Eur J Orthop Surg Traumatol DOI 10.1007/s00590-013-1405-9

ORIGINAL ARTICLE

Primary total hip arthroplasty with a proximally HA-coated titanium femoral component: results at 10–15-year follow-up N. A. Sandiford • A. Butler-Manuel • H. D. Apthorp • D. J. East • B. L. Hinves J. A. N. Shepperd



Received: 17 November 2013 / Accepted: 27 December 2013 Ó Springer-Verlag France 2014

Abstract Introduction Registries in both the United Kingdom and Sweden suggest that the popularity of uncemented femoral components is increasing. As this trend progresses, longterm survival data for such components are becoming increasingly more important. We present the results of a cohort of patients treated with the Omnifit (Stryker, Mahwah, NJ) femoral component with the follow-up of 10–15 years. Methods A prospective study was performed in our unit between 1996 and 2001. Patients were reviewed preoperatively and then at 6, 12, 26 and 52 weeks post-operatively and annually thereafter. They were assessed clinically and radiographically, and the Merle d’Aubigne Postel (MDP) hip score was calculated at each visit. A visual analogue scale (VAS) score and satisfaction score were also recorded to assess patient satisfaction with their procedure. Specific enquiry was made regarding anterior thigh pain. Statistical calculations were performed using the Student’s t test. Kaplan–Meier survival analysis was performed. Results One hundred and four patients (113 hips) were included (48 males, 56 females). Bilateral procedures were performed in nine patients. Mean age was 60.4 years (33–72 years). Mean follow-up was 12.9 years (10–15 years). Mean pre-operative MDP score was 8.8 (3–16) and VAS score 7.8 (1–10) with ten representing the most severe symptoms. At final follow-up, the average MDP and VAS scores were 16.9

N. A. Sandiford (&)  A. Butler-Manuel  H. D. Apthorp  D. J. East  B. L. Hinves  J. A. N. Shepperd Department of Orthopaedics, Conquest Hospital, The Ridge, St Leonards-on-Sea, East Sussex TN37 7RD, UK e-mail: [email protected]

(13–18) and 2.1 (0–6), respectively. High levels of satisfaction were reported by 96.1 % of patients. Two dislocations and two cases of anterior thigh pain occurred. Four patients required revision surgery. Survival of the femoral component with revision for any reason as the end point was 96 %. Conclusion This prosthesis provides symptom relief, return to function and high levels of patient satisfaction in the long term. Survival of this component is comparable to the best results for primary total hip arthroplasty with any means of fixation. Keywords Omnifit  Uncemented  Long term  Survivorship  Proximally HA coated

Introduction The ideal method of fixation of femoral components used in primary total hip arthroplasty (THA) is undecided. The popularity of uncemented components has increased over the last decade [1, 2]. Paradoxically, revision rates for uncemented components are higher than for cemented stems in the first 10 years post-operative period [1, 2]. These data group all designs of uncemented components together. No differentiation is made between hydroxyapatite (HA) and non-HA-coated components. Encouraging clinical results have been reported from specialist units with the use of HA-coated femoral components [3]. Medium- to long-term results from nonspecialist centres are less well known. This paper presents the results of patients treated with an uncemented proximally HA-coated titanium femoral prosthesis in a district general hospital and followed up for an average of 12.9 years post-surgery.

