Distal Biceps Rupture
Hook Test | Supination Loss | Radial Tuberosity | Acute vs Chronic
Critical Must-Knows
- Hook test (O'Driscoll): Flex elbow 90°, supinate - hook finger from lateral under biceps tendon. No cord = rupture (100% sensitivity)
- Supination is the primary deficit (40% loss) - more than flexion (30%) because brachialis compensates for flexion
- Tendon inserts on posterior aspect of radial tuberosity - this posterior footprint provides cam effect for supination
- Lacertus fibrosus if intact can mask Popeye sign but hook test still positive
- Chronic (greater than 4 weeks): Primary repair often impossible - requires allograft reconstruction with inferior outcomes
Clinical Pearls
- "Timing critical: Acute (less than 3-4 weeks) allows primary repair; chronic needs graft
- "LABCN (lateral antebrachial cutaneous nerve) is most commonly injured nerve (5-30%), usually transient
- "Single-incision vs two-incision (Boyd-Anderson): Two-incision has synostosis risk but better anatomic placement
- "Cortical button + interference screw = strongest construct
Clinical Imaging
Imaging Gallery

Exam Warning: Clinical Diagnosis
Hook Test & Lacertus
Hook Test is key (Hollow = Rupture). Intact Lacertus can mask deformity ("Popeye" sign), but Hook test remains abnormal.
Functional Deficit
Primary deficit is lost Supination strength. Flexion is preserved by the Brachialis.
HOOKHOOK Test
| H | Hook Hook finger from lateral under biceps tendon |
| O | O'Driscoll Described the test with 100% sensitivity |
| O | Obvious Hollow if tendon ruptured - no cord to hook |
| K | Key Key clinical sign - works even if lacertus intact |
| H | Hook Hook finger from lateral under biceps tendon | O | Obvious Hollow if tendon ruptured - no cord to hook |
| O | O'Driscoll Described the test with 100% sensitivity | K | Key Key clinical sign - works even if lacertus intact |
L-PNerves at Risk
| L | LABCN Lateral Antebrachial Cutaneous - most common (5-30%) |
| P | PIN Posterior Interosseous Nerve - rare but devastating |
| L | LABCN Lateral Antebrachial Cutaneous - most common (5-30%) |
| P | PIN Posterior Interosseous Nerve - rare but devastating |
BACSFixation Strength Hierarchy
| B | Button Cortical button (Endobutton) - strongest single device |
| A | Anchors Suture anchors - easier, less PIN risk |
| C | Combined Button + Screw = strongest overall construct |
| S | Screw Interference screw - compresses tendon into tunnel |
| B | Button Cortical button (Endobutton) - strongest single device | C | Combined Button + Screw = strongest overall construct |
| A | Anchors Suture anchors - easier, less PIN risk | S | Screw Interference screw - compresses tendon into tunnel |
Anatomy & Pathophysiology
Tendon & footprint:
- The two muscle heads coalesce into a single distal tendon that often rotates 90° before inserting on the posterior aspect of the radial (bicipital) tuberosity.
- This posterior footprint sits furthest from the forearm rotational axis, giving the biceps its cam effect / supination moment arm — the anatomical reason supination is the dominant deficit.
- Anatomic repair must restore the tendon to the posterior footprint; an anterior or non-anatomic re-attachment loses supination torque.
Lacertus fibrosus (bicipital aponeurosis):
- Fascial expansion from the tendon to the flexor-pronator fascia; if intact it tethers the muscle belly and can mask the Popeye deformity — but never the hook test.
Mechanism: Eccentric overload of a flexed, supinated elbow (lifting, catching a falling load). Pre-existing tendinosis and (debated) smoking/anabolic steroid use are predisposing factors. Almost exclusively middle-aged men (dominant arm).
Nerves at risk:
- Lateral antebrachial cutaneous nerve (LABCN): Most commonly injured (skin-flap/retractor traction). Runs between biceps and brachialis — the most frequent neurological complication.
