Aims. We reviewed 34 consecutive patients (18 female-16 male) with isthmic spondylolysis and grade I to II lumbosacral spondylolisthesis who underwent in situ posterolateral arthodesis between the L5 transverse processes and the sacral ala with the use of iliac crest autograft. Ten patients had an associated scoliosis which required surgical correction at a later stage only in two patients with idiopathic curves unrelated to the spondylolisthesis. . Methods. No patient underwent spinal decompression or instrumentation placement. Mean surgical time was 1.5 hours (1 to 1.8) and intra-operative blood loss 200 ml (150 to 340). There was one wound infection treated with antibiotics but no other complication. Radiological assessment included standing posteroanterior and lateral, Ferguson and lateral flexion/extension views, as well as CT scans. . Results. A solid posterolateral fusion was confirmed in all patients at mean latest follow-up of 4.7 years (3.4 to 9.8) beyond skeletal maturity into early adult life. Fusion of the isthmic lesion was documented in nine patients bilaterally and eight patients unilaterally. The poor fusion rate across the spondylolysis has not affected the excellent functional results of the procedure, which in our series depended on achieving a stable lumbosacral junction. . Conclusion. Quality of life assessment demonstrated significant improvement in all functional scores and high patient satisfaction with 28 patients returning to previous sports activities at an elite competitive level. Take home message: Posterolateral arthrodesis in situ with autologous iliac crest bone without instrumentation has achieved a solid fusion between the L5 transverse processes and the sacral ala in patients with grade I to II isthmic lumbosacral spondylolisthesis and this has produced excellent clinical outcomes and high patient satisfaction. Cite this article: Bone Joint J 2016;98-B:88–96

Isthmic spondylolisthesis with pars interarticularis defect is a “ fatigue” fracture. In most cases there is no instability and moderate pain, with no need for treatment. Twenty per cent of the patients have severe back pain, and some also radicular pain, while some young patients have progressive lumbosacral kyphosis and instability with high grade spondylolisthesis. The sacral deformity and kyphosis result from the fracture and could be avoided by healinfg of the defect. Histological studies have shown that the pars defect can be a source of pain. Patients with severe back pain and some with radicular pain or increasing deformity are candidate to surgery. Since many years, the only treatment was fusion with or without instrumentation and with or without correction of the deformity, by anterior or posterior approach. Fusion was mandatory in case of associated disc degeneration, including all the pathological discs into the fusion area. Isthmic repair has been done since many years using several techniques, but only in the absence of olisthesis and disc degeneration. However, it is known that many adult or senile subjects have degenerated discs and no back pain. Thus, what is the rationale to perform fusion in all patients with spondylolisthesis? The problem is to know the source of pain and to treat patients rather than x-rays. This can be achieved by anaesthetic injection of the lytic zone, MRI and discography, which can be helpful to differentiate patients who need fusio from those who do not need it. Initially we used, for isthmic repair, the Morscher hook-screw instrumentation, but in the last ten years we are using DOS instrumentation, which is stiffer. The indications and surgical technique, as well as the results of a comparative study between fusion (91 patients with 40-month follow-up) and repair (95 patients with 30-month followup), wil be presented in terms of duration of surgery, hospital stay, complication rate, number of revisions and return to previous activities. This study shows less postoperative complications and higher rate of return to work or sports for pars repair versus lumbar fusion in a rather similar population. Therefore, isthmic repair seems to be the first surgical option for mild isthmic spondylolisthesis even in the presence of degenerated discs

This paper describes our experience about isthmic reconstruction on younger children. Study design: we carried out 9 operations, the average age was 10 and a half, with bilateral spondylolysis at L5 and persistent disabling symptomatology. All had signs of dysplasia in the lumbar spine. Method: We used the Buck technique. Results: The follow-up was after 3 years. In all cases we checked if consolidation had occurred without complications. We found all the symptomatology had disappeared and patients were thus free of back pain. We did not find any slippage of vertebra L5 after reconstruction, albeit we have not had a long enough follow-up since the children treated have not yet reached adult status. Discussion: According to Wiltse there are 5 types of isthmic lysis. Types 1 and 2 are mainly found in young people and are often confused. Type 1 is a dysplasia often found also in type 2 which instead involves isthmic spondylolysis. Therefore we prefer to speak of isthmic dysplastic spondylolysis and isthmic lithic spondylolysis when referring to children. Conclusions: Is preferable to carry out a reconstruction at an earlier stage to prevent the slippage, as well as the risk of arthrodesis later on

