A 63-year-old patient was diagnosed with acute jejunal diverticulitis and possible perforation. The patient was taken to the operating room for an exploratory laparotomy where a suspected segment of small bowel was resected. However, the surgical team was unsure whether the resected segment was the definite location of the perforation. A novel technique; using intraoperative contrast enhanced ex vivo x-ray photographs aided the surgical team in finding the exact location of the perforation and thus allowing the operating team to confidently and safely proceed with closure of the abdomen.
The use of a highly conforming, anterior-stabilized bearing has been associated with clinical success in a limited number of studies.
We compared Knee Society scores, radiographic results, complication rates, and revision rates with the use of anterior-stabilized bearings compared with cruciate-retaining (CR) bearings.
A series of 382 patients with 468 primary total knee arthroplasties (TKAs) between 2003 and 2008 with minimum 2-year followup were reviewed. Anterior-stabilized bearings comprised 49% (n = 228) of the sample and CR bearings consisted of 51% (n = 240). The decision to use an anterior-stabilized bearing was based on integrity of the posterior cruciate ligament (PCL) intraoperatively or after sacrifice of the PCL to achieve soft tissue balance. The tibial and femoral component designs were the same regardless of bearing choice. Outcomes were measured with Knee Society scores, complications, revision TKA, and survival. Radiographs were analyzed for component alignment and evidence of loosening.
There was no difference in Knee Society knee scores, radiographic alignment, component loosening, manipulation rate, major complications, or time to revision for patients between the two groups. However, the CR group had significantly more revisions than the anterior-stabilized group (21 CR [1.5%] versus seven anterior-stabilized [4.6%], p = 0.03) at a minimum followup of 5 months (mean, 42 months; range, 5–181 months).
The use of a highly congruent anterior-stabilized bearing for PCL substitution has comparable clinical and radiographic results to traditional CR TKA. These results suggest that this approach is an effective method to achieve stability without the PCL in primary TKA.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
A contributory factor to hip osteoarthritis (OA) is abnormal cartilage mechanics. Acetabular retroversion, a version deformity of the acetabulum, has been postulated to cause OA via decreased posterior contact area and increased posterior contact stress. Although cartilage mechanics cannot be measured directly in-vivo to evaluate the causes of OA, they can be predicted using finite element (FE) modeling.
The objective of this study was to compare cartilage contact mechanics between hips with normal and retroverted acetabula using subject-specific FE modeling. METHODS: Twenty subjects were recruited and imaged: ten with normal acetabula and ten with retroverted acetabula. FE models were constructed using a validated protocol. Walking, stair ascent, stair descent and rising from a chair were simulated. Acetabular cartilage contact stress and contact area were compared between groups.
Retroverted acetabula had superomedial cartilage contact patterns, while normal acetabula had widely distributed cartilage contact patterns. In the posterolateral acetabulum, average contact stress and contact area during walking and stair descent were 2.6 to 7.6 times larger in normal than retroverted acetabula (p ≤ 0.017). Conversely, in the superomedial acetabulum, peak contact stress during walking was 1.2 to 1.6 times larger in retroverted than normal acetabula (p ≤ 0.044). Further differences varied by region and activity.
This study demonstrated superomedial contact patterns in retroverted acetabula versus widely distributed contact patterns in normal acetabula. Smaller posterolateral contact stress in retroverted acetabula than in normal acetabula suggests that increased posterior contact stress may not be the link between retroversion and OA.
