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The neurovascular island flap in reconstruction of the thumb
The Neurovascular Island Flap in Reconstruction o[ the T h u m b - - A . C. Buchan
THE N E U R O V A S C U L A R I S L A N D F L A P I N R E C O N S T R U C T I O N OF T H E T H U M B
A. C. BUCHAN, Edinburgh Fifteen or twenty years ago, an absent thumb was sometimes reconstructed by lengthy multi-stage procedures which all too frequently produced a useless, fixed, insensitive opposition post. Many of the problems associated with thumb reconstruction have been solved by the introduction of pollicisation and the neurovascular island flap techniques. The relative merits of the two methods are not well defined and this paper is confined to thumb reconstruction by the skin flap, bone graft and neurovascular island flap method. METHODS
In this small series, pollicisation has been restricted to those cases in which the first carpo-metacarpal joint has been destroyed or in which the range of movement is inadequate and cannot be improved. Pollicisation has been used as the method of choice when one of the fingers is damaged but retains sufficient movement and sensation to make pollicisation worth while. In the early cases, a four-stage method of reconstruction was used, transferring additional skin by a cross arm or trunk flap, followed by the insertion of a bone graft and finally, by a neurovascular island transfer. Apart from the number of operations and time involved, this method had one very serious disadvantage, the frequent occurrence of delayed healing following the skin flap detachment. Experience has shown that a two-stage reconstruction is safe, much quicker and less prone to problems of wound healing. At the first stage, the thumb is elongated by a mainly cancellous bone peg from the iliac crest inserted down the medulla of the metacarpal stump and held in position by two buried transfixion Kirschner wires. The bone graft is covered by a pectoral skin flap. This is tubed round the graft and must be at least 3½ inches wide to allow closure of the skin without tension. Care is taken to place the seam line of the one-stage tube pedicle in the pinch bearing area of the future thumb. At the second stage three to four weeks later, the pedicle of the flap is divided. A neurovascular island flap is taken usually from the ulnar side of the ring finger. It is inserted into the pinch area on the thumb after opening up the junctional scar and carrying out any adjustments that are required on the skin. Three or four months later, excess skin is removed through a dorsal zig-zag incision which allows the skin to be tightened both longitudinally and transversely. If the skin reduction is performed on several occasions, the area covered by the neurovascular island is gradually increased and may cover half the circumference of the reconstructed thumb. INDICATIONS
The same basic method has useful indications in the primary treatment of some thumb injuries. 1. Degloving injuries with retention of the metacarpal and one or both phalanges. 2. An avascular distal segment following partial amputation. 3. Gangrene following the repair of a severe injury. Fractures are reduced and detached distal segments are re-attached using Kirschner wires. Devitalised skin is replaced by a one-stage pectoral skin flap. Loose strands of digital nerves are preserved and divided digital nerves are repaired where possible. In one patient, the nail bed was retained and buried under the skin flap. Nine months after the operation, there has been no evidence of nail growth but it is too soon for a final assessment. 19
The Neurovascular Island Flap in Reconstruction of the Thurnb--A. C. Buchan COMPLICATIONS
Four complications require consideration. I.
Infection. Infection has occurred in one patient at the second stage of the reconstruction. The entire bone graft was lost, even though the fibrous capsule surrounding the bone graft was not disturbed. Careful wound hygiene, bacteriological investigations, and the use of an appropriate antibiotic is desirable at this detachment operation.
II.
Vascular disturbances in the Neurovascular island [tap. Vascular disturbances have arisen in one of the neurovascular island flaps that have been done, The flap only just survived and the complication was due to damage to the superficial palmar arch at the time of the initial injury. During the dissection, two abnormally large communicating vessels between the superficial and deep palmar arches were divided. Previous deep wounds in the palm may preclude the use of neurovascular island flaps and exploration of the vessels may be required before the flap is raised.
III.
Failure of transfer of sensation to thumb. Thirteen neurovascular island flaps have been performed in twelve patients. No referral of sensation to the thumb occured in five flaps. These flaps were in four patients who were all thirty-six years of age or more. The oldest of the eight patients in whom there appeared to be complete referral of sensation was twenty-three, Age is probably a very important factor and the experience of other surgeons will be of interest. The four patients in whom there was a failure to transfer sensation did not complain of any disability or interference with their working capacity due to this sensory disturbance. Transfer of sensation is not regarded as being of great importance.
IV.
