External Rotation Torque Research Articles

The Contralateral Ankle Joint Is a Reliable Reference for Testing Syndesmotic Stability Using Bilateral External Torque CT.

Subtle chronic or latent instabilities are difficult to delineate with currently available diagnostic modalities and do not allow assessment of ligamentous functionality. The noninvasive bilateral external torque computed tomography (CT) was able to reliably detect syndesmotic lesions in a cadaveric study. The aim of the study was to test the external torque device in young, healthy subjects at 3 different torque levels and to demonstrate comparability with the contralateral side. Ten healthy subjects without history of injury or surgery to the ankle joint were enrolled in this cross-sectional study. Four CT scans were performed. During the scans, the lower legs and feet were placed in an external torque device with predefined external rotation torques of 0, 2.5, 5, and 7.5 Nm. Five different radiographic measures of syndesmotic stability were measured: anterior distance (AD), tibiofibular clear space (TCS), posterior distance (PD), external rotation (ER), and β angle. With increasing external torque, slight increases in AD, ER, and β angle were observed, whereas TCS and PD decreased slightly. Large absolute differences were found between the healthy subjects for all measured parameters, regardless of the external torque applied. Differences from the contralateral side using the same external torque were minimal for all parameters, but smallest for AD with a maximum difference of 0.5 mm. Using the healthy contralateral ankle joint is appropriate for assessing syndesmotic stability based on minimal intraindividual side differences using the external torque device. Side differences >0.5 mm in AD and >0.9 mm in PD may be considered abnormal and may indicate significant instability of the syndesmosis. However, future studies are needed to define definitive cutoff values for relevant side differences in acute and chronic syndesmotic instability to guide clinicians in their treatment decisions.

Contributions of capsular releases to femoral exposure in total hip arthroplasty via the direct anterior approach

BackgroundIn total hip arthroplasty via the direct anterior approach, appropriate exposure is critical to allow preparation of the femur. The objective of this study was to explore the optimal soft tissue releases needed to allow broaching of the femur through a combination of experimental tests and computer simulations. MethodsFourteen full-body cadaveric specimens were included in this study. Total hip arthroplasty was performed via the direct anterior approach with the femur at 20° adduction and 20°extension. Soft tissue releases were performed sequentially, namely, the transverse iliofemoral ligament, descending iliofemoral ligament, ischio-femoral ligament, conjoint tendon, and obturator externus. After each release, the femur mobility was assessed by applying a 6 Nm external rotation torque and a 120 N distraction force. Subsequently, using specimen-specific models and models of the broach and handle, the broach passage after each release was simulated, and the release that allowed broach passage was analyzed. FindingsThe average external rotation after releasing the transverse and descending iliofemoral ligaments increased by 14.1° ± 6.1° and 13.8° ± 5.3°. With subsequent soft tissue releases, the rotational mobility increased incrementally, though the impact decreased. Impingement between the broach passage and the pelvis was mainly at the anterior superior iliac spine and the anterior inferior iliac spine. The volume of impingement decreased from 4.8 ± 4.5 cm3 after resection of the femoral head to 1.8 ± 1.6 cm3 and 1.2 ± 1.9 cm3 after release of the transverse and descending iliofemoral ligament, respectively. InterpretationWith sequential soft-tissue releases, the femur mobility increased incrementally. However, the number of releases needed for each femur varied extensively between specimens. Most (10/14) femurs became accessible after the release of the ilio-femoral or ischio-femoral ligament.

Investigation into the effect of deltoid ligament injury on rotational ankle instability using a three-dimensional ankle finite element model.

Injury to the lateral collateral ligament of the ankle may cause ankle instability and, when combined with deltoid ligament (DL) injury, may lead to a more complex situation known as rotational ankle instability (RAI). It is unclear how DL rupture interferes with the mechanical function of an ankle joint with RAI. To study the influence of DL injury on the biomechanical function of the ankle joint. A comprehensive finite element model of an ankle joint, incorporating detailed ligaments, was developed from MRI scans of an adult female. A range of ligament injury scenarios were simulated in the ankle joint model, which was then subjected to a static standing load of 300N and a 1.5Nm internal and external rotation torque. The analysis focused on comparing the distribution and peak values of von Mises stress in the articular cartilages of both the tibia and talus and measuring the talus rotation angle and contact area of the talocrural joint. The dimensions and location of insertion points of ligaments in the finite element ankle model were adopted from previous anatomical research and dissection studies. The anterior drawer distance in the finite element model was within 6.5% of the anatomical range, and the talus tilt angle was within 3% of anatomical results. During static standing, a combined rupture of the anterior talofibular ligament (ATFL) and anterior tibiotalar ligament (ATTL) generates new stress concentrations on the talus cartilage, which markedly increases the joint contact area and stress on the cartilage. During static standing with external rotation, the anterior talofibular ligament and anterior tibiotalar ligament ruptured the ankle's rotational angle by 21.8% compared to an intact joint. In contrast, static standing with internal rotation led to a similar increase in stress and a nearly 2.5 times increase in the talus rotational angle. Injury to the DL altered the stress distribution in the tibiotalar joint and increased the talus rotation angle when subjected to a rotational torque, which may increase the risk of RAI. When treating RAI, it is essential to address not only multi-band DL injuries but also single-band deep DL injuries, especially those affecting the ATTL.

