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Ten-Year Results of the BIRMINGHAM HIP Resurfacing Implant System 

There have been 3 historic cycles of interest in surface replacement of the hip in the last 40 years. The second cycle occurred in the 1980s into the 1990s, when very high failure rates were reported. Biomaterial and design advancements fueled the most recent cycle of interest, which began 12 to 15 years ago. However, the enthusiasm that occurred at the advent of this most recent cycle ebbed as it became increasingly apparent that patient selection is critical and that the fairly difficult hip resurfacing procedure requires experience to reproducibly place the implants correctly. 

In the latest issue of JBJS,  Su et al. report the 10-year results of the post-market-approval study of the BIRMINGHAM HIP Resurfacing (BHR) implant system, a metal-on-metal system approved by the U.S. Food and Drug Administration in 2006. The study included a cohort of 280 hips (253 patients) undergoing primary BHR procedures across 5 sites. The mean patient age at the time of surgery was 51 years; 74% of the BHRs were implanted in male patients, and 95% of the hips had a diagnosis of osteoarthritis.  

Among the findings: 

  • 10-year survivorship free from all-cause component revision was 92.9%. Among male patients <65 years of age at the time of the procedure, the rate was 96%. 
  • Twenty hips underwent revision (at a mean of 5 years).  
  • Whole-blood cobalt and chromium levels were higher at 1 year after surgery compared with preop levels; they remained stable through 5 years, and then decreased somewhat at 10 years.  
  • Improvements in the EQ-5D visual analogue scale score and Harris hip score were noted at 1 year and were maintained through 10 years.  

These outcomes are encouraging, but as Su et al. point out, the cohort is not representative of typical total hip arthroplasty populations, who tend to be older and include a greater percentage of female patients. Moreover, the surgeons who performed the procedures were all experienced. Patient selection remains key, with younger male patients being the best candidates. Data such as these can help sharpen our focus as we refine arthroplasty concepts for further improvement in patient outcomes. 

For additional perspective on this study, see the commentary by Timothy S. Brown, MD 

Marc Swiontkowski, MD
JBJS Editor-in-Chief 

Minimally Invasive Hallux Valgus Correction: Promising Outcomes of Third-Generation Technique  

The field of orthopaedics continually seeks to improve our ability to help patients return to optimal function as quickly and efficiently as possible. New surgical techniques aimed at better outcomes, faster recovery, and smaller (and hopefully less painful) scars are regularly being developed and evaluated. The concept of minimally invasive surgery (MIS) has been around for some time, with newer techniques being utilized in multiple subspecialties. Foot and ankle surgery is no exception, with procedures including MIS for hallux valgus deformity correction. While early generations of such procedures were fraught with complications, newer, third-generation MIS (involving screw fixation of a distal metatarsal osteotomy site) has shown promising early results, with a documented learning curve of 20 to 50 cases.

In the July 7, 2021 issue of JBJSLewis et al. present their results from a consecutive series of third-generation minimally invasive chevron and Akin osteotomies (MICA) in the treatment of hallux valgus. Patient-reported outcome measures (PROMs) collected preoperatively and at a minimum of 2 years postoperatively as well as radiographic outcomes and complications were evaluated.

From the initial series of 333 feet (230 patients), PROMs data were available for 292 feet, or 87.7% (200 patients). PROMs utilized included the Manchester-Oxford Foot Questionnaire (MOXFQ), a tool specifically validated for patients undergoing hallux valgus surgery; the EuroQol-5 Dimensions-5 Level (EQ-5D-5L) Index and EuroQoL visual analogue scale (EQ-VAS), validated quality-of-life measures; and a VAS for pain.

The authors found a significant improvement (greater than the minimal clinically important difference) in each domain of the MOXFQ. They also noted a significant improvement in the VAS-pain score and the EQ-5D-5L Index.

There was an overall 21.3% complication rate, with only 7.8% of the cases requiring a return to the operating room, most frequently for screw removal (6.3%). The operating surgeon was outside the reported learning curve, having previously performed approximately 100 MICA procedures, but there were still complications that can help guide the physician-patient discussion regarding the use of the MICA.

Although radiographic follow-up did not routinely go beyond 6 weeks, the authors found significant improvement in radiographic measures. With >25% of the preoperative deformities being classified as “severe,” the findings suggest the potential utility of the procedure for patients with a range of deformity severity.

