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SICOT e-Newsletter

Issue No. 70 - October 2014

Worldwide News

The Unified Classification System (UCS): improving our understanding of periprosthetic fractures

Citation: Bone Joint J 2014;96-B:713–16.
Abstract: Periprosthetic fractures are an increasingly common complication following joint replacement. The principles which underpin their evaluation and treatment are common across the musculoskeletal system. The Unified Classification System proposes a rational approach to treatment, regardless of the bone that is broken or the joint involved.
Authors: C.P. Duncan, F.S. Haddad (Department of Orthopaedics, University of British Columbia, Canada)

Comment by Ahmed H. Abdel-Azeem

With more prostheses implanted every day, periprosthetic fractures are becoming a huge burden on orthopaedics and traumatology. For every anatomical area, different periprosthetic fracture classification systems are present. Some of them are really helpful and others are only available in books. For a classification system to be helpful it must combine several things like the simplicity of terminology, management relevance and prognostic value. For example, one of the most commonly used fracture classification systems (for normal fracture patterns) is the comprehensive AO classification, which is very easy using letters and numbers as well as being of great clinical relevance regardless of the anatomical region.

Recognising the fact that, regardless of the anatomical area, the principles of management of periprosthetic fractures are the same, the authors presented what they named the 'Unified Classification System' (UCS) as a simple system that combines simple terminology as well as a simple outline to an algorithmic approach for management.

They used the well-known and successful Vancouver classification for the fractures following total hip replacement, modifying it and adding specific items to fit all common and uncommon fracture patterns, regardless of the implants used or the anatomical site. Using simple ordered alphabetic letters and a simple mnemonic for easy recall, they identified six types according to the fracture site in relation to the implant(s) present:
  • Type A, Apophyseal (i.e. protuberance of bone, to which one or more soft-tissue structures are attached).
  • Type B, Bed supporting or adjacent to the implant.
  • Type C, Clear of the implant (i.e. same bone but distal to the stem).
  • Type D, Dividing one bone which supports two joint replacements (i.e. fracture of a bone supporting two replacements).
  • Type E, Each of two bones supporting one joint replacement (i.e. fractures of two bones supporting one replacement).
  • Type F, Facing or articulating with an implant (i.e. fracture of an articular surface involving a joint surface but not replaced or resurfaced).
Then each type is divided in a very simple way to delineate the principle of treatment:
  • Type A: depends on its importance and degree of displacement:
    • Soft tissue attachments are unimportant → observation (even if displaced).
    • Soft tissue attachments are important → early intervention should be considered (especially if displaced).
  • Type B: depends on stability of the implant and bone stock and is subdivided:
    • B1: well-fixed implant → management depends on the already documented outcomes of operative or non-operative treatment of that particular type of fracture.
    • B2: loose implant → revision with a longer stem is a common approach.
    • B3: loose implant + poor bone stock → complex reconstruction should be considered with extensive pre-operative planning.
  • Type C: the implant can be ignored and employ the basic principles of management of normal fractures (as if the implant was not present).
  • Type D: 'block out analysis' for each of the two joints.
  • Type E: 'block out analysis' for each of the two bones and the adjacent component.
    The term 'block out analysis' means concentrating your attention on the fracture and the specific replaced joint (type D) or component (type E) separately.
  • Type F: depends on the displacement:
    • Undisplaced or minimally displaced: conservative and late intervention if symptom appears or persists.
    • Displaced: early intervention should be considered.
Table summarising the UCS:

Unified Classification System (UCS) for periprosthetic fractures


A

Apophyseal

depends on the soft tissue attachment's importance and the degree of displacement:

  • unimportant → observation
  • important → early intervention

B

Bed of implant

depends on stability of the implant and bone stock and is subdivided into:

  • B1 (well-fixed implant) management depends on the already documented outcomes of operative or non-operative treatment of that particular type of fracture
  • B2 (loose implant) revision with a longer stem
  • B3 (loose implant + poor bone stock) complex reconstruction should be considered with extensive pre-operative planning

C

Clear of implant

the implant can be ignored and employ the basic principles of fracture
  


D

Dividing one bone supporting two replacements
 

'block out analysis' for each of the two joints


E

Each of two bones supporting one joint replacement
 

'block out analysis' for each of the two bones and the adjacent component


F

Facing an implant


depends on the degree of displacement:
  • undisplaced → conservative
  • displaced → early intervention

As an orthopaedic surgeon searching for a simple, unified and informative classification system, I find the UCS fitting this criteria. I hope that it will improve our understanding and help in a better quality research and easier comparison between different techniques of management of these increasingly common fractures.