Posterior cruciate-retaining versus posterior stabilized total knee arthroplasty: a meta-analysis of randomized controlled trials

Development and validation of a nomogram for predicting a forgotten joint in patients one year after robotic-assisted total knee arthroplasty

PURPOSE

The Forgotten Joint Score (FJS-12) was designed to assess the extent to which patients were unaware of their artificial joints during daily activities, representing an ideal outcome of TKA. This study aimed to identify the individual predictors and develop a nomogram to predict a forgotten joint in patients 1 year after robotic-assisted total knee arthroplasty (RA-TKA).

METHODS

This retrospective study involved 199 patients with knee osteoarthritis who underwent RA-TKA. All participants completed the FJS-12 questionnaire at 1-year follow-up, with scores above 77.1 considered indicative of a forgotten joint. The demographic data, surgical data, preoperative and postoperative imaging data were collected for analysis. Univariate and multivariate logistic regression analyses were conducted to determine predictors and establish a predictive model. The receiver operating characteristic curve, calibration curve analysis and decision curve analysis (DCA) were used to evaluate the discriminatory ability, calibration and clinical usefulness of the model.

RESULTS

Overall, 44.22% (88/199) of knees achieved a forgotten joint 1 year after RA-TKA. Five variables were identified as independent predictors, including age, sex, prothesis type, operative time and changes in the arithmetic hip-knee-ankle angle (aHKA). The area under the curve (AUC) of the nomogram was 0.726 and 0.725 (95% CI 0.660-0.788) using 500 bootstrap resampling. The Hosmer-Lemeshow test showed that the model was of goodness-of-fit (p = 0.886). And the DCA showed net benefits when the threshold probability was between 20 and 75%.

CONCLUSIONS

A nomogram was developed and internally validated for predicting a forgotten joint 1 year after RA-TKA. Its implementation may enhance patient selection, refine preoperative counseling, and optimize surgical decision-making, potentially improving functional outcomes. Further external validation in broader populations is required to confirm its generalizability.

CLINICAL TRIAL NUMBER

Not applicable.

Comparable outcomes between cruciate-substituting and posterior-stabilized inserts in robotic total knee arthroplasty under the functional alignment principles

PURPOSE

Functional alignment (FA) has emerged as a personalized strategy in total knee arthroplasty (TKA) to optimize outcomes by accounting for patient-specific anatomical and soft tissue characteristics. Limited evidence exists on how polyethylene insert type, specifically cruciate-substituting (CS) versus posterior-stabilized (PS), impacts clinical outcomes and complications in this context.

METHODS

This retrospective comparative study included 329 patients who underwent robotic-assisted TKA with FA principles with a minimum 2-year follow-up. Patients were divided into two groups: CS or PS implants. CS inserts were selected for patients with an intact posterior cruciate ligament (PCL), while PS inserts were used in cases of PCL insufficiency or significant flexion contractures. Preoperative and post-operative outcomes, including Knee Society Scores (KSS), Forgotten Joint Scores (FJS), range of motion (ROM) and complications, were assessed. Implant survivorship was analyzed using the Kaplan-Meier method.

RESULTS

At a median follow-up of 36 months, no significant differences were observed between CS and PS groups in KSS (knee: p = 0.45; function: p = 0.4), FJS (p = 0.7) or ROM (median flexion: 130° in both groups, p = 0.52). Specific complications included intraoperative lateral condyle fractures in the PS group and femoral component revisions due to instability in the CS group. The overall complication rates and implant survivorship were comparable (p = 0.55 and p = 0.85, respectively).

CONCLUSION

This study is the first to evaluate polyethylene insert type in FA and demonstrates that both CS and PS inserts provide comparable outcomes and safety profiles in robotic-assisted TKA. These findings underscore the importance of patient-specific implant selection, with further research needed to assess long-term results.

LEVEL OF EVIDENCE

Level III.

The influence of implant factors on patient outcomes in primary total knee arthroplasty

Background

The influence of implant factors on patient-reported outcome measures (PROMS) after total knee arthroplasty (TKA) has previously been studied but findings are often inconsistent, restricted in scope and biased by confounding factors. This study aims to determine the association between implant-related factors and early post-operative PROMs after TKA.

Methods

Using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) PROMs program, the study included 9487 primary TKA procedures performed in 43 hospitals from July 31, 2018 to December 31, 2020. Data included baseline demographic data, surgical details and PROMs collected pre- and 6 months post-operatively. Seven prosthesis characteristics were incorporated in the multivariable model, with proportional odds ordinal regression analysis used to assess their effects on post-operative Oxford knee score (OKS) and joint pain. Adjustments were made for pre-operative OKS and joint pain, as well as potential patient confounders.

Results

At six months, fixed bearing implants showed higher odds of better OKS compared to mobile bearing implants (odds ratio [OR] = 1.20, 95 % confidence interval [CI] 1.06-1.37. p < 0.004). Similar findings were found with the use of image derived instrumentation (IDI) (OR = 1.27, 95 % CI 1.11-1.46, p < 0.001), robotic assisted vs. non-navigated knees (OR = 1.21, 95 % CI 1.06-1.38, p < 0.005) and no patella resurfacing (OR = 1.10, 95 % CI 1.01-1.20, p < 0.032). For lower pain scores at six months, the use of highly crosslinked polyethylene (OR = 1.12, 95 % CI 1.02-1.22, p < 0.015), cemented femoral components (OR = 1.11, 95 % CI 1.01-1.22, p < 0.024), IDI (OR = 1.20, 95 % CI 1.05-1.37, p < 0.009) or no patella resurfacing (OR = 1.10, 95 % CI 1.01-1.20, p < 0.034) were associated.

Conclusion

Utilizing a fixed bearing or robotic assistance correlated with improved OKS scores, whereas highly crosslinked polyethylene or cemented femoral components were associated with improved pain scores. At six months, the use of IDI compared to non-navigated TKA, and patellar resurfacing showed both improved OKS and pain scores.

Mid-vastus approach induces milder short-term effects on postural control compared to parapatellar approach in total knee arthroplasty

BACKGROUND

Mid-Vastus and Medial Parapatellar techniques are used for total knee arthroplasty. Their short-term effects within the first month after surgery are yet unexplored. The purpose of this study was to compare Mid-Vastus and Medial Parapatellar effects on knee strength and balance control, at 5 days, 2 weeks and one month after surgery. It was hypothesized that Mid-Vastus would induce milder effects on the dependent variables due to its less invasive nature.

METHODS

Twenty females, randomly assigned to either the Mid-Vastus or the Medial Parapatellar group performed knee flexion-extension force and 30 s of bipedal stance before, 5 days, 2 weeks and one month after surgery. Maximum force, weight distribution and travel distance of the Center of Pressure were calculated.

FINDINGS

Both groups showed decreased force output at all post-measurements compared to before surgery. Medial Parapatellar group showcased significantly higher travel distance at the 2 weeks measurement (Z = -2.268, p = .023, |r| = 0.507) compared to before surgery. This result was also imprinted on the travel distance of the non-surgical knee limb in the post (t = 3.259, p = .004, d = 1.456), 2 weeks (Z = -2.570, p = .009, |r| = 0.574) and one month measurement (t = 2.653, p = .016, d = 1.185).

INTERPRETATION

While force is affected for both approaches, Mid-Vastus approach does not affect postural control. Therefore, Mid-Vastus is a less invasive technique compared to Medial Parapatellar. This work highlights the differences between Mid-Vastus and Medial Parapatellar approaches at least until the first month of rehabilitation.

Comparative analysis and validation of posterior cruciate ligament management in mobile-bearing total knee arthroplasty: Meta-analysis and animal study

Total knee arthroplasty (TKA) is an effective treatment for end-stage knee joint diseases. The debate over preserving or sacrificing the posterior cruciate ligament (PCL) in mobile-bearing TKA (MB TKA) still needs to be solved due to the lack of high-quality evidence, particularly meta-analyses comparing these techniques. This study aims to conduct a meta-analysis to compare the outcomes of PCL retention (CR) and PCL sacrifice (PS) in terms of clinical and functional knee scores, range of motion, complication rates, and revision rates and to validate these findings through animal experiments. A comprehensive search was conducted using MEDLINE, Cochrane, and Embase databases. Relevant studies were selected for the meta-analysis using RevMan 5.3. Additionally, an animal experiment using Sprague-Dawley rats simulated MB TKA to compare the effects of PCL retention and sacrifice surgeries. 12 studies were included in the meta-analysis. No significant differences were found between CR and PS techniques regarding HSS, KSS, KSFS, WOMAC, ROM, and medial/lateral instability. However, CR MB showed slight superiority in NKJS, while PS MB had better outcomes in complication and revision rates. In the animal study, CR rats exhibited significant early postoperative inflammation, but both groups' knee structures gradually normalized. The meta-analysis indicates that PCL retention (CR MB) and sacrifice (PS MB) have similar effects on various clinical and functional knee scores. However, PS MB is significantly better at reducing complications and revision rates. The animal experiment confirms PS MB's advantages in reducing inflammation and promoting joint recovery. Despite the strong evidence, long-term follow-up and larger-scale randomized controlled trials are necessary to confirm these findings.

Robotic-assisted total knee arthroplasty reduces soft-tissue releases which improves functional outcomes: A retrospective study

BACKGROUND

There is increasing use of Robotic-Assisted (RA) and personalized alignment techniques in total knee arthroplasty (TKA). The hypothesis of this study was that RA TKA would result in fewer soft-tissue releases, and that fewer soft-tissue releases would be associated with improved clinical outcomes.

