Knee Flexion-induced Translation of Pullout Sutures Used in the Repair of Medial Meniscus Posterior Root Tears.

Medial meniscus posterior root tears (MMPRTs) have recently attracted considerable interest in orthopedics. To date, no in vivo human study has investigated suture translation changes in repaired MMPRTs with different degrees of knee flexion. This study examined suture translation at various degrees of knee flexion in 30 patients undergoing medial meniscus posterior root repair using the modified Mason-Allen suture technique between August 2016 and September 2017. Intraoperatively, sutures were provisionally fixed to an isometric positioner at the tibial site of the desired meniscal attachment, and the suture translation was measured at 0°, 30°, 60°, and 90° of knee flexion. The results showed significant increases in mean suture translation at the knee flexion positions from 0° to 30°, 30° to 60°, and 60° to 90° (p<0.01 for all). Our findings indicate that surgeons should carefully assess the degree of knee flexion at the moment when the meniscus is refixed by surgical sutures.

Effect of Percentage of Femoral Anterior Cruciate Ligament Insertion Site Reconstructed With Hamstring Tendon on Knee Kinematics and Graft Force.

BACKGROUND: Previous studies have stated that closely matching the size of the anterior cruciate ligament (ACL) insertion site footprint is important for biomechanical function and clinical stability after ACL reconstruction. However, the ACL varies widely regarding the area of femoral insertion, tibial insertion, and midsubstance of ACL, and reconstructing the insertion site area with a uniform diameter graft can result in a cross-sectional area that is greater than that of the midsubstance of the native ACL. Therefore, understanding the effect of relative graft size in ACL reconstruction on knee biomechanics is important for surgical planning. PURPOSE: To assess how the percentage of femoral insertion site affects knee biomechanics in single- and double-bundle ACL reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 14 human cadaveric knees were scanned with magnetic resonance imaging and tested using a robotic system under an anterior tibial load and a combined rotational load. In total, 7 knee states were evaluated: intact ACL; deficient ACL; single-bundle ACL reconstruction with approximate graft sizes 25% (small), 50% (medium), and 75% (large) of the femoral insertion site; and double-bundle reconstruction of approximately 50% (medium) and 75% (large) of the femoral insertion site, based on the ratio of the cross-sectional area of the graft to the area of the femoral ACL insertion site determined by magnetic resonance imaging. RESULTS: Anterior tibial translation was not significantly larger than the intact state in single-bundle and double-bundle medium graft reconstructions (P > .05) and was significantly greater in the single-bundle small graft reconstruction (P < .05). Anterior knee translation in single-bundle medium graft and large graft reconstructions was not statistically different (P > .05). In contrast, the anterior tibial translation for double-bundle large graft reconstruction was significantly smaller than for double-bundle medium graft reconstruction at low flexion angles (P < .05). The single-bundle small graft force was significantly different from the intact ACL in situ force (P < .05). The graft force with double-bundle large reconstruction was significantly greater than that with the double-bundle medium reconstruction (P < .05) but was not significantly different from that of the intact ACL (P > .05). CONCLUSION: Knee biomechanics with a single-bundle small graft tended to be significantly different from those of the intact knee. In the kinematic and kinetic data for the single- and double-bundle medium graft reconstruction, only the anterior translation at full extension for the single-bundle reconstruction was significantly different (lower) from that of intact knee. This was a time zero study. CLINICAL RELEVANCE: This study can provide surgeons with guidance in selecting the graft size for ACL reconstruction.

A histological study of the medial meniscus posterior root tibial insertion.

