Labral Augmentation With Either Iliotibial Band Allograft or Dermis Allograft Perform Similarly Regarding Peak Force, Displacement, and Work to Labral Repair in Suction Seal Restoration: A Biomechanical Study.

PURPOSE: To investigate whether allograft substitutes may be used to restore suctional seal properties with labral augmentation, the purpose of the current study was to evaluate the biomechanical properties of the labral suction seal under several scenarios, including: (1) intact labrum, (2) rim preparation, (3) labral repair, (4) labral augmentation with iliotibial band (ITB), and (5) labral augmentation with a dermis allograft. METHODS: Eleven hemi-pelvises were dissected to the level of the labrum and placed in a material testing system for biomechanical axial distraction. Each specimen was compressed to 250 newtons (N) and distracted at 10 mm/s while load, crosshead displacement, and time were continuously recorded. For each of the 5 labral states, 3 testing repetitions were performed. Peak force (N, newtons), displacement at peak force (mm, millimeter), and work (N-mm, newton, millimeter) were calculated and normalized to the intact state of each specimen. RESULTS: Eleven specimens were tested and 8 specimens (age: 58.6 ± 5.4 years, body mass index: 28.6 ± 6.8 kg/m2; 4 female patients; 5 right hips) were included in final analyses. Expressed as a percentage relative to the intact state, the average normalized peak force, displacement at peak force, and work for each labral state were as follows: intact (100.0% ± 0% for all), rim preparation (89.0% ± 9.2%, 93.3% ± 20.6%, 85.1% ± 9.0%), repair (61.3% ± 17.9%, 88.4% ± 36.9%, 58.1% ± 16.7%), ITB allograft (62.7% ± 24.9%, 83.9% ± 21.6%, 59.4% ± 22.4%), and dermis allograft (57.8% ± 27.2%, 88.2% ± 29.5%, 50.0% ± 20.1%). Regarding peak force, intact state was significantly greater compared with the labral repair, augmentation with ITB, and augmentation with the dermis allograft states (P < .001). No significant differences were demonstrated between displacement at peak force (P = .561). Regarding work, both intact state and rim preparation states were significantly greater than the repair, ITB augmentation, and dermis allograft augmentation states (P < .001). In all outcome measures, the dermis allograft augmentation performed with no statistical difference to the ITB augmentation state. CONCLUSIONS: Labral repair and labral augmentation with either ITB allograft or the dermis allograft resulted in significantly lower peak force and work to equilibrium compared with the intact and rim prep states. There was no statistical difference between repair and augmentation states as well as no statistical difference between ITB allograft and dermal allograft at time zero. CLINICAL RELEVANCE: This study compares biomechanical properties of the suction seal of the hip comparing labral states including intact, rim preparation, repair, and augmentation, which can be used for surgical decision-making.

Isolated Posterior Lateral Meniscofemoral Ligament Tears Show Greater Meniscal Extrusion in Knee Extension, and Isolated Posterior Lateral Meniscal Root Tears Show Greater Meniscal Extrusion at 30° Using Ultrasound: A Cadaveric Study.

PURPOSE: To quantify the effects that posterior meniscofemoral ligament (pMFL) lesions have on lateral meniscal extrusion (ME) both with and without concomitant posterior lateral meniscal root (PLMR) tears and describe how lateral ME varied along the length of the lateral meniscus. METHODS: Ultrasonography was used to measure ME of human cadaveric knees (n = 10) under the following conditions: control, isolated pMFL sectioning, isolated PLMR sectioning, pMFL+PLMR sectioning, and PLMR repair. ME was measured anterior to the fibular collateral ligament (FCL), at the FCL, and posterior to the FCL in both unloaded and axially loaded states at 0° and 30° of flexion. RESULTS: Isolated and combined pMFL and PLMR sectioning consistently demonstrated significantly greater ME when measured posterior to the FCL compared with other image locations. Isolated pMFL tears demonstrated greater ME at 0° compared with 30° of flexion (P < .05), whereas isolated PLMR tears demonstrated greater ME at 30° compared with 0° of flexion (P < .001). All specimens with isolated PLMR deficiencies demonstrated greater than 2 mm of ME at 30° flexion, whereas only 20% of specimens did so at 0°. When the pMFL was sectioned following an isolated PLMR tear, there was a significant increase in ME at 0° (P < .001). PLMR repair after combined sectioning restored ME to levels similar to that of controls in all specimens when measured at and posterior to the FCL (P < .001). CONCLUSIONS: The pMFL protects against ME primarily in full extension, whereas the presence of ME in the setting of PLMR injuries may be better appreciated in knee flexion. With combined tears, isolated repair of the PLMR can restore near-native meniscus position. CLINICAL RELEVANCE: The stabilizing properties of intact pMFL may mask the presentation of PLMR tears and delay appropriate management. Additionally, the MFL is not routinely assessed during arthroscopy due to difficult visualization and access. Understanding the ME pattern of these pathologies in isolation and combination may improve detection rates so that the source of patients' symptoms can be addressed to satisfaction.

