An analytical approach to determine the in situ forces in the glenohumeral ligaments

The purpose of this study was to use an analytical approach to determine the forces in the glenohumeral ligaments during joint motion. Predictions from the analytical approach were validated by comparing them to experimental data. Using a geometric model, the lengths of the four glenohumeral ligaments were determined during anterior-posterior loading simulations and forward flexion-extension. The corresponding force in each structure was subsequently calculated based on length data via load-elongation curves obtained experimentally. During the anterior loading simulation at 0 deg of abduction, the superior glenohumeral ligament carried up to 71 N at the maximally translated position. At 90 deg of abduction, the anterior band of the inferior glenohumeral ligament had the highest force of 45 N during anterior loading. These results correlated well with those found in previous experimental studies. We believe that this validated analytical approach can be used to predict the forces in the glenohumeral ligaments during more complex joint motion as well as assist surgeons during shoulder repair procedures.

Effect of joint compression on inferior stability of the glenohumeral joint

To determine the relative importance of negative intraarticular pressure, capsular tension, and joint compression on inferior stability of the glenohumeral joint we studied 17 fresh, normal adult cadaver shoulders using a "3 degrees of freedom" shoulder test apparatus. Translations were measured in intact and vented shoulders while a 50-N superior and inferior directed force was applied to the shoulder. Three different joint compressive loads (22 N, 111 N, 222 N) were applied externally. Tests were performed in 3 positions of humeral abduction in the scapular plane (0 degree, 45 degrees, 90 degrees) and in 3 positions of rotation (neutral, maximal internal, and maximal external). After tests of the intact and vented shoulder, the glenohumeral ligaments were sectioned and tests were repeated. With minimal joint compression of 22 N, negative intraarticular pressure and capsular tension limited translation of the humeral head on the glenoid. Increasing the joint compressive load to 111 N resulted in a reduction of mean inferior translation from 11.0 mm to 2.0 mm at 0 degree abduction, from 21.5 mm to 1.4 mm at 45 degrees abduction, and from 4.5 mm to 1.2 mm at 90 degrees abduction. With a compressive load of 111 N, venting the capsule or sectioning of glenohumeral ligaments had no effect on inferior stability.

CLINICAL RELEVANCE

Glenohumeral joint compression through muscle contraction provides stability against inferior translation of the humeral head, and this effect is more important than negative intraarticular pressure or ligament tension.

Glenoid fracture nonunion presenting as instability in a young athlete

A case of a teenage athlete with a 4-year history of shoulder pain caused by glenoid fracture nonunion is presented. This individual had findings consistent with traumatic anterior shoulder instability as well as normal radiographs. Arthroscopy showed a nondisplaced glenoid fracture that was stabilized successfully through a deltopectoral approach.

The treatment of symptomatic os acromiale

During a four-year period, fourteen individuals (fifteen shoulders) who had been seen at the shoulder service of our institution because of pain in the shoulder had a radiographic finding of an os acromiale. On clinical examination, the pain appeared to be due to an unstable os acromiale because the patients had point tenderness over the acromion and pain on forward elevation of the shoulder. The diagnosis of an os acromiale was confirmed on radiographs, magnetic resonance images, or a bone scan. Eight patients had an associated tear of the rotator cuff. The os acromiale was located in the pre-acromion in one shoulder, the meso-acromion in eleven shoulders, and the meta-acromion in three shoulders. At the operation, the anterior aspect of the acromion was found to be unstable in all shoulders. Eleven patients (twelve shoulders) had open reduction of the os acromiale and insertion of an autogenous iliac-crest bone graft. Of those patients, four (five shoulders) had open reduction and internal fixation with a tension-band procedure with use of pins and wires. Only one of those shoulders had a solid osseous union, and the other four shoulders had a non-union that was due to a disruption of the fixation. The remaining seven patients (seven shoulders) had open reduction and internal fixation with use of cannulated screws and a tension-band construct; a solid osseous union was achieved in all but one of them. One patient had excision of the pre-acromion, which relieved the pain. Two patients who had had failed open reduction and internal fixation had excision of a grossly unstable os acromiale in the meso-acromion; both patients had pain and weakness after this procedure. Of the twelve shoulders that had open reduction and bone-grafting, seven had union of the os acromiale; the average time to radiographic and clinical union was nine weeks (range, seven to twenty weeks). We concluded that, although it is rare, symptomatic unstable os acromiale does occur and can be effectively treated with use of autogenous bone-grafting and internal fixation with a rigid tension-band construct and cannulated screws.

