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Biomedical subjects

H K Uhthoff

Publications and source records attributed to H K Uhthoff.

At least 19 recordsLinked to original sources
PubMed1992

Refractures: a consequence of impaired local bone viability.

Bone necrosis secondary to avascularity may not only delay or inhibit consolidation of a fracture, it may also be a cause of refracture. Both initial trauma und surgical insult will determine the extent of necrosis. Only the latter is under the surgeon's control; it can be reduced by gentle soft tissue handling and by minimizing periosteal stripping. While the impact of avascular necrosis on fracture healing is well recognized, its role in the pathogenesis of refractures has received less attention. Cortical necrosis delays bridging of gaps; these gaps act as stress risers which, following resumption of full activity or after implant removal, can lead to refracture. Evaluation of 28 refractures in 25 patients, with biopsies in 14 patients, suggests that the duration of fracture immobilization through external or internal means must be sufficiently long to allow vascular invasion of necrotic areas, their substitution by new bone and bridging of the fracture. These processes must be followed by radiographic studies prior to implant removal. Special attention needs to be paid to adequate visualization of the fracture gap on successive radiographs.

Adolescent↗
PubMed1992

Periarticular soft tissue conditions causing pain in the shoulder.

Pain originating in periarticular soft tissues of the shoulder is a common clinical problem among the aged patients of both sexes, but it has become increasingly frequent in young individuals because of a health-oriented life style. In the past year, a considerable progress has been made in diagnosing these conditions, especially with the aid of magnetic resonance imaging. Our understanding of the pathogenesis of these conditions, however, has advanced very little, and we hope that more efforts will be devoted in the future to elucidate how the periarticular soft tissues of the shoulder react to diverse injuries they are exposed to.

Humans↗
PubMed1992

The fetal acetabulum. A histomorphometric study of acetabular anteversion and femoral head coverage.

To study the development of the acetabulum in the early fetal period, 39 embryologic specimens were reviewed in detail. Histologic serial sections were made through 47 hips in the transverse plane. Measurements of acetabular anteversion and femoral head coverage revealed that both parameters depend on the exact level of sectioning. However, when measured at the level of the maximum diameter of the femoral head, they did not show significant variation through the embryonic and early fetal stages (six to 20 weeks). This is in contradistinction to the late fetal period. The hip does remain covered during this early fetal period. Congenital dislocation of the hip is not an early developmental condition. This accounts for the absence of any reports of hip dislocations in the first half of gestation.

Acetabulum↗
PubMed1991

Pattern of bone loss of the proximal femur: a radiologic, densitometric, and histomorphometric study.

The pattern of bone loss in the proximal femur was studied in 141 cadaveric femora from 36 women and 39 men ranging from 27 to 89 years of age. Bone mineral density (BMD) of the femoral neck, greater trochanter, Ward's triangle, and tensile and compressive stress regions were measured by dual photon absorptiometry. Radiographs were graded by Singh's method. Histomorphometry of tensile and compressive trabecular areas was performed on ground midsection of the methylmethacrylate-embedded whole proximal femur. Although Singh index had some correlation with BMD of the femoral neck, the various BMD measurements showed that all regions lost bone to the same extent; in particular, no selective bone loss was found at low stress regions (tensile trabeculae or Ward's triangle). Histomorphometry revealed that most of the trabecular bone loss of the proximal femur is attributable to a decrease in thickness of individual trabeculae.

Adult↗
PubMed1991

Usefulness of a new technique for hind limb immobilization in rats for the study of tendon healing.

To study wound repair in rat Achilles tendon, we utilized a novel surgical method for immobilizing only one hind limb. In this technique, the femoral vessels were preserved while the skin, muscles, nerves and the shaft for the femur were transected. The limb was then rotated and sutured to lie on the posterolateral flank of the animal. The recovery was prompt and the procedure affected the routine growth and metabolism of the animal minimally throughout the period of experimentation. In the immobilized limb, healing of the Achilles tendon was studied after subtotal severance in the midsection. The rats were killed at intervals of 1, 2, and 4 weeks postoperatively. After 1 week, the surface of the wound was covered by a thin layer of cells. A gap persisted underneath and showed fibrovascular proliferation at the margins. In 2 weeks, the gap was completely occupied by fibrovascular tissue that was beginning to align along the long axis of the tendon. By the 4th week, remodeling had occurred and the site of the wound had almost blended with the rest of the tendon. We conclude that this new technique of hind limb immobilization causes little stress on the animal, and it can be useful for the study of tendon healing.

