Fluoroscopic and radiostereometric analysis of a bicruciate-retaining versus a posterior cruciate-retaining total knee arthroplasty: a randomized controlled trial.

AIMS: The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA). METHODS: A total of 40 patients with end-stage osteoarthritis were included in this randomized controlled trial. All patients performed a step-up and lunge task in front of a monoplane fluoroscope one year postoperatively. Femorotibial contact point (CP) locations were determined at every flexion angle and compared between the groups. RSA images were taken at baseline, six weeks, three, six, 12, and 24 months postoperatively. Clinical and functional outcomes were compared postoperatively for two years. RESULTS: The BCR-TKA demonstrated a kinematic pattern comparable to the natural knee's screw-home mechanism in the step-up task. In the lunge task, the medial CP of the BCR-TKA was more anterior in the early flexion phase, while laterally the CP was more posterior during the entire movement cycle. The BCR-TKA group showed higher tibial migration. No differences were found for the clinical and functional outcomes. CONCLUSION: The BCR-TKA shows a different kinematic pattern in early flexion/late extension compared to the CR-TKA. The difference between both implants is mostly visible in the flexion phase in which the anterior cruciate ligament is effective; however, both designs fail to fully replicate the motion of a natural knee. The higher migration of the BCR-TKA was concerning and highlights the importance of longer follow-up.Cite this article: Bone Joint J 2023;105-B(1):35-46.

No difference in long-term micromotion between fully cemented and hybrid fixation in revision total knee arthroplasty: a randomized controlled trial.

AIMS: Both the femoral and tibial component are usually cemented at revision total knee arthroplasty (rTKA), while stems can be added with either cemented or press-fit (hybrid) fixation. The aim of this study was to compare the long-term stability of rTKA with cemented and press-fitted stems, using radiostereometric analysis (RSA). METHODS: This is a follow-up of a randomized controlled trial, initially involving 32 patients, of whom 19 (nine cemented, ten hybrid) were available for follow-up ten years postoperatively, when further RSA measurements were made. Micromotion of the femoral and tibial components was assessed using model-based RSA software (RSAcore). The clinical outcome was evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), and visual analogue scale (pain and satisfaction). RESULTS: The median total femoral translation and rotation at ten years were 0.39 mm (interquartile range (IQR) 0.20 to 0.54) and 0.59° (IQR 0.46° to 0.73°) for the cemented group and 0.70 mm (IQR 0.15 to 0.77) and 0.78° (IQR 0.47° to 1.43°) for the hybrid group. For the tibial components this was 0.38 mm (IQR 0.33 to 0.85) and 0.98° (IQR 0.38° to 1.34°) for the cemented group and 0.42 mm (IQR 0.30 to 0.52) and 0.72° (IQR 0.62° to 0.82°) for the hybrid group. None of these values were significantly different between the two groups and there were no significant differences between the clinical scores in the two groups at this time. There was only one re-revision, in the hybrid group, for infection and not for aseptic loosening. CONCLUSION: These results show good long-term fixation with no difference in micromotion and clinical outcome between fully cemented and hybrid fixation in rTKA, which builds on earlier short- to mid-term results. The patients all had type I or II osseous defects, which may in part explain the good results. Cite this article: Bone Joint J 2022;104-B(7):875-883.

Superior Survival of Fully Cemented Fixation Compared to Hybrid Fixation in a Single Design Rotating Hinge Knee Implant.

BACKGROUND: Clinical observations revealed higher rates of aseptic loosening for hybrid fixated rotating hinge knee implants compared to fully cemented ones. We hypothesize that the use of a fully cemented fixation technique had a higher survival rate for aseptic loosening compared to a hybrid fixation technique in a rotating hinge knee implant. METHODS: All procedures of patients who were treated with the RT-PLUS rotating hinge knee implant (Smith & Nephew, Memphis, TN) between 2010 and 2018 were included. Primary outcome was revision for aseptic loosening. Kaplan-Meier survivorship and Cox proportional hazard regression analysis were performed to calculate survival rates and hazard ratios. RESULTS: A total of 275 hinge knee implants were placed in 269 patients (60 primary procedures, 215 revisions). Median follow-up was 7.3 ± 3.9 years. In total, 24 components (16 hybrid femur, 2 fully cemented femur, 6 hybrid tibia; all revision procedures) in 19 patients were revised for aseptic loosening. Kaplan-Meier survivorship analysis showed superior survival rates of fully cemented components (femur 97.1%; tibia 100%) compared to hybrid fixated components (femur 89.5%; tibia 95.9%) at the 10-year follow-up. Multivariate Cox hazard analysis showed a significantly higher risk of aseptic loosening for hybrid fixated components, a prior stemmed component and the femoral component. CONCLUSION: Fully cemented fixation showed superior survival rates for aseptic loosening compared to hybrid fixation in a single design rotating hinge knee implant. A prior stemmed component appears to be a risk factor for aseptic loosening and the femoral component seems to be more prone to loosening.

