Damage to cobalt-chromium surfaces during arthroscopy of total knee replacements.

BACKGROUND: It has been stated that care must be taken not to scratch the metal components during total knee arthroscopy; however, this concern has not been studied. Clinical observation during arthroscopy of total knee replacements suggested the possibility of damage to the femoral component by the arthroscopic cannula; therefore, a bench test was performed to study this potential risk. METHODS: Cobalt-chromium femoral components were tested to determine the surface damage that resulted from moving a stainless-steel arthroscopic cannula and a plastic arthroscopic cannula across the components under a variety of applied loads. Scanning electron microscopy and surface-roughness measurements of the prosthetic surface were used to evaluate the damage. RESULTS: The stainless-steel cannula produced observable alterations to the surface of the femoral component at loads as small as 8 N. The majority of these alterations were deposits of stainless steel from the cannula onto the component. The plastic cannula did not appear to produce alterations on the component surface. Surface roughness increased with increasing loading of the stainless-steel cannula, but there was no noticeable change with increasing loading of the plastic cannula. These forces did, however, severely damage some parts of the plastic cannula. CONCLUSIONS: Alterations to the surface of cobalt-chromium femoral components can occur during arthroscopy with stainless-steel cannulae but not with plastic cannulae. The results of this study support a recommendation to use plastic cannulae during arthroscopy of total knee replacements. CLINICAL RELEVANCE: Arthroscopy of total knee replacements is increasing in the clinical setting, and damage to the prosthesis should be avoided whenever possible. This study provides evidence that damage to the femoral component is possible with a stainless-steel cannula and that use of a plastic cannula may reduce this risk.

Fixation of proximal humeral prostheses and rotational micromotion.

Twenty pairs of cadaveric humeri were used to compare the rotational stability of proximal humeral prostheses fixed by proximal cementation with the stability offered by press fit or full cementation. For each proximally cemented specimen, only the upper portion of the prosthesis was coated with cement. For the fully cemented specimens, a cement restrictor was used just distal to the prosthesis, and a finger-packing technique was used to fill the proximal humeral medullary canal. Torque was applied to the Morse taper of the prostheses, and rotational micromotion was measured at the level of the osteotomy. In each of 11 pairs of cadaveric humeri, one side was press fit and the contralateral side was proximally cemented; in each of 9 pairs, proximal cementation was compared with full cementation. Proximally cemented prostheses' micromotion was significantly less than that of press-fit prostheses (P = .0016). There was no difference in micromotion between proximal cementation and full cementation (P = .82). Proximal cementation increased initial fixation over press fit. Full cementation did not increase rotational stability.

Shoulder dislocations in patients older than 40 years of age.

Shoulder dislocations in patients over 40 years of age are common and are frequently associated with serious injuries to adjacent structures. Associated injuries such as brachial plexus injury, rotator cuff tear, axillary artery injury, fractures about the shoulder, and recurrent dislocation can make shoulder dislocations challenging problems for the clinician. Early diagnosis and treatment of associated injuries and treatment complications are the mainstays in prevention of morbidity and, even, mortality.

Anatomy of provocative tests for impingement syndrome of the shoulder.

The purpose of this study was to describe the extra- and intra-articular anatomic relationships present during the Neer and Hawkins tests. Nine fresh-frozen cadaveric shoulders were positioned in the impingement position described by Neer (n = 5) or that described by Hawkins (n = 4), embedded in polyurethane, and studied with the use of a cross-sectional technique. All shoulders placed in the Neer position demonstrated soft tissue contact with the medial acromion and contact between the articular surface of the rotator cuff tendons and the anterosuperior glenoid rim. Shoulders placed in the Hawkins position demonstrated consistent contact between soft tissues and the coracoacromial ligament. In all Hawkins positioned shoulders, contact between the articular surface of the rotator cuff tendons and the anterosuperior glenoid was observed. The subscapularis tendon was deformed by the coracoid in 1 of the Hawkins positioned specimens. Although factors inherent to human subjects such as edema and muscle tone may influence the anatomy, these provocative tests for subacromial impingement appear to elicit contact consistent with impingement.

Evaluation of impingement syndromes in the overhead-throwing athlete.

OBJECTIVE: We outline impingement entities, describe the history and physical examination, and provide an overview of treatment beyond that routinely used in glenohumeral and scapulothoracic dysfunction. BACKGROUND: In the athlete, pain and dysfunction due to excessive overhead use or abnormal positioning of the shoulder is common and can result from multiple etiologies, including impingement syndromes. Primary, secondary, internal, and coracoid impingement have all been described. DESCRIPTION: These entities will be discussed, including pathology, evaluation, and treatment. CLINICAL ADVANTAGES: Incorporating a systematic evaluation and treatment of impingement syndromes optimizes care for the patient with shoulder pain.

