The role of the synovial fluid and tendon sheath for flexor tendon nutrition. An experimental tracer study on diffusional pathways in dogs

Early Postoperative Rapid Rehabilitation Yields More Favorable Short-term Outcomes in Patients Undergoing Patellar Realignment Surgery for Recurrent Patellar Dislocation: A Prospective Randomized Controlled Study

BACKGROUND

Use of a rapid rehabilitation protocol for postoperative recovery after recurrent patellar dislocation (RPD) has gradually gained attention; nonetheless, evidence of its safety and effectiveness is lacking.

PURPOSE

To compare the short-term postoperative outcomes of early rapid rehabilitation with those of conservative rehabilitation in patients with RPD.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 50 patients with RPD who underwent tibial tubercle osteotomy combined with medial patellofemoral ligament reconstruction were enrolled between January 2018 and February 2019. Postoperatively, the patients were randomly assigned to either the early rapid group (rapid group; n = 25 patients) or the conservative group (control group; n = 25 patients) for rehabilitation training. The rapid group underwent faster progression in weightbearing and range of motion (ROM) training. Knee joint functional scores, ROM, bilateral thigh circumference differences, and imaging data were recorded preoperatively and at 6 weeks and 3, 6, 12, and 24 months postoperatively for comparison. Postoperative complications were recorded over the 24-month follow-up period.

RESULTS

The baseline data did not significantly differ between the 2 groups. Postoperatively, compared with the control group, the rapid group had higher Tegner scores at 6 weeks and 3 months; higher Lysholm scores at 3 and 6 months; higher International Knee Documentation Committee scores at 6 weeks, 3 months, and 12 months; better ROM; and smaller bilateral thigh circumference differences at 24 months (P < .05 for all). However, no differences were observed in the Tegner, Lysholm, and International Knee Documentation Committee scores at 24 months postoperatively. At the 6-week and subsequent follow-up visits, the Caton and Insall indices were lower in the control group than in the rapid group (P < .01 for all). Moreover, compared with the control group, the rapid group had a lower incidence of patella baja at 24 months (0% vs 17%) and fewer complications during the whole follow-up period (P < .01).

CONCLUSION

Early rapid postoperative rehabilitation appears to be safe and effective for patients who undergo tibial tubercle osteotomy combined with medial patellofemoral ligament reconstruction to treat RPD. In the short term, this approach was shown to be more advantageous than conservative rehabilitation in improving functional scores, allowing an earlier return to daily activities, although the lack of difference at 24 months implies no long-term benefits. In addition, it potentially helped to prevent the occurrence of complications, including patella baja.

REGISTRATION

ChiCTR1800014648 (ClinicalTrials.gov identifier).

Flexor Tendon: Development, Healing, Adhesion Formation, and Contributing Growth Factors

Management of flexor tendon injuries of the hand remains a major clinical problem. Even with intricate repair, adhesion formation remains a common complication. Significant progress has been made to better understand the mechanisms of healing and adhesion formation. However, there has been slow progress in the clinical prevention and reversal of flexor tendon adhesions. The goal of this article is to discuss recent literature relating to tendon development, tendon healing, and adhesion formation to identify areas in need of further research. Additional research is needed to understand and compare the molecular, cellular, and genetic mechanisms involved in flexor tendon morphogenesis, postoperative healing, and mechanical loading. Such knowledge is critical to determine how to improve repair outcomes and identify new therapeutic strategies to promote tissue regeneration and prevent adhesion formation.

Assessment of mRNA Levels for Matrix Molecules and TGF-β1 in Rabbit Flexor and Peroneus Tendons Reveals Regional Differences in Steady-State Expression

This study analysed the differences on a molecular level between two segments of the deep flexor tendon, and compared the intrasynovial flexor tendon with the tendon sheath and the extrasynovial peroneus tendon in a rabbit model. The TRIspin method of RNA extraction was combined with the reverse transcription polymerase chain reaction to assess mRNA levels in the tissue segments. Significant differences were detected for all genes studied. mRNA levels for aggrecan, biglycan and collagen III were significantly higher in the fibrocartilaginous proximal segment of the flexor tendon. Collagen I was higher in the flexor tendon than the sheath and the peroneus tendon, and TGF-β1 was significantly lower in the peroneus tendon. This study demonstrates differences at the mRNA level between different segments of tendon, indicating that the tendon tissue may be adapted to its environment.

Orthotic considerations for dense connective tissue and articular cartilage--the need for optimal movement and stress

Orthotic intervention is an essential component of hand rehabilitation, addressing biological factors that affect activity and participation. Functional, pain-free joint mobility requires skeletal stability, healthy articular cartilage, and appropriate extensibility of periarticular dense connective tissues (DCTs). This article addresses basic science underlying clinical reasoning when considering orthoses to maintain or restore structural integrity, mobility and function of DCT structures, and articular cartilage. However, these tissues often have different and sometimes conflicting requirements for the maintenance and restoration of integrity and health. The duration of immobilization, especially at end range, should be carefully considered, as it impairs nutrition of tissues and adversely compresses articular cartilage, causing injury that may not be reversible. Immobilization also reduces extensibility of DCT. Thus, an intermittent orthotic wearing schedule is suggested, allowing movement wherever possible to promote tissue health. To optimize benefits and minimize harmful effects of orthotic intervention, further research on physiological responses of human tissues to immobilization and tension is needed.

