This prospective cohort study by Engh, Bobyn, and Glassman examines what governs bone ingrowth, stress shielding, and clinical outcomes in cementless porous-coated hip arthroplasty. It evaluates 307 patients at two years and 89 patients at five years, with histological confirmation from 11 retrieved specimens. The central question: what technical and patient factors determine whether a cobalt-chrome femoral stem achieves bone ingrowth versus fibrous fixation?
When you insert a cementless femoral stem and confirm cortical contact at both the medial and lateral isthmus on the postoperative film, you are applying the most important technical finding from this paper: that one decision raises bone ingrowth probability from 69% to 93%.
Age, sex, and diagnosis are irrelevant to outcomes here. Technique is what determines whether your patient walks without a limp.
When proximal femoral resorption appears on follow-up films, grade it with the Engh classification. First and second degree changes are expected adaptive remodeling and do not affect clinical results. Third and fourth degree changes are clinically significant and occur almost exclusively with stems ≥13.5 mm, because flexural rigidity scales with the fourth power of stem diameter.
The radiographic criteria Engh defined — spot welds and absence of radio-opaque lines for bone ingrowth; parallel encircling radio-opaque line with radiolucent gap for fibrous ingrowth. Remain the JBJS-recommended criteria for reporting uncemented stem survivorship today. This paper is also why stress shielding on a well-fixed stem is read as a sign of distal fixation, not failure.
This prospective cohort study by Engh, Bobyn, and Glassman examines what governs bone ingrowth, stress shielding, and clinical outcomes in cementless porous-coated hip arthroplasty. It evaluates 307 patients at two years and 89 patients at five years, with histological confirmation from 11 retrieved specimens. The central question: what technical and patient factors determine whether a cobalt-chrome femoral stem achieves bone ingrowth versus fibrous fixation?
When you insert a cementless femoral stem and confirm cortical contact at both the medial and lateral isthmus on the postoperative film, you are applying the most important technical finding from this paper: that one decision raises bone ingrowth probability from 69% to 93%.
Age, sex, and diagnosis are irrelevant to outcomes here. Technique is what determines whether your patient walks without a limp.
When proximal femoral resorption appears on follow-up films, grade it with the Engh classification. First and second degree changes are expected adaptive remodeling and do not affect clinical results. Third and fourth degree changes are clinically significant and occur almost exclusively with stems ≥13.5 mm, because flexural rigidity scales with the fourth power of stem diameter.
The radiographic criteria Engh defined — spot welds and absence of radio-opaque lines for bone ingrowth; parallel encircling radio-opaque line with radiolucent gap for fibrous ingrowth. Remain the JBJS-recommended criteria for reporting uncemented stem survivorship today. This paper is also why stress shielding on a well-fixed stem is read as a sign of distal fixation, not failure.