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PubMed2006

Arthroscopic fixation of bursal-sided rotator cuff tears.

Subacromial decompression and debridement of partial-thickness bursal-sided rotator cuff tears are often reported with a high rate of unsatisfactory outcomes. We describe an arthroscopic procedure to repair partial-thickness bursal-sided rotator cuff tears without converting to a full-thickness tear in patients with a normal articular-sided rotator cuff and an A0B2 or A0B3 pattern of tear (minimum thickness of 25% to 75%). The articular side of the rotator cuff experiences greater tension than the bursal side of the cuff. As such, by leaving the articular footprint intact, we accomplish 3 goals: the intact articular fibers act as an internal splint to protect the bursal-sided repair, a wide and anatomic footprint is recreated, and we are able to minimize any length-tension mismatch because the tissue is not excessively lateralized with repair. After bursectomy and acromioplasty, the frayed edges of the bursal flap are gently debrided and the tuberosity is excoriated to bleeding bone. One or two bioabsorbable anchors are placed, and both sutures are placed through the full thickness of the rotator cuff (one anterior and one posterior) by use of a percutaneous suture lasso in this manner: (1) the lasso is passed through the full thickness of the cuff, and the nitinol wire is shuttled out of a single cannula along with the more medial of the suture limbs; (2) the nitinol wire is then pulled back out of the percutaneous portal along with the suture limb, with the suture being passed through the full thickness of the cuff; and (3) the procedure is repeated for the posterior limb of the suture after a lasso is again passed through the full thickness of the rotator cuff in a more posterior position. This subset of patients is treated with an aggressive rehabilitation protocol because the intact articular rotator cuff fibers act as an internal splint to protect the bursal repair.

Absorbable Implants↗
PubMed2007

Anterior and posterior instability of the long head of the biceps tendon in rotator cuff tears: a new classification based on arthroscopic observations.

PURPOSE: The purpose of this study was to evaluate arthroscopically the frequency and type of instability of the long head of the biceps (LHB) tendon in patients undergoing rotator cuff repair. METHODS: In 200 consecutive patients undergoing arthroscopic rotator cuff repair, LHB instability was assessed statically and dynamically in the anteroposterior direction. In addition, macroscopic lesions of the LHB, as well as lesions of the adjacent rotator cuff tendons, were documented. RESULTS: LHB instability (subluxation or dislocation) was found in 45% of patients, with isolated anterior instability in 16%, isolated posterior instability in 19%, and combined anteroposterior instability in 10%. Whereas LHB subluxations were observed in both directions, dislocations were only seen in anterior LHB instability. Anterior instability was more associated with a subscapularis lesion, whereas posterior instability was more associated with a supraspinatus tear. Lesions of the LHB tendon were strongly associated with LHB instability and the size of the rotator cuff tear. CONCLUSIONS: In 200 patients with rotator cuff tears LHB instability could be observed arthroscopically in 45%, with 16% being anterior, 19% being posterior, and 10% being anteroposterior. LHB instability was associated with LHB lesions, with 15% of the LHB tendons showing a normal appearance when unstable versus 70% when stable. Preoperative O'Brien and Speed tests did not correlate with intraoperative observed LHB pathology. The size of the rotator cuff tear could be correlated with the grade of LHB lesion, becoming more significant with augmenting tear size. On the basis of these observations, we created a new arthroscopic classification of LHB instability with respect to the direction and extent of LHB instability, lesions of the LHB, and status of the adjacent rotator cuff tendons. LEVEL OF EVIDENCE: Level IV, diagnostic study with poor reference standard.

Activities of Daily Living↗
PubMed2004

Asymmetric responses to rotation at high frequencies in central vestibular neurons of the alert cat.