Medial Meniscal Extrusion of Greater Than 3 Millimeters on Ultrasound Suggests Combined Medial Meniscotibial Ligament and Posterior Medial Meniscal Root Tears: A Cadaveric Analysis.

PURPOSE: To evaluate how the meniscotibial ligament (MTL) affects meniscal extrusion (ME) with or without concomitant posterior medial meniscal root (PMMR) tears and to describe how ME varied along the length of meniscus. METHODS: ME was measured using ultrasonography in 10 human cadaveric knees in conditions: (1) control, either (2a) isolated MTL sectioning, or (2b) isolated PMMR tear, (3) combined PMMR+MTL sectioning, and (4) PMMR repair. Measurements were obtained 1 cm anterior to the MCL (anterior), over the MCL (middle), and 1 cm posterior to the MCL (posterior) with or without 1,000 N axial loads in 0° and 30° flexion. RESULTS: At 0°, MTL sectioning demonstrated greater middle than anterior (P < .001) and posterior (P < .001) ME, whereas PMMR (P = .0042) and PMMR+MTL (P < .001) sectioning demonstrated greater posterior than anterior ME. At 30°, PMMR (P < .001) and PMMR+MTL (P < .001) sectioning demonstrated greater posterior than anterior ME, and PMMR (P = .0012) and PMMR+MTL (P = .0058) sectioning demonstrated greater posterior than anterior ME. PMMR+MTL sectioning demonstrated greater posterior ME at 30° compared with 0° (P = .0320). MTL sectioning always resulted in greater middle ME (P < .001), in contrast with no middle ME changes following PMMR sectioning. At 0°, PMMR sectioning resulted in greater posterior ME (P < .001), but at 30°, both PMMR and MTL sectioning resulted in greater posterior ME (P < .001). Total ME surpassed 3 mm only when both the MTL and PMMR were sectioned. CONCLUSIONS: The MTL and PMMR contribute most to ME when measured posterior to the MCL at 30° of flexion. ME greater than 3 mm is suggestive of combined PMMR + MTL lesions. CLINICAL RELEVANCE: Overlooked MTL pathology may contribute to persistent ME following PMMR repair. We found isolated MTL tears able to cause 2 to 2.99 mm of ME, but the clinical significance of these magnitudes of extrusion is unclear. The use of ME measurement guidelines with ultrasound may allow for practical MTL and PMMR pathology screening and pre-operative planning.

Lateral Translation of the Patella in MPFC Reconstruction: A Biomechanical Study of Three Approaches.

The purpose of this study was to investigate whether differences exist in preventing lateral patellar translation between three distinct medial patellofemoral complex (MPFC) reconstruction procedures at varying knee flexion angles. Six cadaveric knee specimens were dissected, potted, and placed in a customized jig for testing. Lateral patellar displacement was measured at intervals between 0 and 90 degrees of knee flexion using a tensile testing machine with a 20 N lateral force applied to the patella. Each specimen was tested with the MPFC intact, sectioned, and after each of the three reconstruction techniques: MPFL, hybrid, and medial quadriceps-tendon femoral (MQTFL) reconstructions. There was significantly increased lateral patellar displacement following MPFC sectioning when compared with the intact state in early degrees of flexion (10-30 degrees) (p < 0.05). All three reconstruction groups restored patella stability and reduced lateral patellar displacement following sectioning from 0 to 30 degrees of flexion (p < 0.05). When compared with the intact group, all three reconstruction groups demonstrated reduced patella translation at full knee extension, while the MPFL and hybrid reconstruction groups additionally demonstrated significant reduction in patella translation at 10 degrees of flexion (p < 0.05). No significant differences were observed between the three reconstruction groups. This biomechanical study demonstrates the efficacy of three MPFC reconstruction techniques in patella stabilization following sectioning. Our results suggest that MPFL reconstruction may provide the most robust patella stabilization, whereas MQTFL reconstruction may be the most forgiving construct. This study suggests that MQTFL and hybrid reconstructions provide adequate resistance to lateral translation and may be used as an alternative to MPFL reconstruction.

Concomitant Meniscotibial Ligament Reconstruction Decreases Meniscal Extrusion Following Medial Meniscus Allograft Transplantation: A Cadaveric Analysis.

