Comparison of a new multifilament stainless steel suture with frequently used sutures for flexor tendon repair

Initial Experience with the PONTiS Tendon Repair System in Traumatic Upper Extremity Injuries

BACKGROUND

Tendon injuries of the upper extremity remain a common surgical condition requiring prompt intervention. We review our initial experience with the PONTiS flexor tendon repair system (PFRS) - a knotless, multifilament stainless steel crimp system.

METHODS

Consecutive patients undergoing repair by our plastic and orthopedic surgeons with the PFRS were reviewed from 2015-2017. Multivariate risk and Kaplan-Meier survival analyses were performed to assess risk factors associated with complications.

RESULTS

Eighty-one patients with mean follow up of 75 days (range 0 - 33 months) were identified. The most common demographics of our patients were right-handed (82.9%), male (71.4%), laborer (35.7%), sustaining laceration injuries (77.1%) at zone 2 (27.2%). There was an average of 3.7 tendon injuries per patient. Associated injuries included fractures (21.4%), arterial injuries (24.3%), and nerve injuries (61.4%). Thirteen (16.0%) patients developed complications: adhesions/contracture (4), rupture (2), flap ischemia (2), arterial thrombosis (1), wound dehiscence (1), tendon lag (1), and erosion of the PFRS through soft-tissue grafts (2). Multivariate analysis identified poor soft-tissue coverage (OR 9.990; p=0.043) and zone 2 involvement (OR 7.936; p=0.016) as risk factors, while epitendinous repairs (OR 0.096; p=0.010) were protective against complications.

CONCLUSIONS

The PFRS system is rapid and simple to deploy and advantageous especially in multiple traumatic tendon injuries. Compared to traditional suture repair, it has a comparable overall complication profile but superior rupture and tenolysis rates. We advise use with caution in cases with poor soft tissue coverage to minimize risks of extrusion and strongly recommend the use of epitendinous sutures concurrently to limit complications.

The effect of fibrin formulation on cell migration in an in vitro tendon repair model

BACKGROUND

The purpose of this study was to determine the effect of fibrinogen concentration on cell viability and migration in a tissue culture tendon healing model.

METHODS

Forty-eight canine flexor digitorum profundus tendons were randomly divided into three groups. In each group the tendons were lacerated and repaired augmented with a canine bone marrow stromal cell seeded fibrin interposition patch using either 5 mg/ml fibrinogen and 25 U/ml thrombin (physiological as a control), 40 mg/ml fibrinogen and 250 U/ml thrombin (low adhesive), or 80 mg/ml fibrinogen and 250 U/ml thrombin (high adhesive). The sutured tendons were cultured for two or four weeks.

RESULTS

Failure load was not significantly different among the groups. Cell-labeling staining showed that the stromal cells migrated across the gap in the control and low adhesive groups, but there was no cell migration in the high adhesive group at two weeks.

CONCLUSION

A high fibrinogen concentration in a fibrin patch or glue may impede early cell migration.

LEVEL OF EVIDENCE

Not applicable because this study was a laboratory study.

Wire Extrusion After Flexor Tendon Repair with a Multifilament Stainless Steel Cable-Crimp Suture System: A Case Report

CASE

We report the case of a 22-year-old man with a ruptured flexor tendon repair associated with wound drainage. The patient subsequently underwent flexor tendon revision with a multifilament stainless steel cable-crimp suture system. Two years after the revision repair, a blister ruptured over the patient's operative site, exposing the stainless steel wire from the revision repair. The wire was removed, and the patient regained full flexion.

CONCLUSIONS

As extrusion of metallic suture material from the skin represents a complication, surgeons should be prepared to recognize this rare complication and to preoperatively counsel patients as to this risk.

Biomechanical Comparison of Tendon Coaptation Methods With a Meshed Suture Construct

PURPOSE

Tendon-to-tendon attachment constructs for tendon reconstructions or transfers need to be secure in order to allow early mobilization after surgery. The purpose of this study was to biomechanically compare 2 common constructs secured with a novel mesh suture versus a nonabsorbable braided suture.

