Cadaver based joint simulators have been a backbone of orthopedic biomechanical experiments to simulate in vivo loading conditions and injury models in order to better understand intact joint kinematics, or develop new repair techniques. The purpose of this study was to develop a cadaver based wrist testing system capable of simulating grip in order to understand carpal kinematics under conditions that mimic the loading conditions seen in vivo. The testing system is based on linear actuators with in series load cells controlled by custom coded Labview software that are connected via sutures to the muscle tendons of wrist flexors/extensors and finger flexors, allowing fully customizable loading protocols. Carpal kinematics are measured using custom posts inserted into the carpus and digitized with a Microscribe 3DLX. Post-experimental dissection and digitization were used to create 3D models of the carpus at each testing position.

The system was validated by comparing the kinematics of the intact carpus in wrist flexion/extension and radial/ulnar deviation to data previously reported in the literature. Data from the new system was comparable to previous reports. Next the effect of grip on intact carpal kinematics was investigated by loading flexor digitorum profundus. Grip caused significant flexion of the scaphoid and lunate with an average flexion of 0.8° for the scaphoid and 0.4° for the lunate. The last phase was to analyze the effect of repetitive grip on a wrist with a scapholunate interosseous ligament tear, an injury known to cause progressive degenerative changes following the initial tear. Following 500 cycles of grip, there were significant changes to the carpus including: increased scaphoid flexion, ulnar deviation, and pronation, lunate extension, widening of the scapholunate gap, and proximal translation of the head of the capitate. Utilizing these kinematic changes seen in cadavers, future studies can be performed to develop new repair strategies for this challenging injury. In conclusion, a validated cadaveric wrist testing system has been developed that has elucidated the effects of grip on the intact wrist, and provided significant information on the effect of functional stresses, such as repetitive grip, have on a wrist with a scapholunate interosseous ligament tear.

Background:

As the incidence of shoulder arthroplasty continues to increase, the number of patients with chronic obstructive pulmonary disease (COPD) undergoing shoulder arthroplasty also increases. COPD has been shown to be a significant risk factor in general surgery, total hip arthroplasty and total knee arthroplasty, where it is associated with an increase in complication rates and mortality after surgery.

Methods:

This was a retrospective administrative database study using the National Inpatient Sample (NIS) from 2001 to 2014. Patients undergoing shoulder arthroplasty were identified using ICD-9-CM procedural codes and split into two groups: patients with COPD and without COPD. Trends of patients undergoing shoulder arthroplasty across the years were determined. Univariate statistical analysis was used to compare demographics, comorbidity and complication rates. Multivariate regression was used to determine the independent risk that COPD contributes to complications. Inpatient cost and length of stay were also compared between groups.

Results:

The incidence of shoulder arthroplasty has increased by 294% between 2001-2014. The number of patients with COPD has also increased, with 324% growth. COPD patients had significantly higher rates of comorbidities, especially congestive heart failure (COPD: 10.42% vs. non-COPD: 3.41%; p < .001) and depression (COPD: 16.75% vs. non-COPD: 11.63%; p < .001). They also had higher rates of post-operative complications, particularly respiratory complications (COPD: 5.70% vs. non-COPD: 1.25%; adjusted OR = 3.51; p < .001), overall complications (COPD: 10.48% vs. 4.37%; adjusted OR = 1.98; p < .001) and higher risk of mortality (COPD: 0.31% vs. non-COPD: 0.13%.; adjusted OR = 1.59; p < .001).

Discussion:

Shoulder arthroplasty in COPD patients is continuing to grow rapidly. COPD patients tend to have greater comorbidity burdens, higher rates of post-operative complications (especially respiratory complications) and increased mortality. Improved pre-surgical optimization and increased attention to post-operative management is necessary to improve outcomes of patients with COPD undergoing shoulder arthroplasty.

Automobile drivers with a diagnosed supraspinatus (SSP) tendon tear following a low-speed rear-end collision often allege the collision is responsible for causing their shoulder injury. The goal was to determine the propensity for acute tear of a healthy SSP tendon during a low-speed rear-end automobile collision. To accomplish this, first the scapula and humerus positions were measured in twenty-one volunteers while in a driver seat. Then these positions were averaged and simulated in a cadaver shoulder to explore three possible injury mechanisms for acute isolated SSP tendon tear: humeral head displacement, tendon impingement, and tendon tension.