Achilles Tendon↗
PubMed1991

Shoulder pain and reflex sympathetic dystrophy.

Shoulder pain has become one of the commonest clinical problems in modern North American society. The pathogenetic mechanisms vary widely, and often times, speculations about the underlying pathology have not been substantiated by investigative studies. In the past year, progress in our knowledge about shoulder pain has not been significant. We discuss the topic by dividing shoulder pain into four categories: 1) shoulder pain of local origin; 2) pain referred to the shoulder; 3) shoulder and neck pain; and 4) shoulder pain and reflex sympathetic dystrophy. It appears that a thorough history taking, an understanding of the psychosocial background of the patient, and a complete physical are equally important in the clinical evaluation of painful shoulders.

Humans↗
PubMed1991

Surgical repair of rotator cuff ruptures. The importance of the subacromial bursa.

We examined biopsy specimens obtained during surgery on 115 patients with complete rotator cuff rupture. The vascularised connective tissue covering the area of rupture and the proliferating cells in the fragmented tendons reflected more of the features of repair than of degeneration and necrosis. The main source of this fibrovascular tissue was the wall of the subacromial bursa. These features clearly indicated a vigorous reparative response which might play an important role in tendon reconstitution and remodelling. We therefore suggest that extensive debridement along with subtotal bursectomy, commonly practised during surgical repair of rotator cuff rupture, should be avoided. Although strong suture margins are essential for good operative results, debridement should be judicious and preserve as much as possible of the bursa and the associated fibrovascular tissue.

Acromioclavicular Joint↗
PubMed1991

Classification and definition of tendinopathies.

The authors have classified tendinopathies into two categories. The majority of the tendinopathies are in the primary category in which lesions arise in the substance of the tendon. The authors emphasize that not all tendinopathies are degenerative in nature. Some primary tendinopathies are reactive, such as calcifying tendinitis.

Athletic Injuries↗
PubMed1990

The development of synovial plicae in human knee joints: an embryologic study.

An embryologic study about the development of the human knee joint cavity was carried out with special attention to the formation of synovial plicae, using a total of 116 knees of embryos and fetuses. The incidence of synovial plicae in the fetal stage was also investigated. Formation of joint space starts at the middle of the interzone at around 8 weeks of gestation. Multiple small cavitations around the femoral condyle and patella coalesce to form larger cavitations. At around 10 1/2 weeks, the knee joint consists of a single cavity with synovial lining. At certain sites, such as at the medial part of patello-femoral and the infrapatellar regions, mesenchymal tissue strands remain. They may become plica. In the fetal stage from 11 to 20 weeks, an infrapatellar plica was found in 50% of specimens, a suprapatellar plica in 33%, and a mediopatellar plica in 37%. Only the infrapatellar plica showed a decrease in incidence.

Embryonic and Fetal Development↗
PubMed1990

Quantitative measures for fracture healing: an in-vitro biomechanical study.

A method is presented to assess the functional capabilities of plated osteotomized canine femora as load bearing structures and to quantify their healing status. In this method the osteotomized bones and their intact contralateral controls are tested in nondestructive bending, in twenty-four planes of loading at 15 degree angular increments. Flexural rigidity (EI), in each of the planes, is determined by using classical beam theory. It has been found that the EI values have the expected elliptical distribution. The 24 EI values, obtained for each bone, are curve fitted by regression analysis and the characteristics of each bone are described by the three parameters defining its ellipse. The parameters of the ellipses of the osteotomized bone and of its contralateral control are used to define four new parameters that may serve as measures for the healing efficiency. One of these serves as an indicator for the fragility of the healed bone and the other three add quantitative information on its mechanical state.

Animals↗
PubMed1990

The early development and ossification of the human clavicle--an embryologic study.

