Introduction. Tibial slope was shown to majorly affect the outcomes of Total Knee Arthroplasty (TKA). More slope of the tibial component could help releasing a too tight flexion gap in cruciate-retaining (CR) TKA and is generally associated with a wider range of post-operative knee flexion. However, an excessive tibial slope could jeopardize the knee stability in flexion. The mechanism by which tibial slope affects the function of CR-TKA is not well understood. Moreover, it is not known whether the tibial bone resection should be performed by referencing the anterior cortex (AC) of the tibia or the center of the tibial plateau (CP) and whether the choice of either technique plays a role. The aim of this study was to investigate the effect of tibial slope on the position of tibiofemoral (TF) contact point, knee ligament forces, quadriceps muscle forces, and TF and patellofemoral (PF) joint contact forces during squat activity in CR-TKA. Methods. A previously validated musculoskeletal model of CR-TKA was used to simulate a squat activity performed by a 86-year-old male subject wearing an instrumented prosthesis [1,2]. Marker data over four consecutive repetitions of a squat motion were tracked using a motion optimization algorithm. Muscle and joint forces and moments were calculated from an inverse-dynamic analysis, coupled with Force-Dependent Kinematics (FDK) to solve knee kinematics, ligament and contact forces simultaneously. The tibial slope in the postoperative case was 0 degree and constituted the reference case for our simulations. In addition, eight additional cases were simulated with −3, +3, +6, +9 degrees of tibial slope, four of them simulating an AC referencing technique and four a CP technique. Results. Compared to the reference case with no added slope, the total excursion of the tibiofemoral contact point increased on both medial and lateral side when more slope was added using the AC referencing technique, and decreased with negative slope. The total excursion of the contact point remained about unchanged when using the CP technique but the contact point shifted of about 1 mm more posteriorly, on the lateral side, and 0.7 mm, on the medial side, on average. In both AC and CP techniques the quadriceps forces, TF and PF contact forces decreased with more slope, but the PF contact forces were more drastically reduced using CP, with 3.5% less force every 3 degrees of added slope in flexion, on average. Medial and lateral collateral ligament became slack in flexion already with +6 degrees of slope when AC technique was used, whereas they always maintained some residual tension using the CP technique even at the highest slope. Discussion and conclusion. Increasing the tibial slope affected substantially the knee function during squatting and the effects differed depending on the referencing technique. The CP referencing helps preserving the flexion gap and knee stability in flexion, by mantaining tension in both collateral ligaments. It also reduces the quadriceps forces and relieves the PF joint contact forces, which could potentially decrease pain in patients with a TKA and achieve a wider range of knee motion

Introductions. In cruciate-retaining total knee arthroplasty (TKA), among many factors influencing post-operative outcome, increasing the tibial slope has been considered as one of the beneficial factors to gain deep flexion because of leading more consistent femoral rollback and avoiding direct impingement of the insert against the posterior femur. In contrast, whether increasing the tibial slope is useful or not is controversial in posterior-stabilized (PS) TKA, Under such recognition, accurate soft tissue balancing is also essential surgical intervention for acquisition of successful postoperative outcomes in TKA. In order to permit soft tissue balancing under more physiological conditions during TKAs, we developed an offset type tensor to obtain soft tissue balancing throughout the range of motion with reduced patello-femoral(PF) and aligned tibiofemoral joints and have reported the relationship between intra-operative soft tissue balance and flexion angles. In this study, we therefore assessed the relationship between intra-operative soft tissue balance assessed using the tensor and the tibial slope in PS TKA. Materials and methods. Thirty patients aged with a mean 72.6 years were operated PS TKA(NexGen LPS-Flex, Zimmer, Inc. Warsaw, IN) for the varus type osteoarthritis. Following each bony resection and soft tissue release using measure resection technique, the tensor was fixed to the proximal tibia and femoral trial prosthesis was fitted. Assessment of the joint component gap (mm) and the ligament balance in varus (°)was carried out at 0, 10, 45, 90and 135degrees of knee flexion. The joint distraction force was set at 40lbs. Joint component gap change values during 10-0°,45-0°, 90-0°, 135-0° flexion angle were also calculated. The tibial slopes were measured by postoperative lateral radiograph. The correlation between the tibial slope and values of soft tissue balance were assessed using linear regression analysis. Results. Average joint component gaps were 11.2, 14.7, 16.7, 18.4 and 17.0 mm and ligament balance in varus were 2.2, 2.9, 5.3, 6.8 and 6.9°at 0, 10, 45, 90 and 135° of flexion, respectively. Average joint component gap changes were 3.5, 5.6, 7.2 and 5.7 mm at each range of motion between 10–0, 45-0, 90–0 and 135–0° of flexion, respectively. The mean tibial slope was 5.0(1.6–9.6) degrees. Joint component gap at 90 (R = 0.537, p<0.01),135(R=0.463, p<0.05) degrees of flexion, and joint component gap change value of 90–0° (R = 0.433, p<0.05) showed positive correlations with tibial slope. The other factors assessed in this study showed no correlation with tibial slope. Discussions. The joint gap toward mid-range of flexion might be measured at anterior part of the tibiofemoral joint, whereas the values of joint gap at high flexion where the femur shifted posterior due to femoral rollback were measured the widened posterior part of the joint gap. In addition, extensor mechanism as well as tibial slope might influence joint gap at deep flexion. In conclusion, even PS TKA, increasing the posterior tibial slope resulting in larger flexion gap compared to extension gap should be taken into account for the flexion-extension gap balancing