PURPOSE: To compare meniscal extrusion (ME) following medial meniscus allograft transplantation (MMAT) with and without meniscotibial ligament reconstruction (MTLR). METHODS: Ten cadaveric knees were size-matched with meniscus allografts. MMAT was performed via bridge-in-slot technique. Specimens were mounted in a testing system and ME was assessed via ultrasound anterior, directly over, and posterior to the medial collateral ligament at the joint line under 4 testing conditions: (1) 0° flexion and 0 newtons (N) of axial load, (2) 0° and 1,000 N, (3) 30° and 0 N, and (4) 30° and 1,000 N. For each condition, "mean total extrusion" was calculated by averaging measurements at each position. Next, MTLR was performed using 2 inside-out sutures through the remnant allograft meniscotibial ligament and secured to the tibia using anchors. The testing protocol was repeated. Differences in ME between MMAT alone versus MMAT + MTLR were examined. Within-group differences between the measurement positions, loading states, and flexion angles also were assessed. RESULTS: "Mean total extrusion" was greater following MMAT alone (2.56 ± 1.23 mm) versus MMAT + MTLR (2.14 ± 1.07 mm; P = .005) in the loaded state at 0° flexion. ME directly over the MCL was greater following MMAT alone (3.51 ± 1.00 mm) compared with MMAT + MTLR (2.93 ± 0.79 mm; P = .054). Posteriorly, in the loaded state at 0°, ME was greater following MMAT alone (2.43 ± 1.10 mm) compared with MMAT + MTLR (1.96 ± 0.99 mm; P = .010). In all conditions, ME was greater in the loaded state versus the unloaded state. CONCLUSIONS: Following MMAT, the addition of MTLR significantly reduced overall ME when compared with isolated MMAT during loading at 0° of flexion in a cadaveric model; given the small absolute values of change in extrusion, clinical significance cannot be gleaned from these findings. CLINICAL RELEVANCE: During medial meniscus allograft transplantation, augmentation with meniscotibial ligament reconstruction may limit meniscal extrusion and improve the biomechanical milieu of the knee joint following transplant.

Medial Patellofemoral Complex Reconstruction Techniques Are Not Equivalent at Lower Flexion in the Setting of Patella Alta: A Biomechanical Comparison.

PURPOSE: To (1) determine the effect of severe patella alta on lateral patellar displacement after medial patellofemoral ligament (MPFL) reconstruction and medial quadriceps tendon-femoral ligament (MQTFL) reconstruction and (2) determine whether lateral displacement significantly differs between MPFL and MQTFL reconstructions in the setting of severe patella alta (Caton-Deschamps Index [CDI] of 1.6). METHODS: Eight cadaveric specimens were included. High-tensile strength suture was used to create a model of adjustable patellar height. Patellar height was set using fluoroscopy to CDI ratios of 1.0 (normal) and 1.6 (alta). Specimens underwent testing (1) with MPFL reconstruction, (2) with MQTFL reconstruction, and (3) in a medial patellofemoral complex (MPFC)-deficient control state, in randomized order, at both CDI settings: 1.0 and 1.6. Lateral patellar translation was measured at 0°, 10°, 20°, 30°, 45°, 60°, and 90° of knee flexion with 10 N of laterally directed load. RESULTS: At a CDI of 1.6, MPFL reconstruction showed significantly lower lateral displacement than MQTFL reconstruction at 0° and 20°. When compared with MPFC-deficient controls at a CDI of 1.6, MPFL reconstruction showed significantly lower displacement at 0° and 20° whereas MQTFL reconstruction was not significantly different at any degree of flexion. CONCLUSIONS: In the setting of severe patella alta (CDI of 1.6), MPFL reconstruction results in less lateral patellar displacement than MQTFL reconstruction at 0° and 20° of knee flexion. At higher flexion angles (≥30°), there is no difference between the 2 reconstruction techniques and the CDI no longer has an effect. At a CDI of 1.0, MPFL reconstruction shows lower displacement than MQTFL reconstruction in full extension only. Surgeons performing MPFC reconstruction should evaluate patients for patella alta and consider patellar height when deciding on the reconstruction technique. CLINICAL RELEVANCE: This study suggests that MQTFL reconstruction may be less stable than MPFL reconstruction in the setting of patella alta, without other known pathoanatomic factors, at early knee flexion angles. Patellar height should be considered when choosing the appropriate reconstruction technique in the absence of a distalization procedure.

The Effect of Rim Preparation, Labral Augmentation, and Labral Reconstruction on the Suction Seal of the Hip.

PURPOSE: To evaluate the biomechanical properties of the labral suction seal in the native labrum and after rim preparation, labral augmentation, and labral reconstruction. METHODS: Eight hemi-pelvises were dissected to the level of labrum and mounted for biomechanical testing. Each specimen was tested in axial distraction starting with the native labrum and then sequentially following rim preparation from 12 to 3 o'clock, labral augmentation, and segmental labral reconstruction using the iliotibial band allograft. In each condition, the specimens were compressed to 250 N and then distracted at 10 mm/s with force and displacement continuously recorded. Each test was repeated 3 times, and the mean peak force, displacement at peak force, and work were calculated. Data were reported as a percentage of the intact values to account for sex and size differences. Statistical testing was performed via a repeated-measures analysis of variance with a post hoc Tukey analysis. RESULTS: Peak loads occurred within 2.21 to 3.11 mm of displacement. The mean peak force, displacement at peak force, and work relative to the intact condition were the following: rim preparation (91.1% ± 8.5%, 94.4% ± 14.3%, 93.4% ± 23.5%, respectively), augmentation (66.1% ± 27.6%, 78.2% ± 16.3%, 55.7% ± 30.7%, respectively), and reconstruction (55.6% ± 25.7%, 64.7% ± 31.4%, 38.7% ± 27.2%, respectively). There was no significant difference in peak force following the rim preparation (P = .807), but peak force was significantly decreased after augmentation and reconstruction (P = .010 and P < .001, respectively). There was no significant difference in displacement at peak force following rim preparation or augmentation (P = .936 and P = .125, respectively), but displacement at peak force was significantly decreased after reconstruction (P = .005). The work from the suction seal was significantly less in both augmentation and reconstruction states compared to the intact labrum (P = .004 and P < .001, respectively) and rim preparation (P = .017 and P < .001, respectively). CONCLUSIONS: The results show that the suction seal is not significantly changed following rim preparation. Relative to the rim preparation, labral augmentation may re-create the labral suction seal better than labral reconstruction. CLINICAL RELEVANCE: This study provides a biomechanical basis for surgical decision making and clinical management of patients with labral tears of the hip.

