Biomechanical analysis of the cruciate four-strand flexor tendon repair

The purpose of this study was to develop and test in vitro a new flexor tendon suture technique that was simple and easy to perform, yet strong enough to withstand the projected forces of an in vivo active motion rehabilitation protocol. Forty human cadaveric flexor digitorum profundus tendons were divided and repaired using 1 of 4 suture techniques (the modified Kessler, the Strickland, the modified 4-strand Savage, and the Cruciate 4-strand repairs). Each repair was tested using a slow-test machine and displacement control at 2 mm/s. Force applied, the resultant gap, and ultimate tensile strength were recorded and statistical comparisons were performed using a two-tailed Student's t-test with level of significance set at p = .05. The Cruciate suture technique was demonstrated to be nearly twice as strong to 2-mm gap formation (44 N) compared with the Kessler, Strickland, and Savage repairs. Ultimate tensile strength was also significantly stronger for the Cruciate technique (56 N) than the Kessler, Strickland, or Savage repairs. The technique was significantly faster to perform than the Savage or Strickland repairs and was comparable in repair time to the 2-stranded Kessler repair. The design of the new suture technique allowed the tendon repair to be completed with the ease and speed of a 2-strand technique, but bestowed on the repair strength that exceeded current 4-strand techniques.     

Biomechanical evaluation of flexor tendon repair techniques

Immediate active mobilization of repaired tendons is thought to be the most effective way to restore function of injured flexor tendons. Sixty human flexor digitorum profundus tendons were used to evaluate techniques for active tendon motion. The tendons were divided equally into six groups, and each group was assigned to one of the following techniques: Kessler core suture plus running peripheral suture, Kessler plus cross-stitch suture, Kessler plus Halsted suture, Tang core suture plus running peripheral suture, Tang plus cross-stitch suture, or Tang plus Halsted suture. Immediately after tendon repair, an Instron tensile testing machine was used to measure the 2-mm gap formation force, ultimate strength, elastic modulus, and energy to failure of the tendons repaired by these techniques. Ultimate strength, elastic modulus, and energy to failure were measured in load displacement curve. Results showed that the ultimate strength of the Tang plus Halsted or cross-stitch was, respectively, 116.8 +/- 9.6 N and 94.6 +/- 7.8 N; and 2-mm gap formation force was, respectively, 86.6 +/- 4.9 N and 71.9 +/- 5.1 N. The Tang plus Halsted or cross-stitch methods had a statistically significant increase in ultimate strength and 2-mm gap formation force as compared with the Kessler core suture or Tang plus running peripheral suture method. Elastic modulus and energy to failure of the Tang plus Halsted or cross-stitch suture were statistically higher than those of other techniques. The Tang plus cross-stitch or Tang plus Halsted sutures had the highest strength among the tested methods and are appropriate techniques for tendon repair in which the goal is immediate active tendon motion.     

A biomechanical analysis of a new interlock suture technique for flexor tendon repair.

Using a computerised tensometer, both the gap-producing and breaking forces of a new interlocking suture for flexor tendon repair were compared to the modified Kessler and the Strickland techniques. 30 porcine deep flexor tendons were used in each group and all repairs were performed with 3/0 polypropylene sutures. The interlock technique withstood gap-producing and breaking forces significantly better than the modified Kessler and Strickland techniques. Also, the gap-producing force was closer to the breaking force with the interlock technique than with the other two techniques.     

Biomechanical assessment of a new type of flexor tendon repair

A four-strand adaptation of the Kessler repair is described and the results of biomechanical testing in pig tendons are reported. The strength of our repair was compared against standard Kessler repairs using Ethibond or Ti.cron as the core sutures. The average tensile strength for the Ethibond Kessler repair was 33 Newtons and that of the Ti.cron Kessler repair was 31 Newtons. The average tensile strength for the Evans repair was 52 Newtons. This new method of flexor tendon repair is significantly stronger than the modified Kessler repair and is simpler to use than other multi-strand repair techniques.     

一种新型肌腱周边缝合方法的生物力学研究

目的通过比较连续周边缝合(Running)、Cross-stitch、Halsted及一种新型肌腱周边缝合方法的生物力学特性,为该方法的临床应用提供理论依据。方法将36根新鲜成年猪后蹄Ⅱ区屈肌腱随机分成4组,分别用连续周边缝合(Running)、Cross-stitch、Halsted及一种新型肌腱周边缝合方法进行修复。将缝合好的肌腱等速拉伸至完全断裂,并用材料力学测定仪(Instron4411)测定2-mm间隙形成负荷、最大负荷,计算断裂功耗。结果新型肌腱周边缝合法的2-mm间隙形成负荷为(53.2±6.0)N、最大负荷为(68.8±6.9)N、刚度为(6.6±0.7)N/mm,为各组中最高;断裂功耗为(0.784±0.075)J与Halsted法相近,高于Cross-stitch及Running法。结论该新型肌腱周边缝合法的生物力学强度高于目前临床应用的Running、Cross-stitch、Hal-sted法,能提供较大的抗张强度、有效抵御间隙形成、操作简便,有利于肌腱早期主被动功能锻炼。     

Biomechanical analysis of knotless flexor tendon repair using large-diameter unidirection barbed suture

Purpose

In traditional flexor tendon repairs, suture knots can be sites of weakness, impair tendon healing, stimulate an inflammatory response, and increase the bulk of the tendon repair. Because of this, there has been an increased interest in knotless flexor tendon repair using barbed suture. Since knots are not required, it may be possible to increase the strength of the tendon repair by using a large-diameter barbed suture. The purpose of this study was to biomechanically compare a traditional four-strand tendon repair using 3-0 braided polyester with a similar knotless four-strand tendon repair using 0 unidirectional barbed suture.