METHODS

We used 100 cadaveric tendons to create 5 different tendon coaptation constructs (a to e) (10 coaptations per group): (a) Pulvertaft weave with a braided suture (PTe); (b) mesh suture (PTm); (c) single-pass, side-to-side (SP-STS) coaptation with 30-mm overlap using a mesh suture (SP-STS-30m); (d) SP-STS 50-mm overlap with a mesh suture (SP-STS-50m); and (e) SP-STS with 30-mm tendon overlap using a braided suture (SP-STS-30e). The tensile strength, bulk, gliding resistance, and failure type were compared.

RESULTS

There was no difference between the various tendon constructs and the suture type in terms of coaptation bulk. All SP-STS constructs with mesh suture had higher peak gliding resistance than any of the PT constructs regardless of suture type. Compared with the PT constructs, the SP-STS constructs with mesh or braided suture had a higher peak load, peak load normalized to repair length, and stiffness. Within each tendon coaptation construct group, Pulvertaft or SP-STS, the suture type did not affect any of the investigated parameters.

CONCLUSIONS

The SP-STS constructs are significantly stronger and stiffer than the PT constructs. The SP-STS with mesh suture exhibited greater gliding resistance than the PT constructs and may result in greater gliding resistance through physiological tissue planes. However, the use of a mesh suture did not affect strength, bulk, gliding resistance, or failure type when compared within a construct group.

CLINICAL RELEVANCE

The use of SP-STS constructs for tendon coaptations produces a stronger and stiffer construct than the PT weave; however, the use of a mesh suture may not provide any benefit over a braided suture.

A Modified Flexor Tendon Suture Technique Combining Kessler and Loop Lock Flexor Tendon Sutures

OBJECTIVES

In the present study, a novel single knot tenorrhaphy was developed by combining the modified Kessler flexor tendon suture (MK) with the loop lock technique.

METHODS

A total of 48 porcine flexor digitorum profundus tendons were collected and randomly divided into six groups. The tendons were transversely cut and then repaired using six different techniques, the MK method, double knot Kessler-loop lock flexor tendon suture (DK), and single knot Kessler-loop lock flexor tendon suture (SK), each in combination with the epitendinous suture (P), and the same three techniques without P. Furthermore, by performing the load-to-failure tests, the biomechanical properties and the time taken to complete a repair, for each tenorrhaphy, were assessed.

RESULTS

Compared to the MK+P method, DK+P was more improved, thereby enhancing the ultimate tensile strength. The SK+P method, which required fewer knots than DK+P, was easier to perform. Moreover, the SK+P repair increased the force at a 2-mm gap formation, while requiring lesser knots than DK+P.

CONCLUSION

As opposed to the traditional MK+P method, the SK+P method was improved and exhibited better biomechanical properties, which may facilitate early mobilization after the repair.

A Controlled Trial Evaluating the Safety and Effectiveness of Ultrasound-Guided Looped Thread Carpal Tunnel Release

