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

The current status of various preclinical therapeutic approaches for tendon repair

Tendons are fibroblastic structures that link muscle and bone. There are two kinds of tendon injuries, including acute and chronic. Each form of injury or deterioration can result in significant pain and loss of tendon function. The recovery of tendon damage is a complex and time-consuming recovery process. Depending on the anatomical location of the tendon tissue, the clinical outcomes are not the same. The healing of the wound process is divided into three stages that overlap: inflammation, proliferation, and tissue remodeling. Furthermore, the curing tendon has a high re-tear rate. Faced with the challenges, tendon injury management is still a clinical issue that must be resolved as soon as possible. Several newer directions and breakthroughs in tendon recovery have emerged in recent years. This article describes tendon injury and summarizes recent advances in tendon recovery, along with stem cell therapy, gene therapy, Platelet-rich plasma remedy, growth factors, drug treatment, and tissue engineering. Despite the recent fast-growing research in tendon recovery treatment, still, none of them translated to the clinical setting. This review provides a detailed overview of tendon injuries and potential preclinical approaches for treating tendon injuries.

Principles for Achieving Predictable Outcomes in Flexor Tendon Repair

Flexor tendon injuries require surgical repair. Early repair is optimal, but staged repair may be indicated for delayed presentations. Zone II flexor tendon injuries are the most difficult to achieve acceptable outcomes and require special attention for appropriate repair. Surgical techniques to repair flexor tendons have evolved over the past several decades and principles include core strand repair using at least a 4 strand technique, epitendinous suture to add strength and gliding properties, and pulley venting. Early postoperative active range of motion within the first 3 to 5 days of surgery is essential for optimizing outcomes.

Wrist-Level Tendon Repairs Utilizing a Novel Tendon Stapler Device: An Efficiency and Biomechanical Study

BACKGROUND

A novel tendon stapler device (TSD) to improve the strength and consistency of primary tendon repairs was recently approved by the U.S. Food and Drug Administration. The authors hypothesized that this TSD would demonstrate faster and superior biomechanical properties compared with a standard suture coaptation. The authors also hypothesized that the TSD biomechanical properties would be consistent across participants with differing tendon repair experiences.

METHODS

Participants included a novice, intermediate, and expert in tendon repairs. Timed comparisons were performed in flexor zones IV and V and extensor zones VI and VII on human cadaver arms. Suture repairs were performed with a modified Kessler technique with a horizontal mattress. TSD repairs were performed on the matched donor arms. Biomechanical testing included 2-mm gap force, ultimate failure load, and mode of failure.

RESULTS

In total, 228 tendon coaptations from 12 donor arms were performed and analyzed. TSD coaptations were 3 times faster and withstood nearly 50% higher forces on 2-mm gap testing and roughly 30% higher forces on ultimate failure testing. These findings did not change when the repair times were analyzed by participant. Suture coaptations failed owing to suture pull-through, suture breakage, or knot failure. TSD coaptation failures only occurred from device pull-through.

CONCLUSIONS

The TSD produces significantly faster and stronger primary tendon coaptations compared with a standard 4-strand core suture repair in human donor arms. The findings demonstrated minimal variability among participants with differing tendon repair experience. Although further investigation is needed, this device has potential to revolutionize tendon repairs.

Zone-specific pitfalls in flexor tendon rehabilitation: management and prevention

Despite significant advancements in flexor tendon repair techniques and rehabilitation strategies, achieving complete restoration of digital motion remains a formidable challenge. The most prevalent complications associated with tendon repair are the development of tendon adhesions and joint contractures. Left unaddressed, these complications can further lead to secondary pathomechanical changes, resulting in fixed deformities significantly affecting hand function. This review of zone-specific considerations in flexor tendon rehabilitation provides an in-depth analysis of the dynamics of tendon motion after repair and strategies to minimize common secondary complications.

The value of local dexmedetomidine as an adjuvant to ultrasound-guided wide awake local anesthesia no tourniquet (WALANT) in flexor tendon repair surgeries: a randomized controlled trial

BACKGROUND

The Wide-Awake Local Anesthesia No Tourniquet (WALANT) technique allows intraoperative motor assessment of tendon repair integrity of the hand compared with general anesthesia or brachial plexus block. No studies have tested the effect of adding dexmedetomidine to lidocaine on the analgesic properties of the WALANT technique, which is the aim of our study.

METHODS

A total of 128 patients aged more than 18 years were scheduled for surgical flexor tendon injury repair using WALANT technique. Patients were divided into two equal groups. Ultrasound-guided subcutaneous injection of lidocaine 1% with dexmedetomidine (1 µg/kg), Group D, or without dexmedetomidine, Group C, was performed at four points: proximal to the wrist joint, the distal forearm, palm region, and proximal phalanges. The primary outcome was total morphine consumption throughout the first postoperative day. Secondary outcomes included number of patients requiring rescue analgesia, time to first analgesic request, and pain score.

RESULTS

Total morphine consumption was significantly (P < 0.001) lower in group D (2.66 ± 0.998) than in group C (3.66 ± 1.144) mg. Number of patients requiring rescue analgesia was significantly (P < 0.001) lower in group D (54.7% (35)) than group C (100.0% (64)). The time for first request for analgesia was significantly (P < 0.001) longer in group D (11.31 ± 6.944) than in group C (5.91 ± 4.839) h. Pain score was significantly higher in group C than D at three (P < 0.001), and six (P = 0.001) hours (P = 0.001) postoperatively.

CONCLUSION

Dexmedetomidine significantly improves the analgesic quality of WALANT when added to lidocaine with less opioid consumption.

TRIAL REGISTRATION

(ID: PACTR202203906027106; Date: 31/07/2023).

Outcome of Flexor Tendon Repair Using Eight-Strand Core Stitch Without Postoperative Finger Splinting

BACKGROUND

There are no reports that detail clinical outcomes using the 8-strand suture techniques and early active mobilization. We aim to report the outcome of using an 8-strand double-cruciate core suture followed by early active motion without finger splinting.

MATERIALS AND METHODS

Thirty-five patients with 41 affected digits were operated and followed up for at least 6 months. A double cruciate repair with 4 single cross-grasping stitches on either side was employed. Active full-range finger flexion/extension exercises were allowed from the third postoperative day with the wrist held in the neutral position.

