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ANTERIOR CRUCIATE LIGAMENT OF KNEE JOINT.
Term Paper ID:24684
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Essay Subject:
Anatomy, structure, physiology, function, biomechanics, diagnostic & stability tests, injury & treatment.... More...
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30 Pages / 6750 Words
25 sources, 71 Citations,
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Paper Abstract:
Anatomy, structure, physiology, function, biomechanics, diagnostic & stability tests, injury & treatment.
Paper Introduction:
ANTERIOR CRUCIATE LIGAMENT OF THE KNEE JOINT
Introduction
This research paper presents information regarding the anterior cruciate ligament (ACL) of the knee joint. Discussion includes anatomy of the knee joint and the ACL, and ACL structure, physiology, function and biomechanics, clinical diagnostic tests and technological diagnosis, and mechanisms of injury and treatment. A comparison of acute ACL stability tests includes the anterior drawer test, Lachman's test, and pivot shift test.
Anatomy & Structure
The anatomy of the knee includes the patellar ligament, patella, articular cartilage, posterior cruciate ligament, anterior cruciate ligament, medial collateral ligament, lateral
Text of the Paper:
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Clinical and technological diagnosis include history ofinjury, functional knee criteria, Lachman's, anterior drawer, and pivotshift tests for stability, arthroscopy, and MRI. Palpation of the knee is next and vascular integrityshould also be assessed. 6. The ACL isdistally attached to a fossa in front of and lateral to the anterior tibialspine. At these knee angles the hamstrings are notefficient synergists to the ACL for preventing anterior translation.Increased duration of hamstring activity may have been demonstratedhowever, this does not imply increased activity magnitude (1 :7). Studies reviewed used a variety of imaging equipment and techniques;variations were found in the field strengths of the MR systems. Anexaminer with small hands used each of the tests on both knees of subjectsand stated which knee was believed to be the most lax, with respect to eachtest. Noyes, F. Studiesdocument mechanical functions of the ACL in vitro, less information isavailable regarding ACL loading in vivo. The ACL is a crucial ligament due to the crossed arrangement of theanterior and posterior ligaments within the knee. Johnson, L. & Rel. Rossvill, I.; Smevik, O.; Nilsen, G.Comparison between magnetic resonance imaging findings and knee stability:measurements after anterior cruciate ligament repair with and withoutaugmentation. Surgical techniques for ACL reconstruction include repair through thepatellar defect, arthroscopically assisted techniques, and theminiarthrotomy technique. Partial ACL tears make up 1 percent to35 percent of all ACL injuries. With an experienced examiner, accuracy of the testis 85 percent in an awake patient and 1 percent in the anesthetizedpatient. 12(6):66 -666; 1996. Patients with ruptures only in superficial medialligament fibers were treated nonoperatively; 91 percent rated excellent orgood and one rated fair. Knee elevation or ice pack can help withpain and apprehension in the patient that may hinder the exam. When the knee moved intomidstance, external moment reversed direction and demanded net quadricepsforce. J. For some, fascicles from the posterior part of the tibialattachment of the ACL may blend with the posterior attachment of thelateral meniscus. 5. Studies suggest that functional kneecriteria are more useful indicators of outcome than intrareconstruction andpostreconstruction arthrometric measures (6:66 ). 23(6):736-745;1995. Medical historical datais informative but should be further substantiated with physicalexamination to differentiate between the mechanical problems of a tornmeniscus and the laxity of a torn ACL. Studies are based on smallsubject numbers and contradictory outcomes are found; some show persistentinstability and others report no instability. Research shows that the greatest change in gait in the ACL-deficientpatient is the flexion-extension moment at the knee. C.; Barrett, T. 1 (2):132-139; 1994. Plant-and-cut, straight leglanding, and l-step stop are common injury mechanisms; these were replacedwith rounding turns, flexed landing, and 3-step stop (11:295-296). In cases with a false negativeLachman test (2 cases), firm reattachment of the torn