METHODS

A retrospective review of an internal company registry was conducted for all primary TKAs performed from Jan 1, 2014, through a database extract date of Nov 4, 2022. These were grouped by whether there was an intentional soft-tissue release performed (STR) during the surgery or not (NSTR) and whether RA was utilized. The incidence of STR was compared between RA-TKAs and those performed with manual instrumentation. Knee Society Score (KSS) and Knee Society Function Scores (KSFS) were collected at 6 months, 1 year and 2 years. Kaplan-Meier survivorship was performed.

RESULTS

The incidence of STR was significantly lower for RA vs. Manual (43.81% Vs 86.62%, p < 0.0001). The TKAs with NSTR had higher KSFS compared to those with STR at 6 months (84.73 Vs. 77.51, p < 0.0001), 1 year (89.87 Vs. 83.54, p < 0.0001) and 2 years (90.09 Vs. 82.65, p < 0.0001). There was no difference in survivorship, or KSS at any time point. However, the NSTR group had improved KSS pain sub score at 2 years.

CONCLUSION

The results of this observational, retrospective analysis found that the incidence of soft-tissue release was lower with RA-TKA. Further, regardless of if RA was used, avoiding releases was associated with improved KSFS and KSS pain scores through 2 years post-operatively.

The Vega advanced third generation posterior stabilized total knee arthroplasty system enables the restoration of range of motion for high demanding daily activities - A 5-years follow-up study

BACKGROUND

The Vega System® PS (Aesculap AG, Tuttlingen, Germany) is an advanced, third generation fixed implant that aims to mimic natural knee kinematics by optimizing pivotal motion while reducing surface stress. This study evaluated mid-term survival and clinical outcomes, including range of motion (ROM) of the modern posterior stabilized implant in order to analyse whether this biomechanically successful implant reaches good results in situ.

METHODS

The first 100 patients to receive the Vega PS System for total knee arthroplasty were invited to take part in this single centre, single surgeon study. Of these, 84 patients were clinically assessed 5-6 years postoperatively. Data which was obtained during this follow-up examination included revision data, range of motion and clinical scores.

RESULTS

The 5-year survival rate for exchange of any component was 97.6%, whereby two patients required replacement of the polyethylene gliding surface. Secondary patella resurfacing was performed in 7 patients. Significantly improved results in comparison to the preoperative state could be obtained at the follow-up: KOOS improved from 39.4 to 78.8, SF-12 PCS improved from 32.1 to 42 SF-12 MCS improved from 46 to 53.8 and patella pain improved from 2.7 to 0.3. The mean ROM of the 84 patients after 5 years was 133.1° and mean total KSS was 189.9.

DISCUSSION & CONCLUSIONS

This study demonstrates a high survival rate of the Vega PS System® and significant improvements in clinical outcomes 5 years after implantation. The obtained mean ROM indicates that this implant provides good flexibility of the knee joint, allowing a high number of activities. However, due to the rate of secondary patella implantation, routine resurfacing of the patella for all PS TKA cases is highly recommended.

CLINICAL TRIALS REGISTRATION

The study was registered at clinicaltrials.gov (NCT02802085).

Comparison of revision rates and epidemiological data of a single total knee arthroplasty system of different designs (cruciate retaining, posterior stabilized, mobile bearing, and fixed bearing): a meta-analysis and systematic review of clinical trials and national arthroplasty registries

BACKGROUND

This study aimed to meta-analyze epidemiological data, revision rates, and incidences of different designs of a single Total Knee Arthroplasty System and compare these factors across different countries.

METHODS

A systematic review was conducted on clinical studies and arthroplasty registries of ATTUNE TKA from 1999 to 2020. The main endpoints analyzed were revision rates and epidemiological data.

RESULTS

The average age of patients was 67.8 years, with a gender distribution of 60% female and 40% male. The pooled average BMI was 29.4 kg/m2. Eight clinical studies showed a pooled revision rate per 100 observed CY of 0.5 (n = 1343 cases). Cumulative revision rates after 1, 3, and 5 years varied among registries, with the Swiss registry having the highest revision data (after 5 years: 6.3%) and the American registry having the lowest revision data (after 5 years: 1.7%). A comparison of the revision rates of mobile bearing and fixed bearing (41,200 cases) as well as cruciate retaining and posterior stabilized (n = 123,361 cases) showed no significant advantage in the first 5 years after implantation.

CONCLUSION

In conclusion, pooled data from 41,200 cases of TKA with a single Total Knee Arthroplasty System in two arthroplasty registries revealed that there was no significant difference in revision rates between the mobile bearing and fixed bearing design within the first 5 years after implantation. In addition, a comparison of the revision rates in n = 123,361 cases showed no significant advantage for cruciate retaining or posterior stabilized in the first 5 years after implantation.

A Polished Cobalt-Chrome Baseplate is not Associated With a Lower Revision Rate Than Matt Titanium in a Single Total Knee Arthroplasty Implant System With Identical Baseplate Design

BACKGROUND

Polished baseplates were introduced into total knee arthroplasty (TKA) systems to reduce the incidence of backside wear. In 2004, a fixed-bearing knee arthroplasty system underwent a change in baseplate material from matt titanium to polished cobalt-chrome (CoCr) with the intention to reduce backside wear. Other design aspects were left unchanged. The aim of this study was to compare these implants with each baseplate using data from the Australian Orthopaedic Association National Joint Replacement Registry.

METHODS

Primary TKA procedures performed between January 2010 and December 2021 for osteoarthritis, using a single design with cross-linked polyethylene inserts and matt titanium or polished CoCr baseplates, were analyzed. The primary outcome was all-cause revision, summarized using Kaplan-Meier estimates, with age- and sex-adjusted hazard ratios estimated from Cox proportional hazards models. In total, there were 2,091 procedures with matt titanium and 2,519 procedures with polished CoCr baseplates.

RESULTS

The 9-year cumulative percent revision was 2.5% (95% confidence interval [CI] 1.8 to 3.5%) and 4.2% (95% CI 3.1 to 5.6%) for the matt titanium and CoCr groups, respectively. Compared to matt titanium, the revision rate of CoCr baseplates was not significantly higher (hazard ratio 1.44; 95% CI 0.96 to 2.15; P = .076).

CONCLUSIONS

Polished CoCr baseplates in a single TKA system were not associated with reduced all-cause revision rates compared to matt titanium up to 11 years post-TKA. Our results suggest that the predicted reduction in wear particle debris production from polished CoCr baseplates may not correlate with reduced revision rates in vivo, but further evaluation is required.

Cementless medial pivot design demonstrates equal or better outcomes compared to cementless cruciate-retaining design following total knee arthroplasty

Introduction

Traditional total knee arthroplasty (TKA) designs fail to reproduce physiologic knee kinematics, which can contribute to patient dissatisfaction. In an attempt to restore more normal knee kinematics, the medial pivot (MP) design may improve knee function and stability as well as patient satisfaction. A limited number of studies have compared postoperative outcomes of exclusively cementless Cruciate-Retaining (CR) TKAs to cementless MP TKAs. We aimed to compare: (1) 90-day, 1-year, and 2-year complications and revisions, (2) preoperative and postoperative range of motion (ROM), (3) Knee Injury and Osteoarthritis Outcome (KOOS-JR), and (4) visual analog scale (VAS) pain scores at 3-month, 6-month, 1-year, and 2-years.

Methods

A retrospective analysis was performed to identify all patients who had previously undergone a TKA at our institution and compare a cementless CR system to a cementless MP design. Categorical variables, including demographics, comorbidities, and complications utilized Chi-square tests in bivariable analysis. Continuous variables, such as age, were compared using Student's t-tests. Significance was defined as p < 0.05.

Results

Cementless CR and cementless MP cohorts showed low profiles of postoperative complications and favorable patient-reported outcome measures (PROMs). The MP cohort had lower VAS pain at 1-year (1.70 vs. 3.76, p < 0.001) and 2-years (1.43 vs. 2.60, p < 0.001) and higher ROM at 3-months (118 vs. 100, p < 0.001), 6-months (113 vs. 103, p < 0.0001), and 1-year (117 vs. 110, p = 0.02), respectively.

Conclusion

This study is the first comparison of postoperative outcomes between a cementless CR TKA and cementless MP TKA designs. Implant design and fixation type are vital components influencing patient satisfaction after TKA. Pain scores and range of motion favored the cementless MP cohort in comparison to the cementless CR cohort.

Better Flexion but Unaffected Satisfaction After Treatment With Posterior Stabilized Versus Cruciate Retaining Total Knee Arthroplasty - 2-year Results of a Prospective, Randomized Trial

BACKGROUND

Both the cruciate-retaining (CR) and posterior-stabilized (PS) implant systems are commonplace in modern total knee arthroplasty (TKA) practice. However, there is controversy regarding functional outcomes and survivorship. The aim of the underlying study was to evaluate differences between CR and PS TKA regarding knee function, patient-reported outcome measures (PROMs) as well as complication rates.

METHODS

140 patients with knee osteoarthritis scheduled for an unconstrained TKA were enrolled in a prospective, randomized study. Patients received either a CR or PS implant. Range of motion and PROMs (Oxford Knee Score, Knee Society Score, European Quality of Life 5 Dimensions 3 Level, University of California Los Angeles Activity scale and subjective satisfaction) were assessed prior to, 3 months, 1 and 2 years after surgery.

RESULTS

We found minor differences between treatment groups regarding demographic factors. Within the PS group duration of surgery was longer (mean PS 81.4 min vs CR 76.0 min, P = .006). We observed better flexion (median PS 120.0° vs CR 115°, P = .017) and an overall better range of motion (median PS 120.0° vs CR 115.0°, P = .008) for the PS group. PROMs did not differ between groups. At 2-year follow-up there were no revisions in either cohort. Five patients needed reoperations. Three patients needed manipulation under anesthesia, 2 in the CR and one in the PS group.

