Morselized Allograft Research Articles

Arthroscopic Bone Graft Technique for Two-Stage Revision Anterior Cruciate Ligament Reconstruction

Revision anterior cruciate ligament reconstruction is an increasingly common procedure, with 2-stage surgery often required to address large bone defects and malpositioned tunnels. The arthroscopic bone grafting technique described herein uses morselized allograft bone to provide reproducible fill of asymmetrical bone defects without autograft harvest or additional loss of native bone. The second stage of the anterior cruciate ligament reconstruction can typically proceed 6 months following bone grafting.

ACETABULAR RECONSTRUCTION IN PAPROSKY TYPE III DEFECTS.

ABSTRACTObjectives:Severe pelvic deficiency presents a difficult problem in hip arthroplasty. Specifically, the goals are to restore the pelvic bone stock, place the acetabular component in the correct anatomical position, and optimize joint stability. Currently, many surgical techniques have been developed for prosthetic revision surgery for acetabular complex defects, but no consensus has been reached on the best treatment. The objective of this study was to review mid-term cases of severe bone defect (Paprosky type III) treated with a bone allograft and ring Bursch-Schneider anti-protrusion cage (BSAC).Methods:A retrospective consecutive series review of the first 23 complex acetabular reconstructions performed between 2006 and 2011 was conducted. The series included the learning curve of the procedure and a minimum 5-year follow-up.Conclusion:Our study confirmed the efficacy of using a frozen morselized allograft combined with a metal ring-type BSAC for acetabular reconstruction. The anatomical location of the center of rotation of the hip must be recovered for long-term success. In massive loosening cases, the anatomical center of rotation can only be restored by bone density reconstruction using a graft protected by a ring to improve the centering of the head. Level of Evidence IV, Case Series.

Impacted morsellised allograft and cemented cup in acetabular revision surgery. A five to nine year follow-up study.

Seventy cemented cups associated with impacted morsellised allograft in revision surgery in hips with an acetabular bone defect greater than 30% (Paprosky Grades 3A and 3B) were analyzed. The mean follow-up was 6.8 years. One hip showed cup migration and was re-revised; this represents a total cumulative probability of re-revision of the cup of 1.4 2.8%. Radiolucent lines were uncommon: six cups showed radiolucent lines in DeLee and Charnley zone 1, five in zones 1 and 2, one in all three zones, while one hip showed migration.Although the frequent use of a metallic mesh makes graft remodeling difficult to evaluate, six hips showed minor and one major bone resorption. The mid-term results with impacted allograft and cemented all-polyethylene cups are favourable in acetabular revision surgery. (Hip International 2002; 12: 281-8).

Dose-Dependent Resorption of Allograft by rhBMP-2 Uncompensated by New Bone Formation—A Canine Study With Implants and Zoledronate

BackgroundImpacted bone allograft is used to restore lost bone in total joint arthroplasties. Bone morphogenetic proteins (BMPs) can induce new bone formation to improve allograft incorporation, but they simultaneously invoke a seemingly dose-dependent allograft resorption mediated by osteoclasts. Bisphosphonates effectively inhibit osteoclast activity. Predicting allograft resorption when augmented with bone morphogenetic protein 2 (BMP-2), we intended to investigate whether a balanced bone metabolism was achievable within a range of BMP-2 doses with systemic zoledronate treatment. MethodsImplants were coated with 1 of 3 BMP-2 doses (15 μg, 60 μg, and 240 μg) or left untreated. Implants were surrounded by a 2.5-mm gap filled with impacted morselized allograft. Each of the 12 dogs included received 1 of each implant (15 μg, 60 μg, 240 μg, and untreated), 2 in each proximal humerus. During the 4-week observation period, zoledronate intravenous (0.1 mg/kg) was administered to all animals 10 days after surgery as anticatabolic treatment. Implant osseointegration was evaluated by histomorphometry and mechanical push-out tests. ResultsUntreated implants had the best mechanical fixation and superior retention of allograft as compared to any of the BMP-2 implants. Both mechanical implant fixation and retention of allograft decreased significantly with BMP-2 dose increments. Surprisingly, there was no difference among the treatment groups in the amount of new bone. ConclusionThe use of BMP-2 to augment impaction-grafted implants cannot be recommended even when combined with systemic zoledronate.

