Repair of Distal Biceps Tendon Avulsion with the Endobutton: A Minimally Invasive Technique

Gregory I Bain, MBBS, FRACS
Senior Visiting Orthopaedic Surgeon, Modbury Public Hospital, Smart Road, Modbury, South Australia.
Hand and Upper Limb Surgeon
196 Melbourne Street
North Adelaide  SA  5006
Telephone:  +61 8 8361 8399
Fax:  +61 8 8239 2237
www.gregbain.com.au

Abstract
Due to the development of heterotopic bone formation and technical simplicity, single anterior incision techniques have again become popular.  With a minimally invasive technique via a 5 cm transverse skin incision, the tendon is sutured to the Endobutton with two number 5 Ethibond Bunnell sutures.  There is no need to perform surgical repair in the depths of the bulky forearm because the tendon is simply sutured external to the wound.  This “prefabricated” Endobutton/tendon unit is then locked into drill holes in the proximal radius. This construct is strong enough to allow early and active mobilization.  It can also be used for partial tendon ruptures.  An autologous hamstring tendon graft is used to lengthen the tendon in patients with a delayed presentation.

Introduction
The majority of authors would recommend a surgical repair of avulsion of the distal biceps tendon because conservative management leads to deficiency of strength and endurance of forearm supination and elbow flexion. (1-3)

Initially anterior surgical approaches were used but came into disrepute because of injury to the radial nerve and posterior interosseous nerve.(4-8)  Because of the risk of nerve injury, Boyd and Anderson in 1961 developed a double incision technique with fixation of the tendon over a bony trough in the radial tuberosity.(4)  The incidence of radioulnar synostosis and the need for two incisions has led some authors to advocate fixation with suture anchors using a single anterior approach.(9,10)

However, tying sutures onto a suture anchor in the bulky forearm depths of a patient with a biceps tendon avulsion is technically difficult.  The tendon needs to be advanced down onto the radial tuberosity, with the elbow flexed, without compromising adjacent neurovascular structures.

The Endobutton (Acuflex, Microsurgical Inc., Mansfield, MA) was developed for fixation of the anterior cruciate ligament graft.  It provides strong fixation which allows early active mobilisation in the knee.  Development of this technique to allow early active mobilisation for biceps tendon was first performed by the author in 1995.  The first twelve patients were subsequently reviewed and the clinical results and a cadaveric study published in the Journal of Shoulder and Elbow Surgery 2000.(11)

The patient often presents with a history of attempting a forced flexion and/or forearm supination against a considerable resisting force. The patient will often have bruising on the medial side of the elbow, pain and swelling.  The biceps muscle will have an unusual contour, with the bulk of the muscle translated proximally.  The normal biceps tendon is not palpable in the cubital fossa when attempting to flex the elbow against resistance.  The power of supination against resistance is considerably reduced compared with the opposite side.

Non-operative treatment is likely to leave the patient with a dull ache in the arm, particularly when performing sustained activities.(12)  Patients have a persistent marked decrease in forearm supination strength, as the biceps tendon is the prime supinator of the forearm.  Loss of elbow flexion power is not so severe as it is supported by other muscles, such as brachialis, brachioradialis and pronator teres.  However, it is the patient’s endurance when performing repetitive activities that is most profound.(13)  The patient who requires repetitive use of the upper limb (particularly in the dominant arm) is likely to be severely disabled with an untreated distal biceps tendon avulsion.

The author routinely performs a set of plain radiographs of the elbow pre-operatively.  Occasionally a small flake of bone will be avulsed with the tendon.  For the patient who presents with obvious biceps tendon avulsion with the proximal migration of the muscle belly, no other pre-operative investigations are required.  The author has witnessed many patients with complete avulsion in which ultrasound and magnetic resonance imaging have been misinterpreted as partial tears or normal tendons surrounded by haematoma.

