Isthmic spondylolisthesis and spondylolysis

Isthmic spondylolisthesis, or spondylolisthesis due to a lesion of the pars interarticularis, is a common source of pain and disability in both the pediatric and adult population. This review examines the current diagnostic and treatment options for patients with this condition. It also reviews the results of the various interventions to facilitate the surgeon in choosing the appropriate treatment option for any given patient.     

Conservative management of spondylolysis and spondylolisthesis

Spondylolysis and spondylolisthesis are pathologic defects that can cause low back pain. While they are often asymptomatic, a thorough radiologic evaluation and correlation with the clinical presentation is necessary to guide appropriate intervention. The physician׳s role in these cases is a timely diagnosis, treatment, and follow-up given the risk of progression that accompanies this type of pathology. Conservative management is currently the first-line for many instances of mild-to-moderate spondylolysis and spondylolisthesis, with the goal of pain relief and return of function.     

Natural history of spondylolysis and spondylolisthesis

Spondylolysis refers to a defect in the pars interarticularis of the vertebrae; spondyolisthesis, or a slippage of one vertebral body on another, can result from spondylolysis or other conditions. Both conditions may be a cause of low back pain, but are also commonly seen as incidental findings in asymptomatic patients. The natural history of these conditions is important to understand in order to counsel patients and determine a course of action when either diagnosis is made, and varies based upon etiology as well as patient characteristics.     

Family study of spondylolysis and spondylolisthesis

Seventy index patients and 222 first-degree relatives with spondylolysis or spondylolisthesis have been studied by means of interview and clinical and radiological examinations. The index patients had an average age of 18 years, and included 43 females and 27 males. Following Wiltse's classification, 18 patients had dysplastic lesions and 52 had isthmic defects. The first-degree relatives included 99 parents and 125 siblings and children of the index patients. Both isthmic and dysplastic defects occurred in most families, regardless of the classification of the index patient. Isthmic defects were consistently more frequent than dysplastic defects. Spina bifida occulta occurred at the lumbosacral area in 61% of the index patients; in the first-degree relatives, spina bifida occulta was most common among the siblings and children of index patients, and occurred more often in relatives of index patients with dysplastic lesions than in those with isthmic lesions.     

腰椎峡部裂和滑脱症外科治疗的探讨

报告自１９６５～１９９１年９２例有症状的腰椎峡部裂和滑脱的外科治疗。１９６５～１９７１年采用经腹椎体间前植骨融合２２例； １９７１～１９７８年采取腹膜外入路椎间植骨融合或Ｒｏｍｂｏｌｄ法后外侧融合术２０例；１９８７～１９９１年峡部裂处植骨、螺钉和横突钢丝内固定１５例，短节段经椎寻根内固定３５例，其中改良Ｄｉｃｋ法７例．Ｓｔｅｆｆｅｅ槽式钢板２８例，同时行后外侧融合。作者认为，症状性的腰椎峡部裂或轻微滑脱，峡部可直接修整植骨、螺钉和横突钢丝固定。滑脱椎可采用经椎弓根Ｓｔｅｆｆｅｅ槽式钢板螺钉得到完全或部分复位．     

Magnetic resonance tomography in spondylolysis and spondylolisthesis

40 patients with spondylolisthesis and/or spondylolysis were studied by magnetic resonance imaging (MR), 12 of whom with correlation to CT. CT proved to be more sensitive in detecting pars defects than MR. Sagittal MR, however, was more accurate in assessing spondylolisthesis than axial CT. At present, CT is superior to MR in demonstrating bony abnormalities. MR appears indicated in the patient undergoing spinal fusion in whom detection of intervertebral disc degeneration in the levels above or below intended fusion may lead to extension of fusion to the degenerated levels. Lack of ionizing radiation makes MR an ideal diagnostic method in evaluating spondylolisthesis in children and adolescents.     

Mechanical factors in spondylolisthesis and spondylolysis.

