Ralph B. Blasier

A standardized method for assessment of elbow function

The American Shoulder and Elbow Surgeons have adopted a standardized form for assessment of the elbow. This form was developed by the Research Committee of the American Shoulder and Elbow Surgeons and subsequently adopted by the membership. The patient self-evaluation section contains visual analog scales for pain and a series of questions relating to function of the extremity. The responses to the questions are scored on a 4-point ordinal scale. The physician assessment section has 4 parts: motion, stability, strength, and physical findings. It is hoped that adoption of this method of data collection will stimulate multicenter studies and improve communication between professionals who assess and treat patients with elbow disorders.

The Effects of Muscle Fatigue on Shoulder Joint Position Sense

Proprioception, or joint position sense, probably plays an important role in shoulder joint function. In this study, we assessed the effect of muscle fatigue on shoulder proprioception in 20 volunteers with no shoulder abnormalities. Shoulder proprioception was measured as the threshold to first detection of humeral rotation with the joint at 90° of abduction and 90° of external rotation. Subjects were tested while rested, exercised on a isokinetic testing machine until fatigued, and then retested in an identical fashion. Both shoulders were tested, and the order of dominant and non-dominant shoulder was randomized. Shoulder proprioception was analyzed for its dependence on arm dominance, direction of rotation, and muscle fatigue. Subjects detected external rotation after significantly less movement than they did internal rotation. Overall, before exercise, motion was detected after a mean of 0.92° of rotation. After exercise, this threshold to detection of movement increased to 1.59°, an increase of 73%. This significant increase occurred with both internal and external rotation. The decrease in proprioceptive sense with muscle fatigue may play a role in decreasing athletic performance and in fatigue-related shoulder dysfunction. It remains to be determined if training can lessen this loss in position sense.

Posterior Glenohumeral Subluxation: Active and Passive Stabilization in a Biomechanical Model*

We examined the role of the glenohumeral and coracohumeral ligaments as well as the forces provided by the rotator cuff muscles, the long head of the biceps, the anterior and middle deltoids, and the pectoralis major in the stabilization of the glenohumeral joint in the posterior direction. Simulated muscle forces were mechanically applied to eight shoulder specimens. The humeroscapular position for testing simulated the 90-degree forward-flexion (humerothoracic) position used clinically for the so-called jerk test, which is the most clinically important position with regard to posterior instability of the shoulder. Experiments were performed with a variety of configurations of ligamentous and capsular cuts, humeral rotation, and levels of muscle force. Stability was investigated by measuring the force required to subluxate the humeral head a specified amount from its reduced position. Of the muscles and ligaments tested, the subscapularis muscle contributed the most to this subluxation force. The coracohumeral ligament was an effective contributor in neutral humeral rotation, and the inferior glenohumeral ligament was an effective contributor in internal humeral rotation. The long head of the biceps was found to reduce the subluxation force in certain positions. CLINICAL RELEVANCE: It is widely agreed that a complex interaction of passive and active stabilizing structures and forces is necessary for clinical stability of the shoulder. The present study identified the contributions of ligaments and muscles to posterior stability of the shoulder in the position of greatest clinical importance—posterior subluxation with the shoulder in forward flexion.

Anterior shoulder stability: Contributions of rotator cuff forces and the capsular ligaments in a cadaver model

