Femoral Lengthening in Achondroplasia - Magnitude of lengthening versus Callus Feature, Stiffness of adjacent joints and fracture Prof. Hae Ryong Song Dr.Ji Yeol Yoon Dr. Jae Woo Cho Department of orthopaedic surgery, Institute of Rare Disease, Guro Hospital, Seoul, Korea

Introduction Extensive limb lengthening  more complications Extensive limb lengthening  more complications (Dahl MT et CORR1994) (Dahl MT et CORR1994) Joints stiffness and fractures Joints stiffness and fractures Fx. (20%) and knee joint stiffness (26%) Fx. (20%) and knee joint stiffness (26%) Lengthened by 20% (Yun et al. JPO 2000) Lengthened by 20% (Yun et al. JPO 2000) Fx. (27%) and knee joint stiffness (65%) Fx. (27%) and knee joint stiffness (65%) :lengthened by 24% (Karger et al 6 CORR 1993) :lengthened by 24% (Karger et al 6 CORR 1993)

Materials and methods 40 femoral lengthening in achondroplasia 40 femoral lengthening in achondroplasia Group A: less than 50% lengthening Group A: less than 50% lengthening Group B: more than 50% lengthening Group B: more than 50% lengthening Comparison parameters Comparison parameters Callus feature ; Ru Li classification Callus feature ; Ru Li classification Hip and Knee stiffness Hip and Knee stiffness refracture refracture

PARAMETERS Shape of callus Shape of callus Feature type of callus Feature type of callus Density of callus using pixel value Density of callus using pixel value fusiform cylindrical concave lateral central

Femoral Lengthening in Achondroplasia: Magnitude of lengthening versus Callus Feature, Stiffness of adjacent joints and Fracture. Fusiform, cylinder, concave, lateral, central

Ru Li et al ’ s classification of callus types PatternLow density Intermediate densityNormal density Sparse Type 1 (soft) Type 5 (half tone) Homogeneous Type 2 (stripe ) Type 6 (uniform) Type 9 (solid) Heterogeneous Type 3 (speckle) Type 7 (irregular) Type 10 (cyst defects) Lucent Type 4 (adjacent) Type 8 (saw tooth)

RU- LI CLASSIFICATION

A. Type 1 (sparse low density) B. Type 2 (homogeneous low density C. Type 3 (heterogeneous low density) D. Type 4 (lucent low density) E. Type 5 (sparse intermediate density) Ru Li et al classification of callus as feature Ru Li et al classification of callus as feature

F. Type 6 (homogeneous intermediate density) G. Type 7 (heterogeneous intermediate density H. Type 8 (lucent intermediate density I. Type 9 (homogeneous normal density J. Type 10 (heterogeneous normal density) Ru Li et al classification of callus as feature Ru Li et al classification of callus as feature

Different pathways that the regenerate takes to mature 1. homogeneous pathway : type 2 → type 6 → type 9 2. heterogeneous pathway : type 3 → type 7 → type 10 3.The lucent pathway : types 4 and 8 : types 4 and 8

Hip flexion contracture and knee extension stiffness

Callus features of regenerate fracture cases in femoral lengthening in achondroplasia. Material and methods 28 cases of femoral lengthening in 14 patients, 28 cases of femoral lengthening in 14 patients, 14 cases of callus fracture: 14 cases of callus fracture: mean lengthening; 9.4 cm, 41% (range 30-55%) mean lengthening; 9.4 cm, 41% (range 30-55%) average timing of callus fracture at 15 months after surgery average timing of callus fracture at 15 months after surgery 14 case of without callus fracture 14 case of without callus fracture 9.1 cm, 30% 9.1 cm, 30%

Central shape callus -- Refracture after removal of fixation

Flexible nailing and bone grafting

Refracture after removal of fixation

Fixation with plate and bone grafting Post opPostop 2 months

Conclusion Fracture & Joint stiffness is a true complication Fracture & Joint stiffness is a true complication  All Fx. : Lucent pathway (concave, lateral, atypical)  30%↑ lengthening & 48%↑ reduction of callus width In our opinion, it is better to stop the distraction or to give gradual compression distraction whenever there is occurrence of concave, lateral and central shapes till the appearance of the satisfactory regenerate