Lateral Laxity Research Articles

Medial center of rotation and 90-degree lateral laxity improve patient-reported outcomes in posterior cruciate retaining total knee arthroplasty

ObjectivesPhysiologic knee kinematics are crucial for successful total knee arthroplasty (TKA) but are often not replicated. Using a medial stabilizing technique (MST) minimizes bone resection but results in lateral laxity. This study aimed to investigate the effects of lateral laxity on knee kinematics and symptoms after TKA. MethodsMobile-bearing cruciate-retaining MST-TKA was performed on 40 knees using a navigation system. In the kinematic analysis, the anteroposterior (AP) translations of the medial femoral condyle (MFC) and lateral femoral condyle (LFC), femoral rotation angles, and medial and lateral component gaps were recorded every 0.1 s. These data were extracted from the software from 0° to 120° flexion in 10° increments. Kinematics were classified as the medial center of rotation (MCR) or non-MCR between 0° to 90° of flexion. Lateral laxity was calculated by subtracting the medial component gap from the lateral component gap. The final follow-up Knee Injury and Osteoarthritis Outcome Scores (KOOS) were evaluated. The relationships between the pre and postoperative kinematics and between postoperative lateral laxity and kinematics were assessed using Spearman’s correlation coefficients. Finally, the correlation between postoperative lateral laxity and KOOS symptoms was evaluated using linear regression analysis. ResultsPreoperative kinematics, including AP translation of the MFC and LFC and femoral rotation, correlated with postoperative kinematics (all P < 0.001). Additionally, postoperative lateral laxity correlated with postoperative AP translation of the MFC, LFC, and femoral rotation (all P < 0.001). Furthermore, the receiver operating characteristic analysis indicated a cutoff value of 0.9 mm on postoperative lateral laxity at 90° flexion for postoperative MCR (P < 0.001). Postoperative lateral laxity at 90° flexion was significantly correlated with KOOS symptoms (β = 0.465, P = 0.025). ConclusionPreoperative kinematics and postoperative lateral laxity correlated with postoperative kinematics after MST-TKA. Postoperative lateral laxity greater than 0.9mm at 90° flexion was associated with physiological kinematic motion, leading to fewer knee symptoms in the PROMs. The key to successful TKA was considered to be keeping the asymmetric gap balance with physiological lateral laxity, rather than the conventional symmetrical gap balance. Level of Evidence Level IIIRetrospective study.

Impact of Joint Laxity on 2-Year KOOS Outcomes of Posterior Stabilized Total Knee Arthroplasty.

The objective of this study was to determine relationships between intraoperative posterior cruciate ligament (PCL) sacrificing posterior stabilized (PS) total knee arthroplasty (TKA) laxity measurements throughout flexion and patient outcomes at 2 years post-TKA and to define clinically relevant laxity thresholds to optimize patient outcomes.In a single-surgeon study, PCL sacrificing TKA using a robotics-assisted platform with a digital joint tensioning device was performed in 115 knees in 115 patients. Final intraoperative joint laxity was recorded, and 2-year Knee Injury and Osteoarthritis Outcome Scores (KOOSs) were obtained. A Simulated Annealing optimization algorithm was used to identify medial and lateral laxity windows which maximized the 2-year KOOS pain score. Wilcoxon nonparametric tests were used to compare outcomes between groups.Significant associations were found between intraoperative joint laxity and 2-year KOOS pain outcomes throughout flexion. Clinically relevant laxity windows were defined medially and laterally in mid-flexion and flexion for improved outcomes, whereas only a lateral laxity window could be defined in extension. When all laxity windows were satisfied, a 14.5-KOOS point improvement was found (97.2 vs. 77.8, p = 0.0060) compared to knees which did not satisfy any window. Improvements in Activities of Daily Living (Δ8.8, p = 0.0143), Sports (Δ22.5, p = 0.0108), and Quality of Life (Δ18.7, p = 0.0011) KOOS subscores were also found in knees which satisfied all windows versus 0-1 window.Intraoperative joint laxity is associated with postoperative outcomes in a PS knee design, wherein patients balanced within identified laxity targets reported improved outcomes over those that did not. Clinically significant thresholds were defined and were predominately found in mid-flexion and flexion for medial and lateral laxity. When target windows were combined further improved outcomes were identified.

