Slip Progression Research Articles

Push-out test behavior and damage detection of steel-UHPC composite using PZT sensing

This present study investigates the failure mechanisms and damage evolution at the steel-UHPC interface through static push-out tests and active sensing monitoring on 15 steel-UHPC specimens. To address the ductility issue of embedded studs in UHPC as specified by Eurocode 4 to be at least 6 mm, the selected parameters particularly include large-diameter studs (≥25 mm), high-strength studs, and bolted connectors, which less frequently involved in current research. The test results indicate that large-diameter studs and bolted connectors can enhance the ductility of the steel-UHPC specimens. However, the use of high-strength studs further reduced the ductility of the specimens due to welding quality issues. Furthermore, to explore the evolution of damage at the steel-UHPC interface, the Piezoelectric Transducer (PZT)-based active sensing system was employed to continuously monitor the development of slip damage at the steel-UHPC interface during the static push-out tests and then evaluate the specimen's damage under different loading conditions. By analyzing the wave response of the piezoelectric sensor, the results reveal a strong correlation between the damage index, obtained through wavelet packet analysis, and the progression of interface slip. This correlation enables precise identification of critical damage, such as interface debonding and connector fracture, during the loading process. Utilizing the test outcomes, a quantitative relationship between the damage index and slip for the purpose of structural damage assessment has been built. Finally, based on the test data, this study assessed the applicability of current shear resistance design equations, proposed a refined load-slip relationship for studs, and offered well-founded design recommendations.

Natural History of Degenerative Spondylolisthesis: A Systematic Review and Meta-analysis

The optimal treatment algorithm for patients with degenerative lumbar spondylolisthesis has not been clarified. Part of the reason for this is that the natural history of DS has not been sufficiently studied. Comprehension of the natural history is essential for surgical decision making. We aimed to determine (1) the proportion of patients that develop de novo DS during follow-up; and (2) the proportion of patients with progression of pre-existent DS by conducting a systematic review and meta-analysis of the literature. This systematic review was conducted in accordance with the PRISMA guidelines. Ovid, EMBASE and the Cochrane Library were searched from their inception through April 2022. Demographic values of the study populations, grade of slip, rate of slippage before and after the follow-up period, and percentage of patients with slip in the populations at baseline and after follow-up were the extracted parameters. Of the 1909 screened records, eventually 10 studies were included. Of these studies, five reported the development of de novo DS and nine reported on the progression of pre-existent DS. Proportions of patients developing de novo DS ranged from 12 to 20% over a period ranging from 4 to 25 years. The proportion of patients with progression of DS ranged from 12 to 34% over a period ranging from 4 to 25 years. Systematic review and metanalysis of DS on the basis of radiologic parameters revealed both an increasing incidence over time as well as an increasing progression of the slip rate in up to a third of the patients over 25 years which is important for counseling patients and for surgical decision making. Importantly, 2/3 of patients did not experience slip progression.

Who Benefits From Allowing the Physis to Grow in Slipped Capital Femoral Epiphysis?

