Surgeon-performed Ultrasound in Flexor Tendon Injury Management: A Practical Guide

Surgeon-performed ultrasound has become a valuable tool in our hand surgery practice. Just like we use fluoroscopy to see and manage fractures in our clinic, ultrasound has enabled us to rapidly evaluate flexor tendons and help in preoperative planning. Surgeons usually find that learning the skill of ultrasound to evaluate flexor tendons is relatively easy because they are so familiar with hand anatomy and pathology that they see every time they operate. Videos available on the internet and in articles like this one enable surgeons and hand therapists to learn these skills at home without the expense of attending courses in person.1–4 The improved cost, access, and portability of ultrasound probes have all made it much easier for surgeons to start doing their own ultrasound. A good place to start is using one of the hospital probes to examine surgeon hand anatomy. Surgeons can use either a handheld probe attached to a smartphone, or a larger nonportable device. For flexor tendon injuries in the hand and forearm, the higher the frequency of the probe, the better one can see details because these structures are superficial. The ultrasound view is as thin as a credit card; so keeping the probe moving will give a better three-dimensional view of the anatomy. Tilting the probe back and forth and side to side helps see the tendons and bones better. Start by looking at a normal finger in the patient’s hand to familiarize yourself with this patient’s anatomy. Our first video demonstrates normal flexor tendon anatomy in the finger and thumb. (See Video 1 [online], which shows ultrasound examination of normal FPL, FDP, and FDS tendons in both axial and sagittal views.) Begin by identifying the easily visible bones of the phalanges and metacarpals from distal to proximal. The volar plates and the joints are also quick to find. The flexor sheath is just volar to the bones and volar plates. The empty sheath will be black with blood or serum.1,2 You can identify the distal white stump of the tendon by seeing it move when you passively flex and extend the DIP or PIP joints. The distal passively moving end of the tendon will come in and out of view in the black empty sheath. The proximal ends of the tendons are easily identified by asking the patient to actively flex and extend the finger or thumb. The tendons actively come in and out of view in the black space of the empty sheath. Like performing X-rays in two views, examine the tendons both in the axial (cross section, probe held transverse on the finger) and sagittal (longitudinal parallel to the tendon, probe held longitudinal on digit) planes for the most complete visualization. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1.","caption":"This video demonstrates ultrasound examination of normal FPL, FDP and FDS tendons in both axial and sagittal views. Side-by-side video is provided demonstrating the ultrasound probe position on the right side of the screen with real-time ultrasound video (both annotated and unedited) on the left side of the screen.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_myjebnqa"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} We illustrate the value of surgeon-performed ultrasound with two clinical cases. The first is a 54-year-old woman who presented with a 3-month-old zone 1 FPL laceration. (See Video 2 [online], which shows an ultrasound examination of a 54-year-old woman with a 3-month-old FPL laceration.) The second case demonstrates the identification and surgery of the proximal and distal tendon ends of a flexor tendon in a 34-year-old woman with an acute zone II FDP laceration of the small finger. (See Video 3 [online], which shows an ultrasound examination of a 34-year-old woman with an acute zone II FDP laceration of the fifth digit. Correct identification of proximal and distal tendon ends is demonstrated.) For a freshly lacerated tendon, doing your own ultrasound will tell you efficiently at the point-of-care where the proximal and distal tendon stumps are in the finger and hand.5 This will enable you to accurately place smaller incisions to find the tendons because you know exactly where they are before you cut. Smaller incisions create less scarring; fewer adhesions; and therefore, less potential risk for tenolysis at a later time.6,7 (See Video 4 [online], which shows why hand surgeons and hand therapists should perform their own ultrasound.) In the clinical case in Video 2 (online), the proximal tendon was located preoperatively by ultrasound and therefore could be easily located at the time of surgery in the thumb incision at the mid metacarpal level. Additional incisions in the wrist and hand were not required to find the tendon, nor were extra attempts at tendon retrieval. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 2.","caption":"This video shows an ultrasound examination of a 54-year old female with a three-month old FPL laceration. Correct identification of proximal and distal tendon ends is demonstrated.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_m3melmlu"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 3.","caption":"This video shows an ultrasound examination of a 34-year old woman with an acute zone II FDP laceration of the fifth digit. Correct identification of proximal and distal tendon ends is demonstrated.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_1xxyni0x"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 4.","caption":"This video shows why hand surgeons and hand therapists should perform their own ultrasound.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_jm92hme2"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} In a recently repaired FDP tendon, when the DIP joint does not move despite the patient’s best efforts, it is either ruptured or stuck in scar adhesions. Surgeon-performed ultrasound provides an efficient examination in the clinic.8–10 If the tendon repair is ruptured, there will be black space in the sheath without a white tendon. If the tendon is stuck in scar, it will be clearly visible in the sheath. The sutures in the tendon can also be clearly seen as intense thin white lines at the repair site. The quick identification of the cause of the problem means the difference between a rapid return to surgery with a rupture versus relative motion splinting or casting motion to mobilize stiffness to tease a profundus repair out of its surrounding scar (See Video 4 [online]).10 During therapy, patients can be encouraged by seeing their own tendon gliding on ultrasound. This can be a useful tool to motivate the patient to mobilize and break down scar adhesion (See Video 4 [online]). Like all new skills, the hardest part is to take the first step of picking up an ultrasound probe and using it for the first time. As soon as a surgeon recognizes the bones of the finger and asks the patient to flex it, the familiar look of the tendon gliding in the sheath will quickly become obvious on the ultrasound screen. The surgeon will quickly feel at home and be glad to have started. The surgeon can now see important soft tissues under the skin with ultrasound. Useful ultrasound tips: Use of a wide linear probe (L12-4) can allow the examiner to include an adjacent uninjured digit with normal anatomy for comparison (See Video 2 [online]). A portable ultrasound probe can also be used. Local anesthetic can provide for painless examination. A copious amount of ultrasound gel will ensure a clear examination and prevent undue pressure on injured digits. Gentle passive or active range of motion while performing ultrasound examination can aid in confirming anatomical structures, such as gliding tendons. Ensure examination is performed in both axial (probe held transverse on digit) and sagittal (probe held longitudinal on digit) views to clearly visualize injuries. Be aware of the artificate of anisotropy, where striated structures seem black or hyperechoic due to the scattering of ultrasound energy (See Video 3 [online]). DISCLOSURE The authors have no financial interest to declare in relation to the content of this article.

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