Mechanical properties of tissue formed in vivo are affected by 3D-bioplotted scaffold microarchitecture and correlate with ECM collagen fiber alignment.

Purpose: Musculoskeletal soft tissues possess highly aligned extracellular collagenous networks that provide structure and strength. Such an organization dictates tissue-specific mechanical properties but can be difficult to replicate by engineered biological substitutes. Nanofibrous electrospun scaffolds have demonstrated the ability to control cell-secreted collagen alignment, but concerns exist regarding their scalability for larger and anatomically relevant applications. Additive manufacturing processes, such as melt extrusion-based 3D-Bioplotting, allow fabrication of structurally relevant scaffolds featuring highly controllable porous microarchitectures.Materials and Methods: In this study, we investigate the effects of 3D-bioplotted scaffold design on the compressive elastic modulus of neotissue formed in vivo in a subcutaneous rat model and its correlation with the alignment of ECM collagen fibers. Polycaprolactone scaffolds featuring either 100 or 400 µm interstrand spacing were implanted for 4 or 12 weeks, harvested, cryosectioned, and characterized using atomic-force-microscopy-based force mapping.Results: The compressive elastic modulus of the neotissue formed within the 100 µm design was significantly higher at 4 weeks (p < 0.05), but no differences were observed at 12 weeks. In general, the tissue stiffness was within the same order of magnitude and range of values measured in native musculoskeletal soft tissues including the porcine meniscus and anterior cruciate ligament. Finally, a significant positive correlation was noted between tissue stiffness and the degree of ECM collagen fiber alignment (p < 0.05) resulting from contact guidance provided by scaffold strands.Conclusion: These findings demonstrate the significant effects of 3D-bioplotted scaffold microarchitectures in the organization and sub-tissue-level mechanical properties of ECM in vivo.

Editorial Commentary: Fluoroscopy Is Seldom Required During Knee Posterolateral Reconstruction.

Identifying the structures of the lateral knee is critical during knee posterolateral corner reconstruction. Several methods exist that can help estimate the femoral insertions of these structures on lateral radiographs. However, it is important to recognize the limitations of these methods and that anatomic visualization is often more practical and more accurate. Until percutaneous or more minimally invasive techniques become standardized, intraoperative fluoroscopy is seldom needed or used for posterolateral corner reconstruction, whereas radiographic analysis of lateral knee structures could be of benefit in cases of failed reconstruction to assess tunnel placement.

In Situ Joint Stiffness Increases During Skeletal Growth but Decreases Following Partial and Complete Anterior Cruciate Ligament Injury.

Partial and complete anterior cruciate ligament (ACL) injuries occur in both pediatric and adult populations and can result in loss of joint stability and function. The sigmoidal shape of knee joint function (load-translation curve) under applied loads includes a low-load region (described by slack length) followed by a high-load region (described by stiffness). However, the impact of age and injury on these parameters is not fully understood. The current objective was to measure the effects of age and injury on the shape of joint function in a porcine model. In response to an applied anterior-posterior tibial load, in situ slack did not change (p > 0.05), despite sevenfold increases in joint size with increasing age. Joint stiffness increased from an average of 10 N/mm in early youth to 47 N/mm in late adolescence (p < 0.05). In situ ACL stiffness increased similarly, and changes in in situ joint stiffness and ACL stiffness were highly correlated across ages. With complete ACL injury, in situ slack length increased by twofold to fourfold and in situ stiffness decreased threefold to fourfold across ages (p < 0.05). Partial ACL injury resulted in less dramatic, but statistically significant, increases in joint slack and significant decreases in in situ joint stiffness in the adolescent age groups (p < 0.05). This work furthers our understanding of the interaction between joint biomechanics and ACL function throughout growth and the impact of ACL injury in the skeletally immature joint.

Biomechanical Function and Size of the Anteromedial and Posterolateral Bundles of the ACL Change Differently with Skeletal Growth in the Pig Model.

