Biomedical subjects

Philip C Noble

Publications and source records attributed to Philip C Noble.

28 records · Page 2Linked to original sources

PubMed2003

Computer simulation: how can it help the surgeon optimize implant position?

Component placement critically affects the performance and longevity of total hip replacements (THRs). Because of limitations of observation and anatomic orientation imposed by the operative site, selection of the correct size, and position of the acetabular and femoral components is best done through preoperative planning. Currently, this is done by comparing two-dimensional templates of prosthetic components with clinical radiographs; however, this method has the inherent limitation that AP and lateral radiographs each provide one projection of the pelvis and the femur. Computer technology makes it possible to observe implantation of the femoral and acetabular components in three dimensions. This approach allows surgeons to template with superior accuracy, while providing an intimate view of the fit of the components in the implantation site. Additionally, computer routines can predict the functional outcome of a preoperative plan before its implementation. Restoration of leg length, center of rotation, ROM of the joint during various activities, and points of bony and prosthetic impingement can be analyzed preoperatively by the surgeon. This is a valuable tool for surgical navigation and surgeon training. With emerging technologic advances in surgical technique, computer-based preoperative planning tools should prove all the more essential to reliable component placement.

Arthroplasty, Replacement, Hip↗

PubMed2003

Three-dimensional shape of the dysplastic femur: implications for THR.

This study evaluates the three-dimensional anatomy of the femur with congenital dysplasia of the hip (CDH) in comparison with healthy controls. Computed tomographic scans were obtained from 207 women (154 with dysplasia; 54 healthy controls) with an average age of 51.6 years (range, 18-82 years). Most of the dysplastic joints were classified as Crowe I (43%), or Crowe II or III (48%), with 9% Crowe IV. Individualized three-dimensional computer models of the femur were generated by reconstruction of the CT scans. Dimensional and morphometric parameters were derived by computer analysis of each of the femoral reconstructions. The dysplastic femurs had shorter necks and smaller, straighter canals than the controls. The shape of the canal became more abnormal with increasing subluxation. Detailed analysis showed that the primary deformity of the dysplastic femur is rotational, with an increase in anteversion of 5 degrees to 16 degrees, depending on the degree of subluxation of the hip. The rotational deformity of the dysplastic femur arises within the diaphysis between the lesser trochanter and the isthmus and is not attributable to a torsional deformity of the metaphysis. This study shows that there is a significant difference in the geometry of the normal femurs and those with CDH, even in mild cases. In CDH cases, we recommend the use of modular or specially-designed components to accommodate the shape of the dysplastic canal.

Adolescent↗

PubMed2002

Functional bracing for distal radioulnar joint instability.

Symptomatic chronic distal radioulnar joint (DRUJ) instability can be a challenging disorder to treat surgically. This study used a cadaver model to assess the effect of functional forearm bracing on DRUJ instability. The specimen upper extremities were mounted on a platform and the DRUJ was destabilized sequentially. The effect of both prefabricated commercial braces and custom-made braces on joint stability was documented by computed tomography. Both braces markedly reduced DRUJ translation in both full pronation and full supination. The custom-made brace overreduced the DRUJ in full pronation. Our results suggest that functional forearm bracing may be effective in reducing instability of the DRUJ without greatly restricting motion of the wrist, forearm, or elbow.

Analysis of Variance↗

PubMed2002

What functional activities are important to patients with knee replacements?

There is interest in quantifying the patient's function and mobility after joint replacement. The current study identified activities important to patients having total knee replacement and the prevalence of limitations to participation in these activities. A Total Knee Function Questionnaire consisting of 55 questions addressing the patient's participation in various activities was developed, validated, and mailed to 367 patients at least 1 year after knee replacement. Patients were asked the frequency with which they did each activity, the activity's importance to them, and the extent to which their participation was limited by their knee replacement. The questionnaire was returned by 176 patients, 40% men and 60% women, with an average age of 70.5 years. The most prevalent activities were stretching exercises (73%), leg strengthening exercises (70%), kneeling (58%), and gardening (57%). The activities most important to the patients were stretching exercises (56%), kneeling (52%), and gardening (50%); those most difficult were squatting (75%), kneeling (72%), and gardening (54%). The current study showed a high correlation between the importance of activities and frequency of patient participation confirming that knee replacement successfully restores a significant degree of function. However, after knee replacement, improvements in knee function still are needed to allow patients to do all activities that they consider important.

