The effect of partial A2 pulley excision on gliding resistance and pulley strength in vitro

Effects of A2 Pulley Venting on Bowstringing and Tendon Slack: A Biomechanical Investigation

BACKGROUND

A2 pulley release is often needed for exposure of the lacerated tendon, retrieval of retracted tendons, placement of core sutures, or to permit full motion and gliding of the repaired and edematous tendon. However, there is no agreement in the literature on the specific quantity of pulley venting that can be performed and recommendations are limited to an undefined "judicious release" of the pulleys when necessary.

METHODS

Following a previously developed testing protocols, finger kinematics, tendon excursion, and bowstringing were evaluated on cadaveric hands for venting in increments of 20% of the pulley length.

RESULTS

In our study, we found a statistically significant influence of venting on bowstringing, although no difference was found between fingers, and a significant difference in tendon slack, which was variable depending on the finger. Bowstringing started increasing at 20% of A2 venting and peaked at full release. Tendon slack did not start until 40% of A2 venting on the index finger, but started at 20% on the middle, ring, and small fingers.

CONCLUSIONS

Venting of the A2 pulley leads to an incremental increase in tendon bowstringing and tendon slack. However, differences in metacarpophalangeal flexion angle were not observed until full A2 pulley release, and only observed in the index finger, and no differences were observed in proximal interphalangeal flexion angles. Therefore, the benefit of releasing the A2 pulley when clinically necessary will likely outweigh the risks of loss of motion or strength.

Outcomes at 3 Months of a Place and Active Hold Method of Flexor Tendon Rehabilitation Following Zone II Injury

Background: Previous studies have shown that outcomes following a place and active hold (PAH) are better than a passive flexion protocol after a two-strand core-suture repair of flexor tendons injuries in zone II. This study aims to determine the outcomes of a PAH protocol of flexor tendon rehabilitation following a four-strand core-suture plus an epitendinous suture repair of the flexor digitorum profundus (FDP) combined with a simple horizontal loop repair of the flexor digitorum superficialis (FDS). Methods: This is a prospective study of patients with complete injury to both flexor tendons in zone II. All tendons were repaired with a simple horizontal loop for FDS and four-strand core-suture plus epitendinous suture for FDP. The PAH protocol was used postoperatively for 6 weeks. The outcome was evaluated using flexion contracture and total active motion (TAM), interpreted using Strickland criteria and categorised as excellent, good, fair and poor at 6 weeks and 3 months. The linear regression model was used to determine predictors of outcomes. Results: The study included 32 patients with flexor tendon injury in 46 fingers. No repairs ruptured, and 24 (52%) digits achieved good or excellent motion 6 weeks after surgery using the Strickland criteria. According to the Strickland criteria, 41 (89%) digits ranked as excellent and good with no poor result at a 3-month follow-up. Four patients had 5-10° of flexion contracture. Age was the predictor of TAM at 6 weeks and accounted for 13% of its variation. Improvement of TAM from 6 weeks to 3 months was related to age and flexion contracture at 6 weeks. Conclusions: The PAH protocol can be considered a safe technique for flexor rehabilitation after four-strand core-suture repair of FDP in zone II. Level of Evidence: Level IV (Therapeutic).

Tensile load on the flexor digitorum profundus tendon during palmar and lateral blocking exercises: Influence on blocking force and distal interphalangeal joint flexion angle

STUDY DESIGN

This is a basic science research.

INTRODUCTION

Isolating excursion of the flexor digitorum profundus (FDP) in zones I and II is common practice in the current management after flexor tendon repair. During this procedure, the proximal interphalangeal joint is sometimes fully extended with unmeasured external forces at the middle phalanx when the distal interphalangeal joint is actively flexed.

PURPOSE OF THE STUDY

The purpose of the study was to investigate the incremental effect of external force with palmar blocking versus lateral blocking and increased angles of flexion on internal tendon forces at the repair site for a safer application of force by the treating therapist.

METHODS

Eight human cadaveric fingers were studied. To simulate palmar or lateral finger blocking, a compression force of blocking was applied from 5N (510 grams) to 25N (2,550 grams) on the skin surface of the palmar or the lateral aspect of each of these middle phalanges in 5N increments. The tensile load on the FDP tendon during distal interphalangeal joint flexion from 0° to 60° was measured in 10° increments.

RESULTS

During palmar blocking, the tensile load was significantly increased with increases in palmar blocking force. However, no significant increase in the tensile load on the FDP tendon was observed at any lateral blocking.

