Objectives

An experimental piglet model induces avascular necrosis (AVN) and deformation of the femoral head but its secondary effects on the developing acetabulum have not been studied. The aim of this study was to assess the development of secondary acetabular deformation following femoral head ischemia.

Excessive acetabular cover secondary to a retroverted acetabulum causes pincer impingement, which may cause early osteoarthritis of the hip. Our aim was to determine if there was a relationship between acetabular version and osteoarthritis of the hip. Using image processing and analysis software we studied 117 CT images of the hip in patients aged less than 65 years who had undergone a CT virtual colonoscopy. The mean CT joint space of the 18 hips with acetabular retroversion was narrower compared with the 99 hips with normal acetabular alignment (p < 0.0001). A correlation of r = 0.46 (p < 0.01) was found between right hip acetabular version and the mean right hip joint space and of r = 0.31 (p = 0.02) between left hip acetabular version and the mean left hip joint space. Acetabular retroversion is associated with radiological evidence of osteoarthritis of the hip. An understanding of the mechanical basis of osteoarthritis of the hip allows early treatment of the underlying structural abnormality and prevents progression of the degenerative condition.

Limb lengthening by callus distraction and external fixation has a high rate of complications. We describe our experience using an intramedullary nail (Fitbone) which contains a motorised and programmable sliding mechanism for limb lengthening and bone transport. Between 2001 and 2004 we lengthened 13 femora and 11 tibiae in ten patients (seven men and three women) with a mean age of 32 years (21 to 47) using this nail. The indications for operation were short stature in six patients and developmental or acquired disorders in the rest.

The mean lengthening achieved was 40 mm (27 to 60). The mean length of stay in hospital was seven days (5 to 9). The mean healing index was 35 days/cm (18.8 to 70.9). There were no cases of implant-related infection or malunion.

Orthopaedic surgeons have accepted various radiological signs to be representative of acetabular retroversion, which is the main characteristic of focal over-coverage in patients with femoroacetabular impingement (FAI). Using a validated method for radiological analysis, we assessed the relevance of these signs to predict intra-articular lesions in 93 patients undergoing surgery for FAI. A logistic regression model to predict chondral damage showed that an acetabular retroversion index (ARI) > 20%, a derivative of the well-known cross-over sign, was an independent predictor (p = 0.036). However, ARI was less significant than the Tönnis classification (p = 0.019) and age (p = 0.031) in the same model. ARI was unable to discriminate between grades of chondral lesions, while the type of cam lesion (p = 0.004) and age (p = 0.047) were able to. Other widely recognised signs of acetabular retroversion, such as the ischial spine sign, the posterior wall sign or the cross-over sign were irrelevant according to our analysis. Regardless of its secondary predictive role, an ARI > 20% appears to be the most clinically relevant radiological sign of acetabular retroversion in symptomatic patients with FAI.

Cite this article: Bone Joint J 2013;95-B:893–9.

Recently, femoroacetabular impingement has been recognised as a cause of early osteoarthritis. There are two mechanisms of impingement: 1) cam impingement caused by a non-spherical head and 2) pincer impingement caused by excessive acetabular cover. We hypothesised that both mechanisms result in different patterns of articular damage. Of 302 analysed hips only 26 had an isolated cam and 16 an isolated pincer impingement. Cam impingement caused damage to the anterosuperior acetabular cartilage with separation between the labrum and cartilage. During flexion, the cartilage was sheared off the bone by the non-spherical femoral head while the labrum remained untouched. In pincer impingement, the cartilage damage was located circumferentially and included only a narrow strip. During movement the labrum is crushed between the acetabular rim and the femoral neck causing degeneration and ossification.

Both cam and pincer impingement lead to osteoarthritis of the hip. Labral damage indicates ongoing impingement and rarely occurs alone.

This review describes the development of arthroscopy of the hip over the past 15 years with reference to patient assessment and selection, the technique, the conditions for which it is likely to prove useful, the contraindications and complications related to the procedure and, finally, to discuss possible developments in the future.

We have compared the biomechanical nature of the reconstruction of the hip in conventional total hip arthroplasty (THA) and surface replacement arthroplasty (SRA) in a randomised study involving 120 patients undergoing unilateral primary hip replacement. The contralateral hip was used as a control.

