Relative contributions of the supraspinatus cord and strap tendons to shoulder abduction and translation.

BACKGROUND: The supraspinatus (SS) is formed by a larger anterior bipennate muscle with a cord-like tendon and a posterior unipennate muscle with a strap-like tendon. There is a tendinous connection between the 2 SS subunits. Yet, the relative mechanical contribution of the SS cord and SS strap musculotendinous units to load transmission and subsequent shoulder abduction force is unknown. We hypothesized that a simulated SS cord vs. an SS strap tear would generate less shoulder abduction force and, further, an intact SS cord would offset the expected abduction loss from an SS strap tear, but the inverse would not be true. MATERIALS AND METHODS: Twenty fresh-frozen cadaveric specimens were tested in a shoulder simulator with physiological load vectors applied to the upper and lower subscapularis, SS cord, SS strap, infraspinatus, and teres minor. The roles of the SS cord and SS strap muscles were delineated by varying their loads, while keeping constant loads on other muscles. The randomized testing trials included a native condition and 4 test cases that simulated tears by dropping the load and force transfer via the SS cord-to-SS strap connection by adding the load. Testing was completed at both 0° and 30° of abduction. During each test, shoulder abduction force, rotator cuff strains, and humeral translation were measured. RESULTS: Simulated isolated SS cord and SS strap tears led to a significantly lower shoulder abduction force (P < .001). A simulated cord tear at 0° and 30° reduced the abduction force by 53% and 38%, respectively. A simulated strap tear at 0° and 30° dropped the abduction force by 27% and 23%, respectively. The decline in the abduction force was larger for the SS cord tear vs. SS strap tear (P ≤ .001). An SS cord tear with full-load transfer to the strap was able to recover to native values at both 0° and 30° (P ≥ .288). Likewise, an SS strap tear with full-load transfer to the SS cord showed a similar recovery to native values at both 0° and 30° (P ≥ .155). During full-load transfer, the tendon strain followed the loading pattern. An SS cord tear or SS strap tear did not cause a change in humeral translation (P ≥ .303). DISCUSSION: The mechanical findings support the efficacy of nonoperative treatment of small (<10 mm) SS tears,11 because an intact SS strap tendon can effectively offset the abduction loss of a torn SS cord tear and vice versa.

The Effect of Lateral Extra-articular Tenodesis in an ACL-Reconstructed Knee With Partial Medial Meniscectomy: A Biomechanical Study.

BACKGROUND: Knee laxity increases with medial meniscectomy in anterior cruciate ligament (ACL)-reconstructed knees; however, the biomechanical effect of an additional lateral extra-articular tenodesis (LET) is unknown. PURPOSE/HYPOTHESIS: The purpose of this study was to determine the kinematic effect of a LET in knees that underwent combined ACL reconstruction (ACL-R) and partial medial meniscus posterior horn (MMPH) meniscectomy. It was hypothesized that the addition of LET would reduce laxity in the ACL-reconstructed knee. STUDY DESIGN: Controlled laboratory study. METHODS: Ten fresh-frozen human cadaveric knees (mean age, 41.5 years) were tested using a robotic system under 3 loads: (1) 89.0 N of anterior tibial (AT) load, (2) 5 N·m of internal rotation (IR) tibial torque, and (3) a simulated pivot shift-a combined valgus of 7 N·m and IR torque of 5 N·m-at 0°, 15°, 30°, 45°, 60°, and 90° of knee flexion. Kinematic data were acquired in 4 states: (1) intact, (2) ACL-R, (3) ACL-R + partial MMPH meniscectomy (MMPH), and (4) ACL-R + partial MMPH meniscectomy + LET (MMPH+LET). RESULTS: In response to AT loading, there was a significant increase seen in AT translation (ATT) in the MMPH state at all knee flexion angles compared with the ACL-R state, with the highest increase at 90° of knee flexion (mean difference, 3.1 mm) (P < .001). Although there was a significant decrease in ATT at 15° of knee flexion with MMPH+LET (P = .022), no significant differences were found at other knee flexion angles (P > .05). In MMPH with IR torque, a significant increase was observed in IR at all knee flexion angles except 90° compared with the ACL-R state (range, 2.8°-4.9°), and this increase was significantly decreased at all flexion angles with the addition of LET (range, 0.7°-1.6°) (P < .05). CONCLUSION: Performing a partial MMPH meniscectomy increased ATT and IR in response to AT and IR loads compared with the isolated ACL-R state in a cadaveric model. However, when the LET procedure was performed after partial MMPH meniscectomy, a significant decrease was seen at all knee flexion angles except 90° in response to IR and torque, and a significant decrease was seen at 15° of knee flexion in response to AT load. CLINICAL RELEVANCE: LET may be a useful adjunct procedure after ACL-R with partial MMPH meniscectomy to reduce knee laxity.

