Effect of Pelvic Osteotomy in the Skeletally Immature on Acetabular Coverage

Background

Although pelvic osteotomy in children has been effective in re-establishing containment of the hip joint, its impact on hip joint development with respect to acetabular coverage is ill defined.

Purpose

The purpose of this study is to determine the prevalence of acetabular overcoverage in patients who had pelvic osteotomy during childhood and its impact on patient function.

Patients and Methods

Between 1980 and 2008, all patients who had a pelvic osteotomy done at our institution for non-neuropathic hip dysplasia (DDH) or secondary to Legg–Calvé–Perthes disease (LCP) prior to skeletal maturity were reviewed. A clinical assessment and the WOMAC, UCLA Activity Score, Marx activity score, and SF-36 quality-of-life questionnaires were completed. A standardized AP pelvic X-ray was performed to determine the acetabular coverage, signs of retroversion, and degenerative changes.

Results

Twenty-eight patients (32 hips) were identified, of which 14 (9 DDH, 5 LCP) agreed to participate. Impingement sign was positive in eight patients (six DDH, two LCP). Crossover and ischial spine signs were each present in ten hips. Tonnis grades were: 0 in 1 hip, 1 in 10 hips, 2 in 2 hips, and 3 in 1 hip. The mean Tonnis angle was 11.6 ± 8.6°. The mean CE angle was 24.0 ± 15.9° with six hips having a CE angle <20° and one hip with a CE angle >40°. There was no correlation between crossover sign or ischial sign and Tonnis grade (p = 0.739), hip pain (p = 0.520), or impingement sign (p = 1.00).

Conclusions

Acetabular overcoverage is common in patients who underwent pelvic osteotomy during childhood. No correlation was identified between retroversion and hip pain in our patient cohort.     

Hip resurfacing in patients under thirty years old: an attractive option for young and active patients

Purpose

Metal-on-metal hip resurfacing is offered as an alternative to traditional hip arthroplasty for young, active adults with advanced osteoarthritis. The concept of hip resurfacing is considered very attractive for this specific population (hard-on-hard bearing component with a large femoral head limiting the risk of dislocation, and allowing femoral bone stock preservation).

Methods

A prospective clinical trial was designed to investigate the outcome of hip resurfacing in young patients (under 30 years old). We studied 24 hips in 22 patients. Mean age at operation was 24.9 years (range 17.1–29.9). No patient was lost to follow-up.

Results

There was no revision at average follow-up of 50.6 months (44–59). Mean UCLA activity score improved from 5.5 (1–9) pre-operatively to 7.6 (1–10) postoperatively (p < 0.001). Mean Harris hip score increased from 43.9 (19–67) to 89.3 (55–100) (p < 0.001). Radiological analysis discerned no osteolysis and no implant migration.

Conclusion

The absence of short-term complications, such as mechanical failure or dislocation, is encouraging and leads us to think that mid-term results will be satisfactory. Moreover, the specific advantages of hip resurfacing (bone stock preservation, excellent stability, low risk of dislocation, large-diameter head) make the procedure a very attractive option for young subjects.     

Dual mobility acetabular component in revision total hip arthroplasty for persistent dislocation: no dislocations in 50 hips after 1–5 years

Background

A dual mobility cup has the theoretic potential to improve stability in primary total hip arthroplasty (THA) and mid-term cohort results are favorable. We hypothesized that use of a new-generation dual mobility cup in revision arthroplasty prevents dislocation in patients with a history of recurrent dislocation of the THA.

Materials and methods

We performed a retrospective cohort study of patients receiving an isolated acetabular revision with a dual mobility cup for recurrent dislocation of the prosthesis with a minimum follow-up of 1 year. Kaplan–Meier survival analyses were performed with dislocation as a primary endpoint and re-revision for any reason as a secondary endpoint.

Results

Forty-nine consecutive patients (50 hips) were included; none of the patients was lost to follow-up. The median follow-up was 29 months (range 12–66 months). Two patients died from unrelated causes. Survival after 56 months was 100 % based on dislocation and 93 % (95 % CI 79–98 %) based on re-revision for any reason. Radiologic analysis revealed no osteolysis or radiolucent lines around the acetabular component during the follow-up period.

Conclusion

The dual mobility cup is an efficient solution for instability of THA with a favorable implant survival at 56 months.

Level of evidence

Level 4, retrospective case series.     

