Quantitative imaging of anterior cruciate ligament (ACL) graft demonstrates longitudinal compositional changes and relationships with clinical outcomes at 2 years after ACL reconstruction

T₁ρ and T₂ magnetic resonance imaging (MRI) may allow for a noninvasive assessment of ligamentization after anterior cruciate ligament (ACL) reconstruction. We hypothesized that ACL graft T₁ρ and T₂ relaxation times would decrease over time, that T₁ρ and T₂ relaxation times would be inversely correlated with Knee Osteoarthritis Outcome Scores (KOOS), and that T₁ρ and T₂ values would be lower for autograft relative to allograft reconstruction. Thirty-nine patients (age: 30.5 ± 8.2 years) were followed prospectively after ACL reconstruction with hamstring autograft (N = 27) or soft-tissue allograft (N = 12). Magnetic resonance (MR) imaging and KOOS surveys were completed at 6, 12, 24, and 36 months after surgery. ACL graft was segmented to define T₁ρ and T₂ relaxation times. Relaxation times were compared between time points with ANOVA tests. Log-transformed autograft and allograft relaxation times were compared with the Student t tests. The relationship between KOOS and relaxation times at 24 months was investigated with Spearman's rank correlation. ACL graft T₁ρ relaxation times were significantly higher at 6 months relative to 12 months (P = .042), 24 months (P < .001), and 36 months (P < .001). ACL graft T₂ relaxation times were significantly higher at 6 months relative to 12 months (P = .036), 24 months (P < .001), and 36 months (P < .001). T₁ρ and T₂ relaxation times were significantly lower for autograft reconstruction vs allograft reconstruction at 24 months postreconstruction. Two-year KOOS Sports, Pain, and Symptoms were significantly inversely correlated with T₁ρ and T₂ relaxation times. T₁ρ and T₂ sequences may offer a noninvasive method for monitoring ACL graft maturation that correlates with patient-reported knee function after ACL reconstruction.     

Recent advances in the surgical management of herniated thoracic discs

Symptomatic thoracic disc herniation is an uncommon entity, without characteristic clinical presentation, and remains a surgical challenge. The initial surgical procedure for thoracic disc herniations was laminectomy with discectomy. The high rate of post-operative neurological deficit makes laminectomy now unacceptable for thoracic disc herniation treatment. Transthoracic, transpedicular, and posterolateral (costotransversectomy) approaches of thoracic discectomy have been used successfully. This review comprises eight papers. Six of them report retrospective series of patients with symptomatic thoracic disc herniations treated by the transpedicular approach (Le Roux, 20 patients), the transfacet pediclesparing approach (Stillermann, 6 patients; Ridenour, 12 patients), modified costotransversectomy (Simpson, 21 patients; Ridenour, 15 patients), the lateral extracavitary approach (Delfini, 20 patients), and the anterior cervical approach (Rossiti, 1 patient with T1-T2 disc). Comparison of the results of the posterolateral and anterolateral approaches does not show clear evidence of better neurological results or pain relief with one type of approach rather than another. Endoscopic or video-assisted techniques have been used recently (Rosenthal, 1 patient; Hae-Dong Jho, 2 patients) and seem attractive.     

Two brothers with a symptomatic thoracic disc herniation at T11–T12: clinical report

Background  In contrast to what is commonly believed, thoracic disc herniations are not rare lesions. Their etiopathogenesis is largely unknown, but may be linked to trauma, Scheuermann’s disease or a degenerative back. Objective  We report two brothers with a symptomatic thoracic disc herniation at T11–T12 and address the possibility of a genetic factor as well as other factors in the etiopathogenesis of (symptomatic) thoracic disc herniations. Clinical features  Both brothers were in their early thirties and had a physically demanding job, however, only the first one was a smoker and was diagnosed with Scheuermann’s disease. Conclusion  The etiology of thoracic disc herniations is likely multifactorial. Their occurrence in siblings may reflect some genetic predisposition or may be merely coincidental, given the high prevalence of thoracic disc herniations in asymptomatic individuals. Further research, including genetic studies, is warranted.     

