- Russell-Taylor classifies subtrochanteric fractures by two binary questions: is the piriformis fossa intact, and is the lesser trochanter involved. The combination gives four patterns that directly guide implant selection.
- Type I (piriformis fossa intact) favours a standard intramedullary nail. The entry point is undamaged, so a cephalomedullary nail sits in the canal as intended and reconstructs the proximal femur from within.
- Type II (piriformis fossa involved) compromises the standard nail entry point. The fracture extends into or through the piriformis fossa, so a standard nail may displace the proximal fragment further — consider a reconstruction (trochanteric entry) nail, a 95-degree blade plate, or a proximal femoral locking plate.
- The lesser trochanter split (A vs. B) matters for medial cortex stability. Loss of the lesser trochanter and medial cortex eliminates the calcar femorale buttress, increasing varus collapse risk and tightening the demand for medial support.
Examiners expect you to classify a subtrochanteric fracture on a radiograph, state the type, and immediately explain what implant you would choose and why. The pass line is: Type I goes to a standard cephalomedullary nail; Type II to a plate or trochanteric-entry nail. If you cannot justify the implant from the anatomy of the fracture line relative to the piriformis fossa, the viva stalls.
The Russell-Taylor Classification
The classification uses two binary decisions applied to anteroposterior and lateral radiographs of the proximal femur.
| Type | Piriformis Fossa | Lesser Trochanter | Implant Implication |
|---|---|---|---|
| I A | Intact | Intact | Standard cephalomedullary nail |
| I B | Intact | Involved / fragmented | Cephalomedullary nail with medial support or cable cerclage |
| II A | Involved | Intact | Trochanteric-entry reconstruction nail or 95-degree plate |
| II B | Involved | Involved / fragmented | Plate fixation (95-degree blade plate or locking plate) preferred; high instability |
Piriformis Intact? — Yes (Type I) or No (Type II). Lesser Trochanter Intact? — Yes (A) or No (B).The two binary decisions
Type I — Nail In. Type II — Nail at risk, consider Plate.Remember the implant logic
Lesser Trochanter = Medial Buttress. Intact = stable. Gone = varus risk.The medial cortex question
The piriformis fossa is the standard entry point for a first-generation (hip-screw type) cephalomedullary nail. If the fracture line passes through it, reaming and nail insertion through that point drive the proximal fragment into external rotation and abduction — a classic cause of malunion in subtrochanteric fractures nailed through an involved fossa.
Anatomical Basis — Piriformis Fossa and the Lesser Trochanter
The piriformis fossa sits at the junction of the femoral neck and the intertrochanteric region, just above the greater trochanteric crest on the medial side of the greater trochanter. It is the standard entry point for most antegrade cephalomedullary nails designed for the adult femur.
When the fracture extends through the piriformis fossa (Type II), the proximal fragment becomes a separate piece with no intact bony bridge to the shaft. Reaming through the fossa widens the fracture gap and separates the fragment further. The nail still needs to capture the proximal fragment, but the entry point itself is damaged.
The lesser trochanter is the insertion of the iliopsoas and an important medial cortical buttress. When it remains attached to the shaft fragment (intact lesser trochanter, subtypes A), the medial cortex of the proximal fragment retains structural support. When the lesser trochanter is fractured away (subtypes B), the proximal fragment loses its medial column and is at high risk of varus collapse — particularly under the bending forces generated by weight-bearing.
In Type I B fractures, the piriformis fossa entry point survives but the medial cortex is stripped of the lesser trochanter. A cephalomedullary nail still works, but the surgeon must supplement medial cortical support with cerclage cables, a medial buttress plate, or accept that reduction to valgus may be necessary to restore medial contact. Ignoring the medial defect and nailing into varus alignment produces early implant failure.
Implant Selection in Detail
| Type | First Choice | Second Choice | Key Technical Point |
|---|---|---|---|
| I A | Standard cephalomedullary nail (piriformis entry) | Long cephalomedullary nail with reconstruction screws if slight extension toward fossa | Standard technique; entry point is reliable |
| I B | Cephalomedullary nail with cerclage cables or reduction clamp to restore medial cortex | Proximal femoral locking plate if medial comminution prevents reduction | Rebuild the medial column before or during nailing; supplementary cables are common |
| II A | Trochanteric-entry (reconstruction) nail or 95-degree blade plate | Proximal femoral locking plate if nail reduction is unreliable | Trochanteric entry avoids the fractured fossa; blade plate gives direct visual control of the proximal fragment |
| II B | 95-degree dynamic condylar screw or blade plate, or proximal femoral locking plate | Trochanteric-entry nail if the fracture can be reduced and held before nailing | Highly unstable — plate allows anatomical reduction of both columns; avoid nailing through a comminuted proximal fragment |
In an exam viva, if shown a Type II subtrochanteric fracture and asked for your implant, lead with the anatomy: the piriformis fossa is involved, so the standard nail entry is lost, and I would choose a 95-degree blade plate or a trochanteric-entry reconstruction nail. Then justify why.
