Developmental Spondylolisthesis Research Articles

Sagittal spinopelvic alignment and body mass index in patients with degenerative spondylolisthesis

The sagittal orientation and osteoarthritis of facet joints, paravertebral muscular dystrophy and loss of ligament strength represent mechanical factors leading to degenerative spondylolisthesis. The importance of sagittal spinopelvic imbalance has been described for the developmental spondylolisthesis with isthmic lysis. However, it remains unclear if these mechanisms play a role in the pathogenesis of degenerative spondylolisthesis. The purpose of this study was to analyze the sagittal spinopelvic alignment, the body mass index (BMI) and facet joint degeneration in degenerative spondylolisthesis. A group of 49 patients with L4-L5 degenerative spondylolisthesis (12 males, 37 females, average age 65.9 years) was compared to a reference group of 77 patients with low back pain without spondylolisthesis (41 males, 36 females, average age 65.5 years). The patient's height and weight were assessed to calculate the BMI. The following parameters were measured on lateral lumbar radiographs in standing position: L1-S1 lordosis, segmental lordosis from L1-L2 to L5-S1, pelvic tilt, pelvic incidence and sacral slope. The sagittal orientation and the presence of osteoarthritis of the facet joints were determined from transversal plane computed tomography (CT). The average BMI was significantly higher (P=0.030) in the spondylolisthesis group compared to the reference group (28.2 vs. 24.8) and 71.4% of the spondylolisthesis patients had a BMI>25. The radiographic analysis showed a significant increase of the following parameters in spondylolisthesis: pelvic tilt (25.6° vs. 21.0°; P=0.046), sacral slope (42.3° vs. 33.4°; P=0.002), pelvic incidence (66.2° vs. 54.2°; P=0.001), L1-S1 lordosis (57.2° vs. 49.6°; P=0.045). The segmental lumbar lordosis was significantly higher (P<0.05) at L1-L2 and L2-L3 in spondylolisthesis. The CT analysis of L4-L5 facet joints showed a sagittal orientation in the spondylolisthesis group (36.5° vs. 44.4°; P=0.001). The anatomic orientation of the pelvis with a high incidence and sacral slope seems to represent a predisposing factor for degenerative spondylolisthesis. Although the L1-S1 lordosis keeps comparable to the reference group, the increase of pelvic tilt suggests a posterior tilt of the pelvis as a compensation mechanism in patients with high pelvic incidence. The detailed analysis of segmental lordosis revealed that the lordosis increased at the levels above the spondylolisthesis, which might subsequently increase posterior stress on facet joints. The association of overweight and a relatively vertical inclination of the S1 endplate is predisposing for an anterior translation of L4 on L5. Furthermore, the sagittally oriented facet joints do not retain this anterior vertebral displacement.

Developmental Spondylolisthesis: Is Slip Angle Related to Quality of Life?

Lumbosacral kyphosis (LSK) is considered to be an important aspect of the deformity in adolescent developmental spondylolisthesis, but its clinical impact is not known. The purpose of this study was to clarify if slip angle (SA), a parameter commonly used to measure LSK, has a significant impact on the quality of life of patient with spondylolisthesis. Eighty-six patients with lumbosacral developmental spondylolisthesis were evaluated. There were 67 low-grade and 19 high-grade spondylolisthesis. All patients completed the SF-12v2 questionnaires. The score of the mental and physical component summary (MCS and PCS) of SF-12v2 were correlated with the slip angle. The correlation of SA was only significant with PCS and not with MCS. PCS decreased significantly with increasing SA (Spearman's rho=-0.40, p<0.001). LSK has a significant impact on the physical aspect of the quality of life of adolescent with spondylolisthesis. LSK is an important part of the deformity in developmental spondylolisthesis and should be included in the routine radiological evaluation of patient with spondylolisthesis.