Morphologic studies of the early development of the clavicle were carried out in 46 human embryos and fetuses ranging in age from 6 to 12 weeks. We confirmed that the clavicle is formed by two membranous primary ossification centers appearing by 6 weeks and fusing approximately 1 week later. Cartilage at both ends of the clavicle then develops. In time, the medial cartilaginous mass contributes more to the growth in length of the clavicle than the lateral cartilaginous mass. The spatial orientation of both ossification centers and the development of enchondral bone formation at the ends of the clavicle lead to its characteristic shape. Interestingly, the primary ossification centers contribute little to the growth in length. The junction of the two centers of ossification is situated between the lateral and middle third of the clavicle and, consequently, does not correspond to the site of congenital pseudarthrosis, which is located in the middle part of the clavicle.

Clavicle↗
PubMed1990

An algorithm for shoulder pain caused by soft-tissue disorders.

Painful shoulders are commonly caused by disorders of periarticular soft tissues, especially rotator cuff tendinopathies. In contrast to arthritic conditions of the shoulder, soft-tissue disorders can present a diagnostic dilemma that often results in the use of such nonspecific or unproved terminologies as periarthritis or bursitis. To promote an efficient use of investigative studies necessary to arrive at a proper diagnosis, an algorithm can serve as a guide for clinicians in the diagnosis and management of common, nonarthritic conditions of painful shoulders.

Algorithms↗
PubMed1990

The microvascular pattern of the supraspinatus tendon.

The vascular pattern of the supraspinatus tendon was studied in 18 human anatomic specimens. The ages of the specimens ranged from 26 to 84 years. Selective vascular injection with a silicon-rubber compound allowed visualization of the vascular bed of the rotator cuff and humeral head. The presence of a hypovascular or critical zone close to the insertion of the supraspinatus tendon into the humeral head was confirmed. However, only a uniformly sparse vascular distribution was found at the articular side, as opposed to the well-vascularized bursal side. This was also confirmed with histologic sections of the tendon. The poor vascularity of the tendon in this area could be a significant factor in the pathogenesis of degenerative rotator cuff tears.

Adult↗
PubMed1990

Acromial enthesopathy and rotator cuff tear. A radiologic and histologic postmortem investigation of the coracoacromial arch.

Changes of the coracoacromial ligament (CAL) at its insertion into the undersurface of the acromion were studied radiologically and histologically in 76 autopsy specimens. Two changes were noted: (1) a downward, bony projection of the acromion, an anatomic variant limited to the area covered by the CAL, which might reduce the height of the subacromial compartment, and (2) a thickened layer of fibrocartilage, constituting a potential cause for narrowing of the subacromial space. The former might act as a predisposing factor for the impingement syndrome, whereas the latter could develop in response to pressure from constituents of the subacromial compartment. The acromial spur was a result of enchondral bone formation. A possible correlation between these changes and rotator cuff tears was investigated. The incidence and severity of cuff tears increased with age. However, there was no correlation between aging and degenerative changes of the undersurface of the acromion, except possibly in very advanced cases. Rotator cuff tears are unlikely to be initiated by impingement; rather, they develop as an intrinsic degenerative tendinopathy.

Acromion↗
PubMed1990

The ultrastructure of the coracoacromial ligament in patients with chronic impingement syndrome.

In an ultrastructural study of the cells and matrix of the coracoacromial ligament (CAL) in 11 patients with impingement syndrome (IS), the cells appeared variegated, in contrast to those in normal CALs. Many showed degenerative changes such as lipid inclusions in the cytoplasms or swelling of cytoplasmic organelles, especially in the vicinity of fibrin exudate where the collagenous matrix disappeared. However, some cells had increased cytoplasmic organelles, including an elaborate Golgi apparatus, indicating enhanced synthetic activity. The matrix, instead of consisting of packed collagenous fibers of fairly uniform diameter as seen in the normal CAL, contained collagen fibers of varying diameters and microfibrils. The ultrastructural features of both the cells and the matrix were suggestive of chronic effects of strain on the ligament. In patients with chronic IS, the CAL has been implicated as the likely cause of impingement when no significant bony or articular abnormality exists. This was not substantiated by the present findings. The changes in the CAL in IS are possibly secondary, and are probably induced by alterations in soft-tissue structures of the subacromial compartment.

Acromion↗