On-Track Lesions with a Small Distance to Dislocation Are Associated with Failure After Arthroscopic Anterior Shoulder Stabilization.

BACKGROUND: Off-track lesions are strongly associated with failure after arthroscopic Bankart repair. However, on-track lesions with a small distance-to-dislocation (DTD) value, or "near-track lesions," also may be at risk for failure. The purpose of the present study was to determine the association of DTD with failure after arthroscopic Bankart repair. METHODS: We performed a retrospective analysis of 173 individuals who underwent primary arthroscopic Bankart repair between 2007 and 2015. Glenoid bone loss and Hill-Sachs lesion size were measured with use of previously reported methods. Patients with failure were defined as those who sustained a dislocation after the index procedure, whereas controls were defined as individuals who did not. DTD was defined as the distance from the medial edge of the Hill-Sachs lesion to the medial edge of the glenoid track. Receiver operating characteristic (ROC) curves were constructed for DTD to determine the critical threshold that would best predict failure. The study population was subdivided into individuals ≥20 years old and <20 years old. RESULTS: Twenty-eight patients (16%) sustained a recurrent dislocation following Bankart repair. Increased glenoid bone loss (p < 0.001), longer Hill-Sachs lesion length (p < 0.001), and decreased DTD (p < 0.001) were independent predictors of failure. ROC curve analysis of DTD alone demonstrated that a threshold value of 8 mm could best predict failure (area under the curve [AUC] = 0.73). DTD had strong predictive power (AUC = 0.84) among individuals ≥20 years old and moderate predictive power (AUC = 0.69) among individuals <20 years old. Decreasing values of DTD were associated with a stepwise increase in the failure rate. CONCLUSIONS: A "near-track" lesion with a DTD of <8 mm, particularly in individuals ≥20 years old, may be predictive of failure following arthroscopic Bankart repair. When using the glenoid track concept as the basis for surgical decision-making, clinicians may need to consider the DTD value as a continuous variable to estimate failure instead of using a binary on-track/off-track designation. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of Levels of Evidence.

Assessing precision and accuracy of false-profile hip radiographs.

PURPOSE: The purpose of this study was to assess the accuracy and precision of pelvic rotation in existing false-profile (FP) radiographs and to devise a method to improve accuracy and precision of FP radiographs. METHODS: An imaging protocol was developed to obtain FP radiographs. Pelvic rotation was calculated using the described method for FP images obtained in the 3 months prior to and after implementation of this protocol. Student's t-test and variance ratio tests were used to determine differences in mean and variance of pelvic rotation between the 2 cohorts. Pelvic rotation calculation methodology was validated by using fluoroscopic C-arm to obtain AP and rotated images of 10 osteologic pelvises. The ratio of the distance between hip centres of each rotated image and AP image (WP/W) was determined. Intraclass coefficient correlation (ICC) was used to verify the relationship between WP/W and pelvic rotation. RESULTS: Mean WP/W was 0.47 (95% CI, 0.45-0.49). There were significant differences in mean pelvic rotation of the pre-protocol group (47.6°; 95% CI, 45.6-49.5°) and the post-protocol group (60.0°; 95% CI, 58.7-61.3°, p < 0.0001). Additionally, there was a significantly wider distribution of measurements in the pre-protocol group (SD = 7.9°) compared to the post-protocol group (SD = 5.7°, p = 0.0035). CONCLUSIONS: The quality of FP radiographs obtained in the clinical setting may be inconsistent. Standardising FP imaging produces more accurate images. Appropriate FP radiographs should have a distance between hip centres that is approximately 0.5 times the same distance found on an anteroposterior (AP) radiograph.

Decreased Glenoid Retroversion Is a Risk Factor for Failure of Primary Arthroscopic Bankart Repair in Individuals With Subcritical Bone Loss Versus No Bone Loss.

