Modal Francesco FalezF. Ghera 2 has also reported early experience. Early experience and technical considerations. No radiological loosening or migration was observed. Mean age at surgery was 49 years range: CasellaMatteo Papalia Orthopedics However, longer follow-up time is proxoma to analyse the results and to confirm the durability of the observed clinical out-comes.
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Tobias Renkawitz: moc. This article has been cited by other articles in PMC. Abstract Background Anatomic short femoral prostheses with a prominent lateral flare have the potential to reduce stress-shielding in the femur through a more physiological stress distribution to the proximal femur.
We present the design rationale of a new short uncemented, proximally fixed anatomic femoral implant and the study design of a prospective multi-centre trial to collect long-term patient outcome and radiographic follow up data. The recruitment target is subjects, patients between the ages of 18 and 70 admitted for primary cementless unilateral THA will be included.
The primary objective is to evaluate the five-year survivorship of the new cementless short stem. The secondary objectives of this investigation are to evaluate the long term survivorship and the clinical performance of the implant, the impact on the subjects health related Quality of Life and the affect of the prosthesis on bone mineral density.
Peri- and postoperative complications will be registered. Clinical and radiographic evaluation of prosthesis positioning will be done post-operatively and at 3, 6, 12, 24, 60, and months follow up. Discussion Shortening of the distal stem can maximise bone and soft tissue conservation. New stem types have been designed to improve the limitations of traditional implants in primary THA.
A new, uncemented femoral short stem is introduced in this paper. A long-term follow up study has been designed to verify stable fixation and to research into the clinical outcome. The results of this trial will be presented as soon as they become available.
Background Although substantial progress has been made in the development of cementless total hip arthroplasty THA in recent years, a number of limitations remain. The implantation of the femoral component requires a large surface area of bone to be prepared [ 1 ]. Osteopenia due to non-physiological loading and stress protection, distal migration of wear particles from the joint space or inadequate stem fixation can increase the risk of aseptic loosening and subsidence of the stem [ 2 - 4 ].
The use of a stiff femoral component may lead to calcar atrophy and cortical thinning, however modern titanium alloy femoral components appear to reduce the risk of this stress-shielding effect [ 5 , 6 ]. Moreover, intense research efforts have been directed at characterising postoperative thigh pain, a clinical limitation in THA that can range from immediate mild postoperative symptoms to severe disabling pain requiring revision surgery [ 7 , 8 ].
Micromotion, loosening, uneven stress patterns or stem tip sclerosis seem to induce such thigh pain [ 9 , 10 ]. Additionally, the use of a long femoral stem increases the risk of thigh pain due to impingement of the stem tip on the femoral cortex [ 11 ] and a direct correlation has been drawn between thigh pain and increased stem sizes [ 12 ].
Research has also been conducted into ways to improve the limitations of traditional surgical techniques in THA. A less invasive surgical technique may lead to less pain in the early postoperative period and improve the postoperative functional status [ 13 , 14 ] although the scientific discussion about the superior outcomes of this technique compared with the traditional surgical procedure is still ongoing [ 15 , 16 ]. To address such limitations, new THA implant designs with shorter stems have been developed.
In addition, anatomic short femoral prostheses can reduce the potential for stress-shielding in the femur through a more physiological stress distribution to the proximal femur [ 20 , 21 ]. The purpose of this study is to conduct a prospective clinical trial to collect long-term clinical, patient outcome and radiographic follow up data. Through the long term follow-up, outcomes measures will be compared to conventional cementless femoral components.
The present paper reports on the design rationale of this new short stem prosthesis and the methodological design of the study. Proximal load transfer In , John C. Koch [ 22 ] proposed his model of the mechanics of the loading of the hip, which included a geometrical description of the femur and a calculation of stresses induced by load that were assumed to occur during gait.
According to his theory, during femoral loading, the superior neck and proximal lateral three quarters of the femoral shaft were under tensile loading while the distal lateral and entire medial femoral surfaces were under compression. Through the inclusion of the iliotibial band as a static lateral tension band and the gluteus medius-vastus lateralis complex as dynamic tension bands along the lateral aspect of the lower limb, the authors demonstrated that compressive loading is actually generated both laterally and medially throughout the femur distal to the greater trochanteric apophysis during the unilateral support phase of gait.
Further consistency of this model was achieved by bone morphology studies with cadaveric femora and femoral CT scans, revealing a significant amount of cortical bone mass at the lateral aspect of the femur. The authors therefore concluded that the femoral component of THA prostheses should engage the proximal lateral femoral cortex as an additional area of support against subsidence, to avoid stress-shielding and subsequent loss of proximal femoral bone.
Lateral flare Walker at al. This analysis showed, that for a standard straight stem, loads are mainly transferred through the distal half of the stem Fig. In contrast, interface contact stresses from a proximally fixed stem with a lateral flare demonstrated that all of the loading from the prosthesis is transferred to the proximal femur Fig. Moreover, the magnitudes of the interface stresses and distal migration during application of the load were both lower in the lateral flare stem.
Additionally, results of radiographic follow-up from these authors showed trabecular attachment onto the lateral flare, providing indirect evidence of load transfer in that area. Accordingly, Leali et al. The proximally fixed cementless femoral component showed an average subsidence of 0. The authors concluded that a proximal lateral flare provides significant initial stability, which has been shown to be vital to obtain long-term stability through early bone ingrowth [ 27 ]. Additionally, a dual-energy X-ray densitometry study of stems with a lateral flare was performed, which demonstrated that the bone content was preserved at the baseline level or above throughout the follow-up period of 1 year.
This was particularly evident in the proximal prosthesis support zones Gruen zones 1, 2, 6 and 7 [ 28 ]. Likewise bone mineral density around the Santori custom short stem was significantly higher in zones 1 and 7 when compared to other conventional cementless implants on a three year follow up [ 29 ].
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