Around-The-Knee Osteotomies Part II: Surgical Indications, Techniques, and Outcomes - State of the Art

Recent advances in surgical techniques and planning for knee-based osteotomies have led to improvements in addressing lower extremity malalignment. Part 1 of this review presented the biomechanical and clinical rationale of osteotomies, emphasizing the importance of osteotomies for restoring normal knee kinematics. In Part 2 of this review, indications, surgical technique, and outcomes of osteotomies to correct coronal, sagittal, and axial plane deformities will be examined. Traditional high tibial and distal femoral osteotomies will be discussed in addition to more recent advanced techniques including biplanar corrections and double level osteotomies, as well as slope correcting osteotomies. Patient specific instrumentation and its use in more complex corrections will also be addressed.

Reverse total shoulder arthroplasty for primary osteoarthritis with restricted preoperative forward elevation demonstrates similar outcomes but faster range of motion recovery compared to anatomic total shoulder arthroplasty

BACKGROUND

Reverse total shoulder arthroplasty (RSA) has been increasingly utilized for a variety of shoulder pathologies that are difficult to treat with anatomical total shoulder arthroplasty (TSA). Few studies have compared the outcomes of TSA vs. RSA in patients with cuff intact glenohumeral osteoarthritis and poor preoperative forward elevation. This study aimed to determine whether there is a difference in functional outcomes and postoperative range of motion (ROM) between TSA and RSA in these patients.

METHODS

This retrospective cohort study included 116 patients who underwent RSA or TSA between 2013 and 2022 for the treatment of rotator cuff intact primary osteoarthritis with restricted preoperative forward flexion (FF) and a minimum 1-year follow-up. Each arthroplasty group was divided into 2 subgroups: patients with preoperative FF between 91° and 120° or FF lower than or equal to 90°. Patients' clinical outcomes, including active ROM, American Shoulder and Elbow Surgeons score, visual analog scale for pain, and subjective shoulder value were collected. Clinical and radiographic complications were evaluated.

RESULTS

There was no significant difference between RSA and TSA in terms of sex (58.3% male vs. 62.2% male, P = .692), or follow-up duration (20.1 months vs. 17.7 months, P = .230). However, the RSA cohort was significantly older (72.0 ± 8.2 vs. 65.4 ± 10.6, P = .012) and weaker in FF and (ER) before surgery (P < .001). There was no difference between RSA (57 patients) and TSA (59 patients) in visual analog scale pain score (1.2 ± 2.3 vs. 1.3 ± 2.3, P = .925), subjective shoulder value score (90 ± 15 vs. 90 ± 15, P = .859), or American Shoulder and Elbow Surgeons score (78.4 ± 20.5 vs. 82.1 ± 23.2, P = .476). Postoperative active ROM was statistically similar between RSA and TSA cohorts in FF (145 ± 26 vs. 146 ± 23, P = .728) and ER (39 ± 15 vs. 41 ± 15, P = .584). However, internal rotation was lower in the RSA cohort (P < .001). This was also true in each subgroup. RSA led to faster postoperative FF and ER achievement at 3 months (P < .001). There was no statistically significant difference in complication rates between cohorts.

CONCLUSION

This study demonstrates that patients with glenohumeral osteoarthritis who have a structurally intact rotator cuff but limited preoperative forward elevation can achieve predictable clinical improvement in pain, ROM, and function after either TSA or RSA. Reverse arthroplasty may be a reliable treatment option in patients at risk for developing rotator cuff failure.

Reversing chronic pseudoparesis secondary to massive, irreparable rotator cuff tear: superior capsular reconstruction vs. reverse total shoulder arthroplasty

INTRODUCTION

Recent studies have defined pseudoparesis as limited active forward elevation between 45° and 90° and maintained passive range of motion (ROM) in the setting of a massive rotator cuff tear (RCT). Although pseudoparesis can be reliably reversed with reverse total shoulder arthroplasty (RSA) or superior capsular reconstruction (SCR), the optimal treatment for this indication remains unknown. The purpose of this study was to compare the clinical outcomes of RSA to SCR in patients with pseudoparesis secondary to massive, irreparable RCT (miRCT).

