Improvement of femoral head roundness after valgus femoral osteotomy in Legg-Calve-Perthes disease Hui Taek Kim, MD and Seong Ho Bae, MD Pediatric Orthopaedic Unit Department of Orthopaedic Surgery Pusan National University Hospital

Introduction Deformation of the femoral head in Legg-Calve-Perthes disease (LCPD) • Latter in fragmentation or early in regeneration stage Best time to perform surgery • Avascular necrosis and fragmentation stage

Introduction Containment of the affected femoral head • Abduction brace • Soft tissue release and/or varus femoral osteotomy • Salter innominate osteotomy The results are frequently poor • > 8 years old • Uncontained femoral head and hinge abduction

Introduction Valgus femoral osteotomy (VFO) • Relieves hinge abduction • Provides better functional range of movement by rotating the less affected femoral head into weight bearing position

Purpose To quantify the changes of femoral head roundness after valgus femoral osteotomy • Using new measuring method

Materials and Methods

48 children Group 1: non-operative Tx. (25 hips) Materials and Methods 48 children • September 1997 to January 2006 Group 1: non-operative Tx. (25 hips) • 21 hips in pillar B (19 > 8 yrs old) • 4 hips in pillar C (2 > 8 yrs old ) Group 2: treated by VFO (23 hips) • 7 hips in pillar B (3 > 8 yrs old) • 16 hips in pillar C (7 > 8 yrs old)

Overall patient age was 8.3 years Materials and Methods Overall patient age was 8.3 years • Group 1 : 8.7 years • Group 2 : 8.1 years Chiari OT : 10.2 years (3 cases) Triple innominate OT : 6.5 years (2 cases) Male : 43 Female : 5 Mean follow-up period : 6.4 years

Soft tissue release or shortening (×) Materials and Methods Indications for VFO • Hip pain • Decreased range of motion • Hinge abduction on MRI and arthrography • Significant deformity of the femoral head Open wedge type Soft tissue release or shortening (×)

Femoral head roundness Materials and Methods Femoral head roundness • Roundness of the lateral third (RLT) • Roundness of the medial third (RMT) • Maximal epiphyseal height in middle third (MEH) • Ratio of radii of curvature of the medial third over the lateral third (RML)

Materials and Methods Radiograph and MRI were taken at the same time (fragmentation stage) MRI enables the visualization of the cartilaginous femoral head

Materials and Methods Measuring methods

Image-analysis software Materials and Methods Most clear image • Entire proximal femur • Fragmentation stage in MRI / residual stage in AP radiograph Image-analysis software • Adobe Photoshop • Microsoft Power Point

Drawing • Femoral shaft axis • Femoral neck axis • Femoral head waist Materials and Methods Drawing • Femoral shaft axis • Femoral neck axis • Femoral head waist • Radius of circle in lateral and medial third of femoral head (RLT and RMT) • Maximal epiphyseal height (MEH) in middle third

First step Materials and Methods • Magnification • Medial aspect of the femoral head and calcar # Medial aspect of the femoral head and calcar are minimally affected during disease process

Second step Materials and Methods • Femoral shaft and neck axis • The most superolateral and inferomedial point of femoral head • Base line a′ A’ a A

Third step Materials and Methods • Divide the base line into thirds • Draw lines parallel to the femoral neck axis through 2 points b′ a′ A’ B’ ‖ ‖ b ‖ B ‖ ‖ ‖ a A

Final step Materials and Methods • Best fitting circle passing a′(A′) and b′(B′) placing the center of circle to the median of the line connecting a′(A′) and b′(B′) ┐ b′ a′ A’ B’ b B r R a A RLT # Definition of circle : The set of all points in a plane which are equidistant from a given point (center of circle)

Materials and Methods The ratio of maximal epiphyseal height (MEH) to the waist of the femoral head • Subchondral bone instead of articular cartilage (in MRI) b′ a′ A’ B’ b B W W a A MEH

Materials and Methods Differential coefficient is decreased as the point of contact moves toward middle portion in ellipse Maximal epiphyseal height represent more effectively the head growth or roundness in the middle third

Final data analysis Materials and Methods • Relative change of RLT (%) = × 100 (%) r – R r ┐ b′ a′ A’ B’ b B r R a A RLT # Definition of circle : The set of all points in a plane which are equidistant from a given point (center of circle)

Final data analysis Materials and Methods • Relative change of MEH (%) = × 100 (%) m – M m b′ a′ A’ B’ b B W W a A MEH

Amount of collapse in lateral portion of deformed femoral head # RML = ROC in medial 1/3 / ROC in lateral 1/3 (Rm / RL) r R R’ r’ ROC in lateral third : r ROC in medial third : r’ The ratio of ROC (RML) : r’/r ROC in lateral third : R ROC in medial third : R’ The ratio of ROC (RML) : R’/R D. Nelson, M. Zenios, K. Ward et al, JBJS 2007 * ROC : Radius Of Circle

Final Stulberg classification Materials and Methods Final Stulberg classification

Results

Measurements Group 23 21.4 7.8 0.65 → 0.81 (0.16) Total RLT (%) MEH (%) RML (△) All hips Nonoperative 25 13.2 3.9 0.74 → 0.84 (0.10) Operative 23 21.4 7.8 0.65 → 0.81 (0.16) 48 Comparison of each value : p < 0.05 by paired t-test

Comparison of each value : p < 0.05 by paired t-test Measurements Group Total RLT (%) MEH (%) RML (△) Lateral pillar group B 28 15.0 4.5 0.76 → 0.88 (0.12) Chron. Age ≤ 8.0 at disease onset Nonoperative 19 16.8 0.76 → 0.90 (0.14) Operative 4 10.2 3.5 0.74 → 0.82 (0.08) 23 Chron. Age > 8.0 at disease onset 2 5.5 4.4 0.82 → 0.88 (0.06) 3 16.7 5.6 0.73 → 0.84 (0.11) 5 Comparison of each value : p < 0.05 by paired t-test

Comparison of each value : p < 0.05 by paired t-test Measurements Group Total RLT (%) MEH (%) RML (△) Lateral pillar group C 26.6 9.6 0.59 → 0.78 (0.19) Chron. Age ≤ 8.0 at disease onset Nonoperative 2 17.4 2.7 0.70 → 0.81 (0.11) Operative 9 31.2 12.5 0.53 → 0.76 (0.23) 11 Chron. Age > 8.0 at disease onset 13.2 4.0 0.69 → 0.78 (0.09) 7 27.3 9.4 0.61 → 0.80 (0.19) 20 20 Comparison of each value : p < 0.05 by paired t-test

Final Stulberg classifications Results Final Stulberg classifications II III Group 1 (n=25) 10 15 Group 2 (n=23) 4 19 p = 0.09 by Pearson chi-square test

Conclusions

Femoral head roundness was improved Conclusions Femoral head roundness was improved with ossification of the affected hip More round femoral head can be expected in the lateral pillar B hips than pillar C

However, VFO performed in the Conclusions However, VFO performed in the fragmentation stage of lateral pillar C hips leads to greater improvement in femoral head roundness than does non-surgical treatment of lateral pillar B hips

Case 1 M/7+3 Group 1

RMT 5.08 5.02 1%

RLT 8.04 6.00 25%

MEH 1.68/4.75 1.78/4.76 6%

RML 5.08/8.04 = 0.63 5.02/6.00 = 0.84 0.21

Case 2 M/10+0 Group 2

RMT 5.80 5.30 9%

RLT 9.29 6.34 32%

MEH 1.80 2.10 17%

RML 5.80/9.29 = 0.62 5.30/6.34 = 0.84 0.22

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