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PubMed2004

Rotator cuff repair in patients fifty years of age and younger.

BACKGROUND: Currently, there is no information on the long-term results of rotator cuff repair in young patients. The purpose of the present study was to determine the results, the risk factors for an unsatisfactory outcome, and the rates of failure of this procedure in patients fifty years of age and younger. METHODS: Thirty-two patients (thirty-six shoulders) who were fifty years of age or younger underwent repair of a full-thickness rotator cuff tear between 1976 and 1987. Seven patients (seven shoulders) died after less than thirteen years of follow-up. The remaining twenty-nine shoulders, which had been followed for a minimum of thirteen years or until revision surgery, were included in the analysis. The most recent follow-up was performed in the clinic for five shoulders and by means of a questionnaire for twenty-four shoulders. RESULTS: There were three small, fifteen medium, six large, and five massive tears. Rotator cuff repair was associated with significant long-term pain relief (p = 0.0001). However, there was no significant long-term improvement in active abduction or external rotation. Postoperative pain, active abduction, and external rotation did not vary significantly according to gender, tear size, repair type, or whether a distal clavicular excision had been performed. There were eleven excellent, five satisfactory, and thirteen unsatisfactory results. Seven shoulders had additional surgery for the treatment of a recurrent tear (five), instability (one), or osteoarthritis (one). Three of the five repairs that were done for the treatment of a recurrent tear were performed ten years or more after the time of the index procedure. CONCLUSIONS: Rotator cuff repair in young patients is associated with long-term pain relief. However, this procedure is not associated with significant long-term improvement in motion, and a large proportion of patients have an unsatisfactory long-term result. The results of rotator cuff repair in young patients appear to be less favorable than those in a mixed-age population.

Adult↗
PubMed2005

Determinants of patient satisfaction with outcome after rotator cuff surgery.

BACKGROUND: The outcome after rotator cuff surgery has been reported frequently with use of condition-specific measures, but patient satisfaction has not been well studied. The purpose of this study was to identify the determinants of patient satisfaction with the outcome after rotator cuff surgery. METHODS: A cohort of 311 patients undergoing rotator cuff surgery was studied prospectively. Two hundred and fifty-four patients had subjective follow-up for a minimum of one year, and fifty-seven patients had subjective and objective follow-up for a minimum of one year. Diagnoses included tendinitis or impingement (eighty patients), a partial-thickness rotator cuff tear (fifty-five patients), and a full-thickness rotator cuff tear (176 patients). The dependent variable was patient satisfaction with the outcome, graded ordinally on a scale of 1 to 10. Independent variables included demographic, surgical, objective follow-up, and subjective follow-up parameters. Univariate and multivariate analyses were performed to identify the determinants of satisfaction. RESULTS: Univariate analysis of demographic variables demonstrated no significant differences (p > 0.05) with respect to patient satisfaction. Analysis of the surgical variables showed significantly decreased satisfaction (p < 0.05) for patients who had debridement for a massive, irreparable cuff tear; those who had subscapularis tears; and those with larger supraspinatus and infraspinatus tears. Analysis of the objective variables at follow-up demonstrated significantly decreased satisfaction (p < 0.05) for patients with diminished and weakened forward elevation, impingement signs, and acromioclavicular joint pain and tenderness. Univariate analysis of subjective variables at follow-up showed significantly decreased satisfaction (p < 0.001) for patients with pain, functional difficulty, and work disability. Multivariate analysis demonstrated significantly decreased satisfaction associated with pain (p < 0.001) and dysfunction (p < 0.05). A significant relationship (p < 0.05) was detected between satisfaction and a willingness to recommend the surgery to another. A significant relationship (p < 0.05) was also found between satisfaction and the American Shoulder and Elbow Surgeons score. CONCLUSIONS: Subjective variables of symptoms and function have the most robust associations with patient satisfaction following rotator cuff surgery. Thus, in assessing the outcome of rotator cuff surgery from the perspective of patient satisfaction with outcome, we emphasize the importance of patient-derived subjective assessment of symptoms and function.

