The effect of tension on collagen remodelling by fibroblasts: a stereological ultrastructural study

Soft-tissue injury in orthopaedic trauma

This paper reviews the current concepts of soft-tissue injury in orthopaedic trauma. Six topics are described in this Injury Supplement, including influencing factors and mechanisms, co-morbidities, biological responses, diagnosis and treatment of closed soft-tissue injury, compartment syndrome and gunshot wounds. Since one of the current AO principles emphasises respect for soft tissue when performing open reduction and internal fixation, this article further discusses the pathophysiology of soft-tissue injury and the specific concerns in treating compartment syndrome and gunshot injury. Understanding the basic and updated principles of soft-tissue management will be beneficial for the clinical practice of orthopaedic trauma surgeons.

Treatment of chronic achilles tendinopathy and ruptures with flexor hallucis tendon transfer: clinical outcome and MRI findings

BACKGROUND

In patients with chronic Achilles tendinopathy, augmentation with flexor hallucis longus (FHL) tendon transfer can be performed to improve pain and functional limitations. There are no reports of postoperative imaging for evaluating tendon integration, inflammatory alterations or degeneration of the FHL muscle. The purpose of this study was to evaluate postoperative MR imaging based on clinical outcome and isokinetic strength.

MATERIALS AND METHODS

13 patients with chronic Achilles tendinopathy (10 ruptures) underwent augmentation with FHL transfer. Clinical parameters, isokinetic strength and outcome measurements (AOFAS, SF-36) were evaluated at an average followup of 46.5 months. Qualitative and quantitative analyses of postoperative MRI were conducted using the non-operated side for comparison.

RESULTS

All patients had a significant reduction of pain. The operated side had a torque deficit of 35% for plantar flexion. Ten patients returned to their former level of activity. MRI showed a complete integration of the FHL tendon in six patients. Fatty atrophy in the triceps surae was found in ten patients. The FHL was free of degeneration in all patients. Hypertrophy of the FHL of more than 15% was observed in eight patients.

CONCLUSION

Augmentation with FHL transfer is a valuable option in the treatment of chronic Achilles tendinopathy with and without rupture. Our results demonstrate high patient satisfaction without donor site morbidity. The FHL tendon is well integrated into the Achilles tendon. Hypertrophy of the FHL muscle suggests functional incorporation into plantar flexion. The primary benefit of the operation is pain relief and increased muscle strength.

Evaluation of the lateral collateral ligament after fibular head transposition in dogs

Cranial transposition of the fibular head stabilizes the stifle joint by displacing the distal attachment of the lateral collateral ligament (LCL). The forces applied to the LCL after displacement may cause ligamentous elongation. This investigation evaluated the morphological, histological, and biomechanical changes of the LCL after fibular head transposition (FHT) in dogs. Unilateral cranial cruciate ligament (CCL) excision and FHT were performed on 25 dogs. Cross-sectional area, length, histological, and structural properties of the LCL were evaluated 3 weeks, 4 months, and 10 months after surgery. Ligament length means were significantly increased at week 3, month 4, and month 10 compared with intraoperative length means. No significant changes in elongation were observed after week 3. Fibrovascular proliferation within the LCL increased the cross-sectional area and associated structural properties.

Development of functional specializations within the maturing rabbit flexor digitorum profundus tendon

Along its length, the rabbit flexor digitorum profundus (FDP) tendon exhibits two functionally specialized regions: classical tendon (CT) and fibrocartilage (FC). We examined their development in rabbits, ranging in age from newborn to nine-months postnatal, using a combination of light microscopic, immunohistochemical and biochemical techniques. There is little histodifferentiation in newborn tendon. Both regions are composed of thin collagenous fibers, numerous fibroblast-like cells and a low molecular weight dermatan-sulfate proteoglycan. Regional specialization has begun by two-weeks postnatal and by three-months postnatal, FC regions have been transformed into a true fibrocartilage characterized by a complex collagenous and elastic fiber network, numerous chondrocytes and a matrix rich in a high molecular weight predominantly chondroitin-sulfate proteoglycan and type II collagen. These features are elaborated between three and nine-months postnatal. CT regions undergo little substantial change during growth and maturation. The rabbit is born altricial and incapable of adult patterns of locomotion. We propose that the developmental expression of functional specializations within the FDP tendon is closely linked with the onset of different physical demands arising from the adoption of adult patterns of locomotion.