Does tobramycin impregnation of allograft bone affect implant fixation? – An experimental study in 12 dogs

Clinical trials have used antibiotic impregnated impacted bone allograft in revisions of infected arthroplasties. By this method high local antibiotic concentration and good control of infection was achieved. Toxicity studies, however, suggest that high local antibiotic concentration can impair osteoblast replication. We therefore asked whether impregnating morselized allograft bone with different quantities of tobramycin before impaction would impair implant fixation. We implanted three cylindrical (10 mm × 6 mm) porous-coated titanium implants into the distal femurs of 12 dogs. The implants were surrounded by a circumferential gap of 2.5 mm into which a standardized volume of morselized allograft bone, with or without tobramycin, was impacted. In each animal, the bone graft was impregnated with either 0 mg (control), 50 mg (low dose), or 200 mg (high dose) of tobramycin per 1 mL of bone graft. At the end of the 4 weeks experimental period, the implants with surrounding bone were evaluated by histomorphometric analysis and mechanical push-out test. We found no difference between the treatment groups regarding new bone formation, bone graft resorption, or implant fixation. There was, however, a tendency toward a decrease in implant fixation with higher tobramycin dose. The present study is unable to provide evidence on whether the use of topical tobramycin with allograft is safe or whether it indeed can impair implant fixation. The tendency toward an impaired implant fixation warrants further preclinical studies. Its current clinical use should be weighed against its possible positive effects on preventing infection in complicated revisions.

High Failure Rate with the GAP II Ring and Impacted Allograft Bone in Severe Acetabular Defects

Reconstruction rings and bone allografts have been proposed to manage severe acetabular bone loss. However, a high early failure rate of the Graft Augmentation Prosthesis (GAP) II reinforcement ring (Stryker Orthopaedics, Mahwah, NJ, USA) has been reported in one small series. We therefore determined (1) the survival of this device in combination with impacted morselized allograft bone in patients with severe defects and (2) the complication rate. We retrospectively reviewed 24 patients (21 aseptic and three septic) with severe acetabular bone loss (10 hips with Type III defects and 14 with Type IV defects according to the American Academy of Orthopaedic Surgeons classification). We determined function and numbers of failures. The minimum followup was 24 months (mean, 34 months; range, 24-72 months). At latest followup, the reconstruction had failed in nine of the 24 patients: six with aseptic loosening, three with infection. The average postoperative Merle d'Aubigné-Postel score of the patients whose reconstructions had not failed was 16.6 points; at latest followup, these patients had radiographic evidence of incorporation and consolidation of bone allografts. Seven of the nine patients whose reconstructions had failed underwent reoperation. Fatigue fracture of the ring at the plate-cup union occurred in five patients at an average of 45 months postoperatively. All patients with failed reconstructions who underwent reoperation were treated with Trabecular Metal(™) (Zimmer Inc, Warsaw, IN, USA) cups and were functioning well at latest followup. We observed a high rate (37%) of early catastrophic failures of the GAP II reconstruction ring, particularly in patients with Type IV defects. Due to this high failure rate, we have abandoned its use. Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

Acetabular reconstruction using morselized allograft and a reinforcement ring for revision arthroplasty with Paprosky type II and III bone loss: Survival analysis of 95 hips after 5 to 13 years

Treatment of acetabular loosening and accompanying bone defects requires that the bone stock be rebuilt, the primary stability ensured, and the hip center of rotation restored to its anatomical location. Acetabular reconstruction using morselized allograft and a reinforcement ring will meet these requirements and ensure medium-term survival. A retrospective study was performed on 95 acetabular revision cases (95 patients) performed between 1987 and 1995. The average age at revision was 69.5 years (42 to 86 years). Among these acetabular loosening cases, 12 cases had a type II Paprosky acetabular bone defect and 83 cases had a type III defect. The average follow-up was 8 years (5 to 13 years). There were seven post-operative dislocations, three deep infections, and two cases of repeated acetabular loosening. The cumulative survival rate at 14 years was 77.9% (95% CI: 61.96% to 93.84%). The average Postel Merle d'Aubigné (PMA) score improved from 8 (range 6-11) preoperatively to 14.8 (range 8-18) at follow-up; the Harris score improved from 35.3 (range 11-52) to 71.1 (range 40-94) (P<0.001). Based on the parameters outlined by Ranawat, the optimal centre of rotation was restored in 45% of cases. Graft integration was found to be good in 60% of cases. The reinforcement ring had migrated in five cases, including two cases of acetabular loosening that required an additional revision. The functional result was better when the hip center of rotation was restored (P<0.05). Conversely, the position of the hip center of rotation had no effect on graft integration or acetabular fixation. This series confirmed that acetabular reconstruction using morselized allograft and a reinforcement ring is effective in the medium term as a treatment for acetabular loosening with severe bone deficiency. It also revealed that restoring the hip center of rotation can improve functional results. Level IV, retrospective study.

