Minimally invasive techniques for harvesting iliac crest bone graft have evolved in an attempt to reduce donor site morbidity and to increase the harvested volume [27
]. Despite their reported advantages such as a reduced risk of infection, less chance of fracture of the ilium, reduced blood loss and operating time, these approaches are still problematic. In the case of tri-cortical autologous iliac crest bone harvesting, local donor site morbidity is significant since the created bone defect is large, palpable, increases the risk of abdominal contents’ hernias and exposes bleeding surfaces of cancellous bone predisposing to hematomas, seromas and infections.
This cohort study describes the safety and efficacy of a specific surgical technique of filling the corticocancellous defect at the donor site. Certain limitations have to be considered in the herein report including the small number of cases evaluated, the retrospective nature of the study and the lack of a control group. However, this is the first report in the literature of the use of this specific xenograft and technique. Strengths of this study include the long follow-up time and the consistency of the surgical technique as one surgeon performed all the procedures. Assessment of graft’s incorporation was based on the report of a senior radiologist being independent from the surgical team and as such any potential bias from the analysis of the radiographs by the surgical team was eliminated. A strength of the study can also be considered the fact that the radiological evidence obtained was supplemented by the clinical findings and the subjective patient-reported outcome.
In general terms, reconstruction of iliac crest bone defects using this cancellous bovine substitution material was associated with a satisfactory radiological and clinical outcome. In clinical practice it offered an easy-to-reproduce technique of addressing sizable donor-site defects after harvesting of tri-cortical iliac bone graft. Graft incorporation is usually related to the vitality of the host bed and the amplitude of local pre-osteogenic or osteogenic cell populations. We believe that the iliac host bed was not only well vascularised but also rich in osteo-progenitor cells [34
]. Moreover, the custom-made sizing of the inserted graft and the press fit insertion, supplemented when needed by screw fixation, offered the required local stability, maximising graft incorporation.
The xenograft serves primarily as void filler that allows osteo-conduction of the host cells into its mass, resulting in progressive incorporation of the graft into the host bone. Incorporation is a series of events (creeping substitution) including gradual replacement of grafted bone by host bone through a mechanism of osteoclastic resorption followed by deposition of new bone [28
]. Experimentally, about half of a massive cortical bone autograft will be replaced by living bone after six months of implantation [29
]. However, in human allografts or xenografts substitution of less than 10 % has been observed at the same period of time [30
The bovine cancellous xenograft used in this study offers many advantages. Its biomechanical characteristics have been well tested indicating no structural deficits after its chemical processing [31
]. The main indications are areas where trabecular bone is required, filling in of bone defects and plastic reconstruction of damaged bone regions. Moreover, these indications can be extended to iliac crest defects of any size and shape, since it can be fashioned without difficulty.
In a recent retrospective study, the clinical and radiological outcomes of subtalar fusion with and without bovine cancellous bone grafting were evaluated [32
]. High rates of failure were found and the authors advised an extreme caution when considering the use of this material in subtalar joint fusions. However, they recognized that vascular insufficiency, which usually characterizes the patients undergoing subtalar fusion, could have contributed to the poor graft integration.
In contrast, Lakdawala et al. [33
] reported satisfactory outcomes with good osseointegration with the use of Tutobone® in patients who underwent revision knee arthroplasty. Furthermore, Meyer et al. [34
] evaluated the histological osseointegration of this substitute used in high tibial osteotomy and revision hip arthroplasty in humans. Analysis of the biopsies showed high biocompatibility of the material without any fibrous tissue filled interface. Similarly, the clinical and radiological outcome of the patients in the present study indicated a good incorporation of the xenograft, no loss of alignment and no loss of bone load or infection. The majority of patients were subjectively satisfied having minimal or no pain and no major complications.
Similar case series exist reporting on other methods of addressing the same problem and offer the comparative groups of cases for the present cohort (Table ) [7
Comparison of different materials used in reconstruction of the iliac crest defects
Bapat et al. [20
] and Dave et al. [21
] used rib autograft for reconstruction of the iliac crest during surgery of thoracic spine. The rib, which was removed at the time of thoracotomy, was used and fixed to the iliac crest with a press-fit technique after fashioning it from both ends. No rib graft complication was recorded, the graft was well incorporated and the patients had significantly lower pain. Rightfully, the authors stated that this technique is limited to patients undergoing thoracotomy or thoraco-phreno-lumbotomy for spinal reconstruction.
Bojescul et al. [19
] reported a prospective randomized study of coralline hydroxyapatite used to backfill iliac crest donor sites versus no void filler in five and seven cases respectively. Seventy-five percent of patients showed bone ingrowth on plain radiographs and CT scan, and 100 % showed biological activity on technetium bone scans. All patients reported mild pain to no pain postoperatively. However, the sample of patients was small and follow-up was limited to 12 months.
Japanese authors [10
] have investigated the long-term results of bioactive ceramic spacers and their efficacy in reconstruction of the iliac donor site defect. They reported satisfactory outcome in high percentages, concluding that ceramic materials can be beneficial for reconstruction of the iliac crest defects.
Recently, a cost-effective technique proposed by Gil-Albarova [16
] included the use of bone graft obtained from the bone defect itself. A transverse fence of appropriate thin tri-cortical chips taken from the posterior lateral wall of the donor site was used to reconstruct the iliac crest. No hardware was placed and bone defect healing was satisfactory. However, further studies are needed to prove the efficacy of this technique in reconstruction of larger defects.