Conditioning of the Achilles tendon via ankle exercise improves correlations between sonographic measures of tendon thickness and body anthropometry

Although conditioning is routinely used in mechanical tests of tendon in vitro, previous in vivo research evaluating the influence of body anthropometry on Achilles tendon thickness has not considered its potential effects on tendon structure. This study evaluated the relationship between Achilles tendon thickness and body anthropometry in healthy adults both before and after resistive ankle plantarflexion exercise. A convenience sample of 30 healthy male adults underwent sonographic examination of the Achilles tendon in addition to standard anthropometric measures of stature and body weight. A 10-5 MHz linear array transducer was used to acquire longitudinal sonograms of the Achilles tendon, 20 mm proximal to the tendon insertion. Participants then completed a series (90-100 repetitions) of conditioning exercises against an effective resistance between 100% and 150% body weight. Longitudinal sonograms were repeated immediately on completion of the exercise intervention, and anteroposterior Achilles tendon thickness was determined. Achilles tendon thickness was significantly reduced immediately following conditioning exercise (t = 9.71, P < 0.001), resulting in an average transverse strain of -18.8%. In contrast to preexercise measures, Achilles tendon thickness was significantly correlated with body weight (r = 0.72, P < 0.001) and to a lesser extent height (r = 0.45, P = 0.01) and body mass index (r = 0.63, P < 0.001) after exercise. Conditioning of the Achilles tendon via resistive ankle exercises induces alterations in tendon structure that substantially improve correlations between Achilles tendon thickness and body anthropometry. It is recommended that conditioning exercises, which standardize the load history of tendon, are employed before measurements of sonographic tendon thickness in vivo.

The role and mechanical behavior of the connective tissue in tendon sliding

After carrying out 215 in-vivo dissections, 65 of which were video-recorded, the authors propose that the current representation of the notion of the tendon sliding is incorrect. It is suggested that tendon sliding is explained by the existence of a mechanical adaptable multimicrovacuolar and fibrillar tissue. This tissue enables complete sliding without any dynamic influence on the surrounding tissues. The new theory is based on a polyhedric fibrillar framework, apparently chaotic and complex, subtending the microvacuolar gel, a concept that is to be found everywhere in the human body.

Prevention of adhesions in surgery of the flexor tendons of the hand: what is the evidence?

INTRODUCTION

Despite advances in knowledge and refinements of technique, the management of flexor tendon injuries within the digital sheath continues to present a formidable challenge. This in turn has led to a massive expansion in search of modified surgical therapies and various adjuvant therapies, which could prevent adhesion formation without compromising digital function.

SOURCES OF DATA

A search of PubMed, Medline, CINAHL and Embase databases was performed using the keywords 'tendon adhesion prevention', 'tendon healing', 'adhesion prevention in tendons' and 'adjuvants for adhesion prevention'. Studies detailing the use of surgical, pharmacological and non-pharmacological agents for adhesion prevention in digital flexor tendons were identified, and their bibliographies were thoroughly reviewed to identify further related articles. This search identified 41 studies, which investigated the use of various pharmacological agents in adhesion prevention in digital tendons.

AREAS OF AGREEMENT

There is a need to develop and utilize an optimal method for the prevention of adhesions in the flexor tendons of the hand, due to post-surgical complications.

AREAS OF CONTROVERSY

Even though there have been significant advances in the prevention of adhesions in flexor tendons, it remains to be proved which, if any, of the current methods are the most beneficial.

GROWING POINTS

The only thing that appears clinically justified in adhesion prevention is the need for early post-operative mobilization of digits after tendon injury or repair but the best method of mobilization remains controversial.

AREAS TIMELY FOR DEVELOPING RESEARCH

Suggested changes in surgical techniques and various proposed pharmacological and non-pharmacological modalities need to withstand the test of adequately powered human trials, before their justification for potential benefit in clinical practice is accepted.

A fresh look at vascularized flexor tendon transfers: concept, technical aspects and results

The authors present the results of their surgical experience based on an original approach in secondary reconstructing 71 flexor tendons of the hand. For 20 years, they have been using vascularized tendon transfers either islanded or as free transfers. Their techniques are based on extensive knowledge of the sliding mechanisms involved around the flexor tendons, for which the authors have developed new scientific explanations resulting from their observations and the fine analysis of movements. This sliding system has a multimicrovacuolar, multifibrillar architecture that is able to accommodate every request for movement. By performing vascularized transfers, the authors also transfer the sliding capability together with the tendon itself, thereby avoiding the two traditional stages of tendon reconstruction. Results are better than with the traditional techniques and the gain in time is considerable. Moreover, the biological and physical advantages of transferring living structures are such that the functional outcome in secondary interventions is much better. Furthermore, the wide variety of transfers available offers possibilities for reconstruction that are better suited to the range of presentations encountered in this challenging area of surgery. This new approach to reconstruction is reserved for complex clinical cases and experienced surgeons.

The scientific basis for advances in flexor tendon surgery

During the last 40 years, there has been an enormous amount of basic scientific research designed to improve our knowledge of the structure of tendons, the biomechanics of their action, their biologic response to injury and repair, the mechanical characteristics of various tendon suture methods, and the effect of postrepair motion stress on tendon strength and healing. These investigative efforts have given rise to improved methods of tendon repair and protocols for the early application of passive and active wrist and digital motion as a means to more rapidly increase the strength and gliding of repaired tendons. The surgical techniques of hand surgeons and the rehabilitation protocols of hand therapists have improved enormously from these scientific efforts and the results of flexor tendon repair have become much more reliable. This article attempts to review many of the important scientific reports dealing with flexor tendons that have been published during the last three-plus decades and indicate how those works have improved our management of these difficult injuries.

