Particulate Allograft Research Articles

Particulate Bone Allograft Incorporation in Regeneration of Osseous Defects; Importance of Particle Sizes

Packing of bone defect with particulate allografts is a commonly performed clinical procedure. However, the ideal size of bone particles used to fill bone defects is ill-defined. For this reason the study of biology of bone allografts with different particle sizes has been performed. Standard size bone defects in the femur and the tibia of experimental animals were filled with freeze-dried cortical bone allografts with particle sizes of 1-2mm, 800-500μm, 500-300μm, 300-90μm, 250-125μm, 125-106μm, 106 to 75μm and 75-25μm. Unfilled defects and those filled with autologous bone served as controls. Cortical bone was chosen because it produced better clinical results than did cancellous bone. Likewise freeze-dried particulate bone effected more rapid healing than did frozen bone. Numerical scores were assigned to each defect based on the gross, radiographic and histomorphometric studies. Particles in the range of 300 to 90 microns produced rapid healing by direct ossification. Particles below 100µm had a significantly reduced osteogenic potential. Particles in the range of 75-25μm failed to heal the defects all together. Healing of defects packed with particles larger than 300μm was slower than with 300 – 90 μm grafts. Rapid healing of bone defects packed with particulate bone allografts in the range of 300 to 90μm indicates such allografts can be used effectively in the filling of bone defects. This is of clinical relevance.

Are Fibula Strut Allografts a Reliable Alternative for Periarticular Reconstruction after Curettage for Bone Tumors?

Bone tumors occurring in periarticular locations may cause a substantial risk of subchondral fracture and collapse. Poly-methylmethacrylate has been used for reconstruction in these instances because of its immediate structural stability. Allogeneic graft allows for biologic incorporation and remodeling, but it takes longer. Adding a fibula strut graft to the construct seems to provide structural stability during incorporation of the particulate graft. Seventeen of 22 (77.3%) patients returned to their full preoperative level of function after this procedure. We believe adding fibula strut to particulate allograft when using the buttress technique provides structural integrity and biologically active reconstruction, while maintaining a recurrence rate similar to those described for other reconstruction techniques.

Comparison of frozen and freeze-dried particulate bone allografts

Freeze-dried and frozen particulate bone allografts are used interchangeably on the assumption that the biologic behavior of these grafts is similar. Dissimilarities in biologic behavior and differences in the rate and extent of bone incorporation of freeze-dried and frozen particulate grafts were demonstrated in a comparative study using a non-human primate model. Freeze-dried particulate allografts induced new bone formation and healing of the osseous defects much faster than the frozen allografts.

Three-Year Analysis of Tapered Screw-Vent Implants Placed into Extraction Sockets Grafted With Mineralized Bone Allograft

With clinicians placing more dental implants, it is becoming increasingly important to maintain bone volume after tooth extraction. This article reports the results of implants placed into extraction sites grafted with particulate mineralized bone allograft (Puros). A total of 313 extraction sites were grafted with mineralized bone graft during a 36-month period. A total of 252 Tapered Screw-Vent dental implants were placed into the grafted extraction sites after a 4- to 7-month healing period. All reentries revealed a bony hard structure acceptable for osteotomy preparation. A total of 244 of these implants have been restored with fixed prosthesis and 6 with removable overdentures for a total of 250 loaded implants. A total of 6 implants failed, which required their removal (2 implants before load and 4 after loading), resulting in a 97.6% implant success rate. We conclude that mineralized human allograft placed into extraction sites is clinically useful to maintain bone volume. This material provided a bony hard structure acceptable for implant placement with good success rates.

Strategies of stem fixation and the role of supplemental bone graft in revision total knee arthroplasty.

Bone loss is commonly encountered at the time of revision total knee arthroplasty because of loosening of the implant, osteolysis, infection, or difficulty with removal of the original implant. Regardless of the etiology of the bone loss, its location and magnitude may compromise adequate fixation, alignment, and ligamentous stability of the revision prosthesis. In the setting of bone stock deficiency, or when an implant with a constrained articulation is used, it is prudent to use a longer stem to effect stress transition that protects weak or newly grafted proximal bone1. Successful stabilization of the implant construct can be achieved with a variety of fixation strategies: cementing the condylar surfaces of the implant while using a cementless press-fit stem2,3, fixation of the entire construct without cement4, or fixation of the entire construct with cement. All have been used with success5-7. Because patterns of bone loss can vary so extensively, a classification of the bone loss that is encountered during revision total knee arthroplasty is useful when selecting patients for bone graft procedures. The classification system of the Anderson Orthopaedic Research Institute (AORI) provides guidelines for bone defect management at the time of revision total knee arthroplasty8( Table I). Type-1 defects can be restored either with local autologous bone grafts that are obtained during the revision or with particulate allograft. Type-2 defects are associated with damaged metaphyseal bone that requires either cement, metal augments, or a bone graft to restore the joint line. Type-2 defects may be subdivided into Type-2A defects (involving only one condyle) or Type-2B defects (involving both condyles). Structural and particulate bone graft may be used for Type-2 defects depending on the need for structural support of the prosthesis. Type-3 defects are characterized by deficient …

