Flexor tendon-tendon sheath interaction after tendon grafting: a biomechanical study in a human model in vitro.

A human cadaver tendon sheath model was used to study the differences in excursion resistance of tendons that might be considered as sources of clinical tendon grafts. The flexor digitorum profundus and superficialis tendons, the extensor indicis proprius tendon used in its normal proximal-distal orientation, the extensor indicis proprius tendon used in a reversed distal-proximal orientation, and the palmaris longus tendon were studied in 7 fingers. The intrasynovial tendons (the flexor digitorum profundus and superficialis tendons and the reversed extensor indicis proprius tendon) produced less excursion resistance (p < .05) than the extrasynovial tendons (the normally oriented extensor indicis proprius tendon and the palmaris longus tendon). In contrast to studies measuring resistance against a single pulley, resistance within a complete tendon sheath may be affected by contact with other structures, particularly in joint extension.     

Flexor tendon rupture caused by gout: a case report

We present a case of primary gouty infiltration of flexor tendons in the hand, causing rupture of both flexor digitorum superficialis and profundus tendons in a single digit. The patient was managed by a single-stage reconstruction of the less involved flexor digitorum superficialis tendon using a segment of the proximal stump of flexor digitorum profundus tendon as a bridge graft. This uncommon etiology of tendon rupture should be considered in all patients with a history of gout presenting with tendon insufficiency.     

Zone I flexor tendon rehabilitation with limited extension and active flexion.

This article describes an immediate active motion protocol for primary repair of zone I flexor tendons treated with tendon to tendon, or tendon to bone repair, and reviews clinical results. A rehabilitation protocol is proposed that will limit excursion of the zone I repair by blocking full distal interphalangeal (DIP) extension and by applying controlled active tension to both the unrepaired flexor digitorum superficialis (FDS) and the repaired flexor digitorum profundus (FDP). The rehabilitation technique utilized a dorsal protective splint with a relaxed position of immobilization with 30 degrees of wrist flexion, 40 degrees of metacarpophalangeal (MP) joint flexion, and a neutral position for the proximal interphalangeal (PIP) joints without dynamic traction. In addition, within the confines of the dorsal splint, the involved DIP joint was splinted at 40-45 degrees to prevent DIP joint extension during the early wound healing phases. Relaxed composite flexion was used to apply active tension to both the uninjured FDS, and the repaired FDP. This technique applies excursion of approximately 3 mm to the zone I tendon in a limited arc (45-75 degrees). The modified position of active flexion applies low loads of force (< 500 g), even with drag considered. This technique is supported by previous mathematical studies of excursion and internal tendon force, and clinical experience. Forty nine cases treated over a 10-year period were reviewed, and eight were excluded for incomplete follow-up. The use of this protocol for 41 zone I flexor digitorum profundus repairs by 12 different surgeons using varied surgical techniques was evaluated. None of the tendon to tendon repairs used more than two suture strands for the core repairs. Mean total active range of motion was 142 degrees (PIP 95 degrees plus DIP 47 degrees), or 81% of normal. Three tendons ruptured in non-protocol-related incidents and were excluded from the study. Results from this clinical study support the use of limited DIP extension combined with active tension with conventional repair in zone I.     

A loop-tendon suture for tendon transfer or graft surgery

PURPOSE: We present a loop-tendon suture technique that was designed for easy tension adjustment and early postoperative rehabilitation in tendon transfer or graft surgeries. This study tested the biomechanical strength of the loop-tendon suture by using chicken flexor tendons and we report the preliminary clinical results. METHODS: We tested the ultimate strength of the loop-tendon suture against the end-weave suture technique in chicken flexor tendons. Forty flexor digitorum longus tendons of chickens were divided into 2 groups according to the suture technique, loop-tendon suture and end-weave suture groups, and then were subjected to linear loading in a tensile load testing machine. From 2000 to 2002 we performed 27 tendon transfer surgeries clinically, including 4 interpositional tendon grafts in 15 patients, using this technique followed by immediate passive motion exercise after surgery. The mean follow-up time was 20 months. RESULTS: The ultimate tensile load of chicken flexor tendons was 31 +/- 6 N for the loop-tendon suture group and 23 +/- 8 N for the end-weave suture group, and the difference was statistically significant. Clinically, 6 patients with an extensor indicis proprius to an extensor pollicis longus transfer showed more than good results in the Geldmacher scheme. Three patients with an extensor indicis proprius to a central tendon transfer achieved proximal interphalangeal extension of less than 15 degrees of extension lag. One patient with a flexor digitorum profundus reconstruction obtained total active motion of 210 degrees. The 5 patients with triple transfers for radial nerve palsy showed more than neutral extension of the wrist and metacarpal joint. There were no tendon ruptures. CONCLUSIONS: The loop-tendon suture method has greater strength than the conventional end-weave technique, and can be used for secondary tendon reconstruction surgery with favorable clinical outcomes. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.     