RESULTS

The total active motion (TAM) calculated for the proximal interphalangeal and distal interphalangeal joints averaged 151° ± 22°, and the TAM% averaged 86% ± 13%. Based on the original Strickland-Glocovac criteria, excellent and good outcomes were achieved in 25 of 29 fingers (86.2%). An average extension lag of 21° ± 11° (range 10°-40°) was observed in 11 (38%) fingers. The Buck-Gramcko scale showed excellent and good results in 10 (83.4%) thumbs. Active interphalangeal range of motion averaged 68° ± 23°. An average extension lag of 12° ± 4° (range 10°-20°) was observed in 7 (58%) thumbs. Complications occurred in 4 thumbs, including bowstringing (2), rupture (1), and flexion contracture of 60° (1).

CONCLUSIONS

Using the 8-strand repair technique and active mobilization performed by the patient is both practical and cost-saving. Intensive supervision of a hand therapist is generally not required. Notably improved outcomes have been achieved while preventing adhesions at the repair site. Further clinical outcome studies devoted specifically to the flexor pollicis longus are recommended to validate early-phase active mobilization following the 8-strand repair.

Biomechanical comparison of different suture materials with different techniques in tendon repair: An ex-vivo study

OBJECTIVES

Sheep Achilles tendons are used as an effective preclinical model of flexor tendon repair in plastic surgery, due to their biomechanical properties, which are similar to humans. The aim of this study was to examine the efficacy and biomechanical outcomes of suture materials and tendon repair techniques in flexor tendon repair.

MATERIAL AND METHODS

72 sheep tendons were obtained for a total of 12 different scenarios. Tendons were repaired using 4 different suture types and 3 different suture techniques. After repair, the tendons were fixed at both ends and subjected to biomechanical tests. Ultimate Failure Load (UFL) and 2-mm Gap Load (GL) per scenario were compared statistically within and between groups.

RESULTS

UFL and GL of all sutures were significantly different between the modified Kessler, Bunnell and Krackow techniques (P < 0.05), and between Monosorb, Ti-Cron and V-loc sutures (P < 0.05). UFL and GL according to repair technique were not significantly different for the Propilen suture (P > 0.05).

CONCLUSION

When UFL and GL were considered together, our findings indicate that optimal strength scenarios were for the modified Kessler technique using Monosorb or V-loc sutures.

[Current Trends in Flexor Tendon Surgery: Results of a National Online Survey]

Within the last 50 years, there has been a change in trend in flexor tendon surgery. After the introduction of the 2-strand technique, the 4-strand technique was propagated in the 1990s. In order to obtain a status quo of which technique is used in Germany and if the gold standard of the 4-strand suture has changed in favour of a 6-strand suture, we conducted an online survey among members of the DGH ("Deutsche Gesellschaft für Handchirurgie", German Society for Hand Surgery) on the suture technique of flexor tendon injuries zone 2.

MATERIAL AND METHODS

An online survey was conducted and sent out by email to all DGH members. The questionnaire included 7 questions. Participants accessed the survey via a link.

RESULTS

155 hand surgeons from Germany participated in the survey. All of them answered the questionnaire in full and all questionnaires were included in the evaluation. The main question of how many strands are currently used for core suturing was answered as follows: 21% (n=32) of the 155 participants (TN) stated that they use a 2-strand suture, 53% used (n=82) a 4-strand suture and 10% used a 6-strand suture. Regarding techniques, 81 TN used the Kirchmayr-Kessler technique or a modification of it, 9 TN used the M-Tang technique, and 15 TN indicated "other technique". The question about the application of an epitendinous suture was overwhelmingly answered with "yes". Here, 98.2% agreed. Only with regard to the suture material, different opinions were found. 68% (n=106) use an absorbable monofilament suture (such as PDS). Just under a quarter (23%, n=36) use a non-absorbable monofilament suture (such as Prolene).

CONCLUSION

Flexor tendon surgery has changed considerably due to intensive advances in research during the last decades. It was interesting to note in our survey that German hand surgeons have adapted their suture technique within the last years based on the results of the literature. Our results clearly show that convincing scientific data has an influence on the choice of surgical technique and that discussions about new techniques, e. g. in the context of annual meetings, may well stimulate the auditorium to rethink.

Effect of loading speed on gap resistance and tensile strength of flexor tendon repair under cyclic loading test

Postoperative digit motion is important for the functional recovery of injured tendons. To date, it is unknown whether the loading speed impacts the biomechanical properties of a repaired tendon. This study investigated the effect of loading speed on the gap resistance and tensile strength of tendon repairs. One hundred porcine flexor tendons were repaired with two core sutures, 4-strand modified Kessler and double Q, and cyclically loaded at the speeds of 10, 40, 80, 160, and 320 mm/min. The number of tendons that formed an initial or 2 mm gap at the repair site during cyclic loading, stiffness at the 1st and 20th loading cycles, gap size between tendon ends when cyclic loading ended, and the ultimate strength were recorded. Under the lowest loading speed, the tendons repaired with the 4-strand modified Kessler suture developed significantly larger gaps and smaller stiffness than those with a greater loading speed. The loading speed did not affect the maximum strength of both tendon repairs. The findings suggest that very slow motion promotes gap formation of tendon repair with inferior gap resistance. The rate corresponds to regular hand action or the tendon core suture possessing a strong gap resistance increases the safety margin during early active finger movement. Our findings help to guide the exercise regimens after tendon surgery.

Inflammatory reaction to suture materials after flexor tendon repair. A retrospective study of 594 patients

We report granuloma formation after using FiberWire^® for flexor tendon repairs. Four subcutaneous granulomas were identified in 115 patients with FiberWire^® core sutures, none in 426 with braided polyester. Foreign body reactions were found in the granuloma cases. We suggest early suture removal if this specific complication is encountered.

Knotless Tendon Repair with a Resorbable Barbed Suture: An In-vivo Comparison in the Turkey Foot

Background: Un-knotted barbed suture constructs are postulated to decrease repair bulk and improve tension loading along the entire repair site resulting in beneficial biomechanical repair properties. Applying this repair technique to tendons has shown good results in ex-vivo experiments previously but thus far no in-vivo study could confirm these. Therefore, this current study was conducted to assess the value of un-knotted barbed suture repairs in the primary repair of flexor tendons in an in-vivo setting. Methods: Two groups of 10 turkeys (Meleagris gallapovos) were used. All turkeys underwent surgical zone II flexor tendon laceration repairs. In group one, tendons were repaired using a traditional four-strand cross-locked cruciate (Adelaide) repair, while in group two, a four-strand knotless barbed suture 3D repair was used. Postoperatively repaired digits were casted in functional position, and animals were left free to mobilise and full weight bear, resembling a high-tension post-op rehabilitation protocol. Surgeries and rehabilitations went uneventful and no major complications were noted. The turkeys were monitored for 6 weeks before the repairs were re-examined and assessed against several outcomes, such as failure rate, repair bulk, range of motion, adhesion formation and biomechanical stability. Results: In this high-tension in-vivo tendon repair experiment, traditionally repaired tendons performed significantly better when comparing absolute failure rates and repair stability after 6 weeks. Nevertheless, the knotless barbed suture repairs that remained intact demonstrated benefits in all other outcome measures, including repair bulk, range of motion, adhesion formation and operating time. Conclusions: Previously demonstrated ex-vivo benefits of flexor tendon repairs with resorbable barbed sutures may not be applicable in an in-vivo setting due to significant difference in repair stability and failure rates. Level of Evidence: Level IV (Therapeutic).