The Lyon’s sulcus-deepening trochleoplasty in previous unsuccessful patellofemoral surgery

Purpose

Trochleoplasty is a relatively rare operation with few published results and it remains a technically demanding procedure which requires careful patient selection. The ideal candidate for surgery remains to be elucidated, and some authors consider it as a good revision option in cases of previous unsuccessful operations for persisting patellar dislocation with underlying trochlear dysplasia. The purpose of this study is to record the results from the application of sulcus-deepening trochleoplasty in patients with trochlear dysplasia and previous unsuccessful surgery for patellar dislocation.

Methods

Twenty-two patients (24 knees) were operated upon during the period 9/1993–9/2006; they had undergone surgery for patellofemoral instability and had persistent patellar dislocation, and were followed-up for a mean of 66 months (24–191). Trochleoplasty was performed in all patients using the same technique and rehabilitation protocol. Additional soft-tissue and bony operations were performed in every case.

Results

Of all cases, 29.1 % had type B and 70.9 % had type D trochlear dysplasia. After trochleoplasty, no patient had a patellar re-dislocation up to the last follow-up. Pain decreased in 72 % and the apprehension sign was negative in 75 % of the cases (p < 0.01). Sulcus angle decreased from 153° ± 14° to 141° ± 10° (p < 0.01), TT-TG distance decreased from 16 ± 6 mm to 12 ± 2 mm (p < 0.001), and patellar tilt decreased from 31° ± 14° to 11° ± 8° (p < 0.0001). Mean pre-operative Kujala score was 44 (25–73) and at the latest follow-up it increased to 81 (53–100), (p < 0.001). At the time of final follow-up, there was no case of patellofemoral arthritis.

Conclusions

Trochlear dysplasia is a key factor in the treatment of recurrent patellar dislocation and its correction could be included in the surgical options. Sulcus-deepening trochleoplasty is an acceptable revision option for the surgical treatment of patients with persisting patellar dislocation and high-grade trochlear dysplasia.     

Is etoricoxib effective in preventing heterotopic ossification after primary total hip arthroplasty?

Purpose

Heterotopic ossification is a common complication after total hip arthroplasty. Non-steroidal anti-inflammatory drugs (NSAIDs) are known to prevent heterotopic ossifications effectively, however gastrointestinal complaints are reported frequently. In this study, we investigated whether etoricoxib, a selective cyclo-oxygenase-2 (COX-2) inhibitor that produces fewer gastrointestinal side effects, is an effective alternative for the prevention of heterotopic ossification.

Methods

We investigated the effectiveness of oral etoricoxib 90 mg for seven days in a prospective two-stage study design for phase-2 clinical trials in a small sample of patients (n = 42). A cemented primary total hip arthroplasty was implanted for osteoarthritis. Six months after surgery, heterotopic ossification was determined on anteroposterior pelvic radiographs using the Brooker classification.

Results

No heterotopic ossification was found in 62 % of the patients that took etoricoxib; 31 % of the patients had Brooker grade 1 and 7 % Brooker grade 2 ossification.

Conclusions

Etoricoxib seems effective in preventing heterotopic ossification after total hip arthroplasty. This finding further supports the use of COX-2 inhibitors for the prevention of heterotopic ossification following total hip arthroplasty.     

Does total hip arthroplasty restore native hip anatomy? Three-dimensional reconstruction analysis

Purpose

Component orientations and positions in total hip arthroplasty (THA) are important parameters in restoring hip function. However, measurements using plain radiographs and 2D computed tomography (CT) slices are affected by patient position during imaging. This study used 3D CT to determine whether contemporary THA restores native hip geometry.

Methods

Fourteen patients with unilateral THA underwent CT scan for 3D hip reconstruction. Hip models of the nonoperated side were mirrored with the implanted side to quantify the differences in hip geometry between sides.

Results

The study demonstrated that combined hip anteversion (sum of acetabular and femoral anteversion) and vertical hip offset significantly increased by 25.3° ± 29.3° (range, −25.7° to 55.9°, p = 0.003) and 4.1 ± 4.7 mm (range, −7.1 to 9.8 mm, p = 0.009) in THAs.

Conclusions

These data suggest that hip anatomy is not fully restored following THA compared with the contralateral native hip.     

Combined anteversion technique reduced the dislocation in cementless total hip arthroplasty

Purpose

The combined anteversion (CA) technique is a method in which the cup is placed according to the stem anteversion in total hip arthroplasty (THA). We examined whether the CA technique reduced the dislocation rate, and the distribution of CA with the manual placement of the cup.

