Optimal hinge level in opening wedge high tibial osteotomy: Biomechanical analysis using finite element method.

BACKGROUND: While the concept of a safe zone, which can minimize the hinge fracture when performing opening wedge high tibial osteotomy, has been introduced, there is a lack of understanding of the biomechanical environment at the lateral tibial cortex. This study aimed to evaluate the effect of the hinge level on the biomechanical environment at the lateral cortex of the tibia with heterogeneous finite element models. METHODS: Finite element models of biplanar opening wedge high tibial osteotomy based on computed tomography images of a control subject and three patients with medial compartment knee osteoarthritis were created. In each model, three different hinge levels (proximal, middle, and distal) were set. The process of opening the gap during the operation was simulated, and the maximum von Mises stress values at the lateral tibial cortex were calculated for each hinge level and correction angle. FINDINGS: The maximum von Mises stress value at the lateral tibial cortex was the lowest when the hinge was at the middle, while the value was the highest when the hinge was at the distal level. Furthermore, it was demonstrated that a higher correction angle yielded a higher probability of lateral tibial cortex fracture. INTERPRETATION: The findings of this study demonstrate that the hinge at the point where the upper end of the articular cartilage of the proximal tibiofibular joint is located provides the least possibility of lateral tibial cortex fracture, as this is an anatomically independent position from the fibula.

Medial Meniscus Posterior Root Repair Restores Contact Pressure and Contact Area to Its Native State Even After Opening-Wedge High Tibial Osteotomy: A Cadaveric Biomechanical Study.

PURPOSE: To elucidate the effect of medial meniscus posterior root (MMPR) repair during opening-wedge high tibial osteotomy (OWHTO) in terms of contact pressure (CP) and contact area (CA). METHODS: Nine fresh-frozen human cadaveric knee specimens were included. Each specimen was tested under 9 conditions comprising 3 different degrees of correction during OWHTO (neutral, 5° of valgus, and 10° of valgus) and 3 different types of MMPR conditions (intact, torn, and repaired). The prepared specimens were attached to a customized tibiofemoral jig in a fully extended state. The CP and CA generated by a tibiofemoral axial load of 650 N was recorded using the Tekscan sensor's pressure mapping software. Statistical analysis was performed using a repeated measures analysis of variance. RESULTS: The increased CP and decreased CA in torn MMPR was decreased and increased, respectively, to the intact MMPR after repairing, irrespective of whether OWHTO was performed. The mean CP at a correction angle of 5° of valgus was 0.4067 ± 0.0768 MPa for intact MMPR, which increased to 0.7340 ± 0.1593 MPa for the torn MMPR and decreased to 0.3614 ± 0.0639 MPa for the repaired MMPR. In addition, the proportion of decrease in CP and increase in CA after MMPR repair was constant, compared with the torn MMPR, irrespective of the degree of correction during OWHTO. CONCLUSIONS: MMPR repair decreases CP and increases CA, irrespective of whether OWHTO is performed. The biomechanical advantage of repairing torn MMPR is maintained, regardless of the degree of correction during OWHTO. CLINICAL RELEVANCE: Both OWHTO and MMPR repair are known to protect the medial compartment of the knee. However, there are concerns in performing 2 procedures simultaneously. Results of our study showed that concurrent repair of the MMPR during OWHTO is useful for protecting the medial compartment of the knee with respect to tibiofemoral contact biomechanics.

Biomechanical Effects of Aspect Ratio of the Knee during Outside-In Anterior Cruciate Ligament Reconstruction Surgery.

We analyzed tunnel length, graft bending angle, and stress of the graft according to tunnel entry position and aspect ratio (ASR: ratio of anteroposterior depth to mediolateral width) of the articular surface for the distal femur during single-bundle outside-in anterior cruciate ligament reconstruction (ACLR) surgery. We performed multiflexible body dynamic analyses with four ASR (98, 105, 111, and 117%) knee models. The various ASRs were associated with approximately 1 mm changes in tunnel length. The graft bending angle increased when the entry point was far from the lateral epicondyle and was larger when the ASR was smaller. The graft was at maximum stress, 117% ASR, when the tunnel entry point was near the lateral epicondyle. The maximum stress value at a 5 mm distance from the lateral epicondyle was 3.5 times higher than the 15 mm entry position, and the cases set to 111% and 105% ASR showed 1.9 times higher stress values when at a 5 mm distance compared with a 15 mm distance. In the case set at 98% ASR, the low-stress value showed a without-distance difference from the lateral epicondyle. Our results suggest that there is no relationship between the ASR and femoral tunnel length. A smaller ASR causes a higher graft bending angle, and a larger ASR causes greater stress in the graft.