The globally acknowledged treatment for mild to moderate slipped capital femoral epiphysis (SCFE) is single screw in situ fixation, also used for prophylactic contralateral fixation. The Free-Gliding Screw (FG; Pega Medical) is a 2-part free-extending screw system designed to allow the growth of the proximal femur. We aimed to analyze the relationship between skeletal maturity and potential growth of the proximal physis and remodeling of the femoral neck using this implant. Females below 12 years and males below 14 years undergoing in situ fixation for stable SCFE or prophylactic fixation were treated using the implant. Three elements of the modified Oxford Bone (mOB 3 ) score were used to measure maturity (triradiate cartilage, head of the femur, and greater trochanter). Radiographs were analyzed immediately postoperatively and at a minimum of 2 years for a change in screw length, posterior-sloping angle, articulotrochanteric distance, α angle, and head-neck offset. The study group comprised 30 (F:M=12:18) of 39 hips treated with SCFE and 22 (F:M=13:9) of 29 hips managed prophylactically using the free-Gliding screw. In the therapeutic group, chronologic age was a less valuable predictor of future screw lengthening than mOB 3 . An mOB 3 of ≤13 predicted future growth of >6mm but did not reach statistical significance ( P =0.07). Patients with open triradiates showed a mean screw lengthening of 6.6mm compared with those with closed triradiates (4.0mm), but this did not reach significance ( P =0.12). In those with mOB 3 ≤13, the α angle reduced significantly ( P <0.01) and the head-neck offset increased significantly, suggesting remodeling. There was no change in these parameters when mOB 3 ≥14. In the prophylactic group, change in screw length was significant with mOB 3 of ≤13 (mean=8.0mm, P <0.05), as was the presence of an open triradiate cartilage (mean=7.7mm, P <0.05). In both cohorts, posterior-sloping angle and articulotrochanteric distance did not change, indicating no slip progression in either treatment or prophylactic groups and minimal effect on the proximal physeal growth relative to the greater trochanter. Growing screw constructs can halt slip progression while allowing proximal femoral growth in young patients with SCFE. Ongoing growth is better when the implant is used for prophylactic fixation. The results in treated SCFE need to be expanded to demonstrate a clinically meaningful cut-off for significant growth, but SCFE patients with an open triradiate remodel significantly more than those where it is closed. Level III-retrospective comparative study.

Comparison between Decompression Alone and with Additional Fusion for Degenerative Lumbar Spondylolisthesis: A Systematic Review and Meta-Analysis.

Degenerative lumbar spondylolisthesis affects approximately 10% of adults over 40. Although decompression has been the treatment of choice, some surgeons note possible instability development after decompression alone (D). Previous studies show that decompression with fusion (DF) has similar complication rates but is better at preventing slip progression and reducing pain. However, others stated the additional instrumentation does not result in superior functional outcomes and has higher costs and complication rates. This study aims to provide an objective, two-arm comparison of the two treatments using systematic review and meta-analysis. The study design was a systematic review and meta-analysis of relevant randomized controlled trials and nonrandomized comparative studies. A systematic search was conducted from April 2021 to September 2021 to identify relevant studies using PubMed, Google Scholar, EMBASE, and Cochrane databases based on PRISMA guidelines. This systematic review included 8 studies (6,669 patients); 7 (6,569 patients) were included in the meta-analysis, with a follow-up period of up to 143 months. The most commonly affected level was L4-5, with females being more affected than males. Visual Analog Scale improvement on back pain was significantly better in DF group (Heterogeneity, I2=32%; WMD -0.72; 95% Confidence Interval (CI), -1.35 to -0.08; P=0.03), as well as postoperative back pain (I2=96%; WMD 0.87; 95% CI, 0.19 to 1.55; P=0.01). The leg pain, Oswestry Disability Index (ODI), satisfaction rate, complication rate, and revision rate were comparable between the two procedures. Current systematic review and meta-analysis proved that DF is better than D in terms of back pain improvement, and the two procedures are comparable in terms of leg pain, ODI, satisfaction rate, complication rate, and revision rate.

Sacral dome resection and single-stage posterior reduction in the treatment of high-grade spondylolisthesis in a young girl

Introduction: The treatment of high-grade spondylolisthesis remains controversial in terms of in situ fusion versus reduction. The aim of operation in this patient is to restore the spino-pelvic alignment, sagittal profile of the spine and prevention of progression of slip with a minimal neurological risk.&#x0D; Case presentation: 18 years old schooling girl referred with a history of backache and right lower limb numbness over lateral aspect of foot for four years duration. She also had intermittent lower back pain, produced by long distant walking and relived by rest. It was aggravated by standing for long duration. There was no radiation of pain, no red flag sign or no cauda equina symptoms. Apart from her right lower limb neurology which was her power MRC grade IV in L5 and S1 myotome, other examinations were normal. X-Ray revealed grade V spondyloptosis. MRI showed evidence of right exiting L5 nerve root entrapment with grade V spondyloptosis. She underwent single stage posterior instrumentation of L4 - S1vertebrae, sacral dome resection, reduction of L5 over S1, interbody fusion of L5 - S1 and posterolateral intertransverse fusion of L4 to S1 vertebrae. She was ambulated on post-operative day one without brace. There was no worsening of neurology.&#x0D; Conclusion: Lumbosacral spondylolisthesis grade V can be treated using posterior approach alone to obtain reduction, decompression, and solid fusion. The sacral dome resection is a shortening osteotomy of the lumbosacral spine which allows a single-stage reduction of L5 without lengthening of lumbosacral region in high-grade spondylolisthesis, which helps to avoid neurological complications.