Purpose/Aim of the study: Posterior root injury of the medial meniscus often leads to articular cartilage degeneration due to altered biomechanics. To avoid dysfunction, the attachment must be repaired using the transtibial pullout technique. To guide appropriate placement of the tibial tunnel, additional details on the normal anatomy of the meniscus insertion are needed. Therefore, we performed a histological analysis of a tibial bone slice with the medial meniscus posterior insertion obtained during total knee arthroplasty surgery. Materials and methods: Horizontal slices of the proximal tibia were obtained from 7 patients with osteoarthritis who underwent total knee arthroplasty. After decalcification, the region of the posterior horn was cut out and segmented into four pieces (2.0 mm thickness; medial to lateral). Sagittal sections were evaluated by safranin O staining or immunohistochemistry with anti-type collagen antibody. Results: Safranin O staining showed that the insertion of the posterior root consisted primarily of fibrocartilaginous layers in segment 2. Anatomically, segment 2 corresponded to the sagittal plane passing through the peak of the medial intercondylar tubercle. In this section, safranin O staining and immunohistochemistry revealed that the anterior one-third of the posterior root insertion was richer in proteoglycans and type II collagen than the central and posterior one-third. Conclusions: Anatomical insertion of the posterior root of the medial meniscus was located at the sagittal plane passing through the peak of the medial intercondylar tubercle. The structure of the medial meniscus posterior insertion was mainly localized in the anterior one-third.

Arthroscopic scoring system of meniscal healing following medial meniscus posterior root repair.

PURPOSE: Medial meniscus posterior root tear (MMPRT) leads to a rapid degradation of articular cartilage. In the treatment of MMPRT, transtibial pullout repair demonstrates a high clinical survival rate. However, there is no reliable method to evaluate the meniscal healing after surgery. We propose an arthroscopic scoring system for evaluating the meniscal healing status. The aim of this study was to investigate the correlations between second-look arthroscopic scores and clinical outcomes after transtibial pullout repair. METHODS: Twenty patients who had MMPRTs underwent transtibial pullout repairs. Clinical outcomes were assessed using the Japanese Knee Injury and Osteoarthritis Outcome Score (KOOS) and pain score evaluated by visual analogue scale at preoperatively and 1 year postoperatively. The healing status of repaired MM was assessed at one year post-operatively using a semi-quantitative arthroscopic scoring system (total, 10 points) composed of three evaluation criteria: (i) anteroposterior width of bridging tissues, (ii) stability of the MM posterior root, and (iii) synovial coverage of the sutures. Linear regression analysis was used to assess the correlation between second-look arthroscopic scores and clinical outcomes. RESULTS: Transtibial pullout repairs of MMPRTs significantly improved clinical evaluation scores at one year post-operatively. A median of second-look arthroscopic scores was 6.5 (5.75-8). A good correlation was observed between the arthroscopic score and KOOS quality of life (QOL) subscale. A moderate negative correlation between the arthroscopic score and pain score was observed. CONCLUSIONS: This study demonstrated that our semi-quantitative scoring system of meniscal healing correlated with the KOOS QOL subscale following MMPRT transtibial pullout repair. Our results suggest that the second-look arthroscopic score using this system may be a useful scale to determine and compare the healing status of the MM posterior root.

Complete tear of the lateral meniscus posterior root is associated with meniscal extrusion in anterior cruciate ligament deficient knees.

This study aimed to evaluate the relationship between preoperative lateral meniscal extrusion (LME) and arthroscopic findings of lateral meniscus posterior root tear (LMPRT) in knees with anterior cruciate ligament (ACL) tear. Thirty-five knees that had LMPRTs with concomitant ACL tears on arthroscopy were evaluated. Patients were divided into two groups, partial and complete root tears, via arthroscopic findings at the time of ACL reconstruction. For comparison, we added two groups, using the same database; 20 normal knees (normal group) and 20 ACL-injured knees without LM injury (intact LM group). We retrospectively measured preoperative LMEs using magnetic resonance imaging (MRI). Twenty-three knees had partial LMPRTs. Complete LMPRTs were observed in 12 knees. The average LME was -0.1 ± 0.4 mm in the normal group, 0.2 ± 0.5 mm in the intact LM group, 0.4 ± 0.8 mm in the partial LMPRT group, and 2.0 ± 0.6 mm in the complete LMPRT group. A significant difference in preoperative LMEs was observed between the complete LMPRT group and the other groups (p < 0.001). The receiver operating curve analysis, which distinguishes a partial tear from a complete tear, identified an optimal cut-off point of 1.1 mm for preoperative LME. This LME cut-off had a sensitivity of 100% and specificity of 83% for complete LMPRT. We found that preoperative LMEs were larger in complete LMPRTs associated with ACL injuries than in partial LMPRTs. Our results suggest that preoperative MRI-detected LME may be a useful indicator for estimating LMPRT severity in ACL-injured knees. LEVEL OF EVIDENCE: Retrospective comparative study level IV. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1894-1900, 2018.

