Biomedical subjects

L K Cheung

Publications and source records attributed to L K Cheung.

At least 19 recordsLinked to original sources

PubMed1996

An animal model for maxillary reconstruction using a temporalis muscle flap.

PURPOSE: This article describes the feasibility of using the temporalis muscle flap to cover a defect after maxillectomy in cats and to evaluate the clinical healing process of this flap in the oral environment. MATERIALS AND METHODS: The material consisted of 30 cats of the Felis catus species. A standardized unilateral maxillectomy was performed and the resulting defect immediately closed with a pedicled temporalis flap. The healing of this flap was clinically assessed at determined intervals. RESULTS: Healing of the temporalis flap in the oral environment of cats progressed from an inflammatory to a proliferative phase, with eventual coverage by a smooth oral mucosa 18 to 24 weeks after surgery. CONCLUSIONS: The cat proved to be a useful model for this type of study.

Animals↗

PubMed1996

Blood loss and transfusion requirements in orthognatic surgery.

PURPOSE: This study quantified the blood loss and transfusion requirements in orthognathic surgery. PATIENTS AND METHODS: Three hundred sixty consecutive healthy orthognathic surgery patients were included in this retrospective study. The female:male ratio was 1.8:1, and the age range was 8 to 49 years (mean, 24). Estimated blood volume (EBV), estimated blood loss (EBL), and transfused blood were calculated. RESULTS: EBL ranged from 50 to 5,000 mL (mean, 600) representing up to 73% of EBV (mean, 16%). In total, 24% (84 patients) were transfused, 8.7% (6 patients) after single-jaw surgery and iliac bone harvest and 26.7% (78 patients) after bimaxillary osteotomies. Forty-seven patients received 1 unit of transfused blood, 25 patients had 2 units, and 12 patients had more than 2 units. Most transfused patients lost 11% to 40% of EBV. CONCLUSIONS: Transfusion is not necessary for single-jaw surgery unless a bicoronal flap or iliac bone harvest are required. Although only 27% of bimaxillary osteotomy patients required transfusion of 1 to 2 units, this group was not predictable based on the type of procedure involved, and a further subgroup (4% of the 291 patients) required a larger transfusion.

Adolescent↗

PubMed1996

The vascular anatomy of the human temporalis muscle: implications for surgical splitting techniques.

Despite the wide application of the temporalis muscle flap and its modifications, understanding of the vascular pattern and territories within the muscle remains poor. This study aimed to evaluate the vascular architecture in the human temporalis muscle for surgical application. The material comprised 15 fresh cadavers (30 muscle specimens), which were divided into three groups for vascular infusion by either Indian ink solution, lead oxide solution, or methylmethacrylate resin. The vascular network in the temporalis muscle was analyzed by stereomicroscopy, radiography, and scanning electron microscopy. The human temporalis muscle was found to have vascular supply from three primary arteries: the anterior deep temporal artery (ADTA), the posterior deep temporal artery (PDTA), and the middle temporal artery (MTA). Each primary artery branched into the secondary arterioles and then the terminal arterioles. The venous network accompanied the arteries, and double veins pairing one artery was a common finding. The capillaries formed a dense, interlacing network with orientation along the muscle fibres. Arteriovenous anastomosis was absent. In the coronal plane, the vessels were located mainly on the lateral and medial aspects of the muscle with a significantly lower vascular density in the midline. Morphometric analysis of the arterial network showed that the PDTA was larger in size at primary and secondary branching levels than the ADTA and the MTA, whereas no differences were present at the terminal arteriolar levels. The distribution of the arterial territories was as follows: the ADTA occupied 21% anteriorly, the PDTA occupied 41% in the middle region, and the MTA occupied 38% in the posterior region. This improved understanding of the vascular architecture within the temporalis muscle complements the anatomic basis of the flap-splitting technique and increases the safety of its application.

Carbon↗

PubMed1996

An unusual facial sinus.

An unusual presentation of a chronic suppurative granuloma on the alar base area originating from a maxillary lateral incisor is reported. Treatment involved adequate endodontic therapy with simultaneous apical surgery and excision of the granuloma and sinus tract. Awareness of the possible dental origin of facial sinuses, despite their unusual location, is emphasized.

Adult↗

PubMed1996

Use of flow cytometry in the analysis of stage III squamous cell carcinoma of the oesophagus and its association with MIB-1.