An Advanced Knee Simulator Model Can Reproducibly Be Used for Ligament Balancing Training during Total Knee Arthroplasty.

A critical and difficult aspect of total knee arthroplasty (TKA) is ligamentous balancing for which cadavers and models have played a large role in the education and training of new arthroplasty surgeons, although they both have several shortcomings including cost, scarcity, and dissimilarity to in vivo ligament properties. An advanced knee simulator (AKS) model based on computed tomography (CT) scans was developed in the setting of these challenges with cadavers and previous models. In this study, we compared the ligament balancing between AKS and human cadaveric knees to assess the validity of using the AKS for ligament balancing training during TKA. A CT scan of a TKA patient with varus deformity was used to design the AKS model with modular components, using three-dimensional printing. Three fellowship-trained arthroplasty surgeons used technology-assisted TKA procedure to plan and balance three cadaver knees and the AKS model. Medial and lateral laxity data were captured using manual varus and valgus stress assessments for cadavers and the model in an extension pose (10 degrees of flexion from terminal extension) and between 90 and 95 degrees for flexion. After preresection assessments, surgeons planned a balanced cruciate-retaining TKA. Following bony cuts and trialing, extension and flexion ligament laxity values were recorded in a similar manner. Descriptive statistics and Student's t-tests were performed to compare the cadavers and model with a p-value set at 0.05. Preresection medial/lateral laxity data for both extension and flexion were plotted and showed that the highest standard deviation (SD) for the cadavers was 0.67 mm, whereas the highest SD for the AKS was 1.25 mm. A similar plot for trialing demonstrated that the highest SD for the cadavers was 0.6 mm, whereas the highest SD for the AKS was 0.61 mm. The AKS trialing data were highly reproducible when compared with cadaveric data, demonstrating the value of the AKS model as a tool to teach ligament balancing for TKA and for future research endeavors.

Large angular correction of arithmetic coronal alignment is associated with residual lateral laxity after total knee arthroplasty in varus knees for Japanese patients.

One of the most common types of coronal plane alignment of the knee (CPAK) is type I, which is characterised by varus alignment and apex distal joint line obliquity. The purpose of this study was to evaluate the association of changes in arithmetic hip-knee-ankle angle (aHKA) with both postoperative joint laxity and patient-reported outcome measures (PROMs) in patients with CPAK type I following mechanical alignment (MA) total knee arthroplasty (TKA). Of 111 consecutive knees in 92 patients with osteoarthritis who underwent primary TKA, 80 knees (72.0%) with CPAK type I phenotype preoperatively were evaluated. All TKAs were performed to achieve neutral MA by a medial stabilising gap balancing technique. Pre- to postoperative change in aHKA was defined as ΔaHKA. The 80 CPAK type I knees were divided into a larger ΔaHKA group (>7°) and a smaller ΔaHKA group (≤7°). PROMs, including the Knee Society Score and Forgotten Joint Score-12, were assessed before and 2 years after surgery. Pre- and postoperative joint laxity was assessed using a Telos arthrometer. Twenty-two knees showed a larger ΔaHKA, and postoperative lateral joint laxity in varus stress was significantly greater in these patients than in those with a smaller ΔaHKA (6.8° vs. 4.5°, p = 0.006). There were no significant differences between the groups in PROMs (p = n.s.). Postoperative lateral laxity was associated with larger aHKA changes than smaller aHKA changes in CPAK type I knees after TKA. However, no statistically significant differences in PROMs were found according to the amount of change in aHKA. Level III.

Intraoperative lateral laxity greater than 4° is associated with inferior functional improvement in posterior-stabilised total knee arthroplasty.