Contribution of the Medial Iliofemoral Ligament to Hip Stability After Total Hip Arthroplasty Through the Direct Anterior Approach

BackgroundDislocation after total hip arthroplasty (THA) is a primary reason for THA revision. During THA through the direct anterior approach (DAA), the iliofemoral ligament, which provides the main resistance to external rotation (ER) of the hip, is commonly partially transected. We asked: (1) what is the contribution of the medial iliofemoral ligament to resisting ER after DAA THA? and (2) how much resistance to ER can be restored by repairing the ligament? MethodsA fellowship-trained surgeon performed DAA THA on 9 cadaveric specimens. The specimens were computed tomography scanned before and after implantation. Prior to testing, the ER range of motion of each specimen to impingement in neutral and 10° of extension was computationally predicted. Each specimen was tested on a 6-degrees-of-freedom robotic manipulator. The pelvis was placed in neutral and 10° of extension. The femur was externally rotated until it reached the specimen’s impingement target. Total ER torque was recorded with the medial iliofemoral ligament intact, after transecting the ligament, and after repair. Torque at extremes of motion was calculated for each condition. To isolate the contribution of the native ligament, the torque for the transected state was subtracted from both the native and repaired conditions. ResultsThe medial iliofemoral ligament contributed an average of 68% (range, 34 to 87) of the total torque at the extreme of motion in neutral and 80% (58 to 97) in 10⁰ of extension. The repaired ligament contributed 17% (1 to 54) of the total torque at the extreme of motion in neutral and 14% (5 to 38) in 10⁰ of extension, restoring on average 18 to 25% of the native resistance against ER. ConclusionsThe medial iliofemoral ligament was an important contributor to the hip torque at the extreme of motion during ER. Repairing the ligament restored a fraction of its ability to generate torque to resist ER.

Reductions in rearfoot eversion posture due to proximal muscle strengthening are dependent on foot-ankle varus alignment

BackgroundStrengthening the hip and trunk muscles may decrease foot pronation in upright standing due to expected increases in hip passive torque and lower-limb external rotation. However, considering the increased pronation caused by a more varus foot-ankle alignment, subjects with more varus may experience smaller or no postural changes after strengthening. ObjectiveTo investigate the effects of hip and trunk muscle strengthening on lower-limb posture during upright standing and hip passive torque of women with more and less varus alignment. MethodsThis nonrandomized controlled experimental study included 50 young, able-bodied women. The intervention group (n = 25) performed hip and trunk muscle strengthening exercises, and the control group (n = 25) maintained their usual activities. Each group was split into two subgroups: those with more and less varus alignment. Hip, shank, and rearfoot-ankle posture and hip passive external rotation torque were evaluated. Mixed analyses of variance and preplanned contrasts were used to assess prepost changes and between-group differences (α = 0.05). ResultsThe less-varus subgroup of the intervention group had a reduced rearfoot eversion posture (P = 0.02). No significant changes were observed in the less-varus subgroup of the control group (P = 0.31). There were no significant differences in posture between the control and intervention groups when varus was not considered (P ≥ 0.06). The intervention group had increased hip passive torque (P = 0.001) compared to the control group, independent of varus alignment. ConclusionDespite the increases in hip passive torque, the rearfoot eversion posture was reduced only in women with a less-varus alignment. Having more foot-ankle varus may prevent eversion reductions.

The Effect of Varying Sizes of Ramp Lesions in the ACL-Deficient and Reconstructed Knee: A Biomechanical Robotic Investigation

Background: Conflicting evidence has been reported regarding the biomechanical relevance of ramp lesions (RLs) on knee kinematics. Furthermore, the influence of the defect size of the RLs on anterior tibial translation (ATT) and external rotation (ER) is currently unknown. Purpose: To evaluate the influence of RL defect size on knee kinematics in anterior cruciate ligament (ACL) deficiency and after simulated ACL reconstruction (sACLR). Study Design: Controlled laboratory study. Methods: Eight cadaveric knee specimens were tested in a 6 degrees of freedom robotic test setup. Force-controlled clinical laxity tests were performed with 200 N of axial compression in 0°, 30°, 60°, and 90° of flexion: 5 N·m internal rotation (IR)/ER torque, 134 N ATT force, and an anteromedial drawer test consisting of 134 N ATT force under 5 N·m ER torque. After determining the native knee kinematics, the ACL was cut at the tibial insertion, followed by a transosseous refixation to simulate a surgical repair or reconstruction (simulated ACL reconstruction; sACLR). An RL was sequentially created with a length of 1, 2, and 3 cm. Each state of the RL was evaluated in the ACL-deficient state and after sACLR. Results: In the ACL-deficient state, only an RL of 3 cm length resulted in a significant increase of ATT in 30° of flexion (mean difference 0.73 mm; 95% CI, 0.36-1.1 mm). After sACLR, an RL had no significant effect. When looking at ER, an RL significantly increased ER in full extension in the ACL-deficient state in 2 cm (mean difference 0.9°; 95% CI, 0.08°-1.74°) and 3 cm length (mean difference 1.9°; 95% CI, 0.57-3.25). Furthermore, a 3-cm RL significantly increased IR in 0° of flexion in the ACL-deficient state (mean difference 1.9°; 95% CI, 0.2°-3.6°). No effect of ramp lesions on rotation was found after sACLR. Conclusion: RLs result in a small increase in ATT, ER, and IR in ACL-deficient knees at early flexion angles, but not after sACLR. Clinical Relevance: Small RLs did not change time-zero knee kinematics and may, therefore, be left untreated, especially when the ACL is reconstructed.

