Effect of knee flexion angle on Achilles tendon force and ankle joint plantarflexion moment during passive dorsiflexion

Progression of partial to complete ruptures of the Achilles tendon during rehabilitation: A study using a finite element model

Substantial research on complete Achilles tendon ruptures is available, but guidance on partial ruptures is comparatively sparse. Conservative management is considered acceptable in partial tendon ruptures affecting less than 50% of the tendon's width, but supporting experimental evidence is currently lacking. Using a previously validated finite element model of the Achilles tendon, this study aimed to assess whether loading conditions simulating an early functional rehabilitation protocol could elicit progression to a complete rupture in partial ruptures of varying severity. In silico tendon rupture simulations were performed to locate the most likely rupture site for least, moderate, and extreme subtendon twist configurations. These three models were split at the corresponding rupture site and two sets of partial ruptures were created for each, starting from the medial and lateral sides, and ranging from 10% to 50% loss of continuity. Simulations were conducted with material parameters from healthy and tendinopathic tendons. Partial ruptures were considered to progress if the volume of elements showing a maximum principal strain above 10% exceeded 3 mm3 . To assess whether the tendinopathic tendons typical geometric characteristics could compensate for the inferior material properties found in tendinopathy, an additional model with increased cross-sectional area in the free tendon region was developed. Progression to complete ruptures occurred even with less than a 50% loss of continuity, regardless of subtendon twisting, and material parameters. The tendinopathic tendon model with increased cross-sectional area showed similar results. These findings suggest the current criteria for surgical treatment of partial ruptures should be reconsidered. Statement of clinical significance: The clinical significance and most appropriate treatment of partial ruptures of the Achilles tendon is unclear. Despite the widespread use of the "50% rule" in treatment decisions of partial tendon ruptures, experimental evidence supporting it is missing. The present study provides new data, from a validated aponeurotic and free Achilles tendon finite element model, showing that partial ruptures may progress to complete ruptures under loading conditions elicited from functional rehabilitation protocols, even for partial ruptures affecting less than 50% of the tendon's width. Under these novel findings, the current criteria for surgical treatment of partial ruptures should be reconsidered.

A comparative biomechanical study of the krackow suture technique with three common percutaneous suture techniques in the treatment of Achilles tendon ruptures

BACKGROUND

The aim of this study was to compare the biomechanical resistance under tensile forces of the Krackow suture technique with the frequently used Dresden, Carmont & Maffulli, and Ma & Griffiths percutaneous repair techniques in bovine models of Achilles tendon rupture.

METHODS

Transverse Achilles tendon rupture models were created from 4 cm proximal of the calcaneal insertion point in a total of 20 bovine Achilles tendon specimens. These were randomly allocated to 4 groups and repaired with configurations appropriate to the Dresden, Carmont & Maffulli, Ma & Griffiths and Krackow techniques. Failure mechanisms were recorded with force values (as Newton units) creating a 5 mm gap and load to failure under tensile loading at a rate of 10 mm/sec in a static testing device.

RESULTS

In the Dresden technique group, the force required for a 5 mm gap was mean 41.21 ± 13.19 N and for load to failure, mean 193.83 ± 30.16 N, which were evaluated as statistically significantly higher than in the other techniques (p < 0.05). The lowest values were determined in the Ma & Griffiths technique group (5 mm gap: 11.06 ± 8.12 N, load to failure: 97.73 ± 29.60 N) but these were not significantly lower than the values in the Krackow and Carmont & Maffulli technique groups (p > 0.05).

CONCLUSION

The results of this study showed that the Dresden technique was biomechanically superior against tensile forces compared to the Krackow technique, and the other frequently used percutaneous techniques of Carmont & Maffulli and Ma & Griffiths.

Differential elongation of the gastrocnemius after Achilles tendon rupture: a novel technique of selective shortening to treat push-off weakness with case series and literature review

PURPOSE

Differential elongation of the gastrocnemius after Achilles tendon rupture (ATR) may compromise the ability of athletes to return to competition. Recognition of this differential elongation of the gastrocnemius relative to the soleus is vital to treat patients with weakness in push-off. This paper describes a novel technique performed for selective shortening of the gastrocnemius to treat push-off weakness.

METHODS

Three patients with differential proximal retraction of the gastrocnemius greater than 20 mm after treatment for ATR with inability to run and jump underwent surgical correction with this novel technique and were followed-up for 2 years. A novel selective shortening of the gastrocnemius with autologous hamstring graft was performed in these patients. The Achilles Tendon Total Rupture Score (ATRS) and American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score were recorded preoperatively and at the final follow-up.

RESULTS

All three patients were able to return to running and jumping at final follow-up. The ATRS improved significantly in the strength, fatigue, running and jumping domains but there appeared to be a less notable improvement in activities of daily living domain. The AOFAS score showed improvement with the greatest margin in the domain of activity limitation.

CONCLUSION

This procedure is the first described selective shortening method of the gastrocnemius tendons after differential elongation following ATR. It is a safe and reliable technique providing improved ATRS and AOFAS scores in three patients who were all able to return to running and jumping sports at 2-year follow-up.

LEVEL OF EVIDENCE

IV.

Case study: The influence of Achilles tendon rupture on knee joint stress during counter-movement jump - Combining musculoskeletal modeling and finite element analysis

BACKGROUND

Presently, the current research concerning Achilles tendon rupture repair (ATR) is predominantly centered on the ankle joint, with a paucity of evidence regarding its impact on the knee joint. ATR has the potential to significantly impede athletic performance and increase tibiofemoral contact forces in athletes. The purpose of this study was to prognosticate the distribution of stress within the knee joint during a countermovement jump through the use of a simulation method that amalgamated a musculoskeletal model of a patient who underwent Achilles tendon rupture repair with a finite element model of the knee joint.

METHODS

A male elite badminton player who had suffered an acute Achilles tendon rupture in his right leg one year prior was selected as our study subject. In order to analyze his biomechanical data, we employed both the OpenSim musculoskeletal model and finite element model to compute various parameters such as joint angles, joint moments, joint contact forces, and the distribution of knee joint stress.

RESULTS

During the jumping phase, a significantly lower knee extension angle (p < 0.001), ankle dorsiflexion angle (p = 0.002), peak vertical ground reaction force (p < 0.001), and peak tibiofemoral contact force (p = 0.009) were observed on the injured side than on the uninjured side. During the landing phase, the ankle range of motion (ROM) was significantly lower on the injured side than on the uninjured side (p = 0.009), and higher peak vertical ground reaction forces were observed (p = 0.012). Additionally, it is logical that an injured person will put higher load on the uninjured limb, but the finite element analysis indicated that the stresses on the injured side of medial meniscus and medial cartilage were significantly greater than the uninjured side.

CONCLUSIONS

An Achilles tendon rupture can limit ankle range of motion and lead to greater joint stress on the affected area during countermovement jumps, especially during the landing phase. This increased joint stress may also transfer more stress to the soft tissues of the medial knee, thereby increasing the risk of knee injury. It is worth noting that this study only involves the average knee flexion angle and load after ATR in one athlete. Caution should be exercised when applying the conclusions, and in the future, more participants should be recruited to establish personalized knee finite element models to validate the results.

Republication of "A Biomechanical Comparison of Limited Open Versus Krackow Repair for Achilles Tendon Rupture"

Background

Soft tissue complications after Achilles tendon repair has led to increased interest in less invasive techniques. Various limited open techniques have gained popularity as an alternative to open operative repair. The purpose of this study was to biomechanically compare an open Krackow and limited open repair for Achilles tendon rupture. We hypothesized that there would be no statistical difference in load to failure, work to failure, and initial linear stiffness.

Methods

A simulated Achilles tendon rupture was created 4 cm proximal to its insertion in 18 fresh-frozen cadaveric below-knee lower limbs. Specimens were randomized to open or limited open PARS Achilles Jig System repair. Repairs were loaded to failure at a rate of 25.4 mm/s to reflect loading during normal ankle range of motion. Load to failure, work to failure, and initial linear stiffness were compared between the 2 repair types.

Results

The average load to failure (353.8 ± 88.8 N vs 313.3 ± 99.9 N; P = .38) and work to failure (6.4 ± 2.3 J vs 6.3 ± 3.5 J; P = .904) were not statistically different for Krackow and PARS repair, respectively. Mean initial linear stiffness of the Krackow repair (17.8 ± 5.4 N/mm) was significantly greater than PARS repair (11.8 ± 2.5 N/mm) (P = .011).

Conclusion

No significant difference in repair strength was seen, but higher initial linear stiffness for Krackow repair suggests superior resistance to gap formation, which may occur during postoperative rehabilitation. With equal repair strength, but less soft tissue devitalization, the PARS may be a favorable option for patients with risk factors for soft tissue complications.