Arthralgia↗
PubMed2005

Accuracy of office-based ultrasonography of the shoulder for the diagnosis of rotator cuff tears.

BACKGROUND: This prospective multi-institutional study was designed to define the accuracy of ultrasonography, when performed in an orthopaedic surgeon's office, for the diagnosis of rotator cuff tears. METHODS: An anatomic diagnosis and a treatment plan were made on the basis of office-based shoulder ultrasonography, physical examination, and radiographs for ninety-eight patients (ninety-nine shoulders) with a clinical diagnosis of a rotator-cuff-related problem. The results of the ultrasonographic studies were then compared with the results of magnetic resonance imaging and the operative findings. RESULTS: Office-based ultrasonography led to the correct diagnosis for thirty-seven (88%) of forty-two shoulders with a full-thickness rotator cuff tear or both full and partial-thickness tears, twenty-six (70%) of thirty-seven shoulders with a partial-thickness rotator cuff tear only, and sixteen (80%) of twenty shoulders with normal tendons. In no case was the surgical approach (open or arthroscopic) that had been planned on the basis of the ultrasonography altered by the operative findings, but the operative finding of a full-thickness tear resulted in an arthroscopic cuff repair in four shoulders. Magnetic resonance imaging led to the correct diagnosis for forty (95%) of forty-two shoulders with a full-thickness rotator cuff tear or both full and partial-thickness rotator cuff tears, twenty-seven (73%) of thirty-seven shoulders with only a partial-thickness tear, and fifteen (75%) of twenty shoulders with normal tendons. There were no significant differences between magnetic resonance imaging and ultrasonography with regard to the correct identification of a full-thickness tear or its size. The sensitivity of ultrasonography for detecting tear size in the anterior-posterior dimension was 86% (95% confidence interval, 71% to 95%), and that of magnetic resonance imaging was 93% (95% confidence interval, 81% to 99%) (p = 0.26). The sensitivity of ultrasonography for detecting tear size in the medial-lateral dimension was 83% (95% confidence interval, 69% to 93%), and that of magnetic resonance imaging was 88% (95% confidence interval, 74% to 96%) (p = 0.41). CONCLUSIONS: A well-trained office staff and an experienced orthopaedic surgeon can effectively utilize ultrasonography, in conjunction with clinical examination and a review of shoulder radiographs, to accurately diagnose the extent of rotator cuff tears in patients suspected of having such tears. Errors in diagnosis made on the basis of ultrasonography most often consist of an inability to distinguish between partial and full-thickness tears that are approximately 1 cm in size. In this study, such errors did not significantly affect the planned surgical approach.

Arthroscopy↗
PubMed2006

Porcine small intestine submucosa augmentation of surgical repair of chronic two-tendon rotator cuff tears. A randomized, controlled trial.

BACKGROUND: Evidence to justify the use of porcine small intestine submucosa to augment repairs of large and massive rotator cuff tears is based on favorable results found in studies of Achilles tendon and infraspinatus tendon repairs in canines. The purpose of this study was to determine the effectiveness of a small intestine submucosal patch to augment the repair of chronic two-tendon rotator cuff tears in humans. METHODS: Thirty shoulders with a chronic two-tendon rotator cuff tear that was completely repairable with open surgery were randomized to be treated with either augmentation with porcine small intestine mucosa or no augmentation. All patients completed a PENN shoulder-score questionnaire preoperatively and at the time of the latest follow-up (at an average of fourteen months). Magnetic resonance imaging showed that nine shoulders had a large tear and twenty-one had a massive tear. All patients underwent a magnetic resonance imaging scan with intra-articular gadolinium one year after the repair to assess the status of the rotator cuff. RESULTS: The rotator cuff healed in four of the fifteen shoulders in the augmentation group compared with nine of the fifteen in the control group (p = 0.11). The median postoperative PENN total score was 83 points in the augmentation group compared with 91 points in the control group (p = 0.07). Healing of the defects in both groups demonstrated a strong correlation with the patients' clinical scores. The median postoperative PENN total score was 96 points in the group with a healed repair and 81 points in the group with a failed repair (p = 0.007). The percentage change between the preoperative and postoperative patient satisfaction scores was 400% in the group with a healed repair, and 50% in the group with a failed repair (p = 0.04). CONCLUSIONS: Augmentation of the surgical repair of large and massive chronic rotator cuff tears with porcine small intestine submucosa did not improve the rate of tendon-healing or the clinical outcome scores. On the basis of these data, we do not recommend using porcine small intestine submucosa to augment repairs of massive chronic rotator cuff tears done with the surgical and postoperative procedures described in this study.