BACKGROUND: ACL injuries are becoming increasingly common in children and adolescents, but little is known regarding age-specific ACL function in these patients. To improve our understanding of changes in musculoskeletal tissues during growth and given the limited availability of pediatric human cadaveric specimens, tissue structure and function can be assessed in large animal models, such as the pig. QUESTIONS/PURPOSES: Using cadaveric porcine specimens ranging throughout skeletal growth, we aimed to assess age-dependent changes in (1) joint kinematics under applied AP loads and varus-valgus moments, (2) biomechanical function of the ACL under the same loads, (3) the relative biomechanical function of the anteromedial and posterolateral bundles of the ACL; and (4) size and orientation of the anteromedial and posterolateral bundles. METHODS: Stifle joints (analogous to the human knee) were collected from female Yorkshire crossbreed pigs at five ages ranging from early youth to late adolescence (1.5, 3, 4.5, 6, and 18 months; n = 6 pigs per age group, 30 total), and MRIs were performed. A robotic testing system was used to determine joint kinematics (AP tibial translation and varus-valgus rotation) and in situ forces in the ACL and its bundles in response to applied anterior tibial loads and varus-valgus moments. To see if morphological changes to the ACL compared with biomechanical changes, ACL and bundle cross-sectional area, length, and orientation were calculated from MR images. RESULTS: Joint kinematics decreased with increasing age. Normalized AP tibial translation decreased by 44% from 1.5 months (0.34 ± 0.08) to 18 months (0.19 ± 0.02) at 60° of flexion (p < 0.001) and varus-valgus rotation decreased from 25° ± 2° at 1.5 months to 6° ± 2° at 18 months (p < 0.001). The ACL provided the majority of the resistance to anterior tibial loading at all age groups (75% to 111% of the applied anterior force; p = 0.630 between ages). Anteromedial and posterolateral bundle function in response to anterior loading and varus torque were similar in pigs of young ages. During adolescence (4.5 to 18 months), the in situ force carried by the anteromedial bundle increased relative to that carried by the posterolateral bundle, shifting from 59% ± 22% at 4.5 months to 92% ± 12% at 18 months (data for 60° of flexion, p < 0.001 between 4.5 and 18 months). The cross-sectional area of the anteromedial bundle increased by 30 mm throughout growth from 1.5 months (5 ± 2 mm) through 18 months (35 ± 8 mm; p < 0.001 between 1.5 and 18 months), while the cross-sectional area of the posterolateral bundle increased by 12 mm from 1.5 months (7 ± 2 mm) to 4.5 months (19 ± 5 mm; p = 0.004 between 1.5 and 4.5 months), with no further growth (17 ± 7 mm at 18 months; p = 0.999 between 4.5 and 18 months). However, changes in length and orientation were similar between the bundles. CONCLUSION: We showed that the stifle joint (knee equivalent) in the pig has greater translational and rotational laxity in early youth (1.5 to 3 months) compared with adolescence (4.5 to 18 months), that the ACL functions as a primary stabilizer throughout growth, and that the relative biomechanical function and size of the anteromedial and posterolateral bundles change differently with growth. CLINICAL RELEVANCE: Given the large effects observed here, the age- and bundle-specific function, size, and orientation of the ACL may need to be considered regarding surgical timing, graft selection, and graft placement. In addition, the findings of this study will be used to motivate pre-clinical studies on the impact of partial and complete ACL injuries during skeletal growth.

Quadriceps weakness associates with greater T1ρ relaxation time in the medial femoral articular cartilage 6 months following anterior cruciate ligament reconstruction.

PURPOSE: Quadriceps weakness following anterior cruciate ligament reconstruction (ACLR) is linked to decreased patient-reported function, altered lower extremity biomechanics and tibiofemoral joint space narrowing. It remains unknown if quadriceps weakness is associated with early deleterious changes to femoral cartilage composition that are suggestive of posttraumatic osteoarthritis development. The purpose of the cross-sectional study was to determine if quadriceps strength was associated with T1ρ relaxation times, a marker of proteoglycan density, of the articular cartilage in the medial and lateral femoral condyles 6 months following ACLR. It is hypothesized that individuals with weaker quadriceps would demonstrate lesser proteoglycan density. METHODS: Twenty-seven individuals (15 females, 12 males) with a patellar tendon autograft ACLR underwent isometric quadriceps strength assessments in 90°of knee flexion during a 6-month follow-up exam. Magnetic resonance images (MRI) were collected bilaterally and voxel by voxel T1ρ relaxation times were calculated using a five-image sequence and a monoexponential equation. Following image registration, the articular cartilage for the weight-bearing surfaces of the medial and lateral femoral condyles (MFC and LFC) were manually segmented and further sub-sectioned into posterior, central and anterior regions of interest (ROI) based on the corresponding meniscal anatomy viewed in the sagittal plane. Univariate linear regression models were used to determine the association between quadriceps strength and T1ρ relaxation times in the entire weight-bearing MFC and LFC, as well as the ROI in each respective limb. RESULTS: Lesser quadriceps strength was significantly associated with greater T1ρ relaxation times in the entire weight-bearing MFC (R2 = 0.14, P = 0.05) and the anterior-MFC ROI (R2 = 0.22, P = 0.02) of the ACLR limb. A post hoc analysis found lesser strength and greater T1ρ relaxation times were significantly associated in a subsection of participants (n = 18) without a concomitant medial tibiofemoral compartment meniscal or chondral injury in the entire weight-bearing MFC, as well as anterior-MFC and central-MFC ROI of the ACLR and uninjured limb. CONCLUSIONS: The association between weaker quadriceps and greater T1ρ relaxation times in the MFC suggests deficits in lower extremity muscle strength may be related to cartilage composition as early as 6 months following ACLR. Maximizing quadriceps strength in the first 6 months following ACLR may be critical for promoting cartilage health early following ACLR. LEVEL OF EVIDENCE: Prognostic level 1.

