summary Distal Biceps Avulsions are injuries to the biceps tendon at the radial tuberosity insertion that generally occurs due to a sudden excessive eccentric contraction of the biceps brachii. Diagnosis can be made clinically in the setting of complete tears with a hook test. MRI studies can be used to discern between a complete tear and a partial tear. Treatment can be nonoperative or operative depending on patient age, patient activity demands, chronicity of tear, and degree of tear. Epidemiology Incidence rare distal biceps tendon rupture represents about 10% of biceps ruptures. Demographics ruptures tend to occur in the dominant elbow (86%) of men (93%) in their 40s. Anatomic location complete distal biceps avulsion partial distal biceps avulsion partial distal biceps tendon tears occur primarily on the radial side of the tuberosity footprint. intersubstance muscle transection seen when rope wrapped around arm (tug-of-war) Risk factors anabolic steroids smoking has 7.5x greater risk than nonsmokers hypovascularity intrinsic degeneration mechanical impingement in the space available for the biceps tendon Etiology Pathophysiology mechanism excessive eccentric tension as the arm is forced from a flexed to an extended position "flexed elbow unacceptably challenged" vascular watershed mechanical attrition (abrasion during pronosupination) Associated conditions rarely it can lead to symptoms of median nerve compression Anatomy Biceps tendon inserts onto the radial tuberosity. Contents of antecubital fossa (medial to lateral) median nerve (most medial structure), brachial artery, biceps tendon, radial nerve (most lateral structure) radial recurrent vessels lie superficial to biceps tendon Distal biceps tendon possesses two distinct insertions short head attaches distally on radial tuberosity (thin sliver) origin is coracoid processs is a better flexor long head attaches proximally on radial tuberosity (oval footprint) origin is the superior lip of the glenoid and glenoid labrum is a better supinator as attachment is furthest from axis of rotation (attaches to apex of radial tuberosity) independent function to prevent anterior, inferior and superior translation of humeral head against proximal pull of short head of biceps Lacertus fibrosus distal to the elbow crease, the tendon gives off, from its medial side, the lacertus fibrosus (bicipital aponeurosis or biceps fascia) originates from the distal short head of the biceps tendon lacertus passes obliquely across the cubital fossa, running distally and medially, helping to protect the underlying brachial artery and median nerve it is continuous with the deep fascia of the flexor tendon origin, envelopes flexor muscle bellies may be mistaken for an intact distal biceps tendon on clincial exam Presentation History patient often experiences a painful “pop” as the elbow is eccentrically loaded from flexion to extension. Symptoms weakness and pain, primarily in supination, are hallmarks of the injury. Physical exam inspection and palpation varying degree of proximal retraction of the muscle belly “reverse Popeye sign” change in contour of the muscle, proximally medial ecchymosis a palpable defect is often appreciated motor exam loss of more supination than flexion strength loss of 50% sustained supination strength loss of 40% supination strength loss of 30% flexion strength provocative tests Hook test performed by asking the patient to actively flex the elbow to 90° and to fully supinate the forearm examiner then uses index finger to hook the lateral edge of the biceps tendon. with an intact / partially torn tendon, finger can be inserted 1 cm beneath the tendon false positive partial tear intact lacertus fibrosis underlying brachialis tendon sensitivity and specificity 100% Ruland biceps squeeze test (akin to the Thompson/Simmonds test for Achilles rupture) elbow held in 60-80° of flexion with the forearm slightly pronated. one hand stabilizes the elbow while the other hand squeezes across the distal biceps muscle belly. a positive test is failure to observe supination of the patient’s forearm or wrist. sensitivity 96% challenge is to distinguish between complete tear and partial tear. biceps tendon is absent in complete rupture and palpable in partial rupture (otherwise they have a very similar clinical picture) Evaluation Radiographs usually normal occasionally show a small fleck or avulsion of bone from the radial tuberosity MRI positioning in elbow flexion, shoulder abduction, forearm supination increases sensitivity is important to distinguish between complete tear vs. partial tear muscle substance vs. tendon tear degree of retraction Treatment Nonoperative supportive treatment followed by physical therapy indications older, low-demand or sedentary patients who are willing to sacrifice function if the lacertus fibrosis is intact, the functional deficits of biceps rupture may be minimized in a low-demand patient. outcomes will lose 50% sustained supination strength will lose 40% supination strength will lose 30% flexion strength will lose 15% grip strength Operative surgical repair of tendon to tuberosity indications young healthy patients who do not want to