Morbidity at bone graft donor sites

Experimental posterolateral lumbar spinal fusion with a demineralized bone matrix gel

STUDY DESIGN

A controlled rabbit model of lumbar posterolateral intertransverse process arthrodesis was used to evaluate a bone graft substitute.

OBJECTIVE

To determine the efficacy of demineralized bone matrix gel as an autograft extender, using different ratios of demineralized bone matrix to autograft and to determine the efficacy of demineralized bone matrix as an autogenous bone graft enhancer by adding it to the usual quantity of autograft.

SUMMARY OF BACKGROUND DATA

Autogenous bone is considered the most effective bone graft material for posterolateral lumbar arthrodesis, yet nonunions occur in up to 30% of patients. In addition, donor site complications may occur in 25-30% of patients. This has prompted the search for and investigation of bone graft extenders, enhancers, and substitutes. Commercially available demineralized bone matrix gel is one possible graft extender and enhancer, which, unlike mineralized allografts, has osteoinductive properties. Although the gel is in common use, the efficacy of demineralized bone matrix when used for posterolateral spine arthrodesis has not been examined in prospective clinical studies. Furthermore, no known animal studies have tested demineralized bone matrix gel in a posterolateral arthrodesis model.

METHODS

Forty-seven New Zealand white rabbits underwent bilateral posterolateral spine arthrodesis at L5-L6 using autogenous iliac crest bone graft alone or in combination with demineralized bone matrix. Four groups were formed on the basis of the ratio of autograft to demineralized bone matrix: autograft alone (3 mL), 100:0 group; autograft (3 mL) and demineralized bone matrix (1.5 mL), 100:50 group; autograft (1.5 mL) and demineralized bone matrix (1.5 mL), 50:50 group; and autograft (0.75 mL) and demineralized bone matrix (2.25 mL), 25:75 group. Rabbits were killed 6 weeks after surgery. Inspection, manual palpation, radiographic film, and histologic evaluation were used to assess fusion.

RESULTS

All groups had similar fusion rates (66-73%) based on manual palpation. Rabbits implanted with demineralized bone matrix had more mature fusion masses, evidenced by the greater trabecular bone formation seen on radiographic film and histologic study.

CONCLUSIONS

Demineralized bone matrix was effective as a graft extender when used in up to a 3:1 ratio with autograft in a rabbit posterolateral spine fusion model. When less than the standard volume of autograft was used, the addition of demineralized bone matrix gel lead to fusion success rates comparable to those of the standard amount of autograft alone. However, demineralized bone matrix did not increase the frequency of successful fusion when added to the standard amount of autograft.

Application of extracorporeal shock-waves in the treatment of pseudarthrosis of the lower extremity. Preliminary results

Between January 1991 and January 1996, pseudarthroses of the legs were treated prospectively in 48 patients by application of high-energy extracorporeal shock waves with an experimental device. The mean duration of pseudarthrosis was 12 months. On average, 2.4 surgical interventions had previously been performed. A total of 3000 impulses with an energy density of 0.6 mJ/mm2 was applied to the pseudarthrosis. Bony union was achieved in 60.4% of our patients after an average of 3.4 months. Failures were found especially in the atrophic types of pseudarthrosis as well as in congenital bone disorders like fibrous dysplasia or osteogenesis imperfecta. No serious complications were observed. Even after numerous surgical interventions high-energy extracorporeal shock-wave therapy showed a fair success rate. A higher success rate of this non-invasive method for the treatment of bony non-unions may be expected by applying strict selection criteria.

Bovine-derived bone protein as a bone graft substitute in a canine segmental defect model

OBJECTIVES

To evaluate the efficacy of a bone graft substitute in healing of a segmental defect of a weight-bearing long bone.

DESIGN

An established canine model was used to perform a blinded, prospective, randomized study of the performance of bone graft substitute implants. This performance was compared with that of an accepted treatment modality (autograft) in a paired fashion.

SETTING

An accredited animal research facility.

SUBJECTS AND INTERVENTION

Twenty-eight dogs underwent bilateral radial osteotomies with creation of a 2.5-centimeter defect. On one side, the defect in every dog was filled with autogenous cancellous bone graft (ABG). Contralateral defects received, in a blinded, randomized fashion, cylindrical implants of demineralized bone matrix (DBM) allograft or DBM plus a constant dose (3.0 milligrams) of bovine-derived bone protein (DBM + BP). The defects were stabilized by external fixation. Subjects underwent monthly radiographs and were killed at six, twelve, or twenty-four weeks. Regenerate bone was studied by biomechanical testing and histology. Six animals were studied to determine the dose-response characteristics of the protein preparation. Three received implants containing 0.3 milligram of BP (group 1) and three received 1.0 milligram of BP (group 2). These animals were killed at twelve weeks of follow-up.

RESULTS

All twenty-eight ABG radii (100 percent) progressed to radiographic union, as did thirteen of thirteen (100 percent) DBM + BP radii compared with only four of fifteen (27 percent) of DBM radii. The difference between union rates was statistically significant (p < 0.05). Mean values for most biomechanical parameters of DBM + BP radii exceeded those of their contralateral ABG controls at twelve and twenty-four weeks, whereas those for DBM implants did not. Histology revealed microscopic evidence of normal bone healing in all ABG and DBM + BP radii, whereas most DBM radii demonstrated nonunions. In the dose-response arm of the study, six of six ABG radii (100 percent) achieved union; zero of three (0 percent) of group 1 and two of three (67 percent) of group 2 radii achieved grossly stable unions. Biomechanical testing was consistent with radiographic results, indicating that the 3.0-milligram dose was the most effective of those studied.

CONCLUSIONS

The DBM + BP composite implants were more effective at healing critical-sized segmental defects than DBM alone in this canine model when a 3.0-milligram per implant dose of BP was used. Biomechanical and histologic properties of the regenerated bone formed by DBM + BP implants was comparable to that of cancellous autograft.

Influence of local environment on incorporation of ceramic for lumbar fusion. Comparison of laminar and intertransverse sites in a canine model

OBJECTIVES

To evaluate bone growth into macroporous ceramic in a canine model in terms of the effect at the lumbar spine site (lamina versus transverse process site) and the depth of the area within the ceramic block (peripheral or central areas).

SUMMARY OF BACKGROUND DATA

Previous comparative studies have assessed that the efficacy of bone graft substitutes for spine fusion depends on their physicochemical properties and on the mechanical environment, but rarely on the grafting site at the lumbar spine level.

METHODS

Posterior and lateral arthrodesis using pedicular instrumentation was performed at L2, L3, and L4 with a parallelepipedic ceramic block in an experimental group of dogs. A second group of dogs was fused with only autogenous bone graft to compare the fusion stiffness obtained with this material with the stiffness obtained with ceramic. Dogs were studied for 9 months. A biomechanical test and histomorphometric analysis were conducted.

RESULTS

With the biomechanical test, no significant differences were found between ceramic and autogenous bone. The percentage of newly formed bone was higher (P < 0.0001) at the lamina (26.52 +/- 6.45%) than at the transverse process site (17.33 +/- 2.54%). For both locations, the highest amount of newly formed bone was observed in the area of close contact between ceramic and bone, and the lowest was observed in central areas (24.6 +/- 5.9% for the laminar site, 14.79 +/- 1.75% for the transverse process site).