The pathoanatomy of atraumatic partial distal biceps tears: a cadaveric study.

Background: Partial distal biceps tears can occur in the short and/or long heads, leading to forearm pain and weakness. Yet, the pathoanatomy of atraumatic and traumatic partial tears are not understood. The goals of this study are to determine the distal biceps partial tear frequency and tear pattern in a cohort of cadaveric specimens. Methods: Fifty three fresh frozen cadavers (average age 70.4 ± 13.8 years, range 32-94) underwent elbow endoscopy to screen for partial tears. The partial tendon tear pattern was classified into either attritional (atraumatic), detachment on the tendon's lateral side, or avulsion (traumatic) rupture of the tendon fibers from bone on both the lateral and medial sides. The specimens were dissected and laser scanned to make 3D models. The tear location, shape, and area were calculated using gross dissection and the 3D models. Results: Atraumatic partial distal biceps tears were identified in 40% of the specimens, 72% involved both the long and short heads, 14% long head, and 14% short head. In all tears, the tendon fibers were only detached from the lateral side. The greatest tear width occurred near the short and long head junction. Conclusion: Atraumatic partial distal biceps tears are common. The tear originates on the lateral side of the tendon at the short and long head junction. All the tear patterns are attritional and no specimen had surgical treatment. This finding supports the current treatment recommendation of an initial period of nonoperative care for symptomatic atraumatic partial distal biceps tears.

Augmenting ACL Repair With Suture Tape Improves Knee Laxity: A Biomechanical Study.

Background: Anterior cruciate ligament (ACL) repair is an alternative to reconstruction; however, suture tape support may be necessary to achieve adequate outcomes. Purposes: To investigate the influence of suture tape augmentation (STA) of proximal ACL repair on knee kinematics and to evaluate the effect of the 2 flexion angles of suture tape fixation. Study Design: Controlled laboratory study. Methods: Fourteen cadaveric knees were tested using a 6 degrees of freedom robotic testing system under anterior tibial (AT) load, simulated pivot-shift (PS) load, and internal rotation (IR) and external rotation loads. Kinematics and in situ tissue forces were evaluated. Knee states tested were (1) ACL intact, (2) ACL cut, (3) ACL repair with suture only, (4) ACL repair with STA fixed at 0° of knee flexion, and (5) ACL repair with STA fixed at 20° of knee flexion. Results: ACL repair alone did not restore the intact ACL AT translation at 0°, 15°, 30°, or 60° of flexion. Adding suture tape to the repair significantly decreased AT translation at 0°, 15°, and 30° of knee flexion but not to the level of the intact ACL. With PS and IR loadings, only ACL repair with STA fixed at 20° of flexion was not significantly different from the intact state at all knee flexion angles. ACL suture repair had significantly lower in situ forces than the intact ACL with AT, PS, and IR loadings. With AT, PS, and IR loadings, adding suture tape significantly increased the in situ force in the repaired ACL at all knee flexion angles to become closer to that of the intact ACL state. Conclusion: For complete proximal ACL tears, suture repair alone did not restore normal knee laxity or normal ACL in situ force. However, adding suture tape to augment the repair resulted in knee laxity closer to that of the intact ACL. STA with fixation at 20° of knee flexion was superior to fixation with the knee in full extension. Clinical Relevance: The study findings suggest that ACL repair with STA fixed at 20° could be considered in the treatment of femoral sided ACL tears in the appropriate patient population.

Arthroscopic centralization reduces extrusion of the medial meniscus with posterior root defect in the ACL reconstructed knee.