Redefining the Technique for the Radiologic Measurement of Slip in Spondylolisthesis

Comparison of 2 radiographic measurement techniques of slip severity in spondylolisthesis. To analyze the differences between 2 radiologic measurement techniques of slip severity in L5-S1 developmental spondylolisthesis. Different techniques for the assessment of slip in spondylolisthesis have been described in the literature, resulting in 2 different methods to report the position of the L5 vertebra on the S1 superior endplate. The clinical impact of these differences in slip measurement is unknown. Radiographs of 130 subjects with developmental spondylolisthesis were reviewed. Two different techniques were used to assess the grade and percentage of slip. The technique 1 uses a line drawn from the L5 vertebra postero-inferior corner that is perpendicular to the S1 vertebra endplate. The technique 2 uses a line tangential to the L5 vertebra posterior wall that intersects the S1 vertebra endplate. The lumbosacral angle (LSA) was also measured to assess the orientation of L5 over S1. The slip percentage and grade obtained from the 2 techniques were compared. The influence of the LSA on the measurement of slip severity was also assessed. A significant difference (P < 10(-5)) was found between technique 1 (mean = 34.2% +/- 32.6%) and technique 2 (mean = 42.5% +/- 25.8%) with respect to the slip percentage. Eight subjects were found to switch classification from a low to a high-grade slip (or inversely) depending on the technique used. There was a significant relationship between the LSA and the difference in the measurement of slip percentage using either technique 1 or technique 2. The 2 measurement techniques can have a significant impact on the interpretation of slip severity in spondylolisthesis. The differences between the measurement techniques are influenced by the orientation of L5 over S1 and could potentially affect the clinical decision making. It is important to standardize and specify the technique used to plan and assess interventions in L5-S1 developmental spondylolisthesis.

Characteristics of clinical findings and radiological assessment of high grade developmental spondylolisthesis

To investigate clinical appearance and radiological characteristics of high grade developmental spondylolisthesis and their significance. In a retrospective study, a group of 6 female patients, who were diagnosed as high grade developmental spondylolisthesis and treated in Peking University third hospital from March 2007 to December 2008 were included. Clinical and radiological characteristics of the 6 patients were investigated and the following parameters were measured on standing lateral X-ray: PI (pelvic incidence), SK (sacral kyphosis) and LL (Lumbar lordosis). A series of 44 patients who came to out-patient department due to LBP and had no positive findings on lateral lumbar X-ray were selected as the control group. The four parameters were compared between study group and control group. Clinical meanings of significant difference were discussed. Clinical findings of high grade developmental spondylolisthesis included bending of knees, deformity of trunk and sciatica. Radiological appearances were characterized with kyphosis of lumbo-sacral joint, retroverted pelvis and domed sacrum. Spondylolisthesis patients has an average PI of (52 +/- 7) degrees which was significant higher than the control group [(43 +/- 8) degrees ] (P < 0.01). LL of study group [(51 +/- 10) degrees ] was higher than that of the control group [(18 +/- 9) degrees ] (P < 0.01) and SK of the study group [(12 +/- 11) degrees ] were lower than that of the control group [(21 +/- 10) degrees ] (P < 0.05). Characteristics of clinical findings of spondylolisthesis patients have obvious cosmetic appearance, significant pain and lower neurological deficits. Radiological characteristics display deformity of lumbo-sacral joint. PI, LL and SK are significant parameters for high grade spondylolisthesis.

