Abduction causes increased strain gradient compared to forward flexion: Evidence from a cadaver model of simultaneous strain study of the rotator cuff tendons.

BACKGROUND: Various strain studies of the supraspinatus have been done in isolation. Given that rotator cuff muscles function as a group, it may be physiologically representative to measure strain behaviour with the glenohumeral joint intact. Here, we explored a novel method in measuring simultaneous strain behaviour of the rotator cuff tendons and investigated the effect of full-thickness anterior tear of the supraspinatus on the infraspinatus and subscapularis tendons. METHODS: Nine cadaveric shoulders were evaluated on a customized rig. Using linear differential variable transducers to measure strain, each shoulder was subjected to up to 60° of elevation in the coronal, scapular, and sagittal planes. We also assessed 30° of external rotation and up to 60° of internal rotation of the humerus. Full-thickness anterior tear of the supraspinatus was then made before re-assessing strain patterns in the scapular plane. FINDINGS: Strain measurements of the intact tendons revealed a significant strain gradient between the articular and bursal sides of the supraspinatus during increasing degrees of elevation in the coronal and scapular planes. Full thickness anterior tear of the supraspinatus is localised to the tendon and does not affect the surrounding cuff musculature, with a potential shielding effect of the infraspinatus during early glenohumeral abduction. INTERPRETATION: Significant strain gradient exists between the articular and bursal sides of the supraspinatus during abduction but not during forward flexion in an intact glenohumeral joint. Rehabilitation exercises for anterior supraspinatus tears can be appropriately targeted on the remaining intact rotator cuff musculature.

Minimal Clinically Important Differences for Oxford, Constant, and University of California Los Angeles Shoulder Scores After Reverse Shoulder Arthroplasty to Allow Interpretation of Patient-Reported Outcome Measures and Future Statistical Power Analyses.

PURPOSE: To determine the minimal clinically important difference (MCID) for the Constant-Murley Score (CMS), University of California Los Angeles (UCLA) Shoulder Score, and Oxford Shoulder Score (OSS) after reverse shoulder arthroplasty. METHODS: Patients were prospectively followed up between January 2011 and February 2020. Inclusion criteria was that of patients who underwent reverse shoulder arthroplasty for massive irreparable cuff tear, cuff tear arthropathy, and fractures, with and without previous cuff repair, by a fellowship-trained surgeon. Patients were assessed preoperatively and at 3, 6, and 12 months' postoperatively. Functional outcome was assessed by the CMS, UCLA Shoulder Score, and OSS and the respective MCIDs were determined using simple linear regression in consonance with patient satisfaction and expectation fulfilment. RESULTS: A total of 131 patients were followed up for 12 months. The MCIDs at 3 months for CMS, UCLA Shoulder Score, and OSS were 7.2, 3.3, and 6.9, respectively. At 6 months, the MCIDs for CMS, UCLA Shoulder Score, and OSS were 6.6, 2.4, and 4.7, respectively. At 12 months, the MCIDs for CMS, UCLA Shoulder Score, and OSS were 9.3, 2.9, and 6.6, respectively. CONCLUSIONS: CMS, UCLA Shoulder Score, and OSS are valid scores to calculate MCID after reverse shoulder arthroplasty, and the MCID established in this study can be used for the interpretation of these scores to help in statistical power analysis for future studies. LEVEL OF EVIDENCE: III, retrospective cohort study.

Strain behavior of native and reconstructed medial patellofemoral ligaments during dynamic knee flexion - a cadaveric study.

BACKGROUND: Surgical reconstruction of the Medial Patello-Femoral Ligament (MPFL) has been recognized as an effective treatment for patients with instability despite conservative treatment. The purpose of this cadaveric study is to compare the strain patterns within the native and reconstructed single and double-bundle MPFL. This will help ascertain if the native biomechanics are restored with the reconstructions. METHODS: Twelve cadaveric knees were dissected and the native MPFL of each specimen was identified. The knees were subjected to dynamic flexion using a customized jig. Continuous strain measurements were taken for each knee from 0 to 120 degrees flexion and then back to full extension using differential variable reluctance transducers (DVRTs). The MPFL was then cut. Six single bundle and six double bundle MPFL reconstructions were performed using hamstring tendon grafts. The DVRTs were reattached to the grafts and strain measurements were retaken. Statistical analysis was performed using a paired t-test. RESULTS: Strain patterns of the native and reconstructed MPFL showed an increase in strain from 0 to 120 degrees of flexion except for the inferior bundle of the double bundle reconstruction. The strain patterns in the intact specimens were higher than the reconstructed MPFL through different degrees of knee flexion. In the double-bundle group, the superior graft had statistically significantly lower strains compared to the native MPFL with p-value <.05 at all flexion angles. The reconstructed inferior band showed loss of tension as the knee flexed. Higher strain with statistical significance (p-value <.05) was found in the single-bundle compared to the superior band of the double-bundle reconstruction at flexion angles less than 90 degrees. CONCLUSION: The strain variation at progressive angles of knee flexion is dissimilar between the native and reconstructed MPFL. The reconstructed MPFL exhibited non-physiological biomechanics with the inferior band losing tension. Although the single-bundle reconstruction shows a better strain profile compared to double-bundle reconstruction, the grafts are significantly stiffer than the native MPFL.

