Mechanical properties during healing of Achilles tendon ruptures to predict final outcome: a pilot Roentgen stereophotogrammetric analysis in 10 patients.
BACKGROUND
There are presently few methods described for in vivo monitoring of the mechanics of healing human tendon ruptures, and no methods for prediction of clinical outcome. We tested if Roentgen stereophotogrammetric analysis (RSA) can be used to follow the restoration of mechanical properties during healing of ruptured Achilles tendons, and if early measurements can predict clinical results.


METHODS
Achilles tendon repair was studied with RSA in 10 patients with a total rupture. Tantalum beads were implanted in conjunction with surgical repair. The patients were evaluated at 6, 12 and 18 weeks, and after 1 year. RSA was performed with two different mechanical loadings, and the strain induced by increasing load was measured. The transverse area was determined by ultrasound. CT scan at 12 weeks confirmed that the tantalum beads were located within the tendons. Functional testing was done after 1 year. A heel raise index was chosen as primary clinical outcome variable.


RESULTS
The strain was median 0.90, 0.32 and 0.14 percent per 100 N tendon force at 6 weeks, 18 weeks and one year respectively. The error of measurement was 0.04 percent units at 18 weeks. There was a large variation between patients, which appears to reflect biological variation. From 6 to 18 weeks, there was a negative correlation between increase in transverse area and increase in material properties, suggesting that healing is regulated at the organ level, to maximize stiffness. Modulus of elasticity during this time correlated with a heel raise index at one year (Rho = 0.76; p = 0.02).


CONCLUSIONS
We conclude that the RSA method might have potential for comparing different treatments of Achilles tendon ruptures.
Section for Orthopaedics and Sports Medicine, Department of Neurosciences and Locomotion, Faculty of Health Sciences, SE 581 85 Linköping, Sweden. thorsten.schepull@lio.se
Thorsten
T
Schepull
Joanna
J
Kvist
Christer
C
Andersson
Per
P
Aspenberg
D000125:Achilles Tendon / Q000293:injuries*; D000328:Adult; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010780:Photogrammetry / Q000379:methods* / Q000706:statistics & numerical data; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011859:Radiography; D020127:Recovery of Function; D012421:Rupture; D013679:Technology, Radiologic / Q000379:methods* / Q000706:statistics & numerical data; D013708:Tendon Injuries / Q000000981:diagnostic imaging* / Q000534:rehabilitation / Q000601:surgery*; D013718:Tensile Strength; D016896:Treatment Outcome; D014945:Wound Healing