METHODS

This was a retrospective cohort study of consecutive patients aged 40-70 years with pseudoparesis secondary to miRCT who were treated with either RSA or SCR by a single fellowship-trained shoulder surgeon from 2016 to 2021 with a minimum 12-month follow-up. Multivariate linear regression modeling was used to compare active ROM, visual analog pain scale (VAS), Subjective Shoulder Value (SSV), and American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) score between RSA and SCR while controlling for confounding variables.

RESULTS

Twenty-seven patients were included in the RSA cohort and 23 patients were included in the SCR cohort with similar mean follow-up times (26.2 ± 21.1 vs. 21.9 ± 14.7 months, respectively). The patients in the RSA group were significantly older than those in the SCR group (65.2 ± 4.4 vs. 54.2 ± 7.8 years, P < .001) and had more severe arthritis (1.8 ± 0.9 vs. 1.2 ± 0.5 Samilson-Prieto, P = .019). The pseudoparesis reversal rate among the RSA and SCR cohorts was 96.3% and 91.3%, respectively. On univariate analysis, the RSA cohort demonstrated significantly greater mean improvement in active FF (89° ± 26° vs. 73° ± 30° change, P = .048), greater postoperative SSV (91 ± 8% vs. 69 ± 25%, P < .001), lower postoperative VAS pain scores (0.6 ± 1.2 vs. 2.2 ± 2.9, P = .020), and less postoperative internal rotation (IR; 4.6° ± 1.6° vs. 6.9° ± 1.8°, P = .004) compared with SCR. On multivariate analysis controlling for age and osteoarthritis, RSA remained a significant predictor of greater SSV (β = 21.5, P = .021) and lower VAS scores (β = -1.4, P = .037), whereas SCR was predictive of greater IR ROM (β = 3.0, P = .043).

CONCLUSION

Although both RSA and SCR effectively reverse pseudoparesis, patients with RSA have higher SSV and lower pain scores but less IR after controlling for age and osteoarthritis. The results of this study may inform surgical decision making for patients who are suitable candidates for either procedure.

Trends in implementation of evidence-based hip fracture management in a major Canadian city

Aims

The importance of hip fracture care has resulted in an abundance of hip fracture management literature. The degree this evidence is incorporated into clinical practice is unknown. We examined 5 trends in hip fracture management: arthroplasty versus fixation, total hip arthroplasty (THA) versus hemiarthroplasty (HA), cemented versus uncemented femoral stem fixation, short versus long cephalomedullary nail (CMN) fixation, and time from admission to surgery. Our primary aim was to understand and assess hip fracture management trends in relation to pertinent literature.

Methods

Data were collected from acute hip fractures in patients aged 50 years or older who presented from 2008 to 2018. ICD-10 diagnostic codes were assigned using preoperative radiographs. Surgical management was confirmed using intraoperative and postoperative radiographs and split into 6 categories: (1) short CMN, (2) long CMN, (3) cannulated screws, (4) dynamic hip screw, (5) HA, and (6) THA. Appropriate statistical tests were used to analyze trends.

Results

In 4 assessed trends, hip fracture management aligned with high-level evidence. This was the case for a trend toward arthroplasty for displaced femoral neck fractures, increased use of THA relative to HA, increased use of short relative to long CMNs, and consistent decrease in surgical wait times. Despite the literature highlighting the disadvantages of uncemented femoral stems, our data demonstrated increased use of uncemented femoral stems.

Conclusion

Evidence to guide orthopaedic practice is constantly emerging but may not be effectively used by clinicians. Our findings demonstrate the successes and failures of integrating evidence into hip fracture management and highlight that orthopaedic surgeons have an ongoing responsibility to strive for evidence-based practice.

