBT, 80 ± 29 months; APT, 63 ± 27 months). The APT group was older (average age: APT2, 70 years; MBT, 64.7 years) and had a lower BMI than the MBT group (APT2, 30.8; MBT, 33.8).

RESULTS

Survivorship, as defined by revision for any reason, was 99% for the APT group and 97% for the MBT group. There were four (2%) tibial failures in the MBT group in patients with a BMI of greater than 40. There were no revisions for loosening or osteolysis in the APT group.

CONCLUSION

APT implants perform as well as MBT implants in a non-age- or activity-selected TKA population with a BMI of less than 37.5.

Can a high-flexion total knee arthroplasty relieve pain and restore function without premature failure?

BACKGROUND

High-flexion TKA prostheses are designed to improve flexion and clinical outcomes. Increased knee flexion can increase implant loads and fixation stresses, creating concerns of premature failure. Whether these goals can be achieved without premature failures is unclear.

QUESTIONS/PURPOSES

We assessed pain relief, knee motion, function, incidence of premature failure, and radiographic appearance in patients with a mobile-bearing high-flexion TKA and determined whether preoperative knee flexion affects postoperative knee flexion.

PATIENTS AND METHODS

We prospectively followed all 142 patients implanted with 154 mobile-bearing high-flexion TKAs between 2004 and 2007. We obtained Knee Society scores (KSS) and assessed radiographs for loosening. Minimum followup was 24 months (mean, 46 months; range, 24-79 months).

RESULTS

Average knee flexion improved from 123° to 129°. Patients with preoperative flexion of 100° to 120° had a greater postoperative flexion increase (mean, 13°; range, 114°-126°) than patients with preoperative flexion of greater than 120° (mean, 3.0°; range, 128°-131°). The mean KSS improved from 41 to 95 postoperatively. Patients with preoperative flexion of less than 120° had a greater improvement in KSS (62 versus 48). Posterior femoral radiolucent lines were observed in 43% without evidence of prosthetic loosening.

CONCLUSIONS

Our data were similar to those reported in patients implanted with traditional and other designs of high-flexion TKA. We found no increased incidence of premature failure, although a higher than expected incidence of posterior femoral radiolucent lines merit continued observation. Patients with less preoperative motion were more likely to benefit from a high-flexion TKA.

The natural history of anterior knee pain in 2 posterior-stabilized, modular total knee arthroplasty designs

Anterior knee pain (AKP) has been a persistent complaint after total knee arthroplasty; however, the natural course of this complaint has not been fully investigated. This is a 10-year follow-up report of a prospective, randomized study between the Insall-Burstein II (Zimmer, Warsaw, IN) and the Press Fit Condylar Modular (Johnson & Johnson, Raynham, MA) knees. Up to one third of total knee arthroplasties will experience mild to moderate AKP at 1-year follow-up, which will persist in approximately 30% of these previously symptomatic knees at 10-year follow-up. New-onset AKP will develop in approximately 10% of previously asymptomatic knees.

Anterior-posterior glide mobile-bearing total knee arthroplasty: complications related to prosthesis design

The aim of this study was to evaluate complications related to prosthesis design in patients managed with cemented total knee arthroplasty using anterior-posterior glide mobile-bearing prosthesis. One hundred eighty-three total knee arthroplasties were performed using this prosthesis on 146 patients, with a minimum of 7 years of follow-up. There were late dislocations of the bearing in 2 knees, anterior soft tissue impingements in 6 knees at an earlier follow-up, excessive anteroposterior translation in 5 knees, and a fracture of the femoral component induced by osteolysis in 1 knee. Design modifications in the restraint mechanisms of the anterior-posterior glide mobile-bearing prosthesis may be required to minimize the development of complications with regard to sagittal instability and to improve the prosthesis' longevity.

The risk of subsequent joint arthroplasty after primary unilateral total knee arthroplasty, a 10-year study

The purposes of this study were to determine the probabilities of subsequent lower extremity arthroplasty after index knee arthroplasty for osteoarthritis and to evaluate the demographic as well as radiographic factors that may predict progression to arthroplasty in the contralateral knee. Between 1984 and 1994, 646 patients, aged 40 to 75 years, with a primary cruciate-retaining knee were identified. The 10-year probability of having a contralateral knee after index knee was 36%. When grade 4 radiographic changes were present, the probability increased to 70%. Demographic factors played no role in the risk of future contralateral knee. The radiographic grade of the contralateral knee at the time of index surgery was found to correlate strongly with the future risk of contralateral total knee.