AIMS: To examine the prognostic and pathobiological importance of DNA content in oesophageal squamous cell carcinomas in Hong Kong Chinese subjects; to evaluate its association with the immunohistochemical proliferative marker MIB-1. METHODS: Paraffin wax embedded tumour tissue and adjacent normal tissue (control tissue) samples from 45 resected stage III oesophageal squamous cell carcinomas were studied using flow cytometric analysis. The DNA content and the clinicopathological data of these patients were analysed together with the MIB-1 labelling index. RESULTS: DNA aneuploidy was present in 14 (31%) of the 45 cases. However, the DNA content did not correlate significantly with the age, sex, or survival of the patients, nor the length, location, differentiation and MIB-1 labelling index of the oesophageal carcinomas. The synthetic (S) phase fraction of diploid tumours bore no relation to the patients' survival or MIB-1 score. CONCLUSIONS: Flow cytometry was not as useful as the MIB-1 labelling index in predicting the biological characteristics of the tumours and the prognosis of patients with oesophageal squamous cell carcinomas. This study does not support the routine use of DNA flow cytometric analysis in oesophageal cancers.

Aged↗

PubMed1996

The blood supply of the human temporalis muscle: a vascular corrosion cast study.

Knowledge as to the blood supply of the human temporalis muscle is limited to its extramuscular path and relations, little information existing about the intramuscular vascular architecture. To investigate the 3-dimensional vascular network in the human temporalis muscle, in 5 fresh cadavers an infusion of methylmethacrylate resin was made via the carotid vessels with subsequent removal of the organic tissues by a corrosion process. The vascular corrosion casts of the temporalis muscle were studied by stereomicroscopy and scanning electron microscopy. In 6 well perfused muscle specimens, the temporalis muscle was found to be consistently supplied by 3 arteries: the anterior and posterior deep temporal arteries, and the middle temporal artery. Each primary artery branched into the secondary arterioles and then terminal arterioles. The venous network accompanied the arteries, and double veins pairing a single artery was a common finding. Arteriovenous anastomosis was absent, whereas arterioarterial and venovenous anastomoses were common. The capillaries formed a dense interlacing network with an orientation along the muscle fibres. Understanding of the intramuscular angioarchitecture of the temporalis provides the vascular basis for surgical flap manipulation and splitting design.

Arterioles↗

PubMed1995

Titanium miniplate fixation for osteotomies in facial fibrous dysplasia--a histologic study of the screw/bone interface.

In four patients who had osteotomies of the jaws affected by fibrous dysplasia (FD), screws embedded in bone blocks were removed at a re-entry operation 20 months postoperatively. Morphometric measurement of the bone density and calculation of the bone contact percentage were performed. Both normal and dysplastic bone were found to have some direct bone contact with the titanium screws. Although the bone contact percentage was higher in the normal bone when compared with FD, statistics failed to show any significant difference (P < 0.05). The dysplastic bone healed well around the titanium screws without inflammatory reaction and direct dysplastic bone/screw contact was noted. Longer screws should be used in facial FD in order to compensate for the reduced bone contact percentage.

Adult↗

PubMed1995

Overgrowth of a costochondral graft in an adult male.

This paper is the first report of overgrowth of a costochondral graft in an adult male. The case supports the notion that this graft partly exhibits features of a primary growth center with inherent potential for growth.

Adult↗

PubMed1994

The 3-dimensional stability of maxillary osteotomies in cleft palate patients with residual alveolar clefts.

OBJECTIVES: To evaluate the stability of maxillary osteotomies in cleft palate patients using miniplate fixation. DESIGN: A prospective clinical study. SUBJECTS: 46 consecutive cleft palate patients with residual alveolar clefts and maxillary hypoplasia in one or more dimensions. These patients underwent standardised maxillary osteotomies and simultaneous bone grafting of the alveolar cleft over 44 months during 1988-1992. Titanium mini-plate fixation was used for the maxilla in all patients. Follow-up ranged from 6 to 51 months with a mean of 28 months. MAIN OUTCOME MEASURES: The 3-dimensional stability of maxillary osteotomies in cleft palate patients in the long term. RESULTS: In the unilateral clefts, relapse in the horizontal plane was 22% and in the vertical plane 22.5%; in bilateral clefts, the relapse was 17.5% and 7% respectively, with no statistically significant difference between the two groups. Longitudinal analysis of the repositioned maxilla over a 3-year period showed that most of the relapse occurred in the first 6 months and stabilised at 2 years postoperatively. Relapse in the transverse plane, based on analysis of the study models of 26 cases, ranged from 13.4% to 33.6%. A clockwise rotational relapse of the maxilla was noted in bilateral cases. Postoperative orthodontics compensated for the horizontal relapse by increasing incisor proclination to maintain positive overjet. There was no significant difference between the relapse of bimaxillary cases and that of maxillary osteotomies alone. CONCLUSION: The long-term 3-dimensional surgical stability, using miniplate fixation, has decreased the relapse of cleft maxillary osteotomies with simultaneous alveolar bone grafting to a level comparable to that of maxillary osteotomies in non-cleft patients.

