Total hip replacement with an uncemented Wagner cone stem for patients with congenital hip dysplasia

The Wagner Cone Stem for Atypical Femoral Anatomy in Total Hip Arthroplasty: A Report of 320 Cases with Minimum 5-Year Follow-up

BACKGROUND

The Wagner Cone Prosthesis was designed to address complex femoral deformities during total hip arthroplasty (THA), but its mid-term component survivorship and functional outcomes remain undetermined. The objectives of this study were to determine the implant survivorship, patient satisfaction, functional outcomes, osseointegration as seen radiographically, implant subsidence, and complications of THA using the Wagner Cone Prosthesis stem at intermediate-term follow-up.

METHODS

This study involved 302 patients with proximal femoral deformities, including developmental hip dysplasia and Legg-Calvé-Perthes disease, who underwent a total of 320 primary THAs using the Wagner Cone Prosthesis. The average age at the time of surgery was 49.4 ± 14.5 years (range, 18.8 to 85.6 years). Patient satisfaction was recorded using a self-administered questionnaire assessing satisfaction in 4 domains. The University of California at Los Angeles (UCLA) activity score, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Oxford Hip Score (OHS), the Forgotten Joint Score (FJS), radiographic outcomes, and complications were recorded. The mean follow-up time was 10.1 years (range, 5.2 to 15.5 years).

RESULTS

Survivorship of the Wagner Cone Prosthesis was 98.7% (95% confidence interval [CI]: 97.2% to 100%) with stem revision as the end point and 95.8% (95% CI: 93.5% to 98.2%) with reoperation for any reason as the end point at 10 years postoperatively. In total, 3 stems were revised: 2 for infection and 1 for chronic hip dislocation. The median patient satisfaction score was 95 (interquartile range [IQR], 80 to 100), median UCLA score was 6 (IQR, 6 to 7), median WOMAC score was 18 (IQR, 16 to 22), median OHS was 40 (IQR, 36 to 47), and median FJS was 80 (IQR, 76 to 88) at the time of final follow-up. All Wagner Cone stems that were not revised showed radiographic evidence of osseointegration, with a mean stem subsidence of 0.9 ± 0.8 mm at the most recent follow-up.

CONCLUSIONS

The use of the Wagner Cone Prosthesis stem in patients with complex femoral anatomy undergoing primary THA is associated with excellent component survivorship, high levels of patient satisfaction, good functional outcomes, and reliable osseointegration with minimal stem subsidence as seen on radiographs at intermediate-term follow-up.

LEVEL OF EVIDENCE

Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Single-taper conical tapered stem in total hip arthroplasty for developmental dysplasia of the hip: A long-term evaluation

INTRODUCTION

Conical tapered stems may be useful implants to manage the reconstruction of complex dysplastic anatomies. The aims of this paper were to assess: 1) the preoperative CT features of the dysplastic femurs; 2) survival rates, complications and reasons for revision; 3) the clinical outcomes; 4) the radiographic outcomes of single-taper conical stems in dysplasia (defined as center edge angle < 20°) at a long-term follow-up.

HYPOTHESIS

Monoblock conical stem provides a 10-year survival rate of at least 95%, with excellent clinical outcomes and bony ingrowth.

MATERIALS AND METHODS

In total, 100 THAs in 85 patients (15 bilateral cases) were enrolled. The average age of the patients at surgery was 50.9±11.5 years. Assessment of the native femoral morphology was performed using CT-scan, coronal (neck-shaft angle, offset, center of rotation position) and axial parameters (anteversion, mediolateral and anteroposterior femoral diameters). Clinical (HHS score) and radiological (osseointegration, subsidence and offset reconstruction) outcomes were evaluated at the last available follow-up.

RESULTS

The mean follow-up was 9.34±5.61 years. Severely distorted anatomies from Crowe I to Crowe IV were included, with a mean canal flare of 4.3 and a mean femoral antetorsion of 34°. The survival rates were stable at long-term (98.9% at 10 and 15 years): no aseptic loosening occurred. The mean postoperative HHS was 89.8±6.8 points. Ninety-nine percent of the stems showed bone ingrowth, from 6 months to the last available follow-up. Subsidence occurred in 18% of the cases (mean value: 2.5mm, range: 1-6mm) in the first month, with subsequent stabilization. A mild proximal stress shielding occurred in 28% of the THAs. Radiolucent lines were detected in the 8% of the cases. There was a postoperative loss of offset in 12% of the cases.

DISCUSSION

Conical stems in dysplastic hips achieved bony ingrowth at long-term outcome, even in complex anatomies. Subsidence, proximal stress shielding and imperfect offset restoration may occur with this implant.

LEVEL OF PROOF

IV; retrospective study.

