Histological evaluation of repair of the rotator cuff in a primate model.

The establishment of a suitable animal model of repair of the rotator cuff is difficult since the presence of a true rotator cuff anatomically appears to be restricted almost exclusively to advanced primates. Our observational study describes the healing process after repair of the cuff in a primate model. Lesions were prepared and repaired in eight 'middle-aged' baboons. Two each were killed at four, eight, 12 and 15 weeks post-operatively. The bone-tendon repair zones were assessed macroscopically and histologically. Healing of the baboon supraspinatus involved a sequence of stages resulting in the reestablishment of the bone-tendon junction. It was not uniform and occurred more rapidly at the sites of suture fixation than between them. Four weeks after repair the bone-tendon healing was immature. Whereas macroscopically the repair appeared to be healed at eight weeks, the Sharpey fibres holding the repair together did not appear in any considerable number before 12 weeks. By 15 weeks, the bone-tendon junction was almost, but not quite mature. Our results support the use of a post-operative rehabilitation programme in man which protects the surgical repair for at least 12 to 15 weeks in order to allow maturation of tendon-to-bone healing.

Comparative anatomy of the rotator cuff.

While the evolution of the bony skeleton of the shoulder girdle is well described, there is little information regarding the soft tissues, in particular of the rotator cuff. We dissected the shoulders of 23 different species and compared the anatomical features of the tendons of the rotator cuff. The alignment and orientation of the collagen fibres of some of the tendons were also examined histologically. The behaviour of the relevant species was studied, with particular reference to the extent and frequency of forward-reaching and overhead activity of the forelimb. In quadrupedal species, the tendons of supraspinatus, infraspinatus and teres minor were seen to insert into the greater tuberosity of the humerus separately. They therefore did not form a true rotator cuff with blending of the tendons. This was only found in advanced primates and in one unusual species, the tree kangaroo. These findings support the suggestion that the appearance of the rotator cuff in the evolutionary process parallels anatomical adaptation to regular overhead activity and the increased use of the arm away from the sagittal plane.

Modulation of aggrecan and ADAMTS expression in ovine tendinopathy induced by altered strain.

OBJECTIVE: To evaluate histologic, immunohistochemical, and molecular changes in tendon induced by altered strain in a large-animal model. METHODS: A full-thickness partial-width laceration of the infraspinatus tendon was created in 5 sheep, while 5 sham-operated sheep were used as controls. Sheep were killed after 4 weeks, and 4 differentially stressed tendon regions (tensile or near bone attachment from overstressed or stress-deprived halves) were evaluated for histopathology, proteoglycan (PG) accumulation, and characterization of glycosaminoglycans and aggrecan catabolites. Gene expression of matrix components, enzymes, and inhibitors was analyzed by reverse transcriptase-polymerase chain reaction. RESULTS: Histopathologic changes were detected in both overstressed and stress-deprived tensile tendon, but only in stress-deprived tendon near bone. In overstressed and stress-deprived tensile tendon, levels of keratan sulfate, chondroitin 4-sulfate, and chondroitin 6-sulfate were increased. In overstressed tensile tendon, levels of ADAMTS-generated aggrecan catabolites were increased. There was increased matrix metalloproteinase 13 (MMP-13) and decreased fibromodulin and decorin expression in all regions. Increased MMP-1, MMP-9, MMP-14, and ADAMTS-1 expression, and decreased type II collagen expression were restricted to stress-deprived tendon. In stress-deprived bone-attachment regions, messenger RNA (mRNA) for aggrecan was decreased, and ADAMTS was increased. In overstressed tensile tendon, aggrecan mRNA was increased, and ADAMTS was decreased. CONCLUSION: The distinct molecular changes in adjacent tissue implicate altered strain rather than humoral factors in controlling abnormal tenocyte metabolism, and highlight the importance of regional sampling. Tendon abnormalities induced by increased strain are accompanied by increased aggrecan, decreased ADAMTS, and low PG expression, which may negatively impact the structural integrity of the tissue and predispose to rupture.

