Interprosthetic fractures can be successfully and permanently stabilised with special prostheses such as the RescueSleeve from LINK – as confirmed by studies [1-5]. Effective stabilisation is also achieved when LINK prostheses are combined with implants from other manufacturers
The increasing use of stemmed prostheses today means that the stems of hip and knee prostheses often have to be coupled in the femur. According to Soenen et al , the risk of interprosthetic fracture increases dramatically if the distance between the stem tips is less than 100mm. Weiser et al , on the other hand, concluded that the distance between the stem tips has scarcely any influence on the risk of fracture, but rather the bone quality of the cortex is the decisive factor. Irrespective of the cause of these interprosthetic fractures, they can be effectively and permanently stabilised with custom-made prostheses. Very good results have been achieved with sleeve couplings, like the RescueSleeve from LINK, for stem-stem coupling . This applies both to LINK® stems and to combinations of LINK prostheses with implants from other manufacturers.
Anatomical angle between the connection components is possible
Essentially, the sleeves can be either single-ended or double-ended (twin sleeve). In the case of the single-ended version, the component that is in contact with the sleeve can consist of an intramedullary stem or a joint component that anchors the prosthesis, which is held by the sleeve, in the medullary canal, or connects it to another joint. Figure 1 shows an example for a single-sided RescueSleeve which connects an in-situ Wagner hip stem to LINK MEGASYSTEM-C® components and Endo-Model® rotational knee prosthesis after recurrent periprosthetic fracture. The double-ended sleeve (Figure 2), on the other hand, connects the two opposing stemmed prostheses following an interprosthetic fracture. Figure 3 shows a case example for a twin RescueSleeve that connects an in-situ Wagner hip stem with a stemmed knee prosthesis after interprosthetic fracture.
The sleeve can be designed so that an anatomical angle (varus/valgus) is provided in the lock of the connecting components. Sleeve connections of this kind entail a certain bone loss of 170-200mm, but the coupling is so strong that the held prosthesis stem usually fractures before the connection fails. Furthermore, the joint regions in the knee or hip are not impaired by the intervention. The stability of the sleeve connection was proven by tests performed by Professor Morlock, Director of the Institute of Biomechanics at Hamburg University of Technology .
To create the coupling, the holding sleeve is first filled with bone cement, and then the prosthesis stem is pushed into the holding sleeve while the cement is still soft. Primary fixation of the stem is then achieved with the circumferentially arranged fixation screws. Once the cement has hardened, the result is a stable, loadable connection between the in-situ prosthesis stem and the sleeve prosthesis. Patel et al  describe a similar method, in which the stem of one prosthesis component has a sleeve at the anchoring end, and the sleeve is cannulated to provide better adhesion of the cement to the internal wall. The revision rate after 5.6 years is described as 6.7 per cent for 15 patients .
The LINK RescueSleeve is available as a custom-made product for individual patients.
Soenen, Marc et al “Stemmed TKA in a Femur with a Total Hip Arthroplasty. Is there a safe distance between the stem tips?”, Journ. of Arth., 28 (2013) 1437-1445.
Weiser, L. et al “The role of interprosthetic fractures of the femur”, JBJS Vol 96-B, No 10, Oct 2014, pp 1378-1384.
Citak, Mustafa et al “Treatment of interprosthetic femoral fractures with an interposition prosthesis”, Acta Orthopedica 2013, 84 (3): 326-327.
Internal report by Prof. Michael M. Morlock, Publication in preparation.
Patel, Nirav K. et al “Custom-made Cement-Linked Mega Prostheses: A Salvage Solution for Complex Periprosthetic Femoral Fractures”, The Journ. of Arth. 29 (2014) 204-209.
Study: Interposition sleeve (RescueSleeve) as a treatment option for interprosthetic femoral fractures
An interposition sleeve is an option for the treatment of interprosthetic femoral fractures when osteosynthesis is not possible or uncertain due to a major bone defects. This is the conclusion of a study  in which the six LINK Lubinus Classic Plus® Hip Prostheses and LINK Endo-Model®-M Knee Prostheses with different stem lengths were implanted with cement in bone specimens. Interprosthetic femoral fractures were then induced using a four-point bending test. The fractures were repaired with an interposition sleeve from LINK before repeating the four-point bending test. The load-to-failure of the prostheses prior to fracture was significantly higher than after treatment with the interposition sleeve (10681 N versus 5083 N; p = 0.002). The failure mechanism of the femurs in the bending test was a deformation of the hip and knee prostheses. The interposition sleeve did not fail with any construct.
- Weiser L, et al: The interposition sleeve as a treatment option for interprosthetic fractures of the femur: a biomechanical in vitro assessment (Int Orthopaedics (SICOT), April 24, 2015).
Waldemar LinkGmbH & Co KG