Relationship to Other Classifications
The Russell-Taylor classification is one of several systems for subtrochanteric fractures. The AO/OTA system (31-A) also applies and is more widely used in some centres, but it does not directly encode the piriformis fossa involvement that determines nail suitability.
- Seinsheimer classification (1978) subdivides by number of fragments and includes a specific category for fractures involving the lesser trochanter. It is anatomically detailed but less operationally useful for implant choice.
- Fielding classification (Types I, II, III) divides by distance from the lesser trochanter to the fracture line. Simple but does not address the entry point or medial cortex.
- Russell-Taylor is preferred when the clinical question is "can I nail this through the piriformis fossa?" — it is the only system that makes that decision explicit.
Evidence Base
Classifications in Brief: The Russell-Taylor Classification of Subtrochanteric Hip Fracture
- Comprehensive review of the Russell-Taylor classification explaining the four types based on piriformis fossa and lesser trochanter involvement
- Type I fractures (piriformis fossa intact) are amenable to standard cephalomedullary nailing through the piriformis entry point
- Type II fractures (piriformis fossa involved) require trochanteric-entry reconstruction nails or plate fixation
Cephalomedullary nails in the treatment of high-energy proximal femur fractures in young patients: a prospective, randomized comparison of trochanteric versus piriformis fossa entry portal
- Prospective randomised trial comparing trochanteric and piriformis fossa entry portals for cephalomedullary nailing in high-energy proximal femur fractures
- Trochanteric entry avoided further displacement of the proximal fragment in fractures extending through the piriformis fossa
- Piriformis fossa entry was associated with fracture comminution of the proximal fragment when the entry point was involved in the fracture
Biologic plating versus intramedullary nailing for comminuted subtrochanteric fractures in young adults: a prospective, randomized study of 66 cases
- Randomised controlled trial comparing biological plating with intramedullary nailing for comminuted subtrochanteric fractures
- Intramedullary nailing achieved faster union and lower infection rates in patterns with an intact piriformis fossa (Russell-Taylor Type I)
- Biological plate fixation produced better outcomes in severely comminuted patterns where the piriformis fossa was involved (Russell-Taylor Type II B)
Nonunion of fractures of the subtrochanteric region of the femur
- Retrospective review of nonunion patterns in subtrochanteric fractures treated with various fixation methods
- Nonunion was most common after nailing through an involved piriformis fossa with loss of medial cortical support
- Plate fixation with anatomical reduction and bone grafting achieved reliable union in Russell-Taylor Type II B patterns that failed initial nailing
Second generation intramedullary nailing of subtrochanteric femur fractures: a biomechanical study of fracture site motion
- Biomechanical comparison of second-generation intramedullary nails for subtrochanteric fractures, including trochanteric-entry reconstruction nails
- Trochanteric-entry reconstruction nails provided significantly better stability at the fracture site when the piriformis fossa was simulated as fractured
- Standard piriformis-entry nails lost proximal fragment control when the entry point was involved in the fracture line
Exam Viva
Practise clinical reasoning and management decisions out loud
“A 72-year-old woman is brought in after a fall. Radiographs show a subtrochanteric fracture of the right femur. The fracture line extends from below the lesser trochanter to the mid-shaft, and the lesser trochanter is fractured away from the proximal fragment. The piriformis fossa appears intact. How would you classify this fracture and what would your management plan be?”
“A 55-year-old man sustains a high-energy subtrochanteric fracture in a road traffic collision. Radiographs show the fracture line passing through the piriformis fossa with extension into the greater trochanter. The lesser trochanter is fractured and the medial cortex is comminuted over a 6 cm segment. What classification applies and what are your fixation options?”
The four types
- Type I A: piriformis fossa intact, lesser trochanter intact — standard cephalomedullary nail
- Type I B: piriformis fossa intact, lesser trochanter involved — nail with cerclage or medial support
- Type II A: piriformis fossa involved, lesser trochanter intact — trochanteric-entry nail or blade plate
- Type II B: piriformis fossa involved, lesser trochanter involved — plate preferred (blade plate or locking plate)
The two binary questions
- Question 1: Is the piriformis fossa intact? — Yes = Type I, No = Type II
- Question 2: Is the lesser trochanter intact? — Yes = A, No = B
- The piriformis fossa question determines nail suitability
- The lesser trochanter question determines medial cortex stability
Key clinical rules
- Type I: nail it through the intact piriformis fossa
- Type II: the standard entry is lost — do not force a piriformis-entry nail
- Type I B and II B: medial cortex is gone — plan for varus collapse prevention
- Type II B: highest instability — plate or reconstruction nail, not standard nail
Differential from other classifications
- AO/OTA 31-A: does not encode piriformis fossa involvement — less useful for implant choice
- Seinsheimer: based on fragment count — anatomically detailed but not operationally focused
- Fielding: based on distance from lesser trochanter — simple but ignores entry point
- Russell-Taylor is the only classification that directly answers 'can I nail through the fossa?'