HIP ISSN 1120-7000

Hip Int 2015; 25 (1): 72-75 DOI: 10.5301/hipint.5000187

ORIGINAL ARTICLE

Long-term result of cementless femoral stem in avascular necrosis of the hip Kin W. Cheung, Kwok H. Chiu, Kwong Y. Chung Department of Orthopaedics and Traumatology, Prince of Wales Hospital, Shatin - Hong Kong

ABSTRACT Avascular necrosis (AVN) of the hip may have extensive involvement of the proximal femur which may affect boney ingrowth into cementless femoral stems. From 1994 to 2004, 182 total hip arthroplasties (in 144 patients, 117 AVN hips and 65 non-AVN hips) were performed using hydroxyapatite coated femoral stems. All patients were followed up prospectively. Mean age was 51 years and mean follow-up 14.7 years (range 9.7-19.1 years). Four stems were revised because of aseptic loosening, 3 in AVN group and 1 in non-AVN group. The overall mechanical failure rate was 2.2%, the mechanical failure rate in AVN and non-AVN group was 2.6% and 1.5% respectively (p = 1). The 19.1 year survival using revision for aseptic loosening as an endpoint for AVN and non-AVN patients were 97.1% and 96.2% respectively (p = 0.654). Stable boney ingrowth was present in 99.5% hips. This study represents 1 of the largest series reporting the long-term follow-up of the use of cementless femoral stems in treating AVN of the hip. We report excellent long-term survival of cementless total hip arthroplasty used in managing AVN of the hip and is comparable to that seen in non-AVN total hip arthroplasty. Keywords: Total hip arthroplasty, Cementless femoral stem, Avascular necrosis hip, Osteonecrosis, Uncemented, Hip

Introduction The success of total hip arthroplasty (THA) over the last 40 years is widely reported (1-10) with cemented and cementless femoral stems having broadly reported similar results (11). Most studies however, report the results of treating primary osteoarthritis (3, 5-6, 8-9, 12-13), with few studies reporting the long-term outcome in managing avascular necrosis of the hip (AVN) (6-7, 10). AVN hip is the most common indications for THA in Hong Kong (12-14). Saito reported the extensive involvement of avascular necrosis of the hip, which may theoretically affect boney ingrowth into cementless femoral stems (15). We aimed to compare the long-term outcome of hydroxyapatite coated cementless femoral stems in total hip arthroplasty for AVN hip and non-AVN hip.

Materials and Methods From 1994 to 2004, 182 hydroxyapatite coated cementless femoral stems, Omnifit-HA (Osteonics, Allendale, NJ) were implanted in 144 patients (86 male, 58 female (see Accepted: July 17, 2014 Published online: September 1, 2014 Corresponding author: Kin Cheung Department of Orthopaedics and Traumatology Prince of Wales Hospital 30-32 Ngan Street Shatin, N.T., Hong Kong [email protected]

Fig. 1)). All bilateral cases were staged procedures. The Omnifit-HA femoral stem is a collarless titanium alloy stem. The proximal third of the stem is microtextured circumferentially with grit blasting and coated with 50 μm hydroxyapatite. Cobalt chrome femoral heads (28 mm) were used in all cases. There were 117 (64.3%) AVN hips. Of these, 66 hips (56.4%) were alcohol induced, 22 (18.8%) post-traumatic, 19 (16.2%) idiopathic and 10 hips (8.6%) steroid induced AVN. Among the 65 non-AVN hips, 10 hips (15.4%) were ankylosing spondylitis, 24 (36.9%) dysplastic hip with secondary osteoarthritis, 7 (10.8%) primary osteoarthritis and 24 hips (36.9%) were inflammatory arthritis (22 rheumatoid, 2 psoriatic). All procedures were performed using a posterior approach by or under the supervision of the senior author (KHC). Four acetabular cups were used in this series (71 Omnifit PSL HA cup (Osteonics, Allendale, NJ), 95 Secur-Fit PSL HA cup (Osteonics, Allendale, NJ), 5 Exeter cup (Stryker Inc, Warsaw, IN) and 11 Trident cup (Stryker Inc, Warsaw, IN)). The outcome and survival of the acetabular cups was not studied due to the implant heterogeneity and previously reported inferior result of Omnifit PSL HA cup (16). Radiographic stability of stems was assessed using the modified Engh’s criteria (17). Survival of the femoral stem using revision surgery for aseptic loosening as the endpoint is reported. Potential prognostic factors, including age (≥50), gender, preoperative diagnosis, surgeon’s experience (>20 cases in cementless THA), body mass index (BMI), mobility status (>30 minutes each interval), stem alignment (varus vs valgus) and outlier status in stem alignment (>5°) were analysed using a Cox Regression model. All patients were followed up prospectively. Preoperative and latest © 2014 Wichtig Publishing

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Fig. 2 - Survival of AVN and non-AVN hips using revision for aseptic loosening as endpoint.

Fig. 1 - Hydroxyapatite coated cementless femoral stem, Omnifit-HA.

postoperative Harris Hip Scores (HHS) were compared. Student t-test and Fisher exact tests were used for continuous and categorical variables respectively. Statistical analysis was performed using the Statistical Package for the Social Sciences software package 15.0 (SSPS, Chicago, Illinois). and a significance level of 0.05 utilised.

Results Mean age of the whole study group was 51 years (range 25-78 years) with no significant difference between AVN and non-AVN groups (p = 0.253). Thirty-five patients with 44 stems died of unrelated causes during the study period. One hundred and nine patients (138 femoral stems) were available for complete clinical and radiological assessment. None of the deceased patients reported aseptic loosening and/or revision surgery. Mean follow-up was 14.7 years (range 9.7-19.1 years). © 2014 Wichtig Publishing

The pre- and latest postoperative HHS did not differ significan­ tly between the two groups (p = 0.187 and 0.347 respectively). The mean preoperative HHS of AVN and non-AVN groups were 35.6 (range 0-67) and 38.5 (range 6-63) respectively. The mean latest postoperative HHS of AVN and non-AVN group were 83.8 (range 34-100) and 84.8 (range 21-100) respectively. HHS of both groups improved significantly after THA (p

Long-term result of cementless femoral stem in avascular necrosis of the hip.

Avascular necrosis (AVN) of the hip may have extensive involvement of the proximal femur which may affect boney ingrowth into cementless femoral stems...
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