Biomedical subjects

W R Walsh

Publications and source records attributed to W R Walsh.

80 records · Page 5Linked to original sources

PubMedDate not supplied

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.

Acromioclavicular Joint↗

PubMedDate not supplied

Detrimental effects of an omega-3 fatty acid-enriched diet on wound healing.

The omega-3 fatty acids contained in fish oils have anti-inflammatory effects with potential beneficial clinical applications. However, these same effects may alter wound healing, a process dependent upon an adequate inflammatory response. The hypothesis that a diet enriched with omega-3 fatty acids could be detrimental to wound healing was tested in male rats fed complete diets differing only in their fat composition (17% menhaden oil + 3% corn oil vs 20% corn oil by weight) for 21 days before wounding and for 10 or 30 days after wounding (n = 16 per group). The wounding protocol included a dorsal 5-cm skin incision used for mechanical testing and a 2-cm incision used for subcutaneous polyvinyl alcohol sponge implantation. At 10 or 30 days postinjury, the 5-cm skin wounds were harvested and mechanically tested. The sponges were removed at 30 days and analyzed for collagen content. Food consumption and weight gain were the same in the two dietary groups. No differences in the mechanical properties of the wounds were detectable 10 days after injury. At 30 days, however, wounds harvested from rats fed the menhaden oil diet were significantly weaker than those from corn oil-fed animals. This difference in tensile strength was not explained by differential collagen accumulation, inasmuch as the collagen content of the sponges at 30 days was the same in both groups. Dietary consumption of a diet rich in omega-3 fatty acids may conspire against the quality of wounds by altering the fibroplastic or maturational phases of the healing response.

Animals↗

PubMedDate not supplied

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.

Acromioclavicular Joint↗

PubMedDate not supplied

In vitro structural properties of braided tendon grafts.

In an effort to increase strength in hamstring tendon grafts for anterior cruciate ligament reconstruction, braiding or weaving of the tendons has been suggested. The purpose of this study was to examine the biomechanical properties of two braiding techniques compared with a four-stranded tendon graft using a sheep model. Digital extensor tendons from 5 adult sheep were harvested in 28 matched pairs and randomly allocated to French plait or four-stranded weave. The grafts were tested in a hydraulic testing machine with the tendons secured in brass grips frozen with liquid carbon dioxide. The tendons were preconditioned to a distraction of 1 mm for 10 cycles followed by testing to failure at 50 mm/sec, with a data acquisition rate of 1,000 Hz. The stiffness, ultimate load to failure, and the mode of failure were recorded. All braided samples failed at the midsubstance, while the four-stranded controls failed at the grip interface. There was a significant reduction in strength and stiffness of the braided samples compared with the controls. This study demonstrated that braiding decreases the strength and stiffness of a four-stranded tendon graft by up to 54% and 85%, respectively. This finding is supported by the work of Hearle et al. (1969), who demonstrated that the decrease in strength of fiber bundles is equal to the square of the cosine of the twist angle. The twist angle in our samples was approximately 45 degrees, which equates to a decrease in strength of 50%.

Analysis of Variance↗

PubMedDate not supplied

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.

Animals↗

PubMedDate not supplied

Patellar tendon-to-bone healing using high-density collagen bone anchor at 4 years in a sheep model.

BACKGROUND: This study reports the long-term histologic and mechanical properties of the healing patellar tendon-bone interface reconstructed using a high-density type I collagen bone anchor (HDC) compared to a metal anchor in sheep. HYPOTHESIS: To determine the long-term histology and mechanical properties of extra-articular tendon-bone healing and in vivo response to a HDC anchor. STUDY DESIGN: Controlled laboratory study. METHODS: The structural properties, tendon-bone histology, and device histology in the bone were examined out to 208 weeks in a sheep model. RESULTS: The patellar tendon-proximal tibia bone interface continued to remodel with time but, by 4 years, had yet to develop the well-defined zones of tendon, fibrocartilage, calcified cartilage, and bone of the native patellar tendon to bone insertion. The insertion repair strength did not vary between the repaired tendons and the nonoperated controls at any time. CONCLUSION: The healing tendon-bone interface undergoes a gradual remodeling process, which had yet to reconstitute back to the control interface by 208 weeks. The HDC device remained essentially intact at 208 weeks showing little signs of degradation. CLINICAL RELEVANCE: Tendon-bone healing is mechanically equivalent to the contralateral side by 26 weeks whereas histologic structure requires much longer to remodel back to the native insertion.

Animals↗

PubMedDate not supplied

Healing characteristics of a type I collagenous structure treated with corticosteroids.

One hundred twenty-eight skeletally mature New Zealand White rabbits were used to study the effect of a single corticosteroid injection on the biomechanical, biochemical, and histologic aspects of ligamentous healing. Two steroid dosages were used. The amount of the low-dose steroid was calculated by determining the corticosteroid concentration at which fibroblastic synthesis of collagen was inhibited in vitro. A human equivalent dose of betamethasone was used as the high-dose steroid injection. These two steroid doses and a saline control were injected around a transected medial collateral ligament. At 10 days all groups showed significantly inferior biomechanical properties relative to noninjected controls. By 3 weeks the human equivalent steroid dose group continued to demonstrate significantly inferior properties. Histologic and biochemical analyses confirmed the biomechanical results. The clinical relevance of the study was that the delivery of a human equivalent steroid dose into an acutely injured ligament significantly impairs the healing process relative to a noninjected ligament at 10 days and at 3 weeks after injury. This implies that a corticosteroid-treated injured ligament may not be able to withstand the mechanical loads of early vigorous rehabilitation.

Animals↗

PubMedDate not supplied

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.

Biomechanical Phenomena↗