Posterior-stabilized Total Knee Arthroplasty Research Articles

Clinical and Computational Evaluation of an Anatomic Patellar Component

Anatomic patellar components for total knee arthroplasty (TKA) have demonstrated favorable in vivo kinematics. A novel failure mechanism in patients implanted with anatomic patella components was observed, prompting a clinical and computational investigation to identify patient and implant-related factors associated with suboptimal performance. A retrospective evaluation was performed comparing 100 TKA patients implanted with anatomical versus 100 sex-, age-, and BMI-matched patients implanted with dome patellar components. All were implanted with the same posterior-stabilized (PS) TKA system with a minimum 1-year follow-up duration. Several radiographic parameters were assessed. A separate computational evaluation was performed using finite-element analysis, comparing components. Bone strain energy density was measured at the proximal and distal patellar poles. Patients who had anatomic patellar components had a significantly higher prevalence of anterior knee pain (AKP; 18 versus 2%, P < 0.001), chronic effusions (18 versus 2%, P < 0.001), and superior patellar pole fragmentation (36 versus 13%, P < 0.001) versus those who had dome patellar components. The anatomic group also demonstrated more lateral patellar subluxation (2.3 versus 1.1 mm, P < 0.001) and lateral tilt (5.4 versus 4.0 mm, P = 0.013). There was a higher, but not significant, number of revisions in the anatomic group (7 versus 3, P = 0.331). In computational evaluation, all simulations demonstrated increased bone strain energy density at the superior patellar pole for the anatomic patella. Resection thickness < 13 mm resulted in an over 2-fold increase in strain energy density, while a negative 7° resection angle resulted in a 6-fold higher superior pole strain energy. Patients who had this design of anatomic patellar component showed higher rates of AKP, effusion, and superior pole fragmentation than patients who had dome patellae, with higher superior patella pole strain energy confirmed on computational evaluation. Avoiding higher resection angles and excessive patellar resection may improve the performance and survivorship of the anatomic patella.

Prior Patellectomy: A Systematic Review and Meta-Analysis Comparing Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty Survivorship and Reported Outcomes

IntroductionIn the setting of total knee arthroplasty, prior patellectomy historically prompted the use of increased constraint implants, specifically posterior-stabilized (PS) designs. However, modern case series have reported similar outcomes utilizing cruciate-retaining (CR) implants. The primary outcome of this study was to compare implant retention rates between these two implant designs in prior patellectomy patients. Secondary outcomes included a comparison of patient-reported outcome scores and cause for revision. MethodsA comprehensive systematic review was performed using Web of Science, PubMed, and Scopus databases per Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Boolean operator search terms included “patellectomy AND (arthroplasty) OR (replacement).” Case reports, review articles, < 2 years of follow-up, and studies in which the implant design could not be ascertained were excluded. An initial screening of titles and abstracts for inclusion was performed, followed by a full manuscript review of eligible articles. Single-data extraction was performed, followed by subsequent statistical analysis. ResultsA total of 9 studies (209 knees) met the inclusion criteria. The average time from patellectomy to TKA was 16.1 years. While all patients had significant improvement in functional outcomes, CR implants displayed proportionally greater improvement in Knee Society Scores compared to PS implants (+108 versus +98%, P = < 0.001). However, there was a significantly greater rate of revision in the CR cohort compared to PS (18.6 versus 2.6%, P = 0.002). ConclusionsPrior patellectomy patients undergoing TKA have significant improvements in patient-reported functional outcomes and high mid-term retention rates. While CR implant designs portend a potentially greater improvement in functional outcomes, they also have a greater risk for revision than their PS implant counterparts. However, contemporary implant designs and operative techniques likely render revision rates equivocal between CR and PS implants in post-patellectomy patients.

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

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). 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. 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. 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.

