Three- to six-year follow-up results after high-flexion total knee arthroplasty: can we allow passive deep knee bending?

A high-flexion design total knee prosthesis: a ten to twelve-year follow-up study

BACKGROUND

The purpose of this study was to investigate the clinical and radiographic outcomes and to determine the survivorship of a high-flexion design total knee arthroplasty (TKA) prosthesis, the LOSPA knee system, over a follow-up period of 10-12 years.

METHODS

The study included 386 patients (503 TKAs) who were treated with TKA from 2011 to 2013 (follow-up period 10-12 years).The patients were assessed clinically using range of motion (ROM) of the knee, the Knee Society scoring system (KSS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). For radiographic analysis, the positions of femoral and tibial implants as α, β, γ, and δ angles, hip knee ankle (HKA) angle, and radiolucent lines were used. Kaplan-Meier survival analysis was performed.

RESULTS

Mean ROM improved significantly from the preoperative baseline of 117.3° to 126.5° at the final follow-up (p < 0.001). The mean KSS and WOMAC scores also both showed significant improvement after surgery (all p < 0.001). A non-progressive radiolucent line less than 2 mm was observed in 23 cases (4.7%). Nine patients underwent revision surgery on the knee during the follow-up period. Revision surgery was performed on four patients due to aseptic loosening, three patients due to infection, one patient due to ankylosis, and one patient due to instability. When the endpoint of survival was the entire surgical cases, the survival rate was 96.2%. The survival rate, with revision for any reason as the endpoint, was 97.2%, and 97.8% for aseptic causes.

CONCLUSIONS

The LOSPA knee system, a high-flexion design total knee prosthesis, showed excellent long-term survivorship and improvements in clinical outcomes at 10- to 12-year follow-up.

A Bone Health Optimization Framework for Malaysia: a position paper by the Malaysian Bone Health Optimization Network (MyBONe)

This position paper aims to establish and standardise Bone Health Optimization (BHO) strategies for older patients undergoing elective orthopaedic surgeries in Malaysia. It emphasises pre-, intra-, and post-operative assessments and tailored management. Adopting the "5IQ" approach, it proposes clinical standards and a registry to improve surgical outcomes and patient care.

PURPOSE

Osteoporosis and osteopenia are highly prevalent among older patients scheduled for elective arthroplasties and spinal surgeries. This position paper aims to establish, promote, and standardise effective Bone Health Optimization (BHO) strategies for such patients within orthopaedic practices in Malaysia. It emphasises the need for bone health assessments to be undertaken at the pre-operative, intra-operative, and post-operative stages, with tailored management strategies to meet individual patient needs.

METHODOLOGY

A comprehensive literature review was conducted, focusing on articles published from 2019 to 2024. Twelve broad themes were defined including definitions and importance of BHO, epidemiological data, assessment techniques, risk stratification, management strategies, and outcome metrics.

RESULTS

Elective surgeries on patients with poor bone health are associated with adverse outcomes, such as periprosthetic fractures, aseptic loosening of implants, and complications after spinal surgeries. This position paper advocates for routine bone health assessments and monitoring during the pre-operative, intra-operative, and post-operative phases. It provides summaries of imaging modalities, risk assessment tools, and techniques for each phase. By adapting the successful "5IQ" approach from secondary fracture prevention, we propose 5IQ-based Clinical Standards for BHO, including 18 Key Performance Indicators. A Malaysian BHO Registry is proposed to benchmark care in real-time and support a national quality improvement programme. Practical resources, such as a BHO algorithm and key practice points, are included.

CONCLUSION

This position paper proposes a paradigm shift in the management of bone health for patients undergoing elective orthopaedic surgery in Malaysia, aiming to improve surgical outcomes and patient care through standardised BHO strategies.

Five-year migration of uncemented femoral components in total knee arthroplasty with either highly cross-linked or conventional polyethylene inserts: a blinded randomized controlled trial using radiostereometric analysis

Aims

The aim of this study was to compare the migration of the femoral component, five years postoperatively, between patients with a highly cross-linked polyethylene (HXLPE) insert and those with a conventional polyethylene (PE) insert in an uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary aims included clinical outcomes and patient-reported outcome measures (PROMs). We have previously reported the migration and outcome of the tibial components in these patients.

Methods

A double-blinded randomized controlled trial was conducted including 96 TKAs. The migration of the femoral component was measured with radiostereometry (RSA) at three and six months and one, two, and five years postoperatively. PROMs were collected preoperatively and at all periods of follow-up.

Results

There was no clinically relevant difference in terms of migration of the femoral component or PROMs between the HXLPE and PE groups. The mean difference in migration (maximum total point motion), five years postopeatively, was 0.04 mm (95% CI -0.06 to 0.16) in favour of the PE group.

Conclusion

There was no clinically relevant difference in migration of the femoral component, for up to five years between the two groups. These findings will help to establish a benchmark for future studies on migration of femoral components in TKA.

Long-Term Outcomes of High-Flexion Design Total Knee Arthroplasty with a Short Posterior Flange

Background

The purpose of this study was to evaluate the clinical and radiological outcomes of high-flexion total knee arthroplasty (TKA) using Vega Knee System (B. Braun, Aesculap) at a long-term follow-up and to analyze the implant survivorship.

Methods

We enrolled 165 patients (232 knees) with a minimum 7-year follow-up after TKA (VEGA Knee System). For clinical assessment, range of motion (ROM), Knee Injury and Osteoarthritis Outcome Score (KOOS), and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) were used. For radiologic assessment, hip-knee-ankle angle, component position, and the existence of radiolucent lines and loosening were used. Survival analysis was conducted using the Kaplan-Meier method.

Results

The mean follow-up period was 9.8 years. The mean ROM increased from 124.4° to 131.4° at the final follow-up. The WOMAC score decreased from 38.5 to 17.4 at the final follow-up (p < 0.001). All 5 subscales of the KOOS improved at the final follow-up (all subscales, p < 0.001). Revision TKA was performed in 10 cases (4.3%), which included 9 cases of aseptic loosing and 1 case of periprostatic joint infection. Of the 9 aseptic loosening cases (3.9%), 8 cases (3.4%) were loosening of the femoral component and 1 case (0.4%) was loosening of the tibial component. When revision for any reason was considered an endpoint, the 10-year survivorship was 96.2% (95% confidence interval [CI], 93.9%-98.5%). On the other hand, when revision for aseptic loosening was considered the endpoint, the 10-year survivorship was 96.6% (95% CI, 94.4%-98.8%).

Conclusions

The Vega Knee System provided good clinical results in the long-term follow-up period. Although the VEGA Knee System showed acceptable implant survivorship, loosening of the femoral component occurred in about 3.4% of the patients. For more accurate evaluation of the survivorship of high-flexion design TKA with a short posterior flange, it is necessary to conduct more long-term follow-up studies targeting diverse races, especially Asians who frequently perform high-flexion activities.

Early- to Mid-Term Review of a Prospective, Multi-Center, International, Outcomes Study of an Anatomically Designed Implant with Posterior-Stabilized Bearing in Total Knee Arthroplasty

Background and Objectives: National joint registries report higher total knee arthroplasty (TKA) revision rates in posterior-stabilized (PS) systems compared to non-posterior-stabilized designs. The purpose of this study was to investigate the implant survivorship and clinical outcomes of an anatomic implant with a PS bearing. Materials and Methods: An early- to mid-term follow-up of a prospective, multi-center, non-controlled outcomes study of patients who received primary TKA between November 2014 and June 2017 was performed. A total of 800 cases using PS bearings that were implanted in 664 patients were monitored post-operatively for their implant survivorship and adverse events for up to five years. The Knee Society Knee and Function scores, patient satisfaction, the five-dimensional European Quality of Life questionnaire, and range of motion (ROM) were evaluated pre-operatively and post-operatively at six weeks, six months, one year, two years, three years, and five years. Results: The mean follow-up period was 3.7 ± 1.3 years, and the three-year implant survival rate was 99.3% (95% CI: 98.4%, 99.7%) with five revisions during the five-year follow-up. Patient satisfaction was 96.1% at six weeks and increased to 99.3% at one year. All patient-reported outcome measures significantly (p < 0.0001) increased up to the one-year follow-up and then remained stable up to the five-year follow-up. Conclusions: This study supports the excellent survivorship and patient-reported outcomes of the Persona® Knee system using cemented, fixed bearing, posterior-stabilized components with minimal complications at early- to mid-term follow-up in an international Asian population. Ongoing observations are being performed to investigate the mid- to long-term survivorship and clinical outcomes associated with this knee system.