The Columbus® knee system was designed as a standard knee implant that allows high flexion without the need for additional bone resection. The aim of this retrospective study was to investigate the correlation between the maximum flexion achieved at five years and the slope of the tibial component. The hypothesis was that increased slope would give increased flexion. The study design was a retrospective cohort study at a single centre. The inclusion criterion was having had a navigated cemented Columbus primary TKA implanted between March 2005 and December 2006 using the image free OrthoPilot® navigation system (Aesculap, Tuttlingen, Germany) in our institution. Follow-up had been carried out at review clinics by an independent arthroplasty team. Patient-related data had been recorded either in case notes, the departmental proprietary database or as radiographic images. In addition to demographics, five-year follow-up range of motion (ROM) was collected. All available radiographs on the national Picture Archiving and Communication System (Eastman Kodak Company, 10.1_SP1, 2006), whether taken at our institution or at the patient's local hospital, were analysed by a trainee orthopaedic surgeon (NCS) who was independent of the patients' care. Component position according to the Knee Society TKA scoring system was determined from the five-year review lateral x-ray. The tibial slope was calculated as 90° minus the angle of the tibial component so giving a posterior slope as a positive number and an anterior slope as a negative number. The correlation between maximum flexion angle and tibial slope was calculated. Further to this a subgroup of only CR prostheses and patients with BMI <35 were analysed for a relationship. The tibial slope of the group of patients having 90° or less of flexion (poor flexion) was compared to those having 110° or more (good flexion) using a t-test, as was the flexion of the those with BMI <30 to those with BMI > 35. A total of 219 knees in 205 patients were identified. 123 had five-year radiograph and maximum flexion measurement available. Cohort demographics were mean age 68(8.6), mean BMI 32.0(5.9) and mean maximum flexion at five years of 101°(11°). The tibial slope angle showed variation around the mean of 2°(2.8°). There was no correlation between tibial slope and maximum flexion for either that whole cohort (r=-0.051, p=0.572, Figure 1b) or the subgroup of CR and BMI <35 patients (n=78, r = −0.089, p=0.438). The mean tibial slope of those patients having poor flexion was 2° (SD2.6°) and this was not significantly different to the mean for those with good flexion, 3° (SD3.1°) p=0.614. The mean flexion of those with BMI <30 was 100° (SD8.7°) and this was not significantly different to those with BMI >35, mean 101° (SD11.4°). This study did not find any correlation between the tibial slope and maximum flexion angle in 123 TKAs at five year follow up. Further studies with a more accurate measurement of tibial slope should be carried out to confirm whether a relationship exists in the clinical setting

Injuries to the posterior cruciate ligament (PCL) and the posterolateral corner (PLC) of the knee remain a challenging orthopaedic problem. Studies evaluating PCL and PLC reconstruction have failed to demonstrate a strong correlation between the degree of knee laxity as measured by uniplanar testing and subjective outcome or patient satisfaction. The effect that changing the magnitude of posterior tibial slope has on multiplanar, rotational stability of the PCL-deficient knee has yet to be determined. We aimed to evaluate the effect that changes in posterior tibial slope would have on static and dynamic stability of the PCL-PLC deficient knee. Ten knees were used for this study. Navigated posterior drawer and standardised reverse mechanised pivot shift maneuvers were performed in the intact knee and after sectioning the PCL, the lateral collateral ligament (LCL), the popliteofibular ligament (PFL) and the popliteus muscle tendon (POP). Navigated high tibial osteotomy (HTO) was performed to obtain the desired change in tibial plateau slope (+5® or −5® from native slope). We then repeated the posterior drawer and the reverse mechanised pivot shift test for each of the two altered slope conditions. Mean posterior tibial translation during the posterior drawer in the intact knee was 1.4 mm (SD = 0.48 mm). In the PCL-PLC deficient knee, posterior tibial translation increased to 18 mm (SD = 5.7 mm) (P < 0.001). Increasing the amount of posterior tibial slope by 5® reduced posterior tibial translation to 12 mm (SD = 4.7 mm) (P < 0.01). Decreasing the amount of posterior slope by 5® compared to the native knee, increased posterior tibial translation to 21 mm (SD = 6.8 mm) (P < 0.01). There was a significant negative correlation between the magnitude of tibial plateau slope and the magnitude of the reverse pivot shift (R2 = 0.71; P < 0.0001). Mean posterior tibial translation during the reverse mechanised pivot shift test in the intact knee was 7.8 mm (SD = 2.8 mm). In the PCL-PLC deficient knee, posterior tibial translation increased to 26 mm (SD = 5.6 mm) (P < 0.001). Increasing the amount of posterior tibial slope by 5® reduced posterior tibial translation to 21 mm (SD = 6.7 mm) (P < 0.01). Decreasing the amount of posterior slope by 5® compared to the native knee, increased posterior tibial translation to 34 mm (SD = 8.2 mm) (P < 0.01). There was a significant negative correlation between the magnitude of tibial plateau slope and the magnitude of the reverse pivot shift (R2 = 0.72; P < 0.0001). Decreasing the magnitude of posterior slope of the tibial plateau resulted in an increase in the magnitude of posterior tibial translation during the posterior drawer and the reverse mechanised pivot shift test in the PCL-PLC deficient knee. Conversely, increasing the slope of the tibial plateau reduced the amount of posterior tibial translation during the posterior drawer and the reverse mechanised pivot shift test. However, the effect of the increase in slope was not sufficient to reduce posterior tibial translation to levels similar to those of the intact knee

