We describe our technique and the early results of compaction morselised bone grafting (CMBG) for displaced tibial plateau fractures using fresh frozen allograft. This technique has been performed by the senior author since July 2006 on eight patients.

Clinical and radiological follow-up was performed on seven remaining patients at an average 12 months (range 4–19) following surgery. One patient died of an unrelated cause three months following surgery. One patient underwent a manipulation under anaesthesia at three months for knee stiffness. One patient developed a painless valgus deformity and underwent corrective osteotomy at 15 months. The height of the tibial plateau on radiographs has been maintained to an excellent grade (less than 2 mm depression) in all but one patient.

CMBG using fresh frozen allograft in depressed tibial plateau fractures provides structural support sufficient to maintain the height of the tibial plateau, is associated with few complications in complex patients with large bone loss and has theoretical advantages of graft incorporation and remodelling.

Introduction/Aims: Initial implant stability is crucial for long-term implant survival. A new surgical technique, compaction, has increased in vivo stability of implants inserted with pressþt. However, gaps often exist in total joint replacements between the implant bone bed and the implant. Therefore, we examined in a gap model whether the compaction technique would increase þxation of hydroxylapatite (HA) implants when compared with the conventional drilling technique. Methods: HA coated titanium implants (diameter 6 mm) were inserted bilaterally in the proximal humerus of 7 dogs for 2 weeks. The implant cavity was randomized to either drilling with an 8 mm drill or to compaction by radial enlarging an initial 5 mm drill hole to 8 mm. Implants were tested to failure by push-out test, and histomorphometry was performed. Data are presented as medians with interquartile range in brackets. The Wilcoxon Signed Ranked Test tested differences between compaction and drilling. P-values < 0.05 were considered signiþcant (*).

Conclusion: In this gap model, compaction signiþcantly increased mechanical and histological þxation of HA coated implants.

Aims

Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes.

Background: Impaction bone-grafting in revision hip surgery generates high forces that may be transmitted through the graft to the femoral cortex, generating high surface strains and a concomitant risk of femoral fracture. Concern of inducing fracture may lead to under-compaction of the graft, with subsequent risk of implant migration. Vibration is commonly used in civil engineering applications to increase aggregate compressive and shear strengths. We have therefore examined the hypotheses that vibration-assisted graft compaction would (a) increase graft compaction compared with the standard femoral impaction grafting technique and subsequently reduce prosthesis migration and (b) reduce femoral hoop strains in the production of graft of a given density and mechanical properties.

Method: Physiological composite femurs were adapted to represent femurs encountered in revision hip surgery by widening of the internal diameter and thinning of the outer shell. In the control group, revision with the standard Exeter technique was simulated using highly washed morcellised bone graft from fresh-frozen human femoral heads. In the study group, vibration-assisted graft compaction was used. The femurs were mounted on a 5kN capacity load cell to measure the total force imparted during graft impaction. Strain gauges placed at the medial calcar and midshaft, measured hoop strains generated during the impaction process. On completion of graft impaction, an Exeter stem was cemented in place. Implant subsidence under physiological cyclic loading (5x 105 cycles) and graft density using micro CT were measured after compaction.

Results: There were no significant differences between the two groups in the peak forces (3.8-4.1kN) imparted during the impaction process. Similar peak hoop strains were observed in the both groups (1.2-1.4%). However a greater graft density was seen in the vibration group with minimal implant subsidence under cyclic loading.

Conclusion: The use of vibration during the impaction process allowed improved graft compaction to be achieved without increasing hoop strains in the femoral cortex. This has implications in preventing failure from under impaction without increasing the risk of fracture. Furthermore, this analysis is applicable to the study of novel synthetic grafts / mixtures in the impaction process for orthopaedic application.