Effect of Surgical Technique, Implant Design, and Time of Examination on Contact Kinematics: A Study of Bicruciate-Stabilized and Posterior-Stabilized Total Knee Arthroplasty

BackgroundBicruciate-stabilized (BCS) total knee arthroplasty (TKA) designs attempt to approximate natural knee mechanics. Multiple surgical techniques, including gap balancing (GB) and measured resection (MR), have been developed to provide optimal implant positioning and soft-tissue balance. The goal of this study was to determine the effect of surgical technique on BCS TKA contact kinematics. Secondary goals included investigating the change of kinematics over time and comparing BCS TKA kinematics to a posterior-stabilized (PS) design. MethodsThe study included the BCS-GB, BCS-MR, and PS-MR groups. The BCS-GB and BCS-MR groups underwent weight-bearing radiostereometric analysis for multiple knee flexion angles at 3 months and 1 year postoperatively, whereas the PS-MR group was imaged at 1 year postoperatively. The medial and lateral contact kinematics were determined from implant poses. ResultsThere were no differences in BCS TKA kinematics between the GB and MR techniques. There were differences in the mid-flexion ranges when comparing the 3-month and 1-year kinematics of the BCS design; however, they were less than 1.5 mm. Differences existed between the kinematics of the BCS and PS designs at all flexion angles for the medial condyle (P < .0006) and at 0° of flexion on the lateral condyle (P < .0001). ConclusionsContact kinematics for a BCS design were similar for both surgical techniques, suggesting both are appropriate for this design. Small, likely clinically insignificant differences were found between 3-month and 1-year kinematics. The BCS TKA kinematics differed from the PS design; however, it is unclear whether these differences improve clinical outcomes.

Minimum 19-Year Clinical Results and Patient Satisfaction After Total Knee Arthroplasty

BackgroundLong-term (minimum 19-year) outcome data on clinical results and patient satisfaction after posterior-stabilized total knee arthroplasties (TKAs) are missing in the literature. The purpose of the study was to evaluate the clinical and radiographic results as well as patient satisfaction at a mean of 21.2 years after posterior-stabilized TKAs. MethodsThis study included 756 patients (1,350 knees) who had undergone TKAs. There were 96 men and 660 women (mean age, 58 years; range, 40 to 84). The mean follow-up was 21.2 years (range, 19 to 23). At each follow-up visit, the patients were assessed radiographically and clinically. Furthermore, patient satisfaction was determined. ResultsThe Knee Society total, pain, function, and deformity scores were 42, 18, 33, and 5 points, respectively, at the final follow-up. The mean Western Ontario and McMaster Universities Arthritis Index score was 25 points at the final follow-up. With revision or aseptic loosening as the end point, the 23-year intimated survival for the implant was 96% (95% confidence interval, 91 to 100%). The overall patient satisfaction score at the final follow-up was 83.3 points (range, 81 to 86). Patient satisfaction scores with regard to pain, housework, recreation, and surgery were 84, 81, 82, and 86 points, respectively. ConclusionsThe findings of the present, mean 21-year follow-up clinical study suggest excellent results with regard to the revision rates and survivorship of the posterior-stabilized total knee implants. However, consistent with the literature, we found that about 80% of patients expressed overall satisfaction with their primary TKAs. About 8% of patients were either somewhat or very dissatisfied with the procedure.

Improved Clinical Outcomes With Dynamic, Force-Controlled, Gap-Balancing in Posterior-Stabilized Total Knee Arthroplasty

BackgroundOptimal soft-tissue management in total knee arthroplasty (TKA) may reduce symptomatic instability. We hypothesized that TKA outcomes using a computer-assisted dynamic ligament balancer that acquires medial and lateral gap sizes throughout the motion arc would show improved Knee Society Scores (KSS) compared to TKAs done with a traditional tensioner at 0 and 90°. We also sought to quantify the degree to which the planned femoral rotation chosen to optimize medio-lateral balance throughout the arc of motion deviated from the femoral rotation needed to achieve a rectangular flexion gap at 90° alone. MethodsBaseline demographics, clinical outcomes, KSSs, and femoral rotations were compared in 100 consecutive, computer-assisted TKAs done with the balancer (balancer group) to the immediately prior 100 consecutive computer-assisted TKAs done without the balancer (control group). Minimum follow-up was 13 months and all patients had osteoarthritis. Mean knee motion did not differ preoperatively (110.1 ± 13.6° balancer, 110.4 ± 12.5° control, P = .44) or postoperatively (119.1 ± 10.3° balancer, 118.8 ± 10.9° control, P = .42). Tourniquet times did not differ (93.1 ± 13.0 minutes balancer, 90.7 ± 13.0 minutes control, P = .13). Postoperative length of stay differed (40.2 ± 20.9 hours balancer, 49.0 ± 18.3 hours control, P = .0009). There were 14 readmissions (7 balancer, 7 control), 11 adverse events (4 balancer, 7 control), and 3 manipulations (1 balancer, 2 control). The cohorts were compared using Student’s t-tests, Shapiro-Wilk normalities, Wilcoxon rank-sums, and multivariable logistic regression analyses. ResultsPostoperative KSS improvements were higher in the balancer group (P < .0001). In multivariable regression analyses, the balancer group experienced 7 ± 2 point improvement in KSS Knee scores (P < .0001) and 4 ± 2 point improvement in KSS Function scores (P = .040) compared to the control group. ConclusionsThe statistically and clinically significant improvements in postoperative KSS demonstrated in the balancer cohort are likely driven by improved stability throughout the motion arc. Further study is warranted to evaluate replicability by non-design surgeons.

