Category Archives: Total Joint Arthroplasty

11th International Conference on Arthroplasty 2018 Course Description

by Subashini G

Venue: London, UK

Date: September 24-25, 2018

Short name: Arthroplasty 2018

Link to more information and registration

Mail-id :  arthroplasty@pulsusmeetings.org

arthroplasty@surgeonsociety.com

Time:  9:00 AM to 6:00 PM

Description:

Arthroplasty-2018 takes immense pleasure in welcoming all the participants from across the globe to attend “11th International Conference on Arthroplasty” during September 24-25, 2018 at London, UK. The conference comprises eminent personalities with their keynote presentations, verbal speeches, productive poster presentations and exhibitions along with a discussion forum providing the insights on the advances of the Arthroplasty.

Arthroplasty-2018 is an International gathering that unites all the innovators to glaze the entire field of Arthroplasty and to experience the advancements in the research and development of the Orthopedics. It is the platform for all the scholars, researchers, scientist, organizations and industries to exhibit the recent advancements in diagnosis, treatment and postoperative managements of Arthroplasty. The event comprises the various aspects of arthroplasty with discussion on causes and types of Arthroplasty with their rehabilitation methods. The new emerging prosthesis with applied technologies of biomaterials, nanotechnology and Tissue engineering in Orthopedics are comprised in the conference.

This conference provides scope and experience for all eminent participants to grab the advancements in the field of Arthroplasty and to expose their research work across the global network and expose an international gathering on life science.

 

About Conference:

Arthroplasty 2018 is an International Conference organized by Pulsus, welcomes all the eminent researchers and scholars around the globe to be the member of “11th International Conference on Arthroplasty” scheduled on September 24-25, 2018at London, UK. The Objective of the Conference is to reach the Advancement in the Field of Arthroplasty by the global gathering and meeting of peoples from various diversities to share the knowledge by paper presentations, poster presentation and by the delivery of speech & lectures on the research work. Arthroplasty 2018 is eagerly waiting in addressing all the participants, scholars, researchers and industrial expects to make the gathering more successful.

Arthroplasty is the field which has dramatic growth throughout these years. The development of artificial prosthesis that are more durable and biocompatible, brings new innovations each day in diverse field of Nanotechnology, Tissue engineering and in Ayurveda. This Conference provides the opportunity to combine all these diverse field in a single place to share and innovate ideas among the members of other countries. The development of Biomaterial has built many Industries, which contributes the major share of the global economy. It is stated that among all the field, Orthopedists are the one who earn an average salary of $443,000 annually. Since 2015, Orthopedics are at the top of Medscape physician compensation list, where Cardiology stands second in that list. The sub-specialists earning the highest in Orthopedics are Spine surgeries, Tumor surgeons and Joint replacement specialists.

 

Conference Highlights

1.              Arthroplasty

2.              Dimensions of Arthroplasty

3.              Fracture and its Classifications

4.              Complication of Fractures

5.              Rehabilitation of Fractures

6.              Injury to Joints

7.              Radial Head Arthroplasty

8.              Paediatric Orthopedics

9.              Total Shoulder Arthroplasty

10.           Total Elbow Arthroplasty

11.           Forearm and Wrist Arthroplasty

12.           CMC Joint Arthroplasty

13.           PIP Joint Arthroplasty

14.           Spine Arthroplasty

15.           Hip Arthroplasty

16.           knee Arthroplasty

17.           Ankle Arthroplasty

18.           Biomaterials in Arthroplasty

19.           Infections of Bones and Joints

20.           Advances in Arthroplasty

 

 

Who should attend?

•                Orthopedics Surgeons

•                Sports Medicine Doctors

•                Trauma Surgeons

•                Trauma Specialists

•                Orthopaedic Nurses

•                Spine Surgeons

•                Foot and Ankle Surgeons

•                Shoulder and Upper Limb Surgeons

•                Intensivists

•                Internists

•                Emergency Medicine Doctors

•                Orthopedics resident

•                Physiotherapists

•                Technicians

•                Pain Therapists

•                Medical Students

•                Rheumatologists

•                Manufacturing Medical Devices Companies

•                Business Entrepreneurs and Industry professionals

 

Why should attend?

