Introduction. Hip resurfacing has become a popular procedure for young active patients with osteonecrosis of the femoral head. However, it is not yet clear exactly how much osteonecrosis would permit this procedure and how much would be a contraindication. The aim of the present study was to analyze the resurfaced femoral head using finite element models and, in particular, to examine the influence of the extent of osteonecrosis and metaphysical stem shaft angles within the femoral head. Methods. We evaluated biomechanical changes at various extents of necrosis and implant alignments, using the finite element analysis method. We established three patterns of necrosis by depth from the surface of femoral head and five stem angles. Extension of necrosis as a quarter of femoral head diameter is type A, from a half is type B, and three-fourths is type C. We set five types of different stem angles from 125 to 145 degrees for the axis of femoral shaft. For these models, we evaluated biomechanical changes associated with the extent of necrosis and the stem alignment. Results. Stress distribution near the bone-cement interface increased with expansion of the necrosis. The stress concentration was particularly evident in the Type C model which had wide cement mantle replacement on the resurfaced femoral head. The maximum stress on the prosthesis was decreased with stem angles ranging from 130 to 140 degrees. Stress concentration at the stem shaft was observed when implanted varus or valgus alignment. Stress concentration of cement was observed at the anterior and inferior edges in each model. Regardless of the extent of necrosis replaced by cement, the stress values at the inferior edge increased as the stem shaft angle became varus. Conclusion. This study suggests that hip resurfacing for patients in whom osteonecrosis extends widely should be considered carefully; increased stress concentration near the bone-cement interface may occur when all the necrotic bone is replaced by cement. Furthermore, excessive varus or valgus implantation of the prosthesis has potentially adverse biomechanical effects for implants and the cement mantle

We performed a systematic review to compare outcomes of cemented versus uncemented trapezio-metacarpal joint (TMCJ) replacement for treatment of base-of-thumb arthritis. We assessed improvements in pain and function, range of movement (ROM), strength, complications and need for revision surgery. A thorough literature search was performed. A total of 481 studies were identified from the literature search (179 Medline, 253 Embase, 27 CINAHL, 22 Cochrane). Of 43 relevant titles 28 were selected for full-text review after assessment of the abstracts. Duplicate studies were removed. 18 studies met inclusion criteria on full-text review. All studies were of level IV evidence. There were no randomised controlled trials or meta-analyses. The studies were critically appraised using a validated scoring system. Most studies reported good outcomes for pain and strength, and functional outcome was comparable for both groups. ROM was generally improved for both prosthetic types, however statistical calculation was lacking in many studies. Trapezial component loosening was the main problem for both cemented and uncemented prostheses, however radiological loosening did not necessarily correlate with implant failure. This systematic review has found that both cemented and uncemented replacements generally give good outcomes for the treatment of TMCJ arthritis, however young, male, patients with manual occupations and with disease in the dominant hand and patients with poor trapezial bone stock appear to be at higher risk for implant failure due to cup loosening. We recommend the construction of a joint registry to record implantation and revision rates

