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Background Patient-specific instrumentation potentially improves surgical precision and decreases operative time in total knee arthroplasty (TKA) but there is little supporting data to confirm this presumption. Questions/purposes We asked whether patient-specific instrumentation would require infrequent intraoperative changes to replicate a single surgeon’s preferences during TKA and whether patient-specific instrumentation guides would fit securely. Methods We prospectively evaluated the plan and surgery in 60 patients treated with 66 TKAs performed with patient-specific instrumentation and recorded any changes. A subset of six postoperative radiographic changes to the femoral and tibial components (implant size, coronal and sagittal alignment) was analyzed to determine if surgeon intervention was beneficial. Each guide was evaluated to determine fit. We compared patient demographics and implant sizing in the patient-specific instrumentation group with a control group in which traditional instrumentation was used. Results We recorded 161 intraoperative changes in 66 knee arthroplasties (2.4 changes/knee) performed with patient-specific instrumentation. The predetermined implant size was changed intraoperatively in 77% of femurs and 53% of tibias. We identified a subset of 95 intraoperative changes that could be radiographically evaluated to determine if our changes were an improvement or detriment to reaching goal alignment. Eighty-two of the 95 changes (86%) made by the surgeon were an improvement to the recommended alignment or size of patient-specific instrumentation. The guide did not fit securely on eight femurs (12%) and three tibias (5%). Tourniquet time and blood loss were not improved with patient-specific instrumentation. Conclusions We caution surgeons against blind acceptance of patient-specific instrumentation technology without supportive data. Level of Evidence Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Acetabular dysplasia is a known cause of hip osteoarthritis. In addition to abnormal anatomy, changes in kinematics, joint reaction forces (JRFs), and muscle forces could cause tissue damage to the cartilage and labrum, and may contribute to pain and fatigue. The objective of this study was to compare lower extremity joint angles, moments, hip JRFs and muscle forces during gait between patients with symptomatic acetabular dysplasia and healthy controls. Marker trajectories and ground reaction forces were measured in 10 dysplasia patients and 10 typically developing control subjects. A musculoskeletal model was scaled in OpenSim to each subject and subject-specific hip joint centers were determined using reconstructions from CT images. Joint kinematics and moments were calculated using inverse kinematics and inverse dynamics, respectively. Muscle forces and hip JRFs were estimated with static optimization. Inter-group differences were tested for statistical significance (p≤0.05) and large effect sizes (d≥0.8). Results demonstrated that dysplasia patients had higher medially directed JRFs. Joint angles and moments were mostly similar between the groups, but large inter-group effect sizes suggested some restriction in range of motion by patients at the hip and ankle. Higher medially-directed JRFs and inter-group differences in hip muscle forces likely stem from lateralization of the hip joint center in dysplastic patients. Joint force differences, combined with reductions in range of motion at the hip and ankle may also indicate compensatory strategies by patients with dysplasia to maintain joint stability.

The relatively high incidence of labral tears among patients presenting with hip pain suggests that the acetabular labrum is often subjected to injurious loading in vivo. However, it is unclear whether the labrum participates in load transfer across the joint during activities of daily living. This study examined the role of the acetabular labrum in load transfer for hips with normal acetabular geometry and acetabular dysplasia using subject-specific finite element analysis. Models were generated from volumetric CT data and analyzed with and without the labrum during activities of daily living. The labrum in the dysplastic model supported 4–11% of the total load transferred across the joint, while the labrum in the normal model supported only 1–2% of the total load. Despite the increased load transferred to the acetabular cartilage in simulations without the labrum, there were minimal differences in cartilage contact stresses. This was because the load supported by the cartilage correlated with the cartilage contact area. A higher percentage of load was transferred to the labrum in the dysplastic model because the femoral head achieved equilibrium near the lateral edge of the acetabulum. The results of this study suggest that the labrum plays a larger role in load transfer and joint stability in hips with acetabular dysplasia than in hips with normal acetabular geometry.

Visualization of hip articulation relative to the underlying anatomy (i.e., arthrokinematics) is required to understand hip dysfunction in femoroacetabular (FAI) patients. In this exploratory study, we quantified in-vivo arthrokinematics of a small cohort of asymptomatic volunteers and three symptomatic patients with varying FAI deformities during the passive impingement, FABER, and rotational profile exams using dual fluoroscopy and model-based tracking. Joint angles, joint translations, and relative pelvic angles were calculated. Compared to the 95% confidence interval of the asymptomatic cohort, FAI patients appeared to have decreased adduction and internal rotation during the impingement exam and greater flexion and less abduction/external rotation in the FABER exam. During the rotational profile, only the FAI patient with the most severe deformities demonstrated considerable rotation deficits. In all participants, contact between the labrum and femoral head/neck limited motion during the impingement exam, but not the rotational profile. Substantial pelvic motion was measured during the impingement exam and FABER test in all participants. Femoral translation along any given anatomical direction ranged between 0.69 and 4.1mm. These results suggest that hip articulation during clinical exams is complex in asymptomatic hips and hips with FAI, incorporating pelvic motion and femur translation. Range of motion appears to be governed by femur–labrum contact and other soft tissue constraints, suggesting that current computer simulations that rely on direct bone contact to predict impingement may be unrealistic. Additional research is necessary to confirm these preliminary results. Still, dual fluoroscopy data may serve to validate existing software platforms or create new programs that better-represent hip arthrokinematics.

