Cameron G. Walker

Early Clubfoot Recurrence After Use of the Ponseti Method in a New Zealand Population

BACKGROUND Nonoperative treatment of idiopathic clubfoot has become increasingly accepted worldwide as the initial standard of care. The Ponseti method has become particularly popular as a result of published short and long-term success rates in North America. The purpose of the current study was to examine the early rate of clubfoot recurrence following the use of the Ponseti treatment method in a New Zealand population and to analyze patient characteristics to identify factors predictive of recurrence. METHODS Fifty-one consecutive babies with a total of seventy-three clubfeet treated by the Ponseti technique were followed prospectively for a minimum of two years from the start of treatment. Recurrence, defined as the need for any subsequent operative treatment, was analyzed with respect to the severity at presentation, the time of presentation, the number of casts needed to obtain the initial correction, any family history of clubfoot, ethnicity, and the compliance with postcorrection abduction bracing. Recurrence was classified as minor, defined as requiring a tendon transfer or an Achilles tendon lengthening, or major, defined as requiring a full posterior or posteromedial surgical release to achieve a corrected plantigrade foot. RESULTS Twenty-one (41%) of the fifty-one patients had a recurrence, which was major in twelve of them and minor in nine. The parents of twenty-six babies (51%) complied with the abduction bracing protocol, and only three of these children had a major recurrence. Compliance with abduction bracing was associated with the greatest risk reduction for recurrence (odds ratio, 0.2; p = 0.009). When the parents had not complied with the bracing protocol, the patient had a five times greater chance of having a recurrence. With the numbers studied, no significant relationships were found between recurrence and the severity at presentation, the time of presentation, the number of casts needed to obtain correction, ethnicity, or a family history of clubfoot. CONCLUSIONS Compliance with the postcorrection abduction bracing protocol is crucial to avoid recurrence of a clubfoot deformity treated with the Ponseti method. When the parents comply with the bracing protocol, the Ponseti method is very effective at maintaining a correction, although minor recurrences are still common. When the parents do not comply with the bracing protocol, many major and minor recurrences should be expected.

Simultaneous disruption recovery of a train timetable and crew roster in real time

This paper describes the development and implementation of an optimization model used to resolve disruptions to an operating schedule in the rail industry. Alterations to the existing train timetable and crewing roster are made simultaneously in real time--previous treatments in the literature have always decoupled these two problems and solved them in series. An integer programming model is developed that constructs a train timetable and crew roster. This model contains two distinct blocks, with separate variables and constraints for the construction of the train timetable and crew roster, respectively. These blocks are coupled by piece of work sequencing constraints and shift length constraints, which involve variables from both blocks. This unique parallel construction process is then used as the basis of a method to deal with the resolution of train disruptions in realtime. Favourable results are presented for both the combined train/driver scheduling model and the real-time disruption recovery model.

Accuracy of a computer-assisted navigation system for total knee replacement

The object of this study was to develop a method to assess the accuracy of an image-free total knee replacement navigation system in legs with normal or abnormal mechanical axes. A phantom leg was constructed with simulated hip and knee joints and provided a means to locate the centre of the ankle joint. Additional joints located at the midshaft of the tibia and femur allowed deformation in the flexion/extension, varus/valgus and rotational planes. Using a digital caliper unit to measure the coordinates precisely, a software program was developed to convert these local coordinates into a determination of actual leg alignment. At specific points in the procedure, information was compared between the digital caliper measurements and the image-free navigation system. Repeated serial measurements were undertaken. In the setting of normal alignment the mean error of the system was within 0.5 degrees . In the setting of abnormal plane alignment in both the femur and the tibia, the error was within 1 degrees . This is the first study designed to assess the accuracy of a clinically-validated navigation system. It demonstrates in vitro accuracy of the image-free navigation system in both normal and abnormal leg alignment settings.

Ponseti Method Compared with Surgical Treatment of Clubfoot A Prospective Comparison