Background: Open carpal tunnel release typically requires several weeks of recovery. A less invasive, ultrasound-guided percutaneous technique of releasing the transverse carpal ligament using a thread (thread carpal tunnel release [TCTR]) has been described. To date, its clinical effectiveness and safety have been evaluated exclusively by the group that developed the technique, using a single outcome measure without a control comparison. The objective of this study was to independently evaluate the safety and effectiveness of TCTR using multiple outcome measures and a control comparison. Methods: A convenience sample of 20 participants with refractory moderate or severe carpal tunnel syndrome underwent TCTR of their most symptomatic hand. Outcome measures included pre-TCTR and 1-, 3-, and 6-month post-TCTR Boston questionnaire; pre-, 3-, and 6-month post-TCTR monofilament sensibility, strength, ultrasound, and electrodiagnostic testing; weekly post-TCTR phone interviews for 1 month; and satisfaction surveys at 3 and 6 months post-TCTR. Results: No complications were reported. During the month post-TCTR, significant prompt improvements in hand pain and dysfunction occurred. The following significant improvements were demonstrated in the treated versus control hand: Boston Questionnaire scores, median nerve distal motor latency, transcarpal tunnel motor and sensory conduction velocities and sensory nerve action potential amplitudes. No significant differences in sensibility, pinch or grip strength, median nerve cross-sectional area (CSA) at the carpal tunnel inlet, or wrist: forearm median nerve CSA ratio were documented between TCTR and control sides. Satisfaction with the TCTR procedure was high (85%-90%). Conclusions: This study supports previous reports that the TCTR procedure is safe and effective.

Biomechanical Study of a Multifilament Stainless Steel Cable Crimp System Versus a Multistrand Ultra-High Molecular Weight Polyethylene Polyester Suture Krackow Technique for Achilles Tendon Rupture Repair

Currently, Achilles tendon rupture repair is surgically addressed with an open or minimally invasive approach using a heavy, nonabsorbable suture in a locking stitch configuration. However, these sutures have low stiffness and a propensity to stretch, which can result in gapping at the repair site. Our study compares a new multifilament stainless steel cable-crimp repair method to a standard Krackow repair using multistrand, ultra-high molecular weight polyethylene polyester sutures. Eight matched pairs of cadavers were randomly assigned for Achilles tendon repair using either Krackow technique with polyethylene polyester sutures or the multifilament stainless steel cable-crimp technique. Each repair was cyclically loaded from 10 to 50 N for 100 loading cycles, followed by a linear increase in load until complete failure of the repair. During cyclic loading, 4 of the 8 Krackow polyethylene polyester suture repairs failed, whereas none of the multifilament stainless steel cable crimp repairs failed. Load to failure was greater for the multifilament stainless steel cable crimp repairs (321.03 ± 118.71 N) than for the Krackow polyethylene polyester suture repairs (132.47 ± 103.39 N, p = .0078). The ultimate tensile strength of the multifilament stainless steel cable crimp repairs was also greater than that of the Krackow polyethylene polyester suture repairs (485.69 ± 47.93 N vs 378.71 ± 107.23 N, respectively, p = .12). The mode of failure was by suture breakage at the crimp for all cable-crimp repairs and by suture breakage at the knot, within the tendon, or suture pullout for the polyethylene polyester suture repairs. The multifilament stainless steel cable crimp construct may be a better alternative for Achilles tendon rupture repairs.

Biomechanical Properties of a Novel Mesh Suture in a Cadaveric Flexor Tendon Repair Model

PURPOSE

Conventional suture repairs, when stressed, fail by suture rupture, knot slippage, or suture pull-through, when the suture cuts through the intervening tissue. The purpose of this study was to compare the biomechanical properties of flexor tendon repairs using a novel mesh suture with traditional suture repairs.

METHODS

Sixty human cadaveric flexor digitorum profundus tendons were harvested and assigned to 1 of 3 suture repair groups: 3-0 and 4-0 braided poly-blend suture or 1-mm diameter mesh suture. All tendons were repaired using a 4-strand core cruciate suture configuration. Each tendon repair underwent linear loading or cyclic loading until failure. Outcome measures included yield strength, ultimate strength, the number of cycles and load required to achieve 1-mm and 2-mm gap formation, and failure.

RESULTS

Mesh suture repairs had significantly higher yield and ultimate force values when compared with 3-0 and 4-0 braided poly-blend suture repairs under linear testing. The average force required to produce repair gaps was significantly higher in mesh suture repairs than in conventional suture. Mesh suture repairs endured a significantly greater number of cycles and force applied before failure compared with both 3-0 and 4-0 conventional suture.