The patient who presents with a true partial tear, in which case the biceps tendon and muscle are not proximally migrated, is difficult to assess.  A high index of clinical suspicion is required, and an understanding of the mechanism of injury is the key to ensure that this problem is identified from the history of injury.  The patient may have localised tenderness over the tendon and weakness with elbow flexion and forearm supination against resistance.  Formal dynamic isometric muscle testing can be performed to document the level of weakness.  In this complex group of patients the author has used ultrasound and MRI scanning to assess the biceps tendon insertion.  However, in the acute and chronic situation the diagnosis is difficult to confirm using these imaging modalities.

Technique
Set-up
The patient is given a general anaesthetic, the arm is exsanguinated and tourniquet inflated.  The arm is placed onto an arm table with the elbow extended.

Approach
A 5 cm transverse incision is made 2 cm distal to the elbow skin crease.  The lateral cutaneous nerve of the forearm is identified and taped.  The deep fascia is incised and an inflammatory bursa filled with haemo-serous fluid is identified in the space previously occupied by the avulsed biceps tendon. The surgeon can usually easily identify the tendon, which is retracted proximally, and deliver it into the wound. By placing the elbow into full extension and supination, the radial tuberosity is exposed with the aid of a hand-held right angle retractor.  These retractors are preferred to levers to minimise the chance of injury to the adjacent neurovascular structures.  The neurovascular structures are not formally explored in the acute case, as the surgeon can simply operate through the tract previously occupied by the tendon.

Preparation of the Radius
A cortical window large enough to accommodate the biceps tendon is made with the aid of a high speed burr.  The surgeon must stay as medial as possible, with the arm held at maximal supination so that it reproduces the normal anatomical position of the biceps insertion into the radial tuberosity.  A 4.5 mm drill with a guard is then introduced through the anterior-medial cortical window in the proximal radius.  This is drilled through the posterior cortex, ensuring that an adequate bridge of bone between the window and drill hole is maintained.

Fixation of Endobutton to Tendon
The biceps tendon is then delivered external to the wound and the necrotic tendon end is debrided.  Two number 5 Ethibond (Ethicon Inc., Sommerville, NJ) sutures are used to secure the tendon to the two central holes of the Endobutton.  Bunnell sutures are placed along the medial and lateral aspects of the tendon, preserving the middle section to maintain vascularity.  The Bunnell suture is commenced proximally and advanced distally through the holes of the Endobutton before returning proximally to be tied.  A gap of 2 mm is left between the Endobutton and the tendon end to allow the Endobutton to be manipulated across the cortex of the radius.  The sutures are tied proximally so that they are away from the Endobutton and do not interfere with it locking into the radius.

An extra suture is placed into each of the two outer holes of the Endobutton.  These are used to manipulate the Endobutton across the radius.  Sutures of different colour are chosen (eg Ethibond and Prolene) so that the surgeon is orientated as to which suture is controlling which end of the Endobutton.  These are referred to as leading and trailing sutures.

At this point the Endobutton/tendon unit is “prefabricated”, ready for fixation to the radius (Fig. 1,2).  All the suturing and preparation of the radius has been performed, with the tendon delivered from the wound and with the elbow extended.  This is fundamentally different to suture anchors that provide fixation by tying the sutures down onto the radius in a bulky forearm with the elbow flexed.

The wound is irrigated to minimize the chance of heterotopic bone formation.  A Beath straight-eyed needle is then advanced through the cortical window and out through the dorsal aspect of the proximal forearm.  This needle delivers the two sutures which control and allow manipulation of the Endobutton.  It is important that this needle be advanced directly posterior (Fig. 3a).  A cadaveric cross-sectional anatomical study has demonstrated that there is a safe zone between 0º and 30°.  If the pin is advanced out as far as 45° it is possible that a posterior interosseous nerve injury will occur (Fig. 3b).(11)

The elbow is only then flexed and fully supinated.  Care is taken to ensure that the tendon is appropriately aligned.  Traction is then placed on the leading and trailing sutures to deliver the Endobutton to the dorsal aspect of the proximal radius (Fig. 3c).  By placing tension onto the trailing suture, the Endobutton locks into position and prevents proximal migration of the tendon (Fig. 3d).  Fluoroscopy is useful to assess the position of the Endobutton as it is advanced through the radius and locked into position.(14)  The leading and trailing sutures are simply removed.  The elbow is taken through a full range of motion to ensure that the tendon is secure.

