Ten to fourteen year survival and functional analysis of the AGC total knee replacement system

The Optimal Dose, Efficacy and Safety of Tranexamic Acid and Epsilon-Aminocaproic Acid to Reduce Bleeding in TKA: A Systematic Review and Bayesian Network Meta-analysis

OBJECTIVE

The optimal dose and efficacy of tranexamic acid (TXA) and epsilon-aminocaproic acid (EACA) in total knee arthroplasty (TKA) were under controversial, and we aimed to make comparisons between different doses of TXA and EACA in intravenous (IV) or intra-articular (IA) applications in patients undergoing TKA.

METHODS

This network meta-analysis was guided by the Priority Reporting Initiative for Systematic Assessment and Meta-Analysis (PRISMA). According to the administrations of antifibrinolytic agents, patients in eligible studies were divided into three subgroups: (i) IA applications of TXA and EACA; (ii) IV applications (g) of TXA and EACA; (iii) IV applications (mg/kg) of TXA and EACA. Total blood loss (TBL), hemoglobin (HB) drops and transfusion rates were the primary outcomes, while drainage volume, pulmonary embolism (PE) or deep vein thrombosis (DVT) risk were the secondary outcomes. A multivariate Bayesian random-effects model was adopted in the network analysis.

RESULTS

A total of 38 eligible trials with different regimens were assessed. Overall inconsistency and heterogeneity were acceptable. Taking all primary outcomes into account, 1.0-3.0 g TXA were most effective in IA applications, 1-6 g TXA and 10-14 g EACA were most effective in IV applications (g), while 30 mg/kg TXA and 150 mg/kg EACA were most effective in IV applications (mg/kg). None of the regimens showed increasing risk for pulmonary embolism (PE) or deep vein thrombosis (DVT) compared with placebo.

CONCLUSION

0 g IA TXA, 1.0 g IV TXA or 10.0 g IV EACA, as well as 30 mg/kg IV TXA or 150 mg/kg IV EACA were most effective and enough to control bleeding for patients after TKA. TXA was at least 5 times more potent than EACA.

Combination of Intravenous and Intra-Articular Application of Tranexamic Acid and Epsilon-Aminocaproic Acid in Primary Total Knee Arthroplasty: A Prospective Randomized Controlled Trial

OBJECTIVE

There were limited randomized controlled trials (RCTs) of epsilon-aminocaproic acid (EACA) versus tranexamic acid (TXA) in total knee arthroplasty (TKA). The aim of the study was to compare the efficacy and safety of TXA and EACA in the combination of intravenous (IV) and intra-articular (IA) administration on reducing blood loss in patients following primary TKA.

METHODS

From January 2020 to January 2021, a total of 181 patients undergoing a primary unilateral TKA were enrolled in this prospective randomized controlled trial. Patients in the TXA group (n = 90) received 20 mg/kg of intravenous TXA preoperatively, 1 g of intra-articular TXA intraoperatively, and three doses of 20 mg/kg intravenous TXA at 0, 3, 6 h postoperatively. Patients in the EACA group (n = 91) received 120 mg/kg of intravenous EACA preoperatively, 2 g of intra-articular EACA intraoperatively, and three doses of 40 mg/kg intravenous EACA at 0, 3, 6 h postoperatively. The primary outcomes were total blood loss (TBL), transfusion rates and drop of hemoglobin (HB) level. The secondary outcomes included postoperative hospital stays and postoperative complications. The chi-square tests and Fisher's exact tests were utilized to compare categorical variables, while the independent-samples t-tests and Mann-Whitney tests were used to compare continuous variables.

RESULTS

The patients who received TXA averaged less TBL than the patients who received EACA (831.83 ml vs 1065.49 ml, P = 0.015), and HB drop in TXA group was generally less than that of EACA group on postoperative day 1 and 3 (20.84 ± 9.48 g/L vs 24.99 ± 9.40 g/L, P = 0.004; 31.28 ± 11.19 vs 35.46 ± 12.26 g/L, P = 0.047). The length of postoperative stays in EACA group was 3.66 ± 0.81 day, which is longer than 2.62 ± 0.68 day in TXA group (P < 0.001). No transfusions were required in either group. The risk of nausea and vomiting in TXA group was significantly higher than that in EACA group (11/90 vs 0/91, P < 0.01).

CONCLUSION

Although the TBL and HB drop were slightly greater in EACA group, these results were not clinically important, given that no transfusions were required. EACA could be an alternative to TXA, especially for patients with severe nausea and vomiting after using TXA postoperatively. Further studies are needed to adjust dosage of EACA to make better comparison of the two drugs.

Anthropometric Measures of the Posterior Condyles: Gender Differences and Correlation to Implant Sizing

There is abundant data concerning morphological dimensions of the distal femur, particularly in women, which has led to redesign of the femoral component in total knee arthroplasty (TKA). Clinical experience reveals existing asymmetry of the femoral posterior condyles, yet current implant designs have a symmetrical femoral component. The objectives of this study were to analyze the dimensions of posterior condylar bone resection from a group of patients undergoing TKA and correlate the measurements to one prosthetic system. We retrospectively reviewed single surgeon morphological data from the posterior condyles of 105 knees during TKA. The study included 54 males and 51 females. Measurement of the posterior condylar bones was performed with a standard metric metal ruler by one investigator. Known dimensions of a single type of implant design were compared with the resection data. The average difference of posterior medial and lateral condylar width was 5.7 and 5.3 mm in males and females, respectively. The average host posterolateral condylar bone was 5.4 mm less than the trial implant across five sizes in both males and females. Results suggest that the dimension of the posterior lateral condyle is much smaller than the dimension of the implant in both groups of patients. Dimension of the posterior medial is close to dimension of the implant. Overhang of the component posterolaterally can create soft tissue irritation and result in postoperative pain and decreased range of motion. Our results increase awareness of the dimensions of the native posterolateral condyle and may influence future design of femoral implants used in total knee arthroplasty.

Comparison of simultaneous bilateral versus unilateral total knee replacement on pain levels and functional recovery

BACKGROUND

Total knee replacement is a common operative procedure to improve pain, function, and quality of life in patients with end stage knee osteoarthritis. The current study aimed to compare simultaneous bilateral versus unilateral total knee replacement on pain intensity and recovery of function.

METHODS

A total of 80 patients (bilateral 50, unilateral 30) aged 63.28 (9.4) years undergone total knee replacement participated in the current study. The participants were admitted for 5-7 days in the hospital. Participants in both the group received similar inpatient and outpatient physiotherapy sessions. Pain intensity and function capacity were assessed at baseline, day 7, and day 30 postoperatively using visual analogue scale and lower extremity functional scale, respectively. Repeated measures analysis of variance was used to analyze the data.