Jigless Knotless Internal Brace Versus Other Minimal Invasive Achilles Tendon Repair Techniques in Biomechanical Testing Simulating the Progressive Rehabilitation Protocol

The jigless knotless internal brace surgery (JKIB), an alternative method for minimal invasive surgery (MIS) repair of acute Achilles tendon rupture, has advantages of preventing sural-nerve injury in MIS and superficial wound infection in open surgery, as previous clinical research demonstrates. However, no comparative study on the biomechanical performance between JKIB and other MIS techniques has been reported until now. In this study, 50 fresh porcine Achilles tendons were used to compare the JKIB with open surgery (two-stranded Krachow suture) with other MIS techniques, including Percutaneus Achilles Repair System (PARS), Speedbridge (SB), and Achillon Achilles Tendon Suture System (ACH), using a biomechanical testing with cyclic loading at 1 Hz. This test was used to simulate a progressive rehabilitation protocol where 20 to 100 N was applied in the first 250 cycles, followed by 20 to 190 N in the second 250 cycles, and then 20 to 369 N in the third 250 cycles. The cyclic displacement after 10, 100 and 250 cycles were recorded. The survived cycles were defined as a sudden drop in measured load. In survived cycles, the JKIB group (552.3 ± 72.8) had significantly higher cycles than the open, PARS, and ACH groups (204.3 ± 33.3, 395.9 ± 96.0, and 397.1 ± 80.9, respectively, p < .01) as analyzed by post hoc analysis, but no significant difference as compared with the SB group (641.6 ± 48.7). In cyclic displacement after 250 cyclic loadings, the JKIB group (11.29 ± 1.29) showed no significant difference as compared with PARS, SB, and ACH groups (12.21 ± 1.18, 9.80 ± 0.80, and 11.57 ± 1.10 mm, respectively) and significant less displacement than the open group (14.50 ± 1.85, p < .01). These findings suggest that JKIB could be an option for acute Achilles tendon repair in the MIS fashion due to no larger cyclic elongation compared with other MIS techniques.

Biomechanical Comparison of Knotless Suture Anchor Versus Percutaneous End-to-End Technique for Mid-Substance Achilles Tendon Rupture Repair

Percutaneous Achilles tendon repairs can be performed with 2 distal fixation techniques: knotless suture anchor repair (KL) or percutaneous end-to-end repair (ETE). There is a paucity of literature comparing the biomechanical strength of these 2 distal fixation techniques. The aim of this study was to compare the strength of KL and ETE repairs using flat-braided suture for mid-substance Achilles tendon rupture during simulated progressive rehabilitation. Nine matched pairs of fresh-frozen below-knee cadaveric extremities were randomly assigned into these 2 repair groups. Each specimen was tested in 2 parts sequentially; Part I simulating passive ankle range of motion (cyclic: 20N-100N), and Part II simulating ambulation in a walking boot (cyclic: 20N-190N). The number of cycles, gap displacement, and the mode of failure were recorded for each repair. Achilles tendon repairs using the percutaneous methods of ETE and KL techniques showed no significant difference in the number of cycles to clinical failure, mean gap displacement, or overall failure rate. During Part I, the survival rate in terms of clinical failure for KL and ETE groups was 8 of 9 repairs and 7 of 9 repairs, respectively. During Part II, all repairs experienced clinical failure in both groups. Five repairs in the KL group experienced suture anchor pull out from the calcaneus, and 3 repairs failed at suture-tendon interface. Four repairs in the ETE group failed due to knot slippage and 5 repairs failed at suture-tendon interface. Both techniques are viable options in treating acute mid-substance Achilles tendon ruptures.

Foundational Principles and Adaptation of the Healthy and Pathological Achilles Tendon in Response to Resistance Exercise: A Narrative Review and Clinical Implications

Therapeutic exercise is widely considered a first line fundamental treatment option for managing tendinopathies. As the Achilles tendon is critical for locomotion, chronic Achilles tendinopathy can have a substantial impact on an individual's ability to work and on their participation in physical activity or sport and overall quality of life. The recalcitrant nature of Achilles tendinopathy coupled with substantial variation in clinician-prescribed therapeutic exercises may contribute to suboptimal outcomes. Further, loading the Achilles tendon with sufficiently high loads to elicit positive tendon adaptation (and therefore promote symptom alleviation) is challenging, and few works have explored tissue loading optimization for individuals with tendinopathy. The mechanism of therapeutic benefit that exercise therapy exerts on Achilles tendinopathy is also a subject of ongoing debate. Resultingly, many factors that may contribute to an optimal therapeutic exercise protocol for Achilles tendinopathy are not well described. The aim of this narrative review is to explore the principles of tendon remodeling under resistance-based exercise in both healthy and pathologic tissues, and to review the biomechanical principles of Achilles tendon loading mechanics which may impact an optimized therapeutic exercise prescription for Achilles tendinopathy.

Comparison of Biomechanical Failure Loads Between Tape-Type and Conventional Sutures in Internal Knotless Anchor–Based Constructs

Background:

Despite the increasing prevalence of tape-type sutures, whether internal knotless anchors can consistently affix tape-type sutures has not been thoroughly investigated.

Purpose:

To evaluate whether substituting tape-type sutures for conventional sutures influences the suture-holding strength of internal knotless anchors.

Study Design:

Controlled laboratory study. Level of evidence, 5.

Methods:

A total of 3 internal knotless anchors were tested: a spiral core clamping anchor (Footprint Ultra PK), a winged clamping anchor (PopLok), and a spooling anchor (ReelX STT). Four constructs were compared for each type of anchor, with the anchor double or quadruple loaded with tape-type sutures or conventional sutures. The testing protocol comprised preloading suture tension to 10 N; cyclic loading, in which tension increased in increments of 10 N from 10 to 90 N; and a load-to-failure stage set at a speed of 0.5 mm/s. The clinical failure load (CFL) was defined as suture slippage of ≥3 mm. Also, 1-way analysis of variance and power analysis were used to compare the CFLs of the constructs.

Results:

For the quadruple-loaded spiral core clamping anchors, a significant reduction in CFLs was seen with conventional sutures over tape-type sutures (138.10 ± 4.73 vs 80.00 ± 12.25 N, respectively; P < .001). This reduction was not observed under the double-loaded condition (conventional vs tape type: 76.00 ± 5.48 vs 80.00 ± 10.00 N, respectively). Substitution of the suture materials did not significantly reduce the CFLs for the winged clamping anchors (conventional vs tape type: 40.00 ± 10.00 vs 30.00 ± 7.07 N for double loaded, respectively, and 64.00 ± 13.41 vs 50.00 ± 10.00 N for quadruple loaded, respectively) or the spooling anchors (conventional vs tape type: 62.00 ± 19.23 vs 56.32 ± 20.20N for double loaded, respectively, and 72.00 ± 21.68 vs 84.00 ± 13.42 N for quadruple loaded, respectively).

Conclusion:

Substituting tape-type sutures for conventional sutures increased the CFLs of some internal knotless anchors. With specific suture-anchor combinations, quadruple-loaded conventional suture anchors had CFLs higher than those of double-loaded conventional suture anchors.

Clinical Relevance:

When multiple tape-type sutures are used in conjunction with a clamping anchor, clinicians should note a possible reduction in CFLs and resultant early suture slippage.

Biomechanical comparisons of three minimally invasive Achilles tendon percutaneous repair suture techniques

BACKGROUND

While no gold standard exists for the management of Achilles tendon ruptures, surgical repair is common in healthy and active patients. Minimally invasive repair methods have become increasingly popular, while biomechanical equivalency hasn't been proven yet.

METHODS

A mid-substance Achilles tendon rupture was created 6 cm proximal to the calcaneal insertion in 27 fresh-frozen cadaveric ankles. Specimens were randomly allocated to 1 of 3 repair techniques: Huttunen et al. (2014) (1) PARS Achilles Jig System, Nyyssönen et al. (2008) (2) Achilles Midsubstance SpeedBridge™, Schipper and Cohen (2017) (3) Dresdner Instrument and subsequently subjected to cyclic loading with 250 cycles each at 1 Hz with 4 different loading ranges (20-100 N, 20-200 N, 20-300 N, and 20-400 N).

FINDINGS

After 250 cycles no significant differences in elongation were observed between PARS and Dresdner Instrument(p = 1.0). Furthermore, SpeedBridge™ repairs elongated less than either Dresdner Instrument (p = 0.0006) or PARS (p = 0.102). Main elongation (85%) occurred within the first 10 cycles with a comparable elongation in between 10 and 100 and 100-250 cycles. While all repairs withstood the first 250 cycles of cyclic loading from 20 to 100 N, only the PARS (468 ± 175) and Midsubstance SpeedBridge™ (538 ± 208) survived more cycles. Within all 3 groups suture cut out was seen to be the most common failure mechanism.

INTERPRETATION

Within all groups early repair elongation was seen. While this was least obvious within the SpeedBridge™ technique, ultimate strengths of repairs (cycles to failure) were comparable across PARS and SpeedBridge™ with a decline in the Dresdner Instrument group.

Biomechanical Evaluation of Achilles Tendon Midsubstance Repair: The Effects of Anchor Angle and Position

BACKGROUND

The percutaneous knotless repair technique for Achilles tendon ruptures utilizes a Percutaneous Achilles Repair System (PARS) device for suturing the proximal tendon and 2 suture anchors for fixing the sutures into the calcaneus. Determining the best position of the suture anchors may optimize the strength of this repair.

METHODS

Twelve pairs of human ankle cadaveric specimens were randomly assigned to receive suture anchors placed at 45°, 90°, or 135° from the sagittal plane. The anchors were tensioned according to a protocol representing progressive, postoperative rehabilitation. Load, number of loading cycles, displacement, and mode of failure were recorded.

RESULTS

With the anchors placed at 45°, 90°, and 135°, the ultimate failure loads were mean 265 ± 64 N, 264 ± 75 N, and 279 ± 40 N, and the total number of loading cycles were mean 459 ± 166, 466 ± 158, and 469 ± 110, respectively. The effect of anchor angle on failure load, number of loading cycles, and displacement was not statistically significant. Visually, the anchors at 45° and 90° demonstrated sutures cutting through the bone.

CONCLUSION

We found no statistically significant difference in pullout strength between the 3 different anchor angles. Sutures cutting through the bone may be a concern with acute anchor angles. This suggests that a 135° anchor angle may result in a lower risk of tendon elongation with the percutaneous knotless repair technique.