Knee laxity following anterior cruciate ligament (ACL) injury is a complex phenomenon influenced by various biomechanical and anatomical factors. The contribution of soft tissue injuries – such as ligaments, menisci, and capsule – has been previously defined, but less is known about the effects of bony morphology. (Tanaka et al, KSSTA 2012) The pivot shift test is frequently employed in the clinical setting to assess the combined rotational and translational laxity of the ACL deficient knee. In order to standardise the maneuver and allow for reproducible interpretation, the quantitative pivot shift test was developed. (Hoshino et al, KSSTA 2013) The aim of this study is to employ the quantitative pivot shift test to determine the effects of bone morphology as determined by magnetic resonance imaging (MRI) on rotatory laxity of the ACL deficient knee. Fifty-three ACL injured patients scheduled for surgical reconstruction (36 males and 17 females; 26±10 years) were prospectively enrolled in the study. Preoperative magnetic resonance imaging (MRI) scans were reviewed by two blinded observers and the following parameters were measured: medial and lateral tibial slope, tibial plateau width, femoral condyle width, bicondylar width, and notch width. (Musahl et al. KSSTA 2012). Preoperatively and under anaesthesia, a quantitative pivot shift test was performed on each patient by a single experienced examiner. An image analysis technique was used to quantify the lateral compartment translation during the maneuver. Subjects were classified as “high laxity” or “low laxity” based upon the median value of lateral compartment translation. (Hoshino et al. KSSTA 2012) Independent t-tests and univariate logistic regression were used to investigate the relationship between the pivot shift grade and various features of bone morphology. Statistical significance was set at p<0.05. A high inter-rater reliability was observed in all MRI measurements of bone morphology (ICC=0.72–0.88). The median lateral compartment translation during quantitative pivot shift testing was 2.8mm. Twenty-nine subjects were classified as “low laxity” (2.8mm). The lateral tibial plateau slope was significantly increased in “high laxity” patients (9.3+/−3.4mm versus 6.1+/−3.7mm; p<0.05). No other significant difference in bone morphology was observed between the groups. This study employed an objective assessment tool – the quantitative pivot shift test – to assess the contribution of various features of bone morphology to rotatory laxity in the ACL deficient knee. Increased lateral tibial plateau slope was shown to be a significant independent predictor of high laxity. These findings could help guide treatment strategies in patients with high grade rotatory laxity. Further research into the role of tibial osteotomies in this sub-group is warranted

Tibial plateau fracture reduction involves restoration of alignment and articular congruity. Restorations of sagittal alignment (tibial slope) of medial and lateral condyles of the tibial plateau are independent of each other in the fracture setting. Limited independent assessment of medial and lateral tibial plateau sagittal alignment has been performed to date. Our objective was to characterize medial and lateral tibial slopes using fluoroscopy and to correlate X-ray and CT findings. Phase One: Eight cadaveric knees were mounted in extension. C-arm fluoroscopy was used to acquire an AP image and the C-arm was adjusted in the sagittal plane from 15° of cephalad tilt to 15 ° of caudad tilt with images captured at 0.5° increments. The “perfect AP” angle, defined as the angle that most accurately profiled the articular surface, was determined for medial and lateral condyles of each tibia by five surgeons. Given that it was agreed across surgeons that more than one angle provided an adequate profile of each compartment, a range of AP angles corresponding to adequate images was recorded. Phase Two: Perfect AP angles from Phase One were projected onto sagittal CT images in Horos software in the mid-medial compartment and mid-lateral compartment to determine the precise tangent subchondral anatomic structures seen on CT to serve as dominant bony landmarks in a protocol generated for calculating medial and lateral tibial slopes on CT. Phase Three: 46 additional cadaveric knees were imaged with CT. Tibial slopes were determined in all 54 specimens. Phase One: Based on the perfect AP angle on X-ray, the mean medial slope was 4.2°+/-2.6° posterior and mean lateral slope was 5.0°+/-3.8° posterior in eight knees. A range of AP angles was noted to adequately profile each compartment in all specimens and was noted to be wider in the lateral (3.9°+/-3.8°) than medial compartment (1.8°+/-0.7° p=0.002). Phase Two: In plateaus with a concave shape, the perfect AP angle on X-ray corresponded with a line between the superiormost edges of the anterior and posterior lips of the plateau on CT. In plateaus with a flat or convex shape, the perfect AP angle aligned with a tangent to the subchondral surface extending from center to posterior plateau on CT. Phase Three: Based on the CT protocol created in Phase Two, mean medial slope (5.2°+/-2.3° posterior) was significantly less than lateral slope (7.5°+/-3.0° posterior) in 54 knees (p<0.001). In individual specimens, the difference between medial and lateral slopes was variable, ranging from 6.8° more laterally to 3.1° more medially. In a paired comparison of right and left knees from the same cadaver, no differences were noted between sides (medial p=0.43; lateral p=0.62). On average there is slightly more tibial slope in the lateral plateau than medial plateau (2° greater). However, individual patients may have substantially more lateral slope (up to 6.8°) or even more medial slope (up to 3.1°). Since tibial slope was similar between contralateral limbs, evaluating slope on the uninjured side provides a template for sagittal plane reduction of tibial plateau fractures