•                10+ Eminent Keynote Speakers

•                50+ Erudite speaker faculty over 2 full days sharing evidence-based care practices

•                5+ Workshops

•                13 interactive sessions

•                Mixture of Health Care Units and Academia Delegates

•                Networking around the Globe

•                Best Poster Award for the Young Researchers

•                Present and Discuss the recent works in the International forum

•                The exotic experience in the world best tourist place

 

Why London?

London, the capital of United Kingdom is the largest city in Europe located around the famous River of Thames. London is the busiest city for both Business and tourist destination across the world, where million people visits annually. The city is fully packed with history of arts, cultures, finance, entertainment and research & development which resides 8.788 million peoples. The city of London is considered the eminent financial centres of the world for International finance. The transportation across the city is easily accessible through underground tubes, Buses and trams, aviation, cable car and through various rails.

The climate across the city is lovely at autumn and the weather is mild throughout with festival times. It ranks first in most visited cities across United Kingdom and be top in the everyone’s Wishlist. The most popular tourist icons of the city are Big Ben Clock Tower, ZSL London Zoo, Tower Bridge, British Museum, Buckingham Palace, London Eye, Tower of London, Trafalgar Square, St. Paul’s Cathedral, Palace of Westminster, Westminster Abbey.

“You find no man, at all intellectual, who is willing to leave London. No, Sir, when a man is tired of London, he is tired of life; for there is in London all that life can afford.”

                                                                                                      — Samuel Johnson

The city of London has maximal number of Educational institutes in Europe and known for the leading Education teaching and Research. The city comprises many global hospitals and research centres that are based on arthroplasty and its clinical development and research. The great city London includes, 11 Top Universities related to Orthopedics, 17 Top Hospitals with specialists on Arthroplasty Surgeries and 3 Top Ranked Industries sharing the world economy share. It’s just not the place only for Education and business, but also a great destination for entertainment and fun.

Using a Soft Tissue Force Sensor in Total Knee Replacement Arthroplasty, Discussion and Case Report

by Scott Hadley, MD and Joseph Fetto, MD

 ABSTRACT

An 82-year old female patient with a fixed 20 degree valgus deformity of her right knee underwent total knee replacement with complete deformity correction with a non-constrained knee design. Preoperatively, the patient’s right knee range of motion was limited to 20 – 110 degrees of flexion with a 20 degree fixed valgus deformity. She was confined to minimal housebound ambulation with a walker. The pt underwent a total knee replacement under epidural anesthesia with intraoperative use of the eLIBRA™ Soft Tissue Force Sensor to assist in soft tissue balancing. No lateral soft tissue releases were needed. The valgus deformity was corrected intra-operatively and ROM achieved 10 – 120 of flexion. By 6 months post-surgery, the patient had achieved 10 – 130 degrees of right knee flexion, and complete correction of her valgus deformity.

INTRODUCTION

Total Knee Replacement (TKR) is a highly successful procedure which can reduce pain and improve range of motion and function by correcting angular deformities and restoring the integrity of articulating surfaces.1–3 TKR, however, is a misnomer as this operation does not actually “replace” the knee joint as is the case of Total Hip Replacement procedures. Rather it is more accurate to describe TKR
as a re-surfacing of the knee joint. Classically, TKR was accomplished with bony cuts which may be supplemented with soft tissue releases, prior to affixing the component parts, by either cement or non-cement techniques, to the bony surfaces. Over the past three decades, instrumentation has been developed to make the outcome of a TKR more reproducible and predictable.4 However, maximizing simultaneous restoration of range of motion (ROM) and stability has remained a significant challenge.

The knee is an inherently unstable articulation, with two large convex condylar surfaces resting on a relatively flat tibial plateau. Its stability, functionality and longevity are totally dependent upon soft tissues: ligaments, muscle-tendons and to a lesser degree the medial and lateral menisci.

In the knee there are four major ligaments (MCL, LCL,
ACL and PCL) that form the static stabilizers of the joint. Each ligament is composed of two parts, one part maximally tightens at the extreme of flexion and the other at the extreme of extention. Compromise of the structural integrity of any of these major ligaments creates significant knee instability, accelerated wear and dysfunction of the articulation. In addition to these four major ligaments, there are many minor ligaments distributed about the perimeter of the knee. As well, there are transversely directed ligaments attached to the medial and lateral aspects of the distal femur which serve to stabilize the patella within the femoral trochlear groove.

