Metal-on-metal articulations are increasingly used in THR. Hypersensitivity reactions to the metal ions can occur. The symptoms and signs are similar to a patient presenting with an infected prosthesis. Correct diagnosis before revision surgery is crucial to implant selection and operation planning. We present a practical approach to this diagnostic problem.

The history, clinical findings, hip scores, radiology, serum metal ions, ESR, C-RP, hip arthroscopy and aspirate results, synovial fluid metal ion levels, labelled white cell/colloid scan, 99m-technetium scan, revision hip findings and histology of a typical patient who had an allergic response to a metal-on-metal hip articulation are presented, and how the findings differ from a patient with an infected implant. Clinical examination, hip scores and serum metal ion levels were repeated one year after revision of the metal-on-metal hip articulation to a ceramic-on-ceramic.

In hypersensitivity, the periarticular tissues undergo lymphocyte-dominated infiltration, the histology differs from that found in infection. The white cell labelled/colloid scan also uses this difference for diagnosis. Hip aspiration is the single best investigation for infection.

Conclusion: There is no single investigation available in most hospitals that will reliably differentiate infection from allergy in the painful THR. Hip aspiration, labelled white cell/colloid scan and histology obtained from hip arthroscopy biopsy are the most useful investigations.

Background: The Profix Total Knee Arthroplasty (Smith and Nephew, Memphis, USA) is designed to replace less bone than is resected from the posterior femoral condyles, and as a consequence the posterior condylar offset is reduced. The net effect of this is to increase the flexion gap with no effect on the extension gap. This is a deliberate design philosophy aimed at increasing postoperative flexion. This prospective cohort study has tested this theory.

Methods: 60 patients underwent primary posterior cruciate retaining (CR) TKA using this prosthesis. A matched group of patients, employing a different CR prosthesis which replaces excised bone in full, served as historical controls. Intra-operative measurements were made of the posterior condylar bone resected in each case. These measurements were then correlated with the flexion achieved both intra-operatively and at 6 months post-operatively.

Results: A positive correlation between pre-operative and post-operative flexion was found. However, there was no correlation between the relative increase in flexion gap secondary to the reduction in posterior offset and the resulting flexion range.

Conclusion: Post-operative flexion range is not increased by the resection of more bone from the posterior femoral condyles than is replaced by the prosthesis in TKA. The loss of bone stock will have implications for revision surgery and should be avoided.

Introduction: Spondylolysis is amongst the commonest causes of low back pain in the athletic child. We observed increased uptake in the pedicles of the affected segment and a triangular pattern of uptake in the sagittal projection of tomographic studies of fractures of the pars interarticularis. The hypothesis that these observations were specific for fractures of the pars interarticularis was tested in a variety of spinal disorders.

Methods:. A retrospective study of 25 young athletes with a variety of spinal disorders was undertaken (17males, 8 females; average age 13.5 years [range: nine to16 years]). The patients were referred from a specialised sports clinic. Back pain was present for an average of four months (Range six weeks to 11 months). All children had planar and tomographic scintigraphic bone scans with special reconstruction. The diagnosis was confirmed by radiological studies and/or response to treatment.

Results:. All 15 children with spondylolysis had evidence of increased uptake in the ipsilateral (12/15) or contra-lateral pedicle (3/15). None of the cases of muscle insertion injury, facet joint or disc disease demonstrated this pattern. A triangular shaped pattern of uptake was only seen in the sagittal view of the tomographic studies in patients with fractures of the pars interarticularis.

Conclusion:. We have described two unique features of spondylolysis that add to the confidence with which the scintigraphic diagnosis may be made.

Introduction: Labelled leukocyte scintigraphy has been shown to be a sensitive and specific technique for the detection of pedal osteomyelitis in patients with diabetes mellitus. There has however been little data relating the efficacy of the technique to outcomes.

Aim: To examine the prognostic value of sequential 99m Tc labelled leukocyte scans at diagnosis and after 3–4 weeks of appropriate antibiotic therapy.

Method: Twenty-three patients with proven pedal osteomyelitis or persistent uptake on the sequence of scans were studied.

Results: Five additional episodes of osteomyelitis developed in the group over the period of the study. Eleven patients demonstrated persistent uptake in the sequential scans. Nine progressed to amputation. The remaining two patients were biopsy negative for infection, did not have cutaneous ulceration and were thought to have rapidly progressive arthropathy.

Conclusion: Sequential leukocyte scintigraphy accurately predicted the need for amputation and circumvented ineffective prolonged antibiotic therapy.