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Biomedical subjects

R W Pho

Publications and source records attributed to R W Pho.

At least 19 recordsLinked to original sources
PubMed2001

The microvasculature of the nail bed, nail matrix, and nail fold of a normal human fingertip.

The organization of the microvasculature of the dorsal human fingertip based on a vascular corrosion cast was examined using a stereoscopic microscope. The variations of the superficial capillary network of the 3 specialized areas of skin of the dorsal fingertip (the nail bed, the nail matrix, and the nail fold) are described. In the nail bed numerous capillary loops were observed arising from a deeper regular arrangement of sagittally aligned, parallel rows of vessels. The size and direction of inclination of the capillary loops varied, getting longer and more inclined to the nail bed distally, with the longest capillary loops seen at the hyponychium. There were no capillary loops at the nail matrix region, but there was a single, layered, rectangular plexus of capillaries in the plane of the nail matrix. This extended distally to sagittally stretched coils of vessels that straightened out as the nail matrix enters the nail bed region. At the edge of the proximal nail fold the capillary loops looked like fine bristles and were approximately 3 times shorter than those found on the nail bed and hyponychium. This study provides a baseline for future work in understanding the changes in the microvasculature of the dorsal fingertip due to injury or pathology.

Adult↗
PubMed2001

Esthetic prostheses in minor and major upper limb amputations.

In summary, the impact and value of esthetic prostheses on amputee rehabilitation and their long-term use were demonstrated in this study to have no correlation with the severity of injury and level of amputation. All patients with traumatic amputation should be given equal opportunity to receive prostheses if the service is readily available. Whether use of prostheses is temporary or long-term, they help patients cope with the traumatic life experience of limb loss.

Amputation, Traumatic↗
PubMed1999

An unusual case of multiple recurrence of a glomangioma.

Glomus tumour is a benign lesion arising from the glomus apparatus of the skin and subcutaneous tissue. Glomangioma is the angiomatous variant, which is uncommon. We report a very rare presentation of a glomangioma with multiple recurrences. We advocate preoperative angiography to delineate the extent of the lesion to facilitate complete excision.

Adult↗
PubMed1999

Split flexor carpi radialis muscle.

A detailed anatomic and intramuscular neural staining study in 22 human and 5 monkey upper limbs revealed that the flexor carpi radialis can be raised on its proximal neurovascular pedicle and that the muscle can be split along its tendon into two independently functioning neuromuscular compartments, each with its own nerve and blood supply. A study of the muscle architecture in the human specimens found the radial compartment to have significantly longer fiber length and a larger physiologic cross-sectional area than the ulnar compartment. Independence of function of each compartment was demonstrated in electrical stimulation studies in six monkeys (Macaca fascicularis), but no significant difference was noted in the peak isometric load between the two compartments (p = 0.68) in the monkey. The extra functioning muscle units become important in local transfers for restoring function in multiple nerve palsies as in Hansen's disease, severe traumatic loss of muscle in crush injuries and compartment syndromes, and after wide resection in infective and neoplastic conditions in the forearm and hand.

Animals↗
PubMed1999

Creating a model for fabricating a partial hand glove prosthesis using the realigned casts of the contralateral digits.

A method for creating a model for fabricating a partial hand glove prosthesis is described. The realigned casts of the corresponding digits of the contralateral uninjured hand were used to substitute for the lost digits on a cast of the stump. The technique allows an exact reproduction of the anatomical and fine surface details of the digits. It has the advantage of customisation, allowing a close match in the size, shape and surface characteristics of the prosthesis to that of the remaining digits of the hand.

Adult↗
PubMed1999

RTV silicone elastomers in hand prosthetics: properties, applications and techniques.