Articular contact patterns of the normal glenohumeral joint

The purpose of this study was to determine the articular contact patterns of the normal glenohumeral joint, and to correlate these findings with cartilage and subchondral bone architecture. We studied 10 normal shoulders of cadavers. We removed all soft tissues except the joint capsule and rotator cuff and then placed the shoulders on a testing apparatus that allowed freedom of translation in three planes. After the humerus was placed in a neutral position of rotation, articular contact patterns were measured with specially prepared prescale Fuji film so that it could be inserted between the joint surfaces. Articular contact was analyzed with 222 and 444 N of joint compressive load, and the humerus was positioned in scapular plane abduction of 0 degree, 45 degrees, and 90 degrees. The contact patterns were then digitized to determine percentage contact of the humeral head on the glenoid. We studied 12 additional cadaver shoulders with fine microradiographs and histologic techniques after we sectioned the glenoids in the anterior-posterior and superior-inferior planes. We then analyzed articular and subchondral architecture. We found that when the shoulder was adducted the contact area of the humeral head on the glenoid was limited to the anatomic region of the central glenoid known as the "bare area." This was histologically and radiographically an area of cartilage thinning and increased subchondral bone density. As the shoulder was abducted the articular congruity and percentage contact area increased. We concluded that there was a slight articular mismatch with the shoulder adducted in the normal shoulder. Histologic and radiographic studies suggested that the central bare area region of the glenoid was a region of increased compressive loading. As the shoulder was abducted the joint became more congruent and thus the contact area of the humeral head on the glenoid increased.

Serratus anterior dysfunction. Recognition and treatment

Recognition of scapular winging may be difficult, and potential errors in treatment can result. Such treatment errors may cause morbidity for the patient. In addition, electrical evidence of long thoracic nerve injury usually is required to confirm the etiology of scapular winging as being caused by serratus anterior dysfunction. Although various conditions may result in scapular winging, primary serratus anterior dysfunction can be treated effectively by transfer of the pectoralis major tendon; however, this surgical approach sometimes may given an unacceptable cosmesis, and there may be local morbidity to the donor site of the iliotibial band graft that is used to augment the tendon transfer. The authors report eight patients with primary chronic scapulothoracic winging refractory to conservative treatment. Five of these patients had an incorrect diagnosis, and this resulted in 17 surgical procedures without resolution of their pain or improvement of function. Of the eight patients who required additional surgery to stabilize the scapula, only five patients had an electromyographic study that showed long thoracic nerve palsy, although all patients had profound scapulothoracic winging. All patients underwent a modified pectoralis major transfer with autogenous semitendinosus and gracilis tendon augmentation using two small incisions. Although one patient had a postoperative infection develop, the remaining seven patients had resolution of their winging, improved function, and satisfactory cosmesis.

A dynamic analysis of glenohumeral motion after simulated capsulolabral injury. A cadaver model

We used a dynamic shoulder-testing apparatus and nine fresh-frozen, entire upper extremities from cadavera to evaluate the effects of varying degrees of capsulolabral injury on the kinematics of the glenohumeral joint during abduction in the scapular plane and external rotation. Joint kinematics were recorded with use of a six-degrees-of-freedom magnetic tracking device before and after the creation of each capsulolabral lesion in a progressive manner. Dislocation did not occur after simulation of a large Bankart lesion or even after sectioning of the anterior aspect of the joint capsule. However, division of the entire joint capsule (that is, both the anterior aspect and the posterior aspect) resulted in a significant increase (p < 0.05) in posterior translation during abduction in the scapular plane, and two of the nine shoulders dislocated posteriorly. External rotation of the abducted extremity produced no increase in anterior or posterior translation.

