5- to 9-year survivorship of single-radius, posterior-stabilized TKA

Long-term survivorship of total knee arthroplasty with a single-radius, high-flexion posterior stabilized prosthesis

BACKGROUND

The purpose of this study was to determine functional outcomes, implant survival rate, and complications of a single-radius, high-flexion posterior stabilized (PS) total knee prosthesis at a minimum follow up of 10 years for a consecutive series.

METHODS

This retrospective observational study included 395 consecutive patients who underwent 585 single-radius, PS total knee arthroplasties (TKAs) between January 2009 and December 2009. Their functional outcomes, implant survival rates, radiological findings, and complications were evaluated.

RESULTS

At a mean follow up of 11.2 years (range, 10.6-11.8 years), 395 (80.8%) patients were available for review. At final follow up, preoperative Knee Society knee scores were improved from 37.3 to 80.1 (P < 0.05) and function scores were improved from 35.7 to 80.5 points (P < 0.05). Sixteen knees (2.7%) in 15 patients required revision surgery due to 11 septic loosening (1.9%) and five aseptic loosening events (0.8%). Cumulative survival for the prosthesis was 97.3% for any cause at 10 years. A total of 34 radiolucent lines (5.8%) were detected an average of 2.4 years following surgery and radiological assessment did not reveal any evidence of component migration at final follow up.

CONCLUSIONS

Single-radius, high-flexion PS TKA showed good long-term survival rates and clinical outcomes. Further study is required to determine whether limited radiolucency findings at the tibial component-tibial plateau could progress to or result in the loosening of components.

Comparison of functional outcomes between single-radius and multi-radius femoral components in primary total knee arthroplasty: a meta-analysis of randomized controlled trials

PURPOSE

Our purpose in the current meta-analysis was to compare the functional outcomes in patients who have received single-radius (SR) or multi-radius (MR) femoral components in randomized controlled trials (RCTs) for primary total knee arthroplasty (TKA). The hypothesis was that there would be no statistically significant difference between two groups in terms of functional outcomes.

MATERIALS AND METHODS

We searched the international electronic databases PubMed, Embase, and the Cochrane Central Register of Controlled Trials up to February 2020 for RCTs that compared functional outcomes of SR and MR femoral component designs after primary TKA. We performed a meta-analysis of nine RCTs using the Knee Society Score for the knee (KSS-knee), KSS-function, Knee Injury and Osteoarthritis Outcome Score (KOOS), Oxford Knee Score (OKS), degree of knee flexion, extension, and complications, including postoperative infection and revision surgery.

RESULTS

The meta-analysis revealed no statistically significant differences in all the analyzed variables, including KSS-knee, KSS-function, KOOS, OKS, knee flexion, and knee extension. For postoperative complications, no statistically significant differences were detected for femoral component designs in postoperative infection or incidence of revision surgery between the two groups.

CONCLUSIONS

The current meta-analysis of RCTs did not show any statistically significant differences between SR and MR femoral component designs in terms of postoperative functional outcomes. Evaluated outcomes included functional outcome scores, degree of knee flexion, extension, and complications. However, because of the limited clinical evidence of this study owing to the heterogeneity between the included RCTs, a careful approach should be made in order not to arrive at definite conclusions.

Mechanical alignment changes during flexion in total knee arthroplasty without affecting clinical outcomes

BACKGROUND

Primary aim of this study is to investigate if Hip-Knee-Ankle angle, measured in the coronal plane, changes with knee flexion after total knee arthroplasty. The secondary aim is to assess the relationship between Hip-Knee-Ankle during knee flexion and clinical outcome at mid-term follow up.

METHODS

334 computer assisted total knee arthroplasties were retrospectively evaluated. A total of 233 patients were available for assessment of clinical outcomes at last follow up (mean 35 months). Hip-Knee-Ankle angle at different degrees of knee flexion and components' alignment were recorded intraoperatively.

FINDINGS

Patients were stratified based on the preoperative alignment: 202 varus knees, 99 neutral knees, and 33 valgus knees. In the varus knee group, 146 patients (89%) maintained a neutral overall limb alignment when flexed to 20°, 118 (72%) remained neutrally aligned at 45° and 92 (54%) at 90°. In valgus knee group, 26 (90%) remained neutrally aligned at 20°, 22 (75%) at 45° and 16 (55%) at 90°. In neutrally-aligned knee group, 88 (96%) remained neutrally aligned at 20°, 73 (79%) at 45° and 61 (66%) at 90°. Femoral component external rotation was correlated with varus alignment in flexion. Good outcomes were reported in 181 (78%) cases, fair results in 28 (12%) cases, poor results in 24 (10%) of cases. Poor results were not correlated to Hip-Knee-Ankle angle at different knee flexion angles.