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Patients and methods This prospective study was performed between 1996 and 2001. One hundred and four patients (113 hips) underwent primary THA using the Omnifit (Stryker, Mahwah, New Jersey, USA) proximally HA-coated femoral component. This group included 48 males and 56 females. Bilateral procedures were performed in nine patients. All procedures were performed by or under the direct supervision of a consultant orthopaedic surgeon via an anterolateral approach. Procedures were performed in an operating theatre with laminar flow. The Securfit (Stryker, Mahwah, New Jersey, USA) acetabular component was used in all cases. Patients were assessed clinically and radiologically preoperatively and at 6 weeks, 3 months, 6 months and 1 year post-operatively and annually thereafter. Pain, function and mobility were assessed at each visit using the Merle D’Aubigne Postel (MDP) score. Patients were also asked to rate their satisfaction on a visual analogue scale (VAS) where a score of ten represented those with significant symptoms (and therefore very unhappy) and 1 represented a happy patient. They were also asked specifically whether they perceived their operated hip to be wholly better, partially better or worse compared with their pre-operative state. At each review, anteroposterior radiographs of the pelvis and lateral views of the operated hip were obtained. These were assessed for signs of migration of the prostheses as well as other signs of loosening (lytic lesions and radiolucent lines, (RLLs)), stress shielding and heterotopic ossification. Migration was measured as a change in the distance between the tip of the greater trochanter and the shoulder of the implant. Radiolucent lines were defined as linear lucencies at the bone–prosthesis interface greater than 2 mm wide [4] and occupying greater than 30 % of any Gruen zone [5]. Stress shielding was defined as selective resorption of bone from the calcar region of the femoral neck [6]. Lytic lesions were defined as balloon-shaped lucencies occurring at the bone–prosthesis interface. Significant stress shielding was considered to be present if there was selective resorption of bone from the calcar region of the femoral neck. Heterotopic ossification was classified according to the system of Brooker et al. [7]. Statistical analysis Our results were analysed using Student’s t test. Statistical significance was set at p=0.05. Survival analysis was performed using the Kaplan–Meier method with 95 % CI (GraphPad software, CA, USA).

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Table 1 Demographics of our patient cohort N Males

56

Females

48

Age/years (range)

60.3 (33–72)

Primary osteoarthritis (OA)

100

Developmental dysplasia

2

Avascular necrosis

1

Rheumatoid arthritis

1

Post-traumatic OA

0

Table 2 Pre-operative and post-operative clinical and visual analogue scale scores up to the final follow-up visit Preoperative

6 months postsurgery

1 year postsurgery

5 years postsurgery

Final FU

MDP score

8.8

16.5

16.5

16.8

16.9

VAS

7.8

P value \0.0001

1.7

1.7

1.6

2.1

\0.0001

\0.0001

\0.0001

\0.0001

MDP Merle d’Aubigne Postel, VAS visual analogue scale

Results The average age of our cohort was 60.4 years (range 33–72 years). Average duration of follow-up was 12.9 years (range 10–15 years). Patient demographics are shown in Table 1. Two patients (0.1 %) from this group were lost to follow-up at 10 and 12 years as they moved out of the area. Both had been reviewed within 1 year of migrating and were included in the study. The mean MDP score was 8.7 (range 3–16) pre-operatively and 16.7 (13–18) at final follow-up (p\0.0001). Mean VAS score was 7.9 (range 1–10) before surgery and 2.1 (range 0–6) at final follow-up (p\0.0001) (Table 2). Ninety-seven patients (93.3 %) reported that their operated hip felt wholly better, while five thought they were only partially better. Revisions Nine patients in this group (nine hips) underwent revision surgery. Femoral components were revised in three cases. Reasons for the revision of the femoral component included early dislocation (one femoral component was revised to a higher offset stem at 1 week after the index procedure for recurrent dislocation), deep infection 1 year after the primary procedure (one stem) and aseptic loosening at 5 years (one stem). Indications for revision are presented in

Eur J Orthop Surg Traumatol Table 3 Indications for revision procedures Indication

N

Acetabular component Aseptic loosening

7

Dislocation

1

Ceramic liner fracture

0

Infection

1

Femoral component Aseptic loosening

1

Infection

1

Dislocation

1

Fig. 2 Omnifit prosthesis 12 years post-insertion showing trabeculae and spot welds extending to the HA-coated region in its proximal 1/3

Time/months 0

60

72

96

108

120

Number at risk

98

97

95

91

80

113

Fig. 1 Kaplan–Meier graph and table showing numbers at risk over time in this population