Introduction. Recent technological advancements have led to the introduction of robotic-assisted total knee arthroplasty to improve the accuracy and precision of bony resections and implant position. However, the in vivo accuracy is not widely reported. The primary objective of this study is to determine the accuracy and precision of a cut block positioning robotic arm. Method. Seventy-seven patients underwent total knee arthroplasty with various workflows and alignment targets by three arthroplasty-trained surgeons with previous experience using the ROSA® Knee System. Accuracy and precision were determined by measuring the difference between various workflow time points, including the final pre-operative plan, validated resection angle, and post-operative radiographs. The mean difference between the measurements determined accuracy, and the standard deviation represented precision. Results. The accuracy and precision for all angles comparing the final planned resection and validated resection angles was 0.90° ± 0.76°. The proportion within 3° ranged from 97.9% to 100%. The accuracy and precision for all angles comparing the final intra- operative plan and post-operative radiographs was 1.95 ± 1.48°. The proportion of patients within 3° was 93.2%, 95.3%, 96.6%, and 71.4% for the distal femur, proximal tibia, femoral flexion, and tibial slope angles when the final intra-operative plan was compared to post-operative radiographs. No patients had a postoperative complication requiring revision at the final follow-up. Conclusions. This study demonstrates that the ROSA Knee System has accurate and precise coronal plane resections with few outliers. However, the tibial slope demonstrated decreased accuracy and precision were measured on post-operative short-leg lateral radiographs with this platform

Abstract. Aims. Growth disturbances after transphyseal paediatric ACL reconstruction have led to the development of physeal-sparing techniques. However, evidence in their favour remains weak. This study reviews the literature to identify factors associated with growth disturbances in paediatric ACL reconstructions. Materials and Methods. Web of Science, Scopus and Pubmed were searched for case series studying paediatric ACL reconstructions. Titles, abstracts, text, results and references were examined for documentation of growth disturbances. Incidences of graft failures were also studied in these selected studies. Results. 78 studies with 2693 paediatric ACL reconstructions had 70 growth disturbances (2.6%). Of these 17 were varus, 26 valgus, 13 shortening, 14 lengthening and 5 patients had reduced tibial slope. Coronal plane deformities were seen more frequently with eccentric physeal arrest and lengthening with intraepiphyseal tunnelling. Shortening and reduced tibial slope were related to large central physeal arrest and anterior tibial physeal arrest respectively. Extraphyseal technique were least likely to have growth disturbances. 62 studies documented 166 graft failures in 2120 patients (7.83%). Conclusion. Growth disturbances resulting from transphyseal ACL reconstruction can be minimised by keeping drill size small, drilling steep and away from the physeal periphery. Insertion of bone plug, hardware or synthetic material through the drilled physis should be avoided. The evidence to accurately quantify such growth disturbances till skeletal maturity remains weak. Robust long term studies such as national ligament registries may standardise preoperative and postoperative outcome assessment to further characterise the risk of growth disturbance and re-ruptures

Background. Multiple retrospective studies have compared UC with traditional bearings and shown comparable results and outcomes when looking at clinical and radiologic variables, complications rates, and implant survivorship; however, debate still exists regarding the optimum bearing surface. The present study seeks to determine whether there are any preoperative patient demographic or medical factors or anatomic variables including femoral condylar offset and tibial slope that may predict use of a UC bearing when compared to a standard CR group. Methods. The study cohort consisted of 117 patients (41 males, 76 females) who underwent primary TKA with the senior author. The implants utilized were either the CR or UC polyethylene components of the Zimmer Persona Total Knee System. Insert selection was based on intraoperative assessment of PCL integrity and soft tissue balancing. Patient demographics (age, gender, BMI) and co-morbidities (hypertension, diabetes, depression, cardiac disease, and lung disease) were recorded. Intraoperative variables of interest included extension and flexion range of motion, estimated blood loss (EBL), tourniquet time, and polyethylene and femoral component sizes. We calculated change in tibial slope and femoral condylar offset from pre- to post-surgery and computed the percentage of patients for whom an increase in tibial slope or femoral condylar offset was determined. Postoperative variables, including length of stay, complication rates and reoperation rates, were recorded. All dependent variables were compared between patients who received the UC component and patients who received the CR component. Continuous variables were assessed using independent samples t-tests, while categorical variables were compared using the chi-square test of independence. Results. There were 39 patients who received a UC insert and 78 patients who received CR insert. Patient age (p = 0.58), BMI (p = 0.34), or sex distribution (p = 0.84) did not differ between the UC and CR groups. Mean LOS (3.59 vs. 3.08; p = 0.017), EBL (54.5 vs. 46.7; p=0.021), and tourniquet time (61.2 vs. 57.4; p=0.032) were greater for the UC group. Intraoperative implant variables, including polyethylene component (p = 0.49), femoral component (p = 0.56), use of a narrow femoral component (p = 0.85), and patellar component size (p = 0,83), were similar between groups. Additionally, preoperative (p = 0.46) and postoperative (p = 0.19) condylar offset and preoperative (p = 0.66) and postoperative (p = 0.23) tibial slope were not different between the groups. However, the proportion of patients for whom tibial slope increased postoperatively was greater for the UC group compared to the CR group (43.6 vs. 21.8% respectively, p=0.018). Conclusions. Our results showed that no preoperative medical co-morbidities or demographic factors predicted use of the UC bearing; however, postoperative tibial slope was increased for a greater number of patients who received the UC implant. Patients who have an increase in their slope from their native anatomy during tibial preparation may require additional balancing of the flexion gap, and use of a UC component may be beneficial in this particular group of patients