Boundary conditions at the tendon-bone interface.

The reconstruction of a tendon-bone interface, as in rotator-cuff repairs, remains a challenging surgical problem. There is however, little data to show what effect joint position or repair loading under physiological conditions have on the repaired tendon-bone interface. A change in the amount of contact area or load at the tendon-bone interface may influence healing. In this study we investigated the effect of limb position and boundary conditions on the tendon-bone interface in an in vitro rabbit tendon-bone repair model using both unlinked and linked suture repairs.

Mechanical properties of the rotator cuff: response to cyclic loading at varying abduction angles.

The rotator cuff is loaded under static as well as dynamic conditions. Whilst the static properties of the rotator cuff muscle-tendon junctions have been reported, the dynamic mechanical behaviour has not. This study reports the dynamic mechanical properties with varying abduction angles in a human cadaver rotator cuff. No significant effect was found with varying the angle of testing or in the presence of a tear in the tendon. The supraspinatus was found to be the stiffest of the rotator cuff tendons followed by the subscapularis and infraspinatus.

Anatomic variance of the coracoclavicular ligaments.

The coracoclavicular ligaments vary widely in morphology and anatomic descriptions. Few authors have adequately described the coracoclavicular ligaments' anatomy, and a number of discrepancies exist in the anatomy literature. This study examines the complex anatomy of the coracoclavicular ligaments and their relationships to clinically important bony landmarks. The geometric dimensions of 24 coracoclavicular ligament specimens from fresh human cadaveric shoulders were examined and quantified with 13 different measurements. Particular attention was given to any inter-specimen anatomic variance. The coracoid insertions of the conoid ligaments displayed high variance, with 33% (8/24) being confluent with the lateral fibers of the superior transverse scapular ligament. A further 15% (3/24) presented an additional lateral fascicle. The distance from the lateral trapezoid ligament to the distal clavicle averaged 15.3 mm. Three distinct and previously unreported conoid ligament variants lend themselves to an anatomic classification (types I, II, and III). A safety margin of 15 mm is suggested for distal clavicle resection in incomplete acromioclavicular joint injuries to preserve the intact coracoclavicular ligament.

A novel, resorbable suture anchor: pullout strength from the human cadaver greater tuberosity.

The pullout strength of a collagen bone anchor that creates interference fixation as the result of radial swelling on hydration was compared with a Mitek rotator cuff anchor after insertion into the greater tuberosity of human cadaver humeri. Bones were fully hydrated at 37 degrees C. Stiffness, peak load, and the mode of failure were recorded. Real and apparent bone densities were measured. Peak load for the collagen anchor at 15 minutes (121.0N +/- 81.3N) was greater than at 2 minutes (60.5N +/- 38.5N) after insertion (P <.05). At between 5 and 60 minutes after insertion, peak loads for the Mitek and the collagen anchors did not differ. After 30 minutes from insertion, the mode of failure of the collagen anchor changed from pullout with minor body damage to pullout with major body damage. Peak load at pullout correlated with bone density for the Mitek (P <.05, r = 0.516) but for the collagen bone anchor appeared unaffected by bone density.

Laminated tears of the human rotator cuff: a histologic and immunochemical study.

Laminated tears of the rotator cuff are often lined by a cellular layer that has an appearance suggestive of synovium. This study demonstrates, by histologic and immunohistochemical means, that the lining cells are synovial. It remains unclear whether these cells arise by synovial extension from the joint or bursa, or by metaplasia in the presence of synovial fluid, and this has implications for surgical repair of laminated cuff defects. We suggest that these defects be curetted, to remove at least some of this synovial lining, before suture repair.

Stabilization of the posterior limb of the medial canthal tendon using biodegradable tag anchors: a cadaveric model.

