No differences in clinical outcomes or isokinetic performance between cruciate-substituting ultra-congruent and posterior stabilized total knee arthroplasties: a randomized controlled trial

Cruciate-substituting and posterior-stabilised total knee arthroplasties had similar gait patterns in the short term

PURPOSE

Surgeons want to achieve native kinematics in primary total knee arthroplasty (TKA). Cruciate-substituting (CS) implants could restore the knee kinematics more efficiently than posterior-stabilised (PS) TKA. This study aimed to compare gait patterns in patients with CS or PS TKA at 6 months. The hypothesis was that CS implants would demonstrate comparable gait parameters to PS implants at 6 months.

METHODS

In this prospective case-control study, 38 primary TKA without coronal laxity were divided into 2 groups: 19 cruciate-substituting (CS) and 19 posterior-stabilised (PS) implants. The type of prosthesis was determined according to the surgical period. Exclusion criteria were TKA revision, associated procedures and inability to walk on a treadmill. Gait analysis was conducted on a treadmill 6 months postoperatively for each patient with a knee assessment device (KneeKG®). Gait characteristics included analysis in three spatial dimensions (flexion-extension, abduction-adduction, internal-external rotation, anterior-posterior translation). Clinical outcomes (Knee Society Score and Forgotten Joint Score) were compared between both groups at 6 months postoperatively.

RESULTS

At 6 months, the gait analysis did not demonstrate any significant difference between CS and PS implants. The range and the maximum anteroposterior translation were similar in both groups (9.2 ± 6.5 mm in CS group vs. 8.1 ± 3 mm in PS group (n.s.); and - 5.2 ± 5 mm in CS group vs. - 6.3 ± 5.9 mm in PS group (n.s.), respectively). The internal/external rotation, the flexion, and the varus angle were similar between CS and PS implants. The KSS Knee score was higher at 6 months in the CS group than in the PS group (92.1 ± 5.6 vs. 84.8 ± 8.9 (p < 0.01)).

CONCLUSION

Cruciate-substituting and posterior-stabilised TKA had similar gait patterns at 6 months postoperatively, despite a non-equivalent posterior stabilisation system. CS prostheses were an interesting option for primary TKA for knee kinematics restoration without requiring a femoral box.

LEVEL OF EVIDENCE

Prospective, case-control study; Level II.

Ultracongruent Designs Compared to Posterior-Stabilized and Cruciate-Retaining Tibial Inserts - What Does the Evidence Tell Us? A Systematic Review and Meta-Analysis

BACKGROUND

Posterior-stabilized (PS) and cruciate-retaining (CR) have been the most common tibial designs used in total knee arthroplasty. Ultra-congruent (UC) inserts are becoming popular because they preserve bone without relying on the posterior cruciate ligament balance and integrity. Despite increasing use, there is no consensus on how UC inserts perform versus PS and CR designs.

METHODS

A comprehensive literature search of 5 online databases was performed for articles from January 2000 to July 2022 comparing the kinematic and clinical outcomes of PS or CR tibial inserts to UC inserts. There were nineteen studies included. There were 5 studies comparing UC to CR and 14 comparing UC to PS. Only one randomized controlled trial (RCT) was rated "good quality".

RESULTS

For CR studies, pooled analyses showed no difference in knee flexion (n = 3, P = .33) or Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores (n = 2, P = .58). For PS studies, meta-analyses showed better anteroposterior stability (n = 4, P < .001) and more femoral rollback (n = 2, P < .001) for PS but no difference in knee flexion (n = 9, P = .55) or medio-lateral stability (n = 2, P = .50). There was no difference with WOMAC (n = 5, P = .26), Knee Society Score (n = 3, P = .58), Knee Society Knee Score (n = 4, P = .76), or Knee Society Function Score (n = 5, P = .51).

CONCLUSION

Available data demonstrates there are no clinical differences between CR or PS and UC inserts in small short-term studies ending around 2 years after surgery. More importantly, high-quality research comparing all inserts is lacking, demonstrating a need for more uniform and longer-term studies beyond 5 years after surgery to justify increased UC usage.

