The efficiency of genetically modified mesenchymal stromal cells combined with a functionally graded scaffold for bone regeneration in corticosteroid-induced osteonecrosis of the femoral head in rabbits.

Core decompression (CD) with mesenchymal stromal cells (MSCs) is an effective therapy for early-stage osteonecrosis of the femoral head (ONFH). Preconditioning of MSCs, using inflammatory mediators, is widely used in immunology and various cell therapies. We developed a three-dimensional printed functionally graded scaffold (FGS), made of ß-TCP and PCL, for cell delivery at a specific location. The present study examined the efficacy of CD treatments with genetically modified (GM) MSCs over-expressing PDGF-BB (PDGF-MSCs) or GM MSCs co-over-expressing IL-4 and PDGF-BB and preconditioned for three days of exposure to lipopolysaccharide and tumor necrosis factor-alpha (IL-4-PDGF-pMSCs) using the FGS for treating steroid-induced ONFH in rabbits. We compared CD without cell-therapy, with IL-4-PDGF-pMSCs alone, and with FGS loaded with PDGF-MSCs or IL-4-PDGF-pMSCs. For the area inside the CD, the bone volume in the CD alone was higher than in both FGS groups. The IL-4-PDGF-pMSCs alone and FGS + PDGF-MSCs reduced the occurrence of empty lacunae and improved osteoclastogenesis. There was no significant difference in angiogenesis among the four groups. The combined effect of GM MSCs or pMSCs and the FGS was not superior to the effect of each alone. To establish an important adjunctive therapy for CD for early ONFH in the future, it is necessary and essential to develop an FGS that delivers biologics appropriately and provides structural and mechanical support.

Superior Capsule Reconstruction Using Acellular Dermal Allograft Secured at 45° of Glenohumeral Abduction Improves the Superior Stability of the Glenohumeral Joint in Irreparable Massive Posterosuperior Rotator Cuff Tears.

PURPOSE: The purpose of the current study was to create a dynamic cadaveric shoulder model to determine the effect of graft fixation angle on shoulder biomechanics following SCR and to assess which commonly used fixation angle (30° vs 45° of abduction) results in superior glenohumeral biomechanics. METHODS: Twelve fresh-frozen cadaveric shoulders were evaluated using a dynamic shoulder testing system. Humeral head translation, subacromial and glenohumeral contact pressures were compared among 4 conditions: 1) Intact, 2) Irreparable supra- and infraspinatus tendon tear, 3) SCR using acellular dermal allograft (ADA) fixation at 30° of abduction, and 4) SCR with ADA fixation at 45° of abduction. RESULTS: SCR at both 30° (0.287 mm, CI: -0.480 - 1.05 mm; P < .0001) and 45° (0.528 mm, CI: -0.239-1.305 mm; P = .0006) significantly decreased superior translation compared to the irreparably torn state. No significant changes in subacromial peak contact pressure were observed between any states. The average glenohumeral contact pressure increased significantly following creation of an irreparable RCT (373 kPa, CI: 304-443 vs 283 kPa, CI 214-352; P = .0147). The SCR performed at 45° (295 kPa, CI: 226-365, P = .0394) of abduction significantly decreased the average glenohumeral contact pressure compared to the RCT state. There was no statistically significant difference between the average glenohumeral contact pressure of the intact state and SCR at 30° and 45°. CONCLUSION: SCR improved the superior stability of the glenohumeral joint when the graft was secured at 30° or 45° of glenohumeral abduction. Fixation at 45° of glenohumeral abduction provided more stability than did fixation at 30°. CLINICAL RELEVANCE: Grafts attached at 45° of glenohumeral abduction biomechanically restore the glenohumeral stability after SCR using ADA better than fixation at 30° of glenohumeral abduction.

The effect of genetically modified platelet-derived growth factor-BB over-expressing mesenchymal stromal cells during core decompression for steroid-associated osteonecrosis of the femoral head in rabbits.