Acetabular Revision Total Hip Arthroplasty Using an Impacted Morselized Allograftand a Cementless Cup: Minimum 10-Year Follow-Up

This study was undertaken to analyze the clinical and radiologic results of acetabular revision arthroplasty using an impacted morselized allograft and a cementless cup and was performed on 71 hips of 62 patients who were followed up for a minimum of 10 years (10 years to 14 years 8 months; mean, 12 years). The acetabular bone defects were classified using the American Academy of Orthopaedic Surgeons Committee on the Hip and Paprosky classifications. Cementless hemispherical cups were inserted via a press-fit technique, using an impacted morselized allograft. The mean Harris hip score at the last follow-up visit was 92. Only 3 cases were re-revised, and the 12-year survival rate was thus 95.8%. The study shows that acetabular revision arthroplasty using an impacted morselized allograft and a cementless cup is an excellent treatment option.

First-time revision using impacted morsellised allograft bone with a cemented Exeter stem

Previously, radiostereometric analysis following hip revision performed using impacted morsellised allograft bone and a cemented Exeter stem has shown continuous subsidence of the stem for up to five years. It is not known whether the subsidence continues thereafter. In our study, 17 of 25 consecutive osteo-arthritic patients with aseptically loose stems who underwent first-time revision using impacted morsellised allograft bone and a cemented Exeter stem were followed by yearly radiostereometric examinations for nine years. The mean subsidence at six weeks was 1.1 mm (0.1 to 2.3), from six weeks to one year 1.3 mm (0 to 2.6), from one to five years 0.7 mm (0 to 2.0), and from five to nine years 0.7 mm (0.1 to 3.1). That from six weeks to nine years was 2.7 mm (0 to 6.4) (95% confidence interval 2.0 to 3.5). The Charnley pain score significantly improved after revision, and was maintained at nine years, but walking ability deteriorated slightly as follow-up extended. Of the eight patients who were not followed for nine years, two had early subsidence exceeding 11 mm. Our findings show that in osteo-arthritic patients who undergo revision for aseptic loosening of the stem using impacted morsellised allograft bone and a cemented Exeter stem, migration of the stem continues over nine years at a slower rate after the first year, but without clinical deterioration or radiological loosening.

Revision Total Hip Arthroplasty Using Acetabular Reinforcement Ring - Midterm Follow-up Result -

Purpose: To evaluate the clinical and radiographic outcomes of the revision total hip arthroplasty using the acetabular reinforcement ring. Materials and Methods: Thirty-six acetabular revisions were performed in 36 patients with use of the reinforcement ring and structural or morselized allograft, between 1997 and 2005, in thirty-six patients. According to the AAOS classification, thirty-four cases of acetabular defects were Ttype III, and two were Ttype IV. Mean follow-up period after surgery was 7.2 years. Results: The mean Harris hip score was 92.3, which was significantly increased compared with the preoperative score. (p<0.001). There were five failures: a case of aseptic loosening of Muller ring, two cases of infection (5.4%) and two cases of hip dislocation (5.4%). Graft incorporation and bone remodeling occurred successfully in all hips, but in the case of aseptic loosening in which the ring fixation had been inadequate at the time of surgery. The success rate was 91.7% with a mean follow-up of 7.2 years, if the cases of revision or loosening of the component were classified into failure cases. Conclusion: Patients treated with acetabular revision with three kinds of reinforcement ring had reconstitution of periacetabular bone stock as well as good clinical and radiographic results. For the good results, the secure implant fixation during the surgery should be confirmed and we should completely understand the characters of the each kinds of reinforcement rings.

The combined effect of parathyroid hormone and bone graft on implant fixation

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant. Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1-34) 5 μg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters. These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks.

