Biomechanical Assessment of Hip Capsular Repair and Reconstruction Procedures Using a 6 Degrees of Freedom Robotic System.

BACKGROUND: Although acetabular labral repair has been biomechanically validated to improve stability, capsular management of the hip remains a topic of growing interest and controversy. PURPOSE: To biomechanically evaluate the effects of several arthroscopically relevant conditions of the capsule through a robotic, sequential sectioning study. STUDY DESIGN: Controlled laboratory study. METHODS: Ten human cadaveric unilateral hip specimens (mean age, 51.3 years [range, 38-65 years]) from full pelvises were used to test range of motion (ROM) for the intact capsule and for multiple capsular conditions including portal incisions, interportal capsulotomy, interportal capsulotomy repair, T-capsulotomy, T-capsulotomy repair, a large capsular defect, and capsular reconstruction. Hips were biomechanically tested using a 6 degrees of freedom robotic system to assess ROM with applied 5-N·m internal, external, abduction, and adduction rotation torques throughout hip flexion and extension. RESULTS: All capsulotomy procedures (portals, interportal capsulotomy, and T-capsulotomy) created increases in external, internal, adduction, and abduction rotations compared with the intact state throughout the full tested ROM (-10° to 90° of flexion). Reconstruction significantly reduced rotation compared with the large capsular defect state for external rotation at 15° (difference, 1.4°) and 90° (difference, 1.3°) of flexion; internal rotation at -10° (difference, 0.4°), 60° (difference, 0.9°), and 90° (difference, 1.4°) of flexion; abduction rotation at -10° (difference, 0.5°), 15° (difference, 1.1°), 30° (difference, 1.2°), 60° (difference, 0.9°), and 90° (difference, 1.0°) of flexion; and adduction rotation at 0° (difference, 0.7°), 15° (difference, 0.8°), 30° (difference, 0.3°), and 90° (difference, 0.6°) of flexion. Repair of T-capsulotomy resulted in significant reductions in rotation compared with the T-capsulotomy condition for abduction rotation at -10° (difference, 0.3°), 15° (difference, 0.9°), 30° (difference, 1.3°), 60° (difference, 1.7°), and 90° (difference, 1.5°) of flexion and for internal rotation at -10° (difference, 0.9°), 60° (difference, 1.5°), and 90° (difference, 2.6°) of flexion. Similarly, repair of interportal capsulotomy resulted in significant reductions in abduction (difference, 0.9°) and internal (difference, 1.4°) rotations compared with interportal capsulotomy at 90° of flexion. In most cases, however, after the repair procedures, ROM was still increased in comparison with the intact state. CONCLUSION: The results of this study suggest that common hip arthroscopic capsulotomy procedures can result in increases in external, internal, abduction, and adduction rotations throughout a full range (-10° to 90°) of hip flexion. However, capsular repair and reconstruction succeeded in partially reducing the increased rotational ROM caused by common capsulotomy procedures. Thus, consideration should be allotted toward capsular repair or reconstruction in cases with an increased risk of residual instability. CLINICAL RELEVANCE: Although complete restoration of joint stability may not be fully achieved at time zero, capsular repair and reconstruction may lead to improved patient outcomes by bringing hip rotational movements nearer to normal values in the immediate postoperative period, especially in cases in which extensive capsulotomy is performed.

An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 2: Anterolateral Ligament Reconstruction Combined With Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Recent biomechanical studies have demonstrated that an extra-articular lateral knee structure, most recently referred to as the anterolateral ligament (ALL), contributes to overall rotational stability of the knee. However, the effect of anatomic ALL reconstruction (ALLR) in the setting of anterior cruciate ligament (ACL) reconstruction (ACLR) has not been biomechanically investigated or validated. PURPOSE/HYPOTHESIS: The purpose of this study was to investigate the biomechanical function of anatomic ALLR in the setting of a combined ACL and ALL injury. More specifically, this investigation focused on the effect of ALLR on resultant rotatory stability when performed in combination with concomitant ACLR. It was hypothesized that ALLR would significantly reduce internal rotation and axial plane translation laxity during a simulated pivot-shift test compared with isolated ACLR. STUDY DESIGN: Controlled laboratory study. METHODS: Ten fresh-frozen cadaveric knees were evaluated with a 6 degrees of freedom robotic system. Knee kinematics were evaluated with simulated clinical examinations including a simulated pivot-shift test consisting of coupled 10-N·m valgus and 5-N·m internal rotation torques, a 5-N·m internal rotation torque, and an 88-N anterior tibial load. Kinematic differences between ACLR with an intact ALL, ACLR with ALLR, and ACLR with a deficient ALL were compared with the intact state. Single-bundle ACLR tunnels and ALLR tunnels were placed anatomically according to previous quantitative anatomic attachment descriptions. RESULTS: Combined anatomic ALLR and ACLR significantly improved the rotatory stability of the knee compared with isolated ACLR in the face of a concurrent ALL deficiency. During a simulated pivot-shift test, ALLR significantly reduced internal rotation and axial plane tibial translation when compared with ACLR with an ALL deficiency. Isolated ACLR for the treatment of a combined ACL and ALL injury was not able to restore stability of the knee, resulting in a significant increase in residual internal rotation laxity. ALLR did not affect anterior tibial translation; no significant differences were observed between the varying ALL conditions with ACLR except between ACLR with an intact ALL and ACLR with a deficient ALL at 0° of flexion. CONCLUSION: In the face of a combined ACL and ALL deficiency, concurrent ACLR and ALLR significantly improved the rotatory stability of the knee compared with solely reconstructing the ACL. CLINICAL RELEVANCE: Significant increases in residual internal rotation and laxity during the pivot-shift test may exist in both acute and chronic settings of an ACL deficiency and in patients treated with isolated ACLR for a combined ACL and ALL deficiency. For this subset of patients, surgical treatment of the ALL, in addition to ACLR, should be considered to restore knee stability.

