Prospective sequential comparison of femoral roll-back between cruciate-retaining and posterior-stabilized total knee arthroplasty using an intra-operative sensor

BackgroundImplant design and surgical techniques affect postoperative knee kinematics in total knee arthroplasty (TKA). This study aimed to compare femoral roll-back between cruciate-retaining (CR) and posterior-stabilized (PS) TKA in the same knee by objectively quantifying the contact point kinematics of the tibiofemoral joint using a sensor.MethodsIn the present prospective study, we used an intraoperative sensor to compare medial and lateral roll-back during 0-120° knee flexion in 33 knees that underwent CR and PS TKA. We also examined the relationship between mediolateral balance and the lateral-to-medial roll-back ratio. We defined the contact percentage position as the vertical length to the contact point divided by the anteroposterior length of the tibial plate.ResultsThe roll-back percentage following PS TKA (19.8 ± 5.1%) was significantly higher than that after CR TKA in both the medial (19.8 ± 5.1% versus 7.1 ± 2.5%, P < 0.001) and lateral (26.8% ± 3.8% versus 18.7 ± 3.8%, P < 0.001) compartments. The medial contact pressure at 90° was significantly correlated with the increased lateral-to-medial roll-back ratio in both CR and PS TKA (both P < 0.001).ConclusionPS TKA resulted in a higher percentage of femoral roll-back in the medial and lateral compartments than CR TKA. CR TKA caused a higher lateral-to-medial roll-back ratio compared to PS TKA. To reproduce medial pivot knee motion similar to that of a normal knee, the medial soft tissue needed to be balanced more tightly than the lateral soft tissue during TKA. These findings provide some clinical evidence of TKA design selection and proper mediolateral balancing for successful TKA.     

Comparison of intraoperative kinematics and their influence on the clinical outcomes between posterior stabilized total knee arthroplasty and bi-cruciate stabilized total knee arthroplasty

BackgroundOf all the intraoperative kinematic parameters recorded using navigation systems, femorotibial rotational alignment is reportedly associated with the clinical outcomes of cruciate retaining and posterior stabilized (PS) total knee arthroplasty (TKA). However, to our knowledge, there are no reports on the relationship of newly designed bi-cruciate stabilized (BCS) TKA and intraoperative rotational kinematics. We aimed to clarify and compare the relationships between the intraoperative kinematics and clinical outcomes of BCS TKA and PS TKA.MethodsWe compared the intraoperative rotational kinematics and clinical outcomes at two years postoperatively of 56 BCS TKA patients and 55 PS TKA patients. Further, we evaluated the relationship between the femorotibial rotational kinematics and clinical outcomes.ResultsThe maximum flexion angle and the pain subscale of the Knee injury and Osteoarthritis Outcome Score (KOOS) in BCS TKA were significantly better than those in PS TKA. The intraoperative kinematic data of BCS TKA showed “screw-home” movement, while that of PS TKA did not show this movement. The rotational angular differences between at maximum flexion angle and at 60° flexion of BCS TKA showed positive correlations with the improvement of KOOS pain, symptom, activity of daily living and sports subscales. The rotational angular differences between at maximum flexion angle and at 30° flexion in PS TKA showed positive correlations with the maximum flexion angle.ConclusionIntraoperative femorotibial rotational kinematics and its influence on the clinical outcomes were different between BCS and PS TKA. BCS TKA showed more normal-like kinematics and better clinical results than PS TKA.     