CONCLUSIONS

This ex vivo biomechanical study of flexor tendon repairs using a novel mesh suture reveals significant increases in average yield strength, ultimate strength, and average force required for gap formation and repair failure with mesh suture repairs compared with conventional sutures.

CLINICAL RELEVANCE

Mesh suture-based flexor tendon repairs could lead to improved healing at earlier time points. The findings could allow for earlier mobilization, decreased adhesion formation, and lower rupture rates after flexor tendon repairs.

[Suture techniques and material in surgery of flexor tendons]

Adhesions and scar formation between flexor tendons and the surrounding tissue are only contemporarily avoidable by movement of flexor tendons. Concepts with active follow-up protocols are more favorable than passive mobilization. The main risks of flexor tendon repair are rupture of the tendon suture, insidious gap formation and resistance to tendon gliding within the tendon sheath. Currently, there is no consensus with respect to the optimal suture technique or suture material. Nevertheless, there are some principles worth paying attention to, such as using stronger suture material, blocking stitches, suture techniques with four or more strands as well as circular running sutures. A technically acceptable compromise, even for the less experienced, is currently the four-strand suture combined with a circular running suture. It maintains sufficient stability for active motion follow-up protocols without resistance.

Effect of Fibrin Formulation on Initial Strength of Tendon Repair and Migration of Bone Marrow Stromal Cells in Vitro

BACKGROUND

Cell-based tissue engineering techniques have been introduced to improve tendon repair outcomes. The purpose of this study was to determine optimal concentrations of fibrinogen and thrombin for use as a scaffold to deliver stromal cells to the tendon repair site.

METHODS

Lacerated flexor digitorum profundus tendons from forty canine forepaws underwent simulated repair with fibrin gel interposition. The tendons were divided into five groups with different ratios of fibrinogen (mg/mL) to thrombin (NIH units/mL) used to form the gels. These ratios, which ranged from those found in normal hemostasis to those used clinically as adhesives, were 5:25 (the physiological ratio, used as a control), 40:250 (a low adhesive concentration of fibrinogen and a low adhesive concentration of thrombin [low-low group]), 80:250 (high-low group), 40:500 (low-high group), and 80:500 (high-high group). The failure load and tensile stiffness at time zero, compressive stiffness of the fibrin gel, and cell viability and migration were evaluated.

RESULTS

The failure loads of the high-low and high-high groups were significantly higher than that of the control group. The tensile stiffness of the high-high group was significantly higher than that of the control group. The high-low and high-high groups had significantly higher compressive stiffness than the other groups. While there was no significant difference among the groups regarding cell viability, the cells in the control, low-low, and low-high gels were spindle-shaped whereas those in the high-low and high-high groups were rounded. Cells migrated across scratch gaps within twenty-four hours in the control, low-low, and low-high groups, but not in the high-low and high-high groups.

CONCLUSIONS

Higher concentrations of fibrinogen resulted in stronger and stiffer gels, but the strength was far less than that of a tendon suture and these gels were associated with a more rounded cell morphology and reduced cell migration. Therefore, lower concentrations of fibrinogen should be used if a fibrin gel is employed to deliver cells for tendon repair.

CLINICAL RELEVANCE

Concentrations of fibrinogen lower than those used in fibrin glue may be more appropriate if fibrin is employed to create a cell delivery matrix for tendon repair.

Comparison of Flexor Tendon Suture Techniques Including 1 Using 10 Strands

PURPOSE

To compare mechanical properties of a multistrand suture technique for flexor tendon repair with those of conventional suture methods through biomechanical and clinical studies.

METHODS

We describe a multistrand suture technique that is readily expandable from 6 to 10 strands of core suture. For biomechanical evaluation, 60 porcine flexor tendons were repaired using 1 of the following 6 suture techniques: Kessler (2-strand), locking cruciate (4-strand), Lim/Tsai's 6-strand, and our modified techniques (6-, 8-, or 10-strand). Structural properties of each tenorrhaphy were determined through tensile testing (ultimate failure load and force at 2-mm gap formation). Clinically we repaired 25 flexor tendons using the described 10-strand technique in zones I and II. Final follow-up results were evaluated according to the criteria of Strickland and Glogovac.

