Impacted Morselized Bone Graft Research Articles

Uncemented total hip replacement with impaction bone grafting in protrusio acetabuli

Protrusio acetabuli is a central acetabular defect resulting from migration of femoral head medial to Kohler’s line. Idiopathic central displacement of femoral head within the acetabulum is quite rare. However, it may be seen in arthritic hips secondary to rheumatoid arthritis, ankylosing spondylitis, previous trauma, osteomalacia, etc. Primary Total Hip Replacement (THR) in such cases is difficult because of the deficient medial bone, decreased peripheral bony support to the acetabular component and proximal and medial migration of the joint centre. Several techniques described previously in the surgical management of protrusio acetabuli include cemented acetabular components with cement alone or in association with morselized bone graft to reconstruct the acetabulum. However, cement has high rates of migration and loosening of cemented acetabular components in young patients leads to more revision surgeries within the first decade of implantation. The purpose of the study is to describe the technique and results of using impacted morselized bone graft with a porous coated cementless acetabular component in patients with protrusio acetabuli.A total of 20 primary THR’s (10 unilateral and 5 bilateral) in 15 patients (8 females and 7 males) with protrusio acetabuli were performed between 2018 and 2021, out of which 4 had mild,7 had moderate and 9 had a severe grade of protrusion. A total of 10 hips were affected by rheumatoid arthritis,3 by ankylosing spondylitis and 7 had unknown etiology. After the surgery, all bone grafts had united by the sixth month with no perceptible change in acetabular component position in any case. The mean preoperative Harris Hip Score was 48 which improved to 82 at the latest follow-up. 45% had excellent,33% had good, and 22% had fair results. There was no dislocation. The use of impacted morselized autograft with a cementless porous acetabular component is a good technique of restoration of hip biomechanics and sound fixation in cases of protrusio acetabuli.

One stage revision single-bundle anterior cruciate ligament reconstruction with impacted morselized bone graft following a failed double-bundle reconstruction.

Although double-bundle anterior cruciate ligament (ACL) reconstruction has theoretical benefits such as more accurate reproduction of ACL anatomy, it is technically more demanding surgery. This report describes the case of a one stage revision single-bundle ACL reconstruction after primary double-bundle ACL reconstruction. A professional dancer had an ACL previously reconstructed with a double-bundle technique, but the femoral tunnels were malpositioned resulting in residual laxity and rotational instability. The previous femoral tunnel positions were vertical and widened. The previous vertical tunnels were filled with impacted bone graft and a revision single-bundle ACL reconstruction was performed via the new femoral tunnel with a 2 O’clock position between the previous two tunnels. After 10 months of postoperative rehabilitation, the patient returned to professional dancing with sound bony union and without any residual instability.

Survivorship Analysis of Eighty Revised Hip Arthroplasties With the Impaction Grafting Technique Using Whole Femoral Head Allografts With the Articular Cartilage

BackgroundAcetabular impaction bone grafting aims to restore anatomy in hip revision surgery. This is an effective but expensive and time-consuming technique. Usually, the articular cartilage is removed from the femoral head allograft. We aimed to reproduce the same results retaining the cartilage of the allograft. MethodsEighty acetabular revisions using impacted morselized bone graft retaining the articular cartilage and a cemented cup were studied retrospectively. Six were lost during follow-up. The mean follow-up was 6.5 years (range 1-13). Clinical and radiological assessment was made using the Oxford Hip Score, Hodgkinson's criteria for socket loosening, and the Gie classification for evaluation of allograft incorporation. ResultsSixty-three sockets (85.1%) were considered radiologically stable (type 0, 1, and 2 demarcations), 8 (10.8%) were radiologically loose (type 3), and 3 (4.1%) presented with migration. Fifty-one (68.9%) cases showed good trabecular remodeling (grade 3), 20 (27%) showed trabecular incorporation (grade 2), and 3 (4.1%) showed poor allograft incorporation. Mean preoperative hip score was 43 and postoperative score was 28. Six (8.1%) cases presented heterotopic ossification around the revised implants, 2 patients (2.7%) had periprosthetic fractures, and 4 (5.4%) had dislocations. The Kaplan-Meier survivorship at a mean of 6.5 years with revision of the cup for any reason was 95.9% (95% confidence interval 5.6-7.5). ConclusionThe mid-term results of our technique are promising. Particularly when the supply of fresh-frozen allografts and surgical time is limited, using whole femoral head with articular cartilage is both safe and effective.

