Pilot study of three novel implants-GSK triangular system, locking hip screw and controlled sliding dynamic hip screw, for fixation of fracture of the neck of femur.

ABSTRACT

BACKGROUND AND OBJECTIVE: Intra capsular fracture of the neck of femur (FNF) treated traditionally with a dynamic hip screw (DHS) or three cancellous screws (3CS) has a high incidence of complications with reoperation rates between 20 % and 45 %. We hypothesized that FNF unites by primary healing. Therefore, intra-operative compression and absolute stability post-operatively until healing are essential. We postulated that FNF requires 2 types of implants- those which provide absolute stability for young patients with good bone stock and another with sliding mechanism for elderly patients with osteoporosis. We developed three novel fixation systems at our research institute in India using a modified DHS. In patients with good bone stock, locking DHS, called LHS and GSK triangular system (GSKT) provided intra-operative compression and absolute stability during the post-operative period. In those with poor bone stock, the controlled sliding DHS (CSDHS)was used as a locking implant might penetrate the hip joint. MATERIALS AND METHOD: 42 patients of FNF <55 years of age were studied. Among 39 patients with good bone stock, LHS was used in five patients and GSKT system was used in 34 patients. CSDHS was used in three patients with poor bone stock or communition. The patients were followed up for a minimum of eight months up to a maximum of two years, with the average follow up duration of 14 months. RESULTS: 32 out of 34 fractures treated by GSKT system united. Five cases managed by LHS and three by CSDHS, all united. The union rate was 95.2 %. Of the two failed cases, one patient had nonunion (NU), the other had deep infection. Avascular necrosis of the head (AVN) was detected in three patients treated with GSKT system in the second year following surgery. Two of them had hip pain while one was asymptomatic. Eight cases of FNF Pauwels type III underwent a primary valgus osteotomy. All of them united without complications. CONCLUSION: In patients with good bone stock, LHS and GSKT system allowed intra-operative compression and absolute post-operative stability without sliding of head fragment as the triangle construct is biomechanically the strongest. When bones are osteoporotic, a CSDHS provided controlled sliding (1 to 5 mm only). This pilot study showed a promising success rate of 95.2 %. We propose that the GSKT system may be used to treat intertrochanteric and other metaphyseal fractures as well. Further biomechanical studies are underway to strenghten the evidence needed for the widespread use of these implants.