Limited effect of anatomical insert geometry on in vitro laxity in balanced anatomic posterior cruciate ligament retaining total knee arthroplasty.

PURPOSE: The present study assessed the effect of insert articular surface geometry (anatomical versus conventional insert design) on anteroposterior (AP) translation and varus-valgus (VV) laxity in balanced posterior cruciate ligament (PCL) retaining total knee arthroplasty (TKA). Secondly, we evaluated if the AP translation and VV laxity in the reconstructed knee resembled the stability of the native knee. METHODS: Nine fresh-frozen full-leg cadaver specimens were used in this study. After testing the native knee, anatomical components of a PCL-retaining implant were implanted. The knee joints were subjected to anteriorly and posteriorly directed forces (at 20° and 90° flexion) and varus-valgus stresses (at 20°, 45° and 90° flexion) in both non-weightbearing and weightbearing situations in a knee kinematics simulator. Measurements were performed in the native knee, TKA with anatomical insert geometry (3° built-in varus, medial concave, lateral convex), and TKA with symmetrical insert geometry. RESULTS: In weightbearing conditions, anterior translations ranged between 2.6 and 3.9 mm at 20° flexion and were < 1 mm at 90° flexion. Posterior translation at 20° flexion was 2.7 mm for the native knee versus 4.0 mm (p = 0.047) and 7.0 mm (p = 0.02) for the symmetrical insert and the anatomical insert, respectively. Posterior translation at 90° flexion was < 1.1 mm and not significantly different between the native knee and insert types. In non-weightbearing conditions, the anterior translation at 20° flexion was 5.9 mm for the symmetrical and 4.6 mm for the anatomical insert (n.s.), compared with 3.0 mm for the native knee (p = 0.02). The anterior translation at 90° flexion was significantly higher for the reconstructed knees (anatomical insert 7.0 mm; symmetrical insert 9.2 mm), compared with 1.6 mm for the native knee (both p = 0.02). Varus-valgus laxity at different flexion angles was independent of insert geometry. A valgus force in weightbearing conditions led to significantly more medial laxity (1°-3° opening) in the native knee at 45° and 90° flexion compared with the reconstructed knee for all flexion angles. CONCLUSIONS: Insert geometry seems to have a limited effect with respect to AP translation and VV laxity, in the well-balanced PCL-retaining TKA with an anatomical femoral component. Secondly, AP translation and VV laxity in the reconstructed knee approximated the laxity of the native knee.

Restoration of pre-operative joint line orientation and alignment does not affect KSS and KOOS 1 year after total knee arthroplasty.

PURPOSE: The objectives of this study were to examine the relation between clinical outcomes 1 year postoperatively, in a cohort of mechanically aligned total knee arthroplasties (TKA), and (1) the degrees of alignment change of the tibial, femoral and the hip-knee-ankle (HKA) angle; (2) the change of phenotype; (3) the postoperative knee joint line orientation to the floor. METHODS: Pre-operative and postoperative long-leg X-rays of 90 patients were used to determine the coronal alignment. The absolute difference between the pre-operative and postoperative measurements was determined and the outcomes were categorized in whether or not a change in phenotype had occurred. Finally, the orientation of the knee joint line relative to the floor (tibial joint line angle-TJLA) was measured. Clinical outcomes were determined with the KOOS and KSS at 1-year follow-up. RESULTS: The clinical outcomes (1) did not correlate with the absolute difference of the alignment measured; (2) did not show a difference between patients with or without a change in phenotype; and (3) were higher (KOOS ADL, Sport and QoL) in patients with a medial open TJLA. CONCLUSION: This study showed no correlation between clinical outcomes and joint line restoration of the femur, tibia or HKA in patients after TKA. Leaving the prosthesis with some degrees of under correction on the coronal plane maintaining the phenotype, was not associated to better clinical results compared to TKA overcorrection. Nevertheless, the results showed that patients with a medial open TJLA had better clinical outcomes than patients with a lateral open TJLA. LEVEL OF EVIDENCE: III.