Midterm results of titanium conical Wagner stem with challenging femoral anatomy: Survivorship and unique bone remodeling

BACKGROUND

Complex anatomy of the proximal femur makes total hip arthroplasty (THA) more challenging. Short, straight, fluted and conical titanium stem like the Wagner Cone can be helpful to address small femoral canal, increased femoral neck version, important leg length discrepancy or proximal femoral deformity. The outcome in these patients is less assured and associated with high rate of complications. Therefore, we did a retrospective study aiming to answer: 1) can the Wagner Cone stem provide acceptable mid- to long-term implant survivorship; 2) help minimizing perioperative adverse events; 3) produce favorable clinical outcome measured by WOMAC score; and 4) be associated with a favorable radiographic femoral bone remodeling at the last follow-up?

HYPOTHESIS

Wagner Cone stem is an advantageous solution for the distorted proximal femur in complex THA.

PATIENTS AND METHOD

Our cohort was derived from the patient registries where medical records of 88 patients (103 hips) who underwent primary THA using the Wagner prosthesis were retrospectively reviewed. Then, data was analyzed for patients' demographics and surgical data, and comparing preoperative, immediate postoperative and last follow-up data. Eleven patients (12 hips) were excluded (7 hips followed up less than 2 years or lost to follow-up, 3 hips that had the Wagner stem for revision and 2 Wagner stems inserted for periprosthetic fracture). This left 77 patients (91 hips) with Wagner cone stems implanted for more than 2 years between March 2003 and February 2017 by 7 surgeons in 3 academic hospitals. Implant revision, reoperations, WOMAC score and radiographic analyses were recorded at last follow-up.

RESULTS

After a mean follow-up of 7.8 (range, 2.0-16.2) years, Wagner stem survivorship was 98.9% (95% CI: 94 to 100%) with one (1.1%) stem revision for failure of osteointegration. Five (5.5%) acetabular revisions, one for aseptic loosening, 2 for adverse reaction to metal debris and 2 for infection. One (1.1%) sciatic neuropathy and 4 (4.4%) intraoperative fractures were encountered. The mean WOMAC score was 90.5±11.4 (59-100). Radiographic analysis showed clear signs of stem osseointegration and hypertrophic bone remodeling in 82 cases (92.1%).

CONCLUSIONS

Used in complex cases with proximal distorted femurs, the Wagner Cone stem demonstrated a low complication rate, a high-rate consistent adaptive bone remodeling, excellent clinical results, and midterm survival. It is a safe, reliable and advantageous option in complex primary THA. However, the contribution of the underlying cause of the secondary osteoarthritis on the long-term survival of the stem remains to be demonstrated.

LEVEL OF EVIDENCE

IV; retrospective study.

Outcome of the Wagner Cone femoral component for difficult anatomical conditions during total hip arthroplasty

PURPOSE

Total hip arthroplasty (THA) in patients with small or unusual proximal femoral anatomy is challenging due to sizing issues, control of version, and implant fixation. The Wagner Cone is a monoblock, fluted, tapered stem with successful outcomes for these patients; however, there is limited information on subsidence, a common finding with cementless stems.

METHODS

We retrospectively reviewed our cases using the modified Wagner Cone (Zimmer, Warsaw, IN) implanted over a 13-year period (2006-2019) in patients with small or abnormal proximal femoral anatomy. We performed 144 primary THAs in 114 patients using this prosthesis. Mean follow-up was 4.5 ± 3.4 years (range, 1-13 years). Common reasons for implantation were hip dysplasia (52%) and osteoarthritis in patients with small femoral proportions (22%). Analysis of outcomes included assessment of stem subsidence and stability.

RESULTS

Survival was 98.6% in aseptic cases; revision-free survival was 97.9%. Femoral subsidence occurred in 84 cases (58%). No subsidence progressed after 3 months. Of those that subsided, the mean distance was 2.8 ± 2.0 mm. There was less subsidence in stems that stabilized prior to six weeks (2.2 ± 1.4 mm) compared to those that continued until 12 weeks (3.9 ± 1.6, p = 0.02). Harris Hip, UCLA, and WOMAC scores significantly improved from pre-operative evaluation (p < 0.001*, p < 0.003*, p ≪ 0.001*); there was no difference in outcome between patients with and without subsidence (p = 0.430, p = 0.228, p = 0.147).

CONCLUSION

The modified Wagner Cone demonstrates excellent clinical outcomes in patients with challenging proximal femoral anatomy. Subsidence is minor, stops by 3 months, and does not compromise clinical outcome.

Mid-term outcomes of the Wagner Cone Prosthesis™ stem for developmental dysplasia of the hip: minimum two year follow-up

PURPOSE

Treatment of symptomatic developmental dysplasia of the hip (DDH) requires a technically demanding total hip arthroplasty (THA) reconstruction. In patients with DDH, prostheses can be difficult to implant and often face the risk of fracture, mismatch, and loosening. The Wagner Cone Prosthesis™ is a tapered, conical stem which can improve treatment success in this population. We look at midterm survivorship and outcomes of THA for DDH using the Wagner Cone Prosthesis™.