The evolution of early mobilization of the repaired flexor tendon

The most important difference between the various approaches to postoperative digital flexor tendon rehabilitation is how the repaired tendon is treated during the first three to six weeks, in the earliest stages of healing. Early mobilization is the most commonly reported method of managing the healing flexor tendon. There are many different protocols and abundant research to support published approaches to tendon management. With so many choices, today's hand therapist must understand not only what those choices are, but also why and when to use them. There is no one correct way to manage a repaired flexor tendon; the specialist who does not understand how current techniques evolved is ill-equipped to design the appropriate treatment for a given patient. This article presents an overview of management options and how they have been developed over time, with special attention to changes in splint and exercise design in the crucial first few weeks after repair.

History of flexor tendon repair

The first issue of Hand Clinics published 20 years ago was devoted to flexor tendon injuries. This was most appropriate, because no subject in hand surgery has sparked more interest or discussion. That inaugural issue included excellent presentations on the basic science of tendon injuries (anatomy, biomechanics, nutrition, healing, adhesions) and the clinical practice of tendon repair. Of interest, there was no presentation on the fascinating history of flexor tendon surgery. It is most appropriate, therefore, that this current update of the flexor tendon begins with a historical review of the evolution of flexor tendon repair.

Biomechanics of the flexor tendons

This article examines basic tendon biomechanics, the anatomy and mechanics of digital flexor tendons, and the digital flexor pulley system. It also explores the various models that have tried to simulate the motion of the flexor tendons and several testing modalities that have been used. Finally, clinical applications are considered, including the biomechanics of flexor tendon repairs and tendon transfers. As we reach limits in the care of flexor tendon injuries, research into molecular, biochemical, and micromechanical methods of tendon repair will become the forefront of future investigation.

Flexor tendon biology

Significant advances in the understanding of intrasynovial flexor tendon repair and rehabilitation have been made since the early 1970s. The concept of adhesion-free, or primary tendon healing--that tendons could heal intrinsically without the ingrowth of fibrous adhesions from the surrounding sheath has been validated both experimentally and clinically in studies over the past 25 years. Recent attempts to understand and improve the results of intrasynovial flexor tendon repair have focused upon restoration of the gliding surface, augmentation of early post-operative repair site biomechanical strength and on the elucidation of the molecular biology of early post-operative tendon healing. The goals of the surgical treatment of patients with intrasynovial flexor tendon lacerations remain unchanged: to achieve a primary tendon repair of sufficient tensile strength to allow application of a post-operative mobilization rehabilitation protocol. This program should inhibit the formation of intrasynovial adhesions and restore the gliding surface, while facilitating the healing of the repair site.

Dorsal and palmar material properties of the adult human flexor profundus tendon in Zone II

Nineteen fresh frozen adult human flexor digitorum profundus (FDP) tendons in Zone II were studied to compare the differences in material properties between the dorsal (dFDP) and palmar (pFDP) side of each tendon biomechanically, biochemically and histologically. We have found that tissue from the dorsal side of each flexor tendon has (1) greater strength; (2) less collagen crosslinking (hydroxypyridinium); and (3) a larger single bundle cross-sectional area than tissue from the palmar side of the same tendon. These data clearly demonstrate that the dorsal and palmar sides of the adult human (FDP) tendon in Zone II differ materially. These differences suggest that there may be biomechanical advantages in placing core sutures dorsally when repairing flexor tendons, a technique that we have previously described.

Healing of full-thickness tears of avian supracoracoid tendons: in situ hybridization of alpha1(I) and alpha1(III) procollagen mRNA

Although clinically significant, much remains unknown about the healing of the torn rotator cuff tendon, because of unavailability of appropriate animal model. The human supraspinatus tendon faces the subacromial bursa superiorly, and the joint capsule inferiorly, while the digital flexor tendon is surrounded by the synovium. We hypothesized that the supraspinatus tendon heals by the process which is different from that observed with digital flexor tendons, in which epitenon cells migrate into the torn portion circumferentially. The avian supracoracoid tendon was adopted for this experiment because of its similarity to the human supraspinatus tendon. We developed a full-thickness tendon laceration followed by primary suture. The objective of this study was to detect localization of the responsible cells for repair of the tendon. We examined the process using histology and in situ hybridization. Starting at week 1 the peritendon cells of the bursal side proliferated and migrated into the laceration site. At week 6, the tendon stumps were continuous with new connective tissue. High-level expression of procollagen mRNA in the proliferating peritendon cells on the bursal side demonstrates to contribute to the reparative process, which progressed to the joint side. This mode of repair is different from that of the digital flexor tendon.

The effectiveness of ADCON-T/N, a new anti-adhesion barrier gel, in fresh divisions of the flexor tendons in Zone II

In a prospective randomized clinical trial, ADCON-T/N was investigated with regard to its effectiveness in fresh traumatic injuries of the flexor tendons in Zone II of the hand. Thirty patients participated in the trial. Following a standardized technique of tendon repair, the total active motion (TAM) and total extension lag (TEL) were determined after 12 weeks and evaluated according to the Buck-Gramcko score. Excellent results were achieved in 15 out of 16 patients in the ADCON-T/N group and 12 out of 14 in the control group. However, no statistically significant difference was found between the mean TAM and TEL in the two groups.

