Radiographic anatomic structure of the arthritic acetabulum and its influence on total hip arthroplasty.

Acetabular bone structure is not the same in all patients and can be defined by the radiolucent triangle superior to the acetabulum. Of 132 hips, 81 had an isosceles triangular shape, which was named type A acetabulum. Forty-six hips had an extension of the triangle into the teardrop, which created a thickened medial wall and was named type B. Five hips had a right-angle triangle, which was found only with congenital disease of the hip and was named type C. The density of the superior acetabular bone in the triangle could be normally radiolucent (stage I), have vertical and transverse trabeculae throughout the triangle (stage II), or have the triangle filled with bone and cysts (stage III). The relationship between progressive radiolucent lines and acetabular type showed that type A3 (thin medial wall with dense triangle bone) had the highest incidence of progressive radiolucent lines (P < .05).

Fracture analysis of retrieved orthopedic wires.

Ten retrieved samples of 316L stainless steel wires, implanted for times from 11 months to 11 years, were examined fractographically and metallurgically to evaluate the effects of a physiological environment on their fracture. Seven samples were from L-rod instrumentation, and three samples were from trochanter reattachment. Of 16 breaks in the 10 samples, 94% were caused primarily by cyclic loading (fatigue), and 6% were caused by tensile forces. Two factors were found to influence the effective life of an implanted wire. First, the surface condition (deformation) appeared to be most important, and second, corrosion pits present on most wire surfaces could possibly be an influence in initiating a crack. Biomechanical forces on wires enveloping L-rods tended to promote metal deformation and faceting, which decreased time to fracture. This decrease in wire life was evident from a substantial hardness increase in faceted areas.

Biomechanics of the shoulder.

Man's shoulder girdle is of the general pattern of his tree-swinging ancestors. With assumption of the upright posture, man's thorax has flattened from anterior-posterior. This results in a rotation of the scapula to a position of 45 degrees with the sagittal plane. In addition to this, man's forearm is habitually used in a position of approximately 45 degrees of internal rotation. This places the biceps tendon "off its trolley" and leads to biceps tinosynovitis. Motions of the glenohumeral joints result from the force couple of the deltoid muscle plus the rotator cuff muscles. The rotator cuff alone can abduct the arm with 50% force throughout the full range of its motion. In the absence of the supraspinatus muscle, however, the force couple is disrupted. Although initiation of abduction is with full force, the force rapidly falls off to 90 degrees. Above 90 degrees the arm can barely support its own weight. Although the shoulder undergoes progressive degenerative changes with age, the necessity for a joint implant, either partial or total--although successful--is rare.

Environmental bacteriology in the unidirectional (vertical) operating room.

An integrated body exhaust/clean air operating room system was evaluated in terms of the microbiologic and particulate contamination control it afforded. The clean air unit was of a vertical unidirectional airflow design and employed high-efficiency particulate air filters to provide air low in both microbes and particulates. The body exhaust portion of the system was composed of an exhaust tube the surgeon's mask, a transparent plastic faceplate, and a microbe-retentive surgical gown and hood. Measurements were made of airborne and surface contamination at the wound site and of microbial burden levels associated with the surgical team. Sampling techniques were designed to parallel those used in a previous study of a horizontal flow/body exhaust system so as to provide comparative data on the effect of airflow configuration on wound site contamination. The data showed the vertical flow room to exhibit significantly lower (P less than .05) contamination levels than the horizontal flow enclosure. Surgical lights, draping techniques, and personnel and material positoning unobstructive to the airstream were judged to the prime factors in reducing wound site contamination.

Reduction of deep sepsis after total hip arthroplasty.

The role of the operating room environment in the development of deep sepsis after total hip arthroplasty was studied at four centers. The incidence of deep sepsis after 5,865 total hip arthroplasties performed in the four centers varied from 0.5% to 2.3%. Procedures performed in a conventional operating room were associated with the highest incidence of deep sepsis (1.3%). The use of a vertical, unidrectional airflow system with a helmet aspirator suite was associated with the lowest incidence of deep sepsis (0.6%). Although patients with previous hip surgery had an increased incidence of deep sepsis regardless of the operating room environment, those procedures performed in a vertical, unidrectional facility had a lower incidence of deep sepsis. Newer techniques designed for the reduction of airborne contamination of the operative wound seem to reduce the incidence of deep-wound sepsis after total hip arthroplasty, especially in patients with previous hip surgery.

Use of ultrasound to detect fat emboli during total hip replacement.

Use of the Doppler principle with an ultrasound flowmeter provided a method of detecting fat emboli during total hip replacement. A measure of the quantity of fat emboli and when the embolism occurs during the operative procedure is possible with this method. By the use of a suction catheter inserted in the intramedullary canal or the placement of large drill holes in the lateral cortex of the femur the amount of fat released into the venous circulation can be reduced. Although no definite signature could be obtained for the audible "chirps" by energy density spectrum analysis the observer could readily distinguish these chirps from the burbling noise produced by air emboli. Ultrasound is an easy, noninvasive and reliable technique for detecting fat emboli during total hip replacement.