Locked plating of comminuted distal femur fractures: does unlocked screw placement affect stability and failure?

OBJECTIVES: Locked plates provide greater stiffness, possibly at the expense of fracture healing. The purpose of this study is to evaluate construct stiffness of distal femur plates as a function of unlocked screw position in cadaveric distal femur fractures. METHODS: Osteoporotic cadaveric femurs were used. Four diaphyseal bridge plate constructs were created using 13-hole distal femur locking plates, all with identical condylar fixation. Constructs included all locked (AL), all unlocked (AUL), proximal unlocked (PUL), and distally unlocked (DUL) groups. Constructs underwent cyclic axial loading with increasing force per interval. Data were gathered on axial stiffness, torsional stiffness, maximum torque required for 5-degree external rotation, and axial force to failure. RESULTS: Twenty-one specimens were divided into AL, AUL, PUL, and DUL groups. Axial stiffness was not significantly different between the constructs. AL and PUL demonstrated greater torsional stiffness, maximum torque, and force to failure than AUL and AL showed greater final torsional stiffness and failure force than DUL (P < 0.05). AL and PUL had similar axial, torsion, and failure measures, as did AUL and DUL constructs. All but 2 specimens fractured before medial gap closure during failure tests. Drop-offs on load-displacement curves confirmed all failures. CONCLUSIONS: Only the screw nearest the gap had significant effect on torsional and failure stiffness but not axial stiffness. Construct mechanics depended on the type of screw placed in this position. This screw nearest the fracture dictates working length stiffness when the working length itself is constant and in turn determines overall construct stiffness in osteoporotic bone.

Rare combination of ipsilateral acetabular fracture-dislocation and pertrochanteric fracture.

Acetabular fracture-dislocations are severe injuries that require urgent closed reduction of the hip and often require surgery to restore hip stability. Other authors have described acetabular fracture-dislocations associated with femoral neck fractures, but to our knowledge, this case report is the first to describe an acetabular fracture-dislocation in association with an ipsilateral pertrochanteric fracture and subtrochanteric extension. The polytraumatized patient initially was not stable enough for prolonged surgery. Through a 3-cm anterolateral hip incision, a 5-mm Schanz screw was introduced percutaneously into the femoral head through the primary fracture site under fluoroscopic guidance. With inline traction on the leg, the Schanz screw was used to manipulate the femoral head back into the acetabular fossa. The Schanz screw was removed, the head remained reduced, and a skeletal traction pin was placed to maintain length and alignment of the pertrochanteric fracture until definitive stabilization was possible. We propose a staged treatment strategy consisting of early closed reduction of the hip, and after the patient has been stabilized, reduction and fixation of the fractures. This strategy may be useful in managing an unstable polytraumatized patient or a patient who requires prolonged transfer to receive definitive care.

Methicillin-resistant Staphylococcus aureus infections among healthy full-term newborns.

OBJECTIVE: Methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged in the community, causing disease among healthy people lacking traditional risk factors for MRSA infection. This article describes an outbreak of MRSA among healthy full-term newborns. DESIGN: Cases were identified and corresponding medical information collected. Telephone interviews were conducted with mothers of cases and surveillance cultures from mothers and newborns were performed. MRSA isolates were genotyped. SETTING: Hospital in Chicago, Illinois, USA. PARTICIPANTS: Newborns, their mothers and hospital healthcare workers. INTERVENTION: Nursery infection control practices were enhanced. The MRSA-colonised healthcare workers received intranasal mupirocin. MAIN OUTCOME: Within 4-23 days of birth, 11 newborns were identified with pustules, vesicles or blisters located on the head, groin, perineum, ears, legs, chin and trunk. All received antimicrobials and recovered without incident. RESULTS: None of 432 peripartum women, one of 399 newborns, and two of 135 healthcare workers were nasal MRSA carriers. Available isolates from six patients, two healthcare workers, and one from an MRSA-colonised newborn were similar by pulsed-field gel electrophoresis. Other than contact with the hospital, no common exposures of MRSA transmission were identified. CONCLUSIONS: MRSA strains that initially emerged in the community are now causing disease in healthcare settings. Providers should be aware that MRSA can cause skin infections among healthy newborns. Adherence to standard infection control practices is important to prevent transmission of MRSA in nurseries.

Quantitative variation in vascular endothelial growth factor mRNA expression during early flexor tendon healing: an investigation in a canine model.

Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis, with direct mitogenic activity on cells of endothelial origin. We quantified the temporal accumulation of VEGF mRNA at the repair site of an in vivo canine intrasynovial flexor tendon repair and rehabilitation model by means of quantitative Northern blot analysis, in order to detail a molecular signal involved in the intrinsic angiogenic process that accompanies early flexor tendon healing. Significant accumulation of VEGF mRNA occurred at the flexor tendon repair site at 7 days post-operatively, with peak levels seen at post-operative days 7 and 10. Levels returned to baseline by day 14. Local VEGF mRNA accumulation at the repair site temporally precedes and is spatially distinct from the vascular ingrowth itself, which has been shown to occur maximally at day 17. These data suggest that cells within the flexor tendon repair site are involved in molecular processes other than the synthesis of extracellular matrix, such as modulation of angiogenesis.

Capture and identification of folding intermediates of cystinyl proteins by cyanylation and mass spectrometry.

Trapping folding intermediates of cystinyl proteins by covalent modification of free sulfhydryl groups provides the opportunity for isolation, purification, and structural elucidation of individual species. The disulfide structure of the intermediates, coupled with their temporal abundance, provides a 'snapshot' of the pathway experienced by the refolding protein in a particular medium. Here, intermediates of cystinyl proteins containing free cysteines are trapped by cyanylation through reaction with an acidic (pH 3.0) solution of 1-cyano-4-dimethylamino-pyridinium (CDAP) tetrafluoroborate. The cyanylated species are separated by reversed-phase high-performance liquid chromatography, where the resulting chromatogram gives a visual indication of the distribution of intermediates at a designated time after commencing the refolding process. The disulfide structure of an intermediate can be determined by cleaving its cyanylated derivative and by mass mapping of the resulting fragments to the sequence of the original protein. Cleavage of a cyanylated species represented by any given peak in the chromatogram is achieved by treatment of that fraction with 1M NH4OH at room temperature for 1 h; the resulting fragments are analyzed by matrix-assisted laser desorption ionization (MALDI) or electrospray mass spectrometry. Examples will be presented from in vitro refolding experiments with human epidermal growth factor (hEGF), for which more than 10 folding intermediates were isolated and identified at different time points, and a mutant of insulin-like growth factor-I, for which three intermediates were isolated and identified.

Mass spectrometric evidence for mechanisms of fragmentation of charge-derivatized peptides.

Mass spectrometry of charged derivatives of peptides has been a growing area of interest in the past decade. Fragmentation of charged derivatives of peptides is believed to be different from than that of protonated peptides when analyzed by collisionally activated dissociation-tandem mass spectrometry (CAD-MS/MS). The charged derivatives fragment by charge-remote fragmentation mechanisms, which are usually classified as high-energy (HE)-CAD processes. Our objective in the present study is to investigate the mechanism of fragmentation of charged derivatives of peptides when analyzed by matrix-assisted laser desorption/ionization-postsource decay-mass spectrometry (MALDI-PSD-MS) and electrospray ionization (ESI)-CAD-MS/MS (ion trap), which involve low-energy processes. Three major types of hydrogens (alpha, beta, and amide) are available for migration during the formation of the *a(n) ions (the predominant ion series produced from these charged derivatives). To pinpoint which of the three hydrogens is involved in the formation of the *a(n) ions, deuterium-labeled peptide derivatives with labels at specific sites were synthesized and analyzed by MALDI-PSD-MS and ESI-CAD-MS/MS. Our results suggest that the amide hydrogen of the residue at which the cleavage occurs shifts during the formation of *a(n); this observation serves as evidence for the mechanism proposed earlier by Liao et al. for fragmentation of such charged derivatives. The results also help elucidate the structure of the *a(n) ions, *b(n) ions, and others formed during cleavage at the proline residue, as well as the ions formed during loss of the C-terminal residue from these charged derivatives.

Determination of the disulfide structure of sillucin, a highly knotted, cysteine-rich peptide, by cyanylation/cleavage mass mapping.