Background: The lateral center-edge angle (LCEA) is an important measurement in understanding acetabular morphology and has had multiple interpretations. Misunderstanding of the LCEA and its relationship with acetabular 3-dimensional (3D) morphology may result in misdiagnosis and poor outcomes. Purpose: To determine the discrepancy between bone-edge and sourcil-edge LCEA measurements on anteroposterior (AP) radiographs and to determine the 3D anatomic location of the sourcil-edge and bone-edge LCEA measurements. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: The LCEA was measured on radiographs to both the sourcil-edge and bone-edge on AP images of 60 symptomatic hips. On computed tomography (CT), coronal slices producing an LCEA matching the magnitude of each AP LCEA were identified. These coronal slices were mapped to a sagittal image of the acetabulum, which was divided into a standard clockface (3 = anterior, 12 = superior). We identified clockface locations corresponding to the AP sourcil-edge and bone-edge LCEA measurements. Paired t tests identified differences in magnitude and location of the bone and sourcil LCEAs. Limits of agreement were calculated for the differences between measures. Intraclass correlation coefficients (ICCs) assessed inter- and intraobserver repeatability. Results: On the AP radiographs, the bone-edge LCEA was a mean 4.7° (95% CI, −4.0° to 13.3°) greater than the sourcil-edge LCEA (P < .001). On CT, the sagittal clockface location of the sourcil-edge LCEA was more anterior compared with the sagittal clockface location of the maximum bone-edge LCEA (1:03 ± 0:42 vs 12:06 ± 0:30, respectively; P < .001). In hips with a difference >5° between sourcil-edge and bone-edge measurements, the coronal CT slice corresponding to the sourcil-edge LCEA was significantly more anterior (1:26 ± 0:35) than the CT slice corresponding to the bone-edge LCEA (11:46 ± 0:29; P < .001). This significant difference was similar in location but less pronounced in hips with a difference ≤5°: the sourcil-edge LCEA occurred at 12:50 ± 0:40, while the bone-edge LCEA occurred at 12:00 ± 0:11 (P < .001). Interobserver repeatability was excellent for all LCEA and clockface location measurements (all ICCs >0.82). Conclusion: The sourcil-edge LCEA represents anterosuperior acetabular coverage while the bone-edge LCEA represents superior/lateral coverage. This information can be used in preoperative evaluation of and perioperative planning for hip preservation procedures.

Background With as many as 25% of patients reporting residual knee symptoms after primary total knee arthroplasty (TKA), alternative implant designs and surgical techniques have been proposed to further reduce these symptoms. There is growing evidence that retention of the anterior cruciate ligament (ACL) results in more natural knee kinematics; thus, implants with more normal joint mechanics could provide improved physical function postoperatively and reduce the amount of residual symptoms. Advancements in the bicruciate-retaining (BCR) TKA implant design have been made, and based on these, we wished to compare the BCR with a more traditional cruciate-retaining (CR) implant. Questions/purposes (1) Was there a difference in the risk of reoperation after primary TKA between BCR and CR implant designs? (2) Was there a difference in the radiographic findings of radiolucent lines (RLLs) between the implant designs? (3) Was there a difference in patient-reported and clinical outcomes between the two implant designs? Methods Between January 2013 and May 2014, two surgeons performed 475 primary TKAs. During this time, 78 (16%) of these were performed with BCR implants and 294 (62%) with CR implants; the remainder were performed with anterior-stabilized or more constrained designs as a result of increased deformity and/or ligamentous deficiencies. During this period, the general indications for BCR TKA were arthritic knees with only slight to moderate deformity and sufficient ligamentous integrity of both the ACL and posterior cruciate ligament. The indications for CR TKA were similar other than these patients presented with a deficient ACL. A total of 66 (85%) of the BCR and 237 (81%) of the CR TKAs were available for followup at a minimum of 12 months or when reoperation occurred before 12 months (mean, 18 months; range, 2–32 months). With the numbers available, there were no differences between the groups in terms of age and sex, but the patients undergoing CR TKA had a greater mean body mass index (33 ± 7 versus 31 ± 5 kg/m 2 , p = 0.032). The frequency of early reoperation was compared between the groups as were radiographic evidence of RLL, patient-reported outcomes, and knee range of motion (ROM). Results Knees in the BCR group had a higher frequency of all-cause revision (5% [three of 66] versus 1.3% [three of 237]; hazard ratio (HR), 7.44; 95% confidence interval [CI], 1.24–44.80; p = 0.028). Knees in the BCR group had a higher frequency of irrigation and débridement with component retention (HR, 0.07; 95% CI, 0.02–0.28; p < 0.001). No differences were found between groups for subsequent manipulation (HR, 0.34; 95% CI, 0.08–1.42; p = 0.137). The proportion of RLLs was greater in the BCR group (HR, 2.93; 95% CI, 1.62–5.32; p < 0.001) compared with the CR group. There were no differences between the groups in terms of the Physical Function Computerized Adaptive Test scores, Global10 scores or knee ROM outcomes. Conclusions Preliminary short-term findings suggest the BCR implant has inferior survivorship and concerning radiographic findings when compared with a conventional CR implant with respect to complications after primary TKA. These findings raise concerns about the new BCR design; however, further randomized trials are necessary to determine superiority between alternative implant designs. Level of Evidence Level III, therapeutic study.

