-- Joel
Photo Credit: eMedicine.com
Clarification: this is not an x-ray of Holbert's knee, but an x-ray of some other poor soul's dislocation.
Aside from the damage to the ACL and PCL it is very possible to also tear either the Lateral Collateral Ligament (LCL) or the Medial Collateral Ligament (MCL). This injury will more than likely also result in some probable meniscus damage to the Posterior(back)/Lateral(outside) portion of the knee. It is also possible to have a fracture of the tibial plateau as well as a dislocated patella.
The bigger issue in this type of injury is the potential damage to the neuro-vascular structures, Particularly the Popliteal artery and the Peroneal nerve. This will be the first thing the Orthopedist will check for once the knee is reduced back into place.
Knee Dislocation Classification (From eORIF.com)
- The knee dislocation is classified by the direction of tibial dislocations: anterior; posterior (increased risk of Popliteal Artery injury); medial; lateral (increased risk of Peroneal Nerve injury).
- With Vascular Injury: closed reduction ASAP followed by a repeat Neuro-Vascular exam. If vascular injury remains acute revascularization is indicated. Arteriogram can be performed in the OR to lessen ischemia (inadequate blood supply (circulation) to a local area due to blockage of the blood vessels to the area.) time. Consider acute repair of postero-lateral structures, capsular structures and avulsion fractures +/- temporary spanning external fixation with delayed ACL/PCL reconstruction.
- Open dislocation: immediate irrigation and debridement. Vascular repair as indicated. Consider acute repair of postero-lateral structures, capsular structures and avulsion fractures +/- temporary spanning external fixation with delayed ACL/PCL reconstruction.
The ACL-PCL Injury
The repair of the PCL injury is virtually the same as the ACL injury, as discussed here, though it is more difficult to gain exposure and to achieve placement of the graft. MCL and LCL injuries rarely require surgical intervention and will heal if properly immobilized.
The Meniscal Tear
As discussed here.
The Tibial Plateau Fracture
When a fracture occurs into or around a joint surface, that joint is at high risk of developing arthritis due to the injury. Unfortunately, even if the bone and cartilage surfaces are lined up perfectly, there is still a risk of developing arthritis due to injury to the cartilage cells.
Treatment:
Non-Displaced Tibial Plateau Fractures
Non-displaced fractures are cracks in the bone seen on x-ray, but with the bones remaining in their proper position and alignment. Most non-displaced fractures of the tibial plateau can be treated without surgery, but they usually require an extended period (about 3 months) of protection from walking.
Some non-displaced fractures are at risk for displacing (shifting position) in the days and weeks following injury, and therefore an orthopedic surgeon must closely watch these injuries. If displacement occurs, surgery may be needed to realign the bone fragments and hold them in position.
Displaced Tibial Plateau Fractures
Displaced fractures often require surgery to realign the bones and restore stability and alignment of the knee joint. There are several surgical options in the treatment of tibial plateau fractures; choosing the type of procedure depends on the fracture pattern--certain types of fractures may or may not be amenable to treatment with a particular type of surgery.
Surgical treatments usually involve the placement of screws and plates into the fractured bone. If the bones are lined up well, this procedure may be treated with small incisions using x-ray to line up the bones. If there is more displacement of the fragments of bone, a larger incision will be needed to piece together the fragments.
To hold the bone fragments in place, either screws alone, or plates and screws can be used. Screws alone are usually used when one piece of bone has broken off, and can be easily repositioned. If the tibial plateau fracture requires additional support, a plate will be placed along the bone to help support the fragments while healing takes place.
This page is a great resource on the tibial plateau fracture.
Peroneal Nerve Palsy
As defined here.
Popliteal Artery Injury
This is the most important collateral injury to be assessed when diagnosing a knee dislocation.
Incidence of vascular injuries is more common w/ posterior than anterior dislocations because of higher force needed to produce this injury and is more likely to result in direct injury & even rupture of popliteal artery (isolated transection). Anterior (front) dislocations cause stretching of the popliteal artery and may lead to intimal disruption & thrombosis (damage is over a longer segment of the artery), fractures of the distal femur or tibial plateau may also cause contusion of popliteal artery with intimal disruption and thrombosis. A pulse deficit is seen in up to 84% of limbs, whereas indications of ischemia are present in only 60%; however, distal pulses, even when obtained by Doppler, do not rule out arterial injury.
Indications for arteriogram are unclear, since cases w/ clinical evidence of vascular injury should proceed immediately to the OR (where an intra-operative arteriogram can be obtained); in most cases, popliteal artery injury is at the level of the knee joint, and an arteriogram in the face of obvious injury is not required and causes unnecessary delay for arterial reconstruction.
Arterial Reconstruction:
Surgical Exposure:
Surgical approach is through a postero-medial incision, which begins at the adductor tubercle and ends distally 10 cm below the joint line; the saphenous vein and nerve are protected. The pes anserinus tendons are transected as are the semimembranosus tendons, 2 cm above their insertions; these can be tagged for lateral closure.
The gastroc is then transected at its tendinous origin, it is necessary to have exposure of the popliteal artery from the adductor hiatus to the trifurcation. Direct exposure of the artery may be difficult due to an associated fracture and hematoma, in this case, first expose uninvolved areas of the arterial system where proximal and distal control of popliteal artery are obtained.
The vessel is then debrided; and grafting w/ contra-lateral saphenous vein is procedure of choice except in select cases in which an end-to-end anastomosis can be accomplished without undue tension.
Prosthetic grafts should be reserved for use in those pts in whom saphenous vein grafting is not possible. Note that in general prosthetic grafts have a poor tract record when used below the knee. Completion arteriography outlines any technical defects. A fasciotomy may be performed to reduce the incidence of a compartment syndrome at this point if needed.