In this technical note, an overview of RTV (room-temperature-vulcanising) silicone elastomers is provided. The properties and applications of 3 different types of RTV silicones in producing prostheses for the hand are discussed. Vinyl polysiloxanes are excellent silicone impression materials that offer the advantages of a rapid cure, near exact duplication of fine details and ease of removal of the cured impression without permanent deformation. RTV-2 dimethyl polysiloxanes are ideal for mould-making and fabricating prostheses given their favourable qualities that range from ease of pigmentation, adjustable consistency, manageable curing rate and accuracy in recording fine details in the liquid state to excellent stain-resistance, elasticity and biodurability in the vulcanised state. RTV-1 dimethyl polysiloxanes are self-curing, ready-for-use silicones that adhere adequately well to most substrates and are useful for extrinsic hue modifications and waterproofing of the prosthesis. The basic techniques for each of these applications are also discussed. The cure-inhibition of addition-curing RTV silicones by sulphur-, tin- and nitrogen-containing contaminants and its damaging consequence is highlighted. A compilation of known contaminating agents is provided so that prior contact with these objects can be avoided when working with addition-curing silicones. The precautionary measures to prevent the problem are also outlined.

Elasticity↗
PubMed1999

Metamerism in aesthetic prostheses under three standard illuminants--TL84, D65 and F.

This study looks at the effect of metamerism in colour-matching and the assessment of multi-layered silicone rubber finger prostheses. The aim was to identify the choice of illuminants for colour matching the prostheses that would give rise to the least metameric effect between the prostheses and the human skin or the best colour match. The prostheses were prepared and colour matched to a fair-skinned subject under 3 reference illuminants--TL84, D65, F and a combination of illuminants--TL84, D65 and F. The prostheses were then measured for colour using a spectrophotometer based on the CIE indices L*, a*, b* with each prosthesis assessed separately against the subject's index finger under the reference illuminants--TL84, D65 and F. The prostheses were also assessed by a panel of 50 observers and scored according to colour-match. Colour differences between the skin and prosthesis were measured in the illuminant under which the prostheses were prepared and then under the other reference illuminants. A relationship was obtained between the measured mean colour difference, deltaE*, and the mean visual assessment score for each prosthesis. This paper points out the concerns related to the optical phenomenon of metamerism with the colour pigments used. This can affect the colour match of the prosthesis as perceived by the patient. The findings seem to suggest that this metameric colour difference can be minimised if the prosthesis is matched under a combination of lights, which were found to give the best-perceived match.

Fingers↗
PubMed1999

The neuromuscular compartments of the flexor carpi ulnaris.

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Report on the vascular supply and innervation pattern of the flexor carpi ulnaris. 2. Describe the muscle architecture of the flexor carpi ulnaris, including the physiological cross-sectional area and fiber length. 3. State the uses of the flexor carpi ulnaris both for resurfacing defects in the vicinity of the elbow and in local functional tendon transfers. 4. Understand the principles of splitting skeletal muscles based on neurovascular supply to enhance its utilization in reconstructive procedures. The aim of this study was to describe the intramuscular innervation and vascular supply of the human flexor carpi ulnaris, with confirmation of findings by a similar study in the primate. Two distinct intramuscular nerve branches running parallel to each other, on either side of a central tendon, from the proximal quarter of the muscle belly to its insertion were found. The muscle could then be split into a humeral and an ulnar compartment, each with its own primary nerve branch. Perfusion studies confirmed the adequacy of circulation to the two compartments. In the primate flexor carpi ulnaris, electrical stimulation of the respective branches revealed independent contraction of each compartment. This study provides useful information for enabling the local transfer of the muscle as a whole, both for resurfacing in the vicinity of the elbow and for functional tendon transfers. It will also enable the transfer of the muscle as one or two separate compartments (for resurfacing, in tendon transfers for muscle paralysis, congenital defects, and muscle defects resulting from trauma, and after resections for neoplasm and infection).

Animals↗
PubMed1999

Lengthening in free vascularized fibular graft.

A free vascularized fibular bone transfer was successfully performed in a 1-year-old child to reconstruct the loss of the right humeral shaft following neonatal osteomyelitis. Subsequent growth of the child resulted in gross arm length discrepancy, with associated functional deficits. Callostatic distraction-lengthening of the vascularized fibular graft was carried out to compensate for this limb length discrepancy by using an Ilizarov external fixator. Lengthening of 6 cm over a 3-month period, representing a 75% increase in the original length of the transplanted fibula, was achieved. Active bone regeneration, good corticalization and endosteal medullary cavity formation was observed in the lengthened fibula. The combined modalities of vascularized bone transfer and Ilizarov callostatic distraction-lengthening offer a solution for reconstruction for large segmental bone loss associated with growth arrest of the epiphyseal plates in children.