RESULTS

Both groups showed a significant reduction of pain intensity (Day 0, mean 8.9, SD 1.0; Day 30, mean 2.2, SD 1.3 in bilateral total knee replacement; Day 0, mean 8.8, SD 1.1; Day 30, mean 2.0, SD 1.5 in unilateral total knee replacement; p < 0.001) and improvement in the functional capacity (Day 0, mean 16.2, SD 10.1; Day 30, mean 55.6, SD 14.6 in bilateral total knee replacement; Day 0, mean 19.1, SD 9.1; Day 30, mean 56.7, SD 15.8 in unilateral total knee replacement; p < 0.001) following total knee replacement at 30 days post-operatively. However, there was a non-significant difference noted between bilateral versus unilateral total knee replacement on the reduction of pain intensity (mean changes, 6.9 versus 6.8) and improvement in the functional capacity (mean changes, 39.4 versus 37.6) at 30 days post-operatively (p > 0.05).

CONCLUSION

Simultaneous bilateral total knee replacement was associated with a similar reduction of pain intensity and recovery of function compared to unilateral total knee replacement, suggesting the use of simultaneous bilateral total knee replacement in patients with bilateral knee osteoarthritis since its costs and rehabilitation process could be reduced compared to staged bilateral total knee replacement.

Convincing long-term results independent from the postoperative leg alignment following cementless total knee arthroplasty

BACKGROUND

Cementless primary total knee arthroplasty shows numerous advantages compared with cemented implants (e.g., shorter operation time, preservation of the bone stock). Up to now an increasing number of clinical long-term studies exist. Despite this fact, there is no evidence about the influence of the postoperative leg alignment on the results of cementless knee arthroplasty. There is no work on the clinical outcome of the specific implant, which was used in this study (VANGUARD®, ZimmerBiomet). The purpose of this study was to assess the clinical and radiological long-term results after cementless knee arthroplasty in relation to the postoperative mechanical leg alignment.

METHODS

Clinical and radiological results were retrospectively assessed in 83 patients at 10.3 years (ranging from 9.6 to 11.8 years) after implantation. Hip-knee-ankle angle (HKA) was measured, and the patients were separated into a corrected (HKA between three degrees of varus and three degrees of valgus, n = 60) and a varus/valgus (HKA > 3° of varus and valgus, n = 23) group.

RESULTS

Up to the time of the clinical follow-up, three out of 83 patients already underwent a revision surgery due to a deep infection (3.6%). Tegner-Lysholm Knee scale was 89.1 in the corrected group and 88.8 in the varus/valgus group (p = .94). The mean Knee Injury and Osteoarthritis Outcome score (KOOS) was 81.2 in the corrected group and 82.4 in the varus/valgus group (p = .63).

CONCLUSIONS

Results of this study showed convincing clinical and radiological results after primary cementless knee arthroplasty. Under- or overcorrected postoperative mechanical leg alignments did not influence the long-term clinical results.

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.

Effect of Methylprednisolone in Periarticular Infiltration for Primary Total Knee Arthroplasty on Pain and Rehabilitation

BACKGROUND

Optimal pain management after total knee arthroplasty (TKA) is important to ensure timely rehabilitation and patient satisfaction. This study examines the efficacy of adding corticosteroid in periarticular infiltration cocktail with relation to postoperative pain management and rehabilitation in patients undergoing simultaneous bilateral TKA.

METHODS

Fifty patients with symptomatic end-stage bilateral knee osteoarthritis undergoing bilateral TKA under the same anesthetic were recruited. More painful knee was operated first, and the study solution containing ropivacaine, clonidine, epinephrine, and ketorolac with methylprednisolone was infiltrated in one knee and an identical mixture but without methylprednisolone was infiltrated in the second knee. Outcome measures included comparison of visual analogue scale on movement of each knee and range of motion achieved during the first three days after surgery.

RESULTS

Differences in visual analogue scale score and range of motion at day one and three between the two groups of knees were significant (P < .05). Postoperative inflammation and the ability to straight leg raise showed better trends in the knees receiving prednisolone although this did not reach statistical significance.

CONCLUSION

Addition of methylprednisolone to periarticular infiltration cocktail for patients undergoing TKA has significant influence on reduction of pain in the early postoperative period and patients are able to regain knee flexion more quickly.

A study on dynamic monitoring, components, and risk factors of embolism during total knee arthroplasty

BACKGROUND

Fat embolism is a common complication of orthopedic surgery. However, the exact component and risk factor responsible for this complication remains unelucidated. This study aimed to detect the origin of the pulmonary embolus and identify relevant risk factors of pulmonary embolism in total knee replacement.

METHODS

A total of 40 osteoarthritis patients who underwent primary unilateral TKA were recruited into this study. Transesophageal echocardiography (TEE) was utilized to dynamically monitor the embolism. Pulmonary arterial pressure was recorded and biopsies were obtained from the medullary cavity during surgery.

RESULTS

After tourniquet release, the arterial embolism was observed by TEE to have a peak signal at 30 seconds when pulmonary arterial pressure was increased by 25% to 40% (P = .002). The pathology study of the embolism revealed its bone marrow origin. Total embolus quantity was positively correlated with age (P = .021), body mass index (BMI, P = .041), and fat content of the bone marrow (P = .003). Logistic regression analysis revealed that the fat content of the marrow (OR: 1.432, 95% CI: 1.335-1.592), age (OR: 1.632, 95% CI: 1.445-1.832), and BMI (OR: 1.231, 95% CI: 1.032-1.381) were risk factors for pulmonary hypertension.

CONCLUSION

This study revealed that the embolus detected in the right atrium was derived from bone marrow tissues, and this led to pulmonary arterial pressure fluctuations after tourniquet release. Therefore, elderly patients who have high BMI or bone marrow fat content are at high-risk for pulmonary fat embolism during TKA.

