Anterior-posterior Laxity Research Articles

Efficient probabilistic representation of tibiofemoral soft tissue constraint

Verified and efficient representations of knee ligamentous constraints are essential to forward-dynamic models for prediction of knee mechanics. The objectives of this study were to develop an efficient probabilistic representation of knee ligamentous constraint using the advanced mean value (AMV) probabilistic approach, and to compare the AMV representation with the gold standard Monte Carlo (MC) approach. Specifically, the effects of inherent uncertainty in ligament stiffness, reference strain and attachment site locations on joint constraint were assessed. An explicit finite element model of the knee was evaluated under a series of anterior–posterior (AP) and internal–external (IE) loading at full extension and 90° flexion. Distributions of AP and IE laxity were predicted using experimentally-based levels of ligament parameter variability. Importance factors identified the critical properties affecting the predicted bounds, and agreed with reported ligament recruitment. The AMV method agreed closely with MC results with a four-fold reduction in computation time.

Double-bundle versus single-bundle ACL reconstruction using the horizontal femoral position: a prospective, randomized study

The aim of this study was to evaluate whether anterior cruciate ligament (ACL) reconstruction using the double bundle technique (DB) improves stability in the knee compared with the single bundle technique (SB) with the femoral tunnel in a more horizontal position (2 or 10 o'clock). We conducted a randomized, prospective study. Forty patients were randomized to the DB group (20 patients) and the SB group (20 patients). Four-stranded semitendinosus and gracilis autologous grafts were used in the SB group and in the DB group the conventional four tunnel technique was carried out using the same tendons. The IKDC complete form was used for the preoperative evaluation, and in the follow-up the IKDC subjective knee evaluation form, IKDC current health assessment form and IKDC knee examination form were used. Anteroposterior (AP) laxity was evaluated by standardised and forced radiology in all patients. No significant preoperative between-group differences were found. During the follow-up, no differences were found between groups, except for significant between-group differences (P < 0.05) between the preoperative and postoperative evaluations. The IKDC index also showed significant differences in the 2-year follow-up. Median scores increased from 48 (range 41-54) to 81 (range 75-87) (P = 0.01) in the SB group and from 52 (range 46-58) to 80 (range 72-88) (P = 0.02) in the DB group. There were no significant differences between the groups in terms of functional scores. In conclusion, the 2 and 10 o'clock placements showed no significant differences between SB and DB techniques in the pivot-shift test, manual and radiological anterior posterior laxity and IKDC scores. However, significant between-group differences were found between the preoperative and postoperative evaluations.

Collagen-Platelet Composites Improve the Biomechanical Properties of Healing Anterior Cruciate Ligament Grafts in a Porcine Model

Background The outcome of anterior cruciate ligament (ACL) reconstruction is variable, and many patients have increased joint laxity postoperatively. Hypothesis Placement of a collagen-platelet composite (CPC) around the graft at the time of ACL reconstruction decreases postoperative knee laxity and improves the structural properties of the graft compared with standard ACL reconstruction. Study Design Controlled laboratory study. Methods Thirteen immature pigs underwent unilateral ACL reconstruction with a bone–patellar tendon–bone allograft. In 6 pigs, a standard allograft was used to reconstruct the ACL. In 7 pigs, a CPC was placed around the allograft. After 15 weeks of healing, the animals were euthanized, and the anterior-posterior (AP) knee laxity and structural properties of the graft were measured. Qualitative histology of the grafts was also performed. Results The AP laxity values of the reconstructed knees, normalized to the contralateral control, were significantly reduced by 28% and 57% at 60° and 90° of knee flexion, respectively, with the addition of CPC (P <. 001). Significant improvements in the graft structural properties were also found; the normalized yield (P =. 044) and maximum failure loads (P =. 025) of the CPC group were 60% higher than the standard ACL-reconstructed group. Although cellular and vessel infiltration were observed in the grafts of both groups, regions of necrosis were present only in the standard ACL-reconstructed group. Conclusion These data demonstrate that the application of CPC at the time of ACL reconstruction improves the structural properties of the graft and reduces early AP knee laxity in the porcine model after 15 weeks of healing. Clinical Relevance Application of a CPC to an ACL graft at the time of surgery decreased knee laxity and increased the structural properties of the graft after 15 weeks of healing.