INTRODUCTION. Loosening is a major cause for revision in uncemented hip prostheses due to insufficient primary stability. Primary stability after surgery is achieved through press-fit in an undersized cavity. Cavity preparation is performed either by extraction (removing bone) or compaction (crushing bone) broaching. Densification of trabecular bone has been shown to enhance primary stability in human femora; however, the effect of clinically used compaction and extraction broaches on human bone with varying bone mineral density (BMD) has not yet been quantified. The purpose of this study was to determine the influence of the broach design and BMD on the level of densification at the bone-cavity interface, stem seating, the bone-implant contact area and the press-fit achieved. METHODS. Paired human femora (m/f=11/12, age=60±18 y) were scanned with quantitative computed tomography (QCT, Philips Brilliance 16) before broaching, with the final broach, after its removal and after stem implantation. Compaction broaching (n=4) was compared in an in situ (cadaver) study against extraction broaching with blunt tooth types (n=3); in an ex situ (excised femora) study, compaction broaching was compared against extraction broaching with sharp tooth types (n=8 each). QCT data were resampled to voxel sizes of 1×1×1 mm (in situ) and 0.5×0.5×1 mm (ex situ). Mean trabecular BMD of the proximal femur was determined. The cavity volumes were segmented in the post-broach images (threshold: −250 mgHA/cm3, Avizo 9.2) and a volume of interest (VOI) of one-voxel thickness was added around the cavity to capture the interfacial bone. VOIs were transferred to the pre-broach image and bone densification was calculated within each VOI as the increase from pre- to post-broach image (MATLAB). Detailed surface data sets of broaches and stems were collected with a 3D laser-scanner (Creaform Handyscan 700) and aligned with the segmented components in the CT scans (Fig. 1). Stem seating was defined as the difference between the top edge of the stem coating and the final broach. Distance maps between the stem and cavity surface were generated to determine the bone-implant contact area and press-fit. All parameters were analysed between 5 mm distal to the coating and 1 cm distal to the lesser trochanter and analysed with related-samples Wilcoxon signed rank and Spearman's correlation tests (IBM SPSS Statistics 22). RESULTS. Trabecular BMD ranged from 81 to 221 mgHA/cm3. Densification was higher with compaction compared to sharp (p=0.034), but not blunt extraction broaching (p=1.000). Proximal bone-implant contact area, press-fit and stem seating did not differ between broaching methods. Bone-implant contact area and bone densification increased with trabecular BMD (rs=0.658, p=0.001 and rs=0.443, p=0.034), press-fit with stem seating (rs=0.746, p<0.001) and contact area with bone densification (rs=0.432, p=0.039). DISCUSSION. Sharp extraction broaching reduces densification at the bone-cavity interface, but does not affect the press-fit or contact area. Trabecular BMD was positively associated with contact area, and stem seating with press-fit. Future studies will aim to link these findings to primary stability and influence on periprosthetic fractures. For any figures or tables, please contact authors directly

Morsellised bone graft is used extensively in revision arthroplasty surgery. The impaction technique at the time of surgery has a significant effect on the subsequent elastic and inelastic properties of the bone graft bed. Differences in values reported in the literature for the mechanical properties of morsellised cortico-cancellous bone (MCB) can be attributed to the different loading histories used during testing. We performed serial confined compaction tests to assess the optimum compaction strategy. Compaction of the samples was carried out using repeated standardised loading cycles. Optimal preparation of MCB is dependant on the force and frequency of compaction. The maximum compactive pressure the samples were subjected to was 3 N/mm. 2. based on the clinical experience of Ullmark & Nilsson. 1. in MCB preparation at the time of surgery. This paper presents the Young’s Modulus, E, vs. number of compaction cycles and inelastic strain, . ie. , vs. number of compaction cycles curves for MCB. Qualitative and quantitative descriptions of the material behaviour of MCB are developed. The importance of frequent percussive episodes prior to implant insertion is illustrated. MCB was also found to exhibit significant visco-elastic response, with stress relaxation under displacement controlled loading continuing for several hours following initial load application. Bone graft substitutes do not at present exhibit a similar beneficial shock absorbing visco-elastic response. Our experiments indicate that the material properties of MCB are dependent on the force of impaction and the number of impactions applied with a hammer at the time of surgery. A minimum of 10 to 20 compaction episodes, or hammer blows are required for MCB to achieve 60 to 70% of its long term predicted stiffness

