Abstract & Commentary
Synopsis: Atrophic and hypertrophic nonunions had similar blood supply on biopsy.
Source: Reed AA, et al. J Orthop Res. 2002;20(3):593-599.
Traditional classifications divide nonunions into 2 groups, hypertrophic or atrophic, according to their radiographic appearance. The prevalent teaching is that hypertrophic nonunions are biologically active and have a sufficient blood supply to progress to union if the fracture site is stabilized. On the other hand, atrophic nonunions are considered to be avascular and biologically inactive and will not heal even if stabilized.
Reed and colleagues tested the hypothesis that atrophic nonunions are less vascular than aseptic, hypertrophic nonunions and than healing fractures. Several biopsies were taken from the fracture site of patients with healing fractures, or the gap present in patients with hypertrophic or atrophic nonunions. Blood vessels were quantified in all specimens and there was no statistically significant difference in the median vessel count. Reed et al conclude that their findings do not support their hypothesis that the atrophic fracture nonunion is less vascular than hypertrophic nonunions or healing fractures.
Comment by James R. Slauterbeck, MD
This article challenges a key concept regarding the basic science of fracture nonunions. Most of us were trained with the idea that the blood supply and healing potential of an atrophic nonunion were diminished compared to that in a hypertrophic nonunion. And most treatment regimens were based on this premise. Although the ultimate treatment outcome may not change based upon this new literature, the basic science behind the treatment may be different. Nevertheless, I remain confident that we need to stabilize the hypertrophic nonunion and will need to bone graft and likely stabilize the atrophic nonunion.
Therefore, as we move along in technology and basic science advances, the problem with nonunions actually may not be the blood supply but the molecular factors needed to heal fractures. For example, the blood supply may be adequate but the local fracture site may be devoid of the osteogenic growth factors needed for healing. Therefore, the bone grafting procedure brings these factors to the environment and healing progresses to union. The osteogenic factors are likely present in the hypertrophic nonunion and the fracture simply needs better fixation.
This article clearly challenges one of the basic teachings in orthopedics. I look forward to further literature that will define the molecular differences at the nonunion sites and possible how new innovative less invasive measure may be used to stimulate bone growth potential.
Dr. Slauterbeck, Associate Professor, Department of Orthopedic Surgery, Texas Tech University Health Sciences Center, Lubbock, TX, is Associate Editor of Sports Medicine Reports.
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