Multiparametric MR imaging reveals early cartilage degeneration at 2 and 8 weeks after ACL transection in a rabbit model

In this study, the rabbit model with anterior cruciate ligament transection (ACLT) was used to investigate early degenerative changes in cartilage using multiparametric quantitative magnetic resonance imaging (qMRI). ACLT was surgically induced in the knees of skeletally mature New Zealand White rabbits (n = 14). ACL transected and contralateral knee compartments—medial femur, lateral femur, medial tibia, and lateral tibia—were harvested 2 (n = 8) and 8 weeks (n = 6) postsurgery. Twelve age-matched nonoperated rabbits served as control. qMRI was conducted at 9.4 T and included relaxation times T₁, T₂, continuous-wave T_1ρ (CWT_1ρ), adiabatic T_1ρ (AdT_1ρ), adiabatic T_2ρ (AdT_2ρ), and relaxation along a fictitious field (T_RAFF). For reference, quantitative histology and biomechanical measurements were carried out. Posttraumatic changes were primarily noted in the superficial half of the cartilage. Prolonged T₁, T₂, CWT_1ρ, and AdT_1ρ were observed in the lateral femur 2 and 8 weeks post-ACLT, compared with the corresponding control and contralateral groups (P < .05). Collagen orientation was significantly altered in the lateral femur at 2 weeks post-ACLT compared with the corresponding control group. In the medial femur, all the studied relaxation time parameters, except T_RAFF, were increased 8 weeks post-ACLT, as compared with the corresponding contralateral and control groups (P < .05). Similarly, significant proteoglycan loss was observed in the medial femur at 8 weeks following surgery (P < .05). Multiparametric MRI demonstrated early degenerative changes primarily in the superficial cartilage with T₁, T₂, CWT_1ρ, and AdT_1ρ sensitive to cartilage changes at 2 weeks after surgery.     

High-resolution/high-contrast MRI of human articular cartilage lesions

Background?Magnetic resonance microscopy (MRM) is an important experimental tool in the identification of early cartilage lesions.

Methods?Normal and degenerated cartilage samples were imaged at 11.74 T using a standard spin echo sequence. Quantitative MR measurements for T₁, T₂, and ADC were obtained and mapping for T₂ and ADC was performed. The bi-exponential model for T₂ relaxation was also explored. Histology was carried out for comparison with MR images.

Results?MR images of cartilage samples displaying early stages of degeneration were positively correlated to their histological appearance in 23-μm high-resolu-tion images and also with much shorter imaging times at 47-μm resolution. T₂ maps enable delineation of the actual cartilage zones, distinguishing the super?cial zone in particular. The bi-exponential model can reflect cartilage components at different stages of degeneration.

Interpretation?At 11.74 T, with 23-μm resolution or with 47-μm resolution and shorter imaging times, MRM provides images that allow visualization of early stages of cartilage degeneration, including super?cial ?brillation. This has not been shown previously. The images also allow quantitative measurements (T₁, T₂, and ADC) in each cartilage region, which can be indicative of different stages of cartilage degeneration.     

The relationship of symptomatic thoracolumbar disc herniation and Scheuermann’s disease

Purpose

Symptomatic disc herniations in the thoracolumbar spine between T10/11 and L1/2 can be collectively called thoracolumbar disc herniation (TLDH). The etiology of this disorder is unclear. However, it is interesting that we have noted numerous TLDH patients have radiographic features of another spinal disorder which is Scheuermann’s disease (SD). The purpose of this study is to investigate the relationship between symptomatic TLDH and SD in a symptomatic TLDH cohort.

Methods

A cohort of 63 patients with symptomatic TLDH, who had surgery was investigated. Incidences of associated SD and four radiographic signs of SD that were Schmorl’s node, irregular vertebral end plate, posterior bony avulsion of the vertebra and wedge-shaped vertebra, average thoracolumbar kyphotic angle and incidences of disc herniation at segments with and without radiographic signs of SD were examined. Data from the TLDH group were compared with 57 patients undergoing surgery for lower lumbar disc herniation (LDH, L3/4–L5/S1) in the same period.

Results

The incidences of the four radiographic signs of SD and the incidence of associated SD were all significantly higher in the TLDH group than in the LDH group. 95.2 % of the patients in the TLDH group were diagnosed with SD (either classical SD or its atypical form). The average thoracolumbar kyphotic angle of the TLDH group was 16.9°, while that of the LDH group was 7.6° (P = 0.000). In the TLDH group, the incidences of disc herniation at segments with radiographic signs of SD were all significantly higher than at segments where no sign of SD was found.

