An experimental study of the repair and gliding function of digital flexor tendon following injury

Summary The profundus tendons of young adult chickens have been used to study flexor tendon healing within the digital sheath. Histological observation has shown that the preserved digital sheath prevented the tendon healing with adhesions and that the epitendon played a leading role in the process of tendon repair. Muscle tension must be removed from the sutured site for tendon repair without adhesion. Post-operative immobilisation in the tension-reducing position, in which an operated digit is flexed and the rest of the digits are extended, is believed to be one of the most efficient procedures for removing tension from the sutured site of the tendon. Three methods of tendon suture were used — Bunnell crisscross stitch, modified double right-angle suture, and interrupted suture. Least adhesions were noted in the tendons sutured by interrupted suture, and the tensile strength of the tendons sutured by interrupted suture tended to be highest between three and six weeks postoperatively. To achieve tendon healing with good gliding function, the following procedures should be observed: (1) preservation of the digital sheath, (2) an atraumatic technique for tendon suture, and (3) immobilisation in the tension-reducing position.

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Résumé On a utilisé le tendon fléchisseur profond du poulet pour étudier la cicatrisation des tendons fléchisseurs des doigts à l'intérieur de la gaine digitale. Les examens anatomo-pathologiques ont montré que la conservation de la gaine évitait la formation d'adhérences et que l'épitendon jouait un rôle majeur dans le processus de réparation du tendon, en l'absence de ces adhérences.Pour obtenir cette cicatrisation sans adhérences, il faut supprimer toute tension en regard de la zone suturée. L'immobilisation post-opératoire dans une position de relâchement, le doigt opéré étant fléchi et les autres étendus, paraît être un des meilleurs procédés pour supprimer cette tension.Parmi les trois méthodes de suture tendineuse: laçage à la Sterling Bunnell, suture modifiée à double angle droit et suture à points séparés, c'est cette dernière qui donne le moins lieu à la formation d'adhérences. Et c'est entre la 3ème et la 6ème semaine post-opératoire que la résistance à la traction du tendon ainsi suturé est la plus élevée.Pour obtenir la cicatrisation tendineuse avec une bonne récupération fonctionnelle, les points de technique suivants sont donc essentiels: (1) préservation de la gaine digitale, (2) technique atraumatique de suture du tendon et (3) immobilisation du doigt en position de relâchement.

     

Studies in flexor tendon reconstruction: biomolecular modulation of tendon repair and tissue engineering

The Andrew J. Weiland Medal is presented each year by the American Society for Surgery of the Hand and the American Foundation for Surgery of the Hand for a body of work related to hand surgery research. This essay, awarded the Weiland Medal in 2011, focuses on the clinical need for flexor tendon reconstruction and on investigations into flexor tendon biology. Reconstruction of the upper extremity is limited by 2 major problems after injury or degeneration of the flexor tendons. First, adhesions formed after flexor tendon repair can cause decreased postoperative range of motion and hand function. Second, tendon losses can result from trauma and degenerative diseases, necessitating additional tendon graft material. Tendon adhesions are even more prevalent after tendon grafting; therefore these 2 problems are interrelated and lead to considerable disability. The total costs in terms of disability and inability to return to work are enormous. In this essay, published work from the past 12 years in our basic science laboratory is summarized and presented with the common theme of using molecular techniques to understand the cellular process of flexor tendon wound healing and to create substances and materials to improve tendon repair and regeneration. These are efforts to address 2 interrelated and clinically relevant problems that all hand surgeons face in their practice.     

Spontaneous flexor tendon rupture of the flexor digitorum profundus secondary to an anatomic variant

We report a case of the flexor digitorum profundus tendon rupture of the little finger, which was predisposed by an anatomic variation of the tendon. Intraoperative findings and magnetic resonance imaging of the opposite hand suggested that the flexor digitorum profundus tendons of the ring and the little finger bifurcated. The patient had tendon reconstruction and regained function. We believe that reconstructing the tendon so that it resembles the normal anatomy prevents the recurrence of tendon rupture.     