Long-term results of revision total knee arthroplasty using a rotating hinge implant

BackgroundRotating hinge implants are commonly used in revision total knee arthroplasty (TKA) in the setting of significant ligamentous instability or bone deficiency. These highly constrained implants have been associated with variable clinical outcomes and uncertain long-term survivorship. The aim of this study is to establish long-term functional outcomes, radiographic results, and survivorship after revision TKA with a rotating hinge implant.MethodThis is a retrospective study of prospectively collected data of 41 consecutive patients undergoing revision TKA with rotating hinge components and minimum 10-years follow-up. The study included 22 females (53.7%) and 19 males (46.3%) with a mean age of 66.6 ± 8.5 years. Clinical outcomes recorded included the Oxford Knee Score (OKS) preoperatively and at latest follow-up. Range of motion, implant survivorship, and complications were also recorded. Predefined radiological outcomes were obtained using plain radiographs.ResultsThere was a significant improvement in OKS after revision TKA with a rotating hinge implant compared to preoperative scores (40.7 ± 4.2 vs. 21.4 ± 4.9 respectively, p < 0.001). At latest follow-up, mean range of motion was 111.5° ± 9.3° and mean overall limb alignment was 0.2° ± 2.0° varus. Implant survivorship at minimum 10-year follow-up was 90.2%. Radiographic lucent lines were observed in 14 patients (34.1%).ConclusionRevision TKA with a rotating hinge implant leads to satisfactory clinical outcomes and very good implant survivorship at long-term follow-up. Surgeons should have a low threshold to use these versatile implants in complex revision knee arthroplasty.     

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

BackgroundThe purpose of this study was to determine functional outcomes, implant survival rate, and complications of a single-radius, high-flexion posterior stabilized (PS) total knee prosthesis at a minimum follow up of 10 years for a consecutive series.MethodsThis retrospective observational study included 395 consecutive patients who underwent 585 single-radius, PS total knee arthroplasties (TKAs) between January 2009 and December 2009. Their functional outcomes, implant survival rates, radiological findings, and complications were evaluated.ResultsAt a mean follow up of 11.2 years (range, 10.6–11.8 years), 395 (80.8%) patients were available for review. At final follow up, preoperative Knee Society knee scores were improved from 37.3 to 80.1 (P < 0.05) and function scores were improved from 35.7 to 80.5 points (P < 0.05). Sixteen knees (2.7%) in 15 patients required revision surgery due to 11 septic loosening (1.9%) and five aseptic loosening events (0.8%). Cumulative survival for the prosthesis was 97.3% for any cause at 10 years. A total of 34 radiolucent lines (5.8%) were detected an average of 2.4 years following surgery and radiological assessment did not reveal any evidence of component migration at final follow up.ConclusionsSingle-radius, high-flexion PS TKA showed good long-term survival rates and clinical outcomes. Further study is required to determine whether limited radiolucency findings at the tibial component–tibial plateau could progress to or result in the loosening of components.     

Clinical and objective gait outcomes remained stable seven years after total knee arthroplasty: A prospective longitudinal study of 28 patients

BackgroundThere is a paucity of data on mid to long-term gait outcomes after total knee arthroplasty. The aims of this longitudinal study were: to assess the evolution of both clinical and gait outcomes before and up to seven years after primary total knee arthroplasty (TKA) in a cohort of patients with knee osteoarthritis.MethodsThis study included 28 patients evaluated before and up to seven years after primary TKA with both gait analysis and patient reported outcomes; of these, 20 patients were evaluated one year after surgery as well. Kinematic outcomes during gait (gait velocity, dimensionless gait veolicity, maximal knee flexion and knee range of motion), pain relief, Western Ontario and MacMaster Osteoarthritis Index (WOMAC), quality of life and patient satisfaction were assessed and compared at each visit with the paired Wilcoxon signed rank test (p < 0.05).ResultsThe significant improvement achieved at one year after TKA was stable up to seven years after surgery, with all clinical and kinematic outcomes unchanged, except for gait velocity, with a significant decrease over time (1.3 (1.1–1.4) m/s one year after TKA versus 1.0 (0.9–1.1) m/s, p < 0.05 up to seven years after).ConclusionPatients with knee osteoarthritis significantly improve their clinical and kinematic outcomes at one year postoperatively and maintain the gain up to seven years after primary TKA, except for gait velocity which decreases over time, most likely along with ageing.     