Combined Bankart and HAGL lesion associated with anterior shoulder instability

Traumatic anterior shoulder instability has been shown to be associated with a spectrum of capsulolabral pathology, including separation of the labrum (Bankart lesion), capsular rupture, and humeral avulsion of the glenohumeral ligaments (HAGL lesion). We describe a case of combined Bankart and HAGL lesions, a condition that has not been described before. Careful anatomic repair of both components of this bipolar capsular injury resulted in an excellent outcome.

Shoulder kinematics with two-plane x-ray evaluation in patients with anterior instability or rotator cuff tearing

The goals of this study were to define biplanar glenohumeral kinematics and glenohumeral-scapulothoracic motion relationships in normal patients with a two-plane radiograph series and then in patients with anterior shoulder instability or rotator cuff tear both before surgery and after surgical repair and postoperative rehabilitation. A two-plane radiographic series of x-ray films in the scapular and horizontal (axillary) planes was performed. With these films, measurements of the relationship between the centers of the humeral head and glenoid and measurements of the component contributions of glenohumeral and scapulothoracic motion to total arm abduction were made. Six normal adults underwent x-ray evaluation to establish normal control values. Kappa analysis was used to determine reliability of technique. Eighteen patients with confirmed anterior shoulder instability (group A) and 15 with confirmed rotator cuff tears (group B) were studied before surgery. Seven (39%) of 18 of the patients in group A and all 15 (100%) of the patients in group B demonstrated superior translation of the humeral head during scapular plane abduction. In the horizontal plane 14 (78%) of 18 patients in group A (instability) and none in group B (rotator cuff tear) demonstrated abnormal anterior translation of the humeral head on the glenoid. Both groups demonstrated altered glenohumeral-scapulothoracic motion relationships compared with the normal control group. Two years after surgery 12 patients from group A and 14 patients from group B were restudied. All of these patients had demonstrated abnormalities of humeral head translation before surgery. For group A 12 (100%) of 12 patients demonstrated normal glenohumeral kinematics in both planes after open anterior stabilization. For group B 12 (86%) of 14 patients demonstrated normal glenohumeral kinematics in both planes after open rotator cuff repair. In group A the altered glenohumeral-scapulothoracic motion relationships persisted, whereas in group B these relationships became normal.

Surgical treatment of postoperative deltoid origin disruption

Although it is well recognized that deltoid disruption after shoulder surgery is associated with poor function, little information is available regarding results of surgical treatment for this problem. Twenty-four patients underwent direct repair or rotational deltoidplasty reconstruction of a detached muscle origin after shoulder surgery. The original surgical procedure was rotator cuff repair in 12, acromioplasty in four, and lateral acromionectomy with or without rotator cuff repair in eight. The average duration of symptoms before deltoid reconstruction was 17 months. The mean followup was 39 months (range, 13-84 months). Twelve patients reported moderate to severe pain, whereas 12 had minimal pain. Two patients required a shoulder fusion for intractable pain. Overall, one (4%) excellent, seven (29%) good, and 16 (67%) unsatisfactory results were observed. A poor outcome was associated with a prior lateral acromionectomy, involvement of the middle deltoid, a massive rotator cuff tear with weakness in external rotation, and a residual postoperative defect larger than 2 cm. In select cases, repair or deltoidplasty can improve function and pain.