To compare preoperative and postoperative Health Related Quality of Life (HRQoL) scores in operated Adolescent Idiopathic Scoliosis (AIS) patients with and without concomitant isthmic spondylolisthesis. A retrospective study of a prospective cohort of 464 individuals undergoing AIS surgery between 2008 and 2018 was performed. All patients undergoing surgery for AIS with a minimum 2-year follow-up were included. We excluded patients with prior or concomitant surgery for spondylolisthesis. HRQoL scores were measured using the SRS-22 questionnaire. Comparisons were performed between AIS patients with vs. without concomitant spondylolisthesis treated non-surgically. AIS surgery was performed for 36 patients (15.2 ±2.5 y.o) with concomitant isthmic spondylolisthesis, and 428 patients (15.5 ±2.4 y.o) without concomitant spondylolisthesis. The two groups were similar in terms of age, sex, preoperative and postoperative Cobb angles. Preoperative and postoperative HRQoL scores were similar between the two groups. HRQoL improved significantly for all domains in both groups, except for pain in patients with spondylolisthesis. There was no need for surgical treatment of the spondylolisthesis and no slip progression during the follow-up duration after AIS surgery. Patients undergoing surgical treatment of AIS with non-surgical management of a concomitant isthmic spondylolisthesis can expect improvement in HRQoL scores, similar to that observed in patients without concomitant spondylolisthesis

Purpose of the study: Isthmic reconstruction has been proposed as an alternative to spinal fusion for the treament of symptomatic spondylolysis unresponsive to conservative treatment. The purpose of this work was to assess long-term outcome after isthmic reconstruction according to R. Louis. Material and methods: Fifty-one patients were reviewed at four to 23 years. The sex ratio was 3F/1M; age range was 11 to 43 years. The surgical method included: 1) isthmic reconstruction using a graft followed by temporary screw-plate fixation; 2) ablation of implants, verification of the fusion and intervertebral mobility, arthrolysis as needed. Pain and resumption of occupational and sports activities were used to assess clinical outcome. Radiological criteria included linear and angular measurements in the sagittal plane, isthmic consolidation, slipping, disk height, intersegmentary angular mobility. Results: Clinically, outcome was very good or good in 75% of the cases, fair in 21% and poor in 4%. For L5 reconstructions, outcome was very good or good in 83.5% and fair in 16.5%. Mean relative overall gain was 66%, reaching 72% for L5 reconstructions and only 31% for L3 or L4 reconstructions. Patients resumed their occupational activities in 92% of the cases. Most of those with sports activities resumed practice. Radiologically, fusion was achieved in 70% of the cases. The rate of consolidation was 80% for L5. Reduction in the immediately caudad and cephalad disk height was 33% for L5 reconstructions. Mobility was reduced 63% for the L5-S1 space and 50% for the L4-L5 space. Clinical outcome was correlated with isthmic consolidation. Residual mobility was inversely proportional to the duration of osteosynthesis. Conclusion: Isthmic reconstruction using a graft and temporary ostheosynthesis is a surgical method providing very good anatomic isthmic consolidation. Despite the need for two operations and the relative stiffness of the immedicately caudad space, this procedure can provide good functional results and avoid the need a few years later for a more complex operation

Between March 2000 and February 2006, we carried out a prospective study of 100 patients with a low-grade isthmic spondylolisthesis (Meyerding grade II or below), who were randomised to receive a single-level and instrumented posterior lumbar interbody fusion with either one or two cages. The minimum follow-up was for two years. At this stage 91 patients were available for review. A total of 47 patients received one cage (group 1) and 44 two cages (group 2). The clinical and radiological outcomes of the two groups were compared. There were no significant differences between the two groups in terms of post-operative pain, Oswestry Disability Score, clinical results, complication rate, percentage of post-operative slip, anterior fusion rate or posterior fusion rate. On the other hand, the mean operating time was 144 minutes (100 to 240) for patients in group 1 and 167 minutes (110 to 270) for those in group 2 (p = 0.0002). The mean blood loss up to the end of the first post-operative day was 756 ml (510 to 1440) in group 1 and 817 ml (620 to 1730) in group 2 (p < 0.0001). Our results suggest that an instrumented posterior lumbar interbody fusion performed with either one or two cages in addition to a bone graft around the cage has a low rate of complications and a high fusion rate. The clinical outcomes were good in most cases, regardless of whether one or two cages had been used