A three-dimensional finite element analysis on the effects of implant materials and designs on periprosthetic tibial bone resorption.

INTRODUCTION: Implant material is a more important factor for periprosthetic tibial bone resorption than implant design after total knee arthroplasty (TKA). The virtual perturbation study was planned to perform using single case of proximal tibia model. We determined whether the implant materials' stiffness affects the degree of periprosthetic tibial bone resorption, and whether the effect of material change with the same implant design differed according to the proximal tibial plateau areas. MATERIALS AND METHODS: This three-dimensional finite element analysis included two cobalt-chromium (CoCr) and two titanium (Ti) tibial implants with different designs. They were implanted into the proximal tibial model reconstructed using extracted images from computed tomography. The degree of bone resorption or formation was measured using the strain energy density after applying axial load. The same analysis was performed after exchanging the materials while maintaining the design of each implant. RESULTS: The degree of periprosthetic tibial bone resorption was not determined by the type of implant materials alone. When the implant materials were changed from Ti to CoCr, the bone resorption in the medial compartment increased and vice versa. The effect of material composition's change on anterior and posterior areas varied accordingly. CONCLUSIONS: Although the degree of bone resorption was associated with implant materials, it differed depending on the design of each implant. The effect on the degree of bone resorption according to the materials after TKA should be evaluated while concomitantly considering design.

Regeneration of a full-thickness defect in rotator cuff tendon with umbilical cord-derived mesenchymal stem cells in a rat model.

Although rotator cuff disease is a common cause of shoulder pain, there is still no treatment method that could halt or reveres its development and progression. The purpose of this study was to investigate the efficacy of umbilical cord-derived mesenchymal stem cells (UC MSCs) on the regeneration of a full-thickness rotator cuff defect (FTD) in a rat model. We injected either UC MSCs or saline to the FTD and investigated macroscopic, histological and biomechanical results and cell trafficking. Treatment with UC MSCs improved macroscopic appearance in terms of tendon thickness at two weeks, and inflammation, defect size, swelling/redness and connection surrounding tissue and slidability at four weeks compared to the saline group. Histologically, UC MSCs induced the tendon matrix formation recovering collagen organization, nuclear aspect ratio and orientation angle of fibroblast as well as suppressing cartilage-related glycosaminoglycan compared to saline group at four weeks. The UC MSCs group also improved ultimate failure load by 25.0% and 19.0% and ultimate stress by 27.3% and 26.8% at two and four weeks compared to saline group. UC MSCs labeled with PKH26 exhibited 5.3% survival at four weeks compared to three hours after injection. This study demonstrated that UC MSCs regenerated the FTD with tendon tissue similar properties to the normal tendon in terms of macroscopic, histological and biomechanical characteristics in a rat model.

Regeneration of a full-thickness defect of rotator cuff tendon with freshly thawed umbilical cord-derived mesenchymal stem cells in a rat model.

BACKGROUND: It is difficult to immediately use mesenchymal stem cells (MSCs) for the patient with rotator cuff disease because isolation and culture time are required. Thus, the MSCs would be prepared in advanced in cryopreserved condition for an "off-the-shelf" usage in clinic. This study investigated the efficacy of freshly thawed MSCs on the regeneration of a full-thickness tendon defect (FTD) of rotator cuff tendon in a rat model. METHODS: We evaluated morphology, viability, and proliferation of cultured umbilical cord-derived MSCs (C-UC MSCs) and freshly thawed umbilical cord-derived MSCs (T-UC MSCs) at passage 10 in vitro. In animal experiments, we created a FTD in the supraspinatus of rats and injected the injured tendon with saline, cryopreserved agent (CPA; control), C-UC MSCs, and T-UC MSCs, respectively. Two and 4 weeks later, macroscopic, histological, biomechanical, and cell trafficking were evaluated. T test and ANOVA were used with SPSS. Differences with p < .05 were considered statistically significant. RESULTS: T-UC MSCs had fibroblast-like morphology and showed greater than 97% viability and stable proliferation comparable to the C-UC MSCs at passage 10. In animal experiments, compared with the control group, the macroscopic appearance of the T-UC MSCs was more recovered at 2 and 4 weeks such as inflammation, defect size, neighboring tendon, swelling/redness, the connecting surrounding tissue and slidability. Histologically, the nuclear aspect ratio, orientation angle of fibroblasts, collagen organization, and fiber coherence were improved by 33.33%, 42.75%, 1.86-fold, and 1.99-fold at 4 weeks, and GAG-rich area decreased by 88.13% and 94.70% at 2 and 4 weeks respectively. Further, the T-UC MSCs showed enhanced ultimate failure load by 1.55- and 1.25-fold compared with the control group at both 2 and 4 weeks. All the improved values of T-UC MSCs were comparable to those of C-UC MSCs. Moreover, T-UC MSCs remained 8.77% at 4 weeks after injury, and there was no significant difference between C-UC MSCs and T-UC MSCs. CONCLUSIONS: The morphology, viability, and proliferation of T-UC MSCs were comparable to those of C-UC MSCs. Treatment with T-UC MSCs could induce tendon regeneration of FTD at the macroscopic, histological, and biomechanical levels comparable to treatment with C-UC MSCs.