METHODS

We retrospectively analyzed 28 patients (33 hips) with DDH undergoing THA using the Wagner Cone Prosthesis™ between January 2008 and January 2020. Ten, nine, and fourteen included patients were classified as Hartofilakidis A, B, and C, respectively. Survivorship according to Kaplan-Meier analysis was the primary outcome, with re-operation and revision as endpoints. The Oxford hip score (OHS) was used to assess clinical outcome. We used multivariate analysis to determine predictors of poor outcomes. The average follow-up was 4.6 years, with a minimum of two years.

RESULTS

Kaplan-Meier survivorship over the 13-year study period was 93.9 ± 4.2% for all-cause revision as an endpoint and 96.9 ± 3.1% for stem revisions only. The overall reoperation rate was 6.1%, with periprosthetic fracture and dislocation being reasons for re-operation. No patients were revised for aseptic loosening, and no patients were revised for subsidence. OHS improved from 19.3 ± 9.6 (4-39) pre-operatively to 37.6 ± 8.4 (19-48) at latest follow-up (p < 0.05).

CONCLUSION

In patients with DDH, THA with the Wagner Cone Prosthesis™ demonstrates excellent clinical, radiographic, and patient-reported functional outcomes at midterm follow-up.

Total Hip Arthroplasty With the Wagner Cone Femoral Stem in Patients With Crowe IV Developmental Dysplasia of the Hip: A Retrospective Study

BACKGROUND

The aim of this study is to assess treatment of Crowe type IV hip dysplasia with the Wagner cone femoral stem combined with transverse subtrochanteric shortening osteotomy and augmenting the osteotomy site using the intercalary segment as a strut autograft.

METHODS

One hundred twenty-seven hips of 91 patients diagnosed with Crowe type IV hip dysplasia and treated with total hip arthroplasty using the Wagner cone stem combined with transverse subtrochanteric shortening osteotomy were retrospectively evaluated by clinical and radiographic outcomes as well as complications.

RESULTS

The mean follow-up was 8.4 years. The Harris Hip Score and the Western Ontario and McMaster University Osteoarthritis Index scores were significantly improved postoperatively (P = .000). Intraoperative femoral cracks were observed in 70 hips (55.1%) and all femurs healed smoothly. Femoral cracks did not have a significant effect on clinical outcomes, except for heterotopic ossifications (P = .032). The probability of 10-year survivorship of the components free of revision for any reasons as end point was 94.5%; when only the femoral components were considered the survivorship was of 96.9%.

CONCLUSION

Transverse subtrochanteric shortening and augmenting the osteotomy site using the intercalary segment of bone resected from the shortened femur with the Wagner cone stem is an effective and reliable technique in the management of total hip arthroplasty in Crowe type IV hip dysplasia. Stable and firm placing of the femoral component which leads to an increased frequency of intraoperative femoral cracks does not have an unfavorable effect on clinical and radiological outcomes.

Clinical Outcomes of Conical Hip Prosthesis Used In Primary Total Hip Arthroplasty

INTRODUCTION

Congenital dysplasia of the hip, presence of intramedullary bony pedestals, and related pathologies present unique challenges to the orthopaedic surgeon when considering total hip arthroplasty (THA). In these circumstances, a conical prosthesis has proven to be effective. The purpose of this study is to report the short-term radiological and clinical outcomes of the Wagner Cone Prosthesis® (Zimmer Biomet, Warsaw, Indiana) utilized for a range of etiologies at a major North American healthcare system.

MATERIALS AND METHODS

A retrospective study was performed at a single healthcare system between 2007 and 2018. Demographic variables, including age, sex, and laterality, as well as surgical variables, including femoral head size, neck-shaft angle, stem diameter, surgical approach, and indication for THA, were collected for each hip. Radiographs were also examined for subsidence, limb length discrepancy (LLD), and Crowe classification if the hip was dysplastic.

RESULTS

Thirty-one THAs were performed using a Wagner Cone Prosthesis®. No intraoperative or postoperative implant-related complications were reported. Fourteen hips were dysplastic, and of these, 10 were classified as Crowe I, one as Crowe II, two as Crowe III, and one as Crowe IV. No implant was observed to have subsidence greater than 1cm. The average LLD following arthroplasty was 1.38mm ± 9.4mm shorter than the contralateral side.

CONCLUSION

The Wagner Cone Prosthesis® serves as a useful implant for THA. In our sample, it had excellent survivorship, impressive postoperative radiographic measurements obtained from most recent follow up, minimal mean subsidence, and minimal complication rates.

Cementless total hip arthroplasty for failed treatment of subtrochanteric fracture

Background

Failed treatment of subtrochanteric fractures commonly leads to pain, limping, and poor limb function. Cementless total hip arthroplasty (THA) could serve as an efficient salvage procedure in such cases. This study aimed to evaluate the outcomes and complications of salvage THA in failed subtrochanteric fracture fixation cases.

Methods

From January 2001 to December 2017, cementless THA for failed treatment of subtrochanteric fractures was performed in 18 hips of 11 men and 7 women (average age, 74 years; age range, 57.0–89.0 years). Patients were followed up for clinical and radiological assessments in terms of implant survival and complications after a minimum follow-up of 2 years. The Wagner femoral stems (Zimmer, Warsaw, USA) were used in all 18 patients (100%), with the long-length stem (Wagner SL stem) and standard-length stem (Wagner cone stem) used in 11 and 7 patients, respectively.

Results

The mean follow-up period was 5.2 years (range: 2.2–10.8 years). The mean Harris hip score (HHS) was 38.2 (range: 24–56) preoperatively and 85.4 (range: 79–92) at the last follow-up. The mean postoperative limb length discrepancy was 6.4 mm (range: 4–9 mm). Only one patient underwent revision due to bone in-growth failure of the femoral stem. One patient had an episode of postoperative dislocation and was treated with closed reduction without reoccurrence. Delayed union of the fracture site occurred in one patient. Patients who were previously treated with an intramedullary nail had a significantly shorter surgical duration, lesser intraoperative blood loss, and fewer blood transfusions than those who were previously treated with plate and screws. Kaplan–Meier survival rate with an endpoint of revision was 94.4% (95% confidence interval 72.7–99.9) at 5 years.

Conclusion

Our results indicate that cementless THA is a beneficial and effective procedure for salvaging the failed treatment of subtrochanteric fractures. The Wagner conical prosthesis has shown satisfactory function outcomes, stable fixation, and survival rate for these complex situations. However, attention should be paid to increased operation time, blood loss, and complications when performing THA for subtrochanteric fractures with failed fixation devices especially, plates and screws.

Ten-year results of 55 dysplasia hips of hip offset and leg length reconstruction in total hip arthroplasty with cementless tapered stems having a high offset option designed for dysplastic femur

PURPOSE

In developmental dysplasia of the hip (DDH), the centers of hip rotation move in the superior and lateral direction. In total hip arthroplasty for such cases, movement of the center of hip rotation is in the inferior and medial direction. It causes an increase in leg length and a decrease in acetabular offset. We therefore evaluated the change of hip offset and leg length before and after surgery with two stems having a high offset option.

PATIENTS AND METHODS

The preoperative diagnosis was secondary osteoarthritis due to DDH excluded Crowe IV. A stem selection was decided based on preoperative two-dimensional templating. Total 55 hips in 50 patients were followed up for minimum 10 years. Pre- and postoperative clinical evaluations were performed using a hip joint function scoring system. Radiographic evaluations were used for offset and leg length measurements and other associated factors.

RESULTS

Both stems showed excellent clinical results. A high offset option was used in 60% of all cases. No postoperative dislocations were observed. The biological fixation was stable in all cases. The hip offset was restored without excessive leg lengthening in most cases.

CONCLUSION

Anatomical consistency could be maintained by using a stem which matched geometry of the proximal part and had offset option. These cementless tapered stems having a high offset option are suitable for Crowe I to III hip dysplasia if two-dimensional X-ray templates fit the shape of the proximal femurs. They were associated with excellent clinical results and biological fixation. The offset option may be useful to adjust leg length and offset in DDH patients.

Total Hip Arthroplasty With a Monoblock Conical Stem in Dysplastic Hips: A 20-Year Follow-Up Study

BACKGROUND

Total hip arthroplasty in patients with hip dysplasia is challenging as a result of complex anatomic deformities in the hip. The aim of the study was to evaluate the survivorship, the clinical and radiographic outcomes of cementless Wagner Cone stem in patients with dysplastic hip.

METHODS

This retrospective study reports on 102 patients (135 hips) who have undergone total hip arthroplasty between 1993 and 1997. The mean age of patients was 51 years (range, 21-73). Minimum follow-up was 20 years. According to the Crowe classification, 38 hips presented dysplasia of grade I, 41 of grade II, 37 of grade III, and 19 of grade IV.

RESULTS

Kaplan-Meier survivorship for aseptic loosening was 97% (95% confidence interval, 94.4-99.6) at 20 years. The average Harris hip score increased from 43.4 points (range, 22-51) to 86.4 points (range, 39-100) (P < .0001) and average Merle d'Aubignè score increased from 8.4 (range, 4-13) to 15 (range, 5-18) (P < .0001); at the last follow-up, average University of California at Los Angeles activity score and visual analog score were 4.53 (range, 1-9) and 1.25 (range, 0-6), respectively; 17% of heterotopic ossification and 19.2% of radiolucency lines around the stem were reported.

CONCLUSION

Monoblock Wagner Cone stem is a reliable option in dysplastic hip with an excellent survivorship and good clinical and radiographic outcome in the long term.

Comparison of two different on-shelf femoral stems for Crowe type IV developmental dysplasia of the hip

Objective

This study was performed to evaluate the proximal anatomical compatibility of stems for treatment of Crowe IV developmental dysplasia of the hip (DDH) using a previously developed three-dimensional comparison technique.