Methods

We retrospectively reviewed 634 hips in 579 patients with primary cementless THA. In 230 hips using the CA technique [CA(+)], a CA of 50 ± 10° was the aim. In the remaining 404 hips [CA(−)], the cup was first placed targeting 20° of anteversion. The post-operative CA was measured using the computed tomography (CT) images in 111 hips.

Results

One hip (0.4 %) had a dislocation in the CA(+) group, whereas ten hips (2.5 %) had a dislocation in the CA(−) group. A multivariate analysis showed that primary diagnosis, head size and CA technique significantly influenced the dislocation rate. Patients in the CA(−) group were 5.8 times more likely to have a dislocation compared to the CA(+) group. In the 111 hips with CT images, 81 hips (73.0 %) achieved the intended CA.

Conclusions

Although the manual placement of the cup resulted in 27 % of outliers from the intended CA, the CA technique significantly reduced the dislocation after primary THA.     

Late dislocation is associated with recurrence after total hip arthroplasty

Purpose

This study was conducted to examine the risk factors for recurrent dislocation after total hip arthroplasty (THA) and test the hypothesis that late dislocations are associated with recurrence.

Methods

A total of 1,250 hips in 1,017 patients were retrospectively reviewed. All operations were performed through the posterolateral approach with posterior soft tissue repair. An early or late dislocation was defined as a dislocation occurring before or after one year postoperatively, respectively.

Results

Dislocation occurred in 36 hips (2.9 %) and 20 of them experienced recurrence. Recurrent dislocations were observed in ten out of 25 hips (40.0 %) with early dislocation; however, ten out of 11 hips (90.9 %) with late dislocation experienced recurrence (p = 0.0046). Multivariate analysis revealed that late dislocation was significantly associated with recurrence with odds ratio of 5.94 per year. Seven in 20 hips with recurrent dislocation required surgical treatment.

Conclusion

Late dislocation significantly contributed to the development of recurrent dislocations.     

Evaluation of a reconstruction reverse shoulder for tumour surgery and tribological comparision with an anatomical shoulder arthroplasty

Purpose

The functional results after reconstruction of the proximal humerus in tumour surgery are poor. Therefore, a reversed proximal humerus replacement was developed in our institution (MUTARS humerus inverse). A low degree of wear on the polyethylene is required because of the patients’ youth and demands on shoulder function. A special type of polyethylene with shock-absorbing properties has been developed to minimise polyethylene wear in the MUTARS inverse proximal humerus replacement. We compared the tribological properties of an anatomical shoulder prosthesis (CAPICA) with the new reversed proximal humerus replacement (MUTARS humerus inverse).

Methods

Both prostheses were tested up to 5 × 10⁶ cycles. Every millionth cycle the surface was inspected and a gravimetric measurement was performed. A measurement of surface roughness was done before testing and after 5 × 10⁶ cycles.

Results

In both prostheses after 5 × 10⁶ cycles there were no major defects, such as delamination, observed. In the reversed proximal humerus replacement abrasion of 28 mg/10⁶ cycles was detected. The mean abrasion of the anatomical prosthesis was 9.28 mg/ 10⁶ cycles.

Conclusion

The glenoid component of the first reversed humerus replacement (MUTARS humerus inverse) has wear properties comparable to those of normal reversed shoulder prostheses. This is important, as this type of prosthesis is used in young patients after resection of bone tumours, with a good functional outcome. It can, therefore, be expected that the revision rate due to wear will be as high as in patients with normal reversed shoulder prostheses.     

A comparative and retrospective study of three hundred and twenty primary Charnley type hip replacements with a minimum follow up of ten years to assess wether a dual mobility cup has a decreased dislocation risk

Purpose

Mid- and long-term follow-up of Charnley total hip arthroplasty (THA) demonstrated good functional results with 85 % survivorship at 25-year follow-up. However, dislocation still remains an unsolved problem. Dislocation may occur throughout the patient’s and implant’s life. The aim of this study is to answer the question: does a dual mobility cup (DMC) decrease the dislocation risk?

Methods

We report comparative results at ten years of follow-up of two groups of primary cemented Charnley-type THA, one with a standard polyethylene cup (group 1, n = 215) and the other one with a DMC (group 2, n = 105).