The Effect of Congruent Tibial Inserts in Total Knee Arthroplasty: A Network Meta-Analysis of Randomized Controlled Trials

Objective: The aim of this study was to determine whether modern congruent tibial inserts are associated with superior outcomes in total knee arthroplasty (TKA). Background: Ultracongruent fixed-bearing (UCFB) and medial congruent fixed-bearing (MCFB) inserts have been known to be effective in total knee arthroplasty with patient satisfaction. Nonetheless, no supporting evidence to date exists to rank the clinical outcomes of these various congruent inserts in TKA compared with other important considerations in TKA including cruciate-retaining fixed-bearing (CRFB) and posterior-stabilized fixed-bearing (PSFB) inserts. Methods: We searched PubMed, Embase, the Cochrane Central Register of Controlled Trials, Web of Science, and Scopus up to 15 May 2022. We selected studies involving an active comparison of UCFB or MCFB in TKAs. We performed a network meta-analysis (NMA) of randomized controlled trials (RCTs) and compared different congruent inserts. We ranked the clinical outcomes by SUCRA score with the estimate of the best treatment probability. Our primary outcomes were revision rates and radiolucent lines. Secondary outcomes were functional scores, including the range of motion (ROM), the Knee Society Score (KSS), the Oxford Knee Score (OKS), and WOMAC. Results: Eighteen RCTs with 1793 participants were analyzed. Our NMA ranked MCFB, CRFB, and UCFB with the lowest revision rates. CRFB and UCFB had the fewest radiolucent lines. UCFB had overall the best ROM. UCFB and MCFB had the best OKS score overall. Conclusions: The ranking probability for better clinical outcomes in congruent inserts demonstrated the superiority of congruent tibial inserts, including UCFB and MCFB. UCFB may be associated with better ROM and postoperative functional outcomes. However, integrating future RCTs for high-level evidence is necessary to confirm these findings.

Favorable outcomes of posterior cruciate-stabilized inserts over ultracongruent inserts in total knee arthroplasty

OBJECTIVE

Posterior cruciate-stabilized (PS) and ultracongruent (UC) inserts are used during total knee arthroplasty (TKA), but superiority in gaining postoperative knee flexion and functionality remains contested. Therefore, this study compared postoperative outcomes between PS and UC inserts.

METHODS

A retrospective review evaluated unilateral or bilateral TKAs with PS or UC inserts from August 2011 to March 2020. Nonparametric statistics were performed to evaluate differences in patient demographics, pre- and postknee flexion and Knee Society Knee (KSS-K) and Function Score (KSS-F). Univariate and multivariable regressions were performed to evaluate the influence on postoperative knee flexion ≥ 120°, presented as odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Patient demographics were not significantly different between the 577 PS and 399 UC knees evaluated. Postoperatively, a larger proportion of UC knees demonstrated knee flexion < 120° (36.0% vs. 18.6%, p < 0.001) and lower KSS-K (91.0 ± 8.7 vs. 91.6 ± 10.3, p < 0.001) and KSS-F (76.8 ± 21.6 vs. 79.9 ± 21.6, p = 0.007) than the PS group. The PS group had greater improvement in flexion angle (4.9° ± 14.9° vs. 1.0° ± 15.6°, p < 0.001) and KSS-F (27.3 ± 23.3 vs. 23.1 ± 25.3, p = 0.007) as compared to that of UC patients. Patients with preoperative flexion < 120° (OR 2.787, CI 2.066-3.761; p < 0.001), higher body mass index (OR 1.033, CI 1.006-1.061; p = 0.017) and UC insert (OR 2.461, CI 1.832-3.307; p < 0.001) were less likely to achieve flexion ≥ 120°.

CONCLUSION

Favorable clinical and functional outcomes were noted in the PS group as compared to UC inserts in TKA. The greater improvement in overall knee flexion may suggest the PS insert may be especially appropriate for patients with lower preoperative range of motion.

LEVEL OF EVIDENCE

III, retrospective comparative study.