Single-Strand “Short Isometric Construct” Medial Collateral Ligament Reconstruction Restores Valgus and Rotational Stability While Isolated Deep MCL and Superficial MCL Reconstruction Do Not

Background: Historical MCL (medial collateral ligament) reconstruction (MCLR) techniques have focused on the superficial MCL (sMCL) to restore valgus stability while frequently ignoring the importance of the deep MCL (dMCL) in controlling tibial external rotation. The recent recognition of the medial ligament complex importance has multiple studies revisiting medial anatomy and questioning contemporary MCLR techniques. Purpose: To assess whether (1) an isolated sMCL reconstruction (sMCLR), (2) an isolated dMCL reconstruction (dMCLR), or (3) a novel single-strand short isometric construct (SIC) would restore translational and rotational stability to a knee with a dMCL and sMCL injury. Study Design: Controlled laboratory study. Methods: Biomechanical testing was performed on 14 fresh-frozen cadaveric knee specimens using a custom multiaxial knee activity simulator. The specimens were divided into 2 groups. The first group was tested in 4 states: intact, after sectioning the sMCL and dMCL, isolated sMCLR, and isolated dMCLR. The second group was tested in 3 states: intact, after sectioning the sMCL and dMCL, and after single-strand SIC reconstruction (SICR). In each state, 4 loading conditions were applied at 0°, 20°, 40°, 60°, and 90° of knee flexion: 8-N·m valgus torque, 5-N·m external rotation torque, 90-N anterior drawer, and combined 90-N anterior drawer plus 5-N·m tibial external rotation torque. Anterior translation, valgus rotation, and external rotation of the knee were measured for each state and loading condition using an optical motion capture system. Results: sMCL and dMCL transection resulted in increased laxity for all loading conditions at all flexion angles. Isolated dMCLR restored external rotation stability to intact levels throughout all degrees of flexion, yet valgus stability was restored only at 0° of flexion. Isolated sMCLR restored valgus and external rotation stability at 0°, 20°, and 40° of flexion but not at 60° or 90° of flexion. Single-strand SICR restored valgus and external rotation stability at all flexion angles. In the combined anterior drawer plus external rotation test, isolated dMCL and single-strand SICR restored stability to the intact level at all flexion angles, while the isolated sMCL restored stability at 20° and 40° of flexion but not at 60° or 90° of flexion. Conclusion: In the cadaveric model, single-strand SICR restored valgus and rotational stability throughout the range of motion. dMCLR restored rotational stability to the knee throughout the range of motion but did not restore valgus stability. Isolated sMCLR restored external rotation and valgus stability in early flexion. Clinical Relevance: In patients with anteromedial rotatory instability in the knee, neither an sMCLR nor a dMCLR is sufficient to restore stability.

Bilateral External Torque CT Reliably Detects Syndesmotic Lesions in an Experimental Cadaveric Study.

If tibiofibular syndesmotic injury is undetected, chronic instability may lead to persistent pain and osteoarthritis. So far, no reliable diagnostic method has been available. The primary objectives of this study were to determine whether defined lesions of the syndesmosis can be correlated with specific tibiofibular joint displacements caused by external rotational torque and to compare the performance of bilateral external torque computed tomography (BET-CT) and arthroscopy. Secondary objectives included an evaluation of the reliability of CT measurements and the suitability of the healthy contralateral ankle as a reference. Seven pairs of healthy, cadaveric lower legs were tested and assigned to 2 groups: (1) supination-external rotation (SER) and (2) pronation-external rotation (PER). In the intact state and after each surgical step, an ankle arthroscopy and 3 CT scans were performed. During the scans, the specimens were placed in an external torque device with 2.5, 5.0, and 7.5 Nm of torque applied. The arthroscopic and CT parameters showed significant correlations in all pairwise comparisons. The receiver operating characteristic (ROC) curve analyses yielded the best prediction of syndesmotic instability with the anterior tibiofibular distance on CT, with a sensitivity of 84.1% and a specificity of 95.2% (area under the curve [AUC], 94.8%; 95% confidence interval [CI], 0.916 to 0.979; p < 0.0001) and with the middle tibiofibular distance on arthroscopy, with a sensitivity of 76.2% and specificity of 92.3% (AUC, 91.2%; 95% CI, 0.837 to 0.987; p < 0.0001). Higher torque amounts increased the rate of true-positive results. BET-CT reliably detects experimental syndesmotic rotational instability, compared with the healthy side, with greater sensitivity and similar specificity compared with the arthroscopic lateral hook test. Translation of these experimental findings to clinical practice remains to be established. Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Length-Tension Differences Between Concentric and Eccentric Shoulder Rotation Strength.

