The structure and mechanics of the cell cortex depend on the location and adhesion state.

Cells exist in different phenotypes and can transition between them. A phenotype may be characterized by many different aspects. Here, we focus on the example of whether the cell is adhered or suspended and choose particular parameters related to the structure and mechanics of the actin cortex. The cortex is essential to cell mechanics, morphology, and function, such as for adhesion, migration, and division of animal cells. To predict and control cellular functions and prevent malfunctioning, it is necessary to understand the actin cortex. The structure of the cortex governs cell mechanics; however, the relationship between the architecture and mechanics of the cortex is not yet well enough understood to be able to predict one from the other. Therefore, we quantitatively measured structural and mechanical cortex parameters, including cortical thickness, cortex mesh size, actin bundling, and cortex stiffness. These measurements required developing a combination of measurement techniques in scanning electron, expansion, confocal, and atomic force microscopy. We found that the structure and mechanics of the cortex of cells in interphase are different depending on whether the cell is suspended or adhered. We deduced general correlations between structural and mechanical properties and show how these findings can be explained within the framework of semiflexible polymer network theory. We tested the model predictions by perturbing the properties of the actin within the cortex using compounds. Our work provides an important step toward predictions of cell mechanics from cortical structures and suggests how cortex remodeling between different phenotypes impacts the mechanical properties of cells.

Spontaneous motility of passive emulsion droplets in polar active gels.

We study by computer simulations the dynamics of a droplet of passive, isotropic fluid, embedded in a polar active gel. The latter represents a fluid of active force dipoles, which exert either contractile or extensile stresses on their surroundings, modelling for instance a suspension of cytoskeletal filaments and molecular motors. When the polarisation of the active gel is anchored normal to the droplet at its surface, the nematic elasticity of the active gel drives the formation of a hedgehog defect; this defect then drives an active flow which propels the droplet forward. In an extensile gel, motility can occur even with tangential anchoring, which is compatible with a defect-free polarisation pattern. In this case, upon increasing activity the droplet first rotates uniformly, and then undergoes a discontinuous nonequilibrium transition into a translationally motile state, powered by bending deformations in the surrounding active medium.

Glenohumeral osteoarthrosis. A late complication of the Putti-Platt repair.

Osteoarthrosis of the glenohumeral joint is a potential late complication of anterior Putti-Platt capsulorrhaphy. In ten patients (eleven shoulders), disabling pain in the shoulder began an average of 13.2 years after a Putti-Platt repair that had been done for recurrent anterior unidirectional instability. In all of the patients, the osteoarthrosis of the glenohumeral joint resulted in substantial limitation of motion. Seven shoulders were successfully treated non-operatively, and a technique of anterior release was successful in four shoulders.

Atlanto-axial rotatory fixation. (Fixed rotatory subluxation of the atlanto-axial joint).

In seventeen cases of irreducible atlanto-axial rotatory subluxation (here called fixation), the striking features were the delay in diagnosis and the persistent clinical and roentgenographic deformities. All patients had torticollis and restricted, often painful neck motion, and seven young patients with long-standing deformity had flattening on one side of the face. The diagnosis was suggested by the plain roentgenograms and tomograms and confirmed by persistence of the deformity as demonstrated by cineroentgenography. Treatment included skull traction, followed by atlanto-axial arthrodesis if necessary. Of the thirteen patients treated by atlanto-axial arthrodesis, eleven had good results, one had a fair result, and one had not been followed for long enough to determine the result. Of the remaining four patients, one treated conservatively had not been followed for long enough to evaluate the result, two declined surgery, and one died while in traction as the result of cord transection produced by further rotation of the atlas on the axis despite the traction.

The three-part fracture of the proximal part of the humerus. Operative treatment.

A retrospective review of the cases of fifteen patients with a three-part fracture of the proximal part of the humerus is presented. Fourteen of the fractures were treated with tension-band wiring and one, with an AO buttress plate. The patients were evaluated for pain, range of motion, strength, and function of the involved shoulder and the radiographic result at an average of fifty-four months after the injury. At follow-up, the shoulders had an average of 126 degrees of active elevation, 29 degrees of active external rotation, 81 degrees of active abduction, and internal rotation to the second lumbar vertebra. The only early complication was failure of fixation in the patient who had been treated with a buttress plate. In two patients, radiographic evidence of avascular necrosis of the humeral head later developed, and one of them required revision to a hemiarthroplasty. In conclusion, we recommend operative treatment for the healthy, active individual who has a three-part fracture of the proximal part of the humerus. We found that the best results with these difficult fractures are obtained using tension-band wiring.

