Isolated Chronic Rupture of the Short Head of a Bifurcated Distal Biceps Tendon: A case report

Connor S. Kasik, DOa, Benjamin A. Cox, DOa, Christopher L. Wilcox, DOa,b
aMcLaren-Greater Lansing Orthopedic Hospital, Lansing, MI, USA
bDepartment of Osteopathic Surgical Specialties, Michigan State University, East Lansing, MI, USA

The biceps brachii muscle is composed of two heads that originate proximally from the scapula, and proceed to coalesce distally to insert onto the radial tuberosity.  Isolated rupture of the short head component of a bifurcated distal biceps tendon is a rare injury that has been reported infrequently1.  Multiple anatomic anomalies of the insertion of the biceps brachii tendon have been identified that can further create difficulties in diagnosis and treatment2,3.  This delay can contribute to the chronicity of injuries, and have adverse affects on long-term outcomes. 

Over time, tendon retraction and fibrosis occurs which prevents primary anatomic repair.  We present a case of a 43-year-old male who sustained a selective rupture of the short head of the biceps with intra-operative findings of a bifurcated distal biceps tendon with separate musculotendinous junctions.  A delay in diagnosis led to significant tendon and muscle belly retraction.  Surgical treatment involved semitendinosus hamstring allograft reconstruction of the torn and retracted short head, along with independent repair of the long head component.  To the best of our knowledge, this is the first case report involving surgical treatment of a chronic selective rupture of the short head component of a bifurcated distal biceps tendon.

A 43-year-old right hand dominant male presents as an outside referral for complaints of chronic right elbow weakness following a lifting injury that occurred 11 months prior.  The patient reported subjective weakness to both flexion and supination that significantly interfered with his occupation.  Physical examination revealed a medial sided reverse Popeye deformity, with a visible muscle belly over the medial aspect of the upper arm.  Strength testing revealed objective weakness to both forearm supination and elbow flexion.  The Hook test of the distal biceps tendon in the antecubital fossa was negative. 

An MRI was obtained and revealed the presence of a bifurcated distal biceps tendon with a complete tear and significant retraction of the short head component (Fig 1).  The long head component was intact, with the presence of a partial tear at the attachment of the radial tuberosity (Fig 2).

Fig 1
Fig 1.  Coronal T2-weighted image demonstrating a complete disruption and retraction of the medial short head biceps tendon.

Fig 2
Fig 2.  Sagittal T2-weighted image demonstrating an intact long head of the biceps inserting onto the bicipital tuberosity.

The patient elected for surgical reconstruction.  The procedure was performed using a single incision technique utilizing the anterior Henry approach in order to expose the radial tuberosity and the proximally retracted short head of the biceps tendon stump. 

Upon full exposure, it was noted that the short head and long head each had separate musculotendinous junctions that could be traced proximally.  The long head of the biceps was intact and inserted distally onto the radial tuberosity.  The separate short head tendon was torn and retracted proximally into the upper arm approximately 14 cm from the radial tuberosity (Fig 3). 

Fig 3
Fig 3.  Photograph showing an intact long head of biceps (LH) tendon with a torn and retracted short head of biceps (SH) tendon.

Due to the significant retraction and inability to mobilize the short head biceps tendon for primary repair, reconstruction with allograft augmentation was chosen.  A semitendinosus hamstring allograft was utilized to reconstruct the short head of the biceps.  The allograft was sutured to the short head muscle belly and remaining tendon stump utilizing a Krakow technique.  The long head tendon insertion was then detached from its insertion on the radial tuberosity.  A whipstitch was used to create side-by-side suture approximation of the hamstring allograft tendon and the lateral long head tendon. 

Care was taken in order to set the proper tension on the allograft while suturing it to the native long head biceps tendon. This combined tendon unit was then secured to the radial tuberosity using a cortical button and interference screw fixation (Fig 4).

Fig 4
Fig 4.  Photograph showing allograft reconstruction of the short head (SH) tendon with side-by-side suture approximation of the long head (LH) tendon.

Fig 5
Fig 5.  Photograph showing final repair

Post-operatively, the patient was splinted at 90° of elbow flexion for two weeks.  The patient was then transitioned into a hinged elbow brace with a gradual weekly increase in active range of motion.  Passive and active assisted supination exercises were initiated.  Isometric biceps strengthening was initiated at eight weeks.  At six-month follow-up appointment, the patient had full range of motion with no reported weakness in elbow flexion and forearm supination.

The biceps brachii muscle has been historically reported to contain two heads that combine distally to create one single tendon for insertion onto the radial tuberosity.  Multiple anatomic variations with anomalous insertions of the biceps brachii tendon have been previously described in the literature2,3.  However, recent studies have reported the presence of two distinct distal tendons at the attachment site.  This bifurcation of the distal biceps tendon has been reported to occur in up to 48% of cadaver specimens4–6.  This case likely demonstrates an embryologic failure of fusion of the biceps brachii muscle2.  Each musculotendinous bundle possessed a distinct insertion onto the radial tuberosity.  The distinction allowed for selective isolated rupture of the short head component of the distal biceps7.  The intact long head tendon remained attached to the radial tuberosity, creating difficulty in diagnosis.
Studies have demonstrated that non-operative treatment of distal biceps ruptures leads to deficits in elbow flexion and supination8,9.  The long head of the biceps tendon inserts more proximally on the radial tuberosity, providing a lever arm for supination.  The short head component inserts more distally onto the radial tuberosity, thus playing a greater role in elbow flexion3–5,7,10.  

Late reconstruction of a chronic biceps rupture can be difficult and challenging.  Significant tendon retraction and scar formation limits any attempt at primary repair due to decreased excursion and immobility of the tendon11.  There is also an increased incidence of post-operative complications associated with chronic partial distal biceps ruptures12.  Disability associated with chronic ruptures can cause difficulty with activities of daily living that involve flexion and supination activities11.  Satisfactory results have been reported with late reconstruction of chronic distal biceps ruptures utilizing Achilles tendon allograft11.  Given the patient’s decreased strength and function that was interfering with occupation related activities, we believe an attempt at surgical reconstruction should be performed.  

Rupture of the short head component of a bifurcated distal biceps tendon is a rare injury that is difficult to diagnose and can be easily mistreated.  A physical examination and meticulous evaluation of MRI imaging is required to differentiate this injury from a partial or complete tear of a common distal biceps tendon.  When diagnosed appropriately, late reconstruction for chronic selective rupture of the short head of the biceps utilizing allograft augmentation can be successfully performed for patients with functional demands in forearm supination and elbow flexion.


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