Introduction                       

Hip ankylosis is usually either spontaneous or surgical arthrodesis done for hip arthritis. Spontaneous hip ankylosis can be caused by hematogenous bacterial infection, posttraumatic arthritis, ankylosing spondylitis, tuberculous infection, and postoperative infection. The patients with hip ankylosis have a short leg, walk with a slow asymmetric and arrhythmic gait, although they may have a stable painless hip. The effects of hip fusion on other joints are significant. Often the ipsilateral knee is limited in motion, with a variable degree of ligamentous laxity, and has a tendency for valgus malalignment. Arthrodesis of one hip also applies greater mechanical stress to the opposite hip. In long-term, these patients develop symptomatic arthritis in spine, ipsilateral knee and contralateral hip. These patients have difficulty in activities of daily living which involve hip flexion, sitting for prolonged period or in cramped spaces. In addition bilateral hip ankylosis results in marked limitation of ambulation, sexual function, personal hygiene and low back pain. The indications for conversion of an ankylosed hip to an arthroplasty include (i) pain in the low back, ipsilateral knee, or contralateral hip, (ii) a need for improved mobility, especially in the face of a stiff spine, and (iii) limb-length discrepancy.

One of the most common cause of bony ankylosis is ankylosing spondylitis, with the reported incidence being as high as 23.1%.1 Bony ankylosis, especially in stiff spine, may present several exclusive challenges in its management. These patients are usually young and have problems related to function, posture, and locomotion rather than pain. While planning THA in these patients, technical problems related to the position of patients on the operation theater table and accurate positioning of the components are required to be tackled. Other problems after THA in these patients include unpredictable gain in range of motion,2,3 higher incidence of ectopic bone formation, and reankylosis.4

 

Preoperative                   Planning                   

The patient should be carefully evaluated preoperatively as to the initial reason of the ankylosis. If the ankylosis is due to infection then a thorough evaluation is required to rule out presence of active infection. The functions of adjacent joints and spine should be carefully assessed. In patients with ankylosing spondylitis, X-rays of spine should be done to rule out presence of pseudoarthrosis or Anderson lesion in spine. In case of presence of pseudoarthrosis in spine, further evaluation is required to assess the stability of spine. The leg-length discrepancy should be measured. Preoperative CT can be helpful in determining the adequacy of bone stock and the presence of a pseudarthrosis.

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In patients with long-standing ankylosis from childhood infections, there is extensive scar formation, limb shortening, and diminutive size of the hemipelvis and proximal femur. In such cases it may be difficult to restore equal leg length and any attempts at lengthening

>4 cms may lead to sciatic nerve injury.5,6 The small size of the hemipelvis and proximal femur necessitates the use of smaller components.

Total Hip Arthroplasty

 

The function of the abductors is often difficult to evaluate before surgery, but in some patients active contraction of these muscles can be palpated. The abductor muscles are probably adequate in patients whose hip has been fused since childhood and the trochanter looks normal. However, if the bone around the hip is grossly distorted by disease or by one or more fusion operations, the abductor muscles may be inadequate. Weak abductor musculature is associated with poorer functional outcome.

 

Surgical                    Technique                    

Preoperative templating is of paramount importance to have an estimate of the component size and position of the acetabular cup (Fig. 26.1).

The conversion of an ankyosed hip to a total hip arthroplasty entails a technical challenge of a difficult exposure and difficulty in location of the native acetabulum. The exposure is difficult because of distortion of anatomic planes, medialization of hip center and soft tissue contracture.

Once the patient has been anaesthetized, utmost care must be taken in positioning of the patient. In cases of bilateral hip involvement, the positioning of pelvis may be hindered by the opposite hip. The chief operating surgeon should be present at the time of positioning in order to make himself acquainted with the deformities in the pelvis and spine, so as to ensure optimum positioning of components.

An incision is given for the posterior approach (Fig. 26.2). The sciatic nerve is often displaced close to the hip and may be fixed in scar tissue, hence careful monitoring of the tension in the nerve is necessary.