RESULTS

In the biomechanical study, tensile properties were strongly affected by repair technique; tendons in the 10-strand group had approximately 106%, 66%, and 39% increased ultimate load to failure (average, 87 N) compared with those in the 4-, 6-, and 8-strand groups, respectively. Tendons in the 10-strand group withstood higher 2-mm gap formation forces (average, 41 N) than those with other suture methods (4-strand, 26 N; 6-strand, 27 N; and 8-strand, 33 N). Clinically, we obtained 21 excellent, 2 good, and 2 fair outcomes after a mean of 16 months (range, 6-53 mo) of follow-up. No patients experienced poor results or rupture.

CONCLUSIONS

The 10-strand suture repair technique not only increased ultimate strength and force at the 2-mm gap formation compared with conventional suture methods, it also showed good clinical outcomes. This multistrand suture technique can greatly increase the gap resistance of surgical repair, facilitating early mobilization of the affected digit.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

A comparative study of the effects of growth and differentiation factor 5 on muscle-derived stem cells and bone marrow stromal cells in an in vitro tendon healing model

PURPOSE

To investigate the ability of muscle-derived stem cells (MDSCs) supplemented with growth and differentiation factor-5 (GDF-5) to improve tendon healing compared with bone marrow stromal cells (BMSCs) in an in vitro tendon culture model.

METHODS

Eighty canine flexor digitorum profundus tendons were assigned into 5 groups: repaired tendon (1) without gel patch interposition (no cell group), (2) with BMSC-seeded gel patch interposition (BMSC group), (3) with MDSC-seeded gel patch interposition (MDSC group), (4) with GDF-5-treated BMSC-seeded gel patch interposition (BMSC+GDF-5 group), and (5) with GDF-5-treated MDSC-seeded gel patch interposition (MDSC+GDF-5 group). After culturing for 2 or 4 weeks, the failure strength of the healing tendons was measured. The tendons were also evaluated histologically.

RESULTS

The failure strength of the repaired tendon in the MDSC+GDF-5 group was significantly higher than that of the non-cell and BMSC groups. The stiffness of the repaired tendons in the MDSC+GDF-5 group was significantly higher than that of the non-cell group. Histologically, the implanted cells became incorporated into the original tendon in all 4 cell-seeded groups.

CONCLUSIONS

Interposition of a multilayered GDF-5 and MDSC-seeded collagen gel patch at the repair site enhanced tendon healing compared with a similar patch using BMSC. However, this increase in vitro was relatively small. In the clinical setting, differences between MDSC and BMSC may not be substantially different, and it remains to be shown that such methods might enhance the results of an uncomplicated tendon repair clinically.

CLINICAL RELEVANCE

Muscle-derived stem cell implantation and administration of GDF-5 may improve the outcome of tendon repair.

Repopulation of intrasynovial flexor tendon allograft with bone marrow stromal cells: an ex vivo model

PURPOSE

Delayed healing is a common problem whenever tendon allografts are used for tendon or ligament reconstruction. Repopulating the allograft with host cells may accelerate tendon regeneration, but cell penetration into the allograft tendon is limited. Processing the tendon surface with slits that guide cells into the allograft substrate may improve healing. The purpose of this study was to describe a surface modification of allograft tendon that includes slits to aid cell repopulation and lubrication to enhance tendon gliding.

