We identified a weak evidence base for use of AAS to improve functional and physiological outcomes post-TKR. However, both studies
13
14 reported trends towards improvement in their AAS cohorts across all measured outcomes, with the sole exception of timed walking speed. Across the two studies, AAS patients showed greater improvements in postoperative quadriceps and hamstring strength, bone mineral density and sit-to-stand testing. They also scored more highly on the FIM, KSS and KSS function score. AAS patients had a shorter length of hospital stay and less need for inpatient rehabilitation. A number of these observed differences were statistically significant, including quadriceps strength at all time points, standing as assessed by the FIM and KSS score. Between group differences on the sit-to-stand test at 9 months were almost statistically significant (p=0.05). It is possible that other positive effects did not reach significance due to very small sample sizes. Interestingly, neither study reported that the placebo group surpassed the AAS cohort at any point on any of the outcomes tested.
Knee OA is accompanied by marked lower limb weakness which typically worsens after TKR.
22 Isometric flexion strength decreases by 17% in operated knees while no significant difference is measured on the contralateral side.
23 These deficits persist long into the postoperative period. Operated knees attain hamstring peak torques comparable to the contralateral side after 12 months whereas quadriceps function is still limited two years later.
24 Significant improvements have been reported with minimally invasive TKR techniques. For example, patients undergoing TKR using the mini-subvastus technique were found to match preoperative quadriceps strength after only 3 months. Quadriceps strength even surpassed preoperative levels by 17% at 6 and 30% at 12 months.
25Lower limb muscle strength is important as weakness is accompanied by worse functional outcomes. Both quadriceps and hip abductor strength are independently associated with improved ability to ascend and descend stairs.
26 Quadriceps strength is also significantly correlated with walking speed.
27 Both preoperative and postoperative quadriceps strength predicts improved functional performance one year after TKR.
7
8Attempts to improve lower limb muscle strength have achieved mixed success. Randomised trials comparing exercise training pre-TKR with usual care have reported improved lower limb strength, reduced pain and greater function postoperatively in the treated groups.
28
29 In contrast, a Cochrane review of two prospective studies on postoperative neuromuscular stimulation reported no significant differences in quadriceps strength.
12 A range of laboratory, animal and population studies on athletes have confirmed the ability of AAS to improve muscle strength.
19
30 The studies reported in this review support the potential for AAS to improve quadriceps strength and functional outcomes post-TKR.
13
14AAS can be administered through oral, buccal, intramuscular, subcutaneous or transdermal routes. However, they have been associated with a range of adverse effects. As many as 96% of regular AAS users report one or more objective side effects, commonly including acne, testicular atrophy, injection site pain, cutaneous striae and gynaecomastia.
31 Serious adverse effects include hepatic,
32
33 cardiovascular
19
34 and neuropsychiatric disease.
35
36 Long-term use may stimulate myocardial hypertrophy with subsequent myocardial infarction, systolic dysfunction, arrhythmias and sudden death.
37
38 There is also a risk of dependence with 84% of athletes reporting withdrawal effects on AAS cessation and 57% satisfying DSM-III criteria for dependence.
39However, the safety profile is likely to differ between AAS
use on physician advice and
abuse. For example, bodybuilders use up to 6000 mg/week testosterone, significantly higher than that administered by Amory
et al (600 mg) or Hohmann
et al (50 mg bi-weekly). Over half of bodybuilding users report sourcing AAS from underground laboratory facilities and 96% use other drugs concurrently, such as stimulants, fat loss agents and adjuvant anabolic compounds.
40 For these reasons, it is important not to overstate the dangers of AAS use.
41
42 Adverse effects are dose-related and largely reversible following cessation of use.
43
44 This supports the finding by Amory
et al13 that serum testosterone did not differ significantly between treated and placebo limbs at five weeks post-TKR. Importantly, researchers using AAS therapeutically in patient populations have not reported adverse effects.
13
14–18The trials selected for this review suggest AAS could help mitigate quadriceps weakness post-TKR and improve functional outcomes. Early mobilisation and rehabilitation are known to shorten hospital length of stay, reduce cost and improve functional performance.
45 In the absence of adverse effects reported in patient populations, AAS may provide another tool with which to expedite recovery after TKR. Although there is currently insufficient evidence to recommend the routine use of AAS, this preliminary evidence clearly justifies a randomised trial sufficiently powered to identify between-group differences likely to be of clinical significance.