Engineering 3D-Bioplotted scaffolds to induce aligned extracellular matrix deposition for musculoskeletal soft tissue replacement.

PURPOSE: Tissue engineering and regenerative medicine approaches have the potential to overcome the challenges associated with current treatment strategies for meniscus injuries. 3D-Bioplotted scaffolds are promising, but have not demonstrated the ability to guide the formation of aligned collagenous matrix in vivo, which is critical for generating functional meniscus tissue. In this study, we evaluate the ability of 3D-Bioplotted scaffold designs with varying interstrand spacing to induce the deposition of aligned matrix in vivo. MATERIALS AND METHODS: 3D-Bioplotted polycaprolactone scaffolds with 100, 200, or 400 µm interstrand spacing were implanted subcutaneously in a rat model for 4, 8, or 12 weeks. Scaffolds were harvested, paraffin-embedded, sectioned, and stained to visualize cell nuclei and collagen. Quantitative image analysis was used to evaluate cell density, matrix fill, and collagen fiber alignment within the scaffolds. RESULTS: By 4 weeks, cells had infiltrated the innermost scaffold regions. Similarly, collagenous matrix filled interstrand regions nearly completely by 4 weeks. By 12 weeks, aligned collagen was present in all scaffolds. Generally, alignment along the scaffold strands increased over time for all three interstrand spacing groups. Distribution of collagen fiber alignment angles narrowed as interstrand spacing decreased. CONCLUSIONS: 3D-Bioplotted scaffolds allow for complete cell infiltration and collagenous matrix production throughout the scaffold. The ability to use interstrand spacing as a means of controlling the formation of aligned collagen in vivo was demonstrated, which helps establish a design space for scaffold-based meniscus tissue engineering.

Risk Factors for Infection After Knee Arthroscopy: Analysis of 595,083 Cases From 3 United States Databases.

PURPOSE: To identify and quantify patient- and procedure-related risk factors for post-arthroscopic knee infections using a large dataset. METHODS: An administrative health care database including 8 years of records from 2 large commercial insurers and Medicare (a 5% random sample) was queried to identify all knee arthroscopies performed on patients aged at least 15 years using Current Procedural Terminology (CPT) codes. Each CPT code was designated as a high- or low-complexity procedure, with the former typically requiring accessory incisions or increased operative time. Deep infections were identified by a CPT code for incision and drainage within 90 days of surgery. Superficial infections were identified by International Classification of Diseases, Ninth Revision infection codes without any record of incision and drainage. Patients were compared based on age, sex, body mass index, tobacco use, presence of diabetes, and Charlson Comorbidity Index. RESULTS: A total of 526,537 patients underwent 595,083 arthroscopic knee procedures. Deep postoperative infections occurred at a rate of 0.22%. Superficial infections occurred at a rate of 0.29%. Tobacco use and morbid obesity were the largest risk factors for deep and superficial infections, respectively (P < .001; relative risk of 1.90 and 2.19, respectively). There were also higher infection rates among patients undergoing relatively high-complexity arthroscopies, men, obese patients, diabetic patients, and younger patients (in order of decreasing relative risk). Increased Charlson Comorbidity Index was associated with superficial and total infections (P < .001). CONCLUSIONS: Post-arthroscopic knee infections were more frequent among morbidly obese patients, tobacco users, patients undergoing relatively complex procedures, men, obese patients, diabetic patients, relatively young patients, and patients with increased comorbidity burdens in this study population. This knowledge may allow more informed preoperative counseling, aid surgeons in patient selection, and facilitate infection prevention by targeting individuals with higher inherent risk. LEVEL OF EVIDENCE: Level IV, cross-sectional study.

Initial medical management of rotator cuff tears: a demographic analysis of surgical and nonsurgical treatment in the United States Medicare population.

BACKGROUND: Rotator cuff tears have a lifetime incidence between 25% and 40% in the United States, but optimum treatment strategies and protocol have not yet been widely accepted. This study evaluated the proportions of patients treated with nonoperative and operative modalities and how this proportion has changed during an 8-year period (2005-2012) among patients with Medicare. METHODS: Using the PearlDiver patient record database, we identified Medicare patients having been diagnosed with a rotator cuff tear. These patients were then stratified on the basis of treatment with physical therapy, subacromial/glenohumeral injection, or rotator cuff repair. We analyzed the data in regard to standard demographic information, comorbidities, and the Charlson Comorbidity Index. RESULTS: During the study period, 878,049 patients were identified and 397,116 patients had rotator cuff repair. The proportion of patients treated initially with physical therapy dropped from 30.0% in 2005 to 13.2% in 2012, and the subacromial/glenohumeral injection proportion decreased from 6.00% to 4.19% (P < .001). The proportion of patients who had rotator cuff repair increased from 33.8% to 40.4% from 2005 to 2012 (P < .001). Charlson Comorbidity Indexes were significantly lower in operative patients compared with each nonoperative treatment examined. DISCUSSION: This analysis demonstrates a significant decrease in the initial trial of nonoperative treatment and an increase in the rate of surgery. Patients undergoing rotator cuff repair had fewer comorbidities than those undergoing nonoperative treatments. It also demonstrates that patients who had a trial of injection had a higher incidence of eventual rotator cuff repair compared with the patients with an initial trial of physical therapy.

