Biomedical subjects
Publications and source records attributed to L K Cheung.
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.
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.
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.
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.
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.
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.
Ceftazidime use at our institution, a 580-bed county teaching hospital, has steadily increased since its addition to the formulary in 1986. In response to this increased use and because the institutional antibiogram showed increased resistance by Pseudomonas aeruginosa (from 10 to 28% resistant), the P & T Committee requested that a drug use evaluation (DUE) of ceftazidime be conducted. Analysis of this retrospective pilot study showed that 87% of ceftazidime use was inappropriate. To further evaluate ceftazidime use, to identify problems not assessed during retrospective review, and to correct problems while patients were receiving the drug, a concurrent ceftazidime use evaluation was conducted. The methods and results of the concurrent review are presented below.
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.
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.
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.
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.
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.
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Tenoxicam is a long-acting nonsteroidal anti-inflammatory agent that appears to have the ability to control pain of musculoskeletal origin. A double-blind randomized crossover study was designed to determine the efficacy of tenoxicam for pain relief following third molar surgery by comparing it with paracetamol. Immediately before surgery, 30 Chinese patients with bilateral symmetrically impacted mandibular third molars were given 40 mg of tenoxicam for surgery on one side and 1,000 mg of paracetamol for surgery on the other. Both paracetamol and tenoxicam were efficient as pain relievers after third molar surgery. Tenoxicam had comparable efficacy to paracetamol, but did not provide any advantage in terms of duration of action. The discrepancy between the clinical observation and pharmacokinetic prediction may be related to the strong serum binding property of tenoxicam.
Two examples are presented of osteotomies performed simultaneously with surgical recontouring in cases of fibrous dysplasia of the jaws. Osteotomies are necessary when a coexistent discrepancy in jaw relationship is present. This provides a functional as well as aesthetic result. Rigid miniplate fixation was utilised, and dysplastic bone healing was uneventful, and found clinically not to differ from that of normal bone. Osteotomy is thus feasible in dysplastic bone, and may complement recontouring in achieving a better result.
A case is reported of the rare melanotic neuroectodermal tumour of infancy involving the maxilla of a 4-month-old girl. The role of CT is discussed with particular reference to the diagnosis.
Total occlusion of the left main coronary artery (LMCA) is a rare finding in patients with stable angina pectoris. To the best of our knowledge, it has not been described in Hong Kong Chinese before. In this paper, we report the clinical and angiographic findings of a Hong Kong Chinese with this condition treated in our unit.
In a double blind study in Hong Kong Chinese, 250 mg of diflunisal, 500 mg of paracetamol or placebo were given for post-operative pain relief following 77 third molar surgical procedures. The intensity of pain was recorded on a visual analogue scale. The first and second doses of paracetamol reduced pain significantly more than placebo, while this was true only for the second dose of diflunisal. There was no significant difference in pain reduction with the first and second dose of paracetamol, when compared with the first and the second dose of diflunisal. In this study in Hong Kong Chinese, neither the dose nor the interval between ingestion of the analgesic tablets in patients, who needed analgesics for postoperative pain, were significantly different to that reported before in non-Chinese, in contrast to the popular belief that Chinese patients have higher pain thresholds. However, a higher proportion of Chinese than that reported in non-Chinese did not need any analgesics for relief of postoperative pain.