Does hip joint positioning affect maximal voluntary contraction in the gluteus maximus, gluteus medius, tensor fasciae latae and sartorius muscles?

BACKGROUND: Minimally invasive total hip arthroplasty (THA) is presumed to provide functional and clinical benefits, whereas in fact the literature reveals that gait and posturographic parameters following THA do not recover values found in the general population. There is a significant disturbance of postural sway in THA patients, regardless of the surgical approach, although with some differences between approaches compared to controls: the anterior and anterolateral minimally invasive approaches seem to be more disruptive of postural parameters than the posterior approach. Electromyographic (EMG) study of the hip muscles involved in surgery [gluteus maximus (GMax), gluteus medius (GMed), tensor fasciae latae (TFL), and sartorius (S)] could shed light, the relevant literature involves discordant methodologies. We developed a methodology to assess EMG activity during maximal voluntary contraction (MVC) of the GMax, GMed, TFL and sartorius muscles as a reference for normalization. A prospective study aimed to assess whether hip joint positioning and the learning curve on an MVC test affect the EMG signal during a maximal voluntary contraction. HYPOTHESIS: Hip positioning and the learning curve on an MVC test affect EMG signal during MVC of GMax, GMed, TFL and S. METHODS: Thirty young asymptomatic subjects participated in the study. Each performed 8 hip muscle MVCs in various joint positions recorded with surface EMG sensors. Each MVC was performed 3 times in 1 week, with the same schedule every day, controlling for activity levels in the preceding 24h. EMG activity during MVC was expressed as a ratio of EMG activity during unipedal stance. Non-parametric tests were applied. RESULTS: Statistical analysis showed no difference according to hip position for abductors or flexors in assessing EMG signal during MVC over the 3 sessions. Hip abductors showed no difference between abduction in lateral decubitus with hip straight versus hip flexed: GMax (19.8±13.7 vs. 14.5±7.8, P=0.78), GMed (13.4±9.0 vs. 9.9±6.6, P=0.21) and TFL (69.5±61.7 vs. 65.9±51.3, P=0.50). Flexors showed no difference between hip flexion/abduction/lateral rotation performed in supine or sitting position: TFL (70.6±45.9 vs. 61.6±45.8, P=0.22) and S (101.1±67.9 vs. 72.6±44.6, P=0.21). The most effective tests to assess EMG signal during MVC were for the hip abductors: hip abduction performed in lateral decubitus (36.7% for GMax, 76.7% for GMed), and for hip flexors: hip flexion/abduction/lateral rotation performed in supine decubitus (50% for TFL, 76.7% for S). DISCUSSION: The study hypothesis was not confirmed, since hip joint positioning and the learning curve on an MVC test did not affect EMG signal during MVC of GMax, GMed, TFL and S muscles. Therefore, a single session and one specific test is enough to assess MVC in hip abductors (abduction in lateral decubitus) and flexors (hip flexion/abduction/lateral rotation in supine position). This method could be applied to assess muscle function after THA, and particularly to compare different approaches. LEVEL OF EVIDENCE: III, case-matched study.

Short-term comparison of postural effects of three minimally invasive hip approaches in primary total hip arthroplasty: Direct anterior, posterolateral and Röttinger.

INTRODUCTION: There is renewed interest in total hip arthroplasty (THA) with the development of minimally invasive approaches. The anterior and Röttinger approaches are attractive for their anatomical and minimally invasive character, but with no comparative studies in the literature definitely suggesting superiority in terms of quality of functional recovery. We therefore performed a case-control study, assessing: 1) whether the postural parameters of patients operated on with the anterior, Röttinger and posterior minimally invasive approaches were similar to those of asymptomatic subjects, and 2) whether there were any differences in postural parameters between the three approaches at short-term follow-up. HYPOTHESIS: We hypothesized that the anterior and Röttinger approaches are less disruptive of postural parameters than the posterior approach. METHODS: Seventy subjects (44 primary THA patients and 26 asymptomatic control subjects) were enrolled. Operated subjects were divided into 3 experimental groups corresponding to the 3 minimally invasive approaches: posterior (n=14), anterior (n=15) and Röttinger (n=15). Two single-leg stance tests (left followed by right leg stance; 10s per test) were carried out on a stabilometric platform, within 2months after surgery for all THA patients, and for controls. Six significant parameters were selected for statistical analysis: test performance, mediolateral and anteroposterior displacements of the center of pressure (CP), path length, average CP displacement speed, and the ellipse containing 95% of CP projections. Non-parametric statistical tests were used to compare groups. RESULTS: There was no difference between the 3 study groups and the control group according to age, gender, BMI, or side (or between study groups regarding WOMAC score). No significant differences between approaches were found for success on postural tests (P=0.14). Subjects operated on with the anterior or Röttinger approach showed significant differences from asymptomatic subjects for 2 postural parameters: path length (Röttinger P=0.04, anterior P=0.03) and average CP displacement speed (Röttinger P=0.04, anterior P=0.03). Subjects operated on through the posterior approach showed no significant differences from asymptomatic subjects. DISCUSSION: The study hypothesis, that the anterior and Röttinger approaches for hip arthroplasty are less disruptive of postural parameters than the posterior approach, was not confirmed. The anterior and Röttinger approach groups showed higher average CP displacement speed and path length, suggesting that they use up more energy resources to maintain static balance. The posterior approach had the least impact on postural parameters in the first 2 postoperative months. LEVEL OF EVIDENCE: III, case-control study.

Transsupraspinatus arthrotomy through an enlarged transacromial approach for total shoulder replacement.

The authors describe a step-by-step technique for anatomic total shoulder arthroplasty using transsupraspinatus arthrotomy via the enlarged transacromial approach. This technique seems ideal to ensure adequate postoperative tensional balance of the infraspinatus and the subscapularis, which is critical for the rotator cuffs to function properly and to achieve optimal arthroplasty stability. Reviewing these different steps helps understanding each rotator cuff individual component's contribution to achieve optimal arthroplasty stability.

Tension-free cuff repairs with excision of macroscopic tendon lesions and muscular advancement: results in a prospective series with limited fatty muscular degeneration.

Recurrent tears after rotator cuff repairs are frequent. These could be influenced by excessive tension on a degenerated tendinous stump and by fatty degeneration of the cuff muscles. The goal of this study was to evaluate the anatomic and functional results of tension-free cuff repairs with the excision of macroscopic tendon lesions in a series with limited muscular fatty degeneration of the infraspinatus and a global fatty degeneration index of rotator cuff muscles equal to or lower than 2. We studied 27 tears, comprising 13 cases involving both supraspinatus and infraspinatus tears, 13 cases with 3-tendon tears, and 1 case with only a supraspinatus tear. All shoulders were operated on through a transacromial approach easily repaired with 2 titanium screws with washers. To obtain a repair without tension, a single advancement was performed in 20 cases and a double advancement of both the supraspinatus and infraspinatus was done in 7 cases. The shoulders were evaluated clinically preoperatively and postoperatively with the non-weighted Constant score and anatomically with computed arthrotomography scans. The mean age at operation was 59.5 years, and the length of follow-up ranged from 1 to 4 years. Of the cuffs, 23 (85%) were watertight 1 year after surgery. No predictive factor of retear could be found. The functional improvement was statistically significant only for watertight cuffs, with an improvement of the Constant score from 57.8 to 75. The only predictive factor of functional outcome in this watertight group was the preoperative Constant score. Single and double advancements yielded similar functional results regardless of the extent of the initial tear, provided that the cuff was watertight at revision.