Long-term clinical outcomes of medial pivot total knee arthroplasty for Asian patients: A mean 10-year follow-up study

BackgroundMany Asian populations have a unique floor-based lifestyle that might cause mechanical stress of the knees. It is important to clarify the longevity of a medial pivot total knee arthroplasty, as its prosthetic design could cause mechanical stress onto the insert. The purpose of this study was to clarify the clinical results of medial pivot total knee arthroplasty for Asian patients in a 10-year follow-up study.MethodsConsecutive, primary total knee arthroplasties (n = 257) were analyzed in the study using the medial pivot knee system. The clinical outcomes were assessed preoperatively and at the final follow-up. The patient-reported Forgotten Joint Score-12 and radiological outcomes were measured at the final follow-up. The survival rate was assessed with reoperation or revision as the end-point.ResultsThe mean follow-up period was 10.1 ± 1.7 years. The lost to follow-up was 4.5%. All clinical outcomes improved significantly after surgery (p < 0.001). The mean postoperative knee flexion was 118° ± 11° and the mean Forgotten Joint Score-12 was 59.7 ± 27 points. The radiolucent line was observed in 29 patients (11.3%), however there was no aseptic loosening noted. The survival rates with reoperation or revision were 96.3% or 98.4% at 10 years after the operation.ConclusionsMedial pivot total knee arthroplasty used for Asian patients showed good longevity and patient-reported outcome measurement in a mean 10-year follow-up study. Medial pivot total knee arthroplasty has long-term stability among patients who have a floor-based lifestyle.Level of evidence: III.     

Comparison of intraoperative soft tissue balance measurement between two tensor systems in total knee arthroplasty

BackgroundDifferences in measurement outcomes using different tensors in total knee arthroplasty (TKA) remain unknown. This study aimed to compare intraoperative soft tissue balance between two measurement systems in TKA.MethodsThis study included 24 cruciate-retaining (CR) and 27 posterior-stabilized (PS) TKAs for varus-type osteoarthritis. All TKAs were performed with the measured resection technique. Intraoperative soft tissue balance was assessed with femoral component placement and patellofemoral joint reduction throughout the range of motion. Measurements were performed using the Offset Repo-Tensor (Zimmer) and Ligament Sensor Tensor (Depuy). Joint component gaps and varus/valgus ligament balance were compared statistically in CR and PS TKAs.ResultsJoint component gaps with the Offset Repo-Tensor were significantly larger at 0°, 10°, 30°, and 60° of knee flexion in CR TKA and at all knee flexion angles, except 0° and 135°, in PS TKA than those with the Ligament Sensor Tensor (P < .05). Varus balance with the Offset Repo-Tensor was significantly larger at 0°, 10°, and 30° of knee flexion in CR TKA and at 10°, 30°, 60°, 90°, and 120° of knee flexion in PS TKA than that with the Ligament Sensor Tensor (P < .05).ConclusionSurgeons should consider the discrepancy in assessing intraoperative soft tissue balance depending on the tensor used. The Ligament Sensor Tensor tended to underestimate soft tissue balance in CR and PS TKAs compared with the Offset Repo-Tensor, especially in PS TKA. Thus, surgeons should know the difference in values between the offset-type tensor with consistent distraction force and a spring-loaded tensor.     

