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Sixty-three cases of femoral osteolytic cavities were analyzed in a consecutive series of 680 low-friction arthroplasties of the hip performed in 598 patients between 1971 and 1979. Follow-up evaluation averaged 15 years 9 months (range, 2-22 years). The total cumulative probability of osteolysis developing after 20 years was 11% according to survivorship analysis. The mean time of appearance of the osteolytic lesion was 9 years 3 months after operation. Most of the cavities were seen in Gruen zones 3, 5, and 7 in decreasing order. Osteolytic cavities were classified as follows: group 1, cavities in cases with radiographic definite stem loosening (20 cases); group 2, cavities in cases with an acetabular wear equal to or greater than 2 mm (22 cases); and group 3, cavities in cases combining both of the above-mentioned findings (21 cases). Cementing defects such as voids and thin mantles were less frequent in group 2 than in groups 1 and 3 (P < .005). Poor clinical results were more frequent in groups 1 and 3 (P < .05), in all instances). Focal cavities were more frequent in group 2, and multifocal and diffuse cavities were more frequent in groups 1 and 3 (P < .05). The average planimetric area on radiographic diagnosis was 0.81 cm2, and the average approximate volume was 1.86 cm3, with significant differences among the three groups of cavities. Progression of the cavity area and volume was linear over time (P < .001) and more aggressive in groups 1 and 3 than in group 2 (P < .05). Thus, loosening of the stem was a more deciding factor than acetabular wear in the progression of cavities.

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.

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.

Eighty consecutive low-friction arthroplasties in 64 patients with secondary arthritis due to severe acetabular dysplasia (Crowe grades III and IV) are analyzed. Two groups of patients were considered. In group 1 over 20% of the cup was not covered by the acetabulum and was reconstructed with a femoral head graft (32 cases; in group 2) a femoral head graft was not used because the cup was adequately covered (48 cases). The mean follow-up period was 9.4 years (range, 3-17 years) for group 1 and 8.8 years (range, 3-18 years) for group 2. Early complications were frequent (19%). To study long-term results only 78 hips were assessed since two patients were excluded due to deep infection. In these 78 hips, group 1 patients showed "better" results after 16 years (69.6% good results) than group 2 (nongraft procedures) (52.2%), but these differences were not significant (P > or = .05). Early cup loosening was more frequent in group 2 than in group 1, and good coverage was obtained in 91% of the group 1 cups and in 71% of the group 2 cups (P > or = .05). Acetabular cup loosening was not correlated with acetabular cup position. Bone-grafts appeared consolidated in all cases, but resorption areas were frequently observed. Radiographic stem aseptic loosening appeared in 10 cases, cortical hypertrophy in 7 cases, and endosteal osteolysis in 3 cases. Although limb discrepancy was frequent in both groups (75%), the average discrepancy was 1.7 cm.

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.