Methods

Patients with Crowe IV DDH who underwent computed tomography were retrospectively analyzed. The femoral medullary canals were three-dimensionally reconstructed, and models of cementless modular (S-ROM; DePuy Synthes) and conical (Wagner Cone; Zimmer Biomet) implants were used for virtual implantation. The negative point percentages (NPPs) were applied to verify fitting. The average distance (deviation) and the root mean square of the distance (RMSd) were used to quantify geometric compatibilities.

Results

Four (16.7%) and 12 (50.0%) femoral medullary canals could not be fitted properly with either the modular or conical implant. The NPPs in the distal comparison region were significantly greater in the conical than modular group. The deviation was significantly smaller in the modular than conical group. The RMSd was also significantly smaller in the modular than conical group.

Conclusions

Compared with conical implants, modular implants might be more effectively used in patients with Crowe type IV DDH. However, some Crowe IV DDH femurs with severe deformity cannot be fitted with either of these two on-shelf implants.

Wagner Cone Midterm Survivorship and Outcomes

BACKGROUND

Total hip arthroplasty (THA) in patients with abnormal proximal femoral anatomy requires an individualized treatment approach to prevent complications. Metaphyseal engaging stems in this population risk fracture, size/offset mismatch, and aseptic loosening. The Wagner conical femoral implant is a short diaphyseal engaging femoral stem that could improve treatment success in this difficult patient population.

METHODS

We identified 302 consecutive patients undergoing THA using the Wagner cone femoral prosthesis between January 2010 and January 2017. Clinical, radiographic, and patient-reported outcomes were obtained through chart review and radiographic measurements of postoperative X-rays. We used multivariate analysis to determine predictors of poor outcomes. Kaplan-Meier curves were created to demonstrate implant survivorship with reoperation and revision as endpoints. The average follow-up was 3.2 years, with a minimum of 2 years.

RESULTS

The implant retention survival rate during the 3.2-year study period was 98.7%. The overall reoperation rate was 4.2%, with infection followed by fracture being the most common reasons for reoperation. No patients were revised for aseptic loosening, and no patients were revised for subsidence. The average subsidence was 1.1 mm. The Harris Hip Score improved from 48.6 ± 7.3 (range, 28-64) preoperatively to 86.1 ± 8.5 (range, 66-100) at latest follow-up. The patient-reported satisfaction rate was 98.3%.

CONCLUSION

The Wagner cone femoral prosthesis demonstrated excellent clinical, radiographic, and patient-reported functional outcomes at midterm follow-up. We recommend use of the Wagner cone in THA patients with challenging proximal femoral anatomy, small femoral diameter, or poor metaphyseal bone quality.

[Total hip arthroplasty with Wagner Cone stem and subtrochanteric shortening osteotomy in treatment of Crowe developmental dysplasia of hip in adults]

Objective

To investigate the short-term effectiveness of total hip arthroplasty with Wagner Cone stem combined with subtrochanteric shortening osteotomy for adult patients with Crowe Ⅳ developmental dysplasia of the hip (DDH).

Methods

A clinical data of 18 patients (20 hips) with Crowe Ⅳ DDH between January 2015 and June 2017 was retrospectively analyzed. There were 5 males (6 hips) and 13 females (14 hips), with an average age of 42 years (range, 20-67 years). There were 18 cases with unilateral DDH and 2 cases with bilateral DDHs. The "4" sign and Trendelenburg sign of affected hip were positive. Preoperative Harris score and visual analogue scale (VAS) score were 41.95±6.90 and 5.05±1.15, respectively. The length discrepancy was (4.76±2.59) cm in patients with unilateral DDH. And the lengths of bilateral lower limbs in patients with bilateral DDH were equal. The acetabular anteversion angle, femoral anteversion angle, and combined anteversion angle were (32.82±2.79), (46.18±6.80), and (79.01±7.54) °, respectively. All patients were treated by total hip arthroplasty with Wagner Cone stem and subtrochanteric shortening osteotomy. The length of osteotomy ranged from 2.0 to 3.5 cm (mean, 2.38 cm).

Results

The operation time was 116-161 minutes (mean, 138.4 minutes); the volume of intraoperative blood loss was 600-1 200 mL (mean, 795 mL); the volume of drainage after operation was 100-630 mL (mean, 252 mL). All incisions healed by first intention. The symptom of sciatic nerve injury occurred in 1 case and relieved after symptomatic treatment. All patients were followed up 12-29 months (mean, 18.4 months). The "4" sign and Trendelenburg sign of affected hip were negative. The Harris score and VAS score at last follow-up were 87.50±5.06 and 0.75±0.85, respectively. The acetabular anteversion angle, femoral anteversion angle, and combined anteversion angle were (16.21±4.84), (18.99±2.55), and (35.20±5.80)°, respectively. There were significant differences in above indexes between pre- and post-operation ( P<0.05). The length discrepancy was (0.72±0.70) cm in patients with unilateral DDH, which was significant shorter than the preoperative value ( t=7.751, P=0.000). And the lengths of bilateral lower limbs in patients with bilateral DDH were equal. X-ray films showed that the osteotomy of femur healed at 3-6 months (mean, 4.1 months) without the signs of loosening, sinking, osteolysis, and dislocation.

