A biomechanical analysis of rotator cuff deficiency in a cadaveric model

We conducted this cadaveric study to define a biomechanical rationale for rotator cuff function in several deficiency states. A dynamic shoulder testing apparatus was used to examine change in middle deltoid muscle force and humeral translation associated with simulated rotator cuff tendon paralyses and various sizes of rotator cuff tears. Supraspinatus paralysis resulted in a significant increase (101%) in the middle deltoid force required to initiate abduction. This increase diminished to only 12% for full glenohumeral abduction. The glenohumeral joint maintained ball-and-socket kinematics during glenohumeral abduction in the scapular plane with an intact rotator cuff. No significant alterations in humeral translation occurred with a simulated supraspinatus paralysis, nor with 1-, 3-, and 5-cm rotator cuff tears, provided the infraspinatus tendon was functional. Global tears resulted in an inability to elevate beyond 25 degrees of glenohumeral abduction despite a threefold increase in middle deltoid force. These results validated the importance of the supraspinatus tendon during the initiation of abduction. Glenohumeral joint motion was not affected when the "transverse force couple" (subscapularis, infraspinatus, and teres minor tendons) remained intact. Significant changes in glenohumeral joint motion occurred only if paralysis or anatomic deficiency violated this force couple. Finally, this model confirmed that rotator cuff disease treatment must address function in addition to anatomy.

Arthroscopic shoulder stabilization. Overview of indications, technique, and efficacy

The importance of patient selection for arthroscopic shoulder stabilization cannot be overemphasized. A significant learning curve involving both proper patient selection and correct surgical technique exists for arthroscopic Bankart repair using the Suretac device. Nevertheless, with appropriate selection criteria, knowledge of the anatomic limitations of the procedure and mastering of the operative technique, one can expect excellent outcomes with results approaching those found with open capsulorrhaphy. In addition, patients can anticipate a reliable return of motion that is nearly symmetric to the contralateral shoulder.

Technique for selecting capsular tightness in repair of anterior-inferior shoulder instability

Part I of our study consisted of sending a survey questionnaire to all members of the American Shoulder and Elbow Surgeons in which specific questions were asked about their technique of surgical repair in patients with anterior instability who had capsular laxity or injury in conjunction with marked inferior laxity. Part II is a description of the technique and preliminary results in 18 patients of a modified anterior-inferior capsular shift technique that tightens the inferior capsule with the shoulder positioned in abduction and external rotation and the superior capsule with the shoulder in adduction and external rotation. Of the members of the Society of the American Shoulder and Elbow Surgeons who responded to the survey, 80% agreed that preservation of external rotation was important and that shoulder position at the time of capsular repair might influence the ultimate range of motion obtained. However, no more than 50% of the respondents agreed on any one position for the arm when repairing the capsule. The most common responses for each position were flexion 0 degrees (49%) (range, 0 degrees to 40 degrees), abduction 30 degrees (24%) (range, 0 degrees to 80 degrees), and external rotation 30 degrees (37%) (range, 0 degrees to 70 degrees). The average postoperative follow-up period for the 18 patients was 27 months (range, 24 to 39 months). Of the 18 patients, 11 (61%) maintained symmetric motion; the others had minimal loss of external rotation compared with that of the contralateral shoulder. Six of eight patients with repair on the dominant side were able to return to full premorbid recreational throwing or racquet sports, and seven with repair on the nondominant side returned to full participation in overhead sports such as basketball and swimming. We conclude that this method of "selective" capsular repair may be a useful guideline to gauge the degree of capsular tightening in patients who have capsular injury or laxity.

Transient trochlear nerve palsy following anterior temporal lobectomy for epilepsy

Three of 22 patients (14%) who underwent anterior temporal lobectomy for treatment of medically intractable epilepsy at our institution from July 1987 through July 1993 experienced diplopia immediately after surgery. We found ipsilateral paresis of the superior oblique muscle in all three patients. Their ophthalmoplegia resolved completely within 14 weeks. We did not observe any new structural or ischemic changes on postoperative MRIs to account for their deficits. Trochlear nerve palsy--not oculomotor nerve palsy, as is reported in most reference texts--is a relatively common cause of transient diplopia following temporal lobectomy. Indirect (ie, traction) injury of the trochlear nerve is a plausible mechanism that would explain this complication.