The purpose of this study was to quantify in a biomechanical model the contributions to shoulder joint stability that are made by tensions in the four tendons of the rotator cuff and by static resistance of defined portions of the capsular ligaments. A materials testing machine was used to directly determine anterior joint laxity by measurement of the force required to produce a standard anterior subluxation. Shoulders were tested in external or neutral humeral rotation. Data were analyzed by multiway analysis of variance with regression analysis. This model simulated tensions in the rotator cuff musculature by applying static loads at the tendon insertion sites acting along the anatomic lines of action. A load in any of the cuff tendons resulted in a measurable and statistically significant contribution to anterior joint stability. The contributions between different tendons were not significantly different and did not depend on the humeral rotation (neutral or external). In neutral humeral rotation the superior and middle glenohumeral ligaments together function equally with the inferior glenohumeral ligament as primary stabilizers against anterior humeral translation. The posterior capsule is a secondary stabilizer. The external rotation of the abducted humerus increases anterior stability by more than doubling the stability contribution from the inferior glenohumeral ligament. The stability contribution from the posterior capsule is larger in external rotation than in neutral rotation but is still of secondary magnitude. In external rotation the stability contribution of the anterior capsule, including the superior glenohumeral ligament and the middle glenohumeral ligament, becomes insignificant. The model presented here simulates the combined effect of two major sources of shoulder stability. This versatile model permits the direct measurement of the contributions to anterior shoulder stability that are made by tensions in the rotator cuff tendons and by static resistance of defined capsular zones. The use of multiple regression analysis-a standard statistical technique but one relatively new to the orthopaedic literature-permits quantitative determination of the contribution of each independent variable to the dependent variable, shoulder stability.

Efficacy and Safety of Enoxaparin to Prevent Deep Venous Thrombosis after Hip Replacement Surgery

