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Journal ArticleDOI

3D-printed Patient-specific Guides for Hip Arthroplasty.

15 Aug 2018-Journal of The American Academy of Orthopaedic Surgeons (Ovid Technologies (Wolters Kluwer Health))-Vol. 26, Iss: 16

TL;DR: Early results indicate consistent accurate positioning of implants with the use of PSI in hip arthroplasty but with added costs and uncertain effect on clinical outcomes.

AbstractSurgeons and engineers constantly search for methods to improve the surgical positioning of implants used for joint arthroplasty. Rapid prototyping is being used to develop patient-specific instrumentation (PSI) and has already been successfully translated into large-scale clinical use for knee arthroplasty. PSI has been used in shoulder arthroplasty; however, it is not yet known whether PSI provides improved accuracy and outcomes compared with conventional methods in either shoulder arthroplasty or knee arthroplasty. In the hip, PSI has been limited to the positioning of custom-manufactured implants and a small number of surgeons testing the emerging solutions from different manufacturers. Early results indicate consistent accurate positioning of implants with the use of PSI in hip arthroplasty but with added costs and uncertain effect on clinical outcomes.

Topics: Arthroplasty (58%)

Summary (3 min read)

Introduction

  • The clinical function of a hip ar- throplasty depends on surgical, implant, and patient factors.
  • The surgeon can then plan prosthesis ori- entation and position in relation to a chosen standard frame of reference and execute the plan using simple intra- operative patient-specific guides.
  • Here, the authors present the currently commercially available guides and summarize the relevant literature regarding PSI for hip arthroplasty in order to provide an overview of PSI and describe the evidence regarding its use in clinical practice.
  • Rapid prototyping was initially de- veloped in the mid 1980s for the production of toys and household machinery and has been used for a wide variety of medical and nonmedical purposes since that time.
  • 12 PSI has evolved out of this and has been taken up in numerous fields of surgery.

Clinical Application in Hip Arthroplasty

  • PSI is being used in hip arthroplasty to improve the accuracy of acetabular and femoral component position- ing.22-24 Acetabular guidance systems aim to optimize the cup size, implant medialization, anteversion, and incli- nation.
  • Four commercial systems are currently available internationally .
  • CT provides well-defined bony anat- omy with low levels of artifact; however, it has limitations in demonstrating soft tissue.
  • It is as yet uncertain which is the optimal imag- ing modality for creation of PSI in total hip replacement and both are currently available depending on the commercial system chosen (Table 1).
  • The frames of reference and target positioning/orientation of the implants can be tailored to the surgeon’s preference.

Does Patient-specific Instrumentation Improve the Accuracy of Cup Orientation?

  • Buller et al29 undertook a dry bone simulation study, with seven sur- geons performing THA performed with standard instrumentation, fol- lowed by PSI-guided THA.
  • In a prospective randomized con- trolled trial, Small et al32 compared 18 patients undergoing THA with conventional instrumentation and 18 patients undergoing THA with PSI.
  • Results demonstrated a statistically significant difference in version of the acetabu- lar component between standard instrumentation and PSI (P = 0.018; mean difference from planned versus actual anteversion of 26.9 6 8.9 for standard instrumentation and 20.2 6 6.9 for PSI cases).
  • A posterolateral surgical approach was used for each patient, and the PSI laser guidance system was used for the accurate placement of the acetabular implants.
  • CT scans were used for preoperative planning.

Does the Use of Patient- specific Instrumentation Affect the Duration of Surgery?

  • Hananouchi et al33 reported a mean surgical time of 106.1 minutes with PSI, compared with 116.3 minutes with standard instrumentation.
  • In the PSI group, the mean time to use the surgical guide was 3.6 minutes.
  • Ito et al34 used PSI for femoral component insertion and demonstrated a mean surgical time of 111 minutes.
  • Small et al32 demonstrated a mean surgical time of 95 minutes for the PSI group versus 88 minutes for the standard instrumentation group; this trend was not found to be statistically significant.

Is Patient-specific Instrumentation Useful in Cases With Massive Bone Defects and Abnormal Anatomy?

  • Substantial deformity and insufficient bone structure or quality are contra- indications for the use of currently available PSI guides for hip arthro- plasty.
  • The dynamic modeling used preoperatively with PSI requires nor- mal anatomy and sites of rigid attachment for guiding instruments intraoperatively.
  • Further develop- ments in the design of these guides may result in the ability to use these systems in patients with more severe deformity.