Several studies have highlighted the relationship between anterior cruciate (ACL) injury and knee geometry particularly tibial slope (TS). However, clinical data are inconsistent, whether the lateral or medial or slopes have a different influence on ACL injury. Our goal was to assess whether the medial, lateral slopes are associated with ACL injury and whether meniscus geometry is associated with ACL injury. In addition, we sought to determine if lateral meniscal height could serve as a simple surrogate measurement for ACL injury risk. A case-controlled study compared 68 patients with an ACL injury and 68 matched nested controls. Radiological analysis of MRI measured the anterior-posterior distance of the medial and lateral plateaus, the tibial slope of both plateaus and meniscus geometry. Groups were compared using a Mann-Whitney test and α < 0 .05. The lateral tibial plateau slope was significantly higher in the ACL injured group (6.92 degrees ±5.8) versus the control group 2.68 ±5.26 (p 0.0001). In addition, the lateral meniscal slope was significantly steeper with (ACL injuries: −1 ±4.7 versus −4.73 ±4.4 (p 0.0001) in the control group. The ACL Injured group had a significantly lower lateral meniscal height 0.76 cm ±0.09, compared to the control group that has 0.88 cm ±0.12 (p 0.0001). The Lateral meniscal height had a sensitivity of 76.47% and specificity 75% for predicting ACL injury using a cut off of. Patients with ACL-injury had significantly higher lateral tibial plateau slope. Lateral meniscus height was found to be an easy measurement to make on MRI with a high specificity for predicting ACL injury. Lateral tibial slope and meniscal Geometry can be used to identify patients with high risk of an ACL injury, that might benefit from further surgery to optimize rotational stability in high-risk patients

Total knee arthroplasty (TKA) is an effective technique to treat end-stage knee osteoarthritis, targeting the restore a physiological knee kinematics. However, studies have shown abnormal knee kinematics after TKA which may lead to suboptimal clinical outcomes. Posterior slope of the tibial component may significantly impact the knee kinematics. There is currently no consensus about the most appropriate slope. The goal of the present study was to analyse the impact of different prosthetic slopes on the kinematics of a PCL-preserving TKA, with the hypothesis that posterior slopes can alter the knee kinematics. A PCL-retaining TKA (Optetrak CR, Exactech, Gainesville, FL) was performed by a board-certified orthopaedic surgeon on one fresh frozen cadaver that had a non arthritic knee with an intact PCL. Intact knee kinematic was assessed using a computer-assisted orthopaedic surgery (CAOS) system (ExactechGPS®, Blue-Ortho, Grenoble, FR) Then, TKA components were implanted using the guidance of the CAOS system. The implanted tibial baseplate was specially designed to allow modifying the posterior slope without repeatedly removing/assembling the tibial insert with varying posterior slopes, avoiding potential damages to the soft-tissue envelope. Knee kinematic was evaluated by performing a passive range of motion 3 separate times at each of the 4 posterior slopes: 10°, 7°, 4° and 1°, and recorded by the navigation system. Femorotibial rotation, antero-posterior (AP) translation and hip-knee-ankle (HKA) angle were plotted with regard to the knee flexion angle. Tibial slopes of 1° and 4° significantly altered the normal rotational kinematics. Tibial slopes of 7° and 10° led to a kinematics close to the original native knee. All tibial slopes significantly altered the changes in HKA before 90° of knee flexion, without significant difference between the different slopes tested. The magnitude of change was small. There was no significant change in the AP kinematics between native knee and all tested tibial slopes. Changing the tibial slope significantly impacted the TKA kinematics. However, in the implant studied, only the rotational kinematics were significantly impacted by the change in tibial slope. Tibial slopes of 7° and 10° led rotational kinematics that were closest to that of a normal knee. Alterations in knee kinematics related to changing tibial slope may be related to a change in the PCL strain. However, these results must be confirmed by other tests involving more specimens

Background. Adjusting the joint gap length to be equal in both extension and flexion is an important issue in total knee arthroplasty (TKA). Tight flexion gaps occur sometimes, particularly with the cruciate-retaining (CR) type of TKA, and it impede knee flexion. In posterior stabilizing (PS) TKA, because sacrificing the PCL increases the flexion gap, the issue of gap balancing with PS-TKA is usually focused on decreasing the enlarged flexion gap to be equal to the extension gap. It is generally known that posterior tibial slope would affect the flexion gap, however, the extent to which changes in the tibial slope angle directly affect the flexion gap remains unclear. This study aimed to clarify the influence of tibial slope changes on the flexion gap in CR- or PS-TKA. Methods. The flexion gap was measured using a tensor device with the femoral trail component in 20 cases each of CR- and PS-TKA. A wedge plate with a 5° inclination was placed on the tibial cut surface by switching its front–back direction to increase or decrease the tibial slope by 5°. The flexion gap in changing the tibial slope was compared to that of the neutral slope measured with a flat plate that had the same thickness of the wedge plate center. Results. When the tibial slope decreased or increased by 5°, the flexion gap decreased or increased by 1.9 ± 0.6 mm or 1.8 ± 0.4 mm, respectively, with CR-TKA and 1.2 ± 0.4 mm or 1.1 ± 0.3 mm, respectively, with PS-TKA. Conclusions. The influence of changing the tibial slope by 5° on the flexion gap was approximately 2 mm with CR-TKA and 1 mm with PS-TKA. Clinical relevance. This information is useful to consider the effect of manipulating the tibial slope on the flexion gap when performing CR- or PS-TKA