“Delta fixation” was developed to treat low-grade L5 isthmic spondylolisthesis. It involves placement of pedicle screws into L5 and from S1 through the L5/S1 disc into L5 (Fig.1). A biomechanical comparison to standard Posterior Lumbar Interbody Fusion (PLIF) with two anterior cages and pedicle screws in L5 and S1 was made. Eight fresh frozen human specimens were instrumented with both fixations and tested. Delta fixation was significantly more stable in resisting rotation. It requires less manipulation of the nerve roots and spares the cost of the fusion cages. Our objective is to compare the stability of Delta versus PLIF fixation in the treatment of low grade isthmic spondylolisthesis. Delta fixation provides superior initial stability, and therefore is an acceptable alternative to PLIF for the treatment of low grade isthmic spondylolisthesis of L5-S1. Symptomatic low-grade isthmic spondylolisthesis of L5 is often managed with PLIF. This procedure requires extensive manipulation of the cauda equine, posterior resection of the disc and the placement of two inter-body cages as spacers in addition to pedicle screws in L5 and S1. Delta Fixation has been developed to provide stable fixation with less nerve root manipulation and without the use of inter-body cages. It is therefore a safer alternative method of fixation that spares the additional cost of the fusion cages. When comparing Delta fixation to PLIF fixation the only statistically significant difference was found in axial rotation. Delta fixation had 2.05 degrees less ROM and 0.90 degrees less NZ compared to PLIF fixation with P values of 0.0052 and 0.0104 respectively. This demonstrates that the delta fixation is more stable than PLIF fixation. Eight fresh frozen human spines were used. Matched pairs were created and block randomization used to create two groups: PLIF fixation and Delta fixation groups. The specimens were instrumented with a grade II spondylolisthesis of L5-S1, tested, and then re-instrumented with the alternative fixation and tested again. Vertical displacement, axial rotation, flexion– extension and side bending were tested using an MTS machine. Please contact author for tables and/or diagrams

Spondylolysis can be associated with severe back or leg pain requiring surgical management. Fusion is the most often performed procedure since disk degeneration is frequently present. In a limited number of cases, when there is no disk disease or only limited dehydration, isthmic reconstruction may be considered, saving mobility and avoiding adjacent level stress. We review 30 patients submitted to L4 or L5 posterior arch reconstruction and 60 patients submitted to a one level (L4L5 or L5S1) posterior or interbody fusion. Through Prolo scores, SF36 and Oswestry questionnaires, the every day, professional and sports functional and satisfaction rates are evaluated. Present data fail to show better functional results in the isthmic reconstruction group. However, even longer follow up will be necessary in these groups of young adults with a great life expectancy to show potentially less degenerative deterioration in adjacent levels. Meanwhile, isthmic reconstruction proved to be an effective technique, comparable to fusion in patients with no associated disk disease, with no need for further surgery and minimal complications

Posterior lumber interbody fusion (PLIF) has the theoretical advantage of optimising foraminal decompression, improving sagittal alignment and providing a more consistent fusion mass in adult patients with isthmic spondylolisthesis (IS) compared to posterolateral fusion (PLF). Previous studies with only short-term follow-up have not shown a difference between fusion techniques. An observational cohort study was performed of a single surgeon's patients treating IS over a ten year period (52 patients), using either PLF (21 pts) or PLIF (31pts). Preoperative and 12-month data were collected prospectively, and long-term follow-up was by mailed questionnaire. Preoperative patient characteristics between the two groups were not significantly different. Average follow-up was 7 years, 10 months, and 81% of questionnaires were returned. Outcome measures were Roland Morris Disability Questionnaire (RMDQ), Low Back Outcome Score (LBOS), SF-12v2 and SF-6D R2. The SF-6D R2 is a “whole of health” measure. PLIF provided better short- and long-term results than PLF. The PLIF group had significantly better LBOS scores in the long term, and non-significantly better RMDQ scores in the long term. As measured by RMDQ Minimum Clinically Important Difference (MCID) short term set at 4, RMDQ MCID set at 8, the LBOS MCID set at 7.5 points and by SF-12v2 physical component score (PCS), PLIF patients performed better than PLF patients. When analysing single level fusions alone, the difference is more pronounced, with PCS, mental component scores and SF-6D R2 all being significantly better in the PLIF group rather than the PLF group. This paper strongly supports the use of PLIF to obtain equivalent or superior clinical outcomes when compared to PLF for spinal fusion for lumbar isthmic spondylolisthesis. The results of this study are the first to report to such long-term follow-up comparing these two procedures