Does the Use of Patient- Specific Instrumentation Have Any Other Intraoperative Effects?

  • Hananouchi et al33 demonstrated a mean blood loss of 655.9 mL for PSI versus 683.9 mL for standard instrumentation; this difference was not statistically significant, also known as Blood Loss.
  • Ito et al34 reported a mean estimated blood loss of 356 mL using PSI for the femoral component.
  • Small et al32 demon- strated mean estimated blood loss of 200 mL in the PSI group compared with 150 mL in the traditional in- strumented group; this trend was not found to be statistically significant.
  • Spencer-Gardner et al27 reported one complication in a series of 100 patients in whom PSI was used for cup placement—a fractured ceramic liner due to incomplete seating requiring revision liner exchange, also known as Complications.
  • In a randomized controlled trial of 18 PSI versus 18 standard instrumentation cases, Small et al32 demonstrated no com- plications in the PSI group and one complication in the standard instru- mentation group (anterior dislocation).

How Does Patient-specific Instrumentation Compare With Robotic and ComputerNavigated Systems?

  • Robotic-assisted systems are designed to either physically prepare the bone or prevent the surgeon from reaming outside the predefined boundaries (semi).
  • Its acceptance has been limited because of concerns about its ease of use and costs.
  • 37 Computer-navigated hip arthro- plasty surgery is a passive system using CT, fluoroscopy, or imageless naviga- tion techniques.
  • 37 PSI for hip arthroplasty is still in its early phases of clinical use; although studies determining the accuracy of implant positioning seem promising, longer term clinical data have not been published.
  • PSI also increases the overall costs of the operation, while potentially adding time to the surgery duration depending on the complexity of the case and surgeon experience.

Summary

  • PSI hip guides have been shown to improve the accuracy of implant positioning and may have a role to play in reconstructing complex anat- omy, particularly in revision surgery.
  • More clinical outcomes data are required to convince the surgeon that the benefits of PSI in terms of accuracy are worth the challenges of the learning curve involved and the increased costs.
  • Walch G, Vezeridis PS, Boileau P, Deransart P, Chaoui J: Three-dimensional planning and use of patient-specific guides improve glenoid component position: J Shoulder Elbow Surg 2015; 24:302-309. 20.
  • Stegman J, Casstevens C, Kelley T, Nistor V: Patient-specific guides for total hip arthroplasty: A paired acetabular and femoral implantation approach.

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1
3D-printed Patient-specific Guides for Hip Arthroplasty
Johann Henckel, MD Thomas J. Holme, MD Warwick Radford, MD John A. Skinner, MD
Alister J. Hart, MD
Abstract
Surgeons and engineers constantly search for methods to improve the surgical positioning of
implants used for joint arthroplasty. Rapid prototyping is being used to develop patient-
specific instrumentation (PSI) and has already been successfully translated into large-scale
clinical use for knee arthroplasty. PSI has been used in shoulder arthroplasty; however, it is
not yet known whether PSI provides improved accuracy and outcomes compared with
conventional methods in either shoulder arthroplasty or knee arthroplasty. In the hip, PSI has
been limited to the positioning of custom-manufactured implants and a small number of
surgeons testing the emerging solutions from different manufacturers. Early results indicate
consistent accurate positioning of implants with the use of PSI in hip arthroplasty but with
added costs and uncertain effect on clinical outcomes.
Introduction
The clinical function of a hip ar- throplasty depends on surgical, implant, and patient factors.
Surgical factors include component position- ing,
1
which is a modifiable risk factor and is
known to contribute to patient dissatisfaction,
2
dislocation, wear, impingement, decreased
range of motion, and leg length discrepancy.
3-7
Acetabular loosening occurs in up to 50% of
cases after hip arthroplasty.
8
Computer-aided surgery and robot- ics have been used to improve the accuracy of component
positioning in hip arthroplasty but have had limited uptake because of high costs, increased
operating times, and other logistic issues.
9,10
Reports of image-guided hip arthroplasty are
encouraging, but data from the National Joint Registry show that conventional instrumented
sur- gery remains the standard treatment.
11
More recently, patient-specific in- strumentation (PSI) has been developed to guide the
positioning of components during hip arthroplasty. This technique uses imaging techniques
such as CT and MRI to plan surgery in a virtual three- dimensional (3D) environment. The
surgeon can then plan prosthesis ori- entation and position in relation to a chosen standard
frame of reference and execute the plan using simple intra- operative patient-specific guides.
Here, we present the currently commercially available guides and summarize the relevant
literature regarding PSI for hip arthroplasty in order to provide an overview of PSI and
describe the evidence regarding its use in clinical practice.
Rapid prototyping was initially de- veloped in the mid 1980s for the production of toys and
household machinery and has been used for a wide variety of medical and nonmedical
purposes since that time.
12
PSI has evolved out of this and has been taken up in numerous
fields of surgery. The first reported use in orthopaedics was in the spine in 1998 for
producing guides to aid in the placement of