No effect of dynamic loading on bone graft healing in femoral segmental defect reconstructions in the goat

We studied if a static or dynamic mode of nail fixation influenced the healing of segmental defect reconstructions in long bones. Defects in the femur of goats were reconstructed using a cage filled with firmly impacted morsellised allograft mixed with a hydroxyapatite paste (Ostim). All reconstructions were stabilised with an intramedullary nail. In one group (n=6) the intramedullary nail was statically locked, in the second group (n=6) a dynamic mode of nail fixation was applied. We hypothesised that dynamisation of the nail would load, and by that stimulate the healing of the bone graft. Mechanical torsion strength of the reconstructions of the femur with the static and dynamic mode of nail fixation appeared to be 74.8±17.5% and 73.0±13.4%, respectively as compared with the contralateral femurs after 6 months. In all reconstructions, the grafts united radiographically and histologically to the host bone, and remodelled into a new vital bone structure. No large differences were found between newly formed bone areas inside and outside the mesh of the two groups. The area of callus outside the mesh in the dynamic mode of fixation group was smaller (p=0.042), whilst the percentage of bone outside the mesh was larger (p=0.049), as compared to the static mode of fixation group. The data suggest that healing of these defects with impacted morsellised graft in a cage is not significantly influenced by the mode of fixation of the nail in this model.

The Effect of Soaking Allograft in Bisphosphonate: A Pilot Dose-response Study

Long-term survival of uncemented total joint replacements relies on osseointegration. With reduced bone stock impacted morselized allograft enhances early implant fixation but is subject to resorption. We therefore asked whether soaking morselized allograft in different concentrations of bisphosphonate before impaction would enhance fixation. In each of 10 dogs, we implanted four unloaded titanium implants surrounded by a 2.5-mm gap into the proximal humerus, two implants in each humerus. The gap was filled with impacted morselized allograft soaked in saline or a low-, middle-, or high-dose bisphosphonate solution (0.005, 0.05, or 0.5 mg zoledronate/mL). At 4 weeks, the implants were evaluated by histomorphometric analysis and mechanical pushout test. The low dose of zoledronate increased new bone formation in the allograft but the high dose decreased new bone formation. The high dose of zoledronate resulted in the greatest inhibition of allograft resorption, whereas the low dose of zoledronate resulted in the lowest inhibition of allograft resorption. Implants surrounded allograft soaked in the low dose of zoledronate or saline had better fixation for all three mechanical parameters compared with implants surrounded by allograft soaked in the middle or high dose of zoledronate. These data suggest bisphosphonate may enhance osseointegration of allografted implants and emphasize the need for preclinical testing of antiresorptive therapies.

USE OF AXIAL AND SUBAXIAL TRANSLAMINAR SCREW FIXATION IN THE MANAGEMENT OF UPPER CERVICAL SPINAL INSTABILITY IN A SERIES OF 7 CHILDREN

The management of upper cervical spinal instability in children continues to represent a technical challenge. Traditionally, a number of wiring techniques followed by halo orthosis have been applied; however, they have been associated with a high rate of nonunion and poor tolerance for the halo. Alternatively, C1-C2 transarticular screws and C2 pars/pedicle screws allow more rigid fixation, but they are technically demanding and associated with vertebral artery injuries. Recently, C2 translaminar screws have been added to the armamentarium of the pediatric spine surgeon as a technically simple and biomechanically efficient method of fixation. However, subaxial translaminar screws have not been described in the pediatric population. We describe our experience with axial and subaxial translaminar screws in 7 pediatric patients. Seven pediatric patients with the diagnosis of upper cervical spinal instability required surgical fixation (age, 19 months-14 years; sex, 4 boys and 3 girls; follow-up, 4-21 months; etiology, trauma [3 patients], os odontoideum/os terminale [2 patients], hypoplastic dens [2 patients]). All patients underwent axial and/or subaxial translaminar screw insertion. Iliac crest bone graft was used for fusion in 4 patients; bone morphogenic protein and cancellous morselized allograft was used for fusion in 3 patients. A rigid cervical collar was applied for 12 weeks postoperatively in all cases. No intraoperative image guidance was used for insertion of the translaminar screws. All patients had a postoperative computed tomographic scan. Two patients underwent placement of bilateral crossing C2 translaminar screws. Two patients had subaxial translaminar screw placement at C3 and the upper thoracic spine, respectively. Hybrid constructs (a C2 translaminar screw combined with a C2 pars screw) were incorporated in 3 patients. No patients were found to have a breach of the ventral laminar cortex. All patients achieved solid fusion. One patient had a perioperative complication: prolonged dysphagia probably related to C1 lateral mass screw insertion rather than C2 translaminar screw placement. To our knowledge, this report represents the only series of pediatric patients treated with axial and subaxial translaminar screws. This series shows that axial and subaxial translaminar screw fixation is a viable option for upper cervical spinal fusion in children. The technique is safe and results in adequate fixation with high fusion rates and minimal complications.

