Comparison of Pelvic Landmarks for Leg Length Discrepancy Measurement With Robotic Arm-Assisted Total Hip Arthroplasty.

Background: Leg length discrepancy (LLD) is a common complication after total hip arthroplasty (THA) leading to significant morbidity and dissatisfaction for patients. A popular system for robotic arm-assisted THA utilizes preoperative computed tomography (CT) scans for surgical planning. Accurate measurement of leg length is crucial for restoring appropriate patient anatomy during the procedure. This study investigates the interobserver and interlandmark reliability of 3 different pelvic landmarks for measuring preoperative LLD. Methods: We compiled preoperative pelvic CT scans from 99 robotic arm-assisted THAs for osteoarthritis. Radiologic leg length measurement was performed using the robotic arm-assisted THA application by 2 orthopaedic residents using reference lines bisecting the following pelvic landmarks: the anterior superior iliac spines, acetabular teardrops, and most inferior aspect of the ischial rami. Results: On multivariate analysis, there was no significant difference found (P value = .924) for leg length measurement based on the 3 different pelvic anatomical landmarks. Leg length measurements showed interobserver reliability with significant Pearson correlation coefficients (r = 1.0, 0.94, 0.96, respectively) and nonsignificant differences in LLD means between subjects on paired sample (P value = .158, .085, 0.125, respectively) as well as between landmarks on pairwise comparison. Conclusions: The 3 pelvic landmarks used in this study can be used interchangeably with the lesser trochanter as the femoral reference point to evaluate preoperative LLD on pelvic CT in patients undergoing robotic-arm assisted THA. This study is the first of its kind to evaluate the interobserver and interlandmark reliability of anatomical landmarks on pelvic CT scans and suggests interchangeability of 3 pelvic landmarks for comparing leg length differences.

The use of a laminar spreader for the reduction of extra-articular distal radius fractures: A technical trick.

Extra-articular distal radius fractures are often accompanied with shortening, loss of radial height, and radial displacement of the articular segment relative to the shaft of the radius, all seen in the coronal plane. Reduction can be somewhat challenging when reliance on traction and ligamentotaxis fails, especially in subacute or osteoporotic fractures. In this technical report, we describe a technique where application of a laminar spreader between the radius and the ulna in the metaphyseal region can easily reduce the fracture and help attain anatomic alignment in the coronal plane. An acute and a subacute fracture are shown for illustration of the technique.

Salvage of Bone Transport with the Induced Membrane Technique in an Open Tibia Fracture with a Segmental Defect: A Case Report.

CASE: A 29-year-old man with an open tibia fracture and a 15-cm bone defect was treated with irrigation, debridement, intramedullary nailing, soft-tissue flap, and bone transport with a frame over the nail. He developed osteomyelitis of his bone transport segment close to docking, which required bone resection and an induced membrane technique to salvage his transport segment and achieve union. CONCLUSIONS: This report illustrates the combined use of bone transport and induced membrane technique to achieve union in a 15-cm tibial defect. It demonstrates the use of the Masquelet technique to salvage an infected bone transport segment.

Robotic Arm-Assisted Total Hip Arthroplasty to Correct Leg Length Discrepancy in a Patient With Spinopelvic Obliquity.

Leg length discrepancy is not an uncommon result of total hip arthroplasty and a major cause of patient dissatisfaction. Spinopelvic obliquity is a less-recognized cause of limb length differences in patients undergoing total hip arthroplasty. The robotic arm has recently been introduced to enhance implant positioning during surgery and to achieve more predictable leg length and offset goals. In this article, we illustrate the case of a patient who presented with a leg length discrepancy associated with significant spinopelvic obliquity. We show the use of the robotic arm total hip application to improve her pelvic obliquity and limb length discrepancy. This approach helped with the patient's symptoms and gait as well as her radiographic pelvic alignment.

Clinical outcomes of Bryan cervical disc arthroplasty a prospective, randomized, controlled, single site trial with 48-month follow-up.