hip; cartilage mechanics; finite element; acetabular retroversion; osteoarthritis
Accurate measurements of in-vivo hip kinematics may elucidate the mechanisms responsible for impaired function and chondrolabral damage in hips with femoroacetabular impingement (FAI). The objectives of this study were to quantify the accuracy and demonstrate the feasibility of using dual fluoroscopy to measure in-vivo hip kinematics during clinical exams used in the assessment of FAI. Steel beads were implanted into the pelvis and femur of two cadavers. Specimens were imaged under dual fluoroscopy during the impingement exam, FABER test, and rotational profile. Bead locations measured with model-based tracking were compared to those measured using dynamic radiostereometric analysis. Error was quantified by bias and precision, defined as the average and standard deviation of the differences between tracking methods, respectively. A normal male volunteer was also imaged during clinical exams. Bias and precision along a single axis did not exceed 0.17 and 0.21 mm, respectively. Comparing kinematics, positional error was less than 0.48 mm and rotational error was less than 0.58°. For the volunteer, kinematics were reported as joint angles and bone-bone distance. These results demonstrate that dual fluoroscopy and model-based tracking can accurately measure hip kinematics in living subjects during clinical exams of the hip.
clinical biomechanics; femoroacetabular impingement; motion analysis; musculoskeletal; orthopaedics
Statistical shape modeling (SSM) was used to quantify 3D variation and morphologic differences between femurs with and without cam femoroacetabular impingement (FAI). 3D surfaces were generated from CT scans of femurs from 41 controls and 30 cam FAI patients. SSM correspondence particles were optimally positioned on each surface using a gradient descent energy function. Mean shapes for groups were defined. Morphological differences between group mean shapes and between the control mean and individual patients were calculated. Principal component analysis described anatomical variation. Among all femurs, the first six modes (or principal components) captured significant variations, which comprised 84% of cumulative variation. The first two modes, which described trochanteric height and femoral neck width, were significantly different between groups. The mean cam femur shape protruded above the control mean by a maximum of 3.3 mm with sustained protrusions of 2.5–3.0 mm along the anterolateral head-neck junction/distal anterior neck. SSM described variations in femoral morphology that corresponded well with areas prone to damage. Shape variation described by the first two modes may facilitate objective characterization of cam FAI deformities; variation beyond may be inherent population variance. SSM could characterize disease severity and guide surgical resection of bone.
hip; statistical shape modeling; femoroacetabular impingement; cam
An objective measurement technique to quantify 3D femoral head shape was developed and applied to normal subjects and patients with cam-type femoroacetabular impingement (FAI). 3D reconstructions were made from high-resolution CT images of 15 cam and 15 control femurs. Femoral heads were fit to ideal geometries consisting of rotational conchoids and spheres. Geometric similarity between native femoral heads and ideal shapes was quantified. The maximum distance native femoral heads protruded above ideal shapes and the protrusion area were measured. Conchoids provided a significantly better fit to native femoral head geometry than spheres for both groups. Cam-type FAI femurs had significantly greater maximum deviations (4.99±0.39 mm and 4.08±0.37 mm) than controls (2.41±0.31 mm and 1.75±0.30 mm) when fit to spheres or conchoids, respectively. The area of native femoral heads protruding above ideal shapes was significantly larger in controls when a lower threshold of 0.1 mm (for spheres) and 0.01 mm (for conchoids) was used to define a protrusion. The 3D measurement technique described herein could supplement measurements of radiographs in the diagnosis of cam-type FAI. Deviations up to 2.5 mm from ideal shapes can be expected in normal femurs while deviations of 4 to 5 mm are characteristic of cam-type FAI.
cam FAI; femur morphology; asphericity
Slipped capital femoral epiphysis (SCFE), causing posterior and inferior displacement and retroversion of the femoral head, is a well-recognized etiology for femoroacetabular impingement (FAI) and can lead to premature arthritis in the young adult. The treatment of malunited SCFE remains controversial. Surgical dislocation and subcapital correction osteotomy (SCO) has been described as a powerful method to correct the proximal femoral deformity.
Between January 2003 and January 2010, 11 patients (12 hips) with closed femoral physes and symptomatic FAI from malunited SCFE were treated with surgical dislocation and SCO. We performed a retrospective review of patient histories, physical exams, operative findings, and pre and postoperative anteroposterior (AP) and groin lateral (GLat) radiographs. Mean follow-up was 61 months.