The study aimed to determine the impact of intraoperative lateral laxity at extension on clinical and functional outcomes 1 year after posterior-stabilised total knee arthroplasty (PS-TKA). In total, 91 varus-type osteoarthritic knees that underwent PS-TKA using the medial preservation gap technique were included. After the femoral trial component placement and patellofemoral joint reduction, the soft-tissue balance was assessed using an offset-type tensor with a 40-lb joint-distraction force. Patients were divided into the following three groups according to the intraoperative lateral laxity at extension (i.e., varus ligament balance) using the mean ± 1 standard deviation: Groups A, ≤0°; B, 0-4°; and C, >4°. The 2011 Knee Society Score (KSS) and 3-m timed up-and-go test (TUG) time 1-year postoperatively, and their improvements were compared among the groups. While significant improvements were observed in all subscales of the 2011 KSS and TUG post-TKA (p < 0.05), the improvement of functional activities and TUG time were significantly lower in Group C than in Group B (p < 0.05). However, no significant differences were observed in symptom improvement, patient satisfaction or patient expectation scores among the groups. An excessive lateral laxity (varus angle) >4° at extension was associated with lower improvement in functional ability 1-year postoperatively. Therefore, excessive intraoperative lateral laxity should be avoided in PS-TKA. Level IV.

Lateral Laxity in Flexion Influences Patient-Reported Outcome After Total Knee Arthroplasty

IntroductionSlight lateral laxity exists in normal knee especially in flexion. The lateral laxity in flexion has possibility to affect the outcome after total knee arthroplasty (TKA).PurposeThe purpose of this study was to determine how intraoperative laxity in flexion affects patient-reported outcome after total knee arthroplasty.MethodsWe retrospectively analysed 98 knees with osteoarthritis that underwent total knee arthroplasty. After bone resection, ligament imbalance and joint component gaps were measured using an offset-type tensor while applying a 40-lb joint distraction force at 0° and 90° of knee flexion. The lateral laxity in flexion was determined by subtracting polyethylene insert thickness from the lateral gap at 90°. All patients were divided into three groups: ≤ 2 mm (A), 2–5 mm (B), and > 5 mm (C). One year after surgery, patients were asked to fill out questionnaires using the new Knee Society Score after examination outside the consultation room.ResultsThe mean intraoperative lateral laxities at 90° were − 0.2 ± 2.1 mm, 3.5 ± 0.7 mm, and 6.7 ± 1.9 mm in groups A, B, and C, respectively. The symptom score of group C was significantly lower than those of groups A or B. There were no significant differences in terms of satisfaction or the expectation and activity scores among all groups. There were no significant differences in terms of alignment after total knee arthroplasty among all groups.ConclusionsExcessive lateral laxity possibly resulted in worse patient-reported outcomes. However, slight lateral laxity of 2–5 mm might have no effect on patient-reported outcome and this slight varus imbalance could be acceptable. Altogether, our findings would lead to avoidance of excessive medial release in soft tissue balancing.

Laxity, Balance, and Alignment of a Simulated Kinematic Alignment Total Knee Arthroplasty.

Kinematic alignment (KA) and related personalized alignment strategies in total knee arthroplasty (TKA) target restoration of native joint line obliquity and alignment. In practice, deviations from exact restoration of the prearthritic joint surface are tolerated for either the femur or tibia to achieve ligamentous balance. It remains unknown what laxity, balance, and alignment would result if a pure resurfacing of both femur and tibia were performed in a KA TKA technique. We used data from 382 robot-assisted TKA performed with a digital joint tensioner to simulate TKA with a pure resurfacing KA technique for both femur and tibia. All knees had the posterior cruciate ligament retained. Knees were subdivided into 4 groups based on preoperative coronal alignment: valgus, neutral, varus, and high varus. Medial and lateral laxity in extension and flexion, balance in extension and flexion, and coronal plane alignment were compared between groups using analysis of variance testing. In simulated pure resurfacing KA TKA across a range of preoperative coronal plane deformities, only 11%-31% of knees would have mediolateral extension ligament balance within ±1 mm, and 20%-41% would have a medial flexion gap that is looser than the lateral flexion gap. Over 45% of knees would have coronal hip-knee-ankle angle >3 degrees from mechanical neutral. In simulations of pure resurfacing KA TKA, there was wide variability in the resulting laxity and alignment outcomes. Most knees had alignment and balance outcomes outside of normally accepted ranges. Techniques that deviate from pure resurfacing in order to achieve balance appear favorable.

The Correlation between Objective Ligament Laxity and the Clinical Outcome of Mechanically Aligned TKA.

