A comparison of three adjustable cortical button ACL fixation devices.

PURPOSE: Adjustable cortical fixation has gained popularity recently for ACL reconstruction; however, one concern with these types of devices is the potential for laxity occurring post-operatively. An indicator of clinical laxity is cyclic displacement during bench-top mechanical testing. The hypothesis was that the cyclic displacement and maximum strength of different adjustable buttons currently on the market would vary depending on their mechanism of fixation. METHODS: Three devices were studied: Biomet's ToggleLoc with ZipLoop Technology (ZL), Arthrex's TightRope RT (TR), and DePuy Mitek's RIGIDLOOP Adjustable (RLA). Each was tested in isolation on a servohydraulic test machine. The implants were pre-conditioned from 5 to 67 N for 10 cycles and then tested from 50 to 250 N for 1000 cycles at 1 Hz. Following cyclic loading, a load to failure test was conducted at a rate of 20 mm/min. Total displacement was calculated from the 1st to the 1000th cycle, and ultimate strength and failure mode were recorded. RESULTS: Results showed that the RLA had significantly lower displacement versus both the TR (p = 0.012) and the ZL (p < 0.001). The TR also showed significantly lower displacement than the ZL (p < 0.001). The RLA and the ZL were both significantly stronger than the TR (p < 0.001). CONCLUSIONS: Both the RLA and TR showed clinically acceptable amounts of cyclic displacement and maximum strength. The clinical relevance of this study is that cyclic displacement results from bench-top tests may correlate with post-operative laxity, which ideally should be kept to a minimum.

Mechanical properties of revision ACL reconstruction.

The aim of this study is to evaluate the mechanical properties of a revision anterior cruciate ligament (ACL) reconstruction after redrilling the original tibial bone tunnel through a retained composite screw compared with initial soft tissue graft fixation. A total of 24 porcine tendons were fixed to porcine tibial tunnels with a 10 × 35 mm composite interference screw. Following the pullout test, a revision tunnel was drilled through the first interference screw and a second graft was fixed in the bone tunnel using a larger composite screw (11 × 35 mm). Following insertion of the revision screw, the graft was reloaded as described for the primary reconstruction. Load versus displacement data were recorded for each test. There were no significant differences between the primary and revision reconstruction constructs for yield load (p = 0.62), linear stiffness (p = 0.18), maximum failure load (p = 0.57), and yield displacement (p = 0.46). These results indicate that the mechanical properties of tibial fixation for ACL reconstruction with a composite screw following a revision provide similar fixation compared with initial reconstruction in this model. Revising a failed composite ACL construct by means of overdrilling and reinstrumenting may provide fixation equivalent to the initial reconstruction.

Essentials of disaster management: the role of the orthopaedic surgeon.

Disaster preparedness and management education is essential for allowing orthopaedic surgeons to play a valuable, constructive role in responding to disasters. The National Incident Management System, as part of the National Response Framework, provides coordination between all levels of government and uses the Incident Command System as its unified command structure. An "all-hazards" approach to disasters, whether natural, man-made, intentional, or unintentional, is fundamental to disaster planning. To respond to any disaster, command and control must be established, and emergency management must be integrated with public health and medical care. In the face of increasing acts of terrorism, an understanding of blast injury pathophysiology allows for improved diagnostic and treatment strategies. A practical understanding of potential biologic, chemical, and nuclear agents and their attendant clinical symptoms is also prerequisite. Credentialing and coordination between designated organizations and the federal government are essential to allow civilian orthopaedic surgeons to access systems capable of disaster response.

Contact area and pressure in suture bridge rotator cuff repair using knotless lateral anchors.

PURPOSE: To evaluate whether the use of knotless lateral anchors in a suture bridge construct produces better contact area and pressure parameters than a suture bridge construct with standard lateral anchors that require knots or a double-row repair. The hypothesis was that knotless lateral anchors would produce better contact area and pressure parameters than the other two constructs. METHODS: A total of fifteen matched pairs of cadaveric shoulders were divided into three groups. In Group 1, a suture bridge using knotless anchors for the lateral row was performed on five shoulders. A suture bridge using standard lateral row anchors that require knots was performed on the contralateral shoulders. In Group 2, suture bridge with knotless lateral row anchors was compared with double-row repair. In Group 3, suture bridge using standard lateral row anchors was compared with double-row repair. The contact conditions of the rotator cuff footprint were measured using pressure-sensitive film. RESULTS: There were no statistically significant differences between any of the techniques regarding contact area F(2, 15.7) = 3.09, P = 0.07 or mean contact pressure F(2, 15.1) = 2.35, P = 0.12. A post hoc power analysis suggests differences between techniques are likely less than 91-113 mm(2) for area and 0.071-0.089 N for pressure. CONCLUSIONS: The use of knotless anchors in the lateral row of a suture bridge repair did not increase the footprint contact area or contact pressure when compared to a suture bridge repair requiring knots laterally or to a double-row repair.

