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1.  Dual-mobility cups for revision due to instability are associated with a low rate of re-revisions due to dislocation 
Acta Orthopaedica  2012;83(6):566-571.
Background and purpose
Revision total hip arthroplasty (THA) due to recurrent dislocations is associated with a high risk of persistent instability. We hypothesized that the use of dual-mobility cups would reduce the risk of re-revision due to dislocation after revision THA.
Patients and methods
228 THA cup revisions (in 228 patients) performed due to recurrent dislocations and employing a specific dual-mobility cup (Avantage) were identified in the Swedish Hip Arthroplasty Register. Kaplan-Meier survival analysis was performed with re-revision due to dislocation as the primary endpoint and re-revision for any reason as the secondary endpoint. Cox regression models were fitted in order to calculate the influence of various covariates on the risk of re-revision.
Results
58 patients (25%) had been revised at least once prior to the index cup revision. The surgical approach at the index cup revision was lateral in 99 cases (44%) and posterior in 124 cases (56%). Median follow-up was 2 (0–6) years after the index cup revision, and by then 18 patients (8%) had been re-revised for any reason. Of these, 4 patients (2%) had been re-revised due to dislocation. Survival after 2 years with the endpoint revision of any component due to dislocation was 99% (95% CI: 97–100), and it was 93% (CI: 90–97) with the endpoint revision of any component for any reason. Risk factors for subsequent re-revision for any reason were age between 50–59 years at the time of the index cup revision (risk ratio (RR) = 5 when compared with age > 75, CI: 1–23) and previous revision surgery to the relevant joint (RR = 1.7 per previous revision, CI: 1–3).
Interpretation
The risk of re-revision due to dislocation after insertion of dual-mobility cups during revision THA performed for recurrent dislocations appears to be low in the short term. Since most dislocations occur early after revision THA, we believe that this device adequately addresses the problem of recurrent instability. Younger age and prior hip revision surgery are risk factors for further revision surgery. However, problems such as potentially increased liner wear and subsequent aseptic loosening may be associated with the use of such devices in the long term.
doi:10.3109/17453674.2012.742395
PMCID: PMC3555442  PMID: 23116439
2.  The risk of revision due to dislocation after total hip arthroplasty depends on surgical approach, femoral head size, sex, and primary diagnosis 
Acta Orthopaedica  2012;83(5):442-448.
Background and purpose
The effects of patient-related and technical factors on the risk of revision due to dislocation after primary total hip arthroplasty (THA) are only partly understood. We hypothesized that increasing the femoral head size can reduce this risk, that the lateral surgical approach is associated with a lower risk than the posterior and minimally invasive approaches, and that gender and diagnosis influence the risk of revision due to dislocation.
Patients and methods
Data on 78,098 THAs in 61,743 patients performed between 2005 and 2010 were extracted from the Swedish Hip Arthroplasty Register. Inclusion criteria were a head size of 22, 28, 32, or 36 mm, or the use of a dual-mobility cup. The covariates age, sex, primary diagnosis, type of surgical approach, and head size were entered into Cox proportional hazards models in order to calculate the adjusted relative risk (RR) of revision due to dislocation, with 95% confidence intervals (CI).
Results
After a mean follow-up of 2.7 (0–6) years, 399 hips (0.5%) had been revised due to dislocation. The use of 22-mm femoral heads resulted in a higher risk of revision than the use of 28-mm heads (RR = 2.0, CI: 1.2–3.3). Only 1 of 287 dual-mobility cups had been revised due to dislocation. Compared with the direct lateral approach, minimally invasive approaches were associated with a higher risk of revision due to dislocation (RR = 4.2, CI: 2.3–7.7), as were posterior approaches (RR = 1.3, CI: 1.1–1.7). An increased risk of revision due to dislocation was found for the diagnoses femoral neck fracture (RR = 3.9, CI: 3.1–5.0) and osteonecrosis of the femoral head (RR = 3.7, CI: 2.5–5.5), whereas women were at lower risk than men (RR = 0.8, CI: 0.7–1.0). Restriction of the analysis to the first 6 months after the index procedure gave similar risk estimates.