Instability is one of the causes of failure in total knee arthroplasty (TKA). The aim of this study was to analyze the correlation between objective ligament laxity and the clinical outcome of mechanically aligned TKA. Fifty-one knees in 47 patients were evaluated at a minimum follow-up of 6 months. The correlation between the angular displacement and functional scores (Knee Society Score and Knee Injury and Osteoarthritis Score) was analyzed. A negative correlation (p-value < 0.05) was observed between medial laxity ≥5° at 0, 30, 60, and 90° of flexion and the outcome measures. Lateral laxity did not correlate with the clinical outcome. At 30° of knee flexion, a total varus and valgus laxity ≥10° was related to poorer outcomes. The same amount of angular displacement did not influence the outcome in the other flexion angles. There was no difference in single-radius vs multi-radius implants in terms of medial and lateral laxity and clinical outcome. A valgus displacement ≥5° measured at 0, 30, 60, and 90 degrees of flexion correlated with an inferior clinical outcome. In contrast, the same amount of displacement measured on the lateral compartment did not influence the clinical outcome after TKA.

Optimizing Asymmetric Native Knee Flexion Gap Balance Promotes Superior Outcomes in Primary Total Knee Arthroplasty.

Replicating native knee kinematics remains the ultimate goal of total knee arthroplasty (TKA). Technology, such as robotics, provides robust intraoperative data; however, no evidence-based targets currently exist for improved clinical outcomes. Furthermore, some surgeons target a rectangular flexion space in TKA unlike the native knee. This study evaluated the effect of in vivo flexion gap asymmetry on patient-reported outcome measures (PROMs) in contemporary TKA. In vivo tibiofemoral joint space dimensions were measured during 129 TKAs using a calibrated tension device before and after complete posterior cruciate ligament resection. PROMs were compared based on the final dimensions and the change in flexion gap dimensions at 90° of flexion: (1) equal laxity, (2) lateral laxity, and (3) medial laxity. Groups did not differ by demographics ( P ≥ 0.347), clinical follow-up ( P = 0.134), tibiofemoral alignment ( P = 0.498), or preoperative PROMs ( P ≥ 0.093). Mean follow-up for the cohort was 1.5 years (range, 1-3). Pain with climbing stairs, pain while standing upright, and knees "always feeling normal" scores were superior for patients with equal or lateral laxity compared with medial laxity ( P ≤ 0.064). Pain with level walking, University of California Los Angeles activity level, KOOS JR, and satisfaction scores also tended to be superior for patients with equal or lateral laxity, although it lacked statistical significance ( P ≥ 0.111). Results of this study suggest that patients with either an equally tensioned rectangular flexion space or with later-flexion lateral laxity after posterior cruciate ligament resection may achieve superior PROMs. Findings support the clinical benefit of facilitating posterolateral femoral roll back in flexion, which mimics native knee kinematics and further helps define targets for advanced technology.

An Abdominoplasty Modification for Postpregnancy Abdomen with Rectus Diastasis and Midline Hernia: The Technique and Results.

After pregnancy, some women experience severe rectus diastasis (RD), with body control dysfunction, midline hernia, or other quality-of-life impairment. The purpose of this study was to describe the authors' experience using hydrodissection and epidural anesthesia for lateral plication modification of abdominoplasty to restore abdominal wall firmness. A total of 46 consecutive patients with RD after pregnancy were enrolled. The mean intraoperative inter-rectus distance was 4.6 cm. RD is not always the only structure that has been elongated. Firmness of the abdominal wall also depends on lateral fascia structures. This study reports the total plicated distance addressing the lateral laxity in the abdominal wall. In this series, total plication was 7.8 cm, and 16 patients had a midline hernia. No hernia recurrences occurred, and the rectus bellies were less than 5 mm apart from each other in all participants, verified with ultrasound after 2 years of follow-up. Patient perspective of care and surgical outcome were recorded. Health-related quality-of-life domains were significantly improved postoperatively. Lumbar back pain visual analogue scale score was 4.5 ± 2.3 preoperatively and 0.5 ± 0.9 postoperatively. The ability to perform sit-ups increased from zero to 11, suggesting better motor control. The total complication rate was 10.9%. Hydrodissection and epidural anesthesia for lateral plication modification offers a reliable and effective treatment method for RD repair with and without a small midline hernia with a low complication rate. Therapeutic, IV.