Regeneration of the rotator cuff tendon-to-bone interface using umbilical cord-derived mesenchymal stem cells and gradient extracellular matrix scaffolds from adipose tissue in a rat model.

Regeneration of the gradient structure of the tendon-to-bone interface (TBI) is a crucial goal after rotator cuff repair. The purpose of this study was to investigate the efficacy of a biomimetic hydroxyapatite-gradient scaffold (HA-G scaffold) isolated from adipose tissue (AD) with umbilical cord derived mesenchymal stem cells (UC MSCs) on the regeneration of the structure of the TBI by analyzing the histological and biomechanical changes in a rat repair model. As a result, the HA-G scaffold had progressively increased numbers of hydroxyapatite (HA) particles from the tendon to the bone phase. After seeding UC MSCs to the scaffold, specific matrices, such as collagen, glycoaminoglycan, and calcium, were synthesized with respect to the HA density. In a rat repair model, compared to the repair group, the UC MSCs seeded HA-G scaffold group had improved collagen organization and cartilage formation by 52% at 8 weeks and 262.96% at 4 weeks respectively. Moreover, ultimate failure load also increased by 30.71% at 4 weeks in the UC MSCs seeded HA-G scaffold group compared to the repair group. Especially, the improved values were comparable to values in normal tissue. This study demonstrated that HA-G scaffold isolated from AD induced UC MSCs to form tendon, cartilage and bone matrices similar to the TBI structure according to the HA density. Furthermore, UC MSC-seeded HA-G scaffold regenerated the TBI of the rotator cuff in a rat repair model in terms of histological and biomechanical properties similar to the normal TBI. Statement of Significance We found specific extracellular matrix (ECM) formation in the biomimetic-hydroxyapatite-gradient-scaffold (HA-G-scaffold) in vitro as well as improved histological and biomechanical results of repaired rotator cuff after the scaffold implantation in a rat model. This study has four strengths; An ECM scaffold derived from human adipose tissue; only one-layer used for a gradient scaffold not a multilayer used to mimic the unique structure of the gradient tendon-to-bone-interface (TBI) of the rotator cuff; UC-MSCs as a new cell source for TBI regeneration; and the UC-MSCs synthesized specific matrices with respect to the HA density without any other stimuli. This study suggested that the UC-MSC seeded HA-G-scaffold could be used as a promising strategy for the regeneration of rotator cuff tears.

Tendon Regeneration After Partial-Thickness Peroneus Longus Tendon Harvesting: Magnetic Resonance Imaging Evaluation and In Vivo Animal Study.

