T1-VIBE and STIR MRI of lumbar pars interarticularis injuries in elite athletes: fracture characterisation and potential prognostic indicators

OBJECTIVES

To assess how pars interarticularis fracture characteristics on T1-VIBE and STIR MRI relate to healing and identify anatomical parameters that may impact healing.

MATERIALS AND METHODS

A retrospective review of an MRI series of lumbar pars interarticularis injuries in elite athletes over a 3-year period. Fracture configurations, signal intensities and anatomical parameters were recorded by two radiologists. Statistical analysis employed multilevel mixed-effects linear regressions, adjusted for repeated measures and baseline covariates.

RESULTS

Forty-seven lumbar pars interarticularis injuries among 31 athletes were assessed. On final scans for each athlete, 15% (7/47) injuries had worsened, 23% (11/47) remained stable, 43% (20/47) partially healed and 19% (9/47) healed completely. Healing times varied, quickest was 49 days for a chronic fracture in a footballer. Bone marrow oedema signal was highest in worsened fractures, followed by improved, and lowest in stable fractures. As healing progressed, T1-VIBE signal at the fracture line decreased. Bone marrow oedema and fracture line signal peaked at 90-120 days before decreasing until 210-240 days. Fractures with smaller dimensions, more vertical orientation and a longer superior articular facet beneath were significantly associated with better healing (p < 0.05).

CONCLUSION

Most diagnosed athletic pars interarticularis injuries improve. Normalising T1-VIBE signal at the fracture line is a novel measurable indicator of bony healing. Contrastingly, bone marrow oedema signal is higher in active fractures irrespective of healing or deterioration. Injuries initially perceived as worsening may be exhibiting the normal osteoclastic phase of healing. Better outcomes favour smaller, vertical fractures with a longer superior articular facet beneath.

Is MRI screening for bone marrow oedema useful in predicting lumbar bone stress injuries in adult male professional cricketers? A New Zealand pilot study

OBJECTIVES

The aims were to (1) prospectively observe the incidence of bone marrow oedema in asymptomatic adult male domestic professional cricketers during a season and evaluate its relationship to the development of lumbar bone stress injury and (2) further understand the practicalities of implementing a Magnetic Resonance Imaging-based screening program to prevent lumbar bone stress injury in New Zealand cricket.

DESIGN

Prospective observational cohort.

METHODS

Adult male pace bowlers received 6-weekly pre-planned Magnetic Resonance Imaging scans over a single season to determine the presence and intensity of bone marrow oedema in the posterior vertebral arches of the lumbar spine. The participants bowling volume and back pain levels were monitored prospectively.

RESULTS

22 participants (mean age 25.3 years (range 20-32 years)) completed all 4 scans. Ten participants had a prior history of lumbar bone stress injury. Ten participants (45 %, 95 % confidence interval 24-68 %) had bone marrow oedema evident on at least one scan, with 9 (41 %) participants recording a bone marrow oedema intensity ≥ 2 and 5 (23 %) participants demonstrated an intensity ≥ 3. During the study one participant was diagnosed with a lumbar bone stress reaction. No participants developed a lumbar bone stress fracture.

CONCLUSIONS

Due to the lower incidence of lumbar bone stress injuries in adult bowlers coupled with uncertainty over appropriate threshold values for bone marrow oedema intensity, implementation of a resource intense screening program aimed at identifying adult domestic cricketers at risk of developing a lumbar bone stress injury is not currently supported.

What is the C2 pedicle, pars interarticularis, and isthmus? Anatomical study and review of the literature regarding these confusing terms with proposal of new nomenclature

INTRODUCTION

The atypical anatomy of the C2 vertebra has led to terminological discrepancies within reports and studies in the literature regarding the location of its pedicle, pars interarticularis, and isthmus. These discrepancies not only limit the power of morphometric analyses, but they also confuse technical reports regarding operations involving C2, and thus confuse our ability to properly communicate this anatomy. Herein, we examine the variations in nomenclature regarding the pedicle, pars interarticularis, and isthmus of C2, and via an anatomical study, propose new terminology.