Conclusions

The high proportion of associated SD and the tendency of SD’s signs to promote disc herniation in symptomatic TLDH patients suggest a close relationship between these two disorders. Symptomatic TLDH should be seen as a truly different surgical entity, that is, a special form of SD rather than just an indicator of a failing back.     

Half-life of alpha-fetoprotein in neonatal sacrococcygeal teratoma

Background

Alpha-fetoprotein (AFP) is useful as a tumor marker for sacrococcygeal teratoma (SCT). We investigated the half-life of AFP in SCT.

Prediction of lumbar disc herniation resorption in symptomatic patients: a prospective,multi-imaging and clinical phenotype study

BACKGROUND CONTEXTSymptomatic lumbar disc herniations (LDH) are very common. LDH resorption may occur by a “self-healing” process, however this phenomenon remains poorly understood. By most guidelines, if LDH remains symptomatic after 3 months and conservative management fails, surgical intervention may be an option.PURPOSEThe following prospective study aimed to identify determinants that may predict early versus late LDH resorption.STUDY DESIGN/SETTINGProspective study with patients recruited at a single center.PATIENT SAMPLENinety-three consecutive patients diagnosed with acute symptomatic LDH were included in this study (n=23 early resorption and n=67 late resorption groups) with a mean age of 48.7±11.9 years.OUTCOMES MEASUREBaseline assessment of patient demographics (eg, smoking status, height, weight, etc.), herniation characteristics (eg, the initial level of herniation, the direction of herniation, prevalence of multiple herniations, etc.) and MRI phenotypes (eg, Modic changes, end plate abnormalities, disc degeneration, vertebral body dimensions, etc.) were collected for further analysis. Lumbar MRIs were performed approximately every 3 months for 1 year from time of enrollment to assess disc integrity.METHODSAll patients were managed similarly. LDH resorption was classified as early (<3 months) or late (>3 months). A prediction model of pretreatment factors was constructed.RESULTSNo significant differences were noted between groups at any time-point (p>.05). Patients in the early resorption group experienced greater percent reduction of disc herniation between MRI-0-MRI-1 (p=.043), reduction of herniation size for total study duration (p=.007), and percent resorption per day compared to the late resorption group (p<.001). Based on multivariate modeling, greater L4 posterior vertebral height (coeff:14.58), greater sacral slope (coeff:0.12), and greater herniated volume (coeff:0.013) at baseline were found to be most predictive of early resorption (p<.05).CONCLUSIONSThis is the first comprehensive imaging and clinical phenotypic prospective study, to our knowledge, that has identified distinct determinants for early LDH resorption. Early resorption can occur in 24.7% of LDH patients. We developed a prediction model for early resorption which demonstrated great overall performance according to pretreatment measures of herniation size, L4 posterior body height, and sacral slope. A risk profile is proposed which may aid clinical decision-making and managing patient expectations     

Association of MR relaxation and cartilage deformation in knee osteoarthritis

We assessed the relationship between cartilage MR relaxation times and biomechanical response of tibiofemoral articular cartilage to physiological loading in healthy subjects and patients with osteoarthritis (OA). Female subjects above 40 years of age with (N₁ = 20) and without (N₂ = 10) OA were imaged on a 3T MR scanner using a custom made loading device. MR images were acquired with the knee flexed at 20° with and without a compressive load of 50% of the subject's bodyweight. The subjects were categorized based on the clinical MRI scoring of medial and lateral cartilage surfaces. Data were stratified twice into two equal groups (low and high) at the median value of T_1ρ and T₂ relaxation time. The change in contact area and cartilage deformation was measured within these groups. Paired Student's t‐test (α = 0.05) was used to analyze the effect of loading on contact area and deformation. The average area of the contact region in the medial compartment was significantly higher in OA subjects compared with normal subjects in both unloaded (314 ± 112 mm² vs. 227 ± 106 mm², p = 0.023) and loaded (425 ± 128 mm² vs. 316 ± 107 mm², p = 0.01) conditions. The overall relative change of cartilage thickness in the medial compartment was significantly higher than the lateral compartment (?5.3 ± 9.9% vs. ?1.9 ± 9.2%, p = 0.042). When cartilage was divided into deep and superficial layers, superficial layers showed higher changes in relaxation time (T_1ρ and T₂) than the changes in relaxation time of whole cartilage (Normal: 12.5% vs. 6.9%; OA: 10.9% vs. 4.6%). The average T_1ρ and T₂ times, change in area of contact region, and change in cartilage thickness in subjects with OA were higher when compared to normal subjects. This study provides support for a relationship between the mechanical response of cartilage to physiological loading (cartilage‐on‐cartilage contact area and cartilage deformation) and MR relaxation times (T_1ρ and T₂) in both OA patients and normal subjects. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:919–926, 2012     

