**4.5 Arthroscopy technique**

250 Modern Arthroscopy

Despite the clinical experience, most patients with symptomatic TKA complain about anterior knee pain, there is small number of patients with posterior knee pain. Although a rare scenario it can be painful and debilitating for the patients with total knee replacements. There is limited evidence in the literature regarding this particular impingement, probably because of difficulty in diagnosing the pathology. Diduch has reported only 4 cases of PCL stump impingement in his study on cruciate substituting knees. The posterior cruciate ligament stump may be quite prominent in the case of posterior cruciate sacrificing (PS) knees and are prone for impingement and interference with cam mechanism. Rarely, PCL impingement as a whole can also be seen after total knee replacement using cruciate retaining prosthesis, especially if the debridement around the notch and PCL is inadequate.

Generally in a routine total knee replacement using cruciate sacrificing prosthesis, removing the PCL makes it easier to balance the collateral ligaments. Since the evolution of high flexion mobile bearing posterior cruciate ligament substituting knee designs, it is necessary to completely resect the PCL. Any residual stump of the PCL may impinge in the cam/spine mechanism causing pain and limited motion. Keeping in mind, resection of the PCL may influence the height of the flexion and extension gaps. It has been postulated, that most likely, it is the postero-medial bundle of PCL stump, which is the main culprit. However, there have been only few reported cases of PCL impingement after cruciate retaining total

The patients usually come with severe posterior knee pain while flexing of the knee over 70° to 90°, which increases posterior translation of the tibia. This is seen when the PCL stump from the intercondylar notch gets entrapped in the medial tibio-femoral joint, resulting in severe posterior pain. This residual stump can get incarcerated and interfere with cam

It is very hard to diagnose PCL stump impingement clinically as the symptoms are not usually typical. Special scans like MRI and CT scans are also of limited value due to their scatter and artifacts associated with metallic implants. However, arthroscopy has an important role in this with regards to both diagnostic and therapeutic significance. If an arthroscopy is performed in these patients, it is recommended a complete inspection of the joint including the posterior compartments as is done in non-TKA patients with posterior

Non-operative treatments involve measures for pain relief and frequent visits to the physical therapists. These measures are effective only in few cases, since patients continue to be in a vicious cycle of increasing pain and reduced range of movement. As we know it is usually confirmed only on arthroscopy, it can certainly be treated at the same time. Diduch, in his

**4. Posterior cruciate ligament stump impingement** 

**4.1 Pathogenesis** 

knee replacements.

**4.2 Clinical features** 

**4.3 Investigations** 

knee pain.

**4.4 Treatment** 

mechanism of the knee preventing any further flexion.

Literature suggests that on few occasions' additional portals to assist adequate visualization of the posterior compartments and also to avoid iatrogenic damage to prosthetic component in a struggle to see at the back of total knee replacement is required. Although Diduch describes adequate view with standard anterior portals, there are suggestions of posteromedial and posterolateral portals in addition to the standard anterior ones (Landsiedl). Before attempting to see into posterior compartment, it is advised to release or resect any adhesions, which enables complete inspection of the anterior compartment of the knee joint, including soft tissue impingements, evaluation of the inlays and tracking of the patella.

It is recommended, through the standard anteromedial portal, a wide semicircular notchplasty should be performed (diameter of about 8 to 10 mm) in the posterior superolateral region of the notch just above the posterior condyle of the femoral component, to allow entrance of the arthroscope into the posterolateral compartment from the anteromedial portal. Due to the semicircular shape of the notchplasty, the arthroscope and the resecting instruments are mobile and otherwise inaccessible areas can be inspected and treated. A 1.2-mm can be inserted through posterolateral portal into the joint under arthroscopic control. A posterolateral portal is established with a stab incision. After blunt preparation down to the capsule, a working cannula is inserted using a sharp trocar for penetration parallel to the cannula to avoid slipping along the posterolateral capsule, frequently happens with blunt trocars. This usually provides an adequate view of the posterolateral compartment. Impingement of degenerated tissue in flexion can be seen much better from this portal than from the trans-fossa approach. Similarly, posteromedial portal can be established to work your way around the PCL stump. After resection of the PCL stump and its posterior synovial sheath, the posteromedial compartment can be inspected completely using the anteromedial or posterolateral portals.

#### **4.6 Technical challenges**

Technical problems lay in mirror images with problems in orientation, and the possibility of damaging the components by manipulation of the optic sheet or motorized instruments. The key points are the exact location of the portals and a smooth introduction of the trocar. For orientation, the use of a probe is mandatory to distinguish between reality and mirror image. The use of additional portals helps to avoid damaging the prosthesis components, especially by using motorized shavers and visualizing the tracing behavior of the patella. Alterations to the surface of cobalt-chromium femoral components can occur during arthroscopy with stainless-steel cannulae. Damage and degradation of the articulating surfaces of a total knee replacement have been associated with release of wear debris. There is a correlation between surface roughness of cobalt-chromium femoral components and polyethylene wear of the tibial component. In addition, studies have shown extensive foreign-body giant-cell reactions to polyethylene particles and synovial membrane reactions to loose cobalt chromium particles. To avoid this Raab recommends the use of plastic cannulae instead of metallic ones.

Arthroscopy Following Total Knee Replacement 253

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Fig. 12. PCL impingement seen during arthroscopic examination of PCL retaining prosthesis.