Study design: Long-term retrospective study of the low grade isthmic Spondylolisthesis treated by means of instrumented posterolateral fixation in adults. Objective: To evaluate clinical and functional survival of surgical treatment of the espondylolisthesis after minimum 10 years of follow-up. To study the radiologic behaviour of the fused and the adjacent level. Summary of background: It’s been suggested in many different series that posterolateral instrumented fusion is not always capable to improve the lumbar pain neither to stabilize a vertebral segment if the anterior column is not supported. The need to perform and interbody fusion in the surgical treatment of isthmic spondilolysthesis is still unknown. Material and method: From a total of 42 patients operated by low grade isthmic espondylolisthesis, it’s been obtained a clinic and radiological follow up in 31 patients, 19 females and 12 males. The average age at the moment of surgery was 34.9 years and in the last review was 46.5 years. The average follow up has been 11.8 years. Pain and functional disability was quantified by a visual analogical Scale (VAS) and the Oswestry Disability Index (ODI). Quality of life was assessed by the SF-36. The preoperative and postoperative percentage of slip and lumbosacral kyphosis was evaluated in serial radiographs at the fused level. The intervertebral disc height and dynamic behaviour was evaluated at the adjacent level. Results: Spondylolisthesis was present at L5 in 24 patients, L4 in 6 patients and at L3 in 1 patient. In the 87% of cases the fusion was one level and the 3% was two levels. The mean (range) anterior slip at postoperative was 21.9%, and 23.1% at the final follow up. The average angle for the lumbosacral kyphosis was 19.4° in the postoperative and 19.5° in the follow up. The Oswestry Disability Index scores average at follow up was 13,6. 75.8% of patients were considered with a minimum disability and 17.2% with a moderate disability. The 67.7% of the patients develop rewarded activities, the 25.6% develop domestic tasks and the 6.45% are in a disability situation. There was no statistically significant difference between the study population SF-36 scores and those of the general population, same age and gender, in any of the eight domains. Conclusions: Long-term clinical and radiographic outcomes after “in situ” posterolateral instrumented fusion of adult low-grade Spondylolisthesis were satisfactory. This study further confirms that such surgery is appropriate for these selected patients

Aims: To evaluate the outcome of surgery in patients with lumbar spine degenerative disease or isthmic spon-dylolisthesis. Methods: Lumbar spine fusion with or without decompression was performed in 132 consecutive patients. Altogether 115 patients attended to follow-up an average 3.4 years after operation. The overall result was assessed by the patient and by an independent observer. Moreover, the disability was measured using Oswestry questionnaire and fusion rate was assessed from flexion and extension radiographs. Results: The complications of surgery were: misplacement of screws in 2 patients, paresis of peroneal nerve in 1 patient, superficial wound infection in 4 patients, breakage of fixation device in 1 patient and spinal fluid fistulas in 2 patients. According to patient’s own opinion the result of surgery was excellent, good or fair in 86 percent of the patients and even 89.6% of them benefited from the surgery. The average postoperative Oswestry score was 28. According to radiographs the fusion rate was 93 percent. At the time of operation 40 patients were retaired and 66 (93%) out of the 75 patients who were still at working age returned to work. Conclusion: Lumbar spine fusion is an effective and safe treatment of degenerative lumbar spine disease and isthmic spondylolisthesis. However, the careful selection of patients is an important factor for success

