Gliding resistance and modifications of gliding surface of tendon: clinical perspectives

Flexor Tendon Injuries

Flexor tendon injuries are complex, and management of these injuries requires consideration of the surgical timing, injury location, approach, and soft tissue handling. Complications are common, including adhesions, tendon rupture, infection, and a high reoperation rate for zone 2 repairs. Special considerations are given to chronic ruptures, concomitant fractures, and pediatric cases. We discuss current concepts that may improve patient outcomes.

The Direct Tendon Suture and Paratenon Repair Technique for Acute Tendinous Mallet Finger: A Case Series

(1) Introduction: Tendinous mallet finger is a frequent deformity that occurs after an extensor tendon injury during sports or daily life activities. Despite the existence of numerous non-operative and operative techniques to address this deformity, there is a controversy on its optimal management. In this study, we aimed to present a direct tendon suture technique using the distal interphalangeal (DIP) joint open approach for treating tendinous mallet finger injury. (2) Methods: Between 2019 and 2021, 19 patients with closed non-fracture tendinous mallet fingers underwent the direct tendon and paratenon repair technique. After skin incision, we opened the paratenon with lazy S shape incision and found the ruptured proximal and distal tendon ends. We reapproximated the tendons using a simple interrupted suture with Prolene #6/0. After that, we meticulously performed paratenon repair using PDS #6/0 for preventing readherence. Temporary trans-articular Kirschner wire fixation was used for 4 weeks. (3) Results: All patients were followed-up for 3-8 months (mean: 4.8 months). The mean final extension lag was 6.5 degrees, and the overall rate of cases with excellent and good outcomes using Crawford's criteria was 85%. (4) Conclusions: In conclusion, this surgical approach could be a reliable alternative for the treatment of tendinous mallet finger injuries.

Reoperation Following Zone II Flexor Tendon Repair

BACKGROUND

The goal of zone II flexor tendon surgery is to perform a repair with sufficient strength to withstand the forces encountered during rehabilitation. Postoperative rerupture and adhesion formation may lead to reoperation. This study aimed to determine the factors associated with reoperation after primary zone II flexor tendon repair.

METHODS

In this retrospective case series, a total of 252 fingers in 201 patients underwent zone II flexor tendon repair. A medical record review was performed to collect data regarding patient demographics, injury and treatment characteristics and postoperative complications including reoperation. Reoperation was defined as any unplanned surgical procedure performed after initial flexor tendon repair.

RESULTS

There were 49 fingers (19%) in 42 patients that underwent reoperation at a median of 5.5 (interquartile range: 2.8-7.9) months. Older age, workers' compensation, and a Kessler-type repair of the flexor digitorum profundus were independently associated with reoperation.

CONCLUSIONS

In vitro studies suggest that Kessler-type repairs are inferior compared with other suture configurations. Our study demonstrates a clinical correlation to these biomechanical studies. Our results suggest that Kessler-type repairs are inferior compared with non-Kessler-type repairs, due to postoperative complications requiring secondary surgeries.

Bio-Enhanced Neoligaments Graft Bearing FE002 Primary Progenitor Tenocytes: Allogeneic Tissue Engineering & Surgical Proofs-of-Concept for Hand Ligament Regenerative Medicine

Hand tendon/ligament structural ruptures (tears, lacerations) often require surgical reconstruction and grafting, for the restauration of finger mechanical functions. Clinical-grade human primary progenitor tenocytes (FE002 cryopreserved progenitor cell source) have been previously proposed for diversified therapeutic uses within allogeneic tissue engineering and regenerative medicine applications. The aim of this study was to establish bioengineering and surgical proofs-of-concept for an artificial graft (Neoligaments Infinity-Lock 3 device) bearing cultured and viable FE002 primary progenitor tenocytes. Technical optimization and in vitro validation work showed that the combined preparations could be rapidly obtained (dynamic cell seeding of 10⁵ cells/cm of scaffold, 7 days of co-culture). The studied standardized transplants presented homogeneous cellular colonization in vitro (cellular alignment/coating along the scaffold fibers) and other critical functional attributes (tendon extracellular matrix component such as collagen I and aggrecan synthesis/deposition along the scaffold fibers). Notably, major safety- and functionality-related parameters/attributes of the FE002 cells/finished combination products were compiled and set forth (telomerase activity, adhesion and biological coating potentials). A two-part human cadaveric study enabled to establish clinical protocols for hand ligament cell-assisted surgery (ligamento-suspension plasty after trapeziectomy, thumb metacarpo-phalangeal ulnar collateral ligamentoplasty). Importantly, the aggregated experimental results clearly confirmed that functional and clinically usable allogeneic cell-scaffold combination products could be rapidly and robustly prepared for bio-enhanced hand ligament reconstruction. Major advantages of the considered bioengineered graft were discussed in light of existing clinical protocols based on autologous tenocyte transplantation. Overall, this study established proofs-of-concept for the translational development of a functional tissue engineering protocol in allogeneic musculoskeletal regenerative medicine, in view of a pilot clinical trial.