Mid-term clinical outcomes of a posterior stabilized total knee prosthesis for Japanese patients: A minimum follow-up of 5 years

BACKGROUND

A high-flexion posterior-stabilized total knee prosthesis has been developed for the Asian population. The component design was based on computed tomography images of Japanese osteoarthritic knees. The femoral component is composed of zirconia ceramics, which exhibit low friction and high durability. The present study aimed to evaluate the mid-term clinical outcomes of this implant.

METHODS

This study included 334 knees of 210 patients who underwent primary total knee arthroplasty with this implant at our hospital between October 2010 and December 2014. The patients comprised 28 men and 172 women with an average age of 73 years. The average follow-up period was 5.9 years, and the follow-up rate was 71.1%. Clinical outcomes were assessed using the Knee Society scoring system, 2011 Knee Society questionnaire, and Knee Injury and Osteoarthritis Outcome Score. Kaplan-Meier survivorship analysis was performed to determine the cumulative prosthesis survival rate.

RESULTS

In terms of clinical outcomes at the final follow-up, the average ranges of motion were -2.0 in extension and 126.7 in flexion. The Knee Society knee and function scores were 94.2% and 72.6%, respectively. With revision surgery or radiographic failure for any reason as the endpoint, the survival rates at 5 and 9 years were 98.2% and 95.5%, respectively. The most common reason for revision surgery or radiological failure was aseptic loosening.

CONCLUSIONS

Despite several revision cases mainly due to aseptic loosening, the present study found that this new high-flexion posterior-stabilized total knee arthroplasty prosthesis design showed comparable results for Asian populations with other PS prosthesis.

LEVELS OF EVIDENCE

Level Ⅱ (Prospective cohort study).

Early Aseptic Loosening with Increased Presence and Severity of Backside Burnishing in the Optetrak Logic Posterior-Stabilized Total Knee Arthroplasty Femoral Component

Concerns persist that the Optetrak Logic posterior-stabilized (PS) total knee arthroplasty (TKA) femoral component might correlate with early failures due to aseptic loosening. The primary aim of this study was to examine if the use of the Optetrak Logic PS femoral component is associated with early (<5 years) and more extensive aseptic loosening compared with other PS femoral components. This is a single-institution retrieval analysis and revision registry study (based on prospectively collected data) of 27 failed primary PS TKA patients with loose femoral components that underwent revision TKAs between 2016 and 2019. Patients were stratified by components type: Group A (n = 16) received the Optetrak Logic PS femoral component, while Group B (n = 11) received other PS femoral components. Burnishing (macroscopic polishing of the component's backside) was observed and graded as a marker for relative motion at the cement-implant interface. No significant differences were found between the two groups regarding the baseline demographic, radiographic, and clinical characteristics. Mean length of implantation for Group A (3.8 ± 2.9 years) was significantly shorter (p < 0.001) than that of Group B (12.0 ± 6.7 years). A significant difference (p = 0.009) was found in presence of backside femoral burnishing between Group A (15 of 16 patients; 93.8%) and group B (5 of 11 patients; 45.6%). Furthermore, we found a significant difference (p < 0.001) in the severity of burnishing between Group A (13 of 16 patients with severe degree of burnishing; 81.3%) and Group B (1 of 11 patients with severe degree of burnishing; 9.1%). In contrast to Group B, a distinctive macroscopic pattern found in Logic retrieved femoral components (Group A) was the total absence of cement in the backside surface. The use of the Optetrak Logic PS TKA femoral component was associated with early aseptic loosening and increased presence and severity of backside burnishing with early cement-implant interface debonding compared with other commercially available types of PS TKA femoral components. The earlier failure rate with this implant is of concern.

Ten-Year Follow-Up of High-Flexion Versus Conventional Total Knee Arthroplasty: A Matched-Control Study

BACKGROUND

High-flexion total knee arthroplasty (HF-TKA) prostheses were designed with hopes of improving knee function. Studies have suggested increased failure with HF-TKAs. The purpose is to compare clinical results of HF-TKA versus conventional TKA (C-TKA) from the same implant system with long-term follow-up.

METHODS

This review of prostheses implanted between 2004 and 2007 matched 145 of 179 possible HF-TKAs with 145 of 1347 possible C-TKAs. Mean follow-up was 121.5 ± 20.3 months. We were unable to match 12 HF-TKAs. HF-TKAs with less than 8-year follow-up were excluded. The primary outcome was failure requiring revision. Secondary outcomes included range of motion (ROM), Knee Society Scores (KSS), and radiolucent lines.

RESULTS

In the matched cohort, there were 15 HF-TKA reoperations, 8 of which involved component revisions. There were 12 reoperations in the C-TKA cohort but no component revisions (P = .001). The analysis of the unmatched cohorts revealed a higher revision rate for HF-TKAs (P = .039) (HF-TKA: 10/179 vs C-TKA: 27/1347). At final follow-up, HF-TKAs exhibited more prosthesis radiolucent lines without evidence of loosening. Particularly, HF-TKAs demonstrated more femoral zone IV radiolucencies (38.7%) at final follow-up compared with C-TKAs (13.8%) (P < .001). There were no differences found between cohorts in ROM or KSS.

CONCLUSION

This study found an increased incidence of failure requiring revision with the HF-TKA in the matched and unmatched analyses. Higher incidences of radiolucent lines were found with HF-TKA. With no observed differences in ROM or KSS and a higher rate of failure with HF-TKA, there appears to be no advantage for use of the HF-TKA.

Medium-Term Clinical Results of High-Flexion Knee Prostheses in Patients with Rheumatoid Arthritis

Objective

This study was performed to evaluate the function and satisfaction outcome of patients with rheumatoid arthritis (RA) who underwent total knee arthroplasty (TKA) with high‐flexion prostheses.

Materials and methods

Twenty‐two patients (35 knees) using high‐flexion prostheses (Zimmer, Warsaw, IN) were followed up for a period of 7–11 years from February 2007 to December 2009. Clinical and radiographic follow‐up was performed using Hospital for Special Surgery (HSS), Short‐Form 36 scores (SF‐36), American Knee Society score (KSS), and Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System. Patient satisfaction assessments took place at the final follow‐up sessions using the Marsh Satisfaction Questionnaire.

Results

The average ROM improved from preoperative 68.43° ± 33.78° to 95.54° ± 7.03° at the final follow‐up. The HSS score and KSS score for pain improved from (46.49 ± 12.73) points to (85.46 ± 3.90) points and from 20.57 ± 5.91 points to 47.43 ± 3.51 points at the follow‐up evaluation, respectively. Physical Component Summary(PCS) and Physical Component Summary (MCS) scores were 45.38 and 52.56, respectively by the end of follow‐up. Deep venous thrombosis developed in one patient and one patient required surgical revision due to infection. There were no instances of prosthetic loosening. The satisfaction rate of patients was 95.5%.

Conclusion

Although this particular model of TKA did not yield high‐flexion angles (ie, 140°) required for kneeling, squatting, or rising from the floor, significant clinical and radiographic gains were evident in these patients with RA.