Primary repair of a flexor tendon after a human bite

Successful uncomplicated primary closure of a human bite injury of the hand with simultaneous zone II flexor tendon injury has not been previously reported to our knowledge. We report the case of a man who was bitten on his left ring and right middle and index fingers. He was treated with antiseptic lavage, intravenous antibiotics, and operation. He had complete transsection of the flexor digitorum profundus at the middle phalanx. This was repaired primarily and he made a good recovery.     

Surface modification counteracts adverse effects associated with immobilization after flexor tendon repair

Although post‐rehabilitation is routinely performed following flexor tendon repair, in some clinical scenarios post‐rehabilitation must be delayed. We investigated modification of the tendon surface using carbodiimide derivatized hyaluronic acid and lubricin (cd‐HA‐Lub) to maintain gliding function following flexor tendon repair with postoperative immobilization in a in vivo canine model. Flexor digitorum profundus tendons from the 2nd and 5th digits of one forepaw of six dogs were transected and repaired. One tendon in each paw was treated with cd‐HA‐Lub; the other repaired tendon was not treated. Following tendon repair, a forearm cast was applied to fully immobilize the operated forelimb for 10 days, after which the animals were euthanized. Digit normalized work of flexion (nWOF) and tendon gliding resistance were assessed. The nWOF of the FDP tendons treated with cd‐HA‐Lub was significantly lower than the nWOF of the untreated tendons (p < 0.01). The gliding resistance of cd‐HA‐Lub treated tendons was also significantly lower than that of the untreated tendons (p < 0.05). Surface treatment with cd‐HA‐Lub following flexor tendon repair provides an opportunity to improve outcomes for patients in whom the post‐operative therapy must be delayed after flexor tendon repair. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1940–1944, 2012     

Comparison of pullout button versus suture anchor for zone I flexor tendon repair

PURPOSE: To evaluate the clinical outcome after repair of zone I flexor tendon injuries using either the pullout button technique or suture anchors placed in the distal phalanx. METHODS: Between 1998 and 2002 we treated 26 consecutive zone I flexor tendon injuries. Thirteen patients had repairs from 1998 to 2000 using a modified pullout button technique (group A) and 13 patients had repair using suture anchors placed in the distal phalanx (group B). Patient characteristics were similar for both groups. The same postoperative flexor tendon rehabilitation protocol and follow-up schedule were used for both groups. Evaluation included range of motion, sensibility and grip strength, failure, complications, and return to work. The Student t test was used to determine significant differences. RESULTS: All patients completed 1 year of follow-up evaluation. There were 2 infections in group A that resolved with oral antibiotics and no infections in group B. There were no tendon repair failures and no repeat surgeries in either group. At final follow-up evaluation there were no statistically significant differences for the following end points: sensibility (Semmes-Weinstein monofilament testing and 2-point discrimination), active range of motion (at the proximal interphalangeal joint, distal interphalangeal joint, or their combined motion), flexion contracture (at the proximal interphalangeal joint, distal interphalangeal joint, or their combined contracture), and grip strength (injured tendon as a percent of the contralateral uninjured tendon). The suture anchor group had a statistically significant improvement for time to return to work. CONCLUSIONS: There was no significant difference in the clinical outcome after flexor tendon repair using either suture anchors or the pullout button technique. A significant improvement was found for time to return to work for repairs using the suture anchor technique. Flexor tendon repair can be achieved using suture anchors placed in the distal phalanx, thereby avoiding the potential morbidity associated with the pullout button technique. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic, Level III.     