Giordano, KA, Cassidy, MM, and Oliver, GD. Length-tension differences between concentric and eccentric shoulder rotation strength. J Strength Cond Res 38(2): 253-258, 2024-Eccentric contractions generally produce more force than concentric contractions. However, if length-tension relationships affect both contractions equally remains unknown. Therefore, our purpose was to compare concentric versus eccentric shoulder external and internal rotation strength across a continuous 90° arc. Fifty-two physically active individuals performed isokinetic concentric and eccentric shoulder external rotation and internal rotation through a 90° arc (forearm horizontal to forearm vertical) with the shoulder elevated in both the frontal and scapular planes. Statistical parametric mapping analysis compared concentric and eccentric trials within subjects. Frontal plane eccentric external rotation torque was greater than concentric 30°-90° (p < 0.01) external rotation, and concentric external rotation torque was greater 5°-15° external rotation (p = 0.01). Frontal plane, eccentric internal rotation torque was greater than concentric 15°-55° external rotation (p < 0.01), and concentric torque was greater at forearm horizontal (p = 0.05) and 70°-90° external rotation (p < 0.01). Scapular plane eccentric external rotation torque was greater than concentric 30°-90° external rotation (p < 0.01) and concentric external rotation torque was greater 5°-20° external rotation (p < 0.01). Scapular plane eccentric internal rotation torque was greater than concentric 15°-60° external rotation (p < 0.01), and concentric torque was greater at forearm horizontal (p = 0.05) and 78°-90° external rotation (p = 0.02). Coaches, clinicians, and researchers should interpret data from studies reporting isokinetic data with the understanding that isokinetic peak strength values are not comparing the same muscle length and are not an appropriate measure for all muscle lengths. Furthermore, shoulder stability is affected through decreased eccentric force production at end ranges of shoulder rotation.

NOVEL SINGLE-STRAND ‘SHORT ISOMETRIC CONSTRUCT’ (SIC) MEDIAL COLLATERAL LIGAMENT RECONSTRUCTION RESTORES VALGUS AND ROTATIONAL STABILITY THROUGHOUT KNEE RANGE OF MOTION

AbstractIntroductionPersistent medial laxity increases the risk of failure for ACL reconstruction. To address this, multiple reconstruction techniques have been created. To date, no single strand reconstruction constructs have been able to restore both valgus and rotational stability. In response to this, a novel single strand Short Isometric Construct (SIC) MCL reconstruction was developed.MethodsEight fresh-frozen cadaveric specimens were tested in three states: 1) intact 2) after sMCL and dMCL transection, and 3) after SIC MCL reconstruction. In each state, four loading conditions were applied at varying flexion angles: 90N anterior drawer, 5Nm tibial external rotation torque, 8Nm valgus torque, and combined 90N anterior drawer plus 5Nm tibial external rotation torque.ResultsTransection of the sMCL and dMCL resulted in increased laxity with external rotation torque, valgus torque, and combined anterior drawer plus external rotation. SIC MCL reconstruction restored external rotation and valgus stability to intact levels throughout all degrees of flexion. In the combined test SIC MCL reconstruction also restored stability to intact levels for both anterior distraction and external rotation throughout the range of motion. No significant differences were noted between intact and SIC reconstruction.ConclusionThe single-limb short isometric construct (SIC) MCL reconstruction restored native valgus and rotatory stability to a sMCL- and dMCL-deficient knee in biomechanical testing.

DEEP MEDIAL COLLATERAL LIGAMENT RECONSTRUCTION OF THE KNEE RESTORES ROTATIONAL STABILITY THROUGHOUT FULL RANGE OF MOTION WHILE CONTEMPORARY MCL RECONSTRUCTION ONLY DOES IN EXTENSION