Long-term clinical outcomes following the use of synthetic hydroxyapatite and bone graft in impaction in revision hip arthroplasty

Impaction grafting using morsellised allograft bone restores bone stock, but carries the potential for transmission of infection. Synthetic bone graft substitutes can eliminate this risk but may, however, influence outcome. In this study we tested the hypothesis that a 50/50 mix of hydroxyapatite and allograft does not affect long-term function, survival or radiological outcome. Sixty-five patients had revision hip arthroplasty using impaction grafting with either pure allograft (42 patients) or a 50/50 mixture of allograft and solid particulate hydroxyapatite. Harris hip scores were assessed pre-operatively and annual intervals thereafter. Function was analyzed using multilevel modeling, the Kaplan–Meier method used for survival analysis and graft incorporation was assessed radiologically. The hip score improved in both groups but showed a small annual decline (average 1.2/year, p < 0.01). This decline was higher for females (average 3.4, p = 0.025) and significantly related to pre-op scores ( p < 0.001). After adjusting for these, allograft patients had marginally higher scores (difference = 3.1, p = 0.3). The majority of revisions were for aseptic loosening. At 13 years survival in the allograft group was 84%, and 82% in the mixture group ( p = 0.96, log rank test). Radiologically the graft incorporation was similar in both groups ( p = 0.62). We conclude that long-term prosthesis survival and function following revision arthroplasty with a 50/50 mixture of allograft and hydroxyapatite are comparable to allograft alone.

Use of Axial and Subaxial Translaminar Screws in the Management of Upper Cervical Spinal Instability in Children

INTRODUCTION: The management of upper cervical spinal instability in children represents a technical challenge. A number of wiring techniques followed by halo orthosis have been applied; however, they have been associated with a high nonunion rate and poor tolerance for the halo. Screw fixation allows more rigid fixation, but it is technically demanding and associated with vertebral artery injuries. Recently, C2 translaminar screws have been added to the armamentarium of the pediatric spine surgeon as a safe and efficacious method of fixation. However, subaxial translaminar screws have not been described in children. We describe axial and subaxial translaminar screw fixation in six pediatric patients. METHODS: Six pediatric patients with the diagnosis of upper cervical spinal instability required surgical fixation (age, 19 mo–10 yr; sex, three males and three females; follow-up duration, 2–18 mo). The etiologies were trauma (n = 2), os odontoideum/os terminale (n = 2), and hypoplastic dens (n = 2). All patients underwent axial and/or subaxial translaminar screw insertion. Iliac crest bone graft was used for fusion in three patients, and BMP and cancellous morselized allograft was used in three patients. A rigid cervical collar was applied postoperatively in all cases for 12 weeks. RESULTS: All patients had postoperative computed tomographic scans. Subaxial translaminar screws were placed at C3 and in the upper thoracic spine. Hybrid constructs (C2 translaminar screw plus C2 pars screw) were incorporated in three patients. There were no perioperative complications related to translaminar screw placement. No patients were found to have a breach of the ventral laminar cortex. All patients with at least a 3-month follow-up achieved solid fusion. CONCLUSION: This represents the only series of pediatric patients treated with axial and subaxial translaminar screws to date. Axial and subaxial translaminar screw fixation is a viable option for upper cervical spinal fusion in children. The technique is safe and results in high fusion rates.

Impaction Grafting for Femoral Component Revision in a Goat Model Using Washed Morselized Cancellous Allograft

To determine whether washing morselized cancellous bone allograft in impaction grafting for revision hip arthroplasty would improve mechanical and biologic performance, left hip hemiarthroplasty with a collarless stem cemented into impacted morselized cancellous bone was performed in 22 goats. Washed allograft was used in the experimental group, and standard allograft was used in the control group. One of 11 experimental and 4 of 11 control implants were observed to be loose at 8 weeks. Washing allowed significantly more morselized cancellous bone to be placed in the experimental group compared to the control group (7.7+/-1.9 and 6.2+/-2.0 g, respectively, P<.05). Significantly less in vivo subsidence over the 8-week study period also was demonstrated in the experimental group compared to the control group (0.4+/-0.4 and 2.2+/-2.3 mm, respectively, P<.05). Angular motion during cyclic +/-1.5 Nm loading demonstrated significant differences between the 2 groups at time zero (2.67 degrees +/-1.02 degrees for the control group and 1.98 degrees +/-0.47 degrees for the experimental group, P<.05) and at 8 weeks (2.40 degrees +/-0.38 degrees for the control group and 1.74 degrees +/-0.55 degrees for the experimental group, P<.05). Histology showed little difference between the 2 groups, but there was a trend toward less inflammation in the experimental group.

