Flexor tendon pulley reconstruction

The flexor tendon pulley mechanism causes the tendons to work with maximum efficiency. Without its competency,flexor tendons will bowstring causing significant losses of digital motion and strength. Without an intact pulley system, increased flexor tendon excursion is required to affect joint motion and flexion contractures may develop over time. Recent investigators have described the properties of the intact flexor pulley system as well as those of flexor pulley reconstructive techniques. Reconstruction of the flexor pulley system should take into account both strength and length of the construct and in most cases a loop of either flexor tendon graft or wrist extensor retinaculum is used. Other methods are available including the use of the palmar plate as well as the superficialis tendon.     

Palmar and digital flexor tendon pulleys

Retinacular structures, called pulleys, maintain the flexor tendons of the hand in constant relationship to the joint axes and promote economy and efficiency in finger flexion. This system is composed of the transverse carpal ligament, the palmar aponeurosis pulley, and the digital flexor pulley system. Of these three components, the digital pulleys are the most critical to finger flexion. In their normal state, these pulley components are ideal in all aspects including configuration and location, which accomodates a 260 degrees arc of motion without impingement and with minimum friction while at the same time using muscle tendon excursion that is well within the natural range of the muscle. An absent pulley results in an increased moment arm and requires increased tendon excursion to produce the same arc of motion. Because muscle excursion is not a limitless factor and is directly proportional to muscle fiber length, the effectiveness of tendon excursion is dependent on maintenance of the critical relationship between pulleys and the adjacent joints. Preservation and reconstruction of this system is based on knowledge of the anatomy and an understanding of the relative functional significance of each component of the system.     

The Omega "Omega" pulley plasty. A new technique to increase the diameter of the annular flexor digital pulleys

The authors report a new technique of pulley plasty of the flexor digital system. It is not an operative procedure to reconstruct a damaged pulley but an original way to expand the volume of an intact pulley in order to adapt its volume to the diameter of the repaired flexor tendon. The flexor tendons ruptures in Verdan zone II and particularly in Tang zones IIA and IIB are often accompanied by an osteofibrous tunnel injury. Initially, the tendon sheath closure was advised after tendons repair. This sheath recovery had to have an effect on tendons nutrition by establishing the synovial cavity continuity and particularly to protect the tendons from adhesions formation. The closure of the digital tube was rapidly shown to be unnecessary creating an obstacle to the tendons movements without any effect on tendons healing. In primary tendon management, the tendon repair is associated with an increase of the tendon diameter. An incongruence appears with the surrounding digital tube with gliding resistance complicating the tendon injury recovery. In secondary tendon injury management, the flexor digital tube is subject to healing and inflammatory process. This situation with the absence of the flexor tendon generates a retraction with a collapse of the digital tunnel over the injured area. This incongruence between the repaired flexor tendons and the narrowed digital tube required a release of the retracted zone to restore an adequate volume. The only way reported is the "Venting" of a part or the total length of the pulley. This procedure even if it resolves the tendon gliding resistance, is still unacceptable. Indeed it destroys an important anatomical structure of the flexor tendon dynamic system. The flexor pulley Omega plasty "Omega" consists in releasing the lateral palmar attachment of the pulley enhancing its internal volume and increasing the flexor tendon gliding area. The digital tube is composed by the succession of five annular and three cruciform pulleys. The cruciform pulleys are thin and flexible. They retract during the digital flexion assuring the continuity of the digital tube, while the annular pulleys are thicker and fill a biomechanical function. There are two types of annular pulleys: the joint pulleys as A1, A3 and A5; they are attached to the palmar plates of the MP, PIP and DIP joints respectively. During the digital movement, they retract approximately 50% of their length. The osseous pulleys as A2 and A4 are fixed over the lateral and palmar borders of the first and the second phalanx respectively. It is on these pulleys that the Omega plasty is practised. The operative procedure is simple. It consists on a periosteal dissection over the one lateral border of the phalanx. The liberation is undergone palmarly releasing the lateral attachment of the pulley. It respects the anatomical continuity of the pulley and its mechanical properties. Indeed, the continuity of the pulley is fully respected with the periosteal flap of the digital tube floor maintaining sufficient attachment to the pulley to resist to the flexor tendon forces. The level of the flexor tendon injury and the digit position during the initial trauma will determine the level of tendon resistance and where the pulley plasty must be made. If the flexor zone II injury occurred with the digit in an extension position, the tendon conflict appears with the A2 pulley, while it arises with the A4 pulley if the digit was in flexed position. The Omega plasty creates the ideal conditions for an optimal flexor tendon movement recovery. It is a simple and a reproducible procedure. It doesn't distort the mechanical properties of the pulley and the digital tube. We used this pulley Omega plasty fifteen times in twelve patients. In 60% of the cases, the injury concerned the dominant hand, and in 67% of the cases, it was a work accident. In eight of our cases, the omega plasty was done in emergency at the same time of flexor tendon repair, while in the other seven cases, the pulley Omega plasty accompanied the late flexor tendon repair forgotten during the initial trauma management. In ten cases, the plasty concerned the A4 annular pulleys, while in the other five cases, it concerns the A2 annular pulleys. Four cases necessitate a secondary tenolysis three months after the tendon repair. Two patients moved out and cannot be included in our results. On the thirteen-remainder cases, nine retrieved a full digital flexion particularly those who underwent digital tenolysis, while the other four cases retrieved a satisfying digital function in spite of the partial DIP flexion. In our hand, the pulley Omega plasty "Omega" becomes almost a systematic procedure in conjunction with the flexor tendon repair. It offers the ideal conditions for a tendon healing and a physiological flexor tendons motion recovery.     

