'Lumbar Degenerative Kyphosis' Is Not Byword for Degenerative Sagittal Imbalance: Time to Replace a Misconception

Lumbar degenerative kyphosis (LDK) is a subgroup of the flat-back syndrome and is most commonly caused by unique life styles, such as a prolonged crouched posture during agricultural work and performing activities of daily living on the floor. Unfortunately, LDK has been used as a byword for degenerative sagittal imbalance, and this sometimes causes confusion. The aim of this review was to evaluate the exact territory of LDK, and to introduce another appropriate term for degenerative sagittal deformity. Unlike what its name suggests, LDK does not only include sagittal balance disorder of the lumbar spine and kyphosis, but also sagittal balance disorder of the whole spine and little lordosis of the lumbar spine. Moreover, this disease is closely related to the occupation of female farmers and an outdated Asian life style. These reasons necessitate a change in the nomenclature of this disorder to prevent misunderstanding. We suggest the name "primary degenerative sagittal imbalance" (PDSI), which encompasses degenerative sagittal misalignments of unknown origin in the whole spine in older-age patients, and is associated with back muscle wasting. LDK may be regarded as a subgroup of PDSI related to an occupation in agriculture. Conservative treatments such as exercise and physiotherapy are recommended as first-line treatments for patients with PDSI, and surgical treatment is considered only if conservative treatments failed. The measurement of spinopelvic parameters for sagittal balance is important prior to deformity corrective surgery. LDK can be considered a subtype of PDSI that is more likely to occur in female farmers, and hence the use of LDK as a global term for all degenerative sagittal imbalance disorders is better avoided. To avoid confusion, we recommend PDSI as a newer, more accurate diagnostic term instead of LDK.