AN ALTERNATIVE MODEL FOR TEACHING TENDON REPAIR AND SURGICAL TECHNIQUE IN HAND SURGERY

Introduction

At the beginning of the medical career, the orthopedic surgeon in academic training needs valid methodologies for training complex surgeries in tissues that simulate real situations. With training in animal tissue, adapted to approach human tissue, it is possible to simulate procedures and decisions that will be necessary in real situations.

Objective

This study consists in presenting a simple and reproducible simulation model for surgical repair of tendons by training on fresh tendons fixed on a wooden frame.

Methodology

The model construction consists of a flat piece of Medium Density Fiberboard (MDF) and two threaded hooks were used on the board, to which Nylon threads are attached to tie the tendon, allowing a satisfactory simulation of a human tendon.

Conclusion

This is a simple, inexpensive, and effective method for tendon suturing training, through which the trainee can develop repair techniques and basic surgical principles, such as instrument handling, safety, and sharps disposal. This approach aims to improve the trainee's skills and dexterity when placed in live surgery. The surgical techniques developed include the modified Kessler and Bunnel sutures. Level of Evidence IV, Descriptive Study .

Medium-term clinical outcomes of Zone 2B/2C finger flexor tendon repairs: influence of management of flexor digitorum superficialis

III.

Fibrocartilaginous Tissue: Why Does It Fail to Heal?

Tendons and ligaments are critical components in the function of the musculoskeletal system, as they provide stability and guide motion for the biomechanical transmission of forces into bone. Several common injuries in the foot and ankle require the repair of ruptured or attenuated tendon or ligament to its osseous insertion. Understanding the structure and function of injured ligaments and tendons is complicated by the variability and unpredictable nature of their healing. The healing process at the tendon/ligament to bone interface is challenging and often frustrating to foot and ankle surgeons, as they have a high failure rate necessitating the need for revision.

Investigations into flexor tendon repair: a research journey over three decades

In this article, I review how my team and I addressed clinical concerns in Zone 2 flexor tendon repair, and how major findings in each step of our research were translated into clinical practice. The focus of the article is on the thought processes behind each new investigation, the interpretation of research findings and conclusions drawn from the basic and clinical studies.

The consistency and reliability of six-strand and four-strand flexor tendon repairs: a comparative porcine cadaveric study

The aim of this study was to compare the consistency and reliability of the six-strand Gan modification of the Lim-Tsai flexor tendon repair with the four-strand Adelaide repair, both with 3-0 sutures and with eight to ten runs of simple 5-0 running peripheral suture as well as the influence of the surgeons' level of experience on the strength of the repair in a cadaveric animal setup. Thirty-nine surgeons repaired 78 porcine flexor digitorum profundus tendons with either the Adelaide technique (39 tendons) or the modified Lim-Tsai technique (39 tendons). Each repaired tendon was tested in a material testing machine under a single cycle load-to-failure test. The forces were recorded when the gap between the two tendon stumps reached 1 and 2 mm and when irreversible elongation or total rupture occurred. We found no significant differences in gap formation force and yielding strength of the tendons between the two methods. The surgeon's previous experience in tendon repairs did not improve the consistency, reliability or tensile strength of the repairs. We conclude that if a strong peripheral suture is added, the modified Lim-Tsai repair has the same technical reliability and consistency as the Adelaide repair in term of ultimate loading strength in this test setup.

Investigation of the effects of two-, four-, six- and eight-strand suture repairs on the biomechanical properties of canine gastrocnemius tenorrhaphy constructs

OBJECTIVE

To determine the effects of 2-, 4-, 6- and 8-strand suture repairs on the biomechanical properties of canine gastrocnemius tenorrhaphy constructs in an ex vivo model.

SAMPLE

56 cadaveric gastrocnemius musculotendinous units from 28 adult large-breed dogs.

PROCEDURES

Tendons were randomly assigned to 4 repair groups (2-, 4-, 6- or 8-strand suture technique; n = 14/group). Following tenotomy, repairs were performed with the assigned number of strands of 2-0 polypropylene suture in a simple interrupted pattern. Biomechanical testing was performed. Yield, peak, and failure loads, the incidence of 1- and 3-mm gap formation, forces associated with gap formation, and failure modes were compared among groups.

RESULTS

Yield, peak, and failure forces differed significantly among groups, with significantly greater force required as the number of suture strands used for tendon repair increased. The force required to create a 1- or 3-mm gap between tendon ends also differed among groups and increased significantly with number of strands used. All constructs failed by mode of suture pull-through.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that increasing the number of suture strands crossing the repair site significantly increases the tensile strength of canine gastrocnemius tendon repair constructs and their resistance to gap formation. Future studies are needed to assess the effects of multistrand suture patterns on tendon glide function, blood supply, healing, and long-term clinical function in dogs to inform clinical decision-making.

The impact of transverse components on 4-strand tendon repairs

We investigated the effects of the transverse components of a tendon core suture on tensile resistance and strength of 4-strand repairs. Forty-four pig flexor tendons were repaired with one of the following four methods: double Tsuge, U-shaped, 4-strand cross and 4-strand rectangular repairs. We recorded the number of the repaired tendons that formed a 2 mm gap between the tendon ends during cyclic loading for 20 cycles, stiffness of the tendon at the 1st and 20th cycle, gap distance at the repair site and ultimate strength of the repair at the 20th cycle. When transverse components were added to the core suture, a greater number of tendons formed a 2 mm gap during cyclic loading. The stiffness gradually decreased, and the repair site's gap distance after cyclic loading increased with the presence of transverse components of the sutures. We conclude that the core suture's transverse components negatively impact the tensile resistance of 4-strand tendon repairs.

Rehabilitation after flexor tendon repair and others: a safe and efficient protocol

In this review I detail the protocol that I use after flexor tendon repair and outline my experience regarding how its framework might be used for other disorders. The early passive-active flexion protocol has a sufficient number of cycles of active flexion in each exercise session, which is at least 40, and ideally 60 to 80. The frequency of exercise sessions may range from 4 to 6 a day, distributed in the morning, afternoon and evening. Increasing the number of daily sessions without a sufficient number of runs in each session is ineffective. In the first 2-3 weeks after surgery, active digital flexion should go through only a partial range. In weeks 4-6, the patient gradually moves through the full range. With modifications, I suggest generalization of the partial-range finger motion to therapy after treating other hand injuries. I consider partial-range active flexion a generalizable working principle for different hand disorders.