Percutaneous trigger finger release: a comparison of a new push knife and a 19-gauge needle in a cadaveric model.

An instrument was developed for percutaneous release of the A1 pulley and this procedure was compared with percutaneous release using a 19-gauge needle in 20 fresh-frozen cadaver hands. This instrument was developed to avoid the complications of incomplete release and flexor tendon damage previously reported with percutaneous release using a 19-gauge needle. Seventy-eight fingers were used in the study. The push knife was used to release 52 fingers. The A1 pulley was completely released in 51 fingers (98%) and there were no incidents of flexor tendon damage. A 19-gauge needle was used to release 26 fingers. The A1 pulley was completely released in only 10 fingers (38%) and the flexor tendon was damaged in 19 (73%). In cadaveric hands, this instrument proved to be more effective at creating a complete release of the A1 pulley and demonstrated less disruption of the flexor tendon surface compared with current needle techniques.     

Pulley plasty versus resection of one slip of the flexor digitorum superficialis after repair of both flexor tendons in zone II: a biomechanical study

BACKGROUND: The outcome of repair of zone-II lacerations of the flexor digitorum superficialis and flexor digitorum profundus tendons remains suboptimal. We investigated the effects of two strategies to improve postoperative gliding in a human cadaveric hand. METHODS: The second, third, and fourth digits were harvested from ten fresh-frozen human cadaveric hands. Complete lacerations and repairs were made to the profundus and superficialis tendons at a location where both repair sites would pass beneath the A2 pulley with the proximal interphalangeal joint in 45 degrees of flexion. The gliding resistance of the flexor digitorum profundus tendon was measured following pulley plasty and following excision of one slip of the flexor digitorum superficialis. The breaking strength of the remaining slip of the flexor digitorum superficialis tendon was then measured. RESULTS: Pulley plasty and resection of one slip of the flexor digitorum superficialis tendon both significantly decreased gliding resistance compared with repair of both slips (p < 0.001). There was no difference in the mean gliding resistance between the pulley plasty and one-slip resection groups. The flexor digitorum superficialis slip was stronger after repair with a Becker suture (28.8 +/- 9.0 N) than after repair with a modified Kessler (16.4 +/- 4.5 N) or a zigzag suture (15.0 +/- 5.7 N). CONCLUSION: Both pulley plasty and resection of one slip of the flexor digitorum superficialis reduce gliding resistance after tendon repair in zone II of the hand.     

