Introduction

Despite improvements in prosthesis design, the clinical outcome of total hip arthroplasty still has 10% failure rate after 10 years. Component malpositioning can lead to instability, impingement, excessive wear and loosening. Computer-assisted procedures are expected to improve the accuracy of component positioning, and therefore the long-term outcome. We present an original hip navigation system that allows controlling leg lengthening, offset and stability without the use of the pelvic anterior plane.

Introduction

Reoperations to manage unstable total hip arthroplasty are reported with a high failure rate. The dual mobility cup (figure 1) (mobile polyethylene component between the prosthetic head and the outer metal shell) is a useful option in such cases. The purpose of this retrospective study was to assess the clinical and radiologic features associated with the dual mobility cup.

Purpose of the study: The ceramic-on-ceramic bearing for total hip arthroplasty (THA) has been widely used in Europe for many years. There have however been few publications on its long-term outcome. The purpose of this study was to examine the outcome at nine years follow-up of 100 THA implanted without cement using a ceramic-on-ceramic bearing.

Material and methods: The first 100 ceramic-on-ceramic THA implanted from November 1999 in our unit in patients aged less than 65 years were studied. The clinical assessment included the physical examination with search for complications and the Harris and Postel-Merle-d’Aubigné scores noted preoperatively and at last follow-up. The radiographic assessment was performed by two surgeons (double reading) to search for peri-prosthetic lucency, osteolysis, ossifications and implant migration. The state of the calcar was noted. The Delee-Charnley classification was used to classify the lucent lines for the acetabulum and the Gruen McNiece and Amstutz classification for the femur.

Results: Among the 100 THA, 20 patients were lost to follow-up. The Harris score was 42.6 (29–55) preoperatively and 93.9 (67–100) at last follow-up. The PMA was 8 (5–11) preoperatively and 16.7 (9–18) at last follow-up. One hip was revised to change the acetabular implant at five years. There were six early dislocations [one episode (n=4), two episodes (n=2)], one late dislocation, and two episodes of subluxation without recurrence. There were no fractures of the femoral head. The radiographic analysis identified moderate bone absorption of the calcar without real osteolysis in nearly all of the patients. For a few patients, a lucent line seen early postoperatively had disappeared at last follow-up. No implant migration (cup, stem) was noted.

Discussion: The clinical and radiographic outcomes are in agreement with the literature. The relatively high rate of dislocation can be explained by the diverse levels of experience of the surgical teams. The prostheses presenting dislocation did not have an unfavourable outcome, particularly radiographically.

Conclusion: These clinical and radiographic results at nine years follow-up, and the current systematic use of computer assisted navigation for optimal implant positioning favour continuation of the implantation of the ceramic-on-ceramic bearing in patients aged less than 65 years.

Purpose of the study: Few data are available concerning the proper management of patients with a periprosthetic fracture of the hip who presents biological signs of inflammation (increased WBC, sedimentation rate, or C-reactive protein). The purpose of this work was to determine the prevalence of elevated biological markers in this type of patient and to determine the reliability of such markers for the diagnosis of periprosthetic infection.

Material and methods: A periprosthetic hip fracture was diagnosed in 204 patients from 2000 to 2006. The WBC count, the sedimentation rate and the serum CRP level were noted at admission to the emergency ward. The diagnosis of infection was confirmed by at least two positive bacteriological samples of tissue biopsy and/or joint fluid collected at surgery. A statistical analysis was conducted to determine the prevalence of elevated biological markers of inflammation, the sensitivity, their specificity and their positive predictive value for deep infection.

Results: Twenty-one patients (11.6%) developed a periprosthetic infection. Among the 204 patients, the WBC count increased in 16.2%, sedimentation rate in 33.3% and CRP in 50.5%. The sensitivity was 24% (WBC), 50% (sedimentation rate) and 83% (CRP). The specificity was 85% (WBC), 69% (sedimentation rate) and 56% (CRP). The positive predictive value was low (18, 21 and 29% respectively).

Discussion: Markers of inflammation are frequently ordered before surgery to search for infection but can be elevated for various reasons. Most often, these markers are elevated because of the patient’s general status and are thus related to other co-morbid conditions and/or reaction to the new fracture. In this population, the WBC count did not contribute to the diagnosis of infection as only 24% of the infected patients had a high count. CRP and sedimentation rate and the WBC count had low positive predictive values.

Conclusion: This study shows that an isolated elevation of biological markers of inflammation in a patient with a periprosthetic fracture is not a good indicator of infection.

Purpose of the study: An unstable hip prosthesis is a therapeutic challenge. The prevalence of revision is 5 to 26.6% in the literature. We evaluated the contribution of double-mobility implants for revisions of unstable hip implants.

Material and methods: This series was composed of 45 patients who underwent revision between January 2000 and December 2003 for hip instability (44 dislocations, 1 subluxation). The same implant was used for all patients, either for the first-intention version (press-fit or cemented), or for the revision version (press-fit). For certain patients, the first-intention implant was cemented in an armature. The series included 28 females and 17 males, mean age 66.5 years (range 36–48 years). The initial diagnosis was osteoarthritis in 34 cases (76%), dysplasia in seven (16%), osteonecrosis in two (4%), Paget’s disease in one (2%) and rheumatoid disease in one (2%). The patients had had 2.8 dislocations on average (range 1 – 10). Time from first dislocation to the first-intention operation was 45.6 months (range 15 days – 20 years). Mean time from the first-intention operation to revision was 64.3 months (range 3 weeks – 20 years). Risk factors for instability were repeated hip surgery (> 3 operations) for 13 patients, wear for seven, nonunion of the greater trochanter for five, neurological and cognitive impairment in five, and malposition in three.

Results: Mean follow-up was 25.2 months. None of the patients were lost to follow-up. Two patients died late after the operation. Among the complications observed, there were: two cases of recurrent dislocation, one case of subluxation, two cases of infection (one with favorable outcome after surgical cleaning and antibiotics the other followed by patient death), two cases of deep vein thrombosis, one case of popliteal paresia with favorable outcome, one case of delirium tremens. Surveillance was the therapeutic option for the patient with subluxation. For patients with dislocation, revision surgery was performed using the same implant. For one of these patients, the dislocation occurred following early loosening.

Conclusion: Use of double-mobility implants for prosthetic revision undertaken because of prosthesis instability provides encouraging results, with a rate of dislocation (4%) close to that observed with first-intention implants.