Results
The author has published the results of his first twelve cases at an average follow-up of 17 months.(11)  All patients were satisfied with their outcome and were able to return to activities of daily living. No neurovascular complications occurred.  There was no clinical or radiological evidence of radioulnar synostosis in any patient.  All patients had an intact biceps tendon and had a return of grade 5 power.  The average range of flexion was from 5° to 146°.  The average supination was 81° and average pronation 80°.  The only complication in the series was a patient who developed an abscess six months after the surgery which resolved with incision, drainage and antibiotics.

Complications
To our knowledge, re-rupture has not occurred with any of the 40 cases using the Endobutton technique performed by the author.

A cadaveric study assessing the safety of this technique has been performed (Fig. 3b).(11)  On the anterior aspect of the elbow the structure most at risk is the ulnar artery, which on average is 6 mm from the biceps tendon.  The distance from a Beath pin to the posterior interosseous nerve is quite variable.  If the Beath pin is advanced in a posterolateral direction at 45° then injury to the posterior interosseous nerve can occur.  It is important when advancing the pin that it is advanced directly posterior to minimize the chance of this complication. The use of hand-held right angle retractors are much less likely to cause anterior neurovascular structure injury than various levers.  The author is concerned that the use of Hohmann retractors may lead to injury to anterior neurovascular structures.

There is the potential to sustain a proximal radius fracture.  It is important that the bony bridge between the anterior cortical window and posterior drill hole is adequate to minimise the risk of fracture.  Irrigation of the wound and the minimally invasive technique reduce the risk of heterotopic ossification.  The author has witnessed heterotopic bone with this technique but this is usually minimal and does not affect function.

Post-operative Management
The author has managed his patients with a plaster back-slab, with the elbow at 90° of flexion and the forearm in full supination for the first week after surgery. The back-slab is then removed and the patient provided with a sling, with advice that it can be removed and the elbow mobilised as tolerated.  The patient is advised not to  perform any heavy lifting or grasping for a period of three months and not to perform any maximal flexion or supination of the forearm for a period of six months.  We have not used anti-inflammatory medications or physiotherapy.

The surgical management of the patient with a delayed tendon rupture is much more difficult than that of an acute repair.  A complete open Henry’s approach is required to ensure that neurovascular safety is maintained throughout the procedure.  The biceps tendon will be adherent to the adjacent muscle and will be difficult to deliver.  It can be seen that the biceps tendon concertinas and shortens.  Even with traction it is usually impossible to re-establish its normal anatomical length.  It is interesting that if the bicipital aponeurosis is intact the aponeurosis will maintain its normal length, as will the tendon proximal to the aponeurosis.  Morrey has recommended an Achilles’ tendon autograft or synthetic ligament augmentation devise (LAD).(3)  The author prefers a medial hamstring tendon, which is harvested with the aid of a tendon stripper.  The tendon is then interwoven into the native biceps tendon.  The Endobutton is attached to the distal aspect of the tendon graft using the technique described for the acute avulsion. It is also important to consider that the lacertus fibrosis/biceps tendon unit spans the ulna and radius and contains the median nerve and brachial artery.  If biceps tendon is too tight, then the neurovascular structures will be strangled in pronation as the biceps wraps around the radius.

Discussion
The surgical exposure used in this technique is minimally invasive as it requires only a small anterior incision, which takes the surgeon to the deep fascia where the biceps tendon is located.  This anterior approach is also being used by other authors for other fixation techniques.(15)  In acute cases the tendon can usually be identified and mobilised.  However, after four to six weeks the tendon will be adherent to the adjacent muscle, and much greater exposure is required to be able to perform this safely.

The concept of pre-fabrication is where the tendon is delivered from the wound and the sutures are then used to fix the Endobutton to the tendon.  The extra sutures are added to the Endobutton to allow it to be manipulated.  At this point the construct is prefabricated such that by advancing the sutures across the radius, the Endobutton can then be used to deliver and lock the tendon into position.