Ten-year outcomes of a nitrided Ti-6Al-4V titanium alloy fixed-bearing total knee replacement with a highly crosslinked polyethylene-bearing in patients with metal allergy

BackgroundMetal hypersensitivity in patients with a total knee arthroplasty (TKA) is a rare condition and a very controversial topic. Despite the lack of data concerning the real effective impact of allergy on TKA failures, most of the manufactures offer the choice of ‘non-allergenic’ implants both for primary and revision TKA, some of which provide the same designs and surgical techniques as the conventional ones. Only a few studies are available on outcomes on these ‘hypersensitivity-friendly’ implants and even fewer specifically on allergic patients with a mid- to long-term follow-up.MethodsBetween 2007 and 2015, we enrolled 72 patients (57 females, 15 males), who underwent TKA treated with a non-allergenic posterior-stabilized (PS) total knee implant for a declared and proven metal allergy.Patients were followed clinically and radiographically for a mean 10 years of follow-up.ResultsWith revision as an endpoint the Kaplan–Meier survival estimate showed a survival rate of 97.2% at five years and 95.1% at 10 years. Significant improvements in range of motion (ROM), Knee Society Scoring (KSS) and Hospital for Special Surgery (HSS) knee scores were registered at final follow-up (P < 0.0001). At final follow-up validated Patient-Reported Outcome Measures (PROMs) showed the following scores: Oxford Knee Score (OKS) 42.1, EQ5D 0.80, EQ VAS 80.1, Forgotten Joint Score 71.2.ConclusionsThis nitrided Ti-6Al-4V titanium alloy fixed-bearing total knee replacement with a highly crosslinked polyethylene-bearing showed interesting results and survival rates in patients with metal allergy at mid- to long-term follow-up.     

Evaluation of anteroposterior accelerometric change after bi-cruciate stabilized total knee arthroplasty and posterior stabilized total knee arthroplasty

BackgroundIn conventional total knee arthroplasty (TKA), the anterior cruciate ligament (ACL) is resected. ACL dysfunction causes knee instability and is regarded as one factor in poor TKA outcomes. In bi-cruciate stabilized (BCS) TKA, the implant reproduces ACL function and provides anterior stability. The objective of this study was to evaluate preoperative and postoperative X-rays and accelerometer gait measurements in patients who underwent BCS TKA and posterior-stabilized (PS) TKA to assess the postoperative acceleration changes of knees after these procedures and to compare them in terms of joint range of motion (ROM) and the New Knee Society Score (New KSS).MethodsThe subjects were 60 patients, 30 of whom underwent BCS TKA and 30 PS TKA. Joint ROM, New KSS, lateral X-rays of the standing extended knee, and accelerometer data were evaluated 12 months postoperatively.ResultsThere was no significant difference in joint ROM between the groups. Both had good New KSS results, but the functional activity score was significantly higher after BCS TKA than after PS TKA. X-rays showed a lower posterior offset ratio after BCS TKA than after PS TKA, with anteroposterior positioning closer to that of the normal knee.Accelerometer data showed that postoperative anteroposterior acceleration on the femoral side in the stance phase and swing phase was lower after BCS TKA than after PS TKA.ConclusionCompared with PS TKA, BCS TKA resulted in a higher functional activity score, closer positioning to that of the normal knee on lateral X-ray, and lower anteroposterior acceleration on the femoral side.     

Survivorship of constrained polyethylene inserts in primary total knee replacements

BackgroundVarus–valgus constrained (VVC) inserts are used in primary total knee arthroplasty (TKA) when stability cannot be achieved with a traditional insert. Concern has been raised regarding premature loosening and failure of these primary TKAs due to the increased load transfer through the prosthesis. This study seeks to assess the survival, clinical outcomes and radiographic assessment of VVC total knee inserts used in a single primary TKA system without diaphyseal stem extensions.MethodsA consecutive cohort of 74 primary TKAs with VVC inserts was identified from an institutional database. A two-to-one matched group of 136 posterior-stabilized (PS) primary TKAs was generated from the same database. Survival analysis was assessed for all-cause revision surgery. Patient outcome measures were the Oxford Knee Score (OKS) and patient reported satisfaction. Radiographs were assessed in accordance with the Knee Society radiographic scoring system for radiolucency.ResultsSurvival rates at three and five years were 98.1% and 95.1% for the VVC liner group and 98.1% and 98.1% for the PS liner group, respectively. OKS improved from pre-op to post-op for both groups (p < .001). OKS was reduced in the VVC liner group compared to the PS liner group at latest available follow-up (p = .012). However, clinical satisfaction rates did not differ between the two groups. Small, non-progressive radiolucent lines existed on several radiographs; however, no components in either group were deemed radiographically loose.ConclusionThe survivorship, clinical, and radiographic outcomes of VVC knees were similar to the PS comparison group at short- to mid-term follow-up.     

