Abstract
PurposeIn total hip arthroplasty, uncemented short stems have been used more and more frequently in recent years. Especially for short and curved femoral implants, bone-preserving and soft tissue-sparing properties are postulated. However, indication is limited to sufficient bone quality. At present, there are no curved short stems available which are based on cemented fixation.MethodsIn this in vitro study, primary stability and maximum fracture load of a newly developed cemented short-stem implant was evaluated in comparison to an already well-established cemented conventional straight stem using six pairs of human cadaver femurs with minor bone quality. Primary stability, including reversible micromotion and irreversible migration, was assessed in a dynamic material-testing machine. Furthermore, a subsequent load-to-failure test revealed the periprosthetic fracture characteristics.ResultsReversible and irreversible micromotions showed no statistical difference between the two investigated stems. All short stems fractured under maximum load according to Vancouver type B3, whereas 4 out of 6 conventional stems suffered a periprosthetic fracture according to Vancouver type C. Mean fracture load of the short stems was 3062 N versus 3160 N for the conventional stems (p = 0.84).ConclusionPrimary stability of the cemented short stem was not negatively influenced compared to the cemented conventional stem and no significant difference in fracture load was observed. However, a clear difference in the fracture pattern has been identified.
Highlights
Cemented total hip arthroplasty (THA) has a long history of success, being a safe strategy for the treatment especially for elderly patients with potentially reduced bone quality [1]
The calculated rotation around the femoral axis was in direction of retroversion for both stems, with values of 0.03° (SD 0.02°) for the short stem and 0.04° (SD 0.02°) for the conventional stem (p = 0.44; Table 2)
Whereas 4 out of 6 conventional stems suffered a periprosthetic fracture according to type C
Summary
Cemented total hip arthroplasty (THA) has a long history of success, being a safe strategy for the treatment especially for elderly patients with potentially reduced bone quality [1]. Promising medium- and longterm term data already exist for several shorter cementless implant models [16, 17]. Some authors propagate a limitation of this implant group, especially in poor bone quality, due to the shorter and ostensibly metaphyseal fixation [21, 22]. A markedly reduced bone quality was seen to be associated with a dramatically increased risk for postoperative periprosthetic femoral fractures using a cementless calcar-guided short stem [23]. Taking this contraindication into account, implant survival rates up to 100% at 8 years have been reported [24]
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