Arthroscopic-assisted rotator cuff repair: patient selection and treatment outcome

Over a 4-year period 24 patients out of 376 who required a rotator cuff repair were selected for arthroscopic-assisted rotator cuff repair. Preoperative selection criteria were refractory pain in the setting of good range of motion and strength (after an impingement test), absence of radiographic superior humeral head translation, and magnetic resonance imaging evidence of minimally retracted tear without rotator cuff muscle atrophy. Intraoperative selection criteria were the findings of an avulsion-type tear configuration with good tendon quality and absence of subscapularis tendon involvement. Based on these intraoperative criteria, 7 of the 24 patients were converted to an open approach to mobilize retracted and friable tendon tissue in a complex tear configuration. The remaining 17 patients underwent a transosseous arthroscopic-assisted rotator cuff repair with an average postoperative follow-up of 23 months. Evaluation by an independent therapist determined the postoperative American Shoulder and Elbow Surgeons Shoulder Function Index of 96 +/- 3 for the operative shoulder. The Functional Rating Scores for Activities of Daily Living and Sports Activity Score were 89% +/- 10% and 87% +/- 12%, respectively. Instrumented isometric strength for abduction and external rotation strength in the operated shoulder were 94% +/- 20% and 93% +/- 20%, respectively, compared with the contralateral unoperated side. Five of eight patients who performed overhead sports returned to a premorbid level of performance, and 14 of 15 patients available for follow-up believed that their result was excellent. We conclude that through careful selection one can identify patients optimally suited for arthroscopic-assisted rotator cuff repair, but some may have to be converted to an open end approach because of the quality of the tendon tissue and configuration of the tear requiring soft tissue releases.

Arthroscopic release of postoperative capsular contracture of the shoulder

A loss of motion after an operation on the shoulder often cannot be treated successfully with physical therapy or closed manipulation. Although open release techniques generally improve motion, they involve extensive dissection. We developed a technique of arthroscopic capsular release and applied it in eighteen patients who had postoperative stiffness of the shoulder. The patients were selected for the arthroscopic release technique if a conservative program of physical therapy and an attempted closed manipulation had failed to restore motion and if they had no known extra-articular contractures. Five of the thirteen patients who had had a global loss of shoulder motion had motion restored with the anterior capsular release, and six needed an additional release of the posterior aspect of the capsule--that is, a combined (anterior and posterior) capsular release. The arthroscopic procedure could not be completed in the remaining two patients because of an extra-articular scar involving the subscapularis, but those patients were managed successfully with an open release. As five patients had lost only internal rotation and flexion, they had only a posterior capsular release. For the eleven patients who had had either an anterior or a combined (anterior and posterior) capsular release, the mean improvement in the score of Constant and Murley was 43 points (range, 31 to 62 points) and all improvements in motion were significant (p < 0.01). Flexion improved a mean of 51 degrees (range, 10 to 65 degrees); external rotation in adduction and abduction, 31 degrees (range, 10 to 50 degrees) and 40 degrees (range, 5 to 80 degrees), respectively; and internal rotation in adduction and abduction, six spinous-process levels (range, three to eleven levels) and 41 degrees (range, 20 to 70 degrees), respectively. For the five patients who had an isolated posterior capsular release, the score of Constant and Murley improved a mean of 20 points (range, 5 to 35 points) and the improvements in motion also were significant (p < 0.05 and 0.005). Internal rotation in adduction and abduction improved a mean of four spinous-process levels (range, one to ten levels) and 42 degrees (range, 30 to 60 degrees), respectively. Eight patients had an arthroscopic acromioplasty for concomitant impingement disease. One patient who had had a combined (anterior and posterior) release and one who had had a posterior capsular release continued to have pain because of injury of the articular cartilage from a previous operation. We concluded that arthroscopic capsular release is a reliable method for restoring motion with minimum morbidity in carefully selected patients who have postoperative stiffness of the shoulder. When necessary, it can be converted to an open release.

Optic nerve contact and compression by the carotid artery in asymptomatic patients

PURPOSE

To estimate the frequency and clinical correlates of contact and compression of the intracranial optic nerve by the supraclinoid carotid artery in asymptomatic patients.

