Effects of extensor pollicis longus transposition and extensor indicis proprius transfer to extensor pollicis longus on thumb mechanics

PURPOSE: The spatial relationship of the extensor pollicis longus (EPL) to the thumb carpometacarpal (CMC) joint may be altered by its transposition from the third dorsal wrist compartment and by subcutaneous extensor indicis proprius (EIP) to EPL tendon transfer. Changes in tendon position could alter thumb function. This study examined changes in the EPL adduction moment arm after EPL tendon transposition from its extensor compartment or EIP transfer. METHODS: The EPL adduction moment arm at the thumb carpometacarpal joint was determined under 4 tendon conditions: (1) intact extensor pollicis longus, (2) transposed extensor pollicis longus, (3) extensor indicis proprius to extensor pollicis longus tendon transfer through an extensor retinacular pulley, and (4) extensor indicis proprius tendon transfer through a subcutaneous route. Each tendon condition was tested in 2 wrist positions: neutral and 40 degrees of flexion. RESULTS: The wrist neutral/flexion moment arms for the 4 tendon conditions, in millimeters, were 9.2/7.3, 3.6/1.2, 8.3/5.1, and 4.8/1.0. CONCLUSIONS: EPL transposition produces a significant decrease of its adduction moment arm at the thumb CMC joint, an effect exacerbated by wrist flexion. The moment arm mechanics of the pulley and subcutaneous EIP tendon transfer resemble those of the intact and transposed EPL, respectively. Diminution of the adduction moment arm could impair thumb function, especially adduction.     

Optimum tensioning position for extensor indicis to extensor pollicis longus transfer.

This study evaluates various wrist and thumb positions for tensioning the extensor indicis proprius when transferred to the extensor pollicis longus tendon to determine which positions provide optimum passive range of flexion and extension of the thumb. In five adult cadaver upper limbs, transfer of the extensor indicis proprius to the extensor pollicis longus was simulated. The limbs were fixed with the elbow in 90 degrees flexion and the forearm and wrist in neutral. Surface bone markers were digitized to determine the thumb and wrist positions in three-dimensional space and their intersegmental joint angles. Twelve combinations of thumb (the interphalangeal and metacarpophalangeal joints) and wrist positions for tensioning were tested. A fixed tension of 80 N was applied to the tendon ends for each of the tensioning positions and during the transfer to ensure that the tendon remained taut. A wrist tenodesis effect was used subsequently to assess the passive range of thumb motion as an indicator of the outcome of the transfer. The results showed that the better tensioning position was with the thumb fully extended and the wrist in neutral. In six patients in whom an extensor indicis proprius to extensor pollicis longus transfer was done, the tendons were tensioned with the thumb in full extension and the wrist in neutral. A prospective review and functional assessment at an average of 18.6 months' followup was done. No significant differences between the surgically treated and normal thumbs were seen for the Jebsen Taylor, 9-peg, and grip and pinch strength tests. The study suggests that in an extensor indicis proprius to extensor pollicis longus transfer, tensioning of the tendons with the thumb in full extension and the wrist in neutral gives good thumb flexion and extension range.     

Calculation of flexor pollicis longus moment arm for wrist motion in a cadaver model validates the tenodesis effect for therapy

IntroductionSynergies of fingers and wrist motion have been incorporated into therapies for finger flexor tendon injuries to improve repair outcomes. Similar synergistic therapy strategies have not been well documented for the thumb.Purpose of the StudyThe purpose of this study was to investigate the extent to which wrist motion enables a synergistic effect at the thumb in a cadaveric model by measuring flexor pollicis longus excursion and calculating the moment arm of this tendon at the wrist joint.Study DesignThis is a basic science research.MethodsEight fresh-frozen cadaveric arms were obtained from our anatomical bequest program. The proximal arm was fixed in neutral pronation/supination position, and motion of the wrist was guided through either flexion/extension or radial/ulnar deviation. Fingers were fixed in extension, thumb interphalangeal and metacarpophalangeal joints were fixed in neutral extension, and the carpometacarpal joint was fixed at 30° palmar abduction. The flexor pollicis longus tendon was exposed proximal to the wrist crease and connected to a rotary potentiometer to measure tendon excursion. Optical markers were attached to the hand to capture kinematics. Wrists were moved from a neutral position over the range of flexion and extension and then from the neutral position through the range of radial to ulnar deviation. Moment arms were calculated.ResultsMoment arm calculation indicated that the flexor pollicis longus acts as a wrist flexor over the entire motion range and as a weak radial deviator at ulnarly-deviated positions.ConclusionsThis study provides a mechanistic rationale for passive interphalangeal joint motion in varying wrist positions when treating thumb flexor tendon injuries, with benefits seen primarily for wrist extension.     

