Background:
The biomechanical effect of lateral extra-articular tenodesis (LET) performed in conjunction with anterior cruciate ligament (ACL) reconstruction (ACLR) on load sharing between the ACL ...graft and the LET and on knee kinematics is not clear.
Purpose/Hypothesis:
The purpose was to quantify the effect of LET on (1) forces carried by both the ACL graft and the LET and (2) tibiofemoral kinematics in response to simulated pivot shift and anterior laxity tests. We hypothesized that LET would decrease forces carried by the ACL graft and anterior tibial translation (ATT) in response to simulated pivoting maneuvers and during simulated tests of anterior laxity.
Study Design:
Controlled laboratory study.
Methods:
Seven cadaveric knees (mean age, 39 ± 12 years range, 28-54 years; 4 male) were mounted to a robotic manipulator. The robot simulated clinical pivoting maneuvers and tests of anterior laxity: namely, the Lachman and anterior drawer tests. Each knee was assessed in the following states: ACL intact, ACL sectioned, ACL reconstructed (using a bone–patellar tendon–bone autograft), and after performing LET (the modified Lemaire technique after sectioning of the anterolateral ligament and Kaplan fibers). Resultant forces carried by the ACL graft and LET at the peak applied loads were determined via superposition. ATT was determined in response to the applied loads.
Results:
With the applied pivoting loads, performing LET decreased ACL graft force up to 80% (44 ± 12 N; P < .001) and decreased ATT of the lateral compartment compared with that of the intact knee up to 7.6 ± 2.9 mm (P < .001). The LET carried up to 91% of the force generated in the ACL graft during isolated ACLR (without LET). For simulated tests of anterior laxity, performing LET decreased ACL graft force by 70% (40 ± 20 N; P = .001) for the anterior drawer test with no significant difference detected for the Lachman test. No differences in ATT were deteced between ACLR with LET and the intact knee on both the Lachman and the anterior drawer tests (P = .409). LET reduced ATT compared with isolated ACLR on the simulated anterior drawer test by 2.4 ± 1.8 mm (P = .032) but not on the simulated Lachman test.
Conclusion:
In a cadaveric model, LET in combination with ACLR transferred loads from the ACL graft to the LET and reduced ATT with applied pivoting loads and during the simulated anterior drawer test. The effect of LET on ACL graft force and ATT was less pronounced on the simulated Lachman test.
Clinical Relevance:
LET in addition to ACLR may be a suitable option to offload the ACL graft and to reduce ATT in the lateral compartment to magnitudes less than that of the intact knee with clinical pivoting maneuvers. In contrast, LET did not offload the ACL graft or add to the anterior restraint provided by the ACL graft during the Lachman test.
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FSPLJ, NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Background:
There is concern that utilization of lateral extra-articular tenodesis (LET) in conjunction with anterior cruciate ligament (ACL) reconstruction (ACLR) may disturb lateral compartment ...contact mechanics and contribute to joint degeneration.
Hypothesis:
ACLR augmented with LET will alter lateral compartment contact mechanics in response to simulated pivoting maneuvers.
Study Design:
Controlled laboratory study.
Methods:
Loads simulating a pivot shift were applied to 7 cadaveric knees (4 male; mean age, 39 ± 12 years; range, 28-54 years) using a robotic manipulator. Each knee was tested with the ACL intact, sectioned, reconstructed (via patellar tendon autograft), and, finally, after augmenting ACLR with LET (using a modified Lemaire technique) in the presence of a sectioned anterolateral ligament and Kaplan fibers. Lateral compartment contact mechanics were measured using a contact stress transducer. Outcome measures were anteroposterior location of the center of contact stress (CCS), contact force from anterior to posterior, and peak and mean contact stress.