Improvement in the medial meniscus posterior shift following anterior cruciate ligament reconstruction.

PURPOSE: Anterior cruciate ligament (ACL) reconstruction can reduce the risk of developing osteoarthritic knees. The goals of ACL reconstruction are to restore knee stability and reduce post-traumatic meniscal tears and cartilage degradation. A chronic ACL insufficiency frequently results in medial meniscus (MM) injury at the posterior segment. How ACL reconstruction can reduce the deformation of the MM posterior segment remains unclear. In this study, we evaluated the form of the MM posterior segment and anterior tibial translation before and after ACL reconstruction using open magnetic resonance imaging (MRI). METHODS: Seventeen patients who underwent ACL reconstructions without MM injuries were included in this study. MM deformation was evaluated using open MRI before surgery and 3 months after surgery. We measured medial meniscal length (MML), medial meniscal height (MMH), medial meniscal posterior body width (MPBW), MM-femoral condyle contact width (M-FCW) and posterior tibiofemoral distance (PTFD) at knee flexion angles of 10° and 90°. RESULTS: There were no significant pre- and postoperative differences during a flexion angle of 10°. At a flexion angle of 90°, MML decreased from 43.7 ± 4.5 to 41.4 ± 4.5 mm (P < 0.001), MMH from 7.5 ± 1.4 to 6.9 ± 1.4 mm (P = 0.006), MPBW from 13.1 ± 2.0 to 12.2 ± 1.9 mm (P < 0.001) and M-FCW from 10.0 ± 1.5 to 8.5 ± 1.5 mm (P < 0.001) after ACL reconstruction. The PTFD increased from 2.1 ± 2.8 to 2.7 ± 2.4 mm after ACL reconstruction (P = 0.015). CONCLUSIONS: ACL reconstruction affects the contact pattern between the MM posterior segment and medial femoral condyle and can reduce the deformation of the MM posterior segment in the knee-flexed position by reducing abnormal anterior tibial translation. It possibly prevents secondary injury to the MM posterior segment and cartilage that progresses to knee osteoarthritis. LEVEL OF EVIDENCE: IV.

Tibial eminence width can predict the presence of complete discoid lateral meniscus: A preliminary study.

BACKGROUND: To compare the plain knee radiograph finding of tibial eminence width between knees with complete discoid lateral meniscus, incomplete discoid lateral meniscus, and normal lateral meniscus. MATERIALS AND METHODS: The study included 27 knees with discoid lateral meniscus, including 13 knees with complete discoid lateral meniscus and 14 knees with incomplete discoid lateral meniscus. A control group of 14 knees with normal lateral meniscus was also included. Tibial eminence width and the lateral slope angle of the medial tibial eminence were assessed using plain frontal knee radiographs. Individual differences in knee size were corrected by dividing tibial eminence width by tibial width to obtain the tibial eminence width percentage. RESULTS: Mean tibial eminence width and tibial eminence width percentage in the complete discoid lateral meniscus group was significant larger than other groups. Mean lateral slope angle in the complete discoid lateral meniscus group was significantly smaller than other groups. A tibial eminence width cut-off of 13.9 mm showed a sensitivity and specificity of 100% and 83%, respectively. A tibial eminence width percentage cut-off of 18.8% showed a sensitivity and specificity of 100% and 90%, respectively. A lateral slope angle cut-off of 27.1° showed a sensitivity and specificity of 71% and 83%, respectively. CONCLUSION: There were clear differences in tibial eminence width, tibial eminence width percentage, and lateral slope angle between the complete discoid lateral meniscus group and the other groups. The plain radiographic parameters identified by this study could be useful for complete discoid lateral meniscus screening. STUDY DESIGN: Clinical.

Tensile strength of the pullout repair technique for the medial meniscus posterior root tear: a porcine study.