A Variability Study of Computerized Sagittal Sacral Radiologic Measures

A radiographic study was conducted to investigate the accuracy of computer-assisted measurement of sacral morphology in a population with developmental L5-S1 spondylolisthesis. The purpose of this study was to evaluate the inter- and intraobserver variability of computer measurements of sacral morphology. Recent studies have shown differences in sacral morphology among patients with spondylolisthesis. The sacral table angle (STA) is a fundamental sacral anatomic parameter that is specific and constant to each individual, while the S1 superior and S2 inferior angles are defined as anatomic measures specific to S1 and S2. Sacral kyphosis measured by Ferguson or Cobb method has also been used to evaluate the sagittal shape of the sacrum. Currently, computerized measures are gaining popularity for the study of sagittal balance, but their reliability especially in sacral morphology has never been properly evaluated. The standing lateral radiographs of 30 adolescents were randomly selected from the radiographic database of our institution: 10 radiographs of asymptomatic individuals, 10 of subjects with low grade L5-S1 spondylolisthesis and 10 with high grade L5-S1 developmental spondylolisthesis. Three surgeons measured sacral morphologic variables on the 30 radiographs at 2 occasions, with a 15 days interval between the 2 sessions, using a computer assisted technique. Intraclass correlation coefficients (ICCs) were used for statistical analysis. The ICC values measured within observers varied between 0.951 to 0.995, whereas the ICC measured between observers varied between 0.957 to 0.995. There was a slight decrease of the ICC measured in the high grade L5-S1 spondylolisthesis group compared to the normal subjects. However, the difference was not statistically significant. These results confirm the reliability and repeatability of computer-assisted angular measurement of sacral morphology in subjects with L5-S1 spondylolisthesis, even in the presence of lumbosacral junction dysplasia. The use of computerized measurements can be recommended for the evaluation of the sagittal sacral anatomy in future clinical and research studies.

Novel concepts in the evaluation and treatment of high-dysplastic spondylolisthesis

The classification system of spondylolisthesis proposed by Marchetti and Bartolozzi is the most practical regarding prognosis and treatment and includes the description of both low- and high-dysplastic developmental spondylolisthesis (HDDS). Unfortunately, it does not provide strict criteria on how to differentiate between these two subtypes. The accepted treatment for HDDS is surgical. However, there is no consensus on how to surgically stabilize this subtype of spondylolisthesis, and although the concept of reducing spinal deformity before fusion is attractive, the issue of surgical reduction versus in situ fusion remains controversial, especially for HDDS (Meyerding Grades III and IV). The purpose of this study was (1) to describe the severity index (SI) as a simple method that can be used in the identification of low-dysplastic developmental spondylolisthesis from HDDS allowing earlier surgical stabilization to prevent slip progression, (2) to provide guidelines for using the unstable zone for the inclusion of L4 in stabilization, and (3) to describe a surgical technique in the reduction and stabilization of this challenging surgical entity in an attempt to decrease the risk of iatrogenic L5 neurologic injury. The concepts of SI and unstable zone in the evaluation and treatment of HDDS are relatively new. In our study, patients with an SI value >20% were classified as having HDDS and surgical stabilization was offered. In addition, all vertebrae that were contained in the defined unstable zone were surgically instrumented and fused with attempts at anatomic reduction. This case series involved the retrospective radiological review of 25 consecutive patients surgically treated for HDDS between April 2000 and September 2004 by two senior surgeons. All 25 patients had a minimum 3-year follow-up. Reduction of slip, lumbosacral kyphosis, sacral inclination, fusion rate, maintenance of reduction, and iatrogenic L5 neurologic injury were evaluated. Twenty-two patients underwent a single-level L5-S1 fusion. Three patients had extension of the L5-S1 fusion to include L4 because it fell into the unstable zone. Slip improved from 67.2 to 13.6%, focal L5-S1 kyphosis improved from +17.5 degrees to -6.4 degrees . There were no pseudoarthroses and all patients had radiographic evidence of solid bony fusion at latest follow-up. To date, there have been no re-operations secondary to progression of deformity or loss of fixation. Two re-operations were performed, one for a superficial wound infection, the other for further laparoscopic decompression for continued L5 nerve root symptoms after the index surgery. One patient developed an iatrogenic L5 radiculopathy with dysaesthesiae 3 days postoperatively which completely resolved over 6 weeks. HDDS is best treated surgically. Early identification and stabilization of this challenging surgical entity could prevent the progression of slip and deformity making the index surgery less technically demanding. Vertebrae that are contained in the unstable zone can be instrumented and stabilized so that progression of the deformity and re-operation might be avoided. The authors suggested surgical technique can provide a way to restore sagittal balance, provide an environment for successful fusion, and decrease the risk of iatrogenic L5 neurologic injury.