No difference of survival between cruciate retaining and substitution designs in high flexion total knee arthroplasty

The aim of this study was to compare the long-term implant survival and outcomes in patients with high-flexion cruciate-retaining (CR) or high-flexion posterior cruciate-substituting (PS) knee implants. A total of 253 knees (CR group: 159 vs. PS group: 94) were available for examination over a mean follow-up of 10 years. Clinical outcomes were assessed including the Hospital for Special Surgery score, Knee Society score and Western Ontario and McMaster Universities Osteoarthritis Index score at the final follow-up. Radiologic measurements were also assessed including the hip-knee-ankle angle and radiolucent lines according to the KSS system at the final follow-up. The survival rate was analyzed using the Kaplan–Meier method. At the final follow-up, the mean total HSS scores were similar between the two groups (p = 0.970). The mean hip-knee-ankle angle at the final follow-up was similar between groups (p = 0.601). The 10- and 15-year survival rates were 95.4% and 93.3% in the CR group and 92.7% and 90.9% in the PS group, respectively, with no significant difference. Similar clinical and radiographic outcomes could be achieved with both the high-flexion CR and high-flexion PS total knee designs without a difference in survival rate after a 10-year follow-up.

Femoral Cementation in Knee Arthroplasty-A Comparison of Three Cementing Techniques in a Sawbone Model Using the ATTUNE Knee

Femoral component loosening is a rare but severe complication in total knee arthroplasty. Former studies have repeatedly demonstrated radiolucent lines behind the ventral and dorsal anchoring shields of the femoral components, which has led us to investigate this matter further. Therefore, three different cementing techniques were tested in a group of nine Sawbone samples each. These differed in the amount of cement applied on the femoral component as well as in the pressure application. Computed tomography was performed to evaluate and classify the cement penetration into the bone adjacent to the prosthesis according to the zones defined by the Knee Society scoring system. The results show significantly deeper cement penetration in all zones when a pressurizer is used. In the other two groups, no significant difference in the dorsal bevel cement penetration was noted. Additionally, no difference in ventral and dorsal cement penetrations (Zones 1 and 4) was delineated. In contrast, there was a significant difference in both the ventral bevel (Zone 2) as well as the distal anchoring surface (Zones 5-7). The use of a pressurizer results in greater cement penetration into all anchoring areas. Completely covering the component back surface results in a significantly higher penetration, which is mainly due to differences in volume. These data show significantly improved cementation results when using a pressurizer. Whether this improves the biomechanical properties and ultimately the revision rate requires further investigation.

Why do knees after total knee arthroplasty fail in different parts of the world?

OBJECTIVE

The aim of this narrative review was to provide an overview of failure modes after total knee arthroplasty in different parts of the world based on data from worldwide representative studies and National Joint Registries.

METHODS

A review of the available literature was performed using the keyword terms "total knee arthroplasty", "revision", "failure", "reasons", "causes", "complications", "epidemiology", "etiology"; "assessment", "painful knee", "registry" and "national" in several combinations. The following databases were assessed: Pubmed (https://pubmed.ncbi.nlm.nih.gov), Cochrane Reviews (https://www.cochrane.org), Google Scholar (https://scholar.google.com). In addition, registry data were obtained directly from national registry archives. Due to the heterogeneity of available data it was decided to present the review in a narrative manner.

RESULTS

Current literature report that infection has become the primary acute cause of TKA failure, while aseptic loosening and instability remain the overall most frequent reasons for revisions. Based on national registries certain tendencies can be deducted. The predominant overall failure mode of aseptic loosening is particularly found in Japan, United Kingdom, New Zealand and Switzerland. Leading early TKA failure mode represents infection with percentages of 20-30% in Sweden, Australia, New Zealand, Japan and the United States. Higher numbers could only be found in clinical studies on the Asian continent such as Korea (38%), China (53%), Iran (44%) and India (87%).

CONCLUSION

Although there are regional differences in TKA failure modes, TKA fails worldwide especially due to infections and aseptic loosening. It is important to diagnose these in good time and reliably using appropriate, standardized diagnostics in order to recommend the best possible therapy to the patient.

Do the increment of femoral condyle curvature and the change of tibia shape improve clinical outcome in total knee arthroplasty? A propensity score matching analysis

PURPOSE

Recently, the Persona total knee arthroplasty (TKA) system with more anatomical features and a similarly high flexion to the previous version, LPS-Flex, was introduced and is widely used. This study aimed to compare the early outcomes obtained using Persona versus an LPS-Flex fixed PS implant.

METHODS

A total of 784 knees that underwent primary TKAs (162: Persona group and 622: LPS-Flex group) were included. After 1:2 propensity score matching, there were 143 and 286 knees in Persona and LPS-Flex groups, respectively. Range of motion at the 2-year follow-up was the primary variable. Secondary variables were functional score, ability to perform activities requiring deep knee flexion, patient satisfaction, and radiographic measurements, including radiolucent line (RLL).

RESULTS

The average postoperative maximal flexion measured by goniometer at 2 years after TKA was 126.1° ± 10.8° (range 95°-140°) for the Persona group and 132.7° ± 11.7° (range 103°-145°) for the LPS-Flex group (P < 0.05). This significant difference was observed from 1 year postoperatively (P < 0.05). The two groups did not show a significant difference in functional score, postoperative ability in high flexion activities, and satisfaction at the 2-year follow-up. The rate of RLL was significantly lower in the Persona group (P < 0.05).

CONCLUSION

At the 2-year follow-up, the Persona group had less maximal flexion; however, the difference in flexion did not seem to affect clinical outcomes. According to the radiological results, the Persona system shows less RLL than does the LPS-Flex system.

LEVEL OF EVIDENCE

III.

Comparison of Posterior Cruciate-Retaining and High-Flexion Cruciate-Retaining Total Knee Arthroplasty Design

BACKGROUND

High-flexion prostheses have been developed to achieve deep flexion after total knee arthroplasty. The purpose of this study is to compare standard NexGen (CR, cruciate-retaining) and high-flexion NexGen (CR-flex) total knee prostheses in terms of range of motion, clinical and radiologic outcomes, rates of complications, and survivorship in long-term follow-up.

METHODS

From January 2000 to December 2008, 423 consecutive knees underwent total knee arthroplasty using standard CR or CR-flex prostheses. Fifty-three patients were lost to follow-up or declined to participate and 54 died, leaving 290 knees. The minimum duration of follow-up was 8 years (mean 10.1 years). Physical examination and knee scoring of patients were assessed preoperatively, at 6 months and 1 year after surgery, and annually thereafter. Supine anteroposterior and lateral radiographs and standing anteroposterior hip-to-ankle radiographs were obtained preoperatively and at each follow-up.

RESULTS

Mean postoperative range of motions in the standard CR group and the CR-flex group were similar, showing no significant difference between the 2 groups (P = .853). At the time of the final follow-up, mean total Hospital for Special Surgery scores were similar between the 2 groups (P = .118). Mean Knee Society pain (P = .325) and function scores (P = .659) were also comparable between the 2 groups. Western Ontario and McMaster Universities Osteoarthritis Index score showed no intergroup difference either (P = .586). The mean hip-knee-ankle angle at the final follow-up was approximately the same (P = .940). Mean coronal angles of femoral and tibial component at final follow-up were also similar (P = .211 and P = .764, respectively). The prevalence of the radiolucent line was 0.6% in the standard CR group and 0.9% in the CR-flex group. Estimated survival rate according to Kaplan-Meier survival analysis was 97.2% in the standard CR group and 95.6% in the CR-flex group at mean follow-up of 10.1 years.

CONCLUSION

This study suggests that excellent clinical and radiographic outcomes could be achieved with both standard and high-flexion CR total knee designs. High-flexion CR prosthesis did not show any advantages over the standard design.

Ten-Year Minimum Outcomes and Survivorship With a High Flexion Knee System

BACKGROUND

The purpose of this study is to report the long-term outcomes and survivorship of a high flexion knee system.

METHODS

We identified 1312 patients (1664 knees) who underwent primary total knee arthroplasty with the Vanguard Complete Knee System with 10-year minimum follow-up. Preoperative and postoperative range of motion, Knee Society scores, complications, and reoperations were evaluated.

RESULTS

At an average of 11.9 years of follow-up, 88 knees were revised (5.3%). The deep infection rate was 1.4%. There was an average range of motion improvement of 3.9°, pain level decreased by 35.8, Knee Society clinical scores improved by 48, and Knee Society functional scores improved by 15.1 (all P < .001). Survival was 96.4% at 10 years for aseptic causes and 95.5% for all causes.