There were 4 female and 7 male patients with an average age of 15 years at the time of SCO. On the AP radiograph the mean inferior femoral head displacement (AP epiphyseal-neck angle) was significantly improved (-26° to -6°, p<0.001). On the groin lateral radiograph the mean posterior femoral head displacement (Lateral epiphyseal-neck angle) was significantly improved (-45° to -3°, p<0.001). The mean alpha angle was also significantly improved on both views (AP: 85° to 56°, P<0.001; GLat: 85° to 46°, p<0.001). Operative findings included one femoral osteochondral defect, 8 Outerbridge grade 3-4 acetabular cartilage lesions, and 10 labral lesions. Significant improvement of the mean Harris hip score (HHS) was seen at latest follow-up (54 to 77, p=0.016). Complications occurred in 4 of the 12 cases with AVN in two patients, a worse postoperative HHS in one patient, and failure of fixation treated successfully with revision open reduction internal fixation in one patient.
Subcapital correction osteotomy as an adjunct to surgical dislocation and osteochondroplasty can be used to correct the deformity of the proximal femur associated with malunited SCFE. Normalization of proximal femoral anatomy may postpone progression to severe osteoarthritis and thus delay the need for arthroplasty in this young patient population. However, surgeons and patients should be aware that the risks of this procedure in this population are significant.
Little data exists regarding outcomes following TKA performed with surface-cementation for the fixation of modular tibial baseplates with press-fit keels. Thus, we retrospectively reviewed the clinical and radiographic outcomes of 439 consecutive primary TKAs performed with surface cemented tibial components. There were 290 female patients and 149 male patients with average age of 62 years (range 30–84). Two tibial components were revised for aseptic loosening (0.5%) and four tibial components (0.9%) were removed to improve instability (n = 2) or malalignment (n = 2). Complications included 13 deep infections treated with 2-stage revision (12) and fusion (1). These results support the surface cement technique with a modular grit-blasted titanium surface and cruciform stem during primary TKA.
Quantifying cartilage contact stress is paramount to understanding hip osteoarthritis. Discrete element analysis (DEA) is a computationally efficient method to estimate cartilage contact stresses. Previous applications of DEA have underestimated cartilage stresses and yielded unrealistic contact patterns because they assumed constant cartilage thickness and/or concentric joint geometry. The study objectives were to: 1) develop a DEA model of the hip joint with subject-specific bone and cartilage geometry, 2) validate the DEA model by comparing DEA predictions to those of a validated finite element analysis (FEA) model, and 3) verify both the DEA and FEA models with a linear-elastic boundary value problem. Springs representing cartilage in the DEA model were given lengths equivalent to the sum of acetabular and femoral cartilage thickness and joint space in the FEA model. Material properties and boundary/loading conditions were equivalent. Walking, descending, and ascending stairs were simulated. Solution times for DEA and FEA models were ~7 seconds and ~65 minutes, respectively. Irregular, complex contact patterns predicted by DEA were in excellent agreement with FEA. DEA contact areas were 7.5%, 9.7% and 3.7% less than FEA for walking, descending stairs, and ascending stairs, respectively. DEA models predicted higher peak contact stresses (9.8–13.6 MPa) and average contact stresses (3.0–3.7 MPa) than FEA (6.2–9.8 and 2.0–2.5 MPa, respectively). DEA overestimated stresses due to the absence of the Poisson’s effect and a direct contact interface between cartilage layers. Nevertheless, DEA predicted realistic contact patterns when subject-specific bone geometry and cartilage thickness were used. This DEA method may have application as an alternative to FEA for pre-operative planning of joint-preserving surgery such as acetabular reorientation during peri-acetabular osteotomy.
