Mid-term outcomes after distally locked-to-standard primary stem exchange in 29 hip-prosthesis patients.

BACKGROUND: Cementless locked femoral stems are used for revision surgery in patients with bone loss to induce spontaneous bone reconstruction, allowing subsequent replacement by a standard primary stem. The small number of patients and short follow-ups available to date preclude a valid assessment of this strategy. HYPOTHESIS: After distally locked stem revision, replacement by a standard primary stem does not induce complications, and the quality of the bone reconstruction allows strong fixation of a regular primary stem. MATERIALS AND METHODS: We retrospectively evaluated 29 patients in whom a distally locked femoral stem was replaced by a standard primary stem between 1998 and 2010 (cemented in 27, cementless in 2 cases). The reason for the procedure was stem breakage, stem migration, or thigh pain. Mean patient age was 63 years (range, 39-78 years). Outcomes were evaluated based on the Postel-Merle d'Aubigné [PMA] score and Harris Hip Score [HHS]. In addition, radiographs were obtained to assess prosthesis fixation and the Hofmann cortical index measured the bone reconstruction. RESULTS: The distally locked stem was removed via a postero-lateral approach without femoral osteotomy in all the 29 cases. In one patient, an intra-operative fracture occurred during femoral preparation. Mean follow-up after the exchange procedure was 75 months (range, 3-188 months). Postoperative ccomplications occurred in 9 (32%) patients and consisted of chronic infection in 2 patients (after 3 and 76 months), post-traumatic peri-prosthetic fractures treated with internal fixation in 3 patients (after 100, 138, and 182 months), aseptic loosening in 3 patients (after 13, 39, and 122 months), and recurrent instability in one patient (after 63 months). All cause revision stem survival after 75 months was 72% (95% confidence interval, 47%-87%). In the 19 patients who still had their revision stem at last follow-up, the mean PMA score was 16.7 (range, 13-18) and the mean HHS was 88.2 (range, 59-99). The Hofmann index remained unchanged [36.5% (range, 28%-58%) before the exchange and 32.9% (range, 20%-57%) after the exchange; P=0.129]. DISCUSSION: This study confirms the feasibility of substituting a distally locked stem with a standard primary stem. No specific complications occurred and no technical difficulties arose when extracting the long stems. However, the 32% complication rate and, more specifically, the occurrence of loosening in 10% (3/29) of patients mandates caution in the use of this technique, which should not be proposed routinely, and suggests a need for considering cementless fixation of the standard primary stem. LEVEL OF EVIDENCE: Level IV, retrospective study.

Trypanotolerance, an option for sustainable livestock production in areas at risk from trypanosomosis.

Trypanosomosis is one of the major constraints on animal production in areas of Africa which have the greatest potential for significant increases in domestic livestock populations and livestock productivity. While the eradication of trypanosomosis from the entire continent is an unrealistic goal, considerable effort has been invested in the control of this disease through the use of trypanocidal drugs, management of the vector and exploitation of the genetic resistance exhibited by indigenous breeds. There is little hope that a conventional, anti-infection vaccine will be produced in the near future. Drug resistance is developing faster than generally thought. The control of the tsetse fly has been attempted over many decades. The decreasing efficacy of available trypanocidal drugs and the difficulties of sustaining tsetse control increase the imperative need to enhance trypanotolerance through selective breeding, either within breeds or through cross-breeding. Trypanotolerance has been defined as the relative capacity of an animal to control the development of the parasites and to limit their pathological effects, the most prominent of which is anaemia. A major constraint on selection for trypanotolerance in cattle, for both within-breed and cross-breeding programmes, has been the absence of practical reliable markers of resistance or susceptibility. Distinct humoral immune response to trypanosome infection is the major feature of bovine trypanotolerance. The role that these responses play in the control of infection or disease is being addressed by ongoing research, but remains a matter of speculation at present. Results in recent years have shown that packed cell volume (PCV) in particular and parasitaemia, the two principal indicators of trypanotolerance, are strongly correlated to animal performance. However, although direct effects of trypanosome infections on PCV and growth are obvious, more sensitive diagnostic methods for reflecting parasite control are required so that individual animals can be categorised reliably for their parasite control capability. One key finding is the major contribution made by each of the indicators evaluated to the overall trypanotolerance variance. Preliminary genetic parameters for PCV provide evidence that trypanotolerance is not only a breed characteristic but is also a heritable trait within the N'Dama population; this brings new opportunities for improved productivity through selection for trypanotolerance. More reliable estimation of genetic parameters of the indicators may well show that these parameters must be handled simultaneously for optimal progress. This would require diagnostics for assessing parasite control capability that identify trypanosome species more accurately, especially in mixed infections. A major advantage of trypanotolerant livestock, particularly N'Dama cattle, is the resistance or adaptation of this breed to many of the important pathogenes which prevail in the sub-humid and humid tropics. Research on practical indicators of resistance to these conditions will be required to establish relevant integrated strategies based on disease-resistant livestock. Selective breeding will require the integration of the traits that farmers hold important for their production systems.

