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Biomedical subjects

R B Blasier

Publications and source records attributed to R B Blasier.

33 records · Page 2Linked to original sources
PubMed1990

Intraoperative positioning for arthrodesis of the hip with the double beanbag technique.

The double beanbag technique allows the surgeon to select the position of the lower limb before an arthrodesis of the hip. During the procedure, the surgeon can freely manipulate the limb, confident that it can be replaced in the exact position that was chosen for the arthrodesis. The technique is not cumbersome, and only commonly available equipment is needed. For the method to be effective, there must be enough residual motion of the hip to allow positioning and preparation of the skin. Also, rigid internal fixation must be used to maintain the selected position of arthrodesis at the conclusion of the operation.

Arthrodesis↗
PubMed1989

Improved results with the "inverted T" modification of the Bristow procedure.

The results of two modifications of the Bristow procedure in 21 patients were compared an average of 53 months after surgery. Twelve patients had an "inverted T" modification (group T) and nine patients had May's modification (group M). Recurrence rates and functional limitation were determined, as well as range of motion, pain, and apprehension with abduction and external rotation. Preoperative instability was classified according to the method of Protzman. Surgical outcome was graded using the rating scale devised by Rowe in 1978. There were no postoperative dislocations. Overall results were 16 excellent, three good, one fair, and one poor. All 12 patients in group T had an excellent result. In group M, there were four excellent, three good, one fair, and one poor result. Clinical score was 95 in group T and 75 in group M. Pre- and postoperative external rotation at 90 degrees abduction were 91 and 89 degrees in group T, and 99 and 77 degrees in group M.

Adolescent↗
PubMed1989

Malignant neuroepithelioma (peripheral neuroblastoma). A case report.

Malignant neuroepithelioma is a rare neoplasm arising within the peripheral nervous system. It usually occurs in the lower extremities and may involve patients in any age group. In children younger than the age of five years, the tumor must be differentiated from a metastatic neuroblastoma; in adolescents and adults the tumor must be distinguished from other malignant round-cell tumors. The poor prognosis and the need for aggressive, combined surgical and chemotherapeutic modalities in treating this tumor necessitate a prompt and accurate diagnosis.

Adult↗
PubMed1988

Management of posterior fracture-dislocations of the shoulder.

Posterior fracture-dislocation of the shoulder is rare. Comprehensive treatment guidelines for posterior fracture-dislocation of the shoulder with fracture of the humeral head have not been previously published. Although open reduction and internal fixation of the proximal humerus for posterior fracture-dislocation has been reported in several series, the successful reconstruction of the articular surface by rigid internal fixation of a large osteochondral fragment has not been reported. This paper describes two cases of posterior fracture-dislocation of the shoulder with a substantial defect of the anteromedial humeral head resulting from the cleavage of a large osteochondral fragment. Preoperative computed axial tomographic (CAT) scanning of the injured shoulders helped in operative planning by precisely defining the extent of the articular injury. Accurate reconstruction of the articular surface restored joint stability and gave excellent clinical results. Large humeral head osteochondral fracture fragments require accurate reduction and internal fixation.

Adult↗
PubMedDate not supplied

Active and passive factors in inferior glenohumeral stabilization: a biomechanical model.

This study examines the stabilizing factors of the glenohumeral joint against inferior translation over a range of subluxations. Factors examined included the glenohumeral capsular ligaments, the coracohumeral ligament, the rotator cuff forces, and the long head of the biceps force. Simulated muscle forces were applied to eight shoulder specimens with the arm near 0 degrees abduction. Stability was defined as the force required to inferiorly sublux the joint to a specified translation from the centered position and was evaluated under varying configurations of capsule cuts, humeral rotation, and muscle loads. The supraspinatus and biceps muscle forces were found to be important active stabilizers. Thus, tension in the long head of the biceps did not tend to depress the humeral head. The inferior glenohumeral ligament was an important passive stabilizer in external rotation. Understanding the effects of these factors adds insight into the underlying biomechanics of clinical shoulder instability.

Biomechanical Phenomena↗
PubMedDate not supplied

The low incidence of suprascapular nerve injury after primary repair of massive rotator cuff tears.

We measured the incidence of cuff retear and injury to the suprascapular nerve after mobilization and repair of a massive rotator cuff tear. Of one hundred four rotator cuff repairs performed over a 5-year period, 10 patients (7 men and 3 women, age range 22 to 68 years) had primary repairs of massive rotator cuff tears requiring cuff mobilization and an acromioplasty as their only procedure. These patients were evaluated at a mean of 2.5 years (range 2.0 to 3.0 years) after surgery. At follow-up electromyographic examination confirmed that 1 of the 10 patients had an iatrogenic suprascapular nerve injury, whereas ultrasound evaluation revealed that 2 of 10 repairs failed. Pain relief was achieved in the eight patients with intact repairs and not in the two with recurrent tears. All patients had some limitation of active motion or strength, especially in external rotation. Thus 7 of 10 patients had neither evidence of nerve injury nor recurrent rotator cuff tears yet still showed limited active motion or weakness. It appears that operative injury to the suprascapular nerve during cuff mobilization can occur, but other factors such as inadequate cuff muscle function are more frequently responsible for the poor functional outcomes seen after successful repairs of massive rotator cuff tears.

Adult↗
PubMedDate not supplied

The mechanism of creation of superior labrum, anterior, and posterior lesions in a dynamic biomechanical model of the shoulder: the role of inferior subluxation.

