Surgically oriented measurements for three-dimensional characterization of tunnel placement in anterior cruciate ligament reconstruction

Vault perforation after eccentric glenoid reaming for deformity correction in anatomic total shoulder arthroplasty

BACKGROUND

The management of glenoid deformity during anatomic total shoulder arthroplasty remains controversial. In this study, we evaluate variable correction of glenoid deformity by eccentric reaming. We hypothesize that partial correction of modified Walch B/C-type glenoid deformities can achieve 75% bone-implant contact area (BICA) with a reduced vault perforation risk compared with complete correction.

METHODS

Fifty shoulder computed tomographic scans with glenohumeral osteoarthritis were retrospectively evaluated. The Tornier BluePrint v2.1.5 software simulated 3 eccentric reaming scenarios including no, partial, and complete deformity correction. Each scenario was evaluated at 4 BICAs and using 3 implant fixation types. Three-dimensional surface representations were used to evaluate medialization and vault perforation.

RESULTS

The patients had mean glenoid retroversion and inclination of 18.5° and 8.8°, respectively, and mean posterior humeral head subluxation of 76%. With 75% BICA, the 3 fixation types had glenoid vault perforation in 6%-26% and 26%-54% of cases for partial and complete glenoid deformity correction, respectively. The central and posterior-inferior implant components were most likely to perforate across all scenarios.

DISCUSSION

Eccentric reaming for glenoid deformity correction increases the risk of vault perforation. Severe glenoid deformity required increased medialization to achieve 75% BICA. Pegged implants have increased chances of perforation compared with a keeled design; the central and posterior-inferior components were most likely to perforate during deformity correction.

CONCLUSION

Partial deformity correction of modified Walch B/C-type glenoid deformities can achieve 75% BICA while reducing the risk of vault perforation compared with complete correction at the time of anatomic total shoulder arthroplasty.

Anatomic ACL reconstruction: the normal central tibial footprint position and a standardised technique for measuring tibial tunnel location on 3D CT

PURPOSE

The aim of this study was to define the normal ACL central tibial footprint position and describe a standardised technique of measuring tibial tunnel location on 3D CT for anatomic single-bundle ACL reconstruction.

METHODS

The central position of the ACL tibial attachment site was determined on 76 MRI scans of young individuals. The central footprint position was referenced in the anterior-posterior (A-P) and medial-lateral (M-L) planes on a grid system over the widest portion of the proximal tibia. 3D CT images of 26 young individuals had a simulated tibial tunnel centred within the bony landmarks of the ACL footprint, and the same grid system was applied over the widest portion of the proximal tibia. The MRI central footprint position was compared to the 3D CT central footprint position to validate the technique and results.

RESULTS

The median age of the 76 MRI subjects was 24 years, with 32 females and 44 males. The ACL central footprint position was at 39 (±3 %) and 48 (±2 %), in the A-P and M-L planes, respectively. There was no significant difference in this position between sexes. The median age of the 26 CT subjects was 25.5 years, with 10 females and 16 males. The central position of the bony ACL footprint was at 38 (±2 %) and 48 (±2 %), in the A-P and M-L planes, respectively. The MRI and CT central footprint positions were not significantly different in relation to the medial position, but were different in relation to the anterior position (A-P 39 % vs. 38 %, p = 0.01). The absolute difference between the central MRI and CT reference positions was 0.45 mm.

CONCLUSIONS

The ACL's normal central tibial footprint reference position has been defined, and the technique of measuring tibial tunnel location with a standardised grid system is described. This study will assist surgeons in evaluating tibial tunnel position in anatomic single-bundle ACL reconstruction.

LEVEL OF EVIDENCE

III.

Variability of landmark acquisition affects tunnel calculation in image-free ACL navigation

PURPOSE

The purpose of this study was to determine the inter- and intraobserver variability of intraarticular landmark identification for tunnel position calculation in image-free anterior cruciate ligament (ACL) navigation.

METHODS

In a test/retest scenario, thirteen experienced ACL surgeons (>50 reconstructions year) experienced in image-free ACL navigation were asked to identify the landmarks required for image-free ACL navigation in the same cadaver knee. Landmark positions were registered using a fluoroscopic ACL navigation system. Positions were determined using validated radiological measurement methods. For variability analysis, mean positions, deviations between the test/retest positions, standard deviations (SD) and range were calculated.

RESULTS

Interobserver analysis showed a mean variability (SD) for the tibial landmark positions of 3.0 mm with deviations of up to 24.3 mm (range). Mean femoral landmark variability was 2.9 mm (SD) with deviations of up to 11.3 mm (range). Intraobserver analysis showed a tibial reproducibility of 2.2 mm (SD 2.0 mm; range 10.9 mm) and a femoral of 1.9 mm (SD 1.9 mm; range 10.4 mm).

CONCLUSION

The data of the presented study suggest that a considerable inter- and intraobserver variability in intraarticular landmark identification exists. Reasonable ranges were found that have to be considered as a potential risk for miscalculation of tunnel positions in image-free ACL reconstruction.

CLINICAL RELEVANCE

Landmark acquisition affects tunnel calculation in image-free ACL.

LEVEL OF EVIDENCE

IV.

Three-dimensional characterization of the femoral footprint of the posterior cruciate ligament

PURPOSE

The purpose of this study was to define an anatomic standard for the femoral footprint of the posterior cruciate ligament (PCL) based on 3-dimensional (3D) surface reconstructions of computed tomography (CT) scans of cadaveric knees.

