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PubMed2002

Subfailure damage in ligament: a structural and cellular evaluation.

Subfailure damage in ligaments was evaluated macroscopically from a structural perspective (referring to the entire ligament as a structure) and microscopically from a cellular perspective. Freshly harvested rat medial collateral ligaments (MCLs) were used as a model in ex vivo experiments. Ligaments were preloaded with 0.1 N to establish a consistent point of reference for length (and strain) measurements. Ligament structural damage was characterized by nonrecoverable difference in tissue length after a subfailure stretch. The tissue's mechanical properties (via stress vs. strain curves measured from a preloaded state) after a single subfailure stretch were also evaluated (n = 6 pairs with a different stretch magnitude applied to each stretched ligament). Regions containing necrotic cells were used to characterize cellular damage after a single stretch. It should be noted that the number of damaged cells was not quantified and the difference between cellular area and area of fluorescence is not known. Structural and cellular damage were represented and compared as functions of subfailure MCL strains. Statistical analysis indicated that the onset of structural damage occurs at 5.14% strain (referenced from a preloaded length). Subfailure strains above the damage threshold changed the shape of the MCL stress-strain curve by elongating the toe region (i.e., increasing laxity) as well as decreasing the tangential modulus and ultimate stress. Cellular damage was induced at ligament strains significantly below the structural damage threshold. This cellular damage is likely to be part of the natural healing process in mildly sprained ligaments.

Algorithms↗
PubMed2002

Hindlimb unloading alters ligament healing.

We investigated the hypothesis that hindlimb unloading inhibits healing in fibrous connective tissue such as ligament. Male rats were assigned to 3- and 7-wk treatment groups with three subgroups each: sham control, ambulatory healing, and hindlimb-suspended healing. Ambulatory and suspended animals underwent surgical rupture of their medial collateral ligaments, whereas sham surgeries were performed on control animals. After 3 or 7 wk, mechanical and/or morphological properties were measured in ligament, muscle, and bone. During mechanical testing, most suspended ligaments failed in the scar region, indicating the greatest impairment was to ligament and not to bone-ligament insertion. Ligament testing revealed significant reductions in maximum force, ultimate stress, elastic modulus, and low-load properties in suspended animals. In addition, femoral mineral density, femoral strength, gastrocnemius mass, and tibialis anterior mass were significantly reduced. Microscopy revealed abnormal scar formation and cell distribution in suspended ligaments with extracellular matrix discontinuities and voids between misaligned, but well-formed, collagen fiber bundles. Hence, stress levels from ambulation appear unnecessary for formation of fiber bundles yet required for collagen to form structurally competent continuous fibers. Results support our hypothesis that hindlimb unloading impairs healing of fibrous connective tissue. In addition, this study provides compelling morphological evidence explaining the altered structure-function relationship in load-deprived healing connective tissue.

Animals↗
PubMedDate not supplied

In vivo and in vitro cellular ingrowth into a new generation of artificial ligaments.

Artificial ligaments are a useful tool in ligament reconstruction. Although the new generation of artificial ligaments shows encouraging clinical results, in contrast to earlier generations studies on the biological properties are lacking. Biopsies were taken from a ligament advancement reinforcement system (LARS) 6 months after implantation and investigated by histochemistry. An in vitro study seeding human fibroblasts or osteoblast-like cells (up to 10(6) cells for 21 days) on ligament pieces (5 x 5 mm) was conducted and analyzed by histochemistry. The biopsies showed complete cellular and connective tissue ingrowth in the LARS ligament. In vitro fibroblasts and osteoblast-like cells encapsulated the fibers by building a cellular net around them. To our knowledge, these findings demonstrate for the first time the cellular ingrowth into the LARS ligament. This mechanism might explain the strength and the inert behavior of the ligament without the synovialitis shown in clinical studies.

Adult↗
PubMed1989

Innervation of the incisors and periodontal ligament in several rodents: an immunohistochemical study of neurofilament protein and glia-specific S-100 protein.