BACKGROUND: Approximately one third of patients undergoing core decompression (CD) for early-stage osteonecrosis of the femoral head (ONFH) experience progression of the disease, and subsequently require total hip arthroplasty (THA). Thus, identifying adjunctive treatments to optimize bone regeneration during CD is an unmet clinical need. Platelet-derived growth factor (PDGF)-BB plays a central role in cell growth and differentiation. The aim of this study was to characterize mesenchymal stromal cells (MSCs) that were genetically modified to overexpress PDGF-BB (PDGF-BB-MSCs) in vitro and evaluate their therapeutic effect when injected into the bone tunnel at the time of CD in an in vivo rabbit model of steroid-associated ONFH. METHODS: In vitro studies: Rabbit MSCs were transduced with a lentivirus vector carrying the human PDGF-BB gene under the control of either the cytomegalovirus (CMV) or phosphoglycerate (PGK) promoter. The proliferative rate, PDGF-BB expression level, and osteogenic differentiation capacity of unmodified MSCs, CMV-PDGF-BB-MSCs, and PGK-PDGF-BB-MSCs were assessed. In vivo studies: Twenty-four male New Zealand white rabbits received an intramuscular (IM) injection of methylprednisolone 20 mg/kg. Four weeks later, the rabbits were divided into four groups: the CD group, the hydrogel [HG, (a collagen-alginate mixture)] group, the MSC group, and the PGK-PDGF-BB-MSC group. Eight weeks later, the rabbits were sacrificed, their femurs were harvested, and microCT, mechanical testing, and histological analyses were performed. RESULTS: In vitro studies: PGK-PDGF-BB-MSCs proliferated more rapidly than unmodified MSCs (P < 0.001) and CMV-PDGF-BB-MSCs (P < 0.05) at days 3 and 7. CMV-PDGF-BB-MSCs demonstrated greater PDGF-BB expression than PGK-PDGF-BB-MSCs (P < 0.01). However, PGK-PDGF-BB-MSCs exhibited greater alkaline phosphatase staining at 14 days (P < 0.01), and osteogenic differentiation at 28 days (P = 0.07) than CMV-PDGF-BB-MSCs. In vivo: The PGK-PDGF-BB-MSC group had a trend towards greater bone mineral density (BMD) than the CD group (P = 0.074). The PGK-PDGF-BB-MSC group demonstrated significantly lower numbers of empty lacunae (P < 0.001), greater osteoclast density (P < 0.01), and greater angiogenesis (P < 0.01) than the other treatment groups. CONCLUSION: The use of PGK-PDGF-BB-MSCs as an adjunctive treatment with CD may reduce progression of osteonecrosis and enhance bone regeneration and angiogenesis in the treatment of early-stage ONFH.

The efficacy of lapine preconditioned or genetically modified IL4 over-expressing bone marrow-derived mesenchymal stromal cells in corticosteroid-associated osteonecrosis of the femoral head in rabbits.

Cell-based therapy for augmentation of core decompression (CD) using mesenchymal stromal cells (MSCs) is a promising treatment for early stage osteonecrosis of the femoral head (ONFH). Recently, the therapeutic potential for immunomodulation of osteogenesis using preconditioned (with pro-inflammatory cytokines) MSCs (pMSCs), or by the timely resolution of inflammation using MSCs that over-express anti-inflammatory cytokines has been described. Here, pMSCs exposed to tumor necrosis factor-alpha and lipopolysaccharide for 3 days accelerated osteogenic differentiation in vitro. Furthermore, injection of pMSCs encapsulated with injectable hydrogels into the bone tunnel facilitated angiogenesis and osteogenesis in the femoral head in vivo, using rabbit bone marrow-derived MSCs and a model of corticosteroid-associated ONFH in rabbits. In contrast, in vitro and in vivo studies demonstrated that genetically-modified MSCs that over-express IL4 (IL4-MSCs), established by using a lentiviral vector carrying the rabbit IL4 gene under the cytomegalovirus promoter, accelerated proliferation of MSCs and decreased the percentage of empty lacunae in the femoral head. Therefore, adjunctive cell-based therapy of CD using pMSCs and IL4-MSCs may hold promise to heal osteonecrotic lesions in the early stage ONFH. These interventions must be applied in a temporally sensitive fashion, without interfering with the mandatory acute inflammatory phase of bone healing.