Anatomical superficial medial collateral ligament reconstruction with posteromedial capsule reefing successfully restores valgus knee laxity.

The goal of this study was to present the results of an anatomical superficial medial collateral ligament (sMCL) reconstruction combined with reefing of the posteromedial capsule in a series of 10 patients with symptomatic valgus instability complaints in combined injuries of the knee. All patients under- went an sMCL reconstruction with reefing of the posteromedial capsule. If cruciate ligament insuf- ficiency was present, this was reconstructed as well. Pre- and postoperatively, multiple subjective knee outcome scores were obtained, and valgus stress radiographs objectively evaluated laxity. Median valgus laxity of the injured knee on valgus stress radiographs improved significantly. There was no statistically significant difference between post- operative valgus laxity of the injured knee and valgus laxity of the uninjured knee. All subjective knee outcome scores improved significantly compared with the preoperative situation. The described procedure restores valgus laxity to a level comparable to the uninjured knee.

Maximal flexion and patient outcomes after TKA, using a bicruciate-stabilizing design.

INTRODUCTION: Physiological motion after total knee arthroplasty (TKA) should result in a large range of motion, which would lead to good clinical outcomes. An adjusted design of a bicruciate-stabilizing TKA was developed to reproduce physiological motion. The aim of this study was to (1) investigate the maximal knee flexion of this knee system, 1 year post-operatively; (2) determine the clinical and functional improvement and compare the outcomes between patients with and without high maximal flexion; and (3) evaluate the adverse events. MATERIALS AND METHODS: In this prospective study, 62 patients with osteoarthritis received a bicruciate-stabilizing TKA. Maximum flexion was measured on a lateral X-ray pre- and post-operatively. Clinical and functional scores and the adverse events were reported up until 2 years after surgery. RESULTS: Pre-operatively, the median (range) maximal flexion was 131.5 (90-153)° and 1 year post-operatively, it was 130 (82-150)°. The results for the clinical scores showed an improvement between pre-operative values and post-operative values. The Kujala score and Knee Osteoarthritis Outcome Score (KOOS) symptoms, sport and quality of life score were better in patients with high maximal flexion (≥ 125°). Ten (serious) adverse device events were reported. CONCLUSIONS: In conclusion, the bicruciate-stabilizing TKA obtained a maximal flexion comparable to the flexion pre-operatively and resulted in good clinical and functional outcomes. Patients with high flexion ability seem to perform better on clinical and functional outcomes. Furthermore, the adjusted design of the bicruciate-stabilizing TKA reduced the number of adverse events. LEVEL OF EVIDENCE: Prospective cohort study, Level II.

Long-Term Outcome Following Revision Total Knee Arthroplasty is Associated With Indication for Revision.

BACKGROUND: There is limited information about long-term clinical outcomes following revision total knee arthroplasty (TKA) in relation to the indication for revision. Previously, a clear relation between indication for revision and clinical outcome was shown after 2 years. Present study evaluated (1) whether the reported association at 2 year remains present at 7.5 years, and (2) how clinical outcome at 7.5 years developed compared to baseline and 2-year follow-up, and (3) whether patients had additional adverse events. METHODS: A cohort of 129 patients with a total system revision TKA was selected. Range of motion, Visual Analog Scale for pain and satisfaction, and clinical and functional Knee Society Score were obtained preoperatively, at 3 months, 1, 2, and 7.5 years. Reasons for revision were septic loosening, aseptic loosening, malposition, instability, and severe stiffness. RESULTS: Patients revised for severe stiffness had significantly worse outcomes. No difference was found between the other indications. The clinical outcome after revision TKA at 7.5 years remained stable for septic and aseptic loosening, malposition, and instability but deteriorated slightly for the severe stiffness group. Visual Analog Scale satisfaction remained constant for all indications. There were 11 additional complications between 2- and 7.5-year follow-up, 9 of which necessitated reoperation. CONCLUSION: All indications except severe stiffness had a similar clinical outcome which was maintained up to 7.5-year follow-up. The severe stiffness group had worse outcomes and deteriorated slightly at longer follow-up. Outcome at 3 months seems predictive for long-term outcome. Additional complications did not differ significantly for the different reasons for revision. LEVEL OF EVIDENCE: Level III, prognostic study.

What Is the Reliability of a New Classification for Bone Defects in Revision TKA Based on Preoperative Radiographs?

