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Purpose: To investigate the influences of time from injury to surgery and meniscal injuries on knee rotational laxity in anterior cruciate ligament (ACL)-deficient knees using the electromagnetic system retrospectively., Methods: Ninety-four unilateral ACL-injured patients (44 male and 50 female, mean age: 27.3 ± 11.8 years) were included. The pivot-shift test was performed before ACL reconstruction, as was a quantitative evaluation using the electromagnetic system to determine tibial acceleration. Patients were divided into 4 groups according to the chronicity: group 1, within 3 months (22 patients); group 2, between 3 and 6 months (29 patients); group 3, between 6 and 12 months (23 patients); and group 4, more than 12 months (20 patients). The presence of meniscal injuries was examined arthroscopically., Results: The tibial acceleration was significantly greater in group 4. There was a positive correlation between tibial acceleration and the time from injury to surgery (r = 0.47, P = .02). In groups 1, 2 and 3, the tibial acceleration in patients with a lateral meniscal injury was significantly greater than in patients with a medial meniscal injury and without meniscal injury. When patients with lateral meniscal injury were excluded (leaving those with medial meniscus injury or without meniscal injury), group 4 had significantly greater accelerations than other groups., Conclusions: In ACL-deficient knees, rotational laxity increased with time and the increased rotational laxity was evident more than 1 year after injury whereas it increased with concomitant lateral meniscal injuries within 1 year after injury., Level of Evidence: Ⅳ, diagnostic study of nonconsecutive patients., (Copyright © 2020 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the tension deprivation through the tunnels with and without preconditioning at the time of fixation, and the influences of cyclic loading and pretensioning on graft tension in anatomic single bundle anterior cruciate ligament (ACL) reconstruction using a hamstring tendon., Methods: Nine fresh-frozen cadaveric knees underwent anatomic ACL reconstruction using hamstring grafts. Each specimen was examined to ensure that there was no severe osteoarthritic change, ligament insufficiency, or torn menisci by manual and arthroscopic evaluation. Applied graft tension was measured at the tibial tunnel outlet using a graft tensor with a load cell. Intra-articular graft tension was evaluated by using an originally developed microforce sensor, which was sutured into the graft. Both tensions were simultaneously measured just after initial tensioning under 3 different conditions: condition 1, just after initial tensioning of 20 N at 20° of knee flexion without preconditioning; condition 2, after the same initial tensioning following 5 rounds of passive cyclic flexion-extension movement; and condition 3, after the same initial tensioning following 5 minutes of static pretensioning of 20 N., Results: The intra-articular tension was 12.7 ± 5.3 N in condition 1, 12.0 ± 4.8 N in condition 2, and 13.5 ± 4.8 N in condition 3. In these 3 conditions, intra-articular graft tension was significantly lower than the applied tension of around 20 N (no pretension: P = .009, cyclic pretension: P = .004, static pretension: P = .008), with no difference among the 3 conditions (P = .82)., Conclusions: The intra-articular graft tension was significantly lower than the applied tension from the outside of the joint, even after cyclic loading and pretensioning., Clinical Relevance: It is difficult to evaluate the intra-articular graft tension precisely on the basis of the extra-articular tension at time zero in ACL reconstruction., (Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate quantitatively the biomechanical function of anterior cruciate ligament (ACL) remnants in patients with ACL injuries. Anterior tibial translation (ATT) with KT-1000 and during the Lachman test with an electromagnetic measurement system (EMS) and tibial acceleration during the pivot shift test with EMS were measured., Methods: A total of 121 unilateral ACL injuries were examined. ACL remnants were morphologically classified as being attached to the posterior cruciate ligament (PCL group), to the roof of the intercondylar notch (RIN group), to the lateral wall of the intercondylar notch (LWIN group), or as having no substantial remnants (NONE group). Partial ACL tears were excluded. ATT was measured using KT-1000. ATT during the Lachman test and tibial acceleration during the pivot shift test were measured using EMS., Results: ACL remnant patterns were as follows: PCL group, 27 knees; RIN group, 34 knees; LWIN group, 27 knees; and NONE group, 33 knees. The ATT side-to-side difference in LWIN group (3.4 ± 0.7 mm) by KT-1000 was significantly smaller than the RIN (5.7 ± 