Allogenic bone chips are not the answer to avoiding cement leakage in vertebroplasty

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Dong Ki Ahn (Department of Orthopedic Surgery, Seoul Sacred Heart General Hospital, Seoul, South Korea) and others report in Clinics in Orthopedic Surgery that vertebroplasty with fresh frozen allogenic bone chips is not a feasible alternative to vertebroplasty with conventional bone cement because it is associated with worse clinical outcomes. Therefore, bone chips could not be used as a way of avoiding cement-related complications in vertebroplasty.

Ahn et al report that cement leakage following vertebroplasty for the management of osteoporotic vertebral compression fractures is an ongoing concern with the procedure. Therefore, they devised the novel method of using fresh frozen allgoenic bone chips rather than bone cement as a way avoiding most of the problems associated with bone cement. They add that allogenic bone chips have already been successfully used in revision total hip arthroplasty, commenting: “This material was presumed to withstand mechanical compression force, much like wet sand in a closed space.”

In the study, osteoporotic patients with a single vertebral compression fracture between T10 and L3 chose to undergo vertebroplasty with bone chips or vertebroplasty with bone cement. The null hypothesis was that clinical and radiological results of the two groups would be equivalent. Of the 40 patients in the study, 12 chose the experimental vertebroplasty approach and 28 chose conventional vertebroplasty.

Ahn et al explain that with the experimental approach, bone fragments were harvested from distal femoral and proximal tibial condyle of patients who underwent arthroplasty of knee joints and milled into 1mm bone chips. They add the bone chips (after being frozen for three months and subsequently thawed) were then inserted into the fractured vertebral body via 3mm cannulas to the “maximum impaction”.

Although the patients in both groups saw significant improvements in their Visual Analogue Scale scores at the first postoperative day, patients who underwent vertebroplasty with bone cement had significantly greater improvements compared with patients who received vertebroplasty with the bone chips (p<0.001 for the comparison). Furthermore, at the first postoperative day, the bone chip group had significant reductions in vertebral kyphotic angle but not local kyphotic angle, whereas the bone cement group had significant reductions in both of these parameters.

A significant difference in survival was found between groups, with Ahn et al noting: “The odds ratio of survival was 5.2 times higher in the vertebroplasty with bone cement group [compared with the vertebroplasty with bone chips group].”  Also while both groups saw a loss of correction angle at four postoperative measurements (day one, three, six, and 12 months), the loss was more significant in the bone chip group (p<0.001).  

The authors comment: “The results were completely different from our assumption. Immediate pain reduction [with the bone chips approach] was less than with vertebroplasty with bone cement and pain relapsed as time elapsed. After three months, it was reduced again; however, this considered the natural history of fracture healing.” They add that vertebroplasty with bone chips is a “totally unacceptable” technique because “the clinical and radiological survival rate was only 25% in three months and the odds ratio of failure was five times greater than vertebroplasty using bone cement.”

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