Field T. Blevins

Reconstruction of the anterior and posterior cruciate ligaments after knee dislocation results using fresh-frozen nonirradiated allografts

We reviewed the results in 13 patients who underwent simultaneous allograft reconstruction of both the anterior and posterior cruciate ligaments after a knee dislocation (nine acute and four chronic injuries). Seven patients sustained related medial collateral ligament injuries and six patients had posterolateral complex injuries. Ligament reconstructions were performed using fresh-frozen Achilles or patellar tendon allografts. At follow-up evaluation (mean of 38 months), only one patient described the reconstructed knee as normal. Six patients had returned to unrestricted sports activities and four had returned to modified sports. The average extension loss was 3° (range, 0° to 10°) and average flexion loss was 5° (range, 0° to 15°). The KT-1000 arthrometer measurements at 133 N anterior-posterior tibial load showed a mean side-to-side difference of 4.5 mm (range, 0 to 10) at 20° and 5.0 mm (range, 0 to 9) at 70°. The mean Lysholm score was 88 (range, 42 to 100). International Knee Documentation Committee ratings were six nearly normal, five abnormal, and one grossly abnormal. Two patients required manipulations for knee stiffness. This study demonstrates that reconstruction of both cruciate ligaments can restore stability sufficient to allow sports activity in most patients with knee dislocations, but “normal” results are difficult to achieve.

Arthroscopic assisted rotator cuff repair: Results using a mini-open deltoid splitting approach

Out of 78 patients identified who underwent mini-open cuff repair, 64 were interviewed and returned a detailed questionnaire and 47 returned for a physical examination. Their average age was 64 years (31 to 85 years); and the average follow-up was 29.2 months (range, 12 to 65 months). The average tear size was 8 cm2. Preoperatively, all patients complained of pain and weakness. Ninety-six percent of patients displayed positive impingement signs preoperatively compared with 16% postoperatively. Active elevation increased significantly (P < .05) from 129 degrees to 166 degrees. At the time of follow-up there was no significant difference between active elevation in the operative and contralateral shoulders (P > .05). Weakness was detectable by physical examination in 83% of patients initially, and in 22% at the time of the final examination. The average pain and function scores improved significantly. Eighty-nine percent were satisfied with the results of their surgery. Three patients required further surgery on their shoulder. We found no correlation between cuff tear size and final Hospital for Special Surgery shoulder score.

BIOLOGY OF THE ROTATOR CUFF TENDON

Tendons are complex composite material composed primarily of water, collagen, proteolycans, and cells, designed to transmit tensile loads from muscle to bone. Although rotator cuff tendons differ in many ways from other tendons in the body, a knowledge of basic tendon structure and function is helpful in understanding rotator cuff tendon biology, injury, and repair. In addition to type I collagen, rotator cuff tendons contain small amounts of type III collagen, which play a role in healing and repair. In comparison with other tendons, the increased glycosaminoglycan and proteoglycan content seen in rotator cuff tendons may be adaptive, pathologic, or both. The etiology of rotator cuff pathology is probably related to trauma, aging, and degeneration. As our understanding of these processes increases, we will be able to develop and implement improved preventative and therapeutic interventions for rotator cuff pathology.

Biomechanics of the Coracoclavicular Ligament Complex and Augmentations Used in Its Repair and Reconstruction

Augmentation is a well-accepted and common component of coracoclavicular ligament repairs and reconstructions. The purpose of this study was to examine and compare the strength, stiffness, and mode of failure of the coracoclavicular ligament complex and four different augmentation techniques in cadaveric shoulders. There was no significant difference in the mean failure load between the intact ligament complex (724.9 230.9 N) and augmentations performed with braided polydioxanone (PDS) (676.7 115.4 N) or braided polyethylene placed through (986.1 391.1 N) or around (762.7 218.2 N) the clavicle. The mean failure load for augmentations using a 6.5-mm cancellous screw through the clavicle and into a single cortex of the coracoid (390.1 253.6 N) was significantly lower than that for the intact coracoclavicular ligaments. There was no difference in mean stiffness between the intact coracoclavicular ligament complex (115.9 36.2 N/mm) and the braided polyethylene augmentations placed through (99.8 22.2 N/mm) or around (90.0 25.5 N/mm) the clavicle. Polydioxanone augmentations were significantly less stiff (27.4 3.3 N/mm) than the intact complex, while screw augmentations were significantly stiffer (250.4 88.2 N/mm). There were no significant differences in strength or stiffness of braided polyethylene reconstructions placed around or through a drill hole in the clavicle.

