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The repair reaction of flexor tendon within the digital sheath
The Repair Reaction of Flexor Tendon within the Digital Sheath-Phillip Matthews and Harold Richards
T H E R E P A I R R E A C T I O N OF F L E X O R T E N D O N WITHIN THE DIGITAL SHEATH
PHILLIP MATTHEWS and HAROLD RICHARDS, Cardiff Failure to achieve acceptable functional results following the direct repair of divided digital flexor tendons is due mainly to the adhesions which tend to form between the site of anastomosis and the surrounding tissues. These adhesions prevent free movement of the tendon and the range of active movement possible becomes very limited. Adhesion formation is widely believed to be an essential part of the repair process of injured tendon. Experimental studies (Skoog and Persson, 1954; Potenza, 1962; Harper, Lowery and Wray, 1970) have suggested that tendon is a tissue which lacks any properties of regeneration and its repair is thus dependent on the ingrowth of fibroblastic tissue from outside. Various reasons have been given to account for the poor healing of tendon. Bier (1920) thought that it was due to some hormonal substance present in the synovial fluid and Maibach hinted that this might be hyaluronidase. Another possibility suggested is that the tenocytes of mature tendon are too highly differentiated to take part in repair processes (Potenza, 1962) and are incapable of synthesising .fibrous protein (Weiner and Peacock, 1971). The concept that tendon is passive in the matter of its own healing is of more than theoretical interest and has a clear relevance to the clinical problem. If the theory is correct, then it follows that for restoration of continuity to a divided tendon adhesions are indispensible and that any techniques aimed at their avoidance are doomed to failure. We have found some difficulty in accepting the proposition that tendon, which is a living, vascularised tissue should be totally lacking in healing capacities. The possibility appeared to exist that in previous studies failure to demonstrate any such activity might have been due to adverse experimental factors. To test this hypothesis an investigation has recently been carried out to study the pattern of healing of traumatised tendons under ideal conditions (Matthews and Richards). EXPERIMENTAL WORK
The digital flexor tendons of the rabbit forepaw were selected for study. The experimental model was so designed that repair of a traumatised tendon could take place free from the influence of tendon suture and immobilisation and within a synovial sheath which was essentially normal. These requirements were met in the following way. In order to preserve the integrity of the sheath as far as possible, the profundus tendon was exposed not through the digit but by a more proximal approach in the palm and by opening up the synovial reflexion. By traction on the tendon and full flexion of the digit it was then possible to draw a considerable length of the intra-synovial portion of the tendon into the wound (Fig. 1). When the traction was released the tendon slid back to lie well within an u~adisturbed portion of the sheath. The tendon was cut transversely with a sharp scalpel, but the cut stopped just short of complete section. In this way the necessity for both sutures and immobilisation was avoided. After skin closure, the limbs were not splinted. The Hand--Vol. 7
No. 1
1975
27
The Repair Reaction of Flexor Tendon within the Digital S h e a t h - Phillip Matthews and Harold Riehards
Fig. 1. Experimental Technique: The profundus tendon has been exposed proximally in the palm. Having opened the synovial reflexion at the base of the sheath, a considerable length of the intra-synovial part of the tendon can be drawn into the wound. The tendon is about to be traumatised by cutting across it transversely with a scalpel. Fig. 2. Zone of tendon injury at three weeks. Partial retraction of the severed fibres has occurred and the resulting defect is beginning to fill in with repair tissue.
The rabbits were killed at intervals and the operated area examined. In all the tendons studied, healing occurred without adhesions and the tendon itself appeared to be the sole agent in bringing about reconstitution of the defect. Coincident with an initial period of retraction of the divided fibres, a process of repair was set in train. This was effected firstly by the transformation of resting tenocytes into an active tenoblast form, and then by the proliferation of these cells and the production of new collagen. The defect was gradually filled in by a glistening, gelatinous repair tissue (Figs. 2, 3) which slowly matured so that by the tenth week the area of injury was indistinguishable f r o m normal by gross examination. On microscopic examination the defect had been replaced by new tendon fibres and the appearance suggested that tensile strength had been restored. At no stage in the repair was there any indication that the reparative tissue had originated from the synovial sheath and adhesions were never seen.
