Question 1

What is the capitellum and why does a fracture here cause so many problems?

Accepted Answer

The capitellum is the rounded knob on the lower end of the humerus (upper arm bone) that forms the outer/lateral side of the elbow joint - it articulates with the radial head (top of radius bone in forearm) and is critical for smooth elbow rotation (supination/pronation turning palm up/down) and flexion-extension (bending/straightening). Capitellum fractures cause severe problems because: (1) INTRA-ARTICULAR FRACTURE: The capitellum is entirely covered with articular cartilage (smooth joint surface). ANY fracture through this surface creates a step-off that damages opposing radial head cartilage during motion → post-traumatic arthritis inevitable if not perfectly reduced. (2) TENUOUS BLOOD SUPPLY: Capitellum blood vessels enter from posterior (back) side only. Fracture disrupts these vessels → avascular necrosis (AVN) risk 10-30% even with perfect surgery (bone fragment dies, collapses like Legg-Calve-Perthes in hip). (3) MECHANICAL BLOCK: Displaced capitellum fragment acts like a loose body in the elbow joint - jams between radial head and humerus, prevents full flexion or extension (like a pebble stuck in door hinge). (4) DIFFICULT SURGERY: Fragment is small, thin wafer of bone (coronal shear fracture - like slicing sausage front-to-back). Screws must be buried beneath cartilage surface (headless screws) or they'll impinge on radial head. Technically demanding surgery with high complication rate 20-40%. (5) STIFFNESS RISK: Elbow joint hates immobilization (capsule scars quickly causing permanent contracture). But capitellum fracture needs time to heal (6-12 weeks). Balancing early motion (prevent stiffness) vs protection (allow healing) is challenging - most patients lose some motion permanently 10-30 degrees.

Question 2

Why can't this fracture heal with just a cast like other fractures?

Accepted Answer

Capitellum fractures nearly ALWAYS require surgery (90-95% surgical vs <10% non-surgical) because: (1) ARTICULAR SURFACE INTOLERANCE: The elbow is one of the most congruent joints in the body (precise fit between bones for smooth motion). Even 1-2mm articular step-off causes point loading on cartilage → rapid arthritis development within 2-5 years. Non-surgical treatment accepts this step-off → guaranteed poor outcome. Surgery restores anatomic surface (screw fixation compresses fragment flush with surrounding cartilage). (2) FRAGMENT DISPLACEMENT INEVITABLE WITH CASTING: Capitellum fragment has NO intact muscle/ligament attachments (pure bone fragment sheared off). Biceps, brachialis, brachioradialis muscles all pull radius FORWARD (flexion) → radial head pushes anteriorly on capitellum fragment → fragment displaces forward out of elbow joint during casting despite immobilization. Studies show 50-70% non-displaced capitellum fractures displace during cast treatment (fragment migrates anterior, becomes irreducible loose body). (3) AVASCULAR NECROSIS RISK: Capitellum blood supply enters from posterior intact bone. Fracture disrupts vessels to anterior fragment. If fragment not rigidly fixed back to parent bone (surgical screws compress fragment allowing revascularization), fragment dies from lack of blood supply → AVN 40-60% with casting vs 10-20% with surgery. Dead bone collapses, severe arthritis ensues. (4) MECHANICAL BLOCK PERSISTS: Displaced capitellum fragment jams in elbow joint preventing motion. Cast immobilizes elbow but doesn't REDUCE fragment back into position. When cast removed 6 weeks later, elbow still blocked, fragment now scarred in displaced position → requires difficult revision surgery to excise fragment (worse outcome than primary ORIF). (5) STIFFNESS WORSE WITH CASTING: Prolonged elbow immobilization 6-8 weeks in cast → severe capsular contracture, lose 40-60 degrees motion (vs surgery with early motion 2 weeks → lose 10-30 degrees). WHEN CASTING ACCEPTABLE (rare <10%): Truly non-displaced fragment <1mm on CT scan. Elderly low-demand patient (minimal functional needs, surgery risks prohibitive). Patient understands high failure rate and accepts poor outcome possibility. Even then, serial X-rays every 1-2 weeks mandatory - convert to surgery immediately if ANY displacement develops.

Question 3

What are headless compression screws and why are they used for capitellum fractures?