2
pedicle screws
13
and has since spread to include guides for shoulder, hip, knee, and ankle
elective and trauma surgery.
PSI has been increasingly commer- cially used in total knee arthroplasty to produce custom-
made pinning and cutting guides;
14
however, recent lit- erature has questioned whether the
use of PSI improves the accuracy of im- plant alignment or clinical outcomes compared with
standard instrumenta- tion.
15,16
Studies using PSI for shoulder and ankle arthroplasty show
promis- ing early results in terms of the accu- racy of implant placement; however,
commercial applications have not been developed and no study has demon- strated improved
clinical outcomes in shoulder or ankle arthroplasty.
17-21
Clinical Application in Hip Arthroplasty
PSI is being used in hip arthroplasty to improve the accuracy of acetabular and femoral
component position- ing.
22-24
Acetabular guidance systems aim to optimize the cup size,
implant medialization, anteversion, and incli- nation. Femoral guidance systems aim to
optimize the stem size and positioning, offset, leg length (height of neck cut), and stem
version. Four commercial systems are currently available internationally (Table 1 and Figures
1–3). In addition, a number of patents have been registered on devices that have been
modified with the intent to improve on current designs. The Signature Hip (Zimmer Biomet),
OPS (Corin Group), and MyHip (Medacta) are currently available for use in the United States
and Europe, whereas the Hip Plan (Symbios) is currently avail- able for use only in Europe.
All systems required preoperative imaging with either CT or MRI to cre- ate the patient-
specific model and tem- plate the guides and implants required. CT provides well-defined
bony anat- omy with low levels of artifact; however, it has limitations in demonstrating soft
tissue. The commercial systems available use a low-dose radiation protocol, delivering
slightly higher radiation exposure compared with conventional radiographs, with a 2011
study reporting a scan time of 11 minutes and a direct per-patient cost of V52.80 ($54.94).
25
Although MRI is better for visualizing detail within the soft tissues, it offers less well-defined
soft tissue–bone boundaries compared with CT. For example, it is difficult to differentiate
osteophytes from soft tisues on MRI. Neither imaging modaility has been proved to be su-
perior for PSI in total hip arthroplasty (THA), and which is used depends on the system
chosen (Table 1). It is as yet uncertain which is the optimal imag- ing modality for creation of
PSI in total hip replacement and both are currently available depending on the commercial
system chosen (Table 1).
PSI requires 3D preoperative plan- ning and therefore incorporates the known and obvious
advantages of 3D compared with 2D planning.
26
Three- dimensional reconstruction software
is used to create a 3D computer model. This 3D model is used to virtually plan the
positioning and sizing of the prostheses. The frames of reference and target
positioning/orientation of the implants can be tailored to the surgeon’s preference. Two of the
commercially available models include kinematic simulation to take into account the
influence of pelvic tilt and assess the potential functional effect of a chosen implant position
in terms of bony and implant impingement (ie, MyHip, OPS). The guide is de- signed to fit
and complement the patient’s native anatomy using bony and soft-tissue landmarks on the CT