DISCUSSION

Lateral blocking exercise can be performed with less tensile force on the FDP tendon when performing blocking exercise after flexor tendon injury repair.

CONCLUSIONS

This study supports the concept that lateral blocking with incremental joint angles allows a safer application of force for the healing tendon.

Is releasing pulleys during flexor tendon repair "part and parcel"? Narrative review of the current evidence

BACKGROUND

The complex hand flexors pulleys system is essential in achieving efficient flexor tendons' function. Previous cadaveric studies demonstrated that A2 and A4 are the crucial pulleys in maintaining normal digits biomechanics. Realistically, the preservation of A2 and A4 pulleys during repairing flexor tendon laceration in zones one and two can be extremely challenging. We review the current published evidence in this article to answer the question of whether releasing the pulleys cause bowstringing or affects clinical outcomes.

METHODS

Literature search of the available databases.

RESULTS

There was no published comparative evidence. Retrospective case series have reported that no clinical bowstringing was noted after releasing flexor pulleys during flexor tendon repairs. Outcomes have been reported according to Tang and or Strickland criteria to assess range of motion (ROM). No functional hand scores or patients' satisfactions scores have been reported.

CONCLUSION

Releasing flexor pulleys during tendon repair to allow access or prevent impingement of the repaired tendon does not seem to cause bowstringing or affect outcome based on the limited available evidence. Future research is needed.

LEVEL OF EVIDENCE

Level 4.

[Tenolysis of extensor and flexor tendons of the hand]

BACKGROUND

Unrestricted gliding of extensor and flexor tendons is essential for normal functioning of the hand. If tendon gliding is impaired, a restricted range of motion of finger joints and, finally, joint stiffness result.

OBJECTIVES

To answer the questions about the causes of tenodesis in the hand, which examinations are most informative, how tenolysis is technically performed, and what results can be expected.

METHODS

The reasons, examinations, surgical technique, and results of extensor and flexor tendon tenolysis are presented.

RESULTS

Based on the data in the literature tenolysis of flexor tendons leads to range of motion that is only 50-60% of the preoperative range of motion. In about 20% of patients, deterioration as serious as secondary tendon rupture is observed. Meaningful results of extensor tendon tenolysis have not yet been published.

CONCLUSIONS

Tenolysis of extensor and flexor tendons in the hand is a demanding surgical procedure, and in addition to detailed knowledge of anatomy and biomechanics, it requires sufficient experience-especially following the primary repair of tendon injuries. The earliest indication for tenolysis can occur at about 3 months, usually after 6 months, if continuous intensive hand therapy and splinting have not been successful. General and individual benefits and risks must be carefully weighed. The key to successful tenolysis is the patient's access to and unrestricted participation in competent postoperative treatment, ideally performed by a specialist in hand therapy, which may last for weeks or months.

Zone 2 Flexor Tendon Repair Location and Risk of Catching on the A2 Pulley

PURPOSE

To determine the region of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons in zone 2 that, when involved by a laceration repair, will reliably catch on the A2 pulley after surgery.

METHODS

Using fresh-frozen cadavers (5 hands, 20 digits), excursions of the FDP and FDS tendons were measured in relation to the A2 pulley. The C1, A3, and C2 pulleys were resected. The digit was maximally flexed by applying traction to the flexor tendon in the forearm. An 8-0 suture tag was placed in the flexor tendons immediately distal to the A2 pulley. The digit was then passively fully extended to measure tendon excursion. Measurements were repeated with 50% venting and 100% release of the A4 pulley. Reference points such as tendon insertions and flexion creases were obtained. This protocol was repeated sequentially for the index, middle, ring, and little fingers.

RESULTS

For all 20 fingers, the suture placed into the FDP just distal to the A2 pulley with the finger fully flexed traveled 1.6 ± 1.9 mm distal to the proximal edge of the A4 pulley with passive extension of the finger. The mean excursion for the FDP was 24.6 ± 3.2 mm, and 16.9 ± 3.1 mm for the FDS. The mean A2 pulley length was 16.2 ± 3.5 mm, and the mean distance between the distal edge of the A2 pulley and the proximal edge of the A4 pulley was 23.0 ± 3.3 mm. Venting the A4 pulley 50% and 100% increased FDP excursion a maximum of 0.9 and 1.9 mm, respectively.

