Introduction. Both measured resection technique and gap balancing technique have been important surgical concepts in total knee arthroplasty (TKA). Modified gap technique has been reported to be beneficial for the intra-operative soft tissue balancing in posterior-stabilizing (PS) -TKA. On the other hand, we have found joint distraction force changed soft tissue balance measurement and medial knee instability would be more likely with aiming at perfect ligament balance at extension in modified gap technique. The medial knee stability after TKA was reported to essential for post-operative clinical result. We have developed a new surgical concept named as “medial preserving gap technique” for varus type osteoarthritic (OA) knees to preserve medial knee stability and provide quantitative surgical technique using tensor device. The purpose of this study was to compare post-operative knee stability between medial preserving gap technique (MPGT) and measured resection technique (MRT) in PS-TKA. Material & Method. The subjects were 140 patients underwent primary unilateral PS-TKA for varus type OA knees. The surgical technique was MPGT in 70 patients and MRT in 70 patients. There were no significant differences between two groups in the pre-operative clinical features including age, sex, ROM and deformity. Originally developed off-set type tensor device was used to evaluate both center gap and varus angle with 40 lbs. of joint distraction force. The extension gap preparation was identical in both group. In MPGT group, femoral component size and external rotation angle were adjusted depending on the differences of center gaps and varus angles between extension and flexion before posterior femoral condylar osteotomy. The knee stabilities at extension and flexion were assessed by stress radiographies; varus-valgus stress test with extension and stress epicondylar view with flexion, at one-month and one-year after TKA. We measured joint opening distance (mm) at medial and lateral compartment at both knee extension and flexion. Joint opening distances were compared between two groups using unpaired t-test, and the difference between medial and lateral compartment in each group was compared using paired t- test (p<0.05). Results. Joint opening distances at medial compartments with both extension and flexion were significantly smaller than lateral in both groups. There were no significant differences in join opening distance between two groups at medial compartment, but those at lateral were significantly smaller in MPGT than MRT with both knee extension and flexion. Discussion. In the present study, we found MPGT resulted in equal postoperative medial knee stability as in MRT, and superior to MRT as for the lateral knee stability. This finding would be the result of different femoral external rotation angle and femoral component size selection between two groups. We used the difference of varus angle and center gap between flexion and extension for the femoral component size selection and external rotation angle in MPGT. Quantitative surgical concept; MPGT, was found to be safer and feasible gap technique in PS-TKA to preserving medial knee stability and control lateral laxity in varus type OA knee. MPGT would be an advantageous gap technique to enhance clinical outcome

Introduction. To achieve well aligned and balanced knee is essential for the post-operative outcome in total knee arthroplasty (TKA). Gap balancing technique can adjust the bone cut depending on the soft tissue balance in addition to soft tissue releases. Therefore, gap balancing technique would be more advantageous in soft tissue balance comparing to measured resection technique (MRT) in which soft tissue balancing relayed on soft tissue releases alone. Nevertheless, the influence of surgical technique on the post-operative knee stability has not been fully investigated. Objective. We introduced a new surgical technique (medial gap technique: MGT) according to modified gap technique regarding medial knee stability as important. The intra-operative soft tissue balance and post-operative knee stability were compared between MGT and MRT in posterior-stabilized (PS) TKA for varus type osteoarthritic knees. Materials & Methods. Sixty varus type osteoarthritis knees were involved in this study. PS type TKAs (NexGen LPS flexR) were performed using MGT in 30 knees (MGT group) and MRT in 30 knees (MRT group). The extension gap was made in the same manners in both groups. Both femoral and tibial bone cuts were perpendicular to the mechanical axis. Medial soft tissue releases were limited until the spacer block with the thickness corresponding to the resected lateral tibial condyle could be inserted. After extension gap was prepared, OFR-tensorR was used to assess soft tissue balance (center gap, varus angle) at extension and flexion prior to posterior femoral condyle bone resection. Both differences of the center gap and varus angle between at extension and flexion were calculated and used for size selection and external rotation angle of femoral component in MGT. The final joint component gaps were evaluated using OFR-tensorR with both femoral trial in place and patello-femoral joint reduced at 0, 10, 30, 45, 60, 90, 120 and 135 degrees of flexion. Quantitative stress radiographies were performed at 1 month, 6 months and 1 year post-operatively to assess joint stability. Joint opening distance (mm) at both medial and lateral joint compartment were measured with knee extension and flexion. Each parameter was compared between MGT and MRT group using unpaired t-test (p<0.05). Results. Pre-operative factors showed no significant differences between 2 groups. The joint component gaps were significantly larger in MRT group from 45 to 135 degrees of flexion (Fig.1). The joint opening at the lateral compartment was significantly larger than medial at both knee extension and flexion in both groups. The joint openings were significantly larger bilaterally in MRT group comparing to MGT group at both extension and flexion (Fig.2, 3). Discussions. Medial instability has been reported as a possible reason for the persistent knee pain after TKA in the varus knees. We proposed a new surgical technique (MGT) not to deteriorate medial stability and allow lateral looseness in TKA. Post-operative knee stability was superior in MGT group comparing to MRT group from one month to one year after surgery. The difference of the intra-operative soft tissue balance might play an important role on the post-operative knee stability