Hip; cartilage; cartilage mechanics; contact stress; discrete element analysis; finite element analysis; computational modeling
Although most cases of acute pancreatitis are attributed to gallstones or alcohol, many remain idiopathic. The authors describe a case of acute pancreatitis in a 75-year-old gentleman who presented with acute epigastric pain, fevers and shortness of breath. Serum amylase was 2164. CT showed free mesenteric air, and a partly cystic/partly gas-containing mass in the uncinate lobe of the pancreas. Gastrograffin meal revealed duodenal and jejunal diverticular disease, but no contrast leak. Further CT analysis pinpointed fine tracts of air leading from a jejunal diverticulum up toward the pancreas, suggesting causation by a sealed jejunal diverticular perforation. He responded well to intravenous antibiotics and conservative management. Although small bowel diverticular disease is linked to chronic pancreatitis, evidence for association with acute pancreatitis is scarce. The authors believe this is the first reported case of jejunal diverticular disease causing acute pancreatitis, and it highlights micro-perforation as a potential disease mechanism.
The indication for hip arthrotomy accompanied by intraarticular work during periacetabular osteotomy (PAO) has not been precisely defined. To validate a role for routine hip arthrotomy accompanied by intraarticular work, frequent intraarticular pathology must exist, and the adjunct procedures must not be associated with inferior relief of pain, reduced function, radiographic osteoarthritis progression, or conversion to THA.
(1) What is the prevalence of intraarticular pathology at the time of PAO? (2) Does concomitant hip arthrotomy with associated intraarticular work negatively affect PAO as reflected by differences in Harris hip scores (HHS), Tönnis grade, and failure rates?
We retrospectively reviewed the intraarticular findings in all 151 patients who underwent PAO accompanied by routine hip arthrotomy and intraarticular work from 2002 to 2009. Using multivariate regression models, we compared the HHS and Tönnis grades of patients receiving arthrotomy with a cohort of 39 patients who received PAO alone.
The overall prevalence of intraarticular pathology identified during PAO was 89%. Eight (5.3%) failures were identified within the arthrotomy cohort with mean postoperative HHS, postoperative Tönnis grade, postoperative change in HHS, and postoperative change in Tönnis grade of 87.5, 0.7, 29.8, and 0.3, respectively. By contrast, seven (17.9%) failures were identified in the nonarthrotomy cohort. The mean postoperative HHS, postoperative Tönnis grade, postoperative change in HHS, and postoperative change in Tönnis grade for the nonarthrotomy cohort were 83.1, 1.3, 19.0, and 0.3, respectively.
We believe the high prevalence of intraarticular pathology is sufficient to warrant routine joint inspection at the time of PAO. Hip arthrotomy accompanied by intraarticular work at the time of PAO is safe and does not impose additional patient morbidity.
Level of Evidence
Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
Patient-specific instrumentation potentially improves surgical precision and decreases operative time in total knee arthroplasty (TKA) but there is little supporting data to confirm this presumption.
We asked whether patient-specific instrumentation would require infrequent intraoperative changes to replicate a single surgeon’s preferences during TKA and whether patient-specific instrumentation guides would fit securely.
We prospectively evaluated the plan and surgery in 60 patients treated with 66 TKAs performed with patient-specific instrumentation and recorded any changes. A subset of six postoperative radiographic changes to the femoral and tibial components (implant size, coronal and sagittal alignment) was analyzed to determine if surgeon intervention was beneficial. Each guide was evaluated to determine fit. We compared patient demographics and implant sizing in the patient-specific instrumentation group with a control group in which traditional instrumentation was used.
We recorded 161 intraoperative changes in 66 knee arthroplasties (2.4 changes/knee) performed with patient-specific instrumentation. The predetermined implant size was changed intraoperatively in 77% of femurs and 53% of tibias. We identified a subset of 95 intraoperative changes that could be radiographically evaluated to determine if our changes were an improvement or detriment to reaching goal alignment. Eighty-two of the 95 changes (86%) made by the surgeon were an improvement to the recommended alignment or size of patient-specific instrumentation. The guide did not fit securely on eight femurs (12%) and three tibias (5%). Tourniquet time and blood loss were not improved with patient-specific instrumentation.
We caution surgeons against blind acceptance of patient-specific instrumentation technology without supportive data.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
The field of hip preservation surgery has grown substantially over the past decade. Although open hip procedures reportedly relieve pain and restore function, arthroscopic treatment has increasingly become a reasonable alternative. In 2008, we formed a comprehensive hip preservation service (HPS) to address clinical, educational, and research needs.
