Classification of Distal Tibia and Fibula Deformity

Classification of Distal Tibia and Fibula Deformity Doug Beaman, MD Portland , OR Paul Fortin, MD Royal Oak, MI Todd Irwin, MD Ann Arbor, MI Paxton Gehling, BM Portland, OR Disclosure •  DB: Acumed (royalties), Consultant -­‐Smith & Nephew •  PF: Research Grant-­‐MTF; Consultant/Advisor-­‐Stryker, Smith & Nephew, Tornier •  TI: Consultant/Advisor-­‐Smith & Nephew; Board Member/
Committee-­‐AOFAS Background •  Beaman, Domenigoni. Distraction and deformity correction for ankle arthritis. LLRS, Toronto, 2004 •  Workman, Beaman, Gellman. Ankle joint distraction for osteoarthritis: Results and prognostic indicators. Inman lectures, UCSF, 2007 •  Identified 4 deformity patterns: tibia only, fibula only, equal tibia and fibula, unequal tibia and fibula •  Current study: confirm these findings, define a method to evaluate radiographs, assess fibular deformity Methods •  Multi-­‐center retrospective case review •  Inclusion criteria: distal tibia +/-­‐ fibula deformity correction for ankle arthritis ( joint preservation surgery), or symptomatic distal tibia+/-­‐ fibula deformity •  Exclusion criteria: neuroarthropathy, tibial nonunion, osteomyelitis, ankle fusion, TAA, tibial diaphyseal deformity Demographics •  24 patients were identified that met criteria •  19 patients had adequate radiographs •  Age: 8 -­‐ 59 (mean 40.3) •  12 Male, 7 Female •  Diagnoses: 15 ankle arthritis, 12 tibial malunion, 6 congenital deformity, 2 ankle instability, 1 fibula nonunion •  17 standard film radiographs, 2 digital Methods •  Radiographic measurements of both lower extremities: AP and lateral views of ankle to include tibia •  Contralateral limb used as comparison unless deformed •  Measurements within 5 degrees/5mm considered equal Measurements •  AP view (9): LDTA, talocrural angle-­‐TCA, fibular-­‐
transmalleolar angle-­‐FTMA, fibular length, fibular tip to axis length, fibular angle, tibial deformity, CORA level of tibia and fibula •  Lateral view (5): ADTA, fibular angle, tibial deformity, CORA level of tibia and fibula Measurements •  Tibial axes: proximal anatomic axis (2 mid-­‐
diaphyseal points 10 cm apart), distal mechanical axis •  Fibula axes: proximal anatomic axis (2 mid-­‐
diaphyseal points in distal ½), distal anatomic axis based on 2 points (1 cm above plafond, widest point distal to plafond) AP View Measurements Tibial CORA LDTA TCA FTMA Fibular Length Fibular Angle Tip to Axis Length Lateral View Measurements Fibular Angle Fibular CORA Tibial CORA ADTA Classification System •  Type 1= Equal: tibia and fibula aligned equally wrt normal limb •  Type 2=Unequal: mismatch between tibia and fibula alignment wrt normal limb Classification System •  Type 2 (unequal) patterns: –  2a= both bones deformed to different degrees –  2b= tibia only deformity –  2c= fibula only deformity Results: Frequency of Pre-­‐Operative Classifications 6 5 5 5 5 2 were unable to determine due to poor visualization of distal fibula 4 3 2 2 1 0 Eq UnB UnT UnF Results: Correlation of fibular angle to other fibular-­‐
related parameters •  TCA ρ= -­‐.23 •  FTMA ρ= .46 •  Fibular Length ρ= .11 •  Fibular Tip to Axis Length ρ= .76 LDTA •  TCA inversely correlates (ρ= -­‐.65) with Fibular Length. Fibular Length Fib. Tip to Axis Length Fibular Angle FTMA TCA CORA Level in Type 1 AP Results
CORA Level in Type 2a AP 140 100 120 80 100 80 Tib CORA 60 Fib CORA 40 20 60 Tib CORA 40 Fib CORA 20 0 0 -­‐20 1 2 3 4 5 -­‐20 1 2 3 Lateral 4 5 Lateral 90 80 70 60 50 40 30 20 10 0 80 60 Tib CORA Fib CORA 40 Tib CORA 20 Fib CORA 0 -­‐20 1 2 3 4 5 -­‐40 1 2 3 4 Type 1: Equal Tib-­‐fib deformity Type 2a: Unequal tib-­‐fib deformity Type 2b -­‐ Tibia Only Type 2c – Fibula Only Conclusions •  This study demonstrates a simple 4 part classification system for distal tibia and fibula deformity •  Radiographic visualization of the fibula is essential •  Contralateral (normal) X-­‐rays assist in defining fibula alignment Conclusions •  Utilizing fibular anatomic axes was a useful method to describe deformity •  Further study will analyze the effects of this system on surgical planning and clinical results