Proposed Topic (Most preferred): :
Research and Innovations (new projects / technology / innovations / service models)
Proposed Topic (Second preferred): :
HA Young Investigators Session (Projects to be presented by HA staff who had joined HA for 10 years or less)
Authors (including presenting author) :
Li MLM (1), Wong KC (1), Chiu WK (1), Lau HW (1)
Affiliation :
(1) Orthopaedics and Traumatology, Prince of Wales Hospital
Introduction :
Osteosarcoma is the most common primary malignant bone tumor of children and adolescents. With the advances in chemotherapy, imaging modalities and surgical techniques, outcomes of these patients have greatly improved. Orthopaedic surgeons at the same time, can avoid more amputations and perform limb salvage surgeries to retain limb function.
Endoprosthetic reconstruction is the mainstay of treatment following the resection of bone sarcoma in limb-salvage surgery. With improving survival, endoprosthesis related complications are also expected to increase. Studies have shown that long-term survivors with endoprosthesis may have to undergo an average of 2.7 further operations at the mean follow-up of 29.4 years. Risk factors for these failures included smaller stem size, higher bone to stem ratio, and a greater percentage of bone resected.
It lacks large studies reporting long-term results in Asian paediatric and adolescent patients. Given Asians have a smaller body built; the stem size used will be smaller and a greater percentage of bone will be resected for the same size tumor as compared to Caucasians. It seems inevitable that there will be higher failure rates for Asians.
However, results from our institution have suggested otherwise. Our endoprosthesis have demonstrated better longevity. There were less failure rates, better survivorship of implants despite presence of conventional risk factors for failures.
Objectives :
The objectives were to report (1) the survival of the endoprosthesis, (2) the primary outcome as the mode of failure of the endoprosthesis, and (3) the secondary outcome by analyzing the factors leading to the mechanical failure of patients after the resection of lower extremity bone sarcoma.
Methodology :
38 paediatric patients (mean 13.29, range 6–18) with primary bone sarcoma of lower extremity undergone chemotherapy and limb salvage surgery with tumor endoprosthesis between 2003 and 2016 were reviewed. All hospital notes were reviewed for any type of failures. Risk factors for implant loosening like stem size, remaining bone length, stem length, extracortical bone bridge ingrowth (EBBI), the ratio of resected bone length to whole bone length, bone stem ratio and custom-made versus modular were analyzed. The limb function was recorded by Musculoskeletal Tumor Society (MSTS) score. Median follow-up time was 7.42 years (3.0–15.4 years) and minimum follow-up for surviving patients was 2 years
Result & Outcome :
Endoprosthesis survivorship, according to Kaplan Meier was 94.7%, 85.4% and 66.2% at 2, 5 and 10 years respectively. Type II failure occurred in three patients (7.9%). Type III failure occurred in four patients (10.5%). Type IV failure occurred in two patients (5.2%). Only EBBI independently predicted implant loosening (p = .007). Risk factors like stem size, remaining bone length, stem length, the ratio of resected bone length to whole bone length and custom-made versus modular were not associated with increase in implant loosening (p > .05). The mean stem size was 9.41 mm in asymptomatic group, comparable with 9.22 mm in the failure group (p = .79). The MSTS score was 29.62
Our data suggests that paediatric Chinese patients with small body built had good and excellent mid-term results in implant survival and limb function respectively. EBBI is important in preventing loosening in tumor endo-prosthesis. In contrast to the reported higher failure risk with stem size < 12 mm, we found no increased loosening rate with smaller stem size endoprosthesis.
Overall, the improved longevity of the paediatric endoprosthesis is beneficial for all parties. Patients enjoy a better quality of life and are able to return to premorbid status, while for the hospital, there be less operations for revisions which lead to less hospital admissions, operative sessions so that manpower and resources can be redistributed to the more needy aspects.