Overlapping repair and epitenon healing are more stable biomechanically than side to side repair and endotenon healing in achilles tendon lengthening with Z plasty

BACKGROUND

The current study aimed to compare biomechanical stability and healing process of side-to-side repair with overlapping repair after Achilles tendon lengthening with Z-plasty.

METHODS

In our study, 22 Sprague Dawley male rats were used. Side-to-side repairs were classified as group 1 and overlapping repairs as group 2. The left and right legs of seven rats were used to compare early group 1 and early group 2 biomechanical test results at day 0. Seven rats were used to compare late group 1 and late group 2 biomechanical test results at day 28. Both the right and left tendons were tested from the four rats examined in the biomechanically in the untreated control group. The last remaining four rats were used for histopathological evaluation of tendon repair, at 28-days from the index procedure.The ultimate load to failure was compared between groups.

RESULTS

At time 0, there were no measurable differences between group 1 (3.8 ± 1.4 N) and group 2 (3.7 ± 1.1 N), and both could endure less than one-tenth of the untreated control (49 ± 12). At 28 days, ultimate load to failure improved significantly in both group 1 (16.2 ± 3.5 N) and even more in group 2 (36 ± 8.1 N). While there was a significant difference between group 1 and group 2, neither were able to meet the untreated control (49 ± 12). Histopathological evaluation in the post-healing period showed that fibrosis, neovascularization, and inflammation increased in both groups.

CONCLUSION

The overlapping suture technique and epitenon healing have more stability compared to side-to-side suture technique and endotenon healing. Human population trials may or may not exist, our study suggests it should be considered and further investigation needed before actual clinical application.

The Use of an Adipofascial Flap to Prevent Extensor Tendon Adhesions After Plating of the Proximal Phalanx of the Fingers: A Comparative Study

BACKGROUND

Extensor tendon adhesions occurring after proximal phalangeal (P1) fractures are not uncommon. A previous report described the use of an adipofascial flap (AFF) to prevent adhesions after dorsal plating of the P1. The purpose of the study is to examine the results of open reduction and internal fixation with the use of an AFF (F group) and without (N group, that is, no flap used) in a larger group of patients.

METHODS

A retrospective study involving a period of 11 years was conducted involving results of 21 unstable fractures of the P1 of the fingers in 18 patients. In all, 12 fingers were treated without any flap (N group) and 9 fingers were treated with the AFF (F group). For each patient, the total active motion (TAM) ratio, and the grip strength (Jamar) ratio were assessed, and adverse effects and the 10-point visual analogue scale (VAS) score were recorded. For statistical analysis, sample characteristics were described using mean ± standard deviation and median, and a Bayesian approach was used for inferential analysis.

RESULTS

In the F group, the TAM ratio (84% ± 13% vs 65% ± 17%) was higher with a lower rate of adverse effects (OR: 0.067, 95% CI, 0.0035-0.58,) and a lower VAS score with evidence of the positive effect of the AFF. The Jamar ratio was similar in the 2 groups (F group 80% ± 25% vs N group 79% ± 19%) with no associated effect of the AFF on grip strength.

CONCLUSIONS

The AFF is a reliable tool to reduce adhesions between plates and the extensor apparatus of the P1 and may be useful to improve finger function after plating of P1 fractures.

TYPE OF STUDY/LOE

Therapeutic, Retrospective, Level IV.

Optimizing the Pulvertaft Weave Technique: A Comprehensive Systematic Review of Comparative Biomechanical Studies

PURPOSE

The Pulvertaft weave continues as a staple technique for tendon coaptations. Many have proposed minor alterations to the original technique to improve its strength, though a lack of consensus exists. Our aim was to explore how the number of weaves and suture characteristics contribute to the overall strength of the coaptation.