Pulley plasty versus resection of one slip of the flexor digitorum superficialis after repair of both flexor tendons in zone II: a biomechanical study

BACKGROUND: The outcome of repair of zone-II lacerations of the flexor digitorum superficialis and flexor digitorum profundus tendons remains suboptimal. We investigated the effects of two strategies to improve postoperative gliding in a human cadaveric hand. METHODS: The second, third, and fourth digits were harvested from ten fresh-frozen human cadaveric hands. Complete lacerations and repairs were made to the profundus and superficialis tendons at a location where both repair sites would pass beneath the A2 pulley with the proximal interphalangeal joint in 45 degrees of flexion. The gliding resistance of the flexor digitorum profundus tendon was measured following pulley plasty and following excision of one slip of the flexor digitorum superficialis. The breaking strength of the remaining slip of the flexor digitorum superficialis tendon was then measured. RESULTS: Pulley plasty and resection of one slip of the flexor digitorum superficialis tendon both significantly decreased gliding resistance compared with repair of both slips (p < 0.001). There was no difference in the mean gliding resistance between the pulley plasty and one-slip resection groups. The flexor digitorum superficialis slip was stronger after repair with a Becker suture (28.8 +/- 9.0 N) than after repair with a modified Kessler (16.4 +/- 4.5 N) or a zigzag suture (15.0 +/- 5.7 N). CONCLUSION: Both pulley plasty and resection of one slip of the flexor digitorum superficialis reduce gliding resistance after tendon repair in zone II of the hand.     

Biomechanical influence of the vincula tendinum on digital motion after isolated flexor tendon injury: a cadaveric study

PURPOSE: The vincula are specialized mesotendinous structures attaching to the flexor tendons of the hand. In addition to providing vascular supply to the tendons, the vincula can be mechanically important. The purpose of this study was to quantify the influence of intact vincula on digital flexion after flexor tendon laceration and to assess the ultimate strength and stiffness of the vincula. METHODS: The index, middle, and ring fingers of 12 fresh-frozen cadaveric fingers were dissected free at the level of the metacarpophalangeal joint, preserving at least 10 cm of the flexor and extensor tendons. A 9.8-N load was applied to each flexor tendon, and using digital photography and image analysis software, the degree of flexion at the proximal and distal interphalangeal joints and excursion of tendons proximal to the metacarpophalangeal joint was recorded before and after division of the flexor digitorum profundus and flexor digitorum superficialis tendons at their insertions. Load to failure and stiffness of the vincula were measured via a uniaxial material testing apparatus. Analysis of means was performed with a paired t-test. RESULTS: After division of the flexor digitorum superficialis tendon, proximal interphalangeal joint flexion secondary to the influence of the intact vincula was 93% of that compared with the uninjured digit. Distal interphalangeal joint flexion after flexor digitorum profundus transection was 69% of normal. The increased excursion of transected tendons compared with testing before division was 4 mm for flexor digitorum superficialis and 2 mm for flexor digitorum profundus. Load to failure was 27 N, and stiffness was 6 N/mm. CONCLUSIONS: The vincula breve can facilitate digital flexion after distal tendon transection, allowing tendons to act indirectly across the interphalangeal joints. The intact vincula breve can facilitate an almost normal range of motion across the interphalangeal joints, making the diagnosis of a flexor tendon injury difficult. In the immediate postinjury period, the vincula breve can hold a divided tendon within a few millimeters of its insertion. Testing against resistance is important to avoid missing the diagnosis of a tendon injury.     

