Dull reamers can kill glenoid bone

Thermal effects of glenoid reaming during shoulder arthroplasty in vivo

These authors point out that glenoid component loosening is a common cause of failure of total shoulder arthroplasty. It has been proposed that the heat generated during glenoid preparation may reach temperatures capable of producing osteonecrosis at the bone-implant interface. They hypothesized that temperatures sufficient to induce thermal necrosis can be produced with routine drilling and reaming during glenoid preparation for shoulder arthroplasty in vivo. Furthermore, they hypothesized that irrigation of the glenoid during reaming can reduce this temperature increase. They used real-time, high-definition, infrared thermal video imaging to determine the temperatures produced by drilling and reaming during glenoid preparation in ten consecutive patients undergoing total shoulder arthroplasty. The maximum temperature and the duration of temperatures greater than the established thresholds for thermal necrosis were documented. 

The first five arthroplasties were performed without irrigation and were compared with the second five arthroplasties, in which continuous bulb irrigation was used during drilling and reaming. A one-dimensional finite element model was developed to estimate the depth of penetration of critical temperatures into the bone of the glenoid on the basis of recorded surface temperatures.

The first hypothesis was supported by the recording of maximum surface temperatures above the 56°C threshold during reaming in four of the five arthroplasties done without irrigation and during drilling in two of the five arthroplasties without irrigation. The estimated depth of penetration of the critical temperature (56°C) to produce instantaneous osteonecrosis was beyond 1 mm (range, 1.97 to 5.12 mm) in four of these patients during reaming and one of these patients during drilling, and two had estimated temperatures above 56°C at 3 mm. 

The second hypothesis was supported by the observation that, in the group receiving irrigation, the temperature exceeded the critical threshold in only one specimen during reaming and in two during drilling. The estimated depth of penetration for the critical temperature (56°C) did not reach a depth of 1 mm in any of these patients (range, 0.07 to 0.19 mm).

They concluded that temperatures sufficient to induce thermal necrosis of glenoid bone can be generated by glenoid preparation in shoulder arthroplasty in vivo. Frequent irrigation may be effective in preventing temperatures from reaching the threshold for bone necrosis during glenoid preparation.

Another article is relevant, Thermal and Cutting Dynamics of New and Used Glenoid Reamers During Total Shoulder

These authors suggest that inaccurate reaming and thermal osteonecrosis from heat generated during the reaming process may contribute to TSA failure by creating a suboptimal bone-implant interface. They investigated the differences in depth penetration and heat generation of used community glenoid reamers in comparison to previous unused reamers.

They used a MTS Servohydraulic machine to test new and used community glenoid

reamers by applying the clinically relevant force of 54.7 N over a defined time. The depth of

penetration was measured via the MTS machine and the thermal profile was obtained via an

infrared camera. The used reamers were then set by the MTS machine to reach the same depth as the new reamers for all respective sizes while recording the force differential generated and capturing the thermal profile. 

At a constant force and time, the new reamers penetrated a greater depth (4.18 mm ± 2.17 mm) than the community used reamers (0.41 mm ± 0.22 mm), a difference of 3.80 mm ((95% CI, 2.23 mm to 5.31 mm), p < 0.001) without generating temperatures above 50°C. 

When programmed to reach the same average depth as the new reamers of equivalent sizes, the community reamers generated more heat on average (50.02 °C ± 2.88 °C), a difference of 5.98 °C ((95% CI, 3.40 to 8.53), p < 0.001). The used reamers on average also required 218.20 N more force than the new reamers (54.71 N ± 28.69 N) to reach the same depth, with the medium (303.47 N ± 96.71 N) and large (261.72 N ± 55.28 N) reamers specifically requiring the largest amount of force.

They concluded that the sharpness of glenoid reamers varies in the community. In order to reach the necessary depth for adequate fixation of implants, orthopedic surgeons may be required to exert a substantially larger force when using dulled reamers in comparison to sharp reamers. As a consequence, the heat generated could increase the risk of thermal osteonecrosis contributing to glenoid loosening.

Comment: These articles point to the ability of reaming to generate bone-killing levels of heat in the glenoid bone. This heat may interfere with the healing of bone in a ream and run procedure and with the stability of fixation in total shoulder arthroplasty.

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Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).