Flexor tendon blood vessels

The aim of this study was to assess rabbit long flexor tendon vascularity in a qualitative and quantitative manner using immunohistochemistry. The endothelial cell surface marker CD31 was targeted with a specific monoclonal mouse-anti-human antibody with good species cross-reactivity. Subsequent signal amplification and chromogen labelling allowed vessel visualization. Computer image analysis was performed. Values for vessel number and total vessel area per section, as well as the sections' cross-sectional tendon areas, were obtained. There was a consistent deep tendon avascular zone between the A2 and A4 pulley in the rabbit forepaw. This was not the case in the hindpaw, with dorsally orientated longitudinal vessels coursing the length of the intrasynovial tendon. The area of least vascularity in the hindpaw was around the metacarpophalangeal joint. We therefore recommend the use of hindpaw tendons when using the rabbit as a flexor tendon experimental model. This is because its vascular pattern is similar to that of the human flexor digitorum profundus.

The effect of circumferential taping on flexor tendon pulley failure in rock climbers

The purpose of this study was to determine whether circumferential taping of the base of the finger increases the A2 pulley's load to failure in a model simulating a rock climber's grip. Nine pairs of fresh-frozen cadaveric hands, 20 to 47 years of age, were rigidly mounted in a specialized jig that maintained the finger in the climber's "crimp" position. Two of the four fingers of each hand were reinforced over the A2 pulley with three wraps of cloth adhesive tape. The flexor digitorum profundus and superficialis tendons were distracted until pulley or tendon failure. Overall, A2 pulley strength was greater in male specimens than in female specimens, and the A2 pulley of the small finger was the weakest tested. The A2 pulley failed simultaneously with the A3 and A4 pulleys in 55% of the tests. In the remaining trials, a single pulley failed initially followed by the remainder of the sheath. Of the 72 fingers studied, complete data were available for comparison of 22 pairs of fingers. No statistically significant difference in load to A2 pulley failure was noted between the taped and untaped finger pairs. Based on our findings we do not support taping the base of the fingers as a prophylactic measure against flexor tendon sheath injury in the climbing athlete.

Controlled active motion following primary flexor tendon repair: a prospective study over 9 years

One hundred and thirty patients with 339 divided flexor tendons affecting 208 fingers were studied prospectively between 1988 and 1996, to assess a regime of primary flexor tendon suture and active postoperative motion, combined with a modified Kleinert dynamic traction splint. The tendon suture technique used was a high-strength multistrand technique using a modified Kessler core and a Halsted peripheral stitch. The results were influenced by the zone in which the tendon was divided, by the physiotherapy and to a lesser extent by the grade of surgeon operating. Overall results by Strickland criteria were 92% excellent or good, 7% fair and 1% poor. There were 43 complications in 31 patients including five zone 2 ruptures (5.7%) and one further rupture in zone 5. This method of flexor tendon repair requires good physiotherapy and splint-making capability but gives good results with minimal need for further surgery.

Quantitative evaluation of nutritional pathways for the posterior cruciate ligament and the lateral collateral ligament in rabbits

The cruciate ligament of the knee receives its nutrition from a direct vascular supply and by permeation of nutrients from the synovial fluid. The contributions of these two routes as nutritional pathways are not known in detail. In this study, we injected [3H]methyl glucose as a tracer intravenously or directly into the knee of rabbits. Tracer concentrations in plasma, synovial fluid, the posterior cruciate ligament (PCL), and the lateral collateral ligament (LCL) were analysed by a pharmacokinetic compartment model. The contribution of [3H]methyl glucose permeation from the synovial fluid during steady state was calculated at 44.3% in the PCL and at 39.0% in the LCL. Although these results indicated that more than half the nutrition for both ligaments is provided by its vascular supply, synovial fluid permeation is also an important transport route for small molecules for the PCL and the LCL, which is an extra-articular structure.

Double armed reinsertion suture (DARS) of the profundus flexor tendon with immediate active mobilization of the finger. 63 cases

Between 1982 and 1994, the authors performed 63 flexor digitorum profundus tendon reinsertions according to the "lost-suture" DARS method (double armed reinsertion suture). This technique consists of 2 Bunnell sutures fixed to the lateral and anterior parts of the cut surface of the tendon. Nylon suture material is passed through a transverse hole made in the base of the distal phalanx. Active flexion without resistance is commenced postoperatively. A similar limit to extension is only applied in the case of an associated lesion if the neurovascular pedicle. Forty tendons were reviewed for this study (patients between the ages of 7 and 75 years, 35 males for 5 females). The lesion involved the thumb in 13 cases and long fingers in 27 cases. According to the authors' criteria, the results were scored as excellent 20% (8 cases); good 70% (28 cases); poor 10% (10 cases). The "lost-suture" DARS technique is a simple method which allows immediate active mobilization of the finger and appears to guarantee satisfactory functional results with no risk of tendon rupture.