METHODS

A comprehensive electronic search was conducted using PubMed, Cochrane Library, and Scopus. Criteria for inclusion consisted of cadaveric human or animal biomechanical studies evaluating ultimate failure load (Newtons, N) as well as number of weaves, suture characteristics, tendon source, and number of coaptations. Weaves with minimum averages of 75 N were deemed successful, and those with >120 N were considered high performing.

RESULTS

A total of 347 tendon transfers from 15 studies met inclusion criteria. Average strength by number of weaves was 36.4 N (n=52) for 1 weave; 54.2 N (n=58) for 2 weaves; 115.9 N (n=174) for 3 weaves; and 81.7 N (n=63) for 4 weaves. Statistical differences were observed between 1 and 2 weaves (p<0.0001); 2 and 3 weaves (p<0.0001); 3 and 4 weaves (p<0.003); and 2 and 4 weaves (p<0.0001). High performing tendon transfers utilized 3 weaves, 3-0 or 4-0 braided sutures, and figure-of-eight or mattress core sutures.

CONCLUSIONS

Contrary to the current dogma of 'the more the better', our findings show that Pulvertaft weave strength is optimized when 3 weaves are used to combine donor and recipient tendons. Braided sutures with either figure-of-eight or mattress sutures were associated with highest strength of repair.

A Biomechanical Comparison of Gliding Resistance between Modified Lim Tsai and Asymmetric Tendon Repair Techniques in Zone II Flexor Tendon Repairs

Background: Early active motion protocols have shown better functional outcomes in zone II flexor tendon lacerations. Different techniques of tendon repair have different effects on gliding resistance, which can impact tendon excursion and adhesion formation. For successful initiation of early active mobilisation, the repair technique should have high breaking strength and low gliding resistance. Previous studies have shown the Modified Lim-Tsai technique demonstrates these characteristics. The Asymmetric repair has also shown superior ultimate tensile strength. This study aims to compare the gliding resistance between the two techniques. Methods: FDP tendons from ten fresh frozen cadaveric fingers were randomly divided into two groups, transected completely distal to the sheath of the A2 pulley and repaired using either the Modified Lim-Tsai or Asymmetric technique. The core repair was performed with Supramid 4-0 looped sutures and circumferential epitendinous sutures were done with nylon monofilament Prolene 6-0 sutures. The gliding resistance and ultimate tensile strength were then tested. Results: The gliding resistance of the Asymmetric and Modified Lim-Tsai repair techniques were 0.2 and 0.95 N respectively. This difference was significant (p = 0.008). The Modified Lim-Tsai technique had a higher ultimate tensile strength and load to 2 mm gap formation, though this was not significant. Conclusions: Gliding resistance of the Asymmetric repair is significantly less than that of Modified Lim-Tsai. Ultimate tensile strength and load to 2 mm gap formation are comparable.

Dynamic Tendon Grip (DTG™) novel knot array compared to traditional sutures for zone two flexor tendon injury - a biomechanical feasibility study

BACKGROUND

Flexor tendon injuries pose many challenges for the treating surgeon, the principal of which is creating a strong enough repair to allow early active motion, preserving a low-profile of the repair to prevent buckling and subsequent pulley venting. A main concern is that a low-profile repair is prone to gap formation and repair failure. The Dynamic Tendon Grip (DTG™) all suture staple device claims to allow a strong and low-profile repair of the flexor tendon. The purpose of this study is to test the effects of the DTG™ device in early active motion simulation on range of motion, load to failure and gap formation and to compare it to traditional suturing technique.

METHODS

Twelve fresh-frozen cadaveric fingers were assigned to two groups: DTG™ device (n = 9) and traditional suturing (double Kessler 4-core suture and a peripheral suture, n = 3). The deep flexor was incised and repaired in zone 2, and active motion simulation was carried out with a cyclic flexion-extension machine. Finger range of motion and gap formation were measured, as well as load to failure and method of repair failure.

