Does metatarsus primus elevatus really exist in hallux rigidus? A weightbearing CT case-control study.

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Citation: Archives of Orthopaedic & Trauma Surgery. 2021 Sep 09PMID: 34505168Institution: MedStar Union Memorial HospitalDepartment: Orthopaedic SurgeryForm of publication: Journal ArticleMedline article type(s): Journal ArticleSubject headings: IN PROCESS -- NOT YET INDEXEDYear: 2021ISSN:
  • 0936-8051
Name of journal: Archives of orthopaedic and trauma surgeryAbstract: BACKGROUND: Elevated first metatarsal, Metatarsus primus elevatus (MPE), has been a topic of controversy. Recent studies have supported a significantly elevated first metatarsal in hallux rigidus on weight-bearing radiographs (WBR). However, conventional radiographs have limitations for accurate measurement. Our objective was to comparatively assess MPE and other variables which can affect the spatial relationship of the forefoot in the HR group compared to controls using weight-bearing CT (WBCT).CLINICAL RELEVANCE: The present study demonstrated significantly increased MPE in HR on WBCT and MPE greater than 4.19 mm on WBCT can be used as a diagnostic threshold for HR. Copyright (c) 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.CONCLUSION: Our results confirmed a significantly elevated first metatarsal in the HR group compared to controls on WBCT. A MPE greater than 4.19 mm was found to be diagnostic for symptomatic HR. Significant number of patients in the HR group (70%) had dorsal translation of the first metatarsal at the first TMT joint which can contribute to increased MPE.METHODS: In this single-center, retrospective, case-control study, 25 patients (30 feet) with symptomatic HR and 30 controls were selected. WBCT parameters were measured by two independent investigators. Inter-observer reliabilities were assessed using intra-class correlation coefficients (ICCs). MPE was evaluated by measuring the direct distance between 1st and 2nd metatarsals. Independent t tests were performed to compare the two groups. A threshold of MPE to diagnose HR was calculated using the Receiver Operating Characteristic (ROC) curve.RESULTS: HR groups had increased hallux valgus angle (HVA) (8.52degree in control vs 11.98degree in HR) and MPE (2.92 vs 5.09 mm), decreased 1st metatarsal declination angle (21.09degree vs 19.07degree) 1st/2nd metatarsal declination ratio (87.45 vs 79.71) indicating elevated first metatarsal compared to controls. Dorsal translation of the first metatarsal at the first tarsometatarsal joint was observed in 21 (70%) patients of the HR group when defined as a step-off or discontinuation of the curvature along the first TMT joint. The threshold of MPE for diagnosis of HR was 4.19 mm with 77% sensitivity and 77% specificity.All authors: de Cesar Netto C, Godoy-Santos A, Hembree WC, Iehl CJ, Lalevee M, Lee HY, Maly C, Mansur NSFiscal year: FY2022Digital Object Identifier: Date added to catalog: 2021-11-01
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Journal Article MedStar Authors Catalog Article 34505168 Available 34505168

BACKGROUND: Elevated first metatarsal, Metatarsus primus elevatus (MPE), has been a topic of controversy. Recent studies have supported a significantly elevated first metatarsal in hallux rigidus on weight-bearing radiographs (WBR). However, conventional radiographs have limitations for accurate measurement. Our objective was to comparatively assess MPE and other variables which can affect the spatial relationship of the forefoot in the HR group compared to controls using weight-bearing CT (WBCT).

CLINICAL RELEVANCE: The present study demonstrated significantly increased MPE in HR on WBCT and MPE greater than 4.19 mm on WBCT can be used as a diagnostic threshold for HR. Copyright (c) 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

CONCLUSION: Our results confirmed a significantly elevated first metatarsal in the HR group compared to controls on WBCT. A MPE greater than 4.19 mm was found to be diagnostic for symptomatic HR. Significant number of patients in the HR group (70%) had dorsal translation of the first metatarsal at the first TMT joint which can contribute to increased MPE.

METHODS: In this single-center, retrospective, case-control study, 25 patients (30 feet) with symptomatic HR and 30 controls were selected. WBCT parameters were measured by two independent investigators. Inter-observer reliabilities were assessed using intra-class correlation coefficients (ICCs). MPE was evaluated by measuring the direct distance between 1st and 2nd metatarsals. Independent t tests were performed to compare the two groups. A threshold of MPE to diagnose HR was calculated using the Receiver Operating Characteristic (ROC) curve.

RESULTS: HR groups had increased hallux valgus angle (HVA) (8.52degree in control vs 11.98degree in HR) and MPE (2.92 vs 5.09 mm), decreased 1st metatarsal declination angle (21.09degree vs 19.07degree) 1st/2nd metatarsal declination ratio (87.45 vs 79.71) indicating elevated first metatarsal compared to controls. Dorsal translation of the first metatarsal at the first tarsometatarsal joint was observed in 21 (70%) patients of the HR group when defined as a step-off or discontinuation of the curvature along the first TMT joint. The threshold of MPE for diagnosis of HR was 4.19 mm with 77% sensitivity and 77% specificity.

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