Load-Dependent Characteristics of Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty: A Biomechanical Study.

Background: Increased load bearing across the patellofemoral and tibiofemoral articulations has been associated with total knee arthroplasty (TKA) complications. Therefore, the purpose of this study was to quantify the biomechanical characteristics of the patellofemoral and tibiofemoral joints and simulate varying weight-bearing demands after posterior cruciate ligament-retaining (CR) and posterior-stabilized (PS) TKAs. Methods: Eight fresh-frozen cadaveric knees (average age, 68.4 years; range, 40-86 years) were tested using a custom knee system with muscle-loading capabilities. The TKA knees were tested with a CR and then a PS TKA implant and were loaded at 6 different flexion angles from 15° to 90° with progressively increasing loads. The independent variables were the implant types (CR and PS TKA), progressively increased loading, and knee flexion angle (KFA). The dependent variables were the patellofemoral and tibiofemoral kinematics and contact characteristics. Results: The results showed that at higher KFAs, the position of the femur translated significantly more posterior in CR implants than in PS implants (36.6 ± 5.2 mm and 32.5 ± 5.7 mm, respectively). The patellofemoral contact force and contact area were significantly greater in PS than in CR implants at higher KFAs and loads (102.4 ± 12.5 N and 88.1 ± 10.9 N, respectively). Lastly, the tibiofemoral contact force was significantly greater in the CR than the PS implant at flexion angles of 45°, 60°, 75°, and 90° KFA, the average at these flexion angles for all loads tested being 246.1 ± 42.1 N and 192.8 ± 54.8 N for CR and PS implants, respectively. Conclusions: In this biomechanical study, CR TKAs showed less patellofemoral contact force, but more tibiofemoral contact force than PS TKAs. For higher loads across the joint and at increased flexion angles, there was significantly more posterior femur translation in the CR design with a preserved posterior cruciate ligament and therefore significantly less patellofemoral contact area and force than in the PS design. The different effects of loading on implants are an important consideration for physicians as patients with higher load demands should consider the significantly greater patellofemoral contact force and area of the PS over the CR design.

Cruciate-retaining Arthroplasty in Patients with Severe Varus Deformity: A Retrospective Comparative Study.

Introduction: There has been debate regarding the advantages of cruciate-retaining over posterior stabilized (PS) knee arthroplasty and vice versa. Many authors consider any coronal plane deformity > 15° as a contraindication for cruciate-retaining total knee arthroplasty. We aimed to compare whether functional outcome, deformity correction, and survivorship of cruciate retaining knee arthroplasty (CR) for severe varus deformity are equivalent to that ofposterior cruciate ligament substituting (PS) for 6 years. Materials and Methods: We conducted a retrospective comparative study among patients who underwent Total Knee Replacement in the Orthopedics Department of a tertiary care hospital between 2016 and 2018 August who had a varus deformity of more than 15°. The first author exclusively performed CR operation (Group A) for all complex knees. In contrast, the second author performed PS surgery (Group B) for any coronal plane deformity over 15°. Clinical evaluation included completing a Knee Society Score (KSS) Evaluation Form. Pre-operative scoring was collected from the hospital database. All clinical examinations and radiographs at the final follow-up were done by the third author, who was unbiased and not involved with the initial patient care. Results: here were 39 patients in Group A (CR) and 28 patients in Group B (PS). In Group A, the mean pre-operative varus was 22.05 ± 2.72° and the pre-operative KSS was 32.94 ± 6.79. Postoperatively, the deformity corrected to a mean valgus of 5.48 ± 1.8° and mean KSS of 89.17 ± 5.79. In Group B, the mean pre-operative varus was 22.14±3.82° and pre-operative KSS was 32.82 ± 5.98. Postoperatively, the deformity corrected to a mean valgus of 4.85 ± 2.1° and mean KSS of 90.17 ± 5.13. The mean insert thickness was 11.76 ± 1.75 mm and 11.42 ± 1.75mm among the CRand PS groups, respectively. Concerning deformity correction (P = 0.19) and functional outcome (P = 0.46), both groups showed equal improvement with a 100% survival rate for 6 years. Conclusion: We concluded that CRknee replacements are possible with excellent functional and radiological outcomes in severe varus arthritic knees with a 100 % survival rate.