Patterns of Trypanosoma vivax and T. congolense infection differ in young N'Dama cattle and their dams.

Trypanosome infection was detected by the dark ground/phase contrast buffy coat microscopic technique in N'Dama cattle in a high natural tsetse challenge situation in Zaire. The data were used to compare the pattern of infection in very young animals and in their dams, and to evaluate how the pattern evolved in calves from birth to maturity, and thereafter in the different age groups represented by their dams. Five hundred and fourteen calves were evaluated at 3 week intervals for an average of 26 months each, over varying periods between birth and 42 months of age. Two hundred and sixty nine dams had matching records from parturition to calf weaning at 10 months. One month after weaning, animals were equally infected with Trypanosoma vivax and Trypanosoma congolense. From then until 42 months, the proportion of time an animal was infected with T. vivax relative to T. congolense gradually decreased. In the dams this trend continued from 4 years to at least 8 years of age by which time T. vivax infection was only one-third that of T. congolense infection. This finding is regarded as strong evidence of the ability of N'Dama cattle, in this region of Africa, to acquire significant control of the development of parasitaemia following T. vivax infection but apparently not following T. congolense infection. Pre-weaner calves, grazing with their dams, appeared to have considerable protection from, or be more resistant to, both T. vivax and T. congolense infections compared with their dams and to their own immediate post-weaning situations.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative phenotyping of N'Dama cattle for aspects of trypanotolerance under field tsetse challenge.

Matching animal health and performance data were recorded over the 2 year period from weaning at 10 months of age on 255 N'Dama cattle in a high natural tsetse challenge situation in Zaire. Four parameters that are regarded as possible indicators of trypanotolerance, species of trypanosomes detected, length of time parasitaemic, intensity of parasitaemia (parasitaemia score), and anaemic condition as estimated by packed cell volume (PCV) values, were measured and the relative effects of changes in these parameters on trypanocidal drug requirements and growth were assessed. The effects of species of trypanosome on drug requirements and growth were directly measurable. In the case of the other three indicators, the effects on drug requirements and growth that would be brought about by a change of one standard deviation in each were calculated. This allowed comparison of similar sized changes in these three indicators that are of necessity recorded in dissimilar units. Trypanosoma vivax and Trypanosoma congolense infections had equal effects on the number of trypanocidal drug treatments required, an average of 0.61 treatments being administered to each infected post-weaner. A reduction of one standard deviation (SD) in length of time infected reduced the number of treatments required by 0.23 or 36% and an increase of 1 SD in PCV reduced the number required by 0.27 or 43%. Changes in parasitaemia score were not important. In the case of growth, a T. congolense infection reduced growth by 12.4 g day-1 or 8% more than a T. vivax infection. A reduction of 1 SD in length of time infected increased growth by 9.8 g day-1 or 6.5%, a reduction of 1 SD in parasitaemia score increased growth by 9.0 g day-1 or 6.0%, and an increase of 1 SD in average PCV increased growth by 8.4 g day-1 or 5.6%. The necessity to simultaneously measure the four criteria is clearly indicated by their approximately equal effects on the final performance trait of daily liveweight gain. Thus, absence of information on any of these criteria would significantly affect the accuracy of the estimate of an animal's overall trypanotolerance phenotype in this central African situation and reduce the progress possible in production projects involving N'Dama cattle.