A Descriptive Study of the Centralization Phenomenon: A Prospective Analysis.

A Descriptive Study of the Centralization Phenomenon: A Prospective Analysis Werneke M, Hart DL, Cook D (NovaCare at Southern Ocean Center for Health, Forked River, NJ; Focus on Therapeutic Outcomes Inc, Great Falls, Va; Automotive Motors at Thomasville, Thomasville, NC), Spine. 1999;24:676-683.

The authors studied the occurrence and treatment responses of the centralization phenomenon (CP) in 289 patients with acute neck and back pain. They sought to standardize the operational definition of CP, determine the occurrence of CP in patients with acute neck and back pain, quantify the reliability of categorizing patients into 3 pain-pattern groups, and determine if there is a difference in clinical outcomes among pain-pattern groups. The authors tested the following hypotheses: (1) The occurrence of the centralization pain pattern will be substantially less than the occurrence of CP previously reported, (2) the 3 pain-pattern groups can be reliably distinguished, and (3) the centralization pain-pattern group will have better outcomes than those of the other 2 groups.

Patients were categorized into 1 of 3 groups: a centralization group, a noncentralization group, and a partial reduction group. The centralization group was defined by specific criteria, including the fact that certain clinical interventions caused the location of pain to move progressively from a more distal to a more central location during successive visits. In the noncentralization group, either no changes in the location of pain occurred, or the location of pain changed from a central to a more distal location. In the partial reduction group, the location of pain changed from a more distal to a more central location during each visit without a progressive movement, the initial pain location moved toward the mid-line at consecutive visits, and no change in pain location occurred during any one visit but the patient had a gradual decrease in pain over subsequent visits. The 3 pain pattern groups were inclusive and mutually exclusive.

The 289 patients in the study group met the following criteria: 18 to 65 years of age, a diagnosis of neck or low back pain with or without referral, a physician referral for conservative treatment, and symptoms of less than 6 weeks' duration. The majority of the subjects were on workers' compensation and were unable to resume full duty. Twenty-three percent of the subjects reported cervical pain, and 77% reported low back pain. The average duration of symptoms was 13 days. Five physical therapists participated in the study, and the same therapist examined and treated each patient. Three therapists had 15 to 20 years of clinical experience and the other 2 therapists had 5 to 7 years of experience. All therapists were trained in the McKenzie method, and 3 therapists received certificates from the McKenzie Institute.

At the initial visit, each patient completed a body diagram, a pain intensity scale, and an Oswestry Low Back Disability Questionnaire or a neck disability index questionnaire. Each patient received a mechanical evaluation following McKenzie assessment methods. Subsequent visits were scheduled at 24- to 48-hour intervals. Exercises and manual techniques were implemented according to pain responses from repeated end-range movement tests or positioning techniques. Movements associated with centralization identified the direction of exercises. Therapeutic modalities were provided on a limited basis at the therapist's discretion.

Agreement of the therapists who were assessing the coding of location of distal pain and agreement between the therapists who were classifying the patients into pain patterns were quantified using a Cohen's kappa weighted for chance. Differences between each independent variable were analyzed by a [chi square] statistic or by a 1-way ANOVA. The effect of each independent variable on the dependent variables of visits and change scores for pain and perceived function were assessed via a 1- or 2-way ANOVAs with Scheffe post hoc analysis.

The authors found that patients could be categorized reliably according to their movement signs and symptoms. The centralization pain-pattern group had significantly fewer visits than the other 2 groups. Subjects in the centralization group averaged 3.9 visits, whereas subjects in the noncentralization and partial reduction groups averaged 8 and 7.7 visits respectively. There was no difference in visits between the partial reduction and the noncentralization groups. Pain intensity rating and perceived function scores were statistically different between the centralization and the noncentralization groups. However, no difference in treatment response existed between the centralization and partial reduction groups. Frequency of assignment to a pain-pattern group was similar for patients with neck and back pain. The centralization group was assigned to 30.8% of the subjects, the noncentralization group to 23.2% of the subjects, and the partial reduction group to 46%.

According to the authors, the finding that the centralization pain pattern occurred in 30% of the patients was considerably lower than previous studies, which supported the authors' first hypothesis. They believed that centralization and partial reduction pain patterns were equally common and that both were associated with good treatment results. According to the authors, if a reduction in pain location score was not observed by the seventh visit, no further improvements in pain and perceived function were noted.

William J Barnes, PT Lincoln Physical Therapy Associates and Work Adjustment Center, PC Lincoln, Neb