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Background: There are currently limited human in vivo data characterizing the role of the meniscus in load distribution within the tibiofemoral joint. Purpose/Hypothesis: The purpose was to compare the strains experienced in regions of articular cartilage covered by the meniscus to regions of cartilage not covered by the meniscus. It was hypothesized that in response to walking, tibial cartilage covered by the meniscus would experience lower strains than uncovered tibial cartilage. Study Design: Descriptive laboratory study. Methods: Magnetic resonance imaging (MRI) of the knees of 8 healthy volunteers was performed before and after walking on a treadmill. Using MRI-generated 3-dimensional models of the tibia, cartilage, and menisci, cartilage thickness was measured in 4 different regions based on meniscal coverage and compartment: covered medial, uncovered medial, covered lateral, and uncovered lateral. Strain was defined as the normalized change in cartilage thickness before and after activity. Results: Within each compartment, covered cartilage before activity was significantly thinner than uncovered cartilage before activity (P < .001). After 20 minutes of walking, all 4 regions experienced significant cartilage thickness decreases (P < .01). The covered medial region experienced significantly less strain than the uncovered medial region (P = .04). No difference in strain was detected between the covered and uncovered regions in the lateral compartment (P = .40). Conclusion: In response to walking, cartilage that is covered by the meniscus experiences lower strains than uncovered cartilage in the medial compartment. These findings provide important baseline information on the relationship between in vivo tibial com-pressive strain responses and meniscal coverage, which is critical to understanding normal meniscal function. [ABSTRACT FROM AUTHOR] more...

Background: Altered local mechanical loading may disrupt normal cartilage homeostasis and play a role in the progression ofosteoarthritis. Currently, there are limited data quantifying local cartilage strains in response to dynamic activity in normal orinjured knees.Purpose/Hypothesis: To directly measure local tibiofemoral cartilage strains in response to a dynamic hopping activity in normalhealthy knees. We hypothesized that local regions of cartilage will exhibit significant compressive strains in response to hopping,while overall compartmental averages may not.Study Design: Controlled laboratory study.Methods: Both knees of 8 healthy subjects underwent magnetic resonance imaging before and immediately after a dynamic hoppingactivity. Images were segmented and then used to create 3-dimensional surface models of bone and cartilage. These preandpostactivity models were then registered using an iterative closest point technique to enable site-specific measurements ofcartilage strain (defined as the normalized change in cartilage thickness before and after activity) on the femur and tibia.Results: Significant strains were observed in both the medial and lateral tibial cartilage, with each compartment averaginga decrease of 5%. However, these strains varied with location within each compartment, reaching a maximum compressive strainof 8% on the medial plateau and 7% on the lateral plateau. No significant averaged compartmental strains were observed in themedial or lateral femoral cartilage. However, local regions of the medial and lateral femoral cartilage experienced significant compressivestrains, reaching maximums of 6% and 3%, respectively.Conclusion: Local regions of both the femur and tibia experienced significant cartilage strains as a result of dynamic activity. Anunderstanding of changes in cartilage strain distributions may help to elucidate the biomechanical factors contributing to cartilagedegeneration after joint injury.Clinical Relevance: Site-specific measurements of in vivo cartilage strains are important because altered loading is believed tobe a factor contributing to the development and progression of osteoarthritis. Specifically, this methodology and data could beused to evaluate the effects of soft tissue injuries (such as ligament or meniscus tears) on cartilage strains in response to dynamicactivities of daily living. [ABSTRACT FROM AUTHOR] more...