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.

Cruciate-Retaining Total Knee Arthroplasty versus Unicompartmental Knee Arthroplasty in Medial Compartmental Osteoarthritis: A Propensity Score-Matched Analysis of Early Postoperative Recovery.

Background: Cruciate-retaining (CR) total knee arthroplasty (TKA) may provide better physiological knee kinematics, proprioception, and quadricep recovery than posterior-stabilized (PS) TKA. Therefore, we hypothesized that CR TKA with multimodal pain control may provide comparable postoperative pain and recovery as unicompartmental knee arthroplasty (UKA). Methods: This study included patients with isolated medial compartment knee osteoarthritis who underwent CR TKA and UKA. TKA and UKA patients were propensity score-matched with age and body mass index (BMI) and compared using visual analog scales (VAS) for pain scores, total amount of morphine use (TMU), knee flexion angle, straight leg raise (SLR), independent ambulation, length of hospital stay (LOS), and costs during hospitalization. Results: After propensity score matching, 46 patients were included in the TKA and UKA groups, respectively, with no differences in demographic data. VAS at 6-72 h and TMU at 48 h after surgery were comparable between the groups. The knee flexion angle in the UKA group was significantly higher at 24 h (60.0° vs 46.6°; p<0.001) and 48 h (76.9° vs 69.1°; p = 0.021) than that in the TKA group. The SLR in the UKA group was significantly higher than that in the TKA group at 24-72 h. The UKA group ambulated significantly earlier (1.56 vs 2.13 days; p<0.001), had shorter LOS (3.68 vs 4.28 days; p<0.004) and incurred 12.43% lower costs when compared to the TKA group. Conclusion: Patients who underwent CR TKA with multimodal pain management did not experience more postoperative pain or morphine use than those who underwent UKA. However, UKA patients seem to experienced faster recovery and shorter LOS than CR-TKA patients during the early postoperative course. Accordingly, UKA may be considered instead of TKA for patients who are good candidates for UKA and require expedited recovery.

Mid-term outcomes of a kinematically designed cruciate retaining total knee arthroplasty.

BACKGROUND: Advances in implant material and design have allowed for improvements in total knee arthroplasty (TKA) outcomes. A cruciate retaining (CR) TKA provides the least constraint of TKA designs by preserving the native posterior cruciate ligament. Limited research exists that has examined clinical outcomes or patient reported outcome measures (PROMs) of a large cohort of patients undergoing a CR TKA utilizing a kinematically designed implant. It was hypothesized that the studied CR Knee System would demonstrate favorable outcomes and a clinically significant improvement in pain and functional scores. AIM: To assess both short-term and mid-term clinical outcomes and PROMs of a novel CR TKA design. METHODS: A retrospective, multi-surgeon study identified 255 knees undergoing a TKA utilizing a kinematically designed CR Knee System (JOURNEY™ II CR; Smith and Nephew, Inc., Memphis, TN) at an urban, academic medical institution between March 2015 and July 2021 with a minimum of two-years of clinical follow-up with an orthopedic surgeon. Patient demographics, surgical information, clinical outcomes, and PROMs data were collected via query of electronic medical records. The PROMs collected in the present study included the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) and Patient-Reported Outcomes Measurement Information System (PROMIS®) scores. The significance of improvements in mean PROM scores from preoperative scores to scores collected at six months and two-years postoperatively was analyzed using Independent Samples t-tests. RESULTS: Of the 255 patients, 65.5% were female, 43.8% were White, and patients had an average age of 60.6 years. Primary osteoarthritis (96.9%) was the most common primary diagnosis. The mean surgical time was 105.3 minutes and mean length of stay was 2.1 d with most patients discharged home (92.5%). There were 18 emergency department (ED) visits within 90 d of surgery resulting in a 90 d ED visit rate of 7.1%, including a 2.4% orthopedic-related ED visit rate and a 4.7% non-orthopedic-related ED visit rate. There were three (1.2%) hospital readmissions within 90 d postoperatively. With a mean time to latest follow-up of 3.3 years, four patients (1.6%) required revision, two for arthrofibrosis, one for aseptic femoral loosening, and one for peri-prosthetic joint infection. There were significant improvements in KOOS JR, PROMIS Pain Intensity, PROMIS Pain Interference, PROMIS Mobility, and PROMIS Physical Health from preoperative scores to six month and two-year postoperative scores. CONCLUSION: The evaluated implant is an effective, novel design offering excellent outcomes and low complication rates. At a mean follow up of 3.3 years, four patients required revisions, three aseptic and one septic, resulting in an overall implant survival rate of 98.4% and an aseptic survival rate of 98.8%. The results of our study demonstrate the utility of this kinematically designed implant in the setting of primary TKA.

