Introduction

The same cup orientation is classically applied to all cases of hip replacement (45° abduction, 20° anteversion). We hypothesize that this orientation must be adapted to the patient's hip range of motion. We tested this hypothesis by means of an experimental study with respect to hip range of motion, comparing the classical orientation (45° and 20°), and the orientation obtained with computer-assisted navigation.

Introduction: The prosthetic impingement occurs if the range of motion of the hip exceeds implant mobility or in case of component malorientation. This phenomenon is rarely studied in the literature and most data have come from sporadic cases. This study was designed to assess the frequency and the risk factors of this phenomenon.

Material: The frequency and the severity of the impingement were calculated from a continuous series of 413 cups retrievals. These cups were examined macroscopically twice by two independent observers. The cam effect was noted as: absent, grade 1 (visible at gross inspection but measuring < 1 mm), grade 2 (notch measuring 1–3 mm), grade 3 (notch measuring > 3 mm). The risk factors were analyzed for 298 retrievals that had complete clinical charts.

Results: Among the 413 cups explants, the frequency of impingement was 51.3 percent (grade 3 in 12% and grade 2 in 24%). The impingement was the reason for removal in only 1.7 percent (only for hard bearings), meaning that impingement was mainly an unexpected event (98.3 percent). The impingement was more frequent when revisions were performed because of instability (80 percent; odd-ratio 4.2 (1.1–16.2)) than for loosening (52%) osteolysis (59%) or infection (38%) (p =.002). Likewise, impingement was more frequent when the sum of hip motion exceeded 200 degrees (sum of motion in the 6 degrees of freedom of the hip) (66% versus 45% if the sum was below 200°). The other risk factors were: use of heads with skirts (78% versus 55%), liner with an elevated rim (73% versus 55%), and head-neck ratio below 2.

Discusssion and conclusion: This study underlines the impingement is common when assessing cup retrievals (over 50 percent). One should be aware of impingement when performing hip replacement in patients having a high range of motion. This situation may require prostheses with a high head-neck ratio, as well as use of computer-assisted surgery. One should avoid liners with elevated rim as well as heads with skirts to prevent dislocation, particularly when other risk factors are detected.

Introduction: The anterior pelvic plane (APP), described by Lewinnek, is defined by the following points : anterior iliac spines, pubic symphysis. This plan is mostly considered as vertical in weight bearing and is currently used as the reference to guide cup insertion by means of imageless computer assistance (CAS). However, to our knowledge, there is no data that strongly confirm APP is vertical in weight bearing and how much his orientation is modified with regards operative position, or THA insertion. This study assessed these data by means of a radiological analysis.

Material and Methods: The orientation of the APP was measured with regards to the vertical plane on weight-bearing profile X-rays of the pelvis in 106 subjects including:

1) 82 patients with THA (40 who had at least one dislocation, and 42 matched patients without instability randomly selected, 19 of these 42 underwent a profile X-ray of the pelvis before and after THA insertion)

Results: Thirty-eight percent of the subjects in weight-bearing had an orientation of the APP different of more than ± 5° from vertical plane and 13% were out of the interval ±10°. The orientation of the APP was not significantly different between the groups (standard and THA) nor between the groups who had stable or unstable THA. The orientation of the APP was significantly modified between lying and weight-bearing posture, from a mean of 1,2° lying to −2,25° upright. Under these conditions, 12 subjects presented a variation of more than 7°. Insertion of a THA did not significantly modify the orientation of the APP in weight-bearing among the 19 subjects (variations were small (−1° ± 7° [from – 21° to 8°]), but were more than 5° for 7 of the 19 subjects).

Discussion and Conclusion: Most of the surgeons use the APP as a reference to guide navigation for cup insertion, considering it is vertical in weight-bearing. However, it is not true for 38% with a margin of 10°, which is equivalent to approximately half of the anatomical anteversion of the acetabulum. Standing up produced a significant variation of the orientation of the APP with regards to lying position. These errors that are not integrated by most of the CAS without preoperative CT scans, may produce cam effect or dislocation when the patient is moving to sited position. The variations of APP orientation with regards to vertical plane suggest it is not adequate to guide the CAS insertion of the cup. There is no reliable reference, easily identifiable during surgery that integrates the variations of position of the pelvis. This leads us to promote a new CAS for THA insertion free of reference plane, based on kinematics.