Introduction. Modified gap technique has been reported to be beneficial for the intraoperative soft tissue balancing in posterior-stabilized (PS) -TKA. We have found intraoperative ligament balance changed depending on joint distraction force, which might be controlled according to surgeons' fells. We have developed a new surgical concept named as “medial preserving gap technique (MPGT)” to preserve medial knee stability and provide quantitative surgical technique according to soft tissue balance measurement using a tensor device. The purpose of this study was to compare 3-years postoperative knee stability after PS-TKA in varus type osteoarthritic (OA) knees between MPGT and measured resection technique (MRT). Material & Method. The subjects were 94 patients underwent primary unilateral PS-TKA for varus type OA knees. The surgical technique was MPGT in 47 patients and MRT in 47 patients. An originally developed off-set type tensor device was used to evaluate intraoperative soft tissue balance. In MPGT, medial release was limited until the spacer block corresponding to the bone thickness from proximal lateral tibial plateau could be easily inserted. Femoral component size and external rotation angle were adjusted depending on the differences of center gaps and varus angles between extension and flexion before posterior femoral condylar resection. The knee stabilities at extension and flexion were assessed by stress radiographies at 1 and 3 years after TKA; varus-valgus stress test at extension and stress epicondylar view at flexion. We measured medial and lateral joint openings (MJO, LJO) at both knee extension and flexion. MJOs and LJOs at 2 time periods were compared in each group using paired t-test. Each joint opening distance was compared between 2 groups using unpaired t-test. The significance level was set as P < 0.05. Results. The mean extension MJOs at 1 and 3 years after TKA were 2.4, 2.6 mm in MPGT and 3.2, 3.1 mm in MRT respectively. The mean extension LJOs were 3.5, 3.5 mm in MPGT and 4.6, 4.5 mm in MRT. The mean flexion MJOs were 0.95, 0.77 mm in MPGT and 1.5, 1.2 mm in MRT, and the mean flexion LJOs were 2.2, 2.1 mm in MPGT and 3.0, 2.7 mm in MRT. MJOs were significantly smaller than LJOs in each group at 2 time periods. MJOs at extension and flexion, and LJOs at extension were significantly smaller in MPGT than MRT at 2 time periods. Discussion. Medial knee stabilities had been reported to be essential for postoperative clinical results. We reported medial compartment gap was more stable during mid-to-deep knee flexion in MPGT than MRT. MPGT provided the more stable intraoperative soft tissue balance than MRT in PS-TKA. MPGT was useful to preserve the higher medial knee stability than the lateral as well as MRT, and beneficial to enhance postoperative knee stabilities as long as 3-years after PS-TKA in varus OA knees. MPGT would be an objective and safer gap technique to enhance clinical outcomes

Objective. As the aging society progresses rapidly in Japan, the number of elderly patients underwent TKA is increasing. These elderly patients do not expect to do sports, but regain independency in the activity of daily living. Therefore, we measured basic ambulatory function quantitatively using 3m timed up and go (TUG) test. We clinically experienced patient with medially unstable knee after TKA was more likely to result in the unsatisfactory outcome. We hypothesized that post-operative knee stability influenced ambulatory function recovery after TKA. In this study, we evaluated ambulatory function and knee stability quantitatively, and analyzed the effect of knee stability on the ambulatory function recovery after TKA. Materials & Methods. Seventy nine patients with varus type osteoarthritic knees underwent TKA were subjected to this study. The mean age of surgery was 72.4 years old. Preoperative standing coronal deformity was 9.6 degrees in varus. TUG test results in less duration with faster ambulatory function. TUG (seconds) was measured at 3 time periods; pre-operatively, at hospital discharge and 1year after surgery. To standardize TUG recovery time during 1 year after TKA, we defined TUG recovery rate as the percentage of recovery time to the pre-operative TUG as shown in the following equation. TUG recovery rate (%) = (TUG pre-op –TUG 1y po) / TUG pre-op ×100. We also evaluated the knee stability at hospital discharge and 1year after surgery. The knee stability at extension and flexion were assessed by varus and valgus stress radiography using Telos (10kg) and stress epicondylar view with 1.5kg weight at the ankle respectively. Image analyzing software was used to measure joint separation distance (mm) at medial as medial joint opening (MJO) and at lateral as lateral joint opening (LJO) at both knee extension and flexion. (Fig.1). The sequential change of TUG was analyzed using repeated measures ANOVA (p<0.05). The influence of joint opening distances (MJO and LJO at extension and flexion) on TUG 1y po and TUG recovery rate were analyzed using simple linear regression analysis (p<0.05). Results. The mean TUGs were 13.4, 13.7 and 10.8 seconds pre-operatively, at hospital discharge and 1 year after TKA respectively. Significant decrease was found at 1 year after surgery. TUG pre-op did not show significant correlation to any joint openings. TUG 1y po was positively correlated with both flexion and extension MJO at hospital discharge. (Fig.2) TUG recovery rate negatively correlated to flexion-MJO at hospital discharge. (Fig.3). Discussions. The most interesting findings in the present study were that both flexion and extension MJO at hospital discharge were positively correlated with TUG 1y po and negatively correlated with TUG recovery rate. This indicated that early post-operative medial stability played an important role in the recovery of ambulatory function. The early post-operative medial instability would cause pain and deteriorate functional recovery after surgery. There is some disagreement regarding the importance of pursuing the perfect ligament balance, which would be more likely to result in medial instability. Consequently, surgeons should prioritize medial stability for better ambulatory functional recovery after TKA