Quantitative T2* (T2 star) relaxation times predict site specific proteoglycan content and residual mechanics of the intervertebral disc throughout degeneration

Degeneration alters the biochemical composition of the disc, affecting the mechanical integrity leading to spinal instability. Quantitative T2* MRI probes water mobility within the macromolecular network, a potentially more sensitive assessment of disc health. We determined the relationship between T2* relaxation time and proteoglycan content, collagen content, and compressive mechanics throughout the degenerative spectrum. Eighteen human cadaveric lumbar (L4–L5) discs were imaged using T2* MRI. The T2* relaxation time at five locations (nucleous pulposus or NP, anterior annulus fibrosis or AF, posterior AF, inner AF, and outer AF) was correlated with sulfated‐glycosaminoglycan (s‐GAG) content, hydroxyproline content, and residual stress and strain at each location. T2* relaxation times were significantly correlated with s‐GAG contents in all test locations and were particularly strong in the NP (r = 0.944; p < 0.001) and inner AF (r = 0.782; p < 0.001). T2* relaxation times were also significantly correlated with both residual stresses and excised strains in the NP (r = 0.857; p < 0.001: r = 0.816; p < 0.001), inner AF (r = 0.535; p = 0.022: r = 0.516; p = 0.028), and outer AF (r = 0.668; p = 0.002: r = 0.458; p = 0.041). These strong correlations highlight T2* MRI's ability to predict the biochemical and mechanical health of the disc. T2* MRI assessment of disc health is a clinically viable tool showing promise as a biomarker for distinguishing degenerative changes. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1083–1089, 2014.     

显微减压术治疗椎间孔内腰椎间盘突出

目的 :总结显微减压术治疗椎间孔内腰椎间盘突出的临床应用结果。方法 :2005年9月至2013年5月,对16例椎间孔内腰椎间盘突出患者采用显微减压术治疗,其中男12例,女4例;年龄32~56岁,平均38.6岁;L3,41例,L4,510例,L_5S_15例。结果:16例均获随访,时间20~48个月,平均36个月。术后恢复率按Macnab腰腿痛手术治疗评定标准进行疗效评定,优12例,良好4例,未发生与该项技术操作相关的并发症。结论:显微减压术适宜治疗椎间孔内腰椎间盘突出,老年人更容易耐受。     

Evaluation of articular cartilage with quantitative MRI in an equine model of post‐traumatic osteoarthritis

Chondral lesions lead to degenerative changes in the surrounding cartilage tissue, increasing the risk of developing post‐traumatic osteoarthritis (PTOA). This study aimed to investigate the feasibility of quantitative magnetic resonance imaging (qMRI) for evaluation of articular cartilage in PTOA. Articular explants containing surgically induced and repaired chondral lesions were obtained from the stifle joints of seven Shetland ponies (14 samples). Three age‐matched nonoperated ponies served as controls (six samples). The samples were imaged at 9.4 T. The measured qMRI parameters included T₁, T₂, continuous‐wave T_1ρ (CWT_1ρ), adiabatic T_1ρ (AdT_1ρ), and T_2ρ (AdT_2ρ) and relaxation along a fictitious field (T_RAFF). For reference, cartilage equilibrium and dynamic moduli, proteoglycan content and collagen fiber orientation were determined. Mean values and profiles from full‐thickness cartilage regions of interest, at increasing distances from the lesions, were used to compare experimental against control and to correlate qMRI with the references. Significant alterations were detected by qMRI parameters, including prolonged T₁, CWT_1ρ, and AdT_1ρ in the regions adjacent to the lesions. The changes were confirmed by the reference methods. CWT_1ρ was more strongly associated with the reference measurements and prolonged in the affected regions at lower spin‐locking amplitudes. Moderate to strong correlations were found between all qMRI parameters and the reference parameters (ρ = ?0.531 to ?0.757). T₁, low spin‐lock amplitude CWT_1ρ, and AdT_1ρ were most responsive to changes in visually intact cartilage adjacent to the lesions. In the context of PTOA, these findings highlight the potential of T₁, CWT_1ρ, and AdT_1ρ in evaluation of compositional and structural changes in cartilage.     