CONCLUSION

This animal study, which replicated the human procedure in posterolateral lumbar fusion, showed a significant difference of ceramic incorporation between laminar and intertransverse sites. This histomorphometric analysis also confirmed the relationship between bone in-growth and ceramic thickness and ceramic contact area with bone.

Strength and stability of posterior lumbar interbody fusion. Comparison of titanium fiber mesh implant and tricortical bone graft

STUDY DESIGN

A paired comparison was done of the bending flexibility and compression strength of tricortical bone graft and titanium fiber mesh implants in a human cadaver model of posterior lumbar interbody fusion.

OBJECTIVES

To test the hypothesis that a titanium fiber mesh implant and a tricortical bone graft provide adequate and equal mechanical strength and stability in posterior lumbar interbody fusion constructs.

SUMMARY OF BACKGROUND DATA

Although studies of posterior lumbar interbody fusion constructs have been performed, the authors are unaware of any study in which the strength and stability of a titanium fiber mesh implant are compared with those of tricortical bone graft for posterior lumbar interbody fusion in the human cadaver lumbar spine.

METHODS

Changes in neutral zone and range of motion were measured in a bending flexibility test before and after placement of posterior lumbar interbody fusion constructs. Tricortical bone graft and titanium fiber mesh implant construct stability than were compared in a paired analysis. The constructs than were loaded to failure to evaluate construct strength as a function of graft material and bone mineral density.

RESULTS

The posterior lumbar interbody fusion procedure produced statistically significant decreases in neutral zone when compared with the intact spine. No statistically significant differences in neutral zone, range of motion, or strength were detected between the two implants. Construct strength correlated strongly with bone mineral density.

CONCLUSIONS

Posterior lumbar interbody fusion procedures result in equal or improved acute stability for titanium fiber mesh implants and tricortical bone graft implants when used without additional posterior stabilization.

Comparação entre a hidroxiapatita porosa de coral e o enxerto ósseo autógeno em coelhos

O objetivo da pesquisa é a utilização da hidroxiapatita porosa de coral, como um xenoenxerto ósseo. Utilizou-se onze coelhos da raça Nova Zelândia, nos quais fez-se defeito padrão nas metáfises femorais distais. Nesses locais praticou-se o implante de hidroxiapatita porosa de coral ou enxerto ósseo autógeno. Fez-se estudo clínico, macroscópico, exames radiológicos e histológicos em intervalos de duas, quatro e doze semanas. Os resultados comparativos foram similares enter dois tipos de implantes. Concluiu-se que a hidroxiapatita porosa de coral é um substituto adequado para enxertos ósseos autógenos em coelhos.

Revision of anterior cervical pseudoarthrosis with anterior allograft fusion and plating

Anterior cervical discectomy and fusion is an efficacious procedure used to treat a variety of cervical spinal disorders, including spondylosis, myelopathy, herniated discs, trauma, and degenerative disc disease. Pseudarthrosis, or failure of fusion, may be the most common complication of spinal fusion procedures. Nineteen consecutive patients with symptomatic pseudarthrosis following failed anterior cervical fusions were treated with anterior cervical revision using iliac crest allografts and either the Cervical Spine Locking Plate system (10 patients) or the Trapezial Osteosynthetic Plate system (nine patients). The mean age of the nine men and 10 women undergoing treatment was 49.1 years (range 25-72 years). Eleven patients (57.9%) exhibited pseudarthrosis at one level, six (31.5%) at two levels, and two (10.5%) at three levels. The indications for revision were intractable neck pain with radiculopathy (17 patients) or myelopathy (two patients), with evidence of pseudarthrosis on plain cervical radiography as well as computerized tomography (CT) or single-photon emission computerized tomography (SPECT) scanning, or both. All eight patients evaluated with SPECT showed increased focal uptake consistent with pseudarthrosis, which was subsequently confirmed intraoperatively in all eight. The average follow-up period was 22.4 months (range 12-42 months). Solid osseous fusion was achieved over all 28 levels in all 18 patients available for follow-up review (100%). One patient died 4 months postoperatively from myocardial infarction related to preexisting coronary artery disease. There were no intraoperative complications; postoperatively, two patients (10.5%) experienced transient hoarseness. Anterior revision of failed cervical fusions using allograft interbody fusion material and anterior plating is a safe and efficacious procedure. In this series, the use of allografts avoided donor site morbidity without adversely affecting fusion rates. Rigid internal fixation was achieved by means of anterior plating without increasing surgical morbidity rates. The SPECT imaging technique has the potential to reliably confirm the diagnosis of pseudarthrosis.

Autogenous iliac crest bone graft. Complications and functional assessment

Functional outcomes and complications experienced by adult patients who underwent iliac crest bone grafting were evaluated to assess the effect of bone grafts on patient function. In addition to retrospective chart reviews, patients completed the Sickness Impact Profile and a detailed questionnaire on pain. One hundred ninety-two patients met study inclusion criteria. Major complications were recorded in four (2.4%) patients in whom infections developed requiring readmission. Thirty-seven (21.8%) patients had minor complications. One hundred nineteen of 170 patients were available for followup; of these 119 patients, 87 (73.1%) returned completed questionnaires. Thirty-three of 87 (37.9%) patients reported pain 6 months postoperatively. The incidence of pain decreased with time, with 16 of 87 (18.7%) patients continuing to report pain more than 2 years postoperatively. Proportionately more spine patients reported pain at all time points. The mean Sickness Impact Profile score for patients completing questionnaires was nine, suggesting most patients were functioning well 2 years postoperatively. The morbidity of iliac crest grafting remains substantial. Pain symptoms in this study sample seemed to last longer in more patients than earlier series have indicated. Minimizing muscle dissection around donor sites and the advent of bone graft substitutes may help alleviate these problems.

The necessity of acute bone grafting in diaphyseal forearm fractures: a retrospective review

OBJECTIVE

To determine the union rate of forearm fractures where acute bone grafting was recommended but not performed.

DESIGN

Retrospective review.

SETTING

Regional level one trauma center.

PATIENTS

The criteria for inclusion in the study were patients with closed growth plates and a diaphyseal fracture of the radius, ulna, or both (including Monteggia and Galeazzi fracture-dislocations) that were treated with plate fixation. Patients were excluded from the study if they were lost to follow-up before radiographic documentation of bone union. The review identified 198 fractures that were eligible for inclusion. Fifteen fractures were excluded.

INTERVENTION

The method of treatment of each fracture was open reduction and plate fixation with or without bone grafting.

MAIN OUTCOME MEASUREMENT

Fracture union.

RESULTS

The overall union rate in comminuted, nongrafted forearm fractures (open and closed) was 98% (99/101; 95% confidence interval: 93-100%). The union rate in closed, comminuted, nongrafted forearm fractures was 97% (74/76; 95% confidence interval; 91-100%).

