Page 15 - Delaware Medical Journal - November 2016

SCIENTIFIC ARTICLE
approaches will result in long-standing deficits in hip abductor strength. It is also possible that the type of surgical approach will differentially affect functional ability after THA. Muscle weakness is a primary impairment associated with low levels of performance before and after joint arthroplasty.11 Given the lack of prospective, longitudinal data on the effect of surgical approach, the purpose of this study was to compare the effect of surgical approaches on strength and function after THA. We hypothesized that individuals who underwent a posterior approach would have greater strength and functional performance than individuals who underwent an anterolateral or lateral approach one year after surgery. We also hypothesized that there would be no difference in pain or self-reported outcomes at follow-up.
METHODS
Subjects
Individuals between the ages of 40 and 80 who were scheduled for THA for OA were recruited by mail and advertisements placed in physician offices. The subjects in this analysis were part of a larger longitudinal observational cohort study on biomechanical and functional outcomes
after THA. Subjects were excluded if they were undergoing
a revision THA, had neurological or cardiopulmonary conditions that affected their ability walk, had active cancer, were unable to ambulate short distances (10 meters) without an assistive device, or lacked sensation in their feet. All subjects in this study were scheduled to undergo THA at a single Center for Joint Replacement. A total of five surgeons performed surgeries; two performed the posterior approach, two performed the anterolateral approach, and one surgeon used the direct lateral approach. Subjects were classified into Posterior or Lateral (anterolateral and direct lateral) groups. A sensitivity analysis was performed with and without subjects who underwent a direct lateral approach and the results did not change.
Data Collections
Subjects participated in three testing sessions: two to four weeks prior to surgery, three months after surgery, and one year after surgery. At each time point, subjects completed a battery of tests performed by a licensed physical therapist or physical therapy graduate student. Testing was performed in the same order for all individuals and at all timepoints. Age, sex, height, weight, and body mass index were recorded or calculated at each time point.
Self-reported measures included the Hip Outcome Score (HOS) and Verbal Pain Intensity Scale. The HOS is a self- reported measure that has a Sports subsection and an Activities of Daily Living (ADL) subsection. All items consist of a Likert scale from 0-4 and the total score is calculated as a percentage of 100, which indicates no functional limitations.18 Pain was assessed using a single question in which subjects were asked to “Rate your average hip pain over the previous week on scale from 0 to 10, where 0 indicates no pain and 10 indicates worst pain imaginable.”
Functional measures included the Timed Up and Go (TUG), Stair Climb Test (SCT), and Six Minute Walk Test (6MWT). These tests are reliable and valid for individuals with lower extremity pathology and are recommended for patients with lower extremity arthritis.15 The TUG required subjects to stand from a chair (standard height 46 cm) move as quickly as they felt safe and comfortable three meters from the chair then turn around return to the chair to sit. Subjects were allowed to use the arm rests
if they were unable to stand otherwise. The test was started on the testers command of “Go”. The SCT had subjects ascend and descend 12 standard height steps as quickly and safely as possible using one side of the staircase. Subjects were allowed to use a
rail if they were unsafe without the use of one. Subjects were not allowed to skip steps during the test but were allowed to use a step-to or step-to-step pattern depending on their comfort and safety. The test was started on the instructor’s signal. For both the TUG and SCT two trials were performed and the average was taken. The 6MWT was completed along a 102-meter square path. The subject was asked to walk as far as possible within 6 minutes and the distance covered was recorded in meters.
Hip abduction strength was measured isometrically in a side lying position. Subjects were positioned side lying with their
hip and knee in a neutral position. A non-elastic strap was wrapped around their leg and the table to allow 10 degrees of hip abduction. A hand held dynamometer was placed just proximal to the lateral joint line of the knee. Subjects were instructed to lift their leg straight up toward the ceiling and push into the strap as hard as possible for 3 seconds. Subjects were verbally encouraged to provide a maximal effort. Three trials were collected with a 30-second rest period between each trial. The trial with maximal force in kilograms (kg) was recorded. For the purpose of this analysis, force measures were normalized and represented as a percentage of the subject’s body mass.

force produced during an isometric contraction. During knee
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