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Biomedical subjects

J B Richardson

Publications and source records attributed to J B Richardson.

At least 19 recordsLinked to original sources
PubMed2006

Computational simulation of fracture healing: influence of interfragmentary movement on the callus growth.

Bone fractures heal through a complex process involving several cellular events. This healing process can serve to study factors that control tissue growth and differentiation from mesenchymal stem cells. The mechanical environment at the fracture site is one of the factors influencing the healing process and controls size and differentiation patterns in the newly formed tissue. Mathematical models can be useful to unravel the complex relation between mechanical environment and tissue formation. In this study, we present a mathematical model that predicts tissue growth and differentiation patterns from local mechanical signals. Our aim was to investigate whether mechanical stimuli, through their influence on stem cell proliferation and chondrocyte hypertrophy, predict characteristic features of callus size and geometry. We found that the model predicted several geometric features of fracture calluses. For instance, callus size was predicted to increase with increasing movement. Also, increases in size were predicted to occur through increase in callus diameter but not callus length. These features agree with experimental observations. In addition, spatial and temporal tissue differentiation patterns were in qualitative agreement with well-known experimental results. We therefore conclude that local mechanical signals can probably explain the shape and size of fracture calluses.

Bony Callus↗
PubMed2006

Cartilage transplantation.

Chondral injuries are common sequelae following musculoskeletal trauma. This article reviews different techniques of cartilage regeneration undertaken in the past, and focuses on the recent advances in the field of tissue engineering.

Cartilage, Articular↗
PubMed2005

Early results of autologous chondrocyte implantation in the talus.

Autologous chondrocyte implantation (ACI) has been used most commonly as a treatment for cartilage defects in the knee and there are few studies of its use in other joints. We describe ten patients with an osteochondral lesion of the talus who underwent ACI using cartilage taken from the knee and were prospectively reviewed with a mean follow-up of 23 months. In nine patients the satisfaction score was 'pleased' or 'extremely pleased', which was sustained at four years. The mean Mazur ankle score increased by 23 points at a mean follow-up of 23 months. The Lysholm knee score returned to the pre-operative level at one year in three patients, with the remaining seven showing a reduction of 15% at 12 months, suggesting donor-site morbidity. Nine patients underwent arthroscopic examination at one year and all were shown to have filled defects and stable cartilage. Biopsies taken from graft sites showed mostly fibrocartilage with some hyaline cartilage. The short-term results of ACI for osteochondral lesions of the talus are good despite some morbidity at the donor site.

Adolescent↗
PubMed2004

A corrective osteotomy for post-traumatic malrotation and shortening of the femur.

Malrotation following femoral nailing is problematic. We describe a new one-stage technique which utilises three components; a cortico-periosteal sleeve, a "dialled-in"correction of rotation and a peg-shaped osteotomy. Seven patients were treated. The mean correction of malrotation was within 5 degrees of the normal side and the mean correction of length was within 8 mm of the normal side. Clinical union was achieved on average by 6 months (range 4-8 months). The only complication was locking screw breakage in one case. The cortico-periosteal sleeve avoids the need for bone graft, surgery is facilitated by the use of "dialled-in" correction of rotation and a peg to correct length.

Adult↗
PubMed2003

Serum from patients anesthetized with opiates less effective in the support of chondrocyte growth in vitro.

Risk of viral and/or prion disease transmission associated with the use of fetal bovine serum in clinical cell culture has led to the increasing use of autologous human serum in tissue engineering. A relatively large volume of blood is needed and so, to decrease patient discomfort, we have investigated the feasibility of taking blood when the patient is anesthetized. Two serum samples were prepared from each of 22 patients: (1). from the awake patient (PRE) and (2). from the patient 5 min after induction of general anesthesia (PER). The sera were compared for their ability to support the in vitro proliferation of primary human chondrocytes, determined by cell counting. The effects of anesthetic agents on the PER/PRE cell number ratio were established by analysis of variance and stepwise multilinear regression analysis. The PER sample supported higher growth in 2 of 22 patients, equivalent growth in another 11, and significantly lower growth in the remaining 8. Only the opiate analgesics (fentanyl [Sublimaze], alfentanyl [Rapifen], and diamorphine) had a significant and inhibitory effect on chondrocyte proliferation. It is suggested that opiate analgesics be avoided when blood is taken to support the in vitro growth of human cells.

