Biomedical subjects

M D Lazarus

Publications and source records attributed to M D Lazarus.

8 recordsLinked to original sources

PubMed1996

Effect of a chondral-labral defect on glenoid concavity and glenohumeral stability. A cadaveric model.

One of the primary stabilizing mechanisms of the glenohumeral joint is concavity-compression, the maintenance of the humeral head in the concave glenoid fossa by the compressive force generated by the surrounding muscles. This mechanism is active in all glenohumeral positions but it is particularly important in the functional mid-range, in which the capsule and ligaments are slack. The effectiveness of concavity-compression in the stabilization of a joint can be characterized in terms of the ratio between the maximum dislocating force that can be stabilized in a given direction and the load compressing the head into the glenoid (the stability ratio). Glenoid concavity can be described by the lateral humeral displacement during translation across the glenoid. The purpose of the present investigation was to characterize the concavity and stability ratios of normal cadaveric glenoids, to measure the effect of an anteroinferior chondral-labral defect on these parameters, and to measure the effectiveness of a simulated operative reconstruction on the restoration of glenoid concavity and the stability ratio. The chondral-labral defect created in this study reduced the height of the glenoid by approximately 80 per cent and the stability ratio by approximately 65 per cent for translation in the direction of the defect. Reconstruction of the anteroinferior aspect of the glenoid concavity with use of an autogenous biceps-tendon graft restored normal values for these variables.

Aged↗

PubMed1995

Exertional oxygen of limited benefit in patients with chronic obstructive pulmonary disease and mild hypoxemia.

It is unclear whether short-term benefits from supplemental oxygen translate into improved quality of life in patients with severe COPD. In a 12 wk double-blind randomized crossover study, we assessed the effects of supplemental air and oxygen on exercise performance (step tests and 6 min walking distance [6MWD]) initially and after two 6 wk periods at home using exertional cylinder air or oxygen. We measured quality of life at baseline and after the two 6 wk domiciliary periods. The 26 patients (24 males) had a mean age of 73 +/- 6 yr; mean FEV1, 0.9 +/- 0.4 L; mean DLCO, 10.6 +/- 2.4 ml/min/mm Hg; mean resting PO2, 69 +/- 8.5 (range 58 to 82) mm Hg; mean PCO2, 41 +/- 3.3 mm Hg; and mean resting SaO2, 94 +/- 2.1 (mean +/- SD). Laboratory tests were performed breathing intranasal air or oxygen at 4 L/min, and measurements were made of SaO2 and Borg dysnea scores. Supplemental oxygen increased 6MWD and steps by small, statistically significant increments acutely at baseline and after 6 and 12 wk, without corresponding falls in Borg score. Degree of desaturation at baseline did not correlate with increase in 6MWD or steps achieved at baseline or at 6 or 12 wk, nor with the domiciliary gas used. There was no difference in 6MWD or steps achieved while breathing supplemental oxygen after 6 wk of domiciliary oxygen compared with domiciliary air. Small improvements in quality of life indices were found after domiciliary oxygen, and mastery also improved after domiciliary air. There were no differences in quality of life, however, when domiciliary oxygen was compared with domiciliary air. Although oxygen supplementation induced small acute increments in laboratory exercise performance, such improvements had little impact on the patients' daily lives.

Aged↗

PubMed1994

Comparison of the inflammatory response to particulate polymethylmethacrylate debris with and without barium sulfate.

Particulate polymethylmethacrylate debris has been implicated in the inflammatory response observed surrounding loosened cemented implants. The rat subcutaneous pouch model and the Howie implant model (used to study bone resorption) were used to quantify the response to mechanically produced endotoxin-free polymethylmethacrylate debris with and without 10% (wt/vol) BaSO4. In the rat subcutaneous pouch model, the inflammatory response to polymethylmethacrylate particles containing BaSO4 was greater than the response to plain polymethylmethacrylate particles of similar size. Increased inflammation was measured by leukocyte counts and levels of prostaglandin E2, tumor necrosis factor, and neutral metalloprotease. In addition, particulate polymethylmethacrylate with BaSO4 caused significantly greater bone resorption in the Howie model than did particulate plain polymethylmethacrylate. In in vitro studies, particulate polymethylmethacrylate with BaSO4 stimulated more prostaglandin E2, neutral metalloprotease, and tumor necrosis factor from human monocytes in culture and stimulated greater proliferation of synovial cells than did particulate plain polymethylmethacrylate. The presence of BaSO4 appears to significantly intensify the inflammatory response to polymethylmethacrylate debris.

Animals↗

PubMed1993

Advances in the management of musculoskeletal trauma.

During the past year, several important advances have occurred in the diagnosis and treatment of orthopedic trauma. The increased use of magnetic resonance imaging in the diagnosis of acute cervical spine injuries has enhanced the ability to treat these patients. The development of better fixation systems for the lumbar spine, particularly pedicle screw systems, has increased our ability to stabilize and decompress fractures and fracture-dislocations in this region. New techniques for pelvic stabilization have proved useful in the treatment of these complex injuries. In extremity trauma, the association of compartment syndrome with intramedullary nailing has gained more attention and more aggressive treatment is advocated for fractures secondary to penetrating trauma.

