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.

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.

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.

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.

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.

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.

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.

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

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.

Protein sequencing by matrix-assisted laser desorption ionization-postsource decay-mass spectrometry analysis of the N-Tris(2,4,6-trimethoxyphenyl)phosphine-acetylated tryptic digests

We have recently reported a simple procedure by which low picomole quantities of peptides can be modified to the corresponding N-Tris(2, 4,6-trimethoxyphenyl)phosphonium-acetyl (TMPP-Ac) derivatives (Z. H Huang, J. Wu, D. A. Gage, and J. T. Watson, Anal. Chem. 69, 137-144, 1997). This modification significantly facilitates sequence interpretation by providing exclusively N-terminal product ions (mainly a-type ions) in the fast-atom bombardment-MS/MS and matrix-assisted laser desorption ionization-postsource decay(MALDI-PSD)-MS spectra. The TMPP-Ac derivatization approach has been extended now for the direct derivatization of tryptic digests originating from 1-5 microg of proteins with molecular weights from 10-120 kDa. Our new procedure involves tryptic digestion in aqueous solution buffered to pH 8-8.2 with phosphate or Tris-HCl, followed by reaction with TMPP-acetic acid N-hydroxysuccinimide ester (TMPP-AcOSu bromide, 2-4 nmol reagent/microg protein, rt, 20 min) to provide N-terminally derivatized products, while the epsilon-NH2 groups in lysine remain unchanged. The resultant derivatized peptide mixture or its partially separated HPLC fractions are subsequently analyzed by MALDI-PSD-MS using 0.5- to 1-pmol aliquots, giving rise to product ion spectra that are easily interpretable. As there is no need for material transfer and change of buffer media, the tandem enzymatic-chemical reaction/MS analysis process is usually carried out with very high throughput (digestion, 1 h; reaction, 1/3 h; HPLC, 1 h; MALDI-PSD, 3-4 fragments/h). This procedure will be of potential use for obtaining sequence information directly from mixtures or as an adjunct of peptide mass mapping to provide protein identification with high confidence.

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.

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and The Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Treatment of complex lateral plateau fractures using Ilizarov techniques

Fourteen high energy atypical Schatzker Types I and II fractures were treated using a combination of contemporary internal fixation techniques and Ilizarov methodologies. Fracture were atypical if the primary lateral condylar fracture line extended anteromedially with complete detachment of the tibial tubercle, or posteromedially with extension into the medial or posterior medial tibial condyle, both in association with comminution of the lateral condyle and impaction of the lateral articular surface. Preoperative traction computed tomography scans were used to direct incisions to the area of joint involvement. Fixation included hook plate stabilization of anterior tubercle fragments in five fractures. Adjunctive lateral, medial, or posterior antiglide plates were used where olive wire stabilization was contraindicated because of anatomic constraints. Fractures were neutralized by a three-ring Ilizarov external fixator. At followup, average 19.2 months (range, 8-67 months), all fractures had healed, and 85% had good or excellent knee scores (Knee Society clinical rating scale). Five patients had minor pin tract complications and one patient had a superficial wound slough. This combined approach has shown excellent results for this complex fracture pattern without the severe soft tissue complications associated with internal fixation techniques for high energy fractures.

Charge derivatization of peptides for analysis by mass spectrometry

The analysis of peptide derivatives by fast atom bombardment, liquid secondary-ionization mass spectrometry, plasma desorption, electrospray ionization, and matrix-assisted laser desorption/ionization is reviewed. The fragmentation patterns of peptides and of charge-derivatized peptides are compared, and the proposed fragment ion structures are summarized. A variety of derivatization approaches and the distinguishing features of mass spectra produced from these derivatives are described. The most promising derivatization approaches are evaluated, and the strengths and limitations of these approaches are discussed.

Unreamed retrograde intramedullary nailing of fractures of the femoral shaft

OBJECTIVE

To evaluate the efficacy of unreamed retrograde intramedullary (IM) nailing of fractures of the femoral shaft in a second series of patients using modifications suggested from our initial study.

DESIGN

Prospective.

SETTING

Level I trauma center.