Tensile strength of a new suture for fixation of tendon grafts when using a weave technique

PURPOSE: To evaluate a new corner stitch construct for tendon graft or tendon transfer fixation and compare the tensile strength with a conventional central cross-suture design in human cadaver tendons. METHODS: Flexor digitorum profundus tendons of the index, middle, and ring fingers (48 total) were used as recipients and palmaris longus, extensor indicis proprius, and extensor digitorum communis tendons of the index finger (48 total) were used as grafts from 16 fresh-frozen human cadaver hands. We compared the cross-stitch technique with a new corner stitch technique in tendon repairs made with 1, 2, or 3 weaves (8 per group). Tendons were sutured at each weave with either 2 full-thickness cross-stitches or 4 partial-thickness corner stitches of 4-0 nylon. Mattress sutures also were placed through the free tendon end for each repair type. The tensile strength of the tendon-graft composite was measured with a materials testing machine. RESULTS: The tensile strength of the repairs increased significantly with the number of weaves. When 2 or 3 weaves were used with the corner stitch or when 3 weaves were used with the cross-stitch, the repairs were significantly stronger. Although no significant difference in strength to failure was noted when comparing cross and corner stitches with equivalent numbers of weaves, qualitatively there was a difference in mode of failure with the 3-weave corner stitches failing primarily by intrasubstance tendon failure and the 3-weave cross-stitch repairs failing by tendon pullout. CONCLUSIONS: The corner stitch is as strong as conventional cross-stitch repairs and its superficial placement may be more favorable to tendon blood supply. This repair may be advantageous for clinical applications.     

Flexor digitorum profundus tendon tension during finger manipulation.

Abstract The purpose of this study was to measure the tension in the flexor digitorum profundus (FDP) tendon in zone II and the digit angle during joint manipulations that replicate rehabilitation protocols. Eight FDP tendons from eight human cadavers were used in this study. The dynamic tension in zone II of the tendon and metacarpophalangeal (MCP) joint angle were measured in various wrist and digit positions. Tension in the FDP tendon increased with MCP joint extension. There was no tension with the finger fully flexed and wrist extended (synergistic motion), but the tendon force reached 1.77 +/- 0.43 N with the MCP joint hyperextended 45 degrees with the distal interphalangeal and proximal interphalangeal joints flexed. The combination of wrist extension and MCP joint hyperextension with the distal interphalangeal and proximal interphalangeal joints fully flexed, what the authors term "modified synergistic motion," produced a modest tendon tension and may be a useful alternative configuration to normal synergistic motion in tendon rehabilitation.     

Gliding resistance after FDP and FDS tendon repair in zone II

Many suture techniques have been described for flexor tendon repair. While many of these sutures have been tested and used clinically, the interaction between repairs of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) in the same digit has not been rigorously examined. Moreover, while much data are available on the mechanical properties of various suture techniques for FDP repair, much less is known about the mechanical performance of FDS repairs during motion of tendons.

To make up for this lack of information, we measured the gliding resistance of the repaired FDP tendon, as compared to different FDS tendon repairs in a human cadaver model. The FDP tendon was repaired with a modified Kessler technique, while the FDS was repaired with a modified Kessler (n = 10), Becker (n = 10), or a new double running zig-zag suture (n = 10). The modified Kessler repair had a threefold increase from normal gliding resistance, the Becker repair increased twofold, and the zig-zag repair increased twofold. The peak gliding resistance increased twofold with a modified Kessler repair, 2.5-fold with a Becker repair, and 2.5-fold with a zig-zag repair.     

Flexor tendon suture methods: a quantitative analysis of suture material within the repair site

This study compared the cross-sectional area and volume occupied by suture material at the repair site in three common methods of flexor tendon repair. A total of 51 human cadaveric tendons were studied. Zone II flexor digitorum profundus tendon lacerations were created and then repaired using the techniques described by Kessler, Tajima, and Savage. Quantitative cross-sectional area and volumetric measurements of suture material within each repair site were determined using a digital image analysis system. The Tajima repair occupied 27% of the tendon area at the repair site, while the Savage and Kessler repairs occupied 18% and 2%, respectively.     

Resurfacing with chemically modified hyaluronic acid and lubricin for flexor tendon reconstruction

We assessed surface coating with carbodiimide derivatized hyaluronic acid combined with lubricin (cd‐HA‐Lubricin) as a way to improve extrasynovial tendon surface quality and, consequently, the functional results in flexor tendon reconstruction, using a canine in vivo model. The second and fifth flexor digitorum profundus tendons from 14 dogs were reconstructed with autologs peroneus longus (PL) tendons 6 weeks after a failed primary repair. One digit was treated with cd‐HA‐Lubricin, and the other was treated with saline as the control. Six weeks following grafting, the digits and graft tendons were functionally and histologically evaluated. Adhesion score, normalized work of flexion, graft friction in zone II, and adhesion breaking strength at the proximal repair site in zone III were all lower in the cd‐HA‐Lubricin treated group compared to the control group. The strength at the distal tendon/bone interface was decreased in the cd‐HA‐Lubricin treated grafts compared to the control grafts. Histology showed inferior healing in the cd‐HA‐Lubricin group at both proximal and distal repair sites. However, cd‐HA‐Lubricin treatment did not result in any gap or rupture at either the proximal or distal repair sites. These results demonstrate that cd‐HA‐Lubricin can eliminate graft adhesions and improve digit function, but that treatment may have an adverse effect on tendon healing. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 969–975, 2013     

Healing of canine tendon in zones subjected to different mechanical forces.