An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 1: Secondary Role of the Anterolateral Ligament in the Setting of an Anterior Cruciate Ligament Injury.

BACKGROUND: Recent investigations have described the structural and functional behavior of the anterolateral ligament (ALL) of the knee through pull-apart and isolated sectioning studies. However, the secondary stabilizing role of the ALL in the setting of a complete anterior cruciate ligament (ACL) tear has not been fully defined for common simulated clinical examinations, such as the pivot-shift, anterior drawer, and internal rotation tests. HYPOTHESIS: Combined sectioning of the ALL and ACL would lead to increased internal rotation and increased axial plane translation during a pivot-shift test when compared with isolated sectioning of the ACL. STUDY DESIGN: Controlled laboratory study. METHODS: Ten fresh-frozen human cadaveric knees were subjected to a simulated pivot-shift test with coupled 10-N·m valgus and 5-N·m internal rotation torques from 0° to 60° of knee flexion and a 5-N·m internal rotation torque and an 88-N anterior tibial load, both from 0° to 120° of knee flexion via a 6 degrees of freedom robotic system. Kinematic changes were measured and compared with the intact state for isolated sectioning of the ACL and combined sectioning of the ACL and ALL. RESULTS: Combined sectioning of the ACL and ALL resulted in a significant increase in axial plane tibial translation during a simulated pivot shift at 0°, 15°, 30°, and 60° of knee flexion and a significant increase in internal rotation at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120° when compared with the intact and ACL-deficient states. Based on the model results, ALL sectioning resulted in an additional 2.1 mm (95% CI, 1.4-2.9 mm; P < .001) of axial plane translation during the pivot shift when compared with ACL-only sectioning, when pooling evidence over all flexion angles. Likewise, when subjected to IR torque, the ACL+ALL-deficient state resulted in an additional 3.2° of internal rotation (95% CI, 2.4°-4.1°; P < .001) versus the intact state, and the additional sectioning of the ALL increased internal rotation by 2.7° (95% CI, 1.8°-3.6°; P < .001) versus the ACL-deficient state. CONCLUSION: The results of this study confirm the ALL as an important lateral knee structure that provides rotatory stability to the knee. Specifically, the ALL was a significant secondary stabilizer throughout flexion during an applied internal rotation torque and simulated pivot-shift test in the context of an ACL-deficient knee. CLINICAL RELEVANCE: Residual internal rotation and a positive pivot shift after ACL reconstruction may be attributed to ALL injury. For these patients, surgical treatment of an ALL tear may be considered.

Validation of a six degree-of-freedom robotic system for hip in vitro biomechanical testing.

Currently, there exists a need for a more thorough understanding of native hip joint kinematics to improve the understanding of pathological conditions, injury mechanisms, and surgical interventions. A biomechanical testing system able to accomplish multiple degree-of-freedom (DOF) movements is required to study the complex articulation of the hip joint. Therefore, the purpose of this study was to assess the repeatability and comparative accuracy of a 6 DOF robotic system as a testing platform for range of motion in vitro hip biomechanical analysis. Intact human cadaveric pelvises, complete with full femurs, were prepared, and a coordinate measuring machine collected measurements of pertinent femoral and pelvic bony landmarks used to define the anatomic hip axes. Passive flexion/extension path and simulated clinical exam kinematics were recorded using a 6 DOF robotic system. The results of this study demonstrate that the 6 DOF robotic system was able to identify hip passive paths in a highly repeatable manner (median RMS error of <0.1mm and <0.4°), and the robotically simulated clinical exams were consistent and repeatable (rotational RMS error ≤0.8°) in determining hip ranges of motion. Thus, a 6 DOF robotic system is a valuable and effective tool for range of motion in vitro hip biomechanical analysis.

The Anterolateral Ligament: An Anatomic, Radiographic, and Biomechanical Analysis.

