Has the risk of dislocation after total hip arthroplasty performed for displaced femoral neck fracture improved with modern implants?

BACKGROUND: Displaced femoral neck fractures (DFNF) in the elderly can be treated with hemiarthroplasty or total hip arthroplasty (THA). One concern with utilizing THA in this setting is post-operative dislocation. The purposes of this study were to determine the incidence of hip dislocation following THA for DFNF and to identify risk factors for dislocation. METHODS: The charts of 66 posterior-approach THA cases performed for DFNF with mean post-operative follow-up of 4.4 years were retrospectively reviewed. Pre-operative patient demographic data and intra-operative clinical data were recorded including age, race, gender, height, weight, body mass index (BMI), femoral head diameter, acetabular cup diameter, use of an elevated liner, and cementing of femoral component. For patients with available post-operative pelvis radiographs, acetabular cup inclination and version angles were also calculated. RESULTS: Four dislocation (4/66, 6%) events occurred at an average of 51 days after surgery. No specific risk factors for dislocation were identified but the use of a cemented femoral stem did approach significance (p = 0.06). 47% of the acetabular cups were located outside of the Lewinnek safe zone. Although the dislocation rate of THAs with acetabular cups outside of the safe zone was higher than the dislocation rate for THAs with cups in the safe zone (12.5% vs 0%), placement of acetabular cups outside of the safe zone was not a risk factor for dislocation. CONCLUSIONS: Posterior THA with proper cup positioning and meticulous soft tissue repair is an effective treatment option for DFNF with low dislocation risk.

Risk factors for conversion surgery to total hip arthroplasty of a hemiarthroplasty performed for a femoral neck fracture.

INTRODUCTION: The purpose of this study was to determine risk factors for conversion to total hip arthroplasty (THA) in patients originally treated with hemiarthroplasty (HA) for displaced femoral neck fractures. METHODS: In this case-controlled study, we identified 54 patients who were treated with HA for femoral neck fracture (FNF) who subsequently underwent conversion to THA at our institution between 2003 and 2013. We randomly selected 142 control patients who underwent HA for a displaced FNF without conversion surgery during the same time period. We compared demographic data, implant parameters, and radiographic data between the groups to identify risk factors for conversion surgery. RESULTS: In the univariate analysis, younger age at index surgery (mean 75 vs. 80 years, p = 0.006), higher body mass index (26.1 vs. 23.7, p = 0.031), bipolar prosthesis (20% vs. 36%, p = 0.024), absence of dementia (6% vs. 23%, p = 0.01), increased leg length compared to contralateral limb (6.5 mm vs. 0.2 mm, p<0.001), and increased HA femoral head size compared to the contralateral femoral head (2.7 mm vs. 1.5 mm, p = 0.02) were associated with a significantly increased risk of conversion surgery. In the multivariate logistic regression, decreased age at index surgery, no dementia, use of a bipolar head, and increased leg length discrepancy (LLD) were associated with risk of conversion. CONCLUSIONS: Patient characteristics, including younger age, increased BMI, and absence of dementia can lead to increased risk for conversion of HA to THA. Intraoperative considerations of head size and increase in ipsilateral LLD may increase the risk of conversion surgery. These factors should be considered by surgeons who employ HA for displaced FNFs.

Treatment of Periprosthetic Knee Infection With Concurrent Rotational Muscle Flap Coverage Is Associated With High Failure Rates.

BACKGROUND: Soft-tissue deficiency is a potentially devastating complication of the infected total knee arthroplasty (TKA). Rotational muscle flaps are commonly used to address these defects. However, reported success rates vary widely. METHODS: We reviewed 26 consecutive patients who underwent rotational muscle flap surgery for full-thickness anterior soft-tissue defect during treatment of an infected TKA. Twenty-four cases used a medial gastrocnemius rotational flap, 1 used a lateral gastrocnemius flap, and 1 used a rectus femoris-vastus intermedius flap. Implant survival, recurrence of infection, and limb survival were reported. Patient and procedural characteristics were tested for association with failure using χ2 and Student t-test. Kaplan-Meier analysis was used to estimate the failure-free survival function. RESULTS: Mean follow-up time was 3.3 years. Eighteen of 26 patients (69.2%) experienced recurrent infection requiring an average of 5.3 additional operations (range, 1-20). Five (19.2%) required arthrodesis while 6 (23.1%) eventually underwent above-the-knee amputation. Two patients (7.7%) died due to complications of revision surgery or persistent infection. Eleven patients (42.3%) were infection free with a retained prosthesis after treatment at a mean follow-up of 5.3 years (range, 0.7-18.0 years). CONCLUSION: Rotational muscle flap coverage of soft-tissue defects in the setting of the infected TKA remains a viable salvage option. However, despite adequate tissue coverage, many patients experience recurrent infection requiring additional surgical treatment. Patients and surgeons should be aware of the potential high failure rates observed when treating these complex problems.

Step-wise medial collateral ligament needle puncturing in extension leads to a safe and predictable reduction in medial compartment pressure during TKA.

