Trapeziometacarpal Joint Stability: The Evolving Importance of the Dorsal Ligaments

Background

Trapeziometacarpal (TMC) arthritis of the thumb is a common source of hand pain and disability. TMC ligamentous instability may play a role in TMC degeneration. However, the relative importance of the TMC ligaments in the etiology of degeneration and the use of surgery to treat instability in early-stage arthritis are unclear.

Questions/purposes

In this review, we addressed several questions: (1) What are the primary ligamentous stabilizers of the thumb TMC joint? (2) What is the evidence for ligament reconstruction or ligament imbrication in the treatment of thumb TMC joint osteoarthritis? And (3) what is the evidence for thumb metacarpal osteotomy in the treatment of thumb TMC joint osteoarthritis?

Methods

We performed a systematic review of the literature using PubMed (MEDLINE^®) and Scopus^® (EMBASE^®) for peer-reviewed articles published until November 2012. Fifty-two studies fit the inclusion criteria. Twenty-four studies were anatomic, biomechanical, or histopathologic studies on TMC joint ligamentous anatomy, 16 studies were clinical studies concerning ligament reconstruction, and 12 studies were clinical studies on thumb metacarpal osteotomy.

Results

Over the past two decades, increasing evidence suggests the dorsoradial ligament is the most important stabilizer of the TMC joint. Other ligaments consistently identified are the superficial anterior oblique, deep anterior oblique, intermetacarpal, ulnar collateral, and posterior oblique ligaments. Ligament reconstruction and metacarpal osteotomy relieve pain and improve grip strength based on Level IV studies.

Conclusions

The dorsal ligaments are the primary stabilizers of the TMC joint. Ligament reconstruction and metacarpal osteotomy ameliorate ligamentous laxity and relieve pain based on Level IV studies.

Electronic supplementary material

The online version of this article (doi:10.1007/s11999-013-2879-9) contains supplementary material, which is available to authorized users.     

Are Quadrilateral Surface Buttress Plates Comparable to Traditional Forms of Transverse Acetabular Fracture Fixation?

Background

Several construct options exist for transverse acetabular fracture fixation. Accepted techniques use a combination of column plates and lag screws. Quadrilateral surface buttress plates have been introduced as potential fixation options, but as a result of their novelty, biomechanical data regarding their stabilizing effects are nonexistent. Therefore, we aimed to determine if this fixation method confers similar stability to traditional forms of fixation.

Questions/purposes

We biomechanically compared two acetabular fixation plates with quadrilateral surface buttressing with traditional forms of fixation using lag screws and column plates.

Methods

Thirty-five synthetic hemipelves with a transverse transtectal acetabular fracture were allocated to one of five groups: anterior column plate + posterior column lag screw, posterior column plate + anterior column lag screw, anterior and posterior column lag screws only, infrapectineal plate + anterior column plate, and suprapectineal plate alone. Specimens were loaded for 1500 cycles up to 2.5x body weight and stiffness was calculated. Thereafter, constructs were destructively loaded and failure loads were recorded.

Results

After 1500 cycles, final stiffness was not different with the numbers available between the infrapectineal (568 ± 43 N/mm) and suprapectineal groups (602 ± 87 N/mm, p = 0.988). Both quadrilateral plates were significantly stiffer than the posterior column buttress plate with supplemental lag screw fixation group (311 ± 99 N/mm, p < 0.006). No difference in stiffness was identified with the numbers available between the quadrilateral surface plating groups and the lag screw group (423 ± 219 N/mm, p > 0.223). The infrapectineal group failed at the highest loads (5.4 ± 0.6 kN) and this was significant relative to the suprapectineal (4.4 ± 0.3 kN; p = 0.023), lag screw (2.9 ± 0.8 kN; p < 0.001), and anterior buttress plate with posterior column lag screw (4.0 ± 0.6 kN; p = 0.001) groups.

Conclusions

Quadrilateral surface buttress plates spanning the posterior and anterior columns are biomechanically comparable and, in some cases, superior to traditional forms of fixation in this synthetic hemipelvis model.

Clinical Relevance

Quadrilateral surface buttress plates may present a viable alternative for the treatment of transtectal transverse acetabular fractures. Clinical studies are required to fully define the use of this new form of fixation for such fractures when accessed through the anterior intrapelvic approach.     

Are Copy Number Variants Associated With Adolescent Idiopathic Scoliosis?

Background

Adolescent idiopathic scoliosis (AIS) is a complex genetic disorder that causes spinal deformity in approximately 3% of the population. Candidate gene, linkage, and genome-wide association studies have sought to identify genetic variation that predisposes individuals to AIS, but the genetic basis remains unclear. Copy number variants are associated with several isolated skeletal phenotypes, but their role in AIS, to our knowledge, has not been assessed.