Despite two-stage revision remaining the gold standard in treating periprosthetic infection of total knee arthroplasty (TKA), there remains uncertainty regarding the actual success rate and the risk factors for failure. We retrospectively reviewed 58 knees with mean follow-up of 38 months who underwent two-stage revision TKAs from 1998 to 2012 by a single surgeon. Failure was defined as persistent infection or reoperation after two-stage revision TKA surgery. Failure occurred in 36%. The overall mortality was 22%. The mean time to reinfection was 26 months. Polymicrobial infection was associated with a higher risk of failure (RR 3.31, P < 0.001 ). Knees requiring soft tissue coverage were also at a greater risk of failure (RR 2.67, P = 0.001 ), as were knees that underwent four or more additional surgeries after the primary TKA and prior to stage-one explantation (RR 2.25, P = 0.020 ). Thus, opportunities exist for improvement in management of infected TKA.

Background Since the modern description of femoroacetabular impingement (FAI) a decade ago, surgical treatment has become increasingly common. Although the ability of open treatment of FAI to relieve pain and improve function has been demonstrated in a number of retrospective studies, questions remain regarding predictability of clinical outcome, the factors associated with clinical failure, and the complications associated with treatment. Questions/purposes We therefore described the change in clinical pain and function after open treatment, determined whether failure of treatment and progression of osteoarthritis was associated with Outerbridge Grade IV hyaline cartilage injury, and described the associated complications. Methods We retrospectively reviewed all 94 patients (96 hips) (55 males and 39 females; mean age, 28 years) who underwent surgical dislocation for femoroacetabular impingement between 2000 and 2008. Seventy-two of the 96 hips had acetabular articular cartilage lesions treated with a variety of methods, most commonly resection of damaged hyaline cartilage and labral advancement. Patients were followed for a minimum of 18 months (mean, 26 months; range, 18–96 months). Results Mean Harris hip scores improved from 67 to 91 at final followup. Six of the 96 hips (6%) were converted to arthroplasty or had worse Harris hip score after surgical recovery. Four of these six had Outerbridge Grade IV acetabular cartilage lesions and two had Legg-Calvé-Perthes disease or slipped capital epiphysis deformities. Two hips (2%) had refixation of the greater trochanter. Conclusions At short-term followup, open treatment for femoroacetabular impingement in hips without substantial acetabular hyaline cartilage damage reduced pain and improved function with a low complication rate. Treatment of Outerbridge Grade IV acetabular cartilage delamination remains the major challenge. Level of Evidence Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Background The use of a highly conforming, anterior-stabilized bearing has been associated with clinical success in a limited number of studies. Questions/purposes We compared Knee Society scores, radiographic results, complication rates, and revision rates with the use of anterior-stabilized bearings compared with cruciate-retaining (CR) bearings. Methods A series of 382 patients with 468 primary total knee arthroplasties (TKAs) between 2003 and 2008 with minimum 2-year followup were reviewed. Anterior-stabilized bearings comprised 49% (n = 228) of the sample and CR bearings consisted of 51% (n = 240). The decision to use an anterior-stabilized bearing was based on integrity of the posterior cruciate ligament (PCL) intraoperatively or after sacrifice of the PCL to achieve soft tissue balance. The tibial and femoral component designs were the same regardless of bearing choice. Outcomes were measured with Knee Society scores, complications, revision TKA, and survival. Radiographs were analyzed for component alignment and evidence of loosening. Results There was no difference in Knee Society knee scores, radiographic alignment, component loosening, manipulation rate, major complications, or time to revision for patients between the two groups. However, the CR group had significantly more revisions than the anterior-stabilized group (21 CR [1.5%] versus seven anterior-stabilized [4.6%], p = 0.03) at a minimum followup of 5 months (mean, 42 months; range, 5–181 months). Conclusions The use of a highly congruent anterior-stabilized bearing for PCL substitution has comparable clinical and radiographic results to traditional CR TKA. These results suggest that this approach is an effective method to achieve stability without the PCL in primary TKA. Level of Evidence Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.