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We studied 178 patients undergoing total hip arthroplasty (66 men and 112 women) retrospectively, with regard to the incidence and severity of heterotopic ossification and the significance of postoperative prophylaxis with non-steroid anti-inflammatory drugs. The overall incidence of heterotopic ossification was 32% 1 year after surgery. The factors increasing the incidence were male gender, previous arthroplasty of the contralateral hip joint, previous surgery on the hip, absence of preoperative treatment with non-steroidal anti-inflammatory drugs and an operating time of more than 100 min. The incidence of heterotopic ossification was lower in the patients of 0 blood group.Résumé Nous avons étudié la fréquence et la sévérité d'ossification hétérotopique dans 178 cas d'arthroplastie totale de la hanche avec une prophylaxie postopératoire par AINS. Une année après la chirurgie la fréquence totale était de 32%. Les facteurs qui augmentent le risque étaient le sexe masculin, une arthroplastie de la hanche contrelaterale, des antécédents chirurgicaux sur hanche, l'absence de traitement préopératoire par AINS et une durée opératoire de plus de 100 min. La fréquence d'ossification hétérotopique était inférieure chez les patients du groupe sanguin 0. IntroductionHeterotopic ossification (HO) is a significant complication of total hip arthroplasty (THA). An incidence, without prophylaxis, has been reported of between 8% and 90% [1,13]. Two methods of treatment are commonly used, non-steroidal anti-inflammatory agents (NSAID) and irradiation [5]. The aim of this study was to record the incidence and severity of HO after THA and to determine the relevance of risk factors. Materials and methodsThe notes of 178 patients (66 men and 112 women) who underwent THA in the Clinic of Traumatology and Orthopaedics, Tartu University, between 1995 and 1996 were reviewed retrospectively. The requirement for THA was degenerative arthritis in 160 cases, rheumatoid arthritis in nine cases and trauma of the hip in nine. All patients were treated prophylactically with NSAIDs up to 30 days postoperatively. All patients also received antithrombotic prophylaxis with 0.3 ml (2500 IU) fractioned heparine (Fraxiparine) daily. The prostheses used were all cemented; Lubinus IP in 120 cases, Lubinus SP II in 51 cases and the Link Dysplasia hip prosthesis in seven. In all cases the posterolateral approach was used.The data collected included age, gender, diagnosis, surgery on the ipsi-and contralateral hip performed before or after THA, the operating time, the type of anaesthesia, blood loss and preoperative treatment with NSAIDs. The preoperative anteroposterior radiographs were reviewed, and those taken on the 1st postoperative day and at 3, 6, 9 and 12 months postoperatively, and were assessed according to the Brooker classification, in which HO is classified at stages I-IV, of which stages III and IV are clinically and functionally significant [4].The analysis of preoperative radiographs included the assessment of osteophytes and the s...

Heterotopic ossifications (HOs) formed after total endoprosthetic replacement of the hip joint were collected during revision surgery (n = 7). Tissues collected during regular hip arthroplasty (n = 12) were used as reference. Histomorphometric analysis was performed for assessment of bone formation activity in HOs and reference bone. HOs were dissected with histological guidance into three zones: formed bone, zone of active bone formation, and zone with fibrous connective and fibrocartilagineous tissue. Relative expression of the mRNA for bone morphogenetic protein 2 (BMP-2), transforming growth factor beta2 (TGF-beta2), and TGF-beta3 was determined by reverse-transcription polymerase chain reaction relative to beta-actin. Expression of all three growth factors was higher than in orthotopic bone. Similarly, the osteoid surface density was increased in HOs. The levels of all growth factors were higher in the zone of active bone formation or remodeling than in the zone of formed bone. In matured HOs, the osteoid surface density as well as mRNA levels were lower, although still significantly raised, indicating that bone formation slows down after 2 years. Immunohistochemical analysis demonstrated the presence of TGF-beta1, TGF-beta2, TGF-beta3, and BMP-2 proteins in the zone of bone formation. We conclude that bone formation after heterotopic bone induction is initially intense, slows down within 2 years, and thereupon continues as active remodeling mainly on the border of HO. Our data indicate that BMP-2, TGF-beta2, and TGF-beta3 are involved in bone formation in HO.