Modern Total Knee Arthroplasty Bearing Designs and the Role of the Posterior Cruciate Ligament

The role of the posterior cruciate ligament (PCL) in total knee arthroplasty (TKA) surgery continues to be a source of debate among the adult reconstruction community. In native knee flexion, the PCL is comprised of an anterolateral and posteromedial bundle that work together to limit posterior tibial translation and allow adequate femoral rollback for deep flexion. In the arthritic knee, the PCL can often become dysfunctional and attenuated, which led to the development of posterior stabilized (PS) TKA bearing options. PS TKAs implement a cam-post construct to functionally replace a resected PCL. While PS designs may facilitate balancing knees with significant deformity, they are associated with complications such as postfracture, increased wear, and patellar clunk/crepitus. In recent years, newer designs have been popularized with greater degrees of congruency and incorporation of medial and lateral pivoting to better recreate native knee kinematics. The American Joint Registry has confirmed the recent predilection for ultra-congruent and cruciate-retaining TKA inserts over PS TKAs during the last decade. Studies have failed to identify an overall clinical superiority between the cruciate substituting and sacrificing designs. The literature has also failed to identify clinical consequences from PCL resection with modern, more conforming TKA designs. In this article, we review modern PCL sacrificing designs and discuss the impact of each on the kinematics after TKA. We also will delineate the role of the PCL in modern TKA in the hopes to better understand the recent surge in sacrificing but not substituting knee implants.

Patellar resurfacing in total knee arthroplasty leads to better isokinetic performance

BACKGROUND

For decades there have been concerns about patellar resurfacing (PR) in total knee arthroplasty (TKA) and the individual preference of the surgeon is still the main determinant of whether or not resurfacing is applied. According to preference, surgeons can be categorized in 3 main groups of those who usually, selectively, or rarely resurface. The aim of this prospective, randomized, controlled study was to compare the isokinetic performance and clinical outcome of TKAs with PR and without PR.

METHODS

A total of 50 patients scheduled to undergo TKA for primary osteoarthritis of the knee were randomly assigned to either the PR or non-PR groups. There were no significant differences between the groups in respect of age, BMI, gender and preoperative Knee Society Score (KSS) and isokinetic performance. Patients were evaluated at postoperative 3, 6, and 12 months with KSS and at 6 months and 1 year with isokinetic measurements.

RESULTS

The PR group had a higher mean score, especially in the functional component of KSS, but the difference was not statistically significant. Knee extension peak torque was significantly higher in the PR group at 6 months (p = 0.029) and 1 year (p = 0.004) postoperatively. There were no significant differences between the groups in respect of knee flexion peak torque values following TKA.

CONCLUSIONS

The results of this study demonstrated that PR during TKA is associated with better isokinetic performance and higher knee scores. These results support routine/usually resurfacing of the patella. For surgeons who selectively resurface the patella, the advantage of better isokinetic performance may be taking into consideration in favor of resurfacing the patella where they are undecided.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Robust Randomized Controlled Data Is Lacking in Total Joint Arthroplasty

INTRODUCTION

 Randomized controlled trials (RCTs)are regarded as highest level of scientific evidence. There is belief that while prospective randomized control trials (PRCTs) are the gold standard for evaluating efficacy of interventions, there are very few conducted on lower extremity joint arthroplasty. However, there was a more than adequate amount (n=197) of published RCTs in knee arthroplasty during the 2021 calendar year. Therefore, we studied RCTs on knee arthroplasties for 2021 and assessed them for overall study topic reasons (i.e., devices as well as prostheses, rehabilitation, pain control, blood loss [tranexamic acid], and other), which were then subcategorized by: (1) country of origin; (2) sample size; and (3)whether or not they were follow-up studies. After this, we specifically focused on the studies (n=26) concerning devices or prostheses.

METHODS

 A search of PubMed on "knee arthroplasty" specifying "RCT" using their search function and dates between January 1, 2021 to December 24, 2021 resulted in the analyzed reports. A total of 17.3% reports analyzed rehabilitation methods while 28.4% studied pain control. A total of 20.3% examined blood loss topics and 20.8% investigated other topics.

RESULTS

 We found that 26 studies (13.2%) involved prosthetic design and implantation. Overall, only 15% knee arthroplasty RCTs were conducted in the United States, the mean total final sample size was 133±146 patients, and 7% were follow-up studies. None of the prostheses studies were performed in the United States, and the mean total final sample size of all of these studies was 86±54 patients, and 23% were follow-up studies. Total knee arthroplasty prospective RCTs were not performed in the United States.

CONCLUSION

 The authors believe that other study designs, such as database or registry analyses, are also appropriate in this rapidly advancing field of joint arthroplasty for the continuing evaluation and approval of new prostheses and techniques, while we await more PRCTs in our field.