Juxta-articular synovial cyst of the shoulder

A case of an unusual synovial cyst with both intra- and extraosseous components found in the proximal humerus of a patient with osteoarthritis is presented. The importance of this lesion is that it should be recognized as a manifestation of the underlying osteoarthritis and does not represent a more serious primary lesion.

A new dynamic testing apparatus to study glenohumeral joint motion

A dynamic shoulder testing apparatus has been developed to examine unconstrained glenohumeral joint motion in human cadaveric full upper extremities. Six computer-controlled hydraulic cylinders are used to simulate muscle action, while the corresponding tendon excursions and six-degree of freedom joint motion are measured. Trials showed that the testing apparatus creates highly reproducible glenohumeral joint motion in the scapular plane. The apparatus can be used to examine the function of the shoulder musculature and capsuloligamentous structures during normal and pathologic motion at the glenohumeral joint.

Uncommon causes of shoulder pain in the athlete

Injuries to the shoulder are very common in athletes. In addition to common causes of shoulder pain in the athlete, such as instability, it is important to consider less common causes. Familiarity with these uncommon entities will lead to appropriate diagnosis and treatment in a timely fashion.

Shoulder instability in the athlete

Glenohumeral instability in the athlete represents a spectrum of disorders, which has been recognized and treated with increasing frequency. The first challenge for a clinician treating an athlete with shoulder instability is recognition and understanding of the instability pattern. The second challenge is to make the right therapeutic decision that will enable the athlete to return to his or her previous level of function with the shortest possible period of disability. Although most patients can be managed nonoperatively, arthroscopic and open stabilization are good options when these procedures are warranted.

Shoulder muscle forces and tendon excursions during glenohumeral abduction in the scapular plane

Muscle force values and tendon excursions across the glenohumeral joint during unconstrained glenohumeral abduction in the scapular plane were evaluated with a dynamic shoulder testing apparatus. This evaluation was achieved by simulated rotator cuff and middle deltoid activity applied in four plausible muscle force ratios: (1) equal force to each tendon, (2) 2:3 ratio of force applied to the middle deltoid/supraspinatus tendons, (3) 3:2 ratio of force applied to the middle deltoid/supraspinatus tendons, and (4) zero force applied to the supraspinatus tendon to simulate supraspinatus paralysis. The glenohumeral joint was then moved to 5 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, and maximum glenohumeral abduction while muscle forces, tendon excursions, and glenohumeral joint kinematics were monitored. Full glenohumeral abduction was achieved in all four test conditions. When the muscle force combination favored the middle deltoid, the smallest supraspinatus force was required from 30 degrees to maximum glenohumeral abduction; however, when the supraspinatus was favored, the largest supraspinatus force was necessary to achieve maximum glenohumeral abduction. With simulated supraspinatus paralysis the middle deltoid required the greatest increase in force from 15 degrees through 45 degrees of glenohumeral abduction. These results indicate that muscle efficiency during glenohumeral abduction is highly dependent on the ratio of applied force between the middle deltoid and supraspinatus. A larger contribution of force from the supraspinatus was required near the beginning of motion, whereas the middle deltoid was more important near the end of glenohumeral abduction in the scapular plane. Tendon excursion for the middle deltoid (6.4 +/- 0.2 cm) and supraspinatus (3.8 +/- 0.2 cm) were proportionately larger than those for the subscapularis and infraspinatus. Humeral head translations on the glenoid were less than 2 mm in all four conditions evaluated; therefore the glenohumeral joint behaves kinematically as a "ball-and-socket" articulation during glenohumeral abduction. Simulated supraspinatus paralysis does not change normal joint kinematics and does not prevent full glenohumeral abduction.

