Aim: A study to compare bone remodeling (BMD changes) around the femoral component of a cemented and uncemented THR using DXA scan and Finite element analysis and to check the predictive value of remodelling simulations as a pre-clinical implant testing tool.

Methods: Twenty patients were recruited, ten for each implant type (Exeter and ABG-II). All volunteers underwent unilateral hip replacement. No patient had any metabolic bone disease or were on medication that would alter BMD. Each patient had a preopera-tive CT scan of the hip, in order to provide 3D bone shape and density data needed to construct a computer model. Each patient’s changes of BMD over a period of 12 months postoperatively were evaluated in a series of 4 follow-up DXA scans taken at 3 weeks, 3, 6 and 12 months post-op. For the computer simulation, Finite Element (FE) models of the affected femur were constructed for each patient and BMD changes predicted using strain adaptive bone remodelling theory. These patients were clinical followed up to access the hip scores (Merle d’Aubigne Postel)

Results: All the patients were Charnely group A and had excellent postoperative hip scores (average pain 5.5, walking 5.4 and range of motion 5.3) The Exeter stem DXA results show bone resorption in Gruen zone 3 (2.8% on average) and 4 (3.3%) whereas there is a tendency for bone deposition at regions 1, 6 and 7 (2% on average). The ABG-II stem results show bone resorption developing at regions 7 and 4 (6% and 2% respectively) and some bone formation at region 6 (2%). The simulation results have a tendency to overestimate amounts of bone resorption (20% at region 7 for the ABG-II, 12% at region 3 for the Exeter).

Conclusion: A comparison of the remodelling around a cemented and a non-cemented hip implant show important differences in the emerging patterns of adaptation. To our knowledge, very few published studies provide information on bone remodelling around cemented stems, and compare the results to those of an uncemented stem. Additionally, the simulation results suggest that these formulations can reproduce realistic patterns of bone adaptation. This study aims at providing the means for comparison and subsequent improvement of the accuracy of the simulations and thus helps develop a hip prosthesis that would led to least bone resorption.

Aim: Impaction bone grafting is an established technique for the restoration of bone loss at revision hip surgery. Preformed stainless steel meshes have been recently introduced to augment graft containment. We present our results of acetabular impaction grafting at a mean of 4 years, with particular reference to the use of preformed steel meshes.

Methods: 72 consecutive total hip replacements (7 primary and 65 revision) in 69 patients underwent acetabular impaction grafting with morsellised fresh frozen allograft through a posterior approach. In 47 cases there were uncontained defects (46 segmental or combined deficiencies, one pelvic discontinuity) necessitating the use of a preformed steel mesh, secured with multiple small fragment screws to contain the impacted bone graft. All the operations were done by the senior author in a district general hospital.

Results: At mean follow-up of 4 years (range 18 to 92 months), no case has been lost to follow up. The Merle d’Aubigne Postel hip scores averaged 5.3 (pain), 4.2 (walking ability), and 5.3 (range of movement). (Charnley group A -26 patients, group B -19, group C -24). There were no peri-operative deaths or deep infections. There have been no revisions for septic or aseptic loosening. There were 2 cases of early post operative dislocation which stabilised after closed reduction. One case of recurrent disclocation required cup revision. There was one case of radiographic loosening without cup migration. This patient remains pain free and there are no plans for revision. In all other cases, radiographs suggest graft incorporation, with no significant radiolucent lines, acetabular component or mesh migration. There have been no complications relating to the use of the preformed mesh.

Conclusion: The results of this study are encouraging. By using preformed metallic meshes it is possible to manage all cases of acetabular loss, irrespective of severity, encountered during total hip replacement with acetabular impaction grafting.