Female↗
PubMed1998

Comparison of the size of plates for fracture fixation with the size of phalanges and metacarpals in cadavers of Asian origin.

The size and volume of plates and screws for fracture fixation of the hand (1.5-mm screws and titanium miniplates, 2.0-mm screws and stainless-steel AO miniplates, and 2.7-mm screws and stainless-steel AO miniplates) were compared against the phalanges and metacarpal bones and the surrounding soft tissue from male cadavers of Asian decent. In the cadaver study, it was first established that the difference between anatomic measurements and radiologic measurements for the interarticular bone length and midshaft width were not significant (p = .09). Second, the volume occupied by the bone showed a close association to interarticular bone length. This finding would suggest that the volume occupied by the bone may be estimated from the radiographs. When the length of the plates was compared to that of the bones, the analysis showed 4-hole and 6-hole 1.5-mm titanium miniplates, and the 4-hole and 6-hole 2.0-mm AO plates were not suitable for the middle phalanx, although only rarely are fractures in the middle phalanx fixed with plates. For the proximal phalanx, only the 4-hole 1.5-mm and 2.0-mm plates were suitable in length. The 6-hole 2.0-mm AO plate was found to be suitable for only the longer proximal phalanx of the middle digit. For the metacarpals, the 5-hole 2.7-mm AO plate was found not to be suitable for the thumb (in length) and the ring digit (in width). The commonly used plates and screws for fracture fixation of the hand may not be suitable in size for groups of people with smaller hand sizes, in particular some Asians and women.

Adult↗
PubMed1998

Fitting a hand-glove prosthesis to enhance the reconstructed mutilated hand.

Microsurgical reconstruction of the severely mutilated hand aimed at improving prehensile functions often does not address the esthetic aspects of the hand. The poor appearance of the reconstructed hand affects its active display and use. A hand-glove prosthesis may be prescribed in this instance to enhance the overall form and function of the mutilated hand. We reviewed 16 cases of mutilating hand injuries in which surgical reconstructions were performed and the patients were subsequently fitted with a hand-glove prosthesis to augment the outcome. An improved appearance was achieved in all patients fitted with the prosthesis. The patients' sense of confidence was also enhanced, which in turn promoted the active and open use of the reconstructed hands. While prescribed primarily to improve the appearance of the reconstructed hands, these prostheses were documented to enhance the physical hand functions in 11 cases by increasing the span of the hand and providing an opposable post and a palmar base for holding and for anchorage. The prosthesis enhanced assistive functions of the reconstructed hands and freed the contralateral normal hand for use in bimanual activities, such as holding a wallet and taking out money, supporting a note pad for writing, and holding a plate at buffet receptions. At the 18-month follow-up visit, 13 (87%) of the patients continued to use their prosthesis. Wear and tear were problems associated with the frequent use of the prosthesis. The expected life span of the prosthesis with daily use ranged from 2 to 3 years. All the patients acknowledged that the prosthesis played a role in their rehabilitation and that it helped them to overcome the initial psychological trauma and to come to terms with their physical loss.

Activities of Daily Living↗
PubMed1998

Neurovascular supply of the gracilis muscle: a study in the monkey and human.

A comparison of the gross anatomy, extramuscular nerve branches, and intramuscular blood supply of the gracilis muscle showed similar patterns in both monkey and human. The number and pattern of distribution of the extramuscular terminal branches to the muscle were similar. The intramuscular neural pattern demonstrated with the Sihler's staining technique was also similar in both species. In vivo electrical stimulation studies in the monkey revealed that stimulating each extramuscular terminal nerve branch produced a distinct segmental contraction of the muscle. Independent contraction with force generation was observed when the monkey muscle was split into anterior and posterior segments and stimulated through each of the two subdivisions of the main nerve trunk to the muscle. Angiograms verified that circulation was preserved in these two segments.