The role of the long head of the biceps brachii in superior stability of the glenohumeral joint

We studied seven patients who had isolated loss of the proximal attachment of the tendon of the long head of the biceps brachii, documented operatively or with magnetic resonance imaging, in order to identify and measure superior translation of the humeral head on the glenoid. Four true anteroposterior radiographs were made of both shoulders, before and after the operation, with 0, 45, 90, and 120 degrees of humeral abduction in the scapular plane. Four patients were managed with arthroscopic acromioplasty with an open biceps tenodesis; one, with open biceps tenodesis alone; and one, with debridement of a ruptured biceps stump; the remaining patient was managed non-operatively. Two to six millimeters of superior translation of the humeral head was noted in each patient in all positions of humeral abduction except 0 degrees. This translation was significant compared with the contralateral (control) shoulder. Kappa statistical analysis showed excellent reproducibility and interobserver reliability of the technique of radiographic measurement. The results of this study support the role of the tendon of the long head of the biceps brachii as a stabilizer of the humeral head in the glenoid during abduction of the shoulder in the scapular plane.

Arthroscopic Bankart repair with the Suretac device. Part II: Experimental observations

Arthroscopic Bankart repair using the Suretac device (Acufex Microsurgical, Mansfield, MA) was developed as an alternative to both the staple and suture repair techniques. While offering some technical advantages compared with these other approaches, it's technical limitations and pitfalls have only been described anecdotally based on the clinical experience of several surgeons. The purpose of this study was to define these limitations and pitfalls. Eight cadaver shoulders underwent arthroscopic Bankart repair using the Suretac device after first arthroscopically creating a Bankart lesion. These shoulders were then dissected to reveal the placement of the Suretacs and the adequacy of the Bankart lesion repair. Glenoids were transected in the transverse plane and embedded in clear methylmethacrylate to show placement of the Suretac device relative to the articular surface. There were several technical errors that occurred: (1) Inadequate abrasion of the anterior and inferior juxta-articular scapular neck; (2) inadequate superior and medial shift of the inferior glenohumeral ligament before placement of the lowest Suretac, (3) medial placement of the Suretac relative to the articular margin; and (4) insufficient capture and compression of capsular tissue by the Suretac device. This procedure is technically difficult and careful attention must be paid to each step of preparation and repair. Recognition of the common errors may help the surgeon to avoid these pitfalls in the clinical situation.

Arthroscopic Bankart repair with the Suretac device. Part I: Clinical observations

Although arthroscopic Bankart repair has become an accepted surgical stabilization technique for anterior shoulder instability, the failure rate remains unacceptably high. Little information is available concerning healing of the Bankart repair. The purpose of this article is to clarify this issue by analyzing a cohort of 15 patients who underwent a "second-look" arthroscopy to evaluate and treat pain or recurrent instability following arthroscopic Bankart repair with the Suretac device (Acufex Microsurgical, Mansfield, MA). "Second-look" arthroscopy was performed at an average of 9 months following the index surgical procedure. The reasons for this second surgery were recurrent instability in 7, pain in 6, and pain and stiffness in 2. In the 7 patients with recurrent instability, the Bankart repair was found to be completely healed in 3 (43%), partially healed in 1 (14%), and had recurred in 3 (43%); however, 6 of 7 were observed to have lax capsular tissue. In 4 of these cases, retrospective review of the index surgical procedure showed that a technical error had been made during the repair. Two cases had biopsy of the repair site on "second-look" at 6 to 8 months, and this showed residual polyglyconate polymer debris surrounded by a histiocytic infiltrate. In the remaining 8 cases with stable shoulders, the Bankart repair had completely healed in 5 cases (62.5%) and partially healed in 3 cases (37.5%). The higher failure rate with this approach compared with open approaches appears to result from improper patient selection and errors in surgical technique. There is some question concerning healing strength of the Bankart repair, although complete healing of the Bankart does not seem to be a prerequesite for shoulder stability. Success of the procedure might be expected to improve by selecting only patients with unidirectional, posttraumatic, anterior instability who are found to have a discrete Bankart lesion and well-developed ligamentous tissue.

Arthroscopic repair of combined Bankart and superior labral detachment anterior and posterior lesions: technique and preliminary results

Over a 3-year period nine of 585 patients undergoing shoulder surgery were found to have a superior labral detachment anterior and posterior (SLAP) lesion. Seven patients also had an associated Bankart lesion and underwent arthroscopic repair of the entire anterior-inferior-superior-posterior labral detachment using the Suretac (Acufex Microsurgical Inc., Mansfield, MA) fixation device. The technique used requires an accessory anterior-lateral portal to access the superior-posterior labral detachment and an accessory anterior-inferior portal to access the Bankart lesion. Three to four Suretacs were required for repair in these cases. At an average follow-up of 19 months (range 15-22), five of seven patients had no pain, full range of motion, and a full premorbid activity level. One patient redislocated at 4 months postoperatively and was successfully managed with an open repair, and one patient developed a stiff shoulder that was successfully managed with arthroscopic release and manipulation. We conclude that this arthroscopic technique is a useful method to manage extensive labral detachment in selected patients.

