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Bone & Joint Research
Vol. 1, Issue 4 | Pages 50 - 55
1 Apr 2012
O’Neill F Condon F McGloughlin T Lenehan B Coffey C Walsh M


The objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants on bone.


Pushout studies were performed with the dynamic hip screw (DHS) and the DHS Blade in both cadaveric femoral heads and artificial bone substitutes in the form of polyurethane foam blocks of different density. The pushout studies were performed as a means of comparing the force displacement curves produced by each implant within each material.

The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 5 | Pages 616 - 621
1 May 2011
O’Neill F Condon F McGloughlin T Lenehan B Coffey JC Walsh M

We biomechanically investigated whether the standard dynamic hip screw (DHS) or the DHS blade achieves better fixation in bone with regard to resistance to pushout, pullout and torsional stability. The experiments were undertaken in an artificial bone substrate in the form of polyurethane foam blocks with predefined mechanical properties. Pushout tests were also repeated in cadaveric femoral heads. The results showed that the DHS blade outperformed the DHS with regard to the two most important characteristics of implant fixation, namely resistance to pushout and rotational stability.

We concluded that the DHS blade was the superior implant in this study.

The Journal of Bone & Joint Surgery British Volume
Vol. 85-B, Issue 3 | Pages 363 - 365
1 Apr 2003
Fleming P Lenehan B O’Rourke S McHugh P Kaar K McCabe JP

Injuries to the sciatic nerve are an occasional complication of surgery to the hip and acetabulum, and traction is frequently the causative mechanism. In vitro and animal experiments have shown that increased tensile strain on peripheral nerves, when applied for prolonged periods, impairs nerve function.

We have used video-extensometry to measure strain on the human sciatic nerve during total hip replacement (THR). Ten consecutive patients with a mean age of 72 years undergoing primary THR by the posterior approach were recruited, and strains in the sciatic nerve were measured in different combinations of flexion and extension of the hip and knee, before dislocation of the hip. Significant increases (p = 0.02) in strain in the sciatic nerve were observed in flexion of the hip and extension of the knee. The mean increase was 26% (19% to 30%). In animal studies increases of this magnitude have been shown to impair electrophysiological function in peripheral nerves. Our results suggest that excessive flexion of the hip and extension of the knee should be avoided during THR.