BACKGROUND: In recent years, the use of the anterior half of the peroneus longus tendon (AHPLT) as an autograft source for ligament reconstruction has gained popularity. However, no reports are available regarding tendon regeneration after harvesting of the AHPLT. HYPOTHESIS: When half of the tendon is preserved during tendon harvesting, the quality of the regenerated tendon is better than that of the regenerated tendon after full-thickness harvesting. STUDY DESIGN: Case series; Level of evidence, 4; controlled laboratory study. METHODS: A total of 21 patients who underwent AHPLT harvesting for lower extremity ligament reconstruction participated in the magnetic resonance imaging (MRI) study to evaluate tendon regeneration 1 year after the harvesting. An in vivo animal study was performed to compare the quality of the regenerated tendon after partial-thickness and full-thickness tendon harvesting. A total of 30 adult female Sprague-Dawley rats were allocated to 2 groups-15 rats underwent partial-thickness Achilles tendon harvesting (partial-thickness harvesting [PTH] group), and 15 rats underwent full-thickness Achilles tendon harvesting (full-thickness harvesting [FTH] group). The quality of the regenerated tendons was compared 180 days after tendon harvesting. RESULTS: All 21 patients showed regeneration of the peroneus longus tendon (PLT) (homogeneously dark on both T1- and T2-weighted sequences). The cross-sectional area of the regenerated tendon divided by that of the preoperative tendon was 92.6% and 84.5% at 4 cm and 9 cm proximal to the tip of the distal fibula, respectively. In the animal study, the mean histologic score was better for the PTH group compared with the FTH group (9.17 ± 1.35 vs 14.72 ± 0.74; P < .001). The ultimate strength and the stiffness of the regenerated Achilles tendon were significantly higher for the PTH group compared with the FTH group (35.5 ± 8.3 vs 22.4 ± 8.3 N, P = .004; and 31.6 ± 7.7 vs 23.5 ± 4.8 N/mm, P = .016). CONCLUSION: The PLT was found to regenerate after partial-thickness harvesting on MRI. In the animal study, the quality of the regenerated tendon when half of the tendon was preserved during tendon harvesting was better than that after full-thickness tendon harvesting.

Comparison of Tibiofemoral Contact Mechanics After Various Transtibial and All-Inside Fixation Techniques for Medial Meniscus Posterior Root Radial Tears in a Porcine Model.

PURPOSE: To compare tibiofemoral contact mechanics after fixation for medial meniscus posterior root radial tears (MMPRTs). METHODS: Seven fresh knees from mature pigs were used. Each knee was tested under 5 conditions: normal knee, MMPRT, pullout fixation with simple sutures, fixation with modified Mason-Allen sutures, and all-inside fixation using Fastfix 360. The peak contact pressure and contact surface area were evaluated using a capacitive sensor positioned between the meniscus and tibial plateau, under a 1,000-N compression force, at different flexion angles (0°, 30°, 60°, and 90°). RESULTS: The peak contact pressure was significantly higher in MMPRTs than in normal knees (P = .018). Although the peak contact pressure decreased significantly after fixation at all flexion angles (P = .031), it never recovered to the values noted in the normal meniscus. No difference was observed among fixation groups (P = .054). The contact surface area was significantly lower in MMPRTs than in the normal meniscus (P = .018) and increased significantly after fixation at all flexion angles (P = .018) but did not recover to within normal limits. For all flexion angles except 60°, the contact surface area was significantly higher for fixation with Mason-Allen sutures than for fixation with simple sutures or all-inside fixation (P = .027). At 90° of flexion, the contact surface area was significantly better for fixation with simple sutures than for all-inside fixation (P = .031). CONCLUSIONS: The peak contact pressure and contact surface area improved significantly after fixation, regardless of the fixation method, but did not recover to the levels noted in the normal meniscus after any type of fixation. Among the fixation methods evaluated in this time 0 study, fixation using modified Mason-Allen sutures provided a superior contact surface area compared with that noted after fixation using simple sutures or all-inside fixation, except at 60° of flexion. However, this study had insufficient power to accurately detect the differences between the outcomes of various fixation methods. CLINICAL RELEVANCE: Our results in a porcine model suggest that fixation can restore tibiofemoral contact mechanics in MMPRT and that fixation with a locking mechanism leads to superior biomechanical properties.

A Comparative Biomechanical Study of Femoral Cortical Suspension Devices for Soft-Tissue Anterior Cruciate Ligament Reconstruction: Adjustable-Length Loop Versus Fixed-Length Loop.