Differential Contributions of the Quadriceps and Patellar Attachments of the Proximal Medial Patellar Restraints to Resisting Lateral Patellar Translation.

PURPOSE: To define the contributions of the of the medial patellofemoral ligament (MPFL) and medial quadriceps tendon femoral ligament (MQTFL) to lateral patellar translation as the knee moves through a 90° arc of motion. METHODS: Six pairs of bilateral cadaveric knee specimens (12 knees) were dissected and potted in perfect lateral position using fluoroscopy. An eye screw was placed in the midpoint on the lateral aspect of the patella. Each knee underwent testing in 4 conditions after sequential sectioning: intact, lateral retinacular release, randomized MQTFL or MPFL sectioning, and complete proximal medial patellar restraint (PMPR) sectioning. With a custom machined jig, all knees were tested at 0, 10, 20, 30, 45, 60, and 90° of flexion on an MTS machine with 20N of lateral patellar force applied and displacement recorded. RESULTS: PMPR extensor mechanism insertion on all specimens was identified 50% on the quadriceps tendon and 50% on the proximal aspect of the medial patella. Isolated MPFL sectioning resulted in significantly increased lateral displacement compared to the lateral release state at all flexion angles tested except 0°. There was significantly increased lateral patellar displacement with complete sectioning compared with isolated proximal sectioning at all degrees of knee flexion except 0°. However, complete sectioning following isolated MPFL sectioning did not demonstrate significance at any angle. CONCLUSIONS: Compared with the MQTFL, the MPFL is primarily responsible for resistance to lateral patellar translation throughout a 0° to 90° arc of motion. The MPFL provides a similar resistance to lateral patellar displacement as the fully intact PMPR; however, the MQTFL may contribute to resistance in full extension. CLINICAL SIGNIFICANCE: Proximal medial patellar restraint reconstruction techniques involving both the patellar and quadriceps insertion have been described; however, the unique contributions of the native anatomy to lateral patellar restraint have not been investigated.

Biomechanical comparison of subscapularis peel and lesser tuberosity osteotomy for double-row subscapularis repair technique in a cadaveric arthroplasty model.

INTRODUCTION: Management of the subscapularis during shoulder arthroplasty is controversial. The purpose of this study was to compare the biomechanical performance of subscapularis peel (SP) and lesser tuberosity osteotomy (LTO) in a cadaveric model. METHODS: The subscapularis and proximal humerus were dissected from all soft tissues in 21 fresh-frozen human cadaveric shoulders and randomized to undergo SP, LTO, or standard subscapularis tenotomy (ST, control). For SP and LTO, six #5 sutures were passed through eyelets in the implant (on lateral border and through drill holes in bicipital groove [2] and under trunion [4]). Double-row repair was performed using two lateral row transosseous sutures and four medial row sutures through the tendon (SP) or osseotendinous junction (LTO). Biomechanical properties and mode of failure were tested. RESULTS: There were no significant differences in elongation amplitude, cyclic elongation, or maximum load to failure between the three groups (P > 0.05). Mean stiffness was significantly higher in LTO (P = 0.009 vs. SP and ST). In the ST group, 7/7 specimens failed at the tendon-suture interface. For SP, 4/7 failed at the tendon-suture interface, one at the suture-bone interface, one fractured around the implant stem, and one at the knots. For LTO, 3/7 failed at the tendon-suture interface, two at the suture-bone interface and two fractured around the implant stem. CONCLUSIONS: In this cadaveric model, subscapularis repair via ST, SP, and LTO techniques was biomechanically equivalent. Additional studies are needed to confirm these findings and determine the influence of biologic healing on healing rates and clinical outcomes. LEVEL OF EVIDENCE: N/a, biomechanical laboratory study.

Biomechanical Analysis of All-Suture Suture Anchor Fixation Compared With Conventional Suture Anchors and Interference Screws for Biceps Tenodesis.