CONCLUSION

While PS TKA achieved a better flexion capability, PROMs were similar in CR and PS TKA. The CR implant design continues to be a reliable option for patients with an intact posterior cruciate ligament.

Can pain be improved with retention of the posterior cruciate ligament during total knee arthroplasty?

PURPOSE

The purpose of the current study was to determine if differences exist between cruciate-retaining (CR) and posterior-stabilized (PS) implant articulations for total knee arthroplasty (TKA) with regards to early post-operative pain.

METHODS

We retrospectively reviewed patients who underwent primary TKA, with the same TKA implant design, at our institution between January 2018 and July 2021. Patients were stratified based on whether they received a CR or non-constrained PS (PSnC) articulation and propensity score matched in a 1:1 ratio. A sub-analysis matching patient who received a constrained PS implant (PSC) to those undergoing CR TKA and PSnC TKA was also carried out. Opioid dosages were converted to morphine milligram equivalents (MME).

RESULTS

616 patients after CR TKA were matched 1:1 to 616 patients with a PSnC implant. There were no significant differences between demographic variables. There were no statistically significant differences in opioid usage measured by MME on post-operative day (POD) 0 (p = 0.171), POD1 (p = 0.839), POD2 (p = 0.307), or POD3 (p = 0.138); VAS pain scores (p = 0.175); or 90-day readmission rate for pain (p = 0.654). A sub-analysis of CR versus PSC TKA demonstrated no significant differences in opioid usage on POD0 (p = 0.765), POD1 (p = 0.747), POD2 (p = 0.564), POD3 (p = 0.309); VAS pain scores (p = 0.293); and 90-day readmission rate for pain (p > 0.9).

CONCLUSION

Our analysis demonstrated no significant difference in post-operative VAS pain scores and MME usage based on implant. The results suggest that neither the type of articulation or constraint used for primary TKA has a significant impact on immediate post-operative pain and opioid consumption.

LEVEL III EVIDENCE

Retrospective Cohort Study.

The effectiveness of cruciate-retaining versus posterior-stabilized designs on extensor mechanism function and knee function in patients after simultaneous bilateral total knee arthroplasty: A two-year retrospective follow-up study

INTRODUCTION

The importance of the posterior-cruciate ligament in knee functionality is known; however, the effect of preserving the posterior-cruciate ligament in total knee arthroplasty (TKA) on extensor mechanism function and knee function is not clear. We aimed to compare extensor mechanism function and knee function between patients operated with the cruciate-retaining and posterior-stabilized designs for simultaneous bilateral TKA.

HYPOTHESIS

Patients operated with the cruciate-retaining design would produce better outcomes than those operated with the posterior-stabilized design.

MATERIALS AND METHODS

A total of 104 patients were divided into two groups as the cruciate-retaining (n=52) and posterior-stabilized (n=52) groups. The groups were compared for extensor mechanism function (chair-rise test) and knee function (Hospital for Special Surgery [HSS] knee score). The follow-up points were six weeks, three months, six months, one year and two years.

RESULTS

No statistically significant effect on chair-rise performance of the group-by-time interaction (χ2 [5, n=104]=5.32, p=.37) or of group (χ2 [1, n=104]=1.69, p=.19). In the HSS knee score, the group-by-time interaction was statistically significant (F [5.510]=6.24, p<.001). A statistically significant difference of 7.4 points in favor of the posterior-stabilized group was found at six weeks (p=.002). No statistically significant differences were found between the groups at the other follow-up points.

DISCUSSION

The cruciate-retaining and posterior-stabilized designs have similar outcomes with regard to extensor mechanism function and knee function in the long-term period in patients who underwent simultaneous bilateral TKA. In the short-term period, the posterior-stabilized design shows better knee function than the cruciate-retaining design.

LEVEL OF EVIDENCE

III; a retrospective study.

Equivalence of clinical and radiological outcomes in cruciate-retaining and cruciate-substituting total knee arthroplasty with medial pivot knee: A comparative study

Introduction

Total knee arthroplasty (TKA) has been recognized as the most efficacious surgical intervention for individuals suffering from advanced arthritis; however, there is ongoing debate on the technical details of the procedure. It remains unknown whether preservation of the posterior cruciate ligament (PCL) significantly affects the mid-to long-term performance of ADVANCE® medial-pivotal (AMP) knee implants to enhance patient satisfaction. The hypothesis of this study was to investigate whether the preservation of the PCL has a substantial impact on the functional outcomes of medial pivot (MP) implants in patients undergoing TKA. Therefore, this study aimed to compare the midterm clinical and radiographic outcomes of cruciate-retaining (CR) and cruciate-substituting (CS) TKA using MP prostheses.

Methods

We included 376 consecutive patients who underwent unilateral TKA between January 2011 and April 2014. Follow-up evaluations were conducted in April 2021. After propensity score matching analysis, clinical and radiological outcomes and complication rates were compared between patients in the CR and CS groups.

Results

The postoperative outcomes in the two groups significantly improved the preoperative conditions of the patients (all p > 0.05). The postoperative outcomes (WOMAC score, p = 0.517; KSS, p = 0.107; KSFS, p = 0.240; ROM, p = 0.795; FJS, p = 0.822) and radiographic outcomes (preoperative FTA, p = 0.997; postoperative FTA, p = 0.646; aLDFA, p = 0.094; aMPTA, p = 0.970; PTS, p = 0.243) were comparable between the two groups. The complication and revision rates between the groups were not statistically significant (p = 0.34). The Kaplan-Meier cumulative survival of patients in the CRTKA and CSTKA groups was 100 % and 98.6 %, respectively.

Conclusions

This study supports the hypothesis that when MP prostheses are used, both CR and CS procedures achieve equally good mid-to long-term clinical and radiographic outcomes and complication rates. These findings suggest that PCL preservation may not significantly affect the overall performance of MP implants in patients undergoing TKA.

12-Year clinical and radiological results of a double-blind randomized controlled trial comparing posterior cruciate-retaining versus posterior-stabilized total knee arthroplasty

BACKGROUND

A subject of ongoing debate among orthopedic surgeons is the importance of preserving the posterior cruciate ligament in total knee arthroplasty (TKA), but long-term survival studies are scarce. The aim of this study was to compare long-term survival rates, and clinical and radiological follow up of a double-blind randomized controlled trial comparing posterior cruciate-retaining (PCR) versus posterior-stabilizing (PS) implant design of an AGC TKA.

METHODS

A total of 114 patients were included in the survival analysis (PCR n = 61; PS n = 53). Forty-five patients (PCR n = 25; PS n = 20) participated in the long-term follow up using patient-reported outcome measures (Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short-Form Health Survey (SF-36) and Kujala score (measuring anterior knee pain)). Thirty-one patients were assessed with a physical test (Knee Society Score (KSS)) and radiographs.

RESULTS

Overall survival rate was 95.6% (PCR 98.4% vs. PS 92.5%), with five patients having a major revision (PCR n = 1 vs. PS n = 4, respectively). Satisfying outcome scores for both groups were described at on average 12-year follow up with no significant differences in KSS knee and function scores, WOMAC, SF-36, or Kujala scores between groups. Radiographically, there were no findings of femoral or tibial loosening or polyethylene wear in either group.

CONCLUSIONS

Good long-term survival rates were described for the PCR and the PS design of an AGC TKA. There were no significant differences in clinical and radiological outcomes between a PCR and a PS design 12 years postoperatively.

Optimizing Asymmetric Native Knee Flexion Gap Balance Promotes Superior Outcomes in Primary Total Knee Arthroplasty

INTRODUCTION

Replicating native knee kinematics remains the ultimate goal of total knee arthroplasty (TKA). Technology, such as robotics, provides robust intraoperative data; however, no evidence-based targets currently exist for improved clinical outcomes. Furthermore, some surgeons target a rectangular flexion space in TKA unlike the native knee. This study evaluated the effect of in vivo flexion gap asymmetry on patient-reported outcome measures (PROMs) in contemporary TKA.

METHODS

In vivo tibiofemoral joint space dimensions were measured during 129 TKAs using a calibrated tension device before and after complete posterior cruciate ligament resection. PROMs were compared based on the final dimensions and the change in flexion gap dimensions at 90° of flexion: (1) equal laxity, (2) lateral laxity, and (3) medial laxity. Groups did not differ by demographics ( P ≥ 0.347), clinical follow-up ( P = 0.134), tibiofemoral alignment ( P = 0.498), or preoperative PROMs ( P ≥ 0.093). Mean follow-up for the cohort was 1.5 years (range, 1-3).

RESULTS

Pain with climbing stairs, pain while standing upright, and knees "always feeling normal" scores were superior for patients with equal or lateral laxity compared with medial laxity ( P ≤ 0.064). Pain with level walking, University of California Los Angeles activity level, KOOS JR, and satisfaction scores also tended to be superior for patients with equal or lateral laxity, although it lacked statistical significance ( P ≥ 0.111).

DISCUSSION

Results of this study suggest that patients with either an equally tensioned rectangular flexion space or with later-flexion lateral laxity after posterior cruciate ligament resection may achieve superior PROMs. Findings support the clinical benefit of facilitating posterolateral femoral roll back in flexion, which mimics native knee kinematics and further helps define targets for advanced technology.

Patients Who Have Kellgren-Lawrence Grade 3 and 4 Osteoarthritis Benefit Equally From Total Knee Arthroplasty

BACKGROUND

Recently, some payers have limited access to total knee arthroplasty (TKA) to patients who have Kellgren-Lawrence (KL) grade 4 osteoarthritis only. This study compared the outcomes of patients who have KL grade 3 and 4 osteoarthritis after TKA to determine if this new policy is justified.

