THE SHORT STEM: PROMISES AND PITFALLS

Abstract

As an increasing number of young, active large patients become candidates for total hip replacements, there is an increasingly urgent need to identify arthroplasties that will be durable, highly functional and amenable to possible future successful revision. In an era when cemented femoral stems were the primary implant option, the concept of a surface replacement was attractive and, perhaps, appropriate. However, cementless femoral stems of many designs now provide dependable long term fixation and excellent, near normal function.

However, a number of issues related to cementless stem fixation could be further improved:

1. –

   Optimisation of load transfer to proximal femur to minimize fracture risk and maximize bone preservation

2. –

   Elimination of proximal-distal mismatch concerns, including bowed femurs

3. –

   Facilitation of femoral stem insertion, especially with MIS THA exposures

4. –

   Facilitation of revision with implants capable of providing durable fixation for active patients.

The potential benefits of short stem femoral THA implants include:

1. –

   Ease of insertion

2. –

   Avoidance of issues related to proximal-distal anatomic mismatch or variations in proximal femoral diaphyseal anatomy (e.g. femoral bowing)

3. –

   Facilitation of MIS surgical approaches, especially anterior exposures.

4. –

   Optimisation of proximal femoral load transfer with consequent maximisation of proximal bone preservation.

However, a number of potential drawbacks may be associated with the use of cementless short stems:

1. –

   Initial and durable fixation may be highly sensitive to implant design and surface treatment.

2. –

   The implants may not be suitable for patients with osteopenia. Consistent, reliable identification of patients appropriate for these implants may be difficult.

3. –

   There may be a significant learning curve associated with the use of short stem implants.

At this time, it is important to realize that not all short stem implants are equal. In view of the reliability of a large number of uncemented femoral stems of conventional length, surgeons should base their use of specific short stems upon clinical evidence of their safety and durability.