Orthopedics

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Feature Article 

Two-stage Flexor Tendon Reconstruction in Zone II Using Hunter's Technique

Siguo Sun, PhD; Yong Ding, PhD; Baoan Ma, PhD; Yong Zhou, PhD

Abstract

Tendon injuries in the digital flexor sheath area (zone II) are the most difficult to treat and remain a focus of both clinical attention and basic investigations. Although some new techniques have been developed, the clinical results are still not satisfying, especially in old injuries. This retrospective study was designed to investigate the results of delayed zone II flexor tendon repair using Hunter rods.

Between July 1974 and June 1998, 81 patients at our institution underwent 2-stage reconstruction using Hunter’s technique. Sixty-one patients with 106 fingers were included in this study. Digital flexor tendon resection and Hunter rod implantation were performed in the first-stage operation. Combined digital nerve injuries and damaged pulleys were repaired or reconstructed at the same time. Plaster was used to immobilize the hand for 3 weeks. During the second-stage operation, performed 2 to 6 months later, palmaris longus or plantaris were grafted into the pseudosheath formed surrounding the Hunter rods. The proximal end of the transplanted tendon was fixated with flexor digitorum profundus tendon using the Pulvertaft method, and the distal end was fixated to the distal phalanx using Bunnell’s pullout wire method. Early controlled motion was performed in all cases. Evaluation based on total active motion was good to excellent in 84%, fair in 12%, and poor in 4% of patients.

Flexor tendon reconstruction using Hunter technique is an effective way to restore digital function in delayed zone II flexor tendon injuries.

Despite advances in knowledge and refinements in technique, reconstruction of the flexor tendon system in zone II remains a challenge for the hand surgeon because the healing tendon tends to adhere to its fibro-osseous tunnel. It was termed “no man’s land” by Bunnell1 because of the poor outcome in range of motion (ROM) following this tendon repair. The outcome is worse in old injuries, which often need tendon graft to restore flexion function of digits.

Primary or delayed primary repair of flexor tendon injuries, with changes in technique, rehabilitation, and technology, has moved to the forefront of treatment options. Secondary reconstruction, however, long the mainstay of treatment for these injuries, remains an important technique in the care of certain injuries. Several techniques have been developed to improve the functional result of flexor tendon repair in zone II. Two-stage flexor tendon reconstruction using a silicone rod in the first stage and a free tendon graft through the pseudosheath formed around the silicone in the second stage, as described in 1971 by Hunter and Salisbury,2 is the most widely accepted treatment for poor prognosis patients (Boyes grade 2-5).3-11 Several studies of this 2-stage reconstruction method have been reported during the past 30 years, and the results in these reports vary.2-11 To advocate wider use of this technique, clear evidence is essential. This article presents our results of 2-stage zone II flexor tendon reconstruction using Hunter rods.

Between July 1974 and June 1998, 81 patients with old laceration of the flexor tendon in the “no man’s land” of the hand underwent 2-stage reconstruction using Hunter’s technique in our institution. Records of 69 patients (55 men, 14 women; average age, 29 years [range, 17-52 years]) with 106 digits (11 thumbs, 26 index fingers, 29 long fingers, 21 ring fingers, and 19 little fingers) followed for at least 12 months were reviewed. Only patients with complete lacerations in zone II of the flexor digitorum profundus and flexor digitorum superficialis (long fingers) and the flexor pollicis longus (thumb) were included in this study. Patients with associated phalangeal fractures, soft tissue defects, extensor tendon lesions, or signs of infection, and those who were followed for <12 months, were excluded from…

Abstract

Tendon injuries in the digital flexor sheath area (zone II) are the most difficult to treat and remain a focus of both clinical attention and basic investigations. Although some new techniques have been developed, the clinical results are still not satisfying, especially in old injuries. This retrospective study was designed to investigate the results of delayed zone II flexor tendon repair using Hunter rods.

