Ultrasound assessment of medial crural cutaneous nerve and infrapatellar branch and of the saphenous nerve: establishing a safety zone for preventing nerve injury in knee surgery and injections.

PURPOSE: Our study aimed to illustrate the positional relationship of the two branches of the saphenous nerve: the infrapatellar branch of the saphenous nerve (IPBSN) and medial crural cutaneous nerve (MCCN), as well as the anatomical landmarks using high-resolution ultrasound (HRUS) to help prevent iatrogenic nerve injury. METHODS: We used HRUS to explore the positional relationships among the anatomical landmarks, IPBSN, and MCCN in 40 knees of 20 participants. The distances from these branches to key reference points were recorded. Using the ultrasound caliper mode, we measured the depth from the skin surface to the nerves at four distinct points. RESULTS: The average distances between IPBSN and medial border of patella (MBP) and IPBSN and medial border of patellar ligament (MBPL) were 47 ± 7 mm and 42 ± 9 mm, respectively. MCCN showed mean distances of 94 ± 9 mm and 96 ± 9 mm to MBP and MBPL, respectively. The mean distance from the upper edge of pes anserine to IPBSN at the patellar apex (PA) level was 24 ± 10 mm and to MCCN was 34 ± 9 mm. CONCLUSION: We used high-resolution ultrasound to evaluate IPBSN and MCCN and their positions relative to anatomical landmarks. The study results offer valuable insights into the course of these nerves, which can help establish a safety zone to prevent accidental nerve injuries during knee surgeries and injections.

Risk assessment of dorsal scapular nerve injury in the medial scapular area associated with upper extremity position: An ultrasonographic study.

INTRODUCTION/AIMS: Injuries to the dorsal scapular nerve (DSN) in the interscapular region are relatively uncommon. Physicians may therefore underestimate the risk of damage to the DSN during procedures. The aim of this study was to identify the topographic position of the DSN in the interscapular region and to identify injection positions for the upper extremities that minimize the risk of damage to the DSN during procedures. METHODS: The positional relationships between the DSN and scapula were quantified by ultrasonography in 46 healthy volunteers. The distances between the medial scapular line and DSN and the DSN depths from the surface in Zones 1 (the superior angle), 2 (the scapular spine), and 3 (between the scapular spine and inferior angle) were measured in the anatomical and contralateral shoulder touch positions (positions 1 and 2, respectively). RESULTS: The DSN was located further away from the medial border of the scapula and closer to the skin in position 2 than in position 1. The horizontal distance of the DSN in Zone 2 differed significantly between the two positions (0.85 ± 0.38 vs 1.23 ± 0.38, P < .001). The results suggest a safe area as just medial to the medial scapular border in Zone 2 in position 2. The safety margin should be considered at least 1.5 cm medial to the medial border of the scapula in Zone 3 in position 1. DISCUSSION: Performing invasive procedures in the interscapular region, appropriate individualized positioning may reduce the risk of DSN injury.

Ultrasonographic Assessment of the Safe Zone for Carpal Tunnel Intervention: A Comparison Between Healthy Individuals and Patients With Carpal Tunnel Syndrome.

OBJECTIVE: To compare transverse and longitudinal safe zones using ultrasonography between healthy individuals and patients with carpal tunnel syndrome (CTS). METHODS: This was a prospective observational case-control study. Forty wrists from 20 healthy individuals and 40 wrists from 24 patients with CTS were examined. Patients with CTS were classified into three groups (mild, moderate, and severe CTS) based on electrodiagnostic findings. Using ultrasonography, we measured the distance between the median nerve and ulnar vessels to identify the transverse safe zone, and between the distal flexor retinaculum and superficial palmar artery arch to identify the longitudinal safe zone. RESULTS: The transverse and longitudinal safe zones were significantly different between participants with CTS and those without CTS. The transverse safe zone significantly differed between the mild and severe CTS groups, while the longitudinal safe zone was not significantly different between the groups. The cross-sectional area of the median nerve negatively correlated with the transverse and longitudinal safe zones. CONCLUSION: Transverse and longitudinal safe zones were narrower in patients with CTS than in the healthy group. A significant difference was observed between patients with mild CTS and those with severe CTS. Furthermore, the cross-sectional area of the median nerve was directly proportional to the degree of narrowing of the transverse and longitudinal safe zones.

Risk Assessment of Injury to Palmar Cutaneous Branch of the Median Nerve Using High-Resolution Ultrasound.

OBJECTIVE: To evaluate the relationship between the palmar cutaneous branch of median nerve (PCBMN) and surrounding anatomical structures by using high-resolution ultrasound (HRUS) to assess the risk of PCBMN injury. METHODS: The PCBMN course and the characteristics of bilateral distal forearms and wrists of 30 healthy volunteers were identified. The distance between PCBMN and other anatomical structures at three different levels along its course were measured using HRUS. Moreover, the depth of PCBMN from skin and its cross-sectional area (CSA) were measured. RESULTS: HRUS showed the PCBMN in all subjects. PCBMN branched off from the radial aspect of the median nerve (MN) at 4.69±0.89 cm proximal to the bistyloid line (BSL) and extended radially toward the flexor carpi radialis (FCR) tendon. PCBMN was within the ulnar edge of FCR tendon sheath, and became more superficial and perforated the antebrachial fascia between the FCR tendon laterally and the palmaris longus (PL) tendon medially. PCBMN was located at 4.08±0.72 mm on the ulnar aspect of the FCR tendon and 4.78±0.36 mm radially on the PL tendon at BSL. At the distal wrist crease level, the PCBMN was located at 5.68±0.58 mm on the ulnar side of the FCR tendon. The PCBMN depth from skin at BSL and its branching point was 1.92±0.41 and 7.95±0.79 mm, respectively. The PCBMN CSA was 0.26±0.15 mm2 at BSL. CONCLUSION: HRUS can be used to identify PCBMN and its relationship with other anatomical structures. Our data can be used to predict PCBMN location, and prevent complications associated with invasive procedures involving the wrist.

Carpal Tunnel Syndrome Assessment With Ultrasonography: A Comparison Between Non-diabetic and Diabetic Patients.

OBJECTIVE: To investigate the diagnostic value of cross-sectional area (CSA) and wrist to forearm ratio (WFR) in patients with electro-diagnosed carpal tunnel syndrome (CTS) with or without diabetes mellitus (DM). METHODS: We retrospectively studied 256 CTS wrists and 77 healthy wrists in a single center between January 1, 2008 and January 1, 2013. The CSA and WFR were calculated for each wrist. Patients were classified into four groups according to the presence of DM and CTS: group 1, non-DM and non-CTS patients; group 2, non-DM and CTS patients; group 3, DM and non-CTS patients; and group 4, DM and CTS patients. To determine the optimal cut-off value, receiver operating characteristic (ROC) curve analysis was performed. RESULTS: The CSA and WFR were significantly different among the groups (p<0.001). The ROC curve analysis of non-DM patients revealed CSA ≥10.0 mm2 and WFR ≥1.52 as the most powerful diagnostic values of CTS. The ROC curve analysis revealed CSA ≥12.5 mm2 and WFR ≥1.87 as the most powerful diagnostic values of CTS. CONCLUSION: Ultrasonographic assessment for the diagnosis of CTS requires a particular cut-off value for diabetic patients. Based on the ROC analysis results, improved accurate diagnosis is possible if WFR can be applied regardless of presence or absence of DM.