Bart Kerens

Revision from unicompartmental to total knee replacement: the clinical outcome depends on reason for revision.

Although it has been suggested that the outcome after revision of a unicondylar knee replacement (UKR) to total knee replacement (TKR) is better when the mechanism of failure is understood, a comparative study on this subject has not been undertaken. A total of 30 patients (30 knees) who underwent revision of their unsatisfactory UKR to TKR were included in the study: 15 patients with unexplained pain comprised group A and 15 patients with a defined cause for pain formed group B. The Oxford knee score (OKS), visual analogue scale for pain (VAS) and patient satisfaction were assessed before revision and at one year after revision, and compared between the groups. The mean OKS improved from 19 (10 to 30) to 25 (11 to 41) in group A and from 23 (11 to 45) to 38 (20 to 48) in group B. The mean VAS improved from 7.7 (5 to 10) to 5.4 (1 to 8) in group A and from 7.4 (2 to 9) to 1.7 (0 to 8) in group B. There was a statistically significant difference between the mean improvements in each group for both OKS (p = 0.022) and VAS (p = 0.002). Subgroup analysis in group A, performed in order to define a patient factor that predicts outcome of revision surgery in patients with unexplained pain, showed no pre-operative differences between both subgroups. These results may be used to inform patients about what to expect from revision surgery, highlighting that revision of UKR to TKR for unexplained pain generally results in a less favourable outcome than revision for a known cause of pain.

Patient-specific guide for revision of medial unicondylar knee arthroplasty to total knee arthroplasty: Beneficial first results of a new operating technique performed on 10 patients

Background and purpose Unicompartmental to total knee arthroplasty revision surgery can be technically demanding. Joint line restoration, rotation, and augmentations can cause difficulties. We describe a new technique in which single-way fitting guides serve to position the knee system cutting blocks. Method Preoperatively, images of the distal femur and proximal tibia are taken using CT scanning. These images are used to create a patient-specific guide that fits in one single position on the contours of the bone and the prosthesis in situ. The guides are fixed with pins and then removed. The pins determine the position of the cutting blocks. 10 consecutive revisions were performed using this technique. Results All guides fitted well. 7 of 10 femoral prostheses were within the desired AP and sagittal angle ± 3°. However, 1 proximal tibia did not have enough bone stock on the medial plateau for adequate fixation of the guide, so conversion to intramedular referencing was performed. This was to be expected after the preoperative planning. All tibial components were within the desired AP angle ± 3° and 7 of 10 were within the desired sagittal angle. Hip-knee-ankle angle was within 0 ± 3° in 8 of 10 cases. Interpretation This new technique makes preoperative planning and execution of this plan during surgery less demanding. Problems such as the need for augmentations can be predicted at the preoperative planning. The instrumentation must be redesigned in order to make this technique work in cases where there is minimal bone stock present.

No radiographic difference between patient-specific guiding and conventional Oxford UKA surgery

PurposeImplant position is an important factor in unicompartmental knee arthroplasty (UKA) surgery. Results on conventional UKA alignment are commonly described in literature. Patient-specific guiding (PSG) is a new technique for positioning the Oxford UKA. Our hypothesis is that PSG improves component position without affecting the HKA angle.MethodsThis prospective study compares the results of our first thirty cases of cementless Oxford UKA using PSG with thirty cases using conventional outlining. Baseline characteristics for both groups were identical. Details on handling of the guide, estimated blood loss and operation time were recorded. Postoperative screened radiographs and standing long-leg radiographs of both groups were compared.ResultsMedian AP position of the femoral component was 3 degrees varus (−5 to 9) using PSG versus 2 degrees varus (−10 to 8) for the conventional group. For the femoral flexion, this was 9 degrees flexion (0–16) using PSG versus 12 degrees flexion (0–20). The tibial median AP position was 1 degree varus (−3 to 7) using PSG versus 2 degrees varus (−5 to 10). The median tibial posterior slope was 5 degrees (1–10) using PSG versus 5 degrees (0–12). All guides aligned well. No conversion to conventional outlining was performed, and no significant changes had to be made to the original approved plan. Operation time, estimated blood loss and postoperative haemoglobin drop were not significantly different between both groups.DiscussionImplant position was not different between both groups, even in the early phase of the learning curve. Perioperative results were not different between both groups.Level of evidenceIII.

Patient-specific positioning guides for total knee arthroplasty: no significant difference between final component alignment and pre-operative digital plan except for tibial rotation

AbstractPurposeTo assess whether there is a significant difference between the alignment of the individual femoral and tibial components (in the frontal, sagittal and horizontal planes) as calculated pre-operatively (digital plan) and the actually achieved alignment in vivo obtained with the use of patient-specific positioning guides (PSPGs) for TKA. It was hypothesised that there would be no difference between post-op implant position and pre-op digital plan.Methods Twenty-six patients were included in this non-inferiority trial. Software permitted matching of the pre-operative MRI scan (and therefore calculated prosthesis position) to a pre-operative CT scan and then to a post-operative full-leg CT scan to determine deviations from pre-op planning in all three anatomical planes.ResultsFor the femoral component, mean absolute deviations from planning were 1.8° (SD 1.3), 2.5° (SD 1.6) and 1.6° (SD 1.4) in the frontal, sagittal and transverse planes, respectively. For the tibial component, mean absolute deviations from planning were 1.7° (SD 1.2), 1.7° (SD 1.5) and 3.2° (SD 3.6) in the frontal, sagittal and transverse planes, respectively. Absolute mean deviation from planned mechanical axis was 1.9°. The a priori specified null hypothesis for equivalence testing: the difference from planning is >3 or <−3 was rejected for all comparisons except for the tibial transverse plane.ConclusionPSPG was able to adequately reproduce the pre-op plan in all planes, except for the tibial rotation in the transverse plane. Possible explanations for outliers are discussed and highlight the importance for adequate training surgeons before they start using PSPG in their day-by-day practise.Level of evidenceProspective cohort study, Level II.