CONCLUSION

At a 10-year minimum follow-up, this high flexion knee system demonstrates excellent survivorship.

Fixed-bearing versus high-flexion RP total knee arthroplasty (TKA): midterm results of a randomized controlled trial

Background

We compared the midterm results after total knee arthroplasty (TKA) using PFC Sigma RP-F mobile model with PFC Sigma PS fixed model.

Materials and methods

In this randomized controlled trial, we analyzed 50 knees that underwent TKA with PFC Sigma RP-F and 60 knees with PFC Sigma PS fixed model. The follow-up period ranged from 76 to 104 months.

Results

The knee score, function score, and radiographic evaluation were significantly not different between the two groups at final follow-up. No revisions, subluxations, dislocations, or infections were seen. Also, no radiographic evidence of component loosening, osteolysis, or malalignment was observed in any knee. The results for both groups show good patient satisfaction.

Conclusions

The midterm clinical and radiographic results of the two prostheses did not show significant differences between the two groups.

Level of evidence

Level of evidence is level II.

Comparison of Revision Rates Due to Aseptic Loosening between High-Flex and Conventional Knee Prostheses

Purpose

The purpose was to evaluate and compare the revision rate due to aseptic loosening between a high-flex prosthesis and a conventional prosthesis.

Materials and Methods

Two thousand seventy-eight knees (1,377 patients) with at least 2 years of follow-up after total knee arthroplasty were reviewed. Two types of implants were selected (LPS-Flex and LPS, Zimmer) to compare revision and survival rates and sites of loosened prosthesis component.

Results

The revision rate of the LPS-Flex (4.9%) was significantly higher than that of the conventional prosthesis (0.6%) (p<0.001). The 5-, 10-, and 15-year survival rates were 98.9%, 96.2% and 92.0%, respectively, for the LPS-Flex and 99.8%, 98.5% and 93.5%, respectively, for the LPS. The survival rate of the high-flex prosthesis was significantly lower than that of the conventional prosthesis, especially in the mid-term period (range, 5 to 10 years; p=0.002). The loosening rate of the femoral component was significantly higher in the LPS-Flex prosthesis (p=0.001).

Conclusions

The LPS-Flex had a higher revision rate due to aseptic loosening than the LPS prosthesis in the large population series with a long follow-up. The LPS-Flex should be used carefully considering the risk of femoral component aseptic loosening in the mid-term (range, 5 to 10 years) follow-up period after initial operation.

Cementing technique affects the rate of femoral component loosening after high flexion total knee arthroplasty

BACKGROUND

The purpose of this study was to determine the effects of different cementing techniques on the rate of early femoral loosening of high-flexion total knee arthroplasties (TKAs).

METHODS

A total of 734 knees from 486 patients treated with high-flexion design TKA between July 2001 and July 2010 were divided into two groups based on the cementing technique used. For 403 knees (group N), cement was applied onto the distal and anterior cut surfaces of the femur and the posterior flanges of the femoral component without pressurization. For 331 knees (group P), cement was applied onto distal and anterior femoral cut surfaces with digital pressurization and whole cement surfaces of the femoral component. Two groups were subjected to clinical and radiological evaluation with a minimum five year follow-up period. Cox proportional hazards model with revision surgery of the prosthesis or radiological loosening as an endpoint was used to evaluate the effect of the cementing technique and other covariates.

RESULTS

The pressurizing and bi-surface cementing technique resulted in significant reduction in femoral radiological loosening incidence compared to that without pressurization (0.3% vs. 2.5%, P=0.015) and revision rate for aseptic causes (0.9% vs. 3.2%, P=0.032). Cox proportional hazard regression analysis revealed a significant difference in component survival rate between the two groups if femoral radiological loosening was considered as failure (hazard ratio, 4.229, 95% confidence interval (CI): 1.256-14.243, P=0.020).

CONCLUSION

Pressurizing and bi-surface cementation can reduce the occurrence rate of early loosening around the femoral component in high-flexion TKAs.

Early Clinical Outcomes of a New Posteriorly Stabilized Total Knee Arthroplasty Prosthesis: Comparisons with Two Established Prostheses

Purpose

We sought to determine whether early clinical performance of new posterior stabilized (PS) knee system, the Vega-PS (Aesculap), is better than that of two established total knee arthroplasty (TKA) prostheses, the E.motion-PS (Aesculap) and the Genesis II (Smith & Nephew) in terms of functional outcomes, patient satisfaction, and incidence of adverse events.

Materials and Methods

We compared the clinical outcomes of 206 consecutive TKAs using Vega-PS with those of 205 TKAs using E.motion-PS and 216 TKAs using Genesis II at 2 years of follow-up.

Results

Overall, the knees with the Vega-PS had better functional outcome scores than the knees with the E.motion-PS, but had similar outcome scores to the knees with the Genesis II, as evident from the American Knee Society knee score (94.2 vs. 92.5 vs. 93.2), Western Ontario McMaster Universities Osteoarthritis (WOMAC) stiffness index (1.8 vs. 2.3 vs. 2.0), WOMAC function index (11.8 vs. 16.8 vs. 18.5), Short Form 36 (SF-36) physical component summary score (41.9 vs. 39.3 vs. 41.6), and SF-36 mental component summary score (50.0 vs. 45.8 vs. 46.9). Patient satisfaction was higher in the Vega-PS and Genesis II groups than the E.motion-PS group. No notable group differences were found in terms of the incidence of adverse events.

Conclusions

The Vega-PS, a newly developed PS fixed bearing prosthesis, had comparable or superior clinical performance in comparison with the two established fixed or mobile bearing PS prostheses.

Comparison of ultra-congruent mobile- and fixed-bearing navigation-assisted total knee arthroplasty with minimum 5-year follow-up

PURPOSE

The purpose of this study was to compare the midterm outcomes between fixed and mobile ultra-congruent (UC) bearings in total knee arthroplasty (TKA).

METHODS

This is a retrospective matched-pairs case-control study of patients who underwent primary navigation-assisted TKA with a minimum 5-year follow-up. A total of 182 cases involved the fixed UC bearing system as Group 1 and 101 cases involved mobile UC bearing system group as Group 2. After 1:1 matching, 73 knees in each group were enrolled. Clinical and radiographic outcomes were evaluated.

RESULTS

The overall survival was 143 of 146 cases (97.9 %) at final follow-up, and 72 of 73 cases (96.3 %) in Group 1 and 71 of 73 cases (95.8 %) in Group 2 at final follow-up based on an endpoint of revision surgery. The reasons of revision TKA were periprosthetic fracture in Group 1, infection and bearing dislocation in Group 2. There was no statistical difference in Hospital for Special Surgery (HSS) scores, Knee Society Scores (KSS), WOMAC index score evaluations between groups.

CONCLUSIONS

This study demonstrated that the fixed-bearing UC prosthesis could provide satisfactory performance compared with that of the mobile-bearing UC prosthesis with minimum 5-year follow-up. The fixed-bearing UC prosthesis could be considered in navigation-assisted TKA with theoretical advantages of UC design.

LEVEL OF EVIDENCE

IV.

Total knee arthroplasty using NexGen LPS-flex® improves clinical outcomes without early loosening: minimum 6-year follow-up results

Background

The authors analyzed clinical and radiological 6-year follow-up results after total knee arthroplasty (TKA) with NexGen LPS-flex® and implant survivorship.

Methods

The medical records of 80 patients that underwent 122 TKAs using NexGen LPS-flex® from February 2005 to November 2008 and followed up for at least 6 years were reviewed. The Internal Knee Documentation Committee (IKDC) subjective form, Western Ontario and McMaster Universities Arthritis Index (WOMAC), and Knee Injury and Osteoarthritis Outcome Score (KOOS) scores and preoperative and postoperative ranges of motion (ROMs) were recorded. Radiological assessments were performed by simple radiography preoperatively, immediately postoperatively, and at the final follow-up.