Correction of post-traumatic kyphosis in the thoracolumbar spine through Ponté osteotomy and interbody fusion with impacted morsellized bone graft

Objective To describe Ponte osteotomy and interbody fusion with impacted morsellized bone graft and to investigate the safety and efficacy for the correction of post-traumatic kyphosis (PTK) in the thoracolumbar spine.Methods From June 2010 to March 2013,13 patients with PTK in the thoracolumbar spine were treated through Ponte osteotomy and interbody fusion with impacted morsellized bone graft.There were 7 males and 6 females,aged from 32 to 78 years,average 54.5 years.The apex level of kyphosis was T11 in 1,T12 in 4,L1 in 5 and L2 in 3.There was failure of first surgery in seven patients,and inappropriate conservative treatment in six,that all suffered from pain,progressive deformity,and deteriorating neurologic status.During the operation,the intervertebral space was loosened radically through Ponte osteotomy and discectomy,and the kyphosis was firstly corrected using the morcellized impacted graft technique.Then the kyphosis was corrected using the correction rod technique with the hinge of the morcellized impacted graft.Radiographical assessments included localized kyphosis,thoracic kyphosis,lumbar lordosis,sacral tilt angle,sagittal vertical axis,bony fusion and the relative height of the interbody fusion vertebra.Visual analogue scale (VAS),Oswestry disability index (ODI) and ASIA were evaluated before and after surgery,and the operative duration,blood loss were recorded.Results All patients were successfully followed up for an average time of (20.0±9.1) months.Bony fusion was achieved in all patients at 12 months follow-up.Localized kyphosis was reduced from an average of 42.2° (26° to 54°) to 7.1° (-7° to 13°) with an correction rate of 83.2％ on average.Sagittal alignment from T1 to the sacrum became more physiologic from 2.91cm (-3.0 to 7.8 cm) to 1.35cm (-0.5 to 3.8 cm).Thoracic kyphosis,lumbar lordosis and sacral tilt angle all improved at followup.The average VAS score was 6.38±0.87 (range,5 to 8) before operation and 2.23±0.83 (range,1 to 4) at final follow-up.The average ODI score was 55.0± 12.1 (range,39 to 72) before operation and 20.6±7.3 (range,11 to 34) at final follow-up.Neurological function improved from C to D in two patients,from C to E in four patients,and from D to E in seven patients.Conclusion Application of Ponte osteotomy and interbody fusion with impacted morsellized bone graft for the correction of PTK in the thoracolumbar spine has several advantages:large angle correction,high fusion rate,mini-invasion,and little nerve complications. Key words: Thoracic vertebrae; Lumbar vertebrae; Spinal fractures; Kyphosis; Spinal fusion; Bone transplantation

Femoral stem impaction grafting: extending the role of cement

Femoral revision after cemented total hip replacement (THR) might include technical difficulties, following essential cement removal, which might lead to further loss of bone and consequently inadequate fixation of the subsequent revision stem. Femoral impaction allografting has been widely used in revision surgery for the acetabulum, and subsequently for the femur. In combination with a primary cemented stem, impaction grafting allows for femoral bone restoration through incorporation and remodelling of the impacted morsellized bone graft by the host skeleton. Cavitary bone defects affecting meta-physis and diaphysis leading to a wide femoral shaft, are ideal indications for this technique. Cancellous allograft bone chips of 1 mm to 2 mm size are used, and tapered into the canal with rods of increasing diameters. To impact the bone chips into the femoral canal a prosthesis dummy of the same dimensions of the definitive cemented stem is driven into the femur to ensure that the chips are very firmly impacted. Finally, a standard stem is cemented into the neo-medullary canal using bone cement. To date several studies have shown favourable results with this technique, with some excellent long-term results reported in independent clinical centres worldwide.