Animals↗
PubMed1998

Giant cell tumor of lumbar vertebra. A case report with 13-year followup.

A combined one stage anterior and posterior approach was used to excise a giant cell tumor involving the second lumbar vertebra. The tumor involved the anterior and posterior elements of the vertebra. A wide excision was feasible with immediate stabilization using the Luque instrumentation posteriorly and fibular strut grafts supporting the vertebral bodies anteriorly. The followup period was 13 years. There is no recurrence, and the patient has no symptoms of disease, and the fibular grafts are fully incorporated.

Adult↗
PubMed1997

Modified Sihler's technique for studying the distribution of intramuscular nerve branches in mammalian skeletal muscle.

BACKGROUND: A largely forgotten technique initially designed by Sihler for staining nerve tissue has not been fully explored for staining intramuscular nerve branches in skeletal muscles. METHODS: Fresh, long heads of triceps from locally bred New Zealand white rabbits were used for this study. Immediately after their removal, the muscles with their motor nerve branches from the radial nerve were fixed in 10% unneutralized formalin, followed by maceration and depigmentation in 3% aqueous potassium hydroxide, decalcification in Sihler's solution I, micro-dissection, staining in Sihler's solution II, destaining in Sihler's solution I, neutralization in 0.05% lithium carbonate, and clearance in increasing concentrations of glycerin. RESULTS: A clear three-dimensional orientation of the distribution of the intramuscular nerve branches within the muscle belly was visualized. It was found in all specimens that the long head of triceps in the rabbit was constantly innervated by three main intramuscular nerve branches and each of them supplied different amounts of muscle fibers with some variation. CONCLUSION: The Sihler's neural staining technique can be applied to the study of the distribution of intramuscular nerve branches in limb skeletal muscles. Extension of the technique may be utilised in the identification of neuromuscular compartments in skeletal muscles. Such information may be usefully applied in free muscle transfer of segments of skeletal muscle.

Animals↗
PubMed1997

Distribution of primary motor nerve branches and terminal nerve entry points to the forearm muscles.

BACKGROUND: The information available on innervation pattern of the human forearm muscles in standard anatomy texts, although adequate for routine procedures, is not detailed enough for surgical reconstruction in complex injuries of the limb and for paralytic conditions of the forearm from peripheral nerve and spinal cord injuries. METHODS: The innervation pattern in 10 cadaveric forearms was studied. The contributions of the main nerve trunks to each forearm muscle was examined. The location and number of the primary motor nerve branching points and of the terminal nerve entry points to each muscle were investigated. The location of both the primary nerve branching points and terminal nerve entry points was presented as a percentage of forearm length measured from the lateral humeral epicondyle to the radial styloid. RESULTS: Seven of 19 forearm muscles were innervated from a single branch from the main nerve trunk. The remaining 12 received more than one primary branch. Two of 19 forearm muscles had only one terminal nerve entry point. The others had two or more each. In 13 of 19 forearm muscles, the statistical median location of the primary motor nerve branching points was within the proximal one-third of the forearm length and either more proximally or distally for the remainder. The statistical median location of the terminal nerve entry points was within the proximal one-third in 9 forearm muscles and within the middle one-third of the forearm in 8 forearm muscles. In two, it was located proximal to the elbow and in the distal one-third of the forearm, respectively. CONCLUSIONS: In lacerations across the forearm, where main nerve trunks are divided, mere repair of the nerve trunks would not address the denervation of muscle or segments of muscle by the division of the primary (or secondary) nerve branches traversing the wound and which took origin proximal to the laceration either from the divided nerve trunks or from other undamaged nerve trunks. Although the main nerve trunks may be intact, segmental crush injuries will defunction muscles by direct muscle damage or by damage to the terminal nerve entry points to the muscle. Knowledge of the location of the nerve branches and the terminal nerve entry points facilitates the insertion of electrodes at the motor points of forearm muscles for functional electrical stimulation in upper motor neuron lesions. The information in this study may also be usefully applied in selective denervation procedures to balance muscles in spastic upper limbs.

Adult↗