METHODS

In a retrospective study, we identified asymptomatic patients who had undergone magnetic resonance imaging with sequences that could be used to evaluate the relation between the intracranial optic nerve and the carotid artery. These patients underwent neuroimaging evaluations for reasons unrelated to loss of vision, optic neuropathy, or carotid artery disorders. The relation between the optic nerve and carotid artery was graded in a standardized manner. The effect of a number of clinical covariates on the risk of compression was evaluated using multiple logistic regression.

RESULTS

The frequencies of some of the artery-nerve relationships included contact of one or both optic nerves in 70 (70%) of 100 patients; bilateral compression in 12 (12%) of 100 patients; and unilateral compression with no arterial contact or compression on the opposite side in five (5%) of 100 patients. The estimated odds of compression were significantly increased as the diameter of the carotid artery increased.

CONCLUSIONS

Among asymptomatic patients, supraclinoid carotid artery contact with the intracranial optic nerve occurs frequently. Anatomic compression, on the other hand, especially when unilateral, occurs infrequently. The risk of anatomic compression of the optic nerve is directly proportional to the diameter of the carotid artery.

The rotator cuff. Commentary

To add clinical perspective to the articles of this two-issue collection, eight prominent shoulder surgeons discuss their approach to the treatment of rotator cuff disease. There is broad agreement in many areas, however, significant controversies remain.

Rotator cuff disease. An arthroscopic view

Rotator cuff disease has become a treatable entity by using the arthroscope; however, a sound understanding of pathology and an appreciation of relevant physical findings are necessary if the arthroscope is to be used effectively. Arthroscopic examination confirms the extent of rotator cuff disease and co-morbid pathology and allows for treatment of many problems related to the rotator cuff.

Single-tendon tears of the rotator cuff. Evaluation and treatment of subscapularis tears and principles of treatment for supraspinatus tears

Successful surgical treatment of single-tendon tears, which involve the supraspinatus or the subscapularis requires careful attention to technical details. In supraspinatus tears, careful mobilization and secure repair of the tendon will usually give a good outcome. In subscapularis tears, the diagnosis is not difficult if one carefully evaluates the patient for the classic pathognomonic findings of such a tear. If the tear is confirmed by CT or MR imaging and an acute repair is performed, the outcome is usually satisfactory.

Arthroscopic release for chronic, refractory adhesive capsulitis of the shoulder

Idiopathic adhesive capsulitis usually responds to gentle physical therapy or, if that fails, to closed manipulation with the patient under anesthesia. In some patients, however, loss of motion may be refractory to either of these treatments and an operative release may be indicated. We are reporting on the technique and results of arthroscopic capsular release as a new alternative for the management of such patients. During a three-year period, we managed twenty-three patients who had idiopathic adhesive capsulitis that had failed to respond to physical therapy or closed manipulation. These patients had an arthroscopic anterior capsular release and received forty-eight hours of intensive physical therapy as inpatients. During the physical therapy, the patients received an interscalene regional analgesic with use of repeated nerve blocks or with a continuous infusion through an interscalene catheter. This was followed by a supervised outpatient physical-therapy program. Six patients also had an arthroscopic acromioplasty for the treatment of impingement. There were no complications related to any of the procedures. At a mean of thirty-nine months (range, twenty-four to sixty-four months) after the arthroscopic procedure, the improvement in the score of Constant and Murley averaged 48 points (range, 13 to 77 points). The mean improvement in motion was 49 degrees (range, 0 to 105 degrees) for flexion; 42 degrees (range, 10 to 80 degrees) and 53 degrees (range, 0 to 100 degrees) for external rotation in adduction and abduction, respectively; and eight spinous-process levels (range, three to fourteen levels) and 33 degrees (range, 30 to 60 degrees) for internal rotation in adduction and abduction, respectively. These gains in motion were all significant (p < 0.01) compared with the preoperative values and were within a mean of 7 degrees of the values for the contralateral, normal shoulder. We concluded that, in patients who have loss of motion that is refractory to closed manipulation, arthroscopic capsular release improves motion reliably with little operative morbidity.