BACKGROUND Current trends in the treatment of idiopathic clubfoot have shifted from extensive surgical release to more conservative techniques. The purpose of the present study was to prospectively compare the results of the Ponseti method with those of surgical releases for the correction of clubfoot deformity. METHODS We prospectively compared patients who had idiopathic clubfoot deformities that were treated at a single institution either with the Ponseti method or with below-the-knee casting followed by surgical release. The clinical records of the patients with a minimum duration of follow-up of two years were reviewed. All scheduled and completed operative interventions and associated complications were recorded. RESULTS Fifty-five patients with eighty-six clubfeet were treated; forty feet were included in the group that was treated with the Ponseti method, and forty-six feet were included in the group that was treated with below-the-knee casts followed by surgery (with three of these feet requiring casting only). There was no difference between the groups in terms of sex, ethnicity, age at the time of first casting, pretreatment Pirani score (average, 5.2 in both groups), or family history. The average number of casts was six in the Ponseti group and thirteen in the surgical group. Of the feet that were treated with below-the-knee casts, forty-three underwent surgery, with forty-two undergoing major surgery (posterior release [eleven] or posteromedial release [thirty-one]). In the Ponseti group, fourteen feet required fifteen operative interventions for recurrences, with only one foot requiring revision surgery. Four of these fifteen were major (necessitating posterior [one] or posteromedial release [three]) while eleven were minor. Thirteen feet in the surgical group required fourteen surgical revisions. Two postoperative complications were seen in each group. CONCLUSIONS While both cohorts had a relatively high recurrence rate, the Ponseti cohort was managed with significantly less operative intervention and required less revision surgery. The Ponseti method has now been adopted as the primary treatment for clubfoot at our institution.

Comparison of functional outcomes of reverse shoulder arthroplasty with those of hemiarthroplasty in the treatment of cuff-tear arthropathy: a matched-pair analysis.

BACKGROUND Rotator cuff-tear arthropathy has traditionally represented a challenge to the shoulder arthroplasty surgeon. The poor results of conventional total shoulder arthroplasty in rotator-cuff-deficient shoulders due to glenoid component loosening have led to hemiarthroplasty being the traditional preferred surgical option. Recently, reverse total shoulder arthroplasty has gained increasing popularity because of a clinical perception of an improved functional outcome, despite the lack of comparative data. The aim of this study was to compare the early functional results of hemiarthroplasty with those of reverse shoulder arthroplasty in the management of cuff-tear arthropathy. METHODS The results of 102 primary hemiarthroplasties for rotator cuff-tear arthropathy were compared with those of 102 reverse shoulder arthroplasties performed for the same diagnosis. Patients were identified from the New Zealand Joint Registry and matched for age, sex, and American Society of Anesthesiologists (ASA) scores. Oxford Shoulder Scores (OSS) collected at six months postoperatively as well as mortality and revision rates were compared between the two groups. RESULTS There were fifty-one men and fifty-one women in each group, with a mean age of 71.6 years in the hemiarthroplasty group and 72.6 years in the reverse shoulder arthroplasty group. The mean OSS at six months was 31.1 in the hemiarthroplasty group and 37.5 in the reverse shoulder arthroplasty group. At the time of follow-up, there were nine revisions in the hemiarthroplasty group and five in the reverse shoulder arthroplasty group. No difference in mortality rate was seen between the two groups. CONCLUSIONS In this unselected population with rotator cuff-tear arthropathy, controlled for age, sex, and ASA score, reverse shoulder arthroplasty resulted in a functional outcome that was superior to that of hemiarthroplasty. Longer-term follow-up is needed to confirm these findings.

Functional outcome of femoral peri prosthetic fracture and revision hip arthroplasty: A matched‐pair study from the New Zealand Registry

Background and purpose The number of periprosthetic fractures following total hip arthroplasty (THA) is increasing. There is, however, limited data on the functional outcome following these injuries. We analyzed functional outcome for revision THA following periprosthetic fracture, and compared this to the outcome of elective revision THA performed for aseptic loosening. Methods 232 patients undergoing revision THA for femoral fracture were identified from the New Zealand National Registry. Functional outcome was measured using the Oxford 12 hip score (OHS). A reference group of 232 patients undergoing elective revision THA was selected and matched for age and sex. Results Outcome was worse following revision THA for periprosthetic fracture than in reference patients (mean OHS: 29 vs. 24, p = 0.006). A higher 6‐month mortality rate was seen in periprosthetic fracture patients (7.3% vs. 0.9%, p < 0.001), along with a higher likelihood of re‐revision (7.3% vs. 2.6%, p = 0.06). Interpretation This large comparative series of periprosthetic fractures following THA shows that patients with periprosthetic fracture have poorer functional outcome and higher death rates than patients undergoing revision THA for aseptic loosening.