PURPOSE: This study describes and tests in a cadaveric model a new method of fixation designed for potential stabilization of the posterior limb of the medial canthal tendon, using biodegradable Tag anchors. METHODS: Study of the possibility of performing surgery to repair medial ectropion using biodegradable polyglyconate Tag anchors was commenced in the sheep cadaveric head model, and in the whole dry human skull model. This was then performed using five preserved human cadaveric whole heads, and pullout tensions were estimated in four of these. Computed tomography and magnetic resonance imaging were obtained for this model in the fifth head, and computed tomography was performed on the whole dry human skull. Dissections were carried out to establish the site of the bony defect in each of the heads. RESULTS: It was possible to obtain good Tag anchor fixation in bone overlying the maxillary and ethmoidal sinuses of the sheep, and in a young human skull. It was also possible to place adequately the anchor in the medial wall of the orbit close to the posterior lacrimal crest in all cases in the human cadaveric model. Pullout strengths were evaluated and found to range from 3.5 N to 12.4 N (mean, 7.5 N). Computed tomography and magnetic resonance imaging failed to demonstrate the biodegradable anchors in both the dry human whole skull and in the fifth cadaveric head, but did demonstrate the bony defects in the medial orbital walls through which the anchor passed. CONCLUSIONS: We have shown, for the first time, the stability of biodegradable Tag anchor fixation in a human cadaveric head model using pullout tensions and dissection studies. This method would allow adequate strength and stability to provide for control of fixation of the medial end of the lower eyelid in patients with medial ectropion and medial canthal tendon laxity.

A novel suture anchor of high-density collagen compared with a metallic anchor. Results of a 12-week study in sheep.

We report the early mechanical properties and histologic findings of a high-density, type I collagen bone anchor. This new anchor was compared with a traditional metallic anchor in a sheep patellar tendon model. No difference in strength of the repair was noted between the two devices at any time point. The insertions on the repaired side approached the strength of the nonoperated side by 12 weeks. Histologic analysis showed that the collagen anchor integrated with the surrounding bone by 6 weeks, and there was little degradation at 12 weeks. The high-density collagen anchor supported tendon healing to bone comparable with that seen with a traditional metallic device, but it has the potential advantage of the anchor being incorporated into bone.

Mechanical and histologic evaluation of Collagraft in an ovine lumbar fusion model.

The purpose of this study was to determine the effectiveness of a composite material composed of Type I bovine dermal collagen, 65% hydroxyapatite, and 35% tricalcium phosphate ceramic (Collagraft Bone Graft Matrix Strip NeuColl Incorporated, Palo Alto, CA) as a bone graft substitute for spinal fusion with and without the use of autologous bone marrow in an ovine lumbar spine model with pedicle screw fixation. Twenty-four adult sheep underwent a single level posterolateral (intertransverse process) L3-L4 lumbar fusion with one of three graft materials combined with rigid pedicle screw fixation. The three graft materials were Collagraft, Collagraft with marrow, and autogenous corticocancellous bone graft. Animals were euthanized 6 months after surgery and evaluated using dual energy x-ray absorptiometry, radiographs, histologic analysis, and mechanical testing. Dual energy xray absorptiometry between the transverse processes revealed that the mineral densities for the two Collagraft groups were significantly higher than the autogenous bone graft group. Histologic analysis confirmed that Collagraft was highly compatible and was well incorporated into the fusion mass. Both Collagraft groups had thick trabeculae and a mixture of lamellar and plexiform bone. The autogenous bone graft group had a smaller fusion complex, composed primarily of lamellar bone with thinner and fewer trabeculae. All three groups had similar mechanical properties. These results support the use of Collagraft in spinal fusion with pedicle screw fixation.

Structural properties of the intact and the reconstructed coracoclavicular ligament complex.