Recurrent posterior instability (subluxation) of the shoulder.

A retrospective survey of fifty shoulders in thirty-five patients with recurrent posterior instability revealed generally poor results of treatment, particularly of operative treatment. Only eleven of the shoulders had a primary traumatic insult as the event initiating the instability. Although forty-one of the affected shoulders demonstrated voluntary instability, it was the associated involuntary, unintentional instability of these shoulders that prompted the patients to seek medical attention. Pain and functional impairment relating to work and to the activities of daily living were not significant in most of these patients. The results of surgical reconstruction were generally poor, the recurrence rate was 50 per cent (thirteen of twenty-six shoulders), and there were complications in five of the twenty-six shoulders that had been operated on. Attention is drawn to the complication of degenerative osteoarthritis that is associated with posterior glenoid osteotomy. We advise care in the selection of patients for surgical reconstruction.

Surgery for full-thickness rotator-cuff tears.

We reviewed the cases of 100 patients who were operated on for a tear of the rotator cuff and found significant improvements in pain in all of them and in function in the majority of patients. The size of the cuff tear did not significantly affect the results, although patients with a smaller tear tended to fare slightly better.

Release of the subscapularis for internal rotation contracture and pain after anterior repair for recurrent anterior dislocation of the shoulder.

Ten patients who had an internal rotation contracture and pain after an anterior repair for recurrent dislocation of the shoulder were treated by release of the subscapularis muscle. For six of the patients, radiographs demonstrated severe osteoarthrotic changes in the shoulder as well. The release was done an average of eleven years after the original procedure, which, for most patients, had been a Putti-Platt repair. After release of the subscapularis, each patient had less pain in the shoulder and an average increase of 27 degrees of external rotation. Release of the subscapularis can offer relief of pain and of functional limitations associated with the symptoms caused by an internal rotation contracture after an anterior repair of the shoulder.

Spine fusion for atlanto-axial instability.

A follow-up study was done on fifty-seven spine fusions for atlanto-axial instability, classified as Type I - deficient odontoid (twenty-eight patients), Type II - deficient ligaments (twenty-three patients), and Type III - rotatory fixation (six patients). The average age of the patients at the time of the fusion was thirty years, and half had had significant trauma. Symptoms had been present for an average of 12.3 months before fusion. Preoperatively pain was the predominant complaint in twenty-nine; neurological complaints, in twenty-four; and instability in the rest. Of the forty-six Gallie fusions, there was one non-union and of the eleven occipitocervical fusions, two non-unions. Follow-up averaging 4.2 years revealed resolution of symptoms in almost all patients.

Os Odontoideum.

A review of the cases of thirty-five patients with os odontoideum, the largest series reported to date, supports the concept that trauma is the etiology of the abnormality. Most of the patients had roentgenographic instability of the affected spinal segment, and were treated with spine fusion. Eleven patients had lesions attributable to injuries received before they were four years old, although surgical treatment usually was delayed for one to eight years. Nine patients had documented roentgenographic evidence of a normal odontoid process prior to the development of the os odontoideum. Only one-third of the patients had any signs or symptoms indicative of neural deficits, although most patients had cervical pain. Surgical treatment alleviated the pain and instability.

Locked posterior dislocation of the shoulder.

Of forty patients with forty-one locked posterior dislocations of the shoulder, the diagnosis had been missed by the initial physician in the majority. A motor-vehicle accident, a seizure, an alcohol-related injury, or electroshock therapy had caused the dislocation in these patients, and the average interval from injury to diagnosis was one year. Twenty-five of the forty-one dislocations had been diagnosed in less than six months. An axillary radiograph confirmed the diagnosis in all shoulders and demonstrated the approximate size of the impression defect. There were no associated displaced fractures of the humerus, but in twenty of the shoulders there was an undisplaced fracture of the proximal part of the humerus. The average length of follow-up was 5.5 years. For seven shoulders the deformity was accepted. Treatment in the others consisted of closed reduction, which was attempted in twelve shoulders and was successful in six of the twelve; transfer of the subscapularis tendon, which was attempted in nine shoulders and was successful in four; transfer of the lesser tuberosity, which was successful in all four shoulders that were so treated; hemiarthroplasty, which was performed in nine shoulders and was successful in six (the other three required revision); and total arthroplasty in ten shoulders, one of which dislocated postoperatively and was not treated. Once the diagnosis is established, the majority of patients with this lesion can be successfully managed.

