Clinical Prediction Rule Segmental Spinal Stabilization

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Agatha Conley
7 years ago
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1 Clinical Prediction Rule Segmental Spinal Stabilization Clinical prediction rules (CPR) are simply tools to assist clinicians in the decision-making process. They are an adjunct to the clinical reasoning skills that all therapists should be striving to develop and fine-tune. CPR s can improve diagnostic accuracy or predict outcome. They should represent information that can be readily applied by the clinician in the diagnosis of the problem within their patient, or in the prediction of the most likely outcome to an appropriate intervention. Some readily applicable examples of CPR s in the medical literature include: CPR s for: o Accuracy of diagnosing ankle fractures (Stiell, Ann Emerg Med, 1992) o Likelihood of death in coronary disease (Mark, N Eng J Med, 1991) o Diagnosis of cervical radiculopathy (Wainner, Spine, 2003) o When to order cervical radiographs (Stiell, JAMA, 2001) Perhaps the most readily recognizable CPR within orthopedic manual therapy is the manipulation CPR, that is, the CPR for patients with low back likely to experience dramatic improvement with spinal manipulation (Flynn et al, 2002; Childs et al, 2004). Hicks et al (2005) developed a CPR for determining which patients with low back pain would respond to a stabilization exercise program. Similar to the previously reported CPR for manipulation for low back pain, they conducted a prospective, cohort study of patients with non-radicular LBP referred to physical therapy (PT). Subjects were recruited from 3 outpatient PT clinics located in the Pittsburgh, PA, area or the outpatient PT clinic at Keesler Air Force Base Medical Center (Biloxi, MS). Eligibility: All new patients with complaints of LBP, with or without leg pain, over the age of 18 were eligible for participation. Exclusion criteria: previous spinal fusion surgery; LBP attributable to current pregnancy; acute fracture, tumor, or infection; and presence of 2 or more of the following signs of nerve root compression: diminished lower-extremity strength, sensation, or reflexes. 1

2 Methods: At baseline, 54 subjects were evaluated by the treating physical therapist and the evaluation consisted of the collection of basic demographic information, subject selfreport measures, questions of history, and physical examination measures. Then, regardless of the evaluation/ examination data collected, all 54 subjects took part in an 8 week (2 times per week) standardized stabilization exercise program. It is important to note that minimal attention was paid to developing the deep corset action (transversus abdominus and lumbar multifidus) and the program emphasized strengthening rather than motor control. As the table below shows, the aim was for co-contraction among all spinal stabilizing muscles. Outcome analysis: The Oswestry Low Back Disability Questionnaire (ODQ) was assessed at baseline and after 8 weeks of treatment and served as the reference standard for determining the success of the treatment program. Success was operationally defined as a percentage change of 50% or greater on the ODQ. Results: The study reported 18 out of the 54 (33.3%) demonstrated success with the stabilization exercise program. Therefore, the pre-test probability for success with stabilization was 33%. They then looked at all the variables (examination items both subjective history and objective measurements) and ran multivariate analyses to determine which set of variables were predictive of success. The items most predictive of success were: Age less than 40 years Positive prone instability test Presence of aberrant spinal movements Average straight leg raise > 91 2

3 By using the sensitivity, specificity and positive likelihood ratios, the researchers were able to determine that the presence of at least 3 of the 4 predictors provided a positive likelihood ratio (+LR) of only 4.0 indicating that the presence of the predictor variables had only a moderate effect on the outcome. Given the pre-test probability of success with stabilization was determined to be 33.3%, the +LR of 4.0 was only able to increase the post-test probability of success with stabilization to 67%. This was obviously not as dramatic a post-test probability of 95% for the manipulation CPR. Clinical Prediction Rule 3 or more present: + prone instability test 33% aberrant movement present Average SLR > 91º Age < 40 yrs 67% Pre-test Probability of Success +LR = 4.0 Post-test Probability of Success 44 3

4 The researchers decided to further operationalize the outcomes by classifying subjects who experienced at least 6 points improvement on their ODQ but less than a 50% improvement as improved with stabilization. Subjects who experienced a worsening in their ODQ (increased points) or less than a 6 point improvement were classified as failure. By classifying the 54 subjects into these three outcomes, success, improvement and failure, they were able to determine that they had 18 (33.3%) in the success group, 21 (38.9%) in the improved group and the remaining 15 (27.8%) in the failure group. The table below demonstrates the ODQ scores at baseline (initial) and after 8 weeks of the stabilization exercises (final). The researchers decided to evaluate the negative likelihood ratio (-LR) because this statistic represented the change in odds favoring the condition of interest (some improvement with stabilization) when the criteria of the prediction rule were not met. In their study, the prevalence of some success (improvement) with stabilization was 72% (33.3% %). The post-test probability of improvement with stabilization for a patient with fewer than 2 of the 4 predictor variables in the clinical prediction rule (negative LR,.18) would be reduced to 32%, indicating that such a subject would more likely benefit from an alternative treatment approach. Another way of looking at this was that the +LR for this criterion (improvement) was 6.3 and increases the likelihood of experiencing at least some improvement from 72% to 94%. When a cutoff score of 3 or more positive findings was used, the +LR increased to 18.8, thereby increasing the probability of experiencing some improvement from 72% to 97% when 3 or more variables were present. 4

5 Clinical Prediction Rule 3 or more present: + prone instability test 72% aberrant movement present Hypermobility with lumbar spring test 97% FABQ physical activity subscale score 9 Pre-test Probability of Some Improvement +LR = 18.8 Post-test Probability of Some Improvement 45 Fritz et al (2007) in their clinical commentary on the evolution of the Classification Approach to Physical Therapy (Delitto Classification Based Treatment) noted that the CPR for spinal stabilization demonstrated greater accuracy for identifying patients who were not likely to receive even minimal benefit (5 or fewer points of improvement on the Oswestry) from a stabilization intervention. 5

6 There were 4 factors predictive of failure: negative prone instability test, absence of aberrant movements during sagittal plane lumbar ROM, absence of lumbar hypermobility (assessed with posterior-to-anterior pressure), a score of 9 or higher on the FABQ physical activity subscale. As noted previously, the presence of at least 3 of these findings was highly predictive of failure (positive LR, 18.8), indicating that if a patient was presumed to have a 25% probability of failing, the presence of at least 3 of these factors would increase the probability of failure to 86%. Therefore, the CPR for stabilization exercises appears to have been developed more successfully for predicting those patients who will not likely improve with such exercises rather than those that would. 6

Selkäkipu ajoissa hallintaan kliiniset testit terapian perustana

Selkäkipu ajoissa hallintaan kliiniset testit terapian perustana Markku Paatelma Auron OMT Keskus Helsinki, Finland What is a clinical reasoning? With the expanding roles of physiotherapists and greater