Is quality of life after surgery for adolescent idiopathic scoliosis affected by the presence of a concomitant low-grade isthmic spondylolisthesis non-surgically treated? A retrospective cohort study.

The HRQoL after surgery for adolescent idiopathic scoliosis (AIS) is not affected by the presence of concomitant isthmic spondylolisthesis non-surgically treated. Improvement in QoL after surgery was similar for AIS patients with and without concomitant spondylolisthesis. The purpose is to compare preoperative and postoperative Health-Related Quality of Life (HRQoL) scores in operated 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 versus 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 grade I spondylolisthesis can expect improvement in HRQoL scores, similar to that observed in patients without concomitant spondylolisthesis.

Comparison of spinous process-splitting laminectomy versus posterolateral fusion for lumbar degenerative spondylolisthesis.

Although several studies have recently shown that spinous process-splitting laminectomy (SPSL) maintains lumbar spinal stability by preserving posterior ligament components and paraspinal muscles as compared with conventional laminectomy, evidence is scarce on the treatment outcomes of SPSL limited to lumbar degenerative spondylolisthesis. We herein compare the surgical results and global alignment changes for SPSL versus posterolateral lumbar fusion (PLF) without instrumentation for lumbar degenerative spondylolisthesis. A total of 110 patients with Grade 1 lumbar degenerative spondylolisthesis who had undergone SPSL (47 patients) or PLF (63 patients) with minimum 1-year follow-up were retrospectively enrolled from a single institutional database. Mean operating time per intervertebral level and intraoperative blood loss per intervertebral level were comparable between the SPSL group and PLF group. Japanese Orthopaedic Association scores, Oswestry disability index, and visual analog scale scores were significantly and comparably improved at 1year postoperatively in both groups as compared with preoperative levels. The numbers of vertebrae with slip progression to Grade 2 and slip progression of 5% or more at 1year postoperatively were similar between the groups. In the SPSL group, mean pelvic tilt (PT) was significantly decreased at 1year postoperatively. In the PLF group, mean lumbar lordosis (LL) was significantly increased, while mean sagittal vertical axis, PT, and pelvic incidence-LL were significantly decreased at 1year after surgery. Compared with PLF without instrumentation, SPSL for Grade 1 lumbar degenerative spondylolisthesis displayed comparable results for slip progression and clinical outcomes at 1year postoperatively.

A Retrospective Study of Risk Factors and Outcomes in the Surgical Management of Slipped Capital Femoral Epiphysis.

Purpose:Slipped capital femoral epiphysis is commonly treated with in situ pinning (ISP) and more recently the modified Dunn procedure (MDP). This study retrospectively examines the preoperative risk factors and postoperative complications of patients treated with either ISP or MDP over a 12-year period.Methods:A single-center, retrospective review was conducted on patients diagnosed and surgically treated with slipped capital femoral epiphysis from 2004 to 2016. Patients must have had preoperative imaging and a minimum of 6 months of clinical follow-up. Six preoperative demographic data (age, sex, intensity of symptoms, stability, trauma, and severity of slip), surgical details, and treatment outcomes were collected. Descriptive statistics were used to identify pertinent preoperative risk factors and postoperative complications in each treatment group.Results:A total of 129 hips in 98 patients were treated (118 with ISP and 11 with MDP). Complications developed in 12 hips. Six hips developed osteonecrosis, two hips developed osteonecrosis and chondrolysis, two hips developed osteonecrosis and slip progression, and two hips developed slip progression only. Four of the 11 hips (36.4%) treated with MDP developed complications; 8 of the 118 hips (6.8%) treated with ISP developed complications.Discussion:Complications developed in 9.3% of hips treated with ISP or MDP, with a higher rate of complications observed in the MDP group compared with the ISP group. This study is limited by the small sample size of the cohort and the disproportion in the number of cases in each treatment group. A multicenter study with larger sample sizes will be required to confirm these findings.