INTERPRETATION

This study demonstrates that intraoperative Hip-Knee-Ankle angle changes as the knee moves into deeper flexion. However, neutral Hip-Knee-Ankle through the range of motion does not correlate with superior outcomes.

Cementless Posteriorly Stabilized Total Knee Arthroplasty: Seven-Year Minimum Follow-Up Report

BACKGROUND

The purpose of this study is to evaluate (1) implant survivorship; (2) patient outcomes; (3) complications; and to (4) perform a radiographic analysis of cementless posteriorly stabilized total knee arthroplasty (TKA) patients at a minimum of 7-year follow-up.

METHODS

Our original cohort was composed of 114 consecutive cementless posteriorly stabilized total knee arthroplasties (110 patients) performed by a single surgeon between 2008 and 2010. Since our original report, 4 (1 bilateral) patients died and 2 were lost to follow-up. Therefore, there were 104 patients who had 107 knees available for final follow-up. The final cohort included 43 men and 61 women, who had a mean age of 69 years (range 47-87) and were followed from 7 to 9 years (mean 8 years). Patient outcomes and complications were obtained from electronic medical records. Radiographic assessment was done using the Knee Society Radiographic Evaluation System.

RESULTS

The all-cause survivorship was 98% (95% confidence interval 1.01-0.96). Since the original report, there has been 1 post-traumatic loosening of the tibial baseplate, and 1 revision for instability. There were no femoral revisions or patella revisions. The mean Knee Society pain score was 93 points (range 80-100) and the function score was 78 points (range 68-95). Excluding revisions, there was no evidence of progressive loosening of any implant components.

CONCLUSION

Based on these 7-year minimum follow-ups, femoral, tibial, and patellar cementless hydroxylapatite-coated beaded implants perform well at up to 9 years postoperatively and offer surgeons and patients a cementless option that may provide long-lasting biological fixation.

Long-term follow-up and survivorship of single-radius, posterior-stabilized total knee arthroplasty

BACKGROUND

We sought to determine the 10-year survivorship of single-radius, posterior-stabilized total knee arthroplasty (TKA) in Asian patients. We also aimed to determine whether the long-term clinical and radiographic results differed between patients with and without patellar resurfacing.

METHODS

This retrospective study included 148 (115 patients) consecutive single-radius, posterior-stabilized TKAs. Ten-year survivorship analysis was performed using the Kaplan-Meier method with additional surgery for any reason as the end-point. Furthermore, long-term clinical and radiographic results of 109 knees (74%; 84 patients) with more than 10-year follow-up were analyzed. Ten-year survivorship and long-term outcomes after surgery were determined, and outcomes were compared between patients with and without patellar resurfacing.

RESULTS

The cumulative survival rate of the single-radius posterior-stabilized TKA of 148 knees was 97.7% (95% confidence interval, 93.1%-99.3%) at 10 years after surgery. Three knees required additional surgery during the 10-year follow-up because of one case of instability and two cases of periprosthetic infections. Mean postoperative Knee Society knee score and function score were 97 points and 75 points, respectively. There were no cases of aseptic loosening of the prosthesis, even though a non-progressive radiolucent line was found in 10 (9%) knees. There were no differences in postoperative scores and degree of patellar tilt and displacement between patients with and without patellar resurfacing.

CONCLUSIONS

Single-radius, posterior-stabilized TKA showed satisfactory long-term clinical and radiographic outcomes in Asian patients regardless of patellar resurfacing, with comparable survivorship to that reported in westerners.

Better functional outcome after single-radius TKA compared with multi-radius TKA

PURPOSE

To determine whether the design of the femoral component influenced patient outcomes.

METHODS

Two hundred and thirty-seven patients were randomized to compare functional outcomes between single-radius TKA (SR, 118 patients) and multi-radius TKA (MR, 119 patients) with a minimum follow-up of 5 years. Prospective pre- and postoperative assessments were performed by the clinical and radiological criteria of the Knee Society Score (KSS), WOMAC and Short-Form 12 (SF12) questionnaires. The extension mechanism was assessed based on the quadriceps strength and chair test. Patient satisfaction was also assessed.