METHODS

This was a secondary analysis of a series originally established to collect outcomes for a single, cemented implant design. A total of 152 patients underwent primary, unilateral TKA at two centers from 2014 to 2016. Only patients who had KL grade 3 (n = 69) or 4 (n = 83) osteoarthritis were included. There was no difference in age, sex, American Society of Anesthesiologists score, or preoperative Knee Society Score (KSS) between the groups. Patients who had KL grade 4 disease had a higher body mass index. KSS and Forgotten Joint Score (FJS) were collected preoperatively and at 6 weeks, 6 months, 1 year, and 2 years postoperatively. Generalized linear models were used to compare outcomes.

RESULTS

Controlling for demographics, improvements in KSS were comparable between the groups at all time points. There was no difference in KSS, FJS, and the proportion that achieved the patient acceptable symptom state for FJS at 2 years.

CONCLUSION

Patients who had KL grade 3 and 4 osteoarthritis experienced similar improvement at all time points up to 2 years after primary TKA. There is no justification for payers to deny access to surgical treatment for patients who have KL grade 3 osteoarthritis and have otherwise failed nonoperative treatment.

Factors that impact the patellofemoral contact stress in the TKA: a review

Abnormal retro patellar stress is believed to contribute to patellofemoral complications after total knee arthroplasty (TKA), but the causal link between TKA and patellofemoral contact stress remains unclear. By reviewing the relevant studies, we found that both TKA implantation and additional patellar resurfacing increase retro patellar pressure. The rotation and size of the femoral component, thickness and position of the patellar component, installation of the tibial component, prosthesis design and soft tissue balance further influence patellofemoral stress. Specific measures can be applied to reduce stress, including the installation of the femoral prosthesis with an appropriate external rotation angle, placing the tibial component at a more posterior position and the patellar button at a more medial position, avoiding over-sized femoral and patellar components, selecting posterior-stabilized design rather than cruciate-retaining design, using gender-specific prosthesis or mobile-bearing TKA system, and releasing the lateral retinaculum or performing partial lateral facetectomy. Despite these measures, the principle of individualization should be followed to optimize the patellofemoral biomechanics.

Comparison of clinical outcomes among total knee arthroplasties using posterior-stabilized, cruciate-retaining, bi-cruciate substituting, bi-cruciate retaining designs: a systematic review and network meta-analysis

BACKGROUND

Despite the advent of innovative knee prosthesis design, a consistent first-option knee implant design in total knee arthroplasty (TKA) remained unsettled. This study aimed to compare the clinical effects among posterior-stabilized (PS), cruciate-retaining (CR), bi-cruciate substituting (BCS), and bi-cruciate retaining designs for primary TKA.

METHODS

Electronic databases were systematically searched to identify eligible randomized controlled trials (RCTs) and cohort studies from inception up to July 30, 2021. The primary outcomes were the range of knee motion (ROM), and the secondary outcomes were the patient-reported outcome measures (PROMs) and complication and revision rates. Confidence in evidence was assessed using Confidence in Network Meta-Analysis. The Bayesian network meta-analysis was performed for synthesis.

RESULTS

A total of 15 RCTs and 18 cohort studies involving 3520 knees were included. The heterogeneity and inconsistency were acceptable. There was a significant difference in ROM at the early follow-up when PS was compared with CR (mean difference [MD] = 3.17, 95% confidence interval [CI] 0.07, 7.18) and BCS was compared with CR (MD = 9.69, 95% CI 2.18, 17.51). But at the long-term follow-up, there was no significant difference in ROM in any one knee implant compared with the others. No significant increase was found in the PROMs and complication and revision rates at the final follow-up time.

CONCLUSIONS

At early follow-up after TKA, PS and BCS knee implants significantly outperform the CR knee implant in ROM. But in the long run, the available evidence suggests different knee prostheses could make no difference in clinical outcomes after TKA with extended follow-up.

Cruciate-Retaining Total Knee Arthroplasty: Current Concepts Review

Posterior cruciate-retaining (CR) total knee arthroplasty for osteoarthritis of the knee is a popular implant choice. At present, there is no consensus on whether sacrifice or retention of the posterior cruciate ligament (PCL) offers superior outcomes. This review explores the current literature available on CR total knee arthroplasty (TKA). PubMed was searched by keyword to find relevant articles for inclusion. Additional sources came from article references and joint registry reports. CR design knees have distinct kinematic gait patterns from posterior-stabilizing (PS) knees and exhibit paradoxical anterior femoral movement with less femoral rollback. While CR implants offer less flexion than PS designs, the difference is not clinically detectable as clinical scores are similar in the short and long term. CR implants have better long-term survival compared to PS knees, likely due to lower risk of aseptic loosening. CR total knee arthroplasties also have shorter operating times and lower risk of peri-prosthetic fractures. Because the CR implant is unconstrained, there may be an increased risk of instability compared to PS designs, but the literature is mixed. Overall, the current literature supports the continued use of CR TKAs due to their lower risk of complications, durability, and demonstrated equivalence in function to posterior-substituting models.

Anterior knee pain and sit-up tests predicts patients' satisfaction and improvement in quality of life after anterior stabilized total knee replacement without patellar resurfacing

PURPOSE

The purpose of this study was to assess patient satisfaction and identify risk factors for dissatisfaction after anterior stabilised conventional total knee arthroplasty (TKA) without patellar resurfacing, using the Goodman score.

METHODS

We conducted a cross-sectional study using data from our institutional database from 1 January 2018 to 1 March 2021. Patients who underwent TKA with the Vanguard® Cruciate Retaining Anterior Stabilized Knee System (Zimmer Biomet, Warsaw, Indiana, USA) without patellar replacement were included. Patients with other bearing surfaces (posterior stabilised or medial congruent) or diagnosed with infection or instability were excluded. Patients' reported outcomes, body mass index (BMI), passive range of motion, the timed up-and-go test, sit-up test, and algometry were assessed. Patients were also asked if they had anterior knee pain. Satisfaction was assessed using the Goodman scale, and logistic multivariate regression was used to identify variables associated with dissatisfaction and perceived improvement in quality of life.

RESULTS

A total of 131 TKA patients were included in the study. The median satisfaction score was 100 (interquartile range [IQR], 87.5 to 100), with the 75-point threshold at the 90th percentile according to Section A of Goodman. Section B of Goodman showed that 113 TKA patients (86.26%) reported "great improvement" or "more than I ever dreamed." Multivariate logistic regression revealed that anterior knee pain (OR 5.16, 95% CI 1.24 to 21.39), the sit-up test (OR 0.63, 95% CI 0.49 to 0.81), and BMI (OR 0.84, 95% CI 0.70 to 0.99) were significantly associated with patient dissatisfaction and a worse perceived improvement in quality of life. The receiver operating characteristics curve for the models had areas under the curve of 0.83 (95% CI 0.69 to 0.97) and 0.82 (95% CI 0.70 to 0.94), respectively.

CONCLUSION

Anterior stabilised TKA without patellar resurfacing can achieve 90% satisfaction and 86% improvement in quality of life. To improve these results, it is essential to prevent and treat anterior knee pain and enhance quadriceps strength.

LEVEL OF EVIDENCE

Level III (retrospective cohort study).

No difference in clinical outcomes between functionally aligned cruciate-retaining and posterior-stabilized robotic-assisted total knee arthroplasty

PURPOSE

To compare the clinical outcomes of subjects undergoing primary robotic-assisted total knee arthroplasty (RA-TKA), following functional alignment (FA) principles, with cruciate-retaining (CR) or posterior-stabilized (PS) bearing designs, at a minimum of 24 months of follow-up.

METHODS

This observational, retrospective study included 167 consecutive patients undergoing RA-TKA with cemented PS and cementless CR implants performed with a CT-base robotic-arm assisted system (Mako, Stryker), following FA principles, between 2017 and 2020. Patients were followed up with a clinical and radiographic assessment and were administered the Forgotten Joint Score-12 (FJS-12), Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR), and the 5-level Likert scale (5-LLS).

RESULTS

Three TKA revisions were performed (2 PS, 1 CR); therefore, a total of 164 knees with a mean age of 71.7 years (SD 8.9) were considered (80 cemented PS; 84 cementless CR). No statistically significant differences were recorded between study groups relative to FJS-12, KOOS-JR, and 5-LLS at a minimum of two year follow-up (FJS-12 89.3 ± 9.2 vs 87.5 ± 12.8, p-value 0.46; KOOS-JR 88.8 ± 10.0 vs 86.7 ± 14.0, p-value 0.31; 5-LLS 4.5 ± 0.7 vs 4.5 ± 0.8, p-value 0.34).

CONCLUSION

No significant outcome differences were reported between patients undergoing PS and CR RA-TKA at a minimum of two year follow-up. RA-TKA achieves excellent clinical results and high satisfaction scores, regardless of the implant design used.

Higher use of fixed-bearing over mobile-bearing and posterior-stabilized over medial pivot designs in total knee arthroplasty (TKA): a systematic comparative analysis using worldwide arthroplasty registers from England and Wales, Australia, Norway, New Zealand, Germany and Switzerland

INTRODUCTION

The aim of this study was to compare the use of mobile-bearing, fixed-bearing, posterior-stabilized (PS) and medial pivot design to describe epidemiological differences and subsequent outcomes.

MATERIALS AND METHODS

A systematic literature search was performed using the NORE website to identify the relevant arthroplasty registers. Inclusion criteria were the following: (1) reports had to be publicly available, (2) reports had to be written in German or English language, (3) differentiation between mobile- and fixed-bearing, posterior-stabilized, and if possible, medial pivot designs had to be possible from the present reports, and (4) data had to be reported for at least three consecutive years and the latest report had to be from the year 2020 to retrieve recent data.