PURPOSE: The purpose of this study was to evaluate the effects of arthroscopic meniscal centralization reinforcement for a medial meniscus (MM) posterior root defect on knee kinematics and meniscal extrusion in the anterior cruciate ligament reconstructed (ACLR) knee. The hypothesis was that the medial meniscus centralization would reduce extrusion and anterior laxity in ACLR knee with a medical meniscal defect. METHODS: Fourteen fresh-frozen human cadaveric knees were tested using a six-degrees-of-freedom robotic system under the following loading conditions: (a) an 89.0 N anterior tibial load, (b) 5.0 Nm internal and external rotational torques, (c) a 10.0 Nm valgus and varus loadings, and (d) a combined 7.0 Nm valgus moment and then a 5.0 Nm internal rotation torque as a static simulated pivot shift. The tested knee states included: (1) anatomic single-bundle cruciate ligament reconstruction with intact medial meniscus (MM Intact), (2) anatomic single-bundle cruciate ligament reconstruction with medial meniscus posterior root defect (MM Defect), (3) Anatomic single-bundle cruciate ligament reconstruction with medial meniscus arthroscopic centralization (MM Centralization). Medial meniscus arthroscopic centralization was performed using 1.4 mm anchors with #2 suture. The MM extrusion (MME) was measured using ultrasound under unloaded and varus loading conditions at 0° and 30° of flexion. RESULTS: Anterior tibial translation (ATT) increased significantly with MM posterior root defect compared to MM intact at all flexion angles. With MM centralization, ATT was not significantly different from the intact meniscus at 15° and 30° of flexion. Meniscus extrusion increased significantly with the root defect compared to intact meniscus and decreased significantly with meniscal centralization compared to the root defect at both flexion angles. CONCLUSIONS: In ACL reconstruction, cases involving irreparable medial meniscal posterior root tears, applying arthroscopic centralization for avoiding the meniscal extrusion should be considered. Clinically, in ACL reconstruction cases with irreparable medial meniscal posterior root tears, applying arthroscopic meniscal centralization for avoiding the meniscal extrusion should be considered. Meniscal centralization decreases the extrusion of the MM and offers improvements in knee laxity.

No Difference in Knee Kinematics Between Anterior Cruciate Ligament-First and Posterior Cruciate Ligament-First Fixation During Single-Stage Multiligament Knee Reconstruction: A Biomechanical Study.

Background: For combined reconstruction of both the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), there is no consensus regarding which graft should be tensioned and fixed first. Purpose: The purpose of this study was to determine which sequence of graft tensioning and fixation better restores normal knee kinematics. The hypothesis was that ACL-first fixation would more closely restore normal knee kinematics, graft force, and the tibiofemoral orientation in the neutral (resting) position compared with PCL-first fixation. Study Design: Controlled laboratory study. Methods: A total of 15 unpaired human cadaveric knees were examined using a robotic testing system under the following 4 conditions: (1) 89.0-N anterior tibial load at different knee angles; (2) 89.0-N posterior tibial load at different knee angles; (3) combined rotational 7.0-N·m valgus and 5.0-N·m internal rotation load (simulated pivot shift) at 0°, 15°, and 30° of flexion; and (4) 5.0-N·m external rotation load at 0°, 15°, and 30° of flexion. The 4 evaluated knee states were (1) intact ACL and PCL (intact), (2) ACL and PCL deficient (deficient), (3) combined anatomic ACL-PCL reconstruction fixing the ACL first (ACL-first), and (4) combined anatomic ACL-PCL reconstruction fixing the PCL first (PCL-first). A 9.0 mm-diameter quadriceps tendon autograft was used for the ACL graft, tensioned with 40.0 N at 30° of flexion. A 9.5 mm-diameter hamstring tendon autograft (gracilis and semitendinosus, quadrupled loop, and augmented with an additional allograft strand if needed), tensioned with 40.0 N at 90° of flexion, was used for the PCL graft. Results: There were no statistically significant differences between ACL-first and PCL-first fixation regarding knee kinematics. ACL-first fixation restored anterior tibial translation to the intact state at all tested knee angles, while PCL-first fixation showed higher anterior tibial translation than the intact state at 90° of flexion (9.05 ± 3.05 and 5.87 ± 2.40 mm, respectively; P = .018). Neither sequence restored posterior tibial translation to the intact state at 30°, 60°, and 90° of flexion. At 15° of flexion, PCL-first fixation restored posterior tibial translation to the intact state, whereas ACL-first fixation did not. Conclusion: There were no differences in knee laxity between ACL-first and PCL-first fixation with the ACL graft fixed at 30° and the PCL graft fixed at 90°. Clinical Relevance: This study showed that there was no evidence to support the use of one tensioning sequence over the other in single-stage multiligament knee reconstruction.

The Rotator Cable Does Not Stress Shield the Crescent Area During Shoulder Abduction.

BACKGROUND: It is accepted by the orthopaedic community that the rotator cable (RCa) acts as a suspension bridge that stress shields the crescent area (CA). The goal of this study was to determine if the RCa does stress shield the CA during shoulder abduction. METHODS: The principal strain magnitude and direction in the RCa and CA and shoulder abduction force were measured in 20 cadaveric specimens. Ten specimens underwent a release of the anterior cable insertion followed by a posterior release. In the other 10, a release of the posterior cable insertion was followed by an anterior release. Testing was performed for the native, single-release, and full-release conditions. The thicknesses of the RCa and CA were measured. RESULTS: Neither the principal strain magnitude nor the strain direction in either the RCa or the CA changed with single or full RCa release (p ≥ 0.493). There were no changes in abduction force after single or full RCa release (p ≥ 0.180). The RCa and CA thicknesses did not differ from one another at any location (p ≥ 0.195). CONCLUSIONS: The RCa does not act as a suspension bridge and does not stress shield the CA. The CA primarily transfers shoulder abduction force to the greater tuberosity. CLINICAL RELEVANCE: The CA is important in force transmission during shoulder abduction, and efforts should be made to restore its continuity with a repair or reconstruction.

