We present the mid-term results of our consecutive series of 155 hips treated with ASR extra-large (XL) Acetabular System (ASR XL) and with ASR Hip Resurfacing System (ASR). We reviewed the clinical records of patients with implanted ASR or ASR XL. All patients were recalled and invited to come to our hospital for a periodic clinical, hematological and radiological evaluation.114 ASR XL and 41 ASR were implanted between 2004 and 2008 in 145 patients (69 men and 76 women) with a mean age of 57 years. 21 patients (23 hips) were lost from follow-up. Average follow-up was 76 months (50 to 91). Up now 42 ASR implants have been revised (27.0%): revision involved 9 hips on 41 treated with resurfacing (21.9%) and 33 hips on 114 treated with XL total hip arthroplasty (28.9%). Main reasons for revision were aseptic loosening with or without metallosis in 23 hips (56%), infection in 3 hips (7%), recurrent dislocation in 1 hip (2%), periprosthetic fractures in 1 hip (2%), elevation of blood metal ion in 6 (14%), pain in 2 (5%), unknown in 6 (14%). The cumulative survival for our ASR implants series was 61.6% with revision for any reason as the end-point after a mean follow-up of 76 months. The cumulative survival with revision for any reason as the end-point for ASR and ASR XL were respectively 67.0% and 59.1%. For patients who did not undergone revision, the mean Harris hip score improved to 91 (57 to 100) at five years and the mean satisfaction after the operation was graded 4.4 in a score from 1 to 5. Periprosthetic osteolysis was not found around any unrevised hip. Average cup inclination was 48° for the functioning hips and 55° for the revised hips. Metal ions plasma concentration analysis was conducted in 83 patients (87 hips). Elevated metal ion concentration (>7 μg/l) was found in 39 patients (42 hips, 48%) with average plasma concentrations of 37.3 μg/l for chromium and 81.5 μg/l for cobalt. Lower metal ions levels (<7 μg/l) were found in 44 patients (45 hips, 52%) with average plasma concentrations of 1.2 μg/l for chromium and 1.9 μg/l for cobalt. Our current concerns involve our large series of 30 asymptomatic patients (31 hips) with a radiographically stable implant without osteolysis signs but with elevated blood metal ion concentrations.
Second-generation metal-on-metal bearings have been used since the late 1980s as alternative bearings to eliminate aseptic loosening due to polyethylene wear. The aim of the present study was to evaluate the long-term results of a series of Metasul (Zimmer GmbH, Winterthur, Switzerland) metal-on-metal total hip arthroplasty (THA). Between January 1993 and September 1996, 149 cementless THAs with a 28 mm Metasul articulation were performed in 111 consecutive patients. Implant survivorship was calculated and clinical and radiographic evaluations were performed on 82 hips still available for follow-up at a mean of 18 years postoperatively. Nine hips (6.0%) were revised. The cumulative probability of survival of the overall implant at 18 years postoperatively with revision for any reason as the end point, was 0.937 (95% confidence interval, 0.888 to 0.985). The cumulative probability of survival of Metasul with revision for any reason as the end point, was 0.956 (95% confidence interval, 0.916 to 0.997). Various degrees of radiolucencies and osteolysis were found proximally around the femoral components of 25 hips (20%). Cementless Metasul THA showed high survival at 18 years postoperatively.