PURPOSE: The purpose of this study was to compare the load-to-failure of different common suturing techniques with a new technique for the medial meniscus posterior root tear (MMPRT). METHODS: Thirty porcine medial menisci were randomly assigned to three suturing techniques used for transtibial pullout repair of the MMPRT (n = 10 per group). Three different meniscal suture configurations were studied: the two simple suture (TSS) technique, the conventional modified Mason-Allen suture (MMA) technique, and the new MMA technique using the FasT-Fix combined with the Ultrabraid (F-MMA). The ultimate failure load was tested using a tensile testing machine. RESULTS: The MMA and F-MMA groups demonstrated significantly higher failure loads than the TSS group (P = 0.0003 and P = 0.0005, respectively). No significant differences were observed between the MMA and F-MMA groups (P = 0.734). CONCLUSIONS: The ultimate failure load was significantly greater in the F-MMA than the TSS group and similar to the conventional MMA technique.

A giraffe neck sign of the medial meniscus: A characteristic finding of the medial meniscus posterior root tear on magnetic resonance imaging.

BACKGROUND: The posterior root ligament of the medial meniscus (MM) has a critical role in regulating the MM movement. An accurate diagnosis of the MM posterior root tear (MMPRT) using magnetic resonance imaging (MRI) is important for preventing sequential osteoarthritis following the MMPRT. However, diagnosis of the MMPRT is relatively difficult even after using several characteristic MRI findings. The aim of this study was to identify a useful meniscal body sign of the MMPRT for improving diagnostic MRI reading. METHODS: Eighty-five patients who underwent surgical treatments for the MMPRT (39 knees) and other types of MM tears (49 knees) were included. The presence of characteristic MRI findings such as cleft sign, ghost sign, radial tear sign, medial extrusion sign, and new meniscal body shape-oriented "giraffe neck sign" was evaluated in 120 MRI examinations. RESULTS: Giraffe neck signs were observed in 81.7% of the MMPRTs and in 3.3% of other MM tears. Cleft, ghost, and radial tear signs were highly positive in the MMPRTs compared with other MM tears. Medial extrusion signs were frequently observed in both groups. Coexistence rates of any 2 MRI signs, except for medial extrusion sign, were 91.7% in the MMPRT group and 5% in other MM tears. CONCLUSIONS: This study demonstrated that a new characteristic MRI finding "giraffe neck sign" was observed in 81.7% of the MMPRT. Our results suggest that the combination of giraffe neck, cleft, ghost, and radial tear signs may be important for an accurate diagnostic MRI reading of the MMPRT.

A novel suture technique using the FasT-Fix combined with Ultrabraid for pullout repair of the medial meniscus posterior root tear.

Medial meniscus posterior root has an important role in the maintenance of knee articular cartilage. Although pullout repair of the medial meniscus posterior root tear has become a gold standard, it has several difficulties for suturing. We have developed a modified Mason-Allen suture technique using the FasT-Fix all-inside suture device combined with Ultrabraid. The present suture technique allows a strong grasping of the medial meniscus posterior horn for arthroscopic pullout repair.

The distribution of vascular endothelial growth factor in human meniscus and a meniscal injury model.

BACKGROUND: The meniscus plays an important role in controlling the complex biomechanics of the knee. Meniscus injury is common in the knee joint. The perimeniscal capillary plexus supplies the outer meniscus, whereas the inner meniscus is composed of avascular tissue. Angiogenesis factors, such as vascular endothelial growth factor (VEGF), have important roles in promoting vascularization of various tissues. VEGF-mediated neovascularization is beneficial to the healing of injured tissues. However, the distribution and angiogenic role of VEGF remains unclear in the meniscus and injured meniscus. We hypothesized that VEGF could affect meniscus cells and modulate the meniscus healing process. METHODS: Menisci were obtained from total knee arthroplasty patients. Meniscal injury was created ex vivo by a microsurgical blade. VEGF mRNA and protein expression were detected by the polymerase chain reaction and immunohistochemical analyses, respectively. RESULTS: In native meniscal tissue, the expression of VEGF and HIF-1α mRNAs could not be detected. However, VEGF and HIF-1α mRNAs were found in cultured meniscal cells (VEGF: outer > inner; HIF-1α: outer = inner). Injury increased mRNA levels of both VEGF and HIF-1α, with the increase being greatest in the outer area. Immunohistochemical analyses revealed that VEGF protein was detected mainly in the outer region and around injured areas of the meniscus. However, VEGF concentrations were similar between inner and outer menisci-derived media. CONCLUSIONS: This study demonstrated that both the inner and outer regions of the meniscus contained VEGF. HIF-1α expression and VEGF deposition were high in injured meniscal tissue. Our results suggest that injury stimulates the expression of HIF-1α and VEGF that may be preserved in the extracellular matrix as the healing stimulator of damaged meniscus, especially in the outer meniscus.

