Aim: The aim of this study was to determine if a correlation exists between the impingement test and the arthroscopic findings at the acetabular rim in non-dysplastic hips. Secondarily, we also wanted to establish if there was a correlation between the pain experienced on the impingement test and the pathology identified.

Patients and Methods: Sixty-two consecutive patients who were due to have an arthroscopy of the hip in our unit were prospectively recruited into the study. All the dysplastic hips were excluded from the study. One observer was involved in examining all the patients and another one in performing all the arthroscopies. The impingement test was considered positive if at 90 degrees of flexion, adduction and internal rotation, the patient complained of discomfort or pain. If the patient experienced pain this was described as a strongly positive test and if there was discomfort experienced it was considered as a weakly positive test. The test was performed on the morning of the arthroscopy and all the intra-articular findings recorded at arthroscopy. A tear of the acetabular labrum and chondral damage in the antero-superior margin of the acetabulum were considered as positive pathology at the acetabular rim.

Results : There were 40 males and 22 females in the study group. The impingement test was positive in 57 patients, strongly positive in 42 and weakly positive in 15. The arthroscopy revealed positive pathology in terms of an acetabular labrum tear and/or chondral damage at the acetabular rim in 55 patients. A negative test was recorded in 5 patients but there was positive rim pathology in two of these 5 patients.

Conclusion: The impingement test correlates positively with the pathology at the acetabular rim; the sensitivity of the test for diagnosing acetabular rim pathology is 96.4 % and the specificity is only 60 % in non-dysplastic hips. However, we did not identify any correlation between the level of pain and the pathology observed.

Resurfacing arthroplasty of the hip is currently enjoying a resurgence in popularity. There are many reasons why resurfacing may be indicated, but one is that the absence of proximal femoral reaming at surgery may reduce the occurrence of heterotopic ossification (HO) after surgery. The objective of this study was to compare the prevalence of postoperative HO for patients undergoing two different types of hip surgery, resurfacing arthroplasty or total hip replacement. Data were gathered from 43 consecutive patients undergoing metal on metal hip resurfacing (MoM-R) and 37 consecutive patients undergoing metal on metal total hip replacement (MoM-THR) with a minimum of six months’ follow up. The Brooker classification was used to grade HO from postoperative radiographs1. We found that, when undergoing MoM-R, women had a lower chance of developing HO than men (p=0.04). In addition, women who received a MoM-R had a reduced incidence of developing HO than women who received a MoM-THR (p=0.04). There were no differences in the incidence of postoperative HO between men undergoing either MoM-R or MoM-THR. It can be concluded from this study that resurfacing does reduce the incidence of HO in women and that care must be taken when selecting women to undergo total hip replacement in preference to hip resurfacing. This study has highlighted the need to inform patients of HO as a common complication when consenting for hip arthroplasty, and has established an 18% rate of postoperative HO for hip resurfacing arthroplasty.

Aims: Cobalt (Co) and chromium (Cr) ion associated carcinogenesis and chromosomal damage in animals have raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum Co and Cr levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.

Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, 108 Ultima MOM THR with 28 mm CoCrMo bearing were identified. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery, activity level and weight. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry (ICP-MS) Statistical analysis used the Mann-Whitney U test.

Results: The median serum Co level after unilateral MOM THR was 22 nmol (range 15 to 37 nmol) compared to 42 nmol (range 19 to 221 nmol) for bilateral MOM THR (p=0.001). The median serum Cr level after unilateral MOM THR was 19 nmol (range 2 to 35 nmol) compared to 52 nmol (range 19 to 287 nmol) for bilateral MOM THR (p=0.04).

Conclusions: This study has shown that the serum Co and Cr levels in patients with bilateral MOM THR are significantly higher than those with unilateral MOM THR. With levels of up to 50 times the upper of limit of normal, this finding may be of relevance for the development of potential long-term side effects.