LEVELS OF EVIDENCE

Cadaveric laboratory study.

An Identical Twin Study on Human Achilles Tendon Adaptation: Regular Recreational Exercise at Comparatively Low Intensities Can Increase Tendon Stiffness

Achilles tendon adaptation is a key aspect of exercise performance and injury risk prevention. However, much debate exists about the adaptation of the Achilles tendon in response to exercise activities. Most published research is currently limited to elite athletes and selected exercise activities. Also, existing studies on tendon adaptation do not control for genetic variation. Our explorative cross-sectional study investigated the effects of regular recreational exercise activities on Achilles tendon mechanical properties in 40 identical twin pairs. Using a handheld oscillation device to determine Achilles tendon mechanical properties, we found that the Achilles tendon appears to adapt to regular recreational exercise at comparatively low intensities by increasing its stiffness. Active twins showed a 28% greater Achilles tendon stiffness than their inactive twin (p < 0.05). Further, our research extends existing ideas on sport-specific adaptation by showing that tendon stiffness seemed to respond more to exercise activities that included an aerial phase such as running and jumping. Interestingly, the comparison of twin pairs revealed a high variation of Achilles tendon stiffness (305.4–889.8 N/m), and tendon adaptation was only revealed when we controlled for genetic variance. Those results offer new insights into the impact of genetic variation on individual Achilles tendon stiffness, which should be addressed more closely in future studies.

Jigless knotless internal brace versus other open Achilles tendon repairs using a progressive rehabilitation protocol: a biomechanical study

BACKGROUND

The jigless knotless internal brace surgery (JKIB), a modified minimal invasive surgery (MIS) for acute Achilles tendon injury, has advantages of preventing sural-nerve injury in MIS and superficial wound infection in open surgery, as demonstrated in previous clinical research. However, to date, biomechanical testing has not yet been validated.

MATERIALS AND METHODS

Sixty fresh porcine Achilles tendons were used to compare the JKIB with other open surgery techniques, the four-stranded Krackow suture (4sK) and the triple-bundle suture (TBS) in biomechanical testing with cyclic loading set at 1 Hz. This approach simulated a progressive rehabilitation protocol where 20-100 N was applied in the first 1000 cycles, followed by 20-190 N in the second 1000 cycles, and then 20-369 N in the third 1000 cycles. The cycles leading to repair gaps of 2 mm, 5 mm, and 10 mm were recorded. The survival cycles were defined as repair gap of 10 mm.

RESULTS

With respect to survival cycles, a significant difference was found among the three groups, in which the TBS was the most robust, followed by the JKIB and the 4sK, where the mean survived cycles were 2639.3 +/- 263.55, 2073.6 +/- 319.92, and 1425.25 +/- 268.96, respectively. Significant differences were verified via a post hoc analysis with the Mann-Whitney U test after the Bonferroni correction (p < 0.017).

CONCLUSIONS

The TBS was the strongest suture structure in acute Achilles tendon repair. However, the JKIB could be an option in acute Achilles tendon repair with the MIS technique due to it being more robust than the 4sK, which has been typically favored for use in open repair.

Joint Angle, Range of Motion, Force, and Moment Assessment: Responses of the Lower Limb to Ankle Plantarflexion and Dorsiflexion

There is limited research on the biomechanical assessment of the lower limb joints in relation to dynamic movements that occur at the hip, knee, and ankle joints when performing dorsiflexion (DF) and plantarflexion (PF) among males and females. This study investigated the differences in joint angles (including range of motion (ROM)) and forces (including moments) between the left and right limbs at the ankle, knee, and hip joints during dynamic DF and PF movements in both males and females. Using a general linear model employing multivariate analysis in relation to the joint angle, ROM, force, and moment datasets, the results revealed significant main effects for gender, sidedness, phases, and foot position with respect to joint angles. Weak correlations were observed between measured biomechanical variables. These results provide insightful information for clinicians and biomechanists that relate to lower limb exercise interventions and modelling efficacy standpoints.

Loss of the knee-ankle coupling and unrecognized elongation in Achilles tendon rupture: effects of differential elongation of the gastrocnemius tendon

PURPOSE

The biarticular anatomy of the gastrocnemii is an important mechanism of knee-ankle coupling and differential elongation may affect this function leading to weakness of the push-off phase during the gait. Achilles tendon ruptures may cause detachment of the gastrocnemius tendon from the soleus aponeurosis with subsequent differential elongation of the individual subtendons. This study investigated the effects of such detachment by investigating tendon fusion levels of the two muscle groups, and the effect of sequential differential elongation of the gastrocnemius on the Achilles tendon resting angle (ATRA) and to the knee-ankle coupling.

METHODS

Conjoined tendon length (CTL) was measured in 23 cadavers. ATRA in knee extension (ATRA 0) and 90-degree knee flexion (ATRA 90) was measured with the gastrocnemius tendons (GT) intact, transected and with the gap reduced in 5-mm increments. In 15 specimens, knee-ankle coupling was examined.

RESULTS

Considerable anatomical variation was present with CTL ranging from 2 to 40% of fibular length. In the intact triceps, surae ATRA 0 differed from ATRA 90 by 6 degrees (p < 0.001). Cutting the gastrocnemius caused an immediate separation of the tendon ends by 19 mm. ATRA 0 and ATRA 90 increased 8 and 4 degrees (p < 0.001), significantly larger increase for ATRA 0 (p < 0.001). Lengthening the gastrocnemius 10 mm altered the coupling point 10 degrees towards dorsiflexion. Transfixing the gastrocnemius at the level of the gap where the Achilles was sectioned, decoupled the knee-ankle coupling in all but two specimens. A moderate correlation between CTL and length of the medial gastrocnemius tendon was found.

CONCLUSIONS

A greater relative ATRA 0 than relative ATRA 90 indicates differential elongation of the gastrocnemius. By elongating the gastrocnemius the knee-ankle coupling point shifts dorsally, and 20 mm elongation completely decouples the knee-ankle coupling. Independent lengthening of the gastrocnemius may explain the loss of power experienced by some patients following acute Achilles tendon rupture despite what would appear to be appropriate approximation of the ruptured tendon ends. Recognizing this occurrence is crucial when treating Achilles tendon ruptures and such patients require surgical correction in order to avoid long-term weakness of push-off strength.

The Ankle Joint Range of Motion and Its Effect on Squat Jump Performance with and without Arm Swing in Adolescent Female Volleyball Players

A flexible ankle joint is suggested to be a contributing factor for vertical squat jump (SQJ) performance. The purpose of the study was to investigate the effect of the active (ACT) and passive (PAS) ankle joint range of motion (ROM) on SQJ performed by adolescent female volleyball players. ACT and PAS ankle ROM at knee extension angles of 90, 140, and 180 degrees (180 degrees: full extension) were measured with a video analysis method for 35 female post-pubertal volleyball players (16.3 ± 1.1 yrs, 1.80 ± 0.04 m, 68.8 ± 6.8 kg). Additionally, the players fulfilling previously recommended criteria were assigned to the flexible (n = 10) and inflexible (n = 8) groups and executed SQJ with and without an arm swing on a force-plate. Results of the 2 × 2 × 3 MANOVA revealed a significant (p < 0.05) flexibility type and knee angle effect, as ankle ROM was larger in PAS compared to ACT and as the knee joint progressed from 90 to 180 degrees extension. The 2 × 2 ANOVA revealed a significant (p < 0.05) group effect, as flexible players jumped higher in the arm swing SQJ, along with a significant arm swing effect on key SQJ kinetic parameters. In conclusion, a more flexible ankle joint result in improved SQJ performance. Therefore, ankle flexibility training should be implemented in youth volleyball players.

Phantom material testing indicates that the mechanical properties, geometrical dimensions, and tensional state of tendons affect oscillation-based measurements

OBJECTIVE

There is an increasing interest in the application of oscillation-based measurement techniques to evaluate the mechanical stiffness of healthy and diseased tendons. These techniques measure the stiffness of a tendon indirectly by registering the oscillation response of a tendon to an external mechanical impulse. Although these measurement techniques seem to be comparatively easy and time-saving, their applicability is implicitly limited by their indirect measurement principle.

APPROACH

In this study, we aim to find evidence that the oscillation response of a tendon to an external mechanical impulse is not only affected by the stiffness of a tendon but also by the tendons' cross-sectional area (CSA), length, and tension. Therefore, we reviewed the current literature on oscillation-based techniques that measure in vivo tendon properties. Further, a phantom material was used to mimic the nature of tendons and to test the impact of four factors on oscillation-based measurements.

MAIN RESULTS

Our results indicate that the mechanical properties, geometrical dimensions (length and CSA), and tensional state affect oscillation-based measures. Surprisingly, most studies on tendon behavior often exclusively associate their oscillation-based measurements with the mechanical stiffness of a tendon.

SIGNIFICANCE

While this narrow perspective bears the risk of misinterpretation or false implications, a broader understanding of oscillation-based measurements has the potential to shed new light on the interaction of muscles and tendons in vivo.

Accessibility to Talar Dome in Neutral Position, Dorsiflexion, or Noninvasive Distraction in Posterior Ankle Arthroscopy

BACKGROUND

Osteochondral lesions of the talus are frequent pathologies of the ankle joint. Especially through arthroscopy, the treatment is kept as minimally invasive as possible. However, there are some drawbacks as to the reachability because of the high congruency of the ankle joint. Here, either noninvasive distraction or maximal dorsiflexion may be an option for better access to the lesion. The purpose of this study was to evaluate maximal dorsiflexion compared to neutral position or noninvasive distraction of the ankle joint in the arthroscopic reachability of the talar dome. The hypothesis of this study was that maximal dorsiflexion would allow for greater accessibility of the talar dome compared to neutral position or noninvasive distraction of the joint.