CONCLUSIONS

Open reduction and internal fixation of comminuted diaphyseal forearm fractures without bone grafting in this study produced union rates comparable to those reported for open reduction and internal fixation of comminuted forearm fractures with acute bone grafting. This study suggests that routine use of bone grafting in comminuted forearm fractures is not indicated.

Coralline hydroxyapatite: a bone graft alternative in foot and ankle surgery

The use of coralline hydroxyapatite has become a viable bone grafting alternative. Its efficacy has been well established through multiple human and animal studies. Coralline hydroxyapatite enhances osteogenesis by providing a biocompatible lattice for the passage and assembly of vascular, fibroblastic, and osteoblastic tissues. It also provides support for surrounding osseous structures. The uses of this material are expanding into the realm of foot and ankle surgery. Its consideration as an appropriate bone graft substitute as well as multiple case studies demonstrating its surgical applicability are discussed. The implants utilized at Thorek Hospital and Medical Center over the past eight years, with an average follow-up of three and one-half years, have proven to be a valuable resource for augmentation where an osseous defect has occurred.

Treatment of acute fractures with a collagen-calcium phosphate graft material. A randomized clinical trial

A prospective, randomized clinical trial was conducted concurrently at eighteen medical centers in order to compare the safety and efficacy of two types of graft material for the treatment of fractures of long bones: autogenous bone graft obtained from the iliac crest, and a composite material composed of purified bovine collagen, a biphasic calcium-phosphate ceramic, and autogenous marrow. Two hundred and thirteen patients (249 fractures) were followed for a minimum of twenty-four months to monitor healing and the occurrence of complications. We observed no significant differences between the two treatment groups with respect to rates of union (p = 0.94, power = 88 per cent) or functional measures (use of analgesics, pain with activities of daily living, and impairment in activities of daily living; p > 0.10). The prevalence of complications did not differ between the treatment groups except for the rate of infection, which was higher in the patients who were managed with an autogenous graft. Twelve patients who were managed with a synthetic graft had a positive antibody titer to bovine collagen; seven of them agreed to have intradermal challenge with bovine collagen. One patient had a positive skin response to the challenge but had no complications with regard to healing of the fracture. We concluded that, for traumatic defects of long bones that necessitate grafting, use of the composite graft material appears to be justified on the grounds of safety, efficacy, and elimination of the increased operative time and risk involved in obtaining an autogenous graft from the iliac crest.

Iliac crest donor site morbidity in foot and ankle surgery

The authors retrospectively reviewed anterior iliac crest donor site morbidity in 40 consecutive patients (42 donor sites) who underwent graft harvesting for reconstructive foot or ankle surgery. The mean time to follow-up was 22 months (range, 1 to 48 months). The overall complication rate was 2.4%, with one early minor complication and no major complications. The authors conclude that anterior iliac crest-harvesting techniques that rely on minimal soft tissue dissection and the removal of small-to-moderate volumes of bone have reduced frequencies of minor and major donor site complications.

Utilization of type I collagen gel, demineralized bone matrix, and bone morphogenetic protein-2 to enhance autologous bone lumbar spinal fusion

Autologous bone grafts are currently considered "gold standard" material for achieving long-term spinal arthrodesis. The present study was performed to determine whether demineralized bone matrix (DBM), type I collagen gels, or bone morphogenetic protein-2 (BMP-2) can improve autologous bone spinal fusions. Using a unilateral decompression-contralateral fusion technique in dogs, each of these materials was added to an autologous bone graft. Volumetric analysis, histological analysis, and biomechanical testing were performed to assess the effectiveness of each material. The DBM had an inhibitory effect on solid bone fusion of the spine, whereas the type I collagen gels improved the bony interface between the graft and the host spine. The BMP-2 strongly enhanced the amount of bone deposition at the fusion site and increased the number of intervertebral levels that were solidly fused. This study strongly supports the use of BMP-2 as an additive to autologous bone grafts in spine stabilization.

Enhanced healing of segmental tibial defects in sheep by a composite bone substitute composed of tricalcium phosphate cylinder, bone morphogenetic protein, and type IV collagen

Diaphyseal segmental defects in the tibia of 18 sheep were used to evaluate the healing potential of a composite bone substitute device (CBS) composed of a tricalcium phosphate cylinder (TCP), naturally occurring sheep bone morphogenetic protein (sBMP), and type IV collagen. A total of 100 mg of sBMP and 20 mg of type IV collagen in the high-dose group (CBSH), and 13 mg of sBMP and 2.5 mg of type IV collagen in the low-dose group (CBSL) were adsorbed to TCP cylinders, respectively. TCP cylinders impregnated with type IV collagen alone (TCPC) were used as control. A significantly larger area and more highly integrated intensity of newly formed external callus between CBSH and CBSL or TCPC group were quantified by computerized image analyzer at both 3 and 6 weeks. A torsion test showed that the maximal torque capacity, maximal angular deformation, and bone stiffness of healed osteotomized tibia with implants recovered 117-125% in CBSH, 72-109% in CBSL, and 63-80% in TCPC, compared with the corresponding contralateral tibia at 16 weeks. A healing superiority of the segmental bone defects replaced by the implants was demonstrated in the CBSH group. Thus, the composite bone substitute device defined in this study was shown to possess osteoinductivity, osteoconductivity, and mechanical strength.

Morbidity from iliac crest bone harvesting

PURPOSE

The iliac crest is the most common donor site for autogenous bone grafting in maxillofacial surgery. The aim of this study was to evaluate retrospectively the morbidity of bone harvesting from the inner table of the anterior iliac crest.

PATIENTS AND METHODS

Sixty-five patients were recalled 1 to 4 years after iliac crest bone harvesting. The morbidity as well as the patient's satisfaction were evaluated by a survey of the medical record, a mail-in questionnaire, and a standardized physical examination.

RESULTS

There was good acceptance of this bone harvesting procedure, and the morbidity was low.

CONCLUSION

Bone harvesting from the inner table of the anterior iliac crest is a good option for reconstructing bone defects.

Video-assisted lateral intertransverse process arthrodesis. Validation of a new minimally invasive lumbar spinal fusion technique in the rabbit and nonhuman primate (rhesus) models

STUDY DESIGN

Cadaveric anatomic and in vivo survival animal studies were performed to develop a new arthrodesis technique for the lumbar spine.

OBJECTIVES

To examine the feasibility, efficacy, and safety of a minimally invasive lumbar intertransverse process arthrodesis technique using an osteoinductive growth factor (rhBMP-2) delivered in a collagen sponge carrier. The technique was first developed using a rabbit model and modified for the nonhuman primate (rhesus monkey), a larger animal with the most similar bone biology to humans.

SUMMARY OF BACKGROUND DATA

The morbidity of conventional posterolateral lumbar intertransverse process arthrodesis includes graft donor site morbidity; paraspinal muscle devascularization, denervation, and scarring and nonunion in up to 36% of patients. Minimally invasive anterior lumbar interbody arthrodesis techniques have been developed, but these often require a metal implant and carry risks to major vessels and development of retrograde ejaculation. A minimally invasive technique for posterolateral intertransverse process arthrodesis has not been described previously.