Results

In group 1, 26 dislocations (12.9 %) occurred. In group 2 only one dislocation (0.9 %) occurred. This dislocation was successfully reduced by closed reduction, without any recurrence. This difference was statistically significant (p = 0.0018). In group 1, the reason for revision was recurrent dislocation in 21 cases. Five patients were revised for other reasons. The global revision rate was 12.9 %. In group 2, two patients needed revision surgery for aseptic loosening. The global revision rate was 2.1 %. This difference was statistically significant (p = 0.054). The goal was reached for the patients of group 2 who had more risks factors for dislocation (age, aetiology, American Society of Anesthesiologists and Devane scores) than those of group 1.

Conclusions

When using a DMC, we observed a low rate of dislocation in primary THA (0.9 %). This surgical choice seems to be a safe and effective technique in Charnley-type THA, especially in a high-risk population.     

The locking attachment plate for proximal fixation of periprosthetic femur fractures-a biomechanical comparison of two techniques

Purpose

Mechanical properties of a locking attachment plate construct (LAP-LCP), allowing bicortical screw placement laterally to the prosthesis stem, are compared to a cerclage-LCP construct.

Methods

Eight right synthetic femora with implanted uncemented hip endoprosthesis were cut distally and fixed with LCP, monocortical locking screws and either LAP (n = 4) or cerclage (n = 4). Cyclic testing was performed with monotonically increasing sinusoidal load until failure. Relative movements at the plate–femur interface were registered by motion tracking. Statistical differences were detected by unpaired t-test and general linear model repeated measures.

Results

Stiffness of the LAP-LCP was significantly higher at the beginning (875.4 N/mm ± 29.8) and after 5000 cycles (1213.0 N/mm ± 101.1) compared to the cerclage-LCP (644.96 N/mm ± 50.1 and 851.9 N/mm ± 81.9), with p = 0.013. Relative movements for AP-bending (B) and axial translation (T) of the LAP-LCP at the beginning (0.07° ± 0.02, 0.20 mm ± 0.08), after 500 cycles (0.16° ± 0.10, 0.26 mm ± 0.07) and after 5000 cycles (0.26° ± 0.11, 0.31 mm ± 0.07) differed significantly from the cerclage-LCP (beg.: 0.26° ± 0.04, 0.28 mm ± 0.05; 500 cyc: 0.47° ± 0.03, 0.53 mm ± 0.07; 5000 cyc.: 0.63° ± 0.18, 0.79 mm ± 0.13), with B: p = 0.02, T: p = 0.04. Relative movements for medial bending were not significantly different between the two constructs. Cycles to failure (criterion 1 mm axial translation) differed significantly between LAP-LCP (19,519 ± 1,758) and cerclage-LCP (11,265 ± 2,472), with p = 0.035.

Conclusions

Biomechanically, the LAP-LCP construct improves proximal fixation of periprosthetic fractures compared to the cerclage-LCP construct.     

The Locking Compression Paediatric Hip Plate?: technical guide and critical analysis

Purpose

Osteotomies of the proximal femur and stable fixation of displaced femoral neck fractures are demanding operations. An LCP Paediatric Hip Plate™ was developed to make these operations safer and less demanding. The article focuses on the surgical technique and critically analyses the device.

Methods

Between 2006 and 2008, 30 hips in 22 patients underwent surgery. Patients’ demographics, perioperative details, postoperative outcome and complications were retrospectively collected and analysed.

Results

Patients’ diagnoses included persistent congenital hip dysplasia (n = 4), neuropathic hip dysplasia (n = 9), idiopathic ante/retroversion (n = 8), femoral neck fracture (n = 3), Perthes’ disease (n = 2), deformity after slipped capital femoral epiphysis (SCFE), congenital femoral neck pseudarthrosis, deformity after pelvic tumour resection and malunion following proximal femoral fracture (one each). In 21 of 22 patients, the postoperative radiographs showed corrections as planned. Two cases had to be revised for screw loosening. Intraoperative handling using the plate was excellent in all cases.

Conclusions

In our case series of 30 hip operations, the LCP Paediatric Hip Plate™ was shown to be safe and applicable in the clinical setting with excellent results and a low complication rate. We consider that the LCP Paediatric Hip Plate™ is a valuable device for correction of pathological conditions of the proximal femur and for fixation of displaced femoral neck fractures in children. Larger studies should be carried out to better quantify the risk of clinically relevant complications.     

Correlation between groin pain and cup design of hip-resurfacing implants: a prospective study

Purpose

Cup design has been incriminated as the source of groin pain after hip resurfacing but has not been well described; thus, it was assessed in a prospective study looking at three implant types.

Methods

A group-match was done between three groups of hip resurfacing devices according to age, sex, body mass index, activity level, osteoarthritis aetiology and pre-operative scores.