Enoxaparin is a low-molecular-weight heparin with an average molecular weight of 4500 daltons that is obtained by controlled depolymerization of standard unfractionated porcine intestinal mucosal heparin (average molecular weight, 15 000 daltons) [1]. Enoxaparin and unfractionated heparin inhibit clotting indirectly by accelerating the formation of irreversible complexes between antithrombin III and several activated clotting factors, including factors IIa and Xa [2, 3]. Enoxaparin has several biological properties that differ from those observed in unfractionated heparin. In animal models, prevention of venous thrombosis by equipotent dosage regimens of enoxaparin or unfractionated heparin had equivalent antithrombotic activity. However, reduced hemorrhage was observed with enoxaparin [4, 5]. In in vitro studies, enoxaparin at concentrations with equivalent anti-factor Xa activity had four times less anti-factor IIa activity compared with unfractionated heparin [2, 3, 6]. Furthermore, in contrast to unfractionated heparin, enoxaparin had reduced interactions with platelets and plasma proteins in ex vivo experiments [7, 8]. Enoxaparin also has pharmacologic properties that are advantageous compared with unfractionated heparin. Administered intravenously, the half-life of enoxaparin was four times greater than that of unfractionated heparin (4.4 hours compared with 0.35 hours) [9, 10]. Its bioavailability after subcutaneous injection was more than 90% compared with 29% for unfractionated heparin [10]. These characteristics give enoxaparin potential clinical advantages, including a more predictable dose response and a reduced frequency of administration. Deep venous thrombosis and pulmonary embolism occur frequently in patients having total hip replacement surgery. Deep venous thrombosis has been observed in 40% to 70%, asymptomatic pulmonary embolism in as many as 25%, symptomatic pulmonary embolism in 4% to 19%, and fatal pulmonary embolism in as many as 6.7% of these patients [11-16]. Previous clinical trials showed that it was effective and safe for preventing deep venous thrombosis in patients having total hip replacement when administered after [17, 18] or before surgery [19]. A substantial risk reduction (71%) without an increase in hemorrhage was observed in the incidence of proximal and distal deep venous thrombosis in patients who had total hip replacement and were given 30 mg of enoxaparin subcutaneously after surgery every 12 hours for as long as 14 days, compared with patients who received placebo [17]. Although this study showed the efficacy of enoxaparin administered after surgery, it did not determine an optimum dose or satisfactorily define the drugs safety profile because only one enoxaparin dosing regimen was tested and too few patients were studied. Our dose-ranging study was done to compare the efficacy and safety of three postoperative enoxaparin dose regimens to prevent deep venous thrombosis in patients having total hip replacement surgery. It was designed to identify a clinically effective dose of enoxaparin with a minimal risk for hemorrhagic complications. We compared subcutaneous postoperative administration of 10 mg of enoxaparin once daily, 40 mg of enoxaparin once daily, and 30 mg of enoxaparin every 12 hours. Methods Study Design This multicenter study was conducted as a randomized, double-blind, parallel-group clinical trial, with 32 institutions participating. The protocol and informed consent forms were approved by each centers institutional review board. Patients All patients gave written informed consent before entering the study. Men and women who were 31 years or older and were scheduled for hip replacement surgery, including primary and revision procedures, were eligible. Revision procedures included revision of the acetabular component, the femoral component, or both components. Noninvasive vascular examinations, including strain gauge or impedance plethysmography, Doppler sonography, and duplex or b-mode ultrasonography, were done within 14 days before surgery to provide baseline information and to exclude patients with identifiable deep venous thrombosis. Patients excluded from the study were women with child-bearing potential and patients who had ipsilateral hip surgery within 3 months. Other exclusion criteria included a history of deep venous thrombosis, pulmonary embolism, or both; heparin-associated thrombocytopenia; hemorrhagic disorders; allergy to heparin, protamine sulfate, or radiocontrast agents; eye, spinal cord, or nervous system surgery within 3 months; active ulcerative disease of the alimentary tract; uncontrolled hypertension; or use of nonsteroidal anti-inflammatory agents during the 4 days before surgery. Enrollment began in December 1988 and continued through September 1990. Dosing Schedule The efficacy and safety of three enoxaparin (Rhone-Poulenc Rorer Pharmaceuticals, Collegeville, Pennsylvania) dose schedules were compared: 10 mg once daily, 40 mg once daily, and 30 mg every 12 hours. All doses of study medication were administered by subcutaneous injection. The first dose of study medication was administered within 24 hours after surgery, and the drug was continued for as long as 7 days. Evaluations and Scheduling The primary assessment for deep venous thrombosis was bilateral contrast venography performed on day 7 of treatment, earlier if clinically indicated, or on discharge from the hospital. Institutional physicians who were unaware of patient treatment assignment interpreted venograms and noninvasive vascular examinations. Additional assessments included daily clinical evaluations and noninvasive vascular examinations on treatment days 4 and 7 or as clinically indicated. Clinical evidence of venous thromboembolic disease was defined as documented treatment of clinically evident or symptomatic deep venous thrombosis or pulmonary embolism. Clinical Analysis The primary determinant of efficacy was the incidence of deep venous thrombosis as determined by venography, noninvasive vascular examinations, and clinical evidence. Clinical evidence included reported deep venous thrombosis or pulmonary embolism as an adverse event or the occurrence of symptoms and signs of venous thromboembolic diseases and associated therapy. The primary study conclusions for efficacy and safety outcomes were based on an analysis of all treated patients that included all patients who received at least one dose of study medication [20]. In addition, efficacy was analyzed for evaluable patients, those who received at least 75% of study medication, had adequate bilateral venography, and completed the study with no protocol violation. The primary determinants of safety were the incidence of major and minor hemorrhagic episodes, a decrease in hemoglobin of 20 g/L (2 g/dL) or more compared with the postoperative predose value, hemoglobin values less than 80 g/L (8 g/dL), clinically significant abnormal laboratory results, the number of transfusions required, and the occurrence of serious adverse events. Serious adverse events included death, life-threatening events, and events that resulted in prolonged hospitalization. A major hemorrhagic episode was overt hemorrhage associated with one or more of the following: death or a life-threatening clinical event; acute myocardial infarction or stroke; retroperitoneal or intracranial hemorrhage; postoperative transfusion of more than two units of packed red blood cells (excluding autologous blood); or a decrease of 20 g/dL or more in hemoglobin that was directly attributable to the overt hemorrhagic episode. A minor hemorrhagic episode was an overt hemorrhagic episode that did not meet criteria for classification as major. Interim Analysis Our study was changed from a three-arm to a two-arm trial on 11 May 1990 as a result of a blinded interim analysis conducted in March 1990. The analysis was done on 305 patients and resulted in the discontinuation of a treatment group identified only as A because of the high rate of treatment failure observed in that group. The study blinding was not broken when treatment group A was discontinued. Treatment group A was revealed to be the group receiving 10 mg of enoxaparin when the blinding was formally broken. Because of the smaller number of patients recruited into the group receiving 10 mg, the precision of the estimated incidence of deep venous thrombosis in that group was not as high as that for the other two treatment groups. Statistical Analysis The study population required was determined before initiation and assumed deep venous thrombosis rates of 25% in the group receiving 10 mg of enoxaparin once daily and 12.5% in groups receiving 40 mg once daily and 30 mg every 12 hours. Approximately 195 patients were required per treatment group to achieve 80% power when using a two-tailed test at a significance level of 0.05. Patients were assigned to treatment groups in a 1:1:1 ratio in blocks of six, using a computer-generated randomization schedule. A two-way logistic regression model, including factors for treatment group and center, was used to compare the treatment. Significance testing was done at the 0.025 level based on a Bonferroni correction for the two primary comparisons, 10 mg of enoxaparin once daily compared with 40 mg enoxaparin once daily and 30 mg every 12 hours, respectively [21]. The P values for these comparisons were multiplied by a factor of two to reflect the Bonferroni adjustment. Significance testing between the group receiving 30 mg of enoxaparin every 12 hours and that receiving 40 mg once daily was done at the 0.05 level of significance without Bonferroni adjustment. The incidence of treatment failure was summarized by treatment group in patient subpopulations defined by 1) demographic characteristics [age, sex, and race]; 2) type of surgery [primary or revision arthroplasty]; 3) type of anesthesia; or 4) use of acrylic bone cement and graduated compression stocki