METHODS

Twenty matched pairs (n=40) of anatomical ankle specimens were used. The effects of neutral position, maximal dorsiflexion, and noninvasive distraction of the ankle joint on arthroscopic accessibility of the ankle joint were tested. After disarticulation of the talus, reach was measured and compared between the 3 positions.

RESULTS

In neutral position, 13.7±1.2 mm of the talar dome was reached laterally and 14.0±1.0 mm medially. In maximal dorsiflexion, the distance was 19.0±1.1mm laterally and 19.8±1.4 mm medially, and in noninvasive distraction it was 16.1±1.5 mm laterally and 15.7±1.0 mm medially. The statistical comparison showed a significantly better reach in dorsiflexion laterally (P = .003) and medially (P = .026).

CONCLUSION

Accessibility of the talar dome in maximal dorsiflexion was superior to that in neutral position or noninvasive distraction.

CLINICAL RELEVANCE

Results of this study may allow for better planning in arthroscopic treatment of osteochondral lesions of the talus.

Comparison of channel-assisted minimally invasive repair and 3 common Achilles tendon restoration techniques

The present study aimed to investigate the biomechanical comparison of channel-assisted minimally invasive restoration and three common Achilles tendon restoration techniques in an in vitro model via a progressive rehabilitation program. The 42 porcine tendons were randomly assigned to the following six groups of tendons (n=7/group): Achillon, percutaneous Achilles repair system (PARS), Krackow, channel-assisted minimally invasive repair (CAMIR), CAMIR augmentation (CAMIR⁺), CAMIR-5 (repair with No. 5 Ethibond suture). There was no significant difference in elongation among groups following the first 10 loading cycles, which consisted of 20-100 N at 1 Hz. The elongation of the CAMIR group (7.51±1.77 mm) was significantly longer than the Achillon group (3.19±0.57 mm) and PARS group (3.73±0.66 mm; P<0.05) following 1,000 cycles. However, the CAMIR group exhibited no significant difference vs. the Krackow (7.32±1.09 mm) and CAMIR⁺ groups (7.11±1.50 mm) following 1,000 cycles. Following 2,000 cycles, there was no significant difference between the CAMIR-5 (7.99±1.68 mm) group, and the Achillon (3.19±0.57 mm) and PARS groups (3.73±0.66 mm). At the point of restoration construct failure, the total cycles of the CAMIR group (median, 1,000; range, 1,000-1,000) were significantly less than the Achillon group (median, 2,000; range, 2,000-2,013) and PARS group (median, 2,000; range, 2,000-2,010; P<0.05), but had no significant difference compared with the Krackow group (median, 1,000; range, 1,000-1,000) and CAMIR⁺ group 1,000 (median, 1,000; range, 1,000-1,004). There was also no significant difference between the CAMIR-5 group (median, 2,000; range, 2,000-2,000), and the Achillon group (median, 2,000; range, 2,000-2,013) and PARS group (median, 2,000; range, 2,000-2,010). Restricted by the strength of suture, the one-suture CAMIR restoration technique was weaker than the three-suture Achillon and PARS restoration techniques, but there was no significant difference with the open Krackow restoration technique, which provides a reliable mechanical strength for repairing. CAMIR has an advantage of reducing the risk of suture reactivity.

Proximal Medial Gastrocnemius Recession and Stretching Versus Stretching as Treatment of Chronic Plantar Heel Pain

BACKGROUND:

Plantar heel pain is a common disorder that can lead to substantial pain and disability. Gastrocnemius recession has been described as an operative treatment option, but there is a lack of prospective clinical and biomechanical outcome data. The aim of this study was to evaluate the clinical and biomechanical outcomes of gastrocnemius recession and stretching compared with a stretching exercise protocol for patients with plantar heel pain lasting more than 12 months.

METHODS:

Forty patients with plantar heel pain lasting more than 1 year were randomized to a home stretching exercise program only or to surgery consisting of a proximal medial gastrocnemius recession in addition to stretching exercises. The main outcome was the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score at 12 months. Secondary clinical outcomes were the Short Form-36 (SF-36) and visual analogue scale (VAS) pain scores. The biomechanical outcome parameters were ankle dorsiflexion, Achilles function evaluated by a test battery with 6 independent tests, and plantar pressure evaluated by pedobarography. All data were obtained at baseline and at 12-month follow-up.

RESULTS:

The AOFAS score increased from 59.5 (42-76) to 88.0 (50-100; P < .001) for the operative group and from 52.5 (37-73) to 65.5 (31-88; P = .138) for the nonoperative group. The AOFAS, VAS pain, and SF-36 scores were significantly better in the operative compared with the nonoperative group at 12-month follow-up ( P < .05). Ankle dorsiflexion increased from 6 degrees (-3 to 15) to 10.5 degrees (0 to 23; P < .001). No between-group difference was observed for Achilles function at follow-up. The average forefoot plantar pressure for the operative group increased from 536 KPa (306-708) to 642 KPa (384-885) at follow-up ( P < .001).

CONCLUSION:

Proximal medial gastrocnemius recession with a stretching program was a safe and efficient method of treating chronic plantar heel pain.

LEVEL OF EVIDENCE:

Level 1, randomized clinical trial.

Previous foot injuries associated with a greater likelihood of Achilles tendon ruptures in professional American football players

OBJECTIVES

The purpose of this study was to build on current understanding of Achilles tendon (AT) ruptures in football through the examination of lower extremity injury rates (IR) in the season prior to AT rupture.

METHODS

An online review was conducted to document AT ruptures in the National Football League (NFL) from the 2010-11 through 2016-17 seasons. Player-specific information was gathered through the online search, injury reports, or video analysis. Injury incidence was recorded for each season. Descriptive statistics were calculated for all variables. IRs per 1000 athlete-exposures with 95% confidence intervals (CI) were established. Injury rate ratios (IRR) with 95% CI were calculated to evaluate differences in IR with statistical significance established at p < 0.05.

RESULTS

From the 2010-11 to 2016-17 NFL seasons, 109 AT ruptures were identified. 36 athletes participated in the NFL the season prior and sustained a total of 40 injuries. Thirty-two (32/40, 80%) of the injuries involved the lower extremity. The most frequent body parts injured in the NFL season prior to AT rupture were the knee (n = 8, 22.5%), upper leg and thigh (n = 7, 17.5%), lower leg and shin (n = 5, 12.5%), and ankle (n = 5, 12.5%). The overall IR for the AT rupture group was not significantly different than the NFL group (IRR: 0.94, 0.68-1.31 95% CI, p = 0.73). The AT rupture group demonstrated a significantly increased rate of foot injuries compared to the NFL cohort (IRR: 2.58, 1.16-5.77 95% CI, p = 0.02).

CONCLUSION

There was an increased identified incidence of AT ruptures in the NFL from 2010 to 2017 compared to AT ruptures reported from 1997 to 2002. There was no significant difference in lower extremity IR the season prior to AT rupture. Only foot injuries demonstrated an increased IR the season prior to AT rupture compared to an NFL cohort. Eleven athletes sustained 2 AT ruptures and all 11 players sustained the subsequent AT rupture to the contralateral limb.

Can Weakness in End-Range Plantar Flexion After Achilles Tendon Repair Be Prevented?

Background

Disproportionate end-range plantar flexion weakness, decreased passive stiffness, and inability to perform a heel rise on a decline after Achilles tendon repair are thought to reflect increased tendon compliance or tendon lengthening. Since this was first noted, we have performed stronger repairs and avoided stretching into dorsiflexion for the first 12 weeks after surgery.

Hypothesis

Using stronger repairs and avoiding stretching into dorsiflexion would eliminate end-range plantar flexion weakness and normalize passive stiffness.

Study Design

Case series; Level of evidence, 4.

Methods

Achilles repairs with epitendinous augmentation were performed on 18 patients. Plantar flexion torque, dorsiflexion range of motion (ROM), passive joint stiffness, and standing single-legged heel rise on a decline were assessed at 43 ± 24 months after surgery (range, 9 months to 8 years). Maximum isometric plantar flexion torque was measured at 20° and 10° of dorsiflexion, neutral position, and 10° and 20° of plantar flexion. Passive dorsiflexion ROM was measured with a goniometer. Passive joint stiffness was computed from the increase in passive torque from 10° to 20° of dorsiflexion. Tendon thickness was measured by use of digital calipers. Plantar flexion electromyographic (EMG) data were recorded during strength and functional tests. Analysis of variance and chi-square tests were used to assess weakness and function.

Results

Marked weakness was evident on the involved side at 20° of plantar flexion (deficit, 26% ± 18%; P < .001), with no weakness at 20° of dorsiflexion (deficit, 6% ± 17%; P = .390). Dorsiflexion ROM was decreased 5.5° ± 8° (P = .015), and tendon width was 8 ± 3 mm greater on the involved side (P < .001). Passive joint stiffness was similar between the involved and noninvolved sides. Only 2 of 18 patients could perform a decline heel rise on the involved side compared with 18 of 18 on the noninvolved side (P = .01). No difference in EMG amplitude was found between the involved and noninvolved sides during the strength or heel rise tests.

Conclusion

The use of stronger repair techniques and attempts to limit tendon elongation by avoiding dorsiflexion stretching did not eliminate weakness in end-range plantar flexion. EMG data confirmed that end-range weakness was not due to neural inhibition. Physiological changes that alter the force transmission capability of the healing tendon may be responsible for this continued impairment. This weakness has implications for high-demand jumping and sprinting after Achilles tendon repair.