Hydroxyapatite Block for Reconstruction of Severe Dysplasia or Acetabular Bone Defects in Total Hip Arthroplasty: Operative Technique and Clinical Outcome

Fourteen hips in 14 patients (all female; average age, 64 years) with severe bone defects due to developmental dysplasia of the hip or migration of the socket were treated with hydroxyapatite block with impacted morselized bone graft in conjunction with a cemented socket. All patients were followed clinically in a prospective fashion, and radiographs were analyzed retrospectively. One initial patient had 17-year follow-up, whereas the remaining 13 patients had follow-up between 4 and 6.5 years. No acetabular components were revised, including the socket of a 17-year postoperative case that remains rigidly fixed and supported by the graft and hydroxyapatite block with only mild polyethylene wear and minor osteolysis. Osteointegration and good clinical outcome were achieved in all cases by reconstruction with this technique in total hip arthroplasty.

Acetabular Reconstruction with Impaction Bone-Grafting and a Cemented Cup in Patients Younger than Fifty Years Old

In a previous report, we presented our results of forty-two acetabular reconstructions, performed with use of impaction bone-grafting and a cemented polyethylene cup, in thirty-seven patients who were younger than fifty years and had a minimum of fifteen years of follow-up. The present update study shows the results after twenty to twenty-eight years. Eight additional cups had to be revised--four because of aseptic loosening, three because of wear, and one during a revision of the stem. Three additional cups were considered loose on radiographs. Survivorship of the acetabular reconstructions, with an end point of revision for any reason, was 73% after twenty years and 52% after twenty-five years. With revision for aseptic loosening as the end point, survival was 85% after twenty years and 77% after twenty-five years; for signs of loosening on radiographs, survival was 71% at twenty years and 62% at twenty-five years. In conclusion, our previous results have declined but the technique of using impacted morselized bone graft and a cemented cup is useful for the purpose of restoring bone stock in young patients whose acetabular defects require primary or revision total hip arthroplasty.

Acetabular Revision with Impacted Morselized Cancellous Bone Graft and a Cemented Cup in Patients with Rheumatoid Arthritis

We previously reported our results at a minimum of three years after thirty-five revisions of total hip arthroplasty acetabular components in twenty-eight patients with rheumatoid arthritis. The revisions were performed with use of impacted morselized bone graft and a cemented cup. This update report presents the results at eight to nineteen years after the surgery, which, to our knowledge, is the longest follow-up available in the literature. No patient was lost to follow-up. Since our previous report, there were two additional cup failures due to aseptic loosening, at ten and sixteen years postoperatively. Kaplan-Meier analysis showed the probability of survival of the acetabular component at twelve years to be 80% (95% confidence interval, 65% to 95%) with removal of the cup for any reason as the end point and 85% (95% confidence interval, 71% to 99%) with aseptic loosening as the end point. Cup revisions performed with cement and use of impaction bone-grafting in patients with rheumatoid arthritis led to acceptable long-term prosthetic survival rates. This technique is attractive from a biological standpoint because of the possibility of maintaining acetabular bone stock.