Bony landmark between the attachment of the medial meniscus posterior root and the posterior cruciate ligament: CT and MR imaging assessment.

OBJECTIVES: (1) To reveal the prevalence of the bony recess (posterior dimple) and (2) to determine the position of the posterior dimple on the tibial plateau using three-dimensional computed tomography (3DCT). MATERIALS AND METHODS: In this study, a retrospective review of 112 patients was performed to identify the posterior dimple and to evaluate its position on 3DCT. Magnetic resonance images (MRIs) were also used to determine the positional relationship among the posterior cruciate ligament (PCL), medial meniscus posterior insertion (MMPI), and posterior dimple. RESULTS: The posterior dimple was observed in 100 of 112 knees (89.3%) on 3DCT. The center of the posterior dimple was 13.6 ± 0.8 mm from the medial tibial eminence apex. MRI showed that the posterior dimple separated the tibial attachment of the PCL and MMPI. CONCLUSION: This is the first study to discuss the prevalence and position of the bony recess in the posterior intercondylar fossa.

Formation of ring-shaped lateral meniscus following anterior cruciate ligament reconstruction: A case report.

INTRODUCTION: We presented the first case in the literature of inter-horn bridge formation involved in ring-shaped lateral meniscus after anterior cruciate ligament (ACL) reconstruction. PRESENTATION OF CASE: A 22-year-old man underwent anatomic double-bundle ACL reconstruction using semitendinosus tendon autograft. At the surgery, the lateral meniscus showed a normal appearance without meniscal tears and had no instability. There were no meniscal anomalies such as discoid meniscus and ring-shaped meniscus. Magnetic resonance image examination was performed before second-look arthroscopy at 1 year postoperatively. A coronal plane showed a small triangular fragment located at the medial border of the lateral tibial plateau. An axial plane demonstrated a ring-shaped lateral meniscus. On second-look arthroscopy, there was a meniscus-like tissue formation that connected the anterior horn to the posterior horn of the lateral meniscus at the lateral intercondylar tubercle. DISCUSSION: Ring-shaped meniscus is an extremely rare malformation of the meniscus. Our hypothesis was that drilling debris and remaining remnant of ACL might induce a scar tissue formation. CONCLUSION: This is the first case in the literature of inter-horn bridge formation involved in ring-shaped lateral meniscus following ACL reconstruction.

Hyaluronan stimulates chondrogenic gene expression in human meniscus cells.

Purpose/Aim of the Study: Inner meniscus cells have a chondrocytic phenotype, whereas outer meniscus cells have a fibroblastic phenotype. In this study, we examined the effect of hyaluronan on chondrocytic gene expression in human meniscus cells. MATERIALS AND METHODS: Human meniscus cells were prepared from macroscopically intact lateral meniscus. Inner and outer meniscus cells were obtained from the inner and outer halves of the meniscus. The cells were stimulated with hyaluronan diluted in Dulbecco's modified Eagle's medium without serum to the desired concentration (0, 10, 100, and 1000 µg/mL) for 2-7 days. Cellular proliferation, migration, and polymerase chain reaction analyses were performed for the inner and outer cells separately. Meniscal samples perforated by a 2 mm diameter punch were maintained for 3 weeks in hyaluronan-supplemented medium and evaluated by histological analyses. RESULTS: Hyaluronan increased the proliferation and migration of both meniscus cell types. Moreover, cellular counts at the surface of both meniscal tissue perforations were increased by hyaluronan treatments. In addition, hyaluronan stimulated α1(II) collagen expression in inner meniscus cells. Accumulation of type II collagen at the perforated surface of both meniscal samples was induced by hyaluronan treatment. Hyaluronan did not induce type I collagen accumulation around the injured site of the meniscus. CONCLUSION: Hyaluronan stimulated the proliferation and migration of meniscus cells. Our results suggest that hyaluronan may promote the healing potential of meniscus cells in damaged meniscal tissues.

