Nonunion of the bone fragments during total hip replacement with T. Paavilainen osteotomy — causes of failure

Background. Conservative treatment options for hip dysplasia and hip dislocation in early childhood allow for good results in cases of a timely diagnosis. The preferred treatment option for patients with hip dislocation in adulthood is total hip joint replacement. The shortening osteotomy, proposed by T. Paavilainen, allows the surgeon to restore the difference in the lengths of the lower extremities during arthroplasty of the hip joint. However, according to the results of the Paavilainen technique, as presented by Russian orthopedic surgeons, the problem of nonunion of the greater trochanter fragment with the diaphysis of the femur remains unresolved, as evidenced by a massive group of clinical cases. Aim. The aim of this study was to identify factors affecting the consolidation of bone fragments after osteotomy of the greater trochanter, according to T. Paavilainen, during total hip arthroplasty and evaluate their significance after fixation with cerclage screws in comparison with a special trochanteric fork-plate. Materials and methods. The present study includes 208 cases that were treated at the Russian Scientific Research Institute of Traumatology and Orthopedics named after R.R. Vreden from 2003 to 2019 using various fixation techniques of the greater trochanter fragment. Patients were divided into two groups depending on their type of fixation. The quality of consolidation of a greater trochanter fragment with the femur was assessed during a follow-up period of six months or longer. The fragment of the greater trochanter was divided into the part that was not in contact with the diaphysis, or A , and the part that was in contact with the diaphysis, or B . We assessed the effect of the absolute value of the contact between fragments, the B / A ratio, the distance between the points of insertion of the screws into the diaphyseal part of the femur, the quality of the bone by the modified Barnet-Nordin index, and the history of previous surgical interventions on this joint on the consolidation. Results. When the part of the greater trochanter was in contact with the diaphysis of the femur ( B ) was less than 3.5 cm, the risk ratio of nonunion of the greater trochanter fragment with the diaphysis of the femur increased. Also, a significant factor is the index of the contact of the greater trochanter fragment ( B / A less than 1) with the diaphysis of the femur using the T. Paavilainen technique. In addition, the presence of surgical intervention in the hip joint history significantly increases the relative risk (RR) of nonunion of the greater trochanter fragment with the diaphysis of the femur with this method of shortening osteotomy of the femur. Conclusion. In the absence of timely diagnosis and conservative treatment of children with hip dislocation, reconstructive-plastic techniques on the hip joint do not allow the achievement of proper results and increase the complexity of total hip arthroplasty. According to the results of this study, the absolute value of the contact between fragments ( B ), the index of the greater trochanter contact with the diaphysis of the femur, and the history of previous surgical intervention on this joint are objective tools for the prognostic assessment of the probability of fragment unions during total hip arthroplasty with the T. Paavilainen technique.