PURPOSE: To determine whether there are differences between adjustable-length loop and fixed-length loop devices in terms of the amount of displacement, temporal pattern of displacement, and ultimate failure load when tested using 4,500 cycles of sinusoidal loading with high loads (100-400 N). METHODS: Two cortical suspension devices with a fixed- or adjustable-length loop were tested. For our comparisons, a 20-mm fixed-length loop device and a fixed-length loop device with the same loop length were used. Comparisons between the devices used both a device-only model (DOM) and a device-bone-soft-tissue graft construct model (CM). RESULTS: In the DOM, the adjustable-length loop device showed weaker mechanical properties. Mean cumulative peak displacement was 1.91 mm for the adjustable-length loop device and 0.74 mm for the fixed-length loop device (P = .001). The displacement of the adjustable-length loop device increased between 1,000 and 4,500 cycles; in contrast, that of the fixed-length loop device reached a plateau. However, there was never displacement greater than 3 mm. In addition, the adjustable-length loop device showed a weaker ultimate failure load (925 N vs 1,410 N, P = .001). In the CM, the difference in cumulative peak displacement between the 2 groups decreased and did not reach statistical significance. The displacement of both devices showed a similar pattern. In addition, there was no difference in ultimate failure load between the 2 groups. CONCLUSIONS: There was no significant difference in terms of total displacement, temporal pattern of displacement, and ultimate failure load between the 2 devices in the CM, which is the more clinically relevant model. Furthermore, even in the DOM, the difference in total displacement was small and did not reach a clinically meaningful level. Therefore, both devices can be used effectively during anterior cruciate ligament reconstruction with soft-tissue graft. CLINICAL RELEVANCE: Both femoral cortical suspension devices with adjustable- and fixed-length loops can be used with similar mechanical properties during anterior cruciate ligament reconstruction.

Effect of femoral tunnel positions on graft stress in outside-in ACL reconstruction surgery during continuous knee motion: A simulation study.

BACKGROUND: Previous studies regarding the optimal femoral tunnel location for an anterior cruciate ligament (ACL) reconstruction were based on static experiments at specific angles, and did not consider continuous motion of the knee. METHODS: Twenty-four surgical sites were set and continuous kinematic data, obtained from motion analysis, was used to describe knee movement. The bending angle and stress of the ACL graft as well as the length of the femoral tunnel was calculated through multi-flexible body dynamics analysis. RESULTS: The lowest stress was found at both 5 mm and 10 mm radius at a proximal posterior of 45°, and the highest stress was also found at a distal 15 mm radius. Relatively high stresses were also identified between the distal and anterior regions as well as the distal and posterior regions at 15 mm radius. CONCLUSION: Considering the availability of surgery, it was identified that the optimum femoral tunnel location is at 10 mm radius locations at a proximal posterior of 45°.

High Axial Loads While Walking Increase Anterior Tibial Translation in Intact and Anterior Cruciate Ligament-Deficient Knees.

PURPOSE: To evaluate the effect of high axial loading (AL) on anterior tibial translation (ATT) according to the increase in knee flexion and the effect of valgus stress (VS) and internal rotation (IR) combined with high AL in intact and anterior cruciate ligament (ACL)-deficient knees according to the increase in knee flexion. METHODS: We used 10 fresh-frozen, human cadaveric knees. Different loading conditions (134-N anterior drawer, 1,000-N AL, 10-Nm VS, and 5-Nm IR) were sequentially combined, and ATT was measured at 0°, 15°, 30°, 45°, and 60° of flexion in the intact and ACL-deficient knees. RESULTS: ATT increased significantly by adding high AL in intact knees (P = .001) and ACL-deficient knees (P < .0001) according to the change in flexion angle (P < .0001). Under high AL, ATT in the ACL-deficient knees was significantly larger than that in the intact knees for all loading conditions, and it also increased gradually according to the increase in knee flexion (P = .0001). ATT increased significantly after adding IR or VS with high AL in intact knees (VS, P = .002; VS/IR, P = .03) and ACL-deficient knees (VS, P = .0004) at some of the flexion angles. CONCLUSIONS: The added high AL increased ATT in intact and ACL-deficient knees from 0° to 60° of flexion. The effect of high AL on ATT became greater in ACL-deficient knees than in intact knees, and ATT also gradually increased according to the increase in knee flexion from 0° to 60°. In both the intact and ACL-deficient knees, ATT increased significantly after valgus stress or IR from 0° to 60°. CLINICAL RELEVANCE: ATT during weight bearing increases stress to the ACL, which worsens with valgus stress and/or IR forces. This finding should be considered when one is studying ACL injury mechanisms, as well as prescribing rehabilitation after ACL surgery.

Evaluation of physical and emotional responses to vibrotactile stimulation of the forearm in young adults, the elderly, and transradial amputees.