Results

At the last follow-up visits, average ROM improved from 115.0° (80°–135°) to 131.76° (80°–150°), average IKDC subjective score from 30.54 (13–48) to 53.53 (31–80), average WOMAC score from 59.81 (35–90) to 15.98 (1–47), and average KOOS score from 75.33 (38–115) to 115.0 (52–174). The clinical results of 66 knees that had >130° of postoperative flexion and 56 knees that had <130 of postoperative flexion were compared. Radiolucent lines were found in 7 knees in those with a flexion angle of >130° and in 6 knees in those with a flexion angle of <130°, but the lines did not progress and meaningful loosening was not observed. Similarly, the occurrences of radiolucent lines in those with a flexion angle of >130° or <130° were not significantly different (p > 0.05).

Conclusions

TKA with NexGen LPS-flex® showed satisfactory clinical improvements, including high flexion, and no early loosening was found at 6-year follow-up visits.

Active Flexion in Weight Bearing Better Correlates with Functional Outcomes of Total Knee Arthroplasty than Passive Flexion

PURPOSE

Correlations between maximum flexion and functional outcomes in total knee arthroplasty (TKA) patients are reportedly weak. We investigated whether there are differences between passive maximum flexion in nonweight bearing and other types of maximum flexion and whether the type of maximum flexion correlates with functional outcomes.

MATERIALS AND METHODS

A total of 210 patients (359 knees) underwent preoperative evaluation and postoperative follow-up evaluations (6, 12, and 24 months) for the assessment of clinical outcomes including maximum knee flexion. Maximum flexion was measured under five conditions: passive nonweight bearing, passive weight bearing, active nonweight bearing, and active weight bearing with or without arm support. Data were analyzed for relationships between passive maximum flexion in nonweight bearing by Pearson correlation analyses, and a variance comparison between measurement techniques via paired t test.

RESULTS

We observed substantial differences between passive maximum flexion in nonweight bearing and the other four maximum flexion types. At all time points, passive maximum flexion in nonweight bearing correlated poorly with active maximum flexion in weight bearing with or without arm support. Active maximum flexion in weight bearing better correlated with functional outcomes than the other maximum flexion types.

CONCLUSIONS

Our study suggests active maximum flexion in weight bearing should be reported together with passive maximum flexion in nonweight bearing in research on the knee motion arc after TKA.

Is High-Flexion Total Knee Arthroplasty a Valid Concept? Bilateral Comparison With Standard Total Knee Arthroplasty

BACKGROUND

The purpose of this study was to determine whether the high-flexion total knee prosthesis significantly improves knee flexion in vivo.

METHODS

Forty-four patients undergoing same-day bilateral total knee arthroplasty for primary osteoarthritis of both knees were randomized to receive a standard posterior-stabilized knee prosthesis (P.F.C. Sigma; DePuy Johnson & Johnson, Warsaw, IN) in one knee and a high-flexion concept posterior-stabilized knee prosthesis (LOSPA; Corentec, Inc, Seoul, Korea) in the other knee and were followed up for 2 years postoperatively.

RESULTS

The mean postoperative range of motion was 128.8° (range, 100°-144°) in the LOSPA group and 128.5° (range, 100°-142°) in the P.F.C. Sigma group (P = .744). There were no significant differences in the postoperative mean Knee Society score and Western Ontario and McMaster Universities Osteoarthritis Index score between the LOSPA and P.F.C. Sigma groups (P = .839 and P = .972, respectively).

CONCLUSION

Despite theoretical range of motion advantages of high-flexion prosthesis, there were no group differences with regard to range of motion, clinical outcomes, and the incidence of radiolucent lines at final follow-up assessment.

Two- to Four-Year Follow-up Results of Total Knee Arthroplasty Using a New High-Flexion Prosthesis

Purpose

The purpose of this study was to evaluate minimum 2-year follow-up results of total knee arthroplasty (TKA) performed using a new high-flexion prosthesis design (LOSPA).

Materials and Methods

The 2- to 4-year results of 191 consecutive TKAs (177 patients) with the LOSPA posterior-stabilized prosthesis were evaluated. The patients were assessed clinically and radiographically using the Knee Society scoring system (KSS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

Results

The mean range of motion (ROM) increased significantly from 117.4° (range, 75° to 140°) preoperatively to 126.7° (range, 80° to 144°) postoperatively (p<0.001). The mean KSS and WOMAC scores improved significantly from 121.4 (range, 42 to 185) and 56.1 (range, 23 to 88) preoperatively to 174.0 (range, 130 to 200) and 16.4 (range, 0 to 85) postoperatively, respectively (both, p<0.001). One knee required revision for deep infection. No knee had aseptic loosening or osteolysis. Radiolucent lines were noted in 15 knees (7.9%).

Conclusions

The new high-flexion total knee prosthesis resulted in no early aseptic loosening of the component and improved postoperative ROM comparable to other high-flexion TKA prostheses at 2- to 4-year follow-ups.

Functional Outcomes of a New Mobile-Bearing Ultra-Congruent TKA System: Comparison With the Posterior Stabilized System

We determined whether a new mobile-bearing ultra-congruent (UC) TKA system provides better functional outcomes than an established posterior-stabilized (PS) prosthesis. The functional outcomes (motion arc, AKS scores, WOMAC Index, and SForm-36 scores evaluated at 1 and 2 years postoperatively), satisfaction and incidences of adverse events were compared between the knees implanted with mobile-bearing UC prosthesis (n=103) and the mobile-bearing PS prosthesis (n=99). At 2 years, mobile-bearing UC TKAs showed similar functional outcomes and satisfaction, but smaller motion arc compared to mobile-bearing PS TKAs (126° vs. 131°). There were no differences in the incidence of adverse events. Mobile-bearing UC prosthesis can be considered a safe and viable alternative to the PS design, with an expectation of smaller postoperative maximum flexion.

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.

Performing high flexion activities does not seem to be crucial in developing early femoral component loosening after high-flexion TKA

Background

It is still unclear whether high flexion (HF) activities correlated with the early loosening of the femoral component and whether HF activities are possible. We investigated what is the capability for performing various HF activities, and whether high flexion activities increase the chance of aseptic loosening after HF-TKA.

Methods

We retrospectively analysed 260 patients who underwent HF-TKA using the NexGen LPS Flex between 2001 and 2009. The mean follow-up was 6.7 years (range, 5–13). We evaluated range of motion, Knee Society scores, WOMAC, and serial radiographs for aseptic loosening. Responses to questions on individual HF activities were recorded on 5-point Likert scales based on difficulty (0–4). Patients were divided two groups based on their responses to squatting and kneeling, which were important weight-bearing HF activities in Asian population (HF group vs. non-HF group) for comparisons of aseptic loosening and clinical outcomes.

Results

More than 80 % of patients positively responded for various HF activities. The capability of HF activities showed that cross-legged sitting, squatting, and kneeling were 97.7, 51.1 and 52.7 % at the latest follow-up, respectively. Aseptic loosening was identified in two tibial components (0.8 %) but none in femoral components in non-HF group. There was no significant difference of aseptic loosening based on HF activities (0.8% vs. 0%, p = 0.063).

Conclusions

The results of this study suggest that HF activities do not seem to be associated with aseptic loosening of femoral component after HF-TKA.

Clinical Outcomes in Men and Women following Total Knee Arthroplasty with a High-Flex Knee: No Clinical Effect of Gender

While it is generally recognized that anatomical differences exist between the male and female knee, the literature generally refutes the clinical need for gender-specific total knee prostheses. It has been found that standard, unisex knees perform as well, or better, in women than men. Recently, high-flex knees have become available that mechanically accommodate increased flexion yet no studies have directly compared the outcomes of these devices in men and women to see if gender-based differences exist. We retrospectively compared the performance of the high-flex Vanguard knee (Biomet, Warsaw, IN) in 716 male and 1,069 female knees. Kaplan-Meier survivorship was 98.5% at 5.6–5.7 years for both genders. After 2 years, mean improvements in Knee Society Knee and Function scores for men and women (50.9 versus 46.3; 26.5 versus 23.1) and corresponding SF-12 Mental and Physical scores (0.2 versus 2.2; 13.7 versus 12.2) were similar with differences not clinically relevant. Postoperative motion gains as a function of preoperative motion level were virtually identical in men and women. This further confirms the suitability of unisex total knee prostheses for both men and women.

