Tim S. Peltz

Influence of Locking Stitch Size in a Four-Strand Cross-Locked Cruciate Flexor Tendon Repair

PURPOSE The 4-strand cross-locked cruciate technique (Adelaide technique) for repairing flexor tendons in zone II is a favorable method in terms of strength and simplicity. The purpose of this study was to investigate the effects of varying the cross-lock stitch size in this repair technique. Outcomes measured were load to failure and gap formation. METHODS We harvested 22 deep flexor tendons from adult pig forelimbs and randomly allocated them into 2 groups. After cutting the tendons at a standard point, we performed a 4-strand cross-locked cruciate repair using 3-0 braided polyester with either 2-mm cross-locks (n = 11) or 4-mm cross-locks (n = 11). All repairs were completed with a simple running peripheral suture using 6-0 polypropylene. Repaired tendons were loaded to failure and the mechanism of failure, load to failure, stiffness, and load to 2-mm gap formation were determined. RESULTS All repairs failed by suture breakage; we noted no suture pullout. There was no difference in load to failure (71.7-71.1 N; p = .89) or stiffness (4.1-4.6 N/mm; p = .23) between the 2-mm cross-lock and the 4-mm cross-lock groups. There was a trend toward higher resistance to 2-mm gap formation with the 4-mm cross-locks (55-62.2 N; p = .07). CONCLUSIONS Four-strand cross-locked cruciate repairs with cross-lock sizes of 2 and 4 mm provide high tensile strength and are resistant to pullout. Repairs with 4-mm cross-locks tend to provide a more central load distribution and better gapping resistance than repairs with 2-mm cross-locks.

Performance of a knotless four-strand flexor tendon repair with a unidirectional barbed suture device: a dynamic ex vivo comparison

With increased numbers of reports using barbed sutures for tendon repairs we felt the need to design a specific tendon repair method to draw the best utility from these materials. We split 30 sheep deep flexor tendons in two groups of 15 tendons. One group was repaired with a new four-strand barbed suture repair method without knot. The other group was repaired with a conventional four-strand cross-locked cruciate repair method (Adelaide repair) with knot. Dynamic testing (3–30 N for 250 cycles) and additional static pull to failure was performed to investigate gap formation and final failure forces. The barbed suture repair group showed higher resistance to gap formation throughout the test. Additionally final failure force was higher for the barbed suture group compared with the conventional repair group. When used appropriately, barbed suture materials could be beneficial to use in tendon surgery, especially with regard to early loading of the repair site and gap formation.

The relationship between gap formation and grip-to-grip displacement during cyclic testing of repaired flexor tendons.

The assessment of repair site gap formation during cyclic loading of reconstructed flexor tendons provides important data on the performance of repair techniques in the early postoperative period. This study describes our cyclic testing protocol and evaluates the relationship between changes in optical gap and grip-to-grip displacement. Sixteen sheep hind limb deep flexor tendons were randomized into four repair groups (n=4 per group): a 2-strand repair (modified Kessler) and 4-strand repair (Adelaide), both with and without a simple running peripheral suture. Repaired tendons were cycled for 1000 cycles at appropriate rehabilitation loads for the reconstruction. Tendons were paused at 18 pre-determined cycle points to measure gap and displacement. A strong positively linear relationship between gap and displacement was demonstrated for all repair groups (R²>0.90). An initial non-linear region during the first 10 cycles was noted with some combined core and peripheral repairs. Although trends in displacement after 10 cycles can be used to reflect gapping behaviour, direct optical measurement of gap remains preferable. We hypothesized that the adjustment of suture strands and equilibration of forces within the reconstruction occurs mostly during the initial 10 cycles. Gap-cycle curves provide a good illustration of dynamic changes at the repair site, and should be added more frequently to cyclic testing studies.

Biomechanical evaluation of flexor tendon repair using barbed suture material: a comparative ex vivo study.

To the Editor: We read the article by Zeplin et al with great interest, evaluating barbed suture repair of an injured flexor tendon. Barbed sutures theoretically distribute loads throughout their intratendinous path. This is particularly appealing for resisting repair site gapping. Gap formation, preferably measured under dynamic conditions, is therefore an important end point when testing barbed suture tenorrhaphy. The use of load to failure measurements is less important with modern multistrand repairs. Nonethe-

A Biomechanical Assessment of Repair Versus Nonrepair of Sheep Flexor Tendons Lacerated to 75 Percent

