Periprosthetic Fracture after Total Hip Arthroplasty: Treatment and Outcomes
Creators: name: Amarasekara, Sumedha
Publisher: name: The Australian National University
Year: 2016
Subjects: Periprosthetic fracture
Total hip arthroplasty
Mechanical Jig
Mechanical testing
Fixation methods
Cables
Screws
SuperCables

description: Treatment of periprosthetic fractures (PPF) following total hip arthroplasty (THA) is seldom easy, often complex and always expensive. Although international data on periprosthetic fracture outcomes have been reported, there has been no published Australian data. We therefore sought to examine the long-term outcomes of patients treated in our centre and to compare them against previously published data from other centres outside Australia. By so doing we hoped to evaluate our performance and, more importantly, reflect on current surgical practice with respect to periprosthetic fracture treatment and its effectiveness. Another focus for this thesis was the testing of different fixation constructs with a view to examining potential opportunities for improving patient outcomes. The resulting body of work contained in this thesis includes a review of the literature, a retrospective cohort study and a biomechanical study. The questions examined include: what is known about PPF (Chapter 2), how our experience and outcomes in a regional centre compare with other published data (Chapter 3), how newer methods of fracture fixation compare with other established methods (Chapters 4 and 5) and finally, how we should manage this challenging problem in the future (Chapter 6). A review of the literature revealed that although PPF following THA is an uncommon complication, the number is increasing with the increase in THA procedures being performed. PPF are more common in uncemented prostheses than in cemented prostheses and in revision surgery than in primary surgery. Currently, the Vancouver classification system is most commonly used by clinicians when treating this group of fractures. This classification is based on the relationship of the fracture position to the prosthesis, the stability of the prosthesis and the amount of host bone loss. The best results have been achieved in Vancouver B2 PPF where a stem revision is required, whereas results after Vancouver B1 PPF where the stem is not normally revised, have been less successful. Vancouver C fractures have been reported to result in surprisingly poor outcomes. Over the twelve-year period of the retrospective cohort study, 51 patients were treated at the Canberra hospital for 56 PPF of the femur following THA. There were four Vancouver B1 fractures, four Vancouver C fractures and one Vancouver B2 fracture fixation failures. At the time of writing this thesis 29 deaths were recorded and failure of PPF fixation was the most common surgical complication. The biomechanical study was designed to examine the effectiveness of a new cable/plate system (SuperCable, Kinamed Inc., Camarillo, CA, USA) which claims to overcome the slippage and fretting encountered when using metal cables. The experiment used 12 synthetic femurs which had been obliquely sectioned at the midshaft. These were used to compare three fixation constructs: an 8-hole plate with, SuperCables, steel cables and screws. The specimens were tested under compression compression cyclical loading up to 10,000 cycles at 1 Hz with maximum and minimum loads of 2.2kN and 0.2kN respectively. At the end of 10,000 cycles the average displacement of the fracture gap was the largest for SuperCable fixation, while it was the least for screw fixation, being 243µm and 3µm, and 144µm and 0µm for the relative vertical and horizontal displacement respectively. The corresponding values for fracture gap displacement for steel cable fixation was 35µm and 55µm. Conversely, the cable migration was least marked for SuperCables. From their original location, SuperCable migration varied by a magnitude of 82 to 173 µm, while the steel cable migration varied by a magnitude of 173µm to 225µm. It is suggested that the increased movement at the fracture site as reflected in the magnitude of the measured displacement of the fracture gap, implies a greater potential for secondary healing with SuperCable fixation but this hypothesis needs clinical evaluation. The results of this thesis indicate that our clinical and patient reported outcomes are comparable to the international literature. It also suggests that the clinical outcomes in the treatment of Vancouver B1 and C fractures are suboptimal and new treatment paradigms are probably required. Our biomechanical testing suggests important implications in terms of fracture healing and possible earlier weight bearing in patients with PPF. Finally, we suggest the need for a national or international registry to monitor progress in future PPF outcomes