CONCLUSIONS

An FDP repair proximal to the A4 pulley will slide under the A2 pulley with full active digital flexion after surgery. If the distal FDP stump lies underneath the A4 pulley with the digit fully extended, the FDP repair will not likely engage the A2 pulley with full flexion after surgery. The FDP excursion can be reliably predicted as a percentage of the A2 (distal) to the A4 (distal) pulley distance. Most importantly, the distance between the repair site and the A4 pulley approximately equals the length of the A2 pulley that requires release to avoid postoperative triggering.

CLINICAL RELEVANCE

Knowledge of this high-risk region of flexor tendon repair will guide surgeons regarding the potential need for partial release of the A2 pulley.

Current Concepts in the Management of Trigger Finger in Adults

Trigger finger (TF) is one of the most common causes of hand disability. Immobilization of TF with a joint-blocking orthosis has been demonstrated to effectively relieve pain and improve function. The efficacy of steroid injections for TF varies based on the number of affected digits and the clinical severity of the condition. Up to three repeat steroid injections are effective in most patients. When conservative interventions are unsuccessful, open surgical release of the A1 pulley effectively alleviates the subjective and objective manifestations of TF and currently remains the benchmark procedure for addressing TF. Although several studies have emerged suggesting that a percutaneous approach may result in improved outcomes, this technique demands a learning curve that may predispose patients to higher risk of procedure-related complications. There is no role for preoperative antibiotics in patients who undergo elective soft-tissue procedures of the hand. WALANT anesthesia has gained popularity because it has been associated with improved patient outcomes and a clear cost savings; however, proper patient selection is critical. Similar to other soft-tissue hand procedures, TF surgery rarely necessitates a postoperative opioid prescription.

The evidence-base for the management of flexor tendon injuries of the hand: Review

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There is no consensus on the optimal flexor tendon repair technique at each anatomical flexor zone.

•

There is paucity of high quality evidence.

•

Heterogenous study designs limit inter-study comparisons.

•

Patient reported outcome measures are crucial but there is a perennial need for robust disease-specific tools to be utilised.

Gliding Resistance After Epitendinous-First Repair of Flexor Digitorum Profundus in Zone II

PURPOSE

The importance of flexor tendon repair with both core and epitendinous suture placement has been well established. The objective of this study was to determine whether suture placement order affects gliding resistance and bunching in flexor digitorum profundus tendons in a human ex vivo model.

METHODS

The flexor digitorum profundus tendons of the index, middle, ring, and little fingers of paired cadaver forearms were tested intact for excursion and mean gliding resistance in flexion and extension across the A2 pulley. Tendons were subsequently transected and repaired with either an epitendinous-first (n = 12) or a control (n = 12) repair. Gliding resistance of pair-matched tendons were analyzed at cycle 1 and during the steady state of tendon motion. The tendon repair breaking strength was also measured.

RESULTS

The mean steady state gliding resistance was less for the epitendinous-first repair than for the control repair in flexion (0.61 N vs 0.72 N) and significantly less in extension (0.68 N vs 0.85 N). Similar results were seen for cycle 1. None of the repairs demonstrated gap formation; however, control repairs exhibited increased bunching. Load to failure was similar for both groups.

CONCLUSIONS

The order of suture placement for flexor tendon repair is important. Epitendinous-first repair significantly decreased mean gliding resistance, allowed for easier placement of core sutures, and resulted in decreased bunching.

CLINICAL RELEVANCE

Epitendinous-first flexor tendon repairs may contribute to improved clinical outcomes compared with control repairs by decreasing gliding resistance and bunching.

Clinical results of releasing the entire A2 pulley after flexor tendon repair in zone 2C

We report the results of complete release of the entire A2 pulley after zone 2C flexor tendon repair followed by early postoperative active mobilization in seven fingers and their comparisons with 33 fingers with partial A2 pulley release. In seven fingers, release of the entire A2 pulley was necessary to allow free gliding of the repairs in five fingers and complete release of both the A2 and C1 pulleys was necessary in two. No bowstringing was clinically evident in any finger. Two fingers required tenolysis. Using Tang's criteria, the function of two digits was ranked as excellent, four good and one fair; there was no failure. The functional return in these seven fingers was similar with that in 33 fingers with partial A2 pulley release; in these patients only one finger required tenolysis. Our results support the suggestion that release of the entire A2 pulley together with the adjacent C1 pulley does not clinically affect finger motion or cause tendon bowstringing, provided that the other pulleys are left intact.

