COMPARATIVE STUDY
JOURNAL ARTICLE

Theoretically optimum position of the prosthesis in total hip arthroplasty to fulfill the severe range of motion criteria due to neck impingement

Takashi Hisatome, Hideo Doi
Journal of Orthopaedic Science: Official Journal of the Japanese Orthopaedic Association 2011, 16 (2): 229-37
21359509

BACKGROUND: The purpose of this investigation is to determine the optimum position of the prosthesis in total hip arthroplasty for reducing neck impingement using a mathematical formula.

METHODS: We calculated the cup inclination, cup anteversion, and stem antetorsion in cases with various sizes of femoral head (28, 32, 36, and 44 mm in diameter) to fulfill severe range of motion criteria: (1) flexion more than 120°, (2) extension more than 30°, (3) internal rotation at 90° flexion more than 60°, and (4) external rotation at neutral more than 40°.

RESULTS: When the areas to fulfill the severe range of motion criteria were compared by femoral head diameter, the area for 28 mm was extremely small relative to those of 32, 36, and 44 mm. Theoretically, the optimum position of the prosthesis in total hip arthroplasty without neck impingement should be oriented at a cup inclination of 45° combined with the cup anteversion and stem antetorsion so that the sum of the cup anteversion plus 0.7 times the stem antetorsion equals 42° with a head diameter more than 32 mm. This study also recommends the optimum position of the prosthesis as 45° cup inclination, 25° cup anteversion, and 25° stem antetorsion when the surgeon can choose a freely adjustable modular stem system. However, this theory assumes that the pelvic inclination has no changes caused by aging and can be validated in the lying, sitting, and standing positions.

CONCLUSIONS: The prosthesis in total hip arthroplasty without neck impingement should be oriented at a cup inclination of 45° combined with cup anteversion and stem antetorsion determined by the formula: cup anteversion + 0.7 × stem antetorsion = 42°. A range of acceptable positions would be more helpful and realistic to a surgeon trying to ensure adequate prosthesis positions.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read
21359509
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"