Results

The global groin pain rate was 5.7 % at six months and 2.7 % at last follow-up. Groin pain rate was significantly different between the three groups (p = 0.004) and had a strong influence on the subjective results (p = 0.04). No groin pain emerged between six months and last follow-up. No clinical differences were noted in Harris hip score and Merle d’Aubigné-Postel score at last follow-up. However, the Oxford hip score and Devane activity score were significantly lower for cups with macrostructures.

Conclusion

The low groin pain rate in this prospective cohort was probably secondary to the specific surgical technique used and seems to be correlated with cup design. Macrostructures on the external part of the cup could be significantly harmful.     

Long-term results of cementless hip arthroplasty with ceramic-on-ceramic articulation

Purpose

The goal of the study was to evaluate long-term results of hip arthroplasty in patients with ceramic-on-ceramic articulation.

Methods

The follow-up involved 220 primary total hip arthroplasty procedures (188 patients, 101 women and 87 men) after implantation of the Mittelmeier cementless hip endoprosthesis. The mean age of patients at surgery was 44.5 years and the mean follow-up was 19.6 years, with a minimum of 12.3 years. Dysplastic, idiopathic and post-traumatic coxarthrosis were the most frequent forms of degenerative hip changes. The Merle d’Aubigné and Postel classification, as modified by Charnley, was used for clinical evaluation.

Results

Very good results were obtained in 39.5 % of the patients, good results in 43.6 %, satisfactory results in 9.1 % and poor results in 7.8 %. Twelve-year survival for the whole prosthesis was 86.36 %, for the acetabulum 89.99 % and for the stem 91.36 %.

Conclusions

Long-term results of hip arthroplasty using the Mittelmeier prosthesis are fairly encouraging with their low incidence of loosened prosthesis components after surgery.     

Three dimensional-CT evaluation of femoral neck anteversion, acetabular anteversion and combined anteversion in unilateral DDH in an early walking age group

Purpose

At present, the indications for femoral derotational osteotomy remain controversial due to the inconsistent findings in femoral neck anteversion in developmental dysplasia of the hip (DDH). Moreover, combined anteversion is not assessed in unilateral DDH using three dimensional-CT. Therefore, the purposes of our study were to observe whether the femoral neck anteversion (FA), acetabular anteversion (AA) and combined anteversion (CA) on the dislocated hips were universally presented in unilateral DDH according to the classification system of Tönnis.

Methods

Sixty-two patients with unilateral dislocation of hip were involved in the study, including 54 females and eight males with a mean age of 21.63 months (range, 18–48 months). The FA, AA and CA were measured and compared between the dislocated hips and the unaffected hips.

Results

Although no significant difference was observed in FA between the dislocated hips and the unaffected hips (P = 0.067, 0.132, respectively) in Tönnis II and III type, FA was obviously increased on the dislocated hips compared with the unaffected hips in Tönnis IV type. Increased AA on the dislocated hips was a universal finding in Tönnis II, III and IV types. Meanwhile, a wide safe range of CA from 24° to 62° was demonstrated on the unaffected hips.

Conclusion

Femoral derotational osteotomy seems not to be necessary in Tönnis II and III types in unilateral DDH. Femoral derotational osteotomy should be considered in DDH, especially in Tönnis IV type, if the CA is still above 62° and the hip joints present instability in operation after abnormal acetabular anteversion, acetabular index and acetabular coverage of the femoral head are recovered to normal range through pelvic osteotomy.     

The techniques of soft tissue release and true socket reconstruction in total hip arthroplasty for patients with severe developmental dysplasia of the hip

Purpose

Total hip arthroplasty (THA) is an effective procedure for developmental dysplasia of the hip (DDH); however, it is sometimes difficult to complete for severe cases because of femoral head dislocation, dysplasia of the acetabulum and the femur, disparity in limb length, soft tissue contraction, and muscular atrophy. We aimed at exploring the efficiency of the techniques of release and balance of soft tissues and reconstruction of true socket THA for patients with severe DDH.

Methods

From January 2000 to January 2009, 46 adult patients with severe DDH (50 hips) were included in this study. According to the classification system, there were 26 type III and 24 type IV. Among them there were 32 women and 14 men, aged from 38 to 77 years. THA was performed via a lateral approach. All acetabular sockets were reconstructed at the original anatomical location following a meticulous technique of soft tissue release and balance around the hip to restore limb length, to strengthen the abductor and improve its function.