Active and passive factors in inferior glenohumeral stabilization: a biomechanical model.

This study examines the stabilizing factors of the glenohumeral joint against inferior translation over a range of subluxations. Factors examined included the glenohumeral capsular ligaments, the coracohumeral ligament, the rotator cuff forces, and the long head of the biceps force. Simulated muscle forces were applied to eight shoulder specimens with the arm near 0 degrees abduction. Stability was defined as the force required to inferiorly sublux the joint to a specified translation from the centered position and was evaluated under varying configurations of capsule cuts, humeral rotation, and muscle loads. The supraspinatus and biceps muscle forces were found to be important active stabilizers. Thus, tension in the long head of the biceps did not tend to depress the humeral head. The inferior glenohumeral ligament was an important passive stabilizer in external rotation. Understanding the effects of these factors adds insight into the underlying biomechanics of clinical shoulder instability.

The mechanism of creation of superior labrum, anterior, and posterior lesions in a dynamic biomechanical model of the shoulder: The role of inferior subluxation

Lesions of the superior glenoid labrum are a source of shoulder disease. However, the mechanisms of injury to this region are unknown, and controversy exists regarding the role of shoulder instability in creation of this lesion. With a cadaver model that simulates physiologic rotator cuff forces and produces traction on the biceps tendon, the creation of type II superior labrum, anterior, and posterior (SLAP) lesions and the role of glenohumeral subluxation were investigated: Left and right shoulders from each of 8 paired cadavers (age 62 +/- 7.2 years, 5 male and 3 female) were randomized to be tested in either a 20 mm inferiorly subluxed position or in a reduced position. The long head of the biceps tendon was held near the musculotendinous junction with a novel cryogenic clamp. Traction on the long head of the biceps tendon was applied at a fast rate of 12.7 cm/sec with a servohydraulic testing machine. A load cell was used to monitor the biceps tendon load. After testing to failure, the presence or absence of a type II SLAP lesion was determined by 2 experienced shoulder surgeons masked to the test group. The production of type II SLAP lesions differed significantly (P = .03) between reduced shoulders (2 SLAP lesions out of 8 tests) and the shoulders with inferior subluxation (7 SLAP lesions out of 8 tests). This experiment has shown that traction on the biceps tendon in this biomechanical model can reproducibly create type II SLAP lesions, and inferior subluxation facilitates the generation of such lesions.