We compared (1) volume, type, and corresponding improvement in pain and function of open and arthroscopic treatments; (2) orthopaedic resident test performance; and (3) academic productivity before and after creation of the HPS.
We retrospectively reviewed 212 patients undergoing 220 open procedures from 1996 to 2007 (Group 1) and 260 patients undergoing 298 procedures (153 open, 145 arthroscopic) from 2008 to May 2010 (Group 2). At each clinic visit, we recorded Harris hip score (HHS) and conversion to THA. Minimum followup was 1 year for Group 1 (mean, 4 years; range, 1–13 years) and Group 2 (mean, 1.5 years; range, 1–3 years). We compared orthopaedic resident performance on two standardized tests and the number of academic works (publications, book chapters, electronic media) and peer-reviewed grants funded before and after creation of the HPS.
Mean HHS improved from 63 to 90 in Group 1 and from 76 to 91 in Group 2. Rate of conversion to THA was similar between groups despite expansion of surgical volume. Standardized orthopaedic resident test performance improved. Academic productivity as measured by publications and grant funding was facilitated by the HPS.
Early experience with a multidisciplinary HPS was positive; it facilitated clinical volume expansion while maintaining improvement in pain and function in young adults. Additional benefits included educational and academic productivity gains.
Level of Evidence
Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
Coxa profunda, or a deep acetabular socket, is often used to diagnose pincer femoroacetabular impingement (FAI). Radiographically, coxa profunda is the finding of an acetabular fossa medial to the ilioischial line. However, the relative position of the acetabular fossa to the pelvis may not be indicative of acetabular coverage.
We therefore determined the incidence of coxa profunda and evaluated associations between coxa profunda and other radiographic parameters of acetabular coverage commonly used to diagnose pincer FAI and acetabular dysplasia.
We evaluated the radiographs of three cohorts for coxa profunda, lateral center edge (LCE) angle, acetabular index, posterior wall sign, and crossover sign. Data from 67 collegiate football players were collected prospectively (Cohort 1). We identified two patient cohorts through retrospective review of all 179 hips undergoing hip preservation surgery from 2002 to 2008 (83 periacetabular osteotomies [Cohort 2] and 96 surgical dislocation and osteochondroplasties [Cohort 3]).
In all three cohorts, we detected no difference in the LCE angle or acetabular index between hips with and without coxa profunda. Coxa profunda existed in hips representing the spectrum of acetabular coverage measured by LCE angle (−18° to 60°) and acetabular orientation determined by the crossover sign.
Coxa profunda was a common radiographic finding in both symptomatic patients and asymptomatic football players. Coxa profunda existed in hips representing the spectrum of acetabular coverage and was not associated with an overcovered acetabulum. We conclude coxa profunda is unrelated to overcoverage and suggest its use in diagnosis of pincer FAI be abandoned in favor of other determinants of focal or general overcoverage.
Level of Evidence
Level III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.
The fundamental processes of membrane fission and fusion determine size and copy numbers of intracellular organelles. While SNARE proteins and tethering complexes mediate intracellular membrane fusion, fission requires the presence of dynamin or dynamin-related proteins. Here we study these reactions in native yeast vacuoles and find that the yeast dynamin homolog Vps1 is not only an essential part of the fission machinery, but also controls membrane fusion by generating an active Qa SNARE- tethering complex pool, which is essential for trans-SNARE formation. Our findings provide new insight into the role of dynamins in membrane fusion by directly acting on SNARE proteins.