屈肌腱愈合早期在曲线模型中生物力学变化的实验研究

目的比较握持缝合法(改良Kessler法)和锁扣缝合法(Tsuge法)修复屈肌腱在术后不同时间曲线模型下的生物力学变化规律和特点。方法分别以改良Kessler法和Tsuge法缝合三黄鸡的第3趾屈趾深肌腱各42条,分别于术后即刻,1,4,7,10,14,21d取材,进行生物力学测试。测试内容包括拉伸断裂负荷和功耗。结果拉伸断裂负荷：改良Kessler法在术后10d出现明显降低(13N),术后21d恢复到即刻水平;Tsuge法术后10d以后持续性降低(21N);Tsuge法术后即刻组和术后7d组较改良Kessler。法能承受更高的拉伸断裂负荷。拉伸断裂功耗：改良Kessler法术后10d(65mJ),14d(40mJ)组较术后即刻(170mJ),1(222mJ),4(188mJ),7d(196mJ)组明显降低,术后21d恢复到即刻水平;Tsuge法术后14d(72mJ),21d组(59mJ)较术后即刻(283mJ),1(219mJ),4(216mJ),7(279mJ),10d(191mJ)组明显降低;Tsuge法术后即刻组(283mJ)较改良Kessler法(170mJ)具有更高的拉伸断裂功耗。结论两种缝合方法都是在术后10d以后生物力学性能显著下降,改良Kessler法在术后21d恢复到即刻水平,而Tsuge法则不能在术后21d恢复到即刻水平。两种缝合方法的力学性能在术后10d以后无差异。     

Early healing of flexor tendon insertion site injuries: Tunnel repair is mechanically and histologically inferior to surface repair in a canine model.

Orthopedic injuries often require surgical reattachment of tendon to bone. Tendon ends can be sutured to bone by direct apposition to the bone surface or by placement within a bone tunnel. Our objective was to compare early healing of a traditional surface versus a novel tunnel method for repair of the flexor digitorum profundus (FDP) tendon insertion site in a canine model. A total of 70 tendon-bone specimens were analyzed 0, 5, 10 or 21 days after injury and repair, using tensile and range of motion mechanical testing, histology and densitometry. Ultimate force (a measure of repair strength) did not differ between surface and tunnel repairs at day 0. Both repair types had reduced strength at 10 and 21 days compared to 0 days, indicative of deterioration of suture grasping strength (tendon softening). At 21 days, tendons repaired in a bone tunnel had 38% lower ultimate force compared to surface repairs (p = 0.017). Histological findings were comparable between repair groups at 5 and 10 days but differed at 21 days, when we saw evidence of maturation of the tendon-bone interface in the surface repairs compared to an immature fibrous interface with no evidence of tendon-bone integration in the tunnel repairs. After accounting for bone removed by the tunnel, no difference in bone mineral density or trabecular bone volume existed between surface and tunnel repairs. If the results of our animal study extend to healing of the human FDP insertion, they indicate that FDP tendons should be reattached to the distal phalanx by suture to the cortical surface rather than suture in a bone tunnel.     

Gliding resistance of flexor tendon associated with carpal tunnel pressure: A biomechanical cadaver study

The purpose of this study was to investigate the effect of carpal tunnel pressure on the gliding characteristics of flexor tendons within the carpal tunnel. Eight fresh human cadaver wrists and hands were used. A balloon was inserted into the carpal tunnel to elevate the pressure. The mean gliding resistance of the middle finger flexor digitorum superficialis tendon was measured with the following six conditions: (1) as a baseline, before balloon insertion; (2) balloon with 0 mmHg pressure; (3) 30 mmHg; (4) 60 mmHg; (5) 90 mmHg; (6) 120 mmHg. The gliding resistance of flexor tendon gradually increased as the carpal tunnel pressure was elevated. At pressures above 60 mmHg, the increase in gliding resistance became significant compared to the baseline condition. This study helps us to understand the relationship between carpal tunnel pressure, which is elevated in the patient with carpal tunnel syndrome (CTS) and tendon gliding resistance, which is a component of the work of flexion. These findings suggest that patients with CTS may have to expend more energy to accomplish specific motions, which may in turn affect symptoms of hand pain, weakness and fatigue, seen commonly in such patients. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:58–61, 2011     

Adhesions in a murine flexor tendon graft model: Autograft versus allograft reconstruction