ACL graft with extra-cortical fixation rotates around the femoral tunnel aperture during knee flexion.

PURPOSE: An understanding of the behavior of a new ACL graft in the femoral tunnel during knee motion and external loading can provide information pertinent to graft healing, tunnel enlargement, and graft failure. The purpose of the study was to measure the percentage of the tunnel filled by the graft and determine the amount and location of the graft-tunnel contact with knee motion and under external knee loads. METHODS: Single bundle anatomical ACL reconstruction was performed on six cadaveric knees. Specimens were positioned with a robotic testing system under: (1) passive flexion-extension, (2) 89-N anterior and posterior tibial loads, (3) 5-N m internal and external torques, and (4) 7-N m valgus moment. The knees were then dissected, repositioned by the robot and the geometry of the femoral tunnel and graft were digitized by laser scanning. The percentage of tunnel filled and the contact region between graft and tunnel at the femoral tunnel aperture were calculated. RESULTS: The graft occupies approximately 70% of the femoral tunnel aperture and anterior tibial loading tended to reduce this value. The graft contacted about 60% of the tunnel circumference and the location of the graft-tunnel contact changed significantly with knee flexion. CONCLUSION: This study found that the graft tends to rotate around the tunnel circumference during knee flexion-extension and contract under knee loading. The "windshield-wiper" and "bungee cord" effect may contribute to femoral tunnel enlargement, affect graft healing, and lead to graft failure. There can be a considerable motion of the graft in the tunnel after surgery and appropriate rehabilitation time should be allowed for graft-tunnel healing to occur. To reduce graft motion, consideration should be given to interference screw fixation or a graft with bone blocks, which may allow an earlier return to activity.

Low to moderate risk of nerve damage during peroneus longus tendon autograft harvest.

PURPOSE: This study aims to evaluate the proximity of the tendon stripper to both the peroneal and sural nerves during peroneus longus tendon (PLT) autograft harvesting. METHODS: Ten fresh-frozen human cadaveric lower extremities were used to harvest a full-thickness PLT autograft using a standard closed blunt-ended tendon stripper. The distance to the sural nerve from the PLT (at 0, 1, 2 and 3 cm proximal to lateral malleolus (LM), and the distance to the peroneal nerve and its branches from the end of the tendon stripper were measured by two separate observers using ImageJ software. RESULTS: The average distance from the PLT to the sural nerve increased significantly from 0 to 2 cm proximal to LM. The average distance to the sural nerve at the LM was 4.9 ± 1.5 mm and increased to 10.8 ± 2.4 mm (2 cm proximal to LM). The average distance from the tendon stripper to the deep peroneal nerve was 52.9 ± 11.4 mm. The average distance to the PLT branch of peroneal nerve was 29.3 ± 4.2 mm. The superficial peroneal nerve, which coursed parallel and deep to the tendon stripper, was on average 5.2 ± 0.7 mm from the end of the stripper. No transection injuries of the nerves were observed in any of the ten legs after harvesting. CONCLUSION: This cadaver study found during a full-thickness PLT harvest, the distances between the tendon stripper and the nerves were greater than 5 mm with an initial incision at 2 cm proximal to LM which is recommended.

Arthroscopic Centralization for Lateral Meniscal Injuries Reduces Laxity in the Anterior Cruciate Ligament-Reconstructed Knee.

