Progression of Bone Ingrowth and Attachment Strength for Stability of Percutaneous Osseointegrated Prostheses

Abstract

Background Percutaneous osseointegrated prosthetic (POP) devices have been used clinically in Europe for decades. Unfortunately, their introduction into the United States has been delayed, in part due to the lack of data documenting the progression of osseointegration and mechanical stability.Questions/purposes We determined the progression of bone ingrowth into porous-coated POP devices and established the interrelationship with mechanical stability. Methods After amputation, 64 skeletally mature sheep received a custom porous-coated POP device and were then randomized into five time groups, with subsequent measurement of percentage of bone ingrowth into the available pore spaces (n = 32) and the mechanical pullout force (n = 32). Results Postimplantation, there was an accelerated progression of bone ingrowth (*48% from 0 to 3 months) producing a mean pullout force of 5066 ± 1543 N. Subsequently, there was a slower but continued progression of bone ingrowth (*23% from 3 to 12 months) culminating with a mean pullout force of 13,485 ± 1855 N at 12 months postimplantation. There was a high linear correlation (R = 0.94) between the bone ingrowth and mechanical pullout stability. Conclusions This weightbearing model shows an accelerated progression of bone ingrowth into the porous coating; the amount of ingrowth observed at 3 months after surgery within the porous-coated POP devices was sufficient to generate mechanical stability. Clinical Relevance The data document progression of bone ingrowth into porous-coated POP devices and establish a strong interrelationship between ingrowth and pullout strength. Further human data are needed to validate these findings.

Osseointegration: a review of the fundamentals for assuring cementless skeletal fixation

“…98 Additionally, recent studies by Jeyapalina et al confirmed that when an immediate-loading protocol was used with percutaneous OI implants placed within the intramedullary canal, there were no signs of implant loosening postoperatively for up to 1 year. 63,[99][100][101] The appositional bone index, calculated at predetermined time points, demonstrated progressive bone interconnection and further validated the importance of "fit and fill" (Figure 5). These findings provide further evidence for an immediate implant loading once primary implant stability has been achieved.…”

Radiographic Evaluation of Bone Adaptation Adjacent to Percutaneous Osseointegrated Prostheses in a Sheep Model

“…It was found that anatomic shape of the implant and the surgical protocols helped to achieve and maintain at least five contact/ apposition zones (Table 3) throughout the length of the each implant. It was believed that these contact zones, mainly at the distal regions, might provide the initial stability to prevent micromotion-related implant loosening and help to achieve the robust osseointegration, which was demonstrated by pullout strength data in a related study [16]. The absence of radiolucent and neocortex formation within this porous region, observed in 12-month radiographs, indicated that the implant was osseointegrated within this region.…”

“…10) present within the fluted region of these specimens further confirmed implant fixation by regional osseointegration. Although the implant was intentionally porous coated to a length of only 1 cm of structure at the distal end, the pullout strength study of this device showed extremely robust osseointegration with approximately 1000-N pullout at Time 0 and exceeding 13,000 N at 12 months [16]. If this attachment strength can be achieved in the human situation, this particular POP design would likely be bone sparing in the event of revision surgeries that require implant removal.…”

“…At necropsy, seven of the 14 specimens were harvested and subjected to mechanical testing and reported elsewhere [16]. Using an established method, the remaining seven specimens [3 sections per each region (porous, fluted and smooth regions; Fig. 2)] were processed for histologic analyses [14,15].…”

Sex and Laterality Differences in Medullary Humerus Morphology

“…Percutaneous OI systems rely on adequate initial fixation, and circumferential fill of the medullary canal, for bone ingrowth and long‐term stability (Engh et al, ; Shelton et al, ; Jeyapalina et al, ; Al Muderis et al, ). Additionally, such systems must be compatible with placement at multiple locations along the bone to accommodate variable amputation levels.…”