BACKGROUND: Recent publications have described significant variability in the femoral attachment and overall anatomy of the anterolateral ligament (ALL). Additionally, there is a paucity of data describing its structural properties. PURPOSE: Quantitative data characterizing the anatomic and radiographic locations and the structural properties of the ALL may be used to guide graft selection and placement and to facilitate the future development of an evidence-based approach to ALL reconstructions. STUDY DESIGN: Descriptive laboratory study. METHODS: Identification of the ALL was performed by a combined outside-in and inside-out anatomic dissection of 15 nonpaired fresh-frozen cadaveric knees. Quantitative anatomic relationships were calculated using a 3-dimensional coordinate measuring device. Measurements on anteroposterior (AP) and lateral radiographs were obtained by use of a picture archiving and communications system program. Structural properties were characterized during a single pull-to-failure test using a tensile testing machine. All anatomic, radiographic, and biomechanical measurements were reported as mean values and 95% CIs. RESULTS: The ALL was identified as a thickening of the lateral capsule coming under tension with an applied internal rotation at 30° of flexion. Its femoral attachment was located 4.7 mm (95% CI, 3.5-5.9 mm) posterior and proximal to the fibular collateral ligament attachment and coursed anterodistally to its anterolateral tibial attachment approximately midway between the center of the Gerdy tubercle and the anterior margin of the fibular head; the tibial attachment was located 24.7 mm (95% CI, 23.3-26.2 mm) and 26.1 mm (95% CI, 23.9-28.3 mm) from each structure, respectively. On the AP radiographic view, the ALL originated on the femur 22.3 mm (95% CI, 20.7-23.9 mm) proximal to the joint line and inserted on the tibia 13.1 mm (95% CI, 12.3-13.9 mm) distal to the lateral tibial plateau. On the lateral view, the femoral attachment was 8.4 mm (95% CI, 6.8-10.0 mm) posterior and proximal to the lateral epicondyle. The tibial attachment was 19.0 mm (95% CI, 17.1-20.9 mm) posterior and superior to the center of the Gerdy tubercle. The mean maximum load was 175 N (95% CI, 139-211 N) and the stiffness was 20 N/mm (95% CI, 16-25 N/mm). Failure occurred by 4 distinct mechanisms: ligamentous tear at the femoral (n = 4) or tibial (n = 1) attachment, midsubstance tear (n = 4), and bony avulsion of the tibial attachment (Segond fracture; n = 6). CONCLUSION: Defined ALL attachment locations can be reproducibly identified with intraoperative landmarks or radiographs. The biomechanical analysis suggests that most traditional soft tissue grafts are sufficient for ALL reconstruction. CLINICAL RELEVANCE: The ALL was consistently found in all knees. Segond fractures appear to occur primarily from the avulsion of the ALL.

Ankle syndesmosis: a qualitative and quantitative anatomic analysis.

BACKGROUND: Syndesmosis sprains can contribute to chronic pain and instability, which are often indications for surgical intervention. The literature lacks sufficient objective data detailing the complex anatomy and localized osseous landmarks essential for current surgical techniques. PURPOSE: To qualitatively and quantitatively analyze the anatomy of the 3 syndesmotic ligaments with respect to surgically identifiable bony landmarks. STUDY DESIGN: Descriptive laboratory study. METHODS: Sixteen ankle specimens were dissected to identify the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), interosseous tibiofibular ligament (ITFL), and bony anatomy. Ligament lengths, footprints, and orientations were measured in reference to bony landmarks by use of an anatomically based coordinate system and a 3-dimensional coordinate measuring device. RESULTS: The syndesmotic ligaments were identified in all specimens. The pyramidal-shaped ITFL was the broadest, originating from the distal interosseous membrane expansion, extending distally, and terminating 9.3 mm (95% CI, 8.3-10.2 mm) proximal to the central plafond. The tibial cartilage extended 3.6 mm (95% CI, 2.8-4.4 mm) above the plafond, a subset of which articulated directly with the fibular cartilage located 5.2 mm (95% CI, 4.6-5.8 mm) posterior to the anterolateral corner of the tibial plafond. The primary AITFL band(s) originated from the tibia 9.3 mm (95% CI, 8.6-10.0 mm) superior and medial to the anterolateral corner of the tibial plafond and inserted on the fibula 30.5 mm (95% CI, 28.5-32.4 mm) proximal and anterior to the inferior tip of the lateral malleolus. Superficial fibers of the PITFL originated along the distolateral border of the posterolateral tubercle of the tibia 8.0 mm (95% CI, 7.5-8.4 mm) proximal and medial to the posterolateral corner of the plafond and inserted along the medial border of the peroneal groove 26.3 mm (95% CI, 24.5-28.1 mm) superior and posterior to the inferior tip of the lateral malleolus. CONCLUSION: The qualitative and quantitative anatomy of the syndesmotic ligaments was reproducibly described and defined with respect to surgically identifiable bony prominences. CLINICAL RELEVANCE: Data regarding anatomic attachment sites and distances to bony prominences can optimize current surgical fixation techniques, improve anatomic restoration, and reduce the risk of iatrogenic injury from malreduction or misplaced implants. Quantitative data also provide the consistency required for the development of anatomic reconstructions.

A quantitative analysis of hip capsular thickness.

PURPOSE: The purpose of this study was to provide a comprehensive quantitative analysis of capsular thickness adjacent to the acetabular rim in clinically relevant locations. METHODS: Dissections were performed and hip capsular measurements were recorded on 13 non-paired, fresh-frozen cadaveric hemi-pelvises using a coordinate measuring device. Measurements were taken for each clock-face position at 0, 5, 10 and 15 mm distances from the labral edge. RESULTS: The capsule was consistently thickest at 2 o'clock for each interval from the labrum with a maximum thickness of 8.3 at 10 mm [95 % CI 6.8, 9.8] and 15 mm [95 % CI 6.8, 9.7]. The capsule was noticeably thinner between 4 and 11 o'clock with a minimum thickness of 4.1 mm [95 % CI 3.3, 4.9] at 10 o'clock at the labral edge. Direct comparison between 0 and 5 mm between 9 and 3 o'clock showed that the hip capsule was significantly thicker at 5 mm from the labrum at 9 o'clock (p = 0.027), 10 o'clock (p = 0.032), 1 o'clock (p = 0.003), 2 o'clock (p = 0.001) and 3 o'clock (p = 0.001). CONCLUSIONS: The hip capsule was thickest between the 1 and 2 o'clock positions for all measured distances from the acetabular labrum and reached its maximum thickness at 2 o'clock, which corresponds to the location of the iliofemoral ligament.

A qualitative and quantitative analysis of the attachment sites of the proximal hamstrings.

