Aims

There has been a recent resurgence in interest in combined partial knee arthroplasty (PKA) as an alternative to total knee arthroplasty (TKA). The varied terminology used to describe these procedures leads to confusion and ambiguity in communication between surgeons, allied health professionals, and patients. A standardized classification system is required for patient safety, accurate clinical record-keeping, clear communication, correct coding for appropriate remuneration, and joint registry data collection.

We measured the orientation of the acetabular and femoral components in 45 patients (33 men, 12 women) with a mean age of 53.4 years (30 to 74) who had undergone revision of metal-on-metal hip resurfacings. Three-dimensional CT was used to measure the inclination and version of the acetabular component, femoral version and the horizontal femoral offset, and the linear wear of the removed acetabular components was measured using a roundness machine.

We found that acetabular version and combined version of the acetabular and femoral components were weakly positively correlated with the rate of wear. The acetabular inclination angle was strongly positively correlated with the rate of wear. Femoral version was weakly negatively correlated with the rate of wear. Application of a threshold of > 5 μm/year for the rate of wear in order to separate the revisions into low or high wearing groups showed that more high wearing components were implanted outside Lewinnek’s safe zone, but that this was mainly due to the inclination of the acetabular component, which was the only parameter that significantly differed between the groups.

We were unable to show that excess version of the acetabular component alone or combined with femoral version was associated with an increase in the rate of wear based on our assessment of version using CT.

We carried out metal artefact-reduction MRI, three-dimensional CT measurement of the position of the component and inductively-coupled plasma mass spectrometry analysis of cobalt and chromium levels in whole blood on 26 patients with unexplained pain following metal-on-metal resurfacing arthroplasty.

MRI showed periprosthetic lesions around 16 hips, with 14 collections of fluid and two soft-tissue masses. The lesions were seen in both men and women and in symptomatic and asymptomatic hips. Using three-dimensional CT, the median inclination of the acetabular component was found to be 55° and its positioning was outside the Lewinnek safe zone in 13 of 16 cases. Using inductively-coupled plasma mass spectrometry, the levels of blood metal ions tended to be higher in painful compared with well-functioning metal-on-metal hips.

These three clinically useful investigations can help to determine the cause of failure of the implant, predict the need for future revision and aid the choice of revision prostheses.

We performed a prospective, randomised controlled trial of unicompartmental knee arthroplasty comparing the performance of the Acrobot system with conventional surgery. A total of 27 patients (28 knees) awaiting unicompartmental knee arthroplasty were randomly allocated to have the operation performed conventionally or with the assistance of the Acrobot. The primary outcome measurement was the angle of tibiofemoral alignment in the coronal plane, measured by CT. Other secondary parameters were evaluated and are reported.

All of the Acrobot group had tibiofemoral alignment in the coronal plane within 2° of the planned position, while only 40% of the conventional group achieved this level of accuracy. While the operations took longer, no adverse effects were noted, and there was a trend towards improvement in performance with increasing accuracy based on the Western Ontario and McMaster Universities Osteoarthritis Index and American Knee Society scores at six weeks and three months. The Acrobot device allows the surgeon to reproduce a pre-operative plan more reliably than is possible using conventional techniques which may have clinical advantages.

We have investigated nine patients with cemented Furlong (JRI, London, UK) titanium hip replacements who presented with early pain despite a well-fixed, aseptic prosthesis. All were followed up clinically and radiologically at regular intervals. Pain was located in the thigh and was worse at night. Radiographs showed cortical hypertrophy of the femur around the tip of the stem. Eight of the nine patients subsequently required single-stage revision using an uncemented prosthesis, which relieved the pain. At revision, the pH of the tip of the stem was found to be highly acidic with macroscopic evidence of corrosion consisting of multiple layers of titanium oxides when studied by X-ray dispersive analysis. Cemented titanium implants have a potential for crevice corrosion leading to cortical hypertrophy and intractable pain.

Needle biopsies, performed on 208 consecutive patients and interpreted at the London Bone Tumour Service over a two-year period, were reviewed. A correct diagnosis was reached in 97% (133 out of 137) using this technique alone. Needle biopsy is safe and accurate when undertaken in consultation within a bone tumour service; it offers considerable advantages to both patient and surgeon over conventional open biopsy.

There is no firm published evidence to support the use of closed suction drains. Over 20 years ago, large studies by the Public Health Laboratory Service and the National Research Council found that drains were risk factors for wound infection. A prospective randomised study of the use of closed suction drains after surgery for fractured neck of femur in 70 patients failed to show that drains improved wound healing. Drained cases had more complications.