Autograft Quality is Dependent on the Harvesting Technique

January 7, 2013 By Bill Rodriguez, M.S. Leave a Comment

Spine surgeons have known for quite some time that the source (location) of autogenous bone graft is important; and although many surgeons utilize local bone, iliac crest is the gold standard for autograft. A recent study¹ revealed that harvesting methods have a profound impact on the quality of autograft. The study compared autograft harvested by two methods—a rongeur and the relatively new technique of harvesting bone shavings from a high speed burr.

Methods

14 patients undergoing laminectomy had bone harvested from their laminae and spinous process by each method (i.e., rongeur and high speed drill).
- During the drilling process, bone tissue was chilled using saline solution and collected using an in-line suction trap as described in previous studies.
Each sample was tested to determine its osteogenic potential.

Results

Histological analysis immediately following autograft harvesting
	Rongeur samples (bone chips)	High speed drill samples (bone shavings)
Bone tissue appearance	Tiny intact pieces of bone with concentric lamellae surrounding the Haversian Channels.	Tissue was disintegrated into tiny fragments and remnants of the interstitial lamellae were observed.
Osteoblast environment	Osteoblasts were surrounded by lacunae of extracellular matrix.	Osteoblasts were separated from lacunae and located loosely between the lamellar fragments.
Blood vessels	Intact blood vessels visible.	Blood vessels not observed.

Evaluation of samples after plating
	Rongeur samples	High speed drill samples
Time until 1^st osteoblast release/emigration from sample	5.6 days (average)	14.8 days (average)
Amount of samples with osteoblast release	100% (14/14)	57% (8/14)
Osteoblast viability	98%	98%

Evaluation following 3 weeks of culturing
	Rongeur samples	High speed drill samples
Osteoblast yield (average per gram of bone)	1.25 x 10⁶	1.73 x 10⁵
Population doubling time	50.5 h	121 h
Histological analysis	Stained positive for mineralization	Stained negative for mineralization

In summary, autograft harvested via ronguer scored better than autograft harvested via high speed drill on the following measures:

Time for osteoblasts to release/emigrate from samples
Osteoblast doubling time
Osteoblast yield
Preservation of osteoblasts’ natural environment
Mineralization by osteoblasts after culturing

Conclusion

These data reveal that autograft harvesting techniques matter. The rougher the technique (i.e., greater manipulation) means greater stress on cells and, therefore, a longer time is required for cells to adjust then proliferate. Additionally, more manipulation always increases chance of damaging or killing cells. The theory of using high speed burr shavings is attractive and the shavings may meet the technical criteria for use as autograft; however, they are inferior to autograft obtained via rongeur. Finally, a previous post dealt with evaluating biologic products, and the same requirements can and should be applied to new techniques as well.

¹Eder C, Chavanne A, Meissner J, Bretschneider W, Tuschel A, Becker P, Ogon M. Autografts for spinal fusion: osteogenic potential of laminectomy bone chips and bone shavings collected via high speed drill. 2011. Eur Spine J 20:1791-1795.