Fixation of humeral prostheses and axial micromotion.

Surgeons often avoid cementing a proximal humeral prosthesis. Occasionally bony augmentation is needed. This study was undertaken to compare proximal cementation in combination with distal press with total cementation or press fit alone. In phase 1 axial micromotion with axial loading was measured in 15 pairs of humeri: 5 fully cemented versus proximally cemented, 5 fully cemented versus press fit, and 5 proximally cemented versus press fit. X-ray films of the specimens were obtained to assess canal fill. In phase 2 axial micromotion was measured in 5 pairs of high mineral density and 5 pairs of low mineral density to compare proximal cementation with press fit. The 3 M modular prosthesis was used in both phases. No difference was found in phase 1 among the 3 fixation techniques. A strong reverse statistical correlation (P = .007) (r = .55) was seen between axial micromotion and fill of the canal with the prosthesis. In the second phase no statistically significant difference was found between the techniques of fixation or between the 2 bone densities. Fill of the canal at the distal end of the prosthesis was the only variable found that affected axial micromotion, but it accounted for only approximately 30% of the variance. Bone quality and augmentation of the proximal bone with cement did not affect axial micromotion in this experiment but warrant further study.

Posterior to anterior transglenoid pins: anatomy at risk.

Pneumothorax was noted after an arthroscopic procedure during which a small guidewire overpenetrated the glenoid from a posterior-superior direction. This anatomic study was undertaken to determine the structures at risk from pins overpenetrating from the posterior-superior aspect and to determine whether scapulothoracic position altered the risk. The glenoid was intentionally overpenetrated with wooden dowels from the posterior-superior aspect of the glenoid in seven fresh cadaveric shoulders. The dowels were placed arthroscopically using the Suretac instrumentation (Acufex Microsurgical, Mansfield, MA). The specimens were planed, and the relationship of these wooden pins to vital structures was evaluated. In all specimens, the dowels entered the thoracic cavity between the first and second ribs, regardless of scapular position. The pins consistently passed posterior to the neurovascular bundle but were precariously close, with an average distance to the closest neurovascular structure of 7.4 mm (range, 1 to 19 mm). Scapular position did not seem to affect this relationship.

Superior glenoid impingement.

Superior glenoid impingement, a recently recognized mechanism of injury, puts five structures at risk: (1) the rotator cuff, (2) the superior labrum, (3) the greater tuberosity, (4) the superior glenoid, and (5) the inferior glenohumeral ligament. The clinical picture depends on which structures are injured and is still poorly described; however, the natural history is comprehensive for overhead athletes.

Superior glenoid impingement. Current concepts.

In the current decade impingement syndrome is becoming a less precise diagnostic entity. It is splitting into several categories of more exact diagnoses. The concept development, clinical picture, and currently recommended treatment of 1 of these entities, the superior glenoid impingement is reviewed. The complaint may be acute or chronic and may involve 1 or more of 5 structures: (1) superior labrum, (2) rotator cuff tendon, (3) inferior glenohumeral ligament, (4) greater tuberosity, and (5) the bony glenoid. The most commonly seen clinical entity is chronic dorsal shoulder pain in an athlete who throws with a positive relocation test. Treatment consists of strengthening of the cuff and scapular rotators. When there has been excessive inferior ligament stretch this must be augmented by anterior reconstruction.

Spinal accessory nerve in a trapezius-splitting surgical approach.

To elucidate the safe limits for muscle-splitting incisions of the trapezius muscle, 25 cadaver shoulders were studied. To describe the position of the nerve distances were expressed as a percentage of the distance from the tips of the vertebral spinous processes to the lateral tip of the acromion. The spinal accessory nerve was found to run a vertical course medial and parallel to the vertebral border of the scapula. Three to six nerve branches (average 3.8) also ran a vertical course lying between 33% to 50% of the distance from the tips of the vertebral spinous processes to the lateral tip of the acromion. The most lateral branch lay an average at 44% distance and never beyond 50%. Muscle-splitting incisions are relatively safe in the lateral 50% of the muscle. In the medial half they are to be avoided or pursued with great caution.

Posterior superior glenoid impingement: expanded spectrum.

Posterior superior glenoid impingement is a recently recognized mechanism of injury producing rotator cuff injury in athletes. Usually the mechanism is repetitive overhand activity such as throwing. A survey of the author's practice was undertaken to show a wider spectrum of this mechanism both in the activity that caused it and the number of structures at risk of injury from this mechanism. The survey revealed 11 patients who had a clear recollection of their mechanism of injury and an objective documentation of the injury by arthroscopy or imaging studies. The majority of shoulders had damage to more than one of the five structures at risk from this mechanism of injury. Six cases were not sports related. Glenoid impingement may injure one or more of the following: (1) superior labrum, (2) rotator cuff tendon, (3) greater tuberosity, (4) inferior glenohumeral ligament or labrum, and (5) superior glenoid bone. Injury to more than one structure may be the rule and injury to one structure may indicate investigation of the other four.