PURPOSE: To determine whether glenoid retroversion is an independent risk factor for failure after arthroscopic Bankart repair. METHODS: This was a retrospective review of patients with a minimum 2-year follow-up. In part 1 of the study, individuals with no glenoid bone loss on magnetic resonance imaging (MRI) and who failed arthroscopic Bankart repair (cases) were compared with individuals who did not fail Bankart repair (controls). In part 2 of the study, cases with subcritical (<20%) glenoid bone loss as measured on sagittal T1 MRI sequences who failed arthroscopic Bankart repair were compared with controls who did not. For each part of the study, glenoid version was measured using axial T2 MRI sequences. Positive angular measurements were designated to represent glenoid anteversion, whereas negative measurements were designated to represent glenoid retroversion. Independent t tests were conducted to determine the association between glenoid version and failure after arthroscopic Bankart repair. RESULTS: There were 20 cases and 40 controls in part 1 of the study. In part 2, there were 19 cases and 21 controls. There was no difference in baseline characteristics between cases and controls. Among individuals with no glenoid bone loss, there was no difference in glenoid version between cases and controls (cases: 6.0° ± 8.1° vs controls: 5.1° ± 7.8°, P = .22). Among individuals with subcritical bone loss, cases (3.8° ± 4.4°) were associated with significantly less mean retroversion compared with controls (7.1° ± 2.8°, P = .0085). Decreased retroversion (odds ratio 1.34; 95% confidence interval 1.05-1.72, P = 20) was a significant independent predictor of failure using univariable logistic regression. CONCLUSIONS: While glenoid retroversion is not associated with failure after arthroscopic Bankart repair in individuals with no glenoid bone loss, decreased retroversion is associated with failure in individuals with subcritical bone loss. LEVEL OF EVIDENCE: Level 3: Retrospective review.

Return to sport testing at 6 months after arthroscopic shoulder stabilization reveals residual strength and functional deficits.

OBJECTIVES: A good outcome after arthroscopic stabilization for recurrent shoulder instability is often characterized by a successful return to sport while minimizing complications. There is currently no consensus regarding timing or objective criteria for return to sport. The objective of this study is to evaluate the ability of postoperative patients to meet expected goals by using standardized objective evaluations of strength and physical function. METHODS: Forty-three (10 females, 76.7% male) subjects (mean age, 18.1 ± 3.7 years) who underwent arthroscopic shoulder stabilization surgery (anterior or posterior) from 2016 until 2018 were referred during their postoperative rehabilitation for functional testing at 6 months postoperatively to evaluate their readiness for return to sport. The Closed Kinetic Chain Upper Extremity Stability test and Unilateral Seated Shot Put test were used to assess shoulder function. Posterior rotator cuff activation was evaluated using a repetition to failure technique with 5% body weight at 0° and 90° of abduction with the goal of 90% of nonoperative extremity. Isokinetic strength testing of external rotation (ER) and internal rotation (IR) was evaluated using a Biodex isokinetic dynamometer at angular velocities of 60° and 180° per second, and a passing score was considered achieving 90% of nonoperative shoulder strength at both 60° and 180° per second. RESULTS: All subjects were competitive athletes (20 collegiate, 23 high school). The dominant extremity was the surgical extremity in 22 subjects. Only 5 subjects were able to successfully pass the battery of tests for strength and function. Strength testing revealed that 7 patients achieved 90% of the strength of the nonoperative extremity in both repetitions to failure (23 of 43) and comparative isokinetic testing (7 of 43). More subjects were able to meet IR strength (20 of 43) than ER strength (12 of 43) goals. Functional test goals were more frequently achieved, with 26 of 43 subjects meeting both functional test goals (33 Closed Kinetic Chain Upper Extremity Stability, 34 Unilateral Seated Shot Put). Only 2 subjects were able to achieve strength goals but did not pass functional tests, whereas 21 subjects passed functional tests without meeting strength goals. CONCLUSION: A substantial number of athletes in our cohort do not meet the expected goals for their operative shoulder in achieving appropriate function and strength, compared with the contralateral shoulder. Functional goals were more often met than strength. IR strength goals were more frequently achieved than ER strength. Strength and functional testing could provide more reliable criteria than arbitrary passage of time for return to play after shoulder stabilization surgery.

Does Overexertion Correlate With Increased Injury? The Relationship Between Player Workload and Soft Tissue Injury in Professional American Football Players Using Wearable Technology.