RESULTS

The median follow-up was 5.7 (range 5-7) years. At last follow-up, significant better KSSs (p = 0.001), range of motion (p = 0.001), extension lag (p = 0.020), quadriceps strength (p = 0.004), chair test (p = 0.032) and WOMAC pain (p = 0.002) were found in the SR group. Moreover, the improvements of these variables were early in the SR group (from 6 postoperative months). There were no significant differences in WOMAC function or SF12 physical and mental components. The revision rate and implant survival were similar in both groups. Satisfaction rate was significantly higher in SR group (p = 0.032).

CONCLUSION

This study shows better results with SR cruciate-retaining femoral component than MR component. The use of SR system is recommended because, although the clinically relevant differences were moderate, the functional improvement was earlier and the patient satisfaction higher with this design.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Up to seven years' follow-up of short cemented stems in complex primary total knee arthroplasty: A prospective study

BACKGROUND

Although primary total knee arthroplasty (TKA) shows good clinical, functional and radiological results, it can be complicated by certain conditions or pathologies. The main objective of this study was to evaluate the global performance of short cemented metaphyseal stem components in patients undergoing complex primary TKA.

METHODS

This is a single-surgeon prospective case series of 91 patients who underwent complex primary TKA requiring short stem fixation between January 2009 and October 2014. Knee Society Scores, physical examinations, and radiological assessments were performed pre- and postoperatively at six weeks, three months, six months, 12months, and annually thereafter.

RESULTS

There were 40 females (46 TKAs) and 40 males (45 TKAs) in the study cohort. The left knee accounted for 52.7% of the surgeries. The average body-mass index (BMI) was 31.8kg/m². Knee Society Scores obtained at the latest follow-up showed 96.4% and 95.5% good-to-excellent results respectively for the Knee and Function sub-scores. Radiological assessment showed that all Knee Society roentgenographic scores were below 10, without any evidence of impending or possible failure. Only one revision was required in this cohort for a patient suffering a deep chronic infection. At seven years, the Kaplan-Meier survivorship analysis revealed a 100% survivorship for aseptic loosening and a 98.9% survivorship for infection and revision of the components for any reason.

CONCLUSION

This study demonstrated that TKA with short cemented stems resulted in good functional, clinical, and radiological outcomes for up to seven years for patients requiring complex TKA.

Annual revision rates of partial versus total knee arthroplasty: A comparative meta-analysis

BACKGROUND

Utilization of unicompartmental knee arthroplasty (UKA) and patellofemoral arthroplasty (PFA) as alternatives to total knee arthroplasty (TKA) for unicompartmental knee osteoarthritis (OA) has increased. However, no single resource consolidates survivorship data between TKA and partial resurfacing options for each variant of unicompartmental OA. This meta-analysis compared survivorship between TKA and medial UKA (MUKA), lateral UKA (LUKA) and PFA using annual revision rate as a standardized metric.

METHODS

A systematic literature search was performed for studies quantifying TKA, MUKA, LUKA and/or PFA implant survivorship. Studies were classified by evidence level and assessed for bias using the MINORS and PEDro instruments. Annual revision rates were calculated for each arthroplasty procedure as percentages/observed component-year, based on a Poisson-normal model with random effects using the R-statistical software package.

RESULTS

One hundred and twenty-four studies (113 cohort and 11 registry-based studies) met inclusion/exclusion criteria, providing data for 374,934 arthroplasties and 14,991 revisions. The overall evidence level was low, with 96.7% of studies classified as level III-IV. Annual revision rates were lowest for TKA (0.49%, CI 0.41 to 0.58), followed by MUKA (1.07%, CI 0.87 to 1.31), LUKA (1.13%, CI 0.69 to 1.83) and PFA (1.75%, CI 1.19 to 2.57). No difference was detected between revision rates for MUKA and LUKA (p=0.222).

CONCLUSIONS

Revisions of MUKA, LUKA and PFA occur at an annual rate of 2.18, 2.31 and 3.57-fold that of TKA, respectively. These estimates may be used to inform clinical decision-making, guide patient expectations and evaluate the cost-effectiveness of total versus partial knee replacement in the setting of unicompartmental OA.

Higher Total Knee Arthroplasty Revision Rates Among United States Blacks Than Whites: A Systematic Literature Review and Meta-Analysis

BACKGROUND

Reportedly 2% to 5.7% of total knee arthroplasties (TKAs) require revision within 5 years. The purpose of this study was to determine whether blacks are at higher risk of TKA revision than whites in the United States.

