Pressure pain perception in the diabetic Charcot foot: facts and hypotheses

Buccal Nerve Trunk Block Anesthetizes the Buccal Mucosa Beyond the Papilla of the Parotid Duct

PURPOSE

The limited area of anesthesia of the buccal mucosa with concomitant conventional buccal nerve block (conventional BNB) may be involved in failed inferior alveolar nerve block (IANB). The aims of this study were to examine the extent of anesthesia by buccal nerve trunk block (BNTB) and compare the success rates of IANB with BNB.

METHODS

This prospective parallel-group randomized single-blinded clinical trial included patients scheduled for removal of a mandibular third molar at the Nippon Dental University Hospital between September 2021 and March 2022. The primary predictor variable was the approach for BNB (BNTB vs conventional BNB). The primary outcome was the extent of tactile sensory loss and anesthesia of the buccal mucosa. The secondary outcomes included onset time and duration of BNBs and the success rate of the IANB with concomitant BNB for third molar extraction, assessed by the proportions of intraoperative pain perception and supplemental infiltration anesthesia. The other study variables were sex, age, and injection side. Comparisons were analyzed by Fisher's exact test or the Mann-Whitney U test. The P value was set to .05.

RESULTS

A total of 38 patients (14 male, 24 female) with a mean age of 28.9 years (range, 18 to 67 years) were enrolled, with 19 patients each in the BNTB group and conventional BNB group. The effective tactile sensory loss rates at ∼5 mm above the height of the papilla of the parotid duct of the premolar and molar regions were greater following BNTB (71 and 95%, respectively) than following conventional BNB (37%; P < .01 and 58%; P < .01, respectively). The proportions of intraoperative pain perception of the BNTB group and the conventional BNB group were 10 and 42% (P = .06), respectively, and those of supplemental infiltration anesthesia were 5 and 26% (P = .18), respectively.

CONCLUSIONS

BNTB provided a wider extent of anesthesia of the buccal mucosa than conventional BNB and may improve the anesthesia success of IANB for removal of mandibular third molars.

Inferior Alveolar Nerve Block Using the Anterior Technique to Anesthetize Buccal Nerve and Improve Anesthesia Success Rates for Third Molar Extraction: A Randomized Controlled Trial and Magnetic Resonance Imaging Evaluation

PURPOSE

The lack of anesthesia to the buccal nerve and an insufficient volume of anesthetic have been reported to be responsible for failed inferior alveolar nerve blocks (IANBs) using the Halsted approach (conventional IANB). We aimed to determine the extent of anesthesia in the buccal nerve innervation area and evaluate the anesthetic efficacy of injecting a larger volume of anesthetic during IANB using the anterior approach (anterior technique) in the clinical setting and with magnetic resonance imaging (MRI) analysis.

PATIENTS AND METHODS

The prospective randomized controlled trial included patients scheduled for removal of a mandibular third molar. The primary predictor variables were the approach for IANB (anterior technique vs conventional IANB) and anesthetic dose (1.8 vs 2.7 mL). The primary outcome variables were the extent of anesthesia and the anesthesia success rate, defined as completion without additional anesthesia. The secondary outcome variable was the anesthetic drug distribution related to the pterygomandibular space measured on T2-weighted MRI scans. Statistical independence of the anesthesia success rate among the primary predictor variables was tested with statistical significance set at P ≤ .05.

RESULTS

A total of 108 patients and 10 volunteers were enrolled in the clinical and MRI studies, respectively. Anesthesia of the buccal nerve was evident in patients receiving the anterior technique with 2.7 mL of anesthetic. The success rate of the anterior technique with 2.7 mL of anesthetic (96%) was greater than that with 1.8 mL of anesthetic (67%; P = .0113), and increasing the dose had no effect on the efficacy of conventional IANB (78% vs 81%; P = 1.000). The MRI study showed that the anesthetic was distributed over the anterior surface of the temporalis tendon and in the pterygomandibular space after the anterior technique.

CONCLUSIONS

Anesthesia of the buccal nerve using the anterior technique with 2.7 mL of anesthetic solution might contribute to increasing the success rate of anesthesia for removal of mandibular third molars.