Adult↗
PubMed2002

Phenotypic modulation of human articular chondrocytes by bistratene A.

Chondrocytes undergo phenotypic alterations following extended periods in monolayer culture, i.e., they become bipolar and flattened, proliferate, and synthesise type I as opposed to type II collagen. This process has been termed chondrocyte dedifferentiation. Bistratene A is a macrolide polyether that specifically activates the delta isoform of protein kinase C (PKCdelta) in some cell types. Here, we show that dedifferentiated human articular chondrocytes became rounded and underwent cell growth arrest after treatment with bistratene A. In addition, bistratene A-treated chondrocytes became more immunopositive for type II collagen, but less immunopositive for type I collagen. These phenotypic changes were associated with a prior and extensive disruption of actin microfilaments and translocation of PKCdelta to the nuclear membrane. Concurrent treatments of chondrocytes with a specific inhibitor of PKCdelta, rottlerin, partially blocked the morphological effects of bistratene A.

Journal Article↗
PubMed2001

Matrix turnover in human cartilage repair tissue in autologous chondrocyte implantation.

OBJECTIVE: Autologous chondrocyte implantation (ACI) is a form of tissue engineering that is being used increasingly to treat damaged articular cartilage. What happens at the graft site subsequent to the transplantation of chondrocytes beneath a periosteal flap has largely remained a matter of conjecture. We examined biopsy samples from the graft site using a panel of specific antibodies to investigate the cellular mechanisms involved and to determine whether remodeling of the matrix occurs. METHODS: Ten full-depth core biopsy samples were obtained from patients who had undergone ACI 9-30 months previously (ages 28-53 years), in addition to 6 "control" biopsy samples. Cryosections were evaluated by standard histologic examination using polarized light and immunohistochemistry. Antibodies specific for type II collagen (CIIC1) were used, as well as antibodies against the C-propeptide of type II collagen (R160) and its denaturation product (Col2-3/4m), as indicators of anabolism or catabolism. In addition, antibodies to the matrix proteinase-generated neoepitopes of the aggrecan core protein were used to demonstrate either aggrecanase (BC-3 and BC-13) or matrix metalloproteinase (MMP) (BC-4 and BC-14) activity. RESULTS: All biopsy samples stained for type II collagen, even in areas of fibrocartilaginous morphology. There was evidence of newly synthesized type II collagen in addition to denatured collagen. MMP and aggrecanase activity on the proteoglycan population was evident, with aggrecanase being more active in fibrocartilaginous areas. CONCLUSION: The findings of this study indicate that ACI is capable of not only cartilage repair but, in some cases, regeneration. This may be achieved by the turnover and remodeling of an initial fibrocartilaginous matrix via enzymatic degradation and synthesis of newly formed type II collagen.

Adolescent↗
PubMed2001

Survey of stalking at WPI.

The purpose of this study was to ascertain the amount of stalking taking place on the Worcester Polytechnic Institute (WPI) campus in which computers play such a huge role in the lives of the students. Our results were then compared with those reported in a stalking study done at West Virginia University (WVU). Surprisingly (to us), a smaller percentage of both females and males were stalked at WPI. The use of the Internet did not play a major role in stalking as we had expected. Results reported in a TV news report and a newspaper article indicate, however, that much less stalking occurs among the general population than does at WVU and WPI.

Adult↗
PubMed2001

Fracture stiffness in callotasis determined by dual-energy X-ray absorptiometry scanning.