Good validity and reliability of the forgotten joint score in evaluating the outcome of total knee arthroplasty

Background and purpose - When evaluating the outcome after total knee arthroplasty (TKA), increasing emphasis has been put on patient satisfaction and ability to perform activities of daily living. To address this, the forgotten joint score (FJS) for assessment of knee awareness has been developed. We investigated the validity and reliability of the FJS. Patients and methods - A Danish version of the FJS questionnaire was created according to internationally accepted standards. 360 participants who underwent primary TKA were invited to participate in the study. Of these, 315 were included in a validity study and 150 in a reliability study. Correlation between the Oxford knee score (OKS) and the FJS was examined and test-retest evaluation was performed. A ceiling effect was defined as participants reaching a score within 15% of the maximum achievable score. Results - The validity study revealed a strong correlation between the FJS and the OKS (intraclass correlation coefficient (ICC) = 0.81, 95% CI: 0.77-0.85; p < 0.001). The test-retest evaluation showed almost perfect reliability for the FJS total score (ICC = 0.91, 95% CI: 0.88-0.94) and substantial reliability or better for individual items of the FJS (ICC? 0.79). We found a high level of internal consistency (Cronbach's? = 0.96). The ceiling effect for the FJS was 16%, as compared to 37% for the OKS. Interpretation - The FJS showed good construct validity and test-retest reliability. It had a lower ceiling effect than the OKS. The FJS appears to be a promising tool for evaluation of small differences in knee performance in groups of patients with good clinical results after TKA.

Comparison of mouse and human ankles and establishment of mouse ankle osteoarthritis models by surgically-induced instability

OBJECTIVE

Prevalence of ankle osteoarthritis (OA) is lower than that of knee OA, however, the molecular mechanisms underlying the difference remain unrevealed. In the present study, we developed mouse ankle OA models for use as tools to investigate pathophysiology of ankle OA and molecular characteristics of ankle cartilage.

DESIGN

We anatomically and histologically examined ankle and knee joints of C57BL/6 mice, and compared them with human samples. We examined joints of 8-week-old and 25-month-old mice. For experimental models, we developed three different ankle OA models: a medial model, a lateral model, and a bilateral model, by resection of respective structures. OA severity was evaluated 8 weeks after the surgery by safranin O staining, and cartilage degradation in the medial model was sequentially examined.

RESULTS

Anatomical and histological features of human and mouse ankle joints were comparable. Additionally, the mouse ankle joint was more resistant to cartilage degeneration with aging than the mouse knee joint. In the medial model, the tibiotalar joint was markedly affected while the subtalar joint was less degenerated. In the lateral model, the subtalar joint was mainly affected while the tibiotalar joint was less altered. In the bilateral model, both joints were markedly degenerated. In the time course of the medial model, TdT-mediated dUTP nick end labeling (TUNEL) staining and Adamts5 expression were enhanced at early and middle stages, while Mmp13 expression was gradually increased during the OA development.

CONCLUSION

Since human and mouse ankles are comparable, the present models will contribute to ankle OA pathophysiology and general cartilage research in future.

Does knee awareness differ between different knee arthroplasty prostheses? A matched, case-control, cross-sectional study

Background

Low knee awareness after Total Knee Arthroplasty (TKA) has become the ultimate goal in trying to achieve a natural feeling knee that meet patient expectations. To accommodate this manufacturers of TKAs have developed new prosthetic designs that potentially could give patients a more natural feeling knee during activities.

The purpose af this study was to compare the Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) of patients treated with a previous generation standard Cruciate Retaining (CR) TKA to the scores obtained by patients treated with a newer generation CR TKA or a mobile bearing CR TKA.

Methods

We identified all patients receiving a new generation CR TKA or mobile bearing TKA at our institution between 2010 and 2012. These were matched to a population of patients receiving a standard CR TKA regarding age, gender, year of surgery, Kellgren-Lawrence (KL) grade and pre- and postoperative knee alignment. Patients were asked to complete the FJS and OKS questionnaires. Of the 316 patients completing the survey 64 standard CR TKAs to 35 new generation CR TKAs and 121 standard CR TKAs to 68 mobile bearing TKAs were matched. The FJS and OKS scores of the three TKA designs were compared.

Results

When comparing the new generation CR TKAs to the standard CR TKAs we found statistically significant higher OKS and FJS scores (6 (p = 0.04) and 16 (p = 0.03) points respectively) for the new generation CR TKAs. When comparing the mobile bearing TKAs to the standard CR TKAs we found a statistically significant higher OKS score (3 points, p = 0.04), and a higher but non-significant FJS score (4 points, p = 0.48) for the mobile bearing TKAs.

Conclusions

Patients receiving the new generation CR TKA obtained higher FJS and OKS scores when compared to patients receiving a standard CR TKA, indicating that the use of this newer prosthetic design facilitate less knee awareness and better function after TKA.

Knee awareness and functionality after simultaneous bilateral vs unilateral total knee arthroplasty

AIM: To investigate knee awareness and functional outcomes in patients treated with simultaneous bilateral vs unilateral total knee arthroplasty (TKA).

METHODS: Through a database search, we identified 210 patients who had undergone unilateral TKA (UTKA) and 65 patients who had undergone simultaneous bilateral TKA (SBTKA) at our institution between 2010 and 2012. All TKAs were cemented and cruciate retaining. The mean follow-up period was 3.2 (2 to 4) years. All the patients had symptomatic and debilitating unilateral or bilateral osteoarthritis for which all conservative and non-surgical treatments were failed, thus preoperatively the patients had poor functionality. All patients were asked to complete Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) questionnaires. The patients were matched according to age, gender, year of surgery, Kellgren-Lawrence score and pre- and postoperative overall knee alignment. The FJS and OKS questionnaire results of the two groups were then compared.

RESULTS: A mixed-effects model was used to analyze differences between SBTKA and UTKA. OKS: The mean difference in the OKS between the patients who had undergone SBTKA and those who had undergone UTKA was 1.5, which was not statistically significant (CI = -0.9:4.0, P-value = 0.228). The mean OKS of the SBTKA patients was 37.6 (SD = 9.0), and the mean OKS of the UTKA patients was 36.1 (SD = 9.9). FJS: The mean difference in the FJS between the patients who had undergone SBTKA and those who had undergone UTKA was 2.3, which was not statistically significant (CI = -6.2:10.8, P-value = 0.593). The mean FJS of the SBTKA patients was 59.9 (SD = 27.5), and the mean FJS of the UTKA patients was 57.5 (SD = 28.8).

CONCLUSION: SBTKA and UTKA patients exhibited similar joint functionality and knee awareness. Our results support the use of SBTKA in selected patients suffering from clinically symptomatic bilateral osteoarthritis.

Long term survivorship following Scorpio Total Knee Replacement

BACKGROUND

The Scorpio Total Knee Replacement (TKR) is one of the most commonly used prosthesis in the United Kingdom. Concerns arose at our institution that there was a high revision rate for this prosthesis. No study has assessed survivorship of this prosthesis over 10 years.