The horizontal rotatory vestibulo-ocular reflex (VOR) stabilizes gaze by moving the eyes at an angular velocity proportional to head velocity, and can accomplish this for a broad range of frequencies and amplitudes of head motion. Rotation at 5 Hz and above may be processed differently than lower frequencies by the VOR network. We recorded discharges and calculated spike densities of a small sample of vestibular neurons in alert cats during low-velocity rotation at frequencies up to 8 Hz. At high frequencies, we found both vestibular-only (V-only) and eye-movement-sensitive (EM) cells that generated asymmetric output signals. Asymmetry was primarily of the cutoff type, i.e., changes in spike density were smallest for rotation in the inhibitory direction. Most cells were identified as secondary neurons. The mean spike density was 23 sp/s, which was lower than previously reported in vestibular neurons of monkeys. A few neurons had very high sensitivities, associated with phase-locking, to rotation at high frequencies. In general, vestibular neurons carried a high-pass-filtered version of rotational signals. When synaptic inputs from the vestibular commissure were quantified, we found that the immediate change in probability of firing due to commissural vestibular input was inversely correlated with the degree of high-pass filtering. At high frequencies, increased asymmetry and phase-locking occurred in some neurons. A small number of neurons responded with increased probability of firing to both directions of rotation. Together, these observations suggest that high frequencies of rotation may be encoded differently than low frequencies by central vestibular neurons in alert animals.

Action Potentials↗
PubMed2006

Podokinetic after-rotation in Parkinson disease.

Walking on a rotating platform for 15 min causes healthy subjects to involuntarily turn when walking without vision. This adaptive response, called podokinetic after-rotation (PKAR), uses the same kinematic patterns as voluntary turning suggesting that PKAR and voluntary turning share common mechanisms. The purpose of this study is to determine whether people with Parkinson disease (PD), a condition that produces substantial disability from turning difficulties, can adapt to the rotating platform. Initial testing of people with PD revealed that most were unable to step on the rotating platform for 15 continuous minutes. We thus tested a less intense version of the paradigm in eight healthy people. On one day, subjects walked on the platform for 15 continuous minutes; on another day, they walked on the platform for three 5-minute intervals separated by 5-minute rests. After both sessions, subjects rested for 5 min then walked in place for 30 min without vision, while we recorded rotational velocity of PKAR. Continuous and interval protocols effectively elicited robust PKAR. We then tested eight subjects with PD and matched controls using the 5-minute interval protocol and recorded PKAR responses for 10 min. There were no significant differences between the PD and control groups. We conclude that PD subjects can adapt to the rotating platform and develop PKAR from interval training. Future studies are needed to determine whether the rotating platform may act as a rehabilitative tool to reinforce motor patterns for turning and alleviate turning difficulties in people with PD.

Adaptation, Physiological↗
PubMed2006

Nitric oxide affects preimplantation embryonic development in a rotating wall vessel bioreactor simulating microgravity.

Microgravity was simulated with a rotating wall vessel bioreactor (RWVB) in order to study its effect on pre-implantation embryonic development in mice. Three experimental groups were used: stationary control, rotational control and clinostat rotation. Three experiments were performed as follows. The first experiment showed that compared with the other two (control) groups, embryonic development was significantly retarded after 72 h in the clinostat rotation group. The second experiment showed that more nitric oxide (NO) was produced in the culture medium in the clinostat rotation group after 72 h (P<0.05), and the nitric oxide synthase (NOS) activity in this group was significantly higher than in the controls (P<0.01). In the third experiment, we studied apoptosis in the pre-implantation mouse embryos after 72 h in culture and found that Annexin-V staining was negative in the normal (stationary and rotational control) embryos, but the developmentally retarded (clinostat rotation) embryos showed a strong green fluorescence. These results indicate that microgravity induced developmental retardation and cell apoptosis in the mouse embryos. We presume that these effects are related to the higher concentration of NO in the embryos under microgravity, which have cause cytotoxic consequences.

Animals↗
PubMed2005

Changes in the long head of the biceps tendon in rotator cuff tear shoulders.

