Staged flexor tendon reconstruction

Staged flexor tendon reconstruction James M. Hunter, M.D.*

Attempts to reconstruct a scarred tendon system with a one-stage tendon graft have frequently resulted in failure, particularly in the complex flexor system. One of the most challenging aspects of reconstructive hand surgery is the restoration of good function of the damaged tendon motor system. Restitution of a stiff, scarred tendon complex to a gliding, pliable state can be accomplished by a carefully planned two-stage tendon graft program 1. 2 that uses a flexible silicone tendon implant at the first stage. Restoration of the damaged fibro-osseous canal by reconstruction of new pulleys around the gliding tendon implant results in improved gliding mechanics. A fluid nutrition system is induced that can nourish a gliding implant and subsequently allow second-stage free tendon grafting. 6 This discussion reviews the ongoing experience with flexor tendon reconstruction at our Hand Center. The technique and management advances that have resulted in improved results will be discussed.

Indications for tendon implant A tendon implant is indicated for finger flexor tendon reconstruction in the following situations: (1) as temporary segmental spacer in selected primary injuries where tendon repair is not possible; (2) in scarred tendon beds where a tendon graft can be predicted to adhere; and (3) for replacement of a profundus tendon through a scarred intact flexor superficialis tendon. 2 The two-stage procedure has also been utilized successfully for extensor tendon reconstruction and in the following: (1) reconstruction of fingers in a severely mutilated hand; (2) hands with congenitally deficient tendon systems;3 and (3) tendon transfer surgery where the tendon would have to traverse a suboptimal bed. The most recent indication for a two-stage procedure has been in replantation surgery. In multiple digital amputations the use of a tendon implant in the flexor system at the time of replantation may significantly simplify the postoperative rehabilitation. The implant can maintain the fibro-osseous canal and help regenerate a flexor tendon sheath in damaged areas while the fracture or fusion is healing and the neurovascular status becomes stabilized. The passive flexion and active extension rehabilitation program can simplify the postoperative management and improve the function of replanted digits. If the replantation is at the palmar or wrist level, it is reasonable to repair the flexor tendons and median and ulnar nerves primarily and place extensor tendon implants dorsally since the wrist is usually flexed to protect the neurovascular repairs. Again, the postoperative rehabilitation is simplified. Reprint requests: James M. Hunter, M.D., Hand Rehabilitation Center, 901 Walnut St., Philadelphia, PA 19107. *Professor, Orthopaedic Surgery and Chief, Section on Hand Surgery, Jefferson Medical College of Thomas Jefferson University, Philadelphia.

Acute infection is an absolute contraindication to this procedure. Appropriate surgical and antimicrobial treatment and subsequent wound healing will allow the procedure to be carried out at a later date. A digit that has borderline nutrition, bilateral digital nerve injuries, and severe joint stiffness may better be treated by amputation rather than reconstruction. This type of digit could possibly be salvaged; however, this should probably be undertaken only in the patient with very special requirements. Subsequent functional expectations, of course, are limited. Prior to tendon surgery, all patients should be placed on a hand therapy program designed to mobilize stiff joints and maximally improve the condition of the soft tissue. The timing of stage I tendon surgery should combine the judgments of the surgeon and hand therapist, for patient input and motivation are the keys to a successful result.

Care of silicone rubber implants Silicone rubber is highly electrostatic, and as a result it attracts airborne particles and surface contaminants. Once silicone implants are removed from the sterile package, they should be kept moist in a sterile solution of saline, Ringer's lactate, or triple antibiotic solution. Gloves and sponges coming into contact with the tendon implant should always be wet. They should preferably be handled with atraumatic instruments. Attention to these details will prevent the development of a foreign body synovitis that could interfere with the subsequent development of the neosheath.

Passive tendon implant4, 5 Several types of Hunter tendon implants have evolved from the experience gained in experimental and clinical trials during the past 22 years: At this time the implants are available as Swanson-Hunter flexible tendon spacers, Hunter passive tendon implants, and Hunter active tendon implants (Fig. 1, A to C). The spacer and passive gliding implants 4 • 5 imply that their distal ends are fixed securely to bone (Fig. 2, A and B) by plate and screw or to tendon by secure suture while the proximal end glides freely in the proximal palm or forearm. Movement of the implant is produced by active extension and passive flexion of the digit. A new sheath begins to form quickly around the implant during the period of gliding that follows stage 1. 6 The new sheath matures and produces a fluid system that supports gliding during stage I and nutrition and gliding for the tendon graft after stage II. In approximately 3 to 4 months after stage I, the tendon implant may be replaced with a tendon graft.