The "arthroscopic impingement test"

Arthroscopic acromioplasty is an effective technique to treat refractory impingement syndrome of the shoulder; however, it is a technically demanding procedure and failure due to inadequate acromial resection has been reported. The purpose of this study was to describe a more reliable technique of arthroscopic acromioplasty ("arthroscopic impingement test") that allows determination of subacromial space available (SSA) during shoulder flexion after acromioplasty. During a 2-year period, 70 consecutive patients (group I) underwent arthroscopic acromioplasty by a conventional technique and 50 consecutive patients (group II) underwent the modified technique. Both groups were comparable in terms of age, gender, chronicity of symptoms, incidence of workman's compensation cases, side of surgery, and operative findings. In group I, four patients (6%) failed due to inadequate acromioplasty and at time of revision were found to have 0 mm SSA at 120 degrees flexion (contact of cuff on acromion). After revision acromioplasty, SSA at 120 degrees flexion was measured as > 3 mm, and impingement symptoms resolved postoperatively. In group II, there were no failures and SSA after initial acromioplasty was found to average 13 mm at 0 degree 10 mm at 45 degrees, 8 mm at 90 degrees, and 6 mm at 120 degrees flexion. In four cases, the "arthroscopic impingement test" determined that there was inadequate SSA at 120 degrees (< 3 mm) after initial acromioplasty, and these were revised by further acromioplasty at time of surgery. It was concluded that the "arthroscopic impingement test" improves reliability of arthroscopic acromioplasty by verifying adequate acromial resection in a position of impingement.

Diagnosis for anterior cruciate ligament surgery

We have reviewed the important aspects of the history, physical examination, and other diagnostic tools available to help diagnose ACL injuries. We feel that, in the hands of an experienced clinician, greater than 90% of ACL disruptions can be diagnosed at the time of injury. Appropriate evaluation will enable the clinician to advise the appropriate treatment, whether it be operative or nonoperative. We have also briefly outlined the variables that we consider to be the most important in the decision-making process of treatment options after ACL disruption.

Reconstruction of the antero-superior shoulder capsule with the subscapularis tendon: A case report

A 14-year-old boy presented with recurrent, anteroinferior, and multidirectional instability of his dominant shoulder. Examination with the patient under anesthesia demonstrated marked anterior and inferior translation when drawer testing was performed in adduction; however, abduction of the shoulder reduced the magnitude of humeral head translation in both these directions. Arthroscopy and open surgical dissection revealed the absence of any capsuloligamentous structures above the anterior band of the inferior glenohumeral ligament complex. This superior capsular defect could not be closed by a capsular shift procedure; therefore it was reconstructed with a portion of the subscapularis tendon. This case provides a clinical correlation of capsular anatomy with laxity on drawer testing. The glenohumeral laxity documented on examination with the patient under anesthesia supports experimental ligament-cutting studies that suggest the inferior glenohumeral ligament complex is the important stabilizer in abduction, whereas the superior and middle glenohumeral ligaments are more important in adduction.

Anatomic considerations in harvesting the semitendinosus and gracilis tendons and a technique of harvest

Although the semitendinosus and gracilis tendons have long been used in ligamentous reconstruction procedures of the knee, their anatomic relationships have not been explicitly detailed. Therefore, cadaveric dissections were performed on fresh-frozen adult knees to examine these relationships. Several key anatomic points are useful in the harvest of these tendons. Their conjoined insertion site is medial and distal to the tibial tubercle. They become distinct structures at a point that is farther medial and slightly proximal. Tendon harvest is facilitated by identifying the tendons proximal to this point. The superficial medial collateral ligament lies deep to the tendons in this area and should not be disturbed. The tendons are ensheathed in a dense fascial layer that may impede tendon stripping. The accessory insertion of the semitendinosus tendon (which was present in 77% of the knees dissected) should be identified and transected to avoid tendon damage at harvest. Knee flexion may reduce the risk of injury to the saphenous nerve as it crosses the gracilis tendon. Variation in tendon diameter affects graft strength.

