Biomedical subjects

Jason Koh

Publications and source records attributed to Jason Koh.

8 recordsLinked to original sources

PubMed2006

A citric acid-based hydroxyapatite composite for orthopedic implants.

We describe a novel approach to process bioceramic microparticles and poly(diol citrates) into bioceramic-elastomer composites for potential use in orthopedic surgery. The composite consists of the biodegradable elastomer poly(1,8-octanediol-citrate) (POC) and the bioceramic hydroxyapatite (HA). The objective of this work was to characterize POC-HA composites and assess the feasibility of fabricating tissue fixation devices using machining and molding techniques. The mechanical properties of POC-HA composites with HA (40, 50, 60, 65wt.%) were within the range of values reported for tissue fixation devices (for POC-HA 65wt.%, S(b)=41.4+/-3.1, E(b)=501.7+/-40.3, S(c)=74.6+/-9.0, E(c)=448.8+/-27.0, S(t)=9.7+/-2.3, E(t)=334.8+/-73.5, S(s)=27.7+/-2.4, T(s)=27.3+/-4.9, all values in MPa). At 20 weeks, the weight loss of POC-HA composites ranged between 8 and 12wt.%, with 65wt.% HA composites degrading the slowest. Exposure of POC-HA to simulated body fluid resulted in extensive mineralization in the form of calcium phosphate with Ca/P of 1.5-1.7 similar to bone. POC-HA supported osteoblast adhesion in vitro and histology results from POC-HA samples that were implanted in rabbit knees for 6 weeks suggest that the composite is biocompatible. Synthesis of POC-HA is easy and inexpensive, does not involve harsh solvents or initiators, and the mechanical properties of POC-HA with 65wt.% HA are suitable for the fabrication of potentially osteoconductive bone screws.

Animals↗

PubMed2005

Osteoarthritis in other joints (hip, elbow, foot, ankle, toes, wrist) after sports injuries.

Osteoarthritis of nonknee joints, although less common than knee osteoarthritis, remains a significant and disabling condition for many present and former athletes. These injuries can be caused by repeated loads or following a specific traumatic event. The resulting pain and loss of motion can limit function and ability. Arthroscopic techniques in many cases enable surgeons to symptomatically treat limitations of range of motion and pain, prolonging active careers. Joint replacement remains the ultimate solution for hip osteoarthritis, and may be a viable option in ankle osteoarthritis.

Ankle Injuries↗

PubMed2005

Computer-assisted navigation and anterior cruciate ligament reconstruction: accuracy and outcomes.

As many as 175,000 anterior cruciate ligament (ACL) reconstructions are performed annually in the United States at a cost >1 billion dollars. Estimates of the rate of revision surgery are as high as 10%-20%, potentially resulting in as many as 35,000 revisions a year. In addition, errors that are not obvious at short-term or mid-term follow-up may have significant long--term effects in young patients. Studies have demonstrated that the majoriity of visions are related to technical errors, primarily tunnel placement. Computer-aided navigation systems provide enhanced precision in tunnel placement and may reduce the rate of revision surgery. Computer-aided systems can provide valuable data on rotational and translational laxity of the knee.

Anterior Cruciate Ligament↗

PubMed2004

Revision total knee arthroplasty complication rates in Northern Illinois.

A paucity of population-based data exist which describe the rapid growth of revision total knee arthroplasties, changes in patient characteristics, or the association of hospital volume with complication rates. We analyzed whether inpatient complications for 2986 revision knee arthroplasties done on patients admitted to 63 hospitals in northern Illinois from 1993-1999 were correlated with volume of revision total knee arthroplasties. Coded complication rates for hospitals with less than seven, seven to 14, or greater than 14 annual procedures were compared using logistic regression to control for clinical and demographic characteristics of patients, hospital teaching status, and the proportion of the hospitals' patients discharged to rehabilitation facilities. Revision total knee arthroplasties increased 59%, and the overall complication rate declined from 9.3% during 1993-1996 to 7.3% during 1997-1999 (p = .04). When compared with the lowest volume hospitals, medium-volume hospitals had higher complication rates, whereas the highest volume hospitals were not significantly different. The absence of volume-outcome effects may be related to the relatively high volume of primary knee arthroplasties done at almost all area hospitals, surgeon group coverage across multiple hospitals, and the small annual number of revision total knee arthroplasties done during these years.