METHODS

Four hundred and fifty-six consecutive patients, who underwent a primary Scorpio TKR, were clinically and radiologically evaluated. WOMAC, Oxford Knee Score and all complications including the reason for revision surgery were recorded. The Knee Society Roentgenographic Evaluation and Scoring System was used to evaluate all radiographs for prosthesis alignment and degree of subsequent lucency. Survival analysis for the prosthesis was calculated using Kaplan-Meier curves, with revision as an end-point. Patient reported outcome measures were compared against radiographic evaluation.

RESULTS

At a mean of 12.5 years (range 10-14 years), 196 (43.0%) patients were available for review; 124 (27.2%) were lost to follow-up and 136 (29.8%) patients had died of unrelated causes. Seven (3.6%) patients required revision surgery at a mean of 5.4 years; five because of aseptic loosening and two because of septic loosening. Cumulative survival for the prosthesis was 99.5% for any cause at five years and 97.4% at 14 years. The mean OKS and WOMAC score at final follow-up was 30.64 (range 12-48) and 74 (18.9-100) respectively.

CONCLUSION

The Scorpio TKR has good long term survivorship and functional outcomes. There is no apparent increased revision rate for this prosthesis in our study.

LEVEL OF EVIDENCE

Level IV case series.

Knee arthroplasty with a medial rotating total knee replacement. Midterm clinical findings: a district general experience of 38 cases

BACKGROUND

The Medial Rotating Knee replacement (MRK) was first used in 1994, reporting high rates of satisfaction. It is designed to replicate natural knee kinematics and improve stability and function. There are limited studies on the mid-term clinical outcomes, in particular in a district general hospital (DGH) environment. This is the first study that we are aware of that evaluates the learning curve of the implementation of this knee system in this environment.

PATIENTS/METHOD

Between 2007 and 2009 we performed 38 consecutive MRK replacements (MAT ORTHO, UK) in 36 patients. The mean follow-up was four years. Patients were evaluated clinically, using OKS and patient questionnaire and radiographically (good/acceptable/poor) to assess outcome.

RESULTS

Mean age was 73.0 years. Mean pre-operative OKS was 17.7 (range 8-29), which rose to 38.1 (range 23-48) at latest follow up (p<0.005). Overall 71% of the patients were either satisfied (29%) or very satisfied (42%). 81% felt an improvement of the ability to go up or down stairs and 92% felt stable. All poor radiographic and the majority of acceptable outcomes were experienced in the first 50% of cases.

CONCLUSION

The MRK can be successfully implanted in a DGH environment. It improves pain and function comparably to standard TKRs, however, subjective improvement may be higher. Radiographic evaluation shows an acceptable learning curve.

LEVEL OF EVIDENCE

Level IV case series.

Does intramedullary canal irrigation reduce fat emboli? A randomized clinical trial with transesophageal echocardiography

The effect of medullary cavity irrigation on fat emboli during total knee arthroplasty (TKA) was evaluated. Thirty female patients with osteoarthritis were randomly assigned to undergo conventional TKA without irrigation (conventional group) or with medullary canal saline irrigation (irrigation group). The four-chamber view was monitored by transesophageal echocardiography (TEE) and echogenic reflections of fat emboli were observed. The grey-scale score and area ratio of fat emboli were calculated during TKA. Hemodynamic parameters were simultaneously monitored and showed no obvious change between two groups (P>0.05). The average grey-scale score (P=0.016) and area ratio (P=0.033) of emboli were significantly decreased in irrigation group. Removal of medullary contents by irrigation could significantly reduce the formation of fat emboli during TKA.

Risk factors for revision within 10 years of total knee arthroplasty

BACKGROUND

An in-depth understanding of risk factors for revision TKA is needed to minimize the burden of revision surgery. Previous studies indicate that hospital and community characteristics may influence outcomes after TKA, but a detailed investigation in a diverse population is warranted to identify opportunities for quality improvement.

QUESTIONS/PURPOSES

We asked: (1) What is the frequency of revision TKA within 10 years of primary arthroplasty? (2) Which patient demographic factors are associated with revision within 10 years of TKA? (3) Which community and institutional characteristics are associated with revision within 10 years of TKA?

METHODS

We identified 301,955 patients who underwent primary TKAs in New York or California from 1997 to 2005 from statewide databases. Identifier codes were used to determine whether they underwent revision TKA. Patient, community, and hospital characteristics were analyzed using multivariable regression modeling to determine predictors for revision.

RESULTS

The frequency of revision was 4.0% at 5 years after the index arthroplasty and 8.9% at 9-years. Patients between 50 and 75 years old had a lower risk of revision than patients younger than 50 years (hazard ratio [HR], 0.47; 95% CI, 0.44, 0.50). Black patients were at increased risk for needing revision surgery (HR, 1.39; 95% CI, 1.29, 1.49) after adjustment for insurance type, poverty level, and education. Women (HR, 0.82; 95% CI, 0.79, 0.86) and Medicare recipients (HR, 0.82; 95% CI, 0.79, 0.86) were less likely to undergo revision surgery, whereas those from the most educated (HR, 1.09; 95% CI, 1.02, 1.16) and the poorest communities (HR, 1.08; 95% CI, 1.01, 1.15) had modest increases in risk of revision. Mid-volume hospitals (200-400 annual cases) had a reduction of early revision (HR, 0.91; 95% CI, 0.83, 0.99) compared with those performing less than 200 cases annually, whereas higher-volume hospitals (greater than 400 cases) showed little effect compared with low-volume hospitals.

CONCLUSIONS

Patient, community, and institutional characteristics affect the risk for revision within 10 years of index TKA. These data can be used to develop process improvement and implant surveillance strategies among high-risk patients.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

A retrospective medium- to long-term results of 1500 AGC total knee replacements - An independent centre functional follow up and survivorship

BACKGROUND

The AGC knee is one of the most widely used knee replacements in the world with good survivorship in national joint registries, including the Swedish within which it remains the gold standard of risk.

PURPOSE

However, there are few long term survivorship reviews from the centre other than those affiliated with the designer that also offer any insight into functional outcome. In this review, we present the results of one of the largest non-designer, medium- to long term follow-ups of the AGC knee replacement.

METHODS

A total of 1538 AGC knees were performed during a 15 year period, of which 902 were followed up by postal or telephone questionnaire using Oxford Knee Scores, Visual Analogue Scores (VASs) of function and pain and survival analysis.

