Aim

The aim of our study was to identify pathogens involved in septic knee arthritis after ACLR and to describe clinical features, treatment and outcome of infected patients.

Purpose: The reputation of unicompartmental knee prostheses (UKP) has suffered from “errors of youth” but within the limits of the indication and with precise implantation, they have provided excellent results with miminal morbidity. We evaluated the five-year clinical and radiological outcomes with the Alpina-UNI prosthesis.

Material and methods: Fifty-eight Alpina-UNI prostheses (88% medial) were implanted in 1995 by two operators. Radiographic analysis was performed by an independent observer. The mean patient age at implantation was 72 years. Patients were evaluated at three months and one and five years. The Knee Society knee score as well as radiographic findings were noted. Indications were essential, traumatic, and necrotic non-displaced lateralised degeneration. Cemented implants were used for 92% of the knees. Results were analysed with SPSS software.

Results: At five years, 51 patients were reviewed, there were four deaths, one patient lost to follow-up and two early failures (secondary ACL tear, anterior descent of the tibial baseplate). Follow-up at 70 months was 95%. The KSS was significantly improved (+61%, p< 0.001) and remained stable during follow-up. Mean flexion at five years was 131°. Radiographic findings were satisfactory: no degradation of the contralateral compartment or the patellofemoral joint, no implant loosening or migration, no abnormal polyethylene wear. Stable lucent lines were observed for 17% of the implants, all measuring less than 1 mm. The mean tibial slope was 5°. There was no significant difference between the pre- and postoperative femoroatibial epiphyseal inclinations. The mechanical axis (HKA) was significantly improved (p< 0.001) and remained unchanged throughout follow-up, maintaining a 1°–5° undercorrection.

Discussion: The conclusions of the 1995 SOFCOT symposium emphasised the importance of indications and precise implant position for the prevention of early failure. The Alpina-UNI system has enabled reproducible accuracy for the femoral and tibial epiphyseal inclinations in the cuts allowing restoration of the initial anatomy, the correction of the HKA being explained solely by wear correction. This can explain the low rate of loosening and wear in this series. Unicompartmental replacement remains an excellent solution in the older patient due to the lesser morbidity. Mid-term results are encouraging. Further ten-year evaluation will provide information on implant longevity.

Purpose: We report a retrospective series of 98 consecutive total hip prostheses implanted without cement: the Aura stem and the Alizé cup coated with hydroxyapatite; reviewed at mean 9.6 years. The purpose of this analysis was to examine implant stability and wear.

Material and methods: Total hip prostheses implanted in 98 patients from January 1991 to January 1992 were reviewed: 60 women and 38 men, operated on by the same surgeon using an Alizé cup and an Aura stem without cement. Mean age at implantation was 66.5 years (30–85). Mean follow-up was 9.67 years. We retained 56 patients for this analysis (17 patients had died, 13 were lost to follow-up, 9 could not be followed, and 3 stem removals (3.1%)). This was the first procedure in all patients. Clinical outcome was assessed with the Postel-Merle-d’Aubigné (PMA) score and with a self-administered questionnaire. Radiologically, we assessed stability (tilt, implant displacement) and implant wear using MetrOs software data processing of digitalized radiograms. We also searched for qualitative radiographic signs of bone reaction to the implant.

Results: The overall PMA score improved from 11.96 preoperatively to 17.42 at the 5-year assessment and then fell to 15.67 at last follow-up. At five years 94% of the patients (92 hips) were satisfied and 98.3% (56 hips) were reviewed at 10 years. There were two fractures of the ceramic head after direct fall on the greater trochanter (requiring replacement of the femoral implant, the head and the polyethylene insert). There was one infra-prosthetic fracture which required stem replacement. Analysis of the radiograms did not demonstrate any abnormal ossification or lucency. MetrOs was used on 52 files: mean wear was 0.77 mm at 10 years (0.16–2.24 mm): wear and impaction (0.789 mm) of the stem were significantly correlated at 10 years while stem tilt was negligible.

Discussion: This radioclinical analysis demonstrated that these hydroxyapatite coated implants are stable over time. The clinical results are satisfactory with a small regression of the PMA score related to patient ageing. The radiographic measurements obtained with a precise rigorous tool were very encouraging. We compared our results with those of series using comparable implants.

Purpose: Polyethylene wear in total hip arthroplasty remains the most limiting factor for implant survival. Several predictive factors are well identified, but the position of the articulating pieces remains to be studied in detail. We searched for a correlation between polyethylene wear and the position of the femoral and acetabular pieces, particularly the femoral offset.

Material and methods: Sixty-six patients underwent total hip arthroplasty for osteoarthritis or osteonecrosis. The patients were reviewed at 10.8 years (four bilateral prostheses). The preoperative, immediate postoperative (1 month) and last follow-up (10 years) AP pelvis views were digitalized. A dedicated software traced the different axes for measurement. Wear at ten years, femoral offset, cup eccentration or medialisation, ascent or descent, and cup inclination were measured.