METHODS

In Part 1, we examined seven New Zealand white rabbits and five rhesus monkeys at necropsy and during nonsurvival surgeries to determine the best access routes and to develop special instruments for video-assisted lateral intertransverse process arthrodesis. In Part 2, 38 New Zealand white rabbits underwent L4-L5 intertransverse process arthrodesis: the "OPEN" group (n = 16) underwent a standard open muscle-splitting approach using rhBMP-2 (bone morphogenetic protein) and collagen as a bone graft substitute; the "video-assisted control" group (n = 6) underwent video-assisted lateral intertransverse process arthrodesis with the collagen implant only (no growth factor); and the "video-assisted-BMP" group (n = 16) underwent video-assisted lateral intertransverse process arthrodesis with rhBMP-2 and collagen as the graft material. In Part 3, rhesus monkeys (n = 4) underwent video-assisted lateral intertransverse process arthrodesis using rhBMP-2 and collagen after laminectomy of L4-L5.

RESULTS

In Part 1, we identified expedient, minimally invasive routes to the intertransverse process interval appropriate for each species: an intermuscular approach for the rabbit and a lateral, extramuscular approach for the rhesus monkey. In Part 2, all rabbits in the OPEN and video-assisted-BMP groups achieved solid intertransverse process lumbar fusions when assessed at 10 weeks. There were no neurologic impairments nor any difference between the two groups in the frequency of postoperative infection or other complications. None of the animals in the video-assisted control group showed evidence of fusion. In Part 3, exposure, decortication and grafting with rh-BMP-2 and collagen was accomplished successfully in all four monkeys through the video-assisted minimally invasive approach without complications.

CONCLUSION

Video-assisted lateral intertransverse process arthrodesis is a feasible, effective, and safe method of lumbar spinal fusion in the rabbit and rhesus monkey. Use of this arthrodesis procedure will minimize the morbidity of paraspinal muscle denervation and devascularization seen with open intertransverse process fusion techniques, and the use of an osteoinductive growth factor will eliminate the problem of graft donor site morbidity and possibly increase the chances for successful fusion.

Superior gluteal artery injury during iliac bone grafting for spinal fusion. A case report and literature review

STUDY DESIGN

This article reports a complication encountered when harvesting bone graft from the posterior iliac crest during a contemplated spinal fusion.

OBJECTIVES

Posterior iliac crest bone grafting is commonly performed with posterior spinal instrumentation and fusion.

SUMMARY OF BACKGROUND DATA

Review of the literature reveals a few case reports of damage through the superior gluteal artery during harvesting of bone grafts; this complication is managed with direct vessel ligation.

METHODS

This article reviews the pertinent anatomy of posterior iliac crest bone grafting and addresses areas of caution important in preventing this complication.

RESULTS

The case report offers alternative management, that is, selective arterial embolization for hemodynamic control of the massive life-threatening bleeding that can occur with superior gluteal artery lacerations.

CONCLUSIONS

Injury to the superior gluteal artery is a common complication in pelvic trauma. In this patient, therapeutic arterial embolization proved to be a useful tool in controlling hemorrhage, which prevents additional bleeding problems. Superior gluteal artery injury after elective bone graft surgery is a relatively uncommon, serious, but avoidable complication. In this patient, the use of radiographically controlled arterial embolization of the lacerated vessel proved to be a quick and effective solution to this potentially life-threatening complication.

The effects of internal fixation on calcium carbonate. Ceramic anterior spinal fusion in dogs

STUDY DESIGN

An anterior interbody fusion was performed in the canine thoracic spine. Either calcium carbonate or autologous iliac crest bone graft was used to fill a surgically created spinal defect between T7 and T8. Some of the spines were stabilized intraoperatively with anterior instrumentation. Four experimental arthrodesis groups were studied: iliac crest bone graft with or without instrumentation and ceramic with or without instrumentation.

OBJECTIVE

To evaluate the effects of internal fixation on an anterior interbody fusion using calcium carbonate ceramic, and to compare this with autologous iliac crest bone grafting.

SUMMARY OF BACKGROUND DATA

Bone grafting can be associated with significant morbidity, and an acceptable substitute material is sought. In vivo analysis of ceramic as a substitute has revealed fracture and failure of the implant. Creating a stable environment with internal fixation may improve the performance of ceramic as a bone graft substitute.

METHODS

Fusions were evaluated in 20 adult beagles 8 weeks after surgery. Structural properties of the fusion segment were evaluated with biomechanical testing. Histologic analysis was performed to determine junction healing, new bone formation, and revascularization.

RESULTS

Fusion segments with iliac crest bone graft and instrumentation were significantly stiffer than the other three groups in all tested modes of angular deformation. Greater junction healing was seen when instrumentation was used with iliac crest bone graft. Greater junction healing, new bone formation, and revascularization were observed when instrumentation was used with calcium carbonate ceramic. Most of the ceramic implants without fixation demonstrated near complete isolation with no revascularization.

CONCLUSIONS

Internal fixation resulted in histologically and biomechanically superior healing of autologous iliac crest bone graft in this canine model of anterior interbody fusion. Although fixation did not statistically improve the biomechanical properties of ceramic fusion segments, it had a profound effect on the ability of the ceramic to be revascularized and remodeled. Porous ceramic bone graft substitutes appear to depend on a stable environment for incorporation.

The application of allograft bone in foot and ankle surgery

This article presents a synopsis of the classification, processing, basic physiology, clinical applications, complications, and future direction of allogenic bone implantation. Indications and techniques for the use of allogenic bone in the foot and ankle are thoroughly discussed. Additionally, the advantages and disadvantages of allogenic bone as compared with autogenous bone are reviewed.

Coralline hydroxyapatite bone graft substitutes

The authors present a review of the various bone grafts currently available with special attention to coral bone grafts. Several of the benefits of coralline hydroxyapatite bone graft substitutes, such as safety and biocompatibility, will be addressed in this article, part of an ongoing investigation of coral bone grafts used in triple arthrodesis procedures. To date, eight cases have been performed. In seven cases, granular chips were employed to pack the subtalar joint. The final case, presented in this article, represents a 26-year-old male who, 2 years previously, sustained a calcaneal fracture with resultant shortening along the lateral column. A coralline hydroxyapatite block was used at the calcaneocuboid joint to achieve distraction. Clinically, the patient is progressing well at 10 months postoperatively. Radiographically, one can still clearly appreciate the margins of the bone graft at 5 months.

The use of bone grafts in the management of nonunions

Nonunions can be frustrating complication for the lower extremity surgeon. The cessation of bone healing requires an understanding of its etiology before it may be treated appropriately. This article will review nonunions and, in the context of this special issue, discuss the role of bone grafts in their treatment.

Molecular methods of enhancing lumbar spine fusion

OBJECTIVE

An optimal method for spinal fusion would induce rapid growth of bone via an osteoconductive and osteoinductive implant. This study examines the spinal fusion enhancement potential of some osteoconductive and osteoinductive biomaterials.