Intraoperative evaluation of total knee replacement: kinematic assessment with a navigation system

Interest in the kinematics of reconstructed knees has increased since it was shown that the alteration of knee motion could lead to abnormal wear and damage to soft tissues. We performed intraoperative kinematic measurements using a navigation system to study knee kinematics before and after posterior substituting rotating platform total knee arthroplasty (TKA). We verified intraoperatively (1) if varus/valgus (VV) laxity and anterior/posterior (AP) laxity were restored after TKA; (2) if TKA induced abnormal femoral rollback; and (3) how tibial axial rotation was influenced by TKA throughout the range of flexion. We found that TKA improved alignment in preoperative osteoarthritic varus knees which became neutral after surgery and maintained a neutral alignment in neutral knees. The VV stability at 0 degrees was restored while AP laxity at 90 degrees significantly increased after TKA. Following TKA, the femur had an abnormal anterior translation up to 60 degrees of flexion, followed by a small rollback of 12 +/- 5 mm. TKA influenced the tibia rotation pattern during flexion, but not the total amount of internal/external rotation throughout whole range of flexion, which was preserved after TKA (6 degrees +/- 5 degrees ). This study showed that the protocol proposed might be useful to adjust knee stability at time zero and that knee kinematic outcome during total knee replacement can be monitored by a navigation system.

Intercondylar roof impingement pressure after anterior cruciate ligament reconstruction in a porcine model

Anterior cruciate ligament (ACL) graft impingement against the intercondylar roof has been postulated, but not thoroughly investigated. The roof impingement pressure changes with different tibial and femoral tunnel positions in ACL reconstruction. Anterior tibial translation is also affected by the tunnel positions of ACL reconstruction. The study design included a controlled laboratory study. In 15 pig knees, the impingement pressure between ACL and intercondylar roof was measured using pressure sensitive film before and after ACL single bundle reconstruction. ACL reconstructions were performed in each knee with two different tibial and femoral tunnel position combinations: (1) tibial antero-medial (AM) tunnel to femoral AM tunnel (AM to AM) and (2) tibial postero-lateral (PL) tunnel to femoral High-AM tunnel (PL to High-AM). Anterior tibial translation (ATT) was evaluated after each ACL reconstruction using robotic/universal force-moment sensor testing system. Neither the AM to AM nor the PL to High-AM ACL reconstruction groups showed significant difference when compared with intact ACL in roof impingement pressure. The AM to AM group had a significantly higher failure load than PL to High-AM group. This study showed how different tunnel placements affect the ACL-roof impingement pressure and anterior-posterior laxity in ACL reconstruction. Anatomical ACL reconstruction does not cause roof impingement and it has a biomechanical advantage in ATT when compared with non-anatomical ACL reconstructions in the pig knee. There is no intercondylar roof impingement after anatomical single bundle ACL reconstruction.

The use of platelets to affect functional healing of an anterior cruciate ligament (ACL) autograft in a caprine ACL reconstruction model

Many anterior cruciate ligament (ACL) reconstructions have increased laxity postoperatively. We hypothesized that enhancing an ACL graft with a collagen-platelet composite (CPC) would improve knee laxity and graft structural properties. We also hypothesized the platelet concentration in the CPC would affect these parameters. Twelve goats underwent ACL reconstruction with autologous patellar tendon graft. In six goats, a collagen-platelet composite was placed around the graft (CPC group). In the remaining six goats, the collagen scaffold only was used (COLL group). Three goats were excluded due to complications. After 6 weeks in vivo, anterior-posterior (AP) laxity and tensile properties of the ACL reconstructed knees were measured and normalized against the contralateral intact knee. At a knee flexion angle of 30 degrees, the average increase in AP laxity was 40% less in the CPC group than the COLL group (p = 0.045). At 60 degrees, the AP laxity was 30% less in the CPC group, a difference that was close to statistical significance (p = 0.080). No differences were found between treatment groups with respect to the structural properties (p > 0.30). However, there were significant correlations between serum platelet concentration and AP laxity (R2 = 0.643; p = 0.009), maximum load (R2 = 0.691; p = 0.006), and graft stiffness (R2 = 0.840; p < 0.001). In conclusion, use of a CPC to enhance healing of an allograft ACL reconstruction inversely correlated with early sagittal plane laxity and the systemic platelet count was highly predictive of ACL reconstruction graft strength and stiffness at 6 weeks. These findings emphasize the importance of further research on delineating the effect of platelets in treating of ACL injuries.