Results:
On average, augmenting ACLR with LET shifted the lateral compartment CCS anteriorly compared with the intact knee and compared with ACLR in isolation by a maximum of 5.4 ± 2.3 mm (P < .001) and 6.0 ± 2.6 mm (P < .001), respectively. ACLR augmented with LET also increased contact force anteriorly on the lateral tibial plateau compared with the intact knee and compared with isolated ACLR by a maximum of 12 ± 6 N (P = .001) and 17 ± 10 N (P = .002), respectively. Compared with ACLR in isolation, ACLR augmented with LET increased peak and mean lateral compartment contact stress by 0.7 ± 0.5 MPa (P = .005) and by 0.17 ± 0.12 (P = .006), respectively, at 15° of flexion.
Conclusion:
Under simulated pivoting loads, adding LET to ACLR anteriorized the CCS on the lateral tibial plateau, thereby increasing contact force anteriorly. Compared with ACLR in isolation, ACLR augmented with LET increased peak and mean lateral compartment contact stress at 15° of flexion.
Clinical Relevance:
The clinical and biological effect of increased anterior loading of the lateral compartment after LET merits further investigation. The ability of LET to anteriorize contact stress on the lateral compartment may be useful in knees with passive anterior subluxation of the lateral tibia.
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FSPLJ, NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Background:
The way in which force increases in the anterolateral tissues and the lateral extra-articular tenodesis (LET) tissue to resist internal rotation (IR) of the tibia after anterior cruciate ...ligament (ACL) reconstruction in isolation and after LET augmentation, respectively, is not well understood.
Purpose:
(1) To compare in a cadaveric model how force increases (ie, engages) in the anterolateral tissues with IR of the tibia after isolated ACL reconstruction and in the LET tissue after augmentation of the ACL reconstruction with LET and (2) to determine whether IR of the tibia is related to engagement of the LET tissue.
Study Design:
Controlled laboratory study.
Methods:
IR moments were applied to 9 human cadaveric knees at 0°, 30°, 60°, and 90° of flexion using a robotic manipulator. Each knee was tested in 2 states: (1) after isolated ACL reconstruction with intact anterolateral tissues and (2) after LET was performed using a modified Lemaire technique with the LET tissue fixed at 60° of flexion under 44 N of tension. Resultant forces carried by the anterolateral tissues and the LET tissue were determined via superposition. The way force increased in these tissues was characterized via parameters of tissue engagement, namely in situ slack, in situ stiffness, and tissue force at peak applied IR moment, and then compared (α < .05). IR was related to parameters of engagement of the LET tissue via simple linear regression (α < .05).
Results:
The LET tissue exhibited less in situ slack than the anterolateral tissues at 30°, 60°, and 90° of flexion (P≤ .04) and greater in situ stiffness at 30° and 90° of flexion (P≤ .043). The LET tissue carried greater force at the peak applied IR moment at 0° and 30° of flexion (P≤ .01). IR was related to the in situ slack of the LET tissue (R2≥ 0.88; P≤ .0003).
Conclusion:
LET increased restraint to IR of the tibia compared with the anterolateral tissue, particularly at 30°, 60°, and 90° of flexion. IR of the tibia was positively associated with in situ slack of the LET tissue.
Clinical Relevance:
Fixing the LET at 60° of flexion still provided IR restraint in the more functionally relevant flexion angle of 30°. Surgeons should pay close attention to the angle of internal and/or external tibial rotation when fixing the LET tissue intraoperatively because this surgical parameter is related to in situ slack of the LET tissue and, therefore, the amount of IR of the tibia.
Full text
Available for:
FSPLJ, NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Objectives:
Lateral extra-articular tenodesis (LET) reduces ACL graft failure rates two years after surgery when performed as an adjunct to ACL reconstruction (ACLR). Interestingly, previous ...biomechanical studies have shown that LET may reduce tibial rotation beyond that of the intact knee, while others found no such kinematic overconstraint. Parameters of ligament engagement have proven useful in characterizing the biomechanical function of the ACL and the anterolateral ligament; however, they have not been used to describe the biomechanics of LET. In this study, we compared engagement parameters (engagement point, in situ stiffness, and tissue force at peak applied load) of an LET-reconstructed knee compared to the native lateral tissues in response to an internal rotation torque at 0°, 30°, 60°, and 90° of knee flexion.
