Anaesthetic risks in osteoarticular disorders

Juvenile Idiopathic Arthritis for the Pediatric Orthopedic Surgeon

Juvenile idiopathic arthritis includes conditions characterized by joint inflammation of unknown etiology lasting longer than 6 weeks in patients younger than 16 years. Diagnosis and medical management are complex and best coordinated by a pediatric rheumatologist. The mainstay of therapy is anti-inflammatory and biologic medications to control pain and joint inflammation. Orthopedic surgical treatment may be indicated for deformity, limb length inequality, or end-stage arthritis. Evaluation of the cervical spine and appropriate medication management in consultation with a patient's rheumatologist are essential in perioperative care. Preoperative planning should take into account patient deformity, contracture, small size, osteopenia, and medical comorbidities.

[Anesthesia and rheumatoid arthritis]

BACKGROUND AND OBJECTIVES

Rheumatoid arthritis (RA) is a chronic inflammatory disease of unknown etiology. It is known that RA patients have a reduced life expectancy when compared with the general population. Rheumatic diseases are numerous and occur with high variability; some of them develop very rapidly while others occur chronically provoking disability throughout life. Anesthetic risks in osteoarticular disorders involve not only the mechanical deformations caused by the disease, but also the cardiovascular, respiratory, renal, and digestive systems.

CONTENTS

The purpose of this review was to stress the importance of stages in disease process that may affect anesthesia control before, during, and after surgery, highlighting the authors' experience in a retrospective review of patients with juvenile rheumatoid arthritis (JRA) undergoing placement of orthopedic prosthesis with emphasis on intubation techniques.

CONCLUSIONS

Rheumatoid arthritis patients can present a number of complex problems for the anesthesiologist. This requires careful preoperative evaluation; anesthesia requires experience with the technique; and postoperative care should be judiciously chosen to meet the specific needs of the patient. The procedure requires effective communication among surgeon, rheumatologist and anesthesiologist so each member of the multidisciplinary team can contribute with his/her expertise in order to better benefit the patient.

Threaded screw head inserts improve locking plate biomechanical properties

OBJECTIVES

The purpose of this study was to determine if the stiffness and fatigue life of locking one third tubular plates are enhanced by placing a locking screw head to fill the empty hole of the plate. We hypothesize that both the stiffness and fatigue life of the plates will be improved at physiologically relevant loads by filling the empty center hole of each plate.

METHODS

The mechanical stiffness and fatigue life of plates with an open versus filled center hole were assessed through finite element analysis and experimentally using a synthetic bone model under four-point bending. Two plate manufacturers were evaluated, Synthes (n) and Stryker (r). Five-hole one third tubular plates were mechanically cycled with and without filling the central screw hole while load, displacement, and number of cycles were collected. Stiffness was calculated and cycles to failure and mode of failure were monitored. Five plates were evaluated for the filled (F) and open (O) configurations for the n and r plates.

RESULTS

Finite element analysis indicated that filling the hole resulted in reduction in maximum stress at the periphery of the center hole by a factor of 2.43 and 2.29 for the n and r plates, respectively. Experimentally, a fourfold improvement was observed in fatigue life of the Synthes plates when a screw head was used to fill the central screw hole (P < 0.005; nF = 45,450 cycles versus nO = 10,305 cycles). The Stryker plates reached the maximum number of cycles (1 million) without fatigue failure in both O and F configurations. Improved bending stiffness was noted for both the n and r plates when the central hole was filled compared with open. For the Stryker plate, this increase was statistically significant (P < 0.011).

CONCLUSIONS

The methodology proposed in this study for extending fatigue life and increasing stiffness of locking plates can potentially be extended to any locking plate. Adding a screw head or screw heads to open holes in locking plates adds little additional time or expense and no morbidity to the procedure but can have substantial effects on the mechanical properties of the implant, particularly in lower-profile plates that are initially less rigid and robust.

[Anesthesia for surgery of degenerative and abnormal cervical spine]

A feature common to all congenital or inflammatory abnormalities of the cervical spine is an actual or potential reduction in the lumen of the spinal canal. The spinal cord and nerve roots are at risk. During intubation, and positioning the patient on the table, all untoward movements of the cervical spine may lead to spinal cord compression. Abnormalities of the cervical spine carry the risk of a difficult intubation. If there is much debate as to what constitutes optimum management of the airway, there is no evidence that any one method is the best. Recognizing the possible instability and intubating with care, are probably much more important in preserving neurological function than any particular mode of intubation. During maintenance of anaesthesia, the main goal is to preserve adequate spinal cord perfusion in order to prevent further damage. Spinal cord blood flow seems to be regulated by the same factors as cerebral blood flow. Hypercapnia increases cord blood flow while hypocapnia decreases it. Therefore, normocapnia or mild hypocapnia is recommended. Induced hypotension is frequently used to decrease blood loss. However, in patients with a marginally perfused spinal cord, the reduction in blood flow may cause ischaemia of the spinal cord and may therefore be relatively contraindicated. In addition to standard intraoperative monitoring, spinal cord monitoring is almost mandatory. Monitoring somatosensory evoked potentials is used routinely. However, the major limitation is that this technique only monitors dorsal column function; theoretically, motor paralysis can occur despite a lack of change in recorded signals. Neurogenic motor evoked potentials may now be used to monitor anterior spinal cord integrity.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of aging on preoperative evaluation

Approximately 40% of physician office time and 33% of hospital time are devoted to patients 65 years of age or older. Over half of the older population requires some surgical intervention. Because of decreased physiologic reserve and increased number of underlying medical disorders, the older patient is at increased risk for intraoperative and postsurgical complications. Since cardiovascular, pulmonary, and renal complications are frequent in the elderly patient, the preoperative evaluation should emphasize these organ systems. Risk factors should be assessed initially by a focused history and physical examination and by simple tests. Additional diagnostic testing should be reserved for the patient who is not clearly at low or high risk. For optimal preoperative evaluation of the elderly patient, the physician should identify systemic disease, determine if the patient is receiving appropriate therapy, delineate the operative risks, and make recommendations that can potentially reduce the operative risks and postoperative complications.