A Small Amount of Retraction Force Results in Inadvertent Piriformis Muscle Damage During a Piriformis-Sparing Approach to the Hip.

BACKGROUND: Piriformis-sparing approaches to the hip allow surgeons to avoid releasing the piriformis tendon during total hip arthroplasty; however, the consequences of retracting an intact piriformis tendon during such an approach remain ill-defined. The present study aimed to determine the upper limit of force that can be applied during retraction of the piriformis tendon to expose the hip, and to quantify the resultant damage to the piriformis musculotendinous complex. METHODS: A patent-pending instrumented retractor was designed to record the applied force, duration, and angle of retraction during a piriformis-sparing posterior approach to the hip. In addition to the data collected with use of the instrumented retractor, damage to the piriformis muscle and tendon was quantified by a blinded observer. RESULTS: There was no damage to the piriformis tendon in 22 (96%) of 23 hips during piriformis retraction for visualization of the hip capsule; however, there was complete or partial damage to the piriformis muscle at the sacral origin, belly, or musculotendinous junction (i.e., outside the surgical field) noted in 21 (91%) of 23 hips. The mean peak force to failure of the piriformis muscle was exceedingly small (29.0 ± 9.4 N; range, 10.1 to 44.9 N). CONCLUSIONS: The mean peak force applied to the piriformis retractor is much less than the force required for several common daily activities, such as opening a door or crushing an empty aluminum can. Soft-tissue damage that occurs outside the surgical field during the retraction of unreleased muscles, like the piriformis muscle, is common and remains an uncontrolled surgical variable. This inadvertent soft-tissue damage is not routinely accounted for when accessing the invasiveness of a procedure. Hence, it is no longer adequate to define a minimally invasive surgical procedure simply as an approach that involves the limited release of anatomical structures. CLINICAL RELEVANCE: The use of instrumented retractors may redefine surgical invasiveness by providing data that could alter our understanding of the soft-tissue damage caused by retraction and open the possibility of robot-assisted or damage-limiting retractor systems.

The Hip Suction Seal, Part I: The Role of Acetabular Labral Height on Hip Distractive Stability.

BACKGROUND: The acetabular labrum has been found to provide a significant contribution to the distractive stability of the hip. However, the influence of labral height on hip suction seal biomechanics is not known. HYPOTHESIS: The smaller height of acetabular labrum is associated with decreased distractive stability. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 23 fresh-frozen cadaveric hemipelvises were used in this study. Hips with acetabular dysplasia or femoroacetabular impingement-related bony morphologic features, intra-articular pathology, or no measurable suction seal were excluded. Before testing, each specimen's hip capsule was removed, a pressure sensor was placed intra-articularly, and the hip was fixed in a heated saline bath. Labral size was measured by use of a digital caliper. Maximum distraction force, distance to suction seal rupture, and peak negative pressure were recorded while the hip underwent distraction at a rate of 0.5 mm/s. Correlations between factors were analyzed using the Spearman rho, and differences between groups were detected using Mann-Whitney U test. RESULTS: Of 23 hips, 12 satisfied inclusion criteria. The maximum distraction force and peak negative pressure were significantly correlated (R = -0.83; P = .001). Labral height was largely correlated with all suction seal parameters (maximum distraction force, R = 0.69, P = .013; distance to suction seal rupture, R = 0.55, P = .063; peak negative pressure, R = -0.62, P = .031). Labral height less than 6 mm was observed in 5 hips, with a mean height of 6.48 mm (SD, 2.65 mm; range, 2.62-11.90 mm; 95% CI, 4.80-8.17 mm). Compared with the 7 hips with larger labra (>6 mm), the hips with smaller labra had significantly shorter distance to suction seal rupture (median, 2.3 vs 7.2 mm; P = .010) and significantly decreased peak negative pressure (median, -59.3 vs -66.9 kPa; P = .048). CONCLUSION: Smaller height (<6 mm) of the acetabular labrum was significantly associated with decreased distance to suction seal rupture and decreased peak negative pressure. A new strategy to increase the size of the labrum, such as labral augmentation, could be justified for patients with smaller labra in order to optimize the hip suction seal. CLINICAL RELEVANCE: The height of the acetabular labrum is correlated with hip suction seal biomechanics. Further studies are required to identify the clinical effects of labral height on hip stability.