METHODS

We performed a systematic review of English-language articles published from 2000 to 2015. Study inclusion criteria were (1) performance of the study in the United States, (2) TKA as the primary procedure studied, (3) a follow-up period at least 2 years, (4) reporting of revision rates, and (5) analysis of patient race as an independent predictor of revision. We then performed a random-effects meta-analysis to calculate a pooled hazard ratio for TKA revision in blacks compared with whites.

RESULTS

A total of 4,286 studies were identified and screened by title; 106, by abstract; and 24, by full text. Six studies met the inclusion criteria. Only 4 of the 6 studies could undergo meta-analysis because of overlapping study populations in 3 of them. The meta-analysis represented 451,960 patients who underwent TKA, of whom 28,772 (6.4%) were black. Of the total, 31,568 patients (7.0%) underwent revision surgery. The risk of revision TKA was significantly higher among blacks than whites (pooled hazard ratio, 1.38; 95% confidence interval, 1.20 to 1.58; p < 0.001). Analysis of the 3 studies with overlapping study populations demonstrated discordant results as a result of adjustment compared with non-adjustment for insurance eligibility, a surrogate for socioeconomic status.

CONCLUSIONS

Blacks in the United States are at higher risk of revision TKA than whites. Socioeconomic status contributed to revision risk and is an important confounder in analyses of race.

LEVEL OF EVIDENCE

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

Total knee implant posterior stabilised by a third condyle: Design evolution and post-operative complications

BACKGROUND

Despite excellent long-term outcomes, posterior stabilisation by a third condyle continues to receive unwarranted criticism regarding patellar complications and instability.

HYPOTHESIS

Complication rates with a tri-condylar posterior-stabilised implant are similar to those with other posterior-stabilised prostheses and have diminished over time due to improvements in prosthesis design.

MATERIAL AND METHODS

Post-operative complications and revision rates were assessed retrospectively in a prospective cohort of 4189 consecutive patients who had primary total knee arthroplasty (TKA) using a tri-condylar posterior-stabilised implant (Wright-Tornier) and were then followed-up for at least 24 months. The analysis included 2844 knees. The prosthesis generations were HLS1^®, n=20; HLS2^®, n=220; HLS Evolution^®, n=636; HLS Noetos^®, n=1373; and HLS KneeTec^®, n=595. Complications were compared across generations by applying Fisher's exact test, and survival was compared using the Kaplan-Meier method.

RESULTS

At last follow-up, there had been 341 (12%) post-operative complications in 306 (10.8%) knees, including 168 (5.9%) related to the implant, 41 (1.4%) infections, and 132 (4.6%) secondary complications unrelated to the implant. Re-operation was required for 200 complications (7%), including 87 (3.1%) consisting in revision of the prosthesis. Implant-related complications were stiffness (n=67, 2.4%), patellar fracture (n=34, 1.2%), patellar clunk syndrome (n=25, 0.9%), patellar loosening (n=3, 0.1%), tibial/femoral loosening (n=15, 0.5%), polyethylene wear (n=3, 0.1%), and implant rupture (n=1, 0.04%). Significant differences across generations were found for stiffness (P<0.0001), patellar fracture (P=0.03), clunk syndrome (P=0.03), and polyethylene wear (P=0.004), whose frequencies declined from one generation to the next. Overall 10-year survival was 92% with no significant difference across generations (P=0.1).

DISCUSSION

Outcomes of tri-condylar posterior-stabilised TKA are similar to those obtained using other posterior-stabilised implants. Neither patellar complications nor instability are more common, and improvements in implant design have contributed to correct early flaws.

LEVEL OF EVIDENCE

IV, historical cohort, retrospective assessment of prospectively collected data.

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.

Kinematic alignment produces near-normal knee motion but increases contact stress after total knee arthroplasty: A case study on a single implant design

BACKGROUND

Kinematically aligned total knee arthroplasty (TKA) is of increasing interest because this method might improve postoperative patient satisfaction. In kinematic alignment the femoral component is implanted in a slightly more valgus and internally rotated position, and the tibial component is implanted in a slightly more varus and internally rotated position, than in mechanical alignment. However, the biomechanics of kinematically aligned TKA remain largely unknown. The aim of this study was to compare the kinematics and contact stresses of mechanically and kinematically aligned TKAs.