The present immunohistochemical study by use of antisera against neurofilament protein (NFP) and S-100 protein dealt with the innervation of the upper incisors and periodontal ligament in five species of rodents including the guinea pig, hamster, Mongolian gerbil (Meriones unguicularis), mouse and squirrel (Tamias sibiricus). The innervation pattern of the periodontal ligament and dental pulp in the incisors of five rodents was fundamentally identical to that in the rat, which we have previously demonstrated by the same method. The NFP-positive Ruffini-like corpuscles were concentrated in the middle region of the lingual periodontal ligament in all the species examined, suggesting that this particular arrangement of Ruffini-like corpuscles, possibly stretch receptors, was essential to the rodent incisor. The labial periodontal ligament, on the other hand, contained less numerous NFP-positive nerves, these terminating among collagen fibers as free endings. The gerbil and squirrel in particular possessed only a few nerve fibers in the labial periodontal ligament. It was thus presumed that the labial periodontal ligament might be less significant as a mechanoreceptive site than the lingual periodontal ligament. The NFP-positive pulpal nerves, beaded or smooth in shape, ran parallel to the tooth axis, but never extended to the odontoblastic layer; no subodontoblastic plexus was found in the incisors of any of the rodents. S-100-immunopositive nervous elements were distributed in the periodontal ligament and dental pulp of all the rodent species examined, showing a distribution pattern similar to the NFP-positive nerves. Only in the squirrel did odontoblasts show an intense S-100 immunoreactivity.

Animals↗
PubMedDate not supplied

A cyclooxygenase-2 inhibitor impairs ligament healing in the rat.

Celecoxib was the first of a new class of nonsteroidal antiinflammatory drugs, the cyclooxygenase-2 (COX-2) specific inhibitors, marketed as having the same antiinflammatory efficacy as other nonsteroidal antiinflammatory drugs without their increased risk of gastrointestinal ulceration. Among the widest uses of nonsteroidal antiinflammatory drugs is in the treatment of acute soft tissue injuries. Although the benefits of celecoxib have been shown when used for rheumatoid arthritis and osteoarthritis, we are unaware of any studies concerning its effect on soft tissues. We used the surgically incised medial collateral ligament of male Sprague-Dawley rats as an experimental model for acute ligament injuries to investigate the effects of celecoxib on ligament healing. Fifty rats underwent surgical transection of the right medial collateral ligament. Postoperatively, half were given celecoxib for the first 6 days of recovery, the other half were not. The animals were sacrificed 14 days after the operation, and both the injured and uninjured medial collateral ligaments were mechanically tested to failure in tension. Celecoxib-treated/injured ligaments were found to have a 32% lower load to failure than untreated/injured ligaments. The results of this study do not support use of cyclooxygenase-2 specific inhibitors in the treatment of ligament injuries.

Animals↗
PubMedDate not supplied

The biomechanical effect of posterior cruciate ligament reconstruction on knee joint function. Kinematic response to simulated muscle loads.

BACKGROUND: The effectiveness of posterior cruciate ligament reconstruction in restoring normal kinematics under physiologic loading is unknown. HYPOTHESIS: Posterior cruciate ligament reconstruction does not restore normal knee kinematics under muscle loading. STUDY DESIGN: In vitro biomechanical study. METHODS: Kinematics of knees with an intact, resected, and reconstructed posterior cruciate ligament were measured by a robotic testing system under simulated muscle loads. Anteroposterior tibial translation and internal-external tibial rotation were measured at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 120 degrees of flexion under posterior drawer loading, quadriceps muscle loading, and combined quadriceps and hamstring muscle loading. RESULTS: Reconstruction reduced the additional posterior tibial translation caused by ligament deficiency at all flexion angles tested under posterior drawer loading. Ligament deficiency increased external rotation and posterior translation at angles higher than 60 degrees of flexion when simulated muscle loading was applied. Posterior cruciate ligament reconstruction reduced the posterior translation and external rotation observed in posterior cruciate ligament-deficient knees at higher flexion angles, but differences were not significant. CONCLUSION: Under physiologic loading conditions, posterior cruciate ligament reconstruction does not restore six degree of freedom knee kinematics. CLINICAL RELEVANCE: Abnormal knee kinematics may lead to development of long-term knee arthrosis.

Aged↗
PubMedDate not supplied

Elbow medial ulnar collateral ligament insufficiency alters posteromedial olecranon contact.