LEVEL OF EVIDENCE

IV.

Flexor tendon injury, repair and rehabilitation

Injuries to the flexor tendons remain among the most difficult problems in hand surgery. Historically, lacerations to the intrasynovial portion of the flexor tendons were thought to be unsuitable for primary repair. Despite continuing advances in our knowledge of flexor tendon biology, repair, and rehabilitation, good results following primary repair of flexor tendons remain challenging to achieve.

Effect of triggering and entrapment on tendon gliding properties following digital flexor tendon laceration: in vitro study on turkey tendon

The optimal management of partial flexor tendon laceration is controversial and remains a clinical challenge. Abnormal tendon gliding (triggering and entrapment) was assessed at the A2 pulley in 40 turkey tendons in three groups: intact, partially divided (palmar or lateral), and trimmed. Testing was of gliding resistance and friction coefficient at 30° and 70° of flexion, loaded with 2 and 4 N. We observed for triggering and entrapment. The changes in gliding properties were compared and analysed using Wilcoxon matched pair testing. A significant difference was found in the change in gliding properties of intact to lacerated and lacerated to trimmed tendons and between tendons that glided normally compared with those exhibiting triggering or entrapment. This suggests that palmar and lateral lacerations which, through clinical examination and visualization, are found to glide normally should be treated with early mobilization. However, partial lacerations that exhibit triggering or entrapment should be trimmed.

Sonographic analyses of pulley and flexor tendon in idiopathic trigger finger with interphalangeal joint contracture

This study investigated the sonographic appearance of the pulley and flexor tendon in idiopathic trigger finger in correlation with the contracture of the interphalangeal (IP) joint in the thumb or proximal IP (PIP) joint in the other digits. Sonographic measurements using axial images were performed in 177 affected digits including 17 thumbs and 34 other digits judged to have IP or PIP joint contracture and 77 contralateral control digits. The A1 pulley of the contracture group was significantly thicker than that of the non-contracture group in all digits, whereas the flexor tendon was thicker only in digits other than the thumb. In the analysis using calculated cut-off values, A1 pulley thickening in the thumb and A1 pulley and flexor tendon thickening in the other digits showed statistically significant correlations with IP or PIP joint contracture. This study sonographically confirmed previous reports showing that enlargement of the flexor tendons contribute to the pathogenesis of PIP joint contracture.

The Effect of Pulley Reconstruction on Maximum Flexion, Bowstringing, and Gliding Coefficient in the Setting of Zone II Repair of FDS and FDP: a Cadaveric Investigation

PURPOSE

The purpose of this experiment was to determine the effect of A2 pulley reconstruction on gliding coefficient (GC), bowstringing, and proximal interphalangeal (PIP) joint maximum flexion angle after zone II repair of flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) lacerations.

METHODS

Fresh frozen cadaver forearms were mounted, and the wrist and MCP joints fixed. FDS and FDP tendons were dissected free, and sequential loads were applied while digital images were captured. The dissected digit with intact native A2 pulley, FDS, and FDP tendons was used as the control (group 1). Zone II lacerations followed by four-stranded repair of FDP plus epitendinous suture and repair of FDS were then performed, and the data recorded (group 2). A2 pulley excision and reconstruction with a loop of palmaris longus autograft was then completed and the specimens sequentially loaded and photographed (group 3). Using the digital images, GC, bowstringing, and maximum flexion angle were calculated.

RESULTS

No difference in maximum flexion angle was observed across the three testing conditions. Zone II laceration and subsequent FDS and FDP tendon repair significantly increased the GC for group 2 specimens; however, pulley reconstruction alleviated some of this increase for group 3. Bowstringing was significantly greater after pulley reconstruction, with a mean increase of 1.9 mm at maximum flexion for group 3 specimens relative to group 1 controls.

DISCUSSION

Strong flexor tendon repairs are needed to prevent gap formation and subsequent triggering; however, the increased bulk from these large repairs can itself produce deleterious triggering, as well as tendon abrasion. Pulley reconstruction, in the setting FDP and FDS repair (group 3), significantly reduced the GC relative to tendon repair alone (group 2). While bowstringing was significantly greater after pulley reconstruction (group 3), it averaged only 1.9 mm over group 1 specimens and did not compromise maximum flexion angle compared to the uninjured controls (group 1) or the isolated tendon repair digits (group 2).