METHODS

Four similar canines received unilateral posterolateral fusions on the left side at T13-L1 and L4-L5 and on the right side at L2-L3 and L6-L7. The experiments were grouped as follows: Group A, autogenous bone harvested from the iliac crest; Group B, autogenous bone and collagen; Group C, no implant; and Group D, autogenous bone, collagen, and recombinant human bone morphogenetic protein-2. Radiographic assessment, three-dimensional computed tomographic volumetric analysis, and biomechanical testing were performed at each level.

RESULTS

For Groups A and B, the fusions demonstrated moderate bone formation at 6 and 12 weeks postoperatively. Group D fusions exhibited earlier and more dramatic increases in volume and radiodensity and eventually were comparable in size to the vertebral bodies. Average fusion volumes computed from three-dimensional computed tomographic analysis were: Group A = 1.243 cc, Group B = 0.900 cc, Group C = 0.000 cc, and Group D = 6.668 cc (P = 0.003 compared to Group A). Group D exhibited flexion and extension biomechanical properties much greater than controls. The addition of recombinant human bone morphogenetic protein-2 consistently yielded the strongest fused segments and, on average, enhanced extension stiffness by 626% and flexion stiffness by 1120% over controls.

CONCLUSION

The most advantageous spinal fusion implant matrix consisted of recombinant human bone morphogenetic protein-2, autogenous bone, and collagen. Future investigators, however, need to examine the appropriate quantities of the individual components and clarify the efficacy of the matrix for the various types of spinal fusion approaches.

Utilization of autogenous corticocancellous bone graft from the distal tibia for reconstructive surgery of the foot and ankle

Procurement of corticocancellous autogenous bone graft from any donor site is not without potential complications. Increased postoperative morbidity, fracture at the donor site, an additional surgical procedure, increased operative time, excessive blood loss, hematoma, and increased relative cost are all factors that must be considered, regardless of donor site. The authors have been using the distal tibia as a source of corticocancellous bone since 1988. A review of 16 patients with distal tibial bone grafts at our institution has demonstrated this area to be readily available and effective with limited morbidity. The distal tibial metaphyseal area has been found to be an excellent source of corticocancellous bone for grafting in reconstructive foot and ankle surgery.

Radiographic evaluation of bone grafts

Autogenous and allogenic bone grafts are frequently used in foot and ankle surgery. Indications may include treatment of nonunions, acute fractures, arthrodesis procedures, and reconstructive osteotomies. Proper perioperative management of these procedures requires a through understanding of the radiographic changes that occur after bone grafting. This article describes normal and abnormal radiographic presentations in both the recipient and donor sites after bone graft surgery.

Complications of iliac crest bone graft harvesting

Autologous bone grafts harvested from the iliac crest are commonly used in reconstructive orthopaedic surgery. Autologous bone is used to help promote bone healing in fractures and to provide structural support for reconstructive surgery. The results of autologous bone grafting are more predictable than the use of xenografts, cadaveric allografts, or synthetic bone substitutes because autologous bone grafts provide osteoinductive and osteoconductive properties, are not immunogenic, and are usually well incorporated into the graft site. In a retrospective review of 414 consecutive cases of iliac crest bone graft procedures performed at Brooke Army Medical Center from 1983 to 1993, 41 (10%) minor and 24 (5.8%) major complications were identified. Minor complications included superficial infections, superficial seromas, and minor hematomas. Major complications included herniation of abdominal contents through massive bone graft donor sites, vascular injuries, deep infections at the donor site, neurologic injuries, deep hematoma formation requiring surgical intervention, and iliac wing fractures. Harvesting of iliac crest bone graft can be associated with significant morbidity. However, with adequate preoperative planning and proper surgical technique, the incidence of these complications can be reduced.

Quantitative analysis of cancellous bone graft available from the greater trochanter

To quantify the amount of cancellous bone graft available from the greater trochanteric region, 20 paired iliac crest-proximal femur specimens were harvested and compared in 10 adult pelvises. A 1.3 x 1.3-cm cortical window was made in the lateral aspect of the proximal femur 2 cm distal from the tip of the greater trochanter. Cancellous bone evacuation was performed by curettage. The extent of harvest was mechanically limited by the medial wall of the trochanter and by curette impingement on the margins of the cortical window. The graft was quantitated after maximal digital compression in a 10-ml syringe and compared with cancellous graft obtained from the paired anterior iliac crest. The average compressed volume of cancellous bone harvested from the greater trochanter was 6.5 ml (range, 4.2-9.6 ml). The average iliac crest cancellous bone volume was 6.0 ml (range, 2.7-8.8 ml). Differences in graft volume between the anterior iliac crest and the trochanter were not statistically significant. The resulting defect in the proximal femur remained isolated to the trochanteric region. In this study, we demonstrate that cancellous bone is available from the greater trochanteric region in an amount similar to that available from the anterior iliac crest. We also show that it is obtainable in a reproducible manner. Our clinical experience of over 100 cases has demonstrated acceptable morbidity associated with this technique. The greater trochanteric region may be used as a secondary source of autogenous cancellous bone graft when specific procedures demand more bone graft than available from the iliac crest alone, or in patients who have had previous iliac crest graft harvest.

Evaluation of collagen ceramic composite graft materials in a spinal fusion model

Autogenous bone graft is highly effective in inducing a bone healing response in most clinical settings. However, significant morbidity can occur related to the harvest of an autograft. This makes the development of synthetic or purified nontissue bone grafting materials highly desirable. Both purified bovine Type I collagen and calcium phosphate ceramics have been proposed as promising osteoconductive bone graft substitute materials. One collagen ceramic composite, Collagraft, is approved for use in acute long bone fractures. This study evaluated composites of purified bovine Type I fibrillar collagen and a granular biphasic hydroxyapatite/tricalcium phosphate ceramic in the posterior segmental canine spinal fusion model. Materials were compared based on union score and mechanical testing in 3 separate fusion sites (L1-2, L3-4, L5-6). All composites were found to be inferior in union score to an equal volume of autogenous cancellous bone. In addition, the combination of the collagen ceramic composite with autogenous cancellous bone graft reduced the effectiveness of the autogenous bone graft significantly. These data should be a caution to the clinician who may consider use of collagen ceramic composites similar to Collagraft for spinal fusion applications.

Results of distal tibial bone grafting in hindfoot arthrodeses

Distal tibial bone grafting is a safe and effective means of obtaining cancellous bone for hindfoot arthrodesis procedures, providing a sufficient quantity and quality of cancellous bone graft. Fusion rates using this bone graft are no less than those reported in the literature using autologous bone obtained from other sites. The 1% significant complication rate (fracture) of the donor site is low. Relative contraindications to the procedure include concomitant clinically significant peripheral neuropathy and severe osteopenia. Since cortical bone is not available from the distal tibia, procedures requiring corticocancellous strut or block grafts cannot rely solely on distal tibial grafting, although this procedure can be used to supplement iliac crest grafting when necessary.

