RESUMO
OBJECTIVE: Although a wide range of sacral dysmorphisms has been documented with lumbosacral transitional vertebrae (LSTV) variations, quantitative characterization of the upper segment morphology and articular anatomy across the array of lumbosacral transitions are hardly found in the literature. This study presents LSTV anomalies as a series of sequential morphological changes (the LSTV spectrum) and quantitatively compares 6 LSTV subtypes with normative sacral dimensions including the anatomy at the upper sacral segments used for percutaneous sacroiliac screw insertion. METHODS: Seven linear dimensions were measured from LSTV subtypes and normal sacral variants from dried adult sacral specimens. The auricular, superior articular and facet surface areas were quantified. Obliquity and thickness of osseous corridors used for sacroiliac screw fixation were measured. Data were statistically compared within and between LSTV subtypes and the normal variants. RESULTS: LSTVs presented a wide range of morphometric differences in comparison to the normal bones. Grouping LSTV according to auricular surface positions (high, normal, and low) demonstrated significant between-group differences in the obliquity and thickness at the S1 and S2 segmental corridors. CONCLUSION: Frequent occurrence of LSTV in the general population may require evaluation of anatomical parameters in these variations for safe sacroiliac instrumentation around this region.
RESUMO
In the lumbosacral region, anatomical variations occur with changes in the number of sacral vertebra either by deletion of first sacral vertebra or by the union of fifth lumbar or first coccygeal vertebra with sacrum. Lumbasacral transitional vertebrae (LSTV) is the most common congenital anomalies of the lumbosacral region. It most commonly involves the fifth lumbar vertebra showing signs of fusion to the sacrum known as sacralisation or the first sacral vertebra shows signs of transition to a lumbar configuration commonly known as lumbarisation. Complete transition can result in numerical abnormalities of the lumbar and sacral vertebral segments. Lumbarisation of first sacral vertebra is seen with a very low incidence of 2%. Knowledge of presence of such vertebral variation will be helpful for the clinicians to diagnose and treat patients with low back pain. Although sacralisation of fifth lumbar vertebrae is most commonly seen when compared to lumbarisation of first sacral vertebrae, we report here a case of lumbarisation of first sacral vertebrae for its rarity among the LSTV and clinical implications.
En la región lumbosacra, las variaciones anatómicas se basan en cambios en el número de las vértebras sacras, ya sea por ausencia de la primera vértebra sacra o por unión de la quinta lumbar o primera vértebra caudal con el sacro. Las vértebras de transición lumbasacra (VTLS) son las anomalías congénitas más frecuentes de la región lumbosacra. La VTLS más común se produce a nivel de la quinta vértebra lumbar, con signos de fusión al sacro, proceso conocido como sacralización; mientras que la primera vértebra sacra también puede mostrar signos de transición a una configuración lumbar. A esto último se lo denomina lumbarización. La transición completa puede provocar anomalías numéricas a nivel de los segmentos vertebrales lumbares y sacros. La lumbarización de la primera vértebra sacra se observa con una incidencia muy baja, de solo 2%. El conocimiento de la presencia de dicha variación vertebral será de utilidad para los médicos al momento de diagnosticar y tratar a los pacientes con dolor en la parte baja de la espalda. Aunque la sacralización de la quinta vértebra lumbar se produce más frecuentemente en comparación con la lumbarización de la primera vértebra sacra, se presenta aquí un caso de lumbarización de la primera vértebra sacra, rara entre las VTLS, y con implicaciones clínicas.