Reduction of restrictive adhesions by local aprotinin application and primary sheath repair in surgically traumatized flexor tendons of the rabbit

The effects of microsurgical and medical treatments on reduction of adhesions in surgically traumatized flexor tendons of rabbits are quantified in this study. The effects of the mentioned techniques were investigated for the following 4 groups: (1) neither primary sheath repair nor aprotinin application was done, (2) primary sheath repair was done but no aprotinin was used, (3) primary sheath repair was not done but local aprotinin (15,000 IU/kg) was applied, and (4) primary sheath repair was done and local aprotinin was applied. At the sixth and twelfth postoperative weeks, the flexor digitorum profundus tendons of the second and the third digits were subjected to biomechanical tests. Only the third digit was used in macroscopic and histopathologic evaluations. There were 6 digits included in each subgroup of biomechanical tests and 4 digits per subgroups in macroscopic and histopathologic evaluations. Work of flexion (WOF) values were obtained by calculating the area under the load-displacement curve. Percent resistive work of flexion (PRWOF) was obtained by calculating the difference between the WOF value for the repaired right digit and the WOF value for the contralateral corresponding nonrepaired digit. Combined primary sheath repair and medical treatment yielded the best results in reducing the restrictive adhesions in injured tendons. The differences between the PRWOF values of group 4 were 33.7% +/- 8.2% and 15.8% +/- 7.7% for the sixth and twelfth postoperative weeks, respectively. The corresponding values for group 1 were 95.7% +/- 13.8% and 51.75% +/- 10.25%.

Intrinsic healing capacity and tearing process of torn supraspinatus tendons: in situ hybridization study of alpha 1 (I) procollagen mRNA

To determine the healing potential and healing process of torn supraspinatus tendons, in situ hybridization was used to localize cells containing alpha 1 type-I procollagen mRNA. Biopsy specimens of torn supraspinatus tendons from 19 patients with complete-thickness tears and 13 patients with incomplete-thickness tears were obtained during surgery. Four macroscopically normal supraspinatus tendons were obtained to serve as normal controls. Specimens were fixed in 10% buffered formalin and embedded in paraffin. A 22-mer oligonucleotide probe was labeled with digoxigenin and used as an in situ marker. The labeled cells were mainly composed of tenocytes and undifferentiated mesenchymal cells. In complete-thickness-tears, the labeled cells at the proximal tendon-stumps in the specimens that were obtained less than 4 months after trauma were significantly more abundant than in the specimens obtained 4 months or more after trauma. However, the number of labeled cells was maintained at the torn portion even in long-standing incomplete-thickness tears. The labeled cells at the margins of concomitant intratendinous extensions of the tears were detected even in the long-standing tears. The intratendinous extensions exhibited more labeled cells than the bursal-side or joint-side layers of the tendon substance in the incomplete-thickness tears (p < 0.05). The torn supraspinatus tendon may possess an intrinsic healing capability in the intermediate and late phases of tendon healing. Incomplete-thickness tears and concomitant intratendinous extensions can continue to rupture after the initial injury.

Biomechanical and histologic evaluation of tendon sheath management

The effect of changes in diameter of the flexor sheath after tendon repair on tendon function was studied using the long toes of 64 white leghorn chickens. Biomechanical studies of gliding excursion, toe flexion, and ultimate load were carried out at 6 and 12 weeks after tendon repair to determine functions of the tendons healed in narrowed, directly closed, partially excised, and enlarged flexor sheath experimental groups. Histologic examination was used to evaluate the extent of adhesions, healing status of the tendons, and status of the managed sheath. At 6 weeks, gliding excursions and range of toe flexion were statistically the smallest in the group with sheath narrowing, statistically larger in the groups with direct sheath closure or sheath excision, and statistically the largest in the sheath enlargement group (p < .01). These differences in gliding excursions and range of toe flexion were persistently observed at 12 weeks. The ultimate load of the repaired tendons was statistically the weakest in the group with sheath narrowing at either 6 or 12 weeks (p < .01). However, the ultimate load of the groups with sheath enlargement, direct sheath closure, and partial sheath excision was statistically the same. Results of histologic examination demonstrated more severe adhesions and worsened tendon healing in specimens with sheath narrowing. The repaired tendons in the group with sheath enlargement healed better and had less severe peritendinous adhesions than those in the group with sheath narrowing. The extent of adhesions and tendon healing were similar in the groups with sheath enlargement and direct sheath closure. This study demonstrates that the diameter of the repaired sheath exerts significant influence on flexor tendon function. Enlargement of the digital flexor sheath may provide an additional way to improve function of repaired tendons.

Reconstruction of the flexor tendon sheath. An experimental study in rabbits

The role of the tendon sheath in flexor tendon healing was investigated in rabbits. Tendon sheath was reconstructed with syngeneic parietal peritoneum or a non-tanned processed porcine collagen membrane. Resection of the tendon sheath led to adhesions. Reconstruction of the sheath with either graft resulted in a synovial-like lining, resembling a neo-tendon sheath. Even when combined with tendon repair a neo-tendon sheath was seen after reconstruction with both grafts, without adhesions. Subcutaneously implanted processed porcine collagen membrane was completely resorbed in less than 3 months.

Comparative mechanical analysis of dorsal versus palmar placement of core suture for flexor tendon repairs

This study was designed to evaluate the effect of core suture placement in the coronal plane on the tensile strength of flexor tendon repairs. We compared the tensile strength of modified Kessler core sutures placed in the palmar versus the dorsal side of matched-lacerated human cadaver flexor digitorum profundus tendons tested in vitro under static loading. We also compared the relative strengths of the dorsal and palmar portions of the flexor digitorum tendons. The mean failure load of a dorsal-side modified Kessler suture was 26.5% greater than that of a palmar-side modified Kessler suture. The mean strength of the dorsal half of the flexor digitorum tendons was 58.3% greater than that of the palmar half of the flexor digitorum tendons. Our data demonstrate that the dorsal tendon can sustain greater loads-to-failure than the palmar tendon. This suggests that there are biomechanical advantages to dorsal as opposed to palmar placement of the core suture in clinical tendon repair.

