Arthroscopic removal of palmar/plantar osteochondral fragments (POF) in the metacarpo- and metatarso-phalangeal joints of standardbred trotters--outcome and possible genetic background to POF.

A clinical material of 133 Standardbred horses with palmar/plantar osteochondral fragments (POF) in the metacarpo- and metatarsophalangeal joints were studied. All horses had their fragments removed with arthroscopic surgery. 102 of the horses were 3 years old or younger when surgery was performed. Anatomical localisations of the fragments were in agreement with earlier reports. There was no statistical significant difference in month of birth in the POF--group compared to the total population. Eighty % of the horses that had raced before surgery came back to racing. The racing performance relative to their contemporaries remained the same after the POF operation. 65% of the horses that had not raced before surgery raced after the operation. The breeding index BLUP (Best Linear Unbiased Prediction) was used to evaluate if the POF-horses differed genetically in racing ability from the total population. The average BLUP value of the POF group was 103.4 (+/- 0.65), while the mean BLUP value of the total population was 98.9. This difference was highly significant and indicated that these POF horses belonged to a selected group. A homogeneity test of allele frequencies in blood type systems was performed to evaluate if any genetic difference was persistent between POF horses compared to the total population. The statistical analysis of gene frequencies for alleles in blood type systems indicated a genetic discrimination in blood type systems D and Tf.