Stress fractures of the pelvis and legs in athletes: a review.

CONTEXT: Stress fractures are common injuries in athletes, often difficult to diagnose. A stress fracture is a fatigue-induced fracture of bone caused by repeated applications of stress over time. EVIDENCE ACQUISITION: PubMed articles published from 1974 to January 2012. RESULTS: Intrinsic and extrinsic factors may predict the risk of stress fractures in athletes, including bone health, training, nutrition, and biomechanical factors. Based on their location, stress fractures may be categorized as low- or high-risk, depending on the likelihood of the injury developing into a complete fracture. Treatment for these injuries varies substantially and must account for the risk level of the fractured bone, the stage of fracture development, and the needs of the patient. High-risk fractures include the anterior tibia, lateral femoral neck, patella, medial malleolus, and femoral head. Low-risk fractures include the posteromedial tibia, fibula, medial femoral shaft, and pelvis. Magnetic resonance is the imaging test of choice for diagnosis. CONCLUSIONS: These injuries can lead to substantial lost time from participation. Treatment will vary by fracture location, but most stress fractures will heal with rest and modified weightbearing. Some may require more aggressive intervention, such as prolonged nonweightbearing movement or surgery. Contributing factors should also be addressed prior to return to sports.

Effect of insertion of a single interference screw on the mechanical properties of porcine anterior cruciate ligament reconstruction grafts.

The objective of this study was to evaluate the mechanical properties of soft-tissue grafts following a single interference screw insertion of 4 different commercially available bioabsorbable interference screws. Twenty-four bovine proximal tibiae (12 matched pairs) were prepared and sagittally split to make 48 bone samples for testing. Tibiae were prepared for a 9 mm porcine tendon graft and were instrumented with 1 of 4 commercially available 10 x 35 mm composite screws, each with a different thread design. The samples were tensile loaded to failure at 200 mm/min and values for yield load, maximum load, and stiffness were recorded to quantify any differences on the function of the grafts. No graft showed macroscopic evidence of laceration following screw insertion and there were no statistically significant differences for yield load (P = .41), maximum load (P = .35), or stiffness (P = .68) among the different screw types. There is no significant difference in the mechanical properties of an anterior cruciate ligament graft following insertion of the 4 bioabsorbable screws tested in this study, in terms of yield load, stiffness, or failure load.

Effects of single-bundle and double-bundle ACL reconstruction on tibiofemoral compressive stresses and joint kinematics during simulated squatting.

The purpose of this study was to compare tibiofemoral (TF) kinematics and TF compressive stresses between single bundle- (SB-) and double bundle-ACL reconstruction (DB-ACLR) during simulated squatting. Twelve matched pairs of fresh frozen cadaver knees were utilized. A simulated squat through 100° of knee flexion was performed in the ACL-intact joint. The ACL was transected and SB- and DB-ACLR procedures were performed in one knee of each pair. The squat was repeated. Knee kinematics were measured using a motion tracking system and the TF compressive forces were measured using thin film pressure sensors. The posterior shifts of the tibia for SB- and DB-ACLR knees were significantly greater than the ACL-intact condition for knee flexion angles 0° to 40° (p<.05). However, there was no difference between the SB- and DB-ACLR knees at any flexion angle (0° to 100°; p=.37). SB- and DB-ACLR knees had greater IE rotation than intact knees from 90° through 50° of flexion (p<.05), but not between 40° and full extension. There was no difference between SB- and DB-ACLR knees (p=.68). The TF compressive stresses of the DB-ACLR were significantly lower than intact for all angles except 10° (p=.06), whereas SB-ACLR knees did not differ from intact at flexion angles between 30° and 50° (p>.32). There were no significant differences between the two reconstruction conditions (p=.74). This study showed that there was no difference in the TF kinematics or compressive stresses between SB- and DB-ACLR, and only minor differences when compared to the intact state.