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At least 217 records · Page 12Linked to original sources

Mapping lubricin in canine musculoskeletal tissues.

Lubricin, also known as superficial zone protein or PRG4, has many distinct biological functions, including lubrication, antiadhesion, and as a regulator of cell growth. This study investigated lubricin in canine musculoskeletal tissues using RT-PCR and immunohistochemistry. One or more variants were noted in canine flexor digitorum profundus (FDP) tendon, Achilles tendon, patellar tendon, A2 pulley, anterior cruciate ligament (ACL), knee lateral collateral ligament (LCL), articular cartilage, meniscus, muscle, and skin. We found 6 N-terminal lubricin splicing variants. The variants with larger sizes were identified in FDP tendon, ACL, LCL, A2 pulley, and cartilage. Lubricin was distributed both on the tissue surfaces and at the interface of fiber bundles within tissues, but this distribution varied by tissue type. We conclude that lubricin is present in many tissues; variations in splicing and physical distribution suggest that the variants of lubricin may play different roles in different locations.

Alternative Splicing↗

Internal derangements of the knee: rates of occurrence at MR imaging in patients referred by orthopedic surgeons compared with rates in patients referred by physicians who are not orthopedic surgeons.

PURPOSE: To compare the occurrence at magnetic resonance (MR) imaging of clinically important knee abnormalities in patients referred by orthopedic surgeons with that in patients referred by other physicians. MATERIALS AND METHODS: Knee MR images in all patients referred for evaluation of internal derangement for 12 months were retrospectively reviewed. Meniscus, ligament, and articular cartilage abnormalities were tabulated. The numbers of abnormalities detected in the patients referred by orthopedic surgeons were compared with those in the patients referred by all other physicians by using chi(2) analysis. Significance was defined at P less than .05. RESULTS: Knee MR images in 439 patients were reviewed; 328 patients were referred by orthopedic surgeons, and 111 were referred by other physicians. There was no significant difference in the rates of occurrence of meniscus tear (149 [45%; orthopedic surgeon referrals] vs 50 [45%; other physician referrals], P = .96); ligament tear (82 [25%] vs 21 [19%], P = .25); isolated hyaline cartilage defect (77 [23%] vs 20 [18%], P = .29); meniscus or ligament tear (167 [51%] vs 55 [50%], P = .86); or meniscus, ligament, or articular cartilage tear (242 [74%] vs 72 [65%], P = .34). The proportion of patients who subsequently underwent surgery of the knee was also similar (39% [118 of 300] vs 28% [23 of 82], P = .14). CONCLUSION: There was no significant difference in the occurrences of clinically important knee internal derangement at MR imaging between patients referred by orthopedic surgeons and those referred by other physicians.

Adolescent↗

An intra-articular knee cyst in a 2-year-old associated with an aberrant anterior cruciate ligament.

Intra-articular ganglia of the knee occur infrequently, with an overall incidence estimated to be from 0.2 to 1.9%. To date, the youngest patient reported with an intra-articular ganglion was an adolescent. In this paper, we describe a 2-year-old patient with a massive intra-articular knee cyst and an aberrant anterior cruciate ligament (ACL) origin. The cyst was successfully treated with arthroscopic debridement. Proposed pathology and treatment recommendations for intra-articular cysts are reviewed.

Anterior Cruciate Ligament↗

Biomechanics of knee ligaments.

Significant advances have been made during the past 25 years in characterizing the properties of ligaments as a tissue and as an individual component in the bone-ligament-bone complex. The contribution of ligaments to joint function have also been well characterized. We have presented many studies that sought to characterize the tensile and viscoelastic properties of ligaments. As a result of these investigations, some of the most important experimental and biologic factors affecting the measurements of these properties have been identified and elucidated. The identification of the tensile properties of normal ligaments can serve as the basis for evaluating their success in healing and repair after injury. Furthermore, characterization of normal ligament function is crucial for diagnosing joint injuries as well as for evaluating reconstruction strategies and developing rehabilitation protocols. The recent introduction of robotic technology to the study of joint kinematics has resulted in significant advances in the understanding of the relative importance of ligaments to joint function. With the more accurate simulation of joint kinematics that include multiple degrees of freedom motion, data on the in situ forces in ligaments can be used to improve the treatment of ligament repair and reconstruction. More complex external loading conditions that mimic sports activities and rehabilitation protocols can also be introduced in the future. Furthermore, this technology can be extended to study other frequently injured joints, such as the shoulder.