METHODS

Canine flexor digitorum profundus tendons were used for this study. Cyclic gliding resistance was measured over 1000 cycles. Tensile stiffness was assessed for normal tendon, tendon decellularized with trypsin and Triton X-100 (decellularized group), tendon decellularized and perforated with multiple slits (MS group) and tendon decellularized, perforated with slits and treated with a carbodiimide-derivatized hyaluronic acid and gelatin (cd-HA-gelatin) surface modification (MS-SM group). To assess tendon repopulation, bone marrow stromal cells (BMSCs) were used in the decellularized and MS groups. DNA concentration and histology were evaluated and compared to normal tendons and nonseeded decellularized tendons.

RESULTS

The gliding resistance of the decellularized and MS groups was significantly higher compared with the normal group. There was no significant difference in gliding resistance between the decellularized and MS group. Gliding resistance of the normal group and MS-SM group was not significantly different. The Young's modulus was not significantly different among the four groups. The DNA concentration in the MS group was significantly lower than in normal tendons, but significantly higher than in decellularized tendons, with or without BMSCs. Viable BMSCs were found in the slits after 2 weeks in tissue culture.

CONCLUSIONS

Tendon slits can successfully harbor BMSCs without compromising their survival and without changing tendon stiffness. Surface modification restores normal gliding function to the slit tendon.

CLINICAL RELEVANCE

A multislit tendon reseeded with BMSCs, with a surface treatment applied to restore gliding properties, may potentially promote tendon revitalization and accelerate healing for tendon or ligament reconstruction applications.

The effect of surface modification on gliding ability of decellularized flexor tendon in a canine model in vitro

PURPOSE

To investigate the gliding ability and mechanical properties of decellularized intrasynovial tendons with and without surface modification designed to reduce gliding resistance.

METHODS

We randomly assigned 33 canine flexor digitorum profundus tendons to 1 of 3 groups: untreated fresh tendons, to serve as a control; tendons decellularized with trypsin and Triton X-100; and tendons decellularized as in group 2 with surface modification using carbodiimide-derivatized hyaluronic acid and gelatin (cd-HA-gelatin). Tendons were subjected to cyclic friction testing for 1,000 cycles with subsequent tensile stiffness testing. We qualitatively evaluated the surface roughness after 1,000 cycles using scanning electron microscopy.

RESULTS

The gliding resistance of the decellularized group was significantly higher than that of both the control and cd-HA-gelatin tendons (0.20, 0.09, and 0.11 N after the first cycle; and 0.41, 0.09, and 0.14 N after 1,000 cycles, respectively). Gliding resistance between the control and cd-HA-gelatin groups was not significantly different. The Young modulus was not significantly different between groups. The surfaces of the control and cd-HA-gelatin-treated tendons appeared smooth after 1,000 cycles, whereas those of the decellularized tendons appeared roughened under scanning electron microscopy observation.

CONCLUSIONS

Decellularization with trypsin and Triton X-100 did not change tendon stiffness. However, although this treatment was effective in removing cells, it adversely altered the tendon surface in both appearance and gliding resistance. Surface modification with cd-HA-gelatin improved the tendon surface smoothness and significantly decreased the gliding resistance.

CLINICAL RELEVANCE

The combination of decellularization and surface modification may improve the function of tendon allografts when used clinically.

Comparison of a multifilament stainless steel suture with FiberWire for flexor tendon repairs--an in vitro biomechanical study

Our goal was to investigate and compare the mechanical properties of multifilament stainless steel suture (MFSS) and polyethylene multi-filament core FiberWire in flexor tendon repairs. Flexor digitorum profundus tendons were repaired in human cadaver hands with either a 4-strand cruciate cross-lock repair or 6-strand modified Savage repair using 4-0 and 3-0 multifilament stainless steel or FiberWire. The multifilament stainless steel repairs were as strong as those performed with FiberWire in terms of ultimate load and load at 2 mm gap. This study suggests that MFSS provides as strong a repair as FiberWire. The mode of failure of the MFSS occurred by the suture pulling through the tendon, which suggests an advantage in terms of suture strength.