The stability of impacted morsellized bone grafts in a metal cage under dynamic loaded conditions: an in vitro reconstruction of a segmental diaphyseal bone defect

Reconstructions of segmental diaphyseal bone defects with massive allografts are related to complications like nonunion and fractures. A reconstruction of these defects with a cage filled with an impacted morsellized bone graft could be an alternative. The bone graft in these cages should ideally be loaded to prevent resorption. Loading of morsellized bone grafts however can cause instability. The goal of this study was to assess the stability of an impacted morsellized bone graft in a cage under dynamic loaded conditions in an in vitro reconstruction of a segmental diaphyseal bone defect. The second goal was to assess the influence of cage type, washing of the graft and bone-cage fit. Two different cage types were filled with impacted morsellized bone graft. The grafts were used washed and unwashed and in variable bone-cage fit conditions. We recorded the bone graft deformation in the cage under dynamic loaded conditions. Stability appeared to be not very sensitive to the cage type and whether the bone chips were washed or not. However, quality of the fit of the cage with the bone segment was an important parameter and should be optimized during surgery. Morsellized impacted bone graft in a cage is stable in dynamic loaded conditions in an in vitro reconstruction of a segmental diaphyseal bone defect. We believe that this method of reconstruction is a promising alternative for the reconstruction of large diaphyseal bone defects and should be tested relative to its biological merits in animal experiments.

Is an Impacted Morselized Graft in a Cage an Alternative for Reconstructing Segmental Diaphyseal Defects?

Large diaphyseal bone defects often are reconstructed with large structural allografts but these are prone to major complications. We therefore asked whether impacted morselized bone graft could be an alternative for a massive structural graft in reconstructing large diaphyseal bone defects. Defects in the femora of goats were reconstructed using a cage filled with firmly impacted morselized allograft or with a structural cortical autograft (n = 6 in both groups). All reconstructions were stabilized with an intramedullary nail. The goats were allowed full weightbearing. In all reconstructions, the grafts united radiographically. Mechanical torsion strength of the femur with the cage and structural cortical graft reconstructions were 66.6% and 60.3%, respectively, as compared with the contralateral femurs after 6 months. Histologically, the impacted morselized graft was replaced completely by new viable bone. In the structural graft group, a mixture of new and necrotic bone was present. Incorporation of the impacted graft into new viable bone suggests this type of reconstruction may be safer than reconstruction with a structural graft in which creeping substitution results in a mixture of viable and necrotic bone that can fracture. The data suggest that a cage filled with a loaded morselized graft could be an alternative for the massive cortical graft in reconstruction of large diaphyseal defects in an animal model.

Reprise des descellements acétabulaires aseptiques par cupule non cimentée, vissée et allogreffe morcelée impactée

Purpose of the study Impaction grafting can be used in cementless fixation with morsellized bone, bone graft, and hemispherical cup. The first goal of impaction grafting in revision of total hip arthroplasty is to transform segmental defects into cavitary defects and obtain a full compaction of the graft in order to restore the bone stock. The second goal is to achieve primary stability of the cup. The third goal is to restore the hip center of rotation with a cup anatomically located in the acetabulum. The aim of our study was to evaluate the results of a surgical technique with impacted morsellized bone graft and a cementless press-fit cup for the revision with defect type III according to the AAOS classification. Material and methods We performed a retrospective study including 34 hip reconstructions during revision of acetabular aseptic loosening with type III AAOS acetabular defects. All the revisions were performed in the same center by two senior surgeons. Mean age at surgery was 58 years. There were 23 women and 11 men. All reconstructions were performed with a cementless cup and a morsellized impacted bone graft. The analysis of the acetabular defects was done preoperatively according to the AAOS classification. We analyzed postoperatively and at follow-up: position and stability of the acetabular cup, restoration of the hip center and graft integration. Results Mean follow-up was 6.6 years (range 3-13 years). Complications included three dislocations, two trochaanteric nonunions. Two acetabular components were revised for septic loosening. According to the Kaplan-Meier survival curves, with endpoint criteria defined as acetabular cup removal, survival was 91.3% at 10 years (95CI: 86.3-96.3). The preoperative Harris hip score was 53 points (range 26-86) and at last follow-up 94 (47-100). Concerning the subjective clinical outcome, 96% of patients were satisfied or very satisfied at last follow-up. 100% of cups were considered stable at follow-up and bone integration was good in 100%. The center of rotation was located in anatomic position mediolaterally in 66% and in the craniopodal plane in 44%. Discussion Restoration of bone stock is one of the main goals during hip reconstruction after aseptic loosening. Clinical experience in our series has shown the reliability of the impacted morsellized bone graft allowing relocation of the center of rotation and good cup stability. Biological fixation of the cup and graft integration seems good at mid-term follow-up. The cup that we used in our series combined the advantages of a press-fit cup and those of a reinforcement ring. The combination of this type of cup with morsellized bone graft seems to be a reliable solution for restoring bone stock, relocating the hip center, and stabilizing the cup in revision total hip arthroplasty with type III acetabular defect according to the AAOS classification.