This series—which the authors note is the largest of the third-generation MICA technique— opens the door for possible head-to-head comparison with traditional hallux valgus surgery via a randomized trial to further define the role of MICA in the treatment of patients with hallux valgus.

A Video Summary of this article can be found here.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

The Cost-Effectiveness of Fragility-Fracture Screening and Prevention

After nearly 2 decades, the orthopaedic community has made a good start on assuming our responsibility in the diagnosis of osteoporosis after a patient’s initial low-energy fracture. We are seeing a positive impact from programs such as the American Orthopaedic Association’s “Own the Bone” initiative as well as from the expanded creation of multidisciplinary fracture liaison services, through which patients who sustain a fragility fracture can receive appropriate follow-up to reduce the risk of subsequent injury.   

There is still work to do to convince the wider orthopaedic surgeon community that leadership on this issue falls in our area. Primary care, rheumatology, and physiatrist practices are overwhelmed with patients with other clinical issues that require their resources. At the same time, it is easier to identify patients who may need treatment for low bone density during their initial encounter in the orthopaedist’s office or during a hospital admission. There is good evidence to suggest that patients are much more receptive to following through with laboratory testing and bone-density screening when they are being treated for a serious metaphyseal fracture.  

In the July 7 issue of JBJS, Saunders et al. examine the cost-effectiveness of a fracture liaison service, presenting their findings of a cost analysis of the Fracture Screening and Prevention Program (FSPP) of Ontario, Canada. Established in 2007, the FSPP was gradually implemented in 37 outpatient fracture clinics in the province; in 2011, the initial education-communication model was replaced by a more intensive strategy, with fracture risk assessment and referrals to specialists being added.  

The researchers’ goal was to determine the cost-effectiveness of the current FSPP compared with usual care (no program). They developed a Markov model and simulated a cohort of patients with a fragility fracture starting at 71 years of age, with model parameters obtained from the published literature and the FSPP.  

The authors concluded that, from the public health-payer perspective, the program is indeed less costly (by $274) and more effective (by 0.018 quality-adjusted life-year) over the lifetime of the patient. Read the full report here.  

We have seen that fracture liaison services can be beneficial to the individual patient. Data such as those from Saunders et al. can help to quantify—for payers and health systems—the value of those services, as our specialty takes on the responsibility of ensuring that patients receive appropriate screening for fracture risk and prevention.

Marc Swiontkowski, MD 
JBJS Editor-in-Chief 

Use of Machine Learning to Predict Improvement After Hip Arthroscopy 

The management of expectations is crucial when counseling patients undergoing treatment for a musculoskeletal injury or condition. In hip arthroscopy, this is especially critical when discussing with patients—including athletes seeking to return to play—their anticipated outcomes following surgical treatment for femoroacetabular impingement syndrome (FAIS).

In the latest issue of JBJS, Kunze et al. report on their investigative efforts to develop and internally validate machine learning algorithms that can yield patient-specific predictions of which athletes will reach clinically relevant improvement in function after arthroscopy for FAIS.

A total of 1,118 athletes, identified through a retrospective review of clinical registry data, met the inclusion criteria. The primary outcome was attaining the minimal clinically important difference (MCID) in the Hip Outcome Score-Sports Subscale (HOS-SS) at a minimum of 2 years postoperatively. Six machine learning algorithm models were tested.

The authors found that 23.1% of the athletes did not achieve the MCID for the HOS-SS. Six variables optimized algorithm performance, with the following cutoffs found to decrease the likelihood of achieving the MCID:

  • Preoperative HOS-SS score of ≥58.3
  • Tönnis grade of 1 (early osteoarthritis)
  • Alpha angle of ≥67.1° on anteroposterior radiograph
  • Body mass index (BMI) of >26.6 kg/m2
  • Tönnis angle of >9.7° (indicating subtle instability or dysplasia)
  • Patient age of >40 years

The elastic-net penalized logistic regression (ENPLR) model was the most accurate model in this study.

