Lateral extraarticular reconstructions are used as isolated procedures in knees with moderate rotatory instability and as "backups" in knees requiring primary repair or intraarticular reconstruction for major rotatory instability. We used an experimental knee testing system to analyze the immediate postoperative mechanical effect of an iliotibial band tenodesis on an intraarticular reconstruction of the ACL in fresh cadaver knees using a composite graft consisting of a bone-patellar tendonbone segment augmented with the Kennedy Ligament Augmentation Device (LAD, 3M Co., St. Paul, MN). The intraarticular graft was standardized by using a forcesetting technique. Ligament and graft forces were measured using buckle transducers, and joint motion was measured using an instrumented spatial linkage as 90 N anteriorly directed tibial loads were applied to seven fresh knee specimens at 0 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion. The following knee states were tested in each specimen: intact ACL, excised ACL, intraarticular reconstruction, intraarticular reconstruction with the tenodesis added, and tenodesis with the intraarticular reconstruction added. Adding the iliotibial band tenodesis to an existing standardized intraarticular reconstruction significantly decreased the force in the ACL composite graft by an average of 43%. When the standardized intraarticular reconstruction was added to an existing tenodesis, the graft forces were an average of 15% below the level of when the reconstruction was performed alone. The force in the tenodesis was significantly less than the composite graft force at extension; however, the differences between the tenodesis and total graft force were not significant from 30 degrees to 90 degrees of flexion.(ABSTRACT TRUNCATED AT 250 WORDS)

The goal of this study was to use a segmental defect model in the rat femur to determine if osteogenic protein-1 (OP-1) is capable of inducing bone formation in the presence of bacterial contamination. A 6 mni segmental defect was surgically created and stabilized with a polyacetyl plate and Kirschner wires in one femur in each of 126 Sprague-Dawley rats. The animals were divided into eight groups in which the defect was either left untreated, or subjected to various combinations of OP-l (1 I or 50 pg), lyophilized bovine type I collagen (carrier for the OP-I), and 10' colony-forming units of Strcphy1ococcu.r ciureus. The animals were euthanized at either 2, 4, or 9 weeks. Quantitative radiographic and histologic analyses were performed on the harvested tissue. The initial contamination progressed to infection in all animals receiving bacteria, as determined by qualitative bacteriology. There was very little, if any, bone formation in the untreated defects, and in the contaminated defects with or without collagen carrier. Bone formation was significantly greater in contaminated defects with either dose of OP-1, compared with contaminated defects without 01'-1. The 50 pg dose of OP-1 induced significantly more bone formation than the 11 pg dose, both with and without bacteria. This investigation has demonstrated that OP-l maintains its osteoinductive capability in a contaminated segmental defect. OP-1 may potentially be used in the clinical management of Contaminated fractures.

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The aims of this study were to measure the forces in the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) and the motion in the tibiotalar and subtalar joints during simulated weight-bearing in eight cadaver ankle specimens. An MTS test machine was used to apply compressive loads to specimens held in a specially designed testing apparatus in which the ankle position (dorsiflexion-plantarflexion and supination-pronation) could be varied in a controlled manner. The forces in the ATFL and CFL were measured with buckle transducers. Tibiotalar motion and total ankle joint motion were measured with an instrumented spatial linkage. The specimens were positioned sequentially at 10 degrees dorsiflexion, neutral, and 10 degrees and 20 degrees plantarflexion, and this sequence was repeated at 15 degrees supination, neutral pronation/supination, and 15 degrees pronation. Force and motion measurements were recorded in each of these positions with and without a 375 N compressive load simulating weight-bearing. From 10 degrees dorsiflexion to 20 degrees plantarflexion, all motion occurred in the tibiotalar joint. In contrast, the ratio of subtalar motion to tibiotalar motion was 3:1 for supination-pronation and 4:1 for internal-external rotation. Inverse loading patterns were observed for the ATFL and CFL from plantarflexion to dorsiflexion. Compressive loading did not affect CFL tension, but it magnified the pattern of increasing ATFL tension with plantarflexion. The largest increase in ATFL force was observed in supination and plantarflexion with a compressive load (76 +/- 23 N), whereas CFL tension mainly increased in supination and dorsiflexion with a compressive load (109 +/- 28 N). In conclusion, the results showed that the ATFL acted as a primary restraint in inversion, where injuries typically occur (combined plantarflexion, supination and internal rotation). Also, the subtalar joint was of primary importance for normal supination-pronation and internal-external rotation.

The aim of this study was to characterize a new model of chronic osteomyelitis with clinically relevant features. A segmental defect of critical size was surgically created in the rat femur, stabilized with a polyacetyl plate and Kirschner wires, and contaminated with bacteria. The animals were allowed to recover while the contamination progressed to a chronic infection. At a later point in time, the defect was surgically debrided without removing the implant. Further treatments of interest, such as antibiotic therapy or application of an osteogenic agent, could be introduced at this time. To implement this model, an initial experiment was performed to determine the bacterial inoculum and time from contamination that would reliably result in an infected defect without causing excessive bone damage by the time debridement surgery was performed. The number of recovered bacteria, degree of radiographic bony lysis, and torsional stiffness of the defect fixation were measured in 192 rats as a function of 4 inocula of Staphylococcus aureus (lo', lo4, 10' or lo6 CFUs) and 4 times from contamination (1,2, 3 or 4 weeks). A lo4 CFU inoculum over 2 weeks was found to consistently create an infection without severe lysis and loss of fixation stability. Based on these values, a second experiment was performed in 96 rats to characterize the debrided defect over time (2,4,8 and 12 weeks after debridement), with and without 4 weeks of the antibiotic ceftriaxone, in terms of the same outcome variables. Infection was persistent in all animals in spite of debridement and antibiotic therapy. Antibiotic therapy did not reduce the degree of bony lysis. Compared with animals not given antibiotic, bacterial counts significantly decreased during the period of antibiotic therapy, but then rebounded to significantly higher levels at 12 weeks. This model allows us to perform further studies on differing regimens of antibiotic therapy and their relationship to surgical dtbridement, and on the efficacy of osteogenic agents in the presence of infection.