Background: Tears of the medial meniscus posterior horn attachment (PHA) occur clinically, and an anterior cruciate ligament (ACL)–deficient knee may be more vulnerable to this injury.
Hypothesis: The PHA forces from applied knee loadings will increase after removal of the ACL.
Study Design: Controlled laboratory study.
Methods: A cap of bone containing the medial meniscus PHA was attached to a load cell that measured PHA tensile force. Posterior horn attachment forces were recorded before and after ACL removal during anteroposterior (AP) laxity testing at ±200 N and during passive knee extension tests with 5 N·m tibial torque and varus-valgus moment. Selected tests were also performed with 500 N joint load.
Results: For AP tests with no joint load, ACL removal increased laxity between 0° and 90° and increased PHA force generated by applied anterior tibial force between 30° and 90°. For AP tests with an intact ACL, application of joint load approximately doubled PHA forces. Anteroposterior testing of ACL-deficient knees was not possible with joint load because of bone cap failures from high PHA forces. Removal of the ACL during knee extension tests under joint load significantly increased PHA forces between 20° and 90° of flexion. For unloaded tests with applied tibial torque and varus-valgus moment, ACL removal had no significant effect on PHA forces.
Conclusion: Applied anterior tibial force and external tibial torque were loading modes that produced relatively high PHA forces, presumably by impingement of the medial femoral condyle against the medial meniscus posterior horn rim. Under joint load, an ACL-deficient knee was particularly susceptible to PHA injury from applied anterior tibial force.
Clinical Relevance: Because tensile forces developed in the PHA are also borne by meniscus tissue near the attachment site, loading mechanisms that produce high PHA forces could also produce complete or partial radial tears near the posterior horn, a relatively common clinical observation.
Background: Allograft tissue remains a valuable alternative for anterior cruciate ligament reconstruction. No study to date has correlated the effect of donor age to bone mineral density (BMD) in a large series of irradiated bone–patellar tendon–bone (BPTB) allograft tissue.
Hypothesis/Purpose: The authors attempted to correlate donor age with BMD in a large group of BPTB allograft specimens treated with low-dose gamma irradiation (1.0-1.3 Mrad) collected over a 4-year period. They hypothesized there would be no effect of donor age on the BMD of irradiated BPTB allografts.
Study Design: Descriptive laboratory study.
Methods: A total of 110 BPTB allograft specimens from 44 male and 66 female donors with a mean age of 46 years (range, 21-58 years) were analyzed. Bone mineral density data were obtained from both the patellar and tibial bone plugs of the BPTB complex. Statistical analyses were conducted using linear regression for correlations and 2-tailed Student t tests for comparisons between groups.
Results: The mean BMD of the patellar bone plug (0.471 g/cm2) was significantly greater than the mean BMD of the tibial bone plug (0.328 g/cm2) (P < .001). No correlation was identified between donor age and BMD for either the patella or tibial bone plugs (R2 = .014 and .011, respectively). Both patellar and tibial BMD was significantly greater for the male grafts than the female ones.
Conclusion: No correlation was found between donor age and BMD for irradiated BPTB allograft tissue. The patellar bone plugs were noted to have a greater BMD than the tibial bone plugs. Allograft tissue from male donors had higher BMD values than that harvested from female donors.
Background: While single-bundle anterior cruciate ligament reconstruction reduces anterior-posterior laxity, studies have demonstrated residual rotational instability. Improved pivot-shift results have been shown with the double-bundle graft; however, no study has compared rotational laxity outcome of these surgical techniques in vivo under quantified, isolated torsional loading.
Hypothesis: The anterior cruciate ligament–deficient knee exhibits greater rotational laxity than the contralateral uninjured knee. The double-bundle reconstruction restores rotational joint stability to a greater extent than single-bundle surgery.
Study Design: Controlled laboratory study.
Methods: Rotational laxity of 32 patients with unilateral anterior cruciate ligament injury was assessed in both knees at full extension and 30° of flexion using a magnetic resonance imaging–compatible torsional loading device. Patients were randomly allocated either a single- or double-bundle reconstruction and reassessed 5 months after surgery.
Results: The anterior cruciate ligament–deficient knees demonstrated greater laxity to internal rotational torque in the extended position, but not in the 30° flexed position. No significant differences in rotational laxity were found between single- and double-bundle reconstructions. In extension, excessive internal rotational laxity of injured compared with contralateral knees was reduced by anterior cruciate ligament reconstruction. The single-bundle reconstruction did not affect internal rotation compared with contralateral or preoperative groups. In response to internal rotational torque in the flexed knee position, the double-bundle reconstruction reduced laxity to 10.8° from the pre-operative value of 15.3° (P = .058); postoperative rotation was also significantly less than the contralateral laxity of 16.4° (P = .022).
Conclusion: The ruptured anterior cruciate ligament resulted in increased internal rotational laxity only in the extended position. The single-bundle reconstruction did not affect rotational restraint compared with contralateral or preoperative groups. The double-bundle procedure significantly reduced internal laxity in the flexed position when compared with normal.
Clinical Relevance: As the anterior cruciate ligament is not the primary restraint to rotation, its contribution to joint stability is limited under isolated torsional load. While the double-bundle graft demonstrates superior rotational constraint, this may be excessive for isolated anterior cruciate ligament rupture.
Background: Women with anterior cruciate ligament reconstruction have different neuromuscular strategies than noninjured women during functional tasks after ligament reconstruction and rehabilitation.
Hypothesis: Landing from a jump creates high loads on the knee creating dynamic instability in women with anterior cruciate ligament reconstruction, whereas noninjured women have stable knee landing mechanics.
Study Design: Controlled laboratory study.
Methods: Fifteen noninjured women and 13 women with anterior cruciate ligament reconstruction performed 5 trials of a single-legged 40-cm drop jump and 2 trials of a 20-cm up-down hop task. Multivariate analyses of variance were used to compare hip and knee joint kinematics, knee joint moments, ground-reaction forces, and electromyographic findings between the dominant leg in noninjured women and reconstructed leg in women with anterior cruciate ligament reconstruction.
Results: No statistically significant differences between groups were found for peak hip and knee joint angles for the drop jump task. Statistically significant differences in neuromuscular activity (P = .001) and anterior-posterior knee shear forces (P < .001) were seen in women with anterior cruciate ligament reconstruction compared with noninjured women in the drop jump task. However, no statistically significant differences (P > .05) between groups were found for either peak hip and knee joint angles, peak joint kinetics, or electromyographic findings during the up-down hop task.
Conclusion: Women with anterior cruciate ligament reconstruction have neuromuscular strategies that allow them to land from a jump similar to healthy women, but they exhibit joint moments that could predispose them to future injury if they participate in sports that require jumping and landing.