The pulley system of the thumb: anatomic and biomechanical study

To examine the precise conformation of the annular and oblique pulleys of the thumb flexor sheath, anatomic dissections were undertaken on 14 hands. In all specimens a distinct pulley was found between the A1 and oblique pulleys. This is named the variable annular pulley or Av pulley. There appear to be 3 discrete forms of this pulley designated type I to III. The biomechanical study was done on 8 limbs by using linear strain transduction techniques. The analysis showed that the strain in the oblique pulley was greater in extension than in flexion of the thumb. This statement remains true even after division of either the A1 or Av pulley and after section of both pulleys. The oblique pulley does not prevent bowstringing of the flexor pollicis longus when A1 and Av pulleys have been sectioned. These studies challenge current concepts of both the anatomy and mechanics of the thumb pulley system with implications for clinical procedures such as trigger thumb release and pulley reconstruction.     

Tendon transfers for thumb opposition: a biomechanical study of pulley location and two insertion sites

PURPOSE:The purpose of this biomechanical study was to test 5 proximal tendon pulley sites or routes of tendon transfer and 2 distal tendon insertion sites that are used commonly for performing a thumb opposition transfer. METHODS: Five fresh-frozen cadaver arms were used to test (1) an around flexor carpi ulnaris (FCU) pulley, (2) an FCU loop pulley, (3) a Guyon's canal pulley, (4) a junction of the distal edge of the transverse carpal ligament and the ulnar border of the palmar aponeurosis (Royle-Thompson pulley), and (5) a palmar thenar subcutaneous transfer (Camitz). Two tendon insertion sites were tested: a palmar radial insertion into the abductor pollicis brevis and a dorsal ulnar insertion into the thumb proximal phalanx. RESULTS: The Guyon's canal and Royle-Thompson pulleys produced the greatest amount of approximation of the thumb pulp to the fifth metacarpal head. The around the FCU pulley, FCU loop pulley, and Camitz transfer produced the greatest palmar abduction. The Guyon's canal and Royle-Thompson pulleys were the most mechanically efficient pulleys, producing the least amount of transmitted force. The palmar radial insertion site produced better thumb opposition, metacarpophalangeal joint abduction, metacarpophalangeal joint flexion, and approximation of the thumb pulp to the fifth metacarpal head. CONCLUSIONS: We conclude that the choice of the proximal pulley used may depend on the needs of the transfer, and a palmar radial thumb insertion is more effective than the dorsal ulnar insertion.     

Closed flexor pulley injuries in nonclimbing activities

Closed flexor pulley injuries have been reported in rock climbers. We report 6 digital flexor pulley injuries in 6 patients aged 5 to 73 years that were not associated with a climbing injury. Excellent outcomes were achieved through conservative therapy in 5 patients and surgical therapy in 1 patient.     

Closed rupture of the thumb flexor tendon pulleys

Closed flexor tendon pulley ruptures are relatively rare injuries. All previously reported cases have been in the long finger pulleys. To our knowledge, there has not been a case of closed thumb flexor tendon pulley rupture reported in the literature. This paper presents two cases of this pathology and discusses appropriate treatment of it.     

