Four Anchor Repair of Jersey Finger

BackgroundVarious surgical techniques for treating avulsions of the flexor digitorum profundus tendon at the distal phalanx have been published but no ideal technique has emerged. We introduce a new all-internal 4-anchor flexor tendon repair technique and evaluate outcomes in three clinical cases.MethodsIn this retrospective case series, we reviewed three patients that sustained an avulsion of the flexor digitorum profundus tendon at the distal phalanx. All patients were surgically treated with the four-anchor repair technique. Two titanium anchors were inserted into the distal phalanx and two all-suture anchors were inserted distal to the first set of anchors. The tendon was then attached to these four anchors using a Krackow stitch pattern and the anchors were sown to each other. Active flexion and extension of the proximal and distal interphalangeal joint were measured at 3-month, 12-month, and 5-year follow-up. Postoperative complications were documented.ResultsAll patients achieved excellent clinical outcomes according to assessment criteria. At 3-month follow-up, all patients regained full flexion; two patients had full extension, while one patient was 3 degrees short of full extension. At 12-month follow-up, all patients had full flexion and extension. Five-year follow-up demonstrated the same results with no loss of function, sensation or grip strength. The repairs healed without rupture, and no complications were reported.ConclusionThe 4-anchor flexor tendon repair is a viable surgical technique for zone 1 flexor digitorum profundus tendon repair or reconstruction. Further studies are needed to replicate these promising results and biomechanically validate this technique.Level of Evidence: IV     

Differential expression of transforming growth factor-beta receptors in a rabbit zone II flexor tendon wound healing model

Flexor tendon repair in zone II is complicated by adhesions that impair normal postoperative gliding. Transforming growth factor-beta (TGF-beta) is a family of growth factors that has been implicated in scar formation. The TGF-beta family of proteins binds to three distinct classes of membrane receptors, termed RI, RII, and RIII. In this study, we analyzed the temporal and spatial distribution of TGF-beta receptor isoforms (RI, RII, and RIII) in a rabbit zone II flexor tendon wound healing model.Twenty-eight adult New Zealand White rabbit forepaws underwent isolation of the middle digit flexor digitorum profundus tendon in zone II. The tendons underwent transection in zone II and immediate repair. The tendons were harvested at increasing time points: 1, 3, 7, 14, 28, and 56 days postoperatively (n = 4 at each time point). The control flexor tendons were harvested without transection and repair (n = 4). Immunohistochemical analysis was used to detect the expression patterns for TGF-beta receptors RI, RII, and RIII.Immunohistochemical staining of the transected and repaired tendons demonstrated up-regulation of TGF-beta RI, RII, and RIII protein levels. TGF-beta receptor production in the experimental group (transection and repair) was concentrated in the epitenon and along the repair site. Furthermore, the TGF-beta receptor expression levels peaked at day 14 and decreased by day 56 postoperatively. In contrast, minimal receptor expression was observed in the untransected and unrepaired control tendons.These data provide evidence that (1) TGF-beta receptors are up-regulated after injury and repair; (2) peak levels of TGF-beta receptor expression occurred at day 14 and decreased by day 56 after wounding and repair; and (3) both the tendon sheath and epitenon have the highest receptor expression, and both may play critical roles in flexor tendon wound healing. Understanding the up-regulation of TGF-beta isoforms and the up-regulation of their corresponding receptors during flexor tendon wound healing provides new targets for biomolecular modulation of postoperative scar formation.     

A combined regimen of controlled motion following flexor tendon repair in "no man's land"

A program of controlled motion following repair of flexor tendons in the hand is presented. This regimen incorporates the features of active extension against rubber band passive flexion, as well as those of controlled passive extension and passive flexion. In this prospective study, 44 digits with complete lacerations of the flexor digitorum profundus and flexor digitorum superficialis in zone 2 were treated. Using the Strickland formula of total active motion of the interphalangeal joints, 36 fingers (82 percent) were rated "excellent"; 7 fingers (16 percent) were rated "good"; 1 finger (2 percent) was rated "fair"; none was rated "poor". There was no statistical difference between the results of delayed primary repair and immediate primary repair.     