BACKGROUND: The relationship of training load to injury using wearable technology has not been investigated in professional American football players. The primary objective of this study was to determine the correlation between player workload and soft tissue injury over the course of a football season utilizing wearable global positioning system (GPS) technology. HYPOTHESIS: Increased training load is associated with a higher incidence of soft tissue injuries. STUDY DESIGN: Case-control study. LEVEL OF EVIDENCE: Level 3. METHODS: Player workloads were assessed during preseason and regular-season practice sessions using GPS tracking and triaxial accelerometry from 2014 to 2016. Soft tissue injuries were recorded during each season. Player workload during the week of injury (acute) and average weekly workload during the 4 weeks (chronic) prior to injury were determined for each injury and in uninjured position-matched controls during the same week. A matched-pairs t test was used to determine differences in player workload. Subgroup analysis was also conducted to determine whether observed effects were confounded by training period and type of injury. RESULTS: In total, 136 lower extremity injuries were recorded. Of the recorded injuries, 101 injuries with complete GPS and clinical data were included in the analysis. Injuries were associated with greater increases in workload during the week of injury over the prior month when compared with uninjured controls. Injured players saw a 111% (95% CI, 66%-156%) increase in workload whereas uninjured players saw a 73% (95% CI, 34%-112%) increase in workload during the week of injury (P = 0.032). Individuals who had an acute to chronic workload ratio higher than 1.6 were 1.5 times more likely to sustain an injury relative to time- and position-matched controls (64.6% vs 43.1%; P = 0.004). CONCLUSION: Soft tissue injuries in professional football players were associated with sudden increases in training load over the course of a month. This effect seems to be especially pronounced during the preseason when player workloads are generally higher. These results suggest that a gradual increase of training intensity is a potential method to reduce the risk of soft tissue injury. CLINICAL RELEVANCE: Preseason versus regular-season specific training programs monitored with wearable technology may assist team athletic training and medical staff in developing programs to optimize player performance.

Over-the-top ACL reconstruction restores anterior and rotatory knee laxity in skeletally immature individuals and revision settings.

PURPOSE: To investigate the objective outcomes following anterior cruciate ligament reconstruction (ACLR) with the over-the-top (OTT) technique. METHODS: Thirty-five ACL-deficient patients with mean follow-up of 2.2 years were retrospectively reviewed. This included 14 skeletally immature individuals (age: 14 ± 1 years) who underwent primary OTT ACLR (adolescent group) and 21 skeletally mature individuals (age: 25 ± 8 years) who underwent OTT revision ACLR (revision group). The tibial tunnel was created at the anatomic position for all cases. No lateral extra-articular tenodesis was performed. Before and after surgery, the side-to-side difference (SSD) in anterior laxity was measured using KT-1000 arthrometer. Lachman and pivot-shift tests were assessed according to IKDC grade. The graft failure rate was assessed. RESULTS: The post-operative SSD in anterior laxity was significantly reduced in the adolescent (pre-op, 3.9 ± 1.8 mm; post-op, 1.2 ± 0.8 mm; p = 0.040) and revision groups (pre-op, 4.2 ± 1.7 mm; post-op, 1.2 ± 1.4 mm; p < 0.001). Postoperative knee laxity measured by Lachman and pivot-shift tests were also significantly improved in both groups. Graft rupture occurred in two patients in the adolescent group (14.3%), and one patient in the revision group (4.8%). CONCLUSION: ACLR with the OTT technique restored anterior and rotatory knee laxity in skeletally immature individuals and in revision settings. This one-step procedure may be a good option for skeletally immature individuals and revision settings. LEVEL OF EVIDENCE: IV.

Wearable sensors for monitoring the internal and external workload of the athlete.

The convergence of semiconductor technology, physiology, and predictive health analytics from wearable devices has advanced its clinical and translational utility for sports. The detection and subsequent application of metrics pertinent to and indicative of the physical performance, physiological status, biochemical composition, and mental alertness of the athlete has been shown to reduce the risk of injuries and improve performance and has enabled the development of athlete-centered protocols and treatment plans by team physicians and trainers. Our discussions in this review include commercially available devices, as well as those described in scientific literature to provide an understanding of wearable sensors for sports medicine. The primary objective of this paper is to provide a comprehensive review of the applications of wearable technology for assessing the biomechanical and physiological parameters of the athlete. A secondary objective of this paper is to identify collaborative research opportunities among academic research groups, sports medicine health clinics, and sports team performance programs to further the utility of this technology to assist in the return-to-play for athletes across various sporting domains. A companion paper discusses the use of wearables to monitor the biochemical profile and mental acuity of the athlete.