Conclusion

Total hip arthroplasty with Wagner Cone stem and subtrochanteric shortening osteotomy can obviously improve the hip joint function and restore the length of lower limb. The short-term effectiveness is satisfactory, but the long-term effectiveness and survival rate of prosthesis need to be further observed.

Current concepts in developmental dysplasia of the hip and Total hip arthroplasty

Developmental dysplasia of the hip (DDH) is a spectrum of pathology that involves dysplasia of both the acetabulum and the femur. If left untreated, it can develop to hip pain and osteoarthritis, which eventually require total hip arthroplasty (THA). A broad array of anatomical abnormalities of the acetabulum and femur, plus the younger age of DDH patients make THA a great challenge. Meticulous operation planning with various options is one of the most important prerequisites of a successful THA. This review presents the current concepts of acetabular and femoral reconstruction in THA for DDH, including high hip center, acetabular bone deficiency, highly porous metal, correction of femoral anteversion, femoral shortening osteotomy, stem selection, among others.

Challenging Implantation of Hip Prosthesis in a 32-year-old Patient with Kniest Syndrome

INTRODUCTION

Kniest dysplasia is associated with short body stature (dwarfism) and impairment of the musculoskeletal system due to a mutation in the COL2A1 gene coding for a protein that forms type II collagen. Hip endoprosthesis for patients with Kniest system requires a specific femoral shaft design since the medullar space is limited due to the underlying dysplasia. The Wagner cone stem has shown excellent results. It is especially suitable for patients with small or dysplasic femur. However, no data exist regarding hip endoprosthesis in a patient with Kniest syndrome.

CASE REPORT

A 32-year-old female patient with Kniest syndrome presented at our department with a painful pseudarthrosis after femoral valgisation osteotomy 8 years ago. A Wagner cone stem and acetabular roof cup with a cemented Ecofit cup 2M (dual-articulation acetabular cup system) were implanted due to a dysplastic femur with a small medullary space. The Ecofit cup itself is associated with a reduced risk of dislocation. The patient was satisfied with the range of motion after hip endoprosthesis and reported a significant increase in quality of life. The patient is still comfortable with the hip prosthesis at the most recent follow-up 4 years after implantation. Follow-up radiographs over 4 years have not revealed any signs of loosening or migration, and no Trendelenburg sign was reported for the affected side.

CONCLUSION

The Wagner cone stem provides a good solution in challenging femora caused by previous osteotomies, fractures, or dysplasia. Additional stability of hip prosthesis can be achieved using a dual articulation acetabular cup system. Furthermore, we applied an attachment tube based on the concept of tumorprosthesis where the abductor muscle group got reattached.

Is a short stem suitable for patients with hip dysplasia? A report on technical problems encountered during femoral reconstruction

INTRODUCTION

A wide variety of stems have been used for the treatment of osteoarthritis secondary to advanced hip dysplasia. Since evidence for using short stems in dysplastic hips is limited, we planned to analyse the technical problems encountered when reconstructing the proximal femur of patients with osteoarthritis secondary to congenital dysplasia of the hip treated with total hip arthroplasty (THA) using a type 2B short stem.

METHODS

We prospectively analysed 17 patients (22 hips) treated with primary THA performed with a single-branded short uncemented stem with metaphyseal fixation (MiniHip™; Corin). We excluded cases in which other type of stems were used, or in which retrospective data was only available. Mean follow-up was 41.22 months (minimum 24). We analysed clinical outcome using the modified Harris Hip Score (mHHS) and pain using the visual analogue scale (VAS). Radiographs were examined in order to determine causes of complications and revision surgery.

RESULTS

All patients showed statistically significant improvement when preoperative and postoperative values for mHHS (54.19 vs. 94.57; p = 0.0001) and for pain VAS (8.71 vs. 0.71; p = 0.0003) were compared. No cases of thigh pain, instability or infection were found. 1 case of acetabular cup loosening and 1 case of periprosthetic fracture were diagnosed at 8 months and 45 days, respectively. Overall survival was 84.7% at 5 years (CI 95%, 64.4-105.3) with revision for any reason as an end point. When stem performance was separately evaluated, it showed a survival rate of 100% at 5 years with revision for aseptic loosening as an end point.

CONCLUSIONS

THA with a type 2B short stem for the treatment of dysplastic osteoarthritis showed very few technical intraoperative problems, being a useful alternative for femoral reconstruction.

Long-term survival of the cemented Müller CDH stem: a minimum follow-up of 10 years

INTRODUCTION

Total hip arthroplasty in patients with altered anatomy of the hip and femur, such as in congenital dysplasia of the hip, is challenging and often requires specially designed stems. Müller straight stems have shown excellent long-term results; however, long-term data on the analogous cemented Müller CDH stem are still missing. The aim of this study was to analyze long-term survival, identify potential risk factors for aseptic loosening, and analyze radiological outcome of the cemented Müller CDH stems.