INTRODUCTION. Total knee arthroplasty (TKA) is an effective technique to treat end-stage osteoarthritis of the knee. One important goal of the procedure is to restore physiological knee kinematics. However, fluoroscopy studies have consistently shown abnormal knee kinematics after TKA, which may lead to suboptimal clinical outcomes. Posterior slope of the tibial component may significantly impact the knee kinematics after TKA. There is currently no consensus about the most appropriate slope. The goal of the present study was to analyze the impact of different prosthetic slopes on the kinematics of a PCL-preserving TKA. The tested hypothesis was that the knee kinematics will be different for all tested tibial slopes. MATERIAL. PCL-retaining TKAs (Optetrak Logic CR, Exactech, Gainesville, FL) were performed by fellowship trained orthopedic surgeons on six fresh frozen cadaver with healthy knees and intact PCL. The TKA was implanted using a computer-assisted surgical navigation system (ExactechGPS®, Blue-Ortho, Grenoble, FR). The implanted tibial baseplate was specially designed (figure 1) to allow modifying the posterior slope without repeatedly removing/assembling the tibial insert with varying posterior slopes, avoiding potential damages to the soft-tissue envelope. METHODS. Knee kinematics was evaluated by performing a passive range of motion (ROM) from full extension to at least 100 degrees of flexion. Passive ROM was repeated three times at each of the 4 posterior slopes selected: 10°, 7°, 4°, and 1° using the adjustable tibial component (figure 1). Respective 3D positioning of femur and tibia implants was recorded by the navigation system. Hip-knee-ankle (HKA) angle, femoro-tibial antero-posterior (AP) translation and internal-external (I/E) rotation were plotted according to the knee flexion angle. RESULTS. HKA angle (figure 2B): all 4 different tibial slopes induced a physiologic motion curve, and the kinematic differences between 10°, 7°, 4°, and 1° of posterior slope with the native knee were small. All slopes induced a varus angle beyond 60° of flexion, most likely was due to the external rotation of the femoral component. Femoro-tibial AP translation (figure 2C): all 4 different tibial slopes induced a physiologic motion curve and all slopes induced a large posterior translation before 80° of flexion, which was proportional to the slope. I/E rotation (figure 2A): all slopes induced an excessive internal rotation before 60° of flexion. DISCUSSION. A change in the tibial slope may impact significantly the TKA kinematics. Slopes of 1° and 4° seemed to be the better compromise with the specific implant used. Navigation systems are able to assess the knee kinematics after TKA. The test protocol has been assessed for reproducibility in a separate study with satisfactory results. Changing the tibial slope significantly impacted the TKA kinematics. With the specific implant used, rotational and coronal kinematics was only marginally impacted by the change in tibial slope. AP kinematics was significantly impacted by the change in tibial slope. These changes may be related to a change in the PCL strain. Slopes of 1° and 4° induced the more physiologic compromise

Component alignment and soft tissue constraints are key factors affecting function and implant survival after total knee replacement (TKR). Knee kinematics contribute to knee function whilst soft tissue constraints and component alignment impact polyethylene wear. This study experimentally investigated the effect of soft tissue constraints and component alignment on the kinematics and wear of a TKR. A six station electromechanical ProSim knee simulator was used with the ISO 14243-1:2009 standard force control inputs; axial force, flexion-extension (FE), tibial rotation (TR) torque and anterior-posterior (AP) force. This allowed the kinematics to vary with the test conditions. The soft tissue constraints were simulated using virtual springs. DePuy Sigma XLK fixed bearing TKRs were tested in 25% bovine serum (in 0.04% sodium azide) lubricant. The average output kinematics across 6 stations were found for each test and the peak values compared. The wear rates were calculated over 2 million cycles (MC), the serum was changed every 350,000 cycles and the tibial inserts weighed after every MC. A one way ANOVA and post hoc Tukey's test was used to compare the kinematics and wear with significance taken at p<0.05. The kinematics and wear rates for three soft tissue conditions were established under ideal alignment (Table 1). The ISO standard springs for a cruciate substituting (CS) and a cruciate retaining (CR) prosthesis were used to represent a knee with a resected ACL and PCL and a knee with a resected ACL respectively. The third spring condition was based on clinical data to represent a “stiff” knee. Three other alignment conditions were then assessed using “stiff” knee springs; 4° varus, 14° rotational mismatch and 10° posterior tibial slope. These alignments were chosen to represent the range found in clinical data. Under ideal alignment the “stiff” knee springs had significantly lower peak AP and TR displacements (0.9mm, 2mm, 2mm and 3.6°, 7.1°, 7.8° for the “stiff”, CR and CS springs respectively) than the other springs (p<0.01). The “stiff” knee spring had a significantly lower wear rate than the CR spring; 1.58 ±1.20mm³/MC compared to 4.71±1.29 mm³/MC (p<0.01). The varus and rotated components had significantly larger peak AP displacements of 2.56mm and 2.42mm respectively, than the ideal and tibial slope fixtures (1.97mm and 0.92mm respectively) (p<0.01). The rotated components had significantly higher internal rotation of 12.2° compared to 4.4°, 3.7° and 3.5° for the tibial slope, varus and ideal components respectively (p<0.01). The ideal and varus components had significantly lower wear than the tibial slope and rotated components (1.58±1.20mm³/MC and 0.15±0.83mm³/MC compared to 8.24±7.72mm³/MC and 5.19±1.12mm³/MC respectively) (p<0.01). This may be due to increased AP and TR displacements with the rotated components and the increased anterior AP displacement with the tibial slope components, resulting in wear on the posterior edge of the tibial insert. Soft tissue constraints and component alignment had a significant effect on the kinematics and wear. Experimental simulation should test a variety of soft tissue and alignment conditions to reflect the range observed clinically and determine causes for early failure. For any figures or tables, please contact the authors directly