Tension studies of human knee ligaments. Yield point, ultimate failure, and disruption of the cruciate and tibial collateral ligaments.

Ultimate failure strengths of human tibial collateral and anterior and posterior cruciate ligaments were determined at two different loading rates (12.5 and fifty centimeters per minute) using an Instron Tension Analyzer. The posterior cruciate ligament was significantly stronger than the tibial collateral and anterior cruciate ligaments, which were of equal strength. At ultimate failure the ligaments were intact macroscopically but electron microscopy revealed widespread disruption of the collagen fibrils. Only after further application of stress did actual macroscopic disruption occur, suggesting that microscopic failure of the collagen fibrils in grossly intact ligaments may be a significant cause of clinical instability.

Unilateral facet dislocation of the cervical spine. An analysis of the results of treatment in 26 patients.

Twenty-six patients with unilateral facet dislocation of the cervical spine were analyzed to determine the best method of treatment of this injury, the incidence of late pain and instability, and the indications for surgical stabilization. This review showed that all patients with a unilateral facet dislocation of the cervical spine should be treated initially with halo traction in an attempt to obtain reduction. If reduction is obtained, then nonoperative treatment in the form of a halo thoracic apparatus may be the best method of treatment. Failure to obtain reduction with axial traction is an indication for open reduction and one-level posterior cervical fusion. Patients left in the displaced position and allowed to heal in that position usually develop late pain as a complication of this method of treatment.

Posterior instability of the glenohumeral joint. A technique of repair.

Seventeen patients underwent posterior capsulotendinous tensioning procedures to eliminate recurrent posterior glenohumeral instability. Fourteen patients were evaluated an average of 44 months (range, 18 to 98) after surgery. The average patient age was 27 years. Before surgery, all patients were unable to perform their activities of daily living, occupational activities, and athletic activities. Preoperatively, the average pain rating score on a visual analog scale was 5 of 10 at rest and 9 of 10 with activities. Six patients had previous anterior reconstructions. After surgery, the average range of motion was 174 degrees of forward elevation and 69 degrees of external rotation; internal rotation was to the thumb level of T-8. No patient had a recurrence of posterior instability. After surgery, the average pain rating score was 2 of 10 at rest and 4 of 10 with activities. All patients improved after their operations, but four patients were minimally disabled from activities of daily living; six patients experienced shoulder fatigue at work; and four patients had difficulty with sports activities. Overall, 13 of the 14 patients were satisfied with their surgical procedures and their outcomes.

Impingement syndrome in athletes.

Athletes, particularly those who are involved in sporting activities requiring repetitive overhead use of the arm (for example, tennis players, swimmers, baseball pitchers, and quarterbacks), may develop a painful shoulder. This is often due to impingement in the vulnerable avascular region of the supraspinatus and biceps tendons. With the passage of time, degeneration and tears of the rotator cuff may result. Pathologically the syndrome has been classified into Stage I (edema and hemorrhage), Stage II (fibrosis and tendonitis), and Stage III (tendon degeneration, bony changes, and tendon ruptures). The impingement syndrome may be a problem for the young, active, and competitive athlete as well as the casual weekend athlete. The "impingement sign" which reproduces pain and resulting facial expression when the arm is forceably forward flexed (jamming the greater tuberosity against the anteroinferior surface of the acromion) is the most reliable physical sign in establishing the diagnosis. Flexibility exercises, strengthening programs, and special training techniques are a preventive and treatment requirement. Rest and local modalities such as ice, ultrasound, and antiinflammatory agents are usually effective to lessen the inflammatory reaction. Surgical decompression by resecting the coracoacromial ligament or a more definitive anterior acromioplasty may rarely be indicated.

Acute patellar dislocations. The natural history.

Of 27 patients sustaining primary patellar dislocations, 20 were treated with immobilization and subsequent physiotherapy (including nine patients who underwent arthroscopy) and seven with immediate surgical stabilization and lateral release. The patients with predisposing factors such as patellofemoral malalignment, abnormal patellar configuration, and a history of prior symptoms of instability were more prone to recurrent dislocation and may benefit from operative intervention. Although the incidence of recurrence among those individuals can be decreased, at least 30% to 50% of all patients having sustained a primary patellar dislocation will continue to have symptoms of instability and/or anterior knee pain.

Followup of the acute nonoperated isolated anterior cruciate ligament tear.