Hyaluronic acid diminishes the resistance to excursion after flexor tendon repair: an in vitro biomechanical study

Adhesion between the tendon and tendon sheath after primary flexor tendon repair is seen frequently, and postoperative finger function is occasionally unsatisfactory. A reduction of the friction may facilitate tendon mobilization, which in turn may reduce the risk of the adhesion and restriction of range of motion. We considered the possibility of utilizing the hyaluronic acid (HA) as a lubricant. To evaluate the effect of HA, the gliding resistance between the canine flexor digitorum profundus tendon repaired by a modified Kessler suture technique with running epitendinous suture and the annular pulley located on the proximal phalanx (corresponding to the A2 pulley in humans) was evaluated and compared before and after administration of HA. The HA solution measurement groups were identified as follows; intact tendon as a control; repaired tendon; tendon soaked in 0.1, 1, and 10 mg/ml HA. The resistance increased after repairing, then it decreased after soaking in 10 mg/ml HA solution. The results of this study revealed that HA diminishes the excursion resistance after flexor tendon repair. We believe that some style of administration of the HA might reduce the excursion resistance and prevent adhesion until the synovial surface is fully developed.     

Staged reconstruction of flexor tendons with a silicone rod and a "pedicled" sublimis transfer

We report the results in 11 cases of secondary flexor tendon reconstruction, employing a silicone rubber rod and a sublimis/profundus tenorrhaphy in the first stage, then hinging out the sublimis tendon on the profundus motor at the second stage. Achievement of a healed proximal tenorrhaphy before the second stage allows (1) inspection of the proximal tenorrhaphy (with assessment of its location, apperance, and strength) and (2) early postoperative motion in a controlled range (with greater confidence in the proximal tenorrhaphy, as rupture after free tendon grafting is not uncommon. The functional results attained were comparable to those in other series of secondary flexor tendon reconstructions.     

Analysis of cumulative strain in tendons and tendon sheaths

Twenty-five fresh frozen flexor digitorum profundus tendons stratified by sex were subjected to uniaxial step stress and cyclic loads in twelve intact human cadaver hands. By attaching specially designed clip strain gage transducers on tendons just proximal and distal to an undisrupted carpal tunnel, the interactions of the tendons, tendon sheath and retinacula were measured. The elastic and viscous response of the tendon composites to step stresses were found to fit fractional power functions of stress and time respectively. A significant and quantifiable decrease in strain from the proximal to the distal tendon segment was found to be a function of wrist deviation. The results indicate that an accumulation of strain does occur in tendinous tissues during physiologic loading.     

Moment arms of the human digital flexors

For the extrinsic hand flexors (flexor digitorum profundus, FDP; flexor digitorum superficialis, FDS; flexor pollicis longus, FPL), moment arm corresponds to the tendon's distance from the center of the metacarpalphalangeal (MP), proximal interphalangeal (PIP), or distal interphalangeal (DIP) joint. The clinical value of establishing accurate moment arms has been highlighted for biomechanical modeling, the development of robotic hands, designing rehabilitation protocols, and repairing flexor tendon pulleys (Brand et al., 1975; An et al., 1983; Thompson and Giurintano, 1989; Deshpande et al., 2010; Wu et al., 2010). In this study, we define the moment arms for all of the extrinsic flexor tendons of the hand across all digital joints for all digits in cadaveric hands.     

