Introduction

Because of concerns regarding excessive wear and short-term failures attributed to the metal-on-metal bearings, the use of metal-on-metal hip resurfacing arthroplasty (MOMHRA) has been greatly reduced since 2008, despite great mid-term results for well-designed implants and in certain patient populations. The true cause of excessive wear was then unknown. Therefore, identification of true risk factors for the procedure became paramount to refine indications and improve survivorship outcomes.

Recently, monoblock cups have increased in popularity for hip resurfacing and large femoral head total hips. However, there have been no studies specifically evaluating the durability of this type of cup. The purpose of this study was to define the mid-term survivorship of cobalt-chrome alloy, monoblock acetabular components.

A retrospective radiographic review of 426 consecutive hip resurfacings using the ConserveÒPlus prosthesis was performed with specific attention to the acetabular component.

Radiographs were analyzed for cup position, the presence of radiolucencies, cup migration, bead shedding, osteolysis and stress remodeling of the pelvic bone. Kaplan-Meier (KM) survival estimates were calculated using revision for aseptic loosening of the acetabular component as the end point.

Average follow-up was 8.6 years (range 5.4 to 12.3). Mean abduction angle and anteversion angle were 46.6° (± 6.8°), and 21.6° (± 8.6°), respectively. Radiolucent gaps behind the cup from incomplete seating were visible in zone 2 in 16% of cases. These were typically 1 to 2 mm in size and radiographically filled in all but 2 cases. No cups with early lucencies went on to fail. Late radiolucencies developed in zone 1 in 8 cups (1.9%), in zone 2 in 8 cups (1.9%), and in zone 3 in 19 cups (4.5%). Radiolucencies in multiple zones were seen in 6 cups (1.4%).

Small amounts of socket migration (2mm or less) were suspected in 3 cups (0.7%) but each of these has remained stable. There were no cases of bead shedding. Small osteolytic lesions were suspected in 12 hips (2.8%). There were 2 revisions for aseptic loosening of the cup at 5 and 8 years, and one revision for protrusion of the cup through the medial wall 4 days after surgery.

Additionally, one cup at 9 years follow-up is believed to be loose but has yet to be revised. The KM survival estimate was 99.6% at 5 years (95% C.I. 98.4% to 99.9%) and 98.7% at 10 years (95% C.I. 94.5% to 99.7%).

In conclusion, this study demonstrates excellent mid-term survivorship of a cobaltchrome alloy monoblock acetabular component, which matches that of conventional titanium implants. Small early gaps seen behind the cup from incomplete seating do not appear to effect cup survivorship as long as a good peripheral press-fit is obtained. Osteolysis with this prosthesis is rare but does occur.

Ion levels in the serum and urine of patients with metal-on-metal hip resurfacing implants can provide a means to monitor bearing wear. This presentation will discuss the current results, now out to 5 years for the Conserve Plus resurfacing. In particular, the effect of bilateral implantation on ion levels was examined

Forty-eight patients were studied. Forty-three of these cases were initially implanted with a unilateral resurfacing. Nine of these cases subsequently were implanted with a resurfacing implant on the contra-lateral side 4 to 48 months following the first implantation (staged implantations). Five cases had bilateral resurfacings done simultaneously. All surgeries were done in one institution by a single surgeon. Serum and urine samples were collected pre-operatively, and at 4 months, 12 months and annually thereafter. The samples were analysed for cobalt and chromium using atomic absorption spectrometry with a detection limit of 0.3 to 0.03ng/ml respectively. The data were compared between the groups and also correlated with UCLA activity scores, cup angle, BMI and component size.

All patients showed a rise in ions following implantation. The simultaneous bilateral levels were higher at all time periods compared with the staged bilaterals monitored at the same time point for the second hip, for example cobalt serum at 12 month uni = 2.24, simultaneous bilat = 2.53, staged bilat = 2.05ng/ml, and at 4 years uni = 1.20, simultaneous bilat = 2.93, staged bilat = 2.27ng/ml. There was no correlation between ion levels and UCLA activity score, gender, component size or cup angle (but only 4 hips had cups > 55 degrees).

Bilateral metal-on-metal hip resurfacings performed simultaneously resulted in higher levels of metal ions, particularly chromium, compared to staged implantations monitored at the same time periods. With the exception of a small number of outliers, the levels in this group of hip resurfacings were within the range of metal levels reported for other metal-on-metal total hips.