Reconstruction of flexor tendons often results in adhesions that compromise joint flexion. Little is known about the factors involved in the formation of flexor tendon graft adhesions. In this study, we developed and characterized a novel mouse model of flexor digitorum longus (FDL) tendon reconstruction with live autografts or reconstituted freeze‐dried allografts. Grafted tendons were evaluated at multiple time points up to 84 days post‐reconstruction. To assess the flexion range of the metatarsophalangeal joint, we developed a quantitative outcome measure proportional to the resistance to tendon gliding due to adhesions, which we termed the Gliding Coefficient. At 14 days post‐grafting, the Gliding Coefficient was 29‐ and 26‐fold greater than normal FDL tendon for both autografts and allografts, respectively (p < 0.001), and subsequently doubled for 28‐day autografts. Interestingly, there were no significant differences in maximum tensile force or stiffness between live autograft and freeze‐dried allograft repairs over time. Histologically, autograft healing was characterized by extensive remodeling and exuberant scarring around both the ends and the body of the graft, whereas allograft scarring was abundant only near the graft–host junctions. Gene expression of GDF‐5 and VEGF were significantly increased in 28‐day autografts compared to allografts and to normal tendons. These results suggest that the biomechanical advantages for tendon reconstruction using live autografts over devitalized allografts are minimal. This mouse model can be useful in elucidating the molecular mechanisms in tendon repair and can aid in preliminary screening of molecular treatments of flexor tendon adhesions. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:824–833, 2008     

Partial laceration of the flexor tendon as an unusual cause of trigger finger

Abstract

We present two cases of trigger finger caused by partial laceration of a flexor tendon. Both patients had preceding skin injury and required operative treatment with resection of the lacerated portion of the tendon and incision of the A1 pulley. We describe keys to the diagnosis of this type of lesion.     

Expression and mapping of lubricin in canine flexor tendon.

Matrix composition and the biomechanical environment are intimately interdependent in most connective tissues. Lubricin has many distinct biological functions, including lubrication, antiadhesion, and cytoprotection in cartilage, tendons, and other tissues. This study investigated the distribution of lubricin in the canine flexor digitorum profundus (FDP) tendon by immunohistochemistry. Lubricin was found both on the tendon surface and at the interface of collagen fiber bundles within the tendon, where the cells are subjected to shear force in addition to tension and compression. The expression of lubricin in regions of the canine flexor tendon that differ in mechanical or nutritional environment was also investigated using RT-PCR. Six N-terminal splicing variants were identified from six distinct anatomical regions of flexor tendon. The variants with larger sizes were noted in regions subjected to significant shear and compressive forces. Lubricin is ubiquitous in the FDP tendon, with variations in distribution and splicing that appear to correspond to discrete anatomic locations that differ by mechanical or nutritional environment.     

克氏针远指间关节屈曲固定加牵引治疗小儿屈指肌腱止点断裂

正2008年8月~2015年6月,我们采用克氏针远指间关节屈曲固定加牵引治疗18例屈指深肌腱止点断裂患儿,疗效满意,报道如下。1材料与方法1.1病例资料本组18例,男12例,女6例,年龄1.5~5岁。其中拇指8例,示指6例,中指4例。伤口位于远指间关节附近,肌腱止点处断裂,形状为横行或斜行。致伤原因:水果刀割伤10     

The effect of muscle loading on flexor tendon‐to‐bone healing in a canine model

Previous tendon and ligament studies have demonstrated a role for mechanical loading in tissue homeostasis and healing. In uninjured musculoskeletal tissues, increased loading leads to an increase in mechanical properties, whereas decreased loading leads to a decrease in mechanical properties. The role of loading on healing tissues is less clear. We studied tendon‐to‐bone healing in a canine flexor tendon‐to‐bone injury and repair model. To examine the effect of muscle loading on tendon‐to‐bone healing, repaired tendons were either cut proximally (unloaded group) to remove all load from the distal phalanx repair site or left intact proximally (loaded group). All paws were casted postoperatively and subjected to daily passive motion rehabilitation. Specimens were tested to determine functional properties, biomechanical properties, repair‐site gapping, and bone mineral density. Loading across the repair site led to improved functional and biomechanical properties (e.g., stiffness for the loaded group was 8.2 ± 3.9 versus 5.1 ± 2.5 N/mm for the unloaded group). Loading did not affect bone mineral density or gapping. The formation of a gap between the healing tendon and bone correlated with failure properties. Using a clinically relevant model of flexor tendon injury and repair, we found that muscle loading was beneficial to healing. Complete removal of load by proximal transection resulted in tendon‐to‐bone repairs with less range of motion and lower biomechanical properties compared to repairs in which the muscle‐tendon‐bone unit was left intact. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res