Medial Patellotibial Ligament Reconstruction Improves Patella Tracking When Combined With Medial Patellofemoral Reconstruction: An In Vitro Kinematic Study.

PURPOSE: To investigate the isolated and combined effects of medial patellofemoral ligament (MPFL) and medial patellotibial ligament (MPTL) deficiency and reconstruction on patellofemoral kinematics. METHODS: Sixteen matched-paired female cadaveric knee specimens with a mean age of 53.5 years (range, 26-65) were tested in 5 conditions: (1) intact, (2) MPFL or MPTL cut, (3) MPFL and MPTL combined cut, (4) MPFL or MPTL reconstruction, and (5) MPFL and MPTL combined reconstruction. Dynamic testing allowed continuous analysis of kinematics from 0° to 90° of knee flexion. Knees were also tested statically using a lateral load of 45 N at 0°, 30°, 60°, and 90° of flexion. In both dynamic and static loading tests, a motion capture system detected patellar position for each testing state to distinguish changes in patellar kinematics. Random-intercepts linear mixed-effects models were used to compare patellar kinematics. RESULTS: The MPFL is the primary restraint to lateral translation of the patella at all knee flexion angles. MPTL deficiency alone did not create significant patella instability, but further increased instability when the MPFL was deficient. Isolated MPFL and combined reconstruction provided improved stability. Through full range of motion native patella tracking was best recreated with combined ligament reconstruction. CONCLUSIONS: The MPFL plays the greatest role in medial patellar stability, but the MPTL appears to have an influence on patella tracking. This study provides further understanding to the impact of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking. CLINICAL RELEVANCE: This study provides further understanding of the role of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking.

The Effect of Mesenchymal Stem Cell Sheets on Early Healing of the Achilles Tendon in Rats.

Bone marrow-derived mesenchymal stem cells (BMSCs) have potential to accelerate flexor tendon healing and allow for earlier rehabilitation. The ideal BMSC construct and delivery method to the repair site remains unknown. We investigated the efficacy of interposed scaffold-free BMSC sheets on early Achilles tendon healing in rats. BMSCs were isolated from the femora and tibias of male Sprague-Dawley rats aged 8-12 weeks and BMSC sheets were produced on temperature-responsive culture dishes. Ninety-five male Sprague-Dawley rats aged 8-12 weeks were utilized. A bilateral Achilles tendon repair model was created. One side was randomly selected, and the tendon was repaired with the interposed BMSC sheet (BMSC group). The other side was repaired without BMSCs (control group). The bilateral tendons were harvested at 5, 6, 7, 10, and 14 days postoperatively for biomechanical analysis, measurement of the gene expression level of tendon markers scleraxis and tenomodulin by real-time polymerase chain reaction, and histological evaluation. The BMSC group had significantly higher maximum load to failure and stiffness at 5 and 6 days compared with the control group. Moreover, the BMSC group showed significantly increased gene expression of scleraxis and/or tenomodulin at all timepoints. The cross sectional areas in the BMSC group were significantly larger at 5, 6, and 14 days. However, hematoxylin and eosin staining of the central part of the repair site revealed no significant differences at all timepoints. These results suggest that the increased biomechanical strength afforded by BMSC sheet implantation into tendon repair sites may allow for the earlier onset of rehabilitation and improved clinical outcomes in flexor tendon surgery. Impact Statement We investigated the efficacy of interposed bone marrow-derived mesenchymal stem cell (BMSC) sheets on early Achilles tendon healing in rats. The tendons repaired with BMSC sheets revealed significantly increased mechanical strength compared with the control repairs (without the BMSC sheet) at 5 and 6 days. These data reveal that BMSC sheet implantation into tendon repair sites may allow for earlier onset of rehabilitation and improved clinical outcomes in flexor tendon surgery.