Background. The posterior slope of the tibial component in total knee arthroplasty (TKA) has been reported to vary widely even with computer assisted surgery. In the present study, we analyzed the influence of posterior tibial slope on one-year postoperative clinical outcome after posterior-stabilized (PS) -TKA to find out the optimal posterior slope of tibial component. Materials and Method. Seventy-three patients with varus type osteoarthritic (OA) knees underwent PS-TKA (Persona PS. R. ) were involved in this study. The mean age was 76.6 years old and preoperative HKA angle was 14.3 degrees in varus. Tibial bone cut was performed using standard extra-medullary guide with 7 degrees of posterior slope. The tibial slopes were radiographically measured by post-operative lateral radiograph with posterior inclination in plus value. The angle between the perpendicular line of the proximal fibular shaft axis and the line drawn along the superior margin of the proximal tibia represented the tibial slope angle. We assessed one-year postoperative clinical outcomes including active range of motion (ROM), patient satisfaction and symptoms scores using 2011 Knee Society Score (2011 KSS). The influences of posterior tibial slope on one-year postoperative parameters were analyzed using simple linear regression analysis (p<0.05). Results. The average posterior tibial slope was 6.4 ± 2.0 °. The average active ROM were −2.4 ± 6.6 ° in extension and 113.5± 12.6 ° in flexion. The mean one-year postoperative patient satisfaction and symptom scores were 29.3 ± 6.4 and 19.6 ± 3.9 points respectively. The active knee extension, satisfaction and symptom scores were significantly negatively correlated to the posterior tibial slope (r = −0.25, −0.31, −0.23). Discussion. In the present study, we have found significant influence of the posterior tibial slope on the one-year postoperative clinical outcomes in PS-TKA. The higher posterior slope would induce flexion contracture and deteriorate patient satisfaction and symptom. We had reported that the higher tibial posterior slope increased flexion gap and the component gap change during knee flexion in PS-TKA. Furthermore, another study reported that increase of the posterior tibia slope reduced the tension in the collateral ligaments and resulted in the knee laxity at flexion. The excessive posterior slope of tibial component would result in flexion instability, and adversely affected the clinical results including patient satisfaction and symptom. Conclusion. In the PS-TKA for varus type OA knees, excessive tibial posterior slope was found to adversely affect one-year postoperative knee extension and clinical outcome including patient satisfaction and symptom. Surgeons should aware of the importance of tibial slope on one-year postoperative clinical results and pay more attentions to the posterior tibial slope angle not to be excessive

Introduction. Optimal alignment of the tibial component in TKA is an important consideration. General agreement exists on the appropriate coronal alignment. However there is no consensus on sagittal alignment (posterior slope). Some surgeons target a fixed posterior slope (usually between 0 and 10 degrees), while others attempt to match the patient's intrinsic anatomy. The purpose of this study was to evaluate the tibial posterior slope in patients undergoing TKA. Methods. 13,586 CT scans of patients undergoing patient specific were analyzed. Three-dimensional reconstructions were performed and the posterior tibial slope was measured. Mean slope and ranges were determined. Results. Mean tibial posterior slope was 7.2 +/− 3.7 degrees (range −5 to 25 deg.) 35% of patients had tibial slope measurements more than 3 degrees different from the mean slope of this population. Conclusion. This study demonstrated a remarkable variability of tibial slope in patients undergoing TKA. This information may be useful to surgeons in determining “optimum” sagittal alignment of the tibial component for an individual patient. A patient with preoperative tibial slope very different from “average” may be at risk for sagittal malalignment of the tibial component. Additionally, large preoperative to postoperative changes in tibial slope may adversely affect knee kinematics and clinical outcome

Introduction. Component position and overall limb alignment following total knee arthroplasty (TKA) have been shown to influence prosthetic survivorship and clinical outcomes. Robotic-assisted (RA) total knee arthroplasty has demonstrated improved accuracy to plan in cadaver studies compared to conventionally instrumented (manual) TKA, but less clinical evidence has been reported. The objective of this study was to compare the three-dimensional accuracy to plan of RATKA with manual TKA for overall limb alignment and component position. Methods. A non-randomized, prospective multi-center clinical study was conducted to compare RATKA and manual TKA at 4 U.S. centers between July 2016 and August 2018. Computed tomography (CT) scans obtained approximately 6 weeks post-operatively were analyzed using anatomical landmarks. Absolute deviation from surgical plans were defined as the absolute value of the difference between the CT measurements and surgeons’ operative plan for overall limb, femoral and tibial component mechanical varus/valgus alignment, tibial component posterior slope, and femoral component internal/external rotation. We tested the differences of absolute deviation from plan between manual and RATKA groups using stratified Wilcoxon tests, which controlled for study center and accounted for skewed distributions of the absolute values. Alpha was 0.05 two-sided. At the time of this abstract, data collections were completed for two centers (52 manual and 58 RATKA). Results. Comparing absolute deviation from plan between groups, RATKA demonstrated clear benefits for tibial component alignment (median absolute deviation from plan: 1.5° vs. 0.8°, manual vs RATKA, p<.001), tibial slope (2.7° vs. 1.1°, manual vs RATKA, p<.001), and femoral component rotation (1.4° vs. 0.9°, manual vs RATKA, p<0.02). Femoral component and overall limb alignment accuracy were comparable (p>0.10). Discussion and Conclusions. In this study, compared to manual TKA, RATKA cases were 47% more accurate for tibial component alignment, 59% more accurate for tibial slope, and 36% more accurate for femoral component rotation (percent differences of median absolute deviations from plan). Further clinical data is needed to study the longer-term benefits of robotic technologies. Nevertheless, this study supports improved accuracy to plan utilizing RATKA compared to manual TKA. For any figures or tables, please contact authors directly

