Three-dimensional (3D) printing has numerous applications and has gained much interest in the medical world. The constantly improving quality of 3D-printing applications has contributed to their increased use on patients. This paper summarizes the literature on surgical 3D-printing applications used on patients, with a focus on reported clinical and economic outcomes. Three major literature databases were screened for case series (more than three cases described in the same study) and trials of surgical applications of 3D printing in humans. 227 surgical papers were analyzed and summarized using an evidence table. The papers described the use of 3D printing for surgical guides, anatomical models, and custom implants. 3D printing is used in multiple surgical domains, such as orthopedics, maxillofacial surgery, cranial surgery, and spinal surgery. In general, the advantages of 3D-printed parts are said to include reduced surgical time, improved medical outcome, and decreased radiation exposure. The costs of printing and additional scans generally increase the overall cost of the procedure. 3D printing is well integrated in surgical practice and research. Applications vary from anatomical models mainly intended for surgical planning to surgical guides and implants. Our research suggests that there are several advantages to 3D-printed applications, but that further research is needed to determine whether the increased intervention costs can be balanced with the observable advantages of this new technology. There is a need for a formal cost–effectiveness analysis.

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3D-printing techniques in a medical setting: a systematic literature review

Recent increased interest in less invasive surgical techniques has led to a concurrent resurgence in unicompartmental knee arthroplasty. The procedure has evolved significantly over the past three decades. Proponents of unicompartmental knee arthroplasty cite as advantages lower perioperativ

Unicompartmental knee arthroplasty.

α-Tocopherol-doped irradiated UHMWPE for high fatigue resistance and low wear

Our hypothesis was that cross-linked, ultrahigh-molecular weight polyethylene (UHMWPE) stabilized with vitamin E (alpha-tocopherol) would be wear-resistant and fatigue-resistant. Acetabular liners were radiation cross-linked, doped with vitamin E, and gamma-sterilized. Hip simulator wear rate of vitamin E-stabilized UHMWPE was approximately 1 and 6 mg/million-cycles in clean serum and in serum with third-body particles, respectively, a 4-fold to 10-fold decrease from that of conventional UHMWPE. The ultimate strength, yield strength, elongation at break, and fatigue resistance of vitamin E-stabilized UHMWPE were significantly higher than that of 100 kGy-irradiated and melted UHMWPE, and were unaffected by accelerated aging. Rim impingement testing with 3.7-mm-thick acetabular liners up to 2 million-cycles showed no significant damage of the cross-linked liners compared with conventional, gamma-sterilized in inert UHMWPE, vitamin E-stabilized liners. The data indicate good in vitro wear properties and improved mechanical and fatigue properties for vitamin E-stabilized, cross-linked UHMWPE.

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Wear resistance and mechanical properties of highly cross-linked, ultrahigh-molecular weight polyethylene doped with vitamin E.

A prosthesis system for replacing a knee joint between a femur and a tibia can include a femoral component (16), a tibial component (18), a bearing (20), a first yoke (22), and a first key (182). The femoral component can include a first condylar portion (26), a second condylar portion (28), a first sidewall (40) extending superiorly from the first condylar portion, a second sidewall (42) extending superiorly from the second condylar portion where the first and second sidewalls collectively comprise a first hinge portion (44). The tibial component can have a bone engaging inferior surface (56) and a bearing engaging superior surface (58). The bearing can have an inferior surface (96) that engages the bearing engaging surface and a superior femoral engaging surface (90,92). The bearing can define an opening (94). The first yoke can have an inferior portion (122), a superior portion (120) and a yoke keyway (126) extending through the therethrough.

Knee joint prosthesis system and method for implantation

The purpose of this study was to evaluate, via experimental models, the effect of larger head sizes for total hip arthroplasty on the type of impingement, range of motion (ROM), and joint stability. Testing was conducted using an anatomic full-size hip model (anatomic goniometer) and a novel anatomic dislocation simulator with 28-, 32-, 38-, and 44-mm diameter femoral heads within a 61-mm acetabular shell. Femoral heads >32-mm provided greater ROM and virtually complete elimination of component-to-component impingement. A significant increase in both flexion before dislocation and displacement between the femoral head and acetabulum to produce dislocation occurred with femoral heads >32-mm in diameter. These data indicate that larger femoral heads offer potential in providing greater hip ROM and joint stability.