The Effect of Minor Adjustments to Tibial and Femoral Component Position on Soft Tissue Balance in Robotic Total Knee Arthroplasty

BackgroundIdeal goals for alignment and balance in total knee arthroplasty (TKA) remain controversial. We aimed to compare initial alignment and balance using mechanical alignment (MA) and kinematic alignment (KA) techniques and to analyze the percentage of knees that could achieve balance using limited adjustments to component position. MethodsProspective data on 331 primary robotic TKAs (115 MAs and 216 KAs) were analyzed. Medial and lateral virtual gaps were recorded in both flexion and extension. A computer algorithm was used to calculate potential (theoretical) implant alignment solutions to achieve balance within 1 millimeter (mm) without soft tissue release given an alignment philosophy (MA or KA), angular boundaries (±1, ±2, or ±3°), and gap targets (equal gaps or lateral laxity allowed). The percentage of knees that could theoretically achieve balance was compared. ResultsLess than 5% of TKAs were initially balanced. Limited adjustments to component position increased the percentage of TKAs that could be balanced in a graduated manner, with no difference between MA and KA start points: adjustments of ±1 (10% versus 6%, P = .17), ±2 (42% versus 39%, P = .61), or of ±3 (54% versus 51%, P = .66). A higher percentage of TKAs could be balanced when a greater range for lateral gap laxity was allowed. Balancing from KA resulted in increased joint line obliquity in the final implant alignment. ConclusionA high percentage of TKAs can be balanced without soft tissue release using minor adjustments to component position. Surgeons should consider the relationship between alignment and balance goals when optimizing component positioning in TKA.

Avoiding Lateral Laxity in Robotic Arm-Assisted Total Knee Arthroplasty-A Surgical Technique Describing a New Method of Gap Capture and Balancing Strategy.

Optimal flexion-extension gap balancing is an important factor in outcomes after total knee arthroplasty. Knees with varus deformities are commonly associated with a greater degree of lateral laxity both in extension and flexion. Residual lateral laxity could be encountered by surgeons during component trialling after robotic-assisted total knee arthroplasty (RATKA), necessitating additional medial soft tissue release for a thicker insert. This study describes a new technique of gap assessment during RATKA and we propose a functional alignment based balancing strategy to avoid residual lateral laxity. This surgical technique was prospectively employed in 105 patients undergoing primary MAKO® (Stryker, Kalamazoo, Michigan) RATKA for osteoarthritis of the knee with varus deformity, between January 2021 and July 2021. Patients included had an initial lateral extension laxity of more than 24mm. Surgical data points collected consisted of characterization of the laxity profile of the knee using the medial and lateral extension and flexion initial gap captures, final gap captures after dynamic balancing with a functional alignment strategy, and residual lateral extension gap laxity in millimeters at the end of implantation. The mean initial lateral extension gap was 25.76mm (standard deviation [SD]=1.47) and the mean lateral flexion gap was 24.4mm (SD=1.94). Balance was achieved in all the patients with a 9 or 11mm insert, with a mean residual lateral laxity of 0.51mm (SD=0.73, range 0-2mm). The majority of patients (n=66, 62.85%) had zero lateral laxity at the end of final implantation while 24 patients (22.8%) had 1mm of residual lateral laxity. Residual lateral joint laxity can be avoided consistently and predictably in RATKA cases with initial gap capture of up to 30mm in lateral extension and flexion with this new technique of gap capture and employing various steps of balancing strategy described.