RESULTS

Following motion simulation, ROM decreased from 244.0 ± 9.9° to 234.5 ± 5.8° for the DTG™ device compared to 234.67 ± 6.51° to 211.67 ± 10.50° for traditional suturing. The DTG™ repair demonstrated gap formation of 0.93 ± 0.18 mm in 3 of 8 specimens after applying 1 kg load, which negated after load removal. Load to failure averaged 76.51 ± 23.15 N for DTG™ and 66.31 ± 40.22 N for the traditional repair. Repair failure occurred as the suture material broke for the DTG™ array and at the knot level for the traditional repair.

CONCLUSIONS

The DTG™ all-suture stapling concept achieved a strong low-profile repair in zone 2 flexor tendon injury after active motion simulation. Further clinical studies will be needed to determine the effectiveness of this device compared to traditional techniques.

Combination of Hyaluronan and Lyophilized Progenitor Cell Derivatives: Stabilization of Functional Hydrogel Products for Therapeutic Management of Tendinous Tissue Disorders

Cultured progenitor cells and derivatives have been used in various homologous applications of cutaneous and musculoskeletal regenerative medicine. Active pharmaceutical ingredients (API) in the form of progenitor cell derivatives such as lysates and lyophilizates were shown to retain function in controlled cellular models of wound repair. On the other hand, hyaluronan-based hydrogels are widely used as functional vehicles in therapeutic products for tendon tissue disorders. The aim of this study was the experimental characterization of formulations containing progenitor tenocyte-derived APIs and hyaluronan, for the assessment of ingredient compatibility and stability in view of eventual therapeutic applications in tendinopathies. Lyophilized APIs were determined to contain relatively low quantities of proteins and growth factors, while being physicochemically stable and possessing significant intrinsic antioxidant properties. Physical and rheological quantifications of the combination formulas were performed after hydrogen peroxide challenge, outlining significantly improved evolutive viscoelasticity values in accelerated degradation settings. Thus, potent effects of physicochemical protection or stability enhancement of hyaluronan by the incorporated APIs were observed. Finally, combination formulas were found to be easily injectable into ex vivo tendon tissues, confirming their compatibility with further translational clinical approaches. Overall, this study provides the technical bases for the development of progenitor tenocyte derivative-based injectable therapeutic products or devices, to potentially be applied in tendinous tissue disorders.

Improving flexor tendon gliding by using the combination of carboxymethylcellulose‑polyethylene oxide on murine model

The current approach to flexor tendon injuries is complex and is no longer limited to suturing techniques. Strategies for improving hand function currently include rehabilitation protocols, appropriate suturing materials and techniques, changing the gliding surface by using lubricants and providing growth factors. One product, originally used in spinal surgery, has been shown to be effective in preventing postoperative adhesions. It is a combination of carboxymethylcellulose and polyethylene oxide-Dynavisc^® (FzioMed, Inc.). The aim of the present study was to test the effect of Dynavisc^® on acute injuries of the intrasynovial flexor tendons in the prevention of postoperative adhesions and the improvement of functional results. The study was performed on 20 Wistar rats distributed in two groups. The control group, represented by 10 rats, in which after the reconstruction of the flexor tendon, the peritendinous area was injected with saline solution and the study group, in which the peritendinous area was injected with a single administration of the lubricating gel, Dynavisc^® (carboxymethylcellulose and polyethylene oxide). At 4 and 12 weeks, the rats were sacrificed and tissue biopsy consisted of tendon fragments and adjacent tissue. The evaluation of the results was performed by measuring the adhesion score and observing histological parameters. The presence of important adhesions was found in the control group compared with the group treated with Dynavisc^®, where a supple and smooth tendon, with significantly fewer adhesions were found. The differences between the two groups were significant, thus indicating the efficiency of the lubricant in preventing adhesions. This study supported the important role of Dynavisc^® in the regeneration of the tendon and the peritendinous structures, by limiting aberrant fibrous proliferation in the regeneration process and helping to build a peritendinous space.

The Effect of Gelatin Molecular Weight on Tendon Lubrication Utilizing an Extrasynovialized Turkey Flexor Tendon Model

INTRODUCTION

Flexor tendon injuries are common hand injuries among the military population often resulting in functional impairment. Flexor tendon gliding friction has been linked to adhesion formation, especially with the use of extrasynovial grafts. Carbodiimide-derivatized hyaluronic acid with gelatin (cd-HA-gelatin) can reduce gliding friction of the tendon graft; however, the effects of gelatin molecular weight (MW) have not been studied. The turkey model has been shown to better match humans, but extrasynovial tendons are unavailable. The purpose of this study was to (1) manually roughen turkey flexor digitorum profundus (FDP) tendons to simulate extrasynovial tendons and (2) investigate the effects of gelatin MW on tendon friction.