Superoinferior translation in the intact and vented glenohumeral joint

The purpose of this investigation was to measure inferior translation in the intact and vented shoulder in different positions of abduction and rotation. Fifteen shoulders from adult cadavers were tested before and after venting of the joint capsule on an apparatus that permitted unconstrained translation when a 50 N inferior force was applied to the humeral shaft. The greatest inferior translation in the intact shoulder occurred at 45° abduction in neutral rotation. Venting the capsule significantly increased inferior translation in all positions but 45° abduction, and the greatest effect was seen at 0° glenohumeral abduction in neutral rotation. The so-called "sulcus sign" is the result of intraarficular vacuum effect and capsular laxity. Venting the capsule results in a significant increase in inferior translation. This is an important effect to consider during procedures for repairing instability of the shoulder, because failure to appreciate the normal "play" in inferior glenohumeral translation might lead the surgeon to believe that perceived laxity represents actual instability.

Management of Complications of Surgery for Anterior Shoulder Instability

Both operative and nonoperative management of the unstable shoulder requires a thorough understanding of the natural history of instability, as well as the normal anatomy and biomechanics of the shoulder joint. Failure of management may occur at any time during the course of treatment, and may be a result of either physician or patient error, or a combination of both. The correct diagnosis allows for selection of the most appropriate treatment, and the success of surgical treatment depends on proper recognition of the pattern of instability and technically adequate anatomic capsulolabral reconstruction. Complications that can occur include making the shoulder too loose or too tight, injury to the neurovascular elements about the shoulder, and articular injury from hardware usage about the shoulder.

Scapulothoracic motion in normal shoulders and shoulders with glenohumeral instability and impingement syndrome. A study using Moiré topographic analysis

Qualitative visual inspection and manual muscle testing are traditional methods of evaluation that may overlook subtle weakness of the axioscapular musculature. A modification of the standard technique of Moiré topographic analysis of spinal deformity was applied to assess axioscapular muscle function in 51 subjects: 22 asymptomatic individuals, 22 with shoulder instability, and seven with impingement syndrome. Static Moiré evaluation demonstrated scapulothoracic asymmetry or increased topography in 14% of asymptomatic subjects, compared with 32% and 57% in the instability and impingement groups, respectively. The dynamic Moiré test demonstrated an abnormal Moiré pattern in 18% of asymptomatic individuals, compared with 64% and 100% in the instability and impingement groups, respectively. Axioscapular muscle dysfunction is common with both instability and impingement syndrome of the shoulder, although it remains to be determined whether this represents a primary or secondary phenomenon.

Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint

The purpose of this study was to determine the contributions of specific capsuloligamentous structures to restraining superior-inferior translation of the glenohumeral joint. Eleven cadaveric shoulders were tested using a four degrees-of-freedom test apparatus. The humerus was free to translate in three planes and free to flex and extend when a superior and inferior force of 50 N was applied. Testing was performed in three positions of abduction (0 degree, 45 degrees, and 90 degrees) and three positions of rotation (neutral, maximum internal, and external). Shoulders were tested intact, vented, and after division of specific capsuloligamentous structures. The primary restraint to inferior translation of the adducted shoulder was the superior glenohumeral ligament. The coracohumeral ligament appeared to have no significant suspensory role. With progressive abduction, the anterior and posterior portions of the glenohumeral ligament become the main static stabilizers resisting inferior translation: the anterior portion was the primary capsular restraint at 45 degrees of abduction, while the posterior portion was the primary restraint at 90 degrees of abduction, neutral rotation. Our results indicate that clinical assessment of glenohumeral translation in the superior-inferior plane should be performed in multiple positions of abduction and rotation.

Accessory head of the biceps brachii. Case report demonstrating clinical relevance

Although anatomic variations in the origin of both the coracobrachialis or biceps brachii have been observed, there have been no previous reports of clinical relevance. In a 22-year-old man, recognition and mobilization of an accessory long head of the biceps brachii was necessary for adequate exposure of the shoulder joint dislocation through a deltopectoral incision.