Postural Model of Sagittal Spino-Pelvic Alignment and Its Relevance for Lumbosacral Developmental Spondylolisthesis

Comparative study of sagittal spino-pelvic alignment in children and adolescents with developmental lumbosacral spondylolisthesis compared with asymptomatic subjects. To develop a global postural model of sagittal spino-pelvic alignment. The relationships between parameters of sagittal spino-pelvic alignment in developmental spondylolisthesis are still unclear. Radiographs of 120 control subjects and 131 subjects with developmental spondylolisthesis (91 low-grade, 40 high-grade) were reviewed. Subjects with high-grade spondylolisthesis were divided according to their sacro-pelvic alignment: balanced versus retroverted sacro-pelvis. Parameters of the sacro-pelvis (pelvic incidence, pelvic tilt, sacral slope), lumbosacral region (lumbosacral angle, slip percentage), lumbar spine (lumbar lordosis, lumbar tilt), thoracic spine (thoracic kyphosis, thoracic tilt), and global balance (spinal tilt, sagittal offset between C7 and femoral heads) were assessed. Parameters were compared between all groups and a correlation study was performed between all parameters. A postural model that includes the measured parameters was used to analyze the obtained correlations. Significant differences in all parameters are found between all groups, except for sagittal offset. The pattern and strength of correlations is similar between normal and low-grade subjects, showing interdependence between sacro-pelvic, lumbosacral, lumbar, and thoracic regions. The pattern of relationships was altered in high-grade spondylolisthesis, especially for subjects with a retroverted sacro-pelvis for which correlations between pelvic incidence and pelvic tilt, and between the sacro-pelvic unit and lumbar spine geometry are lost. Children and adolescents stand with a relatively constant global sagittal spino-pelvic alignment, regardless of the local lumbosacral deformity. A normal posture is maintained in low-grade spondylolisthesis and in high-grade spondylolisthesis with a balanced sacro-pelvis. Posture is abnormal in high-grade spondylolisthesis associated with a retroverted sacro-pelvis, suggesting that surgical reduction of the local lumbosacral deformity in these patients could be attempted to restore a normal posture.

Influence of Sacral Morphology in Developmental Spondylolisthesis

A radiographic study was conducted to investigate sacral morphology in a children and adolescent population with developmental L5-S1 spondylolisthesis. To determine the relationship between sacral morphology and developmental L5-S1 spondylolisthesis. The morphology of the adult sacrum has been recently shown to be abnormal in low grade spondylolisthesis. However, sacral morphology has never been evaluated in a pediatric population where remodeling and secondary changes are less pronounced. It remains unknown if these changes in sacral morphology are primary or secondary in developmental L5-S1 spondylolisthesis. The lateral standing radiographs of 131 subjects, aged 6 to 20 years old with developmental L5-S1 spondylolisthesis (91 low grade and 40 high grade) were analyzed with a dedicated software allowing to measure the following parameters, which were analyzed for each subject by the same individual and compared to a cohort of 120 subjects without any spinal pathology with similar age and sex distribution: the sacral table index (STI), sacral table angle (STA), sacral kyphosis (SK), S1 superior angle, S2 inferior angle, and grade of spondylolisthesis. Student t test was used to compare the parameters between the groups. This study demonstrated that STA is significantly smaller (P < 0.01) in children and adolescents with L5-S1 spondylolisthesis compared to a similar control group. Furthermore, STA is significantly smaller in high-grade spondylolisthesis when compared to subjects with low grade. There is also a significant difference in segmental sacral morphology (S1 and S2 anatomy) in the spondylolisthesis group. Increasing sacral kyphosis is also found to be significantly associated with spondylolisthesis. The sagittal sacral morphology is a constant anatomic variable specific to each individual and unaffected by the position of the patient in space. The anatomy of the sacrum in children and adolescents with L5-S1 spondylolisthesis is particular and different from a control group. This study suggests that sacral anatomy may have a direct influence on the progression of spondylolisthesis; a lower STA and higher sacral kyphosis may be 2 factors predisposing to vertebral slip in developmental spondylolisthesis.