Biomechanical and Histopathological Analysis of a Retrieved Dermal Allograft After Superior Capsule Reconstruction: A Case Report.

The purpose of this study was to evaluate biomechanical and histopathological results of a retrieved acellular human dermal allograft (AHDA) after superior capsule reconstruction (SCR). A 67-year-old man with pseudoparalysis was treated with SCR for an irreparable posterosuperior rotator cuff tear. The patient failed clinically 4.5 months postoperatively and elected to undergo reverse total shoulder arthroplasty (RTSA). At the time of RTSA, the AHDA was harvested. Biomechanical and histopathologic analyses were performed and compared to native grafts. Failure loads for the explanted graft and native grafts 1 and 2 were 158, 790, and 749 N, respectively. The stiffness values were 20.2, 73, and 100.5 N/mm. The displacement at failure for each graft was 10.1, 27.9, and 17.0 mm. Hematoxylin and eosin and Masson's trichrome staining revealed the presence of cells in all portions of the AHDA. The medial portion presented extensive cellular infiltration, the middle portion moderate, and the lateral portion the least infiltration. Although the only identifiable cells in the lateral portions were found in pockets on the interior of the graft, cells were mainly localized on the exterior. Postoperative cell incorporation could be found in acellular dermal allograft after SCR. However, biomechanical properties in the early postoperative phase were inferior compared with unimplanted allografts.

Influence of Medial Meniscus Bucket-Handle Repair in Setting of Anterior Cruciate Ligament Reconstruction on Tibiofemoral Contact Mechanics: A Biomechanical Study.

PURPOSE: To compare the impact of an inside-out repair versus meniscectomy of a medial meniscus bucket-handle tear in restoring native contact areas and pressures across the tibial plateaus in the setting of an anterior cruciate ligament (ACL) reconstruction (ACLR). METHODS: Ten fresh-frozen cadaveric knees were tested in 6 knee conditions (1: intact; 2: ACL torn and bucket-handle tear of medial meniscus, flipped; 3: bucket-handle tear of medial meniscus, reduced; 4: bucket-handle tear of medial meniscus, repaired via inside-out vertical mattress suture technique; 5: ACLR with bone patella tendon bone autograft and bucket-handle repair; 6: ACLR and medial meniscus bucket-handle tear debridement) at 4 flexion angles (0°, 30°, 45°, and 60°), under a 1,000-N axial load. Contact area and pressure were measured with Tekscan sensors. RESULTS: ACLR with a concurrent medial meniscectomy for a medial meniscus bucket-handle tear resulted in significantly decreased contact area (P < .05) and increased mean and peak pressure in both the medial and lateral compartments across all tested flexion angles (P < .05). The ACLR with medial meniscectomy state also demonstrated significantly lower contact area than the bucket-handle repair state between 30° and 60° of flexion (all P < .05). CONCLUSIONS: Resection of a bucket-handle medial meniscus tear concurrent with an ACLR resulted in significant increases in mean and peak contact pressures in not only the medial but also the lateral compartment. Preservation of the medial meniscus in the face of a bucket-handle tear is essential to more closely restore native tibiofemoral biomechanics. CLINICAL RELEVANCE: The increased mean and peak tibiofemoral contact pressure seen with excision of a bucket-handle medial meniscus tear would over time result in increased cartilaginous degradation and resultant osteoarthritis. Decreasing both of these factors through concomitant ACLR and inside-out bucket-handle meniscal repairs should improve patient outcomes by restoring knee biomechanics and kinematics closer to that of the native state.

Low-Profile Dual Small Plate Fixation Is Biomechanically Similar to Larger Superior or Anteroinferior Single Plate Fixation of Midshaft Clavicle Fractures.