Further experience in rehabilitation of zone II flexor tendon repair with dynamic traction splinting

A review of all flexor tendon repairs in the "no man's land" performed from January of 1985 to June of 1987 was done to evaluate the efficacy of our method of rehabilitation. There were 60 fingers (57 patients) with complete laceration of the flexor digitorum profundus and flexor digitorum superficialis tendons in zone II. Fingers with phalangeal fractures, joint injuries, or significant skin loss were excluded. Follow-up ranged from 12 to 48 months. Rehabilitation consisted of a 12-week protocol using the U.S. military combined regimen of controlled motion. Features from the technique of controlled active extension against rubber band passive flexion as well as those of controlled passive extension and passive flexion were incorporated. The palmar pulley modification of Kleinert's dynamic traction splint was utilized. Strickland's total active motion formula was employed to determine results. The results were classified into the four categories of excellent, good, fair, and poor. Fifty-two fingers (86 percent) were rated excellent, 4 fingers (7 percent) were rated good, 1 finger (2 percent) was rated fair, and 3 fingers (5 percent) were rated poor.     

Biomechanical properties of the crimp grip position in rock climbers

Rock climbers are often using the unique crimp grip position to hold small ledges. Thereby the proximal interphalangeal (PIP) joints are flexed about 90 degrees and the distal interphalangeal joints are hyperextended maximally. During this position of the finger joints bowstringing of the flexor tendon is applying very high load to the flexor tendon pulleys and can cause injuries and overuse syndromes. The objective of this study was to investigate bowstringing and forces during crimp grip position. Two devices were built to measure the force and the distance of bowstringing and one device to measure forces at the fingertip. All measurements of 16 fingers of four subjects were made in vivo. The largest amount of bowstringing was caused by the flexor digitorum profundus tendon in the crimp grip position being less using slope grip position (PIP joint extended). During a warm-up, the distance of bowstringing over the distal edge of the A2 pulley increased by 0.6mm (30%) and was loaded about 3 times the force applied at the fingertip during crimp grip position. Load up to 116N was measured over the A2 pulley. Increase of force in one finger holds by the quadriga effect was shown using crimp and slope grip position.     

The effect of finger extensor mechanism on the flexor force during isometric tasks.

The role of the intrinsic finger flexor muscles was investigated during finger flexion tasks. A suspension system was used to measure isometric finger forces when the point of force application varied along fingers in a distal-proximal direction. Two biomechanical models, with consideration of extensor mechanism Extensor Mechanism Model (EMM) and without consideration of extensor mechanism Flexor Model (FM), were used to calculate forces of extrinsic and intrinsic finger flexors. When the point of force application was at the distal phalanx, the extrinsic flexor muscles flexor digitorum profundus, FDP, and flexor digitorum superficialis, FDS, accounted for over 80% of the summed force of all flexors, and therefore were the major contributors to the joint flexion at the distal interphalangeal (DIP), proximal interphalangeal (PIP), and metacarpophalangeal (MCP) joints. When the point of force application was at the DIP joint, the FDS accounted for more than 70% of the total force of all flexors, and was the major contributor to the PIP and MCP joint flexion. When the force of application was at the PIP joint, the intrinsic muscle group was the major contributor for MCP flexion, accounting for more than 70% of the combined force of all flexors. The results suggest that the effects of the extensor mechanism on the flexors are relatively small when the location of force application is distal to the PIP joint. When the external force is applied proximally to the PIP joint, the extensor mechanism has large influence on force production of all flexors. The current study provides an experimental protocol and biomechanical models that allow estimation of the effects of extensor mechanism on both the extrinsic and intrinsic flexors in various loading conditions, as well as differentiating the contribution of the intrinsic and extrinsic finger flexors during isometric flexion.     

Analysis of the gliding pattern of the canine flexor digitorum profundus tendon through the A2 pulley