Simultaneous Double-Bundle Anterior Cruciate Ligament and Posterior Cruciate Ligament Reconstruction With Autogenous Hamstring Tendons

The purpose of this study was to evaluate the clinical results of simultaneous double-bundle anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstruction. We performed arthroscopic reconstruction in 21 cases of combined ACL/PCL rupture, 14 chronic and 7 acute, with autogenous hamstring tendons in 1 stage, both in a double-bundle and 4-tunnel manner. The semitendinosus tendon and gracilis tendon from the uninjured leg were used to make two 4-stranded grafts to reconstruct the PCL, and those from the injured leg were used to make two 4-stranded grafts to reconstruct the ACL. The grafts were suspended with a mini-plate and buttons. The patients were followed up for a minimum of 2 years and evaluated according to the International Knee Documentation Committee (IKDC) and Lysholm rating scale. The anterior-posterior knee laxity was assessed by KT-1000 examination (MEDmetric, San Diego, CA). At the last follow-up, all patients showed normal knee extension. One patient had a 10 degrees flexion limitation, and four had a 5 degrees flexion limitation. KT-1000 examination showed that the side-to-side difference in overall anterior-posterior laxity at 70 degrees flexion was 0 to 2 mm in 16 patients, 3 to 5 mm in 4 patients, and 6 to 10 mm in 1 patient; the side-to-side difference in overall anterior-posterior laxity at 25 degrees flexion was 0 to 2 mm in 14 patients, 3 to 5 mm in 6 patients, and 6 to 10 mm in 1 patient. The IKDC subjective, Lysholm, and Tegner scores were 85.5 +/- 5.8, 91.9 +/- 4.2, and 5.0 +/- 1.9, respectively. According to the last IKDC evaluation, the results were graded as normal in 13 patients (61.9%), nearly normal in 7 patients (33.3%), and abnormal in 1 patient (4.8%). Simultaneous double-bundle ACL and PCL reconstruction with autogenous hamstring tendons can yield normal results in 61.9% of patients and nearly normal results in 33.3% at a minimum of 2 years. Level IV, therapeutic case series.

Simulated Pivot-Shift Testing with Single and Double-Bundle Anterior Cruciate Ligament Reconstructions

One of the principal rationales for performing a double-bundle reconstruction of the anterior cruciate ligament is the suggestion that it may be superior to a single-bundle reconstruction in restoring a normal pivot-shift sign. The purpose of this study was to measure the abilities of single-bundle and anatomic double-bundle reconstructions to restore normal knee kinematics and graft forces during a simulated pivot-shift test. Graft force and knee kinematics were recorded during a simulated pivot-shift event with and without the anterior cruciate ligament and after graft reconstructions. With a single bundle, the graft was tensioned to restore anterior-posterior laxity at 30 degrees of flexion. With double-bundle reconstructions, the anteromedial graft was first tensioned as above and then the posterolateral graft tension was set with use of one of four protocols: posterolateral tension = anteromedial tension at 10 degrees of flexion (DB1); posterolateral tension = anteromedial tension at 30 degrees (DB2); posterolateral tension = (anteromedial tension + 30 N) at 10 degrees (DB3); and posterolateral tension = (anteromedial tension + 30 N) at 30 degrees (DB4). A single-bundle reconstruction restored all displacements and rotations during the pivot shift to the intact knee levels. The mean tibial rotations and lateral plateau displacements during the pivot shift with DB2, DB3, and DB4 reconstructions were less than those in the intact knee and also less than those in a single-bundle reconstruction. Before the pivot shift, the mean graft forces with all reconstructions were greater than that of the intact knee; the mean graft forces with the DB3 and DB4 reconstructions were also greater than that of a single-bundle reconstruction. After the pivot shift, the mean graft forces for all reconstructions were less than the levels before the pivot shift with single-bundle forces lower than intact knee levels and DB4 forces higher than intact knee levels. Reduction or elimination of the pivot-shift sign is an important goal for anterior cruciate ligament reconstruction. In our model, the results show that a single-bundle reconstruction was sufficient to restore intact knee kinematics during a simulated pivot-shift event. The higher graft forces with some double-bundle graft-tensioning protocols reduced the coupled rotations and displacements from an applied valgus moment to less than the intact levels. This overcorrection should theoretically make the knee less likely to pivot but could have unknown clinical consequences.