Biological activity of tri‐calciumphosphate/hydroxyl‐apatite granules mixed with impacted morsellized bone graft. A study in rabbits

Reconstruction of bone defects with impacted morsellized cancellous bone grafts (MCB) is a popular method. Because of a shortage of human bone, mixing with biomaterials may be attractive. Ceramics may be used as bone graft extenders. In this study, various volume mixtures of biphasic tri-calciumphosphate/hydroxyl-apatite (TCP-HA) granules (1.5-2 mm) with MCB were examined in a non-loaded defect model in rabbits. Direct post-operatively, many 10-150 microm TCP-HA particles were present due to impaction. Irrespective to the group, after 8 weeks, virtually all MCB was resorbed and most TCP-HA granules were osseous-integrated with newly formed bone. The cross-sectional areas of TCP-HA after 8 weeks was generally smaller compared with direct post-operatively and the number of small 10-150 microm TCP-HA particles seemed reduced. Macrophages and giant cells were sparse after 8 weeks. In conclusion, the osteoconductivity of various mixtures of MCB and TCP-HA granules is not dependent on the ratio of TCP-HA over MCB. The reduced number of the 10-150microm TCP-HA particles after 8 weeks, may suggest that a cellular mediated resorption process of TCP-HA granules took place. Based on these favorable biological findings subsequent in-vivo experiments are warranted in load-bearing conditions to investigate whether these findings hold for joint reconstruction purposes.

Larger bone graft size and washing of bone grafts prior to impaction enhances the initial stability of cemented cups: Experiments using a synthetic acetabular model

Background Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. On the acetabular side, the effects on initial cup stability of washing bone grafts prior to impaction and bone graft size remain unclear. Related to these variables, cement penetration and inter-particle shear resistance have been suggested to be critical factors to ensure initial cup stability.Methods Using a synthetic acetabular model, we studied the effects of (1) washing bone grafts prior to impaction, and (2) bone graft size on the initial stability of cemented cups. In addition, cement penetration was measured using CT scans.Results Reconstructions with large, washed bone grafts provided the highest stability during mechanical compression and in a lever-out situation. Washing of the bone grafts had a positive effect on initial cup stability, but the size of the bone grafts appeared to be more important. Cement penetration was affected by bone graft size but not by washing.Interpretation From a mechanical standpoint, large bone grafts that have been washed prior to impaction may be preferable in order to obtain optimal cup stability using the bone impaction grafting technique.

Cemented Cup Stability during Lever-Out Testing after Acetabular Bone Impaction Grafting with Bone Graft Substitutes Mixes Containing Morselized Cancellous Bone and Tricalcium Phosphate-Hydroxyapatite Granules

Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. In the near future the amount of bone grafts available for surgical purposes will be insufficient. Ceramic calcium phosphates [tricalcium phosphate (TCP) and hydroxyapatite (HA)] have been widely considered as potential bone graft substitutes or bone graft extenders. In the past, mechanical experiments have been performed to determine implant stability of bone grafts and ceramic TCP-HA granules mixes under a compressive load. However, in-vivo migration studies suggest that shear loading may be equally important. This in-vitro study investigated the initial stability of cups reconstructed with various mixes of bone grafts and ceramic TCP-HA granules in a lever-out situation, where shearing is the predominant loading mode. It was found that the cups reconstructed with mixes of bone graft and TCP-HA granules exhibited greater mechanical stability than the cups reconstructed with bone grafts only. It is concluded that from a mechanical standpoint, when considering shear force resistance, 50-50 per cent volume mix and 25-75 per cent volume mix of morselized cancellous bone graft and TCP-HA granules both provide adequate initial cup stability and can be used for acetabular reconstructions with the bone impaction grafting technique.

Rinsing morselized allografts improves bone and tissue ingrowth.

Bone defects in revision hip surgery can be reconstructed with impacted morselized bone grafts. Rinsing these trabecular allografts may enhance graft incorporation by washing out immunogenic factors present in blood, marrow, and fat. However, it has been proposed that impaction of the graft releases biologically active factors, which can provide sufficient activity to stimulate new bone formation. Rinsing before impaction could enhance bone allograft incorporation, but rinsing after impaction could diminish the incorporation process of impacted bone graft. To study the effect of rinsing and impaction of morselized bone grafts on bone ingrowth, a bone chamber study was done in goats. Autografts and allografts were divided into three treatment groups: (A) impacted; (B) rinsed and impacted; and (C) rinsed, impacted, rinsed, and impacted again. Ten goats received three bone chambers in each proximal tibia. The chambers were filled with either allograft or autograft, yielding six different implants per goat. After 6 weeks, histologic analyses were done and bone and tissue ingrowth were measured. New bone and total tissue ingrowth were higher in autografts than in allografts, especially in the nonrinsed group. With rinsing, total tissue ingrowth increased in the allograft group to approach that of autografts. Rinsing after impaction did not additionally alter bone ingrowth. The current findings show that incorporation of allografts can be improved by rinsing the grafts before impaction.

Incorporation of morselized bone grafts: a study of 24 acetabular biopsy specimens.

Animal studies have shown almost complete incorporation of impacted morselized bone grafts. To determine whether this also is true in humans, 24 acetabular bone biopsy specimens from 21 hips of 20 patients were examined. Biopsy specimens were obtained 3 months to 15 years after acetabular reconstruction in primary and revision total hip arthroplasties in combination with a cemented cup. Histologic examination showed rapid revascularization of the graft, directly followed by osteoclastic resorption and woven bone formation on the graft remnants. New bone also was formed on fibrin accumulations or without any scaffold in the fibrous stroma tissue that had invaded the graft. Thereafter the mixture of graft, new bone, and fibrin was remodeled completely into a new trabecular structure, with normal lamellar bone and only scarce remnants of graft material. Localized areas of nonincorporated bone graft surrounded by fibrous tissue remained, irrespective of the followup period. Large nonincorporated fragments of cartilage also were found, particularly in cases in which femoral head bone chips were produced by a bone mill. In general, impacted trabecular bone chips incorporate by a mechanism that is similar to that previously observed in animal studies. In some patients, however, areas of nonincorporated bone graft remained and long-term alterations were found, probably related to the loosening process.

Acetabular defect reconstruction with impacted morsellized bone grafts or TCP/HA particles. A study on the mechanical stability of cemented cups in an artificial acetabulum model

In revision surgery of the acetabulum bone defects can be filled with impacted human morsellized bone grafts. Because of a worldwide limited availability of human bone, alternatives are being considered. In this study we compared the initial stability of acetabular cups after reconstructing a cavitary defect with various compositions of impacted tricalciumphosphate-hydroxyapatite (TCP/HA) particles and mixes of TCP/HA particles and human grafts in a realistic acetabulum model. Primary cemented cups and reconstructions with impacted human cancellous grafts were used as reference. A dynamic load displaced the acetabular cups superomedially. The primary cemented cups showed the highest stability. The cups with impacted human grafts produced the most displacement. All reconstructions with the TCP/HA particles showed a high stability of the cups. However, especially when using large TCP/HA particles this was probably due to a large amount of cement penetration. Mixing TCP/HA particles with human grafts seemed to decrease cement penetration, although still a high stability was obtained. In this perspective, we concluded that TCP/HA particles might be useful as a bone graft extender in the reconstruction of acetabular bone defects.

