Malrotation of the femoral component is a cause of patellofemoral maltracking after total knee arthroplasty. Its precise effect on the patellofemoral mechanics has not been well quantified. We have developed an in vitro method to measure the influence of patellar maltracking on contact. Maltracking was induced by progressively rotating the femoral component either internally or externally. The contact mechanics were analysed using Tekscan. The results showed that excessive malrotation of the femoral component, both internally and externally, had a significant influence on the mechanics of contact. The contact area decreased with progressive maltracking, with a concomitant increase in contact pressure. The amount of contact area that carries more than the yield stress of ultra-high molecular weight polyethylene significantly increases with progressive maltracking. It is likely that the elevated pressures noted in malrotation could cause accelerated and excessive wear of the patellar button

Component malrotation in total knee arthroplasty (TKA) is a reason for early failure and revision. Assessment of possible component malrotation using computed tomography (CT) might be useful when other differentials have been excluded. The aims of our study were to determine the proportion of symptomatic patients with component malrotation on CT, and review the subsequent management of such patients. A retrospective review of case notes was performed locally for all patients who had a CT scan for a painful TKA. Measurements of the femoral and tibial component rotations were done according to the standard Berger protocol, giving net degrees of either external rotation (ER) or internal rotation (IR). Any subsequent surgery was noted, and patients were followed up as per local practice. Between 2007 and April 2012, 69 knees in 68 patients had CT scans. There were 25 males and 43 females, and mean age at primary surgery was 65.03 years. The mean femoral component rotation for all knees was 0.1° ER (range 7.0° ER – 6.7° IR), and the mean tibial component rotation for all knees was 19.1° IR (6.6° ER – 37.0° IR). No statistically significant difference was found comparing the mean femoral and tibial component rotations between patients with and without further surgery. Further surgery was performed on 39 (56.5%) knees. Overall, there were ten cases (14.5%) of isolated femoral malrotation, 26 tibial malrotation (37.7%), and two cases (2.9%) had malrotation of both components. Out of these 38 cases, secondary surgery was performed in 22 knees (57.9%), of which a satisfactory outcome was achieved in fifteen cases (68.1%). It is impossible to establish component malrotation as the only cause of pain following TKA, however, our study does show that the Berger protocol has its uses when other causes have been excluded

Metacarpal fractures represent up to 33% of all hand fractures; of which the majority can be treated non-operatively. Previous research has shown excellent putcomes with non-operative treatment yet surgical stabilisation is recommended to avoid malrotation and symptomatic shortening. It is unknown whether operative is superior to non-operative treatment in oblique or spiral metacarpal shaft fractures. The aim of the study was to compare non-operative treatment of mobilisation with open surgical stabilisation. 42 adults (≥ 18 years) with a single displaced oblique or spiral metacarpal shaft fractures were randomly assigned in a 1:1 pattern to either non-operative treatment with free mobilisation or operative treatment with open reduction and fixation with lag screws in a prospective study. The primary outcome measure was grip-strength in the injured hand in comparison to the uninjured hand at 1-year follow-up. The Disabilities of the Arm, Shoulder and Hand Score, ranges of motion, metacarpal shortening, complications, time off work, patient satisfaction and costs were secondary outcomes. All 42 patients attended final follow-up after 1 year. The mean grip strength in the non-operative group was 104% (range 73–250%) of the contralateral hand and 96% (range 58–121%) in the operatively treated patients. Mean metacarpal shortening was 5.0 (range 0–9) mm in the non-operative group and 0.6 (range 0–7) mm in the operative group. There were five minor complications and three revision operations, all in the operative group. The costs for non-operative treatment were estimated at 1,347 USD compared to 3,834USD for operative treatment; sick leave was significantly longer in the operative group (35 days, range 0–147) than in the non-operative group (12 days, range 0–62) (p=0.008). When treated with immediate free mobilization single, patients with displaced spiral or oblique metacarpal shaft fractures have outcomes that are comparable to those after operative treatment, despite some metacarpal shortening. Complication rates, costs and sick leave are higher with operative treatment. Early mobilisation of spiral or long oblique single metacarpal fractures is the preferred treatment. Trial registration number: ClinicalTrials.gov NCT03067454

Objectives

This study reports on a secondary exploratory analysis of the early clinical outcomes of a randomised clinical trial comparing robotic arm-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis of the knee with manual UKA performed using traditional surgical jigs. This follows reporting of the primary outcomes of implant accuracy and gait analysis that showed significant advantages in the robotic arm-assisted group.

Malpositioning of the trochanteric entry point during the introduction of an intramedullary nail may cause iatrogenic fracture or malreduction. Although the optimal point of insertion in the coronal plane has been well described, positioning in the sagittal plane is poorly defined.

The paired femora from 374 cadavers were placed both in the anatomical position and in internal rotation to neutralise femoral anteversion. A marker was placed at the apparent apex of the greater trochanter, and the lateral and anterior offsets from the axis of the femoral shaft were measured on anteroposterior and lateral photographs. Greater trochanteric morphology and trochanteric overhang were graded.

The mean anterior offset of the apex of the trochanter relative to the axis of the femoral shaft was 5.1 mm (sd 4.0) and 4.6 mm (sd 4.2) for the anatomical and neutralised positions, respectively. The mean lateral offset of the apex was 7.1 mm (sd 4.6) and 6.4 mm (sd 4.6), respectively.

Placement of the entry position at the apex of the greater trochanter in the anteroposterior view does not reliably centre an intramedullary nail in the sagittal plane. Based on our findings, the site of insertion should be about 5 mm posterior to the apex of the trochanter to allow for its anterior offset.

Cite this article: Bone Joint J 2014;96-B:1274–81.

We have investigated the errors in the identification of the transepicondylar axis and the anteroposterior axis between a minimally-invasive and a conventional approach in four fresh-frozen cadaver knees. The errors in aligning the femoral prosthesis were compared with the reference transepicondylar axis as established by CT.

The error in the identification of the transepicondylar axis was significantly higher in the minimal approach (4.5° of internal rotation, sd 4) than in the conventional approach (3° of internal rotation, sd 4; p < 0.001). The errors in identifying the anteroposterior axis in the two approaches were 0° (sd 5) and 1.8° (sd 5) of internal rotation, respectively (p < 0.001).

A complete cement mantle is important for the longevity of a total hip replacement. In the minimally-invasive direct anterior approach used at the Innsbruck University hospital, the femoral component has to be inserted into the femoral canal by an angulated movement. In a cadaver study, the quality and the extent of the cement mantle surrounding 13 Exeter femoral components implanted straight through a standard anterolateral transgluteal approach were compared with those of 13 similar femoral components implanted in an angulated fashion through a direct anterior approach. A third-generation cementing technique was used. The inner and outer contours of the cement mantles was traced from CT scans and the thickness and cross-sectional area determined.

In no case was the cement mantle incomplete. The total mean thickness of the cement mantle was 3.62 mm (95% confidence interval 3.59 to 3.65). The mean thickness in the group using the minimally-invasive approach was 0.16 mm less than that in the anterolateral group. The distribution of the thickness was similar in the two groups. The mean thickness was less on the anteromedial and anterolateral aspect than on the posterior aspect of the femur.

There is no evidence that the angulated introduction of Exeter femoral components in the direct anterior approach in cadavers compromises the quality, extent or thickness of the cement mantle.