Predictors Of Outcome Of Invasive Procedures And Of Disability

Pain management has become more technologically sophisticated and aggressive (and expensive!) in its approach. One of the more common contemporary uses of the psychological evaluation has been to determine the appropriateness of a potential candidate for implantation of a spinal cord stimulator (SCS) or drug delivery system. This is usually based on a set of predetermined, empiric psychosocial characteristics. Nelson and colleagues,36 conducting a meta-analysis of the literature on this topic, concluded that patients should be excluded from implantable spinal cord stimulators if they had evidence of:

• active psychosis;

• untreated major depression;

• somatization disorder;

• alcohol or drug dependency;

• compensation/litigation disincentive to recovery;

• lack of social supports;

• cognitive deficits.

Additional considerations for exclusion include:

• unusual pain ratings or pain drawings;

• personality disorders;

• physical incongruence;

• a high elevation on the Depression scale of the MMPI;

• elevations on four or more MMPI scales.

Doleys et al.,37 however, were not as optimistic about the predictability of these factors. They concluded that there were no definitive multicenter studies that could identify any statistically significant psychological factor or combination of factors that predict outcome. They did indicate that the psychological evaluation is useful if not necessary, but caution about interpreting test data. One of the limiting factors in evaluating the data in these studies is that the definition of SCS success is not standard. One predictive factor they did identify is that serious personality disorder patients are not likely to improve.

Under some circumstances, the MMPI has also been shown to be a very powerful predictor of the success of lumbar surgery. In one study, six MMPI scales administered preoperatively were predictive of surgical outcome in a herniation but not stenosis group.38 In another study, 84 patients evaluated before lumbar discectomy with an objective evaluation system (neurological signs, sciatic-tension signs, MMPI, and lumbar myelography) accurately predicted treatment outcome one year later (accounting for 40 percent of the variance).39[IV] The MMPI was the most powerful predictor of treatment outcome.

Similar to the prediction of success with implantable pumps and stimulators, Block and Callewart40 have developed a presurgical scoring card that predicts surgical success based on three groups of factors.

1. Medical: chronicity of condition, previous spine surgery, smoking, and/or obesity.

2. Psychological interview: litigation, workers' compensation, job dissatisfaction, heavy lifting job, substance abuse, family reinforcers of pain, marital dissatisfaction, abuse, and/or a preinjury psychiatric history.

3. Psychological Testing: elevations on these five MMPI scales (Hs, D, Hy, Pd, Pt), as well as choosing poor coping strategies on the Coping Strategies Questionnaire.

Unresolved traumatic stress can help maintain chronic pain for many years or actually activate physical pain many years later. In a study of 100 spinal surgery patients, of patients who recalled no developmental traumas

(physical, sexual, or emotional abuse, or alcohol/drug abuse in caregiver, or abandonment), 95 percent had a successful postsurgical outcome.41 Only 15 percent of patients who recalled three or more of these traumas/risk factors had a successful postsurgical outcome. Thus, childhood traumas were significantly predictive of surgical success many years later. The authors of this study theorized that for those patients with a history of abuse, surgery is another traumatic event that reactivates the childhood template of abuse. Patients who can be consoled are likely to improve; those who have been psychologically traumatized and are not readily consolable may not improve.

As disability claims are increasing in alarming rapidity, another purpose of the psychological evaluation has arisen: the prediction of the development of disability. Gatchel et al.42 conducted a prospective study of 504 acute low back pain patients to identify work status one year later. A logistic regression analysis identified 91 percent of patients' work status one year later. Patients were more likely not to be at work if they were female, had workers' compensation injuries, scored high on self-reported pain and disablity, and scored high on the "hysteria'' scale of the MMPI.

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