This study compared the pullout forces of the initial implantation and the “cement-in-cement” revision technique for short and standard-length (125 mm vs. 150 mm) Exeter^® V40 femoral stems used in total hip arthroplasty (THA). The idea that the pullout force for a double taper slip stem is relative to the force applied to the femur and that “cement-in-cement” revision provides the same reproduction of force.

A total sample size of 15 femoral stems were tested (Short, n = 6 and Standard, n = 9). 3D printed fixtures for repeatable sample preparation were used to minimize variance during testing. To promote stem subsidence and to simulate an in vivo environment, the samples were placed in an incubator at 37°C at 100% humidity and experienced a constant compressive loading of 1335 N for 14 days. The samples underwent a displacement-controlled pullout test. After the initial pullout test, “cement-in-cement” revision will be performed and tested similar to the initial implantation to observe the efficacy of the revision technique. To compare the pullout forces between the two groups, a Kruskal-Wallis test using a significance level of 0.05 was conducted.

The mean maximum pullout force for the short and standard-length femoral stems were 3939 ± 1178 N and 5078 ± 1168 N, respectively. The Kruskal-Wallis test determined no statistically significant difference between the two groups for the initial implantation (p = 0.13). The “cement-in-cement” revision pullout force will be conducted in future testing.

This study demonstrated the potential use of short stem designs for THA as it provides similar levels of fixation as the standard-length femoral stem. The potential benefits for using a short stem design would be providing similar load transfer to the proximal femur, preserving proximal metaphyseal femoral bone in primary replacement, and reducing the invasiveness during revision.

Reverse shoulder arthroplasty (RSA) is commonly used to treat patients with rotator cuff tear arthropathy. Loosening of the glenoid component remains one of the principal modes of failure and is the main complication leading to revision. For optimal RSA implant osseointegration to occur, the micromotion between the baseplate and the bone must not exceed a threshold of 150 µm. Excess micromotion contributes to glenoid loosening. This study assessed the effects of various factors on glenoid baseplate micromotion for primary fixation of RSA.

A half-fractional factorial experiment design (2k-1) was used to assess four factors: central element type (central peg or screw), central element cortical engagement according to length (13.5 or 23.5 mm), anterior-posterior (A-P) peripheral screw type (nonlocking or locking), and bone surrogate density (10 or 25 pounds per cubic foot [pcf]). This created eight unique conditions, each repeated five times for 40 total runs. Glenoid baseplates were implanted into high- or low-density Sawbones™ rigid polyurethane (PU) foam blocks and cyclically loaded at 60 degrees for 1000 cycles (500 N compressive force range) using a custom designed loading apparatus. Micromotion at the four peripheral screw positions was recorded using linear variable displacement transducers (LVDTs). Maximum micromotion was quantified as the displacement range at the implant-PU interface, averaged over the last 10 cycles of loading.

Baseplates with short central elements that lacked cortical bone engagement generated 373% greater maximum micromotion at all peripheral screw positions compared to those with long central elements (p < 0.001). Central peg fixation generated 360% greater maximum micromotion than central screw fixation (p < 0.001). No significant effects were observed when varying A-P peripheral screw type or bone surrogate density. There were significant interactions between central element length and type (p < 0.001).

An interaction existed between central element type and level of cortical engagement. A central screw and a long central element that engaged cortical bone reduced RSA baseplate micromotion. These findings serve to inform surgical decision-making regarding baseplate fixation elements to minimize the risk of glenoid loosening and thus, the need for revision surgery.

The purpose of this study is to quantify the distribution of bone density in the scapulae of patients undergoing reverse shoulder arthroplasty (RSA) to guide optimal screw placement. To achieve this aim, we compared bone density in regions around the glenoid that are targeted for screw placement, as well as bone density variations medial to lateral within the glenoid.

Specimen included twelve scapula in 12 patients with a mean age of 74 years (standard deviation = 9.2 years). Each scapula underwent a computed tomography (CT) scan with a Lightspeed+ XCR 16-Slice CT scanner (General Electric, Milwaukee, USA). Three-dimensional (three-D) surface mesh models and masks of the scapulae containing three-D voxel locations along with the relative Hounsfield Units (HU) were created. Regions of interest (ROI) were selected based on their potential glenoid baseplate screw positioning in RSA surgery. These included the base of coracoid inferior and lateral to the suprascapular notch, an anterior and posterior portion of the scapular spine, and an anterosuperior and inferior portion of the lateral border. Five additional regions resembling a clock face, on the glenoid articular surface were then selected to analyze medial to lateral variations in bone density including twelve, three, six, and nine-o'clock positions as well as a central region. Analysis of Variance (ANOVA) tests were used to examine statistical differences in bone density between each region of interest (p < 0 .05).