METHODS

A musculoskeletal computer simulation was used to determine the effects of mechanically or kinematically aligned TKA. Knee kinematics were examined for mechanically aligned, kinematically aligned, and kinematically aligned outlier models. Patellofemoral and tibiofemoral contact forces were measured using finite element analysis.

RESULTS

Greater femoral rollback and more external rotation of the femoral component were observed with kinematically aligned TKA than mechanically aligned TKA. However, patellofemoral and tibiofemoral contact stresses were increased in kinematically aligned TKA.

CONCLUSIONS

These findings suggest that kinematically aligned TKA produces near-normal knee kinematics, but that concerns for long-term outcome might arise because of high contact stresses.

Advantage of minimal anterior knee pain and long-term survivorship of cemented single radius posterior-stabilized total knee arthroplasty without patella resurfacing

BACKGROUND

The single radius total knee prosthesis was introduced with the advantage of reduced patellar symptoms; however, there is no long-term follow-up study of the same. The purpose of this study was to determine the survival rate of single radius posterior-stabilized total knee arthroplasty and patellofemoral complication rates in a consecutive series.

METHODS

Seventy-one patients (103 knees) who underwent arthroplasty without patellar resurfacing using a single radius posterior-stabilized total knee prosthesis were followed up for a minimum 10 years. Clinical evaluation using Knee Society knee and function scores and radiologic evaluation were performed at regular intervals. Anterior knee pain as well as patellofemoral complications were evaluated with a simple questionnaire. The Kaplan-Meier product-limit method was used to estimate survival.

RESULTS

Seventeen patients (23 knees) were excluded due to death (12 knees) or lost to follow-up (11 knees). Of the 80 knees enrolled, all femoral components and 78 tibial components were well fixed without loosening at final follow-up. Two revisions were performed because of tibial component loosening and periprosthetic joint infection. One patient with tibial component loosening refused to have revision surgery. No obvious tibial insert polyethylene wear was observed. The survivorships at 132 months were 96.7% using revision or pending revision as end points. Anterior knee pain was present in 6 patients (6 knees, 7.5%) at the latest follow-up. No patellofemoral complication requiring revision was encountered.

CONCLUSIONS

The single radius posterior-stabilized total knee prosthesis demonstrated an excellent minimum 10-year survivorship. The low rates of implant loosening and 7.5% of anterior knee pain as a patellofemoral complication are comparable with those reported for other modern total knee prosthesis.

In vivo kinematic analysis of posterior-stabilized total knee arthroplasty for the valgus knee operated by the gap-balancing technique

BACKGROUND

Most in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).

METHODS

A total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.

RESULTS

The average flexion angle was 111.3°±7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.

CONCLUSIONS

We conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small.

LEVEL OF EVIDENCE

IV.

No benefit of patient-specific instrumentation in TKA on functional and gait outcomes: a randomized clinical trial

BACKGROUND

Although some clinical reports suggest patient-specific instrumentation in TKA may improve alignment, reduce surgical time, and lower hospital costs, it is unknown whether it improves pain- and function-related outcomes and gait.

QUESTIONS/PURPOSES

We hypothesized that TKA performed with patient-specific instrumentation would improve patient-reported outcomes measured by validated scoring tools and level gait as ascertained with three-dimensional (3-D) analysis compared with conventional instrumentation 3 months after surgery.

METHODS

We randomized 40 patients into two groups using either patient-specific instrumentation or conventional instrumentation. Patients were evaluated preoperatively and 3 months after surgery. Assessment tools included subjective functional outcome and quality-of-life (QOL) scores using validated questionnaires (New Knee Society Score(©) [KSS], Knee Injury and Osteoarthritis Outcome Score [KOOS], and SF-12). In addition, gait analysis was evaluated with a 3-D system during level walking. The study was powered a priori at 90% to detect a difference in walking speed of 0.1 m/second, which was considered a clinically important difference, and in a post hoc analysis at 80% to detect a difference of 10 points in KSS.

RESULTS

There were improvements from preoperatively to 3 months postoperatively in functional scores, QOL, and knee kinematic and kinetic gait parameters during level walking. However, there was no difference between the patient-specific instrumentation and conventional instrumentation groups in KSS, KOOS, SF-12, or 3-D gait parameters.

CONCLUSIONS

Our observations suggest that patient-specific instrumentation does not confer a substantial advantage in early functional or gait outcomes after TKA. It is possible that differences may emerge, and this study does not allow one to predict any additional variances in the intermediate followup period from 6 months to 1 year postoperatively. However, the goals of the study were to investigate the recovery period as early pain and functional outcomes are becoming increasingly important to patients and surgeons.