Location of the tibial tunnel aperture affects extrusion of the lateral meniscus following reconstruction of the anterior cruciate ligament.

The anterior root of the lateral meniscus provides functional stability to the meniscus. In this study, we evaluated the relationship between the position of the tibial tunnel and extrusion of the lateral meniscus after anterior cruciate ligament reconstruction, where extrusion provides a proxy measure of injury to the anterior root. The relationship between extrusion and tibial tunnel location was retrospectively evaluated from computed tomography and magnetic resonance images of 26 reconstructed knees, contributed by 25 patients aged 17-31 years. A measurement grid was used to localize the position of the tibial tunnel based on anatomical landmarks identified from the three-dimensional reconstruction of axial computed tomography images of the tibial plateaus. The reference point-to-tibial tunnel distance (mm) was defined as the distance from the midpoint of the lateral edge of the grid to the posterolateral aspect of the tunnel aperture. The optimal cutoff of this distance to minimize post-operative extrusion was identified using receiver operating curve analysis. Extrusion of the lateral meniscus was positively correlated to the reference point-to-tibial tunnel distance (r 2 = 0.64; p < 0.001), with a cutoff distance of 5 mm having a sensitivity to extrusion of 83% and specificity of 93%. The mean extrusion for a distance >5 mm was 0.40 ± 0.43 mm, compared to 1.40 ± 0.51 mm for a distance ≤5 mm (p < 0.001). Therefore, a posterolateral location of the tibial tunnel aperture within the footprint of the anterior cruciate ligament decreases the reference point-to-tibial tunnel distance and increases extrusion of the lateral meniscus post-reconstruction. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1625-1633, 2017.

Pseudoaneurysm of the Perforating Branch of the Deep Femoral Artery Following Anterior Cruciate Ligament Reconstruction.

The present report describes the first known, case of a pseudoaneurysm of the perforating branch of the deep femoral artery following anterior cruciate ligament (ACL) reconstruction. A 19-year-old man underwent ACL reconstruction using the outside-in femoral tunnel-creation method. Seven days after the surgery, he complained of abnormal thigh pain and had swelling with local heat on the distal lateral thigh. Magnetic resonance imaging, computed tomography, and color Doppler ultrasonography showed the pseudoaneurysm in the thigh. Resection surgery was successfully performed by a vascular surgeon 12 days after ACL reconstruction. Careful examination and awareness of postoperative symptoms such as thigh pain and swelling after ACL reconstruction were critical for the early diagnosis of pseudoaneurysm.

Features of human autologous hamstring graft elongation after pre-tensioning in anterior cruciate ligament reconstruction.

PURPOSE: Precise pre-tensioning protocol of the graft has not been determined in anterior cruciate ligament (ACL) reconstruction. The aims of this study are to measure the human autologous graft elongation, and to reveal what portion of the graft elongated greater after pre-tensioning in ACL reconstruction. METHODS: Twenty-four hamstring tendon grafts which were harvested from patients were included. A continuous load of 150 N was applied to the graft twice for 30 seconds each (150 N-1 minute), and the same loading was repeatedly applied (150 N-2 minute). The amount of elongation of the tendon portion (Length T) and the stitched portion (Length S) were measured after each pre-tensioning. RESULTS: Length S gradually increased by 1.57 ± 0.67 mm after the 150 N-1 minute pre-tensioning and by 2.12 ± 0.76 mm after the 150 N-2 minute pre-tensioning, respectively. Length T was not significantly elongated after 150 N-1 min (p = 0.66) and 150 N-2 min (p = 0.59). CONCLUSIONS: Graft elongation of the approximately 2 mm was observed, particularly in the stitched portion. It is necessary for a surgeon to focus on careful removal of slack from each stitch during suturing.

The anterior cruciate ligament-lateral meniscus complex: A histological study.