Rotator Cuff Pathology in Athletes

SummaryThe rotator cuff is the primary dynamic stabiliser of the glenohumeral joint and is placed under significant stress during overhead and contact sports. Mechanisms of injury include repetitive microtrauma, usually seen in the athlete involved in overhand sports, and macrotrauma associated with contact sports. Rotator cuff injury and dysfunction in the overhand athlete may be classified based on aetiology as primary impingement, primary tensile overload, and secondary impingement and tensile overload resulting from glenohumeral instability. A thorough history and physical examination are paramount in the evaluation, classification and treatment planning of the athlete with rotator cuff pathology. Imaging studies are a helpful adjunct to the history and physical.Athletes with primary impingement are usually middle aged or older and often have chronic shoulder pain and sometimes weakness associated with overhand sporting activities. Night pain is typical of full thickness rotator cuff tears. Impingement signs are positive and strength of elevation and external rotation are often limited. They usually respond to a nonoperative rehabilitation programme centred on decreasing inflammation, restoring range of motion and strengthening the rotator cuff and scapular stabilisers. Depending on the degree of cuff pathology, acromioplasty, debridement of partial cuff tears, and repair of full thickness tears are usually successful in those who fail a rehabilitation programme.Overhand athletes with cuff pathology secondary to subtle anterior instability are usually young and complain of pain and decreased throwing velocity. Instability may be so subtle that it is only detectable through a positive relocation test on examination. The majority of these athletes do not have a Bankart lesion on magnetic resonanace imaging or arthroscopic examination. Arthroscopic examination usually demonstrates anterior capsular laxity (positive ‘drive-through’ sign), as well as superior-posterior labral and cuff injury typical of internal impingement. If rehabilitation alone is not successful, a capsulolabral repair followed by rehabilitation may allow the athlete to return to their previous level of competition.The athlete with an acute episode of macrotrauma to the shoulder resulting in cuff pathology usually presents with pain, limited active elevation and a positive ‘shrug sign’. Arthroscopy and debridement of thickened, inflamed or scarred subacromial bursa with cuff repair or debridement as indicated is usually successful in those who do not respond to a rehabilitation programme.

Functional morphology of the supraspinatus tendon

Grossly normal supraspinatus tendons were analyzed by stereomicroscope dissection and three-dimensional serial-section reconstruction. Four structurally independent subunits were identified: the tendon proper extended from the musculotendinous junction to approximately 2.0 cm medial to the greater tuberosity. It was composed of parallel collagen fascicles oriented along the tensional axis and separated by a prominent endotenon region. There was no interdigitation of fascicles, and an 18% incidence of fascicle convergence as the fascicles coursed from muscle toward greater tuberosity. The attachment fibrocartilage extended from the tendon proper to the greater tuberosity, consisted of a complex basket-weave of collagen fibers, and stained diffusely with alcian blue. The densely packed unidirectional collagen fibers of the rotator cable extended from the coracohumeral (CH) ligament posteriorly to the infraspinatus, coursing both superficial and deep to the tendon proper. The capsule was composed of thin collagen sheets each with uniform fiber alignment that differed slightly between sheets. These data describe a specialized tendon capable of internally compensating for changing joint angles through fascicles which are structurally independent and can slide past one another. The tendon attachment exhibits a structure adapted to tensional load dispersion and resistance to compression.

Dissociation of modular humeral head components: a biomechanical and implant retrieval study.

In vivo dissociation of the Morse-taper of shoulder arthroplasty modular humeral components has been reported. The incidence of this complication appears to be approximately 1:1000. The objective of this study was to identify conditions that might affect the Morse-taper interface strength in humeral components. Mechanical tests were performed to load and dissociate humeral heads from the humeral stems (titanium). The effect of loading rate, load amplitude, and number of impactions was investigated. Dissociation force was measured after the taper was contaminated with water, oil, blood, and bone cement particles. The mean dissociation force after two impactions with a mallet was 2926 +/- 955 N. Dissociation force was linearly proportional to impaction force. Repetitive loading beyond two impactions did not significantly increase taper strength. Contamination of the taper with as little as 0.4 ml of fluid could prevent fixation of the taper.

Effect of humeral head component size on hemiarthroplasty translations and rotations

Glenohumeral translation and rotation were measured in 6 grossly normal, fresh frozen shoulder preparations while a manual load was applied to the humerus. The same tests (maximum elevation, total rotation, anterior/posterior (A/P) translation, and inferior translation) were repeated for each shoulder through 8 series: 1 with the shoulder intact, 1 with the shoulder vented, and 6 with progressively larger humeral head components after hemiarthroplasty. There was an inverse linear relation between humeral head component size and all 4 outcome variables. Replacing the native head with a component of equal diameter reduced elevation 20%, rotation 40%, A/P translation 50%, and inferior translation 60% in the vented shoulder. Replacing the native head with a component of equal effective volume decreased elevation 8%, rotation 20%, A/P translation 25%, and inferior translation 40% in the vented shoulder. Increasing humeral head component size decreased rotation, A/P translation, and inferior translation by similar percentages and elevation somewhat less. Humeral head component size is better described in terms of volume than in terms of diameter or offset.