Lesión anteroposterior del rodete glenoideo superior
La resonancia magnética con sustancia de contraste con gadolinio es efectiva para revelar una lesión anteroposterior del rodete glenoideo superior, pero la evaluación clínica es vital para confirmar el diagnóstico como causa del dolor.
Many shoulder-pain patients present with symptoms suggestive of a superior labrum anterior and posterior (SLAP) lesion. These include pain with specific shoulder positions, pain during overhead activities such as tennis or throwing sports, or impaired shoulder strength. A range of patients with varying ages and activity profiles can experience these symptoms. As a result of the clinical frequency of SLAP-like symptoms, approaches to SLAP lesion management currently generate much discussion, including the possibility of surgical overtreatment.
The rise of magnetic resonance imaging (MRI) with gadolinium dye helped bring more attention to SLAP lesions. These advances made it possible to visualize SLAP lesions preoperatively.
Identifying causal factors
To minimize the risk of overtreatment, renewed effort should be directed toward meticulous execution of the initial clinical exam and correct diagnosis, according to Mayo Clinic orthopedic surgeon Shawn W. O'Driscoll, M.D., Ph.D. "The greatest need right now in the treatment of SLAP lesions is to raise the level of diagnostic certainty that a SLAP lesion is responsible for patients' symptoms, or the substantial contributing factor, and not just a coincidental finding," Dr. O'Driscoll says.
Adds his colleague, Steven J. Hattrup, M.D., of the Department of Orthopedic Surgery at Mayo Clinic in Arizona: "The challenge rests on distinguishing a painful SLAP lesion from an anatomic variation. Degenerative lesions and age-related wear, along with fraying or splitting of the labrum, have to be ruled out. They are not the source of the pain — and, therefore, likely will not benefit from a repair."
Dr. O'Driscoll frames the diagnostic challenge this way: "The basic question we address in our research on improving diagnosis is, how do you determine a SLAP lesion is causing pain, and how do you know a patient with pain has a SLAP lesion?"
SLAP lesion mimics
As imaging continues to improve and more people undergo MRI studies, physicians are finding that a significant percentage of people within the general population have labral changes that do not cause symptoms or need repair. In particular, there are age-related changes that can cause degenerative splits and tears in the labrum. While they may not be symptomatic, visually they can mimic a SLAP lesion. When these appear in MRI studies, misleading assumptions may be made between the images and the patient symptoms.
"Key clinical skills that a practicing orthopedic surgeon needs are familiarity assessing a patient with shoulder pain and a means for determining the presence or absence of a causal relationship among anatomic pathology, symptoms and functional impairment," explains Dr. O'Driscoll. Complicating the task of making the correct SLAP lesion diagnosis is the fact that SLAP lesions can occur as part of other pathologies, such as partial thickness rotator cuff tears or biceps tears.
Dynamic labral shear test
Realización de la prueba dinámica de cizallamiento en el rodete
La maniobra clínica desarrollada por el Dr. O'Driscoll, la prueba dinámica de cizallamiento en el rodete (DLST), se utiliza para diagnosticar una lesión anteroposterior del rodete glenoideo superior (SLAP). El paciente se debe colocar en posición de decúbito supino y el brazo afectado debe estar fuera de la camilla de exploración. El hombro debe permanecer cerca del borde de la camilla, de modo que el colchón de la camilla de exploración sostenga el omóplato, pero el húmero quede en el aire.
To raise the level of diagnostic certainty when a SLAP lesion is suspected, Dr. O'Driscoll has developed a clinical maneuver, the dynamic labral shear test (DLST). The DLST reproduces the shearing mechanism that can cause a SLAP tear. Easy to perform in the exam room, the DLST yields reliable results that isolate a SLAP lesion's causal role in symptoms and impaired function.
To prepare for the DLST, the patient is supine and relaxes the affected arm off the side of the examining table. The shoulder is close to the edge of the bed so that the examining table mattress supports the scapula, but the humerus is free.
Performing the DLST
For the right shoulder, with the arm at the side, the examiner flexes the right elbow 90 degrees and grasps the olecranon and distal humerus with his or her left hand. This hand is used to maintain 90 degrees of elbow flexion, passively rotate the shoulder externally to its natural limit with the force of gravity alone pulling down on the forearm, drop the elbow back into its natural limit of horizontal abduction (toward the floor), and passively elevate the shoulder while maintaining both the horizontal abduction and the external rotation at their natural limits under gravitational force alone.
During elevation of the shoulder, the magnitude of horizontal abduction will vary and must be permitted to do so without constraint. Similarly, the degree of external rotation will also vary throughout the arc of elevation and must be unconstrained. While the shoulder is being elevated in the manner just described, the examiner's right hand is kept on the acromion to stabilize the scapula and to detect any palpable click transmitted through the bony structures. The click will usually be felt by the left hand on the olecranon, as well as the distal humerus. After full overhead elevation, the entire motion is reversed and the arm is brought down to the side while the natural limit of shoulder external rotation and horizontal abduction is maintained.
Interpretación de resultados
La prueba dinámica de cizalladura del labrum ayuda a los profesionales clínicos de la salud a diagnosticar lesiones del labrum superior anterior y posterior (SLAP), ya que permite establecer, durante el examen clínico, una conexión causal entre los síntomas del paciente en el hombro y la lesión en el labrum. Es importante tener en cuenta que la prueba se debe realizar con suavidad, para evitar lastimar a un paciente que presente indicios de tener una lesión SLAP.
Interpreting the results requires skill and experience with the maneuver and its physiologic effects.
In a preliminary report to the American Academy of Orthopaedic Surgeons in 2007, Dr. O'Driscoll's team reviewed 105 shoulders, comparing DLST, magnetic resonance imaging and arthroscopy to diagnose SLAP lesions. The Mayo Clinic team found sensitivity for diagnosing a type II SLAP lesion by DLST was 0.86 (95 percent confidence interval, 0.75-0.93). This level was as good as MRI with gadolinium, and better than MRI without gadolinium contrast dye. A negative DLST indicates that either there is no SLAP lesion or, if there is, it is asymptomatic.
Comments Dr. O'Driscoll: "Since using that test over a number of years, it has proved to be more reliable than MRI or arthroscopic findings in determining whether the patient's symptoms are caused by SLAP lesions. It comes back to something we learn in orthopedics very early: Often the clinical assessment of the patient is the most reliable way to determine what is causing the pain. The imaging certainly helps us understand the pathology responsible for the pain, but the clinical exam establishes causality."