Lesions of the superior glenoid labrum are a source of shoulder disease. However, the mechanisms of injury to this region are unknown, and controversy exists regarding the role of shoulder instability in creation of this lesion. With a cadaver model that simulates physiologic rotator cuff forces and produces traction on the biceps tendon, the creation of type II superior labrum, anterior, and posterior (SLAP) lesions and the role of glenohumeral subluxation were investigated: Left and right shoulders from each of 8 paired cadavers (age 62 +/- 7.2 years, 5 male and 3 female) were randomized to be tested in either a 20 mm inferiorly subluxed position or in a reduced position. The long head of the biceps tendon was held near the musculotendinous junction with a novel cryogenic clamp. Traction on the long head of the biceps tendon was applied at a fast rate of 12.7 cm/sec with a servohydraulic testing machine. A load cell was used to monitor the biceps tendon load. After testing to failure, the presence or absence of a type II SLAP lesion was determined by 2 experienced shoulder surgeons masked to the test group. The production of type II SLAP lesions differed significantly (P = .03) between reduced shoulders (2 SLAP lesions out of 8 tests) and the shoulders with inferior subluxation (7 SLAP lesions out of 8 tests). This experiment has shown that traction on the biceps tendon in this biomechanical model can reproducibly create type II SLAP lesions, and inferior subluxation facilitates the generation of such lesions.

Aged↗
PubMedDate not supplied

Ligamentous restraints to external rotation of the humerus in the late-cocking phase of throwing. A cadaveric biomechanical investigation.

The late-cocking phase of throwing is characterized by extreme external rotation of the abducted arm; repeated stress in this position is a potential source of glenohumeral joint laxity. To determine the ligamentous restraints for external rotation in this position, 20 cadaver shoulders (mean age, 65 +/- 16 years) were dissected, leaving the rotator cuff tendons, coracoacromial ligament, glenohumeral capsule and ligaments, and coracohumeral ligament intact. The combined superior and middle glenohumeral ligaments, anterior band of the inferior glenohumeral ligament, and the entire inferior glenohumeral ligament were marked with sutures during arthroscopy. Specimens were mounted in a testing apparatus to simulate the late-cocking position. Forces of 22 N were applied to each of the rotator cuff tendons. An external rotation torque (0.06 N x m/sec to a peak of 3.4 N x m) was applied to the humerus of each specimen with the capsule intact and again after a single randomly chosen ligament was cut (N = 5 in each group). Cutting the entire inferior glenohumeral ligament resulted in the greatest increase in external rotation (10.2 degrees +/- 4.9 degrees). This was not significantly different from sectioning the coracohumeral ligament (8.6 degrees +/- 7.3 degrees). The anterior band of the inferior glenohumeral ligament (2.7 degrees +/- 1.5 degrees) and the superior and middle glenohumeral ligaments (0.7 degrees +/- 0.3 degrees) were significantly less important in limiting external rotation.

Aged↗
PubMedDate not supplied

The Bankart repair illustrated in cross-section. Some anatomical considerations.

The Bankart repair for chronic anterior shoulder instability effectively addresses the pathologic components responsible for repeated dislocation or subluxation. However, contrary to popular belief, the Bankart repair does not precisely restore the premorbid anatomy. The capsule is reattached to the boney rim of the anterioinferior glenoid deep to and lateral to the torn cartilagenous labrum, thus excluding the labrum from the joint anteriorly. This was demonstrated by cross-sectional cadaver dissections performed to illustrate this complex surgical anatomy to orthopaedic residents in training. In addition, when correlated with double-contrast computerized axial tomography, we noted five predominant patterns of anatomical lesions which by common use have been collectively termed the "Bankart lesion." These are: 1) the rare "classic" Bankart lesion in which the cartilagenous labrum and capsular origin are torn from the glenoid rim; 2) the capsule stripped from the scapular neck and the labrum detached from the glenoid rim remaining fixed to the overlying capsule; 3) the capsule stripped from the scapular neck and the labrum separated from the glenoid rim, but separately; 4) the labrum abraded away and no longer radiographically detectable; and 5) glenoid rim fracture.

Humans↗
PubMedDate not supplied

The effects of muscle fatigue on shoulder joint position sense.

Proprioception, or joint position sense, probably plays an important role in shoulder joint function. In this study, we assessed the effect of muscle fatigue on shoulder proprioception in 20 volunteers with no shoulder abnormalities. Shoulder proprioception was measured as the threshold to first detection of humeral rotation with the joint at 90 degrees of abduction and 90 degrees of external rotation. Subjects were tested while rested, exercised on a isokinetic testing machine until fatigued, and then retested in an identical fashion. Both shoulders were tested, and the order of dominant and nondominant shoulder was randomized. Shoulder proprioception was analyzed for its dependence on arm dominance, direction of rotation, and muscle fatigue. Subjects detected external rotation after significantly less movement than they did internal rotation. Overall, before exercise, motion was detected after a mean of 0.92 degrees of rotation. After exercise, this threshold to detection of movement increased to 1.59 degrees, an increase of 73%. This significant increase occurred with both internal and external rotation. The decrease in proprioceptive sense with muscle fatigue may play a role in decreasing athletic performance and in fatigue-related shoulder dysfunction. It remains to be determined if training can lessen this loss in position sense.

Adult↗