The repair technique is strong and was the first technique where active mobilisation following a biceps tendon repair was recommended.  This is due to the fact that two strong number 5 Ethibond sutures can be used to secure the robust Endobutton.  The tendon, once secured, is positioned within the intramedullary canal which maximises the surface area between the tendon and the radial tuberosity.

A comparison with the Endobutton and suture anchors is made in Table 1.  The suture anchor usually utilises a smaller number 2 suture and, in a male patient with a big bulky forearm requires the surgeon to advance the knot and tendon down onto the radial tuberosity.  If the surgeon is successful in advancing the tendon then it relies on healing onto the cortical surface with a relatively minimal contact area.  If there is any gapping at the suture anchor due to inability to tighten the suture, there will be a gap between the tendon and the cortical surface.

The two-incision technique described by Boyd and Anderson requires the use of two incisions and has the risk of heterotopic bone formation.(4)  The strength of fixation is reduced as it requires sutures to be secured over a bone bridge, and for this reason early active mobilisation has not been recommended.

The Endobutton technique is relatively simple.  We have found the use of fluoroscopy to be useful in identifying the exact position of the Endobutton at the time of advancing it across the radius.

Further details with regard to this technique can be obtained from ww.gregbain.com.au

Acknowledgment
Ron Heptinstall for his assistance with preparation of manuscript
Deidre Craig for the art work provided in this manuscript

Tables
Table 1

Figures

References
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2.         Meherin, J. M., and Kilgore, E. S.: The treatment of ruptures of the distal biceps brachii tendon. American Journal of Surgery, 99: 636-40., 1960.

3.         Morrey, B. F.; Askew, L. J.; An, K.-N.; and Dobyns, J. H.: Rupture of the distal tendon of the biceps brachii. A biomechanical study. Journal of Bone and Joint Surgery, 67A: 418-21., 1985.

4.         Boyd, H. B., and Anderson, L. D.: A method for reinsertion of the distal biceps brachii tendon. Journal of Bone and Joint Surgery, 43A: 1011-1043, 1961.

5.         Bunnell, S.: Surgery of the Hand. Edited, 586-587., Philadelphia.etc,. J B.Lippincott., 1948.

6.         D'Alessandro, D. F.; Shields, C. L.; Tibone, J. E.; and Chandler, R. W.: Repair of distal biceps tendon ruptures in athletes. The American Journal of Sports Medicine, 21: 114-19., 1993.

7.         Davis, S. M., and Yassine, Z.: An etiologic factor in the tear of the distal tendon of the biceps brachii. Journal of Bone and Joint Surgery, 38A: 1365-138., 1956.

8.         Dobbie, R. P.: Avulsion of the lower biceps brachii tendon: analysis of fifty-one previously unreported cases. American Journal of Surgery, 51: 662-683, 1941.

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10.       Lintner, S., and Fisher, T.: Repair of the distal biceps tendon using suture anchors and an anterior approach. Clinical Orthopaedics and Related Research, 322: 116-19., 1996.

11.       Bain, G. I.; Prem, H.; Heptinstall, R. J.; Verhellen, R.; and Paix, D.: Repair of distal biceps tendon rupture: a new technique using the Endobutton. Journal of Shoulder and Elbow Surgery, 9(2): 120-6., 2000.

12.      Jaslow, I. A., and May, V. R.: Avulsion of the distal tendon of the biceps brachii muscle. Guthrie Clinical Bulletin, 15: 124, 1946.

13.      Bain, G. I.; Hunt, J.; and Mehta, J. A.: Operative fluoroscopy in hand and upper limb surgery.  One hundred cases. Journal of Hand Surgery, 22B(5): 656-658, 1997.

14.       Agins, H. J.; Chess, J. L.; Hoekstra, D. V.; and Teitge, R. A.: Rupture of the distal insertion of the biceps brachii tendon. Clinical Orthopaedics and Related Research, 234: 34-8., 1988.

15.       Kelly, E. W., and O'Driscoll S, W.: Mini-incision technique for acute distal biceps tendon repair. Techniques in Shoulder and Elbow Surgery, 3(1): 57-62, 2002.