Luis Munuera

Early and late loosening of the acetabular cup after low-friction arthroplasty.

Between 1971 and 1979, 680 low-friction arthroplasties of the hip were performed in 598 patients. The average duration of follow-up was twelve years and eight months. Sixty-one acetabular cups had loosening as seen on roentgenograms eighteen years postoperatively, resulting in a total cumulative probability of loosening of 19 per cent, according to survivorship analysis. In twenty-nine cups, the loosening appeared within ten years after the operation (early loosening) and in thirty-two, more than ten years after the operation (late loosening). Early loosening was associated with deficient structure of the bone of the acetabulum, a previous congenital dislocation of the hip, acetabular fracture, or acetabular protrusion in all instances (p < 0.01). Late loosening was associated with the depth of acetabular wear. Of the thirty-two cups that had more than two millimeters of wear, eighteen (56 per cent) had loosening on the roentgenograms (p < 0.001). In hips that had early loosening, migration was the most frequent finding, and its rate of progression was higher than in hips that had late loosening (p < 0.001). In late loosening, a complete bone-cement radiolucency of more than two millimeters was the most frequent finding. Clinical failure was seen in twenty-two (76 per cent) of the twenty-nine cups that loosened early and in nine (28 per cent) of the thirty-two cups that loosened late. The probability of extensive resorption of bone necessitates close observation of patients who have early loosening, while a reasonable period of observation is possible for those who have late loosening.

Treatment of fractures of the distal radius with a remodellable bone cement

We performed a prospective, randomised study on 110 patients more than 50 years old with fractures of the distal radius to compare the outcome of conservative treatment with that using remodellable bone cement (Norian skeletal repair system, SRS) and immobilisation in a cast for two weeks. Patients treated with SRS had less pain and earlier restoration of movement and grip strength. The results at one year were satisfactory in 81.54% of the SRS patients and 55.55% of the control group. The rates of malunion were 18.2% and 41.8%, respectively. There was a significant relationship between the functional and radiological results. Soft-tissue extrusion was present initially in 69.1% of the SRS patients; most deposits disappeared progressively, but persisted in 32.73% at one year. We conclude that the injection of a remodellable bone cement into the trabecular defect of fractures of the distal radius provides a better clinical and radiological result than conventional treatment.

Mittelmeier ceramic—ceramic prosthesis after 10 years

The clinical status of 83 Mittelmeier ceramic-ceramic (Mark II) cementless total hip prostheses (Autophor, Osteo AG, Selzach, Switzerland) implanted between 1978 and 1984 was analyzed. Retrieved tissue from the revised hips was studied histologically. The mean patient age was 47.5 years (range, 19-71 years). One or both components of 12 hips were revised (16% at 16 years in the survival study). Eleven acetabular components and seven stems were revised, with three of the sockets fractured. The mean follow-up period for the patients with unrevised hips was 12.3 years. Osseointegration was uncommon in both the cup and stem. Radiographic cup loosening was observed in 53% of hips at 16 years in the survival study, with most having a complete radiolucent line of 2 mm around the cup. Radiographic stem loosening appeared in 15% of hips at 16 years. Fibrous stable fixation was present in 64% of stems. Significant radiographic acetabular wear was not observed in any hip. The Mittelmeier Mark II prosthesis had worse long-term results than reported with cemented or other uncemented prostheses. Although there was no significant acetabular wear, intracellular ceramic wear debris was seen in the retrieved tissues.

Dislocation in low-friction arthroplasty

In a series of 2,050 low-friction arthroplasties, 61 cases (2.97%) of dislocation were analyzed. The mechanism of production was malposition of the components (group 1, 33%), deficiency of the abductor mechanism (group 2, 34%), or the association of both (group 3, 26%). Failure to find a cause was even more rare (group 4, 7%). The best treatment is prevention by careful surgical technique, since good results with different procedures have only been attained in 51% of dislocated hips.