Biomechanical Threshold Values for Identifying Clinically Significant Knee-Related Symptoms Six Months Following Anterior Cruciate Ligament Reconstruction.

CONTEXT: Slower habitual walking speed and aberrant gait biomechanics are linked to clinically significant knee-related symptoms and articular cartilage composition changes linked to posttraumatic osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR). OBJECTIVE: To determine specific gait biomechanical variables that can accurately identify individuals with clinically significant knee-related symptoms post-ACLR, and the corresponding threshold values, sensitivity, specificity, and odds ratios for each biomechanical variable. DESIGN: Cross-sectional analysis. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Seventy-one individuals (n=38 female; age=21±4 years; height=1.76±0.11 m; mass=75.38±13.79 kg) who were 6 months post-primary unilateral ACLR (6.2±0.4 months). MAIN OUTCOME MEASURES: 3D motion capture of 5 overground walking trials was used to calculate discrete gait biomechanical variables of interest during stance phase (1st and 2nd peak vertical ground reaction force [vGRF]; midstance minimum vGRF; peak internal knee abduction and extension moments; and peak knee flexion angle), along with habitual walking speed. Knee Injury and Osteoarthritis Outcome Scores (KOOS) was used to dichotomize patients as symptomatic (n=51) or asymptomatic (n=20) using the Englund et al. 2003 KOOS guidelines for defining clinically significant knee-related symptoms. Separate receiver operating characteristic (ROC) curves and respective areas under the curve (AUC) were used to evaluate the capability of each biomechanical variable of interest for identifying individuals with clinically significant knee-related symptoms. RESULTS: Habitual walking speed (AUC=0.66), vGRF at midstance (AUC=0.69), and 2nd peak vGRF (AUC=0.76), demonstrated low-to-moderate accuracy for identifying individuals with clinically significant knee-related symptoms. Individuals who exhibited habitual walking speeds ≤1.27 m/s, midstance vGRF ≥0.82 BW, and 2nd peak vGRF ≤1.11 BW, demonstrated 3.13, 6.36, and 9.57 times higher odds of experiencing clinically significant knee-related symptoms, respectively. CONCLUSIONS: Critical thresholds for gait variables may be utilized to identify individuals with increased odds of clinically significant knee-related symptoms and potential targets for future interventions.

Association of Serum Biochemical Biomarker Profiles of Joint Tissue Inflammation and Cartilage Metabolism With Posttraumatic Osteoarthritis-Related Symptoms at 12 Months After ACLR.

BACKGROUND: Anterior cruciate ligament injury and anterior cruciate ligament reconstruction (ACLR) are risk factors for symptomatic posttraumatic osteoarthritis (PTOA). After ACLR, individuals demonstrate altered joint tissue metabolism indicative of increased inflammation and cartilage breakdown. Serum biomarker changes have been associated with tibiofemoral cartilage composition indicative of worse knee joint health but not with PTOA-related symptoms. PURPOSE/HYPOTHESIS: The purpose of this study was to determine associations between changes in serum biomarker profiles from the preoperative sample collection to 6 months after ACLR and clinically relevant knee PTOA symptoms at 12 months after ACLR. It was hypothesized that increases in biomarkers of inflammation, cartilage metabolism, and cartilage degradation would be associated with clinically relevant PTOA symptoms after ACLR. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Individuals undergoing primary ACLR were included (N = 30). Serum samples collected preoperatively and 6 months after ACLR were processed to measure markers indicative of changes in inflammation (ie, monocyte chemoattract protein 1 [MCP-1]) and cartilage breakdown (ie, cartilage oligomeric matrix protein [COMP], matrix metalloproteinase 3, ratio of type II collagen breakdown to type II collagen synthesis). Knee injury and Osteoarthritis Outcome Score surveys were completed at 12 months after ACLR and used to identify participants with and without clinically relevant PTOA-related symptoms. K-means cluster analyses were used to determine serum biomarker profiles. One-way analyses of variance and logistic regressions were used to assess differences in Knee injury and Osteoarthritis Outcome Score subscale scores and clinically relevant PTOA-related symptoms between biomarker profiles. RESULTS: Two profiles were identified and characterized based on decreases (profile 1: 67% female; age, 21.4 ± 5.1 years; body mass index, 24.4 ± 2.4) and increases (profile 2: 33% female; age, 21.3 ± 3.2 years; body mass index, 23.4 ± 2.6) in sMCP-1 and sCOMP preoperatively to 6 months after ACLR. Participants with profile 2 did not demonstrate differences in knee pain, symptoms, activities of daily living, sports function, or quality of life at 12 months after ACLR compared to those with profile 1 (P = .56-.81; η2 = 0.002-0.012). No statistically significant associations were noted between biomarker profiles and clinically relevant PTOA-related symptoms (odds ratio, 1.30; 95% CI, 0.23-6.33). CONCLUSION: Serum biomarker changes in MCP-1 and sCOMP within the first 6 months after ACLR were not associated with clinically relevant PTOA-related symptoms.