BACKGROUND: Morphologic changes in the long head of the biceps tendon have been described in association with rotator cuff disease, yet mechanical significance of these changes remains unclear. METHODS: An experiment was designed to test the hypotheses that the cross-sectional area and material properties of the long head of the biceps tendon are different in shoulders with full thickness rotator cuff tears and shoulders with intact rotator cuff tendons. Seven pairs of cadaver shoulders were tested. In each pair one shoulder had a full thickness rotator cuff tear and the other did not. Thus, a matched design was used. Cross sectional areas were measured. Tendon material properties were measured using an optical strain system. FINDINGS: We were unable to detect a statistically significant difference in the long head of the biceps area or material properties between tendons in shoulders with and without rotator cuff tears. An a priori power analysis was conducted indicating the sample size was sufficient to detect a difference of 70 MPa in the elastic modulus measurement. INTERPRETATION: Our data indicate there is no difference in the long head of the biceps cross sectional area or material properties. Therefore, the long head of the biceps tendon appears to retain its material properties in the presence of a rotator cuff tear. The clinical significance of this finding is that the long head of the biceps can be retained in the presence of a rotator cuff tear without concern that mechanical properties have substantially deteriorated.

Anatomy, Cross-Sectional↗
PubMed2005

How much can carpus rotate axially? An in vivo study.

BACKGROUND: Supination and pronation movements occur primarily at the forearm though are possible at the wrist joint too. The axial rotation of the wrist also called the radiometacarpal rotation has been quantified but for its passive range which may never occur during the day-to-day routine activities. It is normally not possible for the wrist joint to rotate axially in an active manner. However, voluntary effort to rotate the forearm while keeping the hand fixed on a custom designed device is able to provide active rotation of the wrist which occurs in a manner similar to that occurring during the daily routine activities. METHODS: The present study measured axial rotation of the wrist in 20 asymptomatic volunteers who had axial CT done of their wrist with elbow in 10-30 degrees flexion and forearm positioned parallel to the long axis of the table with thumb pointing up towards the roof. The examination was repeated twice while the subject actively tried to supinate and pronate the forearm against the fixed hand and the metacarpals using maximum voluntary effort on a custom designed positioning device. FINDINGS: The mean radiometacarpal supination and pronation were 17.15 degrees (SD 7.9) and 17.0 degrees (SD 10) respectively. The movement was found to occur predominantly at midcarpal joint with radiocarpal joint contributing only 18% to supination and 31% to pronation. INTERPRETATION: The radiometacarpal rotation has a crucial bearing in the development of the wrist prostheses. The design of the prostheses should consider accommodating axial movements that occur in the carpus during the activities of daily living.

Activities of Daily Living↗
PubMed2005

Rotation sequence as an important factor in shoulder kinematics.

BACKGROUND: The International Society of Biomechanics has proposed a standardization recommendation for motion recordings of the upper extremity defining the set of bony landmarks, local coordinate systems and joint coordinate systems. The aim of our study was to verify the clinical interpretation of the proposed rotation sequence for the glenohumeral joint and to compare it with other sequences. METHODS: Fifteen glenohumeral movements in their maximal ranges were tested on five healthy subjects. The movements were separated into five groups (flexion, extension, abduction, horizontal flexion and circumduction) with three humeral rotation positions (full external, full internal and neutral). Four glenohumeral rotation sequences were constructed using YXY, YXZ, ZXY and XZY orders and angle amplitudes were examined in terms of gimbal lock and amplitude coherence. FINDINGS: The results of the gimbal lock incidence and amplitude coherence should be taken into account together. Therefore, the suitable rotation sequences for all rotation variations of abduction and extension were found and no tested rotation sequence was found to be clinically interpretable for all tested movements. INTERPRETATION: Before glenohumeral three-dimension experiments the choice of the rotation sequence should be made in agreement with the no-gimbal lock incidence and amplitude interpretability of the performed movements.

Adult↗
PubMed2005

Effects of dynamic rotation on event-related brain potentials.

Event-related potentials were recorded during a mental rotation task. Subjects were shown pairs of letter-like shapes and were asked to make a parity judgment. The shape on the left was always in its canonical position and the shape on the right could either be in its canonical position or be a mirror image. Two variables were manipulated for the shape on the right. First, it could appear at different orientations (50 degrees , 100 degrees or 150 degrees ); second, it could be presented in a stationary position, in a dynamic congruent direction (the shape slowly rotating toward its normal upright position) or in a dynamic incongruent direction (the shape slowly rotating in the opposite direction to its normal upright position). Orientation- and direction-dependent modulations of a negative slow wave were found. For orientation, the typical amplitude effect over parietal sites was found, the amplitude becoming more negative as the rotational angle increased. For direction, the amplitude of the negative slow wave was larger for stationary and dynamic incongruent trials than for dynamic congruent trials at 100 degrees and 150 degrees . This result suggests that presentation of a stimulus in a dynamic congruent direction facilitates the mental rotation process. At 50 degrees , differences between dynamic incongruent trials and both stationary and dynamic congruent trials were found, suggesting that the incongruent movement elicits an obstructing effect over the mental rotation process. In summary, the present experiment provides new evidence in support of the idea that the amplitude modulation over the parietal cortex is a psychophysiological marker of the mental rotation process.