Accepted Answer

Headless compression screws (Herbert screws, Acutrak screws) are specialized titanium screws that are threaded at BOTH ends with different thread pitches and have NO screw head protruding above the bone surface - they are specifically designed for small bone fragments in articular (joint surface) locations where traditional screws would interfere with joint motion. HOW HEADLESS SCREWS WORK: Traditional screw has threads on shaft and a HEAD that sits above bone surface (like wood screw - head prevents screw from sinking through). Headless screw has threads at BOTH ends: Leading threads (distal end that advances first) have COARSE pitch (wide-spaced threads, advance 2-3mm per turn). Trailing threads (proximal end near screw driver) have FINE pitch (narrow-spaced threads, advance 1mm per turn). When screw inserted and turned, leading end advances FASTER than trailing end → screw COMPRESSES bone fragments together (leading end pulls far fragment toward trailing end which pulls near fragment - like tightening rope between two posts). Entire screw countersinks BELOW cartilage surface (no head protruding - fully buried 2-3mm beneath joint surface). WHY NEEDED FOR CAPITELLUM: (1) AVOID RADIAL HEAD IMPINGEMENT: Capitellum articulates with radial head (radius rotates around capitellum during pronation/supination). ANY screw prominence above cartilage surface → screw head impinges on radial head during forearm rotation → painful clicking, catching, eventual screw breakage or radial head cartilage damage. Headless screw buried beneath surface → smooth cartilage allows normal radial head gliding. (2) COMPRESSION HEALING: Headless screw design generates 100-300N compression force between fragments (pulls fragment tightly against parent bone, eliminates micro-motion at fracture site). Compression stimulates bone healing (Wolff's law - mechanical stress promotes bone formation) → higher union rate 90-95% vs traditional K-wires 70-80%. (3) SMALL FRAGMENT FIXATION: Capitellum fragment is thin wafer of bone (coronal shear - 5-15mm thick anterior slice). Headless screw can be inserted from POSTERIOR (back of fragment through intact bone) advancing anteriorly through thin fragment. Screw countersinks into posterior cortex (good purchase) and compresses thin anterior fragment without protruding through articular surface. DISADVANTAGES: Expensive ($500-1,000 per screw vs $20 traditional screw - titanium, precision manufacturing, specialty instrument set required). Technically demanding insertion (must countersink to exact depth 2-3mm below surface - too shallow impinges, too deep loses compression). Require perfect reduction FIRST (screws lock fragments in position they're in when inserted - if mal-reduced, screw locks in bad position making revision impossible). OUTCOMES: Headless screw fixation revolutionized capitellum fracture treatment - union rates improved from 60-70% (K-wires, traditional screws) to 85-95%, reoperation rates decreased from 30-40% to 10-15%. They are now GOLD STANDARD for capitellum ORIF despite cost.

Question 4

What is avascular necrosis (AVN) and why is it common after capitellum fractures even with surgery?

Accepted Answer

Avascular necrosis (AVN, also called osteonecrosis) means bone DEATH from loss of blood supply - occurs in 10-30% of capitellum fractures even with perfect surgery because the capitellum has a precarious blood supply that is disrupted by the fracture itself. CAPITELLUM BLOOD SUPPLY ANATOMY: Capitellum is an EPIPHYSEAL fragment (developed from separate growth center during childhood, fused to humerus by age 14-16). Blood vessels enter capitellum from only ONE direction: Posterior (back) blood vessels from main humerus shaft penetrate into capitellum (branches of radial recurrent artery and profunda brachii artery). NO blood vessels from anterior, lateral, or medial (capitellum completely covered by articular cartilage on those surfaces - cartilage is avascular, blocks vessel penetration). Fracture occurs in CORONAL PLANE (front-to-back shear) → fracture line disrupts the posterior blood vessels → anterior capitellum fragment CUT OFF from blood supply. WHY SURGERY DOESN'T PREVENT AVN: Surgery FIXES fragment back in place with screws (restores anatomic position, allows mechanical healing). However, surgery CANNOT reconnect tiny blood vessels <1mm diameter that were torn by fracture. Fragment relies on: (1) CREEPING SUBSTITUTION: Slow process where new blood vessels grow from fracture edges into dead fragment over 3-12 months (like ivy growing up wall - gradual revascularization). (2) BONE REMODELING: Dead bone reabsorbed by osteoclasts, new living bone deposited by osteoblasts (turnover process). During this 3-12 month window, fragment is mechanically WEAK (dead bone being replaced) → risk of COLLAPSE if loaded too aggressively (fragment squashes like crushed aluminum can). AVN TIMELINE: Weeks 0-12 post-surgery: Fragment LOOKS normal on X-ray (bone density unchanged, screws holding position). Radiographs CANNOT detect AVN early. Months 3-6: AVN becomes visible on X-ray as SCLEROSIS (fragment appears WHITER/denser than surrounding bone - counterintuitive but dead bone is denser because not being remodeled). MRI shows AVN earlier (low signal on T1 weighted images indicates marrow death). Months 6-12: If AVN severe, fragment COLLAPSES (subchondral bone crushes, articular surface sinks 2-5mm creating step-off and incongruity). Elbow pain increases, catching/locking develops. Collapse is IRREVERSIBLE - requires revision surgery to excise dead fragment. Months 12-24: If AVN mild, revascularization completes without collapse (fragment survives, heals, maintains position - good outcome). Risk factors for AVN: Type II comminuted fracture (smaller fragment, worse blood supply disruption 30-40% AVN vs Type I 10-20%). Delay to surgery >7-14 days (longer ischemia time, more bone cell death). High-energy trauma (greater vessel disruption). Smoking (impairs revascularization, doubles AVN risk). CANNOT PREVENT AVN: Surgeon CANNOT predict which fragments will develop AVN (some heal perfectly, others collapse unpredictably). Early surgery minimizes risk but doesn't eliminate it. If AVN occurs, treatment is fragment excision (accept capitellum deficiency, mediocre outcome 60-70% function).