The optimal method of fixation in total knee arthroplasty is still debated. Hybrid total knee arthroplasty (TKA), with cemented tibial and cementless femoral components, is a proposed method of fixation to improve outcomes. Although several studies have shown favorable outcomes, there is still lack of consensus in the literature. We hypothesized that hybrid TKA yields similar clinical, radiographic, and survivorship results compared to fully cemented TKA. The clinical and radiographic outcomes of 304 cruciate retaining TKAs with minimum two-year followup, including 193 hybrid (mean followup of 4.1 years) and fully cemented TKAs (mean followup of 3.2 years) were evaluated. Knee society scores were similar between the two groups. The total number of femoral radiolucencies was also similar between the two groups, while a greater number of femoral Zone 4 radiolucencies were seen in the cemented group (9% versus 1.6%, P = 0.005). The hybrid group demonstrated a 99.2% survival rate of the femoral component out to seven years for aseptic loosening. No significant difference in survivorship was seen between the groups for all cause or aseptic failure at seven years. We conclude that hybrid fixation leads to similar intermediate-term outcomes as fully cemented components and remains a viable option in total knee arthroplasty.
Our objectives were to determine cartilage contact stress during walking, stair climbing and descending stairs in a well-defined group of normal volunteers and to assess variations in contact stress and area among subjects and across loading scenarios. Ten volunteers without history of hip pain or disease with normal lateral center-edge angle and acetabular index were selected. Computed tomography imaging with contrast was performed on one hip. Bone and cartilage surfaces were segmented from volumetric image data, and subject-specific finite element models were constructed and analyzed using a validated protocol. Acetabular contact stress and area were determined for seven activities. Peak stress ranged from 7.52±2.11 MPa for heel-strike during walking (233% BW) to 8.66±3.01 MPa for heel-strike during descending stairs (261% BW). Average contact area across all activities was 34% of the surface area of the acetabular cartilage. The distribution of contact stress was highly non-uniform, and more variability occurred among subjects for a given activity than among activities for a single subject. The magnitude and area of contact stress were consistent between activities, although inter-activity shifts in contact pattern were found as the direction of loading changed. Relatively small incongruencies between the femoral and acetabular cartilage had a large effect on the contact stresses. These effects tended to persist across all simulated activities. These results demonstrate the diversity and trends in cartilage contact stress in healthy hips during activities of daily living and provide a basis for future comparisons between normal and pathologic hips.
Hip; Finite Element; Biomechanics; Cartilage Contact Stresses; Cartilage Pressure
We performed a retrospective review of 40 consecutive modern cementless THAs with 65-month mean followup in 34 patients under the age of 30 primarily for diagnoses other than inflammatory arthritis. We found acceptable functional improvement and radiographic outcomes at mean 5-year followup. We found a high transfusion rate, dislocation rate (10%), and midterm overall aseptic revision rate (17%). Twenty-eight (67.5%) of hips in this series were metal on metal, with a large percentage of aseptic revisions related to metallosis (57%). When revisions due to metallosis were excluded, the aseptic revision rate was 7.5%. The high prevalence of prior pediatric hip surgery in these patients (50%) may predispose to increased technical difficulty resulting in increased complications and higher revision rates. Although our revision rate was high in these young patients, it is favorable compared to older techniques and consistent with the limited data available with modern cementless techniques in patients of similar age. Cementless THA with modern designs remains a viable option for the treatment of arthritis in the young patient.
TLR9 localizes to a novel intracellular compartment called the T granule to
promote immune signaling by platelets.
Human and murine platelets (PLTs) variably express toll-like receptors (TLRs),
which link the innate and adaptive immune responses during infectious
inflammation and atherosclerotic vascular disease. In this paper, we show that
the TLR9 transcript is specifically up-regulated during pro-PLT production and
is distributed to a novel electron-dense tubular system-related compartment we
have named the T granule. TLR9 colocalizes with protein disulfide isomerase and
is associated with either VAMP 7 or VAMP 8, which regulates its distribution in
PLTs on contact activation (spreading). Preincubation of PLTs with type IV
collagen specifically increased TLR9 and CD62P surface expression and augmented
oligodeoxynucleotide (ODN) sequestration and PLT clumping upon addition of
bacterial/viral ODNs. Collectively, this paper (a) tracks TLR9 to a new
intracellular compartment in PLTs and (b) describes a novel mechanism of TLR9
organization and signaling in human PLTs.