The patella is a sesamoid bone imbedded within the quadriceps mechanism. As such, its tracking is determined by the anatomic relationship between the dynamic quadricepsmuscle, the geometry of the trochlear groove and the by the patello-femoral ligaments. The pelvis is wider than the distance between the knees and as a result the normal femur and tibia are not aligned in a straight line, but rather at a 5 – 7 degree valgus angle. This orientation of the bony structures results in a laterally directed force being applied to the patella with active contraction of the quadriceps. This laterally directed force is resisted by a combination of the oblique fibers of the vastus medialis muscle (VMO) dynamically, and statically by the medial retinaculum and the medial patello-femoral ligament.

The muscle-tendon structures at the knee provide dynamic stability, over which an individual may exert some measure of control. Anteriorly, the quadriceps-patellar tendon mechanism, with its broad retinacular expansion, is responsible for active extension and resistance of flexion of the knee. Posteriorly, the medial and lateral hamstrings are well positioned to actively flex the knee, decelerate knee extension and provide some dynamic rotational stability. In addition across the postero-lateral aspect of the knee, there is an obliquely oriented, “upside-down”, popliteus muscle.
Its function is to assist in control of internal rotation of the femur on the tibia, thereby modulating rotational stresses transmitted to the weight-bearing knee through the ankle due to pronation of the subtalar joint.

With such complexity of soft tissue structures determining knee stability and function, it is obvious how important the restoration of “soft tissue balance” is to the successful outcome of a TKR procedure.2,5

There have been significant evolution and development in TKR instrumentation over the past three decades, beginning from very simplistic rectangular “cutting blocks”, which crudely served to determine the location and orientation of femoral and tibial bone resection cuts, to advances in computer assisted navigation, “customized” instrumentation and application of robotic technology designed to restore “normal anatomy”.4, 6–9 While these technological advances have the potential to more accurately guide the surgeon in the restoration of bony alignment, they do not and have not yet resolved the problem of how to accurately and reproducibly restore the soft tissue balance to the damaged knee.

Today “soft tissue balance” is assessed in a very subjective manner. After implantation of provisional components the surgeon visually inspects the ROM of the knee, the tracking of the patella and manually tests medial / lateral, posterior / anterior knee stability by applying stress in the appropriate directions with the knee in full extension, mid-range and full flexion. If not satisfied with the result achieved he / she may then choose to perform what are termed “soft tissue releases” or re-cut the bones, based on what is felt to be lacking in the reconstruction. Most commonly, dissatisfaction occurs due to poor patello-femoral tracking with knee flexion and/or limitation in ROM. Unfortunately, today’s standard of practice does not supply surgeons with any objective methodology or tool with which to measure the result achieved or improve the likelihood of achieving the outcome desired.

In an effort to address this deficiency, a new instrument has been developed which can objectively measure the relative pressures within the medial and lateral compartments before final bony cuts are performed. It is designed to equalize the compressive pressure within the compartments by the controlled application of a distracting force. In so doing this device will permit appropriate internal / external rotational orientation of the femoral component, relative to the longitudinal axis of the femur, and in so doing achieve “soft tissue balance” of the tissues, particularly those responsible for static control of patello-femoral tracking. This device (eLIBRA™ Soft Tissue Force Sensor manufactured by Synvasive, El Dorado Hills, CA) may reduce the necessity of certain soft tissue releases being performed, such as lateral patellar retinacular release.

This case study is presented to demonstrate the use of this device and the possible clinical application in an arthritic knee with a severe flexion-valgus deformity.

 CASE REPORT

N.H. is an 82 year old, slightly built white female with an atraumatic progressive painful deformity of her right knee. The patient had become limited to minimal housebound ambulation requiring a walker and/or wheelchair for independent mobility within her home. She had difficulty transferring from a sitting position and could no longer negotiate stairs without assistance. As a consequence of her growing dependence on her uppe extremities, the patient was developing bilateral carpal tunnel, ulnar nerve irritation and shoulder discomfort. Her pain was in proportion to her activities and was unresponsive to NSAID medication. She had a history of blunt trauma to the right tibia after a fall that was complicated by a brief period of cellulites, treated successfully with oral antibiotics. Otherwise, she had no history of co-morbidities related to her knee complaints.

