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Tripod index: a new radiographic parameter assessing foot alignment.
Foot Ankle Int. 2013 Oct; 34(10):1411-20.FA

Abstract

BACKGROUND

No single radiographic measurement takes into account complete foot alignment. We have created the Tripod Index (TI) to allow assessment of complex foot deformities using a standing anteroposterior (AP) radiograph of the foot. We hypothesized that TI would demonstrate good intraobserver and interobserver reliability and correlate with currently accepted radiographic parameters, in both flatfoot and cavovarus foot deformities.

METHODS

Three groups of patients were studied: 26 patients (30 feet) with flatfoot, 29 patients (30 feet) with cavovarus foot, and 51 patients (60 feet) without foot deformity as controls. Weight-bearing radiographs were obtained: foot AP with a hemispherical marker around the heel plus standard lateral and hindfoot alignment views. Radiographic measurements were made by 2 blinded investigators. Statistical analysis included intraclass correlation coefficients (ICCs), correlation of the TI with existing radiographic measurements using Pearson coefficients, and comparison between patient groups using analysis of variance.

RESULTS

Intraobserver and interobserver ICCs of TI (0.99 and 0.98, respectively) were excellent. In the flatfoot group, TI significantly correlated with AP talonavicular coverage angle (r = 0.43), medial cuneiform-fifth metatarsal height (r = -0.59), coronal plane hindfoot alignment (r = 0.53), and clinical hindfoot alignment (r = 0.39). In the cavovarus foot group, TI correlated significantly with AP talonavicular coverage angle (r = 0.77), calcaneal pitch angle (r = 0.39), medial cuneiform-fifth metatarsal height (r = -0.65), coronal plane hindfoot alignment (r = 0.55), and clinical hindfoot alignment (r = 0.61). Statistically significant differences between flatfoot-control and cavovarus foot-control were found in TI, AP talonavicular coverage angle, lateral talo-first metatarsal angle, calcaneal pitch angle, medial cuneiform-fifth metatarsal height, coronal plane hindfoot alignment, and clinical assessment of hindfoot alignment (all with P < .001).

CONCLUSION

The TI was demonstrated to be a valid and reliable radiographic measurement to quantify the magnitude of complex foot deformities when evaluating flatfoot and cavovarus foot.

CLINICAL RELEVANCE

The TI may be helpful as an integrated assessment of complex foot deformities. Further clinical studies are recommended.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Authors+Show Affiliations

Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, Iowa, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

23657663

Citation

Arunakul, Marut, et al. "Tripod Index: a New Radiographic Parameter Assessing Foot Alignment." Foot & Ankle International, vol. 34, no. 10, 2013, pp. 1411-20.
Arunakul M, Amendola A, Gao Y, et al. Tripod index: a new radiographic parameter assessing foot alignment. Foot Ankle Int. 2013;34(10):1411-20.
Arunakul, M., Amendola, A., Gao, Y., Goetz, J. E., Femino, J. E., & Phisitkul, P. (2013). Tripod index: a new radiographic parameter assessing foot alignment. Foot & Ankle International, 34(10), 1411-20. https://doi.org/10.1177/1071100713488761
Arunakul M, et al. Tripod Index: a New Radiographic Parameter Assessing Foot Alignment. Foot Ankle Int. 2013;34(10):1411-20. PubMed PMID: 23657663.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Tripod index: a new radiographic parameter assessing foot alignment. AU - Arunakul,Marut, AU - Amendola,Annunziato, AU - Gao,Yubo, AU - Goetz,Jessica E, AU - Femino,John E, AU - Phisitkul,Phinit, Y1 - 2013/05/08/ PY - 2013/5/10/entrez PY - 2013/5/10/pubmed PY - 2013/12/16/medline KW - Tripod Index KW - cavovarus foot KW - flatfoot KW - radiographic parameter SP - 1411 EP - 20 JF - Foot & ankle international JO - Foot Ankle Int VL - 34 IS - 10 N2 - BACKGROUND: No single radiographic measurement takes into account complete foot alignment. We have created the Tripod Index (TI) to allow assessment of complex foot deformities using a standing anteroposterior (AP) radiograph of the foot. We hypothesized that TI would demonstrate good intraobserver and interobserver reliability and correlate with currently accepted radiographic parameters, in both flatfoot and cavovarus foot deformities. METHODS: Three groups of patients were studied: 26 patients (30 feet) with flatfoot, 29 patients (30 feet) with cavovarus foot, and 51 patients (60 feet) without foot deformity as controls. Weight-bearing radiographs were obtained: foot AP with a hemispherical marker around the heel plus standard lateral and hindfoot alignment views. Radiographic measurements were made by 2 blinded investigators. Statistical analysis included intraclass correlation coefficients (ICCs), correlation of the TI with existing radiographic measurements using Pearson coefficients, and comparison between patient groups using analysis of variance. RESULTS: Intraobserver and interobserver ICCs of TI (0.99 and 0.98, respectively) were excellent. In the flatfoot group, TI significantly correlated with AP talonavicular coverage angle (r = 0.43), medial cuneiform-fifth metatarsal height (r = -0.59), coronal plane hindfoot alignment (r = 0.53), and clinical hindfoot alignment (r = 0.39). In the cavovarus foot group, TI correlated significantly with AP talonavicular coverage angle (r = 0.77), calcaneal pitch angle (r = 0.39), medial cuneiform-fifth metatarsal height (r = -0.65), coronal plane hindfoot alignment (r = 0.55), and clinical hindfoot alignment (r = 0.61). Statistically significant differences between flatfoot-control and cavovarus foot-control were found in TI, AP talonavicular coverage angle, lateral talo-first metatarsal angle, calcaneal pitch angle, medial cuneiform-fifth metatarsal height, coronal plane hindfoot alignment, and clinical assessment of hindfoot alignment (all with P < .001). CONCLUSION: The TI was demonstrated to be a valid and reliable radiographic measurement to quantify the magnitude of complex foot deformities when evaluating flatfoot and cavovarus foot. CLINICAL RELEVANCE: The TI may be helpful as an integrated assessment of complex foot deformities. Further clinical studies are recommended. LEVEL OF EVIDENCE: Level III, retrospective comparative study. SN - 1071-1007 UR - https://www.unboundmedicine.com/medline/citation/23657663/Tripod_index:_a_new_radiographic_parameter_assessing_foot_alignment_ L2 - http://journals.sagepub.com/doi/full/10.1177/1071100713488761?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -