Mechanical evaluation of different techniques for Achilles tendon repair

Natural, synthetic and commercially-available biopolymers used to regenerate tendons and ligaments

Tendon and ligament (TL) injuries affect millions of people annually. Biopolymers play a significant role in TL tissue repair, whether the treatment relies on tissue engineering strategies or using artificial tendon grafts. The biopolymer governs the mechanical properties, biocompatibility, degradation, and fabrication method of the TL scaffold. Many natural, synthetic and hybrid biopolymers have been studied in TL regeneration, often combined with therapeutic agents and minerals to engineer novel scaffold systems. However, most of the advanced biopolymers have not advanced to clinical use yet. Here, we aim to review recent biopolymers and discuss their features for TL tissue engineering. After introducing the properties of the native tissue, we discuss different types of natural, synthetic and hybrid biopolymers used in TL tissue engineering. Then, we review biopolymers used in commercial absorbable and non-absorbable TL grafts. Finally, we explain the challenges and future directions for the development of novel biopolymers in TL regenerative treatment.

•

Both natural and synthetic biopolymers are reviewed for regeneration of TL and their interface tissues.

•

Advances on hybrid-composite biopolymers to fabricate TL scaffolds were reviewed.

•

The current biopolymers used in commercial TL grafts are discussed.

•

The challenges and emerging strategies for biopolymer development are presented.

Rates of complications in Achilles tendon rupture repair using absorbable and nonabsorbable suture material; A systematic review

BACKGROUND

The impact of suture type on tensile strength, re-rupture rates and infection risk in Achilles tendon rupture repair is not been well established. The aim of this review is to evaluate existing literature on the associated risk of postoperative infection with absorbable and non-absorbable suture materials in Achilles tendon rupture repair.

METHODS

A systematic review of search databases PubMed; Google Scholar; and OVID Medline was made to identify studies related to complications associated with Achilles tendon rupture repair. PRISMA guidelines were utilised for this review. Meta-analysis was used to compare rupture rates and infections following rupture repair.

RESULTS

12 studies with a total of 460 patients, 230 in both nonabsorbable and absorbable suture groups were included for analysis. Risk of wound complications was significantly higher in patients with non-absorbable sutures (p < 0.001).

CONCLUSION

Nonabsorbable braided sutures is associated with the highest risk of postoperative wound complications following Achilles tendon rupture repair.

Modified triple Kessler with least risk of elongation among Achilles tendon repair techniques: a systematic review and network meta-analysis of human cadaveric studies

PURPOSE

Current treatment recommendations emphasize early loading, with preservation of tendon length and physiologic tension. The objective of this systematic review and network meta-analysis was to compare failure load and elongation after cyclic loading of Achilles tendon repair techniques at time-zero.

METHODS

The databases PubMed, CENTRAL and Web of Science were searched for all published in-vitro studies comparing Achilles tendon repair techniques, or augmentation with autografts/biomaterials, and reports of failure load or elongation after cyclic loading. Only studies using human cadaveric Achilles tendons and matched pairs, or randomized specimen allocation, were selected for quantitative synthesis. A network meta-analysis per primary outcome was performed. Results were summarized as P score rankings and their validity was assessed using statistical methods.

RESULTS

Sixteen studies, comprising 367 tendon repairs, were included. The following repair techniques were used (n = number of studies): Krackow (n = 8), Achillon (n = 4), double Krackow (n = 3), Bunnell (n = 3), Percutaneous Achilles Repair System (n = 3), Percutaneous Achilles Repair System Midsubstance (n = 2), Kessler (n = 3), double Kessler (n = 1), modified triple Kessler (n = 1), triple bundle (n = 1), a multifilament stainless steel cable-crimp technique (n = 1) and a double loop knot stitch (n = 1). Five studies assessed augmentation with autografts/biomaterials. Regarding the failure load, biomaterial augmented Krackow repairs occupied the first four positions in the ranking, followed by the multifilament stainless steel cable-crimp and Percutaneous Achilles Repair System Midsubstance techniques. Concerning elongation after cyclic loading, the triple Kessler was ranked first, followed by the Achillon and Percutaneous Achilles Repair System Midsubstance techniques. A negligible correlation between ranks was found (r_s = 0.11; p = 0.75n.s.), meaning that a higher repair tensile strength is not necessarily related to improved performance in regard to avoidance of elongation.

CONCLUSION

In the failure load network meta-analysis, biomaterial augmented Krackow repairs ranked highest, but noticeable statistical heterogeneity was found. Regarding elongation with cyclic loading, the modified triple Kessler stitch showed the highest probability of ranking first.

LEVEL OF EVIDENCE

Level IV.

An ex vivo biomechanical comparison of two suture materials and two pattern combinations for equine superficial digital flexor tendon tenorrhaphy

OBJECTIVE

To compare biomechanical characteristics of three-loop pulley (3LP) pattern versus Bunnell technique (BT) using polydioxanone (PDS) suture; to determine the influence of polyester tape (PT) versus PDS on the BT for equine superficial digital flexor tendon (SDFT) tenorrhaphy; to compare BT with PT versus 3LP with PDS.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

Forty equine forelimb SDFT.

METHODS

Two experiments were performed: (1) 10 SDFT pairs were repaired with 3LP or BT using PDS; (2) 10 SDFT pairs were repaired with PDS or PT using BT. Load at failure, mode of failure, load at 2 mm gap, and gap at failure were obtained using a material testing machine.

RESULTS

In experiment 1, 3LP + PDS₁ had higher loads at failure (p < .001) and at 2 mm gap (p < .001), and smaller gap at failure than BT + PDS₁ (p = .024). In experiment 2, BT + PT₂ had higher loads at failure (p < .001) and at 2 mm gap (p = .001), and larger gap at failure (p = .004) than the BT + PDS₂ . 3LP + PDS₁ and BT + PT₂ mostly failed by suture/implant pull-through while BT + PDS failed by suture breakage. BT + PT₂ had greater load (p = .035) and gap at failure (p < .001) than 3LP + PDS_1, with no difference in load at 2 mm gap (p = .14).

CONCLUSION

The use of BT may be justified over 3LP if combined with PT. However, the larger size of the PT required stab incisions in the tendon for placement and was subjectively more difficult to place than PDS.

CLINICAL SIGNIFICANCE

The BT + PT, although the strongest among the tested repairs, would only be able to withstand 12%-24% of the load encountered by the SDFT at walk.

The influence of an orthopaedic walker boot on forefoot force

BACKGROUND

In the treatment of an Achilles tendon rupture the patients are commonly equipped with an orthopaedic walker boot with wedges. To what extent this influences the tensile force placed on the Achilles tendon is unclear.

PURPOSE

To assess the forefoot force and describe changes in muscle activity of the medial gastrocnemius, soleus and tibialis anterior when using one or three wedges during ambulation in a weightbearing orthopaedic walker boot.

METHODS

The force on the forefoot was measured with a force sensor insole and muscle activity of the medial gastrocnemius, soleus and tibialis anterior were measured using surface electromyography in 10 healthy participants. Three different types of ambulation were performed (walking without crutches (unass.), walking with crutches (+crutch) and walking with crutches and verbal instructions to place body weight on heel (heel+crutch) with one and three heel wedges respectively.

FINDINGS

The total peak force displayed an interaction where forefoot force decreased when wearing three wedges only for the +crutch ambulation type (80N, p=0.001) although there was a trend to decrease with three wedges also for the heel+crutch ambulation type (48N, p=0.05). The relative peak force on the forefoot showed a main effect with a significant decrease when using three wedges compared to one wedge across all three ambulation types (19.1%, p=0.009).

INTERPRETATION

The force on the forefoot and hereby the Achilles tendon significantly decreased when using three wedges compared to one wedge. These findings have important implications for the rehabilitation post Achilles tendon rupture.

Comparison of the double loop knot stitch and Kessler stitch for Achilles tendon repair: A biomechanical cadaver study

Tendon elongation after Achilles tendon (AT) repair is associated with the clinical outcome. Reliable suture techniques are essential to reduce gap formations and to allow early mobilization. Cyclic loading conditions represent the repetitive loading in rehabilitation. The aim of this study was to compare the Kessler stitch and double loop knot stitch (DLKS) in a cyclic loading program focussing on gap formation. Sixteen human cadaveric ATs were transected and sutured using either the Kessler stitch or DLKS (eight matched pairs). The suture-tendon configurations were subjected to cyclic loading and additional ultimate load to failure testing using the Zwick 1446 universal testing machine. Each AT survived cyclic loading, with a mean gap formation less than 5 mm after 1000 cycles. The mechanical properties of the Kessler stitch and DLKS were not significantly different after cyclic loading with a mean displacement of 4.57 mm (± 1.16) for the Kessler stitch and 4.85 mm (± 1.14) for the DLKS (P = .76). There were no significant differences in the ultimate load testing (P = .85). Both bioprotective techniques prevent excessive gaping in cyclic testing when tendon loading is moderate. Our data and those from literature of gap formation in cyclic and ultimate loading allow the conclusion, that early aggressive AT loading after repair (e.g. full weightbearing) overstrain simple as well as complex suture configurations. Initial intraoperative tightening of the knots (preloading) before locking is important to decrease postoperative elongation.

A biomechanical comparison of Achilles tendon suture repair techniques: Locking Block Modified Krackow, Kessler, and Percutaneous Achilles Repair System with the early rehabilitation program in vitro bovine model

BACKGROUND

The Krackow technique has the advantage of high strength, though it is not minimally invasive. The "Locking Block Modified Krackow" (LBMK) peri-tendon fixation technique was designed for minimally invasive surgery. This study aimed to compare the biomechanics of LBMK with Kessler and Percutaneous Achilles Repair System (PARS) techniques using a simulated early rehabilitation program.

MATERIALS AND METHODS

Thirty-fresh bovine Achilles tendon specimens were randomly assigned to the LBMK, Kessler, and PARS groups (n = 10). In LBMK group, the main suture configuration was the LBMK technique, and the transverse suture was used as the secondary suture configuration. The Kessler group employed three suture configurations, two sagittal, one coronal plane. In the PARS group, two transverse and one locking sutures were placed at either end of the tendon. Each repaired specimen underwent two cyclic loading protocols (20-100 N, 20-190 N), 500 cycles, followed by measurement of the gap between the tendon ends. All specimens underwent a load-to-failure test at a 25 mm/s stretching rate.

RESULTS

After the first loading cycle, the average gaps of the LBMK, Kessler and PARS groups were 0.76 ± 0.44 mm, 1.80 ± 0.82 mm, and 2.66 ± 1.04 mm, respectively. The LBMK group had a significantly reduced gap than the other groups (p < 0.01). The LBMK group gaps were all within 2 mm. The Kessler and PARS groups had six, and two specimens within 2 mm, respectively. After the second loading cycle, the average end gaps of the LBMK, Kessler, and PARS groups were 3.68 ± 1.08 mm, 5.70 ± 0.89 mm and 7.59 ± 1.26 mm, respectively. The LBMK group had a significantly reduced average gap than the other groups (p < 0.01). The maximum load-to-failure was highest 732.8 ± 138 N in the LBMK than the other groups (p < 0.01).

CONCLUSION

The biomechanical strength of the LBMK suture was significantly greater than Kessler and PARS. The reduced gap in the LBMK group suggests superior resistance to gap formation, which may occur during early postoperative rehabilitation.

Clinical Outcomes and Cadaveric Biomechanical Analysis of Endoscopic Percutaneous Achilles Tendon Rupture Repair With Absorbable Suture

Background:

Percutaneous repair of acute Achilles tendon rupture (ATR) continues to gain in popularity. The primary aim of the study was to review the outcomes of a patient cohort undergoing a novel technique of endoscopic percutaneous Achilles tendon repair with absorbable suture. A secondary purpose of this study was to evaluate the basic biomechanical properties of the technique.

Methods:

A cohort of 30 patients who underwent percutaneous ATR repair was retrospectively analyzed with Achilles Tendon Rupture Scores (ATRS), complications, and additional outcome measures. For a biomechanical analysis portion of the study, 12 cadaveric specimens were paired and randomized to either novel percutaneous repair or open Kessler repair with absorbable suture. These specimens were subjected to 2 phases of cyclical testing (100 cycles 10-43 N followed by 200 cycles 10-86 N) and ultimate strength testing.

Results:

In the clinical portion of the study we report excellent patient reported outcomes (mean ATRS 94.1), high level of return to sport, and high patient satisfaction. One partial re-rupture was reported but with no major wound or neurologic complications. In the biomechanical portion of the study we found no significant difference in tendon gapping between percutaneous and open repairs in phase 1 of testing. In phase 2, increased gapping occurred between percutaneous (17.8 mm [range 10.7-24.1, SD 6.4]) and open repairs (10.8 mm [range 7.6-14.9, SD 2.7, P = .037]). The ultimate load at failure was not statistically different between the 2 repairs.

Conclusions:

A percutaneous ATR repair technique using endoscopic assistance and absorbable suture demonstrated low complications and good outcomes in a cohort of patients, with high satisfaction, and excellent functional outcomes including high rates of return to sport. Cadaveric biomechanical testing demonstrated excellent survival during testing and minimal increase in gapping compared with open repair technique, representing sufficient strength to withstand forces seen in early rehabilitation. A percutaneous Achilles tendon repair technique with absorbable suture may minimize risks associated with operative repair while still maintaining the benefit of operative repair.

Level of Evidence:

Level IV, retrospective case series.

Tensile Strength of Novel Nonabsorbable PTFE (Teflon®) versus Other Suture Materials: An In Vitro Study

Objective

To compare the in vitro tensile strength of sutures used in implant surgery according to the type of thread and the immersion time in artificial saliva.

Methods

For the development of the study, three suture materials were used: polyglactin 910 (PG), black silk (BS), and Teflon (PTFE) 4-0; 150 samples were used, which were divided among each type of suture and then subdivided into five groups of 10 according to the various immersion times (baseline, 3, 7, 14, and 21 days) in artificial saliva. A universal test machine was used to measure the tensile strength at a speed of 25 cm/min, stretch each sample until the material fails, and record the maximum strength in Newtons (N). Finally, the failure point of the samples was evaluated at 10× increase using a stereromicroscope (Leica Biosystems).

Results

When analyzing the tensile strength of the various groups of sutures, it was evidenced that PG maintained its strength, which was lowest at baseline and highest at 21 days. When performing the statistical inference of PG and PTFE, it was found that the force necessary to achieve detachment was not statistically significant (p < 0.05). However, it was shown that the force necessary to achieve rupture in the BS group was statistically significant (p=0.001).

Conclusion

To sum up, when comparing the in vitro tensile strength of PG, BS, and PTFE sutures at baseline and 3, 7, 14, and 21 days, there was no statistically significant difference. This indicates that all sutures used present sufficient performance that remains resistant as time progresses.

The Ruptured Achilles Tendon Elongates for 6 Months After Surgical Repair Regardless of Early or Late Weightbearing in Combination With Ankle Mobilization: A Randomized Clinical Trial

BACKGROUND

Treatment strategies for Achilles tendon rupture vary considerably, and clinical outcome may depend on the magnitude of tendon elongation after surgical repair. The aim of this project was to examine whether tendon elongation, mechanical properties, and functional outcomes during rehabilitation of surgically repaired acute Achilles tendon ruptures were influenced by different rehabilitation regimens during the early postsurgical period.

HYPOTHESIS

Restricted early weightbearing that permits only limited motion about the ankle in the early phase of tendon healing limits tendon elongation and improves functional outcome.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

75 consecutive patients with an acute Achilles tendon rupture were included. They underwent surgical repair, and tantalum beads were placed in the distal and proximal parts of the tendon; thereafter, the patients were randomized into 3 groups. The first group was completely restricted from weightbearing until week 7. The second group was completely restricted from weightbearing until week 7 but performed ankle joint mobilization exercises. The first and second groups were allowed full weightbearing after week 8. The third group was allowed partial weightbearing from day 1 and full weightbearing from week 5. All patients received the same instructions in home exercise guidelines starting from week 9.

RESULTS

The rehabilitation regimen in the initial 8 weeks did not significantly influence any of the measured outcomes including tendon elongation. Achilles tendon elongation and tendon compliance continued for up to 6 months after surgery, and muscle strength, muscle endurance, and patient-reported functional scores did not reach normal values at 12 months.

CONCLUSION

Differences in rehabilitation loading pattern in the initial 8 weeks after the repair of an Achilles tendon rupture did not measurably alter the outcome. The time to recover full function after an Achilles tendon rupture is at least 12 months. Registration: NCT02422004 ( ClinicalTrials.gov identifier).

Assessment of the Resistance of Several Suture Techniques in Human Cadaver Achilles Tendons

Many treatments are available for acute Achilles tendon ruptures, conservative and surgical, with none superior to another. For surgical treatment, one can use various techniques. Recent studies have shown that double stitches are superior to simple sutures. Therefore, in the present study, we sought to determine the suture technique that is the most resistant to rupture. We performed an experimental anatomic study with 27 fresh-frozen human cadaveric Achilles tendons obtained through the body donation program of the University of Barcelona, testing the maximum strength. We simulated a rupture by performing resection in the middle portion of the tendon, 4 cm proximal to the calcaneus insertion. We then evaluated the double Kessler, double Bunnell, Krackow, and percutaneous Ma and Griffith technique. We used absorbable suture (polydioxanone no. 1) with all the techniques. Traction was performed using a machine that pulls the tendon at 10 to 100 N in 1000 repetitive cycles. Statistical analysis was performed using the χ² test and analysis of variance, with the 95% confidence intervals (p < .05). All repairs failed at the site of the suture knots, with none pulling out through the substance of the tendon. We found no significant differences among the different open suture techniques (p > .05). The Krackow suture presented with superior resistance, with a rupture rate 16.70% but with a mean elongation of 7.11 mm. The double Bunnell suture had the same rupture rate as the Krakow suture (16.70%) but with an inferior mean elongation of 4.53 mm. The Krackow and Bunnell suture were superior in endurance, strength of failure, and primary stability compared with the other suture types. However, the former presented with greater tendon elongation, although the difference was not statistically significant. Therefore, according to our findings and the published data, we recommend double Bunnell sutures for the surgical treatment of acute Achilles tendon rupture.

The biomechanical study of rupture of Achilles Tendon and repair by different suture techniques

Objective

To study the biomechanical properties of different suture methods, and to provide evidence for the clinical application of this suture methods in repairing acute Achilles tendon rupture.

Methods

Twenty four fresh frozen cadaver Achilles tendon specimens were collected and randomly divided into three groups (n=8), Group-A Bunnell suture method, Group-B Bosworth suture and Group-C anchor suture respectively. 5 N tensions were applied to tighten the tendon. The actual length of the tendon between the upper and lower clips was measured with a ruler. The length of the long axis and the short axis of the three sections of the tendon was measured by vernier caliper. The cross sectional area of the tendon was calculated according to the elliptical area formula and the mean value was obtained.

Results

There was no significant difference in the length and cross-sectional area of each tendon among three groups (F=0.26, P=0.86; F=0.09, P=0.96). There was no significant difference in the maximum load of tendon and failure displacement in Group A and B (P>0.05). The maximal load of Group-C was significantly larger than that of Group A and B (P<0.05), and there was no significant difference between the failure displacement and Group A and B (P>0.05).

Conclusion

Three suture methods can provide good biomechanical properties, but the anchor suture is more effective in solving the shortcomings of traditional methods. It is a safe and effective method, and is worthy of promotion.

Biomechanical Head-to-Head Comparison of 2 Sutures and the Giftbox Versus Bunnell Techniques for Midsubstance Achilles Tendon Ruptures

Background:

Acute midsubstance Achilles tendon ruptures are a common orthopaedic problem for which the optimal repair technique and suture type remain controversial. Head-to-head comparisons of current fixation constructs are needed to establish which stitch/suture combination is most biomechanically favorable.

Hypothesis:

Of the tested fixation constructs, Giftbox repairs with Fiberwire will exhibit superior stiffness and strength during biomechanical testing.

Study Design:

Controlled laboratory study.

Methods:

Two biomechanical trials were performed, isolating stitch technique and suture type, respectively. In trial 1, 12 transected fresh-frozen cadaveric Achilles tendon pairs were randomized to receive either the Giftbox-modified Krackow or the Bunnell stitch with No. 2 Fiberwire suture. Each repair underwent cyclic loading, oscillating between 10 and 100 N at 2 Hz for 1000 cycles, with repair gapping measured at 500 and 1000 cycles. Load-to-failure testing was then performed, and clinical and catastrophic failure values were recorded. In trial 2, 10 additional paired cadaveric Achilles tendons were randomized to receive a Giftbox repair with either No. 2 Fiberwire or No. 2 Ultrabraid. Testing and data collections protocols in trial 2 replicated those used in trial 1.

Results:

In trial 1, the Bunnell group had 2 failures during cyclic loading while the Giftbox had no failures. The mean tendon gapping after cyclic loading was significantly lower in the Giftbox repairs (0.13 vs 2.29 mm, P = .02). Giftbox repairs were significantly stiffer than Bunnell (47.5 vs 38.7 N/mm, P = .019) and showed more tendon elongation (5.9 ± 0.8 vs 4.5 ± 1.0 mm, P = .012) after 1000 cycles. Mean clinical load to failure was significantly higher for Giftbox repairs (373 vs 285 N, P = .02), while no significant difference in catastrophic load to failure was observed (mean, 379 vs 336 N; P = .61). In trial 2, there were no failures during cyclic loading. The Giftbox + Fiberwire repairs recorded higher clinical load-to-failure values compared with Giftbox + Ultrabraid (mean, 361 vs 239 N; P = .005). No other biomechanical differences were observed in trial 2.

Conclusion:

Simulated early rehabilitation biomechanical testing showed that Giftbox-modified Krackow Achilles repair technique with Fiberwire suture was stronger and more resistant to gap formation at the repair site than combinations that incorporated the Bunnell stitch or Ultrabraid suture.

Clinical Relevance:

A more in-depth understanding of the biomechanical properties of the Giftbox repair will help inform surgical decision making because stronger repairs are less likely to fail during accelerated postoperative rehabilitation.

Treatment Algorithm for Chronic Achilles Tendon LesionsReview of the Literature and Proposal of a New Classification

Chronic Achilles tendon lesions (CATLs) ensue from a neglected acute rupture or a degenerated tendon. Surgical treatment is usually required. The current English literature (PubMed) about CATLs was revised, and particular emphasis was given to articles depicting CATL classification. The available treatment algorithms are based on defect size. We propose the inclusion of other parameters, such as tendon degeneration, etiology, and time from injury to surgery. Partial lesions affecting less than (I stage) or more than (II stage) half of the tendon should be treated conservatively for healthy tendons, within 12 weeks of injury. In II stage complex cases, an end-to-end anastomosis is required. Complete lesions inferior to 2 cm should be addressed by an end-to-end anastomosis, with a tendon transfer in the case of tendon degeneration. Lesions measuring 2 to 5 cm require a turndown flap and a V-Y tendinous flap in the case of a good-quality tendon; degenerated tendons may require a tendon transfer. Lesions larger than 5 cm should be treated using two tendon transfers and V-Y tendinous flaps. A proper algorithm should be introduced to calibrate the surgical procedures. In addition to tendon defect size, tendon degeneration, etiology of the lesion, and time from injury to surgery are crucial factors that should be considered in the surgical planning.