PURPOSE: Proximal hamstring tears represent a challenge. Surgical repair of such tears has been reported utilizing both open and endoscopic techniques. It was hypothesized that the proximal attachments of the hamstring muscle group could be reproducibly and consistently measured from pertinent bony anatomical reference landmarks. METHODS: Fourteen fresh-frozen, human cadaveric specimens were dissected, and measurements were taken regarding the proximal attachments of the hamstring muscle group in reference to bony landmarks. A highly precise coordinate measuring device was used for three-dimensional measurements of tendon footprints and bony landmarks, and relevant distances between structures were calculated. RESULTS: The semitendinosus and long head of the biceps femoris shared a proximal origin (conjoined tendon), having an oval footprint with an average area of 567.0 mm(2) [95 % CI 481.0-652.9]. The semimembranosus (SM) footprint was crescent-shaped and located anterolateral to the conjoined tendon, with an average area of 412.4 mm(2) [95 % CI 371.0-453.8]. The SM footprint had an accessory tendinous extension that extended anteromedially forming a distinct footprint. A consistent bony landmark was found at the medial ischial margin, 14.6 mm [95 % CI 12.7-16.5] from the centre of the conjoined tendon footprint, which coincided with the distal insertion of the sacrotuberous ligament. CONCLUSION: The conjoined tendon was the largest attachment of the proximal hamstring group. Two other distinct attachment footprints were identified as the SM footprint and the accessory tendinous extension. The sacrotuberous ligament insertion served as a bony landmark. The anatomical data established in this study may aid in better restoring the anatomy during repair of proximal hamstring tears.

An anatomical study of the acetabulum with clinical applications to hip arthroscopy.

BACKGROUND: The clock face has been employed to define the position of labral pathology in relation to identifiable arthroscopically relevant acetabular landmarks. The purpose of this study was to qualitatively and quantitatively describe arthroscopically relevant anatomy of the acetabulum. We aimed to present a surgical landmark that is located in close proximity to the usual location of labral pathology as an alternative to the midpoint of the transverse acetabular ligament as a reference point. METHODS: Fourteen fresh-frozen cadaveric hemipelves were dissected to evaluate osseous landmarks and relevant surrounding soft-tissue structures of the acetabulum. With use of a coordinate-measuring device, we determined the location, orientation, and relationship of key arthroscopic landmarks and the footprint areas formed by the insertions of the rectus femoris, capsule, and labrum. RESULTS: An analysis of variability of reference points around the acetabulum in relation to the anterior inferior iliac spine (AIIS) revealed that the superior margin of the anterior labral sulcus (psoas-u) was the most consistent anatomic landmark. The AIIS comprised superior and inferior facets, demarcated by the origins of the direct head of the rectus femoris and the iliocapsularis. The inferolateral corner of the footprint of the direct head of the rectus femoris was located 19.2 mm (95% confidence interval [CI], 18.0 to 20.4 mm) from the acetabular rim and the inferolateral aspect of the iliocapsularis footprint, 12.5 mm (95% CI, 10.1 to 15.0 mm) from the rim. CONCLUSIONS: The superior margin of the anterior labral sulcus (psoas-u) was a reliable landmark for reference of the clock face on the acetabulum. We propose that this point, denoting 3:00, be adopted as the new standard clock-face reference for intra-articular hip structures because of its universal presence and reliable arthroscopic visualization. This marker is also beneficial because of its proximity to the typical location of labral pathology. The data presented provide a comprehensive analysis of pertinent arthroscopically relevant acetabular anatomy. CLINICAL RELEVANCE: The establishment of a new standard reference point within the acetabulum will enhance the consistency of interpretation of the location of labral pathology and improve arthroscopic orientation and navigation.

Posterior cruciate ligament graft fixation angles, part 2: biomechanical evaluation for anatomic double-bundle reconstruction.

BACKGROUND: Prior studies have suggested that anatomic double-bundle (DB) posterior cruciate ligament reconstruction (PCLR) reduces residual laxity compared with the intact state better than single-bundle PCLR. Although the anterolateral bundle (ALB) and posteromedial bundle (PMB) reportedly act codominantly, few studies have compared commonly used graft fixation angles and the influence that graft fixation angles have on overall graft forces and knee laxity. HYPOTHESIS: Graft fixation angle combinations of 0°/75° (PMB/ALB), 0°/90°, 0°/105°, 15°/75°, 15°/90°, and 15°/105° would significantly reduce knee laxity from the sectioned PCL state while preventing in vitro graft forces from being overloaded between any of the graft fixation angles. STUDY DESIGN: Controlled laboratory study. METHODS: Nine cadaveric knees were evaluated for the kinematics of the intact, PCL-sectioned, and DB PCLR techniques. The DB technique was varied by fixing the PMB and ALB grafts at the following 6 randomly ordered fixation angle combinations: 0°/75° (PMB/ALB), 0°/90°, 0°/105°, 15°/75°, 15°/90°, and 15°/105°. A 6 degrees of freedom robotic testing system subjected each specimen to an applied 134-N posterior tibial load at 0° to 120° of flexion and 5-N·m external, 5-N·m internal, and 10-N·m valgus rotation torques applied at 60°, 75°, 90°, 105°, and 120° of flexion. The ALB and PMB grafts were fixed to load cells that concurrently measured graft forces throughout kinematic testing. t tests compared the kinematics between groups, and 2-factor models assessed the contribution of ALB and PMB grafts after DB PCLR (P < .05). RESULTS: Consistently, DB PCLR significantly reduced posterior translation compared with the sectioned PCL and was comparable with the intact state during applied posterior tibial loads at flexion angles of greater than 90°; a mean residual laxity of 1.5 mm remained compared with the intact state during applied posterior tibial loads. Additionally, fixing the PMB graft at 15° resulted in significantly larger PMB graft forces compared with fixation at 0° during applied posterior loading, internal rotation, external rotation, and valgus rotation. Similarly, fixing the ALB graft at 75° resulted in significantly larger ALB graft forces compared with fixation of the ALB graft at 90° or 105° during all loading conditions. CONCLUSION: Fixation of the PMB graft at 0° to 15° and the ALB graft at 75° to 105° during DB PCLR were successful in significantly reducing knee laxity from the sectioned state. However, fixation of the PMB graft at 15° versus 0° resulted in significantly increased loads through the PMB graft, and fixation of the ALB graft at 75° versus 90° or 105° resulted in significantly increased loads through the ALB graft. CLINICAL RELEVANCE: This study found that all 6 fixation angle combinations significantly improved knee kinematics compared with the sectioned state at time zero; however, it is recommended that fixation of the PMB graft be performed at 0° because of the significant increases in PMB graft loading that occur with fixation at 15° and that fixation of the ALB graft be performed at 90° or 105° rather than 75° to minimize ALB graft forces, which could lead to graft attenuation or failure over time.