Anesthesia When a passive tendon implant is to be inserted, this is done under axillary block or general anesthesia. If patient participation is required to determine function, e.g., for THE JOURNAL OF HAND SURGERY

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Fig. 2. A, Fixation of tendon implant to the phalanx by means of plate-screw technique. B, Fixation of tendon implant to tendon stump by use of multiple-sutures technique.

Fig. 1. A, Swanson-Hunter flexible tendon spacer is a molded silicone rod that is unreinforced and radiopaque (Dow Coming Corp.). It is available in 6,5,4, and 3 mm diameters and may be cut to the approximate length. B, Hunter passive tendon implant available in 3, 4, 5, and 6 mm diameters. C, Hunter active tendon implant available in 4 mm diameter. (Both Hunter implants available through Holter Hausner International.) tenolysis or active tendon implant insertion, we prefer to use local anesthesia (I % lidocaine infiltration) and tourniquet control augmented by intravenous analgesia such as Innovar (droperidol and fentanyl) or titrated intravenous Demerol (meperidine) and Valium (diazepam). This will allow patient cooperation to assess function of the tenolysis or help establish the appropriate tension for an active tendon implant. Selected second-stage procedures have also been done in this manner. This allows appropriate tension of the graft to be determined. In order to perform these complicated procedures under local anesthesia, it is necessary to employ a qualified anesthesiologist and keep the patient sufficiently sedated to allow tolerance of the tourniquet. The patient should, however, be arousable when his compliance is required. Adequate premedication and a good rapport between the anesthesia personnel and the patient are mandatory. Patients have tolerated the tourniquet for consecutive periods of I hour in this manner. The tourniquet is deflated intermittently approximately every 30 minutes and function is tested. If the patient cannot tolerate this procedure, the anesthesiologist can provide general anesthesia. Stage 14,5 Surgery. In the finger and palm, a volar zigzag incision is preferred. This incision spares the deep vascular connections to the tendon bed and permits a complete exposure of the tendon bed. All the undamaged segments of the fibro-osseous pulley system and the transverse digital arteries are spared. The scarred tendons are carefully excised through transverse window incisions in the flexor canal between At and A z , the cruciates, and mid-A z pulley levels (Fig. 3,A). A generous segment of the distal profundus tendon, at least I cm, is preserved distally; and the joint capsule is left intact. It will

probably be necessary to sacrifice the A5 pulley to perform this adequately. If resection of scarred tendons and deep connective tissue fails to release the contracture, scarring of the joint capsule should be suspected and a capsulotomy may be necessary. In severe cases a compromise in ultimate function may become necessary, and a reasonable way to proceed is to create a "superficialis finger," i.e., the distal attachment of the implant is placed on the middle phalanx. Pulley reconstruction. The basic anatomy of the flexor pulley system (Fig. 3, A ) has a precise biomechanical design that permits lubricated gliding of two tendons while the power of the forearm musculature is transmitted to the bones of the fingers. Unless this arrangement can be restored at stage I surgery, the functional arc of motion for grip cannot be restored despite good hand therapy programs. Either a flexor digitorum superficialis or profundus tendon that is to be discarded provides excellent material for pulley building. Several techniques may be applied, depending on the location of injury and the surgeon's preference. I prefer to pass the graft extraperiosteally under the extensor tendon apparatus and to wrap it twice around the phalanx and suture it to itself or to the rim of the fibro-osseous canal (Fig. 3, Band C). This is performed over a sizer implant to prevent making the pulley too tight. The pulley should be made as wide as possible. The tendon implant is passed through the pulley system. As the finger is held flat on the table, the tendon implant is moistened and pulled gently back and forth to check its freedom of excursion. A malleable blunt tendon carrier is passed deep through the carpal tunnel to present in the forearm deep to the superficialis and superficial to the profundus tendons. The length of the implant is determined so that on full extension of the finger, the proximal end can be seen I to 2 inches proximal to the wrist crease. The implant may be terminated at the lumbrical muscle level in the palm provided there is no evidence of inflammation or scarring in the palm. The implant is then secured to the distal phalanx as previously described. Passive gliding of the implant is tested by moistening the implant bed with saline solution and holding the wrist and digit in neutral flexion while passively flexing and extending the finger. Motion should be free with a measured range of motion of between 3 and 4 em at the proximal end. Buckling of the implant may occur distal to a retained tight pulley,

