Gradual　correction　using　external　fixator　has　been　advocated　as　a　minimally　invasive　solution　for　limb　deformity　and　is　widely　used　in　the　clinic.　This　treatment　manner　requires　a　long-term　distraction　process,　which　is　guided　by　a　preplanned　correction　path.　However,　bone　cross-section　(BCS)　collision　and　soft　tissue　(ST)-distraction　rod　(DR)　collision　may　occur　on　the　path　and　then　affect　the　continuity　of　the　process.　Thus,　collision　detection　should　be　carried　out　before　performing　distraction.　Existing　detection　solutions　do　not　simultaneously　consider　these　two　types　of　collisions,　and　primarily　target　long-bone　deformity.　To　solve　these　issues,　taking　more　complex　foot　and　ankle　deformity　as　the　research　object,　a　novel　analytical　detection　approach　is　proposed　in　this　paper.　By　modelling　the　contours　of　BCS,　ST,　and　DRs　as　convex　envelope　planes/bodies　using　different　spatial　line　styles,　the　spatial　posture　relations　of　their　boundaries　can　be　reproduced　on　the　correction　path,　and　collision　detection　can　be　transformed　into　the　mathematical　problem　of　calculating　point-plane　and　point-line　distances.　Subsequently,　two　algorithms　are　proposed　for　BCS　and　ST-DR　collision　detections,　and　adjustment　strategies　are　provided　to　resolve　algorithm　anomalies.　Clinical　case　simulation　proves　the　effectiveness　and　applicability　of　the　approach.　Since　the　detection　is　used　for　pre-distraction　prediction　rather　than　real-time　monitoring,　the　correction　path　with　potential　collision　risk　can　be　re-planned　before　distraction,　and　finally,　guarantees　the　safety　of　gradual　correction.　©　2022