Right phrenic nerve: anatomy, CT appearance, and differentiation from the pulmonary ligament.

The pulmonary ligament appears on computed tomographic (CT) sections as a thin, high-attenuation line, frequently seen above or at the level of the diaphragm and usually extending from the region of the esophagus. However, another line coursing laterally from the midportion of the inferior vena cava has also been identified as the pulmonary ligament. The authors examined sections from eight cadavers and 80 chest CT examinations to more clearly delineate the pulmonary ligament from this second structure. Anatomic and CT correlation proves that the line seen at the midportion of the inferior vena cava represents the right phrenic nerve and that the right pulmonary ligament is located posterior to it.

Stabilizing mechanisms preventing anterior dislocation of the glenohumeral joint.

We investigated the stabilizing mechanism of the glenohumeral joint that prevents anterior dislocation by anatomical dissections of the subscapularis, the shoulder capsule, and the superior, middle, and inferior glenohumeral ligaments in thirty-six shoulders of embalmed cadavera. We also performed roentgenographic studies of ten unembalmed cadaver shoulders in which radiopaque markers were used to demonstrate the position, tightness, and laxity of the subscapularis muscle and of the middle and inferior glenohumeral ligaments during external rotation of the shoulder at zero, 45, and 90 degrees of abduction. The subscapularis muscle and the three glenohumeral ligaments were cut in different sequences to determine their relative contributions to stability (limitation of external rotation). The conclusions from these experiments were that at zero degrees of abduction, the subscapularis muscle stabilizes the joint to a large extent; at 45 degrees of abduction, the subscapularis, middle glenohumeral ligament, and anterosuperior fibers of the inferior glenohumeral ligament provide the stability; and as the shoulder approaches 90 degrees of abduction, the inferior glenohumeral ligament prevents dislocation during external rotation.

The anterior aspect of the knee joint.

The anterior structures of forty-eight knees were dissected analyzed quantitatively. Correlations were established among the twelve measured parameters of the distal quadriceps complex. Patellar height, width, and thickness tended to correlate with the dimensions of the soft-tissue structures and not with each other. To a high degree of predictability, the shape of the patella correlated with several parameters of the quadriceps complex. The width of the lateral patellofemoral ligament was the parameter most closely related to patellar shape.

The anterior cruciate ligament. A functional analysis based on postmortem studies.

In forty fresh human cadaver knees the function of the anterior cruciate ligament and of its two component parts, the posterolateral part and the anteromedial band, were studied by cutting these ligaments and others in different sequences and combinations and then manually stressing the knees. The anterior drawer sign cannot be obtained unless the anteromedial band is severed. The postolateral part and the medial collateral ligament are, respectively, the secondary and tertiary restraints limiting the anterior drawer sign. Both internal and external rotation are limited by the anterior cruciate ligament, especially when the knee is in extension. The anterior cruciate ligament also limits hyperextension.

The anterior drawer sign: what is it?

1. The anterior drawer is a test of anterior cruciate ligament integrity. 2. The anterior cruciate ligament is composed of two parts: the anteromedial band and the posterolater bulk. 3. The anteromedial band is the primary check against anterior drawer. 4. Other structures may contribute to the resistance of anterior drawer only if the anteromedial band has been injuried. 5. The posterior cruciate ligament is a check against posterior drawer. 6. In long term follow-up, the presence of anterior drawer is associated with poor overall results.

The cruciate ligaments of the knee joint. Anatomical, functional and experimental analysis.

The anatomical and functional details of the cruciate ligamants of the knee were studied on 20 cadaver knees and 24 fresh knees. Each anterior cruciate ligament was found to consist of 2 parts: a distinct anteromedial band (AMB) and a main posterolateral part. The exact geometry of the ligaments and their relationship to bony landmarks were recorded in detail. The state of the cruciate ligaments, i.e. tightness or looseness was recorded in the various positions of the knee as the basis for classification of the function of the various anatomical components. Selective cutting of the anterior cruciate ligament resulted in an increase of anterior drawer flexion and extension. External and internal rotation were increased in both flexion and extionsion. Hyperextension also was increased. It is suggested that the AMB of the anterior cruciate is responsible for the in anteroposterior drawer with flexion. The selective cutting of the posterior cruciate ligament demonstrated that it is important in the flexed knee and produces an.increased posterior drawer sign. Rotational stability was unchanged in extension, but altered in flexion after cutting the posterior cruciate.