AbstractIntroductionHistoric MCL reconstruction techniques focused on the superficial MCL to restore valgus stability while overlooking tibial external rotation and the deep MCL. This study assessed the ability of a contemporary medial collateral ligament (MCL) reconstruction and a deep MCL (dMCL) reconstruction to restore rotational and valgus knee stability.MethodsSix pairs fresh-frozen cadaveric knee specimens with intact soft tissue were tested in four states: 1) intact 2) after sMCL and dMCL sectioning, 3) contemporary MCL reconstruction (LaPrade et al), and 4) dMCL reconstruction. In each state, four loading conditions were applied at varying flexion angles: 8Nm valgus torque, 5Nm tibial external rotation torque, 90N anterior drawer, and combined 90N anterior drawer plus 5Nm tibial external rotation torque.ResultsTransection of the sMCL and dMCL resulted in increased laxity with valgus torque, external rotation torque, and combined anterior drawer plus external rotation. dMCL reconstruction restored external rotation stability to intact levels throughout all degrees of flexion but did not restore valgus stability at any flexion angle. Contemporary MCL reconstruction restored valgus and external rotation stability at 0° and 20° and valgus stability at 40°. In the combined anterior drawer plus tibial external rotation trial, the dMCL restored stability at 20° and improved stability between 40° and 90° flexion. Conversely, the contemporary MCL reconstruction did not restore stability at any degree of flexion.ConclusionDeep MCL reconstruction restored rotational stability to the knee throughout range of motion but not valgus stability. The contemporary MCL reconstruction restored stability only near full extension.

Poster 140: The Effect of Posterior Tibial Slope and Flexion Angle on Posterior Medial Meniscal Root Forces

Objectives: Although the biomechanical and clinical consequences of posterior medial meniscal root (PMMR) tears have been previously reported, these have not been fully evaluated in terms of overall bony morphology. It is well documented that higher flexion angles lead to higher postero-medial pressure, with many groups proposing that PMMR tears are caused by elevated compression and shear forces at the root when the loaded knee is at high flexion angles. Additionally, several authors have advocated that increasing tibial plateau slope (PTS) is an anatomical risk factor for PMMR tears, due to the higher posterior shear forces at the root insertion site. Thus, the purposes of this study are to evaluate the forces across the PMMR utilizing a novel three-dimensional forces sensor with varying posterior tibial slopes and flexion angles. We hypothesized that an increased flexion angle and/or posterior tibial slope will result in increased posterior shear forces acting on the PMMR. Methods: Ten fresh-frozen cadaveric knees (53.2 mean age, all male) were tested in all combinations of the three states of posterior tibial slope (5⁰, 10⁰, 15⁰) and the four states of varying flexion angles (0⁰, 30⁰, 60⁰, and 90⁰). A novel three-axis sensor that determines force measurements in three orthogonal directions was installed below the posterior tibial plateau, with the specimen being mounted to a load frame which applied a 500-N axial load. A 5-Nm internal rotational (IR) torque was then applied. After the IR torque, a 5-Nm external rotational torque was applied. The amount of compression-tension and shear forces acting on the PMMR were measured. Results: Increased tibial slope significantly decreased tension and significantly increased compression of the PMMR (5°→10°: p = 0.0368, 5°→15°: p &lt; 0.0001, 10°→15°: p &lt; 0.0001) when the joint was loaded in compression. Increased tibial slope significantly increased anterior shear of the PMMR (5°→10°: p &lt; 0.0001, 5°→15°: p &lt; 0.0001, 10°→15°: p &lt; 0.0001) when the joint was internally rotated. Increased tibial slope significantly decreased compression of the PMMR (5°→10°: p = 0.0188, 5°→15°: p &lt; 0.0001) when the joint was externally rotated. Increased flexion angle significantly increased medial shear forces of the PMMR (0°→30°: p = 0.0362, 0°→60°: p = 0.0005, 0°→90°: p &lt; 0.0001, 30°→90°: p = 0.0434) when the joint was loaded in compression. 90° of flexion significantly increased tension of the PMMR (0°→90°: p = 0.0438, 30°→90°: p &lt; 0.0001, 60°→90°: p = 0.0005) when the joint was internally rotated. 30° of flexion angle significantly increased compression of the PMMR (0°→30°: p = 0.0004, 30°→60°: p = 0.0118, 30°→90°: p &lt; 0.0001) when the joint was externally rotated. Conclusions: Increased PTS results in an increase in compression forces acting on the posterior horn of the medial meniscus when the knee joint is loaded. Increases in flexion angles displays an increase in medial shear forces seen at the PMMR under a load. This increase in force may place the PMMR at increased risk of stress and potential failure after repair. This study begins to provide clinicians with information to create safer protocols to decrease the forces experienced at the PMMR after injury or postoperatively.

Poster 297: Deep medial collateral ligament reconstruction of the knee restores rotational stability throughout full range of motion while contemporary MCL reconstruction only does in extension