Post-operatively, the femoral offset was significantly increased with THA (mean 5.1 mm; −2.8 to 11.6) and decreased with SRA (mean −3.3 mm; −8.9 to 8.2). Femoral offset was restored within sd 4 mm in 14 (25%) of those with THA and in 28 (57%) of the patients receiving SRA (p < 0.001). In the THA group, the leg was lengthened by a mean of 2.6 mm (−6.04 to +12.9), whereas it was shortened by a mean of 1.9 mm (−7.1 to +2.05) in the SRA group, compared with the contralateral side. Leg-length inequality was restored within sd 4 mm in 42 (86%) of the SRA and 33 (60%) of the THA patients. The radiological parameters of acetabular reconstruction were similar in both groups.

Restoration of the normal proximal femoral anatomy was more precise with SRA. The enhanced stability afforded by the use of a large-diameter femoral head avoided over-lengthening of the limb or increased offset to improve soft-tissue tension as occurs sometimes in THA. In a subgroup of patients with significant pre-operative deformity, restoration of the normal hip anatomy with lower pre-operative femoral offset or significant shortening of the leg was still possible with SRA.

We prospectively followed 191 consecutive collarless polished tapered (CPT) femoral stems, implanted in 175 patients who had a mean age at operation of 64.5 years (21 to 85). At a mean follow-up of 15.9 years (14 to 17.5), 86 patients (95 hips) were still alive. The fate of all original stems is known. The 16-year survivorship with re-operation for any reason was 80.7% (95% confidence interval 72 to 89.4). There was no loss to follow-up, with clinical data available on all 95 hips and radiological assessment performed on 90 hips (95%). At latest follow-up, the mean Harris hip score was 78 (28 to 100) and the mean Oxford hip score was 36 (15 to 48). Stems subsided within the cement mantle, with a mean subsidence of 2.1 mm (0.4 to 19.2). Among the original cohort, only one stem (0.5%) has been revised due to aseptic loosening. In total seven stems were revised for any cause, of which four revisions were required for infection following revision of the acetabular component. A total of 21 patients (11%) required some sort of revision procedure; all except three of these resulted from failure of the acetabular component. Cemented acetabular components had a significantly lower revision burden (three hips, 2.7%) than Harris Galante uncemented components (17 hips, 21.8%) (p < 0.001).

The CPT stem continues to provide excellent radiological and clinical outcomes at 15 years following implantation. Its results are consistent with other polished tapered stem designs.

Ceramic-on-ceramic bearings in hip replacement have low rates of wear and are increasingly being used in young adults. Our aim was to determine the incidence of audible phenomena or other bearing-related complications.

We retrospectively analysed 250 ceramic-on-ceramic hip replacements in 224 patients which had been implanted between April 2000 and December 2007. The mean age of the patients at operation was 44 years (14 to 83) and all the operations were performed using the same surgical technique at a single centre.

At a mean follow-up of 59 months (24 to 94), the mean Oxford hip score was 40.89 (11 to 48). There were six revisions, three of which were for impingement-related complications. No patient reported squeaking, but six described grinding or clicking, which was usually associated with deep flexion. No radiological evidence of osteolysis or migration of the components was observed in any hip.

The early to mid-term results of contemporary ceramic-on-ceramic hip replacement show promising results with few concerns in terms of noise and squeaking. Positioning of the acetabular component remains critical in regard to the reduction of other impingement-related complications.

Between 1978 and 1997 all newborns in the Austrian province of Tyrol were reviewed regarding hip dysplasia and related surgery. This involved a mean of 8257 births per year (7766 to 8858). Two observation periods were determined: 1978 to 1982 (clinical examination alone) and 1993 to 1997 (clinical examination and universal ultrasound screening). A retrospective analysis compared the number and cost of interventions due to hip dysplasia in three patient age groups: A, 0 to < 1.5 years; B, ≥ 1.5 to < 15 years; and C, ≥ 15 to < 35 years.

In group A, there was a decrease in hip reductions from a mean of 25.2 (sd 2.8) to 7.0 (sd 1.4) cases per year. In group B, operative procedures decreased from a mean of 17.8 (sd 3.5) to 2.6 (sd 1.3) per year. There was a 75.9% decrease in the total number of interventions for groups A and B.

An increase of €57 000 in the overall cost per year for the second period (1993 to 1997) was seen, mainly due to the screening programme. However, there was a marked reduction in costs of all surgical and non-surgical treatments for dysplastic hips from €410 000 (1978 to 1982) to €117 000 (1993 to 1997). We believe the small proportional increase in costs of the universal ultrasound screening programme is justifiable as it was associated with a reduction in the number of non-surgical and surgical interventions. We therefore recommend universal hip ultrasound screening for neonates.