PURPOSE: To compare the biomechanical properties of all-suture suture anchors (ASSAs) with conventional interference screws (CISs) and conventional suture anchors (CSAs) for long head of the biceps tendon fixation during proximal biceps tenodesis (BT). METHODS: We randomized 21 fresh-frozen human cadaveric shoulders into 3 subpectoral BT treatment groups: ASSA, CSA, and CIS. Each construct was cyclically loaded from 5 to 70 N for 500 cycles (1 Hz). All specimens that survived cyclic loading were then pulled to failure (1 mm/s). Elongation, maximum load, energy, and failure mode were recorded. The humerus was stripped of tissue and then subjected to torsional displacement at a rate of 1°/s until fracture occurred. Maximum load, displacement, stiffness, and energy were recorded. RESULTS: During tendon testing, 3 specimens (43%) in the CIS group failed early during cyclic testing by the tendon tearing at the screw-tendon interface. All other specimens in the CIS group, as well as all specimens in the ASSA and CSA groups, survived cyclic testing and failed during pull-to-failure testing. Failure occurred at the tendon-anchor or -screw interface in all specimens (100%), with no anchor or screw pullout. The CIS group had significantly decreased elongation (8.9 ± 2.23 mm) at maximum load compared with the ASSA (19.2 ± 5.2 mm) and CSA (18.9 ± 2.23 mm) groups (P = .001). During torsional testing, the ASSA group was able to withstand significantly greater torsional displacement (9.22° ± 0.86°) before failure and had greater energy to failure (497.3 ± 45 Nmm-degrees) than the CIS group (6.13° ± 1.24° and 256.6 ± 70.3 Nmm-degrees, respectively; P = .005). CONCLUSIONS: This study shows that the biomechanical properties of ASSA, CSA, and CIS constructs are similar. The interference screw group had lower tendon elongation at maximum load but had several early failures compared with the suture anchor groups. The use of suture anchors results in maximum tendon and torsional bone loads similar to interference screws for the long head of the biceps tendon. Torsional testing of the CIS resulted in spiral fractures traversing the screw tunnel in 100% of the specimens, which was not found in the suture anchor groups. CLINICAL RELEVANCE: The ASSA is a viable fixation method for BT in comparison with the CSA and CIS.

A biomechanical comparison of two arthroscopic suture techniques in biceps tenodesis: whip-stitch vs. simple suture techniques.

BACKGROUND: The aim of this study was to compare the biomechanical performance of whip-stitch (WS) and simple suture techniques (SST) of the long head of the biceps tendon in suprapectoral intraosseous tenodesis with interference screw fixation. METHODS: A total of 10 paired cadavers (61.1 ± 4.6 years) were randomized to receive WS or SST biceps tenodesis beginning at the musculotendinous junction. Both groups implemented a No. 2 FiberLoop wire and underwent suprapectoral fixation with a polyetheretherketone interference screw at the bicipital grove. A Materials Testing System performed cyclic testing (500 cycles), followed by load to failure at 1 mm/s. Load, displacement, and time were recorded during cyclic and failure testing. A 2-tailed Student's t-test and χ2 analysis were performed for failure load and mode of failure, respectively. RESULTS: Two SST specimens and 1 WS specimen failed during cyclic loading via tendon rupture at the screw-tendon interface. There was no significant statistical difference in the cyclic displacement after 500 cycles between the WS (12.9 mm ± 4.4 mm) and SST groups (14.0 mm ± 3.8 mm, P = .2); cyclic strain, defined as the peak displacement at the 500th cycle divided by the initial gauge length, between the WS (0.4 ± 0.2) and SST groups (0.7 ± 0.7, P = .3); maximal load (162.7 N ± 56.8 N vs. 153.1 N ± 39.3 N, respectively, P = .6); and stiffness (50.5 N/mm ± 17.7 N/mm vs. 43.3 N/mm ± 10.9 N/mm, respectively, P = .3). All specimens ruptured at the screw-tendon interface. CONCLUSION: The WS technique can provide equivalent biomechanical performance to the SST in suprapectoral intraosseous biceps tenodesis with interference screw fixation.

Biomechanical Analysis of Medial-Row All-Suture Suture Anchor Fixation for Rotator Cuff Repair in a Pair-Matched Cadaveric Model.

PURPOSE: To compare the biomechanical properties of all-suture suture anchors (ASSAs) with conventional suture anchors (CSAs) for double-row rotator cuff repair (RCR). METHODS: Fourteen fresh-frozen human cadaveric shoulders were randomized into 2 RCR treatment groups: ASSA and CSA. All constructs received a double-row repair, with the lateral-row implants consisting of two 5.5-mm PEEK (polyether ether ketone) Footprint anchors. Each construct was loaded to a 10-N preload for 2 minutes, followed by cyclic loading from 10 to 160 N at a rate of 100 N/s for 100 cycles. Load-to-failure testing was performed immediately after cyclic loading testing at 1 mm/s from the zero position until failure. Cyclic creep, elongation amplitude, maximum load, stiffness, energy, and failure mode were recorded. RESULTS: No significant difference in cyclic creep (P = .117) or elongation amplitude (P = .428) was found between the ASSA and CSA groups during cyclic testing. Three specimens in each group (43% in each) failed by the suture tearing through the tendon. The remaining specimens in each group failed by the anchor pulling out of the humeral head. The mean maximum load was 617.73 ± 177.77 N and 545.13 ± 212.98 N for the ASSA and CSA groups, respectively (P = .339). Maximum elongation before failure was not different between groups (P = .122). Mean energy and stiffness were not statistically different between the ASSA and CSA groups (P = .629 and P = .973, respectively). CONCLUSIONS: In this cadaveric analysis with a simplified unidirectional experimental setup, failure mechanics and maximum load between the ASSA and CSA constructs were similar, with no difference in energy and stiffness. Although the ASSA group showed slightly larger elongation than the CSA group, these differences may not be clinically relevant. CLINICAL RELEVANCE: This study provides a biomechanical head-to-head comparison of ASSAs and CSAs, indicating that ASSAs may be clinically equivalent to CSAs for use in an RCR.