The findings suggest that patient selection is paramount to the ability to achieve clinically relevant improvements in outcomes for patients treated with arthroscopy for FAIS. Multiple studies have demonstrated that increasing arthritis level and age, along with BMI, are associated with inferior patient-reported outcomes. In addition, hip instability and increased Tönnis angle have been shown to be associated with worse outcomes following hip arthroscopy. A greater alpha angle indicates a larger “deformity” and thus the potential for more damage at the time of surgery that cannot be completely addressed with today’s surgical techniques. “Higher” preoperative HOS-SS (although on a scale of 0 to 100, 58 is not that high) may make it more difficult for a patient to achieve enough of an improvement in their outcome score to be considered as having attained the MCID.

The ENPLR  model was converted into an open-source application, although as Kunze et al. point out, external validation is necessary before wider adoption of the application. Nonetheless, the model demonstrates the potential to help hip surgeons better educate our patients on expected outcomes and to assist with proper patient selection for the ever-evolving treatment of FAIS.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

Co-author Kyle N. Kunze, MD discusses this study in an “Author Insights” video, found here.

E-Scooter Injury Data Can Help Inform Treatment Planning

Epidemiologic studies are often useful when it comes to detecting changes in treatment patterns, identifying disease trends, or understanding the acceptance of a new treatment. A recent study by Shichman et al. helps bridge the span between epidemiologic data and direct clinical care. In the June 16, 2021 issue of JBJS, the authors report on the fracture patterns and the mechanisms and management of injuries related to the use of electric scooters (e-scooters) as documented in their trauma center in Tel-Aviv, Israel. Among their findings:

  • A total of 716 fractures were diagnosed in 563 patients during the study period (2017 to 2020); 46.6% of the patients required hospitalization. Surgical treatment was recommended for 225 fractures.
  • Of the 492 upper-limb fractures, 89.2% occurred in a rider fall, and of the 210 lower-limb fractures, 15.7% occurred in rider-vehicle collisions. Head concussions and maxillofacial injuries were the most common associated injuries.
  • By AO/OTA classification, a radial-head fracture (2R1A, 2R1B, 2R1C) was the most common upper-limb fracture, followed by a distal radial fracture (2R3A, 2R3B, 2R3C). The most common upper-limb procedure was open reduction and internal fixation (ORIF) of the distal part of the radius.
  • The most common lower-limb fracture was a tibial plateau fracture (AO/OTA 41A, 41B, 41C). ORIF of the proximal part of the tibia was the most common lower-limb procedure.

The use of e-scooters is expanding in metropolitan areas worldwide, primarily in the form of street rentals. E-scooters can reach speeds in excess of 25 mph, and they require some practice in steering and braking. While an appealing alternative form of transportation for many, they present concerns and challenges related to safety.

The report by Shichman et al. can help trauma centers and orthopaedic surgeons understand the injury patterns they may encounter, and their potential incidence, should an e-scooter service become popular in their city. Such data can support the planning of resources to manage any increase in moderate-velocity vehicular injuries—and help inform conversations on e-scooter safety.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Co-author Ittai Shichman, MD discusses this study in an “Author Insights” video, found here.

Isoelastic Monoblock vs Modular Press-Fit Cup 

As the volume of total hip arthroplasty (THA) cases continues to rise, so too will the need for revision surgery. Revision THA can be complicated by insufficient bone stock on either the femoral or acetabular side, and researchers are gaining further insight into bone loss potentially related to implant design, such as loss that may occur through stress-shielding from press-fit implants.  

 In a randomized controlled trial recently reported in JBJS, Brodt et al. evaluated reduction in bone mineral density (BMD), primarily periacetabular BMD, as measured in 2 groups: patients who received a press-fit isoelastic monoblock cup (24 patients analyzed) and those who received a modular titanium press-fit cup (23 patients analyzed). At question was whether an isoelastic monoblock cup, with an elastic modulus similar to that of bone, would lead to less stress-shielding and thus less bone loss compared with a conventional modular titanium cup. 

Periprosthetic BMD was assessed at 1 week postoperatively (baseline) and at 4 years postoperatively using dual x-ray absorptiometry (DXA). The authors evaluated 4 regions of interest (ROIs) around the acetabular component and 7 ROIs around the femoral component based on regions previously described in the literature for assessing periprosthetic bone loss. 

Baseline patient characteristics, operative time, and improvement in clinical outcome scores did not differ between the groups.  A decrease in overall periacetabular BMD was found in both groups, but the difference between the groups was not significant. 

