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Concept: Pars interarticularis


INTRODUCTION: Spondylolysis is most commonly observed in the lumbar spine, particularly L5, and is associated with spondylolisthesis, or anterior “slippage” of a vertebra in relation to an adjacent vertebra. Isthmic spondylolisthesis is the result of a pars interarticularis defect and will be the only type of spondylolisthesis addressed in this review. CONCLUSIONS: Spondylolysis and spondylolisthesis represent a relatively common cause of low back pain, especially in young athletes, and a less common cause of neurologic compromise. When discovered in a symptomatic patient with corroborating imaging findings, early intervention provides an excellent prognosis. Herein, we review the anatomy and pathology of spondylosis and spondylolisthesis of the L5 vertebra.

Concepts: Spinal disc herniation, Low back pain, Lumbar vertebrae, Vertebra, Spondylolisthesis, Medical school, Spondylolysis, Pars interarticularis


Spondylolysis is a fracture of the pars interarticularis, the portion of the neural arch that lies between the superior articular facets and the inferior articular facets. Clinical evidence has suggested repetitive trauma to be the most probable cause, even though morphological weakness of the vertebra is probably also involved. Prevalence is between 3% and 8% in modern populations, while in archaeological samples it varies from 0% to 71.4%. Considering that very little data about this condition is available in past populations from the southern extreme of South America, the aim of this paper is to analyze the spondylolysis in a human skeletal sample from Southern Patagonia and, at the same time, to explore the prevalence of spondylolysis in archaeological contexts around the world to gain a better understanding of the results presented here. The Southern Patagonian skeletal series analyzed here showed a prevalence of 20%, with lower prevalence in the pre contact sample (11.1%) than in the contact period (23.1%). Skeletons from the Salesian Mission “Nuestra Señora de La Candelaria” showed a higher prevalence (25%) than the sample of skeletal remains recovered from outside the mission (20%), suggesting that changes in lifestyle of hunter-gatherers during contact could be implicated in the development of spondylolysis in this sample. A worldwide survey displays a wide range of prevalence figures in American and Asian samples and low diversity between African and European populations. Hunter-gatherers from Southern Patagonia showed similar values to those observed in other American samples.

Concepts: Sample, Skeletal system, Vertebra, South America, Human skeleton, Spondylolysis, Patagonia, Pars interarticularis


Although direct repair (DR) with screw fixation at the pars defect is a common surgical treatment for lumbar spondylolysis, it is unknown whether DR leads to better outcomes for young patients with spondylolysis than traditional non-surgical treatment.

Concepts: Clinical trial, Lumbar vertebrae,, Spondylolisthesis, Skeletal disorders, Conservatism, Spondylolysis, Pars interarticularis


Pars defect and spondylolisthesis are frequent conditions, while bone tumors-particularly the primaries-are rare. The contemporary occurrence can delay the diagnosis of the tumor, if symptoms are considered related to spondylolisthesis, or can make reconstruction more demanding. To our knowledge, only two case reports of this contemporary occurrence have been published in the literature. Being such rare, guidelines on surgical treatment have not been proposed yet.

Concepts: Medical terms, Brain tumor, Tumor, Spondylolisthesis, Spondylolysis, Pars interarticularis


Acquired spondylolysis represents an uncommon complication of spine surgery, of an unknown incidence and etiology. We studied patients presenting this rare entity, with the purpose to investigate the incidence, imaging findings, patients' clinical characteristics, as well as to provide an interpretation of the mechanisms that may lead to this phenomenon. The presented working hypothesis, regarding etiology, suggests that there is a relation between variations in spinopelvic sagittal alignment and acquired spondylolysis. Between January 2010 and January 2015, six patients presented spondylolysis after short-segment transforaminal lumbar interbody fusion, at a mean time of 43 months after surgery. The preoperative intactness and postoperative defect of pars interarticularis were documented with computed tomography scans in all patients. Standard radiographical spinopelvic parameters were measured before and after surgery. The optimum values of lumbar lordosis (LL) and pelvic incidence minus lumbar lordosis modifier (PI-LL mismatch) were calculated as well. The incidence of acquired spondylolysis was 0.95% among patients with short-segment lumbar fusion. Patients presented high-grade PI with a vertically orientated sacral endplate, while LL was found 9° greater and PI-LL mismatch 9° lower than the respective optimum values, indicating a non-harmonized alignment. In conclusion, acquired spondylolysis, though rare, may occur in patients with high-grade PI and sacral slope, and suboptimal spinopelvic sagittal alignment after lumbar spine surgery, thereby highlighting the importance of detailed preoperative planning in spine surgery, along with the study of sagittal balance.

Concepts: Medicine, Skeletal system, Lumbar vertebrae, Vertebral column, Vertebra, Spondylolysis, Lordosis, Pars interarticularis


Lumbar spondylolysis and isthmic spondylolisthesis are common conditions. However, double-level lumbar spondylolysis and spondylolisthesis are rare. We report 24 cases of it along with a review of literature and a briefly description of the clinical and radiological features and integrated management of patients with this condition.