end of the ACL to theproximal part of the posterior cruciate ligament and a bucket handle tearof the medial meniscus was found. The Lachman is considered the best test for diagnosingthe presence of an ACL disruption (25:619). The Lachman test increases accuracy and sensitivity of clinicaltesting for ACL laxity. J. The Lachman test was found to be the most sensitive for diagnosis ofchronic ACL injuries. A.; Blankevoort, L.; Huiskes, R.; Kooloos, J. Forthese patients the anterior drawer test was positive in 68.4 percent ofpatients, in 89.5 percent of those having the Lachman test, and in 63.2percent with the pivot shift test (14:237). T.; Youngberg, R. D.;Nguyen, P. 317:237-242; 1995.15. High forces were carried by veryfew fiber bundles at each flexion angle. Am. Grade 2 are incomplete tears with a small increase inlaxity. Conclusions The ACL is a crucial ligament within the knee structure. Different groups of fasciclesfunction together throughout the range of joint motion (4:134). Muscular substitution duringambulatory activities may adapt dynamically for the stability lost at theknee. L.; Johnson, A. The human posterior cruciate ligament complex: an interdisciplinary study. 23(2):17 -172; 1995. A lack of proven method of diagnosis complicatesattempts of follow-up studies of incomplete ACL tears (17:111). Cruciate ligaments are intraarticular and extrasynovial(4:132). It turns on itself in an outward spiral,probably due to its bony attachments. J. Studies show that ACL is composed of multiple wide collagen fiberbundles separated by columns of cells in fibrous capsules which group intofascicles varying in size. Results show that overall sensitivity for MRI of the menisci andcruciates was .88; specificity was .94. It is hypothesized that these bone bruises mayresult in degeneration of the overlying articular cartilage; long-term MRIstudies are needed. Types of sensory endings in the human ACL include two typesof Ruffini end organs, pacinian corpuscles, and free nerve endings. Anatomic studies are not conclusive with regard to the synovialreflections around the cruciate ligaments and whether the ACL and the PCLhave separate synovial sheaths or one single sheath enveloping them withinthe same extrasynovial space. G.; Hoekman, R. The cost-effectiveness of MR imaging remains controversialhowever, since retrospective and arthroscopic follow-up is lacking andpatient criteria is undefined; MR may be more cost-effective for chronicsymptoms rather than for patients with acute knee injuries (2:913). W.; Livesay, G. K.; Barton, J. percent to9.6 percent) is reported however, therefore there is a possibility that theuninjured knee may previously damaged (24:133-134). When the knee is flexed, the anteromedial fibers are tautand the ligament twists 9 degrees on itself. Factors of genu valgum,VMO hypoplasia, and femoral anteversion will increase laterally directedforces on the PF joint and the medial compartment and the medial collateralligament. The posterior convexity is "parallel to the posteriorarticular margin of the lateral femoral condyle" (4:132-133). J.; Dixon, A. The drop leg Lachmantest is easier to perform and it is a sensitive method to demonstrateanterior laxity in an ACL-deficient knee (1:32 ). Harner, C. P.; Grood, E. The flexion-extensionmoment during stance phase was interpreted by the net quadriceps or netknee flexor demand (hamstrings and/or gastrocnemius) during stance phase.At heel-strike there was usually an external moment extending the kneejoint or demanding net knee flexor force. Functional outcome for incomplete ACL tears iscontroversial, however evidence shows that knees that initially seem stablewill progress to symptomatic ACL deficiency. Tibial tunnel placement in ACLreconstruction. Problems that occur with this test include difficulty testing alarge limb, control of flexion and rotation, and lack of patient relaxation(1:32 ). Functional demands of the patient arefactors for the recommendation for surgical or conservative ACL treatment.Age is one of the factors to consider; conservative treatment or activitymodification is less effective for school age patients. L. Apatellar dislocation or subluxation can look like an acute ACL rupture; itshould be examined for a positive patellar apprehension sign. Usually, females have lower centers of gravity, a widerpelvis, shorter legs, greater genu valgus, increased femoral anteversion,less vastus medialis obliquus (V
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