which test is positive in non union lateral epiconlye varus stress or valgus and reason
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non-union lateral epicondyle fracture varus stress test positive reason
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https://pmc.ncbi.nlm.nih.gov/articles/PMC3828487
Here is the complete, well-sourced answer:
Non-union of the Lateral Epicondyle: Varus Stress Test is Positive
The Answer
Varus stress test is positive in non-union of the lateral epicondyle.
Additionally, the lateral pivot shift test (posterolateral rotatory instability test) is also positive in these cases.
Anatomical Reason
The lateral epicondyle is the bony origin of the lateral collateral ligament (LCL) complex, which includes:
- The radial collateral ligament (RCL)
- The lateral ulnar collateral ligament (LUCL)
- The annular ligament
When a lateral epicondyle fracture fails to unite (non-union), the entire lateral ligament complex remains attached to the ununited fragment rather than to the humerus. This means:
- The lateral stabilizers of the elbow are functionally detached from the humerus
- The elbow becomes deficient on the lateral side
- Any force trying to close the medial side / open the lateral side (i.e., varus force) will demonstrate excessive laxity
Varus stress opens the lateral compartment - and since the lateral stabilizers are incompetent due to the non-union, the elbow gaps open laterally, making the varus stress test positive.
Why NOT valgus?
Valgus stress tests the medial structures - primarily the medial collateral ligament (MCL/UCL). The medial epicondyle is the origin of the MCL. In lateral epicondyle non-union, the medial structures are intact, so valgus stress test is negative.
Valgus stress opens the medial side - this is tested when you suspect medial instability (e.g., medial epicondyle fracture/non-union, thrower's elbow).
Clinical Signs in Lateral Epicondyle Non-union
| Test | Result | Reason |
|---|---|---|
| Varus stress test | Positive | LCL complex attached to ununited fragment; lateral side incompetent |
| Lateral pivot shift test | Positive | LUCL deficiency causes posterolateral rotatory instability |
| Valgus stress test | Negative | Medial structures intact |
The PMC case report on lateral epicondylar non-union confirms: under fluoroscopy, varus stress showed "obvious instability at the non-union site, with displacement of the epicondylar fragment when the elbow was stressed in varus." The lateral pivot shift test was also positive in that patient.
Summary in One Line
Varus stress test is positive because the lateral collateral ligament complex originates from the lateral epicondyle - when this epicondyle fails to unite, the entire lateral stabilizing apparatus is detached from the humerus, causing lateral (varus) instability of the elbow.
chronic non-union fracture of lateral humeral condyle is seen with its lateral displacement. Remodeling with sclerotic margins is seen at the fracture site. There is distortion of the elbow joint with malalignment of the radial head with capitellum suggestive of chronic radio-capitellar subluxation. based on the above ncct information what clinical findings should be expected with length of arm and forearm and special tests
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chronic lateral humeral condyle non-union clinical features cubitus valgus tardy ulnar nerve arm length radiocapitellar subluxation
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lateral condyle non-union forearm shortening overgrowth cubitus valgus carrying angle tardy ulnar nerve clinical examination findings
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Now I have all the information needed. Here is a complete, structured clinical answer based on the NCCT findings:
Expected Clinical Findings: Chronic Lateral Condyle Non-Union with Radio-Capitellar Subluxation
Interpreting the NCCT
The scan tells you three things happening simultaneously:
- Non-union of the lateral condyle with lateral displacement - the condyle never healed, the fragment migrated
- Remodeling with sclerotic margins - this is a long-standing (months to years) non-union, not acute
- Radio-capitellar subluxation - the radial head has lost its normal articulation with the capitellum, meaning the entire lateral column has lost its mechanical integrity
These three together represent the classic neglected lateral condyle fracture scenario. Here is what you will find clinically:
1. Deformity at the Elbow
Cubitus Valgus (PRIMARY deformity)
- Increased carrying angle, typically 20-55 degrees (normal: 5-15 degrees in males, 10-20 in females)
- The lateral condyle, which normally acts as the lateral buttress of the distal humerus, has failed to unite and migrated laterally/proximally
- The medial physis continues to grow, pushing the elbow into progressive valgus
- The longer the non-union, the worse the valgus
Why valgus and not varus? Because the fracture fragment (lateral condyle) migrates proximally and laterally with the pull of the common extensor origin. The medial side of the humerus keeps growing. The result is loss of lateral column height → progressive valgus tilt.