 

 

After detaching the external rotators, the femoral neck is exposed (Fig. 26.3). The line of neck resection is identified by approaching the inferior neck and feeling the pubofemoral arch and the lesser trochanter. An in situ osteotomy of the femoral neck is usually required to visualize the femoral neck and acetabulum (Figs 26.4A and B). A wedge of bone may be removed from the neck to improve the orientation. Caution is exercised to avoid cutting into the greater trochanter or dividing the posterior acetabular wall while performing the neck resection.

 

Figure 26.1: Preoperative templating should be done to have an estimate of the size and position of the acetabular cup

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Total Hip Arthroplasty for Bony Ankylosis

 

Figures 26.4A and B: The neck is osteotomized in situ

 

Figure 26.2: An incision is given for posterior approach

 

Figure 26.3: The hip has been exposed by posterior approach and the Hohmann retractor has been placed along on the superior and inferior aspect of the neck

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Sometimes in severe external rotation deformity, the neck may be identified by dissecting anterior to the greater trochanter and the abductor muscles and then the neck is osteotomized. One of the challenges in acetabular preparation is the identification of the orientation of the acetabulum. The acetabular fovea and obturator foramen are used as landmarks for acetabular positioning. The most caudal extent of the acetabulum is marked by the obturator foramen. The pulvinar fat in the acetabular fovea can be uncovered with a curette. The

Total Hip Arthroplasty

 

anterior inferior iliac spine is often intact and serves as a landmark.

Acetabular preparation is started with the removal of the remaining femoral head piecemeal (Fig. 26.5). Reaming with sequentially larger reamers is then done in the medial direction (Fig. 26.6). The identification of foveal soft tissue during acetabular reaming indicates the location of the original joint plane. The acetabular preparation must be done carefully so as to preserve the anterior and posterior columns. Conscious effort is made to leave a spike of bone at the superolateral acetabular margin. This superolateral bone spike preserved during the reaming provides purchase to the cementless cup and checks the tendency to place the acetabular cup in a vertical position (Figs 26.7A and B).

The femoral canal is prepared in the usual manner according to the femoral implant.

 

 

Adductor tenotomy, iliopsoas muscles release, and anterior capsulectomy is often required to correct severe contractures. Forcible correction of the flexion contracture without adequate

 

 

 

Figure 26.5: The neck has been osteotomized and femoral head is removed piecemeal

 

Figure 26.6: The acetabulum is prepared by reaming with sequentially large reamers in a medial direction

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Total Hip Arthroplasty for Bony Ankylosis

 

Figures 26.7A and B: The prepared acetabulum after reaming. Note the spike of bone is left on the superolateral aspect of acetabulum to provide purchase to the acetabular cup and check the tendency to place the cup in a vertical postion

 

 

Figure 26.8: The acetabular cup has been implanted

 

release of the soft tissues can be dangerous and can result in fracture of the stiff spine with dire neurological consequences.7

Trial reduction is done after positioning of the trial components to check for the stability in all directions, correction of fixed deformity and limb length. Sciatic nerve is palpated at this stage with the knee extended to ensure its mobility. Definitive components are then implanted (Figs 26.8 and 26.9). The capsule and short external rotator muscles should be closed and the wound closed in layers over a drain.

Fixed flexion contracture can lead to tilting of the pelvis and malposition of the acetabular component especially when combined with fixed adduction or abduction deformity of the opposite limb. The pelvis is tilted anteriorly in patients with fixed adduction and flexion deformity, thereby creating the possibility of inserting the cup with less anteversion than desired. In patients, with fixed abduction and flexion deformity, the cup may be inserted with exaggerated anteversion.8 In patients in which the contralateral hip is fixed in abduction or

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Total Hip Arthroplasty

 

Figure 26.9: The femoral components have been implanted and final reduction done

 

 

 

 

Figures 26.10A and B: (A) The pelvis is tilted cephalad if the contralateral limb is fixed in abducted position. Inserting a cup with an inclination of 40° referenced to the ground level creates the possibility of inserting the cup with less inclination than desired. (B) If the contralateral limb is fixed in the adducted position the opposite happens

 

adduction deformity, there may also be an error in determining the true inclination of the acetabular cup. The pelvis is tilted cephalad if the contralateral limb is fixed in abducted position, inserting a cup with an inclination of 40° referenced to the ground level creates the possibility of inserting the cup with less inclination than desired. If the contralateral limb is fixed in the adducted position, the opposite happens8 (Figs 26.10A and B).