The disulfide structure of sillucin, a highly knotted, cysteine-rich, antimicrobial peptide, isolated from Rhizomucor pusillus, has been determined to be Cys2--Cys7, Cys12--Cys24, Cys13--Cys30, and Cys14--Cys21 by disulfide mass mapping based on partial reduction and CN-induced cleavage enabled by cyanylation. The denatured 30-residue peptide was subjected to partial reduction by tris(2-carboxyethyl)phosphine hydrochloride at pH 3 to produce a mixture of partially reduced sillucin species; the nascent sulfhydryl groups were immediately cyanylated by 1-cyano-4-(dimethylamino)pyridinium tetrafluoroborate. The cyanylated species, separated and collected during reversed phase high-performance liquid chromatography, were treated with aqueous ammonia, which cleaved the peptide chain on the N-terminal side of cyanylated cysteine residues. The CN-induced cleavage mixture was analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry before and after complete reduction of residual disulfide bonds in partially reduced and cyanylated species to mass map the truncated peptides to the sequence. Because the masses of the CN-induced cleavage fragments of both singly and doubly reduced and cyanylated sillucin are related to the linkages of the disulfide bonds in the original molecule, the presence of certain truncated peptide(s) can be used to positively identify the linkage of a specific disulfide bond or exclude the presence of other possible linkages.

The use of a surgical grade calcium sulfate as a bone graft substitute: results of a multicenter trial.

In a prospective, nonrandomized, multicenter study, 109 patients with bone defects were treated with a surgical grade calcium sulfate preparation as a bone graft substitute. The calcium sulfate pellets were used in place of morselized cancellous bone graft for the treatment of patients with bone defects who usually would require grafting secondary to trauma, periprosthetic bone loss, tumor, or fusion. The calcium sulfate was used alone or mixed with other materials such as bone marrow aspirate, demineralized bone matrix, or autograft. The defects that were treated were contained and were not necessary for the stability of the bony structure. Radiographic and clinical data were collected at predetermined intervals for 12 months. At 6 months postoperatively, radiographic results for all patients showed that 99% of the calcium sulfate had been resorbed and 88% of the defect was filled with trabeculated bone. There were 13 complications; however, only four (3.6%) were attributable to the product. The results of a subgroup of 46 patients with benign bone lesions treated in the same manner are identical to the results of the overall study population. Surgical grade calcium sulfate pellets are considered a convenient, safe, and readily available bone graft substitute that yield consistent successful results.

Long-term use of a left ventricular assist device for end-stage heart failure.

BACKGROUND: Implantable left ventricular assist devices have benefited patients with end-stage heart failure as a bridge to cardiac transplantation, but their long-term use for the purpose of enhancing survival and the quality of life has not been evaluated. METHODS: We randomly assigned 129 patients with end-stage heart failure who were ineligible for cardiac transplantation to receive a left ventricular assist device (68 patients) or optimal medical management (61). All patients had symptoms of New York Heart Association class IV heart failure. RESULTS: Kaplan-Meier survival analysis showed a reduction of 48 percent in the risk of death from any cause in the group that received left ventricular assist devices as compared with the medical-therapy group (relative risk, 0.52; 95 percent confidence interval, 0.34 to 0.78; P=0.001). The rates of survival at one year were 52 percent in the device group and 25 percent in the medical-therapy group (P=0.002), and the rates at two years were 23 percent and 8 percent (P=0.09), respectively. The frequency of serious adverse events in the device group was 2.35 (95 percent confidence interval, 1.86 to 2.95) times that in the medical-therapy group, with a predominance of infection, bleeding, and malfunction of the device. The quality of life was significantly improved at one year in the device group. CONCLUSIONS: The use of a left ventricular assist device in patients with advanced heart failure resulted in a clinically meaningful survival benefit and an improved quality of life. A left ventricular assist device is an acceptable alternative therapy in selected patients who are not candidates for cardiac transplantation.

Open reduction and internal fixation of posterior wall fractures of the acetabulum.

The results of 94 patients with posterior wall fractures of the acetabulum associated with hip instability treated within 3 weeks of injury by open reduction and internal fixation were reviewed. Patients were followed up for an average of 3.5 years (range, 1-13 years). Fracture reductions were graded as anatomic (0-1 mm displacement) in 92 patients and imperfect (2-3 mm displacement) in two patients, as determined by plain radiography. However, postoperative computed tomography scans obtained in 59 patients revealed incongruency of more than 2 mm in six patients and fracture gaps of 2 mm or more in 44 patients. Complications included deep wound infection (one patient), deep vein thrombosis, (seven patients), and revision surgery to redirect an errant screw (one patient). Clinical outcome was graded as excellent in 34 patients (36%), good in 49 (52%), fair in two (2%), and poor in nine (10%). Radiographic results were excellent in 79 hips (84%), good in four (4%), fair in two (2%), and poor in nine (10%). There was a strong association between clinical outcome and radiographic grade. Variables identified as risk factors for an unsatisfactory result included age greater than 55 years, a delay greater than 24 hours from the time of injury for reduction of a hip dislocation, a residual fracture gap greater than 1 cm, and severe intraarticular comminution. The apparent disparity between the accuracy of surgical fracture reduction, as determined by plain radiographs obtained postoperatively, and clinical outcome is explained only partially by the limitations of plain radiography. Other variables are involved, many of which are under the surgeon's control but some are not. As is the case with other acetabular fracture types, the best results are predicated on anatomic fracture reduction.