Numerous procedures have been described for the operative management of acromioclavicular joint injuries, but surprisingly little information is available on the ultimate mechanical behavior of the native coracoclavicular ligament complex or on the various methods of reconstruction. We tested 19 fresh-frozen cadaveric bone-ligament-bone preparations of the coracoclavicular ligament in uniaxial tension at 25 mm/min until failure. Seven specimens were left intact, six had the trapezoid ligament sectioned, and six had the conoid ligament sectioned. Reconstruction of the coracoclavicular ligament was achieved using coracoacromial ligament transfers, woven polyester slings, suture anchors, and Bosworth screws; all reconstructions were also tested to failure. The intact coracoclavicular ligament failed by avulsion or midsubstance tear at 500 (+/-134) N, with a stiffness of 103 (+/-30) N/mm and elongation to failure of 7.7 (+/-1.9) mm. There was no significant difference between the contributions of the conoid or trapezoid ligaments in this loading configuration. Coracoclavicular slings and suture anchors provided strength similar to that of the coracoclavicular ligament, but with significantly greater deformations (14 to 26 mm). Screw fixation resulted in comparable stiffness and superior strength to the coracoclavicular ligament, but only if bicortical purchase was obtained. Coracoacromial ligament transfers were the weakest and least stiff, and augmentation with another form of coracoclavicular fixation is recommended. These results provide a useful baseline for comparison of the initial performance of reconstructive techniques with the performance of the native coracoclavicular ligament.

Resurfacing of the glenoid in total shoulder arthroplasty. A comparison, at a mean of five years, of prostheses inserted with and without cement.

BACKGROUND: Clinically evident loosening of a glenoid component inserted with cement in total shoulder arthroplasty is infrequent, but radiographic changes that indicate loosening at the implant-bone interface are common and have been associated with functional limitation. We compared the results of total shoulder arthroplasties in which the glenoid implant had been inserted with cement with those of arthroplasties in which a bone-ingrowth glenoid implant had been inserted without cement. METHODS: The results of eighty-six consecutive total shoulder arthroplasties, performed by the same surgeon, were retrospectively reviewed between four and seven years after the operation. Fifty-eight shoulders in which the primary glenoid implant was in situ were assessed with use of the Simple Shoulder Test and Short Form-36 questionnaires, clinical examination, and fluoroscopic imaging of the glenoid implant-bone interface. Thirty-two of the glenoid components had been fixed with cement and twenty-six, without cement. RESULTS: Complications occurred in 16 percent (fourteen) of the eighty-six shoulders, and 9 percent (eight) of the shoulders needed a revision operation. None of the revisions were done because of loosening of the glenoid component. Five of the eight revisions involved implants that had been inserted without cement. Three of these implants were revised because of early instability and two, because the polyethylene component had separated from the metal tray of the glenoid implant. With the numbers available, we could not detect any significant differences between the groups with respect to pain, range of motion, function of the shoulder, or general health. Radiographic analysis demonstrated a high level of interobserver agreement (kappa = 0.89). Radiolucent lines were observed after 41 percent (thirteen) of the thirty-two arthroplasties performed with cement compared with 23 percent (six) of the twenty-six arthroplasties performed without cement. The proportion of implants classified as probably loose was approximately three times greater in the group in which cement had been used. Eccentric wear of the posterior rim of the metal tray and focal osteolysis under the metal tray were observed in the group in which the component had been inserted without cement; these findings may indicate a potential for progression of radiographic loosening with increased durations of follow-up. CONCLUSIONS: We concluded that, despite the higher rate of early complications, the intermediate-term outcomes of arthroplasties in which the glenoid implant is inserted without cement are comparable with those of arthroplasties with cementing of the glenoid component.

[Not Available]. / Schulterarthrodese: Beschreibung einer modifizierten Technik.