METHODS

The femoral insertion of the PCL was identified and marked with drill holes in 7 cadaveric knees. CT scans were performed on each specimen, and 3D computer models were generated. The distance from the condyle edges to the margins of the footprint were referenced to the total condylar size parallel and perpendicular to the femoral axis and intercondylar notch.

RESULTS

The mean ratio of the anteroposterior width of the medial femoral condyle referenced parallel to the intercondylar notch measured 0.08 ± 0.02 for the anterior border, 0.60 ± 0.08 for the posterior border, 0.16 ± 0.05 for the proximal border, and 0.44 ± 0.06 for the distal border. The mean ratio of the superior-inferior height of the medial femoral condyle with respect to the apex of the intercondylar notch corrected and referenced perpendicular to the intercondylar notch measured 0.14 ± 0.04 for the anterior border, 0.44 ± 0.07 for the posterior border, 0.03 ± 0.02 for the proximal border, and 0.56 ± 0.07 for the distal border.

CONCLUSIONS

This cadaveric study provides an anatomic reference for mathematical analysis of the femoral PCL footprint using CT-based 3D topographic modeling. The average PCL center point is located 25% down from the roof of the notch and 38% from anterior to posterior from the anterior condyle with regard to total medial femoral condyle length.

CLINICAL RELEVANCE

This study provides a standard of measurement for future studies that use advanced imaging to evaluate the accuracy of PCL reconstruction.

Variability in ACL tunnel placement: observational clinical study of surgeon ACL tunnel variability

BACKGROUND

Multicenter and multisurgeon cohort studies on anterior cruciate ligament (ACL) reconstruction are becoming more common. Minimal information exists on intersurgeon and intrasurgeon variability in ACL tunnel placement. Purpose/

HYPOTHESIS

The purpose of this study was to analyze intersurgeon and intrasurgeon variability in ACL tunnel placement in a series of The Multicenter Orthopaedic Outcomes Network (MOON) ACL reconstruction patients and in a clinical cohort of ACL reconstruction patients. The hypothesis was that there would be minimal variability between surgeons in ACL tunnel placement.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Seventy-eight patients who underwent ACL reconstruction by 8 surgeons had postoperative imaging with computed tomography, and ACL tunnel location and angulation were analyzed using 3-dimensional surface processing and measurement. Intersurgeon and intrasurgeon variability in ACL tunnel placement was analyzed.

RESULTS

For intersurgeon variability, the range in mean ACL femoral tunnel depth between surgeons was 22%. For femoral tunnel height, there was a 19% range. Tibial tunnel location from anterior to posterior on the plateau had a 16% range in mean results. There was only a small range of 4% for mean tibial tunnel location from the medial to lateral dimension. For intrasurgeon variability, femoral tunnel depth demonstrated the largest ranges, and tibial tunnel location from medial to lateral on the plateau demonstrated the least variability. Overall, surgeons were relatively consistent within their own cases. Using applied measurement criteria, 85% of femoral tunnels and 90% of tibial tunnels fell within applied literature-based guidelines. Ninety-one percent of the axes of the femoral tunnels fell within the boundaries of the femoral footprint.

CONCLUSION

The data demonstrate that surgeons performing ACL reconstructions are relatively consistent between each other. There is, however, variability of average tunnel placement up to 22% of mean condylar depth, likely reflecting the difference in individual surgeons' preferred tunnel locations. Individual surgeons are relatively consistent in their cases of ACL tunnels.

Arthroscopic agreement among surgeons on anterior cruciate ligament tunnel placement

BACKGROUND

Little is known about surgeon agreement and accuracy using arthroscopic evaluation of anterior cruciate ligament (ACL) tunnel positioning.

PURPOSE

To investigate agreement on ACL tunnel position evaluated arthroscopically between operating surgeons and reviewing surgeons. We hypothesized that operating and evaluating surgeons would characterize tunnel positions significantly differently.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve surgeons drilled ACL tunnels on 72 cadaveric knees using transtibial (TT), medial portal (MP), or 2-incision (TI) techniques and then completed a detailed assessment form on tunnel positioning. Then, 3 independent blinded surgeon reviewers each arthroscopically evaluated tunnel position and completed the assessment form. Statistical comparisons of tunnel position evaluation between operating and reviewing surgeons were completed. Three-dimensional (3D) computed tomography (CT) scans were performed and compared with arthroscopic assessments. Arthroscopic assessments were compared with CT tunnel location criteria.

RESULTS

Operating surgeons were significantly more likely to evaluate femoral tunnel position (92.6% vs 69.2%; P = .0054) and femoral back wall thickness as "ideal" compared with reviewing surgeons. Tunnels were judged ideal by reviewing surgeons more often when the TI technique was used compared with the MP and TT techniques. Operating surgeons were more likely to evaluate tibial tunnel position as ideal (95.5% vs 57.1%; P < .0001) and "acceptable" compared with reviewers. The ACL tunnels drilled using the TT technique were least likely to be judged as ideal on the tibia and the femur. Agreement among surgeons and observers was poor for all parameters (κ = -0.0053 to 0.2457). By 3D CT criteria, 88% of femoral tunnels and 78% of tibial tunnels were placed within applied criteria.

CONCLUSION

Operating surgeons are more likely to judge their tunnels favorably than observers. However, independent surgeon reviewers appear to be more critical than results of 3D CT imaging measures. When subjectively evaluated arthroscopically, the TT technique yields more subjectively poorly positioned tunnels than the TI and MP techniques. Surgeons do not agree on the ideal placement for single-bundle ACL tunnels.

CLINICAL RELEVANCE

This study demonstrates that surgeons do not currently uniformly agree on ideal single-bundle tunnel placement and that the TT technique may yield more poorly placed tunnels.