Early active mobilization of tendon grafts using mesh reinforced suture techniques

The flexor digitorum profundus tendon in 11 digits with division of both flexor tendons in zone 2 was reconstructed with a palmaris longus tendon graft in a two-stage procedure. The distal and proximal fixation of the graft was reinforced with a polyester mesh sleeve placed around the ends of the graft during stage 1. All digits were mobilized with a combination of active extension and active and passive flexion within 3 days of the second stage. There were three ruptures, one due to faulty technique and two due to falls on outstretched hands during alcohol intoxication and football. Excluding the ruptures, the mean active composite distal and proximal interphalangeal joint range of motion 6 weeks and 6 months post-operatively was 141 degrees and 136 degrees respectively. The results indicate that palmaris longus tendon grafts can survive and heal during early active mobilization, with few or no adhesions of functional significance. The techniques described here represent one possible approach to the safe implementation of early active mobilization after tendon grafting procedures.

Effects of hydroxyapatite and alumina sheaths on postoperative peritendinous adhesions in chickens

Two experimental methods for restoring flexor tendon sheath integrity and preventing adhesions around traumatized flexor tendons utilizing artificial tendon sheaths made of either hydroxyapatite (HAp) or alumina were studied in a flexor tendon-trauma model and compared to a standard tendon sheath repair and a control. Eighty toes were divided equally into a control group, a sheath repair group, an HAp group, and an alumina group. Profundus tendons in zone II were divided and repaired after sublimis excision in all groups. In the sheath repair group, the flexor sheath was also repaired after suturing the tendon. In artificial sheath groups, sheaths made of HAp and alumina were placed over the repair sites to protect them from the surrounding tissues. In the control group, after repairing the tendon, the flexor sheath was excised and no artificial sheaths were used. Each toe was immobilized in a plaster cast for 3 weeks. After three weeks, the plaster cast was removed followed by the removal of the sheaths in the artificial sheath groups through a small incision in the skin in zone II. Active mobilization was encouraged in each group. Postoperative adhesions were examined at 3, 6, 9, and 12 week intervals by using light microscopic techniques. To further explore the effects of artificial sheaths on tendon healing, transmission electron microscopy was done for the HAp and alumina groups at 3, 6, and 12 week intervals. Results demonstrated decreased severity of postoperative adhesions in the HAp as well as in the alumina groups in comparison with the sheath repair and controls. A space resembling the fibro-osseous canal was formed around the tendon after removing the sheaths. This space remained patent until 12 weeks, 9 weeks after removing the sheaths, and a newly formed tendon sheath-like structure lined by synovial cells and with a peritenon-like structure over the tendon surface was observed. In the sheath repair and control groups, the severity of adhesions was decreased with the passage of time, to some extent due to unrestricted mobility. However, a newly formed tendon sheath or peritenon-like structure was not observed. Electron microscopic studies confirmed good healing at the suture in the HAp and alumina groups with no evidence of necrosis. These results are qualitative in nature as no statistical tests were performed. From these results we conclude that if the tendon is separated from the surrounding granulation tissue by a barrier with good biocompatibility, the tendon can heal with fewer adhesions.(ABSTRACT TRUNCATED AT 400 WORDS)

Flexor sheath closure during delayed primary tendon repair

We studied the effect of flexor tendon sheath closure on flexor tendon function after delayed primary flexor tendon suture in white leghorn chickens. The tendon suture was carried out after a tendon laceration. In the left foot the tendon sheath was closed after tendon suture, and in the right the sheath was excised over the tendon suture. Tendon gliding, joint motion, the fate of the closed sheath, peritendinous adhesions, and tendon healing were studied. The sutured sheath disappeared after suturing and was associated with poor tendon healing. Sheath closure did not improve flexor tendon function in a delayed primary repair.

Dorsal and circumferential sheath reconstructions for flexor sheath defect with concomitant bony injury

Dorsal and circumferential flexor sheaths were reconstructed by autogenous sheath graft in flexor tendon repair in 28 white leghorn chickens. The effect of the sheath reconstructions was evaluated by use of an experimental model of tendon transection associated with bony injury, superficial tendon excision, and 3 weeks of immobilization. Six weeks after reconstruction, the gliding excursion was assessed and adhesion formation, tendon healing, and survival of the grafted sheath were evaluated both macroscopically and histologically. Dorsal and circumferential sheath grafts resulted in tendon gliding that was significantly better than the group with sheath defect not reconstructed. The adhesion formation was apparently less severe, and tendon healing was better in the groups with sheath reconstruction than in the group without reconstruction. The group with dorsal sheath reconstruction did not differ significantly from that with circumferential reconstruction in gliding excursion and adhesion formation. This study demonstrates that separation of the injured tendons from the bony surface by autogenous sheath grafts may be beneficial to tendon gliding and for reducing adhesion formation.