Concepts: Lumbar vertebrae, Retrospective, Radiology, Spondylolisthesis, Skeletal disorders, Spondylolysis, Pars interarticularis


BACKGROUND Osteoid osteomas are benign bone-forming tumors characterized by local inflammation and pain. They are also characterized by a small osteolytic lesion (nidus). Spondylolysis is a defect of the pars interarticularis, which may lead to stress fractures, and is a common cause of low back pain in adolescence. Osteoid osteoma occurs predominantly in the posterior elements of the spine. Magnetic resonance imaging (MRI) signal abnormality suggesting bone marrow edema is a common finding in osteoid osteoma and early-stage spondylolysis without prominent defect. CASE REPORT An 18-year-old male was suffering from low back pain. He was diagnosed with lumbar spondylolysis on initial MRI and computed tomography (CT). Subsequent thin-slice CT demonstrated a nidus at the pars interarticularis, and variously-sliced MRI could detect widespread bone marrow edema. On the diagnosis of an osteoid osteoma, the nidus and surrounding osteosclerosis were resected. The patient’s pain disappeared after surgery. CONCLUSIONS Osteoid osteoma in the pars interarticularis can be difficult to diagnosis, because MRI and CT findings for osteoid osteoma at the pars interarticularis are similar to those of the lumbar spondylolysis. The possibility of osteoid osteoma should be kept in mind when examining adolescents with low back pain.

Concepts: Spinal disc herniation, Medical imaging, Lumbar vertebrae, Brain tumor, Magnetic resonance imaging, Spondylolysis, Pars interarticularis, Osteoma


OBJECTIVE Spondylosis with or without spondylolisthesis that does not respond to conservative management has an excellent outcome with direct pars interarticularis repair. Direct repair preserves the segmental spinal motion. A number of operative techniques for direct repair are practiced; however, the procedure of choice is not clearly defined. The present study aims to clarify the advantages and disadvantages of the different operative techniques and their outcomes. METHODS A meta-analysis was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The following databases were searched: PubMed, Cochrane Library, Web of Science, and CINAHL ( Cumulative Index to Nursing and Allied Health Literature). Studies of patients with spondylolysis with or without low-grade spondylolisthesis who underwent direct repair were included. The patients were divided into 4 groups based on the operative technique used: the Buck repair group, Scott repair group, Morscher repair group, and pedicle screw-based repair group. The pooled data were analyzed using the DerSimonian and Laird random-effects model. Tests for bias and heterogeneity were performed. The I2 statistic was calculated, and the results were analyzed. Statistical analysis was performed using StatsDirect version 2. RESULTS Forty-six studies consisting of 900 patients were included in the study. The majority of the patients were in their 2nd decade of life. The Buck group included 19 studies with 305 patients; the Scott group had 8 studies with 162 patients. The Morscher method included 5 studies with 193 patients, and the pedicle group included 14 studies with 240 patients. The overall pooled fusion, complication, and outcome rates were calculated. The pooled rates for fusion for the Buck, Scott, Morscher, and pedicle screw groups were 83.53%, 81.57%, 77.72%, and 90.21%, respectively. The pooled complication rates for the Buck, Scott, Morscher, and pedicle screw groups were 13.41%, 22.35%, 27.42%, and 12.8%, respectively, and the pooled positive outcome rates for the Buck, Scott, Morscher, and pedicle screw groups were 84.33%, 82.49%, 80.30%, and 80.1%, respectively. The pedicle group had the best fusion rate and lowest complication rate. CONCLUSIONS The pedicle screw-based direct pars repair for spondylolysis and low-grade spondylolisthesis is the best choice of procedure, with the highest fusion and lowest complication rates, followed by the Buck repair. The Morscher and Scott repairs were associated with a high rate of complication and lower rates of fusion.

Concepts: Evidence-based medicine, Systematic review, Rates, Meta-analysis, Spondylolysis, Pars interarticularis, Scotties Tournament of Hearts


Lumbar spondylolysis usually occurs as a stress fracture in the pars interarticularis of the vertebra. It is a prevalent sports-related disorder and a common cause of low back pain. We encountered five athletes (4 males, 1 female) with severe low back pain. Mean age was 14.5 years. All five patients were found to have bilateral pars fracture. In all cases, staging based on the findings from computed tomography scan of the right and left pars fracture was different. On short tau inversion recovery magnetic resonance imaging (STIR-MRI) of the comparatively newer more recently injured side, high signal intensity changes were obvious and dominant at the intra- and extraosseous area, which would indicate tissue edema and/or bleeding. Furthermore, the imaging findings corresponded to the side of the low back pain. In conclusion, STIR-MRI can effectively distinguish between painful pars fracture and painless pars fracture.

Concepts: Spinal disc herniation, Medical imaging, Radiography, Pain, Acupuncture, Virtopsy, Spondylolysis, Pars interarticularis


If the articular facets of the vertebra grow in an asymmetric manner, the developed bone geometry causes an asymmetry of loading. When the loading environment is altered by way of increased activity, the likelihood of acquiring a stress fracture may be increased. The combination of geometric asymmetry and increased activity is hypothesised to be the precursor to the stress fracture under investigation in this study, spondylolysis. This vertebral defect is an acquired fracture with 7% prevalence in the paediatric population. This value increases to 21% among athletes who participate in hyperextension sports. Tests were carried out on porcine lumbar vertebrae, on which the effect of facet angle asymmetry was simulated by offsetting the load laterally by 7mm from the mid-point. Strain in the vertebral laminae was recorded using six 3-element stacked rosette strain gauges placed bilaterally. Specimens were loaded cyclically at a rate of 2Hz. Fatigue cycles; strain, creep, secant modulus and hysteresis were measured. The principal conclusions of this paper are that differences in facet angle lead to an asymmetry of loading in the facet joints; this in turn leads to an initial increase in strain on the side with the more coronally orientated facet. The strain amplitude, which is the driving force for crack propagation, is greater on this side at all times up to fracture, the significance of this can be observed in the increased steady state creep rate (p = 0.036) and the increase in yielding and toughening mechanisms taking place, quantified by the force-displacement hysteresis (p = 0.026).

Concepts: Vertebra, Spondylolysis, Pars interarticularis