- Posterior interosseous nerve (PIN): Threatened by far-cortex over-drilling for a cortical button, or by anterior dissection past the tuberosity. Mitigate by pronating the forearm (wraps PIN posteriorly) and limiting over-penetration.
- Radial / superficial radial nerve: At risk laterally in the two-incision exposure.
Clinical Assessment
History:
- Sudden extension force against flexed elbow.
- "Pop" sensation.
- Pain in antecubital fossa.
Examination:
- Inspection: Ecchymosis. "Popeye Sign" (muscle belly retracts proximally).
- Palpation: Tenderness at tuberosity.
- Hook Test: (O'Driscoll). Flex elbow 90°, supinate. Try to hook finger from lateral side under tendon.
- Intact: Finger hooks tendon.
- Rupture: No tendon palpated.
- Strength: Weakness in supination greater than flexion.
Differential Diagnosis
Differentiating Distal Biceps Rupture
Investigations
- Clinical first: The hook test is the primary investigation — sensitivity and specificity 100%, outperforming MRI (O'Driscoll 2007). A confident clinical diagnosis needs no imaging.
- Radiographs: Usually normal; exclude a radial tuberosity avulsion fracture and confirm no bony pathology.
- Ultrasound: Operator-dependent; useful, cheap, dynamic — good first-line imaging in limited-resource settings.
- MRI: Reserve for equivocal cases, suspected partial tears, and chronic ruptures (quantifies % tear, gap/retraction, muscle atrophy and Goutallier fatty-infiltration grade for surgical planning). FABS view (Flexed Abducted Supinated) improves visualization of the distal footprint.
Management Algorithm

Surgical Options
Timing:
- Acute (less than 3-4 weeks): Primary repair.
- Chronic (greater than 4 weeks): Tendon retracts and scars. Often needs allograft (Achilles/Hamstring).
Approaches:
-
Single Incision (Anterior):
- Pros: Simple, one incision.
- Cons: Higher risk of LABCN injury. Harder to get anatomical posterior footprint (loss of supination torque?).
- Fixation: Cortical Button (Endobutton) + Interference Screw.
-
Double Incision (Boyd-Anderson):
- Anterior incision to retrieve tendon, Posterior incision (splitting common extensor/ulna) to fix to tuberosity.
- Pros: Anatomical posterior fixation.
- Cons: Risk of Synostosis (Radio-ulnar), Heterotopic Ossification.
Fixation Devices:
- Cortical Button (Suspension): Strongest.
- Suture Anchors: Easier, less risk to PIN.
- Interference Screw: Compresses tendon into bone tunnel.
- Combined (Button + Screw) creates strongest construct.