Fixed-Bearing and Higher Postoperative Knee Flexion Angle as Predictors of Satisfaction in Asian Patients Undergoing Posterior-Stabilized Total Knee Arthroplasty

Fixed-Bearing and Higher Postoperative Knee Flexion Angle as Predictors of Satisfaction in Asian Patients Undergoing Posterior-Stabilized Total Knee Arthroplasty

Improvement of rotational arc during deep flexion range of a novel designed polyethylene insert for posterior-stabilised total knee arthroplasty

BackgroundOne of the remaining issues in total knee arthroplasty (TKA) is achieving sufficient rotational arc during deep flexion range of the knee for specific postures such as the ‘seiza’ or cross-legged sitting. This study aimed to evaluate whether there was a change in the actual in vivo rotational arc during deep flexion range before and after a design change of polyethylene (PE) inserts. MethodsIn 50 posterior-stabilised TKA cases, knee kinematics, including rotational movement, were measured intraoperatively using an image-free navigation system to compare a newly designed PE insert with reduced the posterior lip with a conventional PE insert. Femoral–tibial rotational angles at 30°, 45°, 60°, 90°, 120°, and 130° knee flexion were evaluated. Varus/valgus instability, knee range of motion, and femoral rollback were also measured. Obtained parameters were compared between new and conventional PE inserts. The independent factors associated with rotational arc during deep flexion range (120° and 130° knee flexion) were analysed using multivariate analysis. ResultsThe newly designed PE insert demonstrated a significant increase in the rotational arc at 120° (22.9 ± 8.7° vs. 30.1 ± 11.9°, P < 0.001) and 130° (24.3 ± 9.5° vs. 32.5 ± 12.4°, P < 0.001) knee flexion compared with that with the conventionally designed posterior-stabilised insert. Multivariate analysis demonstrated that using the newly designed PE insert was an independent predictor of improved rotational arc during deep flexion range: regression coefficient was 11.2 (95% confidence interval 7.1–15.3, P < 0.001). ConclusionThe design change, which reduced the posterior lip of the PE insert, contributed to improved rotational arc in 120° and 130° deep flexion ranges.

Residual varus alignment after posterior-stabilized total knee arthroplasty limits medial soft tissue remodeling

BackgroundProper lower limb alignment and soft tissue balance are significant indicators to measure the success of total knee arthroplasty (TKA). Previous studies have confirmed that soft tissue relaxation around the knee after TKA will change over time; however, the relationship between lower limb alignment and soft tissue balance after TKA remains unclear. We studied (1) whether the change of soft tissue balance around the knee with time after posterior-stabilized (PS) TKA would affect the alignment of the lower limbs; (2) Whether the accuracy of lower limb alignment during PS TKA affects postoperative soft tissue remodeling.MethodsIn this study, 100 patients were recruited after PS TKA. Among them, 50 patients with a hip knee ankle (HKA) angle of ≤ ± 3° were set as the neutral group, and 50 patients with an HKA angle of > ± 3° were set as the deviation group. The imaging results measured the HKA angle before the operation as well as the HKA, varus, and valgus angles at 1, 3, 6, 12, and 24 months after TKA. Clinical assessment included range of motion (ROM), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score (KSS).ResultsEight people were excluded from the study. After the exclusion, the study enrolled 47 patients in the neutral group and 45 patients in the deviant group and were followed for up to 2 years. There was no statistical significance in mean varus angles as well as HKA angle changes during the follow-up phase of each groups (P > 0.05). The mean valgus angles of the patients in the neutral group group were 2.47°, 3.45°, 3.63°, 3.60° and 3.63°, and in the deviation group were 2.45° (P = 0.841), 2.88° (P < 0.001), 3.07° (P < 0.001), 3.06° (P < 0.001), and 3.10° (P < 0.001). ROM, WOMAC and KSS of the two groups were significantly improved after operation, with no difference between the two groups.ConclusionThis study shows that whether the alignment is accurate or not in the early stage after TKA, the relaxation of the medial and lateral soft tissues of the knee joint change; however, this change will not significantly affect the alignment of the lower limbs. Postoperative residual varus deformity limits medial soft tissue remodeling.Level of evidenceIII.

