AM Open Cell porous Ti Structures were investigated for compressive strength, morphology (i.e. pore size, struts size and porosity), and wear resistance with the aim to improve design capability at support of implant manufacturing. Specimens were manufactured in Ti6Al4V using a SLM machine. Struts sizes had nominal diameters of 200µm or 100µm, pores had nominal diameters of 700µm, 1000µm or 1500µm. These dimensions were applied to three different open-cell geometrical configurations: one with unit-cells based on a regular cubic arrangement (Regular), one with a deformed cubic arrangement (Irregular), and one based on a fully random arrangement (Fully Random). Morphological analysis was performed by image analysis applied onto optical and SEM acquired pictures. The analyses estimated the maximum and minimum Feret pores diameter, and the latter was used as one of the key parameters to describe the interconnected network of pores intended for bone colonization. Outcome revealed the systematic oversizing of the actual struts diameter Vs designed diameter; by opposite min. Feret diameters of the pores resulted significantly smaller than nominal pore diameters, thus better fitting within the range of pores dimension acknowledged to favor the osseointegration. Consequently, the actual total porosity is also reduced. Many technologic factors are responsible for the morphologic differences design vs actual, among these the influence of melting pool dimension, the struts orientation during building and the layer thickness have a significant impact. Mechanical compression was performed on porous cylinder samples. Test revealed the Yield Strength and Stiffness are highly sensitive to the actual porosity. Deformation behavior follows densification phenomenon at lower porosity, whereas at higher porosity the Gibson-Ashby model fits for most of the structure tested. The relationship among load direction, struts alignment and the collapse behavior of the unit cell geometries are discussed. Stiffness of the porous structure is evaluated in both quasistatic and cyclic compression. Wear was investigated according to Taber test method. The abrasion resistance is measured by scratching a ceramic wheel against the different AM porous structures along a circular path. Metal debris eventually loss were quantified by gravimetric analysis at different number of cycles. Correlation among AM porous structure geometry, porosity and wear loss is discussed. All the tested structures showed a debris loss within the limit suggested by FDA for the porous coating in contact with the bone tissue. The actual AM porous Titanium unit cell geometry and features are a key design input. In combination with all the other design factors of a device they may result helpful in address the stress shielding and prevent metal debris release issues. The study underlines the importance of the research activity in AM to support Design for Additive Manufacturing (DFAM) capability. For any figures or tables, please contact authors directly

A statement of the purposes of the study

This study examined the stability of two different hexapod frames at increasing strut angles and the possible use of an additional strut to aid stability.

We determined the midterm survival, incidence of peri-prosthetic fracture and the enhancement of the width of the femur when combining struts and impacted bone allografts in 24 patients (25 hips) with severe femoral bone loss who underwent revision hip surgery. The pre-operative diagnosis was aseptic loosening in 16 hips, second-stage reconstruction in seven, peri-prosthetic fracture in one and stem fracture in one hip. A total of 14 hips presented with an Endoklinik grade 4 defect and 11 hips a grade 3 defect. The mean pre-operative Merle D’Aubigné and Postel score was 5.5 points (1 to 8).

The survivorship was 96% (95% confidence interval 72 to 98) at a mean of 54.5 months (36 to 109). The mean functional score was 17.3 points (16 to 18). One patient in which the strut did not completely bypass the femoral defect was further revised using a long cemented stem due to peri-prosthetic fracture at six months post-operatively. The mean subsidence of the stem was 1.6 mm (1 to 3). There was no evidence of osteolysis, resorption or radiolucencies during follow-up in any hip. Femoral width was enhanced by a mean of 41% (19% to 82%). A total of 24 hips had partial or complete bridging of the strut allografts.

This combined biological method was associated with a favourable survivorship, a low incidence of peri-prosthetic fracture and enhancement of the width of the femur in revision total hip replacement in patients with severe proximal femoral bone loss.

We retrospectively evaluated 18 patients with a mean age of 37.3 years (14 to 72) who had undergone pelvic reconstruction stabilised with a non-vascularised fibular graft after resection of a primary bone tumour. The mean follow-up was 10.14 years (2.4 to 15.7). The mean Musculoskeletal Tumor Society Score was 76.5% (50% to 100%). Primary union was achieved in the majority of reconstructions within a mean of 22.9 weeks (7 to 60.6). The three patients with delayed or nonunion all received additional therapy (chemotherapy/radiation) (p = 0.0162). The complication rate was comparable to that of other techniques described in the literature.

Non-vascularised fibular transfer to the pelvis is a simpler, cheaper and quicker procedure than other currently described techniques. It is a biological reconstruction with good results and a relatively low donor site complication rate. However, adjuvant therapy can negatively affect the outcome of such grafts.