Operative vs Non-operative — Meta-analysis
- Systematic review and meta-analysis, 62 studies, 2481 cases (2402 operative, 79 non-operative); mean age 47 years, 98.5% male
- Operative repair gave a mean +27.6% supination strength and +33.9% supination endurance versus non-operative (both p less than 0.0001)
- Operative repair also superior for flexion strength (+25.7%) and flexion endurance (+11.1%)
- DASH and Mayo Elbow Performance Score significantly better after surgery
Operative vs Non-operative — Strength Ratios
- Systematic review and meta-analysis, 53 studies, 1380 patients
- Supination strength (injured/uninjured ratio) 89.2% operative vs 62.6% non-operative (p less than 0.001)
- Flexion strength 94.7% operative vs 83.0% non-operative (p less than 0.001)
- Surgical complications: ~10% heterotopic ossification, ~10% transient sensory nerve injury, 1.6% transient motor injury, 0.1% persistent motor deficit; all fixation methods equivalent, single-incision gave slightly better pronation ROM
Hook Test — Original Description
- Diagnostic cohort of 45 patients undergoing surgical exploration (33 complete avulsions, 12 partial tears)
- Hook test abnormal in 33/33 complete avulsions and intact in 12/12 partial tears — sensitivity and specificity both 100%
- Partial tears: hook test was intact but painful in 9 of 12 (pain-positive hook flags a partial tear)
- Hook test outperformed MRI (sensitivity 92%, specificity 85%)
Single vs Double-Incision Repair — RCT
- Randomized trial: single-incision (suture anchors, n=47) vs double-incision (transosseous tunnels, n=44), all male, acute ruptures
- No difference in ASES, DASH, PREE or supination strength at 2 years
- Double-incision had a 10% advantage in final isometric flexion strength (104% vs 94%, p=0.01)
- Single-incision had far more transient LABCN neurapraxia (19/47 vs 3/43, p less than 0.001); 4 reruptures overall, all from early non-compliance/reinjury
Fixation Biomechanics — Cortical Button
- Cadaveric study, 20 matched specimens, cyclically loaded 3600 cycles
- Standard cortical button load-to-failure 389 N vs tension-slide technique 432 N (no significant difference, p=0.28)
- Tension-slide significantly reduced gap formation (1.26 mm vs 2.79 mm, p=0.03)
- Adding an interference screw to the tension-slide construct did not significantly change load-to-failure or gap formation
Direct Repair of Chronic Ruptures
- Systematic review, 8 studies, 124 chronic tears (mean delay 122 days) repaired directly without graft
- Chronic direct repair had a slightly higher but mostly transient LABCN palsy rate (12.1% vs 7.9% acute, p=0.75)
- Only 3 reruptures (3.2%) across studies reporting this complication
- Good patient satisfaction, ROM and functional scores when residual tendon excursion and quality permit direct repair
Complications
Complications of Biceps Repair
Controversies & Areas of Uncertainty
- Single- vs double-incision: Modern level-I/meta-analysis data show equivalent function; the double-incision retains a small flexion-strength edge and lower LABCN irritation, while the single-incision risks synostosis less. Choice is surgeon-dependent rather than evidence-mandated.
- Fixation device: Cortical button is biomechanically strongest, but clinical meta-analysis shows all constructs (button, anchors, transosseous, interference screw) yield equivalent outcomes. The "button + screw" mantra is biomechanical, not a clinical requirement.
- Cut-off for "chronic": The 4-week threshold is a convention, not a biological switch. Direct repair without graft can succeed well beyond 4 weeks when tendon excursion and quality permit (Tzeuton 2023) — intra-operative retrievability matters more than the calendar.
- Partial tears: No randomized evidence. High-grade (greater than 50%) tears in active patients are usually completed and repaired, but the threshold and the decision to debride vs preserve intact fibres remain expert opinion.
- HO prophylaxis: Indomethacin and the value of single-dose radiotherapy after two-incision repair are not supported by high-quality trials.
- Non-operative management: Acceptable for low-demand/elderly patients; the magnitude of supination loss (meta-analysis ~27-37% deficit) drives the decision more than age alone.
References
- O'Driscoll SW, Goncalves LBJ, Dietz P. The hook test for distal biceps tendon avulsion. Am J Sports Med. 2007;35(11):1865-9. PMID 17687121.
- Grewal R, Athwal GS, MacDermid JC, et al. Single versus double-incision technique for repair of acute distal biceps tendon ruptures: a randomized clinical trial. J Bone Joint Surg Am. 2012;94(13):1166-74. PMID 22760383.
- Looney AM, Day J, Bodendorfer BM, et al. Operative vs. nonoperative treatment of distal biceps ruptures: a systematic review and meta-analysis. J Shoulder Elbow Surg. 2022;31(4):e169-e189. PMID 34999236.
- Cuzzolin M, Secco D, Guerra E, et al. Operative versus nonoperative management for distal biceps brachii tendon lesions: a systematic review and meta-analysis. Orthop J Sports Med. 2021;9(10):23259671211037311. PMID 34734095.
