The "Comma" Sign Following Arthroscopic Anterior Cruciate Ligament Reconstruction

Basso O, Johnson D, Jewell F, Wakeley C

Following arthroscopic anterior cruciate ligament (ACL) reconstruction using the bone-patella tendon-bone (BPTB) graft technique, radio-opacities were noted on the lateral and postero- anterior post- operative radiographs of the operated knees. A stripe of radio- opaque material of curvilinear shape, resembling a comma termed the Œcomma¹ sign occupied an area in close contact with the lateral femoral condyle. The records and radiographs of 50 consecutive cases of BPTB - ACL reconstruction were reviewed and the radiological features of the radio- opacities were defined. The roentgenographic and clinical findings were correlated.

The results demonstrated that there was no statistically significant difference between the patients presenting the radio-opacity and those without it, in terms of loss of motion at six, twelve, twenty- six and fifty- two weeks postoperatively (P>0.50). Assessment of the roentgenographic progression, made on a second set of radiographs taken between 3 and 6 months postoperatively, disclosed that this radio- opaque material tended to disappear early in the postoperative period. No correlation was found between presence of radio- opacities and other postoperative clinical features such as duration of pain, effusion, analgesia requirement, discharge timing, time to driving and time to work. A protocol of postoperative early weight- bearing mobilisation had been followed in all cases which may have played a role in promoting the faster dissolution of the debris.

The "Comma" sign was deemed to have been caused by the swarf and cancellous debris, produced by arthroscopic drilling of the femoral screw hole, which accumulated in the postero- lateral joint space as a result of the figure- of- four position of the leg during drilling. The debris did not result in any pain, additional swelling, loss of motion, arthrofibrosis or delay rehabilitation compared to a normal group of patients. Nevertheless, it is recommended that, following endoscopic ACL reconstruction, a thorough irrigation of the postero- lateral compartment be routinely carried out.

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