Who Doesn’t Have a Screw Loose?
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
Fracture fixation with a plate and screws has been around for a century—and so has the problem of screw loosening. Part of the cause of screw loosening seems to be toggling caused by radial forces arising from plate micromotion. Several decades ago, locked screws were designed to prevent loosening and provide better fixation, but screws still loosen.
Two tests can predict screw loosening associated with bone microfracture and absorption: axial pullout stress and toggling radial stress. Recent studies have investigated two hypotheses: radial stress is a predominant cause of screw loosening, and bone resorption is triggered by high radial stress.
Finite Element Analyses
A finite elemental model was used to replicate fixation of a tibial fracture with a 3-mm gap using either a dynamic compression plate (DCP) or locking compression plate (LCP).1 The model included contact with bone, tension on screw insertion, and the placement of two inner screws and one outer screw on either side of the fracture for an 8-hole plate. Axial loading, torsional loading, and bending were applied. Forces exceeding 55 megapascal (MPa) were considered adequate to cause microfracture, whether by radial or axial force. (For reference, 55 MPa is just about 8,000 pounds per square inch.)
The principal finding was that more bone was damaged by radial than by axial stress in both types of plates. Both plate types had more bone damaged by radial stress at the central two screws than at the two end screws for all bending models.
Radiographic Analyses
A separate study evaluated clinical radiographs of fixation for humeral, radial, ulnar, femoral, and tibial shaft fractures. Researchers looked for screw migration or bone absorption of ≥1 mm around the screw. Both DCPs and LCPs were reviewed.
Researchers found that the outer screws loosened only after the inner screws loosened. There were 3 cases of bone loss with no loosening, 17 cases of bone loss with screw displacement, and no cases of screw loosening without bone loss. This strongly suggests that bone loss must occur for loosening to take place and that the earliest screw loosening occurs closer to the facture site.
Taken together, these results imply that the use of larger inner screws and/or the use of a different angle of fixation might reduce bone absorption that leads to loosening. In addition, radial stress testing might be more important than axial testing. Still, LCPs remain superior at resisting axial loading and bending moments, while DCPs remain superior at resisting torsional loading of unstable fractures.
Reference
- Feng X, Lin G, Fang CX, Lu WW, Chen B, Leung FKL. Bone resorption triggered by high radial stress: The mechanism of screw loosening in plate fixation of long bone fractures. J Orthop Res. 2019 Jul;37(7):1498-1507. doi: 10.1002/jor.24286. Epub 2019 Apr 8 PMID: 30908687
Delaying Knee Replacement: Driven to Distraction?
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
Some symptomatic patients with knee osteoarthritis (OA) present relatively early in the radiographic disease process, while others present after serious articular cartilage loss has occurred. In either case, young knee OA patients are often looking for ways to get relief while postponing a total knee arthroplasty (TKA).
One such recently introduced alternative is knee joint distraction (KJD), a joint-preserving surgery used for bicompartmental tibiofemoral knee osteoarthritis or unilateral OA with limited malalignment. Significant long-term clinical benefit as well as durable cartilage tissue repair have been reported in an open prospective study with 5 years of follow-up.1 A more recent study of distraction2 presents 2-year follow-up results of a 2-pronged trial that measured patient-reported outcomes, joint-space width (JSW), and systemic changes in biomarkers for collagen type-II synthesis and breakdown.
In one arm, end-stage knee OA patients who were candidates for TKA were randomized to KJD (n=20) or TKA (n=40). In the second arm, earlier-stage patients with medial compartment OA and a varus angle <10° were randomized to KJD (n=23) or high tibial osteotomy (HTO; n=46). In the distraction patients, the knee was distracted 5 mm for 6 weeks using external fixators with built-in springs, placed laterally and medially, and weight-bearing was encouraged. WOMAC scores and VAS pain scores were assessed at baseline and at 3, 6, 12, 18, and 24 months.
At 24 months, researchers found no significant differences between the KJD and HTO groups in that part of the trial. In the KJD/TKA arm, there was no difference in WOMAC scores between the two groups, but VAS scores were lower in the TKA group. The improvement in mean joint space width seen at one year in the KJD group of the KJD/TKA arm decreased by two years, though the values were still improved compared to baseline. However, the joint space width improvement seen at 1 year for both groups in the KJD/HTO arm persisted for two years. For all KJD patients, the ratio of biomarkers of synthesis over breakdown of collagen type-II was significantly decreased at 3 months but reversed to an increase between 9 and 24 months.