Spino-pelvic alignment after surgical correction for developmental spondylolisthesis

This study is a retrospective multi-centre analysis of changes in spino-pelvic sagittal alignment after surgical correction of L5-S1 developmental spondylolisthesis. The purpose of this study was to determine how sagittal spino-pelvic alignment is affected by surgery, with the hypothesis that surgical correction at the lumbo-sacral level is associated with an improvement in the shape of the spine and in the orientation of the pelvis. Whether L5-S1 high grade spondylolisthesis should or should not be reduced remains a controversial subject. A popular method of treatment has been in situ fusion, but studies have reported a high rate of pseudarthrosis, slip progression and persistent cosmetic deformity. Spinal instrumentation with pedicle screws has generated a renewed interest for reduction, but the indications for this treatment and its effect on spino-pelvic alignment remain poorly defined. Recent evidence indicates that reduction might be indicated for subjects with an unbalanced (retroverted or vertical) pelvis. This is a retrospective multi-centre analysis of 73 subjects (mean age 18 +/- 3 years) with developmental spondylolisthesis and an average follow-up of 1.9 years after reduction and posterior fusion with spinal instrumentation or cast immobilisation. Spinal and pelvic alignment were measured on standing lateral digitised X-rays using a computer software allowing a very high inter and intra observer reliability. Pelvic incidence was unaffected by surgery. The most important changes were noted for grade, L5 Incidence, lumbo-sacral-angle, and lumbar lordosis, which all decreased significantly towards normal adult values. At first evaluation, pelvic tilt, sacral slope and thoracic kyphosis appeared minimally affected by surgery. However, after classifying subjects into balanced and unbalanced pelvis, significant improvements were noted in pelvic alignment in both the sub-groups, with 40% of cases switching groups, the majority from an unbalanced to a balanced pelvis alignment. The direction and magnitude of these changes were significantly different by sub-group: sacral slope decreased in the balanced pelvis group but increased in the unbalanced group, while pelvic tilt values did the opposite. While pelvic shape is unaffected by attempts at surgical reduction, proper repositioning of L5 over S1 significantly improves pelvic balance and lumbar shape by decreasing the abnormally high lumbar lordosis and abnormal pelvic retroversion. These results emphasise the importance of sub-dividing subjects with high grade developmental spondylolisthesis into unbalanced and balanced pelvis groups, and further support the contention that reduction techniques might be considered for the unbalanced retroverted pelvis sub-group.

Is there a sagittal imbalance of the spine in isthmic spondylolisthesis? A correlation study