Anterior displacement in spondylolisthesis is a slow process. The forces contributing to anterior shear arise from the vertical load on the spine above the lesion, from activity in the muscles of the spine and trunk, and from the effects of movements. The shear is normally resisted by the annulus fibrosus, compression of the facets at the apophyseal joints, and by tension in the anterolateral layers of cortical bone in the pars interarticularis. The anterior shear-strength of the disk is not known though Cyron and Hutton have shown that it is a major contributor to the total stiffness; in the early stages of spondylolysis it provides the only resistance. The capacity of the pars for resisting tensile forces anteriorly has been studied in tests of single vertebrae in which posterior forces were applied to the inferior articular processes. Forces at failure at L4 and L5 have been reported at up to 2500 N by Cyron et al. and up to 5800 N by Lamy et al. with means of 1800 N and 3200 N respectively. The mean posterior displacement of the inferior facets reported by Cyron et al. was 6.5 mm at failure. Too little is known of the mechanical factors in the etiology of spondylolysis for a definition of the postures and movements of the body which put the lumbar neural arch at greatest risk. While a combination of fatigue-failure and high strain-rate of forces induced in extended postures seems likely, further investigations are needed to elucidate the pathogenesis in many cases.     

Surgical therapy for spondylolysis and spondylolisthesis

The therapy for spondylolysis and spondylolisthesis is challenging in view of the large variety of treatment options. A general, standardized therapeutic concept has still not been established. Adequate therapy depends on different parameters and personal experience. Beside direct repair surgery of spondylolysis and low grade spondylolisthesis, dorsal, ventral and combined dorsoventral surgery, with or without instrumentation, are indicated depending on patients age and severity of the slip.Complications such as pseudarthrosis and progression of the slip develop in a given percentage of cases, but these are not significantly correlated with clinical symptoms. Decompression is necessary in high grade slippage with neurologic impairment, especially paresis. Reposition is associated with a higher risk of neurologic complications.Fusion in situ without instrumentation, even in moderate and severe spondylolisthesis, shows good clinical results with high fusion rates and without the increased risk of progression and pseudarthrosis. In many cases, it is an effective, safe and economic therapeutic option.     

Nerve root compression in spondylolysis and spondylolisthesis

Thirty-four bony specimens of isthmic spondylolysis were examined and, in a significant number (32%), stenosis of the intervertebral foramen was noted. Although not emphasised in previous reports, this finding may be an important factor in the aetiology of nerve root compression when this is associated with spondylolysis and spondylolisthesis. Anatomical guidelines for adequate surgical decompression are suggested.     

Treatment of spondylolisthesis and spondylolysis in children.

There are 2 fairly common types of spondylolisthesis in children - dysplastic and isthmic. The dysplastic type is secondary to congenital defects at the lumbosacral joint. The isthmic is usually due to a fatigue fracture of the pars interarticularis but there is also an hereditary element in this type. Most children with spondylolisthesis never develop significant symptoms and even of those who do, the vast majority can be treated without surgery. If symptoms persist or if further olisthesis is occurring, a one-level spinal fusion done through a paraspinal approach is recommended. It is most important not to allow olisthesis to develop to the point that the child shows the cosmetically undesirable stigmata characteristic of the condition. Solid fusion can be obtained in every case and will stop further slip.     

Surgical management of adult spondylolysis and spondylolisthesis

The surgical management of spondylolisthesis depends on the type of spondylolisthesis, the grade of slip, and the clinical setting. The surgical approaches may broadly be divided into decompression alone, fusion alone, and a combination of decompression and fusion. Fusion options can be further subdivided into non-instrumented vs. instrumented, anterior vs. posterior, with or without interbody support, and/or combined approaches, often referred to as circumferential fusions. The indication for surgical treatment of spondylolysis is persistent, disabling back pain refractory to conservative management. In conclusion, an evidence-based approach combined with shared decision making with informed patients will lead to successful outcomes.     

The natural history of spondylolysis and spondylolisthesis

We performed a prospective roentgenographic study to determine the incidence of spondylolysis, spondylolisthesis, or both, in 500 unselected first-grade children from 1955 through 1957. The families of the children with spondylolysis were followed in a similar manner. The incidence of spondylolysis at the age of six years was 4.4 per cent and increased to 6 per cent in adulthood. The degree of spondylolisthesis was as much as 28 per cent, and progression of the olisthesis was unusual. The data support the hypothesis that the spondylolytic defect is the result of a defect in the cartilaginous anlage of a vertebra. There is a hereditary pre-disposition to the defect and a strong association with spina bifida occulta. Progression of a slip was unlikely after adolescence and the slip was never symptomatic in the population that we studied.     