LEVEL OF EVIDENCE

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

Comparative Survivorship of Different Tibial Designs in Primary Total Knee Arthroplasty

BACKGROUND

Few registry-based studies in the United States have compared the survivorship of different knee implant designs in total knee arthroplasty. The purpose of this study was to compare differences in survivorship of commonly used tibial implant designs in primary total knee arthroplasty.

METHODS

A total of 16,584 primary total knee arthroplasties in 11,992 patients were performed at a single institution from 1985 to 2005. Patients were prospectively followed at regular intervals to ascertain details of subsequent revisions. Overall revision rates and revisions for aseptic loosening, wear, and osteolysis were compared across twenty-two tibial implant designs using Cox proportional hazards regression models adjusting for age, sex, calendar year, and body mass index.

RESULTS

In comparison with metal-backed modular implants, all-polyethylene tibial components had a significantly lower risk of revision (hazard ratio, 0.3; 95% confidence intervals: 0.2, 0.5 [p < 0.0001]). The risk reduction with all-polyethylene tibial components was not affected by age, sex, or body mass index. With metal-backed modular tibial designs, cruciate-retaining knees performed better than the posterior-stabilized knees (p = 0.002), but this finding was limited to one specific metal-backed modular tibial component, the Press Fit Condylar design. With all-polyethylene tibial components, there was no survivorship difference between cruciate-retaining and posterior-stabilized designs.

CONCLUSIONS

All-polyethylene tibial components were associated with better outcomes than metal-backed modular components. Cruciate-retaining and posterior-stabilized designs performed equally well, except with the Press Fit Condylar design. Obese patients may have superior results with all-polyethylene and posterior-stabilized components.

LEVEL OF EVIDENCE

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

Patient-specific guides do not improve accuracy in total knee arthroplasty: a prospective randomized controlled trial

BACKGROUND

Recently, patient-specific guides (PSGs) have been introduced, claiming a significant improvement in accuracy and reproducibility of component positioning in TKA. Despite intensive marketing by the manufacturers, this claim has not yet been confirmed in a controlled prospective trial.

QUESTIONS/PURPOSES

We (1) compared three-planar component alignment and overall coronal mechanical alignment between PSG and conventional instrumentation and (2) logged the need for applying changes in the suggested position of the PSG.

METHODS

In this randomized controlled trial, we enrolled 128 patients. In the PSG cohort, surgical navigation was used as an intraoperative control. When the suggested cut deviated more than 3° from target, the use of PSG was abandoned and marked as an outlier. When cranial-caudal position or size was adapted, the PSG was marked as modified. All patients underwent long-leg standing radiography and CT scan. Deviation of more than 3° from the target in any plane was defined as an outlier.

RESULTS

The PSG and conventional cohorts showed similar numbers of outliers in overall coronal alignment (25% versus 28%; p = 0.69), femoral coronal alignment (7% versus 14%) (p = 0.24), and femoral axial alignment (23% versus 17%; p = 0.50). There were more outliers in tibial coronal (15% versus 3%; p = 0.03) and sagittal 21% versus 3%; p = 0.002) alignment in the PSG group than in the conventional group. PSGs were abandoned in 14 patients (22%) and modified in 18 (28%).

CONCLUSIONS

PSGs do not improve accuracy in TKA and, in our experience, were somewhat impractical in that the procedure needed to be either modified or abandoned with some frequency.

Mid-term Results of Single-Radius Cruciate Retaining Total Knee Arthroplasty: Minimum 5 Year Follow-up

Purpose

The single-radius design of the knee implant was introduced to improve the results of total knee arthroplasty (TKA) by reducing maximum extensor forces, and it also represents more physiologic quadriceps force pattern, which could have a positive effect on knee function after TKA. We studied mid-term results of single-radius designed cruciate retaining (CR) TKA.

Materials and Methods

We analyzed the functional improvement and radiological osteolytic pattern after TKA using the single-radius Scorpio CR prosthesis. TKA was performed on 102 knees. The mean follow-up period was 73.8 months. For clinical assessment, the range of motion (ROM), Harris hip score, and functional outcome score were obtained preoperatively and at last follow-up.

Results

The average ROM was 100.2° preoperatively and 121.7° at last follow-up. The average knee score was 59.2 points preoperatively and 92.9 points at last follow-up. The average functional outcome score was improved from 51.9 points preoperatively to 85.4 points at last follow-up. Radiolucency was observed in four knees but all were non-progressive lesions smaller than 2 mm.

