Purpose of the study: The correct position of the femoral and tibial tunnes for anterior cruciate ligament (ACL) reconstruction is a determining factor for favorable outcome. We used a novel computer-assisted system which enables intraoperative localization of the tunnel centers on the lateral view of the knee before drilling. This technique uses fluoroscopy combined with a passive system for computer-assisted image acquisition and processing to provide the surgeon with the desired positions. We report the anatomic and clinical results observed in a prospective series comparing this technique with the classical technique of independent blind tunnels.

Material and methods: Thirty-seven patients underwent computer-assisted surgery and 36 classical surgery without computer assistance performed by a senior surgeon. Mean patient age was 27 years in both groups. The patients were reviewed at mean 2.2 years (range 1–4.5 years). Data recorded included the KT-1000 laxity, radiographic drawer and the IKDC score (1999).

Results: Mean time from ACL tear to reconstruction was 30 months in both groups. Computer assistance increased operative time 9.3 minutes (range 4–13). The IKDC score was 67.9% A, 29.7% B, and 2.7% C in computer-assistance surgery patients and 60% A, 37.1% B and 2.9% B for classical surgery patients. The mean IKDC function score was 89.7/100 for the computer-assisted patients and 89.5/100 for the others. Mean manual maximal laxity (KT-1000) was 7 mm before surgery and less than 2 mm at last follow-up. Differential laxity was less than 2 mm in all patients who underwent computer-assisted surgery and in 97.7% of the others. The mean differential laxity for the medial compartment as measured on the postoperative stress films was 2.4 mm (range 0–12 mm) for computer-assisted surgery patients and 3 mm (range 0–10 mm) for the others. In the computer-assised surgery patients, the femoral tunnels were centered on a smaller area. There was not significant difference in the IKDC score, the KT-1000 findings and the stress x-rays between the two techniques.

Conclusion: The results of these two techniques in this report are similar to data reported in the literature. Computer-assistance enables more accurate and reproducible tunnel positioning with no significant clinical impact.

Purpose of the study: Staphylococcus lugdunensis, described in Lyon in 1988 by Freney, appears to be a member of the cutaneous perineal flora. Since the first description, S. lugdunensis infections are regularly reported. The germ has been reported as the causal agent for endocarditis on valve prostheses with a very severe prognosis, requiring surgery in addition to medical management. We wanted to ascertain the prognosis of such infections on joint prostheses and to determine if it is different from that with other staphylococcal species.

Material and methods: Since 1991, seven S. lugdunensis infections on a joint prosthesis (three total hip prostheses and four total knee arthroplasties) were identified in our department. The Api Id 32 staph (BioMérieux SA) test battery was used for identification. All patients underwent surgical treatment and were given a prolonged antibiotic regimen. Simple joint cleaning was performed in three cases, one requiring a one-stage prosthesis replacement. There were four two-stage prosthesis replacements. The antibiotic regimen was always long (3–8 months) and was continued as a palliative treatment in two patients who underwent simple cleaning.

Results: One elderly woman with multiple co-morbid conditions died after prosthesis removal before the replacement procedure could be performed. There were no cases of recurrent infection at 16 months and 6 years for the four prosthesis replacements (one- and two-stage procedures). Arthroscopic cleaning without removal of the TKA was a failure in one patient who required prosthetic replacement later. Two simple cleanings in elderly patients were failures and required continuous palliative antibiotics.

Discussion: Staphylococcus lugdunensis is generally considered to be very susceptible to antibiotics in vitro. In our experience, search for minimum inhibitory concentrations and minimum bactericidal concentrations have shown cures with rapid shifts which must be taken into consideration when choosing an antibiotic. With surgical removal of the prosthesis and adapted antibiotics, the prognosis of these infections is not different from other staphylococcal infections of joint prostheses. We did however note two cases of secondary infections, probably related to hematogeneous spread, which developed from an unidentifiable point in time.

Conclusion: Staphylococcus lugdunensis is a coagulase-negative staphylococcus with poorly known virulence properties. In our very small series of joint prostheses infections, therapeutic failure occurred when the infected prosthesis was not removed.

Purpose of the study: The Alpina unicompartimen-tal knee prosthesis (Biomet) is an anatomic prosthesis inserted with a femoral cut, a tibial base plate made of titanium and a flat modular polyethylene insert. Cemented and non-cemented versions are available with hydroxyapatite ceramic (HAC) coating.

Material and methods: We retrospectively reviewed the radiological outcome at more than five years (fie to eight years follow-up) in a consecutive series of patients who had an Alpina HAC prosthesis with tibial fixation completed with a titanium screw. Clinical and radiological findings were recorded. Radiologically: pre- and postoperative angles, implant position, reliability of the instrument set. At last follow-up, we studied the presence of lucent lines, polyethylene wear easily measured on the flat insert, and bone remodeling around the tibial fixation screw.

Results: At last follow-up (5 to 8 years), three patients were lost to follow-up and three had died. Radiological outcome was thus assessed for 44 implants (41 medial and 3 lateral). One patient required an early total knee prosthesis (diagnostic error). Three patients underwent revision at 5–7 years (for rupture of the polyethylene insert in two very active patients, and for significant polyethylene wear in the third). Two had a revision procedure for a partial knee prosthesis and the third for a total knee prosthesis. For the 40 other patients, the following observations were made: partial lucent line along the tibial polyethylene plate with no functional impact (n=1), polyethylene wear visible but measuring less than 1 mm (n=12), remodeling around the tibial fixation screw probably corresponding to a granuloma but not threatening the implant (n=10).