Rotating platform spinouts with cruciate-retaining mobile-bearing knees

Spinout or dislocation is a complication of mobile-bearing total knee arthroplasty. We have observed this complication in 7 of 1255 cruciate-retaining mobile-bearing total knees (0.56%). Patient factors associated with a spinout included female sex, obesity, and preoperative valgus deformity. Operative treatment was generally successful, but significant complications occurred in 3 of the 7 patients.

[TKA revision of semiconstraint components using the 3-step technique]

OBJECTIVE

The surgical goal is to achieve a pain free and stable knee joint after revision total knee arthroplasty in three steps. An important component of the technique is the reproducible restoration of the joint line.

INDICATIONS

Revision total knee arthroplasty.

CONTRAINDICATIONS

Complete bone loss at the knee joint (epicondyles and tibia plateau), persistent joint infection, loss of the extension apparatus, and neurological disease with progressive ligament instability.

SURGICAL TECHNIQUE

Implantation of revision components is performed in three steps. The first step is the positioning of the tibia component at the correct height and rotation. As the position of the tibial articular surface is independent of the knee position, the tibia serves as a reference both in extension and in flexion. The second step consists of balancing the knee joint in flexion and, thereby, definition of the flexion gap and the rotation of the femoral component. In the third step, the reconstruction and balancing of the knee joint in extension is performed.

POSTOPERATIVE MANAGEMENT

Mobilization with weight bearing and range of motion as tolerated depending on osseous and soft tissue condition at surgery. The surgical technique does not influence the further treatment.

RESULTS

In a prospective study, 168 consecutive knee revisions operated by the first author were examined clinically and radiologically preoperatively and at a mean follow-up of 38 months (range 22-61 months). There were 96 knees from women and 72 were from men with an average age of 74.6 years (range 51-92 years). Clinical results were based on the American Knee Society score. The score showed 47.6 (range 32-63) preoperatively and 81.5 (range 62-95) at follow-up. Radiologically, 92.7% of the knees showed a malposition <3°. The joint line was correctly reconstructed in 86.3% based on the preoperative plan; 89% of the patella showed correct tracking in the patella tangential view.

Sensitivity of knee soft-tissues to surgical technique in total knee arthroplasty

Restricted range of motion and excessive laxity are both potential complications of total knee arthroplasty (TKA). During TKA surgery, the surgeon is frequently faced with the question of how tightly to implant the prosthesis. The most common method of altering implantation tightness is to vary the thickness of the polyethylene inlay after the bone cuts have been made and the trial components inserted. We have sought to quantify how altering the polyethylene thickness may affect post-operative soft tissue tension for a range of prosthetic designs. Four different prosthetic designs were implanted into fresh-frozen cadaveric knee joints. All four designs were implanted in the standard manner, with a 100 Newton distraction force used to set soft tissue balance. The tibiofemoral force was then recorded at 15° intervals throughout the passive flexion range. After the standard implantation of each prosthesis, the tibial component was raised or lowered to mimic increasing and decreasing the polyethylene thickness by 2mm and the force measurements repeated. Tibiofemoral force in extension correlated with implantation tightness for all prosthesis designs. Between 15° and 90° of knee flexion, all four designs were insensitive to changes in implantation tightness. Beyond 90° the effect was more notable in rotating platform mobile-bearing and cruciate-retaining prostheses than in posterior-stabilised mobile-bearing designs. The findings of this research may be useful in assisting surgical decision-making during the implantation of TKA prostheses.

Dermatitis associated with chromium following total knee arthroplasty

All metal implants release metal ions because of corrosion. Although 20% to 25% of patients develop metal sensitivity after total joint arthroplasty, which is 10% higher than that in the general population, only very few highly susceptible patients exhibit symptoms. Even patients with known metal allergy often do not react to their metal prosthesis. Systemic allergic contact dermatitis is particularly uncommon with total knee arthroplasty because there is no metal-on-metal contact between the femoral and tibial components. We present a case report of 62-year-old man with dermatitis most likely caused by chromium after total knee arthroplasty and review the relevant literature. Although this complication is very rare, it sometimes can be painful enough for the patient to undergo revision surgery.