Femoral neck fracture is a common short-term hip resurfacing failure mode, but later term fractures are starting to be reported. The fracture pattern may indicate whether etiology is primarily mechanical or biological¹. This study evaluated fracture patterns in conjunction with histology to determine etiology in a varied group of hip resurfacings.

Central 3mm thick coronal slices were cut from each of 50 cemented and 2 cementless fractured femoral components (27 males, 25 females). Fracture patterns were grouped as: “edge to edge”, “inside head”, “outside” and “edge to outside”¹. Sections were decalcified and processed for routine histology to examine viability and remodelling. Bone viability was judged on the presence of osteocyte nuclei. Components were judged to be unseated if the cement mantle was more than twice the manufacturers recommended thickness. Histological and clinical data were correlated with fracture pattern.

Overall average time to fracture was 6 months (1–85 months). There were 25 “edge to edge”, 12 “inside head”, 4 “outside” and 11 “edge to outside” fractures, which occurred after a median of 2.0, 13, 1.5, and 2.0 months respectively. The majority of the heads were viable, and the fractures occurred through a region of healing bone involving one or both edges. Fifteen heads with a substantial proximal avascular segment fractured at the interface between necrotic and viable bone, typically inside the component. Eleven implants (21%) were considered unseated. All 4 “outside” fractures were found to be unseated. All “inside head” fractures were seated, but 83% (10/12) of them were found to be avascular. The latest failure (85 months) occurred in association with wear-induced osteolysis. Both cementless components fractured early with an “edge to outside” pattern and were found to be substantially avascular.

Avascular heads failed from one month to four years, usually inside the component. Viable heads tended to fracture early through an area of healing bone at or below the rim. Most fractures were technical failure-sand might be avoided with better patient selection and surgical technique.

Introduction: Management of Ficat stage III and IV hip osteonecrosis remains a formidable challenge in regards to long term care. We report a case of a hemiresurfacing arthroplasty lasting 23 years in a patient who received the implant for osteonecrosis associated with corticosteroid use following kidney transplantation. In 1981, a moderately obese, 27-year-old man presented with bilateral osteonecrotic collapse of the femoral heads secondary to heavy immunosuppressive corticosteroid therapy associated with a kidney transplant. The patient had suffered a loss of both kidneys after a bout of severe nephritis that resulted in replacement with a cadaver kidney in 1979. A cemented THARIES (total hip articular replacement with internal eccentric shells) metal-on-polyethylene resurfacing (Zimmer, Warsaw, Indiana) was implanted in the right hip in 1981. At 3 years post-operatively, the patient complained of acute, exacerbated pain in his right hip. The THARIES components were removed for acetabular and femoral loosening and replaced with a total hip replacement.

Surgery: The acetabular cartilage of the other hip was rated intraoperatively as Grade III (no or minimal acetabular cartilage involvement), and was deemed suitable for hemiresurfacing. A 50 millimeter custom cemented titanium shell (Zimmer, Warsaw, Indiana) was implanted using a lateral incision and a trans-trochanteric approach. The patient continued to be assessed by the surgeon on a regular basis, and returned to an active lifestyle while his kidney function continued to be regulated with corticosteroids and imoran. In 1989, eight years following hemiresurfacing, the left hip radiographs showed a reduced joint space, with further new bone in the acetabular fossa, and the patient continued to do well. UCLA hip scores were 9, 9, 10, and 7 for pain, walking, function and activity, respectively compared with 6, 6, 4, and 4 preoperatively. Radiographs taken at 18 years post-operatively showed further narrowing of the joint space, but the patient continued to be asymptomatic. At the 22-year clinic visit, the patient, now 50 years old, complained of slight groin pain, and some minor limitation in his activities, but was still able to walk without any method of support, and able to participate in recreational exercise including swimming, baseball, and weight lifting. The resurfacing hip was revised to a total hip at 23 years post-op and the specimen was submitted for implant retrieval analysis. This involved sectioning the component into three, 3-millimeter thick coronal slices, which were decalcified and routinely embedded in paraffin.

Results: Hematoxylin and Eosin stained sections showed that the bone within the head was osteopenic but viable with areas of healed old necrotic segments of trabeculae which were surrounded by appositional new bone with some focal areas of recently formed woven bone. A fibrous membrane ranging from a few microns to 1.8 millimeters in thickness was present along most of the cement interface and this contained scattered particle-filled macrophages. There were occasional osteoclastic resorption fronts of bone against this membrane, but osteoblasts were also occasionally seen lining the non-membrane surface. The resurfaced head and neck showed remarkable preservation of bone stock. Although there was minimal cement penetration into the bone, either because of lack of initial penetration or from fragmentation of the cement over the years, the component was functionally well fixed. The bone was viable and there were minimal effects of the small amount of titanium metal debris.

