Alumina-alumina artificial hip joints. Part II: characterisation of the wear debris from in vitro hip joint simulations.

Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses. The introduction of microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of approximately 0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2-27.5 nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1-35nm). however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.021 microm) and scanning electron microscopy (SEM) (0.05-->10 microm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05-3.2 microm size range. and TEM revealed particles in the 5-90 nm size range, indicating that microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.

Wear of HIPed and non-HIPed alumina-alumina hip joints under standard and severe simulator testing conditions.

Wear and the biological response to wear debris of artificial joints remain major concerns in total hip arthroplasty (THA). The long-term effects of UHMWPE wear debris are well documented and these have led to interest in alternate bearing materials for THA. Alumina ceramic-ceramic hip joints have been successfully used for more than 30 years with low wear and little incidence of osteolysis. The most common wear pattern observed on retrieved components is an elliptical wear 'stripe' on the heads and a corresponding worn area on the cup with an approximated wear rate of 1-5 mm3 pa. More severe wear has also occasionally occurred, usually in association with an abnormal clinical history. Modern alumina-alumina THAs use an improved HIPed (hot isostatically pressed) alumina ceramic-bearing material which may be more resistant to severe wear. Previous in vitro simulator studies have not replicated in vivo wear rates or mechanisms. The aim of this study was to compare previous generation non-HIPed alumina and modern HIPed alumina in a hip joint simulator under 'normal' and 'harsh' testing conditions. HIPed alumina was found to have a lower wear rate than non-HIPed alumina, although the difference was not statistically significant at the 95% confidence level. Testing in Gelofusine and water lubricants did not elevate the wear rates of either material. Elevated swing phase load testing also had no significant effect on the wear rates of either material. Testing in the absence of any lubricant produced very severe wear of the non-HIPed material in one specimen only.

Comparative analysis of two different types of alumina-alumina hip prosthesis retrieved for aseptic loosening.

We compared and quantified the modes of failure and patterns of wear of 11 Mittelmeier and 11 Ceraver-Ostal retrieved alumina-alumina hip prostheses with reference to the corresponding clinical and radiological histories. Macroscopic wear was assessed using a three-dimensional co-ordinate measuring machine. Talysurf contacting profilometry was used to measure surface roughness on a microscopic scale and SEM to determine mechanisms of wear at the submicron level. The components were classified into one of three categories of wear: low (no visible/measurable wear), stripe (elliptical wear stripe on the heads and larger worn areas on the cups) and severe (macroscopic wear, large volumes of material lost). Overall, the volumetric wear of the alumina-alumina prostheses was substantially less than the widely used metal and ceramic-on-polyethylene combinations. By identifying and eliminating the factors which accelerate wear, it is expected that the lifetime of these devices can be further increased.

Posterolateral release for idiopathic clubfoot: review of 18 patients.

The authors treated and reviewed 18 patients with 26 idiopathic clubfeet by posterolateral release and elongation of the tendo Achillis at a mean age of 14.6 months (range 7-32 months). The mean follow-up of these patients was 43 months (range 6- 100 months). Function, appearance, and pain were studied. The mean ankle dorsiflexion was 20 degrees at the time of review. In all but one case, the hindfoot equinus had been well corrected. Subtalar movement was 75% of normal in six feet, and 50% of normal in 16 feet. Revision of the posterolateral release combined with anteromedial release was carried out for six patients with residual hindfoot varus and forefoot adduction at an average of 13.5 months following the initial procedure. In one patient, the deformity was overcorrected, but the results of the rest of the revision operations were otherwise good. No skin or wound problems were observed in this series. In conclusion, of 26 feet undergoing posterolateral release for severe clubfoot, 70% had a satisfactory result. Six feet required further surgery (reoperation rate of 23.1%).

A 4- to 10-year follow-up study of the Tricon-M noncemented total knee replacement.

This study reviews the clinical and radiographic results of 207 consecutive noncemented Tricon-M (Smith & Nephew Inc, Memphis, Tenn) total knee replacements (TKRs) in 189 patients. The patella was surfaced in 119 cases, and mean follow-up was 8 years (range: 4-10 years). At final follow-up, mean Hospital for Special Surgery score improved 45 points in 187 cases. Survivorship, with failure defined as the need for revision, was 98% at 4 years, 97% at 7 years, 94% at 8 years, and 90% at 10 years. Twenty-one (11.3%) patients went on to revision. Results for overweight and obese patients did not differ significantly from normal-weight patients. The noncemented Tricon-M TKR prosthesis yields acceptable results; however, patella surfacing and the use of a tibial polyethylene insert > or = 12 mm thick are recommended.