- Sethi P, Obopilwe E, Rincon L, Miller S, Mazzocca A. Biomechanical evaluation of distal biceps reconstruction with cortical button and interference screw fixation. J Shoulder Elbow Surg. 2010;19(1):53-7. PMID 19574061.
- Tzeuton S, Johns W, Campbell B, et al. Outcomes and patient satisfaction of delayed distal biceps repairs without graft augmentation: a systematic review. JBJS Rev. 2023;11(5). PMID 37141425.
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Acute Distal Biceps Rupture in High-Demand Patient - Counseling and Surgical Decision
"A 45-year-old bodybuilder presents to your clinic 3 days after feeling a sudden pop in his right elbow whilst deadlifting a heavy weight. He describes an immediate sharp pain in the antecubital fossa followed by swelling and bruising. He has continued to train with modifications but notices significant weakness when doing pulling exercises and when turning his wrist (such as using a screwdriver). On examination, there is ecchymosis in the antecubital fossa and a visible high-riding biceps muscle belly in the upper arm (Popeye sign). His elbow range of motion is full (0-145°) but painful at terminal flexion. When you perform the hook test - asking him to flex his elbow to 90° and actively supinate while you attempt to hook your index finger from the lateral side under the biceps tendon in the cubital fossa - you cannot palpate any cord-like structure beneath the skin. There is just a hollow space. His flexion strength is moderately reduced (4/5) but his supination strength against resistance is markedly reduced compared to the contralateral side. He is right-hand dominant and this is his dominant arm. He asks whether he really 'needs' surgery or if he can just continue training and let it heal naturally. How do you counsel him regarding diagnosis, natural history without surgery, surgical options, and your recommendation?"
Scenario 2: Partial vs Complete Distal Biceps Rupture - Clinical Differentiation and Surgical Decision
"A 38-year-old carpenter presents to your clinic 10 days after injuring his right (dominant) elbow whilst catching a falling ladder at work. He felt immediate pain in the front of his elbow but was able to continue working that day with some difficulty. Over the past week, he has had persistent anterior elbow pain and weakness, particularly when using power tools that require forearm rotation (screwdrivers, drills). He can perform most daily activities but notices definite weakness compared to his normal strength. On examination, there is mild swelling and tenderness in the antecubital fossa. There is NO obvious Popeye sign - the muscle belly contour appears symmetric to the contralateral side. When you perform the hook test (elbow 90° flexion, active supination), you CAN palpate a cord-like structure under your finger when hooking from lateral to medial, but it feels somewhat thinner than the contralateral side and he has significant pain when you do this maneuver. His active elbow flexion is full range (0-145°) with 4+/5 strength (mild weakness). His supination strength is noticeably reduced compared to the contralateral side - approximately 60-70% of normal strength by your estimation. Plain radiographs of the elbow are normal with no fracture or dislocation. You order an MRI which reports: 'High-grade partial tear of the distal biceps tendon involving approximately 60-70% of the tendon substance. The tear is located 2cm proximal to the radial tuberosity insertion. There is retraction of the torn fibers with a 1cm gap. The remaining intact fibers (30-40%) are attenuated and show high T2 signal indicating degeneration. No complete discontinuity. Mild surrounding soft tissue edema. Radial tuberosity shows normal marrow signal.' He asks whether he needs surgery or if this can heal with rest. He is highly motivated to return to full carpentry work which requires significant upper extremity strength. How do you counsel him and what is your management plan?"
