The role of intraoperative extensor digitorum brevis muscle MEPs in spinal surgery

PURPOSE

Intraoperative muscle motor evoked potentials (m-MEPs) are widely used in spinal surgery with the aim of identifying a damage to spinal cord at a reversible stage. Generally, lower limb m-MEPs are recorded from abductor hallucis [AH] and the tibialis anterior [TA]. The purpose of this work is to study an unselected population by recording the m-MEPs from TA, AH and extensor digitorum brevis (EDB), with the aim of identifying the most adjustable and stable muscles responses intraoperatively.

METHODS

Transcranially electrically induced m-MEPs were intraoperative recorded in a total of 107 surgical procedures. m-MEPs were recorded by a needle electrode placed in the muscle from TA, AH and EDB muscles in the lower extremities.

RESULTS

Overall monitorability (i.e., at least 1 Lower Limb m-MEP recordable) was 100/107 (93.5%). In the remaining 100 surgeries in 3 cases, the only muscle that could be recorded at baseline was one AH, and in other 2 the EDB. Persistence (i.e., the recordability of m-MEP from baseline to the end of surgery) was 88.7% for TA, 89.8% for AH and 93.8% for EDB.

CONCLUSION

In our series, EDB m-MEPs have demonstrated a recordability superior to TA and a stability similar to AH. The explanations may be different and range from changes in the excitability of the cortical motor neuron to the different sensitivity to ischemia of the spinal motor neuron. EDB can be used alternatively or can be added to TA and AH as a target muscle of the lower limb in spinal surgery.

Factors associated with improvement in tibialis anterior weakness due to lumbar degenerative disease

BACKGROUND

The weakness of the tibialis anterior remains to be a controversial topic. There has been no study that used electrophysiological assessment of the function of the lumbar and sacral peripheral motor nerves. The aim is to evaluate surgical outcomes in patients with weakness of the tibialis anterior using neurological and electrophysiological assessments.

METHODS

We enrolled 53 patients. Tibialis anterior weakness was quantified by muscle strength, as assessed using a manual muscle test on a scale of 1 through 5, with scores <5 indicating weakness. Postoperative improvement in muscle strength was classified as excellent (5 grades recovered), good (more than one grade recovered), or fair (less than one grade recovered).

RESULTS

Surgical outcomes for tibialis anterior function were categorized as "excellent" in 31, "good" in 8, "fair" in 14 patients. Significant difference in outcomes were observed depending on diabetes mellitus status, type of surgery, and the compound muscle action potentials amplitudes of the abductor hallucis and extensor digitorum brevis (p < 0.05). Surgical outcomes were classified into two groups, patients with excellent and good outcomes (Group 1) and patients with fair outcome (Group 2). Using the forward selection stepwise method, sex and the compound muscle action potentials amplitudes of the extensor digitorum brevis were identified as significant factors for their positive association with Group 1 status. The diagnostic power of the predicted probability was as high as 0.87 in terms of area under curve of the receiver operating characteristic curve.

CONCLUSIONS

There was a significant correlation between the prognosis of tibialis anterior weakness and sex and the compound muscle action potentials amplitude of extensor digitorum brevis, suggesting that recording the compound muscle action potentials amplitude of extensor digitorum brevis will aid the outcome assessment of future surgical interventions for tibialis anterior weakness.

The reverse flow extensor digitorum brevis flap for dorsal foot defects-A single center study

BACKGROUND

Defects on the dorsum of the foot remain a reconstructive challenge for plastic surgeons. There are very few pedicled flaps that have a reach up to the distal foot and those too with a threat of poor perfusion. Very often distal foot has to be resurfaced with free flap even with small defects. This study describes our experience with the reverse extensor digitorum brevis muscle (EDB) flap for small- to medium-sized defects on the dorsum of the foot.

METHODS

The study was conducted on 12 patients between February 2018 and March 2020 who presented with defects on the dorsum of the foot. The mean age of the patients was 30.8 years and the mean defect size was 20.17 cm². The EDB was applied on 10 male and 2 female subjects and resurfaced with a split thickness skin graft. The donor site was closed primarily.

RESULTS

All flaps survived well. Two patients had small graft loss and 2 partial wound dehiscence of donor site, all of which healed on conservative treatment. Three patients had temporary sensory disturbance which resolved in few weeks.

CONCLUSION

The reverse EDB flap is a reliable flap for the coverage of small- to medium-sized dorsal foot defects. The flap has the advantage of robust vascularity, expendable muscle with little donor site morbidity, an easy to learn technique, short operating time, and acceptable esthetic outcome, and it can be used as the primary option in cases of small to medium dorsal foot defects.