Discussion: Studies report osteonecrosis of the femoral head developing in approximately 11% of hips and 20% of patients receiving organ transplants and for young patients conservative methods need to be pursued. While the best choice of treatment for osteonecrosis is not universally agreed upon, the options are limited once collapse of the femoral head has occurred. Treatment for these patients should be based on the progression of the disease, the age of the patient, and the patient’s long-term needs. This patient had a hemiresurfacing and a metal-on-polyethylene resurfacing; the latter succumbed to polyethylene induced osteolysis, but the hemiresurfacing provided good clinical function in a young, normally active patient for 23 years. While it is recognized that hemiresurfacing is not suitable for every patient with osteonecrosis, it remains a treatment option for some patients.

Introduction: Management of osteonecrosis of the hip for Ficat stage III and IV disease remains controversial with the average age of the patients in the mid ‘30’s, and inferior long-term results of THA for this group. Consequently, some surgeons have favored bone-preserving procedures, and hemiresurfacing arthroplasty has been our preferred method of treatment.

Materials and Methods: Fifty-five hips (47 patients) with Ficat Stage II, III, or early IV osteonecrosis treated with hemiresurfacing by a single surgeon (HCA) were reviewed. The average age of the patients was 34 years (range, 18–52) and 74% of the patients were men. Three different resurfacing materials were used over the years: Titanium (11 hips), Alumina (12 hips), and cobalt-chromium (32 hips).

Results: The average follow-up was 13 years (range 2.6–26.5). There were no dislocations, femoral neck fractures, or osteolysis. The average UCLA hip scores for pain, walking, function, and activity improved from 4.8, 5.8, 5.2, and 4.2 to 7.9, 8.7, 7.7, and 5.6, respectively, at last follow-up. The Kaplan-Meier survival estimate was 81.8%, 58.3%, and 44.2% at 5, 10, and 15 years, using any revision as end point. Seventeen hips were converted: 15 for acetabular cartilage wear, one for enigmatic pain at 12 months, and one for sepsis at 3 months. We found no difference in survivorship between component materials (log-rank test; p=0.447).

Discussion: This experience indicates a greater that 80% survivorship at 5 years for this conservative procedure. Four patients have passed the 20-year landmark (one of them was revised at 23 years). The pain and function scores are lower than with THA or modern full resurfacing devices. A shorter duration of symptoms before surgery is favorable to survivorship of the procedure because we believe that articular cartilage is healthier. When necessary, conversion to total hip replacement is similar to a primary THA.

Introduction: The results of total hip arthroplasty and prior hip resurfacing designs with polyethylene in osteonecrosis (ON) have been less satisfactory than for patients with other etiologies. Metal-on-metal resurfacing is bone preserving and permits a wide selection of revision options for young patients.

Methods: From a cohort of 1000 hips of all etiologies, 84 hips (70 patients, average age 40 years), with ON Ficat Stage III (19 hips) and IV (65 hips) were treated with hybrid metal-on-metal resurfacing. There were 81% men and 19% women. One-third of the patients had previous surgeries including core decompression (17 hips), hemi-resurfacing arthroplasty (3 hips), pinning (5 hips), free vascularized fibula graft (2 hips) and Judet graft (1 hip). Seventy-one hips (85%) presented with femoral head defects larger than 1 centimeter.

Results: The average follow-up was 6 years (1-1). The average femoral component size was 46 millimeters. The clinical scores were comparable to that of the rest of the cohort except for the activity score which was lower in average (7.0 vs. 7.5, p=0.0015). Three hips were revised: 2 for femoral loosening at 22 and 61 months, and one for a fracture of the acetabular wall (over reaming in osteopenic bone) with protrusio of the cup one day post surgery. There were no other complications. Radiographic analysis revealed 3 cases of neck narrowing (1 bilateral) and 2 cases of femoral radiolucencies in 3 zones around the metaphyseal stem. The Kaplan-Meier 5-year survival estimate was 97.1% (95% Confidence Interval 88.7 to 99.2). There have been no femoral component loosenings for patients implanted after August of 1997.

Discussion: Our results highlight that the etiology of osteonecrosis itself does not constitute a contraindication for resurfacing despite large defects. Technique is critical in achieving initial femoral fixation and promoting long-term durability.