Adult↗

PubMed2004

Biomechanical and histological evaluation of osteochondral transplantation in a rabbit model.

BACKGROUND: Biomechanical and histological properties of osteochondral transplantation have not been extensively examined. HYPOTHESIS: Osteochondral grafts have properties similar to native articular cartilage. STUDY DESIGN: Controlled laboratory study. METHODS: A 2.7 mm (diameter) x 4.0 mm (depth) osteochondral defect was created in 17 New Zealand white rabbit knees. An osteochondral graft, harvested from the contralateral knee, was transplanted into the defect. Eight rabbits were sacrificed each at 6 and 8 weeks. RESULTS: The 12-week grafts (1213.6 +/- 309.0 N/mm) had significantly higher stiffness than the 6-week grafts (483.1 +/- 229.1 N/mm; P <.001) and of normal cartilage (774.8 +/- 117.1 N/mm; P <.003). Stiffness of the 6-week grafts was significantly lower than normal cartilage (P <.036). At all time points, full-thickness defects had significantly lower stiffness than normal cartilage (P <.001). Histologically, transplanted grafts scored significantly higher than the full-thickness defects (P <.001). The defects showed inconsistent, fibrocartilage healing. The grafts demonstrated cartilage viability, yet with a persistent cleft between the graft and host. CONCLUSIONS: Osteochondral transplants undergo increased stiffness in the short term, with evidence of structurally intact grafts. CLINICAL RELEVANCE: Osteochondral transplantation may be a viable treatment option; however, long-term investigation on graft function is necessary.

Animals↗

PubMed2003

Plantar ganglion cyst associated with stress fracture of the third metatarsal.

Ganglion cysts of the foot and ankle occur relatively infrequently. Metatarsal stress fractures occur in a variety of athletes who subject their lower extremities to repetitive loading. In this article, we report the case of a professional football player with a plantar forefoot ganglion cyst associated with a stress fracture of the third metatarsal. After the cyst resolved with aspiration, the stress fracture healed with conservative, nonsurgical treatment.

Adult↗

PubMedDate not supplied

Stress injury of the proximal ulna in professional baseball players.

BACKGROUND: To date, stress injury of the proximal ulna has been infrequently reported as a cause of elbow pain in the throwing athlete. PURPOSE: We describe a syndrome of osseous stress injury of the proximal ulna in the professional throwing athlete. STUDY DESIGN: Retrospective review. METHODS: We evaluated the clinical, radiographic, and magnetic resonance imaging findings of seven professional baseball players with osseous stress injury of the proximal ulna. RESULTS: Plain radiographs of the involved elbows failed to demonstrate any significant findings. All of the clinically significant lesions were detected with magnetic resonance imaging. In addition, magnetic resonance imaging was found to be of value in following the course of healing of the injuries. All of the lesions originated on the posteromedial aspect of the proximal ulna. The ulnar collateral ligament was intact in all seven athletes. One athlete had two occurrences of this injury. Six of the seven athletes returned to their previous level of play after a nonoperative course of treatment. CONCLUSIONS: We believe that this injury should be considered in the differential diagnosis of elbow pain in the throwing athlete. Magnetic resonance imaging is the diagnostic test of choice when this injury is suspected.

Adolescent↗

PubMedDate not supplied

An uncommon dental presentation during pregnancy resulting from multiple eating disorders: pica and bulimia: case report.

Pica is a compulsive eating disorder involving non-nutritive substances. The etiology of this eating disorder is unknown but it often is associated with subclinical mineral deficiencies. This article focuses on the simultaneous occurrence of two types of eating disorders, the co-existence of depression during four pregnancies, and the resulting dental clinical implications. The literature is substantial enough to support a possible etiological association between these eating disorders and depression during pregnancy. Associations between eating psychopathology, depression, and anxiety have been described consistently. The diagnosis of pica and the dental treatment related to it are not a common part of most dental practices; knowing the clinical features and detecting the condition depend on careful questioning and diligence. At present, no one has described the physiologic or psychological basis for pica. This article reviews the published literature pertaining to pica, specifically pagophagia.

Bulimia↗