With Radio-Capitellar Subluxation:
- The radial head will be palpable posterolaterally or laterally - out of its normal position
- There may be a visible lateral lump/prominence at the elbow
- The forearm may appear to bow slightly outward
2. Limb Length Measurements
Arm (Humerus):
- Apparent shortening of the arm on the affected side
- The proximal migration of the lateral condylar fragment effectively reduces the length of the lateral column
- Clinically: measured from the acromion to the lateral epicondyle - this distance is reduced compared to the normal side
Forearm (Radius + Ulna):
- The forearm is relatively unaffected in length
- However, due to radio-capitellar subluxation, the radius may appear relatively short at the wrist because the radial head is displaced proximally - this can cause a subtle positive ulnar variance at the wrist over time
- Some texts describe an apparent forearm shortening due to the radial head migration, but the ulna length itself is preserved
Overall Limb:
- True shortening is mainly in the arm (lateral column of humerus)
- The forearm length (ulna) is normal
- With proximal radial head migration: radius relatively short compared to ulna at the wrist
3. Range of Motion
| Movement | Finding | Reason |
|---|---|---|
| Flexion | Mildly restricted (may be near-normal early) | Joint distortion |
| Extension | Loss of full extension (flexion contracture) | Capsular fibrosis, joint incongruity |
| Pronation/Supination | Restricted - especially supination | Radio-capitellar subluxation disrupts the proximal radio-ulnar and radio-capitellar joint mechanics |
| Extension lag | May be present | Posterolateral laxity |
4. Special Tests
| Test | Result | Reason |
|---|---|---|
| Varus stress test | Positive | LCL complex attached to ununited lateral condyle fragment; lateral side incompetent |
| Lateral pivot shift test | Positive | LUCL deficiency → posterolateral rotatory instability |
| Tinel's sign at cubital tunnel | Positive (if tardy ulnar nerve palsy present) | Valgus deformity stretches the ulnar nerve over the medial side |
| Froment's sign | Positive (if TUNP advanced) | Ulnar nerve intrinsic muscle weakness |
| Valgus stress test | Usually negative | Medial structures intact |
5. Neurological Findings: Tardy Ulnar Nerve Palsy (TUNP)
This is the most important late complication - the literature confirms it is the most common cause of TUNP.
The mechanism: progressive cubitus valgus stretches the ulnar nerve over the medial epicondyle over years.
Sensory signs:
- Numbness and tingling over the little finger and medial half of ring finger (ulnar 1.5 fingers)
- Hypoesthesia over the ulnar side of the palm
Motor signs:
- Claw hand (ring and little finger clawing) - due to loss of lumbricals 3 and 4
- Weakness of finger abduction/adduction (interossei)
- Froment's sign positive - patient grips paper with flexed IP joint of thumb (FPL compensates for weak adductor pollicis)
- Wartenberg's sign - little finger abducted at rest (extensor digiti minimi unopposed)
- Hypothenar wasting
- First dorsal interosseous wasting
6. Summary Table of All Expected Findings
| Category | Finding |
|---|---|
| Deformity | Cubitus valgus (increased carrying angle), radial head prominence laterally |
| Arm length | Shortened (lateral column height reduced) |
| Forearm | Normal ulna length; radius may appear relatively short at wrist |
| Elbow motion | Loss of full extension, restricted supination |
| Stability tests | Varus stress test +ve, Lateral pivot shift +ve |
| Nerve | Tardy ulnar nerve palsy: claw hand, sensory loss ulnar 1.5 fingers, Froment's +ve, Tinel's +ve at cubital tunnel |
| Muscle wasting | Hypothenar eminence, first dorsal interosseous |
| Palpation | Sclerotic/fibrous mass at lateral elbow, radial head posterolateral |
Clinical Pearl
The triad to remember for chronic lateral condyle non-union:
Cubitus valgus + Tardy ulnar nerve palsy + Radiocapitellar subluxation
The radio-capitellar subluxation noted on your NCCT adds restricted forearm rotation (especially supination) and radial head prominence to the expected clinical picture - this indicates a significantly neglected, longstanding injury. - Campbell's Operative Orthopaedics 15th Ed, p. 1780-1781
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