Novel model for the induction of postnatal murine hip deformity

Acetabular dysplasia is a common, multi-etiological, pre-osteoarthritic (OA) feature that can lead to pain and instability of the young adult hip. Despite the clinical significance of acetabular dysplasia, there is a paucity of small animal models to investigate structural and functional changes that mediate morphology of the dysplastic hip and drive the subsequent OA cascade. Utilizing a novel murine model developed in our laboratory, this study investigated the role of surgically induced unilateral instability of the postnatal hip on the initiation and progression of acetabular dysplasia and impingement up to 8-weeks post-injury. C57BL6 mice were used to develop titrated levels of hip instability (i.e., mild, moderate, and severe instabillity or femoral head resection) at weaning. Joint shape, acetabular coverage, histomorphology, and statistical shape modeling were used to assess quality of the hip following 8 weeks of destabilization. Acetabular coverage was reduced following severe, but not moderate, instability. Moderate instability induced lateralization of the femur without dislocation, whereas severe instability led to complete dislocation and pseudoacetabulae formation. Mild instability did not result in morphological changes to the hip. Removal of the femoral head led to reduced hip joint space volume. These data support the notion that hip instability, driven by mechanical loss-of-function of soft connective tissue, can induce morphometric changes in the growing mouse hip. This work developed a new mouse model to study hip health in the murine adolescent hip and is a useful tool for investigating the mechanical and structural adaptations to hip instability during growth. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Molecular structure of three mutations at the maize sugary1 locus and their allele-specific phenotypic effects

Starch production in all plants examined is altered by mutations of isoamylase-type starch-debranching enzymes (DBE), although how these proteins affect glucan polymer assembly is not understood. Various allelic mutations in the maize (Zea mays) gene sugary1 (su1), which codes for an isoamylase-type DBE, condition distinct kernel phenotypes. This study characterized the recessive mutations su1-Ref, su1-R4582::Mu1, and su1-st, regarding their molecular basis, chemical phenotypes, and effects on starch metabolizing enzymes. The su1-Ref allele results in two specific amino acid substitutions without affecting the Su1 mRNA level. The su1-R4582::Mu1 mutation is a null allele that abolishes transcript accumulation. The su1-st mutation results from insertion of a novel transposon-like sequence, designated Toad, which causes alternative pre-mRNA splicing. Three su1-st mutant transcripts are produced, one that is nonfunctional and two that code for modified SU1 polypeptides. The su1-st mutation is dominant to the null allele su1-R4582::Mu1, but recessive to su1-Ref, suggestive of complex effects involving quaternary structure of the SU1 enzyme. All three su1- alleles severely reduce or eliminate isoamylase-type DBE activity, although su1-st kernels accumulate less phytoglycogen and Suc than su1-Ref or su1-R4582::Mu1 mutants. The chain length distribution of residual amylopectin is significantly altered by su1-Ref and su1-R4582::Mu1, whereas su1-st has modest effects. These results, together with su1 allele-specific effects on other starch- metabolizing enzymes detected in zymograms, suggest that total DBE catalytic activity is the not the sole determinant of Su1 function and that specific interactions between SU1 and other components of the starch biosynthetic system are required.

Purification and characterization of soluble starch synthases from maize endosperm

This study identified and characterized the soluble starch synthase of maize endosperm that was initially revealed as the SSII activity peak in anion exchange chromatography (J. L. Ozbun et al. (1971) Plant Physiol. 48, 765-769). At least six different genes coding for starch synthases are expressed in maize, although previously it was not known which of these is responsible for the SSII activity peak. The enzyme activity in the SSII peak was neutralized to a large extent by antibodies raised against the product of the Du1 gene, but was not affected by antibodies specific for the other highly expressed soluble starch synthase, zSSI, or for the zSSIIa or zSSIIb isoforms. These data provide direct evidence that Du1 codes for the starch synthase responsible for the SSII activity peak. This starch synthase was purified approximately 350-fold from endosperm extracts. The following enzymatic properties of the SSII activity were determined: temperature optimum, thermostability, pH effects, K(m) for different glucan primers and the glucosyl unit donor ADPGlc, V(max) using various primers, and stimulation by citrate. These properties were compared to those of zSSI purified over 1600-fold from maize endosperm by a parallel procedure. The major differences between the two enzymes were that the SSII activity displayed higher K(m) values for ADPGlc, a distinct temperature range for maximal activity, and different relative activities toward specific exogenous substrates. The purified SSI and SSII activities both were shown to be capable of elongating maltooligosaccharide primers in vitro.