Vibrotactile stimulation (VS) is widely used in the biomedical and biomechanics fields. Most studies have attempted to verify the effects and/or function of VS, but few studies have evaluated emotional response (ER) to VS, although emotions play a critical role in human behavior. This study aimed to evaluate the subjective response (SR) to VS in young, elderly, and amputee adults and to verify whether VS on the forearm evokes displeasure. Twenty-four young adults (YM: male 13, YF: female 11), 31 elderly subjects (EM: male 15, EF: female 16), and 19 transradial amputees (AM: male 11, AF: female 8) participated. Eight equally spaced vibration motors were attached around the circumference of the forearm (channels 1-4 on the lateral site and channels 5-8 on the medial site) and were located 25% of the proximal forearm. Vibration stimuli with frequencies ranging from 37Hz to 258Hz were applied. An SR 10-level test and ER (displeasure or not) test were performed. In all 3 groups, SRs to the lateral site were higher than those to the medial site (YM group, p<0.001; YF group, p=0.002; EM group, p<0.001; EF group, p=0.031; AM group, p<0.001; AF group, p=0.021). Additionally, SRs were saturated at certain frequencies (YM group, 149Hz; YF and EM groups, 198Hz; EF and AM groups, 120Hz; AF group, 176Hz). Several subjects (YM group, 7; YF group, 4; EM group, 2; EF group, 6; AM group, 3; AF group, 1) expressed displeasure, and ERs were different according to sex, age, or amputation. As a result, the lateral site was more sensitive to VS than the medial site, regardless of sex, age, or amputation. Furthermore, VS may evoke displeasure.

Effect of axial loading during knee flexion on ACL end-to-end distance in healthy and ACL-deficient knees.

PURPOSE: The purpose of this study was to determine the effect of physiological axial loading during knee flexion on changes in anterior cruciate ligament (ACL) end-to-end distance for normal and ACL-deficient knees. METHODS: Biomechanical tests were conducted on ten cadaveric knees using an Instron machine. We gathered positional data of the tibia and femur at low to middle flexion angles (0°, 15°, 30°, 45° and 60°) with/without axial loading. First, no external load was applied to the specimens at each angle, and then, a 1000-N axial load was applied to the knees. The same test protocols were repeated after transection of the ACL. Using computer software (Geomagic Studio 10), we regenerated positional data and calculated the end-to-end distances of the anteromedial, posterolateral and the entire ACL bundle at each angle. RESULTS: Compared with ACL-intact knees without axial loading, knees under axial loading did not show significant increases in end-to-end distance. Under axial loading, we found no significant differences in end-to-end distances between bundles in ACL-intact knees according to the increase in knee flexion angle. After ACL transection, axial loading significantly increased end-to-end distances of all three bundles (P < 0.001), and the distances increased significantly with flexion angle (P < 0.05 at all angles in all bundles). CONCLUSION: The changing patterns of the ACL end-to-end distance in ACL-deficient knees were different from those in healthy knees after applying physiological axial loading, and the ACL end-to-end distances in ACL-deficient knees increased remarkably as knee flexion angles increased.

Biomechanical effect of altered lumbar lordosis on intervertebral lumbar joints during the golf swing: a simulation study.

Although the lumbar spine region is the most common site of injury in golfers, little research has been done on intervertebral loads in relation to the anatomical-morphological differences in the region. This study aimed to examine the biomechanical effects of anatomical-morphological differences in the lumbar lordosis on the lumbar spinal joints during a golf swing. The golf swing motions of ten professional golfers were analyzed. Using a subject-specific 3D musculoskeletal system model, inverse dynamic analyses were performed to compare the intervertebral load, the load on the lumbar spine, and the load in each swing phase. In the intervertebral load, the value was the highest at the L5-S1 and gradually decreased toward the T12. In each lumbar spine model, the load value was the greatest on the kypholordosis (KPL) followed by normal lordosis (NRL), hypolordosis (HPL), and excessive lordosis (EXL) before the impact phase. However, results after the follow-through (FT) phase were shown in reverse order. Finally, the load in each swing phase was greatest during the FT phase in all the lumbar spine models. The findings can be utilized in the training and rehabilitation of golfers to help reduce the risk of injury by considering individual anatomical-morphological characteristics.

Inferior anchor cortical perforation with arthroscopic Bankart repair: a cadaveric study.

