JAAOS

JAAOS, Volume 12, No. 4


Analgesic pharmacology: I. Neurophysiology.

The transmission of a pain signal from the periphery to the central nervous system is complex and only partially understood. Tissue damage results in peripheral release of endogenous chemicals that can directly activate nociceptive afferent fibers, sensitize nociceptors, or cause increased local extravasation and vasodilatation. These algesiogenic substances may be found in local tissues, plasma, and nerve terminals. Release of these substances may be caused by mechanical injury, radiation, or heat, or release may be stimulated by the by-products of tissue injury (ie, catecholamines or collagen). Peripheral nociceptors may be further sensitized by repeated noxious stimuli. Nociceptive afferents have their neurons in the dorsal root ganglion and contact second-order neurons in the dorsal horn or, less often, in the medulla. Modulation of the pain signal in the dorsal horn involves local inhibitory and facilitatory interneurons as well as diverse excitatory and inhibitory neurotransmitters. The neuronal circuitry in the dorsal horn can change and modulate with time so that pain signals sometimes long outlast the original peripheral tissue injury. This central sensitization is thought to be mediated largely through the NMDA receptor complex.

    • Keywords:
    • Afferent Pathways|Analgesics|Analgesics

    • Opioid|Humans|Nervous System Physiological Phenomena|Nociceptors|Pain|Peripheral Nervous System|Spinal Cord

    • Subspecialty:
    • Pain Management

    • Basic Science

Analgesic pharmacology: II. Specific analgesics.

Methods of treatment are different for acute and chronic pain. For acute pain, analgesics such as nonsteroidal anti-inflammatory drugs and opiates are commonly used, sometimes combined with regional anesthesia, such as peripheral nerve block or peridural local anesthesia. The mechanism of transition from an acute to a chronic pain state is poorly understood. Only NMDA receptor antagonists and epidural morphine have shown relatively consistent results as preemptive analgesics. Agents more successfully used to manage chronic pain include those that modify the neurochemistry of the spinal cord dorsal horn, such as tricyclic antidepressants, anticonvulsants, gamma-amino butyric acid agonists, local anesthetic analogs, and NMDA antagonists. Opiates may be used chronically, but tolerance and lack of efficacy may then develop. In selected patients with refractory chronic pain, centrally administered analgesics may be considered, including opiates, dilute local anesthetic, NMDA receptor antagonists, clonidine, midazolam, baclofen, or calcium channel blockers. For both acute and chronic pain, a single agent may be less effective than combinations of analgesics with different mechanisms of action.

    • Keywords:
    • Acute Disease|Analgesics|Chronic Disease|Humans|Pain

    • Subspecialty:
    • Pain Management

    • Basic Science

Clinical nerve conduction and needle electromyography studies.

The electrodiagnostic study, consisting of nerve conduction studies and needle electromyography, is a useful adjunct to the clinical examination of the peripheral nervous system. The three types of nerve conduction study are motor, sensory, and mixed, of which motor is the least sensitive. Electromyography records the intrinsic electrical activity of muscle fibers, thus providing the physiologic status of muscle function. To interpret the electrodiagnostic study results, the clinician must understand the anatomic and physiologic basis of the studies. Peripheral nerve entrapment initially results in focal demyelination; thus, nerve conduction velocity slows across the site. However, with radiculopathy and nerve root compression, the nerve conduction study may be normal. Both nerve trauma and polyneuropathy show marked differences in their effect on the results of electrodiagnostic studies.

    • Keywords:
    • Action Potentials|Electromyography|Humans|Neural Conduction|Peripheral Nervous System|Peripheral Nervous System Diseases|Synaptic Transmission

    • Subspecialty:
    • Trauma

    • General Orthopaedics

    • Basic Science

Congenital scoliosis.

Congenital scoliosis is caused by early embryologic errors in vertebral column formation. Defining the deformity, predicting the natural history, and applying the correct treatment can help ensure successful management. Most congenital spine anomalies can be classified, and many have a predictable natural history. Because the deformities are associated with other organ system anomalies in more than half of patients, the surgeon should look for cardiac, auditory, genitourinary, and renal anomalies. Intraspinal abnormalities are present in approximately one third of patients with congenital spine deformities. Curve progression is best documented by measuring identical landmarks on sequential radiographs. Magnetic resonance imaging is warranted when curve progression is established or when surgical intervention is planned. Management of progressive deformity is generally by early in situ fusion because orthotic treatment is rarely appropriate. Other surgical techniques include combined anterior and posterior epiphysiodesis, hemivertebra resection, and reconstructive osteotomies.