High-Flexion Total Knee Arthroplasty Using NexGen LPS-Flex System: Minimum 5-year Follow-up Results

PURPOSE

This study is to report clinical and radiological results of high-flexion total knee arthroplasty (TKA) using NexGen LPS-flex system at a minimum 5-year follow-up, and to analyze the implant survivorship based on the results.

MATERIALS AND METHODS

A total of 80 patients (118 knees) who underwent patellar preserving TKA using NexGen LPS-flex implant between February 2007 and February 2008 and could be followed for minimum 5 years were reviewed. The range of motion (ROM), hip-knee-ankle angle, Knee Society Knee score (KSKS), and Knee Society Function score (KSFS) were assessed preoperatively and at the last follow-up and analyzed. Implant position of the femoral and tibial components on the immediate postoperative and last follow-up X-rays were compared.

RESULTS

The mean ROM was 110.2°±14.5° (range, 60° to 140°) preoperatively and 132.4°±5.2° (range, 90° to 145°) at the last follow-up. KSKS was 36.9°±6.4° preoperatively and 94.2°±3.2° at the last follow-up. KSFS was 30.5°±5.7° preoperatively and 93.7°±4.1° at the last follow-up. There was no statistically significant change in the implant position measured as α, β, γ, and δ angles at the last follow-up compared to the immediate postoperative values. Radiolucent lines were observed in 13 knees (11%) on the last follow-up X-rays. Revision TKA was performed due to aseptic implant loosening in 1 knee (0.84%), and the survival rate at the 5th postoperative year was 99.2%.

CONCLUSIONS

The clinical and radiological outcomes of high-flexion TKA using NexGen LPS-Flex implant design were satisfactory with 99.2% implant survival rate after 5 years of protected activities of daily living.

No difference between standard and high flexion cruciate retaining total knee arthroplasty: a prospective randomised controlled study

PURPOSE

The purpose of this prospective, randomised, double-blind study was to test the hypotheses that patients with high-flexion total knee arthroplasty (TKA) have (1) a wider/greater range of motion (ROM) post-operatively and (2) higher levels of knee society score (KSS) and WOMAC score post-operatively compared to standard TKA.

METHODS

In this study, 28 high flexion with 31 standard TKAs were compared. We measured ROM, pre-operatively, on day 3, 7, 28, and after 6 and 36 months post-operatively as well as KSS and WOMAC score pre-operatively, on day 28 and after 6 and 36 months post-operatively.

RESULTS

No statistically significant differences were found between both groups with regard to the target parameters. The mean ROM was 113° (range 80°-140°, SD 13.4°) in the control group (standard TKA) and 117° (range 90°-140°, SD 12.3) in the study group (high-flexion TKA) at 36 months follow-up [p = not significant (n.s.)]. The KSS pre-operatively was 38.2 (range 8-64, SD 15.8) in the control group and 45.9 (range 8-74, SD 16.0) in the study group (n.s.) increasing to 157.6 in the control group and 156.7 in the study group (p = n.s) at 36 months follow-up.

CONCLUSION

This study could not confirm significant benefits of high-flexion TKA compared to standard TKA with regard to ROM and higher levels of KSS and WOMAC score.

LEVEL OF EVIDENCE

I.

Squatting-related tibiofemoral shear reaction forces and a biomechanical rationale for femoral component loosening

Previous gait studies on squatting have described a rapid reversal in the direction of the tibiofemoral joint shear reaction force when going into a full weight-bearing deep knee flexion squat. The effects of such a shear reversal have not been considered with regard to the loading demand on knee implants in patients whose activities of daily living require frequent squatting. In this paper, the shear reversal effect is discussed and simulated in a finite element knee implant-bone model, to evaluate the possible biomechanical significance of this effect on femoral component loosening of high flexion implants as reported in the literature. The analysis shows that one of the effects of the shear reversal was a switch between large compressive and large tensile principal strains, from knee extension to flexion, respectively, in the region of the anterior flange of the femoral component. Together with the known material limits of cement and bone, this large mismatch in strains as a function of knee position provides new insight into how and why knee implants may fail in patients who perform frequent squatting.

Does flexion of the femoral implant in total knee arthroplasty increase knee flexion: a randomised controlled trial

INTRODUCTION

Prosthetic and operative modifications in total knee arthroplasty (TKA) have been proposed to maximise post-operative knee flexion as it is essential in routine functional activities.

METHODS

We performed a double blind randomised controlled trial to compare clinical outcomes of primary cruciate-retaining TKA for osteoarthritis with the femoral component implanted in either 4° flexion in the sagittal plane (F) or in a neutral position (C). The primary outcome of knee flexion and secondary outcomes knee extension, quadriceps strength, WOMAC, SF-12v2, timed stand test, stair climb test and satisfaction were assessed at 1 year. Knee flexion and extension were also assessed intra-operatively. Implant flexion was measured from true lateral radiographs.

RESULTS

Thirty-nine participants (40 knees) were recruited, 20 knees per group. Three subjects from the control group and two from the flexed group were lost to 1 year follow-up but numbers were sufficient to satisfy the sample size calculation. Significant differences were found between the groups in knee flexion (F: 113.6±8.8° pre-operative, 122.4±6.0° intra-operative, 110.2±7.5° 1 year, C: 117.4±11.7°, 117.4±7.6°, 103.5±10.7°. p=0.031) and mental component score of the SF12-v2 (F 53.3±13.2, C 61.1±7.3, p=0.009) but there were no significant differences in other outcomes and patients were equally satisfied.

CONCLUSION

Flexing the femoral implant in this cruciate retaining TKA system provided a significant difference in knee flexion compared to a neutral position. The improvement appears to occur predominantly at surgery and was not associated with a clinical or functional benefit at 1 year. (ACTRN12606000325505).

LEVEL OF EVIDENCE

Level 1; randomised controlled trial.

Seven-year survivorship and functional outcomes of the high-flexion Vanguard complete knee system

Certain recreational, cultural, occupational, and religious practices may require knee flexion exceeding typical daily living activity needs. Some total knee prostheses mechanically accommodate high flexion to help meet such demands, e.g., the Vanguard knee (Biomet, Inc., Warsaw, IN) which can mechanically achieve 140°-145°. This multicenter, prospective clinical study of 957 Vanguard knees (865 patients) examined mid-term outcomes. The Kaplan-Meier survivorship estimate was 97.8% (95% CI: 96.5-98.7%) at 7.0 years. For patients with ≥ 2-year follow-up (n=627), mean peak flexion increased from 116.8° to 124.8° (P<0.001). For knees with pre-operative flexion of <95°, 95°-105°, and >105°, the mean increases were 27.8°, 22.0°, and 3.6°, respectively. Mean Knee Society Knee and Function scores increased from 45.9 and 45.5 points to 92.0 and 73.8 points, respectively (P<0.001).

Probability of mechanical loosening of the femoral component in high flexion total knee arthroplasty can be reduced by rather simple surgical techniques

BACKGROUND

Some follow-up studies of high flexion total knee arthoplasties report disturbingly high incidences of femoral component loosening. Femoral implant fixation is dependant on two interfaces: the cement-implant and the cement-bone interface. The present finite-element model (FEM) is the first to analyse both the cement-implant interface and cement-bone interface. The cement-bone interface is divided into cement-cancellous and cement-cortical bone interfaces, each having their own strength values. The research questions were: (1) which of the two interfaces is more prone to failure? and (2) what is the effect of different surgical preparation techniques for cortical bone on the risk of early failure.?

METHODS

FEM was used in which the posterior-stabilized PFC Sigma RP-F (DePuy) TKA components were incorporated. A full weight-bearing squatting cycle was simulated (ROM=50°-155°). An interface failure index (FI) was calculated for both interfaces.

RESULTS

The cement-bone interface is more prone to failure than the cement implant interface. When drilling holes through the cortex behind the anterior flange instead of unprepared cortical bone, the area prone to early interface failure can be reduced from 31.3% to 2.6%.