Effect of pulley integrity on excursions and work of flexion in healing flexor tendons

We investigated the effect of incision of a single critical pulley on excursions and work of flexion in healing flexor tendons. Forty-two long toes from 21 white leghorn chickens were used as the experimental model. Gliding excursions of the flexor digitorum profundus tendons and work of flexion of the long toes were studied 8 weeks after tendon repair to determine the functions of the healed tendons in intact, incised, or enlarged A2 pulleys. Eleven additional chickens (22 long toes) were used to obtain tendon excursion measurements in normal chicken toes. At 8 weeks, gliding excursions were statistically smaller in the intact pulley group than in the incised or enlarged pulley groups; the excursions were 73% +/- 4% for the intact pulley group, 88% +/- 9% for the incised pulley group, and 91% +/- 8% for the enlarged sheath group compared with the normal group. Work of flexion of the toes in the intact pulley group was statistically greater than that in the incised or enlarged pulley groups. Excursion efficiency of the flexor tendons was not statistically different among the toes receiving different treatments in the pulley. The results of this study demonstrate that release of a single pulley after repair of the tendons in this area improved gliding excursions of the tendons and reduced resistance to motion of the repaired tendons, and provide support for partial A2 pulley incision after repair of the tendons in the area of the pulley.     

Distal stenosing tenosynovitis

Three patients are described with distal stenosing tenosynovitis involving the flexor digitorum profundus and the A3 pulley. One patient had isolated distal stenosing tenosynovitis and two patients had combined distal and proximal stenosing tenosynovitis of the flexor digitorum superficialis and the A1 pulley. All three patients with four digits involved had improvement of their symptoms after release of the A3 pulley. When involved, the A1 pulley was released at the same time. Patients with proximal stenosing tenosynovitis may have an associated distal stenosing tenosynovitis that if overlooked may cause persistence of symptoms after surgical treatment.     

A splint for controlled active motion after flexor tendon repair. Design, mechanical testing, and preliminary clinical results

A splint for controlled active motion after flexor tendon repair is described. It incorporates a single core-coated elastic band passing around a palmar pulley and attached proximally to a spring wire. Its mechanical properties were tested against six other systems. The tension in various systems all rose near full extension. However, the palmar pulley, the spring wire, and the elastic band each could lower the tension significantly. When the bending moments at the interphalangeal joints were measured, all systems produced a peak during the latter part of extension. With the palmar pulley, spring wire, and elastic band, the rise was minimal and in fact, the bending moments diminished near full extension. Initial results in 28 flexor tendon repairs using this splint showed less flexion contracture when compared with 78 flexor tendon repairs using a standard rubber band anchored at the wrist.     

Trigger Finger Release With Stepwise Preservation of the A1 Pulley: A Functional Pulley-Preserving Technique

The first annular (A1) pulley is an important structure of the hand, providing a biomechanical support to the metacarpophalangeal joint and maintaining joint stability and flexor tendon alignment. Albeit uncommon, disruption of this pulley can result in dislocation or ulnar drift of the digit, particularly pronounced in patients with rheumatoid arthritis. Despite this, the A1 pulley is commonly divided without reconstruction in trigger finger. Several annular pulley reconstructive techniques have been developed to preserve its function. However, development of recurrent triggering has been observed due to fibrosis, largely due to inadequate release of the pulley. We have developed a technique to increase the volume within the flexor sheath while preserving the A1 pulley by way of stepwise lengthening. This has enabled an increase in the diameter of the pulley to 4 times its original size. A prospective study was performed comprising 10 trigger finger releases with stepwise lengthening of the A1 pulley. In all patients, there were no complications, and good hand function was achieved with no recurrence of triggering at 6 weeks of follow-up. This technique can thus safely achieve trigger release without sacrifice of the function of the A1 pulley.     

Restoration of function of the thumb flexor apparatus requires repair of the oblique and one adjacent flexor tendon pulley