The influence of acetabular cup angle on the wear of "BIOLOX Forte" alumina ceramic bearing couples in a hip joint simulator.

The wear of "Biolox Forte" alumina ceramic bearing couples has been investigated at two different acetabular cup angles in a physiological hip joint simulator. All cups were set in the anatomical position of 45 degrees inclination in the M/L plane for the first two million cycles and then four of the six cups were re-aligned to 60 degrees for a further three million cycles. A "running-in" wear of 0.14 mm3 per million cycles was observed for the first million cycles, after which a steady state wear rate of 0.05 mm3 per million cycles was observed. Increasing the acetabular cup angle to 60 degrees did not significantly affect the wear rate.

Ethnic factors in Perthes disease: a retrospective study among white and Asian population living in the same environment.

The aim of this study was to find out about the incidence of Perthes disease in different ethnic groups living in similar environments. Among the child population of Bradford, between 1991-1997, we identified from the file notes twenty-five cases of Perthes disease among the white European population (with an incidence of 5:54500 for the year 1997) and one case of Perthes disease among Asians (with an incidence of 0:16100 for the year 1997). There were two positive family histories of Perthes disease and only a case of bilateral Perthes disease. There was no significant difference in the incidence of Perthes disease among the rural and urban population. We conclude that under similar environmental circumstances the genetic factor plays an important role in the predisposition to Perthes disease.

Analysis of retrieved alumina ceramic components from Mittelmeier total hip prostheses.

This study analyses explanted prostheses from a single surgeon's 16-yr series of Mittelmeier cementless total hip replacements. The patient group was young (patients aged 15-60, average 40) and active. Revision was related to various factors. All components were measured using a Kemco 3D coordinate measurement machine. Wear surfaces and linear wear penetrations of 11 retrieved Mittelmeier Autophor ceramic hip components (average implantation time 8.6 yr, range 1-13 yr) were analysed and the different types of wear identified. Surface analysis was then performed using Talysurf contacting profilometry and scanning electron microscopy. Three types of wear were identified: low wear (1 case), stripe wear (6 cases) and severe wear (4 cases). Stripe wear was characterised as a stripe of worn area on the head up to 150 microns deep whilst the rest of the head showed very low wear. The cups in the stripe wear cases were worn over about 40-50% of the surface. Severe wear cases had very large areas of heavy wear and visible volume loss on both heads and cups. The four cases of severe wear were associated with abnormal clinical histories.

Cementless ceramic hip arthroplasties in patients less than 30 years old.

Twenty-six cementless ceramic hip arthroplasties were performed in 22 patients with an average age of 24 years (range, 17-30 years) at the time of operation. One patient was lost to follow-up evaluation. Twenty-one patients (25 hips) were reviewed with an average follow-up period of 6.5 years (range, 4-13 years). Two hips had to undergo revision of the ceramic acetabular components because of fractures in the upper part of the cup in both. One further hip was explored because of persistent wound discharge, but a mass of indurated tissue was removed and there was no evidence of deep infection. No organisms were grown from the samples taken during operation. Harris hip scores were good to excellent in 64%, fair in 16%, and poor in 20% of cases. There was no or slight pain in 14 (56%), mild pain in 7 (28%), and moderate pain in 4 (16%) hips. Apart from the two sockets revised, progressive radiolucent lines were seen in five cups (20%) and significant vertical migration was present in nine cups (36%) with an average migration of 1.3 mm/y. In total, acetabular changes were observed in 11 cases (44%). Femoral stem subsidence of between 3 and 6 mm was seen in five cases (20%). The total number of hips showing loosening of one or both components was five (20%). Overall radiographic changes (migration and loosening) in one or both components were present in 13 hips (54%).

Long-term results of minimally invasive lumbar disc surgery.

Long-term results of minimally invasive primary lumbar discectomies are processed. The operation was fairly simple and inexpensive, with reduced hospital stay (24 hours). The subsequent rehabilitation was compared to the more extensive procedures. The Oswestry-style questionnaires were found to be gratifying with a high percentage (80.9%) of patients, who returned to normal or nearly normal lives. No significant difference was found with published results of microdiscectomy.

Examination of alumina ceramic components from total hip arthroplasties.