Long-term results of the subtubercle tibial osteotomy using the circular external fixator for medı̇al compartment osteoarthrı̇tı̇s of knee

BackgroundWe evaluated the long-term clinical and radiographic outcomes of patients who underwent subtubercular tibial osteotomy (STO) with Ilizarov external fixation used for high tibial osteotomy for medial knee osteoarthritis (MKOA).MethodsBetween October 2003 and December 2011, 42 knees of 40 patients who had undergone STO with Ilizarov external fixator with a diagnosis of MKOA were evaluated. Survival analysis was performed by examining the duration of total knee arthroplasty (TKA). Clinical and radiological variables were collected at the time of admission after removal of the fixator and at outpatient follow up.ResultsMean age was 49.3 ± 5.68 (range 37–61) years, mean postoperative follow up time was 14.22 ± 2.93 (range 9–18) years, and mean fixator duration was 14.6 (range 13–20) weeks. Survival analysis showed 100% at 5 years, 95.2% at 10 years and 88.1% at 15 years. Clinical examination of the patients showed significant improvement in American Knee Society score (KSS), KSS functional score and Oxford Knee Score (OKS) score (P = 0.005). In the study, it was observed that the patients' knee osteoarthritis had progressed over time. On examination, radiographic measurements including mechanical axis deviation, medial proximal tibial angle, femorotibial angle, and joint line alignment angle improved significantly after deformity correction (P = 0.001).ConclusionSTO using the Ilizarov method offers long-term survival. It provides effective treatment in young patients with isolated MKOA. Achieving the desired amount of correction in the coronal and sagittal planes can be presented as a surgical technique for the treatment of MKOA as an effective method in clinical and radiological correction.     

Effect of osteoarthritis severity on survival and clinical outcomes after high tibial osteotomy

BackgroundThis study aimed to evaluate the effect of osteoarthritis severity on clinical outcomes using the 2011 Knee Society Score (KSS2011) and survival rates after closed wedge high tibial osteotomy (CWHTO).MethodsIn this retrospective study, KSS2011 questionnaires were mailed to patients who had undergone CWHTO between January 1991 and December 2011. The completed questionnaires returned by the patients were analyzed. Preoperative osteoarthritis severity was evaluated by Kellgren-Lawrence (K-L) grade. KSS2011 was compared between the K-L grade groups. To determine the effect of K-L grade for revision surgery, Kaplan-Meier survival curves were created using the need for total knee arthroplasty (TKA) as the endpoint to estimate the probability of failure.ResultsThere were 16, 81, and 47 knees with preoperative K-L 2, 3, and 4, respectively. Among the KSS2011 sub-scores, the symptom score showed significant differences between the groups (p = 0.006). However, no significant difference was found regarding satisfaction, expectation, and functional activity scores. No significant difference in the symptom score was found between the K-L 2 and 3 groups (p > 0.05). Eighteen knees were treated with TKA at a mean of 9 years after CWHTO. Using the Kaplan-Meier survival estimates, the K-L 4 group showed a significantly higher rate of total knee arthroplasty conversion than the K-L 2 and 3 groups (p < 0.001).ConclusionsOsteoarthritis severity affects clinical outcomes and survival rates during long-term follow-up after CWHTO. Surgeons should consider the preoperative osteoarthritis grade for long-term outcomes when considering CWHTO for patients with varus knees.     

