Improperly placed anterior cruciate ligament grafts: correlation between radiological parameters and clinical results

[Intraoperative quality control of the placement of bone tunnels for the anterior cruciate ligament]

The reconstruction of a ruptured anterior cruciate ligament (ACL) is a frequently performed operation, however technically demanding with a revision rate of approximately 10%. The correct placement of bone tunnels in femur and tibia is the most important variable to achieve a successful outcome. A distinct knowledge of the anatomic insertion sites is crucial. The ideal location for the femoral bone tunnel is achieved when a 1-2 mm posterior wall is left to the over-the-top position and when the entry to the bone tunnel is at 10 o'clock (right knees) or 14 o'clock (left knees) in the frontal plane. The femoral bone tunnel can be drilled through the tibial bone tunnel (transtibial technique) or through an anteromedial arthroscopic portal. According to recent studies the use of an anteromedial portal helps to reduce the risk of misplacement of the bone tunnel. The center of the tibial bone tunnel should be located on an imaginary line between medial border of the anterior horn of the lateral meniscus and the medial tibial spine. The position of the tibial guide wire has to be far enough posterior to avoid impingement of the graft with the roof of the intercondylar notch. Measures for quality control include the intraoperative use of an image intensifier (fluoroscopy), instrumented laxity measurements and a postoperative radiograph in 2 planes. The use of computer assisted surgery cannot routinely be recommended at present.

Revision anterior cruciate ligament reconstruction using autografts with a polyester fixation device

Twenty-nine patients who had undergone anterior cruciate ligament (ACL) revision were evaluated retrospectively between 1992 and 2000. A similar surgical technique was used in all cases. Twenty-six patients underwent revision following failed primary and revision surgery with the ABC scaffold ligament. There were 2 failed primary semitendinosus/gracilis (STG) autografts and one failed bone patella tendon bone (BPTB) autograft. Autologous hamstring tendons (STG) were used in 26 knees, quadriceps tendon in 2 and BPTB autograft in 1 knee. The Mark I Soffix soft tissue fixation device was used in 16 patients and 13 patients underwent reconstruction with the Mark II BH (Button Hole ) Soffix. Follow up evaluation included clinical examination, KT 2000 arthrometric side to side difference (SSD) assessment, Lysholm, Tegner and IKDC scoring. The average follow up time was 50+/-22 months. The overall SSD was 1.66+/-1.5 mm, a mean Lysholm score of 87.2+/-12.5 was obtained and 22 patients had an IKDC score of nearly normal (B). In the Mark II (BH Soffix) group knees were significantly tighter than in the Mark I Soffix group (P<0.05) with a mean SSD of 1.23+/-1.3 and 2.0+/-1.6 mm, respectively. However there were no significant differences in the other measured parameters between the two fixation devices. Multiply re-operated knees tended to have lower IKDC and Lysholm scores (not statistically significant). We concluded that the technique reported in this study can restore stability to the knee following failed primary or revision ACL reconstruction and the results in the non-multiply operated knees are comparable to primary reconstruction.

Anterior cruciate ligament tunnel placement: Comparison of insertion site anatomy with the guidelines of a computer-assisted surgical system

PURPOSE

With the development of computer-assisted surgery (CAS) systems, the surgeon's ability to operate a CAS planning station will become essential. For example, default parameters in computed tomographic (CT) data are being used to place tunnels in anterior cruciate ligament (ACL) reconstruction. The goal of this study was to compare the location of the insertion sites in ACL reconstruction anatomically, via roentgenographic images and via CT scan data and to validate these tunnel placement parameters.

TYPE OF STUDY

Cadaveric analysis.

METHODS

Eight human cadaveric knees were marked with 6 copper wires 1 mm in diameter around the circumference of the insertions of the ACL. Using lateral roentgenograms and CT scans that were subsequently transferred to the CAS planning station, the tunnel locations were determined. These were based on a distance from the back of the condyle (location A) and from the roof of the notch (location B) on the femur and on a distance posterior from the tuberosity to the posterior margin along the tibial plateau, which is set as the CAS planning station's default. Locations according to roentgenograms and CT scans were then compared and the accuracy of the CAS planning station was assessed.

RESULTS

Comparison of roentgenograms and CT revealed a femoral insertion at 27.5% +/- 3.2% and 26.9% +/- 3.5% (roentgenograms) and 26.6% +/- 1.9% and 26.3% +/- 2.4% (CT), respectively. The CAS planning station provided a tunnel location that was 1.3 +/- 1.0 mm (0.3 to 2.5 mm) away from the actual femoral ACL insertion. The tibial tunnel was placed according to the copper wire markers and was found to be at 46.2% +/- 2.8% (roentgenograms) and 45.4% +/- 2.1% (CT). No statistical differences between position in CT and roentgenograms could be detected (P >.05).

CONCLUSIONS

The compared methodologies showed similar locations of the ACL insertions, assuring accurate preoperative planning with the CAS system. However, the CAS system requires adjustment to each individual knee anatomy.

Accuracy of anterior cruciate ligament tunnel placement with an active robotic system: a cadaveric study

PURPOSE

The objective of this study was to evaluate the accuracy of tunnel placement for ACL reconstruction performed with an active robotic system.

TYPE OF STUDY

Cadaveric analysis.

METHODS

A reference screw containing 4 fiducials was placed in the femur and tibia of 13 fresh-frozen cadaveric knees. A preoperative plan was developed using images from 3-dimensional computed tomography reconstructions of the knee. The active robotic system then drilled the tunnels. The location and direction of each planned tunnel in the femur and tibia were determined from the preoperative plan. To compare these parameters postoperatively, a mechanical digitizer and a tunnel plug were used. The deviation in location and direction between the planned and drilled tunnel was determined.

RESULTS

In preliminary trials, the tibial tunnel was located inaccurately because slippage of the drill bit occurred on the bone at the start of tunnel drilling. This was minimized by decreasing the feed rate of the robot by 75%. For the remaining 10 knees, deviations with respect to the preoperative plan were found of 2.0 +/- 1.2 mm and 1.1 degrees +/- 0.7 degrees for the intra- articular tibial tunnel location and direction, respectively. For the femur, the deviations were 1.3 +/- 0.9 mm for the tunnel location (intra-articular) and 1.0 degrees +/- 0.6 degrees for the tunnel direction.

CONCLUSIONS

The active robotic system is highly accurate for tunnel placement during ACL reconstruction, meaning that the robot drills the tunnels very close to the surgeon's plan. Comparison to a control group of surgeons could not be made because no preoperative plan is usually created in traditional surgery. However, accuracy values in this study were found to be below the values for precision of repeated tunnel placements reported in the literature.

An audit of tunnel position in anterior cruciate ligament reconstruction

We audited 114 primary anterior cruciate ligament (ACL) reconstructions. Notes were reviewed and tunnel positions assessed on lateral and AP radiographs. A literature review established optimal tunnel position. Sixteen surgeons performed 57 arthroscopic and 57 open reconstructions, using 24 hamstring and 90 bone-tendon-bone autografts. Eighty-five sets of radiographs were available for review. Sixty-five percent of femoral tunnels and 59% of the tibial tunnels were malpositioned in the sagittal plane. Guidelines for best practice are required for key procedures in each speciality. Tunnel position in ACL reconstruction can be easily measured and should be correct in at least 90% of cases.