Introduction: Impaction grafting has become a popular technique to revise implants. The Norwegian Arthroplasty Registry reports its use for a third of all revisions. Yet, the technique is seen as demanding. A particular challenge is to achieve sufficient mechanical stability of the construction. This work tests two hypotheses: (1) Graft compaction is an important determinant of mechanical stability, and (2) Graft compaction depends on compaction effort and graft properties. Methods: Impaction grafting surgery was simulated in laboratory experiments using artificial bones with realistic elastic properties (Sawbones, Malmö, Sweden). Bone stock was restored with compacted morsellised graft, and the joint reconstructed with a cemented implant. The implant was loaded cyclically and its migration relative to bone measured. In a second study, morsellised bone of various particle sizes and bone densities, with or without added ceramic bone substitutes, was compacted into a cylindrical mould by impaction of a plunger by a dropping weight. Plunger displacement was measured continuously. Results: Initial mechanical stability of the prostheses correlated most strongly with degree of graft compaction achieved. Graft compaction to similar strength was achieved with less energy for morsellised bone with larger particles, higher density, or bone mixed with ceramic substitutes. Conclusion: Initial mechanical stability of impaction-grafted joint reconstructions depends largely on degree of graft compaction achieved by the surgeon. Compaction depends partly on the vigour of impaction, and partly on graft quality. Higher bone density, larger particle size and mixing with ceramic particles all help to facilitate graft compaction, giving a stronger compacted mass with less effort

Aims

Femoral impaction bone grafting was first developed in 1987 using morselised cancellous bone graft impacted into the femoral canal in combination with a cemented, tapered, polished stem. We describe the evolution of this technique and instrumentation since that time.

We present the 10- to 17-year results of 112 computer-assisted design computer-assisted manufacture femoral components. The total hip replacements were performed between 1992 and 1998 in 111 patients, comprising 53 men and 58 women. Their mean age was 46.2 years (24.6 to 62.2) with a mean follow-up of 13 years (10 to 17). The mean Harris Hip Score improved from 42.4 (7 to 99) to 90.3 (38 to 100), the mean Oxford Hip Score from 43.1 (12 to 59) to 18.2 (12 to 51) and the mean Western Ontario MacMasters University Osteoarthritis Index score from 57.0 (7 to 96) to 11.9 (0 to 85). There was one revision due to failure of the acetabular component but no failures of the femoral component. There were no revisions for aseptic loosening. The worst-case survival in this cohort of custom femoral components at 13.2 years follow-up was 98.2% (95% confidence interval 95 to 99). Overall survival of this series of total hip replacements was 97.3% (95% confidence interval 95 to 99).

These results are comparable with the best medium- to long-term results for femoral components used in primary total hip replacement with any means of fixation.

An experimental sheep model was used for impaction allografting of 12 hemiarthroplasty femoral components placed into two equal-sized groups. In group 1, a 50:50 mixture of ApaPore hydroxyapatite bone-graft substitute and allograft was used. In group 2, ApaPore and allograft were mixed in a 90:10 ratio. Both groups were killed at six months. Ground reaction force results demonstrated no significant differences (p > 0.05) between the two groups at 8, 16 and 24 weeks post-operatively, and all animals remained active. The mean bone turnover rates were significantly greater in group 1, at 0.00206 mm/day, compared to group 2 at 0.0013 mm/day (p < 0.05). The results for the area of new bone formation demonstrated no significant differences (p > 0.05) between the two groups. No significant differences were found between the two groups in thickness of the cement mantle (p > 0.05) and percentage ApaPore-bone contact (p > 0.05).

The results of this animal study demonstrated that a mixture of ApaPore allograft in a 90:10 ratio was comparable to using a 50:50 mixture.