BACKGROUND: A lateral meniscal (LM) disorder is one factor that causes rotational laxity after anterior cruciate ligament (ACL) reconstruction (ACLR). There are different types of irreparable meniscal disorders, one of which is a massive meniscal defect. HYPOTHESIS/PURPOSE: The purpose of this study was to evaluate the kinematic effects of arthroscopic centralization on an irreparable LM defect. The hypothesis was that arthroscopic centralization for an irreparable LM defect with concomitant ACLR would improve knee rotational stability. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 14 fresh-frozen human cadaveric knees were tested in 4 states: (1) intact ACL and intact lateral meniscus, (2) reconstructed ACL and intact lateral meniscus, (3) reconstructed ACL and lateral meniscus defect, and (4) reconstructed ACL and centralized lateral meniscus. Anatomic ACLR was performed using an 8 mm-diameter hamstring tendon graft. An LM defect (20% of the anteroposterior length) was created arthroscopically, and arthroscopic centralization was performed. Kinematics were analyzed using a 6 degrees of freedom robotic system under 4 knee loads: (1) an 89.0-N anterior tibial load, (2) a 5.0-N·m external rotation tibial torque, (3) a 5.0-N·m internal rotation tibial torque, and (4) a simulated pivot-shift load with a combined 7.0-N·m valgus and 5.0-N·m internal rotation tibial torque. RESULTS: LM centralization reduced anterior tibial translation similar to that of the ACLR intact LM state under anterior tibial loading (~2 mm at 30° of flexion) and showed 40% to 100% of tibial displacement in the 4 knee states under simulated pivot-shift loading. The procedure overconstrained the knee under internal rotation tibial torque and simulated pivot-shift loading. CONCLUSION: Arthroscopic centralization reduced knee laxity after ACLR for a massive LM defect in a cadaveric model. CLINICAL RELEVANCE: In cases involving irreparable LM injuries during ACLR, consideration should be given to arthroscopic centralization for reducing knee laxity. However, the procedure may overconstrain the knee in certain motions.

Locating the rotator cable during subacromial arthroscopy: bursal- and articular-sided anatomy.

BACKGROUND: The rotator cable (RCa) is an important articular-sided structure of the cuff capsular complex that helps prevent suture pull out during rotator cuff repairs (RCRs) and plays a role in force transmission. Yet, the RCa cannot be located during bursal-sided RCRs. The purpose of this study is to develop a method to locate the RCa in the subacromial space and compare its bursal- and articular-sided dimensions. METHODS: In 20 fresh-frozen cadaveric specimens, the RCa was found from the articular side, outlined with stitches, and then evaluated from the bursal side using an easily identifiable reference point, the intersection of a line bisecting the supraspinatus (SS) tendon and posterior SS myotendinous junction (MTJ). Four bursal-sided lengths were measured on the SS-bisecting line as well as the RCa's outside anteroposterior base. For the articular-sided measurements, the rotator cuff capsular complex was detached from bone and optically scanned creating 3D solid models. Using the 3D models, 4 articular-sided lengths were made, including the RCa's inside and outside anteroposterior base. RESULTS: The RCa's medial arch was located 9.9 ± 5.6 mm from the reference point in 10 intact specimens and 4.1 ± 2.4 mm in 10 torn specimens (P = .007). The RCa's width was 10.9 ± 2.1 mm, and the distance from the lateral edge of the RCa to the lateral SS insertion was 13.9 ± 4.8 mm. The bursal- and articular-sided outside anteroposterior base measured 48.1 ± 6.4 mm and 49.6 ± 6.5 mm, respectively (P = .268). The average inside anteroposterior base measurement was 37.3 ± 5.9 mm. DISCUSSION: The medial arch of the RCa can be reliably located during subacromial arthroscopy using the reference point, analogous to the posterior SS MTJ. The RCa is located 10 mm in intact and 4 mm in torn tendons (P = .007) from the posterior SS MTJ. If the above 6-mm shift in location of the RCa is not taken into consideration during rotator cuff suture placement, it could negatively affect time zero repair strength. The inside anteroposterior base of the RCa measures on average 37 mm; therefore, rotator cuff tears measuring >37 mm are at risk of rupturing part or all of the RCa's 2 humeral attachments, which if not recognized and addressed could impact postoperative function.

Effect of Percentage of Femoral Anterior Cruciate Ligament Insertion Site Reconstructed With Hamstring Tendon on Knee Kinematics and Graft Force.