The use of barbed suture for surgical closure has been associated with lower operative times, equivalent wound complication rate, and comparable cosmesis scores in the plastic surgery literature. Similar studies would help determine whether this technology is associated with low complication rates and reduced operating times for orthopaedic closures.
We compared a running barbed suture with an interrupted standard suture technique for layered closure in primary TKA to determine if the barbed suture would be associated with (1) shorter estimated closure times; (2) lower cost; and (3) similar closure-related perioperative complication rates.
We retrospectively compared two-layered closure techniques in primary TKA with either barbed or knotted sutures. The barbed group consisted of 104 primary TKAs closed with running barbed suture. The standard group consisted of 87 primary TKAs closed with interrupted suture. Cost analysis was based on cost of suture and operating room time. Clinical records were assessed for closure-related complications within the 6-week perioperative period.
Average estimated closure time was 2.3 minutes shorter with the use of barbed suture. The total closure cost was similar between the groups. The closure-related perioperative complication rates were similar between the groups.
Barbed suture is associated with a slightly shorter estimated closure time, although this small difference is of questionable clinical importance. With similar overall cost and no difference in perioperative complications in primary TKA, this closure methodology has led to more widespread use at our institution.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
The present study examined the role of endogenous noradrenaline on glial and neuronal plasticity in the spinal cord in rats after peripheral nerve injury. An intrathecal injection of dopamine-β-hydroxylase antibody conjugated to saporin (DβH-saporin) completely depleted noradrenergic axons in the spinal cord and also reduced noradrenergic neurons in the locus coeruleus (A6) and A5 noradrenergic nucleus in the brainstem and noradrenergic axons in the paraventricular nucleus of the hypothalamus. DβH-saporin treatment itself did not alter mechanical withdrawal threshold, but enhanced mechanical hypersensitivity and intrathecal clonidine analgesia after L5–L6 spinal nerve ligation (SNL). In the spinal dorsal horn of SNL rats, DβH-saporin treatment increased choline acetyltransferase (ChAT) immunoreactivity as well as immunoreactivity in microglia of ionized calcium binding adaptor molecule 1[IBA1] and in astrocytes of glial fibrillary acidic protein [GFAP], and brain derived nerve growth factor (BDNF) content. DβH-saporin treatment did not, however alter the fractional release of acetylcholine from terminals by dexmedetomidine after nerve injury. These results suggest that endogenous tone of noradrenergic fibers is not necessary for the plasticity of α2-adrenoceptor analgesia and glial activation after nerve injury, but might play an inhibitory role on glial activation.
This study demonstrates that endogenous noradrenaline modulates plasticity of glia and cholinergic neurons in the spinal cord after peripheral nerve injury and hence influences the pathophysiology of spinal cord changes associated with neuropathic pain.
neuropathic pain; noradrenaline; acetylcholine; brain-derived neurotrophic factor; microglia; astrocytes
The relatively high incidence of labral tears among patients presenting with hip pain suggests that the acetabular labrum is often subjected to injurious loading in vivo. However, it is unclear whether the labrum participates in load transfer across the joint during activities of daily living. This study examined the role of the acetabular labrum in load transfer for hips with normal acetabular geometry and acetabular dysplasia using subject-specific finite element analysis. Models were generated from volumetric CT data and analyzed with and without the labrum during activities of daily living. The labrum in the dysplastic model supported 4-11% of the total load transferred across the joint, while the labrum in the normal model supported only 1-2% of the total load. Despite the increased load transferred to the acetabular cartilage in simulations without the labrum, there were minimal differences in cartilage contact stresses. This was because the load supported by the cartilage correlated to the cartilage contact area. A higher percentage of load was transferred to the labrum in the dysplastic model because the femoral head achieved equilibrium near the lateral edge of the acetabulum. The results of this study suggest that the labrum plays a larger role in load transfer and joint stability in hips with acetabular dysplasia than in hips with normal acetabular geometry.
acetabular labrum; hip; cartilage mechanics; finite element; dysplasia