Purpose of the study: Most systems used for computer-assisted total hip arthroplasty require preparatory computed tomography acquisition or use of multiple bone markers fixed on the pelvis. In order to overcome these problems, we developed a novel system for CT-free computer assisted hip surgery based on a functional approach to the hip joint. The concept is to orient the cup within a cone describing hip motion. The purpose of the present study was to analyze preliminary results obtained with this new system.

Material and methods: This new system was used to implant 18 primary total hip arthroplasties in 16 women and 2 men (mean age 68±7.8 years, age range 54–83 years) with degenerative disease. Two optoelectronic captors were fixed percutaneously on the pelvis and the distal femur. The acetabulum was reamed, then the femur prepared with instruments of increasing caliber. The last reamer positioned in the shaft carried an upper head which matched the size of the prepared acetabulum. Hip joint motion was recorded to determine the cone of maximal hip mobility. The system then oriented the cup so that this cone was completely included the cone described by the prosthesis.

Results: There was one traumatic posterior dislocation (fall in stairs) at three weeks, without recurrence. The Postel Merle d’Aubigné score improved from 8±2.9 (3–12) preoperatively to 17±0.8 (16–18) at last follow-up. None of the patients complained about the sites where the percutaneous markers were inserted and ther were no cases of hematoma or fracture. Mean leg length discrepancy was 5.6±7.5 mm (range 0–25 mm) before surgery and 0.6±3 mm (range −5 to 10 mm) at last follow-up. Mean anteversion of the femoral implant was 22.3±6.7° (14–31). Anatomic anteversion of the cup (measured from a marker linked to the pelvis and thus independently of the position of the pelvis) was 25.9±10.4° (12–40). The sum of the femoral and acetabular anteversions was 48.2±14.6° (range 27–71°).

Conclusion: This method can be used in routine practice without lengthening operative time excessively. It provides a safe way to control the length of the limb and helps position the cup. This study demonstrated that there is no ideal position for the cup that can be applied for all patients. Because of the wide spread of the inclination and anteversion figures, half of the cases were outside the safety range recommended by Lewinnek.

Purpose of the study: In order to evaluate the influence of prosthesis design and resurfacing on the outcome of total hip arthroplasty (THA) implanted without cement, we reviewed the orthopedic literature from 1980 to 2004.

Material and methods: The PubMed database was screened from 1980 to 2004 for publications reporting cementless THA with a follow-up analysis. The same criteria were used to screen three registries. In all, the publications retained had studied 50,162 cementless THA (mean patient age 48.9 years, mean follow-up 6.5 years) where were studied according to rate of revision, presence of osteolysis, and presence of operative fractures. Eleven families of components grouped together the majority of prostheses: five acetabular families [screw fixation without resurfacing (n=2997), screw fixation with hydroxyapatite (HA) resurfacing (n=3618), screw fixation with corindon resurfacing (2360), press-fit mac-roporous (15691), press-fit HA (6094)]; and six families of femoral pivots [straight macroprous (n=7502), straight HA (n=3255), straight corindon (n=6136), anatomic HA (n=3468), anatomic macroporous (n=1215), anatomic corindon (n=1041)].

Results: The rates of revision and of osteolysis were higher for screw fixed cups without resurfacing. For screw fixed or press-fit cups, HA resurfacing did not reduce the rate of revision compared with corindon coated or macroporous implants. For anatomic pivots, adjunction of HA resurfacing reduced the rate of revision but at the shortest follow-up and without reducing the rate of osteolysis. Corindon-coated pivots gave comparable results for straight or anatomic implants. Conversely, HA-coated pivots gave better results with an anatomic design. The shape of the pivot had les effect than resurfacing on osteolysis and revision, but had a greater influence on operative fractures (2.9% for straight implants versus 4.6% for anatomic versions).