The stem and the rasp for cemented arthroplasty are typically designed to obtain a cement mantle 2–5 mm thick. However, sometimes a line-to-line cementation is preferred, where the femoral cavity is prepared with the same dimension as the actual stem. There are contrasting reports [1,2] about the suitability of this technique to withstand the long-term fatigue loads. While the theoretical geometry allows no space for the cement, a sort of cement mantle is formed as the cement penetrates in the spongy bone. The scopes of this study were: 1) developing a dedicated in vitro method to test line-to-line cementation; 2) assessing if a short, polished hip stem designed for a standard cementation can be safely cemented line-to-line. In order to perform long-term mechanical in vitro tests, composite bones must be used, as cadaveric bones cannot withstand millions of loading cycles [3]. For this study, the Sawbones Mod. 3406-4 were chosen: they feature an open-cell polyurethane core simulating low-density spongy bone. Post-implantation x-rays confirmed that a relevant cement-bone interdigitation was obtained. Four femurs were prepared with a CoreHip (Aesculap) with regular cement mantle (Regular). Another 4 femurs were rasped to the same rasp size, and implanted with line-to-line cementation with a larger stem (Line-to-line). The implanted femurs were subjected to an accelerated test derived from a validated protocol [3] which replicates the most demanding motor tasks of 24 years of patient activity. Implant elastic micromotions and permanent migrations were measured throughout the test. The implants were then sectioned and treated with dye penetrants to highlight the cement cracks. Elastic and permanent motions did not show any loosening trend, and never exceeded few micrometers. As expected, some damage was visible in the cement mantles after test completion, for both types of implantation (similar to retrieved cement mantles surrounding stable implants [3]. The cement damage was similar in all specimens. No sign of major disruption was visible, neither within the Regular nor in the Line-to-line specimens: in fact, the cracks were limited in length, did not seem to cross the entire mantle thickness, and did not result in any loose cement fragments. The cracks in the line-to-line implants showed the same position and distribution compared to those found in the regular implants, but were slightly longer in some specimens. This in vitro study confirmed the feasibility of simulating line-to-line cementation in vitro. Our results suggest that a stem designed for a regular cement mantle could induce slightly more damage when implanted line-to-line, but no significant trend toward loosening

Over 70,000 hip fractures occur annually in the UK. Both SIGN (111) and NICE (124) give guidance on optimal management of these patients. Both suggest cemented hemiarthroplasty should be used in those without contra-indications, as cemented implants are associated with less thigh pain, subsidence and a better functional outcome. Cardiorespiratory compromise secondary to bone cement implantation syndrome (BCIS) is however a concern in those with pre-existing cardiorespiratory disease (NYHA grade 3–4, pulmonary hypertension) or pathological fracture [3]. The aim of our study was to audit the practice of a University of Glasgow hospital with regard to cemented hemiarthroplasty. We retrospectively reviewed data on all patients treated with hemiarthroplasty for hip fracture at the Southern General Hospital between 01/01/12-02/04/12. Patient demographics, pre-operative plan, procedure performed, ASA grade and pre-morbid mobility were recorded. Results. Twenty-three hemiarthroplasties were performed. The median age was 82 (70–101). No patient aged over 90 underwent cemented hemiarthroplasty. Cemented implants (JRI, Furlong) were used in 26% (n=6) while 74% (n=17) underwent uncemented (Stryker, Austin-Moore) hemiarthroplasty. ASA grade was recorded in eight (35%). There were four ASA-2 patients (mild systemic disease not limiting activity) of which 75% underwent uncemented hemiarthroplasty. Pre-morbid mobility was recorded in eight (35%). All three independently mobile patients underwent uncemented hemiarthroplasty. Six (26%) had a documented pre-operative plan with regards to cement use. This study highlights the disparity between current recommendations and our Centres’ practice. Most notable were: poor recording of pre-operative mobility, poor documentation of a pre-operative surgical plan, the low use of cemented fixation even in fit mobile patients and the lack of ASA grade recording (stratification of risk) by our anaesthetic colleagues. We suggest a documented pre-operative discussion between the surgeon and anaesthetist to establish BCIS risk and decide on use of cemented arthroplasty taking into account age and mobility

We studied the effects of coating titanium implants with teicoplanin and clindamycin in 30 New Zealand White rabbits which were randomly assigned to three groups. The intramedullary canal of the left tibia of each rabbit was inoculated with 500 colony forming units of Staphylococcus aureus. Teicoplanin-coated implants were implanted into rabbits in group 1, clindamycin-coated implants into rabbits in group 2, and uncoated implants into those in group 3. All the rabbits were killed one week later. The implants were removed and cultured together with pieces of tibial bone and wound swabs. The rate of colonisation of the organisms in the three groups was compared.

Organisms were cultured from no rabbits in group 1, one in group 2 but from all in group 3. There was no significant difference between groups 1 and 2 (p = 1.000). There were significant differences between groups 1 and 3 and groups 2 and 3 (p < 0.001). Significant protection against bacterial colonisation and infection was found with teicoplanin- and clindamycin-coated implants in this experimental model.