Biomechanical properties of different techniques used in vitro for suturing mid-substance Achilles tendon ruptures

BACKGROUND

The Dresden technique preserves the paratenon during Achilles tendon repair and may improve the plantarflexor mechanism when combined with mobilization during early rehabilitation. However, the surgical repair design for Achilles tendon ruptures can affect rates of re-rupture or lengthening. Therefore, the aim of this study was to determine the biomechanical properties of the Krackow, Double-Kessler, Double-Dresden, and Triple-Dresden techniques used for repairing mid-substance Achilles tendon ruptures during cyclical and maximum traction.

METHODS

Sixty mid-substance bovine tendons repaired after transverse rupturing were divided randomly into four groups by repair technique: Krackow, Double-Kessler, Double-Dresden, and Triple-Dresden. Cyclical tractions of 4.7, 5.8, 7.9, and 11.7mm (equivalent to 5°, 8°, 10°, and 15° of dorsal flexion, respectively) were applied to determine gapping, tensile strength, nominal suture stress, repair deformation, and specimens with clinical failure (gap>5mm). Maximal traction was applied to measure maximum strength and failure type (i.e. suture, knot, or tendon).

FINDINGS

The Triple-Dresden technique resulted in decreased gapping, nominal suture stress, repair deformation, and quantity of specimens with clinical failure as compared to the other techniques. Furthermore, Triple-Dresden tendons showed greater comparative tensile and maximum strength. During maximal traction testing, this technique presented tendon failure, whereas the Krackow, Double-Kessler, and Double-Dresden techniques had suture failures.

INTERPRETATION

Triple-Dresden repair results in better cyclical and maximum traction strengths, suggesting that this technique might be more appropriate when performing early mobilization after mid-substance Achilles tendon rupture repair.

Optimizing Arthroscopy for Osteochondral Lesions of the Talus: The Effect of Ankle Positions and Distraction During Anterior and Posterior Arthroscopy in a Cadaveric Model

PURPOSE

To quantify arthroscopic accessibility of the talar dome with predefined ankle positions through anterior and posterior approaches.

METHODS

Fourteen below-knee cadaver specimens underwent preoperative range of motion assessments. A 30° 2.7-mm arthroscopic camera was used to mark accessible areas at varying ankle positions. Accessible regions were quantified using a surface laser scanner and digital 3 × 3 grid. Statistical analyses were performed to detect differences in arthroscopic accessibility between different flexion angles and noninvasive distraction.

RESULTS

The mean arthroscopic accessibility of the talus was 58.5% and 49.8% for the anterior and posterior approaches, respectively (P < .001). During anterior arthroscopy, accessibility increased with up to 30° of plantarflexion (P < .001). There were no significant differences in accessibility between flexion groups for the posterior approach. There was significantly greater central zone accessibility for anterior arthroscopy (87.7%) when compared with posterior arthroscopy (74.3%; P = .002). Arthroscopic accessibility increased with increasing ankle distraction for both the anterior and posterior approaches (parameter estimates ± standard error): anterior = 6.5% ± 1.3%/mm of distraction, P < .001; and posterior = 7.0% ± 2.8%/mm, P = .026. Frequency analysis showed that the posterior third of the talus was completely inaccessible in 7 out of 14 of ankles during anterior arthroscopy. The anterior third of the talus during posterior arthroscopy was inaccessible in 11 out of 14 ankles during posterior arthroscopy.

CONCLUSIONS

Ankle plantarflexion up to 30° may be adequate for anterior arthroscopy for osteochondral lesions of the talus (OLTs). Noninvasive distraction also increases accessibility during both anterior and posterior arthroscopy. Anterior arthroscopy should be used for central third OLTs due to greater accessibility.

CLINICAL RELEVANCE

Ankle positioning is an important consideration for anterior arthroscopy. Surgical approach used should match with the location of the OLTs.

A Biomechanical Comparison of Limited Open Versus Krackow Repair for Achilles Tendon Rupture

Background:

Soft tissue complications after Achilles tendon repair has led to increased interest in less invasive techniques. Various limited open techniques have gained popularity as an alternative to open operative repair. The purpose of this study was to biomechanically compare an open Krackow and limited open repair for Achilles tendon rupture. We hypothesized that there would be no statistical difference in load to failure, work to failure, and initial linear stiffness.

Methods:

A simulated Achilles tendon rupture was created 4 cm proximal to its insertion in 18 fresh-frozen cadaveric below-knee lower limbs. Specimens were randomized to open or limited open PARS Achilles Jig System repair. Repairs were loaded to failure at a rate of 25.4 mm/s to reflect loading during normal ankle range of motion. Load to failure, work to failure, and initial linear stiffness were compared between the 2 repair types.

Results:

The average load to failure (353.8 ± 88.8 N vs 313.3 ± 99.9 N; P = .38) and work to failure (6.4 ± 2.3 J vs 6.3 ± 3.5 J; P = .904) were not statistically different for Krackow and PARS repair, respectively. Mean initial linear stiffness of the Krackow repair (17.8 ± 5.4 N/mm) was significantly greater than PARS repair (11.8 ± 2.5 N/mm) ( P = .011).

Conclusion:

No significant difference in repair strength was seen, but higher initial linear stiffness for Krackow repair suggests superior resistance to gap formation, which may occur during postoperative rehabilitation. With equal repair strength, but less soft tissue devitalization, the PARS may be a favorable option for patients with risk factors for soft tissue complications.

Clinical failure after Dresden repair of mid-substance Achilles tendon rupture: human cadaveric testing

PURPOSE

The purpose of this study was to describe the angle of clinical failure during cyclical mobilization exercises in the Achilles tendon of human cadaveric specimens that were repaired using the Dresden technique and FiberWire^® No. 2. The secondary aim was to identify the secure limit of mobilization, the type of failure, and the type of apposition.

METHODS

The lower limbs of eight males (mean age: 60.3 ± 6.3 years) were repaired with the Dresden technique following complete, percutaneous mid-substance Achilles tendon rupture. A basal tension of 10 N at 30° of plantarflexion was placed on each specimen. The angle of the ankle during clinical failure (tendon ends separation >5 mm) was then tested via cyclical exercises (i.e. 100 cycles between 30° and 15° of plantarflexion; 100 cycles between 15° of plantarflexion and 0°; 100 cycles between 0° and 15° of dorsiflexion; and 100 cycles between 15° of dorsiflexion and full dorsiflexion). Clinical failure was determined using the Laplacian edge detection filter, and the angle of clinical failure was obtained using a rotatory potentiometer aligned in relation to the intermalleolar axis of each foot specimen. The type of failure (knot, tendon, or suture) and apposition (termino-terminal or non-termino-terminal) were determined. Descriptive statistics were used to obtain the mean; standard deviation; 95 % confidence interval; 1st, 25th, 50th, 75th, and 100th percentiles; and the standard error of the mean for angle data. Proportions were used to describe the type of failure and apposition.

RESULTS

The main results were a mean angle of clinical failure equal to 12.5° of plantarflexion, a limit of mobilization equal to 14.0° of plantarflexion, tendon failure type, and non-termino-terminal apposition in all specimens.

CONCLUSIONS

While the mean angle of clinical failure in human cadaveric models was 12.5° of plantarflexion, after 14.0° of plantarflexion, the percutaneous Dresden technique was found insecure for cyclical mobilization exercises, with a 5 % range of error. These findings are clinically relevant as they provide mechanical limits for diminishing the risk of Achilles lengthening during immediate rehabilitation.

Effect of Suture Caliber and Number of Core Strands on Repair of Acute Achilles Ruptures: A Biomechanical Study

BACKGROUND

Controversy exists regarding the ideal Achilles rupture treatment; however, operative treatment is considered for athletes and active patients. The ideal repair construct is evolving, and the effect of suture caliber or number of core strands has not been studied.

METHODS

Simulated mid-substance Achilles ruptures were performed in 24 cadavers. Specimens were randomized to three 6-core-strand style repair constructs: (1) 4 No. 2 sutures and two 2-mm tapes (2T); (2) 2 No. 2 sutures and four 2-mm tapes (4T); (3) 12 (double-6-strand) strand repair (12 No. 2-0 sutures [12S]). Repairs were subjected to a cyclic loading protocol representative of postoperative rehabilitation. These data were compared to a previously published standard open repair technique (6-core strands with No. 2 sutures) on 9 specimens tested under the same conditions.⁶ Results: No significant elongation differences were observed between the repair groups and the previously published standard repair group in the first 2 stages of the simulated rehabilitation protocol. Both the 2T and 12S repairs survived a significantly greater number of cycles to failure ( P = 0.0005, P = 0.0267, respectively) and had a significantly higher failure load ( P = .0005, P = .0118, respectively) compared to the previously published data. These 2 constructs consistently survived the advanced stages of the simulated rehabilitation protocol. The majority of repairs failed at the knots.

CONCLUSIONS

In this study, the 2T and 12S constructs survived the later stages of our simulated rehabilitation protocol, suggesting that they may be able to accommodate a more aggressive clinical rehabilitation protocol. Substituting suture-tape for 2 core strands or doubling the core strands with a smaller-caliber suture created a biomechanically stronger construct.

CLINICAL RELEVANCE

Achilles repair with an added nonabsorbable, high-tensile strength tape allowed for a stronger construct that may allow for a more aggressive, early rehabilitation protocol and earlier return to function.

Interlocking horizontal mattress suture versus Kakiuchi technique in repair of Achilles tendon rupture: a biomechanical study

BACKGROUND

In recent years, the type of surgical treatment for Achilles tendon rupture has been the subject of controversial debate. This biomechanical study evaluates for the first time in literature the ultimate failure load (UFL) of interlocking horizontal mattress (IHM) suture as compared with Kakiuchi suture in Achilles tendon rupture. The hypothesis is that IHM suture can be performed also for Achilles tendon rupture and ensures higher resistance compared with the traditional Kakiuchi suture.

