Spondylolysis and its relation to spondylolisthesis

SPONDYLOLYSIS AND ITS RELATION SPONDYLOLISTHESIS” CAPT. M.

P. RHODES MEDICAL

S

CORPS,

CAPT. C. COLANGELO

AND ARMY

PONDYLOLYSIS Iiterally means dissoIution of a11 or part of a vertebra. Through common usage it has become synonymous with defects of the neural arch. It has been shown that the most important arch defects are those of the isthmus region, l,* and therefore it is to these defects that the term spondyIoIysis is applied in this paper. SpondyloIisthesis is a well recognized cIinica1 entity. 3 The frequent coexistence of spondyIoIisthesis in spondyIoIysis has shown the need for an evaIuation of this relationship from a roentgenoIogica1 and clinical standpoint. The diagnosis of spondyIoIysis with or without spondyIoIisthesis is established by adequate x-ray studies. An understanding of the gross anatomy of the Iower lumbar region is required for proper interpretation of the roentgenograms. RoutineIy these incIude an anteroposterior projection (Fig. I), a Iateral projection (Fig. 2) and frequently a spot lateral projection of the Iumbosacral joint. The anatomica structures revealed are indicated by corresponding diagrams. The anteroposterior view (Fig. I) indicates the number of lumbar vertebrae, and outlines the bodies and transverse processes, the depth of the upper lumbar intervertebral spaces and the alignment of the vertebral column. Due to angulation produced by the lumbosacral curvature and other physica factors, the presacra1 vertebra is poorIy delineated and there is imperfect definition of the articular processes, the apophysea1 joints and the interarticular or isthmus segments. From the diagram (Fig. 4) it can be seen that the lateral view reliably presents the

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THE

UNITED

STATES

outIine of each vertebral body, the depth of the intervertebral and IumbosacraI spaces, the anteroposterior alignment of the vertebrae and the configuration of the spinous processes. The usefulness of the Iateral view is limited bv two features: (I) It superimposes the “images of each half of the neura1 arch so that the Iamina, articuIar processes, apophyseal joint and isthmus of the right side cannot be distinguished from the left, and (2) the apophyseal joint which Iies at an angle ranging from 35 to 50 degrees anterior to the sagittal plane is not visualized nor are its components. Because of these features, specitic roentgen information about each half of the neural arch, particularly the pars interarticularis, can onIy be obtained by rotating the contralateral side anteriorIy away from the cassette with the subject in the supine position. Thus the pIane of the apophyseal joint in question is made to coincide with the tube-target beam and the corresponding articular processes, pars interarticularis and lamina for that half or side of the neura1 arch are clearly revealed. This is the essence of the oblique projection (Fig. 5) and the graphic representation (Fig. 6) confirms its primary importance in discIosing Iesions of the isthmus and neighboring structures. Spondylolysis and spondylolisthesis, when seen roentgenographically, affect the Iast or presacra1 lumbar vertebra aImost exclusively. The presence and degree of displacement are determined from the lateral views using the criteria of Ferguson” although a recently described method is aIso of merit.” The lateral view reveaIs isthmus defects but does not dis-

* From Veterans’ Hospital, Dayton Ohio. Published with permission of the hledical Director, Veterans Administration, who assumes no responsibility for the opinions expressed or conclusions drawn by the authors. 20

tinguish ljetween unilateral defects, nor does it indicate involved. This point is F’rgure -.

or bilateral which side is illustrated in

[:I(;. 3. Diagram of ~lnteroi”)stt,rior

lilm.

The lateral projection also indicates alterations in the disks, the inter\-ertebral spaces, the intervertebral foramina and the vertebral bodies. The defect of spondvlolysis as seen in the oblique \.ic\v is ;I gaP in that segment of

the neural arch kvhich connects the inferior articulnr proc~ess with the pedicle and the Iamina. It is smooth in outline, usually bilateral and \aries in width \vith the de-

1;1c..1. Ihgr:m

of I:ltcr.ll

film.

gree of spond\.lolisthesis. Its presence ma> be suspected by a posterior indentation of Morton’s S-shaped line6 indicating recession of that apophysis continuous with the defective (shortened) Iamina. Figure 8 illustrates the defect of spondylolysis.

22

Americxn

Journal

of Surgery

Rhodes,

Colangelo-SpondyIolysis

FrequentIy, there are associated anomaIies and abnormalities of the neural arch such as spina b&da occuIta, or varying

FIG. 5. Normal obIique (Icftl film.

FIG. 7. LateraI fiIm showing isthmus defect.

degrees of maIdeveIopment of the Iamina and articular processes. The defect must be distinguished from fracture of the isthmus and from acces-

JULY, 1946

sory ossicles of the inferior articuIar processes. The former condition is seen as an irreguIar defect with scIerotic mar-

FIG. 6. Diagram of obtique film.

FIG. 8. Oblique Hm showing isthmus defect.

gins, usuaIIy producing caIIus and aImost always unilateral. The Iatter condition is biIatera1 and seen as a smaI1 bone having a smooth outline and a we11 defined cortex,

located beneath the tip of each inferior articular process. M’hilc :I unilateral or bilateral defect ma? occur with or without slipping of a vertebra, in no instance in this series did sI)c”‘d!:lolisthesis occur without :I defect of the isthmus whether unilateral or bilateral. The presence of sponclylolisthesis is thereforr believed to be prima facie e\ iclence 04 spondylol\3is. II must be bo;nc -in mind that man) conditions ma> produce symptoms similar to I hose of spend.\ loI?-sis and spondylolisthesis w,ith roentgen findings which are quite cliffewnt. The more important ones subluxation of the of this nature are: of the apophyses, apoptl~ SC‘S, arthritis and \,:lrious forms of disk disorders.