Restoration of the injured flexor tendon surface: a possible role for endotenon cells. A morphological study of the rabbit tendon in vivo

The ability of rabbit deep flexor tendons to restore the gliding surface and to heal, without the normal contribution of the superficial epitenon layer of the tendons, was studied by light and scanning electron microscopy. The epitenon layer was carefully removed from defined segments of the tendons. The remaining central tendon tissue was divided, sutured and placed in diffusion chambers subcutaneously in the back of the rabbits. After two weeks of culture, most of the sutured gaps were bridged and the tendons were encapsulated by flattened and spindle-shaped cells which covered a random network of thin collagen fibres. After five and 11 weeks, fibroblast-like cells in multiple layers formed a cobblestone-like surface. Thus, a tendon deprived of its epitenon layer still contains cells which can produce collagen, bridge the gap and restore the injured tendon surface.

Genetic expression for type I procollagen in the early stages of flexor tendon healing

To determine the precise mechanism by which contact tendon healing occurs at the cellular level, the production of pro alpha (I) collagen messenger RNA (mRNA) produced by fibroblasts of healing intrasynovial flexor tendons was determined by an in situ hybridization technique. The repair site and the proximal and distal tendon stumps of repaired tendons treated with early controlled passive mobilization were fixed and buffered in formalin, 3, 7, 10, and 17 days after repair. A complimentary DNA (cDNA) probe corresponding to alpha (I) procollagen mRNA was labeled with [32P]d-CTP. After hybridization, autoradiography, and staining of the sections, the level of procollagen mRNA was assessed by microscopic examination. Rising levels of procollagen mRNA, indicating progressively increasing levels of synthetic collagen activity, were detected in the healing tendons through 10 days. A moderate decrease in procollagen mRNA was seen at 17 days. Genetic expression for procollagen mRNA was localized specifically to the epitenon cells on the tendon surface overlying the repair site and to cells in the gap between the tendon stumps. No detectable expression was noted in endotenon fibroblasts. The finding of high levels of expression for procollagen type I mRNA in the surface layer of healing tendons demonstrates that cells intrinsic to tendon epitenon contribute the greatest quantity of native tendon collagen to the repair site during these important early intervals after tendon suture.

The contents of macromolecule solutes in flexor tendon sheath fluid and their relation to synovial fluid. A quantitative analysis

The importance of synovial environment for minimal adhesion formation in flexor tendon healing has recently gained attention. Various techniques have been used to restore an injured synovial tendon sheath. Therefore a quantitative analysis of flexor tendon sheath fluid is of interest to increase our knowledge about the specific synovial milieu and to evaluate the success of different types of sheath reconstructions from a biochemical point of view. Samples of tendon sheath fluid from trigger digits and tendon sheaths containing ganglions have been assayed for contents of hyaluronic acid and proteins of different molecular weights. The results show concentrations of hyaluronate and several proteins similar to those in normal joint fluid. These results indicate that flexor tendon sheath fluid has a character similar to synovial fluid of joints and apparently has specific functions such as soft tissue lubrication and nutrition of avascular tendon tissue.

The double armed suture: tendon repair with immediate mobilization of the fingers

The double armed suture (DAS) method of repairing flexor and extensor tendons allows almost immediate mobilization of the involved digits. The technique protects the tendon juncture from stress during muscle contraction and hand therapy, which is begun a few days after surgery. This technique has been used in 76 patients since 1972. Good or excellent results have been obtained in 90% of the cases over a 16-year period.

Exogenous hyaluronate as an adjunct in the prevention of adhesions after flexor tendon surgery: a controlled clinical trial

Postoperative adhesions that restrict tendon gliding are a major cause of failure after tendon repair and grafting in zone II. Several experimental reports have claimed that exogenously administered sodium hyaluronate helps to prevent the formation of such adhesions. In a prospective double-blind, randomized, clinical study with open therapeutic control sodium hyaluronate or physiologic saline solution was injected into the tendon sheath after completion of tenorrhaphy or tendon grafting in 120 digits. Sodium hyaluronate had no statistically significant effect as evaluated on total active motion at follow-up.

Primary flexor tendon repair: surgical techniques based on the anatomy and biology of the flexor tendon system

The anatomy, biology and bio-mechanics of the flexor tendon system demand a precise approach to flexor tendon repair. Within the fibroosseous canal, the synovial fluid and a complex intratendinous vascular network provide nutrition for intrinsic flexor tendon healing. Retention of the synovial sheath theoretically maintains an enclosed tendon/tendon sheat environment in which the tendon repair is bathed in synovial fluid, and may glide within a smooth tunnel. The preservation of the intricate double tendon inter-relationship and the annular pulley system is vital to the efficiency of finger flexion. This review details surgical and postoperative techniques aimed at restoring the normal anatomy and providing optimal conditions for the return of flexor tendon function.

Reconstruction of sheath with fascial graft in flexor tendon repair. An experimental study

Using chicken's toes as an experimental model, we compared the healing process and function recovery of partially injured flexor tendons when the sheath was repaired with fascial graft, sheath patch or was left as a defect. Post-operatively, the toes were immobilised or mobilised immediately. Histological study and the measurement of tendon sliding revealed that the sheath reconstruction and mobilised groups were better than the sheath defect or immobilised groups. We also found the fascial graft was superior in the reconstruction of tendon sheath and may become synovial-like tissue under the sliding pressure of the tendon.