Methods

Twenty-two matched cadaveric flexor digitorum profundus tendons were lacerated and assigned to repair by a four-strand modified Kirchmayr–Kessler technique using 3-0 braided polyester (n = 11) or knotless four-strand modified Kirchmayr–Kessler repair using 0 unidirectional barbed suture (n = 11). Repaired tendons were linearly distracted to failure at 20 mm/min after 1 N preload. Maximum load and load at 2-mm gap formation were recorded. Maximum load and load at 2-mm gap formation were compared with the Student’s t test, and p values ≤ 0.05 were considered significant.

Results

The mean maximum load of the barbed, knotless suture repair was higher than that of the traditional repair (52 vs. 42 N). There was no difference between the two groups in the mean load required to produce a 2-mm gap.

Conclusions

The four-strand knotless tendon repairs using a large-diameter unidirectional barbed suture were stronger than the traditional four-strand repairs using 3-0 braided polyester, and had similar 2-mm gap resistance.     

Biomechanical studies of running suture for flexor tendon repair in dogs

A new running-locking loop suture technique has been developed to increase tendon repair strength and to provide better tendon edge inversion. Biomechanical analysis documented the failure mechanism and the failure strength of various circumferential repair techniques. When compared with two well-known techniques, the simple circumferential running suture and Lembert running suture, the locking suture technique was shown to have 3.77 and 1.68 times greater tensile failure strength and 1.73 and 1.26 times greater stiffness than these traditional suture methods. A running peripheral locking suture may help augment the strength of tendon repair.     

The biomechanical analysis of a tendon fixation device for flexor tendon repair

PURPOSE: Stainless steel suture is high in tensile strength but is not widely used in flexor tendon repair because of difficulty with handling and knot tying. The purpose of this study was to examine the biomechanical characteristics of the single-strand multifilament stainless steel Teno Fix device (Ortheon Medical, Winter Park, FL) designed for zone II flexor digitorum profundus (FDP) tendon repair. METHODS: Sixty cadaveric flexor tendons were transected and randomized to receive a Teno Fix or 4-stranded (3-0 or 4-0 braided polyester) suture repair; all repairs were tested with and without a 5-0 monofilament polypropylene circumferential epitendinous suture. By using a material testing system all tendons were tested to failure in tension using a linear model with a loading rate of 1 mm/s. Stiffness, force, and energy at both 2-mm gap and peak force were calculated from the resulting force-displacement curves. RESULTS: The 2-mm gapping force was significantly greater for the Teno Fix and the 3-0 repairs than for the 4-0 repairs. The energy absorbed up to 2-mm gap was significantly greater for the Teno Fix, however, than for all suture repairs both with and without a circumferential suture. There was no statistically significant difference in peak force or energy absorbed at peak force between the Teno Fix and suture repairs; the average gap at peak force for all repairs was 5.2 mm. The addition of a circumferential suture increased the 2-mm gapping and peak forces of the Teno Fix repair to 54.5 N and 66.7 N, respectively. CONCLUSIONS: Increased strength and energy absorbed at 2-mm gap and ease of installation makes the Teno Fix a promising repair method.     

Biomechanical comparison of double grasping repair versus cross-locked cruciate flexor tendon repair

Purpose

This study was conducted to compare the in vitro biomechanical properties of tensile strength and gap resistance of a double grasping loop (DGL) flexor tendon repair with the established four-strand cross-locked cruciate (CLC) flexor tendon repair, both with an interlocking horizontal mattress (IHM) epitendinous suture. The hypothesis is that the DGL-IHM method which utilizes two looped core sutures, grasping and locking loops, and a single intralesional knot will have greater strength and increased gap resistance than the CLC-IHM method.

Methods

Forty porcine tendons were evenly assigned to either the DGL-IHM or CLC-IHM group. The tendon repair strength, 2-mm gap force and load to failure, was measured under a constant rate of distraction. The stiffness of tendon repair was calculated and the method of repair failure was analyzed.

Results

The CLC-IHM group exhibited a statistically significant greater resistance to gapping, a statistically significant higher load to 2-mm gapping (62.0 N), and load to failure (99.7 N) than the DGL-IHM group (37.1 N and 75.1 N, respectively). Ninety percent of CLC-IHM failures were a result of knot failure whereas 30 % of the DGL-IHM group exhibited knot failure.