Evaluation of biomechanical properties on partial and complete epitendinous suture in human cadaver flexor tendon repair

Objective

This study was designed to compare the ultimate tensile strength and force to 2 mm gap formation among 50% partial, 75% partial, and complete circumferential epitendinous suture with a combination of 4-strand core suture in human cadaver flexor tendon.

Materials and methods

Forty-five flexor tendons from four soft human cadavers were used to evaluate the biomechanical property among 50% partial, 75% partial, and complete circumferential epitendinous suture with a combination of 4-strand core suture.

Results

The force to 2 mm gap of complete epitendinous was significantly greater than partial epitendinous suture (P < 0.05); however, there was no difference between 50% partial and 75% partial epitendinous suture (P > 0.05). For the ultimate strength, there was no significant difference between partial and complete epitendinous suture (P > 0.05). The partial epitendinous was approximately 60% of the complete epitendinous suture in force to 2 mm gap and also 70% of complete epitendinous suture in ultimate tensile strength with a combination of core sutures.

Conclusions

The complete epitendinous suture showed better ultimate tensile strength and force to 2 mm gap compared with a partial 50% and 75% epitendinous suture. However, in some clinical scenario which the complete epitendinous suture is not possible to perform, the authors suggested only partial epitendinous suture with 50% circumference is recommended as the additional epitendinous repair up 75% circumference cannot provide any mechanical benefit to the repaired site.

Basic Research on Tendon Repair: Strategies, Evaluation, and Development

Tendon is a fibro-elastic structure that links muscle and bone. Tendon injury can be divided into two types, chronic and acute. Each type of injury or degeneration can cause substantial pain and the loss of tendon function. The natural healing process of tendon injury is complex. According to the anatomical position of tendon tissue, the clinical results are different. The wound healing process includes three overlapping stages: wound healing, proliferation and tissue remodeling. Besides, the healing tendon also faces a high re-tear rate. Faced with the above difficulties, management of tendon injuries remains a clinical problem and needs to be solved urgently. In recent years, there are many new directions and advances in tendon healing. This review introduces tendon injury and sums up the development of tendon healing in recent years, including gene therapy, stem cell therapy, Platelet-rich plasma (PRP) therapy, growth factor and drug therapy and tissue engineering. Although most of these therapies have not yet developed to mature clinical application stage, with the repeated verification by researchers and continuous optimization of curative effect, that day will not be too far away.

Ex vivo evaluation of novel core tenorrhaphy patterns in dogs

OBJECTIVE

To compare the biomechanical properties and gapping characteristics of four novel tenorrhaphy patterns in a canine flexor tendon model.

STUDY DESIGN

Ex vivo, randomized, biomechanical study.

SAMPLE POPULATION

Superficial digital flexor tendons of 60 forelimbs (30 dogs).

METHODS

Each tendon was transected 25 mm distal to its musculotendinous junction prior to tenorrhaphy with 2-0 polypropylene. Repair patterns included the three-loop pulley (3LP, control), exposed double-cross-lock (ExDCrL), embedded double-cross-lock (EmDCrL), triple-circle-lock (TCiL), and Modified-Tang patterns (MTang) were randomly assigned to each experimental group (n = 12/group). Yield, peak, and failure loads, gap formation and failure modes were compared.

RESULTS

Tendons repaired with ExDCrL (p < .0001), EmDCrL (p < .0001), and MTang (p < .0001) sustained yield, peak, and failure loads ~2.2x, ~2.0x, and ~1.9x, respectively, greater than those repaired with 3LP. Loads to 1 and 3 mm gapping were also higher for ExDCrL (p < .0001), EmDCrL (p < .0004), and MTang constructs (p < .0017) compared to 3LP. Although TCiL constructs sustained higher loads, their resistance to gap formation did not differ from that of 3LP repairs. Failure mode differed between groups (p < .0001), EmDCrL, ExDCrL, MTang, and TCiL constructs failing predominantly by suture breakage compared to 3LP repairs that failed by suture pull-through.

CONCLUSION

Use of novel patterns ExDCrL, EmDCrL, and MTang improved resistance to loads and gap formation and were biomechanically superior compared to 3LP in healthy canine tendon repairs.

CLINICAL SIGNIFICANCE

These results justify in vivo evaluation of ExDCrL, EmDCrL, or MTang pattern for tenorrhaphy in dogs.

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.

Evaluation of a continuous locking novel epitendinous suture pattern with and without a core locking-loop suture on the biomechanical properties of tenorrhaphy constructs in an ex vivo model of canine superficial digital flexor tendon laceration

OBJECTIVE

To evaluate the effect of a continuous locking novel epitendinous suture (nES) pattern with and without a core locking-loop (LL) suture on the biomechanical properties of ex vivo canine superficial digital flexor tendon (SDFT) tenorrhaphy constructs.

SAMPLE

54 cadaveric forelimb SDFTs from 27 musculoskeletally normal adult dogs.

PROCEDURES

Tendons were assigned to 3 groups (18 SDFTs/group): sharply transected and repaired with a core LL suture alone (group 1), an nES pattern alone (group 2), or a combination of a core LL suture and nES pattern (group 3). All constructs underwent a single load-to-failure test. Yield, peak, and failure loads; gap formation incidence; and mode of failure were compared among the 3 groups.

RESULTS

Mean yield, peak, and failure loads differed significantly among the 3 groups and were greatest for group 3 and lowest for group 1. Mean yield, peak, and failure loads for group 3 constructs were greater than those for group 1 constructs by 50%, 47%, and 44%, respectively. None of the group 3 constructs developed 3-mm gaps. The most common mode of failure was suture pulling through the tendon for groups 1 (12/18) and 2 (12/18) and suture breakage for group 3 (13/18).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested augmentation of a core LL suture with an nES pattern significantly increased the strength of and prevented 3-mm gap formation at the tenorrhaphy site in ex vivo canine SDFTs. In vivo studies are necessary to assess the effectiveness and practicality of the nES pattern for SDFT repair in dogs.

Effects of Different Core Suture Lengths on Tensile Strength of Multiple-Strand Sutures for Flexor Tendon Repair

Purpose

To compare 2 types of newly devised 8-strand quadruple-looped suture (QLS) techniques with a 6-strand triple-looped suture (TLS) technique; and to assess the effects of different core suture lengths (CSLs) (the length between 2 locking sites of a suture strand) within each suture row on tensile strength.