RESULTS

87.5% of patients reported excellent or good functional reports at final follow up and 90.3% reporting excellent or good pain scores. There is a mean survivorship of 95.88% at 15 years from the 1538 knees. 85.7% of patients had an Oxford score of between 12 and 40, with 71.2% scoring between 0 and 30. 65.6% of patients responded with a VAS of 0 or 1 at rest (minimum pain = 0) and 53.9% reported a VAS of 0 or 1 while walking.

INTERPRETATION

Our study shows excellent mid to long term results in a large group of patients was achieved using the AGC TKR implanted by a variety of Consultants and trainee surgeons. This review and data from national registries suggest that in terms of both survivorship and function demonstrate the AGC knee replacement still remains the knee that newer designs must be measured against.

A minimum 5-year follow-up of an oxidized zirconium femoral prosthesis used for total knee arthroplasty

BACKGROUND

Bearing surface wear remains a potential concern amongst younger patients undergoing total knee arthroplasty (TKA). Because of the potential for lower prosthetic wear rates, oxidized zirconium is a potentially attractive bearing surface for TKA in young, active patients. This material is also well suited for patients with suspected nickel sensitivities as it has no measurable nickel content, in contrast to standard femoral bearings made of cobalt-chromium alloys. Although in vitro testing on knee wear simulators has demonstrated favorable wear characteristics of oxidized zirconium compared to traditional cobalt-chrome bearings, in vivo clinical outcome data with this novel bearing surface are sparse.

METHODS

We retrospectively reviewed 109 consecutive TKAs in 82 patients at a minimum of five years postoperatively to determine prosthetic survivorship and to assess whether any adverse clinical consequences could be attributed to this bearing. Knees were evaluated with Knee Society scores, UCLA activity scores, clinical examinations, and radiographs. The mean age for this cohort was 58.7 years.

RESULTS

Survivorship free of bearing related complications was 100% at a minimum of five years post-surgery. There were no revisions for loosening, osteolysis, implant failure, or deep infection. There were no knees with radiographic failure, visible wear, loosening, or osteolysis.

CONCLUSION

Oxidized zirconium remains an attractive option for patients with nickel sensitivities and in those patients at risk for prosthetic wear due to young age or high activity levels.

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

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

Do patients care about higher flexion in total knee arthroplasty? A randomized, controlled, double-blinded trial

Background

Little information exists to support that patients care about flexion beyond what is needed to perform activities of daily living (ADL) after Total knee arthroplasty (TKA). The purpose of this study was to investigate if the achievement of a higher degree of knee flexion after TKA would result in a better patient perceived outcome.

Methods

The study is a randomized, double-blinded, controlled trial in which 36 patients (mean age: 67.2 yrs) undergoing one-stage bilateral TKA randomly received a standard cruciate-retaining (CR) TKA in one knee and a high-flex posterior-stabilized (PS) TKA in the contra lateral knee. At follow-up ROM, satisfaction, pain, “feel” of the knee and the abilities in daily activities were assessed.

Results

At 1-year follow-up we found an expected significantly higher degree of knee flexion of 7° in the high-flex knees (p = 0.001). The high-flex TKA’s showed a mean active flexion of 121°. In both TKA’s the median VAS pain score was 0, the median VAS satisfaction score was 9, and the median VAS score of the patient “feel” of the knee was 9 at 1-year follow-up. Further, there were no significant differences between the knees in the performance of daily activities.

Conclusions

As expected the high-flex TKA showed increased knee flexion, but no significant differences in the patient perceived outcomes were found. This suggests little relevance to the patients of the difference in knee flexion – when flexion is of this magnitude – as pain free ROM and high patient satisfaction were achieved with both TKA’s.

Trial registration

ClinicalTrials.gov: NCT00294528

Ten-year results of the Press Fit Condylar Sigma total knee replacement

We report ten-year clinical and radiological follow-up data for the Sigma Press Fit Condylar total knee replacement system (Sigma PFC TKR). Between October 1998 and October 1999 a total of 235 consecutive PFC Sigma TKRs were carried out in 203 patients. Patients were seen at a specialist nurse-led clinic seven to ten days before admission and at six and 18 months, three, five and eight to ten years after surgery. Data were recorded prospectively at each clinic visit. Radiographs were obtained at the five- and eight- to ten-year follow-up appointments. Of the 203 patients, 147 (171 knees) were alive at ten years and 12 were lost to follow-up. A total of eight knees (3.4%) were revised, five for infection and three to change the polyethylene insert. The survival at ten years with an endpoint of revision for any reason was 95.9%, and with an endpoint of revision for aseptic failure was 98.7%. The mean American Knee Society Score (AKSS) was 79 (10 to 99) at eight to ten years, compared with 31 (2 to 62) pre-operatively. Of 109 knee with radiographs reviewed, 47 knees had radiolucent lines but none showed evidence of loosening.

Early migration of tibial components is associated with late revision: a systematic review and meta-analysis of 21,000 knee arthroplasties

PURPOSE

We performed two parallel systematic reviews and meta-analyses to determine the association between early migration of tibial components and late aseptic revision.

METHODS

One review comprised early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were determined according to that of several national joint registries: < 5% revision at 10 years.

RESULTS

Following an elaborate literature search, 50 studies (involving 847 total knee prostheses (TKPs)) were included in the RSA review and 56 studies (20,599 TKPs) were included in the survival review. The results showed that for every mm increase in migration there was an 8% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, migration up to 0.5 mm was considered acceptable during the first postoperative year, while migration of 1.6 mm or more was unacceptable. TKPs with migration of between 0.5 and 1.6 mm were considered to be at risk of having revision rates higher than 5% at 10 years.

INTERPRETATION

There was a clinically relevant association between early migration of TKPs and late revision for loosening. The proposed migration thresholds can be implemented in a phased, evidence-based introduction of new types of knee prostheses, since they allow early detection of high-risk TKPs while exposing only a small number of patients.

Five-year results of total knee arthroplasty with the Vario Knee System: a prospective analysis

There have been no published reports detailing the clinical performance of the Vario Knee System (VKS) total knee arthroplasty (TKA) since its introduction in 2001. The current study was therefore undertaken to provide 5-year clinical and radiographic follow-up data for this implant. Over a 24-month period, 146 VKS TKAs were performed in 131 patients (mean age, 69 years). Prospective data and radiographs were obtained at 3 months, 1 year, and 5 years after surgery. Surgeons employed an anteromedial approach in which the cruciate was retained. The fixation method was hybrid (cemented tibia, uncemented femur) in 70% of patients, uncemented in 23%, and cemented in 7%. At 5 years, 106 patients (118 knees) were alive. Six patients (six knees) were lost to follow-up. Three knees (three patients) were revised. Five-year survival was 97.4% (95% confidence interval [CI]: 92.8-99.5) with an endpoint of revision for any reason and 99.0% (95% CI: 97.5-100) with an endpoint of revision for aseptic failure. Using the worst-case scenario, in which all six of these patients were considered as failures, survival was 91.4% (95% CI: 83.4-96.0). The mean preoperative knee and function scores improved from 37.5 and 62.1, respectively, to 90.6 and 97.4, respectively, 5 years after surgery. Radiographic loosening of either component was not observed in any of the 100 radiographs obtained. In conclusion, good clinical outcomes were observed after 5 years with the VKS TKA. Additional follow-up studies will be needed to ascertain whether this performance is maintained in the long term.