STUDY DESIGN: Prospective, randomized, controlled. Level 1 evidence. OBJECTIVE: To report functional outcomes at 48 months follow-up on prospectively randomized patients to either the Bryan cervical disc prosthesis or anterior cervical discectomy and fusion (ACDF) at a single site. SUMMARY OF BACKGROUND DATA: Surgical treatment of cervical disc pathology can involve discectomy and fusion (ACDF), the gold standard technique. The safety and effectiveness of this procedure has been established and demonstrated in the literature, however, limitations have evolved and alternatives such as disc replacement are being investigated. Intervertebral disc replacement is designed to preserve motion, both at affected and adjacent levels avoiding limitations of fusion such as adjacent level degeneration. New onset degenerative changes and possible recurring neurologic symptoms may be deferred or eliminated with cervical disc replacement. A recent multicenter trial with 24 months follow-up has shown the Bryan disc to compare favorably with ACDF. Continued follow-up is needed to further evaluate and compare functional outcomes in both these cohorts. METHODS: A total of 47 patients were enrolled at our site as part of an ongoing multicenter prospectively randomized study investigating ACDF versus Bryan cervical disc prosthesis. Functional outcomes are now reported at 48 months follow-up for our cohort of participants. Neck disability index score (NDI), VAS neck and arm and SF-36 both physical and mental as well as complications and reoperations will be reported. RESULTS: Functional outcome data collected at routine follow-up for 48-months has favorably demonstrated improved functional outcomes for NDI, neck/arm pain VAS scores, and the SF-36 physical/mental health component scores for the Bryan arthroplasty and ACDF cohorts. The NDI scores for the Bryan arthroplasty preoperatively was 51 and at 48 months 10. For ACDF preoperative NDI score was also 51 and at 48 months 16.7. At 48 months NDI success, measured by >or=15 points NDI improvement demonstrated a 93.3% success for Bryan arthroplasty and an 82.4% success for ACDF. VAS neck pain scores for the Bryan arthroplasty preoperatively was 76.2 and at 48 months was 13.6. VAS neck pain scores for ACDF preoperatively was 80.6 and at 48 months was 28.1. Arm Pain scores were also measured and for the Bryan arthroplasty preoperatively measured 78.8 and at 48 months 10.8. For ACDF arm pain scores preoperatively measured 77.1 and at 48 months 21.7. These outcomes have not been associated with any degradation of outcome measures from 2 to 4 years. During the 48 months of follow-up at our institution we also report 6 secondary surgeries in our control group (ACDF) and only 1 in our investigational group (Bryan). Of the 6 surgeries in the control group performed, 3 or 12% to date were for adjacent level degenerative disease and 1 or 4% for remote level degenerative disc disease. The remaining 2 surgeries were performed on the same patient for a pseudarthrosis. In the investigational group there was only 1 secondary surgery performed to date for adjacent level disease 5%. CONCLUSIONS: At 48 months, cervical arthroplasty with the Bryan cervical disc prosthesis continues to compare favorably to ACDF at our institution. There has been no degradation of functional outcomes from 24 to 48 months for NDI, VAS of neck and arm, and SF-36. There has been a lower incidence of secondary surgeries for the Bryan arthroplasty cohort to date.

A house divided: ceramide, sphingosine, and sphingosine-1-phosphate in programmed cell death.

Programmed cell death is an important physiological response to many forms of cellular stress. The signaling cascades that result in programmed cell death are as elaborate as those that promote cell survival, and it is clear that coordination of both protein- and lipid-mediated signals is crucial for proper cell execution. Sphingolipids are a large class of lipids whose diverse members share the common feature of a long-chain sphingoid base, e.g., sphingosine. Many sphingolipids have been shown to play essential roles in both death signaling and survival. Ceramide, an N-acylsphingosine, has been implicated in cell death following a myriad of cellular stresses. Sphingosine itself can induce cell death but via pathways both similar and dissimilar to those of ceramide. Sphingosine-1-phosphate, on the other hand, is an anti-apoptotic molecule that mediates a host of cellular effects antagonistic to those of its pro-apoptotic sphingolipid siblings. Extraordinarily, these lipid mediators are metabolically juxtaposed, suggesting that the regulation of their metabolism is of the utmost importance in determining cell fate. In this review, we briefly examine the role of ceramide, sphingosine, and sphingosine-1-phosphate in programmed cell death and highlight the potential roles that these lipids play in the pathway to apoptosis.

Sphingosine kinase-1 is cleaved by cathepsin B in vitro: identification of the initial cleavage sites for the protease.