Wearable sensors for monitoring the physiological and biochemical profile of the athlete.

Athletes are continually seeking new technologies and therapies to gain a competitive edge to maximize their health and performance. Athletes have gravitated toward the use of wearable sensors to monitor their training and recovery. Wearable technologies currently utilized by sports teams monitor both the internal and external workload of athletes. However, there remains an unmet medical need by the sports community to gain further insight into the internal workload of the athlete to tailor recovery protocols to each athlete. The ability to monitor biomarkers from saliva or sweat in a noninvasive and continuous manner remain the next technological gap for sports medical personnel to tailor hydration and recovery protocols per the athlete. The emergence of flexible and stretchable electronics coupled with the ability to quantify biochemical analytes and physiological parameters have enabled the detection of key markers indicative of performance and stress, as reviewed in this paper.

Does Pelvic Rotation Alter Radiologic Measurement of Anterior and Lateral Acetabular Coverage?

PURPOSE: The purpose of this study was to determine the radiologic tolerance of the lateral center edge angle (LCEA) and anterior center edge angle (ACEA) to pelvic rotation. METHODS: Eleven dry cadaveric pelvises from an osteological collection were reconstructed and placed in anatomic position with corresponding bilateral proximal femurs. Conventional anteroposterior (AP) and false-profile (FP) pelvic radiographs were taken at 5° increments with fluoroscopy from 0° to 25° of rotation. LCEA and ACEA were measured for conventional and rotated AP and FP fluoroscopic views, respectively. Statistical analysis was conducted to determine the error in ACEA and LCEA with pelvic rotation. RESULTS: The mean LCEA was 29.1° (95% confidence interval [CI], 25.5°-32.7°). Mean ACEA was 38.9° (95% CI, 34.1°-43.8°). There was significant change in the LCEA past 10° of rotation (P = .041). There was significant change in the ACEA with 5o or more of rotation (P < .001). The FP view rotated 40° from an AP view produced 6.8° (95% CI, 4.7-8.9) of error, whereas one rotated 90° from an AP view produced 13.2° (95% CI, 11.2°-15.3°) of error in the ACEA. An AP view rotated 25° toward the x-ray beam produced 2.3° (95% CI, 1.1°-3.4°) error, whereas one rotated 25° away from the beam produced 2.6° (95% CI, 1.5°-3.8°) of error. CONCLUSIONS: Rotation of AP and FP radiographs significantly affects the measured values of the LCEA and ACEA, respectively. The ACEA experiences more dramatic changes with rotation of the FP view compared with the LCEA with the same amount of rotation of an AP view. This study illustrates the importance of verifying the quality of the FP radiograph when using ACEA to guide therapy for hip pathology. CLINICAL RELEVANCE: This study emphasizes the importance of evaluating pelvic rotation when using the center edge angle to assess femoral head coverage.

Use of the False-Profile Radiographic View to Measure Pelvic Incidence.

BACKGROUND: Pelvic incidence (PI) is an important variable in assessing spinopelvic balance that is associated with hip pathology. A lateral radiograph of the pelvis can be used to measure PI, but this view is not routinely performed in the clinical setting during evaluation of hip pain. The false-profile (FP) radiographic view of the hip is commonly obtained to measure acetabular coverage. PURPOSE: To evaluate the tolerance of PI measurements to pelvic rotation and assess the feasibility of using an FP radiograph to obtain an accurate measurement of PI. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: A mathematical model was developed to predict the change in PI with rotation. Fluoroscopic images were obtained of 6 reconstructed cadaveric adult pelvis and femur specimens at varying degrees of rotation, including a perfect lateral and FP image. PI was measured with the midpoint between the centers of the femoral heads as a reference point. The findings were confirmed clinically by retrospectively reviewing FP radiographs and computed tomography (CT) scans of 40 clinical patients. PI was measured on FP radiographs and CT scans by 2 independent reviewers. RESULTS: With dry cadaveric pelvis specimens, the discrepancy in PI measured between fluoroscopic FP and lateral views was 1.6° (95% CI, 0.7°-2.4°). There was excellent agreement between CT and FP radiographs with regard to measurement of PI (intraclass correlation coefficient = 0.92; 95% CI, 0.78-0.98). Mean discrepancy in PI measured between the 40 clinical FP radiographs and CT scans was 2.8° (range, 0.1°-9.1°). CONCLUSION: Increased rotation from a lateral view results in greater error in measuring PI, although relatively nominally with a 2.8° error with the 25° of rotation in clinical true FP views. These data demonstrate that FP radiographs can be used to measure PI with reasonable accuracy.