Table 3. Survival of the femoral component at a mean of 10 years with revision for aseptic loosening as the end point is 96.8 % (95 % CI 92–100 %) and 92.9 % at 12.9 years post-op (95 % CI 74.4–98.4 %). If revision for any reason is considered to be the end point, then survival at an average of 10 years is 91.3 % (95 % CI 84.3–95.3 %) and 88.1 % at an average of 12.9 years post-surgery (95 % CI 77.4–94.1 %) (Fig. 1). The 10-year survivorship figures are presented because the numbers at risk at 12 years are small compared with numbers at risk at 10 years post-surgery. Radiological results Two stems subsided by 2 and 3 mm at 1 and 2 years postsurgery, respectively. These were asymptomatic and were noted to have stabilised on subsequent radiographs. Heterotopic ossification was noted in six cases (5.3 %): grade 2 (one case), grade 3 (four cases) and grade 4 (one case). Radiolucent lines were noted around five femoral stems

(4.8 %): zones 1 and 7 (4 cases), and ten acetabular components (8.8 %): zone 1 (eight cases) and zones 1 and 2 (two cases). RLLs were noted in zones 1–7 in one stem which was symptomatically loose and required revision. No lytic lesions were encountered. Stress shielding was found in five femora. In all other cases, signs of solid fixation were noted with bone trabeculae extending to the prosthesis surface and spot welds in the proximally HA-coated region (Fig. 2). Complications Fourteen complications occurred in this group (Table 4), including one intraoperative femoral fracture that was treated successfully with bed rest and protected mobilisation using crutches for 6 weeks post-surgery. One patient suffered a pulmonary embolism at 5 weeks post-operatively, which was successfully managed with anticoagulants. Two dislocations occurred at 1 week and 2 years post-operatively. The first case was thought to be due to a reduced femoral offset leading to instability. This was managed by revising the femoral component to one with a higher offset. The second case was managed with closed reduction and an abduction brace for 6 weeks. Neither case has recurred. Four patients complained of anterior thigh pain in this group. In one case, this has led to restriction of activity, but the patient has refused revision up to the last review. One deep infection occurred at 2 years post-surgery. This was due to haematogenous seeding from a

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Eur J Orthop Surg Traumatol Table 4 Complications encountered in this cohort Complications

N

Deep vein thrombosis (DVT)

3

Pulmonary embolism (PE)

1

Calcar crack

4

Anterior thigh pain

4

Dislocations

2

urinary tract infection. Escherichia coli was isolated, and it was managed with a two-stage revision. No deaths occurred in this cohort up to the last follow-up.

Discussion Hydroxyapatite-coated components were introduced in the 1980s as a means of enhancing the speed of formation and strength of the bone–prosthesis interface by facilitating ‘biological fixation’ [3] between the host bone and the surface of the prosthesis. Encouraging short- and mediumterm results have previously been reported for the Omnifit component. Few studies with a prospective design have been reported with a duration of follow-up similar to the current study, however, as we have extended the follow-up to a mean of 12.9 years. The average age of our cohort at the time of surgery was 60.4 years compared with the national average of 65.4 years for patients being treated with uncemented THA [2]. These patients were able to return to their normal working and social lives without restriction after their procedures. Significant improvements in their levels of pain as well as their mobility and function were achieved in the early post-operative period and maintained up to the time of last follow-up (Table 2). This corresponded to improvements in their VAS scores as well as the subjective sense of overall improvement in hip function (or the hip being made ‘wholly better’) expressed by 96.1 % of this group. These results reflect practice within a district general hospital setting. Several surgeons with differing levels

of experience performed these procedures. This suggests not only that the surgical technique can be taught and learnt, but that such encouraging results can be achieved by a variety of surgeons with differing skills and expertise. Concerns have been raised about the solubility of HA in vivo. This has been demonstrated to occur after approximately 8 years of exposure to the in vivo environment [8]. The results of this study as well as others [3, 9, 10] have not demonstrated a corresponding increase in femoral loosening or revision rates at this time interval despite osteopenia and an increasing corticomedullary ratio which occur with ageing. As a result, we do not believe that this issue influences mid- to long-term survival or clinical function (Fig. 1). It has been suggested that the circumferential HA coat provides a seal against the ingress of wear particles into the bone–prosthesis interface [11]. Aseptic loosening occurred in one femoral component (0.9 %). Radiolucent lines were noted around four stems which have been nonprogressive on serial radiographs and the not associated with clinical symptoms. These patients continue to be followed up. These findings have been in patients with evidence of wear and RLLs in their acetabular components as well. One patient (not included in the above group) had RLLs in zones 1–7 with a clinically loose stem which required revision at 5 years after her index procedure. These findings contrast with our observations using a fully coated stem with a 150 lm thick layer of high crystallinity HA (compared to the 50 lm layer on the Omnifit stem) in which no RLLs or aseptic loosening was noted at a mean follow-up of 22.5 years [12], even after aseptic loosening and failure of the acetabular component. It is possible that the strength of the seal formed by HA is proportional to the thickness of the HA coat. A limitation of this study is that a power analysis was not performed, although a large patient population was included. The results presented in this study represent one of the longest prospectively followed cohorts treated with the Omnifit stem by nondesigner surgeons in a district hospital setting with operations performed by several surgeons.