Methods

We repaired 24 flexor tendons from 12 rabbits using the TLS and QLS techniques, with equal CSL (QLS) or unequal CSL (unequal QLS) among each suture row. The QLS was composed of 4 looped sutures on the anterolateral and posterolateral aspects of the tendon. The cross-sectional area of the locking portion of each thread in the QLS was equal to that in the TLS. In the QLS technique, the CSL on each aspect of the tendon was 13 mm. In the unequal QLS technique, the CSL on each aspect of the tendon was 13 and 17 mm. The load at 1- and 2-mm gaps, the maximum load until the 3-mm gap, and the ultimate load were compared among the 3 techniques.

Results

The QLS was significantly stronger than the unequal QLS and the TLS for loads at 1-mm and 2-mm gaps, maximum load until 3-mm gap, and ultimate load. There was no significant difference between the unequal QLS and TLS techniques. The QLS technique showed an approximately 30% increase in gap resistance and ultimate strength compared with the TLS technique.

Conclusions

The QLS technique showed an estimated increase in tensile strength proportional to the number of suture strands compared with the TLS technique. Our study suggests that a consistent CSL in each suture row provides the highest strength in multistrand sutures consisting of the same configuration of suture rows.

Clinical relevance

The QLS technique may reduce the risk for tendon rupture associated with early active mobilization after flexor tendon repair.

Beyond the Core Suture: A New Approach to Tendon Repair

Despite significant improvements in zone II flexor tendon repair over the last 2 decades, function-limiting complications persist. This article describes 2 novel repair techniques utilizing flexor digitorum superficialis (FDS) autografts to buttress the flexor digitorum profundus (FDP) repair site without the use of core sutures. The hypothesis being that the reclaimed FDS tendon autograft will redistribute tensile forces away from the FDP repair site, increasing overall strength and resistance to gapping in Zone II flexor tendon injuries compared with the current clinical techniques.

Methods

Two novel FDP repair methods utilizing portions of FDS have been described: (1) asymmetric repair (AR), and (2) circumferential repair. Ultimate tensile strength and cyclical testing were used to compare novel techniques to current clinical standard repairs: 2-strand (2-St), 4-strand (4-St), and 6-strand (6-St) methods. All repairs were performed in cadaveric sheep tendons (n = 10/group), by a single surgeon.

Results

AR and circumferential repair techniques demonstrated comparable ultimate tensile strength to 6-St repairs, with all 3 of these techniques able to tolerate significantly stronger loads than the 2-St and 4-St repairs (P < 0.0001). Cyclical testing demonstrated that AR and circumferential repair were able to withstand a significantly higher total cumulative force (P < 0.001 and P = 0.0064, respectively) than the 6-St, while only AR tolerated a significantly greater force to 2-mm gap formation (P = 0.042) than the 6-St repair.

Conclusion

Incorporating FDS as an autologous graft for FDP repair provides at least a comparable ultimate tensile strength and a significantly greater cumulative force to failure and 2-mm gap formation than a traditional 6-St repair.

Flexor digitorum profundus with or without flexor digitorum superficialis tendon repair in acute Zone 2B injuries

A total of 53 patients with complete cuts of two flexor tendons in Zone 2B treated over a 9-year period was reviewed. Twenty-three patients (28 fingers) had only flexor digitorum profundus repair, while 30 patients (36 fingers) had both flexor digitorum profundus and flexor digitorum superficialis repairs, with a mean follow-up of 21 months (range 12-84). The decision to repair the flexor digitorum superficialis was made according to intraoperative judgement of ease of repair and gliding of the flexor digitorum profundus tendon. Two groups of patients showed no significant differences in total range of active or passive digital motion and power grip percentage to the contralateral hand. However, the values of power grip were statistically superior in the patients with both tendons repaired. The patients after flexor digitorum profundus-only repairs showed significantly greater but still mild flexion contracture (mean 20 °) of the operated digits. The Tang gradings were the same with 89% good and excellent rates in both groups. The conclusion is that although repair of both flexor digitorum profundus and flexor digitorum superficialis tendons is slightly more preferable based on increased grip strength, the repair of the flexor digitorum superficialis together with flexor digitorum profundus is not mandatory. Whether or not to repair flexor digitorum superficialis is an intraoperative decision based on the ease of gliding of the repaired tendon(s).Level of evidence: III.

Evolving concepts in ventral hernia repair and physical therapy: prehabilitation, rehabilitation, and analogies to tendon reconstruction

PURPOSE

The abdominal wall and musculoskeletal tendons share many anatomic, physiologic, and functional characteristics. This review aims to highlight these similar characteristics and to present a rationale why the treatment principles of successful musculoskeletal tendon reconstruction, including principles of surgical technique and physical therapy, can be used in the treatment of complex abdominal wall reconstruction or ventral hernia repair.

METHODS

The MEDLINE/PubMed database was used to identify published literature relevant to the purpose of this review.

CONCLUSIONS

There are several anatomical and functional similarities between the linea alba and musculoskeletal tendons. Because of this reason, many of the surgical principles for musculoskeletal tendon repair and ventral hernia repair overlap. Distribution of tension is the main driving principle for both procedures. Suture material and configuration are chosen to maximize tension distribution among the tissue edges, as seen in the standard of care multistrand repairs for musculoskeletal tendons, as well as in the small bites for laparotomy technique described in the STITCH trial. Physical therapy is also one of the mainstays of tendon repair, but surprisingly, is not routine in ventral hernia repair. The evidence surrounding physical therapy prehabilitation and rehabilitation protocols in other disciplines is significant. This review challenges the fact that these protocols are not routinely implemented for ventral hernia repair, and presents the rationale and feasibility for the routine practice of physical therapy in ventral hernia repair.

Improving Strength and Quality of Epitendinous Repairs

Background: Epitendinous sutures not only join the 2 severed tendon edges but also supply strength and support to the repair. Multiple techniques have been described, but none of them include another thread of suture. This could potentially increase the strength of the repair without affecting gliding. Methods: Caprine tendons were harvested, transected, and sutured with 6-0 Prolene. Four groups were created: single thread running (SR), single thread locking (SL), double thread running (DR), and double thread locking (DL). An Instron 5542 was used to pull the repaired tendons apart, and the energy at the break was calculated (gf/mm). For gliding resistance, we harvested a human A2 pulley. A pre- and postrepair value was obtained, and a ratio was elaborated. A single-factor analysis of variance and independent sample t tests were performed. Results: The SR group had a mean energy at break of 9339.71 ± 1630.212 gf/mm; the SL group, 9629.96 ± 1476.45 gf/mm; and the DR group, 9600.221 ± 976.087 gf/mm, with no statistical significance. The DL group was significantly higher at 14 740.664 ± 2596.586 gf/mm (P < .05). When comparing SR with DL for gliding, SR had less than half of the resistance than DL (0.018 ± 0.004 and 0.049 ± 0.015 N/mm, respectively), with statistical significance (P < .05). Conclusion: Using a single suture thread for running epitendinous repair is no different than locking with a single thread or using an extra thread in a running fashion. Performing a double suture thread with a locking technique is significantly stronger than the previously mentioned repairs, with the disadvantage of more resistance at the pulley.