Objectives: The past decade has taught the importance of identifying and treating the concomitant injuries that frequently occur at the time of ACL rupture. Failure to do so can result in increased stresses on the ACL graft and subsequently increased risk of failure. While the focus has largely been on the menisci and the anterolateral soft tissues, recent studies have highlighted high frequency at which injuries to the medial structures occur in previously presumed isolated ACL tears and the increased risk of poor outcomes when they are not addressed. Injuries to the medial ligament complex result in valgus and anteromedial rotatory instability (AMRI). Historic MCL reconstruction techniques have focused on the superficial MCL in an effort to restore valgus stability while frequently ignoring the importance of the deep MCL in controlling tibial external rotation. The recent recognition of the importance of the medial ligament complex has led to multiple studies revisiting medial sided anatomy and questioning contemporary MCL reconstruction techniques. The objective of this study is to assess and compare the ability of a contemporary medial collateral ligament (MCL) reconstruction and a deep MCL (dMCL) reconstruction to restore rotational and valgus stability to the knee. Methods: Six pairs fresh-frozen cadaveric knee specimens were included and with intact soft tissue, the distal femur and tibia were potted in PVC pipes to facilitate biomechanical testing using a customized multi-axial knee activity simulator. Four states were tested: 1) intact 2) after sectioning of the sMCL and dMCL, 3) contemporary MCL reconstruction as described by LaPrade et al, and 4) dMCL reconstruction. In each state, the knees were tested under four loading conditions at varying flexion angles (0°, 20°, 40°, 60° and 90°): 8 Nm valgus torque, 5 Nm tibial external rotation torque, 90N anterior drawer, and combined 90 N anterior drawer plus 5 Nm tibial external rotation torque. Results: Transection of the sMCL and dMCL resulted in increased laxity with the application of the valgus torque, external rotation torque, and combined anterior drawer plus external rotation at all flexion angles. dMCL reconstruction restored external rotation stability to intact levels (all p&lt;0.05) throughout all degrees of flexion (Figure 1), yet dMCL reconstruction did not restore valgus stability at any flexion angle (Figure 2). Contemporary MCL reconstruction restored valgus and external rotation stability at 0° and 20° and valgus stability at 40° (p&lt;0.01). In response to a combined anterior drawer plus tibial external rotation, the dMCL restored stability back to the intact level at 20° and improved stability between 40° and 90° flexion (Figures 3 and 4). In contrast, the contemporary MCL reconstruction did not restore stability at any degree of flexion (p&gt;0.05). Conclusions: Deep MCL reconstruction restored rotational stability to the knee throughout range of motion but did not restore valgus stability. The contemporary MCL reconstruction restore stability only near full extension.

LOW FORCE DIRECT ANTERIOR HIP ARTHROPLASTY

The trend towards more minimal access has led to a series of instruments being developed to enable adequate access for Direct Anterior Approach (DAA) for hip arthroplasty. These include longer levers, hooks attached to the operating table and a series of special attachments to the operating table to position the leg and apply traction where necessary. The forces applied in this way may be transmitted locally, damaging muscle used as a fulcrum, or the knee and ankle joints when torque has to be applied to the femur through a boot. The arthroplasty surgeon's aim is to minimise the forces applied to both bone and soft tissue during surgery.We surmised that the forces needed for adequate access were related to the extent of the capsular and soft tissue releases, and that they could be measured and optimised. with the aim of minimising the forces applied to the tissues around the hip.Eight fresh frozen specimens from pelvis to mid tibia from four cadavers were approached using the DAA. A 6-axis force/torque sensor and 6-axis motion tracking sensor were attached to a threaded rod securely fastened to the tibial and femoral diaphysis. The torque needed to provide first extension, then external rotation, adequate for hip arthroplasty were measured as the capsular structures were divided sequentially.The Zona Orbicularis (ZO) and Ischiofemoral Ligament(IFL) contributed most of the resistance to both extension (4.0 and 3.1Nm) and external rotation torque (5.8 and 3.9Nm). The contributions of the conjoint tendon (1.5 and 2.4Nm) and piriformis (1.2 and 2.3Nm) were substantially smaller.By releasing the Zona Orbicularis and Ischiofemoral Ligament, the torque needed to deliver the femur for hip arthroplasty could be reduced to less than the torque needed to open a jar (2.9–5.5Nm).

The Effects Of Differing Density Of Swim-Training Sessions On Shoulder Range Of Motion and Isometric Force Production In National and University Level Swimmers.

Well-developed physical qualities (i.e., greater load capacity) in athletes can provide protection against injuries. Although higher competitive level swimmers have more developed physical qualities, no studies have investigated how physical qualities of the shoulder respond to a swim-training session in different competitive levels. To compare baseline shoulder external rotation range of motion (ER ROM) and isometric peak torque of the shoulder internal rotators (IR) and external rotators (ER) between national and university level swimmers with differing training volumes. To compare the post-swim changes of these physical qualities between groups. Cross-sectional. Ten male swimmers (age= 18.7 ± 1.2 years) were divided into high-load (N= 5 national-level, weekly swim-volume= 37.0 ± 2.7 km) and low-load groups (N= 5 university-level, weekly swim-volume= 6.8 ± 1.8 km). For each group, shoulder active ER ROM and isometric peak torque of the shoulder IR and ER were measured before and immediately after a high-intensity swim-training session (for each group, the hardest swim-session of the week was analyzed). The results were evaluated by the level of significance (p-value), effect size, and whether changes exceeded the measurement error. University-level swimmers had lower baseline ER torque (p= 0.006; d= 2.55) and IR torque (p= 0.011; d= 2.42) than national-level swimmers. For post-swim analysis, ER ROM decreased more in university swimmers (change= -6.3° to -8.4°; d= 0.75-1.05) than national counterparts (change= -1.9° to -5.7°; d= 0.43-0.95). Greater drops in rotation torque were found in university swimmers (IR change= -15% to -21.0%; d= 0.83-1.66; ER change= -9.0% to -17.0%; d= 1.14-1.28) compared to national swimmers (IR change= -10.0% to -13.0%; d= 0.61-0.91; ER change= -3.7% to -9.1%; d= 0.50-0.96). The average change of all tests in university swimmers exceeded the minimal detectable change (MDC), whereas in national level swimmers some tests exceeded the MDC. Despite this, only post-swim ER torque in the dominant side (p= 0.003; d= 1.18) was significantly lower in university swimmers (possibly due to the small sample size). University swimmers have less baseline shoulder external and internal rotator torque and had greater drops of all shoulder physical qualities after a swim-training session, which may have implications for injury risk. However, due to the sample size, the results have to be interpreted with caution. 3.