Screw Thread Configuration Has No Effect on Outcomes of In Situ Fixation for Stable Slipped Capital Femoral Epiphysis.

No consensus exists regarding the optimal surgical management of slipped capital femoral epiphysis (SCFE). Treatment goals include avoiding slip progression and sequelae such as avascular necrosis (AVN). Factors associated with surgical implants merit further research. This study investigates the effect of screw thread configuration and the number of screws on surgical outcomes. A total of 152 patients undergoing cannulated, stainless steel, in situ screw fixation of SCFE between January 2005 and April 2018 were included. Procedure laterality, screw number and thread configuration (partially threaded/fully threaded), bilateral diagnosis, Loder classification, final follow-up, patient demographics, and endocrinopathy history were analyzed. Primary outcomes were return to the operating room (ROR), AVN, hardware failure/removal, and femoroacetabular impingement (FAI). Most patients received a single (86.2%), partially threaded (81.6%) screw; most were unilateral (67.8%) and stable (79.6%). Mean follow-up was 2.0±2.7 years, with a 15.8% rate of ROR, 5.3% exhibiting AVN, 6.6% exhibiting FAI, and 9.2% experiencing hardware failure/removal. Number of screws was the sole predictor of ROR [odds ratio (OR)=3.35, 95% confidence interval (CI): 1.18-9.49]. Unstable SCFE increased the odds of AVN (OR=38.44; 95% CI: 4.35-339.50) as did older age (OR=1.43, 95% CI: 1.01-2.03). Female sex increased risk for FAI (OR=4.87, 95% CI: 1.20-19.70), and bilateral SCFE elevated risk for hardware failure/removal versus unilateral SCFE (OR=4.41, 95% CI: 1.39-14.00). Screw thread configuration had no significant effect on any outcome (for each, P ≥0.159). Rates of ROR, AVN, FAI, and hardware failure/removal did not differ between patients treated with partially threaded or fully threaded screws. The use of 2 screws was associated with an increased likelihood of ROR. These findings suggest that screw thread configuration has no impact on complication rates, whereas screw number may be an important consideration in SCFE fixation. Level III-retrospective cohort study.

Factors Affecting Slip Progression After In Situ Screw Fixation of Stable Slipped Capital Femoral Epiphysis.

Slip progression after in situ fixation of slipped capital femoral epiphysis (SCFE) has been reported as occurring in up to 20% of patients. We review SCFE treated with in situ single screw fixation performed at 2 hospitals over a 15-year period to determine the factors associated with slip progression. This case-control study reviews SCFE treated with in situ single cannulated screw fixation with minimum follow up of 1 year and full closure of the affected physis. Slip progression (failure) was defined as worsening of the Southwick slip angle of 10 or more degrees or revision surgery for symptomatic slip progression. Univariate and multivariate analyses were performed comparing success and failure groups for patient characteristics, screw type and position, and radiographic measurements. Ninety three patients with 108 slips met all criteria, with 15 hips (14%) classified as having slip progression (failure). All failures had 3 threads or fewer across the physis. Five hips had 2 threads across the physis, and 4 of the 5 were classified as failures. Lower modified Oxford bone scores were found in the failure group, though the difference was small (0.9, P=0.013). Failure was also associated with partially threaded screws (P=0.001). Failed hips were associated with lower initial Southwick angles (32.8 degrees) than successful hips (40.4 degrees) (P=0.047). In the stepwise model for multivariate regression, 4 factors were identified as significant, with lower initial number of threads (P<0.0001), mild initial Southwick category (P=0.0050), male sex (P=0.0061), and partially threaded screw type (P=0.0116) predicting failure. This study is the largest to date evaluating risk factors for slip progression after SCFE fixation, and the first to consider revision surgery for symptomatic slip progression. For stable SCFE, we demonstrate that 4 threads across the physis with a fully threaded screw of 6.5 mm diameter or greater was sufficient to avoid slip progression. We provide a risk stratification for progression of slip showing that in some cases 3 threads across the physis may be sufficient. Level III-case-control study.