Wide awake surgery for flexor tendon primary repair: A literature review

Flexor tendon injuries are extremely challenging conditions to manage for hand surgeons. Over the last few years enormous progress has been made for the treatment of these lesions with new surgical approaches being performed. One of these is the wideawake local anesthesia no tourniquet (WALANT) technique, also known as Wide Awake Technique that allows tendon repair under local anesthesia, enabling the tendon to move actively during surgery. Dynamic movement of the tendon during surgery is crucial for the orthopedic surgeon in order to understand if the tendon has been correctly repaired before leaving the operatory table. An electronic literature research was carried out on Pubmed, Google Scholars and Cochrane Library using ((Flexor tendon injury) OR (flexor tendon) OR (injury muscle tendon) OR (flexor pollicis longus tendon) AND ((wide awake repair) OR (wide awake) OR (wide awake hand surgery))as search terms. Authors believe that WALANT is an enormous add-on in the management of patients with flexor tendon injuries mainly because it allows direct visualization of the repair during flexion and extension movement of the fingers and also because it avoids general anesthesia or brachial plexus being more cost effective. The aim of these review was therefore to sum up the evidences available so far on the wade awake technique as an emerging treatment for patients with flexor tendon injuries.

Biomechanical analysis of a new 8-strand technique for flexor tendon repair

We sought to compare the strength and rupture sites of a new 8-strand suture technique with those of an established 6-strand flexor tendon repair through biomechanical analysis. This new 8-strand suture pattern places minimal suture material in the remodeling zone and focuses on protecting the knot, a well-known weak point of the suture construct. The knot was buried within the tendon so as to not interfere with tendon gliding. In a biomechanical simulation, strength and rupture sites were compared with those of the 6-strand repair. We repaired a total of 54 porcine flexor tendons using one of the two techniques (n=27 each). Tensile strength at 2-mm gap formation and ultimate failure load were determined. Afterwards, we dissected the tendons to identify the rupture site of the suture material. The new 8-strand suture had a significant higher ultimate load to failure (87.7N) and 2-mm gap load (71.6N) compared to the 6-strand technique (57.7N and 45.9N) (P<0.001). Whereas the rupture site of the core suture in the 6-strand technique was mainly located next to the knot (81.5%), the suture seemed to fail independently from this weak spot in the 8-strand technique (11.1%). This new 8-strand technique achieves a strong flexor tendon repair in a biomechanical model. Additional cross-locking on either side of the knot seems to contribute to the repair's strength. The resulting higher ultimate failure load and 2-mm gap load may allow more aggressive active motion-based postoperative rehabilitation.

Effects of a Q Suture Technique on Resistance to Gap Formation and Tensile Strength of Repaired Tendons: An Ex Vivo Mechanical Study

PURPOSE

The repair of digital flexor tendons following laceration should aim to prevent gapping at the repair site and restore the tensile strength of the tendons to facilitate postoperative movement. We present here a simple Q suture and test its effects on gap formation and tensile strength of the repaired tendons.

METHODS

Sixty porcine tendons were repaired with 3 2-strand sutures (Kessler, Kessler plus 2Q, and Kessler plus running sutures) and 3 4-strand sutures (double Kessler, double Kessler plus 2Q, and double Kessler plus running sutures). The specimens were subjected to a cyclic loading. At each cycle, the number of tendons that initiated gapping or formed a 2-mm gap at the repair site was determined. After the cyclic load testing, the gap distance between tendon ends and the ultimate strength of the repaired tendons was measured.

RESULTS

In both 2-strand and 4-strand tendon repairs, augmentation by insertion of the 2Q sutures reduced the number of tendons that showed 2-mm gaps ends during loading. Compared with the single Kessler and Kessler plus running sutures, Kessler plus 2Q suture significantly increased the ultimate strength of the tendon repair. Compared with the double Kessler and double Kessler plus running sutures, double Kessler plus 2Q suture significantly decreased the gap distance at the repair site after cyclic loading.

CONCLUSIONS

The Q suture technique effectively enhances the resistance to gap formation of 2-strand and 4-stand tendon repair. It also improves the tensile strength of 2-strand Kessler repairs.

CLINICAL RELEVANCE

The Q suture is a simple technique that can resist gap formation and strengthen the tensile strength of the repaired tendons in the laboratory setting.

[Primary treatment of flexor tendon injuries]

The treatment of flexor tendon injuries is still challenging, especially in the region of the narrow annular ligaments and tendon sheaths of the 3‑segment fingers and the thumb (zone 2). In the course of time, the primary suture of the flexor tendons has prevailed over traditional recommendations for a secondary tendon replacement after healing of the wound. Improvements regarding suture techniques and materials and, above all the follow-up treatment, have been crucial for better results and remarkable changes in flexor tendon surgery. The suture techniques are determined by the location of the injury but the experience and preferences of the surgeon are also important. Although no technique was found to be optimal, published research and clinical experiences provide important indications for the presumption of successful treatment. To achieve this an early functionally active protocol should be implemented. The tendon suture should enable this by having a high primary strength and therefore at least a 4-strand core suture technique with a ring suture should be given preference. Further important prerequisites for success are the undisturbed gliding of the repaired tendon in its "bed" paying special attention to the annular ligaments and preservation of the blood supply to the tendons.

Rupture Rates Between 2-Strand and 4-Strand Flexor Tendon Repairs: Is Less More?

The purpose of this study was to explore the difference in clinical outcome of 2-strand and 4-strand flexor tendon repairs in a single unit in adult population. A total of 109 complete divisions of a single flexor tendon were analyzed from 2016 to 2018 retrospectively. Thirty flexor tendons were repaired with 2-strand and 79 tendons were repaired with 4-strand technique. There was no significant difference in the complication rate including rupture, infection, and adhesions. These results support that 4-strand is not superior than 2-strand and that lower volume type of repair would be preferable.