Can suture repair of ACL transection restore normal anteroposterior laxity of the knee? An ex vivo study

Recent work has suggested the transected anterior cruciate ligament (ACL) can heal and support reasonable loads if repaired with sutures and a bioactive scaffold; however, use of a traditional suture configuration results in knees with increased anterior-posterior (AP) laxity. The objective was to determine whether one of five different suture repair constructs when performed at two different joint positions would restore normal AP knee laxity. AP laxity of the porcine knee at 60 degrees of flexion was evaluated for five suture repair techniques. Femoral fixation for all repair techniques utilized a suture anchor. Primary repair was to either the tibial stump, one of three bony locations in the ACL footprint, or a hybrid bony fixation. All five repairs were tied with the knee in first 30 degrees and then 60 degrees of flexion for a total of 10 repair constructs. Suture repair to bony fixation points within the anterior half of the normal ACL footprint resulted in knee laxity values within 0.5 mm of the ACL-intact joint when the sutures were tied with the knee at 60 degrees flexion. Suture repair to the tibial stump, or with the knee at 30 degrees of flexion, did not restore normal AP laxity of the knee. Three specific suture repair techniques for the transected porcine ACL restored the normal AP laxity of the knee at the time of surgery. Additional studies defining the changes in laxity with cyclic loading and in vivo healing are indicated.

Contributions of the Posterolateral Bundle of the Anterior Cruciate Ligament to Anterior-Posterior Knee Laxity and Ligament Forces

The purpose of this study was to measure changes in anterior-posterior (AP) laxity and graft forces after cutting the posterolateral (PL) bundle of the anterior cruciate ligament (ACL). Twelve fresh-frozen cadaveric knees underwent AP laxity testing at +/- 100 N of applied tibial force. Resultant forces in the ACL were recorded during passive extension from 120 degrees to 0 degrees with no tibial force, 100 N of anterior tibial force, 100 N of quadriceps force, and 5 Nm of internal tibial torque. The femoral origin of the PL bundle was identified, the ligament fibers were dissected from bone, and tests were repeated. Cutting the PL bundle significantly increased mean laxity by +1.3 mm (at 0 degrees ), +1.1 mm (at 10 degrees ), and +0.5 mm (at 30 degrees ). For the passive knee extension tests, cutting the PL bundle significantly decreased mean ACL force at 0 degrees for all loading modes; the mean decreases were 31 N (with no tibial force), 50 N (with 100 N of anterior force), 33 N (with 100 N of quadriceps force), and 40 N (with 5 Nm of internal torque). The decreases in ACL force at 0 degrees from cutting the PL bundle are consistent with the commonly accepted view that the PL bundle tightens with knee extension. Cutting the taut PL bundle did significantly increase AP laxity between 0 degrees and 30 degrees , but the increases were relatively small. Therefore we conclude that the PL bundle plays a relatively minor role in controlling anterior tibial translation. In view of our findings, the need to reconstruct the PL bundle for better restoration of a normal AP laxity profile is questioned.

Fresh-Frozen Free-Tendon Allografts Versus Autografts in Anterior Cruciate Ligament Reconstruction: Delayed Remodeling and Inferior Mechanical Function During Long-term Healing in Sheep

The objective of this study was to investigate the biologic healing and restoration of the mechanical function of a free soft tissue autograft and compare these to an identical nonsterilized fresh frozen allograft for anterior cruciate ligament (ACL) reconstruction in an in vivo sheep model. Forty-eight merino sheep received either an allograft or autograft ACL reconstruction with a long flexor tendon. Each group was analyzed at 6, 12, and 52 weeks for descriptive analysis of histologic changes and quantitative analysis of recellularization, revascularization, and mechanical function. Recellularization and revascularization was significantly delayed at 6 and 12 weeks of healing, while at 52 weeks, differences had become less distinct. Overall remodeling had not been completed compared to the intact ACL. Significantly lower structural and mechanical properties and anterior-posterior laxity were found at 52 weeks for allografts, with no differences at the early healing time points. Allograft remodeling is delayed in ACL reconstruction and resulted in reduced long-term stability and mechanical function compared to autologous ACL reconstruction. Caution should be used with early full-weight bearing after allograft ACL reconstruction, because remodeling is delayed and long-term stability might be affected. Clinical studies should be warranted to examine the impact of varying rehabilitation protocols on long-term outcome.