Conclusions

The clinical outcome of TKA using the single-radius CR prosthesis was good during the mid-term follow-up and the incidence of osteolysis was very rare.

Excellent fixation achieved with cementless posteriorly stabilized total knee arthroplasty

Cementless posteriorly stabilized (PS) total knee arthroplasty has not been widely accepted primarily because of prior unpredictable results and concern about micromotion at the tibial fixation interface caused by the cam/post interaction. A prospective consecutive series of 114 cementless, tricompartmental periapatite-coated single-radius PS implants in 110 patients with a mean age 62 years was performed to determine if initial stability and biologic fixation could be achieved. At a mean follow-up of 36 months, all implants demonstrated radiographic evidence of stable biologic fixation with no evidence of loosening, osteolysis, stress shielding, or progressive radiolucent lines. Based on these early results, cementless, periapatite-coated single-radius PS total knee arthroplasty offers marked promise.

Aseptic tibial debonding as a cause of early failure in a modern total knee arthroplasty design

BACKGROUND

We observed isolated tibial component debonding from the cement in one modern primary TKA design (NexGen LPS 3° tibial tray; Zimmer, Warsaw, IN, USA). This failure mechanism is sparsely reported in the literature.

QUESTIONS/PURPOSES

We (1) assessed survivorship of this tibial tray with special emphasis on debonding; (2) described clinical and radiographic features associated with tibial failure; and (3) compared patient and radiographic features of the failures with a matched cohort.

METHODS

A total of 1337 primary TKAs were performed with a cemented NexGen LPS 3° tibial tray over an 11-year period. Twenty-five knees (1.9%) were revised for tibial debonding. BMI and radiographic alignment in the tibial debonding group were compared with a matched control group. Implant survivorship was assessed using tibial debonding as the end point.

RESULTS

Survival free of revision from tibial debonding was 100% at 1 year and 97.8% at 5 years. The tibial failures shared a typical radiographic pattern with debonding at the cement-implant interface and subsidence into varus and flexion. We found no link between limb alignment or individual component alignment and failure because 22 of the 25 failures occurred in well-aligned knees.

CONCLUSIONS

Our standardized followup of patients undergoing TKA at routine intervals allowed us to discover a higher rate of revision resulting from tibial debonding. We have discontinued the use of this particular tibial tray for primary TKA and surveillance for patients undergoing TKA continues to be warranted.

The John Insall Award: no functional advantage of a mobile bearing posterior stabilized TKA

BACKGROUND

Mobile bearing (MB) total knee design has been advocated as a means to enhance the functional characteristics and decrease the wear rates of condylar total knee arthroplasty (TKA). However, it is unclear if these designs achieve these goals.

QUESTIONS/PURPOSES

We asked whether function of patients or survivorship would be greater or complications would be lesser in groups of patients with MB compared with fixed bearing (FB) TKA. We also sought to describe retrieval findings.

METHODS

We randomized 507 primary TKAs in 416 eligible patients to receive MB (n = 252) or FB (n = 255) devices from November 2001 to August 2007 (Investigational Device Exemption G000180, ClinicalTrials.gov registration number NCT00946075). Patients were blinded to treatment allocation. WOMAC Index, SF-12 Health Survey, knee range of motion, and Knee Society scores were collected and compared preoperatively and at 6, 12, and 24 months postoperatively. We recorded device failures and complications until October 2009. Kaplan-Meier survivorship was compared using the log rank test. Twelve retrieved MB devices underwent pathologic analysis. The minimum postoperative time was 2.2 years (mean, 5.9 years; range, 2.2-7.9 years).

RESULTS

We found no differences in mean clinical assessment scores or mean score changes from baseline at any postoperative interval through 2 postoperative years. Nineteen of the 252 MB and 13 of the 255 FB knees had undergone revision of any component. Estimated survival at 6 postoperative years was similar for the two devices: 90.1% (95% confidence interval [CI], 84.1-93.9) for MB and 94.2% (95% CI, 90.1-96.6) for FB. Two MB and no FB tibial components were revised for loosening. There was one case of MB insert dislocation. Retrieved MB devices demonstrated no unexpected wear or mechanical device failures.

CONCLUSION

We found no evidence of functional advantage of the MB design. Survivorship was similar, although the study is limited by short duration of followup.