Introduction: The purpose of the present study was to assess the clinical results of metal-on-metal hip resurfacing for the treatment of hip arthrosis in patients with a BMI of 30 or more.

Materials and Methods: From a consecutive series of over 1000 Conserve® Plus metal-on metal hybrid resurfacings, 148 hips were resurfaced in 138 patients with a BMI of 30 or more at the time of surgery. Average age was 49.4 years (range, 18 to 72) with 88% male. The average weight was 104.6 kg (range 74 to 164) and average BMI 33.4 (30.0 to 46.4). “Idiopathic” OA was the dominant etiology with 80.0%. The femoral metaphyseal stem was cemented in 43 hips and press-fit in the remaining 105. All acetabular components were press-fit.

Results: Average follow-up was 6.2 years (range, 2.0 to 10.2). UCLA hip scores improved significantly (pain: 3.5 to 9.4; walking: 5.9 to 9.5; function: 5.4 to 9.2; activity: 4.3 to 7.1). There were no cases of acetabular or femoral component loosening. 2 hips (1.4%) were revised, 1 for femoral neck fracture and one for acetabular cup protrusio the day after surgery in a bilateral patient with poor bone quality. 3 hips (2.0%) have radiolucencies about the femoral stem. All are asymptomatic and none have progressed for an average of 5.2 years (range 4.5 to 6.8). There were no revisions for any reason and no radiolucencies observed in patients with a BMI of 35 or more (n=27).

Conclusions: Metal-on-metal resurfacing arthroplasty of the hip is performing extremely well in patients with high BMI, in contrast with the results of conventional THR. These results are in agreement with our previous finding that weight is protective of prosthesis durability with resurfacing. This could be explained by a greater fixation area on the femoral side, a greater bone mineral density, and a slightly reduced (but still high) activity level in this patient population compared to patients with a BMI less than 30 (7.1 vs 7.6, p=0.002).

Introduction: ‘Revisability’ has been touted as one of the major advantages of resurfacing arthroplasty of the hip. However, this theoretical advantage has never been clearly demonstrated. The objective of the present study was to test the hypothesis that a failed, modern generation metal-on-metal resurfacing arthroplasty (MMRA) can be converted to a total hip (THA) as easily and with comparable results as a primary (THA).

Methods: Twenty-two failed MMRA’s in 21 patients with an average age of 49.5 years (23 – 72 years) were converted to a THA. In 18 hips, the acetabular component was retained, and in 4 hips both components were revised. The control group of primary THA’s, implanted during the same time period by the same surgeon, consisted of 64 patients with an average age of 50.8 years (27 – 64 years).

Results: There was no significant difference in operative time, blood loss and complication rates between the conversions and the controls. The average follow-up was 47 months (12 – 113 months) for the conversions and 57 months (24 – 105 months) for the controls. Clinical outcomes measures were comparable with average Harris Hip Scores of 92.7 and 90.3 for the MMRA conversions and primary THA’s, respectively. The UCLA activity scores were 6.6 and 6.4 in the conversion group and THA group, respectively. There have been no cases of aseptic loosening of the femoral or acetabular components in either group, and there have been no dislocations after MMRA conversion.

Conclusion: Conversion of failed MMRA to a THA appears to be as safe and effective as a primary THA.

Eighty-three patients (ninety hips) with well-fixed cementless socket retained during revision of a femoral component were reviewed. At revision, 33% of patients had acetabular osteolysis and 52% were grafted. At mean follow-up 9.6 years (5.5 – 15.9) after femoral revision and 14.8 years (7.1–20.2) after primary arthroplasty, survivorship was 96.5% (95% CI, 91.5% to 100%) at five years and 81%(95% CI, 61% to 99%) at ten years after femoral revision. Revision of a cementless acetabular component solely on the basis of the duration that it was in vivo or whether a previous revision had been done does not appear to be warranted.

Removal a well fixed cementless acetabular component can result in an increased operative morbidity. Data that can be used to predict the long-term survival of retained well-fixed cementless acetabular components are therefore needed.

Retention of the well-fixed cementless acetabular component during femoral revision is a predictable technique.

Revision of a cementless acetabular component solely on the basis of the duration that it was in vivo or whether a previous revision had been done does not appear to be warranted.