Posterior cruciate ligament graft fixation angles, part 1: biomechanical evaluation for anatomic single-bundle reconstruction.

BACKGROUND: Currently, no consensus exists for the optimal graft fixation angle for anatomic single-bundle (SB) posterior cruciate ligament reconstructions (PCLRs). Additionally, direct graft forces have not been measured. Alternative graft fixation angles and the resultant graft forces should be investigated to optimize the stability of SB PCLRs without overconstraining the knee. HYPOTHESIS: Graft fixation angles of 75°, 90°, and 105° for SB PCLR were hypothesized to improve knee stability compared with the sectioned posterior cruciate ligament state with no evidence of knee overconstraint. STUDY DESIGN: Controlled laboratory study. METHODS: Nine fresh-frozen human cadaveric knees were biomechanically evaluated for the intact, sectioned, and SB PCLR states with the anterolateral bundle graft fixed at 75°, 90°, and 105°. A 6 degrees of freedom robotic system assessed knee laxity with a 134-N posterior load applied at 0° to 120° and 5-N·m external, 5-N·m internal, and 10-N·m valgus rotation torques applied at 60° to 120°. By securing the graft to an external load cell, graft forces were measured throughout kinematic testing. RESULTS: No significant kinematic differences were found among the 3 fixation angles. Each fixation angle resulted in significantly less posterior translation than in the sectioned state at all flexion angles (P < .05), with 4.1 mm of average residual laxity during an applied posterior loading. For all graft fixation angles, internal rotation was significantly increased between 60° and 120° of flexion, and external rotation was significantly increased at 90°, 105°, and 120° of flexion compared with the intact state. Graft forces were not significantly different among the 3 fixation angles and remained below reported loads observed during activities of daily living. CONCLUSION: All tested SB PCLR graft fixation angles restored knee laxity to similar levels; however, persistent laxity resulted in significant increases in knee laxity compared with the intact state during posterior tibial loading at all flexion angles, internal rotation at flexion angles ≥60°, and external rotation at ≥75° of flexion. CLINICAL RELEVANCE: The results of this study suggest that SB PCL graft fixation angles of 75°, 90°, and 105° were comparable in restoring knee kinematics and exposed the graft to similar time-zero loads. However, SB PCLRs did not fully reduce knee laxity to the intact state.

Characterization of robotic system passive path repeatability during specimen removal and reinstallation for in vitro knee joint testing.

Robotic testing systems are commonly utilized for the study of orthopaedic biomechanics. Quantification of system error is essential for reliable use of robotic systems. Therefore, the purpose of this study was to quantify a 6-DOF robotic system's repeatability during knee biomechanical testing and characterize the error induced in passive path repeatability by removing and reinstalling the knee. We hypothesized removing and reinstalling the knee would substantially alter passive path repeatability. Testing was performed on four fresh-frozen cadaver knees. To determine repeatability and reproducibility, the passive path was collected three times per knee following the initial setup (intra-setup), and a single time following two subsequent re-setups (inter-setup). Repeatability was calculated as root mean square error. The intra-setup passive path had a position repeatability of 0.23 mm. In contrast, inter-setup passive paths had a position repeatability of 0.89 mm. When a previously collected passive path was replayed following re-setup of the knee, resultant total force repeatability across the passive path increased to 28.2N (6.4N medial-lateral, 25.4N proximal-distal, and 10.5 N anterior-posterior). This study demonstrated that removal and re-setup of a knee can have substantial, clinically significant changes on our system's repeatability and ultimately, accuracy of the reported results.

Qualitative and Quantitative Anatomic Investigation of the Lateral Ankle Ligaments for Surgical Reconstruction Procedures.

