JAAOS

JAAOS, Volume 11, No. 2


Dislocation after total hip arthroplasty: implant design and orientation.

Implant design and positioning are important factors in maintaining stability and minimizing dislocation after total hip arthroplasty. Although the advent of modular femoral stems and acetabular implants increased the number of head, neck, and liner designs, the features of recent designs can cause intra-articular prosthetic impingement within the arc of motion required for normal daily activities and thus lead to limited motion, increased wear, osteolysis, and subluxation or dislocation. Minimizing impingement involves avoiding skirted heads, matching a 22-mm head with an appropriate acetabular implant, maximizing the head-to-neck ratio, and, when possible, using a chamfered acetabular liner and a trapezoidal, rather than circular, neck cross-section. Computer modeling studies indicate the optimal cup position is 45 degrees to 55 degrees abduction. Angles <55 degrees require anteversion of 10 degrees to 20 degrees of both the stem and cup to minimize the risk of impingement and dislocation.

    • Keywords:
    • Arthroplasty

    • Replacement

    • Hip|Biomechanics|Hip Dislocation|Hip Joint|Hip Prosthesis|Humans|Prosthesis Design

    • Subspecialty:
    • Adult Reconstruction

Instability of the proximal tibiofibular joint.

Injury to the proximal tibiofibular joint is typically seen in athletes whose sports require violent twisting motions of the flexed knee. Instability of this joint may be in the anterolateral, posteromedial, or superior directions. With acute injury, patients usually complain of pain and a prominence in the lateral aspect of the knee. A closed reduction should be attempted in patients with acute dislocation. If this is unsuccessful, open reduction and stabilization of the joint with repair of the injured capsule and ligaments can be done. Patients with chronic dislocation or subluxation report lateral knee pain and instability with popping and catching, which may be confused with lateral meniscal injury. Symptoms of subluxation may be treated nonsurgically with physical therapies such as activity modification, supportive straps, and knee strengthening. For patients with chronic pain or instability, surgical options include arthrodesis, fibular head resection, and proximal tibiofibular joint capsule reconstruction.

    • Keywords:
    • Athletic Injuries|Biomechanics|Fibula|Humans|Joint Instability|Knee Injuries|Tibia

    • Subspecialty:
    • Foot and Ankle

    • Sports Medicine

Internal fracture fixation in patients with osteoporosis.

Because of the decreased holding power of plate-and-screw fixation in osteoporotic bone fractures, internal fixation can have a high failure rate, ranging from 10% to 25%. Screws placed into cortical bone have better resistance to pullout than do those placed into adjacent trabecular bone. Plates should not be used to bridge unstable regions of bony comminution in osteoporotic patients. Fixation stability is optimized by securing stable bone contact across the fracture site and by placing screws both as close to and as far from the fracture as possible. Intentional shortening can improve stability and load sharing of the fracture construct. Structural bone graft or other types of fillers can be used to fill voids when comminution prevents stable contact. Load-sharing fixation devices such as the sliding hip screw, intramedullary nail, antiglide plate, and tension band constructs are better alternatives for osteoporotic metaphyseal locations. Proper planning is essential for improved fracture fixation in this high-risk patient group.

    • Keywords:
    • Fracture Fixation

    • Internal|Fractures

    • Bone|Humans|Osteoporosis

    • Subspecialty:
    • Trauma

    • Spine

Scapular dyskinesis and its relation to shoulder pain.

Scapular dyskinesis is an alteration in the normal position or motion of the scapula during coupled scapulohumeral movements. It occurs in a large number of injuries involving the shoulder joint and often is caused by injuries that result in the inhibition or disorganization of activation patterns in scapular stabilizing muscles. It may increase the functional deficit associated with shoulder injury by altering the normal scapular role during coupled scapulohumeral motions. Scapular dyskinesis appears to be a nonspecific response to shoulder dysfunction because no specific pattern of dyskinesis is associated with a specific shoulder diagnosis. It should be suspected in patients with shoulder injury and can be identified and classified by specific physical examination. Treatment of scapular dyskinesis is directed at managing underlying causes and restoring normal scapular muscle activation patterns by kinetic chain-based rehabilitation protocols.

    • Keywords:
    • Athletic Injuries|Humans|Muscle

    • Skeletal|Scapula|Shoulder Joint|Shoulder Pain

    • Subspecialty:
    • Sports Medicine

    • Shoulder and Elbow

Surgical management of the rheumatoid elbow.

Many patients with rheumatoid arthritis demonstrate elbow involvement that may limit upper extremity function, usually within 5 years of disease onset. Initial management consists of nonsurgical measures that address synovitis and capsular inflammation in an effort to diminish pain and maintain elbow range of motion. Disease progression may result in articular damage and ligamentous compromise, causing increased symptoms, elbow instability, and functional debilitation. For patients unresponsive to nonsurgical management, open or arthroscopic synovectomy may provide relief of symptoms. For those with more advanced disease, elbow arthroplasty is a reasonable alternative. Advancements in prosthetic technology and surgical techniques allow elbow arthroplasty to be reliably performed in patients with severe rheumatoid arthritis of the elbow.

    • Keywords:
    • Arthritis

    • Rheumatoid|Arthroplasty

    • Replacement|Biomechanics|Elbow Joint|Humans|Synovial Membrane

    • Subspecialty:
    • Shoulder and Elbow

Tumorlike lesions and benign tumors of the hand and wrist.

A broad spectrum of tumorlike lesions and neoplasms can occur in the hand and wrist, although with somewhat less frequency than in other parts of the body. A thorough understanding of the differential diagnosis of these lesions and a comprehensive strategy for evaluation are central for effective care. Plain radiographs are diagnostic for most bony lesions, whereas magnetic resonance imaging may be necessary to help differentiate a benign soft-tissue lesion from the rare malignant neoplasm. In spite of the complex anatomy, adherence to proper oncologic principles most often will lead to a satisfactory outcome.

    • Keywords:
    • Bone Neoplasms|Diagnosis

    • Differential|Hand|Humans|Soft Tissue Neoplasms|Wrist

    • Subspecialty:
    • Hand and Wrist

    • Musculoskeletal Oncology

Use of electrical bone stimulation in spinal fusion.

Spinal fusion is commonly done to manage deformity, restore stability, and eliminate excessive motion at specific spinal levels. Pseudarthrosis limits the clinical success of spinal fusion. Three types of electrical stimulation, which is used to manage non-union in long bones, recently have been applied in an attempt to enhance the rate of spinal fusion. Direct current electrical stimulation is internal and thus eliminates dependence on patient compliance. Pulsed electromagnetic fields and capacitively coupled electrical stimulation are external techniques that require patient compliance but do not have the increased risk associated with implantable devices. Firm conclusions about efficacy are difficult to establish because of inconsistencies in both determining a reliable, reproducible end point for fusion and in incorporating the effect of patient parameters. Most data indicate a positive effect for use of direct current stimulation, but further studies are necessary to determine its appropriateness as an adjuvant to spinal fusion.

    • Keywords:
    • Animals|Electric Conductivity|Electric Stimulation Therapy|Humans|Risk Factors|Spinal Diseases|Spinal Fusion

    • Subspecialty:
    • Spine

    • General Orthopaedics

    • Basic Science

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