Peak vertical ground reaction force used to identify sub-groups of individuals with differing biomechanical gait profiles post-anterior cruciate ligament reconstruction.

Lesser peak vertical ground reaction force (vGRF) has been widely reported among individuals with anterior cruciate ligament reconstruction (ACLR). Peak vGRF remains less than uninjured controls and relatively stable during the first year following ACLR. However, it is unknown whether there are subgroups of individuals exhibiting consistently greater peak vGRF in the first 6-months following ACLR and if individuals with consistently greater peak vGRF exhibit kinematic and kinetic gait differences compared to individuals with low vGRF. The purpose of this study was to determine if distinct clusters exist based upon magnitude of peak vGRF 2- and 6-months post-ACLR. Subsequently, we explored between cluster differences in vGRF, knee flexion angle, and sagittal and frontal plane knee kinetics throughout stance between clusters. Forty-three individuals (58.1%female, 21.4 ± 4.4 years-old, 95.3% patellar-tendon autograft) completed five gait trials at their habitual walking speed 2- and 6-months post-ACLR. A single K-means cluster analysis was used to identify clusters of individuals based on peak vGRF at 2- and 6-months post-ACLR. Functional waveform analyses were used to compare gait outcomes between clusters with and without controlling for gait speed and age. We identified two clusters that included a subgroup with high vGRF (n = 16) and low vGRF (n = 27). The cluster with high vGRF demonstrated greater vGRFs, knee flexion angles, and knee extension moments during early stance as compared to the low vGRF cluster 2- and 6-months post-ACLR. Individuals with peak vGRF ≥1.02 times body-weight 2-months post-ACLR had 35.4 times greater odds of being assigned to the high vGRF cluster.

Comparison of fixation methods after anteromedialization osteotomy of the tibial tubercle for patellar instability.

PURPOSE: The aim of this study was to evaluate the biomechanical strength of two 4.5-mm screws and three 3.5-mm screws for fixation of the tibial tubercle after anteromedialization osteotomy. METHODS: Anteromedialization of the tibial tubercle was performed on 5 pairs of fresh-frozen cadaveric lower extremities. One leg from each pair was randomized to fixation with two 4.5-mm screws and the contralateral leg to fixation with three 3.5-mm screws. Each specimen was loaded cyclically to simulate an active straight-leg raise and then to failure while displacement of the tubercle fragment was recorded. RESULTS: There was no difference in mean tubercle fragment displacement under cyclic loading at any cycle number (P > .352). Maximum failure load for osteotomies secured with two 4.5-mm screws was 1,459 ± 540 N, and for three 3.5-mm screws it was 1,360 ± 707 N. This was not a statistically significant difference (P = .723). Tubercle migration of 7 mm was chosen as clinical failure. At this amount of displacement, mean load was 1,085 ± 398 N and 764 ± 313 N in the 4.5-mm and 3.5-mm groups, respectively, which was also not significantly different (P = .146). CONCLUSIONS: Both 2 × 4.5-mm and 3 × 3.5-mm screw constructs after tibial tubercle anteromedialization are equally capable of withstanding physiologic forces like those encountered during an active straight-leg raise and have similar failure strength. CLINICAL RELEVANCE: Although both configurations are comparable, the use of the smaller 3.5-mm screws may reduce the need for hardware removal related to prominence and soft tissue irritation.

Access to outpatient care for adult rotator cuff patients with private insurance versus Medicaid in North Carolina.