BACKGROUND: Accurate quantification of bone loss facilitates preoperative planning and standardization for research purposes in patients who undergo revision TKA. The most commonly used classification to rate bone defects in this setting, the Anderson Orthopaedic Research Institute classification, does not quantify diaphyseal bone loss and reliability has not been well studied. QUESTIONS/PURPOSES: We developed a new classification scheme to rate bone defects in patients undergoing revision TKA and tested (1) the intraobserver and interobserver reliability of this classification for revision TKA based on preoperative radiographs, and (2) whether additional CT images might improve interobserver reliability. METHODS: This was a preregistered observational study. Interobserver reliability was analyzed using preoperative radiographs of 61 patients who underwent (repeat) revision TKA, and their bone defects were rated by five experienced orthopaedic surgeons. For intraobserver reliability, ratings were repeated at least 2 weeks after the first rating (Timepoints 1 and 2). Directly after the radiographic assessments of Timepoint 2, the observers were provided with CT images of each patient and asked to rate the bone defects for a third time (Timepoint 3), to assess the additional value of CT. Intraobserver and interobserver reliability were tested using Gwet's agreement coefficient 2, which is a measure of agreement between observers in categorical data. Substantial agreement was defined as coefficients between 0.61 to 0.8 and almost perfect agreement as > 0.8. RESULTS: The intraobserver reliability varied between 0.55 (95% CI 0.40 to 0.71) and 0.87 (95% CI 0.78 to 0.96) in the epiphysis, between 0.69 (95% CI 0.58 to 0.80) and 0.98 (95% CI 0.95 to 1) in the metaphysis, and between 0.95 (95% CI 0.90 to 0.99) and 0.99 (95% CI 0.98 to 1) in the diaphysis. The interobserver reliability varied between 0.48 (95% CI 0.39 to 0.57) and 0.49 (95% CI 0.42 to 0.56) in the epiphysis and between 0.81 (95% CI 0.75 to 0.87) and 0.88 (95% CI 0.83 to 0.93) in the metaphysis, and was 0.96 (95% CI 0.93 to 0.99) in the diaphysis at Timepoint 1. The interobserver reliability at Timepoint 2 was similar to that of Timepoint 1. The addition of CT images did not improve reliability (Timepoint 3). CONCLUSIONS: The bone defect classification was less reliable in the epiphyseal area compared with the metaphysis and diaphysis. This finding may be explained by prosthetic components obscuring this region or the more severe bone defects in this region. The addition of CT scans did not improve reliability. Further testing of reliability with observers from other institutions is necessary, as well as validity testing, by testing the classification in relation to intraoperative findings. LEVEL OF EVIDENCE: Level III, diagnostic study.

Posterolateral corner reconstruction in combined injuries of the knee: Improved stability with Larson's fibular sling reconstruction and comparison with LaPrade anatomical reconstruction.

BACKGROUND: The goal of this prospective cohort study was to present the clinical results of a two-year follow-up of a Larson's posterolateral corner reconstruction (fibular sling) in patients with symptomatic instability of the knee. These data were compared with data of an anatomical reconstruction of the posterolateral corner as described by LaPrade et al. (combined tibial tunnel and fibular sling) [1]. METHODS: Eleven patients underwent a Larson's posterolateral corner reconstruction. Cruciate ligament ruptures were reconstructed if present. Multiple subjective knee outcome scores (VAS satisfaction score, Tegner, Lysholm, Noyes score, and IKDC subjective knee score) were obtained pre-operatively and two years after surgery. Laxity of the joint was measured using bilateral varus stress radiographs. RESULTS: All patients had concomitant ACL or PCL surgery. VAS satisfaction, the Tegner, Noyes and the IKDC subjective knee score all improved significantly. Median varus laxity of the injured knee on varus stress radiographs improved significantly from 6.2° (3.1-10.1) to 3.9° (1.1-5.7), p = .0076. Post-operative varus laxity did not return to the level of the uninjured knee: 2.7° (1-5.7), p = .028. In comparison with our data on the reconstruction technique according to LaPrade, no statistically significant differences in clinical outcome were observed. CONCLUSION: Reconstruction of the posterolateral corner in combined injuries of the knee using a Larson fibular sling technique results in improved varus stability but not to the level of the uninjured knee. Functional knee scores improved significantly. We found no differences in functional and radiological outcome between the Larson's fibular sling reconstruction and LaPrade anatomical reconstruction. LEVEL OF EVIDENCE: IV.

Mid-flexion laxity in the asymptomatic native knee is predominantly present on the lateral side.