However, the researchers found a significant difference between the groups in BMD changes in certain periprosthetic regions. On the acetabular side, the group with the modular titanium cup had a 15.9% decrease in BMD in zone 2 (the superior pole of the acetabulum) compared with a decrease of 4.9% in the group with the isoelastic monoblock cup. And on the femoral side, the group with the modular titanium cup had a 15.4% decrease in BMD in zone 1 (along the greater trochanter) compared with a loss of 7% in the group with the isoelastic monoblock cup. None of the other regions differed significantly between the groups.   

Despite the relatively short follow-up and small (but adequately powered) numbers, these results are worthy of our consideration. I agree with the authors that longer follow-up is needed before conclusions can be drawn. As implant design can impact component longevity, it is critical that we evaluate differences to better understand the long-term implications. 

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media 

 

Caution Appropriate as We Investigate New Approaches to Pain Management 

The dangers of chronic opioid use have rightly been at the forefront of orthopaedic practice considerations in recent years. The widespread use of regional anesthesia and periarticular-injection cocktails, targeted NSAID utilization, and strict limitations on opioid use have become standard approaches for postoperative pain management.  

With the availability of cannabinoids in numerous state jurisdictions, attention has now turned to the potential of these compounds to enhance patient comfort in the postoperative period. However, as we contemplate their use, it’s imperative that we also evaluate the impact of these compounds on clinically important outcomes such as  bone-healing and fusion. The track record of nicotine, NSAIDs, and other compounds in terms of the impact on bone-healing is enough to suggest caution.   

In the June 2, 2021 issue of JBJS, Yun et al. provide new insight into this topic. Specifically, they evaluated the impact of cannabinoid receptor agonist WIN55 on osteogenic differentiation in vitro and bone regeneration and spinal fusion in a preclinical rat model.  

They found that WIN55 had no adverse impact on osteogenic differentiation of primary bone marrow stem cells in vitro. As noted by the authors, “mRNA expression levels of Runx2 and Alp were similar among cells treated with vehicle alone and WIN55. Likewise, exposure to WIN55 did not inhibit ALP [Alkaline phosphatase] activity or bone matrix mineralization.”  

In addition, no adverse impact of WIN55 on spinal fusion or bone regeneration was found. Forty-five rats (15 per group) underwent L4-L5 posterolateral spinal fusion with bilateral placement of collagen scaffolds soaked with rhBMP-2. The rats were treated with vehicle alone or 0.5 or 2.5 mg/kg WIN55 by way of daily intraperitoneal injections for 5 days. Radiography, manual palpation-based fusion scoring, microCT, and histology were used for assessment. No significant differences among the groups in the mean fusion score, fusion rate, and new bone volume were demonstrated. 

These findings are intriguing, and such research helps set the stage for carefully designed in vivo research projects, eventually moving toward randomized controlled trials, before recommending widespread use of cannabinoids for post-surgical pain management. 

Marc Swiontkowski, MD
JBJS Editor-in-Chief 

 

“Normal” Ultrasound May Not Rule Out DDH Later in Childhood

Some years ago, we moved away from calling hip dysplasia “congenital” and started using the term “developmental dysplasia of the hip” (DDH). Indeed, it is developmental. As a surgeon specializing in pediatric orthopaedics and hip preservation, I see not only infants when DDH is of potential concern but also young adults with more mature manifestations of hip dysplasia not previously diagnosed or treated.

Screening protocols have successfully helped in the early identification of DDH and dislocation, but what is the likelihood that infants with risk factors for dysplasia but normal ultrasound results will go on to experience DDH in childhood? And which risk factors are predictive?

In a recent report in JBJS Open Access, Humphry et al. provide new insight into these challenging questions. This study from the UK included 1,053 children from a cohort of 2,191 children who had been assessed as newborns and had at least 1 of 9 perinatal risk factors for DDH. All had undergone ultrasound at a mean of 8 weeks and were followed clinically.

The mean age of the children in the current study was 4.4 years (range, 2.0 to 6.6 years). Thirty-seven of the participants had been treated for DDH in the postnatal period, predominantly with a harness.

Assessing the acetabular index (AI) on pelvic radiographs, the authors found that:

  • 27 of the children had “severe” hip dysplasia (an AI of >2 standard deviations above age and sex reference values). Girls were more likely to have this outcome. Only 3 of the 27 received treatment for DDH in infancy.
  • 146 (13.9%) of the children had an AI of >20°, only 12 of whom had been treated during infancy; 92% had no prior diagnosis of DDH. On multivariate analysis, female sex and breech presentation at birth were significantly predictive of this “mild” dysplasia (breech presentation demonstrated a nearly twofold increased odds of an AI of >20° at ≥3 years of age), while first-born status had a protective effect.