The effect of external force environment on the healing of a partial thickness injury to canine flexor tendon was studied. A 50% laceration was made in either the fibrocartilaginous (compressive) zone or in the tendinous (tensile) zone of canine flexor digitorum profundus tendons. After three or six weeks, the tendons were harvested. An optical method for determining zone-specific material properties showed that, in response to injury, the structural stiffness decreased in the tensile zone of the tendon but increased in the compressive zone. The mechanical properties and failure mechanism of canine tendon and their changes in response to injury vary according to tendon zone, and differences in the healing process in mechanically specialised zones of the flexor tendon are discussed.     

Flexor tendon repair using a stainless steel external splint. Biomechanical study on human cadaver flexor tendons

A stainless steel external tendon splint was used in repair of cadaver tendons and compared with standard tendon repairs with suture. The splint was combined with a Kessler repair and tested against the Kessler, Becker, and Savage repairs in fresh human cadaver flexor digitorum profundus tendons. Biomechanical testing was done on a tensile testing machine, and load-displacement curves were generated. The repairs using the external tendon splint demonstrated a range of improvement of 32 to 146% in mean maximal tensile strength and a 20 to 185% improvement of mean ultimate tensile strength compared with all other repairs. The external tendon splint is relatively easy to apply to a tendon. The repair is strengthened and becomes capable of withstanding early active range of motion exercises. In vivo testing will be needed to assess the potential clinical usefulness of such a device.     

Gliding resistance after FDP and FDS tendon repair in zone II: an in vitro study

Many suture techniques have been described for flexor tendon repair. While many of these sutures have been tested and used clinically, the interaction between repairs of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) in the same digit has not been rigorously examined. Moreover, while much data are available on the mechanical properties of various suture techniques for FDP repair, much less is known about the mechanical performance of FDS repairs during motion of tendons. To make up for this lack of information, we measured the gliding resistance of the repaired FDP tendon, as compared to different FDS tendon repairs in a human cadaver model. The FDP tendon was repaired with a modified Kessler technique, while the FDS was repaired with a modified Kessler (n = 10), Becker (n = 10), or a new double running zig-zag suture (n = 10). The modified Kessler repair had a threefold increase from normal gliding resistance, the Becker repair increased twofold, and the zig-zag repair increased twofold. The peak gliding resistance increased twofold with a modified Kessler repair, 2.5-fold with a Becker repair, and 2.5-fold with a zig-zag repair.     

环指指深屈肌腱闭合性断裂机制的探讨

目的　应用生物力学的方法 ,探讨指深屈肌腱闭合性断裂中环指多发的原因。方法　取成人防腐尸手 10只及新鲜离体手 8只 ,指深屈肌腱的长度应包括 ～ 区在内。将各指于掌指关节处离断 ,置于 WE- 60型液压万能试验机上 ,测试 2～ 5指指深屈肌腱断裂瞬间所承受的最大负荷值。结果　环指指深屈肌腱抵止部的断裂阈值明显低于中指 ,两者差异有非常显著性意义 ( q=2 2 .15 ,P<0 .0 1)。结论　指深屈肌腱断裂以环指末节多见的原因 ,和其指深屈肌腱的抵止部相对薄弱有关     

Zone 2 flexor digitorum profundus and superficialis rupture treated with single-stage tendon reconstruction using an Active Hunter Rod Implant

To our knowledge, no report has been published of a flexor tendon rupture as a result of a closed phalangeal fracture.A 58-year-old woman with multiple medical comorbidities presented with a closed, apex volar fracture of her long finger proximal phalynx with clinically intact flexor digitorum profundus and superficialis tendons in zone 2 of the flexor tendon sheath. After 5 weeks of nonoperative treatment, the patient reported hearing a pop in her finger, and clinical findings suggested rupture of the flexor digitorum profundus and superficialis tendons. Intraoperatively, the nonreparable attritional rupture was underneath the A2 pulley. A bony prominence in the tendon sheath floor from the healed phalynx fracture made rerupture a concern with a tendon graft. A Hunter Active Tendon Implant (Wright Medical Technology, Inc, Arlington, Tennessee) was used to reconstruct the flexor digitorum profundus tendon to avoid a second procedure. The patient progressed well and had regained a functional arc of active finger range of motion by 2 months postoperatively.The Hunter Active Tendon Implant provided a suitable alternative to a 2-staged procedure, with the added benefit that a good tendon bed was developed in the event that a second procedure was needed.     