PURPOSE: During total knee arthroplasty (TKA), an orthopaedic surgeon is focused on soft-tissue balance in extension (0°) and in flexion (90°). Patients with instability problems of the knee often report a feeling of instability during daily life activities, at around 30° knee flexion. There are no reference values available for knee laxity of healthy subjects in mid-flexion (30°) and flexion (90°) for comparison with the TKA population. Therefore, the aim was to quantify varus and valgus knee laxity in extension, mid-flexion and flexion in the asymptomatic native knee. METHODS: In 40 healthy volunteers matched for age, gender and BMI with the TKA-population, varus and valgus knee laxity in extension (0°), mid-flexion (30°) and flexion (90°) was measured on low-dose radiographs. For each subject, one randomly selected knee was stressed in extension, mid-flexion and flexion (with 15 Nm) using a stress device. RESULTS: Varus laxity in mid-flexion was higher than in extension and flexion (p < 0.01). Valgus laxity tended to be highest in mid-flexion laxity; however, no differences in knee laxity between flexion angles were seen (n.s.). Varus knee laxity in extension was higher in females than in males (p < 0.05). CONCLUSIONS: Mid-flexion laxity in the native knee is more prominent on the lateral side of the knee, while the medial side is more stable and constrained. Varus knee laxity in extension was shown to be higher in females than in males. LEVEL OF EVIDENCE: Prognostic Level II.

Age, gender, functional KSS, reason for revision and type of bone defect predict functional outcome 5 years after revision total knee arthroplasty: a multivariable prediction model.

PURPOSE: The number of revision total knee arthroplasties (rTKA) is increasing. Unfortunately, not all patients benefit from revision surgery. The aim of this study was to develop a clinical prediction model that can be used to predict the functional outcome 5 years after rTKA. METHODS: Data of patients receiving rTKA at Sint Maartenskliniek, Nijmegen, The Netherlands, from 2004 onwards were prospectively collected. Demographic and clinical variables and patient-reported outcome scores were collected and considered as potential predictors. Beneficial outcome was defined as an increase of ≥ 20 points on the functional knee society scores (fKSS) or an absolute fKSS ≥ 80 points 5 years after surgery. The prediction model was developed using backward logistic regression. Regression coefficients were converted into an easy to use prediction rule. RESULTS: Overall, 295 rTKA patients were included of whom 157 (53%) had beneficial fKSS 5 years later. Age, gender, femoral bone defects, preoperative fKSS, and stiffness as reason for revision were included in the model. Men had a higher chance of beneficial fKSS than women (OR 1.59, 95% CI 0.91-2.78). Patients with major bone defects (OR 0.44, 95% CI 0.22-0.85), higher age (IQR OR 0.39, 95% CI 0.26-0.58), higher preoperative fKSS (IQR OR 0.42, 95% CI 0.30-0.59), and severe stiffness (OR 0.48, 95% CI 0.20-1.15) had a lower chance of successful outcome. The model's AUC was 0.76, 95% CI 0.70-0.81. CONCLUSION: Easily determinable characteristics of patients who need rTKA can be used to predict future functional outcome. Young men with low preoperative fKSS without severe stiffness are more likely to achieve a beneficial outcome. LEVEL OF EVIDENCE: IV.

A combined procedure with Bereiter-type trochleoplasty leads to a stable patellofemoral joint at 5-year follow-up.

PURPOSE: Trochlear dysplasia is a major risk factor predisposing to patellar instability and has been reported to occur in up to 85% of patients with recurrent patellar dislocation. Different operative techniques have been described to correct trochlear dysplasia, including the Bereiter technique, in which subchondral bone is removed and the cartilage can be compressed into a U-shaped groove. The hypothesis was that after a Bereiter-type trochleoplasty combined with medialisation of the tibial tubercle and MPFL reconstruction, patellar pain and instability decreased and anatomic reconstruction can be seen radiographically after 5-year follow-up. METHODS: Between 2004 and 2011, a combined procedure including Bereiter-type trochleoplasty was performed on 21 consecutively included patients (22 knees) with objective patellar instability and severe trochlear dysplasia. Instability and pain were assessed preoperatively and 3, 6, 12, 24 and 60 months postoperatively with the visual analogue scale (VAS) for pain and instability, Kujala, International Knee Documentation Committee Subjective Knee Evaluation (IKDC SKE) and Short Form Health Survey (SF-36). Pre- and postoperatively, a true lateral radiograph was made to investigate the presence of the crossing sign and to measure the trochlear bump and trochlear depth, as well as a sunrise patella view to measure the sulcus angle. RESULTS: VAS pain and instability, Kujala and IKDC SKE improved significantly 5 years after trochleoplasty (p < 0.05). SF-36 showed no significant improvement. None of the patients reported patellar dislocations postoperatively. Sport activities remained limited. Postoperative radiographs showed no crossing sign. There was a significant increase in trochlear depth (p < 0.0001) and also a significant decrease in trochlear bump and sulcus angle (both p < 0.0001). CONCLUSIONS: A combined procedure consisting of Bereiter-type trochleoplasty, medialisation of the tibial tubercle and MPFL reconstruction in patients with objective patellar instability and severe trochlear dysplasia resulted in a clear decrease of pain and instability. Radiological assessment showed anatomical reconstruction. Nevertheless, residual symptoms remain and the possibility of future cartilage damage is uncertain. LEVEL OF EVIDENCE: IV.