Lateral versus central tendon-splitting approach to insertional Achilles tendinopathy: a retrospective study.

INTRODUCTION: This study aimed to compare operative outcomes between the lateral approach (LA) and the central approach (CA) to insertional Achilles tendinopathy (IAT). METHODS: We retrospectively reviewed patients who underwent surgical treatment for IAT using the LA or CA. Patients' demographic data, postoperative complications and satisfaction rate were reviewed. Clinical outcomes were prospectively assessed preoperatively, at three months postoperatively and at the last visit, including patients' visual analogue scale (VAS) scores for pain, American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale scores and 36-item Short Form Health Survey (SF-36) scores. RESULTS: There were 39 patients in the LA group and 32 in the CA group. In each group, average VAS and AOFAS Scale scores improved significantly. SF-36 scores improved in most parameters. No significant difference in baseline score; average AOFAS Scale score at each visit; and mean VAS score preoperatively and at last visit; satisfaction rate; and overall complication rate were observed between the groups. The mean VAS score in the LA group at postoperative three months was significantly lower than that in the CA group (2.7 ± 2.5 vs. 4.4 ± 3.0; p = 0.016). There were significantly more cases of delayed wound healing in the LA group than in the CA group (2.6% vs. 15.6%; p = 0.049). CONCLUSION: Both approaches had comparable outcomes for IAT in terms of functional improvement, pain relief, overall enhancement of patients' health condition and overall postoperative complication rate. The LA provided better short-term pain relief and reduced delayed wound healing compared with the CA.

Recovery in knee range of motion reaches a plateau by 12 months after total knee arthroplasty.

PURPOSE: The primary aim of this study was to identify the time point at which improvements in knee range of motion reach a plateau, if any. The secondary aim of this study was to investigate the correlation between the improvements in knee range of motion and patient-reported outcomes [Oxford knee score (OKS) and SF-36]. The hypothesis is that there is a time point at which the recovery in the knee range of motion after total knee arthroplasty (TKA) plateaus. METHOD: A prospective study of 145 patients who underwent TKA was conducted. All TKAs were performed by the same surgeon. OKS and SF-36 scores were measured preoperatively and at 6, 12, and 24 months. Range of motion was measured preoperatively and at 1, 3, 6, 12, and 24 months postoperatively. RESULTS: This study shows that for surgeon/therapist reported range of motion, a plateau in recovery was reached at 12 months after TKA. It was also found that range of extension is significantly correlated with OKS, whereas range of flexion was not significantly correlated with OKS. CONCLUSIONS: Knowledge of when patients fully recover after TKA will allow appropriate counseling of patients during preoperative consultation. Also, this knowledge will enable surgeons/therapists to better monitor the rehabilitation progress of TKA patients, and make adjustments to the rehabilitation protocol. In addition, our study shows that objective surgeon-/therapist-measured outcome (range of motion) has a significant correlation with subjective patient-reported outcomes (OKS). Hence, both outcome measures should be employed in the postoperative monitoring of patient progress. LEVEL OF EVIDENCE: Prospective case series, Level IV.

Role of the anterior intermeniscal ligament in tibiofemoral contact mechanics during axial joint loading.

The anterior intermeniscal ligament (AIML) is an anatomically distinct structure that connects the anterior horns of the medial and lateral menisci. We hypothesized that both menisci work together as a unit in converting axial joint loading into circumferential hoop stresses, due to intermeniscal attachments. Therefore, loss of the AIML could lead to increased tibiofemoral contact stress and predispose to arthritic change. In this cadaveric study, we compared tibiofemoral contact pressures on axial loading, before and after sectioning of the AIML. Five fresh frozen human cadaveric knees were mounted on a linear x-y motion table and loaded in extension under axial compression of 1800N (about 2.5 times body weight for a 70kg individual), using a materials testing machine. Tibiofemoral contact pressures before and after sectioning of the AIML were measured using resistive pressure sensors. Contrary to our hypothesis, sectioning of the AIML produced no statistically significant increase in mean contact pressure, peak contact pressure or change in contact area, in either the medial or lateral compartment of the knees. This implies that the menisci work independently in converting axial loads into circumferential hoop stresses, and is probably due to their individual root attachments to the tibia. Based on this study, inadvertent sectioning of the AIML during knee surgery, e.g., arthroscopy, anterograde tibia nailing, anterior cruciate ligament reconstruction, meniscus transplantation and unicondylar knee replacement, is functionally insignificant.