Dislocation is the most relevant early complication after primary total hip replacement (THR) in literature. Many factors have been advocated for dislocation, either surgeon-related either patient-related. Component positioning seems to be of major importance in determining dislocation. We evaluated 152 randomised THR with a CT study between 985 THR done at our Institute since november 2004 to november 2006. 152 randomised primary THR on a total of 985. The same prosthetic pattern (head size, stem, cup). Lateral approach with total capsulectomy and external rotator tendon resection. All 152 patients underwent a post operative standardized CT study assessing cup antiverion and inclination angles and stem antiversion angle. Dislocated patients where furthermore analysed for any detail concerning their procedure and follow-up. A safe zone was then deduced for safer positioning. During the follow-up period dislocation occurred in 5 hips (only one in the randomised group) assessing our rate of dislocation at 0.5%. All dislocation were managed with closed reduction and an articulated hip brace. No open reduction or revision surgery were further needed. The mean cup abduction was 47° in the dislocated hips and 49° in the control group. Mean cup anteversion was 29° in both groups. The mean stem anteversion was 8.2° in the dislocated group and 3.1° in the control group. No statistical difference could be reached between dislocation and cup positioning. A correlation between hip dyspalsia (Crowe II) as primitive diagnosis and dislocation could be reached considering all the THR procedures. In THR inappropriate cup and stem positioning is considered an important risk factor of postoperative dislocation. Accurate and reproducible measurement is mandatory for implant positioning evaluation. Conventional radiographs cannot provide accurate and reproducible measurement. CT can provide a precise measurement of prosthetic components. Several studies failed to demonstrate a correlation between component positioning and dislocation often because of small number of patients and many bias. We tried to reduce bias using the same prosthetic pattern and the same surgical approach. Notwithstanding we could not reach a statistical difference in term of prosthetic positioning between dislocated and control group. Perhaps the dislocated group was too small to have a statistical meaning. We could determine a Safe Zone of cup and stem positioning for our patients: cup anteversion between 24° and 33°, cup inclination between 42° and 50°, stem anteversion between −3° and 10°. Dislocation is the main early complication after THR. Its etiology depends on many factors. Sometimes the cause can’t be identified. Orientation of prosthetic components may be responsable for dislocation but its truly correlation can be hard to be assessed. In this study we found no correlation between implant positioning and occurrence of dislocation, but we defined a tighter Safe Zone than previous reported, in which the risk of dislocation is nought. A correlation between hip dyspalsia (Crowe II) as primitive diagnosis and dislocation could be reached.
Metal on Metal coupling in total hip replacement has been widely used since many years. After the rebirth of resurfacing a new trend to use very large diameter metal-metal coupling with standard stem prostheses has been started. New prostheses, old and new problems. We analyze first failures with new large diameter metal on metal coupling. The analysis focused on seven early failures of large diameter metal-metal prostheses (two resurfacing and five cementless prosthesis with XL head) over the first series of 350 cases (100 resurfacing and 250 cementless) in the first year. Synovial fluid aspiration have been performed in all failed patients searching for metal ions and bacterial proliferation. Moreover, prosthetic component positioning was also studied as a possible primum movens of these failures. Some failed patients underwent epicutaneous patch test for skin reaction to metal. One resurface prosthesis failed as a result of an vascular necrosis and conseguent fracture of the femoral neck and revealed a moderate increment in metal ion concentration in blood and synovial fluid obtained at time of revision. One resurface prosthesis failed as a result of an infected metallosis with a huge intraabdominal mass and revealed a huge increment in metal ion concentration in blood, addominal and synovial fluid. This patient underwent a lumbotomy to evacuate the abdominal retroperitoenal mass before prosthesis removal for a two step procedure. Out of the five failures of metal on metal cementless prosthesis with XL head four were the result of aseptic loosening and one was the result of a low grade infection discovered at coltures after revision surgery. Three showed clear metallosis caused by wrong positioning (more than 50° of cup inclination). All of these three presented an articular noise and elevated blood and sinovial fluid metal ion concentration. The fourth patient with aseptic loosening had a good component positioning but demonstrated an epicutanous allergic reaction to Cobalt. Also one of the three patients with metallosis resulted allergic to Cobalt. The blood and sinovial metal ion values were always elevated but particularly high in patients with cup inclination over 50°. Large head metal on metal prostheses demonstrated a higher percentage of early failure in our experience. They are very sensible to positioning. Blood and sinovial metal ion determination helps to promptly diagnose a bad metal on metal prosthetic functioning. A more accurate analysis about the different metals available on the market and their resistance to edge wear should not be delayed any further.
Total Hip Replacement (THR) in proximal, posterior iliac dislocation of the hip often represents a problematic issue. Reviewing their selected cases (70 patients between 3700 THR from 1986 to 2001), authors focalized some key points for this demanding surgery. The most important steps are acetabular positioning, implant decisioning and surgical approach (exposure and release). Acetabular cup positioning. The natural site (Paleoacetabulum), the ideal place to restore biomechanical and dynamic properties of the joint, many times gives few chances to achieve primary stability. So one site, at least the nearest possible to the natural site must be reached. A CT or MRI study is necessary to assess preoperative planning for cup positioning. We used two different cups, the Zweymuller and the Wagner cup, with good primary stability. A Conus stem (Wagner) or an Alloclassic stem (in less displastic femoral shape) was used. We always performed this surgery as a one step procedure. No preventing traction or release surgery was performed. An anatomic and wide (medial and lateral) exposure of the joint must be performed. We used the Smith-Petersen approach modified by Wagner. A meticulous periarticular release of soft tissue was performed. In same cases a shortening femoral osteotomy was performed to allow refractory reduction. Possible complications are discussed. Good clinical outcomes at more than ten years are shown.
