The art of bone grafting

Safety of a Porous Hydroxyapatite Bone Substitute in Orthopedics and Traumatology: A Multi-Centric Clinical Study

The development of biomaterials in recent years has made it possible to broaden their use in the surgical field. Although iliac crest bone graft harvesting currently remains the gold standard as an autograft, the properties of hydroxyapatite bone substitutes appear to be beneficial. The first fundamental step to consider is the safety of using these devices. The purpose of this retrospective cohort study is to consider all the adverse events observed in our population and assess their relationships with the bone substitute device. The population analyzed consisted of patients undergoing trauma osteosynthesis with at least one implanted porous hydroxyapatite device. We considered a court of 114 patients treated at "Azienda Ospedaliera Universitaria di Ferrara-U.O. di Ortopedia e Traumatologia" in the period from January 2015 to December 2022. Upon analyzing our population, no adverse events related to the device emerged. Taking into consideration different study groups from other National Hospital Centers, no critical issues were detected except for three cases of extrusion of the biomaterial. It is necessary to clarify that bone substitutes cannot replace compliance with the correct principles linked to the biomechanics of osteosynthesis. This report outlines a safety profile for the use of these devices as bone substitutes in trauma orthopedic surgery.

Quantitative analysis of local bone graft harvested from the posterior elements during posterior spinal fusion in Adolescent Idiopathic Scoliosis patients

Objective

This study analyses the quantity of local bone graft obtained from different anatomical parts of the posterior elements during corrective surgery for Adolescent Idiopathic Scoliosis patients.

Summary of background data

Locally harvested autogenous bone graft eliminates possible donor site morbidity and has all the important basic bone graft properties such as osteoinductivity, osteogenicity and osteoconductivity. Its usage was reported to be adequate to achieve fusion but none had quantifies the amount of local bone graft harvested.

Methods

Total of 40 AIS patients were recruited in the study. All posterior spinal fusion surgeries were performed by the same dual surgeons and same anesthetist with a single observer collecting and measuring bone grafts harvested. The bone grafts harvested from each respective posterior element (spinous processes, laminas, facets and transverses processes) and measured accordingly.

Results

There were 36 females and 4 males. Amongst cases recruited, there were 32% Lenke 1, 28% Lenke 2, 8%Lenke 3, 22%Lenke 5 and 10% Lenke 6. Total thoracic levels involved were 333, whereas lumbar levels were 81. The mean total weight of bone graft obtained per case was 36.5 ± 13.7 g. The total weight of lumbar bone graft to the number of lumbar fusion levels (4.5 ± 1.2 g/fusion level) was significantly higher than the total weight of thoracic bone graft to the number of thoracic fusion levels (3.2 ± 1.2 g/fusion level). The amount of bone graft was obtained was highest from lumbar spinous process (42%), followed by thoracic spinous process (32%), lumbar lamina (29%), lumbar facet (28%), thoracic lamina (25%), thoracic facet (22%), and thoracic transverse process (21%).

Conclusions

Lumbar vertebra provided more bone graft than thoracic vertebra. Spinous processes contributed the highest amount of local bone graft in the thoracic and lumbar spine.

Postoperative Complications Associated With rhBMP2 Use in Posterior/Posterolateral Lumbar Fusion

STUDY DESIGN

Retrospective database review.

OBJECTIVE

Posterior/posterolateral lumbar fusion (PLF) is an effective treatment for a variety of spinal disorders; however, variations in surgical technique have different complication profiles. The aim of our study was to quantify the frequency of various complications in patients undergoing PLF with and without human recombinant bone morphogenetic protein 2 (rhBMP2).

METHODS

We queried the orthopedic subset of the Medicare database (PearlDiver) between 2005 and 2011 for patients undergoing PLF procedures with and without rhBMP2. Complication and reoperation rates were analyzed within 1 year of the index procedure. Complications assessed include: acute renal failure, deep vein thrombosis, dural tear, hematoma, heterotopic ossification, incision and drainage, cardiac complications, nervous system complications, osteolysis, pneumonia, pseudarthrosis, pulmonary embolism, radiculopathy, respiratory complications, sepsis, urinary retention, urinary tract infection, mechanical, and wound complications. Chi-square analysis was used to calculate the complication differences between the groups.

