Equipment For Diagnostic Arthroscopy The previous section details the equipment required for diagnostic arthroscopy. Over and above the equipment mentioned in previous chapter, surgeons use a special instrument called Probe that acts like his/her finger. Surgeons use this probe to feel the structures as many a times the defects on soft tissue are not visible and have to be ‘probed’. Probe is a metallic rod-like structure that enters through the portal and can be moved around in the joint without causing any damage to the soft tissue present inside. Thus, obviously, a probe is blunt at its tip. Also, probes come with hooked tips to facilitate probing in and around menisci. While these equipment suffice for diagnosing the disorders or diseases in the knee of the patient, the surgeon is at a loss when he decides to treat these disorders. To treat the disorders, a surgeon requires surgical instruments that can enter the knee through tiny portals made for diagnostic arthroscopy and yet perform all the procedures that the surgeon would in open surgeries. Modern technology has made available instruments that range from simple mechanic ones to complex electric gizmos that serve nearly all the purposes of knee surgeries. There are simple scissors, punches and graspers and there are shaver systems that use motors to cut soft tissue or even abrade hard bone. While going through such surgical instruments, we will first cover manual instruments and then move onto motorised systems and finally joint specific products that are manual but are used in treatment of specific joints only.
Hand Held Manual Instruments As in open surgeries, arthroscopy also finds use of scissors, graspers and punches in surgeries. It should be noted that though they have the same names and functions as their open surgery counterparts, the design of arthroscopy manual instruments is different as it has to provide for the needed levels of strength in extremely thin (around 2-3mm diameter) instruments at the same time maintaining the precision and sharpness to avoid resection of healthy tissue and ensuring minimum surgeon discomfort. Other features that contribute to making a good hand held instrument are maneuverability and safety. Maneuverability is desired to negotiate in the tight spaces of joints like knee and safety is essential to take maximum care of the patient.
The manual instruments typically have three distinct parts, viz.
Motorised Shaver System Besides hand held manual instruments, surgeons also use motorised systems that resect the damaged soft tissue using powered instrumentation. This powered instrumentation that is used for soft tissue resection is called as Shaver System. Shaver system shaves off the unwanted, defective soft tissue. The shaver system comprises of a control unit, a motor drive unit and a foot switch. The actual shaving devise, blades, attach to the motor drive unit and are controlled using the foot switch. The blades perform this function of shaving by rotating in high RPM and cutting the soft tissue with their sharp edges. This rotation of blades is in three directions, clockwise, anti-clockwise and oscillatory. The control unit provides attachment for motor drive unit and the foot switch. It also, generally, displays the speed and direction of rotation of the attached blades. Foot switch provides buttons for controlling the direction of rotation of blades. The motor drive unit is the main part of the shaver system and it is this part which contains the main motor that drives the blades. Motor drive unit also provides for suction of the recessed tissue. Shaver system is used for Synovectomy and resection of other damaged soft tissue in the joint. It is also useful in abrading bones. Modern day shaver systems also act as powered instruments for drilling and sawing hard tissues like bones. Arthroscopy surgeons need to drill or saw bones during ACL/PCL reconstruction surgeries. Besides the ordinary motor drive unit for blades, they also provide for attachment of drill and saw drives. This addition of function necessitates another motor drive unit. Thus, two different motor drive units are used and each is activated when required. Another very important part of any shaver system is the blade that does the actual cutting/shaving. The construction of a blade is similar to that of a scope by virtue of being a cylinder enclosed inside a cylinder. The similarity ends here. Blade is made up of two hollow, concentric cylinders. Each cylinder has a window-like opening at its distal end. The edges of this window vary with the type of blade. The edge can be either toothed or entire but equally sharp. The outer cylinder is fixed while the inner one rotates at high RPM generated by the motor drive unit. The cutting mechanism is achieved by trapping the soft tissue between the edges of two cylinders and slicing across it. It is possible to cut fine edges in the soft tissue without pulling it because of the high speed of blades. Besides blades, burrs also attach to the motor drive unit. Burrs are used for abrading bones. They are different from blades in that instead of having a window at the distal end, they end up in a bulb-like structure which has ridges running down its entire periphery. The material is very hard and ridges very sharp. This combination abrades hard tissue like bone in seconds. At the proximal end of blades/burrs, hubs are provided that engage with the receptacles built inside the motor drive unit. The attachment of blades to the motor drive unit is possible because of these hubs. These hubs are different for different makes making it impossible to use blades of one make with shaver of another. Blades are available in two varieties, reusable and disposable. In any medical equipment business, patient safety is of paramount importance. Disposable blades are in line with this maxim. Anything that enters the body of patient has to be void of all infection. This necessitates the complete sterility of the instrument. Even if reusable blades are autoclaved, they are not 100% infection free. All instruments are minimally infected only untill they are in their sterile packs. Hence, it is advisable to use only those instruments that are opened
Joint Specific Products All the units discussed so far have covered equipment that can be used for Arthroscopy in general. We have discussed them in light of knee but they find equal use in Shoulder, Ankle and other joints. Since the incidence of disorders in knee are more frequently treated arthroscopically, many specialised instruments have been developed for this particular joint. The three most specialised procedures for the knee are Meniscal Repair, ACL/PCL Reconstruction and MosaicPlasty. Of these, the first two procedures are solely for the knee while MosaicPlasty is also done on Ankle. All the instruments that are used for these procedures, with an exception of powered drill for ACL/PCL reconstruction, are manual in nature. These instruments are also very technique specific. Comparatively recent in origin, these techniques are fast gaining popularity among orthopaedic surgeons due, mainly, to increasing sophistication in the instrumentation. Also ACL/PCL reconstruction and meniscal repair is gaining importance because of increasing awareness towards sports medicine. These disorders have maximum incidence in sports persons because of their high activity levels. It should be understood that all these procedures can be carried out using open techniques but are increasingly done only endoscopically because of the latter’s advantages.
ACL/PCL Reconstruction Rupture of ACL is one of the most common injury among sportsmen playing physically demanding games like Soccer, Hockey, Basket Ball, etc. On rupture of ACL, though the patient does not suffer from lots of pain, his/her knee does ‘pop’ during walking or any other activity. If the patient history suggests that he/she has suffered from one of the incidents that could lead to ACL rupture and if it is coupled with this ‘pop’ during walking, he/she is diagnosed for ACL failure.
Diagnosis for ACL is done in three ways:
Surgical Technique For ACL Reconstruction
Once the diagnosis confirms the rupture/failure of ACL, the surgeon proceeds to treat the patient. As the ACL cannot be repaired, the only option to treat the patients suffering from this disorder is to replace this ligament. The basis of selection of replacement graft is as discussed in the chapter dealing with Anatomy and disorders of the Knee. Today, the surgeon has a wide choice of grafts to select from:
As discussed earlier, though Patellar tendon is a popular graft for ACL/PCL, it has two distinct disadvantages, viz. Weakened Patella making it prone to fractures and affected Patellar tracking causing Patello-Femoral pain. Use of Semi Tendinosus ligament takes care of both these problems. Allografts are grafts taken from other individuals. This is required in multiple ligament tears as in case of trauma. But these grafts suffer from the disadvantage of possible transmission of infection/diseases. Finally, attempts have been made to make artificial ligaments but have shown very less strength. Because of this, artificial ligaments have not gained that wide an acceptance so far. In present circumstances, Hamstring graft is gaining maximum popularity and acceptance. A quadrupled soft tissue graft suits the needs of ACL just fine. Semi Tendinosus graft is not preferred only if the LCL and/or MCL are not in order.
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