Idiopathic hypertrophic cranial pachymeningitis: clinical-radiological-pathological correlation of bone involvement

We present the clinical, radiological, and pathological findings in an elderly man who developed a progressive superior orbital fissure syndrome due to idiopathic hypertrophic cranial pachymeningitis. The unique aspect of this case concerned the increased density of the sphenoid ridge and lateral orbital wall observed by using computed tomography, and the enhancement of the marrow signal seen on magnetic resonance imaging. These neuroimaging abnormalities of bone resulted from an indirect nonspecific response of the marrow to the adjacent soft tissue and dural inflammatory process.

An arthroscopic technique for anterior stabilization of the shoulder with a bioabsorbable tack

Arthroscopically assisted repair of the anterior aspect of the labrum with use of a bioabsorbable tack was performed in fifty-two consecutive patients who had chronic anterior instability of the shoulder. The average age of the patients was twenty-eight years (range, sixteen to fifty years). The etiology of the instability was a traumatic injury in forty-nine patients; twenty-six of those injuries were sustained during participation in a contact sport. Fifty shoulders had a Bankart lesion. The patients were evaluated at an average of forty-two months (range, twenty-four to sixty months) after the procedure. Forty-one (79 per cent) of the patients were asymptomatic and were able to participate in sports without restriction. The repair was considered to have failed in eleven (21 per cent) of the patients. In four of them, the failure resulted from a single traumatic reinjury during participation in a contact sport, and three of these reinjuries were treated nonoperatively. The remaining seven failures occurred atraumatically. Eight patients had an open glenoid-based capsulorrhaphy as a consequence of recurrent instability. At the reoperation, no evidence of the tack was found in any patient. In seven patients, the Bankart lesion had completely healed, and the anteroinferior aspect of the capsule was patulous. Anterior stabilization of the shoulder with a bioabsorbable tack may be indicated for patients who have anterior instability but do not need a capsulorrhaphy or capsular imbrication to reduce the joint volume.

Role of proprioception in pathoetiology of shoulder instability

Proprioception is a specialized sensory modality that gives information about extremity position and direction of movement. This kind of afferent sensory feedback is probably important in mediating muscular control of the shoulder joint. As this articulation is minimally constrained, such a coordinated dynamic control of muscles about the joint is necessary for stability during arm motion. The authors evaluated proprioception in individuals with normal shoulders, unstable shoulders, and after surgical stabilization, by assessing threshold to detection of passive motion and the ability to passively reposition the arm in space. In normal shoulders there is no difference between the dominant and nondominant shoulder, though in unstable shoulders there is a significantly decreased proprioceptive ability. Surgical stabilization normalizes proprioception of the shoulder.

Tensile properties of the superior glenohumeral and coracohumeral ligaments

Recent evidence has shown that the superior glenohumeral ligament (SGHL) and coracohumeral ligament (CHL) are important static stabilizers. To clarify the function of these two ligaments, we studied their tensile properties with bone-ligament-bone complexes from fresh-frozen shoulders, 10 SGHLs and 10 CHLs. Each ligament's cross-sectional area was measured, and uniaxial tensile testing of each complex was performed. The stiffness, ultimate load, percent elongation, and energy absorbed to failure of each bone-ligament-bone complex were derived from its load-elongation curve. The cross-sectional area of the coracohumeral ligament was significantly greater than that of the superior glenohumeral ligament of their midportions (CHL, 53.7 +/- 3.2 mm2 vs. SGHL, 11.3 +/- 1.6 mm2, p < 0.05). Results also reveal significant differences between the tensile properties for the two ligaments, with the coracohumeral ligament possessing greater stiffness (CHL, 36.7 +/- 5.9 N/mm vs. SGHL, 17.4 +/- 1.5 N/mm, p < 0.05) and ultimate load (CHL, 359.8 +/- 40.3 N vs. SGHL, 101.9 +/- 11.5 N, p < 0.05) than the superior glenohumeral ligament. Our findings confirm that the coracohumeral ligament is an important capsuloligamentous structure of the glenohumeral joint.