It is hard to believe that 6 weeks of joint distraction could trigger a process that yields such positive and long-lasting results. While much more research with longer follow-up is needed, KJD may prove particularly useful in younger knee OA patients trying to delay joint replacement.
References
- van der Woude, JAD, Wiegant, K, van Roermund, PM, Intema, F, Custers, RJH, Eckstein, F. Five-year follow-up of knee joint distraction: clinical benefit and cartilaginous tissue repair in an open uncontrolled prospective study. Cartilage. 2017;8:263-71.
- Jansen MP, Besselink NJ, van Heerwaarden RJ, Roel J.H. Custers1, Jan-Ton A.D. Van der Woude J-TAD, Wiegant K, Spruijt S, Emans PJ, van Roermund PM, Mastbergen SC, Lafeber FP. Knee joint distraction compared with high tibial osteotomy and total knee arthroplasty: two-year clinical, structural, and biomarker outcomes. ORS 2019 Annual Meeting Paper No. 0026 (Cartilage. 2019 Feb 13:1947603519828432. doi: 10.1177/1947603519828432. [Epub ahead of print])
Placenta-Derived Cells Give Short-term Boost to Tendon Repair
From journal articles to nightly news segments, it’s hard to avoid the barrage of information related to the use of cell-based therapies for musculoskeletal problems. While these approaches may turn out to be enthusiasm outpacing science (see related OrthoBuzz post, “Stemming the Tide of Stem Cell Hype”), one reason for the excitement is rooted in a very simple fact: it is really hard to get many soft tissues to heal, especially in certain patient populations. Moreover, failure of initial repair usually leads to even more biologically inhospitable repair environments. This clinical challenge has led to the zealous investigation of various cell-based compounds to see which ones might assist native soft-tissue cells with the formidable task of quick healing.
In the July 3, 2019 issue of The Journal, Ma et al. investigate the potential for human placenta-derived cells to augment the healing of chemically induced patellar tendon ruptures in rats. The injected placental cells introduced a transitory inflammatory response that led to increased load to failure at the 2-week mark, compared to biomechanical results in control rat tendons injected with saline solution. However, the addition of placenta-derived cells did not increase tendon load to failure beyond 2 weeks, and at no time point were differences seen between the control and experimental groups in tendon strength, stiffness, collagen organization, or cellularity.
While the positive results of this study were short-lived, they are important nonetheless. The animal model used is well thought-out and reproducible, allowing an easy path for future investigators to compare and contrast these results. Placenta-derived cell populations are widely available, and the authors clearly explained how the cells were processed, preserved, and delivered. With the increasing incidence of acute and chronic tendon injuries, and with the results of studies using other cell types being equivocal at best, these findings from Ma et al. are noteworthy.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Stemming the Tide of Stem Cell Hype
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
Despite the absence of research-based guidance, the use of stem cell therapies in musculoskeletal medicine has gained popularity and stimulated patient interest. Consequently, an international consensus was recently established to develop strategies to improve standardization and transparency when describing cell therapies, and to develop a consensus on the contents of a standardized tool for describing cell therapies.1 The tool, dubbed DOSES, was an outgrowth of a call for improvement in communicating about cell-based therapies made during the American Academy of Orthopaedic Surgeons/National Institutes of Health Optimizing Clinical Use of Biologics Symposium in 2018.
The international experts used an iterative Delphi methodology to develop DOSES. The five components of the DOSES tool are Donor (i.e., autologous, allogeneic, xenogeneic), Origin of tissue (fat, bone marrow, etc.), Separation from other cell types/preparation method, Exhibited cell characteristics, and the Site of delivery. The tool should help clinicians, researchers, regulators, and industry professionals describe and communicate about any given stem cell treatment clearly and transparently.
In a commentary on the DOSES article, Scott Rodeo, MD notes that efforts are under way to clarify and classify stem cells by genomics, proteomics, metabolomics, and other approaches.2 Dr. Rodeo believes that the most important component of DOSES is the “E” category, information that will ultimately characterize the biologic activity of the cell preparation. He concludes by encouraging “clinicians, industry, and authors of both laboratory and clinical studies to begin the use of the DOSES tool, and possibly other algorithms, when communicating the results of cell therapy investigations.” This admonition carries over to journal editors, who, Dr. Rodeo says, should “consider adopting such reporting standards as mandatory for publication” of stem cell studies.