Introduction. One of the important criteria of the success of TKR is achievement of the Flexion ROM. Various factors responsible to achieve flexion are technique, Implant and patient related. Creation of the Posterior condylar offset is one such important factor to achieve satisfactory flexion. Aim. To correlate post op femoral condylar offset to final flexion ROM at 1 yr. post op. Methods. This is a clinico-radiological study of the cases done prospectively between September 2011 and August 2012. Inclusion criteria:. All patients undergoing Bilateral TKRs and have agreed for the follow up at 1 yr. Exclusion criteria:. Patients who had previous bony surgery on lower end femur. Patients with previous fracture of lower end femur. All the patients had PS PFC Sigma (De Puy, Warsaw) components cemented. ROMs were measured at 6 weeks, 3 months, & 1 year post op. The last reading was taken as final flexion ROM as measured by a Physiotherapist with the help of a Goniometer. Results. We had 21 cases of Bilateral TKRs who satisfied our criteria. Pre and post op femoral condylar offset was measured in mm. on lateral x ray. Pre and post op flexion was measured. Results showed that variation in the posterior femoral offset by > 3mm in post op x ray was related to loss of flexion of an average 21 deg. (16 – 24 degrees). Greater the deflection from the normal offset, greater was the loss of flexion. These patients also showed lesser improvement in KSS functional score. Discussion. Flexion is one of the most important yardsticks for the measurement of success of TKR. This factor is more important more so in Asian population. Literature has shown that three important determinants for good flexion are…. Posterior Condylar Offset Restoration. Tibial slope restoration. Femoral Roll back in flexion. An increased offset permits greater flexion before impingement between the tibial insert and the femur. In our study we kept Tibial slope and Femoral Roll back constant by using the same prosthesis. The femoral condylar offset changed as per the size of the AP femoral cutting block. (Anterior referencing guide used). Overresection of the posterior condyles reduced the posterior femoral condylar offset and hence significant loss of post op flexion. The shorter posterior condyle of smaller femoral component can increase the potential for bone impingement proximal to the posterior condyles. In our study the opposite side replaced knee acted as a control. It is generally stated that after a TKR flexion can improve upto 1 year and hence was taken as final possible flexion. Conclusion. Keeping Tibial slope and Femoral roll back constant during the surgery, posterior condylar offset restoration within 3 mm of its original pre op offset was necessary to achieve satisfactory flexion at 1 year. Undersizing the femoral component to achieve more flexion is perhaps suboptimal. Appropriate AP femoral sizing is a must to restore the normal offset

The influence of amount of tibial posterior slope changes on joint gap and postoperative range of motion was investigated in 35 patients undergoing unicompartmental knee arthroplasty (UKA). Component gap between the medial tibial osteotomy surface and the femoral trial prosthesis was measured throughout the range of motion using a tensor. The mean tibial posterior slope decreased from 10.2 to 7.3 degrees. Increased tibial slope change was positively correlated with component gap differences of 90° −10°, 120° −10°, and 135° −10° and negatively correlated with postoperative extension angle. Increasing tibial slope should be avoided to achieve full extension angle after UKA

Introduction:. One of the important criteria of the success of TKR is achievement of the Flexion ROM. Various factors responsible to achieve flexion are technique, Implant and patient related. Creation of the Posterior condylar offset is one of the important factors to achieve satisfactory flexion. Aim:. To correlate post op femoral condylar offset to final flexion ROM at 1 yr. post op. Methods:. This is a clinico-radiological study of the cases done prospectively between September 2011 and August 2012. Inclusion criteria:. All patients undergoing Bilateral TKRs and have agreed for the follow up at 1 yr. Exclusion criteria: . 1). Patients who had previous bony surgery on lower end femur. 2). Patients with previous fracture of lower end femur. All the patients had PS PFC Sigma (De Puy, Warsaw) components cemented. ROMs were measured at 6 weeks, 3 months, & 1 year post op. The last reading was taken as final flexion ROM as measured by an independent Physiotherapist with the help of a Goniometer. Results:. We had 21 cases of Bilateral TKRs who satisfied our criteria. Pre and post op femoral condylar offset was measured in mm. on lateral x ray. Pre and post op flexion was measured. Results showed that variation in the posterior femoral offset by > 3 mm in post op x ray was related to loss of flexion of an average 21 deg. (16–24 degrees). Greater the deflection from the normal offset, greater was the loss of flexion. These patients also showed lesser improvement in KSS functional sco. Discussion:. Flexion is one of the most important yardsticks for the measurement of success of TKR. This factor is more important more so in Asian population. Literature has shown that three important determinants for good flexion are…. . 1). Posterior Condylar Offset Restoration. 2). Tibial slope restoration. 3). Femoral Roll back in flexion. An increased offset permits greater flexion before impingement between the tibial insert and the femur. In our study we kept Tibial slope and Femoral Roll back constant by using the same prosthesis. The femoral condylar offset changed as per the size of the AP femoral cutting block. (Anterior referencing guide used). Overresection of the posterior condyles reduced the posterior femoral condylar offset and hence significant loss of post op flexion. The shorter posterior condyle of smaller-sized femoral component can increase the potential for bone impingement proximal to the posterior condyles. In our study the opposite side replaced knee acted as a control and hence eliminating patient bius. It is generally stated that after a TKR flexion can improve upto 1 year and hence that was taken as final possible flexion. Conclusion:. Keeping Tibial slope and Femoral roll back constant during the surgery, posterior condylar offset restoration within 3 mm of its original pre op offset was necessary to achieve satisfactory flexion at 1 year. Undersizing the femoral component to achieve more flexion is perhaps suboptimal. Appropriate AP femoral sizing is a must to restore the normal offset