PURPOSE The benefit of repairing a 75% partial flexor tendon laceration remains controversial. The purpose of this study was to assess the degree of gap formation with and without repair when the 75% lacerated tendon is subjected to cyclic loading. Repair with only a peripheral suture was compared to that using a core and peripheral repair technique. METHODS Sixteen deep flexor tendons from sheep hind limbs were lacerated to 75% of the tendon diameter. The cut tendons were loaded for 100 cycles from 3 N up to 30 N and then back to 3 N, at a rate of 0.2 Hz. Gap formation was measured at 0 and 100 cycles. Tendons were then randomized into 2 repair groups of 8 each: group 1 was repaired with only a simple, running peripheral suture (6-0 polypropylene monofilament), whereas group 2 was repaired with a modified Kessler core suture (4-0 silicone-coated braided polyester) plus a peripheral suture (6-0 polypropylene monofilament). Repaired tendons were tested for 500 cycles, and the gap was measured at 0, 100, and 500 cycles. After cycling, gap was measured at 100 N load, and the peak loads were determined on static failure testing. RESULTS The 75% partially lacerated tendons had >2 mm gap at 100 cycles. This gap was significantly reduced by peripheral or peripheral plus core repairs (p < .001). There was no difference in gap formation between tendons with peripheral repair only and those with both peripheral and core repairs. Gap formation in repaired tendons remained <or=1 mm at 500 cycles. After cycling, neither gap formation at 100 N load or the peak loads on failure testing differed between the 2 repair groups. CONCLUSIONS There is a large gap when an unrepaired 75% partial laceration is cyclically loaded. This gap is significantly reduced with a peripheral repair whether or not a core suture is used.

Looped suture properties: implications for multistranded flexor tendon repair

Multiple-strand repair techniques are commonly used to repair cut flexor tendons to achieve initial biomechanical strength. Looped sutures achieve multiple strands with fewer passes and less technical complexity. Their biomechanical performance in comparison with an equivalent repair using a single-stranded suture is uncertain. This study examined the mechanical properties of double-stranded loops of 3-0 and 4-0 braided polyester (Ticron) and polypropylene monofilament (Prolene). Double loops were generally less than twice the strength of a single loop. Ticron and Prolene had the same strengths, but Ticron was stiffer. The 4-0 double loops had significantly higher stiffness than 3-0 single loops. Increasing the size of sutures had a larger relative effect on strength than using a double-stranded suture. However, a double-strand loop had a larger effect on increasing stiffness than using a single suture of a larger equivalent size. Looped suture repairs should be compared with standard techniques using a thicker single suture.

The Interlocking Modification of the Cross Locked Cruciate Tendon Repair (Modified Adelaide Repair): A Static and Dynamic Biomechanical Assessment.

The 4-strand cross-locked cruciate flexor tendon repair technique (Adelaide technique) has been shown to have comparably high resistance to gap formation and ultimate tensile strength. This study aimed to determine whether an interlocking modification to the Adelaide repair would impart improved biomechanical characteristics. Twenty four sheep flexor tendons were harvested, transected and repaired using either standard or modified Adelaide techniques. Repaired tendons were cyclically loaded. Gap formation and ultimate tensile strength were measured. Additionally, suture exposure on the tendon surface was determined. There was a statistically significant increase in resistance to gap formation in the early phase of cyclic loading within the modified Adelaide group. In the later stages of testing no significant difference could be noted. The average final load to failure in the modified group was higher than the standard group but this did not achieve statistical significance. Interlocking suture techniques in four strand tendon repair constructs can improve gapping behavior in the early phase of cyclic loading.

Animal Models for Tendon Repair Experiments: A Comparison of Pig, Sheep and Human Deep Flexor Tendons in Zone II

BACKGROUND This laboratory study compared pig, sheep and human deep flexor tendons in regards to their biomechanical comparability. METHODS To investigate the relevant biomechanical properties for tendon repair experiments, the tendons resistance to cheese-wiring (suture drag/splitting) was assessed. Cheese-wiring of a suture through a tendon is an essential factor for repair gapping and failure in a tendon repair. RESULTS Biomechanical testing showed that forces required to pulling a uniform suture loop through sheep or pig tendons in Zone II were higher than in human tendons. At time point zero of testing these differences did not reach statistical significance, but differences became more pronounced when forces were measured beyond initial cheese-wiring (2 mm, 5 mm and 10 mm). The stronger resistance to cheese-wiring was more pronounced in the pig tendons. Also regarding size and histology, sheep tendons were more comparable to human tendons than pig tendons. CONCLUSIONS Differences in tendon bio-properties should be kept in mind when comparing and interpreting the results of laboratory tendon experiments.

Evaluation of the artificial cotton roll tendon model for mechanical tendon repair experiments.

flexor tendon, the same method is used to obtain release of adhesions between the palmar aspect of the tendon and the pulley (Figure 1(c)–(d)). Caution must be applied when pulling each limb of the suture perpendicular to the pulley to avoid tearing it. Controlled active motion is started immediately under the supervision of the physiotherapist, without using any kind of splints. We have used this technique for the release of short segments of adhesions with loss of motion in patients who have not responded to conservative management by 6 months after tendon repair, and it has been used in 11 such patients. We are unable to recommend it in patients 12 months or later after repair as we have no experience in its use in this group.