Adult↗
PubMed1997

MR imaging of rotator cuff tears in individuals with paraplegia.

OBJECTIVE: The purpose of this study was to use MR imaging to evaluate the prevalence and extent of rotator cuff tears in paraplegic patients, who are at increased risk for impingement caused by overuse. MATERIALS AND METHODS: Sixty-four MR examinations of the shoulder were evaluated for partial or full-thickness rotator cuff tears and for single or multiple rotator cuff tendon tears. Thirty-seven MR studies were from paraplegic subjects (26 symptomatic, 11 asymptomatic), and 27 MR studies were from able-bodied subjects (17 symptomatic, 10 asymptomatic). RESULTS: Among subjects who were symptomatic and paraplegic, 73% of shoulders imaged showed evidence of rotator cuff tear on MR images compared with 59% of shoulders in able-bodied symptomatic subjects. Of all subjects with paraplegia, 57% of shoulders imaged showed rotator cuff tears. Among all paraplegic subjects, prevalence and severity of tears correlated positively with age and duration of spinal cord injury. Tears that involved the posterior portion of the rotator cuff were revealed on MR images in 74% of the paraplegic subjects compared with 50% of the able-bodied subjects. CONCLUSION: MR imaging revealed a high percentage and degree of severity of rotator cuff tears in individuals with paraplegia and thus proved useful in evaluating shoulders in these patients.

Adult↗
PubMed2000

Ultrasonography of the rotator cuff. A comparison of ultrasonographic and arthroscopic findings in one hundred consecutive cases.

BACKGROUND: There has been limited acceptance of shoulder ultrasonography by orthopaedic surgeons in the United States. The purpose of this retrospective study was to determine the diagnostic performance of high-resolution ultrasonography compared with arthroscopic examination for the detection and characterization of rotator cuff tears. METHODS: One hundred consecutive shoulders in ninety-eight patients with shoulder pain who had undergone preoperative ultrasonography and subsequent arthroscopy were identified. The arthroscopic diagnosis was a full-thickness rotator cuff tear in sixty-five shoulders, a partial-thickness tear in fifteen, rotator cuff tendinitis in twelve, frozen shoulder in four, arthrosis of the acromioclavicular joint in two, and a superior labral tear and calcific bursitis in one shoulder each. All ultrasonographic reports were reviewed for the presence or absence of a rotator cuff tear and a biceps tendon rupture or dislocation. All arthroscopic examinations were performed according to a standardized operative procedure. The size and extent of the tear and the status of the biceps tendon were recorded for all shoulders. The findings on ultrasonography and arthroscopy then were compared for each parameter. RESULTS: Ultrasonography correctly identified all sixty-five full-thickness rotator cuff tears (a sensitivity of 100 percent). There were seventeen true-negative and three false-positive ultrasonograms (a specificity of 85 percent). The overall accuracy was 96 percent. The size of the tear on transverse measurement was correctly predicted in 86 percent of the shoulders with a full-thickness tear. Ultrasonography detected a tear in ten of fifteen shoulders with a partial-thickness tear that was diagnosed on arthroscopy. Five of six dislocations and seven of eleven ruptures of the biceps tendon were identified correctly. CONCLUSIONS: Ultrasonography was highly accurate for detecting full-thickness rotator cuff tears, characterizing their extent, and visualizing dislocations of the biceps tendon. It was less sensitive for detecting partial-thickness rotator cuff tears and ruptures of the biceps tendon.

Arthroscopy↗
PubMed2001

Mini-open rotator cuff repair: an updated perspective.

