Copyright © 2009 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Randy Bindra, MD*,
Loyola University Medical Center, Maywood, Illinois
Posted March 2009
The causal relationship between decreased bone mineral density and distal
radial fracture has been established1-3. Thus, a patient with osteoporosis
is more likely to sustain a distal radial fracture after a fall and, conversely,
a postmenopausal patient who has incurred a low-energy distal radial fracture
has a higher likelihood of having osteoporosis. A recent study emphasizes the
need for the orthopaedic surgeon to take an active role in evaluating the possibility
of a diagnosis of osteoporosis and facilitating the management of the condition,
in addition to providing fracture care4. It remains unproven currently
whether lower bone mineral density is associated with distal radial fractures
of greater severity.
Itoh et al. examined bone mineral density in different regions of the distal
aspect of the radius and ulna and correlated the measurements with fracture pattern
and likelihood of redisplacement after casting5.
They compared bone mineral density in the distal third and distal tenth zones
of the radius and ulna in 1024 healthy women and in eighty-six women who were
being treated for fractures of the distal part of the radius and ulna. On correlating
age with bone mineral density of the radius, the authors noted a rapid decrease
in bone mineral density from the early fifties into the mid-sixties, followed
by a progressive gradual loss into the nineties. They were not able to establish
any correlation between bone mineral density and fracture pattern with use of
the Frykman classification6 and concluded that fracture pattern varies
with several other factors including bone mineral density. Bone mineral density
measured in the distal tenth zone of the radius was an important prognostic indicator
of eventual radial shortening.
Sakai et al. examined the relationship between initial distal radial fracture
deformity and lumbar bone mineral density in a series of 125 patients who had
low-energy distal radial fractures7. The authors took measurements of the radiographs at the
time of presentation and after first manipulation and did not continue to study
the group for early or late collapse during treatment. They noted significant
differences in the respective values of ulnar variance, radial inclination, and
dorsal angulation in the patients who had bone mineral density values that were <70%
of the mean value of young adults as compared with the patients who had bone
mineral density values that were ≥70% (p<0.05).
The correlation between material properties of the radius and fracture patterns
has also been studied in the laboratory. Lill et al. determined the bone mineral
density and geometry of 118 intact human cadaver forearms from elderly donors
with use of conventional radiography and peripheral quantitative computed tomography
and then correlated the bone properties with the fracture patterns that were
produced through mechanical loading8. They found that greater degrees
of osteopenia were associated with decreasing load to failure and increasing
severity of fracture. Among the various parameters that were assessed with use
of peripheral quantitative computed tomography, the highest correlation between
failure load and bone properties was found with regard to cortical area (r =
0.70) and trabecular density (r = 0.60).
The current study further explores the relationship between low bone mineral
density and the severity of distal radial fractures in a clinical setting. The
authors hypothesized that patients with a lower bone mineral density sustain
more severe distal radial fractures and hence are at higher risk of early collapse
after closed reduction, resulting in the need for surgical intervention or, if
cast treatment alone was chosen rather than surgical intervention, in eventual
malunion. They prospectively followed 137 patients (127 women and ten men) who
were older than fifty-five years and who presented with low-energy distal radial
fractures. Each patient had serial wrist radiographs until fracture-healing and
dual x-ray absorptiometry scanning of the hip. Age and ability to live independently
were also recorded. Radiographic parameters of dorsal angulation, ulnar variance,
and carpal malalignment were measured by a single author. Metaphyseal comminution
was subjectively assessed, and fractures were classified with use of the AO/OTA
system. No clinical outcomes were considered.
In the current study, 33% of the fractures had early instability and required
operative intervention, and an additional 27% of fractures were seen as displaced
on radiographs at or after the time of the six-week review. On evaluation of
the observed data, Clayton et al. found a significant correlation between a lower
bone mineral density score and the occurrence of malunion (p = 0.042), similar
to the correlation found by Itoh et al. in their study5. However,
the effect of bone mineral density on carpal malalignment and early instability
was small and did not reach significance (p = 0.14 and p = 0.35 respectively).