Friction between a tendon and its pulley was first quantified using the concept of the arc of contact. Studies of human tendons conformed closely to a theoretical nylon cable/nylon rod model. However, we observed differences in measured friction that depended on the direction of motion in the canine model. We hypothesized that fibrocartilaginous nodules in the tendon affected the measurements and attempted to develop a theoretical model to explain the observations we made. Two force transducers were connected to each end of the canine flexor digitorum profundus tendon and the forces were recorded when it was moved through the A2 pulley toward a direction of flexion by an actuator and then reversed a direction toward extension. The changes of a force as a function of tendon excursion were evaluated in 20 canine paws. A bead cable/rod model was developed to simulate the canine tendon-pulley complex. To interpret the results, a free-body diagram was developed. The two prominent fibrocartilaginous nodules in the tendon were found to be responsible for deviation from a theoretical nylon cable gliding around the rod model, in a fashion analogous to the effect of the patella on the quadriceps mechanism. A bead cable/rod model qualitatively reproduced the findings observed in the canine tendon-pulley complex. Frictional coefficient of the canine flexor tendon-pulley was 0.016+/-0.005. After accounting for the effect created by the geometry of two fibrocartilaginous nodules within the tendon, calculation of frictional force in the canine tendon was possible.     

Connective tissue reinforcing structures of the digital tendon sheaths of the human hand

At a greater number of humid preparated human hands, all the ligamentous supports of the digital tendon sheath were exposed and their dimensions were determined. The osteofibrous channels, which contain the long flexor tendons of the digits, were bounded on the one hand by transversely concave shaft areas of the phalanges and the palmar ligaments and on the other side by the fibrous parts of the tendon sheath. From the second to the 5th finger, it has a regular extension of length, which begins proximal at the heads of the metacarpal bones and runs distal to the base of the nail phalanx. In some cases, there is a continuous communication between the digital tendon sheath of the little finger and the carpal synovial sheath. The tendon sheath of the flexor pollicis longus muscle in comparison with it is always in an open communication with the radial synovial sac of the wrist. At the fibrous supports of the digital tendon sheath, one can find constant and inconstant ligamentous structures. Regular shaped ligaments consist of annular fibers (A1 to A5). The proximal complex of fiber supports is a formation of the A1 and A2 ligaments. The band A1 can be divided into 2 ligaments both of roughly equal length, which lay between the head of the metacarpal bone and the base of the proximal phalanx. The strongest fibrous support of the whole digital tendon sheath represents the band A2. It is attached to the midth of the proximal phalanx and increases in strength from proximal to distal. The middle length varies between 6.7 mm at the thumb and 18.7 mm at the middle finger. The distal margin is strengthened by fibrocartilage tissue to be in accordance with the important function as a pulley. The annular band A4 forms the distal supporting complex height above the shaft of the middle phalanx. At the 2nd to the 5th finger it is, with a middle length of 6 to 7 mm, very much shorter than A2 and restrains first of all the tendon of the flexor digitorum profundus muscle. In the area of the interphalangeal joints, we can find the annular bands A3 and A5, which fiber texture is formed variable. Both ligaments are attached on either both sides with the joint capsule and the palmar plate. The other inconstant supports of the digital sheaths are systematically recorded indeed (C1 to C3), but only in exceptional cases they exist of cruciform fibers (Lig. cruciatum).(ABSTRACT TRUNCATED AT 400 WORDS)     

Finger-specific flexor recruitment in humans: depiction by exercise-enhanced MRI.

To evaluate the spatial distribution of human forearm musculature stressed by finger-specific exercise, magnetic resonance imaging was performed in conjunction with exercise protocols designed to separately stress the flexor digitorum superficialis and flexor digitorum profundus. These muscles were shown to consist of subvolumes selectively recruited by flexion of the individual fingers. Knowledge of the finger-specific regions of muscle recruitment during finger flexion could improve sampling accuracy in electromyography, biopsy, magnetic resonance spectroscopy, and invasive vascular sampling studies of hand exercise.     

A kinematic model of the flexor tendons of the hand

The multi-joint model is a kinematic simulation of the long flexor tendons of the fingers. The tendons modeled are the flexor pollicis longus, the flexor digitorum profundus, and the flexor digitorum superficialis. The simulated tendons are displayed on an Evans and Sutherland PS330 color graphics terminal attached to a display of articulated bones of the hand. As a user changes the position of the joints of the simulated hand, the simulation displays the new tendon path and the excursion of the tendon for the new position of the hand. The multi-joint model is one component of a comprehensive model for use in a hand biomechanics computer workstation.     