Absorption of the bone graft. Absorption of the bone graft has been the most serious and unpredictable of the complications that may occur with this method of thumb reconstruction. There is usually some absorption of the bone graft during the first twelve months. Two types of excessive absorption have been observed. In one, there has been marked absorption followed by a fracture of the graft at its narrowest point where the graft enters the medulla of the metacarpal. This complication has not been seen since longitudinal strips of cancellous grafts have been laid round the junction between the graft and metacarpal and held in position by several catgut sutures. In some patients, there has been general absorption of the graft for no very obvious reason. One patient has had three bone grafts and another has had two, but now requires a third. Infection did not appear to play any part in the absorption of the bone grafts in these two patients. Some patients have shown little or no evidence of absorption and the use of neurovascular island flaps has not reduced the frequency of this complication as far as can be determined from the small number of cases. None of the six cases of degloving injuries or partial amputations with or without the insertion of a neurovascular flap has shown significant absorption of the normal thumb skeleton. SUMMARY
Thumb reconstruction by skin flap, bone graft and neurovascular island flap is not without its problems, but the results are sufficiently encouraging to persist with the method as an alternative to pollieisation. 20
THE N E U R O V A S C U L A R I S L A N D F L A P I N R E C O N S T R U C T I O N OF T H E T H U M B
A. C. BUCHAN, Edinburgh Fifteen or twenty years ago, an absent thumb was sometimes reconstructed by lengthy multi-stage procedures which all too frequently produced a useless, fixed, insensitive opposition post. Many of the problems associated with thumb reconstruction have been solved by the introduction of pollicisation and the neurovascular island flap techniques. The relative merits of the two methods are not well defined and this paper is confined to thumb reconstruction by the skin flap, bone graft and neurovascular island flap method. METHODS
In this small series, pollicisation has been restricted to those cases in which the first carpo-metacarpal joint has been destroyed or in which the range of movement is inadequate and cannot be improved. Pollicisation has been used as the method of choice when one of the fingers is damaged but retains sufficient movement and sensation to make pollicisation worth while. In the early cases, a four-stage method of reconstruction was used, transferring additional skin by a cross arm or trunk flap, followed by the insertion of a bone graft and finally, by a neurovascular island transfer. Apart from the number of operations and time involved, this method had one very serious disadvantage, the frequent occurrence of delayed healing following the skin flap detachment. Experience has shown that a two-stage reconstruction is safe, much quicker and less prone to problems of wound healing. At the first stage, the thumb is elongated by a mainly cancellous bone peg from the iliac crest inserted down the medulla of the metacarpal stump and held in position by two buried transfixion Kirschner wires. The bone graft is covered by a pectoral skin flap. This is tubed round the graft and must be at least 3½ inches wide to allow closure of the skin without tension. Care is taken to place the seam line of the one-stage tube pedicle in the pinch bearing area of the future thumb. At the second stage three to four weeks later, the pedicle of the flap is divided. A neurovascular island flap is taken usually from the ulnar side of the ring finger. It is inserted into the pinch area on the thumb after opening up the junctional scar and carrying out any adjustments that are required on the skin. Three or four months later, excess skin is removed through a dorsal zig-zag incision which allows the skin to be tightened both longitudinally and transversely. If the skin reduction is performed on several occasions, the area covered by the neurovascular island is gradually increased and may cover half the circumference of the reconstructed thumb. INDICATIONS
The same basic method has useful indications in the primary treatment of some thumb injuries. 1. Degloving injuries with retention of the metacarpal and one or both phalanges. 2. An avascular distal segment following partial amputation. 3. Gangrene following the repair of a severe injury. Fractures are reduced and detached distal segments are re-attached using Kirschner wires. Devitalised skin is replaced by a one-stage pectoral skin flap. Loose strands of digital nerves are preserved and divided digital nerves are repaired where possible. In one patient, the nail bed was retained and buried under the skin flap. Nine months after the operation, there has been no evidence of nail growth but it is too soon for a final assessment. 19
The Neurovascular Island Flap in Reconstruction of the Thurnb--A. C. Buchan COMPLICATIONS
Four complications require consideration. I.
Infection. Infection has occurred in one patient at the second stage of the reconstruction. The entire bone graft was lost, even though the fibrous capsule surrounding the bone graft was not disturbed. Careful wound hygiene, bacteriological investigations, and the use of an appropriate antibiotic is desirable at this detachment operation.
II.
Vascular disturbances in the Neurovascular island [tap. Vascular disturbances have arisen in one of the neurovascular island flaps that have been done, The flap only just survived and the complication was due to damage to the superficial palmar arch at the time of the initial injury. During the dissection, two abnormally large communicating vessels between the superficial and deep palmar arches were divided. Previous deep wounds in the palm may preclude the use of neurovascular island flaps and exploration of the vessels may be required before the flap is raised.
III.
Failure of transfer of sensation to thumb. Thirteen neurovascular island flaps have been performed in twelve patients. No referral of sensation to the thumb occured in five flaps. These flaps were in four patients who were all thirty-six years of age or more. The oldest of the eight patients in whom there appeared to be complete referral of sensation was twenty-three, Age is probably a very important factor and the experience of other surgeons will be of interest. The four patients in whom there was a failure to transfer sensation did not complain of any disability or interference with their working capacity due to this sensory disturbance. Transfer of sensation is not regarded as being of great importance.
IV.
Absorption of the bone graft. Absorption of the bone graft has been the most serious and unpredictable of the complications that may occur with this method of thumb reconstruction. There is usually some absorption of the bone graft during the first twelve months. Two types of excessive absorption have been observed. In one, there has been marked absorption followed by a fracture of the graft at its narrowest point where the graft enters the medulla of the metacarpal. This complication has not been seen since longitudinal strips of cancellous grafts have been laid round the junction between the graft and metacarpal and held in position by several catgut sutures. In some patients, there has been general absorption of the graft for no very obvious reason. One patient has had three bone grafts and another has had two, but now requires a third. Infection did not appear to play any part in the absorption of the bone grafts in these two patients. Some patients have shown little or no evidence of absorption and the use of neurovascular island flaps has not reduced the frequency of this complication as far as can be determined from the small number of cases. None of the six cases of degloving injuries or partial amputations with or without the insertion of a neurovascular flap has shown significant absorption of the normal thumb skeleton. SUMMARY
Thumb reconstruction by skin flap, bone graft and neurovascular island flap is not without its problems, but the results are sufficiently encouraging to persist with the method as an alternative to pollieisation. 20