An Analytical Solution for the Initiation and Early Progression of Fretting Wear in Spherical Contacts

Abstract This article derives analytical solutions to calculate the wear volume at the initiation of fretting motion and its early progression over the first few oscillation cycles. The Archard-based model considers a deformable hemisphere that is contact with a deformable flat block. The material pairs investigated are special alloys, the Inconel 617/Incoloy 800H, and Inconel 617/Inconel 617. The analytical study begins with a unidirectional frictional sliding contact, where the local interfacial sliding distance and the nominal sliding distance at the initiation of gross slip are derived. The obtained analytical expressions for unidirectional sliding are then used to derive the corresponding wear volume for the initiation and early progression of gross slip and the wear volume for a general fretting cycle under elastic conditions. These analytical derivations are all verified by the finite element analysis (FEA). The FEA method and the analytical solutions render virtually identical results for both similar and dissimilar material pairs. The effects of plasticity on the wear volume under elastic–plastic conditions are also investigated. It is found that the fretting wear volumes obtained from the FEA simulations, which include plasticity, are close to those obtained from the analytical expressions for purely elastic regimes. All the results are presented in normalized forms, which can be easily generalized and applied to three-dimensional fretting wear of other material pairs.

Telescoping screw fixation compared to traditional in situ screw fixation for slipped capital femoral epiphysis: clinical, radiographic and patient-reported outcomes.

This study compares clinical, radiographic and patient-reported outcomes among telescoping and traditional screws for the treatment of slipped capital femoral epiphysis (SCFE). We hypothesized that telescoping screws would prevent slip progression and result in preserved femoral neck growth and improved patient-reported outcomes. Traditional screws were compared to telescoping screws in a 2:1 matched cohort based on age at initial surgery, length of radiographic follow-up and whether or not the hip was pinned prophylactically or as a treatment for SCFE. Neck length and telescoping screw length were measured. The patient-reported outcomes were obtained at routine clinic visits. Total 42 hips were included with a mean follow-up of 24.5 ± 3.3 months. No patients developed avascular necrosis, chondrolysis or needed revision surgical procedures. Telescoping screws increased in length for the entire cohort by a mean of 6.0 ± 4.3 mm. Neck length change was not different in SCFE hips when treated with traditional screws vs. telescoping screws (P = 0.527). However, there was a difference in neck length change between the two groups when comparing prophylactically treated hips (P = 0.001). There were no significant differences in patient-reported outcomes among hips treated with telescoping screws compared to traditional screws. Traditional and telescoping screws are both effective for the treatment of SCFE. Telescoping screws have an advantage when prophylactically treating hips that are at risk of slipping as they don't lead to the coxa breva that is seen with traditional screws. However, both treatment methods had similar patient-reported outcomes.

Lumbar Endoscopic Unilateral Laminotomy for Bilateral Decompression for Lumbar Spinal Stenosis Provides Comparable Clinical Outcomes in Patients with and without Degenerative Spondylolisthesis