CONCLUSION These findings indicate that, contrary to the currently accepted view, tendon as a tissue does possess a potential for repair and remodelling and is able to heal defects without the ingrowth of adhesions. Healing in these experiments took place under ideal conditions and in the absence of sutures, splintage, or significant damage to the synovial sheath. These factors were not absent in previous experimental work and are not avoided in clinical methods of tendon repair, yet insufficient attention seems to have been paid to their influence on the healing process. It seems very likely that it is factors such as these which are responsible for the inactivity of tendon cells and for adhesion formation rather than some inherent fault in the tendon tissue. The goal but this study It is unlikely, the effects on 28
of restoring full function to divided flexor tendons is still far away provides some theoretical evidence that it m a y at least be possible. however, that this ideal will be achieved until we fully understand tendon, not only of injury, but of our methods of treatment. The H a n d - - V o l . 7
No. 1
1975
The Repair Reaction of Flexor Tendon within the Digital S h e a t h - Phillip Matthews and Harold Richards
Fig. 3. Longitudinal section through the traumatised area of tendon at four weeks, showing the ends of the severed tendon fibres (1) and the highly cellular, immature repair tissue (2). There are no adhesions to the synovial sheath. Haemotoxylin and eosin x 65. ACKNOWLEDGEMENTS
T h e a u t h o r s are g r a t e f u l to Mrs. H e a t h e r Ralis for h e r help with the histological p r e p a r a t i o n s , Mr. P e t e r Blake a n d Mr. Peter L a n g h a m for the p h o t o g r a p h s a n d to Mrs. I r e n e Jones for secretarial assistance. REFERENCES
BIER, A. (1920) Verhandlungen der Deutschen GeseUschaft far Chirurgie. 44 Kongr. HARPER, G. E., LOWERY, S., WRAY, J. B. (1970) Histochemical Studies of Tendon Healing, Surgical Forum, 21: 460-462. MAIBACH, E. Cited by Winckler, G., Anatomie Normale Des Tendons F16chisseurs et Extenseurs de la Main. Prepared for Edition of the Monographies du Groupe d'Etude de la Main. Paris 1970. MATTHEWS, P., RICHARDS, H. The Repair Potential of Digital Flexor Tendon. Journal of Bone and Joint Surgery. British Volume (in Press). POTENZA, A. D. (1962) Tendon Healing Within the Flexor Digital Sheath in the Dog. Journal of Bone and Joint Surgery 44A: 49-64. SKOOG, T. and PERSSON, B. H. (1954) An Experimental Study Of The Early Healing Of Tendons. Plastic and Reconstructive Surgery, 13: 384-399. WEINER, L. J., PEACOCK, E. E. Jr. (1971) Biologic Principles affecting Repair of Flexor Tendons. Advances in Surgery, 5: 145-188.
The H a n d - - V o l . 7
No. 1
1975
29
T H E R E P A I R R E A C T I O N OF F L E X O R T E N D O N WITHIN THE DIGITAL SHEATH
PHILLIP MATTHEWS and HAROLD RICHARDS, Cardiff Failure to achieve acceptable functional results following the direct repair of divided digital flexor tendons is due mainly to the adhesions which tend to form between the site of anastomosis and the surrounding tissues. These adhesions prevent free movement of the tendon and the range of active movement possible becomes very limited. Adhesion formation is widely believed to be an essential part of the repair process of injured tendon. Experimental studies (Skoog and Persson, 1954; Potenza, 1962; Harper, Lowery and Wray, 1970) have suggested that tendon is a tissue which lacks any properties of regeneration and its repair is thus dependent on the ingrowth of fibroblastic tissue from outside. Various reasons have been given to account for the poor healing of tendon. Bier (1920) thought that it was due to some hormonal substance present in the synovial fluid and Maibach hinted that this might be hyaluronidase. Another possibility suggested is that the tenocytes of mature tendon are too highly differentiated to take part in repair processes (Potenza, 1962) and are incapable of synthesising .fibrous protein (Weiner and Peacock, 1971). The concept that tendon is passive in the matter of its own healing is of more than theoretical interest and has a clear relevance to the clinical problem. If the theory is correct, then it follows that for restoration of continuity to a divided tendon adhesions are indispensible and that any techniques aimed at their avoidance are doomed to failure. We have found some difficulty in accepting the proposition that tendon, which is a living, vascularised tissue should be totally lacking in healing capacities. The possibility appeared to exist that in previous studies failure to demonstrate any such activity might have been due to adverse experimental factors. To test this hypothesis an investigation has recently been carried out to study the pattern of healing of traumatised tendons under ideal conditions (Matthews and Richards). EXPERIMENTAL WORK
The digital flexor tendons of the rabbit forepaw were selected for study. The experimental model was so designed that repair of a traumatised tendon could take place free from the influence of tendon suture and immobilisation and within a synovial sheath which was essentially normal. These requirements were met in the following way. In order to preserve the integrity of the sheath as far as possible, the profundus tendon was exposed not through the digit but by a more proximal approach in the palm and by opening up the synovial reflexion. By traction on the tendon and full flexion of the digit it was then possible to draw a considerable length of the intra-synovial portion of the tendon into the wound (Fig. 1). When the traction was released the tendon slid back to lie well within an u~adisturbed portion of the sheath. The tendon was cut transversely with a sharp scalpel, but the cut stopped just short of complete section. In this way the necessity for both sutures and immobilisation was avoided. After skin closure, the limbs were not splinted. The Hand--Vol. 7
No. 1
1975
27
The Repair Reaction of Flexor Tendon within the Digital S h e a t h - Phillip Matthews and Harold Riehards
Fig. 1. Experimental Technique: The profundus tendon has been exposed proximally in the palm. Having opened the synovial reflexion at the base of the sheath, a considerable length of the intra-synovial part of the tendon can be drawn into the wound. The tendon is about to be traumatised by cutting across it transversely with a scalpel. Fig. 2. Zone of tendon injury at three weeks. Partial retraction of the severed fibres has occurred and the resulting defect is beginning to fill in with repair tissue.