Discussion: The clinical results of partial knee prostheses are well known. Mid-term radiographic results of non-cemented unicompartmental prostheses with a flat tibial plateau producing a minimal contact surface has shown: good reliability of the instrument set, excellent bony integration of the HAC-coated implants, but measurable polyethylene wear on more than one quarter of the prostheses, with two ruptures of the polyethylene insert at 5 and 6 years.

Conclusion: A study currently under way will examine finished pieces on a simulator to study wear and failure as a function of several parameters: polyethylene thickness, lateral restraint with a metal rim, presence of a basal stem fixing the polyethylene on the metal base, importance of the femur-polyethylene surface contact.

Purpose: Several studies have reported results of anterior cruciate ligament (ACL) reconstruction showing the influence of the position of the transplant. We choose the anatomic position. In order to optimise this position, we developed a navigation system using intraoperative fluoroscopic imaging.

Material and methods: Thirty-five patients underwent ACL reconstruction using the computer-assisted technique. We used a fluoroscope connected to the computer equipped with an acquisition module and an image processing module which captures the lateral view of the knee provided by the fluoroscope. Surgery was performed arthroscopically. After inserting landmarks (mini-screws for the femoral end and pins for the tibial end) on the theoretically ideal positions, the computer determined the theoretical anatomic position of the tibial and femoral insertions of the ACL. The position was then validated or modified and re-validated. Postoperative radiograms (lateral view of the knee) were used to analyse the position in relation to the anatomic centre of the ACL insertion. Two groups of patients matched for sex and age were compared, 35 patients undergoing ACL reconstruction with the navigation technique versus 35 patients undergoing the same procedure without navigation. Results were compared with the nonparametric Wilcoxon test.

Results: Computer-assisted positioning provided a mean difference of 5.1±1.3 mm between the centre of the transplant and the theoretical ideal point compared with 7.7±1.9 mm without assistance.

Discussion: Comparison using adapted statistical tests (Wilcoxon text) demonstrated a significant difference (p=0.001) between the two groups. These findings demonstrate the improved precision and reproducibility achieved with the navigation technique.

Conclusion: This technique allows the surgeon to obtain an excellent precision of the transplant insertion with excellent reproducibility. There are two drawbacks: the longer operative time (mean 15±7 minutes) and radiation exposure. But this technique is simple, easy to use and low-cost.

Aims: Functional results of anterior cruciate ligament (ACL) is closely related to the anatomical position of the graft. Femoral or tibial miss placements are associated with increase laxity, decrease range of motion. Based on anatomical dissections we developed a triangle method able to be used as fluoroscopic intra-operative landmark to increase the reproductibility of the placements. Methods: A lateral X ray of normal knee is mandatory before the surgical procedure. During the ACL reconstruction using patellar tendon a pin is placed to determine the tibial tunnel, and a small screw is inserted at the femoral ACL location. Under imagine intensifier, a lateral X ray of the operated knee is realised. The picture is exported and analysed on a PC computer. The surgical placement is compared with the ACL center position according to the triangle method. 35 knees have been operated and compared with 35-paired knees operated with the same technique and operator. Results: The mean distance between the ACL center and the surgically chosen femoral position is 7.5 ± 1.9 mm for the standard surgery and 4.9 ± 1.3 mm for the fluoroscopy based surgical navigation. The Wilcoxon test for small-paired series indicates a statistical significance (p=0.001). The mean extra operative time is 15 ± 7mn. Conclusion: This technique is simple, easy and rather fast. It gives to the surgery a significative improvement for positioning the ACL graft on the femoral side. It has to be confirmed for larger and by long term clinical results.

Aims:ACL revision surgery is a second-generation type of knee ligament surgery. The artificial ligaments, the imperfect mastering of arthoscopic assisted surgery and the absence of clinical and radiological analysis of peripheral laxities are among the main factors for failures. Methods:43 patients of a mean age of 29y were previously operated between 1 and 5 times.14 artificial ligaments, 23 patellar tendons and 4 hamstrings tendons failed as a first ACL reconstruction. The mean time between the first operation and the index revision was 44 months. In 6 cases an additional HTO was used. Different tendon grafts were used: quadriceps 11, patellar 19 and hamstrings 8. In 3 occasions an additional extra articular reefing was used. The patients were reviewed by one independent observer using KT 1000, Stress X rays, IKDC form (2000). The mean follow up is 35 months (11–123)Results:The IKDC score in pre operative time was 19 D, 21 C and 1B. At the review the score is 2A, 28 B, 9C, 2D. The functional IKDC form show 37.5% of remaining pain, 44% of stiffness sensation and 12.5% of instability. The mean functional improvement is 44%. The mean laxity improvement is 5.3mm for KT1000 and 4.5mm for stress X rays. Conclusions:Revision ACL surgery is not as good as primary surgery. The reconstruction is technically difficult and must be ‘à la carte’ in order to take in account several simultaneous problems: bone defect, cartilage abnormalities, skin and ligament insufficiencies.