Shoulder instability in the overhand or throwing athlete.

In the young throwing athlete with shoulder pain, it is essential to recognize that glenohumeral joint instability (occult subluxation, rather than impingement) is the primary underlying pathology. Fortunately, conservative management is effective in most chronic overuse injuries. For those athletes with continued symptoms, surgical intervention may become necessary. The anterior capsulolabral reconstruction addresses the problem of glenohumeral joint instability by correcting the capsular redundancy, labrum damage, or both. The authors believe this most recent surgical technique and postoperative rehabilitation program has resulted in a significant improvement in our ability to more predictably and successfully return these athletes to prior competitive levels.

Acromial compromise with use of a transacromial portal: a biomechanical study.

In an experimental evaluation with 14 paired cadaveric scapulae we found that the transacromial arthroscopy portal, used occasionally in the repair of superior labral lesions, will reduce the structural integrity of the acromion to approximately 60% (range 25% to 85%) of its original strength, thereby placing it at increased risk of fracture. These studies provide baseline biomechanical information and suggest that limited shoulder activity is indicated after use of this portal.

Limits imposed on glenohumeral motion by joint geometry.

Contact of the greater tuberosity against the glenoid raises the question of the limits imposed on motion by glenohumeral joint geometry. In 50 cadaveric shoulders the arcs of articular cartilage on the humeral head and glenoid in the frontal and axial planes were measured or calculated. In the coronal plane the humeral heads had an arc of 159 degrees (+/- 8.5 degrees) covered by 96 degrees (+/- 8 degrees) of glenoid, leaving 63 degrees (+/- 10 degrees) of cartilage uncovered. In the transverse plane the humeral arc of 160 degrees (+/- 11 degrees) is opposed by 74 degrees (+/- 6 degrees) of glenoid, leaving 86 degrees uncovered. The 159 degrees of coronal humeral arc articulating with the transverse glenoid has 88 degrees (+/- 9 degrees) of cartilage uncovered. The geometry of the glenohumeral joint limits motions that occur in simple arcs. The obligate external rotation that occurs in elevation is necessary to make more humeral cartilage available for articulation with the glenoid.

Neuroanatomy in elbow arthroscopy.

An injury to the median nerve from within the joint during an arthroscopic synovectomy prompted a study of the relationship of the nerves to the capsule and bones of the elbow. Six pairs of cadaveric elbows frozen in 90 degrees of flexion and one pair frozen in extension were sectioned at 5-mm intervals, and the distances from the major nerves to the bones and capsule were recorded. One elbow joint in each pair was filled with saline solution. Saline solution insufflation increased the nerve-to-bone distance with the elbow in flexion. The results were 12 mm for the median nerve and 6 mm for the radial nerve. The capsule-to-nerve distance was affected little by insufflation and was as narrow as 6 mm in three specimens. Extension eliminated the protective effects of insufflation and brought the nerves closer to the bone. These findings confirm (1) the importance of flexion and insufflation in portal placement, (2) that insufflation does not improve the capsule-to-nerve distance, and (3) the potential for "from within-out" injury in synovial procedures.

Subdeltoid lipoma presenting as subluxation of the glenohumeral joint.

This case illustrates that space-occupying lesions beneath the heavily collagenated portion of the deltoid can produce a confusing clinical picture mimicking subluxation. This patient's clinical presentation was quite extraordinary in its resemblance to glenohumeral instability. The case also illustrates the importance of imaging studies in confirming questionable diagnoses. Such studies should be read by the surgeon, and any discrepancies from the radiologist's reading should be addressed.

Amputation salvage with microvascular free flap from the amputated extremity.

Microvascular surgery has allowed creative primary reconstruction using undamaged parts of amputated limbs as donor sites. We present a case of lower extremity below-knee amputation salvage with a free flap of heel, calcaneus, and soft tissues from the amputated lower leg, ankle, and foot supplied by the posterior tibial neurovascular bundle.

Special properties of living tissue that affect the shoulder in athletes.

The physiologic function of the structures of the shoulder is to withstand the forces that arise from activity without sustaining injury. From our understanding of the biology of these tissues, we can see how they modify themselves to prevent injury and react, appropriately or inappropriately, to injury. This information, and knowledge yet to be discovered in the laboratory, should lead to more effective surgery, physical therapy, and use of medication.