Zonal differences in meniscus MR relaxation times in response to in vivo static loading in knee osteoarthritis

This study assessed the effects of static loading on MRI relaxation times of menisci in individuals with and without radiographic knee OA. High‐resolution fast spin‐echo (FSE) and T_1ρ/T₂ relaxation time MR sequences were obtained with and without loading at 50% body weight in 124 subjects. T_1ρ/T₂ relaxation times were calculated in menisci, and meniscus lesions were assessed through clinical grading. Student's t‐test compared OA and control unloaded relaxation times as well as within‐group changes with loading, Generalized Linear Models evaluated zonal variation, and ANCOVA compared loading response between groups. Unloaded T_1ρ and T₂ in the middle and inner zones of the lateral anterior horn and outer zone of the medial posterior horn were significantly higher in OA and suggest that meniscal OA change occurs unevenly. Zonal T_1ρ and T₂ showed differing patterns between anterior and posterior horns, suggesting differences in macromolecular organization. Significant increases with loading were seen largely in the T₂ of controls and less frequently in subjects with OA. In the medial posterior horn, T_1ρ and T₂ decreased with loading in OA but changed negligibly in controls; these significantly different loading responses between groups may indicate load transmission failure in OA menisci. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:249–261, 2016.     

Should adjacent asymptomatic lumbar disc herniation be simultaneously rectified? A retrospective cohort study of 371 cases that received an open fusion or endoscopic discectomy only on symptomatic segments

BACKGROUND CONTEXTIn the treatment of multiple disc herniations, the decision of whether to include the presumed asymptomatic lumbar disc herniation (asLDH) at adjacent segments remains uncertain. On the one hand, the untouched asLDH might soon become symptomatic and require treatment. On the other hand, additional surgery involving more segments will introduce greater risk, complications, and cost.PURPOSETo investigate the prognosis of untreated asLDH after open fusion or percutaneous endoscopic lumbar discectomy (PELD) on symptomatic lumbar disc herniation (LDHs) in patients.STUDY DESIGNThis is a retrospective cohort study.PATIENT SAMPLEA total of 371 patients with multiple disc herniations who underwent open discectomy and fusion or PELD only for symptomatic levels from January 2012 to July 2018 were included.OUTCOME MEASURESThe primary outcome of interest was the development of symptomatic LDH at the previous asLDH of both groups that required reoperation. A second analysis was performed to compare the reoperation rate due to deterioration of asLDH among different severity grades of herniation. Reoperation rates of the original surgery at the symptomatic segment in both fusion and PELD groups were also reviewed.METHODSThe patients were divided into two groups based on the surgical procedure, with 264 patients undergoing fusion surgery and 107 patients undergoing PELD. Clinical and imaging follow-ups were performed at routine intervals for more than 3 years. The reoperation rates due to deterioration of previously asLDH and failure of original surgery were investigated and compared between the two groups, as well as among the different severity grades of herniation.RESULTSThe follow-up times were 48.2±24.2 and 41.1±17.5 months for the fusion and the PELD groups, respectively. The overall reoperation rate at the previous adjacent asLDH was 6.7% (25/317). According to the severity of the asLDH, a higher grade of asymptomatic herniation yielded a significantly higher rate of reoperation rate in both groups. If the nerve root was displaced by disc material prominently (nG2), the reoperation rate of asLDHs was 42.9% (3/7) in the fusion group and 20% (3/15) in the PELD group. Twenty out of 264 patients (7.6%) in the fusion group and 5 out of 107 patients (4.7%) in the PELD group required reoperation due to deterioration of asLDH. Reoperation rates due to failure of the original surgery were 7.6% (20/264) in the fusion group and 8.4% (9/107) in the PELD group.CONCLUSIONSWith multilevel LDHs, if the asLDH is left untreated, the reoperation rate is closely related to the degree of herniation. When confronting an asLDH graded as G2, a high possibility of reoperation should be clearly discussed with the patient, regardless of open fusion or PELD techniques. Considering that fusion and minimally invasive nonfusion techniques did not yield significantly different overall reoperation rates, ongoing degeneration seemed to have a greater contribution in terms of the deterioration of asLDH.     