Eighty-three consecutive patients (ninety hips) in whom a well-fixed cementless socket had been retained during revision of a femoral component were reviewed. Mean patient age was fifty-four. At the time of revision, 33% of the patients had acetabular osteolysis of which 52% were grafted. At a mean follow-up 9.6 years (5.5 – 15.9) after femoral revision and 14.8 years (7.1–20.2) after primary arthroplasty, 94.5% of the sockets remained in place. With any revision as end point, survivorship was 96.5%(95% CI, 91.5% to 100%) at five years and 81%(95% CI, 61% to 99%) at ten years after femoral revision. With failure of cementless socket as end point (i.e. loosening, deficient locking mechanism), survivorship was 100% (95% CI, 100%) and 94% (95% CI, 82%–100%) at five and ten years after femoral revision and 100% (95% CI, 100%) and 94% (95% CI, 82%–100%) at ten and fifteen years after primary arthroplasty. No cases showed recurrence or expansion of pelvic osteolysis. The overall incidence of dislocation was 15%.

Ninety-four hips with a mean patient age 34.2 (range 15– 40) with a metal/metal surface arthroplasty (SA) were reviewed with 71% men and 14% with previous surgery. The Chandler risk index was calculated as well as the SA risk index (SARI). At a mean follow-up three years, three hips were converted at a mean of twenty-seven months (two to fifty), and ten patients had significant radiological changes. Mean SARI for the thirteen problematic hips versus remaining hips was significantly higher, 4.7 and 2.6, respectively (p=0.00). If SARI > 3 the relative risk of early problems is twelve times greater than if SARI ≤3.

The purpose of this study was to evaluate the early outcome of a hybrid metal on metal surface arthroplasty of the hip in patients forty years and younger and identify potential risk factors.

Surface Arthroplasty Risk Index can help identify patients who may be at increased risk of early failure following metal on metal surface arthroplasty.

Proper patient selection and careful surgical technique may minimize early failures with the re-introduction of surface arthroplasty of the hip.

Ninety-four hips mean age 34.2 (range 15– 40) with metal/metal surface arthroplasty (SA) were reviewed with 71% men and 14% with previous surgery. The Chandler risk index was calculated and SA risk index (SARI). Mean follow-up three years (range 2–5), three hips were converted at a mean of twenty-seven months (2–50), and ten patients had significant radiological changes. Mean SARI for these thirteen problematic hips versus remaining hips was significantly higher, 4.7 and 2.6, respectively (p=0.00). The mean angle between the prosthesis stem and femoral shaft in the problematic group was significantly smaller than the remaining hips (p=0.03): 133° and 139°, respectively. If SARI > 3 the relative risk of early problems is twelve times greater than if SARI ≤3.

Fifty-six hips, mean age 40.4 underwent surface arthroplasty (SA) and twenty-eight hips, mean age 37.2 underwent hemiresurfacing (HSR). Diagnosis was osteo-necrosis in all. UCLA hip function and activity score, SF-12 physical, and Harris Hip score were significantly (p< 0.05) better for SA versus HSR. However, 2 SA were revised to THR, and 5 had evidence of femoral loosening. There was no evidence of femoral loosenings in the hemiresurfacing group. The median femoral component size was significantly larger in HSR than SA. Although the functional results are inferior with HSR, patients are at greater risk of femoral loosening with the full surface arthroplasty.

To determine if differences in outcome exist between HSR and MMSA at five years of follow-up in a group of patients with Ficat Stage III and IV osteonecrosis.

Treatment of osteonecrosis of the hip in the young adult still remains a challenge. The continued use of conservative prosthetic solutions should help minimize the morbidity of revision hip surgery.

Although the functional clinical outcome of MMSA is superior to HSR, patients are at greater risk of femoral loosening. Use of a larger femoral component in MMSA may decrease the risk of femoral loosening.

Eighty-four hips with osteonecrosis were treated with a resurfacing implant: fifty-six with a metal-metal SA, mean age 40.4 and twenty-eight, mean age 37.2 with a hemiresurfacing when the acetabular cartilage was minimally damaged. Male/female ratio was 73%/27% for HSR and 87%/13% for MMSA. Mean follow-up of 4.5 years, UCLA hip scores were significantly (p< 0.05) better for MMSA versus HSR for function (9.3 vs. 7.9) and activity (6.8 vs. 5.5) but not for pain (9.3 vs.8.6) and walking (9.5 vs. 9.0). SF-12 scores were comparable for the mental component but significantly better in the MMSA group (48.4 vs. 38.1, p= 0.001) for the physical component. Harris Hip Score was significantly better for MMSA (92.3 vs. 83.3, p=0.001). 2 MMSA were revised to THR, and five presented with evidence of femoral loosening. There was no evidence of femoral loosenings in HSR. Median femoral component size was significantly larger for HSR (50.0 vs. 46.0, p= 0.001).