Favorable results of acetabular reconstruction with impacted morsellized bone grafts in patients younger than 50 years: a 10- to 18-year follow-up study of 34 cemented total hip arthroplasties.

We report a long-term review of 41 acetabular reconstructions using impacted morsellized bone grafts and a cemented total hip arthroplasty (THA) in patients younger than 50 (22-49; average 38) years. Reconstruction was performed in 23 primary THA (19 patients) and 18 revision THA (17 patients). 3 patients were lost to follow-up and 3 (4 hips) died within 10 years of surgery; none had a revision. Thus, 34 hips (30 patients) were reviewed with an average follow-up of 13 (10-18) years. In 2 hips, a revision was performed for aseptic loosening of the acetabular component 7 and 11 years after surgery. One additional cup was revised after 12 years during a femoral stem revision due to wear and matching problems, but was well fixed. The survival rate of the acetabular reconstruction technique was 94% (95% CI: 90-98%).

An ovine model to evaluate the biologic properties of impacted morselized bone graft substitutes

The objectives of this study were to develop and evaluate a bone-defect model to study the biologic behavior of biomaterials being considered for impaction grafting in revision hip arthroplasty. A miniature impactor was designed to produce pellets of aggregates at a standard compactive effort. In Phase 1, 22 sheep underwent implantation of pellets into six metaphyseal defects in both rear limbs. In Phase 2, eight sheep underwent surgical implantation of four pellets in metaphyseal defects. Defects were sealed with polymethylmethacrylate in both phases. Healing of the defects was evaluated at 7 weeks (Phase 1, n = 11) and 14 weeks (n =19) with computed tomography, histology, and histomorphometry. Complications in Phase 1 included four femoral fractures and migration of cement seals (18/102 defects). No complications occurred in Phase 2. Whereas no difference was found between left and right limbs, osteogenesis and incorporation of biomaterials varied among implantation sites. For comparison of grafting materials, treatment site allocations were randomized according to a Latin square design. This model allows evaluation of several impacted aggregates (including large particles) in the same animal. It is particularly suitable for analyzing the biologic properties of grafting materials prior to evaluation under loading conditions.

The role of femoral stem extension in total knee arthroplasty.

Although stemmed femoral components often are used in revision total knee arthroplasty, no quantitative comparison of the relative stability of a femoral component with and without a stem has been performed previously. A radiostereophotogrammetric analysis was performed to determine the influence of stem extension on mechanical stability in a laboratory experiment. In addition, the contribution of impacted morselized bone graft used for reconstruction of bone defects to stability was determined. Ten fresh frozen distal femoral specimens, of which the bone mineral density was measured, were prepared to fit a cemented femoral component with an uncemented stem. A cyclic axial load of 750 N was applied to the medial part of the femoral component. The loading test was repeated after creation of a standard, unicondylar, uncontained medial bone defect, after reconstruction of the defect with impacted morselized bone graft, after disconnecting the stem from the component, and after removal of the morselized bone graft. A significant difference was found in rotation and translation of the femoral component with the stem and after its functional removal. The femoral component rotated significantly into varus and internal rotation, and the tip of the stem translated significantly laterally after disconnection of the stem. A linear correlation between bone mineral density in the femoral neck and the radiostereophotogrammetric motion data was absent, but a bone mineral density threshold level of 0.55 g/cm2 was present, below which stability decreased considerably. Morselized bone graft provided only a minor contribution to stability compared with a stem.