Background: Bone marrow aspirated from the iliac crest contains
progenitor cells that can be used to obtain bone-healing of nonunions.
However, there is little available information regarding the number and
concentration of these cells that are necessary to obtain bone repair. The
purpose of this study was to evaluate the number and concentration of
progenitor cells that were transplanted for the treatment of nonunion, the
callus volume obtained after the transplantation, and the clinical healing
rate.
Methods: Marrow was aspirated from both anterior iliac crests,
concentrated on a cell separator, and then injected into sixty noninfected
atrophic nonunions of the tibia. Each nonunion received a relatively constant
volume of 20 cm3 of concentrated bone marrow. The number of
progenitor cells that was transplanted was estimated by counting the
fibroblast colony-forming units. The volume of mineralized bone formation was
determined by comparing preoperative computerized tomography scans with scans
performed four months following the injection.
Results: The aspirates contained an average (and standard deviation)
of 612 ± 134 progenitors/cm3 (range, 12 to 1224
progenitors/cm3) before concentration and an average of 2579
± 1121 progenitors/cm3 (range, 60 to 6120
progenitors/cm3) after concentration. An average total of 51
× 103 fibroblast colony-forming units was injected into each
nonunion. Bone union was obtained in fifty-three patients, and the bone marrow
that had been injected into the nonunions of those patients contained >1500
progenitors/cm3 and an average total of 54,962 ± 17,431
progenitors. The concentration (634 ± 187 progenitors/cm3)
and the total number (19,324 ± 6843) of progenitors injected into the
nonunion sites of the seven patients in whom bone union was not obtained were
both significantly lower (p = 0.001 and p < 0.01, respectively) than those
in the patients who obtained bone union. The volume of the mineralized callus
measured at four months on the computerized tomography scans of the patients
who had union ranged from 0.8 to 5.3 cm3 (mean, 3.1
cm3). There was a positive correlation between the volume of
mineralized callus at four months and the number (p = 0.04) and concentration
(p = 0.01) of fibroblast colony-forming units in the graft. There was a
negative correlation between the time needed to obtain union and the
concentration of fibroblast colony-forming units in the graft (p = 0.04).
Conclusions: Percutaneous autologous bone-marrow grafting is an
effective and safe method for the treatment of an atrophic tibial diaphyseal
nonunion. However, its efficacy appears to be related to the number of
progenitors in the graft, and the number of progenitors available in bone
marrow aspirated from the iliac crest appears to be less than optimal in the
absence of concentration.
Level of Evidence: Therapeutic Level III. See
Instructions to Authors for a complete description of levels of evidence.