MATERIALS AND METHODS

The third digit of (n = 48) turkeys were dissected with the proximal pulley, and FDP tendon and the flexor superficialis tendon were preserved. Digits were randomly assigned into four groups: one saline control and three cd-HA-gelatin-treated groups of varying gelatin MW. Flexor digitorum profundus tendon friction was measured at its original condition, serving as a baseline. Tendons were roughened using a custom rig, and tendon friction was measured again. All four groups received treatment and gliding friction was measured every 100 cycles to a total of 1,000 cycles.

RESULTS

Tendon friction significantly increased (P < 0.05) after roughening. Friction in the saline control group increased steadily over repeated cycles, whereas friction of all gelatin-treated tendons decreased significantly compared with the saline control group (P < 0.05), maintaining low friction to 1,000 cycles representing human tendons. There was no significant difference found between gelatin-treated groups.

CONCLUSIONS

We have developed a method to roughen synovial FDP tendons to create extrasynovial-like tendons for lubrication material evaluations. Cd-HA-gelatin effectively reduces tendon friction in this model. Our data suggest medium or low MW gelatin may provide a better reduction in friction compared with high MW gelatin.

Engineering a cell-hydrogel-fibre composite to mimic the structure and function of the tendon synovial sheath

The repair of tendon injuries is often compromised by post-operative peritendinous adhesions. Placing a physical barrier at the interface between the tendon and the surrounding tissue could potentially solve this problem by reducing adhesion formation. At present, no such system is available for routine use in clinical practice. Here, we propose the development of a bilayer membrane combining a nanofibrous poly(ε-caprolactone) (PCL) electrospun mesh with a layer of self-assembling peptide hydrogel (SAPH) laden with type-B synoviocytes. This bilayer membrane would act as an anti-adhesion system capable of restoring tendon lubrication, while assisting with synovial sheath regeneration. The PCL mesh showed adequate mechanical properties (Young's modulus=19±4 MPa, ultimate tensile stress=9.6±1.7 MPa, failure load=0.5±0.1 N), indicating that the membrane is easy to handle and capable to withstand the frictional forces generated on the tendon's surface during movement (~0.3 N). Morphological analysis confirmed the generation of a mesh with nanosized PCL fibres and small pores (< 3 μm), which prevented fibroblast infiltration to impede extrinsic healing but still allowing diffusion of nutrients and waste. Rheological tests showed that incorporation of SAPH layer allows good lubrication properties when the membrane is articulated against porcine tendon or hypodermis, suggesting that restoration of tendon gliding is possible upon implantation. Moreover, viability and metabolic activity tests indicated that the SAPH was conducive to rabbit synoviocyte growth and proliferation over 28 days of 3D culture, sustaining cell production of specific matrix components, particularly hyaluronic acid. Synoviocyte-laden peptide hydrogel promoted a sustained endogenous production of hyaluronic acid, providing an anti-friction layer that potentially restores the tendon gliding environment.

[Tenoarthrolysis after flexor tendon injuries]

Normal function of the fingers and thumb depends on properly gliding flexor tendons and a free range of motion of the involved joints. This normal gliding function may be inhibited by adhesions due to damage of the tendon, tendon sheath and adjacent tissue. When digital function is still limited despite a long-term course of hand therapy and there are no signs of further improvement, surgical intervention should be considered. There are no absolute indications for tenoathrolysis of the flexor tendons. With respect to complications, such as secondary tendon rupture, loss of annular pulleys and scar formation, it is part of a stepwise reconstructive concept including further procedures, such as staged flexor tendon reconstruction. Important preconditions for tenoathrolysis are motivation of the patient, the possibility of readily available and frequent postoperative follow-up hand therapy, healed fractures and osteotomy, mature soft tissue, intact tendons and gliding tissue. Preoperatively, a maximum passive range of motion of the involved joints should be achieved. During the operative procedure all adhesive tissue surrounding the tendon within and outside the tendon sheath is consistently resected preserving the annular pulleys as far as possible. Therefore, extensive approaches, arthrolysis, dissolution of unfavorable scar tissue, resection of scarred lumbrical muscles and annular pulley reconstruction are frequently necessary. Salvage procedures, such as arthrodesis, amputation, ray resection or multistage flexor tendon reconstruction are recommended in failed cases and should be considered even preoperatively. In order to retain the intraoperative functional improvement hand therapy for at least 3-6 months should follow.