BACKGROUND: Lateral ankle sprains are common sports injuries that may require surgery for chronic lateral ankle instability. Anatomic repair or reconstruction is desired, yet there is a scarcity of quantitative information regarding the origins and insertions of the lateral ligaments related to surgically pertinent osseous landmarks. METHODS: Fourteen ankle specimens were dissected to isolate the anterior talofibular ligament, calcaneofibular ligament, posterior talofibular ligament, and cervical ligament. A three-dimensional coordinate measurement device was used to determine the origins, insertions, footprint areas, orientations, and distances from osseous landmarks. RESULTS: A single-banded anterior talofibular ligament was identified in seven of the fourteen specimens, and a double-banded anterior talofibular ligament was identified in the remaining seven. The single-banded anterior talofibular ligament originated an average of 13.8 mm (95% confidence interval [CI], 12.3 to 15.3) from the inferior tip of the lateral malleolus at the anterior fibular border and inserted an average of 17.8 mm (95% CI, 16.3 to 19.3) superior to the apex of the lateral talar process along the anterior border of the talar lateral articular facet. The calcaneofibular ligament originated an average of 5.3 mm (95% CI, 4.2 to 6.5) from the inferior tip of the lateral malleolus at the anterior fibular border and inserted an average of 16.3 mm (95% CI, 14.5 to 18.1) from the posterior point of the peroneal tubercle. The posterior talofibular ligament was the largest ligament and originated an average of 4.8 mm (95% CI, 3.7 to 5.9) superior to the inferior tip of the lateral malleolus in the digital fossa to insert an average of 13.2 mm (95% CI, 11.5 to 14.9) from the talar posterolateral tubercle. The cervical ligament originated on the superior part of the calcaneus and inserted at a point that was approximately 50% of the talar neck anteroposterior distance. CONCLUSIONS: Consistent distances from the anterior talofibular ligament, calcaneofibular ligament, posterior talofibular ligament, and cervical ligament footprint centers to osseous landmarks were identified. CLINICAL RELEVANCE: Footprint center distances from surgically relevant osseous landmarks identified in this study can be used during reconstructive surgery of the lateral ankle ligaments and may result in more anatomically accurate placement of the reconstructed ligaments.

The ligament anatomy of the deltoid complex of the ankle: a qualitative and quantitative anatomical study.

BACKGROUND: The deltoid ligament has both superficial and deep layers and consists of up to six ligamentous bands. The prevalence of the individual bands is variable, and no consensus as to which bands are constant or variable exists. Although other studies have looked at the variance in the deltoid anatomy, none have quantified the distance to relevant osseous landmarks. METHODS: The deltoid ligaments from fourteen non-paired, fresh-frozen cadaveric specimens were isolated and the ligamentous bands were identified. The lengths, footprint areas, orientations, and distances from relevant osseous landmarks were measured with a three-dimensional coordinate measurement device. RESULTS: In all specimens, the tibionavicular, tibiospring, and deep posterior tibiotalar ligaments were identified. Three additional bands were variable in our specimen cohort: the tibiocalcaneal, superficial posterior tibiotalar, and deep anterior tibiotalar ligaments. The deep posterior tibiotalar ligament was the largest band of the deltoid ligament. The origins from the distal center of the intercollicular groove were 16.1 mm (95% confidence interval, 14.7 to 17.5 mm) for the tibionavicular ligament, 13.1 mm (95% confidence interval, 11.1 to 15.1 mm) for the tibiospring ligament, and 7.6 mm (95% confidence interval, 6.7 to 8.5 mm) for the deep posterior tibiotalar ligament. Relevant to other pertinent osseous landmarks, the tibionavicular ligament inserted at 9.7 mm (95% confidence interval, 8.4 to 11.0 mm) from the tuberosity of the navicular, the tibiospring inserted at 35% (95% confidence interval, 33.4% to 36.6%) of the spring ligament's posteroanterior distance, and the deep posterior tibiotalar ligament inserted at 17.8 mm (95% confidence interval, 16.3 to 19.3 mm) from the posteromedial talar tubercle. CONCLUSIONS: The tibionavicular, tibiospring, and deep posterior tibiotalar ligament bands were constant components of the deltoid ligament. The deep posterior tibiotalar ligament was the largest band of the deltoid ligament. CLINICAL RELEVANCE: The anatomical data regarding the deltoid ligament bands in this study will help to guide anatomical placement of repairs and reconstructions for deltoid ligament injury or instability.

Surgically Relevant Bony and Soft Tissue Anatomy of the Proximal Femur.

BACKGROUND: Hip endoscopy facilitates the treatment of extra-articular disorders of the proximal femur. Unfortunately, current knowledge of proximal femur anatomy is limited to qualitative descriptions and lacks surgically relevant landmarks. PURPOSE: To provide a quantitative and qualitative analysis of proximal femur anatomy in reference to surgically relevant bony landmarks. STUDY DESIGN: Descriptive laboratory study. METHODS: Fourteen cadaveric hemipelvises were dissected. A coordinate measuring device measured dimensions and interrelationships of the gluteal muscles, hip external rotators, pectineus, iliopsoas, and joint capsule in reference to osseous landmarks. RESULTS: The vastus tubercle, superomedial border of the greater trochanter, and femoral head-neck junction were distinct and reliable osseous landmarks. The anteroinferior tip of the vastus tubercle was 17.1 mm (95% CI: 14.5, 19.8 mm) anteroinferior to the center of the gluteus medius lateral insertional footprint and was 22.9 mm (95% CI: 20.1, 25.7 mm) inferolateral to the center of the gluteus minimus insertional footprint. The insertions of the piriformis, conjoint tendon of the hip (superior gemellus, obturator internus, and inferior gemellus), and obturator externus were identified relative to the superomedial border of the greater trochanter. The relationship of the aforementioned footprints were 49% (95% CI: 43%, 54%), 42% (95% CI: 33%, 50%), and 64% (95% CI: 59%, 69%) from the anterior (0%) to posterior (100%) margins of the superomedial border of the greater trochanter, respectively. The hip joint capsule attached distally on the proximal femur 18.2 mm (95% CI: 14.2, 22.2 mm) from the head-neck junction medially on average. CONCLUSION: The vastus tubercle, superomedial border of the greater trochanter, and the femoral head-neck junction were reliable osseous landmarks for the identification of the tendinous and hip capsular insertions on the proximal femur. Knowledge of the interrelationships between these structures is essential for endoscopic navigation and anatomic surgical repair and reconstruction. CLINICAL RELEVANCE: The qualitative and quantitative clinically relevant anatomic data presented here will aid in the diagnosis of proximal femur pathology and will provide a template for anatomic repair or reconstruction.