The rabbits were killed at intervals and the operated area examined. In all the tendons studied, healing occurred without adhesions and the tendon itself appeared to be the sole agent in bringing about reconstitution of the defect. Coincident with an initial period of retraction of the divided fibres, a process of repair was set in train. This was effected firstly by the transformation of resting tenocytes into an active tenoblast form, and then by the proliferation of these cells and the production of new collagen. The defect was gradually filled in by a glistening, gelatinous repair tissue (Figs. 2, 3) which slowly matured so that by the tenth week the area of injury was indistinguishable f r o m normal by gross examination. On microscopic examination the defect had been replaced by new tendon fibres and the appearance suggested that tensile strength had been restored. At no stage in the repair was there any indication that the reparative tissue had originated from the synovial sheath and adhesions were never seen.
CONCLUSION These findings indicate that, contrary to the currently accepted view, tendon as a tissue does possess a potential for repair and remodelling and is able to heal defects without the ingrowth of adhesions. Healing in these experiments took place under ideal conditions and in the absence of sutures, splintage, or significant damage to the synovial sheath. These factors were not absent in previous experimental work and are not avoided in clinical methods of tendon repair, yet insufficient attention seems to have been paid to their influence on the healing process. It seems very likely that it is factors such as these which are responsible for the inactivity of tendon cells and for adhesion formation rather than some inherent fault in the tendon tissue. The goal but this study It is unlikely, the effects on 28
of restoring full function to divided flexor tendons is still far away provides some theoretical evidence that it m a y at least be possible. however, that this ideal will be achieved until we fully understand tendon, not only of injury, but of our methods of treatment. The H a n d - - V o l . 7
No. 1
1975
The Repair Reaction of Flexor Tendon within the Digital S h e a t h - Phillip Matthews and Harold Richards
Fig. 3. Longitudinal section through the traumatised area of tendon at four weeks, showing the ends of the severed tendon fibres (1) and the highly cellular, immature repair tissue (2). There are no adhesions to the synovial sheath. Haemotoxylin and eosin x 65. ACKNOWLEDGEMENTS
T h e a u t h o r s are g r a t e f u l to Mrs. H e a t h e r Ralis for h e r help with the histological p r e p a r a t i o n s , Mr. P e t e r Blake a n d Mr. Peter L a n g h a m for the p h o t o g r a p h s a n d to Mrs. I r e n e Jones for secretarial assistance. REFERENCES
BIER, A. (1920) Verhandlungen der Deutschen GeseUschaft far Chirurgie. 44 Kongr. HARPER, G. E., LOWERY, S., WRAY, J. B. (1970) Histochemical Studies of Tendon Healing, Surgical Forum, 21: 460-462. MAIBACH, E. Cited by Winckler, G., Anatomie Normale Des Tendons F16chisseurs et Extenseurs de la Main. Prepared for Edition of the Monographies du Groupe d'Etude de la Main. Paris 1970. MATTHEWS, P., RICHARDS, H. The Repair Potential of Digital Flexor Tendon. Journal of Bone and Joint Surgery. British Volume (in Press). POTENZA, A. D. (1962) Tendon Healing Within the Flexor Digital Sheath in the Dog. Journal of Bone and Joint Surgery 44A: 49-64. SKOOG, T. and PERSSON, B. H. (1954) An Experimental Study Of The Early Healing Of Tendons. Plastic and Reconstructive Surgery, 13: 384-399. WEINER, L. J., PEACOCK, E. E. Jr. (1971) Biologic Principles affecting Repair of Flexor Tendons. Advances in Surgery, 5: 145-188.
The H a n d - - V o l . 7
No. 1
1975
29