Introduction. Mid-flexion stability is believed to be an important factor influencing successful clinical outcomes in total knee arthroplasty. The post of a posterior-stabilizing (PS) knee engages the cam in >60° of flexion, allowing for the possibility of paradoxical mid-flexion instability in less than 60° of flexion. Highly-conforming polyethylene insert designs were introduced as an alternative to PS knees. The cruciate-substituting (CS) knee was designed to provide anteroposterior stability throughout the full range of motion. Methods. As part of a prospective, randomized, five-year clinical trial, we performed quantitative stress x-rays on a total of 65 subjects in two groups (CS and PS) who were more than five years postoperative with a well-functioning total knee. Antero-posterior stability of the knee was evaluated using stress radiographs in the lateral position. A 15 kg force was applied anteriorly and posteriorly with the knee in 45° and 90° of flexion. Measurements of anterior and posterior displacement were made by tracing lines along the posterior margin of the tibial component and the posterior edge of the femoral component, which were parallel to the posterior tibial cortex. (Figures 1–4). Results. In both 45° and 90° of flexion, the PS group demonstrated significantly less total anterior/posterior displacement compared to the CS group, (45°: 7.33 mm vs 12.44 mm, p ≤ 0.0001, 90°: 3.54 mm vs. 9.74 mm, p ≤ 0.0001). (Figures 5,6) The only statistically significant outcomes score difference was seen with the KSS function score in the female subset, with the CS score lower (81.8) compared to the PS score (94.7). (Figure 7) All of the other scores, KSS pain/motion and KSS function scores, as well as the LEAS and FJS scores, were all similar statistically, as was the range of motion and the long axis x-ray alignment. Discussion & Conclusion. The post and cam posterior-stabilized knee has traditionally been thought to be the best choice for providing stability for knee replacement with PCL-insufficiency or sacrifice. However, this difference in stability as measured with stress xrays did not correlate with any detectible differences in any of the clinical outcomes measurements collected (Knee Society Score, Forgotten Joint Score, Lower Extremity Activity Scale) or in the range of motion or coronal alignment, with the exception of the female subgroup KSS function score. In summary, the CS knee demonstrates greater total antero-posterior laxity compared to the PS knee, as measured by stress radiographs, but there is not a strong correlation with clinical outcomes measurements. A greater number of subjects and/or a younger, higher demand population studied with this protocol might produce greater differences in the outcomes, especially in the FJS score. For any figures or tables, please contact the authors directly

Introduction

There are over ½ million total knee replacement (TKR) procedures performed each year in the United States and is projected to increase to over 3.48 million by 2030. Concurrent with the increase in TKR procedures is a trend of younger patients receiving knee implants (under the age of 65). These younger patients are known to have a 5% lower implant survival rate at 8 years post-op compared to older patients (65+ years), and they are also known to live more active lifestyles that place higher demands on the durability and functional performance of the TKR device. Conventional TKR designs increase articular conformity to increase stability, but these articular constraints decrease patient range of knee motion, often limiting key measures of femoral rollback, A/P motion, and deep knee flexion. Without this articular constraint however, many patients report TKR “instability” during activities such as walking and stair descent, which can significantly impede confidence of movement. Therefore, there is a need for a TKR system that can offer enhanced stability while also maintaining active ranges of motion.

Introduction

There are over one-half million total knee replacement (TKR) procedures performed each year in the United States and is projected to increase to over 3.48 million by 2030. Concurrent with the increase in TKR procedures is a trend of younger patients receiving knee implants (under the age of 65). These younger patients are known to have a 5% lower implant survival rate at 8 years post-op compared to older patients (65+ years), and they are also known to live more active lifestyles that place higher demands on the durability and functional performance of the TKR device. Conventional TKR designs increase articular conformity to increase stability, but these articular constraints decrease patient range of knee motion, often limiting key measures of femoral rollback, A/P motion, and deep knee flexion. Without this articular constraint however, many patients report TKR “instability” during activities such as walking and stair descent, which can significantly impede confidence of movement. Therefore there is a need for a TKR system that can offer enhanced stability while also maintaining active ranges of motion.

INTRODUCTION

The intact, healthy human knee joint is stable under anterior-posterior (AP) loading but allows for substantial internal-external (IE) laxity. In vivo clinical studies of the intact knee consistently demonstrate femoral rollback with flexion (Hill et al., 2000, Dennis et al., 2005). A tri-condylar, posterior stabilized (PS) total knee arthroplasty (TKA) with a rotating platform bearing (TKA-A) has been designed to address these characteristics of the intact knee. The third condyle is designed to guide the femoral component throughout the entire flexion arc (AP stability and femoral rollback with flexion), while the rotating platform bearing allows for IE rotation.

This study used a computer model to compare the AP and IE laxity of a new TKA-A to that of two clinically established TKAs (TKA-B: rotating PS TKA, TKA-C: fixed PS TKA) and to demonstrate improvements in AP stability, IE rotation, and femoral rollback.

Introduction

Patients undergoing a total knee arthroplasty (TKA) are now living longer and partaking in more active lifestyles. They expect a high level of post-operative function and long term durability of their implant.