Legg-Calve-Perthes and slipped capital femoral epiphysis may result in alterations of the proximal femoral morphology, leading to the development of secondary hip osteoarthritis as a young adult. Hip surface arthroplasty presents special technical challenges in these patients because of the abnormal anatomy of the head and neck. We reviewed the radiographic and clinical results of patients with a history of either LCP or SCFE, who underwent hip resurfacing between 1996 and 2002. Twenty-three patients (25 hips, 14 with LCP and 11 with SCFE) underwent metal-on-metal surface arthroplasty. The average age at the time of surgery was 38.1 years and 87% of the patients were male. The mean time to follow-up was 26.9 months. UCLA pain, walking, function, and activity scores improved significantly in both groups as well as the SF-12 physical component scores. One patient with LCP required bilateral conversion to THA at 55 months postoperatively secondary to femoral component loosening. There were no dislocations or femoral neck fractures in this series. Of 11 patients who presented leg length discrepancies preoperatively, limb length was postoperatively equalized in six patients, 3 were maintained with the same amount of discrepancy, and 2 decreased their discrepancy by at least 1 cm. In Charnley Class A patients, there was no difference in femoral offset between the operated and the disease-free, contralateral hip after reconstruction.

Despite the challenges in performing hip resurfacing in this patient population, the results to date have been encouraging. Even with the limitations of resurfacing in restoring leg length and offset, the clinical results of this group of patients are comparable to those of the other etiologies.

The purpose of this study was to present our experience with femoral neck fractures that occurred after metal-on-metal hybrid surface arthroplasty and to assess their causation.

Materials and Methods: A series of 600 metal-on-metal surface arthroplasties was performed from late 1996 to early 2003 by the primary author. Failures during this period were assessed radiographically and with implant retrieval analysis to determine the cause of failure. There were five femoral neck fractures in this series (0.83%).

In addition, a review of the femoral neck fracture cases identified from the Conserve+ Multi-Center IDE was performed (19 femoral neck fractures in 1203 cases, 1.6%).

Results: Lead Author Series: Four of the five fractures occurred at the component–neck junction in the first five months after surgery (average three months). All were associated with a traumatic episode but they also had structural and or technical risk factors, which weakened the constructs. The most important technical deficiency was failure to cover all of the reamed bone with the component in three of the five. One fracture was associated with histological changes consistent with osteonecrosis of the head in a case of overpenetration of cement in very soft bone.

Multi-Center IDE: Additional risk factors were identified among which impingement of the neck with the acetabular component, notching of the lateral femoral neck cortex, and leaving the femoral component proud (not completely seated).

Conclusion: It is important to avoid or at least minimize notching the femoral neck by performing the cylindrical reaming at the recommended angle of 140° and to stop reaming before the reamer touches the lateral cortex. Osteophytes should be judiciously removed only if there is a notable impingement when the hip is at 90° of flexion and internally rotated. We believe that understanding the factors that contribute to femoral neck fracture after surface arthroplasty may reduce the already low incidence of this mode of failure.

Introduction and Aims: To review the medium-term clinical and x-ray results of metal-on-metal Surface Arthroplasty (MMSA) in DDH, using the Conserve Plus™.

Method: Fifty hips (44 patients, avg. age 42.7 years) with DDH were treated with hybrid MMSA. Seventy-five percent were female. Ten percent had prior osteotomies. Twenty-five percent had acetabular cysts that were grafted and 64% had femoral cysts (> 1cm in size) and one was grafted. All cases were Crowe Class 1 or 2. A posterior approach was used in all but one case.

Results: Mean follow-up was 4.9 years (3.8–7.8). UCLA hip scores were 3.2, 5.9, 5.5 and 4.4 pre-op and 9.2, 9.5, 9.4 and 7.1 at last follow-up for pain, walking, function and activity. SF-12 scores normalised. Range of motion was 126.6 degrees, 80.5 degrees and 83.2 degrees at last follow-up for flexion, abduction-adduction, and rotation arcs. Four hips were converted to THA: 2 for femoral neck fracture at two and five months, one for recurrent subluxations due to poor offset and impingement due to prior multiple osteotomies, and one for femoral component aseptic loosening. Four technical complications successfully resolved: one trochanteric non-union, one post-op dislocation (closed reduction), one component mismatch (acetabular component exchange) and one femoral nerve palsy. X-ray analysis: two patients presented complete radiolucencies around the metaphyseal stem.