METHODS

Based on the findings of a previous study, we began a clinical series incorporating changes consisting of (a) inclusion of any patient with a femoral shaft fracture amenable to IM nailing (i.e., closed physes), (b) primary use of a split patellar tendon intercondylar distal femoral entry portal, and (c) the use of a full-length femoral implant having variable size availability and dynamization capability. Over a twelve-month period, thirty-four patients with thirty-five femoral shaft fractures were treated. The protocol called for planned dynamization in statically locked stable fractures and unstable fractures showing minimal healing at six to twelve weeks. Functional outcome was assessed by using the Knee Society clinical rating system.

RESULTS

Incorporating the concepts of canal fill and early dynamization, there were only two nonunions (6 percent) in this series as compared with 14 percent in the previously reported series with an overall shorter time to union (12.6 versus 15 weeks). There were no infections or malunions. Postoperative complaints of knee pain were minimal (knee score average: 98 points) and knee function was excellent (knee score average: 97 points).

CONCLUSIONS

Although not advocated as a replacement for other techniques, unreamed retrograde nailing is presented as a safe and beneficial fracture fixation method that should be added to the orthopaedic surgeon's treatment armamentarium. The operative technique is quick and simple, and blood loss is minimal. Early nail dynamization and early weight-bearing are important in minimizing the risk of nonunion.

Optimization of the cleavage reaction for cyanylated cysteinyl proteins for efficient and simplified mass mapping

Peptide chains can be cleaved selectively on the N-terminal side of cysteine residues after cyanylation of sulfhydryl groups to form an amino-terminal peptide and a series of 2-iminothiazolidine-4-carboxyl peptides. This paper describes a systematic study that was carried out to elucidate the effects of peptide structure and reaction conditions on the kinetics of the reactions and the yields of cleavage products. Both cleavage and beta-elimination reactions under different conditions (pH 8.0, 9.0, and 12.0 and 1 M ammonia solution) were quantitatively evaluated using reversed-phase HPLC and matrix-assisted laser desorption/ionization-MS. Contrary to previous reports, our results showed that higher pH greatly accelerates both cleavage and beta-elimination reactions, while the relative yield of beta-elimination products does not increase for most of the peptides studied. Optimal results were obtained in 1 M ammonium hydroxide solution, in which cleavage is complete within an hour at ambient temperature. This improvement also minimizes side reactions otherwise associated with long hours of exposure to alkaline conditions, [original report called for 12 to 80 h of incubation in mildly alkaline (pH 8-9) buffer]. The yields of cleavage reactions depend primarily on the structure of amino acids on the N-terminal side of cyanylated cysteines; the Pro-Cys and Tyr-Cys bonds were resistant to cleavage, promoting beta-elimination as the main reaction. The improved cleavage conditions greatly simplify the analytical procedure, which has been successfully applied to the determination of cysteine status in spinach ferredoxin, ovalbumin, and rabbit muscle creatine phosphokinase.

Outcomes following repair of quadriceps tendon ruptures

OBJECTIVES

The purpose of this study was to examine critically the outcomes of patients sustaining a quadriceps tendon rupture and to compare outcomes in patients with bilateral simultaneous ruptures versus a unilateral rupture.

DESIGN

Retrospective review.

SETTING

Patients were treated at a Level I trauma center.

PATIENTS/PARTICIPANTS

Fifty-one quadriceps tendon ruptures in thirty-nine patients were evaluated. A mean four-year follow-up (range 13 to 204 months) was available for forty-eight tendon ruptures.

INTERVENTIONS

All patients except one were treated with operative repair of the quadriceps tendon rupture(s).

MAIN OUTCOME MEASUREMENTS

Patients were assessed by physical examination, Lysholm and Tegner scores, a functional questionnaire, quadriceps isokinetic testing, and radiographs.

RESULTS

A statistically greater number of patients in the bilateral simultaneous rupture group had a systemic illness associated with tendon rupture (p = 0.014). This result did not adversely affect outcome as compared with patients with unilateral ruptures. Mean range of motion was 123 degrees in injured knees. Eighty-four percent of working patients returned to their previous occupations. More than half the patients, however, in general the most active, could no longer participate in their preinjury recreational activities. Fifty-three percent of unilateral rupture patients had persistent quadriceps strength deficits (>20 percent) in the injured extremity. Both quadriceps and hamstring isokinetic testing correlated significantly with Lysholm and Tegner scores.