METHODS

The articular surface and underlying superior and inferior articular processes and adjacent transverse processes were removed from 15 C2 vertebrae (30 sides). Specifically, the areas regarded as the pedicle, pars interarticularis, and isthmus were evaluated. Morphometrics were performed.

RESULTS

Our results indicate that, anatomically, C2 has no "isthmus" and that a pars interarticularis for C2, when present, is very short. Deconstruction of the attached parts allowed for visualization of a bony arch extending from the anterior most aspect of the lamina to the body of C2. The arch is composed almost entirely of trabecular bone and without its attached parts, e.g., transverse process, really has no cortical bone laterally.

CONCLUSIONS

We propose a more accurate terminology, the pedicle, for pars/pedicle screw placement of C2. Such a term more accurately describes this unique structure of the C2 vertebra and would alleviate terminological confusion in the future literature on this topic.

[Imaging measurement for the posterior pars interarticularis screw fixation on axis]

OBJECTIVE

To explore the safety and feasibility of posterior pars interarticularis screw fixation on axis by CT measurement.

METHODS

The CT data of 137 patients with complete upper cervical spine who underwent full cervical spine CT examination from January 2016 to December 2019 were collected, including 71 males and 66 females, aged from 22 to 65 years old with an average of (41.8±17.4) years old. Mimics 19.0 software was used to measure anatomical data related to the pars interarticularis screw, including the pars width, pars vertical length, pars vertical height, length of pars screw trajectory, upward inclination angle of pars screw trajectory. And the correlation between each index was analyzed.

RESULTS

The axis pars has an average width of (9.05±1.63) mm, an average vertical length of (11.21±1.43) mm, and an average vertical height of (17.53±2.93) mm. The mean length of pars screw trajectory was(19.07±3.20) mm. Regarding to the length of pars screw trajectory, 94.53% of pars measured more than 14 mm, 82.12% of pars measured at 14-16 mm, 63.14% of pars measured at 16-18 mm, 39.78% of pars measured at 18-20 mm. The upward inclination angle of pars screw was 30°-68° with an average of (46.06±8.06) °. There was a highly positive correlation between the length of screw trajectory and upward inclination angle(r=0.965, P=0.000). The vertical length of pars was weakly positively correlated with length of screw trajectory and upward inclination angle(r=0.240, P=0.000;r=0.163, P=0.007). Pars width was moderately negative correlated with length of scrwe trajectory and upward inclination angle(r =-0.333, P=0.000;r=-0.380, P=0.000).

CONCLUSION

The posterior pars interarticularis screw fixation is safe and reliable. It has a more wider applicability than pedicle screw fixation and can be used as an alternative to pedicle screws.

Does Direct Surgical Repair Benefit Pars Interarticularis Fracture? A Systematic Review and Meta-analysis

BACKGROUND

Promising results have been shown in previous studies from direct pars interarticularis repair. These include Scott wiring, Buck repair, pedicle screw repair, and Morscher techniques. In addition, several minimally invasive techniques have been reported to show high union rates, low rates of implant failure and wound complications, shorter length of stay, a lower postoperative pain score with faster recovery, and minimal blood loss.

OBJECTIVES

To compare the evidence on techniques for direct pars interarticularis repair.

STUDY DESIGN

Systematic review and meta-analysis.

SETTING

Review article.

METHODS

We conducted a comprehensive search of databases to identify studies assessing outcomes of direct pars interarticularis defect repair. Two authors independently screened electronic search results, performed study selection, and extracted data for meta-analysis. Sensitivity and subgroup analyses were performed to assess risk of bias.

RESULTS

Forty studies were included in the final analysis. Union rate was higher in the pedicle screw repair group (effect size [ES] 95%; 95% CI, 86% to 100%), followed by the Buck repair group (ES 93%; 95% CI, 86% to 98%), Scott wiring (ES 85%; 95% CI, 63% to 99%), and Morscher method group (ES 63%; 95% CI, 2% to 100%). Positive functional outcome was higher for the Morscher method (ES 91%; 95% CI, 86% to 96%), followed by the Buck repair group (ES 85%; 95% CI, 68% to 97%), pedicle screw repair (ES 84%; 95% CI, 59% to 99%) and Scott repair group (ES 80%; 95% CI, 60% to 95%). Complication rates were highest among the Scott repair group (ES 12%; 95% CI, 4% to 22%) and Morscher method group (ES 12%; 95% CI, 0% to 34%).

