Working Diagnosis:
Complete full-thickness tear of the distal biceps tendon.

Treatment:
The patient was informed of the diagnosis and the need for surgical repair. The potential complications (including cosmetic deformity and loss of muscle strength) should he elect not to have surgical repair were also discussed. He was advised to quit cigarette smoking, instructed to apply an ice pack to the area of discomfort to reduce swelling, provided a sling for comfort, advised to avoid activities (lifting and full extension of the left elbow), and referred to an orthopedic specialist for definitive surgical management. Seven days post-injury, he underwent successful operative repair of the left distal biceps tendon and was subsequently referred to physical therapy for rehabilitation.

Outcome:
Four months after surgical repair, he has resumed exercising and has successfully quit smoking.

Author's Comments:
Rupture of the distal biceps tendon (DBT) is a relatively rare musculoskeletal injury that predominantly occurs in middle-aged males.1,2 Several risk factors have been associated with rupture of the DBT including cigarette smoking, increased age, use of steroids, use of quinolones, and overuse.3 While the exact pathophysiology of DBT ruptures is not completely understood, most tears are believed to occur 1-2 cm above the radial tuberosity.8 The hypovascular zone hypothesis postulates that this area of the DBT has a limited vascular supply and consequently has a decreased ability to support tendon repair which makes it susceptible to tears.2 The mechanism of injury is usually the application of an eccentric extension force loaded on a flexed and supinated forearm.4 Because of its high specificity and sensitivity, MRI is considered the optimal imaging modality for the detection of DBT tears.5 When ordering an MRI, it is important to request a FABS position view (an acronym for having the elbow in 90 degrees of flexion, the shoulder in 180 degrees of abduction, and the forearm supinated) as it allows a longitudinal visualization of the entire length of the distal tendon.2,5

Conservative management may be considered in sedentary or elderly patients, but the mainstay of treatment for most DBT ruptures is early surgical reattachment of the tendon. Early surgical repair results in a decreased rate of complications, faster recovery, restoration of normal cosmesis, and preservation of muscle strength.2 Though there are various rehabilitation protocols, the focus is to gradually improve range of motion - achieve full elbow extension after six weeks postoperatively before increasing the intensity of strengthening exercises.6 Interestingly, it has been shown that patients who have experienced previous DBT ruptures are at a significantly increased risk of sustaining a subsequent rupture of the DBT on the contralateral limb.7 This case illustrates the importance of making an accurate diagnosis as the majority of patients would benefit from prompt surgical repair to prevent the development of muscle weakness and cosmetic deformity.2

Editor's Comments:
Biceps tendon rupture is more likely to occur proximally at the long head of the tendon, but as in this case, may occur at the distal tendon.8 Patients should be counseled on increased body mass index as another modifiable risk factor associated with rupture.9 In addition to MRI, ultrasound examination of the DBT has comparable sensitivity and specificity,10 and can distinguish between low-grade tendinopathy or tear and high-grade partial or complete tears. Despite this, in most cases if there is a clinical concern for DBT rupture, an urgent MRI is performed. Regarding physical exam, though reverse Popeye deformities can be seen in DBT ruptures, obvious deformity is not typically present, with one observational study of 120 patients suffering a traumatic DBT injury reporting reverse Popeye deformity in only 45% of cases.10 Furthermore, the reverse Popeye deformity is an unreliable finding because an intact bicipital aponeurosis may hide the underlying retracted DBT.11 Note that elbow range of motion is often preserved in this injury.

References:
1. Howard, M. Current Management of Distal Biceps Tears. Current Orthopaedic Practice. 2018 May 12; 29(2), 135–139. doi: 10.1097/bco.0000000000000589
2. Cerciello, S., Visonà, E., Corona, K., Filho, P. R. R., & Carbone, S. The Treatment of Distal Biceps Ruptures: An Overview. Joints. 2019 Oct 11; 06(04), 228–231. doi: 10.1055/s-0039-1697615.
3. Hsu D, Chang KV. Biceps Tendon Rupture. [Updated 2019 Nov 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513235/
4. Huynh, T., Leiter, J., Macdonald, P. B., Dubberley, J., Stranges, G., Old, J., & Marsh, J. Outcomes and Complications After Repair of Complete Distal Biceps Tendon Rupture with the Cortical Button Technique. JBJS Open Access. 2019 Aug 27; 4(3). doi: 10.2106/jbjs.oa.19.00013.
5. Fitzpatrick, D., & Menashe, L. Magnetic Resonance Imaging Evaluation of the Distal Biceps Tendon. The American Journal of Orthopedics. 2018 May 23; 47(5). doi: 10.12788/ajo.2018.0037.
6. Ryan G. Miyamoto, Florian Elser and Peter J. Millett. Distal Biceps Tendon Injuries. J Bone Joint Surg Am. 2010 Sept 1;92:2128-2138. doi:10.2106/JBJS.I.01213
7. Green, J., Leslie, B., & Skaife, T. AAHS - Distal Biceps Tendon Rupture Increases the Risk of a Contralateral Biceps Tendon Rupture. 2012 Jan; Retrieved from https://meeting.handsurgery.org/abstracts/2012/P36.cgi.
8. Clayton RA, Court-Brown CM. The epidemiology of musculoskeletal tendinous and ligamentous injuries. Injury 2008; 39:1338.
9. Kelly MP, Perkinson SG, Ablove RH, Tueting JL. Distal Biceps Tendon Ruptures: An Epidemiological Analysis Using a Large Population Database. Am J Sports Med 2015; 43:2012.
10. de la Fuente J, Blasi M, Martínez S, et al. Ultrasound classification of traumatic distal biceps brachii tendon injuries. Skeletal Radiol 2018; 47:519.
11. Quach T, Jazayeri R, Sherman OH, Rosen JE. Distal biceps tendon injuries--current treatment options. Bull NYU Hosp Jt Dis 2010; 68:103.

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