Reducing Muscle Activity when Playing Tremolo by Using Electrical Muscle Stimulation to Learn Efficient Motor Skills

When beginners play the piano, the activity of the forearm muscles tends to be greater than that of experts because beginners move their fingers with more force than necessary. Reducing forearm muscle activity is important for pianists to prevent fatigue and injury. However, it is difficult for beginners to learn how to do so by themselves. We propose using electrical muscle stimulation (EMS) to teach beginners how to reduce this muscle activity while playing a tremolo: a rapid alternation between two notes. Since experts use wrist rotation efficiently when playing tremolos, we propose an EMS-based support system that applies EMS not to muscles that are relevant to moving the fingers but to the supinator and pronator teres muscles, which are involved in wrist rotation. We conducted a user study with 16 beginners to investigate how the forearm muscle activity on the extensor pollicis longus and digitorum muscles changed when using our EMS-based support system. We divided the participants into two groups: an experimental group who practiced by themselves with EMS and a control group who practiced by themselves without EMS and then practiced with instruction. When practicing by themselves, practicing with EMS was more effective than that without EMS; the activity levels of the extensor pollicis longus and digitorum muscles were significantly lower with EMS, and the participants felt less fatigue when playing tremolos. By comparing the improvement in reducing muscle activity between practicing with EMS and practicing with instruction, there was no significant difference. The results suggest that our EMS-based support system can reduce target muscle activity by applying EMS to other muscles to teach beginners how to move limbs efficiently.

Spontaneous Rupture of the Extensor Pollicis Longus Tendon in Systemic Lupus Erythematosus: A Case Report and Literature Review

Spontaneous tendon rupture is a rare entity. Herein, we report a case of spontaneous rupture of the extensor pollicis longus (EPL) tendon in a 61-year-old woman with systemic lupus erythematosus (SLE). The patient worked as an esthetician and had a 42-year history of SLE that was well-controlled using oral steroids. She presented with an inability to extend her left thumb, with no prior history of trauma or symptoms. On imaging, there was no evidence of degenerative changes or osteophyte formation in the gliding area of the EPL tendon. Intraoperatively, there was evidence of tendon rupture around Lister’s tubercle. We performed a tendon transfer of the extensor indicis proprius for repair. The patient recovered active thumb extension and returned to work 4 months after surgery, without any complications. We suspected that spontaneous EPL tendon rupture was caused by a combination of disease-related factors including long-term steroid use, chronic inflammation, and continuous mechanical stress from her work and daily activity. This case report demonstrates the multifactorial etiology of spontaneous tendon rupture in patients with SLE and the importance of monitoring for this complication during routine follow-up.

Lessons learned with the Cobra prosthesis in elderly patients with complex distal radius fractures—a retrospective follow-up study

Introduction Recently, the Cobra prostheses were introduced in the treatment of distal radius fractures (DRF) of elderly patients. Fracture prostheses provide an alternative treatment option for complex fractures where conservative therapy seems not acceptable and osteosynthesis seems not possible. Data reporting the feasibility of the Cobra prosthesis are sparse. Therefore, this retrospective follow-up study investigated the clinical and radiological mid-term outcome of the Cobra implant in complex DRFs of elderly patients. Materials and methods Thirteen patients (mean age 73.5 years, range 65–87 years) were retrospectively evaluated with at least a 1-year follow-up after surgery. Objective and subjective clinical parameters as well as the radiological outcome and complications were analyzed. Results The mean follow-up period was 31.2 months. Seven cases required a cemented prosthesis. The mean relative range-of-motion compared to the healthy side was 72.3% and 51.8% for extension and flexion, respectively, and 87.9% and 85.7% for pronation and supination, respectively. The mean grip strength was 78.3% compared to the non-operated side. Eight patients were very satisfied, five patients were partly satisfied with the result. The DASH, PRWE, MHQ and Lyon-Scores averaged 39.1, 36.2, 64.9 and 63.3 points, respectively. The mean VAS-Score for pain was 1.1 at rest and 3.2 during activities. Perioperative complications included one dissection of the extensor pollicis longus tendon, one heterotopic ossification, one radiocarpal dislocation and two cases of an ulnar impaction syndrome due to implant subsidence. Conclusion The prosthetic treatment of complex DRFs in elderly patients with the Cobra implant led to clinically and radiologically satisfactory mid-term results. The Cobra prosthesis still does not represent a gold standard but can be regarded as a feasible salvage option for complex DRFs when osteosyntheses may not be possible and non-operative treatment will lead to further functional restrictions and wrist pain during performing activities of daily life in high functional demand patients.

Supernumerary extensor pollicis longus tendon masking an extensor pollicis longus rupture following non-surgical treatment of a distal radius fracture

Extensor pollicis longus tendon pathology is a recognised complication following non-surgical treatment of non-displaced distal radius fractures. Tendon entrapment typically presents with pain, but preservation of thumb retropulsion during complete rupture results in loss of active thumb retropulsion and tenodesis effect. We present the case of a 52-year-old woman who developed extensor pollicis longus tendon entrapment with full active thumb extension following a non-displaced distal radius fracture. During her elective third dorsal compartment release, the extensor pollicis longus tendon was found to be completely ruptured and a rare supernumerary extensor pollicis longus tendon was found emerging from the fourth dorsal compartment. Gentle traction of this tendon resulted in thumb interphalangeal joint extension and simultaneous index finger metacarpophalangeal joint extension. An extensor indicis proprius to extensor pollicis longus tendon transfer was performed. At her final 6-month follow-up, she had painless full active thumb motion comparable to her contralateral side.

Snapping thumb: a rare case of stenosing tenosynovitis of the extensor pollicis longus tendon

Tenosynovitis of the extensor pollicis longus (EPL) is rarely reported in patients without rheumatoid arthritis but may lead to thumb snapping as a consequence of EPL stenosing tenosynovitis.This case presents painful thumb snapping that developed after a wrist trauma and repetitive loading. Ultrasound and MRI were used as diagnostic tools, before surgical release of the EPL in the third extensor compartment was performed. Neither EPL tenosynovitis nor thumb snapping were found at follow-up.

The Variable Insertional Anatomy of the Abductor Pollicis Longus: Functional Relevance and Relationship to Adjacent Thumb Extensors

Background The abductor pollicis longus (APL) is classically described as inserting on the base of the first metacarpal. This study analyzed APL insertional anatomy and quantified the size of various elements of the extensor side of the thumb to determine associations with size and function. Methods Twenty-four formalin-preserved upper limbs were dissected. The insertional anatomy of the APL, extensor pollicis brevis, and extensor pollicis longus were characterized, and the capacity of APL tendon slips to perform palmar abduction of the first digit was quantified based on slip size and insertion. Results The mean number of APL tendon slips observed was 2.3. Abductor pollicis longus insertion sites included the base of the first metacarpal, trapezium, abductor pollicis brevis, and opponens pollicis. Only 4 specimens had a solitary metacarpal slip, while 83% of specimens had insertions onto at least 1 thenar muscle. A total of 62.5% of APL tendons exhibited some form of branching that we categorized into “Y” and “Z” patterns. In assessing palmar abduction capacity, we found that APL tendon slips inserting into the base of the first metacarpal were larger in cross-sectional area than nonmetacarpal slips and reproduced complete palmar abduction of the digit in the absence of nonmetacarpal slips. The abduction capacity of APL tendon slips was not correlated to the cross-sectional area. Conclusions There is significant variability in APL tendon slips, branching patterns, and insertional anatomy. These findings provide further understanding of the function of the APL and its surgical implications.