LIMITATIONS

Heterogeneity of the included studies were noted. However, we performed sensitivity analyses from the available data to address this issue.

CONCLUSION

Our results indicate that pedicle screw repair and Buck repair may be associated with a higher union rate and lower complication rates compared to the Scott repair and Morscher method. Ultimately, the choice of technique should be based on the surgeon's preference and experience.

Lumbosacral Spondylolysis and Spondylolisthesis

Repetitive stress on the lumbosacral spine during sporting activity places the athletic patient at risk of developing symptomatic pars defect. Clinical history, physical examination, and diagnostic imaging are important to distinguish spondylolysis from other causes of lower back pain. Early pars stress reaction can be identified with advanced imaging, before the development of cortical fracture or vertebral slip progression to spondylolisthesis. Conservative management is first-line for low-grade injury with surgical intervention indicated for refractory symptoms, severe spondylolisthesis, or considerable neurologic deficit. Prompt diagnosis and management of spondylolysis leads to good outcomes and return to competition for most athletes.

Presence of bone marrow oedema in asymptomatic elite fast bowlers: Implications for management

OBJECTIVES

1) Quantify the intensity of bone marrow oedema (BMO) present in the lumbar vertebrae of asymptomatic elite adult fast bowlers; 2) relate the intensity of BMO to bowling workload and lumbar bone stress injury (LBSI), and; 3) evaluate the utility of MRI screening to reduce the risk of LBSI.

METHODS

Thirty-eight elite Australian fast bowlers (21.6 ± 3.7 years) completed 48 screening MRI over 3 years. BMO intensity was quantified on MRI retrospectively. Standard practices for bowling workload monitoring and injury diagnosis were followed.

RESULTS

Clinically significant BMO (signal intensity ratio ≥ 2.0) was observed in 22 (46%, 95% CI 31-61) screening MRI. These bowlers had a total of 77 (IQR 45-115) days off between seasons, compared to 66 (IQR 41-94) days off for bowlers with a BMO intensity less than 2.0 (p = 0.510). Fifteen bowlers received follow up MRI as part of individualised management based on their screening MRI, of which less than five went on to develop LBSI in the subsequent season. There was no difference in days or balls bowled in the 12 months following screening MRI between those who sustained LBSI and those who did not.

CONCLUSIONS

BMO is common in asymptomatic bowlers. Identification of high-risk bowlers using screening MRI informs individualised management and may prevent progression to LBSI.

Return to play after spondylolysis: An overview

Spondylolysis is increasingly associated with specific sports, timely and effective management of which underpins successful return to sports. Hence, the main purpose of this systematic review of reviews [RoR] is to summarize data from published reviews exploring the return to play in athletes with spondylolysis managed conservatively or surgically, thereby providing for recommendations for future practice and research. A systematic review of review of articles published in English and since 2015 was conducted online using PubMed and Google Scholar, as per Preferred Reporting Items for Systematic reviews and Meta-analyses guidelines. Predefined eligibility criteria were applied, and the data thus compiled were analyzed. Study quality was assessed using the AMSTAR-2 checklist. A total of 7 systematic reviews and meta-analysis consisting of 51 primary studies were included in the review. The result of this RoR highlights the knowledge gap and limitations in RTP research post spondylolysis with existing heterogeneity in methods and reporting amid other factors within primary studies. Further quality of the study was found to be of low to critically low confidence based on the AMSTAR-2 scale, suggesting that the results should be interpreted with great caution. Though both conservative and surgical approaches increase the percentage of athletes returning to play, the evidence remains largely limited and inconclusive as to which is better. However, it appears that surgical interventions give those who failed a trial of conservative approach, a better shot at return to play. There is a need for further high-quality, appropriately powered, well-designed, multicentered studies, and also for consensus regarding "returning to play" definition and outcome measures.