Importance of proximal A2 and A4 pulleys to maintaining kinematics in the hand: a biomechanical study

PURPOSE

The A2 and A4 pulleys have been shown to be important in finger flexor tendon function. Other authors have suggested either reconstruction or venting of portions of these pulleys in an attempt to preserve finger function in certain clinical situations. This study examines the effects of partial incision of these pulleys on finger flexion kinematics and biomechanics.

METHODS

The index and ring fingers of 16 cadaveric hands were studied. The flexor digitorum profundus tendon was isolated and attached to a computer driven servo-motor. Micro-potentiometers measured flexion angles of the metacarpophalangeal, proximal inter-phalangeal and distal inter-phalangeal joints. Joint inertial torques were calculated making use of this experimental kinematic data.

RESULTS

Proximal 50 % incisions of either the A2 or the A4 pulleys resulted in a statistically significant decrease in overall finger motion. This effect was greatest in the proximal inter-phalangeal joint, with a decrease in joint motion, as well as an earlier time to initiation of motion. These changes in finger motion were more pronounced with A2 pulley incision than they were with A4 pulley incision, but the changes were statistically significant in either case. No significant changes in joint inertial torques were shown.

CONCLUSIONS

Our data provides evidence to the importance of the proximal portions of the A2 and A4 pulleys, and may support partial distal incision of these pulleys in certain clinical situations.

Recent developments in flexor tendon repair techniques and factors influencing strength of the tendon repair

Over the last decade, both basic researchers and surgeons have sought to identify the most appropriate techniques to be applied in flexor tendon repairs. Recent developments in experimental tendon repairs and clinical outcomes of newer repair techniques have been reviewed in an attempt to comprehensively summarize the most critical mechanical factors affecting the performance of tendon repairs and the surgical factors influencing clinical outcomes. Among them, attention to annular pulleys, the purchase and tension of the core suture, and the direction and curvature of the path of tendon motion have been found to be determining factors in the results of tendon repair.

Experimental model of trigger finger through A1 pulley constriction in a human cadaveric hand: a pilot study

PURPOSE

Although it can be reasonably assumed that trigger digits occur as the result of a size mismatch in the pulley-tendon system, it is unclear whether locking, histological changes, and nodule formation occur owing to an intrinsically too small pulley or an enlarged digital flexor tendon. Our purposes in this feasibility study were to (1) create a model of trigger digit by pulley constriction in nonpreserved human tissue, (2) measure the change in work of flexion as the force of pulley constriction increased, (3) compare the work of flexion between nontriggering and triggering conditions, and (4) determine whether triggering can occur at the A2, A3, and A4 pulleys under similar conditions.

METHODS

Using a tensiometer, we studied the work of flexion in 4 fingers (thumb, index, middle, and ring) in a human cadaveric hand. The load of flexion was measured as the A1 to A4 pulleys were incrementally constricted in order to induce triggering. Work of flexion was analyzed for differences among trial conditions.

RESULTS

Triggering was successfully induced in all 4 digits through constriction of the A1 pulley. No triggering occurred in any of the A2, A3, or A4 pulley systems in this model.

CONCLUSIONS

We successfully created a trigger model in a human cadaveric hand. Our results demonstrate that the A1 pulley can cause triggering from manual constriction of the pulley alone.

CLINICAL RELEVANCE

A trigger model such as this may allow investigations of pathophysiology, and this may result in novel treatment strategies and modalities.

Tendon healing, edema, and resistance to flexor tendon gliding: clinical implications

Early flexor tendon healing is characterized by peak cellular apoptosis of both inflammatory and tendon cells in the first week, followed by progressively greater tenocyte proliferation in the second and third weeks. Tenocyte apoptosis is a predominant event, but proliferation of tenocytes is minimal in the middle and late healing periods. Edematous subcutaneous tissues, edema of the tendon, the intact annular pulleys, and extensor tendons all greatly contribute to the resistance. Careful consideration of the contributing factors and dynamics offers insight into strategies to reduce repair rupture and maximize tendon gliding through surgery and postoperative motion protocols.

Clinical outcomes of zone II flexor tendon repair depending on mechanism of injury

PURPOSE

To determine whether mechanism of injury affects outcomes of Zone II flexor tendon repairs.