Objective: Retrospective analysis of consecutive paediatric patients treated surgically for high-grade spondylolisthesis by one of three circumferential surgical procedures with emphasis on complications and patient outcome measurements. Methods: Between 1980 and 1998 fourty patients underwent anterior-posterior correction for Meyerding Grade 3 or 4 isthmic dysplastic spondylolisthesis. Ten patients were treated with an anterior reduction according to Louis and anterior interbody fusion followed by posterior decompression and instrumented fusion (group A). Fourteen patients underwent posterior decompression followed by anterior reposition and fusion with tricortical iliac bone crest and posterior instrumented fusion (group B). Sixteen patients underwent progressive reduction by halopelvic traction followed by anterior and posterior fusion (group C). All patients completed the North American Spine Society (NASS) outcome questionnaire and the SF-36. The cosmetic assessment was performed by means of a VAS. The mean follow-up period for group A was 13,5 years, for group B 5,5 years and for group C 15,4 years, respectively. Results: The three groups were comparable with respect to age at operation, radiographic measurement of the slip, lumbosacral kyphosis and lumbar lordosis. The incidence of postoperative extensor hallucis longus weakness was 33% in group A, 50% in group C and 0% in group B (p< 0.001). Pearson correlation coefficient revealed a positive correlation between extensor hallucis longus weakness and the degree of correction of the lumbosacral kyphosis (P=0.56, p=0.024). Postoperative reduction of the sagittal slip (A: 64%, B: 44%, C: 50%) and lumbosacral kyphosis (A: 27°, B: 16°, C: 27°) was significant in all three groups. The incidence of pseudarthrosis was 10% in group A, 7% in group B and 6% in group C. SF-36 and NASS outcome questionnaire results have not been found statistically significant among the groups. Conclusion: Outcomes of function, satisfaction and cosmesis are satisfactory in all three surgical groups. Posterior decompression followed by anterior reduction and fusion using tricortical iliac crest bone graft and posterior instrumented fusion lack neurogenic complications. Therefore it is the standard surgical procedure for severe isthmic dysplastic spondylolisthesis at our department

Study design. A prospective study on predictive factors for the outcome of 164 patients with adult isthmic spondylolisthesis operated on with fusion between 1990 and 2003. Purpose. In view of the need to better select patients for fusion we investigated the use of the pain drawing (PD) and other potential factors for predicting the outcome of fusion. Background. Results on predictive factors of outcome after spinal fusion have been contradictory and large, well defined, patient samples with adequate observation times are lacking. Methods. QuestionnairesF including possible predictive factors as well as PDs were obtained preoperatively. Degree and level of slip were documented. Outcome was quantified by measurement of pain (VAS), Disability Rating Index (DRI), the Oswestry Disability Index and global assessment by the patient into “much better”, “better”, “unchanged” or “worse”. The 2-year follow up rate was 160/164 (98%). Results. In the total sample 49% of patients were much better, 25% better, 14% unchanged and 12% worse. Most factors investigated did not correlate with the outcome including; degree of slip, level of slip, fusion technique, age, smoking, drinking habits, weight, BMI, sciatica, laminectomy, marital status, level of education, type of domicile, possible immigrant status, dominant hand, births and number of children. The following preoperative factors correlated to a worse outcome in the univariate analysis: Not working, no regular exercise, female gender, shortness in stature and a non-organic PD. The multivariate regression analysis showed that work status was the main determinant of outcome. Gender and exercise had less but significant impact (p=0.004 and 0.02, respectively), whereas the PD was of borderline significance (p=0.06). These factors, however, explained only 22% of the variability of outcome. Conclusion. Prediction of outcome after fusion is difficult. Only a limited number of predictive factors were identified, with working preoperatively being the strongest predictor. Also male gender and regular exercise are indicators of a better outcome. Female patients not working, not exercising, or with a non-organic pain drawing, should be informed about their suboptimal chances of an excellent outcome after fusion

We reviewed 20 adult patients with spondylolysis and isthmic spondylolisthesis an average of 10.5 years after treatment by anterior spinal fusion. Nineteen patients had excellent or satisfactory results. Ten of the patients were symptom-free at one year, and 15 were asymptomatic at final follow-up. Anterior spinal fusion can produce results comparable to those of posterior fusion with or without decompression. The results tend to improve with time in contrast to the known worsening of late results after posterior decompression without fusion

