Juvenile pubic symphysectomy as a prophylactic treatment in 4-month-old canines at risk of hip dysplasia

Abstract

Hip Dysplasia (HD) is one of the most common orthopaedic diseases of large-breed dogs. In affected dogs, hip joint laxity, joint incongruency, and secondary osteoarthritis can lead to debilitating pain and adversely affect quality of life. Many surgical options are currently available to treat HD in young growing dogs. These surgical procedures include triple pelvic osteotomy and femoral head and neck excision arthroplasty. Juvenile pubic symphysiodesis (JPS) is a relatively recent but well recognised technique employed to improve the coverage of the dysplastic hip joints in young growing dogs. It involves the application of electro-cautery to the cranial two thirds of the germinal chondral growth plate of the pubic symphysis which results in growth plate closure. The optimal age to utilize this technique is between 4-5 months of age. It is anticipated that the dorsal pelvis and sacrum will continue to grow normally, with subsequent increase in lateral rotation of both acetabulae. This technique thus aims to improve dorsal femoral head coverage by the dorsal acetabular rim. The successes of JPS, lead to a proposed modified technique: juvenile total pubic symphysectomy (JPSec). With the JPSec procedure, the entire growth plate of the pubic symphysis is removed, including all the germinal chondrocytes. The symphysis is then opposed by means of two wire loops placed around the pubic rami. Additionally, the caudal symphysis is apposed with a full cerclage wire. In order to evaluate the efficacy of the JPSec procedure more objectively, both radiographic and computed tomographic (CT) imaging was utilised to compare a control and surgical group pre- and post-operatively. Radiographic evaluation included the Subluxation index (SI) and the Norberg angles. Computed tomographic imaging included the acetabular angle (AA), the dorsal acetabular rim angle (DARA) and the lateral centre edge angle (LCA). Due to the size of the project it was decided to utilize only the Norberg angles to test the set hypothesis in that the JPSec procedure would result in an immediate acetabular ventroversion with improved femur head covering. Young growing puppies at 16 weeks of age were divided into a non-surgical Control Group 1 (N = 7) (HD free) and Group 2 and Group 3 (N = 6) each (HD positive) based on the standardised evaluation criteria. The JPS and JPSec techniques were performed on the HD positive Group 2 and Group 3 respectively and the three groups were compared over time. The pelvic ventro-version angles were assessed pre- and post-operatively at 16, 20, 24 and 52 weeks of age in both these groups. Both the JPS and JPSec procedures resulted in an improved hip coverage with the latter technique changing the ventro-version angle of the acetabulum up to five degrees post-operatively after the first 24-48 hours. This change in ventro-version angle improved much faster than JPS, with the coverage of the femur head by the dorsal acetabular rim and caused a subsequent reduced hip joint laxity. Juvenile pubic symphysectomy did not have any significant effect on the sacral width or conformation. The current study compared the JPSec technique with the normal coxofemoral joint development as well as the current JPS technique over the above mentioned time period. This newly proposed pubic symphysectomy procedure is relatively easy to perform and yields good results without the need for any specialized surgical equipment. The post-operative care is uncomplicated. Additionally, the technique of JPSec involves the use of orthopaedic wire which subsequently serves as an indicator of a previous corrective surgical procedure if such an animal is presented for radiographic hip evaluation when mature.