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Fig. 3. A, Basic anatomy of the flexor pulley system. B, Reconstructing A2 pulley by passing superficialis tendon graft around the proximal phalanx beneath the extensor tendon. C, The second passage of the tendon graft replacing C1 pulley just proximal to the proximal interphalangeal joint.

this must be corrected by reconstructing the pulIey with a free graft before closure or a synovitis can develop between stages I and II and adversely affect the development of the neosheath. Testing the pulley system and recording the range of motion. These are the important last maneuvers of stage I before wound closure. The free proximal end of the implant is grasped and pulIed, bringing the finger from extension to maximum flexion. The folIowing are recorded: (1) the predicted active range of motion versus the passive range of motion; (2) the measured distance of the proximal end of the implant necessary to produce the active function (this wiII assist in the selection of a motor tendon in stage II); (3) the attitude of the finger in relation to the pulley system; if this maneuver does not produce fuII flexion or if a weak pulley ruptures, it may be necessary to modify the pulley system (Fig. 3, A to C); and (4) the security of attachment of the distal end of the tendon implant should be carefully checked. The wound closure and final dressing are carried out with splinting the wrist in 30° of flexion, the metacarpophalangeal joints in 60°/70° of flexion, and the interphalangeal joints in slight flexion. This position after stage I permits the proximal sheath to form in the long position. Postoperative care. During the first 3 weeks, the patient is kept in a dorsal extension block plaster splint. A 48- to 72hour course of antibiotic prophylaxis is initiated in the operating room prior to wound closure. X-ray films of the hand are taken during the first and sixth weeks postoperatively and just prior to stage II surgery to document the excursion of the tendon during passive motion and to ascertain the integrity of the distal juncture. The hand therapist and the surgeon confer with the patient during the first postoperative week. Gentle passive motion of alI joints is started gradualIy during the first week. If a flexion contracture was present preoperatively, or seems to develop, an extension splint is added to the metacarpophalangeal extension block splint. The extension slings are then placed in position between exercise sessions during the first week if

necessary. The protective dorsal splint is removed at 3 weeks, and programmed activity and passive flexion devices are initiated. Extension splinting for persistent flexion contractures wiII continue intermittently around the clock. 7 UsualIy by the sixth week there is a functional range of passive motion. During this time the hand should be examined regularly for evidence of synovitis in the new sheath. If this has not developed within the first 6 weeks, it is not likely to occur and the patient may resume normal activities, including going back to work, until he is ready for the second stage. If synovitis develops, the finger and wrist should be immobilized promptly. The most common cause of synovitis is overzealous therapy or distal loosening of the implant. The timing between stages I and II of surgery can vary depending on the condition of the hand. The sheath system theoreticalIy could carry a tendon graft after 4 weeks, but the primary objective is a soft hand with maximal joint movements. Therefore most often stage II surgery is best planned after a 3- to 4-month interval. The results of our research program indicate that the welI-balanced, compatible stage I implant could remain in place indefinitely without compromising the result of stage II tendon grafting.6 This is an important fact to remember as clinical research progresses toward a total tendon replacement. Complications. Complications are rare if the procedure has been performed meticulously, wi~h careful handling of the soft tissues and the implant. Proper postoperative therapy and careful monitoring of the patient's progress also help alIeviate any complications. The complications are synovitis, infection, and loosening of the distal juncture with proximal migration of the implant. 4. 5 Overzealous therapy can cause synovitis. However, this should resolve fter 5 to 7 days of immobilization folIowed by gradual resumption of activity. If the implant becomes dislodged after stage I, the hand should be put at rest and the second-stage tendon graft can stilI be carried out. Infection is very rare and will usually manifest itself in the early postoperative period. Removal of the implant. immobilization, ade-

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Fig. 4. Goal for the future. A, A 52-year-old man with complete scarring of the flexor tendon system of the middle finger after seven procedures done elsewhere after traumatic injury. Five pulley reconstructions around a 4 mm active tendon. B, At 8 months postoperatively, active tendon excursion is 5.5 cm. C-D, Patient 6 months after tendon graft replacement or 14 months after stage I surgery. Patient had returned to full work prior to stage II.

