Acetabular component loosening and pelvic osteolysis continue to be a significant clinical challenge in revision hip arthroplasty. We present results of 339 cases of acetabular reconstruction with impacted allograft.

All patients who under went acetabular reconstruction with impaction allograft between July 1995 and July 1999 were included. Clinical and radiographic data was collected prospectively.

There were 339 patients identified. Average age was 71 years. The majority were first time revisions (201) but the group includes 2nd, 3rd and 4th revisions with 34 two-stage revisions and 44 primary arthroplasties.

There were multiple surgeons with 2/3 being consultants and 1/3 fellows. Pre and post-operative clinical assessment included Oxford and Harris hip scores, and a modified Charnley score for pain, function and range of movement.

Pre-operative radiographs were classified with the Paprosky classification. Follow up radiographs were assessed for graft thickness, component migration, graft reabsorption and lucent lines.

There were 10 grade I, 205 grade II, and 103 grade III defects with 3 pelvic discontinuities. Reconstruction methods included impaction only, rim and/or medial mesh, KP plate fixation and reinforcement cages.

Follow up average was 6.1 years (4.3 – 8.4) and no patient was lost. Infection was identified in 13 patients (5 recurrent 89% eradication and 8 new 2.6%). There were 6 nerve injuries, 2 remain unresolved and 13 patients dislocated (3.8%). There have been 46 deaths in the group with 3 being peri-operative.

There have been 18 re-operations for aseptic loosening. 7 KP plates fractured, 1 cage migrated and 10 rim meshes failed.

Factors associated with aseptic loosening include use of a large rim mesh particularly with an allograft thickness of > 2cm.

We conclude that impaction allografting is a reliable method for acetabular reconstruction. Careful consideration should be given when allograft thickness will be > 2cm and a large rim mesh is required.

It is well known that the integrity of the bone cement interface is crucial for the long-term survival of a primary total hip arthroplasty (THR). Revision THR with impaction bone grafting has recently offered a solution to gross bone loss due to osteolysis. As graft becomes incorporated, clearly the bone graft/cement interface is as crucial as the equivalent interface in primary THR.

The aim of this study was to examine factors that influence this interface. The effects of bone particle size, cement mixing time, and impaction force were examined.

The study was designed to mimic clinical practice. Fresh femoral heads were harvested from primary THR. These were morcelised into large and small particles. The bone was impacted into a purpose built jig with measured force. Cement was pressurised onto the dried surface of the impacted bone after measured mixing times. Cement pressurisation was measured. The cement/graft specimen was extracted and transected with a band saw. Cement penetration was measured with digital image analysis.

Large fragment size was 29 mm², and small was 7. 1mm². Light impaction was 2. 2 Atm. Medium and heavy were 2. 6 Atm. and 3. 2 Atm. respectively. Cement penetration was inversely proportional to impaction force. Cement mixing time also significantly affected cement penetration. Particle size had no effect.

Allograft should be adequately but not excessively impacted, to allow good cement incursion. Cement should be introduced and pressurised perhaps as early as two minutes. Fragment size does not affect cement penetration.