On physical examination the patient was found to be an alert, oriented female sitting in a wheelchair in no apparent distress. However on attempting to stand and bear weight on the right lower extremity she had significant discomfort. She was able to remove her shoe and stocking from the left foot but required assistance with her right foot. The skin over the right lower extremity was intact and there was no effusion, soft tissue swelling or erythema about the right knee. The right knee was held in a flexed posture. The right knee ROM was relatively painless but limited to 20 –110 degrees of flexion with a 20 degree fixed valgus deformity. (Figures 1 & 2) There was significant crepitus within the patello-femoral and lateral compartments throughout the ROM. ROM of the left knee and both hips were painless and within normal limits. Her left foot had a mild equino-varus contracture limiting left ankle dorsiflexion to -5 degrees from neutral, due to disuse and posterior soft tissue contracture. There was tightness in the posterior calf musculature with the right foot and ankle limited to 0 degrees of dorsiflexion, 30 degrees of plantar flexion, and a fixed 10 degrees of pronation in the subtalar joint. Neurovascular supply to both feet was intact.

X-rays demonstrated a significant valgus deformity of the right knee, erosion of lateral femoral condylar bone and severe tri-compartmental osteo-arthosis. After exhausting all conservative options of treatment, the patient was indicated for right total knee replacement.

The patient underwent a TKR with epidural anesthesia, intra-operative foot pumps and minimal tourniquet utilization except during cementation of the TKR components. The eLIBRA™ Soft Tissue Force Sensor was used to determine optimal external rotation positioning of the femoral component before completion of femoral cuts. (Figure 2) Care was taken throughout the procedure to avoid placing excessive stress on the peroneal nerve. Intra-operatively the patient received a non-constrained TKR with a 9 mm polyethylene insert. The patella was re-surfaced with a 9mm thickness polyethylene component. ROM achieved intra-operatively was 10 – 120 of flexion with no valgus deformity. Post-operatively the patient’s treatment included: routine DVT prophylaxis with epidural PCA × 48 hours, 325mg. enteric coated aspirin, gentle progressive active and active-assisted ROM and weight-bearing activities as tolerance permitted.

The patient had an uneventful post-operative recuperation and was discharged to an acute rehabilitation facility for completion of her early therapy. She returned to her home at three weeks post-surgery, independent in ambulation and full weight bearing with a rolling walker. Rehabilitation continued, initially within the home, and then outside the home by 8 weeks post-surgery. Her limitations at that time were due to the mild equino-varus contracture of her contra-lateral foot and ankle. By 6 months post-TKR, the patient had achieved 10 – 130 degrees of right knee flexion, with no recurrence of her valgus deformity. (Figures 3 & 4) She was ambulatory in her neighborhood with a rolling walker and a splint on her left ankle. Within her home environment, she was able to negotiate short distances without use of a cane or walker.

 DISCUSSION

Soft tissues are extremely important for physiologic functioning of the knee joint.5Severe osteoarthrosis is often associated with deformity and compromise of normal soft tissues. TKR is a highly successful procedure for the relief of painful arthritis.1However, when attempting to restore function and correct abnormalities in ROM and alignment by TKR, it is imperative that attention be given not only to restoration of proper bony alignment, but even more importantly, to soft tissue balancing. Insufficient or incorrect soft tissue balancing may result in limitation in ROM, patellar mal-alignment, knee instability, pre-mature mechanical failure of the TKR components and pain.

Present day instrumentation for TKR offers many approaches for the correction of bony deformity: intra-medullary, extra-medullary guides, cutting blocks based on bony landmarks, computerized navigation, “customized” cutting guides fabricated based on pre-operative radiographic studies, and robotics.4,8 But none of these strategies offer a means to assure reproducible and accurate balancing of the soft tissue structures critical to optimal knee function.

The eLIBRA™ Soft Tissue Force Sensor is a newly developed instrument specifically designed to objectively address the challenge of achieving optimal ligament balancing in TKR. It may be an effective way to restore patello-femoral tracking while reducing the need for lateral release and compromise of the patellar retinaculum. This case report demonstrates the effectiveness of this tool in helping to accurately restore knee kinematics in a knee with significant fixed flexion and valgus deformities. The author has found it to be a very effective tool not only in helping surgeons to objectively assess their surgical technique but also in the training of orthopaedic surgeons to appreciate and achieve proper soft tissue balancing.