Origin of Cam Morphology in Femoroacetabular Impingement.

Cam morphology of the proximal femur is an abnormal contour of the femoral head-neck junction present in approximately 15% to 25% of the asymptomatic population, predominantly in males. Alpha angle and femoral head-neck offset ratio are 2 objective measurement tools that define cam morphology. Both primary (idiopathic) and secondary cam deformity develops through distinct mechanisms. The cause of primary (idiopathic) cam morphology remains incompletely understood. Mounting evidence suggests that idiopathic cam morphology develops during adolescence through alterations in the capital femoral epiphysis in response to participation in vigorous sporting activity. While the exact cause of epiphyseal extension has not yet been determined, preliminary evidence suggests that epiphyseal extension may reflect a short-term adaptive response to provide stability to the physis at the long-term cost of the development of cam morphology. Commonly recognized causes of secondary cam deformity include frank slipped capital femoral epiphysis, Legg-Calve-Perthes disease, and deformity after fracture of the proximal femur. Recent studies also support subtle slipped capital femoral epiphysis as a unique and silent cause of a small percentage of subjects previously thought to have idiopathic cam deformity.

The 'triradiate bump': a novel radiographic sign that may confound assessment of acetabular retroversion.

PURPOSE: The triradiate cartilage transiently projects medially within the pelvic brim around the time of triradiate closure, mimicking the ischial spine sign. The purpose of this study was to characterize this newly identified radiographic sign using a longitudinal radiographic study. METHODS: We identified 72 subjects from a longitudinal radiographic study of healthy adolescents, each with at least four consecutive, annual anterior-posterior radiographs of the left hip, including physeal closure. Images were reviewed to identify the presence of the triradiate bump, the year it was most prominent, and the number of years relative to triradiate closure after which it had completely remodeled. RESULTS: The transient medial projection of the triradiate cartilage (triradiate bump) was identified in 26/40 (65 %) females and 22/32 (69 %) males (p = 0.74). The medial projection of the triradiate cartilage was most prominent at 10.8 ± 0.8 years of age in females and 12.6 ± 0.7 years of age in males (p < 0.001). The triradiate cartilage projected medially a mean of 4.7 ± 0.8 or 5.1 ± 1.4 mm for females and males, respectively (p = 0.29), but remodeled completely in all cases around triradiate closure. CONCLUSIONS: The transient medial projection of the triradiate cartilage within the pelvic brim, the 'triradiate bump sign', is a common radiographic finding in healthy adolescents around the time of closure of the triradiate cartilage that may mimic the ischial spine sign. These two signs can be distinguished as the projection of the ischial spine is located more inferiorly within the pelvic brim and the triradiate bump has a horizontal limb of radiolucency extending to its medial border.

Wearable Performance Devices in Sports Medicine.

CONTEXT: Wearable performance devices and sensors are becoming more readily available to the general population and athletic teams. Advances in technology have allowed individual endurance athletes, sports teams, and physicians to monitor functional movements, workloads, and biometric markers to maximize performance and minimize injury. Movement sensors include pedometers, accelerometers/gyroscopes, and global positioning satellite (GPS) devices. Physiologic sensors include heart rate monitors, sleep monitors, temperature sensors, and integrated sensors. The purpose of this review is to familiarize health care professionals and team physicians with the various available types of wearable sensors, discuss their current utilization, and present future applications in sports medicine. EVIDENCE ACQUISITION: Data were obtained from peer-reviewed literature through a search of the PubMed database. Included studies searched development, outcomes, and validation of wearable performance devices such as GPS, accelerometers, and physiologic monitors in sports. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 4. RESULTS: Wearable sensors provide a method of monitoring real-time physiologic and movement parameters during training and competitive sports. These parameters can be used to detect position-specific patterns in movement, design more efficient sports-specific training programs for performance optimization, and screen for potential causes of injury. More recent advances in movement sensors have improved accuracy in detecting high-acceleration movements during competitive sports. CONCLUSION: Wearable devices are valuable instruments for the improvement of sports performance. Evidence for use of these devices in professional sports is still limited. Future developments are needed to establish training protocols using data from wearable devices.

