Drop Body Syndrome -A distinct form of adult spinal deformity-

Mitsuru Yagi, Shinjiro Kaneko, Yoshiyuki Yato, Takashi Asazuma

Research output: Contribution to journalArticle

7 Citations (Scopus)


STUDY DESIGN.: A retrospective observational study. OBJECTIVE.: This study examined the role of skeletal muscles in the spinal alignment of lumbar degenerative kyphosis (LDK). SUMMARY OF BACKGROUND DATA.: Adult spinal deformity (ASD) may present as LDK, which is unusual in that it typically lacks any coronal deformity. METHODS.: This retrospective study included 367 female ASD. Demographic and radiographic data from LDKs were compared with those with other ASD. The LDK multifidus was also subjected to histological analysis. The muscle volume and strength were analyzed using whole-body dual x-ray absorptiometry (DXA) and pulmonary function tests (PFTs). MRIs were used to determine the cross-sectional area (CSA) and fatty infiltration area (FIA) of the psoas and multifidus. RESULTS.: 15% (52 patients) were classified as LDK. Compared to other ASDs, those with LDK had a significantly larger SVA (16.3?±?5.0?cm), and PI−LL (52.8?±?9.2°). The LDK had significantly lower CSA and higher FIA of the multifidus, but not in the psoas (multifidus CSA 223?±?96?mm vs 477?±?129?mm, P?<?.001; FIA 82% vs 31%, P?<?.001). 86% of LDK had a multifidus CSA?<?300?mm, and 82% had a FIA > 80%. Whole-body DXA showed no significant difference in the other body sections between LDK and other ASDs. The percent-predicted PEF were within normal range in 82% of the LDK. LDK multifidus specimens revealed diffuse, non-uniform muscular fibers and growth of the interstitium and adipose tissue, with no muscular inflammation. We redefined LDK as Drop Body Syndrome, a distinct form of ASD. CONCLUSIONS.: Significantly decreased CSA and increased FIA of the multifidus were observed in LDK, whereas the muscle strength and volume of the other body sections were normal. These findings strongly suggest the presence of isolated lumbar extensor myopathy in LDK.Level of Evidence: 4

Original languageEnglish
Publication statusAccepted/In press - 2016 Dec 2

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Clinical Neurology

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