For the regional evaluation, the coracoid lateral to the suprascapular notch was significantly less dense than the inferior portion of the lateral border (mean difference = 85.6 HU, p=0.03), anterosuperior portion of the lateral border (mean difference = 82.7 HU, p=0.04), posterior spine (mean difference = 97.6 HU, p=0.007), and anterior spine (mean difference = 99.3 HU, p=0.006).

For the medial to lateral evaluation, preliminary findings indicate a “U” pattern with the densest regions of bone in the glenoid most medially and most laterally with a region of less dense bone in-between.

The results from this study utilizing clinical patient CT scans, showed similar results to those found in our previous cadaveric study where the coracoid region was significantly less dense than regions around the lateral scapular border and scapular spine. We also have found for medial to lateral bone density, a “U” distribution with the densest regions of bone most medially and most laterally in the glenoid, with a region of less dense bone between most medial and most lateral. Clinical applications for our results include a carefully planned trajectory when placing screws in the scapula, potentially avoiding the base of coracoid. Additionally, surgeons may choose variable screw lengths depending on the region of bone and its variation of density medial to lateral, and that screws that pass beyond the most lateral (subchondral) bone, will only achieve further purchase if they enter the denser bone more medially. We suspect that if surgeons strategically aim screw placement for the regions of higher bone density, they may be able to decrease micromotion in baseplate fixation and increase the longevity of RSA.

Introduction

The management of early OA in young patients with joint preservation techniques utilizing cartilage repair remains challenging and a suitable treatment remains unclear. The management of bipolar chondral lesions in the patello-femoral (PF) and in the tibio-femoral (TF) compartment with cartilage repair is especially troublesome. The purpose of this study was to evaluate the clinical outcomes and survivorship after ACI for the treatment of bipolar chondral lesions in the PF and TF compartment.

While reverse shoulder arthroplasty (RSA) is a reliable treatment option for patients with rotator cuff deficiency, loss of glenoid baseplate fixation often occurs due to screw loosening. We questioned whether an analysis of the trabecular bone density distribution in the scapula would indicate more optimal sites for screw placement. As such, the purpose of this study was to determine the anatomic distribution of trabecular bone density in regions of the scapula available for screw placement in RSA.

Seven cadaveric shoulders were computed tomography (CT) scanned, and then voxels of the scapulae were isolated from the CT volume (Mimics 15.0 Materialise, Leuven, Belgium). Analyses were conducted in a common, 3D coordinate system. Volumetric regions of interest (ROI) within the scapula were identified based on potential baseplate screw sites. ROIs included areas at the base of the coracoid process lateral and inferior to the suprascapular notch, in the posterior and anterior lateral spine and in the anterosuperior and posteroinferior lateral border. Hounsfield Units (HU) were extracted from voxels corresponding to trabecular bone within each ROI. Overall bone density was summarised as the frequency of HU values above 80% of the ROI's maximum density value. Paired, two-tailed t-tests assuming unequal variance were used for pairwise comparisons (P≤0.05). Intra-region analyses compared two ROIs within the same broad anatomical structure; inter-region analyses compared ROIs between anatomical structures.

Areas of the spine and lateral border of the scapula appeared to be denser than the coracoid process. Intra-region comparisons indicated no significant differences within ROI: coracoid P=0.43, spine P=0.95, lateral border P=0.41. ROI inferior to the suprascapular notch were on average 3.78% (P=0.08) and 6% (P=0.04) less dense than the anterosuperior and posteroinferior lateral border and 7.59% (P=0.006) and 7.72% (P=0.01) less dense than the anterior and posterior lateral spine. ROI lateral to the suprascapular notch were 6% (P=0.05) and 8.21% (P=0.02) less dense than the anterosuperior and posteroinferior lateral border and 9.8% (P=0.006) and 9.94% (P=0.008) less dense than the anterior and posterior lateral spine. There was no significant difference between the anterior spine and anterosuperior and posteroinferior lateral border (P=0.12, P=0.58), nor between the posterior spine and anterosuperior and posteroinferior lateral border (P=0.14, P=0.57).

Results from this study indicate that the spine and lateral border of the scapula contain denser trabecular bone relative to regions in the coracoid. The higher quality bone of the spine and lateral border should be favoured over the coracoid process when fixing the glenoid baseplate in RSA. Further research may support the redesign of the glenoid baseplate geometry to better integrate the anatomy of the scapula and improve implant survival.

Background

Glenoid component aseptic loosening is the most common source of total shoulder arthroplasty (TSA) revision. In an attempt to strengthen cemented glenoid component fixation, divergent pegged glenoids were designed. Divergent peg creation was intended to increase cement purchase and provide resistance to component rocking.