Animals↗

[Clinical evaluation of knee trauma].

Clinical evaluation is of preponderant importance in the management of knee trauma. This evaluation is based on a systematic examination that should be well known to any practitioner treating such patients. During recent years, the symptomatology of knee trauma has required a large number of manipulations and clinical tests that can better identify the location and nature of anatomic lesions and specify their severity. The most important of these clinical signs and their pathological significance are presented in this study. Analysis of the symptoms, with grouping and concordance of the different tests, classifies the knee as having suffered "ligament", "patella", "meniscal" or other injury. Despite its limitations and sometimes too schematic nature, this classifications is highly informative and in most cases should be an indispensible step before prescribing radiology.

Diagnostic Imaging↗

Histopathology of the palmar beak ligament in trapeziometacarpal osteoarthritis.

Eighteen cadaver hands were studied to investigate the relationship between degeneration of the palmar beak ligament and articular disease of the trapeziometacarpal joint. Eight of 18 joints had chondromalacia alone; 10 contained areas of eburnation in the palmar aspect of the joint. Beak ligament degeneration correlated closely with the presence of articular degeneration; all joints with eburnation demonstrated frank detachment of the ligament from its metacarpal insertion site. Histologically, the collagen fibers of the beak ligament were disorganized at the metacarpal attachment. The normal insertional zone of fibrocartilage was often unrecognizable on the metacarpal side and, in more degenerative specimens, an intervening synovial recess appeared at the palmar beak of the metacarpal. The trapezial insertion of the beak ligament showed no degenerative change. Increasingly severe cartilage disease was associated with progressive and selective degeneration of the collagen framework of the beak ligament at its insertion onto the thumb metacarpal. These localized histopathologic findings further support the existence of an anatomically distinct intra-articular beak ligament essential to the normal function of the trapeziometacarpal joint and suggest an etiologic relationship to osteoarthritic disease.

Aged↗

The biomechanics of the human patella during passive knee flexion.

The fundamental objectives of patello-femoral joint biomechanics include the determination of its kinematics and of its dynamics, as a function of given control parameters like knee flexion or applied muscle forces. On the one hand, patellar tracking provides quantitative information about the joint's stability under given loading conditions, whereas patellar force analyses can typically indicate pathological stress distributions associated for instance with abnormal tracking. The determination of this information becomes especially relevant when facing the problem of evaluating surgical procedures in terms of standard (i.e. non-pathological) knee functionality. Classical examples of such procedures include total knee replacement (TKR) and elevation of the tibial tubercle (Maquet's procedure). Following this perspective, the current study was oriented toward an accurate and reliable determination of the human patella biomechanics during passive knee flexion. To this end, a comprehensive three-dimensional computer model, based on the finite element method, was developed for analyzing articular biomechanics. Unlike previously published studies on patello-femoral biomechanics, this model simultaneously computed the joint's kinematics, associated tendinous and ligamentous forces, articular contact pressures and stresses occurring in the joint during its motion. The components constituting the joint (i.e. bone, cartilage, tendons) were modeled using objective forms of non-linear elastic materials laws. A unilateral contact law allowing for large slip between the patella and the femur was implemented using an augmented Lagrangian formulation. Patellar kinematics computed for two knee specimens were close to equivalent experimental ones (average deviations below 0.5 degrees for the rotations and below 0.5 mm for the translations) and provided validation of the model on a specimen by specimen basis. The ratio between the quadriceps pulling force and the patellar tendon force was less than unity throughout the considered knee flexion range (30-150 degrees), with a minimum near 90 degrees of flexion for both specimens. The contact patterns evolved from the distal part of the retropatellar articular surface to the proximal pole during progressive flexion. The lateral facet bore more pressure than the medial one, with corresponding higher stresses (hydrostatic) in the lateral compartment of the patella. The forces acting on the patella were part of the problem unknowns, thus leading to more realistic loadings for the stress analysis, which was especially important when considering the wide range of variations of the contact pressure acting on the patella during knee flexion.