Engine reconditioning workshops: lead contamination and the potential risk for workers: a pilot study

Lead concentrations were measured in surface dust, airborne dust, air, and grinding material from five engine reconditioning workshops to evaluate the impact on blood lead concentrations (PbB) of 10 employees. Lead in the environmental samples ranged from trace amounts to extremely high concentrations (4667 mg/m2). The highest concentrations in surface wipes were found in areas where engine deposits are removed from valves and valve seats. The amounts of lead in long term dustfall accumulation and static air filter samples varied with the position in the workshop and the amount of ventilation. In all but one workshop, the air lead concentrations exceeded Australian occupational guidelines of 150 micrograms Pb/m3. PbB ranged from 4.5 to 25.3 micrograms/dl. There was an empirical relation between the cleanliness, work practices, ventilation of the workshops, lead concentrations in environmental samples and PbB. Office employees not directly exposed to the leaded dust had the lowest PbB. Those who smoked had the highest PbB. Several relatively inexpensive recommendations were made to the owners to minimise exposure of the workers and in most cases these have been implemented.

Identification of the soluble starch synthase activities of maize endosperm

This study identified the complement of soluble starch synthases (SSs) present in developing maize (Zea mays) endosperm. The product of the du1 gene, DU1, was shown to be one of the two major soluble SSs. The C-terminal 450 residues of DU1 comprise eight sequence blocks conserved in 28 known or predicted glucan synthases. This region of DU1 was expressed in Escherichia coli and shown to possess SS activity. DU1-specific antisera detected a soluble endosperm protein of more than 200 kD that was lacking in du1- mutants. These antisera eliminated 20% to 30% of the soluble SS activity from kernel extracts. Antiserum against the isozyme zSSI eliminated approximately 60% of the total soluble SS, and immunodepletion of du1- mutant extracts with this antiserum nearly eliminated SS activity. Two soluble SS activities were identified by electrophoretic fractionation, each of which correlated specifically with zSSI or DU1. Thus, DU1 and zSSI accounted for the great majority of soluble SS activity present in developing endosperm. The relative activity of the two isozymes did not change significantly during the starch biosynthetic period. DU1 and zSSI may be interdependent, because mutant extracts lacking DU1 exhibited a significant stimulation of the remaining SS activity.

Purification and molecular genetic characterization of ZPU1, a pullulanase-type starch-debranching enzyme from maize

This study identified and purified specific isoamylase- and pullulanase-type starch-debranching enzymes (DBEs) present in developing maize (Zea mays L.) endosperm. The cDNA clone Zpu1 was isolated based on its homology with a rice (Oryza sativa L.) cDNA coding for a pullulanase-type DBE. Comparison of the protein product, ZPU1, with 18 other DBEs identified motifs common to both isoamylase- and pullulanase-type enzymes, as well as class-specific sequence blocks. Hybridization of Zpu1 to genomic DNA defined a single-copy gene, zpu1, located on chromosome 2. Zpu1 mRNA was abundant in endosperm throughout starch biosynthesis, but was not detected in the leaf or the root. Anti-ZPU1 antiserum specifically recognized the approximately 100-kD ZPU1 protein in developing endosperm, but not in leaves. Pullulanase- and isoamylase-type DBEs were purified from extracts of developing maize kernels. The pullulanase-type activity was identified as ZPU1 and the isoamylase-type activity as SU1. Mutations of the sugary1 (su1) gene are known to cause deficiencies of SU1 isoamylase and a pullulanase-type DBE. ZPU1 activity, protein level, and electrophoretic mobility were altered in su1-mutant kernels, indicating that it is the affected pullulanase-type DBE. The Zpu1 transcript levels were equivalent in nonmutant and su1-mutant kernels, suggesting that coordinated regulation of ZPU1 and SU1 occurs posttranscriptionally.