PURPOSE: Medial soft tissue release in a varus deformity knee during total knee arthroplasty is essential for accurate balancing of the reconstruction. This study attempts to quantify the effect of sequential needle puncturing of the medial collateral ligament (MCL) using a pressure sensor insert (Verasense by OrthoSensor) and gap measurement under tension. METHODS: Cruciate-retaining arthroplasties were placed in 14 cadaveric knees. The MCL was elongated by step-wise perforation, in five sets of five perforations, with the use of an 18-gauge needle, followed by valgus stress. Following the fifth set of needle perforations, blade perforation was performed on the remaining tense fibers of the MCL. Following each step-wise perforation, corresponding medial compartment pressures and gap measurements under tension were recorded. RESULTS: Sensor measurements correlated closely with step-wise tissue release (R = 0.73, p < 0.0001), and a significant decrease in pressure was found in early needle puncturing (mean 49 N after 5, 83 N after 15, p values < 0.05), although changes diminished at later stages of needle perforation (90 N after 20). Gap measurement demonstrated small gradual changes with early puncturing, but showed significant opening in the later stages of release. There was minimal variation in pressure or gap measurements in flexion versus extension. This finding suggests that MCL needle puncture will not lead to unequal gaps between flexion and extension. There were no cases of MCL over-release after 15 punctures, one case after 20 punctures, and three after blade perforation. CONCLUSION: Needle puncturing of the MCL in extension for up to 15 punctures can be a safe and predictable way to achieve medial opening when balancing a varus knee during TKA as demonstrated in this cadaveric model. Blade perforation should be used with caution to avoid over-release. The needle puncture method can be used by surgeons to achieve reliable reductions in medial compartment pressures, to help achieve a balanced TKA, with minimal risk of over-release.

Risk factors for conversion surgery to total hip arthroplasty of a hemiarthroplasty performed for a femoral neck fracture.

INTRODUCTION: The purpose of this study was to determine risk factors for conversion to total hip arthroplasty (THA) in patients originally treated with hemiarthroplasty (HA) for displaced femoral neck fractures. METHODS: In this case-controlled study, we identified 54 patients who were treated with HA for femoral neck fracture (FNF) who subsequently underwent conversion to THA at our institution between 2003 and 2013. We randomly selected 142 control patients who underwent HA for a displaced FNF without conversion surgery during the same time period. We compared demographic data, implant parameters, and radiographic data between the groups to identify risk factors for conversion surgery. RESULTS: In the univariate analysis, younger age at index surgery (mean 75 vs. 80 years, p = 0.006), higher body mass index (26.1 vs. 23.7, p = 0.031), bipolar prosthesis (20% vs. 36%, p = 0.024), absence of dementia (6% vs. 23%, p = 0.01), increased leg length compared to contralateral limb (6.5 mm vs. 0.2 mm, p<0.001), and increased HA femoral head size compared to the contralateral femoral head (2.7 mm vs. 1.5 mm, p = 0.02) were associated with a significantly increased risk of conversion surgery. In the multivariate logistic regression, decreased age at index surgery, no dementia, use of a bipolar head, and increased leg length discrepancy (LLD) were associated with risk of conversion. CONCLUSIONS: Patient characteristics, including younger age, increased BMI, and absence of dementia can lead to increased risk for conversion of HA to THA. Intraoperative considerations of head size and increase in ipsilateral LLD may increase the risk of conversion surgery. These factors should be considered by surgeons who employ HA for displaced FNFs.

Hemiarthroplasty for Displaced Femoral Neck Fractures in the Elderly Has a Low Conversion Rate.

BACKGROUND: Hemiarthroplasty (HA) has been a mainstay treatment for displaced femoral neck fractures for many years. The purpose of this study was to report the conversion rate of HA to total hip arthroplasty (THA) for displaced femoral neck fractures and compare outcomes between implant constructs (bipolar vs unipolar), fixation options (cemented vs cementless stems), and age groups (<75 years vs ≥75 years). METHODS: We retrospectively reviewed the results of a consecutive cohort of 686 patients who underwent HA for the treatment of femoral neck fractures at our institution between 1999 and 2013 with a minimum of 2-year follow-up. RESULTS: The overall component revision rate, including conversion to THA, revision HA, revision with open reduction internal fixation, and Girdlestone procedure, was 5.6% (39/686). Seventeen patients (2.5%) were converted from HA to THA at an average of 1.9 years after index procedure. A significantly lower conversion rate of 1.4% (7/499 patients) was found in the older patient cohort (≥75 years old) compared to 5.3% (11/187) in the younger cohort. The most common causes for conversion surgery to THA were acetabular wear (5 patients), aseptic loosening (4 patients), and periprosthetic fracture (3 patients). There was a significantly lower rate of periprosthetic fracture (0.4% vs 2.5%, P value .025) in the cemented implant group compared to the cementless group. We observed a higher rate of dislocations in the bipolar vs unipolar group (3.8% vs 1%, P value .02) and no other significant differences between these groups. CONCLUSION: We observed a low reoperation rate for this cohort of patients, relatively higher conversion rates for the younger population, fewer periprosthetic fractures with the use of cemented stems, and no advantage of bipolar over unipolar prostheses.

Prospective Comparison of Blood Culture Bottles and Conventional Swabs for Microbial Identification of Suspected Periprosthetic Joint Infection.

BACKGROUND: Early, accurate detection of infection is vital to successful treatment of periprosthetic joint infection (PJI). Currently, no "gold standard" diagnostic testing exists. The goal of this prospective study was to compare the efficacy of a blood culture bottle system (BCBS) to commonly used culture swabs in confirming PJI in patients with high clinical suspicion. METHODS: Patients were selected for enrollment based on Musculoskeletal Infection Society guidelines for PJI. erythrocyte sedimentation rate and C-reactive protein were obtained before aspiration. Aspirated fluid was divided between BCBS, swab, and synovial fluid analysis. Forty-nine samples were analyzed. RESULTS: BCBS yielded 41 positive cultures vs 19 with swab (P < .0001), particularly with respect to Staphylococcus epidermidis. There were no false positive results in the BCBS group, using strict Musculoskeletal Infection Society guidelines. CONCLUSION: BCBS increased identification of pathogens in lower extremity PJI, providing clinicians with a low-cost, broadly-applicable test.