BACKGROUND: Previous studies have stated that closely matching the size of the anterior cruciate ligament (ACL) insertion site footprint is important for biomechanical function and clinical stability after ACL reconstruction. However, the ACL varies widely regarding the area of femoral insertion, tibial insertion, and midsubstance of ACL, and reconstructing the insertion site area with a uniform diameter graft can result in a cross-sectional area that is greater than that of the midsubstance of the native ACL. Therefore, understanding the effect of relative graft size in ACL reconstruction on knee biomechanics is important for surgical planning. PURPOSE: To assess how the percentage of femoral insertion site affects knee biomechanics in single- and double-bundle ACL reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 14 human cadaveric knees were scanned with magnetic resonance imaging and tested using a robotic system under an anterior tibial load and a combined rotational load. In total, 7 knee states were evaluated: intact ACL; deficient ACL; single-bundle ACL reconstruction with approximate graft sizes 25% (small), 50% (medium), and 75% (large) of the femoral insertion site; and double-bundle reconstruction of approximately 50% (medium) and 75% (large) of the femoral insertion site, based on the ratio of the cross-sectional area of the graft to the area of the femoral ACL insertion site determined by magnetic resonance imaging. RESULTS: Anterior tibial translation was not significantly larger than the intact state in single-bundle and double-bundle medium graft reconstructions (P > .05) and was significantly greater in the single-bundle small graft reconstruction (P < .05). Anterior knee translation in single-bundle medium graft and large graft reconstructions was not statistically different (P > .05). In contrast, the anterior tibial translation for double-bundle large graft reconstruction was significantly smaller than for double-bundle medium graft reconstruction at low flexion angles (P < .05). The single-bundle small graft force was significantly different from the intact ACL in situ force (P < .05). The graft force with double-bundle large reconstruction was significantly greater than that with the double-bundle medium reconstruction (P < .05) but was not significantly different from that of the intact ACL (P > .05). CONCLUSION: Knee biomechanics with a single-bundle small graft tended to be significantly different from those of the intact knee. In the kinematic and kinetic data for the single- and double-bundle medium graft reconstruction, only the anterior translation at full extension for the single-bundle reconstruction was significantly different (lower) from that of intact knee. This was a time zero study. CLINICAL RELEVANCE: This study can provide surgeons with guidance in selecting the graft size for ACL reconstruction.

Partial Distal Biceps Avulsion Results in a Significant Loss of Supination Force.

BACKGROUND: Partial avulsions of the short and/or long head of the distal biceps tendon cause pain and loss of strength. The goal of the present study was to quantify the loss of supination and flexion strength following a series of surgical releases designed to simulate partial and complete short and long head traumatic avulsions. METHODS: Mechanical testing was performed to measure supination moment arms and flexion force efficiency on 18 adult fresh-frozen specimens in pronation, neutral, and supination. The distal biceps footprint length was divided into 4 equal segments. In 9 specimens (the distal-first group), the tendon was partially cut starting distally by releasing 25%, 50%, and 75% of the insertion site. In the other 9 specimens (the proximal-first group), the releases started proximally. Mechanical testing was performed before and after each release. RESULTS: Significant decreases in the supination moment arm occurred after a 75% release in the distal-first release group; the decrease was 24% in pronation (p = 0.003) and 10% in neutral (p = 0.043). No significant differences in the supination moment arm (p ≥ 0.079) or in flexion force efficiency (p ≥ 0.058) occurred in the proximal-first group. CONCLUSIONS: A simulated complete short head avulsion significantly decreased the supination moment arm and therefore supination strength. CLINICAL RELEVANCE: A mechanical case can be made for repair of partial distal biceps tendon avulsions when the rupture involves ≥75% of the distal insertion site.

Suture tape augmentation improves laxity of MCL repair in the ACL reconstructed knee.

PURPOSE: Medial collateral ligament (MCL) injury is very common and surgical repair is sometimes necessary. Especially in the setting of simultaneous anterior cruciate ligament reconstruction (ACLR) as the ACL is the secondary restraint against valgus stress. The goal of this study was to evaluate knee biomechanics after suture repair of the MCL augmented with suture tape, as compared to MCL repair alone, in the setting of concomitant ACL reconstruction (ACLR). METHODS: Fifteen fresh-frozen human cadaveric knees were tested using a six-degrees-of-freedom robotic system under four loadings: (a) an 89.0 N anterior tibial load, (b) a 5.0 Nm internal and external rotation torque, (c) a 10.0 Nm valgus load, (d) a 7.0 Nm valgus load combined with 5.0 Nm internal rotation torque as a static simulated pivot-shift. The tested conditions were ACLR with the following states: (1) MCL intact, (2) MCL deficient, (3) MCL Repair, and (4) MCL repair augmented with suture tape (MCL Repair + ST). Under the different knee loadings, the tibial displacement, and the force in either the intact MCL, suture repaired MCL or repaired MCL-suture tape complex was measured. RESULTS: While neither the MCL Repair nor the MCL Repair + ST restored valgus rotation to the MCL intact state, displacement was significantly smaller after MCL Repair + ST (p < 0.05). The knee rotation under external rotation torque in MCL Repair + ST did not differ MCL intact (n.s.), while with MCL Repair the rotation was significantly greater (p < 0.05). MCL Repair + ST did not cause an over-constraint of the knee in any of the tested loading conditions. CONCLUSION: In a combined ACL-reconstruction-MCL-repair model, MCL Repair augmented with suture tape improved valgus and external rotation laxity when compared to MCL suture repair alone. Suture tape augmentation may provide this additional means of stabilization and can be added at the time of surgical repair of the MCL. Clinically this may result in lower failure rates and less residual laxity after MCL repair, as well as shorter immobilization times and faster return to play.