 

Postoperative                   Regimen                  

Perioperative parenteral antibiotics and postoperative prophylaxis for deep vein thrombosis is used in all patients. In addition, these patients should be given oral indomethacin 25 mg 3 times a day for 14 days9-11 for prophylaxis against heterotopic ossification. Patients are

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mobilized out of the bed the day after surgery, and those with unilateral replacement are encouraged to walk non weight-bearing using crutches.

 

Tips           and           Pearls                      

Astute attention to technical details is paramount in the course of surgery. Both patient as well as component positioning is extremely difficult and error prone. External rotation deformity of the femur and exaggerated femoral anteversion provide special problems. In patients with external rotation deformity sacrificing 2 to 3 mm of the posterior acetabular wall, dissecting anterior to the abductors or performing the neck osteotomy under image intensifier control with patient in supine position are some of the options available.

Often, the bone is osteoporotic due to disuse, and overreaming may compromise the acetabular bone stock. Deliberate effort should be made to leave a spike of bone at the superolateral acetabular margin during the reaming as it provides purchase to the cementless cup. Preserving this superolateral spike of bone from the femoral neck checks the tendency to place the cup in vertical position. Exaggerated anteversion of femoral neck may lead to intraoperative difficulties in the form of impingement of the prosthetic neck or the greater trochanter posteriorly or difficulties in the placement and/or reduction of the hip in addition to causing the anterior instability subsequently. This can be overcome to some extent by using modular femoral stems or extensively coated stems with distal fixation.3

 

Total Hip Arthroplasty for Bony Ankylosis

 

Discussion          and          Results                  

Cases with bony ankylosis present with exceptional features and need THA even in the absence of pain. The major concerns regarding THA in these young patients involve choice of implants, the technical difficulties of performing THA, ensuring optimum positioning of components, heterotopic ossification, and recurrence of ankylosis, pain and loss of movements.12 Although patients with bony ankylosis do not have pain, the presence of severe deformity, functional limitation and remarkable improvements in function and quality of life even after small improvement in hip movements justify THA in young patients. Several reports have demonstrated excellent survivorship of THA in this group with high patient satisfaction.1,10,13

The success of conversion of ankylosis into hip replacement depends on the etiology of ankylosis, age of patient, indication for arthroplasty and interval between ankylosis and hip arthroplasty. Hardinge3 reported the poor range of motion postoperatively in old cases of infantile sepsis, thought to be due to depression of growth of the proximal femur and related musculature. Hip arthrodesis prior to puberty leads to underdevelopment of the abductor musculature and greater trochanter. In patients who had conversion of fused hip to total hip arthroplasty, Joshi et al13 reported that patients who were less than 15-years-old had higher dislocation rates and decreased ability to walk when compared to patients who were older than 15 at the time of their fusion. In cases of ankylosing spondylitis, Joshi reported14 revision in 13.8% of patients (mean age 47) at an average follow-up of 10.3 years.