Conclusions

This study demonstrates that the CLC-IHM flexor tendon repair method better resists gapping and has a greater tensile strength compared to the experimental DGL-IHM method. The authors believe that while the DGL-IHM provides double the number of sutures at the repair site per needle pass, this configuration does not adequately secure the loop suture to the tendon, resulting in a high percentage of suture pullout and inability to tolerate loads as high as those of the CLC-IHM group.     

Biomechanical studies of 3 different 6-strand flexor tendon repair techniques

We investigated the gap formation and ultimate strength, energy to failure, and patterns of failure of tendon repairs with the modified Savage, Lim, and Tang methods. Fifty-four fresh-frozen flexor digitorum profundus tendons were assigned to 3 groups and repaired with one of the previously mentioned methods. Nine tendons from each group were pulled to failure in a tensile testing machine when they were subjected to a linear load. The 2-mm gap formation force of the tendons was 37.4 N for the modified Savage, 44.5 N for the Tang, and 40.2 N for the Lim method. Ultimate strength was 57.8 N for the modified Savage, 60.2 N for the Tang, and 51.3 N for the Lim method. Statistically, the gap formation force was significantly higher in the Tang method than in the modified Savage and the Lim methods. Ultimate strength of the modified Savage and Tang methods was similar and significantly higher than that of the Lim method. The rest of the tendons were subjected to angular tension by placement of the tendons against a pulley. The tests show that resistance of the modified Savage and Tang methods to angular tension was significantly greater than that of the Lim method. The results indicate that the resistance to failure and failure modes of the repairs vary according to number of locking junctions with the tendon, location, and orientation of the sutures regardless of an equal number of strands across the repair site. We conclude that the modified Savage and Tang methods have greater tensile strength than the Lim method and may more effectively resist linear and angular tension generated by postoperative tendon motion.     

Cyclic stress analysis of flexor tendon repair

A method of evaluating flexor tendon repair techniques with the use of cyclic testing is presented. This type of evaluation complements the presently used load-to-failure tests by providing more detailed information about gap formation at the repair site. During load-to-failure testing in this study, core sutures alone demonstrated initial gap formation at 0.85 kg tensile force or more; yet on cyclic testing all techniques demonstrated gap formation of 1.9 mm or greater at 0.5 kg tensile force. Thus cyclic testing demonstrated gap formation not readily apparent on load-to-failure testing. An epitenon stitch placed circumferentially around the laceration site added strength in both load-to-failure and cyclic tests, and significantly reduced gap formation regardless of the core suture technique.     

Eight-strand core suture technique for repair of intrasynovial flexor tendon lacerations

The concept of intrinsic tendon healing, the idea that tendons can heal primarily without the ingrowth of fibrous adhesions from the surrounding fibrous flexor sheath, has been validated both experimentally and clinically. The goals of the surgical treatment of intrasynovial digital flexor tendon lacerations are twofold: 1) to achieve a primary tendon repair of sufficient strength so as to prevent repair site gap elongation and possible rupture, and 2) to prevent the formation of intrasynovial adhesions that cause loss of tendon excursion within the flexor tendon sheath. It is well accepted that repair site strength, both at time zero and within the first 6 postoperative weeks, is directly related to the number of core suture strands crossing the repair site. The factor that limits more widespread use of multistrand suture techniques remains the surgeon's ability to perform the repair while also minimizing trauma to the tendon stumps and the circumferential epitenon. We describe an 8-strand core suture technique used at our institution that has been tested ex-vivo, in-vivo in canines, and used in human subjects over the last 4 years with excellent results.     

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。     

Optimal configuration of the spiral linking technique for tendon repair. Biomechanical evaluation

A previous study described a new spiral linking technique for tendon repairs and demonstrated that it was strong enough to be used in clinical practice as an alternative to the Pulvertaft tendon weave repair. However the repairs were less stiff, needed slightly more tendon length for the same repair and were a little bulkier. In this study two variables have been changed with a view to improving the spiral technique. At first the number of spirals was reduced consecutively, keeping the same number of standard mattress sutures. Once the optimal number of spirals had been identified, repairs with different numbers of sutures were tested using an alternative cross-stitch technique. The spiral repair technique using two spirals linked with six sutures was at least as strong and stiff as a four-weave Pulvertaft technique and was also easier to do.     

A biomechanical analysis of the modified Tsuge suture technique for repair of flexor tendon lacerations

Thirty-six flexor tendons from fresh frozen cadavers were randomized to three types of repairs: a Kessler-Tajima, a 4-strand modified Tsuge, and a 6-strand modified Tsuge. All repairs were accompanied by a standard epitendinous suture. The repaired tendons were then tested to initial gap and ultimate failure in an Instron machine. The average forces to ultimate failure were 31.8 N (SD, 8.8), 48.4 N (SD, 10.7), and 64.2 N (SD, 11.0) respectively. The 6-strand modified Tsuge suture was significantly stronger than the other repairs and the 4-strand modified Tsuge was significantly stronger than the 2-strand Kessler-Tajima. The 6-strand and 4-strand modified Tsuge repairs appear strong enough to withstand the forces generated during early active range of motion flexor tendon rehabilitation protocols. Clinical trials are required to evaluate the usefulness of these repairs.