Classification in Brief: The Meyerding Classification System of Spondylolisthesis.

Spondylolisthesis, from the Greek root spondyl, referring to vertebrae, and oliothesis, referring to slipping or dislocation, is a pathologic defect that refers to the translation of one vertebral body on another [26]. Spondylolisthesis has a reported incidence of 4% to 6% in childhood,withmost being isthmic and occurring at L5 toS1 [11, 23]. Incidence increases to 5% to 10% in adults, becoming predominately degenerative, is more common in women, and most frequently occurs at L4 to L5, followed by L5 to S1 [11, 16, 43, 44]. Although there is evidence to suggest that spondylolisthesis is not present at birth, it has been shown to have a genetic component in 15% to 69% of patients [25, 37]. The most common symptoms in children include lower back or buttock pain that is worse with activity, pain with back hyperextension, and hamstring tightness [37, 43]. For adults with degenerative spondylolisthesis, symptoms may consist of lower back pain, radiculopathy or neurogenic claudication, with possible relief of symptoms occurring when sitting [16]. Worsening spondylolisthesis can have specific neurologic involvement, including radicular pain, potential bowel and bladder symptoms among other neurologic deficits, and in severe cases, cauda equina syndrome [23, 31]. Progression of spondylolisthesis and symptoms has been demonstrated to be quite variable, however, worse grades may have a higher predilection for progression [15, 16, 37]. As spondylolisthesis is most often asymptomatic, there may be inconsistency in presentation as well as during the physical exam; although the exam is not reliable for diagnosing spondylolisthesis, it can aid in evaluation [10]. Physical exam findings include flattening of the lumbar spine, pain with flexion and extension and muscle spasm [26]. The etiology of spondylolisthesis may present with specific physical exam findings. For example, in degenerative spondylolisthesis one may feel a step-off at the level above the slip, whereas in isthmic the step-off may be palpated below [16, 26, 40]. A prominent sacrum and hamstring tightness is also apparent [16, 26, 40, 45]. Other findings more common in children with isthmic deformity include a positive one-legged hyperextension test, also called the stork test, that produces ipsilateral back pain and an associated scoliotic deformity [23, 45]. Nerve root compression and spinal stenosis signs such as motor weakness, reflex changes, or sensory deficit are more commonly seen in the elderly who have degenerative spondylolisthesis and in patients with more severe translation [23, 45]. Wiltse et al. [45] categorized spondylolisthesis into five types based on etiology. Type I is congenital dysplasia with doming of the S1 vertebra, allowing the L5 vertebra to slip anteriorly. Type II, or isthmic, is caused by stress fractures in the pars interarticularis and occurs most frequently in children. Type III is degenerative, occurs in older people, and is caused by degenerative changes as a result of stress loading, leading to anterior slip. Type IV, traumatic, is caused by an acute injury as a result of trauma. Type V is pathologic fracture of the pars [45]. Although this classification provides valuable information, it is more of a descriptive classification and does not allow for tracking of progression, account for severity, or aid in treatment planning. Each author certifies that neither he, nor any member of his immediate family, has funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.