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  • Injury may either be a  
    • complete distal biceps avulsion
    • partial distal biceps avulsion
      • partial distal biceps tendon tears occur primarily on the radial side of the tuberosity footprint. q 
    • intersubstance muscle transection
      • seen when rope wrapped around arm (tug-of-war)
  • 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.
    •  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
  • 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
  • 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
  • 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)
  • 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 q
      • complete tear vs. partial tear    
      • muscle substance vs. tendon tear
      • degree of retraction
  • 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.
Surgical 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.
      • 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
  • 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
  • Suture rupture (if bone tunnel method used)

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