Distal Biceps Tendon Rupture; Diagnosis and Surgical Repair; the Author’s experience
Mar 27, 2020
The distal biceps tendon is at risk of tearing from eccentric loading of the flexed arm and commonly avulses from its insertion site at the radial tuberosity. The injury is frequently seen in younger males with a large muscle bulk, and the proximal muscle migration and bulge at the distal biceps is pathognomic.
However in partial tears the diagnosis may be less obvious and may require a clinical assessment with an examination utilising the “Hook” test where the normal side is examined first and compared to the injured side. The lateral border of the distal biceps tendon is easily palpated. With the patient’s elbow flexed at 90deg and fully supinated the examiner’s finger is able to hook underneath the tendon and compare the quality of tendon on each side. The difference with a tear is usually obvious, but occasionally swelling and discomfort can make the examination a challenge to perform. On the medial side of the tendon the bicipital aponeurosis or lacertus fibrosus is a fascial band that arises from the biceps to cross over the deep ulnar flexors, covering the underlying brachial artery and median nerve, to insert onto the ulna. It is invariably intact and may give rise to the diagnosis of a partial tear even in cases where the main tendon (the confluence of the long and short heads of biceps) is avulsed completely but not retracted.
Fig 1. Hook test – examiner’s finger under lateral side of tensed biceps tendon
Imaging studies are helpful to fully assess the tear, but are not necessary in a clinically obvious rupture. Ultrasound can demonstrate a completely torn and retracted tendon quite reliably, but is operator dependent, and in cases of partial tears or minimally retracted tears cannot reliably demonstrate the degree of rupture and for these MRI is a more informative test. The optimal MRI scan is taken in a position of FABS (Flexed Elbow; Abducted shoulder and Supinated forearm). The position helps to lengthen the biceps muscle at the shoulder whilst bringing the tuberosity into prominence at the elbow. The intact proximal muscle belly of biceps is identified and traced distally to identify the insertional tear.
The option for non-operative management can be considered for older, sedentary patients, particularly where the non-dominant arm is affected, but in active patients the loss of strength is significant. The reduction in supination strength is most pronounced at 40-50%. To demonstrate the loss of strength: try tightening a screw with a screwdriver using your right hand with your elbow out straight (the position defunctions biceps as a supinator). Flexion strength is reduced by 30% (try performing a biceps curl with your forearm pronated; the position defunctions biceps as an elbow flexor) and grip strength is reduced by by 15% (1).
Surgery is best done acutely (before significant scaring has occurred around the biceps). Preferably prior to 2-3 weeks, but a primary repair may be attempted after as long as 6 to 8 weeks from injury. A chronic rupture may require a tendon reconstruction with tendon grafting, rather than a primary repair.
My preferred method of repair is with the single incision endobutton technique. The incision is placed longitudinally over the proximal radius starting 1cm below the elbow crease with the forearm fully supinated. Surgery is preferably performed without tourniquet inflation. The region contains a branch of the radial artery (the leash of Henry) that crosses over the path of the distal biceps tendon just proximal to the radial tuberosity, and a plethora of blood vessels. There are also cutaneous nerves and a significant branch of the radial nerve (the PIN posterior interosseous nerve) at risk during the procedure. Retractor placement has to be done carefully. A second more medial incision above the elbow crease is helpful (to retrieve the tendon that can be significantly retracted) and avoids crossing the flexor crease. My modification of the classic endobutton technique (2) is to use a 4 stranded no. 2 ethibond loop suture to capture the tendon, with 2 strands exiting the tendon 2cm proximal to the end (the position of the knot ties). The tendon is then passed under the leash of Henry to the tuberosity and inserted into the canal of the radius via a drill hole on the ulna aspect of the radius and secured with an endobutton passed across the far cortex (aimed in a more proximal direction away from the PIN). The knots are tied at the surface of the tendon with the elbow flexed at 90deg and using a knot pusher. This is the most effective way to seat the tendon in the canal using the endobutton technique.
In most cases the patient can be discharged home on the day of surgery and commence full range of motion exercises from Day 1 post-operatively. A sling is required for 6 weeks, followed by progressive strengthening and return to full function after 3months. The surgery can be challenging and the reported complication rate in the literature is as high as 25%. The complications include: stiffness, re-rupture, tendon gapping/ loss of fixation, heterotopic ossification, PIN nerve palsy, sensory nerve palsy and haematoma/ bleeding. However I would suggest the complication rate can be much lower than this and it is possible to perform the surgery safely and reliably using the described technique.
- Morrey BF, Askew LJ, An KN, Dobyns JH. Rupture of the distal tendon of
the biceps brachii. A biomechanical study. J Bone Joint Surg Am. 1985 Mar;67 (3):418-21.
- Savin DD, Watson J, Youderian AR et al. Surgical Management of Acute Distal Biceps Tendon Ruptures. J Bone Joint Surg Am, 2017 May; 99: 785-96
Dr Philip Markham
P: 02 4209 5218
F: 02 4208 0644