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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XVIII | Pages 33 - 33
1 May 2012
McNamara I Ong M Rayment A Brooks R Prevost T Best S Rushton N
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Problems associated with allograft are well known. The addition of hydroxyapatite (HA) to allograft has various mechanical advantages, especially within revision arthroplasty. The mixing of bone and HA results in mechanical properties different from the individual parts. However, at present the changes in material properties the mix have not been fully investigated and the optimum mixing ratio not characterized. A compressive uniaxial chamber was used to investigate the change in mechanical properties occurring with the addition of HA in varying proportions to morcellised bone graft (MBG).

Materials and methods

MBG was prepared using femoral heads donated from patients undergoing total hip replacement surgery using a bone mill in a standard manner. Non porous HA (npHA) was prepared using a precipitation method of Calcium Carbonate and Orthophosphoric acid. The porous HA, (pHA) is a 60% macroporosity HA commercially prepared.

Chamber

The uniaxial compression chamber was a 30mm diameter, steel chamber. Holes were drilled to allow fluid drainage. Loads were applied using a 10 kN load cell. Specimens were prepared in the volumetric proportions pure HA, pure MBG, 2:1, 1:1, 1:2 ratio of MBG to HA. The samples were subjected to compressive forces of incrementally increasing loads of up to 2 KN for 60 cycles. The sample was then allowed to creep under a stress of 2 kN. MBG was also tested up to forces of 7 kN. The mechanical parameters that were examined were the stiffness of the sample at the 60th cycle, (Ec60), and creep


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_IV | Pages 497 - 497
1 Oct 2010
Mcnamara I Parker M Prevost T Sharma A
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Background: Venous thromboembolism (VTE) remains a significant cause of morbidity and mortality of patients following hip fracture. It is not known preoperatively which patients are at greater risk of developing VTE complications following their surgery. This study reports the incidence of VTE following neck of femur fracture, the timing of the diagnosis of VTE and any risk factors associated with VTE development.

Materials and Methods: We analysed the prospectively recorded complications of patients that presented with a neck of femur fracture. Those patients that developed VTE were compared to those with no complications and their risk factors compared.

Results: A total of 5300 patients were analysed. The incidence of VTE was 2% despite thromboprophylaxis. The significant risk factors for VTE were poor pre operative mobility (p< 0.01), those preoperatively living in their own home (p< 0.01), low mental test score (p< 0.01), high postoperative haemoglobin (p< 0.03), intertrochanteric fractures and fixation with a dynamic hip screw (p< 0.01).

Conclusions: This is the largest group of patients to be prospectively analysed for risk factors for developing VTE following surgery for neck of femur fractures. There were a number of groups that were at a significantly higher risk of developing VTE than others. Orthopaedic surgeons should be aware of these groups in the management of these vulnerable patients.