Biomechanical Analysis of Latarjet Screw Fixation: Comparison of Screw Types and Fixation Methods.

PURPOSE: To compare the initial fixation stability, failure strength, and mode of failure of 5 different screw types and fixation methods commonly used for the classic Latarjet procedure. METHODS: Thirty-five fresh-frozen cadaveric shoulder specimens were allocated into 5 groups. A 25% anteroinferior glenoid defect was created, and a classic Latarjet coracoid transfer procedure was performed. All grafts were fixed with 2 screws, differing by screw type and/or fixation method. The groups included partially threaded solid 4.0-mm cancellous screws with bicortical fixation, partially threaded solid 4.0-mm cancellous screws with unicortical fixation, fully threaded solid 3.5-mm cortical screws with bicortical fixation, partially threaded cannulated 4.0-mm cancellous screws with bicortical fixation, and partially threaded cannulated 4.0-mm captured screws with bicortical fixation. All screws were stainless steel. Outcomes included cyclic creep and secant stiffness during cyclic loading, as well as load and work to failure during the failure test. Intergroup comparisons were made by a 1-way analysis of variance. RESULTS: There were no significant differences among different screw types or fixation methods in cyclic creep or secant stiffness after cyclic loading or in load to failure or work to failure during the failure test. Post-failure radiographs showed evidence of screw bending in only 1 specimen that underwent the Latarjet procedure with partially threaded solid cancellous screws with bicortical fixation. The mode of failure for all specimens analyzed was screw cutout. CONCLUSIONS: In this biomechanical study, screw type and fixation method did not significantly influence biomechanical performance in a classic Latarjet procedure. When performing this procedure, surgeons may continue to select the screw type and method of fixation (unicortical or bicortical) based on preference; however, further studies are required to determine the optimal method of treatment. CLINICAL RELEVANCE: Surgeons may choose the screw type and fixation method based on preference when performing the Latarjet procedure.

Biomechanical Performance of Medial Row Suture Placement Relative to the Musculotendinous Junction in Transosseous Equivalent Suture Bridge Double-Row Rotator Cuff Repair.

PURPOSE: To compare the biomechanical performance of medial row suture placement relative to the musculotendinous junction (MTJ) in a cadaveric transosseous equivalent suture bridge (TOE-SB) double-row (DR) rotator cuff repair (RCR) model. METHODS: A TOE-SB DR technique was used to reattach experimentally created supraspinatus tendon tears in 9 pairs of human cadaveric shoulders. The medial row sutures were passed either near the MTJ (MTJ group) or 10 mm lateral to the MTJ (rotator cuff tendon [RCT] group). After the supraspinatus repair, the specimens underwent cyclic loading and load to failure tests. The localized displacement of the markers affixed to the tendon surface was measured with an optical tracking system. RESULTS: The MTJ group showed a significantly higher (P = .03) medial row failure (5/9; 3 during cyclic testing and 2 during load to failure testing) compared with the RCT group (0/9). The mean number of cycles completed during cyclic testing was lower in the MTJ group (77) compared with the RCT group (100; P = .07) because 3 specimens failed in the MTJ group during cyclic loading. There were no significant differences between the 2 study groups with respect to biomechanical properties during the load to failure testing. CONCLUSIONS: In a cadaveric TOE-SB DR RCR model, medial row sutures through the MTJ results in a significantly higher rate of medial row failure. CLINICAL RELEVANCE: In rotator cuff tears with tendon tissue loss, passage of medial row sutures through the MTJ should be avoided in a TOE-SB RCR technique because of the risk of medial row failure.

Effect of highly purified capsaicin on articular cartilage and rotator cuff tendon healing: An in vivo rabbit study.

Highly purified capsaicin has emerged as a promising injectable compound capable of providing sustained pain relief following a single localized treatment during orthopedic surgical procedures. To further assess its reliability for clinical use, the potential effect of highly purified capsaicin on articular cartilage metabolism as well as tendon structure and function warrants clarification. In the current study, rabbits received unilateral supraspinatus transection and repair with a single 1 ml injection of capsaicin (R+C), PEG-only placebo (R+P), or saline (R+S) into the glenohumeral joint (GHJ). An additional group received 1 ml capsaicin onto an intact rotator cuff (I+C). At 18 weeks post-op, cartilage proteoglycan (PG) synthesis and content as well as cell viability were similar (p>0.05) across treatment groups. Biomechanical testing revealed no differences (p>0.05) among tendon repair treatment groups. Similarly, histologic features of both cartilage and repaired tendons showed minimal differences across groups. Hence, in this rabbit model, a single injection of highly purified capsaicin into the GHJ does not induce a deleterious response with regard to cartilage matrix metabolism and cell viability, or rotator cuff healing. These data provide further evidence supporting the use of injectable, highly purified capsaicin as a safe alternative for management of postoperative pain following GHJ surgery.