PREOPERATIVE MEDIAL LAXITY IN MIDFLEXION AND FLEXION CORRELATES WITH POORER KOOS-12 FUNCTION SCORES PRIOR TO TKA

Preoperative ligament laxity can be characterized intraoperatively using digital robotic tensioners. Understanding how preoperative knee joint laxity affects preoperative and early post-operative patient reported outcomes (PROMs) may aid surgeons in tailoring intra-operative balance and laxity to optimize outcomes for specific patients.This study aims to determine if preoperative ligament laxity is associated with PROMs, and if laxity thresholds impact PROMs during early post-operative recovery.106 patients were retrospectively reviewed. BMI was 31±7kg/m2. Mean age was 67±8 years. 69% were female. Medial and lateral knee joint laxity was measured intraoperatively using a digital robotic ligament tensioning device after a preliminary tibial resection.Linear regressions between laxity and KOOS12-function were performed in extension (10°), midflexion (45°), and flexion (90°) at preoperative, 6-week, and 3-month time points. Patients were separated into two laxity groups: ≥7 mm laxity and &lt;7 mm laxity. Student's t-tests determined significant differences between laxity groups for KOOS12-function scores at all time points.Correlations were found between preoperative KOOS12-function and medial laxity in midflexion (p&lt;0.001) and flexion (p&lt;0.01). Patients with &lt;7 mm of medial laxity had greater preoperative KOOS12-function scores compared to patients with ≥7 mm of medial laxity in extension (46.8±18.2 vs. 29.5±15.6, p&lt;0.05), midflexion (48.4±17.8 vs. 32±16.1, p&lt;0.001), and flexion (47.7±18.3 vs. 32.6±14.7, p&lt;0.01). No differences in KOOS12-function scores were observed between medial laxity groups at 6-weeks or 3-months. All knees had &lt;5 mm of medial laxity postoperatively. No correlations were found between lateral laxity and KOOS12-function.Patients with preoperative medial laxity ≥7 mm had lower preoperative PROMs scores compared to patients with &lt;7 mm of medial laxity. No differences in PROMs were observed between laxity groups at 6 weeks or 3 months. Patients with excessive preoperative joint laxity achieve similar PROMs scores to those without excessive laxity after undergoing gap balancing TKA.

Clinical and arthroscopic outcomes of single-bundle anterior cruciate ligament reconstruction using autologous hamstrings augmented with ligament augmentation and reconstruction systems compared with four-strand hamstring tendon grafts alone.

To compare the clinical, radiological, and second-look arthroscopic outcomes in patients who underwent anterior cruciate ligament (ACL) reconstruction using a four-strand hamstring tendon graft (hamstring group) either without augmentation or with ligament augmentation and reconstruction system (LARS) augmentation (LARS augmentation group). From January 2018 to December 2019, patients who underwent ACL reconstruction were included. Patient-reported outcome measures (PROMs) were undertaken pre-operatively and at three, six, 12, and 24months post-operatively. Arthroscopic evaluation was performed focusing on the morphology of the graft based on graft tension, graft tear, and synovial coverage. A total of 178 consecutive patients received single-bundle ACL reconstruction, 89 patients in each group, and 20 patients were lost to follow-up in the first twoyears. At the threemonth follow-up, the LARS augmentation group had significantly higher Lysholm scores, IKDC scores, and KOS-ADLS scores than the hamstring group (P < 0.001). At the three, six and 12-month follow-ups, there were significantly higher Tegner scores and ACL-RSI scores in the LARS augmentation group than in the hamstring group (P < 0.05). At the three and sixmonth follow-ups, the LARS augmentation group had significantly higher rates of return to sports and return to sports at their preinjury level (P < 0.05). There were no between-group differences in other outcomes, including arthroscopic outcomes, graft signal intensity, post-operative complications or rerupture rates. Autologous hamstring augmented with the LARS augmentation technique provides good and realistic clinical and functional results during the early post-operative period with high levels of satisfaction of patients, including participation in sports and physical activity, and high rates of return to sports at the preinjury level, without any apparent complications compared with hamstring ACL reconstruction alone. No increases in complication, reinjury rates, or increased lateral laxity were observed at the 12-month or 24-month follow-up.

Intraoperative midflexion medial laxity using navigation affects patient expectations following posterior stabilized total knee arthroplasty.

Patient satisfaction and expectations are now recognized as an outcome measure for successful total knee arthroplasty (TKA). The purpose of this study was to determine which factors including soft tissue balance during surgery affect patient satisfaction and expectations after TKA. A total of 135 patients (157 knees) with knee osteoarthritis who underwent primary TKA with a posterior stabilized design were studied. After implantation of all components, varus/valgus laxity of the knee was measured intraoperatively with the knee at 0°, 30°, 60°, 90°, and 120° guided by an image-free navigation system. Factors that affected patient satisfaction and expectations, including lateral and medial laxities, were evaluated using the 2011 Knee Society score. The mean intraoperative lateral laxity was 1.1°, 1.6°, 0.9°, 1.3°, and 1.7° with the knee at 0°, 30°, 60°, 90°, and 120°, respectively. The mean intraoperative medial laxity was 1.1°, 1.4°, 1.1°, 1.1°, and 1.7° with the knee at 0°, 30°, 60°, 90°, and 120°, respectively. Patient satisfaction after TKA correlated positively with symptom (R = 0.61, p < 0.01) and functional activity (R = 0.47, p < 0.01) scores. Patient expectations after TKA weakly positively correlated with symptom (R = 0.29, p < 0.01) and functional activity (R = 0.20, p = 0.01) scores, and weakly negatively with medial laxity at 30° (R = -0.21, p < 0.01). Midflexion medial laxity was associated with worse patient expectations after TKA. Avoiding medial laxity could be one of the important techniques during TKA.