Progression of Radiolucent Lines Adjacent to the Acetabular Component and Factors Influencing Migration after Charnley Low-Friction Total Hip Arthroplasty*†

We analyzed the progression of radiolucent lines around the acetabular cup after 452 Charnley low-friction arthroplasties that had been performed in 392 patients between 1971 and 1976. The average duration of follow-up was twenty years (range, eleven to twenty-five years) for the 442 hips (382 patients) that had the original component in place at ten years. The demarcation of the bone-cement interface was classified according to the system of Hodgkinson et al. We sought to determine if there was a relationship between the progression of the radiolucent line and the age, gender, and weight of the patient; the level of activity; the preoperative diagnosis; or the amount of wear of the acetabular cup. The demarcation increased over time in 138 (31 per cent) of the 452 hips. Radiographs made at the time of the latest follow-up showed migration of eleven (5 per cent) of the 233 acetabular cups with no demarcation on the initial postoperative radiograph, eighteen (11 per cent) of the 167 cups with type-1 demarcation, twelve (35 per cent) of the thirty-four cups with type-2 demarcation, and thirteen of the eighteen cups with type-3 demarcation. Preoperative acetabular protrusion, inflammatory arthritis, and severe acetabular dysplasia as well as a previous operation were associated with the extent of the radiolucent line on the most recent radiograph (p ⩽ 0.05 for all). A high level of activity and more than two millimeters of wear of the acetabular cup also were related to the progression of the radiolucent line (p = 0.0004 and p < 0.0001, respectively). Kaplan-Meier survivorship analysis demonstrated that the greater the demarcation on the initial postoperative radiograph, the greater the risk of migration (p < 0.0001, Mantel-Cox test). Our data suggest that, after a Charnley low-friction arthroplasty, any cemented cup, even one with the least amount of demarcation (types 0 and 1), can migrate. As the type of the initial postoperative demarcation increases, so does the risk of migration of the cup, particularly when there is loss of the acetabular bone stock.

Update on UHMWPE research From the bench to the bedside

Ultra-high molecular weight polyethylene (UHMWPE) is the key material for achieving excellent long-term results in total joint arthroplasties. Despite the fact that there has been a substantial amount of research and development over the years, new aspects of this material are still controversial and the most recent innovations have had a variable reception regarding clinical use. Advancements in conventional UHMWPE in the 1990s (nitrogen atmosphere irradiation, barrier package) were further improved by introduction of first-generation crosslinked polyethylene, as seen both from laboratory findings and clinical results. However, while clinical data on first-generation highly crosslinked polyethylene (HXLPE) showed reduced wear in the medium-term, academic and industrial research have helped to refine the material further, to overcome criticisms regarding residual oxidation and potential material fracture. Present concerns, although less nowadays, relate to the post-irradiation techniques used to stabilize the crosslinked polyethylene, namely annealing and remelting. Current topics of research interest include in vivo oxidation, second-generation highly crosslinked polyethylene, vitamin E doped or blended polyethylene, fracture mechanics, and consequences of wear. Some of these improvements derived from recent research are already available to the orthopedic community, and others will appear in the next few years. This review gives an overview of these topics, and the latest advancements are described in detail with a view to help the orthopedic surgeon make scientifically sound decisions when selecting material for total-joint implants. We conclude the review by affirming that todays state-of-the-art material is no longer conventional UHMWPE, but HXLPE.

The pattern of the fracture and displacement of the fragments predict the outcome in proximal humeral fractures

Our aim was to determine the effect of the initial pattern of fracture and the displacement of fragments on the outcome of proximal humeral fractures treated conservatively. We followed 93 consecutive patients prospectively for one year. Final movement and strength were compared with those of the contralateral side. The final American Shoulder and Elbow Society score and the Disabilities of Arm, Shoulder and Hand and Short-Form 36 questionnaires were compared with those provided by the patient on the day of the injury. Radiographs and CT scans with three-dimensional reconstruction were obtained in all patients. The pattern of the fracture and the displacement of individual fragments were analysed and correlated with the final outcome. There were two cases of nonunion and six of avascular necrosis. The majority of the fractures (84 patients; 90%) followed one of the following four patterns: posteromedial (varus) impaction in 50 patients (54%), lateral (valgus) impaction in 13 (14%), isolated greater tuberosity in 15 (16%), and anteromedial impaction fracture in six (6%). Head orientation, impaction of the surgical neck and displacement of the tuberosity correlated strongly with the outcome. In fractures with posteromedial impaction, a poor outcome was noted as the articular surface displaced inferiorly increasing its distance from the acromion. A poorer outcome was noted as a fractured greater tuberosity displaced medially overlapping with the posterior articular surface. Lateral impaction fractures had a worse outcome than other patterns of fracture.