To investigate and compare the clinical and radiological outcomes of lumbar endoscopic unilateral laminotomy for bilateral decompression (LE-ULBD) for lumbar spinal stenosis (LSS) patients with and without degenerative spondylolisthesis (DS). A total of 129 patients who underwent LE-ULBD for single-level LSS were retrospectively reviewed. The patients were classified into 2 groups based on the presence of DS. Clinical outcomes were assessed with the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire and numeric rating scale (NRS) for low back pain, lower limb pain, and lower limb numbness. Scores were obtained at baseline and final follow-up (mean follow-up, 28.6 months [range, 24-63 months]). The follow-up rate was 77.5% (103 patients). All domains of the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire and NRS evaluations significantly improved during the follow-up period in both groups; group differences were not significant except for the postoperative NRS limb numbness score, which was higher in patients with DS. The Macnab outcome classification was excellent or good in 80% of patients without DS and 77.1% of patients with DS. During the follow-up period, the increase of vertebral slip was observed in 31% of the patients with DS that includes vertebral slip progression defined as percent slip >5% in 4% of the patients. The increase of vertebral slip was not related to a clinical outcome. Segmental motion of the affected intervertebral disc did not increase after surgery. LE-ULBD provides a comparably favorable outcome in LSS patients with and without DS. Postoperative segmental instability did not occur in patients with DS.

Age-Specific Characteristics of Lumbopelvic Alignment in Patients with Spondylolysis: How Bilateral L5 Spondylolysis Influences Lumbopelvic Alignment During the Aging Process

To elucidate the influence of spondylolysis on age-related lumbar degenerative changes, age-specific lumbopelvic alignment in patients with or without spondylolysis was examined. Sagittal reconstructed computed tomography images of the lumbar spine in consecutive patients (n=581) undergoing computed tomography scans of abdominal or lumbar regions for reasons other than low back disorders were obtained. Lumbar lordosis (LL), L5-S1 angle, and sacral slope (SS) were measured. Lumbopelvic parameters in patients with or without spondylolysis were evaluated in 3 age groups (<50, 50-69, and ≥70). The influence of bilateral L5 spondylolysis (L5-lysis) and L5 vertebral slip on each lumbopelvic parameter, as well as correlation between cross-sectional area (CSA) of paraspinal muscles and the degree of vertebral slip, were examined by multiple regression analysis. Patients with bilateral spondylolysis showed greater LL and SS than patients without spondylolysis. When analyzing the influence of L5-lysis, only elderly patients (≥70) with L5-lysis showed significantly greater LL and SS than nonspondylolysis (nonlysis) patients. L5-lysis patients more frequently showed L5 vertebral slip than nonlysis patients, and a smaller L5-S1 angle was observed when L5 vertebral slip accompanied L5-lysis. The degree of vertebral slip was significantly correlated with CSA of psoas muscles, but not with CSA of paraspinal extensor muscles. When patients have L5-lysis, lumbar lordosis and pelvic anteversion occurred age dependently. In elderly patients with L5-lysis, L5 vertebral slip with decrease of the L5-S1 angle occurs frequently. The progression of vertebral slip was correlated with atrophy of psoas muscles, but not that of paraspinal extensor muscles.

Factors of Adjacent Segment Disease Onset After Microsurgical Decompression for Lumbar Spinal Canal Stenosis

Few studies have examined the underlying cause of adjacent segment disease (ASD) after decompression surgery for lumbar spinal stenosis. The goal of this study is to investigate factors related to the onset of ASD after decompression surgery based on the imaging results. We examined 95 patients who underwent single-level decompression for lumbar spinal stenosis (L3/4, L4/5) and follow-up for 5 or more years. Radiographic images were performed preoperatively and at each year of follow-up. We then examined image parameters by focusing on the level operated on and adjacent segments in relation to the postoperative onset of symptomatic ASD. During the mean observation period of 7.5 years, 39 of 95 patients developed symptomatic ASD. Patients with a high preoperative sagittal rotation angle in adjacent segments possibly developed postoperative ASD (P= 0.0006). Furthermore, postoperative ASD tended to be unlikely in patients who exhibited postoperative slip progression at the operated level (P= 0.025). Based on receiver operating characteristic analysis, ASD developed with a probability of 91.3% in patients with a preoperative sagittal rotation angle of ≥7.5° in adjacent segments when there was no postoperative slip progression at the operated level. However, ASD developed in only 16.7% of patients with a preoperative adjacent segment sagittal rotation angle of 7.5° or less when there was postoperative slip progression at the operated level. Biomechanical changes at the operated level and adjacent segments contribute to the onset of ASD after lumbar decompression. Preoperative high sagittal rotation angle of adjacent segments and negative postoperative slip progression at the operated level are risk factors of ASD.