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

BackgroundA 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. MethodsA 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. ResultsOverall 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. ConclusionsGood 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.

The Impact of Patellar Position on Mediolateral Joint Gap in Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty: A Prospective Study

BackgroundThis prospective study aimed to investigate the influence of patellar position (ie, eversion, lateralization, and reduction) on medial and lateral gap measurements during total knee arthroplasty (TKA) in both cruciate-retaining (CR) and posterior-stabilized (PS) TKA designs. MethodsThe present work analyzed 50 knees with primary osteoarthritis that underwent TKA between July and November 2019. Medial and lateral gaps were measured at different knee flexion angles (0°, 45°, 90°, and 120°) in 3 patellar positions after sequentially inserting CR type and PS type trial component in the same knee. ResultsIn CR TKA, medial gaps in patellar reduction showed significantly smaller gaps at 90° and 120° of knee flexion compared to those in eversion and lateralization (P < .001). Lateral gaps in patellar reduction were also significantly larger than those in eversion and lateralization (P < .001). The mediolateral gap difference in patellar reduction was significantly greater at all flexion angles compared to those in eversion and lateralization (P < .001). In PS TKA, similar patterns were observed for medial gaps, lateral gaps, and mediolateral gap differences (P < .001). ConclusionsThe ligament balancing with the patella everted or subluxed may lead to an overly tight medial gap and/or loose lateral gap in the knee with a closed arthrotomy, which has potential consequences for knee function in both CR and PS TKA designs. The results of this study highlight the importance of considering patellar position to ensure optimal soft-tissue balance and joint stability in TKA.

Effect of posteromedial vertical capsulotomy with medial collateral ligament liberation on intraoperative medial component gap mismatch between extension and mid-flexion during total knee arthroplasty.

The aim of this study was to quantify the effect of posteromedial vertical capsulotomy on intraoperative component gaps and angles from extension through mid-flexion to flexion during total knee arthroplasty (TKA). In the present study, 47 cases of primary posterior-stabilized TKA using the measured resection technique for varus knee osteoarthritis (hip-knee-ankle angles < 0°) were reviewed. Component gaps and angles at 0°, 10°, 45°, 90°, and maximum flexion were measured intraoperatively, before and after posteromedial vertical capsulotomy. Differences in pre- and post-posteromedial vertical capsulotomy medial and lateral component gaps and angles and medial component gap mismatches among knee flexion angles were assessed using the Wilcoxon signed rank test for two paired samples. The medial component gaps at 0° and 10° of flexion of post-posteromedial vertical capsulotomy were significantly greater, exceeding the minimal detectable change, than those pre posteromedial vertical capsulotomy (change of the gap after the procedure at 0° of flexion was 0.7 ± 0.7mm and at 10° of flexion was 0.8 ± 0.8mm; all P values < 0.05). The medial component gap mismatches between both 0° and 10°, and 45°, 90°, and maximum flexion were significantly smaller post posteromedial vertical capsulotomy than pre posteromedial vertical capsulotomy, with the values of the change exceeding the minimal detectable change (change of the gap mismatch after the procedure: knee flexion at 0° and 45° was - 0.6 ± 0.9 [mm], at 0° and 90° was 0.7 ± 1.0, at 0° and maximum flexion was - 0.6 ± 1.2, at 10° and 45° was - 0.7 ± 0.9, at 10° and 90° was - 0.8 ± 0.9, at 10° and maximum flexion was - 0.7 ± 1.1; all P values < 0.05). Posteromedial vertical capsulotomy increased the medial component gaps during knee extension but not during mid-flexion or full flexion during posterior-stabilized TKA. Posteromedial vertical capsulotomy improved mild medial component gap mismatch between extension and mid-flexion and full flexion during posterior-stabilized TKA. Surgeons can consider posteromedial vertical capsulotomy when there is intraoperative constriction of the medial component gap during extension in patients undergoing posterior-stabilized TKA.