3
or MRI scan. The physical 3D guide is created and produced using a number of methods,
including selective laser sintering and additive materials manufacturing (3D printing) and
sterilized before delivery to the surgeon’s center. The whole process can take as little as 3
weeks from start to finish;
27
however, there is typically a lead time of approximately 6 to 8
weeks while the PSI guide is created.
Of the commercially available hip PSI systems, all four offer guides for the acetabular
component orientation, but only two of the systems offer a guide for femoral component
orientation (ie, MyHip, OPS). The surgical technique varies between products, with anterior,
posterior, and lateral surgical approaches available depending on the system chosen (Table
1).
The depth of acetabular reaming and therefore planning for accurate medialization of the
implant are still determined by hand and clinical judgment, although future models may
include a guidance feature. Pins can be used to guide alignment of the reamer if desired.
Preoperative 3D printed acetabular models are avail- able to help with understanding the
patient’s unique anatomy and how the guide/implant should fit before attempting insertion
into the patient (Figure 4).
Insertion guides come in two broad categories: constrained and nonconstrained, depending on
whether the guide simply shows the correct direction of implantation or physically guides
insertion. Accurate insertion of the guides depends on bony (ie, acetabular dome, rim, notch)
and soft- tissue (ie, transverse acetabular ligament) landmarks, which are used to place a
custom jig into the acetabulum. As with conventionally guided surgery, the surgical exposure
is important in getting this step right. The positioning of the implants is then guided by either
pins or lasers. All require care when preparing the surgical site, particularly with soft-tissue
removal so that land- marks used in planning are not removed; this is of particular impor-
tance in cases in which osteophytes are removed.
28
Only the MyHip and OPS systems include a femoral component guide. Posterior and anterior
cutting guides are offered so that the surgeon can choose the guide best suited to the preferred
surgical approach. This guides the neck cut level and angle but does not guide stem version.
Does Patient-specific Instrumentation Improve the Accuracy of Cup Orientation?
Buller et al
29
undertook a dry bone simulation study, with seven sur- geons performing THA
performed with standard instrumentation, fol- lowed by PSI-guided THA. The surgical goal
was to accurately place the acetabular implant in 22of anteversion and 40of inclination
as per a preoperative plan. In the standard instrumentation group, six of seven acetabular
components were placed in an unacceptable position with regard to inclination and version
(using “safe zonesof 156 10for anteversion and 406 10for inclination). In the PSI
group, three of seven acetabu- lar components were malpositioned with regard to version, and
none was malpositioned with regard to inclination.
Shandiz et al
30
undertook a cadaver study in which they implanted PSI- guided acetabular
components into 12 hips. Preoperative CT scans were used in surgical planning, and post-
operative CT scans were used to measure implant positioning and ori- entation. This
demonstrated the ability to accurately position the component using the PSI guide to within
2.5of planned, with a maximum deviation from planned of 4.7.

4
Schwarzkopf et al
31
undertook a cadaver study of 14 acetabuli using the Bullseye Hip
Replacement In- struments (Bullseye Hip Replace- ment) PSI for acetabular preparation and
cup placement. CT and MRI were used preoperatively to deter- mine the surgical plan and
create the PSI. Postoperative CT scans were used to demonstrate the accuracy of the
placement of implants. The ace- tabular cup inclination and ante- version angles were within
the target range, and all implanted sizes matched the preoperative surgical planned implant
size.
In a prospective randomized con- trolled trial, Small et al
32
compared 18 patients undergoing
THA with conventional instrumentation and 18 patients undergoing THA with PSI. Pre- and
post-operative CT scans were used to evaluate planned versus actual results. Results dem-
onstrated a statistically significant difference in version of the acetabu- lar component
between standard instrumentation and PSI (P = 0.018; mean difference from planned versus
actual anteversion of 26.96 8.9for standard instrumentation and 20.26 6.9for PSI
cases). The difference for inclination was not statistically significant (mean differ- ence in
abduction from planned versus actual of 1.36 9.1for standard instrumentation and 22.0
6 7.3for PSI cases).
In a nonrandomized prospective study, Hananouchi et al
33
compared 38 patients undergoing
THA with traditional instrumentation to 31 patients undergoing THA with PSI. The planned
versus actual position of the acetabular component was eval- uated with pre- and
postoperative CT scans, determining the incidence of outliers beyond 10from planned
placement in each group. The study authors reported that the use of PSI reduced the number
of outliers compared with the use of standard instrumentation (zero versus 23.7%,
respectively). This trend was statis- tically significant for mean inclina- tion (P = 0.01) but
not for mean anteversion (P = 0.08).
In a prospective study, Spencer- Gardner et al
27
treated 100 patients using the OPS PSI for
cup placement. They used 3D CT planning software to preoperatively choose the optimal
acetabular inclination and version for each patient. A posterolateral surgical approach was
used for each patient, and the PSI laser guidance system was used for the accurate placement
of the acetabular implants. The accuracy of implant placement was evaluated using 3D CT to
compare the actual position with the preoperative plan. They demonstrated accurate place-
ment to within 5in 54% of patients and to within 10in 91% of patients. These results are
comparable with robotic and computer-navigated techniques and superior to reported
freehand techniques.
Ito et al
34
prospectively evaluated 10 patients in whom PSI was used for femoral stem
placement. CT scans were used for preoperative planning. In all patients, noncemented
implants were placed via the posterior surgical approach. Postoperative CT scans were used
to demonstrate the accuracy of the placement of im- plants. Results demonstrated a mean
accuracy of stem tilt of 2.16 4.1, varus/valgus of 1.06 0.7, and anteversion of 4.76
1.2.
Some pitfalls to accurate cup implantation have been highlighted, including errors made
during the impaction process of cup implantation. Extra care should be taken at this stage. In
addition, the presence of osteo- phytes can sometimes pose a challenge to the accurate
placement of the PSI guide and must be taken into account when executing the surgical
plan.
28