Results: Mean polyethylene wear was 1.23 mm at ten years with linear curve of 0.11 mm/yr. Preoperative femoral offset was restored in 71.4% of the cases. Univariate regression analysis revealed that only femoral offset was correlated with less wear at ten years. Polyethylene wear at ten years fell from 1.26 mm for preoperative offset restitution less than 98% to 1.13 mm for restitution greater than 102%.

Discussion: Image processing allowed greater accuracy in the measurement of polyethylene wear. The rate of wear reported in the literature ranges from 0.1 to .015 mm/yr. Restitution of femoral offset guarantees less wear due to the reduction in the resultant force applied on the articulation as well as stress on the implants. Furthermore hip stability is improved. Several factors are involved in production of wear debris and correct restitution of the centre of rotation is only one of the elements which reduce wear.

Conclusion: Wear was not excessive in this series. Among the position parameters, only femoral offset had an influence, having a beneficial effect on polyethylene wear. This emphasises the importance of having a wide variety of implants available in order to respond to the different anatomic presentations of the femur.

Purpose: We report a retrospective continuous series of 107 total hip arthroplasties using a hydroxyapatite-coaated cup followed for a mean 9.67 years. We studied implant stability and component wear.

Material and methods: One hundred total hip arthroplasties were performed between January 1991 and January 1992. The series included 67 women and 40 men operated by the same surgeon who used the same Alizé cup and Aura cementless stem. Mean age at surgery was 66.5 years (range 30–85). Mean follow-up at review was 9.6 years. We retained 63 hips for analysis excluding 17 deaths, 16 patients lost to follow-up, 10 patients who could not be followed correctly, and only one implant ablation (0.9%). The implant was a first intention prosthesis in 90.7% of the cases and a second operation to replace a loosened primary prosthesis.

The Postel Merle d’Aubigné score was used to assess clinical outcome and all patients responded to a self administered questionnaire. Radiographically, we searched for signs of instability (tilt, displacement) and implant wear using precise digitalized measurements on successive digitalized x-rays with MetrOs software. We searched for qualitative radiological signs of bone reaction in contact with the implant.

Results: The overall PMA score improved from 10.63 preoperatively to 16.98 at the intermediary 5-year follow-up and was 15.77 at the 10-year follow-up. Satisfactory results were obtained in 93.9% of the patients at five years and 98.5% of the patients (64 hips) at 10 years. There were two fractures of the ceramic head after direct fall on the greater trochanter (requiring changing the femoral implant, the head and the polyethylene insert). There was one cup loosening at 9.5 years with verticalisation of the implant in an active athlete. Analysis of the x-rays did not demonstrate any abnormal condensation or lucent lines. Bony defects were observed in one case. The MetrOs radiographic data were available for 55 hips. At five years, mean wear was 0.53 mm, which increased to 0.76 mm at ten years (range 0.16 – 2.24 mm). Cup ascension was 0.15 mm at five years and 0.76 mm at 10 years. Mean cup tilt was 46.2° immediately after implantation and varied a mean 0.7° at five years and 1° at ten years.

Discussion and conclusion: This radioclinical study at ten years follow-up demonstrates that the hydroxyapa-tite surfaced Alizé implant is stable over time. The clinical results in this study were satisfactory with minimal regression of the PMA score related to patient ageing. The x-rays analysed with a rigorous and precise measurement instrument provided reassuring results. We discussed the one cup loosening and the clinical course of the two patients who underwent revision procedures after trauma-induced fracture of the ceramic head.

Purpose: Amstuz introduced the notion of a lever arm ratio to describe the relationship between the abductors and weight in arthroplasty. He demonstrated that patients may limp if defective lateralisation produces a low lever arm ratio. We analysed a continuous series of arthroplasty patients with excellent outcome at one year to compare restoration of lateralisation with the preoperative status. We also performed the same analysis in a series of patients who limped after arthroplasty, excluding cases with classical causes of failure. We then compared these two series.

Material and methods: We had a series of 100 arthroplasties with excellent results at one year. These patients had undergone unilateral arthroplasty and had a healthy contralateral hip. The centre of the arthroplasty head was identified on preoperative and one-year AP x-rays of the pelvis (same magnification). We measured the lateralisation in relation to the femoral axis. The position of the cup was measured with a U ratio. Results were expressed in percent restitution of the preoperative status. Amstutz’s lever arm ratio was also measured. Finally, we measured the distance between the pubic symphysis and the outermost point of the femur on the prosthetic and healthy side.

We also had a second population of twelve patients presenting persistent limping at one year with no objective cause. The same parameters were measured for this population.

Results: We found that we had achieved only partial restitution of the initial lateralisation and had a tendency to medialise the acetabulum. The restitution of lateralisation was significantly different between the series with excellent outcome and the series with limping.

Discussion: Deficient lateralisation appears to be a factor involved in persistent limping. There is a threshold for restitution of lateralisation; limping is always observed under this threshold. Data in the literature reveal a very wide variability in lateralisation. It would thus appear important to restore the initial lateralisation to avoid limping; this has led us, like others, to use lateralised implants for certain patients.