Strathy15 reported only 1 failure in the 20 hips of 15 patients who had a spontaneous ankylosis. However, 20 (33%) of the 60 hips of the 60 patients who had a surgical ankylosis had complications associated with the arthroplasty including loosening, infection, and dislocation. In a review of 41 fused hips, Kilgus16 reported failures due to sepsis in 4 patients, femoral component loosening in 4 patients and acetabular component malposition in 1 patient. The failures were seen in patients younger than 50 years at the time of arthroplasty, those with a history of two or more previous surgeries and those with a history of hip injury. However, older patients with a history of spontaneous ankylosis as a result of childhood sepsis without previous surgery did particularly well. Bhan et al17 reviewed 54 patients (92 hips) who underwent cementless total hip arthroplasty for bony ankylosis in ankylosing spondylitis. At a mean follow-up of 8.5 years, the average preoperative Harris Hip Score of

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49.5 improved to 82.6 postoperatively. Postoperatively, 10 hips had mild-to-moderate pain. Anterior dislocation occurred in 4 (4.3%) hips, and sciatic nerve palsy in 1 (1.1%) hip. Although heterotopic ossification was seen in 12 patients, there was no case with reankylosis. Thirteen (14%) arthroplasties were revised because of aseptic loosening.

Total Hip Arthroplasty

 

The choice of implant is particularly important for long-term fixation and hip function, as well as durability in this relatively young and active group of patients where decreased mobility of the spine may result in increased forces at the hip joint.9 Use of cementless implants with potential for biologic ingrowth may increase the longevity and reduce failure rates especially in younger patients.

Tang and Chiu10 have reported hyperextension at the hip in patients with AS, which is evident as the exaggerated longitudinal dimensions of the obturator foramen on plain standing radiographs. They postulated that this anatomic abnormality may lead to more anteverted and vertical inclination of the acetabular cup, which may predispose the prosthesis to anterior dislocation. The other reasons for the propensity of these prostheses to dislocate anteriorly are an abnormal, exaggerated femoral anteversion often seen in these patients as well as frequently pre-existent external rotation deformity with the contracture of soft tissues

High rates of heterotopic ossification have been reported in the patients with ankylosing spondylitis, varying from 40 to 76%4,9,12,18 Presence of bony ankylosis may indicate further propensity to form excessive bone because high rates of heterotopic ossification (65%-100%) have been reported after a second procedure when heterotopic bone developed after the arthroplasty of the first hip.3,19 Heterotopic ossification of the class III and IV, which denote clinically important quantities of bone, has been reported in 11 to 36% cases with ankylosing spondylitis and the use of prophylaxis against heterotopic ossification is recommended.

Reankylosis rates of 6 to 100% as shown in the literature have been reported to correlate with ankylosis of the hip before THA.14 Also, range of motion has been shown to decline with time when the hip arthroplasty is done for fused hips.

 

Conclusion

 

Cementless THA in osseous ankylosis is a worthwhile surgical intervention. Newfound mobility, maneuverability and improved ability to sit comfortably are the outcomes that alleviate the patient’s misery. However, the technically demanding nature of the procedure should not be underestimated.

 

Illustrative                      Case                     

A 26-year-old male patient suffering from ankylosing spondylitis presented with severe pain in the right hip joint, which severely restricted his activities of daily living. On examination he had fixed flexion deformity of 10 degree and painful restriction of all movements of right hip joint, the left hip was painless and fixed in 40 degree of flexion, 20 degree abduction and 10 degree of external rotation. The radiographs revealed bony ankylosis in the left hip joint and arthritis of right hip joint (Fig. 26.11A). A bilateral simultaneous hip replacement was done using the posterior approach.

The ankylosed left hip was exposed using the posterior approach and in situ osteotomy of femoral neck was done. The femoral head was removed piecemeal using the acetabular reamers. During reaming, an utmost care was taken to leave a superolateral bony spike. A cementless acetabular cup (R3TM Cup, Smith and Nephew) with screws and cementless femoral stem (Synergy stemTM, Smith and Nephew) was implanted (Fig. 26.11B).

The right hip was also exposed using the posterior approach. The hip was dislocated and femoral neck osteotomy was performed. As the bone quality was found to be good, a mid head resection was done and Birmingham Mid Head Resection StemTM (Smith and Nephew) implanted along with a large head and cementless Birmingham Hip Resection acetabularTM (Smith and Nephew) Component.