BACKGROUND: The effect of elbow medial ulnar collateral ligament injury on posteromedial compartment contact is unknown. HYPOTHESIS: Medial ulnar collateral ligament injury causes altered contact area and pressure in the posteromedial compartment of the elbow. STUDY DESIGN: Controlled laboratory study. METHODS: Seven elbow cadaveric specimens were tested in an apparatus that positioned the elbow at 30 degrees and 90 degrees of flexion. Partial and full tears were simulated by releasing the medial ulnar collateral ligament. Pressure-sensitive film was placed in the posteromedial compartment for each condition. Valgus torques of 1.25 and 2.0 N.m were applied for each ligament condition, and kinematic data were obtained at each flexion angle using a 3-dimensional digitizer. RESULTS: Both ligament condition and valgus load had significant effects on contact area and pressure (P<.05). For a given load and flexion angle, the contact area decreased and the pressure increased with increasing medial ulnar collateral ligament insufficiency. Within these trends, statistical significance was found at 30 degrees of elbow flexion for both area and pressure (P<.05); at 90 degrees of elbow flexion, increasing medial ulnar collateral ligament insufficiency did not significantly affect contact area or pressure (P>.05). DISCUSSION: Medial ulnar collateral ligament insufficiency alters contact area and pressure between the posteromedial trochlea and olecranon and helps explain the development of posteromedial osteophytes.

Athletic Injuries↗
PubMed2005

The effects of low-intensity ultrasound on medial collateral ligament healing in the rabbit model.

BACKGROUND: Ruptured medial collateral ligaments are capable of healing over time, but biomechanical and biochemical properties remain inferior to normal tissue. Low-intensity ultrasound may improve healing. HYPOTHESIS: Medial collateral ligaments treated with ultrasound will demonstrate superior healing. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-one late-adolescent male rabbits underwent bilateral ligament transection. One ligament from each rabbit received ultrasound treatment every other day for 6 total treatments. Contralateral ligaments received sham treatments. After 3 or 6 weeks, ligaments were evaluated biomechanically and assayed for collagen concentration and the relative proportions of types I and III collagen. RESULTS: Areas of sonicated specimens were significantly larger (10.6% +/- 4.90%) at 6 weeks. Ultimate load (39.5% +/- 17.0%), ultimate displacement (24.5% +/- 8.0%), and energy absorption (69.1% +/- 22.0%) were significantly higher for sonicated specimens at 6 weeks. No significant biomechanical differences were observed at 3 weeks. The relative proportion of type I collagen was significantly higher in sonicated ligaments at 3 weeks (8.61% +/- 4.0%) and 6 weeks (6.91% +/- 3.0%). No significant differences in collagen concentration were observed at either 3 or 6 weeks. CONCLUSION: Subtle improvement with ultrasound treatment may be apparent by 3 weeks after injury, suggested by increased proportion of type I collagen. Ultrasound appears to improve some structural properties and to modestly increase scar cross-sectional area and type I collagen present at 6 weeks after injury in this model. CLINICAL RELEVANCE: Ultrasound treatments after ligament injury may facilitate earlier return to activities and decrease risk of reinjury.

Animals↗
PubMed2005

The effect of analgesic agents on the healing rat medial collateral ligament.

BACKGROUND: Studies have suggested that some nonselective nonsteroidal anti-inflammatory drugs, including piroxicam, may improve ligament healing, whereas other nonsteroidal anti-inflammatory drugs, including ibuprofen and the cyclooxygenase-2 inhibitor celecoxib, may have no effect on the mechanical properties or may even deter the healing process. These results might reflect variations in cyclooxygenase enzyme selectivity by different drugs or, alternatively, may be related to their analgesic properties because it is generally accepted that early activity improves ligament healing. HYPOTHESIS: Nonselective nonsteroidal anti-inflammatory drugs improve ligament healing, whereas other analgesics provide lesser degrees of improvement, and cyclooxygenase-2 inhibitors are detrimental. STUDY DESIGN: Controlled laboratory study. METHODS: One hundred fifty-five Sprague-Dawley rats were divided into 7 treatment groups (piroxicam, naproxen, rofecoxib, butorphanol, 2 doses of acetaminophen, and control). The right medial collateral ligament of each rat was transected, and the drugs were administered postoperatively on days 1 to 6. On day 14, the rats were sacrificed, and mechanical testing was performed on the medial collateral ligament. RESULTS: The piroxicam group demonstrated significantly greater load to failure (27%) compared with the control. No significant differences were observed between other groups. CONCLUSIONS: Piroxicam improves ligament healing, but this effect cannot be attributed to all nonselective nonsteroidal anti-inflammatory drugs. Opiate analgesics, acetaminophen, and cyclooxygenase-2 inhibitors do not appear to categorically affect ligament healing. CLINICAL RELEVANCE: In the treatment of ligament injury, piroxicam may be a drug of choice.

