The elastic properties of patellar tendon in jumping athletes with and without patellar tendinopathy

Pao Yue-kong Library Electronic Theses Database

The elastic properties of patellar tendon in jumping athletes with and without patellar tendinopathy

 

Author: Zhang, Zhi Jie
Title: The elastic properties of patellar tendon in jumping athletes with and without patellar tendinopathy
Degree: Ph.D.
Year: 2015
Subject: Patella -- Mechanical properties.
Patella -- Pathophysiology.
Patella -- Diseases.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Rehabilitation Sciences
Pages: xxxi, 208 pages : color illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2828149
URI: http://theses.lib.polyu.edu.hk/handle/200/8254
Abstract: A tendon acts like a spring in absorbing and storing elastic energy for energy efficient movements.In this thesis,the elastic properties of the patellar tendon are assessed on relation to performance enhancement and injury prevention. Because jumping athletes experience a high landing impact, there is a strong rationale for examining the effects of sports participation on the elasticity of the patellar tendon among volleyball and basketball players. If weakness in hip muscles is found in patients with anterior knee pain, a similar observation may also occur in patients with patellar tendinopathy. In addition, the existing findings on the modulation on tendon stiffness in patients with tendinopathy are inconsistent.Most individuals with tendinopathy experience pathological changes and pain at the proximal region of the patellar tendon. Therefore, it is worth re-examining possible regional change in tendon elasticity and its correlation with pain and function. To further establish the relationships between patellar tendon elasticity, pain, and dysfunction, an interventional study is needed to assess whether the changes in the patellar tendon elastic properties are associated with the modulation of pain. This thesis includes cross-sectional and prospective studies.Supersonic shearwave imaging (SSI) technology was hypothesized to provide reliable measurements on regional tendon elasticity. Using this technology, the elastic properties of patellar tendon in jumping athletes such as volleyball and basketball players was assessed to ascertain whether the elastic properties of patellar tendons were modulated when compared with age- and gender-matched sedentary subjects. The strength of the hip abductors and external rotators was likely to be weaker in volleyball and basketball players with patellar tendinopathy when compared with healthy players. The muscle strength might also be associated with patellar tendon elasticity.Moreover, the reduced in tendon elasticity in players with unilateral tendinopathy might be associated with the magnitude of pain. Finally, after a session of extracorporeal shockwave therapy, the changes in the patellar tendon elastic properties could relate to the modulation of pain in the treatment group.Experiment 1: The elastic properties of the eight fresh patellar tendons of pigs were measured by SSI technology and compared with the tangent traction modulus calculated from a material testing system (MTS). Spearman correlation coefficient between the shear elastic modulus from the SSI and tangent traction modulus from the MTS was 0.82 to 1.00 (p<0.05) on the eight tendons.The intra- and inter-operator reliabilities of test-retest measurements were conducted on 11 healthy subjects were 0.98 and 0.97, respectively.Experiment 2 to 5: Male volleyball and basketball players aged between 18 and 35 were recruited from local university and community teams.All athletes practiced their sports for at least two days per week.Sedentary subjects of similar age and gender, but who did not participated in any regular sporting activity, were recruited from local university community. Athletes with patellar tendinopathy were recruited from the same sport teams. All of the assessments and interventions were conducted at the Hong Kong Polytechnic University. Experiment 2: The tendon shear elastic modulus of the subjects was measured at the proximal patellar tendon to test tendon elasticity and to compare between sedentary and jumping athletes. Experiment 3: The muscle strength of the hip abductors and external rotators of athletes with and without patellar tendinopathy was measured using a hand-held dynamometer. Experiment 4: The magnitude of pressure pain and activity-related pain were quantified by a hand held algometer and the Victorian Institute of Sport Assessment-patella (VISA-P) questionnaire in players with unilateral patellar tendinopathy. Experiment 5: Tendon shear elastic modulus of the proximal patellar tendon, pressure pain, single-legged declined-squat tests (SLDST) were conducted before and after a session of extracorporeal shock wave therapy (ESWT).
The results from these studies demonstrated that elastic properties of the patellar tendon could be adapted with sports participation. Male individuals with long-term participation in volleyball and basketball had better tendon compliance than sedentary subjects, in that they showed a lower tendon elastic modulus at the proximal patellar tendon. The volleyball players showed better tendon compliance compared with the basketball players (by 24.9%). Age was the only anthropometric factor found to be related with the patellar tendon elasticity of the volleyball players (r=0.53; p=0.003). The results further showed that the athletes with patellar tendinopathy had lower normalized isometric muscle strength in the hip abductors and external rotators when compared with the healthy controls. The magnitude of reduction was 18.2% and 11.2% in the hip abductors and external rotators,respectively. In addition,significant increases in the elastic shear modulus of the patellar tendon (by 48.0%) and vastus lateralis muscle (by 26.5%) were detected in players with patellar tendinopathy when compared with healthy controls.Moreover, a negative correlation was established between the shear elastic modulus of patellar tendon and normalized hip strength,in that weaker hip strength was associated with a stiffer tendon. In athletes with unilateral patellar tendinopathy,significant correlations were found between the tendon shear elastic modulus ratio (shear elastic modulus of painful over non-painful tendons) and the intensity of pressure pain, VISA-P scores,and the sub-scores of the VISA-P scores for going down stairs, lunges, single leg hopping,and squatting. After a session of ESWT on the patellar tendon, a significant reduction in the tendon shear elastic modulus was observed.More importantly, the reduction in the tendon shear elastic modulus was related to the reduction in squatting pain and the composite change on knee range and squatting pain during the SLDST in the treatment group (r=0.52 and 0.59, respectively). This relationship was not observed in the sham group. Five main conclusions could be drawn from the study findings:1)SSI was a reliable technique for measuring regional tendon elastic properties.2) Jumping athletes had better compliance at the patellar tendon compared with the sedentary subjects. The volleyball players also showed better tendon compliance when compared with the basketball players,which might be related to the different physical activities and demands of the two jumping sports. 3) Decreased in muscle strength of the hip abductors and external rotators was observed in athletes with patellar tendinopathy when compared with healthy controls,and the weakness in these muscles was associated with elasticity in the patellar tendon. 4) Tendon compliance was reduced at the painful site in athletes with patellar tendinopathy and the reduced in tendon compliance was associated with the magnitude of pain. 5)A session of ESWT induced a reduction in tendon stiffness that was also associated with the reduction in the magnitude of pain. Taking together, with previous findings, these findings indicated that tendon compliance could be modulated.The findings further demonstrated that the reduction in patellar tendon compliance was associated with weakness in the hip muscle and the magnitude of pain. A session of ESWT also induced short-term improvements in tendon compliance and pain. These findings strongly suggest that the strengthening programs for volleyball and basketball players should include exercise for the hip abductors and external rotators muscles. Finally,intervention for improving in tendon compliance, such as ESWT,can be used to individuals with patellar tendinopathy.

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