Transvertebral anterior key hole foraminotomy without fusion for the cervicothoracic junction

Background

Various surgical procedures have been used to repair disc herniations and osteophytes at the cervicothoracic junction. Among these procedures, transvertebral anterior foraminotomy without fusion is a relatively less invasive, safe and useful method, although the majority of spinal surgeons remain unfamiliar with this method. We describe the surgical procedure for a transvertebral anterior keyhole foraminotomy without fusion at the cervicothoracic junction, and we assess the middle-term clinical and radiological outcomes.

Methods

Of 118 patients undergoing this surgery in our institute between 2007 and 2010, five (4.2?%) had C8 radiculopathy causing C7/T1 disc herniations or osteophytes. We studied five patients who underwent trans-C7 vertebral keyhole foraminotomy without fusion. We retrospectively examined clinical data, pre- and postoperative neurological status.

Results

In all cases, surgical decompression was successfully achieved without difficulty when accessing the pathology. No complications related to the surgical procedure were reported. The follow-up period was 12–28 (mean 20) months. In all patients, the visual analogue scale (VAS) due to radicular pain immediately decreased after the operation and did not increase thereafter. The mean VAS decreased from 7.8 (4.5–9.6) to 1.0 (0–2.1). The Cobb angle at C2-T1 in a neutral position improved from ?12.6 (?2.8 to ?24.7) degrees to ?6.9 (4.2 to ?25.4). The postoperative C7/T1 disc height decreased from 5.4?to 4.9?mm, indicating minimal loss.

Conclusions

This procedure allows for direct access to the pathology and is less invasive. In this study, we clarified that this technique yields excellent radiological and clinical outcomes.     

Local tissue properties of human osteoarthritic cartilage correlate with magnetic resonance T1rho relaxation times

The objective of this study is to examine the local relationship between T_1ρ relaxation times and the mechanical behavior of human osteoarthritic articular cartilage using high‐resolution magnetic resonance imaging (MRI) and local in situ microindentation. Seven human tibial plateaus were obtained from patients who underwent total knee arthroplasty due to severe osteoarthritis (OA). Three to six sites were selected from each sample for visual classification using the ICRS Outerbridge scale (a total of 36 sites). Samples were imaged by MR, and the local distribution of T_1ρ relaxation times were obtained at these selected sites. The elastic and viscoelastic characteristics of the tissue were quantified nondestructively using dynamic microindentation to measure peak dynamic modulus, energy dissipation, and phase angle. Measured Outerbridge scores, MR T_1ρ relaxation times, and mechanical properties were highly heterogeneous across each cartilage surface. Site‐specific measures of T_1ρ relaxation times correlated significantly with the phase angle (p < 0.001; R = 0.908), a viscoelastic mechanical behavior of the cartilage. The novel combination of high‐resolution MR imaging and microindentation allows the investigation of the local relationship between quantitative MRI and biomechanical properties in highly heterogeneous OA cartilage. These findings suggest that MRI T_1ρ can provide a functional assessment of articular cartilage. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1312–1319, 2011     

Slower Walking Speed Is Related to Early Femoral Trochlear Cartilage Degradation After ACL Reconstruction

Post-traumatic patellofemoral osteoarthritis (OA) is prevalent after anterior cruciate ligament reconstruction (ACLR) and early cartilage degradation may be especially common in the femoral trochlear cartilage. Determining the presence of and factors associated with early femoral trochlear cartilage degradation, a precursor to OA, is a critical preliminary step in identifying those at risk for patellofemoral OA development and designing interventions to combat the disease. Early cartilage degradation can be detected using quantitative magnetic resonance imaging measures, such as tissue T₂ relaxation time. The purposes of this study were to (i) compare involved (ACLR) versus uninvolved (contralateral) femoral trochlear cartilage T₂ relaxation times 6 months after ACLR, and (ii) determine the relationship between walking speed and walking mechanics 3 months after ACLR and femoral trochlear cartilage T₂ relaxation times 6 months after ACLR. Twenty-six individuals (age 23 ± 7 years) after primary, unilateral ACLR participated in detailed motion analyses 3.3 ± 0.6 months after ACLR and quantitative magnetic resonance imaging 6.3 ± 0.5 months after ACLR. There were no limb differences in femoral trochlear cartilage T₂ relaxation times. Slower walking speed was related to higher (worse) femoral trochlear cartilage T₂ relaxation times in the involved limb (Pearson's r: −0.583, p = 0.002) and greater interlimb differences in trochlear T₂ relaxation times (Pearson's r: −0.349, p = 0.080). Walking mechanics were weakly related to trochlear T₂ relaxation times. Statement of clinical significance: Slower walking speed was by far the strongest predictor of worse femoral trochlear cartilage health, suggesting slow walking speed may be an early clinical indicator of future patellofemoral OA after ACLR. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:645–652, 2020     