Kinematic analysis of the posterior cruciate ligament, part 2: a comparison of anatomic single- versus double-bundle reconstruction.

BACKGROUND: A more thorough understanding of the posterior cruciate ligament (PCL) has led to an increase in awareness and treatment of complex PCL injuries. Controversy exists about whether PCL reconstruction (PCLR) using an anatomic single-bundle (aSB) or anatomic double-bundle (aDB) technique is the most effective. HYPOTHESIS: An aDB PCLR provides significantly better anterior-posterior and rotatory knee stability compared with an aSB PCLR and more closely recreates normal knee kinematics. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 18 match-paired, cadaveric knees (mean age, 54.8 years; range, 51-59 years; 5 male and 4 female pairs) were used to evaluate the kinematics of an intact PCL, an aSB and aDB PCLR, and a complete sectioned PCL. A 6 degrees of freedom robotic system was used to assess knee stability with a 134-N applied posterior tibial load, 5-N·m external and internal rotation torques, 10-N·m valgus and varus rotation torques, and a coupled 100-N posterior tibial load and 5-N·m external rotation torque at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120°. RESULTS: The aDB PCLR had significantly less posterior translation than the aSB PCLR at all flexion angles of 15° and greater. The largest difference in posterior translation was seen at 105° of flexion, where the aSB PCLR had 5.3 mm (P = .017) more posterior translation than the aDB PCLR. The aDB PCLR also had significantly less internal rotation than the aSB PCLR at all tested angles of 90° and greater. Neither reconstruction was able to fully restore native knee kinematics. CONCLUSION: An aDB PCLR more closely approximated native knee kinematics when compared with an aSB PCLR. Specifically, the aDB PCLR demonstrated significantly more restraint to posterior translation at flexion angles between 15° and 120° and less internal rotational laxity at high flexion angles 90° to 120°. CLINICAL RELEVANCE: Comparison of the 2 reconstruction techniques illustrates the time-zero kinematic advantage imparted by the addition of the posteromedial bundle reconstruction. The benefit is most pertinent for resistance to posterior translation across a full range of flexion and rotational stability beyond 90° of knee flexion.

Superficial medial collateral ligament anatomic augmented repair versus anatomic reconstruction: an in vitro biomechanical analysis.

BACKGROUND: When surgical intervention is required for a grade 3 superficial medial collateral ligament (sMCL) tear, there is no consensus on the optimal surgical treatment. Anatomic augmented repairs and anatomic reconstructions for treatment of grade 3 sMCL tears have not been biomechanically validated or compared. HYPOTHESIS: Anatomic sMCL augmented repairs and anatomic sMCL reconstruction techniques will reproduce equivalent knee kinematics when compared with the intact state, while creating significant improvements in translational and rotational laxity compared with the sMCL sectioned state. STUDY DESIGN: Controlled laboratory study. METHODS: Eighteen match-paired, fresh-frozen cadaveric knees (average age, 52.6 years; range, 40-59 years) were each used to test laxity of an intact sMCL, a deficient sMCL, and either an anatomic augmented repair or an anatomic reconstruction. Knees were biomechanically tested in a 6 degrees of freedom robotic system, which included valgus rotation, internal and external rotation, simulated pivot shift, and coupled anterior drawer with external rotation. RESULTS: Anatomic augmented repairs and anatomic reconstructions had significantly less medial joint gapping than the sectioned state at all tested flexion angles and showed significant reductions in valgus rotation compared with the sectioned state at all flexion angles. No significant differences between the anatomic augmented repair and anatomic reconstruction were found for any test performed. Despite the similar behavior between the 2 reconstruction groups, neither technique was able to reproduce the intact state. CONCLUSION: Anatomic sMCL augmented repairs and anatomic sMCL reconstructions were not significantly different when tested at time zero. Both the anatomic augmented repair and the anatomic reconstruction were able to improve knee stability and provide less than 2 mm of medial joint gapping at 0° and 20° of flexion. CLINICAL SIGNIFICANCE: These results suggest that both an anatomic sMCL augmented repair and an anatomic sMCL reconstruction improve knee kinematics compared with a deficient sMCL and provide equivalent joint stability.

Kinematic analysis of the posterior cruciate ligament, part 1: the individual and collective function of the anterolateral and posteromedial bundles.