Acetabular reconstruction with morcellized allograft and ring support: A medium-term review

Acetabular bone stock deficiency is commonly encountered in revision hip surgery. A number of techniques are available to address this problem, including the use of particulate allograft with reconstruction rings in an effort to provide a stable construct and replenish bone stock. Our technique and results using such devices in complex acetabular deficiencies are described. In the setting of a large medial segmental or cavitary acetabular defect, morcellized bone-graft is used to reconstitute the acetabular floor. This graft is reverse reamed until its depth allows screw fixation of a metallic support ring. The screws also serve to compress the graft. A polyethylene acetabular component is then cemented into the reconstituted acetabulum with full freedom of orientation. A series of 48 patients in whom this technique was employed is presented. These cases have been clinically and radiologically reviewed with a mean follow-up of 64 months (range, 25–102 months). Good bony incorporation with stable acetabular components was seen in all but the two cases in which sepsis predominated.

2- to 10-year follow-up study of acetabular revisions using allograft bone to repair bone defects

The failure rates of revision of acetabular components have been high; however, long-term success has been reported with the use of particulate allografts or autografts with large-diameter prosthetic cups to correct bone deficiencies when host-cup contact is at least 30% to 50%. The purpose of this study was to review 2- to 10-year follow-up data on complex acetabular revisions in which contact between allograft bone and the prosthetic cup was at least 50%. In the 47 hips monitored clinically and radiographically for a mean of 5 years, results were classified as excellent in 37%, good in 26%, fair in 17%, and poor in 19%. The mean Harris hip score was 82.5 (range, 39–100). The prosthetic cups migrated in 3 hips, but 2 stabilized within 1 year. Three cups had complete radiolucent lines without migration; the lines did not correlate with location of the allografts. Although bone ingrowth into porous surfaces from allografts is debatable, the results of the study show that massive allograft reconstruction of the acetabulum can provide both immediate and long-term stability of the prosthetic cup and restore bone stock.

Implant stability in revision total hip arthroplasty: Allograft bone packing following extended proximal femoral osteotomy

One method of revising the femoral component in revision total hip arthroplasty in the presence of compromised femoral bone stock is to pack the upper femur with particulate allograft and then to cement the femoral component into the allograft bed. This technique is being used clinically with encouraging results. Additionally, surgical exposure of the femoral canal during revision total hip arthroplasty can be greatly improved with an extended trochanteric osteotomy, which is subsequently repaired with wires or cables. To assess the feasibility of performing the allograft bone packing technique following an extended trochanteric osteotomy, the stability of this construct in a cadaver model was measured, using micromotion sensing instruments and loads applied on a materials testing machine. The stability of the cemented allograft impaction construct following extended trochanteric osteotomy was comparable to the stability of the control construct, which consisted of a similar impacted allograft construct without osteotomy. The stability of the osteotomized side was comparable to that of the control side. It is concluded that the initial in vitro stability of the allograft impaction technique following extended proximal femoral osteotomy is adequate to justify experimental in vivo use.

Impacted particulate allograft for femoral revision total hip arthroplasty: In vitro mechanical stability and effects of cement pressurization

The initial migration and micromotion of the revision femoral stem stabilized with morselized impacted cancellous allograft and bone—cement and the influence of cement pressurization on fixation of the cement/allograft composite to the host were examined with human cadaver femurs. The stability of the allograft/cemented reconstruction was found to be intermediate between those of conventional cemented and cementless stems. In most cases, the stability of the reconstruction was closer to that of cemented than to that of cementless stems. This may account for histologic findings of graft incorporation in experimental and retrieved specimens reported by other authors. Although increased cement pressurization led to greater penetration of cement into the graft bed, greater cement penetration did not increase fixation strength of the cement/allograft composite to the host.