Damage to the pulleys of the thumb flexor apparatus may cause bow-stringing of the tendon and affect muscle function. An experiment using the hands and distal forearms of cadavers was designed to determine which damaged pulleys increase excursion length of the flexor tendon with constant tendon and resisting loads. Each specimen was mounted to a loading frame with a dead weight pinned to the tip of the thumb. The thumb flexor tendon was clamped to an actuator that applied a fixed load and measured excursion of the tendon. Ranges of motion of the thumb joint were also measured. The thumb flexor apparatus of each specimen was tested intact first, with the hand in flexed, neutral, and extended positions; then it was tested with progressive sectioning of pulleys from proximal to distal in one group and from distal to proximal in a second group. The length of excursion increased significantly with all pulleys cut but there was no effect on on overall range of motion of the thumb. With proximal to distal sectioning, no change in tendon excursion occurred when the flexor retinaculum and the first annular pulleys were cut, until the oblique pulley was sectioned, leadving only the second annular pulley intact (range, 1.17–1.31 times that of intact excursion, dependent on position of the hand). With distal to proximal sectioning, tendon excursion was not affected when the second annular and oblique pulleys were cut but did increase when the first annular pulley was sectioned, leaving only the flexor retinaculum intact (range, 1.28–1.36 times that of intact excursion). Dependent on the location of damage, therefore, an intact oblique or first annular pulley can maintain normal excursion of the tendon.     

Effects of superficialis tendon repairs on lacerated profundus tendons within or proximal to the A2 pulley: an in vivo study in chickens

PURPOSE: In a flexor tendon injury model in chickens we undertook a study to evaluate effects of the flexor digitorum superficialis (FDS) tendon repairs on excursions, work of flexion, and adhesions of the repaired flexor digitorum profundus (FDP) tendon after their injuries within or proximal to the equivalent of the A2 pulley and early tendon motion. METHODS: Thirty-five leghorn chickens were divided into 3 groups. In group 1 the FDS and FDP tendons of the long toes on both sides were transected in the area covered by the pulley. In group 2 the tendons were transected proximal to the pulley. In the first 2 groups, both tendons were repaired on the left feet, and only the profundus was repaired with superficialis excision on the right. The operated toes underwent simulated passive flexion for 3 weeks and results were evaluated 8 weeks after surgery. Chickens in group 3 were unoperated and served as the controls. RESULTS: When the tendons were cut within the pulley the FDP excursions and work of flexion were significantly better in the toes in which the FDS was excised than in those with both tendon repairs. When they were cut proximal to the pulley the repairs of both tendons had outcomes similar to that with excision of the FDS. Adhesions were more severe when both tendons were repaired under the pulley as compared with those after repair of a single tendon. CONCLUSIONS: This study showed different effects of the surgical repair or excision of the FDS on the FDP tendon within or proximal to a major pulley. Repair of both tendons worsens the gliding of the FDP tendon and increases adhesions within the major pulley; however, repair of both tendons yields outcomes equivalent to that after repair of only the FDP tendon proximal to the pulley.     

Feasibility of partial A2 and A4 pulley excision: residual pulley strength

We investigated residual digital flexor pulley strengths after 75% excision of the A2 and A4 pulleys. For direct pull-off tests, A2 and A4 pulleys from cadaveric fingers were tested by pulling on a loop of flexor digitorum profundus tendon through the pulley. For functional loading tests, fingers were positioned with the metacarpophalangeal joint flexed to 90 degrees for A2 testing, and with the proximal interphalangeal joint in 90 degrees flexion for A4 testing (with all other joints in full extension). Excision of 75% of A2 and A4 pulleys reduced pulley strengths determined by both testing methods. For the functional loading tests, which are more clinically relevant, mean tendon forces at failure after partial excision of A2 and A4 pulleys were 224 and 131 N respectively, which is sufficient to withstand flexor tendon forces expected during activities of daily living.     

Impact of flexor digitorum superficialis on gliding function of the flexor digitorum profundus according to regions in zone II