OBJECTIVES: Stabilization of the glenohumeral joint to relieve pain and to improve function in instances of muscle paralysis secondary to plexus palsy, destruction of the joint with massive bone loss and large irreparable cuff tears. INDICATIONS: Paralysis of the rotator cuff or deltoid muscles secondary to brachial plexus lesions or polio. Severe joint degeneration following infection. Massive irreparable cuff tears. Failed arthroplasty. Severe rheumatoid disease. CONTRAINDICATIONS: Advanced arthritis of the ipsilateral elbow. Arthroplasty of the ipsilateral elbow. Extensive loss of scapulothoracic muscles. Severe thoracic scoliosis and advanced arthritis of the sternoclavicular and acromioclavicular joints are relative contraindications. SURGICAL TECHNIQUE: Anterolateral lazy S-incision. Retraction of deltoid. Osteotomy of the lateral acromion. Exposure and denuding of humeral and glenoid articular surfaces. Freshening of the undersurface of the acromion. Internal fixation with an 8- to 10-hole pelvic reconstruction plate in a position of 20 to 40° of abduction, 20 to 40° of flexion and 30 to 50° of internal rotation. Apposition of acromion. Postoperative immobilization for a period of at least 6 weeks on a splint prepared before surgery. This splint allows early mobilization of the elbow. RESULTS: Report on 60 shoulder arthrodeses (42 men, 18 women, average age 28 years, average length of follow-up 4 years). Plate loosening was observed 5 times, leading to a nonunion in 2 patients. A fracture beneath the plate occurred twice, in 5 patients the pain relief was not satisfactory. Revision became necessary in 2 patients due to poor position of the transglenoid screw. The time to union calculated in 49 patients amounted to an average of 7.9 months, in general union took longer following a failed arthroplasty and was shortest after brachial plexus palsy.

Biomechanical performance of Bankart repairs in a human cadaveric shoulder model.

The objective of this study was to develop a method to evaluate the biomechanical performance of Bankart repairs in a human cadaveric shoulder in a clinically relevant orientation. Twenty fresh-frozen human cadaveric shoulder girdles were used to compare the biomechanical performance of intact anteroinferior capsulolabral complexes with the biomechanical performance of three Bankart lesion reconstruction techniques. Repairs were performed on surgically created Bankart lesions. Evaluations were performed with the shoulders in glenohumeral abduction and external rotation. The repair techniques employed interosseous sutures, Mitek GII suture anchors, or Acufex T-Fix devices. The suture material used in all repairs was No. 2 Ti-Cron. The biomechanical performance of the three reconstruction techniques did not differ, but each was significantly inferior compared with that of the intact shoulder samples. The interosseous repairs failed by suture pullout through soft tissue. Repairs in the Mitek GII group failed by pullout of the suture anchors, suture breakage, or pullout of the suture through soft tissue. Repairs in the T-Fix group failed by pullout of the suture through soft tissue or failure of the polymer portion of the T-Fix suture.

Cytokines and matrix metalloproteinases mRNA expression in archival human tissues from failed total hip arthroplasty using in situ hybridization and color video image analysis.

Reports on the histological and biochemical nature of periprosthetic fibrous/granulomatous tissue has, to date, been largely limited to frozen tissue sections. This study reports the cytokine and matrix metalloproteinase profiles found in periprosthetic interface tissues in THA which have failed due to aseptic loosening and in capsular tissues obtained at primary surgery. The study employs immunohistochemistry, in situ hybridization, and color video image analysis on formalin fixed and paraffin embedded sections.

The clinical role of shoulder ultrasound.

BACKGROUND: Rotator cuff surgery is facilitated by accurate pre-operative information regarding the presence and size of cuff tears, and the extent of any cuff retraction or lamination. METHODS: A total of 117 consecutive patients who underwent shoulder ultrasound followed by surgical management were assessed, and the pre-operative ultrasound diagnoses were correlated with the operative findings. RESULTS: Ultrasound was found to be reliable for the detection of full-thickness cuff tears (positive predictive value 96%). In the assessment of partial thickness tears, ultrasound produced few false positives, but failed to diagnose a significant proportion of these lesions. Lamination and other interstitial cuff pathology were not reliably detected by ultrasound. In the diagnosis of subacromial impingement, ultrasound produced few false positives (positive predictive value 95%), but did produce a significant number of false negative results (negative predictive value 66%). CONCLUSIONS: Ultrasound is cheaper than MRI and arthrography, and is both non-invasive and 'dynamic'. It is reliable in the diagnosis of full-thickness cuff tears and is a useful adjunct in the diagnosis of cuff impingement and partial thickness tears, but is very much operator-dependent.