Acetaminophen↗
PubMed2006

Biomechanical evaluation of 2 techniques for ulnar collateral ligament reconstruction of the elbow.

BACKGROUND: Elbow medial ulnar collateral ligament tears often result in pain and instability that may be career threatening in overhead-throwing athletes. Surgical reconstruction is frequently chosen to treat this injury. Ulnar collateral ligament reconstruction as described by Jobe is the most commonly used technique. Testing of this construct has not demonstrated that the biomechanical parameters of the native ligament are restored. A more recent construct, the docking technique, may more reliably reproduce these factors. HYPOTHESIS: Increasing the number of strands of palmaris longus tendon graft used in ulnar collateral ligament reconstruction and tensioning them using the docking technique result in a construct with improved biomechanical parameters as compared with the Jobe technique. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty-three fresh-frozen human cadaveric elbows were randomized into 3 subgroups: Jobe (11), docking (12), and native (10). The Jobe and docking groups underwent reconstruction using their described palmaris tendon graft constructs. The ulnar collateral ligament was left intact in the native group. Elbows were potted and tested using a servohydraulic materials testing machine to apply a valgus moment at 30 degrees of elbow flexion. Maximal moments to failure, stiffness, and strain at maximal moment and with a 3 N.m force applied were determined using a 2-camera motion analysis system to track reflective markers spanning the site. RESULTS: The docking (14.3 N.m) and native (18.8 N.m) subgroups resulted in higher maximal moment to failure than did the Jobe (8.9 N.m) subgroup (P < .001). There was no significant difference between native and docking groups (P > .05). Native ligaments were stiffer (301.4 N.m) than were Jobe (74.3 N.m) or docking (80.8 N.m; P < .001). Native ligaments demonstrated lower strain at maximal force (0.087 mm/mm) and 3 N.m forces (0.030 mm/mm) than did the Jobe (0.198/0.057 mm/mm) or docking (0.287/0.042 mm/mm) subgroups. There was no difference in stiffness or strain between the Jobe and docking subgroups (P > .05). CONCLUSION: Neither technique reproduced the biomechanical profile of the native ulnar collateral ligament; the findings of this study suggest that the docking construct may offer initial biomechanical advantage over the Jobe construct.

Analysis of Variance↗
PubMedDate not supplied

Articular and ligamentous contributions to the stability of the elbow joint.

This preliminary study of four elbow specimens investigates the relationship of articular geometry and ligamentous structures in providing stability to the elbow joint. A technique is presented that describes the constraining features of varus-valgus and distraction in extension and at 90 degree of elbow flexion. Valgus stability is equally divided among the medial collateral ligament, anterior capsule, and bony articulation in full extension; whereas, at 90 degrees of flexion the contribution of the anterior capsule is assumed by the medial collateral ligament which provides approximately 55% of the stabilizing contribution to valgus stress. Varus stress is noted to be resisted primarily by the anterior capsule (32%) and the joint articulation (55%) with only a small (14%) contribution from the radial collateral ligament. At 90 degrees of flexion, little change is noted in the contribution to the radial collateral ligament (9%), but the anterior capsule offers only 13%, with the remaining stability (75%) arising from the joint articulation. In extension, the soft tissue resistance to distraction is provided minimally by either the radial (5%) or the medial (5%) collateral ligaments, and thus primarily originates from the anterior capsule (85%). At 90 degrees of flexion, however, the capsule offers virtually no resistance to distraction (8%). The radial collateral ligament contributes 10% of the stability, while the medial collateral ligament accounts for 78% of the resistance to distraction in this position. Too few specimens have been studied to form any conclusions for direct clinical applications at this time. However, the technique provides a reliable tool with additional studies for different positions and loading conditions underway. These efforts should disclose useful information that might be applied to the management of chronic elbow instability, radial head or olecranon fracture, the design and implantation of elbow prostheses, or provide a rationale for other reconstructive procedures.