Methods:
Seven cadaveric knees (mean age: 39 ± 12; range: 28-54; 4 male) were mounted to a robotic manipulator. The robot applied an internal rotation torque of 5 Nm while monitoring the resulting internal tibial rotation (ITR) (in degrees). Each knee was tested following a bone-patellar tendon-bone ACL reconstruction with intact lateral tissues (consisting of the anterolateral ligament and Kaplan fibers) and after sectioning these tissues and performing LET (modified Lemaire technique). Resultant forces carried by the native lateral tissues and the LET were determined via superposition. The parameters of engagement were determined for both the native lateral tissues and the LET and compared via two-way repeated measures ANOVA (p < 0.05).
Results:
During an internal rotation test at full extension (0° of flexion), both the LET-reconstructed and native lateral tissues did not engage. At 30°, 60°, and 90° knee flexion, the native lateral tissues exhibited more in situ slack than the LET-reconstructed lateral tissues. Specifically, the native lateral tissues had 8° (p < 0.001), 13° (p < 0.001), and 14° (p < 0.001) more in situ slack than the LET-reconstructed lateral tissues at 30°, 60°, and 90° knee flexion, respectively. At 30° of flexion, the LET-reconstructed lateral tissues were 9° (p < 0.001) and 10° (p < 0.001) more slack than at 60° and 90° knee flexion. Across all three tested knee flexion angles (30°, 60°, and 90°), the LET-reconstructed lateral tissues had greater in situ stiffness than the native lateral tissues. The LET carried greater force at the peak applied internal rotation torque by 29 N at 30° of flexion (p = 0.006), but no statistical differences were identified at the other flexion angles.
Conclusions:
LET creates a supraphysiologic restraint to the native lateral tissues by engaging with less internal tibial rotation than the native lateral tissue at all flexion angles tested but full extension. The LET also carried greater force at the peak applied load and had a greater in situ stiffness at 30° of flexion than the native lateral tissues. On the whole, LET is a supraphysiological restraint to internal tibial rotation at 30° of flexion. The engagement point of LET may be modified surgically by altering the flexion angle, degree of tibial rotation at which the tenodesis is fixed, and/or the tension applied. Thus, discrepancies between previous biomechanical studies may arise from variations in one or more of these modifiable surgical parameters.
Figure 1.
Mean tissue force versus internal tibial rotation response of the LET and native lateral tissues with applied internal rotation torque at 0,30,60, and 90° of knee flexion. Whiskers represent one standard deviation. Engagement point denoted in yellow. Tissue force at peak applied internal tibial rotation torque denoted in blue.
Objectives:
Utilization of lateral extra-articular tenodesis (LET) in conjunction with anterior cruciate ligament reconstruction (ACLR) has increased in recent years, however, the biomechanical ...impact of LET, when performed with contemporary techniques, on both load sharing between the ACL graft and the LET and on knee kinematics is not completely clear. The purpose of this study was to quantify the effect of LET performed with ACLR, in the presence of a compromised anterolateral tissues, on (1) forces carried by the ACL graft and the LET and (2) knee kinematics, during simulated pivot shift.
Methods:
manipulator equipped with a six-axis force-torque sensor. The robot applied multiplanar torques simulating two types of pivot shift (PS) subluxing the lateral compartment at 15° and 30° of knee flexion. The following loading combinations were applied: (PS1) 8 Nm of valgus and 4 Nm of internal rotation torques; (PS2) 100 N compression force, 8 Nm valgus torque, 2 Nm internal rotation torque, and 30 N anterior force. Anteroposterior (AP) translation in the lateral compartment of the knee was recorded in the following states: ACL intact, sectioned, reconstructed and, finally, after sectioning the anterolateral ligament (ALL) and kaplan fibers and performing a LET. ACLR was performed utilizing a bone-patellar tendon-bone autograft, via medial parapatellar arthrotomy. LET was performed using a modified lemaire technique with a metal staple femoral fixation at 60° of flexion in neutral rotation. Resultant forces carried by the ACL graft and LET at the peak applied load in all tested conditions were determined utilizing the principle of superposition and serial sectioning.