METHODS

We retrospectively analyzed patients who underwent Zone II flexor tendon repair between 2001 and 2010 with a minimum of 12-month follow-up. Exclusion criteria included fingers with fracture, pulley reconstruction, or flexor tendon bowstringing. The saw group injuries were from saws or from tearing mechanisms; the sharp group had clean transection injuries from knives or glass. At final evaluation, primary outcomes were total passive motion (TPM) and total active motion (TAM) at the proximal interphalangeal and distal interphalangeal joints. Secondary comparisons included strength, Disabilities of the Shoulder, Arm, and Hand (DASH) score, percentage of postoperative tendon rupture, and percentage of patients requiring secondary surgery. The saw group had 13 patients with 17 fingers studied. The sharp group had 21 patients with 24 fingers studied. All patients had primary flexor digitorum profundus repairs in Zone II. Operative records review confirmed for all but 1 patient that flexor digitorum profundus injuries were repaired with a minimum of a 4-strand core suture technique. In the saw group, 9 of 14 fingers with a 50% or greater laceration of flexor digitorum superficialis were repaired; in the sharp group, 15 of 18 such flexor digitorum superficialis injuries were repaired. Average follow-up was 4 years (range, 1-9 y).

RESULTS

The saw group had significantly less TAM and TPM compared with the sharp group. There was no significant difference in DASH scores, strength measurements, or tendon rupture rates. The rate of secondary surgery was significantly higher in the saw group.

CONCLUSIONS

Tearing types of injury, such as those caused by saws, led to poorer outcomes for Zone II flexor tendon injuries compared with sharp injuries at an average follow-up of 4 years. Our results can be useful when discussing expected outcomes. Mechanism of injury in Zone II flexor tendon lacerations may eventually help define optimal treatment.

The effects of oblique or transverse partial excision of the A2 pulley on gliding resistance during cyclic motion following zone II flexor digitorum profundus repair in a cadaveric model

PURPOSE

To compare the gliding resistance of flexor tendons after oblique versus transverse partial excision of the A2 pulley in a human cadaveric model, to determine the effect of the angle of pulley trimming.

METHODS

We obtained 36 human flexor digitorum profundus tendons from the index through the little finger and repaired them with a modified Massachusetts General Hospital suture using 4-0 FiberWire. We repaired all tendons with a similar epitendinous stitch. We randomly assigned the tendons to 1 of 3 groups: intact pulley, transverse partial excision, or oblique partial excision. We measured peak and normalized peak gliding resistance between the repairs and the A2 pulley during 1,000 cycles of simulated motion.

RESULTS

There was no significant difference in the peak or normalized peak gliding resistance at any cycle among the 3 groups.

CONCLUSIONS

Both transverse and oblique trimming of the A2 pulley had similar effects on the peak and normalized gliding resistance after flexor tendon repair.

CLINICAL RELEVANCE

When partial pulley resection is needed after flexor tendon repair, the transverse or oblique trimming of pulley edge does not affect repaired tendon gliding resistance.

LENGTHENING THE LOCKING LOOP REPAIR FOR ZONE 2 FLEXOR TENDON LACERATION AND PARTIAL LATERAL RELEASE OF THE TENDON SHEATH

The authors present the clinical outcomes of nine zone 2 flexor tendon repairs using a locking loop technique (i.e. the Modified Pennington technique). The locking loops were located approximately 10 mm away from the lacerated tendon ends to "lengthen" the locking loop repair, as experimentally and clinically recommended. The partial lateral release of the tendon sheath, including the A2 and/or A4 pulley, was performed not only to locate the sutures but also to allow a full range of motion of the repair without catching on the tendon sheath, as clinically recommended. All the patients were followed up for six months or more except for one. All digits were evaluated as excellent or good at the final follow-up by the original Strickland criteria. No rupture occurred and no bowstring of the flexor tendon was observed. The clinical outcomes of the current study indicate that "lengthening" the locking loop repair is effective for zone 2 flexor tendon repair and that the partial lateral release of the tendon sheath, including the A2 and/or A4 pulley, does not result in the bowstring of the flexor tendon.

CLINICAL RESULTS OF EARLY ACTIVE MOBILISATION AFTER FLEXOR TENDON REPAIR

Between 2005 and 2006, ten patients with flexor digitorum profundus zone II injuries were included. The mean age was 41 (19–84) years. One thumb, two index, four middle, one ring and two little fingers were injured. Repair method comprised four-strand core suture and 6-0 circumferential sutures. Post-operative rehabilitation included immediate active extension, progressive passive full flexion and active hold in dorsal block splint. Follow-up was four (three to seven) months. Grip strength, pinch strength, ROM was 90% (70%–90%), 90% (60%–110%) and 90% (80%–100%) of normal digit, respectively. Mayo wrist scores were five excellent, two good and three fair. All patients were satisfied. Compared with another group of ten patients with the same suture method and Kleinert splintage, grip strength, pinch strength and ROM were 50%, 40% and 40% of normal side, respectively. All differences between these two groups were statistically significant (p < 0.01) by paired samples T-test. There was no re-rupture.