Revision Risk for Total Knee Arthroplasty Polyethylene Designs in Patients 65 Years of Age or Older: An Analysis from the American Joint Replacement Registry

BACKGROUND

Polyethylene bearing design may influence the risk of revision after total knee arthroplasty (TKA). Previous investigations from outside of the United States have suggested the potential for an increased risk of all-cause revision and revision for infection with the use of posterior-stabilized bearings. We examine the risk of revision based on the polyethylene bearing design selection for primary TKA.

METHODS

An analysis of the American Joint Replacement Registry (AJRR) data from 2012 to 2019 was performed. We identified all primary TKAs over the study period and linked cases to supplemental U.S. Centers for Medicare & Medicaid Services (CMS) data where available. Patient demographic characteristics, polyethylene characteristics, procedure dates, and cause for revision were recorded. Analysis was performed to compare minimally stabilized implants (cruciate-retaining, anterior-stabilized, or pivot bearing designs) with posterior-stabilized implants. Cumulative incidence function (CIF) curves and Cox proportional hazard ratios (HRs) were created for all-cause revision and revision for infection in each group.

RESULTS

We identified 305,279 cases with reported minimally stabilized or posterior-stabilized implant characteristics. There were 161,486 cases (52.9%) that utilized posterior-stabilized bearings compared with 143,793 cases (47.1%) with minimally stabilized bearings. For minimally stabilized bearings, 1,693 cases (1.18%) had all-cause revision and 334 cases (0.23%) had revision for infection. For posterior-stabilized bearings, 2,406 cases (1.49%) had all-cause revision and 446 cases (0.28%) had revision for infection. The use of posterior-stabilized bearings had HRs of 1.25 (95% confidence interval [CI], 1.2 to 1.3; p < 0.0001) for all-cause revision and 1.18 (95% CI, 1.0 to 1.4; p = 0.02) for revision for infection.

CONCLUSIONS

Similar to investigations from international registries, we found an increased risk of all-cause revision and revision for infection when using posterior-stabilized bearings in TKA in the United States. Surgeons should consider this finding when considering bearing selection for primary TKA.

LEVEL OF EVIDENCE

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

Increased posterior translation but similar clinical outcomes using ultracongruent instead of posterior stabilized total knee arthroplasties in a prospective randomized trial

PURPOSE

The aim of this study was to compare the posterior tibial translation after ultracongruent (UC) and posterior-stabilized (PS) total knee arthroplasty (TKA) with two different UC with different heights in the anterior lip, and two different PS designs. This study also aimed to compare the range of motion (ROM) and outcomes scores after the use of these TKA models. It was hypothesised less posterior tibial translation after PS than after UC TKA, and less posterior tibial translation with a higher anterior lip in the UC insert than with a lower one.

METHODS

It was designed as a prospective randomized study of a group of 120 patients operated with a cemented TKA. To clarify the main purpose of the study, four groups were analysed using different polyethylene designs: Triathlon PS insert in group one, Triathlon UC insert in group two, U2 PS insert in group three and U2 UC insert in group four. One year after surgery, a forced posterior drawer with a Telos Stress applying 15 kg of force posteriorly on the proximal tibia at 90° of knee flexion was analysed in the lateral radiograph. Limb alignment, tibial posterior slope and posterior condylar offset were also studied.

RESULTS

30 patients were included in each group. The average age was 73 years. There were 72.2% female and 27.8% male patients. There were no significant differences in any demographic or radiographic studied variables, preoperative range of motion (ROM) or preoperative Knee Society Scores (KSS) among the different groups. One year after surgery, the average postoperative ROM and the postoperative KSS Knee and KSS Function scores improved in respect of the preoperative values in all the groups. There were no significant differences in the postoperative outcome scores among the different groups (p = n.s.). Postoperative alignment of the limb, tibial posterior slope and posterior condylar offset were similar in the 4 study groups (p = n.s.). The postoperative posterior tibial translation was different between groups: the PS groups (groups 1 and 3) showed significant inferior values (p < 0.001) in respect of the UC groups (groups 2 and 4). There were no differences between both groups of PS models, but there was a significant increase in the posterior tibial translation of the Triathlon UC insert (11.2 mm SD 3.2) in respect of the U2 UC insert (6.1 mm SD 4.5) (p = 0.004).

CONCLUSIONS

UC inserts restrict the posterior tibial translation after TKA less than PS inserts, but a design with a high anterior lip in the polyethylene UC insert can better control the posterior tibial translation than an insert with a small anterior lip.