BACKGROUND: Limited biomechanical data exist for dual small plate fixation of midshaft clavicle fractures, and no prior study has concurrently compared dual small plating to larger superior or anteroinferior single plate and screw constructs. PURPOSE: To biomechanically compare dual small orthogonal plating, superior plating, and anteroinferior plating of midshaft clavicle fractures by use of a cadaveric model. STUDY DESIGN: Descriptive laboratory study. METHODS: The study used 18 cadaveric clavicle specimens (9 pairs total), and 3 plating techniques were studied: anteroinferior, superior, and dual. The dual plating technique used smaller diameter plates and screws (1.6-mm thickness) than the other, single plate techniques (3.3-mm thickness). Each of the 9 clavicle pairs was randomly assigned a combination of 2 plating techniques, and randomization was used to determine which techniques were used for the right and left specimens. Clavicles were plated and then osteotomized to create an inferior butterfly fracture model, which was then fixed with a single interfragmentary screw. Clavicle specimens were then potted for mechanical testing. Initial bending, axial, and torsional stiffness of each construct was determined through use of a randomized nondestructive cyclic testing protocol followed by load to failure. RESULTS: No significant differences were found in cyclical axial (P = .667) or torsional (P = .526) stiffness between plating groups. Anteroinferior plating demonstrated significantly higher cyclical bending stiffness than superior plating (P = .005). No significant difference was found in bending stiffness between dual plating and either anteroinferior (P = .129) or superior plating (P = .067). No significant difference was noted in load to failure among plating methods (P = .353). CONCLUSION: Dual plating with a smaller plate-screw construct is biomechanically similar to superior and anteroinferior single plate fixation that uses larger plate-screw constructs. No significant differences were found between dual plating and either superior or anteroinferior single plating in axial, bending, or torsional stiffness or in bending load to failure. Dual small plating is a viable option for fixing midshaft clavicle fractures and may be a useful low-profile technique that avoids a larger and more prominent plate-screw construct. CLINICAL RELEVANCE: Plate prominence and hardware irritation are commonly reported complaints and reasons for revision surgery after plate fixation of midshaft clavicle fractures. Dual small plate fixation has been used to improve cosmetic acceptability, minimize hardware irritation, and decrease reoperation rate. Biomechanically, dual small plate fixation performed similarly to larger single plate fixation in this cadaveric model of butterfly fracture.

Biomechanical Comparison of Vertical Mattress and Cross-stitch Suture Techniques and Single- and Double-Row Configurations for the Treatment of Bucket-Handle Medial Meniscal Tears.

BACKGROUND: Given the variety of suturing techniques for bucket-handle meniscal repair, it is important to assess which suturing technique best restores native biomechanics. PURPOSE/HYPOTHESIS: To biomechanically compare vertical mattress and cross-stitch suture techniques, in single- and double-row configurations, in their ability to restore native knee kinematics in a bucket-handle medial meniscal tear model. The hypothesis was that there would be no difference between the vertical mattress and cross-stitch double-row suture techniques but that the double-row technique would provide significantly improved biomechanical parameters versus the single-row technique. STUDY DESIGN: Controlled laboratory study. METHODS: Ten matched pairs of human cadaver knees were randomly assigned to the vertical mattress (n = 10) or cross-stitch (n = 10) repair group. Each knee underwent 4 consecutive testing conditions: (1) intact, (2) displaced bucket-handle tear, (3) single-row suture configuration on the femoral meniscus surface, and (4) double-row suture configuration (repair of femoral and tibial meniscus surfaces). Knees were loaded with a 1000-N axial compressive force at 0°, 30°, 60°, 90°, and 120° of flexion for each condition. Resultant medial compartment contact area, average contact pressure, and peak contact pressure data were recorded. RESULTS: Intact state contact area was not restored at 0° ( P = .027) for the vertical double-row configuration and at 0° ( P = .032), 60° ( P < .001), and 90° ( P = .007) of flexion for the cross-stitch double-row configuration. No significant differences were found in the average contact pressure and peak contact pressure between the intact state and the vertical mattress and cross-stitch repairs with single- and double-row configurations at any flexion angles. When the vertical and cross-stich repairs were compared across all flexion angles, no significant differences were observed in single-row configurations, but in double-row configurations, cross-stitch repair resulted in a significantly decreased contact area, average contact pressure, and peak contact pressure (all P < .001). CONCLUSION: Single- and double-row configurations of the vertical mattress and cross-stitch inside-out meniscal repair techniques restored native tibiofemoral pressure after a medial meniscal bucket-handle tear at all assessed knee flexion angles. Despite decreased contact area with a double-row configuration, mainly related to the cross-stitch repair, in comparison with the intact state, the cross-stitch double-row repair led to decreased pressure as compared with the vertical double-row repair. These findings are applicable only at the time of the surgery, as the biological effects of healing were not considered. CLINICAL RELEVANCE: Medial meniscal bucket-handle tears may be repaired with the single- or double-row configuration of vertical mattress or cross-stitch sutures.