Previous work has identified sphingosine kinase-1 (SK1) as a substrate for the cysteine protease cathepsin B in vitro. In this study, the mechanism of SK1 cleavage by cathepsin B was investigated. We identified two initial cleavage sites for the protease, the first at histidine 122 and the second at arginine 199. Mutation analysis showed that replacement of histidine 122 with a tyrosine maintained the activity of SK1 while significantly reducing cleavage by cathepsin B at the initial cleavage site. The efficacy of cleavage of SK1 at arginine 199, however, was not affected. These studies demonstrate that SK1 is cleaved by cathepsin B in a sequential manner after basic amino acids, and that the initial cleavages at the two identified sites occur independently of each other.

Protein kinase C-induced activation of a ceramide/protein phosphatase 1 pathway leading to dephosphorylation of p38 MAPK.

Recently we showed that, in human breast cancer cells, activation of protein kinase C by 4beta-phorbol 12-myristate 13-acetate (PMA) produced ceramide formed from the salvage pathway (Becker, K. P., Kitatani, K., Idkowiak-Baldys, J., Bielawski, J., and Hannun, Y. A. (2005) J. Biol. Chem. 280, 2606-2612). In this study, we investigated intracellular signaling events mediated by this novel activated pathway of ceramide generation. PMA treatment resulted in transient activation of mitogen-activated protein kinases (ERK1/2, JNK1/2, and p38) followed by dephosphorylation/inactivation. Interestingly, fumonisin B1 (FB1), an inhibitor of the salvage pathway, attenuated loss of phosphorylation of p38, suggesting a role for ceramide in p38 dephosphorylation. This was confirmed by knock-down of longevity-assurance homologue 5, which partially suppressed the formation of C(16)-ceramide induced by PMA and increased the phosphorylation of p38. These results demonstrate a role for the salvage pathway in feedback inhibition of p38. To determine which protein phosphatases act in this pathway, specific knock-down of serine/threonine protein phosphatases was performed, and it was observed that knock-down of protein phosphatase 1 (PP1) catalytic subunits significantly increased p38 phosphorylation, suggesting activation of PP1 results in an inhibitory effect on p38. Moreover, PMA recruited PP1 catalytic subunits to mitochondria, and this was significantly suppressed by FB1. In addition, phospho-p38 resided in PMA-stimulated mitochondria. Upon PMA treatment, a mitochondria-enriched/purified fraction exhibited significant increases in C(16)-ceramide, a major ceramide specie, which was suppressed by FB1. Taken together, these data suggest that accumulation of C(16)-ceramide in mitochondria formed from the protein kinase C-dependent salvage pathway results at least in part from the action of longevity-assurance homologue 5, and the generated ceramide modulates the p38 cascade via PP1.

Modulation of total Akt kinase by increased expression of a single isoform: requirement of the sphingosine-1-phosphate receptor, Edg3/S1P3, for the VEGF-dependent expression of Akt3 in primary endothelial cells.

Akt kinase is an important downstream effector of VEGF in primary endothelial cells (EC), promoting angiogenesis by increased cellular survival, motility and tubulogenesis. Akt1 is the founding member of a family of serine threonine kinases thought to have overlapping function. We sought to determine if other Akt family members were also regulated by VEGF in EC. We show that treatment of EC with the angiogenic inducers VEGF or sphingosine-1-phosphate (S1P) results in an increased stabilization of Akt3 mRNA, concurrent with a PI3 kinase-dependent, Akt1-independent increase in both the protein and its phosphorylation. Given the similarity of Akt3 regulation by VEGF and S1P, the sensitivity of VEGF stimulation to the Gi-protein uncoupling reagent, pertussis toxin was tested and shows that VEGF stimulation requires Gi-protein signaling. We show that the VEGF stimulates the expression of Edg3/S1P3 (S1P3) and that expression of this Gi-protein-coupled receptor is both sufficient and necessary for the expression of Akt3. Blockade of a single isoform does not overtly affect cellular function, whereas inhibition of both kinases results in an increase in apoptosis and a down-regulation of cyclin D3. These results suggest a model whereby extracellular cues maintain total Akt kinase levels through the regulation of specific isoform expression providing a fail-safe mechanism to maintain necessary levels of Akt kinase activity.

Oxidized LDL immune complexes induce release of sphingosine kinase in human U937 monocytic cells.