RESULTS

Our data revealed higher overall complication rates in patients undergoing PLF with rhBMP2 versus no_rhBMP2 (76.9% vs 68.8%, P < .05). Stratified by gender, rhBMP2 males had higher rates of mechanical complications, pseudarthrosis, and reoperations compared with no_rhBMP2 males (P < .05), whereas rhBMP2 females had higher rates of pseudarthrosis, urinary tract infection, and urinary retention compared with no_rhBMP2 females (P < .05).

CONCLUSION

Our data revealed higher overall complication rates in PLF patients given rhBMP2 compared with no_rhBMP2. Furthermore, our data suggests that rhBMP2-associated complications may be gender specific.

Extraordinary biological properties of a new calcium hydroxyapatite/poly(lactide-co-glycolide)-based scaffold confirmed by in vivo investigation

This study examined the potential of a new porous calcium hydroxyapatite scaffold covered with poly (lactide-co-glycolide) (PLGA) as a bone substitute, identifying its advantages over Geistlich Bio-Oss®, considered the gold standard, in in vivo biofunctionality investigations. Structural and morphological properties of the new scaffold were analyzed by scanning electron and atomic force microscopy. The biofunctionality assays were performed on New Zealand white rabbits using new scaffold for filling full-thickness defects of critical size. The evaluated parameters were: the presence of macrophages, giant cells, monoocytes, plasma cells, granulocytes, neoangiogenesis, fibroplasia, and the percentage of mineralization. Parallel biofunctionality assays were performed using Geistlich Bio-Oss®. The appearance of bone defects 12 weeks after the new scaffold implantation showed the presence of a small number of typical immune response cells. Furthermore, significantly reduced number of capillary buds, low intensity of fibroplasia and high degree of mineralization in a lamellar pattern indicated that the inflammation process has been almost completely overcome and that the new bone formed was in the final phase of remodeling. All biofunctionality assays proved the new scaffold's suitability as a bone substitute for applications in maxillofacial surgery. It showed numerous biological advantages over Geistlich Bio-Oss® which was reflected mainly as a lower number of giant cells surrounding implanted material and higher degree of mineralization in new formed bone.

In vitro degradation of calcium phosphates: Effect of multiscale porosity, textural properties and composition

The capacity of calcium phosphates to be replaced by bone is tightly linked to their resorbability. However, the relative importance of some textural parameters on their degradation behavior is still unclear. The present study aims to quantify the effect of composition, specific surface area (SSA), and porosity at various length scales (nano-, micro- and macroporosity) on the in vitro degradation of different calcium phosphates. Degradation studies were performed in an acidic medium to mimic the osteoclastic environment. Small degradations were found in samples with interconnected nano- and micropores with sizes below 3µm although they were highly porous (35-65%), with maximum weight loss of 8wt%. Biomimetic calcium deficient hydroxyapatite, with high SSA and low crystallinity, presented the highest degradation rates exceeding even the more soluble β-TCP. A dependence of degradation on SSA was indisputable when porosity and pore sizes were increased. The introduction of additional macroporosity with pore interconnections above 20µm significantly impacted degradation, more markedly in the substrates with high SSA (>15m²/g), whereas in sintered substrates with low SSA (<1m²/g) it resulted just in a linear increase of degradation. Up to 30 % of degradation was registered in biomimetic substrates, compared to 15 % in β-TCP or 8 % in sintered hydroxyapatite. The incorporation of carbonate in calcium deficient hydroxyapatite did not increase its degradation rate. Overall, the study highlights the importance of textural properties, which can modulate or even outweigh the effect of other features such as the solubility of the compounds.

STATEMENT OF SIGNIFICANCE

The physicochemical features of calcium phosphates are crucial to tune biological events like resorption during bone remodeling. Understanding in vitro resorption can help to predict the in vivo behavior. Besides chemical composition, other parameters such as porosity and specific surface area have a strong influence on resorption. The complexity of isolating the contribution of each parameter lies in the close interrelation between them. In this work, a multiscale study was proposed to discern the extent to which each parameter influences degradation in a variety of calcium phosphates, using an acidic medium to resemble the osteoclastic environment. The results emphasize the importance of textural properties, which can modulate or even outweigh the effect of the intrinsic solubility of the compounds.