Comparison of postoperative clinical outcome in medial-pivotal and gradually reducing radius design cruciate-retaining total knee arthroplasty-A multicenter analysis of propensity-matched cohorts.

Purpose: To clarify differences in surgery duration, postoperative knee range of motion (ROM), anterior and posterior (AP) laxity, and Forgotten Joint Score (FJS) in patients undergoing medial-pivot (MP) and GRADIUS cruciate-retaining (CR) total knee arthroplasty (TKA) surgeries. Methods: We examined patients who underwent either MP or CR TKA at six different Japanese centres. Patients were propensity score matched for age, sex, and preoperative hip-knee angle (HKA). We compared the groups' average surgery duration, postoperative knee ROM, AP laxity, and FJS 1 year after surgery. Results: There were 86 study patients: 43 MP and 43 CR TKA matched for age, sex, and preoperative HKA. The MP group enjoyed a significantly shorter surgery duration (89.1 ± 10.9 mins vs. 95.7 ± 12.0 mins, p = 0.0091) and significantly better postoperative knee flexion than the CR group (123.7 ± 9.1° vs. 115.3 ± 12.4°, p < 0.001). The MP had significantly smaller postoperative AP laxity with 30° of knee flexion than the CR group (3.4 ± 1.3 vs. 5.6 ± 2.2 mm, p < 0.001). Conversely, postoperative AP laxity with 90° of knee flexion was significantly larger for the MP group (3.6 ± 1.3 vs. 2.7 ± 1.9 mm, p = 0.0098). There were no between-group differences in postoperative FJS. Conclusions: The MP group showed better postoperative knee flexion, midrange AP knee stability, and shorter surgery duration. Level of Evidence: Level III, retrospective comparative study.

Does Selective Posterior Tibial Slope Technique in Cruciate-Retaining Total Knee Arthroplasty Result in the Elimination of Posterior Cruciate Ligament Management?

In cruciate-retaining total knee arthroplasty (CR-TKA), intraoperative posterior cruciate ligament (PCL) management is necessary because retention of optimum PCL tension with high reproducibility is difficult. If PCL management is not performed appropriately, problems such as postoperative pain, poor range of motion, and a feeling of instability may occur. The posterior tibial slope (PTS) has a major influence on the tension of the PCL in CR-TKA. Changes in femoral posterior condylar offset also influences PCL tension in CR-TKA. We designed a surgical procedure in which the PTS is adjusted in association with the posterior condylar offset during surgery. The postoperative clinical results of the primary total knee arthroplasty 159 knee performed by this procedure were favorable. In addition, none of the knees required management of PCL. In our procedure, PCL management, which is the main problem in CR-TKA, is not necessary, and this may be the main advantage of the new procedure.

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.

The Early Clinical Outcomes Following Unrestricted Caliper Verified Kinematic Alignment Using a Medial Stabilized Design Total Knee Arthroplasty With a Cruciate Retaining Insert.