Improved clinical outcomes after revision arthroplasty with a hinged implant for severely stiff total knee arthroplasty.

PURPOSE: Management of the severely stiff total knee arthroplasty (TKA) is challenging, with the outcome of revision arthroplasty being inferior compared to the outcome for other indications. The aim of this study was to analyse the outcome after revision TKA with hinged-type implants for severely stiff TKA [range of motion (ROM) ≤ 70°] at 2 years. METHODS: A cohort of 38 patients with a hinged-type revision TKA (Waldemar Link or RT-Plus) and preoperative ROM ≤ 70° were selected from a prospectively collected database. ROM, visual analogue scale (VAS) for pain and satisfaction and Knee Society Score (KSS) were obtained preoperatively and at 3 months, 1 year and 2 years. Pre- and postoperative outcome were compared at 2 years. RESULTS: There was a significant increase in ROM and KSS. VAS pain scores did not differ significantly. The median ROM at 2 years was 90° (range 50°-125°) with a median gain of 45° (range 5°-105°). Median VAS pain was 28.5 (range 0-96) points and median VAS satisfaction was 72 (range 0-100) points at 2 years. Twelve patients suffered a complication. Recurrent stiff knee was the most frequently reported complication (n = 5). CONCLUSIONS: Hinged-type revision TKA following a severely stiff TKA renders a significant, although moderate, clinical improvement at 2 years. LEVEL OF EVIDENCE: Retrospective case series. Level IV.

Flexing and downsizing the femoral component is not detrimental to patellofemoral biomechanics in posterior-referencing cruciate-retaining total knee arthroplasty.

PURPOSE: When downsizing the femoral component to prevent mediolateral overhang, notching of the anterior femoral cortex may occur, which could be solved by flexing the femoral component. In this study, we investigated the effect of flexion of the femoral component on patellar tendon moment arm, patellofemoral forces and kinematics in posterior-referencing CR-TKA. Our hypothesis was that flexion of the femoral component increases the patellar tendon moment arm, reduces the patellofemoral forces and provides stable kinematics. METHODS: A validated musculoskeletal model of CR-TKA was used. The flexion of the femoral component was increased in four steps (0°, 3°, 6°, 9°) using posterior referencing, and different alignments were analysed in combination with three implant sizes (3, 4, 5). A chair-rising trial was analysed using the model, while simultaneously estimating quadriceps muscle force, patellofemoral contact force, tibiofemoral and patellofemoral kinematics. RESULTS: Compared to the reference case (size 4 and 0° flexion), for every 3° of increase in flexion of the femoral component the patellar tendon moment arm increased by 1% at knee extension. The peak quadriceps muscle force and patellofemoral contact force decreased by 2%, the patella shifted 0.8 mm more anteriorly and the remaining kinematics remained stable, with knee flexion. With the smaller size, the patellar tendon moment arm decreased by 6%, the quadriceps muscle force and patellofemoral contact force increased by 8 and 12%, and the patellar shifted 5 mm more posteriorly. Opposite trends were found with the bigger size. CONCLUSION: Flexing the femoral component with posterior referencing reduced the patellofemoral contact forces during a simulated chair-rising trial with a patient-specific musculoskeletal model of CR-TKA. There seems to be little risk when flexing and downsizing the femoral component, compared to when using a bigger size and neutral alignment. These findings provide relevant information to surgeons who wish to prevent anterior notching when downsizing the femoral component.

Stability and alignment do not improve by using patient-specific instrumentation in total knee arthroplasty: a randomized controlled trial.