Management of post-traumatic bone defects of the tibia using vascularised fibular graft combined with Ilizarov external fixator

INTRODUCTION

Post-traumatic bone defects of the tibia present a difficult reconstructive challenge. Various methods of reconstruction are available, such as allografts, vascularised fibular graft (either free or pedicled) and bone transport technique.

PATIENTS AND METHODS

Fourteen patients with an average age of 34.1 years at operation (range, 12-65) with post-traumatic bony defects of the tibia were selected for reconstruction with vascularised fibular graft combined with Ilizarov external fixation. There were 12 male and two female. The size of the bony gap was 10.4 cm (range, 7-13) and the average length of the fibula used was 16.4 cm (range, 14-21).

RESULTS

The mean follow up period was 20.4 months (range, 10-37). All patients had bony union at both proximal and distal ends of the fibula primarily except one patient that required secondary iliac bone graft at the distal end of the fibula to obtain union. The average time for bone healing was 3.9 months (range, 3-9). The average time spent in Ilizarov frame was 5.9 months (range, 5-11). Unprotected full weight-bearing was achieved within an average of 7.3 months (range, 6-12).

CONCLUSION

Vascularised fibular bone graft combined with an Ilizarov frame is a successful approach to safely and effectively reconstruct bone defects of the tibia. It has the advantages of vascularised fibular bone grafts together with the biomechanical advantages of Ilizarov frame that allows weight bearing to start almost immediately after surgery. This leads to a good outcome regarding the union and function.

Posterior lumbar fusion: choice of approach and adjunct techniques

The choice among the many options of approach and adjunct techniques in planning a posterior lumbar fusion can be problematic. Debates remain as to whether solid fusion has an advantage over pseudarthrosis regarding long-term symptom deterioration and whether an instrumented or a noninstrumented approach will best serve clinically and/or cost effectively, particularly in elderly patients. Increased motion resulting in higher rates of nonunion and the use of nonsteroidal anti-inflammatory drugs have been studied in animal models and are presumed risk factors, despite the lack of clinical investigation. Smoking is a proven risk factor for pseudarthrosis in both animal models and level III clinical studies. Recent long-term studies and image/clinical assessment of lumbar fusions and pseudarthrosis show that, although imaging remains a key area of difficulty in assessment, including an instrumented approach and a well-selected biologic adjunct, as well as achieving a solid fusion, all carry important long-term clinical advantages in avoiding revision surgery for nonunion.

Bone regeneration in sheep using acropora coral, a natural resorbable scaffold, and autologous mesenchymal stem cells

Tissue constructs containing mesenchymal stem cells (MSC) are an appealing strategy for repairing massive segmental bone defects. However, their therapeutic effectiveness does not match that of autologous bone grafts; among the complicating reasons, the scaffold resorbability has been identified as a critical feature for achieving bone regeneration. In the present study, the osteogenic potential of constructs obtained by expanding autologous MSC onto granules of Acropora coral, a natural fully-resorbable scaffold, was investigated. MSC adhered and proliferated well in vitro after 1 week. When implanted in vivo into long-bone, critical-size defects in sheep (n=5), these constructs exhibited a two-fold increase in bone formation 6 months postimplantation compared to Acropora scaffolds alone (n=5). Interestingly, osteogenesis, mediated by MSC, within these constructs was found continuous not only with the bony stumps, but also at the core of the implants. Scaffold resorption was almost complete at 6 months, leading to full bone regeneration in one animal. Acropora coral appear to be an appealing scaffold for bone tissue engineering because it supported in vitro MSC adhesion and proliferation. Moreover, these results provided evidence that MSC could promote bone regeneration in sheep when loaded one a natural fully resorbable scaffold.