Materials analysis has been conducted on retrieved Mittelmeier-Autophor ceramic components from total hip arthroplasties, correlating articulating surface wear morphology with clinical reasons for failure. Plastically deformed, agglomerated wear debris (30-60 microns) has been identified on femoral head articulation wear surfaces, displaying exaggerated wear, especially during the initiation stage. Such surfaces were associated with clinical failures involving displacement of the acetabular cup and perforation of the cortex by the femoral stem. It is thought that this wear debris may play an important role in the promotion of the 'avalanche' wear mechanism, as it is adherent and thus difficult to remove from the wear interface.

The three-dimensional anatomy of the proximal femur in Perthes' disease.

A new method of recording the three-dimensional anatomy of the proximal femur from a single anteroposterior radiograph is described. This technique shows that in Perthes' disease the femoral head and neck are in significant anteversion and true varus. This anatomical configuration may be important in the pathogenesis and treatment of this disorder.

Perthes' disease. The family tree.

The discovery and use of roentgenograms by Wilhelm Röntgen in 1895 was one of the most important turning points in the history of orthopedics. Within only a few years, immense advances were made in the recognition and definition of bone and joint disorders that, until then, had been thought to be different or unusual forms of musculoskeletal tuberculosis. Perthes' disease has become one of the Lieblingsthema of orthopedics. The study of the history of Perthes' disease is fascinating: the sources of many "original" thoughts can be traced back across the world, through the years. This review begins with the 19th century, traces the emergence of the definition of Perthes' disease and some related conditions, and follows the story of the disease in the first decade of its history as a separate entity.

Bilateral Perthes' disease.

Bilateral Perthes' disease is defined as the form of the condition where radiological changes affect both hips simulatneously. The radiological abnormalities are commonly more severe on one side than on the other. In a small proportion of patients a clear time interval exists between the onset of radiological changes in the two hips. It is suggested that this form of the condition is two unilateral and separate attacks of Perthes' disease and it is more akin to 'recurrent' Perthes' disease.

Osteochondritis occurring at multiple sites.

Five patients with osteochondritis juvenalis occurring at multiple sites are presented. In all cases at least one hip was affected, one child developing symptoms at the age of 8 months. Other sites included the tarsal navicular, the patella and the calcaneal apophysis. The relevance of these observations to the aetiology of coxa plana is discussed.

The treatment of tennis elbow with triamcinolone acetonide.

Twenty-seven patients with tennis elbow were treated with triamcinolone acetonide (40 mg/ml) injected locally into the tender area without local anaesthetic. Reduction of pain or complete relief was achieved in 1 to 72 hours, although in 9 cases exacerbation of pain occurred before relief was given. The recurrence rate at 6 months was 17.8%. The study shows that triamcinolone acetonide is a useful preparation in the relief of this condition.

The treatment of congenital vertical talus.

Operative correction of congenital vertical talus in nine feet in six patients is described. The operation consists of the comprehensive lengthening of the tendons in the foot and full peritalar release without excision of the navicular; it is performed through a dorsal transverse incision.

Perthes' disease: a new genetic hypothesis.

We describe the sex and age distributions of the onset of Perthes' disease in our own and six other large published series. The mathematical features of these distributions, together with the evidence for familial aggregations, agree with the theory that the disease is autoaggressive in aetiology and that two genetically-distinctive groups are at risk. We consider the frequency of affected sides - left, right, bilateral - in our own and other series: concordance for affected side(s) within sibships suggests that laterality might be genetically determined. Following Gray et al. we believe that predisposition to the disease is polygenic and we propose a simple scheme - involving an X-linked "recessive" factor and an autosomal homozygous allele in each genotype - that is reasonably consistent with the slender evidence.

Hip dysplasia without dislocation in one-year-old boys.

Six boys were examined during the second year of life, each with symptoms in one hip. The affected femoral capital epiphysis was smaller or more irregular (or both) than that of the unaffected hip but was neither subluxed nor dislocated. The subsequent radiographs revealed changes similar to those in severe Perthes' disease. Nevertheless, we give reasons for believing that this disorder in boys under two years of age should be distinguished from Perthes' disease.

Rotational displacement of the lower tibial epiphysis due to trauma.

A rare form of injury to the distal tibial growth plate is described. Only two patients with such an injury have been reported previously. The injury, rotational displacement of the distal tibial epiphysis with posterior displacement of the fibula but without fracture, can be reduced easily and appears to have no lasting ill-effects.