Regional mechanical properties of human patellar tendon allografts.

PURPOSE: Very little is known regarding regional biomechanical properties of patellar tendon allografts. METHODS: Ten human bone-tendon-bone (BTB) patellar grafts were separated into equal thirds and underwent cyclic and failure testing. Grafts were non-irradiated and processed using proprietary sterilization methods. RESULTS: The central third was the thickest region (4.9 ± 0.4 mm) compared to the medial and lateral (p < 0.05). The lateral third was the longest region (58.8 ± 8.8 mm) compared to the medial (47.9 ± 8.5 mm) and central (47.2 ± 8.8 mm) portions (p < 0.05). Cyclic testing demonstrated no regional differences with respect to elongation (n.s.) and creep strain (n.s.). Failure testing demonstrated increased maximum load and stiffness in the central region (1,680 ± 418 N and 278 ± 67 N/mm, respectively) as compared to the medial (1,033 ± 214 N, p < 0.002, 201 ± 37 N/mm, p < 0.03) and lateral thirds (908 ± 412 N, p < 0.03, 173 ± 66 N/mm, p < 0.002). Elongation at maximum load did not vary between regions. Central region maximum stress (41.0 ± 12.5 MPa) was greater than that of the medial third (28.1 ± 3.6 MPa, p < 0.02), with strain at maximum stress larger in the central third (0.21 ± 0.03) compared to lateral (0.16 ± 0.03, p < 0.01). CONCLUSIONS: The central third of a non-irradiated, human bone-patellar tendon-bone construct is thicker and biomechanically superior to the medial and lateral regions in most respects. These findings reinforce the use of the central third of a patellar tendon allograft in anterior cruciate ligament reconstruction. Further investigations are required to determine whether the decreased biomechanical properties of the medial and lateral third of the BTB construct negatively influence the mechanical function of hemi-BTB grafts.

Biomechanical analysis of the pectoralis major tendon and comparison of techniques for tendo-osseous repair.

BACKGROUND: Various described surgical techniques exist for the repair of pectoralis major ruptures at the tendo-osseous junction. It is unclear how these techniques restore the native properties of the pectoralis major tendon because its biomechanical properties have not been described. HYPOTHESIS: All repairs will have lower initial biomechanical profiles than the native attachment, and transosseous sutures will demonstrate improved initial biomechanical performance compared with anchors or buttons. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-four fresh-frozen cadaveric shoulders were randomized to 4 equal groups, including 3 experimental repair groups and 1 control group of intact pectoralis major tendons. The characteristics of the native anatomic footprint were recorded, and the experimental groups underwent pectoralis detachment, followed by subsequent repair. The restoration of the anatomic footprint was recorded. All specimens were tested with cyclic loading and load-to-failure protocols with load, displacement, and optical marker data simultaneously collected. RESULTS: Under cyclic loading, the intact specimens demonstrated a significantly higher secant stiffness (74.8 ± 1.6 N/mm) than the repair groups (endosteal Pec Button [PB], 46.2 ± 6.4 N/mm; suture anchor [SA], 45.9 ± 8.7 N/mm; transosseous [TO], 44.2 ± 5.5 N/mm). Measured as a percentage change, the PB and SA groups showed a significantly higher initial excursion than the intact group (PB, 24.0% ± 11.7%; SA, 17.5% ± 6.9%; intact, 2.2% ± 1.0%), and the PB group demonstrated a significantly higher cyclic elongation than the intact group (PB, 7.5% ± 2.9%; intact, 1.5% ± 1.5%). Under load-to-failure testing, the intact group showed a significantly greater maximum load (1454.8 ± 795.7 N) and linear stiffness (221.0 ± 111.7 N/mm) than the 3 repair groups (PB, 353.5 ± 88.3 N and 63.5 ± 6.9 N/mm; SA, 292.0 ± 73.3 N and 77.0 ± 7.8 N/mm; TO, 359.2 ± 110.4 N and 64.5 ± 14.1 N/mm, respectively). All repair constructs failed via suture pulling through the tendon. CONCLUSION: The biomechanical characteristics of the transosseous repair, suture anchors, or Pec Button repair were inferior to those of the native pectoralis tendon. There was no significant difference in any of the biomechanical outcomes among the repair groups. Further refinement and evaluation of suture technique and configuration in pectoralis major repair should be considered. CLINICAL RELEVANCE: Transosseous repair, suture anchors, and endosteal Pec Buttons appear to confer similar biomechanical integrity for pectoralis major repair. Restricting early activities to thresholds below the identified failure loads seems prudent until soft tissue healing to bone is reliably achieved.