We reviewed the clinical outcome of arthroscopic femoral osteochondroplasty for cam femoroacetabular impingement performed between August 2005 and March 2009 in a series of 40 patients over 60 years of age. The group comprised 26 men and 14 women with a mean age of 65 years (60 to 82). The mean follow-up was 30 months (12 to 54).

The mean modified Harris hip score improved by 19.2 points (95% confidence interval 13.6 to 24.9; p < 0.001) while the mean non-arthritic hip score improved by 15.0 points (95% confidence interval 10.9 to 19.1, p < 0.001). Seven patients underwent total hip replacement after a mean interval of 12 months (6 to 24 months) at a mean age of 63 years (60 to 70). The overall level of satisfaction was high with most patients indicating that they would undergo similar surgery in the future to the contralateral hip, if indicated. No serious complications occurred.

Arthroscopic femoral osteochondroplasty performed in selected patients over 60 years of age, who have hip pain and mechanical symptoms resulting from cam femoroacetabular impingement, is beneficial with a minimal risk of complications at a mean follow-up of 30 months.

We report the outcome of the flangeless, cemented all-polyethylene Exeter acetabular component at a mean of 14.6 years (10 to 17) after operation. Of the 263 hips in 243 patients, 122 prostheses are still in situ; 112 patients (119 hips) have died, 18 hips have been revised, and three patients (four hips) were lost to follow-up. Radiographs at the final review were available for 110 of the 122 surviving hips. There were acetabular radiolucent lines in 54 hips (49%). Two acetabular components had migrated but neither patient required revision. The Kaplan-Meier survivorship at 15 years with 61 hips at risk with revision for any cause as the endpoint was 89.9% (95% confidence interval (CI) 84.6 to 95.2) and for aseptic loosening of the acetabular component or lysis 91.7% (95% CI 86.6 to 96.8). In 210 hips with a diagnosis of primary osteoarthritis, survivorship with revision for any cause as the endpoint was 93.2% (95% CI 88.1 to 98.3), and for aseptic loosening of the acetabular component 95.0% (95% CI 90.3 to 99.7).

The cemented all-polyethylene Exeter acetabular component has an excellent long-term survivorship.

Slipped upper femoral epiphysis (SUFE) with an open physis is rare in an adult and the condition may present without prior diagnosis of an underlying medical condition. We have treated a 29-year-old man with bilateral SUFE associated with autoimmune hypothyroidism. The management was delayed and complicated by co-existing autoimmune chronic active hepatitis. He underwent thyroxine therapy and bilateral pinning in situ with a single ASNIS screw. Closure of the physis occurred after five months on the right side. The left side required a further corrective intertrochanteric osteotomy, and it was only after 13 months that complete fusion of this physis was seen. The case highlights the need to consider endocrine and metabolic conditions in atypical presentation of SUFE.

The management of joint replacement in lysosomal storage diseases has not been well reported. We present three patients with progressive degenerative changes of the hips who required bilateral total hip replacement in early childhood. The stature of the patients make it essential to have access to appropriately scaled prostheses. Consideration has to be given to associated disorders of the skeleton which must be carefully screened to ensure safety in providing appropriate anaesthesia as well as ensuring that there is no cardiac abnormality. In one patient, a periprosthetic fracture was sustained in one hip in the early post-operative course requiring internal fixation.

The patient made a full recovery and all six hips were clinically and radiologically satisfactory at mid-term review.

The β-angle is a radiological tool for measuring the distance between the pathological head-neck junction and the acetabular rim with the hip in 90° of flexion in patients with femoroacetabular impingement. Initially it was measured using an open-chamber MRI. We have developed a technique to measure this angle on plain radiographs. Correlation analysis was undertaken to determine the relationship between the range of movement and the β-angle in 50 patients with femoroacetabular impingement and 50 asymptomatic control subjects. Inter- and intra-observer reliability of the β-angle was also evaluated.

Patients with femoroacetabular impingement had a significantly smaller (p < 0.001) mean β-angle (15.6°, 95% confidence interval (CI) 13.3 to 17.7) compared with the asymptomatic group (38.7°, 95% CI 36.5 to 41.0). Correlation between internal rotation and the β-angle was high in the impingement group and moderate in the asymptomatic group. The β-angle had excellent inter- and intra-observer reliability in both groups.