Routine surveillance of modular PFC TKA shows increasing failures after 10 years

BACKGROUND/RATIONALE

A 10-year survivorship of 100% was reported for patients with PFC cruciate-retaining prostheses. Beyond 10 years, we observed additional polyethylene wear likely related to thin liners gamma-irradiated in air and were concerned this wear might predispose to implant construct failure.

QUESTIONS/PURPOSES

We therefore determined (1) the functional scores at a minimum of 15 years followup, (2) rates of radiographic failure, (3) overall revision rates, and (4) mode of failure after 10 years and the fate of the revised implants.

METHODS

We retrospectively reviewed 75 patients with 101 press-fit condylar posterior cruciate-retaining prostheses. At a minimum followup of 15 years, 35 patients (47 knees) were living and evaluated clinically. No patients were lost to followup.

RESULTS

There were no revisions during the first 11 years and six reoperations subsequently were performed in five patients (6% overall rate of revision but 12.8% in patients who survived more than 15 years). Three of six revisions had concerning liner wear at 10 years and all six were revised for polyethylene wear. Polyethylene exchange was performed in four of the five patients who underwent revisions, all of whom were doing well at an average of 7.2 years (range, 4.7-9.1 years) after the revision procedure.

CONCLUSIONS

At long-term followup, the overall revision rate remained low (6%). For patients surviving 15 years or more, the rate of revision was 12.8% and all revisions were secondary to aseptic sequelae of polyethylene wear. All revisions occurred more than 10 years after the initial procedures.

LEVEL OF EVIDENCE

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

Adverse events in total knee arthroplasty: Results of a physician independent survey in 260 patients

Purpose

Identification of all common and potentially avoidable adverse events is crucial to further improve the quality of medical care. The intention of the current study was to evaluate a standardized physician independent survey format on adverse events in total knee arthroplasty. The protocol for reporting adverse drug events following the International Conference of Harmonisation of technical requirements for registration of pharmaceuticals for human use (ICH) was adopted for adverse events occurring during surgical interventions.

Material and methods

Data of a prospective sequential cohort trial introducing a clinical pathway for total knee arthroplasty was analysed. Reporting of adverse events was done by a physician independent study nurse using the modified ICH-Good Clinical Practice (GCP) format (Structure and Content of Clinical study reports - E3) in 260 patients. The adverse events were graded to their severity and their potential relation to surgical treatment.

Results

A total of 55 patients (21%) suffered from an adverse event and 16 (6%) from a serious adverse event. In 38 patients' one adverse event occurred, 12 patients showed 2 adverse events and 5 patients suffered from a combination of an adverse and a serious adverse event. A serious adverse event alone occurred in 11 patients. The incidence of adverse events (Fisher p = 0.448) and serious adverse (p = 0.126) events showed no significant difference between the two cohorts. The most common adverse events were deep vein thrombosis (8% and 5%) followed by wound healing problems (1% and 0%) and haematoma (1% and 3%). A wide range of non surgical adverse events were recorded with low incidence levels.

Conclusion

The use of the modified ICH-GCP format supports standardization of adverse event reporting. Routine assessment of adverse events by a study nurse revealed higher incidence rates of adverse events in total knee arthroplasty. We recommend the implementation of trained paramedical staff for the documentation of adverse events in routine clinical care.

The Bi-Surface total knee arthroplasty: minimum 10-year follow-up study

The Bi-Surface Knee System (Japan Medical Material, Kyoto, Japan), which has a unique ball-and-socket joint and whose femoral component is made from alumina ceramic, was designed to improve deep knee flexion and long-term durability after total knee arthroplasty. The purpose of this study was to review the clinical results of a minimum 10-year follow-up. Between 1989 and 1997, 507 total knee arthroplasties were carried out in 371 patients. Forty three patients (56 knees) were lost to follow-up. The mean age of the patients at operation was 68.5 years, and the patients were followed up for a mean of 11.7 years. The knees were evaluated on the basis of Knee Society knee score and functional score, radiographs, and Kaplan-Meier survivorship analysis. The knee score was improved from 38.9+/-17.4 points preoperatively to 93.3+/-7.8 points at the latest follow-up (p<0.001). The functional score was improved from 34.9+/-19.3 points to 52.7+/-24.1 points (p<0.001). The mean range of flexion was improved from 118.7+/-21.7 degrees to 124.2+/-20.8 degrees (p<0.001). The critical angle, which means the border to gain more range of flexion postoperatively, was 130.1 degrees. Kaplan-Meier survivorship at 10-year was 95.9% with any operation or radiographic failure as the end point. The corresponding rate was 97.4% with revision of any component as the end point. No ceramic component fracture occurred. The present study demonstrates that good range of flexion was maintained for a long time after total knee arthroplasty with excellent durability. The Bi-Surface Knee System appears to have achieved its design objectives.

