Picometer-scale surface roughness measurements inside hollow glass fibres.

A differential profilometry technique is adapted to the problem of measuring the roughness of hollow glass fibres by use of immersion objectives and index-matching liquid. The technique can achieve picometer level sensitivity. Cross validation with AFM measurements is obtained through use of vitreous silica step calibration samples. Measurements on the inner surfaces of fibre-sized glass capillaries drawn from high purity suprasil F300 tubes show a sub-nanometer roughness, and the roughness power spectrum measured in the range [5 · 10(-3) m(-1) 10(-1) m(-1)] is consistent with the description of the glass surface as a superposition of frozen capillary waves. The surface roughness spectrum of two capillary tubes of differing compositions can be quantitatively distinguished.

Effects of finite probe size on self-affine roughness measurements.

The roughness of fracture surfaces exhibits self-affinity for a wide variety of materials and loading conditions. The universality and the range of scales over which this regime extends are still debated. The topography of these surfaces is however often investigated with a finite contact probe. In this case, we show that the correlation function of the roughness can only be measured down to a length scale Deltax{c} which depends on the probe size R, the Hurst exponent zeta of the surface and its topothesy l, and exhibits spurious behavior at smaller scales. First, we derive the dependence of Deltax{c} on these parameters from a simple scaling argument. Then, we verify this dependence numerically. Finally, we establish the relevance of this analysis from AFM measurements on an experimental glass fracture surface and provide a metrological procedure for roughness measurements.

Hidden order in crackling noise during peeling of an adhesive tape.

We address the longstanding problem of recovering dynamical information from noisy acoustic emission signals arising from peeling of an adhesive tape subject to constant traction velocity. Using the phase space reconstruction procedure we demonstrate the deterministic chaotic dynamics by establishing the existence of correlation dimension as also a positive Lyapunov exponent in a midrange of traction velocities. The results are explained on the basis of the model that also emphasizes the deterministic origin of acoustic emission by clarifying its connection to stick-slip dynamics.

The crack tip: a nanolab for studying confined liquids.

We study the equilibrium properties of a liquid phase condensed at the nanoscale between the surfaces of a sharp crack in fused silica in a moist controlled atmosphere. The extension of the condensed phase along the fracture is measured by in situ atomic force microscopy phase imaging and it is shown to be determined by a critical distance between the opposite crack surfaces, which is an increasing function of humidity. The present technique is very promising for measuring the properties of confined liquids at the nanoscale as well as for modeling the physics and chemistry of slow crack propagation in glasses.

Pernicious effect of physical cutoffs in fractal analysis.

Fractal scaling appears ubiquitous, but the typical extension of the scaling range observed is just one to two decades. A recent study has shown that an apparent fractal scaling spanning a similar range can emerge from the randomness in dilute sets. We show that this occurs also in most kinds of nonfractal sets irrespective of defining the fractal dimension by box counting, minimal covering, the Minkowski sausage, Walker's ruler, or the correlation dimension. We trace this to the presence of physical cutoffs, which induce smooth changes in the scaling, and a bias over a couple of decades around some characteristic length. The latter affects also the practical measure of fractality of truly fractal objects. A defensive strategy against artifacts and bias consists in carefully identifying the cutoffs and a quick-and-dirty thumb rule requires to observe fractal scaling over at least three decades.

Correlation of estradiol in pregnancy and anterior cruciate ligament laxity.

The purpose of this study was to determine whether a correlation existed between estradiol in pregnancy and laxity of the anterior cruciate ligament by measuring anterior tibial translation. All patients underwent measurement of anterior tibial translation using KT-1000 knee arthrometer testing and serum estradiol determination during the third trimester of pregnancy and postpartum. Forty knees were studied. The average serum estradiol levels decreased from 10,755.0 ng/L to 50.3 ng/L. There was an average decrease anterior tibial translation with a manual maximum displacement of 3.0 mm (range, 1 mm-5 mm) from the first to second examinations. Average measurement of anterior tibial translation in pregnant women showed a statistically significant increase in laxity in the third trimester of pregnancy compared with the postpartum laxity. The results of this study show that high serum estradiol levels during the third trimester of pregnancy correlate with increased anterior tibial translation and that this anterior tibial translation decreases with the return of serum estradiol to nonpregnant levels.