Our findings suggest that the measurement of the β-angle on plain radiography may represent a valid, reproducible and cost-effective alternative to open MRI in the assessment of the pathological bony anatomy in patients with cam, pincer and mixed femoroacetabular impingement.

The crucial differentiation between septic arthritis and transient synovitis of the hip in children can be difficult. In 1999, Kocher et al introduced four clinical predictors which were highly predictive (99.6%) of septic arthritis. These included fever (temperature ≥ 38.5°C), inability to bear weight, white blood-cell count > 12.0 × 10⁹ cells/L and ESR ≥ 40 mm/hr; CRP ≥ 20 mg/L was later added as a fifth predictor. We retrospectively evaluated these predictors to differentiate septic arthritis from transient synovitis of the hip in children over a four-year period in a primary referral general hospital. When all five were positive, the predicted probability of septic arthritis in this study was only 59.9%, with fever being the best predictor. When applied to low-prevalence diseases, even highly specific tests yield a high number of false positives and the predictive value is thereby diminished.

Clinical predictors should be applied with caution when assessing a child with an irritable hip, and a high index of suspicion, and close observation of patients at risk should be maintained.

We retrospectively examined the long-term outcome of 96 asymptomatic hips in 96 patients with a mean age of 49.3 years (16 to 65) who had radiological evidence of femoroacetabular impingement. When surveillance commenced there were 17, 34, and 45 hips with cam, pincer, and mixed impingement, respectively. Overall, 79 hips (82.3%) remained free of osteoarthritis for a mean of 18.5 years (10 to 40). In contrast, 17 hips (17.7%) developed osteoarthritis at a mean of 12 years (2 to 28). No statistically significant difference was found in the rates of development of osteoarthritis among the three groups (p = 0.43). Regression analysis showed that only the presence of idiopathic osteoarthritis of the contralateral diseased hip was predictive of development of osteoarthritis on the asymptomatic side (p = 0.039).

We conclude that a substantial proportion of hips with femoroacetabular impingement may not develop osteoarthritis in the long-term. Accordingly, in the absence of symptoms, prophylactic surgical treatment is not warranted.

Between 1988 and 1998 we implanted 318 total hip replacements (THRs) in 287 patients using the Plasmacup (B. Braun Ltd, Sheffield, United Kingdom) and a conventional metal-on-polyethylene articulation. The main indications for THR were primary or secondary osteoarthritis.

At follow-up after a mean 11.6 years (7.6 to 18.4) 17 patients had died and 20 could not be traced leaving a final series of 280 THRs in 250 patients. There were 62 revisions (22.1%) in 59 patients. A total of 43 acetabular shells (15.4%) had been revised and 13 (4.6%) had undergone exchange of the liner. The most frequent indications for revision were osteolysis and aseptic loosening, followed by polyethylene wear. The mean Kaplan-Meier survival of the Plasmacup was 91% at ten years and 58% at 14 years. Osteolysis was found around 36 (17.1%) of the 211 surviving shells. The median annual rate of linear wear in the surviving shells was 0.12 mm/year and 0.25 mm/year in those which had been revised (p < 0.001). Polyethylene wear was a strong independent risk factor for osteolysis and aseptic loosening. The percentage of patients with osteolysis increased proportionately with each quintile of wear-rate.

There is a high late rate of failure of the Plasmacup. Patients with the combination of this prosthesis and bearing should be closely monitored after ten years.

We present the 10- to 17-year results of 112 computer-assisted design computer-assisted manufacture femoral components. The total hip replacements were performed between 1992 and 1998 in 111 patients, comprising 53 men and 58 women. Their mean age was 46.2 years (24.6 to 62.2) with a mean follow-up of 13 years (10 to 17). The mean Harris Hip Score improved from 42.4 (7 to 99) to 90.3 (38 to 100), the mean Oxford Hip Score from 43.1 (12 to 59) to 18.2 (12 to 51) and the mean Western Ontario MacMasters University Osteoarthritis Index score from 57.0 (7 to 96) to 11.9 (0 to 85). There was one revision due to failure of the acetabular component but no failures of the femoral component. There were no revisions for aseptic loosening. The worst-case survival in this cohort of custom femoral components at 13.2 years follow-up was 98.2% (95% confidence interval 95 to 99). Overall survival of this series of total hip replacements was 97.3% (95% confidence interval 95 to 99).

These results are comparable with the best medium- to long-term results for femoral components used in primary total hip replacement with any means of fixation.