Context: Although changes in anterior knee laxity (AKL) across the menstrual cycle have been reported, the effects of cyclic knee laxity changes on the underlying characteristics of the load-displacement (stiffness) curve generated during anterior loading of the tibia relative to the femur are relatively unknown. Objective: To describe the anterior load-displacement curve during anterior loading of the tibia relative to the femur using incremental stiffnesses and to compare underlying stiffness measures between days of the cycle when AKL is at its minimum and maximum. Design: Descriptive laboratory study. Setting: University laboratory. Patients or Other Participants: Fifty-seven recreationally active women. Main Outcome Measure(s): Anterior knee laxity and 6 incremental stiffness measures (N/mm) were obtained with an instrumented knee arthrometer on days 1-6 of menses and days 0-8 postovulation during 2 consecutive menstrual cycles. Participants were then classified in fertiles based on the maximum change (difference between maximum and minimum) in AKL, and incremental stiffness was compared on days of minimum versus maximum laxity between the lowest (<1.24 mm cyclic laxity change = laxity "nonresponders" [n = 19]) and highest (>1.75 mm cyclic laxity change = laxity "responders" [n = 19]) tertiles. Results: All participants displayed decreasing stiffness initially (0-20 N > 20-40 N and 40-60 N), followed by incrementally increasing stiffness (40-60 N < 60-80 N < 80- 100 N < 100-130 N) (P < .05). Responders demonstrated decreased stiffness between the days of minimum and maximum AKL at the 10-130-N increment versus the 0-20-N and 20-40-N increments (P < .05); nonresponders had no change in stiffness. Conclusions: Participants who experienced larger magnitudes of cyclic changes in AKL also experienced decreases in terminal (100-130 N) stiffness during anterior knee joint loading. Decreases in incremental stiffness at higher anterior directed loads may adversely affect passive restraint systems, resulting in altered arthrokinematics during functional activity. [ABSTRACT FROM AUTHOR] more...

Introduction/Purpose: Management of hindfoot osteomyelitis involves eradication of infection, deformity correction, and bony stabilization in the setting of bone loss and poor bone quality. In this case series of 12 patients, we present a two-stage technique; debridement, deformity correction, joint surface preparation, and intramedullary reaming with placement of antibiotic rod and ring external fixation followed by a second stage of external fixator removal and exchange of antibiotic rod for definitive hindfoot rod. The purpose of this poster is to highlight techniques that can improve the success of obtaining stable fixation, remission of infection, and ultimately fusion. Techniques highlighted are ring fixator placement, preparation of the antibiotic rod, intramedullary canal preparation, rod exchange, and use of blocking screws to enhance compression and axial loading of the fusion. Methods: Twelve patients were treated with this two-stage protocol. The most common indication was post-traumatic osteomyelitis followed by neuropathic (Charcot) joint. All were treated in a staged manner with an initial debridement of nonviable tissue including osteomyelitic bone. The tibiotalar and talocalcaneal joints were resected and prepared for fusion at the initial debridement. Provisional stabilization and compression were obtained through the use of a ring external fixator. An intramedullary antibiotic impregnated cement coated rod was introduced through the calcaneus, talus, and the intramedullary space of the tibia. The patients were kept in the fixator until the skin was healed and all incisions were dry. At this point, the fixator was removed, and the antibiotic rod was exchanged for the definitive hindfoot fusion rod. Results: Cultures were positive for Staphylococcal or Streptococcal species in 58% of cases, fungal in 8%, and Gram negative organisms in 33%. On average patients spent 93 days in the fixator while wounds were healing, and they were receiving systemic antibiotics. One patient died while in the frame. There have been no amputations in the series. Of the patients that have completed the protocol, all have gone on to either bony fusion or stable fibrous union. All are able to walk unaided. And thus far, all are free of active infection. Secondary procedures are described. Conclusion: This technique of staged fusion for hindfoot osteomyelitis offers the following advantages. the first stage involves thorough debridement and deformity correction. Oftentimes there is extensive scarring and the soft tissue envelope is not conducive to internal fixation. This technique allows the soft tissues to heal before placing the definitive internal fixation. It also allows for graduated compression at the fusion site with the ring fixator. The antibiotic rod not only delivers high concentration of local antibiotics, but it prevents deformity recurrence during the compression phase. The definitive rod provides support of pathologic bone and maintains deformity correction. [ABSTRACT FROM AUTHOR] more...