Recent studies suggested a predominant role of spinopelvic parameters to explain lumbosacral spondylolisthesis pathogeny. We compare the pelvic incidence and other parameters of sagittal spinopelvic balance in adolescents and young adults with developmental spondylolisthesis to those parameters in a control group of healthy volunteers. We compared the angular parameters of the sagittal balance of the spine in a cohort of 244 patients with a developmental L5-S1 spondylolisthesis with those of a control cohort of 300 healthy volunteers. A descriptive and correlation study was performed. The L5 anterior slipping and lumbosacral kyphosis in spondylolisthesis patients was described using multiple regression analysis study. Our study demonstrates that the related measures of sagittal spinopelvic alignment are disturbed in adolescents and young adults with developmental spondylolisthesis. These subjects stand with an increased sacral slope, pelvic tilt and lumbar lordosis but with a decreased thoracic kyphosis. Pelvic incidence was significantly higher in spondylolisthesis patients as compared with controls but was not clearly correlated with the grade of slipping. We showed the same "sagittal balance strategy" in spondylolisthesis patients as in the control group regarding correlations between pelvic incidence, sacral slope, pelvic tilt and lumbar lordosis. We believe that the lumbosacral kyphosis is a stronger factor than pelvic incidence which need to be taken into account as a predominant factor in theories of pathogenesis of lumbosacral spondylolithesis. We thus believe that increased lumbar lordosis associated with L5-S1 spondylolisthesis is secondary to the high pelvic incidence and is an important factor causing high shear stresses at the L5-S1 pars interarticularis. However, the "local" sagittal imbalance of the lumbosacral junction is compensated by adjacent mobile segments in the upper lumbar spine, the pelvis orientation and the thoracic spine. The result is not optimal but a satisfactory global sagittal balance of the trunk, even in the most severe grade of slipping.

Anatomische Reposition und monosegmentale Fusion bei hochgradiger dysplastischer Spondylolisthese L5/S1

Developmental spondylolisthesis leads to lumbosacral kyphosis with retroversion of the sacrum and lumbar hyperlordosis. The overall sagittal profile of the spine is affected. The deformity is progressive during growth. This retrospective study describes a technique for complete reduction with clinical and radiological evaluation. Thirty-four patients (mean age 16 years 3 months, 10 males, 24 females) with severe developmental spondylolisthesis L5/S1 (Meyerding grades 3 to 5) were operated on between February 1997 and July 2002. Reduction was achieved by temporary transpedicular instrumentation of L4. These screws were removed at the end of the operation or 12 weeks later. Mean slippage was corrected from 76 % preoperatively to 10 % postoperatively. Segmental kyphosis L5/S1 improved from + 21 degrees preoperatively to - 7 degrees postoperatively. Sacral inclination was 34 degrees preoperatively, 43 degrees postoperatively, and 47 degrees at latest follow-up. 76 % of the patients were pain free at the latest follow-up. In 4 patients a fusion at L4/5 was performed due to subsequent decompensation. The technique described allows for a nearly anatomic reduction with correction of slippage as well as segmental kyphosis. Correction of the local deformity with monosegmental fusion L5/S1 improves dramatically the overall sagittal profile of the spine. Fusion of the primarily healthy segment L4/5 can be avoided.

Anatomic Reduction and Monosegmental Fusion in High-Grade Developmental Spondylolisthesis

A retrospective review of the clinical and radiographic outcomes of reduction by temporary instrumentation of L4 and monosegmental fusion of L5/S1 in patients with high-grade developmental spondylolisthesis. To assess the efficacy of this technique in the reduction of local deformity and correction of overall sagittal profile. In situ fusions as well as partial reduction with fusion L4-S1 via various approaches have been described previously. To date and to our knowledge, there have been no reports describing complete reduction and monosegmental fusion for high-grade developmental spondylolisthesis. A total of 27 consecutive patients with severe developmental spondylolisthesis of L5/S1 were treated with operative reduction via temporary instrumentation of L4 and monosegmental fusion of L5/S1. The clinical and radiographic outcomes were retrospectively reviewed for each case at a minimum of 2 years (mean follow-up of 45 months; range 24-80). Mean age at surgery was 16.7 years (range 9-29). At most recent follow-up, 23 patients were pain free. There were 4 patients who had moderate pain. All radiographic parameters improved. Mean slippage improved from 74.0% before surgery to 11.0% after surgery and 10.0% at latest follow-up. Slip angle improved from 36.6 degrees before surgery to 8.1 degrees after surgery and 7.6 degrees at latest follow-up. Sacral inclination improved from 34.6 degrees before surgery to 43.4 degrees after surgery and 47.2 degrees at latest follow-up. The overall sagittal profile improved dramatically. There was 1 superficial infection, 6 patients had L5 root symptoms (5 of these resolved, 1 patient had a persistent sensory deficit). Four patients had decompensation at L4/5 (2 reoperations). Reduction of L5/S1 with temporary instrumentation of L4 and monosegmental fusion of L5/S1 is an effective technique for the treatment of high-grade developmental spondylolisthesis. A complete reduction of local deformity and excellent correction of overall sagittal profile can be achieved. Fusion of the primarily healthy segment L4/5 can be avoided.

