Biomedical subjects
R W Pho
Publications and source records attributed to R W Pho.
The sequelae of osteomyelitis of the proximal ulna occurring in early childhood.
Three patients presented with upper limb problems caused by the loss of the proximal ulnar shaft due to osteomyelitis which occurred in early childhood. The three patients had several features in common: instability of the elbow, dislocation of the radial head and shortness and bowing of the forearm, but hand and wrist function were largely unaffected. One patient had evidence of impaired function of the posterior interosseous nerve, presumably a traction injury. The treatment of these problems is discussed. In one patient, a child who had a functioning ulno-humeral joint, successful reconstruction of the ulna using a vascularised fibular graft was possible.
Modified technique of sternomastoid transfer for elbow flexion.
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The reverse radial forearm flap in the severely injured hand: an anatomical and clinical study.
An anatomical study in 25 cadaveric upper limbs quantified the communications between the radial and ulnar arteries immediately proximal to the carpus. These studies suggest that the reverse radial forearm flap can safely be used in severe hand trauma where reliable pre-operative assessment of the palmar collateral circulation is not possible. It is recommended that the pedicle is pivoted 4 cm from the styloid process at which point there is a 96% probability of leaving the superficial palmar branch and one other communication intact and a 77% probability of leaving two other communications intact. Two clinical cases are outlined for illustration.
Fetal limb allograft transplants in young rabbits.
The behavior and growth pattern of a transplanted fetal allograft limb in young rabbits were studied. No previous similar studies have been reported in the English literature. Ninety-four fetuses of four-weeks gestation were obtained through hysterectomy. The left hind limb of the fetus was dissected and disarticulated at the hip joint, preserving the long pedicle consisting of the inferior vena cava and abdominal aorta. The skin was stripped and nails were removed from the fetal limb prior to transplantation into a subcutaneous pouch on the medial aspect of the right thigh of a six-week old rabbit. The aorta and the inferior vena cava of the fetus were anastomosed to the femoral vessels of a recipient young rabbit, using the operating microscope. The rabbits were radiographed at fortnightly intervals to assess growth in the transplanted fetal limb. The rabbits were divided into three experimental groups: Group 1 (n = 26)--vascularized fetal allograft; Group 2 (n = 6)--non-vascularized fetal allograft; Group 3 (n = 5)--vascularized fetal allograft with Cyclosporin A. Preliminary results in Group 1 showed growth in the vascularized fetal limb allograft, with a maximum accelerated growth in the first four weeks. All Group 2 non-vascularized fetal allografts showed no growth. Group 3 showed an increased and accelerated limb growth in the first six weeks of transplant. The results demonstrated that vascularized fetal allograft has the potential for low-grade immunogenicity and of growth at the initial stage, especially with adjunctive immunosuppressive therapy.
Cervical disc calcification in children. A long-term review.
Four cases of symptomatic cervical disc calcification in children are presented. Three cases were followed for more than 10 years. In one case, persistent flattening of the adjacent vertebral body remained into adulthood. To quantify the deformity, the height and width of each vertebral body was measured. These permanent changes may be associated with early degenerative changes seen radiologically in young adults.
Cadaveric study on the vascular anatomy of the ulnar nerve at the elbow--a basis for anterior transposition?
The clinical results of anterior transposition of the ulnar nerve in compressive ulnar neuropathy have been unsatisfactory. This study aims at qualifying and quantifying the vascular anatomy of the ulnar nerve at the elbow so as to enable us to appreciate the possible effects of anterior transposition of the ulnar nerve. In our study of 16 cadaveric limbs, we found that the average number of nutrient vessels supplying the ulnar nerve is 14.3. The main contributing vessel in the arm is the superior ulnar collateral artery, at the elbow, the inferior ulnar collateral artery proximally, and the posterior ulnar recurrent artery distally. In the forearm, the main supply is from the ulnar artery. The average length of the nutrient vessels ranges from 1 cm at the elbow to about 2.6 cm in the arm. The nutrient vessels at the elbow are short, small and numerous. Blood supply to the nerve is segmental in nature. In our histological study of the nerve at the elbow, we found that overall, there are more vascular channels in the intrinsic system than the extrinsic system (statistical significance p < 0.01). From this study, we were able to postulate that there is devascularisation of the ulnar nerve following an anterior transposition. The significance of the devascularisation will require further studies.
Objective assessment of research performance.
Research output in academic institutions need critical and objective assessment. Publications are an important avenue by which research by an academic can be evaluated. Journals in which such publications appear may be ranked and weight age given to publications in highly ranked journals. The number of citations of an academic's work by peers is another assessment of quality of research output. Firstly subjective peer assessment although flawed by interpersonal bias has its merits especially when evaluation is by an outsider of the institution.
Hand surgery.
A historical outline of the development of Hand Surgery in Singapore is presented. It traces its growth from the Orthopaedic Surgery Unit at General Hospital Singapore in the early 1950's, to the present times. During this period, the Singapore Society of Hand Surgery was established in 1982, the Department of Hand Surgery at the Singapore General Hospital in 1985 and the Hand and Reconstructive Microsurgery Department was officially established at the National University Hospital in 1990.
The dropped big toe.