For stem cell therapy to progress clinically in the future, researchers and clinicians must apply a consistent nomenclature to describe cell therapies and actual cell formulations.3 This is lacking in today’s applications.
References
- Murray IR, Chahla J, Safran MR, Krych AJ, Saris DBF, Caplan AI, LaPrade RF. International Expert Consensus on a Cell Therapy Communication Tool: DOSES. J Bone Joint Surg Am. 2019 May 15;101(10):904-911. doi: 10.2106/JBJS.18.00915. PMID: 31094982
- Rodeo SA. A Call for Standardization in Cell Therapy Studies: Commentary on an article by Iain R. Murray, BMedSci(Hons), MRCS, MFSEM, PhD, et al.: “International Expert Consensus on a Cell Therapy Communication Tool: DOSES”. J Bone Joint Surg Am. 2019 May 15;101(10):e47. doi: 10.2106/JBJS.19.00189. PMID: 31094994.
- Jones IA, Chen X, Evseenko D, Vangsness CT Jr. Nomenclature Inconsistency and Selective Outcome Reporting Hinder Understanding of Stem Cell Therapy for the Knee. J Bone Joint Surg Am. 2019 Jan 16;101(2):186-195. doi: 10.2106/JBJS.17.01474. PMID: 30653050
Subacromial Balloon May Benefit Irreparable Cuff Tears
The surgical options for treating irreparable tears of the supraspinatus—cuff reconstruction, tendon transfers, and shoulder replacement—are limited and complicated. But biomechanical results from a cadaveric study of 14 shoulders by Lobao et al., published in the June 5, 2019 issue of JBJS, suggest that a biodegradable balloon spacer inserted subacromially could effectively treat such insufficiencies, possibly postponing the need for more aggressive procedures.
Using an irreparable supraspinatus tear model and sophisticated instruments, the authors determined that, at postoperative time 0, the saline-inflated balloon:
- Restored intact-state glenohumeral contact pressures at most abduction angles
- Moved the humeral head inferiorly by a mean of 6.2 mm at 0° of abduction and 3.0 mm at 60°
- Increased deltoid load by 8.2% at 0° and by 11.1% at 60°.
The balloon, however, did not restore glenohumeral contact area to that of an intact shoulder.
Although the authors cite a previous clinical case series using this approach,1 they are quick to point out that “it is not possible to correlate our findings with clinical scenarios.” Nevertheless, they say that the biomechanical data obtained from this cadaveric study “suggest that the balloon may be of benefit clinically, at least in the immediate postoperative setting.”
Reference
- Deranlot J, Herisson O, Nourissat G, Zbili D, Werthel JD, Vigan M, Bruchou F. Arthroscopic subacromial spacer implantation in patients with massive irreparable rotator cuff tears: clinical and radiographic results of 39 retrospectives cases. Arthroscopy. 2017 Sep;33(9):1639-44. Epub 2017 Jun 8
Meniscal Extrusions: Imaging and Repair
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
Loss of hoop stress by either medial or lateral menisci can cause meniscal extrusion, which results in increased forces on articular cartilage. The degree of meniscal extrusion is typically measured as a 2-dimensional distance with MRI. However, investigators recently used 3-D MRI to analyze the relationship between medial meniscal extrusion (MME) and femoral cartilage change in patients with these tears.1
Fifteen males (mean age of 56 years) with a medial meniscal degenerative tear (grade 3 by the Mink classification) based on MRI were included. The cartilage area was reconstructed in 3-D, and the femoral cartilage was projected in 2-D by 3-D MRI analysis. The femoral cartilage of the femorotibial joint was divided into 4 segments, and the cartilage area ratio was defined as the ratio of cartilage with thickness ≥1.0 mm in each segment. The tibial MME area (mm2) and volume (cm3), excluding osteophytes, were measured by 3-D MRI.
The projected cartilage area ratio (cartilage thickness ≥1.0 mm) at the posteromedial segment was lower than the ratio at the other 3 segments. The cartilage area ratio at the posteromedial segment was not correlated with the MME distance measured by the 2-D MRI, but it was negatively correlated with MME area (r=-0.53, p=0.045) and MME volume (r=-0.62, p=0.016) as measured by 3-D MRI. Overall, the 3-D imaging more accurately reflected cartilage damage.