Reliability of the KT1000 arthrometer and the Lachman test in patients with an ACL rupture

The underlying study is a cross sectional study on the reliability of the KT1000 arthrometer and the Lachman test to determine the within-session inter-rater reliability and intra-rater reliability of the KT1000 arthrometer and the Lachman test.Twenty patients with a complete tear of the anterior cruciate ligament (ACL) were examined in a single session each. During the assessment, two physical therapists measured the anterior–posterior translation of the knee using both the KT1000 arthrometer and the Lachman test. One examiner performed a repeated measurement of each test for determination of intra-rater reliability. The examiners were blinded to the findings of their colleague. The intraclass correlation coefficient (ICC) was used to describe the degree of reliability of the measurements.High ICCs were found for the intra-rater reliability and the inter-rater reliability of the Lachman test (ICC = 1.0 and 0.77). For the KT1000 arthrometer both ICCs were clearly lower (ICC = 0.47 and 0.14).The KT1000 arthrometer shows inadequate reliabilities, even when measurements are repeated within a single measurement session. Contrastingly, the Lachman test is a reliable measurement to determine the anterior–posterior laxity of the ACL deficit knee. The results of the present study suggest good within-session intra-rater reliability as well as inter-rater reliability for the Lachman test.

Biomechanical and Anatomical Assessment after Knee Hyperextension Injury

Background Knee hyperextension can be a serious and disabling injury in both the athletic and general patient population. Understanding the pathoanatomy and pathomechanics is critical for accurate surgical soft tissue reconstructions. Purpose To quantify the effects of knee hyperextension injury on knee laxity in a human cadaveric model and to qualitatively assess the anatomical injury pattern through surgical dissection. Study Design Descriptive laboratory study. Methods Six fresh-frozen cadaveric knees were rigidly mounted on a custom knee testing system that simulates clinical laxity tests. The knee laxity measurements consisted of anterior-posterior laxity, internal-external rotational laxity, and varus-valgus laxity using a custom testing setup and a Microscribe 3DLX system. The laxity data were collected at both 30° and 90° of knee flexion for the intact specimens and then after 15° and 30° hyperextension injury. After biomechanical assessment a detailed dissection was performed to document the injured structures in the knee. Repeated-measures analysis of variance with a Tukey post hoc test (P < .05) was used for statistical comparison. Results The results from this study suggest progressive damage to translational and rotational knee soft-tissue restraints with increasing knee hyperextension. Knee hyperextension to 30° caused the most significant increase in anterior-posterior and rotational laxity. Anatomical dissections showed a general injury pattern to the posterolateral corner, partial femoral anterior cruciate ligament avulsion in 4 of 6 specimens, and no gross posterior cruciate ligament injuries. Conclusion Injuries to the posterolateral corner of the knee can result from isolated knee hyperextension. Clinical Relevance The clinician should be aware of the potential for posterolateral corner injuries with isolated knee hyperextension. This will allow early surgical planning and primary surgical repair.

Popliteus Bypass and Popliteofibular Ligament Reconstructions Reduce Posterior Tibial Translations and Forces in a Posterior Cruciate Ligament Graft