The anterior root of the lateral meniscus (LM) dives underneath the tibial attachment of the anterior cruciate ligament (ACL). Although the distinct role of meniscal attachments has been investigated, the relationship between the LM anterior insertion (LMAI) and ACL tibial insertion (ACLTI) remains unclear. This study histologically analyzed the LMAI and ACLTI. Samples were divided into four regions in an anterior-to-posterior direction. Histological measurements of these insertion sites were performed using safranin O-stained coronal sections. Distribution and signal densities of type I and II collagen were quantified. The ACLTI and LMAI formed the ACL-LM complex via fiber connections. The anterior part of the ACLTI had a widespread attachment composed of dense fibers. Attachment fibers of the LMAI became dense and wide gradually at the middle-to-posterior region. The ACL-LM transition zone (ALTZ) was observed between the LMAI and the lateral border of the ACLTI at the middle part of the ACL tibial footprint. Type II collagen density of the LMAI was higher than that of the ACLTI and ALTZ. Our results can help create an accurate tibial bone tunnel within the dense ACL attachment during ACL reconstruction surgery.

Evaluation of the semitendinosus tendon graft shift in the bone tunnel: an experimental study.

PURPOSE: The purpose of this study was to measure the semitendinosus tendon graft shift at the tunnel aperture with graft bending using a simulated femoral bone tunnel. METHODS: Eight semitendinosus tendon grafts were used in this study. The median age of the specimen was 53 years (range 46-63). After stripping excess soft tissue, the semitendinosus tendon was doubled over the loop of the EndoButton CL (Smith and Nephew Inc.). The diameter of the graft was measured using a graft-sizing tube (Smith and Nephew Inc.) and verified to be 7.0 mm. A custom-made aluminium fixture, the size was 40.0 mm(3), with 7.0-mm-diameter hole was used as a simulated femoral bone tunnel. The graft was inserted to the tunnel, and EndoButton was positioned to the outside of the tunnel on the fixture. The distal end of the graft was tensioned with 30 N at an angle of 15°, 30°, 45°, 60°, 75° that reproduced the graft bending angle during knee range of motion. The photograph of the tunnel aperture was taken at each graft bending angle using a digital camera, and the graft shift amount in the simulated tunnel was analysed using the computer software (ImageJ). RESULTS: The amount of the graft shift significantly increased when the graft bending angle was increased (P < 0.05). The biggest shift was observed when the graft bending angle was 75° in all specimens, and the value was 1.10 mm ± 0.12. CONCLUSION: The present study suggests that even if the femoral tunnel was created in the centre of the ACL insertion site, the graft shifted within the tunnel in the direction of the tension applied to the graft during knee range of motion. Surgeons may have to consider the graft shift within the bone tunnel as well as the tunnel position in the restoration of the native ACL anatomy.

Effect of fixation angle and graft tension in double-bundle anterior cruciate ligament reconstruction on knee biomechanics.

PURPOSE: To compare the effect of graft fixation angle and tension in double-bundle anterior cruciate ligament (ACL) reconstruction on knee biomechanics. METHODS: Fourteen cadaver knees were tested using a robotic system under two loadings: (1) an 89-N anterior tibial load (ATL) at full extension (FE), 15°, 30°, 45°, 60°, and 90°, and (2) combined 7 N m valgus and 5 N m internal tibial torques (simulated pivot-shift test) at FE, 15° and 30°. Four graft fixation angles and tensions were used for the anteromedial (AM) and posterolateral (PL) bundles, respectively: (Recon 1) 30°/20N and FE/20N, (Recon 2) 30°/30N and FE/10N, (Recon 3) 45°/20N and 15°/20N, and (Recon 4) 45°/30N and 15°/10N. RESULTS: All fixation protocols closely restored the intact knee kinematics under ATL and simulated pivot-shift loading. For the AM bundle under ATL, the in situ force (ISF) with Recon 3 at the FE was significantly lower than that of the intact knee. For the PL bundle under ATL, the ISF with Recon 3 at the FE, 15° and 30° was significantly higher than that of the intact knee. In PL bundle under simulated pivot-shift loading, the ISF with Recon 1 and Recon 2 at FE was lower and the ISF of the PL bundle with Recon 3 at the 15° was higher than that of the intact knee. CONCLUSION: The AM-45°/30N and PL-15°/10N fixation most closely matched intact knee kinematics; however, stabilizing the knee during anterior tibial translation may risk an imbalance of the AM and the PL bundle loading. The results indicate that ACL bundle forces may not be restored even if the clinical assessment shows good results with the Lachman test and pivot-shift test. This may alter the loading on other structures of the knee.