Use of bone morphogenetic protein-2 in the rabbit ulnar nonunion model

The ability of the osteoinductive protein and recombinant human bone morphogenetic protein-2, combined with polylactic glycolic acid porous microspheres and autologous blood clot to heal a large segmental defect was tested in a rabbit diaphyseal defect model. Two centimeter nonuniting defects were surgically created in the bilateral ulnae of 50 male New Zealand white rabbits. Each defect was then implanted with a pastelike polylactic glycolic acid/blood clot combination that was mixed with 5 different concentrations of recombinant human bone morphogenetic protein-2. The forearms were radiographically assessed on a biweekly schedule for 8 weeks. At 8 weeks, all animals were sacrificed and forearms radiographed. Radiographs were then scored by 3 independent observers for bone formation and union rates. United limbs were tested in torsion for mechanical strength using a Burstein torsion tester. All nonunited limbs were analyzed histologically as were 2 united limbs from each dosage group. Radiographic evaluation revealed that there was a dose dependent response in healing of the ulnar defect with a higher bone formation rate in the 2 higher dose limbs than in the lower dose limbs. Union was achieved in 100% of the highest dose limbs, whereas only 50% of the lowest dose limbs achieved bony union. No defects implanted with carrier alone achieved union. Biomechanical studies revealed significantly stiffer bone than age matched controls. Histologic analysis demonstrated normal bone formation with abundant normal appearing osteoid. These dose response data further support the role of recombinant human bone morphogenetic protein-2 as a potent morphogen in bone regeneration.

Porous ceramics as bone graft substitutes in long bone defects: a biomechanical, histological, and radiographic analysis

Three porous ceramic bone graft materials were compared with regard to their ability to heal a 2.5 cm defect created surgically in a bilateral canine radius model. The ceramic materials were analyzed at 12 and 24 weeks after surgery and included tricalcium phosphate, hydroxyapatite, and collagen hydroxyapatite, which contained a mixture of 35% tricalcium phosphate and 65% hydroxyapatite with added collagen. Each material was evaluated alone and with added bone marrow aspirate. All the implants were compared with a graft of autogenous cancellous bone in the contralateral radius. Biomechanical testing and radiographic evaluation revealed that the addition of bone marrow aspirate was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable with those of cancellous bone. Collagen hydroxyapatite performed well without the addition of bone marrow, although the addition of marrow did have a positive effect. Further qualitative radiographic and histological analysis demonstrated that tricalcium phosphate was the only ceramic that showed any sign of degradation at 24 weeks. This observed degradation proved to be an important factor in evaluating radiographs because the radiodensity of collagen hydroxyapatite and hydroxyapatite interfered with the determination of radiographic union. At 24 weeks, tricalcium phosphate with bone marrow was the material that performed most like cancellous bone. In this study, the biomechanical and radiographic parameters of tricalcium phosphate with bone marrow were roughly comparable with those of cancellous bone at 12 and 24 weeks. Tricalcium phosphate was the only implant that showed significant evidence of degradation at 24 weeks by both histological and radiographic evaluations, and this degradation took place only after a degree of mechanical competence necessary for weight-bearing was achieved.

Deep-frozen allogeneic cancellous bone grafts in 10 dogs: a case series

Deep-frozen, aseptically collected and processed allogeneic cancellous bone was implanted in eight dogs during the surgical repair of diaphyseal long bone fractures and in two dogs during arthrodeses. A combined allogeneic and autogeneic cancellous bone graft was used in two fractures with a segmental bone loss of more than 5 cm. Bone union occurred in five fractures and in both arthrodeses. Failure of fixation occurred in two dogs with nonunion fractures and in a third dog with an open, infected fracture. Biopsies from the fracture sites were obtained from these dogs following failure of their fracture fixation. The cancellous bone graft appeared to be in the process of normal incorporation in each case. Failure of fixation was attributed to technical or case management errors or both, in each of the three fractures that failed to achieve bony union. Frozen allogeneic cancellous bone grafts were effectively incorporated when used in the primary repair of fractures and arthrodeses. Combined autogenous and allogeneic cancellous bone grafts may be particularly useful in the repair of fractures with large segmental diaphyseal bone defects. The use of allogeneic cancellous bone grafts in nonunion fractures requires further investigation before it can be recommended.

Evaluation of ground cortical autograft as a bone graft material in a new canine bilateral segmental long bone defect model

The recent orthopaedic literature reflects a growing number of bone graft substitutes and osteogenic growth factors under investigation in a number of animal models. We attempted to establish a well-controlled, large animal model of a segmental defect in a weight-bearing long bone by developing a bilateral diaphyseal radial defect model in the canine. We also evaluated the effectiveness of ground cortical autograft as a graft material. Twenty-three adult mongrel dogs underwent bilateral radial osteotomies with creation of a 2.0-2.5-cm diaphyseal defect on each side. All dogs received cancellous autograft (CAN) on one side, nine received no graft material (DEF) on the opposite side, and 14 received morselized cortical autograft (CORT) on the opposite side. Radii were stabilized by external fixation. Animals were followed radiographically at 6-week intervals to evaluate the healing process. Thirteen dogs were sacrificed at short-term follow-up (8-12 weeks postsurgery) and 10 at long-term (16-24 weeks). Biomechanical torsion testing to failure and histological evaluation were performed on each defect. All CAN radii achieved union (100%) while only one of nine DEF radii (11%) and none of 14 (0%) of CORT radii achieved union. Statistically significant differences in biomechanical parameters between both test groups and their corresponding autograft control radii were found. Histology revealed fibrous nonunions in the DEF and CORT radii. These results demonstrate that the bilateral canine radial defect model represents a consistent and reproducible model for bone healing of segmental defects in weight-bearing long bones and that ground cortical autograft is an ineffective graft material.

The role of a composite, demineralized bone matrix and bone marrow in the treatment of osseous defects

The efficacy of demineralized bone matrix (DBM) used alone and with bone marrow as a graft material in the treatment of osseous defects was evaluated in 48 patients. Of these 48 patients, 39 were available to follow up and review. Follow up averaged 19 months for all patients. In the entire series, 30 of 39 patients demonstrated osseous union for a 77% success rate. Patients with fracture nonunion represented the most recalcitrant group clinically, with union achieved in only 61% of these cases. Overall, the 39 patients grafted with DBM demonstrated healing that was comparable to results achieved with standard iliac crest bone graft. The results indicate the DBM and marrow composite grafting is a suitable alternative to autologous iliac crest bone graft for use in certain clinical situations, such as bone defects in children, comminuted fractures with associated bone loss, nonunited fractures, or to augment an intended arthrodesis site.

Protein release kinetics of a biodegradable implant for fracture non-unions

Non-union of long bone fractures is often a serious complication of fracture healing. It is estimated that 100 000 non-unions occur in the united States annually and result in the loss of function of the involved limb. The present study was performed to develop a microporous polylactic acid-polyglycolic acid (PLA-PGA) implant for the delivery of bone morphogenetic protein (BMP) to sites of fracture non-unions, and to characterize the protein release kinetics of such an implant in vitro. A 50:50 copolymer of PLA-PGA was used to fabricate the implants using a gel formation technique. The implants were subjected to hydrolytic degradation in phosphate-buffered saline at 37 degrees C for up to 72 d. The protein release and the polymer degradation were monitored during this time period. The release kinetics of these implants were studied using a model protein, soybean trypsin inhibitor (TI), as well as BMP. The results indicate that there is a burst release of the proteins in the initial 48 h followed by a lower elution rate. The release of both the proteins followed similar trends. The molecular weight of the polymer decreased at a faster rate compared to its mass.