Algorithms↗

Discomallear and malleomandibular ligaments: anatomical study and clinical applications.

Phylogenesis, ontogenesis and anatomy show the existence of two discomallear and malleomandibular ligaments, arising from the first branchial arch and uniting the middle ear with the temporomandibular joint and to the mandible. The intra-articular discomallear ligament is the involuted tendon of the lateral pterygoid muscle on the primitive quadrato-articular joint. The malleomandibular ligament is the fibrous remnant of Meckel's cartilage. In the physiology of the temporomandibular joint, the discomallear ligament alone limits the anterior movement of the disc. Its stretching accompanies disco-condylar disunity, hyperlaxity and temporomandibular dislocation. The malleomandibular ligament, wrongly limited to its sphenomandibular part in classic anatomy, has no physiological role. However, it can be responsible for the dislocation of the ear ossicle chain after disarticulation or temporomandibular trauma. These two ligaments do not play any role in otological manifestations in dysfunction of the manducatory apparatus.

Humans↗

Healing of a surgically created partial detachment of the posterior cruciate ligament using marrow stimulation: an experimental study in dogs.

The inability of intra-articular (cruciate) ligaments to generate a substantive reparative response may preclude the primary surgical repair of such lesions. A marrow stimulation technique that provides access to a fibrin scaffold, cytokines, and mesenchymal stem cells has been shown to be successful in generating a repair response in articular cartilage. We hypothesized that a similar approach may be effective in initiating and supporting a healing response in cruciate ligament injuries. The ability to treat cruciate ligament injuries by primary repair may have significant advantages over the more extensive reconstructive procedures currently advocated. Bilateral subtotal (75% of width) lacerations were made in the proximal aspect of the posterior cruciate ligament (PCL) in 10 adult mongrel dogs. A marrow stimulation technique in which small holes were made through the femoral origin of the PCL into the marrow cavity immediately adjacent to the lesion was performed in one limb. The contralateral limb served as the non-stimulated control. Twelve weeks after surgery the extent of healing and the histological character of the repair tissue in both groups were compared. Marrow stimulation resulted in a statistically significant (P<.05) improvement in the healing of subtotal lacerations made in the PCL. The marrow-stimulated repair tissue was more cellular and had a more organized extracellular matrix than the repair tissue in the non-stimulated group. Our hypothesis was confirmed. Marrow stimulation can induce a "healing response" in intra-articular (cruciate) ligaments. This technique may have clinical applications in primary surgical repair of these structures.

Animals↗

Loose intra-articular body following anterior cruciate ligament reconstruction.

We report a case of intra-articular fracture of a bioabsorbable fixation device from the femoral tunnel in an anterior cruciate ligament reconstruction using a bone-tendon-bone graft. Thirteen months after successful reconstruction surgery, the patient experienced episodes of locking and medial joint pain. There was no history of trauma and no symptoms of instability or swelling. On revision arthroscopy, a fractured tip of a bioabsorbable RIGIDfix cross pin (Mitek, Westwood, MA) was identified in the medial compartment of the knee. There was a broad area of chondral erosion affecting the medial femoral condyle and a small defect to the medial tibial plateau where the loose body had been lodged. The bone-tendon-bone graft was intact without disruption. After arthroscopy, the patient was symptom free for 3 weeks but then developed further symptoms of locking. Magnetic resonance imaging showed another loose body within the knee. A repeat arthroscopy was performed 6 weeks after the earlier procedure and another piece of the polylactic acid RIGIDfix cross pin was removed, this time from the lateral gutter. This case raises concern about the potential for breakage and resultant loose body formation that may occur after bioabsorbable cross-pin fixation and, particularly, the associated chondral damage that can occur if early intervention is not conducted.

Absorbable Implants↗