LEVEL OF EVIDENCE

Level I. Randomised controlled trial.

In vivo kinematic comparison between an ultra-congruent and a posterior-stabilized total knee arthroplasty design by RSA

PURPOSE

The aim of the present study was to compare the in vivo under weight-bearing kinematic behavior of a posterior-stabilized (PS) and an ultra-congruent (UC) total knee arthroplasty (TKA) model during a sit-to-stand motor task, a common activity of daily life.

METHODS

A cohort of 16 randomly selected patients (8 PS Persona Zimmer, 8 UC Persona Zimmer) was evaluated through dynamic radiostereometric analysis (RSA) at a minimum of 9 months after TKA, during the execution of a sit-to-stand. The anteroposterior (AP) translation of the femoral component and the AP translation of the low point of medial and lateral femoral compartments were compared through Student's t test (p < 0.05).

RESULTS

A significantly greater anterior translation of the femoral component was found for the PS group compared to the UC group. The flexion interval where statistical significance was found was between 30° and 0° (p = 0.017). Both groups showed a significantly greater anterior translation of the low point of the lateral compartment with respect to the medial one (PS: p = 0.012, UC: p = 0.018). This was consistent with a medial-pivot pattern. Furthermore, a significantly greater anterior translation of the medial compartment was found in the PS group compared to the UC group (p = 0.001). The same pattern was observed for the lateral compartment (p = 0.006).

CONCLUSIONS

The TKA designs evaluated in the present study showed comparable in-vivo kinematics with regards to medial pivot pattern but differences in absolute AP translation. Specifically, the UC design showed greater AP stability than the PS design. This finding could be positive in terms of implant stability, but negative in terms of premature polyethylene wear and thus implant failure. This remains to be verified in studies with a larger sample size and longer follow-up.

LEVEL OF EVIDENCE

IV.

Comparative Analysis of Contemporary Fixed Tibial Inserts: A Systematic Review and Network Meta-analysis of Randomized Controlled Trials

Background

Multiple options are available for the tibial insert in total knee arthroplasty (TKA). A systematic review (SR) and network meta-analysis (NMA) to compare available randomized controlled trials (RCTs) could assist with decision making. We aim to show that designs with increased conformity may improve function and satisfaction without an increase in complications though posterior stabilized (PS) inserts will likely have more flexion.

Methods

A search of MEDLINE, EMBASE, and the Cochrane Library was performed. Studies were limited to RCTs evaluating cruciate retaining (CR), PS, anterior stabilized (AS), medial pivot (MP), bicruciate retaining (BR), and bicruciate stabilizing (BCS) inserts. Mean differences (MD) were used for patient reported outcome measures (PROMs) and odds ratios (OR) for reoperation rates and MUA. A systematic review was performed for satisfaction.

Results

27 trials were identified. The NMA showed no difference from a statistical or clinical standpoint for PROMs evaluated. There was a statistical difference for increased flexion for PS knees (3 degrees p 0.04). There were no differences in the MUA or reoperation rates. There was insufficient information to determine if a specific insert improved satisfaction.

Discussion

The results of this NMA show no statistical or clinical difference in PROMs. There was higher flexion for PS knees though the amount was not clinically significant. There was insufficient data for conclusions on patient satisfaction. Therefore, the surgeon should evaluate the clinical situation to determine the best insert rather than choose and insert based on functional scores, patient satisfaction, or complication rates.

Trends in Polyethylene Design and Manufacturing Characteristics for Total Knee Arthroplasty: An Analysis From the American Joint Replacement Registry

BACKGROUND

Advances in polyethylene bearing characteristics have led to various options for total knee arthroplasty. We examine trends in use of polyethylene in the United States.

METHODS

An analysis of American Joint Replacement Registry data from 2012 to 2019 for primary total knee arthroplasty procedures was conducted. Design and manufacturing characteristics were obtained and validated in the American Joint Replacement Registry dataset. Polyethylene bearing design and manufacturing use characteristics were compared by year, gender, age group, and geographic region of the procedure. Descriptive analysis was performed.