Adolescent↗
PubMed2004

Effect of instrument rotation on handheld keratometry.

PURPOSE: To study the effect of instrument rotation on handheld automated keratometry. SETTING: Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong SAR, China. METHODS: In 33 recruited subjects, corneal curvature in 1 eye (randomly selected) was measured using a Medmont topographic keratometer and a Nidek handheld keratometer. In handheld keratometry, measurements were obtained holding the instrument in the upright position and rotating it anticlockwise 5 degrees, 10 degrees, and 15 degrees and then clockwise 5 degrees, 10 degrees, and 15 degrees. The sequence of measurements was randomly assigned. The steepest and flattest corneal curvatures as well as the axis along the flattest meridian were compared in different conditions. The corneal power was converted to vector representation (M, J0, J45) for a second comparison. RESULTS: There was a significant difference in the steepest and flattest curvatures in different conditions (repeated-measures analysis of variation, P<.05). However, the mean difference between handheld and topographic keratometry was approximately 0.25 diopter (D) for the steepest curvature and 0.05 D for the flattest curvature regardless of the direction and amount of rotation. The intraclass correlation coefficients were nearly 1, which indicated good clinical reliability. The mean difference in axis determination followed the direction and amount of rotation. With vector representation, the difference between the devices increased with the amount of rotation, especially J0 and J45. CONCLUSIONS: Handheld keratometry was in agreement with topographic keratometry. However, practitioners should adjust the axis manually according to the direction and amount of rotation. The difference between handheld and topographic keratometry increased with the rotational effect, which was seen with vector representation. Practitioners are advised to use the handheld keratometer in the upright position.

Adult↗
PubMedDate not supplied

Movement of the projected pedicles relative to the projected vertebral body in a fourth lumbar vertebra during axial rotation.

BACKGROUND: One use of the anteroposterior lumbar radiograph is to determine axial (y-axis) rotation of the lumbar vertebrae. Rotation might be an element of interest to clinicians seeking to evaluate vertebral positioning. OBJECTIVES: Correlate and quantify movements of the projected pedicles relative to the projected vertebral body during axial rotation and determine if vertebral asymmetry and changes in object film distance affect these movements. DESIGN: A three-dimensional computer model of the fourth and fifth lumbar vertebrae, a modeled radiograph source, and a modeled film were produced. The vertebral model was placed in various degrees of axial rotation at a number of different object film distances. Lines from the source were passed through the pedicles of the fourth lumbar vertebral model and additional lines erected tangent to the lateral body margins. These lines were extended to points of contact with the modeled film. RESULTS: The projected pedicles move relative to the projected vertebral body during y-axis rotation. Vertebral asymmetry and object film distances can also affect the distance of the projected pedicle relative to the projected lateral body margin. CONCLUSION: Axial rotation produces movement of the projected pedicles relative to the projected vertebral body. However, vertebral asymmetry and changes in object film distance also affect the position of the projected pedicles relative to the projected lateral body margin and might serve as confounders to the clinician seeking to analyze vertebral rotation through the use of the projected pedicles.

Anthropometry↗
PubMed2006

Foot rotation--a potential target to modify the knee adduction moment.

