Orthopedic Implants and Instruments

Introduction

The latest and modern concept of Fracture fixation is MIPO referred to as the Minimally invasive plate osteosynthesis. It is used to maximize the healing process and preserve the biology of the site of fracture so that rapid recovery can happen with the painless movement of the joints and soft tissues. With proper fracture exposure, this process can be carried out with the insertion of a plate in extraperiosteally position, submuscular position, etc. with the minimum disturbance caused to the bony fragments. 

Internal fixators

The scope and application of MIPO have been enhanced with the introduction of Internal fixators. Various kinds of Ortho Implants can be used for fixation. The internal fixators are introduced subcutaneously while the external fixators are positioned submuscular. These internal fixators have a unique pattern of designing which is known as the locking head screw or LHS. The head of these locking screws is composed of double comical thread which can be used for secured fixation purposes into the plate hole. For the construction of a kind of degree for the angular stability is imparted by this feature as the head of the lock screw is locked into the plate hole. Against the underlying bones, the screw head nowhere presses the plate while tightening the screw which happens in the case of the standard screws such as cancellous bone screws or cortex screws. 

The suitability of Internal fixators for MIPO is due to their great features which include, 

•    The plate is prevented from pressing in the underlying bone due to LHS.
•    Due to LHS as the bone is not pulled against the plate so any kind of primary reduction loss cannot be found. 
•    There is no requirement for the contouring of the plate which is the best advantage for MIPO.
•    The loss of secondary reduction is also prevented due to angular stability. 
•    The headlock screws or internal fixators are easy to be applied in MIPO due to the self-tapping and self-drilling property of the LHS. 

For the distal femur, a specific internal fixator named LISS (Less invasive stabilization system) was designed specifically for the MIPO. The versatility of the system increases with demand and the use of LISS becomes apparent. This later results in the development of the Small locking compression plate (LCP). This Locking Plate for Hand Fracture has a specific function and designed with a combination hole, one half of it is designed as dynamic compression so that it can also be used with the standard screws while the other half is for the application of LHS. When there is only the use of LHS then the LCP can function for both internal fixation and compression plate. 

When the LCP is used as the internal fixator there is no requirement for contouring but in the case of epi-metaphyseal segments of the bone, some amount of contouring can be required. If it is not done, then it can result in becoming prominent subcutaneously or can even result in soft tissue irritation. The introduction of specifically designed metaphyseal plates was done to solve this issue. The plate has a thin juxta-articular end which is its special feature and there are two distal holes which are at an 11-degree angle towards the center of the thinned area. This results in the optimal use of LHS for avoiding penetration of the articular surfaces in the Epiphyseal area. The development of a refined pre-shaped anatomical Locking compression plate for the parts of the metaphysis of the skeleton lowers down so many issues. The major advantage of it is while using the standard screws the indirect fracture reduction occurs. There are various examples of it like, LCP proximal lateral tibia, LCP distal radius, Locking Proximal humerus plate (PHP), LCP distal tibia, and LCP lateral radius. 

Conventional plates and standard screws 

As the locking compression plate is suitable for MIPO, it is also possible to perform it by using standard screws. The use of conventional plates such as limited contact dynamic compression plate and dynamic compression plate along with the fixed condylar screws. For the successful application, while performing such conventional MIPO Implants special precautions are needed to be taken. 

Bridging plates

Majorly with the complex fracture, the bridging plate mode is used despite the use of locking compression or conventional plate in MIPO. Stress concentration and long plates are required to avoid any kind of irregularities while placing holes for screw one and screw two away from the site of fracture. Relative stability is provided with this kind of fixation although it can also impair somehow with the flexibility degree. With the formation of callus, the healing of fractured bones is promoted which is fast and reliable in comparison to primary bone healing. In the case of multifragmentary fractures, it can prove to be helpful.