Pilon fractures. Treatment protocol based on severity of soft tissue injury.

One hundred seven pilon fractures in 107 patients were treated according to a staged prospective protocol. All pilon fractures were stabilized immediately by the application of calcaneal traction. Open fractures or fractures in patients with multiple injuries were stabilized with traveling traction that was applied in the operating room. A distraction computed tomography scan was obtained before definitive treatment. Treatment groups were based on the degree of soft tissue compromise. Forty-one patients with Tscherne Grade 0 or Grade I injuries underwent open reduction and internal fixation (open plating) using contemporary techniques and low-profile implants. Sixty-four patients with Tscherne Grade II and Grade III closed injuries and all patients with open fractures underwent definitive treatment with limited open reduction and stabilization using small wire circular external fixators. Clinical and radiographic evaluations were performed at an average 4.9 years after injury. For all fracture types (AO classification), 81% of the patients who were treated with external fixation and 75% of the patients who were treated with open plating had good or excellent results. For severe fracture patterns (Type C), patients in both groups had significantly poorer results than patients with Types A and B fractures. The patients in the open plating group had a significantly higher rate of nonunion, malunion, and severe wound complications compared with the patients who received external fixation for Type C fracture patterns. Because of the increased incidence of bony and soft tissue complications when treating open or closed Type C fractures, use of limited exposures and stabilization with small wire circular external fixators is recommended.

Investigation of the tris(trimethoxyphenyl)phosphonium acetyl charged derivatives of peptides by electrospray ionization mass spectrometry and tandem mass spectrometry.

Charged derivatives of peptides are useful in obtaining simpler collision-activated dissociation (CAD) mass spectra. An N-terminal charge-derivatizing reagent capable of reacting with picomole levels of peptide has been recently reported (Huang et al. Anal. Chem. 1997, 69, 137-144) in the contexts of analyses by fast atom bombardment (FAB) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Electrospray ionization (ESI) mass spectrometric investigation of these tris(trimethoxyphenylphosphonium) acetyl derivatives are described in this article, including studies by in-source fragmentation (ISF) and tandem mass spectrometry (MS/MS). Results from ISF are compared with those from MS/MS. Similarities and differences between ESI-ISF, MALDI-post-source decay (PSD), and FAB-CAD data are presented. Differences in fragmentation of these charged derivatives in the triple quadrupole and ion trap mass spectrometers also are discussed. Application of this derivatizing procedure to tryptic digests and subsequent analysis by liquid chromatography-mass spectrometry is also shown.

Probing the folding pathways of long R(3) insulin-like growth factor-I (LR(3)IGF-I) and IGF-I via capture and identification of disulfide intermediates by cyanylation methodology and mass spectrometry.

This report describes an integrated investigation of the refolding and reductive unfolding of insulin-like growth factor (IGF-I) and its variant, long R(3) IGF-I (LR(3)IGF-I), which has a Glu(3) to Arg(3) substitution and a hydrophobic 13-amino acid N-terminal extension. The refolding performed in glutathione redox buffer was quenched at different time points by adjusting the pH to 2.0-3.0 with a 1 N HCl solution of 1-cyano-4-dimethylaminopyridinium tetrafluoroborate, which trapped intermediates via cyanylation of free sulfhydryl groups. The disulfide structure of the intermediates was determined by chemical cleavage followed by mass mapping with mass spectrometry. Six refolding intermediates of IGF-I and three refolding intermediates of LR(3)IGF-I were isolated and characterized. Folding pathways of IGF-I and LR(3)IGF-I are proposed based on the time-dependent distribution and disulfide structure of the corresponding trapped intermediates. Similarities and differences in the refolding behavior of IGF-I and LR(3)IGF-I are discussed.