RESULTS

Six registries (England and Wales, Australia, Norway, New Zealand, Germany, Switzerland) offered sufficient data according to the inclusion criteria. In all countries, the dominant type of bearing used for total knee arthroplasty (TKA) was fixed-bearing, with percentages ranging from 60.8% to 84.1% in 2018, 63.6% to 85.7% in 2019 and 66.2% to 87.4% in 2020. A large variation was observed concerning mobile-bearing design, which showed a range from 2.8% to 39.2% in 2018, 2.6% to 36.4% in 2019 and 2.9% to 33.8% in 2020. Some variation was found regarding the use of PS TKA, as its percentage frequency ranged from 9.7% to 29.2% in 2018, 9.8% to 29.4% in 2019 and 10.1% to 28.5% in 2020. Medial pivot design had a share of 9.1% in 2018, 8.6% in 2019 and 8.4% in 2020 in Australia, while it only accounted for 1.4% in 2018, 2.1% in 2019 and 2.5% in 2020 in Germany.

CONCLUSION

The comparison of arthroplasty registers from England and Wales, Australia, Norway, New Zealand, Germany and Switzerland revealed large differences regarding the application of posterior-stabilized designs, but also common ground considering the overwhelming use of fixed-bearing inserts, which, when inserted correctly, eradicate the potential complication of bearing dislocation. Arthroplasty registers offer a real-world clinical perspective with the aim to improve quality and patient safety.

Posterior-Stabilized Versus Cruciate-Retaining Prostheses for Total Knee Arthroplasty: An Overview of Systematic Reviews and Risk of Bias Considerations

Background

Numerous systematic reviews have been published comparing the outcomes of patients undergoing posterior stabilized (PS) versus cruciate-retaining (CR) procedures in total knee arthroplasty (TKA), but with some overlaps and contradictions. The objectives of this study were (1) to perform an overview of current systematic reviews comparing PS versus CR in TKA, by evaluating their methodological quality and risk of bias, and (2) to provide recommendations through the best evidence.

Methods

A systematic search of systematic reviews comparing PS and CR in TKA, published until June 2021 was conducted using the MEDLINE, EMBASE, and Cochrane Library databases. Included systematic reviews were assessed for methodological quality and risk of bias by the AMSTAR2 instrument and ROBIS tool, respectively. The choice of best evidence was conducted according to the Jadad decision algorithm.

Results

A total of eight systematic reviews were eligible for inclusion in this study. The Jadad decision algorithm suggested that reviews with the highest AMSTAR2 scores should be selected. According to the ROBIS tool, there were three reviews with a low risk of bias and five with a high risk of bias. Consequently, one systematic review conducted by Verra et al. with the highest AMSTAR2 score and low risk of bias was selected as the best evidence.

Conclusions

Although current systematic reviews demonstrated some statistical differences in clinical presentation and functional outcomes between PS and CR, the current outcome indicators cannot be taken to provide recommendations for undergoing PS or CR. The decision for prosthesis selection could be made mostly based on the surgeon's preference, indications and other indicators.

Preoperative Factors Predicting the Preservation of the Posterior Cruciate Ligament in Total Knee Arthroplasty

Objective

Predicting the successful preservation of posterior cruciate ligament (PCL) in total knee arthroplasty (TKA) is an important step for preoperative planning to secure the satisfactory outcomes. We aimed to examine the preoperative factors predicting the successful preservation of the PCL in cruciate‐retaining TKA and the outcome of sacrificing the PCL.

Methods

In this retrospective study, we analyzed TKAs consecutively performed by a single surgeon between January 2019 and August 2021 who had been preoperatively planned to undergo implantation of cruciate‐retaining (CR) prostheses. The outcome of the current study was whether the PCL was retained or sacrificed. Anterior‐stabilized (AS) tibial bearings when the PCL was sacrificed as needed were used intraoperatively. Age, sex, body mass index (BMI), and preoperative diagnosis from the patients' medical records were obtained. The medial‐lateral width of epicondyle (MLW), the medial posterior condyle height (MPCH), the lateral posterior condyle height (LPCH), the ratio of MLW and MPCH, the ratio of MLW and LPCH, the Insall–Salvati index, and the severity of the varus or valgus deformity were measured using preoperative radiographs. Univariate and multivariate regression were fitted to assess the association of these factors with the successful retention of PCL. To examine the influence of sacrifice of the PCL on the surgical procedure, the size of the tibial and femoral components, the thickness of the polyethylene insert, and the rate of patella replacement between the CR group and AS group were also compared using t tests or chi‐square tests.

Results

Among 307 TKAs included, PCL was sacrificed with concurrent use of AS prostheses in 89 (29.0%) procedures. Knees with rheumatoid arthritis (P < 0.01), lower Insall–Salvati index (P < 0.01), and more severe varus deformity (P = 0.011) were at a higher risk of sacrificing the PCL intraoperatively. There was no significant difference in age, sex, BMI, MLW, MPCH, LPCH, ratio of MLW and MPCH, ratio of MLW and LPCH, size of the tibial and femoral components, or replacement of the patella between the CR and AS groups. Converting from CR to AS was associated with a higher risk of using a thicker polyethylene insert (P < 0.01).

Conclusion

Rheumatoid arthritis, lower Insall–Salvati index, and more severe varus deformity were associated with an increased risk of sacrificing the PCL in TKAs planned to undergo implantation CR prostheses. Converting to AS tibial bearing may result in a thicker polyethylene insert. These factors should be carefully considered for the appropriate selection of prosthesis type preoperatively.

Kinematics of bicruciate stabilized and cruciate retaining total knee arthroplasty

Few studies have been reported about kinematic comparison between bicruciate stabilized and cruciate retaining total knee arthroplasty with the same anatomical surface geometry. The aim of this study was to demonstrate the in vivo kinematics and postoperative patient-reported outcomes of these two surgeries with the same anatomical surface geometry. We analyzed 17 bicruciate stabilized and 18 cruciate retaining total knee arthroplasties using single-plane fluoroscopic surveillance with two- to three-dimensional registration techniques during squatting from minimum to maximum flexion. Flexion angle, femoral external rotation, anteroposterior position of the medial and lateral sides, and postoperative 2011 Knee Society Scores were analyzed. Maximum flexion angles were larger for bicruciate stabilized than for cruciate retaining total knee arthroplasties. There was no significant difference in femoral external rotation between the two types. The medial and lateral femoral condyles in bicruciate stabilized type translated more posteriorly during deeper flexion and at maximum flexion angle, respectively, than those in cruciate retaining total knee arthroplasty. Both groups revealed medial pivots in early flexion, but during deep flexion, bicruciate stabilized total knee arthroplasty revealed bicondylar roll-back and cruciate retaining total knee arthroplasty revealed paradoxical anterior motion. Both groups exhibited similar results in postoperative 2011 Knee Society Scores. Bicruciate stabilized and cruciate retaining total knee arthroplasties with the same anatomical articular surfaces demonstrated different kinematics patterns during squatting. However, there were no significant differences in postoperative 2011 Knee Society Scores between the two types of surgery.

Octogenarians Are the New Sexagenarians: Cruciate-Retaining Total Knee Arthroplasty Is Not Inferior to Posterior-Stabilized Arthroplasty in Octogenarian Patients

Purpose: The primary goal of this study was to compare survivorship and functional results in individuals aged 80 and over who underwent total knee arthroplasty (TKA) with cruciate-retaining (CR) or posterior-stabilized (PS) implants. Methods: We prospectively analyzed the clinical records of two consecutive cohorts for a total of 96 implants in patients aged 80 years or over. The first cohort consisted of 59 consecutive cemented PS cases, while the second cohort comprised 37 consecutive cemented CR cases. The decision to either perform a PS or CR arthroplasty was taken based on preoperative magnetic resonance imaging and intraoperative findings. The clinical evaluation entailed evaluating each patient’s visual analogue scale for pain (VAS), range of motion (flexion and extension), Knee Society Score (KSS), and Oxford Knee Score (OKS). Each patient was clinically evaluated the day before surgery (T0) and at two consecutive follow-ups at least 1 (T1) and 2 (T2) years after surgery. Implant survival was calculated using the Kaplan−Meier method. Results: Both groups showed statistically significant improvements at each follow-up compared with the preoperative values (p < 0.05). The CR group showed a higher flexion degree at T1 than the PS group (116.14 ± 5.57° versus 113.16 ± 7.66°; p = 0.048). No differences were found between the two groups regarding survival rate (chi-squared test p-value = 0.789). Three failures were noted in the CR group, while there were four in the PS group. Conclusions: This prospective clinical study demonstrates that CR and PS TKA had similar clinical outcomes in octogenarians with regard to knee function, postoperative knee pain, and other complications. Prosthesis survivorship for CR and PS TKA were both satisfactory, and in selected octogenarian patients, CR TKA should always be considered because of the reduced surgical time.

Impact of femoro-tibial size combinations and TKA design on kinematics

INTRODUCTION

The variability in patients' femoral and tibial anatomy requires to use different tibia component sizes with the same femoral component size. These size combinations are allowed by manufacturers, but the clinical impact remains unclear. Therefore, the goals of our study were to investigate whether combining different sizes has an impact on the kinematics for two well-established knee systems and to compare these systems' kinematics to the native kinematics.

MATERIALS AND METHODS

Six fresh frozen knee specimens were tested in a force controlled knee rig before and after implantation of a cruciate retaining (CR) and a posterior-stabilized (PS) implant. Femoro-tibial kinematics were recorded using a ultrasonic-based motion analysis system while performing a loaded squat from 30° to 130°. In each knee, the original best fit inlay was then replaced by different inlays simulating a smaller or bigger tibia component. The kinematics obtained with the simulated sizes were compared to the original inlay kinematics using descriptive statistics.