Preoperative Lateral Laxity in the Extensor Position and Intraoperative Medial Soft Tissue Release Affect Postoperative Ligament Balance in Osteoarthritis Knees Undergoing TKA in Women

Purpose: Adequate ligament balance is important for long-term outcomes after Total Knee Arthroplasty (TKA). We retrospectively evaluated preoperative factors and intraoperative medial soft tissue release techniques that affected adequate ligament balance after TKA for varus knee. Method: One hundred knees with Osteoarthritis (OA) in women were included. X-rays were taken preoperatively and postoperatively with varus and valgus stress in the extension and flexion positions. Knees were postoperatively, classified as stable (n=49) or laxity (n=51). Results: Factors associated with adequate ligament balance include joint inclination angle of varus at extension, and superficial Medial Collateral Ligament (sMCL) release. Postoperative ligament balance was significantly associated with preoperative joint inclination angle of varus at extension of 7°. Conclusion: Preoperative lateral laxity in the extensor position under stress X-ray and sMCL release may affect postoperative ligament balance. A 7° preoperative lateral joint inclination may be useful in predicting postoperative ligament balance.

The lateral joint line opening: a radiographic indicative parameter for high grade varus knees

PurposeIt is usually assumed that the severity of varus osteoarthritis (OA) of the knee is correlated with the axis deviation of the limb. Despite this, there is currently no clear radiographic definition to define a so-called ‘high degree’ varus knee, which is characterized by a pronounced lateral ligamentous laxity. The purpose of this study was to radiographically determine if the lateral joint line opening (LJLO) is an indicative parameter when defining so-called high grade varus knees.MethodsTwo hundred forty Full length radiographs of patients with end-stage varus osteoarthritis who were scheduled for Total knee arthroplasty (TKA) were evaluated. The Hip-knee-ankle-angle (HKA-angle), Joint-line-convergence-angle (JLCA) and the lateral joint line opening were measured. The lateral joint line opening is the shortest distance between the lateral tibial plateau and the deepest point of the lateral femoral condyle. Linear regression models were used to investigate the relationships between the radiographic measurements.ResultsHip-knee-angle-angle, joint-line-conversion-angle, and lateral joint line opening were all positively correlated (p < 0.001). An increase of 1 mm lateral joint line opening causes an increase of 0.6° joint-line-conversion-angle (p = 0.029) below a cut-off point of 4.7 mm. For lateral opening values beyond 4.7 mm, the gradient increased to 1.2 (p < 0.001). A lateral joint line opening of 4.7 mm corresponds to a hip-knee-ankle-angle of 6.0° (95% CI [5.5; 6.5]).ConclusionA lateral joint line opening of more than 5 mm in end-stage OA knees is indicative of increased lateral joint laxity. Those knees can be radiographically classified as so-called ‘high-grade’ varus knees.Level of evidenceTherapeutic study, Level III.

Primary constrained-condylar-knee designs outperform posterior-stabilized and cruciate-retaining designs in high-grade varus osteoarthritic knees during short-term follow-up: a pilot study.