Long-term follow-up of anatomic graduated component total knee arthroplasty: a 15- to 20-year survival analysis

The aims of this study were to determine survival rate, the clinical performance, and radiologic results of an Anatomic Graduated Component (AGC) total knee arthroplasty (TKA). Survival analysis was assessed by analyzing all hospital records of 211 AGC TKAs in 177 patients after 15 to 20 years. The survival rate was 87%, with failure defined as revision for any reason including infection. The main reasons for failure were infection and failure of the metal-backed patellar component. Clinical evaluation of 30 patients (33 TKAs) and questionnaires of 20 patients (23 TKAs) were taken, showing moderate to good results (mean Knee Society Score, 51; mean Western Ontario and McMaster Universities Osteoarthritis index, 82; mean University of California Los Angeles score, 4). Radiologic evaluation of 13 TKAs in 12 patients showed that none was suspect for loosening. Three knees showed significant medial wear but no clinical complaints. In conclusion, this is one of the first studies showing that AGC total knee prosthesis has good results 15 to 20 years after surgery.

Validity of published outcome data concerning Anatomic Graduated Component total knee arthroplasty: a structured literature review including arthroplasty register data

PURPOSE

Total knee arthroplasty (TKA) as a treatment for end-stage osteoarthritis of the knee shows good results in terms of patient satisfaction. For the assessment of outcome and revision rate after total joint arthroplasty, there are two major data sources: clinical studies and national arthroplasty registers. The purpose of this study was to analyse the outcome of Anatomic Graduated Component (AGC) TKA reported in clinical studies and to perform a comparison with the outcome reported by national arthroplasty registers.

METHODS

A systematic literature review was performed using standardised methodology in order to determine the outcome and revision rate of AGC TKA. In a comprehensive meta-analysis of clinical studies and worldwide register results we examined the quality of the basic data and the occurrence and influence of potential bias factors. Confidence intervals were calculated to determine the statistical significance of differences.

RESULTS

We found significant differences as regards the revision rate measured in revisions per 100 observed component years. Compared to worldwide register data it turned out to be significantly lower in clinical studies published by the implant development team. Actually, they reported a revision rate of 0.18 revisions per 100 observed component years, whereas annual reports of national arthroplasty registers report 0.74 revisions per 100 observed component years. A comparison of the results from national arthroplasty registers of different countries revealed a significantly higher revision rate for Denmark in relation to worldwide register data.

CONCLUSIONS

A conventional meta-analysis of clinical studies is affected by the influence of the development team and therefore subject to bias. For the assessment of outcome arthroplasty register data should be rated as superior and, being used as reference data for the detection of potential bias factors in the clinical literature, could make an essential contribution to the quality of scientific meta-analysis.

Total knee arthroplasty in younger patients: a 13-year follow-up study

Total knee arthroplasty (TKA) is a well-established treatment at the end stage of a degenerated knee joint. This operative treatment generally relieves pain, improves physical function, and has a high level of patient satisfaction, especially in the elderly. Younger patients, however, are demanding and have a higher level of physical activity compared to elderly patients. One could therefore expect more mechanical problems such as prosthetic loosening and polyethylene wear after long-term follow-up. The goal of this retrospective cohort study was to determine the survival and long-term results of TKA in young patients. Patients who received a TKA at age 60 years or younger for any reason were included. Minimum follow-up was 10 years. Thirty-nine TKAs (Anatomic Graduate Components; Biomet, Warsaw, Indiana) in 31 patients were included. Average patient age was 52.6 years. There were 3 revisions because of infection; in 1 knee the patella was revised because of aseptic loosening. After an average 13-year follow-up, the survival rate was 89.7% and function scores showed a reasonably functioning TKA. There was no difference in survival rate and function scores between patients with rheumatoid arthritis and those with primary or secondary (posttraumatic) osteoarthritis. Our experience with TKA in a younger patient population has been encouraging. The risk of loosening and wear of the implant in our study is low, and this type of TKA also seems to be an effective and safe treatment for younger patients.

Comparison of simultaneous bilateral and staged bilateral total knee arthroplasty in terms of perioperative complications

We compared bilateral total knee arthroplasty (TKA) performed at a single session vs those performed at 2 separate sessions with respect to complications, amount of blood loss, and length of hospital stay. Study participants included 119 consecutive patients undergoing simultaneous bilateral TKA and an additional 119 patients undergoing staged bilateral TKA. Systemic complication in the simultaneous bilateral TKA was significantly higher statistically than that in the staged bilateral TKA. Therefore, performing simultaneous bilateral TKA in elderly or high-risk patients results in a significantly higher rate of systemic complications. Simultaneous bilateral TKA is a relatively safe and beneficial procedure with a minimal increase in the risk of systemic complications. However, this procedure should be conducted carefully, particularly in elderly and high-risk patients.

Retention of the posterior cruciate ligament versus the posterior stabilized design in total knee arthroplasty: a prospective randomized controlled clinical trial

BACKGROUND

Prosthetic design for the use in primary total knee arthroplasty has evolved into designs that preserve the posterior cruciate ligament (PCL) and those in which the ligament is routinely sacrificed (posterior stabilized). In patients with a functional PCL the decision which design is chosen depends largely on the favour and training of the surgeon.The objective of this study is to determine whether the patient's perceived outcome and speed of recovery differs between a posterior cruciate retaining total knee arthroplasty and a posterior stabilized total knee arthroplasty.