Increased superior translation following multiple simulated anterior dislocations of the shoulder.

Recurrent shoulder dislocations can result in kinematic changes of the glenohumeral joint. The number of prior shoulder dislocations may contribute to increased severity of capsulolabral lesions. The kinematics of the glenohumeral joint following multiple dislocations remain poorly understood. The purpose of this study was to assess the kinematics of the glenohumeral joint during anterior dislocations of the shoulder, and more specifically, altered translational motion following multiple dislocations. The kinematics of the glenohumeral joint were hypothesized to change and correlate with the number of dislocations. Eight fresh-frozen cadaveric shoulders were dissected free of all soft tissues except the glenohumeral capsule. Each joint was mounted in a robotic testing system. At 60 degrees of glenohumeral abduction, an internal and external rotational torque (1.1 Nm) were applied to the humerus, and the resulting joint kinematics were recorded. Anterior forces were applied to the humerus to anteriorly dislocate the shoulder and the resulting kinematics were recorded during each dislocation. Following each dislocation, the same rotational torque was applied to the humerus, and the resulting joint kinematics were also recorded. A repeated-measures analysis of variance (ANOVA) was used to compare the kinematics following each dislocation. During the 7th, 8th, 9th, and 10th dislocations, the humerus significantly translated superiorly compared with the shoulder during the 1st dislocation (p < 0.05). Following the 3rd, 4th, 5th, and 10th dislocations, the humeral head significantly translated superiorly compared with the shoulder following the 1st dislocation in the position of 60 degrees of abduction in response to external rotation torque (p < 0.05). Multiple anterior shoulder dislocations lead to abnormal translational kinematics and result in increased superior translation of the humerus. This may contribute to pathologic superior extension of capsulolabral injuries. Superior translation of the humerus with overhead motion in the setting of recurrent instability may also place the shoulder at risk for extension of the capsulolabral injuries.

The effects of relative trunk rotation velocity on ball speed and elbow and shoulder joint torques during baseball pitching

ABSTRACT In baseball pitching, suppressing trunk rotation while rotating the pelvis in the early phase of arm cocking is important for throwing a fast ball. However, quantitative evaluation of trunk rotation during pitching has not been established, and its associations with elbow and shoulder torques are unclear. The purpose of this study was to examine the correlation of a new measure of trunk rotation suppression with ball speed and elbow and shoulder torques during pitching. Eighteen adult male baseball pitchers (21.7 ± 1.2 years old) participated. Three qualified pitches were analysed using a three-dimensional motion capture system. Trunk rotation velocity, normalised to the peak velocity, was derived at the time of peak pelvic velocity. Pearson’s correlation coefficient was used to determine correlations. The normalised trunk rotation velocity at the peak pelvic velocity was significantly correlated with elbow valgus torque (R = −0.508, P = 0.032), shoulder external rotation torque (R = −0.507, P = 0.032) and ball speed (R = −0.504, P = 0.033). A smaller normalised trunk rotation angular velocity at the time of peak pelvic rotation velocity could increase ball speed but may also increase elbow and shoulder torques among pitchers who demonstrate trunk rotation after foot contact.

Portable Dynamic Ultrasonography is a Useful Tool for the Evaluation of Suspected Syndesmotic Instability