Battling adhesions: from understanding to prevention

Adhesions represent a major burden in clinical practice, particularly following abdominal, intrauterine, pericardial and tendon surgical procedures. Adhesions are initiated by a disruption in the epithelial or mesothelial layer of tissue, which leads to fibrin adhesion sites due to the downregulation of fibrinolytic activity and an increase in fibrin deposition. Hence, the metabolic events involved in tissue healing, coagulation, inflammation, fibrinolysis and angiogenesis play a pivotal role in adhesion formation. Understanding these events, their interactions and their influence on the development of post-surgical adhesion is crucial for the development of effective therapies to prevent them. Mechanical barriers, antiadhesive agents and combination thereof are customarily used in the battle against adhesions. Although these systems seem to be effective at reducing adhesions in clinical procedures, their prevention remains still elusive, imposing the need for new antiadhesive strategies.

Lipid-hyaluronan synergy strongly reduces intrasynovial tissue boundary friction

Hyaluronan (HA)-lipid layers on model (mica) surfaces massively reduce friction as the surfaces slide past each other, and have been proposed, together with lubricin, as the boundary layers accounting for the extreme lubrication of articular cartilage. The ability of such HA-lipid complexes to lubricate sliding biological tissues has not however been demonstrated. Here we show that HA-lipid layers on the surface of an intrasynovial tendon can strongly reduce the friction as the tendon slides within its sheath. We find a marked lubrication synergy when combining both HA and lipids at the tendon surface, relative to each component alone, further enhanced when the polysaccharide is functionalized to attach specifically to the tissue. Our results shed light on the lubricity of sliding biological tissues, and indicate a novel approach for lubricating surfaces such as tendons and, possibly, articular cartilage, important, respectively, for alleviating function impairment following tendon injury and repair, or in the context of osteoarthritis. STATEMENT OF SIGNIFICANCE: Lubrication breakdown between sliding biological tissues is responsible for pathologies ranging from dry eye syndrome to tendon-injury repair impairment and osteoarthritis. These are increasing with human longevity and impose a huge economic and societal burden. Here we show that synergy of hyaluronan and lipids, molecules which are central components of synovial joints and of the tendon/sheath system, can strongly reduce friction between sliding biological tissues (the extrasynovial tendon sliding in its sheath), relative to untreated tissue or to either component on its own. Our results point to the molecular origins of the very low friction in healthy tendons and synovial joints, as well as to novel treatments of lubrication breakdown in these organs.

A murine model of a novel surgical architecture for proprioceptive muscle feedback and its potential application to control of advanced limb prostheses

OBJECTIVE

Proprioceptive mechanisms play a critical role in both reflexive and volitional lower extremity control. Significant strides have been made in the development of bionic limbs that are capable of bi-directional communication with the peripheral nervous system, but none of these systems have been capable of providing physiologically-relevant muscle-based proprioceptive feedback through natural neural pathways. In this study, we present the agonist-antagonist myoneural interface (AMI), a surgical approach with the capacity to provide graded kinesthetic feedback from a prosthesis through mechanical activation of native mechanoreceptors within residual agonist-antagonist muscle pairs.

APPROACH

(1) Sonomicrometery and electroneurography measurement systems were validated using a servo-based muscle tensioning system. (2) A heuristic controller was implemented to modulate functional electrical stimulation of an agonist muscle, using sonomicrometric measurements of stretch from a mechanically-coupled antagonist muscle as feedback. (3) One AMI was surgically constructed in the hindlimb of each rat. (4) The gastrocnemius-soleus complex of the rat was cycled through a series of ramp-and-hold stretches in two different muscle architectures: native (physiologically-intact) and AMI (modified). Integrated electroneurography from the tibial nerve was compared across the two architectures.

MAIN RESULTS

Correlation between stretch and afferent signal demonstrated that the AMI is capable of provoking graded afferent signals in response to ramp-and-hold stretches, in a manner similar to the native muscle architecture. The response magnitude in the AMI was reduced when compared to the native architecture, likely due to lower stretch amplitudes. The closed-loop control system showed robustness at high stretch magnitudes, with some oscillation at low stretch magnitudes.

