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Our current understanding of knee mechanics and anterior cruciate ligament (ACL) function is predominately based on data recorded during simulations of clinical examinations or the application of nonphysiologic loads and motions. These methodologies provide little information on knee and ACL mechanics during activities of daily living (ADLs). Additionally, researchers have not directly measured knee kinetics, knee contact pressures, and ACL forces, and it is unknown how these parameters change with different activities. This study quantified the effects of activity level on vertical ground reaction forces, knee kinematics, and joint and ligament forces during in vivo motions. Five female Suffolk sheep were walked twice weekly on a treadmill during level (0°), inclined (+6°), and declined (−6°) gait for 12 weeks. Electromagnetic (EM) trackers were surgically implanted onto the left distal femur and the left proximal tibia, and in vivo motions were recorded for all activities. Following sacrifice, the in vivo motions were applied to their respective knees using a serial robot with a multi‐axis load cell. In vitro simulations were repeated to measure (a) total knee forces, (b) contact pressure maps, and (c) ACL‐only forces. Declining the gait surface led to increased posterior translation during the swing phase and decreased flexion at hoof‐strike, decreased medial contact pressure at push‐off, decreased ACL force at hoof‐strike and increased ACL force at push‐off. This study established a system that can be used to examine knee mechanics and ACL forces during ADLs for different knee states to define design requirements for ACL reconstruction techniques. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine how in vitro mechanical stimulation of tissue engineered constructs affects their stiffness and modulus in culture and tendon repair biomechanics 12 weeks after surgical implantation. Using six female adult New Zealand White rabbits, autogenous tissue engineered constructs were created by seeding mesenchymal stem cells (0.1 x 106 cells/ml) in collagen gel (2.6 mg/ml) and combining both with a collagen sponge. Employing a novel experimental design strategy, four constructs from each animal were mechanically stimulated (one 1 Hz cycle every 5 rain to 2.4% peak strain for 8 h/day for 2 weeks) while the other four remained unstretched during the 2 week culture period. At the end of incubation, three of the mechanically stimulated (S) and three of the nonstimulated (NS) constructs from each animal were assigned for in vitro mechanical testing while the other two autogenous constructs were implanted into bilateral full-thickness, full-length defects' created in the central third of rabbit patellar tendons (PTs). No significant differences were found in the in vitro linear stiffnesses between the S (0.15 [+ or -] 0.1 N/mm) and NS constructs (0.08 [+ or -] 0.02 N/mm; mean [+ or -] SD). However, in vitro mechanical stimulation significantly increased the structural and material properties of the repair tissue, including a 14% increase in maximum force (p =0.01), a 50% increase in linear stiffness (p=0.001), and 23-41% increases in maximum stress and modulus (p=0.01). The S repairs achieved 65%, 80%, 60%, and 40% of normal central PT maximum force, linear stiffness, maximum stress, and linear modulus, respectively. The results for the S constructs exceed values obtained previously by our group using the same animal and defect model, and to our knowledge, this is the first study to show the benefits of in vitro mechanical stimulation on tendon repair biomechanics. In addition, the linear stiffnesses for the construct and repair were positively correlated (r=0.56) as were their linear moduli (r=0.68). Such in vitro predictors of in vivo outcome hold the potential to speed the development of tissue engineered products by reducing the time and costs of in vivo studies. [DOI: 10.1115/1.2800769]

Background: Many authors have speculated that altered neuromuscular control and strength of the lower extremity are responsible for the gender disparity in knee ligament injury rates. Hypothesis: Significant increases in [...]

Background: Although neuromuscular indices have been extensively studied in adolescents and adults, limited data exist for prepubescent children. Hypothesis: No differences exist between prepubescent boys and girls in lower limb [...]