RESULTS

For all size combinations, the difference to the original kinematics reached an average of 1.3 ± 3.3 mm in translation and - 0.1 ± 1.2° in rotation with the CR implant. With the PS implant, the average differences reached 0.4 ± 2.7 mm and  - 0.2 ± 0.8°. Among all knees, no size combination consistently resulted in significantly different kinematics. Each knee showed a singular kinematic pattern. For both knee systems, the rotation was smaller than in the native knee, but the direction of the rotation was preserved. The PS showed more rollback and the CR less rollback than the native knee.

CONCLUSION

TKA systems designed with a constant tibio-femoral congruency among size combinations should enable to combine different sizes without having substantial impact on the kinematics. The rotational pattern was preserved by both TKA systems, while the rollback could only be maintained by the PS design.

Biomechanics and Outcomes of Modern Tibial Polyethylene Inserts

PURPOSE OF REVIEW

There have been many attempts to use variations in tibial polyethylene design to better recreate normal knee kinematics in the total knee arthroplasty. The goal of this review is to provide an overview of the various types of tibial inserts that exist and review the theoretical mechanics versus what was demonstrated in vivo.

RECENT FINDINGS

Many polyethylene inserts have been attempted to re-create normal knee kinematics, but none have been able to successfully do so. Previously the only two types of inserts were posterior stabilized (PS) and cruciate retaining (CR) polyethylene inserts. Both of these have shown excellent long-term survival but neither has demonstrated native kinematics. Initially, it was thought that retention of the posterior cruciate ligament (PCL) would allow for more native kinematics, but fluoroscopic evidence has shown that the PCL alone cannot accomplish this. Newer inserts try to restore femoral roll back and the screw home mechanism. The bicruciate retaining total knee inserts are having the most "normal" kinematics, suggesting the importance of both the ACL and PCL in knee biomechanics. Modern polyethylene inserts show favorable short-term data with bicruciate retaining inserts having the best kinematics; however, long-term studies are still needed to determine if survivorship and patient outcomes remain favorable.

Effect of Early Electroacupuncture Combined with Enhanced Recovery after Surgery (ERAS) on Pain Perception and Dysfunction in Patients after Total Knee Arthroplasty (TKA)

Objective

A retrospective case-control study was performed to observe the effect and clinical significance of early electroacupuncture combined with enhanced recovery after surgery (ERAS) on pain perception and dysfunction after total knee arthroplasty (TKA).

Methods

About 100 patients who diagnosed with TKA from February 2019 to April 2021 were enrolled in our hospital. The patients were arbitrarily assigned into control group and study group. The former group was cured with electroacupuncture in the early stage, and the latter group was intervened on the basis of early electroacupuncture combined with the concept of ERAS. The curative effect, the time of getting out of bed for the first time after operation, the time of postoperative rehabilitation, postoperative rehabilitation cost, pain score and knee joint function score, range of motion (ROM) of knee joint, low shear of whole blood viscosity, plasma viscosity, fibrinogen level, and postoperative complications were compared.

Results

There exhibited no statistical difference in clinical data. In terms of the treatment effects, there were 27 cases of markedly effective, 22 cases of effective, and 1 case of ineffective in the study group, and the total effective rate was 98.00%; in the control group, 15 cases were markedly effective, 28 cases were effective, and 13 cases were ineffective, and the total effective rate was 86.00%. Compared to the control group, the total effective rate of the study group was higher (P < 0.05). And the first time to get out of bed and the postoperative rehabilitation time in the study group were lower. Compared to the control group (10113.42 ± 524.83) yuan, the postoperative rehabilitation cost in the study group (12401.71 ± 530.77) yuan was higher. In terms of the scores of VAS and HSS, there exhibited no remarkable difference before treatment (P > 0.05). After treatment, the VAS score lessened and the HSS score augmented the study group VAS score (1.76 ± 0.28); the score in the control group was lower compared to the control group (3.45 ± 0.36), and HSS scoring (83.48 ± 11.23) points higher compared to the control group (65.82 ± 10.44) points (P < 0.05). The ROM of knee joint augmented successively at the 1st, 2nd, 4th, and 8th week after treatment comparison between groups, the ROM of the knee joint in the study group at the 1st, 2nd, 4th, and 8th week was (49.47 ± 3.60)°, (64.38 ± 5.32)°, (86.93 ± 6.72)°, and (104.20 ± 9.11)°, is higher compared to the control group (46.53 ± 3.41)°, (61.52 ± 5.20)°, (78.42 ± 6.45)°, and (98.77 ± 8.67)° (P < 0.05). One day after operation, there exhibited no remarkable difference in whole blood viscosity low shear, plasma viscosity, and fibrinogen level (P > 0.05). However, there exhibited no remarkable difference in plasma viscosity and fibrinogen level at 1 day and 7 days after operation (P > 0.05). Seven days after operation, the whole blood viscosity, plasma viscosity, and fibrinogen in the study group were lower (P < 0.05). The probability of postoperative complications was compared. In the study group, there were 2 cases of limb swelling and pain, 1 case of joint stiffness, and no swelling and pain complicated with deep venous thrombosis, and the total incidence was 6.00%. In the control group, there were 5 cases of limb swelling and pain, 3 cases of joint stiffness, and 3 cases of swelling and pain complicated with deep venous thrombosis, with a total incidence of 22.00%. The incidence of adverse reactions in the study group was lower (χ 2 = 5.317 P < 0.05).

Conclusion

Early electroacupuncture combined with ERAS is of positive significance to the patients after TKA, which can reduce the pain, enhance the function of the knee joint, and promote the ROM of the knee joint, and can effectively shorten the first time out of bed and postoperative rehabilitation time and reduce whole blood viscosity low shear, plasma viscosity, and fibrinogen level, but the overall rehabilitation cost is high, and clinical application should be combined with the actual situation of patients.

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.

Comparison of posterior cruciate retention and substitution in total knee arthroplasty during gait: a systematic review and meta-analysis

Background

To compare the gait patterns between posterior cruciate retention and substitution in total knee arthroplasty (TKA).

Methods

Electronic databases including the PubMed, Embase, CINAHL, Web of Science, and Cochrane databases were searched to identify clinical trials investigating posterior cruciate retention versus substitution in TKA. The outcome measurements were the kinematic gait parameters (flexion at heel strike, maximum flexion during loading response, flexion range during loading, minimal flexion at terminal stance, maximal flexion at the swing, and total flexion during the gait cycle), Knee Society Score (KSS), knee flexion, knee extension, and walking speed. Statistical software Review Manager 5.4 and Stata 14.0 were used for data analysis.

Results

There were finally 9 studies included in this meta-analysis. The results did not reveal differences between posterior cruciate retention (CR) and posterior cruciate substitution (PS) groups in TKA, in terms of kinematic gait parameters, knee extension, walking speed, and KSS. However, the PS group had a significantly larger knee flexion angle than that in the CR group [weighted mean difference = − 3.20, 95% CI − 6.13 to − 0.28, P = 0.03].

Conclusion

Both the posterior cruciate retention and posterior cruciate substitution lead to obvious improvements in patient function and have their advantages in getting a good cup position. The PS design is significantly better on the knee flexion, while there are no statistical differences in kinematic gait parameters and outcome scores between them. This might indicate that surgeons do not necessarily need a PS design to substitute the posterior cruciate ligament during TKA.

Survivorship Comparisons of Ultracongruent, Cruciate-Retaining and Posterior-Stabilized Tibial Inserts Using a Single Knee System Design: Results From the Australian Orthopedic Association National Joint Replacement Registry

BACKGROUND

Ultracongruent (UC) tibial inserts can increase knee replacement stability, but how survivorship compares to cruciate retaining (CR) or posterior stabilized (PS) inserts is unclear.

METHODS

Data from a large joint registry were used to calculate the cumulative percent revision of a single popular knee design used with different inserts. There were 67,523 procedures, of which 12,434 were UC, 21,635 CR, and 33,454 PS. Revision rates and reasons for revision were analyzed.

RESULTS

The cumulative percent revision at 18 years was 8.3% for UC, 9.2% for CR, and 8.9% for PS. There was no difference when UC was compared to CR, but PS had a higher risk of revision. Revision reasons were similar.

CONCLUSION

Compared to the CR, an UC insert did not increase revision rates and was actually lower than a PS insert. An UC insert does not compromise long-term total knee arthroplasty survivorship in the Genesis II prosthesis.

Conforming Polyethylene Inserts in Total Knee Arthroplasty: Beyond the Posterior-Stabilized and Cruciate-Retaining Debate

Total knee arthroplasty continues to be one of the most commonly performed surgical procedures worldwide. However, considerable controversy exists regarding the optimal implant design. Total knee implants with both posterior-stabilized and cruciate-retaining designs have excellent long-term outcomes with inadequate data demonstrating superiority of either design. Recently, the popularity of total knee designs with more conforming polyethylene liners has increased. These polyethylene inserts prevent paradoxical anterior translation of the femur, without relying on a cam and post mechanism, and promote more physiologic native knee kinematics. This review summarizes the design rationale of several commercially available implants, discusses the kinematic data of several designs, and reviews the available clinical data.

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.

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

PURPOSE

Whether ultra-congruent (UC) or posterior cruciate ligament-stabilized (PS) inserts should be used in posterior cruciate ligament (PCL)-sacrificing total knee arthroplasty (TKA) remains debatable. Therefore, the aim of this prospective randomized controlled study was to compare the isokinetic performance and clinical outcomes of these inserts in PCL-sacrificing TKA.

METHODS

Sixty-six patients diagnosed with primary knee osteoarthritis were randomly assigned to either the UC or the PS group. There were no significant differences between the groups in terms of age, body mass index or sex. The Knee Society score (KSS) and isokinetic performance results for each patient were recorded preoperatively and at 3, 6 and 12 months postoperatively. The physiatrist that performed the isokinetic tests and the patients were blinded to the study groups.