1.0 mm) and NONE groups (5.9 ± 1.0 mm) (P < .05). The ATT side-to-side difference during the Lachman test was significantly smaller in the LWIN group (5.3 ± 1.2 mm) than the PCL (8.6 ± 1.4 mm), RIN (8.5 ± 1.2 mm), and NONE groups (7.6 ± 1.0 mm) (P < .05). Tibial accelerations were 2.0 ± 0.4, 1.7 ± 0.2, 1.9 ± 0.2, and 1.8 ± 0.3 m/s(2) in the PCL, RIN, LWIN, and NONE groups, respectively. There were no significant differences among groups., Conclusions: ACL remnants attached to the lateral wall of the intercondylar notch partially contributed to anterior-posterior stability but did not contribute to dynamic knee stability. These findings suggest that ACL remnants attached to nonanatomic insertion sites do not contribute significantly to knee stabilization., Level of Evidence: Level III, diagnostic study of nonconsecutive patients., (Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To compare the tunnel enlargement of double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) with and without suturing of autologous ruptured tissue to hamstring graft in patients with subacute anterior cruciate ligament injury., Methods: Ten patients with subacute (≤3 months after injury) anterior cruciate ligament rupture were randomly allocated to undergo DB ACLR with suturing of the ruptured tissue to hamstring graft (n = 5) or conventional DB ACLR (n = 5). When autologous ruptured tissue was used, remnant ruptured tissue was then harvested, divided into 4 pieces, placed between the loops at the distal and proximal portions of the graft, and secured with the suture. As the primary endpoint, tunnel volume assessment by 3-dimensional multi-detector row computed tomography (MDCT) was performed 1 year after ACLR. To assess the efficacy of these procedures, the Lysholm score, anterior tibial translation (measured with a KT-1000 arthrometer [MEDmetric, San Diego, CA]), and rotational instability (measured by the pivot-shift test) were evaluated after 2 years., Results: Tunnel volume enlargement between 3 weeks and 1 year after ACLR as assessed by 3-dimensional MDCT was significantly less for ACLR using ruptured tissue than for conventional ACLR, especially at the femoral site (P < .05). However, the postoperative Lysholm score, anterior stability of the knee measured with the KT-1000 arthrometer, and rate of negative manual pivot-shift test results did not differ significantly between the 2 groups. There was no correlation to the clinical outcomes in terms of tunnel size., Conclusions: The Lysholm score, anterior laxity measured with the KT-1000 arthrometer, and rotational instability according to the pivot-shift test did not differ significantly between ACLR using ruptured tissue and the conventional technique. However, ACLR using ruptured tissue produced less femoral tunnel enlargement as assessed by MDCT, warranting further long-term follow-up to elucidate its effectiveness., Level of Evidence: Level II, prospective comparative study., (Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the biomechanical function of anterior cruciate ligament (ACL) remnants in ACL-deficient knees with both partial and complete tears., Methods: Twenty partial ACL-deficient (group P), 20 complete ACL-deficient (group C), and 40 contralateral ACL-intact knees were examined. The end point during the Lachman test, side-to-side differences of KT-1000 measurements, and the pivot shift test were evaluated. Additionally, the side-to-side difference of anterior tibial translation during the Lachman test and the acceleration during the pivot shift test were calculated using an electromagnetic measurement system (EMS)., Results: The end point was found in 9 patients in group P, whereas it was not detected in group C. In KT-1000 measurements, the mean side-to-side differences were 3.8 ± 2.4 mm in group P and 5.4 ± 2.3 mm in group C. There was a significant difference between these 2 groups (P < .05). In the pivot shift test evaluation in group P, one patient was evaluated as grade 0, 17 patients as grade 1+, and 2 patients as grade 2+. In group C, 10 patients were evaluated as grade 1+, 9 patients as grade 2+, and one patient as grade 3+. Using the EMS, mean side-to-side differences during the Lachman test were 3.1 ± 2.1 mm in group P and 7.2 ± 3.2 mm in group C. The anterior-posterior displacement in group P was significantly less than that in group C (P < .05). In the quantitative pivot shift test, the mean acceleration in the contralateral ACL-intact knees was -632.7 ± 254.5 mm/s(2), whereas it was -1107.5 ± 398.9 mm/s(2) in group P and -1652.2 ± 754.9 mm/s(2) in group C. Significant differences were detected between the 3 knee conditions (P < .05)., Conclusions: The quantitative assessments of knees with partial ACL ruptures during the Lachman test and the pivot shift test using the EMS showed less laxity than did knees with complete ACL tears, whereas