RESULTS

We identified 993,292 cases over the study period. In total, 791,233 (80%) cases had complete device data available and were included in analysis. In addition, 366,280 (49.4%) cases utilized minimally stabilized bearings compared to 374,809 (50.6%) for posterior-stabilized bearings. Posterior-stabilized use was stable over the study period and highest in the Northeast (64.5%; P < .0001). Cruciate-retaining use decreased from 29.7% to 20.2% and anterior-stabilized use increased from 17.4% to 25.2%. Conventional polyethylene use decreased from 42.8% to 21.9%, and was highest in the 81+ age group (37.8%; P < .0001) and Northeast (43.0%; P < .0001). Highly cross-linked polyethylene (HXLPE) with antioxidant use increased from 9.08% to 31.8%, while HXLPE without antioxidant use remained constant.

CONCLUSION

There was an increase in use of anterior-stabilized and pivot bearings and an increase in use of HXLPE with antioxidant. Additionally, there were noted age group and regional differences in the use of various bearings. Further study should evaluate if these changing utilization trends are related to clinical outcomes, or due to regional training, preferences, or manufacturer pressures.

LEVEL OF EVIDENCE

Level III, retrospective.

Similar outcomes including maximum knee flexion between mobile bearing condylar-stabilised and fixed bearing posterior-stabilised prosthesis: a case control study

Purpose

Prosthesis design influences stability in total knee arthroplasty and may affect maximum knee flexion. Posterior-stabilised (PS) and condylar-stabilised (CS) designed prosthesis do not require a posterior-cruciate ligament to provide stability. The aim of the current study was to compare the range of motion (ROM) and clinical outcomes of patients undergoing cemented total knee arthroplasty (TKA) using either a PS or CS design prosthesis.

Methods

A total of 167 consecutive primary TKAs with a CS bearing (mobile deep-dish polyethylene) were retrospectively identified and compared to 332 primary TKA with a PS constraint, with similar design components from the same manufacturer. Passive ROM was assessed at last follow-up with use of a handheld goniometer. Clinical scores were assessed using Patient-Reported Outcome Measures (PROMs); International Knee Society (IKS) knee and function scores and satisfaction score. Radiographic assessment was performed pre and post operatively consisting of mechanical femorotibial angle (mFTA), femoral and tibial mechanical angles measured medially (FMA and TMA, respectively) on long leg radiographs, tibial slope and patella height as measured by the Blackburne-Peel index (BPI).

Results

Both groups had a mean follow-up of 3 years (range 2–3.7 years). Mean post-operative maximum knee flexion was 117° ± 4.9° in the PS group and 119° ± 5.2° in the CS group (p = 0.29). Postoperative IKS scores were significantly improved in both groups compared to preoperative scores (p < 0.01). The mean IKS score in the PS group was 170.9 ± 24.1 compared to 170.3 ± 22.5 in the CS group (p = 0.3). Both groups had similar radiographic outcomes as determined by coronal and sagittal alignment, tibial slope and posterior condylar offset ratio measurements. When considering the size of tibial slope change and posterior-condylar offset ratio, there was no differences between groups (p = 0.4 and 0.59 respectively). The PS group had more interventions for post-operative stiffness (arthrolysis or manipulation under anaesthesia) 8 (2.7%) compared to 1 (0.6%) in the CS group (p = 0.17).

Conclusion

Condylar-stabilised TKA have similar patient outcomes and ROM at a mean follow-up of 3 years compared to PS TKA. Highly congruent inserts could be used without compromising results in TKA at short term.

Level of evidence

Level IV, retrospective case control study.

Ultracongruent insert design is a safe alternative to posterior cruciate-substituting total knee arthroplasty: 5-year results of a randomized controlled trial

PURPOSE

If substitution of the posterior cruciate ligament in total knee arthroplasty is necessary, there are two options available: posterior stabilized (PS) design with a post-cam mechanism or anterior-lipped ultracongruent (UC) inserts. UC inserts have the advantage that no femoral box is necessary and a standard femoral component can be used. The aim of this study was to compare the range of motion (ROM) and patient-reported outcome (PRO) after UC and PS fixed-bearing TKA. Better ROM in PS TKA and no difference in PRO between both designs was hypothesized.

METHODS

A randomized controlled trial with 127 patients receiving a fixed-bearing UC or PS design of the same knee system was performed. Nine patients died and there were four revision surgeries. 107 patients completed the 5-year follow-up. Patient-reported outcome was assessed. Patellofemoral problems were evaluated using selected applicable questions of the Oxford Knee Score (getting up from a table, kneeling, climbing stairs).