The Importance of Spino-Pelvic Balance in L5–S1 Developmental Spondylolisthesis

A review article. The purpose of this article is to review pertinent radiologic measurements for the evaluation of spino-pelvic balance in developmental spondylolisthesis, based on the experience of the Spinal Deformity Study Group. Over the past decade, pelvic morphology has been shown to significantly influence spino-pelvic balance of the human trunk in normal and pathologic conditions. This finding has important implications for the evaluation and treatment of developmental spondylolisthesis and has fostered a renewed interest in the radiologic evaluation of spino-pelvic balance in this condition. The lateral standing radiographs of the spine and pelvis of subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence, sacral slope, pelvic tilt, L5 incidence angle, lumbosacral angle, lumbar lordosis, thoracic kyphosis, and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of an adult and child reference population. The pelvic shape, best quantified by the pelvic incidence angle, determines the position of the sacral endplate. The spine reacts to this position by adapting through lumbar lordosis, the amount of lordosis increasing as the sacral slope increases in order to balance the trunk in the upright position. Pelvic incidence, sacral slope, pelvic tilt, and lumbar lordosis are found to be significantly greater in subjects with developmental spondylolisthesis, while thoracic kyphosis is significantly lower when compared to a reference population. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases, suggesting that pelvic anatomy has a direct influence on the development of a spondylolisthesis. Studies also indicate that pelvic incidence is unaffected by surgical reduction and instrumentation. Pelvic tilt, sacral slope, and thoracic kyphosis are slightly affected, while grade, L5 incidence angle, lumbosacral angle, and shape of the lumbar spine are significantly improved after surgery. A postoperative improvement in L5 incidence angle and lumbosacral angle appears correlated with a better outcome while subjects with a poor outcome have a higher preoperative grade. Spino-pelvic balance in the sagittal plane can be considered as an open linear chain linking the head to the pelvis where the shape and orientation of each successive anatomic segment are closely related and influence the adjacent segment. Pelvic morphology and spino-pelvic balance are abnormal in developmental spondylolisthesis. These abnormalities should be quantified on lateral standing radiographs of the spine and pelvis and have important implications for the evaluation and treatment of this pathologic condition.

New Concepts on the Pathogenesis and Classification of Spondylolisthesis

A review of the literature in the English language pertaining to the pathogenesis and classification of spondylolisthesis. To review the morphology and biomechanics of the lumbosacral junction as it relates to spondylolisthesis. To present contemporary theories of the development and progression of spondylolisthesis and an etiology-based classification system. The proper treatment of spondylolisthesis is dependent on recognizing the type of slip and its natural history. Although a number of clinical and radiographic features have been identified as risk factors, their role as primary causative factors or secondary adaptive changes is not clear. In particular, confusion persists over the classification of slips with "isthmic defects." The early identification of spondylolisthesis that will progress to a high grade without intervention remains elusive. A review of English language literature regarding the pathogenesis and classification of spondylolisthesis. RESULTS.: Current literature suggests that spinopelvic parameters, in addition to the morphology and biomechanics of the lumbosacral junction, play a causative role in the development of spondylolisthesis. Progression of developmental slips may be due to growth deficiencies of the anterosuperior sacrum, analogous to Blount's disease at the knee. The Marchetti-Bartolozzi classification system emphasizes the distinction between developmental dysplastic slips and acquired laminar stress fractures, both of which may have isthmic defects. These two types of spondylolisthesis have significantly different natural histories, suggesting the need for different treatment strategies. The Marchetti-Bartolozzi system also allows for the classification of postsurgical, pathologic, and degenerative forms of spondylolisthesis. The morphology of the lumbosacral junction resists high shear and compressive forces. The loss of the posterior restraint through an incompetent bony hook may result in the forward displacement of one vertebra on the subjacent vertebra. The spinopelvic parameters, such as pelvic incidence, may be greater determinants of development and progression than previously appreciated. The Marchetti-Bartolozzi classification system is applicable to all forms of lumbar spondylolisthesis,and seems to be clinically relevant in terms of treatment decisions. Their system emphasizes the distinction between developmental spondylolisthesis with lysis and acquired spondylitic spondylolisthesis, which have been included together in previous classification systems and caused confusion over natural history and treatment. Developmental slips have a greater propensity toward progression, which may be secondary to growth deficiencies of the upper sacrum. Further study is required to confirm these observations.

