Most hospitals have introduced digital radiography (PACS) systems. Accurate pre-operative templating prior to hip arthroplasty requires precise information on the magnification of the digital image. Without this information the benefits of expensive digital templating programs (Orthoview-£10000) cannot be realised.

To determine the magnification of a digital image involves the placement of a “calibration object” at the level of the hip joint. This is unpopular with patients and radiographers alike. We describe a method that requires a single measurement to be made from the greater trochanter to the digital film.

An AP pelvis x-ray was taken of 50 patients with hip replacements. The “predicted” magnification was calculated using the new method. As the size of the head of the prosthesis was known the “actual” magnification could be calculated also. There was no significant difference at 0.05, Wilcoxon T, 2-tail test.

Conventional radiography, which assumes a magnification of 20%, results in errors up to 11%. Templating may therefore predict an incorrectly sized prosthesis. Our method is as accurate as methods using a calibration object whilst being acceptable to patients and staff. Its use should lead to more accurate pre-operative templating prior to total hip arthroplasty

Purpose: Chondroblastomas are a lesion of immature cartilage found in a typically epiphyseal location. The peak incidence is in teenagers. Current surgical treatment is a balance between complete excision, with potential for physeal and articular cartilage damage, and local recurrence. A minimally invasive technique with a low complication rate providing effective treatment may be provided by radiofrequency (RF) thermocoagulation. Already the treatment of choice for Osteoid Osteoma – another lesion that can occur in the epiphysis.1,2,3 Literature to date on clinical use of RF thermocoagulation in chondroblastoma is scarce.4 The high water content of chondroblastoma should ensure its sensitivity to RF ablation. Our units experience in osteoid osteoma has been extended to RF thermocoagulation of chondroblastoma.

Patients: Four patients were treated with RF thermocoagulation for a chondroblastoma. Minimum follow up one year.

Methods: A RITA Starburst probe thermocoagulates the lesion for at least 5 minutes at 90 degrees centigrade. Overnight stay and outpatient follow up until skeletal mature, or two years following treatment.

Results: Two chondroblastomas were in the proximal tibia, one in the distal femur and one in the proximal humerus. One patient had surgery previously and one patient presented with collapse of the proximal tibial plateau. All patients were treated successfully and are pain free. All patients, accepting the one with pre-existing collapse, have a full range of movement. There has been no local recurrence at one year.

Conclusion & Discussion: Our experience suggests that radiofrequency thermocoagulation is a safe and effective treatment method for patients with chondroblastoma.

Restriction of straight leg raising (SLR) is usually associated with patients suffering leg pain due to a postero-lateral disc protrusion.

We report a group of twelve patients presenting with acute mechanical low back pain only, and no leg pain, who also demonstrated similar restriction of SLR.

The MRI scans of these patients, when compared with the scans of patients suffering typical sciatic pain, revealed that the disc protrusions in the back pain group were more likely to be smaller, central and at a higher lumbar level than the leg pain group.

Anatomical considerations would suggest that the source of back pain was the anterior theca being compressed by a central disc protrusion.