Background: Although various total knee arthroplasty (TKA) implant designs are widely used, the ideal TKA design is yet to be agreed upon. Although the benefits of cruciate-retaining (CR) TKA and medial stabilized (MS) TKA have been reported in literature, the early clinical outcomes of an MS TKA with CR inserts have not been reported. This study aims to report on the patient-reported clinical and radiological outcomes of MS-TKA combined with a CR insert. Methods: A prospective single-surgeon series evaluated the clinical- and patient-reported outcomes of 115 patients implanted with GMK Sphere CR. Patient outcomes were assessed with the Oxford Knee Score, Knee Injury and Osteoarthritis Outcome Scores (KOOS), Forgotten Joint Score, and Visual Analogue Scale for Satisfaction. Radiological assessment for alignment along with active flexion and extension were also assessed. Results: Improvement in all scores was observed between the preoperative and 1-year follow-up timepoints, with statistical significance seen for Oxford Knee Score as well as KOOS Symptoms, Pain, Sport, quality of life, and activities of daily living subscales. The mean active flexion between the preoperative and both postoperative timepoints at 6 months and 1 year was also statistically significant (P = .021 and P = .001). Conclusions: MS-TKA with a CR insert can facilitate symptom relief and improve overall function of the knee after surgery. Both the patient and clinical outcomes were comparable to 1-year outcomes utilizing other MS-TKA designs and were superior to those at 1-year follow-up following implantation of CR-TKA. Most notability, the KOOS symptoms and sports score were higher for the MS-TKA with a CR insert than for an MS-TKA design.

Less wear in deep-dished mobile compared to fixed bearing total knee arthroplasty of the same design at 5-year follow-up: a randomised controlled model-based Roentgen stereophotogrammetric analysis trial.

PURPOSE: The aim of this prospective randomised controlled study was to compare wear characteristics and functional outcome between deep-dished mobile bearing (MB) and fixed bearing (FB) cemented total knee arthroplasty (TKA). We hypothesised that deep-dished MB reduces polyethylene wear and improves patient-reported outcome measures. METHODS: A total of 50 patients were randomised to receive a MB or FB tibia component of the same cemented TKA design. Patients were evaluated over a 5-year follow-up period. Medial and lateral wear were assessed using model-based Roentgen Stereophotogrammetric Analysis (RSA) and compared with the direct postoperative minimal joint space measurement. Functional outcome was assessed by the clinician-derived KSS and OKS, WOMAC, LEAS, and FJS-12. All data were derived using a general linear mixed model. RESULTS: At 5-year follow-up, decreased wear in the MB compared to the FB group was observed on the lateral side (0.07 ± 0.17 mm, p = 0.026), but not on the medial side (0.31 ± 0.055 mm, p = 0.665). Functional outcomes improved with a statistical significant effect over time, with no significant differences between groups (all p > 0.17). CONCLUSION: This model-based RSA study with 5-year follow-up showed that cemented deep-dished MB reduced lateral polyethylene wear as compared to FB in a single TKA system, whilst clinical outcomes were comparable. Longer follow-up is needed to establish clinical implications of these altered wear patterns and determine type of wear. LEVEL OF EVIDENCE: Level 1 randomised controlled trial.

Comparison of finite helical axis of the knee joint before and after bi-cruciate-preserving knee arthroplasty.