Biomechanical effects of laminectomies in the human lumbar spine: a finite element study

BACKGROUND CONTEXT

Previous studies have analyzed the effect of laminectomy on intervertebral disc (IVD), facet-joint-forces (FJF), and range of motion (ROM), while only two have specifically reported stresses at the pars interarticularis (PI) with posterior element resection. These studies have been performed utilizing a single subject, questioning their applications to a broader population.

PURPOSE

We investigate the effect of graded PI resection in a three-dimensional manner on PI stress to provide surgical guidelines for avoidance of iatrogenic instability following lumbar laminectomy. Additionally, quantified FJF and IVD stresses can provide further insight into the development of adjacent segment disease.

STUDY DESIGN

Biomechanical finite element (FE) method investigation of the lumbar spine.

METHODS

FE models of the lumbar spine of three subjects were created using the open-source finite element software, FEBio. Single-level laminectomy, two-level laminectomy, and ventral-to-dorsal PI resection simulations were performed with varying degrees of PI resection from 0% to 75% of the native PI. These models were taken through cardinal ROM under standard loading conditions and PI stresses, FJF, IVD stresses, and ROM were analyzed.

RESULTS

The three types of laminectomy simulated in this study showed a nonlinear increase in PI stress with increased bone resection. Axial rotation generated the most stress at the PI followed by flexion, extension and lateral bending. At 75% bone resection all three types of laminectomy produced PI stresses that were near the ultimate strength of human cortical bone during axial rotation. FJF decreased with increased bone resection for the three laminectomies simulated. This was most notable in axial rotation followed by extension and lateral bending. IVD stresses varied greatly between the nonsurgical models and likewise the effect of laminectomy on IVD stresses varied between subjects. ROM was mostly unaffected by the laminectomies performed in this study.

CONCLUSIONS

Regarding the risk of iatrogenic spondylolisthesis, the combined results are sufficient evidence to suggest surgeons should be particularly cautious when PI resection exceeds 50% bone resection for all laminectomies included in this study. Lastly, the effects seen in FJF and IVD stresses indicate the degree to which the remainder of the spine must experience compensatory biomechanical changes as a result of the surgical intervention.

Radiological healing of lumbar spine stress fractures in elite cricket fast bowlers

OBJECTIVES

Review magnetic resonance imaging (MRI) of elite adult fast bowlers with a history of lumbar spine stress fracture for evidence of bone healing. The findings will determine whether bone healing can occur in this population, and whether MRI may be used as a tool to assess bone healing and inform clinical decision making.

DESIGN

Retrospective cohort.

METHODS

Participants were elite Australian fast bowlers who sustained a lumbar spine stress fracture confirmed on MRI and had at least one subsequent MRI. Two radiologists independently reviewed all images.

RESULTS

Thirty-one fractures from 20 male fast bowlers were reviewed. Median maximum fracture size was 6mm (range 2-25mm). Twenty-five fractures achieved bone healing, with a median 203 (IQR 141-301) days between the initial MRI (to confirm diagnosis) and the MRI when bone healing was observed. Fracture size and signal intensity of bone marrow oedema were positively associated with the number of days to the MRI when bone healing was observed (r²=0.245, p<0.001 and r²=0.292, p<0.001 respectively). Fractures which occurred at the same site as a previously united fracture took longer to heal than the first fracture (median 276 days to the MRI when bone healing was observed compared to 114 days for first fracture; p=0.036).

CONCLUSIONS

Lumbar spine stress fractures in elite adult fast bowlers are capable of achieving complete bone healing, as demonstrated in the majority of bowlers in this study. Larger fractures, greater bone marrow oedema, and history of previous injury at the same site may require longer healing time which may be monitored with MRI.