A new friction tester of the flexor tendon.

We have developed a new device to measure the friction force and calculate the friction coefficient between a rabbit flexor tendon, a pulley and a proximal phalanx. The flexor digitorum fibularis tendon of a rabbit was taken intact with the proximal phalanx, and tendon pulleys were attached to both ends of the bone. Both ends of the tendon were clamped to acrylic plates and connected to stainless-steel plates equipped with strain gauges. A pretension of 1.96 N was applied so as not to loosen the tendon. The proximal phalanx was fixed to an acrylic plate on the actuator, which gave 8 mm of transfer to the acrylic plate at a speed of 2 mm/s. The interface between the tendon and the surrounded tissue created the friction force, when the load was applied on the distal pulley. The friction force could be obtained from the difference between the tension of both ends of the tendon, which was measured with strain gauges and sampled with a personal computer. The friction force and the friction coefficient were calculated from the measured force and the applied load. The load and the pre-loading time, which was defined as loading duration before gliding, were varied in order to observe the change of the friction coefficient. The friction coefficient was not affected by the load and increased with the pre-loading time. The value of mu(s) ranged from 0.027 to 0.111 (0.072 +/- 0.023), and that of (mu)d ranged from 0.010 to 0.069 (0.039 +/- 0.014) (pre-loading time was 5 s). Our method will allow for the examination of various surgical treatments and lubricants. Moreover, it can be applied to other tissues of any animals with similar structures to the rabbit's digitorum.     

In vivo forces generated by finger flexor muscles do not depend on the rate of fingertip loading during an isometric task

Risk factors for activity-related tendon disorders of the hand include applied force, duration, and rate of loading. Understanding the relationship between external loading conditions and internal tendon forces can elucidate their role in injury and rehabilitation. The goal of this investigation is to determine whether the rate of force applied at the fingertip affects in vivo forces in the flexor digitorum profundus (FDP) tendon and the flexor digitorum superficialis (FDS) tendon during an isometric task. Tendon forces, recorded with buckle force transducers, and fingertip forces were simultaneously measured during open carpal tunnel surgery as subjects (N=15) increased their fingertip force from 0 to 15N in 1, 3, and 10s. The rates of 1.5, 5, and 15N/s did not significantly affect FDP or FDS tendon to fingertip force ratios. For the same applied fingertip force, the FDP tendon generated more force than the FDS. The mean FDP to fingertip ratio was 2.4+/-0.7 while the FDS to tip ratio averaged 1.5+/-1.0 (p<0.01). The fine motor control needed to generate isometric force ramps at these specific loading rates probably required similar high activation levels of multiple finger muscles in order to stabilize the finger and control joint torques at the force rates studied. Therefore, for this task, no additional increase in muscle force was observed at higher rates. These findings suggest that for high precision, isometric pinch maneuvers under static finger conditions, tendon forces are independent of loading rate.     

Insertions and functions of certain flexor muscles in the hind leg of rodents

This survey includes 58 genera of rodents from 26 families. The medial tarsal bone is probably unique to the order. Its presence, nature, and constant relationship with M. tibialis posterior are discussed. This muscle inverts and supinates the pes at the astragulo-navicular joint and moves the ankle. The M. flexor tibialis inserts on the medial sesamoid, on this sesamoid and the integument, on the sesamoid and the tendon of M. flexor fibularis, on the latter tendon only, or on the integument only. The occurrence, nature, and cam-like action of the sesamoid are described. A distal segment of the tendon of M. flexor tibialis usually extends from the sesamoid to either the first phalanx of the first digit or to fascia of an adjacent muscle. Functions of the medial sesamoid include (1) stabilization of the tendon of M. flexor tibialis, (2) deflection of this tendon to benefit flexion of the first phalanx, (3) winching of the medial tarsal ligament to flex the first metatarsal, (4) control of the angle of insertion of the tendon to provide flexion or abduction of the first digit as appropriate during swimming, (5) mechanical multiplication of the tension in the tendon between the segments proximal and distal to the sesamoid, and (6) longitudinal folding of the sole of the pes to grip the substrate, as in climbing.     

