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: The indication for humeral or total shoulder prosthesis in patients with avascular osteonecrosis of the shoulder depends on the radiographic stage of the necrosis. The purpose of this study was to analyse the prognostic radiographic features enabling proper identification of the indications for humeral or total prostheses.

Material and methods: This retrospective multicentric study included 53 shoulders operated on for prosthetic repair of avascular osteonecrosis. There were 20 men and 29 women, mean age 57 years. A humeral prosthesis was used in 34 cases and a total prosthesis in 19. Clinical assessment was based on the Constant score and the radiographic analysis used the Arlet and Ficat classification. Staging was II (n=4), III (n=16), IV (n=21) and V (n=12). Independently of the radiographic stage of necrosis, three characteristic groups were defined. Group 1 (19 shoulders) included necrosis without bony collapse of the humeral head. Group 2 (20 shoulders) included necrosis with bony collapse of the humeral head with preservation of the anatomic relations with the glenoid cavity. Group 3 (14 shoulders) included necrosis with bony collapse and impaction of the humeral head in the glenoid with medialisation of the humerus.

Results: Preoperatively, presence of bony collapse was associated with decreased pain and motion score. Major joint stiffness was noted in group 3 (8). The humeral prosthesis gave similar results for groups 1 and 2 (Constant score 73 and 75.3). Less satisfactory results was the rule in group 3 (Constant score 51.6). There was a postoperative erosion of the glenoid cavity in 83% of the shoulders in group 3 versus 12.5% in group 1 and 17% in group 2. The total prosthesis optimised results despite persistence of a difference between groups 2 and 3 (Constant score 83 and 64 respectively).

Discussion: Destabilisation of the glenohumeral joint by impaction of the humeral head against the glenoid cavity has an effect on the clinical result of the prosthetic surgery. Preservation of the anatomic relations of the articulation (groups 1 and 2) appears to be necessary for good results. Impaction medialisation of the humerus has a negative effect on the clinical result of humeral prostheses with a risk of glenoid erosion.

Conclusion: Independently of radiographic stage of necrosis, the presence of humeral impaction with medi-alisation should be considered individually as it has a negative effect on the clinical outcome of these prostheses, particularly humeral prostheses.

Purpose: The double mobility of the G. Bousquet cup—head-polyethylene,polyethylene metal cup—considerably reduces the risk of total hip arthroplasty displacement.

Material and methods: We observed seven cases of “intra-prosthetic” displacement in patients with this type of cup. Progressive wear of the polyethylene retention ring allowed displacement of the femoral head. These displacements occurred in six patients (one bilateral case) aged 43–58 years, on the average ten years after the implantation (range 3.5 – 15 years).

All patients underwent revision.

Results: The polyethylene retention ring was worn in all cases allowing the femoral head to escape. Revision surgery was performed very early in six hips to change the modular base and the polyethylene ring and re-establish retaining capacity. A satisfactory result was achieved in all cases. One patient required revision five years later to change the prosthesis subsequent to haematogenous infection. Another patient underwent a late revision to change the modular base and the entire cup of a press fit implant. This hip was in excellent condition but revision was decided on because of four dislocations.

Discussion: Intra-prosthetic displacement of the polyethylene head of a double-mobility cup is exceptional in our experience. Wear of the retention ring is favoured by different elements: 1) direct phenomena: neck and head diameter causing early contact between the neck and the cup; 2) indirect phenomena: factors limiting the mobility of the polyethylene metal cup couple (fibrosis, repeated interventions, ossification).

In our experience, intra-prosthetic displacement occurs more readily in patients with favouring conditions (alcoholism, muscle deficiency, psychiatric disorder, obesity) observed in six of our seven cases.

Conclusion: Intra-prosthetic displacement of a double-mobility cup is a possible but exceptional complication requiring a technically simple revision. Some teams use this type of cup systematically and for us is an essential element for preventive treatment in high-risk patients and for curative revision of recurrent dislocation.

Purpose: The purpose of this study was to analyse the factors affecting outcome after prosthesis implantation for osteonecrosis of the humerus in order to ascertain details concerning the indications for humerus or total prostheses in this condition.

Material and methods: Forty-seven women and 27 men, mean age 57 years with osteonecrosis of the humerus underwent surgery for implantation of 80 shoulder prostheses. According to the Arlet and Ficat classification as modified by Cruess there were five grade II, fifteen grade III, 41 grade IV and fourteen grade V shoulders, with five unclassifiable shoulders. there were 14 supraspinatus tears and five infraspinatus tears. The 26 total shoulder prostheses and 54 humeral prostheses were reviewed at a mean 47 months follow-up. Pre-operative x-rays were available for 65 shoulders and postoperative x-rays for 58.

Results: The subjective outcome was considered good irrespective of the grade (very satisfied 60%, satisfied 30%, dissatisfied 4%). The mean postoperative Constant score was 70 ± 15. The preoperative score was lower for more advanced disease but the difference was not significant at postoperative assessment. The total prosthesis provided better results in grade V shoulders and the hemiprosthesis in grade II and III shoulders.

The result of the humeral prostheses depended on the grade of necrosis. The postoperative Constant score was lower for advanced necrosis with lower scores for motion, force and pain (which was not influenced by age). At last follow-up, 31% of the x-rays revealed a significant narrowing of the glenoid-head space. The clinical outcome was significantly less satisfactory for all Constant scores. Rotator cuff tears, preoperative stiffness favoured glenoid wear. Tears of both cuff tendons led to poor outcome. Bone collapse with impaction of the head into the glenoid and medialisation of the humerus was a significant factor predictive of less satisfactory outcome.

Discussion: The grade of necrosis is a determining factor for indications for humerus or total shoulder arthroplasty for the treatment of osteonecrosis. Our objective results lead us to recommend a humeral prosthesis for grade II and III patients and a total shoulder arthroplasty for grade V patients. For grade IV patients, the choice depends on patient age, shoulder stiffness, the status of the cuff, and most importantly, collapsus of the head of the humerus with impaction-medialisation of the humerus.