The Hip: Preservation, Replacement and Revision

Conversion of Fused Hip to THR


- Discussion:
    - can reduce back and knee pain;
    - improved ability to sit for longer periods of time;
    - increased incidence of dislocation;
    - indications for conversion:
          - painful pseudarthrosis
                - pseudorthrosis rates are 0-10% using modern techniques for fusion;
                - be sure to rule out infection;
          - mechanical low back pain - most frequent complaint of patients with fused hips;
                - multi-level arthritic changes seen in LS spine 32.9 years following fusion (Amstutz et al, (1975));
                - malposition (especially increased abduction) is a major cause;
                - excessive leg length inequality also causes LBP over time;
                - Total joint replacement for ankylosed hips. Indications , technique, and preliminary results.
          - knee pain/instability - ipsilateral pain if the hip is fused with increased adduction;
                - contralateral pain more likely with increased hip abduction;
          - contralateral hip pain - rarely on isolated problem;
    - preoperative evaluation:
          - ensure that patient has a good indication for conversion
          - exam to check skin incisions, leg lengths, nerve function;
          - AP pelvis and cross table lateral to identify bone stock, hardware;
          - Judet views are helpful to identify anterior or posterior column deficiencies;
          - these plain films also help assess the status of the greater trochanter;
          - it will sometimes be insufficient due to prior surgery or insufficient growth secondary to pediatric pyarthrosis;
          - CT scan can sometimes be helpful for identifying bone stock, the proximity of heterotopic bone to neurovascular structures and 
                 abductor muscle mass;
    - surgical approach:
          - we prefer a standard posterior approach though others report success with a direct lateral or a trans-trochanteric approach;
          - we have 3 indications for an trochanteric osteotomy:
                 - exposure;
                 - to decrease injury to atrophied/weakened abductors during the case;
                 - advancement at the end of the case to improve stability
          - existing hardware should be removed if it limits exposure or if it is in the way of component placement;
          - heterotopic bone should be removed as is possible.
          - old hardware can often guide one to the correct plane for bone removal;
          - neck cut in situ:
                 - care must be taken since Amstutz has described 2 eases where cuts were too proximal resulting in fractures of the pubis and the 
                        ischium;
                 - if in doubt, place guide pins and obtain a radiograph;
                 - soft tissue releases (ilio psoas, adductors, etc.) are frequently required;
    - acetabular component:
          - structural grafting is sometimes required;
          - one should be prepared to cement the socket if the shell has <50 % contact with native bone;
          - a constrained liner is frequently required because of insufficient soft tissue tension post-op (esp. abductors);
    - femoral component:
          - we recommend modular femoral components in order to restore hip mechanics and improve hip stability;
          - uncemented stems are sometimes useful if screw holes are present in the proximal femur;
          - if cement is used, unicortical screws can be placed in the femur to keep cement in the canal;
          - if the trochanter is bald and there are no abductors, the proximal femur can be sewn to the tensor fascia lata anteriorly and te gluteus 
                 maximus and ITB posteriorly;
    - results:
          - relief of low back pain occurs 70-95% of the time
          - leg lengths can usually be improved
          - ipsilateral knee pain typically improves but it persists in at least 1/3 (especiailly if instability was a problem pre-op)
          - a trendelenberg gait typically persists though abductor function improves for 2-5 years;
          - results from conversion of spontaneous fusions are typically better than results of conversion of surgical fusions;
    - complications:
          - deep infection 1.9-15.3% (higher in conversion of surgical fusion)
          - dislocation 1.7 - 6.25%
          - sciatic nerve palsy 1.8-13.4%
          - femoral nerve palsy 3.6%


The treatment of the painful hip in cerebral palsy by total hip replacement or hip arthrodesis.

Hip arthrodesis in young patients. A long-term follow-up study.

Thompson arthrodesis of the hip in children.

Hip arthrodesis. A long-term follow-up

Contralateral Total Hip Arthroplasty or Ipsilateral Total Knee Arthroplasty in Patients Who Have a Long-Standing Fusion of the Hip.

Hip fusion in young adults. Using a medial displacement osteotomy and cobra plate.

Walking patterns of men with unilateral surgical hip fusion.

Joint replacement for ankylosed hips.

Total knee arthroplasty in patients with prior ipsilateral hip fusion.




Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Tuesday, May 15, 2012 3:09 pm