Purpose:

The reverse total shoulder arthroplasty (RTSA) was approved for use by the United States FDA in 2004. Since its introduction, its popularity for treating a number of shoulder conditions has grown considerably. However, many patients inquire about the potential to return to playing recreational golf, and at present there are no published data about how the RTSA prosthesis affects the golf swing. The purpose of this study is to evaluate the biomechanics of the golf swing in patients with RTSA, as well as the postoperative changes in handicap, driving distance, and holes played/week.

Introduction:

External rotation (ER) of the shoulder is a commonly used clinical measurement to assess the glenohumeral joint; however, the position in which these measurements are obtained varies between clinicians. The purpose of this study was to compare the following: ER in the upright & supine positions, motion capture & goniometric values of ER, active & passive ER, ER in the right & left shoulders, and ER in male & female subjects.

Aims

Several national studies have shown that the rates of joint replacement are rising and this increase may be greater than that expected by population ageing. The aim of this study was to assess local rates of joint replacement at a district general hospital (DGH) and to investigate whether there had been a change in pre-operative functional status of patients over the study period to account for any change in rates of arthroplasty.

To assess the clinical outcomes of patients undergoing ACI in the patellofemoral joint.

Hypothesis

Cartilage defects pretreated with marrow stimulation techniques will have an increased failure rate. The first 321 consecutive patients treated at one institution with autologous chondrocyte implantation for full-thickness cartilage defects that reached more than two years of follow-up were evaluated by prospectively collected data. Patients were grouped based on whether they had undergone prior treatment with a marrow stimulation technique. Outcomes were classified as complete failure if more than 25% of a grafted defect area had to be removed in later procedures because of persistent symptoms.

Marrow stimulation techniques such as drilling or microfracture are first-line treatment options for symptomatic cartilage defects. Common knowledge holds that these treatments do not compromise subsequent cartilage repair procedures with autologous chondrocyte implantation (ACI). We present our experience with ACI after prior marrow stimulation. This study reviewed prospectively collected data for the first 321 consecutive patients treated at our institution with ACI for full-thickness cartilage defects that have reached more than 2 years of follow-up. Patients were grouped based on whether they had undergone prior treatment with a marrow stimulation technique. Outcomes were classified as complete failure if more than 25% of a grafted defect area had to be removed in later procedures due to persistent symptoms. This includes treatment with revision ACI, allograft transplantation, partial or total knee replacement. 522 defects in 321 patients (325 joints) were treated with ACI. Patient average age was 35 (13–60), there were 185 men and 136 women, with a follow-up of 2–12 Years. On average, there were 1.7 lesions per patient (range, 1–5) with a transplant area of 4.8 cm2 per lesion and 8.1 cm2 per knee. 111 of these joints had previously undergone surgery that penetrated the subchondral bone: microfracture (n=25), abrasion chondroplasty (n=33), and drilling (n=53). 214 joints had no prior treatment that affected the subchondral bone and served as control. Within the marrow stimulation group, there were 27 (24%) failures compared with 17 (8%) failures in the control group. In our review of 321 patients, defects that had prior treatment affecting the subchondral bone failed at a rate 3 times that of non-treated defects. These data demonstrate that marrow stimulation techniques have a strong negative effect on subsequent cartilage repair, and should be used judiciously in larger cartilage defects that could require future treatment with ACI.

Traditionally, the results of autologous chondrocyte implantation (ACI) in the patellofemoral joint have been considered inferior to those in the weightbearing femoral condyles. This study investigated the clinical effectiveness of patellofemoral ACI in a large, single-surgeon cohort.

This study reviewed prospectively collected data of patients treated with ACI for defects of the trochlea and/ or patella with a minimum follow-up of 2 years. Clinical outcomes were evaluated by SF-36; WOMAC, Knee Society Score, modified Cincinnati Score and a patient satisfaction survey.

130 patients reached a minimum follow-up of 2 years (2–9 years, average 56.5 months) after treatment involving the patellofemoral articulation. There were 77 men (59%) and 53 women (41%), the average age at the time of implantation was 37.5 years (15–57 years). The treatment groups included

isolated patella (n = 14);

The average surface area of patellar and trochlear defects was 4.7 cm2 (n = 63) and 5.8 cm2 (n = 98), respectively. The average resurfacing per knee was 11 cm2. There were 16 failures (12%) that could be attributed to a patellar or trochlear defect. 80% of patients rated their outcome as good or excellent, 18% rated their outcome as fair, and 2% rated outcome as poor.

ACI of the patellofemoral articulation provided a Significant improvement in quality of life as measured by functional scores and patient satisfaction survey. The failure rate was comparable to ACI used in other locations, such as the weightbearing femoral condyles.