    • Keywords:
    • Humans|Scoliosis

    • Subspecialty:
    • Pediatric Orthopaedics

    • Spine

Hemophilic arthropathy.

The most common clinical manifestation of hemophilia is arthropathy secondary to recurrent hemarthroses and chronic synovitis. Joint-surface erosions secondary to chronic synovitis often occur in early childhood and progress to advanced arthropathy by late adolescence. The knee, elbow, ankle, hip, and shoulder are the most commonly involved joints. Management of hemophilic arthropathy has advanced with the development of purified clotting factor concentrates and procedures to prevent chronic synovitis. Radiosynovectomy using beta particle-emitting radiocolloids has been effective in dramatically reducing the frequency of hemarthroses and resolving chronic synovitis. The most common surgical procedures used to manage hemophilic arthropathy are synovectomy, joint debridement, fusion, and joint arthroplasty. Late infection and arthrofibrosis complicate joint arthroplasty more often in these patients than in patients with other forms of arthritis. The high incidence of late infection may relate to frequent intravenous self-infusion of clotting factor combined with immune suppression. Despite the medical and surgical complexities of hemophilic arthropathy, orthopaedic procedures have a high incidence of patient satisfaction.

    • Keywords:
    • Autoantibodies|Blood Coagulation Factors|Chronic Disease|HIV Infections|Hemarthrosis|Hemophilia A|Humans|Joint Diseases|Orthopedic Procedures|Synovitis

    • Subspecialty:
    • General Orthopaedics

    • Adult Reconstruction

Innovations in locking plate technology.

Plating techniques remain the mainstay for managing most periarticular and selected long bone fractures. However, movement toward more biologically appropriate plating techniques is occurring in an attempt to minimize soft-tissue stripping, decrease the need for bone grafting, and improve union rates. Internal fixation with locking plates creates a toggle-free, fixed-angle construct. Early data on the biomechanical and clinical performance of these implants are encouraging. Current indications for locked plating include periarticular fractures, typically those with metaphyseal comminution. Although impressive union rates have been reported, malunion remains a concern, especially when percutaneous techniques are used. Further clinical and biomechanical research on locking plate technology is needed to define its place fully alongside existing technology in orthopaedic trauma.

    • Keywords:
    • Biomechanics|Bone Plates|Bone Screws|Fracture Fixation

    • Internal|Fractures

    • Bone|Humans

    • Subspecialty:
    • Trauma

    • Basic Science

Lateral compression injuries in the pediatric elbow: Panner's disease and osteochondritis dissecans of the capitellum.

Lateral compression injuries of the elbow typically occur in throwing athletes and gymnasts. In the preadolescent and adolescent patient, these injuries predominantly include Panner's disease and osteochondritis dissecans. Panner's disease, an osteochondrosis of the capitellum, is a rare disorder that usually affects the dominant extremity in individuals younger than age 10 years. Symptomatic management of Panner's disease consisting of reduction of stressful activities of the elbow is usually sufficient to allow resolution. Although a prolonged period is required for healing, most patients demonstrate excellent long-term results. Osteochondritis dissecans of the capitellum typically occurs in adolescents and is associated with loose body formation. Panner's disease and osteochondritis dissecans likely represent a continuum of disordered endochondral ossification with presentation and prognosis dependent primarily on age at onset.

    • Keywords:
    • Adolescent|Athletic Injuries|Child|Elbow Joint|Female|Humans|Male|Osteochondritis|Osteochondritis Dissecans

    • Subspecialty:
    • Sports Medicine

    • Pediatric Orthopaedics

    • Shoulder and Elbow

Sacroiliac joint pain.

The sacroiliac joint is a source of pain in the lower back and buttocks in approximately 15% of the population. Diagnosing sacroiliac joint-mediated pain is difficult because the presenting complaints are similar to those of other causes of back pain. Patients with sacroiliac joint-mediated pain rarely report pain above L5; most localize their pain to the area around the posterior superior iliac spine. Radiographic and laboratory tests primarily help exclude other sources of low back pain. Magnetic resonance imaging, computed tomography, and bone scans of the sacroiliac joint cannot reliably determine whether the joint is the source of the pain. Controlled analgesic injections of the sacroiliac joint are the most important tool in the diagnosis. Treatment modalities include medications, physical therapy, bracing, manual therapy, injections, radiofrequency denervation, and arthrodesis; however, no published prospective data compare the efficacy of these modalities.

    • Keywords:
    • Arthralgia|Humans|Sacroiliac Joint

    • Subspecialty:
    • Spine

    • Pain Management

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