Outcomes of distally un-threaded screw fixation of slipped capital femoral epiphysis at skeletal maturity: a matched cohort study.

The most common treatment for slipped capital femoral epiphysis worldwide is in situ fixation with a threaded screw. Un-threaded screws are designed to prevent slip progression without hindering residual growth of the proximal femur. This study aimed to compare growth, remodelling and long-term outcomes after fixation with un-threaded screws and a matched cohort of patients treated with a standard screw. Six patients (nine hips) treated with un-threaded screws and 16 patients (21 hips) treated with standard screws matched for age, skeletal maturity, sex and Southwick angle were recruited. Clinical records were reviewed for patient demographics, medical history and complications. Radiographs were reviewed for residual growth and time to physeal closure. Growth velocity was calculated. Absence of cam deformity signified complete remodelling. Clinical assessment was graded from excellent to poor and patient-reported outcomes were recorded. There was significantly more growth recorded in the un-threaded screw group in femoral neck length (7.6 mm, P = 0.003), articulo-lesser trochanter distance (5.3 mm, P = 0.028), pin-joint ratio (7.439%, P = 0.006) and pin-physis ratio (8.244%, P = 0.001). The probability of revision operations due to ongoing growth was higher in this group (risk ratio: 6.57, P = 0.0008). Time to physeal closure was not significantly different, but growth velocity was significantly higher in the un-threaded group. The lower probability of cam deformity was not significant. Functional and clinical results were not significantly different at average 11.2 years' follow-up. Un-threaded screws allow for significantly more growth than standard threaded screws. The un-threaded screw could not be recommended due to the higher re-operation rates, without any proven benefit.

P45. Radiological features of slip progression in adult patients with isthmic spondylolisthesis

BACKGROUND CONTEXT Lumbar spondylolysis is generally recognized as a stress fracture of pars interarticularis occurring in childhood and adolescence. Non-union after pars fracture in the spinal motion segment may lead to isthmic spondylolisthesis. Various factors such as disc degeneration and sagittal radiological parameters contributing to slip progression in adult isthmic spondylolisthesis have been discussed. In the relationship between L5 isthmic spondylolisthesis and deformities of the sacral table, it was reported that the mechanism of vertebral slippage was different between immature and mature spine in animal studies. There are two types of isthmic spondylolisthesis which occur before and after skeletal maturity: adolescent slip with sacral deformities and adult slip without sacral deformities. However, in these two types of isthmic spondylolisthesis, there are no reports that have clarified whether there is a difference in the slip progression radiologically. PURPOSE Purpose of this study is to clarify the predictive risk factors contributing to progression of vertebral slippage in adults diagnosed with isthmic spondylolisthesis and treated conservatively. STUDY DESIGN/SETTING This is a retrospective study using 29 adult patients with isthmic spondylolisthesis. PATIENT SAMPLE Patients who were 20 to 59 years old and diagnosed with isthmic spondylolisthesis by ICD-9 and ICD-10 between 2007 and 2017 were included in this study through a Northwestern Medicine Enterprise Data Warehouse search. Patients who were diagnosed with dysplastic, traumatic, degenerative or pathologic spondylolisthesis, patients who have lumbar scoliosis, patients who have past medical history of spine surgery were excluded. OUTCOME MEASURES Slip progression and slip progression percent during follow-up. METHODS We evaluated their plain radiographs of the lumbar spine which were followed up for more than 3 years and analyzed factors affected the slip progression. RESULTS Patients’ mean age was 41.6 (± 7.9) years old. The follow-up period was 68.6 (± 20.8) months. Slip and slip% were 6.7 (± 4.1) mm, 15.5 (± 10.2) % at initial X-ray, and 10.0 (± 4.6) mm, 22.7 (± 10.6) % at final X-ray respectively. All of them progressed anterior slip during the follow-up period (P CONCLUSIONS All patients who were followed-up conservatively progressed anterior slip in this study cohort. However, the degree of their slip was not correlated with the sacral deformity or other factors described in the previous reports compared to normal group. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Surgical management of high-grade spondylolisthesis

