Problems of restoration of tendon movements after repair and grafts

Abstract

Repair of flexor tendons by direct suture or tendon graft is not a difficult operation but, unlike most operations on the hand, the results are frequently unpredictable.The commonest cause of failure is adhesion formation at the site of tendon suturing or grafting. This results in very little, if any, movement of the finger occurring on voluntary contraction. Worse still, a previously mobile digit may be converted into a semi-rigid hook.The prevention of adhesions has taxed the ingenuity of the hand surgeon for many years and has resulted in a host of operative and some nonoperative measures designed to counteract this tendency.In spite of the excellent experimental work studies that have been done on tendon healing by such men as Mason & Allen (1941), Potenza (1964 and others, we seem to disbelieve, distrust or simply disregard the implications of their work. Tendon RepairIt has been shown conclusively that when tendon ends are apposed by suture the healing process takes place from without inwards. The tendon itself has a purely passive role. From the neighbouring tissues there is an ingrowth of fibroblast and capillary buds resulting in the laying down of delicate new collagen fibres. There is no evidence of tenoblastic activity in the stumps. The anatomical environment of a damaged tendon contributes significantly to the process of repair.There can be no justification for surrounding a tendon junction by a permeable or semipermeable membrane in order to prevent adhesions. Adhesions must occur for a while at any rate if the tendon is to heal.When healing has occurred and mobilization starts, in the normal course of events adhesions gradually disappear as the full range of movement develops. The range of movement of a tendon before adhesions have disappeared will, therefore, depend to a certain extent on its anatomical surroundings. Thus, repair at the level of the wrist or in the palm of the hand poses no great problems but the confines of the carpal tunnel and the digital sheath can and do impose restriction of movement. The tendon graft in the finger and the 'bridge graft' in the carpal tunnel were evolved to overcome this anatomical difficulty. Blood SupplyThe blood supply of a flexor tendon is extremely limited and there seems little doubt that part of a tendon's nourishment is derived from the synovial fluid that bathes it. The blood supply of a profundus tendon varies throughout its length. It is richest at the musculotendinous junction, at its insertion and where the vincula join it in the sheath. The level of section may therefore influence healing, depending on the relative vascularity of the stumps. An avascular stump encourages adhesions during attempted revascularization.Flexor pollicis longus has no vincular attachments throughout its length, so it must be as-I 67