Application of an interspinous process device after minimally invasive lumbar decompression could lead to stress redistribution at the pars interarticularis: a finite element analysis

Background

An interspinous process device, the Device for Intervertebral Assisted Motion (DIAM™) designed to treat lumbar neurogenic disease secondary to the lumbar spinal stenosis, it provides dynamic stabilization after minimally invasive (MI) lumbar decompression. The current study was conducted using an experimentally validated L1-L5 spinal finite element model (FEM) to evaluate the limited decompression on range of motion (ROM) and stress distribution on a neural arch implanted with the DIAM.

Methods

The study simulated bilateral laminotomies with partial discectomy at L3-L4, as well as unilateral and bilateral laminotomies with partial discectomy combined with implementation of the DIAM at L3-L4. The ROM and maximum von Mises stresses in flexion, extension, lateral bending, and axial torsion were analyzed in response to the hybrid protocol in comparison with the intact model.

Results

The investigation revealed that decreased ROM, intradiscal stress, and facet joint force at the implant level, but considerably increased stress at the pars interarticularis were found during flexion and torsion at the L4, as well as during extension, lateral bending, and torsion at the L3, when the DIAM was implanted compared with the defect model.

Conclusion

The results demonstrate that the DIAM may be beneficial in reducing the symptoms of stress-induced low back pain. Nevertheless, the results also suggest that a surgeon should be cognizant of the stress redistribution at the pars interarticularis results from MI decompression plus the application of the interspinous process device.

Bilateral persistent 'second' intersegmental vertebral arteries: illustrated with a case

Congenital craniovertebral junction deformities can be associated with an anomalous vertebral artery (VA). At times, the artery crosses the joint posteriorly (i.e., persistent first intersegmental artery) and is at risk during posterior approach. We report a new variant, wherein the bilateral VA coursed medially after exiting the C3 transverse foramina to lie beneath C2 pars interarticularis and enter the foramen magnum (without passing through C2 transverse foramen anywhere along its course). This is possibly a result of bilateral persistent second intersegmental arteries. It is pertinent to recognize this unusual variant to avoid VA injury, especially while inserting C2 pars/transarticular screw.

Biomechanical analysis of spino-pelvic postural configurations in spondylolysis subjected to various sport-related dynamic loading conditions

PURPOSE

To study the risks of spondylolysis due to extrinsic loading conditions related to sports activities and intrinsic spino-pelvic postural parameters [pelvic incidence (PI) and sacral slope (SS)].

METHODS

A comprehensive osseo-disco-ligamentous L4-S1 finite element model was built for three cases with spondylolysis representing three different spino-pelvic angular configurations (SS = 32°, 47°, 59° and PI = 49°, 58°, 72°, respectively). After simulating the standing posture, 16 dynamic loading conditions were computationally tested for each configuration by combining four sport-related loads (compression, sagittal and lateral bending and axial torque). For each simulation, the Von Mises stress, L5-S1 facet contact force and resultant internal loads at the sacral endplate were computed. Significant effects were determined with an ANOVA.

RESULTS

The maximal stress and volume of cancellous bone in the pars with stress higher than 75% of the ultimate stress were higher with 900 N simulated compression (2.2 MPa and 145 mm³) compared to only the body weight (1.36 MPa and 20.9 mm³) (p < 0.001). Combined compression with 10 Nm of flexion and an axial torque of 6 Nm generated the highest stress conditions (up to 2.7 MPa), and L5-S1 facet contact force (up to 430 N). The maximal stress was on average 17% higher for the case with the highest SS compared to the one with lowest SS for the 16 tested conditions (p = 0.0028).

CONCLUSIONS

Combined flexion and axial rotation with compression generated the highest stress conditions related to risks of spondylolysis. The stress conditions intensify in patients with higher PI and SS. These slides can be retrieved under Electronic Supplementary Material.

Fatigue and damage of porcine pars interarticularis during asymmetric loading

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

Spondylolysis in the past: A case study of hunter-gatherers from Southern Patagonia

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

Significance of the Pars Interarticularis in the Cortical Bone Trajectory Screw Technique: An In Vivo Insertional Torque Study

STUDY DESIGN

Retrospective study.