Conclusion: In all:

uncoated implants should be abandoned;

Purpose of the study: Because of its specific properties, linezolid (LZD) is an alternative to glycopeptides for the treatment of BJI causes by resistant Gram-positive cocci. The efficacy and tolerance of long-term (> 28d) administration remain to be determined with precision.

Material and methods: This was a retrospective analysis of the files of patients who received long-term LZD for BJI with a post-treatment follow-up of at least twelve months.

Results: Between January 2001 and December 2003, 68 patients (mean age 54.6 years) received LZD (600 mg/12h) intravenously then orally for a mean duration of 14.6 weeks on average (range 6–36 weeks). The orthopedic implants were infected in 31 patients (45.6%, 27 prostheses and 4 external fixators). A fistulization was diagnosed in 29 patients (42.6%). Medical and surgical treatment was undertaken in 51 patients (75%). Germs isolated from deep samples were staphylococci (n=57, 51 meti-R), and strepotococci (n=11). A polymicrobial infection was recorded in six patients (8.8%). Clinical success was achieved in 52 patients (76.5%) at the end of treatment, a result which was sustained for 48 of them to mean follow-up of 16.8 months (range 12–48). Sixty-three episodes of side effects were noted: anemia (n=29), peripheral neuropathy (n=9), nausea (n=14), headache (n=2), neutropenia (n=2), and thrombopenia (n=1), leading to discontinuation of LZD in 23 patients (33.8%) on average 11.9 weeks (range 6–36) after onset of treatment. Fifteen patients (22.1%) required transfusion.

Discussion: Among the patients in this series with BJI, most caused by a multiresistant germ, the rate of success was satisfactory (48/68, 70.6%) with LZD. Treatment was associated with a high frequency of serious adverse effects leading to discontinuation in one-third of patients.

Conclusion: Long-term treatment of BJI with LZD appears to be effective, including in patients with infected orthopedic material. Conversely, tolerance problems can limit is use to infections caused by mul-tiresistant Gram-positive cocci unresponsive to other compounds.

Purpose: In young active subjects, total hip arthroplasty (THA) raises the risk of early polyethylene wear eventually warranting the use of alternative bearings. The purpose of this study was to analyze outcome in subjects aged less than 50 years implanted with a primary metal-on-metal prosthesis.

Material and methods: Between 1995 and 1998, thirty-nine THA with a metal-on-metal bearing were implanted without cement in 30 consecutive patients aged less than 50 years, mean age 23–50). There were nine bilateral implantations. The cementless implants had surface treatment without hydroxyapatite and 28 mm heads. The indication for THA was necrosis in twenty cases, osteoarthritis in nineteen, most in patients with hip dysplasia. The Devane classification placed 84% of the patients in levels 4 or 5, indicating heavy work and/or sports activities. Inclusion criteria were: 1) age less than 50 years, 2) significant activity (occupation and/or sports), 3) osteoarthritis or necrosis. Patients were included and followed prospectively. Serum cobalt level was measured at last follow-up. None of the patients were lost to follow-up.

Results: The Postel-Merle-d’Aubigné score (PMA) improved from 12.8±2.2 (7–15) before surgery to 17.2±1 (14–18) at 5.1 years (5–6.3). None of the patients complained of hip pain. Two patients has moderate inguinal pain related to a cupiliopsoas conflict. All patients achieved complete weight bearing on the fourth postoperative day excepting three who resumed weight bearing at six weeks due to an acetabular augmentation graft. There were no cases of implant migration and all implants exhibited signs of osteointegration on the radiograms. There were no postoperative dislocations and no cases of osteolysis could be identified, particularly in the eight patients who had increased serum cobalt (four bilateral implants) and who had no other statistically significant favouring factor.

Conclusion: The results at five years suggest that the second-generation metal-on-metal bearing is a reliable alternative when THA is proposed for young active subjects. Long-term follow-up of this cohort of subjects at high risk of wear is necessary to confirm these encouraging results.

Purpose: Femoral revision can be difficult when associated with important loss of bone stock and femoral deformation, particularly when the deformation prevents using a long prosthesis despite major loss where it would be useful. We describe a novel technique allowing a simultaneous solution to these two problems and report preliminary results in five patients.