MATERIALS AND METHODS

Twenty fresh bovine Achilles tendons were obtained. Ten preparations were randomly assigned to each of two different groups: group A (10 specimens) sutured by IHM technique, and group B (10 specimens) sutured by Kakiuchi technique. Each construct was mounted and fixed on a tensile testing machine. Static preconditioning of 50 N was applied for 5 min as initial tensioning to stabilize the mechanical properties of the graft, then a load to failure test was performed at crosshead speed of 500 mm/min.

RESULTS

Ten specimens were tested for each group. The mean UFL was 228.6 ± 98.6 N in the IHM suture group and 96.57 ± 80.1 N in the Kakiuchi suture group. Statistical analysis showed a significant difference (p < 0.05) with better UFL in the IHM group. In both groups, the failure mode registered in each specimen was suture breakage (rupture of suture thread).

CONCLUSIONS

IHM suture achieved better UFL compared with Kakiuchi suture in an animal model of Achilles tendon repair. These results seem to support IHM as a valid option in Achilles tendon rupture.

Medial Gastrocnemius Myotendinous Junction Displacement and Plantar-Flexion Strength in Patients Treated With Immediate Rehabilitation After Achilles Tendon Repair

CONTEXT

Pathologic plantar flexion frequently occurs after operative repair of the Achilles tendon (AT) because of immobilization and non-weight bearing in the first weeks of traditional rehabilitation. Novel rehabilitation strategies that apply mobilization and weight bearing have been proposed, but their effects on medial gastrocnemius myotendinous junction displacement (MJD) and isometric plantar-flexion strength (PFS) are unknown.

OBJECTIVE

To compare the effects of 12 weeks of immediate versus traditional rehabilitation on MJD and PFS in patients with percutaneous AT repair and to compare AT rupture scores (ATRSs) during follow-up.

DESIGN

Controlled laboratory study.

SETTING

Human performance laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 26 amateur soccer players (age = 42.3 ± 9.7 years, body mass index = 29.5 ± 3.9 kg/m²) with percutaneous AT repair.

INTERVENTION(S)

Athletes were randomly divided into 2 groups: an immediate group, given physical therapy from day 1 to day 84, and a traditional group, given physical therapy from day 29 to day 84. We used repeated-measures analysis of variance to compare the data.

MAIN OUTCOME MEASURE(S)

We measured MJD and PFS at days 28 (fourth week), 56 (eighth week), and 84 (12th week) after AT repair.

RESULTS

After 12 weeks of rehabilitation, we observed a large clinically meaningful effect and statistical difference between groups. At day 28, the immediate group showed higher values for PFS (P = .002), MJD (P = .02), and ATRS (P = .002) than the traditional group. At day 56, the immediate group presented higher values for MJD (P = .02) and ATRS (P = .009). At day 84, the immediate group registered more MJD (P = .001).

CONCLUSIONS

Compared with traditional rehabilitation, 12 weeks of immediate rehabilitation after percutaneous AT repair resulted in better MJD, PFS, and ATRS after 4 weeks; better MJD and ATRS after 8 weeks; and better MJD after 12 weeks.

Prospective randomized clinical trial of aggressive rehabilitation after acute Achilles tendon ruptures repaired with Dresden technique

BACKGROUND

Rupture of the Achilles tendon is a common injury during working years. Aggressive rehabilitation may provide better outcomes, but also a greater chance of re-rupture.

OBJECTIVE

To determine if aggressive rehabilitation has better clinical outcomes for Achilles tendon function, Triceps surae function, one-leg heel rise capacity and lower complication rate during twelve weeks after percutaneous Achilles tendon repair compared to conventional rehabilitation.

DESIGN

Randomized controlled trial.

METHOD

Thirty-nine patients were prospectively randomized. The aggressive group (n=20, 41.4 ± 8.3 years) received rehabilitation from the first day after surgery. The conventional group (n=19, 41.7 ± 10.7 years) rested for 28 days, before rehabilitation started. The statistical parameters were the Achilles tendon rupture score (ATRS), verbal pain scale, time to return to work, pain medication consumption, Achilles tendon strength, dorsiflexion range of motion (RoM), injured-leg calf circumference, calf circumference difference, one-leg heel rise repetition and difference, re-rupture rate, strength deficit rate, and other complication rates. Mixed-ANOVA and Bonferroni's post hoc test were performed for multiple comparisons. Student's t-test was performed for parameters measured on the 12th week.

RESULTS

The aggressive group with respect to the conventional group had a higher ATRS; lower verbal pain score; lower pain medication consumption; early return to work; higher Achilles tendon strength; higher one-leg heel rise repetitions; and lower one-leg heel rise difference. The re-rupture rate was 5% and 5%, the strength deficit rate was 42% and 5%, and other complications rate was 11% and 15% in the conventional and aggressive group, respectively.

CONCLUSION

Patients with Dresden repair and aggressive rehabilitation have better clinical outcomes, Achilles tendon function and one-leg heel rise capacity without increasing the postoperative complications rate after 12 weeks compared to rehabilitation with immobilization and non-weight-bearing during the first 28 days after surgery.

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.

Biomechanical comparison of three methods for distal Achilles tendon reconstruction

PURPOSE

To compare the load at failure and stiffness associated with three surgical techniques for distal Achilles tendon reconstruction (AT).

METHODS

Nine matched pairs of fresh-frozen human cadaveric ATs were divided into three groups. Distal AT reconstruction was performed using suture anchors or one of two lengths of tendon overlap (10 or 5 mm). Each tendon was loaded to failure. The load at failure (N), stiffness (N/mm), and mode of failure were recorded. Differences in load at failure and stiffness were analysed.

RESULTS

Mean load at failure was significantly higher in the 10-mm group than in the 5-mm group (p < 0.05) or the suture-anchor group (p < 0.05). Load at failure did not differ significantly between the suture-anchor and 5-mm group, and stiffness did not differ significantly between any two groups. In the 10- and 5-mm groups, failure was caused by the grafts pulling out through the substance of the AT. Modes of failure varied in the suture-anchor group.

CONCLUSIONS

The load at failure was higher in the 10-mm group than in the 5-mm and suture-anchor groups. Although all three surgical techniques provide sufficient primary load-bearing ability, the 10-mm tendon-overlap technique may be more conducive to early post-operative rehabilitation.

A Biomechanical Comparison of an Open Repair and 3 Minimally Invasive Percutaneous Achilles Tendon Repair Techniques During a Simulated, Progressive Rehabilitation Protocol

BACKGROUND

While the nonoperative management of Achilles tendon ruptures is a viable option, surgical repair is preferred in healthy and active populations. Recently, minimally invasive percutaneous repair methods with assistive devices have been developed.

HYPOTHESIS/PURPOSE

The purpose of this study was to biomechanically analyze 3 commercially available, minimally invasive percutaneous techniques compared with an open Achilles repair during a simulated, progressive rehabilitation program. It was hypothesized that no significant biomechanical differences would exist between repair techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

A simulated, midsubstance Achilles rupture was created 6 cm proximal to the calcaneal insertion in 33 fresh-frozen cadaveric ankles. Specimens were then randomly allocated to 1 of 4 different Achilles repair techniques: (1) open repair, (2) the Achillon Achilles Tendon Suture System, (3) the PARS Achilles Jig System, or (4) an Achilles Midsubstance SpeedBridge Repair variation. Repairs were subjected to a cyclic loading protocol representative of progressive postoperative rehabilitation: 250 cycles at 1 Hz for each loading range: 20-100 N, 20-200 N, 20-300 N, and 20-400 N.

RESULTS

The open repair technique demonstrated significantly less elongation (5.2 ± 1.1 mm) when compared with all minimally invasive percutaneous repair methods after 250 cycles (P < .05). No significant differences were observed after 250 cycles between the Achillon, PARS, or SpeedBridge repairs, with mean displacements of 9.9 ± 2.2 mm, 12.2 ± 4.4 mm, and 10.0 ± 3.9 mm, respectively. When examined over smaller cyclic intervals, the majority of elongation, regardless of repair, occurred within the first 10 cycles. Within the first 10 cycles, open repairs achieved 71.2% of the total elongation observed after 250 cycles. Corresponding values for the Achillon, PARS, and SpeedBridge repairs were 81.8%, 77.9%, and 69.0%, respectively. No significant differences were observed in the total number of cycles to failure between minimally invasive percutaneous repairs and open repairs. Minor differences in the mechanism of failure were noted; however, the majority of all repairs failed at the suture-tendon interface.

CONCLUSION

Minimally invasive percutaneous repair techniques demonstrated a susceptibility to significant early repair elongation when compared with open repairs. However, the ultimate strengths of repairs (cycles to failure) were comparable across all techniques.

CLINICAL RELEVANCE

The reduced early elongation of open repairs suggests that patients treated with this technique may be able to progress through an earlier and/or more aggressive postoperative rehabilitation protocol with a lower risk of early irrevocable repair elongation or gapping about the repair site. However, in cases where cosmesis or wound-healing complications are of significant concern, minimally invasive percutaneous techniques provide a biomechanically reasonable alternative based on their repair strengths (cycles to failure). These repairs may need to be protected longer postoperatively to allow for biological healing and avoid early repair elongation and potential gapping between the healing tendon ends.