Question 5

How much elbow stiffness should I expect after surgery? Will I regain full motion?

Accepted Answer

Expect to lose 10-30 degrees of total elbow flexion-extension arc compared to your uninjured side even with successful surgery and aggressive physiotherapy - PERFECT motion recovery is rare <20% of capitellum fracture patients, most (60-70%) regain functional motion (30-130 degrees flexion-extension sufficient for activities of daily living), and severe stiffness (>40 degree loss) occurs 10-20% despite optimal treatment. ELBOW MOTION REQUIREMENTS: FULL normal elbow: 0-140 degrees (full extension 0, full flexion 140, total 140-degree arc). FUNCTIONAL arc for ADLs: 30-130 degrees (eating 85-100 degrees, drinking 75-90 degrees, reaching head 110-120 degrees, perineal care 30-40 degrees - Morrey's functional arc). Post-capitellum fracture REALISTIC goal: 20-120 degrees typical outcome (lose 10-20 degrees extension, lose 10-20 degrees flexion, total arc 100-110 degrees vs normal 140 degrees). This is FUNCTIONAL (can perform ADLs, most sports, light work) but NOT normal. WHY STIFFNESS IS INEVITABLE: (1) INTRA-ARTICULAR INJURY: Fracture damages articular cartilage and underlying bone → inflammation → synovial adhesions (scar tissue forms between joint surfaces like glue). (2) CAPSULAR SCARRING: Elbow capsule (ligament bag surrounding joint) is VERY prone to contracture (stiffens with immobilization faster than any other joint - ankle, knee, shoulder tolerate immobilization better). Even 2-week immobilization → measurable capsule shortening. Capitellum fractures need 6-12 weeks protected motion → significant capsule scarring. (3) ANTERIOR CAPSULE CONTRACTURE: Capitellum fracture swells ANTERIORLY (hematoma in front of elbow). Blood and scar tissue glues anterior capsule in SHORTENED position → flexion contracture (cannot fully extend elbow, lose terminal 10-30 degrees extension MOST COMMON deficit). (4) HETEROTOPIC OSSIFICATION: 10-15% develop extra bone formation in elbow capsule/collateral ligaments/muscles (genetic predisposition, high-energy trauma, delayed surgery increase risk). Bone forms where soft tissue should be → mechanical block to motion (bridging bone prevents full flexion or extension). NSAIDs post-op (indomethacin 75mg daily x6 weeks) reduce HO risk 50% but don't eliminate it. (5) POSTERIOR INTEROSSEOUS NERVE CAUTION: Lateral surgical approach for capitellum is close to PIN (branch of radial nerve motor to finger/thumb extensors). Aggressive stretching into pronation (palm down) or elbow extension risks PIN traction injury → finger drop weakness. Therapy must balance motion gains vs nerve safety. MAXIMIZING MOTION RECOVERY: Start motion EARLY (week 2 post-op in hinged brace - every day delay increases stiffness 1-2 degrees permanently). Aggressive physiotherapy (2-3x/week first 3 months - passive stretching, joint mobilization, contract-relax techniques). Home program compliance CRITICAL (stretch 3-4x daily 10-15 min sessions - patient effort determines outcome more than surgery quality). Static progressive splinting (weeks 8-16 if plateau <100 degrees motion - wear splint forcing gradual stretch 30-60 min sessions 3x daily, can regain 10-20 degrees additional motion with dedicated splinting). Avoid: Prolonged immobilization (splint >2 weeks worsens stiffness), aggressive manipulation under anesthesia (tears soft tissues, causes more scarring and HO - reserved for severe cases <60 degrees motion refractory to 6 months therapy). REALISTIC EXPECTATIONS: Excellent result (lose <10 degrees total arc): 20-30% of patients. Good result (lose 10-30 degrees, arc >100 degrees, functional): 60-70%. Fair result (lose 30-50 degrees, arc 70-100 degrees, limited but adequate for ADLs): 10-20%. Poor result (lose >50 degrees, arc <70 degrees, severely limited): 5-10% (usually from AVN collapse, severe comminution, or delayed treatment). IF SEVERE STIFFNESS PERSISTS: After 6-12 months therapy, if motion plateau <70 degrees and interfering with function → consider surgical capsulotomy (release contracted capsule, remove HO if present). Capsular release adds 20-40 degrees motion in 60-70% but requires repeat aggressive therapy post-op (some patients re-stiffen despite surgery).

Medical Disclaimer

Capitellum Fractures (Elbow Coronal Shear Fractures)

📖What is Capitellum Fractures (Elbow Coronal Shear Fractures)?

🔬What Causes It?

⚠️Risk Factors

You may be at higher risk if:

🛡️Prevention