Induction of bone by a demineralized bone matrix gel: a study in a rat femoral defect model

Demineralized bone matrix contains osteoinductive factors and stimulates filling of gaps and defects with bone; however, it is difficult to handle by itself and various preparations have been tested. Demineralized bone matrix with a gel consistency now is available for clinical use. We studied, in a femoral segment defect in the rat, the effects of rat demineralized bone matrix gel with and without a ceramic substratum. This preparation is analogous to the human demineralized bone matrix in the same carrier, used clinically for humans. One hundred adult male Fischer rats were divided into 10 experimental groups. Independent variables included the presence or absence of hydroxyapatite ceramic cylinders, the presence of demineralized bone matrix in carrier or carrier alone (glycerol), and the duration of observation (1, 2, and 4 months). Defects filled with the gel alone had significantly higher radiographic scores for host-graft union at 4 months compared with ceramic with the gel, ceramic alone, or carrier alone. Demineralized bone matrix gel significantly increased the total histologic score for host-graft union, whether ceramic was present or not, and a three-way interaction occurred among ceramic, the gel, and time. Demineralized bone matrix gel was an effective inducer of bone formation in this model. An additional substratum was not required; in fact, significantly more bone was formed in the absence of the ceramic cylinder. Neither the gel nor the ceramic were impediments to revascularization of the defect. Host-graft union was enhanced by demineralized bone matrix gel but not by the ceramic cylinder.

Lumbar intertransverse-process spinal arthrodesis with use of a bovine bone-derived osteoinductive protein. A preliminary report

The use of a bovine bone-derived osteoinductive protein extract as a bone-graft substitute was evaluated in a rabbit model of intertransverse process arthrodesis of the lumbar spine. Forty-five adult New Zealand White rabbits had arthrodesis between the fifth and sixth lumbar vertebrae with use of one of three graft materials: autogenous iliac-crest bone, osteoinductive protein delivered in an allogeneic demineralized bone matrix/collagen carrier, or demineralized bone matrix/collagen carrier or demineralized bone matrix/collagen carrier without osteoinductive protein. Fusion was assessed by manual palpation, radiography, biomechanical testing, and light microscopy at two and five weeks after the operation. At two weeks, light microscopic analysis of the arthrodesis site in which osteoinductive protein had been used showed that most of the demineralized bone matrix was still present, with small amounts of membranous and endochondral bone formation at the peripheral margins of the implant. Light microscopic analysis of the five-week specimens showed increased new-bone formation and a more homogeneous and mature fusion mass with the osteoinductive bone protein than with the autogenous bone graft. At five weeks, the fusions with the osteoinductive protein extract were characterized by more secondary spongiosa, with formation of bone marrow centrally and a cortical rim peripherally. Of the thirty-five rabbits that were examined at five weeks, all ten in the group that had received osteoinductive bone protein had a solid fusion, but the rate of fusion was significantly less in the other two groups: eight of thirteen rabbits (p = 0.05) in the group that had received autogenous bone graft and two of twelve rabbits (p = 0.0001) in the group that had received demineralized bone matrix/collagen carrier without osteoinductive bone protein. The use of osteoinductive bone protein resulted in stronger (p = 0.02) and stiffer (p = 0.005) fusions compared with those obtained with the use of autogenous iliac-crest graft.

Does xenogeneic demineralized bone matrix have clinical utility as a bone graft substitute?

Autologous bone harvested from the iliac crest is a commonly used grafting material for a number of surgical procedures; however, there is documented morbidity associated with secondary site harvesting. Because demineralized bone matrix (DBM) is inherently osteoinductive (i.e., it facilitates differentiation of uncommitted connective tissue cells into bone-forming cells), it has potential appeal as a bone-graft substitute. Allogeneic DBM usage has intrinsic shortcomings related to procuring, processing and characterizing bone from a human donor pool. Xenogeneic bone represents an unlimited supply of available material if it can be processed to render it safe for transplantation to the human host. It is hypothesized that reported immunogenicity and non-viability of xenogeneic DBM results from lipids and plasma proteins not removed during typical demineralization processes. The authors propose a rigorous examination of this hypothesis, followed by several pivotal studies to determine the effectiveness of xenogeneic DBM.

Effect of recombinant human osteogenic protein-1 on healing of segmental defects in non-human primates

The effect of recombinant human osteogenic protein-1 on the healing of segmental bone defects was studied in twenty-eight African green monkeys (Cercopithecus aethiops). A 2.0-centimeter osteoperiosteal defect was created in the middle of the ulnar shaft in fourteen animals and in the diaphysis of the tibia in the other fourteen. The ulnar defect was filled with an implant consisting of 1000 micrograms of recombinant human osteogenic protein-1 in 400 milligrams of bovine bone-collagen carrier in six animals, with collagen carrier alone in two animals, and with autogenous cancellous bone graft from the contralateral tibia and femur in six animals. The tibial defect was filled with 250, 500 (two tibiae), 1000, or 2000 micrograms of recombinant human osteogenic protein-1 in 400 milligrams of collagen carrier in five animals, with collagen carrier alone in one animal, and with autogenous cancellous bone graft in six animals; in the two remaining animals (controls), the tibial defect was left unfilled. The tibial defects were stabilized with an intramedullary Steinmann pin. All animals were killed at twenty weeks postoperatively. Healing of the defects was evaluated with biweekly radiographs, with histological examination, and with mechanical testing. Radiographically, all of the defects that had been treated with recombinant human osteogenic protein-1 exhibited new-bone formation, but they differed in the degree of healing and remodeling. Five of the six ulnae treated with recombinant human osteogenic protein-1 and four of the five tibiae treated with this substance exhibited complete healing at six to eight weeks, with bridging of the defect by new bone first observed at four weeks. The two unhealed defects both exhibited new-bone formation but incomplete union, which precluded mechanical testing. No defect that had been filled with collagen carrier or that had been left unfilled exhibited any signs of healing or major new-bone formation. None of the six ulnae that had been filled with autogenous bone graft exhibited complete healing, compared with five of the six tibiae that had been so treated. Histological evaluation of the defects treated with recombinant human osteogenic protein-1 revealed the formation of new cortices with areas of woven and lamellar bone and normal-appearing marrow elements at twenty weeks postoperatively. The tibial defects that had been treated with autogenous bone graft had a similar appearance. All control ulnar and tibial defects and all ulnar defects that had been treated with autogenous bone graft had fibrous union with little new-bone formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Distal tibia bone graft for arthrodesis of the foot and ankle

Forty patients since 1988 have had distal tibial bone grafting for 41 arthrodeses of the foot and ankle. Bone graft is obtained through a cortical window made just above the medial metaphyseal distal tibial flare. Average follow-up was 23.3 months. Forty of 41 arthrodesis sites fused; there was only one nonunion. There were no delayed unions. There were no complications at the donor site based on patient examination and radiographs. Ipsilateral ankle motion was not affected by the bone graft procedure. Cited complications from iliac crest bone graft include donor site pain, blood loss, heterotopic bone formation, pelvic instability, iliac hernia, infection, fracture, and deformity. Complications with allografts include disease transmission and immune response. These are avoided by using locally obtained distal tibia autograft for arthrodeses in the foot and ankle.