Does adjustable-loop femoral cortical suspension loosen after anterior cruciate ligament reconstruction? A retrospective comparative study

BACKGROUND Recent biomechanical research has suggested that adjustable-loop graft suspension constructs in anterior cruciate ligament (ACL) reconstruction may loosen after deployment. Our objective was to compare short-term knee stability and graft failure rate between adjustable-loop and fixed-loop femoral cortical suspension in patients undergoing primary ACL reconstruction. METHODS A consecutive series of 188 patients who underwent primary ACL reconstruction using hamstrings autograft by a single surgeon were divided into two groups; 73 received adjustable-loop (TightRope RT (Arthrex Inc., Naples, FL)) and 115 received fixed-loop (RetroButton (Arthrex Inc., Naples, FL)) femoral cortical suspension. The two groups were compared at six months, one year, and two years postoperatively using KT-1000 arthrometer testing and graft failure rate (revision surgery, grade 2+ Lachman test, any pivot shift, >5mm side-to-side KT-1000 difference). RESULTS There was no significant difference between the two groups in maximum side-to-side difference in KT-1000 testing at six months (mean 1.51mm (adjustable-loop group) vs. 1.79mm (fixed-loop group), p=0.23), one year (mean 1.44mm vs. 1.64mm, p=0.48), or two years (mean 1.14mm vs. 1.07mm, p=0.90) postoperatively. There was no significant difference between the two groups in rate of graft failure (10% vs. 11%, p=0.71) or timing of graft failure in affected patients (mean 11.4months vs. 13.8months, p=0.51). CONCLUSIONS We found no significant difference in postoperative knee stability or graft failure rate between adjustable-loop and fixed-loop femoral cortical suspension in patients undergoing primary ACL reconstruction. Our results suggest that adjustable-loop suspension does not clinically loosen after ACL reconstruction. LEVEL OF EVIDENCE III (retrospective cohort study).

Femoral bone density changes after total hip arthroplasty with uncemented taper-design stem: a five year follow-up study

We measured bone density (BD) changes to assess adaptive bone remodelling five years after uncemented total hip arthroplasty with taper-design femoral component using quantitative computed-tomography-assisted osteodensitometry (qCT). Nineteen consecutive patients (21 hips) with degenerative joint disease were enrolled in the study. A press-fit cup and a tapered uncemented stem ceramic−ceramic pairing were used in all patients. Serial clinical, radiological and qCT osteodensitometry assessments were performed after the index operation and at the one, two and five year follow-ups. At the latest follow-up, the clinical outcome was rated satisfactory in all hips. The radiological assessment showed signs of osteointegration with stable fixation of all cups and stems. Overall, there was evidence of a BD loss at year five (p = 0.004). We estimate that BD loss was between 2.2% and 12.1% in comparison with baseline postoperative values. Progressive loss of BD in the metaphyseal region was observed in all hips. We found unremarkable BD changes of diaphyseal cortical BD throughout the five year follow-up period. qCT osteodensitometry technology allows differentiation of cortical and cancellous BD changes over time. Periprosthetic BD changes at the five year follow-up are suggestive of stable stem osteointegration with proximal femoral diaphysis load transfer and metaphyseal stress shielding.

SALSA – a spatially adaptive local smoothing algorithm

We present a nonlinear integer programming formulation for fitting a spline-based regression to two-dimensional data using an adaptive knot-selection approach, with the number and location of the knots being determined in the solution process. However, the nonlinear nature of this formulation makes its solution impractical, so we also outline a knot selection heuristic inspired by the Remes Exchange Algorithm, to produce good solutions to our formulation. This algorithm is intuitive and naturally accommodates local changes in smoothness. Results are presented for the algorithm demonstrating performance that is as good as, or better than, other current methods on established benchmark functions.

Propionibacterium acnes in primary shoulder arthroplasty: rates of colonization, patient risk factors, and efficacy of perioperative prophylaxis

BACKGROUND Recent literature has shown that Propionibacterium acnes can be cultured from superficial and deep layers of the shoulder. Our aims were to assess the rate of P. acnes colonization in patients undergoing primary shoulder arthroplasty, to identify patient-related risk factors, and to evaluate the efficacy of our perioperative antisepsis protocol. METHODS Thirty consecutive patients undergoing primary shoulder arthroplasty were included in our study. Swabs were taken perioperatively (4 superficial and 2 deep wound swabs) and analyzed quantitatively for P. acnes. Cefazolin minimum inhibitory concentration was determined for P. acnes isolates from positive deep cultures. RESULTS Twenty-two patients (73%) had positive cultures for P. acnes. Male gender (P = .024) and presence of hair (P = .005) had significantly higher rates of P. acnes superficial cultures. Subjects with positive superficial P. acnes cultures (P = .076) and presence of hair with a history of steroid injection (P = .092) were more likely to have deep P. acnes-positive cultures, but this was not statistically significant. Local topical antisepsis measures did not eradicate P. acnes (P = .12). Mean cefazolin minimum inhibitory concentration for P. acnes was 0.32 μg/mL. CONCLUSION P. acnes is commonly isolated from the skin and deep surgical wounds of patients undergoing primary total shoulder arthroplasty who have not had previous shoulder surgery. Male gender and presence of hair were significant risk factors for P. acnes colonization. Perioperative local topical antisepsis and cefazolin administration were not effective in eliminating P. acnes colonization.