Case 1. Idiopathic AVN of the femoral head ( TimeLine)(Fig. 1).
Patient Information
A 14-year-old boy was referred to our institution for treatment of his painful and rigid left hip joint, a condition that made him unable to walk without the help of crutches.
Past History
His symptoms started one year ago with an insidious onset of pain in his left groin region. The X-Ray of the hip was normal at that time (Fig. 2a). The laboratory blood tests were negative for the presence of infection of the hip. The physician recommended bed rest for a few days and restriction from sports activities for a few months. Four months later, the gradual increase of the pain and stiffness in the left hip necessitated the patient's hospitalization for ten days to ensure hip immobilization. The laboratory blood tests were again negative for the presence of infection of the hip. The X-Ray at that time revealed a flattening of the lateral half of the capital femoral epiphysis (Fig. 2b). Ten months later, due to deteriorating hip symptoms, he was referred to our institution for further treatment. The X-ray revealed the collapse of the femoral epiphysis (Fig. 2c).
Clinical findings
On clinical examination, a fixed 30° flexion deformity of the left hip was obvious, accompanied by a severe restriction of its movements.
Therapeutic interventions
Hip replacement was considered the only surgical treatment capable of ensuring a painless hip joint. The patient received a femoral head resurfacing implant (no traditional THR) utilizing an uncommon implant (Birmingham Mid Head Resection Prosthesis). It is a metal-on-metal articulation. Although the use of a metal-to-metal prosthesis for adolescents is controversial now, the Birmingham Mid head resection implant (BMHR) was chosen, wrong in my current opinion, as the most suitable for this patient at that time (Fig. 2d). This decision was based on the belief that this ensures the preservation of the femoral neck and 1/3 of the femoral head, postponing the total hip replacement for much later, thus gaining time, which is very important for this patient, mainly due to his young age.
Surgical technique
To avoid failure of the femoral component of the arthroplasty, and the possible femoral neck fracture, the placement of the femoral component of the prosthesis in the valgus position, was considered obligatory. Placing the femoral component in the valgus position increases the required compression forces and reduces the harmful shear forces, acting on the preserved femoral neck. In addition, the placement of the femoral component in the valgus position obliges the most horizontal placement of the acetabulum component (reduced angle of inclination of the acetabulum, 22º), thereby ensuring the congruity of the hip joint implant (Fig. 2d).
Follow up
For the clinical evaluation of the patient preoperative and postoperative, we used the online Harris hip score (Orthotoolkit) (Table 1). No intraoperative or early postoperative complications occurred. The clinical and radiographic follow-up was conducted at six weeks, six months, and then annually (Fig. 3). Full weight-bearing without aids allowed 4 weeks postoperatively.
Case 2. Traumatic AVN of the femoral head due to slipped capital femoral epiphysis (TimeLine) (Fig. 4).
Patient Information
A 13-year-old overweight boy was referred to our hospital for treatment of his painful and rigid right hip joint, a condition that made him unable to walk without the help of crutches.
Past History
It was started with an unstable, acute slipped capital femoral epiphysis (25º posterior tilt), that was partially reduced and treated surgically with fixation of the slipped capital femoral epiphysis with a single screw. The clinical and radiographic follow-up conducted at six weeks, and then at regular intervals of two months, revealed a progressive deterioration of the pain and stiffness of the right hip and progressive destruction of the capital femoral epiphysis due to avascular necrosis. The follow-up, thirteen months postoperatively, revealed femoral head collapse and disabling degeneration of the hip joint (Fig. 5a). The single hip screw was removed five months later (Fig. 5b, c). Hip replacement was considered the only surgical treatment capable of ensuring a painless hip joint and was performed five months after the removal of the hip screw.
Clinical findings
On clinical examination, a fixed 40° flexion deformity of the right hip was obvious, accompanied by a severe restriction of its movements.
Therapeutic interventions
Total hip replacement was considered again the only surgical treatment capable of ensuring a painless hip joint. Autologous Bone grafting of the reconstructed acetabulum, using as graft the excised femoral neck, was considered necessary, due to the thinning of the acetabular wall after the acetabular reaming. The patient underwent a traditional THR [Smith & Nephew Short Modular Femoral Stem (SMF), Oxinium Femoral Head - R3 cup. Oxinium on highly cross-linked polyethylene (HXLPE) liner] (Fig. 6, 7).
Follow up
For the clinical evaluation of the patient preoperative and postoperative, we used the online Harris hip score (Table 1). No intraoperative or early postoperative complications occurred. The clinical and radiographic follow-up was conducted at six weeks, six months, and then annually. Full weight-bearing without aids allowed 4 weeks postoperatively. On the immediately post-operative AP radiograph, the acetabular component of the implant appears to penetrate the medial wall of the acetabulum, but seven years postoperatively, the position of the acetabular component of the implant appears to be unchanged (Fig. 7d).