 REFERENCES

1. Insall J, Tria AJ, Scott WN. The total condylar knee prosthesis: The first 5 years. Clin Orthop Relat Res. 1979;(145)(145):68 – 77.

2. Insall JN, Binazzi R, Soudry M, Mestriner LA. Total knee arthroplasty. Clin Orthop Relat Res. 1985;(192)(192):13 – 22.

3. Sledge CB, Ewald FC. Total knee arthroplasty experience at
the robert breck brigham hospital. Clin Orthop Relat Res. 1979;(145)(145):78 – 84.

4. Laskin RS, Beksac B. Computer-assisted navigation in TKA: Where we are and where we are going. Clin Orthop Relat Res. 2006;452:127 – 131.

5. Griffin FM, Insall JN, Scuderi GR. Accuracy of soft tissue balancing in total knee arthroplasty. J Arthroplasty. 2000;15(8):970 – 973.

6. D’Lima DD, Patil S, Steklov N, Colwell CW,Jr. An ABJS best paper: Dynamic intraoperative ligament balancing for total knee arthroplasty. Clin Orthop Relat Res. 2007;463:208 – 212.

7. Picard F, Deakin AH, Clarke JV, Dillon JM, Gregori A. Using navigation intraoperative measurements narrows range of outcomes in TKA. Clin Orthop Relat Res. 2007;463:50 – 57.

8. Saragaglia D, Chaussard C, Rubens-Duval B. Navigation as a predictor of soft tissue release during 90 cases of computer-assisted total knee arthroplasty. Orthopedics. 2006;29(10 Suppl):S137 – 8.

9. Viskontas DG, Skrinskas TV, Johnson JA, King GJ, Winemaker MJ, Chess DG. Computer-assisted gap equalization in total knee arthroplasty. J Arthroplasty. 2007;22(3):334 – 342.

Extreme Deformity Correction with TAA Alone

by James K. DeOrio, MD

Many ankle replacement systems are best used when the deformity does not exceed varus or valgus greater than 10 degrees and when there is minimal bone loss. However, that would exclude many ankles from being replaced which would leave ankle fusion as the only option. I have chosen to pursue one ankle replacement sytem whenever there is significant deformity. This modular intramedullary total ankle replacement is a fixed-bearing two-component design with a modular stem system for both tibia and talar components.  It is indicated for resurfacing of the ankle in severe inflammatory, traumatic or osteoarthritis. Contraindications include poor skin quality over the anterior ankle, peripheral vascular disease, paralysis and ongoing infection. The tibia is inserted into the intramedulary tibia, but does not resurface the malleoli.  The talar component entirely replaces the superior aspect of the natural talus, after a flat dome resection.  Multiple modular segments may be added to the tibial stem, depending on the surgeon’s determination of how much stability is needed or how much the stem should pass beyond a simultaneous supramalleolar osteotomy performed for tibial malunion.  The talar component’s stem may be limited to the body of the talus or can be can be extended across the subtalar joint into the calcaneus if greater support for the talar component is required or when a simultaneous subtalar arthrodesis is warranted.  The longer talar component calcaneal stem is not currently FDA approved and is only available after approval of compassionate use.

Unique to the modular intramedullary total ankle system is the alignment guide system. The ankle is opened identical to the other ankles between the tibialis anterior and the EHL. The leg is then placed in the leg holder and the rotation of the leg holder aligned parallel to the medial mortise. The calcaneus is fixed with two pins and the foot and lower leg secured to the leg holder with elastic wrap. The large fluoroscopic C-arm is guided into place and the anterior-posterior aiming sites are aligned confirming center location of the guide over the talus and the tibia. Then the lateral centering is accomplished with the C-arm in the lateral view. The AP view is then reobtained with proper centering and the plantar calcaneal heel pad is opened.  This routine technique requires simultaneous alignment of the talus with the tibia.   (For more severe cases I have aligned the talus only and then rotated the talus with the drill bit inserted to obtain tibial alignment.) Once that is achieved, the drill is passed from the plantar foot through the calcaneus, just anterior to the posterior facet, through the center of the talar body into the center of the tibial metaphysis, much like the guide pin for a retrograde ankle arthrodesis nail. While many argue that it is undesirable to violate the subtalar joint when performing TAA, the designers of the alignment guide maintain that if the device is applied appropriately, the drill safely negotiates the subtalar joint between the arterial anastamosis on the inferior talar neck and the posterior facet’s articulation with the inferior talus. No detriment has been observed thus far for this 6 mm hole.