BACKGROUND: Access to orthopaedic care for pediatric patients has been shown in previous studies to be decreased for patients with Medicaid compared with those with private insurance. The relationship between type of insurance and access to care for adult patients with acute rotator cuff tears has not yet been examined. This study aimed to determine if type of health insurance would have an impact on access to care for an adult patient with an acute rotator cuff tear. METHODS: Seventy-one orthopaedic surgery practices within the state of North Carolina were randomly selected and contacted on 2 different occasions separated by 3 weeks. The practices were presented with an appointment request for a fictitious 42-year-old man with an acute rotator cuff tear. Insurance status was reported as Medicaid for the first call and as private insurance during the second call. RESULTS: Of the 71 practices contacted, 51 (72%) offered the patient with Medicaid an appointment, whereas 68 (96%) offered the patient with private insurance an appointment. The difference in these rates was statistically significant (P < .001). The likelihood of patients with private insurance obtaining an appointment was 8.8 times higher than that of patients with Medicaid (95% CI: 2.5, 31.5). CONCLUSION: For patients with acute rotator cuff tears, access to care is decreased for those with Medicaid compared with those with private insurance. Patients with private insurance are 8.8 times more likely than those with Medicaid to obtain an appointment. LEVEL OF EVIDENCE: Basic science, survey study.

Inter-rater agreement of the Goutallier, Patte, and Warner classification scores using preoperative magnetic resonance imaging in patients with rotator cuff tears.

PURPOSE: The purpose of this study was to determine the interobserver reliability of 3 commonly used classification systems in describing preoperative magnetic resonance imaging (MRI) studies of patients undergoing surgery for full-thickness rotator cuff tears. METHODS: Thirty-one patients who underwent arthroscopic rotator cuff repair and had preoperative MRI studies available were selected over a 2-year period. Three board-certified shoulder surgeons independently reviewed these images. Each was instructed in the published method for determining the Patte score on the T2 coronal images, supraspinatus and infraspinatus atrophy on the T1 sagittal images as described by Warner et al., and the Goutallier score of fatty infiltration of the supraspinatus on the T1 coronal/sagittal images. Statistical analysis was then performed to determine the interobserver agreement using the κ statistic, with the level of significance set a priori at P < .01. RESULTS: None of the classification systems studied yielded excellent or high interobserver reliability. The strongest agreement was found with the Patte classification assessing tendon retraction in the frontal plane (κ = 0.58). The Goutallier classification, which grades fatty infiltration of the supraspinatus, showed moderate interobserver agreement (κ = 0.53) when dichotomized into none to mild (grades 0, 1, and 2) and moderate to severe (grades 3 and 4). Muscle atrophy of both the supraspinatus and infraspinatus yielded the worst interobserver reliability, with only 28% agreement. CONCLUSIONS: The Goutallier, Patte, and Warner MRI classification systems for describing rotator cuff tears did not have high interobserver reliability among 3 experienced orthopaedic surgeons. Fatty infiltration of the supraspinatus and tendon retraction in the frontal planes showed only moderate reliability and moderate to high reliability, respectively. These findings have potential implications in the evaluation of the literature regarding the preoperative classification of rotator cuff tears and subsequent treatment algorithms. LEVEL OF EVIDENCE: Level III, diagnostic agreement study with nonconsecutive patients.

Effect of a 6-week strengthening program on shoulder and scapular-stabilizer strength and scapular kinematics in division I collegiate swimmers.

CONTEXT: Shoulder injuries are common in swimmers because of the demands of the sport. Muscle imbalances frequently exist due to the biomechanics of the sport, which predispose swimmers to injury. To date, an effective shoulder-injury-prevention program for competitive swimmers has not been established. OBJECTIVE: To assess the effectiveness of a 6-wk strengthening and stretching intervention program on improving glenohumeral and scapular muscle strength and scapular kinematics in collegiate swimmers. DESIGN: Randomized control trial. SETTING: University biomechanics research laboratory. PARTICIPANTS: Forty-four Division I collegiate swimmers. INTERVENTIONS: The intervention program was completed 3 times per week for 6 wk. The program included strengthening exercises completed using resistance tubing-scapular retraction (Ts), scapular retraction with upward rotation (Ys), scapular retraction with downward rotation (Ws), shoulder flexion, low rows, throwing acceleration and deceleration, scapular punches, shoulder internal rotation at 90° abduction, and external rotation at 90° abduction-and 2 stretching exercises: corner stretch and sleeper stretch. MAIN OUTCOME MEASUREMENTS: Scapular kinematics and glenohumeral and scapular muscle strength assessed preintervention and postintervention. RESULTS: There were no significant between-groups differences in strength variables at pre/post tests, although shoulder-extension and internal-rotation strength significantly increased in all subjects regardless of group assignment. Scapular kinematic data revealed increased scapular internal rotation, protraction, and elevation in all subjects at posttesting but no significant effect of group on the individual kinematic variables. CONCLUSIONS: The current strengthening and stretching program was not effective in altering strength and scapular kinematic variables but may serve as a framework for future programs. Adding more stretching exercises, eliminating exercises that overlap with weight-room training and swim training, and timing of implementation may yield a more beneficial program for collegiate swimmers.

Age- and Sex-Specific Joint Biomechanics in Response to Partial and Complete Anterior Cruciate Ligament Injury in the Porcine Model.