Questions/Purposes

We determined the frequency of recurrent copy number rearrangements, chromosome aneuploidy, and rare copy number variants in patients with AIS.

Methods

Between January 2010 and August 2014, we evaluated 150 patients with isolated AIS and spinal curvatures measuring 10° or greater, and 148 agreed to participate. Genomic copy number analysis was performed on patients and 1079 control subjects using the Affymetrix^® Genome-wide Human SNP Array 6.0. After removing poor quality samples, 143 (97%) patients with AIS were evaluated for copy number variation.

Results

We identified a duplication of chromosome 1q21.1 in 2.1% (N = 3/143) of patients with AIS, which was enriched compared with 0.09% (N = 1/1079) of control subjects (p = 0.0057) and 0.07% (N = 6/8329) of a large published control cohort (p = 0.0004). Other notable findings include trisomy X, which was identified in 1.8% (N = 2/114) of female patients with AIS, and rearrangements of chromosome 15q11.2 and 16p11.2 that previously have been associated with spinal phenotypes. Finally, we report rare copy number variants that will be useful in future studies investigating candidate genes for AIS.

Conclusions

Copy number variation and chromosomal aneuploidy may contribute to the pathogenesis of adolescent idiopathic scoliosis.

Clinical Relevance

Chromosomal microarray may reveal clinically useful abnormalities in some patients with AIS.     

The Effect of Geometric Variations in Posterior-stabilized Knee Designs on Motion Characteristics Measured in a Knee Loading Machine

Background

In different posterior-stabilized (PS) total knees, there are considerable variations in condylar surface radii and cam-post geometry. To what extent these variations affect kinematics is not known. Furthermore, there are no clearly defined ideal kinematics for a total knee.

Questions/purposes

The purposes of this study were to determine (1) what the kinematic differences are caused by geometrical variations between PS total knee designs in use today; and (2) what design characteristics will produce kinematics that closely resemble that of the normal anatomic knee.

Methods

Four current PS designs with different geometries and one experimental asymmetric PS design, with a relatively conforming medial side, were tested in a purpose-built machine. The machine applied combinations of compressive, shear, and torque forces at a sequence of flexion angles to represent a range of everyday activities, consistent with the ASTM standard test for measuring constraint. The femorotibial contact points, the neutral path of motion, and the AP and internal-external laxities were used as the kinematic indicators.

Results

The PS designs showed major differences in motion characteristics among themselves and with motion data from anatomic knees determined in a previous study. Abnormalities in the current designs included symmetric mediolateral motion, susceptibility to excessive AP medial laxity, and reduced laxity in high flexion. The asymmetric-guided motion design alleviated some but not all of the abnormalities.

Conclusions

Current PS designs showed kinematic abnormalities to a greater or lesser extent. An asymmetric design may provide a path to achieving a closer match to anatomic kinematics.

Clinical Relevance

One criterion for the evaluation of PS total knees is how closely the kinematics of the prosthesis resemble that of the anatomic knee, because this is likely to affect the quality of function.     

Primary hyperparathyroidism across the ages: presentation and outcomes

Background

Primary hyperparathyroidism (PHPT) is a disease process traditionally thought to present during middle age, but can occur at any age. The purpose of this study was to compare PHPT patient characteristics based on patient age at the time of surgical referral.

Methods

A retrospective review of a prospectively managed database of adult patients undergoing parathyroid surgery for PHPT was conducted. Patients with a negative family history, no previous parathyroid surgery, and ≥6-mo follow-up were included. Patients were grouped by age for comparison.

Results

From 2001–2012, 1372 patients met inclusion criteria. Age groups were as follows: ≤50 y, 51–60 y, 61–70 y, and >70 y. Female predominance increased with age (P > 0.01). Baseline serum parathyroid hormone levels were higher at the extremes of age (P < 0.001). Young patients had the highest serum calcium (P < 0.01), urinary calcium (P < 0.001), and T-score (P < 0.001) measures, and greater incidence of vitamin D deficiency (P = 0.03). The use of local anesthesia increased with age, whereas use of outpatient parathyroidectomy decreased with age (both P < 0.01). Rates of disease persistence (2.3%–2.9%, P = 0.95) and recurrence (2.1%–3.3%, P = 0.75) were low, and did not differ.

Conclusions

Patients at the extremes of age are referred with more elevated laboratory indices whereas those in the traditional age range have milder biochemical indices. This may result from differential surgical referral. Individuals with laboratory evidence of abnormal calcium and parathyroid hormone regulation should be evaluated for parathyroidectomy regardless of age because all ages can be successfully treated.