Abstract
Background
There are many difficulties during performing total hip replacement in high riding DDH. These difficulties include:
In Acetabular part: bony defect in antero lateral acetabular wall/finding true centre of rotation/shallowness of true acetabulum/hypertrophied and thick capsular obstacle between true and false acetabulum
In Femoral part: small diameter femoral shaft/excessive ante version/posterior placement of greater trochanter
anatomic changes in soft tissue & neurovascular around the hip including: adductor muscle contracture/shortening of abductor muscles/risk of sciatic nerve injury following lengthening of the limb after reduction in true acetabulum/vascular injury
The purpose of this lecture is how to manage above problems with using reinforcement ring (ARR) for reconstruction of true acetabulum and step cut L fashion proximal femoral neck shortening osteotomy in a single stage operation
Method
23 surgeries in 19 patients, including 18 female and one male were performed by me from Jan. 1997 till Dec. 2009. Six patients had bilateral hip dislocation, but till now only four of them had bilateral stepped operation. Left hip was involved in 15 cases (65.2%). The average age was 40 years old. All hips were high riding DDH according to both hartofillokides and crowe classification. Reconstruction of true acetabulum was performed with aid of reinforcement ring and bone graft from femoral head in all cases. Trochantric osteotomy was done in all, followed by fixation with wire in 22 cases which needed two revisions due to symptomatic non union (9%). Hooked plate was use in one case for trochantric fixation. Due to high riding femur, it was necessary to performed femoral shortening in neck area as a step cut L fashion.
In two patient, one with bilateral involvement, after excessive limb lengthening following trial reduction, it was necessary to performed concomitant supracondylar femoral shortening. (3 cases = 13%)
22 mm cup & miniature muller DDH stem were used in 18 cases (78.26%). In 5 cases, one bilaterally, non cemented stem and 28 mm cemented cup in ring were used.
Primary adductor tenotomy was performed in 9 cases. Secondary adductor tenotomy needed in 2 cases (totally = 47.82%). Repair of iatrogenic femoral artery tear after traction injury with retractor, occurred in 2 cases (8.69%).
All patients evaluate retrospectively. Average follow up month is 68.7.
Results
One case of left acetabular component revision due to painful bony absorption in infero medial part of ring with poor inclination wad done, after 2 years of primary operation. Know after 13 years she has had early signs of stem loosening in the same side. Another acetabular component revision following traumatic dislodgment of cup and cement from ring was performed after 13 months from primary operation. Again she had poor implant inclination. So revision rate is 8.69%. (One case will need revision in near future, so the revision rate will increase to 13%) Radiological wires breakage which were used for greater trochanteric fixation, could be seen in 11 cases (47.82%), but only two of them with functional impairment needed to re-fixation with Menen plate(18.18% of trochanteric non union). Average limb lengthening after operation is 4.3 Cm (2-7 Cm). Only one case of transient Sciatic nerve paresis had happened for 2 months followed by complete recovery. Two case of secondary adductor tenotomy wre done, one after traumatic dislocation of prosthesis with pubic fracture, and the other one after restriction of hip abduction. The average Harris hip score from 23 pre -operatively has been increase to 85.38. (The pre op. scores were 12.625 – 40.775/The post op. scores were 64.92 – 96)
No post operative infection was seen.
Discussion
This is a midterm follow up survey, but 7 cases have more than 9 years follow up with only one stem loosening (11% long term loosening rate). It is a challenging procedure for performing joint replacement in high riding DDH, if so using reinforcement ring with graft for true acetabulum reconstruction and getting primary proximal femoral shortening in a step cut L fashion around the lesser trochanteric region would be a worthy procedure. In high riding DDH due to hypoplasia of lesser trochanter, there is not a significant difference in bone resistance and it is possible to get shortening in this area without fearing of deco promising bony stability. The average shortening is 3 Cm.
In specific cases with more severe contracture for preventing neuro-vascular complication, concomitant shortening osteotomy in supracondylar area is recommended.
Although greater trochanter fibrous union has produced less functional impairment, but a better technique should be considered. Distal and lateral advancement of osteotomised greater trochanter lead to better abductor muscle performance and less limp.
Adductor tenotmy has a great importance in contracted soft tissue, so in any case with abduction limitation it should be performed.
