This registry study used 166,231 primary THAs from the Dutch Arthroplasty Register to quantify how femoral head size and surgical approach each affect revision risk for dislocation and for all other causes at 6 years. It asks a question that prior studies rarely addressed directly: does reducing dislocation risk through approach selection or head upsizing come at the cost of higher non-dislocation revisions? The answer is approach-dependent and head-size-dependent — and the tradeoffs are clinically meaningful.
The central teaching from this paper is that dislocation risk and overall revision risk are not the same target — and optimizing one can worsen the other. For head size, the decision is straightforward: 32-mm heads are a clean win across all approaches, reducing dislocation revision by ~40% with no increase in other revisions. Use 32-mm as your default.
The 36-mm decision is approach-dependent. With the posterolateral approach, 36-mm heads provide additional dislocation protection (HR = 0.6 vs. 32-mm) and are appropriate for higher-risk patients — males and those with ASA III–IV. With the anterior approach, 36-mm heads increase non-dislocation revision risk by 50% and should not be used for this purpose.
The anterior approach's lower dislocation rate comes with a measurable cost: the highest non-dislocation revision rate of any approach (2.9%), predominantly from femoral stem loosening. This persisted after conservative learning curve exclusion (first 150 cases per hospital removed). When counseling patients on anterior approach THA, this tradeoff deserves explicit discussion.
This registry study used 166,231 primary THAs from the Dutch Arthroplasty Register to quantify how femoral head size and surgical approach each affect revision risk for dislocation and for all other causes at 6 years. It asks a question that prior studies rarely addressed directly: does reducing dislocation risk through approach selection or head upsizing come at the cost of higher non-dislocation revisions? The answer is approach-dependent and head-size-dependent — and the tradeoffs are clinically meaningful.
The central teaching from this paper is that dislocation risk and overall revision risk are not the same target — and optimizing one can worsen the other. For head size, the decision is straightforward: 32-mm heads are a clean win across all approaches, reducing dislocation revision by ~40% with no increase in other revisions. Use 32-mm as your default.
The 36-mm decision is approach-dependent. With the posterolateral approach, 36-mm heads provide additional dislocation protection (HR = 0.6 vs. 32-mm) and are appropriate for higher-risk patients — males and those with ASA III–IV. With the anterior approach, 36-mm heads increase non-dislocation revision risk by 50% and should not be used for this purpose.
The anterior approach's lower dislocation rate comes with a measurable cost: the highest non-dislocation revision rate of any approach (2.9%), predominantly from femoral stem loosening. This persisted after conservative learning curve exclusion (first 150 cases per hospital removed). When counseling patients on anterior approach THA, this tradeoff deserves explicit discussion.