Activities of Daily Living↗

PubMed2002

The effects of rotation on radiographic evaluation of the tibiofibular syndesmosis.

Radiographs of 12 normal cadaveric lower extremities were prepared with each extremity in seven increments of axial rotation, ranging from 5 degrees of external rotation to 25 degrees of internal rotation. The tibiofibular clear space, the tibiofibular overlap, the width of the tibia and fibula, and the medial clear space were measured on each film. The width of the tibiofibular clear space (syndesmosis A) averaged 3.9+/-0.9 mm (range, 2 to 5.5 mm), but did not change significantly with rotation. Its size was independent of the size of tibia and fibula. All other measurements changed dramatically with rotation. In our specimens, a true mortise view of the ankle joint was obtained by internally rotating the extremity an average of 13.6+/-0.7 degrees (range, 12.0 degrees to 17.0 degrees). Based on our results the width of the tibiofibular clear space on the anterior-posterior view is the most reliable parameter for detecting widening of the syndesmosis on plain radiographs. However, due to its variability among different individuals, comparison views of the contralateral extremity are warranted for confirmation of clinical suspicion of syndesmosis disruption.

Analysis of Variance↗

PubMedDate not supplied

Comminuted olecranon fractures: a comparison of plating methods.

The relative strength of posterior plating and dual medial-lateral plating for comminuted olecranon fractures has not been evaluated. Fifteen male cadaveric elbows with simulated highly comminuted olecranon fractures were tested to failure via cantilever bending. The strength of dual medial-lateral plates and a single posterior plate with and without an intramedullary screw was evaluated. The mean bending moment at failure for the dual-plated specimens was 30.0 +/- 7.5 Nm. The mean bending moment at failure for specimens with a posterior plate without an intramedullary screw was 34.5 +/- 9.1 Nm. The mean bending moment at failure for specimens with a posterior plate and an intramedullary screw was 44.5 +/- 6.9 Nm; this was significantly greater than for dual-plated specimens (P < .05) but not for specimens with a posterior plate without an intramedullary screw. The posterior plate with an intramedullary screw was the most stable construct tested and may, therefore, be the preferred method of fixation for comminuted olecranon fractures. This construct was significantly (48%) stronger than dual medial and lateral plating.

Biomechanical Phenomena↗

PubMedDate not supplied

Scheuermann kyphosis: long-term follow-up.

BACKGROUND CONTEXT: There is considerable controversy as to the optimal treatment of Scheuermann kyphosis. Proposed modalities have included exercise, bracing and surgery. PURPOSE: The purpose of this study was to document the functional capacity and radiographic findings in adults who have been previously treated for Scheuermann kyphosis. STUDY DESIGN: A cohort study of all patients with Scheuermann kyphosis treated in a single institution using three different treatment modalities: exercise and observation, Milwaukee bracing and surgical fusion using the Harrington Compression System. PATIENT SAMPLE: Sixty-three patients were evaluated at a mean of 14 years after treatment (10 to 28 years). OUTCOME MEASURES: Two different functional evaluation instruments were used. Radiographic evaluation was carried out in 38 patients (60%). METHODS: Patient interviews were conducted using a specially designed questionnaire. Patients were then asked to undergo standing radiographs. Patients were divided into groups depending on the location of their kyphosis and the manner in which they had been treated. Standard statistical analysis was then carried out. RESULTS: At time of follow-up evaluation there were no differences in marital status, general health, education level, work status, degree of pain and functional capacity between the various curve types, treatment modality and degree of curve. Patients treated by bracing or surgery did have improved self-image, which they attributed to their treatment. Patients with kyphotic curves exceeding 70 degrees at follow-up had an inferior functional result. At time of final follow-up there were no statistical differences in degree of kyphosis and mode of treatment. CONCLUSIONS: By carefully selecting the appropriate treatment for patients with Scheuermann kyphosis on the basis of the patient's age, spinal deformity and the severity of back pain, it is possible to achieve a similar functional result at long-term follow-up. Despite different treatment protocols, patients with Scheuermann kyphosis tend to achieve a similar functional result at long-term follow-up.