Efficacy of repair techniques of the Achilles tendon: A meta-analysis of human cadaveric biomechanical studies

PURPOSE

Achilles injuries are very common, mainly among young athletes. When indicated, the surgical treatment aims for strong repairs that can resist distraction and consequently ruptures. The majority of the published clinical meta-analyses reported comparisons between broad treatment modalities such as conservative treatment, open, and minimally invasive surgery.

METHODS

A meta-analysis has been conducted to assess further clinical and biomechanical variables on human cadavers related to the efficacy of Achilles repair. A total of 26 studies with 596 legs met the inclusion criteria. The maximal load to failure was set as the primary outcome. Eleven studies were amenable to meta-analysis.

RESULTS

In the reinsertion group, the analysis of the single row vs. double row subgroup showed a significantly higher strength for the latter (1.27, 95% CI=0.748-1.806, I²=81%, P<0.0001). In the mid-tendon repair group, the Achillon vs. Krackow sutures and the Bunnell vs. Krackow sutures subgroups showed no difference while the Bunnell and Krakow sutures were significantly stronger than the Kessler sutures (0.96, 95% CI=0.510-1.405, I²=63.3%, P<0.0001 and 1.37, 95% CI=2.286-0.468, I²=83.4%, P=0.003; respectively).

CONCLUSIONS

The assessment of heterogeneity located variables such as age, suture/material type, number of strands, type of testing machine and software, preloading, ankle position and loading type as potential confounders. The results of this meta-analysis are likely to have a significant impact in clinical practice.

Is the Dresden technique a mechanical design of choice suitable for the repair of middle third Achilles tendon ruptures? A biomechanical study

OBJECTIVE

To compare the mechanical failure of the Dresden technique for Achilles tendon repair with the double modified Kessler technique controlled repair technique. The maximum resistance of the two repair techniques are also compared.

MATERIAL AND METHODS

A total of 30 Achilles tendon ruptures in bovine specimens were repaired with an Ethibond(®) suture to 4.5cm from the calcaneal insertion. Each rupture was randomly distributed into one of two surgical groups. After repair, each specimen was subjected to a maximum traction test. The mechanical failure (tendon, suture, or knot) rates (proportions) were compared using the exact Fisher test (α=.05), and the maximum resistances using the Student t test (α=.05).

RESULTS

There was a difference in the proportions of mechanical failures, with the most frequent being a tendon tear in the Dresden technique, and a rupture of the suture in the Kessler technique.

DISCUSSION

The repair using the Dresden technique performed in the open mode, compared to the Kessler technique, has a more suitable mechanical design for the repair of middle third Achilles tendon ruptures on developing a higher tensile resistance in 58.7%. However, its most common mechanical failure was a tendon tear, which due to inappropriate loads could lead to lengthening of the Achilles tendon.

Bunnell or cross-lock Bunnell suture for tendon repair? Defining the biomechanical role of suture pretension

Background

Suture pretension during tendon repair is supposed to increase the resistance to gap formation. However, its effects on the Bunnell suture technique are unknown. The purpose of this study was to determine the biomechanical effects of suture pretension on the Bunnell and cross-lock Bunnell techniques for tendon repair.

Methods

Eighty porcine hindlimb tendons were randomly assigned to four different tendon repair groups: those repaired with or without suture pretension using either a simple Bunnell or cross-lock Bunnell technique. Pretension was applied as a 10 % shortening of the sutured tendon. After measuring the cross-sectional diameter at the repair site, static and cyclic biomechanical tests were conducted to evaluate the initial and 5-mm gap formation forces, elongation during cyclic loading, maximum tensile strength, and mode of failure. The suture failure mechanism was also separately assessed fluoroscopically in two tendons that were repaired with steel wire.

Results

Suture pretension was accompanied by a 10 to 15 % increase in the tendon diameter at the repair site. Therefore, suture pretension with the Bunnell and cross-lock Bunnell repair techniques noticeably increased the resistance to initial gap formation and 5-mm gap formation. The tension-free cross-lock Bunnell repair demonstrated more resistance to initial and 5-mm gap formation, less elongation, and higher maximum tensile strength than the tension-free Bunnell repair technique. The only difference between the tensioned cross-lock Bunnell and tensioned Bunnell techniques was a larger resistance to 5-mm gap formation with the cross-lock Bunnell technique. Use of the simple instead of cross-lock suture configuration led to failure by suture cut out, as demonstrated fluoroscopically.

Conclusion

Based on these results, suture pretension decreases gapping and elongation after tendon repair, and those effects are stronger when using a cross-lock, rather than a regular Bunnell suture. However, pretension causes an unfavorable increase in the tendon diameter at the repair site, which may adversely affect wound healing.