Interpretation
Patients with femoral neck fracture or osteonecrosis of the femoral head are at higher risk of dislocation. Use of the minimally invasive and posterior approaches also increases this risk, and we raise the question of whether patients belonging to risk groups should be operated using lateral approaches. The use of femoral head diameters above 28 mm or of dual-mobility cups reduced this risk in a clinically relevant manner, but this observation was not statistically significant.
doi:10.3109/17453674.2012.733919
PMCID: PMC3488169  PMID: 23039167
3.  Salvage of failed trochanteric and subtrochanteric fractures using a distally fixed, modular, uncemented hip revision stem 
Acta Orthopaedica  2012;83(5):488-492.
Background and purpose
Treatment options for failed internal fixation of hip fractures include prosthetic replacement. We evaluated survival, complications, and radiographic outcome in 30 patients who were operated with a specific modular, uncemented hip reconstruction prosthesis as a salvage procedure after failed treatment of trochanteric and subtrochanteric fractures.
Patients and methods
We used data from the Swedish Hip Arthroplasty Register and journal files to analyze complications and survival. Initially, a high proportion of trochanteric fractures (7/10) were classified as unstable and 12 of 20 subtrochanteric fractures had an extension through the greater trochanter. Modes of failure after primary internal fixation were cutout (n = 12), migration of the femoral neck screw (n = 9), and other (n = 9).
Results
Mean age at the index operation with the modular prosthesis was 77 (52–93) years and the mean follow-up was 4 (1–9) years. Union of the remaining fracture fragments was observed in 26 hips, restoration of proximal bone defects in 16 hips, and bone ingrowth of the stem in 25 hips. Subsidence was evident in 4 cases. 1 patient was revised by component exchange because of recurrent dislocation, and another 6 patients were reoperated: 5 because of deep infections and 1 because of periprosthetic fracture. The cumulative 3-year survival for revision was 96% (95% CI: 89–100) and for any reoperation it was 83% (68–93).
Interpretation
The modular stem allowed fixation distal to the fracture system. Radiographic outcome was good. The rate of complications, however—especially infections—was high. We believe that preoperative laboratory screening for low-grade infection and synovial cultures could contribute to better treatment in some of these patients.
doi:10.3109/17453674.2012.733917
PMCID: PMC3488175  PMID: 23083435
4.  Survival of uncemented acetabular monoblock cups 
Acta Orthopaedica  2012;83(3):214-219.
Background and purpose
Monoblock acetabular cups represent a subtype of uncemented cups with the polyethylene liner molded into a metal shell, thus eliminating—or at least minimizing—potential backside wear. We hypothesized that the use of mono​block cups could reduce the incidence of osteolysis and aseptic loosening, and thus improve survival compared to modular designs.
Patients and methods
We identified all 210 primary total hip arthroplasty (THA) procedures in the Swedish Hip Arthroplasty Register that used uncemented monoblock cups during the period 1999–2010. Kaplan-Meier and Cox regression analyses with adjustment for age, sex, and other variables were used to calculate survival rates and adjusted hazard ratios (HRs) of the revision risk for any reason. 1,130 modular cups, inserted during the same time period, were used as a control group.
Results
There was a nearly equal sex distribution in both groups. Median age at the index operation was 47 years in the monoblock group and 56 years in the control group (p < 0.001). The cumulative 5-year survival with any revision as the endpoint was 95% (95% CI: 91–98) for monoblock cups and 97% (CI: 96–98) for modular cups (p = 0.6). The adjusted HR for revision of monoblock cups compared to modular cups was 2 (CI: 0.8–6; p = 0.1). The use of 28-mm prosthesis heads rather than 22-mm heads reduced the risk of cup revision (HR = 0.2, CI: 0.1–0.5; p = 0.001).
Interpretation
Both cups showed good medium-term survival rates. There was no statistically significant difference in revision risk between the cup designs. Further review of the current patient population is warranted to determine the long-term durability and risk of revision of monoblock cup designs.
doi:10.3109/17453674.2012.688726
PMCID: PMC3369144  PMID: 22574820
5.  Surgery of skeletal metastases in 306 patients with prostate cancer 
Acta Orthopaedica  2012;83(1):74-79.
Purpose
Skeletal metastases are common in patients with prostate cancer, and they can be a source of considerable morbidity. We analyzed patient survival after surgery for skeletal metastases and identified risk factors for reoperation and complications.
Patients and methods
This study included 306 patients with prostate cancer operated for skeletal metastases during 1989–2010. Kaplan-Meier analysis was used to calculate survival. Cox multiple regression analysis was performed to study risk factors, and results were expressed as hazard ratios (HRs).