A study relating wound tension to scar morphology in the pre-sternal scar using Langers technique

Using the techniques of Karl Langer (1861) a cadaver study has been performed to relate the pattern of skin tension to scar morphology found in the pre-sternal scar. It is demonstrated that hypertrophic scarring occurs in areas of high tension with "pull" in many directions, but that a stretched scar results from increased tension in one axis only.

Membrane-bound intracellular collagen fibrils in fibroblasts and myofibroblasts of regenerating rabbit calcaneal tendons

The ultrastructures of 33 rabbit calcaneal tendons were studied to determine (1) whether vacuolar fibrils are present in three regions of tendons undergoing normal healing after tenotomy and repair, and (2) to stimulate collagen synthesis via functional loading, and hence determine the effect of loading on the presence of vacuolar fibrils in healing tendons. In all the loaded tendons, electron microscopy revealed membrane-bound collagen fibril equivalents in sections of neotendon obtained from the site of tenotomy, and in sections of tendon segments proximal and distal to the site of surgery. Similar vacuolar fibrils were visualized in sections of the proximal and distal segments of the non-loaded regenerating tendons, and also in sections of neotendons formed at the site of tenotomy after 12 and 15 days of healing without functional loading. No such fibrils were visualized in the non-tenotomized normal control tendons. These findings indicate that chemical agents and disease are not necessary to induce the appearance of intracytoplasmic fibrils in vivo and that functional loading augments the presence of fibril-bearing vacuoles in regenerating tendons.

Distribution of 3H-proline within transseptal fibers of the rat following release of orthodontic forces

Maxillary right first molar teeth of rats were tipped mesially with an orthodontic appliance for 2 weeks (experimental group), 3H-proline was injected, and orthodontic forces were removed 6 hr later (time 0). The contralateral molar teeth of treated (internal control group) and age- and weight-matched untreated animals (external control group) were also studied. Diastemata were created between the molar teeth by the orthodontic appliance, and transseptal fibers between first and second (P less than 0.001) and second and third molars (P less than 0.005) were significantly lengthened as compared to external and internal controls at time 0. Diastemata between molar teeth were closed 5 days after removal of orthodontic force. Transseptal fibers adjacent to the source of the orthodontic force (mesial region) had the highest mean number of 3H-proline-labeled proteins at time 0 and at all times following removal of the force (P less than 0.001), and had the highest rate of labeled protein removal (P less than 0.001). Half-lives for removal of 3H-proline-labeled transseptal fiber proteins were significantly greater in mesial and distal regions and significantly less in middle regions of experimentals than in corresponding regions of external controls (P less than 0.001). These data suggest the following: 1) transseptal fibers adjust their length by rapid remodeling in regions experiencing a tensile force; 2) collagenous protein turnover within the middle third of the transseptal fibers is more rapid subsequent to release of orthodontic force than during normal physiologic drift, suggesting that this region adapts rapidly to changes in adjacent tooth position and that these fibers do not play a significant role in relapse of orthodontically relocated teeth; and 3) significant differences in turnover rates of 3H-proline-labeled transseptal ligament proteins of external and internal control quadrants suggest that tooth movement produces both local and systemic effects on collagenous protein metabolism.

Quantitation of phagocytic cells in phenytoin-induced connective tissue proliferation in the rat

This study demonstrates that, in rats, systemically administered phenytoin produces a statistically significant increase in accumulation of phagocytic and esterase positive cells in areas of phenytoin-induced connective tissue proliferation. Many of these cells are perceived to be macrophages. Since macrophages have been shown to produce chemoattractant and mitogens for fibroblasts, they may very well play a major role in the gingival hyperplasia seen in patients taking phenytoin. The results of the study show that the effects of phenytoin on fibroblasts may be more complex than previously thought.