Neck Sparing Stem Designs Or Metaphyseal Hip Replacements (Stubbies)
The concept of using short stems or ‘stubbies’ is exciting as this is a bone sparing procedure; maintenance of bone stock being vital given that revision hip surgery may be required in the future.
Preclinical tests such as mechanical fatigue tests, finite element analysis and photo-elastic techniques are used to design bone conserving stems that can be effective and have the excellent long term outcomes of some of the conventional femoral stems.
The risk of these short stems is perforation of the outer cortical bone; stress shielding and bone loss, leading to implant loosening or even fracture of the implant.
Historically, surgeons such as Freeman and Pipino identified the mechanical advantage of retaining the femoral neck; however early prototypes have been somewhat disappointing in their medium to long-term outcomes.
A number of bone conserving hip joints have been developed and have been used instead of conventional femoral stems. First generation stubbies include Munting, Weber- Huggler Thrust Plate, Stratech, Spiron, Spotorno and the Mayo.
Second generation stems such as the Silent, Proxima, McMinn, Proximal Epiphyseal Replacement (PER), and the MSA Total Hip are now in use. The MSA Total Hip has been designed with a unique lateral T back design to maximise torsional stability and ease of insertion. A modular neck can be utilised with this new ‘stubbie’ design.
Stems with design features that address the properties of the metaphyseal area of the femur are likely to show excellent early and medium term outcomes.
To make an appointment e–mail Sue Misir, secretary to Mr Evert Smith, or telephone:
- 0117 907 4228 (private)
- 0117 323 5194 (NHS)
For an NHS appointment your GP will need to refer you. How?
Evert Smith is an Orthopaedic Surgeon in whom I have absolute faith and confidence.
Bob Gibbons, 2007.