BACKGROUND: Difference in the finite helical axis of the knee joints before and after anterior cruciate ligament-preserving knee arthroplasties such as unicompartmental knee arthroplasty and bi-cruciate-retaining total knee arthroplasty remains unknown. This study compared the knee finite helical axes before and after bi-cruciate-preserving knee arthroplasty. METHODS: Patients undergoing medial unicompartmental knee arthroplasty and bi-cruciate-retaining total knee arthroplasty were included. Under fluoroscopy, participants performed a deep knee bend before and after surgery. A two/three-dimensional registration technique was employed to measure tibiofemoral kinematics. Femoral finite helical axis was calculated in a flexion range of 0-120° using 30° windows (early-, mid-, late-, and deep-flexion phases). FINDINGS: In unicompartmental knee arthroplasty, the preoperative knee vertical angle was larger than the postoperative vertical angle in mid- and deep-flexion phases. The postoperative knee vertical angle was smaller in unicompartmental knee arthroplasty than in bi-cruciate-retaining total knee arthroplasty. In unicompartmental knee arthroplasty, the preoperative horizontal angle was smaller than the postoperative horizontal angle in the early-flexion phase. However, in bi-cruciate-retaining total knee arthroplasty, the preoperative horizontal angle was larger than the postoperative horizontal angle in mid- and deep-flexion phases. The horizontal angle was smaller before unicompartmental knee arthroplasty than that before bi-cruciate-retaining total knee arthroplasty in early-, mid-, and deep-flexion phases. However, the vertical angle was larger after unicompartmental knee arthroplasty than that after bi-cruciate-retaining total knee arthroplasty in the early-flexion phase. INTERPRETATION: The knee finite helical axes before and after unicompartmental knee arthroplasty differed from those before and after bi-cruciate-retaining total knee arthroplasty.

Novel morphogenic knee implant delivers comparable mid-term outcomes as compared to conventional non-morphogenic implants.

INTRODUCTION: Conventional total knee arthroplasty (C-TKA) implants have well-established mid- and long-term outcomes. The novel TKA (N-TKA) implants provide morphogenic implant components with smaller size increments to facilitate anatomical replication. The aim of the study is to evaluate if these advantages provides better clinical outcomes. MATERIALS AND METHODS: Registry data prospectively collected within a single institution from 2014 to 2018 was reviewed and propensity score matching was performed to match C-TKA to N-TKA. 70 pairs of cruciate retaining (CR) TKA and 116 pairs of posterior stabilized (PS) TKA were identified. Range of motion, SF-36, Knee Society Knee Score (KSKS), Knee Society Function Score (KSFS) and Oxford Knee Score (OKS) were assessed preoperatively, 6 and 24 months postoperatively. Satisfaction was assessed 6 and 24 months postoperatively. Independent T test was performed for parametric data, whereas Wilcoxon rank-sum analysis was performed for non-parametric data. RESULTS: Both C-TKA and N-TKA cohorts demonstrated statistically significant improvement for KSKS, KSFS, OKS and SF-36 at 6 and 24 months postoperatively. C-TKA CR patients had better flexion at 6 months as compared to N-TKA CR (108.7° versus 98.3°, respectively, p = 0.046). At 24 months, there was no difference between C-TKA and N-TKA for range of motion, KSKS, KSFS, OKS and SF-36 PCS, regardless of insert type (p > 0.05). CONCLUSIONS: Both models showed great postoperative improvements in KSFS, KSKS, OKS and SF-36 and have comparable early and mid-term outcomes, suggesting that N-TKAs are suitable substitutes for C-TKA. Longer follow-up studies are required to evaluate the long-term outcomes of N-TKAs. LEVEL OF EVIDENCE: lll.

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.

Posterior stabilised total knee arthroplasty is associated with improved post-operative knee specific function, health related quality of life and greater satisfaction when compared to cruciate retaining protheses.

