Image‐based design and 3D‐metal printing of a rat hip implant for use in a clinically representative model of joint replacement

Abstract

The aim of this study was to obtain micro‐computed tomography derived measurements of the rat proximal femur, to create parameterized rat hip implants that could be surgically installed in a clinically representative small animal model of joint replacement. The proximal femoral anatomy of N = 25 rats (male, Sprague‐Dawley, 390‐605 g) was quantified. Key measurements were used to parameterize computer‐aided design models of monoblock rat femoral implants. Linear regression analysis was used to determine if rat hip dimensions could be predicted from animal weight. A correlation analysis was used to determine how implants could be scaled to create a range of sizes. Additive manufacturing (3D printing) was used to create implants in medical‐grade metal alloys. Linear regressions comparing rat weight to femoral head diameter and neck‐head axis length revealed a significant nonzero slope (P < .05). Pearson's correlation analysis revealed five significant correlations between key measurements in the rat femur (P < .05). Implants were installed into both cadaveric and live animals; iterative design modifications were made to prototypes based on these surgical findings. Animals were able to tolerate the installation of implants and were observed ambulating on their affected limbs postoperatively. Clinical significance: We have developed a preclinical rat hip hemiarthroplasty model using image‐based and iterative design techniques to create 3D‐metal printed implants in medical‐grade metal alloys. Our findings support further development of this model for use as a low‐cost translational test platform for preclinical orthopaedic research into areas such as osseointegration, metal‐on‐cartilage wear, and periprosthetic joint infection.

Establishment of a Novel Rat Model of Gram-Negative Periprosthetic Joint Infection Using Cementless Hip Hemiarthroplasty

“…Cementless hemiarthroplasty hip implants made of medical-grade titanium (Ti-6Al-4V) were 3D-printed by a research group at the University of Western Ontario, Canada, using a selective laser melting (SLM) 3D printer (AM‐400; Renishaw) 47 (Fig. 2-A).…”

“…However, this model still lacks the accurate clinical depiction of the periprosthetic joint environment since it does not articulate within a weight-bearing joint, nor does it allow for implant osseointegration 46 . The model described in our current study has a unique ball-in-socket design using 3D-printed, medical-grade titanium (Ti-6Al-4V) implants 47 that replaced the native femoral heads of Sprague-Dawley rats and articulated congruently with their native acetabula 48 . The implant stem sits anatomically within the femoral canal and has a roughened surface to enhance stability and bone ingrowth.…”

A Novel Rat Model to Study Postsurgical Pain After Joint Replacement Surgery

“…13,14 To develop a more effective treatment strategy, it is essential to clarify the basic mechanisms underlying postsurgical pain in the acute phase. There have been some reports of animal models exhibiting JR, [8][9][10][16][17][18] but the authors have made no mention of postsurgical pain. Among them, very few studies [16][17][18] reported on the JR model using rodents, which have been most extensively used for pain research.…”

“…There have been some reports of animal models exhibiting JR, [8][9][10][16][17][18] but the authors have made no mention of postsurgical pain. Among them, very few studies [16][17][18] reported on the JR model using rodents, which have been most extensively used for pain research. Therefore, we decided to develop a novel animal model of JR using rats.…”