Intrinsic Muscle Flaps for Coverage of Small Defects in the Foot

Exposure of critical structures such as joints, bones, ligaments, and tendons necessitates expeditious closure. The longer these structures remain open to the environment, the higher the risk is for that patient developing osteomyelitis and an amputation. Muscle flaps remain often first choice when dealing with bone infections associated with osteomyelitis, soft tissue infections, and large cavities. Foot defects are a challenge especially in the absence of microsurgical expertise. Intrinsic local flaps of the foot can be an option to cover defects. This article describes local intrinsic muscle flaps for coverage of foot defects.

Safety and pharmacodynamics of a novel recombinant botulinum toxin E (rBoNT-E): Results of a phase 1 study in healthy male subjects compared with abobotulinumtoxinA (Dysport®)

Naturally occurring botulinum toxin (BoNT) serotypes have different pharmacological features of therapeutic and aesthetic interest. This phase 1, double-blind, placebo-controlled study (EudraCT: 2016-002609-20) assessed safety, tolerability and pharmacodynamics (PD) of the first recombinant BoNT serotype E (rBoNT-E) versus abobotulinumtoxinA (Dysport®), administered to extensor digitorum brevis (EDB) of healthy males. Subjects were randomised 3:1 (n = 28) to single ascending rBoNT-E (0.04-3.6 ng) doses or placebo. A further 24 subjects received abobotulinumtoxinA (20, 40, or 70 U) or placebo. PD were assessed using compound muscle action potential (CMAP) amplitude. Demographics were similar between groups. All rBoNT-E doses were well tolerated (no severe treatment-emergent adverse events [TEAEs], serious adverse events, or treatment-related toxicities). Most TEAEs were mild/moderate and treatment-unrelated. rBoNT-E had a faster onset of action (days 1-2 post-injection), greater peak effect (>90% CMAP inhibition), and shorter duration of effect at highest tested doses versus abobotulinumtoxinA (onset of action ≤7 days post-injection; 70% maximal CMAP inhibition). rBoNT-E duration of effect was 2-7 weeks versus >26 weeks for abobotulinumtoxinA. Dose-dependent effects were observed for magnitude and duration of EDB CMAP inhibition, plateauing at 0.9 and 3.6 ng. rBoNT-E demonstrated a good safety profile and a PD profile that may address unmet therapeutic and aesthetic patient needs.

Wasting of Extensor Digitorum Brevis as a Decisive Preoperative Clinical Indicator of Lumbar Canal Stenosis: A Single-center Prospective Cohort Study

Background:

The dilemma in managing patients with low back ache lies in differentiating radiculopathy from lumbar canal stenosis. This has a huge bearing in patients being planned for surgical intervention as underperforming leads to failed back syndrome whereas over-doing leads to instability. There still remains a loophole in clinically diagnosing lumbar canal stenosis.

Aim:

We opt to utilize a simple bedside clinical examination in routinely assessing patients presenting with low back ache in ruling out underlying canal stenosis.

Subjects and Methods:

We performed a prospective study on 120 consecutive patients presenting with low back ache in the spine clinic. Each of them was neurologically examined and thoroughly assessed for wasting of extensor digitorum brevis (EDB) muscles. These were then correlated with the radio-imaging and the intraoperative findings.

Results:

Lumbar canal stenosis was mostly observed in the age group of 50–60 years. Diagnosis for L3/4 canal stenosis was made in 44/120 (36.6%), L5-S1 in 52/120 (43.3%), and L3/L4/L5 level in 48/120 (40%) of patients. EDB wasting was seen unilaterally in 72/120 (60%) and bilaterally in 36/120 (30%) of the study group.

Conclusion:

This study appraises the clinical implication of observing for the wasting of EDB muscle so as to aid in the diagnosis of lumbar canal stenosis. This simple bedside clinical pearl can help us in predicting the need of further imaging studies and also in taking right therapeutic decision.

Analysis of the morphometry and variations in the extensor digitorum brevis muscle: an anatomic guide for muscle flap and tendon transfer surgical dissection

The extensor digitorum brevis muscle (EDB) is a practical option for use as an island flap or free flap when reconstructing soft tissue defects in the ankle as well as in the entire lower limb. It is frequently used to correct crossover toe deformity and other painful toe disorders. We evaluated the morphometry of the EDB in 44 formalin-fixed limbs. Length and width of the muscles were measured. Surface area was calculated as the product of length and width of the muscle. The length of each tendon was also measured from its origin to the point of distal attachment. Presence of any additional tendons was noted. Mean length, width, and surface area of the muscle were 7.39±0.71 cm, 4.1±0.37 cm, and 30.5±4.78 cm(2) on the right side and 7.2±0.84 cm, 3.9±0.37 cm, and 28.4±5.35 cm(2) on the left side, respectively. Morphometry of the tendons revealed that the tendon of the great toe had the highest mean length (9.5 cm) and the tendon of the fourth toe had the lowest mean length (6.3 cm). Four of the limbs studied (9.09%) had only three tendons. Three of the limbs studied (6.81%) had five tendons, and in one exceptional case (2.27%), six tendons were detected. These observations have significant value and are applicable to plastic and orthopedic surgery.