Humeral Head

Osteoarthritis (OA) affects the articular cartilage and imderlying bones at the joint. Primary OA is associated with progressive wearing of e humeral head and the posterior aspect of the glenoid (Figure 9.2) (Hill and Norris 2001, Hayes... 

The modern era of shoulder replacement was ushered in by Dr. Charles Neer, II. In 1953, in response to the relatively poor results of humeral head resection for patients with proximal humeral fractures. Dr. Neer implanted a vital-hum humeral component of his own design in a hemiarthroplasty procedure (Figure 9.4). In 1955, he reported on his first series of 12 pahents treated in this way. 

Anatomical Shoulder contemporary shoulder prosthesis system components. An offset humeral head is shown in (A) and the noncemented humeral stem assembly is shown in (B). (Images courtesy of Centerpulse, Austin, TX). 

Anatomical ShoulderModular titanium stem and cobalt chromium humeral head prostheses with UHMWPE four-pegged glenoid components sterilized by gamma in an oxygen-free environment. Developed with Drs. Christian Gerber and Jon Warner, the first implantation was performed in 1995. It is intended for primary, hemiarthroplasty, total, and fracture use with cemented and press-fit fixation. 

Modular Shoulder System. A modular titanium stem humeral component with a keeled UHMWPE glenoid component sterilized by EtO. Cobalt chromium, titanium nitrite, and ceramic humeral heads are available as part of the system. It is intended for primary, hemiarfhroplasty, total, and fracture use with press-fit fixation. 

The reverse total shoulder prosthesis design concept is one in which the humeral head is replaced with a concave polyethylene bearing surface and the glenoid face is augmented by a convex articular metal component. As the name implies, this reverses the normal anatomic geometries of the humeral head and glenoid face. An example of this prosthesis concept is shown in Figure 9.12. 

Reverse shoulder prosthesis system components. The metal screw-fixed ball is implanted in the scapula to replace the glenoid, and the concave polyethylene component mounted on the stem is implanted into the proximal humerus to replace the humeral head (image courtesy of Encore Medical, Austin, TX). 

Neer C.S., 11. 1955. Articular replacement of the humeral head. J Bone Joint Surg 37 215-228. 

With an anterior dislocation the humeral head lies under the coracoid process on the AP radiograph (Fig. 17.5). The Y view shows the head to be displaced... 

Fig. 17.5a-c. AP radiograph showing anterior dislocation with sub-coracoid location of the humeral head. Axial view showing anterior dislocation. Oblique view of a different child (to a and b) showing anterior dislocation... 

Radiologically the Hill-Sachs compression lesion maybe evident. The Hill-Sachs lesion is a compressive fracture of the humeral head and is an important bony sign of previous anterior shoulder dislocation and instability and is significant more common in adult patients. There may also be an avulsion injury to the glenoid rim indicative of an associated Bankart lesion (detachment of the anteroinferior capsule from the glenoid neck). 

Fig. 17.6. AP radiograph of a posterior dislocation. The humeral head has a Tight hulh type appearance...

The ossification centre of the humeral head appears at 6 months. Additional centres develop for the greater tuberosity between 1 and 2 and the lesser tuberosity by 5. The tubersosities fuse together at 5 and fuse with the head between 7 and 14. The proximal physis closes by 19 (Ogden et al. 1978). The contour of the physis can lead to misinterpretation as a fracture. 

Luxatio erecta humeri is a rare type of glenohumeral dislocation. The pathomechanics of this injury involve either direct axial loading on a fully abducted extremity or leverage of the humeral head across the acromion by a hyperabduction force. The humeral head is dislocated interiorly and stuck in a position of abduction. Injury to the axillary vessels and brachial plexus is not uncommon. 

Fig. 24.10a,b. Posterior dislocation of the shoulder. VRT images are useful for the analysis of the displaced humeral bone fragment and for the relationship between the humeral head and the glenoid... 

The glenohumeral joint allows greater freedom of motion than any other joint in the body. The humeral head is convex and has a larger surface area than the concave glenoid fossa on which it moves. The humeral head slides along the surface of the fossa and rolls in various angular motions. 

The capsule of the glenohumeral joint is loose and pleated. The ligaments, which are merely thickenings in the capsule, provide little support. The major support of the humerus into the fossa is provided by the rotator cuff muscles, which hold the head into the fossa. These muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. Abduction-adduction and axial and horizontal rotations are coupled in that angular motions are accompanied by translatory slides. The caudal slide of the humeral head with abduction confers increased freedom of motion on the supraspinatus tendon beneath the coracoacromial ligament. 

The suprahumeral joint acts in concert with the glenohumeral joint as the humeral head... 

Circumduction, a combination of movements causing the arm to describe an irregular cone, with the humeral head moving in a small irregular circle and the hand moving in a wide sweeping circular motion. 

Traction stretch The patient s hand is placed on the physician s shoulder, with his elbow straight. The physician clasps her hands around the patient s upper arm. The physician may then provide a gentle pull, lifting the humeral head away from the fossa. By leaning back, the physician uses her body weight rather than muscular force (Fig. 88-7). 

Chronic dislocation may be a problem if there was a tear of the capsule at the time of original insult. The humeral head may dislocate through this tear when the arm moves into extension, abduction, and external rotation. The apprehension test is helpful in making the diagnosis if the patienl is noi aware of the cause of his pain. 

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