their laxity was greater than the contralateral knees with intact ACLs., Level of Evidence: Level III, diagnostic study of nonconsecutive patients., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to obtain more than 2 years' follow-up after surgery to investigate the effect of the difference in rotatory stability based on our previous data on the clinical outcome among 3 groups: double-bundle (DB) reconstruction group, anteromedial (AM) single-bundle reconstruction group, and posterolateral (PL) single-bundle reconstruction group., Methods: We randomly separated 55 patients with anterior cruciate ligament rupture into 3 groups: 18 in DB group, 18 in AM group, and 19 in PL group. The mean follow-up period is 33.7 months for the DB group, 31.9 months for the AM group, and 33.2 months for the PL group. We evaluated the Lysholm score, Tegner score, anterior laxity with the KT-1000 arthrometer (MEDmetric, San Diego, CA), rotator instability with the pivot-shift test, and muscle strength with knee extensor and flexor isokinetic peak torques at 60°/s., Results: There were no significant differences in postoperative Lysholm score and Tegner score. Anterior stability of the knee, as measured by the KT-1000 arthrometer, was significantly better in the DB group than the PL group (P < .05). The negative rate of the manual pivot-shift test in the DB group was significantly superior to the PL group (P < .05). Muscle strength of the extensor in the DB group was significantly superior to that in the AM group (P < .05), and muscle strength of the flexor in the PL group was significantly inferior to that in both the DB and AM groups (P < .05). Two patients in the PL group had rerupture; however, there was no graft failure in the other groups., Conclusions: At 2 years' follow-up, patients undergoing DB anterior cruciate ligament reconstruction had greater extension strength than patients receiving an AM single-bundle reconstruction. The DB and AM groups had greater flexion strength than the PL group. The DB and AM groups had a similar rate of negative pivot-shift test results, whereas the PL group had fewer negative pivot-shift test results than the DB group. There were no KT-1000 side-to-side differences between the DB and AM groups, whereas the DB group had better results than the PL group. Overall, the clinical outcome as measured by Lysholm and Tegner scores was not different between groups., Level of Evidence: Level II, prospective comparative study., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to assess quantitative anterior/posterior values during the Lachman test by an electromagnetic measurement system and to compare data with KT-1000 arthrometric measurements (MEDmetric, San Diego, CA), as well as the measurement of radiologic laxity by dynamic radiographs., Methods: We used an electromagnetic device to quantitatively evaluate anterior knee displacements. We tested 82 knees in 41 patients (30 isolated anterior cruciate ligament [ACL]-deficient, 11 ACL-reconstructed, and 41 contralateral ACL-intact knees). Anterior displacements during the Lachman test were calculated by the electromagnetic measurement system and fluoroscopic measurement, and anterior displacements were also measured by the KT-1000 arthrometer. Anterior/posterior displacements measured by these methods were compared, and correlations were assessed., Results: In ACL-deficient knees, mean anterior/posterior displacement (±SE) was 22.4 ± 0.8 mm in electromagnetic measurements, 22.0 ± 0.7 mm in fluoroscopic measurements, and 15.0 ± 0.6 mm in KT-1000 measurements. In contralateral ACL-intact knees, it was 15.7 ± 0.6 mm, 15.6 ± 0.5 mm, and 9.9 ± 0.4 mm, respectively. In ACL-reconstructed knees, it was 15.7 ± 0.7 mm, 16.2 ± 0.8 mm, and 11.2 ± 0.6 mm, respectively. In all knee conditions, significant differences between fluoroscopic measurements and KT-1000 measurements were detected (P < .01). Significant differences were also detected between electromagnetic measurements and KT-1000 measurements (P < .01). No significant differences were detected between fluoroscopic measurements and electromagnetic measurements. A strong correlation was obtained between KT-1000 measurements and fluoroscopic measurements (r = 0.62, P < .01) and between electromagnetic measurements and KT-1000 measurements (r = 0.64, P < .01). However, the strongest correlation was observed between electromagnetic measurements and fluoroscopic measurements (r = 0.96, P < .01)., Conclusions: An electromagnetic measurement system to test anterior/posterior tibial translation determined that quantification of the Lachman test could be performed as accurately as fluoroscopic measurements., Level of Evidence: Level II, development of diagnostic criteria on basis of consecutive patients with universally applied reference gold standard., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)