Fixation only of Vancouver B Proximal Femoral Fractures (PFF's), specifically with Cemented Taper Slip stems (CTS) with an intact bone cement interface, has been shown to have reduced blood transfusion requirements and reoperations, compared to revision arthroplasty. This potentially carries the risk of stem subsidence and loosening, which negatively impacts functional outcome. The incidence of stem subsidence and associated fracture morphology have not previously been reported.

We retrospectively reviewed all Vancouver B PFF's in primary THR around CTS stems treated with internal fixation only between June 2015 and March 2021 for fracture morphology (Low Spiral (LS), High Spiral (HS), Metaphyseal Split (MS) and Short Oblique (SO)), fracture union and stem subsidence. Interprosthetic fractures and inadequate follow up were excluded. Secondary outcomes were collected.

Out of 577 cases on our local periprosthetic database, 134 Vancouver B PFF's around CTS stems were identified, of which 77 patients underwent ORIF only. Of these, 50 procedures were identified, 21 were lost to follow up and 6 patients died before 6 months. Age, mortality rate and ASA is presented.

Review of Fracture morphology showed: 100% (3/3) of HS subsided (1 revised for loosening); 68 % (19/28) of MS subsided (1 revised for loosening); 11.1 % (2/18) of LS subsided (0 revised for loosening); 0% (1/1) of SO subsided. There were 2 revisions for non-union (LS group). No dislocations were recorded. There was a statistically significant association between Morphology and Subsidence P value 0.0004)

Major subsidence was observed in 8 patients (3 HS, 4 MS and 1 LS) which was associated with a significance reduction in mobility. Subsidence was associated with negative symptoms (P value < 0.0001).

Fixation of all Vancouver B PFF's does not produce uniformly good results. Revision rates following ORIF do not fully reflect patient outcomes. This trend will affect the NJR, stem rating and patient satisfaction. Subsidence after ORIF was associated with certain morphologies (HS & MS) and stem revision may be preferrable, in keeping with GIRFT. A morphology-based classification system can inform decision making.

Introduction: During femoral impaction bone grafting high forces and hoop strains may be generated with subsequent risk of fracture. Vibration is commonly used in civil engineering applications to increase aggregate compressive and shear strengths. We hypothesized that the use of vibration during impaction bone grafting, reduces the maximum hoop strains, and hence risk of fracture, and improves particle interlocking, producing a stronger aggregate.

Method: A series of femoral impaction bone graftings on physiological composite femurs, using morsellised graft from fresh frozen human femoral heads were performed. The standard Exeter impaction technique was used in the control group and vibration assisted compaction used in the study group. Total force imparted, hoop strains and subsidence rate were measured.

Results: Significantly more allograft was used in the vibration group than in the control group (73.1g, 79.5g, p=0.01). Higher mean peak loads were produced during proximal compaction in the control group (3.28kN) than in the vibration group (1.71kN, p=0.005). Higher mean peak and mid proximal hoop strains were generated in the control group (13.2%, 5.6%) compared to the vibration group (4.2%, 2.7% p=0.009, p=0.006). The mean total axial subsidence after 50,000 cycles was significantly less in the control group (2.47mm, SD 0.55) compared to the vibration group (1.79mm, SD 0.30, p=0.03).

Discussion: The use of vibration leads to reduced peak loads and hoop strains in the femur during graft compaction which may reduce the risk of femoral fracture. Additionally the resulting graft is better able to resist subsidence thus conferring improved mechanical stability. A safer, more flexible method to compact bone graft could lead to the more widespread use of IBG in revision hip surgery.

The demographic challenges of an advancing aged population emphasise the need for innovative approaches to tissue reconstruction to augment and repair tissue lost as a consequence of trauma or degeneration. Currently, the demand for bone graft outstrips supply, a key issue in the field of revision hip surgery where impaction bone grafting of the femur and acetabulum has impressive results in the short and medium term but often requires up to 6 donated femoral heads. Spine and selected tumour and trauma cases are also eminently suitable for this mode of bone stock replacement. In the current study, we examined the histological and biochemical findings of two parallel in-vitro and in-vivo studies using human mesenchymal stem cells on synthetic scaffolds for possible bone augmentation. The first study confirmed that culture expanded bone marrow cells from 3 patients (mean age 76 +/−4) could be successfully seeded onto washed morsellised allograft. The seeded graft was then exposed to a force equivalent to a standard femoral impaction (impulse=474 J/m2) and cultured for 4 weeks in osteogenic media. Examination of cell viability using cell tracker green and ethidium homodimer-1 and confocal microscopy confirmed extensive cell proliferation and viability following impaction and culture. Alcian blue/ Sirius red confirmed matrix production, alkaline phosphatase immunocytochemistry production of enzyme activity and Goldners trichrome enhanced osteoid formation. The second study compared 3 scaffolds; bone allograft, a ß – Tricalcium Phosphate (ß-TCP) graft substitute and a 50:50 mixture of allograft and ß-TCP. The scaffolds were seeded with either immunoselected STRO-1+ human mesenchymal stem cells or unselected marrow cells. The scaffolds were similarly exposed to impaction forces and cultured for 4 weeks in vitro or in vivo, implanted subcutaneously in MF1nu/nu mice. Both studies demonstrated cellular viability, activity and osteogenesis as assessed using confocal microscopy, Goldners trichrome and alcian blue/Sirius cytochemistry. The demonstration of enhanced osteoid formation as a consequence of stem cell proliferation after impaction grafting augers well for the success of autologous stem cell implantation on impacted graft substitute with or without the addition of morsellised allograft. The implications therein for clinical use in the future await clinical trials.