Classification system
Sanders Classification
Sanders Classification of Intra-articular Calcaneal Fractures
The Sanders classification grades displaced intra-articular calcaneal fractures into four types by the number of posterior facet fragments seen on the widest coronal CT image — type I non-displaced, type II two-part, type III three-part and type IV four-part or comminuted — and the type number predicts the outcome of internal fixation.
What the Sanders category means
Sanders scores run from 1 to 4, where a lower score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- Type I — non-displaced1–1
Less than 2 mm of articular displacement. Managed non-operatively.
- Type II — two-part2–2
Subtypes IIA, IIB and IIC. The best reported results after open reduction and internal fixation.
- Type III — three-part3–3
Subtypes IIIAB, IIIAC and IIIBC, with a depressed central fragment. Results are less good than type II.
- Type IV — four-part or comminuted4–4
Poorest results after fixation and the highest rate of later subtalar arthrodesis; primary fusion is a recognised option.
Published criteria and reliability
The published cut-offs that define this instrument, and the measured agreement between observers using it. Each is reported with the population it was derived in.
| Type | Value | Subscale | Population | Follow-up | Source |
|---|---|---|---|---|---|
| Criterion | 2 mm of articular displacement separates type I from types II–IV | — | Coronal CT at the widest point of the posterior facet | — | Sanders R 1993 |
| Criterion | Outcome after open reduction and internal fixation deteriorates progressively from type II to type IV | — | Displaced intra-articular calcaneal fractures treated operatively | Minimum 1 year, with results sustained at 10–20 years | Sanders R 2014 |
| Criterion | Type IV has the highest rate of conversion to subtalar arthrodesis | — | Operatively treated displaced intra-articular calcaneal fractures | 10–20 years | Sanders R 2014 |
Criterion is a published cut-off, definition or performance figure belonging to a classification or decision rule — it is not a change score and should not be read as one.
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
The classification is read from the coronal CT image showing the posterior facet at its widest. Up to two fracture lines may cross the facet on that image, and they are lettered A, B and C from lateral to medial, with line C lying at the junction with the sustentaculum tali. Type I is any intra-articular fracture with less than 2 mm of displacement, regardless of how many fracture lines are present. Type II is a two-part fracture — one line, two fragments, displaced 2 mm or more — and takes the letter of the line involved, giving IIA, IIB or IIC. Type III is a three-part fracture — two lines, three fragments, with the middle fragment typically depressed — and takes both letters, giving IIIAB, IIIAC or IIIBC. Type IV is a fracture with four or more articular fragments and is not lettered. The type number is therefore identical to the number of posterior facet fragments for types II to IV.
Missing data
Displacement alone determines type I, so the fragment count is not required when displacement is under 2 mm. For displaced fractures the fragment count gives the type and the subtype letters are optional; if the letters selected do not match the fragment count — a single line reported with three fragments, for example — the type is still reported and the subtype is withheld with an explanation, rather than a non-existent subtype being produced.
Instrument profile
- Developer
- Roy Sanders and colleagues
- Institution
- Tampa General Hospital, Florida
- First published
- 1993
- Items
- 3
- Response format
- Branching CT assessment
- Score range
- 1 to 4
- Direction
- Lower score = better
- Completion time
- About 2 minutes
- Age range
- Skeletally mature patients
- Regions
- Foot & Ankle
- Conditions
- Calcaneal fracture, Intra-articular calcaneal fracture, Subtalar joint injury, Hindfoot trauma
- Procedures
- Open reduction internal fixation of the calcaneus, Sinus tarsi approach, Primary subtalar arthrodesis, Percutaneous calcaneal fixation
- Validity
- The type number correlates with functional outcome and with the likelihood of later subtalar fusion, which is what distinguishes this system from purely descriptive calcaneal classifications. It was designed as a prognostic tool and is used as one.
- Reliability
- Interobserver agreement is moderate; agreement on the type number is consistently better than agreement on the subtype letters, and both improve with reformatted coronal images and with reader experience.
Normative values
Reference values from published cohorts, for comparison against the score you calculated.
| Population | Age | Mean | SD |
|---|---|---|---|
| Displaced intra-articular calcaneal fractures on CT | — | Type II is the most frequent pattern in the original series; type IV is the least frequent | — |
When to use the Sanders
Well suited to
- Any intra-articular calcaneal fracture with a CT scan, to decide between non-operative treatment, internal fixation and primary arthrodesis.
- Counselling a patient on the likely outcome of surgery, where the type number carries genuine prognostic weight.
- Reporting calcaneal fracture severity in trials and registries, where it is the standard descriptor.
Limitations and poor fits
- On plain radiographs — the type cannot be assigned without CT, and radiographic displacement is systematically underestimated. Use the Essex-Lopresti tongue-type versus joint-depression distinction and Böhler angle on plain films instead.
- For extra-articular calcaneal fractures, including isolated tuberosity, anterior process and sustentacular fractures, which the system does not cover.
- As a complete description of the injury: the tuberosity fragment, hindfoot height and width, varus of the tuberosity and calcaneocuboid involvement all bear on the operative plan and none of them are in the type.
- As the sole basis for choosing surgery — soft-tissue condition, smoking, diabetes, peripheral vascular disease and occupation are at least as important to the decision.
Sanders compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| Böhler Angle | 1 | -90–90 | The Böhler angle is measured on a lateral radiograph of the hindfoot between a line from the highest point of the anterior process to the highest point of the posterior facet and a line from that point to the top of the tuberosity, and it normally measures 20° to 40° — a flattened or negative angle indicates depression of the posterior facet. |
| AOFAS Ankle-Hindfoot | 9 | 0–100 | The AOFAS Ankle-Hindfoot Scale is a 100-point clinician-administered rating combining 40 points for pain, 50 for function across seven items and 10 for alignment — and although it remains the most-reported outcome in the foot and ankle literature, the society that published it withdrew its endorsement in 2011 because it was never validated. |
Copyright and permitted use
Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.
A published computed-tomography classification. No licence is required to describe or apply it.
References
- Sanders R, Fortin P, DiPasquale T, Walling A. Operative treatment in 120 displaced intraarticular calcaneal fractures. Results using a prognostic computed tomography scan classification. Clinical Orthopaedics and Related Research. 1993.
- Sanders R. Displaced intra-articular fractures of the calcaneus. Journal of Bone and Joint Surgery (American). 2000.
- Buckley R, Tough S, McCormack R, et al.. Operative compared with nonoperative treatment of displaced intra-articular calcaneal fractures: a prospective, randomized, controlled multicenter trial. Journal of Bone and Joint Surgery (American). 2002.
- Sanders R, Vaupel ZM, Erdogan M, Downes K. Operative treatment of displaced intraarticular calcaneal fractures: long-term (10–20 years) results in 108 fractures using a prognostic CT classification. Journal of Orthopaedic Trauma. 2014.
Editorial status
This page has not yet been signed off by a named clinical reviewer. The scoring logic is stated in full above so it can be independently verified, and every threshold is traceable to its source. See our editorial methodology.