CONTEXT: Pediatric anterior cruciate ligament (ACL) injury rates are increasing and are highest in female adolescents. Complete ACL tears are typically surgically reconstructed, but few guidelines and very limited data exist regarding the need for surgical reconstruction or rehabilitation for partial ACL tears in skeletally immature patients. OBJECTIVE: To evaluate the effects of partial (anteromedial bundle) and complete ACL transection on joint laxity and tissue forces under anterior and rotational loads in male and female stifle joints throughout skeletal growth in the porcine model. DESIGN: Descriptive laboratory study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: We studied 60 male and female Yorkshire crossbreed pigs aged 1.5, 3, 4.5, 6, and 18 months (n = 6 pigs per age per sex). MAIN OUTCOME MEASURE(S): Joint laxity was measured in intact, anteromedial bundle-transected, and ACL-transected joints under applied anterior-posterior drawer and varus-valgus torque using a robotic testing system. Loading of the soft tissues in the stifle joint was measured under each condition. RESULTS: Anterior-posterior joint laxity increased by 13% to 50% (P < .05) after anteromedial bundle transection and 75% to 178% (P < .05) after ACL transection. Destabilization after anteromedial bundle transection increased with age (P < .05) and was greater in late female than late male adolescents (P < .05). In anteromedial bundle-transected joints, the posterolateral bundle resisted the anterior load. In ACL-transected joints, the medial collateral ligament (MCL) contribution was largest, followed by the medial meniscus. The MCL contribution was larger and the medial meniscus contribution was smaller in male versus female specimens. CONCLUSIONS: Partial ACL transection resulted in moderate increases in joint laxity, with the remaining bundle performing the primary ACL function. Destabilization due to partial ACL transection (anteromedial bundle) was largest in late adolescent joints, indicating that operative treatment should be considered in active, late-adolescent patients with this injury. Increased forces on the MCL and medial meniscus after ACL transection suggested that rehabilitation protocols may need to focus on protecting these tissues.

Worse Tibiofemoral Cartilage Composition Is Associated with Insufficient Gait Kinetics After ACL Reconstruction.

PURPOSE: Greater articular cartilage T1ρ magnetic resonance imaging relaxation times indicate less proteoglycan density and are linked to posttraumatic osteoarthritis development after anterior cruciate ligament reconstruction (ACLR). Although changes in T1ρ relaxation times are associated with gait biomechanics, it is unclear if excessive or insufficient knee joint loading is linked to greater T1ρ relaxation times 12 months post-ACLR. The purpose of this study was to compare external knee adduction (KAM) and flexion (KFM) moments in individuals after ACLR with high versus low tibiofemoral T1ρ relaxation profiles and uninjured controls. METHODS: Gait biomechanics were collected in 26 uninjured controls (50% females; age, 22 ± 4 yr; body mass index, 23.9 ± 2.8 kg·m -2 ) and 26 individuals after ACLR (50% females; age, 22 ± 4 yr; body mass index, 24.2 ± 3.5 kg·m -2 ) at 6 and 12 months post-ACLR. ACLR-T1ρ High ( n = 9) and ACLR-T1ρ Low ( n = 17) groups were created based on 12-month post-ACLR T1ρ relaxation times using a k-means cluster analysis. Functional analyses of variance were used to compare KAM and KFM. RESULTS: ACLR-T1ρ High exhibited lesser KAM than ACLR-T1ρ Low and uninjured controls 6 months post-ACLR. ACLR-T1ρ Low exhibited greater KAM than uninjured controls 6 and 12 months post-ACLR. KAM increased in ACLR-T1ρ High and decreased in ACLR-T1ρ Low between 6 and 12 months, both groups becoming more similar to uninjured controls. There were scant differences in KFM between ACLR-T1ρ High and ACLR-T1ρ Low 6 or 12 months post-ACLR, but both groups demonstrated lesser KFM compared with uninjured controls. CONCLUSIONS: Associations between worse T1ρ profiles and increases in KAM may be driven by the normalization of KAM in individuals who initially exhibit insufficient KAM 6 months post-ACLR.

Prescribing Fewer Opioids After Rotator Cuff Repair and Anterior Cruciate Ligament Reconstruction Lowers Opioid Consumption Without Impacting Patient-Reported Pain Scores.