Results:
Under both simulated pivot shift types and at both flexion angles the ACL force decreased with the addition of a LET, with the least force reduction of 39% for PS2 at 15° (p=0.01) and the most force reduction of 80% for PS1 at 30° (p<0.001). While decreasing ACL force, the LET carried at least 43% of the force carried by the ACL graft when tested without LET for PS2 at 15° and 91% of the force carried by the ACL graft at most, for PS1 at 30° (Table 1). For both combinations of multiplananr torques and at both flexion angles, the anterior tibial translation in the lateral compartment decreased for the ACLR+LET knee compared to the intact knee (5.3mm and 7.6mm decrease, for PS1 15° and 30° respectively, p<0.001; 4.4mm p=0.005 and 7.6mm p<0.001, for PS2 15° and 30°, respectively). (Figure 2).
Conclusion:
During a simulated pivot shift, LET shields the ACL graft from loading. This effect was greatest at 30° of flexion with an 80% drop in ACL graft force. While some shielding of load from the ACL graft can be beneficial, a more significant reduction in the load of the ACL graft may potentially be detrimental to the graft remodeling, maturation and function. The optimal load sharing pattern for improved clinical outcomes is not well understood and merit further investigation. In addition, LET also decreases anterior tibial translation in the lateral compartment to less than that of the intact knee, which represents overconstraint of the lateral compartment. These findings may support the purported “protective” effect of LET on the ACL graft and its important role in stabilizing the lateral compartment in the setting of combined ACL and anterolateral structures deficiency. The influence of overconstraint of the lateral compartment with LET warrants further biomechanical and clinical evaluation.
Table 1.
Mean loads carried by the ACL graft before and after the addition of a LET and loads carried by the LET, under both simulated pivot shift types at 15 ° and 30° of flexion
Mean ACL Graft Loads (n=7)
Mean LET Loads (n=7)
Without LET
With LET
Difference
% Drop*
LET Load
Relative Load**
PS1 15°
58±13 N
20±23 N
29±18 N
49%
31±15 N
53%
PS1 30°
54±13 N
11±7 N
44±12 N
80%
49±17 N
91%
PS2 15°
68±15 N
41±20 N
26±19 N
39%
29±17 N
43%
PS2 30°
71±15 N
21±20 N
50±14 N
70%
49±14 N
70%
PS1=8 Nm of valgus and 4 Nm of internal rotation torques
PS2=100 N compression, 8 Nm valgus, 2 Nm internal rotation, and 30 N anterior force
*the percent of ACL graft force drop
**The percent of load carried by LET relative to the load carried by ACL graft without LET
Figure 1.
Figure 2.
Objectives:
Residual laxity after ACL reconstruction (ACLR) may adversely impact patient outcomes and function and has led to the increasing utilization of lateral extra-articular augmentation ...procedures in conjunction with ACLR and specifically, Lateral Extra-articular Tenodesis (LET). However, concerns of overconstraining the lateral compartment and subsequent increased lateral compartment contact stress and accelerated degenerative changes have been suggested with LET procedures. Therefore, the purpose of this work was to assess the impact of a LET on contact mechanics of the lateral compartment in response to multiplanar torques representing pivoting maneuvers.
Methods:
Nine cadaveric knees (4 male, 37.4 ± 11.6 years old) were mounted to a robotic manipulator equipped with a six-axis force-torque sensor. The robot applied multiplanar torques simulating two types of pivot shift (PS) maneuvers, subluxing the lateral compartment, at 30° of knee flexion. The following loading combinations were applied: (PS1) 8 Nm of valgus and 4 Nm of internal rotation torques; (PS2) 100 N compression force, 8 Nm valgus torque, 2 Nm internal rotation torque, and 30 N anterior force. Kinematics were recorded in the following states: ACL intact, sectioned, reconstructed and, finally, after sectioning the anterolateral ligament (ALL) and kaplan fibers and performing a LET. ACLR was performed utilizing a bone-patellar tendon-bone autograft, via medial parapatellar arthrotomy. LET was performed using a modified lemaire technique with a metal staple femoral fixation at 60° of flexion in neutral rotation. A contact stress transducer was then sutured to the tibial plateau beneath the menisci and the previously-determined kinematics were replayed, while recording the lateral compartment contact stress. At the peak applied loads, the following measures were determined in the lateral compartment: contact force, contact area, the anterior-posterior (AP) location of the center of contact stress (CCS), the mean contact stress, and the peak contact stress and its AP location. Statistical differences were assessed via one-way repeated measures ANOVA with Student-Neumen-Keuls post hoc test (p< 0.05).