Isolating the particular joints/limb segments associated with knee adductor moment variability may provide clinically important data that could help to identify strategies to reduce medial tibiofemoral joint load. The aim of this study was to examine whether or not foot and thigh rotation during human locomotion are significant determinants of knee adductor moment variability. Three-dimensional gait analyses were performed on 32 healthy adult women (mean age 54+/-12 years, mean BMI 25+/-4 kg m(-2)) with radiologically normal knees. The relationships between foot rotation, thigh rotation and the external knee adduction moment were examined during early and late-stance phases of the gait cycle. The degree of foot rotation correlated significantly with the magnitude of the peak knee adduction moment during late stance (r=0.40, p=0.024). No significant associations were apparent between thigh rotation and the peak knee adduction moment. The association between foot rotation and the knee adduction moment in this study suggests that women who walk with external rotation at the foot reduce their knee adduction moment during late stance. This result implies that changes in foot kinematics can modify the medial tibiofemoral load during gait, which may be important in the prevention and management of knee osteoarthritis.

Adult↗
PubMedDate not supplied

The impact of rotator cuff pathology on isometric and isokinetic strength, function, and quality of life.

The purposes of this study were to determine the reliability of strength and self-reporting measures, the relationship of different strength measures to function, and the impact of rotator cuff pathology on patients' quality of life. Patients with nonoperated rotator cuff pathology (n = 36) and unaffected control subjects (n = 48) were assessed by use of the LIDO dynamometer to determine isometric and isokinetic (concentric and eccentric) strength of the shoulder rotators. The Shoulder Pain and Disability Index and Short Form-36 were self-reported by patients. Intraclass correlation coefficients (ICCs) were used to assess reliability, and Pearson correlations and multiple linear regression were used to determine the relationship between strength and function. The findings of this study include the following: (1) measures of self-reported physical disability had high reliability (ICC = 0.89); (2) the LIDO dynamometer reliably measured internal and external shoulder rotation strength in both concentric and isometric modes of testing (ICC = 0.78-0.94), whereas eccentric muscle actions had lower reliability; (3) all shoulder rotation strength measures were predictive of disability, with isometric external rotation strength being the most predictive (r = 0.56); and (4) the presence of rotator cuff pathology was highly predictive of impaired physical health quality of life (R(2) = 0.71, P < .001).

Adult↗
PubMedDate not supplied

The dimensions of the rotator interval.

The purpose of this study was to define the anatomy and dimensions of the rotator interval (RI). Thirty-two fresh-frozen cadaveric shoulders were thawed, all external musculature was removed, and coracoid osteotomy was performed to visualize the rotator cuff and RI. The 3 sides of the RI (triangle) were measured in dynamic glenohumeral positions (neutral and 45 degrees external and internal rotation). An arthroscopic posterior portal, without fluid distention, was used to visualize the RI, defects, and glenohumeral pathology. The RI was sectioned, and histologic analysis and thickness measurements were performed. The mean area of the RI was 414.46 mm(2) (95% confidence interval, 362.66-466.22 mm(2)), measured in neutral position. No statistically significant differences were measured between paired right and left shoulders; however, male specimens had a significantly larger base and area than the female specimens. The dimensions of the RI changed with glenohumeral motion. The RI is definable and dynamic with glenohumeral motion. The RI closes down with internal rotation and is opened up with external rotation. This change in the interval supports the idea that, if the arm is held in internal rotation during imbrication of the capsule, overtightening and a resulting loss of external rotation can occur.

Adult↗
PubMedDate not supplied

The effect of scapular protraction on isometric shoulder rotation strength in normal subjects.

To measure the effect of scapular protraction on isometric shoulder rotation strength, 20 normal subjects completed 2 maximal isometric internal and external rotation contractions in 2 scapular positions (scapula neutral [SN] and scapula protracted [SP]) from 3 arm positions (90 degrees internal rotation [IR], 45 degrees internal rotation [MR], and 90 degrees external rotation [ER]). Scapular protraction reduced shoulder rotation strength in 5 of 6 test positions (P < .0004), with significant interactions between scapular position and arm position (P < .001) and between scapular position and contraction type (P < .0001). Protraction significantly reduced IR strength by 13% to 24% relative to SN. The effect of SP on ER strength was more position-dependent, increasing strength by 6% in the IR position and decreasing it by 7% in the MR position and 20% in the ER position. In conclusion, acute changes in scapular position affect shoulder isometric IR and ER strength. The potential adverse effects of scapular protraction on shoulder rotation strength should be considered during the evaluation and treatment of shoulder pain.

