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Cluster analysis as a method for determining size ranges for spinal implants: disc lumbar replacement prosthesis dimensions from magnetic resonance images.

Dang Lei·Roger L Holder·Francis W Smith·Douglas Wardlaw·David W L Hukins
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Abstract

STUDY DESIGN: Statistical analysis of clinical radiologic data. OBJECTIVE: To develop an objective method for finding the number of sizes for a lumbar disc replacement. SUMMARY OF BACKGROUND DATA: Cluster analysis is a well-established technique for sorting observations into clusters so that the "similarity level" is maximal if they belong to the same cluster and minimal otherwise. METHODS: Magnetic resonance scans from 69 patients, with no abnormal discs, yielded 206 sagittal and transverse images of 206 discs (levels L3-L4-L5-S1). Anteroposterior and lateral dimensions were measured from vertebral margins on transverse images; disc heights were measured from sagittal images. Hierarchical cluster analysis was performed to determine the number of clusters followed by nonhierarchical (K-means) cluster analysis. Discriminant analysis was used to determine how well the clusters could be used to classify an observation. RESULTS: The most successful method of clustering the data involved the following parameters: anteroposterior dimension; lateral dimension (both were the mean of results from the superior and inferior margins of a vertebral body, measured on transverse images); and maximum disc height (from a midsagittal image). These were grouped into 7 clusters so that a discriminant analysis was capable of correctly classifying 97.1% of the observations. The mean and standard deviations for the parameter values in each cluster were determined. CONCLUSIONS: Cluster analysis has been successfully used to find the dimensions of the minimum number of prosthesis sizes required to replace L3-L4 to L5-S1 discs; the range of sizes would enable them to be used at higher lumbar levels in some patients.

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AdultAgedCluster AnalysisHumansIntervertebral DiscLumbar VertebraeMagnetic Resonance ImagingMiddle AgedProstheses and ImplantsProsthesis ImplantationComparative StudyJournal ArticleResearch Support, Non-U.S. Gov't

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Dang Lei, Roger L Holder, Francis W Smith, Douglas Wardlaw, David W L Hukins. 2006-12-01. Cluster analysis as a method for determining size ranges for spinal implants: disc lumbar replacement prosthesis dimensions from magnetic resonance images.. https://doi.org/10.1097/01.brs.0000248414.62802.42

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