Treatment of the neglected Achilles tendon rupture

Achilles tendon ruptures are best managed acutely. Neglected Achilles tendon ruptures are debilitating injuries and the increased complexity of the situation must be appreciated. Surgical management is recommended, and only in the poorest surgical candidate is conservative treatment entertained. Numerous treatment algorithms and surgical techniques have been described. A V-Y advancement flap and flexor halluces longus tendon transfer have been found to be reliable and achieve good clinical outcomes for defects ranging from 2 cm to 8 cm. This article focuses on the treatment options for the neglected Achilles tendon rupture.

Initial Achilles tendon repair strength--synthesized biomechanical data from 196 cadaver repairs

PURPOSE

The study aim was to describe what kind of operative technique performs best with respect to initial strength after the surgical repair of acute Achilles tendon ruptures.

METHODS

We performed a systematic search of the keywords "Achilles tendon AND (suture strength OR biomechanics) AND (cadaver NOT animal)" in the online databases PubMed, EMBASE, CINAHL, and the Cochrane Library. We included studies that employed open, mini-open, or percutaneous Achilles tendon repair in human cadavers, and assessed some measure of tensile strength as a primary outcome.

RESULTS

Our search produced 11 relevant papers reporting results for Kessler, Bunnell, and Krackow sutures in open repair, as well as the Achillon device, the Ma-Griffith repair technique, the triple bundle technique and the "giftbox" technique. The weighted tensile strengths ranged from 81 to 453 N (mean 222.7 N) with the Triple Bundle technique in combination with # 2 Ethibond performing best with a mean of 453 N.

CONCLUSIONS

Due to the small sample sizes, different study designs, and heterogeneity of strength measurement techniques, definite recommendations on surgical technique cannot be made but presented information might help in the decision making process for foot and ankle surgeons.

[Ligament ruptures of the lower extremity in the elderly]

There is an increasing incidence of ligament ruptures of the lower extremities in older patients. This higher incidence is caused by the typical current demographic changes in the population and the higher level of activity and athletic motivation of the older people in our society. In this review we address the most important ligament ruptures of the lower extremity in the old patient. Quadriceps tendon and Achilles tendon ruptures are mostly the result of degenerative and abrasion changes. The ACL rupture on the other hand occurs spontaneously after adequate trauma and without former degenerative changes especially in highly active patients. For a differentiated treatment of the older patient with tendon ruptures, secondary diseases, an increased risk and complication profile and a potentially decreased compliance during rehabilitation must be taken into consideration before indicating operative or conservative therapy. There are no strict age-related limitations for indication of an operative treatment of tendon ruptures in the older patient. In this patient group a differentiated treatment decision is recommended.

Loop security and tensile properties of polyblend and traditional suture materials

Tensile and knot properties of new generation (polyblend) and traditional suture materials in orthopedic surgery were investigated in standard laboratory conditions. Study focused on Fiberwire No. 5 and 2, Ethibond No. 5, 2 and 00, Orthocord No. 2, MaxBraid No. 2, Prolene No. 0 and 00, PDS No. 0 and 00, and Vicryl No. 2, 0 and 00. A 27-cm suture loop was fastened with 10 knots for ten samples for each type. Test parameters were tensile load to failure, elongation at failure point and knot slippage, and volume of 10-fold knots. Results were compared using ANOVA test. Failure load of No. 5 Fiberwire (625.0 ± 30.0 N) was significantly higher compared to all other suture types. Tensile strengths of MaxBraid No. 2 (287 ± 11 N) was significantly stronger compared to two other No. 2 polyblend sutures types and Ethibond No. 5. Knot slippage of Fiberwire No. 5 (14 ± 1.9 mm) was significantly higher compared to all other suture types. Ethibond No. 2 (0.1 ± 0.3 mm) had the lowest knot slippage. Elongation at the failure point of Fiberwire No. 2 (5%) was significantly lower than all other suture types. Mean calculated knot volume of #5 Fiberwire (73 ± 6.9 mm(3)) was significantly higher compared to #5 Ethibond (53 ± 4.8 mm(3)). Results of the study proved presence of significant differences between tensile and knot properties of various suture types and sizes. Loop security of larger diameter sutures is not always higher than thinner sutures. Suture elongation and knot slippage are important failure modes for high-diameter sutures and short-suture loops.

Over-the-top knot placement technique enhances tensile stability of tendon repairs

BACKGROUND

Currently a major concern for the surgical treatment of Achilles tendon rupture repairs is the creation of stable enough fixation to allow early range of motion. It was documented that the weakest point in a suture loop is the knot. Thus, we hypothesized that moving the knot away from the repair junction (over-the-top Krackow technique) would increase the strength of the repair.