The mini-open rotator cuff or arthroscopically assisted surgical procedure for repair of the rotator cuff has become a popular procedure with proven clinical results. The development of this procedure has followed a natural progression toward more minimally invasive means to accomplish rotator cuff repair. For many, it represents a middle ground between the traditional formal open repair and the newer complete arthroscopic rotator cuff repairs. As arthroscopic rotator cuff repair becomes more refined and accepted, the mini-open repair can also represent an excellent transitional technique to someday accomplish the more technically difficult complete arthroscopic repair. Whether used as the definitive rotator cuff repair procedure or as a transitional procedure toward arthroscopic repair, the mini-open repair can be thought of as two different types of procedures, an arthroscopically assisted open repair in which the actual repair is performed in a primarily open fashion, or as a mini-open assisted arthroscopic repair in which most of the repair is performed arthroscopically and an open exposure provided just for bone-tendon fixation. With either strategy, the mini-open repair represents an excellent technique for treating full-thickness rotator cuff tears and offers many of the advantages of either formal or complete arthroscopic repair while minimizing many of the disadvantages.

Arthroscopy↗
PubMed1992

[Ultrasound assessment of reconstructed rotator cuffs].

The evaluation of recurrent shoulder symptoms in patients who have had rotator cuff repair is a diagnostic challenge. Pain and limitation of motion may be caused by a recurrence of the rotator cuff tear. Arthrography is not considered to be helpful in postoperative cases, since it is false-positive in most of them. Pre-operative ultrasonography of the shoulder is regarded as a highly accurate diagnostic tool for rotator cuff tears. The diagnostic criteria used are: the continuity of the rotator cuff, its contour, its thickness and its echogenicity. Our study was aimed at determining which ultrasonographic criteria were significant for a retear. In addition, the "normal" postoperative sonographic appearance of the rotator cuff was established. Of 133 patients with a full thickness rotator cuff tear, 110 were evaluated 4-48 months (mean in 21 months) after surgery. A total of 85 cuffs were reconstructed, in 46 cases by direct suture, in 33 cases by suture to the major tubercle and in 6 cases by tendon transfer (Cofield technique). In 25 cases cuffs the could not be reconstructed. Subacromial decompression was performed routinely. The patients were evaluated clinically by range of movement, force and isometric and impingement tests. The subjective outcome was assessed by the algo-functional index of Patte. Ultrasonography was performed using a 7.5-MHz linear scanner. Each sonographic criterion was referred to the clinical and subjective findings. Ultrasonographic evaluation of the rotator cuffs that could not be reconstructed revealed non-visualization of the tendons. In 13 of the 85 patients in whom reconstruction of the cuff was possible a normal sonographic pattern was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

[The results of arthroscopic repair of full-thickness tears of the rotator cuff].

OBJECTIVES: This study was designed to evaluate the functional results of arthroscopic repair of full-thickness tears of the rotator cuff and to investigate the degree of fatty degeneration of the rotator cuff muscles and recurrent ruptures by magnetic resonance imaging (MRI). METHODS: Twenty-two patients (9 males, 13 females; mean age 56 years; range 38 to 71 years) underwent arthroscopic repair of full-thickness tears of the rotator cuff following conservative treatment for a mean of 15 months (range 45 days to 120 months). Involvement was in the right shoulder in 17 patients, being on the dominant side in 77%. The range of motion was measured with a goniometer, and muscle strength by manual examination. Clinical and functional evaluations were made by physical examination and according to the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) and the UCLA scale. Fatty degeneration of the rotator cuff muscles and recurrence were analyzed by MRI. The mean follow-up was 24 months (range 12 to 36 months). RESULTS: The mean active forward flexion and external rotation increased from 105 degrees to 160 degrees (p<0.05) and from 41 degrees to 44 degrees (p>0.05), respectively. The strength of the supraspinatus and infraspinatus muscles significantly increased (p<0.05). The mean ASES and UCLA scores significantly increased from 25.4 to 86.7 and from 10.6 to 25.6, respectively (p<0.05). The mean healing time was three months (range 1 to 12 months). Twenty patients (90.9%) were satisfied with the result of the treatment. On MRI scans, recurrent ruptures were detected in seven patients (31.8%); the extent of fatty degeneration of the rotator cuff muscles did not differ pre- and postoperatively (p>0.05). CONCLUSION: Arthroscopic repair of full-thickness tears of the rotator cuff yields high clinical and functional success rates.