Compartment Syndromes↗

PubMedDate not supplied

Useful boundaries of the subacromial bursa.

The anatomic boundaries the subacromial bursa may serve as a useful guide for surgical orientation and safety. The goals of this study were to measure the minimum distance between the subdeltoid reflection of the subacromial bursa and the circumflex branch of the axillary nerve and to identify relationships between the margins of the subacromial bursa and the acromion, rotator cuff, and acromioclavicular joint. Seventeen fresh-frozen cadavers (mean age, 69 years), were included. Eleven cadavera were dissected only after the subacromial bursa was injected with a latex solution to define the peripheral boundaries of the bursa. The bursal margins were always 2 cm or more from the anterolateral corner of the bursal acromial surface and the bursa lined the anterior half of the anteroposterior distance of the acromion. The mean distances from all points of the acromion to the axillary nerve averaged approximately 5 cm. The mean minimum distance from the subdeltoid bursal reflection to the axillary nerve was 0.8 +/- 0.5 cm with a range of 0.0 to 1.4 cm. In the unelevated extremity, the inferior bursal reflection was always cephalad to the axillary nerve even when the two structures were apposed. Surgeons should exercise caution when approaching the inferior boundary of the subdeltoid bursal reflection because of the proximity to the axillary nerve. We recommend coupling previously reported "safe deltoid-split" distances to this useful anatomic landmark to prevent nerve injury. Furthermore, the central location of the anterolateral corner of the acromion within the bursal space can be applied to needle placement for injection, arthroscopic diagnosis or treatment and mini-open rotator cuff repairs.

Acromioclavicular Joint↗

PubMedDate not supplied

Practical guidelines to safe surgery about the subscapularis.

Surgical mobilization of an adherent or retracted subscapularis tendon is often necessary whenever an attempt is made to restore function to the glenohumeral joint subsequent to failed anterior reconstructive surgery. Surgical guidelines drawn from this study emphasize how a surgeon might accomplish this task effectively and avoid denervating the subscapularis, a muscle that is essential to anterior glenohumeral stability and strength. In this study we examined subscapularis innervation in 11 fresh-frozen cadaveric shoulders. The position of the subscapular nerve insertion points were recorded relative to easily identified surgical landmarks such as the axillary nerve, the conjoined tendon, and the anterior glenoid rim. The palpable anterior border of the glenoid rim deep to the subscapularis along with the medical border of the conjoined tendon can serve as guides to the subscapularis nerve insertion points, because all the nerves are no closer than 1.5 cm medial to these landmarks for all positions of humeral rotation in the unelevated arm. The lower subscapular nerve was found immediately posterior or just lateral to the axillary nerve. During a standard deltopectoral approach potential injury to the subscapularis innervation can be minimized by locating and protecting the axillary nerve, because it serves as a guide to the insertion point of the lower subscapularis nerve, the nerve closet to the surgical field.

Aged↗

PubMedDate not supplied

Elbow valgus stress radiography in an uninjured population.

Valgus instability of the elbow joint is a clinical diagnosis. However, many authors describe valgus stress radiographs as an aid in making this diagnosis. We studied valgus stress radiographs of 20 men (40 elbows) and 20 women (40 elbows), none with a history of elbow trauma or instability. The medial ulnohumeral distance was measured with no stress, valgus stress by gravity, and an applied valgus stress of 25 N (approximately 5 pounds). Measurements were made with the elbow positioned in extension and in 30 degrees of flexion. The increase in medial ulnohumeral gapping with either gravity or 5 pounds of stress was statistically significant at both extension and 30 degrees of flexion compared with the unstressed condition. The difference in ulnohumeral gapping between gravity stress and 5 pounds of valgus stress in extension and in 30 degrees of flexion was also significant. We found no differences with regard to hand dominance or sex. We conclude that uninjured elbows have significant medial ulnohumeral gapping on valgus stress radiography. Although this is an important tool in diagnosing valgus instability of the elbow, it may yield a false-positive assessment of valgus instability. Valgus stress radiographs comparing contralateral elbows may reduce the false-positive rate since there appears to be no significant difference in medial ulnohumeral gapping between the two elbows.

Adolescent↗

PubMedDate not supplied

Complications of open anterior stabilization of the shoulder.

Complications of surgery for glenohumeral instability are relatively uncommon. When they occur, salvaging failures and obtaining a stable joint can be awesome challenges. Accurate recognition of the cause of the instability and application of the appropriate surgical technique are critical. Deficiencies of the glenoid concavity, the anterior capsule, or the subscapularis may be present and require correction. Overtightening a shoulder and eliminating its normal laxity should be avoided. Loose or malpositioned hardware about the glenohumeral joint must be recognized as soon as possible and removed. The goal of treatment is to correct the deficient stabilizing mechanisms without altering normal glenohumeral function.

Adult↗