Facet joint orientation in spondylolysis and isthmic spondylolisthesis

STUDY DESIGN: The orientation of facet joints (FJs) in a normal population and isthmic spondylolisthesis (IS) population was assessed using magnetic resonance imaging in the lumbar spine. OBJECTIVE: To document the difference in FJ orientation (FJO) between a normal population and a population with spondylolysis of L5 and IS. SUMMARY OF BACKGROUND [corrected] DATA: Spondylolysis and IS have both a familial and mechanical etiology, yet the phenotypic expression of the familial etiology is unknown except for the observation of spinal bifida occulta. Other posterior element abnormalities are unrecognized, and any FJO abnormality below the pars defect has been ignored because of presumed previous mechanical defunctioning by the development of that pars defect at an earlier age. The recognition of multilevel sagittal FJO in L4/5 degenerative spondylolisthesis (DS), raises the possibility that more proximal segment examination may reveal FJ variations in IS. METHODS: Magnetic resonance imaging scans were used to measure the orientation of the FJ at L3/4, L4/5, and L5/S1 in 30 individuals with normal scans, and 30 patients with IS. The angular measurement recorded was in relation to the coronal plane. Repeated measurements confirmed the validity of the method. RESULTS: Mean measurement of axial FJO at L3/4 and L4/5 was 51.1 and 42.5 degrees in the controls, and 45.2 and 35.0 degrees in IS. The more coronal angulation at the levels above a pars defect in IS was highly statistically significant (P = <0.001 at L3/4 and P = <0.0001 at L4/5). At L5/S1, orientations were the same (39 degrees) in each group. CONCLUSIONS: Relative coronal FJO in the lumbar spine may be the phenotypic expression of the familial etiology of IS. This may result in increased stress concentration in the pars between or below coronally oriented FJs. These more coronal FJOs in IS may also explain the common observation of retrolisthesis at L4/5 above IS when the L4/5 disc degenerates, lateral overhang of the L4/5 FJ to the L5 pedicle entry point above an IS, and the rare combination of DS at L4/5 and IS at L5/S1 when both disorders are separately common. This latter observation can be explained by the observation that DS occurs in those individual with sagittal lumbar facets, and that IS occurs in those with more coronal FJs.     

The mechanical etiology of spondylolysis and spondylolisthesis.

There are 3 mechanisms that may result in failure of the neural arch with or without displacement of the vertebral body of the pathological vertebral: flexion overload, unbalanced shear forces and forced rotation. It is understood that all types of overload may be applied simultaneously and in various combinations. Of all the forces acting on the lumbar spine torsional violence is the most disruptive of the neural arch. Besides causing olisthesis, it is also capable of producing lysis of the pars especially if the dorsal spine has the added restraint of high tensile stresses in the posterior ligamentous system. Under normal conditions, the L5-S1 intervertebral joint is subject to the highest forces and it therefore receives the first damage. However, in the presence of antiverse process, damaging stress occurs in the next higher joint. While the antitorsional large transverse process may protect the L5-S1 joint from torsion, it may not protect the L5 vertebra from excessive flexional strains that may fracture the pars. Though lysis may occur in both instances, paradoxically spondylolysis and spondylolisthesis are mutually exclusive conditions. It has long been thought that shear force imbalance was the causative agent in olisthesis. This mechanism remains unconvincing except possibly in instances where there is a pathological condition affecting the skeletal tissue.     

Results of screw osteosynthesis in spondylolysis and low-grade spondylolisthesis

Summary Nineteen patients with spondylolysis and low-degree spondylolisthesis were treated with bone grafting and osteosynthesis of the pars defect with the Morscher hook screw (16 cases) or with Buck's procedure (three cases). Eighteen patients had a followup examination. In the age-group 9–16 years (ten patients) there were 80% excellent or good results with fusion, whereas in the adult group (eight cases) the majority had poor results. It seems that the operative techniques which we applied are useful in juvenile patients; adults require a more reliable fixation.

---

Zusammenfassung Bei neunzehn Patienten mit einer Spondylolyse oder einer geringgradigen Spondylolisthesis wurde eine Osteosynthese sowie eine Spongiosaplastik der Lyse im Isthmusbereich durchgeführt. In sechzehn Fällen kam die Hakenschraube nach Morscher zur Anwendung, in drei Fällen die Verschraubung nach Buck. Achtzehn Patienten konnten nachuntersucht werden. Die Resultate in der Altersgruppe der Neun- bis Sechzehnjährigen (zehn Patienten) waren in 80% sehr gut, in der Gruppe der Erwachsenen (acht Patienten) fanden sich jedoch überwiegend unbefriedigende Ergebnisse. Die angewandten Osteosynthesetechniken eigneten sich für jugendliche Patienten, Erwachsene benötigen unserer Ansicht nach eine stabilere osteosynthetische Versorgung.