Musa Citak

The Effect of Medial Versus Lateral Meniscectomy on the Stability of the Anterior Cruciate Ligament-Deficient Knee

Background: The pivot shift is a dynamic test of knee stability that involves a pathologic, multiplanar motion path elicited by a combination of axial load and valgus force during a knee flexion from an extended position. Purpose: To assess the stabilizing effect of the medial and lateral meniscus on anterior cruciate ligament-deficient (ACL-D) knees during the pivot shift examination. Study Design: Controlled laboratory study. Methods: A Lachman and a mechanized pivot shift test were performed on 16 fresh-frozen cadaveric hip-to-toe lower extremity specimens. The knee was tested intact, ACL-D, and after sectioning the medial meniscus (ACL/MM-D; n = 8), lateral meniscus (ACL/LM-D; n = 8), and both (ACL/LM/MM-D; n = 16). A navigation system recorded the resultant anterior tibial translations (ATTs). For statistical analysis an analysis of variance was used; significance was set at P < .05. Results: The ATT significantly increased in the ACL-D knee after lateral meniscectomy (ACL/LM-D; P < .05) during the pivot shift maneuver. In the lateral compartment of the knee, ATT in the ACL-D knee increased by 6 mm after lateral meniscectomy during the pivot shift (16.6 ± 6.0 vs 10.5 ± 3.5 mm, P < .01 for ACL/LM out vs ACL out). Medial meniscectomy, conversely, had no significant effect on ATT in the ACL-D knee during pivot shift examination (P > .05). With standardized Lachman examination, however, ATT significantly increased after medial but not lateral meniscectomy compared with the ACL-D knee (P < .001). Conclusion: Although the medial meniscus functions as a critical secondary stabilizer to anteriorly directed forces on the tibia during a Lachman examination, the lateral meniscus appears to be a more important restraint to anterior tibial translation during combined valgus and rotatory loads applied during a pivoting maneuver. Clinical Relevance: This model may have implications in the evaluation of surgical reconstruction procedures in complex knee injuries.

Effect of tibial tunnel position on stability of the knee after anterior cruciate ligament reconstruction: is the tibial tunnel position most important?

Background: Minimal attention has been directed toward tibial tunnel position and the native tibial anterior cruciate ligament (ACL) footprint. Purpose: To evaluate the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction. Study Design: Controlled laboratory study. Methods: Ten paired cadaveric knees were subjected to biomechanical testing (standardized Lachman and mechanized pivot-shift examination). With each maneuver, a computer-assisted navigation system recorded the 3-dimensional motion path of a tracked point at the center of the tibia, medial tibial plateau, and lateral tibial plateau. The testing protocol consisted of evaluation in the intact state and after complete ACL transection, after ACL transection with bilateral meniscectomy, and after ACL reconstruction using 3 tibial tunnel positions—over the top (OTT), anterior footprint (AT), and posterior footprint (PT)—with a standard femoral socket placed in the center of the femoral footprint. Repeated-measures analysis of variance with a post hoc Tukey test compared measured translations with each condition. Results: A significant difference in anterior translation was seen with Lachman examination between the ACL-deficient condition and both the OTT and AT reconstructions, but no significant difference was observed between the ACL-deficient and PT reconstruction. The OTT and AT constructs were significantly better in limiting anterior translation of the lateral compartment compared with the PT ACL reconstruction during a pivot-shift maneuver in the ACL- and meniscal-deficient knee. However, anteriorizing the tibial position was accompanied by a correspondingly greater risk and magnitude of graft impingement in extension. Clinical Relevance: The OTT and anterior tibial tunnel positions better control the Lachman and the pivot shift compared with an ACL graft placed in the posterior aspect of the tibial footprint. However, an anterior tibial tunnel position must be balanced against an increased risk and magnitude of graft impingement in extension.