Predictors of radiographic knee osteoarthritis after anterior cruciate ligament reconstruction.

BACKGROUND: Evidence suggests that single-bundle anterior cruciate ligament (ACL) reconstruction does not reliably prevent the development of knee osteoarthritis (OA). PURPOSE: This study was conducted to determine the overall prevalence of and risk factors for the development of radiographic knee OA after single-bundle ACL reconstruction. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: There were 249 individuals who had undergone primary single-bundle ACL reconstruction included in this retrospective cohort study. Follow-up radiographs were scored by a single orthopaedic surgery sports medicine fellow using the Kellgren-Lawrence (KL) scale to determine the degree of OA in the medial, lateral, and patellofemoral compartments. Radiographic OA of the involved knee was considered to be present if, compared with the noninvolved knee, there was at least a 2-grade difference in the KL score in at least 1 compartment or a 1-grade difference in at least 2 compartments. Predictors of OA that were explored included patient age, sex, body mass index (BMI), smoking status activity level, meniscectomy before or concurrent with ACL reconstruction, chondral injury present at the time of ACL reconstruction, graft type and source, tibial and femoral tunnel positions, need for revision, and length of follow-up. Univariable and stepwise multivariable logistic regressions were used to identify factors that were associated with radiographic knee OA. RESULTS: Thirty-nine percent of the patients had radiographic OA an average of 7.8 years after surgery. Female sex, BMI, time from injury to surgery, medial and patellofemoral compartment chondrosis, prior medial or lateral meniscectomy, concurrent medial meniscectomy, and length of follow-up were associated with radiographic knee OA after ACL surgery. Stepwise multivariable logistic regression indicated that prior medial meniscectomy (95% confidence interval [CI], 1.39-6.85), grade 2 or greater medial chondrosis (95% CI, 1.27-6.73), length of follow-up (95% CI, 1.07-1.24), and BMI (overweight 95% CI, 1.08-3.84; obese 95% CI, 1.34-7.80) were the best set of predictors of knee OA. CONCLUSION: Despite reduced laxity and instability and improved activity and participation, individuals who have undergone ACL reconstruction are still at high risk for developing knee OA compared with the general population. The strongest predictors of knee OA after ACL reconstruction were obesity and grade 2 or greater chondrosis in the medial compartment. These results may aid in identifying patients at risk for OA after ACL reconstruction.

Differential maturation and structure-function relationships in mesenchymal stem cell- and chondrocyte-seeded hydrogels.

Degenerative disease and damage to articular cartilage represents a growing concern in the aging population. New strategies for engineering cartilage have employed mesenchymal stem cells (MSCs) as a cell source. However, recent work has suggested that chondrocytes (CHs) produce extracellular matrix (ECM) with superior mechanical properties than MSCs do. Because MSC-biomaterial interactions are important for both initial cell viability and subsequent chondrogenesis, we compared the growth of MSC- and CH-based constructs in three distinct hydrogels-agarose (AG), photocrosslinkable hyaluronic acid (HA), and self-assembling peptide (Puramatrix, Pu). Bovine CHs and MSCs were isolated from the same group of donors and seeded in AG, Pu, and HA at 20 million cells/mL. Constructs were cultured for 8 weeks with biweekly analysis of construct physical properties, viability, ECM content, and mechanical properties. Correlation analysis was performed to determine quantitative relationships between formed matrix and mechanical properties for each cell type in each hydrogel. Results demonstrate that functional chondrogenesis, as evidenced by increasing mechanical properties, occurred in each MSC-seeded hydrogel. Interestingly, while CH-seeded constructs were strongly dependent on the 3D environment in which they were encapsulated, similar growth profiles were observed in each MSC-laden hydrogel. In every case, MSC-laden constructs possessed mechanical properties significantly lower than those of CH-seeded AG constructs. This finding suggests that methods for inducing MSC chondrogenesis have yet to be optimized to produce cells whose functional matrix-forming potential matches that of native CHs.