Proper design of clinical trials for the assessment of bone graft substitutes

Opening-wedge high tibial osteotomy with and without bone graft

Medial opening-wedge has gained popularity in comparison to other techniques of high tibial osteotomy. This technique involves the creation of a gap in the tibia. Filling the gap with autologous iliac bone graft was recommended in the classic description, to prevent complications such as correction loss or delayed bone union. No previous reports have compared grafted and nongrafted osteotomies. This study hypothesized that the use of autologous bone graft in medial opening-wedge high tibial osteotomy (MOWHTO) less than 12.5 mm is unnecessary. A prospective randomized clinical trial was conducted. Forty-six opening-wedge high tibial osteotomies were carried out between April 2007 and December 2008. All had fixation with a type of Puddu stainless steel plate and screws. Patients were randomly divided by software analysis into two groups: group A had osteotomies that were filled with autologous bone graft and group B had osteotomies that were unfilled. Autologous iliac bone graft was harvested in both groups. Clinical and radiographic evaluations were performed twice monthly by blinded investigators. The rates of complications were compared between the groups. There was no difference in demographic data. Mean time to clinical bone union in group A was 12.4 weeks (confidence interval [CI] 11.2-13.6) and in group B was 13.7 weeks (CI 12.5-14.9), but this difference was not significant (P = 0.13). Signals of correction loss occurred in one patient (4.35%) in group A, and in two patients (8.70%) in group B. All osteotomies had achieved bone union. It was concluded that time to bone union was not statistically different between the group with bone graft and the group without graft.

Microparticulate cortical allograft: an alternative to autograft in the treatment of osseous defects

Benign bone tumors are commonly diagnosed and treated. Following tumor removal, the defect in the bone can be filled with auto- or allografts, (degradable) bone substitutes or non-degradable polymethylmethacrylate. The ideal substitute for this purpose should provide immediate structural support and readily incorporate into bone over a short period of time. Experimentally, microparticulate allograft has been shown to incorporate quickly in metaphyseal and metadiaphyseal cortico-cancellous defects in primates [1]. Using a combination of small allogeneic cortical graft particles (< 250 µm), bone defects were filled following intralesional excision in 97 consecutive patients with benign and low grade malignant tumors and tumor-like conditions of bone. The clinical results and rate of radiographic incorporation and osseous consolidation were recorded and analyzed. These patients underwent 104 procedures in which osseous defects were packed with microparticulate allograft. The follow-up was from 23 to 49 months. There were 94 (90.3%) closed defects and 10 (9.7%) open defects. The average size of the grafted defect was 42.8 cm³ (0.48 - 315.0 cm³). Internal fixation was used in 11 of the 104 procedures (10.6 %). Radiographically, incorporation was observed in 91% of patients and consolidation in 60%. There were eleven failures (10.6 %), eight (72 %) due to tumor recurrence. Seven of eight patients with tumor recurrence underwent a second resection and grafting procedure that resulted in allograft incorporation and defect healing. There were two deep infections requiring debridement with retention of the graft; both resolved with satisfactory healing.

Both incorporation and consolidation were observed in over 90% of patients with a low rate of complications. The use of small-particle cortical allograft proved to be an effective alternative to autogenous bone graft in patients with metaphyseal and metadiaphyseal surgical bone defects.

The role and effectiveness of bone marrow in osseous regeneration

Autologous bone marrow serves as the richest and most readily available repository of progenitor cells capable of differentiating into mature bone forming cells. Numerous studies have demonstrated that bone marrow alone or cell suspensions of marrow usually diluted in culture medium affect de novo bone formation when implanted in soft tissue sites. Consequently, when bone marrow is used to enrich orthopaedic grafting matrices such as xenograft, demineralized bone matrix, or ceramic materials it almost invariably produces faster and more consistent defect healing compared to bone marrow or the carrier matrix alone and, in some cases, equivalent healing to autograft. This article evaluates the clinical effectiveness of these grafting materials for various orthopaedic applications such as healing long bone defects and enhancing spinal fusion procedures, and hypothesizes that enrichment with bone marrow is integral to timely and satisfactory graft incorporation. Methods such as centrifugation, culture expansion and selective cell retention that concentrate and deliver marrow-derived osteoprogenitor cells to the graft site as a means of mimicking more closely the consistent bone forming potential of autologous bone graft are also discussed.