Drilling and microfracture lead to different bone structure and necrosis during bone‐marrow stimulation for cartilage repair

Abstract

Bone marrow stimulation is performed using several surgical techniques that have not been systematically compared or optimized for a desired cartilage repair outcome. In this study, we investigated acute osteochondral characteristics following microfracture and comparing to drilling in a mature rabbit model of cartilage repair. Microfracture holes were made to a depth of 2 mm and drill holes to either 2 mm or 6 mm under cooled irrigation. Animals were sacrificed 1 day postoperatively and subchondral bone assessed by histology and micro-CT. We confirmed one hypothesis that microfracture produces fractured and compacted bone around holes, essentially sealing them off from viable bone marrow and potentially impeding repair. In contrast, drilling cleanly removed bone from the holes to provide access channels to marrow stroma. Our second hypothesis that drilling would cause greater osteocyte death than microfracture due to heat necrosis was not substantiated, because more empty osteocyte lacunae were associated with microfracture than drilling, probably due to shearing and crushing of adjacent bone. Drilling deeper to 6 mm versus 2 mm penetrated the epiphyseal scar in this model and led to greater subchondral hematoma. Our study revealed distinct differences between microfracture and drilling for acute subchondral bone structure and osteocyte necrosis. Additional ongoing studies suggest these differences significantly affect long-term cartilage repair outcome. ß

Arthroscopic Acetabular Microfracture With the Use of Flexible Drills: A Technique Guide

“…The fluted design of the drill tip extracts bone, instead of impacting it, creating a clear channel for the flow of the marrow components. An animal study by Chen et al 10 reported on osteochondral characteristics of tissue after drilling as compared with standard awl microfracture. The study showed that the awl technique fractured and compacted bone around holes, sealing off access to viable marrow, in contrast to drilling.…”

“…However, a recent animal study showed that drilling with cooled irrigation did not produce heat necrosis. 10 Among the drawbacks of the technique is the possibility of equipment failure. In certain instances the drill bit may break if the drill is not on full forward speed when the drill contacts the bone.…”

Surgical preparation of bone–scaffold interface is critical for bone regeneration inside tissue engineering scaffold

“…For instance, the preparation of the interface (i.e., the tissue excision) should allow the scaffold access to bone marrow. 8 In this work, we studied the effect of two drilling techniques for preparation of the scaffold implantation site on the long-term bone regeneration.…”

“…While adjacent bone plays a major role in supplying cells, nutrients, and biochemical signals, the importance of the interaction between bone and scaffold has thus far been largely neglected. In a recent study, Chen et al 8 demonstrated that in the bone marrow stimulation technique for cartilage repair, the preparation technique significantly affected the long-term outcome. They observed that the microfracture technique produced fractured and compacted bone around holes, essentially sealing them off from viable bone marrow.…”

“…Indeed, an important effect of drilling trabecular bone might not be the increase in temperature, but the damage to the structure of adjacent trabeculae, which may have serious biological consequences. 8 In the present study, two drilling techniques were used to create a hole in rat distal femurs before the insertion of a bone scaffold. The first drilling technique used a manually driven wood drill bit and the second technique used an electrically driven metal drill bit.…”