Using electromyography (EMG) analysis helps further explain biomechanical findings by giving insight as to what is occurring at the level of the muscles. Normal biomechanics are not restored post-TKA as patients have reduced knee flexion and weakened quadriceps muscles compared to their healthy peers.

INTRODUCTION. Understanding the biomechanics of the anatomical knee is vital to innovations in implant design and surgical procedures. The anterior – posterior (AP) laxity is of particular importance in terms of functional outcomes. Most of the data on stability has been obtained on the unloaded knee, which does not relate to functional knee behavior. However, some studies have shown that AP laxity decreases under compression (1) (2). This implies that while the ligaments are the primary stabilizers under low loads, other mechanisms come into play in the loaded knee. It is hypothesized this decreased laxity with compressive loads is due to the following: the meniscus, which will restrain the femur in all directions; the cartilage, which will require energy as the femur displaces across the tibial surface in a plowing fashion; and the upwards slope of the anterior medial tibial plateau, which stabilizes the knee by a gravity mechanism. It is also hypothesized that the ACL will be the primary restraint for anterior tibial translation. METHODS. A test rig was designed where shear and compressive forces could be applied and the AP and vertical displacements measured (Figure 1). The AP motion was controlled by the air bearings and motor, allowing for the accurate application of the shear force. Position and force data were measured using load cells, potentiometers, and a linear variable differential transducer. Five knee specimens less than 60 years old and without osteoarthritis (OA), were evaluated at compressive loads of 0, 250, 500, 750 N, with the knee at 15° flexion. Three cycles of shear force at ±100 N constituted a test. The intact knee was tested, followed by testing after each of the following resections: LCL, MCL, PCL, ACL, medial meniscus, and lateral meniscus. RESULTS. The average displacement of the tibia without load was 6.17 mm anterior and −4.92 mm posterior. Under load the posterior translation of the tibia was reduced essentially to zero. After ACL resection, the anterior tibial displacement increased substantially, with a further increase after medial meniscus resection. Cartilage deformation had a minimal effect. DISCUSSION. The hypotheses that the ACL and the upwards tibial slope would provide stability under load were validated. The ACL was essential under all load conditions because the posterior tibial surface was flat (figure 2). The medial meniscus provided vertical stability, as a space buffer (figure 3), and in two specimens under load it provided the same restraint as the ACL (figure 2). The experiment was limited by lack of muscle action, the number of specimens, and a single flexion angle. SIGNIFICANCE. The test rig and methodology had capabilities exceeding those of previous work in determining the mechanisms of AP knee stability under load due to its frictionless air bearings. The results have application ranging from sports medicine to total knee design. The stabilizing effect of the tibial slope seen here validates tibial osteotomies for improved stability. The importance of reproducing ACL function in total knee design is emphasized. For figures/tables, please contact authors directly.

Background. In recent literatures, medial instability after TKA was reported to deteriorate early postoperative pain relief and have negative effects on functional outcome. Furthermore, lateral laxity of the knee is physiological, necessary for medial pivot knee kinematics, and important for postoperative knee flexion angle after cruciate-retaining total knee arthroplasty (CR-TKA). However, the influences of knee stability and laxity on postoperative patient satisfaction after CR-TKA are not clearly described. We hypothesized that postoperative knee stability and ligament balance affected patient satisfaction after CR-TKA. In this study, we investigated the effect of early postoperative ligament balance at extension on one-year postoperative patient satisfaction and ambulatory function in CR-TKAs. Materials & Methods. Sixty patients with varus osteoarthritis (OA) of the knee underwent CR-TKAs were included in this study. The mean age was 73.6 years old. Preoperative average varus deformity (HKA angle) was 12.5 degrees with long leg standing radiographs. The knee stability and laxity at extension were assessed by stress radiographies; varus-valgus stress X-ray at one-month after operation. We measured joint separation distance (mm) at medial compartment with valgus stress as medial joint opening (MJO), and distance at lateral compartment with varus stress as lateral joint opening (LJO) at knee extension position. To analyze ligament balance; relative lateral laxity comparing to the medial, varus angle was calculated. New Knee Society Score (NKSS) was used to evaluate the patient satisfaction at one-year after TKA. We measured basic ambulatory functions using 3m timed up and go test (TUG) at one-year after surgery. The influences of stability and laxity parameters (MJO, LJO and varus angle at extension) on one-year patient satisfaction and ambulatory function (TUG) was analyzed using single linear regression analysis (p<0.01). Results. MJOs at knee extension one-month after TKA negatively correlated to patient satisfaction (r=−0.37, p<0.01) and positively correlated to TUG time (r=0.38, p<0.01). LJOs at knee extension had no statistically significant correlations to patient satisfaction and TUG. The extension varus angle had significant positive correlation with patient satisfaction (r=0.40, p<0.01). Discussions. In our study, we have found significant correlations of the early postoperative MJOs at extension to postoperative patient satisfaction and TUG one-year after CR-TKA. Our results suggested that early postoperative medial knee stabilities at extension were important for one-year postoperative patient satisfaction and ambulatory function in CR-TKA. Other interest finding was that postoperative patient satisfaction was positively correlated with extension varus angle. This finding suggested that varus ligament balance; relative lateral laxity to medial stability, was beneficial for postoperative patient satisfaction after CR-TKA. Intra-operative soft tissue balance had been reported to significantly affect postoperative knee stabilities. Therefore, with our findings, surgeons might be better to manage intra-operative soft tissue balance to preserve medial stability at extension with permitting lateral laxity, which would enhance patient satisfaction and ambulatory function after CR-TKA for varus type OA knee. Conclusion. Early postoperative medial knee stability and relative lateral laxity would be beneficial for patient satisfaction and function after CR-TKA