PURPOSE: The aims of this study were to evaluate the incidence of anchor penetration of the far cortex of the glenoid neck after arthroscopic Bankart repair and to compare the biomechanical properties of anchors in the 4- and 5:30- to 6-o'clock positions on the glenoid. METHODS: Twelve (6 matched pairs) fresh-frozen human cadaveric shoulders were used to simulate arthroscopic Bankart repair in the lateral decubitus position. The most inferior anchor (5:30 to 6 o'clock) and that above it (4 o'clock) were inserted via the anteroinferior portal on the glenoid using the standard technique. After both anchor insertions, anchor perforation of the glenoid far cortex was identified. Biomechanical properties were measured to determine cyclic displacement of anchors at 100 and 500 cycles, stiffness, yield load, and ultimate failure strength. RESULTS: All 12 suture anchors (100%) at 5:30 to 6 o'clock penetrated throughout the far cortex, whereas only 4 anchors (33%) at 4 o'clock did so (P = .005). The mean distance the anchor tip traveled into far cortex was significantly longer at 5:30 to 6 o'clock than at 4 o'clock (6.8 ± 1.6 mm v 2.0 ± 1.6 mm, P = .001). In terms of mechanical strength, anchors at 5:30 to 6 o'clock had greater 100- and 500-cycle mean displacements than those at 4 o'clock (3.0 ± 0.5 mm v 2.5 ± 0.3 mm, P = .018 for 100 cycles; 3.5 ± 0.7 mm v 2.8 ± 0.3 mm, P = .018 for 500 cycles), although no differences in ultimate failure strength after cyclic loading were found between 2 positions (133.4 ± 40.3 and 133.7 ± 29.2 N, respectively; P = .985). CONCLUSIONS: For arthroscopic Bankart repair, insertion of the most inferior anchor via the anteroinferior portal with standard technique, in the lateral decubitus position, carries a high risk of perforating the inferior far cortex of the glenoid (100% in our study). This may result in mechanical weakness of the most inferior repair specifically in the early postoperative period. CLINICAL RELEVANCE: Perforation of the glenoid far cortex by the most inferior anchor and its mechanical weakness should be taken into consideration. Further study is needed to improve surgical technique to place the most inferior anchor in an optimal position by arthroscopy.

Tibiofemoral contact mechanics following posterior root of medial meniscus tear, repair, meniscectomy, and allograft transplantation.

PURPOSE: The purposes of this study were to evaluate the effect on tibiofemoral contact mechanics of repair of the posterior root of the medial meniscus and the effect of meniscal allograft transplantation (MAT) with medial collateral ligament (MCL) release at different flexion angles. METHODS: Ten fresh-frozen human cadaveric knees (five pairs) were used. A digital pressure sensor was inserted by capsulotomy, and experiments were performed serially under the following six conditions, that is, with an intact medial meniscus (normal controls), with a root tear, after root repair, after total meniscectomy, after MAT, and after MAT plus MCL release. During each experiment, knees were positioned at 0°, 30°, 60°, and 90° of flexion, and peak pressure (kPa) and contact area (cm2) were measured. RESULTS: At 0° of flexion, contact pressure did not differ among the six experimental settings. However, at 30° and 60° of flexion, contact pressure differed significantly between root tear and root repair specimens (p = 0.04 and 0.03, respectively), and between total meniscectomy and MAT specimens (p = 0.02 and 0.03, respectively). On the other hand, mean contact pressures were different between normal (476.7 ± 473.1 and 573.3 ± 479.1 kPa) and root repair (575.7 ± 357.8 and 598.6 ± 415.8), and between normal and MAT (635.7 ± 437.4 and 674.3 ± 533.2). At 0°, 30°, 60°, and 90° of flexion, contact areas differed significantly between normal and total meniscectomy specimens (p = 0.02, 0.01, 0.02, and 0.02, respectively), and between MAT and total meniscectomy specimens (p = 0.03, 0.02, 0.02, and 0.03, respectively). Contact areas differed significantly between root tear and root repair specimens at 60° of flexion (p = 0.04), and between normal control and root repair specimens at 60° and 90° of flexion (p = 0.03 and 0.04, respectively). The effects of MAT plus MCL release on contact mechanics were not different from the effects of MAT alone (n.s.). CONCLUSIONS: Both meniscal root repair and transplantation of meniscus improved contact mechanics, but it did not appear that repair of the meniscal root or transplantation of meniscus restores the biomechanical function back to normal level. The MAT plus MCL release was similar to those after MAT alone. Therefore, it is better to preserve meniscus and MCL release could be done during the MAT.

