Page 19 - Delaware Medical Journal - November 2016
P. 19
SCIENTIFIC ARTICLE
even improvement in hip abduction strength one year after surgery. Strength in the posterior group at one year surpassed pre-operative levels by 13 percent, while the lateral group had strength values that were 7 percent weaker than the pre-operative levels.
Previous studies, as well as previous analyses in our lab, have found that lower extremity strength is correlated with performance-based measures of function before and after hip and knee arthroplasty.10 Despite this relationship, improved hip abduction strength in the posterior group did not translate into superior functional performance one year after THA. This may be due to the fact that the posterior approach also results in muscular weakness, albeit in different muscle groups. In particular, the hip extensors and external rotators may be affected by the posterior approach, but these muscles were not examined in this study. Given the lack of difference in function between groups, the current recommendations
for choosing a surgical approach based on familiarity, 7 Both groups demonstrate substantial improvements in pain and self- reported outcomes.
outcomes between surgical approaches, it is not without limitations. The subjects in the study were not randomized
to the surgical approach group and there may be an effect of intra- and post-operative management that contributed to the difference in strength. For example, femoral offset has been directly correlated to hip abduction strength27 and was not considered as a covariate on our strength outcomes. However, heterogeneity in post-operative management was not likely a limiting factor, as all patients came from a single joint center that has a standard post-operative care within the acute setting. Since we only evaluated hip abduction strength, we are not able to determine if the posterior approach affected strength in other muscle groups. Previous literature has found external hip rotators to be weaker in the posterior group for both THA21 as well as hip resurfacing procedures.22
In conclusion, the lateral surgical approaches result in weaker
clinically meaningful improvements in functional ability were seen for most subjects, regardless of surgical approach. It is
TABLE III: Descriptive Data for the Pre-Operative, 3 Month, and 1 Year Time Points with Groups Pooled
OUTCOME MEASURE
TIME POINT
Pre
SD
3 months
SD
1 year
SD
Sx Hip Abd Strength (%BW)
14.6
8.0
14.1
7.2
15.7*
6.6
NonSx Hip Abd Strength (%BW)
19.6
8.5
20.5
9.5
20.5
9.6
Sx Quad Strength (%BW)
61.9
28.7
73.0
29.0
81.4*
34.1
NonSx Quad Strength (%BW)
81.6
33.8
86.8
33.4
87.6*
36.3
Timed Up and Go (sec)
9.6
5.0
7.6
2.6
7.5*
2.9
Stair Climbing Test (sec)
16.6
9.1
12.1
3.6
11.6*
3.1
6 Minute Walk (m)
465.0
116.7
551.4
104.7
570.0*
118.9
Hip Outcome Score (%)
58.4
16.2
86.1
13.8
89.9*
12.2
Sx Hip Pain (0-10)
5.6
2.2
0.7
1.0
0.8*
1.7
NonSx Hip Pain (0-10)
0.8
1.7
0.7
1.7
0.7
1.6
TABLE III
* = a significant p value of p<0.05 for main effect of time between the pre-op and one year time point. Sx = surgical side; NonSx = non- surgical side; %BW = percent body weight
Del Med J | November 2016 | Vol. 88 | No. 11
339