SIGNIFICANCE

These results indicate that the AMI has the potential to communicate meaningful kinesthetic feedback from a prosthetic limb by replicating the agonist-antagonist relationships that are fundamental to physiological proprioception.

Pathomechanics and Management of Secondary Complications Associated with Tendon Adhesions Following Flexor Tendon Repair in Zone II

Despite the number of rehabilitation strategies and guidelines developed to maximize the gliding amplitude of repaired tendons, secondary complications, such as decreased range of motion and stiffness associated with tendon adhesions, commonly arise. If left untreated, these early complications may lead to secondary pathomechanical changes resulting in fixed deformities and decreased function. Therefore, an appropriate treatment regimen must not only include strategies to maintain the integrity of the repaired tendon, but must also avoid secondary complications due to reduced gliding amplitude. This review presents a biomechanical analysis of the dynamics of tendon gliding following repair in zone II and rehabilitation strategies to minimize secondary complications related with tendon adhesions.

Rehabilitation following zone II flexor tendon repairs

Ongoing clinical and basic research has improved understanding of flexor tendon mechanics and physiology for surgical repair and rehabilitation after a zone II flexor tendon repair. Yet, the ideal surgical repair technique that includes sufficient strength to allow safe immediate active motion of the finger, without excessive repair stiffness, bulk or rough surfaces resulting in excessive resistance to flexion, does not exist. After optimizing the repair, the surgeon and therapist team must select a rehabilitation plan that protects the repair but helps to maintain tendon gliding. There are 3 types of rehabilitation programs for flexor tendon repairs: delayed mobilization, early passive mobilization, or an early active mobilization. No guideline for rehabilitation should be followed exactly. Many factors influence therapy decisions, including repair technique, associated tendon healing, passive versus active range of motion, edema, and tendon adhesions. These factors can assist in guiding rehabilitation progression and promote functional range of motion, safely mobilize the repaired tendon(s) and prevent gapping, rupture, and adhesions.

Ultrasound-Guided Hyaluronic Acid Injections for Trigger Finger: A Double-Blinded, Randomized Controlled Trial

OBJECTIVES

To investigate the effects of ultrasound-guided injections of hyaluronic acid (HA) versus steroid for trigger fingers in adults.

DESIGN

Prospective, double-blinded, randomized controlled study.

SETTING

Tertiary care center.

PARTICIPANTS

Subjects with a diagnosis of trigger finger (N=36; 39 affected digits) received treatment and were evaluated.

INTERVENTIONS

Subjects were randomly assigned to HA and steroid injection groups. Both study medications were injected separately via ultrasound guidance with 1 injection.

MAIN OUTCOME MEASURES

The classification of trigger grading, pain, functional disability, and patient satisfaction were evaluated before the injection and 3 weeks and 3 months after the injection.

RESULTS

At 3 months, 12 patients (66.7%) in the HA group and 17 patients (89.5%) in the steroid group exhibited no triggering of the affected fingers (P=.124). The treatment results at 3 weeks and 3 months showed similar changes in the Quinnell scale (P=.057 and .931, respectively). A statistically significant interaction effect between group and time was found for visual analog scale (VAS) and Michigan Hand Outcome Questionnaire (MHQ) evaluation (P<.05). The steroid group had a lower VAS at 3 months after injection (steroid 0.5±1.1 vs HA 2.7±2.4; P<.001). The HA group demonstrated continuing significant improvement in MHQ at 3 months (change from 3wk: steroid -2.6±14.1 vs HA 19.1±37.0; P=.023; d=.78).

CONCLUSIONS

Ultrasound-guided injection of HA demonstrated promising results for the treatment of trigger fingers. The optimal frequency, dosage, and molecular weight of HA injections for trigger fingers deserve further investigation for future clinical applications.

[Tenolysis of the flexor tendons in the hand]

BACKGROUND

Properly gliding flexor tendons is mandatory for the normal functioning of the finger and thumb. Any damage to tendons, tendon sheath or adjacent tissue can lead to the formation of adhesions that inhibit the normal gliding function. If adhesions limit the digital function and adequate hand therapy does not provide further progress, then surgical intervention should be considered.

AIM

The authors' strategy and treatment algorithm for flexor tenolysis are presented in the context of the current literature.