RESULTS

There were no significant differences between the groups in terms of the preoperative KSS or isokinetic performance. Gradual improvement in the KSS was observed in both groups, but no significant differences were detected between the groups during the whole follow-up period. The UC and PS groups exhibited similar peak extension and flexion torque values normalized to body weight at 3, 6 and 12 months postoperatively (p > 0.05).

CONCLUSION

The use of UC or PS inserts in TKA did not affect the clinical outcomes or isokinetic performance.The clinical relevance of this study is that the potential differences in clinical outcomes and isokinetic performance between UC and PS inserts do not need to be considered when sacrificing the PCL in TKA.

LEVEL OF EVIDENCE

I.

The Disproportionate Increase of the Intraoperative Flexion and Extension Gap Space after Posterior Cruciate Ligament Resection in Total Knee Arthroplasty

Purpose: Maintaining gap balance is critical for total knee arthroplasty (TKA). This study aimed to elucidate if the extension–flexion gaps would be changed with posterior cruciate ligament (PCL) intact (PI) and PCL resection (PR) during TKA. The flexion gaps were measured using two methods, open-(Fo) and closed-chain position (Fc), based on the definition of kinetic chain position, respectively. Methods: This retrospective study enrolled a total of 33 patients who underwent posterior-stabilized (PS) TKA for symptomatic advanced osteoarthritis of knees. After bone cuts were completed, the extension–flexion gaps before and after PCL resection during TKA were measured using a calibrated tensioning device set at a 100 Nm distraction force. To further differentiate the effect of thigh weight on the 90° flexion gap, two varied methods of examination, either in closed chain (Fc) or open chain (Fo) were performed. Results: The increases in the 90° knee flexion gap after PCL resection were measured by both methods, i.e., ΔFc (PR-Fc—PI-Fc): 2.04 ± 2.06 mm, p < 0.001; and mean ΔFo (PR-Fo—PI-Fo): 1.64 ± 1.36 mm, p < 0.001. However, there were no differences between ΔFc and ΔFo before and after PCL resection. A greater amount of flexion gap was identified in open chain than in closed chain after PCL resection, and the PR-Fo and PR-Fc were 14.36 ± 3.13 and 11.40 ± 3.47 (p < 0.001), respectively. Conclusions: The resection of PCL during TKA distinctly increased the flexion gap, but not the extension gap. This disproportionate increase of the gap will cause a gap balance mismatch. The tensioning maneuver in open-chain was more effective to detect the gap differences than in closed-chain before and after PCL resection during TKA.

Kinematics of bicruciate and posterior stabilized total knee arthroplasty during deep knee flexion and stair climbing

Second-generation bicruciate stabilized (BCS) total knee arthroplasty (TKA) was developed to substitute both anterior and posterior cruciate ligaments and replicate physiological kinematics. This study aimed to evaluate if the postcam mechanism and the surface geometry function effectively. Seventeen and twelve knees implanted with BCS TKA and posterior stabilized (PS) TKA, respectively, were analyzed. In vivo kinematics during deep knee flexion were estimated from single-plane fluoroscopic images using a 2-dimensional to 3-dimensional image registration technique. Flexion angle, anteroposterior translation, femoral external rotation (ER), and postcam engagement were compared between the groups. Postoperative 2011 Knee Society Score (KSS) was obtained at the last follow-up. The medial femoral condyle in BCS was positioned more anteriorly than that in PS from minimum flexion to maximum flexion. Posterior motion of the lateral femoral condyle was observed in both groups. ER of BCS was significantly larger compared to PS from minimum flexion to 100°. However, the amount of ER from minimum flexion to maximum flexion was similar: 6.2° ± 4.5° and 7.7° ± 4.1° in BCS and PS, respectively (P = .364). Anterior postcam engagement was observed in 76.5% and 25.0% in BCS and PS, respectively (P = .006). Posterior postcam engagement was observed in all cases in BCS and PS. There were no significant differences in KSS between the groups. The kinematic differences were likely a result of variations in articular surface geometry.

A Medial Congruent Polyethylene Offers Satisfactory Early Outcomes and Patient Satisfaction in Total Knee Arthroplasty

Background

Although a successful operation, almost 20% of patients are dissatisfied with total knee arthroplasty (TKA). The purpose of this retrospective cohort study was to see if a medial congruent (MC) polyethylene would offer satisfactory early outcomes and patient satisfaction after TKA.

Methods

We reviewed prospectively collected data on 327 TKAs using multiple bearings within the same implant system. Ninety-six received an MC bearing, 70 received a cruciate-retaining (CR) bearing, and 161 received a posterior-stabilized (PS) bearing. We evaluated the visual analog scale pain scores and range of motion (ROM) at 2 weeks, 6 weeks, 3 months, and 1 year; Patient-Reported Outcomes Measurement Information System (PROMIS-10) score and Knee Injury and Osteoarthritis Outcome Score (KOOS) at 3 months and 1 year; and Forgotten Joint Score (FJS-12) at 1 year.

Results

All groups had similar KOOS and PROMIS-10 scores. MC knees had lower visual analog scale scores than PS knees at all time points (P < .05) and a higher ROM than PS at 2 weeks (98.6 vs 93.7, P = .002). MC knees had a significantly higher FJS-12 than CR knees (71.6 vs 58.7, P = .02). More MC knees were “very satisfied” than CR (92.6% vs 81.5%, P = .04). Fewer MC knees were “not at all satisfied” than CR (1.2% vs 9.2%, P = .04). There were similar satisfaction ratings with MC and PS.

Conclusions

An MC bearing provided similar or improved early pain, ROM, KOOS, PROMIS-10, FJS-12, and patient satisfaction as compared with standard bearings in TKA.

Anterior knee pain after total knee arthroplasty: A multifactorial analysis

PURPOSE

Dissatisfaction and an impaired quality of life after total knee arthroplasty (TKA) is often associated with postsurgical anterior knee pain (AKP). The underlying pathological mechanisms are not yet fully understood. Therefore, a multifactorial approach encompassing clinical and radiological parameters seemed reasonable and promising to investigate postsurgical AKP.

METHODS

In this cross-sectional study, 25 patients without and 25 patients with postsurgical AKP after unilateral TKA were randomly recruited from a larger cohort of patients. Multiple clinical and radiological parameters-including real-time shear wave elastography (SWE) to measure the patellar and quadriceps tendon elasticity-were acquired and subsequently associated with AKP. For statistical analysis, SPSS (IBM, version 25) was used.

RESULTS

In total 50 participants (58.0% men, mean age 63.42 years, mean body mass index 29.75 kg/m²), having different prosthetic designs implanted, were included. Independently of key covariates, the strength of the quadriceps muscle (p = 0.021), a thinner inlay (p = 0.041), and a lower position of the patella (p = 0.041) were associated with AKP. Although no correlation with AKP was found (p = 0.346, resp. p = 0.154), we observed significantly decreased Young's modulus of the patellar and quadriceps tendons for the involved knee compared to the uninvolved knee (p < 0.001).

CONCLUSION

In conclusion, quadriceps muscle strength, inlay thickness, and the patella position might be of particular relevance in avoiding postsurgical AKP. Future studies with larger sample sizes are needed to clarify the impact of quadriceps muscle strength and the postoperative patella position as well as the role of SWE as a personalized modifiable prediction marker.

Functional Outcomes are Comparable Between Posterior Stabilized and Cruciate-Substituting Total Knee Arthroplasty Designs at Short-Term Follow-up

BACKGROUND

Posterior stabilized (PS) polyethylene inserts have been shown to have excellent long-term functional results following total knee arthroplasty (TKA). A cruciate-substituting (CS) design has been introduced to minimize bony resection and eliminate concerns regarding wear on the PS post. The purpose of this study is to compare the outcomes of patients who underwent TKA using either a PS or CS insert.

METHODS

We reviewed a consecutive series of 5970 patients who underwent a cruciate-sacrificing TKA and received either a PS (3,314) or CS (2,656) polyethylene liner. We compared demographics, Knee Injury and Osteoarthritis Outcome Score Jr (KOOS Jr), Short-Form 12 (SF-12) scores, and revision rates between the groups at a minimum 2 years followup. A multivariate regression was performed to identify the independent effect of design on functional outcomes.

RESULTS

Revision rates between the groups were comparably low (0.35% for PS vs 0.51% for CS, P = .466) at an overall mean follow-up of 43 months. Patients in the PS cohort had statistically higher KOOS Jr scores at 2 years (69.8 vs 72.9, P < .001). Multivariate regression analysis found CS patients to have lower postoperative KOOS Jr scores (estimate -2.26, P = .003), and less overall improvement in KOOS Jr scores (estimate -2.42, P = .024) than PS patients, but neither was a clinically significant difference.

CONCLUSION

Patients who undergo TKA with a CS polyethylene insert have comparable functional outcomes and revision rates to those with a PS design at short-term follow-up. Longer follow-up is needed to determine whether CS can match the outstanding track record of PS TKA.

Posterior Cruciate Ligament Resection Does Not Consistently Increase the Flexion Space in Contemporary Total Knee Arthroplasty

INTRODUCTION

It is accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion-space by approximately 4mm. Unfortunately, this doctrine is based on historical studies of limited size with variable technique. The aim of this study was to determine the effect of PCL-resection on in vivo tibiofemoral joint space dimensions in a cohort of modern TKAs.

METHODS

Tibiofemoral joint space measurements were made during 129 standardized TKAs by two arthroplasty surgeons. A medial parapatellar approach, computer navigation and provisional bone cuts were performed in all cases with particular attention to preserving PCL integrity. The tibiofemoral gap was measured with a calibrated tension device at extension, 45-degrees, and 90-degrees before and after complete PCL-resection.