Adult↗
PubMed2006

Conservative treatment of rotator cuff injuries.

Across all ages and activity levels, rotator cuff injuries are one of the most common causes of shoulder pain. The anatomy and biomechanics of the shoulder guide the history and physical exam toward the appropriate treatment of rotator cuff injuries. Rotator cuff tears are rare under the age of 40 unless accompanied by acute trauma. Throwing athletes are prone to rotator cuff injury from various causes of impingement (subacromial, internal, or secondary) and flexibility deficits, strength deficits, or both along the kinetic chain. Most rotator cuff injuries may be treated conservatively by using regimens of nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroid injections, and functional rehabilitation therapy. Injury prevention programs are essential for the long-term care of patients with rotator cuff disease, for primary prevention, and for prevention of recurrent injuries, unless a traumatically torn rotator cuff is present. Surgical management is reserved for refractory cases that have exhausted conservative measures.

Adrenal Cortex Hormones↗
PubMed1994

[Simultaneous lesions of the rotator cuff and the brachial plexus].

INTRODUCTION: A simultaneous lesion of the rotator cuff can be associated with a lesion of the brachial plexus and should be considered when treating the lesion of the brachial plexus. The author assesses the value of isolated rotator cuff repair. MATERIAL AND METHODS: 22 patients presented a rotator cuff tear associated with axillary nerve palsy. All of these lesions were traumatic in origin and in 20 cases were secondary to anterior shoulder dislocation. The clinical presentation was that of a "floating shoulder" with a reduction of the scapulo-humeral angle when attempting to elevate the arm. This differed from a pseudo-paralytic shoulder due to massive rotator cuff tear in which the scapulo-humeral angle remains open and from isolated paralysis of the deltoid in which active elevation of the arm is possible due to the intact rotator cuff. All of the patients had surgical repair of the rotator tear without any procedures on the deltoid. The delay from accident to surgery was on the average 65 days (range: 7 days to 9.5 months). 22 cases were followed for an average of 25 months (range: 12 to 45 months). RESULTS: 20 of the 22 cases recovered an active elevation of the arm of 120 degrees despite persistent deltoid paralysis in four cases. DISCUSSION: Our results show that the rotator cuff, especially the supraspinatus constitutes the main "motor" for shoulder elevation.

Adult↗
PubMed1993

Shoulder strength with rotator cuff tears. Pre- and postoperative analysis.

Twenty-five patients with rotator cuff tears had bilateral isokinetic shoulder strength evaluations after a pain-relieving subacromial lidocaine injection. Shoulder strength testing was repeated at six months and again at 12 months after rotator cuff surgery. Strength was recorded as a ratio of peak torques comparing the operative with the nonoperative shoulder. Preoperative strength averaged 37%, 36%, and 33% for abduction, external rotation, and forward flexion. Six-month postoperative strength increased to 68%, 76%, and 66% for abduction, external rotation, and forward flexion, respectively. Twelve-month postoperative strength increased to 104%, 142%, and 97% for abduction, external rotation, and forward flexion. Shoulders with rotator cuff tears demonstrate major objective signs of weakness. Shoulder pain obscures objective evaluation of weakness. Preoperative strength can be accurately measured after subacromial lidocaine injection. Shoulder strength is significantly improved by rotator cuff repair.

Biomechanical Phenomena↗
PubMed2004

Interventions for tears of the rotator cuff in adults.