PURPOSE: To assess whether there were differences in knee specific function, health related quality of life (HRQoL), and satisfaction between patients with a cruciate retaining (CR) or a posterior stabilised (PS) total knee arthroplasty (TKA) at 1 and 2 years postoperatively. METHODS: A retrospective review of TKA (CR and PS) patients from a prospectively collected arthroplasty database. Patient demographics, body mass index and ASA grade, Oxford knee score (OKS) and EuroQol 5-dimension (EQ-5D) 3-level, which was used to assess HRQoL, were collected preoperatively and 1 year and 2 years postoperatively. Regression was used to adjust for confounding factors. RESULTS: The sample included 3122 TKA, of which 1009 (32.3%) were CR and 2112 (67.7%) were PS. The PS group were more likely to be female (odd ratio (OR) 1.26, p = 0.003) and undergo resurfacing of the patella (OR 6.63, p < 0.001). There was a significantly greater improvement in the 1 year OKS in the PS group (mean difference (MD) 0.9, p = 0.016). The PS TKA was independently associated with a greater 1 year (MD 1.1, 95% CI 0.4 to 1.9, p = 0.001) and 2 years (MD 0.8, p = 0.037) post-operative improvements in OKS. PS TKA was also independently associated with a greater 1 year (MD 0.021, p = 0.024) and 2 years (MD 0.022, p = 0.025) post-operative and change in EQ-5D utility compared to the CR group. The PS group was more likely to be satisfied with their outcome at 1 year (OR 1.75, p < 0.001) and at 2 years (OR 1.38, p = 0.001) when adjusting for confounders. CONCLUSION: PS TKA was associated with a better knee specific function and HRQoL when compared to CR, but the clinical significance of this is not clear. However, the PS group was more likely to be satisfied with their outcome compared to the CR group.

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.

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.

Coronal Laxity at Flexion is Larger After Posterior-Stabilized Total Knee Arthroplasty Than With Cruciate-Retaining Procedures.

BACKGROUND: It is unclear whether coronal stability differs between cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA). The purpose of this study was to compare coronal laxity, radiological, and clinical outcomes between CR-TKA and PS-TKA. METHODS: Seventy five CR-TKAs and 72 PS-TKAs with a minimum 2-year follow-up were retrospectively evaluated. Coronal laxity was assessed at knee extension and 80° of flexion on varus and valgus stress radiographs. Radiological evaluation included femoral-tibial angle, hip-knee-ankle angle, and positions of femoral and tibial components. Clinical evaluation included the modified Hospital for Special Surgery score, the Western Ontario and McMaster Universities Osteoarthritis index, and range of motion. RESULTS: PS-TKA resulted in significantly larger varus, valgus, and total laxities at 80° flexion (P = .034, .031, and 0.001, respectively) compared with CR-TKA, while no significant difference was found at extension (P = .513, .964, and .658, respectively). No statistical difference was found in radiological and clinical outcomes between CR-TKA and PS-TKA, but the functional scores were slightly better in CR-TKA. There were adverse correlations between varus laxity at flexion and the Western Ontario and McMaster Universities Osteoarthritis index, the modified Hospital for Special Surgery score, and range of motion (r = 0.933, -0.229, -0.472, respectively). CONCLUSION: Coronal laxity at 80° of flexion was larger after PS-TKA than CR-TKA. In addition, clinical outcomes were adversely affected by the larger varus laxity at flexion. Care should be taken to maintain the coronal stability, especially at flexion, during surgery to obtain better patient-reported outcomes. LEVEL OF EVIDENCE: Level III.

Outcomes of cruciate-retaining total knee arthroplasty for osteoarthritis with severe varus deformity.

BACKGROUND: Varus deformity is common in osteoarthritic knee. The purpose of this study was to investigate the clinical and radiographic outcomes after cruciate-retaining (CR) total knee arthroplasty (TKA) for severely varus osteoarthritic knees and compare them to those of mildly to moderately deformed osteoarthritic knees. METHODS: Eight hundred ninety-four subjects were undergone CR TKA, 137 had severe varus deformity (group 1), and 757 had mild-to-moderate deformity (group 2) of the lower limb preoperatively. Pre- and postoperative outcomes were compared between two groups clinically and radiographically. RESULTS: Mean follow-up period was 54.7 ± 28.9 months. Mean age was 77.8 ± 6.7 years in group 1 and 74.5 ± 7.4 years in group 2 (p < 0.001). Preoperative hip-knee-ankle angle (HKAA) was - 17.7°±2.9° in group 1 and - 6.3° ± 5.1° in group 2 (p < 0.001). Preoperative range of motion (ROM) was 127.7° ± 15.2° in group 1 and 130.8 °± 9.6° in group 2 (p = 0.019). Preoperative Knee Society scores and WOMAC score were not significantly different between two groups. Postoperative HKAA was - 0.4° ± 2.3° in group 1 and 0.6 ° ± 2.0° in group 2 (p < 0.001). Postoperative ROM, Knee Society scores, and WOMAC score were not significantly different between two groups. CONCLUSIONS: CR TKA showed results in subjects with severe varus deformities comparable to those without severe varus deformities. Whether the degree of preoperative varus deformity of the lower limb should be considered when deciding to perform CR-type or PS-type TKA requires further discussion. LEVEL OF EVIDENCE: Retrospective comparative study, Level III.

