A survey of the McKenzie Classification System in the Extremities : prevalence of mechanical syndromes and preferred loading strategies

Background: Classification of patients with extremity problems is commonly based on patho-anatomical diagnoses, but problems exist regarding reliability and validity of the tests and diagnostic criteria used. Alternatively, a classification system based on patient response to repeated loading strategies can be used to classify and direct management.

Objective: The purpose of this study was to investigate the prevalence of McKenzie's classification categories among patients with extremity problems and the loading strategies used in their management.

Design: This was a prospective, observational study.

Methods: Thirty therapists among 138 invited (response rate=22%) with a Diploma in Mechanical Diagnosis and Therapy (MDT) were identified from the McKenzie Institute International registry and recruited worldwide to complete an e-mailed questionnaire. They provided data about their age, years qualified, years since gaining a diploma, and practice, and prospectively provided data on anatomical site and categorization for 15 consecutive patients with extremity problems.

Results: Data were gathered on 388 patients; classification categories were as follows: derangement (37%); contractile dysfunction (17%); articular dysfunction (10%); and “other” (36%), of which 20% were postsurgery or posttrauma. Exercise management strategies and syndrome application varied considerably among anatomical sites. Classification categories remained consistent in 85.8% of patients over the treatment episode.

Limitations: These findings are not generalizable to therapists who are not experienced with use of MDT in the extremities.

Conclusions: This study demonstrates that trained clinicians can classify patients with extremity problems into MDT classifications and that these classifications remain stable during the treatment episode. Further work is needed to test the efficacy of this system compared with other approaches, but if derangements are as common as this survey suggests, the findings have important prognostic implications because this syndrome is defined by its rapid response to repeated movements.