Ultrasound-Guided Dry Needling for Flexor Pulley Injuries in Climbers: Diagnosis & Management

The sport of rock climbing is becoming increasingly more popular both nationally and internationally.¹ Indoor climbing facilities are being built throughout the U.S., and the 2020 Olympics will include rock climbing for the first time.¹ As interest in rock climbing continues to grow, climbing injuries are becoming more prevalent.² Flexor pulley injuries of the hand are one of the most common issues among climbers secondary to gripping and holding requirements.^1-3 However, flexor pulley injuries are difficult to repair and often require specialty rehabilitation.^{1, 4, 5} In the past decade, dry needling has emerged as a popular treatment strategy in the management of a variety of neuromusculoskeletal conditions.^6-9 Recent evidence suggests that dry needling may be useful in the management of flexor pulley injuries, particularly when used in conjunction with diagnostic ultrasound and as part of a multi-modal treatment strategy.^6-9

CLIMBING FINGER GRIP POSITIONS

Rock climbing requires gripping and holding with the hands, which places significant force on the flexor pulley system of the fingers.¹ While there are a variety of ways to hold the rock during climbing, certain grip positions such as a full crimp grip position can place as much as 32 times more force on the A2 flexor pulley as compared to an open-hand grip position.^10-12 The full crimp grip position is performed when the distal interphalangeal (DIP) joints are fully extended while the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints are flexed.^{1, 10-12} The full crimp grip position is often the preferred method for novice climbers due to its mechanical advantage and versatility to various holds and body positions.^{1, 10-12} In contrast, experienced and professional climbers often develop safer gripping techniques for smaller holds, such as the open-hand sloped grip position in which the DIP joints are flexed to approximately 50 degrees, PIP joints are flexed between 20-30 degrees, and MCP joints are in a relatively neutral position.^1,10-12 This open-hand grip position is considerably more difficult to perform,^10-13 as it requires an awareness of body positioning and climbing-specific upper body and finger strength in order to be effective.^10-13 Regardless of gripping preference, far more forces are placed on the fingers while climbing than most daily and/or recreational activities.^10-15 While the fingers can be resilient, the consistent stress and wear and tear over time often lead to overuse injuries, to include partial and full ruptures of the flexor pulley system.^{1-3, 13}

STRUCTURE AND FUNCTION OF THE FLEXOR PULLEY SYSTEM

The flexor pulley system is comprised of five annular ligaments on the volar aspect of the fingers that form a fibro-osseous tunnel.^16-19 The flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons glide through the tunnel during finger motion.^16-19 The pulley system provides strategic constraint to the flexor tendons and prevents “bowstringing” while providing a mechanical advantage to the fingers during forceful activities such as climbing.^1,16-19 Injury to the flexor pulley system in climbers often occurs at the level of the A2 pulley of the ring finger between the MCP and PIP joint and often leads to: (1) general loss of uniform thickness and contour of the annular ligament, and (2) thickening and compatible constriction or entrapment of the flexor tendons.^1,16-19 These changes result in lower mechanical efficiency, reduced finger performance and pain.^1,16-19

The mechanical force placed on the A2 flexor pulley system seems to be a unique injury that is specific to climbers, as it is difficult to reproduce during normal activities of daily living.^{6, 12, 20} In contrast, most repetitive gripping activities unrelated to climbing seem to add force, pressure and friction to the A1 flexor tendon pulley.^{6-8, 21,22}  The location and reduced span of the A1 pulley relative to the A2 pulley also puts it at greater risk of injury during non-climbing activities.^6-8,21 As such, dysfunctions of the A1 flexor pulley system (i.e. trigger finger^6-8,21) are more commonly reported in the literature.

DRY NEEDLING TO THE FLEXOR PULLEY SYSTEM

In theory, dry needling to the tendons or ligaments of the fingers may create excessive micro-trauma to an area of the body that has reduced tissue density and poor vascularization.^17-19 Moreover, repetitive penetration of a long, thin tendon may cause excessive damage and place the tendon at risk for future injury.^23-25 However, after performing sonographically-guided, percutaneous hook knife and needle releases of the A1 pulleys in 50 unembalmed cadavers, no tendon lacerations, A2 pulley damage or vascular injuries were reported.²⁶ Furthermore, another study found that 81.7% of patients experienced full resolution of trigger finger immediately following ultrasound-guided needling to the A1 flexor pulley.²⁷ Furthermore and notably, investigators used a relatively large needle (i.e. 21-gauge) and only minimal complications were reported.²⁷ In a separate study of patients with trigger finger where needle-knife treatment was compared with and without ultrasound guidance to treat patients with trigger finger, a 100% release rate was reported following ultrasound-guided needling, whereas“mild triggering” was still reported in 71.4% of patients following blind needling at a 7-day follow-up.²⁸ Notably, only 1 patient (4.8%) reported complications following the “blind” knife needling;²⁸therefore, using monofilament needles in the volar aspect of the fingers may not pose as much risk for adverse events as previously thought.

