Heterotopic ossification (HO) of the hip after injury to the central nervous system can lead to joint ankylosis. Surgery is usually delayed to avoid recurrence, even if the functional status is affected. We report a consecutive series of patients with HO of the hip after injury to the central nervous system who required surgery in a single, specialised tertiary referral unit. As was usual practice, they all underwent CT to determine the location of the HO and to evaluate the density of the femoral head and articular surface. The outcome of surgery was correlated with the pre-, peri- and post-operative findings.

In all, 183 hips (143 patients) were included of which 70 were ankylosed. A total of 25 peri-operative fractures of the femoral neck occurred, all of which arose in patients with ankylosed hips and were associated with intra-articular lesions in 18 and severe osteopenia of the femoral head in seven. All the intra-articular lesions were predicted by CT and strongly associated with post-operative complications.

The loss of the range of movement before ankylosis is a more important factor than the maturity of the HO in deciding the timing of surgery. Early surgical intervention minimises the development of intra-articular pathology, osteoporosis and the resultant complications without increasing the risk of recurrence of HO.

Background: Early or later dislocation is a frequent complication associated with total hip arthroplasty. The Bousquet’s acetabular component, an original concept of dual mobility socket has been used, for increase stability and mobility. The first mobility is between the femoral head and the polyethylene insert, and the second mobility between the polyethylene and the metal cup socket. The cup, covered with alumina was impacted without cement. The purpose of this study was to evaluate the long-term results of a retrospective series of primary arthroplasty with this cup and a cemented Charnley type femoral component.

Materiel and methods: This study included 437 hip replacements performed between 1984 and 1990, in 389 patients with osteoarthritis (62.5%), dysplasia (11.4%), necrosis (8%), rheumatoid arthritis (5%), post-traumatic and others (13.1%). The average age of the patients at the time of the index procedure was 61 years. The patients were followed at routine intervals for clinical and radiographic review. The clinical results were appreciated with Postel–Merle d’Aubigne score (PMA). Osteolysis was noted according to Gruen zones.

Results: The outcome is known for 345 hips (79%): 164 alive without revision at a mean of 16,5 years follow-up, 137 died without revision, and 44 failures. 92 (21%) were lost at follow up. Revision, for aseptic loosening of femoral or acetabular component, was performed in 30 hips(6.8%). 5 dislocation occurred and were revised: 2 early regarding to technical errors and 3 after 10 years or more of follow up. 7 hips were revised for deep infection, and 2 for unaccountable pain.

At more than 15 years follow-up, the mean PMA hip functional score was 17.1. 66% of the hips was A, 4% were B and 30% were C according to the Charnley’s score. Of the 164 hips in the patients who had survived at least 15 years, 28 had femoral osteolysis in zone 7, and 31 had femoral osteolysis in one (or more) of the other 13 zones. 6 hips had an impingement sign on the neck of the femoral component, without aseptic loosening.

According to Kaplan-Meier analysis, the fifteen year survival rate, was 84.36% with revision for any reason (infection, dislocation, osteolysis…) for end point. The young age of the patients at the time of the index surgery is correlated with loosening.

Conclusion: The long term results of the press fit, double mobility socket with cemented Charnley type femoral stem are good. The prevalence of revision for dislocation is very low in our series. But this concept do not avoid wear, osteolysis and aseptic loosening, specially in young active patients. We can recommand this type of prosthesis for patients over 70 years, and/or with high risk of dislocation.

Purpose: After implantation of a total knee arthroplasty (TKA) for osteoarthritis, early demineralisation of the superior tibial epiphysis occurs with modification of bone mineral density (BMD) in the two compartments. The long-term trend is not known to date. We report the results of 38 prostheses followed prospectively with densitometric measurements at minimum five years.

Material and methods: This prospective analysis included 38 TKA implanted for primary degenerative disease in patients with a mean age of 70±4 years at implantation, 60% women. Clinical assessment (IKS) and radiography (HKA) as well as osteodensitometry were recorded before surgery, at six months, one year, two years and five years. Bone mineral status was assessed using the densitometry of the femoral neck before surgery and at five years for all patients. The DEXA method was used for each knee on the anteroposterior film. Seven zones were defined around the tibial implant, in particular two under the medial and lateral plateaus, and under the stem. We studied changes in each zone over time. The alpha risk was set at 5%. Inter- and intraobserver reproducibility was 2.9% and 2.8% respectively.

Results: At five years follow-up, the mean IKS function score was 85±19 and the knee score was 918. The mean mechanical axis was 180±2° with symmetrical distribution. There were no progressive lucent lines. The BMD of the homolateral femoral neck did not change significantly (0.763 g/cm2 at inclusion and 0.750 g/cm2 at five years), unlike the natural evolution in a reference population (women -4.5%, men -2.4%). The mean BMD in the seven zones decreased significantly (11.6%, p< 0.0001. Mean BMD was 0.936 g/cm2 at inclusion and 0.863 g/cm2 at six months), 0.823 g/cm2 at five years. BMD decreased very strongly from 0 to 6 months (−6.51%, p< 0.0001) then more slowly to the end of the first year (−3%) and finally declining regularly, but non-significantly, at a slower rate from 1 to 5 years. Study of the seven zones showed a difference in changes in the BMD between the medial, lateral and stem zones. The two medial zones decreased significantly from 6.33% to 6.18% especially during the first year (−2.06% and −2.09%) and more moderately from 1 to 5 years (−1.6%, −2.65%). The lateral zones showed a greater average decline in BMD (−10.5%, −8.92%) between 0 and 5 years: −8.57% and −6.75% during the first year then at a slower rate. The greatest loss in BMD was found under the stem; −14.3% at five years. Here again, between 0 and 6 months the decline was rapid: −8.09%. It reached −12.74% at one year then varied little, −1% and −2% between 1 and 5 years.

Conclusion: 1) Bone remodelling under the tibial base plate occurs early after implantation of a TKA. It occurs during the first year (especially the first six months). 2) Remodelling is more pronounced laterally than medially (good realignment but persistent varus stress with greater stress on the medial than lateral side). 3) The greatest loss in BMD occurs under the stem. 4) BMD of the femoral neck remains stable, unlike the evolution observed in a reference population.