Gliding resistance and triggering after venting or A2 pulley enlargement: a study of intact and repaired flexor tendons in a cadaveric model

PURPOSE

This study compared the effect of 2 techniques of pulley management--venting and pulley enlargement (complete A2 incision with pulley repair and sheath closure using a retinacular graft)--on gliding resistance and on the incidence of triggering following zone 2 flexor tendon repairs in human cadaver specimens.

METHODS

In vitro gliding resistance and the incidence of triggering were determined in 10 human cadaver specimens under 5 progressive conditions: (1) intact, (2) tendon repair (both tendons cut and repaired with the sheath intact), (3) condition 2 plus 50% venting of the distal A2 pulley, (4) condition 2 with venting extended to 66% of distal A2, and (5) condition 4 plus pulley enlargement. Triggering was determined in the same specimens by 2 computational algorithms that detected force changes in the load cells used to measure gliding resistance.

RESULTS

Tendon repair increased gliding resistance from the intact condition by an average of 229%. Gliding resistance was reduced in conditions 3, 4, and 5 from the repair condition by 15%, 25%, and 22%, respectively. Triggering commenced with tendon repair in some specimens, and its incidence increased with 50% venting. Further venting reduced triggering, but not as effectively as pulley enlargement did.

CONCLUSIONS

In this cadaveric study, venting and pulley enlargement reduce gliding resistance by equivalent amounts. Triggering persisted despite venting. The surgeon should carefully examine tendon repairs for free gliding. Pulley enlargement might be more effective than venting in reducing the incidence of triggering.

Flexor tendon pulley reconstruction

Flexor tendon pulley reconstruction is relatively uncommon, and many technical treatment options have been described. The paucity of evidence in the literature supporting one technique can make these surgical decisions and surgeries challenging. Here, we present a focused review of the triple loop pulley reconstruction technique.

Digital pulley enlargement allowing early active motion following primary repair of flexor tendons

We present a new technique of pulley enlargement that preserves its continuity without suturing. The principle of this technique is to excise 2 opposite symmetric triangles. For each of these triangles, the incision starts in the middle of the edge of the pulley and ends beyond the middle of its length. The pulley is enlarged over its entire length, both by debridement of the extremities and by plastic deformation. Although this technique precludes complete closure of the digital sheath, it spares the continuity of the pulley and thus allows early active rehabilitation.

Primary tendon sheath enlargement and reconstruction in zone 2: an in vitro biomechanical study on tendon gliding resistance

PURPOSE

To investigate our hypothesis that primary pulley enlargement and repair using an extensor retinaculum graft will reduce tendon repair gliding resistance. The benefit of pulley enlargement has been tested in experimental animals, but its effect on gliding resistance in vitro using human fingers is not known.

METHODS

In vitro gliding resistance in the proximal tendon sheaths (A1 through A3) was measured and compared in 7 cadaver fingers using the method of Uchiyama and colleagues at a fixed 50 degrees over the proximal sheath under 3 conditions: (1) intact tendons with intact proximal sheath; (2) laceration and 2-strand core plus running epitenon repair of the tendons with intact sheath; and (3) repaired tendons with enlargement of the A2 pulley and adjacent proximal sheath by incision and repair with an extensor retinacular graft. Results were analyzed statistically.

RESULTS

Gliding resistance increased from an average of 0.44 N +/- 0.07 in the intact condition to an average of 1.51 N +/- 0.23 (a mean increase of 243%) when the tendons were cut and repaired. Enlarging the proximal sheath by sheath incision and graft repair reduced the gliding resistance from the repair condition to 1.04 N +/- 0.15 (a mean decrease of 31%). These changes are statistically significant.

CONCLUSIONS

In vitro, repaired tendons had a greater resistance to gliding than that of the intact tendons through the proximal sheath when tested by the method of Uchiyama and colleagues. Enlargement and repair with an extensor retinacular graft of the A2 pulley and adjacent sheath significantly reduced resistance to repaired tendon gliding. These findings support further investigation into the concept that primary pulley enlargement may improve tendon function after repair.