Corneal confocal microscopy detects severe small fiber neuropathy in diabetic patients with Charcot neuroarthropathy

AIMS/INTRODUCTION

The aim of the present study was to identify the extent of small fiber neuropathy in diabetic patients with Charcot neuroarthropathy (CN).

MATERIALS AND METHODS

A total of 20 patients with CN were compared with 20 age- and diabetes duration-matched patients with type 2 diabetes and 20 age-matched control participants. All patients underwent corneal confocal microscopy with quantification of corneal nerve morphology and assessment for vibration perception threshold, and a subset of patients with CN underwent assessment of sudomotor function and neuropathic pain.

RESULTS

In patients with CN compared with type 2 diabetes patients and control participants, there was a significant reduction in corneal nerve fiber density (14.94 ± 8.23 vs 23.86 ± 7.71, P = 0.004 vs 34.84 ± 9.13, P < 0.001), corneal nerve branch density (18.61 ± 16.7 vs 41.62 ± 22.67, P = 0.032 vs 76.47 ± 38.44, P < 0.001) and corneal nerve fiber length (8.40 ± 4.83 vs 14.87 ± 4.76, P = 0.001 vs 21.24 ± 6.48, P < 0.001), electrochemical skin conductance on the feet (20.57 ± 13.99 vs 61.50 ± 22.26, P < 0.001 vs 76.23 ± 12.01, P < 0.001) and hands (30.86 ± 18.10 vs 61.13 ± 19.14, P = 0.001 vs 68.31 ± 11.96, P < 0.001), and a significant increase in the vibration perception threshold in the feet (38.46 ± 15.10 vs 14.15 ± 10.25, P < 0.001 vs 7.75 ± 4.01, P < 0.001).

CONCLUSIONS

Patients with diabetes and CN have severe large and particularly small fiber neuropathy.

Conventional deep pressure algometry is not suitable for clinical assessment of nociception in painless diabetic neuropathy

Background

In diabetic persons with painless neuropathic foot ulceration, foot skin was found to be insensate to noxious pinprick stimulation (stimulation area less than 0.05 mm²), while compression of deep subcutaneous foot tissues by Algometer II^® (stimulation area 1 cm²) could evoke a deep dull aching. To elucidate this discrepancy, the Algometer II stimulation technique was critically reviewed by varying probe sizes and anatomical sites in the same study population 3 years later.

Methods

Ten control subjects without neuropathy and 11 persons with painless diabetic neuropathy (PLDN, seven of whom with diabetic foot syndrome, i.e., past painless foot ulcer, or inactive Charcot arthropathy) were re-examined using Algometer II. Deep pressure pain perception threshold (DPPPT) was measured in random sequence with stimulation areas of 0.5 cm², 1 cm², and 2 cm² (separated by 5 min intervals), at the plantar forefoot, the instep, and the hindfoot of both legs.

Results

In the control and PLDN groups, median DPPPTs differed significantly between stimulation areas (highest with 0.5 cm², intermediate with 1 cm², lowest with 2 cm²; p<0.001), and varied moderately by anatomical site. Between-group differences were relatively small. Results of the 1 cm² assessments repeated 3 years apart were similar.

Conclusions

Algometer II readings represent spatial summation of low-threshold pressure-receptor rather than of high-threshold nociceptor stimulation and are, thus, unhelpful for assessing PLDN. Reproducibility of the measurements is good.

[Concept of plantarization for toe correction in diabetic foot syndrome]

OBJECTIVE

Elimination of plantarization of the tip of the toe and torsion of digit 1 (D1) or D5 using percutaneous tenotomy of the flexor hallucis longus (FHL) - or the flexor digitorum longus (FDL) muscle.

INDICATIONS

Flexible, in some cases also fixated hyperflexion misalignment and torsion misalignment of the distal phalanx of the toe with plantarization of physiologically non-loaded bearing parts of the toes in patients with diabetic foot syndrome (neuropathy).

CONTRAINDICATIONS

Critical limb ischemia.

SURGICAL TECHNIQUE

Percutaneous tenotomy of the FHL or FDL tendons using the minimally invasive lancet technique without the use of a tourniquet while the tendon is flexed by causing hyperextension of the distal phalanx and simultaneous extension of the distal interphalangeal (DIP) or interphalangeal (IP) joints.