PURPOSE

Cortical bone trajectory (CBT), a more medial-to-lateral and shorter path than the traditional one for spinal fusion, is thought to be effective for severely degenerated vertebrae because screws are primarily stabilized at the posterior elements. We evaluated the efficacy of this approach through in vivo insertional torque measurement.

OVERVIEW OF LITERATURE

There has been only one prior in vivo study on CBT insertional torque.

METHODS

Between January 2013 and April 2014, a total of 22 patients underwent posterior lumbar fusion using the CBT technique. The maximum insertional torque, which covers the radial strength needed for insertion, was measured for 113 screws, 8 of which were inserted for L5 spondylolysis. The insertional torque for cases with (n=8) and without (n=31) spondylolysis of L5 were compared using one-way analysis of variance (ANOVA). To evaluate vertebral degeneration, we classified 53 vertebrae without spondylolysis by lumbar radiography using semiquantitative methods; the insertional torque for the 105 screws used was compared on the basis of this classification. Additionally, differences in insertional torque among cases grouped by age, sex, and lumbar level were evaluated for these 105 screws using ANOVA and the Tukey test.

RESULTS

The mean insertional torque was significantly lower for patients with spondylolysis than for those without spondylolysis (4.25 vs. 8.24 in-lb). There were no statistical differences in insertional torque according to vertebral grading or level. The only significant difference in insertional torque between age and sex groups was in men <75 years and women ≥75 years (10 vs. 5.5 in-lb).

CONCLUSIONS

Although CBT should be used with great caution in patient with lysis who are ≥75 years, it is well suited for dealing with severely degenerated vertebrae because the pars interarticularis plays a very important role in the implementation of this technique.

Current Evidence Regarding the Etiology, Prevalence, Natural History, and Prognosis of Pediatric Lumbar Spondylolysis: A Report from the Scoliosis Research Society Evidence-Based Medicine Committee

STUDY DESIGN

Structured literature review.

OBJECTIVES

To assess the current state of evidence as a first step in the development of practice guidelines for pediatric spondylolysis.

SUMMARY OF BACKGROUND DATA

Progress in published medical knowledge, changes in societal expectations, and developments in health care economics have led medical organizations to develop evidence-based documents and products.

METHODS

A comprehensive literature search for pediatric spondylolysis was performed with the assistance of a medical librarian. The authors reviewed citations and abstracts. Abstracts were reviewed for exclusions and data from included studies were analyzed by committee. A total of 44 articles provided the best available evidence for the questions of etiology, prevalence, natural history, and prognosis: 9 were graded as level I evidence, 23 were level II, 3 were level III, and 9 were level IV. No level V studies were included in the final list.

RESULTS

There is good evidence that pediatric lumbar spondylolysis is an acquired fracture of the pars interarticularis that can occur unilaterally or bilaterally. Evidence shows that when chronic, bilateral pars defects develop, 43% to 74% of patients will progress to grade 1 or 2 spondylolisthesis. In addition, unilateral, incomplete, and early lesions can obtain bony union. With or without bony union or spondylolisthesis, short-term symptom resolution is the norm. Long-term prognosis is less clear, but there is fair evidence that most patients will have lumbar symptoms compared with the general population. There is also fair evidence that some patients will develop significant symptoms as adults and will undergo surgical treatment. There is insufficient knowledge to predict which patients will continue to do well in the long term with conservative or no treatment and which patients will develop symptoms significant enough to warrant early intervention.

CONCLUSIONS

The current medical literature provides fair to good evidence for clinically relevant questions regarding the etiology, prevalence, natural history, and prognosis of pediatric spondylolysis.

Interpedicular kinematics in an in vitro biomechanical assessment of a bilateral lumbar spondylolytic defect

BACKGROUND

A spondylolytic defect in lumbar vertebra is a common condition during early childhood and adolescence, and is considered a precursor to spondylolisthesis. This study examined whether a bilateral spondylolytic defect in lumbar spine intrinsically results in increased intervertebral translations during different bending motions.