A Comparison of the Effect of Central Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction and Double-Bundle Anterior Cruciate Ligament Reconstruction on Pivot-Shift Kinematics

Background: Biomechanical differences between anatomical double-bundle and central single-bundle anterior cruciate ligament reconstruction using the same graft tissue have not been defined. Purpose: The purpose of this study was to compare these reconstructions in their ability to restore native knee kinematics during a reproducible Lachman and pivot-shift examination. Study Design: Controlled laboratory study. Methods: Using a computer-assisted navigation system, 10 paired knees were subjected to biomechanical testing with a standardized Lachman and mechanized pivot-shift examination. The navigation system recorded the 3D motion path of a tracked point at the center of the tibia, center of the medial tibial plateau, and center of the lateral tibial plateau with each maneuver. The testing protocol consisted of evaluation in the intact state, after complete anterior cruciate ligament transection, after medial and lateral meniscectomy, and after anterior cruciate ligament reconstruction with (1) a single-bundle center-center or (2) anatomical double-bundle technique. Repeated-measures analysis of variance with a post hoc Tukey test was used to compare the measured translations with each test condition. Results: A significant difference in anterior translation was seen with Lachman examination between the anterior cruciate ligament– and medial and lateral meniscus–deficient condition compared with both the double-bundle and single-bundle center-center anterior cruciate ligament reconstruction (P < .001); no significant difference was observed between reconstructions. The double-bundle construct was significantly better in limiting anterior translation of the lateral compartment compared with the single-bundle reconstruction during a pivot-shift maneuver (2.0 ± 5.7 mm vs 7.8 ± 1.8 mm, P < .001) and was not significantly different than the intact anterior cruciate ligament condition (2.7 mm ± 4.7 mm, P > .05). Discussion: Although double-bundle and single-bundle, center-center anterior cruciate ligament reconstructions appear equally effective in controlling anterior translation during a Lachman examination, analysis of pivot-shift kinematics reveals significant differences between these surgical reconstructions. An altered rotational axis resulted in significantly greater translation of the lateral compartment in the single-bundle compared with double-bundle reconstruction. Clinical Relevance: A double-bundle anterior cruciate ligament reconstruction may be a favorable construct for restoration of knee kinematics in the at-risk knee with associated meniscal injuries and/or significant pivot shift on preoperative examination.

Intraoperative 3D imaging in calcaneal fracture care-clinical implications and decision making.

BACKGROUND In operative calcaneal fracture care malposition of screws and joint line incongruity frequently remain unrecognized using fluoroscopy intraoperatively, and are frequently only recognized on postoperative computed tomography scans. The purpose of this study was to analyze the feasibility and utility of a new C-arm-based three-dimensional imaging technology for calcaneal trauma care. METHODS The C-arm-based three- dimensional imaging device (ISO-C-3D) was used in 32 patients during a 2-year period. Patients were indicated for open reduction and internal fixation using standard techniques and fluoroscopy. After reduction and implant placement was determined to be correct, the ISO-C-3D procedure was performed. The time for setup and use, and the consequences were recorded. An assessment was obtained from the surgeon regarding the feasibility and the adequacy and quality of the data provided, using a Visual Analog Scale. RESULTS The average total time required for ISO-C-3D use was 610 seconds. The information obtained from the scan led the surgeon to alter the reduction or screw placement during the procedure in 41% of the patients. Surgeons rating according to a Visual Analog Scale: feasibility 9.5, accuracy and quality 9.2, clinical benefit 8.2. CONCLUSION Intraoperative three- dimensional visualization with the ISO-C-3D provides important information in the operative treatment of calcaneal fractures which cannot always be obtained from plain films or standard fluoroscopy alone. The use of the device adds minimal time to the overall procedure, and was found to be extremely useful in evaluating reduction and implant position intraoperatively in calcaneal fractures.

Intraoperative 3D imaging: value and consequences in 248 cases.

BACKGROUND Intraoperative visualization of articular surfaces is technically demanding, and standard two-dimensional fluoroscopic imaging frequently does not provide adequate detail of nonplanar joints. New imaging modalities allow for intraoperative 3D visualization, which are useful in articular fractures. Purpose of this study was to evaluate the utility of 3D imaging in articular fracture reconstruction. METHODS In a prospective cohort study, we evaluated 248 consecutive patients with intra-articular fractures. After fracture fixation using standard fluoroscopy, 3D imaging was performed intraoperatively using the Iso-C3D system for all patients. Surgeons filled out questionnaires regarding the utility and perceived accuracy of the 3D system. Postoperative CT scans were performed on approximately half of the patients. Main outcome measurements were based on the surgeons decision to immediately revise the articular reduction or implant position. The setup time for the system was recorded. For patients with postoperative CT scans, articular surface gaps of 2 mm or intra-articular hardware placement was again evaluated. RESULTS In 19% of all cases, intraoperative image analysis resulted in immediate adjustment of the reduction or hardware exchange. These revisions were based on Iso-C3D views of the articular surface that were not visible using fluoroscopy. Of the 129 postoperative CT scans, five cases revealed a technical error of the joint reconstruction, and a secondary revision procedure was performed. CONCLUSION In conclusion, the Iso-C3D was a valuable intraoperative tool, providing additional information about the articular surface compared with conventional fluoroscopy in a variety of anatomic regions.