Low relapse with oral antibiotics and two-stage exchange for late arthroplasty infections in 40 patients after 2–9 years

Background and purpose Exchange surgery in late arthroplasty infection is directed against bacteria adhering to implants. Therapies based on antibiotics that are effective intracellularly have been proposed recently. We have combined both strategies to improve the cure rate. Methods 40 consecutive patients (16 hips, 24 knees) were diagnosed with late arthroplasty infection. The organisms isolated were 35 Staphylococcus, 19 of which were methicillin-resistant, 4 Enterococcus, 6 Gram-neg-ative bacilli, and 4 Corynebacterium. The infections were managed by a combined therapy consisting of two-stage exchange surgery and two oral intracellularly-effective antibiotics. The antibiotics were selected according to bacterial sensitivity and intracellular and biofilm effectiveness. Second re-implantation surgery was delayed until clinical and analytical normalization. Patients were in hospital for only 1 week after each surgery, and were followed up prospectively on an outpatient basis (2–9 years). Cure of the infection was defined as absence of clinical, serological, and radiographic signs of infection during the whole follow-up. Results The infection was resolved in 38/40 patients (15/16 hips and 23/24 knees). Interpretation Oral antibiotics that are effective intracellularly in combination with two-stage exchange surgery is a promising alternative for treating late arthroplasty infections. Oral antibiotics shorten hospitalization and reduce patient discomfort.

Long-term results of aseptic cemented Charnley revisions

One hundred eighty low-friction arthroplasties of the hip in 164 patients in first-time revision surgery were operated between 1973 and 1985. This series used only cement fixation, and aseptic loosening and femoral stem fractures were the only indications for revision. The average follow-up period was 11.5 years. Intra-operative and postoperative complications were frequent: femoral shaft fracture (13 cases), femoral shaft perforation (12 cases), deep infection (14 cases), and dislocation (15 cases). Twenty-eight hips were rerevised or removed (resulting in a total cumulative probability of rerevision of 20% after 16 years, according to survivorship analysis). Nineteen cups were rerevised (13% after 16 years, according to survivorship analysis), and 24 femoral stems were rerevised (16% after 16 years, according to survivorship analysis). Radiographic cup and femoral loosening appeared in 29 and 36 cases, respectively (24 and 22% after 16 years, respectively, according to survivorship analysis). Good results were observed when there was a healthy and intact bone bed, whereas poor results were related to inadequate bone stock in the acetabulum and femur. Radiolucent lines were frequent in both components; radiolucent lines less than 2 mm wide were frequent in acetabular zone 1. Pistoning of the prosthesis and the cement within the bone and calcar pivot was the most frequent type of stem loosening.

The femoral component in low-friction arthroplasty after ten years.

In 623 low-friction arthroplasties ten years after implantation, 70 hips (18.04% after 16 years) showed loosening of the femoral component. Eighty-four percent appeared within ten years. Fracture of the stem occurred in 4.3% of cases after 16 years, and resorption over 5 mm of the femoral neck occurred in 9.3%. Calcar cysts appeared in 2.9% and endosteal cavitations in 18.04% after 16 years; both findings were related to acetabular wear greater than 2 mm. Gruens Type III (calcar pivot) was the least common loosening (6.8%) during the first ten years. After this time its incidence increased to 17.1%. Loosening of the femoral component was not related to age, weight, or activity. It was, however, associated with poor surgical technique, i.e., varus position (46%), cementation defects (34%), and/or femoral neck osteotomy on the lesser trochanter (36%).