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

Surgeons want to achieve native kinematics in primary total knee arthroplasty (TKA). Cruciate-substituting (CS) implants could restore the knee kinematics more efficiently than posterior-stabilised (PS) TKA. This study aimed to compare gait patterns in patients with CS or PS TKA at 6months. The hypothesis was that CS implants would demonstrate comparable gait parameters to PS implants at 6months. In this prospective case-control study, 38 primary TKA without coronal laxity were divided into 2 groups: 19 cruciate-substituting (CS) and 19 posterior-stabilised (PS) implants. The type of prosthesis was determined according to the surgical period. Exclusion criteria were TKA revision, associated procedures and inability to walk on a treadmill. Gait analysis was conducted on a treadmill 6months postoperatively for each patient with a knee assessment device (KneeKG®). Gait characteristics included analysis in three spatial dimensions (flexion-extension, abduction-adduction, internal-external rotation, anterior-posterior translation). Clinical outcomes (Knee Society Score and Forgotten Joint Score) were compared between both groups at 6months postoperatively. At 6months, the gait analysis did not demonstrate any significant difference between CS and PS implants. The range and the maximum anteroposterior translation were similar in both groups (9.2 ± 6.5mm in CS group vs. 8.1 ± 3mm in PS group (n.s.); and - 5.2 ± 5mm in CS group vs. - 6.3 ± 5.9mm in PS group (n.s.), respectively). The internal/external rotation, the flexion, and the varus angle were similar between CS and PS implants. The KSS Knee score was higher at 6months in the CS group than in the PS group (92.1 ± 5.6 vs. 84.8 ± 8.9 (p < 0.01)). Cruciate-substituting and posterior-stabilised TKA had similar gait patterns at 6months postoperatively, despite a non-equivalent posterior stabilisation system. CS prostheses were an interesting option for primary TKA for knee kinematics restoration without requiring a femoral box. Prospective, case-control study; Level II.

A Comparative Study of Clinical Outcomes Between Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty: A Propensity Score-Matched Cohort Study.

We investigated a comparison of clinical outcomes between cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty. However, it is still controversial which design leads to better clinical results. In clinical settings, choosing either CR or PS is likely based on the surgeon's preferences. In this study, short-term clinical outcomes between CR and PS in patients who received a single knee prosthesis were compared using propensity score matching. Two hundred and twelve CR and 43 PS of a single knee prosthesis were enrolled in this study. After propensity score matching, 34 knees each in the CR and PS groups were chosen and were without significant differences in age at operation, gender, BMI, preoperative range of motion (ROM), preoperative femorotibial angle (FTA), and presence or absence of patellar replacement. Clinical scores, including ROM, Knee Society score (KSS), knee injury and osteoarthritis outcome score (KOOS), except for the sports subscale, were compared between the CR and PS groups preoperatively and two years postoperatively. Postoperatively, there were no significant differences in FTA, ROM, or KSS. Preoperative scores for the KOOS except for the pain subscale were comparable between the groups. Postoperatively, however, the PS group had a significantly higher score in the ADL subscale compared to the CR group (PS: 89.5 vs. CR: 80.8,p= 0.017). The KOOS subscales other than activities of daily living (ADL) were comparable between the groups. In this propensity score-matched cohort study, PS showed a better outcome for the ADL than the CR design. These findings suggest that choosing either CR or PS should not depend on the surgeon's preferences. A PS design may be preferable to CR for elderly patients.