Table 5 Survival of femoral components in this cohort compared with published results for cemented and uncemented femoral stems Author

Type of stem

Year

N

Hsieh et al [10]

U

2000

166

Hellman et al [11]

U

1999

76

10

Capello et al [15]

U

2003

111

Current study

U

2012

Yates et al [13]

C

2008

Hook et al [14]

C

2006

U uncemented, C cemented

123

Average follow-up/years

Stem survival (%)

Aseptic loosening (%)

Thigh pain (%)

94

2.4

2.6

97

2.6

3.9

12

95.5

0.9

2.7

113

12.9

96.8

0.9

3.5

120

11.1

95.9

0



88

12.7

97.7

2.3



8.2

Eur J Orthop Surg Traumatol

They show that this prosthesis can reliably reduce pain and main function in the medium to long term. They are comparable to the best-published results for both cemented and uncemented primary THA (Table 5). Conflict of interest

There are no conflicts of interest to declare.

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8. Tonino AJ, van der Wal BC, Heyligers IC, Grimm B (2009) Bone remodeling and hydroxyapatite resorption in coated primary hip prostheses. Clin Orthop Relat Res 467(2):478–484 Epub 2008 Oct 15 9. Hsieh PH, Shih CH, Lee PC, Yang WE, Lee ZL (2000) Cementless total hip arthroplasty using the omnifit system: an 8.2 year follow-up study of 166 hips. J Orthop Surg 8(2):45–51 10. Hellman EJ, Capello WN, Feinberg JR (1999) Omnifit cementless total hip arthroplasty. A 10-year average followup. Clin Orthop Relat Res 364:164–174 11. Coathup MJ, Blackburn J, Goodship AE, Cunningham JL, Smith T, Blunn GW (2005) Role of hydroxyapatite coating in resisting wear particle migration and osteolysis around acetabular components. Biomaterials 26(19):4161–4169 12. Sandiford NA et al (2012): Primary total hip arthroplasty with a fully hydroxyapatite coated titanium femoral component: Results at a minimum follow-up of twenty years. Presented at the British Orthopaedic Association annual meeting 13. Yates PJ, Burston BJ, Whitley E, Bannister GC (2008) Collarless polished tapered stem: clinical and radiological results at a minimum of ten years’ follow-up. J Bone Joint Surg Br 90(1):16–22 14. Hook S, Moulder E, Yates PJ, Burston BJ, Whitley E, Bannister GC (2006) The Exeter Universal stem: a minimum ten-year review from an independent centre. J Bone Joint Surg Br. 88(12):1584–90. Avon Orthopaedic Centre, Southmead Hospital, Westbury-on-Trym, Bristol, UK. Erratum in: J Bone Joint Surg Br. 2007 March; 89(3):421 15. Capello WN, Capello WN, D’Antonio JA, Feinberg JR, Manley MT (2003) Ten-year results with hydroxyapatite-coated total hip femoral components in patients less than fifty years old. A concise follow-up of a previous report. J Bone Joint Surg Am 85-A(5):885–889

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Primary total hip arthroplasty with a proximally HA-coated titanium femoral component: results at 10-15-year follow-up.

Registries in both the United Kingdom and Sweden suggest that the popularity of uncemented femoral components is increasing. As this trend progresses,...
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