Aims

Porous metaphyseal cones can be used for fixation in revision total knee arthroplasty (rTKA) and complex TKAs. This metaphyseal fixation has led to some surgeons using shorter cemented stems instead of diaphyseal engaging cementless stems with a potential benefit of ease of obtaining proper alignment without being beholden to the diaphysis. The purpose of this study was to evaluate short term clinical and radiographic outcomes of a series of TKA cases performed using 3D-printed metaphyseal cones.

Due to its popularity of intramedullary nails (IMN) high success rate, newer design (titanium) IMN system have been introduced to replace stainless steel system. However the stability provided by the titanium IMN

may not be adequate, there by influencing the union rate.

We aimed to compare the results of both IMN systems via prospective clinical study and biomechanical testing using RSA.

There has been a longstanding need for a structural biomaterial that can serve as a bone graft substitute or implant construct and is effective for fixation by bone ingrowth. A porous tantalum material was developed to address these issues. The purpose of this paper and presnetation is to describe the properties and 2 to 5 year clinical results of porous tantalum in various reconstructive orthopaedic procedures.

Porous tantalum has been used to manufacture primary and revision acetabular cups, acetabular augments, tibial and patella implants, patellar augments, structural devices for the treatment of osteonecrosis, and spinal fusion implants. Clinical follow-up includes: 2–5 year clinical and radiographic evaluation of: 414 monoblock cups in primary THA, 36 monoblock cups and 587 revision hemispheres used in revision THR, 16 hips revised with acetabular augments and revision hemispheres; 2 to 4 years for 101 tibial implants used in primary TKR and 69 patellas used in cementless TKR; 2–4 years for 11 patellar augments in salvage TKR, 1–5 years for 53 revision TKRs using knee spacers; 1–4 years for 91 osteone-crosis hip implants; and for 15 cervical fusion cases.

This innovative tantalum implant material with trabecular architecture possesses advantages in stiffness, friction coefficient, porosity, rate and extent of tissue ingrowth, and versatility in manufacturing of structural devices. It has been clinically validated in numerous and diverse reconstructive procedures.

Press-fit acetabular reconstructions have become the standard THA; however, controversies remain. The purpose of this study was to critically evaluate serial radiographs for initial cup stability, i.e. gaps and signs of periacetabular interface changes for a porous tantalum monoblock socket.

A multicenter study evaluating 574 primary THRs (542 patients) performed by 9 surgeons at 7 hospitals, all with a monoblock cup without screws. Analyses included clinical outcomes and detailed 2-year minimum radiographic evaluation by one independent observer (mean follow-up, 33 months).

Complications included 9 intra-operative acetabular fractures. Among the 123 cases excluded from radiographic evaluations: deceased (19), lost-to-follow-up (8), 7 early revisions (recurrent dislocations (6) and one trauma-related loosening), and sepsis (3). Patient demographics (414 hips): mean age 65 years (19–93); 58 percent females. Baseline radiographs revealed 113 zones in 85 hips (21 percent) with acetabular gaps; 36 in zone I, 72 in zone II, and 5 in zone III. Of these radiolucencies, 57 zones were 1 mm or less and 56 zones ranged from 2 to 5 mm. At last follow-up, 64 hips (75 percent) had complete gap fill-in, including 100 percent of gaps greater than 3 mm.

There were no socket migrations, no evidence of lysis, no revisions for loosening, and no complete periacetabular interface radiolucencies. The fill-in of preexisting OA cysts and gaps is attributed to adequate initial stability and osteointegration into the porous tantalum. These results suggest that a monoblock cup without screws is an attractive option in THA.

Introduction: The purpose of this study was to review the preliminary clinical outcomes of a clinical study of a new implant for intervening in Stage I & II femoral head osteonecrosis.

Materials & Methods: The porous tantalum (Hedrocel® Trabecular Metal, Zimmer Inc./Implex Corp.) is 80% porous with a modulus of elasticity similar to bone. The implant is 10 mm in diameter, offered in 70 – 130 mm lengths in 5 mm increments, and possesses threads for engagement of the lateral cortex. The investigation is an FDA regulated, prospective IDE study of the implant in comparison to core decompression for patients with Stage I or II osteonecrosis (Steinberg-UPenn). Patients exhibiting unilateral disease are randomized to an implant or core decompression (50–50 chance). All patients exhibiting bilateral disease receive the implant. Clinical outcome measures include HHS and SF-12 scored pre-op, at 6, 12, and 24 months, and radiographic data is collected at these same times, and at 6 and 12 weeks.

Results: Prior to the clinical study, a custom case was performed in 1998, and a second in 1999. Since the study began in June 2000, 12 surgeries have been performed with the implant. All 14 patients are reportedly doing well. Radiographic review shows no evidence of abnormal bone density and no evidence of radiolucencies. All lesions appear similar to the pre-op condition. In one case, at 3-months, there is radiographic evidence that the implant has stabilized a slightly collapsed subchon-dral plate, and that new bone has formed in proximity to the tip of the implant. This patient exhibited mild pain at 8 weeks, which has since subsided.

Discussion: The preliminary clinical experience with this implant is encouraging and suggests that mechanically supporting the subchondral plate with this implant is a viable method of intervening in the early stages of osteonecrosis.