Patient reported outcome measures (PROMs) after total knee arthroplasty (TKA) are typically used to assess longitudinal change in pain and function after total knee arthroplasty (TKA). The Patient's Knee Implant Performance (PKIP) score was developed to evaluate outcomes more broadly including function, stability, confidence, and satisfaction. Although validated in patients having a primary TKA, the PKIP has not been evaluated as an outcome measure for patients having revision TKA. This study examined patient outcomes at one year following primary and revision TKA measured using the PKIP, compared to Oxford Knee Scores. A retrospective analysis of pre-operative and one-year post-operative outcomes was completed for 39 patients (21 female) who had primary (n=27) or revision (n=12) TKA with a single surgeon between 2017 and 2020. The mean age was 69.2±7.4 years, and mean weight 87.4± 5.1kg. The change over time and correlation between the self-reported outcome measures was evaluated. There was a significant improvement in the PKIP overall score at the 12-month follow-up (32± 13 v 69± 15, p= <0.001), with no significant difference between groups (3.3 points, p=0.50). Among the PKIP sub-scores, there was a significant improvement in knee confidence (3.5±2 vs 7.7±2; p<0.001), stability (3.4±2 vs 7.4±3; p<0.001) and satisfaction (2.5±1.7 vs 6.6±3, p<0.001). Between group differences in PKIP sub-scores one year after surgery were small and non-significant. For all patients, the OKS and PKIP scores were moderately correlated before surgery (r=0.64, p=<0.05), and at 1 year after surgery (r=0.61, p= <0.001). Significant improvements in knee confidence, stability, and satisfaction one year after TKA were identified from the PKIP responses, with no significant difference between primary and revision surgery. The moderate correlation with the OKS suggests these questionnaires measure difference constructs and may provide complementary outcome information in this patient cohort

Anterior cruciate ligament (ACL) rupture with associated meniscal pathology commonly occurs in a young, active population. Preserving a greater proportion of the meniscus may improve long-term outcomes by maintaining shock absorption and knee stability. However, meniscal repair procedures involve longer healing and rehabilitation than meniscal debridement, which could affect return to work and activity. The purpose of this study was to examine the functional outcomes and quality of life scores through two years in patients undergoing ACL reconstruction (ACL-R) who had meniscal repair, meniscal debridement, or no meniscal damage at the time of reconstruction. Data for 1814 skeletally mature patients with isolated primary ACL-R was prospectively collected at a single centre from January 2010 to December 2015. Functional testing of operative to non-operative limb performance was completed at one- and two-years following surgery and included single-leg balance, single-leg hop for distance, timed six-meter hop, triple-hop for distance, and triple cross-over hop for distance. ACL-Quality-of-life questionnaires (ACL-QoL) were completed pre-operatively and at 1- and 2-years post-operatively. Descriptive statistics were completed for patient demographics and intra-operative pathology. Unpaired t-tests using 95% confidence intervals were conducted to compare groups. The patient cohort was 45% female, with a mean age of 31 years (SD 11, range 14–66). Meniscal injury was detected in 1229/1814 knees (67.8%). There were 729 debridements and 538 repairs performed. Graft choice was hamstring autograft in 85.8% of cases, bone-patellar-tendon-bone autograft in 2.5%, allograft in 10.1% and other graft types in 1.5%. Pre-operative ACL-QoL scores were 29 and 28.5 for knees without and with meniscal damage, respectively (p>0.05). Of 1814 patients, 1269 (69.9%) completed the ACL-QoL at the two-year appointment, and 1225 (67.5%) completed the functional testing. At two years post-operative, patients with no meniscal damage at surgery demonstrated superior limb symmetry performance on triple-hop for distance compared to patients with meniscal damage (98.4% vs 97.1%, p < 0 .05, CI 0.1–2.5%). No other functional testing parameters showed statistical significance. There was no difference in functional outcome between patients undergoing an isolated meniscal repair versus debridement at one- or two-years. ACL-QoL scores were statistically significantly higher at one- and two-years post-operative for patients without meniscal damage (1-year: 73 vs 70.2, p < 0 .05, CI 0.51–5.1, 2-years: 79.2 vs 76.1, p < 0 .05, CI 0.79–5.4). ACL-QoL scores were minimally higher for isolated meniscal debridement compared to isolated meniscal repair at both time points (1-year: 71.4 vs 68, p < 0 .05, CI 0.4–6.4, 2-years: 78.3 vs 74, p < 0 .05, CI 1.3–7.3). Functional outcomes do not differ at one or two years post-operatively for patients undergoing meniscal repair versus debridement concomitant with ACL-R. Quality of life scores were statistically significantly higher for the patients with no meniscal pathology at both one- and two-years post-operative. ACL-QoL scores were also statistically significantly different for the meniscal repair and debridement groups however these differences are unlikely to be clinically significant. Extended follow-up is needed to determine if the differences detected in ACL-QoL scores are sustained over time, as well as the long-term role of meniscal injury on functional outcomes