Between July 1974 and June 1998, 81 patients at our institution underwent 2-stage reconstruction using Hunter’s technique. Sixty-one patients with 106 fingers were included in this study. Digital flexor tendon resection and Hunter rod implantation were performed in the first-stage operation. Combined digital nerve injuries and damaged pulleys were repaired or reconstructed at the same time. Plaster was used to immobilize the hand for 3 weeks. During the second-stage operation, performed 2 to 6 months later, palmaris longus or plantaris were grafted into the pseudosheath formed surrounding the Hunter rods. The proximal end of the transplanted tendon was fixated with flexor digitorum profundus tendon using the Pulvertaft method, and the distal end was fixated to the distal phalanx using Bunnell’s pullout wire method. Early controlled motion was performed in all cases. Evaluation based on total active motion was good to excellent in 84%, fair in 12%, and poor in 4% of patients.

Flexor tendon reconstruction using Hunter technique is an effective way to restore digital function in delayed zone II flexor tendon injuries.

Despite advances in knowledge and refinements in technique, reconstruction of the flexor tendon system in zone II remains a challenge for the hand surgeon because the healing tendon tends to adhere to its fibro-osseous tunnel. It was termed “no man’s land” by Bunnell1 because of the poor outcome in range of motion (ROM) following this tendon repair. The outcome is worse in old injuries, which often need tendon graft to restore flexion function of digits.

Primary or delayed primary repair of flexor tendon injuries, with changes in technique, rehabilitation, and technology, has moved to the forefront of treatment options. Secondary reconstruction, however, long the mainstay of treatment for these injuries, remains an important technique in the care of certain injuries. Several techniques have been developed to improve the functional result of flexor tendon repair in zone II. Two-stage flexor tendon reconstruction using a silicone rod in the first stage and a free tendon graft through the pseudosheath formed around the silicone in the second stage, as described in 1971 by Hunter and Salisbury,2 is the most widely accepted treatment for poor prognosis patients (Boyes grade 2-5).3-11 Several studies of this 2-stage reconstruction method have been reported during the past 30 years, and the results in these reports vary.2-11 To advocate wider use of this technique, clear evidence is essential. This article presents our results of 2-stage zone II flexor tendon reconstruction using Hunter rods.

Materials and Methods

Between July 1974 and June 1998, 81 patients with old laceration of the flexor tendon in the “no man’s land” of the hand underwent 2-stage reconstruction using Hunter’s technique in our institution. Records of 69 patients (55 men, 14 women; average age, 29 years [range, 17-52 years]) with 106 digits (11 thumbs, 26 index fingers, 29 long fingers, 21 ring fingers, and 19 little fingers) followed for at least 12 months were reviewed. Only patients with complete lacerations in zone II of the flexor digitorum profundus and flexor digitorum superficialis (long fingers) and the flexor pollicis longus (thumb) were included in this study. Patients with associated phalangeal fractures, soft tissue defects, extensor tendon lesions, or signs of infection, and those who were followed for <12 months, were excluded from this study. The injury mechanism included knife cut in 5 cases, glass cut in 14, and contusion in 50. Average time from injury to first-stage operation was 6.9 months (range, 1-24 months). All patients followed the same surgical and postoperative procedure.

Surgical Technique

The surgical technique includes 2 stages. All surgeries were performed under axillary block and tourniquet control. It is important that an aggressive physiotherapy program precedes the first stage to overcome stiffness and achieve maximum passive motion both in flexion and in extension.

Stage I

Palmar zigzag incisions, described by Bruner,12 were made. This approach provided wide exposure of the flexor tendon from the midpalm to the digital tip. Attempting to work through small incisions with limited exposure almost always necessitates blind dissection, which may endanger neurovascular structures and increase postoperative adhesion formation. The injured tendons and scar tissues were removed. During dissection, care must be taken to preserve as much of the annular portions of the flexor sheath as possible.