Both radial tears and posterior horn degeneration can lead to meniscal extrusion. When this injury is seen acutely in younger persons, repairs are often attempted. Recently efforts have been made to do repairs in older individuals. The use of cell-seeded nanofibrous scaffolds to repair radial tears and resulting hoop-structure injuries has been studied for prevention of articular cartilage degeneration using a rabbit model.2
Synovial mesenchymal stem cells were isolated and expanded into sheets that were then wrapped onto poly(e-caprolactone) scaffolds to create stable cell/scaffold tissue-engineered constructs (TECs). Scaffold-alone or TEC + scaffold constructs were then sutured into created radial meniscal defects (12 rabbits in each group).
The TEC-scaffold group maintained the structure of the hyaline cartilage with matrix staining with Safranin O up to 12 weeks after surgery. Although the cartilage coverage decreased in both groups, the TEC-scaffold group did not become significantly worse over time, suggesting stabilization of hoop structure integrity. Only the TEC-scaffold group showed repair tissue that exhibited positive Safranin O staining in the inner zone of the meniscus.
Future studies will be required to determine the role of tissue engineering in the preservation of meniscal coverage in the face of radial tears.
References
- Suzuki S, Ozeki N, Kohno Y, Mizuno M, Otabe K, Katano H, Tsuji K, Suzuki K, Itai Y, Masumoto J, Koga H, Sekiya I. Medial meniscus extrusion (MME) area and MME volume determined by 3D-MRI are more sensitive than MME distance determined by 2D-MRI for evaluating cartilage loss in knees with medial meniscus degenerative tears. ORS 2019 Annual Meeting Poster No. 0514.
- Shimomura K, Rothrauff BB, Hart DA, Hamamoto S, Kobayashi M, Yoshikawa H, Tuan RS, Nakamura N. Enhanced Repair of Meniscal Hoop Structure Injuries Using An Aligned Electrospun Nanofibrous Scaffold Combined with a Mesenchymal Stem Cell-derived Tissue Engineered Construct. ORS 2019 Annual Meeting Poster No. 0519.
Electrocautery Damages Metal Hip Implants in 2 Ways
In the setting of revision total hip arthroplasty (THA), the use of electrocautery—and contact between the thermal device and retained components—cannot always be avoided. In the May 15, 2019 issue of The Journal of Bone & Joint Surgery, Sonntag et al. perform two implant-retrieval analyses and a separate in vitro investigation to determine what kinds of damage take place when electrocautery energy meets titanium femoral stems.
The components for retrieval analyses were removed from patients who experienced a fracture of the femoral stem or femoral neck after revision THA. The authors found superficial discoloration and melting marks on the retrieved components, and elemental analysis indicated that material had been transferred from the electrocautery tip. During in vitro testing of 6 titanium alloy femoral stems, the authors found that electrocautery surface damage reduced load-to-failure by up to 47% when compared to undamaged femoral neck specimens. Microscopic analysis revealed notable changes in metal microstructure in electrocautery-exposed components, whereby certain zones exhibited higher strength than others, which, the authors speculate, might result in lower overall fatigue resistance.
Both the retrieval and in vitro analyses showed that electrocautery damage to femoral implants, particularly in the anterolateral region at the base of the neck, reduced implant fatigue resistance. However, the authors say their results need to “be carefully interpreted,” because they are based on only 2 retrievals and a limited number of test specimens. Nevertheless, they conclude that “electrocautery device contact [with femoral implants] should be avoided and the use of conventional scalpels is recommended, where reasonable.”
NYT Cites Hype of Stem-Cell Treatments for Joint Problems
An active, 71-year old man who declined joint replacement in favor of stem-cell treatment is quoted in a recent New York Times article as saying, “They’re really quick to try to give you fake joints and make a bunch of money off you.” But the NYT article goes on to suggest that making money may be the main objective of some of the many hundreds of clinics that have sprung up around the US to offer cell-based injections to people with aging or damaged joints who want relief without surgery.
The article points out that the FDA has “taken an industry-friendly approach toward companies using unproven cell cocktails” and that the scant scientific evidence about these treatments, which include injections of platelet-rich plasma, is inconclusive.