Material and methods: The technique was applied in five patients. Briefly, one or several osteotomies at different levels were performed to correct the deformation in one or more planes, and fixed with a locked femoral implant. Femorotomy was associated in four patients to facilitate removal of prior implants and constituted one of the correction osteotomies. In one patient, non-union of the greater trochanter was treated with a plated autograft. The series included three men and one woman, mean age 72 years (65–83). According to the SOFCOT score, femoral bone loss was grade II in four patients and grade III in one. All femurs had varus deformation (mean 21°, range 16°–40°), and two femurs exhibited permanent flexion (40° and 45°). One shaft osteotomy was used in four patients and two osteotomies in one. The locked femoral implant measured 250 mm in three and 300 mm in two.

Results: Mean follow-up was 3.5 years (0.5–5). One patient committed suicide at six months. The mean Postel Merle d’Aubigné score improved from 9.4 (7–11) to 16.4 (15–18). The trochanter non-union and all osteotomies head at three to four months except one case of shaft non-union which was well tolerated (PMA=16, in a patient without femorotomy who did not require recalibration of the proximal femur). In these healed cases, remodelling and/or spontaneous reconstruction of the femur was observed without grafting for the shaft. There was no stress shielding aspect in the patients with the longest follow-up although they had non-cemented stems with distal locking and no surface treatment.

Conclusion: The technique proposed for this specific indication enables resolution of the double problem of fixation and correction of deformation while allowing spontaneous reconstruction around the non-cemented locked implant. Use of femorotomy is recommended to allow recalibration and stabilisation of the proximal femur around the stem. Longer follow-up is needed to ascertain longevity of the spontaneous reconstruction. Nevertheless, these non-reintegrated implants behave like locked centromedullary nailing.

Purpose: The Rosenow enriched medium (RW) enables culture of anaerobic germs as well as slow-growing germs sometimes causing chronic infections on implanted material. The purpose of this work was to determine the usefulness of RW for the bacteriological diagnosis of infections on total hip arthroplasty (THA) and total knee arthroplasty (TKA°.

Material and methods: One hundred fifty-four pre- or intraoperative standard and RW samples were obtained in a prospective study of 80 consecutive patients (mean age 67.6 years) with an infected THA (n=56) or TKA (n=24) between January 1998 and June 2000. A bacteria was considered “infecting” if it grew on direct culture on at least two samples after enrichment. A single positive sample after enrichment was considered a contamination except for strict anaerobes for which direct culture could not be achieved. For these germs, growth after enrichment was thus considered significant.

Results: Among the 154 samples, 59 (38%) gave positive direct cultures and 95 (62%) positive enriched cultures. Among the 59 positive direct cultures, the RW culture was concordant in 87% of the cases. For the 13% of discordant cultures, the germs did not grow on standard medium: Staphylococcus (n=6), Pseudomonas (n=1), and enterobacteria (n=1). For the 95 positive enriched cultures, 41 (43.1%) of the RW cultures were condordant with the standard culture; the standard was positive in 13 (13.6%) and the RW negative (11 Staphylococcus including five aureus, one Pseudomonas, and one Corynebacterium), but in 41 cases, the RW was positive while the standard was negative (16 Staphylococcus, including 13 coagulase negative, five Streptococcus, two Entero-coccus, one Corynebacterium, three enterobacteria, and fourteen anaerobes). The infecting nature of the aerobic bacteria was retained because earlier or later samples were positive. The sensitivity and predictive value of a positive RW culture were 86% and 86% respectively.

Discussion: Using RW medium and standard samples is useful if germs grow after enrichment in order to confirm the infecting nature of the isolated germ (double culture). The reliability of RW medium was confirmed since it was concordant in 87% of the cases with a positive “gold standard” culture. For positive cultures after enrichment with a negative standard culture, RW allows correcting the diagnosis of infection in 43% of the cases. Its usefulness lies basically in the isolation of coagulase negative Staphylococcus and anaerobes (especially Propionibacterium spp. and Peptostreptococcus spp.).