Epicondylitis in the athlete.

Epicondylitis plagues a significant proportion of athletes and can result in prolonged symptoms and suboptimal athletic performance. The diagnosis can be confused with many other pathologic entities affecting the elbow, some of which can occur concurrently. Most patients will respond favorably to a well-guided nonsurgical treatment protocol. A minority of patients will have persistent problems and will require surgical intervention that can relieve pain effectively and return patients to their preinjury level of activity.

Epicondylitis in the athlete.

Since the first description of epicondylitis of the elbow in 1882, there have been volumes of descriptive, diagnostic, and therapeutic reports detailing every aspect of this entity. It is now known that epicondylitis can be caused both by occupational and sports-related activities, that its diagnosis may be confused with a variety of other pathologic entities affecting the elbow, that the majority of patients will respond favorably to well-guided nonsurgical treatment, and that in those patients whose rersistent symptoms make them unable to return to their activities, surgical treatment results in reliable pain relief and return to preinjury level of activity.

Medial collateral ligament instability and ulnar neuritis in the athlete's elbow.

Athletes who participate in overhand sports may sustain a host of injuries to the medial elbow. The chronic repetitive stress caused by the high velocity nature of the overhand throwing mechanism predisposes these athletes to overuse injuries. Medial collateral ligament instability and ulnar neuritis are common disorders seen in this patient population. A thorough understanding of the anatomy of the medial elbow as well as the pathophysiology of these disorders and their nonsurgical and surgical treatments are essential to providing these athletes with optimal care and hastening their return to sports.

Failure properties of suture anchors in the glenoid and the effects of cortical thickness.

The ultimate pullout strength and fatigue properties of a screw-design suture anchor implanted in the anterior glenoid rim were investigated and compared with results from a nonscrew-design suture anchor. Twenty-two cadaveric glenoids were harvested and one to two anchors were implanted in the superior and inferior quadrants. Fifty-seven Statak 3.5 anchors (Zimmer, Warsaw, IN) were tested and compared with results obtained in a previous study on 50 Mitek GII anchors (Mitek Products, Inc, Westwood, MA). The specimens were mounted on an Instron fatigue testing machine (Instron Corp, Canton, MA) and cycled between preselected minimum and maximum loads until pullout. The Mitek GII maintained a higher pullout strength than the Statak 3.5 after cyclic loading. Cortical thickness at the implantation sites was measured, and found to decrease monotonically from superior to inferior positions. The ultimate pullout strength, and subsequently the fatigue life, of both types of suture anchors depended directly on cortical thickness. The significantly lower performance of both anchors when placed inferiorly emphasizes the importance of correct anchor selection, number, and placement in this region. All anchors settled during the first 10 to 100 cycles, resulting in partial exposure of the implant. Intraoperative cycling of the anchors before suture tying may be necessary to achieve complete settling and prevent subsequent loss of coaptation between capsule and glenoid. The study shows that for the anchors to last 1,000 cycles or more, less than 50% of the theoretical ultimate pullout strength should be applied cyclically. With aggressive early rehabilitation exercises, this significant decrease in fixation strength could shift reconstruction failure from suture breakage or soft tissue tearing to anchor pullout.

The relationship between passive joint laxity and functional outcome after anterior cruciate ligament injury.