A 1.0-cm distal flexor digitorum profundus stump was preserved, and the proximal stumps of flexor digitorum profundus and flexor digitorum superficialis were sutured to the subcutaneous tissue between zone III and zone V. Hunter rods of proper size were inserted into the rudimental sheaths. The injured pulleys (A2 and A4) were reconstructed over the implant with excised tendons. The distal end of the implant was sutured to the distal stump of flexor digitorum profundus, and the proximal end of the implant was fixed to the proximal stumps of flexor digitorum profundus and flexor digitorum superficialis in the palm or forearm. It is important to keep the proximal end of the Hunter rods and the proximal stumps of the flexor digitorum profundus and flexor digitorum superficialis overlapped with each other for approximately 2 cm, which promises enough length of the pseudosheath to be formed. Digital nerve repair, scar tissue resection, and soft tissue release were also performed during the first-stage operation as necessary.

A dorsal splint with the wrist in 30° flexion, the metacarpophalangeal joint in 70° flexion, and the interphalangeal joints in a slightly flexed position was applied. Passive motion was started 3 weeks postoperatively. The goal was to achieve full passive flexion after the first stage and to preserve it until the second stage was performed.

Stage II

Stage II was performed after 2 to 6 months. A lateral incision at the distal phalanx was used to retrieve the distal stump of the flexor digitorum profundus and the distal end of the silicone rod, and the connecting sutures were divided. A minimal incision at midpalm or the wrist was made to retrieve the proximal junction of the implant and flexor digitorum profundus, which because of its volume was usually identified easily. Any excess pseudosheath was resected to assure free gliding of the proximal graft juncture. Palmaris longus tendon or plantaris tendon of proper length was procured through a minimal incision. The proximal end of tendon graft was sutured temporarily to the distal end of the silicone rod and pulled proximally through the matured pseudosheath. Great care was taken not to open the pseudosheath proximal to the distal interphalangeal joint or to injure any of the middle phalangeal pulleys.

After the appropriate motor tendon was selected and the proximal end of the implant was tagged, the distal juncture of the graft tendon with the stump of the flexor digitorum profundus was secured with Bunnell pullout wire sutures. The proximal suture was made with Pulvertaft weave suture, which made the adjustment of tension easy. The tension was adjusted so that the finger was rested in a position slightly flexed than under normal circumstances. This was best achieved by placing the wrist in neutral and observing the posture of adjacent digits. In general, the posture of the grafted digit should be approximately the same as the adjacent ulnar digit, and in the fifth finger, a position of flexion somewhat greater than that of the fifth finger on the opposite hand would be appropriate. At the conclusion of the proximal tendon juncture, the digit was checked to ensure that it could be extended passively with the wrist in neutral.

Postoperative Care

In the immediate postoperative period, patients were put in clam digger splints, but with the wrist in 20° of flexion, the metacarpophalangeal joints in 60° of flexion, and both interphalangeal joints in full extension. After 24 hours, patients were put in a Kleinert rubber band splint for exercises. No active flexion was permitted during the first 3 weeks. During sleep hours, patients had their fingers immobilized with the distal interphalangeal and proximal interphalangeal joints in full extension to prevent flexion contractures. Three weeks postoperatively, active flexion was started without resistance. Five weeks postoperatively, the splint was removed, and active flexion with resistance was started. The pullout wire was removed 6 weeks postoperatively.

Results

Follow-up ranged from 12 to 38 months (±19 months). The results were measured 12 months after the stage II surgery. No patient with <12 months of follow-up was included in the study. Assessment of our cases was made based on the total active motion system of evaluation.13 The total active motion is calculated by using the extension and flexion for both joints, and is similar to the ROM of the joint, but is for the total active motion observed for the finger as a whole. The calculation formula for the percentage total active motion is shown in the Figure.

Figure: Calculation formula for the percentage total active motion
Figure: Calculation formula for the percentage total active motion. Abbreviations: DIP, distal interphalangeal joint; PIP, proximal interphalangeal joint.