The transformation of macrophages into foam cells is a critical event in the development of atherosclerosis. The most studied aspect of this process is the uptake of modified LDL through the scavenger receptors. Another salient aspect is the effect of modified LDL immune complexes on macrophages activation and foam cell formation. Macrophages internalize oxidized LDL immune complexes (oxLDL-IC) via the Fc-gamma receptor and transform into activated foam cells. In this study we examined the effect of oxLDL-IC on sphingosine kinase 1 (SK1), an enzyme implicated in mediating pro-survival and inflammatory responses through the generation of the signaling molecule sphingosine-1-phosphate (S1P). Intriguingly, oxLDL-IC, but not oxLDL alone, induced an immediate translocation and release of SK1 into the conditioned medium as evidenced by fluorescence confocal microscopy. Immunoblot analysis of cell lysates and conditioned medium revealed a decrease in intracellular SK1 protein levels accompanied by a concomitant increase in extracellular SK1 levels. Furthermore, measurement of S1P formation showed that the activity of cell-associated SK decreased in response to oxLDL-IC compared to oxLDL alone, whereas the activity of SK increased extracellularly. Blocking oxLDL-IC binding to Fc-gamma receptors resulted in decreased levels of extracellular S1P. The data also show that cell survival of human U937 cells exposed to oxLDL-IC increased compared to oxLDL alone. Exogenously added S1P further increased cell survival induced by oxLDL-IC. Taken together, these findings indicate that S1P may be generated extracellularly in response to modified LDL immune complexes and may therefore promote cell survival and prolong cytokine release by activated macrophages.

Loss of sphingosine kinase-1 activates the intrinsic pathway of programmed cell death: modulation of sphingolipid levels and the induction of apoptosis.

Activation of sphingosine kinase-1 (SK1) by overexpression or agonist stimulation promotes cell proliferation, survival, and anti-apoptosis. Studies on the function of endogenous SK1 are lacking. Endogenous SK1 has been shown to be down-regulated under stress, and knockdown of the enzyme reduces the percentage of viable MCF-7 breast cancer cells (Taha, T. A. et al. 2004. J. Biol. Chem. 279, 20546-20554). In this study, we examined the mechanisms by which SK1 loss affects the growth of cells. Knockdown of the enzyme by small interfering RNA caused cell cycle arrest and induced apoptosis. Cell death involved effector caspase activation, cytochrome c release and Bax oligomerization in the mitochondrial membrane, thus placing SK1 knockdown upstream of the mitochondrial pathway of apoptosis. SK1 knockdown also induced significant increases in ceramide levels in whole cells and in mitochondria enriched fractions of cells. Inhibition of de novo sphingolipid biosynthesis with myriocin significantly attenuated Bax oligomerization and downstream caspase activation after SK1 loss. These studies for the first time implicate endogenous SK1 as an important survival enzyme in MCF-7 cells and link the biological consequences of knocking down the enzyme to its biochemical role as a regulator of sphingolipid metabolism.

The coordination of prostaglandin E2 production by sphingosine-1-phosphate and ceramide-1-phosphate.

The ability of pro-inflammatory cytokines such as interleukin-1beta (IL-1beta) to induce the major inflammatory mediator prostaglandin (PG) E(2) depends on the activation of two rate-limiting enzymes, phospholipase A(2) (PLA(2)) and cyclooxygenase 2 (COX-2). PLA(2) acts to generate arachidonic acid, which serves as the precursor substrate for COX-2 in the metabolic pathway leading to PGE(2) production. However, less is known about the mechanisms that coordinate the regulation of these two enzymes. We have provided prior evidence that sphingosine kinase 1 and its bioactive lipid product sphingosine-1-phosphate (S1P) mediate the effects of cytokines on COX-2 induction, whereas ceramide kinase and its distinct product, ceramide-1-phosphate (C1P), are required for the activation and translocation of cPLA(2) (FASEB J 17:1411-1421. 2003; J Biol Chem 278:38206-38213, 2003; J Biol Chem 279:11320-11326, 2004). Herein, we show that these two pathways are independent but coordinated, resulting in synergistic induction of PGE(2). Moreover, the combination of both S1P and C1P recapitulates the temporal and spatial activation of cPLA(2) and with COX-2 seen IL-1beta. Taken together, the results provide, for the first time, a mechanism that assures the coordinate expression and activation in time and space of COX-2 and cPLA(2), assuring maximal production of PGE(2).