Twenty patients with anterior cruciate ligament-deficient knees were studied. Ten patients returned to all sports activities (compensators) and 10 patients were not improved with nonoperative management and required surgical stabilization (noncompensators). Joint laxity was measured using a KT-2000 arthrometer (manual maximum Lachman). Subjects completed a Lysholm questionnaire and Knee Outcome Score. The International Knee Documentation Committee form was also completed. Patients also rated their knee function on a scale of 1 to 100. There was no difference in level and frequency of athletic activity between the two groups before their anterior cruciate ligament injuries as determined by the knee outcome score. The compensator group had a mean side-to-side difference of 3.25 mm at 89 N and the noncompensators had a mean difference of 3 mm preoperatively. Manual maximum tests gave side-to-side differences of 6.7 mm for the compensators and 6 mm for the noncompensators. There were no differences in laxity measures between groups. The correlation between knee outcome scores and side-to-side laxity measurements were not significant. Measurements of anterior laxity in anterior cruciate ligament-deficient patients were not correlated with measures of functional outcome used in this study. Functional outcome measurements that are partially based on joint laxity measures, such as the International Knee Documentation Committee form, may artificially overestimate the disability after anterior cruciate ligament rupture.

Fatigue properties of suture anchors in anterior shoulder reconstructions: Mitek GII.

Suture anchors have simplified anterior capsule labral reconstruction. During rehabilitation the shoulder goes through many repetitions of range of motion exercises. These exercises will repetitively submaximally load the anchor and in theory should reduce the pullout strength of the suture anchor. No published reports exist on the fatigue strengths and properties of one of the most commonly used anchors: Mitek GII suture anchors. Fifty trials of cyclic submaximal load were done on 22 cadaveric glenoids with an average age of 66.8 years (range, 40 to 90 years). At two to three different sites on the same specimen, the anchors were inserted according to manufacturer's specifications. The anchors were tested to failure on a Instron 1331 servohydraulic mechanical testing system at 2 Hertz sinusoidal loading pattern using steel sutures and a predetermined load. There were 22 (44%) tests performed in the superior quadrant and 28 (56%) tests in the inferior quadrant. All anchors pulled out, and no wires broke. There were statistically significant differences between the superior and inferior portion of the glenoid with regard to number of cycles to failure at a given maximum load. The anchors underwent an average of 6,220 cycles before pullout at an average load of 162 N (SD = 73 N). In the superior quadrant, the average ultimate pullout strength was 237 N (SD = 42 N), whereas in the inferior quadrant the average ultimate pullout strength was 126 N (SD = 36 N). Hence, the ultimate pullout strength of the Mitek GII anchor was significantly higher (P < .002) in the superior quadrant than in the inferior quadrant. Using a least squares regression analysis, it was possible to predict the fatigue life of the superiorly and inferiorly placed suture anchors over a wide range of cycles. The R-squared values for trendlines showed good reliability (superior R2 = 0.55; inferior R2 = 0.28). The fatigue life curves for the two different quadrants were normalized using the ultimate pullout strength. This new, universal curve predicts the fatigue life of the Mitek GII anchor as a percentage of the ultimate pullout strength for any selected location. For a clinically relevant number of cycles, no more than approximately 40% to 50% of the ultimate pullout strength of the suture anchor can be cyclically applied to the anchor to guarantee a life for the duration of rehabilitation. For the entire system, the inferiorly placed anchors dictate the amount of cyclically applied load the system can experience without failing, and rehabilitation should be adjusted accordingly.

How much does inferior capsular shift reduce shoulder volume?

The purpose of this study was to quantitate the effect of inferior capsular shift on shoulder volume. Four fresh frozen cadaveric shoulders were analyzed. Volume before and after shift was determined using 3 techniques: (1) Magnetic resonance imaging sequences were digitized to computer and analyzed for volume via a 35-mm camera using Cue 2 software. The capsule was delineated by contrast between light and dark regions. Volume was calculated by summing the total area of respective slices. (2) Ultrasound images, obtained after surgical exposure of the capsule, were digitized. Volume was calculated using the formula for a prolate ellipsoid. (3) An 18-gauge needle was used to inject and evacuate saline via an anterior approach. Quantity of aspirated fluid provided a direct measure of volume. Inferior capsular shift was performed. After the operation, measurements were repeated. Inferior capsular shift reduced volume in all shoulders with each technique. On average, inferior capsular shift reduced joint volume by 57 %). A measurable reduction in shoulder joint volume is an effect of capsular shift. This measurement may have clinical application if volume is an indicator of instability or laxity.