Zone 2 flexor tendon repairs using a tensioned strong core suture, sparse peripheral stitches and early active motion: results in 60 fingers

We report the outcomes of zone 2 tendon repairs in 60 fingers using a strong core suture, sparse peripheral stitches and early active motion. From January 2014 to April 2016, we repaired 60 flexor digitorum profundus tendons with a tensioned 4-strand or 6-strand core suture and three to four peripheral stitches. The A2 or A4 pulleys were vented as necessary. Following early active flexion of the repaired tendons, no repairs ruptured and 52/60 (87%) fingers recovered to good or excellent function using the Tang criteria after follow-up of 8-33 months. We conclude that tensioned multi-strand strong core repairs only require sparse peripheral stitches and are safe for early active flexion. Standard peripheral sutures are not necessary. The core sutures should be properly tensioned to prevent gapping at tendon repair site and pulleys should be sufficiently vented to allow tendon motion. Level of evidence: IV.

New Developments Are Improving Flexor Tendon Repair

New developments in primary tendon repair in recent decades include stronger core tendon repair techniques, judicious and adequate venting of critical pulleys, followed by a combination of passive and active digital flexion and extension. During repair, core sutures over the tendon should have sufficient suture purchase (no shorter than 0.7 to 1 cm) in each tendon end and must be sufficiently tensioned to resist loosening and gap formation between tendon ends. Slight or even modest bulkiness in the tendon substance at the repair site is not harmful, although marked bulkiness should always be avoided. To expose the tendon ends and reduce restriction to tendon gliding, the longest annular pulley in the fingers (i.e., the A2 pulley) can be vented partially with an incision over its distal or proximal sheath no longer than 1.5 to 2 cm; the annular pulley over the middle phalanx (i.e., the A4 pulley) can be vented entirely. Surgeons have not observed adverse effects on hand function after judicious and limited venting. The digital extension-flexion test to check the quality of the repair during surgery has become increasingly routine. A wide-awake surgical setting allows patient to actively move the digits. After surgery, surgeons and therapists protect patients with a short splint and flexible wrist positioning, and are now moving toward out-of-splint freer early active motion. Improved outcomes have been reported over the past decade with minimal or no rupture during postoperative active motion, along with lower rates of tenolysis.

Biomechanical comparison of modified Lim/Tsai tendon repairs with intra- and extra-tendinous knots

We compared the Lim/Tsai tendon repair technique using an extra-tendinous knot with modification using an intra-tendinous knot. The ultimate tensile strength, load to 2 mm gap force, stiffness, mode of failure, location of failure, and time taken to repair each tendon were recorded during a single cycle loading test in 20 tendons with each repair method. We found that the ultimate tensile strength and 2 mm gap force of the modified Lim/Tsai repair with an extra-tendinous knot (56 SD 5 N and 14 SD 2 N, respectively) were statistically significantly higher than that of the modified Lim/Tsai repair with intra-tendinous knot (51 SD 7 N and 11 SD 2 N, respectively). We conclude that the modified Lim/Tsai repair with extra-tendinous knot is stronger, despite having the same number of core strands.

The effect of modified locking methods and suture materials on Zone II flexor tendon repair-An ex vivo study

The failure rate of intrasynovial tendon repair is high due to substantial elongation at the repair site and to the development of adhesions between the tendon’s surface and the surrounding digital sheath. To minimize these complications, we sought to reduce the incidence of gapping and to facilitate the initiation of early motion by improving the time zero structural properties of repair. The Winters-Gelberman 8-strand repair technique was modified by adding surface lock loops and by using Fiberwire suture material. Forty-eight canine flexor digitorum profundus tendons were transected and repaired with one of three 8-strand techniques (Pennington modified Kessler, half hitch loops, or surface locking Kessler) using either 3–0 Supramid or 4–0 Fiberwire suture. Biomechanical testing was performed to determine the physiologic and failure mode properties of the repairs. The surface locking Kessler technique improved repair maximum load, load necessary to create a 2 mm repair site gap, and yield force compared to the modified Kessler and half hitch loop techniques. Fiberwire suture improved maximum load, the load necessary to create a 2 mm repair site gap, stiffness, and yield force compared to Supramid suture. Failure occurred by both suture pull out and by suture breakage in the modified Kessler, Supramid suture repair group. Failure occurred consistently by suture breakage in the surface locking Kessler, Supramid suture repair group. These results reveal that a novel locking Kessler repair is significantly stronger than the current state-of-the art flexor tendon suture repair technique. The use of a surface locking Kessler technique with Fiberwire suture markedly improves the mechanical properties of intrasynovial tendon repair by reducing the risk of post-operative gapping and rupture.

Biomechanical Comparison of a New Loop Suture Technique With Conventional Techniques of Flexor Tendon Repair: An In Vitro Study

INTRODUCTION

Flexor tendon repair techniques that can resist active forces are widely accepted. Despite that many suture techniques have been described, the "perfect repair" for flexor tendons cannot be achieved yet. We aimed to compare a new loop suture technique with commonly used flexor tendon repair methods biomechanically in hen tendon.

METHOD

We used 25 hen flexor tendons for each group (4-strand modified Kessler, grasping cruciate, Tsuge, and new technique groups). After the tendons were divided into 2, they were repaired according to these 4 techniques, were subjected to the initial stretching of 0.5 N, and pulled in the opposite directions. When a gap of 2 mm occurred, the test was terminated and the forces at that time were recorded. These strain forces were compared and evaluated statistically.

RESULTS

New technique had the best tensile strength results statistically. Modified Kessler and grasping cruciate took the second place and Tsuge repair gave the worst strain forces results.

CONCLUSIONS

With loop suture, 4 strands can be obtained with only 2 passes of the needle, and we think that much more tensile strength can be achieved because of the vertical transition and locking configurations of the new loop suture technique.

Results of 4-strand modified Kessler core suture and epitendinous interlocking suture followed by modified Kleinert protocol for flexor tendon repairs in Zone 2

Objective

There has been no consensus in literature for the ideal flexor tendon repair technique. The results of zone 2 flexor tendon lacerations repaired primarily by 4 strand Modified Kessler core suture and epitendinous interlocking suture technique followed by Modified Kleinert protocol were investigated.

Methods

128 fingers of 89 patients who had flexor tendon laceration in zone 2 built the working group. Functional outcomes were evaluated using the Strickland formula. A statistical analysis was made between Strickland scores and some parameters such as age, gender, follow-up time, co-existing injury existence, repair time, single or multiple finger injury, tendon rupture and the effect of FDS injury and repair.