CONCLUSIONS

Most patients with bilateral simultaneous and unilateral tendon repairs can expect a good range of motion and return to their previous occupation, but many have persistent weakness and difficulty returning to higher level sporting activities.

Trapping of intermediates during the refolding of recombinant human epidermal growth factor (hEGF) by cyanylation, and subsequent structural elucidation by mass spectrometry

Human epidermal growth factor (hEGF) contains 53 amino acids and three disulfide bonds. The unfolded, reduced hEGF is allowed to refold under mildly alkaline conditions. The folding is quenched at different time points by adjusting the pH to 3.0 with an acetic acid solution of 1-cyano-4-dimethylamino-pyridinium (CDAP) which traps folding intermediates via cyanylation of free sulfhydryl groups. The mixture of cyanylated intermediates is separated by reversed-phase HPLC; the fractions collected are identified by mass spectrometry. The disulfide structures of the intermediates are then determined by specific chemical cleavage and mass-mapping by MALDI-MS, a novel approach developed in our laboratory. The procedure of quenching and trapping of disulfide intermediates in acidic solution minimizes sulfhydryl-disulfide exchange, and therefore provides a good measure of folding kinetics and preservation of intermediate species. Our cyanylation methodology for disulfide mapping is simpler, faster, and more sensitive than the more conventional approach. Among 18 folding intermediates isolated and identified at different time points, disulfide structures of seven well-populated intermediates, including two non-native isomers with scrambled disulfide structures, one 2-disulfide intermediate, and four 1-disulfide intermediates, have been characterized; most of them possess non-native disulfide structures.

Comparison of the compression hip screw with the Medoff sliding plate for intertrochanteric fractures

The Medoff sliding plate was designed to achieve compression along the femoral neck and the longitudinal axis of the femoral shaft theoretically to improve the treatment of intertrochanteric hip fractures. The Medoff sliding plate was compared with a standard compression hip screw in a randomized, prospective study for the fixation of 160 stable and unstable intertrochanteric fractures with an average followup of 9.5 months (range, 6-26 months). Overall, 91 fractures were treated using the compression hip screw and 69 were treated with the Medoff sliding plate. Stable fracture patterns (46) united without complication in both treatment groups. Unstable fractures (114) had an overall failure rate of 9.6%, 14% (nine patients) with the compression hip screw and 3% (two patients) with the Medoff plate; this difference was significantly different. The time to union for the 114 unstable fractures was not significantly different between the two devices. For all patients, no differences in lengths of hospitalization, return to ambulatory status before fracture, postoperative living status, or postoperative pain was observed between the two device groups. Use of the Medoff plate for all fracture types was associated with a significantly higher amount of blood loss and operating time.

Ultrasound for the early diagnosis of tibial fracture healing after static interlocked nailing without reaming: clinical results

OBJECTIVE

Based on the results of a pilot study indicating the potential value of ultrasound (US) as a diagnostic tool for the early assessment of fracture healing and the related need for secondary operative procedures in patients treated by statically locked intramedullary (IM) nailing without reaming, a protocol was established for a larger scale prospective trial. The purpose of this study was to evaluate the outcome of this follow-up trial.

DESIGN/METHODS

All skeletally mature patients admitted to the Henry Ford Hospital (Detroit, Michigan) from January 1993 to August 1994 who had sustained an acute fracture of the tibial shaft and who were treated by statically locked IM nailing, without reaming, were candidates for study. Forty-seven patients with fifty fractures that could be evaluated by US were included. The adopted determinants for fracture healing were complete disappearance of the IM nail on US examination performed at six weeks postoperatively, or progressive disappearance of the nail noted between the initial six-week study and a second nine-week US examination, both in conjunction with periosteal callus formation. Radiographs were obtained to monitor maintenance of reduction and to further evaluate fracture healing.

RESULTS

Of thirty-eight fractures with a positive US (thirty-two at six weeks, six at nine weeks), thirty-seven healed uneventfully, a positive predictive value of 97 percent. Radiographic fracture healing was not evident until, on average, nineteen weeks after injury. The single false-positive fracture progressed to nonunion. Of the twelve fractures with negative US studies, ten underwent secondary procedures (nine dynamization, one bone graft), with four progressing to nonunion. Two patients refused secondary surgery; screw failure occurred in both. Otherwise, there were no hardware failures in this series.

