J Vet Sci.  2013 Jun;14(2):185-191. 10.4142/jvs.2013.14.2.185.

Effects of intertrochanteric varus osteotomy on Norberg angle and percent coverage of the femoral head in displastic dogs

• Pinna S
• Pizzuti E
• Carli F

• KMID: 1705520
• DOI: http://doi.org/10.4142/jvs.2013.14.2.185

Abstract

This study was conducted to assess the effects of femoral varus osteotomy on joint congruency in dogs affected by early stage hip dysplasia. Preoperative planning to move the femoral head within the acetabulum was carried out. Varisation of the femoral inclination angle (fIA) was achieved by Intertrochanteric Osteotomy (ITO). Norberg angle (NA), percent coverage (PC) of the femoral head by the acetabulum and fIA was measured from preoperative, immediate postoperative and first and second recheck radiographs of seven dogs that underwent an ITO (joint n = 9). There was significant (p < 0.05) improvement of both NA and PC in all patients as indicated by a change in the mean +/- standard deviation of 78.9degrees +/- 7.5 and 36.9% +/- 5.2 to 92.2degrees +/- 6.7 and 50.6% +/- 8.3, respectively. No significant difference (p < 0.05) was observed between the values of the planned femoral inclination angle (pfIA) of the femur and the effective femoral inclination angle (efIA) obtained after surgery (115.9degrees +/- 2.5 and 111.3degrees +/- 6.4, respectively). These findings could encourage the use of ITO in veterinary practice and indicate that intertrochanteric varus osteotomy should be re-considered for the treatment of early stage hip dysplasia in dogs with radiological signs of joint incongruency.

Keyword

femoral inclination angle; hip dysplasia; intertrochanteric osteotomy; subluxation

MeSH Terms

Animals
Dogs
Female
Femur Head/*surgery
Hip Dislocation/surgery/*veterinary
Joint Diseases/surgery/*veterinary
Male
Osteotomy/*methods/veterinary
Radiographic Image Interpretation, Computer-Assisted/*methods

Figure

• 

  Fig. 1 X-ray images of a 14 month old female Border Collie (21 kg) with B1 hip dysplasia. (A) Norberg angle is measured on the radiograph and indicates the amount of joint laxity. (a) Line between the center points on each of the two femoral heads; (b) line between the center of the femoral head and the craniolateral aspect of the acetabular rim. (B) The percent coverage (PC) of the femoral head by the acetabulum is measured as described by Belkoff. PC is an indication of the support provided by the acetabulum to oppose the force transmitted from the femur. (a) Line between the two craniolateral aspects of the acetabular rims; (b1) line touching the medial surface of the femoral head; (b2) line touching the cranial acetabular rim; (c) femoral head diameters. The overlap distances, b1 and b2, are divided by the femoral head diameter to yield the percentage of the femoral head within the acetabulum. (C) Femoral inclination angle (fIA) determined by the Symax method. (a) Line between the center of the head and the center of the circle drawn at the proximal extremities of the femur; (b) line between the center of the circles drawn at the proximal and distal extremities of the femur.

• 

  Fig. 2 X-ray images of an 11 month old female Maremmano-Abruzzese Sheppard (44 kg) with hip joint incongruence. (A) pfIA: planned femoral inclination angle. (B) fIA: femoral inclination angle. CA1: planned correction angle. (C) CA2: shifted correction angle and base of the bony wedge to be removed (arrow).

• 

  Fig. 3 X-ray images of an 11 month old Maremmano-Abruzzese Sheppard (44 kg) taken prior to and after ITO in a standard ventrodorsal projection with the femurs parallel and intrarotated. An illustration of changes between the two point times. (A and A1) fIA and efIA, (B and B1) Norberg angle, (C and C1) percentage of coverage, pre and immediately postoperative, respectively.

• 

  Fig. 4 X-ray images of a 10 month old male Border Collie (24 kg) taken at each evaluation point in standard ventrodorsal projection with the femurs parallel and intrarotated. The perimeter of the femoral head is in the white circle, while the acetabulum is in the black circle. (A) Preoperative radiograph. Joint is not congruent, the two circles are not within one another and the centers are not coincident. (B) Immediately postoperative radiograph. The circles are congruent and the centers are almost coincident. The osteotomy line is visible. (C) One month postoperative. The position of the femoral head within the acetabulum is preserved; the osteotomy line is still visible. (D) Six months postoperative. The two circles are within each other, indicating joint congruency. The osteotomy line is not visible. The implant is in the right site.

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