BACKGROUND: Tears of the rotator cuff tendons, which surround the joints of the shoulder, are one of the most common causes of pain and disability in the upper extremity. OBJECTIVES: To review the efficacy and safety of common interventions for tears of the rotator cuff in adults. SEARCH STRATEGY: We searched the Cochrane Musculoskeletal Injuries Group specialised trail register (July 2002), the Cochrane Controlled Trials Register (The Cochrane Library issue 2, 2002), MEDLINE (1966 to December 2001), EMBASE (1974 to December 2001), Biological Abstracts (1980 to December 2001), LILACS (1982 to December 2001), CINAHL (November 1982 to December 2001), Science Citation Index and reference lists of articles. We also contacted authors and handsearched conference proceedings focusing on shoulder conditions. SELECTION CRITERIA: Randomised or quasi-randomised clinical trials involving tears of the rotator cuff were the focus of this review. All trials involving conservative interventions or surgery were included (non-steroidal anti-inflammatory drugs, intra-articular or subacromial glucocorticosteroid injection, oral glucocorticosteroid treatment, physiotherapy, and open or arthroscopic surgery). DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed suitability for inclusion, methodological quality and extracted data. Dichotomous data were presented as relative risks (RR) and 95% confidence intervals (CI), using the fixed effects model. MAIN RESULTS: Eight trials involving 455 people were included and 393 patients analysed. Trials were grouped in eight categories of conservative or surgical treatment. The median quality score of all trials combined was 16 out of a possible 24 points, with a range of 12-18. In general, included trials differed on diagnostic criteria for rotator cuff tear, there was no uniformity in reported outcome measures, and data which could be summarised were rarely reported. Only results from two studies comparing open repair to arthroscopic debridement could be pooled. There is weak evidence for the superiority of open repair of rotator cuff tears compared with arthroscopic debridement. REVIEWER'S CONCLUSIONS: There is little evidence to support or refute the efficacy of common interventions for tears of rotator cuff in adults. As well as the need for further well designed clinical trials, uniform methods of defining interventions for rotator cuff tears and validated outcome measures are also essential.

Adult↗
PubMed2007

Markedly different effects of hyaluronic acid and chondroitin sulfate-A on the differentiation of human articular chondrocytes in micromass and 3-D honeycomb rotation cultures.

A source of morphologically and functionally available human cartilagenous tissue for implantation is required in the field of tissue engineering. To achieve this goal, we evaluated the effects of hyaluronic acid (HA-810 and 1680 kDa), and chondroitin sulfate (CS-A 16 and C-34 kDa) on human articular chondrocytes (HC) in micromass and rotation culture conditions. Cell proliferation was increased by CS-A 16 kDa under micromass and rotation cultures, while cell differentiation was increased under rotation but not micromass conditions. Proliferation and differentiation due to CS-C 34 kDa were very similar to the control under both culture conditions. With HA, cell proliferation was increased depending on the molecular weight under micromass and rotation conditions. In contrast, chondrocyte differentiation was enhanced under rotation conditions, but decreased under micromass conditions depending on the molecular weight of HA. In both culture conditions, aggrecan gene was continuously expressed. However, the collagen type II gene was more weakly expressed in rotation than the micromass culture conditions. Thus, the chemical structures of polysaccharides, and the culture condition, rotation or micromass, caused differences in chondrogenesis.

Aggrecans↗
PubMed2003

Automatic in-plane rotation for doubly-oblique cardiac imaging.

PURPOSE: To develop and test a method for automatically calculating the in-plane rotation for doubly-oblique slice geometry in order to minimize wrap artifacts for a given FOV. MATERIALS AND METHODS: The equations for in-plane rotation were formulated for doubly-oblique imaging of a cylindrical body with elliptical cross-section. Based on this formulation, automatic in-plane rotation was implemented and tested on a commercial scanner using nominal values for ellipticity of the body. RESULTS: Short axis, doubly oblique, cardiac imaging were acquired with and without in-plane rotation. The desired in-plane rotation proved to be relatively insensitive to the ellipticity of the body, permitting an automatic solution based on a nominal value. CONCLUSION: In-plane rotation is desirable for doubly oblique imaging (e.g., cardiac applications), particularly for reduced-FOV accelerated imaging such as SENSE. The proposed method, which provides an approximate solution for automatic, in-plane rotation for doubly-oblique imaging, was demonstrated.