WITHDRAWN: Somatic sensibility to mechanical vibrations on the forearms of seniors and transradial amputees.

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Relative role changing of lateral collateral ligament on the posterolateral rotatory instability according to the knee flexion angles: a biomechanical comparative study of role of lateral collateral ligament and popliteofibular ligament.

PURPOSE: This cadaveric study assessed the relative role of the lateral collateral ligament (LCL) and popliteofibular ligament (PFL) in limiting tibia external rotation. METHODS: Eight paired cadaveric knees were divided into two groups. The specimens were mounted on a rotational wheel and 5 Nm external rotation torque was applied before and after cutting the ligaments at 0°-30°-60°-90° knee flexion. Three cutting steps were applied: (1) PT (popliteus tendon)-, (2) LCL-, (3) PFL in group I, and (1) PT-, (2) PFL-, (3)LCL in group II. Increased external rotation at each step was taken as the ratio of final external rotation at the end of step 3. Repeated measure ANOVA and a Mann-Whitney U test were used for statistical analysis. RESULTS: At step 2, the ratio of increased external rotation after cutting the LCL (group I) was similar to the ratio after cutting the PFL (group II) at 0° and 30° flexion, but that of group I was lower than group II at 60° and 90° flexion (p = 0.029 and p = 0.029). At step-3, the ratio after cutting the LCL (group II) was less than the ratio after cutting the PFL (group I) at 90° flexion (p = 0.029). CONCLUSION: The PFL and LCL play equally important roles in limiting external rotation at the knee extended position (0°, 30°) but the LCL contribution becomes smaller than PFL at the flexed position (60°, 90°).

Longitudinal tear of the medial meniscus posterior horn in the anterior cruciate ligament-deficient knee significantly influences anterior stability.

BACKGROUND: Longitudinal tears of the medial meniscus posterior horn (MMPH) are commonly associated with a chronic anterior cruciate ligament (ACL) deficiency. Many studies have demonstrated the importance of the medial meniscus in terms of limiting the amount of anterior-posterior tibial translation in response to anterior tibial loads in ACL-deficient knees. HYPOTHESIS: An MMPH tear in an ACL-deficient knee increases the anterior-posterior tibial translation and rotatory instability. In addition, MMPH repair will restore the tibial translation to the level before the tear. STUDY DESIGN: Controlled laboratory study. METHODS: Ten human cadaveric knees were tested sequentially using a custom testing system under 5 conditions: intact, ACL deficient, ACL deficient with an MMPH peripheral longitudinal tear, ACL deficient with an MMPH repair, and ACL deficient with a total medial meniscectomy. The knee kinematics were measured at 0°, 15°, 30°, 60°, and 90° of flexion in response to a 134-N anterior and 200-N axial compressive tibial load. The rotatory kinematics were also measured at 15° and 30° of flexion in a combined rotatory load of 5 N·m of internal tibial torque and 10 N·m of valgus torque. RESULTS: Medial meniscus posterior horn longitudinal tears in ACL-deficient knees resulted in a significant increase in anterior-posterior tibial translation at all flexion angles except 90° (P < .05). An MMPH repair in an ACL-deficient knee showed a significant decrease in anterior-posterior tibial translation at all flexion angles except 60° compared with the ACL-deficient/MMPH tear state (P < .05). The total anterior-posterior translation of the ACL-deficient/MMPH repaired knee was not significantly increased compared with the ACL (only)-deficient knee but was increased compared with the ACL-intact knee (P > .05). A total medial meniscectomy in an ACL-deficient knee did not increase the anterior-posterior tibial translation significantly compared with MMPH tears in ACL-deficient knees at all flexion angles (P > .05). In a combined rotatory load, tibial rotation after MMPH tears or a total medial meniscectomy in an ACL-deficient knee were not affected significantly at all flexion angles. CONCLUSION: This study shows that an MMPH longitudinal tear in an ACL-deficient knee alters the knee kinematics, particularly the anterior-posterior tibial translation. MMPH repair significantly improved anterior-posterior tibial translation in ACL-deficient knees. CLINICAL RELEVANCE: These findings may help improve the treatment of patients with ACL and MMPH longitudinal tear by suggesting that the medial meniscal repairs should be performed for greater longevity when combined with an ACL reconstruction.