Characterization of SU1 isoamylase, a determinant of storage starch structure in maize

Function of the maize (Zea mays) gene sugary1 (su1) is required for normal starch biosynthesis in endosperm. Homozygous su1- mutant endosperms accumulate a highly branched polysaccharide, phytoglycogen, at the expense of the normal branched component of starch, amylopectin. These data suggest that both branched polysaccharides share a common precursor, and that the product of the su1 gene, designated SU1, participates in kernel starch biosynthesis. SU1 is similar in sequence to alpha-(1-->6) glucan hydrolases (starch-debranching enzymes [DBEs]). Specific antibodies were produced and used to demonstrate that SU1 is a 79-kD protein that accumulates in endosperm coincident with the time of starch biosynthesis. Nearly full-length SU1 was expressed in Escherichia coli and purified to apparent homogeneity. Two biochemical assays confirmed that SU1 hydrolyzes alpha-(1-->6) linkages in branched polysaccharides. Determination of the specific activity of SU1 toward various substrates enabled its classification as an isoamylase. Previous studies had shown, however, that su1- mutant endosperms are deficient in a different type of DBE, a pullulanase (or R enzyme). Immunoblot analyses revealed that both SU1 and a protein detected by antibodies specific for the rice (Oryza sativa) R enzyme are missing from su1- mutant kernels. These data support the hypothesis that DBEs are directly involved in starch biosynthesis.

Characterization of dull1, a maize gene coding for a novel starch synthase

The maize dull1 (du1) gene is a determinant of the structure of endosperm starch, and du1- mutations affect the activity of two enzymes involved in starch biosynthesis, starch synthase II (SSII) and starch branching enzyme IIa (SBEIIa). Six novel du1- mutations generated in Mutator-active plants were identified. A portion of the du1 locus was cloned by transposon tagging, and a nearly full-length Du1 cDNA sequence was determined. Du1 codes for a predicted 1674-residue protein, comprising one portion that is similar to SSIII of potato, as well as a large unique region. Du1 transcripts are present in the endosperm during the time of starch biosynthesis, but the mRNA was undetectable in leaf or root tissue. The predicted size of the Du1 gene product and its expression pattern are consistent with those of maize SSII. The Du1 gene product contains two repeated regions in its unique N terminus. One of these contains a sequence identical to a conserved segment of SBEs. We conclude that Du1 codes for a starch synthase, most likely SSII, and that secondary effects of du1- mutations, such as reduction of SBEIIa, result from the primary deficiency in this starch synthase.

Characterization of dull1, a maize gene coding for a novel starch synthase

The maize dull1 (du1) gene is a determinant of the structure of endosperm starch, and du1- mutations affect the activity of two enzymes involved in starch biosynthesis, starch synthase II (SSII) and starch branching enzyme IIa (SBEIIa). Six novel du1- mutations generated in Mutator-active plants were identified. A portion of the du1 locus was cloned by transposon tagging, and a nearly full-length Du1 cDNA sequence was determined. Du1 codes for a predicted 1674-residue protein, comprising one portion that is similar to SSIII of potato, as well as a large unique region. Du1 transcripts are present in the endosperm during the time of starch biosynthesis, but the mRNA was undetectable in leaf or root tissue. The predicted size of the Du1 gene product and its expression pattern are consistent with those of maize SSII. The Du1 gene product contains two repeated regions in its unique N terminus. One of these contains a sequence identical to a conserved segment of SBEs. We conclude that Du1 codes for a starch synthase, most likely SSII, and that secondary effects of du1- mutations, such as reduction of SBEIIa, result from the primary deficiency in this starch synthase.

