CHAPTER SYNOPSIS:
This chapter outlines the indications, surgical technique, and anticipated complications of the Chiari osteotomy for the treatment of osteoarthritis of the hip secondary to acetabular dysplasia. Newer techniques in pelvic osteotomy and improved bearing surfaces in joint replacement surgery have limited the scope of this procedure.
IMPORTANT POINTS:
- 1
Patient selection is important. Patients should have radiographic evidence of osteoarthritis secondary to hip dysplasia but still have a functional range of motion of the hip.
- 2
On abduction radiographs the hip should not center into the acetabulum; these patients may be candidates for varus osteotomy of the femur.
- 3
Patients without a functional range of motion are not candidates.
- 4
Center-edge angle of less than −10 degrees is a contraindication.
- 5
Patients must understand that shortening of the operated extremity and decreased abductor power will occur, which may result in an increased limp.
SURGICAL PEARLS:
- 1
Anteroposterior radiograph of the pelvis, lateral view of the affected hip, and abduction/adduction views should all be performed before a decision is made regarding Chiari osteotomy.
- 2
Supine position; radiolucent table; intraoperative imaging.
- 3
Affected extremity should be draped free.
- 4
Placing the leg in the figure-4 position facilitates dissection on both the medial and lateral aspect of the pelvis. Visualization of the anterior and superior hip capsule is essential to ensure the osteotomy is in the correct position. The osteotomy should be directed slightly superior, going from lateral to medial, so that a tendency for the femoral head to migrate medially is ensured.
- 5
Rigid fixation of the osteotomy is important to ensure early movement of the hip and avoid the need for postoperative immobilization.
CLINICAL/SURGICAL PITFALLS:
- 1
Inadequate exposure of the anterior and superior hip capsule may lead to an inappropriate level of osteotomy.
- 2
The angle of the osteotomy must be carefully planned.
- 3
Minimal posterior displacement of the distal pelvic fragment is encouraged, but excessive posterior displacement may lead to sciatic nerve compression. Posterior displacement should not exceed 5 to 10 mm.
INTRODUCTION
Despite the improvements made in early diagnosis and treatment of developmental dysplasia of the hip, hip dysplasia still remains the most common reason for the development of early hip arthritis. The young patient with hip arthritis poses many difficulties for the treating orthopedic surgeon because of his or her activity level and youth. With the advent of newer technology in bearing surfaces, offering arthroplasty solutions to these patients is becoming more common; however, the likelihood of revision surgery and problems with subsequent bone stock loss are serious concerns. To potentially delay arthroplasty treatment and its inherent drawbacks, many surgeons use pelvic osteotomies as a reconstructive option. These pelvic osteotomies can be broadly divided into redirectional osteotomies, in which the goal of the surgery is to restore normal hip anatomy and biomechanics, and salvage osteotomies, in which the goal is to improve symptoms and potentially change the natural history.
The focus of this chapter is the Chiari salvage osteotomy. The Chiari osteotomy was originally described in the German literature in the 1950s by Chiari. It is a medial displacement osteotomy that improves superolateral coverage of the femoral head by translating the distal pelvis medially. The technique involves a single osteotomy just above the hip joint capsule, which positions cancellous bone from the ilium on top of the hip capsule and over the uncovered femoral head. Histologic evaluation has revealed that the capsule undergoes changes to produce well-vascularized connective tissue with abundant collagen. By 6 months the capsule has undergone metaplastic change to fibrocartilaginous tissue, with some hyaline-like cartilage near the joint surface. Because of this phenomenon the procedure also is referred to as a capsular interposition arthroplasty. These capsular metaplastic changes, in addition to the biomechanically favorable medical displacement of the hip center, help explain the improvement in patients’ symptoms after the procedure. The technique currently is more popular in Asia, where modifications of the original technique have been described.
INDICATIONS
The ideal candidate for this procedure is a patient with developmental dysplasia of the hip or acetabular dysplasia in which the hip articular surface incongruity cannot be restored by either a pelvic or femoral redirectional osteotomy and in which degenerative changes are already present ( Fig. 8-1 ).
The patient must have persistent hip symptoms that have been unresponsive to nonoperative means and that significantly limit the patient in activities of daily living. The patient also must be too young for an arthroplasty solution or does not want to have an arthroplasty solution because of the likely need for revision surgery. The patient also must understand the goal of the surgery is to improve his or her symptoms and that functional improvement may or may not be achieved. The goal of the operation is not to achieve concentric reduction of the femoral head.
Idiopathic developmental dysplasia of the hip and acetabular dysplasia are by far the most common diagnoses requiring a Chiari osteotomy, but other pathologic hip conditions have been treated by a Chiari osteotomy. The literature describes the Chiari osteotomy to various extents with the treatment of Legg-Calvé-Perthes disease, myelomeningocele, and other neuromuscular conditions. The evidence for success in these populations is weak and is probably related to the significantly smaller pelvises these patients have and thus less coverage obtainable from the Chiari.