PURPOSE: The primary aim of the study was to examine stability and alignment after total knee arthroplasty (TKA) using patient-specific instrumentation (PSI) and conventional instrumentation (CI). The hypothesis was that stability and alignment would be better using PSI than CI, 12 months postoperatively. The secondary aim included the evaluation of clinical outcomes after TKA. METHODS: In this prospective randomized controlled trial, 42 patients with knee osteoarthritis received a Genesis II PS prosthesis with either PSI or CI. Patients visited the hospital preoperatively and postoperatively after 6 weeks and 3 and 12 months. To evaluate stability, varus-valgus laxity was determined in extension and flexion using stress radiographs 12 months postoperatively. Three months postoperatively, a long-leg radiograph and CT scan were obtained to measure hip-knee-ankle (HKA) alignment and component rotation. Furthermore, frontal and sagittal alignment of the components, the Knee Society Score, VAS Pain, VAS Satisfaction, Knee injury and Osteoarthritis Outcome score, Patella score (Kujala), University of California Los Angeles activity score, anterior-posterior laxity, (serious) adverse device-related events, and intraoperative complications were reported. The clinical outcomes were compared using independent t tests or non-parametric alternatives, and repeated measurements ANOVA with a significance level of p < 0.05. RESULTS: No significant differences were found between the two groups regarding stability, HKA angle, and rotational alignment. In four patients, the PSI did not fit correctly on the tibia and/or femur requiring intraoperative modifications. Both groups improved significantly over time on all clinical outcomes, with no significant differences between the groups 12 months postoperatively. The PSI group showed less tibial slope than the patients in the CI group [PSI 2.6° versus CI 4.8° (p = 0.02)]. Finally, the PSI group more frequently received a thinner insert size than the CI group (p = 0.03). CONCLUSIONS: Patients operated with PSI did not differ from CI in terms of stability and alignment. However, in the PSI group ligament releases were more often required intraoperatively. Furthermore, the two methods did not show different clinical results. It seems that the preoperative planning for the PSI facilitates more conservative bone cuts than CI, but whether this is clinically relevant should be investigated. Since PSI is more expensive and time consuming than CI, and does not outperform CI with regard to clinical results, we recommend to use CI. LEVEL OF EVIDENCE: I.

Anterior referencing of tibial slope in total knee arthroplasty considerably influences knee kinematics: a musculoskeletal simulation study.

PURPOSE: In total knee arthroplasty (TKA), the posterior tibial slope is not always reconstructed correctly, and the knee ligaments may become too tight in flexion. To release a tight flexion gap, surgeons can increase the posterior tibial slope using two surgical resection techniques: the anterior tibial cortex (ACR) or the centre of tibial plateau (CPR) referencing. It is not known how this choice affects the knee laxity and function during activities of daily living. The aim of this study was to investigate the effect of tibial slope on knee laxity, kinematics and forces during a squatting activity using computer simulation techniques. We hypothesised that the effects depend on the referencing technique utilised. METHODS: A validated musculoskeletal model of TKA was used. Knee laxity tests were simulated in flexion and extension. Then, a squat motion was simulated to calculate: movement of the tibiofemoral joint (TFJ) contact points and patello-femoral joint (PFJ) contact force. All analyses were repeated with more anterior (-3°), neutral (0°), and more posterior tibial slope (+3°, +6°, +9°), and with two referencing techniques (ACR, CPR). RESULTS: Knee laxities increased dramatically with more posterior slope with the ACR technique (up to 400%), both in flexion and in extension. The CPR technique, instead, had much smaller effects (up to 42% variations). During squatting, more slope with the ACR technique resulted in larger movements of the TFJ contact point. The PFJ contact force decreased considerably with more slope with the CPR technique (12% body weight reduction every 3° more posterior slope), thanks to the preservation of the patellar height and quadriceps-femur load sharing. CONCLUSION: ACR technique alters considerably the knee laxity, both in flexion and extensions, and surgeons should be cautious about its use. More slope with CPR technique induces more favourable TFJ kinematics and loading of the knee extensor apparatus and does not substantially alter knee laxity. Preferably, the tibial slope resection should be pre-planned thoroughly and performed using CPR technique as accurately as possible. Surgeons can directly translate the results of this study into the clinical practice.

Single-stage total knee arthroplasty and osteotomy as treatment of secondary osteoarthritis with severe coronal deviation of joint surface due to extra-articular deformity.