The authors then examined the same relationships by substituting predicted values
instead of observed values for early collapse, late carpal malalignment, and
malunion. The predicted values were calculated by applying previously published
algorithms. With use of predicted values, the authors were able to demonstrate
significant correlation of lower T-scores with the three parameters (p = 0.0026).
Interestingly, the effect size (R value) was low, suggesting that there are other
factors in addition to bone mineral density that contribute to fracture severity.
Other authors have demonstrated that other factors, such as type-I collagen polymorphism,
may also affect mechanical properties of bone9. Although lower bone mineral density tended to be
associated with extra-articular fractures, the authors were not able to demonstrate
a correlation between AO fracture type and bone mineral density. This is similar
to observations by other authors and may reflect the fact that most fracture
classifications do not consider metaphyseal comminution.
The current study suggests that lower bone mineral density increases the probability
of early collapse and carpal malalignment. The observed data demonstrate that
a lower bone mineral density is associated with a higher malunion rate. From
the results of this and previous studies, we can conclude that bone mineral density
is one of several factors that affect the mechanical properties of bone and the
risk of fracture. Although fractures in bone with low bone mineral density are
generally extra-articular metaphyseal fractures, the ultimate fracture pattern
produced depends on other factors, such as direction of transmitted forces and
position of the extremity. In a patient with a distal radial fracture, the presence
of a lower bone mineral density will increase the risk of early and late recurrence
of radiographic deformity when the fracture is treated with a cast. This does
not justify routine operative fixation of all distal radial fractures in the
elderly osteoporotic population, but it does make the case for increased vigilance
for seemingly simple fractures in these patients. After obtaining an initial
closed reduction, the treating surgeon must carefully follow these patients and
exercise judgment in selecting the timing and type of surgical intervention on
the basis of the expectations and requirements of the individual patient. What
effect these fracture patterns will have on the clinical outcome of patients
with osteopenia or osteoporosis is a subject worthy of future study.
*The authors did not receive any outside funding or grants in support of their research for or preparation of this work. The author or a member of his or her immediate family received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from a commercial entity (DVO-Tornier, Inc.).
References
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2. Hung LK, Wu HT, Leung PC, Qin L. Low BMD is a risk factor for low-energy Colles' fractures in women before and after menopause. Clin Orthop Relat Res. 2005;435:219-25.
3. Kanterewicz E, Yañez A, Pérez-Pons A, Codony I, Del Rio L, Díez-Pérez A. Association between Colles' fracture and low bone mass: age-based differences in postmenopausal women. Osteoporos Int. 2002;13:824-8.
4. Miki RA, Oetgen ME, Kirk J, Insogna KL, Lindskog DM. Orthopaedic management improves the rate of early osteoporosis treatment after hip fracture. A randomized clinical trial. J Bone Joint Surg Am. 2008;90:2346-53.
5. Itoh S, Tomioka H, Tanaka J, Shinomiya K. Relationship between bone mineral density of the distal radius and ulna and fracture characteristics. J Hand Surg [Am]. 2004;29:123-30.
6. Frykman GK. Fracture of the distal radius including sequelae—shoulder-hand-finger syndrome, disturbance in the distal radio-ulnar joint and impairment of nerve function. A clinical and experimental study. Acta Orthop Scand.1967; Suppl 108:3.
7. Sakai A, Oshige T, Zenke Y, Suzuki M, Yamanaka Y, Nakamura T. Association of bone mineral density with deformity of the distal radius in low-energy Colles' fractures in Japanese women above 50 years of age. J Hand Surg [Am]. 2008;33:820-6.
8. Lill CA, Goldhahn J, Albrecht A, Eckstein F, Gatzka C, Schneider E. Impact of bone density on distal radius fracture patterns and comparison between five different fracture classifications. J Orthop Trauma. 2003;17:271-8.
9. Weichetova M, Stepan JJ, Haas T, Michalska D. The risk of Colles' fracture is associated with the collagen I alpha1 Sp1 polymorphism and ultrasound transmission velocity in the calcaneus only in heavier postmenopausal women. Calcif Tissue Int. 2005;76:98-106.
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