Tumor necrosis factor induces the loss of sphingosine kinase-1 by a cathepsin B-dependent mechanism.

Sphingosine kinase-1 (SK1) has emerged as a key component of cytokine responses, including roles in apoptosis, yet the specific mechanisms by which cytokines regulate SK1 in the apoptotic responses have not been studied. In this study, we show that prolonged treatment of MCF-7 cells with tumor necrosis factor (TNF) induces a dose- and time-dependent decrease in SK1 protein. Inhibition of the upstream caspase 8 by IETD significantly rescued TNF effects on SK1, yet the caspase 7 inhibitor DEVD failed to have any effect, suggesting that the decline in SK1 occurs downstream of the initiator caspase but upstream of the effector caspase. In addition to caspase activation, TNF caused disruption of lysosomes with relocation of the cysteine protease cathepsin B into the cytosol. Down-regulation of cathepsin B using small interfering RNA significantly restored SK1 levels following exposure to TNF, suggesting that SK1 loss was dependent on cathepsin B activity. The regulation of SK1 by the lysosomal protease was further supported by the colocalization of SK1 with the lysosome and cathepsin B in cells and the loss of the colocalization following exposure to TNF. The ability of cathepsin B to regulate SK1 was further corroborated by an in vitro approach where recombinant cathepsin B cleaved SK1 at multiple sites to produce several cleavage fragments. Therefore, these studies show that SK1 down-regulation by TNF is dependent on the "lysosomal pathway" of apoptosis and specifically on cathepsin B, which functions as an SK1 protease in cells.

Sphingosine-1-phosphate receptors: receptor specificity versus functional redundancy.

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid that has recently been shown to bind cell surface S1P receptors (previously called endothelial differentiation gene (Edg) receptors), which are members of the G-protein-coupled family of receptors. Signaling via S1P is a complex process, as cells usually express a number of these receptors on their surfaces. Many of the S1P receptors share common G-proteins, invoking the question of how these receptors are specific in their actions. This review describes the coupling pathways of S1P receptors, and highlights the in vitro and in vivo evidence for the "uniqueness" of each receptor in activating downstream signaling pathways, taking the effect of S1P on migration as an example.

Down-regulation of sphingosine kinase-1 by DNA damage: dependence on proteases and p53.

Sphingosine kinase 1 (SK1), a key enzyme in sphingosine 1-phosphate (S1P) synthesis, regulates various aspects of cell behavior, including cell survival and proliferation. DNA damaging anti-neoplastic agents have been shown to induce p53, ceramide levels, and apoptosis; however, the effects of anti-neoplastic agents on SK have not been assessed. In this study, we investigated the effects of a DNA damaging agent, actinomycin D (Act D), on the function of sphingosine kinase (SK1). Act D caused a reduction in the protein levels of SK1, as indicated by Western blot analysis, with a concomitant decrease in SK activity. The down-regulation was post-transcriptional, because the mRNA levels of SK1 remained unchanged. Similar decreases in SK1 protein were observed with other DNA damaging agents such as doxorubicin, etoposide, and gamma-irradiation. ZVAD, the pancaspase inhibitor, and Bcl-2 annulled the effect of Act D on SK1, demonstrating a role for cysteine proteases downstream of Bcl-2 in the down-regulation of SK1. Inhibition of caspases 3, 6, 7, and 9 only partially reversed Act D-induced SK1 loss. Inhibition of cathepsin B, a lysosomal protease, produced a significant reversal of SK1 decline by Act D, suggesting that a multitude of ZVAD-sensitive cysteine proteases downstream of Bcl-2 mediated the SK1 decrease. When p53 up-regulation after Act D treatment was inhibited, SK1 down-regulation was rescued, demonstrating p53 dependence of SK1 modulation. Treatment of cells with S1P, the product of SK1, partially inhibited Act D-induced cell death, raising the possibility that a decrease in SK1 may be in part necessary for cell death to occur. Furthermore, the knockdown of SK1 by small interfering RNA in MCF-7 cells resulted in a significant reduction in cell viability. These studies demonstrate that SK1 is down-regulated by genotoxic stress, and that basal SK1 function may be necessary for the maintenance of tumor cell growth.