Purpose: To develop a standardized opioid prescribing schedule (SOPS) following anterior cruciate ligament reconstruction (ACLR) and rotator cuff repair (RCR) and evaluate postoperative opioid consumption alongside Patient-Reported Outcome Measurement Information System (PROMIS) pain interference scores. Methods: A prospective observational study was performed on all patients undergoing primary ACLR and RCR from March 2019 to October 2021. Patients taking opioids preoperatively and revision ACLR and RCR were excluded. PROMIS 6B questionnaires were administered before and after implantation of the SOPS initiated on December 15, 2019. Opioid consumption was determined by email surveys. Hypothesis testing was performed with Mann-Whitney U test. Results: A total of 599 patients met inclusion criteria with 188 patients (71 ACLR and 117 RCR) completing surveys. Before the initiation of SOPS, the average number of oxycodone 5-mg tablets prescribed for ACLR was 44.6 (95% confidence interval [CI] 42.4-46.9) and for RCR was 44.7 (95% CI 42.7-46.8). The average usage was 23.1 (95% CI 16.9-29.2) and 22.1 (95% CI 16.2-28.0), respectively. Following SOPS of 30 tablets of oxycodone 5 mg for ACLR and 40 tablets for RCR, the average number of tablets prescribed significantly decreased for both procedures (P < .01 for ACLR and RCR), and the average consumption decreased to 20.5 (95% CI 16.6-24.4) and 18.6 (95% CI 14.6-22.5), respectively. PROMIS 6B responses did not demonstrate statistically significant changes following SOPS. Conclusions: The results of the present study demonstrate that the implementation of a SOPS reduced postoperative opioid prescribing amounts and consumption without significant impacting PROMIS pain interference scores for ACLR and RCR, supporting the possibility to decrease and standardize opioid prescribing following common sports medicine procedures. Level of Evidence: III: Retrospective, comparative, therapeutic study.

Sex-specific biomechanics and morphology of the anterior cruciate ligament during skeletal growth in a porcine model.

Pediatric anterior cruciate ligament (ACL) injuries are on the rise, and females experience higher ACL injury risk than males during adolescence. Studies in skeletally immature patients indicate differences in ACL size and joint laxity between males and females after the onset of adolescence. However, functional data regarding the ACL and its anteromedial and posterolateral bundles in the pediatric population remain rare. Therefore, this study uses a porcine model to investigate the sex-specific morphology and biomechanics of the ACL and its bundles throughout skeletal growth. Hind limbs from male and female Yorkshire pigs aged early youth to late adolescence were imaged using magnetic resonance imaging to measure the size and orientation of the ACL and its bundles, then biomechanically tested under anterior-posterior drawer using a robotic testing system. Joint laxity decreased (p < 0.001) while joint stiffness increased (p < 0.001) throughout skeletal growth in both sexes. The ACL was the primary stabilizer against anterior tibial loading, while the functional role of the anteromedial bundle increased with age (p < 0.001), with an earlier increase in males. ACL and posterolateral bundle cross-sectional area and ACL and anteromedial bundle length were larger in males than females during adolescence (p < 0.01 for all), while ACL and bundle sagittal angle remained similar between sexes. Additionally, in situ ACL stiffness versus cross-sectional area regressions were significant across skeletal growth (r2 = 0.75, p < 0.001 in males and r2 = 0.64, p < 0.001 in females), but not within age groups. This study has implications for age and sex-specific surgical intervention strategies and suggests the need for human studies.

In Vivo Compositional Changes in the Articular Cartilage of the Patellofemoral Joint Following Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: To compare T1ρ relaxation times of the medial and lateral regions of the patella and femoral trochlea at 6 and 12 months following anterior cruciate ligament reconstruction (ACLR) on the ACLR and contralateral extremity. Greater T1ρ relaxation times are associated with a lower proteoglycan density of articular cartilage. METHODS: This study involved 20 individuals (11 males, 9 females; mean ± SD age 22 ± 3.9 years, weight 76.11 ± 13.48 kg, and height 178.32 ± 12.32 cm) who underwent a previous unilateral ACLR using a patellar tendon autograft. Magnetic resonance images from both extremities were acquired at 6 and 12 months post-ACLR. Voxel by voxel T1ρ relaxation times were calculated using a 5-image sequence. The medial and lateral regions of the femoral trochlea and patellar articular cartilage were manually segmented on both extremities. Separate extremity (ACLR and contralateral extremity) by time (6 months and 12 months) analysis of variance tests were performed for each region (P < 0.05). RESULTS: For the medial patella and lateral trochlea, T1ρ relaxation times increased in both extremities between 6 and 12 months post-ACLR (medial patella P = 0.012; lateral trochlea P = 0.043). For the lateral patella, T1ρ relaxation times were significantly greater on the contralateral extremity compared to the ACLR extremity (P = 0.001). The T1ρ relaxation times of the medial trochlea on the ACLR extremity were significantly greater at 6 (P = 0.005) and 12 months (P < 0.001) compared to the contralateral extremity. T1ρ relaxation times of the medial trochlea significantly increased from 6 to 12 months on the ACLR extremity (P = 0.003). CONCLUSION: Changes in T1ρ relaxation times occur within the first 12 months following ACLR in specific regions of the patellofemoral joint on the ACLR and contralateral extremity.