Inter-observer reliability of measurements performed on digital long-leg standing radiographs and assessment of validity compared to 3D CT-scan

BACKGROUND Long-leg radiographs (LLR) are often used in orthopaedics to assess limb alignment in patients undergoing total knee arthroplasty (TKA). However, there are still concerns about the adequacy of measurements performed on LLR. We assessed the reliability and validity of measurements on LLR using three-dimensional computed tomography (3D CT)-scan as a gold standard. METHODS Six different surgeons measured the mechanical axis and position of the femoral and tibial components individually on 24 LLR. Intraclass correlation coefficients (ICC) were calculated to obtain reliability and Bland-Altman plots were constructed to assess agreement between measurements on LLR and measurements on 3D CT-scan. RESULTS ICC agreement for the six observer measurements on LLR was 0.70 for the femoral component and 0.80 for the tibial component. The mean difference between measurements performed on LLR and 3D CT-scan was 0.3° for the femoral component and -1.1° for the tibial component. Variation of the difference between LLR and 3D CT-scan for the femoral component was 1.1° and 0.9° for the tibial component. 95% of the differences between measurements performed on LLR and 3D CT-scan were between -1.9 and 2.4° (femoral component) and between -2.9 and 0.7 (tibial component). CONCLUSION Measurements on LLR show moderate to good reliability and, when compared to 3D CT-scan, show good validity. CLINICAL TRIAL REGISTRATION NUMBER institutional review board Atrium-Orbis-Zuyd, number: 11-T-15. LEVEL OF EVIDENCE Prospective cohort study, Level II.

Patient-specific instrumentation in Oxford unicompartmental knee arthroplasty is reliable and accurate except for the tibial rotation

PurposePatient-specific instrumentation (PSI) is a technique to plan and position the prosthesis components in unicompartmental knee arthroplasty (UKA) surgery. This study assesses whether the definitive component position in the frontal, sagittal and axial plane is according to the preoperative plan, based on the hypothesis that PSI is accurate.MethodsTwenty-six patients who had PSI Oxford UKA surgery were included prospectively. The component position in vivo was determined with a postoperative CT-scan and compared with the planned component position using MRI-based digital 3D imaging. Adjustments to the preoperative plan and implanted component sizes during surgery were recorded.ResultsIntraoperatively, no femoral adjustments were performed; 12 tibial re-resections were necessary. The median absolute deviation from the plan in degrees (range) in the frontal, sagittal and axial plane was 1.8° (− 1.5°–6.5°), 2.0° (− 6.5°–8.0°) and 1.0° (− 1.5°–5.0°) for the femoral component, and 2.5° (− 1.0°–6.0°), 3.0° (− 1.0°–5.0°) and 5.0° (− 6.5°–12.5°) for the tibial component. The femoral component is positioned 0.5 (− 1°–2.5°) mm more lateral and 0.8 (− 1.0°–2.5°) mm more anterior. The tibial component is positioned 2.0 (− 5.0–0.0) mm more lateral and 1.3 (− 3.0–6.0) mm more distal. The femoral and tibial default plans were changed four times (15.4%) and nine times (34.6%), respectively, before approval by the surgeon.ConclusionPSI in Oxford UKA surgery is reliable and accurately translates the preoperative plan into the in vivo situation, except for the tibial rotational position. The preoperative planning is a crucial step in avoiding re-resections that can cause angular deviations in prosthesis position, especially in tibial component rotational position. It is advised to avoid re-resections and to consider this while planning the PSI procedure.Level of evidenceProspective comparative study Level II.

Subcutaneous emphysema after shoulder arthroscopy. A case report and review of the literature

INTRODUCTION Subcutaneous emphysema (SE) and pneumomediastinum are rare complications after shoulder arthroscopy. CASE REPORT A case is presented in which SE was seen after arthroscopic cuff repair. DISCUSSION A review of current literature shows that SE after shoulder arthroscopy can be due to loco-regional anaesthesiology, endotracheal intubation, gas-forming infection, postoperative mobilisation or the arthroscopic procedure itself. During the procedure air can be sucked into the subacromial space due to suction and subsequently transferred into subcutaneous tissue by the positive pressure of the infusion pump. When the condition is recognised early and addressed properly spontaneous resolving is possible with good clinical outcome.

Compartment Syndrome, Femoral Nerve Lesion and Recurrent Haemarthrosis in one and the same Patient after Total Knee Arthroplasty

We present a case of a 53 year old patient that underwent total knee arthroplasty in our hospital for degenerative arthritis and developed a series of very uncommon complications. Compartment syndrome of the calf occurred postoperatively as a result of bleeding from a large, ruptured knee joint cyst. Femoral nerve lesion was diagnosed and was most likely the result of traumatic migration of the femoral nerve catheter in the nerve sheet. Finally, our patient suffered from recurrent haemarthrosis in which anticoagulant therapy is thought to have played a key role. This series of very uncommon complications occurring in one and the same patient stresses the importance for orthopaedic surgeons to continuously and carefully monitor their patients postoperatively in order to adequately diagnose complications, also the rare ones, and to take appropriate measurements to minimize dramatic outcomes of these complications.