To measure the abilities of popliteus tendon (POP) and popliteofibular ligament (PFL) graft reconstructions to limit posterior tibial translations and alter forces in a PCL graft reconstruction after posterior cruciate ligament (PCL) and lateral collateral ligament (LCL) reconstruction. Fifteen fresh frozen cadaveric knees underwent anterior-posterior (AP) laxity testing with 200 N of applied anterior and posterior tibial force. Forces in the native PCL were recorded during passive extension from 120 degrees to 0 degrees with an applied 100-N posterior tibial force. The popliteus tendon was released at its femoral origin, the PFL and LCL were cut, and the PCL was sectioned, creating a combined grade 3 PCL and posterolateral corner injury. The PCL was reconstructed with a single-bundle inlay graft tensioned to restore intact knee laxity to within 1 mm at 90 degrees , and the LCL was reconstructed with an anatomically placed graft. Testing was repeated with POP and PFL posterolateral reconstructions in addition to the PCL and LCL reconstructions. PCL + LCL grafts alone matched intact knee laxities between 20 degrees and 90 degrees of flexion; mean laxity was 3.5 mm greater than intact at 0 degrees and 2.2 mm greater at 10 degrees. The addition of a POP reconstruction to PCL + LCL reconstructions significantly reduced AP laxities from -2.4 mm (0 degrees flexion) to -1.4 mm (90 degrees flexion). Mean laxities with POP and PFL grafts were not significantly different from the intact knee or from each other. Mean PCL graft forces with the PCL + LCL reconstructions alone were not significantly different than those with the native PCL. Mean PCL graft forces with POP and PFL reconstructions were not significantly different from each other; both means were significantly less than those for the PCL + LCL reconstructions alone at flexion angles greater than 55 degrees. After PCL and LCL reconstruction, the popliteus bypass and popliteofibular ligament reconstructions not only eliminated excessive posterior laxity and returned the knee to a normal laxity profile but also resulted in substantial decreases in PCL graft forces. These results provide further rationale for reconstructing torn posterolateral structures with a grade 3 posterolateral injury in combination with a PCL reconstruction.

The anterior–posterior laxity after total knee arthroplasty inserted with a ligament tensor

Goal of this study is to determine the anterior-posterior laxity in 30 degrees of knee flexion for a posterior cruciate retaining total knee arthroplasty with a relative dished insert and implanted with a ligament tensor. Furthermore, the correlation between these AP laxities and the postoperative range of motion (ROM) and postoperative Knee Society Score (KSS) is analysed. Fifty-one balanSys total knee arthroplasties were performed in 49 patients between 1998 and 2000. These arthroplasties are analysed with respect to AP laxity (Rolimeter), ROM and KSS with a mean follow-up of 4.6 years. The mean anterior laxity is 2.8 mm with no posterior laxities at all. The average postoperative ROM is 110 degrees with an average KSS of 142. No correlations between AP-laxity and postoperative ROM or between AP-laxity and postoperative KSS are found. A posterior cruciate retaining TKA with a relative dished insert and implanted with a tensor is very stable in the anterior-posterior direction in 30 degrees of knee flexion. This limited laxity does not seem to disadvantage the mean postoperative ROM and KSS, when compared to other TKA studies.

Anatomical two-bundle versus Rosenberg’s isometric bi-socket ACL reconstruction: a biomechanical comparison in laxity match pretension

It is not well known how much tension should be applied to ACL graft at the time of graft fixation. As a step to determine the optimal initial tension, it is indispensable to know the graft tension to restore normal anterior-posterior (A-P) laxity (laxity match pretension, LMP). The objective was to determine the LMP in ACL reconstruction for the anatomical two-bundle technique and for the Rosenberg's isometric bi-socket one, and to compare these two techniques in LMP. Twenty-four patients with unilateral chronic ACL insufficiency were divided into the following two groups. The anatomical two-bundle technique was performed on 12 patients via two femoral tunnels at 9 and 10 o'clock or 2 and 3 o'clock on the posterior margin of the notch and two tibial tunnels (Group A), while the Rosenberg's isometric bi-socket reconstruction was performed on the remaining 12 patients through two femoral tunnels at 10 and 11 o'clock or 1 and 2 o'clock and one wider tibial tunnel (Group B). After two doubled semitendinosus grafts were fixed with two EndoButton-CL s on the femur, they were temporarily fixed to the tension-adjustable force gauge on the tibia, respectively. The total tension applied to grafts was set at 10, 20, 30, 40, or 50 N at 20 degrees of knee flexion, and the A-P laxity was measured by applying A-P drawer load of 134 N at 20 degrees of flexion. By comparing the measured laxity with that for the opposite healthy knee, the tension to restore the normal A-P laxity (LMP) was estimated. The mean LMP of 7.3 N in Group A was significantly smaller than that of 25.8 N in Group B. The anatomical two-bundle technique makes it possible to more effectively restore A-P stability with lower initial tension than the isometric Rosenberg's bi-socket reconstruction.