CONCLUSIONS

The results of this study indicate that US may provide important prognostic information concerning fracture healing after unreamed tibial nailing, upon which subsequent treatment can be based.

A historical perspective and commentary on pioneering developments in gas chromatography/mass spectrometry at MIT

Klaus Biemann has helped shape many aspects of the field of modern mass spectrometry. This paper reviews and comments on some of his innovative contributions to gas chromatography/mass spectrometry (GC/MS) during the 1960s and 1970s with particular emphasis on the molecular separator, a comprehensive plan for the acquisition and processing of GC/MS data and the application of GC/MS to the analysis of drugs in emergency cases.

Leg kinematics and muscle activity during treadmill running in the cockroach, Blaberus discoidalis: II. Fast running

We have combined kinematic and electromyogram (EMG) analysis of running Blaberus discoidalis to examine how middle and hind leg kinematics vary with running speed and how the fast depressor coxa (Df) and fast extensor tibia (FETi) motor neurons affect kinematic parameters. In the range 2.5-10 Hz, B. discoidalis increases step frequency by altering the joint velocity and by reducing the time required for the transition from flexion to extension. For both Df and FETi the timing of recruitment coincides with the maximal frequency seen for the respective slow motor neurons. Df is first recruited at the beginning of coxa-femur (CF) extension. FETi is recruited in the latter half of femur-tibia (FT) extension during stance. Single muscle potentials produced by these fast motor neurons do not have pronounced effects on joint angular velocity during running. The transition from CF flexion to extension was abbreviated in those cycles with a Df potential occurring during the transition. One effect of Df activity during running may be to phase shift the beginning of joint extension so that the transition is sharpened. FETi is associated with greater FT extension at higher running speeds and may be necessary to overcome high joint torques at extended FT joint angles.

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Leg kinematics and muscle activity during treadmill running in the cockroach, Blaberus discoidalis: I. Slow running

We have combined high-speed video motion analysis of leg movements with electromyogram (EMG) recordings from leg muscles in cockroaches running on a treadmill. The mesothoracic (T2) and metathoracic (T3) legs have different kinematics. While in each leg the coxa-femur (CF) joint moves in unison with the femurtibia (FT) joint, the relative joint excursions differ between T2 and T3 legs. In T3 legs, the two joints move through approximately the same excursion. In T2 legs, the FT joint moves through a narrower range of angles than the CF joint. In spite of these differences in motion, no differences between the T2 and T3 legs were seen in timing or qualitative patterns of depressor coxa and extensor tibia activity. The average firing frequencies of slow depressor coxa (Ds) and slow extensor tibia (SETi) motor neurons are directly proportional to the average angular velocity of their joints during stance. The average Ds and SETi firing frequency appears to be modulated on a cycle-by-cycle basis to control running speed and orientation. In contrast, while the frequency variations within Ds and SETi bursts were consistent across cycles, the variations within each burst did not parallel variations in the velocity of the relevant joints.

Separation and quantitation of linoleic acid oxidation products in mammary gland tissue from mice fed low- and high-fat diets

We have developed an assay for the isolation and quantitation by gas chromatography-mass spectrometry (GC-MS) of free 9- and 13-hydroxyoctadecadienoic acid (9-HODE, 13-HODE) in the mammary glands of female mice. Internal standards consisting of 18O2-labeled analogs of 9- and 13-HODE are added to pulverized frozen tissue prior to extraction with ethanol. Nonlipid materials are removed in a chloroform/methanol/water step. The remaining lipid material is methylated with ethereal diazomethane, and much of the nonoxygenated fatty acid methyl esters are removed via silica solid-phase extraction. Samples are either further derivatized with bis(trimethylsilyl)trifluoroacetamide to form the trimethylsilyl ethers for quantitative analysis by GC-MS or are analyzed as the methyl esters by chiral high-performance liquid chromatography to determine the enantiomeric distribution of the 9- and 13-HODE. The extraction and quantitation protocol was applied to the analysis of mammary glands for free 9- and 13-HODE from mice fed isocaloric diets containing 20% corn oil, 5% corn oil, or 20% beef tallow. Chiral analysis of the products showed higher production of 13(S)-HODE relative to 13(R)-HODE; the enantiomeric excess is most likely due to enzymatic production of 13-HODE superimposed on a background of autoxidative production of 13(R)- plus 9(S)- and 9(R)-HODE. In addition, the effect of sample handling and storage conditions on the formation of 9- and 13-HODE in the samples was assessed by exposing aliquots of a common pool of rat mammary gland tissue to specified conditions prior to analysis. This methodology will be important during investigations of the contribution of linoleate oxidation products to the enhancement of mammary tumorigenesis by dietary fat.