Modified continuous femoral three-in-one block for postoperative pain after total knee arthroplasty.

UNLABELLED: We prospectively studied the continuous "modified" femoral three-in-one block for postoperative pain after total knee arthroplasty. Sixty-two patients undergoing elective knee arthroplasty under spinal anesthesia with bupivacaine (B) and fentanyl were randomized to receive 0.2% B, 0.1% B, or placebo at 10 mL/h for 48 h after an initial bolus of 30 mL of the same solution via the femoral block catheter. The catheters were inserted under the fascia iliaca using a "double pop" technique and a peripheral nerve stimulator and were advanced 15-20 cm cranially. Venous plasma levels of B, desbutylbupivacaine, and 4-hydroxy B were measured daily for 3 days. All patients received patient-controlled analgesia with morphine and indomethacin suppositories for 48 h. Using computed tomography, we evaluated the catheter location for 20 patients. The catheter tips, located superior to the upper third of the sacroiliac joint in the psoas sheath, were labeled as ideally located. The group receiving 0.2% B had a larger block success rate, smaller morphine consumption in the immediate postoperative period (15 vs 22 mg) and during the first postoperative day (9 vs 18 mg), and achieved a greater range of motion in the immediate postoperative period (91 degrees +/- 10 degrees vs 80 degrees + 13 degrees ). Visual analog scores for pain during both rest and activity were low but similar between the groups. Forty percent of the catheters evaluated were ideally located. Ideal location and use of 0.2% B resulted in 100% success of blockade of all three nerves. The S1 root was blocked in up to 76% of patients. The plasma levels of B, 4-hydroxy B, and desbutylbupivacaine were below the toxic range during the infusion. We conclude that continuous fascia iliaca block with 0.2% B results in opioid-sparing and improved range of motion during the immediate postoperative period. Larger doses of bupivacaine may safely be used in the immediate postoperative period if needed. IMPLICATIONS: Continuous fascia iliaca block with 0.2% bupivacaine reduces opioid requirements and improves range of motion in the immediate postoperative period compared with a placebo and 0.1% bupivacaine. Plasma levels are below the toxic range with this dose. Only 40% of the catheters are positioned in the ideal location. With the smaller dose of bupivacaine, the success rate with this block is small.

Retrograde nailing of the femoral shaft.

Retrograde intramedullary nailing of fractures of the femoral shaft with use of a distal intercondylar intra-articular entry portal is a relatively new surgical technique. This method of nailing represents a modification of the previously described procedure in which an extra-articular entry portal in the medial femoral condyle was used. The earlier procedure was plagued by technical difficulties, which limited its use; these problems were mainly related to the fact that the entry portal was not in line with the intramedullary canal, as well as to the fact that purpose-specific implants and instrumentation were not available. Modification of this technique, by using the intercondylar entry portal and a nail designed for retrograde insertion, has proved very effective in clinical studies. There have been theoretical concerns regarding postoperative knee function and intraoperative injury to important anatomic structures, such as branches of the femoral nerve; however, laboratory and clinical findings have dispelled many of these concerns and have provided firm support for continued use of the technique. Nonetheless, further study is required to delineate the long-term outcome of knee joint function. Current indications for use of this technique include multisystem injuries, multiple fractures (including ipsilateral lower-limb combination injuries), ipsilateral vascular injuries, periprosthetic fractures, and morbid obesity.

The REMATCH trial: rationale, design, and end points. Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure.

BACKGROUND: Because left ventricular assist devices have recently been approved by the Food and Drug Administration to support the circulation of patients with end-stage heart failure awaiting cardiac transplantation, these devices are increasingly being considered as a potential alternative to biologic cardiac replacement. The Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) trial is a multicenter study supported by the National Heart, Lung, and Blood Institute to compare long-term implantation of left ventricular assist devices with optimal medical management for patients with end-stage heart failure who require, but do not qualify to receive cardiac transplantation. METHODS: We discuss the rationale for conducting REMATCH, the obstacles to designing this and other randomized surgical trials, the lessons learned in conducting the multicenter pilot study, and the features of the REMATCH study design (objectives, target population, treatments, end points, analysis, and trial organization). CONCLUSIONS: We consider what will be learned from REMATCH, expectations for expanding the use of left ventricular assist devices, and future directions for assessing clinical procedures.