Three Dimensional Reconstruction And Measurement Of The Proximal Femur In Adult Developmental Dysplasia Of The Hip

Background The morphology of the proximal femur of DDH varies a lot from thenormal,the maturation of three-dimensional reconstruction technology provide us a newmethod to study the proximal femur of DDH.But up to now,the three-dimensionalresearches about the proximal femur of DDH are deficient around the world.Objective To three-dimensionally reconstruct the morphology of the proximalfemur of DDH (Developmental dysplasia of the hip) and measure the related anatomicparameters, so that we could have a further understanding of the morphological variationof the proximal femur of DDH, which would help in the preoperative planning andprosthesis design specific for DDH.Methods From Jan.2012to Dec.2014,38patients (47hips) of DDH were adimittedand31volunteers (31hips) were selected as controls. All the patients and volunteers wereexamined by CT scan and pelvic radiographs. The Crowe classification method wasapplied. The CT data were imported into Mimics17.0. The three-dimensional models ofthe proximal femur were then reconstructed, and the following parameters were measured:neck-shaft angle, neck length, offset, height of the centre of femoral head, height of theisthmus, height of greater trochanter, the medullary canal diameter of isthmus(Di), themedullary canal diameter10mm above the apex of the lesser trochanter(DT+10), themedullary canal diameter20mm below the apex of the lesser trochanter(DT-20), and thenDT+10/Di, DT-20/Di and DT+10/DT-20were calculated.Results The neck-shaft angle of the control group,Crowe I DDH,Crowe II-IIIDDH and Crowe IV DDH is respectively:131.8±5.9°,131.8±7.1°,131.7±6.5°,122.8±11.4°;The neck length of the control group,Crowe I DDH,Crowe II-IIIDDH and Crowe IV DDH is respectively:53.1±4.4mm,48.6±6.7mm,50.4±4.7mm,44.6 ±6.6mm;The offset of the control group,Crowe I DDH,Crowe II-III DDH and Crowe IVDDH is respectively:39±4.3mm,35.8±5.8mm,37.3±4.2mm,36.1±4.3mm;DT+10of thecontrol group,Crowe I DDH,Crowe II-III DDH and Crowe IV DDH is respectively:24.6±2.5mm,25.2±3.4mm,21.9±4.2mm,17.2±5.3mm;DT-20of the control group,Crowe IDDH,Crowe II-III DDH and Crowe IV DDH is respectively:17.1±2.3mm,17.1±2.3mm,16.3±3.2mm,12.2±3mm;Di of the control group,Crowe I DDH,Crowe II-III DDH and Crowe IV DDH is respectively:10.1±1.4mm,9.9±2.2mm,8.3±1.8mm,8.7±1.7mm; The height of the control group,Crowe I DDH,Crowe II-III DDH andCrowe IV DDH is respectively:6.1±3.9mm,8.9±7.2mm,7.5±3.3mm,12.1±6.1mm;Theheight of the femoral head of the control group,Crowe I DDH,Crowe II-III DDH andCrowe IV DDH is respectively:46.5±6.2mm,39.6±6.5mm,39.1±4.2mm,38.8±8.6mm;The height of the isthmus is respectively:116.5±10.6mm,106.2±13.8mm,108.8±10.5mm,94.1±19.7mm;DT+10/DT-20of the femoral head of the control group,Crowe IDDH,Crowe II-III DDH and Crowe IV DDH is respectively:1.5±0.2,1.5±0.2,1.4±0.3,1.4±0.2;DT+10/Di of the control group,Crowe I DDH,Crowe II-III DDH and CroweIV DDH is respectively:2.5±0.4,2.6±0.5,2.7±0.6,2±0.4;DT-20/Di of the controlgroup,Crowe I DDH,Crowe II-III DDH and Crowe IV DDH is respectively:1.7±0.2,1.8±0.3,1.9±0.3,1.4±0.2.There is no significant difference in neck-shaft angle between Crowe I-III DDH andthe control group, while the neck-shaft angle is much smaller in Crowe IV DDH. The necklength of Crowe IV DDH is much smaller than that those of Crowe I-III DDH. As for Dithere is neither significant difference between Crowe I DDH and the control group, norsignificant difference between CroweII-III and Crowe IV, but the difference is significantbetween the first two groups and the latter two groups. DT+10/DT-20and the offset have nosignificant difference between the control group and DDH groups. DT-20,DT+10, DT+10/Diand DT-20/Di are much smaller in Crowe IV DDH than that in Crowe I-III and the controlgroups. Height of greater trochanter in Crowe IV is larger than those in Crowe I-III andthe control group. Height of the centre of femoral head in Crowe IV DDH is smaller thanthose in Crowe I-III DDH and the control group.The height of the isthmus in Crowe IV is much smaller than those in Crowe I-III DDH and the control group.Conclusion The neck-shaft angle in DDH groups are not larger than that in thecontrol group, in contrast,it’s much smaller in Crowe IV DDH than that in the controlgroup. Comparing to Crowe I-III DDH and the control group, Crowe IV DDH has adramatic change in the intramedullary and extramedullary parameters. The isthmus andthe great trochanter are higher and there is apparent narrowing of the medullary canalaround the level of the lesser trochanter.