Intramedullary nailing of unstable diaphyseal fractures of the tibia with distal intraarticular involvement

OBJECTIVE

To evaluate the efficacy of intramedullary nailing in diaphyseal tibia fractures with distal intraarticular involvement.

DESIGN

Retrospective.

SETTING

Henry Ford Hospital, a level I trauma center.

PATIENTS/PARTICIPANTS

Twenty patients with twenty fractures at an average of twenty-two months of follow-up were evaluated. There were fifteen closed and five open fractures.

INTERVENTION

All fractures were stabilized with lag screw fixation (with or without supplemental plates) of the intraarticular-fracture extension or ankle fracture, and intramedullary nailing of the diaphyseal tibia fracture.

MAIN OUTCOME MEASUREMENTS

Time to bony union, malunion, knee and ankle range of motion, early arthrosis, and any complications of treatment were assessed.

RESULTS

Nineteen fractures healed, with an average time to bony union of seventeen weeks. One nonunion after a grade IIIB open fracture required exchange nailing and healed after sixty-two weeks. Nineteen fractures had excellent alignment after healing. There were no infections.

CONCLUSIONS

The indications for intramedullary nailing of unstable diaphyseal tibia fractures may be extended to include certain fractures with distal extension into the ankle joint, as well in a tibial shaft fracture occurring in combination with a noncontiguous ipsilateral ankle fracture.

Early complications in the operative treatment of patella fractures

OBJECTIVE

To identify and review early complications in the operative treatment of patella fractures.

DESIGN

Retrospective review.

SETTING

Single tertiary care institution with multiple surgeons, including generalists and fellowship trained subspecialists.

PATIENTS

A consecutive series of eighty-seven patella fractures over a five year period was reviewed. Patients treated nonoperatively or with partial or total patellectomy were excluded. Minimum follow-up to fracture healing (four months) was available in fifty-one fractures.

INTERVENTION

Modified tension band wire fixation was used in forty-nine fractures, whereas two fractures were treated with tension band wires threaded through cannulated screws.

OUTCOME MEASURES

Early complications such as loss of reduction or fixation, infection, or soft-tissue problems were evaluated.

RESULTS

Displacement of > or = 2 mm before healing was noted in eleven fractures. The displacement could be attributed to technical errors in five cases, and to patient noncompliance with postoperative activity restrictions in another five cases. Two cases of superficial infection were documented. Nine patients with symptomatic hardware required hardware removal.

CONCLUSIONS

Twenty-two percent of fractures treated with tension band wiring and early motion displaced > or = 2 mm within the early postoperative period. Technical errors or patient noncompliance were identified as factors. The incidence of early complications in operatively treated patella fractures is higher than previously reported.

A novel methodology for assignment of disulfide bond pairings in proteins

A novel methodology is described for the assignment of disulfide bonds in proteins of known sequence. The denatured protein is subjected to limited reduction by tris(2-carboxyethyl)phosphine (TCEP) in pH 3.0 citrate buffer to produce a mixture of partially reduced protein isomers; the nascent sulfhydryls are immediately cyanylated by 1-cyano-4-dimethylamino-pyridinium tetrafluoroborate (CDAP) under the same buffered conditions. The cyanylated protein isomers, separated by and collected from reversed-phase HPLC, are subjected to cleavage of the peptide bonds on the N-terminal side of cyanylated cysteines in aqueous ammonia to form truncated peptides that are still linked by residual disulfide bonds. The remaining disulfide bonds are then completely reduced to give a mixture of peptides that can be mass mapped by MALDI-MS. The masses of the resulting peptide fragments are related to the location of the paired cysteines that had undergone reduction, cyanylation, and cleavage. A side reaction, beta-elimination, often accompanies cleavage and produces overlapped peptides that provide complementary confirmation for the assignment. This strategy minimizes disulfide bond scrambling and is simple, fast, and sensitive. The feasibility of the new approach is demonstrated in the analysis of model proteins that contain various disulfide bond linkages, including adjacent cysteines. Experimental conditions are optimized for protein partial reduction, sulfhydryl cyanylation, and chemical cleavage reactions.

