108. GAMMA PROBE GUIDED SURGERY FOR BENIGN BONE TUMOURS: SURGICAL RESULTS WITH AVERAGE FOLLOW-UP OF 5 YEARS

Abstract

Purpose: Intra-op localisation of small nidus in Osteiod osteoma and Osteoblastomas is often difficult resulting in failed excision with persistent pain. We report two year follow-up results of the efficacy and reliability of using an intra-operative gamma probe in conjunction with fluoros-copy to aid resection in primary and revision surgeries.

Method: Eight patients (6M; 2F) with a diagnosis of osteoid osteoma (7) and osteoblastoma (1) were seen at our centre. The mean age at presentation was 20.9 years (9–31y). The tumour was localised to cervical (2), thoracic(4) and lumbar (2) posterior elements. All had back or neck pain of varying duration with a mean of 20 months (6–48mo). Three patients had failed treatments including CT-guided radiofrequency ablation in one and surgical excision under fluoroscopy in two. No case had previously utilised an intra-op gamma probe for localisation. All patients had work-up with plain X-rays, CT, MRI and 99 m Technetium bone scan to identify and localise the lesion. A pre-requisite for use of intra-op gamma probe was a positive pre-op bone scan. On the day of surgery, 600 MBq Tech HMDP (hydroxy-methylene-di-phosphate) was administered IV 3 hours prior to surgery. Fluoroscopy was used to confirm anatomical level, permanent mark made on skin and area exposed surgically. A 5 mm cadmium telluride (Cd Te) probe (which converts gamma radiation into electrical signal) and rate meter were used to scan the area containing lesion and counts per second(cps) recorded. The tumour nidus was then excised and cps from tumour bed and excised specimen recorded.

Results: The mean follow-up was 5.85 years (2–12.3y). The mean cps for osteoid osteoma pre-excision was 203.8 (60–515), which fell to 72.5 (10–220) post-excision. The cps reduced from 373 to 40.5 post-operatively for Osteoblastoma. Complete excision was recorded every time and all patients reported characteristic disappearance of pre-operative pain. All had discontinued analgesic medication and returned to normal activity by three months. All patients were followed-up regularly when they filled NDI, ODI and SF-36.

Conclusion: Gamma probe guided surgical excision facilitates accurate localisation of lesion, is less invasive and most importantly confirmation of complete excision of the tumour nidus consistently every time.