Results
The median age at surgery was 72 (49–94) years. The median survival after surgery was 0.5 (0–16) years. The cumulative 1-, 2-, and 3-year survival after surgery was 29% (95% CI: 24–34), 14% (10–18), and 8% (5–11). Age over 70 years (HR 1.4), generalized metastases (HR 2.4), and multiple skeletal metastases (HR 2.3) resulted in an increased risk of death after surgery. Patients with lesions in the humerus (HR 0.6) had a lower death rate. The reoperation rate was 9% (n = 31). The reasons for reoperation were deep wound infection (n = 10), hematoma (n = 7), material (implant) failure (n = 3), wound dehiscence (n = 3), increasing neurological symptoms (n = 2), prosthetic dislocation (n = 2), and others (n = 4).
Interpretation
This study involves the largest reported cohort of patients operated for skeletal lesions from prostate cancer. Our survival data and analysis of predictors for survival help to set appropriate expectations for the patients, families, and medical staff.
doi:10.3109/17453674.2011.645197
PMCID: PMC3278661  PMID: 22206449
6.  A modular cementless stem vs. cemented long-stem prostheses in revision surgery of the hip 
Acta Orthopaedica  2011;82(2):136-142.
Background and purpose
Modular cementless revision prostheses are being used with increasing frequency. In this paper, we review risk factors for the outcome of the Link MP stem and report implant survival compared to conventional cemented long-stem hip revision arthroplasties.
Patients and methods
We used data recorded in the Swedish Hip Arthroplasty Register. 812 consecutive revisions with the MP stem (mean follow-up time 3.4 years) and a control group with 1,073 cemented long stems (mean follow-up time 4.2 years) were included. Kaplan-Meier analysis was used to determine implant survival. The Cox regression model was used to study risk factors for reoperation and revision.
Results
The mean age at revision surgery for the MP stem was 72 (SD 11) years. Decreasing age (HR = 1.1, 95% CI: 1–1.1), multiple previous revisions (HR = 2.6, 95% CI: 1.1–6.2), short stem length (HR = 2.4, 95% CI: 1.1–5.2), standard neck offset (HR = 5, 95% CI: 1.5–17) and short head-neck length (HR = 5.3, 95% CI 1.4–21) were risk factors for reoperation. There was an overall increased risk of reoperation (HR = 1.7, 95% CI: 1.3–2.4) and revision (HR = 1.9, 95% CI: 1.2–3.1) for the MP prostheses compared to the controls.
Interpretation
The cumulative survival with both reoperation and revision as the endpoint was better for the cemented stems with up to 3 years of follow-up. Thereafter, the survival curves converged, mainly because of increasing incidence of revision due to loosening in the cemented group. We recommend the use of cemented long stems in patients with limited bone loss and in older patients.
doi:10.3109/17453674.2011.566145
PMCID: PMC3235281  PMID: 21434792
7.  Distal femoral stem-bone anchorage of a cementless revision total hip arthroplasty 
Acta Orthopaedica  2009;80(3):298-302.
Background and purpose According to the manual of the cementless Link MP reconstruction prosthesis, a distal femoral stem-bone anchorage of at least 80 mm is necessary to gain implant stability. There have been no in vivo studies showing that this distance is either achieved in clinical practice or needed for clinically satisfying results. Thus, we assessed the femoral stem-bone anchorage of the MP prosthesis using CT.
Methods 14 patients with the MP stem were evaluated by CT scans at a median follow-up time of 12 months postoperatively. Femoral stem-bone anchorage was defined as adequate if 50% of the stem flutes or more had cortical bone contact. The length of anchorage was derived from the number of slices with adequate anchorage. Clinical outcome was assessed with VAS for pain and Harris hip score (HHS), both at 1 and 5 years of follow-up.
Results The median length of stem-bone anchorage was 33 mm (interquartile range 10–60), which was shorter than recommended (p = 0.002). Still, at the 1-year control, all patients were fully weight-bearing and only 1/14 complained about mild thigh pain. 7/14 patients did not experience any pain in the affected hip. The patients had a median of 85 points in the HHS. The clinical outcome at 5 years was unchanged.
Interpretation We found that it can be difficult to achieve a stem-bone anchorage of at least 80 mm for the MP Link prosthesis. However, this does not appear to be necessary to obtain stability and to achieve clinically satisfying results.
doi:10.3109/17453670903039403
PMCID: PMC2823214  PMID: 19593722

Results 1-7 (7)