Biomechanical Phenomena↗
PubMedDate not supplied

Enzymatic adaptation in ligaments during immobilization.

Ligaments are a composite of fibroblasts and collagen in a proteoglycan matrix. Seventy-five percent of the organic solid is collagen and 23% is proteoglycan. Fibroblasts are responsible for the overall composition of the ligament, that is the synthesis and the degradation of macromolecular components. Like muscle and bone, ligaments are dynamic, undergoing hypertrophy with exercise and atrophy with immobilization. This paper reviews the structure and composition of ligaments and discusses the cellular events responsible for atrophy of ligaments with immobilization. As an experimental model, one knee of New Zealand White rabbits was immobilized with a pin. After 2, 4, and 8 weeks of immobility, the medial collateral ligaments were isolated and enzyme analysis was performed. Gross and microscopic changes were apparent after 2 weeks. As for enzyme changes, lactic dehydrogenase and malic dehydrogenase decreased in activity. The lysosomal hydrolases responsible for glycosaminoglycan degradation increased in activity, suggesting that enzymatic adaptations mediate the physical and chemical changes in the ligament. The cells switch from an anabolic synthetic state to a catabolic, degradative state during immobility. It would seem from the biochemical viewpoint that, whenever possible, cast-bracing and functional splints may be preferable to rigid plasters in many sports-related ligamentous injuries.

Animals↗
PubMedDate not supplied

Magnetic resonance imaging of the posterior cruciate ligament. Clinical use to improve diagnostic accuracy.

This study was undertaken to determine the accuracy of magnetic resonance image scanning in detecting posterior cruciate ligament injury, and to determine those clinical situations where it can add the most useful information. A retrospective study was conducted on 201 patients who underwent surgery after magnetic resonance scanning of their knees. Two additional patients who did not have surgery but had clinical findings grossly positive for posterior cruciate ligament injury were included in the analysis of magnetic resonance imaging accuracy. In all, there were 190 intact and 13 torn posterior cruciate ligaments. In a review of the clinical findings in the 11 patients with surgically documented tears, we found that all 11 had positive magnetic resonance scans. In 4 of the 11, magnetic resonance imaging provided especially useful information regarding the status of the ligament. For the 190 normal ligaments, there were no false-positive scans; for the 13 torn ligaments, there were no false-negative scans. Therefore, specificity and sensitivity estimates for this group were both 100%. Magnetic resonance imaging proved to be an accurate modality for evaluating the integrity of the posterior cruciate ligament. If used in the proper setting, it can provide useful information for diagnosing posterior cruciate ligament injuries.

Arthroscopy↗
PubMedDate not supplied

Preoperative evaluation of the ulnar collateral ligament by magnetic resonance imaging and computed tomography arthrography. Evaluation in 25 baseball players with surgical confirmation.

A prospective study was completed on 25 baseball players with medial side elbow pain. They were evaluated preoperatively with both computed tomography arthrogram and magnetic resonance imaging examinations of the elbow to assess the ulnar collateral ligament. At surgery, 16 of 25 patients had an abnormal ulnar collateral ligament and 9 patients had a normal ulnar collateral ligament. The computed tomography arthrogram detected abnormalities in 12 of the 14 patients with ulnar collateral ligament tearing (sensitivity, 86%). The magnetic resonance imaging scan indicated abnormalities in 8 of 14 patients (sensitivity, 57%). The specificity of the computed tomography arthrogram was 91% and the magnetic resonance imaging was 100%. A newly described "T-sign" was seen on the computed tomography arthrogram in the patients with an undersurface tear of the ulnar collateral ligament. This represented the dye leaking around the detachment of the ulnar collateral ligament from its bony insertion but remaining contained within the intact superficial layer of the ulnar collateral ligament and capsule. Both the computed tomography arthrogram and the magnetic resonance imaging scan were accurate in diagnosing a complete tear of the ulnar collateral ligament preoperatively in all cases. The main advantage of the computed tomography arthrogram was in evaluating the partial undersurface tear.