Partial triceps tendon disruptions are a rare injury that can lead to debilitating outcomes if misdiagnosed or managed inappropriately. The clinician should have a high index of suspicion when the mechanism involves a fall onto an outstretched arm and there is resultant elbow extension weakness along with pain and swelling. The most common location of rupture is at the tendon-osseous junction. This case report illustrates a partial triceps tendon disruption with involvement of, primarily, the medial head and the superficial expansion. Physical examination displayed weakness with resisted elbow extension in a flexed position over 90°. Radiographs revealed a tiny fleck of bone proximal to the olecranon, but this drastically underestimated the extent of injury upon surgical exploration. Magnetic resonance imaging is essential to ascertain the percentage involvement of the tendon; it can be used for patient education and subsequently to determine treatment recommendations. Although excellent at finding associated pathology, it may misjudge the size of the tear. As such, physicians must consider associated comorbidities and patient characteristics when formulating treatment plans. [ABSTRACT FROM PUBLISHER]

Anterior cruciate ligament reconstruction is the sixth most common procedure performed by orthopaedic surgeons. The goals of the procedure are to restore knee stability and patient function. These goals are dependent on proper graft positioning and incorporation. Anterior cruciate ligament reconstruction involves a technically complicated series of steps, all of which affect graft healing and clinical outcome. A wide variety of graft choices and surgical techniques are currently available for use. It is important for orthopaedic surgeons performing anterior cruciate ligament reconstructions to be aware of the indications for graft selection, techniques for correct graft placement, and the biologic implications related to these factors.

Objective: The objective of our study was to evaluate the clinical significance of grade 2C meniscal [corrected] signal (an extensive triangular or wedge-shaped signal that does not reach the surface on more than one image) on MR imaging of the knee., Materials and Methods: Review of 1106 MR imaging reports over 2 years revealed 88 patients with menisci described as containing triangular, wedge-shaped, extensive, or grade 2C signal. Image review by consensus of two radiologists found 34 menisci in 29 patients that fit criteria for grade 2C signal. Seven menisci containing grade 2C signal were evaluated with arthroscopy. An additional three patients with grade 2C meniscal signal with arthroscopic correlation were identified from 4 previous years., Results: Prevalence of grade 2C signal was 1.5% (34/2212 menisci). Seven (21%) of these 34 menisci had subsequent arthroscopy and three of these had meniscal tears. Including the three additional menisci with grade 2C signal from 4 previous years, five (50%) of 10 menisci with grade 2C signal were torn at arthroscopy. No difference was noted between torn and intact menisci in the number of images with grade 2C signal. In patients with tears, the range was three to 10 images (mean, 6.6 images) compared with a range of two to 10 images (mean, 6.6 images) in patients without tears. The maximal percentage of area of abnormal signal in patients with tears ranged from 70% to 90% (mean, 80%) compared with a range of 60-90% (mean, 82%) in patients without tears. The patient age range was 23-64 years (mean, 47 years) in patients with tears and 16-67 years (mean, 47 years) in patients without tears., Conclusion: Grade 2C meniscal signal has a low incidence. Although half of patients with symptoms meriting arthroscopy have tears, most patients with grade 2C signal are not treated with arthroscopy.

Aging has traditionally been associated with several functional declines within the musculoskeletal system. In this study, we characterized and compared age-related changes in performance in power and endurance activities (ie, power-lifting, stationary rowing). From age 25 to age 85, men's and women's rowing performance decreases 29%; from age 25 to age 55, men's rowing performance decreases 0.12% per year, and women's performance decreases 0.23% per year. The pattern of decline in power-lifting performance is characterized by earlier onset and more rapid progression. During the fourth decade, men's and women's power-lifting performance decreases 3% per year; thereafter, their performance decreases 1% per year. The difference between the age-related change rates for rowing and power-lifting is statistically significant (P = .05). The older athletes' performance in both activities suggests that the capacity for significant function in activities requiring power and endurance persists throughout life in individuals who train and who remain in good health. That strength decreases more rapidly than endurance capacity points to the importance of resistance exercises for minimizing muscle weakness in an aging population.