Does using autograft bone chips achieve consistent bone ingrowth in primary TKA?

BACKGROUND: Cementless fixation remains controversial in TKA due to the challenge of achieving consistent skeletal attachment. Factors predicting durable fixation are not clearly understood, but we presumed bone ingrowth could be enhanced by the quantity of host bone and application of autograft bone chips. QUESTIONS/PURPOSES: We asked: (1) Did the amount of bone ingrowth exceed the amount of periprosthetic and host bone with the addition of autograft bone chips? (2) Did the amount of bone ingrowth increase with implantation time? And (3) did osteolysis along the porous-coated interface and screw tracts progress with implantation time? METHODS: We measured the amount of bone in the porous-coated, periprosthetic, and host bone regions in 19 postmortem retrieved cementless primary total knee implants. The amount of bone in apposition to the implant surface, and alternatively lysed bone, was analyzed radiographically to assess the progression of osteolysis. RESULTS: While bone ingrowth tended to be less than periprosthetic and host bone in all three components, it was only significantly less in the patellar component. Bone ingrowth increased in all three components over time, but progression of osteolysis did not. CONCLUSIONS: Even after long-term followup, the amount of bone ingrowth did not surpass host bone levels, suggesting the amount of a patient's host bone is a limiting factor in the amount of bone ingrowth achievable for this cementless design. It remains unknown whether compromised osteopenic bone could achieve the amount of bone attachment necessary to provide durable fixation over time.

Histologic retrieval analysis of a porous tantalum metal implant in an infected primary total knee arthroplasty.

Porous tantalum (Zimmer, Inc, Warsaw, Ind) has the theoretical advantage of improved biologic fixation because of its high porosity, interconnected pore space, and modulus of elasticity. We present a case report documenting the retrieval and bone ingrowth analysis of a porous tantalum tibial component in an infected total knee arthroplasty. Results demonstrated a significantly larger amount of bone ingrowth present in the tibial posts (36.7%) when compared with the bone ingrowth into the tibial baseplate (4.9%) (P < .001). The data suggest that bone ingrowth seen in the plugs as well as baseplate was suggestive of viable bone tissue with healthy bone marrow, osteocytes, and lamella, resulting in a well-fixed tibial implant even at revision surgery for an infected total knee arthroplasty.

Characterization of the anchoring morphology and mineral content of the anterior cruciate and medial collateral ligaments of the knee.

The manner in which ligament connects to bone remains an area of interest for researchers, bioengineers, and clinicians. Stable fixation of an anterior cruciate ligament (ACL) graft has been shown to be paramount to preventing excess anterior tibial translation and to restoring the normal kinematics of the knee joint. In this study, the surface area of attachment and the mineral characteristics of the ACL and medial collateral ligament (MCL) attachment sites were characterized to determine the factors that contributed to ligament attachment strength. Findings from this study indicated that the area of attachment of the ACL's insertion was significantly greater than the ligament's origin (95.8 mm(2) ± 21.5 vs. 73.2 mm(2) ± 16.2, P = 0.009). Additionally, the ACL was measured to have a greater surface area of attachment when compared with the MCL (84.5 mm(2) ± 18.8 vs. 58.2 mm(2) ± 23.8, P = 0.005); although, the MCL was observed to have a greater region of calcified fibrocartilage (CFC) than the ACL (533.0 µm ± 116.9 vs. 195.5 µm ± 36.6, P = 0.0003). No significant correlation was observed between the ligament's area of attachment and the thickness of the CFC region. Measurements of ash percent suggested that the boundary region, between the CFC and host bone, possessed the least mineral content for the three regions of interest. These data suggest that ligament attachment strength can be attributed to several factors, including the ligament's area of attachment, regional thickness, and mineral content of the CFC.

Does celecoxib have an adverse effect on bone remodeling and ingrowth in humans?

Although celecoxib may provide perioperative pain relief, the effect of the short-term use of celecoxib on bone ingrowth into porous-coated devices has not been previously studied in humans. Bone ingrowth into titanium and tantalum plugs was measured in nine patients who underwent staged bilateral total knee arthroplasty (TKA) and were taking celecoxib as part of a perioperative pain relief protocol. Patients were given tetracycline to measure the mineral apposition rate before and after celecoxib administration. Time zero plugs were implanted and retrieved during the first TKA, and 12 weeks later the contralateral implanted plugs were retrieved at the second TKA. The mineral apposition rate was similar for the titanium (0.97 microm per day) and the tantalum (1.15 microm per day) plugs at 12 weeks as was bone ingrowth (886 microm versus 632 microm, respectively). Celecoxib does not seem to inhibit bone ingrowth or bone formation.

A Method for Cemented Bone Interface Examination Without Polymethylmethacrylate Embedment.

Although effective, the embedment of bone tissue and orthopaedic devices using polymethylmethacrylate (PMMA) has challenges and limitations. To embed using PMMA, specimens must first be fixed in 70% ethanol, dehydrated in ascending grades of ethanol, and then infiltrated and polymerized in polymethylmethacrylate using standard techniques. This process can take more than 22 d for large bone specimens. Additionally, PMMA embedment has been shown to dissolve bone cement, thus enabling the analysis of the bone-cement interfaces. To conserve processing time while preserving the bone-cement interface, a method was developed for processing mineralized bone tissue in preparation for scanning electron microscopy (SEM) imaging that does not require PMMA embedment. This technique does not require the traditional dehydration and PMMA polymerization process. Instead, fresh mineralized cemented bone specimens were serially sectioned and the marrow removed after formalin fixation. The sections were air-dried then desiccated. The sections were then prepared for SEM imaging and examination. This process takes a fraction of the tissue processing time while not compromising the bone-cement integrity. The SEM image quality was shown to be comparative to images obtained with PMMA-embedded bone specimens.