The 175° is the estimate of normal proximal interphalangeal and distal interphalangeal motion. The calculated value is converted into grades of excellent (85%-100%), good (70%-84%), fair (50%-69%), and poor (0%-49%). Of the 106 digits, 61 were excellent, 28 good, 13 fair, and 4 poor. Overall good and excellent grades were achieved in 84% of the digits.

Deep infection was observed in 2 patients (3 digits) in stage I. In both patients, Staphylococcus aureus was cultured. In 1 patient with 1 digit, the silicone rod was removed, and intravenous antibiotic administration and closed irrigation drainage of the pseudosheath were applied. Severe adhesion was formed after stage II in this patient. In the other patient, the infection responded well to conservative treatment, and medium adhesion was formed after stage II. Silicone rod exodus was observed in 1 patient (1 digit), and severe adhesion formation was observed after stage II. In 1 patient (2 digits) the distal attachment of the graft ruptured, and medium adhesion was formed after repair of the rupture. No skin necrosis, rod buckling, silicone synovitis, or proximal tenorrhaphy ruptures (complications that have been reported with the Hunter method2-11) were encountered in this series.

Discussion

Acute flexor tendon injuries should be repaired primarily with an atraumatic technique, which in combination with a postoperative controlled motion rehabilitation protocol can usually prevent adhesion formation and provide good results. However, old flexor tendon injuries, especially in zone II, are usually associated with complications such as tendon retraction in both proximal and distal ends, adhesion formation, and secondary abnormities of digits. Therefore, tendon grafting is usually needed to restore the flexion function of digits.

Although disagreement exists as to which donor tendons should be chosen for free flexor tendon grafting, the palmaris longus and plantaris tendon, when available, likely has the most advocates. Although good results have been obtained by grafting, many patients need tenolysis due to improve tendon moment. Tenolysis is a technically demanding surgical procedure. When performed properly, tenolysis is a worthwhile effort at restoring digital function,14-16 but the clinical efficiency of this procedure is questionable. Tendon rupture is a severe complication after tenolysis.

Adhesion formation is the most frequent complication after primary tendon repair and tenolysis. Methods for preventing adhesions include early postoperative motion protocols, preservation of sheath and pulley components, mechanical barrier to adhesion formation, and chemical and molecular modulation of scar formation. All of these methods proved successful only in few patients. Recently, 5-fluorouracil17 and Hyaloglide (Fidia Advanced Biopolymers s.r.l., Abano Terme, Italy)18 were used for preventing adhesion formation, and good results have been achieved, but they are still under investigation. The few patients with little adhesion suffer from active flexion restriction and flexor power decrease.

For those patients who are not satisfied with result of primary repair and tenolysis and not suitable for single-stage tendon graft, staged flexor tendon reconstruction using a silicone rod provides a good alternative. In the 1950s, Bassett and Carroll19 began using flexible silicone rubber rods to build pseudosheaths in badly scarred fingers, and the method was later refined to a 2-stage reconstruction of the digital flexor tendons by Hunter and Salisbury.2 It is a long process in which many factors must be carefully considered by physician and patient, and the status of the digital tissues, including the skin, nerves, vessels, and joints, weigh heavily in determining the appropriateness of proceeding with such a complex and multi-staged restorative effort. This procedure was used for patients who had their flexor digitorum profundus, flexor digitorum superficialis, and tendon sheath all severely injured, especially in zone II, and it decreased adhesion formation effectively. Hunter’s technique is worthwhile for delayed flexor tendon injury in zone II to prevent adhesion formation.2-11

The main complications of staged flexor tendon reconstruction include adhesion formation, infection, skin necrosis, rod buckling, silicone synovitis, or tenorrhaphy rupture and silicone rod exodus. In this series, the rate of infection was 2.9%, which is slightly higher than the average rate of infection (2%) in our operation theater during the same time. The possible reasons for this include the implanted silicone rod working as foreign body and rareness of soft tissue in digit and extra trauma to the soft tissue due to rough surgical technique and carelessness in aseptic techniques. To prevent the occurrence of those complications, an atraumatic and aseptic technique should be performed during the course of managing tendon and soft tissue. Meanwhile, the pullout wire should be secured carefully intraoperatively, and controlled rehabilitation should be planned in detail and guided throughout the course.