For OrthoBuzz readers who want to dive more deeply into the scientific underpinnings (or lack thereof) related to cell therapies for joint problems, please peruse the following JBJS and JBJS Reviews articles, which have been made openly available for a limited period of time:
- Intra-articular Cellular Therapy for Osteoarthritis and Focal Cartilage Defects of the Knee
- Nomenclature Inconsistency and Selective Outcome Reporting Hinder Understanding of Stem Cell Therapy for the Knee
- International Expert Consensus on a Cell Therapy Communication Tool: DOSES
- Stem Cell Therapy for Knee Pain–What Exactly Are We Injecting, and Why?
- A Call for Standardization in Cell Therapy Studies
- A Comprehensive Review of Stem-cell Therapy
The main message running through all these articles is this: Effective clinical assessment and safe, optimized use of cell-based therapies demands greater attention to study methods; standards for cell harvesting, processing, and delivery; and standardized reporting of clinical and structural outcomes.
Whole-Slide View of Rare Orthopaedic Tumor
JBJS Case Connector debuted digital whole-slide images back in 2016, and the February 27, 2019 case report by Lans et al. put that ability to link to and navigate an entire microscope slide to good use again.
The 27-year-old man described in this case report presented with a progressively painful right forearm. Conventional radiographs and MRI led clinicians to suspect a rare desmoplastic fibroma of the proximal aspect of the radius, but it was not until a CT-guided core biopsy was analyzed histologically that the diagnosis could be confirmed. The histologic findings, depicted in a digital whole-slide image, revealed a fibrous to fibro-osseous lesion composed of fibroblast-like cells with varying degrees of hypercellularity.
The patient subsequently underwent a wide-margin resection that preserved the radial head but created an 8.5-cm defect, which surgeons reconstructed with a vascularized fibular autograft. At the 2-year follow-up, the patient’s QuickDASH score was 2.7 and his PROMIS Upper Extremity and Physical Function Short Form score was 42.
For more information about JBJS Case Connector, watch this video featuring JBJS Editor-in-Chief Dr. Marc Swiontkowski.
A CRISPR/Cas9 Tutorial
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
Understanding recent gene technology can be very daunting. The CRISPR/Cas9 method for gene editing is a prominent example. CRISPR stands for Clustered Regularly Interspersed Short Palindromic Repeats, and Cas9 is an acronym for the CRISPER-Associated Protein 9. Scientists became aware of CRISPR in E. coli in 1987, but they only recently realized that CRISPR constituted an adaptive immune system for bacteria and archae, which are primitive bacteria-like cells.
When infected by a virus (phage), a bacteria’s Cas genes are activated. Cas gene products cut viral DNA sequence sites called protospacers and then insert those sequences into the bacterial DNA. The host bacterium identifies the viral sequences by a protospacer adjacent motif (PAM), which is rarely seen in the host genome. Hence, replication of this sequence will not adversely affect the host. In the event of a second phage attack, Cas genes are activated and they generate CRISPR RNA (crRNA), which recognizes the phage sequence. crRNA associates with Cas nucleases to cleave both DNA strands of the invader.
There are numerous CRISPR modules. Type II CRISPR is one of an expanding number of naturally existing CRISPR families that has have been used for gene editing in eukaryotes. The type II CRISPR family uses crRNA and an additional tracrRNA to target specific DNA sequences. These have been combined to create a single guide RNA (gRNA) to direct sequence-specific Cas9 double-stranded DNA cleavage. The result is a simple, programmable RNA method that has been used for genome targeting and genome editing in eukaryotes.
The accuracy of this system has been markedly enhanced to avoid unwanted mutations. The system is being fashioned to block existing gene expression, modify gene expression by inserting DNA sequences, and activate expression of single or multiple genes. CRISPR technology enables researchers to develop mouse models of disease much more quickly and less expensively than traditional approaches. Larger animal models of disease can also now be produced.
Successful treatment of mouse models of human diseases with CRISPR suggests that the technology can be applied to directly treat human diseases in the future. Preclinical research is underway using CRISPR-ed stem cells or mouse models to study human diseases such as retinitis pigmentosa, Fanconi anemia, Duchenne muscular dystrophy, sickle-cell anemia, and cystic fibrosis.
Thanks to Dr. Gary Gibson for his help with this tip.
Reference
Gibson GJ, Yang M. What rheumatologists need to know about CRISPR/Cas9. Nat Rev Rheumatol. 2017 Apr;13(4):205-216. doi: 10.1038/nrrheum.2017.6. Epub 2017 Feb 9.
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