PURPOSE: Severe extra-articular deformities can be treated with single-stage total knee replacement (TKA) and osteotomy. Aim of this study was to examine the patient-reported outcome measures (PROMs) and the complications after single-stage TKA and osteotomy. We hypothesized patients achieve good outcome after single-stage TKA and osteotomy, which is comparable to outcome after primary TKA without deformity. METHODS: Twenty-one patients with severe extra-articular deformity who underwent single-stage TKA and deformity-correcting osteotomy were reviewed and invited to fill in PROMs including the Oxford Knee Score, the Short Form-12, a Visual Analogue Scale for pain, and questions about satisfaction and quality of life. RESULTS: The mean follow-up period was 64 months. Ten patients were treated with TKA and supracondylar femoral osteotomy. Although PROMs showed good results (mean quality of life score was 85 out of 100), two patients had a revision of the osteotomy due to non-union. Eleven patients were treated with TKA and high tibial osteotomy. Patients were satisfied with the results (mean quality of life score was 81 out of 100). Two patients developed infection requiring debridement, resulting in one arthrodesis and one gastrocnemius transfer for wound closure. CONCLUSION: In general, patients were satisfied with the postoperative result. Outcome was comparable to patients after primary TKA in the literature. However, serious complications need to be taken into account. LEVEL OF EVIDENCE: III.

Comparable Stability of Cemented vs Press-Fit Placed Stems in Revision Total Knee Arthroplasty With Mild to Moderate Bone Loss: 6.5-Year Results From a Randomized Controlled Trial With Radiostereometric Analysis.

BACKGROUND: Short-term stability after revision total knee arthroplasty (TKA) with either fully cemented or hybrid-placed implants is comparable. Interestingly, implant micromotion >1 mm/degree occurred with both techniques which might increase the risk of loosening in the midterm or long-term. Therefore, the present study investigated midterm stability and clinical results of fully cemented vs hybrid-placed revision TKA, with mild to moderate bone loss, using radiostereometric analysis (RSA). METHODS: This study involves the prolonged follow-up of a previous randomized controlled trial. RSA images taken at baseline, 6 weeks, 3 and 6 months, and 1, 2 and 6.5 years of follow-up were analyzed. Stability of the femoral and tibial implants was evaluated using total translation and rotation, based on the micromotion determined with model-based RSA. RESULTS: Of the 30 patients who completed the 2-year follow-up in the original randomized controlled trial, 23 (12 cement, 11 hybrid) were available for follow-up at 6.5-year (range 5.4-7.3). There were no differences in median total translation and rotation of the femoral and tibial components between the 2 groups, and none of the clinical scores differed between the groups. Interestingly, in the group with cemented stems, 5 tibia implants showed >1 mm/degree micromotion compared to none in the hybrid group. CONCLUSION: There was no difference in median micromotion and clinical outcome between fully cemented and hybrid-placed revision TKA 6.5 years postoperatively. Two femur components showed progressive migration over time whereas tibia components migrate especially in the first year followed by a stable situation. Whether this will lead to loosening and re-revisions remains to be investigated.

Revision Total Knee Arthroplasty for Instability-Outcome for Different Types of Instability and Implants.

BACKGROUND: Given the mixed outcome after revision total knee arthroplasty (TKA) for instability in the literature and the relative high recurrence of instability, we were interested in the outcome of a cohort of patients operated for various types of clinical instability and with different types of implants. METHODS: A total of 77 patients with unstable TKA were completely revised (19 hinged and 58 condylar implants). We classified the patients in 3 instability groups based on the literature: (1) anterior-posterior flexion instability (N = 29); (2) medial-lateral flexion instability (N = 16); and (3) multiplane instability (N = 32). Patients were evaluated up to 24 months postoperatively, concerning Knee Society clinical rating system, range of motion, visual analog scale (VAS) pain, and VAS satisfaction. RESULTS: For the total group, all outcome scores improved, but substantial residual pain (VAS = 41) was reported. For type of instability, the clinical outcome was similar for all the groups. For type of implant, the hinged group had lower postoperative outcome scores but similar satisfaction scores compared with those in the condylar group. There was a considerable number of insert changes and secondary patellar resurfacing in the condylar group compared with no reoperations in the hinged group. Recurrent instability was not seen in the anterior-posterior flexion instability group and in patients who received a condylar constraint-type implant. CONCLUSIONS: We recommend 3 options in revision TKA for instability: (1) hinged implants in cases with severe ligament instability in multiple planes or bone loss, (2) condylar implants with a posterior-stabilized insert in cases with isolated posterior cruciate ligament insufficiency, and (3) condylar implants with condylar constraints in all other cases.