Long-term follow-up of the Moberg key grip procedure

The long-term results of the key grip procedure (tenodesis of the flexor pollicis longus tendon to the radius, release of the A1 pulley, and percutaneous pin fixation of the interphalangeal joint of the thumb) were evaluated in 10 tetraplegic patients. Seven patients also had tenodesis of the extensor pollicis longus and brevis tendons to prevent flexion at the metacarpophalangeal (MP) joint. Patients were examined an average of 7.4 years after surgery. Progressive flexion of the MP joint gradually occurred, indicating failure of the extensor tenodesis. Excessive bowstringing of the flexor pollicis longus tendon across the MP joint occurred in nine patients. Because of failure of the extensor tenodesis and bowstringing of the flexor tendon, the patients had to progressively extend the wrist further to pinch small objects. Functional testing demonstrated improved hand use in eight patients. Lateral pinch strength was related to wrist extension torque.     

Posttraumatic volar tendon subluxation out of the first extensor compartment: a case report

Symptomatic volar subluxation of the abductor pollicis longus and the extensor pollicis brevis tendons developed in a 29-year-old man after a sprain that occurred with the wrist in flexion and ulnar deviation. The extensor retinaculum, which forms the extensor compartment, was partially avulsed from its insertion on the radius. Palmar abduction and extension of the thumb with the wrist flexed produced subluxation of the tendons over the volar side of the radius ridge where the retinaculum forming the first extensor compartment attached. Nonoperative treatment including steroid injection and splinting was ineffective. Surgery was performed to reconstruct a new tendon restraint with part of the extensor retinaculum.     

Bilateral subluxation of the base of the thumb secondary to an unusual abductor pollicis longus insertion: a case report

Bilateral subluxation of the trapeziometacarpal joint was related to abnormal insertion of the abductor pollicis longus (APL) tendon and an atrophic extensor pollicis brevis tendon. The APL tendon had four slips, all of which inserted into the fascia of the abductor pollicis brevis muscle distal and palmar to the trapeziometacarpal joint. Active pinch of the thumb resulted in subluxation of the trapeziometacarpal joint. To prevent reciprocal distal deformity, the proximal thumb was held in dynamic balance by attaching two slips of the APL tendon to the radiodorsal base of the first metacarpal. One tendon slip supplemented the tendon of the extensor pollicis brevis muscle. The lax capsule of the trapeziometacarpal joint was reinforced with the remaining tendon slip. The patient retains excellent bilateral function without subjective weakness after surgery.     

Biomechanical changes of the wrist flexor and extensor tendons following loss of scaphoid integrity

Loss of integrity of the scaphoid may change the motion center of the entire carpus, and deformities from scaphoid fractures may alter the location of motor tendons of the wrist, thus altering their biomechanics. The goal of this study was to clarify biomechanical changes in these tendons following loss of scaphoid integrity. Excursions and moment arms of the principal flexor and extensor tendons of the wrist were investigated in seven cadaveric upper extremities in intact wrists after simulation of scaphoid waist fracture and after removal of the proximal scaphoid. Excursions of the flexor carpi radialis and ulnaris extensor carpi radialis longus and brevis, and extensor carpi ulnaris tendons were measured with rotary potentiometers during wrist flexion-extension and radioulnar deviation. Simultaneously, wrist joint angulation was recorded. Moment arms of the tendons were derived from tendon excursions and joint motion. After scaphoid fracture, the moment arms of the flexor carpi radialis and extensor carpi ulnaris tendons increased significantly during wrist flexion-extension, whereas the moment arms of the extensor carpi radialis longus and brevis tendons decreased significantly. After proximal scaphoid excision, the moment arms of the extensor carpi radialis longus and brevis tendons again decreased significantly during wrist flexion-extension. The moment arms of the flexor carpi radialis and extensor carpi radialis brevis tendons increased significantly during radioulnar deviation, whereas those of the wrist motors on the ulnar side decreased. These findings indicate the importance of the integrity of the scaphoid in maintaining normal biomechanics of motor tendons of the wrist. An increase in the moment arm of the radial wrist flexor along with a decrease in moment arms of the radial extensors constitutes an etiology for persistent angulation of the scaphoid and the hump-back deformity. In addition, disturbing the biomechanics of the wrist motor tendons predisposes the carpal joints to abnormal loading, potentially contributing to the development of carpal joint degeneration.     