Clinical and roentgenographic evaluation of hydroxyapatite-augmented and nonaugmented porous total hip arthroplasty.

Sixty osteoarthritic patients undergoing primary, uncemented total hip arthroplasty were matched for age and weight and randomized into one of four groups with respect to implant coating and postoperative, protected weight-bearing status: group 1, hydroxyapatite-augmented, 12 weeks; group 2, nonaugmented, 12 weeks; group 3, hydroxyapatite-augmented, 6 weeks; and group 4, nonaugmented, 6 weeks. Tantalum spheres were implanted periprosthetically into the femur at the time of the arthroplasty, thus providing constant references for stereoscopic radiographs. Patients were then evaluated over a 2-year period with clinical examination, plain radiography, and roentgen stereophotogrammetric analysis. Clinical evaluation using the Charnley scoring system showed no significant preoperative or postoperative intergroup differences, whereas visual analog testing noted less thigh pain with hydroxyapatite-augmented stems at the 12-week and 6-month follow-up evaluations. Plain radiographic analysis produced no significant differences, with no instability detected, and bony ingrowth was uniform in all groups. Stereographic evaluation showed migration in all groups, but there were no significant differences between the augmented and nonaugmented stems or the 6-week and 12-week partial weight-bearing protocols. Charnley, plain radiographic, and stereogrammetric evaluations all suggest that migration is unaltered by enhanced surfaces and early, unprotected weight bearing does not jeopardize implant fixation regardless of coating design. The lower incidence of visual analog thigh pain with the hydroxyapatite-augmented stems, however, may be a reflection of bony ingrowth and, as such, add some validity to the theoretic advantages of enhanced surface prostheses.

An electromyographic analysis of the knee during functional activities. I. The normal profile.

This study describes the fine-wire electromyographic profile of the normal knee. Twenty-two subjects with no prior history of knee injury volunteered for the study. Each subject had fine-wire electromyographic evaluation of 8 muscles (vastus medialis oblique, vastus lateralis, rectus femoris, semimembranosus, biceps femoris, tibialis anterior, gastrocnemius, and soleus muscles) while performing 7 functional activities. The percentage of maximum manual test for each muscle during each phase of the activities was used to determine means and standard deviations for the group. Walking and ramp and stair ascending and descending produced similar electromyographic profiles. Running and cross-cutting demonstrated unique electromyographic profiles with an overall higher muscle activity than the previous 5 activities. A quadriceps-hamstrings muscles' coordinated response was identified consistently in each activity. These findings illustrate the integral nature of each of the 8 examined muscles in knee motion. Furthermore, this study demonstrates a coordinated response of quadriceps-hamstrings muscles in the normal knee and may more thoroughly define the coordinated activity of these 2 antagonist muscle groups. Finally, this study provides a framework within which various knee conditions can be compared and from which specific rehabilitation recommendations can be generated.

An electromyographic analysis of the knee during functional activities. II. The anterior cruciate ligament-deficient and -reconstructed profiles.