Results

All patients had restoration of limb length (range, 2.5–5.5 cm; 30 limbs of more than 4 cm) without injury to the sciatic nerve. One postoperative dislocation occurred due to slight enlargement of the angle of abduction of the acetabulum. The follow-up ranged from 2.2 to 11.5 years (median 6.4 years) in 46 patients, and the Harris score increased from 40.2 preoperatively to 86.5 (P = 0.027). All hips were pain free with good function at the latest follow-up.

Conclusion

The meticulous techniques of soft tissue release and balance can be recommended to ensure anatomical reconstruction of the true acetabular socket and to improve abductor function during arthroplasty for DDH.     

Successful Pavlik treatment in late-diagnosed developmental dysplasia of the hip

Purpose

The objective of this study was to evaluate success and complication rates of the Pavlik harness in late-diagnosed hip dislocation (developmental dysplasia of the hip, DDH). We also set out to assess the additional value of an abduction brace for three to six months, when successful reduction using the Pavlik harness was achieved.

Methods

We included 31 patients (31 hips, 28 female, right/left = 4/27) with late-diagnosed hip dislocation treated with a Pavlik harness between 1995 and 2008. The average age at the start treatment was 27 weeks (21-57). None were lost to follow-up; the mean follow-up was 4.2 years (two-10). Of these patients, 61 % were classified as Tönnis type 2, 32 % as type 3 and 7 % as type 4.

Results

Of 31 hips, 20 (65 %) were successfully reduced after the use of the Pavlik harness. The average duration of Pavlik treatment was seven weeks (three-12). The mean time to stable reduction was six weeks (three-11), after which the patients were weaned off the Pavlik harness. The mean age at final treatment was 19 months (12-28). Five patients (15.0 %) developed radiological signs of osteonecrosis (Kalamchi and MacEwen classification; two group I, one group II and two group IV). When we compared the different Tönnis types a significant difference in successful reduction was found. Seventeen (81 %) of Tönnis type 2 dislocated hips were successfully reduced, while only two (25 %) of Tönnis type 3-4 hips were (odds ratio 25, p = 0.001). Clinical examination (e.g. limited abduction, positive Ortolani, Barlow or Galeazzi) at the time of diagnosis was not significantly related to the success rate of the Pavlik treatment. The mean acetabular index (AI) significantly improved from 36.5 to 30.5° after initial Pavlik treatment to 22.3° at final follow-up (4.1 years).

Conclusions

Prolonged use of the Pavlik harness in late-diagnosed hip dislocation (DDH) Tönnis type <3 is a safe and successful treatment option in the older infant. Although the AI was significantly reduced after the abduction brace, its additional use remains debatable, as no control group was evaluated.     

Long-term survival of the uncemented Balgrist total hip replacement cup

Purpose

The purpose of this study was to evaluate the long-term clinical and radiographic outcomes of the Balgrist total hip replacement cup.

Methods

We report the results of a retrospective review of 195 total hip prostheses with Balgrist cup implanted in 178 patients. There were 59 men and 119 women with a mean age at surgery of 52.3 years (range, 19–72). Cox regression was used to determine the influence of independent variables on the survivorship of the prosthesis.

Results

There were 117 (66 %) of 178 patients, and 131 (67 %) of 195 hips available for assessment at a mean follow-up of 17.4 years. A total of 21 patients (22 hips) were lost from follow-up (12 %). A total of 25 patients (27 hips) required some type of re-operation during the follow-up period. Eight of 27 re-operations (30 %) were directly caused by the Balgrist cup failure due to fatigue fracture of the metallic shell (n = 5; 19 %), polyethylene wear (n = 2; 7 %) and aseptic loosening (n = 1; 4 %). The mean polyethylene wear rate was 0.068 mm/year (range, 0.008–0.230; SD = 0.043). The risk of re-operation for any reason was decreased with dysplastic hip as a primary diagnosis (hazard ratio; HR = 0.250; 95 % CI 0.086–0.725) and with greater age at the time of surgery (HR = 0.923; 95 % CI 0.880–0.969). The 19-year survivorship with re-operation for any reason was 75.6 % (95 % CI 67.0–84.2). The 19-year survivorship with re-operation for the Balgrist cup failure was 90.5 % (95 % CI 83.4–97.6).

Conclusions

The Balgrist cup continues to provide excellent clinical and radiological outcomes. This is associated at least in part with a low polyethylene wear rate. The main reason for the Balgrist cup failure is fatigue fracture of the metallic shell.