Peroneus longus tendon autograft has functional outcomes comparable to hamstring tendon autograft for anterior cruciate ligament reconstruction: a systematic review and meta-analysis.

PURPOSE: This review aimed to assess whether peroneus longus tendon (PLT) autograft would have comparable functional outcomes and graft survival rates when compared to hamstring tendon (HT) autograft for anterior cruciate ligament (ACL) reconstruction. METHODS: PubMed, Web of Science, Cochrane Library, Ovid (MEDICINE), and EMBASE databases were queried for original articles from clinical studies including the keywords: ACL reconstruction and PLT autograft. Studies comparing PLT autograft versus HT autograft were included in this analysis and the following data were extracted from studies meeting the inclusion criteria: graft diameter, functional outcomes (Tegner activity scale, Lysholm score, and International Knee Documentation Committee (IKDC) subjective score), knee laxity (Lachman test), and complications (donor site pain or paresthesia, graft failure). Besides, the American Orthopaedic Foot and Ankle Society (AOFAS) scale and the Foot and Ankle Disability Index (FADI) pre-operation and at last follow-up were also compared among patients using PLT autograft. Meta-analysis was applied using Review Manager 5.3 and p < 0.05 was considered statistically significant. RESULTS: Twenty-three studies including 925 patients with ACL reconstruction met inclusion criteria. Of these, 5 studies included a direct comparison of PLT autograft (164 patients) versus HT autograft (174 patients). No significant difference was observed between PLT and HT autografts for Tegner activity scale, Lachman test, donor site pain, or graft failure. However, PLT groups demonstrated better Lysholm score (mean difference between PLT and HT groups, 1.55; 95% CI 0.20-2.89; p = 0.02) and IKDC subjective score (mean difference between PLT and HT groups, 3.24; 95% CI 0.29-6.19; p = 0.03). No difference of FADI was found (n.s.) but AOFAS was slightly decreased at last post-operative follow-up for patients with PLT autograft compared with pre-operative scores (mean difference of 0.31, 95% CI 0.07-0.54, p = 0.01). CONCLUSION: PLT autograft demonstrated comparable functional outcomes and graft survival rates compared with HT autograft for ACL reconstruction. However, a slight decrease in AOFAS score should be considered during surgical planning. Hence, the PLT is a suitable autograft harvested outside the knee for ACL reconstruction to avoid the complication of quadriceps-hamstring imbalance which can occur when harvesting autografts from the knee. LEVEL OF EVIDENCE: Level II.

Partial meniscectomy does not affect the biomechanics of anterior cruciate ligament reconstructed knee with a lateral posterior meniscal root tear.

PURPOSE: The purpose of this study was to determine the effects of a lateral meniscus posterior root tear, partial meniscectomy, and total meniscectomy on knee biomechanics in the setting of anterior cruciate ligament (ACL) reconstruction. METHODS: Thirteen fresh-frozen cadaver knees were tested with a robotic testing system under an 89.0-N anterior tibial load at full extension (FE), 15°, 30°, 60° and 90° of knee flexion and a simulated pivot-shift loading (7.0 Nm valgus and 5.0 Nm internal tibial rotation) at FE, 15° and 30° of knee flexion. Anterior tibial translation (ATT) and the in-situ force of ACL graft under the different loadings were measured in four knee states: (1) ACL reconstruction with intact lateral meniscus (Intact meniscus), (2) ACL reconstruction with lateral meniscal posterior root tear (Root tear), (3) ACL reconstruction with lateral posterior partial meniscectomy (Partial meniscectomy) and (4) ACL reconstruction with total lateral meniscectomy (Total meniscectomy). RESULTS: Under anterior tibial loading, compared with an intact meniscus, root tear significantly increased ATT at 15° and 30° of knee flexion (p < 0.05) and partial meniscectomy had almost same increased ATT as with root tear at any knee flexion between FE and 90°. Under simulated pivot-shift loading, total meniscectomy increased ATT compared with intact meniscus, root tear, partial meniscectomy at FE (p < 0.05). CONCLUSION: Under anterior tibial and simulated pivot-shift loading, partial meniscectomy has no significant effect on the stability of ACL-reconstructed knee with lateral meniscal posterior root tear, while total meniscectomy increased laxity at less than 30° of knee flexion. Clinically, in cases of irreparable meniscal root tears or persistent pain a partial meniscectomy can be considered in the setting of ACL reconstruction.

Single-bundle MCL reconstruction with anatomic single-bundle ACL reconstruction does not restore knee kinematics.