Association between pre- and postoperative rotational mismatches of the femorotibial components and bones in bi-cruciate retaining and posterior stabilized total knee arthroplasty

To clarify the association between pre- and postoperative rotational mismatches of the femorotibial components and bones for total knee arthroplasty (TKA) with bi-cruciate retaining (BCR) design and with fixed bearing posterior stabilized (PS) design. This retrospective cohort study included 40 BCR TKAs and 50 PS TKAs. Pre- and postoperative rotational mismatches of the femorotibial components and bones were measured by three-dimensional assessment based on computed tomography imaging. The mean value and percentage within ± 5° of pre- and postoperative rotational mismatches were compared between BCR TKA and PS TKA. Correlations between pre- and postoperative rotational mismatches of the femorotibial components and bones were investigated in BCR TKA and PS TKA. There was no significant difference in mean preoperative rotational mismatch of femorotibial components and bones between BCR TKA and PS TKA. Mean postoperative rotational mismatch of femorotibial components and bones was significantly greater in BCR TKA than in PS TKA. Postoperative rotational mismatch of the femorotibial components was within ± 5° in 21 knees (52.5%) for BCR TKA and in 43 knees (86.0%) for PS TKA. The rate of postoperative rotational mismatch of the femorotibial components and bones within ± 5° was significantly lower for BCR TKA than for PS TKA. In BCR TKA, there was a positive correlation between pre- and postoperative rotational mismatches of the femorotibial components and of bones. We consider these results can be attributed to the retention of both cruciate ligaments, which may affect the reduction of rotational permittance of the components and bones.

Investigation into the factors affecting bearing thickness when performing rotating-platform posterior-stabilized total knee arthroplasty

BackgroundRotating-platform posterior-stabilized total knee arthroplasty (PS-TKA) has become a commonly used procedure. It has the potential risk of causing mobile-bearing spinout. In our study, we investigated the factors affecting the bearing thickness when performing rotating-platform PS-TKA. MethodsThis single-arm, prospective, single-hospital cohort study included 100 consecutive patients who underwent rotating-platform PS-TKA between September 2020 and August 2022. We examined the relationship between bearing thickness and several patient characteristics. ResultsThe results of the univariate analysis showed that the bearing thickness was significantly associated with weight (risk ratio = 3.4; 95% confidence interval (CI) = 1.1–11.0; P = 0.016) and implant size of the tibia (risk ratio = 3.4; 95% CI = 1.0–11.5; P = 0.030). We performed multivariate analysis regarding the weight and implant size of the tibia. Neither the weight nor the implant size of the tibia was significantly different from the bearing thickness in the multivariate analysis. ConclusionsIn rotating-platform PS-TKA, body weight and tibia size may affect the bearing thickness. Weight >60 kg and tibial implant size >67 cm may be risk factors for bearing thickening. Therefore, the surgery can be performed better if these risk factors are considered.

Comparison of ultra-congruent anterior-stabilized vs. a posterior cruciate substituting total knee arthroplasty for osteoarthritis with severe varus knee deformity: comparable 2 year outcomes with two design.

In this retrospective study, we compared the functionality and clinical outcomes of patients with severe varus knees who underwent total knee arthroplasty (TKA) that used prostheses with either a posterior stabilized (PS) design or an ultra-congruent (UC) design. Primary TKA was performed in 161 patients; the UC device was used in 82 (51%) cases and the PS device in 79 (49%). Preoperatively and at the final follow-up examination, all patients were evaluated by orthoroentgenography. The mechanical axis angle and radiolucent lines were evaluated according to the Knee Society Roentgenographic Evaluation System on preoperative and 5-year follow-up radiographs. Total Knee Society Score (KSS) (knee score/function score) and Visual Analog Scale scores were obtained at the final follow-up examination. Demographic and surgical data and revision rates were evaluated for all patients. Postoperative angle values were significantly decreased in both the UC and PS groups (p<0.001 and p<0.001, respectively). Postoperative flexion range of motion values were significantly increased in both the UC and PS groups (p<0.001 and p<0.001, respectively). The postoperative KSS function scores were not significantly different between the groups (p=0.194). The mean surgical time of the PS group (54.99±4.18 minutes) was significantly higher than that of the UC group (46.02±4.48 minutes) (p<0.001). No notable differences were found between the UC and PS groups with respect to the clinical and functional parameters examined. Based on these results, UC TKA can be considered a safe alternative to PS TKA in severe varus knees.