5
PSI for the placement of the femoral component of hip resurfacing has also been investigated,
with promis- ing early results in terms of stem-shaft angle and version.
35
Does the Use of Patient- specific Instrumentation Affect the Duration of Surgery?
Hananouchi et al
33
reported a mean surgical time of 106.1 minutes with PSI, compared with
116.3 minutes with standard instrumentation. This difference was not significant. In the PSI
group, the mean time to use the surgical guide was 3.6 minutes.
Spencer-Gardner et al
27
found that the total operating time increases by 3 to 5 minutes with
use of PSI. This compares to time increases in navi- gated THA of 8 to 58 minutes. Ito et al
34
used PSI for femoral component insertion and demonstrated a mean surgical time of 111
minutes. Small et al
32
demonstrated a mean surgical time of 95 minutes for the PSI group
versus 88 minutes for the standard instrumentation group; this trend was not found to be
statistically significant.
Is Patient-specific Instrumentation Useful in Cases With Massive Bone Defects and
Abnormal Anatomy?
Substantial deformity and insufficient bone structure or quality are contra- indications for the
use of currently available PSI guides for hip arthro- plasty. The dynamic modeling used
preoperatively with PSI requires nor- mal anatomy and sites of rigid attachment for guiding
instruments intraoperatively. Further develop- ments in the design of these guides may result
in the ability to use these systems in patients with more severe deformity.
How Much Does Patient- Specific Instrumentation Add to the Operating Costs?
Most surgeons would use the cur- rently available commercial PSIs, which in our experience
add ap- proximately $371 to each surgical case. For individual hospital pro- duction of PSI,
in 2010 Hananouchi et al
33
reported startup costs of up to $150,000, including $15,000 to
$30,000 for software and $120,000 for the rapid prototyping machine itself, along with a
material cost per case of $50 to $100. The long-term effect of these guides in reducing the
need for future medical treatment for early failures of poorly positioned implants is not yet
known, but the potential financial implications of this may well out- weigh the added initial
costs.
Does the Use of Patient- Specific Instrumentation Have Any Other Intraoperative
Effects?
Blood Loss: Hananouchi et al
33
demonstrated a mean blood loss of 655.9 mL for PSI versus
683.9 mL for standard instrumentation; this difference was not statistically significant. Ito et
al
34
reported a mean estimated blood loss of 356 mL using PSI for the femoral component.
Small et al
32
demon- strated mean estimated blood loss of 200 mL in the PSI group
compared with 150 mL in the traditional in- strumented group; this trend was not found to be
statistically significant.
Complications: Spencer-Gardner et al
27
reported one complication in a series of 100
patients in whom PSI was used for cup placement—a fractured ceramic liner due to