Biomechanical Studies of Double-Bundle Posterior Cruciate Ligament Reconstructions

Double-bundle reconstruction of the posterior cruciate ligament has been advocated to better replicate the anatomy of the native ligament and restore normal knee biomechanics. The goal of this study was to measure knee laxities and graft forces following single and double-bundle reconstructions and to compare these values with those for the intact knee in a cadaver model. Forces in the posterior cruciate ligament were measured as the knee was passively extended from 120 degrees to 0 degrees with applied tibial loading. Anterior-posterior laxities were measured as well. An anterolateral tunnel was located at the anterolateral margin of the native ligament footprint, and a posteromedial tunnel was placed at one of two locations within the footprint; one location resulted in a wide bridge separating the tunnels and the other, a narrow bridge. Testing was repeated with a single anterolateral graft tensioned to match, within +/-1 mm, the laxity in the intact knee at 90 degrees of flexion. Double-bundle reconstructions were tested with the addition of a posteromedial graft tensioned at 30 degrees of flexion. Two levels of posteromedial graft tension (10 and 30 N) were studied in both the narrow and the wide-bridge posteromedial tunnels. Mean laxities with a single anterolateral graft were 1.1 to 2.0 mm greater than normal between 0 degrees and 30 degrees of flexion. With the posteromedial graft tensioned to 10 N in the wide-bridge tunnel, the mean laxity of the double grafts was not significantly different from that in the intact knee at any flexion angle. With the posteromedial graft tensioned to 10 N in the narrow-bridge tunnel, the mean laxity at 0 degrees was 0.9 mm greater than that in the intact knee. With the posteromedial graft tensioned to 30 N, the mean laxity at 10 degrees was 1.7 mm less than the intact-knee value in the wide-bridge tunnel and 1.3 mm less than the intact-knee value in the narrow bridge-tunnel. Increasing posteromedial graft tension from 10 to 30 N decreased the mean laxities by 0.5 to 1.1 mm between 0 degrees and 30 degrees . Mean graft forces following a single anterolateral reconstruction were not significantly different from the native posterior cruciate ligament forces under any mode of loading except valgus moment. With the wide-bridge tunnel, the mean forces with the posteromedial graft tensioned to 10 N were somewhat higher than the native posterior cruciate ligament forces at full extension; when the graft was tensioned to 30 N, the mean forces were substantially higher. A single anterolateral graft best reproduced the normal posterior cruciate ligament force profiles, but laxities were greater than normal between 0 degrees and 30 degrees of knee flexion. The addition of a second, posteromedial graft reduced laxity in this flexion range but did so at the expense of higher-than-normal forces in the posteromedial graft.

Simultaneous Arthroscopic Reconstruction of the Anterior and Posterior Cruciate Ligaments With Autogenous Hamstring Tendons

The purpose of this study was to evaluate the clinical results of simultaneous arthroscopic reconstruction of anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) with hamstring tendons. Retrospective case series. Twelve cases of combined ACL/PCL ruptures were reconstructed arthroscopically with hamstring tendons in 1 stage. The semitendinosus tendon of the injured leg was used for 4-stranded ACL reconstruction, and the semitendinosus tendon and gracilis tendon of the uninjured leg were used for 6- to 8-stranded PCL reconstruction. The patients were followed-up for 32 months on average. Function was evaluated according to the International Knee Documentation Committee (IKDC) and Lysholm scales. Anterior and posterior knee laxity were examined using the KT-1000 arthrometer. No patients showed knee extension limitation. Knee flexion was 143 degrees +/- 3.7 degrees on average (range, 130 degrees to 150 degrees ). KT-1000 examination showed that the side-to-side difference of overall anterior-posterior laxity at 70 degrees of flexion was 0 to 2 mm in 7 patients, 3 to 5 mm in 4 patients, and 7 mm in 1 patient; the side-to-side difference of posterior sag at 70 degrees of flexion was 0 to 2 mm in 9 patients and 3 to 4 mm in 3 patients; the side-to-side difference of anterior laxity at 25 degrees of flexion was 0 to 2 mm in 8 patients, 3 to 5 mm in 3 patients, and 7 mm in 1 patient. The Lysholm score of the 9 chronic cases was 66.5 +/- 8.1 before surgery and 91.8 +/- 4.6 at the last follow-up (P < .01). According to the last IKDC evaluation, 7 patients (58.33%) were graded A, 4 patients (33.3%) B, and 1 patient (8.33%) C. Except for 1 patient who complained of mild pain at the donor site of the contralateral healthy knee, no patients complained of donor-site morbidity or dysfunction of the healthy leg. Simultaneous arthroscopic reconstruction of the ACL and PCL with autogenous hamstring tendons is reliable for the restoration of knee stability. Level IV.