Results

Excellent, good, fair, poor results were obtained from 71 (55.5%), 46 (35.9%), 8 (6.3%), 3 (2.3%) fingers, respectively. Time of the repair has a significant effect on the strickland scores. Surgery performed within the first 24 hours following the injury gave better results. 3 fingers (2.3%) had tendon ruptures. Existence of ruptures affected the results significantly. Co-existing injuries were found that they did not have any effect on the results. In the fingers in which both FDP and FDS tendons were lacerated, no significant relationship was found between only FDP repair, both FDP and FDS repair and single FDS slip repair. Additionally no significant relationships between follow-up time, gender, single or multiple finger injury and Strickland scores were observed. 13 fingers (10.1%) had PIP joint contracture above 20°.

Conclusion

The low rupture rate (2.3%) and 91.4% ‘good’ and ‘excellent’ scoring rates in our series support the idea that modified Kessler 4-strand core suture and epitendinous interlocking suture repair combined with modified Kleinert protocol gives satisfactory results. Repair time is one of the most important factors affecting the functional results and surgery should not be delayed if there is an experienced surgeon available.

Level of evidence

Level IV, therapeutic study.

The effect of adipose-derived stem cell sheets and CTGF on early flexor tendon healing in a canine model

Intrasynovial tendon injuries are among the most challenging in orthopedics. Despite significant improvements in operative and rehabilitation methods, functional outcomes continue to be limited by adhesions, gap formation, and rupture. Adhesions result from excessive inflammation, whereas tendon gapping and rupture result from inflammation-induced matrix degradation and insufficient regeneration. Therefore, this study used a combined treatment approach to modulate inflammation with adipose-derived mesenchymal stromal cells (ASCs) while stimulating tendon regeneration with connective tissue growth factor (CTGF). ASCs were applied to the repair surface via cell sheets and CTGF was delivered to the repair center via porous sutures. The effect of the combined treatment was assessed fourteen days after repair in a canine flexor tendon injury model. CTGF, either alone or with ASCs, reduced inflammatory (IL1B and IL6) and matrix degrading (MMP3 and MMP13) gene expression, while increasing anti-inflammatory gene (IL4) expression and collagen synthesis compared to control repairs. The combined treatment was more effective than CTGF treatment alone, reducing the inflammatory IFNG and scar-associated COL3A1 gene expression and increasing CD146+ tendon stem/progenitor cells at the tendon surface and interior along the core suture tracks. Therefore, the combined approach is promising in promoting early flexor tendon healing and worthy of further investigation.

Primary flexor tendons repair in zone 2: Current trends with GEMMSOR survey results

The repair of flexor tendon lesions in zone 2 remains a highly controversial subject in hand surgery. Currently, there is no consensus about the management of these lesions intra- and postoperatively, but the literature suggests that a solid suture will allow early active motion. We hypothesized that the management of flexor tendon injury in zone 2 varies widely. Two online surveys were conducted with surgeons and hand therapists. The questions captured the demographics of the surveyed population, surgical technique, common complications, postoperative management (duration of immobilization, type of splint, rehabilitation techniques and principles of self-rehabilitation). The responses were compared to current literature data. We collected 366 responses to the "surgery" survey and 206 responses to "rehabilitation" survey. Most surgeons performed suture repair with at least 4 strands (75.9%). Active rehabilitation protocols were used in 48.9% of cases. The "rehabilitation" survey underlined the lack of information provided to therapists by surgeons. Therapists used active protocols in 79.7% of cases. This study found a large variation in the management of flexor tendon injuries, which is not always consistent with current published recommendations. Ideally, the suture repair should be a 4-strand pattern with an epitendinous circumferential suture and a release of the pulley in the suture area. Mobilization and rehabilitation should be started on the 3rd day using an active protocol.

Recent evolutions in flexor tendon repairs and rehabilitation

This article reviews some recent advancements in repair and rehabilitation of the flexor tendons. These include placing sparse or no peripheral suture when the core suture is strong and sufficiently tensioned, allowing the repair site to be slightly bulky, aggressively releasing the pulleys (including the entire A2 pulley or both the A3 and A4 pulleys when necessary), placing a shorter splint with less restricted wrist positioning, and allowing out-of-splint active motion. The reported outcomes have been favourable with few or no repair ruptures and no function-disturbing tendon bowstringing. These changes favour easier surgeries. The recent reports have cause to re-evaluate long-held guidelines of a non-bulky repair site and the necessity of a standard peripheral suture. Emerging understanding posits that minor clinically noticeable tendon bowstringing does not affect hand function, and that free wrist positioning and out-of-splint motion are safe when strong surgical repairs are used and the pulleys are properly released.

Sonographic study of repair, gapping and tendon bowstringing after primary flexor digitorum profundus repair in zone 2

We report sonographic findings with clinical outcomes after zone 2 flexor digitorum profundus tendon repairs in ten fingers. The tendons underwent a six-strand M-Tang core repair, no circumferential suture, and partial or complete division of the pulleys. Over 12 months after surgery and using ultrasound, we found no gapping at the repair site during finger motion. When the pulleys were divided, there was sonographic evidence of tendon bowstringing, but the bowstringing was minimal. Clinically, we did not find any fingers that displayed tendon bowstringing or had functional loss. With ultrasound examination, the repaired tendons remained enlarged over 12 months. Two patients developed heterotopic ossifications at the repair site without tendon gliding, and these required tenolysis. We conclude that the tendon repair site does not gap when a strong core suture is used in the repair without adding peripheral sutures. There is no notable tendon bowstringing clinically, though the repaired tendons have sonographic evidence of minor bowstringing.

LEVEL OF EVIDENCE

III.

Cyclic Testing of the 6-Strand Tang and Modified Lim-Tsai Flexor Tendon Repair Techniques

PURPOSE

In this study, we compared the Tang repair technique with the 6-strand modified Lim-Tsai repair technique under cyclic testing conditions.

METHODS

Twenty fresh-frozen porcine flexor tendons were randomized into 2 groups for repair with either the modified Lim-Tsai or the Tang technique using Supramid 4-0 core sutures and Ethilon 6-0 epitendinous running suture. The repaired tendons were subjected to 2 stage cyclic loading. The survival rate and gap formation at the repair site were recorded.

RESULTS

Tendons repaired by the Tang technique achieved an 80% survival rate. None of the modified Lim-Tsai repairs survived. The mean gap formed at the end of 1000 cycles was 1.09 mm in the Tang repairs compared with 4.15 mm in the modified Lim-Tsai repairs.

CONCLUSIONS

The Tang repair is biomechanically stronger than the modified Lim-Tsai repair under cyclic loading.

CLINICAL RELEVANCE

The Tang repair technique may exhibit a higher tolerance for active mobilization after surgery with less propensity for gap formation.