Achilles tendon loading patterns during barefoot walking and slow running on a treadmill: An ultrasonic propagation study

Measurement of tendon loading patterns during gait is important for understanding the pathogenesis of tendon "overuse" injury. Given that the speed of propagation of ultrasound in tendon is proportional to the applied load, this study used a noninvasive ultrasonic transmission technique to measure axial ultrasonic velocity in the right Achilles tendon of 27 healthy adults (11 females and 16 males; age, 26 ± 9 years; height, 1.73 ± 0.07 m; weight, 70.6 ± 21.2 kg), walking at self-selected speed (1.1 ± 0.1 m/s), and running at fixed slow speed (2 m/s) on a treadmill. Synchronous measures of ankle kinematics, spatiotemporal gait parameters, and vertical ground reaction forces were simultaneously measured. Slow running was associated with significantly higher cadence, shorter step length, but greater range of ankle movement, higher magnitude and rate of vertical ground reaction force, and higher ultrasonic velocity in the tendon than walking (P < 0.05). Ultrasonic velocity in the Achilles tendon was highly reproducible during walking and slow running (mean within-subject coefficient of variation < 2%). Ultrasonic maxima (P1, P2) and minima (M1, M2) were significantly higher and occurred earlier in the gait cycle (P1, M1, and M2) during running than walking (P < 0.05). Slow running was associated with higher and earlier peaks in loading of the Achilles tendon than walking.

Limited-Open Achilles Tendon Repair Using Locking Sutures Versus Nonlocking Sutures: An In Vitro Model

BACKGROUND

Several limited-open Achilles tendon repair techniques that use locking or nonlocking sutures have been developed, but direct comparisons of in vitro mechanical properties have not yet been reported in the literature. It was our hypothesis that loads applied to the repaired Achilles tendon would be better resisted by limited-open techniques that use locking stitches compared with limited-open repairs that use nonlocking stitches.

METHODS

The Achilles tendons of 31 fresh-frozen cadaver lower limbs were incised 4 cm proximal to the calcaneal insertion. Tendons were then repaired using 1 of 2 limited-open Achilles tendon repair tools, one using 3 nonlocking sutures and the other using a combination of locking and nonlocking sutures. Repaired specimens were cycled to 1000 cycles from 20 to 100 N and from 20 to 190 N followed by a single load to failure test. Nonparametric analyses were performed to compare the number of cycles to gapping and total load to failure between the 2 repair techniques.

RESULTS

During cyclic loading, more cycles occurred prior to detection of 2-mm and 9.5-mm gaps in the locking suture construct compared with the nonlocking suture construct ( P = .012 and P = .005, respectively). There was no difference in the number of cycles to a gap of 5 mm ( P = .053). The locking suture construct also resisted a significantly greater load to failure compared with the nonlocking suture construct ( P < .001; median 385.0 and 299.6 N, respectively).

CONCLUSION

Limited-open repair techniques using locking sutures provided greater construct strength under both cyclic and ultimate loads compared with a repair technique that used only nonlocking sutures.

CLINICAL RELEVANCE

Limited-open Achilles tendon repairs using locking sutures are better able to resist forces simulating early accelerated rehabilitation than repairs using nonlocking sutures.

Strength of different Krackow stitch configurations using high-strength suture

The purpose of the present study concerning high-strength sutures was to determine whether increasing the number of locking loops with different size sutures or decreasing the suture size with increased suture strands would have any influence on the strength of Achilles tendon repair. A total of 32 fresh bovine Achilles tendon specimens were randomly assigned to 4 groups. For 3 of the groups, 1 suture was used (no. 2 or no. 5 FiberWire™ with 2 or 4 Krackow locking loops). For the fourth group, 2 sutures (2-0 FiberWire™) with 2 locking loops were used. After repair, the study groups underwent cyclic loading (0 to 200 N, 200 cycles) and then underwent tension to failure in a testing machine. Cyclic elongation, peak to peak displacement, ultimate load, stiffness, and failure mode were recorded for each specimen. The tendon width and thickness were measured in all specimens. The mean width, thickness, cyclic displacement, load to failure, and pull-out stiffness showed no differences among the 4 groups. The cyclic peak to peak displacements (0.01 ± 0.01 mm) were smallest with the no. 5 suture with 4 locking loops (p < .05), with no failure during cyclic loading, unlike in the other groups. In the group with 2-0 suture with 4 strands and 2 locking loops, 6 failed during cyclic loading. The number of locking loops used might have had an influence on the strength of the Krackow suture configuration using the larger diameter, high-strength sutures. However, decreasing the suture diameter, with a simultaneous increase in the number of strands, failed to improve the initial strength of the repair.

The effect of isolated gastrocnemius contracture and gastrocnemius recession on lower extremity kinematics and kinetics during stance

BACKGROUND

Isolated gastrocnemius contracture limits ankle dorsiflexion with full knee extension and is potentially problematic during mid-stance of gait when 10° of dorsiflexion and full knee extension are needed. It is during this time that patients with isolated gastrocnemius contracture may demonstrate altered kinematics and/or kinetics. When conservative management fails to resolve painful foot pathologies associated with non-spastic isolated gastrocnemius contracture, gastrocnemius recession surgery has been suggested to resolve contracture and improve function and strength. However, there are no published reports on lower extremity kinematics/kinetics in the non-spastic isolated gastrocnemius contracture population. Assessment of alterations in gait mechanics is necessary to examine the effects of this potential surgical intervention.

METHODS

Lower extremity kinematics and kinetics were assessed in 6 patients clinically diagnosed with isolated gastrocnemius contracture pre- and post-surgical recession compared with 33 healthy control participants.

FINDINGS

Pre-operatively, patients with isolated gastrocnemius contracture demonstrated significantly increased peak knee flexion angles and knee flexion moments during mid-stance. There were no differences in peak ankle dorsiflexion angle or peak plantar flexion moment. Gastrocnemius recession did not alter gait kinematics/kinetics following surgery. Joint kinematic strategies utilized to compensate for isolated gastrocnemius contracture varied minimally between participants with IGC; most employed a flexed knee strategy, while one participant utilized a reduced ankle dorsiflexion strategy.

INTERPRETATION

Select post-surgical gait mechanics were unaltered; however, gait mechanics were not similar between non-spastic isolated gastrocnemius contracture patients and healthy control participants. Surgical intervention for patients with isolated gastrocnemius contracture does not appear to create any negative gait adaptations; however, patients may benefit from gait retraining post-recession as maladaptive gait patterns persist post operatively.

Electromyographic analysis of the triceps surae muscle complex during achilles tendon rehabilitation program exercises

BACKGROUND

Specific guidelines for therapeutic exercises following an Achilles tendon repair are lacking.

HYPOTHESIS

A hierarchical progression of triceps surae exercises can be determined on the basis of electromyographic (EMG) activity.

STUDY DESIGN

Randomized laboratory trial.

METHODS

Bipolar surface electrodes were applied over the medial and lateral heads of the gastrocnemius as well as the soleus on 20 healthy lower extremities (10 participants, 27 ± 5 years old). Muscle activity was recorded during 8 therapeutic exercises commonly used following an Achilles repair. Maximal voluntary isometric contractions (MVICs) were also performed on an isokinetic device. The effect of exercise on EMG activity (% MVIC) was assessed using repeated measures analysis of variance with Bonferroni corrections for planned pairwise comparisons.

RESULTS

Seated toe raises (11% MVIC) had the least amount of activity compared with all other exercises (P < 0.01), followed by single-leg balance on wobble board (25% MVIC), prone ankle pumps (38% MVIC), supine plantarflexion with red elastic resistance (45% MVIC), normal gait (47% MVIC), lateral step-ups (60% MVIC), single-leg heel raises (112% MVIC), and single-leg jumping (129% MVIC).

CONCLUSION

There is an increasing progression of EMG activity for exercises that target the triceps surae muscle complex during common exercises prescribed in an Achilles tendon rehabilitation program. Seated toe raises offer relatively low EMG activity and can be utilized as an early rehabilitative exercise. In contrast, the single-leg heel raise and single-leg jumping should be utilized only during later-stage rehabilitation.

CLINICAL RELEVANCE

EMG activity in the triceps surae is variable with common rehab exercises.

Fixation of the Achilles tendon insertion using suture button technology

BACKGROUND

In the operative treatment of Achilles insertional tendinopathy, no guidelines exist concerning which form of fixation of the Achilles tendon insertion is superior.

HYPOTHESIS

Transcalcaneal drill pin passage does not place any major plantar structures at risk, and the addition of a Krackow stitch and suture button to the fixation technique provides a significant increase in ultimate load to failure in Achilles tendon insertional repairs.

STUDY DESIGN

Controlled laboratory study.

METHODS

The Achilles tendon insertions in 6 fresh-frozen cadaveric ankles were detached, and transcalcaneal drill pins were passed. Plantar dissection took place to evaluate the drill pin relationship to the plantar fascia, lateral plantar nerve and artery, flexor digitorum longus tendon, and master knot of Henry. The Achilles tendons were then repaired with a double-row suture anchor construct alone or with a suture button and Krackow stitch added to the double-row suture anchor construct. The repairs were then tested to maximum load to failure at 20 mm/min. The mode of failure was recorded, and the mean maximum load to failure was assessed using the Student t test for distributions with equal variance.

RESULTS

Transcalcaneal drill pin passage did not place any selected anatomic structures at risk. The mean maximum load to failure for the suture bridge group was 239.2 N; it was 391.4 N for the group with the suture button (P = .014). The lateral plantar artery was the structure placed at greatest risk from drill pin placement, with a mean distance of 22.7 mm (range, 16.5-29.2 mm) between the pin and artery.