sacrifice function partial tears that do not respond to nonoperative management subacute/chronic ruptures may be treated successfully with direct repair (without allograft) may need to hyperflex elbow to achieve fixation hyperflexion does NOT lead to loss of elbow ROM or flexion contracture timing surgical treatment should occur within a few weeks from the date of injury further delay may preclude a straightforward, primary repair. a more extensile approach may be required in a chronic rupture to retrieve the retracted and scarred distal biceps tendon. Techniques Anterior Single-Incision Technique single incision technique was developed to reduce the incidence of HO and synostosis seen with the double incision technique technique limited antecubital fossa incision interval between the brachioradialis and pronator teres radial (lateral) retraction of the brachioradialis and medial retraction of the pronator teres lateral antebrachial cutaneous nerve (LABCN) is identified as it exits between the biceps and brachialis at antecubital fossa. originates from lateral cord of brachial plexus (terminal branch of musculocutaneous nerve) recurrent radial vessels encountered and either coagulated or carefully dissected and retracted protect PIN by limiting forceful lateral retraction and maintaining supination complications injury to the LABCN is most common more LABCN injury than 2-incision approach radial nerve or PIN injury is most severe risk has decreased with new tendon fixation techniques that require less dissection in the antecubital fossa synostosis and resulting loss of pronation/supination avoid exposing periosteum of ulna avoid dissection between the radius and ulna heterotopic ossification less common than with 2 incision technique postoperative immobilize in 110° of flexion and moderate supination Dual Incision Technique developed to avoid injury to radial nerve/PIN technique uses smaller anterior incision over the antecubital fossa and a second posterolateral elbow incision posterior interval is between ECU and EDC avoid exposing ulna do NOT use interval between ECU/anconeus (Kocher's interval) or anconeus and ulna anterior dissection is same as single incision described above after the biceps is identified, the radial tuberosity is palpated, and a blunt, curved hemostat is placed in the interosseous space along the medial border of the tuberosity and palpated on the dorsal proximal forearm hemostat pierces anconeus and tents the skin indicating where the posterolateral incision should be made complications LABCN injury is most common synostosis and heterotopic ossification more common with 2 incision than single incision Distal Biceps Fixation Techniques comparison tolerances elbow at 90°, no load, distal biceps sustains 50N elbow at 90°, with 1kg load, distal biceps sustains 112N force to rupture = 200N repair needs to be able to withstand 50N suture button (400N) > suture anchor (380N) > bone tunnel (310N) > interference screw (230N) combination technique (suture button + interference screw) stronger than single technique bone tunnel 2-incision approach tuberosity is exposed and a guide pin drilled through the center of the tuberosity acorn reamer is used to ream through anterior cortex to recreate a slot of varying depth two or three 2-mm diameter holes are drilled 1 cm apart through the lateral, far side of the radius no. 2 sutures sown to the distal tendon are passed and tied across the bone bridge. suture anchors single-incision approach radial tuberosity is debrided to prepare for bone-to-tendon healing 2 suture anchors inserted into the biceps tuberosity, one distal and one proximal. the distal anchor is tied first to bring the tendon out to length. next, the sutures of the proximal anchor are tied this repair sequence maximizes tendon-to-bone contact and surface area. intraosseous screw fixation single-incision approach similar to the bone tunnel technique, except the No. 2 suture (whip-stitched through the tendon) is passed through a bioabsorbable tenodesis screw. suspensory cortical button single-incision approach tendon end is whip-stitched with the suture ends placed into two central holes of the button. similar to bone tunnel technique, an acorn reamer is used to ream through the anterior cortex after exposing tuberosity. a smaller hole is then drilled through the far cortex to allow the button to be passed across the far cortex. button is flipped to lie on far cortex, and suture ends are tensioned (tension slide) to bring tendon into tunnel Complications LABCN injury most common complication overall (9% incidence) because of overaggressive retraction more common with single incision technique usually resolved in 3-6mth PIN injury more common in single incision than 2 incision technique most commonly injured motor nerve (1-2% incidence) usually resolve in 3-6mth Superficial radial nerve injury 2nd most common cutaneous nerve injured (2-3%) Heterotopic ossification if interosseous membrane and ulnar periosteum disrupted a risk of the 2 incision technique Synostosis Proximal radius fracture from large tunnels or those proximal to the radial tuberosity Suture rupture (if bone tunnel method used)