The purpose was to analyze preoperative symptoms, curve characteristics, and outcome of surgery in patients operated on for isthmic spondylolisthesis with concomitant scoliosis. Overall, 151(9.1%) of 1667 scoliosis patients had spondylolisthesis treated surgically in 21 (13.9%)(19 females, 2 males; 11 low-, 10 high-grade). Patients' age at admission was 13.5(10-17)y. Preoperatively, 5/21 were pain-free (1 high-grade, 4 low-grade), 7 (2 high-grade) had LBP, 2 (both high-grade) radiating pain, and 7 (5 high-grade) had both. Hamstring tightness was present in 5/10 high-grades. Scoliosis was primary thoracic in 3/11 low-grade and secondary lumbar with oblique rotated take-off of L5 in 8/11 low-grade patients. Of the high-grades, 7/10 had sciatic curves and 3 secondary lumbar. In low-grades, the main indication for surgery was pain in 3/11 and lumbar curve progression or the intent to prevent it in 7/11. The operative technique was uninstrumented posterolateral fusion in 8/11, instrumented L4-S1 fusion with reduction of L4-tilt in 2, and direct repair in 1 patient. High-grades were fused to prevent further slipping regardless of subjective symptoms (uninstrumented anterior 5, combined 2, instrumented reduction 3). Selective thoracic fusion for scoliosis was performed in 3 patients. None of the lumbar curves needed fusion. All sciatic curves resolved. The follow-up time was 10.6(2-21)y. Of the low-grade patients, 5 were pain-free, 4 had moderate pain, and 2 had a severe chronic pain syndrome. One had broken pedicle screws without sequelae. Of the high-grade patients, 4 were pain-free, 6 had moderate pain. One had a pain-free peroneal weakness after slip reduction

We reviewed the radiographs of 325 unselected patients with defects in the pars interarticularis of L5 to study whether the incidence of vertebral slip in spondylolysis of L5 remained unchanged after the age of 20 years. MRI was also carried out on 111 of the patients to investigate the relationship between the shape of the transverse process of L5 and the degeneration of the discs adjacent to this level. The incidence of spondylolisthesis increased with age from 17% in the second decade to 51% in the sixth. The transverse process was significantly more slender in patients with less degeneration at L4/5 and advanced degeneration at L5/S1 than in patients with advanced degeneration at L4/5 and less degeneration at L5/S1. Vertebral slip secondary to an isthmic defect of L5 after the age of 20 years was confirmed and the adjacent disc degeneration was significantly related to the vertical thickness of the transverse process of L5

Introduction: Conventional reduction techniques for high-grade isthmic spondylolisthesis do not address important anatomical constraints on the L5 and S1 nerve roots, thereby leading to a significant risk of neurological deficit. We describe a novel three-stage reduction technique carried out in one operative session that respects these anatomical constraints. We report the results in seven cases. Methods: Between 2000 and 2006, four female and three male adolescents with high-grade spondylolisthesis (grade 3 or greater) underwent this 3 stage procedure which included: I) extensive posterior decompression of L5 and S1 nerve roots plus sacral dome osteotomy. II) anterior L5/S1 discectomy. III) reduction of spondylolisthesis with pedicle screw fixation and posterior lumbar interbody fusion using interbody cages. Somatosensory and motor evoked potentials were used during the procedure. Patients were followed up for a mean of 4 years (range1–6). Sagittal balance was restored and assessed by measuring sacral slope, lumbosacral angle, pelvic incidence and pelvic tilt. Results: The mean age at surgery was 14.7 years (range 12–17) and average duration of symptoms was 13.7 months (range6–24). Mean operative time was 6.5 hours (range 5–8), with a mean blood loss of 2242cc (range1400–4200). The mean pre-op slip angle was 57°(range 45°–100°) and the mean post-op slip angle was 37.5°(range28°–57°). Anatomical reduction was achieved in six patients and one patient with spondyloptosis was reduced to grade 2. Sagittal balance was restored in all patients. There were no permanent neurological complications. One patient with grade 4 spondylolisthesis developed transient right L5 nerve root palsy which fully recovered within 3 months. Conclusion: The safety and efficacy of this 3 stage reduction and stabilization procedure showed that immediate reduction of high grade spondylolisthesis with minimal risk of neurological deficit is possible. The procedure is technically demanding and should be performed by spinal surgeons familiar with the principles of anterior and posterior fusion