Postoperative outcomes of total knee arthroplasty compared to unicompartmental knee arthroplasty: A matched comparison

BackgroundThe purpose of this study was to evaluate early postoperative outcomes in patients following UKA (unicompartmental knee arthroplasty) compared to a matched cohort of TKA (total knee arthroplasty) patients.MethodsPatients who met radiographic criteria for a medial UKA who underwent either a TKA or UKA at a single institution were matched based on age, gender, and BMI.ResultsOne hundredy and fifty UKA in 138 patients and 150 TKA in 148 patients were included in this retrospective analysis. Mean age was 62.6 ± 9 years and 65.2 ± 9 years in the UKA and TKA groups respectively (p = .01). Patients who underwent UKA had significantly less pain at two and six weeks postoperatively compared to TKA patients with mean Numeric Pain Rating Scale (NPRS) scores of 3.7 ± 1.1 vs. 7.8 ± 1.2, p < .001 and 2.6 ± 1.3 vs. 4.6 ± 1.6, p < .001 respectively. Knee Society Scores (KSS) were higher in the UKA group at six weeks and two years postoperative (86.5 ± 2.8 vs. 81.4 ± 3.6, p < .001 and 89.5 ± 2.4 vs. 84.5 ± 3.3, p < .001 respectively). Return to work was faster in the UKA group (mean 20.6 ± 7.89 vs. 38.6 ± 6.23 days, p < .001). The UKA group also had higher mean Forgotten Joint Scores of 90.5 ± 3.6 vs. 79.5 ± 9.5 (p < .001).ConclusionsPatients with primarily medial compartment OA who underwent UKA had less postoperative pain, earlier return to work, and higher KSS compared to a matched group who underwent TKA.     

Functional characteristics of female patients based on ambulatory ability 1 year after total knee arthroplasty

BackgroundTotal knee arthroplasty (TKA) is commonly performed to reduce knee pain and improve physical function. Compared with the values for healthy, age-matched women, previous studies have reported large deficits in functional ability, such as muscle strength and ambulatory ability, in women 1 year post-TKA. Ambulatory ability is to move around, particularly by walking and is clinically assessed by the timed up and go test (TUG).AimThis study aimed to clarify the characteristics of knee functions in female patients whose ambulatory ability recovered to a normal level at 1 year after TKA.MethodsThis cross-sectional study included 151 female patients who underwent TKA. The muscle strength of the lower extremity was measured, and the 2011 Knee Society Scoring (2011 KSS) system was used postoperatively. The TUG was conducted to assess ambulatory ability after TKA; then the patients were classified into the fast and slow ambulation groups based on previously reported gait-speed values of healthy female individuals. Then, we identified significant indicators of ambulatory ability at 1 year after TKA.ResultsForty-nine percent of patients after TKA achieved the level of ambulatory ability of a healthy female. Logistic regression analysis identified that the non-operative side knee extensor strength and the functional activity score, as assessed by the 2011 KSS, were variables significantly associated with the mid-term ambulatory ability after TKA.ConclusionFemale patients with high non-operative knee extensor strength and a functional activity score at 1 year postoperatively can achieve better ambulatory ability than those of healthy, age-matched females.     

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

BackgroundMost in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).MethodsA total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.ResultsThe average flexion angle was 111.3° ± 7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.ConclusionsWe conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small. Level of evidence: IV.     

Comparative outcomes of patient-specific instrumentation,the conventional method and navigation assistance in open-wedge high tibial osteotomy: A prospective comparative study with a two-year follow up

