VITAMIN D DEFICIENCY IS ASSOCIATED WITH WORST OUTCOME IN RECURRENT SHOULDER INSTABILITY SURGERY

The active form of vitamin D (calcitriol) exerts its biological effects by binding to nuclear vitamin D receptors (VDRs), which are found in most human cells, including skeletal muscles. Vitamin D deficiency may cause deficits in strength, bone health and increases the risk of injury in athletes. The incidence of vitamin D deficiency in collegial athletes in America is up to 90%. Its role in shoulder instability is unknown. We hypothesize that the incidence of vitamin D deficiency in a cohort of recurrent traumatic shoulder instability (RTSI) will be high and that vitamin D deficiency would be correlated to outcome after shoulder stabilization. This is a prospective cohort study including all patient scheduled for a shoulder stabilization surgery (Bankart or Latarjet) for RTSI. Initial evaluation included physical exam, CT scan, MRI, vitamin D dosage and QoL questionnaires (WOSI, DASH). After surgery, all patients were followed every 3 months the first year and yearly thereafter. The normal value for vitamin D was established at 75 IU. Important deficiency was determined to be less than 50 IU and severe deficiency less than 30 IU. Bone density was measured on CT scan with the Hounsfield scale. All patients with low level of vitamin D received a prescription of 1000 IU daily. A cohort of 77 patients were included in this study, 49 males and 28 females. The mean age at surgery was 30 years (range 18–52) and 74% of patients showed a vitamin D level under 75 IU, 45% under 50 IU and 12% under 30 IU. The mean follow-up was of 3 years (range 1–8). The mean number of dislocations prior to surgery was 14 (range 2–200). Patients with vitamin D levels of 30 IU or less, had a worst outcome at last follow-up (WOSI of 1351 vs 514, p<0.001: DASH of 39.29 vs 12.85, p=0.002). They also had more pain at last follow-up (DASH question 9)(p=0.014). Finally, bone density on the glenoid vault (261 vs 360, p=0.189) and humeral head (118 vs 158, p=0.106) side was lower as measured on the CT scan but it was not significant. Vitamin D deficiency affected the majority of subjects. Vitamin D levels of 30 IU or less in patients with RSTI was associated to worst outcome at last follow up, as measured by WOSI and DASH. They also seem to have lower bone density at presentation. Future studies should consider vitamin D dosage after a first dislocation and impact of a more aggressive supplementation on outcome.