A new modification of extensor indicis proprius transfer to extensor pollicis longus using a retinacular pulley

A new modification of the extensor indicis proprius transfer to the extensor pollicis longus tendon through a fourth dorsal compartment retinacular pulley is described. This new modification has been assessed in cadavers biomechanically via computer simulation and in a limited number of patients with success. It affords the benefit over the standard subcutaneous extensor indicis proprius to the extensor pollicis longus tendon transfer of maintaining the adduction moment arm of the thumb. The moment arm mechanics of the pulley transfer resemble those of the intact extensor pollicis longus. Therefore this new modification offers better thumb function in both adduction and circumduction motions.     

Sehnenrupturen in der Folge distaler Radiusfrakturen

After distal radial fractures, closed ruptures of the extensor pollicis longus (EPL) tendon may be caused by protruding screws of a volar plate but also occur after conservative fracture treatment. The time interval between accident and rupture is a few weeks to a few months. Tendon transfer of the extensor indicis tendon or a tendon interposition graft are good options for reconstruction. Fusion of the IP joint is not a solution, as the second function of the EPL tendon is to withdraw the thumb ray out of volar abduction. Closed ruptures of the flexor pollicis longus (FPL) tendon exclusively occur after volar plate ORIF, the time interval being years to more than a decade. Volar plates of the distal radius should generally be removed after bone healing and urgently when the patient reports tendon crepitation or pain. A ruptured FPL tendon may be reconstructed by tendon interpositional graft or by tendon transfer but IP joint fusion is a good alternative as the flexor pollicis brevis muscle shows a good thumb metacarpophalangeal joint flexion.     

The extensor carpi radialis intermedius tendon

I examined 312 arms from 156 cadavers in the anatomy laboratory of Loma Linda University to find the incidence of the extensor carpi radialis intermedius tendon. I found 29 bodies (12%) that had a good extensor carpi radialis intermedius. In 17 of these 29 bodies, an extra tendon was found bilaterally. Thirty-two extensor carpi radialis intermedius tendons were suitable for transfer operations, and seven were unacceptable. One must be careful to differentiate between a true extensor carpi radialis intermedius tendon and accessory tendinous bands. The relatively high incidence rate and percentage of tendons suitable for transfer operations make this tendon potentially valuable in treating severe quadriplegia with tendon transfers. It can be used successfully for thumb opposition, to motor the flexor pollicis longus, or as a motor for the extensor pollicis longus of the thumb.     

Electromyographic analysis of the thumb: a study of isometric forces in pinch and grasp

An electromyographic study of thumb muscles was performed on eight subjects by means of integrated polyelectromyography and simultaneous recordings of isometric flexion-extension, abduction-adduction, and prehensile pinch and grasp of the thumb. The integrated electromyographic signal proved to be an excellent index of thumb muscle activity, with a linear relationship found at low to middle levels of muscle strength. To facilitate understanding of thumb function, thumb muscles can be classified as primary or secondary on the basis of electrical potential activity. In isometric flexion, the flexor pollicis longus (FPL) was primary, whereas in extension, the extensor pollicis longus (EPL) and abductor pollicis longus were primary. In adduction, the adductor pollicis and EPL were primary and the FPL was secondary. In abduction, the abductor pollicis brevis and opponens pollicis were primary. The adductor pollicis, and FPL were nearly equal during pinch and grasp, with significant electrical activity increasing with greater force requirements. The first dorsal interosseous and EPL contributed secondarily in both pinch and grasp. When surgeons consider tendon transfers for nonfunctioning thumb muscles, the primary muscles should be replaced first to best restore pinch and grasp strength.     

Reconstruction of the thumb in tetraplegia following spinal cord injury

Functional positioning of the thumb is paramount to the restoration of lateral pinch to the hands in patients with tetraplegia as the result of spinal cord injury. Useful lateral pinch can be provided to patients with at least wrist extension control preserved by use of a combination of flexor pollicis longus tenodesis or transfer and carpometacarpal and inter phalangeal joint stabilization. In patients who retain function in the brachioradialis, extensor carpi radialis longus and brevis, pronator teres, and flexor carpi radialis, strong grasp as well as effective lateral pinch can be restored to the hand by surgery. Thumb control for flexion and extension is provided by tendon transfer to the flexor pollicis longus and tenodesis or transfer to the extensor pollicis longus. Proper positioning for lateral pinch can be accomplished by either arthrodesis of the first metacarpal-trapezial joint or tendon transfer to restore adduction-opposition to the thumb. The surgical concepts presented in this paper have been applied to the functional reconstruction of the hands of more than 50 patients with spinal cord injury during the last 15 years. The patients have been pleased with the significant improvement in function, strength, and speed that has resulted from surgery and have been cooperative advocates as the alternate methods of thumb control have been evaluated.     