Effect of early mobilization on healing of nerve repair: histologic observations in a canine model

The effect of early mobilization on the healing of nerve repair was studied in a canine model. Median and ulnar nerves in the left wrist of 16 adult mongrel dogs were transected and immediately repaired. No motion of the repaired forelimb was allowed in the immobilized group (n = 10), while controlled passive motion between 30 and 90 degrees of wrist flexion was begun on the first postoperative day for 10 minutes twice daily in the mobilized group (n = 6). The pattern of revascularization and collagen formation at neurorrhaphy was examined by transillumination of India ink-injected specimen and by conventional histologic sections. Revascularization of nerve repair was found to occur by ingrowth of capillaries from proximal and distal nerve ends, which typically crossed the neurorrhaphy by 3 weeks in the immobilized group. Following early mobilization, there was a persistent "hypovascular zone" at the nerve repair site for up to 6 weeks. In addition, more scar tissue was generated by early motion according to gross observation and quantitative collagen analysis. Early mobilization, therefore, seems to impede nerve regeneration by delaying revascularization and enhancing scar formation.     

A probabilistic finger biodynamic model better depicts the roles of the flexors during unloaded flexion

Previous deterministic finger biomechanical models predicted that the flexor digitorum superficialis (FDS) was silent and the flexor digitorum profundus (FDP) was the only active flexor during finger flexion. Experimental studies in vivo, however, recorded activities of both flexors. In this study, in an attempt to elucidate the roles of the flexors, a probabilistic biodynamic model of the index finger was constructed to estimate the muscle–tendon forces during an experimentally measured index finger flexion movement.A Monte-Carlo simulation was performed with four model parameters, including moment arms, physiological cross sectional areas (PCSA), passive torques, and anthropometric measures as independent random variables. The muscle-tendon forces at each time point were determined using a nonlinear optimization technique. The model predicted that both FDS and FDP contributed to sustaining the movement and the FDS was not necessarily silent. The two distinct force patterns observed in vivo in experimental studies were also corroborated by the simulation. These findings, contrary to previous deterministic models’ predictions but in agreement with experimental measurements, explained the observed coactivation of FDS and FDP, and resolved the controversy regarding the roles of the flexors in finger movement dynamics.     

Macroscopic and microscopic analyses in flexor tendons of the tarsometatarso‐phalangeal joint of ostrich (Struthio camelus) foot with energy storage and shock absorption

Flexor tendons function as energy storage and shock absorption structures in the tarsometatarso‐phalangeal joint (TMTPJ) of ostrich feet during high‐speed and heavy‐load locomotion. In this study, mechanisms underlying the energy storage and shock absorption of three flexor tendons of the third toe were studied using histology and scanning electron microscopy (SEM). Macroscopic and microscopic structures of the flexor tendons in different positions of TMTPJ were analyzed. Histological slices showed collagen fiber bundles of all flexor tendons in the middle TMTPJ were arranged in a linear‐type, but in the proximal and distal TMTPJ, a wavy‐type arrangement was found in the tendon of the M. flexor digitorum longus and tendon of the M. flexor perforans et perforatus digiti III, while no regular‐type was found in the tendon of the M. flexor perforatus digiti III. SEM showed that the collagen fiber bundles of flexor tendons were arranged in a hierarchically staggered way (horizontally linear‐type and vertically linear‐type). Linear‐type and wavy‐type both existed in the proximal TMTPJ for the collagen fiber bundles of the tendon of the M. flexor perforatus digiti III, but only the linear‐type was found in the distal TMTPJ. A number of fibrils were distributed among the collagen fiber bundles, which were likely effective in connection, force transmission and other functions. The morphology and arrangement of collagen fiber bundles were closely related to the tendon functions. We present interpretations of the biological functions in different positions and types of the tendons in the TMTPJ of the ostrich feet.