Limb, joint and pelvic kinematic control in the quail coping with step perturbations

Small cursorial birds display remarkable walking skills and can negotiate complex and unstructured terrains with ease. The neuromechanical control strategies necessary to adapt to these challenging terrains are still not well understood. Here, we analyzed the 2D- and 3D pelvic and leg kinematic strategies employed by the common quail to negotiate visible step-up and step-down perturbations of 1 cm, 2.5 cm, and 5 cm. We used biplanar fluoroscopy to accurately describe joint positions in three dimensions and performed semi-automatic landmark localization using deep learning. Quails negotiated vertical perturbations without major problems and rapidly regained steady-state locomotion. When coping with step-up perturbations, the quail mostly adapted the trailing limb to permit the leading leg to step on the elevated substrate in a similar way as it did during level locomotion. When the quail negotiated step-down perturbations, both legs showed significant adaptations. For small and moderate perturbations (not inducing aerial running) the quail kept the function of the distal joints (i.e., their kinematic pattern) largely unchanged during uneven locomotion, and most changes occurred in proximal joints. The hip regulated leg length, while the distal joints maintained the spring-damped limb patterns. However, to negotiate the largest visible step perturbations, more dramatic kinematic alterations were observed. For these large perturbations, all joints contributed to leg lengthening/ shortening in the trailing leg and both the trailing and leading legs stepped more vertically and less abducted. This indicates a shift from a dynamic walking program to strategies that are focused on maximizing safety.

Characterizing the Magnitude of and Risk Factors for Functional Limb Lengthening in Patients Undergoing Primary Total Knee Arthroplasty

Background: There is little data on the magnitude and factors for functional leg lengthening after primary total knee arthroplasty (TKA). Questions/Purpose: We sought to determine the incidence of and risk factors for functional leg lengthening after primary TKA. Methods: We retrospectively reviewed consecutive unilateral primary TKAs at a single institution from 2015 to 2018. Of the 782 TKAs included, 430 (55%) were performed in women; the mean age was 66 years, and the mean body mass index was 29 kg/m2. Preoperatively, 541 (69%) knees were varus deformities and 223 (29%) were valgus deformities. Hip to ankle biplanar radiographs were obtained preoperatively and 6 weeks postoperatively for all patients. Two independent researchers measured leg length, coronal plane deformity, lateral knee flexion angle, and overall mechanical alignment on all preoperative and postoperative radiographs. Results: The mean overall ipsilateral functional leg lengthening was 7.0 mm. Seven hundred knees (90%) were overall functionally lengthened, including 462 (59%) knees lengthened >5 mm and 250 (31%) knees lengthened 10 mm or more. A valgus deformity and coronal plane deformity of 10° or more were significant risk factors for increased functional lengthening. Patients with severe valgus deformities (>10°) had the largest amount of functional lengthening, at a mean of 13.5 mm. Conclusion: After primary TKA, 90% of limbs are functionally lengthened, including roughly one-third over a centimeter. Valgus knee deformities and severe deformities (>10°) were significant risk factors for increased limb lengthening.

Direct Anterior Total Hip Arthroplasty with Fluoroscopy to Mitigate the Risk of Complications in Patients with Legg–Calve–Perthes Disease

A minority of adult patients with childhood Legg–Calve–Perthes disease (LCPD) will develop secondary arthritis with marked leg length discrepancy (LLD) and multiplanar hip deformity. During total hip arthroplasty (THA), these technical challenges increase the perioperative risks of nerve injury, leg length inequality, and implant malposition. The technique of direct anterior total hip arthroplasty (DA-THA) in combination with fluoroscopic imaging was evaluated to mitigate these risks. We performed a retrospective review of 11 DA-THA procedures performed for patients with LCPD. The mean preoperative LLD for the patient cohort was 17 mm (range, 2–54). The mean postoperative LLD was 6 mm (range, 0–28). Acetabular component orientation was precise and accurate with a mean abduction angle of 44 degrees (range, 42–46) and mean anteversion of 20 degrees (range, 16–24). Clinical outcomes demonstrated a mean hip disability and osteoarthritis outcome score for joint replacement (HOOS, Jr) of 94 points. No patients had leg lengthening more than 26 mm and no nerve palsies were identified. We conclude that DA-THA with fluoroscopic guidance may be a valuable method to improve component placement precision and procedural safety in this potentially high-risk patient group.