CONTRAINDICATIONS
One of the important factors when considering this procedure is the stage of arthritis. An absolute contraindication to the Chiari osteotomy is end-stage Tönnis stage 4 arthritis. In addition, this procedure should not be considered if the patient has minimal symptoms.
Other relative contraindications include a patient age of more than 40 to 50 years. Despite their younger age, patients in this age group and older are better candidates for an arthroplasty solution with further consideration of an alternative bearing surface. The amount of preoperative subluxation and the likelihood of adequate femoral head coverage also should be considered. A center-edge angle of less then −10 degrees has been suggested as a relative contraindication because the surface area of the ilium may be inadequate to get acceptable femoral head coverage. The expertise of the treating surgeon also should be considered. Even though at first glance the operation may be perceived as a simple single osteotomy, small technical considerations are paramount to the success of this procedure. The treating surgeon should have some formal training from an experienced pelvic surgeon skilled at the Chiari osteotomy and possibly have had practice on cadavers before considering this treatment option.
ALTERNATIVES
When considering any form of surgical treatment, other possible alternatives should be reviewed. As previously stated, an arthroplasty treatment should be considered for patients with severe arthritis and those aged 40 to 50 years and older. With newer technology in bearing surfaces, many surgeons are hopeful that the longevity of modern implants will be extended, thus avoiding multiple revision surgeries. Hip arthroscopy is a good alternative for patients with minimal arthritic changes and mechanical symptoms that may be related to femoral acetabular impingement, labral pathology, or loose bodies. Arthrodesis and resection arthroplasty are rarely indicated; but when they are, they tend not to be accepted by most patients.
When considering a pelvic osteotomy, deciphering which osteotomy will achieve the desired goals is important. Patients with hip symptoms that are unresponsive to nonoperative treatment and show evidence of acetabular dysplasia may be candidates for a redirectional osteotomy. The Bernese periacetabular osteotomy developed by Ganz is the procedure currently favored by most pelvic surgeons. The original technique uses one incision and three extraarticular osteotomies to correct the acetabular deformity. The correction often involves medialization of the hip joint to improve the joint reactive forces, lateral rotation to improve uncovering of the femoral head, and correction of the version of the acetabulum. The posterior column remains intact, which permits minimal internal fixation and early ambulation. But this procedure should be considered only when a concentric reduction of the femoral head within the acetabulum is possible.
SURGICAL TECHNIQUE
Preoperative Planning
After appropriate patient selection, the surgeon should counsel the patient regarding the goals of the surgery and expected outcomes. The Chiari osteotomy provides excellent pain relief when the appropriate patient is selected, but the functional outcomes are harder to predict. A quality anteroposterior view of the pelvis and a lateral view of the affect hip usually are sufficient for planning the surgery. However, if a varus or valgus osteotomy also is being considered, abduction and/or adduction radiographs may be needed.
Patient Position and Incision
The patient is positioned supine on a radiolucent table. An adequate intraoperative image must be possible before beginning the surgery. Either image intensification or an intraoperative radiograph can be used. The author prefers image intensification. The patients’ affected extremity is draped free to help with exposure and translation of the distal portion of the pelvis. An anterolateral incision is used, starting on the iliac crest and curving distally between the interval of tensor fascia lata (TFL) and sartorius. This incision can be modified into a “bikini incision” to improve cosmesis. Other incisions also have been described, such as the posterolateral incision and Ollier lateral U approach.
Surgical Dissection and Exposure
Subcutaneous flaps are elevated to help identify the superficial interval between the TFL and sartorius. The figure-4 position and blunt dissection often help identify this interval. The origin of the TFL is then detached from the iliac crest with the anterior portion of gluteus medius and minimus. These are then reflected lateral to expose the outer table of the pelvis as well as the anterolateral portion of the hip capsule. Extend this exposure to the sciatic notch.
Next, follow with exposure of the inner table of the pelvis by subperiosteal dissection to the sciatic notch. Flexing the hip takes tension off the iliopsoas muscle and eases subperiosteal dissection of the inner table. Dissect the rectus origin from the anterior inferior iliac spine and its reflect head from the hip capsule to get good visualization of the hip capsule. Exposure of the insertion of the hip capsule on the acetabular brim is paramount to identifying the correct site for the subsequent osteotomy. The hip capsule is not opened. Carefully position retractors, both on the inner and outer tables within the sciatic notch, for good visualization.
Planning the Osteotomy
Once adequate exposure of the hip capsule and its insertion into the acetabular brim is obtained, begin planning the osteotomy. The osteotomy plan is between the hip capsule and the rectus origin on the anterior inferior iliac spine. Critical to the success of the operation is the placement of the osteotomy. If the osteotomy is too low, then not enough capsule is between the femoral head and displaced ilium superiorly. This can lead to necrosis of the capsule and subsequent lack of capsular metaplasia. If the osteotomy is too high, then it does not provide the desired effect of coverage for the femoral head. After deciding on the starting point of the osteotomy, insert a K-wire in the supraacetabular area in the direction planned. The ideal angle for the osteotomy in the coronal plane is approximately 10 degrees angled superiorly toward the inner table ( Fig. 8-2 ).
