International Journal of Collaborative Research on Internal Medicine & Public Health

Palmaris Longus Agenesis (PLA) among Dusun & Bajau ethnic groups of Northern Borneo

Background: The functional role of Palmaris longus muscle is little to human upper limb, but its long tendon is very useful as a donor tendon in hand reconstructive surgery. In the human body, Palmaris longus muscle is often described as one of the most variable muscles in both number and form. It is only to be consistently found in mammals especially in those using forelimbs for weight-bearing and ambulation. The absence of Palmaris longus in human appears to be hereditary but its possibility through genetic transmission has not been proven yet. The first report in 1559 estimated the Palmaris longus agenesis (PLA) was 17.2% among Indians and 12-24% in Caucasians. It was reported to be 4.6% among Singaporean-Chinese while 12.6% and 26.6% in Nigeria-black and Turkish people respectively. A 2007 UKM study shows prevalence of PLA in Malays was 11.3% followed by Indians (10.7%) and Chinese (6.0%). Studies had indicated that PLA would be associated with other anatomical variations of hand. Borneo is the third largest island in the world and located in the centre of the Maritime Southeast Asia. Sabah, once known as north Borneo, is the second biggest states in Malaysia after Sarawak. The largest indigenous ethnic group in Sabah is Kadazan-Dusun residing mainly on the West Coast region of Sabah, making up about 30% of population. Bajau is the second largest indigenous ethnic group and can be found in east coast of Sabah.

Aim & Objectives: To determine the prevalence of PLA among the two major ethnic groups of Sabah namely Dusun (Kadazan-Dusun & Rungus) and Bajau and to compare the estimates between age and gender

Methods: The presence or absence of Palmaris longus tendon was clinically examined among the ethnic volunteers (18 years and above) by using standard tests namely Schaffer’s test, Thompson’s test, Mishra’s test I and II, Pushpakumar’s test.

Results/Findings: 22 villages from Sandakan, Kudat, Pitas, Kota Belud, Kota Kinabalu (Penanpang and Innanam) area were covered. 397 Dusun (129 males & 268 females) and 201 Bajau (85 males & 116 females) were examined. Only 64.7% of Dusun and 73.6% of Bajau showed presence of Palmaris longus tendon in both hands. The bilateral absence of Palmaris longus tendon was 18.9% among Dusun and 11.4% among Bajau. PL tendon unilateral absence was 16.4% and 14.9% for Dusun and Bajau respectively. The PLA (both bilateral and unilateral) among Dusun 35.3% was significantly higher than the 26.4% of Bajau (χ2 : 4.832 & p:<0.03). The females tend to have a significantly higher prevalence of PLA than males (i.e; 40.3% for Dusun and 31% for Bajau).

Conclusion: The Palmaris longus tendon agenesis (both bilateral and unilateral) among the studied ethnic groups of Sabah was much higher than the prevalence among Malays, Indians and Chinese of 2007 UKM study. Further research is needed to determine the anatomical variations associated with PLA among the ethnic groups of Sabah.

Author(s): Aye Mya Thidar , Tin Tin Myint , Daw Khin Saw Naing , Zainal Ariffin Mustapha

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