MATERIALS AND METHODS

Between 01/1985 and 06/2005, 95 Müller CDH stems (Zimmer, Winterthur, Switzerland) made up of 3 different materials were cemented using 2 different bone cements: 38 of stainless steel/high-viscosity cement, 31 of a cobalt-chrome-based alloy (CoCr)/low-viscosity cement, and 26 of a titanium-based alloy (Ti)/low-viscosity cement. All patients had a prospective clinical and radiological follow-up according to the standards of our institution. The cumulative incidence for revision of the stem was calculated using a competing risk model. To identify demographic and implant-related risk factors for aseptic loosening of the stem, a multivariate regression model for competing risks was performed.

RESULTS

The cumulative risk of revision at 15 years was 12.5% (95% CI 6.6-20.5%) for aseptic loosening of the stem as endpoint, with marked differences for the various stem materials used: stainless steel 2.7% (0.2-12.3%), CoCr 12.9% (4.0-27.3%), and Ti 24.5% (9.6-43.1%). Regression modeling revealed that Ti stems in combination with low-viscosity cement (HR 10.2) and implantation with an axis deviation greater than 3° (HR 3.8) are risk factors for aseptic loosening.

CONCLUSIONS

Long-term survival of the cemented Müller CDH stem is comparable to other Müller-type straight stems and uncemented implants. Similar to the original Ti Müller straight stem, the Ti Müller CDH stem also showed an increased risk for aseptic loosening and should, therefore, no longer be used.

Developmental hip dysplasia treated by total hip arthroplasty using a cementless Wagner cone stem in young adult patients with a small physique

BACKGROUND

Developmental hip dysplasia (DDH) may lead to severe acetabular and femoral abnormalities that can render total hip arthroplasty (THA) challenging, especially in DDH patients with a small physique. Most conventional cemented or cementless femoral components are often difficult to implant in the narrow femoral canal and require slight version correction during surgery. The aim of this study was to present the mid-term results of THA in the treatment of DDH patients with a small physique using a cementless Wagner cone prosthesis (Zimmer®, US).

METHODS

Between January 2006 and March 2010, we retrospectively reviewed 50 patients who were treated at our center. A total of 50 patients (52 hips; 45 women, five men; mean age 32.5 years; range 27 to 38 years) who underwent THA were observed. The mean femoral medullary canal dimension at the isthmus was 7.6 mm (range 6.0 to 8.7). According to the Crowe classification, 19 hips presented dysplasia of grade I, while 33 presented dysplasia of grade II. All patients were treated with THA using a cementless Wagner cone prosthesis. Clinical and radiologic evaluations were performed on all patients.

RESULTS

The mean duration of follow-up was 7.7 years (range 5.4 to 10.5). The Harris hip score (HHS) improved from 63 ± 9 (range 55 to 70) pre-operatively to 92 ± 8 (range 88 to 100) at the last follow-up. The HHS at the most recent follow-up was excellent in 66% of patients (34 hips), good in 26% (14 hips), fair in 6% (3 hips), and poor in 2% (1 hip). Radiographic evaluation demonstrated excellent osteointegration of the implants. Stem subsidence was present in three stems, and the range of stem subsidence was 2 mm in two stems (3.9%) and 3 mm in one stem (1.9%). Femoral osteolysis was observed in nine hips (18%) in the proximal zones, and no distal osteolysis was noted. Heterotopic ossification was observed in three hips (5.8%); of these, two were classified as Brooker's grade 1, and one was classified as Brooker's grade 2 at the most recent follow-up. None of the implants were revised.

CONCLUSIONS

Based on the tapered shape and free setting of anteversion, the Wagner cone femoral stem facilitates its implantation in dysplastic hips. Therefore, this series of short stems with a smaller diameter can ensure safe implantation in narrow medullary canals, especially in young DDH patients with a small physique.

TRIAL REGISTRATION

Registration Number: ChiCTR-ORC-17011181 . Reg Date: 2017-04-19 00:44:59 Retrospective registration.

Can a Conical Implant Successfully Address Complex Anatomy in Primary THA? Radiographs and Hip Scores at Early Followup

BACKGROUND

Total hip arthroplasty (THA) in patients with small or abnormal proximal femoral anatomy is challenging as a result of complex anatomic deformities in the hip. It is unclear which stem is the most appropriate for these patients. One possible implant design that may help meet this need is the modified Wagner Cone prosthesis, whose design consists of monoblock cone with splines; however, to our knowledge, no clinical results have been published using this implant.

QUESTIONS/PURPOSES

We evaluated the hip scores and radiographic results (including signs of osseointegration and subsidence) of complex primary THA using the modified Wagner Cone cementless femoral component in patients with small or abnormal proximal femoral anatomic proportions.