Biomechanical Comparison of 3 Novel Repair Techniques for Radial Tears of the Medial Meniscus: The 2-Tunnel Transtibial Technique, a "Hybrid" Horizontal and Vertical Mattress Suture Configuration, and a Combined "Hybrid Tunnel" Technique.

BACKGROUND: Historically, radial meniscal tears were treated with partial or near-total meniscectomy, which usually resulted in poor outcomes. Radial meniscal tears function similar to a total meniscectomy and are challenging to treat. Repair of radial meniscal tears should be performed to prevent joint deterioration and the need for salvage procedures in the future. PURPOSE/HYPOTHESIS: The purpose was to compare 3 repair techniques for radial tears of the medial meniscus: the 2-tunnel, hybrid, and hybrid tunnel techniques. It was hypothesized that there would be no differences among the 3 groups in regard to gapping and ultimate failure strength. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty human male cadaver knees (10 matched pairs, n = 20; 10 unpaired, n = 10) were used to compare the 2-tunnel, hybrid, and hybrid tunnel repairs. A complete radial tear was made at the midbody of the medial meniscus. Repairs were performed according to the described techniques. Specimens were potted and mounted on a universal material testing machine where each specimen was cyclically loaded for 1000 cycles before experiencing a pull to failure. Gap distances at the tear site, ultimate failure load, and failure location were measured and recorded. RESULTS: After 1000 cycles of cyclic loading, there were no significant differences in displacement among the 2-tunnel repair (3.0 ± 1.7 mm), hybrid repair (3.0 ± 0.9 mm), and hybrid tunnel repair (2.3 ± 1.0 mm; P = .4042). On pull-to-failure testing, there were also no significant differences in ultimate failure strength among the 2-tunnel repair (259 ± 103 N), hybrid repair (349 ± 149 N), and hybrid tunnel repair (365 ± 146 N; P = .26). However, the addition of vertical mattress sutures to act as a "rip stop" significantly reduced the likelihood of the sutures pulling through the meniscus during pull-to-failure testing for the hybrid and hybrid tunnel repairs (4 of 16, 25%) as compared with the 2-tunnel repair (7 of 9, 78%; P = .017). CONCLUSION: The results showed equivalent biomechanical testing with regard to gap distance and pull-to-failure strength among the 3 repairs. The addition of the vertical mattress sutures to act as a rip stop was effective in preventing meniscal cutout through the meniscus. CLINICAL RELEVANCE: Effective healing of radial meniscal tears after repair is paramount to prevent joint deterioration and symptom development. Each tested repair showed a biomechanically equivalent and stable construct to use to repair radial meniscal tears. The authors recommend that rip stop vertical mattress sutures be used, especially in poor-quality meniscal tissue, to prevent suture cutout.

Quantitative and Qualitative Assessment of the Posterior Medial Meniscus Anatomy: Defining Meniscal Ramp Lesions.