Gender and prevalence of knee osteoarthritis types in elderly Koreans

We undertook to document sex differences in the prevalence of knee osteoarthritis (OA) at different disease stages in an elderly Korean population. Prevalence of 3 stages of knee OA (radiographic OA, severe radiographic OA, and candidacy for total knee arthroplasty [TKA]) was investigated in 696 elderly (≥65 years old) Korean subjects. Multivariate logistic regression was performed to evaluate associations between the risk factors of OA at these 3 disease stages. The overall prevalence of knee OA was 38.1% for radiographic OA, 26.4% for severe radiographic OA, and 6.5% for advanced OA warranting TKA. Women had much higher prevalence for all 3 stages. Female sex was found to be the strongest predictor for all 3 disease stages, but this was most remarkable for TKA candidates. This study documents that knee OA is highly prevalent among Korean elderly and that elderly Korean women are at much greater risk of requiring TKA.

Post damage in contemporary posterior-stabilized tibial inserts: influence of implant design and clinical relevance

The mechanisms of damage at the polyethylene post in 3 contemporary tibial insert designs were evaluated and compared with a historical standard (Insall-Burstein II; Zimmer, Warsaw, Ind). One hundred five gamma sterilized posterior-stabilized tibial inserts were revised after an average of 4.7 years (0.05-13.6 years). Retrievals were classified according to their designs: Insall-Burstein II (n = 28); PFC (Johnson & Johnson, Raynham, Mass; n = 30); NexGen (Zimmer; n = 32); and Scorpio (Stryker Orthopaedics, Mahwah, NJ; n = 15). Reasons for revision and patient details were available. Surface damage scoring and photogrammetry were performed on all the retrieved tibial inserts. Oxidation analysis was carried out for traceable historical, gamma air-sterilized and conventional, gamma inert-sterilized tibial inserts (n = 61) with the use of infrared spectroscopy. The posts for all 3 contemporary designs exhibited damage similar to the historical controls. Articular, post, and backside damage scores significantly increased with implantation time. Post damage was insensitive to design and patient factors but was exacerbated by oxidation. An association between damage at the post and articular surface was also confirmed. Logistic models suggested an interaction between post damage, backside surface damage, and implant loosening.

The role of the cemented all-polyethylene tibial component in total knee replacement: a 30-year patient follow-up and review of the literature

Use of an all-polyethylene tibial component in primary total knee arthroplasty remains an attractive option considering the reported durability of the construct, the lowered cost compared to modular metal-backed tibia, and the elimination of backside wear. The two major intra-operative disadvantages include the inability to alter the tibial component thickness after permanent implant placement and the inability to use varus-valgus constrained designs. The long-term disadvantage is the inability to perform a modular insert exchange should this be required. We report the 30-year outcome of a single patient using the duopatellar total knee replacement system. Based on a critical review of the literature we would recommend use in patients 80 years of age or older, consideration in patients 75 to 79 years, and possibly in younger yet less active patients. These three groups would be the least likely to require a modular tibial liner exchange in their lifetime.

Minimum five-year follow-up results of single-radius, high-flex posterior-stabilized TKA

We studied 75 primary total knee arthroplasties (TKAs) performed using a single-radius, high-flex posterior-stabilized insert design with a minimum 5-year follow-up to document its implant specific complications and clinical results. Nonprogressive osteolysis was observed at zone 4 of the femoral component in 6 knees (8%) and at zone 1 of the tibial component in 6 knees (8%). However, no complications associated with high flexion designs, such as early aseptic loosening, were observed.Preoperatively, mean Knee Society Knee Score and Knee Society Function Score were 55.1 and 45.5, respectively (range, 10-83 and 20-80, respectively). At last follow-up, mean Knee Society Knee Score and Knee Society Function Score improved to 94.9 and 85.9, respectively (range, 70-100 [P<.0001] and 45-100 [P<.0001], respectively). Mean maximal flexion was 122.1 degrees (range, 90 degrees -140 degrees ) and mean range of motion (ROM) was 110.3 degrees (range, 80 degrees -135 degrees ) preoperatively, and these values improved to 128.9 degrees (range, 110 degrees -150 degrees [P<.0001]) and 127.8 degrees (range, 110 degrees -150 degrees [P<.0001]), respectively, at last follow-up. Preoperative ROM was found to be the only factor significantly correlated with postoperative ROM at last follow-up by univariate (P=.0020) and multivariate analysis (P<.0067). Accordingly, clinical results were comparable to previous reports of high-flex implants without implant-specific complications.