CONCLUSION

The results clearly demonstrate high risk of early failure at the cement-bone interface. This risk can be reduced by some simple preparation techniques of the cortex behind the anterior flange.

CLINICAL RELEVANCE

High-flexion TKA is currently being introduced. Some reports show high failure rates. FEM can be helpful in understanding failure of implants.

Are the long term results of a high-flex total knee replacement affected by the range of flexion?

PURPOSE

The purpose of this study was to examine the effect of deep flexion on the long-term durability of a high-flex ceramic implant in total knee arthroplasty.

METHODS

Five hundred and five consecutive knees replaced with a Bi-Surface knee system (Kyocera Medical, Osaka, Japan) were divided into two groups according to the range of flexion by 135° postoperatively. Comparison of implant durability was made between the high- and low-flexion groups after a minimum ten year follow-up.

RESULTS

With revision for any surgery as the end point, the survival rates at ten years were 95.5% and 96.2% in the high- and low-flexion group, respectively (p = 0.63). With revision for mechanical failure as the end point, survival rates were 98.7% and 98.5%, respectively (p = 0.94).

CONCLUSION

Implant survival rate was similar for both groups. Deep flexion seemed not to affect long-term durability.

Fixation of high-flexion total knee prostheses: five-year follow-up results of a four-arm randomized controlled clinical and roentgen stereophotogrammetric analysis study

BACKGROUND

High-flexion total knee arthroplasty was introduced to meet the demands of daily activity requiring increased knee flexion. However, concerns have been raised regarding the fixation of high-flexion total knee arthroplasty components and increased rates of loosening have been reported. To date, migration, and thus fixation, of high-flexion total knee arthroplasty components has not been analyzed and the preferential bearing type (mobile or fixed) is unknown.

METHODS

Of eighty-six consecutive eligible patients, seventy-four patients (seventy-eight knees) scheduled for total knee arthroplasty were randomized to one of four Legacy Posterior Stabilized (LPS) total knee prosthesis designs: (1) LPS-Flex mobile, (2) LPS-Flex fixed, (3) LPS mobile, and (4) LPS fixed. The primary outcome was component migration measured with use of Roentgen stereophotogrammetric analysis, and secondary outcomes were postoperative knee flexion and extension and Knee Society Score. Patients were evaluated postoperatively at six, twelve, twenty-six, and fifty-two weeks and annually thereafter. At the five-year follow-up, eight patients had died and two patients were lost to follow-up. Seventy-seven tibial and forty-two femoral components were suitable for migration measurements.

RESULTS

The overall five-year migration of the seventy-seven tibial components was not significantly different among the four total knee prosthesis designs (compared with the LPS fixed design, the range of overall mean differences for the other three designs was 0.02 to 0.25 mm) and migration was comparable at the two and five-year follow-up. Migration stabilized in all but three components (two LPS-Flex mobile and one LPS fixed); one of these components has already been revised and was aseptically loose. The overall five-year migration of the forty-two femoral components was comparable among the four designs (compared with the LPS fixed design, the range of overall mean differences for the other three designs was 0.01 to 0.18 mm) and was similar at two and five years postoperatively. One femoral component (LPS-Flex mobile) migrated excessively. In patients who had a mean postoperative flexion of ≥ 125° or a maximum flexion of ≥ 135° during the one to five-year follow-up period, migration of high-flexion components was comparable with that of conventional components and indicative of appropriate fixation. Postoperative flexion, extension, Knee Society Score, and Knee Society Score function were comparable during the five-year follow-up period and at the two and five-year follow-up.

CONCLUSIONS

The LPS-Flex total knee prosthesis with either a mobile or a fixed bearing had migration comparable that of with its conventional counterpart and is expected to have similar (excellent) long-term survival in these patients.

LEVEL OF EVIDENCE

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

Outcome and range of motion using a high-flexion cruciate-retaining TKA

Increased knee flexion after total knee arthroplasty (TKA) may contribute to patients' increased satisfaction and more active lifestyles. This study evaluated a TKA component designed for high flexion (more than 125°). The design features an anatomic sagittal femoral radius with short, flared femoral condyles to allow for femoral rollback. Fifty TKA procedures in 47 patients were evaluated prospectively regarding clinical outcomes using Knee Society knee and function scores, Short Form 12 physical component scores, and flexion measured clinically and by digital lateral supine active flexion radiographs. Preoperative and 1-year postoperative radiographs were analyzed by an independent observer. Mean maximum flexion measured clinically was 115° preoperatively and 120° one year postoperatively, with 76% of TKAs achieving more than 120° and 44% achieving more than 125°. Sex, body mass index, and preoperative flexion were not predictors of postoperative flexion. Mean flexion by radiograph was 108° preoperatively and 111° one year postoperatively, with 31% of knees achieving more than 120° and 14% more than 125°. Mean Knee Society knee and function scores and the Short Form 12 physical component scores were 52, 55, and 32 preoperatively, respectively, and 89, 77, and 40 one year postoperatively, respectively. Of the 50 knees, 84% had improvement in their Knee Society function scores, and 76% had improvement in their Short Form 12 physical component scores. The study revealed evidence of increased early postoperative flexion with the use of a cruciate-retaining high-flexion TKA design.

Influence of preparation techniques to the strength of the bone-cement interface behind the flange in total knee arthroplasty

INTRODUCTION

Recent clinical studies show an increased risk of femoral loosening in high-flexion TKA. Loosening seems to occur behind the anterior flange, which is covering both cancellous bone and cortical bone. It is important to optimize the interface strength between cement and both bone types to increase femoral component fixation. This study was performed to determine the cement-cortical bone interface strength for different preparation techniques.

MATERIAL AND METHODS

A pure tensile and shear force was applied to interface specimens. The cortical surface area was prepared in three different ways: (1) Unprepared cortical bone with periosteum; (2) Periosteum removed and cortical bone roughened with a rasp; (3) Periosteum removed and three Ø 3.2mm holes drilled through the cortex. A reference group was added with a cancellous bone surface.

RESULTS

The interface tensile strength of Group 1 was 0.06 MPa and the shear strength was 0.05 MPa. For Group 2, respectively 0.22 MPa and 1.12 MPa. For Group 3, respectively 1.15 MPa and 1.77 MPa. For cancellous bone a tensile strength of 1.79 MPa and a shear strength of 3.85 MPa were measured.

CONCLUSION

The strength of the cement-cancellous bone interface is superior to the cement-cortical bone interface. The preferred preparation technique of the cortical bone is to remove all the periosteum and drill holes through the cortex within the footprint of the anterior flange, to prevent cortical weakening.

CLINICAL RELEVANCE

Ultimately, the proposed preparation technique will lead to longer implant survival, particularly for prostheses which are used in the high-flexion range.

No better flexion or function of high-flexion designs in Asian patients with TKA

BACKGROUND

Recently, high-flexion PCL-retaining (CR) and -substituting (PS) knee prostheses were designed to allow greater and safer flexion after TKA. However, the advantages of high-flexion TKA over standard design have been debated in terms of early maximal flexion. A recent study reported a high incidence of early loosening of the femoral component related to the deep flexion provided by high-flexion PS TKA.

QUESTIONS/PURPOSES

We determined whether high-flexion fixed bearing CR and PS prostheses would provide (1) a better flexion, (2) a better function, and (3) a higher incidence of radiographic loosening than TKA performed using standard fixed bearing CR prostheses in Asian patients.

METHODS

From a total of 182 patients with primary unilateral TKA, we retrospectively reviewed 137 TKAs: 47 with high-flexion CR, 42 with high-flexion PS, and 48 with standard CR designs. ROM, Knee Society scores, and WOMAC scores were evaluated and compared among the three groups. Radiographically, we assessed radiolucent zones and component loosening. Minimum followup was 5 years (mean, 6.2 years; range, 5-8 years).

RESULTS

We found no differences among the three groups in mean maximal flexion (high-flexion CR: 135°; high-flexion PS: 134°; standard CR: 136°), Knee Society scores, and WOMAC scores at last followup. Also, there were no differences among the three groups in terms of radiolucent lines around the prosthesis. No patient in any group had loosening of the femoral component.