METHODS

Seven fresh frozen cadaveric kangaroo lumbar (L1-L6) spine specimens were tested in a kinematic spine simulator; first in their intact state, followed by creating a bilateral spondylolytic defect at L4 and retesting. In addition to recording global and segmental range of motions, the pedicles at L3, L4, and L5 vertebrae were digitized bilaterally and virtually tracked throughout testing. Interpedicular kinematic metrics were employed to capture any changes in translatory motions during flexion-extension, bilateral bending, and axial torsion testing modes.

FINDINGS

Following the defect, range of motion at the defect level (L4-L5) increased significantly in all the three motion planes. At L4-L5, normalized interpedicular displacement increased significantly in flexion-extension (median change +156%) and bilateral bending (median change +58%) motions, but changes in bending-plane and out-of-plane intervertebral translations were not significant in any of the testing modes.

INTERPRETATION

In the absence of any significant changes in bending-plane and out-of-plane intervertebral translations at L4-L5, changes in interpedicular displacement would directly correspond with the stretching of posterior annulus of the L4-L5 intervertebral disc. A bilateral spondylolytic defect at L4 may result in significant overstretching of the posterior annulus of the L4-L5 disc during flexion-extension and bilateral bending motions.

Synchronic multiple stress fractures of L5 left hemilamina: a case of an unusual type of lumbar spondylolysis

Lumbar spondylolysis is a stress fracture that commonly occurs in adolescent sports players. It is found in approximately 6% of the adult general population. The condition is usually detected as a defect in the pars interarticularis, sometimes in the pedicle (pediculolysis), and rarely in the lamina (laminolysis). Such fractures are typically seen as one defect in each side of the lamina: multiple stress fractures in the same side of the lamina rarely occur synchronically. Here, we report an unusual type of lumbar spondylolysis in the form of synchronic multiple stress fractures of the L5 left hemilamina in an adolescent baseball player. Conservative treatment was effective for bony healing. Although this type of spondylolysis is very rare, to avoid overlooking it, it is essential to examine reconstructed CT images and take the patient's history carefully. If an accurate diagnosis is made early, conservative treatment may be sufficient to achieve bony healing.

Direct pars repair surgery using two different surgical methods : pedicle screw with universal hook system and direct pars screw fixation in symptomatic lumbar spondylosis patients

Objective

The authors performed a retrospective study to assess the clinical and radiological outcome in symptomatic lumbar spondylolysis patients who underwent a direct pars repair surgery using two different surgical methods; pedicle screw with universal hook system (PSUH) and direct pars screw fixation (DPSF), and compared the results between two different treated groups.

Methods

Forty-seven consecutive patients (PSUH; 23, DPSF; 15) with symptomatic lumbar spondylolysis who underwent a direct pars repair surgery were included. The average follow-up period was 37 months in the PSUH group, and 28 months in the DPSF group. The clinical outcome was measured using visual analogue pain scale (VAS) and Oswestry disability index (ODI). The length of operation time, the amount of blood loss, the duration of hospital stay, surgical complications, and fusion status were also assessed.

Results

When compared to the DPSF group, the average preoperative VAS and ODI score of the PSUH group were less decreased at the last follow-up; (the PSUH group; back VAS : 4.9 vs. 3.0, leg VAS : 6.8 vs. 2.2, ODI : 50.6% vs. 24.6%, the DPSF group; back VAS : 5.7 vs. 1.1, leg VAS : 6.1 vs. 1.2, ODI : 57.4% vs. 18.2%). The average operation time was 174.9 minutes in the PSUH group, and 141.7 minutes in the DPSF group. The average blood loss during operation was 468.8 cc in the PSUH group, and 298.8 cc in the DPSF group. The average hospital stay after operation was 8.9 days in the PSUH group, and 7 days in the DPSF group. In the PSUH group, there was one case of a screw misplacement requiring revision surgery. In the DPSF group, one patient suffered from transient leg pain. The successful bone fusion rate was 78.3% in the PSUH group, and 93.3% in the DPSF group.

Conclusion

The present study suggests that the technique using direct pars screw would be more effective than the method using pedicle screw with lamina hook system, in terms of decreased operation time, amount of blood loss, hospital stay, and increased fusion success rate, as well as better clinical outcome.