Introduction

Tendon cross-sectional area (CSA) and stiffness increase in men during chronic exercise. The increase in tendon CSA and stiffness is not evident in women. In men, exercise increases tendon production of MMPs, IGF-1, and IL-6, which presumably contribute to tendon remodeling during chronic exercise. The purpose of this study was to determine if exercise-induced production of MMPs, IGF-1, and IL-6 are limited in women when compared to men.

Femoral components used in total hip arthroplasty (THA) rely on good initial fixation determined by implant design, femoral morphology, and surgical technique. A higher rate of varus alignment may be of specific concern with short stem implants. Varus placement in uncemented femoral components has been proven not to be detrimental to clinical function; though long-term bone remodeling secondary to varus placement remains unknown. The goal of this study was to compare the clinical and radiographic outcomes in patients who underwent THA with one of two uncemented short stem metaphyseal engaging implants at minimum two-year follow-up.

A review of 105 patients (average age 65 years; BMI 29 kg/m²) who underwent a total of 109 primary THAs using the ABG II short stem femoral implant (Stryker, Mahwah, NJ), and 160 hips in 149 patients (average age 70 years; BMI 28 kg/m²) who underwent primary THA using the Citation stem (Stryker, Mahwah, NJ). The same surgeon (SDS) performed all surgeries through a less invasive posterolateral approach. Pre-operative and post-operative Harris Hips Scores (HHS) and WOMAC scores were collected. Digital radiograph analysis was performed including measuring the stem alignment relative to the femoral shaft. A stem placed with greater than 5 degrees of varus was considered to be in varus.

There was no significant difference in demographics (age, gender or BMI) or pre-operative HHS and WOMAC scores between the two groups. Follow-up HHS was 90 (range 63–100) and 94 (range 70–100) for the ABG II and Citation groups, respectively. Follow-up WOMAC scores were 10 (range 0–24) and 6 (range 0–43) for the ABG II and Citation groups, respectively. There was no statistically significant difference in any of the scores between the two groups (p>0.05).

When looking at AP radiographs for postoperative intramedullary alignment, none of the ABG II implants were placed in varus (>5°), while a small number (4.9%) of Citation implants were implanted in varus alignment. No significant difference was observed in the alignment between the two groups (p>0.05). Average post-op alignment with the ABG was 1.10° (range −4.7–4.9°) and 0.88° (range −4.5–8.9°) with the Citation.

The clinical results associated with the use of these stems in patients of all ages and bone types have been identical to those achieved by uncemented stems of standard length. Both implants in this study had excellent clinical and functional results in primary THA after a minimum 24-month follow up. In addition, postoperative radiographic analysis demonstrated that these stems can be reliably and reproducibly placed in neutral alignment despite their short length. The lateral flare on the Citation implant led to a greater number of implants in varus alignment, potentially affecting offset and leg-length, yet the relative increased incidence compared to the ABG II was not significant. Further research is needed in designing implants that optimize proximal femoral contact while maintaining alignment and overall hip kinematics.

Introduction: Single leg hop for distance is a test often used as a measure of knee performance and stability during rehabilitation after knee surgery or injury. Both distance hopped and qualitative assessment of stability in landing is widely used as parameters of knee joint control. While hop distance is reported as highly reliable, no investigations have studied the reliability of the biomechanical parameters expressing the quality of the landing after a single leg hop. The aim of the present study was to investigate the reliability of hop distance and biomechanical landing parameters during a single leg hop test.

Methods: The study was designed as an intra-tester, inter-day test-retest reliability study. Fourteen (7 males, 7 females) physically active, healthy subjects volunteered to participate. The subjects performed 5 maximal single leg hops for distance including 2 trial jumps, and the mean of the last 3 hops was used for analysis. The test session was repeated after 1 week. In both sessions the same tester placed markers on the lower body (Helen Hayes model) and the subjects landed after maximal hopping on a force plate. The hops were recorded using an 8 camera Vicon 612 system filming at 200 Hz. Kinematic and kinetic data were calculated using inherent Vicon software. Intraclass Correlation Coefficient (2,1) was used for analysis of reliability on selected kinematic and kinetic knee joint parameters.

Results: The ICC of the maximal hop distance was excellent (0.93, p< 0.001). The reliability of the maximal knee joint flexion during landing was poor and non-significant, and also peak knee extensor moment during landing showed poor reliability (ICC: 0.48, p=0.037). The maximal external knee joint varus moment and the relative eccentric power production of the knee joint in comparison to the hip and ankle joints were moderately reliable (ICC: 0.56, p=0.015, and ICC: 0.64, p=0.005, respectively).

Conclusions: This study shows, that in healthy subjects the reliability of the maximal hop distance is excellent, however the underlying biomechanical parameters controlling the knee joint during landing is only moderately or poorly reliable. This may imply, that the subjects use slightly different strategies during landing from the hop and evaluation of knee joint performance based on landing biomechanics may be done with caution. Future reliability and validation studies of the take-off biomechanics may further reveal if the single leg hop test is reliable and valid as a measure of knee joint performance.