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Effects of Non-Weight-Bearing on the Immature Femoral Head Following Ischemic OsteonecrosisAn Experimental Investigation in Immature Pigs
Harry K.W. Kim, MD, MS, FRCSC1; Olumide Aruwajoye, MS1; Jeffrey Stetler1; Alec Stall, MD1
1 Center for Excellence in Hip Disorders, Texas Scottish Rite Hospital for Children, 2222 Welborn Street, Dallas, TX 75219. E-mail address for H.K.W. Kim: harry.kim@tsrh.org
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Investigation performed at the Center for Excellence in Hip Disorders, Texas Scottish Rite Hospital for Children, Dallas, Texas

A commentary by Fred R. Nelson, MD, is linked to the online version of this article at jbjs.org.



Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, one or more of the authors has had another relationship, or has engaged in another activity, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2012 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2012 Dec 19;94(24):2228-2237. doi: 10.2106/JBJS.L.00300
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Abstract

Background: 

Local non-weight-bearing as a treatment for Legg-Calvé-Perthes disease remains controversial since a clear scientific basis for this treatment is lacking. The purpose of this study was to determine the effects of non-weight-bearing on decreasing the femoral head deformity following ischemic osteonecrosis and to investigate its biological effects.

Methods: 

Unilateral femoral head ischemia was induced in sixteen piglets by placing a ligature around the femoral neck and transecting the ligamentum teres. Eight animals received a hind-limb amputation to prevent weight-bearing on the ischemic side (NWB group). The remaining eight piglets were allowed to bear weight as tolerated (WB group). The contralateral femoral heads of the WB group were used as normal controls. All animals were killed at eight weeks after induction of ischemia, when a deformity is expected in this model. Radiographic, microcomputed tomographic (micro-CT), and histomorphometric assessments were performed.

Results: 

Radiographic and micro-CT assessments showed significantly greater flattening of the infarcted epiphysis in the WB group compared with the NWB group. The mean epiphyseal quotient (ratio of femoral head height to diameter) was significantly lower in the WB group (0.29 ± 0.06) compared with the NWB group (0.41 ± 0.06, p < 0.001). Histomorphometric analyses showed that the mean percentage revascularization of the infarcted epiphysis was significantly greater in the NWB group (95% ± 14%) compared with the WB group (34% ± 33%, p < 0.0004), suggesting that revascularization was more rapid in the NWB group. Both histomorphometric and micro-CT analyses of trabecular bone parameters showed significantly decreased bone volume and decreased trabecular number in the infarcted epiphysis of the NWB group compared with the WB group (p < 0.05).

Conclusions: 

Local non-weight-bearing decreased the deformity following ischemic femoral head osteonecrosis and increased the rates of revascularization and resorption of the infarcted epiphysis.

Clinical Relevance: 

Local non-weight-bearing was mechanically protective but biologically suboptimal following ischemic osteonecrosis since it increased the imbalance of bone resorption and formation.

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    References

    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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