Adolescent↗
PubMedDate not supplied

The popliteofibular ligament. Rediscovery of a key element in posterolateral stability.

We have recently become aware of a strong direct attachment of the popliteal tendon to the fibula. To investigate the importance of this attachment, we examined 20 cadaveric knees. The popliteofibular ligament was identified in all 20 knees. The cross-sectional area of the popliteofibular ligament was 6.9 +/- 2.1 mm2, compared with 7.2 +/- 2.7 mm2 for the lateral collateral ligament. Biomechanical testing of these structures, simulating a purely varus stress on the knee, revealed that the lateral collateral ligament always failed first, followed by the popliteofibular ligament, and then the muscle belly of the popliteus. The mean maximal force to failure of the popliteofibular ligament approached 425 N (range, 204 to 778), compared with 750 N (range, 317 to 1203) for the lateral collateral ligament. Our results indicate that the popliteofibular ligament contributes to posterolateral stability.

Adult↗
PubMedDate not supplied

The strain behavior of the anterior cruciate ligament during bicycling. An in vivo study.

Stationary bicycling is commonly prescribed after anterior cruciate ligament injury or reconstruction; however, the strains on the ligament or ligament graft during stationary bicycling remain unknown. In this study we measured ligament strain on eight patients who were candidates for arthroscopic meniscectomy under local anesthesia. Six different riding conditions were evaluated: three power levels (75, 125, and 175 W), each of which was performed at two cadences (60 and 90 rpm). The peak ligament strain values ranged from 1.2% for the 175-W, 90-rpm, condition to 2.1% for the 125-W, 60-rpm, condition. No significant differences were found in peak strain values due to changes in power level or cadence. Thus, the strain values were pooled across the six riding conditions tested. The mean peak strain value was 1.7%, a value that is relatively low compared with other rehabilitation activities previously tested. These data suggest that knee rehabilitation programs can be designed to include this selection of power and cadence levels without significantly changing ligament strain values. Thus, stationary bicycling is a rehabilitation exercise that permits the patient to increase muscle activity by increasing the power level or decreasing the cadence without subjecting the ligament or ligament graft to higher strain values.

Adult↗
PubMedDate not supplied

Evaluation and treatment of posterior cruciate ligament injuries.

Improved basic science data on the anatomy and biomechanics of the human posterior cruciate ligament have provided the orthopaedic surgeon with new information on which to base treatment decisions. Injuries to the posterior cruciate ligament are reported to comprise approximately 3% of all knee ligament injuries in the general population and as high as 37% in an emergency department setting. While the diagnosis of a posterior cruciate ligament injury can often be made with a physical examination, ancillary studies such as radiographs and magnetic resonance images can be very helpful in detecting associated ligament and bony injuries. In general, most partial (grades I and II) posterior cruciate ligament injuries can be treated nonoperatively. However, surgical reconstruction is usually recommended for those posterior cruciate ligament injuries that occur in combination with other structures. In this review, current surgical techniques of posterior cruciate ligament reconstruction based on anatomic and biomechanical studies will be discussed.

Athletic Injuries↗
PubMed2001

Ligamentous restraints of the second tarsometatarsal joint: a biomechanical evaluation.

Ligamentous injury of the tarsometatarsal joint complex is an uncommon, but disabling condition that frequently occurs in elite athletes. There are few options for managing these injuries, in part because the relative mechanical contribution of the ligaments of the tarsometatarsal joint is unknown, complicating decisions regarding which ligaments need reconstruction. In the current study, strength and stiffness of the dorsal, plantar, and Lisfranc ligaments of 20 paired cadaver feet were measured and compared. The plantar and Lisfranc ligaments were significantly stiffer and stronger than the dorsal ligament, and the Lisfranc ligament was significantly stronger and stiffer than the plantar ligament.

Biomechanical Phenomena↗