Assessing healing after distraction limb lengthening is essential to manage patients undergoing callotasis for leg lengthening or bone transport. Direct measurement of fracture stiffness can assess healing but the equipment may not be available. In addition, it requires removal of the fixator, which may be complicated for ring fixators. The present study investigates whether an equivalent measure of healing can be based on the mineral density pattern from dual-energy X-ray absorptiometry (DXA) scans. Nine consecutive patients undergoing callotasis were studied. Bending stiffness of the distraction segment was measured and DXA scans were performed regularly starting 6 weeks after completing distraction. In all, 23 simultaneous readings of bending stiffness and DXA scans were obtained. All density patterns showed a distinct minimum value of bone mineral density. We found a high and significant correlation between fracture bending stiffness and the square of the total mineral content at the location of minimum bone density (r2 = 0.77, P < 0.001). We conclude that DXA scans can be used reliably and effectively to determine fracture bending stiffness, valuable for determining both time of frame removal and delay in union.

Absorptiometry, Photon↗
PubMed2000

The in vitro growth of human chondrocytes.

Autologous chondrocyte implantation (ACI) for the treatment of articular cartilage defects has been described by other workers, however, relatively few details of the in vitro growth of the cells have been published. Here we describe the release of cells from adult human articular cartilage and their growth characteristics in vitro.Cultures were successfully established from 29 of 30 biopsies taken from patients aged 20-72 year. No significant relationship was found between donor age and initial cell yield following cartilage digest, however, the time to primary confluence increased in direct proportion to age. Thereafter the kinetics of cell proliferation was independent of donor age.The proportion of apoptotic or necrotic cells in the cartilage digest was low and increased with time in culture only in those cells which remained non-adherent. Conversely, entry into cell cycle was restricted to those cells which had become adherent.These results illustrate that previously reported techniques for isolating and culturing chondrocytes are reproducible, that adherent chondrocytes have considerable proliferative potential, and that concern about cell growth and viability need not, in itself, limit the clinical application of ACI to younger patients.

Journal Article↗
PubMed1999

Malunion in the lower limb. A nomogram to predict the effects of osteotomy.

Nomograms derived from mathematical analysis indicate that the level of malunion is the most important determinant of changes in the moment arm of the knee, the plane of the ankle and alterations in limb length. Testing in five patients undergoing reconstruction showed a mean error of postoperative limb length of 2.2 mm (SD 0.8 mm), knee moment arm of 4.7 mm (SD 3.3 mm) and ankle angle of 2.6 degrees (SD 2.3 degrees). These nomograms provide the information required when assessing whether a particular degree of angulation may be accepted.

Algorithms↗
PubMed1999

Repair of human articular cartilage after implantation of autologous chondrocytes.

Tissue engineering is an increasingly popular method of addressing pathological disorders of cartilage. Recent studies have demonstrated its clinical efficacy, but there is little information on the structural organisation and biochemical composition of the repair tissue and its relation to the adjacent normal tissue. We therefore analysed by polarised light microscopy and immunohistochemistry biopsies of repair tissue which had been taken 12 months after implantation of autologous chondrocytes in two patients with defects of articular cartilage. Our findings showed zonal heterogeneity throughout the repair tissue. The deeper zone resembled hyaline-like articular cartilage whereas the upper zone was more fibrocartilaginous. The results indicate that within 12 months autologous chondrocyte implantation successfully produces replacement cartilage tissue, a major part of which resembles normal hyaline cartilage.

Adolescent↗
PubMed1999

The audit of orthopaedic trainee teaching improves supervision rates.

Inefficiency in surgical training has been identified as a result of low rates of supervision, with direct teaching of operating by consultants occurring in less than 20% of cases in papers dealing with general surgery and cardiac surgery training. The introduction of an audit system in an orthopaedic training programme was associated with an improvement of teaching from an already high 30% to 40% of cases. A logbook programme was introduced which allows easy analysis of the distribution of experience on an anatomical basis.

Education, Medical, Graduate↗
PubMed1998

Arthroscopic debridement of external fixator pin tracts.

Major external fixator pin tract infection can be managed by curettage, overdrilling or excision of the pin tract. An alternative is arthroscopic debridement which allows thorough curettage with the advantage of direct inspection of the pin tract to ensure clearance of all necrotic tissue from the tract base and walls. To date, arthroscopic pin tract debridement has been used successfully to manage 25 pin tracts in six patients. Adequate visualization of the pin tract throughout its course was possible in all cases. Two patients subsequently underwent intramedullary nailing without complication. No recurrent infection has occurred at review at 13 months.

Arthroscopy↗