The significance of spinal canal dimensions in discriminating symptomatic from asymptomatic disc herniations

Spinal canal dimensions are assumed to play a significant role with regard to the development of symptoms in individuals with disc herniations. The literature is inconclusive on the significance of spinal canal size as a risk factor for sciatica, mainly because of study design problems. The objective of this study, therefore, was to test the hypothesis that spinal canal dimensions are a significant risk factor for the development of sciatica, comparing symptomatic and asymptomatic individuals. Thirty symptomatic patients undergoing lumbar discectomy and 45 asymptomatic volunteers were investigated by clinical and MRI examination. The size of the spinal canal and thecal sac as well as the midsagittal spinal canal diameter were measured using a point counting method and scanner software, respectively. Differences between the groups were compared separately for each level L3/4 to L5/S1. The intra- and inter-observer error ranged between 0.95 and 0.99 for all measurements. In symptomatic patients, the dimensions of the spinal canal and thecal sac as well as the midsagittal spinal canal diameter were smaller at all disc levels. Unpaired t-test demonstrated a significant difference, ranging from P<0.05 to P<0.001. When controlled for age, sex and body height, the odds ratio for a symptomatic disc herniation increased to as high as 35, depending on the spinal level, when the size of the spinal canal was smaller than the mean for controls by two standard deviations or more. In symptomatic patients, spinal canal dimensions are significantly smaller than those in asymptomatic individuals. Spinal canal dimension is an important factor discriminating patients from control subjects. A clinically relevant grading system for disc herniation should therefore be based on the spatial relationship between herniated disc material and neurogenic structures.     

Biomechanical changes in the lumbar spine following spaceflight and factors associated with postspaceflight disc herniation

Background ContextFor chronic low back pain, the causal mechanisms between pathological features from imaging and patient symptoms are unclear. For instance, disc herniations can often be present without symptoms. There remains a need for improved knowledge of the pathophysiological mechanisms that explore spinal tissue damage and clinical manifestations of pain and disability. Spaceflight and astronaut health provides a rare opportunity to study potential low back pain mechanisms longitudinally. Spaceflight disrupts diurnal loading on the spine and several lines of evidence indicate that astronauts are at a heightened risk for low back pain and disc herniation following spaceflight.PurposeTo examine the relationship between prolonged exposure to microgravity and the elevated incidence of postflight disc herniation, we conducted a longitudinal study to track the spinal health of twelve NASA astronauts before and after approximately 6 months in space. We hypothesize that the incidence of postflight disc herniation and low back complaints associates with spaceflight-included muscle atrophy and pre-existing spinal pathology.Study DesignThis is a prospective longitudinal study.Patient SampleOur sample included a cohort of twelve astronaut crewmembers.Outcome MeasuresFrom 3T MRI, we quantified disc water content (ms), disc degeneration (Pfirrmann grade), vertebral endplate irregularities, facet arthropathy and/ fluid, high intensity zones, disc herniation, multifidus total cross-sectional area (cm²), multifidus lean muscle cross-sectional area (cm²), and muscle quality/composition (%). From quantitative fluoroscopy we quantified, maximum flexion-extension ROM (°), maximum lateral bending ROM (°), and maximum translation (%). Lastly, patient outcomes and clinical notes were used for identifying postflight symptoms associated with disc herniations from 3T MRI.MethodsAdvanced imaging data from 3T MRI were collected at three separate time points in relation to spending six months in space: (1) within a year before launch (“pre-flight”), (2) within a week after return to Earth (“post-flight”), and (3) between 1 and 2 months after return to Earth (“recovery”). Fluoroscopy of segmental kinematics was collected at preflight and postflight timepoints. We assessed the effect of spaceflight and postflight recovery on longitudinal changes in spinal structure and function, as well as differences between crew members who did and did not present a symptomatic disc herniation following spaceflight.ResultsHalf of our astronauts (n=6) experienced new symptoms associated with a new or previously asymptomatic lumbar disc protrusion or extrusion following spaceflight. We observed decreased multifidus muscle quality following spaceflight in the lower lumbar spine, with a reduced percentage of lean muscle at L4L5 (-6.2%, p=.009) and L5S1 (-7.0%, p=.006) associated with the incidence of new disc herniation. Additionally, we observed reduced lumbar segment flexion-extension ROM for L2L3 (-17.2%, p=.006) and L3L4 (-20.5%, p=.02) following spaceflight, and furthermore that reduced ROM among the upper three lumbar segments (-24.1%, p=.01) associated with the incidence of disc herniation. Existing endplate pathology was most prevalent in the upper lumbar spine and associated with reduced segmental ROM (-20.5%, p=.02).ConclusionsIn conclusion from a 10-year study investigating the effects of spaceflight on the lumbar spine and risk for disc herniation, we found the incidence of lumbar disc herniation following spaceflight associates with compromised multifidus muscle quality and spinal segment kinematics, as well as pre-existing spinal endplate irregularities. These findings suggest differential effects of spinal stiffness and muscle loss in the upper versus lower lumbar spine regions that may specifically provoke risk for symptomatic disc herniation in the lower lumbar spine following spaceflight. Results from this study provide a unique longitudinal assessment of mechanisms and possible risk factors for developing disc herniations and related low back pain. Furthermore, these findings will help inform physiologic countermeasures to maintain spinal health in astronauts during long-duration missions in space.     