quate irrigation and debridement, and appropriate antibiotic therapy will resolve the problem. After the soft tissues have healed and the infection is resolved, there is no contraindication to perfonning the stage I procedure again. Stage 11 4,5 Surgery. Incisions are made distally and proximally over the previous incisions to identify the tendon sheath and implant. Proximally, the implant is grasped with an instrument (rubber-shod forceps), and the sheath at the site of juncture is carefully examined. The active potential range of motion is recorded, starting with the hand and finger flat on the table. A motor tendon, flexor digitorum superficialis or flexor digitorum prufundus, is selected and identified. A short tendon graft, e.g., palmaris longus, is used for reconstruction of a thumb, fifth finger, or "superficialis finger" and for certain palmar problems. More often the plantaris tendon is preferred, as it is a longer tendon. If the plantaris tendon is absent, a long toe extensor tendon can be used. A Brand tendon stripper is utilized to harvest the grafts. B• 9 The tendon graft, carefully stripped of all peritenon, is sutured to the proximal end of the implant and pulled through the new tendon bed. The implant is detached from the distal phalanx and discarded. A Bunnell-type weaving suture is placed through the distal end of the graft by use of a monofilament stainless steel 4.0 or 5.0 wire;10 the tendon suture is then carried through the bone of the phalanx and reinforced on a button stabilized on the fingernail by petroleum jelly gauze. A pullout wire is no longer utilized. The final phase of stage II surgery is directed toward completing the proximal tendon attachment. The motor unit is selected and the tendon graft is placed through this unit temporarily and sutured with either wire or Mersilene. The attitude of the finger with the wrist in neutral position should be one of slightly more flexion than in the adjacent digit. At this point, the patient's compliance, if he is under leptoanalge-

sia, II alleviates the guesswork in setting the tension of the graft. The patient is asked to flex and extend his fingers, and tension of the graft is then adjusted accordingly. The seleced tendon motor must supply the same or better excursion if a good result is to be achieved. When the correct tension is detennined, the graft is woven through the motor tendon and sutured into place by means of the technique described by Pulvertaft.12 After repeated manipulations, the finger should remain in slightly more flexion than nonna!. The juncture is completed by a second interweave and suture fixation, and the wound is closed. The postoperative plaster splint dressing fits securely with the wrist in 30° of flexion, metacarpophalangeal joints in 70° of flexion, and interphalangeal joints extended. Postoperative care. Therapy after stage II begins in the operating room. The splint should not block full extension of the proximal interphalangeal joints, and it should be secured at the wrist with tape to prevent any slipping, which could result in undue tension on the graft junctures. A light elastic band may be applied on the first day or within the first postoperative week to assist light flexion of the finger without impairing active extension of the finger. Particular attention should be paid to contracture control of the distal and proximal interphalangeal joints. 7 Salvage fingers may have poor extensor tendon function because of tendon attenuation or adhesions. These fingers are especially prone to recurrent contracture. At 5 to 6 weeks, the pull-out button is removed, if used, and by 6 to 8 weeks, the extension block splint is also discarded. Hydrotherapy and gentle active and passive flexion of the wrist and the finger joints are begun. By 8 weeks light, resistive exercises are started. Heavy resistive exercises are not done until 12 weeks postoperatively. Adhesions have been minimized by early tendon gliding after stage II. Those patients who move exceptionally well (70% of the final goal) during the first 3 weeks are protected for longer than 6

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weeks to minimize rupture. Results have steadily improved over the past decade so that 90% of the passive range of motion recorded at stage II should be achieved in the final result.

stage, and the fibrous sheath around the motor tendon unit is kept intact and the tendon graft is slipped through the area occupied by the Dacron loop. The tension is set and the graft is sutured.