A systematic review of comparative studies on bone graft alternatives for common spine fusion procedures

BACKGROUND

The increased prevalence of spinal fusion surgery has created an industry focus on bone graft alternatives. While autologous bone graft remains the gold standard, the complications and morbidity from harvesting autologous bone drives the search for reliable and safe bone graft substitutes. With the recent information about the adverse events related to bone morhogenetic protein use, it is appropriate to review the literature about the numerous products that are not solely bone morphogenetic protein.

PURPOSE

The purpose of this literature review is to determine the recommendations for use of non-bone morphogenetic protein bone graft alternatives in the most common spine procedures based on a quantifiable grading system.

STUDY DESIGN

Systematic literature review.

METHODS

A literature search of MEDLINE (1946-2012), CINAHL (1937-2012), and the Cochrane Central Register of Controlled Trials (1940-April 2012) was performed, and this was supplemented by a hand search. The studies were then evaluated based on the Guyatt criteria for quality of the research to determine the strength of the recommendation.

RESULTS

In this review, more than one hundred various studies on the ability of bone graft substitutes to create solid fusions and good patient outcomes are detailed.

CONCLUSION

The recommendations for use of bone graft substitutes and bone graft extenders are based on the strength of the studies and given a grade.

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) in posterolateral lumbar spine fusion: complications in the elderly

Study design

Retrospective cohort study of 1430 patients undergoing lumbar spinal fusion from 2002 - 2009. Objective: The goal of this study was to compare and evaluate the number of complications requiring reoperation in elderly versus younger patients.

Summary of background data

rhBMP-2 has been utilized off label for instrumented lumbar posterolateral fusions for many years. Many series have demonstrated predictable healing rates and reoperations. Varying complication rates in elderly patients have been reported.

Materials and methods

All patients undergoing instrumented lumbar posterolateral fusion of ≤ 3 levels consenting to utilization of rhBMP-2 were retrospectively evaluated. Patient demographics, body mass index, comorbidities, number of levels, associated interbody fusion, and types of bone void filler were analyzed. The age of patients were divided into less than 65 and greater than or equal to 65 years. Complications related to the performed procedure were recorded.

Results

After exclusions, 482 consecutive patients were evaluated with 42.1% males and 57.9% females. Average age was 62 years with 250 (51.9%) < 65 and 232 (48.1%) ≥ 65 years. Patients ≥ 65 years of age stayed longer (5.0 days) in the hospital than younger patients (4.5 days) (p=0.005).

Complications requiring reoperation were: acute seroma formation requiring decompression 15/482, 3.1%, bone overgrowth 4/482, 0.8%, infection requiring debridement 11/482, 2.3%, and revision fusion for symptomatic nonunion 18/482, 3.7%. No significant differences in complications were diagnosed between the two age groups. Statistical differences were noted between the age groups for medical comorbidities and surgical procedures. Patients older than 65 years underwent longer fusions (2.1 versus 1.7 levels, p=0.001).

Discussion

Despite being older and having more comorbidities, elderly patients have similar complication and reoperation rates compared to younger healthier patients undergoing instrumented lumbar decompression fusions with rhBMP-2.

A novel murine femoral segmental critical-sized defect model stabilized by plate osteosynthesis for bone tissue engineering purposes

Mouse models are invaluable tools for mechanistic and efficacy studies of the healing process of large bone defects resulting in atrophic nonunions, a severe medical problem and a financial health-care-related burden. Models of atrophic nonunions are usually achieved by providing a highly stable biomechanical environment. For this purpose, external fixators have been investigated, but plate osteosynthesis, despite its high clinical relevance, has not yet been considered in mice. We hereby proposed and investigated the use of an internal osteosynthesis for stabilizing large bone defects. To this aim, a 3.5-mm-long segmental bone defect was induced in the mid-shaft of the femur using a Gigli saw and a jig. Bone fixation was performed using a titanium microlocking plate with four locking screws. The bone defect was either left empty or filled with a syngenic bone graft or filled with a coralline scaffold. Healing was monitored using radiographs. The healing process was further assessed using microcomputed tomography and histology 10 weeks after surgery. With the exception of one mouse that died during the surgical procedure, no complications were observed. A stable and reproducible bone fixation as well as a reproducible fixation of the implanted materials with full weight bearing was obtained in all animals tested. Nonunion was consistently observed in the group in which the defects were left empty. Bone union was obtained with the syngenic bone grafts, providing evidence that, although such defects were of critical size, bone healing was possible when the gold-standard material was used to fill the defect. Although new bone formation was greater in the coralline scaffold group than in the left-empty animal group, it remained limited and localized close to the bony edges, a consequence of the critical size of such bone defect. Our study established a reproducible, clinically relevant, femoral, atrophic nonunion, critical-sized defect, low morbidity mouse model. The present study was successful in designing and testing in a small animal model, a novel surgical method for the assessment of bone repair; this model has the potential to facilitate investigations of the molecular and cellular events involved in bone regeneration in load-bearing, segmental-bone defects.