High-grade varus osteoarthrosis (OA) is characterized by a pronounced intra-articular varus deformity and associated insufficiency of the lateral ligamentous complex. When performing a total knee arthroplasty (TKA) in such a knee, traditionally the alignment is restored to neutral, and the medial soft tissue structures are released to compensate for the lateral laxity and balance the joint. However, another option would be to leave the medial soft tissues untouched and accept the lateral laxity but to compensate for it using an ML-stabilized constrained-condylar knee (CCK) design. Our aim was to prove our hypothesis that such knees would demonstrate better clinical stability and better functionality as well as subjective outcome scores. We searched our bicenter database of 912 primary TKAs (from 2016 to 2019) for primary TKA patients with a preoperative varus alignment of > 8°. After inclusion, 60 patients were divided into three groups by implant design: CCK (n = 21), posterior-stabilized (PS) (n = 20) and cruciate-retaining (CR) (n = 19). Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Knee Society Score (KSS), UCLA-activity score, ML instability scores and both radiographic and clinical data were compared between groups. ML stability was significantly better in CCK designs (86% grade 0) compared to CR (37% grade 0) (p = 0.004) but not PS (70% grade 0) designs. No grade II instability was present in CCK and PS implants compared to 16% of CR implants. KSS and UCLA-activity score were higher in CCK designs compared to PS (p = 0.027, p = 0.041) and CR designs (p < 0.001, p = 0.007). OKS and FJS were higher in CCK designs compared to CR (p = 0.025, p = 0.008) but not to PS. The use of a CCK design to compensate for the lateral laxity in high-grade varus OA knees allowed to refrain from a medial release. CCK designs displayed improved clinical stability and better functionality as well as subjective outcome scores compared to less-constrained designs.

Biomechanical Effect of Coronal Alignment and Ligament Laxity in Total Knee Arthroplasty: A Simulation Study.

The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculoskeletal model, which enables the adjustment of ligament length and implant alignment; validate the model; and evaluate the effects of varus/valgus alignment adjustment and unbalanced medial/lateral ligament laxity during gait. A cruciate-retaining total knee arthroplasty musculoskeletal model was constructed and validated against the in vivo contact forces. This model was transformed to 2° varus/valgus alignment of femoral or tibial replacement models and 2° medial/lateral laxity models. The contact forces and ligament tensions of the adjusted models were calculated. The contact forces in the model showed good agreement with the in vivo contact forces. Valgus replacement alignment with balanced ligament models showed a lower contact force at the medial compartment than at the neutral alignment model, whereas the varus replacement alignment with balanced ligament models showed a greater contact force at the medial compartment and medial/posterior cruciate ligament tension. The medial laxity with neutral alignment model showed a similar contact force with decreased medial ligament tension compared to the balanced neutral alignment model, whereas the lateral laxity with the neutral alignment model showed a greater contact force and decreased lateral ligament tension. The cruciate-retaining total knee arthroplasty model was validated using in vivo contact forces (r = 0.939) Two degrees of valgus alignment adjustment with balanced ligament or neutral alignment with 2° of medial laxity can be safe without increasing contact force or ligament tension compared to neutral alignment with a balanced extension gap. However, 2° of varus alignment adjustment with balanced ligament or neutral alignment with 2° of lateral laxity may be unfavorable due to the overloading of the joints and knee ligaments.

Validation of the spontaneous lateral laxity sign for radial collateral ligament sprain of the metacarpophalangeal joint of the fingers: Anatomical study

Severe collateral ligament sprain of the metacarpophalangeal joint (MCP) of the fingers is rare. Clinical examination is mandatory to diagnose severity. The purpose of our study was to validate a clinical sign for MCP joint laxity: the spontaneous lateral laxity sign (SLLS), recently described by Meyer et al. to diagnose severe MCP radial collateral ligament (RCL) sprain, with a comparison with the already validated rotational laxity test (RLT). SLLS and RLT were assessed before RCL transection, after RCL transection and after RCL repair on 40 long fingers in 10 fresh thawed cadavers. SLLS was performed with the elbow on the table, wrist in 70° flexion, in neutral pronation-supination, hands drooping passively with the dorsal side toward the examiner and the ulnar side toward the table. The MCP joints were at rest, in passive slight extension. Positive results were defined as an overlap of the damaged finger on the next, or as an increased abduction of the little finger. Correlation between the two tests was calculated. SLLS was positive in 0% of cases before RCL transection, 100% after transection and 0% after repair. Mean arcs of pronation and supination on RLT were 16 and 19.5 mm before section, 24 and 33 mm after section (52% and 69% increase compared to preoperative data), and 17 and 21 mm after repair (7% and 8% increase). Correlation between the two tests was 100%. The spontaneous lateral laxity sign is a simple and reliable clinical sign for diagnosing complete long-finger MCP RCL tears requiring surgery. Level of evidence: III, case-control study.