CONCLUSION

In this laboratory study, transcalcaneal drill pin passage appeared to be anatomically safe, and the use of suture button technology with a Krackow stitch for Achilles tendon insertional repair significantly increased repair strength.

CLINICAL RELEVANCE

Achilles tendon insertional repair with suture button fixation and a Krackow stitch may facilitate the earlier institution of postoperative rehabilitation and improve clinical outcomes.

Biomechanical comparison of four methods of repair of the Achilles tendon

We tested four types of surgical repair for load to failure and distraction in a bovine model of Achilles tendon repair. A total of 20 fresh bovine Achilles tendons were divided transversely 4 cm proximal to the calcaneal insertion and randomly repaired using the Dresden technique, a Krackow suture, a triple-strand Dresden technique or a modified oblique Dresden technique, all using a Fiberwire suture. Each tendon was loaded to failure. The force applied when a 5 mm gap was formed, peak load to failure, and mechanism of failure were recorded. The resistance to distraction was significantly greater for the triple technique (mean 246.1 N (205 to 309) to initial gapping) than for the Dresden (mean 180 N (152 to 208); p = 0.012) and the Krackow repairs (mean 101 N (78 to 112; p < 0.001). Peak load to failure was significantly greater for the triple-strand repair (mean 675 N (453 to 749)) than for the Dresden (mean 327.8 N (238 to 406); p < 0.001), Krackow (mean 223.6 N (210 to 252); p <  0.001) and oblique repairs (mean 437.2 N (372 to 526); p < 0.001). Failure of the tendon was the mechanism of failure for all specimens except for the tendons sutured using the Krackow technique, where the failure occurred at the knot.

The triple-strand technique significantly increased the tensile strength (p = 0.0001) and gap resistance (p = 0.01) of bovine tendon repairs, and might have advantages in human application for accelerated post-operative rehabilitation.

Xenograft scaffold full-wrap reinforcement of Krackow achilles tendon repair

Standard 4-strand repair of Achilles tendon tears is effective, but additional strength may be desirable in patients who are compromised or those with reruptures. Use of a xenograft scaffold has not been investigated biomechanically in Achilles tendon repair. This study compared stiffness, gap formation, and ultimate load to failure with Krackow repair vs Krackow repair augmented with xenograft scaffold in 6 matched pairs of fresh-frozen human lower extremities. The Achilles tendon was transected 4 cm above the calcaneal insertion. Specimens were randomized to receive standard Krackow repair or Krackow repair augmented with a porcine xenograft scaffold. The graft was wrapped around the repaired tendon, sutured to itself with 2-0 FiberWire (Arthrex, Naples, Florida), and attached to the tendon distally and proximally and then medially and laterally. Specimens were loaded for 200 cycles between 5 and 30 N. Load to 5-mm gapping and load to ultimate failure were measured. Xenograft scaffold augmentation of standard Krakow Achilles tendon repair was significantly stronger and stiffer than standard Krackow repair in a biomechanical model immediately after repair (39.0±8.8 vs 24.4±4.6 N/mm; P=.01). The augmented repair group had significantly higher load to ultimate failure than did the Krackow group (862.7±174.0 vs 479.5±65.5 N; P<.01). Biological factors remain to be investigated, but this augmentation method could provide additional strength in patients who are compromised or those with reruptures.

Effect of knee position on gap size following acute Achilles rupture

BACKGROUND

Acute traumatic rupture of the tendoachilles is a common problem. Following a recent Cochrane review, operative treatment has been shown to have a lower re-rupture rate compared with conservative treatment, but is associated with a slightly higher rate of other complications. Debate concerning the method and duration of conservative treatment remains. We aimed to assess the effect of knee position on the gap in acute tendoachilles ruptures.

MATERIALS AND METHODS

Patients with a history and examination consistent with an acute rupture were collected prospectively. They were investigated by the same musculoskeletal consultant radiologist using ultrasonography. Tendon gap was measured with the foot in neutral and full tolerable equinus with the knee both flexed to 90 degrees and fully extended. A pilot study of 10 patients was used to provide data for a power calculation. Following this a total of 25 consecutive patients were recruited for inclusion. A paired Student t-test was used to compare mean differences between the knee flexed/ankle plantarflexed and knee extended/ankle plantarflexed positions on the gap at the rupture site.

RESULTS

A diagnosis of acute tendoachilles rupture was confirmed in all patients and tendon gap was measured with the knee flexed and extended with the ankle either neutral or plantarflexed. This confirmed there was no significant difference in the tendon gap with the knee flexed or extended provided the foot was in full equinus (p>0.05).

CONCLUSION

This study showed that knee position had no significant effect on the tendon gap at the rupture site. This study could have considerable implications on the rationale behind conservative treatment and splinting of acute tendoachilles ruptures with no apparent role for knee flexed immobilization.

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.

Can footwear affect achilles tendon loading?

OBJECTIVE

To investigate the effects of footwear on Achilles tendon tension by directly measuring Achilles tendon tension and dorsiflexion range of motion.

DESIGN

A total of 48 matched pair tests were performed comparing the effects of shoe type (high-top vs low-top) for each shoelace configuration (tied vs untied). These were performed using the Achilles tendons of 4 human cadaver lower extremities that were instrumented with a customized load cell designed to measure tension. The lower extremity was inverted in a custom testing apparatus designed to inertially invoke dorsiflexion of the foot, putting the Achilles tendon in tension.

SETTING

Research laboratory.

PATIENTS

Left and right lower extremities of 2 human cadavers.

INTERVENTIONS

None. Independent variables were shoe type and shoelace configuration.

MAIN OUTCOME MEASURES

Achilles tendon tension and dorsiflexion range of motion.

RESULTS

High-top shoes significantly reduced peak Achilles tendon tension by an average of 9.9% when compared with low-top shoes. Tied laces significantly reduced peak tension for low-top (3.7%) and high-top (12.8%) shoes when compared with untied laces. With tied laces, high-top shoes significantly reduced peak dorsiflexion angle by an average of 7.2% when compared with low-top shoes. Tied laces with high-top shoes significantly reduced peak dorsiflexion angle by an average of 4.7% when compared with untied laces. A P value of 0.05 was determined to be significant.

CONCLUSIONS

This study offers valuable insight that footwear can affect Achilles tendon loading during dorsiflexion.

A Hybrid Method for Computing Achilles Tendon Moment Arm Using Ultrasound and Motion Analysis

In this article, we outline a method for computing Achilles tendon moment arm. The moment arm is computed from data collected using two reliable measurement instruments: ultrasound and video-based motion capture. Ultrasound is used to measure the perpendicular distance from the surface of the skin to the midline of the tendon. Motion capture is used to determine the perpendicular distance from the bottom of the probe to the ankle joint center. The difference between these two measures is the Achilles tendon moment arm. Unlike other methods, which require an angular change in joint position to approximate the moment arm, the hybrid method can be used to compute the moment arm directly at a specific joint angle. As a result, the hybrid method involves fewer error-prone measurements and the moment arm can be computed at the limits of the joint range of motion. The method is easy to implement and uses modalities that are less costly and more accessible than MRI. Preliminary testing using a lamb shank as a surrogate for a human ankle revealed good accuracy (3.3% error). We believe the hybrid method outlined here can be used to measure subject-specific moment arms in vivo and thus will potentially benefit research projects investigating ankle mechanics.

The non-linear relationship between muscle voluntary activation level and voluntary force measured by the interpolated twitch technique

Interpolated twitch technique (ITT) is a non-invasive method for assessing the completeness of muscle activation in clinical settings. Voluntary activation level (VA), measured by ITT and estimated by a conventional linear model, was reported to have a non-linear relationship with true voluntary contraction force at higher activation levels. The relationship needs to be further clarified for the correct use by clinicians and researchers. This study was to established a modified voluntary activation (modified VA) and define a valid range by fitting a non-linear logistic growth model. Eight healthy male adults participated in this study. Each subject performed three sets of voluntary isometric ankle plantar flexions at 20, 40, 60, 80 and 100% maximal voluntary contraction (MVC) with real-time feedback on a computer screen. A supramaximal electrical stimulation was applied on tibia nerve at rest and during contractions. The estimated VA was calculated for each contraction. The relationship between the estimated VA and the actual voluntary contraction force was fitted by a logistic growth model. The result showed that according to the upper and lower limit points of the logistic curve, the valid range was between the 95.16% and 10.55% MVC. The modified VA estimated by this logistic growth model demonstrated less error than the conventional model. This study provided a transfer function for the voluntary activation level and defined the valid range which would provide useful information in clinical applications.

Positional effects of the knee and ankle on the ends of acute Achilles tendon ruptures

Conservative management of acute Achilles tendon ruptures in a plantarflexed short leg cast or functional brace is a viable alternative to surgery. The ideal plantarflexion angle to allow the free ends of the tendon to oppose one another has not been clearly defined. The purpose of this cadaveric study was to define a plantarflexion angle where the free Achilles tendon ends reliably oppose one another. Ten cadaveric legs amputated at the distal femur were obtained. A laceration of the Achilles tendon was made 4 cm above the calcaneal insertion. A joint-spanning external fixator was placed across the knee. With differing degrees of knee flexion (0, 45, and 90 degrees), the diastasis between the free ends of the Achilles tendon was measured as the ankle was moved from 20 degrees of dorsiflexion to 30 degrees of plantarflexion (-20, -10, neutral, 10, 20, and 30 degrees). Regardless of knee flexion angle, the ankle plantarflexion angle where the free ends of the Achilles tendon opposed one another was 28.0 (95% confidence interval: 25.0-33.6) degrees. The ideal ankle angle in which to immobilize patients appears tightly clustered around 28 degrees of plantarflexion.