The all-polyethylene tibial component in primary total knee arthroplasty

Outcomes of total knee arthroplasties performed with modern all-polyethylene tibial components have been found to be comparable with or better than those of arthroplasties done with metal-backed modular components in numerous mid-to-long-term follow-up studies, radiostereometric analyses, and the few prospective randomized trials available. Advantages of an all-polyethylene tibial component over a metal-backed modular component include lower cost, avoidance of locking-mechanism issues and backside wear, and increased polyethylene thickness after identical bone resections. Disadvantages of an all-polyethylene tibial component compared with a metal-backed modular component include a lack of modularity, limiting intraoperative options; no option for liner removal in the setting of acute irrigation and débridement; and no option for late liner exchange. Primary total knee arthroplasty with a modern all-polyethylene design can be done in many patients, with substantial cost savings across the health-care system.

Surgeon's expectations do not predict the outcome of a total knee arthroplasty

INTRODUCTION

It is fascinating for both the patient and the surgeon to predict the outcome of a TKA at an early stage. Satisfaction after TKA is primarily determined by the preoperative expectations of the patient. The purpose of this study was to investigate if the peri-operative expectations of the surgeon predicted the outcome of a TKA.

PATIENTS AND METHODS

A prospective study of 53 primary TKAs was performed. Preoperatively, the surgeon described the assessment of the difficulty of the TKA on a VAS. Immediately postoperative, the surgeon gave his satisfaction VAS about the procedure. After 1 year the surgeon's satisfaction VAS, the patient's satisfaction VAS and the KSCRS were determined.

RESULTS

The Spearman's correlation coefficients between the preoperative difficulty assessment, the immediate postoperative satisfaction and the outcome measurements after 1 year were all very poor (-0.01 to 0.23).

CONCLUSIONS

The outcome of a TKA depends on multiple factors. Both the surgeon's preoperative assessment of the difficulty and the surgeon's immediate postoperative satisfaction do not independently predict the outcome of a TKA.

Fixed- vs mobile-bearing total knee arthroplasty: does it make a difference?--a prospective randomized study

The purpose of this prospective, randomized study was to compare the early clinical and functional results of primary total knee arthroplasty using a fixed-bearing (FB) and a rotating-platform (RP) prosthesis. Outcomes including range of motion (ROM), Knee Society Score, Western Ontario MacMaster (WOMAC), and Short Form-36 (SF-36) were measured preoperatively and at 6 weeks, 3 months, 6 months, 1 year, and 2 years. Radiographic analysis was performed. There were 72 FB and 68 RP knees. The RP group had a greater ROM at 6 weeks and 1 year. This difference was not statistically significant at 2 years. There were no differences in the ROM at any other period. There were no significant differences in Knee Society Score, Short Form-36, or Western Ontario MacMaster scores at any period. No clinically significant differences were noted in the radiographic analysis. The use of a FB or RP design did not affect the early functional outcomes after total knee arthroplasty.

Prevalence of osteolysis after simultaneous bilateral fixed- and mobile-bearing total knee arthroplasties in young patients

This study aimed to evaluate the clinical and radiographic results and to document the prevalence of osteolysis associated with fixed-bearing (anatomic modular knee) and mobile-bearing (low contact stress) total knee arthroplasties (TKAs) in 61 patients younger than 55 years who had bilateral simultaneous primary TKAs. Forty-five patients were female and 16 patients were male. The mean age of the patients was 48.3 years (range, 34-55 years). The mean postoperative Knee Society knee and functional score were similar in both groups (91 and 90 points and 85 and 86 points, respectively). Three knees (5%) in each group were revised for wear of the tibial bearing, and 1 knee (2%) in the mobile-bearing TKA was revised for dislocation of the meniscal bearing. Osteolysis was identified in both radiographs and computed tomography scans in 6 knees (10%) in the anatomic-modular-knee group and 4 knees (7%) in the low-contact-stress group.