CONCLUSIONS

The high-flexion CR or PS design had no advantages over the standard CR design with respect to ROM, clinical scores, and radiolucent lines around the femoral or tibial component after 5 years' followup.

High-flexion prosthesis improves function of TKA in Asian patients without decreasing early survivorship

BACKGROUND

Two previous studies recently raised the possibility of a high risk of early femoral components loosening with high-flexion (HF) prostheses in Asian populations and suggested that the high failure rate of HF TKAs was associated with HF ability. However, these findings are controversial given other studies reporting a low incidence of aseptic failures in HF prostheses.

QUESTIONS/PURPOSES

We therefore determined (1) the rate of achieving postoperative HF after HF TKA; (2) whether the aseptic loosening rate of HF prostheses is high; and (3) whether the survivorship was worsened in patients who achieved postoperative deep knee flexion in our cohort of Korean patients.

METHODS

We retrospectively reviewed 488 patients who had 698 primary TKAs using the NexGen(®) Legacy Posterior-Stabilized Flex system implanted from 2003 to 2010. There were 40 men and 448 women with a mean age of 68 years. We obtained Hospital for Special Surgery scores, maximal flexion, and radiographs. The minimum followup for functional and radiographic evaluations was 2 years (median, 4.8 years; range, 2-8.7 years). We performed a survival analysis on all patients for aseptic loosening.

RESULTS

Three hundred sixty knees (52%) could achieve ≥ 135° maximum flexion. Six of the 698 knees (0.9%) developed aseptic loosening (three femoral and three tibial). The survival at 5 years for aseptic loosening was 99.1%. The overall survival for aseptic failure did not differ between knees that achieved HF and those that did not.

CONCLUSIONS

We observed a low incidence of early aseptic loosening of HF designs in this series. Our findings suggest HF TKAs have high survival in Asian patients at 5 years although half of the patients attained maximum flexion more than 135° postoperatively.

Brief followup report: Does high-flexion total knee arthroplasty allow deep flexion safely in Asian patients?

BACKGROUND

The long-term survivorship of TKA in Asian countries is comparable to that in Western countries. High-flexion TKA designs were introduced to improve flexion after TKA. However, several studies suggest high-flexion designs are at greater risk of femoral component loosening compared with conventional TKA designs. We previously reported a revision rate of 21% at 11 to 45 months; this report is intended as a followup to that study.

QUESTIONS/PURPOSES

Do implant survival and function decrease with time and do high-flexion activities increase the risk of premature failure?

METHODS

We prospectively followed 72 Nexgen LPS-flex fixed TKAs in 47 patients implanted by a single surgeon between March 2003 and September 2004. We determined the probability of survival using revision as an end point and compared survival between those who could and those who could not perform high-flexion activities. Minimum followup was 0.9 years (median, 6.5 years; range, 0.9-8.6 years).

RESULTS

Twenty-five patients (33 knees) underwent revision for aseptic loosening of the femoral component at a mean of 4 years (range, 1-8 years). The probability of revision-free survival for aseptic loosening was 67% and 52% at 5 and 8 years, respectively. Eight-year cumulative survivorship was lower in patients capable of squatting, kneeling, or sitting crosslegged (31% compared with 78%). There were no differences in the pre- and postoperative mean Hospital for Special Surgery scores and maximum knee flexion degrees whether or not high-flexion activities could be achieved.

CONCLUSIONS

Overall midterm high-flexion TKA survival in our Asian cohort was lower than that of conventional and other high-flexion designs. This unusually high rate of femoral component loosening was associated with postoperative high-flexion activities.

Mid-term Results of Total Knee Arthroplasty Using PFC Sigma RP-F

Purpose

We compared the mid-term results after total knee arthroplasty (TKA) using PFC Sigma RP-F mobile model with PFC Sigma PS fixed model.

Materials and Methods

We analyzed 45 knees that underwent TKA with PFC Sigma RP-Fn (study group) and 45 knees with PFC Sigma PS (control group). The mean follow-up period was 65 months (range, 60-69 months). The evaluation system of the American knee society was used for clinical and radiological assessment. Also, the maximal knee flexion angle was assessed.

Results

The mean maximum flexion angle in the study group (135°) was greater than that in the control group (125°) at the early post-operation & final follow-up period (p=0.033). The range of motion (ROM) in the study group was recovered earlier at the postoperative 6 months, and ROM gain was improved to a greater extent at the final follow-up period (p=0.039). The knee score and function score and radiographic evaluation were no difference between the two groups (p>0.05) at the final follow-up. The two cases of radiolucency in posterior condyle and medial tibial plateau and one case of patellar elongation were seen in the study group.

Conclusions

The PFC Sigma RP-F mobile system appears to facilitate greater maximum flexion angle and ROM gain with two cases of radiolucent line.

High-flex rotating platform knee implants: two- to 6-year results of a prospective study

We prospectively enrolled 48 patients (53 knees), scheduled for high-flex posterior-stabilized rotating platform knee implant arthroplasty (PFCΣRPF) to our study. Performance of this implant, introduced in 2005, has been reported upon only up to 2 years. We report its 2- to 6-year postoperative clinical and radiographic results in 47 patients (52 knees). Mean Knee Society score improved from 35.7 to 96. Mean function score improved from 55.2 to 90.6. Postoperative knee flexion averaged 130° (95°-155°), 81% patients could sit cross legged, 53% could sit on floor, and 21% could squat. Kaplan-Meier survival rate was 100% at average 50.2 months (26-72 months). No patient had any spin-out of rotating bearing. Supervised radiographs were analyzed, which showed no osteolysis or component loosening.

The Columbus Knee System: 4-Year Results of a New Deep Flexion Design Compared to the NexGen Full Flex Implant

The Columbus knee system is designed as a standard knee implant to allow high flexion without additional bone resection. Between August, 2004 and March, 2010 we performed 109 total knee arthroplasties of the Columbus knee system in 101 consecutive patients suffering from primary arthrosis of the knee. Mean age was 72.4 years in women and 70.3 years in men. Mean followup was 47.3 months. The 4-year results of a group of patients who received the NexGen Full Flex implant operated by the same surgeon were used for comparison. Mean total knee score was Columbus: 175.6 and NexGen Flex: 183.4; P = 0.037. Mean operation time was 53 min for Columbus and 66 min for NexGen Flex; P < 0.001. With new streamlined instruments operative time became 60 min for the Columbus; P > 0.05. Radiological assessment showed no signs of loosening for both groups. Therefore, the Columbus knee system can be recommended for flexion angles up to 140°.

A Comparison of the Clinical and Radiographic Results of Press Fit Condylar Rotating-Platform High-Flexion and Low Contact Stress Mobile Bearing Prosthesis in Total Knee Arthroplasty: Short term Results

Purpose

This study compared the results of rotating-platform high-flexion (RP-F) total knee arthroplasty with low contact stress (LCS) for clinical and radiographical assessment after a short-term period.

Materials and Methods

68 total knee arthroplasties using a RP-F and LCS system were analyzed retrospectively. Thirty-five of the 68 were osteoarthritic knees and were followed-up for more than 2 years. The clinical evaluation included range of motion (ROM), Knee Society Knee Score and Function Score (KSKS and KSFS), tailor position and kneeling. The radiographic evaluation included femorotibial angle, position of implants, radiolucent line and position of patella.

Results

The postoperative ROM, KSKS, and KSFS improved statistically in both implants. Comparing RP-F with LCS there were statistically no differences in ROM (p=0.863), KSKS (p=0.835), KSFS (p=0.535) and tailor position (p=0.489). There were no significant radiographic differences.

Conclusions

Total knee arthroplasty with RP-F and LCS showed similar clinical and radiographic results; it also showed excellent and predictable results at the short-term follow up. However, in RP-F there was 1 case of early osteolysis, 1 case of patella clunk syndrome and 1 case of painful patella crepitus; therefore, further case studies and follow-up are needed.

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.