Wider translations and rotations in posterior-stabilised mobile-bearing total knee arthroplasty compared to fixed-bearing both implanted with mechanical alignment: a dynamic RSA study

PurposeThe purpose of this study was to investigate the in vivo kinematics of the same femoral design mechanically aligned posterior-stabilised (PS) total knee arthroplasty (TKA) with either fixed-bearing (FB) or mobile-bearing (MB) inlay, implanted by the same surgeon, using model-based dynamic radiostereometric analysis (RSA). The hypothesis of the present study was that the MB design would show wider axial rotation than the FB design, without affecting the clinical outcomes.Materials and methodsA cohort of 21 non-randomised patients (21 DePuy Attune PS-FB) was evaluated by dynamic RSA analysis at a minimum 9-month follow-up, while performing differently demanding daily living activities such as sit to stand (STS) and deep knee lunge (DKL). Kinematic data were compared with those of a cohort of 22 patients implanted with the same prosthetic design but with MB inlay. Anterior–posterior (AP) translations, varus–valgus (VV) and internal–external (IE) rotations of the femoral component with respect to the tibial baseplate were investigated. Translation of medial and lateral compartment was analysed using the low point method according to Freeman et al. Questionnaires to calculate objective and subjective clinical scores were administered preoperatively and during follow-up visit by the same investigator.ResultsThe FB TKA design showed lower AP translation during STS (6.8 ± 3.3 mm in FB vs 9.9 ± 3.7 mm in MB, p = 0.006*), lower VV rotation (1.9 ± 0.8° in FB vs 5.3 ± 3.3° in MB, p = 0.005) and lower IE rotation (2.8 ± 1.1° in FB vs 9.5 ± 4.3° in MB, p = 0.001) during DKL than the mobile-bearing TKA design. Posterior-stabilised FB group showed significant lower translation of the low point of the medial compartment than the MB group (p = 0.008). The percentage of patients performing medial pivot in the FB group was higher compared to MB group in the examined motor tasks. No significant differences in post-operative range of motion (117° ± 16° for FB group and 124° ± 13° for MB group) and in clinical outcomes emerged between the two cohort.ConclusionsThe FB and MB designs differed in AP translations, VV rotations and IE rotations of the femoral component with respect to the tibial component in STS and DKL. Furthermore, FB cohort reported a significant higher percentage of medial pivot with respect to MB cohort. Despite this, no differences in clinical outcomes were detected between groups. Both designs showed stable kinematics and represent a viable option in primary TKA.Level of evidenceProspective cohort study, II.

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

BackgroundBoth 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. Methods140 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. ResultsWe 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. ConclusionWhile 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 influence of patellar height on patellofemoral contact force during total knee arthroplasty

PurposeResidual anterior knee pain following total knee arthroplasty was reported to be related to high patellofemoral contact force. This study tried to show the relationship between patellar height and patellofemoral contact force in vivo, which has been demonstrated only in vitro thus far. MethodsFifty-five patients who had undergone a primary mobile-bearing posterior-stabilized total knee arthroplasty (28 cases using PFC Sigma and 27 cases using Attune) were included. After all the trial prostheses were placed, the patellar contact forces on the medial and lateral sides were measured using specially designed two uniaxial ultrathin force transducers at 0°–135° of knee flexion guided by the navigation system. Correlations between the pre-operative Insall-Salvati index and the medial or lateral patellar contact force in each flexion angle were analyzed using linear regression. Correlations between each patellar contact force and postoperative flexion angle were also assessed. ResultThere was a positive correlation between Insall-Salvati index and the lateral patellar contact force at 135° of flexion in all the patients, at 120° and 135° of flexion in patients with PFC Sigma and 135° of flexion in patients with Attune. The lateral patellar contact force at 120° and 135° of flexion in patients with PFC Sigma inversely correlated with postoperative flexion angle. ConclusionsPatients with patella alta tended to demonstrate high lateral patellar contact force in deep knee flexion after total knee arthroplasty, which can affect the post operative flexion angle and should be treated to prevent residual anterior knee pain.