Selective Laser Melting: a regular unit cell approach for the manufacture of porous, titanium, bone in-growth constructs, suitable for orthopedic applications

In this study, a novel porous titanium structure for the purpose of bone in-growth has been designed, manufactured and evaluated. The structure was produced by Selective Laser Melting (SLM); a rapid manufacturing process capable of producing highly intricate, functionally graded parts. The technique described utilizes an approach based on a defined regular unit cell to design and produce structures with a large range of both physical and mechanical properties. These properties can be tailored to suit specific requirements; in particular, functionally graded structures with bone in-growth surfaces exhibiting properties comparable to those of human bone have been manufactured. The structures were manufactured and characterized by unit cell size, strand diameter, porosity, and compression strength. They exhibited a porosity (10-95%) dependant compression strength (0.5-350 Mpa) comparable to the typical naturally occurring range. It is also demonstrated that optimized structures have been produced that possesses ideal qualities for bone in-growth applications and that these structures can be applied in the production of orthopedic devices.

2009 Marshall Urist Young Investigator Award: how often do patients with high-flex total knee arthroplasty use high flexion?

Although high-flexion TKA designs aim to safely accommodate deep flexion, it is unknown how often patients use deep flexion outside the laboratory. We used a validated smart-activity monitor to document the prevalence of knee flexion greater than 90 degrees in 20 consecutive patients (21 knees) who had high-flexion TKAs, at a minimum of 2 years' followup. Patients wore the device continuously for a mean of 35.7 +/- 0.5 hours. The 21 knees flexed more than 90 degrees for an average of 10 +/- 3.8 minutes (0.5%). Activities performed with flexion greater than 90 degrees were, on average, 70% in single-limb stance, 12% moving from sitting to standing, 8% walking, 7% moving from standing to reclining, 2% stepping, 0.9% moving from lying to standing, and 0.1% running. Eight knees flexed greater than 120 degrees for an average of 2.2 minutes (range, 0.2-15 minutes), or 0.1% of the testing time. Activities performed with flexion greater than 120 degrees were, on average, 90% in single-limb stance, 6% moving from sitting to standing, 3% walking, 0.6% moving from standing to reclining, 0.3% stepping, and 0.1% moving from lying to standing. Peak flexion used at any time during testing was, on average, 84% +/- 11% of maximum postoperative flexion (125 degrees +/- 12 degrees). These patients rarely used deep flexion.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Cemented versus uncemented fixation of the femoral component of the NexGen CR total knee replacement in patients younger than 60 years: a prospective randomised controlled RSA study

The optimal mode of femoral fixation in total knee arthroplasty (TKA) remains controversial, especially for the young patient. In a prospective randomised study we compared the magnitude and pattern of the fixation of cemented versus uncemented femoral components during 2 years in patients younger than 60 years. Forty-one knees in 41 patients were randomised to receive a NexGen (Zimmer, Warsaw, USA) cruciate-retaining TKA with either a cemented or an uncemented non HA-coated femoral component. The patients were examined by radiostereometric analysis (RSA), as well as clinical and radiological evaluation. The magnitude and pattern of migration as measured by RSA did not differ significantly between the cemented and uncemented fixation during the 2-year follow-up, nor were there any differences between the groups in clinical parameters. These findings suggest that an uncemented and non HA-coated femoral component may behave equally as well as a cemented one in the long-term.

Relationship between joint gap difference and range of motion in total knee arthroplasty: a prospective randomised study between different platforms

The objective of this study was to investigate the range of motion (ROM) of the knee before and four years after total knee arthroplasty (TKA) with a mobile or fixed type of platform and to prospectively evaluate whether there was a difference in ligament balance between the platform types. The subjects were 68 patients involving 76 joints. The mobile type was used in 31 joints and fixed type in 45 joints by employing a prospective randomised method. The passive maximum ROM was measured using a goniometer before and four years after surgery. Also, the intraoperative knee ligament balance was measured. The postoperative extension ROM was significantly improved after TKA using a mobile bearing type compared with that employing a fixed bearing type. In TKA using the former, the intraoperative gap difference was not related to the postoperative flexion angle of the knee. However, they were related in TKA using a fixed bearing type, with a positive correlation regarding the flexion gap.

Unique relationship between osteophyte and femoral-tibia component size mismatch in determining polyethylene wear in primary total knee arthroplasty: a case report

Introduction

Knee pain is a complex problem that can occur after total knee arthroplasty. One cause of knee pain may be due to a retained osteophyte, but it is not clear if the retained osteophyte is sufficient explanation of the pain, as not all patients with retained osteophytes are symptomatic. In fact, the literature shows that excised osteophytes can also recur over a period of time, without any symptoms. Therefore a retained osteophyte alone is probably not sufficient to cause symptoms.