A picomole-scale method for charge derivatization of peptides for sequence analysis by mass spectrometry

A highly activated ester containing a fixed positive charge, S-pentafluorophenyl [tris(2,4,6-trimethoxyphenyl)phosphonium]acetate bromide (TMPP-AcSC6F5 bromide), has been synthesized as a reagent for N-terminal modification of peptides. Stable in aqueous acetonitrile solution during extended storage, TMPP-AcSC6F5 bromide reacts with unprotected peptides through p-(dimethylamino)pyridine (DMAP)-promoted amidation in aqueous acetonitrile (15 min, ambient temperature) to form N-TMPP-Ac derivatives of peptides. These peptide derivatives are readily amenable to analysis by fast atom bombardment (FAB) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Greater than 90% conversion has been observed in transforming low-nanomole quantities of analyte using molar ratios of 1:5:10 (peptide/reagent/ DMAP). For reactions at the picomole level a slightly modified stoichiometry, with molar ratios of 1:10:500, is employed. Owing to the high reaction efficiency and the tolerance to moderate excess reagent and base during analysis by FAB- and MALDI-MS, the reaction mixture containing the modified peptides can be analyzed directly in most cases, without sample cleanup. Examples of the preparation and analysis of a variety of N-TMPP-acetyl-peptides (TMPP-Ac-peptides) ranging from hexamers to 15-mers are given. Collisionally activated dissociation tandem mass spectrometry of TMPP-Ac-derivatives showed dominant a-type ions, accompanied by d- and c-type ions in some cases, allowing sequence determination to be made in a straightforward manner.

Orthopedic implants: a guide to radiographic analysis

Orthopedic technology is growing at a rapid rate. New implants reflect this technology whether it pertains to fracture fixation, joint replacement, spine stabilization, or soft-tissue reconstruction. This monograph is designed to assist both the radiologist and the orthopedist in accurately assessing plain radiographs of commonly used orthopedic implants. We discuss the biologic response of the surrounding bone to these devices; herein lies the key to understanding the radiographic presentation of these devices.

Composition-selective detection of polychlorinated biphenyls (PCBs) by oxygen-chlorine exchange reaction in a tandem mass spectrometer (MS/MS)

The exchange reaction of chlorine by oxygen with polychlorinated biphenyl (PCB) anions was explored as a method for composition-selective detection of PCB congeners in a gas chromatograph/tandem mass spectrometer (GC/MS/MS) experiment. The odd-electron molecular anions of PCBs react with molecular oxygen introduced into the collision cell of a triple-quadrupole mass spectrometer to form a product ion that has 19 mass units less (35Cl - 16O) than the precursor. The even-electron anions which also form in the source do not react when allowed to pass through the precursor analyzer. Multiple reaction monitoring allows the generation of separate chromatograms for each different composition from tetrachloro through nonochloro PCB. Most coelutants are resolved in this way. Response factors for the 12 coplanar congeners that exhibit dioxin-like toxicity relative to octachloronaphthalene vary from 1.6 to 580. Results of the analysis of an Aroclor 1242 sample for the coplanar congeners compare well with previously determined values.

