The study in question is a post market clinical follow up (PMCF) study to follow up the safety and performance of bioabsorbable headless compression screw Inion CompressOn in fracture fixation of the ankle, knee and elbow of pediatric and adolescent patients. The study aims to recruit 80 patients who meet the acceptance criteria. The follow-up time for each study patient is 4 years. The study is a single center single group study which is conducted in Lighthouse Hospital at Turku University Hospital (TYKS) in Finland. The main focus of the study in terms of performance is to follow up the bone healing/ossification of operated areas. The main focus of the study in terms of safety is to evaluate the occurrence of adverse events and required revision surgeries that are or might be related to the study device.

The study in question is a post market clinical follow-up study to follow-up the safety and performance of the bioabsorbable headless Inion CompressOn Screw in fracture fixation operations of the ankle, knee and elbow of pediatric and adolescent patients. The main focus of the study in terms of performance is to follow-up the bone healing/ossification of operated areas. The main focus of the study in terms of safety is to evaluate the occurrence of adverse events and required revision surgeries that are or might be related to the study device.

The Inion CompressOn™ Screws are cannulated headless compression screws made of degradable co-polymers composed of L-lactic acid and D-lactic acid. These polymers have a long history of safe medical use and they degrade in vivo by hydrolysis into alpha-hydroxyacids that are metabolised by the body. The screws retain their initial strength up to 12 weeks after implantation and gradually lose their strength thereafter. Bioabsorption takes place within four years.

The clinical data collection acquired from this study is a requirement of the EU Notified Body as part of the admitted CE mark certification, in cases when the device is initially approved based on the clinical data of an equivalent device. In this case, the equivalent device has been Inion FreedomScrew, which is made of the same material composition and is used for the same indications. Inion CompressOn Screw has new design features such as headless design, and threading which allows compression to the fracture line. Also new sizes have been introduced.

The study recruits 80 pediatric/adolescent patients who meet the acceptance criteria and have signed the informed consent. The follow-up time for each study patient is 4 years. Each patient has 6 follow-up time points related to the study. These time points consist of:

1. screening visit (-180-0 days before operation),
2. operation (day 0),
3. post-operative follow-up 1 (4-8 weeks),
4. post-operative follow-up 2 (3 months after operation +/- 3 weeks),
5. post-operative follow-up 3 (2 years after operation +/- 2 months)
6. post-operative follow-up 4 (4 years after operation +/- 4 months) The first 4 time points are within standard care, the last 2 time points (post-operative follow-up 3 and post-operative follow-up 4) are scheduled for study purposes only to be able to gain performance and safety data based on adequate follow-up time.

The study is a single center single group study which is conducted in Turku University Hospital (TYKS) in Finland.

Inclusion Criteria:

1. Informed consent signed by parents or legal guardians, and assent from the child if of appropriate age and cognitive ability < 18 years 3. Suitable and in need for an operation indicated for subject device 4. Ability to give adequate input for the PROM questionnaires 5. Willingness and ability to comply with rehabilitation instructions. 6. Availability for follow-up visits.

Exclusion Criteria:

1. Active infection
2. Patient conditions including limited blood supply (e.g. patients with severe circulatory disorder of the lower or upper limb)
3. Patient conditions including insufficient quality or quantity of bone (diagnosed osteoporosis, conditions causing secondary osteoporosis e.g. diabetes, rheumatism, eating disorder)
4. Patient conditions where patient cooperation cannot be guaranteed (alcohol use, drug abuse etc.)
5. Patients with known allergy to the implant constituents or its degradation products.
6. Spinal and craniomaxillofacial indications.
7. High-load bearing indications (e.g., diaphyseal fractures of long bones) unless used in conjunction with traditional rigid fixation