Graham J.W. King

Patellar position after total knee arthroplasty: Influence of femoral component malposition

Patellar shift, tilt, and rotation were analyzed in 7 cadaveric knee specimens during simulated quadriceps loading, in the intact knee, and after implant reconstruction. Femoral component medialization, lateralization, and external rotation were also investigated. Relative motion of the patella with respect to the femur was measured using an electromagnetic tracking system. The spatial position of the patella did not change with standardized total knee arthroplasty (P <.05). After malpositioning of the femoral component, patellar rotation also did not change (P >.05); however, patellar tilt was altered by femoral component external rotation malposition (P <.05), and patellar shift was affected by all femoral component malpositions (P <.05). The spatial position of the patella relative to the femoral shaft was changed with any femoral component malposition, suggesting that the soft tissues were abnormally tensioned. This could result in subsequent wear on the patellar component and, therefore, early failure.

Accuracy assessment of an imaging technique to examine ulnohumeral joint congruency during elbow flexion.

A CT-based imaging technique to investigate ulnohumeral joint congruency of elbows undergoing physiologic flexion is introduced. This technique, which employed landmark registration and a previously developed inter-bone distance algorithm, was validated experimentally. Results obtained with this imaging technique were validated in a single specimen by comparing the resulting joint congruency maps to results obtained with experimental casting in a static position. Additionally, the accuracy of the registration technique was assessed in four specimens using fiducial and target registration error to evaluate the positional and angular accuracy. Preliminary data from an intact cadaveric elbow was shown to demonstrate the utility of this technique. The overall accuracy of the registration was better than 1 mm, and the congruency maps showed excellent correspondence with the casting, validating the use of a CT-based imaging technique to examine the congruency of joints undergoing quasi-static flexion.

Evaluation of a computational model to predict elbow range of motion

Abstract Computer models capable of predicting elbow flexion and extension range of motion (ROM) limits would be useful for assisting surgeons in improving the outcomes of surgical treatment of patients with elbow contractures. A simple and robust computer-based model was developed that predicts elbow joint ROM using bone geometries calculated from computed tomography image data. The model assumes a hinge-like flexion-extension axis, and that elbow passive ROM limits can be based on terminal bony impingement. The model was validated against experimental results with a cadaveric specimen, and was able to predict the flexion and extension limits of the intact joint to 0° and 3°, respectively. The model was also able to predict the flexion and extension limits to 1° and 2°, respectively, when simulated osteophytes were inserted into the joint. Future studies based on this approach will be used for the prediction of elbow flexion-extension ROM in patients with primary osteoarthritis to help identify motion-limiting hypertrophic osteophytes, and will eventually permit real-time computer-assisted navigated excisions.

Hemiarthroplasty of the elbow: the effect of implant size on joint congruency.

BACKGROUND Distal humeral hemiarthroplasty is a treatment option for elbow joint disease that predominantly affects the distal humerus, including distal humerus fractures, nonunions, and avascular necrosis. The effect of hemiarthroplasty implants on joint contact has not been reported. The purpose of this in vitro study was to quantify the effects of hemiarthroplasty and implant size on ulnohumeral joint congruency. METHODS Five fresh frozen cadaveric upper extremities were mounted to a custom elbow testing system. Active and passive motion were performed in dependent, horizontal, varus, and valgus positions. A registration and interbone distance algorithm was used to quantify ulnohumeral joint congruency throughout elbow flexion. RESULTS The optimally sized hemiarthroplasty implant demonstrated the greatest joint congruency with the ulna, followed by the oversized implant, then the undersized implant. Joint congruency was greater during active vs. passive flexion, indicating that the elbow joint is more reduced in active flexion than in passive flexion. CONCLUSION This study demonstrates that undersized distal humeral hemiarthroplasty implants have the lowest joint congruency compared with an optimally sized or oversized implant.

Elbow Contracture Release: Open Operative Strategies

Elbow stiffness is an uncommon problem that can interfere with a patient’s ability to perform activities of daily living. The elbow’s primary function is to position and stabilize the hand in space. Unfortunately, patients do not tolerate elbow stiffness well because adjacent joints cannot provide adequate compensatory motion. Morrey et al. showed that a functional arc of motion from 30° to 130° of elbow flexion is required to perform most activities of daily living.1 Patients who have elbow stiffness have varying degrees of impairment in functional abilities, depending on the location in the arc of motion and the magnitude of the contracture. A recent study of volunteers with healthy elbows revealed an ability to adapt to an arc of 70° to 120° for 12 activities of daily living.2 In spite of the marked stiffness that can be tolerated when adjacent joints have full motion, most patients report functional disability and request treatment when flexion contractures approach 40°. Patients who have an arc of motion from 40° to 120° rarely require surgery unless their employment or athletic activity specifically requires terminal elbow flexion or extension. In this chapter, we focus on operative treatment of elbow contracture. We discuss open capsular release and distraction interposition arthroplasty.

Evaluation of an Image-Based Tool to Examine the Effect of Fracture Alignment and Joint Congruency on Outcomes after Wrist Fracture

Some mal-alignment of the wrist occurs in up to 71% of patients following a distal radius fracture. A multiple case study was used to provide proof of principle of an image-based technique to investigate the evolution and impact of post-traumatic joint changes at the distal radioulnar joint. Participants who had a unilateral distal radius fracture who previously participated in a prospective study were recruited from a single tertiary hand center. Long term follow-up measures of pain, disability, range of motion and radiographic alignment were obtained and compared to joint congruency measures. The inter-bone distance, a measure of joint congruency was quantified from reconstructed CT bone models of the distal radius and ulna and the clinical outcome was quantified using the patient rated wrist evaluation. In all four cases, acceptable post-reduction alignment and minimal pain/disability at 1-year suggested good clinical outcomes. However, 10 years following injury, 3 out of 4 patients had radiographic signs of degenerative changes occurring in their injured wrist (distal radioulnar joint/radio-carpal joint). Proximity maps displaying inter-bone distances showed asymmetrical congruency between wrists in these three patients. The 10-year PRWE (patient rated wrist evaluation) varied from 4 to 60, with 3 reporting minimal pain/disability and one experiencing high pain/disability. These illustrative cases demonstrate long-term joint damage post-fracture is common and occurs despite positive short-term clinical outcomes. Imaging and functional outcomes are not necessarily correlated. A novel congruency measure provides an indicator of the overall impact of joint mal-alignment that can be used to determine predictors of post-traumatic arthritis and is viable for clinical or large cohort studies.