A reasonable controlled action technique helps prevent adhesion formation after stage II. It has been widely proven that the digit function is markedly better in patients who received early controlled action rehabilitation than those who did not receive such therapy after tendon management.20,21 After flexor tendon injury, 2 mechanisms for healing were involved: extrinsic and intrinsic. The extrinsic mechanism is predominately mediated by an influx of synovial fibroblasts and inflammatory cells from the tendon sheath. Healing also occurs via the intrinsic mechanism, in which fibroblasts and inflammatory cells from the tendon and epitenon invade the injured site.

During the course of remodification of the injured site, the synovium is also regenerated to restore the smooth surface of tendon. Early controlled passive and active motion decreased adhesion formation, promoted tendon healing by stimulating proliferation of epitenocytes, facilitated remodification of the injured tendon and keeping the tendon surface smooth, and helped keep effective space between the tendon substance and sheath. The pseudosheath was formed after stage I with the silicone rod implanted, which provided a good tunnel for tendon graft, so adhesion formation within this tunnel is nearly impossible. But adhesion can also occur in the juncture of graft and local tendon, so early controlled action is still important for preventing potential adhesion formation. In this series, all 69 patients (106 digits) received early controlled action rehabilitation, and good results were achieved.

To retain good digital function, pulley reconstruction is also important. The pulley system, especially A2 and A4 pulleys, are responsible for preserving digital motion and finger strength (grip and pinch power). Loss of the integrity of these pulleys results in bowstringing, with loss of the A4 pulley causing the greatest change in the efficiency of tendon excursion, work, and force.22 Avoidance of bowstringing is the best management strategy and may be facilitated by performing tendon repair through cruciate pulley windows, using external pulley rings for compromised pulleys, and reconstructing pulleys in a 2-stage procedure when native tissue is unsalvageable.23 The reconstructed pulley should be strong enough and the proper size, so as to keep the tendon close to the phalanges and not confine tendon motion. It is not necessary to reconstruct the pulley when the A2 and A4 pulley are intact, which decreases the trauma and difficulty of the operation.

The appropriate selection of motor tendon is another key point for the success of the entire procedure. Most frequently, the combined profundus mass is chosen for grafts to the middle, ring, and small fingers. The independent profundus to the index finger usually serves as the most appropriate motor for that digit. In certain circumstances, the superficialis muscle tendons can also be used. If the proximal juncture is in midpalm, the scarred lumbrical musculi must be resected, otherwise the proximal interphalangeal joint would extend when the motor muscle contract. Care must be taken to fully mobilize the motor tendon unit.

Conclusion

Two-stage flexor tendon reconstruction is an easy method with minimal trauma that can effectively prevent adhesion formation. There is no absolutely effective method for preventing adhesion formation; however, 2-stage reconstruction is worth attempting for delayed flexor tendon injuries, especially in zone II.

References

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  18. Riccio M, Battiston B, Pajardi G, et al. Efficiency of Hyaloglide in the prevention of the recurrence of adhesions after tenolysis of flexor tendons in zone II: a randomized, controlled, multicentre clinical trial [published online ahead of print August 26, 2009]. J Hand Surg Eur Vol. 2010; 35(2):130-138.
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Authors

Drs Sun, Ding, Ma, and Zhou are from the Department of Orthopedic Surgery, Tangdu Hospital, the Fourth Military Medical University, Xi’an, Shhanxi Province, China.

Drs Sun, Ding, Ma, and Zhou have no relevant financial relationships to disclose.

Correspondence should be addressed to: Yong Ding, PhD, Department of Orthopedic Surgery, Tangdu Hospital, the Fourth Military Medical University, Xi’an, Shhanxi Province, 710038 China (dingyongfmmu@126.com).

doi: 10.3928/01477447-20101021-10

10.3928/01477447-20101021-10

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