Wrist arthrodesis for traumatic conditions: a study of plate and local bone graft application

This study demonstrates the ability to obtain a predictable and complete wrist arthrodesis using local bone graft and a dorsal plate. The donor site morbidity often seen in using iliac crest graft is eliminated with this method. We examined the use of local distal radius bone grafting alone with dorsal plate fixation and its ability to provide a predictable fusion. Twenty-eight consecutive patients underwent wrist arthrodesis by a standard plate fixation technique. Average patient age was 34 years with an average period of symptom duration of 2.1 years. The cohort had undergone 17 previous wrist surgical procedures prior to wrist arthrodesis. The average followup examination period was 2 years. Grip strength, x-ray films, and range of motion were evaluated. All patients had a solid wrist arthrodesis at final follow-up examination. Grip strength, pronation/supination, and digital motion did not change significantly from the preoperative status. No patients complained of wrist pain or instability. Complications included extensor tendinitis at the distal aspect of the plate in four patients requiring plate removal, carpal tunnel syndrome requiring decompression, and distal radioulnar joint pain requiring intra-articular injection of corticosteroid.

Histological and electron microscopic analysis of tissue response to synthetic composite bone graft in the canine

A synthetic composite bone graft material, composed of fibrillar collagen, hydroxyapatite, and tricalcium phosphate, was evaluated in canine femoral shaft defects and compared to ungrafted defects and defects grafted with autogenous bone. The results of mechanical testing of the grafted femora in torsion at 1 year postoperatively were previously reported. This report details the histological and microscopic features of the graft sites. The results of this study suggest that the healing of the graft site is not yet complete at 1 year and that healing may be more complete in defects that received the synthetic graft as compared to ungrafted sites and autogenous bone graft. The bone tissue appears to respond to the graft particles as if they were bone particles.

Arthrodesis of the cervical spine for fractures and dislocations in children and adolescents. A long-term follow-up study

Forty-two patients who had had an arthrodesis for instability of the cervical spine resulting from trauma were followed clinically for a minimum of seven years (median, seventeen years and six months). The ages of the patients at the time of the injury ranged from one year and eleven months to fifteen years and eleven months. On the basis of a new post-traumatic neck score, which includes an assessment of pain, mobility, neurological status, and function, thirty-two patients (76 per cent) had an excellent result, six (14 per cent) had a good result, and four (10 per cent) had a fair result. No patient had a poor result. There was no notable deterioration of the clinical result with an increased duration of follow-up. Current radiographs of the cervical spine in flexion and extension were available for thirty-one (74 per cent) of the forty-two patients. There was no change in stability, deformity, or the fusion mass after healing or with an increased duration of follow-up, but there was a significant increase in osteoarthrotic changes in the unfused segments of the cervical spine after an increased duration of follow-up (p = 0.0001). Complications included spontaneous extension of the fusion mass in sixteen patients (38 per cent), mild pain or dysesthesias at the iliac-crest donor site in six patients (14 per cent), superficial infection at a bone-graft donor site in one patient (2 per cent), an incorrect level of arthrodesis in one patient (2 per cent). One patient had instability secondary to juvenile rheumatoid arthritis, which developed after treatment of the original injury, and she needed a reoperation. We concluded that spinal arthrodesis for fractures and dislocations of the cervical spine in children and adolescents can be accomplished safely, with an acceptable clinical outcome, a low rate of complications, and minimum morbidity after long-term follow-up. Pain, neurological status, and function do not change markedly, but mobility may decrease with an increased duration of follow-up. Our patients had a decrease in mobility, associated with an increase in osteoarthrotic changes, as seen on radiographs (p = 0.05).

The effect of recombinant human osteogenic protein-1 on healing of large segmental bone defects

A rabbit ulnar non-union model was used to evaluate the effect of recombinant human osteogenic protein-1 on the healing of a large segmental osteoperiosteal defect. A 1.5-centimeter segmental defect was created in the mid-part of the ulnar shaft of adult rabbits. The defect was filled with an implant containing either recombinant human osteogenic protein-1 or naturally occurring bovine osteogenic protein. The recombinant human osteogenic protein-1 implants consisted of a carrier of 125 milligrams of demineralized, guanidine-extracted, insoluble rabbit bone matrix (the collagen carrier), reconstituted with 3.13, 6.25, 12.5, twenty-five, fifty, 100, 200, 300, or 400 micrograms of recombinant human osteogenic protein-1. Animals that received recombinant human osteogenic protein-1 were compared with animals that received an implant of 250 micrograms of a preparation of naturally occurring bovine osteogenic protein mixed with the collagen carrier. Limbs that served as controls received either the collagen carrier alone or no implant at all. The treated and the untreated defects were examined radiographically and histologically at eight or twelve weeks after implantation. Mechanical testing was performed on six animals. All implants of recombinant human osteogenic protein-1, except for those containing 3.13 micrograms of the substance, induced complete radiographic osseous union within eight weeks. The defects that were treated with an implant of bovine osteogenic protein also healed within this time-period. The bone induced by both types of implants had new cortices with advanced remodeling and marrow elements. Histological evaluation of this new bone at eight weeks postoperatively revealed primarily lamellar bone, with the formation of new cortices and normal-appearing marrow elements. The average torsional strength and energy-absorption capacity of the union induced by recombinant human osteogenic protein-1 was comparable with that of intact bone. The control defects that had been implanted with collagen carrier alone and those with no implant showed no bridging of the defect.

Mesenchymal stem cells in bone development, bone repair, and skeletal regeneration therapy

Bone formation in the embryo, and during adult fracture repair and remodeling, involves the progeny of a small number of cells called mesenchymal stem cells (MSCs). These cells continuously replicate themselves, while a portion become committed to mesenchymal cell lineages such as bone, cartilage, tendon, ligament, and muscle. The differentiation of these cells, within each lineage, is a complex multistep pathway involving discrete cellular transitions much like that which occurs during hematopoiesis. Progression from one stage to the next depends on the presence of specific bioactive factors, nutrients, and other environmental cues whose exquisitely controlled contributions orchestrate the entire differentiation phenomenon. An understanding of the cellular and molecular events of osteogenic differentiation of MSCs provides the foundation for the emergence of a new therapeutic technology for cell therapy. The isolation and in vitro mitotic expansion of autologous human MSCs will support the development of novel protocols for the treatment of many clinically challenging conditions. For example, local bone defects can be repaired through site-directed delivery of MSCs in an appropriate carrier vehicle. Generalized conditions, such as osteoporosis, may be treatable by systemic administration of culture-expanded autologous MSCs or through biopharmaceutical regimens based on the discovery of critical regulatory molecules in the differentiation process. With this in mind, we can begin to explore therapeutic options that have never before been available.