Analysis of a knotless flexor tendon repair using a multifilament stainless steel cable-crimp system

PURPOSE

To compare the biomechanical and technical properties of flexor tendon repairs using a 4-strand cruciate FiberWire (FW) repair and a 2-strand multifilament stainless steel (MFSS) single cross-lock cable-crimp system.

METHODS

Eight tests were conducted for each type of repair using cadaver hand flexor digitorum profundus tendons. We measured the required surgical exposure, repair time, and force of flexion (friction) with a custom motor system with an inline load cell and measured ultimate tensile strength (UTS) and 2-mm gap force on a servo-hydraulic testing machine.

RESULTS

Repair time averaged less than 7 minutes for the 2-strand MFSS cable crimp repairs and 12 minutes for the FW repairs. The FW repair was performed with 2 cm of exposure and removal of the C-1 and A-3 pulleys. The C-1 and A-3 pulleys were retained in each of the MFSS cable crimp repairs with less than 1 cm of exposure. Following the FW repair, the average increase in friction was 89% compared with an average of 53% for the MFSS repairs. Six of the 8 MFSS specimens achieved the UTS before any gap had occurred, whereas all of the FW repairs had more than 2 mm of gap before the UTS, indicating that the MFSS was a stiffer repair. The average UTS appeared similar for both groups.

CONCLUSIONS

We describe a 2-strand multifilament stainless steel single cross-lock cable crimp flexor repair system. In our studies of this cable crimp system, we found that surgical exposure, average repair times, and friction were reduced compared to the traditional 4-strand cruciate FW repair. While demonstrating these benefits, the crimp repair also produced a stiff construct and high UTS and 2-mm gap force.

CLINICAL RELEVANCE

A cable crimp flexor tendon repair may offer an attractive alternative to current repair methods. The benefits may be important especially for flexor tendon repair in zone 2 or for the repair of multiple tendons.

Use of suture anchors and new suture materials in the upper extremity

Suture anchors are an important tool in the orthopedist's armamentarium. Their use is prevalent in surgery of the entire upper limb. Suture anchors have mostly obviated the need for multiple drill holes when striving for secure fixation of soft tissue to bone. As with most other orthopedic products, the designs of these anchors and the materials used to fabricate them have evolved as their use increased and their applications became more widespread. It is ultimately the surgeon's responsibility to be familiar with these rapidly evolving technologies and to use the most appropriate anchor for any given surgery.

Managing the injured tendon: current concepts

Despite advances in understanding of the mechanical aspects of tendon management with improved suture technique and early stress application with postoperative therapy, clinical results remain inconsistent after repair, especially within the synovial regions. Complementary research to enhance the intrinsic pathway of healing, suppress the extrinsic pathway of healing, and manipulate frictional resistance to tendon gliding is now the focus of current basic science research on tendons. In the future, application of these new biologic therapies may increase the "safety zone" (or tolerance for load and excursion without dysfunctional gapping) as therapists apply stress to healing tendons and may alter future rehabilitation protocols by allowing greater angles of motion (and thus tendon excursion), increased external load, and decreased time in protective orthoses (splints). However, at this time, the stronger repair techniques and the application of controlled stress remain the best and most well-supported intervention after tendon injury and repair in the recovery of functional tendon excursion and joint range of motion. The hand therapist's role in this process remains a critical component contributing to satisfactory outcomes.

Zone 2 flexor tendon injuries: Venturing into the no man's land

Flexor tendon injuries are seen commonly yet the management protocols are still widely debated. The advances in suture techniques, better understanding of the tendon morphology and its biomechanics have resulted in better outcomes. There has been a trend toward the active mobilization protocols with development of multistrand core suture techniques. Zone 2 injuries remain an enigma for the hand surgeons even today but the outcome results have definitely improved. Biomolecular modulation of tendon repair and tissue engineering are now the upcoming fields for future research. This review article focuses on the current concepts in the management of flexor tendon injuries in zone 2.