POSTOPERATIVE MANAGEMENT

Immediate full weight-bearing mobilization in sufficiently wide protective footwear with customized cushioning or a diabetes-adapted foot bed, follow-up in initially frequent intervals (2-4 per week) in order to track the development of the transfer lesions. In the case of existing wounds, more frequent visits and relief of the wounds using a post-operative shoe are required. No thrombosis prevention with full weight-bearing is necessary.

RESULTS

In 138 patients with diabetic foot syndrome with polyneuropathy, of which 90 were men (65.2 %) and 48 were women (34.8 %) with a median age of 65.1 years, a total of 291 toe operations with tenotomy of the FHL- or FDL-tendon were performed. Patients were either acutely affected by apical toe lesions (92.1 %) or showed an increased risk of ulcer formation (7.9 %). The median time to closing of the wound was 13 days. It was longer with higher Wagner stages. Of the surgically treated toes 3.1 % were affected by nosocomial infections. At the 1‑year follow-up 92.4 % of the patients did not show pathological results of the operated toe. Recurrence of the DFS occurred mostly during the first 6 months postoperatively. In the first year postoperatively 68.1 % of the patients remained in remission. Of the toes with Wagner grade 0, 93.7 % were free of local recurrence during the entire monitoring period and 72.2 % of the operated toes with Wagner grade 3. Within the first 1.5-8.5 months 13 % of the patients were affected by transfer lesions.

Charcot foot syndrome

Charcot foot syndrome is an uncommon complication of diabetes but is potentially devastating in its consequences. Outcome is made worse by widespread professional ignorance leading to delayed diagnosis, but it is also hampered by lack of understanding of its causes and lack of treatments with proven effectiveness, other than offloading. There remains a desperate need for studies into its causes as well as comparative audit and trials designed to determine the best treatment for this difficult condition. Such work can probably only be effectively carried out through the establishment of multicentre networks. Nevertheless, improved understanding in recent years of the likely role of inflammatory pathways has raised awareness of the multiple ways in which the effects of neuropathy may be manifest in the development of the Charcot foot. This awareness is also leading to the realization that similar processes may conceivably contribute to the refractoriness of other foot diseases in diabetes, including both chronic unhealing ulcers and osteomyelitis.

Effect of painless diabetic neuropathy on pressure pain hypersensitivity (hyperalgesia) after acute foot trauma

Introduction and objective

Acute injury transiently lowers local mechanical pain thresholds at a limb. To elucidate the impact of painless (diabetic) neuropathy on this post-traumatic hyperalgesia, pressure pain perception thresholds after a skeletal foot trauma were studied in consecutive persons without and with neuropathy (i.e. history of foot ulcer or Charcot arthropathy).

Design and methods

A case–control study was done on 25 unselected clinical routine patients with acute unilateral foot trauma (cases: elective bone surgery; controls: sprain, toe fracture). Cases were 12 patients (11 diabetic subjects) with severe painless neuropathy and chronic foot pathology. Controls were 13 non-neuropathic persons. Over 1 week after the trauma, cutaneous pressure pain perception threshold (CPPPT) and deep pressure pain perception threshold (DPPPT) were measured repeatedly, adjacent to the injury and at the opposite foot (pinprick stimulators, Algometer II^®).

Results

In the control group, post-traumatic DPPPT (but not CPPPT) at the injured foot was reduced by about 15–25%. In the case group, pre- and post-operative CPPPT and DPPPT were supranormal. Although DPPPT fell post-operatively by about 15–20%, it remained always higher than the post-traumatic DPPPT in the control group: over musculus abductor hallucis 615 kPa (kilopascal) versus 422 kPa, and over metatarsophalangeal joint 518 kPa versus 375 kPa (medians; case vs. control group); CPPPT did not decrease post-operatively.

Conclusion

Physiological nociception and post-traumatic hyperalgesia to pressure are diminished at the foot with severe painless (diabetic) neuropathy. A degree of post-traumatic hypersensitivity required to ‘pull away’ from any one, even innocuous, mechanical impact in order to avoid additional damage is, therefore, lacking.