Intrinsic healing of the laceration site in human superficialis flexor tendons in vitro

The intrinsic capability of the human superficialis flexor tendon to heal a reapproximated laceration site in vitro was examined. Segments of lacerated and sutured human superficialis flexor tendons from zone II were cultured for two, four, or eight weeks in vitro and analyzed by use of light and electron microscopy. We noted a specific pattern of intrinsic healing at the repair site during the incubation period. After two weeks, the cells of the epitenon from both tendon stumps proliferated and appeared to migrate into the repair site. Elongated cells of the thickened epitenon bridged the laceration and synthesized new collagen fibers. By eight weeks, a smooth contiguous tendon surface was restored and the internal collagen bundles were brought into intimate contact. The fibroblasts bridging the laceration, both in the epitenon and centrally in the repair site, were oriented perpendicular to the cut surfaces. The cells in the repair site were active in protein synthesis, and new collagen fibers were present. No cellular necrosis was observed in the internal repair site. Our results indicate that human superficialis tendons possess an intrinsic capacity to heal with diffusion and without dependence on extratendinous cells or on adhesions.

Results of primary tendon repair with closure of the tendon sheath

This study reports the results of primary flexor tendon repair combined with closure of the tendon sheath in 31 Zone 2 injuries. In 3 digits, the profundus tendon alone was divided. In a further 7 digits, one tendon was completely divided and the other was incompletely divided. The remaining 21 digits involved complete division of both tendons. Assessment of the results according to the total active motion (TAM) system found 86% of the repairs in the excellent, good and fair categories. Two ruptures occurred (6%). A second assessment employed the criteria of Strickland, excluding the motion of the metacarpophalangeal joint. The results obtained following suture of both tendons were: excellent (39%); good (36%); fair (14%); poor (4%); and rupture (7%). These results lend support to the belief that closure of the tendon sheath decreases external adhesion formation and improves motion without increasing the risks of rupture.

Effect of various methods of restoring flexor sheath integrity on the formation of adhesions after tendon injury

The effect of three different methods of restoring flexor sheath integrity on the formation of adhesions around traumatized flexor tendons was studied by use of a chicken animal model. The three methods were: I, Primary sheath repair; II, a fascia patch; and III, a synthetic polytetrafluoroethylene surgical membrane patch. These were compared with controls in which the flexor sheath was excised. Adhesion formation was assessed both biomechanically by measuring the parameter work of flexion, (which represents the resistance to tendon gliding caused by adhesions), and also histologically. At 3 and 6 weeks there was no significant difference in the work of flexion between either the sheath repair or fascia patch digits, and the sheath excised controls. However, use of the synthetic polytetrafluorethylene patch did result in tendon gliding, which was significantly better than the controls. In contrast, at 12 weeks all three methods of sheath reconstruction had similar tendon gliding biomechanics, and all were significantly better than the controls. Histologically, at 3 weeks, the biologic barriers sheath repair and fascia patch were associated with a layer of granulation tissue, which adhered to the underlying tendon. This was similar to the appearance of the sheath excised control digits. The synthetic patch was not associated with a significant inflammatory reaction at this time period and was clearly separated from the tendon. However, by 6 and 12 weeks the granulation tissue in all three sheath reconstruction groups had undergone remodeling to a greater degree than had the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Participation of human superficialis flexor tendon segments in repair in vitro

We analyzed the healing capability of the human superficialis (sublimus) flexor tendon in response to injury in vitro by performing a morphologic study of tendon repair. Tendon segments were cultured in cell-free medium for 2, 4, or 8 weeks, and the cut-end repair sites were compared with those in fresh control segments on light and electron microscopy. Tendon encapsulation had occurred at 2 weeks, by the proliferation and migration of elongated fibroblasts from the epitenon and from collagen bundles of the endotenon to cover the surface of the cut tendon ends. As migrating epitenon cells approached the cut margin, they consistently shifted from a parallel to a circumferential orientation with respect to the tendon axis. By 4 weeks, the encapsulating surface cells had lost their membranous ruffles and had become flattened. Within the capsule, phagocytic cells engulfed collagen debris, and fibroblasts containing extensive rough endoplasmic reticulum profiles and secretory vesicles participated in protein synthesis. The surface of the capsule was smooth and, at 8 weeks, was almost indistinguishable from the epitenon surface of uncultured controls. The capsule now had a collagen-synthesizing layer of fibroblasts superimposed on layers of maturing collagen bundles that separated resting-phase fibroblasts. These findings demonstrate that segments of human superficialis flexor tendons participate in an intrinsic repair response without contributions from extrinsic cells.

Influences of flexor sheath continuity and early motion on tendon healing in dogs

The healing response of flexor tendons treated with either sheath reconstruction or sheath excision, and early passive motion rehabilitation was investigated in a canine model. Flexor sheath repair, sheath excision, and autogenous sheath grafting were compared for biomechanical characteristics, and biochemical and ultrastructural alterations at the repair site at intervals over a 12-week period. No significant differences could be found in tendons treated with either sheath repair or sheath excision by biomechanical, biochemical, or morphologic assessments. Although ultimate load and linear slope values increased significantly in both groups at each interval (p less than 0.05 for each comparison), there were no significant differences in angular rotation of the distal interphalangeal joint over time. Biochemical findings showed high levels of reducible Schiffbase crosslinks through 12 weeks, indicating a repair process undergoing active remodeling. Ultrastructural studies showed active fibrinogenesis and early evidence of longitudinal alignment of collagen fibrils in the extracellular matrix. In the sheath graft group, strength characteristics did not increase over time, and there was a high degree of disorganization of collagen fibril orientation. These findings demonstrate that reconstruction of the tendon sheath, either by suture or autogenous graft, does not improve significantly the biomechanical, biochemical, or morphologic characteristics of repaired tendons treated with early motion rehabilitation.