The development of metalosis is a not commonly reported complication after THR. The exact reasons are still unknown, but hypersensitivity reaction is favored ahead of toxic effects, immune defects and exogen causes. The phenomenon of metalosis occurred at an unpredictable time in situ and is often misinterpreted as a low grade infection.

In a retrospective study, we analysed all 173 (102 women and 71 men) primary and single cement less PPF THR (STRATEC®) with metal-on-metal (low carbide 0.08%) articulation of 1995. One patient was lost to follow-up, 18 patients were deceased. The average age at the time of surgery was 63.3 years and the follow-up time was 115 months.

40 (23.1%) metalosis cases were observed. Revision was done in 29 (16.8%) patients: three femur fractures, five cases of infection and 21 cases of metalosis. The median HHS at follow-up was 95. 18 cases (10.4%) had metalosis signs: six patients (3.2%) had periprosthetic osteolysis and pain, 16 patients (9.2%) had osteolysis without pain and nine patients (5.2%) had pain without osteolysis in the radiographs. Pain caused by metalosis typically occurred inguinal and at an average time of thirty months postoperatively. Dislocation was observed in 13 cases at an average time of 44 months with an average cup inclination of 48°. Extensive necrosis and diffuse lymphoplasmacytic infiltrates were noted. In most cases the bursa ileopectinea was highly filled and in this synovial fluid extremely elevated levels of chrome (32 – 46095 μg/l) and cobalt (30 – 67410 μg/l) were detected.

Since 2003, we do not implant or recommend metal-on-metal for THR anymore. Close radiographic and computertomographic monitoring with high mark on typical osteolysis and exact clinical evaluation is recommended for metal-on-metal THR. Patients without symptoms with severe osteolysis must be detected, and head and inlay changes must be performed.

In a randomised study, 28 patients with a mean age of 62.2 years (32 to 81) with osteoarthritis or avascular necrosis of the hip received either a ceramic-on-ceramic or a metal-on-metal total hip replacement. Apart from the liners the acetabular and femoral components were made of Ti-Al-Nb alloy. The serum aluminium and cobalt levels were measured before, and at one year after surgery.

The 15 patients in the ceramic-on-ceramic group had a median pre-operative aluminium level of 1.3 μg/l (0.25 to 8.4) and a cobalt level below the detection limit. At one year the aluminium level was 1.1 μg/l (0.25 to 2.3) and the cobalt level was 0.4 μg/l (0.15 to 0.7). The 13 patients in the metal-on-metal group had a median pre-operative aluminium level of 1.9 μg/l (0.25 to 4.4) and a cobalt level below the detection limit. At one year the median aluminium level was 0.9 μg/l (0.25 to 3.9) whereas the cobalt level was 1.4 μg/l (0.5 to 10.5). This increase in the cobalt level at one year was significant (p < 0.001).

Our findings indicate that ceramic-on-ceramic bearings do not cause elevated levels of serum aluminium in the first post-operative year.

We investigated prospectively the bone mineral density (BMD) of the proximal femur after implantation of a tapered rectangular cementless stem in 100 patients with a mean age of 60 years (16 to 87). It was determined using dual energy x-ray absorptiometry, performed one week after surgery and then every six months until the end-point of five years.

The BMD increased significantly in Gruen zones 2, 4 and 5 by 11%, 3% and 11% respectively, and decreased significantly in Gruen zones 1, 6 and 7 by 3%, 6% and 14% respectively, over the five-year period. The net mean BMD did not change over this time period. The changes in the BMD were not confined to the first 12 months after surgery. This investigation revealed no change in the overall periprosthetic BMD, but demonstrated a regional redistribution of bone mass from the proximal to distal zones.

We compared two methods of reconstruction of the abductor mechanism in 15 patients after prosthetic replacement of the upper femur, to assess abductor strength and function.

Six patients in group I had direct fixation of the gluteus medius tendon and a segment of the original bone to the prosthesis. Nine patients in group 2 had the abductor tendon fixed to the iliotibial band. We assessed clinical function, isometric muscle strength and muscle cross-sectional area for each patient.

The patients in group 1 had better clinical and functional results (p = 0.059), with average peak torques for hip abduction of 92% of that in the non-operated leg in group 1, and of 57% in group 2. Group 1 had a mean muscle cross-sectional area of 69% and a mean value of strength per cross-sectional area of 134% when compared with the control side. The respective values for group 2 were 52% and 91%.

Direct fixation of the abductor muscles to the prostheses gave improved function and higher isometric abductor muscle force.

We studied the detection of joint replacements at airport security checks in relation to their weight, using two types of detector arch. A single-source, unilateral detector showed different sensitivities for implants on different sides of a test subject.

All implants weighing more than 145 g were detected by one of the arches. The degree of detection was directly related to the logarithm of the weight of the prosthesis in patients, with a linear correlation (r² = 0.61). A bilateral arch detected all prostheses weighing over 195 g.

With their usual sensitivity settings many joint replacements were detectable; an identification pass containing the site and weight of such prostheses would help to avoid the need for body-search procedures.

We determined serum cobalt levels in 55 patients by atomic absorption spectrophotometry before and after implantation of uncemented total hip arthroplasties. In a randomised, prospective trial 27 wrought Co-28Cr-6Mo-0.2C metal-on-metal articulations were compared with 28 ceramic-on-polyethylene hips which did not contain cobalt. Other sources of iatrogenic cobalt loading were excluded.

The metal-on-metal group produced detectable serum cobalt levels (median 1.1 μg/l after one year) which were significantly different (p < 0.0001) from those of the ceramic-on-polyethylene control group (median below detection limit of 0.3 μg/l after one year). Our findings indicate that metal-on-metal bearings generate some systemic release of cobalt.