Adult↗

PubMed1994

Mandibular reconstruction with the Dacron urethane tray: a radiologic assessment of bone remodeling.

A retrospective study was made of 22 consecutive patients who underwent mandibular reconstruction with a Dacron (Osteo-mesh, Xomed Inc, Jacksonville, FL) tray technique from September 1988 to April 1992. Free autogenous iliac bone, in the form of particulate cancellous chips and marrow, was densely packed into the Dacron tray, that was adapted to bridge the mandibular segmental defect. Sixteen cases underwent uneventful healing with the formation of a continuous bony bridge and union with the remaining mandible. The pattern of bone remodeling and rate of resorption in these cases were assessed by sequential panoramic radiographs taken up to 3 years postoperatively. The mean horizontal dimension of the mandibular defects was 75 mm and the mean vertical reconstructed height was 25 mm. When the grafted bone was radiographically of uniform density, it progressed into a mature trabecular pattern matching that of the normal mandible. However, when there were areas of radiolucency, most likely from inadequate condensation of the graft, such areas were not replaced by bone in the long term. The bony height at both ends and the middle of the reconstructed segment underwent reasonably even resorption and retained about 80% of the bony height over a 3-year period. The rate of resorption was highest in the first 6 months and stabilized at about 2 years. There were six failures, all showing significant irregular bony resorption prior to tray removal.

Adolescent↗

PubMed1994

A comparison of alveolar bone grafting with and without simultaneous maxillary osteotomies in cleft palate patients.

Nineteen unilateral and 19 bilateral alveolar clefts (group A) were grafted with cancellous iliac bone by a standard method, and 21 unilateral and 15 bilateral clefts (group B) underwent simultaneous maxillary osteotomies and alveolar bone grafting with cancellous iliac bone. The two groups were retrospectively evaluated clinically and radiographically for alveolar bone level (ABL), attached keratinized gingiva (AKG), sulcus depth (SD), and persistence of oronasal fistulae (ONF). The follow-up ranged from 6 to 54 months with a mean of 23 months for group A and 26 months for group B. In group A, AKG ranged from 1 to 10 mm (mean 5 mm), most patients having deep or normal SD and type I ABL as measured according to the Oslo method. No persistent ONF was noted. In group B, AKG ranged from 0 to 8 mm (mean 3 mm), half the patients showing a shallow sulcus, most with type II or III ABL. In this group, a 4% failure rate of the bone grafting was noted and 6% fistula persistence. It is concluded that the overall results of standard alveolar bone grafting are better in this series than those of simultaneous osteotomy cases, results which are still quite acceptable because they are comparable with published results of standard alveolar bone grafting. The results of this study indicate that simultaneous osteotomy with alveolar bone grafting in cleft patients does not compromise the outcome of bone grafting; therefore, they support the one-stage surgical management of patients with ungrafted clefts and maxillary hypoplasia.

Adolescent↗

PubMed1994

The use of mouldable acrylic for restoration of the temporalis flap donor site.

Despite the wide popularity of the pedicled temporalis myofascial flap, aesthetic management of the temporalis donor site has received little attention. A technique for immediate camouflage of the temporalis flap donor site with cold-cure methyl methacrylate, either alone or in combination with residual muscle in the temporal fossa, is presented. A retrospective evaluation of this technique in 34 consecutive patients was undertaken, with particular reference to the aesthetic results and morbidity associated with the use of cold-cure acrylic for this form of reconstruction. Apart from transient postoperative swelling and neuropraxia, no major or lasting complications associated with the use of cold-cure acrylic were recorded. The aesthetics of the camouflaged temporalis donor site by acrylic alone, or when combined with part of the temporalis muscle, was judged objectively to be excellent in 25 patients, satisfactory in 3 patients, and poor in 2 patients. 4 patients who did not have acrylic reconstruction, but had part of the temporalis muscle transposed to conceal the anterior fossa depression, leaving the posterior fossa unreconstructed, were judged mostly as satisfactory. Histology of the soft tissues around an acrylic implant after nearly 2 years confirmed the good biocompatibility of this material. It is concluded that this technique is a safe and reliable method for immediate camouflaging of the temporal fossa after harvesting a temporalis muscle flap.

Adolescent↗

PubMed1994

Flow cytometric analysis of DNA ploidy in hepatocellular carcinoma.