A method of restoration of the abduction of the thumb in traumatic tetraplegic patients

A method of restoring extension and abduction of the thumb in traumatic tetraplegia is described. This method includes tenodesis of the abductor pollicis longus, transfer of the distal stump of the extensor pollicis brevis tendon to the flexor carpi radialis tendon, and transfer of the distal stump of the extensor pollicis longus tendon to the brachioradialis tendon. I performed this procedure on 6 hands in 5 patients and monitored each patient for 6 to 12 months. A significant increase in radial abduction of the thumb (0.5 +/- 0.2 cm to 2.8 +/- 0.2 cm) occurred in all hands.     

Complex,multidimensional thumb movements generated by individual extrinsic muscles

The objective of this study was to investigate three‐dimensional thumb joint movements produced by individual extrinsic thumb muscles. Ten cadaveric arms were dissected to expose the musculotendinous junctions of the flexor pollicis longus (FPL), abductor pollicis longus (APL), extensor pollicis brevis (EPB), and extensor pollicis longus (EPL). Each muscle/tendon was loaded to 10% of its maximal force capability whereas three‐dimensional angular movements of the carpometacarpal (CMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints were obtained simultaneously. We found that each extrinsic muscle produced unique joint angular trajectories in multiple directions. The FPL, APL, EBP, and EPL generated two, two, three, and six movements, respectively. The extrinsic muscles all together generated eight movements among the multiple thumb joints. High interjoint coordination was shown between the MCP joint flexion and IP joint flexion by FPL loading, as well as between the MCP joint extension and IP joint extension by EPL loading. High intrajoint coordination was observed between extension and supination at the CMC joint by the APL, EPL, and EPB. We concluded that each muscle produces movements in multiple joints and/or in multiple anatomical directions. The findings provide a novel insight into the biomechanical roles of the extrinsic muscles of the thumb. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1289–1295, 2008     

Extensor pollicis brevis tendon can hyperextend thumb interphalangeal joint in absence of extensor pollicis longus:Case report and review of the literature

We are reporting a case of extensor pollicis longus tendon rupture which did not require tendon transfer owing to the ability of the intact extensor pollicis brevis(EPB) to fully hyperextend the thumb interphalangeal joint. The thumb metacarpophalangeal joint was also able to be fully actively extended by the EPB. Previous anatomical studies have demonstrated that the insertional anatomy of the EPB tendon is highly variable and sometimes inserts onto the extensor hood and distal phalanx, which is likely the mechanism by which our patient was able to fully extend the thumb interphalangeal joint. Despite the potential for the EPB to extend the IP joint of the thumb, virtually all previously reported cases of extensor pollicis longus(EPL) tendon rupture had deficits of thumb IP extension requiring tendon transfer. This case highlights the potential ability of the EPB tendon to completely substitute for the function of the EPL tendon in providing thumb IP joint extension.     

Kinematic Analysis of Six Different Insertion Sites for FDS Opponensplasty

Six variations of opponensplasty were biomechanically studied to determine if there is a significant difference in the amount of opposition produced by altering the insertion site of the tendon transfer while keeping the tendon source and pulley location constant. Five cadaveric arms were used to simulate six described insertion sites for opponensplasty tendon transfers. The arms were mounted through the ulna onto a specially designed stand. The stand was equipped with a calibrated stylus which could be turned 90° in order to accurately measure points in X, Y, and Z planes. Metacarpal-phalangeal flexion and thumb abduction were measured before and after application of a 550-g load. Axial rotation (pronation) was mathematically calculated using reference points on the thumb which were measured with the stylus before and after application of the load. The Bunnell transfer insertion site provided the greatest amount of palmar abduction, the Brand transfer insertion site the greatest metacarpophalangeal flexion, and the Royle transfer insertion site the greatest rotation. Although each of these transfers produced the greatest motion in one plane, they performed relatively poorly in the other two. The Riordan transfer insertion site into the extensor pollicis longus in line with the abductor pollicis brevis was, in our study, the overall best transfer, providing the second greatest change in motion in each of the three planes measured.     

Gliding resistance of the extensor pollicis brevis tendon and abductor pollicis longus tendon within the first dorsal compartment in fixed wrist positions.