Effect of Single-Bundle and Double-Bundle Anterior Cruciate Ligament Reconstructions on Pivot-Shift Kinematics in Anterior Cruciate Ligament– and Meniscus-Deficient Knees

Background: Recent laboratory and clinical studies report no difference between single-bundle (SB) and double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. Hypothesis: Anatomical DB ACL reconstruction would restore knee kinematics in a complex injury model of ACL–meniscus injury closer to the intact state when compared with 2 common SB ACL reconstructions. Study Design: Controlled laboratory study. Methods: Five fresh-frozen cadaveric hip-to-toe lower extremity specimens were used for this study (10 knees). A surgical navigation system recorded the 3-dimensional motion path of a tracked point at the center of the medial and lateral compartments during a 68-N Lachman test and a mechanized pivot-shift test. Testing was performed on the intact knee, after ACL, medial meniscus, and lateral meniscus resection and after 3 ACL reconstructions: anatomical anteromedial SB, nonanatomical SB (posterolateral tibia to anteromedial femur), and anatomical DB. Same-sized hamstring grafts were used for all reconstructions. Repeated-measures analysis of variance with a post hoc Tukey multiple-comparison test was used to compare the anterior tibial translations of the 3 grafts during laxity testing. Results: Regarding the Lachman test, there was no difference between the anatomical anteromedial SB and DB reconstructions. For the mechanized pivot shift, anatomical DB reconstruction restored anterior tibial translation to the intact state; however, significantly greater anterior tibial translation was detected after anatomical anteromedial SB and nonanatomical SB reconstruction, compared with the intact knee. In addition, there was no difference in medial compartment translations during the pivot shift between the intact and reconstructed states. Conclusion: Anatomical DB ACL reconstruction was able to restore intact knee kinematics during the pivot shift even in the severe injury model. Clinical Relevance: Double-bundle ACL reconstruction procedures may be preferred in cases of high-grade instability or meniscus deficiency.

Effect of Tunnel Position and Graft Size in Single-Bundle Anterior Cruciate Ligament Reconstruction: An Evaluation of Time-Zero Knee Stability

PURPOSE To determine whether (1) increased graft size with anatomic anterior cruciate ligament reconstruction (ACLR) would confer proportionally increased time-zero biomechanical stability and (2) larger grafts would compensate for the inferior time-zero biomechanical kinematics of nonanatomic, single-bundle ACLR. METHODS Ten cadaveric knees were allocated for single-bundle ACLR in an anatomic, center-center or nonanatomic, posterolateral-to-anteromedial footprint position with hamstring autograft. Medial arthrotomy defined the native anterior cruciate ligament (ACL) tibial and femoral footprints. ACLR was performed with a 6-mm semitendinosus graft in 6-mm tunnels and repeated with a 9-mm semitendinosus and gracilis graft in 9-mm tunnels for each knee. Lachman and instrumented pivot-shift examinations assessed knee stability in the ACL-intact, ACL-deficient, and ACLR conditions. Medial and lateral meniscectomies after ACL transection created reproducible pivot shifts. Significance was defined as P < .05. RESULTS ACLR in the center-center or posterolateral-to-anteromedial position significantly reduced anterior tibial translation compared with the ACL- and meniscus-deficient conditions (P < .001). Larger graft size, however, did not significantly improve time-zero biomechanical stability compared with a smaller graft in the same position for either reconstruction (P = .41 to .74). A center-center ACLR controlled tibial translation significantly better than a nonanatomic graft position regardless of graft size (P < .001). A smaller graft in the anatomic position controlled tibial translation significantly better than a larger graft in a nonanatomic position (P < .001). CONCLUSIONS This study showed that increasing graft size did not improve the time-zero biomechanical stability of the knee after ACLR. Increased graft size did not compensate for the biomechanical instability documented with the nonanatomic tunnel position. Restoration of native footprint anatomy in ACLR is of paramount importance regardless of graft size and source. CLINICAL RELEVANCE A larger graft size does not ameliorate the inferior time-zero biomechanics associated with nonanatomic tunnel preparation during single-bundle ACLR.