Characterization of the maize gene sugary1, a determinant of starch composition in kernels

In maize kernels, mutations in the gene sugary1 (su1) result in (1) increased sucrose concentration; (2) decreased concentration of amylopectin, the branched component of starch; and (3) accumulation of the highly branched glucopolysaccharide phytoglycogen. To investigate further the mechanisms of storage carbohydrate synthesis in maize, part of the su1 gene locus and a cDNA copy of the su1 transcript were characterized. Five new su1 mutations were isolated in a Mutator background, and the mutant allele su1-R4582::Mu1 was isolated by transposon tagging. The identity of the cloned element as the su1 gene locus was confirmed by the cosegregation of restriction fragment length polymorphisms in the same or nearby genomic intervals with three additional, independent su1 mutations. Pedigree analysis was also used to confirm the identity of su1. A 2.8-kb mRNA that is homologous to the cloned gene was detected in maize kernels, and a 2.7-kb cDNA clone was isolated based on hybridization to the genomic DNA. Specific portions of the cDNA hybridized with multiple segments of the maize genome, suggesting that su1 is part of a multigene family. The cDNA sequence specified a polypeptide of at least 742 amino acids, which is highly similar in amino acid sequence to bacterial enzymes that hydrolyze alpha-(1-->6) glucosyl linkages of starch. Therefore, debranching of glucopolysaccharides is seemingly part of the normal process of starch biosynthesis, and the final degree of branch linkages in starch most likely arises from the combined actions of branching and debranching enzymes.

Genetic analysis of 63 mutations affecting maize kernel development isolated from Mutator stocks

Sixty-three mutations affecting development of the maize kernel were isolated from active Robertson's Mutator (Mu) stocks. At least 14 previously undescribed maize gene loci were defined by mutations in this collection. Genetic mapping located 53 of these defective kernel (dek) mutations to particular chromosome arms, and more precise map determinations were made for 21 of the mutations. Genetic analyses identified 20 instances of allelism between one of the novel mutations and a previously described dek mutation, or between new dek mutations identified in this study; phenotypic variability was observed in three of the allelic series. Viability testing of homozygous mutant kernels identified numerous dek mutations with various pleiotropic effects on seedling and plant development. The mutations described here presumably arose by insertion of a Mu transposon within a dek gene; thus, many of the affected loci are expected to be accessible to molecular cloning via transposon-tagging.

DNA sequence and transcript analysis of transposon MuA2, a regulator of Mutator transposable element activity in maize

The 4942 bp DNA sequence of Zea mays transposon MuA2 was determined. Previous evidence indicated MuA2 controls activity of the Mu1 transposon located in the mutable allele a1-mum2. MuA2 contains two large, ATG-initiated open reading frames (ORFs) of 612 and 232 codons, respectively, located on opposite strands. MuA2 produces two transcripts, each containing one of these ORFs. Four different tandem direct repeat sequences are located downstream of the 612 codon ORF. The restriction map of MuA2 is identical to that of transposon MuR1, which also is known to regulate mutability of a1-mum2. Furthermore, except for a single nucleotide, MuA2 is identical to the Mutator element Mu9.

Molecular characterization of Mutator systems in maize embryogenic callus cultures indicates Mu element activity in vitro

Active Mutator lines of maize (Zea mays L.) are characterized by their ability to generate new mutants at a high rate and by somatic instability at Mutator-induced mutant alleles. Mutagenically active lines with fewer than ten Mu elements per diploid genome have not been observed. Alteration of Mutator activity has been shown to correlate with the state of modification of Hinfl restiction sites that lie within inverted terminal repeats of Mu elements. To determine whether active Mutator systems can be established and maintained in culture, copy number and modification state of Mu elements were investigated in embryogenic callus lines derived from F1S of crosses of active Mutator stock with the inbred lines A188 and H99. All callus lines studied maintain high Mu-element copy numbers, and more than half show a continued lack of modification at the Mu element Hinfl sites; thus, parameters associated with mutagenic activity in planta are present in some, but not all, callus lines. Mutator activity was then tested directly by restriction fragment analysis of subclonal populations from A188/Mu (2) and H99/Mu (2) embryonic cultures. Novel Mu-homologous restriction fragments occurred in 38% of the subpopulations which contained unmodified Mu elements, but not in control cultures containing modified, genetically inactive Mu elements. We conclude that Mu elements from active Mutator parents can remain transpositionally active in embryogenic cell culture. Active Mutator cell lines may be useful for the production of mutations in vitro.