This study using digitized radiographs and custom software demonstrates that patients with spondylolysis and low-grade spondylolisthesis have increased Pelvic and L5 Incidence as well as a more vertically oriented L5-S1 intervertebral disc than patients without radiographic abnormality of the spine. We propose that shear across the more vertical L5-S1 disc may underlie the etiology of spondylolysis when Pelvic Incidence is high, while a “nutcracker” mechanism may be involved when Pelvic Incidence is low. The purpose of this study was to assess whether differences exist in sagittal alignment between normal controls and patients with spondylolysis or low-grade isthmic spondylolisthesis. Standing PA and lateral spine radiographs from eighty-two consecutive patients with spondylolysis or low-grade spondylolisthesis (Average age nineteen, range 15–44) were retrospectively compared with those from one hundred and sixty normal volunteers. The films were digitized with a VIDAR scanner and key landmarks were determined. Customized software was then used to measure geometric indices. Pelvic Incidence (PI), Sacral Slope (SS), Pelvic Tilt (PT), and L5-S1extension angle were compared between seventy-two patients with high PI (> 45°) versus ten patients with low PI (< 45°). Average high-PI vs. low-PI values were, respectively: PI (67.32° vs. 43.13°), SS (51.08° vs. 38.05°), PT (16.23° vs. 5.08°), and L5-S1ext (−8.69° vs. −9.57°). Furthermore, the range of values for L5-S1extension in the low-PI subgroup was much narrower (−17.81° to 0.93°) than that for the high-PI subgroup (−31.58° to 38.12°). This study demonstrates that patients with spondylolysis and low-grade spondylolisthesis have increased Pelvic and L5 incidence, a more vertically oriented L5-S1 intervertebral disc, and less segmental extension between L5 and S1 than patients without radiographic abnormality of the spine. We propose that different mechanisms underlie the etiology of spondylolysis depending on the magnitude of the Pelvic Incidence. These data highlight the importance of seeing localized lumbosacral spine disorders in the context of global alignment of the entire spine and pelvis. Funding: This research was assisted by support from the Spinal Deformity Study Group. This research was funded by an educational/research grant from Medtronic Sofamor Danek

Introduction Spondylolysis and isthmic spondylolisthesis (IS) have both a familial and mechanical aetiology, yet the phenotypic expression of the familial aetiology is unknown except for the observation of spinal bifida occulta. Other posterior element abnormalities are unrecognised, and any facet joint orientation (FJO) abnormality at the effected level has been ignored because of presumed previous mechanical defunctioning by the pars defect. The recognition of multilevel sagittal FJO in L4/5 degenerative spondylolisthesis (DS), begs the question whether more proximal segment examination may reveal FJ variations in IS. Methods MRI scans were used to measure 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 is in relation to the coronal plane. Repeated measures assessment confirmed method validity. Results Mean measurement of axial FJO at L3/4 and L4/5 was 51.1 and 42.5deg in normal subjects, and 45.2 and 35.0deg in IS. The more coronal angulation at the levels above a pars defect in IS was highly statistically significant (p=0.0006 & p=0.00002). At L5/S1 orientations were the same (39deg). Discussion Relative coronal FJO in the lumbar spine may be the phenotypic expression of the congenital aetiology of IS. The mechanism of effect may be increased stress concentration at the pars between or below coronally oriented FJs. These more coronal FJOs in IS 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 exceptionally uncommon combination of DS at L4/5 and IS at L5/S1 when both disorders are independently common. This latter observation can be further explained by the generalization that DS occurs in those individual with sagittal lumbar facets, and that IS occurs in those with more coronal FJs

The October 2023 Spine Roundup. 360. looks at: Cutting through surgical smoke: the science of cleaner air in spinal operations; Unlocking success: key factors in thoracic spine decompression and fusion for ossification of the posterior longitudinal ligament; Deep learning algorithm for identifying cervical cord compression due to degenerative canal stenosis on radiography; Surgeon experience influences robotics learning curve for minimally invasive lumbar fusion; Decision-making algorithm for the surgical treatment of degenerative lumbar spondylolisthesis of L4/L5; Response to preoperative steroid injections predicts surgical outcomes in patients undergoing fusion for isthmic spondylolisthesis