Re: The adult hip joint in Saudi Arabia.

To the Editor: The hip joint presents some of the most fascinating problems in the field of orthopedic surgery. Injuries and diseases of the adult hip are important as they may cause prolonged suffering and serious disability. A review of the Saudi literature to explore the pattern of traumatic and non-traumatic disorders affecting the adult hip joint in Saudis has revealed many interesting observations that raise unanswered questions.

First, osteopenia and osteoporosis were reported to be prevalent (70%) in Saudi females above the age of 50 years,1 yet osteoporosis-related hip fractures are uncommon compared to many other populations. The incidence of hip fractures per 100 000 for male and female patients over the age of 50 years was 71 and 100, respectively, with a female: male ratio of 1.4. This is much less than the incidence of hip fractures in other Western populations.2

Secondly, despite the high prevalence of knee osteoarthritis (OA),3,4 hip OA is very uncommon in Saudi Arabia, reaching 0.04% with 80:1 ratio of knee to hip OA.5,6 This is very low compared to other populations. Developmental dysplasia of the hip is relatively common in Saudi Arabia,7–9 and acetabular dysplasia in adults has not been studied. Both conditions are well known risk factors for hip OA. Furthermore, the main indication for hip arthroplasty among Saudis is avascular necrosis of the femoral head secondary to sickle cell disease,10,11 and not hip OA in elderly patients as is the case in other populations. This type of surgery is done mainly for young adults with sickle cell disease and carries a higher risk of complication.

Thirdly, two studies have shown a unique difference in hip and femoral geometry; both rotational12 and axial13 alignments, in Saudi arthritic knees. Whether this is due to a developmental factor or an adaptive reparative change secondary to OA is unknown. A metabolic element was also presumed to be contributing for this femoral and hip malalignment.

Fourthly, one of the authors has shown that hip joints in Saudis have a significantly increased range of motion in abduction and external rotation compared with western populations.14 This is considered to be related to local habitual cross-legged sitting positions among Saudis. We think this cultural habit has a favorable effect on the hip joint mechanics, nutrition, development and containment.

Whether all these features of the “Saudi hip” are due to special geometric morphologic factors, kinematic elements, or racial genetic and metabolic variables is a matter of speculation. Further studies are needed to elaborate these special “unique” features of adult Saudi hip joints.