The effect of pretreating morselized allograft bone with rhBMP-2 and/or pamidronate on the fixation of porous Ti and HA-coated implants

BMPs stimulate new bone formation, but may also accelerate bone resorption. We added rhBMP-2 and pamidronate to morselized bone allograft packed around uncemented HA-coated and non-coated porous Ti implants in sixteen dogs. Each dog received four implants where the allograft was added (1) nothing, (2) BMP, (3) BP, and (4) BMP + BP. After four weeks, the untreated control implants had better mechanical fixation than all other treatment groups. The rhBMP-2-treated group had abundant formation of new bone on and around the implant. However, almost all allografts were resorbed, rendering the implant mechanically unstable. In the pamidronate-treated group the allograft was preserved, but the implants were covered by fibrous tissue and there was almost no new bone formation. This was also the case for the combined BMP + BP group, although fibrous tissue was absent on these implants. The HA-coated implants had more than twice as good mechanical fixation and improved osseointegration compared to the corresponding Ti implants. RhBMP-2 raised the total metabolic turnover of bone within the allograft with a net negative result on implant fixation. Pamidronate virtually blocked bone metabolism, also when combined with rhBMP-2. The results warrant a conservative approach and emphasize the importance of identifying a therapeutic window for these substances prior to clinical use.

Ceramic bone graft substitute with equine bone protein extract is comparable to allograft in terms of implant fixation: A study in dogs

Background and purpose We studied whether osseointegration and fixation of plasma-sprayed titanium implants grafted with β-TCP granules (Ossaplast) can be improved by adding an osteogenic signal (Colloss E). The results were compared to implants grafted with fresh frozen morselized allograft with and without the Colloss E device.Methods 4 porous-coated Ti implants were placed in the proximal humeri in each of 10 dogs. All implants were surrounded by a 2.5-mm defect, which was grafted with: (A) β-TCP, (B) β-TCP+20 mg Colloss E, (C) allograft, or (D) allograft+20 mg Colloss E. The observation time was 4 weeks.Results Mechanical testing showed that the β-TCP group with Colloss E was twice as well fixed as the control group grafted with β-TCP granules alone, and comparable to both allograft groups. We found that every control implant in the β-TCP grafted group was covered by a dense fibrous membrane. No fibrous tissue was seen in the β-TCP group augmented with Colloss. These implants were well osseointegrated, with new bone covering 10–25% of the implant surface. Both treated groups had increased graft resorption compared to their respective control groups. Colloss E had no effect on new bone formation or fibrous tissue reduction around the allografted implants.Interpretation The Colloss E device improved early osseointegration of implants grafted with β-TCP granules and increased their mechanical implant fixation to the level of allografted implants. The experiment indicates that ceramic bone substitutes may be a viable alternative to allograft when combined with an osteogenic signal such as Colloss E.

High Doses of OP-1 Inhibit Fibrous Tissue Ingrowth in Impaction Grafting

A major concern in using growth factors in impaction grafting is the potential stimulation of the osteoclastic lineage. A solution would be using an osteoconductive material resistant to resorption and providing initial stability after reconstruction. Growth factors may promote bone formation in combination with such graft materials. We determined whether OP-1 would promote the incorporation of impacted morselized allografts and tricalcium phosphate/hydroxyapatite (TCP/HA) into host bone, whether bone formation would be preceded by an initial process of accelerated resorption, and whether the response to OP-1 remodeling/incorporation would be dose-related. We performed two bone chamber studies in goats to ascertain the early effects of OP-1 dose on resorption and incorporation of impacted morselized allografts and TCP/HA. After 4 weeks, the incorporation process of impacted morselized allografts and TCP/HA was not promoted by OP-1. We observed no signs of accelerated resorption preceding bone formation. An increase in OP-1 dose resulted in an inhibition of fibrous tissue formation but OP-1 did not promote bone formation. Early failures in impaction grafting, using mixes with OP-1, might be explained by the lack of fibrous tissue ingrowth and not by increased resorption and remodeling.