BACKGROUND: The posterior cruciate ligament (PCL) is composed of 2 functional bundles and has an essential role in knee function and stability. There is, however, a limited understanding of the role of each individual bundle through the full range of knee flexion. HYPOTHESIS: Both bundles provide restraint to posterior tibial translation across a full range of knee flexion. At higher angles of knee flexion (>90°), the intact PCL also imparts significant rotational stability. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty matched-paired, human cadaveric knees (mean age, 55.2 years; range, 51-59 years; 6 male and 4 female pairs) were used to evaluate the kinematics of an intact, anterolateral bundle (ALB) sectioned, posteromedial bundle (PMB) sectioned, and complete PCL sectioned knee. A 6 degree of freedom robotic system was used to assess knee stability with an applied 134-N posterior tibial load, 5-N·m external and internal rotation torques, 10-N·m valgus and varus torques, and a coupled 100-N posterior tibial load and 5-N external rotation torque at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120°. RESULTS: All sectioned states had significant increases compared with intact in posterior translation, internal rotation, and external rotation at all tested flexion angles, with the exception of the ALB sectioned state at 75° of flexion for external rotation. The significant increases (mean ± standard deviation) in posterior translation during a 134-N posterior tibial load at 90° of flexion were 0.9 ± 0.6 mm, 2.6 ± 1.8 mm, and 11.7 ± 4.0 mm for the PMB, ALB, and complete PCL sectioned states, respectively, compared with the intact state. The largest significant increases in internal rotation were in the PMB and complete PCL sectioned states at 105° of flexion, 1.3° ± 1.0° and 2.8° ± 2.1°, respectively. CONCLUSION: Both the ALB and the PMB assume a significant role in resisting posterior tibial translation, at all flexion angles, suggesting a codominant relationship. The PCL provided a significant constraint to internal rotation beyond 90° of flexion. CLINICAL RELEVANCE: This information broadens the understanding of native knee kinematics and provides a template for the evaluation of single- and double-bundle PCL reconstructions.

Biomechanical comparison of anatomic single- and double-bundle anterior cruciate ligament reconstructions: an in vitro study.

BACKGROUND: Arthroscopic identification of the anteromedial (AM) and posterolateral (PL) bundle locations of the anterior cruciate ligament (ACL) has facilitated an improved quantitative description of ACL anatomy. Few studies have directly compared the biomechanical laxity of anatomic single-bundle (SB) versus anatomic double-bundle (DB) ACL reconstruction techniques based on precise anatomic descriptions. HYPOTHESIS: Anatomic tunnel positioning for SB and DB reconstructions would produce comparable anterior-posterior and rotatory knee laxity. STUDY DESIGN: Controlled laboratory study. METHODS: Nine matched pairs of cadaveric knees were evaluated for the kinematics of intact, ACL-deficient, and either anatomic SB or anatomic DB ACL-reconstructed knees. Reconstruction tunnels were placed either centrally in the ACL footprint or within the AM and PL footprints. A 6 degrees of freedom robotic system was used to assess knee laxity with an 88-N anterior tibial load and a simulated pivot-shift test of combined 10-N · m valgus and 5-N · m internal tibial torques. Rotational motion was measured with internal and external torques of 5 N · m along with varus and valgus torques of 10 N · m. One-sample and 2-sample independent t tests were used to compare between groups (P < .05). RESULTS: No significant differences were found between anatomic SB and DB reconstruction groups during anterior tibial loading. Anterior tibial translations during simulated pivot shift had no significant differences between anatomic reconstruction groups. Tibial rotation for internal/external and varus/valgus torques showed no significant differences between anatomic reconstructions, with the exception of small (<3°) but statistically significant differences in internal rotation at 20° and 30° of flexion. Despite the similar behavior between the 2 anatomic reconstruction groups, neither technique was able to reproduce the intact state during an anterior tibial load. CONCLUSION: No significant differences in anterior translation were found between the anatomic SB and anatomic DB ACL reconstructions for simulated pivot shift or anterior tibial loading. CLINICAL RELEVANCE: Although significant differences between reconstructions were observed for internal rotation, the small magnitude of these differences (<3°) may not have clinical significance.

Qualitative and quantitative anatomic analysis of the posterior root attachments of the medial and lateral menisci.

BACKGROUND: The clinical importance of the meniscal posterior root attachments has been recently reported by both biomechanical and clinical studies. Although several studies have been performed to evaluate surgical techniques, there have been few studies on the quantitative arthroscopically pertinent anatomy of the posterior meniscal root attachments. HYPOTHESIS: The posterior root attachments of the medial and lateral menisci are consistent among specimens, and repeatable quantitative measurements using arthroscopically pertinent landmarks are achievable. STUDY DESIGN: Descriptive laboratory study. METHODS: Twelve nonpaired, fresh-frozen cadaveric knees were used. The positions of the posterior root attachments of the medial and lateral menisci were identified, and 3-dimensional measurements to arthroscopically pertinent landmarks were performed using a coordinate measuring system. RESULTS: The direct distance (±standard error of the mean) between the medial tibial eminence apex and the medial meniscus posterior root attachment center was 11.5 (±0.9) mm. When split into directional components along the knee's main axes, the medial meniscus posterior root attachment center was 9.6 (±0.8) mm posterior and 0.7 (±0.4) mm lateral along the bony surface from the medial tibial eminence apex. It was located 3.5 (±0.4) mm lateral from the medial articular cartilage inflection point and directly 8.2 (±0.7) mm from the nearest tibial attachment margin of the posterior cruciate ligament. The direct distance between the lateral tibial eminence apex and the lateral meniscus posterior root attachment center was 5.3 (±0.3) mm. When it was split into directional components using the knee's main axes, the lateral meniscus posterior root attachment center was 4.2 (±0.4) mm medial and 1.5 (±0.7) mm posterior from the lateral tibial eminence apex. The lateral meniscus posterior root attachment center was located 4.3 (±0.5) mm medial from the nearest articular cartilage margin and directly 12.7 (±1.1) mm from the nearest margin of the tibial attachment of the posterior cruciate ligament. CONCLUSION: This quantitative study reproducibly identified the posterior root attachment centers of the medial and lateral menisci in relation to arthroscopically pertinent landmarks and guidelines. CLINICAL RELEVANCE: These data can be directly applied to assist in anatomic meniscal root repairs.