Clinical and biomechanical assessment of the treatment of type B periprosthetic fractures of the femur

Total hip arthroplasty is a well established treatment modality for the diseased hip. The number implanted rises annually on a global scale which is mirrored by increasing indications. After aseptic loosening and infection, periprosthetic fracture remains one of the commonest complications of this otherwise successful surgery. Management is geared towards restoring function through fixation of the fracture. The general aim of this thesis is to validate the classification of periprosthetic fractures of the femur around total hip arthroplasty, provide evidence towards the outcomes of methods of fixation of these fractures, and present supplementary biomechanical data regarding fixation and implant stress. It is hypothesised that the Vancouver classification will be a reliable and reproducible system to use, that strut grafts, cables and long-stemmed implants will improve function and outcome when used to manage these injuries, and that biomechanical models will provide evidence on why the use of the implants is successful. Study I The purpose of this study was to ensure that the Vancouver Classification of periprosthetic fractures which is most widely used classification system of periprosthetic fractures is repeatable. It was hypothesised that the system would be reliable amongst for all grades of clinician. The inter-rater agreement ranged from 0.61-0.74 and the intra-rater agreement ranged from 0.59-0.67. Validity analysis was scored at 77% (κ = 0.67). The Vancouver Classification was shown to be reliable and reproducible. Study II The purpose of this study was to evaluate the clinical and radiographic outcomes of 40 periprosthetic femoral fractures around stable hip implants treated with cortical onlay strut allografts without revision of the stem. It was hypothesised that this treatment would improve function and result in bony union. At a mean follow-up of 28 months, 98% of patients had radiological evidence of union with all but one of the surviving patients returned to their preoperative functional level within one year. Study III The purpose of this biomechanical cadaveric study was to determine the effect of allograft cortical strut length, configuration, cable number, cable tension and the use of wire or cable on the fixation of periprosthetic femoral fractures. It was hypothesised that an increasing number of struts and the use of cable would improve fracture stability. Fracture stability was found to increase with the use of two rather than one strut, and by using cables rather than wires. Study IV The purpose of this study was to evaluate the clinical and radiological outcomes of using cementless femoral stems in conjunction with cortical struts, cable plating systems, bone allograft and demineralised bone matrix in 26 patients with Vancouver B2 or B3 fractures. It was hypothesised that this treatment would improve function and lead to radiological union. It was found that all fractures were healed clinically and radiologically, and all patients were reported to be satisfied with the outcome. Study V The purpose of this biomechanical study was to determine the strain exerted by an uncemented femoral implant upon a synthetic, composite femur modelling various clinical scenarios. It was hypothesised that strain would be reduced when using a grip, strut or cables. It was found that these devices did reduce the strain exerted upon the femur and may be useful in preventing femoral stem fractures. Study VI The purpose of this study was to evaluate the clinical and radiographic outcomes of treating periprosthetic femoral fractures around unstable hip implants treated with revision to an uncoated locked Kent Hip prosthesis. It was hypothesised that this method of treatment would improve clinical and radiological outcome in the 36 patients included in the study group. Harris Hip Scores improved and fracture union was seen in all but one patient; there were three patients in whom the implant was subsequently revised. Study VII The purpose of this study was to clinically evaluate interlocking long stem femoral prostheses as either temporary functional spacers or as definitive implants in cases of infected periprosthetic femoral fractures. It was hypothesised that these devices would improve the clinical and radiological outcomes of these patients. The Cannulok uncoated stem was used in twelve cases and the Kent Hip Prosthesis in five cases. Patients were asked post-operatively they were satisfied with the outcome achieved. All patients were satisfied and in eleven cases, revision to a definitive stem was undertaken after successful control of the infection and fracture union. Conclusions The management of periprosthetic fractures is a complex issue. There are numerous ways to manage this injury and treatment must be tailored to the patient and to the specific injury sustained. The results of this work demonstrate that classifying periprosthetic fractures using the Vancouver system is valid. Furthermore cortical struts are an effective adjunct with proven biomechanical advantages in non-infected cases around stable implants, whilst long cementless stems lead to excellent outcomes in the presence of a loose implant irrespective of infection.

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