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Re: LISS failure
Andrew H. Schmidt 11 Сентябрь 2004, 16:40
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Although I agree with the comments of the others who have responded, I wanted to add some other information gleaned from my own experience with this device.
In this case, the fixation might have failed because of inadequate purchase of the side plate to the shaft. I say this because the initial lateral xray shows that the plate seems to be fairly anterior to the mid-axis of the femoral shaft. Once the plate pulled off of the shaft, it continued to pull out of the distal segment. With the short unicortical screws used for shaft fixation, it is imperative that the plate be applied precisely at the midline (widest diameter) of the femur. If it is applied even slightly anterior or posterior to the midline, the screws just don¹t engage the cortex. You can¹t tell by feel, since the screws lock firmly into the plate.
The only guidance that imaging provides is to visualize the plate centered exactly on the bone on a good lateral projection, which is difficult to obtain intra-operatively. I have resorted to making a 3-4 cm incision at the top of the plate so that I can verify that the plate is exactly centered over the femur at its proximal tip.
A second "pearl" is to place at least one or 2 lag screws between the condyles for intrafragmentary fixation before applying the LISS. Although screws were used across the coronal plane (Hoffa) fracture, I do not see any lag screws from lateral to medial. The LISS screws are designed to maintain the reduction of the distal femoral condylar mass to the shaft, but they do not function as lag screws. The intra-articular portion of the fracture demands open reduction and rigid internal fixation according to established
principles; the LISS is used to then stabilize the reconstructed distal femur to the shaft.
I think that this could be revised any way that one wishes basically starting over at the beginning. The femoral condyles are first reduced and stabilized with lag screws, then whatever plate one is comfortable with could be used to bridge the metaphysis. If the LISS is used again, be sure that the plate is precisely positioned.
Andy Schmidt
--
Andrew H. Schmidt, M.D.
Faculty, Hennepin County Medical Center
Assoc. Professor, Univ. of Minnesota
Minneapolis, MN
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Re: LISS failure
Josep M. Muсoz Vives 11 Сентябрь 2004, 18:49
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In this case, the fixation might have failed because of inadequate purchase of the side plate to the shaft. I say this because the initial lateral xray shows that the plate seems to be fairly anterior to the mid-axis of the femoral shaft. Once the plate pulled off of the shaft, it continued to pull out of the distal segment. With the short unicortical screws used for shaft fixation, it is imperative that the plate be applied precisely at the midline (widest diameter) of the femur. If it is applied even slightly anterior or posterior to the midline, the screws just don’t engage the cortex.
I was teached not to put the plate in the middle of the shaft in a true lateral view of the femur, but rather slight anterior and internally rotated so the end part will adapt to the trapezoid shape of condyles, but still the screws will be in the maximum diameter of the shaft. On the post-op X-ray you can see a true lateral view of the femur (the posterior part of the condyles are aligned) but not of the plate (you can see them coming under). I can assure you that the plate was completely centered on the shaft.
You can’t tell by feel, since the screws lock firmly into the plate.
But you can tell by the drilling.
The only guidance that imaging provides is to visualize the plate centered exactly on the bone on a good lateral projection, which is difficult to obtain intra-operatively.
On intraoperative fluoroscopy with external rotation of the thight we confirmed that the plate was completely centered in that case.
A second “pearl” is to place at least one or 2 lag screws between the condyles for intrafragmentary fixation before applying the LISS. Although screws were used across the coronal plane (Hoffa) fracture, I do not see any lag screws from lateral to medial.
I fully agree with you, we should have used lag screws between the two condyles.
Dr. Josep M. Muñoz-Vives
Hospital Dr. Josep Trueta.
Girona
Catalonia
Spain
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Re: LISS failure
Kevin Pugh 11 Сентябрь 2004, 18:53
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Andy's point is valid. You must place the screws at the widest diameter to avoid the screw that is cortical only.
That being said, it can be oriented at any point on the "tube". The way I check it is to get a true "head on" view of the plate with the c-arm. If it is in the middle of the femur, you have accomplished your goal, and the screws will be safe.
In this case, the condyles require independent fixation. You have to make a joint before you can put it on the shaft.
Kevin J. Pugh, MD
Chief, Division of Trauma
Department of Orthopaedics
The Ohio State University
N1022 Doan Hall
410 W. 10th Avenue
Columbus, OH 43210
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Re: LISS failure
Mike Shnider 11 Сентябрь 2004, 19:23
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To my mind- remove all hardware, try to reposit the articular surface with 2-3 canulated screws,and
after - fixation by ex-fix (Fixano or AO)
M.Schnider
Haifa
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