Frykman Classification — Distal Radius

Distal radius fractures are the most common fractures in adults, accounting for approximately 17% of all fractures presenting to emergency departments. They occur across the full age spectrum — from high-energy injuries in young adults to low-energy osteoporotic fractures in elderly women (who have a lifetime risk of approximately 15% for a distal radius fracture). The distal radius bears approximately 80% of the axial load through the wrist (the remaining 20% transmitted through the ulna via the TFCC), and disruption of its articular surface, inclination, and length directly affects wrist function and predicts the development of post-traumatic wrist arthritis. Multiple classification systems exist for distal radius fractures; the Frykman classification (1967) was historically the most commonly used and remains important for examinations, although the AO/OTA classification and the Melone classification are more comprehensive and have largely superseded Frykman in modern research.

• Historical context: the term `Colles fracture` (Abraham Colles, 1814) describes the classic distal radius fracture with dorsal displacement (the classic `dinner fork deformity`); `Smith fracture` = volar displacement (the reverse Colles); `Barton fracture` = an intra-articular fracture-dislocation of the distal radius involving the dorsal or volar rim; `Chauffeur`s fracture` (Hutchinson fracture) = an intra-articular fracture of the radial styloid from a direct blow; these eponyms remain in common clinical use
• Radiological parameters of the distal radius: normal measurements that must be restored with reduction or fixation; (1) Radial inclination: 22–23° (measured on AP view — the angle between the radial styloid and the ulnar corner of the radius); (2) Radial height (length): 11–12 mm (the distance from the tip of the radial styloid to the level of the ulnar corner of the distal radius on AP view — a measure of the radial shortening); (3) Volar tilt (palmar tilt): 11–12° (measured on the lateral view — the normal volar tilt of the articular surface); loss of volar tilt (neutral or dorsal tilt) indicates Colles-type deformity; excessive volar tilt indicates Smith-type deformity; (4) Ulnar variance: the relative length of the ulna compared to the radius (normally neutral or slightly negative — the ulna is at or slightly shorter than the radius); positive ulnar variance (ulna longer than radius) from radial shortening predicts TFCC injury and ulnar impaction syndrome

The Frykman classification grades distal radius fractures according to TWO factors: (1) whether the fracture involves the radiocarpal joint (intra-articular vs extra-articular); and (2) whether there is an associated distal ulna fracture. Fractures involving the DRUJ (distal radioulnar joint) are also incorporated. The even-numbered types indicate the presence of an associated distal ulna fracture; the odd-numbered types indicate no ulnar fracture. The system has eight types (I–VIII) arranged in order of increasing severity.

• Frykman memory aids: ODD numbers = no distal ulna fracture; EVEN numbers = WITH distal ulna fracture; Types I-II = extra-articular radiocarpal; III-IV = intra-articular radiocarpal only; V-VI = extra-articular radiocarpal + DRUJ; VII-VIII = both joints intra-articular; increasing type number = increasing severity; Type VIII = the most severe

• The Frykman system has several important limitations that have led to its partial replacement by the AO/OTA and Melone systems: (1) it does NOT describe displacement (the degree of dorsal or volar tilt, radial shortening, or intra-articular step-off — all of which are the most important prognostic factors); (2) it does NOT distinguish between the various patterns of articular comminution (the number of intra-articular fragments, the location of the articular depression, etc.); (3) it has poor inter-observer reliability; (4) it does not guide surgical treatment beyond the distinction intra-articular vs extra-articular; despite these limitations, the Frykman system is important for examinations and remains in wide clinical use for communication

• Acceptable position for non-operative management: multiple thresholds have been proposed; the most commonly cited (based on guidelines from the British Society for Surgery of the Hand, AAOS, etc.): (1) Dorsal tilt ≤10° on lateral view (OR volar tilt up to −10°, i.e. some dorsal tilt is accepted); (2) Radial shortening (loss of radial height) ≤3–5 mm; (3) Intra-articular step-off ≤2 mm; (4) Radial inclination ≥15°; young active patients generally require stricter criteria than elderly low-demand patients; Colles fractures in elderly patients with significant osteoporosis may be managed non-operatively even with moderate displacement if the patient`s activity level is low
• Surgical options: (1) Volar locking plate (VLP — Synthes DVR, Acumed, Trimed) — the current gold standard for most displaced distal radius fractures requiring ORIF; the volar approach (between flexor carpi radialis and the radial artery) provides access to the volar cortex; locking screws in the distal fragment are directed dorsally within the subchondral bone; angular stability allows early mobilisation; (2) External fixation — for severe comminution or open fractures; (3) Dorsal plating — for isolated dorsal rim fractures (Barton variants) or when the volar approach is not suitable; (4) Fragment-specific fixation — for complex multi-part intra-articular fractures; each fragment is addressed with a dedicated pin, screw, or small plate

• Frykman mnemonic: odd = no ulnar fracture; even = ulnar fracture; I/II = extra-articular radiocarpal; III/IV = intra-articular radiocarpal only; V/VI = extra-articular radiocarpal + DRUJ; VII/VIII = both joints; VIII = most severe
• Normal radiological parameters: radial inclination ~22°; radial height ~12 mm; volar tilt ~11°; ulnar variance = neutral; restoration of these parameters is the goal of treatment
• Frykman limitation: does NOT describe displacement; cannot predict prognosis or guide treatment beyond intra/extra-articular distinction; AO/OTA and Melone are more comprehensive; Frykman remains important for examinations but has been superseded in research
• Colles fracture: distal radius fracture with dorsal displacement and dorsal tilt (the classic elderly osteoporotic wrist fracture from a fall onto outstretched hand); Smith fracture = volar displacement; Barton = intra-articular rim fracture-dislocation; Chauffeur`s (Hutchinson) = radial styloid intra-articular
• Operative indications: dorsal tilt >10°; radial shortening >5 mm; intra-articular step-off >2 mm; age-adjusted (younger = stricter criteria); irreducible or re-displaced after reduction; volar locking plate (VLP) is the gold standard ORIF technique
• PRWE and DASH outcome scores: the two most commonly used patient-reported outcome measures for distal radius fractures; PRWE (Patient-Rated Wrist Evaluation); DASH (Disabilities of the Arm, Shoulder and Hand); used in research to compare operative vs non-operative outcomes
• TFCC injury with distal radius fractures: positive ulnar variance (radial shortening) increases ulnar loading → TFCC injury → DRUJ instability; assess DRUJ stability after fixation of the distal radius; if DRUJ is unstable after fracture fixation → TFCC repair or DRUJ stabilisation; if ulnar styloid fracture is large (involving the base) → likelihood of DRUJ instability is higher and requires surgical treatment