High-grade spondylolisthesis, defined as Meyerding grades III, IV, and V or greater than 50% anterior translation, represent a unique spinal pathology. Most commonly isthmic in etiology and predominantly affecting adolescent patients, these slips are associated with unique management considerations and surgical challenges for treatment. Reduction and decompression are controversial management strategies, whereas fusion has long been the definitive surgical modality to prevent slip progression and neurologic deterioration. Fusion methods including posterior in situ, posterior instrumented, anterior, and circumferential have been reported with varying successes. We examine the evolution of our evaluation and surgical management of these challenging clinical scenarios.

Image-Based Markers Predict Dynamic Instability in Lumbar Degenerative Spondylolisthesis.

ObjectiveTo identify possible radiographic predictors markers of dynamic instability including disc height (DH), disc degeneration, and spondylosis in the setting of degenerative spondylolisthesis (DS). MethodsA retrospective review with prospectively collected data was performed on 125 patients with L4–5 DS who underwent decompression and fusion. Patients were divided into groups with dynamic instability and those without. Radiographs of the lumbar spine in neutral, flexion, and extension were used to determine degree of slip, DH, translational motion, angular motion, spondylotic changes, and lumbar lordosis. Magnetic resonance imaging (MRI) scans were reviewed to assess disc degeneration. ResultsThirty-one percent of the patients met criteria for dynamic instability. Significant correlations (p < 0.05) were found between preserved DH and dynamic instability; increased spondylotic changes and decreased translational motion; as well as advanced MRI-based disc degeneration scores with decreased angular motion, respectively. Six radiographic parameters were utilized to create a predictive model for dynamic instability, and a receiver operating characteristic curve was able to validate the predictive model (area = 0.891, standard error = 0.034, p < 0.001). ConclusionIn DS patients, preserved DH was significantly related to dynamic instability. This finding may represent a greater potential for slip progression over time in these patients. In contrast, disc degeneration on MRI, and spondylotic changes were inversely related to dynamic instability and may represent restabilization mechanisms that decrease the chance of future slip progression in DS.

Slip progression in degenerative lumbar spondylolisthesis following minimally invasive decompression surgery is not associated with increased functional disability.

The aim of this study is to determine whether there is a relationship between radiographic slip progression and symptomatic worsening after decompression without fusion for low-grade degenerative lumbar spondylolisthesis (DLS). A retrospective review of 1-2-level minimally invasive surgical decompression for grade I-II DLS was performed. Included subjects had a minimum of 1-year follow-up with prospectively collected baseline and follow-up Oswestry Disability Index (ODI) scores. Fifty-six patients (33 females, 58.9%), having a mean age 65.6years (SD 10.0), met inclusion criteria. Spondylolisthesis slip percentage increased in 55.4% (31/56) of patients. Slip percentage increased significantly (p = 0.002) from baseline (mean 17.2; SD 8.0) to follow-up (mean 20.1; SD 9.6). A logistic regression model identified that females were more likely to have progressive slips compared to males (odd ratio 6.09, 95% CI 1.77-21.01; p = 0.004). ODI scores and spondylolisthesis slip percentage did not correlate at baseline (r = 0.0170; p = 0.90) nor follow-up (r = 0.094; p = 0.49). There was no correlation between the change in ODI scores and change in slip percentage from baseline to final follow-up (r = 0.0474; p = 0.73). Of the 31 patients with slip progression, there was no difference in mean ODI score changes (p = 0.91) for those with 1-5% progression (13/31 [41.9%]; - 18.0 [SD 19.7]) compared to those with > 5% slip progression (18/31 [58.1%]; - 18.7 [SD 16.4]). Despite a small degree of slip progression in the majority of patients, there was no correlation with symptom worsening, as measured by the ODI. These slides can be retrieved under Electronic Supplementary Material.