METHODS/DESIGN

A randomized controlled trial will be conducted. Patients who are admitted for primary unilateral TKA due to primary osteoarthrosis are included when the following inclusion criteria are met: non-fixed fixed varus or valgus deformity less than 10 degrees, age between 55 and 85 years, body mass index less than 35 kg/m(2) and ASA score (American Society of Anaesthesiologists) I or II. Patients are randomized in 2 groups. Patients in the posterior cruciate retaining group will receive a prosthesis with a posterior cut-out for the posterior cruciate ligament and relatively flat topography. In patients allocated to the posterior stabilized group, in which the posterior cruciate ligament is excised, the design may substitute for this function by an intercondylar tibial prominence that articulates with the femur in flexion. Measurements will take place preoperatively and 6 weeks, 3 months, 6 months and 1 year postoperatively.At all measurement points patient's perceived outcome will be assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Secondary outcome measures are quality of life (SF-36) and physician reported functional status and range of motion as determined with the Knee Society Clinical Rating System (KSS).

DISCUSSION

In the current practice both posterior cruciate retaining and posterior stabilized designs for total knee arthroplasty are being used. To date no studies have been performed determining whether there is a difference in patient's perceived outcome between the two designs. Additionally, there is a lack of studies determining the speed of recovery in both designs as most studies only determine the final outcome. This randomised controlled study has been designed to determine whether the patient's perceived outcome and speed of recovery differs between a posterior cruciate retaining total knee arthroplasty and a posterior stabilized total knee arthroplasty.

TRIAL REGISTRATION

The trial is registered in the Netherlands Trial Registry (NTR1673).

The mini-incision mid-vastus approach for total knee arthroplasty

OBJECTIVE

Rapid functional recovery and improved range of motion after total knee arthroplasty (TKA) without compromising implant position.

INDICATIONS

Osteoarthritis of the knee requiring TKA.

CONTRAINDICATIONS

Preoperative flexion < 80 degrees. Flexion contracture > 20 degrees. Body mass index > 40 kg/m(2). Fixed valgus deformity > 15 degrees. Relative: previous open surgery on the knee; systematic steroids (skin fragility); tall muscular males.

SURGICAL TECHNIQUE

Straight skin incision over the medial third of the patella from 2 cm proximal to the patella, and then to the level of the tibial tuberosity. Extension of capsular incision 2 cm into the vastus medialis muscle from a point 2 cm proximal to the patella. Deep incision around the medial border of the patella and distally to the level of the tibial tuberosity. The patella is displaced laterally but is not everted in flexion. Knee flexion and extension as necessary to move the soft-tissue surgical window for proximal or distal exposure. Hyperflexion of the knee only for insertion of the tibial component.

POSTOPERATIVE MANAGEMENT

Knee flexion exercises extension/flexion 0-0-70 degrees using continuous passive motion the day after surgery. Weight bearing to tolerance allowed at 1st day after surgery (walker, two crutches). Thrombosis prophylaxis.

RESULTS

69 patients with 74 TKAs done through the mini-incision mid-vastus approach were available with a minimum 1-year follow-up. A control group was evaluated retrospectively including 52 patients with 57 total knee replacements in which a standard medial parapatellar arthrotomy with patella eversion was used. At all clinical evaluations flexion and the ability to climb stairs were significantly superior in the mid-vastus group indicating a faster recovery and return to functional activities. There were no complications and the radiographic evaluation found no implant or limb malalignment, or signs of early loosening.

Resection arthroplasty for failed patellar components

A total of 1,401 primary total knee arthroplasties (TKA) were reviewed; 44 (3.2%) had at least the patellar component revised. Nine of these knees (eight patients) had insufficient bone stock to allow reimplantation of another patellar component. Clinical data on the nine knees were obtained with recent follow-up evaluation, review of their medical records and radiographs. Evaluation included Hospital for Special Surgery (HSS) scores. Average follow-up was 4 years and 7 months, 2-year range (2 months to 8 years and 4 months). Common factors found in these nine knees included: thin patella after primary TKR status, osteoarthritis, good range of motion and patella alta. Results were good to excellent in seven knees and fair in two. The untoward associations with patellectomy such as quadriceps lag, extension weakness and anterior knee pain were not experienced. Resection of the patellar component, without reimplantation, is an acceptable alternative in revision TKA lacking adequate remaining bone stock.

A randomised controlled trial of cemented versus cementless press-fit condylar total knee replacement: 15-year survival analysis

We report the long-term survival of a prospective randomised consecutive series of 501 primary knee replacements using the press-fit condylar posterior cruciate ligament-retaining prosthesis. Patients received either cemented (219 patients, 277 implants) or cementless (177 patients, 224 implants) fixation. Altogether, 44 of 501 knees (8.8%) underwent revision surgery (24 cemented vs 20 cementless). For cemented knees the 15-year survival rate was 80.7% (95% confidence interval (CI) 71.5 to 87.4) and for cementless knees it was 75.3% (95% CI 63.5 to 84.3). There was no significant difference between the two groups (cemented vs cementless; hazard ratio (HR) 0.83, 95% CI 0.45 to 1.52, p = 0.55). When comparing the covariates there was no significant difference in the rates of survival between the side of operation (HR 0.58, p = 0.07), age (HR 0.97, p = 0.10) and diagnosis (HR 1.25 p = 0.72). However, there was a significant gender difference, with males having a higher failure rate with cemented fixation (HR 2.48, p = 0.004). Females had a similar failure rate in both groups. This single-surgeon series, with no loss to follow-up, provides reliable data of the revision rates of one of the most commonly-used total knee replacements. The survival of the press-fit condylar total knee replacement remained good at 15 years, irrespective of the method of fixation.

A conservative approach is feasible in unexplained pain after knee replacement

Pain is the main indication for performing total knee replacement (TKR). In most patients after TKR there is an improvement, but a few continue to have pain. Generally, the cause of the pain can be addressed when it is identified. However, unexplained pain can be more difficult to manage because revision surgery is likely to be unrewarding in this group. In our study of 622 cemented TKRs in 512 patients with a mean age of 69 years (23 to 90) treated between January 1995 and August 1998, we identified 24 patients (knees) with unexplained pain at six months. This group was followed for five years (data was unavailable for 18 knees) and ten patients (55.5%) went on to show an improvement without intervention.

In the case of unexplained pain, management decisions must be carefully considered, but reassurance can be offered to patients that the pain will improve in more than half with time.