Range of Motion and Stability in Total Hip Arthroplasty With 28-, 32-, 38-, and 44-mm Femoral Head Sizes An In Vitro Study

Using a unique community implant and explant registry, long-term survival of unicompartmental knee arthroplasty was examined and compared with total knee arthroplasty (TKA) survival. All patients with unicompartmental knee arthroplasties done since September 1, 1991 were followed up prospectively to January 31, 2002 to assess survival and reason for revision. Five hundred sixteen unicompartmental knee arthroplasties of nine different designs were done by 23 surgeons. During this period, 39 of the 516 unicompartmental knee arthroplasties were revised. The major revision reasons for unicompartmental knee arthroplasties were progression of arthritis in the uninvolved compartments (51.3%), aseptic loosening (25.6%), and PE wear (20.5%). Kaplan-Meier survival analysis with revision as the end point revealed survival of 92.6% (range, 90.0%-95.2%) at 5 years for these unicompartmental knee arthroplasties and 88.6% (range, 85.0%-92.2%) at 10 years, compared with 94.8% (range, 93.5%-96.0%) at 10 years for primary TKAs. This community registry experience may more accurately reflect the results obtained in community practice, with different surgeons, varying indications, and numerous designs. The current study showed that revision of unicompartmental knee arthroplasties is done most commonly for progression of arthritis in the contralateral compartment, and at a higher rate than revision of primary cemented TKA.

Analysis of unicompartmental knee arthroplasty in a community-based implant registry.

Revision total knee arthroplasty often requires solutions for the multiple complexities that exist on the femoral side, including the treatment of bone loss, component position, ligamentous laxity, and component stability. Surgical decisions regarding the proper use of bone grafts, component augmentation, proper axial and rotational alignment, and femoral stems must be addressed systematically to achieve consistently successful outcomes. A review of currently used femoral revision techniques and their rationale and a classification system of femoral deficiencies designed to guide the surgical decision making process are presented.

Revision total knee arthroplasty: current rationale and techniques for femoral component revision.

Patient specific instrumentation (PSI) was developed to increase total knee arthroplasty (TKA) accuracy and efficiency. The study purpose was to compare immediate post-operative mechanical alignment, achieved using PSI, with conventional and computer assisted surgery (CAS) instruments in high volume TKA practices. This prospective, multicenter, non-randomized study accrued 66 TKA patients using PSI. A computed tomography (CT) based algorithm was used to develop the surgical plan. Sixty-two percent were females, 99% were diagnosed with osteoarthritis, average age at surgery was 66 years, and 33 was the average body mass index. A historical control group was utilized that underwent TKA using conventional instruments (n=86) or CAS (n=81), by the same set of surgeons. Postoperative mechanical alignment was comparable across the groups. Operative time mean and variance were significant.

In-Vivo Alignment Comparing Patient Specific Instrumentation with both Conventional and Computer Assisted Surgery (CAS) Instrumentation in Total Knee Arthroplasty

The present invention provides monopolar acetabular liners (32, 54) that can enclose a femoral head (14) to form a hip replacement prosthesis (30, 50), wherein the liner (32, 54) has a rim (34) that creates an orifice, wherein the orifice has a diameter that is smaller than the diameter of the femoral head (14), and wherein the liner (32, 54) encompasses greater than 50 percent of the volume of the head (14), wherein a constraining ring (56) can be used in conjunction with the monopolar constrained acetabular liner (32, 54) to provide additional support for the femoral head (14) to stay with the acetabular liner (32, 54) and avoid dislocation. Assemblies and complete prosthetic replacements are also provided. Liners (32, 54) and constraining rings (56) having no, one or more recesses (36) also are provided.

Daniel P. Hoeffel

Papers

Range of Motion and Stability in Total Hip Arthroplasty With 28-, 32-, 38-, and 44-mm Femoral Head Sizes An In Vitro Study

Analysis of unicompartmental knee arthroplasty in a community-based implant registry.

Revision total knee arthroplasty: current rationale and techniques for femoral component revision.

In-Vivo Alignment Comparing Patient Specific Instrumentation with both Conventional and Computer Assisted Surgery (CAS) Instrumentation in Total Knee Arthroplasty

Acetabular components that decrease risks of dislocation