Conclusion: SA is stable, except for one subluxation due to impingement with poor offset compared to seven to 10% with THA. The socket fixation is secure without adjunct fixation with grafts incorporating whereas prior SA with PE were poor due primarily to socket loosening. Femoral bone preparation is critical to avoid fractures and loosening.

Introduction and Aims: The purpose of the present study was to review the early results and clinical performance of FDA approved large unipolar heads (36mm and greater) used with a metal-on-metal (MM) bearing.

Method: Fourteen stem type prostheses were implanted in 14 patients. There were eight primary THA, and six conversions of surface arthroplasties in which thin-walled (5mm) porous coated MM sockets were maintained. Mean age was 55.4 years (range 30–72 years). There were nine males and five females. Dislocation precautions were discontinued after capsular healing (six weeks). The initial etiology was OA in 78%.

Results: The median head size was 44mm (36–52) and socket size 54mm. Mean follow-up time was 29.1 months (range 12–81). UCLA hip scores improved for pain, walking, function, and activity from 4.8, 6.2, 6.1, and 4.8 pre-operatively to 9.3, 8.5, 7.5, and 5.4 postoperatively. Range of motion normalised. There were no complications.

Conclusion: This investigation shows excellent clinical results, and suggests that dislocation can be avoided by an anatomical THR with the use of large unipolar femoral heads and thin sockets with low wear bearings. The advantage of MM is the ability to manufacture thin shells with porous beads for fixation and preserve ace-tabular bone stock.

Introduction: THR is still the standard of care for young arthritic patients. However, failure rates remain high at 10 years follow-up, with rates of up to 33% in all cemented designs and 10.5% in cementless designs. With the arrival of new, more wear-resistant bearings, Surface Arthroplasty (SA) has become a viable and promising solution for this patient population. The purpose of the present study was to investigate the results of a metal-on-metal (M/M) hybrid SA and identify appropriate criteria for patient selection.

Method: The first 400 hips (of 620) in 355 patients underwent M/M hybrid surface arthroplasty. Mean age 48.2; 73% males, 27% females; 198 Charnley Class A; 139 Class B and 18 Class C. Diagnosis at surgery: OA 64%, DDH 11%, ON 9%, Post-traumatic 8%, Inflammatory arthritis 3%, SCFE and LCP 4%, Melorheostosis 0.3%.

Results: Mean follow-up 5.2 years (3.9–7.8). Average UCLA hip scores post-op: pain 9.4, walking 9.5, function 9.4, and activity 7.7. The SF-12 physical and mental components were respectively, 31.2 and 46.8 pre-op and 50.1 and 53.0 post-op. Fifteen hips were converted to THA (nine in the first 102): two neck fractures, 10 femoral loosenings, one socket protrusio due to over-reaming, one subluxation due to impingement and one sepsis. The three most important risk factors for femoral loosening and radiolucencies were large cyst formation (p=0.0067), female gender (p=0.0001), and lighter weight in male patients (p=0.0003). The occurrence of femoral loosening or lucency was 18% for the first 100 cases, 9% for the second, 8% for the third, and 1% for the last 100 cases.

Conclusion: Clinical results are excellent, despite very high activity levels. The experience with SA of all cemented metal/UHMWPE bearing demonstrated failure rates of 15 to 33% at three years. At longer follow-up, the preliminary experience is encouraging (3.75% failure rate). Dislocation is rare, and acetabular fixation secure. Initial femoral fixation is critical, as the fixation area is small, especially with osteopenia and cystic degeneration. Cementing the femoral metaphyseal stem appears as a meaningful technical improvement towards the prevention of early femoral radiolucencies. None of the 59 cemented metaphyseal stem had any radiolucency at last review.

Introduction and Aims: Legg-Calve-Perthes disease and slipped capital femoral epiphysis are hip disorders that may result in the alteration of proximal femoral anatomy and subsequent osteoarthritis. LCP often results in a flattened head and short femoral neck; SCFE residual deformity is a retroverted head upon a wide femoral neck. Because of the low head to neck ratio and short neck length in these patients, surface arthroplasty is especially technically difficult.

Method: We examined a cohort of patients with either LCP or SCFE who underwent surface replacement of the hip to assess clinical results and identify pre-operative radiographic factors unique to this group. All patients with arthritis of the hip secondary to either LCP or SCFE, who underwent surface replacement between 1996–2002, were included. Proximal femoral anatomy was assessed by measuring the neck and head length, flattening of the head, anterior head offset and lateral head offset. Hip ROM was measured and SF-12 and UCLA Hip scores were calculated.