Category: Ankle Introduction/Purpose: Portable ultrasonography (P-US) is increasingly used to diagnose syndesmotic instability. The aim of this study was to evaluate syndesmotic instability by measuring the distal tibiofibular clear space (TFCS) in a cadaveric model using P- US with progressive stages of syndesmotic ligamentous transection. Methods: Ten fresh lower leg cadaveric specimens amputated above the proximal tibiofibular joint were used. Using P-US, the TFCS was evaluated in the intact stage and after progressive sectioning of the 1) anterior-inferior tibiofibular ligament (AITFL), 2) interosseous ligament (IOL), and 3) posterior-inferior tibiofibular ligament (PITFL). The TFCS was measured in both the unstressed (0 Nm) state and with 4.5 Nm, 6.0 Nm, 7.5 Nm, and 9.0 Nm of external rotation stress at each stage of ligamentous transection stage using both P-US and fluoroscopy. Results: When assessed with P-US, partial syndesmotic injury encompassing the AITFL and IOL resulted in significant TFCS widening at 4.5 Nm of external rotation torque when compared to intact state with a TFCS-opening of 2.6 +- 2 mm, p = 0.01. In contrast, no significant differences in TFCS were detected using fluoroscopy. Only a moderate correlation was found between P- US and fluoroscopy. Conclusion: P-US is much more sensitive than fluoroscopy in diagnosing syndesmotic instability during external rotation stress examination. Extrapolated to the clinical setting, 4.5 Nm of force can be used when comparing to the stressed, uninjured side, and may be better tolerated by patients than higher torque values. When using P-US, a TFCS-opening of 2.6 mm is likely to correlate with syndesmotic instability. While absolute threshold values may vary between individuals, the ready availability of the contralateral, uninjured side overcomes this constraint.

Arthroscopic centralization reduces extrusion of the medial meniscus with posterior root defect in the ACL reconstructed knee.

The purpose of this study was to evaluate the effects of arthroscopic meniscal centralization reinforcement for a medial meniscus (MM) posterior root defect on knee kinematics and meniscal extrusion in the anterior cruciate ligament reconstructed (ACLR) knee. The hypothesis was that the medial meniscus centralization would reduce extrusion and anterior laxity in ACLR knee with a medical meniscal defect. Fourteen fresh-frozen human cadaveric knees were tested using a six-degrees-of-freedom robotic system under the following loading conditions: (a) an 89.0N anterior tibial load, (b) 5.0 Nm internal and external rotational torques, (c) a 10.0Nm valgus and varus loadings, and (d) a combined 7.0Nm valgus moment and then a 5.0Nm internal rotation torque as a static simulated pivot shift. The tested knee states included: (1) anatomic single-bundle cruciate ligament reconstruction with intact medial meniscus (MM Intact), (2) anatomic single-bundle cruciate ligament reconstruction with medial meniscus posterior root defect (MM Defect), (3) Anatomic single-bundle cruciate ligament reconstruction with medial meniscus arthroscopic centralization (MM Centralization). Medial meniscus arthroscopic centralization was performed using 1.4mm anchors with #2 suture. The MM extrusion (MME) was measured using ultrasound under unloaded and varus loading conditions at 0° and 30° of flexion. Anterior tibial translation (ATT) increased significantly with MM posterior root defect compared to MM intact at all flexion angles. With MM centralization, ATT was not significantly different from the intact meniscus at 15° and 30° of flexion. Meniscus extrusion increased significantly with the root defect compared to intact meniscus and decreased significantly with meniscal centralization compared to the root defect at both flexion angles. In ACL reconstruction, cases involving irreparable medial meniscal posterior root tears, applying arthroscopic centralization for avoiding the meniscal extrusion should be considered. Clinically, in ACL reconstruction cases with irreparable medial meniscal posterior root tears, applying arthroscopic meniscal centralization for avoiding the meniscal extrusion should be considered. Meniscal centralization decreases the extrusion of the MM and offers improvements in knee laxity.

Effect of Anterior Horn Tears of the Lateral Meniscus on Knee Stability.

Background:Investigations on the biomechanical characteristics of the anterior horn of the lateral meniscus (AHLM) related to anterior cruciate ligament (ACL) tibial tunnel reaming have revealed increased contact pressure between the femur and tibia, decreased attachment area, and decreased ultimate failure strength.Purpose/Hypothesis:The purpose of this study was to investigate the influence of a complete radial tear of the AHLM on force distribution in response to applied anterior and posterior drawer forces and internal and external rotation torques. We hypothesized that the AHLM plays an important role in knee stability, primarily at lower knee flexion angles.Study Design:Controlled laboratory study.Methods:A total of 9 fresh-frozen cadaveric knee specimens and a robotic testing system were used. Anterior and posterior drawer forces up to 89 N and internal and external rotation torques up to 4 N·m were applied at 0°, 30°, 60°, and 90° of knee flexion. A complete AHLM tear was then made 10 mm from the lateral border of the tibial attachment of the ACL, and the same tests performed in the intact state were repeated. Next, the recorded intact knee motion was reproduced in the AHLM-torn knee, and the change in the resultant force after an AHLM tear was determined by calculating the difference between the 2 states.Results:In the torn AHLM, the reduction in the resultant force at 0° for external rotation torque (34.8 N) was larger than that at 60° (5.2 N; P < .01) and 90° (6.7 N; P < .01).Conclusion:The AHLM played a role in facilitating knee stability against an applied posterior drawer force of 89 N and external rotation torque of 4 N·m, especially at lower knee flexion angles.Clinical Relevance:This study provides information about the effects of AHLM injuries that may occur during single-bundle ACL reconstruction using a round tunnel.