A new anterior total hip arthroplasty reduction technique for patients who require leg lengthening

Background: When performing anterior total hip arthroplasty (THA) for patients who require leg lengthening, surgeons often encounter difficulties during reduction due to soft tissue tightness. The purpose of this study was to introduce a new THA reduction technique for these patients. Methods: Between October 2018 and September 2019, 545 THAs were performed. In 15 hips (2.8%), reduction was not achieved with a traditional technique. The preoperative diagnosis was Crowe grade II in 4 hips, Crowe grade III in 4 hips, Crowe grade IV in 1 hip, and sequelae of Legg-Calvé-Perthes disease in 6 hips. All procedures were performed using a direct anterior approach. The new reduction technique was to use a lever hooked on the acetabular teardrop as a counter force against the preserved muscles. The lever was connected to the impactor with a wire and the counterforce was transmitted to the impactor. Results: Reduction was achieved in all cases without shortening osteotomy or muscle release. The mean lengthening of the operated limb was 30 mm (range 13–59 mm). Neither sciatic nor femoral nerve palsy were observed. Conclusion: We developed a new anterior THA reduction technique for patients who require leg lengthening. When the centre of the femoral head was reduced to the superior edge of the cup with the traditional technique, reduction was safely achieved with this technique.

Ten-year results of 55 dysplasia hips of hip offset and leg length reconstruction in total hip arthroplasty with cementless tapered stems having a high offset option designed for dysplastic femur

Purpose: In developmental dysplasia of the hip (DDH), the centers of hip rotation move in the superior and lateral direction. In total hip arthroplasty for such cases, movement of the center of hip rotation is in the inferior and medial direction. It causes an increase in leg length and a decrease in acetabular offset. We therefore evaluated the change of hip offset and leg length before and after surgery with two stems having a high offset option. Patients and Methods: The preoperative diagnosis was secondary osteoarthritis due to DDH excluded Crowe IV. A stem selection was decided based on preoperative two-dimensional templating. Total 55 hips in 50 patients were followed up for minimum 10 years. Pre- and postoperative clinical evaluations were performed using a hip joint function scoring system. Radiographic evaluations were used for offset and leg length measurements and other associated factors. Results: Both stems showed excellent clinical results. A high offset option was used in 60% of all cases. No postoperative dislocations were observed. The biological fixation was stable in all cases. The hip offset was restored without excessive leg lengthening in most cases. Conclusion: Anatomical consistency could be maintained by using a stem which matched geometry of the proximal part and had offset option. These cementless tapered stems having a high offset option are suitable for Crowe I to III hip dysplasia if two-dimensional X-ray templates fit the shape of the proximal femurs. They were associated with excellent clinical results and biological fixation. The offset option may be useful to adjust leg length and offset in DDH patients.

Intraoperative monitoring of the femoral and sciatic nerves in total hip arthroplasty with high-riding developmental dysplasia

Aims This study aimed to explore whether intraoperative nerve monitoring can identify risk factors and reduce the incidence of nerve injury in patients with high-riding developmental dysplasia. Patients and Methods We conducted a historical controlled study of patients with unilateral Crowe IV developmental dysplasia of the hip (DDH). Between October 2016 and October 2017, intraoperative nerve monitoring of the femoral and sciatic nerves was applied in total hip arthroplasty (THA). A neuromonitoring technician was employed to monitor nerve function and inform the surgeon of ongoing changes in a timely manner. Patients who did not have intraoperative nerve monitoring between September 2015 and October 2016 were selected as the control group. All the surgeries were performed by one surgeon. Demographics and clinical data were analyzed. A total of 35 patients in the monitoring group (ten male, 25 female; mean age 37.1 years (20 to 46)) and 56 patients in the control group (13 male, 43 female; mean age 37.9 years (23 to 52)) were enrolled. The mean follow-up of all patients was 13.1 months (10 to 15). Results The two groups had no significant differences in preoperative data. In the monitoring group, ten nerve alerts occurred intraoperatively, and no neural complications were detected postoperatively. In the control group, six patients had neural complications. The rate of nerve injury was lower in the monitoring group than in the control group, but this did not achieve statistical significance. The degree of leg lengthening was significantly greater in the monitoring group than in the control group. In further analyses, patients who had previous hip surgery were more likely to have intraoperative nerve alerts and postoperative nerve injury. Conclusion Nerve injury usually occurred during the processes of exposure and reduction. The use of intraoperative nerve monitoring showed a trend towards reduced nerve injury in THA for Crowe IV DDH patients. Hence, we recommend its routine use in patients undergoing leg lengthening, especially in those with previous hip surgery. Cite this article: Bone Joint J 2019;101-B:1438–1446.