Navigated pedicle screw placement: Experimental comparison between CT- and 3D fluoroscopy-based techniques

Objective: Even with CT-based navigation, the misplacement rate for pedicle screws is reported to be as high as 10%. Using fluoroscopy-based 3D navigation, misplacement rates of 1.7 to 6% occur. The purpose of this study was to compare the accuracy of CT-based and Iso-C-based navigation in an experimental context. Methods: A foam spine model and the SurgiGATE® navigation system were used. First, a determination of point accuracy measured the difference between the real positions of markers placed on selected vertebrae and their positions as determined by the navigation system. In the verification mode, the pointer is placed exactly on the markers displayed on the monitor screen, and the deviation of the pointer tip and marker is measured in reality using a caliper. Secondly, pedicle accuracy was measured using pre-drilled holes for pedicle screws. A trajectory was planned into the visible hole and the navigated pointer was placed. Results: The measured accuracy for the markers showed a statistically significant difference between the results with CT and Iso-C navigation for one of six markers placed on the vertebra. Iso-C-based navigation demonstrated a lower mean deviation of 0.5 mm, compared to 1 mm with CT-based navigation. The deviation within the pre-drilled holes was lower when using the Iso-C3D scan. Using Iso-C3D navigation, 76.6% of the measurements showed no deviation at the entrance point, compared with 43% when using CT-based navigation. Also, with Iso-C3D navigation, 78.3% of the inserted pedicle awls hit the defined trajectories in the pre-drilled holes correctly, compared to 66.6% with CT-based navigation. Conclusion: The overall image-to-reality accuracy for CT- and Iso-C-based navigation was assessed in the described experimental setup. An apparent tendency towards higher accuracy with Iso-C-based navigation was evaluated; however, the differences were not significant.

Navigated Iso-C3D-based percutaneous osteoid osteoma resection: A preliminary clinical report

Minimally invasive osteoid osteoma resection under computer tomography (CT) guidance has yielded good results and has become a viable alternative to open surgical procedures. Limited visualization of the actual drill position under CT guidance can frequently result in inadequate and malpositioned drilling, especially at lesions located in less accessible anatomic regions. With the conventional CT-guided drilling technique, sterility and general operative management poorly correlate with standard operating room conditions, and are at risk of intra- and postoperative complications. The new Iso-C3D® imaging device provides intraoperative multiplanar reconstructions. Adequate image quality and implementation in navigation systems were described for numerous indications. On the basis of multiplanar reconstructions, minimally invasive navigated techniques under three-dimensional surgical tool control become possible, which is not the case under fluoroscopic or CT-based navigation. We report on our first three cases of navigated Iso-C3D® osteoid osteoma resection. A minimally invasive resection of the nidus was possible under permanent multiplanar image control. No complications were encountered and all patients reported successful outcomes. Minimally invasive-based navigation offered an effective and reproducible surgical approach. Dependence on CT imaging for proper positioning and complications associated with use away from the operating room environment can be avoided.

Computer Assisted Pelvic Surgery: Registration Based on a Modified External Fixator

A fundamental step in Computer Assisted Surgery (CAS) is the registration, when the preoperative virtual data and the corresponding operative anatomy of the region of interest are merged. To provide exact landmarks for anatomical registration, a tubular external fixator was modified. Two intact pelvic bones (one artificial foam pelvis and one cadaver specimen) were used for the experimental setup. Registration was carried out using a standardized protocol for anatomy-based registration in the control group; anatomical registration was achieved using a modified external fixator in the study group. This external fixator had titanium fiducials wedged into the fixator carbon tubes serving as landmarks for paired-point registration. The tubes were used for surface registration. The standard anterior pelvis fixator assembly was augmented with additional bilateral tubes oriented towards the posterior, enabling registration of the sacroiliac areas. The accuracy of registration was checked by “reversed verification”, where the examiner used only the screen display to control the virtual position of the pointer tip in relation to selected landmarks. By virtual matching, the real distance was measured with a digital caliper. We defined the verification as “accurate” when the residual distance was less than 1 mm; “acceptable” when it was between 1 mm and 2 mm; and “insufficient” when it exceeded 2 mm. The paired T-test with significance levels of p < 0.05 was used for statistical analysis. The anatomical registration based on the external fixator landmarks was statistically as accurate as that obtained using anatomical landmarks on the pelvic bone. This study concludes that the external fixator, a conventional tool in the management of acute traumatic pelvic instability, can also be useful for landmark registration in CAS.