Biomechanical consequences of adding plantar fascia release to metatarsal osteotomies: Changes in forefoot plantar pressures

Biomechanical Comparison of Fiber Tape Device Versus Transarticular Screws for Ligamentous Lisfranc Injury in a Cadaveric Model

BACKGROUND

The preferred method of fixation and surgical treatment for ligamentous Lisfranc injuries is controversial. Transarticular screws, bridge plating, fusion, and flexible fixation have been described, yet none have demonstrated superiority. Furthermore, screw fixation and plating often require secondary surgery to remove implants, leading surgeons to seek alternative fixation methods.

PURPOSE

To compare transarticular screws and a fiber tape construct under a spectrum of biomechanical loads by evaluating the diastasis at 3 joints in the Lisfranc complex.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight matched pairs of fresh, previously frozen lower extremity cadaveric specimens were fixed with either 2 cannulated transarticular crossed screws or a fiber tape construct with a supplemental intercuneiform limb. The diastasis between bones was measured at 3 midfoot joints in the Lisfranc complex: the Lisfranc articulation, the second tarsometatarsal joint, and the intercuneiform joint. Measurements were obtained for the preinjured, injured, and fixation conditions under static loading at 50% donor body weight. Specimens then underwent cyclic loading performed at 1 Hz and 100 cycles, based on 100-N stepwise increases in ground-reaction force from 100 to 2000 N, to simulate postoperative loading from the partial weightbearing stage to high-energy activities. Failure of fixation was defined as diastasis ≥2 mm at the Lisfranc articulation (second metatarsal-medial cuneiform joint).

RESULTS

There were no significant differences in diastasis detected at the Lisfranc articulation or the intercuneiform joint throughout all loading cycles between groups. All specimens endured loading up to 50% body weight + 1400 N. Up to and including this stage, there were 2 failures in the cannulated transarticular crossed-screw group and none in the fiber tape group.

CONCLUSION

The fiber tape construct with a supplemental intercuneiform limb, which does not require later removal, may provide comparable biomechanical stability to cannulated transarticular crossed screws, even at higher loads.

CLINICAL RELEVANCE

Ligamentous Lisfranc injuries are common among athletes. Therefore, biomechanical evaluations are necessary to determine stable constructs that can limit the time to return to play. This study compares the biomechanical stability of 2 methods of fixation for ligamentous injury through a wide spectrum of loading, including those experienced by athletes.

Biomechanical Comparison of Fibertape Device Repair Techniques of Ligamentous Lisfranc Injury in a Cadaveric Model

BACKGROUND

Lisfranc ligamentous injuries are complex, and their treatment, along with the preferred method of fixation, is controversial. Implementing a flexible synthetic augmentation device (fibertape) has been described as an alternative to traditional screw fixation. This biomechanical study evaluated two fibertape devices with interference screw fixation: InternalBrace, and InternalBrace with supplementary intercuneiform stabilization.

METHODS

The diastasis and relative angular displacement between bones were measured at three midfoot joints in the Lisfranc articulation. Measurements were obtained for the pre-injured, injured, and post-fixation stages under static loading. Specimens then underwent stepwise increases in cyclic loading performed at 1 Hz and 100 cycles, at 100 N ground reaction force intervals from 500 to 1200 N to simulate postoperative loading, and then up to 1800 N to simulate high loads. Failure of fixation was defined as diastasis greater than 2 millimeters at the second-metatarsal - medial-cuneiform joint.

RESULTS

InternalBrace specimens demonstrated failures in 3 of 9 (33%) specimens at cyclic loads of 1000 N. Conversely, InternalBrace with Supplementary Limb specimens had 1 failure at 1200 N. The difference in diastasis at the second metatarsal-medial cuneiform joint was statistically significant between the two groups at higher loads of 1600N (p = 0.019) and 1800N (p = 0.029).

CONCLUSION

The use of InternalBrace for ligamentous Lisfranc injuries appears to provide a biomechanically viable alternative for withstanding early postoperative protected weight bearing. Furthermore, the use of a supplementary limb in addition to the InternalBrace fibertape fixation method appears to enhance its biomechanical efficacy.

Biomechanical Evaluation of Spring Ligament Augmentation With the FiberTape Device in a Cadaveric Flatfoot Model

BACKGROUND

The structural importance of the spring ligament complex in arch stability has been described. Furthermore, the pathology of this complex is often noted in patients with posterior tibial tendon dysfunction. The purpose of this biomechanical study was to evaluate spring ligament repair alone versus augmentation with the FiberTape device in a cadaveric flatfoot model.

METHODS

Eight paired, below-the-knee, cadaveric specimens underwent flatfoot creation and reconstruction. The experimental group received augmentation with FiberTape (InternalBrace). After potting, specimens were loaded statically to measure talonavicular contact pressures and flatfoot correction. Cyclic loading was performed in a stepwise fashion. Loading was performed at 1 Hz and 100 cycles, at 100-N intervals from 500 to 1800 N, with the Achilles tendon also loaded to simulate weightbearing in the postoperative period.

RESULTS

Control specimen analysis demonstrated failures of 8 of 8 (100%) spring ligament suture repairs, occurring through suture cut-through (5 specimens), suture fatigue and elongation (2), or knot failure (1). One of 8 (12.5%) FiberTape-augmented repairs failed after cyclic loading. The difference in number of repair failures was statistically significant between the 2 groups ( P = .0014). Analysis revealed that at forces of 1600 N ( P = .03) and 1700 N ( P = .02) there were statistically significant differences between the FiberTape-augmented group and the control group, with a greater collapse in the lateral Meary talo-first metatarsal angle in the controls. There was no significant difference or abnormal increase in contact pressures of the talonavicular joint in both groups.

CONCLUSION

FiberTape augmentation of the spring ligament appears biomechanically safe and effective under cyclic loading.

CLINICAL RELEVANCE

Spring ligament augmentation with this device may be another biomechanically safe and reasonable treatment modality for surgeons during flatfoot reconstruction. It is possible that early protected weightbearing after these procedures may be performed.

Anatomical variations of the plantar fascia's origin with respect to age and sex-an MRI based study

The plantar fascia (PF) plays a significant role in ankle movement and anatomical variations of this structure may significantly alter the biomechanical properties of the foot and lower extremity. The aim of this study was to evaluate the changes of the PF's origin point on the calcaneus (CB), and whether these changes are dependent on age and sex. Two independent observers evaluated two hundred and two foot and ankle MRIs and the following measurements was performed: (A) horizontal length of the AT insertion into the posterior aspect of the CB, (B) horizontal length of the CB and (C) horizontal distance from the most anterior point of the CB to the most posterior part of the PF. Statistical analysis was performed with the results obtained to evaluate both sex and age differences. Based on our results, we observed that: (1) changes of the PF's origin point on the CB is independent of age and sex and (2) the continuity between the PF and AT decreases during aging as a result from changes in the AT's insertion point into the CB. This study concludes that the PF's origin point does not change with respect to age or sex, but the continuity between the PF and AT decreases during aging. Knowledge regarding the biomechanical influences caused by changes in the relationship between the AT and PF may be important in terms of treatment and prophylaxis of both PF and AT pathologies. Clin. Anat. 32:597-602, 2019. © 2019 Wiley Periodicals, Inc.