A cannula is locked into position through the soft tissue and the calcaneus, talus and tibia drilled.  The cutting guide is now applied (its size predetermined on templated x-rays and confirmed intraoperatively) and verified with the C-arm. Alignment of the cutting guide on the drill is accomplished under fluoroscopy and the guide pinned into position. The antirotation drill is used to create a hole in the tibia.  Then the tibia and talus are cut through the saw guide. The saw guide is removed and the bone extracted. The tibia is reamed by applying the reamer onto the reaming rod inserted up through hole previously drilled in the calcaneus and talus. The ankle is then plantar flexed and the hole for the talar stem drilled. Then the cone portion of the prosthesis with one attached cylinder is inserted into the tibia followed by one additional cylinder, then the cylindrical base. The Morse taper tibial component is then tamped into place and the whole prosthesis driven into the tibia.  Next, the talar component is slid into place with the 10mm stem attached. If the longer 14 mm stem is chosen, it is inserted first (same for even longer stems, not yet FDA approved).  Then the talar component is inserted over the top of this stem and locked onto the Morse taper design. Finally, the polyethylene component is inserted and impacted into place. The wound is closed in layers.

Primary modular intramedullary ankle replacement is relatively straightforward. However, malalignment in the form of varus or valgus makes it more difficult to insert the INBONE when it exceeds 10 degrees in either direction and is especially problematic when it is over 15 degrees. However, newer techniques make this possible. For example, with varus malalignment, the use of a complete medial deltoid ligament “peel” combined with the use of lamina spreaders medially to tension the remaining lateral ligaments had led to expanding use of the modular intramedullary TAA for these deformities.   Similarly, lamina spreaders may also be used to align valgus deformities by placing tension laterally and distracting and realigning the ankle before making bone cuts. The surgeon must be prepared in the end to achieve bony alignment with calcaneal and sliding osteotomies, subtalar and TN fusions, Achilles tendon releases or gastrocnemius recessions, ligament reconstructions and even tendon transfers.

Significant bone loss has previously been a contraindication for ankle replacements.  However, the modular intramedullary ankle, by allowing an extended intramedulary stem gives the surgeon the ability to get good stability even with significant bone loss. Once the stem is in, the remaining defects can be bone grafted. Similarly, a flat top cut on the talus with the use of stems which vary in length, can be used to gain as much purchase on the talus as necessary. This is particularly valuable in cases of avascular necrosis where you want living bone to be in contact with the prosthesis.

Previously for tibial malunions, it has been recommended that realignment procedures be done as a staged procedure. However, modularity of the intramedullary tibial stem allows the surgeon to do a simultaneous supramalleolar osteotomy, temporarily hold it with K-wires and/or a plate and then use the intramedulary portion of the tibial stem to fixate it.

For many of these same reasons, the modular intramedullary ankle system is ideally suited to revise failed ankle replacements.  After prophylactic screw fixation has been inserted in the malleoli, existing loose ankles can be removed and well fixed ankle components can be sawed away from ongrowth bone. Then, by resecting minimal bone, again with the use of the lamina spreaders tensioning the soft tissue, a revision ankle can be inserted much like a primary ankle.

Finally, painful ankle fusions can also be taken down and replaced with the modular prosthesis. Of course it helps to have the fibula retained but takedowns have also involved those cases in which the fibula has been removed. Once more, prophylactic screws are recommended in the malleoli because this unstressed bone is weak and could lead to fracture. Placing the cutting jigs on the ankle without recutting the joint line has worked well if the ankle has been fused in a correct position. Afterwards the gutters are opened to once more allow freedom of motion.  If the ankle was fused in malposition, it is first necessary to recreate the ankle joint to allow orthogonal bone cuts.

These newer ankle systems will potentially allow all patients, regardless of deformity, to have an ankle replacement if no other contraindications exist.

Dr. DeOrio is an Associate Professor of Surgery specializing in Orthopaedic Surgery at the Duke University School of Medicine.  His special interests are lower extremity reconstruction, especially total ankle replacements and all other procedures involving the hind foot, midfoot, and forefoot deformities.