Objective. The goal of total knee arthroplasty (TKA) is to achieve a stable and well-aligned tibiofemoral and patello-femoral (PF) joint, aiming at long-term clinical patient satisfaction. The surgical principles of both cruciate retaining (CR) and posterior stabilized (PS) TKA are accurate osteotomy and proper soft tissue balancing. We have developed an offset-type tensor, and measured intra-operative soft tissue balance under more physiological joint conditions with femoral component in place and reduced PF joint. In this study, we measured intra-operative soft tissue balance and assessed the post-operative knee joint stability quantitatively at one month, six months and one year after surgery, and compared these parameters between CR and PS TKAs. Material and Method. Sixty patients with varus osteoarthritis of the knee underwent TKAs (30 CR TKAs: CR and 30 PS TKAs: PS). Mean varus deformity in standing position was 11.1 degrees in CR, and 12.6 degrees in PS. All TKAs were performed by a single surgeon with measured resection technique. The external rotation of posterior femoral condyle osteotomy was performed according to surgical epicondylar axis in pre-operative CT. We measured intra-operative soft tissue balance using an offset-type tensor with 40 lbs of joint distraction force at 0, 10, 30, 45, 60, 90, 120 and 135 degrees of flexion. The joint component gap (mm) and varus angle (degrees) were measured at each flexion angles. One month, six months and one year after surgery, we evaluated the knee stability at extension by varus and valgus stress radiography using Telos (10kg) and at flexion by epicondylar view with 1.5kg weight at the ankle. We measured joint separation distance at medial as medial joint looseness (MJL) and at lateral as lateral joint looseness (LJL). Intra-operative measurements and post-operative joint stabilities were compared between CR and PS using unpaired t-test. The change of joint looseness in each group was analyzed using repeated measures ANOVA. Result. Joint gap kinematics was different between CR and PS (Fig. 1). Joint component gap in PS were significantly higher than CR from 30 to 120 degrees of flexion. Post-operative MJL and LJL changes are shown in figure 2 with knee extension, and in figure 3 with knee flexion. PS showed significantly higher joint looseness than CR at both extension and flexion at three time periods after surgery. There were no significant post-operative changes in both MJL and LJL in CR and PS TKAs. Discussion. We found significant differences in gap kinematics and also in the one year post-operative joint stability between CR and PS. The different characteristics of the intra-operative soft tissue balance between CR and PS TKAs would be a possible reason for the differences in the post-operative knee stability. Our results suggested that TKAs performed by measured resection technique have significantly higher joint stability with CR TKAs comparing to PS TKAs. These findings would be important issues in choosing prosthesis and surgical technique. Conclusion. With measured resection technique, CR TKAs had more consistent joint gap kinematics and higher joint stability after surgery comparing to PS TKAs

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

Introduction. Ligament reconstruction following knee soft tissue injuries, such as posterior cruciate ligament (PCL) tears, aim to restore normal joint function and motion; however, persistant pathomechanical joint behavior indicates that there is room for improvement in current reconstruction techniques. Increased attention is being directed towards the roles of secondary knee stabilizers, in an attempt to better understand their contributions to kinematics of knees. The objective of this study is to characterize the relative biomechanical contributions of the posterior oblique ligament (POL) and the deep medial collateral ligament (dMCL) in PCL-deficient knees. We hypothesized that, compared with the POL, the dMCL would have a more substantial role in stabilizing the medial side of the knee, especially in flexion (slack POL). Methods. Seven fresh-frozen cadaveric knees were used in this study (age 40–62, 4 female, 3). Specimens were potted and mounted onto a VIVO joint motion simulator (AMTI). Once installed, specimens were flexed from 0 to 90 degrees with a 10 N axial load and all remaining degrees of freedom unconstrained. This was repeated with (a) a 67 N posterior load, (b) a 2.5 Nm internal or external rotational moment and (c) a 50 N posterior load and 2.5 Nm internal rotational moment applied to the tibia. During each resulting knee motion, the relative AP kinematics of the dMCL tibial insertion (approximated as the most medial point of the proximal tibia) with respect to the flexion axis of the femur (the geometric center axis, based on the posterior femoral condyles) were calculated at 0, 30, 60 and 90 degrees of flexion. These motions were repeated following dissection of the PCL and then further dissection of either medial ligament (4 POL, 3 dMCL). The changes in AP kinematics due to ligament dissection were analyzed using three-way repeated-measures ANOVA with a significance value of 0.05. Results. Dissection of the dMCL or POL did not result in a statistically significant increase in the posterior displacement of the medial tibial point under posterior directed force, internal rotation moments, or the combined posterior force plus internal rotation moment. Interestingly, under external moment loading, there was a statistically significant increase in anterior displacement of the medial tibia at all flexion angles after POL dissection, by up to 3.0+/−2.6 mm at 0 degrees. Dissection of the dMCL, however, did not have a significant affect. Conclusion. Our results showed that neither the POL nor dMCL play a significant role in resisting posterior tibial displacements on the medial side of a PCL deficient knee. Of the two, the POL appears to have a greater contribution towards preventing anterior translations, particularly when in extension. This finding is rational based on the anatomical path of this ligament wrapping around the femoral medial condyle under external rotational moments. In contrast with our hypothesis, it was observed that the dMCL had less of an effect on medial knee stability. Contributions of these ligaments could be further investigated using more complicated loading, such as those more representative of activities of daily living