MATERIALS AND METHODS

Transected bovine tendons were repaired by the traditional Krackow and over-the-top Krackow techniques using four suture materials (Fiberwire Nos. 5 and 2, Ethibond Nos. 5 and 2). Tendons were cyclically tested at incremental loads beginning from 50 N until 5-mm gap formation. Then all tendons were loaded to failure. The number of cycles to 5-mm gapping, ultimate failure loads and knot slip were compared using t-test and Mann-Whitney tests (with Tukey corrections for multiple comparisons).

RESULTS

Mean number of cycles to 5-mm gapping did not reveal significant differences (p = 0.113) between repair groups. Mean failure load of tendons repaired by over-the-top Krackow technique were significantly higher (p < 0.0001) for all four paired groups than tendons repaired by traditional Krackow technique. Ethibond No. 5, No. 2, and Fiberwire No. 2 suture repairs with over-the-top configuration did not reveal any knot slip.

CONCLUSION

Over-the-top Krackow technique increases the ultimate failure load of repaired tendons. But 5-mm gapping resistivity was not enhanced either by the technique or the suture material.

CLINICAL RELEVANCE

The knot itself is a stress-riser in the suture loop so we suggest that freeing it from tension by our modificiation may achieve more durable repairs.

The strength of achilles tendon repair: a comparison of three suture techniques in human cadaver tendons

BACKGROUND

A previous study suggests the double Krackow suture (locking-loop) weave technique is nearly twice as strong as the single Bunnell or single Kessler suture repair techniques. Our hypothesis was that the strength of different repair techniques would be comparable if a similar number of suture strands cross the repair site.

MATERIALS AND METHODS

Twenty-four fresh-frozen human cadaver Achilles tendons were used to test maximum strength of three suture techniques (double Bunnell, double Kessler, and double Krackow). The simulated ruptures were created in the midsubstance of the Achilles tendon, five centimeters proximal to its calcaneal insertion. All repairs were performed with No. 2 polyester (Mersilene, Ethicon, Sommerville, NJ) nonabsorbable suture in standard fashion for each technique, with four strands crossing the repair site. The tendons were then anchored to a materials testing machine (Instron, Canton, MA) through a calcaneal pin distally and a modified soft tissue clamp proximally. Tendons were loaded with continuous tension at a head speed of 0.85 cm/s.

RESULTS

All repairs failed at the site of the suture knots, none pulling out through the substance of the tendon. A one-way analysis of variance was performed on the maximum force at failure of each repair technique. No statistically significant difference was noted between the double Krackow weave (199.9 +/- 20 N), the double Bunnell weave (196.2 +/- 45 N), and the double Kessler weave (166.9 +/- 51 N).

CONCLUSION

We found that in a laboratory model of cadaveric Achilles tendon repairs there was no significant difference in strength between the Krackow, Bunnell, and Kessler suture techniques, when each was performed with a double suture weave.

CLINICAL RELEVANCE

This is a cadaveric study that attempts to simulate the clinical parameters of Achilles tendon ruptures, repairs, and repair failures to examine the strength of different repair techniques.

The ruptured Achilles tendon: operative and non-operative treatment options

The Achilles tendon is the strongest and thickest tendon in the human body. Like any other tendon in the body, however, it is susceptible to rupture. Many surgeons advocate early operative repair of the ruptured Achilles tendon, citing decreased re-rupture rates and improved functional outcome. Waiting for surgical repair for longer than one month may lead to inferior functional results postoperatively. Non-operative treatment has higher re-rupture rates as compared to surgically repaired tendons, but may be the treatment of choice in some patients. While for many years, patients were rigidly immobilized in a non-weightbearing cast for 6-8 weeks postoperatively, newer studies have shown excellent results with early weightbearing, and this is quickly becoming the standard of care amongst many physicians.

Achilles tendon repair: Achillon system vs. Krackow suture: an anatomic in vitro biomechanical study

BACKGROUND

Limited open repairs of acutely ruptured Achilles tendon, using the Achillon device, are becoming a frequently used method of treatment. To date there are no biomechanical studies comparing the strength of the Achillon repair to the Krackow repair. This study provides a direct comparison of the strength of these two repair techniques.

METHODS

Using 10 paired cadaveric Achilles tendon specimens; repairs were performed using a Krackow technique on one specimen and a repair with the Achillon Suture System on the contralateral specimen. All repairs were made with identical suture material. Specimens were tested for ultimate strength using a servo-hydraulic testing device.

FINDINGS

The mean load to failure of the control group (Krackow suture) was 276N (standard deviation 87.0), and for the experimental group (Achillon suture) was 342N (standard deviation 92.8). Using a Wilcoxon test this result was found to be statically significant (P=0.03).

INTERPRETATION

The current study has demonstrated that the Achillon repair is stronger in a cadaveric biomechanical study than the Krackow repair using identical sutures. This provides biomechanical evidence to support the continued use of the limited open repair as opposed to the traditional open repair.