This study compared the electromyographic activity of normal (N = 22), rehabilitated anterior cruciate ligament-deficient (N = 8), and -reconstructed knees (N = 10) while subjects performed activities. Each subject had evaluation of 8 muscles during 7 functional activities. Sixty-seven percent of the differences in the quadriceps muscle reflected increased activity in the vastus lateralis muscle of the rehabilitated group; 75% of the differences in the hamstrings muscles noted increased biceps femoris muscle activity in the rehabilitated group; 56% of the differences in the lower leg musculature showed increased tibialis anterior muscle activity in the rehabilitated group. Eighty-six percent of the statistically different intervals involved rehabilitated subjects demonstrating increased activity over reconstructed or normal subjects or both. The presence of a quadriceps-hamstrings muscles coordinated response was identified consistently in all 3 groups in each activity. This study supports surgical reconstruction for the anterior cruciate ligament-deficient knee. It also demonstrates the importance of the vastus lateralis, biceps femoris, and tibialis anterior musculature in the rehabilitation of the anterior cruciate ligament-deficient patient. The presence of a quadriceps-hamstrings muscles coordinated response indicates that mechanoreceptors mediating this reflex arc exist in structures other than the cruciate ligament.

Non-operative treatment of ruptures of the anterior cruciate ligament in middle-aged patients. Results after long-term follow-up.

We retrospectively reviewed the records of fifty-two patients who had had a rupture of the anterior cruciate ligament between the ages of forty and sixty years, to determine the results of aggressive non-operative treatment. We were able to locate and re-examine thirty of these patients (mean age, forty-six years) after a mean duration of follow-up of seven years (range, five to thirteen years), and to assess the clinical, radiographic, and functional results. The mean score, according to the scale of Lysholm and Gillquist, was 82 points; eight of the eleven patients who had combined ligamentous injuries had a score of less than 84 points (symptoms with daily activities). Thirteen substantial reinjuries had occurred in eleven patients (37 per cent) during the follow-up period. Twenty-nine patients (97 per cent) had a grade-2 or 3 Lachman test, and a positive pivot-shift test was elicited in twenty-five patients (83 per cent). Plain radiographs revealed minimum or no changes in twenty-six patients (87 per cent). Magnetic resonance imaging in nine patients revealed scarring of the remnant of the anterior cruciate ligament to the posterior cruciate ligament in six. The mean difference in anterior-posterior laxity between the injured knee and the normal, contralateral knee, as measured with the KT-1000 arthrometer, was five millimeters at twenty pounds (eighty-nine newtons). Twenty-five (83 per cent) of these thirty middle-aged patients, who had had guided rehabilitation and had modified activity, had a satisfactory outcome without an operation. However, a few patients, who had combined instabilities and who wished to resume competitive sports activity that required pivoting, were dissatisfied. Such patients may need operative reconstruction to achieve their goals.

Clinical and roentgenographic evaluation of hydroxyapatite-coated and uncoated porous total hip arthroplasty: a preliminary report.

Sixty osteoarthritic patients undergoing primary uncemented total hip arthroplasty were matched for age and weight and randomized into one of four groups with respect to implant coating and postoperative protected weight-bearing status: group 1, hydroxyapatite, 12 weeks; group 2, uncoated, 12 weeks; group 3, hydroxyapatite, 6 weeks; group 4, uncoated, 6 weeks. Tantalum spheres were implanted periprosthetically into the femur at the time of arthroplasty, thus providing constant references for stereoscopic radiographs. Patients were then evaluated over a 1-year period with clinical examination, plain radiography, and roentgen stereophotogrammetric analysis (RSA). Clinical evaluation using Charnley scoring showed no significant preoperative or postoperative intergroup differences, whereas visual analog testing noted less thigh pain with hydroxyapatite-coated stems at 12 weeks and 6 months follow-up. Plain radiographic analysis produced no significant differences, with no instability detected and bony ingrowth noted uniformly in all groups. The preliminary stereographic evaluation showed migration in all groups, but there were no significant differences between coated and uncoated stems or 6-week and 12-week partial weightbearing protocols. The Charnley, plain radiographic, and preliminary stereogrammetric evaluations all suggest that migration is unaltered by enhanced surfaces and that early unprotected weightbearing does not jeopardize implant fixation regardless of coating design. The lower incidence of visual analog thigh pain with the hydroxyapatite-coated stems, however, may be a reflection of bony ingrowth and as such add some validity to the theoretical advantages of enhanced surface prostheses.