The future-Active tendon prosthesis (total tendon replacement)

Conclusions

Two-stage tendon grafting utilizing the passive tendon implant has proved to be a consistently reliable method of salvaging scarred tendon systems. The total active tendon offers the opportunity of "tuning" the tendon muscle interface unit while the neosheath is forming. All implants at this time still require a two-stage surgical procedure. Future research will hopefully yield a permanent tendon prosthesis, which would eliminate the need for any subsequent operative procedure. The active gliding concept in its early stage (1960) centered around the design of an artificial tendon or prosthesis. I However, owing to terminal juncture separation under stress, the method was converted to a passive gliding principle until more advanced research could produce a proximal and distal fixation that was reliable for an extended period. Further research involved the study of juncture strength at the level of a distal juncture made of a titanium plug implanted into a drill hole in the distal phalanx. Within 4 weeks, woven bone ingrowth into the titanium plug occurs, resulting in a strong and durable interface. The proximal juncture is bonded to the muscle by interposing cortical bone grafts between the porous titanium and the muscle. The bone grows into the titanium and the muscle heals to bone. This graded interface tendon prosthesis has been successfully implanted into adult chimpanzees. Currently, active implants are in the clinical investigational stage and results are encouraging. The implants have a special braided or woven Dacron core, which is molded into a radiopaque silicone rubber. The surface finish is smooth and the cross-sectional design to ovoid to aid optimal tendon sheath development. The estimated tensile strength of a tendon replacement is more than 100 pounds. The implant terminates proximally in a loop through which the proximal tendon motor is woven, or terminates in an open braid through which the tendon is interwoven. The active implants also have two types of distal juncture: the previously described screw-plate juncture or a Dacron braid that can be placed through drill holes in the bone or woven into tendon and bone. If a soft loop is available the tendon stump is woven through the loop and back through itself and then sutured. The benefits of the active tendon implant have been the ability to select a motor prior to stage II surgery and to have this muscle "tuned," in that it is actively moving the finger. It also serves to test the pulleys that were reconstructed during the first stage. In most instances patients can return to work for extended periods of full functional activity (Fig. 4, A to D). Future replacement of the implant is carried out in accordance with the judgment of the surgeon. The proximal motor juncture is easily identified in the second

The two-stage tendon graft technique utilizing the flexible spacer and tendon implant has clinically proved to be a reliable technique of salvaging damaged tendon systems. The production of a reinforced neosheath will provide the nutrition system for nourishment of a tendon graft months or years later. This biologic system, combined with early protected gliding of tendon graft, has resulted in minimal postoperative adhesions. The control of contractures and the reconstruction of pulleys of the proper size, number, and location, combined with a supervised therapy program, are keys to' maximal postoperative digital motion (Fig. 4, A toD). The author thanks Evelyn J. Mackin, L.P.T., for her assistance in the preparation of this manuscript.

REFERENCES 1. Hunter 1M: Artificial tendons. Early development and application. Am 1 Surg 109:325-38, 1965 2. Hunter 1M, Salisbury RE: Use of gliding artificial implants to produce tendon sheaths. Techniques and results in children. Plast Reconstr Surg 45:564, 1970 3. Tubiana R: Greffes des tendons flechisseurs des doigts et du pouce. Technique et resultats. Rev Chir Orthop 46:191-214, 1960 4. Hunter 1M, Aulicino PL: Salvage of the scarred tendon systems utilizing the Hunter tendon implant. In Flynn JE, editor: Hand surgery, ed 3. Baltimore/London, 1981, The Williams & Wilkins Co 5. Hunter 1M: Staged flexor tendon reconstruction. In Hunter 1M, Schneider LH, Mackin EJ, Bell lA, editors: Rehabilitation of the hand, ed 2. St. Louis, 1983, The CV Mosby Co 6. Hunter 1M, laeger S, Matsui T, Miyaji N: The pseudosynovial sheath-Its characteristics in a primate model. 1 HAND SURG 8:461,1983 7. Mackin EM: Postoperative therapy following staged flexor reconstruction.ln Hunter 1M, Schneider LH, Mackin El, Bell lA, editors: Rehabilitation of the hand, ed 2. St. Louis, 1983, The CV Mosby Co 8. Brand P: Principles of free tendon grafting, including a new method of tendon suture. J Bone 10int Surg [Br] 41:208,1959 9. White WL: Secondary restoration of finger flexion by digital tendon grafts. An evaluation of seventy-six cases. Am J Surg 91: 662-8, 1956 10. Boyes IH: Bunnell's surgery of the hand, ed 4. Philadelphia, 1964, IB Lippincott Co II. Hunter 1M, Schneider LH, Dumont 1, Erickson lC III: A dynamic approach to problems of hand function: Using local anesthesia supplemented by intravenous fentanyl-droperidol. Clin Orthop 104:112-5, 1974 12. Pulvertaft RG: Tendon grafts for flexor tendon injuries in the fingers and thumb. A study of technique and results. J Bone 10int Surg [Br] 38:175-94, 1956