PURPOSE: Structures and gliding characteristics of the flexor tendons vary remarkably according to regions of zone II in the hand. We studied the impact of the flexor digitorum superficialis (FDS) on the work of flexion and excursion efficiency of the flexor digitorum profundus (FDP) tendon in different regions of zone II. METHODS: Twenty-one fresh-frozen human fingers were used as an experimental model. The FDP was pulled to flex the finger with a tensile machine. The work of flexion of the finger and gliding excursion of the tendon were recorded in the fingers with the FDS intact, after excision of the FDS proximal to, under, or distal to the A2 pulley. RESULTS: The FDS tendon exerts notably different effects on the work of flexion and excursion efficiency of the FDP in subregions of zone II. Removal of the FDS under the A2 pulley affected the FDP most manifestly, causing a 12% decrease in the work of flexion and a loss of the excursion efficiency at the metacarpophalangeal joint. Removal of the FDS proximal to the A2 pulley had a less notable effect on the work of flexion. Removal of the FDS distal to the pulley did not markedly alter the biomechanics of the FDP. CONCLUSIONS: Removal of the FDS tendon in the area of the A2 pulley reduces the work of flexion most notably and causes a loss of excursion efficiency. Removal of the FDS tendon distal to the A2 pulley does not change the work of flexion, and removal of the FDS tendon proximal to the A2 pulley has a notable but less pronounced effect on the FDP tendon.     

Histogenesis and morphology of the flexor tendon pulley system in the human embryonic hand

The number, position, structural and ultrastructural features of the flexor tendon pulley system in six human embryonic hands, aged from 6 to 12 weeks, were studied by light and electron microscope. The pulley system can be recognized from the ninth week; later, at 12 weeks, the structures are easily identified around the flexor tendon in positions closely correlated to those found during post-natal growth and in the adult hand. Structurally and ultrastructurally the pulleys are not simply thickened portions of the sheath. They are formed by three layers: an inner layer, one or two cells thick, probably representing a parietal synovial tendon sheath; a middle layer formed by collagen bundles and fibroblasts whose direction is mainly perpendicular to the underlying phalanx; and an outermost layer consisting of mesenchymal tissue with numerous vessels which extends dorsally in an identical layer, forming a ring that includes flexor and extensor tendons and the cartilaginous model of the phalanx. The pulley does not have a semicircular shape but a much more complicated one, owing to the middle layer which in part runs dorsally and in part ventrally, under the flexor tendons.     

Use of bioprosthetic tendon in digital pulley reconstruction--an experimental study

The potential clinical application of Glutaraldehyde treated bioprosthetic material in the hand as implants to substitute for damaged pulley, tendon or ligament has not been fully explored. This study tries to evaluate the efficacy and safety of the proposed bioprosthetic pulley in an experimental model. One of the digital flexor pulleys of the rabbit's foot was excised and replaced by a bioprosthetic pulley using a standardized technique. Autogenous tendon graft was used as the control on the opposite foot. Altogether twenty rabbits (40 feet) were included in the study and they were sacrificed at different time intervals up to one year. The retrievals were analysed for flexor tendon adhesions and rupture of the pulley macroscopically. Histological and Electron Microscopy study of the 'pulley' and 'pulley-bone' junction were also carried out. Results show consistently the progressive creeping substitution of the bioprosthetic material by the rabbit's own tissue without significant inflammatory reactions. Neither adhesions nor breakage of the pulley were detected, the results comparing favourably with the control group using autografts except for the longer time taken for the substitution process.     

Effect of hyaluronic acid on the excursion resistance of tendon grafts. A biomechanical study in a canine model in vitro

The excursion resistance between the tendon and pulley is an important factor contributing to the limitation of function after surgery to the hand. The administration of hyaluronic acid (HA) in the early rehabilitation after tendon grafting may help to prevent adhesions. We evaluated changes in the excursion resistance between potential sources of flexor tendon grafts and the annular pulley in a canine model after administration of HA. The intrasynovial and extrasynovial tendons were soaked in 10 mg/ml of HA for five minutes. The excursion resistance between these tendons and the annular pulley of an intact proximal phalanx and that of the same tendons of the opposite foot without administration of HA were evaluated. The tendon of flexor digitorum profundus of the second toe without administration of HA was used as a control. The gliding resistance of canine tendons was significantly decreased after the administration of HA especially in the extrasynovial tendons. Our findings suggest that the administration of HA may improve the gliding function of a flexor tendon graft.