This report is an attempt to analyze what happens to an isolated ACL tear that is treated nonoperatively. The results of 40 patients treated initially by nonoperative means for this injury and followed an average of 4 years are reported. A very small percentage of these patients had associated meniscal pathology. Secondary reconstructive surgery was necessary in 12 patients (30%). Primary meniscal tears were present in 4 of 25 knees (16%) and secondary meniscal tears occurred in an additional four of the patients. Giving way was a problem for 36 (86%) of the nonoperated patients, but pain and swelling were not significant problems for most. Full return to unlimited athletic activities was possible for only four (14%) of the patients. Objective signs of ACL insufficiency could be demonstrated on all patients upon clinical examination at followup. Overall grading of the knees revealed 87.5% fair or poor results.

The relationship of the axillary nerve to arthroscopically placed capsulolabral sutures. An anatomic study.

Ten cadaveric shoulders (mean donor age, 60.5 years) underwent arthroscopic placement of capsulolabral sutures as performed during arthroscopic reconstruction for shoulder instability. In relation to the glenoid face, the sutures were placed anterior, anteroinferior, inferior, posteroinferior, and posterior. All sutures entered the capsule approximately 1 cm away from the glenoid and exited beneath the labrum, and were tied using arthroscopic knot-typing techniques. The shoulders were frozen in the lateral arthroscopic position of approximately 45 degrees of abduction and 20 degrees of flexion and sectioned in the plane of the glenohumeral joint. The axillary nerve was then dissected, and the average distance from the nerve to each suture was found to be 16.7 mm at the anterior position, 12.5 mm at the anteroinferior position, 14.4 mm at the inferior position, 24.1 mm at the posteroinferior position, and 32.3 mm at the posterior position. In no specimen was any suture closer to the axillary nerve than 7 mm. We noted a statistically significant trend for the nerve to lie closest to the anteroinferior suture and gradually recede from the remaining sutures lying more posteriorly. This anatomic study is the first to demonstrate a relatively safe margin for arthroscopic suture placement between the capsule and axillary nerve when these sutures are placed approximately 1 cm from the glenoid rim.

Comparative functional analysis of the Bristow, Magnuson-Stack, and Putti-Platt procedures for recurrent dislocation of the shoulder.

Literature on anterior shoulder instability deals most often with elimination of recurrence following reconstruction. We analyzed the subjective function, loss of motion and shoulder strength of three operative procedures: Magnuson-Stack, Bristow, and Putti-Platt. A retrospective review of 27 patients, 9 in each surgical group, with no postoperative dislocations or on-going pain was performed. All patients were male, right hand dominant with the right shoulder affected. Average time of followup was 6.75 years (range, 4.2 to 10.3 years). All patients completed a questionnaire and had their range of motion measured by a hand-held goniometer and their shoulder strength tested on the Cybex II Dynomometer. Peak torque as a percent of body weight and side-to-side differences were calculated for six arm positions and compared to nine right hand dominant controls of similar age and recreational activity. Sixty percent returned to throwing sport. One Magnuson-Stack and Bristow patient felt full functional return to preinjury level. Three patients in each of these two groups returned to unmodified throwing sport whereas no Putti-Platt patient attained this level. Deficit of external rotation at shoulder neutral measured 4.7 degrees, Magnuson-Stack; 12.2 degrees, Bristow; and 21.8 degrees, Putti-Platt. At 90 degrees shoulder abduction, similar deficits in external rotation measured 6.4 degrees, 11.6 degrees, and 28.8 degrees respectively. These values were statistically significant employing analysis of variance. We compared the operative groups as a whole to the controls and compared the operative groups to each other.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of extended play on professional baseball pitchers.

The purpose of this study was to investigate kinematic and kinetic changes as a result of extended play in baseball pitching. Seven major league baseball pitchers were videotaped with high-speed (120 Hz) cameras during multiple innings of the same game. For each athlete, two fastballs (one thrown during the initial inning of play and one from the final inning) were chosen for analysis. Twenty-one physical landmarks were manually digitized from the video data. Kinematic and kinetic parameters were subsequently calculated relative to four phases of the pitching motion: windup, cocking, acceleration, and follow-through. Paired t-tests revealed that seven parameters changed significantly between early and late innings. These included decreases in maximum external rotation of the shoulder, knee angle at ball release, ball velocity, maximum distraction force at both the shoulder and elbow, and horizontal adduction torque at both release and its maximum value. Ultimately, a decline in performance was evident by a 2 m/s (5 mph) drop in ball speed. It is unclear whether the kinematic and kinetic changes occurred because of fatigue or if protective mechanisms were adopted.