BACKGROUND: Meniscal ramp lesions have been defined as a tear of the peripheral attachment of the posterior horn of the medial meniscus (PHMM) at the meniscocapsular junction or an injury to the meniscotibial attachment. Precise anatomic descriptions of these structures are limited in the current literature. PURPOSE: To quantitatively and qualitatively describe the PHMM and posteromedial capsule anatomy pertaining to the location of a meniscal ramp lesion with reference to surgically relevant landmarks. STUDY DESIGN: Descriptive laboratory study. METHODS: Fourteen male nonpaired fresh-frozen cadavers were used. The locations of the posteromedial meniscocapsular and meniscotibial attachments were identified. Measurements to surgically relevant landmarks were performed with a coordinate measuring system. To further analyze the posteromedial meniscocapsular and meniscotibial attachments, hematoxylin and eosin and alcian blue staining were conducted on a separate sample of 10 nonpaired specimens. RESULTS: The posterior meniscocapsular attachment had a mean ± SD length of 20.2 ± 6.0 mm and attached posteroinferiorly to the PHMM at a mean depth of 36.4% of the total posterior meniscal height. The posterior meniscotibial ligament attached on the PHMM 16.5 mm posterior and 7.7 mm medial to the center of the posterior medial meniscal root attachment. The meniscotibial ligament tibial attachment was 5.9 ± 1.3 mm inferior to the articular cartilage margin of the posterior medial tibial plateau. The posterior meniscocapsular attachment converged with the meniscotibial ligament at the most posterior point of the meniscocapsular junction in all specimens. Histological staining of the meniscocapsular and meniscotibial ligament PHMM attachments showed similar structure, cell density, and fiber directionality, with no qualitative difference in the makeup of their collagen matrices across all specimens. CONCLUSION: The anatomy of the area where a medial meniscal ramp tear occurs revealed that the 2 posterior meniscal attachments merged at a common attachment on the PHMM. Histological analysis validated a shared attachment point of the meniscocapsular and meniscotibial attachments of the PHMM. CLINICAL RELEVANCE: The findings of this study provide the anatomic foundation for an improved understanding of the meniscocapsular and meniscotibial attachments of the PHMM, which may help provide a more precise definition of a meniscal ramp lesion.

Effects of Capsular Reconstruction With an Iliotibial Band Allograft on Distractive Stability of the Hip Joint: A Biomechanical Study.

BACKGROUND: The capsular ligaments and the labral suction seal cooperatively manage distractive stability of the hip. Capsular reconstruction using an iliotibial band (ITB) allograft aims to address capsular insufficiency and iatrogenic instability. However, the extent to which this procedure may restore hip distractive stability after a capsular defect is unknown. PURPOSE: To evaluate the biomechanical effects of capsular reconstruction on distractive stability of the hip joint. STUDY DESIGN: Controlled laboratory study. METHODS: Eight fresh-frozen cadaveric hip specimens were dissected to the level of the capsule and axially distracted in 3 testing states: intact capsule, partial capsular defect, and capsular reconstruction with an ITB allograft. Each femur was compressed with 500 N of force and then distracted 6 mm relative to the neutral position at 0.5 mm/s. Distractive force was continuously recorded, and the first peak delineating 2 phases of hip distractive stability in the force-displacement curve was analyzed. RESULTS: The median force at maximum distraction in the capsular reconstruction state (156 N) was significantly greater than that in the capsular defect state (89 N; P = .036) but not significantly different from that in the intact state (218 N; P = .054). Median values for distractive force at first peak (60 N, 72 N, and 61 N, respectively; P = .607), distraction at first peak (2.3 mm, 2.3 mm, and 2.5 mm, respectively; P = .846), and percentage decrease in distractive force (35%, 78%, and 63%, respectively; P = .072) after the first peak were not significantly different between the intact, defect, and reconstruction states. CONCLUSION: Capsular reconstruction with an ITB allograft significantly increased the force required to distract the hip compared with a capsular defect in a cadaveric model. To our knowledge, this is the first study to report an initial peak distractive force and to propose 2 distinct phases of hip distractive stability. CLINICAL RELEVANCE: The consequences of a capsular defect on distractive stability of the hip may be underappreciated among the orthopaedic community; with that said, capsular reconstruction using an ITB allograft provided significantly increased distractive stability and should be considered an effective treatment option for patients with symptomatic capsular deficiency.