Histopathology of the A1 pulley in adult trigger fingers

The histopathology of the central parts of 40 A1 pulleys from adult patients with primary trigger fingers was studied using light and transmission electron microscopes and the findings were compared with those in a control series of 10 normal A1 pulleys. The evaluation of the normal A1 pulley revealed a bi-laminar structure. The deepest layer was composed of dense normal connective tissue. The outermost layer was formed by loose connective tissue. In trigger digits, it was possible to identify a tri-laminar structure. The deepest layer was composed of irregular connective tissue, formed by small collagen fibres and abundant extracellular matrix. A considerable amount of chondroid-metaplasia was present in this layer. The middle layer contained dense, normal connective tissue with some fibrocytes. The outermost layer was formed of loose connective tissue. In conclusion, there was an additional layer in the A1 pulley in pathological cases which was not present in normal pulleys.

Triggering at the distal A2 pulley

We report two cases with triggering at the distal end of the A2 pulley. One was caused by enlargement of the flexor digitorum profundus (FDP) tendon and the other by enlargement of both slips of the flexor digitorum superficialis (FDS) tendon. Both were relieved by reduction tenoplasty and short releases, or venting, of the distal A2 pulley.

Resistance to motion of flexor tendons and digital edema: An in vivo study in a chicken model

PURPOSE

Tissue edema contributes to resistance to motion of flexor tendons during postsurgical exercises. We assessed edema formation and resistance of injured subcutaneous tissue and sheath to motion of the digital flexor tendon in a chicken model.

METHODS

Ninety-four toes of 47 white Leghorn chickens were divided into 6 surgical groups and 1 nonsurgical control. Subcutaneous tissue and the sheath were incised, and the skin incision and the subcutaneous tissue were closed surgically. The toes were evaluated morphologically for severity of edema and tested for the force and work required to move the tendon. The evaluation time points were 1, 2, 3, 4, 5, and 7 days after surgery. Edema in the toes was scored according to severity and extent. The force and energy required to move the tendon were measured at the first and sixth cycles after cyclic loading in a testing machine with customized software and were statistically analyzed.

RESULTS

The force and work increased progressively for the first 4 days, and were relatively consistent from days 4 to 7. The severity of edema peaked at the third and fourth days. At each postsurgical day, edema scores corresponded to increases in the force and work. The force and work were reduced drastically (30%-50%) after the first 6 cycles of toe motion.

CONCLUSIONS

Resistance to tendon motion increased for the initial 4 days after surgery and remained comparatively consistent from the fourth to the seventh days. The severity of digital edema peaks at the third and fourth postoperative days. Motion of the digits for several cycles greatly reduces the resistance to the subsequent movement. We believe that tendon mobilization should not necessarily be started within the initial postoperative days, the optimum time to begin probably is the period from the fourth to the seventh day after surgery, and that judgment of edema helps to determine how aggressive exercise should be.

Investigation of resistance of digital subcutaneous edema to gliding of the flexor tendon: an in vitro study

PURPOSE

Although edema generally is considered to contribute to resistance to tendon mobilization and is a cause of tendon overload during postoperative motion exercise, it is unclear exactly how edema of the peritendinous tissues affects tendon mobilization. We assessed the effects of simulated subcutaneous edema on the gliding resistance of the flexor tendon in an in vitro model using chicken toes.

METHODS

Thirty long toes of white Leghorn chickens were used. Twenty-two toes were divided into 2 groups and another 8 toes were used to determine the preconditions needed. In group 1 we produced 3 levels of edema severity in the subcutaneous tissue over a 1-cm segment by means of saline injection. In group 2 we created moderate tissue edema over 1-cm, 2-cm, or 3-cm segments of the toes. The work required to move the flexor digitorum profundus tendon over a fixed excursion and ultimate force were recorded with a testing machine after each run of flexion.

RESULTS

Work and ultimate force increased significantly in the toes with simulated tissue edema in proportion to the severity and area of the edema. Even the least severe edema increased the work and force; a further increase to moderate edema tripled the energy needed to flex the toes. Increases in edema from 1-cm to a 2-cm and then to a 3-cm toe segment increased the work and force for each increment of extension.

CONCLUSIONS

Simulated edema significantly increases energy and force required to move the tendons. The increase in resistance was proportionate to the severity and area of the edema. These results suggest that postoperative edema may increase significantly the resistance to tendon motion and that limiting both the severity and size of edema likely will reduce the resistance.