BackgroundTo compare and analyze the correction precision, clinical outcomes and complications among the three methods of performing open-wedge high tibial osteotomy (HTO), including patient-specific instrumentation (PSI), conventional method and navigation assistance.MethodsIn this prospective, single-center study, we randomly assigned patients with knee osteoarthritis in a 1:1:1 ratio to undergo Open-wedge high tibial osteotomy (OWHTO) with conventional method, navigation assistance or PSI. The primary outcome was the target/observed hip–knee–ankle (HKA) angle difference at 1 month postoperatively. Secondary outcomes were changes in the postoperative posterior tibial slope (PTS) at 1 month and clinical outcomes including knee pain on a visual analogue scale (ranging from 0 to 100, with higher scores indicating more severe pain), Lysholm and Western Ontario and McMaster Universities Osteoarthritis Index (ranging from 0 to 240) scores at 1 month, 6 months, 12 months, and 24 months.ResultsFrom 2017 through 2019, a total of 608 patients were screened; of those patients, 144 were enrolled, with 48 in each group. The primary outcome of the HKA difference was 2.6 ± 2.0° in the conventional group, 2.3 ± 1.5° in the navigation group and 0.6 ± 1.0° in the PSI group (P < 0.001). Secondary outcomes including changes in the postoperative PTS and clinical outcomes at 1 month, 6 months, and 12 months were in the same direction as the primary outcome. There were no significant differences in the complications among the three groups.ConclusionsIn the present study, none of the three methods showed superiority in objective correction precision and clinical outcomes at 2 years.     

High survival rate at mid-term follow up of porous tantalum cones for bone defects in revision total knee replacement: A 3–11 years follow up report

BackgroundLarge metaphyseal bone losses are commonly encountered in revision total knee arthroplasty (rTKA). Anderson Orthopaedic Research Institute (AORI) type 2 and 3 defects generally require some metaphyseal fixation or augmentation.This study evaluates the midterm results of Porous Tantalum Trabecular Metal™ (TM) cones in revision TKA addressing severe bone loss.MethodsPatients who underwent revision TKA using metaphyseal cones and a varus–valgus constrained (VVC) implant from January 2010 to January 2018 at our institution were identified from a prospective research database. Pre-operative patient characteristics and operative data were reviewed. Postoperative outcomes were compared with pre-operative values. Primary study aims were to evaluate outcomes, including complications and re-operations, radiographic assessment of cones osteointegration, and survivorship.ResultsA total of 101 knees (101 patients) underwent revision TKA with 139 metaphyseal cones (80 tibial, 59 femoral). AORI defect classification was assessed intraoperatively. All patients were available for a minimum of 2 years of clinical and radiographic follow up. Mean follow up was 7.5 years (range 3–11 years).All patients showed significant improvement of clinical outcomes. Fifteen knees required re-operation and nine required revision of the implants, most commonly for recurrent infection (six of nine revisions) with cones removal.Kaplan–Meier survival analysis show a survival rate of 93.9% at 2 years and a survival rate of 90.2% at 5 and 11 years.ConclusionsThis large series illustrates the utility of porous metaphyseal cones in revision TKA with promising clinical and radiographic results and a high survival rate at mid-term follow up.     

Rotational kinematics differ between mild and severe valgus knees in total knee arthroplasty

BackgroundThere is no consensus regarding femorotibial rotational kinematics in total knee arthroplasty (TKA) for valgus knee deformity. Additionally, whether the degree of valgus deformity influences intraoperative rotational kinematics and postoperative clinical scores remains unclear. The objectives of this study were to investigate whether the valgus angle is associated with intraoperative rotational kinematics in TKA for valgus knee deformity and to examine the relationship between rotational kinematics and postoperative clinical results.Materials and methodsA total of 24 knees with valgus deformity for TKA were included in this study and were divided into two groups depending on the femorotibial angle (FTA); there were 11 knees in the severe valgus group (FTA < 160°) and 13 knees in the mild valgus group (FTA ≥ 160°). Intraoperative femorotibial rotational kinematics from knee extension to flexion were evaluated using an image-free navigation system and postoperative clinical results (range of motion and subjective outcomes) were evaluated 1 year postoperatively. All parameters were compared between the two groups.ResultMild valgus knee showed tibial internal rotation during knee flexion before implantation, whereas severe valgus knee showed tibial external rotation during knee flexion before implantation. The postoperative flexion angle was positively correlated with the tibial internal rotation angle after implantation in the mild valgus group only.ConclusionIntraoperative rotational kinematics before implantation differed between mild and severe valgus knee deformity in TKA. Intraoperative tibial rotation influenced the postoperative knee flexion angle in mild, but not severe, valgus knee deformity. Ideal postoperative rotational kinematics may be different between the two groups and the difference may be taken into consideration in implant selections and surgical techniques.     