The findings of this study lend support to radiographic monitoring later in childhood for patients with risk factors such as breech positioning at birth. While the exact algorithm of ultrasound and radiographic workup still needs to be elucidated, it appears that a “normal” ultrasound in infancy does not necessarily rule out the development of hip dysplasia in children with select risk factors.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

Multiligamentous Knee Injury May Not Be Synonymous with Knee Dislocation

Terminology is important in orthopaedics. When teaching, for instance, we stress the need for trainees to be able to articulate what a radiograph is showing using descriptive terms and classification systems.

Over the years, “multiligamentous knee injury” (MLKI) and “knee dislocation” have increasingly been used interchangeably within the orthopaedic vernacular, in part  because of the high energy required to sustain such injuries, but also because of the potentially devastating complications that can be associated with both.

Kahan et al. sought to better characterize these injuries and their associated complications in a study now reported JBJS. They retrospectively evaluated cases treated at their Level-I trauma center between 2001 and 2020.

A total of 123 patients with MLKI were included in the analysis: 45 patients with and 78 patients without a documented knee dislocation. MLKI was defined as disruption of at least 2 of the following: the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. Cruciate ligament injuries and isolated injuries of the superficial medial collateral ligament were not included unless there was disruption of the posteromedial corner, semimembranosus, or medial patellofemoral ligament, indicating a more extensive medial-sided injury.

The investigators found that medial-sided injuries were more common in the dislocation group (53% vs 30%; p = 0.009), and the dislocation group had higher rates of peroneal nerve injury (38% vs 14%; p = 0.004) and vascular injury (18% vs 4%; p = 0.018). Of the 11 total patients with a vascular injury, 8 (73%) were in the dislocation group; 10 of the 11 underwent a vascular surgical procedure.

Not all cases of MLKI are a result of a knee dislocation, and in this adequately powered study, there were differences in the injury pattern and associated injuries between those with and without true dislocation. It is important to note that, although higher rates of neurovascular injury were seen in the dislocation group, such events also occurred in the group without dislocation, so a high index of suspicion must be maintained with these complex injuries. As the authors suggest, it may be better to consider cases of knee dislocation a subset of MLKI with the potential for increased neurovascular compromise.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

 

 

 

Large Lytic Defects Produce Spinal Kinematic Instability

With the increasing effectiveness of immunotherapy and chemotherapy, patients with metastatic disease are surviving longer in much higher numbers. For many primary tumors (lung, breast, thyroid), a common site of metastases is the spine, giving rise to concomitant concerns regarding spine stability and the risk of neurologic compromise.

In the May 19, 2021 issue of JBJS, Alkalay et al. report the results of an in vitro study in which they simulated osteolytic defects in 3-level thoracic and lumbar segments of cadaveric spines. The simulations involved 2 patterns of lytic defects previously reported to be associated with increased risk of pathologic vertebral fracture: anterior-column compromise (40% of the vertebral body) and anterior plus middle-column compromise (extension of the model to include the ipsilateral pedicle and facet joint). The spinal segments were kinematically assessed in axial compression and axial compression with a flexion or extension moment, with testing before and after lesion simulation.

The authors concluded that “critical spinal lytic defects result in kinematic abnormalities and lower the compressive strength of the spine.” With greater lytic involvement, significantly higher translational motion along all 3 anatomic axes, and higher torsional and lateral-bending range of motion under axial compression with both flexion and extension moments were demonstrated.

The precision of the model in this cadaveric study was excellent. And the clinical implications of the findings are real: increasing lytic involvement of the vertebral body along with the pedicles could indicate impending instability, with the potential for neurologic injury. These data will be useful for surgeons and patients when formulating decisions regarding the need for intervention with fixation to limit flexion/extension forces in order to reduce pain and neurologic involvement. Future clinical data on the impact of these decisions in terms of pain and functional outcomes will be very valuable as we seek to optimize treatment of our patients with spinal metastatic disease.

Marc Swiontkowski, MD
JBJS Editor-in-Chief