Artifacts↗
PubMed2002

Application of image registration to measurement of intervertebral rotation in the lumbar spine.

In this study, the precision and accuracy of a new method for measuring axial rotations of the lumbar vertebrae, which are thought to be increased in patients with degenerative spinal instability, were estimated. A standard image registration algorithm involving a user-selected center of rotation was adapted for this purpose. Accuracy was tested on a phantom containing a rotating lumbar vertebra. Calculated rotations were compared to the known values. Images were also obtained in subjects, using a tilting table that provided rotation between thorax and hips. For these measurements precision was estimated by varying the center of rotation. In the phantom the method had an accuracy of 0.2 degrees. In the human subject measurements the precision was 0.60-1.5 degrees. The method measured rotations of lumbar vertebrae with sufficient accuracy and precision to detect clinically significant differences in patients with back pain.

Biomechanical Phenomena↗
PubMed1994

Relationship between asymmetries in striatal dopamine release and the direction of amphetamine-induced rotation during the first week following a unilateral 6-OHDA lesion of the substantia nigra.

In animals with a large unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal dopamine (DA) system the traditional "rotational behavior model" states that amphetamine will induce circling behavior towards the denervated striatum (ipsiversive), that is, away from the side where there is greater amphetamine-stimulated DA release and greater DA receptor stimulation. It is puzzling, therefore, why amphetamine induces contraversive rotation in rats tested 4 days after a unilateral 6-OHDA lesion, despite a 90-95% loss of the dopaminergic input to the striatum by this time. Rats reverse their direction of amphetamine-induced rotation by 8 days post-lesion and turn in the ipsiversive direction thereafter. To try and resolve this paradox, bilateral striatal microdialysis was used to estimate the effects of amphetamine on DA neurotransmission on Day 4 and Day 8 following a large unilateral 6-OHDA lesion of the substantia nigra. On Day 4 post-lesion, amphetamine produced a moderate (around 50% of control) increase in the extracellular concentration of DA in the denervated striatum. This amphetamine-releasable pool of DA was exhausted by a single amphetamine-challenge, because a second injection of amphetamine given 3 h after the first did not produce a comparable increase in DA. It is suggested that on Day 4 post-lesion the amount of DA released by amphetamine in the denervated striatum is sufficient to produce greater DA receptor stimulation on that side, because of DA receptor supersensitivity, and this leads to contraversive rotation. On Day 8 post-lesion, amphetamine induced DA release in the intact striatum but had no effect on extracellular DA in the denervated striatum (DA was nondetectable). On Day 8, therefore, DA receptor stimulation would be greatest in the intact striatum, leading to ipsiversive rotation. In conclusion, it is suggested that the seemingly paradoxical reversal in the direction of amphetamine-induced rotation that occurs over the first week following a unilateral 6-OHDA lesion is consistent with the traditional rotational model, and is due to time-dependent changes in the ability of amphetamine to release DA in the denervated striatum.

Amphetamine↗
PubMed2000

Muscle force arises by actin filament rotation and torque in the Z-filaments.

Actin filament rotation in skeletal muscle is studied by a mechanical model that simulates structure and tension. The four anchoring Z-filaments are twisted around and change the structure of the Z-lattice. The "small square" without twist represents the resting stage of muscle. Torque causes contraction by clockwise rotation (as seen from the Z-band), drilling into the A-band and transition of the "small square" to "basket weave" by increasing the twist and decreasing the torque. Release decreases the torque ("force-depression") by passive clockwise rotation. Stretch causes increased torque ("stretch activation") by passive counterclockwise rotation. Torque arises during Ca(2+)-activation by a conformational change in the highly charged coiled-coils: The four alpha-actinin Z-filaments generate strong torque for the isometric tension. Quick release experiments show that less than one rotation reduces this torque to zero. The 5-12 rotations necessary for isotonic shortening result from torque-generation in the two long tropomyosin coiled-coils. Myosin controls the velocity of active and passive rotations.

Actinin↗