The weak point in an ACL reconstruction immediately after surgery is the tibial fixation of the graft. This factor will often limit the return to load-inducing activities. Many new hamstring-graft fixation devices have been introduced for cruciate ligament reconstruction, but there is little comparative data on their performance. This work tested the hypotheses that some of these devices will resist graft slippage under cyclic loads better than others, and that some will have higher ultimate strength than others. Five devices were tested: WasherLoc, Intrafix fastener; and RCI, Delta Tapered, and Bicortical interference screws. Cyclic loads representing normal walking activity (1000 cycles from 70 to 220 N) and ultimate strength tests were done, using calf tibiae (similar bone density to young human tibiae) and four-strand tendon grafts, with eight tests of each device for each of cyclic and ultimate tensile strength tests. A series of graft creep tests under cyclic loads was also done. The results showed that there was no significant difference in graft construct elongation under cyclic loads (range 0.7-1.3 mm) after allowing for 0.4 mm mean graft creep. The WasherLoc gave the highest ultimate strength (945 N, p<0.001, range 490-945 N). We concluded that all devices performed well under cyclic loads that represented normal walking activity, but the ultimate strengths differed. The performance under cyclic load was better than has been published for conventional interference screws. This evidence suggests that it may now be safe to mobilise younger patients less cautiously immediately after hamstring-graft ACL reconstruction.

We present a case of Mycobacterium avium-intracellulare (MAI) infection of the ankle joint in a patient with HIV infection. The patient presented with a painful, destructive arthropathy of the ankle. Initial microbiological studies were negative but infection with MAI was later identified from biopsies taken during hindfoot fusion. Antibiotic triple therapy was given and the patient remains pain-free without evidence of active infection. To our knowledge, this is the first case of MAI infection of the ankle reported in the literature. A high index of suspicion of (atypical) Mycobacterial infection should be maintained in patients with HIV infection presenting with an indolent but destructive arthropathy of the ankle joint.

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We welcome letters to the Editor concerning articles which have recently been published. Such letters will be subject to the usual stages of selection and editing; where appropriate the authors of the original article will be offered the opportunity to reply.Letters should normally be under 300 words in length, double-spaced throughout, signed by all authors and fully referenced. The edited version will be returned for approval before publication. Radiation therapy for the prevention of heterotopic ossification at the elbowSir, I write to comment on the article in the April 2001 issue entitled 'Radiation therapy for the prevention of heterotopic ossification at the elbow' by Heyd et al.1 In this study, the authors have concluded that on the basis of their nine cases, perioperative radiation therapy should be used to avoid recurrence of heterotopic ossification (HO). They have not, however, provided any control group for comparison and hence no meaningful conclusions can be drawn. All the other studies which the authors have reviewed in this article, including that by McAuliffe and Wolfson, 2 do not have any control group for comparison. The role of radiation therapy in the prevention of recurrence of HO around the elbow remains anecdotal. There have been studies by Viola and Hanel,3 Jupiter and Ring 4 and Denormandie et al 5

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