To examine the prognostic and pathobiologic significance of DNA content, the authors studied the surgically resected hepatocellular carcinomas of 69 patients by flow cytometric analysis. Homogeneity of DNA content within individual tumor nodules was present in 15 (88%) of 17 specimens examined. Similarly, homogeneity of DNA content in tumors having multiple nodules was found in 8 (73%) of 11 specimens. In 64 tumors with homogeneous DNA content evaluated further, DNA aneuploidy was present in 30 (46.9%) specimens, and the proportion of aneuploid tumors was similar in the large (> 5 cm in diameter, n = 35) and small (< or = 5 cm, n = 25) lesions, at 42.9% and 40%, respectively. Overall, the diploid tumors had serum alpha-fetoprotein levels increased to greater than 500 micrograms/mL more frequently than did the aneuploid tumors (P = .037). DNA content did not correlate significantly with hepatitis B surface antigen, presence of liver cirrhosis, cellular differentiation, tumor size, or tumor encapsulation. DNA content also did not influence tumor invasiveness in terms of liver invasion, presence of tumor microsatellites, or venous permeation. With multivariate Cox regression analysis, tumor encapsulation (P = .015), negative resection margin (P = .007), and DNA ploidy pattern stratified according to large and small tumors (P = .024) were favorable prognostic factors. In the small tumors, a diploid DNA pattern was associated with significantly better patient survival than was an aneuploid pattern (P = .012). In the large tumors, on the contrary, a diploid pattern was associated with poorer patient survival than was an aneuploid pattern (P = .029). The authors conclude that DNA ploidy pattern in hepatocellular carcinomas is homogeneous and stable. It supplements other predictors in prognostication when the lesions are stratified into small and large ones by tumor size. It is of particular importance as a predictor because it can be assessed preoperatively in needle-biopsy specimens.

Adult↗

PubMed1994

Reconstructive options for maxillary defects.

Reconstruction of the maxilla should aim to restore appearance, speech and occlusion. With modern reconstructive techniques and availability of an increasing variety of reliable tissue flaps, many of the traditional problems of treatment have been overcome. This paper reviews local and distant tissue flaps useful in rehabilitating an acquired maxillary defect of various dimensions. The local flaps discussed include flaps from the palate, cheek, tongue and the buccal fat pad. The distant flaps considered are the temporalis myofascial flap, pedicled cutaneous and myocutaneous flaps, and vascularized free flaps. Bony reconstruction of the maxilla with particular emphasis on restoring an anatomical alveolar ridge for occlusal rehabilitation by dental implants is presented.

Bone Transplantation↗

PubMed1993

The buccal fat pad in oral reconstruction.

The use of the buccal fat pad (BFP) as an uncovered pedicled graft to close oral defects is relatively recent. A series of 29 consecutive cases of reconstruction utilizing the BFP is presented, showing excellent results and without added surgical morbidity. Indications include defects after benign or malignant tumour resection, and the combined BFP/temporalis myofascial pedicled flap is reported as an additional option in reconstruction. Histologic findings in healed reconstruction sites indicate fibrous replacement of the fat tissue, and epithelialization of its oral surface. From the results of this series, we conclude that the use of the BFP for the reconstruction of appropriate surgical defects in the mouth is worthy of consideration.

Adipose Tissue↗

PubMed1993

Immediate reconstruction following maxillectomy: a new method.

A new method for immediate reconstruction of the maxilla after resection is described. The ipsilateral pedicled temporalis muscle is tunneled into the defect and sagittaly split into two layers. The inner layer is used to line the nasal side. An individually shaped titanium mesh, tightly filled with free autogenous corticocancellous bone, is fixed by titanium screws to the remnant of the zygoma and contralateral maxilla. The outer layer of the split muscle covers the reconstruction, the temporalis fascia forming the oral side. The method resulted in good cosmetic appearance and permitted the re-creation of a maxillary alveolar ridge suitable for endosseous implants or a simple prosthesis.

Adolescent↗

PubMed1993

Bilateral transverse facial clefts and accessory maxillae--variant or separate entity?

We report an extremely rare case of bilateral transverse facial clefts and accessory maxillae with severe mandibular hypoplasia in a 7-year-old Chinese boy. The transverse facial clefts had been repaired in infancy. The accessory maxillae were excised via a combined temporal and oral approach. Functional orthodontic appliance therapy was not feasible due to restricted protrusive movements of the mandible. Bimaxillary osteotomies were performed one year later due to failure mandibular catch-up growth to occur. The pathogenesis of the accessory maxillae in the presence of lateral facial clefting is postulated to be compensatory mesenchymal growth from the temporal region, and a case is made for this condition to be considered as a possible syndrome rather than a variant of the transverse facial cleft.

Child↗

PubMed1993

Apicectomy of posterior teeth--a clinical study.

Studies evaluating periapical surgery of posterior teeth are relatively few. A retrospective study of 32 apicectomies on posterior teeth using both clinical and radiographic means yielded a success rate of 62 per cent. There were five cases (16 per cent) of failure, the majority of which presented as delayed infection between three and six months following surgery. Post-surgical review of at least six months is recommended. Anatomical considerations for posterior tooth apicectomy and the necessity for retrograde fillings are discussed.

Apicoectomy↗