Surgical procedures for exposure of the upper third of the fibula have been known to cause weakness of the long extensor of the big toe post-operatively. The authors present three representative cases of surgically induced dropped big toe. From cadaveric dissection, an anatomic basis was found for this phenomenon. The tibialis anterior and extensor digitorum longus muscles have their origin at the proximal end of the leg and receive their first motor innervation from a branch that arises from the common peroneal or deep peroneal nerve at about the level of the neck of the fibula. However, the extensor hallucis longus muscle originates in the middle one-third of the leg and the nerves innervating this muscle run a long course in close proximity to the fibula for up to ten centimeters from a level below the neck of the fibula before entering the muscle. Surgical intervention in the proximal one-third of the fibula just distal to the origin of the first motor branch to the tibialis anterior and extensor digitorum longus muscles carries a risk of injury to the nerves innervating the extensor hallucis longus.
Microsurgery and its clinical impact.
Microsurgery is a technique of magnifying the visual horizon of the surgeon to enable him to see better, dissect better and perform micro-manipulation. This is to help the surgeon to perform very precise surgery that was not possible in the past. The greatest impact has been in our ability to suture small vessels and to allow us to shift tissues readily from one part of the body to another. It can be considered as a form of "spare part surgery" by using biological tissue consisting of toe, digits, bone, cartilage, skin muscle, intestine and other organs for reconstruction. The techniques are now widely accepted as important techniques in reconstructive surgery. The increasing application of these techniques are now being seen more and more in limb preservation surgery for trauma, tumour resection, congenital abnormality and organ transplant. The potential wide application of the technique in hetero transplant, especially in foetal surgery and foetal tissue transplant is now limited only by immunological rejection.
Challenges in surgery.
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Biomechanical study on the load-bearing characteristics of the fibula and the effects of fibular resection.
The objective of this research was to investigate the load-bearing function of the fibula in relation to donor leg morbidity in patients who have had fibular resections. Biomechanical loading experiments were performed on ten anatomic specimens. Force transducers were mounted in place of resected tibial and fibular segments to allow load transmission to be measured. Load transmission through the fibula varied with ankle position. With the ankle at neutral position, the load distribution to the fibula averaged 7.12% of the total force transmitted through the tibia and fibula. Maximum loads occurred at full dorsiflexion and eversion. Resection of the proximal fibula results in a significant reduction of load through the distal fibular remnant. The values varied between 0.62% and 0.81% of the total force transmitted. When a cortex screw was introduced to anchor the distal fibula remnant to the tibia, the load distribution to the distal fibula remnant was partially restored with values ranging from 1.71% to 5.14% of the total force transmitted depending on the different ankle positions. These observations suggest that more consideration of the loading characteristics of the fibula should be taken into account in planning resection operations.
Neovascularisation of the epiphysis.
Two experiments in the rabbit model have been carried out to see if a vascular pedicle placed in a growing epiphysis would establish new capillaries. In one, the vascular pedicle of peroneus longus muscle was placed in the proximal fibula epiphysis. In the other, the proximal fibula was excised and the epiphysis placed across the saphenous artery and vein in the groin. After 3 months, histological examination of the epiphyses in both experiments showed that no new vessels had grown from the vascular pedicle. Cartilage is known to inhibit vascularisation, and these results suggest that attempts to revascularise the epiphysis, for example, following Perthes' disease, may fail. For the same reason, attempting to supplement the epiphyseal vessels by implanting a new vessel before or after epiphyseal transfer may fail.
A composite neuro-teno-cutaneous forearm flap in the one-stage reconstruction of a large defect of the soft tissue around the ankle.
The vascular anatomy of the radial forearm flap, incorporating the brachioradialis and palmaris tendons together with the superficial radial nerve in 20 fresh cadavers, is described. The radial artery in the cadaveric forearm was irrigated and injected with blue latex. The number and distribution of the cutaneous branches supplying the skin, brachioradialis tendon, palmaris tendon, and superficial radial nerve, were then documented in relation to the distance from the radiocarpal joint. The radial artery was found to provide adequate blood supply to the above structures. This flap has been used as a composite neuro-teno-cutaneous flap to resurface a large defect involving tendon, nerve, and skin loss in the ankle and the foot as a one-stage procedure. This technique avoids multiple-staged operations and thus shortens the convalescent period in rehabilitation of severely traumatized limbs.
Experimental transplantation of limbs.
This article is a brief review of experimental and clinical studies on replantation and transplantation of the whole limbs. Special reference is given to our preliminary study of the foetal limb allograft in young rabbits. The results showed that the vascularised foetal limb allografts of the group with Cyclosporine A (CsA) treatment increased in longitudinal growth in their first 6 weeks of transplantation as compared to the group without CsA treatment. Transplantation of foetal tissue has yielded new possibilities in the treatment of congenital and traumatic limb defects in human in the future. The utility of foetal limb tissues brings us a step closer towards the long road of limb transplantation.
Brachioradialis forearm flap in a case of traumatic bone and skin loss at the elbow.
A case of traumatic skin and bone loss at the elbow is described. This was treated by a long brachioradialis flap, allowing early movements with thick and sensate cover. Anatomical studies delineate the extent of this flap.
Donor site morbidity following resection of the fibula.
Ten adults were studied two to seven years after resection of a fibula for use as a free vascularised bone graft. Six had no symptoms in the donor leg, four had some aching, weakness or paraesthesia and three had definite weakness of the long toe flexors and extensors. All knees and ankles were clinically and radiologically stable, but the distal fibular remnant was osteoporotic in nine patients. Gait analysis of the donor leg and the contralateral normal leg showed definite differences, which could be attributed to weakness of the deep muscles caused by loss of their normal origin and to the change in load transmission through the fibula.