Aims: After Total Hip Replacement (THR), bearing surface pistoning during the gait cycle can affect wear rates. This ‘micro-separation’ has been shown clinically by video-fluoroscopy to be greater with a Metal-on-Polyethylene (MOP) bearing than a Metal-on-Metal (MOM) one. In this study, we quantified the suction forces that these bearings generate during the swing phase of the gait cycle as a result of interfacial tension from the thin fluid film present at the bearing surface. Methods: We used a servo-hydraulic universal testing machine with 250N load cell and programmed a sinusoidal waveform that could vary the loads and frequencies applied to MOP or MOM bearings submerged in 25% serum. We measured the bearing separation (±1μm) at tensile loads of 10N to 100N lasting 0.1s to 0.5s per 1Hz cycle.

Results: MOM bearings resisted tensile loads of up to 35N when applied for 0.1s to 0.5s of the simulated gait cycle. Bearing separation was measured at a maximum of 198 microns. Above 50N, the MOM bearing was unable to prevent separation occurring even when applied for only 0.1s of the simulated gait cycle (p< 0.001). The MOP bearing could not resist separation at any of the applied tensile loads (p< 0.0001).

Conclusions: The suction-fit of the MOM bearing used in this study is insufficient to prevent bearing separation due to gravity (110N). However, it may reduce the total bearing separation distance by delaying the time point at which separation occurs during the finite period of the swing phase (< 0.5s) during the gait cycle. This effect is crucially dependent upon the bearing clearance, bearing diameter, weight of the leg, speed of walking and soft tissue tension around the hip. This ultimately relies upon prosthetic design, patient selection and surgical technique.

Aims: Metal-on-Metal (MOM) bearings for Total Hip Arthroplasty (THA) are known to elevate the serum concentrations of metal ions, raising concern about possible long-term side-effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion, but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown.

Methods: In this study, we measured the serum cobalt and chromium levels from 22 large diameter MOM resurfacing arthroplasties (Cormet2000 & Birmingham Hip Resurfacing) and compared them to 22 THA (Ultima) with a bearing diameter of 28 mm. Patients were prospectively matched for activity level, weight and date after surgery. All were at least 6 months after surgery.

Results: At a median of 16 months (range 7 to 56) after resurfacing arthroplasty, we found the median serum cobalt and chromium levels to be 38 nmol/l (14 to 44) and 53 nmol/l (23 to 165) respectively. Both these figures were significantly greater than the levels after 28 mm MOM THA, which were 22 nmol/l (15 to 87, p=0.021) and 19 nmol/l (2 to 58, p< 0.001) for cobalt and chromium respectively.

Conclusions: As the upper limit of normal in patients without implants is typically 5 nmol/l, both groups had significantly raised metal ion levels, albeit at a relatively short median follow-up period. Large diameter MOM bearings resulted in a greater systemic release of cobalt and chromium ions than did small diameter bearings. This may be of relevance for potential long-term side-effects. It is not known to what extent this difference is due to corrosion of the component surfaces or of the wear particles produced.

Hip arthroscopy is a relative newcomer to the arthroscopic repertoire, yet even in its current infancy has shown the hip joint in a different light. One poorly understood area is the ligamentum teres, thought by many to do little more than carry a blood vessel in the developing hip. Ligamentum injuries have only rarely been described, though in recent years have been arthroscopically classified

We present a large series of ligamentum teres abnormalities treated by hip arthroscopy. Of 925 consecutive hip arthroscopies, 68 patients (73 hips) had either a complete ligamentum tear (Type I), partial ligamentum tear (Type II), or a degenerate ligamentum (Type III).

Only 4 patients had a correct diagnosis given prior to hip arthroscopy. Hyperadduction was the commonest cause of Type I tears, though not all tears had a traumatic aetiology. Complete tears have a shorter history and a higher chance of associated intra-articular damage. Partial tears typically have a long history of ill-defined hip pain. The degenerate ligamentum generally presents with the features of underlying osteoarthritis. At three-year review, Type I and II tears improved significantly following hip arthroscopy, Type III abnormalities less so.

This paper thus presents the largest series of ligamentum tears to-date reported.