RESULTS

Surgical time was 10 min shorter in the UC group (p < 0.001). After 5 years, both groups demonstrated good knee function and health-related quality of life without significant differences between the groups. Both groups demonstrated a high satisfaction score and the majority of patients would undergo this surgery again. Patellofemoral problems were recognized more frequently in the PS group (p = 0.025).

CONCLUSION

Both designs demonstrated similar good results after 5 years. Stabilization with an anterior-lipped UC insert can be considered a safe alternative to the well-established PS design if cruciate substitution is necessary.

Cruciate-Retaining vs Posterior-Stabilized Antibiotic Cement Articulating Spacers for Two-Stage Revision of Prosthetic Knee Infection: A Retrospective Cohort Study

BACKGROUND

Antibiotic cement articulating spacers are recommended during 2-stage revision for prosthetic knee infection because of increased range of motion (ROM) and improved function; however, spacer mechanical complications have been reported. We aimed to determine the association between different constraints of articulating spacers and the rate of complications and infection eradication, functional outcomes, and ROM.

METHODS

A retrospective study of prosthetic knee infection using cruciate-retaining (CR) or posterior-stabilized (PS) spacers was conducted between 2011 and 2018. The rate of spacer mechanical complications, infection eradication after reimplantation and reoperation, Hospital of Special Surgery (HSS) knee score, and ROM during the interim stage were analyzed. All patients were regularly followed up for 2 years.

RESULTS

One hundred forty-one patients were included, with 66 CR and 75 PS spacers. Overall mechanical complication rate was lower in PS (9.3%) than in CR spacers (45.5%) (P < .001), especially in joint dislocation (1.3% vs 30.3%, respectively, P < .001). Overall reoperation rate was lower in PS (16.0%) than in CR spacers (36.4%) (P < .001), especially for mechanical complications (1.3% vs 24.2%, respectively, P < .001). HSS knee score was higher in PS (72.3) than in CR spacers (63.8) (P < .001). ROM was greater in PS (90.3°) than in CR spacers (80.6°) (P = .005), especially at maximum flexion (102.4° vs 89.6°, respectively, P = .003). Infection eradication was comparable between the spacers.

CONCLUSION

Both spacers can control infection; however, PS spacers had a lower rate of mechanical complications and reoperation, better HSS knee scores, and greater ROM than CR spacers.

Comparison of Functional Outcomes, Femoral Rollback and Sagittal Stability of Anterior-Stabilized Versus Posterior-Stabilized Total Knee Arthroplasty: A Systematic Review and Meta-analysis of Randomized Controlled Trials

PURPOSE

Total knee arthroplasty (TKA) has improved leaps and bounds in terms of design to improve clinical outcomes and achieve better rehabilitation of the patients. Ultra-congruent inserts (UC) were designed to replace the need for posterior stabilized (PS) implants. The purpose of this review was to evaluate clinical outcomes, femoral rollback, functional scores, range of motion, sagittal laxity, complication rates, and isokinetic performance between UC and PS TKA among RCTs.

METHODS

Electronic databases such as PubMed, Scopus, opengrey, and Cochrane were searched from date of inception up to mid-April 2021, and meta-analysis was performed following PRISMA guidelines. This study analyzed outcomes, femoral rollback, tibial sagittal laxity and isokinetic performance.

RESULTS

Ten RCTs identified 852 knees, of which 420 underwent UC TKAs and 432 underwent PS TKA. Compared to UC TKA, a significantly better sagittal stability (p = 0.17) and femoral rollback (p < 0.00001) in PS TKAs was noted, although no statistically significant difference was found in the assessment of the range of motion (p = 0.19) and functional scores. Both the groups had similar isokinetic performance with extensor torque (p = 0.97) and flexor torque (p = 0.37).

CONCLUSIONS

We conclude with the current meta-analysis that there are no added benefits for UC over PS inserts and these inserts have a higher sagittal laxity and less femoral roll back in cruciate sacrificing UC knee. But since there are no long-term wear data, UC inserts with CS technique should be used cautiously and may be used only when the PCL cannot be balanced adequately. There is no evidence or only a few to support the superiority of the AS TKA in terms of clinical outcomes or isokinetic performance or femoral external rotation over PS TKA.

LEVEL OF EVIDENCE

Level I, Systematic review and meta-analysis of RCTs.