Fractures of the acromion process: A proposed classification system

Summary: A review of 27 fractures of the acromion process during a 15-year period revealed five distinct types that were classified into three groups. Stress fractures are rare, do not result from acute trauma, and gain little benefit from nonoperative treatment. Type I fractures are minimally displaced. Type IA fractures are avulsion fractures and heal rapidly. Type IB fractures result from direct trauma to the extremity, and are minimally displaced. Most heal with nonoperative treatment. Type II fractures are displaced laterally, superiorly or anteriorly and do not reduce the subacromial space. Most are pain free with full motion after 6 weeks of nonoperative treatment. Type III fractures reduce the subacromial space. This may occur by an inferiorly displaced acromion fracture, or an acromion fracture associated with an ipsilateral, superiorly displaced glenoid neck fracture. Patients in this group sustained significant trauma to the involved extremity. All type III fractures treated nonoperatively develop significant limited shoulder motion with pain, suggesting that early surgical intervention may be indicated.

Ligamentous Restraints to External Rotation of the Humerus in the Late-Cocking Phase of Throwing: A Cadaveric Biomechanical Investigation

The late-cocking phase of throwing is characterized by extreme external rotation of the abducted arm; repeated stress in this position is a potential source of glenohumeral joint laxity. To determine the ligamentous restraints for external rotation in this position, 20 cadaver shoulders (mean age, 65 16 years) were dissected, leaving the rotator cuff tendons, coracoacromial ligament, glenohumeral capsule and ligaments, and coracohumeral ligament intact. The combined superior and middle glenohumeral ligaments, anterior band of the inferior glenohumeral ligament, and the entire inferior glenohumeral ligament were marked with sutures during arthroscopy. Specimens were mounted in a testing apparatus to simulate the late-cocking position. Forces of 22 N were applied to each of the rotator cuff tendons. An external rotation torque (0.06 N m/sec to a peak of 3.4 N m) was applied to the humerus of each specimen with the capsule intact and again after a single randomly chosen ligament was cut (N 5 in each group). Cutting the entire inferior glenohumeral ligament resulted in the greatest increase in external rotation (10.2° 4.9°). This was not significantly different from sectioning the coracohumeral ligament (8.6° 7.3°). The anterior band of the inferior glenohumeral ligament (2.7° 1.5°) and the superior and middle glenohumeral ligaments (0.7° 0.3°) were significantly less important in limiting external rotation.

Interlocking intramedullary nailing of pathological fractures of the shaft of the humerus

We performed a retrospective study of thirteen patients who had had sixteen pathological fractures of the shaft of the humerus secondary to metastatic disease. All but one fracture was stabilized with interlocking intramedullary nailing with use of a closed technique. The mean operative time for the sixteen procedures was ninety-two minutes (range, fifty to 180 minutes), the mean blood loss was 116 milliliters (range, fifty to 200 milliliters), and the mean duration of hospitalization was five days (range, two to ten days). Fourteen extremities had a return to nearly normal function within three weeks after nailing. Relief of pain was rated as good or excellent in all but one patient. Eleven patients (fourteen humeri) received radiation therapy at a mean of seven days (range, three to fourteen days) after the operation. Nine patients died at a mean of four months (range, one to twelve months) postoperatively; the remaining four patients were still alive at a mean of ten months (range, nine to fifteen months). There were no problems related to the wound, deep infections, nerve palsies, or failures of the implant. The fracture was united in all seven of the eleven extremities in patients who survived for at least three months and had radiographs available. Interlocking intramedullary nailing of the humerus for pathological fractures provides immediate stability and can be accomplished with a closed technique, brief operative time, and minimum morbidity, with a resultant early return of function to the extremity.