METHODS

Between 2006 and 2011, we performed 59 THAs on patients whose femoral geometry precluded the use of standard-sized implants. Of these, 49 (83%) received the modified Wagner Cone prosthesis. During this time, our indications for use of the Wagner Cone implant in such patients included: femoral neck retroversion, excessive anteversion of the femoral neck, or small proximal femora not suitable for standard implants. Of those, 40 patients with 49 THAs were available for radiographic and clinical followup at a minimum of 3 years, and no patients were lost to followup. The diagnosis included developmental dysplasia of hip (22 patients, 28 hips), secondary trauma or posttuberculosis osteoarthritis (nine patients, 10 hips), and hip disease secondary to other disorders (eight patients, nine hips) and osteonecrosis (one patients, two hips). Two versions of the stem with 135° (28 hips) or 125° (21 hips) neck angle versions were used to reestablish normal hip biomechanics. Version angle was chosen based on preoperative templating. Cementless cups with screws were used for the acetabulum. Mean followup was 4 years (range, 3-7 years). Study endpoints were the Harris hip score and radiographic evaluations by a surgeon not involved in the clinical care of the patients (QZ); radiographic analysis included evaluating for the presence or absence of signs of osseointegration (including Engh's criteria) and subsidence.

RESULTS

The Harris hip score improved from a mean of 41 ± 9 preoperatively to a mean of 85 ± 10 at last followup (p < 0.01). The mean vertical subsidence was 1.5 ± 1.1 mm. Radiographic evaluation demonstrated stability (no further subsidence) of all implants at last followup. Endosteal spot welds were found in 32 hips (65%). No progressive radiolucencies were observed. One patient (one hip) underwent revision surgery as a result of late infection; no other revisions were performed.

CONCLUSIONS

The modified Wagner Cone femoral stem has provided improvements in hip scores and promising short-term radiographic results at short-term followup in complex cementless THA associated with abnormal or small femoral anatomical proportions in which standard implants are inappropriate. Longer followup will be needed to see if these results endure. Randomized trials are needed to determine the optimal stem design for these patients.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

MODULUS Stem for Developmental Hip Dysplasia: Long-term Follow-up

Between October 2001 and December 2010, 143 patients with developmental dysplasia underwent hip arthroplasty surgery using a conical stem with modular necks (MODULUS system, Lima Corporate, Villanova di San Daniele del Friuli, Italy). Thirty (21.0%) patients had both hips replaced, for a total of 173 implants. The mean age at the time of surgery was 55 years (range: 22-81 years). The mean follow-up was 87 months (range: 36-146 months); average Harris Hip Score increased from 42 (range: 23-65) preoperatively to 92 (range: 76-100) at the last follow-up. Stem revision was required in two cases. The MODULUS stem showed good long-term clinical and radiographic results, with a Kaplan-Meier survivorship of 97.6% (95% CI: 94.8-100.0%) at 8 years.

Total hip arthroplasty with a non-modular conical stem and transverse subtrochanteric osteotomy in treatment of high dislocated hips

Conventional stems may be unsuitable for hypoplastic femurs associated with severe dysplasia, meanwhile, custom-made or modular stems in total hip arthroplasty are often complex and expensive. This series included 21 Crowe type IV dysplastic hips in which a non-modular cementless conical stem was implanted with transverse subtrochanteric femoral osteotomy. Follow up averaged 40months. Twenty hips survived with mean Harris hip score improved from 52 to 90. One hip failed for stem loosening. The average leg lengthening was 3.8cm with transient sciatic nerve palsy occurring in three hips. Femoral offset averaged 3.3cm postoperatively. The non-modular conical stem not only obviated the complexities, high medical cost and potential risk at the neck-stem interface associated with stem modularity, but also simplified surgical technique.

The ratio of femoral head diameter to pelvic height in the normal hips of a Chinese population

OBJECTIVE

The aim of this study was to determine whether the ratio between the femoral head diameter and pelvic height in a Chinese population is the same as that found in Westerners.

MATERIALS AND METHODS

Standard pelvic radiography was performed on a group of 187 Chinese adult subjects consisting of 81 males and 106 females with a mean age of 40 years (21-68 years). Femoral head diameter (vertical distance from the femoral head-neck junction to the highest point of the femoral head) and pelvic height (vertical distance from the highest point of the iliac crest to the edge of the ischial tuberosities) were measured.

RESULTS

There were significant differences between males and females (p < 0.001), and between persons of high height versus low height (p = 0.011) and medium height (p = 0.039). There were no significant differences between persons of different age (p = 0.244), body mass index (p = 0.091), or between persons of low- and medium-height groups (p = 0.69). The overall mean ratio between the femoral head diameter and pelvic height was 0.215 (0.173-0.249) with a 95 % CI = 0.214-0.217. The mean ratios in males and females were 0.221 (0.194-0.249) and 0.211 (0.173-0.238), respectively.

CONCLUSION

The mean ratio in Chinese population was similar to the reported ratio in a western population (about 1:5). We suggest that Chinese surgeons may be able to use the Crowe classification to classify patients with hip dysplasia.