Similar rate of return to sports activity between posterior-stabilised and cruciate-retaining primary total knee arthroplasty in young and active patient.

PURPOSE: Cruciate-retaining and posterior-stabilised implant designs are available for primary total knee arthroplasty. However, whether the implant design is associated with a difference in the level of activity still remains unclear. This clinical trial compared posterior-stabilised and cruciate-retaining implants in sport-related patient-reported outcome measures, range of motion, rate of return to sport, and weekly time dedicated to sport in active adults. It was also hypothesised that in young and active patients both implants lead to a similar rate of return to sport in terms of hours per week, type of sport, and joint mobility. METHODS: All patients were evaluated preoperatively and for a minimum of 36 months follow-up. The University of California Los Angeles activity scores, High-Activity Arthroplasty Score, and Visual Analogue Scale were administered preoperatively and at the last follow-up. The range of motion was investigated at admission and the last follow-up. Data concerning the hours per week dedicated to sports and the type of sport practiced were also collected at admission and at the last follow-up. The Kaplan-Meier Curve was performed to compare implant survivorship. RESULTS: Data from 227 procedures (cruciate-retaining: 109, posterior-stabilised: 118) were prospectively collected. At the last follow-up, no difference was reported in The University of California Los Angeles activity scores (p = 0.6), High-Activity Arthroplasty Score (p = 0.1), Visual Analogue Scale (p = 0.9), flexion (p = 0.7) and extension (p = 0.4). No difference was found in the rate of return (p = 0.1) and weekly hours dedicated to sport (p = 0.3). The Kaplan-Meier curve evidenced no statistically significant difference in implant survivorship (p = 0.6). CONCLUSIONS: At approximately five years of follow-up, no difference was reported between cruciate-retaining and posterior-stabilised implants in active adults in sport-related patient-reported outcomes measures, range of motion, pain, weekly time dedicated to sport, rate of return to sport, and implant survivorship. LEVEL OF EVIDENCE: Level II, prospective study.

Kinematic function of knee implant designs across a range of daily activities.

The aim of this randomized controlled trial was to measure and compare six-degree-of-freedom (6-DOF) knee joint motion of three total knee arthroplasty (TKA) implant designs across a range of daily activities. Seventy-five TKA patients were recruited to this study and randomly assigned a posterior-stabilized (PS), cruciate-retaining (CR), or medial-stabilized (MS) implant. Six months after surgery, patients performed five activities of daily living: level walking, step-up, step-down, sit-to-stand, and stand-to-sit. Mobile biplane X-ray imaging was used to measure 6-DOF knee kinematics and the center of rotation of the knee in the transverse plane for each activity. Mean 6-DOF knee kinematics were consistently similar for PS and CR, whereas MS was more externally rotated and abducted, and lateral shift was lower across all activities. Peak-to-peak anterior drawer for MS was also significantly lower during walking, step-up, and step-down (p < 0.017). The center of rotation of the knee in the transverse plane was located on the medial side for MS, whereas PS and CR rotated about the lateral compartment or close to the tibial origin. The kinematic function of MS was more similar to that of the healthy knee than PS and CR based on reduced paradoxical anterior translation at low flexion angles and a transverse center of rotation located in the medial compartment. Overall, 6-DOF knee joint motion for PS and CR were similar across all daily activities, whereas that measured for MS was appreciably different. The kinematic patterns observed for MS reflects a highly conforming medial articulation in the MS design.