[Measurement of radiological parameters and Logistic regression analysis for adult acquired flatfoot]

To evaluate and compare the radiographic parameters between patients of adult acquired flatfoot and normal participants to provide rationales for diagnosis and operative reconstruction.

The adult acquired deformity group consisted of 85 patients (85 feet) and normal group 90 normal participants (90 feet) from January 2008 to May 2014. The weight-bearing anteroposterior and lateral foot radiographs were taken. And the following parameters were measured and compared: medial column length (MCL), lateral column length (LCL), medial column height (MCH), lateral column height (LCH), talonavicular uncoverage angle (TNUA), talus-first metatarsal angle (TMTA) and calcaneal pitch angle (CPA). Age and all parameters were included for Logistic regression analysis.

On anteroposterior radiographs, the values of MCL for adult acquired deformity and normal groups were (103.5 ± 9.0),(105.8 ± 7.8)mm and LCL (94.6 ± 6.9),(96.2 ± 6.1)mm respectively.No significant difference existed in MCL or LCL (P > 0.05).However, significant inter-group differences existed in TMTA and TNUA (P < 0.01). The values of TMTA were (18.9 ± 2.5)°,(7.8 ± 2.2)° and TNUA (23.6 ± 3.2)°,(8.0 ± 2.2)°.On lateral radiographs, significant inter-group differences existed in MCH, LCH, CPA and TMTA (P < 0.01). And the values of MCH were (16.3 ± 1.7),(23.6 ± 2.8)mm, LCH (14.9 ± 1.1),(13.96 ± 1.39)mm, CPA (14.86 ± 2.76)°,(22.9 ± 1.9)° and TMTA (10.0 ± 2.0)°,(-3.6 ± 1.0)° respectively. According to Logistic regression analysis, the significance of parameters ranged from lateral TMTA (B = 0.032), anteroposterior TNUA (B = 0.014), anteroposterior TMTA (B = 0.015) to lateral MCH (B = -0.012), lateral CPA B (B = -0.009).

No differences exist in anteroposterior MCL or LCL. There are positive differences in lateral TMTA, anteroposterior TNUA and anteroposterior TMTA. And negative differences exist in lateral MCH and lateral CPA between adult flatfoot and normal foot. Lateral TMTA may be an excellent radiographic identifier of patients with adult acquired flatfoot during diagnosis and treatment.