Adolescent↗
PubMed2005

The kinematics and intra- and inter-therapist consistencies of lower cervical rotational manipulation.

The aim of this study was to determine the in vivo kinematics of cervical rotational manipulation in normal subjects and examine the consistency of this technique within and between therapists. A four camera motion analysis system operating at 120 Hz was used to measure the head on trunk angular displacements during manipulation performed by three therapists on eight subjects. One of the therapists performed the manipulation twice for each subject over separate sessions. A consistent pattern of de-rotation prior to thrust was found with little motion other than axial rotation during de-rotation and thrust. The pooled mean de-rotation displacement was 4.8 degrees and the pooled mean thrust angle was 11.3 degrees , but these varied widely, and none of the kinematic parameters recorded proved to be consistent within or between therapists. Most of the kinematic parameters were correlated with the exception of thrust duration. Qualitative analysis shows a consistent technique in cervical rotational manipulation. Pre-manipulation positioning of the head relative to the trunk was fairly consistent for a single therapist over separate sessions, but other than this, the kinematic parameters in cervical rotational manipulation are generally inconsistent within and between therapists.

Adult↗
PubMed2005

Turning away from whiplash. An EMG study of head rotation in whiplash impact.

OBJECTIVE: To determine the response of the cervical muscles to whiplash-type perturbations through low-velocity frontal impacts when the head is rotated to the right and left. METHODS: Twenty healthy volunteers were subjected to increasing acceleration in low-velocity frontal impacts, randomly with head rotated either left or right. Bilateral EMG of the sternocleidomastoids, trapezii, and splenii capitis and acceleration of the sled, torso, and head were recorded. RESULTS: With either direction of head rotation at the time of impact, the muscle responses increased with increasing levels of acceleration (p < 0.01). The time to onset and peak electromyogram for all muscles progressively decreased with increasing levels of acceleration. With the head rotated to the left, the left trapezius generated 77% of its maximal voluntary contraction (MVC) EMG (more than double the response of other muscles). In comparison, the right trapezius generated only 33% of its MVC. The right sternocleidomastoid (25%) and left splenius muscles (32%), the ones responsible for head rotation to the left, were more active than their counterparts (the left sternocleidomastoid generated only 5% of its MVC EMG and the right splenius 9%). On the other hand, with the head rotated to the right, the right trapezius generated 71% of its MVC EMG, while the left trapezius generated only 30% of this value. Again, the left sternocleidomastoid (27% of its MVC EMG) and right splenius (28% of its MVC EMG), being responsible for head rotation to the right, were more active than their counterparts (the right sternocleidomastoid generated only 4% of its MVC EMG and the left splenius 13%). CONCLUSIONS: Frontal impacts tend to generate the most muscle activity in the ipsilateral trapezius muscle, increasing the risk of their injury.

Acceleration↗
PubMed1997

Rotational bias in intact rats following intrastriatal injections of dopaminergic drugs.

Following unilateral 6-OHDA lesions of the striatum, systemic dopamine agonists produce rotation due to receptor supersensitivity. Rotation following intrastriatal dopamine agonists in intact rats also has been reported, although these studies are few and contradictory. Dorsal striatal injection (0.5 microl) of the direct dopamine agonist apomorphine failed to caused rotation. In addition, neither the D1 agonist SKF 81297, the cAMP analogue Sp-cAMPS, nor the D2 agonist quinpirole affected rotation. In contrast, the dopamine releaser amphetamine (1.1, 10.9, 108.7 mM) caused significant contralateral rotation. This effect was reversed by coinjection of the D1 antagonist SCH 23390 (3.1 mM) but not by the D2 antagonist eticlopride. Rotation was also reversed by TTX coinjections (100 microM) but not by the NMDA antagonist AP7 or the kainate/AMPA antagonist CNQX. Thus, direct dopamine agonists in the striatum failed to cause behavioral asymmetry, whereas amphetamine induced contralateral rotation. This effect is mediated primarily by D1 receptors and requires concurrent neuronal activation that appears to be independent of glutamate receptor stimulation. These results are consistent with studies of Fos induction in normosensitive animals following dopamine agonists and are discussed in terms of changes in basal ganglia output pathway activity.

Animals↗