RESULTS

51% of patients were female (66/129) with mean age and BMI of 69.5 years and 34.2 kg/m², respectively. After PCL-resection, mean change in center joint space dimension increased 0.33mm at extension, 0.95mm at 45-degrees, and 1.71mm at 90-degrees (P < .001). The 90-degree flexion-space opened ≥4mm in only 10% of patients. Dividing the flexion-space change by femoral implant dimension to account for patient size, the flexion-space at 90-degrees significantly increased more in females compared to males (P = .020).

CONCLUSION

The tibiofemoral joint space increased progressively from extension to mid-flexion through deep-flexion after PCL-resection, yet was substantially less than reported in historical studies. However, large variation in flexion-space opening was observed with some patients failing to increase the flexion-space whatsoever with PCL-resection. This runs counter to conventional TKA understanding and should be considered in modern surgical education.

LEVEL OF EVIDENCE

Therapeutic Level III.

Evaluating Posterior Cruciate Ligament Integrity in Inflammatory Arthritis Patients Prescribed Biologic Agents: A Radiological Case-Control Study

Introduction

Patients with inflammatory arthropathies present a significant challenge to the arthroplasty surgeon when they present with symptomatic degenerative changes of their knee joint. Debate is ongoing regarding the selection of implants for this cohort of patients. There is conflicting evidence for the use of posterior-stabilising (PS) over cruciate-retaining (CR) designs in this cohort. Biologics are licensed for use in moderate-to-severe disease that has not responded to conventional treatment. To our knowledge, there are no studies that have assessed the integrity of the posterior cruciate ligament (PCL) on magnetic resonance imaging (MRI) in these patients with more advanced disease prescribed biologic agents.

Aim

The aim of this study is to assess the integrity of the PCL on MRI in patients with inflammatory arthritis who are prescribed biologic agents.

Methods

A case-control study was performed, with cases identified through chart review to confirm prescription of biologic agents for inflammatory arthropathies, who also had contemporaneous MRI knee scans performed. Knee MRIs for age- and sex-matched controls with osteoarthritis (OA) and meniscal pathology were identified from the National Joint Registry and the Hospital In-Patient Enquiry (HIPE), respectively.

The MRIs were reviewed by two musculoskeletal radiologists who were blinded to the clinical details. They were asked to assess the MRIs to determine PCL integrity, synovial Inflammation, and any associated pathology.

Results

No difference was noted in the rate of synovitis, PCL attenuation, or PCL tears between the OA and inflammatory arthropathy groups (p > 0.05).

Conclusions

The results of this study show no difference in the integrity and continuity of the PCL in those patients for age- and sex-matched controls on MRI. This finding lends support to the use of CR total knee arthroplasty in patients with inflammatory arthropathy on biologic agents.

CR-lipped bearing is an adequate functional solution to patients with perioperative excessive laxity in cruciate retaining total knee arthroplasty

BACKGROUND

The cruciate retaining lipped (CR-lipped) bearing is designed to provide more anterior-posterior (AP) stability and could be employed to resolve excessive intraoperative laxity during the cruciate retaining TKA (CR-TKA). The aim of the study was to determine whether the CR-lipped bearing in CR-TKAs with a perioperative excessive laxity allows equivalent functional results as compared to the standard CR articulation.

METHODS

A cohort of 111 TKAs with CR-lipped bearings was matched to a cohort of conventional CR bearings regarding age and sex. The CR-lipped bearing was used in patients with excessive knee AP laxity and the regular CR bearing was used in patients without excessive AP laxity during TKA. Various PROMs (WOMAC, KSS, SF-36) were assessed preoperatively and at 5-years postoperative in combination with revision rate and Range of Motion (ROM).

RESULTS

PROMs did not differ significantly between both groups 5-years postoperatively. Mean ROM (flexion) 5-years postoperatively was not significantly different. The implant survivorship was 100% for both cohorts with revision for any reason as end point.

CONCLUSION

Based on these results, the CR-lipped bearing is a safe and effective solution for mild interoperatively assessed PCL laxity during CR-TKA without loss of function or decreased survivorship at 5 years. Peroperative conversion to a PS-TKA in order to obtain satisfactory functional scores might therefore not be necessary when mild PCL laxity is observed during surgery. Further research should focus on verifying this approach and longer follow-up is needed to generate data on long term survivorship.

LEVEL OF EVIDENCE

Level IV therapeutic, retrospective, cohort study.

J-curve design total knee arthroplasty: the posterior stabilized shows wider medial pivot compared to the cruciate retaining during chair raising

PURPOSE

Which total knee arthroplasty (TKA) design represents the better solution to restore a correct knee biomechanics is still debated. The aim of this study was to compare posterior stabilized (PS) and cruciate retaining (CR) version of the same TKA design (femoral component with an anatomic sagittal radius-J-curve design) by the use of dynamic Roentgen stereophotogrammetric analysis (RSA). The hypothesis was that the two models influence differently in vivo knee kinematic.

METHODS

A cohort of 16 randomly selected patients was evaluated 9 months after surgery: Zimmer PERSONA® was implanted, eight with CR design and eight with PS design. The kinematic evaluations were performed using a Dynamic RSA (BI-STAND DRX 2) developed in our Institute, during the execution of the sit-to-stand motor task. The motion parameters were obtained using the Grood and Suntay decomposition and the low-point kinematics methods.

RESULTS

PS TKA lateral femoral compartment had a wider anterior translation (17 ± 2 mm) than the medial one (11 ± 2 mm), while the two compartments of CR TKA showed a similar anterior translation (medial: 9 ± 2 mm/lateral: 11 ± 2 mm). T test for comparison between CR and PS TKA of antero-posterior translation showed a statistically significant difference (p < 0.05) in the flexion range between 15° and 40°. The CR prosthesis did not anteriorly translate during flexion. The PS design translated anteriorly showing a roll-forward mechanism during extension from 80° to 18° of flexion and a posterior translation from 18° to 0°. The same significant differences (p < 0.05) between the PS and CR groups were found comparing the low-point positions of the femoral condyles in the range of flexion between 25° and 40° for the medial compartment and between 15° and 25° for the lateral compartment.

CONCLUSIONS

Dynamic RSA was able to investigate for the first time in vivo the kinematic behaviour of PS and CR version of the same TKA J-curve design. PS type showed a medial pivot during sit-to-stand motion task, while the CR type showed a cylindrical movement. Further studies are needed to evaluate the impact of different TKA designs on clinical results.

LEVEL OF EVIDENCE

IV.

Controversial Topics in Total Knee Arthroplasty: A 5-Year Update (Part 1)

This review article examines updates to the literature during the past 5 years on numerous topics related to total knee arthroplasty which were felt to have ongoing controversy. These include the use of peripheral nerve blocks and local infiltrative analgesia, intrathecal morphine, patellar resurfacing, and bearing designs.

Does contralateral knee range of motion predict postoperative knee range of motion after total knee arthroplasty?

Purpose

The aim of this study was to determine if contralateral knee range of motion is associated with postoperative range of motion in the operative knee after total knee arthroplasty.

Methods

Contralateral (nonoperative) knee range of motion was compared to postoperative knee range of motion after total knee arthroplasty using linear regression models in 59 patients who had undergone primary total knee arthroplasty with a minimum of 4 months postoperative follow-up data (range 4–13 months).

Results

A strong linear relationship was observed between contralateral knee ranges of motion of 115° or greater and postoperative knee ranges of motion after total knee arthroplasty (slope 0.93, 95% CI 0.58–1.29, P < 0.0001), with a mean difference of −7.44° (95% CI −10.3 to −4.63, P < 0.0001). However, there was no association between contralateral knee range of motion and postoperative knee range of motion when contralateral knee range of motion was less than 115°.

Conclusion

Contralateral knee range of motion of 115° or greater correlates linearly with postoperative range of motion after total knee arthroplasty, and thus may be predictive in such cases.

Differences in outcome after cruciate retaining and posterior stabilized total knee arthroplasty

BACKGROUND

Both cruciate retaining (CR) and posterior stabilized (PS) implants are commonly used for primary total knee arthroplasty. There is evidence to support improved range of motion in PS knee replacements, but there is no evidence showing functional superiority. The aim of this study was to compare functional outcomes between CR and PS knee replacements.

PATIENT AND METHODS

Prospectively collected regional joint registry data were used to compare preoperative and postoperative one, 5- and 10-year Oxford and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores in 1287 primary total knee replacements. Differences in functional scores between CR and PS knees were calculated.

RESULTS

The PS group had better functional scores than the CR group at baseline (mean Oxford score 15.59 vs. 14.52 ( p = 0.026) and mean WOMAC score 59.51 vs. 62.35 ( p = 0.012)), at 1 year postoperatively (mean Oxford score 37.94 vs. 36.63 ( p = 0.015) and mean WOMAC score 16.20 vs. 19.73 ( p = 0.001)) with a similar trend at 5 years postoperatively (mean Oxford score 39.66 vs. 38.50 ( p = 0.054) and mean WOMAC score 16.89 vs. 18.83 ( p = 0.131)). There was no difference in the overall functional improvement between the PS and CR groups at 1, 5, or 10 years. WOMAC subcomponent scores showed greater improvement in stiffness; 3.76 versus 3.36 ( p = 0.012) in PS knees at 1 year postoperatively. No significant differences were observed at 5 or 10 years.

CONCLUSIONS

PS knee replacements showed greater improvement in stiffness at 1 year postoperatively. There was no difference observed at 5 or 10 years postoperatively. PS knees had better functional outcomes at 1 year with a similar trend at 5 years postoperatively.

LEVEL OF EVIDENCE

III.