Tailbone Pain Associated with a Keel-Shaped Coccyx

Physical Medicine and Rehabilitation

2009 Sept; 1 (9): S176-S177

Patrick M. Foye, M.D., Evish Kamrava, M.D., Renee Enriquez, M.D.

Coccyx Pain Service, Department of Physical Medicine and Rehabilitation, UMDNJ: New Jersey Medical School, 90 Bergen St., DOC-3100, Newark, NJ 07103-2499. Phone: (973)972-2802. Fax: (973)972-2825. tailbonedoctor.com/.


OBJECTIVE: The objective was to report on the incidence of keel-shaped coccyx morphology in patients with coccydynia (coccyx pain). We define a keel-shaped coccyx as imaging studies showing fused coccygeal segments with an anterior-posterior width of the coccyx that is wider at the distal coccyx than at the proximal coccyx, but not due to an isolated bone spur. To our knowledge, this anatomic variation has not previously been reported nor has its incidence been studied in patients with coccygeal symptoms.

DESIGN: Retrospective chart review of 200 patients with a chief complaint of tailbone pain.

SETTING: Academic-based physiatric outpatient pain management practice with a dedicated Coccyx Pain Service.

PARTICIPANTS: Records were reviewed from 200 patients with a chief complaint of tailbone pain and physical exam findings revealing focal pain with coccyx palpation.

MAIN OUTCOME MEASURES: Incidence of keel-shaped coccygeal appearance was calculated from review of medical records and imaging studies.

RESULTS: Of 200 outpatients with coccyx pain whose records were reviewed, 3 patients had imaging studies showing a keel-shaped coccyx. These 3 case presentations are as follows. A 39 year old female had onset of tailbone pain via trauma (a fall) more than a year before presentation here. A 56 year old female had onset of tailbone pain via trauma (a fall) 17 years prior to presentation here, which resolved until episodes of prolonged sitting prompted return of the pain over the year prior to presentation. Lastly, a 32 year old male had non-traumatic onset of tailbone pain for one year prior to presentation here. All 3 had increased tailbone pain with sitting. All 3 of these 200 patients had a keel-shaped coccyx.

CONCLUSIONS: A keel-shaped coccyx was noted in 1.5% of patients with tailbone pain. Further study is needed to assess whether this anatomic variation increases the risk of developing tailbone pain in the first place (causal relationship) versus whether this coccygeal morphology is just an incidental finding.

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