Results: Fourteen patients with LCP and 11 patients with SCFE had undergone surface replacement with an average age of 38 years; the mean time to follow-up was 26.2 months. Pre-operative radiographs revealed a head-neck ratio of 1.3 in the LCP group and 1.2 in the SCFE group. The amount of head offset was 9.4mm anterior and 6.4mm lateral in the LCP group; and 8.8mm and 4.4mm in the SCFE group. Neck and head length was 42mm in the LCP patients and 56.5mm in the SCFE patients; this measured 46 and 53mm post-operatively. No revisions had been performed in either group. The UCLA scores, SF-12 scores, and hip ROM did not differ from a cohort of patients who had undergone resurfacing for other reasons. No femoral neck fractures occurred in either group.

Conclusion: Despite technically difficult surgeries for hip resurfacing in these patients because of a flattened head and short neck in LCP, and wide femoral neck with retroverted heads in SCFE, the results to date have been good. By taking extra care to avoid notching the neck on the anterior and lateral tension sides, satisfactory results can be achieved.

Introduction and Aims: The purpose of this study was to validate in a clinical series a method to measure femoral component migration in surface arthroplasty based on the principles of EBRA-FCA.

Method: The first 400 hybrid MMSA in 355 patients have an average of 3.5 years follow-up (range two to six years). The average age was 48 years, 73% were men and 35% had secondary osteoarthritis. All patients were evaluated prospectively at three months and then yearly. We reviewed the x-rays of 26 hips that had undergone metal-on-metal resurfacing using EBRA-FCA. Minimum follow-up was 3.5 years. Group 1was free of any clinical or radiographic signs of loosening (17 hips); group 2 had failed from femoral component aseptic loosening (nine hips). Mean age for the whole group was 50.7 years (28–67). Sixty-six percent were male and 63% were operated for osteoarthritis. We recorded migrations of 2mm or greater and the time to initiation of migration.

Results: Group 2 showed significantly greater migration than group 1, respectively: 4.57 mm versus 1.62mm for centre of the head (p=0.005), 4.51mm versus 1.05mm for stem tip (p=0.001). Initial migration was significantly sooner in group 2 versus group 1: 19 months versus 29.2 months (p=0.030). In group 2, the average time to first migration detected with EBRA-FCA was significantly less than time to first clinical symptoms: 19 months versus 29.5 months (p=0.003). More importantly, the time to detection of significant migration was shorter than the time to detection of the first metaphyseal stem radiolucency: 19 months versus 24.3 months (p=0.028).

Conclusion: EBRA-FCA represents a reliable tool to measure migration of femoral component, which may become essential in the assessment of the clinical performance of MMSA. It is best used in large clinical series with standardised x-ray technique and limiting the number of observers.

Introduction and Aims: The importance in assessing clinical outcome is critical in evaluation of total hip replacement. There is now a sufficient body of evidence that activity level is correlated to wear of total hip replacement and wear to the longevity of that implant. The purpose of this study was, using the UCLA activity scale, to evaluate how activity relates to both health-related and disease-specific questionnaires.

Method: One hundred and fifty-two patients who underwent primary hip arthroplasty filled out the health-related questionnaire – SF-12 survey, which has a mental and physical component – with an average score of 50 in the general population for each category. The same day they were clinically evaluated, using the UCLA and Harris hip scoring systems. All patients were evaluated by the same surgeon; at least two years post-surgery, with an average follow-up of 5.2 years. Patient average age at surgery was 52.4, with 66% male. To assess the strength of the relationship between SF-12, UCLA and Harris scores, linear regression analysis was used.

Results: All individual UCLA scores were significantly correlated (p< 0.05) to SF-12 physical component, except for walking. When the single item UCLA activity score was added to Harris hip score, R squared raised from 0.43 to 0.53 in predicting quality of life. The single item Activity from the UCLA scoring system explained 38% of the variability in SF-12 physical component. With the linear regression analysis, all individual UCLA scores were independently significantly correlated (p< 0.05) to SF-12 physical component, except for walking. When the single item UCLA activity score was added to Harris hip score, R squared raised from 0.43 to 0.53 in predicting quality of life represented by the physical component of the SF-12.

Conclusion: Our study has shown that the UCLA activity scale is not only important to assess wear of the bearing surface, but also provides additional information in assessing the clinical outcome of total hip replacement. The single item Activity from the UCLA scoring system explained 38% of the variability in SF-12 physical component and demonstrates the need to integrate activity in outcome measurements after hip arthroplasty.