Results:
Under combined valgus and internal rotation torques (PS1), the addition of a LET to ACLR increased lateral compartment contact force compared to the native knee by 51 ± 51 N (p = 0.035) on average. Contact area also increased by 60 ± 56 mm2 and 61 ± 58 mm2 relative to the ACL intact and ACL reconstructed knee (p ≤ 0.002), respectively. LET also shifted anteriorly the CCS by 4.6 ± 3.6 mm and 5.7 ± 3.1 mm on average relative to the ACL intact and ACL reconstructed knees (p < 0.001) (Fig. 1). No differences were detected for the mean and peak lateral compartment contact stress with the addition of LET compared to the ACL intact or ACL reconstructed knee (p> 0.854). The location of peak contact stress, however, shifted anteriorly compared to the ACL intact and ACL reconstructed knees by 6.2 ± 5.7 mm and 7.6 ± 5.4 mm (p < 0.001). (Fig.1). Similar results were observed under multiplanar torques with compression (PS2) for all outcome measures.
Conclusion:
In response to multiplanar torques representing pivoting maneuvers, the addition of a LET to ACLR, in the presence of compromised anterolateral tissues, did not increase lateral compartment contact stress. As contact force increased with the addition of LET, so did the contact area, likely mitigating changes in the level of contact stress. LET shifted the contact location anteriorly thereby altering regional loading of the lateral articular cartilage. Further study of the impact of changes in regional loading patterns in the lateral compartment on cartilage degeneration is warranted.
Figure 1.
Abstract only
Introduction:
Frailty is a syndrome of functional decline characterized by an increased risk for adverse health outcomes. The association between frailty and left atrial appendage ...closure (LAAC) outcomes has not been extensively studied yet. This study aims to analyze the impact of frailty on adverse health outcomes following LAAC.
Method:
Retrospective review of electronic medical records from June 2016 to December 2021 at the University of Illinois, Chicago identified LAAC patients, who were included if they were followed-up within 6 and 12 months of the procedure. Patients were stratified into frail and non-frail groups based on the Johns Hopkins Claims-based Frailty Indicator, an externally validated index. Outcomes included 6- and 12-months major bleeding event defined by VARC, death, and hospitalization indexes. Two-sample t-tests and chi-squared tests were used to compare continuous and categorical variables, respectively.
Results:
Our cohort included 101 patients (age 72 ± 9 years, 75% male, 24% white): frail (N=34) and non-frail (N=67) groups. There were no statistically significant differences in baseline demographics, comorbidities, and medication except for older age in frail patients (79.6 vs 68.3 years, p=0.000). Although frail patients had higher mortality rate at 6 months (8.82% vs 0%, p=0.014), no differences were seen for nonhome discharges (6.67% vs 1.54%, p=0.184), 6-months major bleeding events (2.94% vs 2.99%, p=0.990), 6-month emergency department visits (38.2% vs 28.4%, p=0.313), and 6-month hospital admission (20.6% vs 25.4%, p=0.593). There were also no differences seen for mortality rate at 12 months (11.8% vs 5.97%, p=0.308), length of hospital stays (1.35 vs 1.37 days, p=0.966), 12-months major bleeding event (2.94% vs 4.48%, p=0.708), and 12-months hospital admission (29.4% vs 31.3%, p=0.842).
Conclusion:
Our results suggest that frail patients are at a higher risk for death within 6 months following LAAC despite no observable differences in comorbidities, medications, other adverse events, and hospitalization indexes, including nonhome discharges. Additional analysis is needed to determine factors that may preclude frail patients from hospital admissions or precipitate earlier death.
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