Mid-term results of complex primary total knee arthroplasty using a rotating-hinge implant

BackgroundThe indications and outcomes of semi- or fully-constrained knee implants in primary total knee arthroplasty (TKA) are still controversially discussed. The present study aims to evaluate the mid-term results and complications of a modular/non-modular rotating-hinge implant in complex primary TKA.MethodsEighty-two patients (86 knees) following primary TKA were retrospectively evaluated with a mean follow-up of 63 months. The functional outcome was assessed using the American Knee Society Score (AKSS) and the Oxford Knee Score (OKS). A Visual Analog Scale (VAS) was used to determine pain levels. Implant survival and reoperation rates were estimated using competing risk analysis. Cox regression analysis was performed to evaluate the influence of modularity on implant survival.ResultsThe survival rate with the endpoint implant revision was 90% (95 %CI:83–98%) and the survival rate with the endpoint all reoperations was 84% (95 %CI:75–94%) at 7 years. The AKSS improved significantly from 24 (SD 14.9, range:0–69) preoperatively to 83 (SD 14.3, range:57–100) postoperatively (p < 0.001); functional AKSS improved significantly from 27 (SD 24.3, range:0–100) to 46 (SD: 32.9, range 0–100) (p = 0.003), and OKS from 19 (SD: 8.3, range:5–43) to 29 (SD: 10.7, range:6–48), respectively (p < 0.0001). VAS decreased significantly from 8 (SD: 2.6, range:0–10) preoperatively to 3 (SD: 2.9, range:0–9) postoperatively (p < 0.0001). There was no significant influence of modularity on revision rates comparing modular to non-modular implants (p = 0.072).ConclusionsThe present rotating-hinge implant provides substantial improvement in function and reduction of pain with good implant survival in the mid-term. Modularity was not associated with higher rates of revision.     

The effect of knee prosthesis design on tibiofemoral biomechanics during extension tasks following total knee arthroplasty

BackgroundDetermine whether the tibiofemoral motion and electromyographic activity of the knee differs in patients with a medial pivot implant, compared to those with cruciate-retaining and posterior-stabilised designs, during knee extension after Total Knee Arthroplasty (TKA).MethodsAn observational study was conducted on a cohort of patients that had undergone TKA for a minimum of 12 months prior. Three matched groups (n = 18) were categorised based on implant type: medial-pivot (MP), posterior-stabilised (PS) and cruciate-retaining (CR). Kinematics, with motion analysis (Vicon, USA) and surface electromyography (Delsys, USA) were assessed during step-ascent and walking tasks.ResultsAll groups displayed a similar amount of knee extension in both tasks. They also paradoxically produced an average mean internal rotation movement during knee extension in both the step-ascent and walking tasks. The only significant difference was found in the step-ascent task, in which the MP group produced a larger absolute amount of rotation than the CR implant group (P = 0.007), but neither group differed from the PS implant group. The groups did not differ in rotation during the walking task (P > 0.05). The MP group displayed significantly (P < 0.01) greater knee extensor activation during the step-ascent than the PS group.ConclusionThe MP design was only significantly different to another implant design for the step-ascent task. Patients with either knee implant types were not strictly limited to producing the traditional “screw-home” mechanism, defined by external rotation during extension. Furthermore, comparison with the non-implant contralateral limb suggested that rotation is not necessarily dictated by implant design.