Adult↗

PubMedDate not supplied

A biomechanical comparison of repair techniques for type II SLAP lesions.

BACKGROUND: Multiple options exist for repair of superior labral tears. PURPOSE: To compare commonly used fixation techniques for superior labral tears. STUDY DESIGN: Biomechanical cadaveric study. METHODS: A comparison of the initial strengths of fixation for type II superior labral anterior posterior (SLAP) lesions was performed in three cadaveric shoulder groups, each containing seven specimens. Two groups were repaired with screw-in anchors; one group had vertical sutures, the other horizontal. Group 3 was repaired using bioabsorbable tacks. Cyclic traction was applied to the biceps tendon. Repair failure (2 mm of permanent displacement) and ultimate failure were measured. RESULTS: Specimen stiffness was similar between groups. The mean load to repair failure was 123 +/- 17 N in group 1, 114 +/- 11 N in group 2, and 95 +/- 13 N in group 3. The mean load to ultimate failure was 163 +/- 15 N, 161 +/- 12 N, and 145 +/- 12 N, respectively. Although the repair failure loads of groups 1 and 2 were 29% and 17%, respectively, greater than the tack group, the differences were not statistically significant (P >.05). All ultimate failures occurred at the labral-implant interface. CONCLUSION: Initial fixation strength of tissue tack and suture anchor repairs of SLAP lesions are comparable.

Absorbable Implants↗

PubMedDate not supplied

A biomechanical analysis of meniscal repair techniques.

BACKGROUND: Various methods are available for repair of meniscal tears: a biodegradable meniscal implant without sutures (Biofix meniscus arrow), a suture anchor device (T-fix), and horizontal and vertical mattress sutures. HYPOTHESIS: There is no difference in repair strength or mode of failure among the techniques compared. STUDY DESIGN: Controlled laboratory study. METHODS: Reproducible tears were created in bovine menisci and repaired with each of the techniques. Residual displacement of the tear immediately after repair and the resistance to displacement under load applied perpendicular to the tear were measured and compared. RESULTS: The residual displacement after repair was highest in the Biofix arrow group (0.70 mm) and lowest in the vertical mattress suture group (0.21 mm). The ultimate strength of repair was strongest for the vertical sutures (202 +/- 7 N) and lowest for the arrow and T-fix (95.9 +/- 8 N and 99.4 +/- 8 N, respectively). The force required to generate 2 mm of tear displacement was greatest for the vertical sutures (143 N) and least for the arrow (43.6 N). CONCLUSIONS: Suture techniques were stronger at all levels of testing. CLINICAL RELEVANCE: Knowledge of biomechanical characteristics aids the surgeon in choosing the appropriate technique for each situation.

Animals↗

PubMedDate not supplied

Multistranded hamstring tendon graft fixation with a central four-quadrant or a standard tibial interference screw for anterior cruciate ligament reconstruction.

BACKGROUND: Tibial fixation of hamstring tendon grafts has been the weak link in anterior cruciate ligament reconstruction. HYPOTHESIS: Use of a central four-quadrant sleeve and screw provides superior fixation when compared with standard interference screw fixation. STUDY DESIGN: Controlled laboratory study. METHODS: In eight pairs of cadaveric knees each anterior cruciate ligament was reconstructed using either an interference screw or a central sleeve and screw on the tibial side. The specimens were then subjected to cyclic loading followed by a load-to-failure test. RESULTS: The load required to cause 1 and 2 mm of graft laxity, defined as the separation of the femur and the tibia at the points of graft fixation, was significantly greater with the sleeve and screw than with the interference screw (at 2 mm: sleeve and screw, 216.1 +/- 30.1 N; interference screw, 167.0 +/- 33.2 N). The force at initial slippage for each of the graft strands was significantly higher with use of the central sleeve and screw. CONCLUSIONS: The four-quadrant sleeve and screw device may provide greater surface area for healing of hamstring tendon grafts and allow equal tensioning of graft strands before fixation. These factors are associated with increased strength of fixation and reduced laxity of the graft after cyclic loading. CLINICAL RELEVANCE: Use of the central four-quadrant sleeve and screw system offers increased strength of fixation in anterior cruciate ligament reconstruction with hamstring tendon graft.

Aged↗