Abnormal Spinal Anatomy in 27 Cases of Surgically Corrected Spondyloptosis

Retrospective review. To review the findings in the cases of spondyloptosis we have treated and to postulate on the possible cause of spondyloptosis. Spondyloptosis (Grade V spondylolisthesis) is rare, even though spondylolisthesis is a relatively common condition. While it is known that progression to spondyloptosis occurs in patients with developmental spondylolisthesis in their childhood and/or adolescent years, the precise factors leading to progression are not known. Between 1979 and 2002, 27 patients with spondyloptosis were treated surgically with L5 resection and reduction of L4 onto S1. During the treatment process, detailed observations of the surgical findings were made through clinical and radiologic means. Six anatomic parameters (pars interarticularis defects, spina bifida of the L5 or sacral segments, dysplasia of the L5-S1 facet joints, L5-S1 disc degeneration, trapezoidal shape of L5, and rounding of the proximal end of the sacrum) were specifically studied. Pars interarticularis defects were present in 24 patients (88.9%), facet dysplasia in 16 patients (59.2%), spina bifida in 24 patients (88.9%), disc degeneration in 25 (92.6%), trapezoidal L5 in 20 patients (74.1%), and rounding of the proximal end of S1 in all 27 patients (100%). Rounding of the proximal sacral endplate was the only constant abnormal anatomic feature in the patients. Damage to the proximal sacrum and sacral growth plate during late childhood and early adolescence, similar to the epiphyseal injury that produces Blount's disease, and slipped capital femoral epiphysis seem to be key factors permitting the progression of developmental spondylolisthesis to spondyloptosis.

Spondylolisthesis, pelvic incidence, and spinopelvic balance: a correlation study.

A retrospective study of the sagittal alignment in developmental spondylolisthesis. To investigate the role of pelvic anatomy and its effect on the global balance of the trunk in developmental spondylolisthesis. Pelvic incidence (PI) is a fundamental anatomic parameter that is specific and constant for each individual, and independent of the three-dimensional orientation of the pelvis. Recent studies have suggested an association between a high PI and patients with isthmic spondylolisthesis. The lateral standing radiographs of the spine and pelvis of 214 subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of a cohort of 160 normal subjects. Student's tests were used to compare the parameters between the curve types and Pearson's correlation coefficients were used to investigate the association between all parameters (alpha = 0.01). PI, SS, PT, and LL are significantly greater (P < 0.01) in subjects with spondylolisthesis, while TK is significantly decreased. PI has a direct linear correlation (0.41-0.65) with SS, PT, and LL. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases. Since PI is a constant anatomic pelvic variable specific to each individual and strongly determines SS, PT, and LL, which are position-dependent variables, this study suggests that pelvic anatomy has a direct influence on the development of a spondylolisthesis.Study participants with an increased pelvic incidence appear to be at higher risk of presenting a spondylolisthesis, and an increased PI may be an important factor predisposing to progression in developmental spondylolisthesis.