Alignment of total joint replacement in the valgus knee can be done readily with intramedullary alignment and hand-held instruments. Intramedullary alignment instruments usually are used for the femoral resection. The distal femoral surfaces are resected at a valgus angle of 5 degrees. A medialised entry point is advised because the distal femur curves toward valgus in the valgus knee, and the distal surface of the medial femoral condyle is used as reference for distal femoral resection. In the valgus knee, the anteroposterior axis is especially important as a reliable landmark for rotational alignment of the femoral surface cuts because the posterior femoral condyles are in valgus malalignment, and are unreliable for alignment. Rotational alignment of the distal femoral cutting guide is adjusted to resect the anterior and posterior surfaces perpendicular to the anteroposterior axis of the femur. In the valgus knee this almost always results in much greater resection from the medial than from the lateral condyle. Intramedullary alignment instruments are used to resect the proximal tibial surface perpendicular to its long axis. Like the femoral resection, resection of the proximal tibial surface is based on the height of the intact medial bone surface. After correction of the deformity, ligament adjustment is almost always necessary in the valgus knee. Stability is assessed first in flexion by holding the knee at 90 degrees and maximally internally rotating the extremity to stress the medial side of the knee, then maximally externally rotating the extremity to evaluate the lateral side of the knee. Medial opening greater than 4mm, and lateral opening greater than 5mm, is considered abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be abnormally tight. Stability is assessed in full extension by applying varus and valgus stress to the knees. Medial opening greater than 2mm is considered to be abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be too tight. Release of tight structures should be done in a conservative manner. In some cases, direct release from bone attachment is best (popliteus tendon); in others, release with pie-crusting technique is safe and effective. In knees that are too tight laterally in flexion, but not in extension, the LCL is released in continuity with the periosteum and synovial attachments to the bone. When this lateral tightness is associated with internal rotational contracture, the popliteus tendon attachment to the femur is also released. The iliotibial band and lateral posterior capsule should not be released in this situation because they provide lateral stability only in extension. The only structures that provide passive stability in flexion are the LCL and the popliteus tendon complex, so knees that are tight laterally in flexion and extension have popliteus tendon or LCL release (or both). Stability is tested after adjusting tibial thickness to restore ligament tightness on the lateral side of the knee. Additional releases are done only as necessary to achieve ligament balance. Any remaining lateral ligament tightness usually occurs in the extended position only, and is addressed by releasing the iliotibial band first, then the lateral posterior capsule, if needed. The iliotibial band is approached subcutaneously and released extrasynovially, leaving its proximal and distal ends attached to the synovial membrane. In knees initially too tight laterally in extension, but not in flexion, the LCL and popliteus tendon are left intact, and the iliotibial band is released. If this does not loosen the knee enough laterally, the lateral posterior capsule is released. The LCL and popliteus tendon rarely, if ever, are released in this type of knee. Finally, the tibial component thickness is adjusted to achieve proper balance between the medial and lateral sides of the knee. Anteroposterior stability and femoral rollback are assessed, and posterior cruciate substitution is done, if necessary, to achieve acceptable posterior stability

Chondral defects on the patella are a difficult problem in the young active patient and there is no consensus on how to treat these injuries. Fresh osteochondral allografts are a valid option for the treatment of full-thickness osteochondral defects and can be used to restore joint function and reduce pain. The primary purpose of this study was to investigate the clinical and subjective outcomes of a series of patients following fresh osteochondral allograft transplantation for isolated chondral defects of the patella. A series of 5 patients underwent surgery using an open approach for graft transplantation. A strict protocol for the allograft tissue was followed. Transplant recipients must be aged <60, have a full-thickness, isolated chondral lesion and have failed previous traditional treatments. The fresh allografts are hypothermically stored at 4°C in X-VIVO10 media for up to 30 days to maintain cartilage viability. Pre- and post-operative clinical measures including knee stability, range of motion, and quadriceps girth were completed. Post-operative plain radiographs were completed including weight-bearing AP, lateral and skyline views. Patient-centred outcome measures including the Knee Osteoarthritis Outcome Score (KOOS) and the Knee Society Score (KSS) were gathered a minimum of 1-year post-operative. Descriptive and demographic data were collected for all patients. A paired t-test was employed to determine the difference between the pre-operative and post-operative outcomes. All patients were female, with a mean age of 27.4 (SD 3.65). Knee ligament stability was similar pre- and post-operatively. Knee ROM assessment of flexion and extension demonstrated a less than 10° increase from pre to post-operative. Quadriceps girth measurements demonstrated a mean change of 0.5 cm from pre- to post-operative for the surgical limb. Post-operative radiographs demonstrated incorporation of the graft in 4/5 cases within 6-months of surgery. One patient developed fragmentation of the graft after 18-months, and one patient had a subsequent trochleoplasty for persistent pain. The mean KOOS domain scores demonstrated significant improvement (p<0.05) as follows: Symptoms pre-op = 28.57, post-op = 55; Pain pre-op 28.89, post-op = 57.22; ADLs pre-op = 48.92, post-op = 66.18; Sports/Recreation pre-op = 6, post-op = 32; and QoL pre-op = 12.5, post-op = 42.5. Mean pre-op surgical versus non-surgical limb KSS scores were 107.4 and 179 respectively. The mean post-op surgical versus non-surgical limb KSS scores were 166 and 200. Isolated chondral defects of the patella can cause substantial pain, reduced function, and can be challenging to address surgically. This series of 5 cases demonstrated improved function, KOOS and KSS for 4/5 patients. To our knowledge this is a novel biological procedural technique for this problem, which has shown promising results making it a viable treatment option for young active patients with osteochondral defects of the patella