With a balanced rotator cuff muscle load, the SSP muscle had the largest change in length for 5 of 8 directions of humeral head displacement; however, the muscle length in 7 of 8 humeral head displacements was less than the muscle length at maximum ROM and changes in SSP tendon length were minimal (0±1 mm) for all humeral head displacements. No acromial impingement of the distal SSP tendon occurred with any of the humeral head displaced positions. Tensile testing of the humerus-SSP tendon complex resulted in a fracture of the humerus at 904 N.

These findings and review of literature suggest that a low-speed rear-end collision may not be an event that predisposes a healthy SSP tendon to tear. Tendon degeneration, non-uniform tendon loading, and pre-existing asymptomatic partial or full-thickness tendon tears may alter the risk of a SSP tendon tear or onset of pain in low-speed rear-end collisions.

ABSTRACT OF THE THESIS

Management of Massive Rotator Cuff Tears in the Wheelchair

Bound, Spinal Cord Injury Population: Study Proposal toward the Establishment of Higher Level of Evidence Care

By

Hansel E. Ihn

Master of Science in Biomedical and Translational Science

University of California, Irvine

2017

Professor Thay Q. Lee, Chair

Background: The wheelchair bound, paraplegic population are heavily reliant on their upper extremities for independence. As a result, there is a high prevalence of rotator cuff tears within this population. However, there is no established clinical practice guideline to help guide the care of this problem.

Aims: The original goal of this thesis was to conduct a systematic review and meta- analysis of the available literature in the hopes of take a step toward establishment of a clinical practice guideline. Once a preliminary evidence- mapping procedure was done, it was decided there was not enough evidence available to warrant a meta- analysis. Consequently, the aim of this thesis then shifted toward the proposal of a potential clinical trial that would provide a high level of evidence.

Methods: The evidence mapping procedure simulated the process ordinarily taken for systematic reviews as outlined in the Preferred Reporting Items for Systematic reviews and Meta- Analyses (PRISMA) guidelines. PubMed, Web of Science, and the Cochrane Library databases were searched using pre-determined search strategies with keywords. The clinical trial proposal process that then followed utilized the evidence gained from the evidence mapping procedure as well as that attained from a literature review of high level of evidence studies in orthopaedic surgery.

Results: The evidence mapping procedure netted a total of 191 studies of which only 6 studies were fully reviewed. Upon review, these six studies were found to be all of level IV evidence. These studies represented a heterogeneous use of surgical techniques and outcome measures. Consequently, they did not meet the inclusion criteria to perform a meta- analysis.

Discussion: The data extraction process made it apparent that the evidence available has multiple methodologic flaws precluding meaningful synthesis. Even by case series standards as outlined by Obremskey et al., these six studies did not meet many of the criteria necessary to provide evidence that would be deemed useful for clinical judgement. To that end, the thesis concludes with a proposal of a clinical trial that would provide a higher level of evidence for clinical management. Specifically, the proposal addresses massive rotator cuff tears in the wheelchair bound, paraplegic population. The interventions compared in the study will be rotator cuff repair with subacromial decompression or subacromial decompression alone. The potential pitfalls and ethical dilemmas that may present during the study are also discussed

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Successful outcome of a Bankart procedure depends on knowledge of the effects of capsulolabral lesions on joint biomechanics. The joint reaction force, through "concavity compression," is integral to glenohumeral stability. In this study, we applied loads to the tendons of the rotator cuff and deltoid (anterior and middle portions) of five cadaver upper limbs. The joint reaction force was measured with a 6 degrees of freedom load cell for the intact condition and each of two test conditions: (1) incision and (2) partial resection of the anteroinferior capsulolabrum. We used analysis of variance to compare joint reaction forces resolved into that which is directed perpendicular (compression force), anterior, and superior to the glenoid. Compression force for the two different capsulolabral lesions of the glenohumeral joint was the same, 133 N +/- 13 N, a small 12% decrease compared to the intact condition (151 N +/- 13 N). This difference was not statistically significant. Results were similar for the components of the joint reaction force directed anterior and superior. Joint reaction force was not meaningfully altered after anteroinferior capsulolabral lesions were simulated. Because glenohumeral joint stability involves complex interplay of static and dynamic restraints, additional shoulder injuries may be necessary for the joint reaction force to be abnormal.