The Effects of the Menstrual Cycle on Anterior Knee Laxity

Female athletes are at a 4- to 6-fold increased risk of anterior cruciate ligament (ACL) injury compared with male athletes. There are several medical, emotional and financial burdens associated with these injuries. Sex hormones may be involved in the ACL injury disparity, with potential associations reported between phases of the menstrual cycle and ACL injury rates. The reported relationships between ACL injury and menstrual status may be related to associated changes in ligament mechanical properties from cyclic fluctuations of female sex hormones. A PubMed electronic database literature search, including MEDLINE (1966-2005) and CINAHL (1982-2005), with the search terms 'menstrual cycle' and 'knee laxity' was used for this systematic review. Studies were included in this systematic review if they were prospective cohort studies and investigated the association between the menstrual cycle and anterior knee laxity in females. Nine prospective cohort studies, published as 11 articles, were included in the systematic review. Six of nine studies reported no significant effect of the menstrual cycle on anterior knee laxity in women. Three studies observed significant associations between the menstrual cycle and anterior knee laxity. These studies all reported the finding that laxity increased during the ovulatory or post-ovulatory phases of the cycle. A meta-analysis, which included data from all nine reviewed studies, corroborated this significant effect of cycle phase on knee laxity (F-value = 56.59, p = 0.0001). In the analyses, the knee laxity data measured at 10-14 days was >15-28 days which was >1-9 days. Future studies testing the relationship between the menstrual cycle and potentially associated parameters should consider the limitations outlined in this article and control for potential biases and confounders. Power analyses should be utilised. Subjects should be randomly entered into the studies at alternate points in the cycle, and standard and consistent data acquisition and reporting methods should be utilised. Future studies should clearly define what constitutes a 'normal' cycle and appropriate control subjects should be utilised. Furthermore, there is a need to define cycle phase (and timing within cycle phase) with actual hormone levels rather than a day of the cycle. Although hormone confirmations were provided in many of the studies that selected specific days to depict a particular cycle for all women, it is unknown from these data if they truly captured times of peak hormone values in all women. A combined systematic review and meta-analysis of the literature indicate that the menstrual cycle may have an effect on anterior-posterior laxity of the knee; however, further investigation is needed to confirm or reject this hypothesis.

Comparison of 2 Surgical Techniques of Posterolateral Corner Reconstruction of the Knee

Background Various surgical techniques to treat posterolateral knee instability have been described. To date, the recommended treatment is an anatomical form of reconstruction, in which the 3 key structures of the posterolateral corner are addressed: the lateral collateral ligament, the popliteofibular ligament, and the popliteus tendon. Hypothesis Two methods of surgical reconstruction will restore posterolateral knee instability, in terms of static laxity as well as dynamic 6 degrees of freedom kinematics, to statistically significant levels compared with the intact state. Study Design Controlled laboratory study. Methods Two surgical techniques (A and B) were used to reconstruct the posterolateral structures in 10 cadaveric knees. Static tests were performed on the intact, sectioned, and reconstructed knees at 30° and 90° of flexion for anterior-posterior laxity and external rotational laxity, as well as at 0° and 30° of flexion for varus laxity; dynamic 6 degrees of freedom kinematic testing, through a path of motion from 90° of flexion to full extension, was also performed. Results For the static varus tests, external rotation and varus laxity were significantly increased after the posterolateral structures were cut. Both reconstruction techniques restored external rotation and varus laxity to levels not significantly different from the intact state. For technique B, dynamic testing did not show any significant difference for all degrees of freedom kinematics compared with the intact state. However, for technique A, a significant internal tibial rotation was observed throughout the entire path of motion from 0° to 90° of knee flexion. Conclusions Both surgical techniques for anatomical posterolateral corner reconstruction showed good results in the static laxity tests. The anatomical reconstruction of all structures, including the popliteus tendon, resulted in an abnormal internal tibial rotation during dynamic testing.