Flexor Tendon Injuries: II. Operative Technique

The repair of flexor tendons (zones I and II) is a technique-intensive surgical undertaking. It requires a strong understanding of the anatomy of the tendon sheath and the normal relationship between the pulleys and the flexor digitorum superficialis and flexor digitorum profundus tendons in the digit. Meticulous exposure, careful tendon retrieval, and atraumatic repair are extremely important, and the repair should be of sufficient strength to resist gapping and permit the early postrepair application of motion forces. Whenever possible, the tendon sheath should be preserved or repaired, and a smooth gliding surface should be reestablished. The author describes an effective method of tendon retrieval and a simplified technique for a four-strand tendon repair with a supplementary peripheral running-lock suture. The repair is considered to maintain sufficient strength throughout healing to allow a postrepair rehabilitation protocol that will impart passive and modest active stress forces to the repaired tendons. Complications include tendon rupture, digital joint flexion contractures, and adhesions that restrict tendon gliding and ultimately necessitate tenolysis.     

Extensor tendon involvement in Smith's and Galeazzi's fractures

Extensor tendon involvement in three Smith's and two Galeazzi's fractures are reported. In two cases of previous Smith's fracture, the extensor indicis proprius tendon had been entrapped and ruptured in one case, and in the other the extensor digitorum communis tendon of the index was pierced by the fragment. Both showed a severe tenodesis effect on the index finger and thumb. In a new case of Smith's fracture, long extensor tendons of the fingers and thumb had been trapped beneath a dorsally displaced third fragment making closed reduction impossible. In the two cases of Galeazzi's fracture; in one the extensor carpi ulnaris tendon was trapped between the dorsally displaced ulnar head and the avulsed styloid process and in the other, the extensor digiti minimi tendon was caught beneath the radial border of the dorsally dislocated ulnar head.     

Twenty-five-year follow-up evaluation of an active silicone/Dacron tendon interposition prosthesis: A case report

A 19-year-old man sustained a severe avulsion wound of the dominant distal forearm, dividing the radial and ulnar arteries, median and ulnar nerves, and all flexor tendons. Initial treatment consisted of revascularization. Shortly thereafter he had sural nerve grafting of the median and ulnar nerves. This was followed by insertion of a silicone/Dacron tendon interposition prosthesis to reconstruct a 4-cm deficit in the flexor profundus tendons and the flexor pollicis longus tendon. Six weeks thereafter an opposition transfer using the extensor indicis proprius and a Brand type 2 intrinsic transfer using the extensor carpi radialis longus and a plantaris tendon graft were performed. Several months later an attempt was made to remove the prosthesis. It was encased in scar tissue, however, and left in place. Evaluation 25 years later revealed that the flexor tendons and prosthesis were functioning well.     

Flexor tendon grafting to the hand: an assessment of the intrasynovial donor tendon-A preliminary single-cohort study

We report the results of a pilot study using intrasynovial donor tendons for flexor tendon reconstruction in 8 patients (10 digits) at a mean follow-up time of 3.8 years for neglected or failed primary repair of zone 2 lacerations and for neglected flexor digitorum profundus avulsions. The flexor digitorum longus to the second toe was used as the donor tendon graft. Four patients (4 digits) underwent single-stage reconstruction and 4 patients (6 digits) had multistage reconstruction. The overall patient satisfaction using a standardized visual analog reporting scale was excellent. There was 1 excellent, 1 good, 1 fair, and 1 poor result in the single-stage reconstruction group, including 1 repair site rupture and 1 digit requiring tenolysis. In the multistage reconstruction group there was 1 excellent, 3 good, 1 fair, and no poor results, including 1 digit requiring tenolysis. One patient was lost to follow-up. There was no donor site morbidity. The average active motion recovery was 64% and 56% for single-stage and multistage reconstructions, respectively, and was 73% overall for single digit reconstructions. The results of this pilot study suggest that intrasynovial tendon grafting may offer an improved alternative for tendon grafting to the synovial spaces of the digit.