Propofol/Alfentanil reduziert die zerebrovaskuläre CO2-Reaktivität im Vergleich zu Isofluran

The present study compared the effects of propofol/alfentanil versus isoflurane anaesthesia on cerebral vascular reactivity to changes in carbon dioxide (CO₂) using transcranial Doppler sonography (TCD). Methods. Seventeen ASA class?I patients undergoing minor elective surgery were studied following IRB approval and informed consent. In group?1 (n=10), anaesthesia was induced with thiopental 4?mg/kg and alfentanil 15?μg/kg. Endotracheal intubation was facilitated by vecuronium 0.1?mg/kg. Anaesthesia was maintained with 1% end-tidal isoflurane and nitrous oxide (N₂O) in oxygen O₂ (6?l/min; FiO₂ 0.3). In group?2 (n=7), anaesthesia was induced with propofol 2?mg/kg, alfentanil 15?μg/kg, and vecuronium 0.1?mg/kg for endotracheal intubation and maintained by infusion of propofol, alfentanil, and N₂O?O₂ (6?l/min; FiO₂ 0.3) according to the following protocol: propofol: 10, 8, and 6?mg/kg·h for 10?min each followed by 4?mg/kg·h; alfentanil: 55?μg/kg·h. Monitoring included measurement of mean arterial blood pressure (MAP, mm?Hg), heart rate (HR), body temperature (T), end-tidal CO₂ (PetCO₂, mm?Hg), isoflurane concentrations, and arterial O₂ saturation (SaO₂, %). Mean blood flow velocity (Vmean, cm/s) was measured in the middle cerebral artery using a bidirectional 2-MHz TCD system (Transpect^T, Medasonics). Mechanical ventilation was adjusted to achieve PetCO₂ levels of 40-50-40-30 and 40?mm?Hg. Ten min-utes of equilibration were allowed at each PetCO₂ level. The CO₂ reactivity index was calculated as ΔVmean/Δ?PetCO₂ (cm/s·mm?Hg). Results. MAP, HR, T, and SaO₂ were constant over time and were not different between groups. The CO₂ reactivity index over the CO₂ range of 30–50?mm?Hg was higher in isoflurane (2.32±1.51?Δ?cm/s·mm?Hg) compared to propofol/alfentanil patients (1.15±0.77?Δ?cm/s·mm?Hg) (mean±SD, P<0.05). Conclusions. The data show that although CO₂ reactivity is maintained during both isoflurane and propofol/alfentanil anaesthesia, the cerebral vascular response to CO₂ was lower in propofol/alfentanil compared to isoflurane patients. This is likely due to propofol/alfentanil-induced cerebral vasoconstriction. These data suggest that CO₂ reactivity is a function of the pre-existing cerebral vascular tone induced by the anaesthetic.