A biomechanical comparison of repair techniques for complete gluteus medius tears.

PURPOSE: The purpose of this study was to compare the biomechanical fixation stability conferred by 2 specific arthroscopic repair techniques for complete gluteus medius tendon tears. METHODS: Twelve fresh-frozen human cadaveric hemi-pelves were tested. Six received double-row repair with massive cuff stitches (DR-MCS), whereas the remaining 6 underwent double-row repair with knotless lateral anchors (DR-KLA). Constructs were preloaded to 10 N, tested from 10 N to 125 N at 90 N/s for 150 cycles, and then loaded to failure at 1 mm/s. Markers were placed on the tissue for video tracking. RESULTS: No significant differences in cyclic outcomes were observed. The DR-KLA construct showed a significantly higher normalized yield load than the DR-MCS construct. Post-yield extension for the DR-MCS construct was significantly higher than that for the DR-KLA construct. At yield load, the optically measured soft-tissue elongation of the DR-KLA construct was significantly higher than that of the DR-MCS construct. CONCLUSIONS: This study strongly suggests that the biomechanical stability conferred by DR-MCS and DR-KLA constructs for gluteus medius tendon repair is similar. Because the failure load of the DR-KLA construct is strongly correlated to bone mineral density (BMD), clinical considerations of bone quality may be particularly important for gluteus medius repairs. CLINICAL RELEVANCE: Maximum load was strongly correlated to BMD in the DR-KLA group. On the basis of this analysis, BMD should be considered during surgical planning.

Biomechanical evaluation of a high tibial osteotomy with a meniscal transplant.

This study determines the biomechanical advantage and the optimal configuration of a high tibial osteotomy (HTO) and meniscus transplantation performed concurrently. Six cadaver knees were placed in a spatial frame, and an HTO was completed. Loading points between a mechanical 6 degrees of varus and 8 degrees ofvalgus were loaded to 800 N for medial meniscal intact, meniscectomized, and transplanted states. Posterior slope was also increased by 3 degrees in these specimens. Contact data was recorded. Peak pressures significantly increased in the meniscectomized state in every degree of varus/valgus (p < 0.05). For both peak and total medial compartment pressures, there was a significant drop (p < 0.001) between neutral and 3 degrees of valgus. Lateral compartment pressures linearly increased from varus to valgus orientation. There was no significant change in the pressure profile of the knee with a 3-degree increase in posterior slope. This biomechanical study confirms the hypothesis that an HTO improves the peak pressures in the medial compartment at all degrees of varus/valgus alignment in the setting of meniscal transplantation. Furthermore, the largest decrease in medial pressures was between neutral and 3 degrees of valgus, suggesting that perhaps neutral aligned knees could benefit from an HTO.

Tibial fixation of anterior cruciate ligament allograft tendons: comparison of 1-, 2-, and 4-stranded constructs.

BACKGROUND: In sum, 1-, 2-, and 4-stranded allografts are used for soft tissue anterior cruciate ligament reconstruction; however, the fixation properties of fixation devices are not well assessed. HYPOTHESIS: There are no differences in the biomechanical characteristics of 1 (Achilles)-, 2 (posterior tibialis)-, and 4 (semitendinosus)-stranded allograft tibial fixation. STUDY DESIGN: Controlled laboratory study. METHODS: Sixty-three fresh-frozen porcine tibiae were used to evaluate the fixation of 1-, 2-, and 4-stranded human tendon allografts (Achilles, posterior tibialis, and semitendinosus) with 3 fixation devices (Delta, Intrafix, and Calaxo screws). With use of a materials testing system, each graft was subjected to 500 cycles of loading (50-250 N, 0.75 mm/sec) to determine displacement and cyclic stiffness, followed by a monotonic failure test (20 mm/min) to determine maximum load and pullout stiffness. RESULTS: For each graft type, there were no significant biomechanical differences between fixation devices. However, the 1-stranded graft (Achilles) construct demonstrated significantly higher mean displacement (3.17 +/- 1.62 mm), lower cyclical stiffness (156 +/- 25 N/mm), lower load to failure (479 +/- 87 N), and lower pullout stiffness (140 +/- 28 N/mm). In comparison with the 2-stranded graft (posterior tibialis), the 4-stranded graft (semitendinosus) exhibited lower displacement (0.86 +/- 0.44 to 1.12 +/- 0.51 mm) and higher ultimate failure load (832 +/- 255 to 656 +/- 168 N). Numerous differences in fixation properties were noted when comparing a device to each of the 3 grafts. CONCLUSION: The 1-stranded allograft demonstrated inferior biomechanical tibial fixation properties when compared with 2 (posterior tibialis)- and 4 (semitendinosus)-stranded allograft constructs for all fixation devices tested. CLINICAL RELEVANCE: This study demonstrated that not all tibial fixation devices are designed to adequately accommodate different types of anterior cruciate ligament allografts. Biomechanical evidence suggests that caution is warranted when using an Achilles allograft fixated solely with an interference device.