Total hip replacement (THR) can be an effective treatment for debilitating conditions of the canine hip. Historically, cemented THR has been employed but cementless THR has gained popularity more recently. Complications have been reported including luxation, femoral fracture and implant loosening. Using the BioMedtrix system, cementless implantation of the acetabular component and concurrent cemented fixation of the femoral component is possible. In this abstract the results of a series of hybrid cemented/cementless THRs are reported.

Clinical records were reviewed from December 2005 to September 2007. Thirty two hybrid THRs were identified in 30 dogs. Mean weight of dogs was 34.1 kg (range 21-66 kg); mean age was 35 months (range 9-108 months). Indications for surgery included hip dysplasia in 26 hips and irreparable femoral neck fractures in 6 hips. Three major intra-operative complications were identified. In one case medial patellar luxation became evident after reduction of the hip necessitating rectus femoris release. Excessive soft tissue laxity in one case was managed by placement of an iliofemoral suture. One dog suffered an iatrogenic acetabular fracture during cup implantation which necessitated conversion of the procedure to a femoral head and neck ostectomy; this dog was not included in further analyses.

Evaluation of immediate postoperative radiographs revealed incomplete seating of the acetabular component in seven of 31 hips. Femoral component positioning was considered good in 30 of 31 hips; endosteal contact by the stem tip was noted in one case in which the stem centraliser had fractured during implantation. Three month postoperative radiographs were available for 22 hips. Sclerosis around the acetabular component was identified in 18 of 22 hips, and cortical remodelling adjacent to the stem tip evident in 21 of 22 hips.

At four weeks postoperatively, lameness had improved in 29 of 31 limbs and pain on manipulation of the hip had decreased in 30 of 31. Lameness and pain did not worsen in any case. Clinical follow up at 12 weeks postoperatively was available for 25 of 31 hips. Lameness had improved in all cases and resolved completely in 21 of 25 limbs. Pain on manipulation was not evident in any case. Major postoperative complications were not identified.

This study demonstrates that hybrid THR can be performed successfully with a low short term complication rate. Further study to evaluate outcome in the longer term is ongoing.