Introduction. The Segond's fracture is described as a cortical avulsion of the lateral tibial plateau at the site of insertion of the middle third of the lateral capsular ligament. The Segond's fracture is usually associated with a tear of the Anterior Cruciate Ligament (ACL) and it is considered as an indirect radiological sign of complete rupture of the ACL. However there are no studies investigating the effect of a Segond's fracture on the kinematic of the knee especially on the rotatory instability and Pivot Shift (PS) phenomenon. The purpose of this study is to investigate the effect of a Segond's fracture on the kinematic of the knee with the use of navigation and the PS test. Methods. Ten whole fresh-frozen cadavers were used. A navigator (2.0 Orthopilot Navigation System, BBraun Aesculap, Tuttlingen, Germany) was used to measure maximum manual Anterior Tibial Translation (ATT) at 30°, 60° and 90° of flexion, maximum manual Internal Rotation (IR) and maximum manual External Rotation (ER) at 0°, 15°, 30°, 45° and 90° of flexion. All procedures were performed three times and the mean value taken as the final result in each case. Moreover a PS test was performed by the senior, most experienced, surgeon, and graded as mild (gliding), moderate (jerk) and severe (subluxation). Navigation measurements and PS tests were performed in each knee with ACL intact, after arthroscopic cutting of the entire ACL and after a Segond's fracure was produced by exposing the antero lateral compartment of the knee underneath the ileo-tibial tract. Statistical analysis was performed using ANOVA 1-way and MANOVA tests and value for statistical analysis was set at p<0.05. Results. Navigation procedure: Cutting the whole ACL resulted in a significant increase of ATT at 30° and 60° of flexion, with no significant effect on IR and ER. Producing the Segond's fracure resulted in a significant increase of ATT at 60° and 90° of flexion, in a significant increase of IR at 30°, 45° and 60° of flexion with no significant effect on ER. PS: The PS was clinically undetectable in all knees with ACL intact. After cutting the ACL it continued to be undetectable in two cases, mild positive in six cases and moderate in two. The addition of the Segond's fracture resulted in an increase of the PS in all cases with a moderate grade detected in three and severe in seven. Conclusions. Despite the limitations of this study, which include manual loads applied to the knee during navigation measurements and subjective evaluation of the PS, the results of this cadaver study indicate that the Segond's fracture has a significant effect on knee stability especially on rotational stability, which is functionally the most important in case of ACL tear. Therefore, in case of an acute ACL tear, when a Segond's fracture is radiologically detected and an ACL reconstruction is performed, an inspection of the lateral compartment with repair of capsule and fixation of the fracture could be advisable in order to better restore knee stability

Adequate soft tissue balance at the time of total knee arthroplasty (TKA) prevents early failure. In cases of varus deformity, once the medial osteophytes have been resected, a progressive release of the medial soft tissue sleeve (MSS) from the proximal medial tibia is needed to achieve balance. The “classic” medial soft tissue release technique, popularised by John Insall et al., consists of a sharp subperiosteal dissection from the proximal medial tibia that includes superficial and deep medial collateral ligament (MCL), semimembranosus tendon, posteromedial capsule, along with the pes anserinus tendons, if needed. However, this technique allows for little control over releases that selectively affect the flexion and extension gaps. When severe deformity is present, an extensive MSS release can cause iatrogenic medial instability and the need to use a constrained implant. It has been suggested that the MSS can be elongated by performing selective releases. This algorithmic approach includes the resection of the posterior osteophytes as the initial balancing gesture. If additional MSS release is necessary in extension, a subperiosteal release of the posterior aspect of the MSS is performed with electrocautery, detaching the posterior aspect of the deep MCL, posteromedial capsule and semimembranosus tendon for the proximal and medial tibia. Dissection is rarely extended more than 1.5 cm distal to the joint line. If additional release is necessary in extension, the medial compartment is tensioned with a laminar spreader and multiple needle punctures (generally less than 8) are performed in the taut portion of the MSS using an 18G or 16G needle. If additional release is necessary to balance the flexion gap, multiple needle punctures in the anterior aspect of the MSS are performed. This stepwise approach to releasing the MSS in a patient with a varus deformity allows the surgeon to target areas that selectively affect the flexion and extension gaps. Its use has resulted in diminished use of constrained TKA constructs and subsequent cost savings. We have not seen an increase in post-operative instability developing within the first post-operative year. We recommend caution when implementing this technique. Unlike the traditional release method, pie-crusting is likely technique-dependent and failure can occur within the MCL itself. Due to the critical importance of the MCL in knee stability, further research and continuous follow up of patients undergoing TKA with this technique are warranted. Intra-operative sensing technology may be useful to quantitate the effect of pie-crusting on the compartmental loads and overall knee balance