PURPOSE: While the etiology of de Quervain's disease is unknown, repetitive motion coupled with awkward wrist position and septation within the first dorsal compartment are considered causative factors. We hypothesize that these conditions might produce high gliding resistance, which could then induce micro-damage of the tendons and retinaculum. The purpose of this study was to measure the gliding resistance of the extensor pollicis brevis and abductor pollicis longus tendons within the first dorsal compartment in a human cadaver model. METHODS: Fifteen human cadaver wrists, which included eight septation and seven non-septation wrists in the first dorsal compartment, were used. Gliding resistance of the extensor pollicis brevis and abductor pollicis longus tendons was measured in seven wrist positions: 60 degrees extension, 30 degrees extension, 0 degrees, 30 degrees flexion, 60 degrees flexion in neutral deviation and 30 degrees ulnar deviation, 15 degrees radial deviation in neutral extension/flexion. RESULTS: The overall gliding resistance was not different between septation and non-septation wrists (0.21 versus 0.19 N for abductor pollicis longus and 0.21 versus 0.15 N for extensor pollicis brevis, respectively), but there was a significant effect on gliding resistance due to wrist position (p<0.05) in both tendons. Interaction between wrist position and septation status was observed in the extensor pollicis brevis tendon (p<0.05). With septation, the gliding resistance of the extensor pollicis brevis was significantly higher in 60 degrees wrist flexion (0.51 N) compared to all other wrist positions tested (all less than 0.26 N) (p<0.05). In the non-septation group, gliding resistance was significantly higher in 60 degrees flexion (0.20 N) and 60 degrees extension (0.22 N) compared to the other five wrist positions (all less than 0.15 N) (p<0.05). Although no significant difference was observed, the extensor pollicis brevis tendon with septation tended to have higher gliding resistance than that without septation in wrist flexion. In 60 degrees of wrist flexion the abductor pollicis longus tendon had significantly higher gliding resistance (0.33 N) than the other wrist positions (all less than 0.26 N) (p<0.05). CONCLUSIONS: A combination of septation and wrist position significantly affected extensor pollicis brevis tendon gliding resistance in this cadaver model. These factors may contribute to the development of de Quervain's disease.     

Pollex abductus in hypoplasia and duplication of the thumb

Pollex abductus is an anomaly in which the flexor pollicis longus attaches not only at its customary insertion, but also into the extensor by a tendon that passes around the radial aspect of the thumb. Contraction of the anomalous flexor abducts the thumb. In the original report, the anomaly occurred in thumb hypoplasia. A similar anomaly is reported in 11 hypoplastic thumbs (35.5% of all cases) and in 9 cases of radial polydactyly (21.4%). The common feature was poor definition of the interphalangeal skin crease, with complete absence of active flexion of that joint. All patients were treated surgically; 13 before the age of 10 months, with correction of the duplication and the hypoplasia, and in the latter with elimination of the abduction deformity and restoration of opposition. The anomalous connection was excised in all patients. Active interphalangeal joint motion after reconstruction of the hypoplastic thumbs averaged 21 degrees.     

Spontaneous rupture of extensor pollicis longus in isolated trapeziometacarpal arthritis

A spontaneous rupture of the extensor pollicis longus (EPL) tendon occurred in a patient with trapeziometacarpal arthritis. We hypothesize that a mechanical attrition by protrusion at the trapeziometacarpal joint alone was responsible of a spontaneous rupture of the extensor pollicis longus tendon.     

Opposition of the thumb: an anatomic and biomechanical study of tendon transfers

Tendon transfers for opposition of the thumb were anatomically and biomechanically studied to help determine the optimal criteria for selecting the best motor unit for a transfer. Forearm and hand muscle volume, mean fiber length, and cross-sectional area were measured in eight fresh specimens of the upper extremity to determine which muscles best replace lost thenar muscle strength. In a separate group of 18 specimens, the effective moment arms for abduction and flexion of the first metacarpal were calculated in vitro and from biplanar radiographic techniques to determine the effect of eight different opposition transfers on thumb abduction, rotation, and strength. Results of these studies demonstrate that the transfers of flexor digitorum superficialis (FDS) of the long finger and extensor carpi ulnaris best replaced lost thenar muscle strength and provided maximal abduction and near full thumb rotation. The transfers of the extensor carpi radialis longus and the FDS of the ring finger replaced 60% and 40% of required thenar muscle strength, respectively. The palmaris longus was the least effective transfer, having good abduction but weak flexion and opposition. Motion, balance, and strength of tendon transfers must be considered for effective thumb opposition.