Despite the relative risks, recent literature indicates that dry needling may be safe and effective for treating tendon pulleys.^6,8 In a recent randomized controlled trial of 58 patients diagnosed with trigger finger, fast-in and fast-out dry needling was used to target nodules in the flexor pulley system.⁶ After a single treatment, and compared to the control group, patients reported a significant improvement in pain, pinch grip strength and function.⁶ Moreover, according to ultrasound images, there was a significant improvement in the tendon-pulley architecture.⁶ In a separate study of patients with trigger finger, acupuncture needles were inserted into the ulnar and radial aspects of the flexor tendon and sheath consistent with the site of the A1 pulley at a depth of 10 mm for 10 minutes.⁸After receiving daily treatments over the course of 5-7 days, patients reported significant improvements in pain, swelling, and reduced “snapping”.⁸ Nevertheless, to date, there are no studies in the literature that report using acupuncture or dry needling to specifically treat A2 flexor pulley injuries in climbers. However, dry needling (i.e. the insertion of needles without injectate) has been used to treat similar conditions related to the wrist and finger flexors.^29,30 In addition, while the A2 and A1 flexor pulleys attach to the proximal phalanx and volar plate, respectively, their structure and function are almost identical.³¹

Dry needling (i.e. the insertion of needles without injectate⁹) has been shown to elicit a number of biochemical, biomechanical, endocrinological, and neurovascular changes.³² However, the direct physiologic effect of dry needling on the flexor pulley system is presently unknown. A number of studies have demonstrated increased blood flow,^33-35oxygen saturation³⁶and collagen organization and proliferation³⁷following dry needling for tendon related-related conditions. Dry needling may also help to break adhesions³⁸ and remodel tissue^39,40 so as to facilitate healing and improve function of the flexor pulley system. Dry needling in the vicinity of peripheral nerves and/or neurovascular bundles has also been shown to effectively address pain related to a number of neuromusculoskeletal conditions.^41-43

ULTRASOUND-GUIDED DRY NEEDLING FOR THE FLEXOR PULLEY SYSTEM

Ultrasound may be a useful tool for diagnosing flexor pulley injuries. A recent study reported 98% sensitivity and 98% specificity for the ability of diagnostic ultrasound to accurately assess flexor pulley injuries in 64 rock climbers with finger injuries.⁷ More specifically, symptomatic climbers presented with increased thickness of the pulley system and increased distance between phalanx and tendon.⁷

Ultrasound-guided dry needling may also be useful in the treatment of injuries to the flexor pulley system. That is, ultrasound-guided dry needling has been used as an alternative to more invasive treatment strategies in the management of Achilles tendinopathy,²⁴ rotator cuff tendinopathy,⁴⁴ lateral epicondylitis,⁴⁵ and patellar tendinosis.³⁵ Image-guided needle-knife procedures have been shown to reduce pain and disability associated with trigger finger;²⁸ however, image-guided dry needling has not yet been attempted for flexor pulley injuries. While previous studies suggest that imaging might not be necessary when needling for flexor pulley injuries,^{6, 8} ultrasound-guided dry needling has been used to accelerate the healing process in patients with tendinosis and neovascularity^{35, 36, 46} without unnecessarily compromising tissue.⁴¹

CONCLUSION

As the sport of rock climbing becomes increasingly more popular, flexor pulley injuries will likely become more prevalent.^1-3 The use of dry needling may help in treating the pain and disability associated with these conditions, especially when incorporated as part of a multi-modal physical therapy strategy.^1,6,14,16 Diagnostic ultrasound can also be used to assess flexor pulley injuries, observe physiological changes, and safely guide needle insertion, angulation and depth in order to achieve optimal outcomes.^47,48

AUTHORS

Kevin Cowell, DPT, OCS, Cert. DN
The Climb Clinic | Physical Therapy & Sports Medicine, Louisville, CO
Fellow-in-Training, AAMT Fellowship in Orthopaedic Manual Physical Therapy

Raymond Butts, PhD, DPT, MSc (Neurosci), Dip. Osteopractic
Senior Instructor, American Academy of Manipulative Therapy
Coordinator, AAMT Fellowship in Orthopaedic Manual Physical Therapy
Louisville, KY

James Dunning, PhD, DPT, MSc (Manip Ther), FAAOMPT, Dip. Osteopractic
Director, AAMT Fellowship in Orthopaedic Manual Physical Therapy
Montgomery, AL

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