Due to frequent bleedings into the musculoskeletal apparatus haemophilic patients suffer from functional deficits and limitations in appropriate postural control. Haemophilic arthropathy resulting in altered proprioceptive input suggests different intermuscular coordination patterns in haemophilic subjects. The purpose of this study was to analyze the patterns of selected shank muscles during non-perturbed upright standing in haemophilic patients.

Intermuscular coordination of five bilaterally recorded ankle joint muscles [tibialis anterior (TA), fibularis longus (FL), medial (GCM), and lateral (GCL) head of gastrocnemius, and soleus (SOL)] was investigated in 25 (42.4 9.2 years) haemophilic patients (H) and 25 (43.0 11.6 years) healthy control subjects (C) by surface EMG (SEMG). To analyze the coordination patterns, patients extremities were separated according to major (MA) and minor (MI) affected joints regarding Orthopaedic Joint Score by Gilbert (1993), respectively. Ankle muscle coordination was assessed by relative amplitude levels (reported as a percentage of total muscle activity, 100%) of all investigated muscles, isolated for each side in H. Data from both sides of C was pooled. Nonparametric two-sample tests compared results and were further adjusted using Holms procedure controlling the familywise error rate (Holm 1979).

Different SEMG muscle activation patterns could be detected during bipedal standing in H compared to C. For the muscles in MA (H vs. C) TA [H: 10.6 (17.1/9.1), median (upper/lower quartile) in percent, C: 7.5 (10.5/5.9)], FL [H: 17.1 (28.3/13.2), C: 13.1 (17.9/10.7)], GCM [H: 14.9 (18.3/12.0), C: 21.9 (36.3/17.4)], and SOL [H: 28.8 (31.2/15.5), C: 34.6 (40.3/26.1)] reached significantly different values (p = 0.05). GCL of MA did not achieved significance [H: 15.2 (21.3/8.9), C: 12.1 (17.3/10.0)]. In MI (H vs. C) only TA [H: 10.9 (18.5/8.8), C: 7.5 (10.5/5.9)], and GCM [H: 15.8 (20.4/11.6), C: 21.9 (36.3/17.4)] activation patterns were different from C. The application of Holms adjustment procedure rejected only FL of MA, whereas other muscles remained at significant levels. The comparisons of the MA vs. MI (within H) showed no statistical differences.

These findings show that H maintain the necessary stability demands during standing by using a different intermuscular coordination pattern. Muscle activation patterns in H showed higher values of TA whereas GCM had lower relative activation magnitudes than C. However, joint integrity appears to be reduced in MA as well as in MI affected joints with TA and GCM seeming to play key roles for neuromuscular control of upright posture in H. The different activation patterns of H could be interpreted as compensational mechanism to maintain upright posture during standing due to restricted motion of the ankle. Exercise therapy should especially consider the neuromuscular control in special rehabilitation programs.

This study was supported by Baxter-Germany.