Figures (5)
Citations
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Journal ArticleDOI
TL;DR: Orthopaedic surgeons should develop guidelines to outline the most effective uses of 3D-printing technology to maximize patient benefits to improve surgical efficiency, shorten operation times and reduce exposure to radiation.
Abstract: The use of three-dimensional (3D) printing is becoming more common, including in the field of orthopaedic surgery. There are currently four primary clinical applications for 3D-printing in hip and pelvic surgeries: (i) 3D-printed anatomical models for planning and surgery simulation, (ii) patient-specific instruments (PSI), (iii) generation of prostheses with 3D-additive manufacturing, and (iv) custom 3D-printed prostheses. Simulation surgery using a 3D-printed bone model allows surgeons to develop better surgical approaches, test the feasibility of procedures and determine optimal location and size for a prosthesis. PSI will help inform accurate bone cuts and prosthesis placement during surgery. Using 3D-additive manufacturing, especially with a trabecular pattern, is possible to produce a prosthesis mechanically stable and biocompatible prosthesis capable of promoting osseointergration. Custom implants are useful in patients with massive acetabular bone loss or periacetabular malignant bone tumors as they may improve the fit between implants and patient-specific anatomy. 3D-printing technology can improve surgical efficiency, shorten operation times and reduce exposure to radiation. This technology also offers new potential for treating complex hip joint diseases. Orthopaedic surgeons should develop guidelines to outline the most effective uses of 3D-printing technology to maximize patient benefits.

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TL;DR: A clear understanding of the relevant biological principles, clinical presentations, investigative measures and treatments for implant-associated inflammatory reactions and periprosthetic osteolysis will help identify and treat patients with this issue earlier and more effectively.
Abstract: Introduction: Total joint replacement is one of the most common, safe, and efficacious operations in all of surgery. However, one major long-standing and unresolved issue is the adverse biological reaction to byproducts of wear from the bearing surfaces and modular articulations. These inflammatory reactions are mediated by the innate and adaptive immune systems.Areas covered: We review the etiology and pathophysiology of implant debris-associated inflammation, the clinical presentation and detailed work-up of these cases, and the principles and outcomes of non-operative and operative management. Furthermore, we suggest future strategies for prevention and novel treatments of implant-related adverse biological reactions.Expert opinion: The generation of byproducts from joint replacements is inevitable, due to repetitive loading of the implants. A clear understanding of the relevant biological principles, clinical presentations, investigative measures and treatments for implant-associated inflammatory reactions and periprosthetic osteolysis will help identify and treat patients with this issue earlier and more effectively. Although progressive implant-associated osteolysis is currently a condition that is treated surgically, with further research, it is hoped that non-operative biological interventions could prolong the lifetime of joint replacements that are otherwise functional and still salvageable.

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Abstract: Surgical prostheses and implants used in hard-tissue engineering should satisfy all the clinical, mechanical, manufacturing, and economic requirements in order to be used for load-bearing applications. Metals, and to a lesser extent, polymers are promising materials that have long been used as load-bearing biomaterials. With the rapid development of additive manufacturing (AM) technology, metallic and polymeric implants with complex structures that were once impractical to manufacture using traditional processing methods can now easily be made by AM. This technology has emerged over the past four decades as a rapid and cost-effective fabrication method for geometrically complex implants with high levels of accuracy and precision. The ability to design and fabricate patient-specific, customized structural biomaterials has made AM a subject of great interest in both research and clinical settings. Among different AM methods, laser powder bed fusion (L–PBF) is emerging as the most popular and reliable AM method for producing load-bearing biomaterials. This layer-by-layer process uses a high-energy laser beam to sinter or melt powders into a part patterned by a computer-aided design (CAD) model. The most important load-bearing applications of L–PBF-manufactured biomaterials include orthopedic, traumatological, craniofacial, maxillofacial, and dental applications. The unequalled design freedom of AM technology, and L–PBF in particular, also allows fabrication of complex and customized metallic and polymeric scaffolds by altering the topology and controlling the macro-porosity of the implant. This article gives an overview of the L–PBF method for the fabrication of load-bearing metallic and polymeric biomaterials.

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TL;DR: Experimental models indicate that larger femoral heads offer potential in providing greater hip ROM and joint stability, and 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.
Abstract: 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.

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TL;DR: Assessment of leg length discrepancy and hip function in 90 patients undergoing primary total hip arthroplasty before surgery and at three and 12 months after found Appropriate placement of the femoral component could significantly reduce a patient's perception of discrepancy of length.
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TL;DR: An alternative technique for computerized tomographic image based preoperative three-dimensional planning and precise surgery on bone structures using individual templates has been developed and has been applied clinically for pelvic repositioning osteotomies in acetabular dysplasia therapy.
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TL;DR: Satisfaction also correlates strongly with postoperative functional scores, relief of pain, restoration of function, and success in meeting patient expectations, which are critical in maximizing patient satisfaction after THA.
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