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In a dysplastic hip there two approaches to restoring function. The approach taken and acetabular reconstruction of the cup placement is influenced by two factors:
1. Bone stock. High hip centres have poor bone stock (particularly if they need to be revised). Anatomical centres in severe dysplasia will require superior augmentation such as shelf auto-graft in order to obtain sufficient superior coverage.
2. Limb length discrepancy.
There are pros and cons to each approach, and each has its advocates and its critics:
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High hip centre |
Anatomic centre |
Pros |
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Cons |
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Technical options to include superior coverage include:
1. Shelf augmentation: Where the femoral head could be used as autograft. Note that cement cannot be used for superior coverage as it has shown very poor results
2. Cotyloplasty: This is a technique that involves making a perforation of the medial wall of a shallow acetabulum and then inserting an acetabular cup with the medial aspect of its dome beyond the Kohler line. This leads to medialisation of the cup by controlled medial wall fracture and bone grafting. This provides more superior coverage to the implant
The technique used is individual to each patient and their individual hip dysplasia categorisation. The approach and technique used also depends upon the surgeons preference and training. In general:
Leg length:
With a femoral reconstruction there are two considerations:
1. The leg length itself
2. The abnormal femoral anatomy
Patients generally want their leg length restored. Techniques used to restore leg length include:
A major limiting factor is the sciatic nerve. To protect the nerve you can safely lengthen up to 4cm or 6% of limb length (whichever is lesser).
Strategies to protect the sciatic nerve include:
Femoral shortening:
Femoral shortening is needed if soft tissue will not allow reduction or if lengthening will increase tension on sciatic nerve. Technical options include:
A posterior approach is used after preparing the femoral stem and the osteotomy is done at the subtrochanteric region. The trial stem is then inserted and the hip is reduced so the amount of definitive resection can be assessed exactly. This is followed by resection of the segment and then insertion of the definite prosthesis. The resected segment is then longitudinally split and wrapped around the osteotomy site and reinforced by two cables.
Altered femoral anatomy:
The canal can be very small and wider antero-posterior than medial-lateral with excess antiversion. Thus to overcome this stems with small diameters (5-10mm) are available to use on which the antiversion can be set independent to the anatomical antiversion such as a modular stem or cemented stem with very small metaphyseal flare (DDH stems).
Need for small components:
Pre-operative planning should include special technical considerations such as ensuring all components are available and performing accurate assessment of leg length.
This is used in order to create a femoral bone bed which will support a cemented long stem.
Technique:
Indications:
Be wary as:
Fully porous coated – Best results (approaching primary stems – 3-7% failure at 13 years).
Often a better option due to the following:
Success is correlated with:
This is useful in decision making where an uncemented revision stem is to be used.
Paprosky protocol:
Points to consider:
Treatment (Walter) - Young patients
Aim here is for a ‘biological solution’ ie reconstruction of bone loss, and no cement.
It involves 2 stage surgery with a long period (many months) of TWB in interim.
1st stage – to stabilise the dissociation and fill the bone defects.
AAOS classification
Segmental = complete loss of bone in supporting hemispherical structure of the acetabulum.
In this classification system the rim includes the medial wall.
Cavitary = Localised volumetric loss of bone, without disruption of acetabular rim.
Type 1 – Segmental deficiency.
Peripheral – Superior, Anterior, Posterior.
Central – medial wall absent.
Type II – Cavitatory.
Peripheral – Superior, anterior, posterior.
Central – Medial wall intact.
Type III – Combined.
Type IV – Pelvic discontinuity.
Type V – Arthrodesis.
Paprosky classification
Type I – Undistorted acetabular rim.
Type II – Distorted but intact rim with adequate bone to support hemispherical cementless cup.
Type III – A non-supportive rim.
Host acetabulum is unable to support an acetabular component in the anatomical hip centre.
Will need augmentation to support a non-cemented cup which will be difficult.
Most likely to require a reconstruction ring of some kind..
Aim of revision
Crucial questions
My ladder of options
Osteolytic defects around stable porous cups
Osteolysis around porous cups tends to be an isolated, expansile lesion, in contrast to the osteolysis seen around cemented cups which tends to be linear.
Removal of the well-fixed cup will likely result in further loss of bone stock, thus treatment is either:
Liner exchange
After removal of the liner the granuloma in the defect can be debrided through any screw holes, and the defect packed with morsellised bone graft.
If locking mechanism is intact simply insert a new liner.
Superior window
This is useful where the granuloma is inaccessible through the cup (either due to its location, or lack of holes in the cup).
Cement a new liner directly into the cup.
If locking mechanism is not intact the poly liner must be moved, debride and graft through the holes, roughen the floor of the cup, and cement in a new cup.
It is contentious whether success depends upon:
The most common indication for a total hip replacement is degenerative arthritis (osteoarthritis) of the hip joint. This type of arthritis is generally seen with ageing, congenital abnormality of the hip joint, or prior trauma to the hip joint. Other conditions leading to total hip replacement include bony fractures of the femoral neck at the hip joint, rheumatoid arthritis, osteonecrosis (death of the femoral head) and developmental dysplasia of the hip.
There are no absolute contraindications however; few relative contraindications include a skeletally immature patient and active sepsis or active infection in the joint. These patients may not be suitable for hip replacement surgery, although infected joints can be managed with a staged hip replacement surgery.
The current hip joint replacement prosthesis is composed of four major components:
A metal socket that replaces the acetabulum
A liner with highly polished inner part representing the articular surface. It is usually plastic but other materials are also used such as ceramic or metal. The liner allows the hip to move smoothly
A metal stem that is inserted in the femoral canal
A ceramic or metal ball (represents the femoral head), which articulates with the liner
There are two types of implants systems used for hip replacement:
Cemented hip replacement system, which was first designed by Sir Charnley and is still currently used with some modifications
A biological non-cemented system, which depends on the body ingrowth or ongrowth on the metal surface
Throughout the last three centuries treatment of hip arthritis has evolved from rudimentary surgery to modern Total Hip Arthroplasty (Total Hip Replacement or THR), which is considered one of the most successful surgical interventions ever developed.
Anthony White (1782-1849) of the Westminster Hospital in London is credited with the first excision arthroplasty in 1821. This procedure reduced hip pain and preserved joint movement but joint instability was a problem, which resulted from the surgery.
John Rhea Barton (1794-1871) from Philadelphia is credited with performing the first osteotomy on an ankylosed(fused) hip in 1826.
Léopold Ollier’s (1830-1900) a surgeon at the Hôtel-Dieu hospital in Lyon, France, in 1885 described the interposition of adipose tissue in uninfected joints.
Berliner Professor Themistocles Glück (1853-1942) led the way in the development of hip implant fixation. In 1891, Glück produced an ivory ball and socket joint that he fixed to bone with nickel-plated screws.
Sir John Charnley (1911-1982) pioneered hip replacement surgery during his time at Wrightington Hospital. In November 1962 the Charnley hip replacement became a practical reality and has become the gold standard for this form of treatment. Clinical and radiographic success of this procedure is now approaching 40 years of follow-up. Charnley's design consisted of two parts; a metal (originally stainless steel) femoral component and a teflon acetabular component; both were fixed to the bone using bone cement (acrylic).
Themistokles Gluck, circa 1901, performed the first documented hip replacement in 1891 with an Ivory ball and socket and fixed the bone with nickel plated screws.
This images show a patient 3 years after undergoing Osseointegration surgery as performed by Professor Munjed Al Muderis.