Appropriate depth of needle insertion during rhomboid major trigger point block.

Area of Science:

• Musculoskeletal ultrasonography
• Anatomy
• Pain management

Background:

• Rhomboid major muscle trigger points are a common cause of shoulder and upper back pain.
• Accurate needle insertion depth is vital for effective trigger point injections and avoiding complications.

Purpose of the Study:

• To investigate and define an appropriate needle insertion depth for trigger point injections into the rhomboid major muscle.
• To establish a safe margin for needle placement based on ultrasonographic measurements.

Main Methods:

• Ultrasonography was used to measure skin-to-rhomboid major muscle (SM) and skin-to-rib (SB) distances in 62 patients.
• Patients were categorized into three groups based on body mass index (BMI): underweight/normal (<23 kg/m²), overweight (23–25 kg/m²), and obese (≥25 kg/m²).
• A safe margin for needle insertion was calculated as the range between mean + 1 SD of SM and mean - 1 SD of SB.

Main Results:

• In underweight/normal BMI individuals, SM was 1.2±0.2 cm, SB was 2.1±0.4 cm, and the safe margin was 1.4–1.7 cm.
• In obese individuals, SM was 1.8±0.3 cm, SB was 2.7±0.5 cm, and the safe margin was 2.1–2.2 cm.
• A safe margin could not be reliably calculated for the overweight BMI group due to high variability in SB measurements.

Conclusions:

• Ultrasonographic measurements provide valuable data for determining safe needle insertion depths for rhomboid major muscle injections.
• BMI influences the anatomical distances, necessitating adjusted needle depths for effective and safe trigger point injections.
• Establishing standardized depths based on BMI can enhance the efficacy and safety of rhomboid major muscle injections, minimizing potential complications.