Ultrasound Guidance for Palmar and Digital Injections: A Cadaveric Study
Introduction: Collagenase injection can be an alternative to surgical release of Dupuytren disease. Real-time imaging can potentially improve the reliability and accuracy of the enzymatic release. The aim of the study was to determine whether the use of ultrasound guidance improves accuracy of injections placed in the palm and digits in the manner used in the setting of Dupuytren disease. Methods: 20 matched-pair cadaveric hand specimens were injected with methylene blue in the ring and small fingers at a total of 4 sites per specimen in the manner typical for collagenase injection. The specimens were injected without (control) or with ultrasound (US) guidance and the rate of erroneous site of dye injection was identified and compared using specimen dissections. Results: 4 (10%) injections in the control group were placed in error, whereas all US-guided injection were made correctly. However, the results did not yield statistically-significant difference. Discussion: The use of US guidance has potential to enhance the accuracy of hand injections, although a large sample is required to demonstrate statistically significant effects. Level of Evidence: Experimental cadaveric study. Keywords: Dupuytren disease; Collagenase release; Musculoskeletal ultrasound imaging.
Dupuytren disease (DD) is a fibromatosis of the palmar and digital fascia that forms pathologic nodules and cords and may cause contractures of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of the fourth and fifth digits. Treatment options for contractures include percutaneous aponeurotomy for milder cases and open fasciectomy for more severe forms . Collagenase injection therapy received FDA approval in 2010 and works via local enzymatic degradation of collagen peptide bonds within the cord structures present directly beneath the skin of the affected palm or digit. The patient typically returns to the office for follow up 1 to 2 days later for cord manipulation . Two multi-center, double-blind, randomized clinical trials evaluating the safety and efficacy of collagenase injection therapy for DD, the CORD I and CORD II trials of 2009 and 2010, enrolled over 1,000 patients with contractures over 20 degrees involving the MCP or PIP joints of the fourth or fifth digits. Collagenase injections were more effective than placebo in correcting contractures to within 5 degrees of full extension. The majority of complications reported were temporary and minor reactions; however, flexor tendon rupture was reported within 1 week in 3 patients (0.3%) [3,4]. After these trials concluded, a few additional cases of flexor tendon rupture have been reported. One involved rupture of both flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons near the small finger MCP joint. In this case, the tendons were repaired primarily . Another involved small-finger FDP rupture near the PIP joint requiring staged reconstruction . Tendon ruptures in these settings are believed to be caused by inadvertent exposure of the underlying tendons to the injected solution, which can render them irreparable due to intrinsic damage from enzymatic degradation. Placing the needle tip deep to the cord structure during the injection places the tendons at risk, although the amount of exposure necessary to cause rupture is unclear. Whether needle penetration of the tendon sheath or tendon proper during the injection predisposes rupture, or whether rupture can occur secondarily via diffusion of the solution despite a well-placed injection, is not known. Key technical aspects of the injection, including avoiding injection near the small finger PIP joint flexion crease and being extremely careful about depth of needle placement in general during the procedure, have been emphasized to minimize this risk. One potential solution is the use of ultrasound guidance to ensure accurate needle placement for the injections. The development of small transducers that provide sufficient resolution of small and superficial structures has made this possible and provides additional diagnostic benefit. Transducers with a frequency of greater than 12MHz in particular have been recommended for hand and wrist applications, and there is some evidence which shows that their use increases accuracy for routine hand and wrist injections [7-9]. For DD, evidence supporting the utility of ultrasound remains limited. The purpose of the present study is to determine whether ultrasound guidance improves injection accuracy in this setting. MATERIALS & METHODS Study Design Palmar and digital injections were performed into the ring and small fingers of 20 matched pair cadaveric hand specimens. All injections were performed by a fellowship-trained hand orthopedic surgeon familiar with collagenase injection technique and the use of ultrasound for hand and wrist diagnostic purposes. Four injections were performed in each hand specimen, for a total of 80 injections performed in the study. For each matched pair of specimens, 1 specimen was randomly selected to receive the 4 injections with ultrasound guidance, and the other was selected to receive the 4 injections without ultrasound (ie, blind technique) as a control. Injection Technique The technique from the Xiaflex® manufacturer’s dosing and administration instructions was followed. 0.25mL of methylene blue dye was injected into the palmar fascia between the distal palmar and palmar-digital creases, and 0.20 mL dye was injected into the digital fascia between the palmar-digital crease and the PIP joint flexion crease. Injections were performed at both the ring and small fingers. A 1-mL syringe with 0.01-mL graduations and a 27-gauge 1/2-inch needle were used for the injections. For the blind injections, palpation of the area preceded needle insertion, and the finger was gently passively manipulated to ensure the needle tip was not in the tendon substance. For the ultrasound-guided injections, an ultrasound machine (GE LOGIQ™ P9) with a 15-MHz hockey stick ultrasound transducer (GE L8-18i-RS) was used, verifying the location of the echogenic needle tip in relation to the flexor tendons and sheath using sagittal and axial probe positioning prior to injection. Data Interpretation Immediately before and after the injections, the specimens were scanned as pairs with magnetic resonance imaging (MRI) (Siemens Verio 3-Tesla model) using axial and sagittal T2-weighted sequences with fat suppression. The MRI scans were interpreted by author US, a musculoskeletal fellowship-trained radiologist. At each injection site, the pre- and post-injection images were compared to determine whether fluid infiltration of the sheath had occurred following injection (Figure 1). The scans were interpreted blinded, without knowledge of which specimens were in each group.