Commentary & Perspective
Radiolucent Tissue and the Straight Child
Commentary on an article by Sanjeev Sabharwal, MD, et al.: ‘‘Intra-Articular Morphology of the Knee Joint in Children with Blount Disease: A Case-
Control Study Using MRI’’
David J. Zaleske, MD
There are many fascinating aspects about treating disorders involving the immature skeleton. The physiology or pathophysiology of
radiolucent tissues may make treatment relatively straightforward or quite complicated for both patient and surgeon. The activities of cells
in the epiphysis or physis, in the periosteum, and within the joint space change as growth occurs. A diaphyseal fracture generally presents
fewer problems if the patient is younger, whereas a physeal fracture that has injured proliferating cartilage early in growth may require
multiple surgical interventions. Furthermore, these cell populations are markedly influenced by mechanical force. An otherwise normal
epiphysis in a developmentally dysplastic hip will not function appropriately if the hip remains dislocated or subluxated, yet if the hip
dysplasia is detected early and the femoral head is relocated for a period of growth, the hip can be restored to a normal developmental
The ability to image radiolucent cell populations is a tremendous asset to the surgeon in guiding therapy. In the example of
developmental hip dysplasia, ultrasonography is particularly valuable before the secondary center of ossification develops to the stage at
which it occupies a large part of the proximal femoral epiphysis. When applicable, ultrasonography is extremely helpful in establishing a
diagnosis and measuring response to treatment. Magnetic resonance imaging (MRI) gives the ability to image these cell populations
Blount disease is a prototypical condition inwhich growth inhibition and alteration of the local mechanical environment are
associated. There clearly is abnormal growth at the proximal posteromedial aspect of the tibia, and (depending on severity of the
condition) other sites of maladaptive growth may also exist, such as at the distal aspect of the femur. This can lead to images made
with use of conventional radiography in which the ossified part of the medial proximal tibial epiphysis is inferior to the relatively
unaffected lateral aspect—i.e., it appears ‘‘depressed.’’
In their study, Sabharwal et al. made specific measurements of radiolucent tissues in the medial compartment of the knee.
They were able to conclude that ‘‘compared with the control group, children with Blount disease had a thicker unossified proximal
medial tibial epiphysis, a thicker and wider medial meniscus, and a greater frequency of abnormal MRI signals in the medial
meniscus, especially affectingtheposteriorhorn.’’Such measurementsareawelcomeadditiontothe literature.As theauthors note,
there have been a variety of opinions about the nature of these tissues and about how best to address the abnormal mechanics in
children with Blount disease. One particular controversy has involved the indication for an intra-epiphyseal osteotomy as well as a
compartment tissues and their relation to outcomes areneeded to provide even betterevidence to guide treatment. The authors are
to be congratulated for adding data helpful to the pursuit of this goal. Extending MRI analysis in Blount disease to the physis,
measuring the anatomical response to treatment, and correlating the response with clinical outcome would be further additions
that would aid clinicians and their patients.
In any clinical entity, the quest for a better treatment that leads to an improved outcome for the patient is best fulfilled when the
skeleton. We have come a long way in understanding the function of the various cell populations of the skeleton and ameliorating the
effects of growth disturbances in many clinical conditions1. Before we can directly address the primary causes of most disturbances of
growth,wewillneed to restore theaffectedstemcellpopulationstonormalfunction.Wehave‘‘milesto go before[we]sleep.’’2But,who
wants to sleep in exciting times for scientific progress...such as now?
COPYRIGHT ? 2012 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED
J Bone Joint Surg Am. 2012;94:e71(1-2)
David J. Zaleske, MD*
Gillette Children’s Specialty Healthcare,
St. Paul, Minnesota
*The author received no payments or services, either directly or indirectly (i.e., via his institution), from a third party in support of any aspect of this work. Neither
could be perceived to influence or have the potentialto influence what is written in this work. Also, the author has not had anyother relationships, orengaged in any
Interest submitted by authors are always provided with the online version of the article.
1. Blount WP, Clark GR. Control of bone growth by epiphyseal stapling; a preliminary report. J Bone Joint Surg Am. 1949;31:464-78.
2. Frost R. Stopping by woods on a snowy evening. 1923.
THE JOURNAL OF BONE & JOINT SURGERY
dMAY 16, 2012
COMMENTARY & PERSPECTIVE