Five-year results of the Sigma total knee arthroplasty

The DePuy Sigma total knee arthroplasty (TKA) was introduced in 1997 as a modification of the Press Fit Condylar Knee (PFC) TKA and has been used extensively in the United Kingdom and worldwide. It is the most commonly used TKA in England and Wales, where it accounts for 36% of all primary TKA. The PFC was well established, with reported 10-year survival rates of 93-97%, but this study reports the first 5-year clinical and radiographic follow-up data for the Sigma TKA. Over a 10-month period, 212 Sigma TKAs were performed in 180 patients. Patients were seen at a specialist nurse-led clinic 7 to 10 days before admission and at 6 months, 18 months, 3 years and 5 years after surgery. Data were recorded prospectively at each visit. Radiographs were obtained at the 5-year follow-up appointment. Of 212 knees, 178 (151 patients) were alive at 5 years. Three were lost to follow up. Six knees (3.0%) were revised, five for infection and one underwent change of polyethylene insert at 4.9 years. Five-year survival with an endpoint of revision for any reason was 97.0%; with an endpoint of revision for aseptic failure it was 99.5%. The median American Knee Society knee rating score was 93 out of 100 at 5 years compared with 25 out of 100 at admission. Of 147 radiographs, none showed radiographic loosening of either component. Seventeen (11.6%) showed radiolucent lines. Twenty-eight (19.0%) had alignment outside the range of 7+/-3 degrees valgus. These results suggest that the Sigma TKA gives acceptable clinical results after 5 years. Further follow-up studies are required to see if this performance is maintained in the long term.

Predicting pain after total knee arthroplasty

Six hundred twenty-two primary total knee arthroplasties were studied prospectively in 512 patients. A group with no pain and one with severe pain at 5 years were statistically compared. The following were significant predictors of poor pain outcomes: age below 60 (17%) compared with above 60 (7%, P < .05). The first knee was most likely to be in the poor outcome group (13%) compared with the second knee (6%). In contrast, patients who underwent simultaneous bilateral arthroplasty faired better (2%, P < .01). Performing lateral release and sacrificing the posterior cruciate ligament also significantly predicted for poor pain outcomes but may have been influenced by selection bias. We conclude that avoiding surgery in patients younger than 60 and choosing a simultaneous approach to bilateral disease reduce the chance of poor pain outcomes.

Avoiding the potential pitfalls of minimally invasive total knee surgery

The performance of TKA through less than traditional visualization presents a new set of problem areas.

Highly cross-linked polyethylene: the debate is over--in opposition

Highly cross-linked polyethylene compared to conventional ultra high molecular weight polyethylene (UHMWPE) results in significantly decreased wear in hip simulators and early prospective randomized clinical studies. However, the contact stresses in a total knee bearing surface are much higher than in a total hip. As a result, fatigue wear mechanisms occur more typically in total knee compared with total hip arthroplasty. Cross-linking reduces the mechanical properties of UHMWPE including fatigue crack propagation resistance, which may limit its role in total knee arthroplasty. Although the in vitro and in vivo studies provide compelling evidence that highly cross-linked polyethylene may improve the longevity of total hip arthroplasty, it does not appear to offer similar benefits for total knee arthroplasty.

A case of dissociation of polyethylene from its metal baseplate in a "one piece" compression-moulded AGC tibial component

The Anatomic Graduated Component (AGC) total knee arthroplasty is a commonly used prosthesis with good long-term results. This longevity is thought to be due to the technique of manufacture of the polyethylene and its "one piece" design reducing backside wear. Despite the perception of the AGC tibial component being a monobloc, we report a case of dissociation of the polyethylene from the baseplate.

Neurological complications of lumbar artificial disc replacement and comparison of clinical results with those related to lumbar arthrodesis in the literature: results of a multicenter, prospective, randomized investigational device exemption study of Charité intervertebral disc

Object. Arthrodesis is the gold standard for surgical treatment of lumbar degenerative disc disease (DDD). Solid fusion, however, can cause stress and increased motion in the segments adjacent to the fused level. This may initiate and/or accelerate the adjacent-segment disease process. Artificial discs are designed to restore and maintain normal motion of the lumbar intervertebral segment. Restoring and maintaining normal motion of the segment reduces stresses and loads on adjacent level segments. A US Food and Drug Administration Investigational Device Exemptions multicentered study of the Charité artificial disc was completed. The control group consisted of individuals who underwent anterior lumbar interbody fusion involving BAK cages and iliac crest bone graft. This is the first report of Class I data in which a lumbar artificial disc is compared with lumbar fusion.

Methods. Of 304 individuals enrolled in the study, 205 were randomized to the Charité disc-treated group and 99 to the BAK fusion—treated (control) group. Neurological status was equivalent between the two groups at 6, 12, and 24 months postoperatively. The number of patients with major, minor, or other neurological complications was equivalent. There was a greater incidence of both major and minor complications in the BAK fusion group at 0 to 42 days postoperatively. Compared with data reported in the lumbar fusion literature, the Charité disc—treated patients had equivalent or better mean changes in visual analog scale and Oswestry Disability Index scores.

Conclusions. The Charité artificial disc is safe and effective for the treatment of single-level lumbar DDD, resulting in no higher incidence of neurological complications compared with BAK-assisted fusion and leading to equivalent or better outcomes compared with those obtained in the control group and those reported in the lumbar fusion literature.

Tight posterior cruciate ligament in posterior cruciate-retaining total knee arthroplasty: a cause of posteromedial subluxation of the femur

Posteromedial subluxation has been reported as a mode of failure with flat-on-flat articular geometry. Medical records were reviewed to find patients who developed progressive subluxation of the femur. From a consecutive series of 2,773 primary anatomically graduated components (AGC) knees, 6 patients developed progressive posterior subluxation of the femur. The mean interval between the index total knee arthroplasty (TKA) and the diagnosis of subluxation was 4.8 years. Five cases were revised at an average of 6.2 years after index TKA. Tightness of the posterior cruciate ligament (PCL) was observed in all revised cases. Progressive posterior subluxation is a rare complication after AGC knees. It is believed that the primary factor causing progressive subluxation is tightness of the PCL. The PCL should be recessed if PCL tightness is seen at surgery.

A study of polyethylene and modularity issues in >1000 posterior cruciate-retaining knees at 5 to 11 years

Polyethylene quality and production technique and monoblock versus modular design of tibial components affect the polyethylene wear of total knee arthroplasties (TKAs). We reviewed >1000 TKAs performed with the AGC prosthesis (Biomet, Warsaw, IN) using a uniform surgical technique with a 5- to 11-year follow-up. Of tibial components, 698 were of compression-molded monoblock design and 353 were of ram-extruded modular assembly design. The effect of the differences in tibial component design on the 5- to 11-year clinical and radiologic outcomes was studied. Higher rates of osteolysis, radiolucent lines, and revision were found with the ram-extruded modular design. This modular design is similar to most tibial component designs currently used in TKA, yet osteolysis in completely cemented components is described rarely. The TKAs done with a compression-molded monoblock design gave better clinical and radiologic results. The improved results may be due to polyethylene quality, assembly design, or a combination of these factors.