PURPOSE: The purpose of this study was to evaluate and compare knee kinematics and kinetics following either single bundle, modified triangular or double-bundle reconstruction of the superficial medial collateral ligament (sMCL) with single bundle anatomic ACL reconstruction. METHODS: Using a cadaveric model (n = 10), the knee kinematics and kinetics following three MCL reconstructions (single-bundle (SB), double-bundle (DB), modified triangular) with single bundle anatomic ACL reconstruction were compared with the intact and deficient knee state. The knees were tested under (1) an 89-N anterior tibial load, (2) 5 N-m internal and external rotational tibial torques, and (3) a 7 N-m valgus torque. RESULTS: Anatomic ACL reconstruction with SB MCL reconstruction was able to restore anterior tibial translation and external rotation to intact knee values but failed to the internal and valgus rotatory stability. Anatomical DB MCL reconstruction (with SB ACL reconstruction) and the modified triangular MCL reconstruction (with SB ACL reconstruction) restored all knee kinematics to the intact value. CONCLUSION: This study shows that clinical presentation with combined ACL and severe sMCL injury, single-bundle MCL with single-bundle ACL reconstruction does not restore knee kinematics. Anatomical double-bundle MCL reconstruction may produce slightly better biomechanical stability than the modified triangular MCL reconstruction, but the modified triangular reconstruction might be more clinically practical with the advantages of being less invasive and technically simpler while at the same time can restore a nearly normal knee joint.

The femoral posterior fan-like extension of the ACL insertion increases the failure load.

PURPOSE: To examine the role of the posterior fan-like extension of the ACL's femoral footprint on the ACL failure load. METHODS: Sixteen (n = 16) fresh frozen, mature porcine knees were used in this study and randomized into two groups (n = 8): intact femoral ACL insertion (ACL intact group) and cut posterior fan-like extension of the ACL (ACL cut group). In the ACL cut group, flexing the knees to 90°, created a folded border between the posterior fan-like extension and the midsubstance insertion of the femoral ACL footprint and the posterior fan-like extension was dissected and both areas were measured. Specimens were placed in a testing machine at 30° of flexion and subjected to anterior tibial loading (60 mm/min) until ACL failure. RESULTS: The intact ACL group had a femoral insertion area of 182.1 ± 17.1 mm2. In the ACL cut group, the midsubstance insertion area was 113.3 ± 16.6 mm2, and the cut posterior fan-like extension portion area was 67.1 ± 8.3 mm2. The failure load of the ACL intact group was 3599 ± 457 N and was significantly higher (p < 0.001) than the failure load of the ACL cut group 392 ± 83 N. CONCLUSION: Transection of the posterior fan-like extension of the ACL femoral footprint has a significant effect on the failure load of the ligament during anterior loading at full extension. Regarding clinical relevance, this study suggests the importance of the posterior fan-like extension of the ACL footprint which potentially may be retained with remnant preservation during ACL reconstruction. Femoral insertion remnant preservation may allow incorporation of the fan-like structure into the graft increasing graft strength.

Notchplasty alters knee biomechanics after anatomic ACL reconstruction.

PURPOSE: The aims of this study were (1) to study the biomechanics of single-bundle anatomic ACL reconstructed knees with and without notchplasty using a robotic testing system and (2) to determine if there would be a difference between performing a small or large notchplasty. METHODS: Fifteen fresh-frozen specimens were used in this study. The ACL reconstruction (ACL-R) was performed using an anatomic single-bundle technique with the 8 mm soft tissue graft fixed at 30° with suspensory fixation on the femoral side and a screw and washer on the tibial side. The notchplasty was then created with a burr. The following knee states were compared: (1) ACL-R, (2) ACL-R with a small (3 mm) notchplasty, and (3) ACL-R with a large (6 mm) notchplasty. Four loading conditions were applied: (1) an anterior drawer with an 89 N anterior tibial load, (2) simulated pivot-shift loading, (3) a 5 Nm internal rotational moment, and (4) a 5 Nm external rotational moment. RESULTS: Under anterior tibial loading, anterior tibial translation increased, and graft force decreased significantly after ACL-R + 3 mm notchplasty and ACLR + 6 mm notchplasty compared to ACL-R alone at FE, 15° and 30° of knee flexion. There were no changes in either anterior tibial translation or graft force under simulated pivot-shift loading, internal rotational moment, or external rotational moment. CONCLUSION: When added to anatomic ACL reconstruction, notchplasty increased anterior tibial translation and decreased graft forces during low knee flexion angles. There was no difference between a small and large notchplasty. The findings of this study are clinically relevant as the purpose of anatomic ACL reconstruction is to restore normal knee laxity, and while notchplasty may be helpful in avoiding graft impingement and improving visualization, removing even 3 mm of bone leads to biomechanical changes.