Porous calcium sulfate ceramics with tunable degradation rate

It would be ideal if bone substitutes could be absorbed by the human body upon the formation of new bone. Although calcium sulfate is absorbable, its biodegradation rate is very fast. Fortunately, this rate can be reduced significantly through various sintering techniques. This study demonstrates that the degradation rate of sintered CS specimens can be adjusted through the introduction of pores. Through various techniques, we introduced spherical pores with amounts ranging from 6.7 to 68 % into sintered CS specimens. The corresponding degradation rate in Hank's solution varied from 1.9 to 7.7 %/day and the cytotoxicity test results indicated low toxicity within the sintered CS specimens.

Free vascularised fibular grafting combined with a locking plate for massive bone defects in the lower limbs: a retrospective analysis of fibular hypertrophy in 18 cases

OBJECTIVE

Free vascularised fibular grafting (FVFG) could be a good option for the restoration of massive bone defects in lower limbs when combined with use of a locking plate. The progress of fibular hypertrophy is closely related to regain of function, as well as to prevention of stress fractures. Multiple variables affecting fibular hypertrophy were investigated in the current study to elucidate correlative factors.

METHODS

Eighteen patients with a massive bone defect in a lower limb reconstructed by FVFG combined with a locking plate were retrospectively enrolled in the current study. The degree of fibular hypertrophy was calculated based on the measurements from anteroposterior imaging at regular intervals of 3 months, 6 months, 1, 2 and 3 years postoperatively. Repeated measures analysis of variance was employed to evaluate and compare correlative factors including gender (male vs. female), age distribution (<30 years vs. >30 years), site (femur vs. tibia) and length of bone defect (6-10 cm vs. >10 cm), previous number of operations (once vs. more than twice) and concomitant infection (detected vs. non-detected).

RESULTS

All defects could be successfully repaired by FVFG and bone union was achieved uneventfully. The degree of fibular hypertrophy was 0.14%, 11.27%, 31.53%, 58.14% and 71.81% retrospectively at the five follow-up time points. Statistical analysis revealed that the above-mentioned factors did not affect the progress of fibular hypertrophy.

CONCLUSIONS

FVFG could be a good choice for the reconstruction of massive bone defects when combined with a locking plate. Factors including gender, age distribution, site and length of bone defects, number of previous operations and infection do not impact the progress of fibular hypertrophy, which implies that intrinsic factors might play an important role in restoration.

Complications and concerns with osteobiologics for spine fusion in clinical practice

STUDY DESIGN

Literature-based topic review.

OBJECTIVE

To review the complications and the concerns that may be associated with all of the commonly used osteobiologic options for spine fusion.

SUMMARY OF BACKGROUND DATA

Obtaining a solid arthrodesis is an important objective in many lumbar surgical procedures, and a wide array of bone graft materials may be used in an attempt to achieve this goal. Iliac crest bone graft, as well as all of the available osteobiologic alternatives, carries potential risks and concerns for both patient and surgeon.

METHODS

Review of literature and expert opinion.

CONCLUSION

Some of the potential complications associated with osteobiologic materials used in spinal fusion are well understood and clearly documented whereas others require further study and clarification. In any given clinical situation, the patient and surgeon need to balance the benefits and performance characteristics of the graft material with the risk profile to optimize clinical management.