Scenario 3: Chronic Neglected Distal Biceps Rupture with LABCN Injury - Complex Reconstruction Challenge
"You are seeing a 48-year-old mechanic in your reconstructive elbow clinic, referred from another state. He sustained a distal biceps tendon rupture 8 months ago when he was pulling on a seized engine part. He was initially seen at a rural emergency department where X-rays showed no fracture and he was told he had a 'biceps strain' and given analgesia and a sling. Over the following weeks, his pain settled but he noticed significant weakness in his right (dominant) arm, particularly when using wrenches and turning bolts. He saw his GP at 6 weeks who ordered an MRI confirming complete distal biceps rupture, and he was referred to a local orthopaedic surgeon. The surgeon offered him surgery, but he was hesitant due to fear of complications and decided to 'live with it.' Over the past 6 months, he has struggled significantly at work - he can no longer perform many mechanical tasks requiring forearm rotation, has had to modify his work duties, and is facing potential job loss. He has relocated to your area and presents requesting surgery. On examination, there is a prominent Popeye sign with the biceps muscle belly high in the arm. When you perform the hook test, there is a completely hollow antecubital fossa with no palpable structure. His elbow range of motion is full (0-140°) but his flexion strength is 3+/5 and supination strength is markedly reduced (2/5, approximately 40% of the contralateral side). There is visible quadriceps atrophy with his right upper arm measuring 4cm less circumference than the left. You review his MRI from 6 months ago which showed complete rupture with 4cm retraction, and you order a new MRI which now shows: 'Complete distal biceps tendon rupture with 7cm retraction of the tendon stump to the mid-arm level. The retracted tendon is scarred and adherent to the brachialis muscle. Marked atrophy of the biceps muscle belly with moderate fatty infiltration (Goutallier grade 2-3). The muscle belly measures 15mm in diameter compared to 28mm on the contralateral side. Dense scar tissue fills the anterior elbow. Radial tuberosity is intact but shows cortical irregularity and bone resorption. No acute abnormality.' He is desperate for surgery as his livelihood depends on returning to mechanic work. He asks: 'Can you fix this? I know I should have had surgery earlier, but can you still repair it now?' How do you counsel him and what is your surgical plan?"
Distal Biceps Quick Reference
Clinical summary
Deficits (Non-op)
- •Supination Strength: -40%
- •Supination Endurance: -50%
- •Flexion Strength: -30%
Hook Test
- •Index finger hooks lateral edge
- •Most sensitive test (100%)
- •Abnormal even if Lacertus intact
Nerves at Risk
- •LABCN (Sensory) - Commonest
- •PIN (Motor) - Worst
Guidelines, Registries & Global Practice
Global epidemiology
- Incidence approximately 1.2-2.5 per 100,000 person-years; rising with increasing recreational weightlifting.
- Demographics are remarkably consistent worldwide: men in the 4th-6th decade, dominant arm, eccentric loading mechanism. Meta-analyses report 98-100% male cohorts (Looney 2022; Cuzzolin 2021).
- Distal tears account for only ~3-10% of all biceps ruptures (the long-head proximal rupture is far commoner).
Society guidance — side by side
How Major Bodies Frame Management
Registry & outcome notes
- There is no dedicated tendon-rupture registry equivalent to the arthroplasty registries (NJR, AJRR, AOANJRR, SHAR); evidence is driven by RCTs (Grewal 2012) and meta-analyses (Looney 2022; Cuzzolin 2021).
- Across these datasets, surgery restores supination strength to ~89% of the contralateral side versus ~63% non-operatively, with fixation device having no measurable effect on outcome.
High- vs limited-resource practice variation
- Well-resourced centres: MRI confirmation when clinically ambiguous, cortical-button/interference-screw constructs, hinged-brace rehabilitation, early semi-urgent listing to stay within the repairable window.
- Limited-resource settings: diagnosis is clinical (hook test, which outperforms MRI anyway); transosseous suture fixation through bone tunnels is a low-cost, effective alternative; chronic presentation is commoner because of referral delay, raising the proportion needing graft or accepting non-operative deficit.
- Universal medicolegal point: a complete rupture mislabelled a "strain" can miss the acute repair window — document the hook test, the timing discussion, and informed consent regarding the natural-history supination deficit.