A strategy to locate cysteine residues in proteins by specific chemical cleavage followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A simple methodology has been developed to characterize the number and location of free cysteine and cystine groups in peptides and proteins, using chemical modification and matrix-assisted laser desorption/ ionization time-of flight mass spectrometry (MALDITOF MS). This new approach employs a specific reaction between free sulfhydryls and 2-nitro-5-thiocyanobenzoic acid (NTCB) to selectively cyanylate cysteine thiols. The N-terminal peptide bond of the modified cysteinyl residue can then be cleaved under alkaline conditions to form an amino-terminal peptide and a series of 2-iminothiazolidine-4-carboxylyl peptides which can be mapped to the sequence by MALDI-MS. The number and location of cysteines can be deduced from mass analysis of the peptide mixture resulting from NTCB chemical processing of the original protein of known sequence under nonreducing conditions. Similar experiments are then performed following disulfide bond reduction to further characterize both cysteine and cystine groups. Experimental conditions are described for protein disulfide bond reduction, sulfhydryl cyanylation, and cleavage reactions performed both in solution and on Zetabind membranes.

Early versus delayed treatment of severe ankle fractures: a comparison of results

A retrospective review of 202 closed Weber B bimalleolar or bimalleolar equivalent ankle fractures treated using open reduction and internal fixation (ORIF) from January 1, 1991, through January 1, 1994 was completed at our institution. A total of 105 ankles (52%) were treated using ORIF within 5 days of injury (early group), with a mean 1.5 days from injury to surgery. A total of 97 ankles (48%) were treated after 5 days (delayed group), with a mean of 13.6 days from injury to surgery. Operative time, length of hospital stay, postoperative range of motion, adequacy of reduction, wound and other complications, and other sequelae were compared between the two groups. No significant difference in range of motion at latest follow-up or in operative time was evident between the groups. Minor wound complications were present in 4.8% of the early group compared with 6.2% in the delayed group. No deep infections or osteomyelitis were present in either group. Anatomic reductions were present in 89% and poor reductions (> 2 mm displacement) in 1% of those ankles treated within 5 days versus 83% anatomic reductions and 3% poor reductions in those treated after 5 days. The differences in wound complications and anatomic reductions between groups was not statistically significant. There was a significantly longer median hospital stay in the early (3 days) versus delayed groups (2 days). We conclude that the results and complications of early versus delayed treatment is not significantly different, except for a shorter median hospital stay in the delayed group. Delayed ORIF is an acceptable alternative when soft-tissue swelling, fracture blisters, or abrasions are present that offer an undesirable environment for surgical incisions. Using contemporary, a traumatic techniques, delayed surgery can provide anatomic reduction with minimal complications in severe ankle fractures.

Retrograde intramedullary nailing, without reaming, of fractures of the femoral shaft in multiply injured patients

Twenty consecutive multiply injured patients who had a total of twenty-two fractures of the femoral shaft were managed with intramedullary nailing without reaming. A retrograde technique through the intercondylar notch of the knee was used. All patients were followed for at least one year or until union of the fracture. The operative time for the nailing averaged seventy-five minutes (range, thirty-five to 105 minutes). Union of the fracture occurred at an average of fifteen weeks. There were three non-unions and one rotational malunion. There were no infections, and no nail or screw failed. Normal motion of the knee was regained by all patients, except one who had had an ipsilateral dislocation of the knee. On the basis of these preliminary results, we concluded that retrograde nailing is a safe and effective technique for multiply injured patients. The apparently higher prevalence of non-union compared with that reported with antegrade nailing with reaming warrants additional study.

Combined intracellular stimulation and high speed video motion analysis of motor control neurons in the cockroach

A complete understanding of motor control circuitry requires detailed analysis of the behavior produced by the circuitry as well as the connections between individual neurons. A technique is described for combining high speed video motion analysis of leg movements in the cockroach with electrophysiological techniques such as intracellular stimulation/recording from central neurons and EMG recording from leg muscles. Using a restrained preparation, we have quantified leg movements evoked by intracellular stimulation of individual motor neurons and local interneurons. By incorporating motion analysis into the recording paradigm, the transfer functions from electrical activity to movements can be derived. Because distinct and characteristic responses to single and multiple action potentials are seen in slow, intermediate, and fast motor neurons, it is often possible to identify the motor neuron targets of local interneurons. The ability to analyze movement in any plane is especially useful in situations such as blind neuropilar penetrations, where a more restricted motion transducer arrangement may not be in register with the impaled cell. In addition, it is possible to record and analyze such complex phenomena as coordinated movements in multiple joints produced by local interneurons and reflexes produced by proprioceptive feedback due to activity of one motor neuron.