METHODS

There is no absolute indication for flexor tenolysis. The decision should be made in a motivated patient who has access to adequate postoperative hand therapy. It should be based on healed fractures and osteotomies, mature soft tissue coverage, intact tendons and gliding tissues, and a full range of passive flexion, and preferably extension of the affected joints. The principle of flexor tenolysis is the consequent resection of all adhesive tissue around the tendon inside and outside the tendon sheath, with preservation of as many pulley sections as possible. Therefore, extensive approaches are frequently necessary. Arthrolysis and the resolution of unfavorable scars, the resection of scarred lumbricals, and pulley reconstruction are additional procedures that are frequently performed.

RESULTS

In the literature, improvement in the range of motion is between 59 and 84 %. Good and excellent functional results are reported in 60-80 % of the cases. Nevertheless, in selected cases, functional deterioration occurs. Flexor tendon ruptures after tenolysis were observed in 0-8 % of the patients.

DISCUSSION

With regard to complications such as secondary tendon ruptures, loss of pulleys, and scar formation, flexor tenolysis is part of a reconstructive ladder that includes further procedures. In the case of failure or complications, salvage procedures such as arthrodesis, amputation, and ray resection or staged flexor tendon reconstruction including tendon grafting are recommended. After successful flexor tenolysis long-term hand therapy for at least 3-6 months is mandatory to maintain the intraoperative gain of function.

Evidence-based flexor tendon repair

The goal of flexor tendon repair is to achieve normal range of motion of the finger or thumb. The surgical approach depends on the level of injury. Multistrand core suture repairs are recommended for primary flexor tendon repair. It is evident that at least 4 strands are required to an initiate and active range of motion protocol. The epitendinous suture can also increase the strength of the repair. Careful attention to the post-operative therapy regiment is critical to a successful repair.

Can an adipofascial flap be used to prevent adhesions after plating of the proximal phalanx? A case report

Tendon adhesions in zone IV after proximal phalangeal fractures are common and may lead to loss of range of motion at the proximal interphalangeal joint. The type of fracture, surgical technique and rehabilitation strategy also influence the final functional outcome. Plate fixation is a reliable solution in cases of comminuted phalangeal fracture. This article describes how adhesions between the plate and extensor apparatus in cases of comminuted fractures of the proximal phalanx can be reduced by using an adipofascial flap.

Parathyroid hormone 1-34 enhances extracellular matrix deposition and organization during flexor tendon repair

Parathyroid hormone (PTH) 1-34 is known to enhance fracture healing. Tendon repair is analogous to bone healing in its dependence on the proliferation and differentiation of mesenchymal stem cells, matrix formation, and tissue remodeling.(1,2,3) We hypothesized that PTH 1-34 enhances tendon healing in a flexor digitorum longus (FDL) tendon repair model. C57Bl/6J mice were treated with either intraperitoneal PTH 1-34 or vehicle-control (PBS). Tendons were harvested at 3-28 days for histology, gene expression, and biomechanical testing. The metatarsophalangeal joint range of motion was reduced 1.5-2-fold in PTH 1-34 mice compared to control mice. The gliding coefficient, a measure of adhesion formation, was 2-3.5-fold higher in PTH 1-34 mice. At 14 days post-repair, the tensile strength was twofold higher in PTH 1-34 specimens, but at 28 days there were no differences. PTH 1-34 mice had increased fibrous tissue deposition that correlated with elevated expression of collagens and fibronectin as seen on quantitative PCR. PTH 1-34 accelerated the deposition of reparative tissue but increased adhesion formation.

[Primary flexor tendons repair in zone 2]

Primary flexor tendon repair is still challenging even in the most experienced hands. With atraumatic surgery, the goal is to suture the tendon in a way that it will be strong enough to allow for tendon gliding without the risk of rupture or adhesions during the 12 weeks needed for the tendon to heal. After reviewing the zone 2 anatomy, the authors describe the state of art for flexor tendon repair along with their personal preferences. Although suture methods and postoperative rehabilitation programs are not universal, most specialized teams now use multistrand suturing techniques with at least 4 stands along with protected and controlled early active mobilization. Although the published rates of failure of the repair or postoperative adhesions with stiffness have decreased, these complications are still a concern. They will continue to pose a challenge for scientists performing research into the mechanics and biology of flexor tendon repairs, especially in zone 2.