AIM

When a hip is replaced using a posterior surgical approach, some of the external rotator muscles are divided. The aim of this study was to assess if this surgery has a long term affect on hip rotation during activities of daily living.

Introduction: The aim of this study was to compare hip movement between normal subjects and patients with a large Metal on Metal hip replacement, undertaking the task of retrieving an object from the floor.

Methods: An electromagnetic tracker was used to measure movement as subjects retrieved an object with flexed hips and straight knees. Measurements were taken from a control group of 10 subjects with bilaterally normal hips, and 10 subjects with unilateral hip replacement. Sensors were attached over the iliac crest and the mid-shaft of the lateral thigh. Data was collected as each subject repeated the movement 3 times. The tracker recorded data at 10 hertz, with an accuracy of 0.15 degree.

Results: For the normal group the mean hip flexion was 90.8 degrees (SD 20.1). For the arthroplasty group the mean flexion on the normal and operated sides were 74.0 (SD 21) and 72.7 degrees (SD 21) respectively. This was not significant (P= 0.83). However there was a significant difference in hip movement between the operated hips and those in the normal control group (P= 0.03).

For the bilaterally normal group the mean hip rotation was 2.9 degrees internal (SD 11.8). For the arthroplasty group the mean rotation on the normal and operated sides were 9.4 degrees external (SD 9.5) and 6.9 degrees internal (SD 13.9) respectively. In this group there was a significant difference between the normal and operated side (P= 0.02).

Discussion: This study has shown that patients with a unilateral hip replacement have no significant flexion difference between hips, when retrieving an object from the floor. However there was a significant difference compared to a control group with normal hips. A significant difference was also observed when comparing the rotation of an operated hip joint to the contra-lateral normal hip in the same individual.

Introduction: A learning curve is a recognised phenomenon in surgery. It implies that the frequency of peri-operative adverse events will decrease with the increase in experience of the surgeon. Evidence shows increased instruction and experience in a specific surgical task leads to improved performance. There is conflicting evidence as to whether there is a learning curve for total ankle replacement, and a paucity of evidence for foot and ankle surgery as a whole. Current evidence is centered on perioperative complications, rather than functional outcome.

Aim: To determine whether a learning curve effect is present during the first year of independent practice by measuring patient outcome.

Materials and Methods: 150 patients underwent elective foot or ankle surgery during the first 12 months of a newly appointed consultant’s practice. Preoperative and six month postoperative functional scores were recorded, together with perioperative complications. Two patients died of unrelated causes in the first 12 months. 121 patients (81.8%) were followed up for a minimum of six months by telephone. Functional outcome was assessed with a modified American Orthopaedic Foot and Ankle Society midfoot Score (85 points). Outcome was compared between the first and second six-month periods using the student’s t-test.

Results: Eighty procedures were undertaken during the first six months compared to 70 in the second. Total ankle replacements were only undertaken in the latter period. Otherwise there was no statistical difference in the caseload. One wound infection occurred during each period and other perioperative complications were equivalent. Functional improvement was greater in the group from the second 6 months (+23.86 v’s +18.69). This difference did not reach statistical significance (p = 0.061).

Discussion and Conclusion: There is a trend, approaching significance, towards a learning curve during a foot and ankle consultant surgeon’s first year of practice. Collating data from other new consultants may demonstrate a learning curve with statistical significance.

Introduction: Patients undergoing total hip arthroplasty are advised to minimise their hip flexion in the early postoperative phase, to reduce the risk of dislocation. One activity that requires hip flexion is picking an object up from the floor. The aim of this study was to investigate the amount of hip flexion required to perform this task, and to see if there is a difference between patients with small and large bearing total hip replacements.

Methods: Nineteen unilateral total hip replacement patients were recruited into the study. Nine had a small bearing (metal on plastic) implant and ten had a large bearing (metal on metal) implant. Each patient had a contra-lateral normal native hip, which provided a control for bilateral comparison.

An electromagnetic tracking system was used to measure the flexion in the operated and normal hip of each patient. Tracker sensors were placed on the iliac crest and the mid-lateral thigh. The patients were then asked to flex forward from a standing position to pick an object up off the floor. This movement was repeated 3 times. Flexion data was collected at 10Hz which was accurate to 0.15 degrees. Spinal flexion was not recorded during the task.

Patients were also asked to complete the Harris and Oxford Hip Score questionnaires to obtain qualitative data regarding their hip replacement.

Results: The mean peak flexion angles (degrees) for each group are given below:

Small bearing group:

Operated side: Peak flexion = 79.3

Comparing the small bearing group with the large bearing group, the peak difference was 6.6. This difference was non-significant with P = 0.43.

All patients reported good – excellent functional results when completing the Harris and Oxford Hip Scores.

Discussion: The investigation showed that picking an object up from the floor requires a peak hip flexion of approximately 80 degrees. This investigation found no significant difference between the normal and operated sides. This would suggest that a Total Hip Replacement restores the “normal” range of motion in a hip joint. Furthermore, there was no significant difference between the small and large bearing hip implants.

DDH incidence falls from 5–20 per 1000 at birth to 1–2 per 1000 by 3 weeks. Some patients present late and frequently require surgical intervention. If the hip cannot be contained without tension, these children undergo open reduction +/− a femoral shortening, varus and derotation osteotomy. Salter’s osteotomy, may be performed either at index surgery or later in the presence of persisting acetabular dysplasia. Our aim was to see if we could predict which cases of persistent DDH would require both femoral and pelvic surgery to contain the affected hip, using a single plain AP radiograph of the pelvis in the outpatient setting.

We performed a retrospective study of all children older than 18 months with persistent DDH of one or both hips, over the last 5 years, who had undergone femoral and/or pelvic surgery to contain the hip. Plain AP pelvic radiographs were standardised according to the method described by Tonnis. From these radiographs the acetabular indices and child’s age in months, were recorded. Syndromic and children with non-standard x-rays were excluded.

Thirty nine hips (34 female, 5 male), age range of 18–102 months, formed our study group. 53% of hips having femoral surgery later required pelvic surgery for persisting acetabular dysplasia. Examining the data in these cases, the difference between the acetabular index of the normal and affected hip was always greater than 20 degrees and the child’s age in months.

Using this method we conclude that it is possible to predict which cases of persistent DDH will require pelvic surgery to fully contain the affected hip and that this can be done with one AP pelvic radiograph in the outpatient clinic. The benefit is avoidance of unnecessary pelvic osteotomies, and being able to determine the cases which should have a pelvic osteotomy at index procedure.