Biomechanical and Functional Indicators in Male Semiprofessional Soccer Players With Increased Hip Alpha Angles vs. Amateur Soccer Players

Matthias Lahner; Christoph von Schulze Pellengahr; Philipp Alexander Walter; Carsten Lukas; Andreas Falarzik; Kiriakos Daniilidis; Lars Victor von Engelhardt; Christoph Abraham; Ewald M Hennig; Marco Hagen

Disclosures

BMC Musculoskelet Disord. 2014;15(88)

Conclusions

Future research is needed to identify characteristic features which display the different stages of FAI process. A challenge for future research is to develop physical training programs for preventing FAI or decelerating the FAI process. These findings support the need for a screening program for competitive soccer players. In cases of a conspicuous gait analysis, FAI must be ruled out by further diagnostic tests.

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Abbreviations
FAI: Femoroacetabular impingement; FOV: Field of view; MRI: Magnetic resonance imaging; NW: No wedges; TE: Echo time; TR: Repetition time; ROM: Range of motion; VW: Valgus wedges.

Competing interests
The authors declare that they have no competing interests.

Authors' contributions
ML, AF, CA, EMH and MH conceived and designed the study. ML, PAW, CL and LVvE performed the MRI measurements. ML, CvSP, PAW, KD, CA, EMH and MH are involved in the execution of the study and the writing of this manuscript. All authors read and approved the final manuscript.

Acknowledgments
The authors thank Coach André Pawlak and the soccer players of the Sportgemeinschaft Wattenscheid 09. The authors thank Dr. Nina Lahner for correcting the manuscript.

Table 1. Demographic information
Group (n)	Age (years)	Height (cm)	Weight (kg)	Body mass index (kg/cm²)
Semiprofessional group (14)	22.21 ± 2.28	180 ± 0.07	76.0 ± 9.18	23.2 ± 1.25
Amateur group (14)	22.71 ± 2.88	181 ± 0.07	81.28 ± 11.11	23.80 ± 3.03
P value	0.496	0.722	0.182	0.500

Table 2. Comparison of the mean of the alpha angles of the two groups
Group division (n)	Mean alpha angle ± SD
Semiprofessional group (14)	55.16 ± 6.58°
Amateur group (14)	51.65 ± 4.43°
P value	0.11

Table 3. Inter-rater reliability of the alpha angles between the two observers
Variables	Inter-rater reliability	95%-confidence interval
Oberserver 1 vs. observer 2		Minimum level	Maximum level
Alpha angle, semiprofessional group	0.966	0.87	0.99
Alpha angle, amateur group	0.967	0.899	0.989

Table 4. NW shod running without inserted valgus wedges
Variables	Semiprofessional group mean	SD	Amateur group mean	SD	P value
Loading rate (bw/s)	101.9	32.2	73.2	8.6	<0.01**
Peak tibial acceleration (g)	7.8	2.3	5.9	2.6	<0.05*
Median power frequency (Hz)	14.7	1.2	13.7	1.1	0.04*
Peak vertical force (bw)	2.7	0.3	2.5	0.3	0.03*
Peak horizontal force (bw)	14.5	3.6	14.1	2.5	0.76
Horizontal impulse (bw × s)	2.6	0.3	2.9	0.2	<0.01**
Maximum rearfoot motion (°)	8.5	2.6	10.9	3.1	0.04*
Peak pressure lateral heel (kPa)	735	294	743	189	0.93
Peak pressure medial heel (kPa)	657	377	719	263	0.62
Peak pressure lateral midfoot (kPa)	343	117	263	57	0.03*
Peak pressure metatarsal head V (kPa)	422	236	480	148	0.45*
Peak pressure metatarsal head III (kPa)	673	203	525	150	0.04*
Peak pressure metatarsal head I (kPa)	713	203	676	191	0.71
Peak pressure hallux (kPa)	581	224	533	266	0.68

**highly significant at P < 0.01, *significant at P < 0.05.

Table 5. VW shod running with inserted valgus wedges
Variables	Semiprofessional group mean	SD	Amateur group mean	SD	P value
Loading rate (bw/s)	97.1	45.5	62.2	12.2	0.01*
Peak tibial acceleration (g)	7.8	3.0	5	2.2	<0.01**
Median power frequency (Hz)	13.9	0.9	12.9	1.3	0.02*
Peak vertical force (bw)	2.7	0.3	2.5	0.3	0.01*
Peak horizontal force (bw)	13.8	3.5	13.2	2.4	0.58
Horizontal impulse (bw × s)	2.6	0.3	2.8	0.3	0.09
Maximum rearfoot motion (°)	9.0	2.9	11.5	2.8	0.03*
Peak pressure lateral heel (kPa)	690	349	513	183	0.11
Peak pressure medial heel (kPa)	516	257	617	229	0.28
Peak pressure lateral midfoot (kPa)	407	177	355	53	<0.05*
Peak pressure metatarsal head V (kPa)	377	193	433	88	0.34
Peak pressure metatarsal head III (kPa)	627	244	462	157	0.04*
Peak pressure metatarsal head I (kPa)	626	172	646	188	0.83
Peak pressure hallux (kPa)	528	271	518	241	0.94