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Figures 26.11A and B: (A) Preoperative X-ray of a patient suffering from ankylosing spondylitis. The left hip has bony ankylosis and the right hip has fibrous ankylosis (B) A Birmingham Mid Head Resection implant™ (Smith and Nephew) has been implanted in the right hip and R3 cup–Synergy stem™ (Smith and Nephew) implanted in the left hip

 

The patient was mobilized with support using a walker for 6 weeks. Patient was started on Indomethacin for prophylaxis against heterotropic ossification.

 

Total Hip Arthroplasty for Bony Ankylosis

 

References                       

1. Sweeney S, Gupta R, Taylor G, Calin A. Total hip arthroplasty in ankylosing spondylitis: outcome in 340 patients. J Rheumatol 2001;28:1862.

2. Bhan S, Malhotra R. Bipolar hip arthroplasty in ankylosing spondylitis. Arch Orthop Trauma Surg 1996;115:94.

3. Hardinge K, Williams D, Etienne A, et al. Conversion of fused hips to low friction arthroplasty. J Bone Joint Surg 1977;59-B:385.

4. Sundaram NA, Murphy JCM. Heterotopic bone formation following total hip arthroplasty in ankylosing spondylitis. Clin Orthop 1986;207:223

5. Amstutz HC, Sakal DN. Total joint replacement for ankylosed hips. J Bone Joint Surg 1975;57A:619-25.

6. Hardinge K, Williams D, Etienne A, et al. Conversion of fused hips to low friction arthroplasty. J Bone Joint Surg 1977;59B:385-92.

7. Mahesh BH, Jayaswal A, Bhan S. Fracture dislocation of the spine after total hip arthroplasty in a patient with ankylosing spondylitis with early pseudoarthrosis. Spine J 2008 May-Jun;8(3):529-33.

8. Yong Lae Kim, Sang Ik Shin, Kwang Woo Nam, Jeong Joon Yoo, Young-Min Kim, Hee Joong Kim. Total Hip Arthroplasty for Bilaterally Ankylosed Hips. The Journal of Arthroplasty 2007;22(7):1037.

9. Bisla RS, Ranawat CS, Inglis AE. Total hip replacement in patients with ankylosing spondylitis with involvement of hip. J Bone Joint Surg Am 1976;58:233.

10. Tang WM, Chiu KY. Primary total hip arthroplasty in patients with ankylosing spondylitis. J Arthroplasty 2000;15:52.

11. Walker LG, Sledge CB. Total hip arthroplasty in ankylosing spondylitis. Clin Orthop Relat Res 1991;262:198.

12. Williams E, Taylor AR, Arden GP, et al. Arthroplasty of the hip in ankylosing spondylitis. J Bone Joint Surg Br 1977;59-B:393.

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13. Joshi AB, Markovic L, Hardinge K, et al. Conversion of a fused hip to total hip arthroplasty. J Bone Joint Surg 2002;84A:1335â.

14. Joshi AB, Markovic L, Hardinge K, Murphy JCM.Total hip arthroplasty in ankylosing spondylitis: an analysis of 181 hips. J Arthroplasty 2002;17:427.

15. Strathy GM, Fitzgerald RH Jr. Total hip arthroplasty in the ankylosed hip. A ten-year follow-up. J Bone Joint Surg 1988;70A:963.

    Total Hip Arthroplasty

     

16. Kilgus JD, Amstutz HC, Wolgin MA, et al. Joint replacement for ankylosed hips. J Bone Joint Surg 1990;72A:45.

17. Surya Bhan, Krishna Kiran Eachempati and Rajesh Malhotra. Primary Cementless Total Hip Arthroplasty for Bony Ankylosis in Patients with Ankylosing Spondylitis. The Journal of Arthroplasty 2008;23(6):859.

18. Kilgus DJ, Namba RS, Gorek JE, et al. Total hip replacement for patients who have ankylosing spondylitis: the importance of formation of heterotopic bone and of the durability of fixation of cemented components. J Bone Joint Surg Am 1990;72:834.

19. De Lee J, Ferrari A, Charnley J. Ectopic bone formation following low friction arthroplasty of the hip. Clin Orthop 1976;121:53.