Case presentation

We present a case of intermittent medial knee pain occurring post-primary total knee arthroplasty, in a patient who underwent several investigations over a period of 5 years. Radiographs showed an osteophyte in the postero-medial femur along with slight tibial component overhang which was normal for that knee implant design. The symptoms eventually settled with excision of only the osteophyte, without altering the tibial component.

Conclusion

A retained osteophyte alone, or tibial component overhang alone, did not seem to cause significant symptoms in our patient whose symptoms completely settled with excision of the osteophyte alone, without changing the tibial component. Therefore, it seems that the combination of retained osteophyte and tibial component overhang (tibia-femoral component size mismatch) are detrimental and therefore best avoided. This report also emphasises the importance of meticulous osteophyte excision and avoiding tibial component overhang during knee arthroplasty.

Early outcome of TKA with a medial pivot fixed-bearing prosthesis is worse than with a PFC mobile-bearing prosthesis

Although the design features of the Medial Pivot fixed-bearing prosthesis reportedly improve kinematics compared with TKAs using fixed-bearings, clinical improvements have not been reported. We asked whether the clinical and radiographic outcomes, ranges of motion of the knee, patient satisfaction, and complication rates would be better in knees with a Medial Pivot fixed-bearing prosthesis than in those with a PFC Sigma mobile-bearing prosthesis. We compared the results of 92 patients who had a Medial Pivot fixed-bearing prosthesis implanted in one knee and a PFC Sigma mobile-bearing prosthesis implanted in the other. There were 85 women and seven men with a mean age of 69.5 years (range, 55-81 years). The minimum followup was 2 years (mean, 2.6 years; range, 2-3 years). The patients were assessed clinically and radiographically using the rating systems of the Hospital for Special Surgery and the Knee Society at 3 months, 1 year, and annually thereafter. Contrary to expectations, we found worse early clinical outcomes, smaller ranges of knee motion, less patient satisfaction, and a higher complication rate for the Medial Pivot fixed-bearing prosthesis than for the PFC Sigma mobile-bearing prosthesis.

LEVEL OF EVIDENCE

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

Minimally Invasive Surgical Technique in Total Knee Arthroplasty: A Learning Curve

Clinical experience of learning a new technique of minimally surgery for total knee arthroplasty is presented. Close monitoring of the technique, pitfalls, learning tips, and tricks are discussed. A “learning phase” is identified as approximately 10 months or 21 knee replacements using minimally invasive technique. It took 50 operations before the surgical time equaled the open technique. There was no incidence of increased complications during the learning phase. Functional results such as stair climbing, walking distance, and walking with aids was significantly better after minimally invasive technique than after standard technique.

Lateral retinacular release rates in mobile- versus fixed-bearing TKA

Controversy exists as to whether bearing mobility facilitates centralization of the extensor mechanism after TKA. To assess the incidence of lateral retinacular release, we retrospectively reviewed 1318 consecutive primary TKAs (1032 patients) performed by one surgeon using either a rotating-platform bearing (940) or a fixed bearing (378) from the same implant system. The selection of a fixed- versus mobile-bearing TKA was primarily based on age with patients younger than 70 years receiving a mobile-bearing TKA. We performed a lateral release whenever continuous symmetric patellar facet contact with the trochlear groove from 0 degrees to 90 degrees of flexion was not obtained using the rule of no thumb after tourniquet release. One hundred four of 1318 knees (7.9%) had a lateral release. We performed more lateral releases in the fixed-bearing group (14.3% [54 of 378]) than in the mobile-bearing group (5.3% [50 of 940]). Patellar tilt occurred more often in the mobile-bearing group (10% [94 of 940]) than in the fixed-bearing group (6.9% [26 of 378]), although the magnitude of mean patellar tilt was small in both groups (mobile-bearing 3.0 degrees ; fixed bearing 2.55 degrees ). No patient had patellar subluxation greater than 5 mm. We suspect the fewer lateral releases in the mobile-bearing group is the result of better extensor mechanism centralization provided by bearing rotation.

LEVEL OF EVIDENCE

Level III, prognostic study. See the Guidelines for a complete description of levels of evidence.